Efficient isolation of cellulose from chestnut burs using deep eutectic solvent pretreatment

The chestnut burs extract exhibited a high content of quinic acid and citric acid. The deep eutectic solvent (DES) composed of p-toluenesulfonic acid (PTSA), ethylene glycol (EG), and choline chloride (ChCl) was developed to treat chestnut burs for extracting cellulose and lignin. Under optimal conditions (140 degrees C, 8 min), the resulting sample contained cellulose (79.85 %), hemicellulose (3.48 %), and lignin (5.52 %). The DES pretreatment effectively retained 79.23 % of the cellulose while removing 95.51 % of the hemicellulose and 91.38 % of the lignin. Following pretreatment, the pretreated residues exhibited a relatively smooth surface and an overall structure characterized by the presence of cracks. Cellulose fibers became discernible, the Crystallinity Index (CrI) increased. DESC prepared at optimal conditions was further nanofibrillated to a width of 20-80 nm and height of 4-7 nm with ultrasonic generator. Overall, this work successfully isolated cellulose from chestnut burs, achieving a high delignification rate within a short reaction time, and prepared lignocellulosic nanofibrils. This method presents a promising approach for the comprehensive utilization of chestnut burs.