Duck feathers were washed with water, dried and cut into small
pieces. The different weight ratios of IL, duck feathers, Na2SO3, and
water were put into beakers and heated to fixed temperature
under magnetic stirring condition. After desired time, the residual
solids were removed by suction filtration immediately under the
high temperature because the increase of viscosity with decreasing
temperature will cause difficulty in filtration. Then, the keratin
solution was added with some water at room temperature to precipitate
keratin. The solid keratin and liquid phase were separated
by suction filtration. IL was recovered from the liquid IL–water
phase by evaporating water, and it can be used repeatedly.
The dissolution rate of feather and yield of keratin were used to
evaluate the optimal extraction condition. The dissolution rate of
feather is expressed as [(M0 mt)/M0] 100%, where M0 is the initial
weight of feather and mt is the weight of residual feather. The
yield of keratin is expressed as [Mt/M0] 100%, where Mt is the
weight of keratin.