Efficient Room-Temperature Chitin Extraction Using a Novel Ternary Deep Eutectic Solvent with Improved Molecular Mobility and Enhanced Recyclability

The deep eutectic solvent (DES) extraction method is considered a promising alternative to the acid/base method in chitin extraction. However, DESs face challenges such as inefficient extraction at room temperature and limited recyclability due to low molecular mobility. In this study, a novel ternary DES composed of N-methylurea, N-methylacetamide, and acetic acid is developed and applied for chitin extraction. Compared to previous DESs, this novel DES not only has significantly reduced melting point (−16.82 °C) and viscosity (7.38 mPa·s at 25 °C) but also exhibits remarkably high extraction efficiency at room temperature, with demineralization and deproteinization reaching 99.07 and 92.67%, respectively. Furthermore, this DES can be repeatedly used without significant changes in viscosity. The results of repeated cycles of use demonstrated that the demineralization and deproteinization remained at 89.78 and 86.84%, respectively, even after 10 cycles of reuse. Experimental and simulation results suggest that the formation of strong hydrogen bonds between the component molecules of the DES disrupts the regular packing of the components in their crystalline state and allows for more flexible and dynamic interactions. This disruption leads to a less ordered structure, which contributes to the decrease in melting point and increase in molecular mobility.