Magnetic-field-assisted fabrication of Fe3O4-enhanced thin-film nanocomposite polyamide nanofiltration membranes with enhanced separation performance

Nanofiltration (NF) membranes are widely used in water treatment and molecular separations, but conventional thin-film composite (TFC) membranes often face a trade-off between permeability and selectivity. Incorporating nanomaterials has shown potential to overcome this limitation, though challenges remain in achieving effective nanoparticle distribution. In this study, a magnetic-field-assisted strategy was developed to fabricate high-performance thin-film nanocomposite (M-TFN) membranes. Hydrophilic Fe 3 O 4 nanoparticles were introduced into the aqueous piperazine phase, and an external magnetic field was applied during interfacial polymerization to direct nanoparticle migration toward the membrane surface. This approach yielded a wrinkled polyamide layer with enhanced surface roughness, reduced thickness, and improved hydrophilicity. The resulting M-TFN membrane exhibited a 2.7-fold increase in water permeability (15.9 L·m −2 ·h −1 ·bar −1 ) compared to the conventional TFC membrane, while maintaining high Na 2 SO 4 rejection (>98 %). It also demonstrated efficient rejection of various dyes, following a molecular weight-dependent size-exclusion mechanism. This work provides a promising route for the design of next-generation NF membranes with simultaneously enhanced flux and selectivity.