Extraction of REE(III), U(VI), and Th(IV) from Nitric Acid Solutions with Carbamoylmethylphosphine Oxides Bearing an Additional Phosphoryl Group

Abstract The extraction of trace amounts of U(VI), Th(IV), and REE(III) from HNO3 solutions with new carbamoylmethylphosphine oxides Ph2P(O)CH2C(O)N(Bu)CH2P(O)Bu2 and Bu2P(O)CH2C(O)N(Bu)CH2P(O)Bu2, containing a phosphoryl group in the amide moiety of the molecule, in dichloroethane has been studied. The stoichiometry of the extracted complexes was determined, and the influence of the extractant structure and aqueous phase composition on the efficiency of U(VI), Th(IV), and REE(III) extraction into the organic phase was examined. It was shown that modification of diphenyl(dialkylcarbamoylmethyl)phosphine oxide by introducing an additional CH2P(O)Bu2 coordinating group via the amide nitrogen atom leads to an increase in the extraction efficiency of REE(III) ions from neutral nitrate solutions and a decrease in their extraction from nitric acid solutions. Replacement of phenyl substituents at the phosphorus atoms in the molecule of diphenyl(dibutylcarbamoylmethyl)phosphine oxide with butyl groups leads to an increase in the extraction efficiency of U(VI) and Th(IV) by the modified compounds from nitric acid solutions and a decrease in the recovery of REE(III) into the organic phase in the presence of an ionic liquid, 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide.