Hydrophilic carbon-carbon covalent linkage network structure for strong acid/alkali resistant and antifouling nanofiltration membrane

The nanofiltration (NF) membrane plays a crucial role in wastewater treatment by separating ions and molecules. However, traditional polyamide (PA) thin-film composite (TFC) NF membranes have limitations in durability under acidic or alkaline conditions and are prone to fouling, which limits their applications and increases costs. In this study, we have successfully developed a new nanofiltration membrane with an active layer composed of hydrophilic carbon-carbon covalent bond linkage network through UV irradiation-initiated polymerization of a kind of sulfobetaine - [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide (DMAPS) - or acrylic acid (AA) on the surface of poly (ether sulfone) (PES) substrate. The carbon-carbon covalent bond (C–C) chemistry used in the preparation of the NF membrane results in exceptional durability towards acid and base, enabling it to maintain its ion separation efficiency (up to 94.2 % and 90.3 % of the initial Na2SO4 rejections) under strong acidic (20 % (w/v) H2SO4) and strong alkaline (2 M NaOH) conditions. Additionally, the water-attracting nature of polyDMAPS and PAA effectively prevents the fouling of protein and bacteria on the NF membrane surface. This breakthrough in manufacturing NF membranes significantly improves their environmental durability, making them suitable for use in highly acidic or alkaline environments (e.g., pH < 0 and pH > 14), including heavily contaminated ones.