Cr(OH)3(s) oxidation induced by surface catalyzed Mn(II) oxidation

Seonyi Namgung, Man Jae Kwon, Nikolla P. Qafoku, Giehyeon Lee

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

We examined the feasibility of Cr(OH)3(s) oxidation mediated by surface catalyzed Mn(II) oxidation under common groundwater pH conditions as a potential pathway of natural Cr(VI) contaminations. Dissolved Mn(II) (50 μM) was reacted with or without synthesized Cr(OH)3(s) (1.0 g/L) at pH 7.0.9.0 under oxic or anoxic conditions. Homogeneous Mn(II) oxidation by dissolved O2 was not observed at pH ≤ 8.0 for 50 days. At pH 9.0, by contrast, dissolved Mn(II) was completely removed within 8 days and precipitated as hausmannite. When Cr(OH)3(s) was present, this solid was oxidized and released substantial amounts of Cr(VI) as dissolved Mn(II) was added into the suspension at pH ≥ 8.0 under oxic conditions. Production of Cr(VI) was attributed to Cr(OH)3(s) oxidation by a newly formed Mn oxide via Mn(II) oxidation catalyzed on Cr(OH)3(s) surface. XANES results indicated that this surface-catalyzed Mn(II) oxidation produced a mixed valence Mn(III/IV) solid phase. Our results suggest that toxic Cr(VI) can be naturally produced via Cr(OH)3(s) oxidation coupled with the oxidation of dissolved Mn(II). In addition, this study evokes the potential environmental hazard of sparingly soluble Cr(OH)3(s), which has been considered the most common and a stable remediation product of Cr(VI) contamination.

Original languageEnglish
Pages (from-to)10760-10768
Number of pages9
JournalEnvironmental Science and Technology
Volume48
Issue number18
DOIs
Publication statusPublished - 2014 Sep 16
Externally publishedYes

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oxidation
Oxidation
oxic conditions
Poisons
Groundwater
Contamination
Oxides
Suspensions
chromium hexavalent ion
environmental hazard
Remediation
anoxic conditions
Hazards
remediation
oxide
groundwater
contamination

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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Cr(OH)3(s) oxidation induced by surface catalyzed Mn(II) oxidation. / Namgung, Seonyi; Kwon, Man Jae; Qafoku, Nikolla P.; Lee, Giehyeon.

In: Environmental Science and Technology, Vol. 48, No. 18, 16.09.2014, p. 10760-10768.

Research output: Contribution to journalArticle

Namgung, Seonyi ; Kwon, Man Jae ; Qafoku, Nikolla P. ; Lee, Giehyeon. / Cr(OH)3(s) oxidation induced by surface catalyzed Mn(II) oxidation. In: Environmental Science and Technology. 2014 ; Vol. 48, No. 18. pp. 10760-10768.
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