ABSTRACT
The depressant action of cyanide on iron sulfide minerals occurs by a different mechanism. Sodium sulfide and hydrosulfide are applied in the depression of sulfide minerals, example, in the separation of chalcopyrite from molybdenite. Electrochemical studies of sulfide ion oxidation on sulfide minerals have shown that polysulfide ion is the product on pyrite and galena at low potentials, whereas elemental sulfur is deposited at higher potentials. Metal ions are used to activate sulfide minerals that do not interact strongly with thiol collectors. It is well established that the interaction between sulfide minerals and thiol collectors takes place by a corrosion-type, "mixed potential" mechanism involving simultaneous electrochemical processes. Heyes and Trahar determined the potential dependence of the rate of flotation of chalcocite with ethyl xanthate as collector. Control of solution pH is one of the most widely used methods for depressing flotation. The depressant action of alkalis results from an increase in the rate of dissolution or oxidation of mineral surface.
