OPTIMIZATION OF THE EXTRACTION AND PREPARATION OF CELLULOSE MICROFIBERS FROM RICE HUSK USING A FULL FACTORIAL EXPERIMENT

Cellulose is one of the most abundant biopolymers on Earth and is of most significant interest due to its properties and uses. Cellulose can be obtained from agro-industrial residues, such as rice husk, whose cellulose content is approximately 30%. In this study, cellulose microfibers were extracted from rice husks. Fibers were obtained by submitting the biomass to alkali (NaOH) and bleaching treatments. These treatments have already been reported in the literature; however, variables such as the concentration of reagents, the time, and the temperature of the chemical treatment have yet to be optimized. A factorial design of experiments with 3 factors and 2 levels for each factor was proposed to optimize the chemical processes. It was determined through the analysis of variance (ANOVA) that the factors evaluated significantly influenced the elimination of non-cellulosic compounds, and that the chemical treatment was more efficient when the factors took high level values. Ultraviolet-visible spectroscopy (UV-Vis) analysis showed the successful removal of undesired components during the alkaline treatment. The effect of the treatments on the morphology upon removing hemicelluloses, lignin, and inorganic material was evaluated through Scanning Electron Microscopy (SEM). The increase in the thermal stability in the alkali-treated rice husk and in cellulose microfibers, compared to the raw rice husk, was established by thermogravimetric analysis (TGA). X-ray diffraction (XRD) indicated that the treatments increased the percentage of crystallinity.