Fabrication of graphene-PEI composite membrane by supercritical CO2 exfoliation for efficient nanofiltration performance

Graphene has emerged as a highly promising material in the field of membrane separation due to its exceptional properties. However, the challenge of scalable production remains a significant barrier to its widespread application. In this study, we directly used graphene nanosheets (GNs) stripped by supercritical fluid as raw materials to prepare composite membranes with excellent performance. By systematically controlling the intercalation and phase-transition expansion of supercritical CO 2 under the guidance of the established exfoliation theory, a graphene dispersion with a concentration of 2.71 mg∙mL −1 was obtained, which is the highest value reported to date using the supercritical exfoliation (SCE) method. 90 % of the exfoliated GNs are <3 layers, 51 % of GNs exhibiting lateral dimensions >3 μm. The fabricated graphene composite membrane exhibited excellent dye rejection performance, achieving a rejection rate of 99.95 % for Congo red. This method addresses the limitations of conventional liquid-phase exfoliation methods, offering a scalable, cost-effective, and eco-friendly route for the production of graphene and related composite membranes.