Cellulose nanofibril stabilized Pickering emulsion templated aerogel with high oil absorption capacity

Nanocellulose-based aerogels, featuring a three-dimensional porous structure, are considered as an ideal green absorbent because of their superior absorption performance, abundance, and renewability. To make them an effective oil absorbent, however, a hydrophobic modification or carbonization is required, which is often environmentally unfriendly and energy intensive. Herein, a Pickering-emulsion-templating approach is used to create a cellulose nanofibril (CNF) aerogel featuring a hierarchical pore structure with ultrahigh oil absorption capacity. n-Hexane-CNF oil-in-water Pickering emulsions are prepared as an emulsion template, which are further lyophilized to create a hollow microcapsule based CNF (HM-CNF) aerogel with density 3.0 – 7.9 mg/cm³ and porosity ≥ 99.5%. The hierarchical pore structure of the HM-CNF aerogel, arising from the CNF Pickering emulsion template, is revealed by scanning electron microscopy and Brunauer-Emmett-Teller analyses, which confirm the very high surface area of 216.6 m²/g with the average pore diameter of 8.6 nm of the aerogel. The maximum absorption capacity of the aerogel reaches 334 g/g and 170 g/g for chloroform and n-hexadecane, respectively, without any surface modification or chemical treatment. After five cycles of absorption-distillation, the aerogel shows 38% of an oil retention (n-hexane). Combined results demonstrate potential of the Pickering emulsion templated CNF aerogel as a sustainable and high-performance oil absorbent.