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Studies of the size-selective extraction of alkali metal ions by the synergistic extraction system, crown ether-di(2-ethylhexyl) phosphoric acid-benzene

Journal Article · · Sep. Sci. Technol.; (United States)

In order to take practical advantage of the size-selective cation-coordinating ability of the cyclic polyethers (crown ethers), experiments seeking a means of avoiding the problem of solubilizing a mineral-acid anion in a nonpolar organic diluent were performed. Mixtures of several known extractants and crown ethers were tried. Results presented indicate that organic soluble cation exchangers mixed in solution with crown ethers produce a synergistic extractant mixture that largely exhibits the size-selective properties expected of the crown ether. Data are presented for the extraction of macro concentrations of alkali metals by di(2-ethylhexyl) phosphoric acid - dicyclohexyl-18-crown-6 mixtures at a single pH, and at nonloading condition (..sigma.. metal conc < 0.04 M) as a function of pH, 2 to 6. In both cases potassium is synergized most strongly presumably because of its best fit to the crown ether cavity. Other data indicate, however, that the size-fit principle is not as consistent for all alkali metal ions and crown ethers as for potassium and dicyclohexyl-18-crown-6. Other effects such as competition for ion hydration and aqueous-phase distribution of the complex may have important effects that have not been elucidated.

DOE Contract Number:
W-7405-ENG-26
OSTI ID:
7149338
Journal Information:
Sep. Sci. Technol.; (United States), Journal Name: Sep. Sci. Technol.; (United States) Vol. 15:4; ISSN SSTED
Country of Publication:
United States
Language:
English