The extraction of uranium(VI), americium and europium by LIX 64 and by a mixture of LIX 64 and tri-n-octylphosphine oxide

The extraction of U(VI), Eu and Am by the aromatic main component (HA) of LIX 64N dissolved in toluene was studied at pH 3-9. The values of pHsub(1/2) for the extraction with 0.146 M HA are 4.0, 5.5 and 5.2, and those of maximum extraction are 6.0, 6.8 and 7.0 for U(VI), Eu and Am, respectively. The stoichiometry of the extracted chelates determined by the slope analysis is UOsub(2)Asub(2) and MAsub(3-n) Ysub(n) (n=1,2) for Eu and Am, the ligand Y is probably the nitrate anion. The addition of tri-n-octylphosphine oxide (TOPO) enhances the extraction of U(VI) and especially of Eu at pH<6. An Eu chelate species solvated by 2 TOPO molecules is extracted at pH 4 by the mixture of HA+TOPO, whereas the species extracted at pH 6.5 is not solvated by TOPO. (author)