低表面能纳米纤维膜用于膜蒸馏过程中增强润湿阻力

ty10086 提交于 周四, 08/26/2021 - 13:10
文章英文标题
Low surface energy nanofibrous membrane for enhanced wetting resistance in membrane distillation process
正文
文摘( # br )具有层次结构的膜由于在其纳米微区提供了更多的气囊,因而具有更高的水接触角,进而被称为更疏水。但是,如在真空膜蒸馏( VMD )过程中,口袋中的空气已经耗尽后,疏水性可能会消失。这里提出了一种本征疏水的电纺纳米纤维膜( ENM ),其疏水性完全取决于这些材料的表面能,在不借助任何分级结构的情况下,促进其抗润湿性能。以聚偏氟乙烯( PVDF )为基体材料制备了新型复合ENMs,并通过简单的浸渍提拉法在其表面包复了低表面能的聚二甲基硅氧烷( PDMS )。复合ENMs中纳米纤维的扫描电镜( SEM )图像几乎不存在分层结构,而理论上认为分层结构是为了降低水接触角。然而,随着纳米纤维表面能的降低,复合ENMs表现出更高的亲水性。因此,复合ENMs在整个MD过程中不能被冷凝蒸汽所润湿,较薄的膜在连续真空MD测试中表现出优异的耐久性。结果表明,对于本征疏水性的ENMs材料而言,低的表面能是VMD过程中表现出强而持久的抗润湿能力的必备品质,这是传统的在膜表面构建层次结构难以实现的。
文章内容(英文)
Abstract(#br)Membranes with hierarchical structure have higher water contact angle due to affording more air pockets in its nano-micro regions, and then have been known as more hydrophobic. However, the hydrophobicity could be vanished after air in pockets has been exhausted such as in the vacuum membrane distillation (VMD) process. Here, an intrinsically hydrophobic electrospun nanofiber membrane (ENM), whose hydrophobicity is entirely depended on these materials surface energy, was proposed to promote the wetting resistance without the aid of any hierarchical structure. The novel composite ENMs were fabricated using polyvinylidene fluoride (PVDF) as matrix material, and then covered it with polydimethylsiloxane (PDMS) of much lower surface energy via a facile dip-coating. Scanning electron microscope (SEM) images of nanofibers in composite ENMs showed almost no hierarchical structure was existed, while the hierarchical structure was supposed to lower water contact angle in theory. However, the composite ENMs exhibited a higher water-repellency as the surface energy of nanofibers became lower. Therefore, the composite ENMs cannot be wetted by condensed vapor throughout the MD process, and a thinner membrane exhibited an excellent durability in the continuous vacuum MD tests. The result indicated that for the ENMs material of intrinsic hydrophobicity, the low surface energy is the essential quality to exhibit the strong and durable wetting resistance in VMD process, what is difficult to achieve by conventionally hierarchical architecture constructing on membrane surface.
来源出处
Journal|[J]DesalinationVolume 476, 2020.
DOI
https://doi.org/10.1016/j.desal.2019.114210

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