The influence of cyanide on pyrite flotation from gold leach residues with sodium isobutyl xanthate

Abstract

Abstract Impedance measurements, linear voltammetry, and flotation tests were carried out to determine the influence of NaCN on the flotation of pyrite from gold leach residues. The mixed potential of the pyrite electrode was found to decrease in the presence of NaCN. However, the decrease of the mixed potential does not adequately explain the depression of pyrite flotation, which is the result of the influence of cyanide on the surface electrochemical reactions. The impedance measurements showed higher impedance values in the low frequency region due to the inhibition of surface electrochemical reactions by cyanide. The decrease of the mixed potential is a result of the inhibition of the cathodic oxygen reduction reaction on the pyrite surface, and is not caused by enhanced anodic oxidation rates. The lower anodic and cathodic current densities are due to a decrease of the number of electrochemically active sites on the pyrite surface in the presence of cyanide. All surface electrochemical reactions, including xanthate oxidation were found to be inhibited by the cyanide. The effect of the cyanide is rapid and the inhibition of the xanthate oxidation reaction was found to be reversible when cyanide was removed from the system. The inhibition of the anodic oxidation of pyrite provides a measure of protection for the pyrite against oxidation during extended exposure to leach conditions. This preservation effect will contribute to the floatability of pyrite after gold leaching in cyanide, provided that cyanide is removed from the system, before flotation is attempted.