2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
P82 ExAMINATION OF ThE MuTuAL
INTERACTION OF hEAVy METALS IN
COuRSE OF ADSORPTION FROM MODEL
SOLuTIONS
Ján VEREŠ a , TOMአBAKALáR b , MILAn BÚGEL b
and MARTIn SISOL b
a Institute of Geotechnics, Slovak Academy of Science, Watsonova
45, 043 53 Kosice, Slovakia,
b Technical University of Kosice, Faculty of Mining, Ecology,
Process Control and Geotechnology, Letna 9, 042 00 Kosice,
Slovakia,
veres@saske.sk
Introduction
Heavy metals contamination occures in aqeous waste
streams of many industries, such as metal plating facilities,
mining operations, tanneries etc. Heavy metals are not biodegradable
and tend to accumulate in living organisms, causing
various diseases and disorders and environmental problems.
Treatment processes for metals contaminated waste streams
include chemical precipitation, ion exchange, membrane
separations (ultrafiltration, reverse osmosis, electrodialysis)
and adsorption. natural materials that are available in large
quantities, or certain waste products from industrial or agricultural
operations, may have potential as inexpensive sorbents.
Due to their low cost, after these materials have been
expended, they can be disposed of without expensive regeneration.
Cost is an important parameter for comparing the
sorbent materials. Adsorption is considered to be the simplest
and most cost-effective technique. The removal of heavy
metal ions from industrial wastewaters using different adsorbents
is currently of great interest 1 .
Zeolites are naturally occuring hydrated aluminosilicate
minerals. They belong to the class of minerals known
as “tectosilicates”. The structures of zeolies consist of threedimensional
frameworks os SiO 4 and AlO 4 tetrahedron. This
structure causes zeolite to have negatively charged surface.
The negative charge is balanced by the exchangable cation
(calcium, sodium or potassium). The fact that zeolite exchangeable
ions are relatively harmless makes them particularly
suitable for removing undesirable heavy metal ions from
industrial effluent waters. 2–4
The zeolite samples from different regions show different
behaviour in ion-exchange processes 5 . The ion exchange
process in zeolites is influenced by several factors such as
concentration and nature of cations and anions, pH value and
crystal structure of the zeolite. In this study, the adsorption
properties of the natural zeolite and synthetic zeolite Slovakite
® with respect to some heavy metal cations in solution
were investigated 6 .
Experimental
M a t e r i a l s a n d C h e m i c a l s
A natural zeolite was obtained from Slovakia (nizny
Hrabovec). The main phase is clinoptilolite and the chemi-
s503
cal compositions are SiO 2 (73.42 %), Al 2 O 3 (12.43 %), CaO
(2.94 %), K 2 O (2.61 %) and Fe 2 O 3 (1.05 %). The synthetic
zeolite Slovakite ® is patented product and the chemical composition
is unrevealed by the producent.
Inorganic chemicals were supplied as analytical reagents
and deionized water was used. The studied metal ions were
Pb 2+ , ni 2+ , Cu 2+ and Zn 2+ . Solution of lead and nickel was prepared
by using their nitrate salts, Pb(nO 3 ) 2 , ni(nO 3 ) 2 .6H 2 O.
The solution of copper and zinc was prepared from their sulphate
salts, CuSO 4 . 5H2 O, ZnSO 4 . 7H2 O.
A d s o r p t i o n T e s t s
The ion exchange of heavy metals on natural zeolite and
on synthetic zeolite Slovakite ® were carried out using the
batch metod. Batch adsorption experiments were conducted
using 2 g of adsorbent with 200 ml of solutions in flasks containing
heavy metal ions of desired concentrations at constant
temperature (25 °C). The initial concentration of heavy
metals in stock solutions was in the range at 5–1,000 mg dm –3 .
Sorption experiments were carried out at pH 5.5. The flasks
were then agitated in an orbital shaker at a speed of 200 rpm
for a period of 2 h. The quantity of elements in solution has
been determined both before the introduction of sorbent and
after the equilibrium time of 24 hours by AAS.
The amount of adsorbed metal was calculated using the
equation:
q
eq
c 0 –ceq
= (1)
c
s
where c 0 and c eq [mg dm –3 ] are the concentrations of the metal
ion in initial and final solutions and c s [g dm –3 ] is the sorbent
concentration.
Results and Discussion
A d s o r p t i o n o f M e t a l s o n n a t u r a l
Z e o l i t e
The adsorption of Pb 2+ , ni 2+ , Cu 2+ , and Zn 2+ onto
natural zeolite as a function of their concentrations was
studied at 25 °C by varying the metal concentration from
5 to 1,000 mg dm –3 while keeping all other parameters constant.
The experimental data were modeled with Langmuir,
Freundlich and Redlich-Peterson isotherms. The adsorption
isotherms which are the most suitable to fitting the adsorption
processes on natural zeolite in single system are shown
in Figs. 1. and 2. The isotherm analyses showed different
adsorption behaviour for Pb 2+ , ni 2+ , Cu 2+ and Zn 2+ . Metal
adsorption increased in the following order: Pb 2+ > ni 2+ >
Cu 2+ > Zn 2+ (Figs. 1. and 2.). Fig. 1. illustrates the dynamic
adsorption process of Cu 2+ and Zn 2+ on natural zeolite. As
shown Fig. 1., the maximum sorption capacity of natural
zeolite was already exhausted (the equilibrium capacity was
achieved) when the metal concentration in solution was in
low range. Fig. 2. presents that the sorption capacity of sorbent
was not expended even by the highest initial concentration
of Pb 2+ and ni 2+ in solution.