Micro-nano manufacturing of a pre-identified organic hydrogel surface for selective oil/water separation with ultra-high flux

Abstract The indiscriminate discharge of industrial wastewater and oil leakage accidents cause serious water pollution and pose threats to aquatic ecosystems and sanitary environments. The oily wastewater system is complex and most membrane materials cannot separate various oil-water mixtures. Serious membrane pollution would cause a decrease in separation flux. We proposed a pre-identified organic hydrogel surface prepared by micro-nano manufacturing technology for selective oil/water separation with ultra-high separating flux. Stimulated by water, the prepared surface is superhydrophilic-underwater superoleophobic, allowing water to pass through, and stimulated by oil, the prepared surface is superoleophilic-underoil superhydrophobic, allowing oil to pass through. Thus, based on the special solvent-responsive property, the prepared surface has a pre-identified function for water and oil, and could achieve the capture of oil droplets in water and water droplets in oil. In addition, the surface maintains an ultra-high separating efficiency and flux of about 99.85% and 17 750 L·m⁻²·h⁻¹, and even after continuous cycles without cleaning, it could keep 99.1% and 16 000 L·m⁻²·h⁻¹ due to the excellent anti-fouling ability. This study provides new ideas and methods for designing intelligent oil-water separation devices, and further guidance for achieving on-demand oily wastewater treatment.