| The effects of small quantities of heavy metal ions on gold cyanidation have been studied by using electrochemical techniques and leaching of gold ores. Electrochemical investigation shows that anodic dissolution rate of gold increases with temperature and stirring speed, but decreases with pH. Cathodic reduction rate of oxygen is proportional to the oxygen concentration in the solution, and the cathodic reduction rate is significantly higher in the presence of peroxide than in absence of it. Addition of heavy metal thallium, bismuth, silver, mercury and lead will greatly widen potential zone of activation dissolution of gold and significantly improve the anodic current density. The suitable concentration of heavy metal ions for the activation is found to be 10-6M for lead, and 10-5M for bismuth, mercury and silver, but gold dissolution rate increases straightly with thallium concentration within the range of 10-6-10-4M. Based on research results on anodic and cathodic process, mixed-potential models of gold dissolution in the presence of heavy metal ions have been constructed. A Viewpoint is proposed that only being associated with cathodic enhancement by using assistant such as hydrogen peroxide do heavy metal ions enhance gold dissolution in cyanide solutions to the greatest extend.Leaching practice of gold ore and concentrate support the mixed potential result. As to sulfide gold concentrates, which contain a large amountof oxygen-consuming sulfide minerals, the heavy metal ions just show function of strengthening gold leaching only hydrogen peroxide is used as auxiliary oxidant, As to oxide gold ores, the addition of individual heavy metal ions shows the function of strengthening, while adding the heavy metal ions and peroxide simultaneously, the gold dissolution rate improve significantly. This research has offered the theoretical and technological foundation for the application of heavy metal ions in strengthen gold cyanidation.
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