Optimization of cellulose nanocrystals extraction from teff straw using acid hydrolysis followed by ultrasound sonication

Abstract

This study presents a novel approach to optimizing the extraction of cellulose nanocrystals (CNCs) from teff straw, addressing the challenge of utilizing agricultural waste effectively. Employing a novel two-stage alkali treatment and bleaching process, enhanced cellulose purity from 39.27 % to 89.75 % while removing lignin. The optimized conditions for the acid hydrolysis were sulfuric acid a concentration of 63.8 %, temperature of 60 °C, and reaction time of 90 mins. This resulted with a minimum CNCs’ size of 31 nm and a maximum yield of 93.8 % w/w. Dynamic light scattering (DLS) analysis revealed the particle size distribution of the CNCs. FTIR and TGA confirmed the functional groups and thermal stability of the CNCs respectively. Scanning electron microscopy (SEM) showed the rod-like or whisker-like morphology of the CNCs. Moreover, X-ray diffraction (XRD) demonstrated that the acid hydrolysis highly affected the amorphous regions of the cellulose. The higher specific surface area, 125 m², and improved cross-linking potential of the CNCs make them attractive for packaging applications. Furthermore, the CNCs exhibited excellent mechanical, thermal, and barrier properties. A statistical analysis supports the robustness of the extraction model, with R-squared values indicating strong predictive capability (R² = 0.992, adjusted R² = 0.983, predicted R² = 0.903).