Formation of 'ferric green rust' and/or ferrihydrite by fast oxidation of iron(II-III) hydroxychloride green rust

Fast oxidation processes of iron(II-III) hydroxychloride green rust GR(Cl-), (Fe3FeIII)-Fe-II (OH)(8)(Cl2H2O)-H-., 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 Mossbauer 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 O-2. Suspensions of GR(Cl-), obtained by mixing 4 x 10(-3) M NaOH with FeCl2 solutions for various R' = [Cl-]/[OH-] values, oxidised rapidly into ferrihydrite-like compounds. (C) 2003 Elsevier Ltd. All rights reserved.