PRIMARY INTERMEDIATE IDENTIFIED DURING HETEROGENEOUS PHOTOLYSIS OF ACID ORANGE 7

Abstract

Acid Orange 7 was photocatalytically degraded in a titanium dioxide slurry using oxygen bubbling and polychromatic radiation from a high-pressure Hg lamp in a back-flow tubular photoreactor. The dye was dissolved in buffers based on aqueous sodium carbonate (pH 10), sodium hydroxide (pH 10), or hydrochloric acid (pH 4). Reaction products were analyzed by NMR and MS spectroscopy as well as HPLC. A previously undescribed primary intermediate, 3-hydroxy-4-[(2-hydroxy-1-naphthyl)diazenyl]benzenesulfonic acid, was detected and isolated on a preparative scale from the photoreactor. The identity of the photolysis product was confirmed by comparison with a chemically synthesized standard. The kinetics of the heterogeneous photolysis of Acid Orange 7 was also investigated.