Cellulose Nanofiber-Based Nanofiltration Membranes for Sustainable Water Purification

Although nanofiltration (NF) membranes enable energy-efficient molecular separations critical for sustainable ecosystem, their conventional fabrication from petrochemical polymers raises end-of-life environmental concerns. Cellulose nanofiber (CNF), as a biodegradable and renewable biomass material, offers a promising green alternative for NF membrane production. However, fabricating dense NF membranes from highly concentrated CNF suspensions remains challenging due to their high viscosity and poor film-forming properties. In this work, we overcame these limitations through an acidification-assisted process that disrupts the CNF gel network, enabling improved processability. Subsequent crosslinking with glutaraldehyde and thermal-induced formation yielded a robust and dense NF membrane with tailored nanostructure. The optimized membrane exhibited effective separation performance, achieving approximately 90% rejection of Na₂SO₄ and 99.4% removal of humic acid while maintaining a water flux over 20 L·m^-2·h^-1. This work proposes a sustainable fabrication route for high-performance nanocellulose membranes, establishing a renewable alternative to conventional petrochemical-based water purification filtration materials.