Highly Compressible and Hydrophobic Anisotropic Aerogels for Selective Oil/Organic Solvent Absorption

Cellulose-based aerogels show great potential as absorbents for oil and chemical spill cleanup due to their low density and excellent absorption capacity. However, the hydrophility and inferior mechanical properties have often limited their practical applications. In this study, high-performance biomass-based aerogels were prepared by freeze-casting aqueous suspensions of polyvinyl alcohol and cellulose nanofibrils in the presence of hydrolyzed methyltrimethoxysilane sol. Successful silylation on the substrate surface was confirmed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermal stability, and water contact angle measurements. Freeze-casting successfully assembled a highly aligned interconnected porous structure, resulting in the prepared aerogels with high modulus and strength in the aligned direction (along the freezing direction) and outstanding compression flexibility in the perpendicular direction (transverse to the freezing direction). The ultralow density (10.2 kg/m 3 ), high hydrophobicity (water contact angle of 140°), and good compressive recovery (84% recovery of its original thickness after 100th compression tests) allow the aerogel to absorb oils and organic solvents 45–99 times higher than its own weight. Meanwhile, good reusability was also observed with an absorption capacity greater than 84% after 35 absorption–squeezing cycles. The novel aerogels prepared in this study are expected to have great potential for application in treating oil and chemical spills.