Durable superhydrophobic cotton fabric from cardanol/POSS-based polybenzoxazine for high-efficiency oil/water separation

Using biomass resources to develop high-performance superhydrophobic materials that can effectively separate oily wastewater has become an urgent demand. Herein, a novel biomass-based benzoxazine (C-aPOSS) from cardanol and aminopropyllsobutyl-POSS was designed and synthesized, and superhydrophobic cotton fabric (PC-aPOSS/CF) was constructed by dipping cotton fabric in C-aPOSS solution and then polymerizing in situ. The PC-aPOSS/CF exhibited high water contact angle of 155.0° ± 0.3° as well as excellent mechanical and chemical resistance. Due to its super-wettability and porosity, the superhydrophobic PC-aPOSS/CF possessed high separation performance for various oil/water mixtures with oil purities higher than 99.86% and oil fluxes above 3600 L·m−2·h−1. Furthermore, the superhydrophobic PC-aPOSS/CF and polyurethane sponge were used to prepare sandwich-like composite filter membrane for separating surfactant-free and surfactant-stabilized water-in-oil emulsions. The composite filter membrane exhibited oil purity greater than 99.93% and ultrahigh oil flux of over 127,289 L m−2 h−1 bar−1 in separating surfactant-free water-in-oil emulsions, and oil purity lager than 99.87% and oil flux higher than 17,895 L m−2 h−1 bar−1 in separating surfactant-stabilized water-in-oil emulsions. After operating 50 separation cycles of surfactant-free water-in-trichloromethane emulsion, oil purity was still above 99.99%, which indicates the outstanding recyclability of the composite filter membrane. Therefore, the development of high performance superhydrophobic PC-aPOSS/CF may provide a route to the oily wastewater treatment and oil purification.