2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures
2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures
2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures
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Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology<br />
P36 bIOLEAChING OF ANTIMONy MINERALS<br />
by bACTERIA ACiDiTHiObACillus<br />
ferrOOxiDANs AND DesulfOvibriO<br />
DesulfuriCANs<br />
ALEnA LUPTáKOVá a , EVA MAČInGOVá a , STEFAnO<br />
UBALDInI b and JAnA JEnČáROVá a<br />
Institute of Geotechnics of Slovak Academy of Sciences, Watsonova<br />
45, 043 53 Kosice, Slovak Republic,<br />
luptakal@saske.sk<br />
Introduction<br />
In several gold ores, gold is trapped in the matrix in of<br />
metallic sulphides (FeS 2 , Sb 2 S 3 etc.). In such cases recovery<br />
of gold from refractory ores requires a pre-treatment to liberate<br />
the gold particles from the host mineral. For the pre-treatment<br />
of gold ores exist several hydro- and biohydrometallurgical<br />
processes 1 . The fundamental of biohydrometallurgical<br />
processing for sulphide minerals is the application of microorganisms,<br />
which on the basis of their metabolic processes<br />
can increase or decrease mobility of metals 2,3,4 .<br />
In the area of biohydrometallurgical processing of goldbearing<br />
antimony sulphide minerals and concentrates the<br />
iron- and sulphur-oxidising bacteria have the very important<br />
function as well as on the ground the new knowledge also<br />
the sulphate-reducing bacteria 5,6,7 . Using involved bacteria<br />
to catalyse the breakdown of sulphides that host the gold<br />
is an important biological method for the pre-treatment of<br />
refractory gold ores. Following this biological treatment<br />
a combination of chemical and physical methods are used for<br />
leaching (e.g. the cyanide process) and concentration (e.g.<br />
the electrowinning) of gold. Although these methods are well<br />
accepted by industry, they harbour limitations in the processing<br />
of low-grade refractory ores, and regulatory agency/public<br />
acceptance of cyanide use. The objectives of this work<br />
were to evaluate the use of iron- and sulphur-oxidising bacteria<br />
Acidithiobacillus ferrooxidans (At. ferrooxidans) and<br />
sulphate-reducing bacteria Desulfovibrio desulfuricans (Dsv.<br />
desulfuricans) in the biohydrometallurgical processing of<br />
gold-bearing antimony sulphide minerals. Experiments were<br />
conducted at laboratory scale on a refractory gold-bearing<br />
stibnite coming from Santa Rosa de Capacirca Mine, Bolivia.<br />
Involved bacteria were used separately at different conditions<br />
for the pre-treatment of the aforementioned sample in order<br />
to increase the subsequent gold recovery during cyanidation<br />
processes. The At. ferrooxidans application is based on the<br />
their ability to oxidize and dissolve pyrite and stibnite, thus<br />
releasing the entrapped gold particles. The using of the bacteria<br />
Dsv. desulfuricans is based on their ability of the bacterially<br />
H 2 S production for the alkaline leaching of stibnite.<br />
Experimental<br />
M i c r o o r g a n i s m s<br />
In the experiment were used bacteria At. ferrooxidans<br />
isolated from the acid mine water 8 (deposit Smolník, Slovakia)<br />
and Dsv. desulfuricans isolated from the potable mineral<br />
s409<br />
water 9 (Gajdovka spring, Kosice, Slovakia). The isolation<br />
was performed by the modified dilution method 10 .<br />
S a m p l e s o f O r e<br />
The sample of gold-bearing antimony sulfide minerals<br />
used was obtained from Bolivia 6 (Santa Rosa de Capacirca<br />
Mine). Mineralogical characterisation by X-ray Diffraction<br />
(XRD) showed the presence of quartz (SiO 2 ), stibnite (Sb 2 S 3 )<br />
and pyrite (FeS 2 ). Their chemical composition includes<br />
21.93 % Si, 4.94 % Sb, 4.28 % Fe and 3.77 % (S). Quantitative<br />
chemical analysis was performed by Inductively Coupled<br />
Plasma Spectrometry (ICP).<br />
B i o l e a c h i n g T e s t b y B a c t e r i a<br />
Bacteria At. ferrooxidans and Dsv. desulfuricans were<br />
used separately. The experimental tests were conducted in a<br />
fed batch reactor at 30 °C under aerobic and dynamic conditions<br />
(with At. ferrooxidans) and anaerobic and static conditions<br />
(with Dsv. desulfuricans). The weight of the sample<br />
of gold-bearing antimony sulfide minerals was of 10 g. The<br />
total volume of feed solution consisted of 100 ml selective<br />
nutrient medium 1 9K(A) for At.f. with pH <strong>2.</strong>5; and DSM-63<br />
medium 10 for Dsv. desulfuricans with pH 7.5. The abiotic<br />
control was carried out without the bacteria application at<br />
the same conditions. Dissolved metals in liquid phase during<br />
the experiments were determined using an atomic absorption<br />
spectrophotometer. After 120 days the solid phases were<br />
recovered by filtration and were saved for the consequently<br />
test of cyanidation.<br />
Results<br />
The results of the bioleaching i.e. the pre-treatment of<br />
gold-bearing antimony sulphide minerals are demonstrated<br />
by Figs. 1.–4.<br />
Fig. 1. Dissolution of Fe by bacteria Acidithiobacillus ferrooxidans<br />
from the sample of gold-bearing antimony sulfide minerals.<br />
c – concentration of Fe, t – time of bioleaching,<br />
– Acidithiobacillus ferrooxidans, – abiotic control<br />
Fig. 1. presents the dissolution of the Fe by bacteria<br />
At. ferrooxidans and in the cases from the start until the end<br />
of experiments the concentration of Fe in liquid phase increase.<br />
From beginning, probably due to interaction between