An environmentally friendly and economical strategy to cyclically produce cellulose nanocrystals with high thermal stability and high yield

Abstract

Cellulose nanocrystals (CNCs) have been widely used in various industries; however, green, efficient, low-cost and recyclable CNC preparation still presents great challenges. Herein, ferric chloride (FeCl₃) solution was used as the solvent to develop a green and recyclable preparation system. Owing to the acidic environment provided by FeCl₃, which is a Lewis acid, and the hydrolysis-promoting properties of Fe³⁺, the amorphous area of the cellulose could be rapidly hydrolyzed under a hydrothermal environment to produce CNCs. More importantly, the used FeCl₃ solution could be reused after simple separation. Throughout the entire cycle, the solvent concentration and pH changed only slightly. In the scanning electron microscopy (SEM) results, the prepared CNCs showed a “rice-like” shape with typical CNC dimensions (diameter of ∼38 nm and length of ∼440 nm). The yield was ∼92%, which was much higher than the yields of previously reported methods of CNC preparation. Furthermore, the produced CNCs also have excellent thermal stability (T_max = ∼350 °C). More importantly, the dispersal performance and large specific surface area of the CNCs were studied by using them as a support for PPy. Owing to the residual Fe³⁺, Py could polymerize uniformly on the surface of the CNCs. Overall, a green and economical method to achieve sustainable mass production of CNC is provided by this work.