A simple approach for the isolation of cellulose nanofibers from banana fibers

The objective of the present work was to extract cellulose nanofibers (CNFs) from banana fibers by simple and cost-effective manner. Cellulose nanofibers were obained by subjecting the banana fiber for alkali treatment followed by oxidizing it with HNO3-NaNO2 mixture and also by directly oxidizing it with HNO3-NaNO2 mixture. SEM analysis showed the morphology of pristine and alkali treated banana fibers that indicated the fibrillation of bundle of fibers into individual fibers and reduction of the diameter of fiber from ∼226.2 m to 10-14 m. TEM analysis of direct oxidation of pristine fiber with HNO3-NaNO2 and NaOH/HNO3-NaNO2 treated fibers showed the reduction in diameter of fibers from microscale (10-14 m) to nanoscale (3-10 nm). Furthermore, x-ray diffraction patterns of NaOH/HNO3-NaNO2 oxidized CNFs showed 80.13% crystallinity, compared to 55.17% crystallinity of CNFs obtained from pristine fiber directly oxidized with HNO3-NaNO2 mixture. Effect on hemicellulose and lignin group during the isolation, and thermal stability of the so-formed nanofibers were studied using FT-IR spectroscopy and TGA/DTG techniques, respectively. The higher crystallinity and small size of CNFs further extends its applicability in the field of catalysis, pharmaceuticals, bio-nanocomposite, and tissue engineering.