Due to water shortages, people have to use wastewater, seawater and brackish groundwater. People prefer to use membrane-based technologies to produce high-quality water, because they are environmentally friendly and have higher energy efficiencies than traditional thermal methods. The desalination nanofiltration (NF) membranes developed demonstrate a trade-off between water permeabilities and selectivities. Researchers are devoted to develop desalination NF membranes with both high water permeabilities and high selectivities. Using novel strategies, we successfully constructed double-high-performance NF membranes with a polyamide-polyester composite layer and a surface layer via a facile additional two-step approach. We used both triethanolamine (TEOA) and piperazine (PIP) to react with trimesoyl chloride (TMC) to form a composite active layer and coated the self-assembled polydopamine (PDA) on the surface of the composite active layer. To our knowledge, their performances are among the topmost of developed NF membranes for desalination and dye pollutant removal. We used scanning electron microscope (SEM), atomic force microscope (AFM) and water contact angle gauge (WCA) to investigate the membrane surface characteristics. The membrane obtained via the two-step approach has a water permeability of up to 21.3 LMH/bar, while that of the control polyamide NF membrane is as low as 8.2 LMH/bar. The developed membrane owes apparently improved water permeability in addition to maintaining high selectivities. Furthermore, the coating of the self-assembled PDA can alleviate membrane fouling. We also performed molecular dynamics (MD) simulations to study why the use of TEOA in addition to PIP to react with TMC improves membrane performances and give guidances and inspirations to future researches.

由于缺水，人们不得不使用废水、海水和微咸地下水。人们更喜欢使用基于膜的技术来生产高质量的水，因为它们对环境无害，并且比传统的热方法具有更高的能源效率。开发的脱盐纳滤 (NF) 膜证明了水渗透性和选择性之间的权衡。研究人员致力于开发兼具高透水性和高选择性的脱盐纳滤膜。使用新颖的策略，我们通过简单的附加两步法成功构建了具有聚酰胺-聚酯复合层和表面层的双高性能纳滤膜。我们使用三乙醇胺 (TEOA) 和哌嗪 (PIP) 与均苯三甲酰氯 (TMC) 反应形成复合活性层，并将自组装聚多巴胺 (PDA) 包覆在复合活性层表面。据我们所知，它们的性能在用于脱盐和染料污染物去除的已开发纳滤膜中名列前茅。我们使用扫描电子显微镜 (SEM)、原子力显微镜 (AFM) 和水接触角计 (WCA) 来研究膜表面特性。通过两步法获得的膜的透水性高达 21.3 LMH/bar，而对照聚酰胺 NF 膜的透水性低至 8.2 LMH/bar。开发的膜除了保持高选择性外，还具有明显改善的透水性。此外，自组装PDA的涂层可以减轻膜污染。我们还进行了分子动力学 (MD) 模拟，以研究为什么除了 PIP 之外还使用 TEOA 与 TMC 反应可以提高膜性能，并为未来的研究提供指导和启发。