Optimization of extractive removal of uranium(VI) from aqueous acidic solutions using commercial amines: Linear solvation energy relation based modeling

Abstract

The extraction of uranium(VI) from acidic sulfate and nitrate media by Alamine 300 and di-n-octyl amine (DOA) solvents (T=298.2 K) is dependent about equally strongly on the types and concentration levels of the carrier, acid and the transferred U(VI) species. Distribution data have been subjected to formulation of an optimization structure for an effective U(VI) separation on the basis of the derivative variation method. Identification of optimum conditions is governed by the range of changes of the first order derivatives of the optimized quantity. Experimentally and analytically defined optimum U(VI) removal efficiencies of amines are ranging about 70–90% and 30–45% for aqueous-phase sulfate and nitrate media, respectively. Three independent variables, i.e. the concentrations of the carrier, acid and U(VI), are adequate for expressing the non-linear dependence of the optimized extraction factors on the properties of relevant system.Modeling efforts based on LSER (linear solvation energy relation) and mass-action law principles have shown considerable success. The LSER-based solvation model using 10 physical descriptors of the solvent and ion provides relatively reliable fits with a mean error of 13% and satisfies established limiting behavior of the physical event. A critical comparison of U(VI) uptake capacities relative to the commercial extractants of basic (Alamine 300, Aliquat 336), acidic (Cyanex 272) and neutral (tri-n-butyl phosphate, TBP) types on an efficiency-basis has been carried out. About 80% stripping degree of UVI) is achieved by sodium carbonate as a strippant.