Complexation of Actinide(III) and Lanthanide(III) with H4TPAEN for a Separation of Americium from Curium and Lanthanides

Previous studies have identified the TPAEN ligand as a potentially appropriate complexing agent in solvent extraction processes for the separation of americium (Am­(III)) from the fission products including lanthanide (Ln­(III)) and curium (Cm­(III)) ions, a challenging issue for advanced nuclear fuel recycling. To get insight into the selectivity of this ligand, the complexation of selected trivalent Ln­(III) and actinide (An­(III)) cations with TPAEN was investigated in solution. First, the structure and stoichiometry of the TPAEN complex with Am­(III) were characterized by extended X-ray absorption fine structure spectroscopy (EXAFS). Then complexation constants and thermodynamics data were acquired for the complexes using different methods: microcalorimetry for the Ln­(III) cations, time-resolved laser fluorescence spectroscopy (TRLFS) for Eu­(III) and Cm­(III), and UV–visible spectroscopy for Nd­(III) and Am­(III).