Treatment of a refractory gold copper su

The investigation aimed at exploring the potential for leaching gold directly from a refractory gold-copper sulfide concentrate using ammoniacal thiosulfate with copper, as an alternative to the traditional methods of roasting and cyanidation. A series of leaching experiments were conducted using a solution consisting of 0.8M S2O3 2-, 0.05M Cu2+, and 4M NH3, achieving over 90% gold and 60% silver recovery. Notably, the dissolution of gold tellurides contributed to this high extraction rate, although their slow leaching rate could limit recovery if present in high concentrations. No evidence indicated partial alteration of pyrite that would affect gold recovery, necessitating pretreatment for liberation of gold inclusions. Further, ultra fine milling pretreatment followed by thiosulfate leaching improved the recovery to 94% gold and 60% silver over 48 hours, while thiosulfate leaching of roasted concentrates yielded 98% gold and 93% silver recovery within 24 hours. The study highlighted substantial reagent consumption ranging from 36-70 kg/t for thiosulfate, which increased with extended leaching times. Preliminary investigations into in-situ generation of thiosulfate revealed promising gold extraction capabilities, suggesting a cost-effective approach by utilizing sulfur dioxide produced from the roasting process. This study offers insights into enhancing gold recovery from refractory ores using innovative leaching techniques.