THE SEPARATION OF NEPTUNIUM AND PLUTONIUM FROM NITRIC ACID USING n-OCTYL(PHENYL)-N, N DIISOBUTYLCARBAMOYLMETHYLPHOSPHINE OXIDE EXTRACTION AND SELECTIVE STRIPPING†

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Abstract
The extraction of neptunium and plutonium in several oxidation states was studied as a function of nitric acid concentration for 0.1M n-octyl(phenyl)-N, N-diisobutylcarbamoyl -methylphosphine oxide in 1.4M tributylphosphate with dodecane diluent. Np(V) is only weakly extractable over the range of acid concentrations studied while Np(IV) and Np(VI) are highly extractable. Pu(IV) and Pu(VI) are also highly extractable while Pu(III) was extracted but with lower efficiency. An Fe(II) reductant was used to reduce neptunium to Np(IV) and plutonium to Pu(III) for the initial extraction. Pu(III) was then stripped with dilute HNO3 in the presence of a holding reductant leaving the Np(IV) in the organic phase. Neptunium may then be recovered to an aqueous phase with one of a number of complexing agents.