BIOLEACHING OF COPPER SLAGS BY MEANS OF DIFFERENT MICROBIAL CULTURES
- 1 University of Mining and Geology, Sofia, Bulgaria
Copper final slags containing 0.62% Cu, 1.07% Zn, 0.08% Co and 32.5% Fe as the most essential components were subjected to chemical (by means of sulphuric acid and ferric ions) and biological leaching by means of chemolithotrophic microorganisms of three different types: mesophilic and moderate thermophilic bacteria and extreme thermophilic archaea, with temperature optimum at 37, 55 and 75 degrees Celsius, respectively. The leaching was carried out by the shake-flask technique and in agitated bioreactors. The highest rates of extraction of the non-ferrous metals and iron were achieved by means of some archaea but at relatively low pulp densities (5 – 10%). The moderate thermophilic bacteria were the most efficient for the leaching at a higher pulp density (within 15 – 20%).