Minimize the trade-off between wetting resistance and water permeance in membrane distillation with ion-sieving coating layer

LJ Jiang and L Chen and L Zhu, CHEMICAL ENGINEERING JOURNAL, 430, 133165 (2022).

DOI: 10.1016/j.cej.2021.133165

The conventional hydrophobic membranes in membrane distillation system are prone to be wetted by surfactants. Meanwhile, there is a trade-off between wetting resistance and water permeance on advanced membrane materials, such as Janus membrane and omniphobic membrane. To overcome this dilemma, a composite membrane with ion-sieving layer was fabricated by self-assembling MXene nanosheets on the commercial PTFE membrane. The coating layer exhibited ordered subnanometer channels, and the stability can be further enhanced by intercalating Ca2+ ions between the two- dimensional MXene pieces. The experiments using SDS-NaCl solution and realistic wastewater demonstrated that such modification can provide an excellent anti-wetting property without sacrificing the permeate flux. The anti-wetting property can be attributed to the ion-sieving effect, which created an energy barrier by the partial dehydration of ions. Simultaneously, the ion-sieving layer has a much lower water transfer resistance than the coating layer on conventional Janus membrane due to its ordered nanostructure, and the hydrophobic substrate can provide a larger effective evaporation interface compared with the omniphobic membrane. This article attempts to provide an insight into the novel membrane distillation system coupled with ion-sieving effect, and paves the way for developing advanced membranes for treating wastewater with low surface tension contaminants.

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