Highly stable graphene oxide composite nanofiltration membrane

Graphene oxide (GO) based membranes are promising for advanced nanofiltration in water treatments but there is a need to improve water flux and membrane stability. Although the interlayer distance of GO membranes can be expanded using intercalants to improve permeability, achieving uniform intercalation without the added complication of water-induced swelling is challenging. Herein, we report the fabrication of GO hybrid lamellar membranes with controllable layer structures to achieve high performance in nanofiltration. The interlayer spacing of the GO hybrid membrane is regulated using TiO₂ intercalants of different sizes, while the stability of GO membranes is enhanced by encapsulating with polyethyleneimine (PEI). The optimal composite membrane delivers a pure water-flux up to 26.0 L m^-2 h^-1 bar^-1 with a 99.9% rejection of methylene blue and eosin under an ultra-low pressure nanofiltration condition. More importantly, the composite membrane sustains good cycling stability after 5 filtration cycles of dye, which enables the potential industrial application in realizing ultra-stable GO based membranes.