Cellulose Nanocrystals Isolated from Bean Seed Hulls: Acetylation and Characterization

Bean seed hulls is an agro-waste with abundant content of lignocellulosic materials but are being wasted due to its underutilization. Cellulose nanocrystals (CNCs) were successfully extracted from bean seed hulls using alkali treatment, bleaching and sulphuric acid hydrolysis. Cellulose triacetate (CTA) was obtained from CNCs by acetylation using acetic anhydride with sulphuric acid as catalyst. CNCs is neutral pH whereas CTA is slightly acidic. CNCs was sparingly soluble in ethanol but CTA was completely soluble in ethanol. CTA has a higher melting point than CNCs. The density of both CNCs and CTA is approximately equal to the density of water. SEM analysis revealed that CNCs is irregular and fragmented in nature and has both more large surface area and porosity than CTA. FTIR analysis showed the presence of the dominant functional groups such as O-H stretch, N-H stretch, C-H stretch, C-O stretch and C-N stretch in both CNCs and CTA. GC-MS analysis revealed the presence of the prevalent organic compounds such as alkanes, alcohols, phenols, alkanones, phthalates, carboxylic acids, esters and triterpene in both CNCs and CTA. Therefore, the isolation of CNCs from bean seed hulls suggests great efficacy to recover the under-utilized agro-wastes thereby preventing air pollution.