Oxidation of Chromium(III) to (VI) by Manganese Oxides

Manganese oxides in soils oxidize Cr from a stable form to a more toxic mobile form

Jae Gon Kim

2016

Scholarcy highlights

  • Manganese oxides in soils oxidize Cr from a stable form to a more toxic mobile form
  • The influence of Mn oxide diversity on Cr oxidation is the subject of this report
  • Oxidation of Cr(III) to Cr(VI) by coarse clay‐size natural Mn oxides, birnessite, todorokite, and lithiophorite was studied at pH 4 and 7, and at 200 and 400 μM initial Cr(III) concentrations
  • The rate of oxidation was greater for todorokite and birnessite that contained the most quadrivalent Mn and least for lithiophorite that contained a greater proportion of trivalent Mn determined by x‐ray photoelectron spectroscopy
  • The deviation of Mn oxidation state from the frequently assumed quadrivalent form in Mn oxides suggests the need for a thorough assessment of the ion species of Mn in Mn oxides that occur in soils
  • At 400 μM Cr(III), the rate of Cr oxidation by the pyrolusite sample was intermediate between birnessite and todorokite suggesting that the sample was not pure pyrolusite
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