INTERACTION OF COPPER(II) IONS WITH PYRITE AND ITS INFLUENCE ON ETHYL XANTHATE ADSORPTION

X-ray photoelectron spectroscopy (XPS) has been used to investigate the interaction of copper(II)-containing aerated aqueous solution (pH 4-10) with pyrite (FeS2) surfaces and its influence on subsequent ethyl xanthate adsorption from solution. Evidence is provided that Cu(II) ions can be adsorbed independent of pH, changing their oxidation state to Cu(I). This is attributed to a new Cu-S surface species. In addition, Cu(II) can be stabilized as a complex hydroxy species on pyrite at pH greater-than-or-equal-to 6. Time-dependent adsorption studies were carried out to elucidate the influence of pH on the copper adsorption rate, considering also the different copper oxidation states. A fast saturation of the sulphide surface with Cu(I) is observed at pH 5, whereas the Cu(I) uptake starts only slowly at pH 8 and pH 10. Prolonged conditioning in alkaline solution results in a precipitation of Cu(II) hydroxy species. Simultaneously, the amount of adsorbed Cu(I) increases until the same Cu(I) level is reached as in acidic media. After subsequent immersion in ethyl xanthate solution of pH 6-9, both Cu(I) and Cu(II) ions adsorbed on pyrite are found to form Cu(I) ethyl xanthate in accordance with previously published infrared spectroscopic and microflotation results.