Qing Weihua, Wang Jianqiang, Ma Xiaohua, Yao Zhikan, Feng Yong, Shi Xiaonan, Liu Fu, Wang Peng, Tang Chuyang Y
Department of Civil Engineering, The University of Hong Kong, Pokfulam 999077, Hong Kong.
Department of Civil Engineering, The University of Hong Kong, Pokfulam 999077, Hong Kong; Key Laboratory of Marine Materials and Related Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China.
J Colloid Interface Sci. 2019 Oct 1;553:99-107. doi: 10.1016/j.jcis.2019.06.011. Epub 2019 Jun 5.
Superhydrophobic polyvinylidene fluoride (PVDF) membrane is a promising material for membrane distillation. Existing approaches for preparing superhydrophobic PVDF membrane often involve separate manipulation of surface roughness and surface chemistry. Here we report a one-step approach to simultaneously manipulate both the surface roughness and surface chemistry of PVDF nanofibrous membranes for enhanced direct-contact membrane distillation (DCMD) performances. The manipulation was realized in a unique solvent-thermal treatment process, during which a treatment solution containing alcohols was involved. We demonstrate that by using different chain-length alcohols in the treatment solvent, surface roughness can be promoted by creating nanofin structures on the PVDF nanofibers using an alcohol which has moderate affinity with PVDF. Meanwhile, surface chemistry can be tuned by adjusting the fraction distribution of crystal phases (nonpolar α phase and polar β phase) in the membrane using different alcohols. PVDF membranes with different surface wettabilities were used to evaluate the effects of surface roughness and surface energy on the DCMD performances. Combining both low surface energy and multi-scale surface roughness, pentanol-treated PVDF membrane achieved best anti-water property (water contact angle of 164.1° and sliding angle of 8.1°), and exhibited superior water flux and enhanced anti-wetting ability to low-surface-tension feed in the DCMD application.
超疏水聚偏氟乙烯（PVDF）膜是一种很有前景的膜蒸馏材料。现有的制备超疏水PVDF膜的方法通常涉及对表面粗糙度和表面化学性质的单独处理。在此，我们报道一种一步法，可同时调控PVDF纳米纤维膜的表面粗糙度和表面化学性质，以提高直接接触式膜蒸馏（DCMD）性能。这种调控是在一个独特的溶剂热处理过程中实现的，在此过程中使用了一种含醇的处理溶液。我们证明，通过在处理溶剂中使用不同链长的醇，使用与PVDF具有适度亲和力的醇在PVDF纳米纤维上形成纳米鳍结构可提高表面粗糙度。同时，通过使用不同的醇调节膜中晶相（非极性α相和极性β相）的分数分布可调整表面化学性质。使用具有不同表面润湿性的PVDF膜来评估表面粗糙度和表面能对DCMD性能的影响。结合低表面能和多尺度表面粗糙度，戊醇处理的PVDF膜具有最佳的抗水性能（水接触角为164.1°，滑动角为8.1°），并且在DCMD应用中对低表面张力进料表现出优异的水通量和增强的抗润湿能力。
