Extraction of keratin with ionic liquids from poultry feather

• Ionic liquid [Bmim]Cl can high efficiently extract keratin from poultry feathers.
• The IL for keratin extraction from feather can be easily recycled.
• The yield of keratin from poultry feather can attain 75.1%.
• Na2SO3 enhances the extraction to unfold disulfide bonds of cystine in keratin.

Ionic liquid (IL) is a new eco-friendly solvent to accelerate dissolution of natural polymer and several common water-soluble imidazole ionic liquids (ILs) have been selected to dissolve poultry feather and extract keratin. [Bmim]Cl has shown the best solubility, thus it has been studied to extract the keratin. Because Na2SO3 can unfold disulfide bond of polypeptide chains in different keratin molecules in feather by forming R-SSO3Na and the addition of water can increase solubility of Na2SO3 and decrease viscosity of solution, Na2SO3 and water have been used to improve the extraction process. During the solubilization process, SEM pictures show that the smooth structure of the feather was destroyed and followed by the dissolution of the keratin into the liquid phase. The keratin was easily separated from the liquid phase as a solid precipitate after adding some more water owing to the miscibility of the IL with water and the immiscibility of the keratin with water. The keratin precipitate was filtrated and the liquid was distilled to remove water, then the IL and Na2SO3 can be recycled. The optimum extraction conditions for keratin are: 20 wt.% of water in IL–water, 10 wt.% Na2SO3 in liquid phase, the weight ratio of liquid/feather = 20, extraction temperature at 90 °C, and extraction time of 60 min; under these conditions, the dissolution rate of feather is 96.7% and the yield of keratin is 75.1%.

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