A heterogeneous polyurethane hybrid foam with enhanced demulsification and dynamic oil cleaning for continuous emulsion separation.

Here, a top-down strategy was presented to fabricate a heterogeneous polyurethane hybrid foam with independent oil-absorbing frameworks and uninterrupted water transport channels for continuous emulsion separation. A commercial polyurethane foam (PUF) was hydrophobically modified to develop oil-absorbing frameworks (HPUF). Superhydrophilic carbon nanotubes/cellulose nanofibers (CNTs/CNFs) aerogels were assembled in the voids of the HPUF to establish independent water transport channels, forming a heterogeneous polyurethane hybrid foam (CHPUF). This design endowed the CHPUF with a heterogeneous wetting structure formed by the hydrophobic HPUF and the hydrophilic CNTs/CNFs aerogels, which allowed it to exhibit super hydrophilicity and underwater oil-absorbing properties. The underwater oil-absorbing properties can promote the dynamic cleaning of oil contamination at the separation interface to improve the continuity of emulsion separation. Meanwhile, the heterogeneous wetting structure of the CHPUF and photothermal-induced effect of CNTs synergistically enhanced their demulsification capability. Leveraging these structural and functional attributes, the CHPUF have demonstrated exceptional potential in continuous emulsion separation, demonstrating a robust separation capacity with a single separation volume surpassing 3000 mL and remarkable recyclability, evidenced by over five stable separation cycles each maintaining the separation efficiency of 98 %. The CHPUF have exhibited promising separation suitability for multiple surfactant-stabilized oil-in-water emulsions, achieving over 800 L·m·hand 99 % of separation flux and efficiency, respectively. Consequently, the CHPUF with dynamic oil cleaning and enhanced demulsification display great potential for treating oily wastewater, while inspiring the development of novel 3D superwetting materials, propelling their application in environmental remediation.