A novel concept of hierarchical cation exchange membrane fabricated from commodity precursors through an easily scalable process

Hierarchical cation exchange membranes were fabricated by blade coating and UV crosslinking a thin layer of ionomer on top of a porous substrate, and used for desalination in an ED process. The ionomer layer was obtained by radically reacting a mixture of 4-vinylbenzene sulfonate lithium salt and urethane acrylate oligomers. The resulting membranes reached a performance approaching state-of-the-art materials. They are produced at remarkably lower cost due to the use of precursors common in the coating industry and employing a solvent free easily scalable fabrication process. Functional coatings with different crosslinking degrees and ion exchange capacity were fabricated, and the effect of these properties on the membrane performance was explored. The best conducting membranes, with ASR below 5 Ω cm2, were obtained for highly hydrophilic coatings. The fabrication method allowed to reach IEC values of 1.05 mmol/g at a WU of 109%. The selectivity of the membranes was observed to increase with denser crosslinking and growing IEC of the coating. In ED experiments current efficiency values up to 88.1% were obtained (vs. 91.7%–93.1% for commercial membranes). A solid proof of concept for the use of this type of low-cost material in electrodialysis was established, which opens a viable pathway for scaling up in view of industrial application.