Xueyi Zhou, Yufan Feng, Tingting Xu, Huining Xiao, Hongqi Dai, Huiyang Bian
The growing discharge of oily wastewater creates an urgent need for efficient, sustainable absorbents capable of high-flux oil-water separation. This study presents a straightforward Pickering emulsion-templating strategy in which a single modifier, vinyltrimethoxysilane (VTMO), serves simultaneously as the sole emulsifier and the cross-linker for cellulose nanofiber (CNF) aerogels, eliminating the need for any surfactant or additional cross-linking agent. Specifically, hydrolyzed VTMO condensed with surface hydroxyl groups of CNF to form covalent Si-O-C bonds, while the self-condensation of silanol groups created a cross-linked Si-O-Si network that locked the pore architecture. During freezing, ice crystals and oil droplets served as dual templates, resulting in aerogels with square micro-channels after freeze-drying. The siloxane network grafted onto the fiber surfaces imparted stable hydrophobicity, enabling the material to endure repeated compression and resist fluid scouring. The optimized aerogel, C1V2 (CNF to VTMO mass ratio of 1:2), possessed a low density of 16.2 mg·cm-3, a water contact angle of 142.1° that remained stable across a wide pH range, and absorption capacities for organic liquids ranging from 38.4 to 79.7 g·g-1. Driven solely by gravity without any external force, the aerogel delivered an oil flux as high as 54,660 L·m-2·h-1 for chloroform-water separation. After ten cycles of solvent-exchange regeneration, the flux still attained 50,674 L·m-2·h-1, a value far exceeding that of most bio-based aerogels reported to date. The aerogel was also integrated with a peristaltic pump for continuous operation. This work offers a simple and sustainable route to high-flux oil-water separation materials derived from renewable cellulose.