Eco-friendly stable cardanol-based benzoxazine modified superhydrophobic cotton fabrics for oil–water separation

Cardanol, a renewable resource derived from the by-product of the cashew nut industry, was applied to react with 3-aminopropyltriethoxy (KH-550) for the synthesis of a novel cardanol-KH550 benzoxazine (CKBO). The long aliphatic chain of CKBO allows grafting on the surface of cotton fabric via the formation of covalent bonds between the siloxanes of CKBO and hydroxyl groups of cotton. Herein, the superhydrophobic cotton fabric can be fabricated via a facile immersion method, which can be easily applied to prepare various superhydrophobic materials (cotton and non-woven fabric), even on a large scale. The CKBO-modified cotton fabric exhibits excellent resistance to high temperature and ultraviolet (UV) irradiation, with good pH stability, mechanical stability, and durability. The superhydrophobic/ superoleophilic materials display high separation efficiency of various immiscible oil-water mixtures, even under harsh conditions or after 15 cycles. The CKBO-modified cotton shows a high absorption capacity towards not only oil on the water surface and under water, but also oil from emulsified oil-water mixtures. The superhydrophobic fabrics, modified with the eco-friendly cardanol-based benzoxazine, are environmentally friendly, low cost, and easy to scale up, exhibiting great potentials in practical applications.