In the past, sulfide ore at Goldstrike was processed through autoclaves followed by a conventional carbon-in-leach (CIL) process using cyanide. More complex double refractory ores containing both sulfide and carbon presented a challenge for this process as they could no longer be treated profitably. Even after sulfide oxidation in the autoclave, during CIL, organic carbon present in the ore would compete with activated carbon for the cyanide gold complex in solution (preg-robbing) and this resulted in gold losses and low recovery when processing these ore types.
The thiosulfate process developed by Barrick and tested at AuTec avoided the issue of preg-robbing as gold present as the thiosulfate complex is not readily adsorbed onto organic carbon in the ore. The thiosulfate process uses key infrastructure already in place at Goldstrike to efficiently treat ore types with high organic carbon and sulfide content. The process involves oxidation of ore through existing autoclaves to treat the sulfide followed by leaching of gold using thiosulfate and resin in leach. The combination of thiosulfate and resin in leach avoid the preg robbing of gold from solution.
AuTec has played a major role in developing the thiosulfate process from bench-scale to continuous pilot plant scale to demonstration, and AuTec has been instrumental in providing support during the commissioning stage.
AuTec and its predecessors spent more than two decades developing thiosulfate processing and developed a high level of scientific and technological expertise. Our team has gained a wide range of knowledge through first-hand experience, from the initial R&D on tank or heap leaching using various thiosulfate reagents to ore variability studies, resin stripping, resin and solution regeneration and finally to being part of the Goldstrike’s success story.