THIOSULFATE LEACHING FOR GOLD HYDROMETALLURGY

Thiosulphate leaching of precious metals has been developed as an alte rnative and non-toxic technique to the conventional cyanidation. This process has advantages over cyanide in a decreased interference from f oreign cations and a lower environmental impact. Ammoniacal thiosulpha te solution allows the solubilization of gold as stable anionic comple x. Leaching of gold occurs at appreciable dissolution rates. The aim o f this work is devoted to a preliminary evaluation of the feasibility of thiosulphate leaching for the extraction of gold from precious meta ls ores on a laboratory scale. The experimental work has allowed the a uthors to point out the influence of temperature, thiosulphate concent ration, ammonia concentration and copper sulphate concentration on the gold dissolution from an ore (51.6 g/t Au) that originated from the D ominican Republic. Gold was recovered from the leach liquors by adsorp tion onto activated carbon or by electrowinning. With the optimisation of the process parameters about 80% gold recovery has been attained, as in the case of conventional cyanidation.