STUDIES ON COMPLEXATION AND SOLVENT-EXTRACTION OF LANTHANIDES IN THE PRESENCE OF DIAZA-18-CROWN-6-DI-ISOPROPIONIC ACID

Stability constants of some lanthanides with K22DAP (diaza-18-crown-6- diisopropionic acid) were determined by potentiometric titration metho d. The logarithmic values of these constants for La(III), Nd(III), Sm( III), Gd(III), Tb(III), Dy(III), Er(III), and Lu(III) are 11.14, 11.43 , 11.78, 11.74, 11.95, 12.09; 11.49, and 10.88, respectively. Solvent extraction studies were carried out on the K22DAP complexes of La(III) , Nd(III) and Lu(III) using TTA (thenoyltrifluoroacetone) as an extrac tant in different diluents. It appears that nitrobenzene, a diluent wi th high dielectric constant, favors the extraction of the complexes. E xtraction rates of the K22DAP complexes of lanthanides were investigat ed at pH 5.5 and 8.0 with TTA in chloroform. The rates of extraction a re found to be dependent upon the nature of the extracted species. Com petitive extractions were carried out to see if selective extractions could be achieved. (C) 1997 Elsevier Science B.V.