Intensification Of Thiosulfate Leaching Of Gold Based On Controlling Thiosulfate Consumption

In recent years the gold leaching technique of thiosulfate has received more and more attention. This approach shows many advantages as one most important non-cyanide technique, such as non-toxic, ease of use, fast speed and high quality of gold leaching, non-sensitive to impurities and so on. However, there are still some problems in its industrialization process, such as (1) consuming too much thiosulfate increases the cost;(2) a host of environmental issues appear with the volatilization of difficult-to-decompose ammonia;(3) effective technique of gold recovering from thiosulfate leach liquor was not established. Considering the complexity of thiosulfate leaching system, therefore, this study will explore the mechanism of consumption and decomposition of thiosulfate at normal temperatures and pressures and optimize the process conditions with a low concentration of thiosulfate.The study discussed the influence characteristic of different process parameters on the stability of thiosulfate in the simulated leaching system and the actual leaching system, and found that copper-ammonia complex was not only the essential factor of gold leaching with thiosulfate but also the main element of promoting the consumption of thiosulfate. Based on the consumption characteristic of thiosulfate, the study further investigated the control technology of consumption of thiosulfate, and found that additives of NaCl, Na2SO3, CMC, humic acid (F) and SDB could significantly reduce the consumption rate of thiosulfate. In the actual leaching system CMC and F effectively improved the gold leaching rate compared with NaCl and SDB. By contrast, Na2SO3obviously depressed the dissolution of gold. In the reinforcement experiment of gold leaching with thiosulfate, due to the addition of CMC the consumption of thiosulfate decreased from42.4kg/t to14.2kg/t,and gold leaching rate improved from78.7%to80.0%; With the addition of F the consumption of thiosulfate decreased from42.4kg/t to21.6kg/t, and gold leaching rate improved from78.7%to79.6%. Therefore, the addition of CMC and F achieved both the control of consumption of thiosulfate and the reinforcement of gold leaching. The result may contribute to the development of the industrialization of gold leaching technique to some extent.