Technical Potential for Bioleaching and Biobeneficiation of Ores to Recover Base Metals (Other than Iron or Copper), Platinum-Group Metals and Silver

Abstract

The extraction of copper from sulfidic copper ores through the agency of acidophilic iron-oxidizing bacteria, e.g., Thiobacillus ferrooxidans, has become an industrially accepted technology in mining and mineral processing, especially for low-grade ore, and is now also receiving serious consideration for high-grade ores and ore concentrates (see chapters 2–6 and also Rossi,1 Ehrlich and Brierley2).Other commercially successful applications of bioleaching have been in the in situ extraction of uranium from some uranium ores, and in the biobeneficiation of precious metal ores, especially sulfidic gold ores. A potential exists for the microbial extraction of base metals besides iron and copper from sulfidic and other types of ores, but none of these processes have so far found commercial application. Among the reasons for lack of commercial exploitation of these processes have been a preconception that some may be technically difficult to run on an industrial scale and/or that their economics are unfavorable. Other reasons include considerations of limited size of pertinent mineral reserves and future demand for a particular metal.3 As stricter environmental laws dealing with control of atmospheric, water, and soil pollution that results from conventional extraction by pyro- and hydrometallurgy are enacted, many processes of base metal extraction by bioleaching currently viewed as unattractive economically are likely to become competitive with the conventional processes, especially if the efficiency of these bioleaching processes can be further improved.