Degradation and kinetics of H₂O₂ assisted photochemical oxidation of Remazol Turquoise Blue

Advanced Oxidation Processes based degradation of organic pollutants along with enzymatic approaches have gained prominence lately for efficient means of remediation of polluted wastewater. In the present study the photolytic oxidation of a model organic pollutant namely Remazol Turquoise Blue (RTB) dye, using H₂O₂ and UV light is reported. The photolytic degradation of RTB obeyed first order kinetics for which apparent rate constants could be calculated. Various parameters that could affect RTB degradation such as RTB concentration, pH, H₂O₂ dose and irradiation time were also studied to come up with optimized degradation conditions. Under optimum operating conditions, 50% decoloration of the dye could be achieved in 10min. In addition, the effect of various ions on RTB degradation was also studied and showed that PO43-,Cl-, and CO32- ions increased the % degradation of this dye, which were most likely due to increased generation of OH radicals by subsequent reactions of these anions in solution. Interestingly, addition of redox active metals like Fe³⁺, Cd²⁺, Ni²⁺ and Zn²⁺ all led to decrease in the % dye decoloration and this effect was explained on the basis of their reactions with hydroxyl radicals. To confirm the actual breakdown of RTB, LC-MS analyses were carried out and the intermediate detected was compared with the previously published data for the enzymatic degradation of RTB. The results showed that one of the low molecular weight intermediates formed in the process was identical to those reported for peroxidase-degraded RTB, thus indicating that both enzymatic and photolytic mediated degradation of RTB may involve a common intermediate.