Surface oxidation studies of chalcopyrite and pyrite by glancing-angle X-ray absorption spectroscopy (REFLEXAFS)

The oxidation of chalcopyrite and pyrite was examined using Fe-K- and Cu-K- edge REFLEXAFS spectroscopy. The Fe XANES of the pyrite proved to be a very sensitive indicator of oxidation, revealing the development of a goethite- like surface species; the EXAFS data showed an increasing O:S ratio with th e degree of oxidation and gave Fe-O distances of c. 1.9 Angstrom. On the ox idized chalcopyrite surfaces, the development of Fe-O and Cu-O species was observed, with both the XANES and EXAFS revealing the progressive developme nt of these species with oxidation. Differences in the sensitivity of the X ANES and EXAFS to the degree of oxidation can be related to the degree of l ong range order and changes in the intensity of the pre-edge feature of the Fe are a function of its oxidation state and coordination geometry in the surface species.