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Owing to its 100% theoretical salt rejection capability, membrane distillation (MD) has emerged as a promising seawater desalination approach to address freshwater scarcity. Ideal MD requires high vapor permeate flux established by cross-membrane temperature gradient (∆T) and excellent membrane durability. However, it’s difficult to maintain constant ∆T owing to inherent heat loss at feedwater side resulting from continuous water-to-vapor transition and prevent wetting transition-induced membrane fouling and scaling. Here, we develop a Ti3C2Tx MXene-engineered membrane that imparts efficient localized photothermal effect and strong water-repellency, achieving significant boost in freshwater production rate and stability. In addition to photothermal effect that circumvents heat loss, high electrically conductive Ti3C2Tx MXene also allows for self-assembly of uniform hierarchical polymeric nanospheres on its surface via electrostatic spraying, transforming intrinsic hydrophilicity into superhydrophobicity. This interfacial engineering renders energy-efficient and hypersaline-stable photothermal membrane distillation with a high water production rate under one sun irradiation.

The electrospinning technique as a method for fabricating hydrophobic membranes for membrane distillation (MD) has received much attention in recent times. In this study, TiO 2 functionalized with 1H,1H,2H,2H-perfluorooctyltriethoxysilane was added directly to the dope solution for electrospinning in order to increase the hydrophobicity of the resulting MD membranes. Three concentrations (10%, 15% and 20%) of polyvinylidene fluoride-cohexafluoropropylene (PH) dope solution were used for electrospinning with various amounts of TiO 2 (1%, 5% and 10%) to generate nanofibers. The electrospun nanofiber membrane (ENM) of 20% PH with 10% TiO 2 exhibited the highest surface hydrophobicity (contact angle = 149°) resulting from good dispersion of the TiO 2 particles, while the highest liquid entry pressure of 194.5 kPa was observed for the ENM comprising 10% PH with 10% TiO 2 due to its reduced pore sizes. Furthermore, the ENMs containing 10% TiO 2 exhibited better flux and stable salt rejection than commercial and ENMs without TiO 2. Notably, there was no severe wetting in the 20% PH ENM with 10% TiO 2 over seven days of operation, despite the high salt concentration (7.0 wt% NaCl) of the feed water.

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