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.

Time-resolved in situ studies on the formation mechanism of iron oxide nanoparticles using combined fast-XANES and SAXS

“…The difference between the centroid of the pre-edge peak for pure Fe 2+ and Fe 3+ is 1.5 eV, in accordance with the literature. [40][41][42] The centroid position of the iron chloride solution pre-edge peak is shifted to higher energies compared to the iron oxides pre-edge peak (see Fig. S6a †).…”