Isolation and characterization of bagasse cellulose nanofibrils by optimized sulfur-free chemical delignification

Abstract

Cellulose nanofibril (CNF) was isolated from bagasse using a modified sulfur-free and bio-refinery-based approach. For this purpose, a chemo-mechanical procedure was designed that consisted of depithing, de-waxing, autohydrolyzing, soda-anthraquinone pulping, elemental chlorine-free bleaching, refining, and ultrafine grinding. In order to obtain a high degree of final fibrillation, the most important parameters in the delignification process were optimized by response surface methodology. Samples were then characterized by optical microscopy, scanning electron microscopy, X-ray diffraction (XRD), National Renewable Energy Laboratory procedure, ASTM (D1103-60 and D1104-56), Kappa number, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and transition transmission electron microscopy (TEM). The microscopic images as well as the results from chemical composition characterization and FTIR analysis indicated that the employed chemical treatments were effective in removing non-cellulosic materials from the fibers. In addition, XRD analysis showed that cellulose crystallinity increased during the treatments. Based on the DLS results, the hydrodynamic diameter of CNF ranged within 860 nm. TEM image analyses showed that a considerable percentage of the isolated CNF had an average diameter of about 11 nm, and the yield of fibrillation was found to be about 99 %. Based on the results obtained, it may be claimed that the chemo-mechanical process developed in this study for the facile preparation of CNF is a promising technique for biocomposite preparation.