Oil-water separation via superhydrophilic materials: Fundamentals and perspectives for 2D/3D system design

For oily wastewater treatment challenges, traditional technologies such as gravity separation and adsorption methods suffer from low efficiency, high energy consumption, or secondary pollution. Superhydrophilic/underwater superoleophobic materials provide a new approach for efficient and environmentally friendly separation by virtue of their high affinity for water and strong repulsion for oil. These materials are mainly divided into two-dimensional (2D) filtration types and three-dimensional (3D) adsorption types: two-dimensional materials achieve oil-water sieving through micro-nano rough structures and hydrophilic modification but are prone to clogging; three-dimensional materials rely on porous structures to selectively absorb oil yet face limitations in adsorption capacity and recyclability. Both encounter challenges in adapting to high-salt, acidic, or surfactant-containing wastewater. This paper systematically reviews research progress on both material types, analyzes their technical bottlenecks, and emphasizes the future need to focus on precise material structure regulation, anti-fouling mechanism optimization, and scaled-up preparation processes. These advancements will promote functional design, enhance environmental adaptability, and enable intelligent development, laying a theoretical foundation for technological innovation in oily wastewater treatment.