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Sectrophotometric Investigation of U(VI) Chloride Complexation in the Naci/NaClO4 system

Published online by Cambridge University Press:  10 February 2011

Patricia Paviet-Hartmann  and
Mavis R. Lin
Patricia Paviet-Hartmann
Affiliation:
Chemical Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87544, USA.
Mavis R. Lin
Affiliation:
Chemical Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87544, USA.
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Abstract

Post closure radioactive release scenarios from geologic salt formation, such as the WIPP (Waste Isolation Pilot Plant) (USA) include hydrologic transport of radionuclides through a chloride saturated aquifer. Consequently, the understanding of actinide solution chemistry in brines is essential for modeling requiring accurate knowledge of the interaction between AnO2 2+ and chloride ions. Complexation constants of two U(VI) chloride species UO2Cl+ and UO2Cl2 0 have been intensively studied for about 40 years using different methods. However, large uncertainties reflect the general difficulty in determining accurate stability constants of weak complexes. In order to model the behavior of U(VI) in brines, we studied the formation of its chloride complexes by UV-Vis spectroscopy as a function of the NaCI concentration at 25 °C. The experiments were performed at constant ionic strength by varying the concentration ratio of NaCI and NaClO4. Deconvolution resulted in single component absorption sepectrum for UO2Cl+ and UO2Cl2 0. The apparent stability constants of UO2Cl+ and UO2Cl2 0 are determined at different ionic strengths. The experimental data are used to parameterize using the SIT approach.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 556: Symposium QQ – Scientific Basis for Nuclear Waste Management XXII , 1999 , 977
Copyright
Copyright © Materials Research Society 1999

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References

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