Thermophilic microorganisms in extraction of metals from ores (Reprinted from Developments in Industrial Microbiology, vol 18, pg 273-284, 1977)

To leach metals from porphyry copper samples in which chalcopyrite (CuFeS2) was the primary mineral, two thermophilic bacteria were used, Sulfolobus a cidocaldarius and "ferrolobus." Ferrolobus has not been classified but is s imilar to Sulfolobus acidocaldarius. Both organisms are mixotrophic, thermo philic, and acidophilic, and oxidize sulfur and iron. Leaching was conducte d in 250-ml Erlenmeyer flasks incubated at 60 C. In 60 days ferrolobus leac hed 51% of the copper from a -65 mesh chalcopyrite concentrate containing 2 9% copper; 8% of the copper was extracted from sterile controls. Leaching t ests were conducted in 6 ft x 0.5 ft glass leach columns heated to 60 C. Th e percentages of copper, molybdenum, zinc, lead, and iron extracted from mi neral samples inoculated with mixed cultures of Sulfolobus acidocaldarius a nd ferrolobus were compared with the extraction of these metals from sample s maintained under identical conditions but sterilized with panacide. Mixed cultures of the thermophilic bacteria leached 38% of the copper from -3 100 mesh Duval Sierrita Corporation chalcopyrite ore (0.31% copper) in 161 days; 4% Of the copper was extracted in the chemical control. Iron concn in solutions were variable over the leach period, with all iron present in th e ferrous form. Molybdenum in solution increased with increasing iron concn . These studies indicate that thermophilic and acidophilic bacteria can ext ract copper from ores and mine wastes containing chalcopyrite.