Porous biomimetic hybrid synergistically reinforced flexible lignin-based carbon nanofibrous membrane for efficient purification of emulsified oily wastewater

High-performance separation membranes with stable physicochemical properties are highly desirable for treating emulsified oily wastewater. Carbon nanofibrous membranes (CNFMs) offer excellent thermal resistance and chemical inertness; however, their intrinsic hydrophobicity and limited mechanical flexibility restrict practical use. Herein, porous Si-containing carbon nanofibrous membranes (CCNFMs) were fabricated by electrospinning PAN/PLA/lignin/TEOS precursor solutions, followed by controlled stabilization and carbonization. TEOS-derived Si O domains formed a biomimetic Si-O/carbon brick-and-mortar hybrid architecture containing defect-rich turbostratic carbon and amorphous Si O phases, which suppressed carbonization-induced collapse and preserved multiscale porosity. PLA acted as a sacrificial porogen and generated intrafiber nanopores that enhanced flexibility by blunting and deflecting crack propagation. Owing to the synergistic effect of the porous structure and hybrid architecture, the optimized membrane showed excellent foldability, rapid water wettability, and underwater superoleophobicity, with an underwater oil contact angle of 150.5°. Under gravity-driven conditions, the membrane achieved a flux of 4060.5 ± 358.4 L·m −2 ·h −1 and a separation efficiency of 99.32 ± 0.12% for a surfactant-free oil/water mixture, as well as a flux of 1560.0 ± 158.3 L·m −2 ·h −1 and an efficiency of 98.32 ± 0.12% for an SDS-stabilized soybean-oil emulsion. The membrane also maintained stable performance after repeated cycling, prolonged storage, and exposure to cold/hot water, acidic solution, and alkaline solution. This work combines TEOS-assisted hybridization, PLA-derived pore engineering, and temperature-regulated carbonization to build a robust porous Si-O/carbon membrane with mechanical flexibility, underwater superoleophobicity, and environmental durability for gravity-driven oil/water separation. It shows potential for emulsified oily wastewater treatment and offers insights into designing lignin-based carbon nanofibrous membranes.