Photocatalytic decolorization of congo red over ZnO powder using Box–Behnken design of experiments

Abstract

 Photocatalytic decolorization of congo red under sunlight illumination has been examined using ZnO catalyst. Batch experiments were conducted and Box–Behnken design has been employed to study the effect of different variables on the photodecolorization. Four variables such as dye concentration (0.05, 0.075, 0.10 g/l), weight of catalyst ZnO (0.025, 0.14, 0.25 g/l), pH (4, 7, 10) and time (1, 2, 3 (h)) were used to identify the significant effects and interactions in the batch studies. A second order polynomial regression model has been developed using the experimental data. It was found that the photodecolorization potential of ZnO was strongly affected by the variations in dye concentration, weight of catalyst ZnO, pH and time. The experimental values were in good agreement with the predicted values and the correlation coefficient was found to be 0.9982. Optimum conditions of the variables for the maximum photodecolorization are dye concentration (0.05 g/l) ZnO (0.16 g/l), pH (7.0) and time (2.0) (h). The maximum percentage of photodecolorization was observed to be 97%.