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 Na 2 SO 4 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. This study developed a sustainable nanofiltration membrane from cellulose nanofibers through acidification-assisted processing and crosslinking. The membrane exhibited 90% Na 2 SO 4 rejection, 99.4% humic acid removal, and >20 L·m -2 ·h -1 water flux, providing a green alternative to petroleum-based membranes. • Cellulose nanofiber, a renewable and biodegradable biomass material, was utilized to fabricate nanofiltration membranes as a sustainable alternative to petroleum-based polymers. • Acid treatment and cross-linking reactions effectively mitigated the high viscosity and poor processability of concentrated cellulose nanofiber suspensions, resulting in the successful fabrication of dense nanofiltration membranes. • The membrane demonstrated 90.0% Na 2 SO 4 rejection and 99.4% humic acid removal while maintaining a water flux exceeding 20 L·m -2 ·h -1 , exhibiting effective sustainable water purification capabilities.