The purification of organic dye pollutants and insoluble emulsified oils in wastewater has become a critical focus of environmental research. In this study, fibrous membranes were prepared through electrostatic spinning by first hydrolyzing polyacrylonitrile and then blending it with water-soluble polyvinylpyrrolidone (PVP). Subsequent hydrothermal treatment was applied to partially remove PVP from the fibers, creating rough and porous surfaces that exposed more functional carboxyl groups and increased the fibers' specific surface area. The resulting membranes exhibited superhydrophilicity (≈0°) and underwater superoleophobicity (≈157°), alongside excellent fouling resistance. The fibrous membranes, characterized by their carboxyl-rich surfaces, exhibited improved adsorption capabilities for cationic dyes, attaining capacities of 735.77 mg/g for malachite green, 429.31 mg/g for methylene blue, and 607.21 mg/g for crystal violet. The membranes achieved a remarkable separation efficiency of 99.8% for oil-in-water emulsions and maintained 98.5% efficiency after 10 cycles of separation and elution, highlighting their outstanding regeneration capability. In summary, this study demonstrates that these fibrous membranes are highly effective in removing cationic dyes and insoluble emulsified oils from wastewater. The membranes show great potential for applications in wastewater treatment, particularly for selective dye removal and oil-water separation.