压电聚偏氟乙烯膜的构筑及其原位振动抗污染机理研究

Poly(vinylidene fluoride) (PVDF) is a membrane material widely employed in water treatment application. Membrane fouling dramatically decreases the permeation flux of PVDF membrane during application process. To improve membrane’s anti-fouling property, ionic liquid was proposed to induce β phase formation during PVDF membrane fabrication. After poling, the membrane will be endowed piezoelectric property, which will cause in situ vibration when AC signal is applied. The synergistic effect of in situ vibration and fluid mechanics will be realized to primarily control membrane fouling. Thermally induced phase separation method will be employed to fabricate PVDF membrane. Due to the high electrostatic interaction between PVDF molecular and ionic liquid, β phase crystals are expected to be formed. Then, strong DC electric field will be conducted to polarize the membrane to make the PVDF membrane piezoelectric and in situ vibrates in the AC electric field. The β phase formation mechanism induced by ionic liquid, the effects of ionic liquid on the membrane microstructure, and the poling method of the PVDF membrane, will be systematically studied, and the fabrication parameter of the piezoelectric PVDF membrane will be optimized. Through membrane fouling experiments, fouling formation on the membrane surface caused by particles and organic macromolecules will be analyzed, and the anti-fouling mechanism of in situ vibrating membrane will be revealed. In addition, principal fabrication and optimization theories of piezoelectric membrane with anti-fouling and self-cleaning properties will be established, supplying basic theory for developing novel anti-fouling/self-cleaning membrane and fouling controlling strategy.

聚偏氟乙烯（PVDF）是一种广泛应用于水处理过程的膜材料，针对膜污染导致PVDF膜通量衰减严重的问题，提出离子液体诱导构筑β相PVDF膜，利用其极化后的压电性能，施加交变电场引起PVDF膜原位振动，实现膜材料原位振动和流体力学协同效应对膜污染的源头控制。项目采用热致相分离法制备PVDF膜，利用离子液体与PVDF之间的强静电相互作用，控制制膜过程，使PVDF结晶成β相，施加强直流电场进行极化，获得在交变电场作用下原位产生振动的压电PVDF膜。系统研究离子液体诱导β相PVDF晶体的形成机理、离子液体性质对PVDF膜微结构的影响规律及PVDF膜的极化方法，确定制备压电PVDF膜的优化条件。通过膜污染实验，分析颗粒和有机大分子在压电PVDF膜振动表面的污染形成规律，揭示原位振动膜抗污染机理，建立抗污染、自清洁压电膜制备及性能优化控制的基本理论，为膜污染控制及新型抗污染自清洁分离膜研发提供理论基础。

聚偏氟乙烯（PVDF）是一种广泛应用于水处理过程的膜材料，针对使用过程中PVDF膜通量衰减严重的问题，本项目采用咪唑类离子液体诱导构筑β相PVDF膜，利用直流电场极化赋予其压电性能，在应用中施加交变电场，引起PVDF膜原位振动，与流体力学协同对膜污染进行源头控制。项目采用热致相分离法制备PVDF膜，利用离子液体与PVDF之间的强静电相互作用，优化控制制膜过程，使PVDF结晶成β相；施加强直流电场进行极化，获得可在交变电场作用下产生原位振动的压电PVDF膜。极化后PVDF膜的平均孔径增大和孔隙率提高，压电PVDF膜的振幅随交流电压的非线性增大而增大。在15V的交流电下，膜的共振频率为600kHz时，极化膜的压电信号值可达11.4mV。过滤实验表明，压电PVDF膜可使CaCO3悬浮体系的稳定通量提高约90.6%，BSA溶液体系的稳定通量提高53.8%。通过分析颗粒和有机大分子在压电PVDF膜振动表面的污染形成规律，揭示了PVDF膜原位振动抗污染机理，建立了抗污染、自清洁压电膜制备及性能优化控制的基本理论，为膜污染控制及新型抗污染自清洁分离膜研发提供理论基础。