Mechanism and kinetics of treatment of acid orange II by aged Fe-Si-B metallic glass powders

The mechanism and kinetics of acid orange II (AOII) treated by aged gas-atomized Fe-Si-B metallic glass (MG) powders were investigated in this study. The decolorization reaction is shown to obey the pseudo-first-order kinetic model, and the treatment processes could be divided into two stages: a slow step followed by a rapid one. This observation is in accordance with the following results, the azo dye is simply adsorbed onto the Fe-based MG powders in the initial stage, because the oxide layer coated on the powder surface depresses the degradation reaction by covering the activity sites, and then the degradation occurs with the desquamation of the powders. The AOII could be degraded with a rapid reaction rate when the Fe-based MG powders are applied to the treatment process again, because of the consumption of the oxide layer and the unchanged core of the Fe-based MGs. These findings will promote the practical application of MGs in degrading azo dyes.