Upcycling Rice Husk for the Synthesis of Cellulose-Based Aerogels

This study focused on upcycling rice husk into cellulose-based aerogels due to their unique physicochemical properties of high porosity, low density, and extensive specific surface area. This work involved the extraction of cellulose by alkaline pulping and bleaching, followed by the synthesis of nanocellulose (cellulose nanofibers─CNFs) hydrogels via different methods: acid hydrolysis + ultrasonication, acid hydrolysis + homogenization, ultrasonication alone, and homogenization alone. Nanocellulose hydrogels were further converted to aerogels via supercritical carbon dioxide (SC–CO2) drying. Acid hydrolysis coupled with ultrasound produced CNF aerogels with the highest surface area (∼231 m2/g), pore volume (1.41 cm3/g), and pore size (∼29 nm). Moreover, the developed aerogels were utilized for potential application in methylene blue adsorption, where the ultrasonicated samples had the highest dye adsorption capacity (∼87%). Overall, this study highlighted the effectiveness of ultrasound-assisted acid hydrolysis in tailoring the physicochemical properties of CNF aerogels derived from rice husk.