Graphene oxide nanofiltration membrane with trimethylamine-N-oxide zwitterions for robust biofouling resistance

Abstract

Biofouling is one of the most critical issues that jeopardizes membrane separation performance, accounting for nearly half of all types of membrane fouling. Herein, inspired by the actions of cuttlefish, we propose an effective strategy to mitigate fouling by fabricating a zwitterionic polymer-brush-modified graphene oxide tethered with trimethylamine-N-oxide (TMAO) head groups. Following a facile vacuum filtration approach with in situ crosslinking, the corresponding 2D membranes (T-GO) were constructed with tunable surface thicknesses and reasonable mechanical robustness. Owing to its unique transport pathways, an optimal membrane exhibits a typical characteristic of nanofiltration with excellent water permeability and a considerably high “solute–solute” selectivity of 18.6 ± 0.3 (toward Congo red/Na2SO4), demonstrating a great potential for desalinating textile wastewaters. As the positively and negatively charged head groups are directly connected via a single covalent N–O bond, the O atom can accept three hydrogen bonds in a single polymeric chain, as revealed by the first-principles molecular dynamics simulations. The robust surface hydration layer, induced by surface hydrophilicity, and the disinfection effect, brought by the quaternary ammonium groups, both contribute to the remarkable antiadhesion and contact inactivation ability of the T-GO membrane. Therefore, the antibacterial properties of the T-GO membrane were significantly enhanced, which was experimentally verified for the first time in both the static contact mode and dynamic microfluidic operations. In general, our results provide a robust methodology for designing a new class of nonfouling zwitterionic membranes for sustainable membrane applications.