Solvent Extraction of Radium with Crown Ether Carboxylic Acids
作者:M. K. Beklemishev、Sadik. Elshani、C. M. Wai
DOI:10.1021/ac00092a036
日期:1994.10.15
The capabilities of a series of 11 crown ether carboxylic acids with different hydrocarbon substituents have been evaluated for solvent extraction of radium in aqueous solutions. The extraction of radium proceeds from alkaline media into chloroform solutions of the crown ethers. The extraction requires no specific counteranions and is reversible with respect to pH. Substitution of tert-butyl groups in the benzene rings of sym-dibenzo-16-crown-5-oxyacetic acid increases the lipophilicity of the macrocyclic compound and enhances the extraction efficiency for radium. Radium forms a RaL(2)-type complex with this tert-butyl-substituted crown ether carboxylic acid with a binding constant of (4.2 +/- 0.7) x 10(8).
Separation of yttrium-90 from strontium-90 by solvent extraction with ionizable crown ethers
作者:Donald J. Wood、S. Elshani、H. S. Du、N. R. Natale、C. M. Wai
DOI:10.1021/ac00058a009
日期:1993.5.15
sym-Dibenzo-16-crown-5-oxyacetic acid and its analogues are selective for the extraction of Y3+ over Sr2+ from aqueous solutions into chloroform. The selectivity and the pH range of extraction are influenced by the structure of the ligand. The size of the macrocyclic cavity, the tether length of the lariat, the attachment of alkyl functional groups to the lariat, and the identity of the ionizable group can affect selectivity and extraction efficiency. When the carboxylic acid at the terminal end of the lariat is replaced by a hydroxamic acid, the selectivity for Y3+ over Sr2+ is significantly increased. Using these ionizable crown ethers as extractants, Y-90 fractions of greater than 99.9% purity can be obtained in a single solvent extraction step from solutions of Sr-90.