Extraction of U(VI), Th(IV), and REE(III) from Nitric Acid Solutions with 2,6-Bis(diphenylphosphorylmethyl)pyridine N-Oxide

Abstract

The extraction of microamounts of U(VI), Th(IV), and REE(III) from HNO₃ solutions in the form of complexes with 2,6-bis(diphenylphosphorylmethyl)pyridine N-oxide (I) was studied in relation to the kind of organic diluent and to the HNO₃ concentration in the equilibrium aqueous phase. The stoichiometry of the extractable complexes was determined. With respect to the ability to extract Th(IV) and REE(III), compound I considerably surpasses tetraphenylmethylenediphosphine dioxide and tetraalkyl-substituted analogs of I.