Biological gold recovery from gold-cyanide solutions

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.