Extraction of REE(III), U(VI), and Th(IV) from HNO3 and HClO4 solutions with (α-pyridyl)tetraphenylmethylenediphosphine N,P,P'-trioxide

Abstract

Extraction of microamounts of U(VI), Th(IV), and REE(III) from HNO3 and HClO4 solutions with solutions of (α-pyridyl)tetraphenylmethylenediphosphine N,P,P'-trioxide in dichloroethane was studied. The stoichiometry of the extractable complexes was determined, and the influence of the extraction structure and aqueous phase composition on the efficiency and selectivity of the extraction of U(VI), Th(IV), and REE(III) into the organic phase was studied. Introduction of the pyridine N-oxide fragment into the methylene bridge of the tetraphenylmethylenediphosphine dioxide molecule to obtain (α-pyridyl)tetraphenylmethylenediphosphine N,P,P'-trioxide leads to a decrease in its ability to extract U(VI), Th(IV), and REE(III) from nitric acid solutions, whereas the U/REE separation factors increase. The REE(III) extraction efficiency considerably increases in going from nitric acid to perchloric acid solutions.