Superhydrophobic, elastic and anisotropic cellulose nanofiber aerogels for highly effective oil/water separation

Nanocellulose-based aerogels have gradually attracted attention in the field of oil/water separation owing to their light weight, excellent absorption properties, and environmental-friendliness. Herein, we report a facile and easily scalable method for fabricating superhydrophobic, elastic and anisotropic cellulose nanofiber (CNF) aerogels. Directional freeze-drying, soaking in polydimethylsiloxane (PDMS) solution and heat treatment were applied to obtain anisotropic and aligned CNF-PDMS aerogel sheets and blocks with superhydrophobicity and high elasticity. The CNF-PDMS aerogel sheets could realize continuous oil/water separation by filtration with a flux up to 2800 L·m−2·h−1 and a separation efficiency of 99.9%. The CNF-PDMS aerogel blocks could separate the oil/water mixture by the absorption–extrusion, and could also be applied in real-time continuous oil/water separation by vacuum suction with a flux as high as 145 L·h−1·g−1 and a separation efficiency of 99.9%. Overall, our anisotropic CNF-PDMS aerogels are the promising materials for low-cost rapid oil/water separation in multiple separation pathways.