Photocatalytic ozonation of phenolic wastewaters: Syringic acid, tyrosol and gallic acid

Abstract

The photocatalytic ozonation of a mixture of 3 phenols (gallic acid, tyrosol and syringic acid) has been conducted under different operating conditions. The individual adsorption of the phenol type compounds onto titanium dioxide (photocatalyst) has been first evaluated. Equilibrium conditions are attained in less than an hour while the isotherm curves reveal that adsorption intensity increases in order: syringic acid < tyrosol < gallic acid. When the photocatalytic ozonation is applied, an optimum in titanium dioxide concentration is experienced (1.5 g L^{− 1}). Direct comparison of the photocatalytic ozonation to other less sophisticated oxidation systems (i.e., single ozonation, catalytic ozonation, photo-ozonation, etc.) indicates a higher efficiency of the former in terms of ozone uptake.

Keywords:

• Ozone
• photocatalysis
• phenols
• titanium dioxide
• water treatment

Acknowledgments

This work has been supported by the CICYT of Spain and the European Region Development Funds of the European Commission (Project PPQ2003/00554). Dr. Gimeno (Ramón y Cajal contract) and Mrs. Carbajo (FPU grant) also thank the Spanish Ministry of Science and Education.

Notes

^a after 120 minutes of treatment

^b after 150 minutes of treatment.