Polydopamine-grafted sustainable superhydrophobic porous polymeric surfaces for multifunctional oil/water separation

In this work, superhydrophobic/superoleophilic novel materials were synthesized with the modification of silica nanoparticles with stearic acid, which were immobilized onto polydopamine-grafted polyurethane to form 3D porous materials (PU-PDA)–Si-SA for removing oily contaminants from oil/water mixtures. (PU-PDA)–Si-SA was synthesized by a facile dip-coating method using recycled PU as a sustainable material. The coupling effect among carboxylates, hydroxyl, and the silanol (Si–OH) surface of the formed silica nanoparticles was also characterized using FTIR, TGA, XRD, TEM, SEM, and EDX analyses of the raw materials. These results indicated a uniform distribution of chemical components across the PU surface. The material exhibited superhydrophobicity with a water contact angle of 164° observed in the water contact angle (WCA) analysis. Furthermore, the absorption capacity of the modified material reached approximately 45 times its original mass, with an average separation efficiency above 98% and an increased oil permeation flux of around 7200 L m⁻² h⁻¹. Interestingly, this material showed superior performance compared to the material in the absence of PDA coating (PU)–Si-SA, in all performance tests. Because these 3D porous nanomaterials are stable over the long term and thermally stable under elevated-temperature conditions, they could represent promising absorbents for large-scale separation.