Pickering emulsion-templated cellulose aerogels for organics/water separation

A highly hydrophobic, high-porosity, ultralight and recyclable cellulose aerogel was fabricated using an oil-in-water Pickering emulsion as the structural template. The emulsion was stabilized by cellulose nanofibers (CNF). Methyltrimethoxysilane (MTMS) served as both a covalent crosslinker and a hydrophobic modifier, while Ca 2+ acted as an ionic crosslinker. Ca 2+ ions adjusted the interlayer spacing of the CNF. Together with MTMS covalent crosslinking, Ca 2+ ionic crosslinking helped construct the three-dimensional network of cellulose aerogels. Combined with isopropanol solvent replacement, this approach synergistically reduced capillary pressure, enabling ambient pressure drying. The resulting aerogel (A-CNFA-M-Ca) possesses a hierarchical porous structure. Pores of 200–400 nm arise from the intrinsic stacking of CNF. Pores in the 2–5 μm range result from the synergistic effect of Ca 2+ crosslinking and the siloxane network. Larger pores of 10–80 μm remain after removal of the oil phase from the Pickering emulsion. A-CNFA-M-Ca displays a water contact angle (WCA) of 146°, a porosity of 91%, and an ultralow density of 22.72 mg∙cm -3 . It exhibited adsorption capacities of 35.46 to 75.97 g∙g -1 for organic compounds such as n-hexane and chloroform, and maintained over 90% of its saturated adsorption capacity after cyclic regeneration. Due to variations in carbon chain length, molecular configuration and hydrogen-bonding strength, the selective adsorption-separation efficiencies of A-CNFA-M-Ca were 45% (n-butanol), 33% (n-propanol), 31% (isopropanol), and 21% (ethanol), with corresponding separation factors of 21.6, 14.7, 11.1 and 5.4. A-CNFA-M-Ca is promising for selective adsorption-separation of organic components from aqueous solutions.