Polyhydroxy Group Functionalized Zwitterion for a Polyamide Nanofiltration Membrane with High Water Permeation and Antifouling Performance

Nanofiltration (NF) membranes have attracted significant attention owing to their widespread applications in water treatment and seawater desalination. However, challenges still remain in improving their antifouling performance and water permeation. Here, a sulfobetaine-based zwitterion with polyhydroxy groups was designed and synthesized successfully. Then, the NF membranes were modified by the reaction of the hydroxyl group of the zwitterion and the acid chloride group on the surface of the initial NF membrane. Hence, the hydrophilicity of the NF membrane was significantly enhanced and resulted in the high promotion of nanofiltration performance and antifouling property. Besides, the flux of the modified NF membrane (A2) reached 9.28 L m–2 h–1 bar–1, which was 2.2 times higher than the flux of pristine NF membrane (A0). Nevertheless, the rejection showed a slight decrease. Also, the modified NF membrane possessed excellent fouling resistance to protein; the flux recovery ratio was nearly 98% after the membrane was treated with bovine serum albumin for 2.5 cycles. The excellent water flux and fouling resistance of this NF membrane advanced its application in wastewater treatment.