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

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 regressio n model has been developed using the experimental data. It was found that t he photodecolorization potential of ZnO was strongly affected by the variat ions in dye concentration, weight of catalyst ZnO, pH and time. The experim ental values were in good agreement with the predicted values and the corre lation coefficient was found to be 0.9982. Optimum conditions of the variab les for the maximum photodecolorization are dye concentration (0.05 g/l) Zn O (0.16 g/l), pH (7.0) and time (2.0) (h). The maximum percentage of photod ecolorization was observed to be 97%.