Synergistic Extraction of Trivalent Lanthanoids with 3-Phenyl-4-benzoyl-5-isoxazolone and Various Sulphoxides

Synergistic extraction of trivalent lanthanoids Nd, Tb and
Tm with mixtures of 3-phenyl-4-benzoyl-5-isoxazolone (HPBI)
and dioctyl sulphoxide (DOSO), bis-2-ethylhexyl sulphoxide
(B2EHSO) or diphenyl sulphoxide (DPhSO) in xylene from perchlorate solution was investigated. Lanthanoids were found to be extracted as Ln(PBI)3 with HPBI alone. In the presence of sulphoxides, Nd(III) was found to be exctracted as Nd(PBI)3 . S and Nd(PBI)3 . 2 S (where S = sulphoxide). On the other hand, Tb(III) and Tm(III) were extracted as Tb(PBI)3. S and Tm(PBI)3 . S respectively. The equilibrium constants of the synergistic species were found to increase monotonically with decreasing ionic radii of these metal ions. The addition of a sulphoxide to the metal chelate system not only enhances the extraction efficiency but also improves the selectivities among these trivalent lanthanoids.