The characteristic and dispersion stability of nanocellulose produced by mixed acid hydrolysis and ultrasonic assistance

Axiolitic shape nanocellulose particles were prepared using a combined mixed acid hydrolysis and ultrasonic treatment. The crystallinity, morphology and stability properties of cellulose were characterized to investigate the mechanism of nanocellulose formation and stability. It was found the hydrodynamic radius decreased from 205 nm to 89 nm, and the crystallinity index of the nanocellulose increased from 62.90% to 72.31% with an increase in hydrolysis time from 2 to 10 h. Sulfate esters and sulfonate group were present in the nanocellulose, and released more COH groups after hydrolysis. The ζ-potential of cellulose decreased from −11.5 to −43.8 mV after 10 h of hydrolysis. These results illustrated the amorphous characteristic of cellulose was removed after acid hydrolysis and ultrasonic treatment. The higher ζ-potential and relatively small cellulose particles caused a more stable suspension, suggesting that electrostatic interactions played an important role in maintaining the stability and dispersibility of the nanocellulose particles.