Polymer inclusion membranes containing macrocyclic carriers for use in cation separations

Development of a novel supported liquid membrane for performing cation separations is reported. The membrane is polymerized from cellulose triacetate (CTA) with a crown ether incorporated into the polymer as a metal ion carrier. The contribution of several independent factors to overall cation transport is described. These factors include the effect of membrane thickness, concentration of the macrocycle in the membrane, and source solution concentration. Quantitative analyses indicate that the membranes adhere to transport models established for facilitated transport in traditional liquid membranes. Cation transport increases linearly with increasing carrier concentration and with the square of source solution concentration. Flux values for K+ with dicyclohexano-18-crown-6 (DC 18C6) as carrier compare favorably to values for other forms of supported liquid membranes. The membrane shows remarkable durability, maintaining constant cation flux for well in excess of three months with no signs of membrane decay or carrier loss to the aqueous phases.