In situ measurements of X-ray absorption spectra during transformation of green rust to ferric oxyhydroxide via aqueous solution

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.