Photocatalytic Degradation of Azo Dyes Using Microreactors: Mechanistic Study of its Effects on H2O2 Addition

The photocatalytic reaction involved in TiO2 photocatalysis was investigated using a microreactor coated with TiO2 film on the glass plate attached on one side of the microreactor. It was confirmed that the effect of H2O2 on the photocatalytic degradation efficiency of azo dyes (acid orange 7, acid red 151, and acid yellow 23) was dependent on the polymorphs (anatase and rutile) of TiO2 coated on the glass plate of the UV-irradiated microreactor. Scavengers of holes (KI) and electrons (p-benzoquinone) were added to the solution of azo dyes, and their effects on the degradation efficiencies of the azo dye (acid orange 7) in the microreactor system were investigated. It was found that the electron scavengers of p-benzoquinone showed much larger effects on the photocatalytic degradation efficiency than the hole scavengers of KI. Based on these results, the mechanism of the photocatalytic degradation of the azo dyes in the presence of H2O2 was proposed.