High-performance polyamide nanofiltration membrane with arch-bridge structure on a highly hydrated cellulose nanofiber support

Nanofiltration (NF) membranes with outstanding performance are highly demanded for more efficient desalination and wastewater treatment. However, improving water permeance while maintaining high solute rejection by using the current membrane fabrication techniques remains a challenge. Herein, polyamide (PA) NF membrane with arch-bridge structure is successfully prepared via interfacial polymerization (IP) on a composite support membrane of salt-reinforced hydrophilic bacterial cellulose nanofibers (BCNs) nanofilm/polytetrafluoroethylene (BCNs/PTFE). The strong hydration of BCNs promotes Marangoni convection along water/organic solvent interface during the IP process, which creates extra area for interfacial reaction and produces a thin PA active layer with arch-bridge structures. These arch-bridge structures endow the resulting PA active layer with substantial larger active area for water permeation. Consequently, the PA NF membrane exhibits exceptional desalination performance with a permeance up to 42.5 L m−2 h−1 bar−1 and a rejection of Na2SO4 as high as 99.1%, yielding an overall desalination performance better than almost all of the state-of-the-art NF membranes reported so far in terms of perm-selectivity.