Degradation mechanism of azo dye C. I. reactive red 2 by iron powder reduction and photooxidation in aqueous solutions

We have made a comparison of the UV–VIS spectra of three azo dyes, C. I. reactive red 2, orange II and C. I. reactive black 8, in aqueous solutions during treatment with iron powder reduction and photooxidation. From this, we propose their mechanisms for reduction–photooxidation. GC/MS analyses of the degradation products of the dye C. I. reactive red 2 demonstrated some important steps producing hydrogenated azo structure, substituted benzene and substituted naphthalene.