Electrochemical Study of Thiosulfate-EDTA-Copper Ion Leaching Gold System

Disodium ethylenediamine tetraacetate (EDTA) was used as copper complex agent instead of ammonia in the thiosulfate-EDTA-copper ion system. The obtained complex had the advantages of good stability and low electrode potential. It could be used as gold leaching solution for gold extraction. The Tafel curves, the open circuit potential, cyclic voltammograms were used to explore the thiosulfate influence on the corrosion of gold, examine the cyclic voltammetric behavior. The results showed that the increase in concentration of thiosulfate could lead to easy corrosion for gold when its concentration was more than 0.1 mol•L-1, the increase of the concentration of thiosulfate could lead to the corrosion of gold difficult due to the passivation on the gold electrode surface; with the increase of copper concentration, thiosulfate reduction potential was negatively shifted and peak current increased, indicating that thiosulfate was more easily consumed under the condition. The cyclic voltammetry showed a linear relationship between peak current and square root of scanning speed, which was diffusion control. During this process, the reduction electron transfer number of thiosulfate was about 1. The cyclic voltammetry of thiosulfate also showed a good linear relationship between lnIp and 1/T, and its activation energy was Ea=5.498 kJ•mol-1, indicating that it was caused by concentration difference polarization. © Editorial Office of Chinese Journal of Rare Metals. All right reserved.