EXTRACTION OF Pu(IV) AND Th(IV) CHLORIDES WITH n-OCTYL(PHENYL)-N,N-DIISOBUTYLCARBAMOYLMETHYLPHOSPHINE OXIDE IN TETRACHLOROETHYLENE∗

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Abstract
The distribution of trace and macro amounts of Pu(IV) and Th(IV) chlorides between solutions of n-octyl(phenyl)-N,N-diiso-butylcarbamoylmethylphosphlne oxide in tetrachloroethylene and aqueous solutions of hydrochloric acid was studied. In extracting macro quantities of Pu(IV), the solvent can be loaded up to a Pu(IV)/extractant ratio of 1:2, but small amounts of a solid are formed which strongly retard phase disengagement. The disengaging problem can be overcome by using a phase modifier such as tributyl phosphate or dibutyl butylphosphonate. Both modifiers only slightly suppress the efficiency of the Pu(IV) extraction. Th(IV) is less extractable than Pu(IV) and a Th(IV) extractant ratio of only 1:3 can be reached even In the presence of excess Th(IV). Both Pu(IV) and Th(IV) form a third phase (second organic phase) at high concentrations of hydrochloric acid or in the presence of chlorides which salt-out hydrochloric acid from the aqueous phase.