Optimization of UV-promoted peroxydisulphate oxidation of C.I. Basic Blue 3 using response surface methodology

In this paper photooxidative decolorization of C.I. Basic Blue 3 (BB3), by a UV/peroxydisulphate process is reported. Response surface methodology (RSM) was employed to investigate the effects of different operational parameters on the photooxidative decolorization efficiency. The variables investigated were the reaction time, initial dye concentration, initial S2O8(2-) concentration and the distance of the solution from the UV lamp. Central composite design (CCD) was used for the optimization of the UV/peroxydisulphate process. Photooxidative decolorization efficiency was enhanced by the addition of an optimum amount of peroxydisulphate. An increase in UV light intensity increased the photooxidative decolorization efficiency. A decrease in photooxidative decolorization efficiency with increasing initial BB3 concentration was observed. Predicted values of photooxidative decolorization efficiency were found to be in good agreement with experimental values (R2 = 99.06% and Adj-R2 = 98.24%), which indicated the suitability of the CCD model employed and the success of CCD in optimizing the conditions of the UV/ peroxydisulphate process. The results of optimization predicted by the model showed that maximum decolorization efficiency (> 98%) was achieved at the optimum conditions: reaction time 11 min, initial dye concentration 10 mg/L, initial peroxydisulphate concentration 1.5 mmol/L and distance of UV lamp from the solution 6 cm. The figure-of-merit electrical energy per order (E(Eo)) was employed to estimate the electrical energy consumption.