Superhydrophobic polyimide/cattail-derived active carbon composite aerogels for effective oil/water separation

The frequent oil spill accidents have created increasingly environmental and ecological problems. Therefore, the development of effective oil-cleaning materials is of great importance. In this study, we prepared superhydrophobic polyimide/cattail-derived active carbon composite (PI/CAC) aerogels for efficient oil/water separation through a facile approach based on freeze-drying and thermal imidization. The resultant aerogel shows ultralight weight (29.7 mg/cm3), superhydrophobicity (water contact angle = 151.3°), excellent compressibility, and ideal chemical stability, which are conducive to the oil sorption and extrusion at various harsh conditions including acidic, alkaline, and saline solutions, as well as oil-in-water emulsions. Typically, the optimized sample PI/CAC-3 aerogel could achieve saturation within 5–20 s, delivering a high oil sorption capacity of 25.1–71.0 g/g for various oils. When used for continuous oil/water separation, high flux of 4.47 × 104 L m-2 h−1 and separation efficiency of 98.3% were achieved for chloroform/water mixture by gravity-driven separation method. Furthermore, due to the high compressibility, the aerogel can be used for cycling separation through sorption-extrusion process with less than 3% decrease in separation efficiency after 10 cycles. These advantages make it a potential candidate for the treatment of wastewater polluted by various oils and/or organic solvents.