The treatment of copper–gold ores by ammonium thiosulfate leaching

The application of ammonium thiosulfate for the treatment of copper–gold ores has been investigated. Copper minerals and copper–gold samples were leached in an ammonium thiosulfate solution under varying experimental conditions, i.e. aeration, temperature and reagent addition. The behaviour of thiosulfate, tetrathionate and sulfate in solution was studied using ion chromatography. Experiments showed that both gold extraction and thiosulfate stability are affected by a combination of aeration and cupric ions in solution. It is important to establish a balance between providing sufficient air and cupric ions for fast gold dissolution, and at the same time minimize the amount of air in the presence of cupric ions to prevent excessive thiosulfate degradation. Promising results, i.e. high gold extractions and low thiosulfate consumption, were obtained during a 24-h leach without forced aeration.