Treatment Of Songhuajiang River Water By Catalytic Ozonation Process Using Nanosize TiO₂

In this experiment, nanosize titanium dioxide was prepared by the sol-gel method. Several materials were chosen as support and titanium dioxide was loaded on them. The removal efficiency of nitrobenzene in catalytic ozonation process using different catalyst was investigated and the mechanism was proposed. The removal efficiency of pollutants in natural water taken from Songhuajiang River was also investigated. The change of organic contents and species after treatment was detected by using GC-MS.The calcination temperature during preparation had great effect on the catalytic performance of the catalysts. The best calcination temperature for titanium dioxide powder and two kinds of loaded catalysts is different. The removal efficiency of nitrobenzene in catalytic ozonation process was much better than ozone alone, and it could be benefit from the increasing of ozone dose. The pH had great effect on the efficiency of nitrobenzene removal, and the best value was about 10.The reaction mechanism was investigated by adding tert-butanol and carbonate into the water sample, and Electron Spin Resonance (ESR) was also adopted. Hydroxyl radical was found to be the most important oxidation species in the process of nitrobenzene decomposition. Hydroxyl radical was induced by OH- in the process of ozonation alone, while induced by surface hydroxyl on the catalyst in the process of catalytic ozonation.The two kinds of loaded catalyst TiO₂/sintered clay, TiO₂/SiO2 granule, also had good catalytic efficiency of removing pollutants from natural water taken from Songhuajiang River. TOC and UV254 could be removed effectively in the process of catalytic ozonation, the efficiency was much better than ozone alone. The concentration of NH4+-N decreased at first and then increased in the process of oxidation, but the oxidation mechanism of nitrogenous organic compounds in the process of ozonation and catalytic ozonation was different. The proportion of small molecule organic compounds in water increased after catalytic ozonation process. The residual organic compounds in water could be more easily assimilated by bacteria. Ozone dose, catalyst dose, temperature could also affect the efficiency of catalytic ozonation process.