Ultrahigh permeance of a chemical cross-linked graphene oxide nanofiltration membrane enhanced by cation-π interaction

Cross-linking with large flexible molecules is a common method to improve the stability and control the interlayer spacing of graphene oxide (GO) membranes, but it still suffers from the limitation of low water flux. Herein, a novel high flux GO membrane was fabricated using a pressure-assisted filtration method, which involved a synergistic chemical cross-linking of divalent magnesium ions and 1,6-hexanediamine (HDA) on a polyethersulfone (PES) support. The membrane cross-linked with magnesium ions and HDA (GO(HDA-Mg2+)) exhibited a high water flux up to 144 L m(-2) h(-1) bar(-1), about 7 times more than that of cross-linked GO membranes without adding magnesium ions (GO(HDA)), while keeping excellent rejection performance. The GO(HDA-Mg2+) membrane also showed an outstanding stability in water for a long time. The effects of magnesium ions on the GO(HDA-Mg2+) membrane were analyzed using several characterization methods, including Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The results indicated that magnesium ions not only promoted reasonable cross-linking, but also improved the stacking of GO sheets to give lower mass transfer resistance channels for water transport in the membranes, resulting in the ultrahigh permeance of the GO membranes.