Preparation and characterization of cellulose nanocrystals via ultrasonication-assisted FeCl3-catalyzed hydrolysis

Cellulose nanocrystals (CNC) was obtained from bamboo pulp via ultrasonication-assisted FeCl₃-catalyzed hydrolysis process, with parameters optimized by response surface methodology. The optimal parameters were reaction temperature: 107 °C, reaction time: 58 min, ultrasonication time: 186 min. The morphological, crystal structural, chemical structural and thermal features of the prepared cellulose nanocrystals were analyzed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction (XRD), Fourier transfer infrared (FTIR) and thermogravimetric analysis. The results showed that the cellulose nanocrystals formed an interconnected network structure and CNC was rod-like with the length of 100–200 nm and the width of 10–20 nm. XRD result revealed that, compared with cellulose pulp, the crystallinity index of CNC increased from 69.5 to 79.4 %, while the cellulose I crystal structure remained. FTIR analysis demonstrated that CNC had the similar chemical structures to that of cellulose pulp, which indicated that the chemical structures of CNC remained unchanged in the presence of FeCl₃-catalyzed hydrolysis process and ultrasonication treatment. Thermogravimetric analysis revealed that the resulting CNC exhibited relatively high thermal stability. The research shows that ultrasonication-assisted FeCl₃-catalyzed hydrolysis could be a highly efficient method for preparing CNC.