面向膜蒸馏过程的水下疏油/疏水复合膜制备及其抗污染机制研究

Commercially available membranes for membrane distillation (MD) process are typically made of hydrophobic materials such as polyvinylidene fluoride (PVDF), polypropylene (PP), polyethylene (PE) and polytetrafluroethylene (PTFE). However, the hydrophobic membranes are inherently prone to fouling by oil and hydrophobic organics due to the long range hydrophobic-hydrophobic interaction. The necessity of using hydrophobic membranes in MD and the abundance of hydrophobic contaminants in wastewaters, pose a challenging dilemma that prevents MD to desalinate wastewater. In this research project, a novel composite membrane with under-water-oleophobic/hydrophobic asymmetric wettability will be developed to try to solve this key problem. The novel composite membrane is to be fabricated through non-solvent induced phase separation (NIPS) method and electrospinning technology. The separation function layer is hydrophobic and consists of PVDF-co-hexafluoropropylene (PVDF-HFP) and hydrophobic silica nano-particles (SiNPs) modified by (heptadecafluoro-1,1,2,2-tetradecyl)trimethoxysilane (FAS), which is prepared via NIPS used a microporous PTFE filter fabric as supported material. On top of the separation function layer, it is under-water-oleophobic layer, which is fabricated through electrospinning method and consists of polyvinyl alcohol (PVA) and chitosan (CS). Due to its hydrophilicity, the PVA-CS layer can prevent membrane fouling induced by oil and hydrophobic organics. It can be expected to obtain a novel composite membrane with asymmetric wettability, high mechanical strength and excellent permeability. The MD reactor will also be set up by using the spun composite membrane as the separation medium to treat the wastewater containing high salinity and high concentration organic compounds. In this research project, the functional properties of the composite membrane will be characterized in detail, the bionic lotus-like micro- and nano-scale structure in membrane surfaces is to be comprehensive investigated. Force spectroscopy for the interactions between an oil droplet and the membrane surfaces are to be measured using a force tensionmeter and atomic force microscopy, and the difference between the composite membrane and the conventional hydrophobic membrane in their interaction with a contacting oil droplet will serve to explain the difference in the fouling propensity between different membranes. This research may be of great scientific and practical significance in development of novel composite membrane and application of MD technology in wastewater treatment.

传统疏水膜材料极易受到苯、烷烃、油类等疏水性有机物污染，项目针对这一限制膜蒸馏技术应用的瓶颈问题，依据国内外最新发展趋势，结合申请人及所在课题组已有研究基础，开展水下疏油/疏水复合膜制备及其抗污染机制研究。项目将非溶剂致相转化膜制备技术与静电纺丝相结合，以高强度聚四氟乙烯微孔滤布为支撑材料，通过非溶剂致相转化法制备疏水分离功能层，利用静电纺丝技术在疏水分离功能层表面构筑水下疏油层，形成具有非对称浸润性的水下疏油、疏水双层梯级界面；调控复合膜梯级界面的微纳粗糙结构与材料组成，研制面向膜蒸馏过程的机械强度高、膜通量大、抗润湿、耐污染新型复合膜，阐释复合膜制备及其优化调控原理；定量解析污染物与膜表面间的微距作用与粘附力学机制，揭示膜表面流体及污染物微观动力学变化过程，阐明复合膜抗污染机制。项目研究可为新型复合膜材料开发及其在典型高盐高有机废水处理中的应用提供理论研究基础与科学依据。

传统疏水膜材料极易受到苯、烷烃、油类等疏水性有机物污染，项目针对这一限制膜蒸馏技术应用的瓶颈问题，实施水下疏油/疏水复合膜制备及其抗污染机制研究。项目以聚四氟乙烯（PTFE）、聚偏氟乙烯（PVDF）等商品膜为疏水亚层，通过静电纺丝、呼吸图模板法以及非溶剂致相转化等技术在疏水膜表面构筑水下疏油层，形成了具有非对称浸润性的水下疏油、疏水双层梯级界面；通过调控复合膜梯级界面的微纳粗糙结构与材料组成，结合后处理技术，最终研制出面向膜蒸馏过程的抗润湿、耐污染系列水下疏油/疏水新型复合膜，阐释了复合膜制备及其优化调控原理。研制了水下污染物力学探针，开发出污染物-膜界面相互作用力学探针测试技术，定量解析了污染物-膜表面间的相互力学作用，阐释了复合膜抗污染机制。依托界面张力测试平台，通过复合膜在低表面张力溶液中“浸渍-提拉”过程膜表面张力测试，揭示了复合膜材料抗润湿原理。以含油高盐废水为进料液，开展了复合膜在高盐高有机废水膜蒸馏浓缩减量过程的应用研究，结果表明在处理含有以油类污染物为代表的疏水性有机污染物的高盐废水时，项目开发的水下疏油/疏水复合膜具有显著的耐润湿和抗污染功能特性、复合膜展示了较好的应用前景。项目研究取得了丰富的研究成果，可为新型复合膜材料开发及其在典型高盐高有机废水处理中的应用提供理论研究基础与科学依据。