Removal of acetyl-rich impurities from chitosan using liquefied dimethyl ether

Chitosan, recognized for its excellent biodegradability, biocompatibility, and antibacterial properties, has several potential applications, particularly in the biomedical field. However, its widespread use is hindered by inherent limitations such as low mechanical strength and safety concerns arising from a low degree of deacetylation and the presence of impurities. This study aimed to introduce an innovative purification method for chitosan via liquefied dimethyl ether (DME) extraction. The proposed technique effectively addresses the challenges associated with chitosan by facilitating deacetylation and impurity removal. Liquefied DME is emerging as the extraction solvent of choice owing to its advantages, such as low boiling point, safety, and environmental sustainability. The degree of deacetylation of chitosan was extensively evaluated using thermogravimetric-differential thermal analysis, Fourier transform infrared spectroscopy, X-ray diffraction, intrinsic viscosity measurements, solid-state nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy, and elemental analysis. The solubility of chitosan in liquefied DME was investigated using Hansen solubility parameters. This study contributes to the improvement of the safety profile of chitosan, thereby expanding its potential applications in various fields. The use of liquefied DME as an extraction solvent proved to be efficient in addressing the existing challenges and is consistent with the principles of safety and environmental sustainability.