Extraction of Hexavalent Uranium by Trilaurylamine Nitrate

Abstract

The effects of amine, uranium, and hydrogen ion concentrations on the extraction of U (VI) from acidic nitrate solutions by tri-n-dodecylamine nitrate in toluene were studied at constant nitrate concentration. Over a wide range of these variables, it was found that the data could be correlated quantitatively on a basis of a mechanism of extraction involving equilibria between amine nitrate monomer and dimer species, extraction of uranium by both of these species, and extraction of nitric acid by the amine nitrate 2R3NHN08 ^ (R*NHNO>)i U02(N03)2 + 2R3NHN03 ^ (R8NHN03)2U02(N03)2 U02(N03)2 + 2(R3NHN03)2 ^ [(R3NHN03)2]2U02(N08)2 hno3 + r3nhno3 ^ r3nhno3-hno3 By determination of the nitric acid extracted into the organic phase by the fourth equilibrium, it was possible to calculate the concentration of amine nitrate available for participation in the other equilibria. From a reported value of K = 110 ± 30 1. mole-1 for the first equilibrium, values of = 50 ± 10 l.1 2 345mole-2 Ku = 200 ± 50 l.2 mole-2 were estimated for the equilibria involving uranium extraction by amine nitrate monomers and dimers, respectively. Data are also presented on the variation of nitrate and hydrogen Ions in the organic phase with uranium loading, from which it is concluded that no species other than the uranyl nitrato complexes are extracted. The difficulties caused by amine nitrate aggregation during studies on the mechanism of extraction of metals by other amines in other diluents are discussed.