Research progress on non-cyanide leaching of refractory gold ores

With the increasing demand for gold and the decreasing of easily treated gold resources, refractory gold ores, which are characterized by low gold recovery and high cyanide consumptions when subjected to direct cyanide leaching, have gradually become the main sources of gold. Thus, reasonable exploitation and utilization of refractory gold ores are of great significance to the sustainable development of the gold industry in China. To ensure a reasonable and efficient utilization of refractory gold ores, refractory gold ores were reviewed and classified in this paper, and the difficulties of handling were briefly reviewed. For over one hundred years, cyanidation has been the predominant process of extracting gold from mineral sources. The major reason for adopting cyanide rather than other lixiviants is its higher chemical stability and lower cost. But in recent years, the utilization of the traditional cyanide method to leach gold have been undesirable; this is mainly because the acute toxicity of cyanide can result in environmental pollution and human health hazard. Moreover, leaching of refractory gold ores by traditional cyanidation techniques also results in poor gold recovery. On this basis, non-cyanide lixiviants have attracted considerable attention in the metallurgical industry, and several non-cyanide leaching methods have been proposed for gold extraction because of their non-toxic nature, acceptable gold leaching rates, and high gold recovery. In this paper, the leaching mechanisms and the latest research progress of non-cyanide gold leaching techniques for refractory gold ores, such as leaching processes with thiosulfate, thiocyanate, thiourea, polysulfide, lime-sulfur-synthetic solution (LSSS) and chlorination, were discussed in detail. Then considering features of non-cyanide gold leaching such as a complex leaching system, unstable leaching agents, and large consumption of leaching agents, and development directions of non-cyanide gold leaching technology for refractory gold ores were proposed.