Ozonation of trace nitrobenzene in water in the presence of a TiO ₂/silica-gel catalyst

Heterogeneous catalytic ozonation was investigated for the degradation of nitrobenzene in the presence of TiO2 supported on Silica-gel as a solid catalyst. The conditions in preparing the catalyst are experimentally optimized. The catalytic activity of the supported TiO2 is strongly influenced by the calcination temperature. The TiO2/Silica-gel calcined at 500°C showed the highest activity for the degradation of nitrobenzene. An approximate increase of 21% in removal efficiency was achieved for catalytic ozonation compared with the case of ozonation alone. Nitrobenzene degradation was significantly influenced by the presence of carbonate and t-butanol, which confirmed that TiO2/Silica-gel catalyzed ozonation followed a radical-type mechanism. Kinetic study demonstrated that catalytic ozonation is pseudo-first-order with no respect to the initial nitrobenzene concentration. The effect of catalyst dosage and pH on the oxidation efficiency of nitrobenzene was also investigated. Catalyst dosage exerted a positive influence on nitrobenzene removal, and nitrobenzene degraded more completely under neutral or basic conditions. Finally, the catalyst stability was tested through repeated experiments.