Eco-friendly superhydrophobic sponges for efficient oil-water separation and resource recycling

Owing to the risk of oil spills in the water pollution and human health, it is urgent to exploit the efficient, simple and low-cost materials to treat oily wastewater. Inspired by the native super-wettability surface of lotus leaves, a green, multi-functionality, multi-response and recyclable superhydrophobic material has been established via an one-step dip-coating method based on waste polyurethane sponges (PU), which is expected to settle the treatment problem of oil/water mixture. And the coating system is mainly constituted by a mixture of silicon resin, nano-Fe 3 O 4 and ultrafine expandable graphene (EG), which can act as lowing low surface energy and fabricating the hierarchical micro-/nano-scaled surface roughness. The water contact angle (WCA) of 156.2 ± 1.4° and water sliding angle (WSA) of 8.0 ± 0.5° have triggered a series of skills in water repellency, self-cleaning and anti-fouling. Most of all, the exceptional oil–water separation capabilities have been achieved that the sorption capacity, separation efficiency and flux for light oil can reach 33.2 g/g, 99.5 % and 31,611 L m -1 h −1 , respectively. Accorded with the intrinsic thermal harvesting ability of Fe 3 O 4 and EG, the excellent photothermal conversion performance has been gained that the temperature of superhydrophobic sponges can reach 68.7 °C in 180 s when the irradiation intensity is 1.2 sunlight, endowing the potential sorption ability of high-viscosity crude oils. Most importantly, the various oil–water separation modes can be also realized that are composed of gravity-driven, magnetism-driven, vacuum-driven and photothermal-driven methods. Except that, the adequate flame retardancy, mechanical durability and chemical stability have been acquired that have raised the high-value-added utilization of modified sponges in fields of environment protection and functional materials.