TECHNIQUE FOR XPS MEASUREMENTS OF VOLATILE ADSORBED LAYERS - APPLICATION TO STUDIES OF SULFIDE FLOTATION

A system for treating XPS samples containing easily volatile and reactive adsorption layers is described. Desorption 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 subsequent evacuation to spectrometer vacuum. The method has been applied to pyrite (FeS2) 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 adsorption layers on FeS2 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.