Oxidation of Acetovanillone by Photochemical Processes and Hydroxyl Radicals

Acetovanillone [Ethanone, 1-(4-hydroxy-3-metoxyphenyl)] is one of the major pollutants that is present in the wastewater produced during the boiling of raw material in the cork industry. The oxidation of its aqueous solutions by monochromatic UV radiation alone and combined with hydrogen peroxide, Fenton's reagent and the photo-Fenton system has been investigated. In the single UV radiation process, the apparent rate constants and the quantum yields are determined, and in the UV/H₂O₂combination, the additional efficiency in the oxidation process due to the presence of hydrogen peroxide is established. The influence of some operating variables, such as initial concentrations of H₂O₂ and Fe(II), as well as the pH, is discussed in the Fenton and photo-Fenton systems, and the partial contribution of the radical pathways to the global oxidation rates are evaluated. The rate constant for the reaction of acetovanillone with hydroxyl radicals is also determined by means of a competition kinetics model, its value being 5.62× 10⁹ M⁻¹s⁻¹. Finally, chemical oxidation experiments of wastewaters generated in this industry were carried out by using the same advanced oxidation processes. Specifically, the elimination of acetovanillone in these effluents was determined, and the removal of the global organic pollutant content was also evaluated.

Key Words:

• Acetovanillone
• Cork processing wastewaters
• Photochemical oxidation
• Quantum yields
• Hydroxyl radicals
• Rate constant for radical reaction.

ACKNOWLEDGMENTS

The authors wish to gratefully acknowledge financial support from the MEC of Spain through Project CTQ2004-00961/PPQ.

Notes

^a In the UV/H₂O₂ experiments, these values correspond to k_UH.

^a Total removal reached at 28 min of reaction.

^b In the photo-Fenton experiments, these values correspond to k_UF.

^a Total removal reached at 90 min of reaction.