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

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 noncellulosic
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.