Selective separation of alkali metal cations by bulk chloroform membranes containing lipophilic crown ether phosphonic acid monoethyl esters |
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| Affiliation: | 1. Department of Public Health, Temple University, 1301 Cecil B. Moore Avenue, Ritter Annex, Philadelphia, PA 19122, United States;2. Department of Biological Sciences, East Tennessee State University, Johnson City, TN 37614, United States;1. A.E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center, Russian Academy of Sciences, Kazan, Russia;2. AlphaChem Innovations Inc., Alachua, FL, USA |
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| Abstract: | A series of crown ether phosphonic acid monoethyl esters with crown ether ring size variation from 12-crown-4 to 24-crown-8 is used in bulk chloroform membranes to separate alkali metal cations from mixtures. Selective proton-coupled transport of alkali metal cations from weakly alkaline aqueous phases is achieved. With individual ionizable crown ether carriers, transport selectivity for Li+, Na+, K+, and Rb+-Cs+ is achieved. A closely related lipophilic phosphonic acid monoethyl ester derivative with a cyclohexyl unit in place of the crown ether exhibits transport selectivity for Li+. However, the corresponding phosphonic acid diethyl ester is devoid of transport activity. Effects of structural variation within the carrier upon the selectivity and efficiency of competitive alkali metal cation transport are assessed. |
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