Leaching of a silicate and carbonate copper ore with heterotrophic fungi and bacteria, producing organic acids

Leaching of metals with carbon‐heterotrophic microorganisms and organic acids as active agents has been performed with Timna copper ore containing 1.1% copper as carbonates and silicate and with some other metal oxides. Aspergillus niger surface cultures on a 14% sucrose fermentation medium yielded 87.3% of total copper from a 10% suspension within 2 weeks of leaching. On sulfite liquor as an industrial waste product A. niger solubilized 73.8% Cu within 4 weeks. In percolators with 14% sucrose medium up to 1780 ppm copper were found in solution. In leaching experiments with a sea water medium containing 7% sucrose only 684 ppm Cu were soluble. Leaching with lactobacilli containing whey yielded 83.4% of the total copper in 4 weeks.