Design of anti-fouling membranes via prebiotic chemistry-inspired aminomalononitrile (AMN) coating strategy: Aldehyde-mediated chemical immobilization of pseudo-zwitterionic compounds

Although zwitterionic polymers were extensively explored for anti-fouling surface modification, the resulting significant loss in membrane permeability is undesirable. Assisted by co-deposition of aminomalononitrile (AMN) and terephthalaldehyde (TA), in this study a high-performance membrane with low fouling propensity was designed via chemical immobilization of a novel pseudo-zwitterionic compound, namely 3-(dimethyl(3-((3-sulfonatopropyl)ammonio)propyl)ammonio)propane-1-sulfonate (DMPDA-QS), onto the polyethersulfone (PES) substrate. The optimal membrane showed high water permeance (∼366 L m−2 h−1 bar−1) and high rejection (>98.0 %) to model proteins. The immobilization of this pseudo-zwitterionic compound led to a nearly neutral surface and enhanced hydrophilicity, and the dynamic fouling experiments proved its excellent antifouling performance against both negatively (i.e., bovine serum albumin, BSA) and positively (i.e., lysozyme, LYZ) charged foulants with flux recovery of >93% and >88% after 3-cycle filtration, respectively. A mathematical model was used to quantify the contribution of mass transfer resistance caused by reversible and irreversible fouling, showing nearly unchanged resistance of the modified membranes in contrast with 260% increase of the pristine PES after 3 filtration cycles. The developed fabrication strategy provided a viable and versatile route for designing high-performance antifouling membranes.