Superhydrophobic ODT-TiO₂ NW-PDA nanocomposite-coated polyurethane sponge for spilled oil recovery and oil/water separation

Frequent occurrences of accidental oil spills, chemical leakages and oily water discharge make the development of effective and efficient methods for spilled oil and organic pollutants clean-ups extremely critical and urgent. Here, a novel superhydrophobic octadecanethiol-TiO₂ nanowires-polydopamine nanocomposites-modified polyurethane sponge was fabricated by a facile and cost-effective synthesis process, wherein, self-polymerization of dopamine was coated on the polyurethane skeleton structure, followed by direct incorporation of TiO₂ nanowires to enhance surface roughness and lastly, surface coating with the low surface energy octadecanethiol molecules. The resultant PU-PDA-TiO₂-ODT sponge showed superhydrophobic and superoleophilic with the water contact angle (WCA) of 154.0 ± 2° and the oil contact angle of 0°, as well as self-cleaning and anti-fouling capabilities. The as-fabricated sponge demonstrated high oil adsorption capacity for a broad variety of oils and organic solvents, also exhibiting good reusability of more than 30 cycles without diminishing adsorption performance. The potential for practical applications was demonstrated through gravity-driven and vacuum assisted continuous separations, yielding more than 99.9% oil purity. Moreover, the as-prepared sponge exhibited superior mechanical strength through exceptional performance in compression, ultrasonication and frictions tests, and consistent superhydrophobicity in harsh environments including exposure to pH, temperature and NaCl concentration variations. Thus, the novel superhydrophobic and superoleophilic sponge has great potential for practical application in oil-water separations.