Optimizing microstructure of polyelectrolyte ion exchange membrane for electrodialysis

In electrodialysis process, polyelectrolyte multilayer membranes (PEMMs) are introduced as a novel ion exchange membrane (IEM), as they can adjust different membrane structures according to the requirement. However, due to the influence of membrane structure on ion permeability and its mechanism have not been deeply studied, it is difficult to select the optimal structure under service conditions, resulting in low separation efficiency or increased energy consumption. Herein, a theoretical method is proposed to establish the structure–activity relationship of PEMMs, and then select the optimal membrane structure. The fixed charge was described by a specific trigonometric function to simulate the PEMMs. The effects of different membrane structures and charges on ion permeability and flux were studied by the modified Poisson-Nernst-Planck (MPNP) equations, and the competitive control relationship between the bilayers number and the charge density of each layer on the membrane performance was found. With our theoretical model, the selectivity and efficiency of PEMMs in electrodialysis can be comprehensively evaluated to guide its design and application.