Ultra-antiwetting\nMembrane for Hypersaline Water Crystallization\nin Membrane Distillation

Membrane distillation (MD) has great potential in the\nmanagement\nof hypersaline water for zero liquid discharge (ZLD) due to its high\nsalinity tolerance. However, the membrane wetting issue significantly\nrestricts its practical application. In this study, a composite membrane\ntailored for extreme concentrations and even crystallization of hypersaline\nwater is synthesized by coating a commercial hydrophobic porous membrane\nwith a composite film containing a dense polyamide layer, a cation\nexchange layer (CEL), and an anion exchange layer (AEL). When used\nin direct contact MD for treating a 100 g L<sup>–1</sup> NaCl\nhypersaline solution, the membrane achieves supersaturation of feed\nsolution and a salt crystal yield of 38.0%, with the permeate concentration\nat <5 mg L<sup>–1</sup>. The composite membrane also demonstrates\nultrahigh antiwetting stability in 360 h of long-term operation. Moreover,\nion diffusion analysis reveals that the ultrahigh wetting resistance\nof the composite membrane is attributed to the bipolar AEL and CEL\nthat eliminate ion crossover. The literature review elucidates that\nthe composite membrane is superior to state-of-the-art membranes.\nThis study demonstrates the great potential of the composite membrane\nfor direct crystallization of hypersaline water, offering a promising\napproach to filling the gap between reverse osmosis and conventional\nthermal desalination processes for ZLD application.