Thiourea leaching of gold from a calcine of gold-bearing arsenical pyrite concentrate

The thiourea leaching of gold from the calcine of gold-bearing arsenical pyrite concentrate of Kangjiawan mine was studied. The effects of the leaching time, the concentrations of thiourea, hydrochloric acid and initial ferric ion on the leaching recovery of gold were investigated, and a regressive model has been established, which showed that the concentrations of thiourea and hydrochloric acid were the most important factors, leaching time the second, and concentration of the initial ferric ion the least. Under the optimal conditions, that is, temperature 50 degrees C, the ratio of liquid to solid 4 : 1, thiourea 12 g/L, hydrochloric acid 1 mol/L, and initial ferric ion 1 g/L, the leaching recoveries of gold and silver were more than 81% and 73%, respectively. The increase of silver recovery and the reduction of thiourea consumption could be attained when sodium sulphite was added.