Reinforcement of C-NFO@GDY Membranes via the Synergistic Effect of the Graphdiyne Honeycomb Nanostructure and Electronegativity for High-Efficiency Oil-in-Water Emulsion Separation

Abstract

Electrospun fiber membranes enable oil–water emulsion separation via tunable morphology and chemistry, yet most face an efficiency–permeability trade-off where enhancing one compromises the other. Herein, optimized membranes (C-NFO@GDY) are synthesized with a uniform honeycomb nanostructure of graphdiyne (GDY) on flexible coal-based preoxidized fibers (C-NFO) through the Glaser‒Hay coupling reaction. The honeycomb nanostructure of GDY effectively disperses external stress on the C-NFO fibers, increasing the tensile strength from 2.8 to 3.2 MPa. In addition, the nanostructure enhances hydration layer formation kinetics, achieving superhydrophilicity (0°) and underwater superoleophobicity (> 150°) of the membrane. When tested against three surfactant-stabilized emulsions (cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and polyoxyethylene sorbitan monooleate (Tween 80)), the membranes demonstrated separation fluxes of 2936 L/(m² h), 2149 L/(m² h), and 1855 L/(m² h), and the corresponding separation efficiencies were 99.6%, 96.6%, and 93.1%. For CTAB-stabilized emulsions, the C-NFO@GDY membrane (zeta potential: − 65.2 mV) exhibits strong electrostatic attraction with cationic surfactants, achieving a high flux of 2936 L/(m² h) and a separation efficiency of 99.6%, surpassing those of recently reported MXene and PANI composites under identical conditions. Overall, the synergy between honeycomb nanostructure and electronegativity of GDY overcomes the flux–efficiency trade-off, offering new ideas for the preparation of oil–water separation membranes.

Graphical Abstract