Photocatalytic degradation kinetics and mechanism of acid blue 40 by TiO2/UV in aqueous solution

Photocatalyzed oxidation kinetics and mechanism of Acid Blue 40 at different pH values by TiO2/UV were studied. It is found that at pH 3, photocatalytic oxidation kinetics of Acid Blue 40 follows the Langmuir-Hinshelwood model, with reaction rate constant k of 0.0074 mM/min and adsorption constant K of 7.05 l/mM; While at higher pH values, no adequate kinetic model can be used. A yellow intermediate has been detected. Its appearance and disappearance with the reaction time are measured in terms of absorbance intensity. More than five hours are needed to completely mineralize the dye and its intermediate. It is found that Fe2+ does not have significant influence on the reaction, while H2O2 could retard the reaction when its concentration is higher than 0.01 mM.