Comparing lead and copper activation on pyrite with different degrees of surface oxidation

Copper ions are often added in the flotation of gold-bearing pyrite to activate pyrite so that high gold and pyrite recoveries can be achieved. However, the residual copper ions are problematic in subsequent cyanidation by consuming cyanide. There is a great need to replace copper ions by lead ions which are beneficial to cyanidation. This study compared lead and copper activation on pyrite with different degrees of surface oxidation at pH 5.0. Flotation tests indicated that lead and copper ions were equally efficient in activating slightly oxidised pyrite and both produced a high pyrite recovery. For moderately oxidised pyrite, copper ions were superior to lead ions in activating pyrite. However, for severely oxidised pyrite, lead ions prevailed over copper ions in activating pyrite. By Cryogenic X-ray photoelectron spectroscopy analysis, it was found that the different behaviour of lead and copper ions in activating pyrite was governed by the lead and copper species adsorbed on pyrite surface. In general, pyrite oxidation generated iron and sulphur oxidation species which inhibited the adsorption of lead and copper ions on pyrite surface. Lead ions had stronger affinity to oxidised pyrite than copper ions but pyrite flotation required a higher amount of lead-activating products than copper-activating products.