A review on photocatalytic ozonation used for the treatment of water and wastewater

• Photocatalytic ozonation is a powerful oxidation process for water/wastewater treatment.
• Synergistic effects are observed by combining various photocatalysts with ozone.
• Photocatalytic ozonation is often more cost-effective than ozonation and photocatalysis.
• Photocatalytic ozonation can moderate the poor mass transfer of fixed catalysts.
• Changing the operational conditions can significantly affect the oxidation efficiency.

The present study aims to describe photocatalytic ozonation as a combination of two different techniques for hydroxyl radical generation; photocatalysis and ozonation, and to highlight its advantages for water and wastewater treatment compared to these two technologies. An extensive review on the mechanisms, kinetics and economic aspects of photocatalytic ozonation has been performed to explore the synergistic effects produced by applying this oxidation method to the degradation, mineralisation and detoxification of different organic pollutants in aqueous media. The influence of experimental parameters such as pollutant concentrations, ozone dose, photocatalytic load and properties, solution pH and temperature, irradiation wavelength and intensity and the effect of the presence of some substances on the efficiency of photocatalytic ozonation is discussed. Finally, plasma-induced photocatalytic systems are introduced as a new approach for handling photocatalytic ozonation treatments.