Physicochemical Properties of Nanocellulose Isolated from Cotton Stalk Waste

In recent years, nanocellulose has become an attractive and high-value-added product. The cotton stalk is a waste product with a high cellulose content. Therefore, nanocellulose can be isolated from the cotton stalk. Properties of nanocellulose are affected by its nanoscale. In this study, the characteristics of cellulose in nanoscale were investigated. A series of cotton stalk nanocelluloses were prepared by sulfuric acid hydrolysis to study their physicochemical properties and the differences of nanocelluloses on different nanoscales. The obtained nanocelluloses were analyzed by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TA), and X-ray diffractometry (XRD). From the morphology analysis, the mean length and width of nanocelluloses were decreased to 90.5 and 7.0 nm, respectively. From the FTIR analysis, with the particle size decreasing, hydrogen bonds were broken and recombined. Acid hydrolysis mainly acted on intramolecular hydrogen bonds of cellulose macromolecules, especially on O(3)H···O(5) bonds. The crystal arrangement model of nanocellulose was investigated. From the TA analysis, the thermal property was decreased with a reduction of nanocellulose particle size. The CrI of the cotton stalk nanocellulose was the highest at up to 87.10%. The differences of cotton stalk nanocelluloses give significant changes to physicochemical behaviors at the nanoscale. The research would provide a theoretical basis for the future application of nanocelluloses.