Comparisons of leaching a silver ore with cyanide, thiosulfate and thiourea solutions

The leaching experiments are performed on samples collected from a silver concentrate with cyanide, thiosulfate and thiourea solutions respectively to compare their extraction effects. The result indicates that, under the optimal process parameters, (Cyanide: ammonium salt added on the pretreated alkali, sodium cyanide concentration being 0.15 mol/L, pH value being 11, liquid-solid rate 2:1, mixing strength 500 r/min, leaching time 48 h; Thiosulfate: oxidizing roasting pretreatment, ammonia concentration of 1.0 mol/L, copper sulfate concentration of 0.01 mol/L, sodium thiosulfate concentration of 0.2 mol/L, pH of 10, liquid-solid rate of 4:1, mixing strength of 500 r/min, leaching time of 12 h; Thiourea: oxidizing roasting and then dilute sulphuric pretreatment acid pre-leaching, Fe³⁺ concentration of 7.5×10^-3 mol/L, thiourea concentration of 0.18 mol/L, pH of 1.0, liquid-solid rate of 3:1, mixing strength of 250 r/min, leaching time of 24 h, the leaching rate of Ag with the method of thiosulfate is 78.58 %, while the rate in the thiourea system is about 62.43 %, 3.33 % lower than that in the cyanide system.