Although cyanidation, as a hydrometallurgical route for gold ores, is well consolidated in theindustry, its environmental implications and specific demands have driven the development ofseveral studies on the use of alternative leaching agents. The use of thiosulphate has been studiedsince the 1980's, having occurred in 2014, the first commercial application at Barrick GoldCorporation (USA).The main motivation for this process is the low affinity of thiosulphate withcarbonaceous ores, avoiding the preg-robbing effect characteristic of cyanidation. In this sense, theobjective of the present study is to evaluate the performance of thiosulphate as a gold leaching agentfor a Brazilian carbonaceous ore. A sample of the ore was homogenized, splitted and submitted tochemical and mineralogical characterization and leaching tests with thiosulphate and to cyanidation.The dosages of thiosulphate and auxiliary chemicals (copper sulphate, ammonia, sodium sulphite)were optimized and the best results were compared with cyanidation (typical industrial dosage). Theleaching times in both processes were also evaluated. The best result was 74.8 % gold extraction in 6hours, with dosages of 60 kg/tore ammonium thiosulphate, 38 kg/tore ammonium, 1 kg/tore coppersulphate and 1.5 kg/tore sodium sulphite. This result is higher than with cyanidation in typical dosageand 8 hours (20.4 %), which is possible due preg-robbing effect. This demonstrates the potential ofthiosulphate's technical viability as an alternative to cyanidation.
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