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

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.