Increasing environmental pollution caused by toxic dyes due to their hazardous nature is a matter of great concern. It has been generally agreed that methyl orange (MO) can be effectively degraded in aerated K2S2O8 homogeneous reaction system using near-UV irradiation. In this paper photocatalytic degradation of MO solutions with K2S2O8 was investigated, with particular attention on the possible underlying mechanisms. This report has shown decolorization efficiency of MO increases with the increasing of the dosage of the catalyst. There is no optimal amount of catalyst in our case, where special attention was paid on the nature of the photocatalyst itself. The current research revealed that the decolorization reaction is a pseudo first-order reaction when the concentration of MO is below 20 mg L−1 and the decolorization reaction is zero-order reaction when the concentration of MO is above 100 mg L−1, but the Langmuir-Hinshewood kinetic model does not describe this. The influence of IO 4−, BrO 3− and H2O2 were investigated in detailed. Several observations indicate that the mechanism is not involved in hydroxyl radical attacks in MO degradation with K2S2O8 by UV irradiation. The possible underlying mechanisms are direct oxidation of the MO by S2O 82− and hydrogen attraction by SO 4•−. <alternatives> [...] </alternatives>
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