Comparative dispersion-free solvent extraction of Uranium(VI) and Thorium(IV) by TBP and dialkyl amides using a hollow fiber contactor

Dispersion-free solvent extraction of U(VI) and Th(IV) from nitric acid medium was studied employing microporous hollow fiber membrane with several monoamide extractants, viz. N,N-di-2-ethylhexyl isobutyramide (D2EHiBA), N,N-dihexyl hexanamide (DHHA), N,N-dihexyl decanamide (DHDA) and N,N-dihexyl octanamide (DHOA), and the results were compared with those obtained with conventional TBP extractant. Effects of flow rate and feed metal ion concentration on the extraction rate were examined. The extraction was principally controlled by the distribution coefficient of the metal ions with the extractants. The studies were performed under different hydrodynamic conditions and the overall mass transfer coefficients of the extracting species were calculated and found to be independent of the flow rates. The overall extraction rates were governed by the viscosity and density of the organic phase. The separation factor between U(VI) and Th(IV) was excellent with branched chain monoamides, viz. D2EHiBA, followed by DHOA. The results indicated the selective recovery of Uranium in the presence of large concentrations of Thorium by monoamides in dispersion-free solvent extraction method. A mathematical model was employed for predicting the extraction behavior of metal ions, which gave an excellent match between the calculated and the experimental results. (C) 2016 Elsevier B.V. All rights reserved.