Frank M. Stewart

New Alternative To Cyanidation: Biocatalyzed Bisulfide Leaching

Abstract Metallurgists have long sought cost-effective techniques for recovering precious metals from their ores. They are increasingly called upon to design processes for ores refractory to conventional recovery techniques. Adding environmental costs (including site remediation) to the total cost of mining has also stimulated a search for alternative to conventional processes. This paper describes progress in development of an alternative to cyanidation, bisulfide leaching, for extracting gold, silver from refractory ores and concentrates. While bisulfide leaching can be implemented abiolically, significant benefits accrue from its practice as a bioprocess integrating precious-metals liberation and extraction steps. Bisulfide leaching appears to offer advantages over the traditional cyanidation process, including lower reagent costs and toxicity as well as an ability to leach “preg-robbing” ores and other ores not amenable to cyanidation. Bisulfide leaching may also offer advantages over cyanidation for ...