Isolation and Characterization of Nanocrystalline Cellulose from Ramie Fibers via Phosphoric Acid Hydrolysis

Nanocrystalline cellulose (NCC) was successfully isolated using cellulose extracted from ramie fibers via chemical pretreatments followed by phosphoric acid hydrolysis. The effects of acid concentrations and hydrolysis times on the characteristics of the NCC were investigated in this work. The obtained NCCs were characterized using Fourier infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). Fourier transform-infrared spectroscopy confirmed that hemicellulose and lignin were removed during the chemical pretreatments and hydrolysis. The results showed that the crystallinity index increased with increasing an acid concentration up to 16 M and then decreased drastically. The optimal acid concentration was found to be 16 M phosphoric acid at 150°C for 90 min during hydrolysis resulting in a rod-shaped NCC with a high crystallinity (89.28%), the average diameter (21.4 nm), and the average length (215.4 nm). The thermal stability was found to decrease with increasing acid concentration. The characteristic of NCCs was affected significantly by the acid concentration but not the hydrolysis time.