Effect of HEH[EHP] impurities on the ALSEP solvent extraction process

ABSTRACT

In solvent extraction processes, organic phase impurities can negatively impact separation factors, hydrolytic performance, and overall system robustness. The resulting inconsistent performance can affect the process-level viability of a separation concept, and thus knowledge of the impurities present, their effects on the process, and how to remove them are vital. Deleterious impurities may be introduced into a system from reagent synthesis, or result from degradation via radiolysis and hydrolysis during use. In this work, the acidic extractant, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP])—proposed for application in extractive processes aimed at separating trivalent minor actinides from lanthanides and other fission products—is characterized with respect to its common impurities and their impact on Am(III) stripping in the Actinide Lanthanide SEParation (ALSEP) system. To control impurities in HEH[EHP], existing purification technologies commonly applied for the acidic organophosphorus reagent were assessed and a new chromatographic purification method specific to HEH[EHP] is presented.

KEYWORDS:

• Purification
• HEH[EHP]
• PC88A
• ALSEP
• phosphonic acid

Acknowledgements

Authors gratefully thank Dr. Robert Young for his assistance with NMR measurements and Marshallton Research Laboratories for generously donating HEH[EHP] sample material. This work was supported by U.S. Department of Energy, Office of Nuclear Energy, through the Nuclear Technologies R&D Program. A portion of the research was performed using EMSL, a DOE Office of Science User Facility sponsored by the Office of Biological and Environmental Research. Pacific Northwest National Laboratory is operated by Battelle Memorial Institute for the US Department of Energy under contract DE-AC05-76RL01830. VEH received support from the Henry W. and Janice J. Schuette Fellowship. Contributions from RFS were sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the US Department of Energy.

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