SELECTIVE EXTRACTION OF LIGHT LANTHANIDES(III) WITH 18-CROWN-6 AND PERFLUOROOCTANOATE

The extraction of La(In), Gd(lII), and Lu(III) with 18-crown-6 (18C6) has been studied using pentadecafluorooctanoate (PDFO) as a counteranion. Very high extractability of La(III) was observed in various organic solvents such as benzene, chloroform, 1,2-dichloroethane, and nitrobenzene. The predominant species extracted into benzene was found to be Ln(PDFO)(3)(18C6), and the extraction constants(K-ex,K-s,K-1 = [Ln(PDFO)(3)(18C6)]org/[Ln(3+)][PDFO](3)[18C6](org)) were 10(13.12) for La(III), 10(9.74) for Gd(III), and 10(9.67) for Lu(III). These values are 10(10) times higher than those in the trichloroacetate-18C6 system reported previously. The present PDFO-18C6 system was superior to the picrate- and bexafluoroacerylacetonate-18C6 system for the separation efficiency of light lanthanides(III).