Synergic extraction of rare earths with 2-thenoyltrifluoroacetone and phosphoryl-type bidentate ligands such as tetraphenyldiphosphine dioxide or bis(diphenylphosphinyl)methane

The synergic extraction of rare earth(III) ions (RE; La, Sm, Tb and Lu) using 2-thenoyltrifluoroacetone (Htta) and phosphoryl-type uncharged bidentate ligands, such as tetraphenyldiphosphine dioxide (tpdpo) or bis(diphenylphosphinyl)methane (bdppm), was investigated in benzene. The synergic enhancement was attributed to the formation of the adduct RE(tta)3Sn (n=1 or 2 for tpdpo and n=1 for bdppm) in benzene, where S denotes the uncharged ligand. The adduct formation constants (βS) and the synergic extraction constants were determined. For each RE(III), the βS,1 value for bdppm is larger than the βS,1 and βS,2 values for tpdpo and the βS values for both ligands decrease with increasing atomic number of RE(III)