Reduced graphene oxide membrane with small nanosheets for efficient and ultrafast removal of both microplastics and small molecules

The clogging of sieving pores due to the complex sewage system of mixed molecules and nanoparticles of different scales is a difficulty in the membrane-based separation process. When the holes are reduced to the point where they can repel small molecules in the contaminants, large-molecule contaminants can adsorb to the holes and decrease the permeability. A similar question remains in new promising graphene oxide (GO) membranes. In this study, we prepared a small lateral-sized reduced graphene oxide (S-rGO) membrane with short Z-type water transport pathways and a lower adsorption energy for pollutant molecules. The S-rGO membrane presented an ultrahigh permeability for large size microplastics (MPs) of 236.2 L m - 2 h - 1 bar-1 (99.9 % rejection rate) and small dye molecules of 234.2 L m - 2 h - 1 bar-1, which was 40 and 25 times higher than the permeability of traditional GO membranes with larger sized sheets, respectively. We evaluated the long-term stability of the membrane in cross-flow system. The membrane maintained more than 212.8 L m - 2 h - 1 bar-1 permeability and a 99.9 % rejection rate under 16 h. Our findings provided a new strategy to address the difficulty of efficient membrane use for complex water pollutants.