Complexation of Ln(III) and Am(III) with the Hydrosoluble TEDGA: Speciation and Thermodynamics Studies

Tridentate hydrosoluble diglycolamide TEDGA (tetraethyldiglycolamide) has been introduced in the EXAm process to complex Cm(III) and heavier lanthanides and allow the recovery of Am(III) alone. An exhaustive study has been carried out on the complexation of the ligand TEDGA with representative cations (La to Lu and An(III)) in order to enhance the knowledge on chemical mechanisms in nitrate solutions. The speciation of complexes LnTEDGAn3+ has been carefully determined with different spectroscopic techniques such absorption spectrometry, ESI-MS, TRLIF and completed by molecular dynamics simulations. The equilibrium constants were measured by independent methods. By providing basic information on the structure of complexes and on the thermodynamics of the chemical systems, this study helps to support the modeling of the related liquid-liquid process.