Biomimetic modification of sponges with alkyl-silica hybrid nanowires for efficient oil-water separation applications

Oil spills present significant environmental challenges due to high remediation costs and secondary pollution. Inspired by the lotus leaf microstructure, a novel SiO 2 NWs@PU composite was developed by modifying polyurethane (PU) sponges with hydrophobic alkyl groups-capped silica nanowires (SiO 2 NWs). This design synergistically optimizes surface energy and roughness by tailoring the alkyl chain length and aspect ratio of SiO 2 NWs, achieving excellent oil-water separation. The composite achieves a low surface energy of 0.73 ± 0.05 mJ/m² and a water contact angle of 154.4°, maintaining superhydrophobicity (>151°) under harsh conditions, including pH 3–11, boiling water, and baking at 150 °C. It also exhibits robust mechanical properties, with a 4.6-fold increase in compressive strength over pure PU and minimal degradation (<15 %) after 100 compression cycles. SiO 2 NWs@PU achieves oil adsorption capacities of 21–49 g/g, with over 95 % separation efficiency under simulated turbulent marine conditions. Versatility of this strategy is demonstrated through substituting PU with melamine sponge, resulting a SiO 2 NWs@ melamine composite with outstanding oil adsorption capacities of 72–163 g/g. With excellent resilience, flame retardancy, and reusability, these scalable and cost-effective composite sponges provide a sustainable solution for oil spill remediation and oily wastewater treatment, addressing critical environmental needs.