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The extraction of Np(IV), Np(VI), Pu(IV) and U(VI) from a nitric acid medium has been carried out with dibutyldecanamide (DBDA), dihexyldecanamide (DHDA), bis-2-ethylhexylsulphoxide (BEHSO) and octyl(phenyl)-N-N-diisobutyl-carbamoylmethylphosphine oxide (CMPO) using n-dodecane as the diluent. The order of extraction for the metal ions is CMPO> BEHSO>DHDA>DBDA. The species extracted into the organic phase was found to be the disolvate with all the extractante while using hexavalent metal ions Np(VI) and U(VI) and also with tetravalent ions Np(IV) and Pu(IV) in the case of BEHSO and CMPO. However, in the case of DBDA and DHDA, Np(IV) and Pu(IV) were extracted as the trisolvate species. The equilibrium constant (K) for the formation of the above species has been evaluated after applying the possible correction factors. In general, log A" increases with increasing basicity of the extractants. In the case of amides, the plot of log A -verses k H (acid uptake equilibrium constant) gave straight lines which could be represented by the empirical equation : logici) = 5.17 k H + 0.18 and log = 3.11 k H + 1.81 for the respective metal ions. With the help of these empirical equations it is possible to predict the equilibrium constant values of amide complexes of U(VI) or Pu(IV) if the k H values of amides are known. The solid complexes of U(VI) with DHDA and CMPO were synthesized and characterized by elemental analysis and IR spectra. Two molecules of DHDA and only one molecule of CMPO are bound with U(VI). The bidentate nature of CMPO in its solid species has been confirmed.

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SummaryThe extraction behaviour of plutonium (IV) and neptunium (IV) was studied from nitric as well as hydrochloric acid employing 3-phenyl-4-benzoyl-5-isoxazolone (PBI) in toluene as the extractant. The forward extraction in hydrochloric acid medium was carried out in presence of several holding oxidants out of which ammonium meta vanadate was found to give the best results. The stripping behaviour of Np and Pu was studied employing a variety of reagents out of which 0.1 M hydroquinione in 1:1 HCl was the most promising. The separation of Np from Pu under simulated conditions was attempted from hydrochloric acid medium giving a decontamination factor value of >10

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