Nature of arsenic sites in arsenian pyrite- A synchrotron radiation X-ray photoelectron spectroscopy (SRXPS) study

Abstract

The observed spatial variability of arsenic substituted in pyrite (arsenian pyrite) was considered to study the nature of arsenic environment using synchrotron X-ray photoelectron spectroscopy. As 3d of arsenian pyrite has shown that bulk As, present as As(-I) in arsenian pyrite, may be an As–As dimer rather than as As–S. This argument was made due to shift in the bulk As 3d component to lower binding energy, a feature observed in the As-As dimer of loellingite (FeAs2). The presence of a pronounced tail in the Fe 2p signal of arsenian pyrite, which is absent in loellingite, implies localised arsenic mineralisation in a dominating pyrite host. Possible As cluster formation producing a subtle shift in binding energy to lower values is also put forward. The surface component found at a binding energy of 41.3 eV in the As 3d of arsenian pyrite was ascribed to polymeric sites generated from surface reconstruction initiated upon fracture of As–As or As–S bond. Except for a polymeric sulphur component at a binding energy of 163.2 eV, the S 2p signal of pyrite and arsenian pyrite are equivalent at high excitation energy.