Janus陶瓷膜材料设计与制备研究

Janus membranes are an emerging class of membrane materials having discrepant properties on two sides. This structure enable Janus membranes to act as fluid diodes for one-way flow regulation. Based on this property, Janus membranes have a huge potential in the treatment of oil-water emulsion by removing the minority component (oil or water) from the mixture, which can greatly improve the separation efficiency and provide a new idea for the treatment of the oil-water emulsion. To develop novel Janus membranes and their applications, this project will focus on the fabrication of Janus ceramic membranes by using porous ceramic substrates. Both the microstructure and the surface property of Janus ceramic membranes will be systematically investigated. The microstructure will be controlled by adjusting of suspension properties as well as the process parameters of coating and thermal treatment. The surface wettability will be tuned by controlling the process parameters of surface grafting and plasma etching. As prepared Janus ceramic membrane will be tested in the separation of oil-water emulsion. Three key issues will be considered and resolved in this project. The first thing is to design and fabricate the asymmetric porous ceramic substrate with a suitable microstructure for Janus membrane. The second thing is to build the relationship between the surface properties and process parameters of surface grafting and plasma etching. The third thing is to find the mass transfer mechanism in Janus ceramic membrane during the separation of oil-water emulsion. The expected results are of great scientific significance in the study of mass transfer mechanism of membrane separation processes, as well as the design and development of new separation membrane materials.

Janus膜作为一种新兴的分离膜材料，其两侧性质具有悬殊差异，可以实现液体的单向传输，具有“液体二极管”之称。利用Janus膜对液体的单向透过性，选择性地将油水乳液中占比较少的油或水分离出来，可以极大程度提高分离效率，为油水乳液的分离提供了新思路。本项目以新型Janus膜的开发及应用为出发点，采用多孔陶瓷材料为载体，通过制膜液参数及热处理工艺的控制实现对陶瓷材料表面微结构的调控，利用接枝改性及等离子刻蚀等表面性质调控方法，赋予膜材料两侧表面异同的润湿性能，并对Janus陶瓷膜材料用于油水分离过程中的性能进行考察。项目将围绕Janus陶瓷膜多孔载体微结构设计与控制、膜两侧异同的表面性质与制备工艺参数的关系、以及Janus陶瓷膜在油水分离过程中的传质机理三个关键问题展开研究。预期结果对研究基于表面性质与微结构协同控制的膜分离传质机理，设计和开发新型分离膜材料具有重要科学意义。

以Janus陶瓷膜的设计与制备为目标，研究微结构及表面性质的精密调控方法，并考察其在油水分离中的应用。在微结构调控方面，提出一种新型的陶瓷膜孔径调节方法。考察了前驱体、溶剂、热处理及底膜的性质对陶瓷膜性能的影响。以异丙醇为溶剂，四异丙醇钛为前驱体，采用原位水解法对截留分子量为5kDa的单管陶瓷膜进行孔径调节，当前驱体浓度到达20wt.%，热处理温度为350℃时，获得了截留分子量在1kDa左右的小孔径氧化钛陶瓷膜。陶瓷膜材料组成的改变不仅会影响膜材料微结构还会对膜材料的表面性质产生影响。进一步采用sol-gel法制备氧化钛掺杂的多孔氧化铝陶瓷膜。当氧化钛的添加量为10dwb%时，显著降低了氧化铝材料的相转变温度，提高了多孔陶瓷膜材料孔径的均一性。氧化钛材料的引入还提高了多孔陶瓷膜材料表面的亲水性。水滴初始接触角由18°降低到12°，同时水滴进入多孔陶瓷膜材料内部的速度也显著提升，由1.5s加速至0.9s。在表面性质调控方面，采用较为绿色的改性工艺，以乙醇为溶剂，十二烷基三甲氧基硅烷为改性剂，通过对改性溶液pH、温度、浓度等的调控，成功制备出了水滴接触角大于150°的疏水陶瓷膜。进一步采用等离子刻蚀工艺对陶瓷膜表层区域的亲疏水性进行调控，获得具有Janus结构的多孔陶瓷膜材料，其孔道呈疏水特性，表面呈亲水性，亲水层厚度约为35μm。利用Janus陶瓷膜两面异同的性质可以分别实现O/W和W/O水体系的高效分离。对于O/W体系，Janus陶瓷膜分离水中正己烷时其稳定通量显著高于常规陶瓷，表现出较好的抗污染性能。此外，还考察了Janus陶瓷膜对异辛烷和四氯化碳的分离效果，截留率均大于99%。其中，异辛烷体系的稳定水通量和正己烷体系相当，约为900Lm−2h−1bar−1，四氯化碳体系的水通量较高，约为1900Lm−2h−1bar−1。对于W/O体系，分别考察了Janus陶瓷膜对正己烷、异辛烷和四氯化碳中水分的去除效果。Janus陶瓷膜对水分的截留率均大于99%，且在重力作用下即可以实现油水分离，渗透通量大于2000Lm−2h−1bar−1。Janus陶瓷膜在油水分离领域展现了良好的应用前景。