Coprecipitation thermodynamics of iron(II–III) hydroxysulphate green rust from Fe(II) and Fe(III) salts

Abstract : Iron(II–III) hydroxysulphate GR(SO42−) was prepared by precipitating a mixture of Fe(II) and Fe(III) sulphate solutions with NaOH, accompanied in most cases by iron(II) hydroxide, spinel iron oxide(s) or goethite. Its [Fe(II)]/[Fe(III)] ratio determined by transmission Mössbauer spectroscopy was 2±0.2, whatever the initial [Fe(II)]/[Fe(III)] ratio in solution. Proportion of Fe(OH)2 increased when the initial [Fe(II)]/[Fe(III)] ratio increased, whereas proportion of α-FeOOH or spinel oxide(s) increased when this ratio decreased. GR(SO42−) is metastable vs. Fe3O4 except in a limited domain around neutral pH. Precipitation from solutions containing both Fe(II) and Fe(III) dissolved species seems to favour GRs formation with respect to stable systems involving iron (oxyhydr)oxides.
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Submitted on : Tuesday, December 18, 2018 - 5:31:10 PM
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Ph Refait, A. Gehin, Mustapha Abdelmoula, J.-M.R. Génin. Coprecipitation thermodynamics of iron(II–III) hydroxysulphate green rust from Fe(II) and Fe(III) salts. Corrosion Science, Elsevier, 2003, 45 (4), pp.659-676. ⟨10.1016/S0010-938X(02)00138-5⟩. ⟨hal-01959509⟩

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