Biomedical Engineering Reference
In-Depth Information
Iron leaching from oxidized minerals with application of microorganisms is well known
[1-3]. Numerous works revealed that rational and ecologically safe method of iron removal is
application of iron-oxidizing microorganisms that transfer iron into soluble form and decrease
its content till 0.7-0.9% in form Fe
2
O
3.
But, after treatment of kaolin by thionic iron-oxidizing
bacteria the process of formation of quite strong iron hydroxide film of surface of minerals
takes place.
Application of microorganisms-producers of organic acids allows to remove residual
concentrations of iron. It is linked to formation of organic acids and other metabolites, which
act as complex forming agents, and to enzymatic and non-enzymatic removal of iron as well
[4-6]. Microorganisms-producers of mineral and organic acids impact minerals by increasing
iron concentration in medium, which activates hydrolysis reaction and carry-over of metal
cations.
The object of study was primary kaolin from Angren deposit and microorganisms
Acidithiobacillus ferrooxidans. Model tests were conducted in Erlenmeyer flasks with ratio
solid: liquid =1:7 with application of association of bacteria A. ferrooxidans K-1, initial pH of
pulp was 1.5. Tests were conducted with partial change of liquid phase (up to 20%) by fresh
nutrient medium. Preliminary cultivation of bacteria was conducted on medium K9
containing 6 g/l of FeSO
4
∙7H
2
O. Fresh nutrient medium with corresponding iron content was
added accordingly. Cultivation period was limited by 2-3 days.
Conducted silicate analysis of cakes of bacterial leaching (BL) revealed that considerable
decrease in concentration of FeO till 0.2% is observed, but, overprecipitation of oxide forms
of iron is observed and, respectively, its increase, which negatively affects product quality.
Further two day treatment of cake of BL by cultural broth of micromycetes allowed to
decrease content of Fe
2
O
3
till 0.27% (Table 1).
Table 1. Results of chemical analysis of BL cake after treatment of primary kaolin by
iron-oxidizing microorganisms A.ferrooxidans K-1 (1 stage) and silicate destroying
microorganisms (2 stage)
Compounds
Content, %
SiO
2
Fe
2
O
3
FeO
TiO
2
Al
2
O
3
CaO СО
2
SO
3
Initial
57.9
0.85
4.1
0.5
22.3
0.5
3.5
0.07
1 stage
58.93
1.12
<0.2
0.5
28.3
<0.5
<0.5
0.21
2 stage
56.3
0.27
<0.2
0.5
13.2
<0.5
<0.5
0.07
Table 2. Results of chemical analysis of BL cake after treatment of AKS grade kaolin
with cultural broth of micromycetes
Compounds
Content, %
SiO
2
Fe
2
O
3
FeO
TiO
2
Al
2
O
3
CaO СО
2
SO
3
Initial
56.48
0.82
0.07
0.5
24.2
0.69
3.52
0.05
After
treatment with
cultural broth
52.5
0.23
<0.2
0.5
13.2
<0.5
<0.5
0.07
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