title: Synergism in a HDEHP/TOPO Liquid-Liquid Extraction System: An Intrinsic Ligands Property?
abstract: Among the proposed mechanisms to predict and understand synergism in solvent extraction, the possibility of a preorganization of the mixture of extractant molecules has never been considered. Whether involving synergistic aggregation as for solubilization enhancement with reverse micelles or favored molecular interaction between the extractant molecules, evaluation of this hypothesis requires characterization of the aggregates formed by the extractant molecules at different scales. We investigate here the HDEHP/TOPO couple of extractant with methods ranging from vibrational spectroscopy and ESI-MS spectrometry to vapor pressure osmometry and neutron and X-ray scattering to cover both molecular and supramolecular scales. These experimental methods are subjected to DFT calculations and molecular dynamics calculations, allowing a rationalization of the results through the different scales. Performed in the absence of any cation, this original study allows a decorrelation of the mechanisms at the origin of synergy: it appears that no clear preorganization of the extractants can explain the synergy and therefore that the synergistic aggregation observed in the presence of cations is rather due to the chelation mechanisms than to intrinsic properties of the extractant molecules.
authors.affiliation: Nuclear Energy Division, RadioChemistry & Processes Department, CEA , 30207 Bagnols-sur-Cèze, France.
authors.forename: O
authors.initials: O
authors.lastname: Pecheur
authors.affiliation: ICSM, Institut de Chimie Séparative de Marcoule UMR 5257 , 30207 Marcoule, Bagnols-sur-Cèze, France.
authors.forename: S
authors.initials: S
authors.lastname: Dourdain
authors.affiliation: Nuclear Energy Division, RadioChemistry & Processes Department, CEA , 30207 Bagnols-sur-Cèze, France.
authors.forename: D
authors.initials: D
authors.lastname: Guillaumont
authors.affiliation: Nuclear Energy Division, RadioChemistry & Processes Department, CEA , 30207 Bagnols-sur-Cèze, France.
authors.forename: J
authors.initials: J
authors.lastname: Rey
authors.affiliation: Nuclear Energy Division, RadioChemistry & Processes Department, CEA , 30207 Bagnols-sur-Cèze, France.
authors.forename: P
authors.initials: P
authors.lastname: Guilbaud
authors.affiliation: Nuclear Energy Division, RadioChemistry & Processes Department, CEA , 30207 Bagnols-sur-Cèze, France.
authors.forename: L
authors.initials: L
authors.lastname: Berthon
authors.affiliation: Nuclear Energy Division, RadioChemistry & Processes Department, CEA , 30207 Bagnols-sur-Cèze, France.
authors.forename: M C
authors.initials: MC
authors.lastname: Charbonnel
authors.affiliation: ICSM, Institut de Chimie Séparative de Marcoule UMR 5257 , 30207 Marcoule, Bagnols-sur-Cèze, France.
authors.forename: S
authors.initials: S
authors.lastname: Pellet-Rostaing
authors.affiliation: LIONS, NIMBE, CEA, CNRS, Université Paris-Saclay, CEA Saclay , 91191 Gif sur Yvette Cedex, France.
authors.forename: F
authors.initials: F
authors.lastname: Testard