Extraction of rare-earth elements from nitric acid solutions with bidentate neutral organophosphorus compounds in the presence of l-butyl-3-methylimidazolium hexafluorophosphate

The distribution of microamounts of La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y nitrates between aqueous HNO 3 solutions and solutions of tetraphenylmethylenediphosphine dioxide, diphenyl(diethylcarbamoylmethyl)phosphine oxide, and dibutyl(diethylcarbamoylmethyl)phosphine oxide in organic solvents in the presence of l-butyl-3-methylimidazolium hexafluorophosphate (BMImPF 6 ) was studied. The stoichiometry of the extractable complexes was determined. The influence of the HNO 3 concentration and the nature of the extractant and organic solvent on the synergistic effect observed in the REE extraction in the presence of BMImPF 6 in the organic phase was analyzed. The possibility of using a macroporous polymeric sorbent impregnated with a mixture of tetraphenylmethylenediphosphine dioxide and BMImPF 6 for the recovery of REE(III), U(VI), and Th(IV) from HNO 3 solution was demonstrated.