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 method. 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 extractant in different diluents. It appears that nitrobenzene, a diluent with high dielectric constant, favors the extraction of the complexes. Extraction rates of the K22DAP complexes of lanthanides were investigated at pH 5.5 and 8.0 with TTA in chloroform. The rates of extraction are found to be dependent upon the nature of the extracted species. Competitive extractions were carried out to see if selective extractions could be achieved.
Lanthanide Selective Sorbents: Self-Assembled Monolayers on Mesoporous Supports (SAMMS)
Through the marriage of mesoporous ceramics with self-assembled monolayer chemistry, the genesis of a powerful new class of environmental sorbent materials has been realized. By coating the mesoporous ceramic backbone with a monolayer terminated with a lanthanide-selective ligand, it is possible to couple high lanthanide binding affinity with the high loading capacity (resulting from the extremely high surface area of the support). This lanthanide-selective ligand field is created by pairing a “hard” anionic Lewis base with a suitable synergistic ligand, in a favorable chelating geometry. Details of the synthesis, characterization, lanthanide binding studies, binding kinetics, competition experiments and sorbent regeneration studies are summarized.
A summary of TTA extraction coefficients
Abstract Extraction with organic solutions of 2-thenoyltrifluoroacetone (TTA) has proved to be a versatile and powerful method for radiochemical separations. A summary of the data in the literature is presented. In general, the logarithm of the extraction coefficient is linear with pH at constant TTA concentration. The slope of this linear relationship and the pH of 50 per cent extraction for 0·2 M TTA in benzene are presented for forty-eight elements in the form of a periodic table. A graph is given by which one may quickly estimate per cent extraction as a function of pH. An equation for the variation of extraction with TTA concentration is given and the effect of changing the organic solvent is discussed. New experimental data are presented for the extraction of Pa(V) and Fe(III) from hydrochloric acid.