Mild annealing reduced graphene oxide membrane for nanofiltration

In this work, we demonstrated for the first time the feasibility of the mild annealing for partially reducing graphene oxide (GO) membranes, to create more ordered two-dimensional (2D) laminar channels for nanofiltration. The physicochemical change of GO membranes during the mild annealing process was systematically characterized, results show mild annealing not only stabilized graphene oxide membranes by transforming the oxygen functional groups and narrowing the laminar channels of the GO membranes but also enable tunable salt rejection of the resultant membranes. Compared to reduced graphene oxide (rGO) membranes thermally treated at a higher temperature (150 °C), the mild annealing reduced GO membrane (MRGO) achieved higher water permeance and Na2SO4 selectivity owing to its more ordered laminar structure. This work sheds light on the preparing of high-performance GO-based membranes as well as the transport mechanism within 2D laminar channels.