Synergistic solvent extraction of trivalent lanthanides and actinide by mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazalone-5 and neutral oxo-donors

The synergistic solvent extraction of trivalent lanthanides such as La, Eu and Lu and a trivalent actinide, Am, has been studied with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazalone-5 (HPMBP) and bis(2-ethylhexyl) sulphoxide (B2EHSO) or octyl (phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in xylene. The extraction data have been analysed by both graphical and theoretical methods by taking into account aqueous phase speciation and all plausible complexes extracted into the organic phase. With HPMBP alone all the trivalent metal ions form M(PMBP)3 - HPMBP type self adducts. With B2EHSO as a neutral donor, the synergistic adduct species are M(PMBP)3 - B2EHSO and M(PMBP)3 - 2 B2EHSO (where M = La, Eu, Lu and Am), whereas with CMPO as a neutral donor the only complex extracted into the organic phase is M(PMBP)3 - CMPO. The synergistic extraction constants of the above species which were deduced by non-linear regression analysis are found to increase monotonically with decreasing ionic radii of these metal ions. 27 refs., 5 figs., 4 tabs