Investigation of cellulose nanocrystals fabricated via sulfuric acid combined with deep eutectic solvent route

Abstract

To make full use of tobacco waste in cigarette production and enhance resource utilization efficiency, cellulose nanocrystals (CNCs) were prepared by a method of sulfuric acid combined with a deep eutectic solvent. This method was compared with conventional methods, and the CNCs were thoroughly characterized. The results indicated that the yield of CNCs prepared by the sulfuric acid combined with a deep eutectic solvent method exceeded 26 %, with the highest yield reaching 29.5 %, surpassing the yields from two other methods of 12.5 %, 17.2 %, corresponding to sulfuric acid and sulfuric acid-oxalic acid, respectively. Scanning electron microscopy revealed a laminar morphology of CNCs, in which the CNCs maintained a cellulose type I structure with well-preserved crystallinity. In addition, CNCs prepared by the sulfuric acid combined with a deep eutectic solvent method exhibited good thermal stability, with maximum mass loss at temperature of 342.8 °C during third pyrolysis stage, higher than that of sulfuric acid at 316.7 °C and sulfuric acid-oxalic acid at 335.9 °C. Steady-state rheological testing revealed that the viscosity of the CNCs suspension decreased with an increasing shear rate, which is characteristic of pseudoplastic fluid shear thinning behavior. CNCs prepared by the sulfuric acid combined with DES method reduced the amount of sulfuric acid, and the yield was much higher than that of the other two methods. Moreover, the method using sulfuric acid combined with DES method was simple and safe, and the obtained CNCs had high thermal stability and viscosity, which expands the application prospects in biocomposite material fields.

Keywords

• Tobacco waste
• Sulfuric acid combined with deep eutectic solvent
• Cellulose nanocrystals
• Characterization