Leaching of a carbonaceous gold concentrate in copper-tartrate-thiosulfate solutions

The leaching behavior of gold from a carbonaceous gold concentrate in copper-tartrate-thiosulfate solutions was studied in this paper. Experimental parameters, including temperature, initial pH, copper, tartrate, and thiosulfate concentration, were systematically investigated. The capability of leaching gold from the carbonaceous gold concentrate by copper-tartrate-thiosulfate solutions is comparable to that in cyanidation or traditional copper-ammonia-thiosulfate systems. The consumption of thiosulfate can be significantly reduced in the presence of tartrate. The mechanism of gold leaching in copper-tartrate-thiosulfate solutions is catalyzed by the mononuclear CuL2H-4-6 complex when the solution pH is beyond 10.5 based on thermodynamic analysis. The stability of the CuL(2)H(-4)(6- )complex increases with an increase in the tartrate content and decreases with increasing copper and thiosulfate concentrations. A moderate increase in solution pH and temperature exhibits less effect on the consumption of thiosulfate or copper-tartrate complex, but a higher temperature may cause a sharp decline in the content of copper-tartrate complex. The recycling of the leaching solutions demonstrates that maintaining a suitable concentration of copper ions and thiosulfate and a suitable solution pH are crucial to obtain a considerable gold leaching rate.