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 2S → S 0− surface + 2 MeX(bulk) The formation of excess elementary sulphur at the surface (S 0-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.