An eco-friendly and efficient process of low potential thiosulfate leaching-resin adsorption recovery for extracting gold from a roasted gold concentrate

Thiosulfate is a promising alternative lixiviant to cyanide for leaching gold from its ores/concentrates due to increased environmental and public concern over the use of poisonous cyanide. However, high thiosulfate consumption and high cost for gold recovery from pregnant solution have limited its industrial application. In this work, an innovative process for extracting gold from a roasted gold concentrate is proposed: firstly, gold leaching with thiosulfate under a low mixed potential; then, gold separation and enrichment with an ion-exchange resin to produce concentrated gold solution that can be refined to metallic gold by electrowinning. Compared with traditional thiosulfate leaching, the mixed potential of stable stage of low potential leaching decreased around 30 mV through using low concentrations of reagents and limiting oxygen supply, a slightly higher gold extraction was obtained, whilst thiosulfate consumption substantially reduced from 34.6 kg/t-concentrate to 15.8 kg/t-concentrate. The amount of undesirable anions particularly cuprous thiosulfate and polythionates in the pregnant solution significantly dropped owing to the mild leaching conditions. This considerably weakened their competitive adsorption with gold (1) thiosulfate onto the resin, contributing to the decrease of resin dosage used for gold recovery. The eluent dosage also declined because of the less interfering ions on resin surface. Based on these results, low potential thiosulfate leaching followed by resin adsorption recovery is put forward, providing an eco-friendly and efficient process for gold extraction from roasted gold concentrate. (C) 2019 Elsevier Ltd. All rights reserved.