IMPROVED EXTRACTION SEPARATION OF ALKALINE-EARTHS AND LANTHANIDES USING CROWN-ETHERS AS ION SIZE-SELECTIVE MASKING REAGENTS - A NOVEL MACROCYCLE APPLICATION

Improved extraction-separation can be achieved in the extractions of a lkaline earths with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone and tri-n -octylphosphine oxide and of lanthanides with bis(2-ethylhexyl)phospho ric acid. In both cases, by adding 18-crown-6 to the aqueous phase as an ion size selective masking reagent, the extractions of metal ions w ith larger ionic radii shifted to the higher pH region, Consequently, the separation among the metal ions was enhanced. Cyclohexane was empl oyed for the organic phase, The distribution ratio of 18-crown-6 betwe en cyclohexane and water is low, i,e,, 18-crown-6 remains quantitative ly in the aqueous phase. The synergistic extraction of alkaline earths with 18-crown-6 was observed along with that with TOPO being subject to the masking reaction when benzene was used for the organic phase, t o which the distribution of 18-crown-6 is not negligible.