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-X-ray photoelectron spectroscopy (XPS) has been used to investigate the interaction of copper(II)-containing aerated aqueous solution (pH 4-10) with pyrite (FeS,) surfaces and its influence on subsequent ethyl xanthate adsorp tion from solution. Evidence is provided that Cu(I1) ions can be adsorbed independent of pH, changing their oxidation state to Cu(1). This is attributed to a new CUS surface species. In addition, Cu(I1) can be stabilized as a complex hydroxy species on pyrite at pH 2 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(1) is observed at pH 5, whereas the Cu(1) uptake starts only slowly at pH 8 and pH 10. Prolonged conditioning in alkaline solution results in a Precipitation of Cu(I2) hydroxy species. Simultaneously, the amount of adsorbed Cu(1) increases until the same Cu(1) level is reached as in acidic media. After subsequent immersion in ethyl xanthate solution of pH 6-9, both Cu(1) and Cu(I1) ions adsorbed on pyrite are found to form Cu(1) ethyl xanthate in accordance with previously published infrared spectroscopic and microflotation results.

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A system for treating XPS samples containing easily volatile and reactive adsorption layers is described. Desorg tion and reactions with atmospheric gases prior to the measurement are avoided by repeated exposure of the sample to an inert atmosphere at room temperature followed by cooling to liquid nitrogen temperature and sub sequent evacuation to spectrometer vacuum.The method has been applied to pyrite (FeS,) samples treated in aqueous potassium ethyl xanthate (dithiocarbonate) solutions. In agreement with previous indirect predictions of infrared and electrochemical measurements, the results confirm, under certain conditions of sample preparation, the presence of dixanthogen adsorp tion layers on FeS, that have not been found previously on XPS measurements.Application of the method to surface studies related to sulphide flotation is especially important because of the volatility of several species possibly existing in the collector adsorption layer. Other potential applications are corrosion and catalysis studies.