Ion-exchange membranes, IEMs, are employed in electrodialysis desalination, but the membranes are confined to purifying brackish water salinities and below. This is because the charge-selective mechanism of Donnan exclusion is overwhelmed in higher ionic strength environments and the osmosis of water across the membrane detrimentally lowers the process productivity. These limitations restrict the broader application of IEM for emerging water challenges such as brine management. First, we analyze the influences of principal membrane characteristics on water recovery and salt removal performance in high-salinity electrodialysis (HSED) desalination. Through the systematic evaluation, the critical electrical, structural, and chemical properties required to realize HSED are identified. Findings of the analysis are then thoughtfully utilized to inform the development of IEMs customized for hypersalinities. When challenged in 4.0 mol/L aqueous NaCl solutions, the fabricated IEMs demonstrated remarkable ability to retain the charge-selective mechanism over conventional membranes. Further, the tailored IEMs exhibited improved suppression of transmembrane osmotic water flux compared to the controls. The development of customized IEMs capable of achieving high performance in hypersaline feed streams can realized the electrodialysis desalination of brine streams, a growing environmental challenge that is technologically-underserved by existing methods.

High-salinity electrodialysis with rationally-designed ion-exchange membranes

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