The weight ratio of total liquid of IL–water system/feather
should influence the dissolution rate, separation of keratin, and
cost of the process, thus, it is very important to determine an optimal
value. Fig. 8 gives the dissolution rate of feather and yield of
keratin with different weight ratios. With increasing weight ratio
from 10 to 20, the dissolution rate of feather greatly increases
and attains to about 95% at 20. Whereas the dissolution rate is
nearly no change with the further increase of the ratio from 20
to 40. As for the yield of keratin, it decreases when the ratio