基于纳米纤维素晶体(CNCs)的纳滤膜构建及性质调控研究

High energy requirement is the major obstacle for the extensive application of nanofiltration (NF). To solve this problem, the properties of the NF membranes need to be improved. To adopt NF in cost-effective application, the membrane permeability and selectivity, along with the antifouling properties of the TFC NF membranes, must be improved. Cellulose nanocrystals (CNCs) are highly hydrophilic and mechanical strong, making them great candidate for membrane properties control. Thin film composite (TFC) incorporated with CNCs will be fabricated and the effects of CNCs on permeability, separation, antifouling properties and mechanical properties will be investigated. In addition, the effects of CNCs physicochemical properties on TFC NF surface chemistry and structures will be systematically studied. A facile route to control NF membrane properties will be developed by CNCs. Based on the above mentioned investigations, CNC-TFC membranes will be designed for application. For the purification requirements and characteristic components of the target water body, the physicochemical properties of the NF membranes will be regulated by CNCs. Therefore, the prepared membranes will involve great permeability and separation performance, along with excellent antifouling properties and mechanical strong. The research ideas of “Properties control-Performance investigation- Preparation guidance” (PPP) will be established by this project, which may provide theoretical and technical support for CNCs application in water filtration membranes.

能耗高是制约纳滤工艺的瓶颈问题。提升纳滤膜性质是解决纳滤能耗问题的有效手段。克服选择性/渗透性互相制约（Trade-off）效应、提升抗污染能力、加强机械性质是纳滤膜亟待突破的技术难点。纳米纤维素晶体（CNCs）具有强亲水性、高机械强度等优异物化性质，是理想的膜性能调控材料。本项目拟通过CNCs提升纳滤膜性能，探明CNCs对纳滤膜渗透性能、分离特性、抗污染能力和机械性质的影响规律；解析CNCs物化特性对纳滤膜表面性质及微观结构影响规律；结合水处理净化需求及特征污染物物化特性，以提升分离特性与透水性能为设计前提，以控制膜污染为制备原则，以强化机械性质为设计导向，实现CNCs复合膜可调控制备。本项目研究将为CNCs在膜法水处理应用建立科学理论依据，课题建立的以“性质调控-性能解析-导向构建”为研究主线的设计体系可为高性能膜材料制备提供理论基础和技术支持。

针对纳滤膜选择性/渗透性互相制约效应（Trade-off Effect）和膜污染问题，通过环境友好型纳米纤维素晶体（CNCs）改性/制备复合纳米膜。通过共混改性和表面涂覆改性调控底部支撑层理化性质，揭示支撑层对界面聚合过程传质机制与纳滤膜活性层特性影响规律。构建了基于CNCs嵌入活性层的薄膜复合纳滤膜（TFN）制备方案,首次证实了CNCs以共价键的形式附存于纳滤膜活性层中。系统研究了CNCs掺入位置对纳滤膜机械性质影响规律，比较了CNCs共混于支撑层和嵌入活性层两种方式对杨氏模量、拉伸应力、弹性模量等机械性质影响效果，得到CNCs与TFN膜的最优接合部位。开发了CNCs中间层调控策略，建立了聚多巴胺（PDA）、两性离子（SBMA）、铁-单宁酸等表面活性层改性提升纳滤膜抗污染能力方法，所制备的膜突破了纳滤膜选择性/渗透性相互制约效应，对二价盐和多种染料的截留率达到99.0%以上，同时提升过滤能力近200%。在以上工作基础上，面向不同应用需求，建立了以亚铁-过硫酸盐氧化和电化学耦合膜滤的预处理技术，通过“工艺-材料”同步调控实现净水效能和膜污染控制的同步提升。本项目为CNCs在纳滤水处理建立了较为前沿和系统的理论依据与应用支撑。