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+/S2O82− process has beenpresented. Cu2+ as photocatalyst and S2O82− ion as photooxidant used in this process. Atextremely 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 beenconsidered, such as pH, concentration of peroxydisulphate ion (S2O82−), concentration of Cu2+ion, concentration of methylene blue and effect of light intensity etc. were observed. Theprogress of the photochemical oxidation was monitored spectrophotometrically. The resultsshowed that the dye was completely oxidized and maximum decolorization efficiency wasachieved at the optimum conditions of the reaction time 120 min. The optimum conditions ofinitial dye, Cu2+ ion, initial peroxydisulphate ion (S2O82−) concentration for photooxidation weredetermined to be 2.8 × 10−5, 4.1 × 10−4 and 3.6 × 10−4 M, respectively and light intensity 62.9mWcm2−. 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-orderkinetics. A suitable tentative mechanism for photochemical oxidation of methylene blue has beenproposed.