Superhydrophobic magnetic cotton fabricated under low carbonization temperature for effective oil/water separation

Carbonization of bio-based porous substrates is a facile, environmentally friendly and cost-effective way to create hydrophobic absorbents for oil/water separation applications. However, the processes usually take place under high temperature, which can cause large consumption of energy. Therefore, it is still a challenge to fabricate such absorbent under low temperature. Herein, a kind of superhydrophobic magnetic cotton was successfully fabricated by dip-coating of cotton with Fe 3 O 4 nanoparticles, adsorption of oleic acid and carbonization at 400 °C. The prepared absorbent was integrated with various excellent properties after modifications, including low apparent density (0.0436 g/cm 3 ), high porosity (92.2%), remote controllability, excellent thermal stability and outstanding hydrophobicity (water contact angle, 157.0 ± 1.8°). It could selectively collect oil from different types of oil/water mixtures with large absorption capacity (13.63–37.39 g/g for the testing oils) and high separation efficiency (higher than 99%). After removed the absorbed oil by distillation or direct combustion, the absorbent could be used again with no obvious performance deterioration. The proposed method offers an energy-saving way to fabricate oil absorbent via carbonization.