THE USE OF CATALYTIC IONS IN BIOLEACHING

Bioleaching is a very interesting possibility for the treatment of sulphide minerals (ores and concentrates). However, it has a great disadvantage: its slow kinetics. In recent years important attempts have been made to improve the process in all respects: biological, microbiological and metallurgical. One possibility is the use of catalytic ions in the process in an attempt to speed up the electron transfer. Both thermophilic and conventional mesophilic micro-organisms are being used. In this way besides incorporating new microbiological possibilities in the process, the kinetic conditions may be improved by working at higher temperatures (68-degrees-C). In this paper, a literature review of this topic is presented, together with the authors' results using catalysts such as Ag, Hg, Bi, Co, As. Mn and Ru. The influence of different concentrations of these ions on the bioleaching of chalcopyrite or on complex sulphides concentrates was studied. For this, a mixed mesophilic culture containing Thiobacillus ferrooxidans, T. thiooxidans and Leptospirillum ferrooxidans and a thermophilic culture of Sulfolobus BC were used. The best results were obtained using, at low temperature, silver, tin and bismuth catalysts. Both the substrate oxidation rate and metal extractions were improved with the use of catalysts.