Isolation and characterization of cellulose nanofibers from bamboo using microwave liquefaction combined with chemical treatment and ultrasonication

• Micro-sized residue with high cellulose content was first produced from bamboo by microwave liquefaction.
• The cellulose enriched residues could be readily purified by subsequent chemical treatments.
• Cellulose nanofibers were isolated from chemically purified residues by gave to high-intensity ultrasonic nanofibrillation.
• The cellulose nanofibers have high thermal stability for thermally stable composites.

Cellulose nanofibers were successfully isolated from bamboo using microwave liquefaction combined with chemical treatment and ultrasonic nanofibrillation processes. The microwave liquefaction could eliminate almost all the lignin in bamboo, resulting in high cellulose content residues within 7 min, and the cellulose enriched residues could be readily purified by subsequent chemical treatments with lower chemical charging and quickly. The results of wet chemistry analyses, SEM images, and FTIR and X-ray spectra indicated the combination of microwave liquefaction and chemical treatment was significantly efficient in removing non-cellulosic compounds. Ultrasonication was used to separate the nanofibrils from the purified residues to extract nanofibers. The TEM images confirmed the presence of elementary fibrils, nano-sized fibril bundles, and aggregated fibril bundles. As evidenced by the TGA analysis, cellulose nanofibers isolated by this novel technique had high thermal stability indicating that the isolated nanofibers could possibly be applied as reinforcing elements in biomaterials.