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Appl Environ Microbiol. 1963 March; 11(2): 105-110

Microbiological Leaching of Metallic Sulfides

British Columbia Research Council, Vancouver, British Columbia, Canada

ABSTRACT

The percentage of chalcopyrite leached in percolators by Thiobacillus ferrooxidans was dependent on the surface area of the ore but not on the amount. Typical examples of ore leaching, which demonstrate the role of the bacteria, are presented. In stationary fermentations, changes in KH₂PO₄ concentration above or below 0.1% decreased copper leaching as did reduction in the MgSO₄·7H₂O and increase in the (NH₄)₂SO₄ concentration. Bacterial leaching of chalcopyrite was more effective than nonbiological leaching with ferric sulfate; ferric sulfate appeared to retard biological leaching, but this effect was likely caused by formation of an insoluble copper-iron complex. Ferrous sulfate and sodium chloride singly accentuated both bacterial and nonbiological leaching of chalcocite but jointly depressed bacterial action. Sodium chloride appeared to block bacterial iron oxidation without interfering with sulfide oxidation. Bacterial leaching of millerite, bornite, and chalcocite was greatest at pH 2.5. The economics of leaching a number of British Columbia ore bodies was discussed.

¹ Present address: Syntex Institute for Molecular Biology, Palo Alto, Calif.