Study on Thiosulfate Leaching of Gold by Cycling Barren Solution

Abstract

Thiosulfate leaching is widely recognized as one of the most promising alternatives to cyanidation for gold leaching, of which the action of cyclic barren solution is of great importance as far as its commercial application is concerned. In this study, the composition of the leaching solution was characterized and its effect on gold leaching was investigated with regard to cycling thiosulfate barren solution. By direct cycling of barren solution without supplement of any chemical reagent, the gold leaching rate for a gold-bearing calcine decreased noticeably with cycle index, from 71.1% with the fresh solution to 17.8% after four cycles. This is mainly attributed to the decrease in thiosulfate concentration, which turned out to be from 0.5 to 0.06 mol/L. By supplementing thiosulfate and copper into the cycling solutions to the same concentration as the initial fresh solution, associated with addition of a certain amount of sodium sulfite as stabilizer, the gold leaching rate was favorably stabilized as being up to 63.0% during four cycles.