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Characterization of Chromium(III) Hydroxide Solids and Their Oxidation by Hydrogen Peroxide

Published online by Cambridge University Press:  17 March 2011

Zhicheng Zhang ,
Linfeng Rao ,
Dhanpat Rai  and
Sue B. Clark
Zhicheng Zhang
Affiliation:
Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720, U.S.A Washington State University, Pullman, WA 99165, U.S.A
Linfeng Rao
Affiliation:
Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720, U.S.A
Dhanpat Rai
Affiliation:
Pacific Northwest National Laboratory, Richland, WA 99352, U.S.A
Sue B. Clark
Affiliation:
Washington State University, Pullman, WA 99165, U.S.A
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Abstract

Chromium is of great concern in the vitrification of high-level nuclear waste sludges because it forms separate crystallites in the molten glass. Inadequate removal of chromium from sludges could result in the production of an unacceptably large volume of HLW glass. Alkaline oxidative leaching is considered one of the pretreatment strategies to remove chromium before the vitrification.

In this study, Cr(III) hydroxide solids were prepared under different conditions and characterized by EXAFS and IR. The rate of oxidation of the solids by hydrogen peroxide in alkaline solutions was studied by UV absorption spectroscopy. EXAFS and IR experiments indicate that the degree of oligomerization in the Cr(III) hydroxide solids increases with the increase in the concentration of NaOH in solution, the aging temperature and the aging time. The rate of oxidation of the solids follows the same order previously observed for Cr(III) oligomers in solution, i.e., species with higher degree of oligomerization are oxidized more slowly.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 824: Symposium CC – Scientific Basis for Nuclear Waste Management XXVIII , 2004 , CC6.5
Copyright
Copyright © Materials Research Society 2004

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