Ultrasound-assisted conversion of cellulose into hydrogel and functional carbon material

Abstract: Microcrystalline cellulose (MCC) was fibrillated using an ultrasound probe to produce a hydrogel, which after freeze-drying and carbonisation under N₂ atmosphere at elevated temperatures produced highly porous carbon. Ultrasound treatment in the absence of acid resulted in high aspect ratio, nanocrystalline cellulose due to fibrillation of the outer layers of the MCC fibre bundles, whereas in the presence of acid, cleavage of glycosidic bonds resulted in smaller aspect ratio fibres. Carbonisation of the acid-generated nanocrystalline cellulose samples at 800 °C provided the highest BET surface area of 917.0 m²/g, with over 18% pore volume in mesopores. The resulting high surface area carbon was able to absorb 100% of methylene blue in a solution having an initial concentration of 10 mg/L in 20 min which is comparable with many commercially available activated carbon products. Graphical Abstract: Ultrasonication of microcrystalline cellulose resulted in nanocrystalline cellulose hydrogel which after freeze drying and carbonisation provided high surface area mesoporous carbon.[Figure not available: see fulltext.].