Microbiological Controls on Geochemical Kinetics 2: Case Study on Microbial Oxidation of Metal Sulfide Minerals and Future Prospects

Sulfide minerals are components of magmatic, igneous, and sedimentary rocks, as well as hydrothermal deposits (ore bodies). They are exploited economically as sources of sulfuric acid and metals, such as Co, Cu, Au, Ni, and Zn that are present either as discrete sulfide phases (e.g., CuS, Gu

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S, NiS, ZnS) or coprecipitates with major iron-sulfide phases such as FeS

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(e.g., chalcopyrite, CuFeS

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). However, in many situations, sulfide minerals (in particular FeS

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, the most abundant sulfide phase in most mineral deposits) are waste (“gangue”) phases associated with mining and metallurgical operations. Exposure of these phases to atmospheric O

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during and after such operations causes acid mine/acid rock drainage (referred to hereafter simply as acid mine drainage or AMD; see Table 9.1 for a list of abbreviations), an environmental problem of major environmental concern (Evangelou and Zhang, 1995). A vast amount of research has been conducted on the mechanisms and controls on sulfide mineral oxidation for the purposes of (i) understanding and predicting environmental risk associated with AMD; (ii) understanding sulfur and metal cycling associated with natural sulfide mineral weathering; and (iii) optimizing commercial recovery of metals from low-grade ores and wastes. Microorganisms play a pivotal role in sulfide mineral oxidation, and this phenomenon represents another premier example of how microbial activity exerts fundamental control on water—rock interaction phenomena.