A novel interfacial polymerization assisted phase inversion process for the facile fabrication of ion-selective nanofiltration membranes

Interfacial polymerization (IP) and non-solvent induced phase inversion (NIPS) are the two most commonly used mainstream technologies to fabricate separation membranes. Taking their advantages, we developed a simple, facile and scalable method to integrate the IP and NIPS processes together for the fabrication of ion-selective nanofiltration membranes. Herein, amphiphilic polysulfone block hyperbranched polyglycerol (PSf-b-hPG) copolymer was synthesized and blended with polyethylene imide (PEI) to prepare a polymer casting solution in organic solvents. After casted into the liquid film of PSf-b-hPG and PEI blending solution, it was then immersed into a cross-linking solution with 0.2 wt.% trimethylchloride (TMC) in n-hexane for the generation of the polyamide layer first on top of the liquid film, and finally transferred into a water coagulation bath for the formation of the porous matrix of PSf-b-hPG membrane. The fabricated membrane exhibited a high water permeance of 12.57 L m -2h- 1 bar-1 and a high separation factor of 25.08 towards Mg2+ and Li+ ions, which is superior to the perm-selectivity of the most reported nanofiltration membranes. This novel and facile process can be directly applied to the NIPS manufacturing line, eliminating a separate IP production line and holding immense potentials and advantages in scale-up production.