Antifouling loose nanofiltration membranes prepared via the fast codeposition of capsaicin-mimic/polydopamine for efficient dye/salt separation

Abstract

Loose nanofiltration membranes (LNMs) are considered promising for dye/salt separation. However, LNM real-world applications are still hindered by membrane fouling. Here, we report the fabrication and relevant properties of novel antifouling LNMs, made by the codeposition of N,N′-((4,5,6-trihydroxy-1,3-phenylene) bis (methylene)) diacrylamide (AMTHBA) and polydopamine (PDA) onto polysulfone (PSf) via Michael addition and Schiff base processes. The introduction of the capsaicin-mimic AMTHBA, which has hydrophilic and antimicrobial properties, can markedly enhance the looseness of the selective layers, increasing the permeability and antifouling capacities of LNMs. The LNM dye/salt separation performance and surface microstructure can be adjusted by varying AMTHBA addition and codeposition time. The optimum PSf/PDA-AM 1.5 LNM achieved ultrahigh water permeance (72.21 L m−2 h−1 bar−1), excellent dye rejection (e.g., 98.69 % Congo Red) and low salt retention (e.g., 6.32 % NaCl). Notably, it also exhibited outstanding antifouling properties towards organic foulants (flux recovery ratio exceeded 98 % after 2 fouling/backwash cycles) and bacteria (sterilizing ratio of E. coli and S. aureus in aqueous solution was 87.53 % and 81.51 %). Furthermore, PSf/PDA-AM LNM maintained stable separation performance in 30 h dye/salt filtration test, and desirable retention efficiency during 12,000 ppm × h chlorination. This work provides opportunities for developing high-performance antifouling LNMs for textile wastewater treatment.