SEPARATION OF Y-90 FROM SR-90 BY SOLVENT-EXTRACTION WITH IONIZABLE CROWN-ETHERS

sym-Dibenzo-16-crown-5-oxyacetic acid and its analogues are selective for the extraction of Y3+ over Sr2+ from aqueous solutions into chloro form. 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 sel ectivity and extraction efficiency. When the carboxylic acid at the te rminal end of the lariat is replaced by a hydroxamic acid, the selecti vity for Y3+ over Sr2+ is significantly increased. Using these ionizab le crown ethers as extractants, Y-90 fractions of greater than 99.9% p urity can be obtained in a single solvent extraction step from solutio ns of Sr-90.