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<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong><br />
<strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (JAAUBAS)<br />
http://www.ees.elsevier.com/jaaubas<br />
JAAUBAS is a biannual peer-refereed international research journal specialized in <strong>the</strong> basic <strong>and</strong> applied sciences. It is issued by <strong>the</strong><br />
College <strong>of</strong> Science at <strong>the</strong> University <strong>of</strong> Bahrain, Kingdom <strong>of</strong> Bahrain, in accordance to <strong>the</strong> resolution <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong><br />
<strong>Universities</strong> Council (Jordan), <strong>and</strong> <strong>the</strong> resolution <strong>of</strong> <strong>the</strong> University <strong>of</strong> Bahrain council (834/2000).<br />
JAAUBAS scope is to publish original research <strong>and</strong> reviews in <strong>the</strong> field <strong>of</strong> basic <strong>and</strong> applied sciences including; Biology, Chemistry,<br />
Physics, Ma<strong>the</strong>matics, Operation Research, Statistics, Astronomy, Geology <strong>and</strong> Engineering. JAAUBAS will assist researchers, from<br />
local, regional <strong>and</strong> international universities <strong>and</strong> institutions, in publishing original research results <strong>and</strong> studies in basic <strong>and</strong> applied<br />
sciences, <strong>and</strong> having <strong>the</strong>ir finding internationally visible <strong>and</strong> available.<br />
EDITORIAL BOARD<br />
Editor-In-Chief (EIC)<br />
Dr. Hashim A. Al-Sayed<br />
General Secretary <strong>of</strong> Society <strong>of</strong> Colleges <strong>of</strong> Science in<br />
<strong>Arab</strong> <strong>Universities</strong>, Dean <strong>of</strong> College <strong>of</strong> Science,<br />
University <strong>of</strong> Bahrain. P.O. Box 32038,<br />
Kingdom <strong>of</strong> Bahrain.<br />
Halsayed4122@hotmail.com<br />
Managing Editor (ME)<br />
Pr<strong>of</strong>. Waheeb E. Alnaser<br />
Vice President <strong>for</strong> Planning <strong>and</strong> Development,<br />
University <strong>of</strong> Bahrain. P.O. Box 32038,<br />
Kingdom <strong>of</strong> Bahrain.<br />
alnaser@gmail.com<br />
Editorial Secretary (ES)<br />
Dr. Mohammad El-Hilo<br />
Department <strong>of</strong> Physics, University <strong>of</strong> Bahrain.<br />
P.O. Box 32038, Kingdom <strong>of</strong> Bahrain.<br />
mhilo@rocketmail.com<br />
University <strong>of</strong> Bahrain Board Members<br />
Pr<strong>of</strong>. Mohamed S. Akhter,<br />
Dept. <strong>of</strong> Chemistry, Univ. <strong>of</strong> Bahrain, Kingdom <strong>of</strong> Bahrain.<br />
Pr<strong>of</strong> . Jameel A. Alkhuzai ,<br />
Dept. <strong>of</strong> Biology, Univ. <strong>of</strong> Bahrain, Kingdom <strong>of</strong> Bahrain.<br />
Pr<strong>of</strong>. Mahmoud Abdel-Aty,<br />
Dept. <strong>of</strong> Ma<strong>the</strong>matics, Univ. <strong>of</strong> Bahrain, Kingdom <strong>of</strong> Bahrain.<br />
Dr. Haifa A Al-Maskati,<br />
Dept. <strong>of</strong> Biology, Univ. <strong>of</strong> Bahrain, Kingdom <strong>of</strong> Bahrain.<br />
AAU Colleges <strong>of</strong> Science Society Advisory Board Members<br />
Pr<strong>of</strong>. Ghassan Owamerain, Dept. <strong>of</strong> Chemistry, King Fahad Univ., Saudi <strong>Arab</strong>ia.<br />
Pr<strong>of</strong>. Redha Al Hassan, Dept. <strong>of</strong> Biology, Kuwait University, Kuwait.<br />
Pr<strong>of</strong>. Ismail A Taqi, Dept. <strong>of</strong> Ma<strong>the</strong>matics, Kuwait University, Kuwait.<br />
Pr<strong>of</strong>. Lateefa E. Al Hoti, Dept. <strong>of</strong> Physics, Qatar University, Qatar.<br />
Pr<strong>of</strong>. Hala K. Horani, Dept. <strong>of</strong> Bilogy, Jordanian University, Jordan.<br />
Pr<strong>of</strong>. Sami M. Hussain, Dept. <strong>of</strong> Physics Jordanian University, Jordan.<br />
Pr<strong>of</strong>. Ahmed H. Abu Hilal, Dept. <strong>of</strong> Earth <strong>and</strong> Envi. Sci., Yarmouk Univ., Jordan.<br />
Pr<strong>of</strong>. Mohammad S. Abu Saleh, Dept. <strong>of</strong> Ma<strong>the</strong>matics, Yarmouk Univ., Jordan.<br />
Pr<strong>of</strong>. Safwan Ashoor, Dept. <strong>of</strong> Chemistry, Allepo University, Syria.<br />
Pr<strong>of</strong>. Mahmoud Kroom, Dept. <strong>of</strong> Bilolgy, Allepo University, Syria.<br />
Pr<strong>of</strong>. Mohammed Othman, Dept. <strong>of</strong> Biology, Damascus University, Syria.<br />
Pr<strong>of</strong>. Mohammed A. Al Najar, Dept. <strong>of</strong> Biology, Lebanese University, Lebanon.<br />
Pr<strong>of</strong>. Huda Hashim, Dept. <strong>of</strong> Chemistry, Lebanese University, Lebanon.<br />
Pr<strong>of</strong>. Adel M. Awad Allah, Dept. <strong>of</strong> Chemistry, Islamic Univ. <strong>of</strong> Gaza, Palestine.<br />
Pr<strong>of</strong>. Mohammed M. Shabat, Dept. <strong>of</strong> Physics, Islamic Univ. <strong>of</strong> Gaza, Palestine<br />
Pr<strong>of</strong>. Mohammed El Sayed Othman, Dept. <strong>of</strong> Biology, Helwan Univ., Egypt.<br />
Pr<strong>of</strong>. Hassan M. El-Hawart, Dean <strong>of</strong> science, Assiut University, Egypt.<br />
Pr<strong>of</strong>. Bader E. Ahmed, School <strong>of</strong> Appl. Earth Science, Al Neelain Univ. Sudan.<br />
International Advisory Board Members<br />
Pr<strong>of</strong>. Ahmed H. Zewail (Nobel laureate), Cali<strong>for</strong>nia Institute <strong>of</strong> Technology, US<br />
Pr<strong>of</strong>. Farouk El-Baz (Geology), Centre <strong>for</strong> Remote Sensing, Boston Univ., USA.<br />
Pr<strong>of</strong>. El-Sayed Mustafa Amr (Chemistry), Florida State University, USA.<br />
Pr<strong>of</strong>. Mourad E.H. Ismail (Ma<strong>the</strong>matics), University. <strong>of</strong> South Florida, USA.<br />
Pr<strong>of</strong>. Ahmed Sameh (Computer Science), Minnesota University, USA.<br />
Pr<strong>of</strong>. Munir H. Nayfeh (Physics), Illinois University, USA<br />
Pr<strong>of</strong>. Riyad Y. Hamzah, Biochemistry, <strong>Arab</strong>ian Gulf Univ., Kingdom <strong>of</strong> Bahrain.<br />
Ethics statements <strong>and</strong> Copyright<br />
The author(s) are entirely responsible <strong>for</strong> accuracy <strong>of</strong> all<br />
statements <strong>and</strong> data contained in <strong>the</strong> manuscript, as well as<br />
accuracy <strong>of</strong> all references, <strong>and</strong> <strong>for</strong> obtaining <strong>and</strong><br />
submitting written permission from <strong>the</strong> author <strong>and</strong>/or<br />
publisher <strong>of</strong> any previously published manuscript used in<br />
<strong>the</strong> submitted manuscript. Copyrights <strong>of</strong> <strong>the</strong> published<br />
paper will be transferred to <strong>the</strong> JAAUBAS upon<br />
notification <strong>of</strong> acceptance.<br />
Reprints<br />
A s<strong>of</strong>t electronic copy (PDF file) <strong>of</strong> <strong>the</strong> published paper<br />
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Correspondence<br />
Editor- in-Cheif, <strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong><br />
<strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences, College <strong>of</strong> Science,<br />
University <strong>of</strong> Bahrain, P.O. Box 32038,<br />
Sakhir, Kingdom <strong>of</strong> Bahrain.<br />
Tel.: (00973) 17437556 / 17437436/ 17437555<br />
Fax: (00973) 17449662<br />
All rights are reserved.<br />
Bahrain Publishing Permission: MAAU 394<br />
ISSN 1815-3852<br />
Imprint: University <strong>of</strong> Bahrain<br />
Printed at <strong>the</strong> University <strong>of</strong> Bahrain Printing Press 2012-085960
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong><br />
<strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences<br />
Volume 11, April 2012<br />
Published by<br />
University <strong>of</strong> Bahrain
Foreword<br />
It fills me with great satisfaction to see <strong>the</strong> 11 th issue <strong>of</strong><br />
JAAUBAS being published in April 2012. This issue<br />
contains 9 articles from <strong>the</strong> Kingdom <strong>of</strong> Bahrain,<br />
Algeria, Palestine, Yemen, Sudan, France, Iraq <strong>and</strong><br />
Malaysia. The articles cover various areas <strong>of</strong> research<br />
such as electric power load <strong>for</strong>ecast, energy saving, steal<br />
mechanical properties, radioactivity measurement in<br />
water, CdS thin films, spectrophotometric study <strong>of</strong><br />
pyrimethamine, improved hardness <strong>of</strong> resin, purification<br />
<strong>of</strong> biodiesel <strong>and</strong> effect <strong>of</strong> herbal extracts on lactic acid<br />
bacteria.<br />
Now <strong>and</strong> after having JAAUBAS hosted by Elsevier, <strong>the</strong> flow <strong>of</strong> papers have<br />
increased rapidly <strong>and</strong> we started to receive research work from various countries in<br />
addition to <strong>Arab</strong> countries. Also <strong>the</strong> published papers are now recognized by various<br />
international data basis like Scopus, Science Direct, Web Science. JAAUBAS starts<br />
to achieve its aims in publishing original research <strong>and</strong> assisting researchers from <strong>the</strong><br />
<strong>Arab</strong> <strong>and</strong> international universities <strong>and</strong> institutions to make <strong>the</strong>ir findings<br />
internationally visible <strong>and</strong> available.<br />
It is a well known fact that scientific research is a key issue in <strong>the</strong> university ranking.<br />
Thus now any published work in JAAUBAS appear as a record <strong>for</strong> <strong>the</strong> university or<br />
<strong>the</strong> institution since it will be picked up by <strong>the</strong> international data basis. Our next step<br />
is to establish <strong>the</strong> link with <strong>the</strong> ISI (Thomson Reuters) to have <strong>the</strong> journal evaluated<br />
after two years <strong>and</strong> obtain <strong>the</strong> impact factor (IF). This only can be done with your<br />
contribution in publishing your first class scientific research in JAAUBAS. Looking<br />
<strong>for</strong>ward to receive your most recent research work.<br />
Dr. Hashim Al Sayed<br />
Editor-in-Chief, JAAUBAS
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, iii<br />
University <strong>of</strong> Bahrain<br />
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong><br />
<strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences<br />
www.elsevier.com/locate/jaaubas<br />
www.sciencedirect.com<br />
CONTENTS<br />
Enhancement, evaluation <strong>and</strong> implementation <strong>of</strong> a load <strong>for</strong>ecasting method<br />
M.R. Qader <strong>and</strong> I. Qamber . . . ........................................................................................... 1<br />
A self-controlled energy efficient <strong>of</strong>fice lighting system<br />
M. Taleb <strong>and</strong> N. Mannsour . . . ........................................................................................... 9<br />
Fracture process <strong>of</strong> C–Mn steel embrittled by hydrogen<br />
N. Saidani, A. Mihi <strong>and</strong> R. Benbouta .................................................................................... 16<br />
Radioactivity measurements in tap water in Gaza Strip (Al-Naser Area)<br />
M.O. El-Ghossain <strong>and</strong> A.A. Abu Shammala . . . .......................................................................... 21<br />
Syn<strong>the</strong>sis, structure, <strong>and</strong> optical properties <strong>of</strong> CdS thin films nanoparticles prepared by chemical bath technique<br />
A.M.A. Al-Hussam <strong>and</strong> S.A.-J. Jassim . . . ................................................................................ 27<br />
Spectrophotometric determination <strong>of</strong> pyrimethamine (PYM) in pharmaceutical <strong>for</strong>mulation using 1,2-naphthoquinone-4-<br />
sulfonate (NQS)<br />
A.A. Elbashir <strong>and</strong> A.H.E. Elwagee . . ..................................................................................... 32<br />
Kinetic study <strong>of</strong> <strong>the</strong> RTM6/TiO 2 by DSC/TGA <strong>for</strong> improved hardness <strong>of</strong> resin<br />
L. Merad, P. Bourson, Y. Guedra, F. Jochem <strong>and</strong> B. Benyoucef ......................................................... 37<br />
Purification <strong>of</strong> biodiesel using activated carbons produced from spent tea waste<br />
A.B. Fadhil, M.M. Dheyab <strong>and</strong> A.-Q.Y. Abdul-Qader ................................................................... 45<br />
Viability <strong>of</strong> lactic acid bacteria <strong>and</strong> sensory evaluation in Cinnamomum verum <strong>and</strong> Allium sativum-bio-yogurts made from<br />
camel <strong>and</strong> cow milk<br />
A.B. Shori <strong>and</strong> A.S. Baba ................................................................................................ 50
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 1-8<br />
تعزيز و تقييم و تنفيذ طريقة التنبؤ بالحمل الكهربائي<br />
1<br />
محمد رضا قادر ،<br />
2<br />
عيسى سلمان قمبر<br />
قسم<br />
1<br />
الهندسة الكهربائية و اإللكترونية ، كليه الهندسة ، جامعة البحرين، ص.ب<br />
22023، البحرين مملكة<br />
،22023<br />
2<br />
عمادة البحث العلمي ،<br />
جامعة البحرين، ص.ب<br />
البحرين مملكة<br />
الملخص:<br />
أثر عدم اليقين لتوقعات الحمل الكهربائي تكون واضحة المعالم إذا كان بعض من سعة االحتياطي<br />
المخزون يتم االستعانة بها لتوفير حمولة زائدة عن الكمية المتوقعة و بالتالي فان االحتياطي المخزون<br />
يخفض. النموذج تم تطويره للحصول على الحمل المتوقع لمملكة البحرين.<br />
طريقة الحساب تمت باستخدام طريقة مونت كارلو لنمذجة الحمل الكهربائي. النموذج المستخدم يستطيع أن<br />
يتنبأ بالحمل الكهربائي مع مرور الزمن خالل فترات سنوية بحيث تم تقسيم كل سنة الى<br />
النموذج المعد للتنبؤ يقوم بحساب الحد األدنى لمتوسط الخطأ التربيعي<br />
25<br />
)MMSE(<br />
اسبوعا.<br />
لمتوسط القدرة المخزونة<br />
المشروط واالنحراف المعياري المشروط في كل فترة محددة للتنبؤ باألحمال الكهربائية المتوقعة. لعمل ذلك،<br />
وضحت النتائج المتوسط المشروط و نماذج التغاير من منظور تصفية خطيه وطبقت تكرار التوقعات<br />
المشروطة على المعادالت العودية لكل فترة تنبؤ عند كل زمن. وقد تم استنباط النتائج وتمت مناقشتها في<br />
هذه الدراسة.<br />
M.R. Qader, I. Qamber
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 1–8<br />
University <strong>of</strong> Bahrain<br />
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong><br />
<strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences<br />
www.elsevier.com/locate/jaaubas<br />
www.sciencedirect.com<br />
ORIGINAL ARTICLE<br />
Enhancement, evaluation <strong>and</strong> implementation<br />
<strong>of</strong> a load <strong>for</strong>ecasting method<br />
M.R. Qader a, *, I. Qamber b<br />
a Department <strong>of</strong> Electrical <strong>and</strong> Electronics Engineering, University <strong>of</strong> Bahrain, P.O. Box 32038, Isa Town, Kingdom <strong>of</strong> Bahrain<br />
b Deanship <strong>of</strong> Scientific Research, University <strong>of</strong> Bahrain, P.O. Box 32038, Sakhir, Kingdom <strong>of</strong> Bahrain<br />
KEYWORDS<br />
Monte Carlo;<br />
Load <strong>for</strong>ecast;<br />
MMSE;<br />
Kingdom <strong>of</strong> Bahrain<br />
Abstract The effect <strong>of</strong> load <strong>for</strong>ecast uncertainty may be well-defined if some <strong>of</strong> <strong>the</strong> spinning reserve<br />
capacity is needed to supply <strong>the</strong> load in excess <strong>of</strong> <strong>the</strong> amount predicted <strong>and</strong>, <strong>the</strong>reby <strong>the</strong> spinning<br />
reserve is reduced. The model was developed <strong>for</strong> load estimation <strong>of</strong> Kingdom <strong>of</strong> Bahrain. The calculation<br />
method involves a Monte Carlo technique <strong>for</strong> <strong>the</strong> simulation <strong>of</strong> <strong>the</strong> load. The model enables <strong>the</strong><br />
predication <strong>of</strong> <strong>the</strong> load against <strong>the</strong> time during years, where each year is divided into 52 weeks. The<br />
<strong>for</strong>ecasting model, computes minimum mean square error (MMSE) <strong>for</strong>ecasts <strong>of</strong> <strong>the</strong> conditional mean<br />
<strong>of</strong> reserve power <strong>and</strong> conditional st<strong>and</strong>ard deviation <strong>of</strong> <strong>the</strong> innovations in each period over a userspecified<br />
<strong>for</strong>ecast possibility. To do this, it views <strong>the</strong> conditional mean <strong>and</strong> variance models from a<br />
linear filtering perspective, <strong>and</strong> applies iterated conditional expectations to <strong>the</strong> recursive equations,<br />
one <strong>for</strong>ecast period at a time. The results are obtained <strong>and</strong> discussed.<br />
ª 2012 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by Elsevier B.V. All rights reserved.<br />
1. Introduction<br />
The prediction method used in <strong>the</strong> present paper is based on<br />
Monte-Carlo simulation in which it is well known that any<br />
approach using <strong>the</strong> Monte Carlo simulation method does<br />
not solve <strong>the</strong> equations describing <strong>the</strong> model. The Monte Carlo<br />
simulation uses a r<strong>and</strong>om number generator. And this generator<br />
is needed to bring <strong>the</strong> stochastic element in <strong>the</strong> calculations.<br />
* Corresponding author.<br />
E-mail address: mrqader@eng.uob.bh (M.R. Qader).<br />
1815-3852 ª 2012 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by<br />
Elsevier B.V. All rights reserved.<br />
Peer review under responsibility <strong>of</strong> University <strong>of</strong> Bahrain.<br />
doi:10.1016/j.jaubas.2012.02.001<br />
Production <strong>and</strong> hosting by Elsevier<br />
The researcher could use a physical r<strong>and</strong>om-number generator<br />
such as electrical load variation through a certain period.<br />
The Monte-Carlo simulation requires <strong>the</strong> creation <strong>of</strong> r<strong>and</strong>om<br />
numbers, in this paper, <strong>the</strong> generated numbers were chosen<br />
to follow <strong>the</strong> normal distribution with average value <strong>and</strong><br />
st<strong>and</strong>ard deviation <strong>of</strong> <strong>the</strong> electrical load <strong>of</strong> Bahrain.<br />
In Bordalo et al. (2006) <strong>the</strong>y presented a probabilistic shortcircuit<br />
approach to generate <strong>the</strong> probability distributions <strong>of</strong><br />
<strong>the</strong> system average variation index. The methodology followed<br />
is based on <strong>the</strong> combination <strong>of</strong> <strong>the</strong> Monte-Carlo simulation<br />
<strong>and</strong> <strong>the</strong> admittance summation method.<br />
In El-Khattam et al. (2006) <strong>the</strong>y presented a novel algorithm<br />
to evaluate <strong>the</strong> per<strong>for</strong>mance <strong>of</strong> electric distribution systems,<br />
including distributed generation. Monte Carlo simulation is<br />
employed to solve <strong>the</strong> system operation r<strong>and</strong>omness problem.<br />
The simulation is implemented to per<strong>for</strong>m <strong>the</strong> analysis <strong>of</strong> all<br />
possible operations <strong>of</strong> <strong>the</strong> system under study. The system loading<br />
follows several typical load curves.<br />
In Ionescu et al. (2006), <strong>the</strong> purpose <strong>of</strong> <strong>the</strong>ir study was to<br />
obtain a per<strong>for</strong>mable tool based on generalized stochastic Petri
2 M.R. Qader, I. Qamber<br />
1800<br />
1600<br />
Load (MW)<br />
1400<br />
1200<br />
1000<br />
800<br />
600<br />
0 10 20 30 40 50 60<br />
WEEKS<br />
Figure 1 Load <strong>for</strong>ecasts <strong>of</strong> one year in Kingdom <strong>of</strong> Bahrain (year <strong>of</strong> 2002).<br />
0.25<br />
0.2<br />
0.15<br />
0.1<br />
reserve MW<br />
0.05<br />
0<br />
-0.05<br />
-0.1<br />
-0.15<br />
-0.2<br />
-0.25<br />
0 5 10 15 20 25 30 35 40 45 50<br />
WEEKS<br />
Figure 2<br />
Translation <strong>of</strong> weekly power to weekly reserve.<br />
Nets (GSPN). After description <strong>and</strong> implementation through<br />
GSPN, each configuration has been evaluated, in order to<br />
choose <strong>the</strong> most appropriate structure.<br />
Batlle <strong>and</strong> Barquín (2004) in <strong>the</strong>ir paper (2004) present a<br />
fuel prices scenario generator in <strong>the</strong> frame <strong>of</strong> a simulation tool<br />
developed to support risk analysis in a competitive electricity<br />
environment. A multivariate Generalized Autoregressive Conditional<br />
Heteroskedastic model has been designed in order to<br />
allow <strong>the</strong> generation <strong>of</strong> future fuel prices paths. The model<br />
makes use <strong>of</strong> a decomposition method to simplify <strong>the</strong> consideration<br />
<strong>of</strong> <strong>the</strong> multidimensional conditional covariance. An<br />
example <strong>of</strong> its application with real data is also presented.<br />
Gonos et al. (2003)present in <strong>the</strong>ir paper (2004), a method<br />
which estimates <strong>the</strong> lightning per<strong>for</strong>mance <strong>of</strong> high voltage transmission<br />
lines based on <strong>the</strong> Monte-Carlo simulation technique.<br />
On several operating Greek transmission lines, <strong>the</strong> method is applied<br />
<strong>and</strong> showing good correlation between predicted <strong>and</strong> field<br />
observation results. The proposed method can be used as a useful<br />
tool in <strong>the</strong> design <strong>of</strong> electric power systems, aiding in <strong>the</strong> right<br />
insulation dimensioning <strong>of</strong> a transmission line.<br />
In Zhaohong <strong>and</strong> Xifan (2002) study (2002) <strong>the</strong>y present a<br />
new variance reduction technique <strong>of</strong> Monte Carlo simulation<br />
– fission <strong>and</strong> roulette method. The proposed method reduces<br />
<strong>the</strong> variance <strong>of</strong> simulation <strong>and</strong> speeds up <strong>the</strong> computation<br />
dramatically.<br />
Wehenkel et al. (1999), <strong>the</strong> authors deal with probabilistic<br />
approach to <strong>the</strong> design <strong>of</strong> power-system special stability controls.<br />
They used Monte-Carlo simulations, which take into ac-
Enhancement, evaluation <strong>and</strong> implementation <strong>of</strong> a load <strong>for</strong>ecasting method 3<br />
0.5<br />
Innovations<br />
Innovation<br />
0<br />
-0.5<br />
0 5 10 15 20 25 30 35 40 45 50<br />
Conditional St<strong>and</strong>ard Deviations<br />
St<strong>and</strong>ard Deviation<br />
0.2<br />
0.1<br />
0<br />
0 5 10 15 20 25 30 35 40 45 50<br />
Forecast <strong>of</strong> STD <strong>of</strong> Residuals<br />
St<strong>and</strong>ard Deviation<br />
0.08<br />
0.075<br />
<strong>for</strong>ecast results<br />
simulation results<br />
0 5 10 15 20 25 30 35 40 45 50<br />
Forecast Period<br />
Figure 3<br />
Application <strong>of</strong> Monte Carlo simulation.<br />
0.08<br />
Approximate Versus Exact Secondary St<strong>and</strong>ard Deviations<br />
0.075<br />
0.07<br />
0.065<br />
0.06<br />
0.055<br />
0.05<br />
0.045<br />
0.04<br />
0 10 20 30 40 50 60 70 80 90 100<br />
Figure 4<br />
Graphical comparisons <strong>of</strong> <strong>the</strong> first realization <strong>of</strong> <strong>the</strong> approximate <strong>and</strong> <strong>the</strong> exact secondary conditional st<strong>and</strong>ard deviations.<br />
count all <strong>the</strong> potential causes <strong>of</strong> blackouts. The approach is<br />
tested on a large-scale study on <strong>the</strong> South–Eastern part <strong>of</strong> <strong>the</strong><br />
extra-high-voltage system <strong>of</strong> Electricite´ de France.<br />
2. Methodology<br />
A wide variety <strong>of</strong> <strong>for</strong>ecasting methods are available to <strong>the</strong><br />
management. The evaluation <strong>of</strong> s<strong>of</strong>t computing techniques<br />
has increased <strong>the</strong> underst<strong>and</strong>ing <strong>of</strong> various aspects <strong>of</strong> <strong>the</strong><br />
problem environment <strong>and</strong> consequently <strong>the</strong> predictability<br />
<strong>of</strong> many events. The concept <strong>of</strong> a time series, an ordered<br />
set <strong>of</strong> observations <strong>of</strong> a time-series correspond to timetagged<br />
indices, or observations, <strong>and</strong> correspond to sample<br />
paths, independent realizations, or individual time series.<br />
In any given column, <strong>the</strong> first row contains <strong>the</strong> oldest observation<br />
<strong>and</strong> <strong>the</strong> last row contains <strong>the</strong> most recent observation.<br />
In this representation, a time-series array is said to<br />
be column-oriented.
4 M.R. Qader, I. Qamber<br />
0.0755<br />
0.075<br />
Forecast <strong>of</strong> STD <strong>of</strong> Residuals<br />
<strong>for</strong>ecast results<br />
simulation results<br />
0.0745<br />
St<strong>and</strong>ard Deviation<br />
0.074<br />
0.0735<br />
0.073<br />
0.0725<br />
0.072<br />
0.0715<br />
0.071<br />
0 5 10 15 20 25 30 35 40 45 50<br />
Forecast Period<br />
Figure 5 Compare <strong>the</strong> first <strong>for</strong>ecast output, i.e., <strong>the</strong> conditional st<strong>and</strong>ard deviations <strong>of</strong> future innovations, with its counterpart derived<br />
from <strong>the</strong> Monte Carlo simulation.<br />
1 x 10 -3 Forecast <strong>of</strong> reserve MW<br />
0.5<br />
0<br />
MMSE<br />
-0.5<br />
-1<br />
-1.5<br />
-2<br />
<strong>for</strong>ecast results<br />
simulation results<br />
-2.5<br />
0 5 10 15 2 2 3 3 4 4 50<br />
Forecast Period<br />
Figure 6 Compare <strong>the</strong> second <strong>for</strong>ecast output, <strong>the</strong> minimum mean square error <strong>for</strong>ecasts <strong>of</strong> <strong>the</strong> conditional mean <strong>of</strong> <strong>the</strong> Kingdom <strong>of</strong><br />
Bahrain reserves power series, with its counterpart derived from <strong>the</strong> Monte Carlo simulation.<br />
In <strong>the</strong> present model, it is assumed that time-series vectors<br />
<strong>and</strong> matrices are time-tagged series <strong>of</strong> observations. If we have<br />
a power series, <strong>the</strong> model lets you convert it to a reserve series<br />
using ei<strong>the</strong>r continuous compounding or periodic compounding.<br />
If it denotes successive power observations made at times<br />
t <strong>and</strong> t +1asP t <strong>and</strong> P t+1 , respectively, continuous compounding<br />
trans<strong>for</strong>ms a power series P t into a reserve series y t as (Bollerslev,<br />
1987; Bollerslev, 1986; Box et al., 1994; Enders, 1995).<br />
y t ¼ log P tþ1<br />
P t<br />
Periodic compounding defines <strong>the</strong> trans<strong>for</strong>mation as:
Enhancement, evaluation <strong>and</strong> implementation <strong>of</strong> a load <strong>for</strong>ecasting method 5<br />
0.7<br />
Forecast <strong>of</strong> STD <strong>of</strong> Cumulative Holding Period<br />
0.6<br />
0.5<br />
St<strong>and</strong>ard Deviation<br />
0.4<br />
0.3<br />
0.2<br />
0.1<br />
<strong>for</strong>ecast results<br />
simulation results<br />
0<br />
0 5 10 15 20 25 30 35 40 45 50<br />
Forecast Period<br />
Figure 7 Compare <strong>the</strong> third <strong>for</strong>ecast output, cumulative holding period power reserves, with its counterpart derived from <strong>the</strong> Monte<br />
Carlo simulation.<br />
y t ¼ log P tþ1<br />
1<br />
P t<br />
Our modeling is typically based on relatively high frequency<br />
data (i.e. weekly observations). The models are designed to<br />
capture certain characteristics that are commonly associated<br />
with time series. Probability distributions <strong>for</strong> quality reserve<br />
<strong>of</strong>ten exhibit fatter tails than <strong>the</strong> st<strong>and</strong>ard normal, or Gaussian<br />
distribution. In addition, power time series usually exhibit a<br />
characteristic known as volatility clustering, in which large<br />
changes tend to follow large changes, <strong>and</strong> small changes tend<br />
to follow small changes. In ei<strong>the</strong>r case, <strong>the</strong> changes from one<br />
period to <strong>the</strong> next are typically <strong>of</strong> unpredictable sign. Large<br />
disturbances, positive or negative, become part <strong>of</strong> <strong>the</strong> in<strong>for</strong>mation<br />
set used to construct <strong>the</strong> variance <strong>for</strong>ecast <strong>of</strong> <strong>the</strong> next period’s<br />
disturbance. In this manner, large shocks <strong>of</strong> ei<strong>the</strong>r sign<br />
are allowed to persist, <strong>and</strong> can influence <strong>the</strong> volatility <strong>for</strong>ecasts<br />
<strong>for</strong> several periods.<br />
3. Forecasting <strong>of</strong> power time series<br />
If we treat a financial time series as a sequence <strong>of</strong> r<strong>and</strong>om<br />
observations, this r<strong>and</strong>om sequence, or stochastic process,<br />
may exhibit some degree <strong>of</strong> correlation from one observation<br />
to <strong>the</strong> next. This correlation structure can be used to predict<br />
future values <strong>of</strong> <strong>the</strong> process based on <strong>the</strong> past history <strong>of</strong> observations<br />
(Engle, 1982; Engle et al., 1987; Glosten et al., 1993;<br />
Hamilton, 1994). The following equation uses <strong>the</strong>se components<br />
to represent a model <strong>of</strong> an observed time series y t .<br />
y t ¼ fðt 1; XÞþe t<br />
where<br />
f(t 1,X) represents <strong>the</strong> <strong>for</strong>ecast, <strong>of</strong> <strong>the</strong> current reserve as a<br />
function <strong>of</strong> any in<strong>for</strong>mation known at time t + 1 , including<br />
past innovations. The variable e t is <strong>the</strong> r<strong>and</strong>om component.<br />
The autoregressive (AR) models include past observation <strong>of</strong><br />
<strong>the</strong> dependent variable in <strong>the</strong> <strong>for</strong>ecast <strong>of</strong> future variances, <strong>and</strong><br />
<strong>for</strong> <strong>the</strong> conditional mean apply to all variance models:<br />
y t ¼ C þ XR<br />
i¼1<br />
/ i y t 1 þ e t þ XM<br />
j¼1<br />
h j e t<br />
j þ XNx<br />
k¼1<br />
b k Xðt; kÞ<br />
With autoregressive coefficients / i , moving average coefficients<br />
h j , regression coefficients b k , innovations e t , <strong>and</strong> reserve y t , C<br />
represents <strong>the</strong> constant. X is an explanatory regression matrix<br />
in which each column is a time series <strong>and</strong> X(t,k) denotes <strong>the</strong> t-<br />
th row <strong>and</strong> k th column. Where, R <strong>and</strong> M represent <strong>the</strong> order<br />
<strong>of</strong> <strong>the</strong> conditional mean model.<br />
4. Probability estimation<br />
Given models <strong>for</strong> <strong>the</strong> conditional mean <strong>and</strong> variance, <strong>and</strong> an<br />
observed reserve series, <strong>the</strong> estimation concludes <strong>the</strong> innovations<br />
(i.e., residuals) from <strong>the</strong> reserve series, <strong>and</strong> estimates,<br />
by maximum probability, <strong>the</strong> parameters needed to fit <strong>the</strong><br />
specified models to <strong>the</strong> reserve series (Nelson, 1991).<br />
Given <strong>the</strong> vector <strong>of</strong> current parameter values <strong>and</strong> <strong>the</strong> observed<br />
data series, <strong>the</strong> log-probability functions conclude <strong>the</strong><br />
process innovations by inverse filtering (Engle, 1982; Engle<br />
et al., 1987; Glosten et al., 1993). This inference, or inverse filtering,<br />
operation rearranges <strong>the</strong> conditional mean equation to<br />
solve <strong>for</strong> <strong>the</strong> current innovation e t :<br />
X R X M X Nx<br />
y t ¼ C þ y t / i y t 1 h j e t j b k Xðt; kÞ<br />
i¼1<br />
j¼1<br />
This equation is a whitening filter, trans<strong>for</strong>ming a correlated<br />
process into an uncorrelated white noise process. The logprobability<br />
function <strong>the</strong>n uses <strong>the</strong> inferred innovations e t to infer<br />
<strong>the</strong> corresponding conditional variances r 2 t<br />
via recursive<br />
k¼1
6 M.R. Qader, I. Qamber<br />
St<strong>and</strong>ard Error <strong>of</strong> Forecast<br />
0.078<br />
0.077<br />
<strong>for</strong>ecast results<br />
simulation results<br />
0.076<br />
St<strong>and</strong>ard Deviation<br />
0.075<br />
0.074<br />
0.073<br />
0.072<br />
0.071<br />
0 5 10 15 20 25 30 35 40 45 50<br />
Forecast Period<br />
Figure 8 Compare <strong>the</strong> fourth <strong>for</strong>ecast output, <strong>the</strong> root mean square errors <strong>of</strong> <strong>the</strong> <strong>for</strong>ecasted power reserves, with its counterpart derived<br />
from <strong>the</strong> Monte Carlo simulation.<br />
substitution into <strong>the</strong> model-dependent conditional variance<br />
equations. Finally, <strong>the</strong> function uses <strong>the</strong> inferred innovations<br />
<strong>and</strong> conditional variances to evaluate <strong>the</strong> appropriate logprobability<br />
objective function. If <strong>the</strong> Gaussian, <strong>the</strong> log-probability<br />
function is:<br />
LLF ¼ T 2 logð2pÞ 1 X T<br />
2<br />
t¼1<br />
log r 2 t<br />
1 X T<br />
2<br />
t¼1<br />
e 2 t<br />
r 2 t<br />
where, T is <strong>the</strong> sample size, i.e., <strong>the</strong> number <strong>of</strong> rows in <strong>the</strong> series<br />
y t .<br />
5. Minimum mean squire error volatility <strong>for</strong>ecasts <strong>of</strong> reserve<br />
This is designed to minimize <strong>the</strong> variance <strong>of</strong> <strong>the</strong> estimation or<br />
<strong>for</strong>ecast error. The volatility <strong>for</strong>ecasts <strong>of</strong> reserve over multi<br />
period holding intervals. That it contains <strong>the</strong> expected stan-<br />
1400<br />
Cumulative Holding Period at Forecast Horizon<br />
1200<br />
1000<br />
800<br />
Count<br />
600<br />
400<br />
200<br />
0<br />
-3 -2 -1 0 1 2 3<br />
reserve MW<br />
Figure 9 Histogram illustrates <strong>the</strong> distribution <strong>of</strong> <strong>the</strong> cumulative holding period reserve obtained if a quality was held <strong>for</strong> <strong>the</strong> full 52-<br />
week <strong>for</strong>ecast possibility. Notice that this histogram is directly related to <strong>the</strong> final <strong>of</strong> <strong>the</strong> root mean square error.
Enhancement, evaluation <strong>and</strong> implementation <strong>of</strong> a load <strong>for</strong>ecasting method 7<br />
1400<br />
Simulated at Forecast Horizon<br />
1200<br />
1000<br />
Count<br />
800<br />
600<br />
400<br />
200<br />
0<br />
-0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3<br />
reserve MW<br />
Figure 10 Histogram illustrates <strong>the</strong> distribution <strong>of</strong> <strong>the</strong> single-period power reserve at <strong>the</strong> <strong>for</strong>ecast possibility. Notice that this histogram<br />
is directly related to <strong>the</strong> final <strong>of</strong> <strong>the</strong> minimum mean square error <strong>and</strong> root mean square errors.<br />
dard deviation <strong>of</strong> reserve <strong>for</strong> assets held <strong>for</strong> one period <strong>for</strong> each<br />
realization <strong>of</strong> series. It also contains <strong>the</strong> st<strong>and</strong>ard deviation <strong>of</strong><br />
reserve <strong>for</strong> assets held <strong>for</strong> two periods as shown in <strong>the</strong> results<br />
obtained during <strong>the</strong> present study. Thus, last contains <strong>the</strong> <strong>for</strong>ecast<br />
<strong>of</strong> <strong>the</strong> st<strong>and</strong>ard deviation <strong>of</strong> <strong>the</strong> cumulative reserve obtained<br />
if an asset was held <strong>for</strong> <strong>the</strong> entire <strong>for</strong>ecast horizon.<br />
There<strong>for</strong>e it computes <strong>the</strong> elements <strong>of</strong> r by taking <strong>the</strong> square<br />
root <strong>of</strong>:<br />
" # 2 ! 2<br />
3<br />
X s<br />
var t ¼ Xs<br />
4 1 þ Xs¼1<br />
w j Eðr 2 tþi Þ 5<br />
i¼1<br />
y tþ1<br />
i¼1<br />
j¼1<br />
where s is <strong>the</strong> <strong>for</strong>ecast horizon <strong>of</strong> interest, <strong>and</strong> w j is <strong>the</strong> coefficient<br />
<strong>of</strong> <strong>the</strong> jth lag <strong>of</strong> <strong>the</strong> innovations process in an infinite-order<br />
representation <strong>of</strong> <strong>the</strong> conditional mean model.<br />
6. Simulation results<br />
To compute <strong>the</strong> load <strong>for</strong>ecasts <strong>for</strong> <strong>the</strong> Kingdom <strong>of</strong> Bahrain reserve<br />
<strong>the</strong> power <strong>for</strong> 52 weeks <strong>for</strong> expecting <strong>the</strong> power in <strong>the</strong> future.<br />
First setting <strong>the</strong> <strong>for</strong>ecast possibility to 52 weeks (i.e., one<br />
year), <strong>the</strong>n <strong>the</strong> <strong>for</strong>ecasting engine, with <strong>the</strong> estimated model<br />
parameters, coefficient, <strong>the</strong> Kingdom <strong>of</strong> Bahrain reserve, <strong>and</strong><br />
<strong>the</strong> <strong>for</strong>ecast possibility. Possibility = 52% which define <strong>the</strong><br />
<strong>for</strong>ecast possibility.<br />
This will simulate reserve <strong>for</strong>ecasts <strong>of</strong> conditional st<strong>and</strong>ard<br />
deviations <strong>of</strong> <strong>the</strong> residuals <strong>for</strong>ecasts <strong>of</strong> <strong>the</strong> Bahrain reserve<br />
power. Forecasts <strong>of</strong> <strong>the</strong> st<strong>and</strong>ard deviations <strong>of</strong> <strong>the</strong> cumulative<br />
holding period reserve power <strong>and</strong> st<strong>and</strong>ard errors associated<br />
with <strong>for</strong>ecasts <strong>of</strong> reserve power.<br />
Monte Carlo simulation uses <strong>the</strong> same estimated model<br />
coefficient which is used in <strong>the</strong> <strong>for</strong>ecast part <strong>of</strong> <strong>the</strong> data simulated,<br />
<strong>for</strong>ecasting, to simulate 20,000 realizations <strong>for</strong> <strong>the</strong> same<br />
52 week period. In this context, referred to as dependent-path<br />
simulation, all simulated sample paths share a common conditioning<br />
set <strong>and</strong> evolve from <strong>the</strong> same set <strong>of</strong> initial conditions,<br />
thus enabling Monte Carlo simulation <strong>of</strong> <strong>for</strong>ecasts <strong>and</strong> <strong>for</strong>ecast<br />
error distributions. For this application <strong>of</strong> Monte Carlo<br />
simulation, <strong>the</strong> simulation generates a relatively large number<br />
<strong>of</strong> realizations, or sample paths, so that it can aggregate across<br />
realizations. The following code simulates 20,000 paths as a result;<br />
each time-series output that reserves are an array <strong>of</strong> size<br />
possibility, 52-by-20,000.<br />
In <strong>the</strong> present paper, we will compare data <strong>of</strong> <strong>the</strong> Kingdom<br />
<strong>of</strong> Bahrain reserve power graphically. It compares <strong>the</strong><br />
<strong>for</strong>ecasts results with <strong>the</strong>ir counterparts derived from <strong>the</strong><br />
Monte Carlo trial described above. Fig. 1 shows <strong>the</strong> load<br />
<strong>for</strong>ecasts <strong>of</strong> one year (year <strong>of</strong> 2002) in <strong>the</strong> Kingdom <strong>of</strong> Bahrain<br />
which clearly shows that power consumption is high between<br />
weeks 20 <strong>and</strong> 40 <strong>of</strong> high season. Fig. 2 is <strong>the</strong><br />
translation <strong>of</strong> weekly power to weekly reserve. To segment<br />
<strong>the</strong> data in an ef<strong>for</strong>t to compare estimation results obtained<br />
from a relatively stable period to those from a period <strong>of</strong> relatively<br />
high instability. By examining <strong>the</strong> reserve power, it<br />
can be seen <strong>the</strong>re is a distinct increase in instability starting.<br />
Fig. 3 shows application <strong>of</strong> Monte Carlo simulation, <strong>the</strong> figures<br />
show <strong>the</strong> production <strong>of</strong> a relatively large number <strong>of</strong> sample<br />
paths, so that it can aggregate across realizations. Because<br />
each underst<strong>and</strong>ing corresponds to a time-series output, <strong>the</strong><br />
outputs are large. The model simulates 20,000 paths. Fig. 4<br />
is a graphical comparison <strong>of</strong> <strong>the</strong> first realization <strong>of</strong> <strong>the</strong><br />
approximate <strong>and</strong> <strong>the</strong> exact secondary conditional st<strong>and</strong>ard<br />
deviations reveal <strong>the</strong> distinction between automatically generated<br />
<strong>and</strong> user-specified pre sample data. Notice that <strong>the</strong><br />
approximate <strong>and</strong> exact st<strong>and</strong>ard deviations are asymptotically<br />
identical. The only difference between <strong>the</strong> two curves<br />
is attributable to <strong>the</strong> transients induced by <strong>the</strong> default initial<br />
conditions. Although <strong>the</strong> figure highlights <strong>the</strong> first realization<br />
<strong>of</strong> conditional st<strong>and</strong>ard deviations, <strong>the</strong> comparison holds <strong>for</strong><br />
any realization <strong>and</strong> <strong>for</strong> <strong>the</strong> inferred residuals as well.
8 M.R. Qader, I. Qamber<br />
7. Comparing <strong>for</strong>ecasts with simulation results<br />
Figs. 5–8 directly compare each <strong>of</strong> <strong>the</strong> <strong>for</strong>ecast outputs, in<br />
turn, with <strong>the</strong> corresponding statistical result obtained from<br />
simulation. Figs. 9 <strong>and</strong> 10 illustrate histograms from which<br />
approximate probability density functions <strong>and</strong> empirical confidence<br />
bounds can be computed.<br />
This illustration merely highlights <strong>the</strong> range <strong>of</strong> possibilities,<br />
<strong>and</strong> provides a deeper underst<strong>and</strong>ing <strong>of</strong> <strong>the</strong> interaction between<br />
<strong>the</strong> simulation, <strong>for</strong>ecasting, <strong>and</strong> estimation model.<br />
Fig. 5 shows <strong>the</strong> convergence <strong>of</strong> st<strong>and</strong>ard deviation with respect<br />
to <strong>the</strong> <strong>for</strong>ecast period. For developing <strong>the</strong> <strong>for</strong>ecasting<br />
models, <strong>the</strong> load dem<strong>and</strong> data <strong>for</strong> 52 week period was tested<br />
from <strong>the</strong> first day <strong>of</strong> January to <strong>the</strong> last day <strong>of</strong> <strong>the</strong> year 2002<br />
which is <strong>the</strong> end <strong>of</strong> December in <strong>the</strong> Kingdom <strong>of</strong> Bahrain.<br />
8. Conclusion<br />
The paper presents estimation <strong>of</strong> <strong>the</strong> load <strong>of</strong> <strong>the</strong> Kingdom <strong>of</strong><br />
Bahrain using <strong>the</strong> Monte Carlo simulation. Satisfactory results<br />
<strong>for</strong> one year <strong>of</strong> Bahrain network was presented <strong>and</strong> verifying<br />
<strong>the</strong> accuracy <strong>of</strong> <strong>the</strong> method used. The presented method can<br />
be easily used <strong>for</strong> any electric power utilities in order to predict<br />
<strong>the</strong> electric load. The result consists <strong>of</strong> <strong>the</strong> MMSE <strong>for</strong>ecasts <strong>of</strong><br />
<strong>the</strong> conditional st<strong>and</strong>ard deviations <strong>and</strong> <strong>the</strong> conditional mean<br />
<strong>of</strong> <strong>the</strong> reserve power is modeled <strong>and</strong> illustrated. Note that <strong>the</strong><br />
calculation <strong>of</strong> <strong>the</strong> st<strong>and</strong>ard deviation is strictly correct <strong>for</strong> continuously<br />
compounded reserve. There<strong>for</strong>e, it is clear that <strong>the</strong><br />
used technique is useful tool <strong>for</strong> electric power system <strong>for</strong> load<br />
estimation.<br />
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Glosten, L.R., Jagannathan, R., Runkle, D.E., 1993. On <strong>the</strong> relation<br />
between expected value <strong>and</strong> <strong>the</strong> volatility <strong>of</strong> <strong>the</strong> nominal excess<br />
return on stocks. The <strong>Journal</strong> <strong>of</strong> Finance 48, 1779–1801.<br />
Gonos, I.F., Ekonomou, L., Topalis, F.V., Stathopulos, I.A., 2003.<br />
Probability <strong>of</strong> backflashover in transmission lines due to lightning<br />
strokes using Monte-Carlo simulation. International <strong>Journal</strong> <strong>of</strong><br />
Electrical Power <strong>and</strong> Energy Systems 25 (2), 107–111.<br />
Hamilton, J.D., 1994. Time Series Analysis. Princeton University<br />
Press.<br />
Ionescu, D.C., Ulmeanu, A.P., Constantinescu, A.C., Rotaru, I., 2006.<br />
Reliability modelling <strong>of</strong> medium voltage distribution systems <strong>of</strong><br />
nuclear power plants using generalized stochastic petri nets.<br />
Computers <strong>and</strong> Ma<strong>the</strong>matics with Applications 51 (2), 285–290.<br />
Nelson, D.B., 1991. Conditional heteroskedasticity in asset returns: a<br />
new approach. Econometrica 59, 347–370.<br />
Wehenkel, L., Lebrevelec, C., Trotignon, M., Batut, J., 1999.<br />
Probabilistic design <strong>of</strong> power-system special stability controls.<br />
Control Engineering Practice 7 (2), 183–194.<br />
Zhaohong, Bie, Xifan, Wang, 2002. Studies on variance reduction<br />
technique <strong>of</strong> Monte Carlo simulation in composite system reliability<br />
evaluation. Electric Power Systems Research 63 (1), 59–64.
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 9-15<br />
نظام إنارة مكتبي<br />
ذو تحكم ذاتي و<br />
الطاقة استهالك في مجدي<br />
1<br />
معمر طالب ،<br />
2<br />
نورالدين منصور<br />
قسم<br />
1<br />
الهندسة الكهربائية وااللكترونية،<br />
قسم<br />
، كلية الهندسة<br />
جامعة البحرين، ص.ب 32038<br />
،<br />
2<br />
الهندسة الكميائية ، كلية الهندسة ، جامعة البحرين، ص.ب ، 32038 البحرين<br />
البحرين<br />
الملخص:<br />
من دون شك أن ألشعة الشمس<br />
فمن هذا المنطلق<br />
المكتب.<br />
مساهمة<br />
قام الباحثون باستخدام<br />
غير مهملة<br />
تتبلور فكرة التحكم في تحقيق االستراتيجية التالية:<br />
مستوى شدة ضوء الشمس<br />
في تحديد كمية وشدة الضوء داخل<br />
المحيط بالمكتب للتحكم في<br />
المكاتب اإلدارية.<br />
مستوى إنارة<br />
حين تزداد شدة أشعة الشمس المحيط بالمكتب ينبغي<br />
تخفيف استهالك الطاقة الكهربائية، وحين تنخفض شدة أشعة الشمس المحيطة بالمكتب ينبغي رفع استهالك<br />
الطاقة الكهربائية.<br />
حالن تحكميان طبقا<br />
وبغية تحقيق االستراتيجية السابقة<br />
قام الباحثون باقتراح<br />
عمليًا باستخدام برنامج حاسوبي معروف باسم<br />
بانجاز أو تركيب دائرة كهربائية اعتمد في بنائها على عناصر الكترونية متفرقة.<br />
الثالثة بميزة التحكم الذاتي.<br />
عن تمخض<br />
مع ثبات مستوى االنارة<br />
تطبيق الحلول التحكمية<br />
داخل المكتب.<br />
بأحد مكاتب جامعة البحرين<br />
في<br />
ثالث حلول تحكمية عملية:<br />
) ،(LABVIEW بينما طبق حل ثالث<br />
%5.04 توفير<br />
تتميز الحلول<br />
التحكمية<br />
من الفاتورة الكهربائية<br />
M. Taleb, N. Mannsour
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 9–15<br />
University <strong>of</strong> Bahrain<br />
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong><br />
<strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences<br />
www.elsevier.com/locate/jaaubas<br />
www.sciencedirect.com<br />
A self-controlled energy efficient <strong>of</strong>fice lighting system<br />
Maamar Taleb a, *, Noureddine Mannsour b<br />
a Department <strong>of</strong> Electrical <strong>and</strong> Electronics Engineering, University <strong>of</strong> Bahrain, P. O. Box 32038, Isa Town, Bahrain<br />
b Department <strong>of</strong> Chemical Engineering, University <strong>of</strong> Bahrain, P. O. Box 32038, Isa Town, Bahrain<br />
Available online 14 December 2011<br />
KEYWORDS<br />
Electric energy saving;<br />
Office lighting control;<br />
LABVIEW<br />
Abstract The fact that ambient sunlight can add significant contribution to <strong>the</strong> lighting level <strong>of</strong> an<br />
<strong>of</strong>fice, has motivated <strong>the</strong> authors into using <strong>the</strong> level <strong>of</strong> sunlight to control <strong>the</strong> dem<strong>and</strong> <strong>of</strong> <strong>the</strong> electric<br />
lighting in an <strong>of</strong>fice. The control strategy is such that <strong>the</strong> level <strong>of</strong> <strong>the</strong> surrounding light increases<br />
<strong>the</strong> supply voltage, hence electric power consumption, to <strong>the</strong> electric lighting system is reduced. Similarly,<br />
when <strong>the</strong> surrounding sunlight decreases <strong>the</strong> supply voltage, <strong>the</strong> electric power consumption,<br />
to <strong>the</strong> electric lighting system is increased. The objective is to save <strong>the</strong> overall electric energy used <strong>for</strong><br />
<strong>of</strong>fice lighting. Three controllers have been proposed to fulfill <strong>the</strong> previous control strategy. Two<br />
controllers were implemented <strong>and</strong> tested using LABVIEW. A third controller designed <strong>and</strong> constructed<br />
using discrete electronic components. All three controllers were self-regulated. The implementation<br />
<strong>of</strong> <strong>the</strong> control strategy in a university <strong>of</strong>fice showed that a 5.40% saving in <strong>the</strong> electricity<br />
bill was achieved whilst maintaining an almost constant lighting level.<br />
ª 2011 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by Elsevier B.V. All rights reserved.<br />
1. Introduction<br />
Most <strong>of</strong> <strong>the</strong> <strong>of</strong>fices worldwide have shifted from using inc<strong>and</strong>escent<br />
bulbs to fluorescent lamps. The primary reason behind<br />
such a shift is that fluorescent lamps are more energy-efficient.<br />
As a matter <strong>of</strong> fact, st<strong>and</strong>ard inc<strong>and</strong>escent bulbs use three to<br />
four times more electricity than fluorescent lamps (Chugach<br />
Electric <strong>Association</strong>, 2011). Moreover, fluorescent lamps last<br />
up to six times longer than inc<strong>and</strong>escent lamps. In spite <strong>of</strong><br />
* Corresponding author.<br />
E-mail addresses: maamar@eng.uob.bh (M. Taleb), nmansour@<br />
eng.uob.bh (N. Mannsour).<br />
1815-3852 ª 2011 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by<br />
Elsevier B.V. All rights reserved.<br />
Peer review under responsibility <strong>of</strong> University <strong>of</strong> Bahrain.<br />
doi:10.1016/j.jaubas.2011.10.002<br />
Production <strong>and</strong> hosting by Elsevier<br />
<strong>the</strong> tremendous cut in <strong>the</strong> energy requirement by <strong>the</strong> fluorescent<br />
lamps those days, research had not stopped from looking<br />
fur<strong>the</strong>r in saving more energy. One alternative <strong>of</strong> <strong>the</strong> saving is<br />
<strong>the</strong> development <strong>of</strong> compact fluorescent lamps (CFLs). CFLs<br />
own several advantages (Greenfeet, LLC, copyright 1999–<br />
2008) when compared to <strong>the</strong>ir counterpart lamps: classic fluorescent<br />
lamps as well as inc<strong>and</strong>escent lamps.<br />
The present contribution treats <strong>of</strong>fice lighting electric energy<br />
saving from ano<strong>the</strong>r perspective. Such a perspective is documented<br />
as follows: It is well recognized that when an<br />
employee enters his/her <strong>of</strong>fice, <strong>the</strong> first thing that he/she will<br />
do is to switch-on <strong>the</strong> light <strong>and</strong> let it shining fully during <strong>the</strong><br />
whole working hours period. A careful glance at <strong>the</strong> working<br />
hours period, can easily make one notice that <strong>the</strong>re is an additional<br />
free source <strong>of</strong> energy that can be considered as a second<br />
contributor to <strong>the</strong> overall <strong>of</strong>fice lighting. This second contributor<br />
consists <strong>of</strong> <strong>the</strong> surrounding natural sunlight (i.e., sunlight or<br />
day light). The sunlight intensity is probably low at <strong>the</strong> earliest<br />
hours <strong>of</strong> <strong>the</strong> working-hours period but starts increasing as time<br />
passes. It reaches a maximum point around noon time. In <strong>the</strong><br />
afternoon, <strong>the</strong> natural sunlight starts decreasing. This<br />
increase <strong>and</strong> decrease behaviors <strong>of</strong> <strong>the</strong> sunlight are actually
10 M. Taleb, N. Mannsour<br />
dependent on <strong>the</strong> location <strong>of</strong> <strong>the</strong> <strong>of</strong>fice towards <strong>the</strong> sun<br />
position.<br />
This paper uses <strong>the</strong> variation <strong>of</strong> <strong>the</strong> surrounding sunlight in<br />
saving some electric energy needed by <strong>the</strong> lighting system <strong>of</strong> an<br />
<strong>of</strong>fice during working-hours periods.<br />
2. Problem motivation <strong>and</strong> rationale<br />
In order to evaluate <strong>the</strong> contribution <strong>of</strong> <strong>the</strong> surrounding sunlight<br />
to <strong>the</strong> overall light <strong>of</strong> an <strong>of</strong>fice, a small experiment was<br />
held in a university <strong>of</strong>fice. The <strong>of</strong>fice light is provided by 6<br />
pairs <strong>of</strong> florescent lamps. Each florescent is rated 36 W. The<br />
experiment consisted <strong>of</strong> recording <strong>the</strong> effects that may occur<br />
on any light sensor device during <strong>the</strong> <strong>of</strong>fice working hours.<br />
In this investigation, <strong>the</strong> <strong>of</strong>fice working hours were pretended<br />
to be between 08:00 <strong>and</strong> 16:00. A light dependent resistance<br />
(LDR) was considered to be <strong>the</strong> light sensor device. It is worth<br />
mentioning that <strong>the</strong> LDR presents large resistance value at low<br />
levels <strong>of</strong> light (i.e., dark environment) <strong>and</strong> small resistance value<br />
at high levels <strong>of</strong> light (i.e., shining environment) (Radio<br />
Spares (RS) Components, 1997).<br />
Four LDRs are connected to four potentiometers as shown<br />
in Fig. 1. The LDRs are located in four different places in <strong>the</strong><br />
<strong>of</strong>fice. This was done in purpose to find out which LDR was<br />
<strong>the</strong> most sensitive to <strong>the</strong> light. The most sensitive LDR will<br />
be taken as a reference signal in <strong>the</strong> controllers that will be discussed<br />
later. The DC voltage supply was fixed at a 12 V. Each<br />
potentiometer <strong>of</strong> <strong>the</strong> four legs <strong>of</strong> Fig. 1 was adjusted so that its<br />
resistance was close to <strong>the</strong> corresponding LDR resistance value<br />
at 08:00 on <strong>the</strong> day <strong>of</strong> <strong>the</strong> experiment. It is expected that <strong>the</strong><br />
voltage across <strong>the</strong> potentiometer to be near 6 V at 08:00. It<br />
is worth stating that once each potentiometer resistance is set<br />
at 08:00, it is left unaltered during <strong>the</strong> day <strong>of</strong> experiment.<br />
The voltage across <strong>the</strong> four potentiometers terminals were recorded<br />
during <strong>the</strong> time from 08:00 to 16:00 h on December 17,<br />
2008. The day <strong>of</strong> December 17, 2008 was a clear <strong>and</strong> bright day<br />
in <strong>the</strong> kingdom <strong>of</strong> Bahrain. Measurements were taken using<br />
LABVIEW s<strong>of</strong>tware facilities <strong>and</strong> PCI-6221 as a data acquisition<br />
card (National Instruments, 2008). Voltage measurements<br />
across <strong>the</strong> four potentiometers were recorded every second as<br />
depicted in Fig. 2.<br />
After a glance at <strong>the</strong> obtained patterns <strong>of</strong> <strong>the</strong> measurements,<br />
<strong>the</strong> next remarks can be noted:<br />
All voltage drops across <strong>the</strong> four potentiometers have been<br />
set to be near 6 V at <strong>the</strong> start-up <strong>of</strong> <strong>the</strong> measurements (i.e.,<br />
at 08:00).<br />
LDR1 <strong>and</strong> LDR2 indicate that <strong>the</strong> surrounding sunlight<br />
peaks up around 10:00.<br />
LDR4 measurements indicate that <strong>the</strong> surrounding light<br />
exhibits a maximum contribution at <strong>the</strong> sensor position<br />
around 13:30. This can be justified by <strong>the</strong> fact that <strong>the</strong><br />
LDR4 will face <strong>the</strong> sun in <strong>the</strong> afternoon ra<strong>the</strong>r than <strong>the</strong><br />
morning. This was not <strong>the</strong> case <strong>for</strong> LDR1 <strong>and</strong> LDR2.<br />
The contribution <strong>of</strong> <strong>the</strong> surrounding light is manifested by<br />
4 V voltage drop between 10:00 <strong>and</strong> 16:00 <strong>for</strong> LDR1 <strong>and</strong><br />
LDR2. The last two LDRs seem to be more sensitive than<br />
LDR4 <strong>and</strong> LDR3.<br />
The main observation that can be deduced from <strong>the</strong> measurements<br />
is that any anticipated occupant <strong>of</strong> this <strong>of</strong>fice will<br />
witness more light in <strong>the</strong> morning <strong>and</strong> less light in <strong>the</strong> afternoon<br />
but what is interesting is that <strong>the</strong> <strong>of</strong>fice occupant(s) will<br />
feel com<strong>for</strong>t in both sessions. There<strong>for</strong>e, it might be a good<br />
idea to reduce <strong>the</strong> main electric supply partially in <strong>the</strong> morning<br />
session <strong>and</strong> use it fully in <strong>the</strong> afternoon session.<br />
Potentiometer 1<br />
Potentiometer 2<br />
Potentiometer 3<br />
Potentiometer 4<br />
LDR 1<br />
LDR2<br />
LDR 3<br />
LDR 4<br />
12 V<br />
Data Acquisition Card<br />
(PCI 6221Card<br />
manufactured by National Instrument )<br />
PC<br />
Figure 1<br />
Effect <strong>of</strong> <strong>the</strong> surrounding light on <strong>the</strong> overall <strong>of</strong>fice lighting system: circuit layout to record <strong>the</strong> online sunlight effects.
A self-controlled energy efficient <strong>of</strong>fice lighting system 11<br />
9<br />
Mesurements recorded on Thursday December 17, 2008<br />
LDR4<br />
Voltage across <strong>the</strong> potentiometer terminals<br />
8<br />
7<br />
6<br />
5<br />
4<br />
LDR2<br />
LDR1<br />
LDR3<br />
3<br />
8 9 10 11 12 13 14 15 16<br />
Time (hour)<br />
Figure 2<br />
Effect <strong>of</strong> <strong>the</strong> surrounding light on <strong>the</strong> overall light in <strong>the</strong> <strong>of</strong>fice under test.<br />
3. Control strategy<br />
The transition from full use to partial use <strong>of</strong> <strong>the</strong> main electric<br />
supply is possible through <strong>the</strong> application <strong>of</strong> power electronics<br />
circuitry. This is possible through <strong>the</strong> implementation <strong>of</strong> <strong>the</strong><br />
circuit <strong>of</strong> Fig. 3. Fig. 3 represents actually <strong>the</strong> schematic diagram<br />
<strong>of</strong> an AC converter. The <strong>the</strong>ory <strong>and</strong> analysis <strong>of</strong> an AC<br />
converter using a triac are documented in several power electronics<br />
textbooks (e.g., Mohan et al., 2003). Three firing angle<br />
controllers are suggested to control <strong>the</strong> operation <strong>of</strong> <strong>the</strong> triac<br />
<strong>of</strong> Fig. 3.<br />
3.1. Firing angle controller<br />
This controller serves at monitoring <strong>the</strong> instant <strong>of</strong> firing <strong>the</strong><br />
gate triac with a periodic train <strong>of</strong> pulses. The controller is<br />
designed in such a way that <strong>the</strong> firing angle can be adjusted<br />
between 0° <strong>and</strong> 90° <strong>and</strong> between 180° <strong>and</strong> 270° during <strong>the</strong><br />
positive <strong>and</strong> negative cycles <strong>of</strong> <strong>the</strong> main voltage supply, respectively.<br />
This is possible through designing a block diagram<br />
similar to <strong>the</strong> one shown in Fig. 4a. Fig. 4a can be split into<br />
two parts: an upper part <strong>and</strong> a lower part. The upper part guarantees<br />
a train <strong>of</strong> pulses to triac gate when <strong>the</strong> ma<strong>the</strong>matical<br />
12 V<br />
Office Light Level<br />
Potentiometer 1<br />
LDR<br />
1<br />
Triggering<br />
Circuit<br />
Firing Angle Controller<br />
Figure 3<br />
6 pairs <strong>of</strong> lamps<br />
Triac<br />
Controllable AC converter.<br />
240 V<br />
50 Hz<br />
+<br />
+<br />
product <strong>of</strong> <strong>the</strong> main supply voltage signal with its derivative<br />
is negative. This is possible between 90° <strong>and</strong> 180° <strong>and</strong> between<br />
270° <strong>and</strong> 360°, respectively. Note that 0° corresponds to <strong>the</strong><br />
zero-crossing point <strong>of</strong> <strong>the</strong> main voltage supply. The lower part<br />
provides a train <strong>of</strong> pulses when <strong>the</strong> absolute value <strong>of</strong> <strong>the</strong> main<br />
supply voltage is greater than a certain level. The latter level is<br />
actually <strong>the</strong> output <strong>of</strong> a limited integrator. The integrator is<br />
positive <strong>and</strong> it is adjusted online during <strong>the</strong> working <strong>of</strong>fice<br />
hours period. That depends on <strong>the</strong> input sign to <strong>the</strong> integrator.<br />
The input to <strong>the</strong> integrator is a constant. It can be positive,<br />
or negative or zero. It is positive when <strong>the</strong> overall <strong>of</strong>fice lighting<br />
is above an upper limit level, negative when <strong>the</strong> overall <strong>of</strong>fice<br />
lighting is below a lower limit level, <strong>and</strong> zero when <strong>the</strong> <strong>of</strong>fice<br />
lighting is between <strong>the</strong> two upper <strong>and</strong> lower limits. The upper<br />
limit <strong>and</strong> <strong>the</strong> lower limit levels correspond to V reference + DV<br />
<strong>and</strong> V reference DV, respectively. In this paper, V reference <strong>and</strong><br />
DV were taken as 6 V <strong>and</strong> 0.2 V, respectively. When <strong>the</strong> voltage<br />
across <strong>the</strong> potentiometer terminals (V potentiometer ) <strong>of</strong> <strong>the</strong> left<br />
sensor exceeds V reference + DV (i.e., 6.2 V), <strong>the</strong> integrator output<br />
level increases <strong>and</strong> consequently <strong>the</strong> generation <strong>of</strong> firing pulses<br />
to <strong>the</strong> triac gate will be delayed. Delaying firing pulses generation<br />
will lower <strong>the</strong> <strong>of</strong>fice light level. Similarly, when <strong>the</strong> measured<br />
voltage across <strong>the</strong> potentiometer terminals <strong>of</strong> <strong>the</strong> left<br />
sensor is below V reference DV (i.e., 5.8 V), <strong>the</strong> integrator output<br />
level decreases <strong>and</strong> consequently an early generation <strong>of</strong> firing<br />
pulses to <strong>the</strong> triac gate is noted. Early generation <strong>of</strong> firing<br />
pulses results in an increase in <strong>the</strong> <strong>of</strong>fice lighting level.<br />
Fig. 4b depicts <strong>the</strong> different wave<strong>for</strong>ms that can be expected<br />
at <strong>the</strong> output <strong>of</strong> <strong>the</strong> different blocks <strong>of</strong> Fig. 4a. In Fig. 4b, it is<br />
assumed that <strong>the</strong> <strong>of</strong>fice lighting level is above an upper limit<br />
(i.e., 6.2 V) <strong>and</strong> <strong>the</strong> firing angle needs to be increased. The<br />
firing angle keeps increasing automatically until <strong>the</strong> <strong>of</strong>fice<br />
lighting falls below a preset upper limit.<br />
It is worth mentioning that <strong>the</strong> proposed firing angle controller<br />
provides a zero firing angle at minimum <strong>of</strong>fice overall<br />
lighting level <strong>and</strong> 90° at maximum <strong>of</strong>fice overall lighting level.<br />
The firing angle controller <strong>of</strong> Fig. 4a has been translated to<br />
a LABVIEW code. The developed LABVIEW code is used to
12 M. Taleb, N. Mannsour<br />
Out<br />
Towards Triac<br />
Gate Driver<br />
π<br />
X<br />
X2<br />
2 π<br />
3 π<br />
ωt<br />
4 π<br />
Sign Indicator<br />
Upper Part<br />
X1<br />
Output =1 if u ≤0<br />
Pulses Generator<br />
Output = 0 if u >0<br />
X4<br />
du<br />
----<br />
dt<br />
X<br />
X5<br />
X2 X3<br />
From Main<br />
Supply<br />
+<br />
a<br />
Z1<br />
+<br />
X6<br />
Voltage<br />
Trans<strong>for</strong>mer<br />
Z<br />
|u|<br />
Y6<br />
Output =1 if u1 ≥ u2<br />
Lower Part<br />
Output = 0 if u1
A self-controlled energy efficient <strong>of</strong>fice lighting system 13<br />
From Sensor<br />
(Potentiomer<br />
Terminals)<br />
From VT<br />
National Instrument Data<br />
Acquisition Card PCI 6221<br />
+ 5 V<br />
Optocoupler<br />
Mosfet<br />
+12 V<br />
Pulse<br />
Trans<strong>for</strong>mer<br />
G<br />
MT2<br />
MT1<br />
To predict <strong>the</strong> per<strong>for</strong>mance <strong>of</strong> <strong>the</strong> integral cycle controller<br />
<strong>of</strong> Fig. 6a <strong>and</strong> b visualizes <strong>the</strong> expected wave<strong>for</strong>ms that can<br />
be generated at <strong>the</strong> output <strong>of</strong> <strong>the</strong> different blocks <strong>of</strong> Fig. 6a.<br />
The wave<strong>for</strong>ms are drawn by pretending a 25% value <strong>for</strong><br />
<strong>the</strong> duty cycle <strong>for</strong> a generated periodic pulse <strong>of</strong> frequency<br />
2.5 Hz. The last wave<strong>for</strong>m <strong>of</strong> Fig. 6b can be interpreted by<br />
<strong>the</strong> fact that <strong>the</strong> triac <strong>of</strong> Fig. 3 will be <strong>of</strong>f <strong>for</strong> 0.1 s (i.e., 0.1 s<br />
corresponds to 5 cycles <strong>of</strong> <strong>the</strong> 50 Hz main supply) <strong>and</strong> conducting<br />
<strong>for</strong> <strong>the</strong> following 0.3 s (i.e., 0.3 s corresponds to 15 cycles<br />
<strong>of</strong> <strong>the</strong> 50 Hz main supply). The integral cycle controller <strong>of</strong><br />
Fig. 6a has been also written in ano<strong>the</strong>r LABVIEW code. Such<br />
LABVIEW code is insulated from <strong>the</strong> power circuit through<br />
<strong>the</strong> hardware <strong>of</strong> Fig. 5.<br />
Figure 5<br />
Insulating firing angle controller from power circuit.<br />
3.3. Conduction period controller<br />
<strong>the</strong> duty cycle reaches 100% value, no firing pulses will be provided<br />
to <strong>the</strong> triac gate <strong>and</strong> consequently no contribution is<br />
marked from <strong>the</strong> main electric outlet.<br />
The intended task from this controller is to provide conducting<br />
<strong>and</strong> non-conducting portions <strong>for</strong> <strong>the</strong> triac during each half<br />
cycle <strong>of</strong> <strong>the</strong> main supply. Fig. 7 suggests a practical circuit that<br />
can provide such intended task. The task is made possible<br />
Out<br />
X<br />
5<br />
0.2 0.3<br />
0.6 0.8<br />
Time (s)<br />
X3<br />
Upper Part<br />
Pulses Generator <strong>of</strong><br />
High Frequency<br />
X2<br />
NOT<br />
Output =1 if u ≥ 0<br />
X X1<br />
Output = 0 if u < 0<br />
Square wave<br />
2.5 Hz<br />
Y4<br />
Duty Cycle<br />
a<br />
Lower Part<br />
1<br />
-0.2<br />
y1 Y2 1 Y3 100<br />
0.2<br />
+ k<br />
-----<br />
- S<br />
Y<br />
0<br />
-1<br />
Integrator Limiter<br />
Vreference<br />
-5<br />
1<br />
0<br />
X1<br />
X2<br />
1<br />
0<br />
6.3<br />
6.0<br />
1<br />
0.3<br />
25<br />
%<br />
5<br />
5<br />
out<br />
X3<br />
0.1<br />
0.4<br />
0.1<br />
0.4<br />
0.1 0.4<br />
V potentiometer<br />
V reference<br />
Y1<br />
Y<br />
Y2<br />
Y3<br />
0.1<br />
0.4<br />
0.1<br />
0.4<br />
b<br />
0.5<br />
0.5<br />
0.5<br />
0.5<br />
0.5<br />
0.8<br />
Time (s)<br />
0.8<br />
Time (s)<br />
0.8<br />
Time (s)<br />
Time (s)<br />
Time (s)<br />
0.8<br />
Time (s)<br />
0.8<br />
Time (s)<br />
Figure 6<br />
Integral cycle controller: (a) control block diagram, (b) expected wave<strong>for</strong>ms at different stages <strong>of</strong> <strong>the</strong> control block diagram.
14 M. Taleb, N. Mannsour<br />
Vrectified<br />
Comparator<br />
+VCC<br />
+<br />
-<br />
R discharching<br />
B<br />
V control<br />
B’<br />
V measured<br />
NO<br />
Oscillator<br />
Timer<br />
+VCC<br />
8<br />
4<br />
3<br />
+VCC<br />
7<br />
pulses<br />
6<br />
2 1 5<br />
Out<br />
Vs<br />
π<br />
2π<br />
V up<br />
3π<br />
V measured<br />
4π<br />
5π<br />
6π<br />
ωt<br />
Vc<br />
V down<br />
A A’<br />
R charging<br />
NO<br />
X1<br />
X2<br />
ωt<br />
ωt<br />
+VCC<br />
Upper Relay<br />
Upper Comparator<br />
+VCC<br />
LED<br />
+<br />
-<br />
X1<br />
+VCC<br />
X2<br />
+<br />
LED<br />
-<br />
Lower Comparator<br />
LDR<br />
Lower Relay<br />
V rectified<br />
V control<br />
Vs<br />
π<br />
π<br />
2π<br />
2π<br />
3π<br />
3π<br />
4π<br />
4π<br />
5π<br />
5π<br />
6π<br />
6π<br />
ωt<br />
ωt<br />
Pulses<br />
+VCC<br />
Vup<br />
+VCC<br />
Vdown<br />
π<br />
2π<br />
3π<br />
4π<br />
5π<br />
6π<br />
ωt<br />
Vs<br />
Out<br />
L<br />
240 V<br />
N<br />
π<br />
2π<br />
3π<br />
4π<br />
5π<br />
ωt<br />
6π<br />
Figure 7<br />
diagram.<br />
Conduction period controller: (a) control block diagram, (b) expected wave<strong>for</strong>ms at different stages <strong>of</strong> <strong>the</strong> control block<br />
through <strong>the</strong> result <strong>of</strong> comparing a rectified signal <strong>of</strong> <strong>the</strong> main<br />
voltage supply with a voltage level across a capacitor. The voltage<br />
level across <strong>the</strong> capacitor is monitored by <strong>the</strong> operation <strong>of</strong><br />
two comparators. The principle <strong>of</strong> operation <strong>of</strong> <strong>the</strong> different<br />
active devices in <strong>the</strong> figure (i.e., Fig. 7a) can be obtained from<br />
Maini (2007).<br />
When <strong>the</strong> <strong>of</strong>fice lighting exceeds a pre-set upper limit (i.e.,<br />
6.2 V), <strong>the</strong> upper comparator will allow <strong>the</strong> upper relay to close<br />
its contacts <strong>and</strong> consequently <strong>the</strong> capacitor voltage starts<br />
increasing through <strong>the</strong> charging resistance (R charging ). Increasing<br />
<strong>the</strong> capacitor voltage shortens <strong>the</strong> conducting periods <strong>of</strong> <strong>the</strong> triac.<br />
Similarly, when <strong>the</strong> <strong>of</strong>fice lighting falls below a pre-set lower<br />
limit (i.e., 5.8 V), <strong>the</strong> lower comparator allows <strong>the</strong> lower relay to<br />
close its contacts <strong>and</strong> consequently <strong>the</strong> capacitor voltage starts<br />
decreasing through <strong>the</strong> discharging resistance (R discharging ).<br />
Decreasing <strong>the</strong> capacitor voltage level extends <strong>the</strong> duration <strong>of</strong><br />
<strong>the</strong> triac conduction periods. When <strong>the</strong> <strong>of</strong>fice lighting is between<br />
<strong>the</strong> preset upper <strong>and</strong> lower limits, both relays contacts are found<br />
open <strong>and</strong> <strong>the</strong>re is a no-need to ei<strong>the</strong>r shorten or extend <strong>the</strong> conduction<br />
periods.
A self-controlled energy efficient <strong>of</strong>fice lighting system 15<br />
Table 1<br />
Controller<br />
Controllers per<strong>for</strong>mance.<br />
Increasing <strong>the</strong> conducting period means that more contribution<br />
<strong>of</strong> <strong>the</strong> main supply to <strong>the</strong> <strong>of</strong>fice lighting is expected<br />
<strong>and</strong> decreasing <strong>the</strong> conducting period means that less contribution<br />
<strong>of</strong> <strong>the</strong> main supply is expected.<br />
Fig. 7b depicts <strong>the</strong> different signals that can be expected at<br />
<strong>the</strong> output <strong>of</strong> <strong>the</strong> different block <strong>of</strong> Fig. 7a. The output port<br />
termed ‘‘Out’’ in Fig. 7a is linked to <strong>the</strong> gate <strong>of</strong> <strong>the</strong> triac <strong>of</strong><br />
Fig. 3 through <strong>the</strong> insulating gate circuit <strong>of</strong> Fig. 5.<br />
4. Controllers per<strong>for</strong>mance<br />
Electric energy Electric energy<br />
consumed by <strong>the</strong> saving index (%)<br />
<strong>of</strong>fice light system<br />
No-controller 2.98 kW h –<br />
Firing angle controller 2.90 kW h 2.68%<br />
Integral cycle controller 2.82 kW h 5.37%<br />
Conduction period controller 2.85 kW h 4.36%<br />
The main target <strong>of</strong> this investigation is to take advantage <strong>of</strong><br />
<strong>the</strong> surrounding sunlight in lighting up an <strong>of</strong>fice. Excess<br />
<strong>of</strong> <strong>the</strong> surrounding sunlight means that a partial cut <strong>of</strong> <strong>the</strong><br />
main electric supply can be practiced <strong>and</strong> <strong>the</strong>re<strong>for</strong>e some<br />
savings in electric energy consumption can be expected. The<br />
partial cut is done by field implementation <strong>of</strong> <strong>the</strong> previous<br />
three controllers <strong>and</strong> testing <strong>the</strong>ir per<strong>for</strong>mance. The per<strong>for</strong>mance<br />
consists <strong>of</strong> recording how much electric energy can be<br />
consumed by <strong>the</strong> electric lighting system <strong>of</strong> <strong>the</strong> <strong>of</strong>fice during<br />
<strong>the</strong> <strong>of</strong>fice working hours period. Table 1 reflects energy consumption<br />
when testing <strong>the</strong> previous three controllers.<br />
As seen from <strong>the</strong> obtained results, a 5.37% <strong>of</strong> electric<br />
energy can be saved when using <strong>the</strong> integral controller. The<br />
saving energy index in <strong>the</strong> third column <strong>of</strong> Table 1 was calculated<br />
as: (Energy consumed without using controller Energy<br />
consumed when using a particular controller) * 100/(Energy<br />
consumed without using controller).<br />
It should be emphasized that <strong>the</strong> energy saving is reached<br />
while <strong>the</strong> <strong>of</strong>fice lighting level is kept between two pre-set upper<br />
<strong>and</strong> lower limits (i.e., 6.2 V <strong>and</strong> 5.8 V, respectively). Note that<br />
<strong>the</strong> two pre-set limits do not harm <strong>the</strong> com<strong>for</strong>t <strong>of</strong> <strong>the</strong> anticipated<br />
<strong>of</strong>fice occupants. The drawback that was encountered<br />
when implementing such controllers is <strong>the</strong> creation <strong>of</strong> some<br />
minor flickering in <strong>the</strong> florescent lamps. Such phenomenon<br />
has been relatively visible when implementing <strong>the</strong> integral cycle<br />
controller.<br />
5. Conclusion<br />
The presence <strong>of</strong> <strong>the</strong> natural sunlight around an <strong>of</strong>fice has a significant<br />
contribution to <strong>the</strong> overall lighting <strong>of</strong> <strong>the</strong> <strong>of</strong>fice. The<br />
contribution consists <strong>of</strong> cutting partially some <strong>of</strong> <strong>the</strong> electric<br />
energy consumption needed presumably by <strong>the</strong> <strong>of</strong>fice lighting<br />
system. The partial cut in <strong>the</strong> electric energy consumption in<br />
this paper has been fulfilled by field implementation <strong>of</strong> three<br />
suggested controllers. In per<strong>for</strong>ming <strong>the</strong> partial cut in <strong>the</strong> electric<br />
energy consumption, a 5.37% as an index <strong>of</strong> electric energy<br />
saving has been reached whilst <strong>the</strong> overall light level in <strong>the</strong><br />
<strong>of</strong>fice is kept nearly com<strong>for</strong>table to <strong>the</strong> <strong>of</strong>fice occupants. Some<br />
flickering phenomenon has been encountered when implementing<br />
<strong>the</strong> three controllers. The idea presented in this paper can<br />
be extended to a number <strong>of</strong> real life processes that may require<br />
a controlled light level to produce a desired optimum output/<br />
level.<br />
Acknowledgment<br />
The financial assistance <strong>of</strong> <strong>the</strong> Deanship <strong>of</strong> Research at<br />
University <strong>of</strong> Bahrain in per<strong>for</strong>ming <strong>the</strong> different tasks <strong>of</strong><br />
<strong>the</strong> present contribution is appreciated by <strong>the</strong> authors.<br />
References<br />
Chugach Electric <strong>Association</strong>, Alaska, USA. <br />
(accessed 4.08.11).<br />
Greenfeet, LLC (copyright 1999–2008). The Benefits <strong>of</strong> Compact<br />
Fluorescent Lighting, Cali<strong>for</strong>nia, USA. (accessed 4.08.11).<br />
Maini, Anil K., 2007. Digital Electronics: Principles, Devices, <strong>and</strong><br />
Applications. John Wiley & Sons Ltd, West Sussex, Engl<strong>and</strong>.<br />
Mohan, N., Undel<strong>and</strong>, T., Robbins, W., 2003. Power Electronics:<br />
Converters, Applications, <strong>and</strong> Design. John Wiley & Sons Ltd.,<br />
West Sussex, Engl<strong>and</strong>.<br />
National Instruments Corporation (2008). Introducing LABVIEW<br />
8.6. Austin, Texas, USA.<br />
Radio Spares (RS) Components, Part 232-3816 (March 1997), Light<br />
Dependent Resistors.
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 16-20<br />
)C – Mn(<br />
عملية الكسر لفوالذ الكربون –<br />
المنجنيز<br />
الهش بالهيدروجين<br />
نور الدين<br />
سعيداني، عبدالقادر ميحي، رشيد بن بوتة<br />
قسم الميكانيك، كلية التكنولوجيا، جامعة باتنة، باتنة 00000،<br />
الجزائر<br />
و<br />
الملخص:<br />
تم فحص بنية عينات تكسرت عن طريق اختبار إجهاد الشد بسرعة تشوه بطيئة، بهدف دراسة أصناف<br />
الكسر )التقصف( باستخدام مجهر مسح إلكتروني.<br />
أرشدت هذه الدراسة إلى تحديد ثالثة أصناف من العينات: عينات غير هشة، عينات خفيفة الهشاشة<br />
وعينات هشة جدا. وتتألف الفئة األولى من عينات االختبار التي تمت تجربتها في الهواء بجهد<br />
08.0-<br />
08.0-<br />
08.0-<br />
فولط مع معدل الهش<br />
فولط. وذلك بسبب هشاشة<br />
08.0 ≥<br />
.08..<br />
كما تم اختبار العينات خفيفة الهشاشة بجهد<br />
أما بالنسبة للعينات المعنية بنسبة الهش أقل من<br />
08..<br />
فتدخل في الفئة<br />
ذات العينات الهشة جدا.<br />
أثبتت دراسات صور االنكسار أن هش الفوالذ الصلب ناتج عن الهش بواسطة الهيدروجين. كما لوحظ<br />
أن البنية )بين الحبيبات وعبر الحبيبات( لمقاطع االنكسار، بالنسبة للفوالذ الهش، هي نموذجية ودالة<br />
الهش بالهيدروجين.<br />
N. Saidani et al.
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 16–20<br />
University <strong>of</strong> Bahrain<br />
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong><br />
<strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences<br />
www.elsevier.com/locate/jaaubas<br />
www.sciencedirect.com<br />
ORIGINAL ARTICLE<br />
Fracture process <strong>of</strong> C–Mn steel embrittled by hydrogen<br />
N. Saidani, A. Mihi, R. Benbouta *<br />
University <strong>of</strong> Batna, Faculty <strong>of</strong> Technology, Mechanical Engineering Department, Batna 05000, Algeria<br />
Available online 31 January 2012<br />
KEYWORDS<br />
Fracture;<br />
Hydrogen embrittlement;<br />
Morphologies;<br />
Fracture modes;<br />
Scanning electron microcopy<br />
(SEM)<br />
Abstract Fracture morphologies <strong>of</strong> tested specimens, by means <strong>of</strong> <strong>the</strong> slow strain rate tensile testing,<br />
were examined to study fracture modes by using scanning electron microscopy.<br />
This study has led to <strong>the</strong> determination <strong>of</strong> three categories <strong>of</strong> specimens: unembrittled specimens,<br />
slightly embrittled specimens <strong>and</strong> severely embrittled specimens. The first category <strong>of</strong> unembrittled<br />
specimens includes specimens tested in air, at potentials <strong>of</strong> 0.80 <strong>and</strong> 0.85 V (SCE) with embrittlement<br />
ratio (ER) P 0.97. In <strong>the</strong> category <strong>of</strong> specimens slightly embrittled, only <strong>the</strong> specimen<br />
tested at 0.9 V with an embrittlement ratio (ER) <strong>of</strong> 0.69 is included. The last category <strong>of</strong> severely<br />
embrittled specimens includes <strong>the</strong> specimens with embrittlement ratio (ER) < 0.69.<br />
The fractographic studies are consistent with <strong>the</strong> embrittlement <strong>of</strong> steel being due to hydrogen<br />
embrittlement. The intergranular <strong>and</strong> transgranular quasicleavage fracture surface morphologies<br />
observed with embrittled specimens are typical <strong>and</strong> characteristic <strong>of</strong> hydrogen embrittlement.<br />
ª 2012 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by Elsevier B.V. All rights reserved.<br />
1. Introduction<br />
* Corresponding author. Tel./fax: +213 0 33 81 21 43.<br />
E-mail address: r_benbouta@yahoo.fr (R. Benbouta).<br />
1815-3852 ª 2012 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by<br />
Elsevier B.V. All rights reserved.<br />
Peer review under responsibility <strong>of</strong> University <strong>of</strong> Bahrain.<br />
doi:10.1016/j.jaubas.2012.01.001<br />
Production <strong>and</strong> hosting by Elsevier<br />
The detrimental effect which hydrogen produces in metals,<br />
generally known as hydrogen embrittlement (HE), has always<br />
been one <strong>of</strong> <strong>the</strong> main problems <strong>of</strong> practical <strong>and</strong> <strong>the</strong>oretical<br />
material technology <strong>of</strong> corrosion <strong>and</strong> protection <strong>of</strong> metals.<br />
Hydrogen is <strong>the</strong> cause <strong>of</strong> damage whenever metal hydrogen<br />
systems are involved in <strong>the</strong> production, transport <strong>and</strong> storage<br />
<strong>of</strong> hydrogen, or fluids containing hydrogen, <strong>and</strong> in <strong>the</strong> presence<br />
<strong>of</strong> electrochemical processes such as pickling, electroplating,<br />
cathodic protection <strong>and</strong> corrosion. Hydrogen when<br />
present ei<strong>the</strong>r as an external gas environment or as a dissolved<br />
proton can produce internal cracking or a dramatic loss <strong>of</strong><br />
toughness in a variety <strong>of</strong> metals (Takeda <strong>and</strong> McMahon,<br />
1981; Gooch, 1974; Woodward <strong>and</strong> Procter, 1988; Hirth <strong>and</strong><br />
Johnson, 1976; Luu <strong>and</strong> Wu, 2001; Wu <strong>and</strong> Wu, 2002).<br />
When considering <strong>the</strong> hydrogen embrittlement phenomenon,<br />
one <strong>of</strong> <strong>the</strong> areas that is <strong>of</strong> most interest is <strong>the</strong> mode <strong>of</strong><br />
hydrogen fracture.<br />
In <strong>the</strong> present work <strong>the</strong> objective was to study <strong>the</strong> fracture<br />
process <strong>of</strong> <strong>the</strong> specimens tested under slow strain rate testing<br />
(SSRT).<br />
2. Experimental procedure<br />
2.1. Material<br />
The material investigated in <strong>the</strong> present study was low carbonmanganese<br />
structural steel BS 4360 grade 50D. The nominal<br />
composition <strong>of</strong> this material <strong>and</strong> its mechanical properties in<br />
<strong>the</strong> condition in which it has been tested are given in Table 1.<br />
The cylindrical tensile specimens with a 25.0 mm gauge length
Fracture process <strong>of</strong> C–Mn steel embrittled by hydrogen 17<br />
Table 1 Mechanical properties <strong>and</strong> chemical composition <strong>of</strong><br />
steel.<br />
Mechanical properties Heat treatment<br />
r 0.2 = 1220 MPa Austenitization <strong>for</strong> 1 min at 1200 °C<br />
U.T.S = 1440 MPa Water quench<br />
RA = 48% Tempered <strong>for</strong> 30 min at 170 °C<br />
Chemical composition wt%<br />
C Si Mn S P Ni Cr Mo<br />
0.16 0.34 1.44 0.011 0.026 0.03 0.06
18 N. Saidani et al.<br />
3.1.2.3. Tests at 0.95 to 1.3 V. The tests carried out at<br />
potentials <strong>of</strong> 0.95 to 1.3 V showed high degree <strong>of</strong> embrittlement<br />
(ER ranged from 0.063 to 0.323). Examination <strong>of</strong> <strong>the</strong><br />
fracture surfaces indicated similarities between <strong>the</strong> fracture<br />
morphologies. The fracture surfaces appeared to have a flat<br />
fracture pr<strong>of</strong>ile normal to <strong>the</strong> loading direction <strong>and</strong> shear type<br />
fracture oriented at about 45° to <strong>the</strong> tensile axis. Typical photomicrographs<br />
<strong>of</strong> fracture are shown in Fig. 5.<br />
In general, <strong>the</strong> fracture surfaces consisted mainly <strong>of</strong> a large<br />
ductile region <strong>and</strong> small brittle area. The brittle area was generally<br />
localized at or near <strong>the</strong> edge <strong>of</strong> <strong>the</strong> fracture surface with<br />
a predominantly intergranular cracking along <strong>the</strong> prior austenite<br />
grain boundaries <strong>and</strong> limited areas <strong>of</strong> quasicleavage. Fig. 6<br />
is characteristic <strong>of</strong> <strong>the</strong> features observed on many fracture surfaces<br />
in this potential range. It was noticed that as <strong>the</strong> potential<br />
became more negative <strong>the</strong> proportion <strong>of</strong> <strong>the</strong> brittle region<br />
increases.<br />
4. Discussion<br />
Figure 3 SEM photomicrograph <strong>of</strong> fractured specimen tested at<br />
0.85 V (SCE).<br />
4.1. Fracture process<br />
4.1.1. Unembrittled specimens<br />
All <strong>the</strong>se specimens fractured in a similar pattern <strong>of</strong> microvoids<br />
coalescence. Usually, <strong>the</strong> microvoids nucleate at regions<br />
<strong>of</strong> highly localized plastic de<strong>for</strong>mation such as inclusions <strong>and</strong><br />
grain boundaries. As <strong>the</strong> stress on <strong>the</strong> specimen increases,<br />
<strong>the</strong> microvoids exp<strong>and</strong> <strong>and</strong> intersect one ano<strong>the</strong>r <strong>and</strong> finally<br />
break up when <strong>the</strong> reduced cross sectional area cannot withst<strong>and</strong><br />
<strong>the</strong> load any longer.<br />
4.2. Slightly embrittled specimens<br />
(a) Gauge section<br />
(b) Fracture surface edge<br />
Figure 4 SEM photomicrographs <strong>of</strong> <strong>the</strong> gauge section <strong>and</strong><br />
fracture surface edge <strong>of</strong> steel at 0.9 V (SCE).<br />
dimples contained in <strong>the</strong> central cup <strong>of</strong> <strong>the</strong> fracture surfaces is<br />
shown in Fig. 2. These dimples are <strong>the</strong> result <strong>of</strong> <strong>the</strong> growth <strong>and</strong><br />
coalescence <strong>of</strong> microvoids which nucleate at particles such as<br />
inclusions <strong>and</strong> precipitates.<br />
3.1.2. Fracture in 3.5% NaCl<br />
3.1.2.1. Tests at 0.8 <strong>and</strong> 0.85 V. For <strong>the</strong> tests per<strong>for</strong>med at<br />
0.8 <strong>and</strong> 0.85 V <strong>the</strong> fracture surface <strong>of</strong> specimens had also a<br />
cup <strong>and</strong> cone appearance similar to that obtained in <strong>the</strong> air<br />
test, Fig. 3.<br />
3.1.2.2. Test at 0.9 V. In this test, some embrittlement was noticed.<br />
Failure occurred with an amount <strong>of</strong> plastic de<strong>for</strong>mation<br />
lower than that observed in tests in air, <strong>and</strong> at 0.8 <strong>and</strong><br />
0.85 V, Fig. 4a. The fracture surface consisted <strong>of</strong> a ragged<br />
fracture path <strong>and</strong> smoo<strong>the</strong>r fracture path inclined at about<br />
45° from <strong>the</strong> loading direction. A few patches, consisted<br />
predominantly <strong>of</strong> intergranular cracking along <strong>the</strong> prior<br />
austenite grain boundaries, were observed at <strong>the</strong> edge <strong>of</strong> <strong>the</strong><br />
ragged fracture path. A photomicrograph <strong>of</strong> <strong>the</strong> brittle area<br />
is shown in Fig. 4b.<br />
In this case, brittle type <strong>of</strong> failure, predominantly intergranular<br />
cracking along prior austenite grain boundaries <strong>and</strong> some quasicleavage<br />
features, accompanied <strong>the</strong> ductile type <strong>of</strong> failure such<br />
as dimples <strong>and</strong> ductile tearing. The proportion <strong>of</strong> <strong>the</strong> brittle region<br />
was minimal, only one or two patches localized at <strong>the</strong><br />
edges <strong>of</strong> <strong>the</strong> specimen. It is believed that <strong>the</strong> presence <strong>and</strong><br />
growth <strong>of</strong> <strong>the</strong>se brittle types <strong>of</strong> fracture cause <strong>the</strong> cross section<br />
<strong>of</strong> <strong>the</strong> specimen, already reduced by necking, to be reduced even<br />
more, <strong>and</strong> thus, <strong>the</strong> specimen will fail earlier than in <strong>the</strong>ir<br />
absence. Because <strong>of</strong> <strong>the</strong> limited amount <strong>of</strong> hydrogen available<br />
under <strong>the</strong>se conditions, <strong>the</strong> cracks do not grow long enough<br />
to cause an earlier reduction in <strong>the</strong> net cross sectional area.<br />
4.3. Severely embrittled specimens<br />
In this category <strong>of</strong> tests, <strong>the</strong> hydrogen availability is very high,<br />
it diffuses into steel through <strong>the</strong> lattice <strong>and</strong> accumulates at defect<br />
sites such as dislocations, inclusions, grain boundaries,<br />
microvoids, phase interface <strong>and</strong> carbides. Its interaction with<br />
certain <strong>of</strong> <strong>the</strong>se defects results in intergranular or transgranular<br />
quasicleavage cracking. Since <strong>the</strong> availability <strong>of</strong> hydrogen is<br />
high, <strong>the</strong> number <strong>of</strong> sites <strong>for</strong> crack nucleation increases <strong>and</strong><br />
<strong>the</strong>y grow long enough so that <strong>the</strong>y could link more easily,<br />
resulting in a surface covered with a large fraction <strong>of</strong> brittle<br />
types <strong>of</strong> failures. Also, as <strong>the</strong> cracks grow faster, <strong>the</strong> reduction<br />
in <strong>the</strong> net cross sectional area occurs at an earlier stage than<br />
when insufficient hydrogen is available.<br />
In summary <strong>the</strong> reduced ductility <strong>of</strong> <strong>the</strong> C–Mn structural<br />
steel when tested in NaCl solution at cathodic applied
Fracture process <strong>of</strong> C–Mn steel embrittled by hydrogen 19<br />
(a) Gauge section (- 1. 1 V ) (b) Fracture surface(- 1. 1 V )<br />
(c) Gauge section (- 1.3 V ) (d) Fracture surface(- 1.3 V )<br />
Figure 5 Typical SEM photomicrographs <strong>of</strong> <strong>the</strong> gauge sections <strong>and</strong> fracture surfaces <strong>of</strong> specimens tested at potentials between 0.95<br />
<strong>and</strong> 1.3 V (SCE).<br />
(a) Tested at –0.95 V<br />
(b) Tested at – 1.1 V<br />
(c) Tested at – 1.3 V<br />
Figure 6 Selected SEM photomicrographs <strong>of</strong> <strong>the</strong> fracture surface edge <strong>of</strong> specimens tested at potentials between 0.95 <strong>and</strong> 1.3 V<br />
(SCE).
20 N. Saidani et al.<br />
potentials is <strong>the</strong> result <strong>of</strong> <strong>the</strong> presence <strong>of</strong> mainly intergranular<br />
cracks induced by cathodically evolved hydrogen. The hydrogen<br />
which has diffused through <strong>the</strong> lattice accumulates at susceptible<br />
interfaces, <strong>and</strong> probably lowers <strong>the</strong> cohesive strength <strong>of</strong><br />
<strong>the</strong> lattice after a critical concentration has been reached, <strong>the</strong>reby<br />
initiating an embrittling event at room temperatures in<br />
ductile steel (Yoshino <strong>and</strong> McMahon, 1974; Wang et al., 2007).<br />
5. Conclusion<br />
This work is devoted to fractographic investigation <strong>of</strong> C–Mn<br />
structural steel under slow strain rate tensile testing. Examination<br />
<strong>of</strong> <strong>the</strong> fracture surfaces using SEM revealed <strong>the</strong> following<br />
results:<br />
1. The intergranular <strong>and</strong> transgranular quasicleavage fracture<br />
surface morphologies observed with embrittled specimens<br />
are typical <strong>and</strong> characteristic <strong>of</strong> hydrogen embrittlement.<br />
2. The reduction in ductility <strong>of</strong> steel is attributed to <strong>the</strong><br />
appearance <strong>of</strong> brittle modes <strong>of</strong> fracture such as intergranular<br />
<strong>and</strong> transgranular quasicleavage features on <strong>the</strong> fracture<br />
surface.<br />
References<br />
Gooch, T.G., 1974. Stress corrosion cracking <strong>of</strong> welded joints in high<br />
strength steels weld. Welding <strong>Journal</strong> 53, 2877.<br />
Hirth, J.P., Johnson, H.H., 1976. Hydrogen problems in energy related<br />
technology. Corrosion 32, 3.<br />
Luu, W.C., Wu, J.K., 2001. Influence <strong>of</strong> aluminium content on<br />
retarding hydrogen transport in Fe–Al binary alloys. Corrosion<br />
Science 43, 2325.<br />
Takeda, Y., McMahon, C.J., 1981. Strain controlled vs stress<br />
controlled hydrogen induced fracture in a quenched <strong>and</strong> tempered<br />
steel. Metallurgical Transactions 12A, 1255.<br />
Wang, M., Akiyama, E., Tsuzaki, K., 2007. Effect <strong>of</strong> hydrogen on <strong>the</strong><br />
fracture behavior <strong>of</strong> high strength steel during slow strain rate test.<br />
Corrosion Science 49, 4081.<br />
Woodward, J., Procter, R.P.M., 1988. Fatigue <strong>of</strong> <strong>of</strong>fshore structures.<br />
In: Dover, W.D., Glinka, G. (Eds.), Proceedings <strong>of</strong> International<br />
Conference, London.<br />
Wu, T.I., Wu, J.K., 2002. Effects <strong>of</strong> thiourea <strong>and</strong> its derivatives on <strong>the</strong><br />
electrolytic hydrogenation behavior <strong>of</strong> Ti–6Al–4V alloy. Materials<br />
Letters 53, 193.<br />
Yoshino, K., McMahon Jr., 1974. The cooperative relation between<br />
temper embrittlement <strong>and</strong> hydrogen embrittlement in a high<br />
strength steel. Metallurgical Transactions 5A, 363.
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 21-26<br />
قياسات األشعة في مياه الشرب في منطقة النصر بغزة<br />
ماهر عمر الغصين،<br />
عبد القادر أبوشمالة<br />
الجامعة اإلسالمية<br />
في غزة،<br />
قسم الفيزياء، ص. ب 801،<br />
فلسطين غزة،<br />
الملخص:<br />
إن األشعة المؤينة تأتي من الكون ومن األرض و حتى من داخل أجسامنا، فهي موجودة في الهواء الذي<br />
نتنفسه وفي الطعام الذي نأكله وفي الماء الذي نشربه وفي مواد البناء التي نبني بها بيوتنا.<br />
ان التعرض لغاز الرادون ومخلفاته يعتقد بأنه يعمل على زيادة خطر االصابة بالعديد من انواع السرطان<br />
ومنها سرطان الرئة في حال استنشاق الغاز. أما في حال تناول ماء يحتوي على غاز الرادون فإنه يعتقد<br />
بان يكون مصاحبا الى زيادة خطورة االصابة بأورام للعديد من االعضاء الداخلية و خاصة المعدة.<br />
في هذه الدراسة، لقد تم قياس شدة النشاط اإلشعاعي لجسيمات ألفا ويبتا وأشعة جاما في مياه الشرب في<br />
منطقة النصر شمال غرب مدينة غزة<br />
.<br />
للقيام بهذا العمل تم استخدام كاشف المسارات النووية<br />
)CR-93(<br />
وبعض الكواشف األخرى مثل عداد جيجر وصوديم أيودين. متوسط النشاط اإلشعاعي لجسيمات ألفا كان<br />
95.53<br />
بيكرل لكل متر مكعب<br />
,<br />
لكل متر مكعب وأصغر قيمة كانت<br />
أي مايعادل<br />
تعرض وتقارن بالمتوسط العالمي وهو<br />
االشعاعي.<br />
0.35.<br />
بيكو كوري لكل لتر, أكبر قيمة كانت<br />
46.46<br />
46.43<br />
55<br />
بيكرل<br />
بيكرل لكل متر مكعب .النتائج من الكواشف األخرى سوف<br />
بيكو كوري لكل لتر, جميع النتائج تدل علي تدني النشاط<br />
M.O. El-Ghossain, A.A. Abu Shammala
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 21–26<br />
University <strong>of</strong> Bahrain<br />
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong><br />
<strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences<br />
www.elsevier.com/locate/jaaubas<br />
www.sciencedirect.com<br />
ORIGINAL ARTICLE<br />
Radioactivity measurements in tap water in Gaza Strip<br />
(Al-Naser Area)<br />
Maher O. El-Ghossain *, Abedalqader A. Abu Shammala<br />
Physics Department, The Islamic University <strong>of</strong> Gaza, Gaza, Occupied Palestinian Territory<br />
Available online 23 November 2011<br />
KEYWORDS<br />
CR-39;<br />
Tap water;<br />
Radiation;<br />
Alpha concentration<br />
Abstract Ionizing radiation comes from outer space (cosmic), <strong>the</strong> ground (terrestrial), <strong>and</strong> even<br />
from within our own bodies. It is present in <strong>the</strong> air we brea<strong>the</strong>, <strong>the</strong> food we eat, <strong>the</strong> water we drink,<br />
<strong>and</strong> in <strong>the</strong> construction materials used to build our homes. Exposure to radon <strong>and</strong> its progeny is<br />
believed to be associated with increased risks <strong>of</strong> several kinds <strong>of</strong> cancer. When radon or its progeny<br />
is inhaled, lung cancer accounts <strong>for</strong> most <strong>of</strong> <strong>the</strong> total incremental cancer risk. Ingestion <strong>of</strong> radon in<br />
water is suspected <strong>of</strong> being associated with increased risk <strong>of</strong> tumors <strong>of</strong> several internal organs, primarily<br />
<strong>the</strong> stomach.<br />
In this work, <strong>the</strong> activity <strong>of</strong> alpha, beta <strong>and</strong> gamma radiation, in tap water in <strong>the</strong> north-east <strong>of</strong><br />
Gaza (Al-Naser area) were measured. For this purpose we used a solid state nuclear track detectors<br />
(CR-39) <strong>and</strong> some o<strong>the</strong>r detectors (Geiger counter, NaI detector). The average gross alpha concentration<br />
from C4-39 is 35.50 Bq/m 3 (0.95 pci/L), <strong>the</strong> maximum concentration is 64.67 Bq/m 3 , <strong>and</strong><br />
minimum concentration is 24.20 Bq/m 3 . Results obtained from all detectors, <strong>and</strong> <strong>the</strong>ir methods will<br />
be shown, <strong>and</strong> compared with <strong>the</strong> word average <strong>of</strong> 15 pci/L, all results indicate low level <strong>of</strong> activity.<br />
ª 2011 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by Elsevier B.V. All rights reserved.<br />
1. Introduction<br />
Most water sources have very low levels <strong>of</strong> radioactive contaminants<br />
(radio nuclides), levels low enough to not be considered<br />
a public health concern. Radio-nuclides emit ‘‘ionizing radiation’’,<br />
a known human carcinogen, when <strong>the</strong>y naturally decay.<br />
* Corresponding author.<br />
E-mail address: ghossain@iugaza.edu.ps (M.O. El-Ghossain).<br />
1815-3852 ª 2011 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by<br />
Elsevier B.V. All rights reserved.<br />
Peer review under responsibility <strong>of</strong> University <strong>of</strong> Bahrain.<br />
doi:10.1016/j.jaubas.2011.10.003<br />
Production <strong>and</strong> hosting by Elsevier<br />
Long-term exposure to radionuclides in drinking water may<br />
cause cancer. Of particular concern are naturally occurring<br />
uranium <strong>and</strong> <strong>the</strong> naturally occurring radium isotopes, radium-226<br />
<strong>and</strong> radium-228, which have been observed to accumulate<br />
to levels <strong>of</strong> concern in drinking water sources. Most <strong>of</strong><br />
<strong>the</strong> naturally occurring radionuclides are alpha particle emitters<br />
(e.g., <strong>the</strong> uranium isotopes <strong>and</strong> radium-226), naturally<br />
occurring beta particle emitters do occur (e.g., radium-228<br />
<strong>and</strong> potassium-40) (Environmental Protection Agency (EPA),<br />
2000; Beir, 2000). The source <strong>of</strong> naturally occurring radionuclides<br />
is <strong>the</strong> earth’s crust. Among <strong>the</strong>se radionuclides <strong>the</strong>re exist<br />
three radioactive series originating from 238 U, 235 U <strong>and</strong> 232 Th<br />
being one <strong>of</strong> <strong>the</strong> most abundant sources <strong>of</strong> naturally occurring<br />
radioactivity, <strong>the</strong> 238 U series has been widely investigated.<br />
Exposure to radionuclides from drinking water results in<br />
<strong>the</strong> increased risk <strong>of</strong> cancer. The radioactive particles (alpha,<br />
beta) <strong>and</strong> gamma photons emitted by radionuclides are called<br />
‘‘ionizing radiation’’ because <strong>the</strong>y ionize (‘‘destabilize’’) nearby
22 M.O. El-Ghossain, A.A. Abu Shammala<br />
atoms as <strong>the</strong>y travel through a cell or o<strong>the</strong>r material. In living<br />
tissue, this ionization process can damage chromosomes or<br />
o<strong>the</strong>r parts <strong>of</strong> <strong>the</strong> cell. This cellular damage can lead to <strong>the</strong><br />
death <strong>of</strong> <strong>the</strong> cell or to unnatural reproduction <strong>of</strong> <strong>the</strong> cell. Exposure<br />
to elevated uranium levels in drinking water has been<br />
shown to lead to changes in kidney function that are indicators<br />
<strong>of</strong> potential future kidney failure (Beir, 2000; Sources <strong>and</strong><br />
health effect <strong>of</strong> ionizing radiation 1980).<br />
EPA has promulgated a limit <strong>for</strong> uranium as required by<br />
<strong>the</strong> 1986 amendments to <strong>the</strong> Safe Drinking Water Act. The<br />
current st<strong>and</strong>ards (‘‘Risk Assessment <strong>of</strong> Radon in Drinking<br />
Water’’, released September 15, 1998,) are: combined radium<br />
226/228 <strong>of</strong> 5 pci/L; a gross alpha st<strong>and</strong>ard <strong>for</strong> all alphas <strong>of</strong><br />
15 pci/L, not including radon <strong>and</strong> uranium; a combined st<strong>and</strong>ard<br />
<strong>of</strong> 4 mrem/year <strong>for</strong> beta emitters (Risk assessment <strong>of</strong> radon<br />
in drinking water, 1998).<br />
2. Experimental methods<br />
Samples were collected from 40 places, from <strong>the</strong> north-west region<br />
<strong>of</strong> Gaza city, Al-Naser region <strong>of</strong> Gaza, which was divided<br />
into four regions in our survey, included Nasser west (A), Nasser<br />
east (B), Nasser shakhradwan (C), Nasser south (D). We<br />
have obtained ten samples from <strong>the</strong> houses <strong>of</strong> each area. After<br />
that, each sample was put in a one liter plastic jar to do <strong>the</strong> test<br />
<strong>of</strong> radiation activity, <strong>the</strong> detectors that used <strong>for</strong> making <strong>the</strong><br />
measurements are:<br />
(a) Solid State Nuclear Track Detectors (SSNTDs) are passive,<br />
low cost, long term method, most widely used <strong>for</strong> measuring<br />
radon <strong>and</strong> can be used <strong>for</strong> site assessment both indoors <strong>and</strong><br />
outdoors. (Durani <strong>and</strong> Ilic, 1997).<br />
The detectors are placed inside <strong>the</strong> dosimeters 1.5 cm above<br />
water. Detectors are usually exposed <strong>for</strong> 2–12 months. When<br />
alpha particles from <strong>the</strong> decay <strong>of</strong> radon <strong>and</strong> its progeny strike<br />
<strong>the</strong> detector, <strong>the</strong>y cause damage tracks. After <strong>the</strong> exposure, <strong>the</strong><br />
detector is chemically treated <strong>and</strong> <strong>the</strong> number <strong>of</strong> tracks over<br />
area counted by an optical microscope <strong>and</strong> radon concentration<br />
or gross alpha concentration is determined (David Bodansky<br />
et al., 1989). The water samples are placed in a calibrated<br />
(El-Ghossain <strong>and</strong> Abusaleh, 2007) plastic cup with plastic cover,<br />
<strong>the</strong> diameter <strong>of</strong> <strong>the</strong> cover equals 6 cm <strong>and</strong> <strong>the</strong> height <strong>of</strong> <strong>the</strong><br />
cup is 11 cm as shown in Figs. 1 <strong>and</strong> 2. The CR-39 detector is<br />
fixed under <strong>the</strong> cover facing <strong>the</strong> water sample <strong>and</strong> <strong>the</strong> radium<br />
source at <strong>the</strong> same distance <strong>of</strong> 1.5 cm, same volume, same<br />
geometry, <strong>and</strong> same temperature.<br />
The detector should remain undisturbed above <strong>the</strong> sample<br />
<strong>for</strong> at least 3 weeks. Solid State Nuclear Track Detector<br />
(CR-39) is used to measure Radon-222 or gross alpha concentration<br />
in water, soil & air at <strong>the</strong> collected sample. Each sample<br />
was put inside <strong>the</strong> cup as shown in Fig. 2. Forty detectors were<br />
exposed to <strong>for</strong>ty samples which concern <strong>the</strong> north-west region<br />
Figure 1<br />
Measurement technique <strong>for</strong> a solid radium source.<br />
Figure 2 Measurement technique using CR-39 to measure alpha<br />
activity in water.<br />
<strong>of</strong> Gaza Strip. This distribution <strong>of</strong> detectors is based on <strong>the</strong><br />
nature <strong>of</strong> <strong>the</strong> tap water type <strong>and</strong> geological location. The<br />
detectors are left in isolated place in <strong>the</strong> laboratory, about<br />
74 days during <strong>the</strong> months April, May <strong>and</strong> June <strong>of</strong> 2005; this<br />
is <strong>the</strong> exposure time to allow radon gas to come to an equilibrium<br />
level with radioactive parents. After <strong>the</strong> exposition was<br />
finished, <strong>the</strong> <strong>for</strong>ty detectors were collected <strong>and</strong> chemically<br />
etched using a 6 M (Mole) solution <strong>of</strong> NaOH, at <strong>the</strong> temperature<br />
<strong>of</strong> 70 °C, <strong>for</strong> 6 h, (st<strong>and</strong>ard etching condition). The CR-39<br />
detectors were mounted vertically in a stainless steel spring <strong>and</strong><br />
<strong>the</strong>n immersed in <strong>the</strong> etching solution. At <strong>the</strong> end <strong>of</strong> <strong>the</strong> etching<br />
process <strong>the</strong> detectors were washed thoroughly with distilled<br />
water <strong>and</strong> <strong>the</strong>n left to dry. Tracks in each detector counted<br />
visually using an optical microscope with a power <strong>of</strong><br />
(40 · 10). We counted <strong>the</strong> average number <strong>of</strong> tracks in 1 cm 2 .<br />
(b) Ano<strong>the</strong>r method used to measure alpha <strong>and</strong> beta activity<br />
in water samples was using <strong>the</strong> Electra Plus (DP6AD, measured<br />
CPM as Geiger counter, LLD 3-12 CPM) (Nuclear<br />
Energy <strong>and</strong> Radiation Protection (NERP), 2005). It is a portable<br />
rate meter based on <strong>the</strong> variety <strong>of</strong> GM <strong>and</strong> scintillation<br />
probes. A rectangular wooden box was filled with a water sample.<br />
The scintillation probes were put on <strong>the</strong> surface <strong>of</strong> <strong>the</strong><br />
water sample <strong>the</strong> window area equals to 100 cm 2<br />
(c) Also field space digital spectrometer (Dose rate 10 nSv/<br />
h-10 Sv/h) (Nuclear Energy <strong>and</strong> Radiation Protection<br />
(NERP), 2005) was used to measure <strong>the</strong> activity <strong>of</strong> gamma<br />
radiation in water. The probe <strong>of</strong> <strong>the</strong> device was put over <strong>the</strong><br />
surface <strong>of</strong> <strong>the</strong> water. The distance between <strong>the</strong> probe <strong>and</strong> <strong>the</strong><br />
water sample in <strong>the</strong> cup equals 0 cm.<br />
(d) The scintillation counter (Na I) (Nuclear Energy <strong>and</strong><br />
Radiation Protection (NERP), 2005) is a very common tool<br />
in nuclear <strong>and</strong> particle physics. It is used <strong>for</strong> measuring <strong>the</strong><br />
energies <strong>of</strong> gamma-ray photons <strong>and</strong> o<strong>the</strong>r elementary particles<br />
(Bell, 2005). The intensity <strong>of</strong> <strong>the</strong> light is proportional to <strong>the</strong><br />
amount <strong>of</strong> energy deposited in <strong>the</strong> crystal by radiation. The<br />
cup <strong>of</strong> <strong>the</strong> sample was used to taking a spectrum which resulted<br />
from <strong>the</strong> water by using scintillation counter where<br />
<strong>the</strong> probe <strong>of</strong> <strong>the</strong> device was put on <strong>the</strong> surface <strong>of</strong> water. The<br />
distances between <strong>the</strong> probe <strong>and</strong> <strong>the</strong> water sample in <strong>the</strong> cup<br />
equals 1 cm. The measurements obtained from <strong>the</strong> scintillation<br />
counter confirm <strong>the</strong>re is low level radiation <strong>of</strong> gamma radiation<br />
in <strong>the</strong> water in north-west <strong>of</strong> Gaza Strip. The basic technique<br />
<strong>for</strong> this measurement is to count <strong>the</strong> number <strong>of</strong> pulses<br />
during a fixed time interval as a function <strong>of</strong> pulse height,<br />
<strong>and</strong> make a graph <strong>of</strong> <strong>the</strong> number <strong>of</strong> pulses versus pulse height.<br />
(e) Geiger-Mu¨ller counters are used where <strong>the</strong> mechanism<br />
<strong>and</strong> methods are based on <strong>the</strong> interaction <strong>of</strong> <strong>the</strong> radiation with<br />
matter. Since ionization is an important process <strong>for</strong> radioactivity,<br />
most detectors exploit <strong>the</strong> signals generated due to ions
Radioactivity measurements in tap water in Gaza Strip (Al-NASER) 23<br />
Table 1 Final results <strong>for</strong> <strong>the</strong> four regions are <strong>of</strong> min, max <strong>and</strong> mean (E) concentrations from CR-39 detectors <strong>for</strong> (A), (B), (C) <strong>and</strong> (D)<br />
regions.<br />
Location No. <strong>of</strong> detectors Min. concentr. (Bq/m 3 ) Max. concentr. (Bq/m 3 ) E (Bq/m 3 ) S.D. (Bq/m 3 )<br />
A 10 21.32 46.33 32.59 1.77<br />
B 10 24.19 71.34 33.08 3.10<br />
C 10 24.22 103.73 45.59 7.60<br />
D 10 24.20 38.95 30.48 1.40<br />
Average 24.20 64.67 35.50 3.45<br />
<strong>and</strong> electrons all <strong>the</strong>se detectors calibrated with normal radioactive<br />
sources Co, Cs, <strong>and</strong> Na.<br />
3. Calculations <strong>of</strong> gross alpha concentration using CR-39<br />
Gross alpha contamination (El-Ghossain <strong>and</strong> Abusaleh, 2007)<br />
in water sample is measured in terms <strong>of</strong> Bq/m 3 . Determination<br />
<strong>of</strong> gross alpha concentration C w <strong>and</strong> <strong>the</strong> st<strong>and</strong>ard deviation r<br />
(S.D.) in a sample <strong>of</strong> water using nuclear track detector is done<br />
by <strong>the</strong> following Eq. (1).<br />
<br />
Bq<br />
C w ¼<br />
C <br />
RT R qw<br />
<br />
ð1Þ<br />
m 3 q R Tw<br />
sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi<br />
P n<br />
k<br />
r n ðS:D:Þ ¼<br />
ðX k<br />
XÞ 2<br />
ð2Þ<br />
n 1<br />
where C w , Concentration <strong>of</strong> activity <strong>of</strong> 222 Rn in a water sample;<br />
C R , Concentration <strong>of</strong> activity <strong>of</strong> 226 Ra (solid radon source)<br />
equal 800 Bq/m 3 ; q R , Track density (number <strong>of</strong> tracks/m 2 )in<br />
detectors exposed to 226 Ra; T R , Exposure time (in days) <strong>of</strong><br />
detectors exposed to 226 Ra, equal 72 days; q w , Track density<br />
(number <strong>of</strong> tracks/m 2 ) in detectors exposed to water samples;<br />
T w , Exposure time (in days) <strong>of</strong> detectors exposed to in water<br />
samples, equal 74 days; X K , Activity concentration <strong>of</strong> a sample;<br />
X, Mean activity concentration <strong>of</strong> n samples; N, number<br />
<strong>of</strong> samples <strong>and</strong> r n (S.D.): st<strong>and</strong>ard de´viation.<br />
4. Calibration <strong>of</strong> CR-39 detectors<br />
Two detectors were exposed to a known activity <strong>of</strong> 226 Ra (solid<br />
radon source) <strong>for</strong> a determined period <strong>of</strong> time. Then <strong>the</strong>se<br />
detectors were treated by chemical etching. The average numbers<br />
<strong>of</strong> tracks/cm 2 were calculated. These detectors were inserted<br />
in <strong>the</strong> same volume (plastic cup) <strong>of</strong> <strong>the</strong> investigated<br />
sample, so <strong>the</strong>y considered as a calibration st<strong>and</strong>ard. (El-<br />
Ghossain <strong>and</strong> Abusaleh, 2007; Raed M. Abusaleh 2005; Mahmoud<br />
Rasas, 2003; Nabil Hamed, 2005). Similar method is<br />
also used <strong>for</strong> detector technique as in (El-Ghossain <strong>and</strong> Abusaleh,<br />
2007) to determine <strong>the</strong> calibration constant (factor) K.<br />
This is derived by dividing <strong>the</strong> track density by <strong>the</strong> total exposure<br />
<strong>of</strong> radon source as in Eq. (3).<br />
<br />
K ¼<br />
C RT R<br />
q R<br />
<br />
; ð3Þ<br />
Then Eq. (1) <strong>for</strong> radon concentration becomes as follows.<br />
<br />
Bq q<br />
C w ¼ K w<br />
m 3 1;2<br />
ð4Þ<br />
T w<br />
where<br />
k 1;2 ¼ðk 1 þ k 2 Þ=2<br />
The calibration factor (K) is determined, where two CR-39<br />
detectors are exposed to 226 Ra (Radium Source) <strong>of</strong> activity<br />
concentration 800 Bq/m 3 (from factory) <strong>for</strong> 72 days. The calibration<br />
process <strong>for</strong> detectors used in this survey was carried<br />
out at <strong>the</strong> nuclear laboratory at physics department in The Islamic<br />
University <strong>of</strong> Gaza (IUG). The density <strong>of</strong> tracks <strong>for</strong> <strong>the</strong><br />
two detectors equals 19.6 · 10 6 tracks/m 2 <strong>and</strong><br />
18.6 · 10 6 tracks/m 2 , <strong>and</strong> <strong>the</strong> average calibration factor K is<br />
3.06 · 10 3 [Bq/m 3 day/tracks/m 2 ], <strong>and</strong> <strong>the</strong> st<strong>and</strong>ard deviation<br />
is 10.5%. Substituting calibration constant in equation, <strong>the</strong><br />
activity concentration <strong>of</strong> alpha particles in water becomes:<br />
<br />
<br />
Bq<br />
C w ¼ 3:06 10 3 q w<br />
ð5Þ<br />
m 3<br />
T w<br />
Where 1 pci/L = 37 Bq/m 3 is used as conversion unit. E in <strong>the</strong><br />
Table 1 is <strong>the</strong> average concentration <strong>and</strong> (S.D.) is <strong>the</strong> st<strong>and</strong>ard<br />
deviation.<br />
4.1. Results from CR-39 detector <strong>and</strong> o<strong>the</strong>r detectors<br />
Gross alpha concentration in water samples were calculated<br />
using Eq. (5) <strong>for</strong> various locations. The minimum <strong>and</strong> <strong>the</strong> maximum<br />
gross alpha concentration in tap water samples measured<br />
in Bq/m 3 units are tabulated in <strong>the</strong> Table 1 as well as<br />
<strong>the</strong> mean value <strong>of</strong> gross alpha concentration (E) <strong>and</strong> St<strong>and</strong>ard<br />
Deviation (S.D.) <strong>for</strong> each location in this study which is mentioned<br />
(El-Ghossain <strong>and</strong> Abusaleh, 2007).<br />
The gross alpha concentration <strong>for</strong> each location was calculated<br />
by summing individual gross alpha concentration values<br />
<strong>of</strong> each detector, <strong>and</strong> <strong>the</strong> sums <strong>of</strong> <strong>the</strong> values were divided by<br />
<strong>the</strong> total number <strong>of</strong> detectors, results shown in Table 2. The<br />
st<strong>and</strong>ard deviation was also (El-Ghossain <strong>and</strong> Abusaleh,<br />
2007) calculated by Eq. (2). Fig. 3 shows <strong>the</strong> average gross alpha<br />
concentration <strong>for</strong> C <strong>and</strong> B locations found higher than D.<br />
The results indicate <strong>the</strong> range: from minimum 24.20 Bq/m 3 to<br />
maximum 64.67 Bq/m 3 in gross alpha concentration in each<br />
location which is very low level radiation, if to compare with<br />
<strong>the</strong> world average <strong>of</strong> 10 kBq/m 3 . This variation in gross alpha<br />
concentration inside <strong>the</strong> locations is mainly due to <strong>the</strong> different<br />
places, <strong>and</strong> different contamination level <strong>of</strong> tap water from<br />
environment.<br />
The results obtained from field space mentioned above<br />
showed <strong>the</strong> relation between <strong>the</strong> gamma activity in water sample<br />
in unit <strong>of</strong> (n Sv/h) as in Fig. 4, <strong>the</strong> minimum, maximum<br />
gamma concentration in tap water, mean value concentration<br />
<strong>and</strong> st<strong>and</strong>ard deviation, we see that, gamma activity in all Naser<br />
having <strong>the</strong> same values due mainly to <strong>the</strong> same exposed<br />
background radiation.<br />
Results <strong>of</strong> <strong>the</strong> alpha activities in water sample in unit <strong>of</strong><br />
(CPS) (which can be converted CPM) obtained from Electra
24 M.O. El-Ghossain, A.A. Abu Shammala<br />
Table 2 All results calculated from CR-39 <strong>for</strong> (A), (B), (C)<br />
<strong>and</strong> (D) regions.<br />
Cw Bq/m 3 No. <strong>of</strong> tracks 1 cm 2 Slides no. Regions<br />
24.19 59 1 Part ‘‘A’’ (Nasser West)<br />
39.77 97 2<br />
27.06 66 3<br />
38.13 93 4<br />
31.98 78 5<br />
21.32 52 6<br />
31.98 78 7<br />
33.21 81 8<br />
46.33 113 9<br />
31.98 78 10<br />
31.16 76 11 Part ‘‘B’’ (Nasser East)<br />
24.19 59 12<br />
25.42 62 13<br />
71.34 174 14<br />
27.88 68 15<br />
24.19 59 16<br />
25.42 62 17<br />
38.13 93 18<br />
38.13 93 19<br />
25.01 61 20<br />
31.98 78 21 Part ‘‘C’’ (Nasser South)<br />
74.21 181 22<br />
27.88 68 23<br />
27.47 67 24<br />
37.72 92 25<br />
27.06 66 26<br />
24.19 59 27<br />
27.88 68 28<br />
103.73 253 29<br />
73.80 180 30<br />
38.95 95 31 Part ‘‘D’’<br />
24.19 59 32 (Nasser Shakhradwan)<br />
27.06 66 33<br />
30.75 75 34<br />
24.19 59 35<br />
37.31 91 36<br />
35.67 87 37<br />
28.29 69 38<br />
27.06 66 39<br />
31.16 79 40<br />
35.50 86.50 Mean value ‘‘E’’<br />
3.45 7.19 St<strong>and</strong>ard deviation<br />
Gross Alpha Contamination(Bq/m3)<br />
120<br />
100<br />
80<br />
60<br />
40<br />
20<br />
0<br />
Figure 3<br />
A B C D Avg<br />
The Regions <strong>of</strong> Nasser<br />
Min.con.<br />
Max.con.<br />
Mean v."E"<br />
S.D.<br />
Gross alpha concentration in each location <strong>and</strong> S.D.<br />
Gamma contamination (nSv/h)<br />
80<br />
70<br />
60<br />
50<br />
40<br />
30<br />
20<br />
10<br />
0<br />
A B C D avg<br />
The Region <strong>of</strong> Nasser<br />
min.con<br />
max.con<br />
E<br />
S.D<br />
Figure 4 Gamma concentration (nSv/h) in each location <strong>and</strong> S.<br />
Alpha Activity (C.P.S)<br />
Beta Activity (C.P.S)<br />
0.07<br />
0.06<br />
0.05<br />
0.04<br />
0.03<br />
0.02<br />
0.01<br />
0<br />
Figure 5<br />
4<br />
3.5<br />
3<br />
2.5<br />
2<br />
1.5<br />
1<br />
0.5<br />
0<br />
Figure 6<br />
A B C D Avg<br />
The Regions <strong>of</strong> Nasser<br />
Alpha activity in Nasser regions (Electra Plus).<br />
A B C D Avg<br />
The regions <strong>of</strong> Gaza<br />
min<br />
max<br />
mean<br />
S.D<br />
min.con<br />
max.con.<br />
E<br />
S.D.<br />
Beta activity in Nasser regions (from Electra Plus).<br />
Plus <strong>and</strong> <strong>the</strong> relation among regions are shown in <strong>the</strong> Fig. 5.<br />
We can see that <strong>the</strong> alpha activity in Nasser Shakhradwan<br />
(C) is greater than in o<strong>the</strong>r regions <strong>and</strong> in Nasser East (B) –<br />
lower than in o<strong>the</strong>r region in activity values <strong>and</strong> <strong>the</strong> difference<br />
is still less than <strong>the</strong> st<strong>and</strong>ard deviation.<br />
Fig. 6 shows results <strong>of</strong> <strong>the</strong> beta activity in water samples in<br />
unit <strong>of</strong> (CPS) obtained from Electra Plus <strong>and</strong> <strong>the</strong> relation<br />
among regions. The results obtained from Electra Plus show<br />
that <strong>the</strong> beta radiation level in <strong>the</strong>se regions is very low if to<br />
compare with o<strong>the</strong>r regions.<br />
The results obtained from Geiger counter showed <strong>the</strong> relation<br />
between <strong>the</strong> radiation activities in water in unit <strong>of</strong> (CPM)<br />
<strong>and</strong> (kBq) calibrated. (The 37 kBq <strong>of</strong> Cesium radioactive<br />
source is used <strong>for</strong> calibration by multiplying by X (0.102) kBq).<br />
The results from all detectors indicate that, <strong>the</strong>re is low level<br />
radiation in <strong>the</strong> studied area, because it is below 10 kBq/m 3 .<br />
Fig. 7 shows <strong>the</strong>re is low level radiation in water samples in<br />
<strong>the</strong> studied area in comparison to each o<strong>the</strong>r. The activities
Radioactivity measurements in tap water in Gaza Strip (Al-NASER) 25<br />
The concentration <strong>of</strong> Radiation<br />
Activity (C.P.M)<br />
14<br />
12<br />
10<br />
8<br />
6<br />
4<br />
2<br />
0<br />
A B C D Avg<br />
The Regions <strong>of</strong> Nasser<br />
min.con.<br />
max.con<br />
E<br />
S.D.<br />
Figure 7 Radiation activity in Nasser regions in CPM <strong>for</strong><br />
comparison.<br />
Figure 8 Spectrum <strong>of</strong> water sample number-25 in Nasser<br />
Shakhradwan (C).<br />
Figure 9<br />
Spectrum <strong>of</strong> background in surrounding air.<br />
in <strong>the</strong>se samples are very low because it is far away from rocks<br />
which contain Uranium <strong>and</strong> o<strong>the</strong>r radioactive material.<br />
The results obtained from scintillation counter showed that<br />
<strong>the</strong>re is low level radiation in <strong>the</strong> studied area. (Region, y-axis<br />
is <strong>the</strong> number <strong>of</strong> counts <strong>of</strong> radiation <strong>and</strong> x-axis is <strong>the</strong> channel<br />
number (energy), spectrum from background, sources were taken<br />
<strong>for</strong> calibration, 137 Cs <strong>and</strong> 60 Co)<br />
In Fig. 8, <strong>the</strong> energy spectrum obtained <strong>for</strong> a water sample,<br />
each spectrum compared with each sample spectra <strong>and</strong> <strong>the</strong> calibration<br />
spectra, which showed no peaks appear in <strong>the</strong> sample<br />
spectra, that indicates that <strong>the</strong> water contain very low level <strong>of</strong><br />
radiation.<br />
The measurements <strong>of</strong> gamma rays made by means <strong>of</strong> <strong>the</strong><br />
scintillation counter confirm that <strong>the</strong>re is low level <strong>of</strong> radiation<br />
because <strong>the</strong> water sample level differs slightly from <strong>the</strong> background<br />
level, see Fig. 9.<br />
5. Conclusion<br />
The study purpose was to measure <strong>the</strong> radiation activity <strong>and</strong> to<br />
find out an approximate mean <strong>and</strong> range <strong>of</strong> radiation concentration<br />
in tap water at Nasser region in Gaza city. Only CR-39<br />
determines concentration <strong>of</strong> alpha particles in terms <strong>of</strong> quantity<br />
in Bq/m 3 , all o<strong>the</strong>r methods give <strong>the</strong> activity <strong>of</strong> radiation<br />
water samples in terms CPM.<br />
Nasser region was divided into four areas, in our survey, included,<br />
Nasser west (A), Nasser east (B), Nasser shakhradwan<br />
(C), <strong>and</strong> Nasser south (D). We used five types <strong>of</strong> detectors.<br />
These detectors <strong>and</strong> <strong>the</strong>ir methods are already explained earlier:<br />
Solid State Nuclear Track Detectors (CR-39), Geiger<br />
counter, Portable Gamma Spectrometer, Scintillation counter<br />
<strong>and</strong> Portable Electra Plus.<br />
In <strong>the</strong> present work all detector results indicate <strong>the</strong> low level<br />
<strong>of</strong> radiation activity in <strong>the</strong> Al-Nasser area. In general most<br />
water samples have very low levels <strong>of</strong> <strong>the</strong> natural radionuclides,<br />
<strong>and</strong> <strong>the</strong> average alpha concentration was 35.95 Bq/m 3<br />
or 0.95 pci/L <strong>for</strong> Al-Nasser <strong>for</strong> <strong>the</strong> four regions <strong>of</strong> study, levels<br />
low enough to not be considered a public health concern as<br />
mentioned earlier in this reference. (‘‘Risk Assessment <strong>of</strong> Radon<br />
in Drinking Water’’, released September 15, 1998).<br />
We are interested mainly in measuring alpha concentration<br />
which measured in Bq/m 3 using CR-39 accurately by counting<br />
alpha tracks, but in general way beta <strong>and</strong> gamma are measured<br />
<strong>for</strong> comparison purposes <strong>of</strong> samples with each o<strong>the</strong>r <strong>and</strong> with<br />
<strong>the</strong> calibration sources <strong>and</strong> not exactly like CR-39.<br />
It is shown that <strong>the</strong> results <strong>of</strong> <strong>the</strong> measurements, <strong>the</strong> radiation<br />
concentration in water vary in <strong>the</strong> low level scale.<br />
The main results <strong>of</strong> radiation measurements in water observed<br />
in <strong>the</strong> present study can be summarized as follows:<br />
1. The radiation concentration in <strong>the</strong> tap water at Nasser is<br />
typically in values close to those normally found in o<strong>the</strong>r<br />
countries <strong>and</strong> much lower than <strong>the</strong> word average 10 kBq/<br />
m 3 (UNSCEAR, 1986).<br />
2. The higher radiation concentration in water at Nasser<br />
south 103.75 Bq/m 3 or 2.8 pci/L, does not create any special<br />
environment <strong>and</strong> or health problem because it is less than<br />
<strong>the</strong> average <strong>of</strong> 10 k Bq/m 3 hopefully, <strong>and</strong> EPA <strong>of</strong> 15 pci/L<br />
<strong>for</strong> gross <strong>of</strong> all alpha st<strong>and</strong>ards, <strong>and</strong> 5 pci/L <strong>for</strong> alphas from<br />
combined radium 226/228.<br />
3. We would like to do more specific measurements on some<br />
<strong>of</strong> naturally occurring radioactive isotopes like potassium,<br />
uranium, radium <strong>and</strong> o<strong>the</strong>rs. This required more equipment<br />
which should be more accurate <strong>for</strong> this low level <strong>of</strong><br />
radiation.<br />
Acknowledgments<br />
Thanks to <strong>the</strong> department <strong>of</strong> physics, <strong>and</strong> <strong>the</strong> dean <strong>of</strong> scientific<br />
research at <strong>the</strong> Islamic University <strong>of</strong> Gaza, <strong>for</strong> <strong>the</strong> partial sup-
26 M.O. El-Ghossain, A.A. Abu Shammala<br />
port <strong>and</strong> help. We thank also <strong>the</strong> Palestinian Energy Authority<br />
<strong>for</strong> <strong>the</strong>ir help in using <strong>the</strong>ir equipments.<br />
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<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 27-31<br />
تركيب<br />
أغشية رقيقة من كبريتيد الكادميوم بلوراتها الجسيمية في حدود النانو<br />
بتقنية الحمام الكيميائي ودراسة خواصها التركيبية والضوئية<br />
عبد اهلل<br />
2<br />
1<br />
الحسام ، صالح عبد الجبار جاسم<br />
1<br />
قسم الكيمياء<br />
، كلية العلوم التطبيقية ، جامعة ذمار، اليمن<br />
2<br />
قسم الفيزياء ، كلية العلوم التطبيقية ، جامعة ذمار، اليمن<br />
الملخص :<br />
رسبت أغشية رقيقة<br />
من كبريتيد الكادميوم بلوراتها الجسيمية في حدود النانو بطريقة الحمام الكيميائي على<br />
شرائح زجاجية وكانت درجة حرارة الترسيب<br />
اليوريا الكبريتية.<br />
الجسيمية في حدود النانو.<br />
الى<br />
80 o C<br />
وزمن الترسيب<br />
6h<br />
باستخدام تركيبتين<br />
وقد تم التعرف على جميع متغيرات الحمام الكيميائي والتي أعطت أغشية<br />
مختلفتين من<br />
رقيقة بلوراتها<br />
أثبتت تحليالت الخواص الضوئية أن فجوة الطاقة لألغشية المحضرة عانت<br />
انحراف باتجاه اللون األزرق كما حسبت البلورات الجسيمية لألغشية المحضرة وتراوحت قيمها بين<br />
62823<br />
نانومتر. 8<br />
A.M.A. Al-Hussam, S.Abdul-Jabbar Jassim
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 27–31<br />
University <strong>of</strong> Bahrain<br />
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong><br />
<strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences<br />
www.elsevier.com/locate/jaaubas<br />
www.sciencedirect.com<br />
Syn<strong>the</strong>sis, structure, <strong>and</strong> optical properties <strong>of</strong> CdS thin films<br />
nanoparticles prepared by chemical bath technique<br />
Abdullah M.A. Al-Hussam a , Salah Abdul-Jabbar Jassim b, *<br />
a Chemistry Department, Faculty <strong>of</strong> <strong>Applied</strong> Science, Thamar University, Thamar, Yemen<br />
b Physics Department, Faculty <strong>of</strong> <strong>Applied</strong> Science, Thamar University, Thamar, Yemen<br />
Available online 13 January 2012<br />
KEYWORDS<br />
Chemical bath deposition;<br />
CdS thin films;<br />
Nanoparticles;<br />
Structural <strong>and</strong> optical studies<br />
Abstract CdS nanocrystalline thin films were deposited onto glass substrates by chemical bath<br />
deposition (CBD). The films deposited at 80 °C <strong>for</strong> 6 h with two different concentrations <strong>of</strong><br />
thiourea. The deposition parameters were optimized. The obtained films were characterized <strong>for</strong><br />
structural <strong>and</strong> optical properties, X-ray diffraction patterns revealed that <strong>the</strong> films were nanocrystalline<br />
in nature with cubic structures. A blue shift in <strong>the</strong> b<strong>and</strong> gap was observed in <strong>the</strong> UV–visible<br />
absorption spectra indicating <strong>the</strong> <strong>for</strong>mation <strong>of</strong> nano particles <strong>of</strong> sizes between 3.826 <strong>and</strong> 8 nm.<br />
ª 2011 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by Elsevier B.V. All rights reserved.<br />
1. Introduction<br />
Semiconductors nano-particles (also known as quantum dots),<br />
belong to state <strong>of</strong> matter in <strong>the</strong> transition region between<br />
molecules <strong>and</strong> solids, have attracted a great deal <strong>of</strong> attention because<br />
<strong>of</strong> <strong>the</strong>ir unique electrical <strong>and</strong> optical properties, compared<br />
to bulk materials (Alivisatos, 1996). Their electrical <strong>and</strong> optical<br />
properties are directly associated with <strong>the</strong> quantum confinement<br />
<strong>of</strong> charge carriers leading to <strong>the</strong> blue shift <strong>of</strong> <strong>the</strong> b<strong>and</strong> gap with<br />
<strong>the</strong> shrinkage <strong>of</strong> <strong>the</strong>ir size (Kotkata et al., 2009). Particularly<br />
When <strong>the</strong> dimension <strong>of</strong> <strong>the</strong> semiconductor quantum dots<br />
* Corresponding author.<br />
E-mail address: salahjassim200@yahoo.com (S.A-J Jassim).<br />
1815-3852 ª 2011 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by<br />
Elsevier B.V. All rights reserved.<br />
Peer review under responsibility <strong>of</strong> University <strong>of</strong> Bahrain.<br />
doi:10.1016/j.jaubas.2011.10.001<br />
Production <strong>and</strong> hosting by Elsevier<br />
reduced close to characteristic length known as <strong>the</strong> exciton Bohr<br />
diameter, <strong>the</strong>se characteristic lengths are usually in <strong>the</strong> range <strong>of</strong> a<br />
few nanometers, <strong>the</strong>re will be large changes in <strong>the</strong>ir properties,<br />
this effect changes <strong>the</strong> surface to volume ration <strong>and</strong> it also shifts<br />
electronic energy levels towards higher energy leading to an increase<br />
in <strong>the</strong> b<strong>and</strong> gap (Alivisatos, 1996). CdS as a semiconductor<br />
material has received much attention due to its direct b<strong>and</strong><br />
gap resulting in emission in <strong>the</strong> visible wavelength. CdS nanostructures<br />
are being widely investigated <strong>for</strong> applications in semiconductor<br />
laser (Dunan et al., 2003), nonlinear optical devices<br />
(Grohs et al., 1994), biological applications (Santos et al.,<br />
2008) display devices (Schmitt-Rink et al., 1989) <strong>and</strong> as window<br />
materials <strong>for</strong> hetero-junction solar cells because it has a high<br />
absorption coefficient (Xiaoxia et al., 2010).<br />
In recent years, considerable ef<strong>for</strong>ts have been made to<br />
syn<strong>the</strong>size CdS nanostructures by several methods such as,<br />
dc- sputtering (Ghosh et al., 2006), solvo<strong>the</strong>rmal route (Ujjal<br />
et al., 2003), sonochemical (Raghvendra et al., 2010) <strong>and</strong> chemical<br />
bath deposition (Dongre et al., 2009). The chemical bath<br />
deposition (CBD) is <strong>the</strong> deposition technique most widely employed<br />
to obtain CdS thin films .The CBD process is a simple<br />
<strong>and</strong> inexpensive technique to obtain homogeneous, hard,<br />
adherent, transparent <strong>and</strong> stoichiometric CdS thin films.<br />
Typically, chemically deposited CdS thin films are <strong>for</strong>med from
28 A.M.A. Al-Hussam, S.Abdul-Jabbar Jassim<br />
<strong>the</strong> reaction between a cadmium salt <strong>and</strong> thiourea in an ammoniacal<br />
alkaline solution. The main role <strong>of</strong> ammonia in <strong>the</strong> CBD<br />
process is as complexing agent <strong>for</strong> <strong>the</strong> cadmium ions in <strong>the</strong><br />
reaction solution. It has been reported that CdS may have ei<strong>the</strong>r<br />
cubic or hexagonal structure depending on <strong>the</strong> syn<strong>the</strong>sis<br />
conditions.<br />
In this work, we report <strong>the</strong> CBD preparation <strong>of</strong> nanostructure<br />
CdS thin films deposited on <strong>the</strong> glass substrates using a<br />
mixed aqueous solution <strong>of</strong> cadmium chloride, thiourea <strong>and</strong><br />
ammonium chloride. Structural <strong>and</strong> optical properties have<br />
been investigated.<br />
2. Experimental detail<br />
CdS thin films are deposited on glass substrates using CBD at<br />
various concentrations <strong>of</strong> thiourea. The substrates used <strong>for</strong> <strong>the</strong><br />
deposition <strong>of</strong> CdS thin films were (35 · 25 · 1) mm commercial<br />
glass slides. Be<strong>for</strong>e <strong>the</strong> deposition <strong>the</strong> substrates must be<br />
cleaned using nitric acid <strong>for</strong> 48 h, scoop water followed by distilled<br />
water <strong>and</strong> finally dried in air. Aqueous solutions <strong>of</strong><br />
0.02 M cadmium chloride with 0.05 M ammonium chloride<br />
NH3Cl in 100 ml distilled water. Then ammonia solution <strong>of</strong><br />
0.55 M as a complexing agent in 50 ml distilled water was<br />
added to <strong>the</strong> solution to adjust <strong>the</strong> PH value <strong>of</strong> <strong>the</strong> bath to<br />
9. The solution was continuously stirred. Then add 0.05 M<br />
thiourea (NH 2 ) 2 CS. Solution was mixed with a magnetic stirrer<br />
<strong>and</strong> after obtaining a clear homogenized bath, <strong>the</strong> stirrer<br />
was turned <strong>of</strong>f <strong>and</strong> glass slides were placed in <strong>the</strong> bath vertically.<br />
The solution temperature was kept constant at 80 °C<br />
<strong>for</strong> given time <strong>of</strong> deposition 6 h .After <strong>the</strong> deposition <strong>the</strong> samples<br />
were pulled out from <strong>the</strong> bath <strong>and</strong> washed with distilled<br />
water <strong>and</strong> dried in air. The CdS films were deposited <strong>for</strong> different<br />
concentrations <strong>of</strong> (NH 2 ) 2 CS as shown in Table 1.<br />
The possible chemical reaction that takes place to produce<br />
CdS films may be as follows:<br />
CdCl 2 þ 4NH 3 ! CdðNH 3 Þ 4<br />
Cl 2<br />
ð1Þ<br />
½CdðNH 3 Þ 4<br />
Š þ2 ! Cdþ 2 þ 4NH 3<br />
NH 3 þ H 2 O ! NH 4 þ 2 þ OH<br />
Cdþ 2 þ 2OH ! CdðOHÞ 2<br />
ð4Þ<br />
ðNH 2 Þ 2<br />
CS þ 2OH !½HSŠ þ þ H 2 O þ CH 2 N 2 ð5Þ<br />
½HSŠ þ þ OH ! S 2 þ H 2 O ð6Þ<br />
½CdðNH 3 Þ 4<br />
Š þ2 þ S 2 ! CdS þ NH 3<br />
ð7Þ<br />
The deposited CdS thin films are uni<strong>for</strong>m, light yellow in<br />
color, highly adhesive, smooth <strong>and</strong> reflecting. For thickness<br />
measurement, gravimetric weight different method with <strong>the</strong><br />
ð2Þ<br />
ð3Þ<br />
relation t = m/(q·A) where, m is <strong>the</strong> mass <strong>of</strong> <strong>the</strong> film<br />
deposited on <strong>the</strong> substrate in g, A <strong>the</strong> area <strong>of</strong> <strong>the</strong> deposited film<br />
in cm 2 <strong>and</strong> q <strong>the</strong> density <strong>of</strong> <strong>the</strong> deposited material (CdS =<br />
4.84 g/cm 3 ).thickness <strong>of</strong> <strong>the</strong> films were 434.7 nm <strong>and</strong><br />
453.36 nm <strong>for</strong> samples (a) <strong>and</strong> (b) respectively.<br />
Optical properties <strong>of</strong> chemical bath deposited CdS thin<br />
films were measured at room temperature by using UV/VIS<br />
spectrophotometer Cary 50 Cm-Exlena in <strong>the</strong> wavelength<br />
range <strong>of</strong> (300–900 nm). X- ray diffraction pattern <strong>of</strong> <strong>the</strong> dry<br />
nanopartical powder was obtained using Siemens D5005<br />
X-ray diffract meter with CuKa radiation (k = 0.1542 nm).<br />
3. Results <strong>and</strong> discussion<br />
3.1. Optical studies<br />
The optical studies <strong>of</strong> <strong>the</strong> CdS films were per<strong>for</strong>med using <strong>the</strong><br />
transmission <strong>and</strong> absorption spectra observed in <strong>the</strong> wavelength<br />
range 300–900 nm.<br />
Fig. 1 shows <strong>the</strong> transmission spectra <strong>of</strong> CdS films, it can be<br />
seen that <strong>the</strong> films present high transmission (72–85%) in <strong>the</strong><br />
visible range which is good <strong>for</strong> opt-electronic devices, especially<br />
<strong>for</strong> solar cell window layers. <strong>and</strong> have sharp fall at <strong>the</strong><br />
b<strong>and</strong> edge, which is an indication <strong>of</strong> good crystallinity <strong>of</strong><br />
CdS in <strong>the</strong> films.<br />
Absorption spectra <strong>of</strong> <strong>the</strong> two syn<strong>the</strong>sized CdS films are<br />
shown in Fig. 2 it can be seen that <strong>the</strong> films show peaks at<br />
478,470 <strong>for</strong> sample (a) <strong>and</strong> (b) respectively that means <strong>the</strong><br />
absorption edge shifted toward blue .The blue shift can be<br />
attributed to <strong>the</strong> exitonic absorbance due to <strong>the</strong> quantum confinement<br />
at low dimensions compared to its bulk counterparts.<br />
The b<strong>and</strong>-gap value (E g ) <strong>of</strong> <strong>the</strong> deposited films were determined<br />
by analyzing <strong>the</strong> optical data with <strong>the</strong> expression <strong>for</strong><br />
<strong>the</strong> optical absorbance a <strong>and</strong> <strong>the</strong> photon energy ht using Taucs<br />
<strong>for</strong>mula relation (Tauc <strong>and</strong> Abeies, 1970).<br />
aht ¼ Cðht E g Þ n ð8Þ<br />
where C is a constant <strong>and</strong> <strong>the</strong> exponent n depends on type <strong>of</strong><br />
transition, n may have values 1/2, 2, 3/2 <strong>and</strong> 3 corresponding<br />
to allowed direct, allowed indirect, <strong>for</strong>bidden direct <strong>and</strong> <strong>for</strong>bidden<br />
indirect transitions, respectively. As CdS nanoparticles<br />
have direct allowed transitions we choose n = 1/2 .The b<strong>and</strong><br />
gap <strong>of</strong> CdS nanoparticals was determined by extrapolating<br />
<strong>the</strong> straight line portion <strong>of</strong> <strong>the</strong> (aht) 2 vs. (ht) graphs to <strong>the</strong><br />
(ht) axis as shown in <strong>the</strong> Fig. 3. It can be observed from<br />
Fig. 3 that <strong>the</strong> b<strong>and</strong> gap <strong>of</strong> CdS nanoparticales is 3.2 eV <strong>and</strong><br />
2.6 eV <strong>for</strong> sample (a) <strong>and</strong> (b), respectively. These values <strong>of</strong> <strong>the</strong><br />
energy gaps reflect a considerable blue-shift relative to <strong>the</strong> corresponding<br />
absorption b<strong>and</strong> edge <strong>of</strong> bulk CdS, such observed<br />
shift reveals quantum size effect in <strong>the</strong> syn<strong>the</strong>sized CdS thin<br />
films. Our present E g values were in a good agreement with<br />
those reported by (Raghvendra et al., 2010; Dongre et al., 2009).<br />
Table 1<br />
The compositions <strong>of</strong> <strong>the</strong> sample in <strong>the</strong> start solution.<br />
Reaction bath pH CdCl 2 (NH 2 ) 2 CS NH 4 Cl NH 3 H 2 O<br />
Mol. (M) Vol. (ml) Mol. (M) Vol. (ml) Mol. (M) Vol. (ml) Mol. (M) Vol. (ml)<br />
Sample-a 9 0.03 50 0.1 50 0.05 50 0.6 50<br />
Sample-b 9 0.03 50 0.05 50 0.05 50 0.6 50
Syn<strong>the</strong>sis, structure, <strong>and</strong> optical properties <strong>of</strong> CdS thin films nanoparticles prepared by chemical bath technique 29<br />
Figure 1<br />
Plot <strong>of</strong> transmittance with wavelength <strong>for</strong> CdS films.<br />
Figure 3 The variation <strong>of</strong> (aht) 2 vs. ht to determine <strong>the</strong> direct<br />
b<strong>and</strong> gap <strong>of</strong> CdS thin films.<br />
Figure 2 The variation <strong>of</strong> optical absorbance vs. wavelength <strong>for</strong><br />
CdS films.<br />
The values <strong>of</strong> <strong>the</strong> b<strong>and</strong>-gap were higher than <strong>the</strong> b<strong>and</strong> gap<br />
<strong>of</strong> bulk CdS (2.42 eV) (Enriques <strong>and</strong> Ma<strong>the</strong>w, 2003) <strong>the</strong>re<strong>for</strong>e,<br />
<strong>the</strong> blue shift <strong>of</strong> b<strong>and</strong> gap edge is 0.78 eV <strong>and</strong> 0.18 eV <strong>for</strong> samples<br />
(a) <strong>and</strong> (b) respectively. The increased effective b<strong>and</strong> gap<br />
makes nanocrystalline CdS a more effective window material<br />
in photovoltaic applications like <strong>the</strong> CdS/CdTe solar cells.<br />
For CdS nanoparticles (Brus, 1986) proposed <strong>the</strong> effective<br />
mass approximation <strong>for</strong>mal (EMA) to explain <strong>the</strong> <strong>the</strong>ory <strong>of</strong><br />
blue shift, which gives energy E nd <strong>for</strong> lowest 1s states as a function<br />
<strong>of</strong> nanoparticle radius, shows as follows:<br />
E np ¼ E bluk<br />
g<br />
þ E comf þ E coul ð9Þ<br />
where E np is <strong>the</strong> b<strong>and</strong> gap <strong>of</strong> CdS nanoparticle, E g is <strong>the</strong> b<strong>and</strong><br />
gap <strong>of</strong> <strong>the</strong> bulk <strong>of</strong> CdS, E comf is <strong>the</strong> electron–hole pair confinement<br />
kinetic energy <strong>and</strong> E coul is <strong>the</strong> coulomb interaction energy<br />
between <strong>the</strong> hole <strong>and</strong> <strong>the</strong> electron, which is given by<br />
E coul ¼ 1:8e 2 =pe o e s R ð10Þ<br />
And E comf ¼ðh 2 p 2 =2R 2 Þð1=m e þ 1=m hÞ corresponding to <strong>the</strong><br />
lowest energy transition.<br />
Now <strong>the</strong> above equation can be written as<br />
E np ¼ E bulk<br />
g<br />
þðhp 2 =2R 2 Þð1=m e þ 1=m h Þ<br />
ð1:8e 2 =4pe o e s RÞ<br />
ð11Þ<br />
where h =h/2p, h is plank constant, R is <strong>the</strong> radius <strong>of</strong> nanoparticles,<br />
m e<br />
is <strong>the</strong> effective mass <strong>of</strong> electron (m e ¼ 0:19m e),<br />
m h is <strong>the</strong> effective mass <strong>of</strong> hole (m h ¼ 0:8m e), m e is <strong>the</strong> mass<br />
<strong>of</strong> electron, e s is <strong>the</strong> dielectric constant <strong>of</strong> material (5.7) <strong>and</strong><br />
e o is <strong>the</strong> permittivity <strong>of</strong> free space. In <strong>the</strong> EMA <strong>for</strong>mula, <strong>the</strong><br />
coulomb term <strong>of</strong> electron–hole interaction was small compared<br />
to electron - hole confinement kinetic energy, which supported<br />
<strong>the</strong> blue shift result.<br />
Applying Eq. (11), values 4 nm (<strong>the</strong> diameter is 8 nm) <strong>and</strong><br />
1.913 nm (<strong>the</strong> diameter 3.826 nm) have been estimated <strong>for</strong><br />
<strong>the</strong> radius <strong>of</strong> <strong>the</strong> two nanoparticales CdS samples (a) <strong>and</strong> (b)<br />
respectively.<br />
It can be seen clearly that <strong>the</strong> decreasing particle size (as <strong>the</strong><br />
thiourea concentrations increases) causes increase in <strong>the</strong> b<strong>and</strong><br />
gap. Similar observation <strong>of</strong> <strong>the</strong> decrease in particle size as <strong>the</strong><br />
thiourea concentrations increased was reported by Yao et al.<br />
(2003). The dependence <strong>of</strong> b<strong>and</strong> gap on particle size in semiconductor<br />
nanocrystals has been extensively studied by Brus<br />
(1984). Particles whose dimensions become comparable to<br />
<strong>the</strong> bulk excition Bohr radius (a B ), equal to 5.3 nm <strong>for</strong> CdS,<br />
are observed to exhibit strong quantum confinement effect,<br />
which result in increase in <strong>the</strong> b<strong>and</strong> gap with decreasing particle<br />
size. So <strong>the</strong>re is a very good agreement with our result.<br />
These values are in good agreement with <strong>the</strong> sizes determined<br />
from XRD.<br />
3.2. X-ray diffraction studies<br />
Fig. 4 shows <strong>the</strong> XRD pattern <strong>of</strong> CdS powered nanoparticles<br />
<strong>for</strong> sample b. Comparing with <strong>the</strong> data <strong>of</strong> <strong>the</strong> JCPDS file (Powder<br />
Diffraction File Card, No. 10-454), it was found that <strong>the</strong><br />
CdS nanoparticles are identified as b-CdS, which belong to
30 A.M.A. Al-Hussam, S.Abdul-Jabbar Jassim<br />
4. Conclusion<br />
An aqueous solution system <strong>for</strong> growing CdS thin film nanocrystals<br />
network was investigated. The present method is simple,<br />
economic <strong>and</strong> easy .The crystal structure <strong>and</strong> grain size <strong>of</strong><br />
<strong>the</strong> particles was determined using XRD. The radius <strong>of</strong> <strong>the</strong><br />
particle was calculated using an effective mass approximation<br />
mode. The calculated radius <strong>of</strong> CdS nanoparticles was found<br />
to be similar to that obtained from XRD through Scherer’s<br />
<strong>for</strong>mula.<br />
UV–VIS spectra <strong>of</strong> <strong>the</strong> films showed blue shift in absorption<br />
edge compared with bulk CdS. The nanocrystals size<br />
was observed in <strong>the</strong> range <strong>of</strong> 3.826–8 nm.<br />
References<br />
Figure 4<br />
sample b.<br />
XRD <strong>of</strong> powder CdS nanoparticales <strong>for</strong> sample <strong>for</strong><br />
<strong>the</strong> cubic crystal system. The XRD peaks are found to be<br />
broad indicating fine size <strong>of</strong> <strong>the</strong> sample grains. The XRD pattern<br />
<strong>of</strong> a typical CdS sample exhibits prominent broad peaks at<br />
2h values <strong>of</strong> 26.7°, 44° <strong>and</strong> 52° which could be indicated as<br />
scattering from <strong>the</strong> (111), (220), <strong>and</strong> (311) cubic phase CdS<br />
plans, respectively, suggesting that <strong>the</strong> nanoparticles are in cubic<br />
(Zinc blend phase) <strong>for</strong>m <strong>and</strong> are in good agreement with<br />
<strong>the</strong> reported data on CdS (Rodrgues et al., 2008; Wang<br />
et al., 2001). No peaks attributable to o<strong>the</strong>r phases were observed.<br />
The broadening <strong>of</strong> <strong>the</strong> diffraction peak provides in<strong>for</strong>mation<br />
about crystallite size. As <strong>the</strong> width increases, <strong>the</strong><br />
particle size decreases <strong>and</strong> vice versa (Banerjee et al., 2000).<br />
From <strong>the</strong> position <strong>of</strong> different peaks <strong>and</strong> by <strong>the</strong> Bragg<br />
condition,<br />
nk ¼ 2d sin h<br />
ð12Þ<br />
where n is <strong>the</strong> order <strong>of</strong> diffraction, k <strong>the</strong> wavelength <strong>of</strong> <strong>the</strong> incident<br />
X-rays, d <strong>the</strong> distance between <strong>the</strong> plans parallel to <strong>the</strong><br />
axis <strong>of</strong> <strong>the</strong> incident beam <strong>and</strong> h is <strong>the</strong> diffraction angle, d-spacing<br />
has been evaluated, <strong>the</strong> obtained value is (3.139 A˚ ).<br />
Nanoparticle lattice constant is calculated using <strong>the</strong> following<br />
<strong>for</strong>mula (Kittel, 1996).<br />
1=d 2 ¼ðh 2 þ k 2 þ l 2 Þ=a 2 ð13Þ<br />
where (a) is <strong>the</strong> lattice constant, <strong>and</strong> (h,k,l) miller indices, (a)<br />
was calculated to be (0.59 nm) <strong>for</strong> our sample, which matches<br />
with <strong>the</strong> earlier reported lattice constant <strong>for</strong> cubical zinc blend<br />
structures <strong>of</strong> CdS nanoparticles (Rodrgues et al., 2008).<br />
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using Scherer’s equation as (Cullity, 1972)<br />
D ¼ Kk=b cosðhÞ<br />
ð14Þ<br />
where <strong>the</strong> constant K is a shape factor usually =0.94, k is <strong>of</strong><br />
X-ray wavelength (0.15418 nm), b is <strong>the</strong> full-width at halfmaximum<br />
(FWHM) <strong>of</strong> <strong>the</strong> peak which has maximum intensity<br />
<strong>and</strong> h is <strong>the</strong> Bragg’s angle. The estimated X-ray domain size <strong>of</strong><br />
this sample was 6.27 nm derived from FWHM <strong>of</strong> peak corresponding<br />
to 2h 26.7° <strong>for</strong> sample (b).<br />
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Santos, B.S., Farias, P.M.A., Fontes, A., Brasil, A.G., Jovino, C.N.,<br />
Neto, A.G.G.C., Silva, D.C.N., Menezes, F.D., Ferreira, R., 2008.<br />
Semiconductor nanocrystal obtained by colloidal chemistry <strong>for</strong><br />
biological application. Appl. Surf. Sci. 255, 796–798.
Syn<strong>the</strong>sis, structure, <strong>and</strong> optical properties <strong>of</strong> CdS thin films nanoparticles prepared by chemical bath technique 31<br />
Schmitt-Rink, S., Chemla, D.S., Miller, D.A.B., 1989. Linear <strong>and</strong><br />
nonlinear optical properties <strong>of</strong> semiconductor quantum wells. Adv.<br />
Phys. 38, 89–188.<br />
Tauc, T., Abeies, F., 1970. Optical Properties <strong>of</strong> solids. IOP Publishing<br />
Ltd, North Holl<strong>and</strong>, Amsterdam, p. 903.<br />
Ujjal, K., Gautam, Ram Seshadri Rao, C.N.R., 2003. A solvo<strong>the</strong>rmal<br />
route to CdS nanocrystals. Chem. Phys. Lett. 375, 560–564.<br />
Wang, G.Z., Wang, Y.W., Chen, W., Liang, C.H., Li, C.H., Zhang,<br />
L.D., 2001. Facile syn<strong>the</strong>sis route to CdS nanocrystals at room<br />
temperature. Mater. Lett. 48, 269–275.<br />
Xiaoxia, J., Fei, C., Hao, X., Ligong, Y., Weiming, Q., Minmin, S.,<br />
Mang, W., Hongzheng, C., 2010. Template-free syn<strong>the</strong>sis <strong>of</strong><br />
vertically aligned CdS nanoroads <strong>and</strong> its application in hybrid<br />
solar cells. Sol. Energy Mater. Sol. Cells 94, 338–344.<br />
Yao, Jian-Xi, Zhao, Gao-Ling, Han, Gao-Rong, 2003. Effect <strong>of</strong> <strong>the</strong><br />
ratio <strong>of</strong> thiourea to Cd 2+ on <strong>the</strong> properties <strong>of</strong> CdS nanoparticles.<br />
Microelectron Eng 66, 115–120.
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 32-36<br />
تحديد بيرمثامين في المتحضرات الصيدالنية عن طريق المطيافئة<br />
باستخدام نافثوكوينون<br />
1 – 2<br />
عبداهلل احمد البشير<br />
، علوية حسين الحسين الوقيع<br />
ص.ب 321<br />
قسم الكيمياء،<br />
كلية العلوم، جامعة الخرطوم،<br />
الخرطوم<br />
، السودان<br />
المخلص:<br />
في هذه الدراسة تم وصف طريقة تمتاز بالدقة والبساطة لتحديد بيرمثامين في المستحضرات الصيدالنية.<br />
تعتمد الطريقة على تكوين مركب ملون نتيجة لتفاعل بيرمثامين مع<br />
–<br />
2-1<br />
مئوية. درجة 06<br />
الطول الموجي<br />
384<br />
لالمتصاصية والتركيز مطاعة<br />
المعايرة ص<br />
نافثوكوينون في درجة حرارة<br />
تمت متابعة التفاعل عن طريق المطيافية الضوئية بقياس الزيادة في االمتصاصية عند<br />
نانوميتر بدالة زمنية.<br />
)ممتثلة(<br />
عند<br />
في المدى<br />
–<br />
الظروف المثلى للتفاعل كانت العالقة بين قانون بيرز<br />
36<br />
12<br />
606142<br />
+<br />
60763<br />
=<br />
ج مع معامل االرتباط<br />
مايكرو جرام/مل ومعادلة االنحدار للبيانات<br />
)60..0(<br />
وامتصاصية مولية بمقدار<br />
*5.8<br />
لتر مول 4 16<br />
1-<br />
ملليتر على التوالي.<br />
-1. سم<br />
كانت النسبة المئوية لبيرمثامين للدفعة<br />
وكان الحد من الكشف النوعي والكمي<br />
4025<br />
وقد طبقت الطريقة المقترحة بنجاح لتحديد بيرمثامين في<br />
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هي 26<br />
+<br />
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طريقة األداء العالية للفصل الكروماتوغرافي السائل الرسمية.<br />
.%6015<br />
مايكرو جرام لكل<br />
أقراص الدواء مع دقة جيدة.<br />
وكانت النتائج في اتفاق جيد مع<br />
A.A. Elbashir, A.H.E. Elwagee
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 32–36<br />
University <strong>of</strong> Bahrain<br />
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong><br />
<strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences<br />
www.elsevier.com/locate/jaaubas<br />
www.sciencedirect.com<br />
ORIGINAL ARTICLE<br />
Spectrophotometric determination <strong>of</strong> pyrimethamine<br />
(PYM) in pharmaceutical <strong>for</strong>mulation using<br />
1,2-naphthoquinone-4-sulfonate (NQS)<br />
Abdalla A. Elbashir *, Alawia H.E. Elwagee<br />
University <strong>of</strong> Khartoum, Faculty <strong>of</strong> Science, Chemistry Department, P.O. Box 321, Khartoum, Sudan<br />
Available online 24 January 2012<br />
KEYWORDS<br />
UV–visible<br />
spectrophotometry;<br />
Pyrimethamine;<br />
NQS;<br />
Pharmaceutical <strong>for</strong>mulation<br />
Abstract A simple <strong>and</strong> sensitive spectrophotometric method <strong>for</strong> <strong>the</strong> quantitative analysis <strong>of</strong> pyrimethamine<br />
(PYM) in pharmaceutical <strong>for</strong>mulations has been described. The method is based on <strong>the</strong><br />
<strong>for</strong>mation <strong>of</strong> colored product between PYM <strong>and</strong> 1,2-naphthoquinone-4-sulfonate (NQS) at 60 °C.<br />
The reaction is followed spectrophotometrically by measuring <strong>the</strong> increase in absorbance at 483 nm<br />
as a function <strong>of</strong> time. Under <strong>the</strong> optimized reaction condition, Beer’s law correlation <strong>for</strong> <strong>the</strong> absorbance<br />
(A) with PYM concentration (C) was obeyed in <strong>the</strong> range 12–40 lgmL 1 <strong>the</strong> regression<br />
equation <strong>for</strong> <strong>the</strong> calibration data was A = 0.704 + 0.0132C, with correlation coefficient (0.996).<br />
The molar absorptivity (e) was 5.8 · 10 3 L mol<br />
1 cm 1 . The limits <strong>of</strong> detection <strong>and</strong> quantification<br />
were 3.25 <strong>and</strong> 10.83 lgmL 1 , respectively. The proposed method was successfully applied to <strong>the</strong><br />
determination <strong>of</strong> PYM in pharmaceutical tablets with good accuracy <strong>and</strong> precision; <strong>the</strong> percentage<br />
<strong>for</strong> PYM was 101.4 ± 1.47% <strong>for</strong> batch 20 <strong>and</strong> 100.4 ± 0.51% <strong>for</strong> batch 13. The results were in<br />
good agreement with those obtained with <strong>the</strong> <strong>of</strong>ficial high per<strong>for</strong>mance liquid chromatography<br />
(HPLC) method.<br />
ª 2012 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by Elsevier B.V. All rights reserved.<br />
1. Introduction<br />
* Corresponding author.<br />
E-mail address: hajaae@yahoo.com (A.A. Elbashir).<br />
1815-3852 ª 2012 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by<br />
Elsevier B.V. All rights reserved.<br />
Peer review under responsibility <strong>of</strong> University <strong>of</strong> Bahrain.<br />
doi:10.1016/j.jaubas.2011.12.003<br />
Production <strong>and</strong> hosting by Elsevier<br />
Pyrimethamine (PYM), 5-(4-chlorophenyl)-6-ethyl-2,4-pyrimidineamine<br />
(Fig. 1) is a drug widely used in <strong>the</strong> treatment <strong>of</strong><br />
parasitic diseases such as malaria <strong>and</strong> toxoplasmosis (Bosch-<br />
Driessen et al., 2002).<br />
The mechanism <strong>of</strong> action <strong>of</strong> PYM is <strong>the</strong> inhibition <strong>of</strong> dihydr<strong>of</strong>olate<br />
reductase (DHFR), an essential enzyme responsible <strong>for</strong> <strong>the</strong><br />
conversion <strong>of</strong> folic acid into folinic acid in <strong>the</strong> nucleic acid biosyn<strong>the</strong>sis<br />
(Anderson, 2005). Some major drawbacks <strong>of</strong> PYR <strong>the</strong>rapy<br />
include a relatively weak inhibitory activity <strong>and</strong> severe side effects<br />
such as nausea <strong>and</strong> neutropenia, which are caused by <strong>the</strong> low<br />
selectivity toward <strong>the</strong> parasite enzyme (Katlama et al., 1996).<br />
Literature survey reveals that various methods have been<br />
reported <strong>for</strong> <strong>the</strong> analysis <strong>of</strong> PYM in pharmaceutical <strong>and</strong> bio-
Spectrophotometric determination <strong>of</strong> pyrimethamine (PYM) 33<br />
N<br />
NH 2<br />
Cl<br />
<strong>of</strong> NaOH (0.2 M) in 100 mL volumetric flask, <strong>and</strong> adjusted by<br />
<strong>the</strong> pH meter. O<strong>the</strong>r buffer solutions <strong>of</strong> different pH values<br />
were also prepared. Amifan tablets were kindly donated by<br />
AMIPHARMA Laboratories Ltd. (Sudan, Khartoum).<br />
Milli-Q water was used <strong>for</strong> preparing all solutions used.<br />
H 2 N<br />
N<br />
2.3. Preparation <strong>of</strong> st<strong>and</strong>ard <strong>and</strong> sample solution<br />
Figure 1<br />
logical samples such as microbiological method (Weidekamm<br />
et al., 1982), gas–liquid chromatography (Cala et al., 1972;<br />
Jones et al., 1981; Midskov, 1984b), thin layer chromatography<br />
(DeAngelis et al., 1975), spectrophotometry (Schmidt<br />
et al., 1953; Sastry et al., 1986; Berzas Nevado et al., 1993;<br />
Khalil et al., 2000; Onah <strong>and</strong> Odeiani, 2002; Zayed et al.,<br />
2005; Nagaraja et al., 2010), fluorimetry (Parimo, 1988) <strong>and</strong><br />
HPLC(Midskov, 1984a,b; Bergqvist <strong>and</strong> Eriksson, 1985;<br />
Timm <strong>and</strong> Weidekamm, 1982; Edstein, 1948a,b) individually<br />
<strong>and</strong> in combination dosage <strong>for</strong>m with o<strong>the</strong>r drugs.<br />
Spectrophotometry is considered <strong>the</strong> most convenient analytical<br />
technique, because <strong>of</strong> its inherent simplicity, low cost,<br />
<strong>and</strong> wide availability in most quality control laboratories.<br />
Spectrophotometric methods have been reported <strong>for</strong> PYM.<br />
These methods were associated with some major drawbacks<br />
such as laborious multiple extraction steps in <strong>the</strong> analysis by<br />
ion-pair based methods (Khalil et al., 2000; Nagaraja et al.,<br />
2010) Fur<strong>the</strong>rmore, <strong>the</strong> analytical reaction was long <strong>and</strong> thus<br />
<strong>the</strong> procedure was time-consuming (Onah <strong>and</strong> Odeiani, 2002).<br />
1,2-Naphthoquinone-4-sulfonate (NQS) has been used <strong>for</strong><br />
<strong>the</strong> determination <strong>of</strong> many compounds containing primary<br />
amine group (Gallo-Martinez et al., 1998; Wang et al., 2004;<br />
Saurina <strong>and</strong> Herna´ndez-Cassuo, 1993). Use <strong>of</strong> NQS as a colored<br />
reagent <strong>for</strong> <strong>the</strong> determination <strong>of</strong> PYM by spectrophotometry<br />
has not been reported yet. There<strong>for</strong>e, <strong>the</strong> present work<br />
was devoted to study <strong>the</strong> reaction between PYM <strong>and</strong> NQS<br />
<strong>and</strong> employment <strong>of</strong> <strong>the</strong> reaction in <strong>the</strong> development <strong>of</strong> a simple<br />
method <strong>for</strong> <strong>the</strong> determination <strong>of</strong> PYM in dosage <strong>for</strong>m.<br />
2. Material <strong>and</strong> methods<br />
Chemical structure <strong>of</strong> PYM.<br />
2.3.1. PYM st<strong>and</strong>ard solutions<br />
An accurately weighed 10 mg <strong>of</strong> PYM was dissolved in methanol,<br />
transferred into a 10 mL st<strong>and</strong>ard flask <strong>and</strong> completed to<br />
<strong>the</strong> mark with methanol. This stock solution was fur<strong>the</strong>r diluted<br />
with <strong>the</strong> same solvent to obtain working solutions in<br />
<strong>the</strong> range 6–60 lgmL 1 .<br />
2.3.2. Tablets sample solution<br />
Twenty tablets were weighed, <strong>and</strong> finely powdered. An accurately<br />
weighed quantity <strong>of</strong> <strong>the</strong> powdered tablets equivalent to<br />
4.25 mg <strong>of</strong> PYM was transferred into a 25 mL calibrated flask,<br />
<strong>and</strong> dissolved in methanol. The prepared solutions were diluted<br />
quantitatively with methanol to obtain a suitable concentration<br />
<strong>for</strong> <strong>the</strong> analysis.<br />
2.3.3. General recommended procedure<br />
Accurately measured 1 mL <strong>of</strong> PYM solution containing 12–<br />
40 lgmL 1 was transferred into a 10 mL volumetric flask.<br />
3 mL <strong>of</strong> buffer solution pH (13.0) was added, followed by<br />
1 mL <strong>of</strong> NQS solution (0.5%, w/v). The reaction solution<br />
was allowed to proceed at 60 °C <strong>for</strong> 15 min. The reaction mixture<br />
was completed to volume with water, <strong>and</strong> <strong>the</strong> resulting<br />
solution was measured at 483 nm against reagent blank.<br />
2.4. Determination <strong>of</strong> PYM by HPLC<br />
According to <strong>the</strong> United States Pharmacopoeia, PYM was<br />
determined in two batches number (batch number 20 <strong>and</strong><br />
13). The analysis was per<strong>for</strong>med on a Phenomenex C18-column;<br />
5 lm (250 mm 4.6 mm i.d.) with a guard column<br />
3<br />
2.1. Instrumentation<br />
All absorbance measurements were made with a Double beam<br />
UV-1800 (SHIMADZU, Japan) ultraviolet–visible spectrophotometer<br />
provided with matched 1-cm quartz cells <strong>and</strong> also<br />
temperature controller was used <strong>for</strong> <strong>the</strong> spectrophotometric<br />
measurements. pH meter model pH211 (HANNA, Italy).<br />
Thermostatically controlled water bath type RE 220 (LAU-<br />
DA, Germany).<br />
Absorbance (Arb.<br />
1.00<br />
0.50<br />
1<br />
2<br />
2.2. Reagents <strong>and</strong> materials<br />
Pyrimethamine (PYM) (AMIPHARMA Laboratories Ltd.,<br />
Khartoum) were obtained <strong>and</strong> used as received; its purity<br />
was 99.7%. A solution <strong>of</strong> 0.5% (w/v) <strong>of</strong> 1,4-naphthoquinone-4-sulfonate<br />
(NQS) (Aldrich chemical Co., St. Louis,<br />
USA) was prepared by dissolving 125 mg in 25 mL double distilled<br />
water. The solution was freshly prepared <strong>and</strong> protected<br />
from light during use. Buffer solution <strong>of</strong> pH 13.0 was prepared<br />
by mixing 25 mL solution <strong>of</strong> KCl (0.2 M) <strong>and</strong> 66 mL solution<br />
0.00<br />
200.0 300.0 400.0 500.0 600.0 700.0<br />
Wavelength (nm)<br />
Figure 2 Absorption spectra <strong>of</strong> Pyrimethamine (20 lgml<br />
1 )<br />
against methanol (1). NQS (0.5% w/v) against water (2). And<br />
<strong>the</strong> reaction product <strong>of</strong> primethamine (30 lgml<br />
1 ) with NQS<br />
against reagent blank (3).
34 A.A. Elbashir, A.H.E. Elwagee<br />
Absorbance<br />
1.6<br />
1.4<br />
1.2<br />
1.0<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
0.0<br />
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6<br />
NQS (% w/v)<br />
Figure 3 Effect <strong>of</strong> NQS concentration on <strong>the</strong> reaction <strong>of</strong> PYM<br />
with NQS. PYM (40 lg/ml): 1 ml; buffer solution (pH 13.0); 3 ml;<br />
temperature 60 °C; reaction time: 15 min.<br />
(4.0 mm · 3.0 mm i.d.). The mobile phase consisting <strong>of</strong> 80%<br />
glacial acetic acid (1:100), 20% acetonitrile <strong>and</strong> 500 lL triethylamine<br />
was delivered as an isocratic elution at a flow rate <strong>of</strong><br />
2 mL/min <strong>and</strong> 10 lL <strong>of</strong> <strong>the</strong> sample was injected. Be<strong>for</strong>e use<br />
<strong>the</strong> mobile phase was degassed by an ultrasonic bath <strong>and</strong> filtered<br />
by a Millipore vacuum filter system equipped with a<br />
0.45 ml HV filter.<br />
3. Results <strong>and</strong> discussion<br />
3.1. Optimization<br />
The absorption spectrum <strong>of</strong> <strong>the</strong> reaction product between<br />
NQS <strong>and</strong> PYM with an absorption maximum at 480 nm is<br />
shown in Fig. 2. Clearly from this figure a broad absorption<br />
b<strong>and</strong> at longer wavelengths is obtained <strong>for</strong> <strong>the</strong> reaction between<br />
NQS <strong>and</strong> PYM.<br />
The optimum conditions <strong>for</strong> <strong>the</strong> development <strong>of</strong> method<br />
were established by varying <strong>the</strong> parameters one at a time while<br />
keeping <strong>the</strong> o<strong>the</strong>rs fixed <strong>and</strong> observing <strong>the</strong> effect produced on<br />
<strong>the</strong> absorbance <strong>of</strong> <strong>the</strong> colored product. In order to establish<br />
experimental conditions, <strong>the</strong> effect <strong>of</strong> various parameters such<br />
as concentration <strong>of</strong> NQS, pH, temperature, <strong>and</strong> time <strong>of</strong> heating<br />
were studied.<br />
The effect <strong>of</strong> NQS concentration was studied over <strong>the</strong> range<br />
0.1–1.5 w/v% as shown in Fig. 3. Increasing <strong>the</strong> concentration<br />
<strong>of</strong> NQS results in more products up to an amount <strong>of</strong> 0.5%<br />
Table 1 Parameters <strong>for</strong> <strong>the</strong> per<strong>for</strong>mance <strong>of</strong> <strong>the</strong> proposed<br />
method.<br />
Parameter<br />
Value<br />
Measurement wavelength (nm) 483<br />
Linear range (lg mL 1 ) 12–40<br />
Intercept 0.704<br />
St<strong>and</strong>ard deviation <strong>of</strong> <strong>the</strong> intercept 0.014<br />
Slope 0.013<br />
St<strong>and</strong>ard deviation <strong>of</strong> <strong>the</strong> slope 0.001<br />
Correlation coefficient (r) 0.996<br />
Limit <strong>of</strong> detection, LOD (lgmL 1 ) 3.25<br />
Limit <strong>of</strong> quantification, LOQ (lg mL 1 ) 10.83<br />
Molar absorptivity, e (1 mol<br />
1 cm 1 ) 5.8 · 10 3<br />
after which <strong>the</strong> absorbance remained almost constant. There<strong>for</strong>e<br />
a concentration <strong>of</strong> 0.5% NQS was considered optimum.<br />
The influences <strong>of</strong> pH on <strong>the</strong> absorbance <strong>of</strong> product I was<br />
investigated in <strong>the</strong> range 1.0 to 14. At pH 1.0–7.0, <strong>the</strong><br />
absorbance <strong>of</strong> <strong>the</strong> product is close to 0, indicating that under<br />
high acidity, PYM does not react with NQS. The possible<br />
reason may be that <strong>the</strong> amino group ( NH 2 ) <strong>of</strong> PYM is<br />
protonated (pk a = 7.26 G.S. La´zaro et al., 2008) <strong>and</strong> converted<br />
into protonated amine salt ð NH þ 3<br />
Þ. So it loses nucleophilic<br />
capability <strong>for</strong> 4-sodium sulfonate <strong>of</strong> NQS, <strong>and</strong> <strong>the</strong><br />
nucleophilic substitution reaction cannot take place easily.<br />
At pH > 10.0, <strong>the</strong> absorbance <strong>of</strong> <strong>the</strong> solution increases rapidly<br />
up to pH 13.0. It may be that protonated amine salt<br />
ð NH þ 3 Þ <strong>of</strong> PYM turns into amino group ( NH 2) again<br />
when <strong>the</strong> acidity <strong>of</strong> <strong>the</strong> solution becomes low. The higher<br />
<strong>the</strong> pH, <strong>the</strong> more effectively <strong>the</strong> protonated amino group removes<br />
<strong>the</strong> proton, <strong>and</strong> more easily <strong>the</strong> nucleophilic substitution<br />
reaction happens. At pH 13.0, <strong>the</strong> absorbance reaches<br />
its maximum; in o<strong>the</strong>r words, <strong>the</strong> degree <strong>of</strong> <strong>the</strong> nucleophilic<br />
substitution reaction is also maximal. At pH > 13.0, <strong>the</strong><br />
absorbance <strong>of</strong> solution decreases sharply again. Presumably<br />
it may be that <strong>the</strong> increase <strong>of</strong> hydroxide ion holds back<br />
<strong>the</strong> nucleophilic substitution reaction between PYM <strong>and</strong><br />
<strong>the</strong> chromogenic reagent. Consequently, <strong>the</strong> absorbance <strong>of</strong><br />
<strong>the</strong> solution reduces. In order to keep <strong>the</strong> high sensitivity<br />
<strong>for</strong> <strong>the</strong> determination <strong>of</strong> PYM, pH 13.0 was selected <strong>for</strong><br />
optimal experimental conditions. Reaction <strong>of</strong> NQS with<br />
compound bearing primary amines at pH 13.0 was reported<br />
(Li <strong>and</strong> Zhang, 2008).<br />
The effect <strong>of</strong> temperature on <strong>the</strong> reaction was studied in <strong>the</strong><br />
range 20–80 °C. About 60 °C was found to be optimal <strong>for</strong><br />
maximum color development.<br />
O<br />
N<br />
NH 2<br />
Cl<br />
+<br />
O<br />
O<br />
N<br />
NH<br />
O<br />
Cl<br />
+ NaHSO 3<br />
H 2<br />
N<br />
N<br />
SO 3<br />
Na<br />
H 2<br />
N<br />
N<br />
Figure 4<br />
Scheme <strong>for</strong> <strong>the</strong> reaction pathway <strong>of</strong> PYM with NQS.
Spectrophotometric determination <strong>of</strong> pyrimethamine (PYM) 35<br />
Table 2<br />
Recovery studies <strong>for</strong> <strong>the</strong> determination <strong>of</strong> PYM, by <strong>the</strong> proposed method.<br />
Sample No. +SD Sample content (lgmL 1 ) Pyr. added (lgmL 1 ) Found Recovery (%)<br />
1 10 14 14.0 100.0 ± 0.01<br />
2 – 18 18.3 101.7 ± 0.03<br />
3 – 26 26.1 100.5 ± 0.01<br />
4 – 32 42.8 101.9 ± 0.09<br />
The influence <strong>of</strong> <strong>the</strong> time <strong>of</strong> heating was also investigated in<br />
<strong>the</strong> range 5–30 min. The experimental results show that heating<br />
in <strong>the</strong> range 15–20 min gave <strong>the</strong> optimal values in kinetic<br />
studies. The color product was stable <strong>for</strong> at least two days at<br />
room temperature.<br />
From <strong>the</strong> above experiments, <strong>the</strong> optimized conditions used<br />
<strong>for</strong> <strong>the</strong> assay were: NQS concentration 0.5% w/v, buffer (pH<br />
13.0), reaction time 20 min <strong>and</strong> temperature 60 °C.<br />
Under <strong>the</strong> optimum conditions, <strong>the</strong> stoichiometry <strong>of</strong> <strong>the</strong> reaction<br />
between PYM <strong>and</strong> NQS was studied by <strong>the</strong> Job’s (1964)<br />
method. The symmetrical bell shape <strong>of</strong> Job’s plot indicated that<br />
<strong>the</strong> ratio <strong>of</strong> PYM:NQS is 1:1. Based on this ratio, <strong>the</strong> reaction<br />
pathway was proposed to proceed as shown in Fig. 4.<br />
3.2. Analytical methods validation<br />
As can be seen from Table 1, linear relationship was found between<br />
absorbance at k max (483) <strong>and</strong> <strong>the</strong> concentration <strong>of</strong> <strong>the</strong><br />
PYM in <strong>the</strong> range 12–40 lg mL 1 . The regression equation<br />
was found as A = 0.0132C + 0.704 (r 2 = 0.996). The limits<br />
<strong>of</strong> detection (LOD) <strong>and</strong> limit <strong>of</strong> quantitation (LOQ) were<br />
determined using <strong>the</strong> <strong>for</strong>mula:LOD or LOQ = KS.D.a/b,<br />
where k = 3 <strong>for</strong> LOD <strong>and</strong> 10 <strong>for</strong> LOQ, SDa is <strong>the</strong> st<strong>and</strong>ard<br />
deviation <strong>of</strong> <strong>the</strong> intercept, <strong>and</strong> b is <strong>the</strong> slope.<br />
The accuracy <strong>of</strong> <strong>the</strong> proposed method was carried out by<br />
applying st<strong>and</strong>ard addition technique. A different amount <strong>of</strong><br />
st<strong>and</strong>ard solution was added to a known concentration <strong>of</strong><br />
<strong>the</strong> drug sample. The average percent recoveries obtained in<br />
range 100.04–101.9. Table 2.<br />
Robustness was examined by evaluating <strong>the</strong> influence <strong>of</strong><br />
small variation <strong>of</strong> method variables including <strong>the</strong> concentration<br />
<strong>of</strong> analytical reagent <strong>and</strong> reaction time on <strong>the</strong> per<strong>for</strong>mance<br />
<strong>of</strong> <strong>the</strong> proposed methods. In <strong>the</strong>se experiments, one<br />
parameter was changed whereas <strong>the</strong> o<strong>the</strong>rs were kept unchanged,<br />
<strong>and</strong> <strong>the</strong> recovery percentage was calculated each<br />
time. It was found that small variation <strong>of</strong> method variables<br />
did not significantly affect <strong>the</strong> procedures; recovery values<br />
were 98.43 101.40 (Table 3).<br />
3.3. Application to <strong>the</strong> pharmaceutical dosage <strong>for</strong>ms<br />
Table 3 Influence <strong>of</strong> small variation in <strong>the</strong> assay conditions<br />
on <strong>the</strong> analytical per<strong>for</strong>mance <strong>of</strong> <strong>the</strong> proposed spectrophotometric<br />
method <strong>for</strong> <strong>the</strong> determination <strong>of</strong> pyr. using NQS<br />
reagent.<br />
Parameters<br />
Recovery (% ± SD)<br />
Recommended conditions 101.4 ± 1.5<br />
NQS concentration (%, w/v) 0.45 100.2 ± 0.1<br />
NQS concentration (%, w/v) 0.55 99.7 ± 0.1<br />
Buffer (pH) 12.75 100.8 ± 0.1<br />
Buffer (pH) 13.25 99.7 ± 0.3<br />
Temperature (°C) 58 99.6 ± 0.2<br />
Temperature (°C) 60 99.9 ± 0.1<br />
Reaction time (min) 14 98.4 ± 0.2<br />
Reaction time (min) 100.5± 0.1<br />
PYM tablets were subjected to <strong>the</strong> analysis by <strong>the</strong> proposed as<br />
well as with <strong>the</strong> <strong>of</strong>ficial HPLC method (United States pharmacopeia,<br />
2006) <strong>and</strong> <strong>the</strong> obtained results were statistically<br />
compared with each o<strong>the</strong>r. The label claim percentage was<br />
101.40 ± 1.47 <strong>and</strong> 102.38 ± 0.51 <strong>for</strong> batch 20 <strong>and</strong> batch 13<br />
respectively (Table 4). With respect to t- <strong>and</strong> F-tests, no significant<br />
differences were found between <strong>the</strong> calculated <strong>and</strong> <strong>the</strong>oretical<br />
values <strong>of</strong> both <strong>the</strong> proposed <strong>and</strong> <strong>the</strong> reported methods at<br />
95% confidence level. This indicated similar accuracy <strong>and</strong><br />
precision in <strong>the</strong> analysis <strong>of</strong> PYM in tablets. Common tablet<br />
excipients such as talc, lactose, starch, avisil, gelatine <strong>and</strong><br />
magnesium stearate did not interfere with <strong>the</strong> assay.<br />
4. Conclusions<br />
The present paper described <strong>the</strong> evaluation <strong>of</strong> NQS as an analytical<br />
reagent in <strong>the</strong> development <strong>of</strong> simple, sensitive, <strong>and</strong><br />
accurate spectrophotometric methods, <strong>for</strong> <strong>the</strong> determination<br />
<strong>of</strong> PYM in pharmaceutical <strong>for</strong>mulations. The described method<br />
is superior to <strong>the</strong> previously reported spectrophotometric<br />
methods in terms <strong>of</strong> simplicity <strong>and</strong> sensitivity. The proposed<br />
method has comparable analytical per<strong>for</strong>mances <strong>and</strong> is devoid<br />
<strong>of</strong> any potential interference. This gives <strong>the</strong> advantage <strong>of</strong> flexibility<br />
in per<strong>for</strong>ming <strong>the</strong> analysis on any available instrument.<br />
There<strong>for</strong>e, this method can be recommended <strong>for</strong> <strong>the</strong> routine<br />
analysis <strong>of</strong> PYM in quality control laboratories.<br />
Table 4<br />
Analysis <strong>of</strong> PYM containing dosage <strong>for</strong>ms by <strong>the</strong> proposed <strong>and</strong> <strong>of</strong>ficial HPLC methods (United States Pharmacopoeia).<br />
Dosage <strong>for</strong>m Recovery % + RSD (n =5) t-value f-value<br />
Proposed<br />
Official<br />
AMIFAN batch 20 101.4 ± 1.5 102.5 ± 1.4 1.21 1.09<br />
AMIFAN batch 13 100.4 ± 0.5 99.7 ± 0.5 2.40 1.18<br />
The tabulated values <strong>for</strong> t <strong>and</strong> f at 95% confidence limit are 2.78 <strong>and</strong> 6.26, respectively.
36 A.A. Elbashir, A.H.E. Elwagee<br />
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Timm, U., Weidekamm, E., 1982. Determination <strong>of</strong> pyrimethamine in<br />
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Wang, H.Y., Xu, L.X., Xiao, Y., Han, J., 2004. Spectrophotometric<br />
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Weidekamm, E., Plozza-Nottebrock, H., Forgo, I., Dubach, U.C.,<br />
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A 62, 461–465.
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 37- 44<br />
/<br />
دراسة حركية راتنج م 6 ثاني أكسيد التيتاني وم<br />
عن طريق التحليل بالقياس الوزني الحراري المسح التفاضلي الحراري<br />
لتحسين صالبة راتنج<br />
/<br />
4<br />
4<br />
3<br />
باتريس بورسون ، يانيك قد ار ، فريدريك جوشام ،<br />
2<br />
بن يوسف بومدين<br />
1<br />
مراد لعرج ،<br />
1<br />
جامعة معسكر ، كلية العلوم والتكنولوجيا، معهد العلوم والتقنيات<br />
صندوق البريد<br />
363<br />
وحدة البحث "المواد والطاقات المتجددة"<br />
صندوق البريد<br />
طريق المامونية، معسكر20222، الجزائر<br />
،110<br />
مخبر المواد الضوئية والفوتونية واالنضمة<br />
قطب بالستيكي الشرق<br />
2<br />
، جامعة تلمسان، كلية العلوم، معهد الفيزياء<br />
تلمسان<br />
،13222<br />
الجزائر<br />
3<br />
، جامعة بول فرالن ماتز،<br />
،3132<br />
53522<br />
4<br />
،<br />
فرنسا ، سان تافولد<br />
فرنسا<br />
الملخص:<br />
الهدف من هذا البحث هو الحصول على إيبوكسي راتنج بأفضل الخصائص باستخدام )التحليل بالقياس<br />
الوزني الحراري<br />
/<br />
المسح التفاضلي الحراري(. االستقرار الحراري والخصائص الحركية لإلبوكسي راتنج<br />
باالستخدام غير المتساوي للحرارة<strong>the</strong>rmogravimetry <strong>the</strong>rmogravimetry/derivative وذلك<br />
من أجل سلسلة من النسب المئوية المختلفة<br />
Tio2-PC500<br />
وهي كالتالي:<br />
%5 ،%2 ،%1<br />
تم تقدير مقدار متغير القيمة الحركية بطرق التكامل و التقريب.<br />
أشارت النتائج إلى أن هذه الخصائص تعتمد على النسب المختلفة لثاني أكسيد التيتانيوم<br />
%11. و<br />
وفقا Tio 2<br />
لمنحنيات قياس )الوزني الحراري( التي تظهر أن طاقة التنشيط )طاقة الحفز( تتزايد مع تزايد النسب<br />
المئوية لجسيمات ثاني أكسيد التيتانيوم ( 2 ،)Tio و راتنج االبوكسي التحليل بمجهر المسح االلكتروني<br />
أوفي بأن توزيع جسيمات ثاني أكسيد التيتانيوم<br />
Tio 2<br />
كان بشكل منتظم ومتجانس ضمن المادة )إيبوكسي<br />
راتنج( هذا من جهة ومن جهة أخرى فالخاصية الميكانيكية التي هي الصالبة تحسنت مع زيادة النسب<br />
لجسيمات<br />
.Tio 2<br />
L. Merad et al.
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 37–44<br />
University <strong>of</strong> Bahrain<br />
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong><br />
<strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences<br />
www.elsevier.com/locate/jaaubas<br />
www.sciencedirect.com<br />
ORIGINAL ARTICLE<br />
Kinetic study <strong>of</strong> <strong>the</strong> RTM6/TiO 2 by DSC/TGA<br />
<strong>for</strong> improved hardness <strong>of</strong> resin<br />
L. Merad a,b, *, P. Bourson c , Y. Guedra d , F. Jochem d , B. Benyoucef b<br />
a Universite´ de Mascara, Faculte´ des Sciences et Technologie, De´partement des Sciences et Techniques, BP: 763,<br />
Route de Mamounia, Mascara 29000, Algeria<br />
b Unite´ de Recherche «Mate´riaux et Energies Renouvelables», URMER, Universite´ de Tlemcen, Faculte´ des Sciences,<br />
BP: 119, Tlemcen 13000, Algeria<br />
c Laboratoire Mate´riaux Optiques, Photoniques et Syste`mes, Universite´ Paul Verlaine-Metz, Supelec, UMR CNRS 7132,<br />
Metz, France<br />
d Poˆle de Plasturgie de l’Est, Saint Avold 57500, France<br />
Available online 9 January 2012<br />
KEYWORDS<br />
DSC;<br />
TG/DTG;<br />
RTM6;<br />
TiO 2 ;<br />
Kinetic parameter;<br />
Mechanical property<br />
Abstract The aim <strong>of</strong> this paper is to obtain an epoxy resin with best properties such as good cure<br />
<strong>of</strong> polymer (by using DSC <strong>and</strong> TGA). The <strong>the</strong>rmal stability <strong>and</strong> kinetic parameters <strong>of</strong> epoxy resin<br />
RTM6 using non-iso<strong>the</strong>rmal <strong>the</strong>rmogravimetry/derivative <strong>the</strong>rmogravimetry (TG/DTG) analysis<br />
with a series <strong>of</strong> different ratios <strong>of</strong> TiO 2 -PC500 1%, 2%, 5% <strong>and</strong> 10% with epoxy resin were evaluated.<br />
The kinetic parameter was evaluated by integral <strong>and</strong> approximation methods. Results<br />
obtained indicated that <strong>the</strong>se parameters were dependent on different ratios <strong>of</strong> TiO 2 . According<br />
to <strong>the</strong> <strong>the</strong>rmogravimetric curves it is shown that <strong>the</strong> activation energy at high <strong>of</strong> higher conversion<br />
increases with increasing <strong>the</strong> percentage <strong>of</strong> TiO 2 particles <strong>and</strong> epoxy resin. The SEM analysis suggests<br />
that TiO 2 particles are uni<strong>for</strong>mly distributed within <strong>the</strong> material, besides <strong>the</strong> mechanical property<br />
<strong>of</strong> materials are found to <strong>the</strong> addition <strong>of</strong> TiO 2 .<br />
ª 2011 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by Elsevier B.V. All rights reserved.<br />
* Corresponding author at: Université de Mascara, Faculté des<br />
Sciences et Technologie, Département des Sciences et Techniques, BP:<br />
763, Route de Mamounia, Mascara 29000, Algeria. Tel.: +213 553 883<br />
884.<br />
E-mail address: laarej_merad@yahoo.com (L. Merad).<br />
1815-3852 ª 2011 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by<br />
Elsevier B.V. All rights reserved.<br />
Peer review under responsibility <strong>of</strong> University <strong>of</strong> Bahrain.<br />
doi:10.1016/j.jaubas.2011.12.002<br />
Production <strong>and</strong> hosting by Elsevier<br />
1. Introduction<br />
Epoxy/TiO 2. was prepared by a solution mixture method, in<br />
which epoxy resin <strong>and</strong> nano-TiO 2 powder were mixed (Hung<br />
et al., 2006). Epoxy resins are widely used in most industrial<br />
applications, such as preparation <strong>of</strong> composites. The kinetics<br />
<strong>of</strong> epoxy resin cure has been widely investigated in <strong>the</strong> literature<br />
under conventional <strong>the</strong>rmal processing conditions<br />
(Navabpour et al., 2006).<br />
Resin transfer moulding (RTM) is rapidly gaining acceptance<br />
as one <strong>of</strong> <strong>the</strong> most promising manufacturing routes <strong>for</strong><br />
composite structures such as <strong>the</strong> aerospace <strong>and</strong> automotive<br />
industries. However, relatively limited in<strong>for</strong>mation is available
38 L. Merad et al.<br />
on <strong>the</strong> chemistry <strong>and</strong> cure characteristics <strong>of</strong> <strong>the</strong> types <strong>of</strong> <strong>the</strong>rmosetting<br />
resins used in such applications (Karkanas et al., 1996).<br />
The aim <strong>of</strong> this study is to describe <strong>the</strong> kinetic investigation<br />
<strong>of</strong> a curing <strong>the</strong>rmoset resin system. A lot <strong>of</strong> experimental techniques<br />
are suitable <strong>for</strong> following <strong>the</strong> rates <strong>and</strong> extents <strong>of</strong> cure<br />
reactions in <strong>the</strong>rmosets. Among <strong>the</strong>m <strong>the</strong>rmal gravimetric<br />
analysis may be considered as one <strong>of</strong> <strong>the</strong> most interesting<br />
techniques <strong>for</strong> macrokinetic analysis <strong>of</strong> cure reactions <strong>and</strong> a<br />
detailed investigation <strong>of</strong> <strong>the</strong>rmal decomposition <strong>of</strong> epoxy<br />
resins containing a commercial TiO 2 PC500 from Millennium<br />
at different percentages <strong>of</strong> 1%, 2%, 5% <strong>and</strong> 10%, <strong>for</strong><br />
evaluating <strong>the</strong> <strong>the</strong>rmal stability <strong>and</strong> to determine <strong>the</strong> <strong>the</strong>rmal<br />
decomposition kinetic parameter (activation energy) <strong>and</strong> to<br />
measure <strong>the</strong> mechanical property (hardness).<br />
2. Experimental<br />
2.1. Reagents<br />
The materials used in this work were <strong>of</strong> a commercially<br />
available grade <strong>of</strong> <strong>the</strong> diglycidyl e<strong>the</strong>r <strong>of</strong> bisphenol A<br />
((4-(2,3-epoxypropoxy)phenyl)propane) abbreviated as<br />
DGEBA. It was used under its commercial presentation<br />
(Dow Chemical Company; DER 332). The cure agent was<br />
4,4 0 -DiaminoDiphenylSulfone (DDS).<br />
Titanium dioxide TiO 2 -PC500 from Millenium Inorganic<br />
Chemicals (anatase > 99%, Surface area 250 m 2 ), crystallite<br />
mean size = (5–10 nm) was used as received.<br />
2.2. Apparatus<br />
2.2.1. DSC<br />
Dynamic scans were per<strong>for</strong>med using a heat-flux DSC (Mettler<br />
Toledo TC11) under nitrogen purge. The instrument was calibrated<br />
with indium.<br />
2.2.2. SEM<br />
The scanning electron microscopic (SEM) studies were per<strong>for</strong>med<br />
on a Hitachi S800-FE operated at 30 kV.<br />
2.3. Methods<br />
2.3.1. DSC<br />
Samples <strong>of</strong> <strong>the</strong> mixture <strong>of</strong> epoxy resin <strong>and</strong> curing agent were<br />
introduced in a furnace maintained at <strong>the</strong> temperature chosen<br />
<strong>for</strong> <strong>the</strong> experiment (100, 135 <strong>and</strong> 150 °C). They were successively<br />
removed <strong>and</strong> after different times <strong>the</strong>y were elapsed (typically<br />
between 1 <strong>and</strong> 6 h with a step <strong>of</strong> 1 h) <strong>and</strong> submitted to a<br />
DSC analysis with a heating rate <strong>of</strong> 10 °C min 1 from 30 to<br />
350 °C. These scans allowed determining <strong>the</strong> heat <strong>of</strong> reaction<br />
DH residual generated by <strong>the</strong> curing <strong>of</strong> <strong>the</strong> remaining epoxy resin<br />
not polymerized in <strong>the</strong> furnace.<br />
A scan per<strong>for</strong>med directly on a sample <strong>of</strong> <strong>the</strong> mixture epoxy<br />
resin/curing agent without heat treatment was allowed to<br />
determine <strong>the</strong> heat <strong>of</strong> reaction DH total generated by <strong>the</strong> complete<br />
polymerization process.<br />
2.3.2. TGA<br />
2.3.2.1. Sample preparation. The epoxy samples were prepared<br />
by <strong>the</strong> following three steps:<br />
1. Heating <strong>the</strong> epoxy resin in an oven at 40 °C.<br />
2. Adding <strong>the</strong> TiO 2 at different percentage 1%, 2%, 5% <strong>and</strong><br />
10%.<br />
3. Heating samples at 135 °C <strong>for</strong> 6 h.<br />
The <strong>the</strong>rmal property <strong>of</strong> Epoxy resin/TiO 2 sample was investigated<br />
by TG/DTG under N 2 environment. The analyses were<br />
carried out using heating rates <strong>of</strong> 5.0, 10.0, 20.0 <strong>and</strong><br />
30.0 °C min 1 <strong>for</strong> each experiment with approximately<br />
20.0 mg up to 850 °C.<br />
3. Kinetic methods<br />
3.1. Thermal analysis<br />
The DSC plots were also fitted using <strong>the</strong> equation described by<br />
Karkanas et al. (1996). The reaction rates <strong>for</strong> this work are calculated<br />
from <strong>the</strong> DSC using <strong>the</strong> following equations:<br />
2.2.3. TGA<br />
The <strong>the</strong>rmogravimetry analysis (TGA) was carried out on a<br />
SETARAM 92-12 apparatus under an N 2 atmosphere.<br />
a ¼ DH t<br />
DH Tot<br />
da<br />
dt ¼ 1dDH t<br />
DH tot dt<br />
ð1Þ<br />
ð2Þ<br />
Figure 1 Chemical structures <strong>and</strong> cure reaction <strong>of</strong> DGEBA by DDS (Farquharson et al., 2007).
Kinetic study <strong>of</strong> <strong>the</strong> RTM6/TiO 2 by DSC/TGA <strong>for</strong> improved hardness <strong>of</strong> resin 39<br />
Table 1 Total heat <strong>of</strong> reaction <strong>of</strong> RTM6 resin at different<br />
heating rates.<br />
Heating rate (°C min 1 ) 1 2 5 10 20 30<br />
DH total (J g 1 ) 439.29 435.32 437.00 434.05 432.89 439.57<br />
where DH t is <strong>the</strong> partial area under DSC trace up to time t <strong>and</strong><br />
DH tot is <strong>the</strong> total enthalpy <strong>of</strong> reaction measured as <strong>the</strong> area under<br />
<strong>the</strong> heat flow against time <strong>for</strong> DSC.<br />
The DSC plots were also fitted using <strong>the</strong> equation described<br />
by Karkanas et al. (1996) <strong>and</strong> Puglia et al. (2003).<br />
@a<br />
@t ¼ðk 1 þ k 2 a m Þð1 aÞ n ð3Þ<br />
@a<br />
@t ¼ k 1ð1 aÞ n 1<br />
þ k 2 a m ð1 aÞ n 2<br />
ð4Þ<br />
where k 1 <strong>and</strong> k 2 are <strong>the</strong> rate constants, m <strong>and</strong> n are <strong>the</strong> reaction<br />
orders.<br />
In <strong>the</strong> non-iso<strong>the</strong>rmal experiments carried out with a<br />
<strong>the</strong>rmobalance, <strong>the</strong> sample mass is measured as function <strong>of</strong><br />
temperature (see Fig. 1).<br />
The calculation <strong>of</strong> kinetic data is based on <strong>the</strong> kinetic Eq.<br />
(5):<br />
@a<br />
@t ¼ kan<br />
where a is <strong>the</strong> amount <strong>of</strong> sample undergoing reaction, n is <strong>the</strong><br />
reaction order, <strong>and</strong> k is <strong>the</strong> specific rate constant. The temperature<br />
dependence <strong>of</strong> k is expressed by Arrhenius Eq. (6):<br />
<br />
k ¼ A exp<br />
E a<br />
RT<br />
<br />
where A is <strong>the</strong> Arrhenius constant, E a is <strong>the</strong> activation energy,<br />
<strong>and</strong> R is <strong>the</strong> gas constant.<br />
The activation energy can be determined by Kissinger’s<br />
method without a precise knowledge <strong>of</strong> <strong>the</strong> reaction mechanism,<br />
using <strong>the</strong> following Eq. (7).<br />
<br />
b<br />
ln ¼ ln AR h i<br />
1 E<br />
þ ln nð1 aÞn ð7Þ<br />
E<br />
T 2 max<br />
RT max<br />
ð6Þ<br />
where T max is <strong>the</strong> temperature corresponding to <strong>the</strong> inflection<br />
point <strong>of</strong> <strong>the</strong> <strong>the</strong>rmodegradation curves which correspond to<br />
<strong>the</strong> maximum reaction rate, a max is <strong>the</strong> conversion at T max<br />
<strong>and</strong> n is <strong>the</strong> reaction order. Taking into account <strong>the</strong> Kissinger’s<br />
approximation which states that:<br />
f 0 ða max Þ¼nð1 a max Þ n 1 ffi const ð8Þ<br />
The activation energy can determined from a plot <strong>of</strong><br />
lnðb=T 2 max Þ against 1/T max.<br />
4. Results <strong>and</strong> discussion<br />
Table 1 shows <strong>the</strong> enthalpy <strong>of</strong> cure <strong>for</strong> DSC curing <strong>for</strong> iso<strong>the</strong>rmal<br />
temperature after curing using DSC.<br />
Fig. 2 shows <strong>the</strong> plots <strong>of</strong> conversion <strong>and</strong> reaction rate <strong>for</strong><br />
<strong>the</strong> iso<strong>the</strong>rmal curing <strong>of</strong> RTM6 cured using DSC. The conversions<br />
<strong>and</strong> reaction rates were obtained using <strong>the</strong> DSC curves<br />
<strong>and</strong> Eqs. (2) <strong>and</strong> (3).<br />
The curves <strong>of</strong> reaction rate on time were fitted to <strong>the</strong> kinetics<br />
Eq. (4). The equation was modified to account <strong>for</strong> <strong>the</strong> diffusion<br />
effect, which occurs when <strong>the</strong> resin is trans<strong>for</strong>med from <strong>the</strong><br />
rubbery to glassy state (Navabpour et al., 2006).<br />
The time interval to reach that maximum value is different<br />
<strong>for</strong> each cure temperature <strong>and</strong> shifts to longer times <strong>for</strong> lower<br />
cure temperatures.<br />
All <strong>the</strong> above observations lead to <strong>the</strong> conclusion that <strong>the</strong><br />
cure <strong>of</strong> <strong>the</strong> specific epoxy-amine system follows a complex<br />
reaction mechanism, with autocatalytic phenomena occurring<br />
during <strong>the</strong> early stages <strong>of</strong> <strong>the</strong> cure.<br />
The reaction schemes <strong>for</strong> epoxies are relatively well established<br />
<strong>and</strong> mainly involve primary <strong>and</strong> secondary amino group<br />
addition to <strong>the</strong> epoxy group, <strong>for</strong> normal curing conditions.<br />
Under extreme conditions <strong>of</strong> high cure temperatures, e<strong>the</strong>rification<br />
may also occur. These reactions may be catalysed by<br />
any impurities present in <strong>the</strong> resin, or by <strong>the</strong> hydroxyl <strong>and</strong><br />
tertiary amine products <strong>for</strong>med, resulting in autocatalysis<br />
(Shoichiro et al., 2005).<br />
Table 2 summarizes <strong>the</strong> parameters obtained from fitting<br />
<strong>the</strong> experimental data to <strong>the</strong> Eqs. (4) <strong>and</strong> (5). Values <strong>of</strong> preexponential<br />
factor <strong>and</strong> activation energy were calculated from<br />
Figure 2 (a) Fractional conversion <strong>for</strong> iso<strong>the</strong>rmal Cure at 100 °C <strong>for</strong> different time <strong>of</strong> reticulation. (b) Reaction rates <strong>for</strong> dynamic cure at<br />
different times <strong>of</strong> cure <strong>for</strong> RTM6 at 100 °C.
40 L. Merad et al.<br />
Table 2<br />
Parameters obtained from fitting <strong>the</strong> iso<strong>the</strong>rmal curing results using DSC.<br />
Cure temperature (°C) k 1 (10 5 s 1 ) k 2 (10 3 s 1 ) m n n 1 n 2<br />
Eq. (4)<br />
@a<br />
@t ¼ðk 1 þ k 2 a m Þð1 aÞ n<br />
100 2.21 0.53 0.95 0.59 – –<br />
135 3.52 0.92 1.09 0.66 – –<br />
150 4.30 1.35 1.11 0.79 – –<br />
@a<br />
Eq. (5)<br />
@t ¼ k 1ð1 aÞ n1 þ k 2 a m ð1 aÞ n2<br />
100 2.15 0.51 0.95 – 0.52 0.66<br />
135 3.43 0.89 1.07 – 0.58 0.73<br />
150 4.11 1.28 1.05 – 0.71 0.86<br />
<strong>the</strong> temperature dependence <strong>of</strong> k 1 <strong>and</strong> k 2 using <strong>the</strong> Arrhenius<br />
equation. Values <strong>of</strong> E 1 <strong>and</strong> E 2 <strong>for</strong> <strong>the</strong> conventionally cured<br />
samples are in agreement with those obtained by Karkanas<br />
<strong>and</strong> Partridge. The values <strong>of</strong> A 1 <strong>and</strong> A 2 were, however, much<br />
smaller than <strong>the</strong> values obtained by <strong>the</strong>m. As in <strong>the</strong>ir analysis<br />
<strong>the</strong>y did not correct <strong>the</strong> kinetics models <strong>for</strong> diffusion control,<br />
<strong>the</strong> fits to <strong>the</strong> experimental data were not as good as in this<br />
work, <strong>and</strong> this might explain <strong>the</strong> observed differences in<br />
pre-exponential factors (see Fig. 3).<br />
A 1 ¼ 22420 s 1 ; E 1 ¼ 71:l kJ mol 1<br />
ð4Þ<br />
A 2 ¼ 10256 s 1 ; E 2 ¼ 55:65 kJ mol 1<br />
A 1 ¼ 25820 s 1 ; E 1 ¼ 73:6 kJ mol 1<br />
A 2 ¼ 25460 s 1 ; E 2 ¼ 61:84 kJ mol 1<br />
4.1. SEM<br />
For appreciation dispersion <strong>of</strong> Nanoparticles TiO 2 .<br />
As shown in Figs. 4 <strong>and</strong> 5 <strong>of</strong> SEM, <strong>the</strong> epoxy resin has a<br />
smooth <strong>and</strong> flat surface in without TiO 2 , with addition <strong>of</strong><br />
percentage <strong>of</strong> TiO 2 it is observed that a relatively little amount<br />
<strong>of</strong> TiO 2 particles are attached to <strong>the</strong> surface <strong>of</strong> resin with a<br />
good dispersion.<br />
The SEM analysis suggests that TiO 2 particles are uni<strong>for</strong>mly<br />
distributed within <strong>the</strong> materials.<br />
The non-iso<strong>the</strong>rmal kinetic study <strong>of</strong> weight loss during a<br />
<strong>the</strong>rmal decomposition process <strong>of</strong> epoxy resin containing<br />
ð5Þ<br />
TiO 2 at 1%, 2%, 5% <strong>and</strong> 10%. Two different methods, all<br />
based on Arrhenius kinetic <strong>the</strong>ory, were used <strong>for</strong> <strong>the</strong> kinetic<br />
analysis <strong>of</strong> <strong>the</strong> TG/DTG data: one based on differential<br />
method <strong>and</strong> o<strong>the</strong>r based on integral method. In all <strong>of</strong> <strong>the</strong>se<br />
methods, calculations were per<strong>for</strong>med to estimate <strong>the</strong> kinetic<br />
parameter activation energy.<br />
For obtaining <strong>the</strong> kinetic in<strong>for</strong>mation, such as <strong>the</strong> activation<br />
energy, <strong>the</strong> TGA study has been conducted with <strong>the</strong><br />
variation <strong>of</strong> <strong>the</strong> heating rates.<br />
Fig. 6(a) shows <strong>the</strong> TGA <strong>the</strong>rmograms <strong>of</strong> epoxy resin<br />
containing different percentage <strong>of</strong> TiO 2 1%, 2%, 5% <strong>and</strong><br />
10% at a constant heating rate 10 °C min 1 .<br />
Fig. 6(b) shows <strong>the</strong> TGA <strong>the</strong>rmograms <strong>of</strong> epoxy resin<br />
containing a 1% <strong>of</strong> TiO 2 , corresponding to dynamic experiments<br />
carried out at different heating rates (5, 10, 20, <strong>and</strong><br />
30 °C min 1 ).<br />
The corresponding differential (DTG) curves <strong>of</strong> this sample<br />
are shown in Figs. 7 <strong>and</strong> 8. The <strong>the</strong>rmal decomposition process<br />
in two steps degradation, probably corresponding to epoxy<br />
resin two step corresponding to <strong>the</strong> degradation <strong>of</strong> e<strong>the</strong>r group<br />
structures in <strong>the</strong> polymer matrix (Santos et al., 2002; Shoichiro<br />
et al., 2005; Hansmann et al., 2003).<br />
The non-iso<strong>the</strong>rmal kinetic study <strong>of</strong> weight loss during a<br />
<strong>the</strong>rmal decomposition process <strong>of</strong> RTM6/TiO 2 samples is<br />
extremely complex because <strong>of</strong> <strong>the</strong> presence <strong>of</strong> two components<br />
<strong>and</strong> <strong>the</strong>ir consecutive reactions. Two different methods, all<br />
based on Arrhenius kinetic <strong>the</strong>ory, were used <strong>for</strong> <strong>the</strong> analysis<br />
<strong>of</strong> TG/DTG data, one on integral method <strong>and</strong> <strong>the</strong> o<strong>the</strong>r based<br />
on approximation method. In all <strong>the</strong>se methods, calculations<br />
Figure 3 (a) Reaction rates <strong>for</strong> dynamic cure at different times <strong>of</strong> cure <strong>for</strong> RTM6 at 135 °C. (b) Reaction rates <strong>for</strong> dynamic cure at<br />
different times <strong>of</strong> cure <strong>for</strong> RTM6 at 150 °C.
Kinetic study <strong>of</strong> <strong>the</strong> RTM6/TiO 2 by DSC/TGA <strong>for</strong> improved hardness <strong>of</strong> resin 41<br />
Figure 4 (a) SEM image <strong>of</strong> RTM6 + 1% TiO 2 , (b) SEM image <strong>of</strong> RTM6 + 2% TiO 2 .<br />
Figure 5 (a) SEM image <strong>of</strong> RTM6 + 5% TiO 2 , (b) SEM image <strong>of</strong> RTM6 + 10% TiO 2 .<br />
Figure 6 (a) TGA <strong>the</strong>rmograms <strong>of</strong> RTM6 with TiO 2 constant heating rate <strong>of</strong> 10 °C min 1 , (b) TGA <strong>the</strong>rmograms <strong>of</strong> RTM6 with 1% at<br />
a <strong>of</strong> TiO 2 at different heating rates.<br />
were per<strong>for</strong>med to estimate <strong>the</strong> kinetic parameter as activation<br />
energy (Ng et al., 1999).<br />
Using <strong>the</strong> Kissinger Eq. (11), lines <strong>of</strong> lnðb=T 2 maxÞ versus 1/<br />
T max <strong>for</strong> each stage <strong>of</strong> <strong>the</strong> <strong>the</strong>rmal degradation were plotted<br />
<strong>for</strong> all samples. Fig. 9(a) shows <strong>the</strong> representative plots <strong>for</strong><br />
each stage <strong>of</strong> <strong>the</strong> <strong>the</strong>rmal degradation <strong>of</strong> epoxy resin at 1%<br />
<strong>of</strong> TiO 2 . The calculated decomposition activation energies<br />
<strong>for</strong> epoxy step <strong>of</strong> all samples are listed in Table 2. The<br />
activation energies <strong>for</strong> epoxy resins contain a different percentage<br />
<strong>of</strong> TiO 2 as compared to <strong>the</strong>m.<br />
The all steps mainly involve <strong>the</strong> degradation <strong>of</strong> carbonyl<br />
groups in <strong>the</strong> resin matrix. However, <strong>the</strong> activation energies<br />
at higher conversions increase with increasing <strong>the</strong> percentage<br />
<strong>of</strong> TiO 2 .<br />
Ano<strong>the</strong>r procedure <strong>for</strong> calculating <strong>the</strong> activation energy is<br />
taking <strong>the</strong> Flynn–Wall–Ozawa equation. At given value <strong>of</strong><br />
<strong>the</strong> conversion, <strong>the</strong> activation energy can be obtained from a<br />
logarithmic plot <strong>of</strong> heating rates as a function <strong>of</strong> <strong>the</strong> reciprocal<br />
<strong>of</strong> temperature, since <strong>the</strong> slope <strong>of</strong> such a line is given by 0.4567<br />
E/R. For <strong>the</strong> present work, <strong>the</strong> conversion values <strong>of</strong> 50% <strong>and</strong><br />
98% were used. The fitting lines <strong>of</strong> different samples at <strong>the</strong><br />
selected conversion values are shown in Fig. 9. All <strong>of</strong> <strong>the</strong><br />
calculated activation energies are listed in Table 3. The activation<br />
energy at different conversions increases with increasing<br />
<strong>the</strong> percentage <strong>of</strong> TiO 2 (Lu et al., 2004).<br />
The experiment realized with different heating rates indicates<br />
<strong>the</strong> same mechanisms with variation kinetic parameter<br />
values. The kinetic parameter obtained by integral <strong>and</strong><br />
approximation methods presented good correlation. In<br />
general, <strong>the</strong> values obtained by <strong>the</strong> Kissinger method were high<br />
<strong>for</strong> <strong>the</strong> first step than <strong>the</strong> values obtained by <strong>the</strong><br />
Flynn–Wall–Ozawa method <strong>and</strong> <strong>for</strong> <strong>the</strong> second step <strong>the</strong> values<br />
obtained by Kissinger were small than <strong>the</strong> values obtained by<br />
<strong>the</strong> Flynn–Wall–Ozawa method. In <strong>the</strong> present study, <strong>the</strong> two
42 L. Merad et al.<br />
Figure 7 (a) TGA <strong>the</strong>rmograms <strong>of</strong> RTM6 with 2% <strong>of</strong> TiO 2 at different heating rates, (b) TGA <strong>the</strong>rmograms <strong>of</strong> RTM6 with 5% <strong>of</strong> TiO 2<br />
at different heating rates.<br />
<strong>of</strong> a viscous flow. The blends undergo melting <strong>and</strong> noncross-linked<br />
reagents leave <strong>the</strong> samples. Maybe <strong>the</strong> rate <strong>of</strong> <strong>the</strong>ir<br />
escape inversely depends on <strong>the</strong> viscosity. Of course, catalytic<br />
reactions with a diffusion control are possible as well. The<br />
diffusion coefficient is inversely proportional to <strong>the</strong> viscosity.<br />
When nano-TiO 2 particles are dispersed in epoxy resin, <strong>the</strong><br />
interaction between larger surface areas <strong>of</strong> particles <strong>and</strong> substrate<br />
will help reduce <strong>the</strong> activity <strong>of</strong> substrate bond. This<br />
interaction improves <strong>the</strong> hardness <strong>of</strong> materials such as <strong>the</strong><br />
mechanical property <strong>of</strong> <strong>the</strong> epoxy resin/TiO 2 . It can be seen<br />
from Fig. 10 that when <strong>the</strong> concentration <strong>of</strong> nanosized TiO 2<br />
powder increases, <strong>the</strong> hardness <strong>of</strong> materials will be improved<br />
(see Tables 4 <strong>and</strong> 5).<br />
5. Conclusions<br />
Figure 8 DTG curve <strong>of</strong> a sample at a constant heating rate <strong>of</strong><br />
10 °C min 1 .<br />
methods show good agreement when used to determine <strong>the</strong><br />
decomposition activation energies at certain conversion values.<br />
The activation energy <strong>for</strong> <strong>the</strong> first step <strong>of</strong> <strong>the</strong> decomposition<br />
is very low (about 25 kJ/mol or 6 kcal/mol). It is too low <strong>for</strong><br />
<strong>the</strong> overwhelming majority <strong>of</strong> high-temperature reactions. It<br />
seems that such energy could be attributed to activation energy<br />
A combination <strong>of</strong> nth order <strong>and</strong> autocatalytic reaction kinetics<br />
was applied to fit data from dynamic <strong>and</strong> iso<strong>the</strong>rmal DSC<br />
scans <strong>of</strong> a commercial RTM resin. A unique set <strong>of</strong> kinetic<br />
parameters was obtained <strong>for</strong> <strong>the</strong> dynamic case, suggesting a<br />
constant reaction mechanism throughout <strong>the</strong> range <strong>of</strong> <strong>the</strong><br />
heating rates used. In <strong>the</strong> iso<strong>the</strong>rmal case, <strong>the</strong> kinetic parameters<br />
required to achieve a good fit were different from those<br />
found in <strong>the</strong> dynamic runs; in particular, <strong>the</strong> reaction orders<br />
had to be allowed to vary with cure temperature. The <strong>the</strong>rmal<br />
Figure 9 (a) Plot <strong>of</strong> lnðb=T 2 max Þ versus 1/T max <strong>of</strong> RTM6 with 1% <strong>of</strong> TiO 2 <strong>for</strong> calculating <strong>the</strong> activation (b) Plots <strong>of</strong> logb versus 1/T <strong>of</strong><br />
RTM6 with 1% <strong>of</strong> TiO 2 <strong>for</strong> calculating <strong>the</strong> activation energies by Kissinger method Flynn–Wall–Ozawa.
Kinetic study <strong>of</strong> <strong>the</strong> RTM6/TiO 2 by DSC/TGA <strong>for</strong> improved hardness <strong>of</strong> resin 43<br />
Table 3<br />
Calculated decomposition activation energies <strong>for</strong> every stage <strong>of</strong> all samples by Kissinger method.<br />
Samples First step Second step<br />
Temperature range (°C) D m (%) T (°C) Temperature range (°C) D m (%) T (°C)<br />
RTM6 + 1%TiO 2 280–500 63.44 410.10 500–834.12 26.42 650.11<br />
RTM6 + 2%TiO 2 280–500 65.43 415.78 500–834.12 28.67 654.67<br />
RTM6 + 5%TiO 2 280–500 68.45 425.76 500–834.12 30.45 699.98<br />
RTM6 + 10%TiO 2 280–500 74.76 435.56 500–834.12 33.56 673.45<br />
loss rates were altered by <strong>the</strong> TiO 2 nanocharges. The kinetic<br />
parameters obtained by approximation <strong>and</strong> integral methods<br />
were satisfactory <strong>and</strong> present good correlation.<br />
This experiment attempts to process materials, using epoxy<br />
resin <strong>and</strong> nanosized TiO 2 powder, <strong>the</strong> hardness will increase<br />
with <strong>the</strong> increase <strong>of</strong> concentration <strong>of</strong> TiO 2 .<br />
References<br />
Figure 10<br />
TiO 2 .<br />
Hardness <strong>of</strong> epoxy/TiO 2 on different concentration <strong>of</strong><br />
stability <strong>of</strong> epoxy resin containing nanocharges TiO 2 was evaluated<br />
by <strong>the</strong>rmogravimetric curves <strong>and</strong> activation energy obtained<br />
from <strong>the</strong>rmogravimetric data. The results obtained<br />
indicated that <strong>the</strong> activation energies at higher conversions increase<br />
with increasing <strong>the</strong> percentage <strong>of</strong> TiO 2 . The degradation<br />
activation energies, decomposition temperatures <strong>and</strong> weight<br />
Farquharson, S., Smith, W., Rose, J., Shaw, M., 2007. Correlations<br />
between molecular (Raman) <strong>and</strong> macroscopic (rheology) data <strong>for</strong><br />
process monitoring <strong>of</strong> <strong>the</strong>rmoset composite. JPAC SM process<br />
Analytical Chemistry, 45–53.<br />
Hansmann, H., 2003. Composite, Compendium, ASM h<strong>and</strong>book/<br />
Extraction Epoxy resins.<br />
Hung, K.S., Nien, Y.H., Chen, J.S., Shieh, T.R., Chen, J.W., 2006.<br />
Syn<strong>the</strong>sis <strong>and</strong> properties <strong>of</strong> epoxy/TiO 2 composite materials.<br />
Polymer Composite 27, 195–200.<br />
Karkanas, P.I., Partridge, I.K., Attwood, D., 1996. Modelling <strong>the</strong> cure<br />
<strong>of</strong> a commercial epoxy resin <strong>for</strong> applications in resin transfer<br />
moulding. Polymer International 41, 183–191.<br />
Lu, L., Lai, M.O., Yan, M.C., Ye, L., 2004. Nanostructured high<br />
strengh Mg–5%Al–x%Nd alloys prepared by mechanical alloying.<br />
Revue Advanced Material Science 6, 28–32.<br />
Navabpour, P., Degamber, B., Fern<strong>and</strong>o, G., Mann, T., Day, R., 2006.<br />
Comparison <strong>of</strong> <strong>the</strong> curing kinetics <strong>of</strong> <strong>the</strong> RTM6 epoxy resin system<br />
Table 4<br />
Calculated decomposition activation energies <strong>for</strong> every stage <strong>of</strong> all samples by Kissinger method.<br />
Samples Region Conversion a T max (K) (b =10°C.min 1 ) Activation Energy E a (kJ/mol) Correlation coefficient r<br />
1% TiO 2 1 Step 0.00–0.50 0.00–0.50 673 21 0.995<br />
Step 0.50–0.98 0.50–0.98 953 155 0.998<br />
2% TiO 2 1 Step 0.00–0.50 0.00–0.50 675.67 23 0.998<br />
2 Step 0.50–0.98 0.50–0.98 960.34 157 0.997<br />
5% TiO 2 1 Step 0.00–0.50 0.00–0.50 678.56 25 0.993<br />
2 Step 0.50–0.98 0.50–0.98 967.78 161 0.995<br />
10% TiO 2 1 Step 0.00–0.50 0.00–0.50 683.56 29 0.996<br />
2 Step 0.50–0.98 0.50–0.98 971.56 168 0.998<br />
Table 5<br />
Calculated decomposition activation energies <strong>for</strong> every stage <strong>of</strong> all samples by Flynn–Wall–Ozawa method.<br />
Samples Region Conversion Activation Energy<br />
E a (kJ/mol)<br />
1% TiO 2 1 Step 0.00–0.50 0.00–0.50 29 0.995<br />
2 Step 0.50–0.98 0.50–0.98 146 0.998<br />
2% TiO 2 1 Step 0.00–0.50 0.00–0.50 25 0.998<br />
2 Step 0.50–0.98 0.50–0.98 153 0.997<br />
5% TiO 2 1 Step 0.00–0.50 0.00–0.50 28 0.993<br />
2 Step 0.50–0.98 0.50–0.98 159 0.995<br />
10% TiO 2 1 Step 0.00–0.50 0.00–0.50 31 0.996<br />
2 Step 0.50–0.98 0.50–0.98 170 0.998<br />
Correlation<br />
coefficient r
44 L. Merad et al.<br />
using differential scanning calorimetry <strong>and</strong> a microwave-heated<br />
calorimeter. <strong>Journal</strong> <strong>of</strong> <strong>Applied</strong> Polymer Science 99, 3658–3668.<br />
Ng, C.B., Scbadler, L.S., Siegel, R.W., 1999. Syn<strong>the</strong>sis <strong>and</strong> mechanical<br />
properties <strong>of</strong> TiO 2 -epoxy nanocomposite. Nanostructured Materials<br />
12, 507–510.<br />
Puglia, D., Valentini, L., Armentano, I., Kenny, J.M., 2003. Effects <strong>of</strong><br />
single-walled carbon nanotube incorporation on <strong>the</strong> cure reaction<br />
<strong>of</strong> epoxy resin <strong>and</strong> its detection by raman spectroscopy. Diamond<br />
<strong>and</strong> Related Materials 12, 827–832.<br />
Santos, J.C.O., Dos Santos, I.M.G., Souza, A.G., Prasad, S., Dos<br />
Santos, A.V., 2002. Thermal stability <strong>and</strong> kinetic study on <strong>the</strong>rmal<br />
decomposition <strong>of</strong> commercial edible oils by <strong>the</strong>rmogravimetry.<br />
<strong>Journal</strong> <strong>of</strong> Food Science 67 (4), 1393–1398.<br />
Shoichiro, Y., Ito, T., Shinoda, K., Ikake, H., Hagiwara, T.,<br />
Sawaguchi, T., Kurita, K., Seno, M., 2005. Properties <strong>and</strong><br />
microstructures <strong>of</strong> epoxy resin/TiO 2 <strong>and</strong> SiO 2 hybrids. Polymer<br />
International 54, 354–361.
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 45-49<br />
تنقية وقود الديزل الحيوي باستخدام الكاربون المنشط المحضر من بقايا الشاي المستنفذ<br />
عبدالرحمن باسل فاضل،<br />
محمد مجبل ذياب،<br />
عبدالقادر يوسف عبدالقادر<br />
قسم<br />
الكيمياء، كليه<br />
جامعة العلوم،<br />
الموصل، الموصل،<br />
العراق<br />
الملخص:<br />
تضمنت<br />
الدراسة الحالية<br />
تحضير<br />
تفاعل انتقال االسترة المحفز بالقاعدة.<br />
استرات<br />
النتائج<br />
المثيل(<br />
المستحصلة<br />
هالم السليكا.<br />
الناتجة وذلك<br />
أظهرت<br />
المثيل وخواص احتراقية<br />
وقود الديزل الحيوي<br />
باستخدام<br />
)استرات المثيل(<br />
بعد فصل الناتج العرضي<br />
الكربون<br />
مع نموذج الديزل الحيوي المنقى<br />
النتائج<br />
أفضل<br />
أن<br />
المستنفذ و استخدامه لنفس الغرض<br />
تنقية الديزل الحيوي باستخدام<br />
مقارنة بطرق التنقية<br />
مرة أخرى.<br />
من زيت القلي المستنفذ<br />
)الكليسيرول(<br />
تم تنقية<br />
المنشط المحضر من بقايا الشاي المستنفذ.<br />
باستخدام طريقة الغسل بالماء،<br />
األخرى<br />
وأظهرت<br />
الكربون<br />
المستخدمة.<br />
النتائج<br />
أعطى المنشط<br />
من خالل<br />
الديزل الحيوي)<br />
قورنت ولقد<br />
وطريقة التنقية باستخدام<br />
حصيلة من استرات<br />
كما تم إعادة تنشيط الكربون المنشط<br />
أيضاً أن الكربون<br />
المنشط<br />
المستنفذ المعاد<br />
تشيطه هو األخر قد أعطى حصيلة أعلى وخواص احتراقية أفضل مقارنة بطرق التنقية األخرى المستخدمة.<br />
A.Fadhil et al.
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 45–49<br />
University <strong>of</strong> Bahrain<br />
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong><br />
<strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences<br />
www.elsevier.com/locate/jaaubas<br />
www.sciencedirect.com<br />
ORIGINAL ARTICLE<br />
Purification <strong>of</strong> biodiesel using activated carbons<br />
produced from spent tea waste<br />
Abdelrahman B. Fadhil *, Mohammed M. Dheyab, Abdul-Qader Y. Abdul-Qader<br />
Department <strong>of</strong> Chemistry, College <strong>of</strong> Science, Mosul University, Mosul, Iraq<br />
Available online 30 January 2012<br />
KEYWORDS<br />
Biodiesel;<br />
Waste cooking oil;<br />
Spent tea waste;<br />
Activated carbons;<br />
Fuel properties<br />
Abstract Waste cooking oil was converted into biodiesel through base catalyzed transesterification.<br />
After separating <strong>the</strong> glycerol, <strong>the</strong> crude methyl esters were purified using activated carbons<br />
produced from spent tea waste. Yield <strong>and</strong> fuel properties <strong>of</strong> <strong>the</strong> produced biodiesels were compared<br />
with those purified by using silica gel <strong>and</strong> conventional method namely water washing method. The<br />
study revealed that using activated carbons <strong>for</strong> <strong>the</strong> purification <strong>of</strong> biodiesel resulted in higher yield<br />
<strong>and</strong> better fuel properties compared to those purified using silica gel <strong>and</strong> water washing method.<br />
Fur<strong>the</strong>rmore, <strong>the</strong> spent activated carbon was regenerated <strong>and</strong> reused <strong>for</strong> <strong>the</strong> same purpose. However,<br />
<strong>the</strong> results showed that <strong>the</strong> yield <strong>and</strong> fuel properties <strong>of</strong> those purified using <strong>the</strong> regenerated<br />
activated carbon were also better than those purified using silica gel <strong>and</strong> water washing method.<br />
ª 2012 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by Elsevier B.V. All rights reserved.<br />
1. Introduction<br />
* Corresponding author.<br />
E-mail address: abdelrahmanbasil@yahoo.com (A.B. Fadhil).<br />
1815-3852 ª 2012 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by<br />
Elsevier B.V. All rights reserved.<br />
Peer review under responsibility <strong>of</strong> University <strong>of</strong> Bahrain.<br />
doi:10.1016/j.jaubas.2011.12.001<br />
Production <strong>and</strong> hosting by Elsevier<br />
The production <strong>of</strong> biodiesel from edible oils competes with <strong>the</strong><br />
use <strong>of</strong> l<strong>and</strong> <strong>for</strong> food production. Moreover, <strong>the</strong> price <strong>of</strong> edible<br />
plant <strong>and</strong> vegetable oils is usually higher than petro diesel.<br />
Thus, finding a cheaper feedstock such as waste cooking oil<br />
<strong>for</strong> biodiesel production reduces <strong>the</strong> cost <strong>of</strong> biodiesel production<br />
since <strong>the</strong> feedstock costs constitutes approximately 70–<br />
95% <strong>of</strong> <strong>the</strong> overall cost <strong>of</strong> biodiesel production. Hence, <strong>the</strong><br />
use <strong>of</strong> waste cooking oils <strong>and</strong> non-edible oils should be given<br />
higher priority over <strong>the</strong> edible oils as biodiesel feedstock<br />
(Chhetri et al., 2008; Canakci, 2007). The purity level <strong>of</strong> <strong>the</strong><br />
biodiesel has strong influence on its fuel properties. Especially,<br />
<strong>the</strong> amount <strong>of</strong> glycerides <strong>and</strong> triglycerides present in <strong>the</strong> fuel<br />
can cause serious problems in application. Ano<strong>the</strong>r factor that<br />
must be taken into account is that <strong>the</strong> fuel must be almost free<br />
<strong>of</strong> water, alcohol, glycerin <strong>and</strong> catalyst; thus, <strong>the</strong> ester layer<br />
has to be treated. There<strong>for</strong>e, <strong>the</strong> refining step <strong>of</strong> <strong>the</strong> products<br />
obtained by transesterification is very important (Karaosmanoglu<br />
et al., 1996; Predojevic, 2008).<br />
In this study, <strong>the</strong> production <strong>of</strong> biodiesel from waste cooking<br />
oil through base catalyzed transesterification was investigated.<br />
After separating <strong>the</strong> glycerol, <strong>the</strong> crude methyl esters<br />
were purified using activated carbons produced from spent<br />
tea waste. The results were compared with those purified by<br />
using silica gel <strong>and</strong> water washing methods. Properties <strong>of</strong> <strong>the</strong><br />
produced fuels were measured <strong>and</strong> compared with those purified<br />
using o<strong>the</strong>r methods. Fur<strong>the</strong>rmore, <strong>the</strong> spent activated
46 A.B. Fadhil et al.<br />
carbon was regenerated <strong>and</strong> reused again <strong>for</strong> <strong>the</strong> same<br />
purpose.<br />
2. Materials <strong>and</strong> methods<br />
2.1. Preparation <strong>of</strong> carbon adsorbents<br />
Tea is <strong>the</strong> second drink after water in Iraq. There<strong>for</strong>e, large<br />
amounts <strong>of</strong> tea are consumed, accumulated <strong>and</strong> discarded.<br />
Such biowaste could be an attractive precursor <strong>for</strong> activated<br />
carbon (AC) preparation. Spent tea waste (STW) was collected<br />
from local c<strong>of</strong>fee shops within <strong>the</strong> city <strong>of</strong> Mosul, north <strong>of</strong> Iraq.<br />
STW was washed thoroughly with tap water <strong>and</strong> by distillated<br />
water several times, <strong>the</strong>n it was dried in an oven at 50 °C <strong>for</strong><br />
5 h. The dried STW was sieved using a 20–40 mesh sieve,<br />
<strong>and</strong> <strong>the</strong> particles <strong>of</strong> 30–40 mesh were used as a precursor <strong>for</strong><br />
activated carbon (AC) production. Two types <strong>of</strong> activated carbons<br />
were prepared from STW as follows:<br />
For batches, 20 g <strong>of</strong> <strong>the</strong> dried STW was placed into a quartz<br />
tube, <strong>and</strong> <strong>the</strong> tube was in turn placed into an electrical tubular<br />
furnace. The furnace was heated gradually until a temperature<br />
<strong>of</strong> 600 °C was reached. The activation was conducted at this<br />
temperature <strong>for</strong> 120 min, to produce <strong>the</strong>rmally activated carbon<br />
(AC TH ). The second type was prepared through placing<br />
20 g <strong>of</strong> <strong>the</strong> dried STW into a stainless steel tube which was<br />
placed into an electrical tubular furnace. The sample was<br />
heated gradually in a flow <strong>of</strong> steam until a temperature <strong>of</strong><br />
600 °C was attained. The activation was per<strong>for</strong>med at this temperature<br />
<strong>for</strong> 120 min to produce (AC ST ). The yield <strong>of</strong> <strong>the</strong> produced<br />
carbons was calculated as following:<br />
Yield% ¼ W ACproduced<br />
W STWused<br />
100<br />
Silica gel was <strong>the</strong>rmally activated at 105 °C <strong>for</strong> 5 h <strong>and</strong> was<br />
kept in a sealed container to be used later.<br />
2.2. Assessment <strong>of</strong> <strong>the</strong> produced carbon adsorbents<br />
Surface area <strong>of</strong> <strong>the</strong> prepared activated carbons (ACs) was<br />
determined by <strong>the</strong>ir adsorptive capacity <strong>of</strong> iodine, referred to<br />
as iodine adsorption number (IAN). The quantity <strong>of</strong> iodine adsorbed<br />
per gram <strong>of</strong> <strong>the</strong> activated carbon was determined by<br />
titration against <strong>the</strong> st<strong>and</strong>ard solution <strong>of</strong> sodium thiosulphate<br />
according to ASTM (1999). Adsorption capacity <strong>for</strong> <strong>the</strong> prepared<br />
carbons was determined through <strong>the</strong>ir adsorption <strong>of</strong><br />
methylene blue (MB) from its aqueous solution. Surface properties<br />
<strong>of</strong> <strong>the</strong> produced carbons such as PH, total acidity <strong>and</strong><br />
oxygen surface groups were determined. The surface functional<br />
groups <strong>of</strong> <strong>the</strong> activated carbons were analyzed by a Fourier<br />
trans<strong>for</strong>m infrared (FTIR) spectroscope.<br />
2.3. Preparation <strong>of</strong> <strong>the</strong> raw oil<br />
Waste cooking oil (WCO) was collected from local restaurants<br />
within <strong>the</strong> city <strong>of</strong> Mosul, north <strong>of</strong> Iraq <strong>and</strong> used as a feedstock<br />
<strong>for</strong> biodiesel production. At first, 500 g <strong>of</strong> <strong>the</strong> oil was mixed<br />
with freshly activated MgSO 4 , <strong>and</strong> left overnight to eliminate<br />
any water content. Then <strong>the</strong> oil was filtered by using cloth filter<br />
to remove any solid impurities <strong>and</strong> MgSO 4 particles, <strong>and</strong> was<br />
kept in a sealed container to be used later. Mean molecular<br />
weight <strong>of</strong> <strong>the</strong> oil was determined according to <strong>the</strong> <strong>for</strong>mula presented<br />
by (Zhu et al., 2006):<br />
MW ¼ 56:1 1000 3=ðSV AVÞ ð2Þ<br />
where, SV is <strong>the</strong> saponification value <strong>and</strong> AV is <strong>the</strong> acid value.<br />
2.4. Transesterification <strong>of</strong> waste cooking oil<br />
Five hundred grams <strong>of</strong> <strong>the</strong> oil was poured into a 250 mL three<br />
necked round bottomed flask equipped with a mechanical stirrer,<br />
<strong>and</strong> a condenser, <strong>and</strong> placed in water bath. Freshly prepared<br />
catalyst solution (KOH = 0.75% w/w <strong>of</strong> oil dissolved<br />
in methanol in a ratio <strong>of</strong> 6:1 MeOH–oil) was introduced into<br />
<strong>the</strong> reactor. The mixture was refluxed <strong>for</strong> 1 h at (60 °C) with<br />
continuous stirring. After <strong>the</strong> reaction was over, <strong>the</strong> mixture<br />
was transferred into a separating funnel <strong>and</strong> left to settle <strong>for</strong><br />
24 h. Two layers were obtained, <strong>the</strong> upper was <strong>the</strong> methyl esters<br />
(ME) <strong>and</strong> <strong>the</strong> lower was <strong>the</strong> glycerol. Glycerol layer was<br />
discarded, <strong>and</strong> <strong>the</strong> methyl ester layer was distillated under vacuum<br />
to recover excess methanol. Finally, <strong>the</strong> methyl ester layer<br />
was kept <strong>for</strong> purification <strong>and</strong> assessment.<br />
2.5. Chemicals<br />
Methanol (reagent grade), acetone, glacial acetic acid, iodine,<br />
potassium iodide, sodium thiosulfate, starch, diethyl e<strong>the</strong>r, isopropyl<br />
alcohol, silica gel <strong>and</strong> <strong>for</strong>mic acid were purchased from<br />
BDH. Potassium <strong>and</strong> sodium hydroxide, <strong>and</strong> magnesium sulfate<br />
were supplied from Merck, whereas chlor<strong>of</strong>orm, n-hexane<br />
<strong>and</strong> hydrochloric acid were supplied from Fluka. Chemicals<br />
were used without any fur<strong>the</strong>r purification.<br />
2.6. Purification <strong>of</strong> biodiesel over activated carbons<br />
A chromatography column <strong>of</strong> (15 cm height <strong>and</strong> 1 cm i.d) was<br />
packed with glass wool, <strong>the</strong>n a bed (2 g = 5 cm) <strong>of</strong> activated<br />
carbon was introduced into <strong>the</strong> column. Next, crude methyl esters<br />
were transferred into <strong>the</strong> column <strong>and</strong> allowed to pass<br />
through <strong>the</strong> adsorbent bed with a flow rate <strong>of</strong> (15 drop/min).<br />
Percentage yield was calculated on a weight basis with respect<br />
to <strong>the</strong> methyl ester introduced into <strong>the</strong> column (Predojevic,<br />
2008). Silica gel was also used <strong>for</strong> <strong>the</strong> same purpose. Purification<br />
using (water washing) method was also adopted.<br />
Table 1<br />
Physicochemical properties <strong>of</strong> <strong>the</strong> raw oil.<br />
Property Test procedure Value<br />
Density @ 16 °C g/ml (D) ASTM D4052-91 0.9233<br />
Kine.Viscosity@ 40 °Cmm 2 /s(KV) ASTM D445 26.50<br />
Flash point °C (T F ) ASTM D93 244<br />
Pour point °C (PP) ASTM D2500 9<br />
Cloud point °C (CP) ASTM D2500 1<br />
Acid value mg KOH/g (AV) ASTM D664 2.82<br />
Iodine number mg I 2 /100 oil(IN) Paquot, 1979 110<br />
Refractive index @ 20 °C (RI) D1747-09 1.470<br />
Conradson carbon residue% (CCR) ASTM D4530 0.35<br />
Sapon. value mg KOH/g oil (SV) ASTM D5555-95 201<br />
Calculated cetane index (CCI) Krisnangkura, 1986 49.15<br />
Higher heating value (HHV) Demirbas, 2008 39.27
Purification <strong>of</strong> biodiesel using activated carbons produced from spent tea waste 47<br />
Table 2<br />
Characteristics <strong>of</strong> <strong>the</strong> prepared carbon adsorbents.<br />
Sample Yield % IAN mg I 2 /g MB mg/g PH Acidity m mol g 1 <strong>Basic</strong>ity m mol g 1<br />
AC ST 27 767 39.30 9 1.57 3.55<br />
AC TH 41 688 43.0 8 1.53 3.15<br />
SG – 478 – – –<br />
2.7. Properties assessment <strong>of</strong> <strong>the</strong> purified biodiesels<br />
Properties <strong>of</strong> <strong>the</strong> parent oil were measured according to <strong>the</strong><br />
ASTM st<strong>and</strong>ards listed in Table 1. Iodine number (IN) was<br />
measured according to <strong>the</strong> Hanus method (Paquot, 1979).<br />
Higher heating value (HHV) was determined depending on<br />
equations proposed by Demirbas (Demirbas, 2008). The calculated<br />
cetane index (CCI) is based on Krisnagkura equation<br />
(Krisnangkura, 1986):<br />
CCI ¼ 46:3 þð5458=SVÞ ð0:225INÞ ð3Þ<br />
Where, SV is <strong>the</strong> saponification value <strong>and</strong> IN is <strong>the</strong> iodine<br />
number.<br />
2.8. Regeneration <strong>of</strong> spent activated carbon<br />
Spent activated carbon (AC ST ) used <strong>for</strong> <strong>the</strong> purification <strong>of</strong><br />
crude methyl esters was regenerated to be reused <strong>for</strong> <strong>the</strong> purpose<br />
explained in (Section 2.6). Then, <strong>the</strong> yield <strong>and</strong> fuel properties<br />
<strong>of</strong> <strong>the</strong> purified methyl esters were determined <strong>and</strong><br />
compared with those purified by <strong>the</strong> au<strong>the</strong>ntic (AC ST ), silica<br />
gel <strong>and</strong> water washing method.<br />
3. Results <strong>and</strong> discussion<br />
3.1. Properties <strong>of</strong> <strong>the</strong> feed stock<br />
Each value <strong>of</strong> <strong>the</strong> measured properties was <strong>the</strong> result <strong>of</strong> at least<br />
two trials, only <strong>the</strong> mean was recorded. The average molecular<br />
weight obtained <strong>for</strong> WCO is 821. It is well known that base<br />
catalyzed transesterification (BCTE) is not suitable <strong>for</strong> oils <strong>of</strong><br />
high free fatty acid content (>1%), <strong>for</strong> it leads to catalyst<br />
deactivation <strong>and</strong> soap <strong>for</strong>mation. As a result, yield decreases<br />
(Sharma et al., 2008). However, reviewing <strong>the</strong> literature indicates<br />
little works about <strong>the</strong> production <strong>of</strong> BD from oils <strong>of</strong> high<br />
fatty acid content using BCTE (Phan <strong>and</strong> Phan, 2008; Araujo<br />
et al., 2011).<br />
3.2. Characterization <strong>of</strong> <strong>the</strong> adsorbents<br />
Yield, total acidity, PH, oxygen surface groups <strong>and</strong> iodine <strong>and</strong><br />
methylene blue adsorption numbers <strong>of</strong> <strong>the</strong> produced biochars<br />
were determined <strong>and</strong> presented in Table 2. Yield <strong>of</strong> <strong>the</strong> produced<br />
carbons was specified as <strong>the</strong> ratio <strong>of</strong> <strong>the</strong> weight <strong>of</strong> final<br />
activated carbons to that <strong>of</strong> initial raw materials used <strong>for</strong> <strong>the</strong><br />
preparation. It can be seen from Table 2 that yield AC ST<br />
was lower than that produced through one step pyrolysis. This<br />
is because steam accelerates fur<strong>the</strong>r removal <strong>of</strong> <strong>the</strong> volatiles<br />
from <strong>the</strong> structure <strong>of</strong> <strong>the</strong> feedstock. As a result, <strong>the</strong> yield decreases.<br />
Iodine adsorption number was used as a function <strong>of</strong><br />
surface area <strong>of</strong> <strong>the</strong> produced carbons. Each 1.0 mg <strong>of</strong> iodine<br />
adsorbed equals to 1.0 m 2 <strong>of</strong> <strong>the</strong> activated carbon internal surface<br />
area (Egwaikhide et al., 2007). Iodine adsorption numbers<br />
<strong>of</strong> <strong>the</strong> adsorbents are listed in Table 2. It can be seen from this<br />
table that AC ST had higher surface area compared to AC TH .<br />
This is because steam activation helps to increase <strong>the</strong> porous<br />
structure through fur<strong>the</strong>r removal <strong>of</strong> volatiles. Consequently,<br />
<strong>the</strong> surface area increases. The adsorption <strong>of</strong> methylene blue<br />
is attributed to its meso porosity. MB values <strong>of</strong> <strong>the</strong> produced<br />
carbons were much lower than those <strong>of</strong> <strong>the</strong> IAN. This means<br />
that <strong>the</strong> produced carbons have micro porous structures. The<br />
values <strong>of</strong> PH showed that both AC ST <strong>and</strong> AC TH had a basic<br />
surface, but <strong>the</strong> surface <strong>of</strong> AC ST was more basic. This was also<br />
confirmed through <strong>the</strong> titration against a (0.06 M) solution <strong>of</strong><br />
HCl. The most important oxygen groups specified by FTIR<br />
spectroscope <strong>for</strong> <strong>the</strong> produced AC are presented in Table 3.<br />
3.3. Purification <strong>of</strong> biodiesel using <strong>the</strong> produced activated<br />
carbons<br />
The main purpose <strong>of</strong> this study was to use <strong>the</strong> produced activated<br />
carbons <strong>for</strong> biodiesel purification, <strong>and</strong> comparing its results<br />
with those purified by using silica gel <strong>and</strong> water washing<br />
methods. Yields <strong>of</strong> <strong>the</strong> produced BD fuels were specified by <strong>the</strong><br />
weight percentage <strong>of</strong> <strong>the</strong> purified BD relative to <strong>the</strong> original<br />
weight <strong>of</strong> <strong>the</strong> crude methyl esters introduced into <strong>the</strong> column.<br />
It can be seen from Tables 4 that using ACs <strong>for</strong> purification <strong>of</strong><br />
<strong>the</strong> crude methyl esters results in higher yields compared to<br />
using SG <strong>and</strong> water washing methods. In comparison to SG,<br />
activated carbon has higher surface area. Besides, it is well<br />
known that <strong>the</strong> adsorption takes place through physical or<br />
chemical interactions between <strong>the</strong> adsorbate <strong>and</strong> <strong>the</strong> adsorbent<br />
surface. Fur<strong>the</strong>rmore, <strong>the</strong> oxygen groups that exist on <strong>the</strong> surface<br />
<strong>of</strong> <strong>the</strong> adsorbent play an important role in <strong>the</strong> adsorption.<br />
As <strong>for</strong> <strong>the</strong> SG, it is well known that <strong>the</strong> only groups that exist<br />
in SG are silanol groups, while many oxygen groups can be<br />
found on <strong>the</strong> surface <strong>of</strong> activated carbon. This is why, purification<br />
using ACs is better. With regard to water washing method,<br />
excessive amounts <strong>of</strong> water are added with gentle shaking<br />
to remove impurities such as glycerol, unreacted methanol <strong>and</strong><br />
base (catalyst). Consequently; part <strong>of</strong> <strong>the</strong> esters is lost in <strong>the</strong><br />
<strong>for</strong>m <strong>of</strong> emulsion <strong>and</strong> soaps decreasing <strong>the</strong> yield. One <strong>of</strong> <strong>the</strong><br />
disadvantages <strong>of</strong> this method is that it produces large amounts<br />
Table 3 Fundamental IR absorption b<strong>and</strong>s <strong>of</strong> <strong>the</strong> produced<br />
carbons.<br />
B<strong>and</strong> cm 1 Possible assignment<br />
3425–3435 OH groups in aliphatic <strong>and</strong> phenolic structures<br />
2925 Represents aliphatic CH, CH 2 <strong>and</strong> CH 3 stretching<br />
modes<br />
1726 C‚O in ketones, aldehydes or carboxyl<br />
1599 VC‚O<br />
1450 C–O Stretching vibrations, C–O–C, O–H bending<br />
modes in carboxylic acids, carboxyl, lactones, esters,<br />
<strong>and</strong> e<strong>the</strong>rs.<br />
874 O–O stretching<br />
716 C‚O stretching
48 A.B. Fadhil et al.<br />
Table 4<br />
ACs.<br />
Property<br />
Yields <strong>and</strong> properties <strong>of</strong> biodiesel purified using <strong>the</strong><br />
WCO<br />
AC ST AC TH SG Washing by DW<br />
Yield% 97 95.50 93 88<br />
Density @ 16 °C g/ml 0.8755 0.8766 0.8800 0.8920<br />
KV @ 40 °Cmm 2 /sec 2.63 2.73 3.22 3.40<br />
AV mg KOH/g oil 0.092 0.144 0.247 0.301<br />
RI @ 20 °C 1.445 1.446 1.448 1.457<br />
(PP) °C 8 8 7 6<br />
T F °C 169 169 172 175<br />
HHV MJ/KG 40.66 40.71 40.93 41.11<br />
<strong>of</strong> highly polluting wastewater. It also increases <strong>the</strong> size <strong>and</strong><br />
cost <strong>of</strong> <strong>the</strong> separation equipment, resulting in yield loss, <strong>and</strong><br />
causes an environmental disposal problem (Saleh et al.,<br />
2010). Pighinelli et al. (2011) prepared ethyl ester from sunflower<br />
oil. They used three methods <strong>for</strong> purifying <strong>the</strong> produced<br />
ethyl esters including acidified water (5% <strong>of</strong> phosphoric acid),<br />
silica gel <strong>and</strong> distillation. The yields <strong>of</strong> <strong>the</strong> produced ethyl esters<br />
obtained by using <strong>the</strong>se purification methods were<br />
(84.4%, 84.6% <strong>and</strong> 92.3%), respectively. Predojevic (2008)<br />
prepared biodiesels from waste cooking. He used three different<br />
methods <strong>for</strong> <strong>the</strong> purification <strong>of</strong> <strong>the</strong> produced methyl esters<br />
including water washing method, washing by acidified water<br />
(5% H 3 PO 4 ) <strong>and</strong> silica gel. He found that purification by <strong>the</strong><br />
acidified water <strong>and</strong> silica gel methods resulted in higher yield<br />
(92%) compared to <strong>the</strong> water washing method (89%). There<strong>for</strong>e,<br />
one can say, that our h<strong>and</strong>ling was better than those applied<br />
by <strong>the</strong> a<strong>for</strong>ementioned studies; it resulted in higher yields.<br />
For BD to be used as a fuel in diesel engines, it should meet<br />
some specifications according to <strong>the</strong> ASTM st<strong>and</strong>ards or<br />
European st<strong>and</strong>ards. Thus, after <strong>the</strong> purification <strong>of</strong> <strong>the</strong> produced<br />
methyl esters by <strong>the</strong> suggested method, some essential<br />
properties were measured, <strong>and</strong> compared to those obtained<br />
by o<strong>the</strong>r methods. These properties were measured according<br />
to <strong>the</strong> ASTM st<strong>and</strong>ards as can be seen in Table 1; fuel properties<br />
<strong>of</strong> <strong>the</strong> produced fuels are given in Table 4.<br />
One <strong>of</strong> <strong>the</strong> most important properties <strong>of</strong> biodiesel is viscosity.<br />
This property should be low. Poor atomization <strong>of</strong> <strong>the</strong> fuel<br />
spray <strong>and</strong> less accurate operation <strong>of</strong> <strong>the</strong> fuel injectors is associated<br />
with high viscosity (Demirbas, 2009). It is obvious from<br />
Table 4 that <strong>the</strong> viscosity <strong>of</strong> <strong>the</strong> methyl esters purified using <strong>the</strong><br />
ACs was lower than that purified by SG <strong>and</strong> water washing<br />
method. This means that <strong>the</strong> ACs is an effective adsorbent in<br />
removing impurities, such as glycerol <strong>and</strong> soaps which accompany<br />
<strong>the</strong> biodiesel during its production, compared to SG <strong>and</strong><br />
water washing. The values were between (2.63 <strong>and</strong> 3.40 mm 2 /<br />
sec). These values were much lower than those recommended<br />
by <strong>the</strong> ASTM <strong>and</strong> <strong>the</strong> European st<strong>and</strong>ards. Density is ano<strong>the</strong>r<br />
important property <strong>of</strong> biodiesel. As in <strong>the</strong> case <strong>of</strong> <strong>the</strong> viscosity<br />
values, <strong>the</strong> density <strong>of</strong> <strong>the</strong> methyl esters purified using ACs were<br />
also lower than that purified using SG <strong>and</strong> water washing<br />
method. The values ranged from (0.8755 to 0.8920 g/mL).<br />
The acid value can be used as a guide in quality control <strong>of</strong><br />
fuels. Acid value <strong>for</strong> <strong>the</strong> produced methyl esters was lower<br />
than that <strong>of</strong> <strong>the</strong> parent oil. Methyl esters purified using ACs<br />
had lower acid values than those purified by using SG <strong>and</strong><br />
water washing method. Lower acid values <strong>of</strong> <strong>the</strong> methyl esters<br />
purified using ACs reflects <strong>the</strong> high refining degree compared<br />
to <strong>the</strong> methyl esters purified using SG <strong>and</strong> water washing<br />
method. The values ranged from (0.092 to 0.301 mg KOH/<br />
g). Refractive index (RI) values <strong>of</strong> <strong>the</strong> fuels were lower than<br />
that <strong>of</strong> <strong>the</strong> parent oil <strong>and</strong> ranged between (1.445 <strong>and</strong> 1.457).<br />
The flash point is <strong>the</strong> lowest temperature at which a fuel will<br />
ignite when exposed to an ignition source (Ghobadian<br />
et al.,2008). Flash point values <strong>of</strong> <strong>the</strong> methyl esters purified<br />
using <strong>the</strong> ACs were lower than those purified using SG <strong>and</strong><br />
water washing method. This is because purification using<br />
ACs leads to fur<strong>the</strong>r elimination <strong>of</strong> impurities such as unreacted<br />
triglycerides, glycerol <strong>and</strong> <strong>the</strong> catalyst, as well as higher<br />
ester content <strong>of</strong> <strong>the</strong>se samples is behind this phenomenon. The<br />
pour point values ranged from ( 6to 8). Such values could<br />
be a good indicator <strong>of</strong> <strong>the</strong> fact that BD fuels prepared in this<br />
study are suitable <strong>for</strong> use in cold wea<strong>the</strong>r conditions prevailing<br />
in Nor<strong>the</strong>rn Iraq in winter. The HHV values ranged from<br />
(40.66 to 41.11) million joules/Kg).<br />
3.4. Regeneration <strong>of</strong> spent activated carbon<br />
Some authors used adsorbents such as Magnesol, SG <strong>and</strong> ion<br />
exchangers <strong>for</strong> BD purification. Borrios <strong>and</strong> Skelton (2008)<br />
used Magnesol <strong>and</strong> ion exchanger resin <strong>for</strong> BD purification.<br />
Predojevic (2008) used SG <strong>for</strong> BD purification. He found that<br />
purification using SG resulted in higher yield <strong>and</strong> better fuel<br />
properties in comparison to water washing method. However,<br />
<strong>the</strong> problem with <strong>the</strong>se adsorbents is that <strong>the</strong>y cannot be recycled.<br />
Besides, it is hard to dispose <strong>of</strong> <strong>the</strong>ir wastes particularly at<br />
a larger scale (Saleh et al., 2010). One <strong>of</strong> <strong>the</strong> attractive characteristics<br />
<strong>of</strong> activated carbon is that it can be regenerated <strong>the</strong>re<strong>for</strong>e<br />
spent activated carbon was regenerated <strong>and</strong> denoted as<br />
(AC SR ). Yield <strong>and</strong> fuel properties <strong>of</strong> BD purified using (AC SR )<br />
are listed in Table 4. It was found that <strong>the</strong> yield <strong>and</strong> <strong>the</strong> fuel<br />
properties especially <strong>the</strong> acid value, kinematic viscosity <strong>and</strong><br />
flash point <strong>of</strong> BD purified using <strong>the</strong> AC SR were lower than<br />
Table 5 Yield <strong>and</strong> properties <strong>of</strong> <strong>the</strong> biodiesel purified using AC SR .<br />
Property<br />
WCO<br />
AC SR AC ST SG Washing by DW<br />
Yield% 94 97 93 88<br />
Density @ 16 °C g/ml 0.8865 0.8755 0.8800 0.8920<br />
KV @ 40 °Cmm 2 /sec 3.10 2.63 3.22 3.40<br />
AV mg KOH/g oil 0.195 0.092 0.247 0.301<br />
RI @ 20 °C 1.449 1.445 1.448 1.457<br />
(PP) °C 7 8 7 6<br />
T F °C 171 169 172 175<br />
HHV MJ/KG 40.89 40.66 40.93 41.11
Purification <strong>of</strong> biodiesel using activated carbons produced from spent tea waste 49<br />
those purified using <strong>the</strong> AC S as can be seen from Table 5. This<br />
can be attributed to <strong>the</strong> reduction <strong>of</strong> <strong>the</strong> active sites available<br />
<strong>for</strong> <strong>the</strong> adsorption. However, in comparison to methyl esters<br />
purified using SG <strong>and</strong> water washing method; purification<br />
using AC SR resulted in higher yield <strong>and</strong> better fuel properties.<br />
Thus, it can be said that AC or AC SR is a good adsorbent <strong>for</strong><br />
<strong>the</strong> purification <strong>of</strong> biodiesel in comparison to <strong>the</strong> SG or water<br />
washing method.<br />
4. Conclusions<br />
Activated carbons prepared from spent tea waste used <strong>for</strong> <strong>the</strong><br />
purification <strong>of</strong> crude biodiesel produced from waste cooking<br />
oil through base catalyzed transesterification. For comparison,<br />
silica gel <strong>and</strong> water washing were also used <strong>for</strong> <strong>the</strong> same purpose.<br />
The study showed that in general, using activated carbons<br />
<strong>for</strong> biodiesel purification resulted in higher yields <strong>and</strong><br />
better fuel properties compared to <strong>the</strong> above mentioned methods.<br />
Moreover, <strong>the</strong> fuel properties met <strong>the</strong> specified limits<br />
according to <strong>the</strong> ASTM st<strong>and</strong>ards. Fur<strong>the</strong>rmore, spent activated<br />
carbon was regenerated <strong>and</strong> reused <strong>for</strong> <strong>the</strong> same purpose.<br />
The results indicated that regenerated activated carbon<br />
was effective to produce a biodiesel fuel <strong>of</strong> higher yield <strong>and</strong><br />
better fuel properties compared to <strong>the</strong> o<strong>the</strong>r methods.<br />
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Fuels 10, 890–895.<br />
Krisnangkura, K., 1986. A simple method <strong>for</strong> estimation <strong>of</strong> cetane<br />
index <strong>of</strong> vegetable oil methyl esters. <strong>Journal</strong> <strong>of</strong> <strong>the</strong> American Oil<br />
Chemists’ Society 3, 552–553.<br />
Paquot, C., 1979. St<strong>and</strong>ard Methods <strong>for</strong> <strong>the</strong> Analysis <strong>of</strong> Oils, Fats <strong>and</strong><br />
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<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 50-55<br />
حيوية بكتيريا اللبن والتقيم الحسي في الزبادي الحيوي بالقرفة او الثوم والمحضره من<br />
حليب االبل والبقر<br />
أمل شوري و أحمد بابا<br />
30605<br />
قسم الكمياء الحيوية ،<br />
معهد علوم<br />
الحياة،<br />
كلية العلوم،<br />
جامعة مااليا<br />
كواللمبور،<br />
ماليزيا<br />
الملخص:<br />
أجريت الدراسة الحالية للتحقق من تأثير الخالصة المائية المحضرة من الثوم<br />
)Allium sativum(<br />
)Cinnamomum verum(<br />
على حيوية بكتيريا اللبن<br />
والقرفة<br />
Lactobacillus spp. (<br />
)Streptococcus <strong>the</strong>rmophilus<br />
12 ثالجة لمدة<br />
للزبادي. تراوحت أعداد<br />
يوم تحت درجة حرارة<br />
4<br />
Lactobacillus spp.<br />
عدم وجود الخالصة المائية للثوم أو القرفة من<br />
و<br />
في الزبادي المحضر من حليب البقر واإلبل خالل فترة حفظه في<br />
درجات مئوية. كما تم خالل هذه الدراسة تقييم الخصائص الحسية<br />
في الزبادي الطازج المحضر من حليب البقر في وجود أو<br />
10 6 X 2.4<br />
إلى<br />
cfu/ml 10 6 X 2.1<br />
في اليوم األول من<br />
البدء في الدراسة. ولم تتغير هذه القيمة بشكل معنوي طوال فترة التخزين المبرد التي استمرت لمدة<br />
أما بالنسبة ألعداد<br />
للثوم والقرفة فقد كانت<br />
12<br />
Lactobacillus spp.<br />
cfu/ml 10 6 X 13.2<br />
البكتيريا بشكل معنوي، بعد إضافة الخالصة المائية للقرفة والثوم ، إلى<br />
يوم.<br />
في الزبادي المحضر من حليب اإلبل بدون الخالصة المائية<br />
في اليوم األول من البدء في الدراسة، وازدادت أعداد<br />
و<br />
10 6 X 26.9 10 6 X 19.2<br />
cfu/ml<br />
على التوالي.<br />
الخالصة المائية. أما بالنسبة ألعداد بكتيريا<br />
في حين أن أعداد هذه البكتيريا انخفضت بشكل خطي في التخزين المبرد بدون<br />
Streptococcus <strong>the</strong>rmophilus<br />
في الزبادي المحضر من<br />
حليب البقر أو حليب اإلبل، سواء بوجود أو في عدم وجود الخالصة المائية، فقد تراوحت من<br />
1.4<br />
cfu/ml 21 8 X 6.3<br />
مع تزايد األعداد في اليوم<br />
24<br />
إلى<br />
من التخزين المبرد. وفيما يتعلق بالخصائص الحسية<br />
فلم توجد اختالفات في الطعم مثل الحموضة أو المرارة أو الحالوة بين كال المجموعتين من الزبادي. إال أن<br />
وجود الخالصة المائية للثوم في زبادي حليب البقر خفضت بشكل معنوي جودة الرائحة إلى<br />
مقارنة بزبادي حليب اإلبل<br />
2.3±0.7<br />
.)5.5±1.0(<br />
A.B. Shori, A.S. Baba
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong> <strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences (2012) 11, 50–55<br />
University <strong>of</strong> Bahrain<br />
<strong>Journal</strong> <strong>of</strong> <strong>the</strong> <strong>Association</strong> <strong>of</strong> <strong>Arab</strong> <strong>Universities</strong> <strong>for</strong><br />
<strong>Basic</strong> <strong>and</strong> <strong>Applied</strong> Sciences<br />
www.elsevier.com/locate/jaaubas<br />
www.sciencedirect.com<br />
ORIGINAL ARTICLE<br />
Viability <strong>of</strong> lactic acid bacteria <strong>and</strong> sensory evaluation<br />
in Cinnamomum verum <strong>and</strong> Allium sativum-bio-yogurts<br />
made from camel <strong>and</strong> cow milk<br />
Amal Bakr Shori *, Ahmad S. Baba<br />
Biomolecular Research Group, Division <strong>of</strong> Biochemistry, Institute <strong>of</strong> Biological Sciences, Faculty <strong>of</strong> Science,<br />
University <strong>of</strong> Malaya, 50603 Kuala Lumpur, Malaysia<br />
Available online 15 December 2011<br />
KEYWORDS<br />
Yogurt;<br />
S. <strong>the</strong>rmophilus;<br />
Lactobacillus spp;<br />
Allium sativum;<br />
Cinnamomum verum<br />
Abstract The present study investigate <strong>the</strong> effect <strong>of</strong> herbal water extract prepared from Allium sativum<br />
<strong>and</strong> Cinnamomum verum on <strong>the</strong> viability <strong>of</strong> lactic acid bacteria (Lactobacillus spp <strong>and</strong> Streptococcus<br />
<strong>the</strong>rmophilus) in cow- <strong>and</strong> camel-milk yogurts during 21 day refrigerated storage. The<br />
organoleptic properties <strong>of</strong> fresh-yogurts were evaluated. Lactobacillus spp count <strong>for</strong> fresh cow<br />
milk-yogurts (0 day) in both present <strong>and</strong> absent <strong>of</strong> C. verum <strong>and</strong> A. sativum was ranged from 1.4<br />
·10 6 to 2.1 · 10 6 cfu/mL. These values were not significantly changed throughout <strong>the</strong> 21 days <strong>of</strong><br />
refrigerated storage. Lactobacillus spp count in fresh plain camel milk- yogurt was 13.2 · 10 6 cfu/<br />
mL whereas fresh C. verum- <strong>and</strong> A. sativum-camel milk- yogurts had higher Lactobacillus spp<br />
counts (19.2 · 10 6 <strong>and</strong> 26.9 · 10 6 cfu/mL respectively; p < 0.05). However, refrigerated storage<br />
to 21 days resulted in linear decrease in Lactobacillus spp counts. Fur<strong>the</strong>rmore, S. <strong>the</strong>rmophilus<br />
counts in fresh cow- <strong>and</strong> camel- milk yogurts in ei<strong>the</strong>r absent or present <strong>of</strong> C. verum or A. sativum<br />
ranged from 2.4 to 3.6 · 10 8 cfu/mL <strong>and</strong> <strong>the</strong>se values increased by day 14 <strong>of</strong> storage. In organoleptic<br />
properties <strong>of</strong> yogurts no differences were observed in sourness, bitterness, <strong>and</strong> overall preference<br />
scores between <strong>the</strong> two groups <strong>of</strong> yogurts. The present <strong>of</strong> A. sativum in cow milk-yogurt reduced<br />
<strong>the</strong> aroma score to (2.3 ± 0.7, p < 0.05) compared to camel milk-yogurt (5.5 ± 1.0).<br />
ª 2011 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by Elsevier B.V. All rights reserved.<br />
* Corresponding author.<br />
E-mail address: shori_7506@hotmail.com (A.B. Shori).<br />
1815-3852 ª 2011 University <strong>of</strong> Bahrain. Production <strong>and</strong> hosting by<br />
Elsevier B.V. All rights reserved.<br />
Peer review under responsibility <strong>of</strong> University <strong>of</strong> Bahrain.<br />
doi:10.1016/j.jaubas.2011.11.001<br />
Production <strong>and</strong> hosting by Elsevier<br />
1. Introduction<br />
Recently, <strong>the</strong> food biotechnology industry has developed a<br />
number <strong>of</strong> commercial products containing a single probiotic<br />
strain or bacterial associations <strong>of</strong> various complexities. Yogurt<br />
has been known <strong>for</strong> its nutraceutical, <strong>the</strong>rapeutic, <strong>and</strong> probiotic<br />
effects (Gu¨ ler-Akın <strong>and</strong> Akın, 2007). Also, lactic acid bacteria<br />
<strong>and</strong> its metabolites have shown to play an important role<br />
in improving microbiological quality <strong>and</strong> shelf-life <strong>of</strong> many<br />
fermented food products. Dairy products have long been consumed<br />
by consumers <strong>and</strong> provide a good example <strong>of</strong> bio-preservation<br />
(Zottola et al., 1994).
Viability <strong>of</strong> lactic acid bacteria <strong>and</strong> sensory evaluation in Cinnamomum verum <strong>and</strong> Allium sativum 51<br />
Today LAB is a focus <strong>of</strong> intensive international research <strong>for</strong><br />
its pivotal role in most fermented foods. <strong>Basic</strong>ally, <strong>for</strong> its ability<br />
to produce various anti-microbial compounds promoting probiotic<br />
properties (Temmerman et al., 2002) that includes antitumoral<br />
activity (De-Vuyst <strong>and</strong> Degeest, 1999; Østlie et al.,<br />
2003), reduction <strong>of</strong> serum cholesterol (Desmazeaud,1996; Jackson<br />
et al., 2002), alleviation <strong>of</strong> lactose intolerance (De Vrese<br />
et al., 2001), stimulation <strong>of</strong> <strong>the</strong> immune system (Isolauri et al.,<br />
2001), <strong>and</strong> stabilization <strong>of</strong> gut micr<strong>of</strong>lora (Gibson et al., 1997).<br />
Fur<strong>the</strong>rmore, LAB strains syn<strong>the</strong>size short chain fatty acids,<br />
vitamins, <strong>and</strong> exopolysaccharides (EPS) that are employed in<br />
<strong>the</strong> manufacturing <strong>of</strong> fermented milk to improve its texture<br />
<strong>and</strong> viscosity (Curk et al., 1996; Ruas-Madiedo et al., 2002).<br />
The main technological properties <strong>of</strong> yogurt bacteria in milk fermentation<br />
are acidification, texture enhancement, flavour production,<br />
<strong>and</strong> <strong>the</strong> final level <strong>of</strong> lactic acid which is <strong>the</strong> main<br />
product <strong>of</strong> <strong>the</strong> metabolic activity <strong>of</strong> starter cultures. However,<br />
<strong>the</strong> acidification rate during yogurt production depends on <strong>the</strong><br />
strains <strong>and</strong> <strong>the</strong>ir associations (Beal et al., 1999).<br />
Development <strong>of</strong> dairy products with new products <strong>and</strong> flavours<br />
has potential health benefits <strong>the</strong>reby increasing sales <strong>and</strong><br />
consumers satisfaction. Traditional preparation <strong>of</strong> yogurt may<br />
be beneficial by including o<strong>the</strong>r ingredients such as soya protein,<br />
vegetables, sweet potato, pumpkin <strong>and</strong> plum (Joo et al., 2001;<br />
Park et al., 2003) to enhance <strong>the</strong> flavour as well as <strong>the</strong> nutritional<br />
quality (Shori <strong>and</strong> Baba, 2011). However, traditional medicinal<br />
plants such as Allium sativum <strong>and</strong> Cinnamomum verum have<br />
been proved to provide important <strong>the</strong>rapeutic values. Besides,<br />
it is highly aromatic <strong>and</strong> possesses anti-microbial activities (Harris<br />
et al., 2001; Gende et al., 2008) that could affect <strong>the</strong> yogurts’<br />
LAB counts <strong>and</strong> <strong>the</strong>ir organoleptic properties. There<strong>for</strong>e, <strong>the</strong><br />
objective <strong>of</strong> <strong>the</strong> present research was to study <strong>the</strong> survival <strong>of</strong><br />
LAB in A. sativum <strong>and</strong> C. verum yogurts made from cow milk<br />
<strong>and</strong> camel milk <strong>and</strong> comparison to <strong>the</strong>ir respective plain yogurts<br />
during 21 day <strong>of</strong> refrigerated storage <strong>and</strong> evaluate <strong>the</strong> organoleptic<br />
properties <strong>of</strong> <strong>the</strong>se yogurts.<br />
2. Materials <strong>and</strong> methods<br />
2.1. Materials <strong>and</strong> chemicals<br />
Commercial fresh <strong>and</strong> pasteurized full cream cow milk (Dutch<br />
Lady, Malaysia) <strong>and</strong> camel milk (Al-Turath, Saudi <strong>Arab</strong>ia)<br />
were purchased from supermarket. Camel milk was frozen<br />
<strong>and</strong> used to make yogurt within 2 weeks from <strong>the</strong> date <strong>of</strong> pasteurization.<br />
The herbs used in <strong>the</strong> present study were C. verum<br />
bark purchased from local store in Saudi <strong>Arab</strong>ia <strong>and</strong> A. sativum<br />
powder (McCormick, Malaysia). Fur<strong>the</strong>r supplies incorporated<br />
in present study were commercially available yogurt<br />
bacteria mixture (Chris-Hansen, Denmark) <strong>and</strong> probiotic mixture<br />
(Bio-Life, Malaysia) in which one capsule contained 5 billion<br />
cfu <strong>of</strong> probiotic bacteria. The agars used in <strong>the</strong> present<br />
study were M.R.S Agar, M17 Agar obtained from Oxoid<br />
(Basingstoke, Hampshire, Engl<strong>and</strong>). Additionally, lactose<br />
monohyrate, C 12 H 22 O 11 ÆH 2 O was obtained from Systerm.<br />
2.2. Water extraction <strong>of</strong> herbs<br />
Ten grams <strong>of</strong> C. verum bark <strong>and</strong> A. sativum powder were<br />
mixed thoroughly with 100 mL <strong>of</strong> distilled H 2 O. The mixture<br />
was incubated overnight in a water bath at 70 °C (Julabo,<br />
Model Sw-21c or Haake Model SWD 20) followed by centrifugation<br />
(Eppend<strong>of</strong>t 5804 R; 10000 rpm) <strong>for</strong> 15 min at 4 °C. The<br />
clear supernatants were harvested <strong>and</strong> used as C. verum <strong>and</strong> A.<br />
sativum water extracts in <strong>the</strong> making <strong>of</strong> herbal yogurts (Behrad<br />
et al., 2009).<br />
2.3. Preparation <strong>of</strong> starter culture<br />
Starter culture <strong>for</strong> making yogurt was prepared by pre-heating<br />
<strong>of</strong> fresh <strong>and</strong> pasteurized full cream milk to 41 °C. A mixture<br />
<strong>of</strong> yogurt bacteria consisting <strong>of</strong> Lactobacillus acidophilus<br />
LA-5, Bifidobacterium bifidum Bb-12, Lactobacillus casei LC-<br />
01 <strong>and</strong> Streptococcus <strong>the</strong>rmophilus Th-4 in <strong>the</strong> ratio <strong>of</strong> 4:4:1:1<br />
<strong>and</strong> a capsule <strong>of</strong> probiotic mix containing L. bulgaricus, L.<br />
rhamnosus, B. infantis <strong>and</strong> B. longum in <strong>the</strong> ratio <strong>of</strong> 1:1:1:1<br />
were mixed thoroughly with <strong>the</strong> preheated milk prior to an<br />
overnight incubation at 41 °C. The yogurt <strong>for</strong>med was refrigerated<br />
(4 °C) <strong>and</strong> used as starter culture within 7 days (Rashid<br />
et al., 2007).<br />
2.4. Preparation <strong>of</strong> yogurts<br />
C. verum <strong>and</strong> A. sativum yogurts were prepared by mixing<br />
10 mL <strong>of</strong> each herbal-water extract with 85 mL <strong>of</strong> pasteurized<br />
full cream milk <strong>and</strong> 5 g <strong>of</strong> starter culture (Shah, 2003). The mixture<br />
was mixed thoroughly followed by incubation at 41 °C. The<br />
pH <strong>of</strong> <strong>the</strong> mixture was determined every 30 min until <strong>the</strong> pH <strong>of</strong><br />
yogurt reached 4.5 by using pH meter (Cyper Scan 510). At that<br />
moment, <strong>the</strong> incubation was terminated by placing <strong>the</strong> yogurts<br />
in ice-bath <strong>for</strong> 60 min. These yogurts were <strong>the</strong>n placed in <strong>the</strong><br />
refrigerator <strong>for</strong> up to 21 days. Control yogurts were prepared<br />
using <strong>the</strong> same procedures except 10 mL <strong>of</strong> distilled H 2 O was<br />
used in place <strong>of</strong> herbal-water extract.<br />
2.5. Microbial viable cell count (VCC) in yogurts<br />
2.5.1. Buffered peptone water<br />
Twenty grams <strong>of</strong> buffered peptone water was mixed with 1 L<br />
distilled water, <strong>the</strong> mixture was distributed into final tubes followed<br />
by autoclaved at 121 °C <strong>for</strong> 20 min. The pH <strong>of</strong> media at<br />
25 °C was 7.2 ± 0.2.<br />
2.5.2. Sample preparation<br />
Yogurt samples (1 mL) were individually mixed with 9 mL <strong>of</strong><br />
0.15% sterile buffered peptone water. The mixtures were thoroughly<br />
stirred <strong>and</strong> serial dilutions were prepared by using buffered<br />
peptone water.<br />
2.5.3. Enumeration <strong>of</strong> Lactobacillus spp using <strong>the</strong> pour plate<br />
method<br />
Lactobacillus spp was enumerated, particularly, as described<br />
by Kailasapathy et al. (2008). MRS agar was prepared by mixing<br />
MRS powder with water (62 g/1 L distilled H 2 O) <strong>and</strong> <strong>the</strong><br />
solution was autoclaved followed by cooling to 45 °C. The<br />
melted MRS agar (15 mL) was <strong>the</strong>n placed in a petri dish.<br />
Appropriately diluted yogurt (1 mL) was <strong>the</strong>n transferred in<br />
<strong>the</strong> molten MRS agar. The mixture was evenly mixed by gently<br />
tilting <strong>and</strong> swirling <strong>the</strong> dish. The plates were sealed with parafilm<br />
<strong>and</strong> were left at room temperature to allow <strong>the</strong> agar to
52 A.B. Shori, A.S. Baba<br />
solidify. Thereafter, <strong>the</strong> plates were inverted <strong>and</strong> placed in <strong>the</strong><br />
incubator (37 °C) <strong>for</strong> 48 h. Viable Lactobacillus spp count was<br />
calculated (Sivakumar <strong>and</strong> Kalaiarasu, 2010) as follows:<br />
CFU Number <strong>of</strong> colonies <strong>for</strong>med dilution factor <strong>of</strong> sample<br />
=mL ¼<br />
1mL <strong>of</strong> sample<br />
*CFU: colony <strong>for</strong>ming unit.<br />
2.5.4. Enumeration <strong>of</strong> S. <strong>the</strong>rmophilus using <strong>the</strong> spread count<br />
method<br />
S. <strong>the</strong>rmophilus was enumerated using M17 agar (Rybka <strong>and</strong><br />
Kailasapathy, 1995). The M17 agar powder was mixed with<br />
water (48.3 g in 950 mL distilled H 2 O) <strong>and</strong> <strong>the</strong> mixture was sterilized<br />
by autoclaving. The molten M17 agar was allowed to cool<br />
to 45 °C prior to <strong>the</strong> addition <strong>of</strong> sterilized lactose solution<br />
(50 mL, 10% w/v). The mixture was dispensed (15 mL) in a petri<br />
dish <strong>and</strong> <strong>the</strong> molten M17 agar was allowed to solidify at room<br />
temperature. Appropriately diluted yogurt (0.1 mL) was placed<br />
on <strong>the</strong> M17 agar <strong>and</strong> <strong>the</strong> sample was spread on <strong>the</strong> surface using<br />
a sterile spreader. The plates were incubated in inverted position<br />
at 37 °C <strong>for</strong> 48 h. Viable microbial count (S. <strong>the</strong>rmophilus) was<br />
calculated (Sivakumar <strong>and</strong> Kalaiarasu, 2010) as follows:<br />
CFU Number <strong>of</strong> colonies <strong>for</strong>med dilution factor <strong>of</strong> sample<br />
=mL ¼<br />
0:1mL <strong>of</strong> sample<br />
*CFU: colony <strong>for</strong>ming unit.<br />
2.6. Organoleptic properties<br />
Organoleptic properties on yogurt were running after 1 day <strong>of</strong><br />
refrigerated storage. Twelve participants were r<strong>and</strong>omly selected<br />
<strong>and</strong> identified <strong>the</strong>mselves as students <strong>and</strong> departmental<br />
staff. Their age range between 20 <strong>and</strong> 35 years <strong>and</strong> were engaged<br />
as untrained panels <strong>for</strong> <strong>the</strong> sensory evaluation. Each panel was<br />
presented with two groups <strong>of</strong> yogurt (cow-milk <strong>and</strong> camel-milk<br />
yogurts) each group contains three coded yogurt samples<br />
(10 mL <strong>for</strong> each). The first group contained<br />
plain-cow-milk yogurt, A. sativum-cow-milk yogurt, <strong>and</strong> C. verum-cow-milk<br />
yogurt. The second group contained plain-camelmilk<br />
yogurt, A. sativum-camel-milk yogurt, <strong>and</strong> C. verum-camelmilk<br />
yogurt. The evaluation was scored on 1–10 point hedonic<br />
scale (1–2 = extremely poor, 3–4 = poor, 5–6 = fair, 7–<br />
8 = good, 9–10 = excellent) according to taste (sour, sweet,<br />
<strong>and</strong> bitter), aroma <strong>and</strong> overall preference.<br />
3.1.1. Bacteria counts <strong>of</strong> Lactobacillus spp<br />
Lactobacillus spp counts were 1.4 · 10 6 , 2.1 · 10 6 , <strong>and</strong><br />
1.7 · 10 6 cfu/mL <strong>for</strong> fresh plain-, C. verum- <strong>and</strong> A. sativumcow-milk<br />
yogurts, respectively (Fig. 1). Lactobacillus spp<br />
counts increased to about 2.3 · 10 6 cfu/mL <strong>for</strong> all three yogurts<br />
by day 7 <strong>of</strong> storage with significant effect (p < 0.05) seen<br />
in plain-cow-milk yogurt. Lactobacillus spp counts in all three<br />
yogurts were almost similar during <strong>the</strong> 14 days <strong>of</strong> storage but<br />
<strong>the</strong> viable cell counts reduced gradually to 1.4 · 10 6 cfu/mL <strong>for</strong><br />
plain- <strong>and</strong> A. sativum-cow-milk yogurts <strong>and</strong> 1.7 · 10 6 cfu/mL<br />
<strong>for</strong> C. verum-cow-milk yogurt by day 21 <strong>of</strong> storage.<br />
In contrast, Lactobacillus spp counts in fresh camel-milk<br />
yogurts were about tenfold higher than in fresh cow-milk yogurts<br />
(Figs. 1 <strong>and</strong> 2). The viable cell count in plain-camel-milk<br />
yogurt was 13.2 · 10 6 cfu/mL; however, <strong>the</strong> addition <strong>of</strong> C. verum<br />
<strong>and</strong> A. sativum increased (p < 0.05) <strong>the</strong> counts to<br />
19.2 · 10 6 <strong>and</strong> 26.9 · 10 6 cfu/mL, respectively. There were<br />
small decreases in Lactobacillus spp counts in yogurts<br />
(p < 0.05, <strong>for</strong> plain-camel-milk yogurt) after 7 days refrigerated<br />
storage. However, pronounced reduction in Lactobacillus<br />
spp counts occurred in plain- <strong>and</strong> A. sativum-camel-milk<br />
yogurts over <strong>the</strong> 14 days with lowest count being 1.3 · 10 6<br />
<strong>and</strong> 1.7 · 10 6 cfu/mL, respectively, on day 21 <strong>of</strong> storage. Lactobacillus<br />
spp counts in C. verum-camel-milk yogurts reduced<br />
slowly during this period resulting in highest counts<br />
(4.3 · 10 6 cfu/mL) amongst <strong>the</strong> three types <strong>of</strong> camel-milk yogurts<br />
on day 21 <strong>of</strong> storage.<br />
3.1.2. Bacteria counts <strong>of</strong> Streptococcus <strong>the</strong>rmophilus<br />
S. <strong>the</strong>rmophilus counts in fresh cow- <strong>and</strong> camel-milk yogurts<br />
ranged 2.0–3.0 · 10 8 cfu/mL (Figs. 3 <strong>and</strong> 4). The viable cell<br />
counts increased with refrigerated storage to similar values<br />
<strong>for</strong> all plain-, A. sativum- <strong>and</strong> C. verum-cow-milk yogurts<br />
<strong>and</strong> reached <strong>the</strong> highest counts 4.30 · 10 8 , 4.90 · 10 8 <strong>and</strong><br />
5.30 · 10 8 cfu/mL, respectively, by day 14 <strong>of</strong> storage; followed<br />
by a small reduction to 3.7 · 10 8 , 4.50 · 10 8 <strong>and</strong> 4.70 · 10 8 cfu/<br />
mL, respectively, by day 21 <strong>of</strong> storage. In comparison, <strong>the</strong><br />
viable cell counts in camel-milk yogurts increased almost<br />
tw<strong>of</strong>old higher by day 14 <strong>of</strong> storage (9.5 · 10 8 , 11.7 · 10 8<br />
<strong>and</strong> 9.9 · 10 8 cfu/mL) <strong>for</strong> plain-, A. sativum- <strong>and</strong> C. verum-camel-milk<br />
yogurts, respectively. Extension <strong>of</strong> storage to day 21<br />
resulted in a decrease in viable S. <strong>the</strong>rmophilus counts to<br />
7.0 · 10 8 cfu/mL <strong>for</strong> both plain- <strong>and</strong> C. verum-camel-milk yogurts<br />
but not <strong>for</strong> A. sativum camel-milk yogurt which was<br />
2.7. Statistical analysis<br />
The experiment was designed according to a 2 · 3 factorial design.<br />
All experiments were per<strong>for</strong>med in three batches (n = 3) <strong>and</strong> <strong>the</strong><br />
average was taken. Data were expressed as mean ± st<strong>and</strong>ard error<br />
using one-way ANOVA by SPSSÒ version 17.0. Means were<br />
compared using Duncan’s multiple range tests, <strong>and</strong> statistical significance<br />
was st<strong>and</strong>ard by ANOVA at p < 0.05.<br />
3. Results<br />
3.1. Survival <strong>of</strong> lactic acid bacteria into plain <strong>and</strong> herbal yogurts<br />
Figure 1 Changes in bacterial counts <strong>of</strong> Lactobacillus spp<br />
(10 6 cfu/mL) during 21 day refrigerated storage (4 °C). C.<br />
verum-cow-milk yogurt, A. sativum-cow-milk yogurt versus<br />
control plain-cow-milk yogurt. Values are presented as<br />
mean ± SEM (n = 3). For C. verum-cow-milk yogurt (0 day)<br />
ANOVA showed a significant effect at 5% level.
Viability <strong>of</strong> lactic acid bacteria <strong>and</strong> sensory evaluation in Cinnamomum verum <strong>and</strong> Allium sativum 53<br />
Figure 2 Changes in bacterial counts <strong>of</strong> Lactobacillus spp<br />
(10 6 cfu/mL) during 21 day refrigerated storage (4 °C). C.<br />
verum-camel-milk yogurt, A. sativum-camel-milk yogurt versus<br />
control plain-camel-milk yogurt. Values are presented as<br />
mean ± SEM (n = 3). For both cow- <strong>and</strong> camel-milk yogurts in<br />
<strong>the</strong> presence <strong>of</strong> C. verum <strong>and</strong> A. sativum ANOVA showed a<br />
significant effect at 5% level during all periods <strong>of</strong> storage.<br />
12.5 · 10 8 cfu/mL. The addition <strong>of</strong> A. sativum- <strong>and</strong> C. verum in<br />
cow-milk yogurts showed no significant effect on <strong>the</strong> survival<br />
rate <strong>of</strong> S. <strong>the</strong>rmophilus compared to <strong>the</strong>ir control (plain yogurt).<br />
However, <strong>the</strong> addition <strong>of</strong> A. sativum in camel-milk yogurts<br />
showed increased (p < 0.05) in S. <strong>the</strong>rmophilus counts<br />
on 7 <strong>and</strong> 21 days compared to its control while, <strong>the</strong>re was no<br />
effect on S. <strong>the</strong>rmophilus counts in <strong>the</strong> presence <strong>of</strong> C. verum.<br />
3.2. Organoleptic properties <strong>of</strong> stored yogurts<br />
The sensory evaluations <strong>of</strong> cow- <strong>and</strong> camel-milk yogurts were<br />
shown in Table 1. No differences were observed in sourness,<br />
bitterness, <strong>and</strong> overall preference scores between <strong>the</strong> two<br />
groups <strong>of</strong> yogurts, both in <strong>the</strong> absence <strong>and</strong> presence <strong>of</strong> A. sativum<br />
or C. verum. The plain yogurt sweetness score was greater<br />
<strong>for</strong> cow-milk yogurt than <strong>the</strong> camel-milk yogurt. However, <strong>the</strong><br />
presence <strong>of</strong> A. sativum <strong>and</strong> C. verum effects on sweetness was<br />
reduced in cow-milk yogurt, but increased in camel-milk yogurt.<br />
The aroma score was slightly greater in cow-milk yogurt<br />
(6.1 ± 1.8) than in camel-milk yogurt (5.4 ± 1.4). The<br />
presence <strong>of</strong> A. sativum reduced aroma score in cow-milk<br />
Figure 3 Changes in bacteria counts <strong>of</strong> Streptococcus <strong>the</strong>rmophilus<br />
(10 8 cfu/mL) during 21 day refrigerated storage (4 °C). C.<br />
verum-cow-milk yogurt, A. sativum-cow-milk yogurt versus<br />
control plain-cow-milk yogurt. Values are presented as<br />
mean ± SEM (n = 3). For all treated yogurt ANOVA showed<br />
no significant effect at 5% level.<br />
Figure 4 Changes in bacteria counts <strong>of</strong> Streptococcus <strong>the</strong>rmophilus<br />
(10 8 cfu/mL) during 21 day refrigerated storage (4 °C). C.<br />
verum-camel milk yogurt A. sativum-camel-milk yogurt versus<br />
control plain-camel-milk yogurt. Values are presented as<br />
mean ± SEM (n = 3). For A. sativum-camel-milk yogurt at 7<br />
<strong>and</strong> 21 days ANOVA showed a significant effect at 5% level.<br />
yogurt (2.3 ± 0.7, p < 0.05) contrary to camel-milk yogurt<br />
(5.5 ± 1.0).<br />
4. Discussion<br />
In this present study, <strong>the</strong> viable counts <strong>of</strong> Lactobacillus spp<br />
<strong>for</strong> both types <strong>of</strong> yogurts confirmed to reduce during refrigerated<br />
storage (by day 14 <strong>for</strong> cow-milk yogurts <strong>and</strong> day 7<br />
<strong>for</strong> camel-milk yogurts). This result was in agreement with<br />
previous study that found refrigerated storage decreased<br />
<strong>the</strong> viable counts <strong>of</strong> Lactobacillus spp significantly by <strong>the</strong><br />
14th day <strong>of</strong> refrigerated storage (Shah <strong>and</strong> Ravula, 2001;<br />
Haynes <strong>and</strong> Playne, 2002; Kailasapathy <strong>and</strong> Sultana, 2003;<br />
Laniewska-Trokenheim et al., 2010). Additionally, <strong>the</strong> reduction<br />
<strong>of</strong> Lactobacillus spp counts could be associated with <strong>the</strong><br />
post-acidification <strong>of</strong> yogurt which causes a fur<strong>the</strong>r reduction<br />
in pH values (Shah, 2000; Omer <strong>and</strong> Eltinay, 2009; Eissa<br />
et al., 2010). However, in this present study, <strong>the</strong> pH <strong>of</strong><br />
cow-milk yogurts reduced at faster rates than camel-milk yogurts<br />
during refrigerated storage (data not shown). Thus, <strong>the</strong><br />
more rapid reduction <strong>of</strong> Lactobacillus spp counts in all camel-milk<br />
yogurts than cow-milk yogurts (Figs. 1 <strong>and</strong> 2)<br />
could be attributed to <strong>the</strong> higher antibacterial properties <strong>of</strong><br />
camel milk than cow milk (El Agamy et al., 1992).<br />
Conversely, <strong>the</strong> increase in <strong>the</strong> viability <strong>of</strong> S. <strong>the</strong>rmophilus<br />
in both cow-milk <strong>and</strong> camel-milk yogurts throughout <strong>the</strong> first<br />
14 days <strong>of</strong> refrigerated storage was in agreement with o<strong>the</strong>r<br />
previous studies (Birollo et al., 2000). To <strong>the</strong> best knowledge<br />
<strong>of</strong> <strong>the</strong> researchers, this is <strong>the</strong> first simultaneous report on <strong>the</strong><br />
survival <strong>of</strong> both Lactobacillus spp <strong>and</strong> S. <strong>the</strong>rmophilus during<br />
refrigerated storage which showed higher survival percentage<br />
<strong>of</strong> <strong>the</strong>se bacteria in cow-milk than in camel-milk yogurts. Fur<strong>the</strong>rmore,<br />
<strong>the</strong> significant drop in <strong>the</strong> viable cell counts <strong>of</strong> S.<br />
<strong>the</strong>rmophilus by day 21 <strong>of</strong> storage in both cow-milk <strong>and</strong> camel-milk<br />
yogurts may be attributed to <strong>the</strong> accumulation <strong>of</strong> organic<br />
acids (Østlie et al., 2003). However, <strong>the</strong> sustained<br />
survival <strong>of</strong> S. <strong>the</strong>rmophilus in A. sativum-camel-milk yogurt<br />
indicated a positive effect <strong>of</strong> its addition into camel milk during<br />
yogurt preparation. The reason is not clear. Thus, fur<strong>the</strong>r<br />
studies are required.<br />
Viable LAB was higher in camel-milk than in cow-milk yogurts<br />
<strong>and</strong> this may be partly explained by <strong>the</strong> higher free amino
54 A.B. Shori, A.S. Baba<br />
Table 1<br />
Mean taste panel scores <strong>for</strong> herbal yogurts versus control (plain yogurt) made from cow <strong>and</strong> camel milk.<br />
P-cow-milk Y a,b,c AS-cow-milk Y a,b,c CV-cow-milk Y a,b,c P-camel-milk Y a,b,c AS-camel-milk Y a,b,c CV-camel-milk Y a,b,c<br />
Sourness 5.83 ± 1.95 6.42 ± 1.73 5.67 ± 1.72 6.42 ± 1.93 5.92 ± 1.68 5.67 ± 1.15<br />
Sweetness 4.83 ± 1.19 3.42 ± 1.16 3.58 ± 1.83 3.83 ± 1.75 4.92 ± 1.38 4.83 ± 1.27<br />
Bitterness 2.92 ± 1.51 3.08 ± 1.88 2.42 ± 1.24 2.42 ± 1.31 2.17 ± 1.27 2.83 ± 1.64<br />
Aroma 6.08 ± 1.83 2.33 ± 0.65 6.33 ± 1.50 5.42 ± 1.44 5.50 ± 1.00 5.75 ± 1.48<br />
Overall preference 6.50 ± 1.45 5.08 ± 1.24 5.92 ± 1.56 6.17 ± 1.64 5.75 ± 1.71 6.00 ± 1.21<br />
a P = plain, AS = A. sativum, CV=C. verum <strong>and</strong> Y = yogurt.<br />
b First group (AS-cow-milk Y, CV-cow-milk Y versus P-cow-milk Y), second group (AS-camel-milk Y, CV-camel-milk Y versus P-camel-milk<br />
Y).<br />
c Values are presented as mean ± SEM, n = 12. Significant <strong>for</strong> aroma at AS-cow-milk Y.<br />
acids in camel milk than in cow milk (Mehaia <strong>and</strong> Al-Kanhal,<br />
1992), <strong>and</strong> higher milk protein proteolysis by L. delbrueckii spp<br />
bulgaricus in camel milk than in cow milk (Abu-Tarboush,<br />
1996). Both factors contribute to apparent higher digestibility<br />
<strong>of</strong> camel milk than cow milk which readily supported growth<br />
<strong>and</strong> metabolism <strong>of</strong> LAB during fermentation <strong>and</strong> refrigerated<br />
storage. There<strong>for</strong>e, <strong>the</strong> higher ‘mortality’ <strong>of</strong> Lactobacillus spp<br />
in camel-milk yogurts during refrigerated storage may not<br />
affect its functional values because <strong>the</strong> viable cell counts <strong>of</strong><br />
LAB on <strong>the</strong> 3rd week <strong>of</strong> storage in camel-milk yogurts were<br />
still higher than those in <strong>the</strong> 2nd week <strong>of</strong> storage <strong>for</strong> cow-milk<br />
yogurts.<br />
Fur<strong>the</strong>rmore, in this present study, <strong>the</strong> decrease in <strong>the</strong> aroma<br />
score <strong>for</strong> A. sativum-camel-milk yogurt could be explained<br />
via study conducted by Hansanugrum <strong>and</strong> Barringer (2010)<br />
which found that milk proved effective in <strong>the</strong> deodorization<br />
<strong>of</strong> AMS (allyl methyl sulphide) latter identified as responsible<br />
<strong>for</strong> <strong>the</strong> ‘garlic odour’ (Block, 2010). Moreover, <strong>the</strong> significant<br />
higher aroma score <strong>for</strong> A. sativum-camel-milk yogurt than A.<br />
sativm-cow-milk yogurt suggested that camel milk was more<br />
effective in <strong>the</strong> deodorization <strong>of</strong> AMS than cow milk.<br />
5. Conclusion<br />
A. sativum <strong>and</strong> C. verum enhanced Lactobacillus spp counts<br />
more in camel-milk yogurts than in cow-milk yogurts with respect<br />
to growth during fermentation except <strong>the</strong>y could not sustain<br />
Lactobacillus spp survival in camel-milk yogurts during<br />
refrigerated storage. However, <strong>the</strong>se herbs did not affect S.<br />
<strong>the</strong>rmophilus counts in camel- <strong>and</strong> cow-milk yogurts both during<br />
fermentation <strong>and</strong> refrigerated storage. The addition <strong>of</strong> A.<br />
sativum <strong>and</strong> C. verum did not affect <strong>the</strong> organoleptic properties<br />
<strong>of</strong> cow- <strong>and</strong> camel-milk yogurts although A. sativum may reduce<br />
<strong>the</strong> aroma score in <strong>the</strong> <strong>for</strong>mer but not in <strong>the</strong> latter.<br />
Acknowledgement<br />
We acknowledge <strong>the</strong> financial support <strong>of</strong> University <strong>of</strong> Malaya<br />
Research Grant (RG023-090BIO).<br />
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