SPATIAL-DISTRIBUTION OF IRON AND SULFUR SPECIES ON THE SURFACE OF PYRITE

XPS, DRIFTS, UV spectroscopy and HPLC were used to investigate the nature and spatial distribution of oxidized superficial phases present on pyrite surfaces. Two pure pyrites with different arsenic contents were used. The surface of the first sample (As = 0.018%) is covered with an important three-dimensional heterogeneous oxidized phase (Fe2(SO4)3, Fe(OH)3, FeO) in equilibrium with two two-dimensional phases (metastable polysulphide (S5S2-) and elemental sulphur (S8)). The superficial phases present at the surface of the second pyrite (As = 0.309%) have the same composition. However, their extension is mainly two-dimensional with lower amounts of polysulphide (S5S2-) and elemental sulphur.