bioleaching

1. Mechanismof bacterial leaching
 Bacterial leaching: It is process based on the ability of micro-
organism to transform solid compounds into soluble and
extractable elements, which can be recovered.
 There are two major mechanism of bacterial leaching .
1. Indirect mechanism
2. Direct mechanism

2. Mechanismof bacterial leaching

3. Mechanismof bacterial leaching
Indirect Mechanism:
 Bacteria produce the strong oxidizing agent such as ferric ion
and sulphuric acid on oxidation of soluble iron or soluble
sulphur.
 Acidic environment is absolutely essential in order to keep
ferric iron and other metals in solution.
Ex; Bacterial leaching of Uranium
UO2 + (FeSO4 )3 UO2SO4 + 2FeSO4
2S+3O2 +2H2O H2SO4

4. Mechanismof bacterial leaching
Direct Mechanism:
 Bacteria directly oxidized minerals and solubilise metals
 A physical contact exist between bacteria and ores and oxidation
of minerals takes place through enzymatically catalyzed steps.
Ex; Pyrite is oxidized to ferric sulphate
2FeS2 +7O2+7H2O 2FeSO4+ 2H2SO4
ZnS+2O2 ZnSO4

5. Mechanismof bacterial leaching
Main factors affecting on bacterial leaching
 Nutrients
 O2 and CO2 content
 Temperature
 Surfactants and organic compounds
 Properties of minerals
 Processing

6. THANK YOU
Pulok Chandra das
bsmrstu