Efficient and Regulable Extraction of Keratin from Yak Hair Using Imidazolium-Based Ionic Liquids

The study developed an efficient method for extracting keratin from yak hair using imidazole-based ionic liquids (ILs). The dissolution rate of yak hair in five ILs was found to be in the sequence of 1-ethyl-3-methylimidazolium acetate ([Emim]OAc) > 1-ethyl-3-methylimidazolium diethylphosphate ([Emim]DEP) > 1-ethyl-3-methylimidazolium chloride ([Emim]Cl) > 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) > 1-allyl-3-methylimidazolium chloride ([Amim]Cl). The study found that the secondary structure of regenerated yak hair keratin changed from β-sheet and random coil conformation to α-helix for [Emim]DEP, [Bmim]Cl, [Emim]Cl, while the regenerated yak hair keratin from [Emim]OAc was greatly damaged. [Emim]DEP was found to have the highest disulfide bond content and relatively complete structure, and it also showed excellent performance in dissolving human hair and goat wool. The dissolution performance of the fifth recycled [Emim]DEP remained steady, suggesting that [Emim]DEP is a potentially efficient solvent for the extraction of keratin from hairs.