Selective extraction of plutonium(IV) over uranium(VI), americium(III), europium(III) and zirconium(IV) with bidentate O-phenoxydiamide ligands: experimental and theoretical study

The performance of a series of novel O-phenoxydiamides extracting Zr(IV), Eu(III), U(VI), Pu(IV) and Am(III) was studied. The result of extraction experiments showed that the coordination abilities of these five congeneric O-phenoxydiamides decrease in the order of CycleDODA > PhenylDODA > ButylDODA > HexylDODA > BenzoDODA, the abilities of different metal ions coordinating with the same ligand decrease in the order of Pu(IV) ≫ U(VI) > Zr(IV), Eu(III), Am(III). At HNO3 concentration of 5.0 mol/L, the distribution ratio of BenzoDODA/n-dodecane extracting Pu(IV) is much larger than those of other metal ions, the separation factors of Pu(IV) over Eu(III), Zr(IV), U(VI) and Am(III) are between 20 and 300, which can be used for recovering Pu(IV) selectively from highly acidic liquid waste. The density functional theory (DFT) calculation of the 25 complexes in geometrical structure, Mayer bond order (MBO) and energy was further studied, the result is consistent with the experimental result.