Magnetically directed interfacial polyamerization of Fe3O4@CdS@CQDs-embedded polyamide nanofiltration membranes with enhanced separation and photocatalytic self-cleaning performance

Membrane fouling and the inherent permeability–selectivity trade-off represent persistent dual challenges constraining the long-term performance and practical application of nanofiltration (NF) membranes. Saline wastewater and dye-containing effluents are typical industrial wastewaters with large discharge volumes, where high salt contents and complex organic components exacerbate fouling and intensify the permeability–selectivity dilemma of conventional NF membranes. In this work, we report a novel magnetic-field-assisted interfacial polymerization strategy to fabricate photocatalytic thin-film nanocomposite (M-TFN) membranes with enhanced antifouling and self-cleaning performance. A multifunctional nanostructure, Fe 3 O 4 @CdS@CQDs, was synthesized via a one-pot hydrothermal method and introduced into the aqueous phase of interfacial polymerization. Under an external magnetic field, the nanoparticles were guided toward the water–organic interface, inducing the formation of a wrinkled polyamide surface with increased roughness, hydrophilicity, and specific surface area. Compared with the conventional TFC (6.1 L·m −2 ·h −1 ·bar −1 , 98.2 % Na 2 SO 4 rejection) and TFN membranes (15.7 m −2 ·h −1 ·bar −1 , 99.0 % Na 2 SO 4 rejection), the resulting M-TFN membranes exhibited a significantly improved water flux of 22.5 m −2 ·h −1 ·bar −1 while maintaining a high Na 2 SO 4 rejection of 99.2 %, thereby effectively overcoming the permeability–selectivity trade-off. Moreover, the membranes demonstrated excellent dye rejection (>95 % for multiple organic dyes) and outstanding photocatalytic self-cleaning behavior under visible light, achieving a flux recovery rate of 98.7 % after five fouling–cleaning cycles. This study provides new insights into the synergistic use of magnetic guidance and photocatalytic enhancement to design next-generation NF membranes for advanced wastewater treatment.