Superhydrophobic composite sponge with magnetically driven and photo-thermal conversion performance for efficient oil-water separation

Facing the increasingly frequent marine oil spill incidents, it is crucial to find effective and environmentally friendly cleaning solutions. Commercial polyurethane (PU) sponges have attracted widespread attention due to their low density, recyclability, and clean, non-polluting nature. However, their inherent superhydrophilic and superoleophilic properties are not effective in addressing oil spill issues. To overcome this limitation, we propose a two-step modification of PU sponges using multi-walled carbon nanotubes (CNTs), Fe₃O₄ nanoparticles (Fe₃O₄ NPs), and polydimethylsiloxane (PDMS) to fabricate a multifunctional superhydrophobic composite sponge with magnetic, photothermal conversion, and flame-retardant properties. The composite sponge we developed exhibited a maximum water contact angle of 159° and maintained its superhydrophobic state for extended periods in both acidic and alkaline environments. The incorporation of CNTs and Fe₃O₄ NPs not only endowed the composite sponge with excellent photothermal conversion capabilities but also imparted magnetism, enabling efficient and directional oil spill treatment on the water surface. Additionally, the introduction of PDMS reduced the surface energy of the sponge and significantly enhanced its flame-retardant properties, improving the safety of oil spill handling on the ocean surface. The experimental results demonstrate that the composite sponge is suitable for various applications in complex or hazardous environments, including oil-water separation, absorption of high-viscosity oils, de-icing, and cleaning, providing a safe, clean, and pollution-free method for addressing marine oil spills.