One-step construction of carbon nanoparticle/graphene oxide nanofiltration membranes with uniform sandwich structure for enhanced water purification

Graphene-based membranes have great potential for water purification. However, it is still a challenge to achieve high solute rejection at high water flow by controlling the water permeation channel. Herein, carbon nanoparticles (CNPs) were uniformly sandwiched between graphene oxide (GO) sheets by one-step vacuum-assisted filtration of CNPs and GO mixed solution, resulting in the formation of CNPs/GO composite nanofiltration membranes with uniform sandwich structure. The addition of CNPs in the composite membrane could help to form a continuous transverse channel of water permeation and greatly increase the water flow. The results showed that the CNPs/GO composite membrane with a mass ratio of 20% exhibited the best performance. The pure water flow rate was 49.9 L m^-2 h^-1, which was 21 times higher than that of the pure GO membrane. The rejection rate for four different organic dyes exceeded 97%. The rejection rate for methylene blue (MB) was still 94.7% after 8 recycling cycles. In addition, the membranes allow the penetration of salts, which makes them promising for dye wastewater desalination. This study provides a simple and effective strategy to tune the channel microstructure of the composite membranes and increases the understanding of the important role of the sandwich particles in achieving a better performance of the membranes.