Extraction of alkali metal cations by lipophilic dibenzo-14-crown-4-carboxylic acids
Journal Article
·
· Separation Science and Technology
- Oak Ridge National Laboratory, TN (United States)
The extraction of alkali metal cations by the lipophilic crown ether, bis-t-octylbenzo-14-crown-4 (BOB14C4), three derivatives of BOB14C4 having pendant carboxylic acid sidearms, and a lipophilic carboxylic acid, 2-methyl-2-heptylnonanoic acid (HMHN) was studied by two-phase potentiometric titration and ion-chromatography. The lipophilic, ionizable crown ethers, BOB14C4-acetic acid (BOB14C4AA), BOB14C4-propanoic acid (BOB14C4PA), and BOB14C4-oxyacetic acid (BOB14C40AA) extract cations efficiently from aqueous mixed alkali metal chloride solutions into 1-octanol by an ion-exchange mechanism in the range p(H) > 7, as does HMHN. The mode of attachment of the ionizable sidearm, via an ether linkage (BOB14C4OAA) versus a carbon linkage (BOB14C4AA and BOB14C4PA), has a significant effect on the cation selectivity and extraction efficiency of these extractants. BOB14C4 exhibits no pH dependent extraction behavior and has no significant effect on the extraction of alkali metal cations by HMHN in a mixture of these two compounds. Although BOB14C4AA and BOB14C4PA extract cations at lower pH than HMHN, all three compounds exhibit similar selectivity for Li+ over Na+, K+, Rb+, and Cs+. A significant reversal in selectivity is observed with BOB14C40AA, which extracts Na+ and K+ selectivity over Li+, Rb+, and Cs+ and at significantly lower pH than BOB14C4AA, BOB14C4PA, or HMHN. The unique behavior of BOB14C4OAA may be attributed to the presence of ether linkage between the crown ether and the pendant carboxylic acid.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 88686
- Report Number(s):
- CONF-931043--
- Journal Information:
- Separation Science and Technology, Journal Name: Separation Science and Technology Journal Issue: 7-9 Vol. 30; ISSN 0149-6395; ISSN SSTEDS
- Country of Publication:
- United States
- Language:
- English
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