A flotation related X-ray photoelectron spectroscopy study of the oxidation of galena surface

The initial steps of the oxidation of galena (PbS) surface with special attention to the oxidation in an aqueous environment were investigated by the X-ray photoelectron spectroscopy method (XPS). Galena monocrystals from two different sources were cleaved and exposed to either air or an aqueous environment. The results show that the presence of organic contamination at the galena surface may exert a dramatic effect on the course of its surface oxidation. In the case of aerial oxidation, the presence of impurities changes the reaction path, suppressing the oxidation of sulfide sulfur to sulfate like species selectively. In the case of aqueous oxidation, the presence of organic contamination at the surface (this contaminants are supposed to be mainly the carboxylic acids and their salts) inhibits the oxidation. Very little oxidation products were found on the galena surface contacted with aqueous solutions at the spontaneously established potential, in accordance with the congruent dissolution-oxidation mechanism.