Analytical and Bioanalytical Chemistry

, Volume 383, Issue 1, pp 48–55

Determination of actinide speciation in solution using high-energy X-ray scattering

Original Paper

DOI: 10.1007/s00216-005-3322-1

Cite this article as:
Soderholm, L., Skanthakumar, S. & Neuefeind, J. Anal Bioanal Chem (2005) 383: 48. doi:10.1007/s00216-005-3322-1

Abstact

High-energy X-ray scattering (HEXS) has been used to understand the coordination environment of the uranyl ion in a perchlorate solution. Assuming the two coordinating oxo ligands bound to U(VI) are represented in a peak in the pair distribution function (PDF) at 1.766(1) Å, integration of the peak intensity is used to quantify the charge located on the oxygens. The dioxo ligands are essentially neutral, as predicted by numerous published calculations, with a charge of −16.4(8) electrons. The peak in the PDF at 2.420(1) Å is consistent with equatorial ligating waters. The intensity of this peak is inconsistent with an integral coordination number and is used to propose a solution equilibrium of five and four waters coordinating to the uranyl(VI) ion favoring the five-coordinate species. This equilibrium is then used to experimentally determine that five-coordinate uranyl is 1.19±0.42 kcal/mol more stable than its four-coordinate counterpart under the conditions of the experiment. Further peaks in the Fourier transform of the scattering data at 4.50, 7, and 8.7 Å are attributed to uranium–solvent correlations.

Keywords

X-ray scattering Solution speciation Uranyl ion Synchrotron studies Actinide ion Uranium 

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Chemistry DivisionArgonne National LaboratoryArgonneUSA

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