The Mechanism of Gold Extraction in Cyanide Ammonia Systems for Copper-Gold Ores

Gold leaching rate was up to 92% with direct cyanide for copper-gold ores,but large quantities of cyanide,about 130 kg/t,were consumed,and the consumption of cyanide wasn't linear with the Cu extraction.In cyanide ammonia system,gold extraction were as high as it in free cyanide solution and the best ammonia to cyanide ratio was 3∶1,and the most consumption of cyanide was 14.7 kg/t.The gold leaching rate wasn′t improved increasing the cyanide additions,and it wasn′t beneficial in proving the gold extraction to increase ammonia concentration.In cyanide ammonia solution,Cu2+ concentration from soluble copper in ores was sufficient,and excessive Cu2+ led to suffered gold extraction.The results showed that Cu(NH3)42+ served as oxidant,and Cu(CN)32-was extractant,and the four stage of copper and gold concentration in cyanide ammonia solution supported above mechanism.