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

Abstract

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