Studies on mono- and di- n-butylphosphoric acids—IV : The extraction of uranium (VI) from aqueous nitrate solution by di- n-butylphosphoric acid

Abstract

The distribution of uranium (VI) between solutions of di- n-butylphosphoric acid (HDBP) in various organic diluents and solutions of nitric acid has been studied as a function of the concentrations of HDBP, nitric acid, nitrate ion, and hydrogen ion, and of the nature of the diluent. The distribution coefficient ( D U, organic/aqueous) for uranium, which depends markedly on the nature of the diluent and increases in the order CHCl 3 < benzene < toluene < CCl 4 < kerosene, can be correlated with the dimerisation constant for HDBP in the diluent. D U shows a complex dependence on the aqueous nitric acid concentration ( C HNO 3 ), being proportional to C HNO 3 −2 from 0·1–1 M HNO 3 and at > 8 M HNO 3, and to C HNO 3 from 3–6 HNO 3. D U is independent of the aqueous nitrate ion concentration in mixtures of nitric and perchloric acids at a constant ionic strength of one. The implications of these relationships on the mechanism of extraction and the types of complexes formed are discussed, and the extraction of uranium (VI) compared with the extraction of other metals from similar systems.