The Identification of Arsenic Chemical Form in Mine Waste Materials Using X-Ray Absorption Spectroscopy

Pre-treatment of samples using selective extraction techniques may alter the chemical form of the arsenic. X-ray absorption spectroscopy is capable of providing detailed chemical and structural information about a specific absorbing element in situ with minor or no pre-treatments. There are two regimes in X-ray Absorption Structure (XAS) Spectroscopy: X-ray Absorption Near-Edge Spectroscopy (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) Spectroscopy. The absorption edge energy in XANES spectra is sensitive to the oxidation state of arsenic, and the position increases with an increase in oxidation state. XANES is applicable to solution or solid-phase samples and sensitive to parts per million. XANES gives chemical identity empirically by comparing sample spectra to known compounds.