Xue Xiangyang, Tan Guangming, Zhu Zhigao
Key Laboratory of New Membrane Materials, Ministry of Industry and Information Technology, School of Environment and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China.
ACS Appl Mater Interfaces. 2021 Sep 29;13(38):45977-45986. doi: 10.1021/acsami.1c12775. Epub 2021 Sep 15.
Novel specially wettable membranes have been attracting significant attention for durable membrane distillation (MD). However, constructing a superhydrophobic interface often has to undergo complex modification procedures including roughness construction and hydrophobic modification. Herein, all-polymer and self-roughened superhydrophobic poly(vinylidene fluoride) fibrous membranes (PVDF FMs) with robustly stable pores were successfully constructed via electrospinning of fluorinated polyhedral oligomeric silsesquioxanes/PVDF (F-POSS/PVDF) emulsion solution in combination with hot-pressing. The comparative experiment reveals that proper hot-pressing, including adequate temperature and pressure, can help improve membrane pore stability by welding the intersecting fibers and increase the membrane surface hydrophobicity by transferring the inner fluorine chains to the outer fiber surface, simultaneously advancing membrane scaling and fouling resistance. Nevertheless, excessive temperature or pressure will destroy the interconnected pores and surface wettability of the PVDF FM. Significantly, the hot-pressing-treated F-POSS/PVDF FM shows a high water recovery (∼90%) and robust stability after five rounds of the concentration process toward concentrating natural seawater as a target. Thus, the all-polymer and self-roughened superhydrophobic PVDF FMs constructed via electrospinning combined with the thermal treatment have potential applications in concentrating hypersaline brines, which make up for the other membrane technology, including reverse osmosis and nanofiltration technologies that failed to concentrate hypersaline solutions.
新型特殊可湿膜在持久膜蒸馏（MD）领域引起了广泛关注。然而，构建超疏水界面通常需要经历复杂的改性过程，包括粗糙度构建和疏水改性。在此，通过将氟化多面体低聚倍半硅氧烷/聚偏氟乙烯（F-POSS/PVDF）乳液溶液进行静电纺丝并结合热压，成功构建了具有稳定孔结构的全聚合物自粗糙化超疏水聚偏氟乙烯纤维膜（PVDF FMs）。对比实验表明，适当的热压，包括合适的温度和压力，能够通过焊接交叉纤维来提高膜孔的稳定性，并通过将内部氟链转移到纤维表面来增加膜表面的疏水性，同时提升膜的抗结垢和抗污染能力。然而，过高的温度或压力会破坏PVDF FM的相互连通孔结构和表面润湿性。值得注意的是，经过热压处理的F-POSS/PVDF FM在以浓缩天然海水为目标的五轮浓缩过程后，显示出高水回收率（约90%）和强大的稳定性。因此，通过静电纺丝结合热处理构建的全聚合物自粗糙化超疏水PVDF FMs在浓缩高盐卤水方面具有潜在应用，弥补了包括反渗透和纳滤技术在内的其他膜技术无法浓缩高盐溶液的不足。
