Thiosulfate leaching of silver, gold and bismuth from a complex sulfide concentrates

Abstract

The intensification of the thiosulfate leaching of silver, gold and bismuth from sulfide concentrates using mechanical activation and mechanochemical pretreatment step was investigated. The physico-chemical changes in a complex sulfide concentrate (Casapalca, Peru) as a consequence of mechanochemical pretreatment had a pronounced influence on the subsequent silver extraction. The optimum results from mechanochemical pretreatment and subsequent leaching of the concentrate with ammonium thiosulfate were achieved with 99% recovery of Ag after only 3 min of leaching. The leaching of gold from a mechanically activated complex sulfide concentrate (Banská Hodruša, Slovakia) using ammonium thiosulfate was studied as follows. Physico-chemical transformations in the concentrate due to mechanical activation have an influence on the rate of extraction and the recovery of gold. It was possible to achieve 99% Au recovery within 45 min for a sample mechanically activated. Mechanical activation proved to be an appropriate pretreatment for this concentrate before extraction of gold into thiosulfate leaching solution. The selective leaching of a bismuth from the lead concentrate (Atacocha, Peru) by using of sodium thiosulfate and mechanical activation as the pretreatment step was examined as the last example. It is possible to achieve more than 90% recovery of a bismuth in leachate even in three minutes for mechanically activated samples.