Electrochemical formation of a new Fe(II)-Fe(III) hydroxy-carbonate green rust: characterisation and morphology

Electrochemical behaviour of iron in deaerated 0.2 M carbonate/bicarbonate solution pH 9.6 and T= 25 degreesC was investigated. Oxidation of iron lead s to the formation of green rust as intermediate product and ferrihydrite a s ultimate product. Characterisation of green rust was done through FTIR, T EM, XRD and Mossbauer spectroscopy. Results point out differences in the st ructure and morphology, such as size of hexagonal crystal lattice, paramete r c and Fe(II):Fe(III) ratio, between our electrochemically formed GR and G R1(CO32-) obtained by oxidation of Fe(OH)(2). Go-precipitation of Fe(II) an d Fe(III) species during the electrochemical procedure leads to a new GR. W e propose the following chemical formula for this GR, [(Fe2Fe2(III))-Fe-(II )(OH)(8)](2+.)[CO3](2-). However, the possibility that incorporation of bot h CO32- and Cl- ions could occur is not ruled out. (C) 2001 Elsevier Scienc e Ltd. All rights reserved.