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Manganese(II) oxidation kinetics on metal oxide surfaces

Davies, Simon H. R. and Morgan, James J. (1989) Manganese(II) oxidation kinetics on metal oxide surfaces. Journal of Colloid and Interface Science, 129 (1). pp. 63-77. ISSN 0021-9797. doi:10.1016/0021-9797(89)90416-5.

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The rates of oxidation of Mn(II) by oxygen in the presence of α-FeOOH, γ-FeOOH, silica, and δ-Al₂O₃ were studied experimentally. These solids enhanced the rate of Mn(II) oxidation over the initial homogeneous solution rate, the order being γ-FeOOH > α-FeOOH > SiO₂ > δ-Al₂O₃. The kinetic data can be partially accounted for by a rate expression of the form −d[Mn(II)]/dt = k^∗{〉SOH}[Mn²⁺]/[H⁺]²·A·pO₂, where {〉SOH} is the surface concentration of hydroxyl sites and A is the mass concentration of solids in suspension. The reaction on α-FeOOH and γ-FeOOH is strongly temperature dependent (apparent activation energy ∼100 kJ mole⁻¹) and is not affected by normal laboratory light levels. The oxidation rates on α-FeOOH are lower at higher ionic strengths, and are appreciably influenced by individual ions; Mg²⁺, Ca²⁺, silicate, salicylate, phosphate, chloride, and sulfate inhibit the overall oxidation reaction. A surface complex formation model was used to describe the adsorption of Mn²⁺ to the oxide surfaces. In terms of the surface species (>SO)₂Mn, a proposed rate law which partially accounts for observations is −d[Mn(II)]/dt = k″{(〉SO)₂Mn}·A·pO₂. An alternative formulation which accounts for the observed rates postulates the surface species >SOMnOH.

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Additional Information:© 1989 Published by Elsevier. Received 18 November 1987, Accepted 15 June 1988. We appreciate the helpful questions and suggestions of P. W. Schindler with respect to interpretation of our results, and the research support of the Noyes Foundation and OOA, NOAA.
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Jessie Smith Noyes FoundationUNSPECIFIED
National Oceanic and Atmospheric Administration (NOAA)UNSPECIFIED
Issue or Number:1
Record Number:CaltechAUTHORS:20201209-122141262
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Official Citation:Simon H.R Davies, James J Morgan, Manganese(II) oxidation kinetics on metal oxide surfaces, Journal of Colloid and Interface Science, Volume 129, Issue 1, 1989, Pages 63-77, ISSN 0021-9797,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106985
Deposited By: George Porter
Deposited On:09 Dec 2020 21:21
Last Modified:16 Nov 2021 18:58

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