Silver sulfide leaching with a copper-thiosulfate solution in the absence of ammonia

Leaching from silver sulfide using a copper-thiosulfate solution in the absence of ammonia was investigated.It is found that silver sulfide could be effectively dissolved in the copper-thiosulfate system without ammonia.The effects of thiosulfate concentration,copper-to-thiosulfate ratio,agitation vigorousness,pH values,and dissolved gases on the leaching of silver sulfide with the copper-thiosulfate solution were studied.A maximum extraction of 95.1% was achieved with the 0.12 mol/L thiosulfate and the 0.048 mol/L copper sulfate.It is shown that copper-to-thiosulfate ratio is an important factor in silver sulfide dissolution and oxygen is not needed to leach silver sulfide,which leads to the instability of the leaching system at high copper-to-thiosulfate ratio.On the other hand,the silver extraction is not affected by the pulp pH values.