Andrzej Pomianowski

Diagrams of electrochemical equilibria of the system copper-potassium ethylxanthate-water at 25°C

Abstract On the basis of thermodynamic calculations, diagrams of metastable electrochemical equilibria of the system copper-potassium ethylxanthate-water, at 25°C were constructed. The equilibria equations and diagrams for the total activity of [EtX−] + [HEtX] + 2 [(EtX)2] (equalling 10−1, 10−4 and 10−7 mol/dm3), are presented. The practical conclusions resulting from these diagrams for the flotation of native copper are discussed.

Mixed potentials and local cells in flotation systems

Abstract The results obtained in earlier potential measurements at galena electrodes under various experimental conditions and measurements of local potentials on polished mineral plates of natural galena and copper sulphide specimens shown the presence of corrosive micro-cells on the mineral surface. The measured local potentials had a mixed potential character. The results obtained seemed to agree with the following electrochemical scheme of reactions involving xanthate ion (X−) reactions with the freshly ground sulphide mineral in an aerated water suspension. The fast surface reaction of binding of xanthate ions 2X − + H 2 O + 1 2 O 2 + srufac → 2 X-surface + 20 H − can be followed by a slow formation of metal xanthate (MeX) as a bulk product 2 2X−surface + Me 2 S → S 0 − surface + 2 MeX(bulk) The formation of excess elementary sulphur at the surface (S0-surface) must be balanced by a slow diffusion of metal ions in the crystal lattice, changing the character and number of lattice defects in the mineral.