Influence of silicon species on the transformation of green rust I(Cl−) in aqueous solution by oxidation

X-ray diffraction (XRD) and solution analysis were used for characterizing the influence of different silicon species on oxidation of green rust (GRI(Cl−)) suspension. While addition of silicon to metallic iron enhanced the formation of β-FeOOH, GRI(Cl−) in aqueous solution oxidized into lepidocrocite and oxidation was delayed in presence of silica and silicate species as noticed from potential, pH, and dissolved oxygen (DO) measurements. Transmission electron micrographs showed that the particle size of lepidocrocite was reduced due to silicate addition. The influence of silicate was attributed to its adsorption on GRI(Cl−) and lepidocrocite particles as confirmed from ICP-AES analysis of supernatant solution.

► Addition of silicate species and silica to GRI(Cl−) increased oxidation time.
► The lepidocrocite particle size in silicate added case has been reduced significantly.
► The influence of silicate was attributed to its adsorption on lepidocrocite.
► Silicate also influenced GRI(Cl−) transformation due to adsorption on it.