Comparative EXAFS Investigation of Uranium(VI) and -(IV) Aquo Chloro Complexes in Solution Using a Newly Developed Spectroelectrochemical Cell
- 21 July 2005
- journal article
- research article
- Published by American Chemical Society (ACS) in Inorganic Chemistry
- Vol. 44 (19) , 6655-6661
- https://doi.org/10.1021/ic048422n
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 LIII-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−Oax = 1.76±0.02 Å, Oeq = 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.Keywords
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