基于液态分子灌注的仿生复合多孔膜及其在膜蒸馏中的抗污染机制研究

For the improvement of antifouling property which prevents the application of membrane distillation (MD) technology, anti-adhesive membrane decorated with liquid molecules is proposed in this study based on the biological characteristics of anti-adhesive nepenthes surface. It is believed to enhance the antifouling spectrum and durability of MD membrane, and address the inherent shortcomings of conventional MD membrane, i.e. insufficient capacity to resist composite fouling, vulnerable structure, etc. Firstly, highly porous anti-adhesive nanofiber membrane is biomimetically fabricated by infusing mesoporous nanofiber membrane with PDMS (polydimethylsiloxane) liquid molecules while maintaining the interspace between nanofibers, and the structure design and performance regulation method of the biomimetic membrane is established. Afterwards, the responding relationship between the interfacial characteristics and membrane properties is explored to provide feedback suggestions for the structure design and performance optimization of the biomimetic membrane. Thirdly, the adsorption and desorption tendency of different foulants on membrane surface and the internal mechanism are evaluated, and the relationship between the antifouling properties of the biomimetic membrane and PDMS configuration is disclosed. The connections between the structural, interfacial characteristics and the antifouling characteristics are concluded to verify the antifouling mechanism of the biomimetic membrane comprehensively. This study might provide an alternative way for the fabrication of novel antifouling MD membrane and to some extent help promote the industrialization of porous membrane for membrane distillation.

本课题从限制膜蒸馏技术应用的膜污染问题出发，针对现有蒸馏用多孔膜综合抗污能力不足、结构脆弱等缺点，基于猪笼草反粘附表面的生物结构特征，提出以液态分子修饰多孔膜，仿生构筑反粘附膜表面，以提升蒸馏膜广谱抗污性和耐久性。拟以PDMS(聚二甲基硅氧烷)液态分子灌注修饰介孔纳米纤维膜，保留纤维间隙，仿生构筑高孔隙率反粘附抗污染纳米纤维膜，建立仿生膜结构设计与性能调控方法；并探究仿生膜界面特性与性能之间的响应关系，形成膜结构设计与性能优化的反馈建议；评估不同污染物在膜表面的附着与脱附倾向及其内在机制，揭示仿生膜抗污染特性与PDMS分子形态之间的内在联系，阐明膜结构特性、界面特性与抗污染特性之间的关系，综合探讨和解析仿生膜抗污染机制。本研究将为新型抗污染蒸馏膜的设计制备提供新思路，也在一定程度上推动膜蒸馏用多孔膜的产业化发展。

膜蒸馏技术在超纯水制备、废水深度处理与回用等领域前景广阔，但其工程应用仍受到多方面因素的限制，其中膜污染与膜润湿问题优为突出。为此，本项目构建了液态润滑膜表面，并探究了其表面特性、结构特性、抗污染特性，以及它们之间的关系，提示了可能的抗污染机制和影响因素。首先基于接枝链类似液态分子的较高运行能力，设计合成聚二甲基硅氧烷（PDMS）基接枝共聚物，并构建接枝态PDMS涂覆纳米纤维膜，该超疏水（水接触角150.4°）、低粘附（水滚动角4.5°）膜表面显著改善了膜耐污染性能，多孔膜对盐溶液的极限回收量提高了约1倍；而后采用溶液灌注的方法，构建液态PDMS改性纳米纤维膜，通过渗透侧加热膜蒸馏工艺揭示了其优异的分离和抗污染特性，实现了改性膜对饱和NaCl溶液的极限运行时间由1.5h延长至4.0h。原子力显微镜等测试结果表明，改性膜表面较低的粘附力（~23nN）在其抗污染机制中发挥重要作用，液态PDMS的高流动性阻碍了污染物在表面上的附着，有效减轻了膜表面结垢和膜孔润湿。此外，基于亲水层水合作用，构建了亲水薄层复合膜，揭示了水合层在膜操作过程中的抗污染特性。本项目的研究成果为膜蒸馏用新型抗污染、抗润湿多孔膜的实践应用提供了新思路和理论支持。