A robust 3D superhydrophobic sponge for in situ continuous oil removing

A variety of materials with superwetting property are fabricated for separation of immiscible oils/organic solvents and water mixture. However, the complex fabrication process, requirement of sophisticated equipment, and associated toxicity strongly limit the development of the superwetting materials. In this paper, a simple two-step dip coating strategy is demonstrated to prepare polydopamine-octadecanethiol modified 3D porous sponge with superhydrophobic and superoleophilic properties (a water contact angle of 156.8° ± 2.5° and an oil contact angle of nearly 0°) through the combination of enhanced surface roughness and low surface energy coating for separation of oil/water mixture. The as-prepared superhydrophobic sponges possess high porosity (greater than 99.2%), low density (below 10 mg/cm³), and 3D porous network structure, which meet well with the needs for adsorption of the actual oil pollutions. More importantly, in situ continuous removal of oil from oil/water mixture is successfully accomplished via a vacuum-assisted system, even in the corrosive environments including turbulent situation, heat, acidic, alkaline, seawater, and glacial water. The continuous oil collection system could avoid the limit in adsorption saturation effectively. We believe that the superhydrophobic sponge with easy large-scale production, economical, and environmentally friendly characteristics can be a superior candidate for the treatment of oily wastewater and practical oil spill accidents.