Preparation and Characterization of Chitosan by a Novel Deacetylation Approach Using Glycerol as Green Reaction Solvent

Abstract

Traditional methods for chitin deacetylation require aqueous solution with high alkali content as reaction solvent, which generate huge environmental pressure for the treatment of vast alkaline wastewater. In this work, glycerol, a nontoxic, biodegradable, and sustainable liquid from biodiesel production, is employed as a novel reaction solvent for chitin deacetylation at elevated temperature. The results showed that the chitosan deacetylation degree (DD) was up to 85.36 ± 1.04% and the corresponding viscosity-average molecular weight (MV) was 30 874 ± 1123 g mol–1 under the optimized conditions of this process. The subsequent Fourier transform infrared (FTIR) characterization structurally demonstrated the occurrence of deacetylation and the fracture of glucosidic bond. Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) analysis further revealed that the DD presented a negative effect on the thermal stability and crystallinity of chitosan. Consequently, the study successfully indicated that using glycerol as a reaction solvent could realize the deacetylation of chitin with lower NaOH concentration and provide an efficient and green process for chitosan preparation from chitin.