Selective separation of Pu(IV) and U(VI) with bisdiglycolamde ligands: solvent extraction and DFT calculations

The extractant tri-n-butyl phosphate (TBP) was used for the separation of Pu(IV) and U(VI) in the PUREX process, which brings phosphorus pollution problems. The ligands in accordance with the “CHON” principle will be helpful to reduce environmental pollution and pressure of subsequent waste treatment. In this work, three environmentally friendly BisDGA ligands in accordance with the “CHON” principle were used for the selective extraction Pu(IV) form U(VI) in 1-octanol system. These ligands showed highly extraction ability for Pu(IV), but hardly extracted U(VI) even under high acidity, which proves that the applicability of these extraction systems for selective separation of Pu(IV) from U(VI). The coordination chemistry of Pu(IV) by slope analyses confirmed that the ligands generated both M:L = 1:1 complexes with Pu(IV). The properties and thermodynamics of the PuL(NO 3 ) 4 complexes formed with Pu(IV) and BisDGA ligands were also investigated with the density functional theory (DFT) calculations, and the results verified the relevant experimental conclusion that the affinity of TH i -PE-BisDGA for Pu(IV) is better than the other two ligands.