新型石墨烯基正渗透膜及水分子流动机理研究

The problem of water shortage is becoming a more and more serious problem in the world, and the technology of forward osmosis (FO) membrane separation is a kind of low energy consumption wastewater treatment. In the subject, graphene oxide and titanium dioxide of super hydrophilic nanoparticles (GO-TiO2) were used to synthesis of a novel graphene based forward osmosis membrane, and the flow behavior of water molecules between the graphene layers of membrane was also studied. We explained the flow characteristic of water molecules in different composite laminated structure for solving the problem of low FO water flux in wastewater treatment process. The new water channel of FO membrane were difference compared to traditional water channel of polymer in this study. The super hydrophilic UV induced and the size of TiO2 nano particles grafted on graphene oxide controlled the water permeability of FO membrane. And the content changes of water molecules between the composite sheet layers were analyzed by NMR spectrometer and near-infrared analyzer. We determined the relationship between composite laminated structure and layer spacing and analyzed the interactions between water molecules and the chemical structure of GO-TiO2 layer. In this research, the flow characteristics of water molecules within the water channel of graphene membrane provide a theoretical basis in preparation of FO membrane with high water flux in future.

世界水资源短缺问题日益严重，正渗透（forward osmosis, FO）膜分离技术是一种低能耗的污水资源化水分离技术。本课题利用氧化石墨烯-超亲水二氧化钛纳米颗粒（GO-TiO2）复合材料制备一种新型石墨烯基FO膜，并以此膜为基础研究水分子层在石墨烯片层之间的渗透流动行为，并解释不同复合片层结构下的水分子流动特性，为解决FO污水资源化过程中低通量问题提供新思路和理论基础。本研究构建的新型FO膜水通道与传统高分子水通道不同，通过改变接枝到GO上的TiO2纳米颗粒大小以及紫外光诱导的超亲水性来实现对FO膜水通道渗透性能的调控，并利用核磁共振以及近红外水分子运动分析等技术研究水分子在复合片层间的含量变化，确定其与复合片层结构及层间距大小之间的关系；分析GO-TiO2化学结构与水分子层之间的相互作用。本课题对于石墨烯膜水通道内的水分子流动特性的研究为今后制备大通量高性能FO膜提供理论基础。

正渗透膜分离技术只依靠渗透压，无需施加外界压力，具有能耗低、无二次污染等优点，符合节能要求，发展潜力巨大。石墨烯由于其独特的二维碳原子晶体结构在分离膜领域成为研究热点之一。本研究将二者的性质结合起来，并通过复合二氧化钛颗粒对新型石墨烯正渗透膜材料进行了探索，本课题在前期研究的基础上，获得一系列原创性成果（1）利用二氧化钛的超亲水性减弱了水分子在膜内的流动阻力，探讨了自组装过程中反应条件对于复合膜结构的影响；（2）通过控制氧化石墨烯片层间距、碳纳米管的碳骨架结构以及利用氧化石墨烯表面含氧基团荷电性对盐离子的唐南排斥效应，探讨了膜内水分子流动机理，揭示了其结构与分离性能之间的关系。得到性能优化的正渗透膜最大水通量达到29 LMH·MPa-1；（3）对聚酰胺正渗透膜的构效关系进行了讨论，总结了其分子结构，表面形貌与分离性能的关系。本研究所得到的理论模型与实验数据为正渗透膜分子层面的优化设计提供了理论与应用基础，同时对于纳米复合膜材料科学具有重要理论价值。