Optimization of homogenization-sonication technique for the production of cellulose nanocrystals from cotton linter

Recently, cellulose nanocrystals (CNCs) have attracted a significant interest in different fields including drug delivery, biomedical, and food applications. In this study, homogenization-ultrasonication as a non-hazardous, time-saving, and organic solvent free technique was applied for fabrication of CNCs from cotton linter, containing over 90% cellulose. First, acid hydrolysis was applied on raw cellulose using sulfuric acid at 55, 60 and 65% for 3, 5 and 7 min and at various homogenization speeds. Final CNCs were produced by ultrasonication (350 W) for 3 min. The physicochemical properties of CNCs, particle size, X-ray diffraction (XRD) pattern, Fourier Transform Infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), atomic force microscopy (AFM) and transmission electron microscopy (TEM) were studied. Production yield of CNCs was 59-72%, and their water holding capacity was two times higher than raw cellulose. The average length of CNCs was 133 nm with a width of 10 nm and the XRD pattern revealed a 82% crystallinity degree. The FTIR spectrum detected almost similar frequencies in the raw and crystalline cellulose, while intensity of CNC peaks was reduced. TEM results showed rod-like CNCs with a length of 229 nm. TGA results also showed that thermal stability of CNCs was reduced compared to raw cellulose.