Photochemical degradation of azure-b with sulphate radical ion generated by peroxydisulphate ion with cupric ion

In this paper, the photochemical degradation of azure-b by Cu2+/S2O8 2− process has been presented. Cu2+ as photocatalyst and S2O8 2− ion as photooxidant used in this process. At extremely low concentrations, cupric ion showed true catalytic activity in the overall process. The influence of various parameters on the performance of the treatment process has been considered, such as pH, concentration of peroxydisulphate ion (S2O8 2−), concentration of Cu2+ ion, concentration of methylene blue and effect of light intensity etc. were observed. The progress of the photochemical oxidation was monitored spectrophotometrically. The results showed that the dye was completely oxidized and maximum decolorization efficiency was achieved at the optimum conditions of the reaction time 120 min. The optimum conditions of initial dye, Cu2+ ion, initial peroxydisulphate ion (S2O8 2−) concentration for photooxidation were determined to be 2.8 × 10−5, 4.1 × 10−4 and 3.6 × 10−4 M, respectively and light intensity 62.9 mWcm2−. The value for the reaction rate constants have been determined and found to be 3.20 × 10−4 s−1. Overall photochemical oxidation of methylene blue was observed to follow first-order kinetics. A suitable tentative mechanism for photochemical oxidation of methylene blue has been proposed.