SYNERGIC SOLVENT EXTRACTION OF RARE EARTHS .I. SPECTROPHOTOMETRIC INVESTIGATION OF HOLMIUM- AND ERBIUM-TTA-TOPO COMPLEXES WITH PERCHLORATE ION

Synergic solvent extraction behavior of holmium and erbium in Ln3+/ClO4-/HTTA/TOPO system have been investigated spectrophotometrically. The formulae of these complexes with perchlorate ion were estimated to be (Ln(TTA)2(TOPO)5)+ClO4- which gave a strong band with a maximum of 445 mμ for holmium and 518 mμ for erbium, respectively, and showed a considerable electric conductivity in a polar organic solvent. When the rare earth is completely extracted into an organic layer, the following equation is assumed. Ln(TTA)3(TOPO)2(0)+3TOPO(0)+H+(a)+CIO-4(a)⇌(Ln(TTA)2(TOPO)5)+CIO-4(0)+HTTA(0) for which the mixed equilibrium constant is defined by κ3 = [(Ln(TTA)2(TOPO)5)+ClO4+](0)-[HTTA](0)/[Ln(TTA)3(TOPO) The log κ3 increases linearly with increase in the dielectric constant of the organic solvent used. The discrepancy in the distribution coefficient of rare earths between ClO4-/HTTA/TOPO and Cl-/HTTA/TOPO systems also increases with increase in the dielectric constant. © 1969.