Study on Synergistic Strengthening of Gold Extraction with Copper Ethylenediamine Thiosulfate Using Pyrite and Nickel Ions

Gold leaching using the copper-ethylenediamine-thiosulfate (Cu2+-en-S2O32-) system, which contains copper-ethylenediamine complexes, instead of the use of copper-ammonia catalysis, is environmentally friendly and cost-effective. In this study, pyrite and Ni2+ were added to the Cu2+-en-S2O32- system to clarify their individual and combined influence on gold leaching. The result obtained showed that when pyrite and Ni2+ were separately added to the system, the dissolution of gold was significantly inhibited. However, the disappearance of the negative impacts of these two substances when they were simultaneously added to the system revealed that they exhibited a synergistic effect on gold dissolution. Notably, Ni2+ weakened the promotional effect of pyrite on the formation of a Cu-containing passivation layer on the gold surface. Furthermore, the separate addition of Ni2+ and pyrite increased the corrosion potential of gold; thus, gold dissolution was inhibited. However, when added together, they brought about a decrease in the corrosion potential of gold, while increasing its dissolution rate. These findings provide a reference for the efficient extraction of pyrite-associated gold, which can be applied to improve the green extraction process of gold.