近日，大湾区城市环境安全与绿色发展教育部重点实验室学术骨干王樟新教授团队和范德堡大学林士弘教授团队在在环境领域顶级期刊《Environmental Science & Technology》上发表了题为“Janus Membrane with a Dense Hydrophilic Surface Layer for Robust Fouling and Wetting Resistance in Membrane Distillation: New Insights into Wetting Resistance”的学术论文。

 论文DOI：https://doi.org/10.1021/acs.est.1c01638

全球性淡水资源短缺已然引起了广泛关注，废水/海水资源化利用的需求日益增长。膜蒸馏作为新兴的热法脱盐技术，能够处理高盐废水。然而，膜蒸馏的实际应用面临着两大难题——膜润湿和膜污染。为了同时解决膜污染和膜润湿的难题，一种以全疏膜为基底，同时具有超亲水皮层的Janus膜被研发了出来。然而，由于全疏膜基底的制备非常复杂，该类Janus膜的大规模制备及应用依旧极为困难。

近来，受到纳滤膜可以去除废水中表面活性剂的启发，一种以PVDF膜为基底，表面带有致密纳滤皮层的Janus膜被研发出来了。虽然该类Janus膜可同时实现抗润湿和抗污染，但是其制备方法依然较为复杂，难以大规模商业化。因此，亟需一种简单可实现商业化的方法去制备具有极强抗润湿和抗污染能力的Janus膜，以应对现有的困境。与此同时，除了关注Janus膜本身具备的强大抗性，其对于抗润湿和抗污染的机理也值得深入研究，因为这可以为未来Janus膜的进一步研发提供重要指导。

在本研究中，我们提出了一种简单且可实现大规模制备Janus膜的方法，以同时解决膜蒸馏过程中膜润湿和膜污染问题。具体来讲，我们在商品化的PVDF膜表面喷涂一层聚乙烯醇（PVA）并进行表面交联，制备了一种具有超亲水的致密PVA表面皮层、疏水微孔膜基底的Janus膜 （图1）。通过膜结构表征与膜蒸馏实验测试，我们证实了所制备的Janus膜可以同时抵御膜污染和膜润湿。我们进一步通过扩散实验、液体突破压力测试与油探针力谱等实验，阐释了该Janus膜抗润湿和抗污染的机理。

英文摘要：

Although membrane distillation (MD) has been identified as a promising technology to treat hypersaline wastewaters, its practical applications face two prominent challenges: membrane wetting and fouling. Herein, we report a facile and scalable approach for fabricating a Janus MD membrane comprising a dense polyvinyl alcohol (PVA) surface layer and a hydrophobic polyvinylidene fluoride (PVDF) membrane substrate. By testing the Janus membrane in direct contact MD experiments using feeds containing a sodium dodecyl sulfate (SDS) surfactant or/and mineral oil, we demonstrated that the dense Janus membrane can simultaneously resist wetting and fouling. This method represents the simplest approach to date for fabricating MD membranes with simultaneous wetting and fouling resistance. Importantly, we also unveil the mechanism of wetting resistance by measuring the breakthrough pressure and surfactant permeation (through the PVA layer) and found that wetting resistance imparted by a dense hydrophilic layer is attributable to capillary pressure. This new insight will potentially change the paradigm of fabricating wetting-resistant membranes and enable robust applications of MD and other membrane contactor processes facing challenges of pore wetting or/and membrane fouling.