Isolation and characterisation of cellulose nanocrystals obtained from sugarcane peel by SEM, XRD and CP/MAS 13NMR

Sugarcane peels are agricultural waste materials discarded before taking the sugarcane juice. In the present study cellulose nanocrystal was isolated from sugarcane peel by sulphuric acid hydrolysis. Two pretreatments; alkaline treatment and bleaching with acidified sodium chlorite were applied. Sulphuric acid hydrolysis was performed at 450C for 45 mins using 64% concentration sulphuric acid. The resulting cellulose nanocrystal (CNC) of the sugarcane peel was characterised by studying the surface morphology using scanning electron microscope (SEM), SEM-EDX was used to identify the elemental composition of the sample. X-ray diffraction (XRD) was studied to identify the crystallinity nature of the CNC. CP/MAS 13C solid- state NMR was used to evaluate the purity and molecular structure of the CNC. The SEM image of the nanocrystal showed that the fibre bundles were separated into individual CNC; with the size decreasing to a nanosize indicating an effective removal of the amorphous region. EDX showed the presence of 0.93 wt% of elemental sulphur impurity with the major components (carbon and oxygen). XRD diffraction pattern showed that the CNC retained the cellulose crystalline structure with crystallinity index of 99.22% and crystallite particle size dimension of 5.56 nm. The NMR spectra of the CNC revealed that all the signals were attributed to six carbon atoms of the glucose unit and the disappearance of several signals also indicated the disruption of the amorphous region. The results revealed effective synthesis of CNC from sugarcane peel, suggesting the leaching of the amorphous domain, apparent crystallinity and purity of the CNC. The cellulose nanocrystal obtained is considered to be a potential material for various industrial applications