Leaching of chalcopyrite and sphalerite using bacteria enriched from a spent chalcocite heap

Native bioleaching microbes were recovered from a spent chalcocite/chalcopyrite/pyrite heap located at Nifty Copper Mine in Western Australia. As part of the study, methods were developed to enrich and isolate iron and/or sulphur oxidising microbes that thrive in low pH environments. Phenotypic characterisation of native isolates revealed diverse substrate utilisation (chalcopyrite, pyrite, ferrous ion, reduced sulphur as tetrathionate and glucose) as well as displaying growth temperatures between 30 and 50 °C. Their tolerance to changes in pH, temperature, salinity and the presence of metals was also examined. The potential for single isolates to assist the leaching of chalcopyrite and sphalerite concentrates was evaluated. Copper and zinc recoveries from the respective concentrates were greater when native isolates were employed, compared with the use of laboratory reference strains or abiotic conditions.