Preparation of antifouling reverse osmosis membrane with polyacrylic acid brushes based on polydopamine coating assisted atom transfer radical polymerization

Abstract

An antifouling polyamide (PA) reverse osmosis (RO) membrane was fabricated in this work by incorporating polyacrylic acid (PAA) brushes onto the membrane surface via polydopamine (PDA)-assisted atom transfer radical polymerization (ATRP). Specifically, a PDA intermediate layer containing the initiator 2-bromoisobutyryl bromide (BIBB) for polymerization was coated on original membrane surface. Then, acrylic acid (AA) was controllably incorporated on the membrane surface in the form of PAA brushes by regulating ATRP reaction time. The PDA-assisted polymerization was mild to the separation layer, and BIBB could be immobilized on the membrane surface with even distribution and controllable density. It was demonstrated that the water contact angle and surface roughness of the RO membranes with PAA brushes was reduced, while the negative charge and hydrophilicity were increased. Simultaneously, the water flux of the membrane was enhanced by 27.8% and the NaCl rejection was maintained compared with that of virgin membrane. Moreover, the modified membrane presented a higher flux recovery ratio and a lower flux decline ratio when lysozyme, bovine serum albumin, humic acid, and sodium alginate were used as model foulants. Besides, the membrane exhibited a satisfactory long-term performance stability. Our work provides a gentle and controllable strategy for the fabrication of antifouling RO membranes with enhanced water permeability and maintained salt rejection, which is crucial for increasing the efficiency of RO processes.