Photocatalytic degradation of commercial azo dyes

Seven azo dyes were photocatalytically degraded in TiO2 suspension. Their d egradation rates were compared with disappearance and TOC elimination rates . It was demonstrated that diazo dye is less degradable than monoazo and th e order of photocatalytic degradation rates was in approximate agreement wi th that of ozonation rates cited from literature. Major intermediates ident ified are aromatic amine, phenolic compounds and several organic acids. It was indicated from this study that in the photocatalytic degradation of azo dye the disappearance proceeds through both oxidation and reduction, where as TOC is eliminated predominantly by oxidation. (C) 1999 Elsevier Science Ltd. All rights reserved.