Improving stability and separation performance of graphene oxide/graphene nanofiltration membranes by adjusting the laminated regularity of stacking-sheets.

The laminated graphene oxide (GO) membranes are promising alternatives in the field of nanofiltration due to their unique stacked interlayer structure and controllable molecular transport channels. However, it is still challenging to obtain satisfactory physical stability and separation performance to meet its practical application. In this study, a novel GO/Gr (graphene) nanofiltration membrane with high stability was engineered by post-hot-pressure treatment, following forward pressure filtration. The impact of GO/Gr loading ratio of the composites nanofiltration membranes for the permeability, selectivity, hydrophilicity and physical stability was investigated. The GO/Gr nanofiltration membranes exhibited high stability and separation performance because of the enhanced regularity and smoothness of the overall stacking layers. It was demonstrated that the satisfactory permeability (12.8-20 L·m-2·h-1) of GO/Gr nanofiltration membranes could be achieved. Compared with the pure GO membranes, GO/Gr-0.5 membranes exhibited a higher Na2SO4, NaCl, MgCl2, and MgSO4 rejection rate of approximately 78.3%, 51.2%, 34.5% and 32.6%, respectively. Meanwhile, the rejection rate (99.5%, 99.9%, 97.3% and 98.6%) of composite membranes for Methylene blue, Congo red, Rhodamine B and Methyl orange could be achieved. This facile way reveals the potential of stacked GO/Gr membranes in developing GO-based nanofiltration membranes.