title: Thermodynamic study of the complexation of protactinium(V) with diethylenetriaminepentaacetic acid.
abstract: The complex formation of protactinium(V) with DTPA was studied at different temperatures (25-50 °C) and ionic strengths (0.1-1 M) with the element at tracer scale. Irrespective of the temperature and ionic strength studied, only one neutral complex with (1:1) stoichiometry was identified from solvent extraction and capillary electrophoresis coupled to ICP-MS (CE-ICP-MS) experiments. Density Functional Theory (DFT) calculations revealed that two complexes can be considered: Pa(DTPA) and PaO(H2DTPA). The associated formation constants were determined from solvent extraction data at different ionic strengths and temperatures and then extrapolated to zero ionic strength by SIT methodology. These constants are valid, regardless of complex form, Pa(DTPA) or PaO(H2DTPA). The standard thermodynamic data determined with these extrapolated constants revealed a very stable complex formed energetically by an endothermic contribution which is counter balanced by a strong entropic contribution. Both, the positive enthalpy and entropy energy terms suggest the formation of an inner sphere complex.
authors.affiliation: CNRS-Université Paris-Sud, IPN 15 rue Georges Clémenceau, F-91406 Orsay, France.
authors.forename: Mickaël
authors.initials: M
authors.lastname: Mendes
authors.forename: Sébastien
authors.initials: S
authors.lastname: Leguay
authors.forename: Claire
authors.initials: C
authors.lastname: Le Naour
authors.forename: Séna
authors.initials: S
authors.lastname: Hamadi
authors.forename: Jérôme
authors.initials: J
authors.lastname: Roques
authors.forename: Philippe
authors.initials: P
authors.lastname: Moisy
authors.forename: Dominique
authors.initials: D
authors.lastname: Guillaumont
authors.forename: Sylvain
authors.initials: S
authors.lastname: Topin
authors.forename: Jean
authors.initials: J
authors.lastname: Aupiais
authors.forename: Christophe
authors.initials: C
authors.lastname: Den Auwer
authors.forename: Christoph
authors.initials: C
authors.lastname: Hennig