par Demoisson, Frédéric ;Mullet, Martine;Humbert, Bernard
Référence Surface and interface analysis, 40, 3-4, page (343-348)
Publication Publié, 2008-03
Article révisé par les pairs
Résumé : This study investigated the oxidation processes of pyrite by dissolved oxygen. Synthetic pyrite suspensions have reacted with dissolved oxygen in a closed-thermostated system for 20 h and at pH values of 2.0 and 3.5. Special emphasis was made on the characterization of the solid phase formed during the reaction process, using X-ray photoelectron spectroscopy (XPS) and confocal Raman microspectrometry. The results revealed a strong heterogeneity of the samples with the identification of two different micrometric areas. E g and Ag Raman pyrite modes were characterized by wavenumber drifts, from 0 to 6, correlated with the shine changes of the micrometric probed area. XPS analyses provided evidence of the distribution of iron and sulfur species at the reacted pyrite surface. The Fe(2p3/2) signals showed an increase in the binding energy range typical of Fe(III)-S and Fe(III)-O compounds. The S(2p) XPS signals included contribution from disulfide, monosulfide, elemental sulfur, and sulfate. Elemental sulfur should be protected from sublimation under ultrahigh vacuum, possibly by an overlaying of other species such as Fe(III) (oxyhydr)oxide species. An overall reaction pathway of the pyrite in oxidizing (Cr(VI), dissolved oxygen, Fe(III)), and acidic media (pH ≤ 3.5) has been established from the present results and previous papers. Copyright © 2008 John Wiley & Sons, Ltd.