Gold Leaching by Using Ammonium Thiosulfate Solution.

Abstract

The sponge gold (99.92% pure) has been leached with ammonium thiosulfate solution. In this investigation, the gold leaching rate (extraction rate) and the thiosulfate oxidation rate (consumption rate) have been studied on the effects of CuSO sub 4 , (NH sub 4 sub 2 S- sub 2 O sub 3 , (NH sub 4 sub 2 SO sub 4 , NH sub 4 OH, stirring speed and retention time. The copper ion acts as a catalyst in gold dissolution, on the other hand, it also accelerates oxidation of thiosulfate (consumption). It was found that the best gold extraction was obtained at 12 hours under following optimum conditions: 8 approx = 1.0 mol/l (NH sub 4 sub 2 S sub 2 O sub 3 , 0.03 mol/l CuSO sub 4 , 2.0 approx = 3.0 mol/l NH sub 4 OH, 0.4 approx = 0.5 mol/l (NH sub 4 sub 2 SO sub 4 , pH 10 plus/minus 0.2 and 150 rpm. The thiosulfate oxidation is about 15% of the initial concentration.