Construction of Bioinspired, Multifunctional, Durable, and Superhydrophobic Sponges for Oil–Water Separation Based on Recycled Flexible Foam

Abstract Aiming at simultaneously settling the problem of waste resource recycling, oily wastewater pollution/health risk, flammability, and durability of traditional oil–water separation materials, this work developed the superhydrophobic/superoleophilic sponge materials (P/APP@ZIF-8@PDA@PU), which were inspired by natural lotus leaves and mussels. The results suggested that the water contact angle (WCA) and oil contact angle (OCA) of P/APP@ZIF-8@PDA@PU reached 154.3 ± 1.1° and ∼0°, respectively. The joint action of PDA/APP@ZIF-8 and PDMS in manufacturing hierarchical roughness and reducing the surface energy of sponges was confirmed. Most of all, the oil/water separation flux and efficiency of P/APP@ZIF-8@PDA@PU for n-hexane/water mixture were still as high as 43,263 L m–2 h–1 and 99.3% even after 20 cycles, indicating that P/APP@ZIF-8@PDA@PU possessed good oil–water separation performance and cyclic separation stability. After 20 adsorption/release cycles, the adsorption capacity of P/APP@ZIF-8@PDA@PU was still as high as 23.58 g/g, which demonstrated good resistance to oil clogging. Moreover, P/APP@ZIF-8@PDA@PU possessed good mechanical stability and chemical durability through a series of sandpaper rubbing, tape stripping, acid-alkali-salt immersion, and washing experiments, which could simulate the effectiveness of oil/water separation materials in practical application scenarios. Compared with PU, the total heat release rate (THR) of P/APP@ZIF-8@PDA@PU was reduced by 32.8%, and the combustion time was extended to 65 s before self-extinguishing, which was expected to solve the fire safety problem of PU materials in the process of usage, storage, and transportation. Thus, this paper exploits an effective and fluorine-free route for synchronously achieving the goals of resource recycling and wastewater treatment.