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Comparative EXAFS Investigation of Uranium(VI) and -(IV) Aquo Chloro Complexes in Solution Using a Newly Developed Spectroelectrochemical Cell

C. Hennig,* J. Tutschku, A. Rossberg, G. Bernhard, and A. C. Scheinost

Forschungszentrum Rossendorf, Institute of Radiochemistry, P.O. Box 510119, 01314 Dresden, Germany

Inorg. Chem., 2005, 44 (19), pp 6655–6661

DOI: 10.1021/ic048422n

Publication Date (Web): July 21, 2005

Author to whom correspondence should be addressed. E-mail: hennig@esrf.fr. Fax: +33 (0)476 88 2505.

Abstract

The coordination of the U(IV) and U(VI) ions as a function of the chloride concentration in aqueous solution has been studied by U L_III-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The oxidation state of uranium was changed in situ using a gastight spectroelectrochemical cell, specifically designed for the safe use with radioactive solutions. For U(VI) we observed the complexes UO₂(H₂O)₅²⁺, UO₂(H₂O)₄Cl⁺, UO₂(H₂O)₃Cl₂⁰, and UO₂(H₂O)₂Cl₃^- with [Cl^-] increasing from 0 to 9 M, and for U(IV) we observed the complexes U(H₂O)₉⁴⁺, U(H₂O)₈Cl³⁺, U(H₂O)₆_-₇Cl₂²⁺, and U(H₂O)₅Cl₃⁺. The distances in the U(VI) coordination sphere are U−O_ax = 1.76±0.02 Å, O_eq = 2.41 ± 0.02 Å, and U−Cl = 2.71 ± 0.02 Å; the distances in the U(IV) coordination sphere are U−O = 2.41 ± 0.02 Å and U−Cl = 2.71 ± 0.02 Å.

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Published In Issue September 19, 2005
Received November 10, 2004

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Article

Comparative EXAFS Investigation of Uranium(VI) and -(IV) Aquo Chloro Complexes in Solution Using a Newly Developed Spectroelectrochemical Cell

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Related Content

EXAFS Investigation of U(VI), U(IV), and Th(IV) Sulfato Complexes in Aqueous Solution

Exploring the Effects of Reduction or Lewis Acid Coordination on the UO Bond of the Uranyl Moiety

Aqueous Uranium(VI) Hydrolysis Species Characterized by Attenuated Total Reflection Fourier-Transform Infrared Spectroscopy

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