Liu Zi-Yu, Jiang Qin, Jin Zhiqiang, Sun Zhenyu, Ma Wangjing, Wang Yanlei
Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry , Chinese Academy of Sciences , Beijing 100190 , People's Republic of China.
State Key Laboratory of Organic-Inorganic Composites, College of Chemical Engineering , Beijing University of Chemical Technology , Beijing 100029 , People's Republic of China.
ACS Appl Mater Interfaces. 2019 Apr 17;11(15):14408-14417. doi: 10.1021/acsami.8b22059. Epub 2019 Apr 2.
The antifouling process of the membrane is very vital for the highly efficient treatment of industrial wastewater, especially high salinity wastewater containing oil and other pollutants. In the present work, the dynamical antifouling mechanism is explored via molecular dynamics simulations, while the corresponding experiments about surface properties of the zwitterionic monomer-grafted polyvinylidene difluoride membrane are designed to verify the simulated mechanism. Water can form a stable hydration layer at the grafted membrane surface, where all the simulated radial distribution function of water/membrane, hydrogen bond number, water diffusivity, and experimental oil contact angles are stable. However, the water flux across the membrane will increase first and then decrease as the grafting ratio increases, which not only depends on the reduced pore size of the zwitterionic monomer-grafted membrane but also results from water diffusion. Furthermore, the dynamical fouling processes of pollutants (taking sodium alginate as an example) on the grafted membrane in water and brine solution are investigated, where both the high grafting ratio and electrolyte CaCl can enhance the fouling energy barrier of the pollutant. The results show that both the enhanced hydrophilic property and the electrostatic repulsion can affect the antifouling capability of the grafted membrane. Finally, the ternary synergistic antifouling mechanisms among the zwitterionic membrane, electrolyte, and pollutant sodium alginates are discussed, which could be helpful for the rational design and preparation of new and highly efficient zwitterionic antifouling membranes.
膜的防污过程对于工业废水尤其是含油及其他污染物的高盐度废水的高效处理至关重要。在本工作中，通过分子动力学模拟探索动态防污机制，同时设计了关于两性离子单体接枝聚偏氟乙烯膜表面性质的相应实验来验证模拟机制。水能够在接枝膜表面形成稳定的水化层，在此处水/膜的所有模拟径向分布函数、氢键数、水扩散率以及实验测得的油接触角均保持稳定。然而，随着接枝率增加，跨膜水通量会先增加后降低，这不仅取决于两性离子单体接枝膜孔径的减小，还源于水的扩散。此外，研究了污染物（以海藻酸钠为例）在水中和盐水溶液中接枝膜上的动态污染过程，其中高接枝率和电解质氯化钙均可增强污染物的污染能垒。结果表明，增强的亲水性和静电排斥作用均会影响接枝膜的防污能力。最后，讨论了两性离子膜、电解质和污染物海藻酸钠之间的三元协同防污机制，这有助于合理设计和制备新型高效两性离子防污膜。
