海水淡化是解决全球水资源短缺的关键策略之一，更高的水/盐渗透选择性和抗污染性是脱盐膜所追求的目标。然而，水的渗透和截盐之间的权衡以及膜污染仍然是聚酰胺（PA）复合（TFC）脱盐膜所面临的挑战。本文中，我们利用具有多孔、超薄（5和9微米）的聚乙烯（PE）膜作为支撑层来制备PA-TFC脱盐膜。通过界面聚合（IP）反应制备了一系列不同厚度PE支撑的PA-TFC膜，所得到的TFCx（X代表PE膜的厚度）膜在反渗透（RO）和正渗透（FO）脱盐过程中展示出良好的水渗透性和较高的截盐率。重氮化作用是利用重氮盐和残余芳香族之间的亲核取代反应来共价接枝PA层。重氮化作用后的TFCx-N膜展现出了同时促进水渗透和截盐以及抗污染性能。所得到的TFC5-N膜在RO条件下，水渗透性达到5.95 L m-2 h-1 bar-1（65℃），以及优异的截盐性能（NaCl>97.8%、MgSO4>98.9%）。2D-GIWAXS证明了重氮化作用改变了PA层的结晶行为。结果表明，重氮化作用后PA分子的平行“π-π”堆积被破坏，转变为以垂直的“T形”配置为主，能够匹配所制备的TFC5-N膜所具备的最佳脱盐性能。
Abstract
Membrane desalination is the most critical strategy for global water scarcity. Anti-fouling and higher water/salt perm-selectivity are consistent goals for desalination membranes. However, the trade-off between the water permeance and salt rejection, and fouling remaining challenges for polyamide (PA) thin–film composite (TFC) desalination membranes. Here, we apply ultrathin (~5 and ~9 μm) polyethylene (PE) textile with highly porous and inter-connected pore structures to constitute the PA–TFC desalination membranes. A series of PE–supported PA–TFC membranes were prepared by interfacial polymerization (IP) reaction, and obtained TFCx (X represents the thickness of PE textile) membranes showed promising water flux as well as high NaCl rejection under reverse osmosis (RO) and forward osmosis (FO) desalination processes. Diazotization utilizes the nucleophilic aryl substitution reaction between the diazonium salt and residual aromatic to covalently graft a PA layer. The resulting TFCx–N membranes after diazotization exhibited simultaneously improved water permeance and salt rejections as well as anti-fouling performances, e.g., the resulting TFC5–N membrane showed water permeability of 5.95 L m-2 h-1 bar-1 at 65 ◦C under RO, and the excellent rejection of salts (NaCl >97.8% and MgSO4 > 98.9%). Two-dimensional (2D) grazing incidence wide-angle X-ray scattering (GIWAXS) demonstrated the crystallization behavior of PA layer by diazotization. The 2D GIWAXS results suggested that the parallel “π–π” stacking of PA molecular packing motifs was destroyed after diazotization, and the perpendicular “T-shaped” configuration might be associated with optimal desalination performance of the TFC5–N membrane.
Desalination 549 (2023), 116307; https://www.sciencedirect.com/science/article/pii/S0011916422007627