USE OF LEAD NITRATE AND OXYGEN TO IMPROVE GOLD RECOVERY OF A COPPER SULPHIDE ORE

摘要

A laboratory study was carried out to evaluate the effect of oxygen and lead nitrate on the recovery of gold by cyanidation of a free milling gold ore, which contains 0.4 percent copper as chalcopyrite. Efficient gold extraction is achieved only under specific conditions. The recovery of gold was increased from less than 90 percent to up to 98 percent by addition of lead nitrate. In the pre-leaching, the kinetics of oxidation of soluble sulphides are not an accurate indication for the length of the treatment. Even though the consumption of cyanide was reduced due to the inhibition of the dissolution of chalcopyrite by increasing additions of lead nitrate, cyanide consumption had to the held above 1.85 kg/t to maintain good recovery of gold. The continued addition of lead nitrate above 300 g/t had no impact on the recovery of gold. It was also found that the addition of lead nitrate at the start of cyanidation gave the same performance as when added during pre-leaching. The addition of oxygen increased the recovery of gold by 1.5 percent. The concentration of NaCN had to be maintained in the range of 700 mg/L because of the high concentration of copper in solution. The recovery of gold dropped significantly when the average NaCN concentration fell below 640 mg/L. Application of the findings of the laboratory study at the industrial scale led to improved plant performance.