In situ Measurements of X-ray Absorption Spectra during Transformation of Green Rust to Ferric Oxyhydroxide Via Aqueous Solution

Abstract

In situ measurements of X-ray absorption spectra at an Fe K absorption edge were carried out during the transformation of chloride-containing green rust (GR(Cl^–)) to oxyhydroxide (that is, lepidocrocite (γ-FeOOH)), by oxidation via aqueous solution. Results showed that the Fe K absorption edge in X-ray absorption near-edge structure (XANES) spectrum shifted toward the higher energy side with increasing oxidation time. The factor analysis of the XANES spectra, using reference data, implied that dissolution of GR(Cl^–) and precipitation of γ-FeOOH occur simultaneously. The fraction of γ-FeOOH in the suspension increased continuously with increasing oxidation time, in response to the continuous decrease of the fraction of GR(Cl^–). The results lead us to conclude that GR(Cl^–) transforms to γ-FeOOH during oxidation under the present experimental conditions.