Effects of phosphate and silicate on the transformation of hydroxycarbonate green rust to ferric oxyhydroxides

摘要: Abstract Hydroxycarbonate green rust (GR1(CO 3 2− )) was prepared by oxidation of aerated aqueous suspensions Fe(II) hydroxide, and the presence light promoted transformation GR1(CO ) dissolved O 2 at pH 7.8 25 °C. Further in conducted orthophosphate (P) or silicate (Si) anions, followed solution analysis solid product characterization using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR). Results show that both P Si anions significantly affect through adsorption on intermediate products. The time required for complete phases, crystallinity morphology products all depend Fe/anion molar ratio. When compared to control, can be low concentrations but retarded P. With decreasing Fe/P ratio, change from acicular goethite (absence P) tabular lepidocrocite (Fe/P: 120-48) mixed phases platelets ferric (EX-GR1) minor ferrihydrite 24-3). In terms Si, are goethites when Fe/Si ratio 48-12, with increasing particle size decrease changes Si) plate-like isodimensional particles. ratios is comparable natural samples commonly found soils. At Fe/Si = 3, EX-GR1 coexisting. likely pathway oxidative control system (Fe/Si ⩾ 12) ) → amorphous γ-FeOOH-like phase → α-FeOOH via a dissolution–oxidation–precipitation mechanism. addition, released during dissolution adsorbed phase catalyzed Fe(II). For system, forms ternary surface complexes mineral surfaces without any catalytic role, leading formation concentrations. Clearly, various crystalline iron oxyhydroxides depends type concentration (Fe/anion ratio) co-existing anions. This study also suggests formed form particles most related ubiquitous silicates soil environments.