JRP 07-05
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ContactDr. Michel MeyerICMUB, 9 avenue A. Savary, 21078, Dijon Cedex, France  
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Free and silica-gel-bound tetraazamacrocycles as complexing agents of actinide cations: investigation of the solid-state and solution coordination schemeStatus
GoalsThe coordination scheme of UO2+2 Pu+4, and Eu+3 (taken as a surrogate of Am+3) complexes incorporating several tetraazamacrocycles bearing either acetate or propionate arms will be investigated by EXAFS both in the solid state and in aqueous solutions. The study encompasses not only the free chelating agents but also surface-modified mesoporous hybrid materials obtained by covalent grafting of the ligands onto Kieselgel. Implemented in a solid/liquid extraction process working at a semi-industrial scale, these silica gels are used for the ultrapurification of radioactive wastewaters produced by the CEA-Valduc center. Hence, unraveling the binding mode of the immobilized ligands is of crucial importance for understanding the metal-uptake properties of the extractant at the molecular level. Expected resultsExpected impact on applied issues in the field of nuclear fission energy EXAFS experiments are sought as a mean to unravel the structural properties of tetraazamacrocyclic actinide complexes incorporating UVI , PuIV , or AmIII (EuIII will be used as a surrogate). The results will give the opportunity to check whether or not the coordination scheme of these ions resembles that found for some lanthanides by X-ray crystallography but also to compare the stereochemical arrangement of the neighboring atoms in the vicinity of an actinide ion for the isolated complex versus that formed on the silica-gel surface. Obviously, the knowledge of the structural requirements for this series of ligands is not only of crucial importance to improve the performances of the sequestering agents, but would also provide the first structural data ever reported for either isolated or grafted tetraazamacrocycles incorporating plutonium. The structural characterization of surface complexes immobilized on mesoporous silica beads is without any doubt a challenging task but constitutes a paradigm for solid/liquid partitioning and recovery that might ultimately lead to further breakthroughs in the area of lanthanide/actinide separation. Expected impact on long term integration The present application is a typical example of long term integrated research in the field of actinide science as it gathers two French teams (CNRS and CEA) and a German one (FZD). The latter partner provides both a unique access to a European-managed large instrument and its expertise in the acquisition and processing of EXAFS data. Owned and operated by FZD, the Rossendorf beamline at ESRF is a member of the pooled facilities of ACTINET. So far, this radiochemistry station is the only one in France and Germany that has the authorisations to handle the 239 Pu isotope. Reports |
