Individualization of cellulose nanofibers from wood using high-intensity ultrasonication combined with chemical pretreatments

Cellulose nanofibers were individualized from poplar wood in two distinct stages. Initially, wood fibers were subjected to a chemical process to eliminate lignin and hemicellulose. The obtained chemical-purified cellulose fibers were then mechanically separated into nanofibers using high-intensity ultrasonication. The diameter distributions of the resulting nanofibers were dependent on the output power of the ultrasonic treatment. TEM and FE-SEM images showed that the diameter of the obtained nanofibers ranged from 5 to 20 nm when the output power of the conducted ultrasonication was greater than 1000 W. FTIR and XRD results indicated that hemicellulose and lignin were removed extensively in the cellulose nanofibers, with a crystallinity of approximately 69%. The TGA results showed that the degradation temperature of the nanofibers was dramatically increased to approximately 335 °C compared with 210 °C of the original wood fibers. The obtained nanofibers may be potentially applied in various fields, such as bio-nanocomposites, tissue engineering scaffolds, filtration media, packaging, and so on.