PRACTICAL APPLICATION OF POTENTIAL-PH DIAGRAMS FOR AU-CS(NH2)(2)-H2O AND AG-CS(NH2)(2)-H2O SYSTEMS FOR LEACHING GOLD AND SILVER WITH ACIDIC THIOUREA SOLUTION

The possibility of gold and silver extraction from products obtained during treatment of copper anodic slimes has been investigated through the construction of potential-pH diagrams for Au-CS(NH2)(2)-H2O and Ag-CS(NH2)(2)-H2O systems. The effect of leach parameters such as thiourea and ferric-ion concentrations in the solution and level of the redox potential were considered. Optimum conditions for gold extraction of 99.8% are leach time of 1 h at the concentration of thiourea 10 g/L and concentration of ferric ion as oxidant 5.0 g/L. The redox potential connected with optimum leaching conditions was 500-523 mV (versus S.H.E.).