Extraction of Gold from Gold Chloride Solution by the Depth Reduction Based on Potential Controlling in the Process of Treating Copper Anode Slime

The recovery of gold from copper anode slime has been paid increasing attention by researchers at home and abroad. To realize the higher reduction rate of gold and purity of gold powder, a novel technology is proposed for reducing gold chloride solution by controlling potential in this work. First, the effects of excess coefficient of Na2SO3, reaction temperature, reaction time and initial H+ concentration on the reduction rate of gold were investigated. The optimized conditions were determined as 30 degrees C for the reaction temperature with an excess coefficient of Na2SO3 of 1.43 and an initial H+ concentration of 1.0 mol/L for a reaction time of 15 min. Under the optimal conditions, the purity of gold powder can reach 99.9%. Then, the relationship among solution potential, concentration of gold ion and reduction rate of gold were explored, indicating that the concentration of gold ion can be reduced to < 5 mg/L and the reduction rate of gold is > 99.7% when the solution potential is < 550 mV, which can achieve the depth reduction of gold chloride solution.