One-step Bleaching Method for Animal Fiber by Persulphate/Hydrogen Peroxide: Degradation Mechanism of Eumelanin

Dark animal fiber is bleached to satisfy the demand of color diversity for clothing. Comparing with frequently-used Fe2+ catalyzed H2O2 (Fe2+/H2O2) bleaching method, the ammonium persulfate (APS)/H2O2 bleaching method based on the persulfate (PDS)-based advanced oxidation process is considered to be an environmentally animal fiber bleaching method, which is advantageous in high efficiency, heavy metal-free and low damage. However, the degradation mechanism of eumelanin of APS/H2O2 bleaching method remains to be explored. Herein, standard eumelanin (SM) which has higher purity of eumelanin was used as reaction model, and SM was proved to degrade into five soluble oligomers by chemical structure analysis. Therefore, a new degradation pathway of eumelanin in APS/H2O2 solution was simulated and proposed by in vitro experiment. In addition, the yak wool fiber was low damage by testing the fiber structure before and after bleaching. The dyeing property of yak wool fabrics had no effect on APS/H2O2 bleaching. This investigation of degradation products provides new insights into the bleaching mechanism of APS/H2O2 environmentally dark animal fiber bleaching method.