Effects of sulphide minerals and dissolved oxygen on the gold and silver dissolution in cyanide solution

To better understand how various sulphide minerals influence the dissolution kinetics of gold and silver in air-saturated and oxygen-enriched cyanide solutions, an extensive study has been carried out using the gold and silver rotating disc method. Special emphasis has been focused on the effects of gold-associated minerals on gold and silver dissolution in atmospheric and oxygen-enriched cyanide solutions. The results demonstrated that the leaching behaviours of gold and silver in the presence of various sulphide minerals depend strongly on both the solubility of the sulphides and the oxygen concentration in solution. Since the degree of sulphide decomposition varied with oxygen concentration, gold and silver dissolution during cyanidation was enhanced or diminished, depending on the type and amount of dissolved constituents. In the oxygen-enriched cyanide solution, the presence of some sulphide minerals, such as pentlandite, chalcopyrite, pyrrhotite, sphalerite, molybdenite, arsenopyrite and pyrite, increased the gold dissolution rate while others, such as galena, stibnite and chalcocite caused the reverse to occur under the experimental conditions. Silver dissolution was also significantly improved by leaching with oxygen-enriched cyanide solution, but the rate of silver dissolution with the association of sulphide minerals was still lower than that without sulphide minerals.