Leaching of Gold from an Oxide Gold Ore with Copper-Tartrate-Thiosulfate Solutions at Elevated Temperatures

The leaching behavior of gold from an oxide gold ore using copper-tartrate-thiosulfate solutions has been investigated. Experimental parameters, including temperature, initial pH, and concentrations of copper tartrate and thiosulfate, were systematically studied. The capability of gold leaching using copper-tartrate-thiosulfate solutions is comparable to that of cyanidation, as well as the traditional copper-ammonia-thiosulfate leaching system at elevated temperatures. The kinetics are much faster than that of gold cyanidation, and thiosulfate consumption was greatly reduced in the presence of the tartrate. A considerable gold extraction of 90.42% was obtained under the optimized conditions of 0.1 mol/L CuSO4, 0.2 mol/L Na2L, 0.3 mol/L Na2S2O3, pH 11.0, and 75 & DEG;C after 16 h of leaching. The process of gold dissolution in copper-tartrate-thiosulfate solutions may be controlled by product layer diffusion under the experimental conditions with an apparent activation energy of 35.474 kJ/mol. Increasing the temperature and the concentration of copper and thiosulfate while decreasing the content of tartrate can accelerate the rate of gold leaching. The system is quite unstable when the solution pH is less than 7.0, causing a noticeably lower content of the thiosulfate and copper-tartrate complex. At an initial pH of 9.0 or higher, however, faster kinetics can be achieved.