Highly efficient homogeneous liquid-liquid extraction of rare earth metal ions from perfluorocarboxylate surfactant solutions using ion-pair phase separation systems

Trivalent rare earth metal ions were extracted from weakly acidic aqueous s olution using a homogeneous liquid-liquid extraction method based on the io n-pair phase separation phenomenon of perfluorooctanoate ion with tetrabuty lammonium ion. Under experimental conditions, the extraction percentage of each rare earth metal was ca. 80-99 % and the maximum concentration factor was ca. 330-fold (90 mul of liquid phase residue from 30 cm(3) of aqueous s olution). The extracted species and the extraction mechanism for the propos ed method were estimated using a normal solvent extraction system in the wa ter/ethyl acetate system. As a result, the extracted species of each rare e arth metal ion was assumed to be a 1:3 species such as the complex salt of a rare earth metal ion and the perfluorooctanoate ion.