Preparation of cellulose nanocrystals by ultrasonication-assisted phosphotungstic acid method: An effective method of high yield and friendly environment

This study aims to develop a green, pollution-free and high yield method to prepare cellulose nanocrystals (CNC). Using microcrystalline cellulose (MCC) as raw material, CNC was successfully obtained under the synergistic effect of ultrasound and phosphotungstic acid (PTA). The optimal preparation conditions were determined by response surface method (RSM) as the concentration of PTA 13.7 %, ultrasonication time 61 min, and reaction time 6 h. Under the optimum process conditions, a short rod-like CNC with a yield of 77.1 % was obtained. Compared with traditional sulfuric acid method and non-ultrasonication PTA method, the CNC obtained by ultrasonication-assisted PTA method has excellent stability, and the synergistic effect of PTA and ultrasound greatly improves the reaction rate, and the crystallinity of CNC can reach 86.93 % at low acid concentration. In addition, PTA has little corrosion damage, and shows high catalytic efficiency and stable cycle performance in at least five uses, which has a positive impact on economics and sustainability. These characteristics fully prove that the ultrasonication-assisted PTA method has a high potential in the industrial production of CNC, which is a new green way to prepare CNC with high yield. [Display omitted] •CNCs with high yield and excellent quality were produced by ultrasonication-assisted PTA method.•The synergistic effect of ultrasound greatly increases the reaction rate and decreases the acid concentration.•PTA has high catalytic efficiency and stable cycle performance.