Extraction of Np(5) by 1-phenyl-3-methyl-4-benzoylpyrazolone-5 and trioctylphosphine oxide mixtures

Np(5) extraction by solutions of 1-phenyl-3-methyl-4-benzoylpyrazolone-5 and trioctylphosphine mixture in cyclohexane was investigated. Pronounced difference in distribution coefficients of direct and back extraction was revealed. It was clarified using absorption spectra of neptunium aqueous and organic solutions, that the reason of disagreement lay in Np(5) reduction up to Np(4) by 1-phenyl-3-methyl-benzoylpyrazolone-5 in organic phase. The dependence of neptunium distribution coefficients on duration of phase contact and reactant concentrations was investigated. Synergism with 20-50 maximal value was revealed. Possibilities of using this extraction system for simultaneous neptunium separation from trivalent transplutonium and rare earth elements, uranium(6) and plutonium(4) were shown