Polymeric Nanofiltration Membranes with Enhanced Hydrophilic, Morphological, Transport, and Antifouling Properties—A Review

Nanofiltration membranes have emerged as a crucial class of pressure-driven separation materials, positioned between ultrafiltration and reverse osmosis in terms of selectivity, permeance, operating pressure, and energy consumption. Their ability to remove fine contaminants—including multivalent ions, organic micropollutants, dyes, and macromolecules—has made them essential in water and wastewater treatment, pharmaceutical processing, and various industrial applications. In spite of their growing relevance, the performance of polymeric nanofiltration membranes, such as polyamide, polysulfone, polyethersulfone, polyvinylidene fluoride, and polyimide, is still constrained by weak hydrophilicity and a strong susceptibility to fouling, which collectively decrease permeance, increase operational costs, and shorten membrane lifespan. In recent years, substantial research efforts have focused on designing and engineering the surface chemistry and structural characteristics of nanofiltration membranes to improve water permeance, reduce foulant adhesion, and improve long-term stability. This review provides a comprehensive and comparative assessment of the most recent modification techniques applied to polymer-based nanofiltration membranes. Strategies such as polymer blending, nanoparticle incorporation, physical surface coating, plasma treatment, chemical attachment, layer-by-layer assembly, and interfacial polymerization are critically examined with respect to their effectiveness and practical limitations supported by recent research examples. Special attention is given to how these modification methods affect membrane morphology, hydrophilicity, permeance, and antifouling properties. Eventually, the review highlights emerging ideas and forward-looking design directions that may guide the next generation of nanofiltration membranes toward higher efficiency, improved durability, and broader industrial applicability.