Studies on thiourea leaching of finely-divided gold ores

Abstract

Laboratory leaching experiments were conducted to ascertain the effectiveness of acidic solutions of thiourea, CS(Nh2)2, for dissolving gold from finely disseminated gold ores. The ores tested were from the Chipmunk orebody of the Northumberland mining district in Nye County, Nevada, USA, and carbonaceous ore from the Carlin orebody in Eureka County, Nevada, USA. Extractions of up to 90 percent were attained from the Chipmunk ore. Extraction was shown to be dependent on thiourea concentration, ferric sulfate oxidant concentration, acid concentration, and leaching time. Optimum conditions were an ambient temperature leach near pH 1.0 utilizing 100-200 kg/t thiourea and 5 kg/t ferric sulfate for 8 to 24 hours. The Carlin carbonaceous ore proved to be more amenable to leaching with thiourea solutions than standard cyanidation. Recoveries of up to 60 percent were attained compared to 3 percent with cyanide treatment. Behavior was similar to that of Chipmunk ore.