ZnO Mediated Degradation of Reactive Brilliant Orange 3R by Visible Light

Abstract

Visible light induced degradation of Reactive Brilliant Orange 3R, RBO, has been done in presence of 0.5 g to 1.7 g ZnO in 45 mL aqueous suspensions containing 3×10-5 M to 6.5×10-5 M dye at fixed pH (5.59). The process of its removal was monitored by recording the change of absorbance at 493 nm with time. Molar absorptivity (Ɛ) was found to be 1.91×104 L/mol cm at 30 ⁰C. The photo degradation has been suggested to be initiated by electronic injection from the photo activated absorbed dye to ZnO followed by creation of different radicals. These radicals are responsible for ultimate mineralization of the dye. The initial rate of ZnO mediated photo degradation of RBO is affected by its initial concentration and the amount of ZnO. The photo degradation kinetics follows model indicating that degradation occurs at the surface of the ZnO particles. More than 51% color of 3×10-5 M in 45 mL suspension containing 1.50 g ZnO vanished within an hour of illumination. The products of mineralization of RBO by visible light in presence of ZnO are suggested to be CO2, H2O, SO42- NO3-, Cland N2. This suggests that the present technique can be optimized for industrial application to photo-mineralize dyes from the dyeing-house effluents.