Biomimetic hierarchical structured carbon nanofibrous membranes with enhanced flexibility and superwettability for oil-in-water emulsions separation

Carbon nanofibrous membranes (CNFMs) are promising materials for treating oily wastewater, but their broad application is limited by challenges such as hydrophobicity, lipophilicity, and poor flexibility. In this study, we developed a superhydrophilic and underwater superoleophobic CNFM with enhanced flexibility through electrospinning using polyacrylonitrile and benzoxazine as precursors. The morphology, mechanical properties, and surface wettability of CNFMs were effectively regulated by incorporating silica nanoparticles (SiO 2 NPs) into the spinning solutions. With an optimal doping level of SiO 2 NPs (over 23 wt% relative to the polymers), the resulting CNFM exhibited a biomimetic hierarchical structure and robust mechanical flexibility. A proposed mechanism indicates that doped SiO 2 NPs within the carbon nanofiber matrix help disperse bending strain and stress. Additionally, these nanoparticles created numerous hydrophilic sites on the CNFM surface, significantly enhancing capillary action for water—resulting in remarkable superhydrophilicity (water contact angle = 0°) and underwater superoleophobicity (oil contact angle > 155°), regardless of water conditions (acidic, alkaline, or saline). Consequently, the obtained CNFM effectively separated various oil-in-water emulsions solely under the force of gravity, and could be easily regenerated. This work offers a promising solution for designing next-generation membranes for oily wastewater treatment in complex environments.