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Issue 2, 1987
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Kinetics of metal oxide dissolution. Oxidative dissolution of chromium from mixed nickel–iron–chromium oxides by permanganate

Abstract

Mixed metal oxides of general formula Nix Fey Crz O4(x+y+z= 3) react with acidic permanganate solution, releasing chromium as CrVI. Little nickel and virtually no iron dissolve. Reaction is extremely slow when z= 1.0, but when z= 1.5 the kinetics of chromium release can be studied. The reaction follows the Crank–Ginstling and Brounshtein equation, implying that the rate-determining step is diffusion through a solid product layer between an unreacted oxide core and the solid–liquid interface. Two oxides have been studied, x= 0.6, y= 0.9 and x= 1.0, y= 0.5. Both show rate saturation with increasing permanganate concentration, consistent with Langmuirian adsorption at the interface, and a strong but less than first-order dependence on acid, from which it is concluded that the rate-limiting diffusion may involve the HMnO4 molecule. Reaction is strongly inhibited by the presence in solution of trivalent cations of Al, Fe, In, Tl and La.

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Article type: Paper
DOI: 10.1039/F19878300371
Citation: J. Chem. Soc., Faraday Trans. 1, 1987,83, 371-382
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    Kinetics of metal oxide dissolution. Oxidative dissolution of chromium from mixed nickel–iron–chromium oxides by permanganate

    A. B. O'Brien, M. G. Segal and W. J. Williams, J. Chem. Soc., Faraday Trans. 1, 1987, 83, 371
    DOI: 10.1039/F19878300371

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