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Sustainable Approach for Cellulose Aerogel Preparation from the DBU–CO₂ Switchable Solvent
- Onwukamike, Kelechukwu N., Lapuyade, Laurine, Maillé, Laurence, Grelier, Stéphane, Grau, Etienne, Cramail, Henri, Meier, Michael A.R.
- ACS sustainable chemistry & engineering 2019 v.7 no.3 pp. 3329-3338
- X-ray diffraction, adsorption, aerogels, cellulose, coagulation, crystal structure, equations, freeze drying, infrared spectroscopy, nitrogen, porosity, porous media, scanning electron microscopy, solubilization, solvents
- We report a sustainable and easy approach for the preparation of cellulose-based aerogels from the DBU–CO₂ switchable solvent system via a solubilization and coagulation approach followed by freeze-drying. The easy, fast, and mild solubilization step (15 min at 30 °C) allows for a rapid preparation procedure. The effect of various processing parameters, such as cellulose concentration, coagulating solvent, and the superbase, on important aerogel characteristics including density, porosity, pore size, and morphology, were investigated. Density values obtained ranged between 0.05 and 0.12 g/cm³, with porosity values between 92% and 97%. The morphology of the obtained cellulose aerogels was studied using scanning electron microscopy (SEM) showing a random and open large macroporous cellulose network with pore sizes ranging between 1.1 and 4.5 μm, depending on the processing conditions. In addition, specific surface areas determined by N₂ adsorption applying the BET equation ranged between 19 and 26 m²/g. The effect of the coagulating solvent and superbase on the crystallinity was investigated using X-ray diffraction (XRD) showing an amorphous crystal structure with a broad 2θ diffraction peak at 20.6°. In addition, no chemical modification was observed in the prepared aerogels from infrared spectroscopy. Finally, the recovery and reuse of the solvent system was demonstrated, thus making the process more sustainable.