Dual-site supported graphene oxide membrane with enhanced permeability and selectivity

Two-dimensional (2D) graphene oxide (GO) membranes continue to attract interest due to their superior permeation and separation performance, and are regarded as a promising technology for water purification. However, the imperfect interlayer microstructure under the applied hydraulic pressure, and the inferior stability are still considerable challenges to achieve high permeability, selectivity and operability. In this paper, we describe for the first time, the development and testing of a dual-site supported GO membrane (SEN-Mg/GO) by introducing biuret (SEN) and Mg2+ inside the interlayer structure. SEN can support the GO sheets in the oxide sites based on a condensation reaction between amino and carboxyl groups, while Mg2+ is fixed in the graphitic sites through a non-covalent cation-π interaction. A synergistic effect of the dual-site crosslinking and support build more favorable nanochannels for the rapid transport of water while also imparting the membrane to maintain a tightly-packed 2D structure, which increases water flux without sacrificing the separation performance. In comparison, SEN-Mg/GO exhibited a water flux 4 times greater than the GO and SEN only cross-linked GO membrane (SEN/GO), with high selectivity towards various model dye molecules (>98%). The SEN-Mg/GO membrane also achieved greater "trade-off" between flux and rejection and significantly improved stability than the Mg2+ only cross-linked GO membranes (Mg/GO). The optimized nanochannels and the interlayer covalent bond are considered to be the dominant factors in improving the separation performance and stability of the membrane, respectively. The dual-site supporting technique provides a new approach for the fabrication of GO membranes of high performance, and can be used in the design of other 2D lamellar membranes.