Robust reduced graphene oxide membranes with high water permeance enhanced by K+ modification

Graphene oxide (GO) lamellar membranes exhibit great potential for application in molecular separation. However, they are still limited by low water permeation and swelling effects. Here, we develop robust K + -crosslinked reduced GO (rGO–K + ) membranes for treating wastewater containing multivalent heavy metal ions. The rGO–K + membranes demonstrated a water permeance of 86.1 L m −2 h −1  bar −1 and a rejection rate of 99.8% for FeCl 3 , which exceed the corresponding values of state-of-the-art nanofiltration (NF) membranes for multivalent metal ion rejection. Further, the rGO–K + membranes exhibited excellent aqueous stability under a high pressure (up to 9 bar) and acidic, neutral, and alkaline conditions. The improved permeability of the rGO–K + membranes was attributed to the cation–π interactions between K + and the rGO sheets, which fixed and enlarged the interlayer spacing, as well as increased the surface hydrophilicity, thus weakening the water transport resistance. The intercalated K + linked the adjacent layers through the cation–π interactions, which enhanced the membrane stability. The prepared rGO–K + membranes have potential for use in membrane separation in industrial applications.