Electrochemical analysis of copper-EDTA-ammonia-gold thiosulfate dissolution system

Ethylenediaminetetraacetic acid disodium (EDTA) can form stable complexes with many metals. To improve the leaching rate of gold and the consumption rate of thiosulfate, EDTA and ammonia were combined with copper ions to form a copper-EDTA-ammonia-thiosulfate system. Electrochemical methods were used to study the effect of thiosulfate, copper ion, EDTA, and polarization voltage. The results showed that increasing the concentrations of thiosulfate, copper ions, and EDTA promoted the dissolution of gold, which changed from electrochemical control to diffusion control after adding EDTA. The order of influence was thiosulfate > EDTA > copper ion. The pure gold leaching experiment showed that the dissolution rate of gold in the EDTA-ammonium-copper thiosulfate system was higher than that in the EDTA-copper-thiosulfuric acid system, thus achieving synergistic gold leaching.