Extraction of thorium(IV) as perchlorate and chloroacetate complexes with 1-phenyl-2,3-dimethyl-5-pyrazolone (antipyrine)

Thorium was extracted quantitatively with the neutral ligand 1-phenyl-2,3-dimethyl-5-pyrazolone (Apy) in the presence of perchlorate (ClO4-) and di/trichloroacetates (DCA/TCA) at pH 2.5 into an organic solvent. Optimization of experimental parameters like pH, equilibration time, solvents, reactant concentrations, best suited conditions for back extraction, interference due to the presence of different anions and cations and effect of metal ion concentration were studied. The composition of the complexes has been established using log-log plots and are represented as [Th(Apy)(2)(ClO4)(4)], [Th(Apy)(2)(TCA)(4)], [Th(Apy)(H2O)(DCA)(4)]. The respective conditional stability constants of the effectively extracted complexes have also been calculated as 9.4 +/- 0.03 and 10.4 +/- 0.04, respectively . The method has been extended for the separation of thorium from a number of cations in binary and multicomponent mixtures. The method is simple, rapid, selective and has a good reproducibility (+/- 0.5%).