Isolation of Cellulose Nanofibers From Sunflower Seed Husks via Formic Acid Hydrolysis

Nanocellulose has garnered great interest among researchers because of its biodegradability, renewability, biocompatibility, high strength and versatile functionality. The present study focuses on the development of an eco-friendly, benign method to extract cellulose nanofibrils (CNFs) from waste sunflower husks (SFHs) using formic acid hydrolysis. Both CNFs and microcrystalline cellulose (MCC) were obtained in high yields from SFHs. The enhanced colloidal stability of CNFs was evident from the ζ potential values, which ranged from −11.8 to −19.6 mV. Varying yields of CNFs were obtained by differing reaction times, though all were found to be thermally stable. SEM and TEM were used for the morphological analysis. The removal of non-cellulose constituents was confirmed by FTIR spectroscopy. The enhancement of crystallinity upon treatment was examined using XRD analysis. The thermal stability of the cellulose extracted was checked via TGA. The present method of extraction of CNFs and MCC from waste SFHs using formic acid could open a new way of bulk production of nanocellulose fibers for the manufacture of green, value-added products in high-end fields, including electronics, agriculture and biomedicine, among others.