Grant: Collaborative Research and Development Grants

In the practice of extracting gold from ores, cyanide is the most common choice of leaching agent because of its selectivity for gold, excellent leaching kinetics, and ease of recovery from solution by adsorption onto coarse particles of activated carbon. However, cyanide is not suitable for extracting gold from carbonaceous ores and there is increasing environmental concern regarding it's toxicity. Because of these drawbacks, there is a need to identify less-toxic alternatives to cyanide that are appropriate for leaching gold from a wide variety of ores. In the search for an alternative to cyanide, thiosulphate has been identified as suitable candidate and shows good initial leaching kinetics for gold provided that ammonium hydroxide and copper sulphate are used as catalysts. However, the presence of these additives can hinder long-term leaching rates because they produce decomposition products that can adsorb on the gold surface and interfere with the leaching mechanism. Some recent studies have shown that adding controlled amounts of organic additives can provide a synergistic effect that improves the leaching rate of gold in thiosulphate systems. In the current research proposal, we will further study an improvement to gold leaching that we have observed when thiosulphate is mixed with small amounts of meso-2,3-dimercaptosuccinic acid (DMSA). The study will be performed in both laboratory controlled solutions as well as electrolytes that are industrially relevant to Barrick Gold corporation. The research may lead to the optimization of the amount of DMSA that should be added with thiosulphate for improved leaching in real ores. Moreover, the research will be performed by students who will learn the industrial practices of gold leaching and should result in personnel that are highly qualified in the metallurgical sector.