Synergic solvent extraction of rare earths—I Spectrophotometric investigation of holmium-and erbium-TTA-TOPO complexes with perchlorate ion

Abstract

Synergic solvent extraction behavior of holmium and erbium in Ln 3+/ClO 4 −/HTTA/TOPO system have been investigated spectrophotometrically. The formulae of these complexes with perchlorate ion were estimated to be (Ln(TTA) 2(TOPO) 5) +ClO 4 − 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)+3 TOPO (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 κ 3 = [(Ln(TTA) 2(TOPO) 5) +ClO 4 +] (0) −[HTTA] (0)/[Ln(TTA) 3(TOPO) The log κ 3 increases linearly with increase in the dielectric constant of the organic solvent used. The discrepancy in the distribution coefficient of rare earths between ClO 4 −/HTTA/TOPO and Cl −/HTTA/TOPO systems also increases with increase in the dielectric constant.