Hierarchically Structured Nanoparticle-Free Omniphobic Membrane for High-Performance Membrane Distillation

Abstract

The functional loss of membranes caused by pore wetting, mineral scaling, or structural instability is a critical challenge in membrane distillation (MD), which primarily hinders its practical applications. Herein, we propose a novel and facile strategy to fabricate omniphobic membranes with exceptionally robust MD performance. Specifically, a substrate with a hierarchical re-entrant architecture was constructed via spray-water-assisted non-solventinduced phase separation (SWNIPS), followed by a direct fluorinated surface decoration via "thiol−ene" click chemistry. Deionized (DI) water contact angle measurements revealed an ultrahigh surface water contact angle (166.8 ± 1.8°) and an ultralow sliding angle (3.6 ± 1.1°) of the resultant membrane. Destructive abrasion cycle and ultrasonication tests confirmed its structural robustness. Moreover, the membrane possessed excellent wetting resistance, as evidenced by the prevention of membrane pore penetration by all lowsurface-tension testing liquids, allowing stable long-term MD operation to treat brine wastewater with a surfactant content of 0.6 mM. In a desalination experiment using shale gas wastewater, the omniphobic membrane exhibited robust MD performance, achieving a high water recovery ratio of ∼60% without apparent changes in water flux and permeate conductivity over the entire membrane process. Overall, our study paves the way for a nanoparticle-free methodology for the scalable fabrication of highperformance MD membranes with surface omniphobicity and structural robustness in hypersaline wastewater treatment.

High-Performance Asymmetric Porous Anion Exchange Membrane with Controllable Morphology via Solvent Evaporation and Water Etching

“…However, a thinner separation layer often leads to a weakening of the mechanical properties of the membrane. Therefore, several strategies, such as the one-pot method, spray-water-assisted nonsolvent-induced phase separation (SWNIPS), dry-jet wet spinning process, NIPS, , and SNIPS, have been developed for preparing membranes with asymmetric structures, including porous support layer and dense separation layer structures. Among these methods, the nonsolvent-induced phase separation (NIPS) method is one of the most widely studied and applied methods in the asymmetric membrane preparation field due to its simplicity, maturity, and facile preparation of membranes with pore sizes from the nanoscale to the microscale .…”

Interplay between Membrane Wetting Resistance and the Carbon Dioxide Absorption Rate in a Membrane Contactor: The Critical Role of the Gas–Liquid Interface

“…However, due to the low surface tensions, these absorbents can gradually intrude the pores of the hydrophobic membrane, inducing membrane wetting. − As a result, the CO 2 absorption rate drastically decreased . Moreover, the entire GLMC system also becomes less robust and more susceptible to fluctuations in operating conditions (e.g., fluid flow rates, temperature, and operating pressure). ,, A common strategy to overcome the challenge of membrane wetting is to develop membranes with enhanced hydrophobicity. − However, for practical GLMC applications, an ideal membrane requires not only excellent wetting resistance but also a high CO 2 absorption rate. Based on previous studies, while membranes with enhanced hydrophobicity exhibit excellent wetting resistance, the associated CO 2 absorption rates are usually low. ,, Such a phenomenon raises a question: does a trade-off between membrane wetting resistance and the CO 2 absorption rate exist in GLMC?…”