Influence of nanosized TiO₂ catalyzed ozonation on the ammonia concentration in Songhua River water

Changes of the ammonia concentration in Songhua River water treatment using catalyzed ozonation were investigated. Nanosized TiO₂ loaded on haydite, silica-gel and zeolite was prepared as the catalyst. The ammonia concentration increased in the first stage, then decreased. After 30 min reaction, the ultimate concentration was close to the initial concentration in ozonation. In catalyzed ozonation which used TiO₂/haydite or TiO₂/silica-gel as the catalyst, the ammonia concentration also increased primarily and then decreased, but the average concentration was higher than that in ozonation alone. In catalyzed ozonation which used TiO₂/zeolite as the catalyst, the ammonia concentration decreased primarily, then increased to a peak value, and decreased again. The removal efficiency was close to 80% after 30 min reaction. Effect of ozone dosage, catalyst dosage and temperature were investigated respectively. Increasing the ozone dosage, the maximum of the ammonia concentration appeared ahead and the average concentration of ammonia decreased either in ozonation or in catalyzed ozonation. Increasing the dosage of TiO₂/haydite or TiO₂/silica-gel, the average concentration of ammonia increased. The removal efficiency of ammonia benefited from the increase of TiO₂/zeolite dosage, but it was affected little when TiO₂/zeolite dosage was above 50 g. When the temperature increased from 10°C to 30°C, the changes of ammonia concentration were not affected in catalyzed ozonation using TiO₂/haydite or TiO₂/silica-gel as the catalyst. While the increase of temperature yielded an increase of ammonia removal efficiency when using TiO₂/zeolite as the catalyst.