Surface charge and hydrophilicity improvement of graphene membranes via modification of pore surface oxygen-containing groups to enhance permeability and selectivity

Abstract

Graphene is a promising material in membrane separation. However, high water permeability as well as high rejection against contaminants is still demanded yet challenging for graphene-based membranes fabrication. In this work, we synthesized an oxygen-containing group-modified reduced graphene oxide membrane (O-rGOM), which was designed by substituting the surface layers of rGO membranes with GO flakes. The number of oxygen-containing groups on membrane surface was modulated by the [GO]/[rGO] ratio during the construction of O-rGOM. Results demonstrated that a [GO]/[rGO] ratio of 1:4 was optimal, with oxygen-containing groups modifying the pore surface of rGO laminates effectively. Furthermore, the O-rGOM showed improved hydrophilicity and water permeability. In addition, modification of the oxygen-containing groups promoted the zeta potential around the membrane pore, resulting in enhanced electrostatic interaction between the membrane and charged contaminants. The O-rGOM structure exhibited 18.2% and 5.2% improvement in acid orange 7 and methylene blue rejection, respectively, as well as ∼2.6 times enhancement in water permeability compared with the rGOM. This work provides a feasible approach for the design of graphene-based membranes to improve filtration performance with enhanced water permeability.