Synergistic Extraction of Rare Earths(III) with β-Diketone and Nitrogen-Containing Terdentate Ligand, 2,2′:6′,2″-Terpyridine

Abstract

Abstract The synergistic extraction of rare earth(III) ions (RE: La, Sm, Tb, and Lu) was investigated using a β-diketone (HA), i.e., trifluoroacetylacetone (Htfa) or hexafluoroacetylacetone (Hhfa), in the presence of a terdentate ligand, 2,2′:6′,2″-terpyridine (terpy) into benzene. The formation of complexes such as RE(A)2+ or RE(A)2+ in the aqueous phase was observed. The synergistic enhancement is attributed to the formation of an adduct RE(A)3terpy in the benzene phase. The adduct formation constants (βS,1) and the synergistic extraction constants were determined. For each RE(III), the βS,1 value in the Htfa–terpy system is smaller than that in the Hhfa–terpy system. The βS,1 values decrease with increasing atomic number of RE(III) in the Htfa–terpy system, but the βS,1 value for La(III) is smaller than that for the other RE(III) in the Hhfa–terpy system.