Influence of the Structure of (О-Phenylenoxymethylene)diphosphine Dioxides on Their Extraction Ability to U(VI), Th(IV), and REE(III) in Nitric Acid Media

Extraction of microquantites of U(VI), Th(IV), and REE(III) from nitric acid solutions with solutions of ( o- phenyleneoxymethylene)diphosphine dioxides with phenyl and butyl substituents at the phosphorus atom in the OCH 2 P(O)R 2 fragment was studied. The stoichiometry of the extracted complexes was determined. The influence of the extractant structure, the concentration of HNO 3 in the aqueous phase, and the nature of the organic solvent on the extraction efficiency of REE(III), U(VI), and Th(IV) into the organic phase is considered. The presented data showed that the phosphoryl groups in the ( o- phenyleneoxymethylene)diphosphine dioxide molecule are not equivalent. In contrast to the noticeable decrease in the efficiency of REE(III) extraction from nitric acid solutions when phenyl radicals are replaced by butyl radicals in the phosphoryl group P(O)R 2 directly attached to the phenylene ring, the replacement of the OCH 2 P(O)Ph 2 fragment in the dioxide molecule by OCH 2 P(O)Bu 2 only slightly reduces the REE(III) distribution factors in such media. At the same time, the extraction efficiency of U(VI) and Th(IV) from nitric acid solutions increases with this replacement.