Oxidation of chukanovite (Fe2(OH)2CO3): Influence of the concentration ratios of reactants

The oxidation of aqueous suspensions of chukanovite (Fe2(OH)2CO3) obtained by mixing NaOH, FeCl2 and Na2CO3 solutions was studied for various [Fe2+]/[OH−] and [CO32−]/[OH−] concentration ratios. The redox potential of a platinum electrode immersed in the suspension was monitored during the oxidation process which reveals the presence of a plateau corresponding to equilibrium conditions between chukanovite and a poorly crystallized Fe(III) oxyhydroxide. The end products were characterized by Infrared spectroscopy and X-ray diffraction. Carbonate favoured the formation of goethite while Fe2+aq favoured lepidocrocite. This effect is mainly due to the influence of these species on the pH of the solution.