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Diglycolamide / Actinides / Neptunium / Plutonium / SeparationSummary. Extraction behavior of Np 4+ and Pu 4+ was investigated using several tetraalkylsubstituted diglycolamide (DGA) extractants such as N,-tetradecyl diglycolamide (TDDGA). The organic phases used were 0.1 M solutions of the diglycolamide extractants in n-dodecane modified with 30% iso-decanol for avoiding third phase formation while the aqueous phases contained dilute nitric acid solutions spikes with the radiotracers. The stoichiometry of the extracted species was ascertained by ligand concentration variation experiments and was found to be M(NO 3 ) 4 ·2L, where M was Np and Pu and L was the substituted DGA ligand. In general, the extraction equilibrium constant (log K ex ) values for both Np 4+ and Pu 4+ showed an increasing trend with increasing alkyl group chain length and the log K ex values were higher for Pu 4+ as compared to those for Np 4+ . While for Np 4+ , the K ex values were 7.03 ± 0.04 for TPDGA which increased steadily up to 7.98 ± 0.05 for TDDGA, for Pu 4+ , the respective value for TPDGA was 7.32 ± 0.05 which increased to 7.78 ± 0.03 for TDDGA. Thermodynamic parameters were also determined for the two-phase extraction equilibrium reaction.

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