SOLVENT-EXTRACTION OF ER(III) AND LU(III) WITH 2-ETHYLHEXYLPHOSPHONICACID MONO-2-ETHYLHEXYL ESTER IN PRESENCE OF SOME REAGENTS

The extraction of Er(III) and Lu(III) from thiocyanate media with 2-et hylhexylphosphonic acid mono-2-ethylhexyl ester (EHEHPA) and also with mixtures of EHEHPA and thenoyltrifluoroacetone (HTTA) or tri-n-octylp hosphine oxide (TOPO) or bis-2-ethylhexyl sulfoxide (B2EHSO) in benzen e has been studied systematically. Synergistic effects have been obser ved with mixtures of EHEHPA + HTTA or TOPO. On the other hand, antagon istic effects have been observed with mixtures of EHEHPA + B2EHSO. The se extraction data have been analyzed theoretically with the aid of a computer by taking into account complexation of the metal in the aqueo us phase by SCN- and plausible complexation in the organic phase. The extraction constants of the various product species have been deduced by non-linear regression analysis. The stability constants for the thi ocyanate complexes of the metal ions have also been determined.