An Investigation of Ammonia Effect on Dissolution and Recovery of Gold in Cyanidation Process of Copper-Gold Ore

The presence of copper oxide next to gold increases the consumption of cyanide in the cyanidation process, reduces the absorption of gold on carbon, and causes many problems in the downstream processes of elution, electrowinning, and smelting. In the current research, increasing the recovery of gold dissolution and its selective adsorption on activated carbon using ammonia additive and the effect of different factors such as the type of ammonia additive, changing the system of contact of gold with carbon from CIL to CIC, and adding hydrogen peroxide and cyanide to the filtered solution were studied. The findings showed that adding ammonium chloride or liquid ammonia to the cyanidation solution, in the sample with high copper grade (1% copper), and in the sample with medium copper grade (0.5% copper), increased the dissolution recovery by 60% and 30%, respectively. Also, the recovery of gold adsorption on activated carbon in sample with a grade of 0.5% copper increased from about 25% during the normal CIL process to about 100% during the ammonia cyanidation process in the form of CIC. Results showed that liquid ammonia provides up to 10% higher dissolution recovery and up to 3% higher absorption recovery compared to ammonium chloride, while reduces the consumption of cyanide by half and the amount of copper absorption on carbon by a third.