Comparative analysis of nanocellulose from Humulus scandens stems using four isolation methods

Sulfuric acid-cellulose nanocrystals (S-CNC), hydrochloric acid-cellulose nanocrystals (H-CNC), ultrasound-cellulose nanofibrils (U-CNF) and stirring-cellulose nanofibrils (S-CNF) were successfully isolated from Humulus scandens stems (HSS) using sulfuric acid hydrolysis, hydrochloric acid hydrolysis, high power ultrasonic and high stirring, respectively. The morphology, chemical structure, crystal structure and thermal stability were characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction patterns and thermal gravimetric analysis. The results suggested that the S-CNC and H-CNC prepared by acid hydrolysis had short rod-like shapes, while the U-CNFs and S-CNFs had reticular shapes. The S-CNC has the highest crystallinity (70.05%) while the S-CNF had the lowest crystallinity of the four kinds of nanocellulose; all maintained cellulose Ⅰ structure. The U-CNF had the best thermal stability with initial decomposition temperature of 261.9 ℃, but the S-CNC was the worst with the initial decomposition temperature of 217.8 ℃.