Role of the Solvent in the Distribution of the Zinc-TTA Chelate and the Adduct Formation with TBP

Abstract

Abstract The distributions of the zinc chelate with thenoyltrifluoroacetone (TTA) between an aqueous solution and twelve inert organic solvents were investigated. After it had been confirmed that the distributed species were ZnA2, the distribution coefficients of the chelate (PM) and those of TTA (PHA) were compared; it was found that there is a correlation which can be expressed as logPM=nlogPHA+const. When TTA and TBP are in the extraction system, the adduct formation constants of chelate were obtained. The activities of all the species which take part in the adduct formation were evaluated on the basis of the regular solution theory. It was found that the adduct formation constant in terms of activity (Ks°) is constant in all the organic solvents; namely, logKs° was found to be 4.05. Finally, the role of the solvent in the synergistic extraction system is explained systematically by a combination of the regularity in the distribution and that in the adduct formation.