Bioleaching of a copper sulphide flotation concentrate using mesophilic and thermophilic microorganisms

Pyrometallurgical treatment of sulphide concentrates generates SO2 and, hen ce, atmospheric pollution. An attractive alternative for metal recovery cou ld be the use of microorganisms due to its low cost and relatively fewer po llution problems compared with conventional hydrometallurgical and pyrometa llurgical processes. Bacterial leaching is being commercially well exploited for the copper reco very from low-grade ores. In the present investigation the possibility of c opper recovery from a copper sulphide flotation concentrate containing: 29. 1% Cu. 21.9% Fe, 1.54% Zn and 23.2% S has been evaluated using both mesophi lic and thermophilic microorganisms. Bacterial leaching of copper sulphide flotation concentrates is a complex p rocess, which occurs at a sequential way: chalcocite and digenite are the f irst minerals to be dissolved? followed by chalcopyrite. Optimal copper rec overy was achieved using a moderate thermophilic culture at 45 degrees C. C opper dissolution reached 85% with a copper concentration of 13.8 g/L in so lution.