基于儿茶酚化学构建高通量“Janus”复合中空纤维膜蒸馏膜及其抗污染抗润湿机制研究

Membrane distillation (MD) technology has shown great potential for reclamation of industrial wastewater due to its merits of small footprint, low energy consumption, high water quality, and capability to utilize low-grade thermal energy. However, current hydrophobic membranes are vulnerable to membrane fouling, pore wetting and low flux in the real applications. The overarching goal of this project is to engineer a novel MD membrane with anti-fouling, anti-wetting properties and enhanced flux for water recovery from industrial wastewater. To achieve this goal, a series of composite hollow fiber membranes will be fabricated via catechol chemistry inspired approaches by coating hydrophilic layer on either outer or inner surface of polyvinylidene fluoride (PVDF) hollow fiber substrates, respectively. The surface chemistry and hierarchical structure of the composite membranes will be studied comprehensively with a range of characterization techniques. On the one hand, the effect of membrane outer layer surface charge on the anti-fouling and anti-wetting properties of the membrane will be investigated thoroughly using bench-scale direct contact membrane distillation (DCMD) experiments, quartz crystal microbalance and atomic force microscope “Colloidal Probe” technologies, respectively. On the other hand, the effect of inner surface chemistry and structure on its flux enhancement will be investigated and discussed. These results will enable us to engineer a novel hydrophilic-hydrophobic-hydrophilic “Janus” hollow fiber membrane with high flux, anti-fouling and anti-wetting properties. The findings in this project will provide significant insights into membrane fouling and wetting as well as flux enhancement mechanism, which will be beneficial for development of next-generation MD membranes in a wide range of applications such as water recovery from high saline industrial wastewater with high fouling potential.

膜蒸馏技术因具有占地面积小、能耗低、出水水质高、可以利用工业余热、废热等优点，在废水回收与利用方面具有显著前景。然而，膜蒸馏技术在应用过程中面临着疏水膜易污染、易润湿和通量低的问题。本项目针对上述问题，基于儿茶酚化学制备一系列复合中空纤维膜蒸馏膜。一方面，通过长周期直接接触膜蒸馏实验，并借助石英晶体微天平和原子力显微镜“胶体探针”表征技术，探明典型表面活性剂及乳化油与膜表面的相互作用机制，阐释原料液一侧膜表面荷电性对其抗污染润湿性能的影响机制。另一方面，通过形貌和表面性质分析，揭示渗出液一侧膜表面亲水层对膜通量提高的作用机理。基于上述两方面工作，本研究期望首次制备具有高通量、抗污染和抗润湿性能的亲水-疏水-亲水的“Janus”复合中空纤维膜蒸馏膜。本项目的研究有助于深入认识膜蒸馏膜污染润湿机制，为新型膜材料设计提供理论基础，并对解决高盐高浓工业废水回用等难题具有重要科学意义和显著应用前景。

膜蒸馏由于具有能耗低、出水水质好、可以利用工业余热、废热和光热驱动等优点，在海水淡化和高盐废水资源化与零排放处理领域具有显著应用前景。然而，传统的商业膜蒸馏膜在实际应用过程中，面临着疏水膜易污染和润湿的问题。本项目针对上述问题，基于儿茶酚化学构建了一系列抗污染抗润湿复合膜。首先，采用邻苯二酚-壳聚糖表面共沉积方法构建了超亲水膜表面，揭示了邻苯二酚在氧化剂作用下，迅速氧化成儿茶素-邻苯醌，邻苯醌进一步与壳聚糖中的氨基通过迈克尔加成或席夫碱反应形成共价键的氧化-自聚合-交联机理。其次，基于邻苯二酚/壳聚糖-聚乙烯亚胺层层自组装技术构建了具有微纳分级结构的超亲水-疏水“Janus”复合膜。复合膜表面存在大量亲水基团如羟基、羧基、醌基和胺基，具有表面超亲水，水下超疏油特性。深入解析了复合膜处理典型表面活性剂及乳化油废水时，污染物与膜表面的相互作用机制。结果表明，复合膜表面亲水性和荷电性对其抗污染抗润湿性能具有显著影响。复合膜处理含有阳离子表面活性剂废水时连续运行近一周无污染和润湿，一方面由于膜表面的亲水基团与周围水分子通过氢键作用形成水化层，有效防止表面活性剂疏水链在膜表面的吸附，另一方面，阳离子表面活性剂荷正电季胺基团与膜表面质子化胺基之间的静电斥力进一步阻碍了表面活性剂在膜表面的吸附。最后，基于连苯三酚/聚乙烯亚胺在气-水界面形成自支撑膜，构建了紧致超滤-微滤“Janus”复合膜。亲水紧致分离层对水蒸气的传质速率没有影响，紧致分离层阻碍了表面活性剂向膜内部的扩散，同时，膜表面亲水水化层防止表面活性剂在膜表面的吸附，从而赋予复合膜优异的抗污染抗润湿性能。本项目为新型抗污染膜材料设计提供了理论基础，对解决高盐有机废水资源化难题具有重要科学意义和显著应用前景。相关研究发表SCI论文5篇，其中中科院一区论文4篇，获发明专利授权2项，培养研究生4名。