Facile Grafting of Zwitterions onto the Membrane Surface To Enhance Antifouling Properties for Wastewater Reuse

Polymeric membranes for wastewater reuse are often fouled by suspended solids and dissolved organic matters, resulting in a dramatic decrease in water flux. Fouling can be mitigated by enhancing hydrophilicity of the membrane surface to avoid favorable interactions between the membranes and foulants. However, the modification of the membrane surface is often complicated and difficult to integrate into industrial membrane production processes. Herein we demonstrate a facile one-step coating of superhydrophilic zwitterions on the surface of ultrafiltration (UF) membranes by codepositing dopamine and sulfobetaine methacrylate (SBMA). In the presence of oxygen, dopamine forms polydopamine (PDA) adhering onto the membrane surface and anchors SBMA via Michael addition to form a robust thin superhydrophilic layer, as confirmed by contact angle measurement and X-ray photoelectron spectroscopy (XPS). The modified UF membranes demonstrate up to 80% higher water flux than the uncoated ones, when tested with water containing bovine serum albumin (BSA) as a model foulant in a crossflow system. This facile approach of membrane modification is also adapted for postmodification of a commercial nanofiltration (NF) membrane module, which demonstrates superior antifouling properties when tested with real wastewater at a wastewater treatment plant.