Electrochemical behavior of the dissolution of gold-silver alloys in cyanide solutions

The dissolution behavior of gold and silver from Au/Ag alloys in aerated cyanide solutions has been investigated using rotating disc electrodes. The variables studied included concentration of cyanide, oxygen partial pressure, and rotating speed of the disc. The dissolution potential and the rate of dissolution were obtained in view of the anodic and cathodic current-potential relationships. The results were discussed in terms of the mixed potential theory. The results showed that the dissolution : rate of gold and silver from the alloys was partially controlled by chemical reaction but largely controlled by transport of either oxygen or cyanide, depending on their relative concentrations under the experimental conditions employed in this study. The diffusion coefficient of free cyanide, D-CN-, was found to be (1.25 +/- 0.05) x 10(-5) cm(2)/s. The diffusion coefficient of oxygen, D-O2, was calculated to be (1.29 +/- 0.02) x 10(-5) cm(2)/s.