Preparation and characterization of cellulose nanofibers isolated from lettuce

Abstract: Cellulose nanofibers (CNFs) were isolated from lettuce peel using specific chemical treatments, i.e., NaOH alkali solution treatment, NaClO2 bleaching and sulfuric acid hydrolysis. Both cellulose and cellulose nanofibers were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Morphological features and particle size distribution of cellulose and nanostructures were explored using transmission electron microscopy (TEM), scanning electron microscope (SEM) and the Malvern laser particle size analyzer. Results showed that particle diameters of the majority of morphological nanofibrillated cellulose were in the range of 10 to 20 nm, and length between 190 to 460 nm. The crystallinity index reached 41.57%, which increased by 117.3% compared with the raw material. The crystalline type of lettuce peel nanofibers belongs to cellulose type I. Moreover，thermal degradation temperature of CNFs is 271.7 °C which is 47.3 °C higher than that of the untreated peel. The CNFs obtained from these treatments can be used as additional biocomposites in reinforced polymer manufacturing processes or the food industry