A combined homogenization-high intensity ultrasonication process for individualizaion of cellulose micro-nano fibers from rice straw

In this study high quality cellulose fibrils, derived from rice straw by the chemical pretreatment, were fibrillated into cellulose micro/nanofibers through a subsequent homogenization and high-intensity ultrasonication processes. Properly comparing of the fibrillation yield and the morphological structure of the ensuing nanofibers, by means of scanning electron microscopy and transmission electron microscopy, revealed that the long and uniform cellulose nanofibers with desired diameters in the possible range of 6–20 nm and a high aspect ratio of about 177 are obtained when the output power and irradiation time of the conducted ultrasonication exceeded 500 W and 40 min, respectively. The accurate characterization of the chemical structure of the isolated cellulose nanofibers using X-ray diffraction and Fourier transform infrared spectroscopy revealed that lignin and hemicellulose were completely removed from the fibrils and crystallinity of the cellulose fibers increased approximately to 65%. As evidenced by thermogravimetric analysis, isolated cellulose nanofibers indicated good thermal stability. Due to the appropriated properties of ultralong isolated cellulose nanofibers, it is typically expected that they could potentially be utilized in various field such as green nanocomposites, filtration media, tissue engineering, and so on.