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

Abstract

Cellulose-based\naerogels show great potential as absorbents for\noil and chemical spill cleanup due to their low density and excellent\nabsorption capacity. However, the hydrophility and inferior mechanical\nproperties have often limited their practical applications. In this\nstudy, high-performance biomass-based aerogels were prepared by freeze-casting\naqueous suspensions of polyvinyl alcohol and cellulose nanofibrils\nin the presence of hydrolyzed methyl­trimethoxy­silane sol.\nSuccessful silylation on the substrate surface was confirmed by Fourier\ntransform infrared spectroscopy, X-ray photoelectron spectroscopy,\nthermal stability, and water contact angle measurements. Freeze-casting\nsuccessfully assembled a highly aligned interconnected porous structure,\nresulting in the prepared aerogels with high modulus and strength\nin the aligned direction (along the freezing direction) and outstanding\ncompression flexibility in the perpendicular direction (transverse\nto the freezing direction). The ultralow density (10.2 kg/m³), high hydrophobicity (water contact angle of 140°), and good\ncompressive recovery (84% recovery of its original thickness after\n100th compression tests) allow the aerogel to absorb oils and organic\nsolvents 45–99 times higher than its own weight. Meanwhile,\ngood reusability was also observed with an absorption capacity greater\nthan 84% after 35 absorption–squeezing cycles. The novel aerogels\nprepared in this study are expected to have great potential for application\nin treating oil and chemical spills.