Abstract Membrane distillation (MD) is a promising technique for desalinating brine and purifying wastewater but low water flux and severe membrane fouling always plague its practical application. Developing new membranes with both high flux and fouling resistance is highly desirable. Here, a hydrophilic/hydrophobic Janus membrane that can simultaneously achieve rapid and robust desalination via vacuum MD (VMD) was designed and fabricated by architecting a polydopamine-based hydrophilic surface coating on a commercial polytetrafluoroethylene (PTFE) membrane. Results demonstrated that such hydrophilic coating had the unique dual function: (1) boosting water evaporation via tuning the state of confined water and timely water replenishment and (2) providing a hierarchical layer with highly underwater oleophobicity. Due to the synergistic effect, the Janus membrane flux soared to 84.3 ± 3.4 kg m−2 h−1 from 19.8 ± 1.5 kg m−2 h−1 of the commercial PTFE membrane when treating a 3.5 wt% NaCl solution (70 °C, −90 kPa), achieving an unprecedented 325.7% of flux enhancement, while also exhibiting long-term stability when desalinating oil-containing brine. Conversely, severe oil fouling occurred on the pristine PTFE membrane, quickly leading to near-zero flux. This work may provide a new platform and methodology for designing high-performance membranes for MD desalination.

中文翻译：

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具有双功能表面涂层的亲水/疏水 Janus 膜，用于快速、稳健的膜蒸馏脱盐

摘要 膜蒸馏（MD）是一种很有前途的盐水淡化和废水净化技术，但水通量低和膜污染严重一直困扰着其实际应用。开发具有高通量和抗污染性的新膜是非常需要的。在这里，通过在商用聚四氟乙烯 (PTFE) 膜上构建基于聚多巴胺的亲水表面涂层，设计和制造了一种亲水/疏水的 Janus 膜，该膜可以通过真空 MD (VMD) 同时实现快速和稳健的脱盐。结果表明，这种亲水涂层具有独特的双重功能：（1）通过调节承压水的状态和及时补水来促进水蒸发；（2）提供具有高度水下疏油性的分层层。由于协同效应，当处理 3.5 wt% NaCl 溶液 (70 °C, -90 kPa) 时，Janus 膜通量从商用 PTFE 膜的 19.8 ± 1.5 kg m-2 h-1 飙升至 84.3 ± 3.4 kg m-2 h-1，实现了前所未有的 325.7% 的通量增强，同时在脱盐含油盐水时也表现出长期稳定性。相反，原始 PTFE 膜上发生严重的油污，很快导致通量接近于零。这项工作可能为设计用于 MD 脱盐的高性能膜提供新的平台和方法。原始的 PTFE 膜上发生了严重的油污，很快导致通量接近于零。这项工作可能为设计用于 MD 脱盐的高性能膜提供新的平台和方法。原始的 PTFE 膜上发生了严重的油污，很快导致通量接近于零。这项工作可能为设计用于 MD 脱盐的高性能膜提供新的平台和方法。