Effect of Diffusion and Migration on the Selectivity of a Polymer Inclusion Membrane Containing Dicyclohexano-18-crown-6

Ion transport and selectivity are compared across a polymer inclusion membrane (PIM) containing dicyclohexano-18-crown-6 (DCH18C6, K+ selective) under two driving forces: concentration gradient (diffusion) and electrical potential gradient (migration). The K+ flux is much larger under diffusion (140 mmol cm−2 h−1) than under migration (≈4 mmol cm−2 h−1). The selectivity of NH4 + over K+ is 86.0 for diffusion and 1.0 for migration. The selectivity of Na+ over K+ is 21.4 for diffusion and 1.16 for migration. Migration transport might induce a change in the orientation of DCH18C6 and reduce selectivity. Therefore, it is more favorable to apply diffusion rather than migration