Light and dark processes involving Fenton reagent are effective in the degradation of Orange II solutions. The degradation time is shown to be strongly dependent on the initial pH of the solution used. Experimental results show that the mineralization rates for Orange II become significant only at pH <∼5. The H2O2 added and O2 evolved were monitored during the degradation cycles allowing optimization for the times for oxidant addition. About 88% dye mineralization in 40 minutes under light irradiation. A model for the degradation has been developed from the available kinetic rates for radical reactions. The model predicts an H2O2 consumption time of ∼100 seconds consistent with the experimental results obtained. A turnover number of 4.7 was estimated for light induced processes in the model system used. Near surface radical formation is shown to be important during the observed photocatalysis. No activation energy was detected during the mineralization suggesting a radical mechanism for this reaction.

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