A heterophotolysis of Acid Orange 7

Abstract

Acid Orange 7 was heterophotolyzed using titanium dioxide, oxygen bubbling, back-flow tubular reactor, polychromatic radiation of high pressure Hg lamp and aqueous sodium bicarbonate, sodium hydroxide or sulfuric acid as solvents. Dependences of reaction rates on Acid Orange 7 concentrations have exhibited either straight-line (for lower initial concentrations) or a convex shape (for higher initial concentrations). Variations in shapes of kinetic curves observed were explained by the effect of decrease in both (i) dye concentration and (ii) absorption of radiation by photocatalyst. The decrease in UV absorption of radiation by catalyst was due to increase in absorption by photolytes formed. An intermediate showing bathochromicly shifted absorption spectrum was, surprisingly, detected by heterophotolysis of Acid Orange 7. Compared with hydroxyls, carbonate anions had insignificant effect on rates of heterophotolyses of dye under study.