| Thiosulfate is widely used as an alternative to cyanide in the most promising non-toxic gold leaching reagent. However, high consumption of traditional copper-ammonia-thiosulfate leaching gold system prevented the method commercial used. Lower consumption of thiosulfate was received when polyamines was used as an alternative to ammonia, But the system of copper(â…¡) complex ion or free copper(â…¡) ion impact on gold dissolution process is not clear.In this paper, the electrochemical measurements using Tafel plot to study ethylenediamine(ammonia) copper (â…¡) thiosulfate leaching of gold systems.Effect of thiosulfate concentration, ethylenediamine(ammonia) concentration and copper (â…¡) concentration on the corrosion current, resistance and corrosion potential was investigated. Using LSV plot to study ethylenediamine(ammonia) copper (â…¡) thiosulfate leaching of gold systems. Effect of thiosulfate concentration, ethylenediamine(ammonia) concentration and copper (â…¡) concentration on the peak potential and peak current was investigated. Using EIS to study ethylenediamine(ammonia) copper (â…¡) thiosulfate leaching of gold systems.Effect of thiosulfate concentration, ethylenediamine(ammonia) concentration and copper (â…¡) concentration on the polarization resistance and dynamic behavior was investigated. To find out which factors impact on gold dissolution process.This study showed that in NH3-Cu2+-S2O32-system or en-Cu2+-S2O32-system, the corrosion potential and polarization resistance of gold decreased, the peak potential of gold, the corrosion current and the peak current increased with the concentration of copper (â…¡) ions increased. The reaction series is 1 with the concentration of copper (â…¡) ions increase from 0.0002mol/L to 0.0008mol/L. But thiosulfate influence on the dissolution of gold electrochemical process is more complicated. Comparing the two kinds of gold leaching system found that ethylenediamine gold leaching systems was better.From the EIS can be concluded:in NH3-Cu2+-S2O32-system,when the concentration of copper (â…¡) ion is less than 0.0008 mol/L, the gold leaching reaction rate control steps are mainly the charge transfer control; When the concentration of copper (â…¡) ion between 0.0008 mol/L-0.002 mol/L, the steps to control the reaction rate are mainly the charge transfer and diffusion control simultaneously; When the concentration of copper (â…¡) ion between 0.002 mol/L-0.008 mol/L, the steps to control the reaction rate are mainly diffusion control. In en-Cu2+-S2O32-system,when the concentration of copper ion is less than 0.008 mol/L, the gold leaching reaction rate control steps are mainly the charge transfer control;When the concentration of copper ion is greater than 0.006 mol/L, the steps to control the reaction rate, mainly the charge transfer and diffusion control at the same time. Combination system of gold leaching of copper (â…¡) distribution and gold leaching control steps of the analysis shows that within a certain range of free copper ions in the solution with gold electron exchange rate on the oxidation of gold dissolution plays a main role. |
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