HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Fendorf, S. E. Articles by Burau, R. G. Search for Related Content PubMed Articles by Fendorf, S. E. Articles by Burau, R. G. Agricola Articles by Fendorf, S. E. Articles by Burau, R. G.

Competing Metal Ion Influences on Chromium(III) Oxidation by Birnessite

Division of Soil Science, Univ. of Idaho, Moscow, ID 83844

Robert J. Zasoski and Richard G. Burau

Dep. of Land, Air, and Water Resources, Univ. of California, Davis, CA 95616

*Corresponding author.

ABSTRACT

The oxidation of Cr(III) to Cr(VI) presents a significant environmental hazard due to the much greater mobility and toxicity of Cr(VI). Despite the importance of Cr(III) oxidation, many factors influencing this important chemical process in soils and waters remain unknown. In this study we investigated the effects of competing metal sorbates on Cr(III) oxidation by -MnO₂. Aluminum, La, Co(II), Mn(II), and Cr(VI) were reacted with -MnO₂ prior to the addition of Cr(III). Only Al affected the extent of Cr(III) oxidation at pH 4, and at pH 5 the presence of Al, with 2.84 µmol Cr(III) initially present, decreased oxidation from 2.80 to 0.28 µmol Cr(VI). None of the competing ions influenced the degree of oxidation at pH 3. Neither of the oxidation reaction products, Mn(II) or Cr(VI), affected the extent of oxidation. Electrokinetic investigations revealed that both Al and La induced a charge reversal on -MnO₂. As pH increased from 3 to 5, the electrophoretic mobility (EM) of -MnO₂ sharply increased at pH 4 in the presence of 2.90 x 10^–4 M Al. The sorption behavior and influences on EM of Al indicate that a surface alteration occurs whereby the oxidizing ability of -MnO₂ (birnessite) is inhibited. High-resolution transmission electron microscopy revealed that an Al-hydroxide surface precipitate formed on -MnO₂, thus accounting for the sorption, EM trends, and Cr(III) oxidation inhibition.

Received for publication November 27, 1991.

This article has been cited by other articles:

				C. Negra, D. S. Ross, and A. Lanzirotti Soil Manganese Oxides and Trace Metals: Competitive Sorption and Microfocused Synchrotron X-ray Fluorescence Mapping Soil Sci. Soc. Am. J., March 1, 2005; 69(2): 353 - 361. [Abstract] [Full Text] [PDF]

				C. A. Guest, D. G. Schulze, I. A. Thompson, and D. M. Huber Correlating Manganese X-Ray Absorption Near-Edge Structure Spectra with Extractable Soil Manganese Soil Sci. Soc. Am. J., July 1, 2002; 66(4): 1172 - 1181. [Abstract] [Full Text] [PDF]

				J. G. Kim, J. B. Dixon, C. C. Chusuei, and Y. Deng Oxidation of Chromium(III) to (VI) by Manganese Oxides Soil Sci. Soc. Am. J., January 1, 2002; 66(1): 306 - 315. [Abstract] [Full Text] [PDF]