Theoretical and experimental investigation of the mechanism of the catalytic ozonation process by using a manganese-based catalyst

The mechanisms of heterogeneous catalytic ozonation using a manganese catalyst have been studied in this work. The effects of catalyst, pH and the radical scavengers on the degradation of a model pollutant (i.e. phenol) were evaluated. The contribution of hydroxyl radicals and molecular ozone on the oxidation of phenol was studied for both homogeneous and heterogeneous systems. It was observed that the contribution of hydroxyl radial was 11–44% at pH 3–9. The heterogeneous catalyst may pose a rather complex mechanism as compared to homogenous catalyst. In presence of manganese catalyst, the decomposition ozone is very fast and generates more hydroxyl radicals. This helps the rapid oxidation of phenol at a wide range of pH 3–9. The surface of the catalyst undergoes multiple oxidation reaction and plays the major role in generation of the hydroxyl radicals. A considerable amount of phenol degradation was observed even at low catalyst dose (i.e. 0.5 g L−1). The effect of catalyst on the ozone mass transfer in water was also studied in this work. It was observed that, the overall performance of the phenol degradation is dependent on both chemical reaction due to catalytic action and gas–liquid mass transfer rate.