The solution electrochemistry of sulfide-xanthate-cyanide systems in sulfide mineral flotation

Extensive thermodynamic calculations have been performed for a number of flotation systems cf metal sulfide minerals using cyanide as a depressant to investigate the physicochemical principles underlying the effective depression processes. It has been shown that selective depression of the flotation of sulfide minerals by cyanide is achieved through the one or more of the following processes: 1. anide dissolves the metal xanthates to form metal-cyanide complexes or combines with surface metal ions to prevent the formation of metal-xanthates; anide reduces the redox potential of the flotation pulp and consumes oxygen in the flotation pulp to prevent the chemisorption and oxidation of xanthate; anide is preferentially adsorbed on the sulphide mineral surfaces as cyanometal complexes to inhibit the adsorption of xanthate and the oxidation of xanthate on mineral surface, anide reacts with elemental sulfur and polysu f des to form thiocyanate, thereby removing the surface hydrophobic entity. ochemical studies on the pyrite electrode have confirmed the above solution chemistry calculations. It has been found that in cyanide solutions, the surface oxidation of pyrite is greatly enhanced. The initial oxidation step involves the electrochemical adsorption of cyanide on pyrite. This inhibits the adsorption of xanthate on the pyrite surface and minimizes the flotation of pyrite. Furthermore, xanthate adsorbed on pyrite surfaces is readily replaced by cyanide when cyanide is added into the pyrite flotation system.