Study On Degradation Of Nitrobenzene Wastewater By Combination Of Different Catalysts

Nitrobenzene,as a highly toxic compound, is stable and difficult to be degraded. Many countries have ranked nitrobenzene wastewater as the first-class restraining contaminant. Catalytic oxidation is an effective method to treat high concentration, toxic organic compounds which are hardly degraded in normal treatment. Its properties, such as high efficiency,low energy consumption,and no secondary pollutions, make it attractive in the treatment of nitrobenzene wastewater.According to single method degradation of nitrobenzene wastewater is most used in China and abroad. Our research presents a nitrobenzene wastewater decay technique that combines the following methods: Ultrasound oxidation and Fenton oxidation, Ultrasound oxidation and metal oxide catalyst-H₂O₂ system, UV photocatalytic and co-doping TiO₂-H₂O₂ system catalytic oxidation, microwave catalytic oxidation and catalyst-H₂O₂ system. The results have shown that using the combination of different methods had better decay effects than using any single method.â’ˆThe Fenton reagent and the ultrasound-Fenton both have promising degeneration effect to nitrobenzene. However, ultrasound-Fenton processing is better than Fenton processing in process effect, which reduces the reaction time. In the optimum condition, the degradation rate is 93.6%, COD removal rate is 34.5% by Single-Fenton method; the destroy rate of nitrobenzene is up to 99.0% and COD decreased is 38.1% by ultrasound-Fenton System.â’‰The CuO/zeolite and the ultrasound-CuO/zeolite both have degeneration effect to the nitrobenzene, but ultrasound-CuO/zeolite processing is better than CuO/zeolite processing in process effect, which reduces the reaction time. At optimum conditions, the degradation rate was 95.5%, COD removal rate is 45.5% by single-Fenton method; the destroy rate of nitrobenzene is up to 99.3% and COD decreased is 48.4% by ultrasound/Fenton system.â’ŠSome studies have been done to improve the performance of TiO₂ and single- impurity TiO₂ is used as catalyst in the photocatalysis oxidation reaction,however, there are few studies of the performance of TiO₂ by co-doping metal elements by now. In this article, it adopt co-doping TiO₂ as catalyst. The research results have shown that the photocatalysis properties of co-doping TiO₂ can be enhanced more largely than single metal doped TiO₂ and undoped TiO₂ under the best conditions. Degradation of nitrobenzene wastewater with co-doping TiO₂-H₂O₂ shows that there are synergistic interaction among UV,co-doping TiO₂ and H₂O₂. In optimum conditions, the degradation rate 99.3%, COD removal rate was 69% by UV-(Ag-Ni-TiO₂ /γ-Al₂O₃)-H₂O₂ system; the degradation rate of nitrobenzene is up to 99.6% and COD decreased is72.7% by UV-(Fe-Ni-TiO₂ /γ-Al₂O₃)-H₂O₂ system.â’‹Activated carbon or modified activated carbon is usually used as a catalyst at the microwave catalytic oxidation reaction. In this article, we adopt zeolite and modified zeolite as catalysts. The experiment that uses microwave-irradiated catalyst-H₂O₂ system have demonstrated the significance of synergistic effects among MW,catalyst and H₂O₂ catalytic oxidation degradation processes: The degradation rate was 99.2%, COD removal rate was 73.91% by MW-CuO/zeolite-H₂O₂ system; the degradation rate of nitrobenzene was up to 98.9% and COD decreased was 73.91% by MW-Bi2O3/zeolite-H₂O₂ system.