Photochemical oxidative decolorization of C. I. basic red 46 by UV/H₂O₂ process: Optimization using response surface methodology and kinetic modeling

In this work Central Composite Design (CCD) based on Response Surface Methodology (RSM) was employed to evaluate the effects of operational parameters (reaction time, initial dye concentration, initial H₂O₂ concentration and distance of UV lamp from the solution) affecting photooxidative decolorization of a dye solution containing C.I. Basic Red 46 (BR46) and for optimization of the process. Predicted values were found to be in good agreement with experimental values (R² = 98.92% and Adj-R² = 97.79%), which indicated suitability of the model employed and the success of CCD in optimizing the conditions of UV/H₂O₂ process. Graphical response surface and contour plots were used to locate the optimum point. The results of optimization predicted by the model showed that maximum decolorization efficiency was achieved at the optimum condition of reaction time 14 min, initial dye concentration 20 mg/L, initial H₂O₂ concentration 1.0 g/L and 16 cm distance between UV lamp and the solution. In addition, a mathematical relation between the apparent reaction rate constant and used H₂O₂ was applied for prediction of the photooxidative decolorization rate constant (k). The results indicated that this kinetic model provided good prediction of the k values for a variety of conditions. The Figure-of-merit electrical energy per order (E_Eo) was employed to estimate the electrical energy consumption.