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Role of the hydroxo function of citric acid within the Am(III) complexation

Abstract : Alpha-hydroxycarboxylic acids are important molecules that can be used as complexing agent or buffer in aqueous phase in actinide selective separation processes. They are also present in the environment as a degradation product of cellulose. Therefore the alpha these molecules are likely to influence the speciation in the fuel cycle processes as well as in the migration mechanisms. In this double context, the behavior and complexation of americium with this type of ligand was studied, taking citric acid as a representative of this family. Actinide(III)-citric acid system was already examined, but most of the studies are incomplete because the citric acid is one of the most complicated compounds of the family due to its three carboxylic acids able to be deprotonated and to coordinate the metallic cation. On one side, the thermodynamic studies provide only complexation constants and the stoichiometry [ , ] of the different complexes without any information on the coordination spheres (the number of complexing carboxylate groups, the presence or not of the hydroxo function as a coordinating group and the ligand protonation state). On the other side, the rare structural studies relate to polynuclear [ ] or polymeric species [ , , , ] unlike the complexes identified in solution in the previous thermodynamic studies. In this study, thermodynamics and structural data were assessed in solution for the same chemical conditions to finally describe the speciation of the Am(III)-citrate system. A focus was done on the role played by the hydroxyl group does it coordinate the actinide? Is it protonated? To better understand its role, the Am-citrate system was compared to the Am-tricarballylate system (analogue to citric acid without the hydroxyl group). The complexation constants have been determined and the complexes were characterized using X-ray absorption, NMR, TRLFS and capillary electrophoresis.
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Submitted on : Wednesday, October 30, 2019 - 9:20:22 AM
Last modification on : Tuesday, April 28, 2020 - 11:28:13 AM


  • HAL Id : cea-02338560, version 1




C. Tamain, L. Bonato, J. Aupiais, T. Dumas, C. Berthon, et al.. Role of the hydroxo function of citric acid within the Am(III) complexation. ATAS 2018, Nov 2018, Nice, France. ⟨cea-02338560⟩



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