Design of niobate nanosheet-graphene oxide composite nanofiltration membranes with improved permeability

Membranes assembled by two-dimensional (2D) nanosheets have high potential for advanced molecular separation. The intercalation of nanomaterials into the laminar membrane is a promising strategy to control the nanochannel structure. We present 2D niobate nanosheet (NbN)-Graphene oxide (GO) composite membranes fabricated by simple vacuum filtration. The effect of the weight ratio of NbN/GO on the membrane structures and performances is investigated. The NbN-rich membranes have a more stable structure in the wet condition and a membrane structure with a larger channel size compared with GO-rich membranes. Especially, NbN55-GO45 (weight ratio of NbN/GO = 55/45) shows a superior water permeability of 20 L m−2 h−1 bar−1, which is around 6 times higher than an NbN membrane (NbN100) and 2 times higher than a GO membrane (GO100), while maintaining good rejection abilities of an anionic dye (nearly 100% for Evans blue) and salt (60% for Na2SO4). Different models for the water pathway through nanochannels can be classified according to the composite ratio of the NbN-GO membranes. [Display omitted] •Niobate nanosheet (NbN)-graphene oxide (GO) composite membranes were fabricated by vacuum filtration.•NbN-rich membranes had a more stable structure in wet condition and larger channel size than GO-rich membranes.•Water permeability of NbN membrane was improved by the addition of GO.•The composite membranes showed high water permeability and rejection against an organic dye and salts.