Nanofiltration membrane based on graphene oxide crosslinked with zwitterion-functionalized polydopamine for improved performances

Abstract

Graphene oxide (GO)-based membranes have received increasing attention recently in liquid separation field. However, the abundant hydrophilic groups of GO nanosheets would cause instability of GO-based membranes under hydrated conditions. In addition, GO-based membranes often suffer from severe membrane fouling in practical application. In this study, polydopamine (PDA) crosslinked GO was synthesized by simply immersing GO into the dopamine alkaline solution and used to prepare GO@PDA/PES composite membranes. Then, a zwitterionic polymer, synthesized by quaterisation reaction of polyethyleneimine (PEI) and sodium chloroacetate, was grafted on the surface of PDA crosslinked GO membrane via Michael addition reaction between amino groups of PEI and quinone groups of PDA. The bonding between GO nanosheets reinforced the structural stability, resulting in the formation of water stable membranes. The grafted zwitterionic polymer coating could improve the membrane surface hydrophilicity, endowing the membranes promising anti-fouling ability. The resulting membrane achieved a flux of 49.5 L m−2 h−1 bar−1 with relatively high rejection of about 100%, 82% and 67% for Congo Red, Orange G and Methyl Orange respectively. The membrane exhibited good anti-fouling properties as well as structural stability under alcohol environments, showing considerable potential in water treatment.