(125a) Concentration Dependence of Ion Exchange Membrane Permselectivity: Modelling and Experimental Validation

The separation performance and energy efficiency of ion exchange membrane (IEM)-based processes, such as electrodialysis and reverse electrodialysis, are a strong function of the IEMs ability to simultaneously allow the passage of counter-ions and prevent the passage of co-ions, a property termed “permselectivity”. While it is well known that permselectivity is a function of the ionic concentration of the solutions in contact with the IEMs, permselectivity is often reported only at specific testing conditions (e.g., 0.5M/0.1M NaCl or KCl as prevalent concentration gradients). Therefore, modelling tools are needed that enable prediction of IEM permselectivity at application-relevant conditions. Through modelling based on the extended Nernst-Planck equation and experimental measurements of permselectivity, we demonstrate that accurate, quantitative predictions of IEM permselectivity as a function of external salt concentrations are possible. Further, we demonstrate that accurate predictions require knowledge of only four easily measured membrane properties: water uptake, water permeability, charge, and thickness.