Formation of ‘ferric green rust’ and/or ferrihydrite by fast oxidation of iron(II–III) hydroxychloride green rust
Résumé
Fast oxidation processes of iron(II–III) hydroxychloride green rust GR(Cl−), FeII3FeIII(OH)8Cl · 2H2O, were simulated by two different methods. The first one consisted in using a strong oxidiser, namely H2O2. The main end product, analysed by X-ray diffraction and Mössbauer spectroscopy, is an iron(III) compound, designated as “ferric GR(Cl−)”, characterised by a layered structure identical to that of normal GR(Cl−). The second method consisted in decreasing the initial concentrations of reactants, thus increasing the proportion of dissolved O2. Suspensions of GR(Cl−), obtained by mixing 4 × 10−3 M NaOH with FeCl2 solutions for various R′=[Cl−]/[OH−] values, oxidised rapidly into ferrihydrite-like compounds.