Biological gold recovery from gold-cyanide solutions

This paper describes a process for recovering gold from aqueous cyanide solutions using naturally occurring soil microorganisms. In this research, microbes successfully liberated gold cations from aurocyanide complexes. The gold was subsequently captured on iron and zinc electron donors. Three sets of bench scale experiments were conducted using cyanide degrading biomass that had been enriched on cyanide as a sole nitrogen source. After cyanide degrading microorganisms populated microcosm reactors, the biomass was fed with a gold cyanide solution. Microorganisms consumed the CN- moiety of aurocyanide complexes, releasing gold cations. A portion of the gold was recovered on steel wool or zinc which served as cathodes. Although gold recovery rates were low, methods for improving efficiency were investigated. (c) 2004 Elsevier B.V. All rights reserved.