Mineralization of genotoxic Acid Violet 7 by AgBr-ZnO under alkaline conditions using direct sunlight

Abstract

The photocatalytic degradation of a genotoxic azo dye, Acid Violet 7 (AV 7), using AgBr-ZnO in aqueous solution has been investigated under solar irradiation at <i style="">p</i>H 12. The photocatalytic activity of AgBr-ZnO is higher than that of bare ZnO (prepared ZnO), commercial ZnO, TiO₂ and Degussa TiO₂-P25 in the degradation of AV 7. Mechanism of degradation by AgBr-ZnO is proposed to explain its higher activity under solar light. The effects of operational parameters such as the amount of photocatalyst, dye concentration, initial <i style="">p</i>H, cations, anions and oxidants, on photomineralization by AgBr-ZnO have been analyzed. The degradation of AV 7 follows pseudo-first order kinetics according to the Langmuir-Hinshelwood model. Based on the intermediates formed during the photodegradation, a degradation pathway is proposed. The mineralization of AV 7 has also been confirmed by chemical oxygen demand measurements.