Solvent Extraction of Pentavalent Neptunium with n-Octyl(phenyl)-N, N-Diisobutylcarbamoylmethylphosphine Oxide

抄録

Solvent extraction of Np(V) from HNO₃ solution was experimentally studied with n-octyl(phenyl)-N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO) as an extractant mixed with TBP and n-dodecane. In the low HNO₃ concentration, the Np(V) is weakly extractable, but effectively extracted in the high HNO₃ concentration (>4 M) due to the disproportionation of Np(V) to Np(IV) and Np(VI). The distribution ratio of Np was increased by use of H₂O₂ as a reductant of Np(V). More than 95% of Np was extracted with 0.8 M H₂O₂ in 2.2 M HNO₃ solution. It was shown that most of the Np extracted is in tetravalent state as expected from redox mechanism. The Np(IV) extracted in the organic phase was effectively stripped to the aqueous phase with H₂C₂O₄.