Cyclic degumming of ramie fiber with alkali-promoted ethylene glycol deep eutectic solvent

Ramie fibers are quite popular textile fibers owing to their antibacterial, breathable, cool, antiseptic, mildew resistant and sweat-absorbing functions. The efficient and green degumming of ramie fibers holds great significance in further enhancing their application value. In this study, a cyclic degumming approach for ramie fiber using a less-polluting alkali-promoted ethylene glycol deep eutectic solvent was proposed. The optimized degumming conditions were screened based on the residual gum content, with a molar ratio of choline chloride to ethylene glycol of 1:6, a NaOH concentration of 0.6%, and a temperature of 140°C. Subsequently, the results of SEM, FTIR, XRD, and TG analysis showed that the gelatinous components such as lignin and hemicellulose were significantly removed after the use of the alkali-promoted ethylene glycol deep eutectic solvent degumming method. Single ramie fibers with a higher crystalline index and maximum rate degradation temperature were obtained. The macroscopic physical and mechanical properties were in accordance with the requirements for refined ramie fibers in the Chinese National Standard. Finally, the degumming waste liquid was reused by adding fresh NaOH and it was proved to maintain its excellent degumming capacity. Owing to the low alkali utilization and high efficiency, the alkali-promoted ethylene glycol deep eutectic solvent method has potential for industrial-scale applications.