Highly Acidic Extractant, 4-Benzoyl-3-phenyl-5-isoxazolone: The Synergistic Extraction of Alkaline Earth and Alkali Metals Combined with Trioctylphosphine Oxide or Bis(diphenylphosphinyl) methane.

The synergistic extraction of alkaline earth (Mg2+, Ca2+, Sr2+, and Ba2+) and alkali metals (Li+ and Na+) with a highly acidic extractant, 4-benzoyl-3-phenyl-5-isoxazolone (HPBI), combined with a synergist, trioctylphosphine oxide (TOPO) or bis(diphenylphosphinyl)methane (BDPPM), has been examined. The results were compared with those of the analogous extractants, 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone (HPMBP) and 3-methyl-1-phenyl-4-trifluoroacetyl-5-pyrazolone (HPMTFP) which are also highly acidic extractants derived from heterocyclic compounds. Owing to the strong acidity of HPBI (pKa = 1.23), alkaline earths were extracted quantitatively from a very low pH region. Especially, alkaline earths were readily extracted at pH 2—3 with the bidentate phosphine oxide, BDPPM, as a synergist. The extraction of Li+ and Na+ with HPBI and TOPO was inferior to that with HPMBP and HPMTFP, though their acidity is weaker. In contrast to the excellent extractability of HPBI, its separation was poor. The extractability...