Kinetics of the Photocatalytic Decolorization of an Azo Reactive Dye in Aqueous ZnO Suspensions

Abstract

The photocatalytic decolorization of Remazol Red RR, a commercial azo reactive textile dye, in ZnO suspension, has been investigated in a quartz batch reactor with the use of artificial light source (UV−C). The reaction kinetics are modeled by pseudo-first-order rate law. Regression analysis related pseudo-first-order rate constant, k, to the catalyst loading, empirically as k ∝ [ZnO]0.6. The decolorization rate increases with increasing pH, attaining maximum value at pH 10. The rate constant is inversely related to the initial dye concentration, empirically according to the relation k ∝ [C0]-1.5. Finally, the rate constant is found proportional to the square root of the light intensity as k ∝ [I] 0.5. These empirical models are therefore combined as k ∝ [ZnO]0.6 [C0]-1.5 [I]0.5