Selective sorption of alkali-metal cations by carboxylic acid resins containing acyclic or cyclic polyether units

Novel ion-exchange resins have been prepared by condensation polymerization with formaldehyde in formic acid of three polyether carboxylic acids which possess two benzo group substituents. The selectivities and efficiencies of competitive alkali-metal cation sorption from aqueous solutions by these polyether carboxylic acid resins are strongly influenced by (1) the pH of the aqueous solution, (2) the acyclic or cyclic nature of the polyether unit, and (3) the conformational positioning of the carboxylic acid group in the resins derived from cyclic polyether (crown ether) compounds. Good sorption selectivity for Na{sup +} was observed for dibenzo-16-crown-5 resin 3 in which the pendant carboxylic acid group is oriented over the polyether cavity. Resin 3 was utilized as a stationary phase for selective column concentration of Na{sup +} from dilute aqueous solution.