Photooxidative Degradation of Acid Red 27 (AR27): Modeling of Reaction Kinetic and Influence of Operational Parameters

Abstract

The decolorization and mineralization of Acid Red 27 (AR27), an anionic monoazo dye of acid class, were studied by UV/H₂O₂ process in laboratory and real samples. Effects of different process parameters such as initial H₂O₂ and AR27 concentrations, pH and EtOH as an electron scavenger have been studied. H₂O₂ and UV light have a negligible effect when they were used on their own. The decolorization rate follows pseudo-first order kinetic with respect to the dye concentration. The rate constant of the attack of ^•OH radicals to the AR27 has been estimated through the adoption of a simplified kinetic model (1.03 × 10⁸ M⁻¹ s⁻¹). This model allows predicting the pseudo-first order rate constant and concentration of AR27 in different illumination times for different initial concentrations of H₂O₂. Mineralization studies showed, the formation of sulfate ions, the decrease of pH and 85% of COD reduction occur in less than 60 min. In the real wastewater color removal could be achieved after only 75 min, whereas 45% of COD reduction occurs after 105 min of illumination.

Keywords:

• Decolorization
• Photooxidation
• UV/H₂O₂
• Kinetic model
• Acid Red 27
• Azo dye

Acknowledgments

The authors thank the Islamic Azad University of North Tehran Branch for financial and other supports.