Realizing ultrahigh nanofiltration performance based on small flake reduced graphene oxide membranes

Graphene - based membranes have attracted considerable attentions in many fields of study such as desalination and water treatment due to their unique physical and chemical characteristics. However, graphene oxide (GO) membranes suffer from a severe permeability-selectivity trade-off, i.e., when high salt rejection rates are obtained, usually the extremely low water permeance (most <1 L m−2 h−1 bar−1) are presented, thus it is now far insufficient to meet the real-world applications. In this work, we demonstrated the feasibility of the small-flakes for reduced graphene oxide (S-rGO) membrane to create more ordered two-dimensional (2D) laminar channels for nanofiltration. The water permeances of S-rGO membrane for rejection Na2SO4 and MgSO4 solutions were 3.7 - and 3.9-fold higher than those of large-flakes rGO (L-rGO) membrane, while the rejections of S-rGO membrane still maintained as high as 87.0 ± 3.8% and 85.4 ± 2.5% for Na2SO4 and MgSO4, respectively. Further, the long-term experiments of the S-rGO membrane demonstrated their high stability. Overall, this work sheds light on the preparing of high nanofiltration performance of GO-based membranes as well as the transport mechanism within 2D laminar channels, and advances the design of GO-based membranes for real world water purification, molecular/ionic sieving, and other environmental applications.