Metal ion production and transfer between sulphide minerals

Abstract

Metal ions produced by minerals, alone and in pairs, was studied by solution analysis, EDTA extraction and LIMS for combinations of pyrite, pyrrhotite, galena, and sphalerite. The effect of grinding, pH, and the presence of xanthate was studied. Metal ion production with minerals in pairs was different from that for single minerals. The amount of metal ions in solution followed a galvanic interaction model: it increased for the anodic mineral and decreased for the cathodic mineral. However, from the EDTA extraction technique, the concentration of metal ions on the mineral surface increased on both minerals. The mechanism of additional metal ion production on the cathodic mineral is unclear: it may be related to reaction between the mineral and OH − ions formed on the surface as a result of galvanic interaction. EDTA extractable metal on a per unit area basis was independent of particle size and extent of grinding. Increasing pH tended to increase ion production, but appeared to reduce galvanic effects. The presence of xanthate decreased metal ion production. Metal ions transferred between two minerals in contact. Generally, the larger proportion of Fe remained on the parent mineral (pyrite and pyrrhotite); however, 50% or more of Zn (from sphalerite) and Pb (from galena) transferred to pyrite.