SOLVENT-EXTRACTION OF LANTHANUM(III), EUROPIUM(III), AND LUTETIUM(III) WITH 5,7-DICHLORO-8-QUINOLINOL INTO CHLOROFORM IN THE ABSENCE AND PRESENCE OF TETRABUTYLAMMONIUM IONS OR TRIOCYTLPHOSPHINE OXIDE

The solvent extractions of lanthanum(III), europium(III), and lutetium(III) (M3+) in 0.1 mol dm-3 sodium nitrate solutions with 5,7-dichloro-8-quinolinol(HA) into chloroform were studied in both the absence and presence of tetrabutylammonium ions (tba+) or trioctylphosphine oxide (TOPO). In the absence of tba+ or TOPO, the extracted species were the MA3 and MA3HA (self-adduct), though MA4-tba+ was found when tba+ was added; MA3TOPO and MA3(TOPO)2 were found when TOPO was added in addition to the above mentioned two species. The anionic complex or TOPO adducts greatly enhanced the extraction. The data were statistically analyzed and the equilibrium constants for the extraction of these species, as well as the constants for the association of the HA, the A-tba+, or the TOPO on the MA3 in the organic phase, were determined. The extraction of the MA3 is better in the order LaA3 < EuA3 < LuA3. Although the values of the association constant of the HA or the TOPO on the MA3 are rather similar for the three metal chelates, the constants for A-tba+ are larger in the same order as mentioned above. Thus, the separation of these three metal ions by solvent extraction with this chelating extractant is not much affected by the addition of TOPO, but is greatly improved by the addition of tba+.