Graphene oxide (GO) is negatively charged and has good antifouling properties. However, its good dispersibility in water makes it challenging for membrane surface modification to improve antifouling properties. Herein, we demonstrate a versatile approach to covalently graft GO onto UF membrane surfaces with different hydrophilicities in aqueous solutions at room temperature. Specifically, we first functionalize the polysulfone (PSf) membrane surface with polydopamine (PDA), a bio-adhesive that can deposit on membranes with a variety of surface characteristics. Second, the GO with carboxyl acid groups on the edges can be activated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). Finally, the activated GO can be covalently grafted onto the PDA layer through the reaction of the carboxyl groups and amines in the PDA. The GO was prepared using the modified Hummers’ method and then etched using H<sub>2</sub>O<sub>2</sub> to reduce the size and maximize the grafting efficiency. The permeation and antifouling properties of the GO modified membranes are thoroughly evaluated in a constant flux crossflow system. GO grafting improves the surface hydrophilicity without decreasing the water permeance. The GO-modification decreases the fouling rate by 63% and increases the critical flux by 20% when challenged using 1 g/L sodium alginate in the constant-flux crossflow system. The modified membranes demonstrate stability for continuous 48-h operation and interval cleanings using NaOH solutions. Given the simplicity of the GO grafting and the versatility of the PDA for various surfaces, our approach can also be used to post-modify modules for industrial use.

Covalently grafting graphene oxide onto ultrafiltration membranes to improve antifouling properties

ACS Fall 2021

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