Hydrolytic cleavage of glycosidic bonds for cellulose nanoparticles (CNPs) production by BmimHSO4 ionic liquid catalyst

Abstract

Highly crystalline cellulose nanoparticles (CNPs) were synthesized from cotton linters using Brønsted acid-type 1-butyl-3-methylimidazolium hydrogen sulfate (BmimHSO4) ionic liquid via the hydrolysis method. The integral properties and thermal stability of CNPs were evaluated under different concentrations of BmimHSO4 ionic liquid (5, 10, 15, 20, and 25 wt.%). It was discovered that 15 wt% BmimHSO4 ionic liquid produced CNPs with the smallest crystallite size. Furthermore, this association with optimized [HSO4]− anions had the potential to form cellulose fibers during the swelling/hydrolysis process induced by water addition. In contrast, excessive mass loading of 20 wt% and 25 wt% of BmimHSO4 ionic liquid to the Microcrystalline Cellulose (MCC) resulted in an increase of viscosity, which weakened the mobility of ions in cellulose fibers. High-resolution transmission electron microscopy (HRTEM) results revealed that CNPs’ length and diameter of around 90 nm and 12 nm, respectively, were observed 2 h after the hydrolysis process. The presence of the OH functional group at 3440 cm–1 for regenerated BmimHSO4 sample proved the occurrence of swelling due to water addition and thus addressed the production of synthesized CNPs. Interestingly, the recovery of ionic liquid for reuse purposes reached up to 90% without creating any hazardous waste. These findings are beneficial to the environment and have great prospect towards enhancing sustainability.