Incorporating Zwitterionic Graphene Oxides into Sodium Alginate Membrane for Efficient Water/Alcohol Separation

For the selective water-permeation across dense membrane, constructing continuous pathways with high-density ionic groups are of critical significance for the preferential sorption and diffusion of water molecules. In this study, zwitterionic graphene oxides (PSBMA@GO) nanosheets were prepared and incorporated into sodium alginate (SA) membrane for efficient water permeation and water/alcohol separation. The two-dimensional GO provides continuous pathway, while the high-density zwitterionic groups on GO confer electrostatic interaction sites with water molecules, leading to high water affinity and ethanol repellency. The simultaneous optimization of the physical and chemical structures of water transport pathway on zwitterionic GO surface endows the membrane with high-efficiency water permeation. Using dehydration of water/alcohol mixture as the model system, the nanohybrid membranes incorporating PSBMA@GO exhibit much higher separation performance than the SA membrane and the nanohybrid membrane utilizing unmodified GO as filler (with the optimal permeation flux of 2140 g m^-2 h^-1, and separation factor of 1370). The study indicates the great application potential of zwitterionic graphene materials in dense water-permeation membranes and provides a facile approach to constructing efficient water transport pathway in membrane.