OXIDATION OF MINERAL SULFIDES BY THERMOPHILIC MICROORGANISMS

Pyrite and arsenopyrite concentrates were oxidized during growth of a variety of acidophilic microorganisms over a wide temperature range. A mesophilic culture, comprising Thiobacillus ferrooxidans and Leptospi rillum ferrooxidans as the principal iron-oxidizing bacteria, was used at 30 degrees C; Sulfobacillus thermosulfidooxidans was active in pur e and mixed cultures at 48 degrees C; and Sulfolobus-like, thermoacido philic archaea were grown at up to 84 degrees C. At low mineral concen trations, the rate of pyrite/arsenopyrite dissolution was proportional to temperature. However, the use of elevated temperatures to increase rates of mineral processing over those obtainable with mesophiles app eared to be most practicable with moderately thermophilic bacteria bec ause growth of Sulfolobus strain BC was inhibited at higher mineral co ncentrations. Two aspects of higher temperature bioleaching were empha sized: the unique capacity of Sulfolobus-like archaea for extensive ch alcopyrite oxidation; and the requirement for progress in leaching at high mineral concentrations before the potential of these organisms ca n be realised in process development. Copyright (C) 1996 Elsevier Scie nce Ltd.