GB801742A - Solvent extraction of neptunium - Google Patents

Abstract

Neptunium is extracted from a strongly acidic aqueous nitric acid solution, which also contains plutonium and/or fission products, by treating the solution, in which the plutonium is in the trivalent state and the neptunium is in the tetravalent or higher state, with tributyl phosphate dissolved in an inert substantially water-immiscible organic solvent. If the plutonium is in the tetravalent or higher state, the original aqueous solution is treated with a reducing agent, e.g. ferous sulphamate, hydroxylamine, or sulphurous acid. The neptunium is preferentially extracted into the organic solvent phase which is scrubbed with 4N nitric acid solution containing a reducing agent; neptunium is returned to aqueous phase by washing with water. The inert organic solvent may be white spirit, benzene, carbon tetrachloride, or kerosene, tributyl phosphate being present in a proportion of 20-30 per cent by volume. When uranium is present, e.g. in solutions obtained by dissolving neutron-irradiated uranium, it may be removed (a) by washing the organic phase with 0.6N nitric acid when uranium remains in the organic phase and neptunium passes into the aqueous phase; or (b) by extracting uranium from the original solution with hexone, using zinc nitrate as salting-out agent. Examples describe the separation of neptunium (a) from solutions containing also uranium, plutonium, americium, curium, and fission products; and (b) from an aqueous solution obtained by extracting irradiated uranium solution according to the process of Specification 801,743 and treating the organic extract with dilute nitric acid containing a reducing agent.