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

Abstract

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.

Modification of Polysulfone Ultrafiltration Membranes via Addition of Anionic Polyelectrolyte Based on Acrylamide and Sodium Acrylate to the Coagulation Bath to Improve Antifouling Performance in Water Treatment

“…Membrane modification techniques for hydrophilization and improvement of antifouling performance involve (1) chemical modification of membrane material, (2) blending with block-copolymers [ 13 , 14 , 15 ], hydrophilic polymers, oligomers [ 16 , 17 , 18 , 19 ] and nanoparticles [ 20 ], (3) surface segregation [ 21 ], (4) grafting [ 22 , 23 , 24 ], (5) surface coating [ 25 , 26 ], (6) nanoparticle immobilization on the selective layer surface [ 27 ] and (7) nanoparticle deposition [ 28 ].…”

Enhancement of the Fouling Resistance of Zwitterion Coated Ceramic Membranes

“…To reduce fouling, surface modifications including zwitterion molecules to polymeric membranes have been proposed [ 35 , 36 , 37 , 38 , 39 , 40 ]. In particular, poly(sulfobetaine methacrylate) (polySBMA) is a zwitterion polymer that is formed by a methacrylate main chain and a sulfobetaine analogue as the pendant group, holding both positive and negative functional groups [ 41 , 42 ].…”

Effect of the Zwitterion, p(MAO-DMPA), on the Internal Structure, Fouling Characteristics, and Dye Rejection Mechanism of PVDF Membranes

“…The downside is that due to oxidation, PEG tends to be very unstable in the presence of oxygen and transition metals [40,45]. More recently, studies have proven that zwitterionic molecules are effective antifouling materials due to their hydrophilicity rendering excellent antifouling ability to membranes [61][62][63][64]. Zwitterionic polymers are polymers that simultaneously contain both the negatively and positively charged ions, which are arranged as the pendent-side chain structure [58].…”

“…The excellent antifouling properties imparted through the incorporation of zwitterionic molecules have led to their exploration as the most effective antifouling medium and have been shown to be ultra-low fouling even when in contact with complex media such as an undiluted human plasma or serum [66]. These materials can be incorporated into membranes via coating [23,49], grafting [44,61], or blending [67,68]. Coating and grafting are two-step processes that take place at the surface of the membrane.…”