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

X-ray photoelectron spectroscopy (XPS) has been used to investigate th e 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) io ns can be adsorbed independent of pH, changing their oxidation state t o 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 p H greater-than-or-equal-to 6. Time-dependent adsorption studies were c arried out to elucidate the influence of pH on the copper adsorption r ate, considering also the different copper oxidation states. A fast sa turation of the sulphide surface with Cu(I) is observed at pH 5, where as the Cu(I) uptake starts only slowly at pH 8 and pH 10. Prolonged co nditioning in alkaline solution results in a precipitation of Cu(II) h ydroxy species. Simultaneously, the amount of adsorbed Cu(I) increases until the same Cu(I) level is reached as in acidic media. After subse quent immersion in ethyl xanthate solution of pH 6-9, both Cu(I) and C u(II) ions adsorbed on pyrite are found to form Cu(I) ethyl xanthate i n accordance with previously published infrared spectroscopic and micr oflotation results.