Study On Simultaneous Removal Of Ammonia Nitrogen And COD By Catalytic Ozonation

With the acceleration of urbanization and industrial development in China,a large amount of life and industrial sewage flows into rivers,lakes,or underground water,causing serious pollution to water bodies,and has serious impact on fishery water and domestic water consumption.Urban sewage pollution has become a constraint on the country.One of the important factors for development.Therefore,the national discharge standards for sewage treatment have become increasingly stringent.Urban sewage treatment has become a research hotspot.Ammonia nitrogen is the most common pollutant other than organic matter in wastewater.During the“Twelfth Five-Year Plan”and“Thirteenth Five-Year Plan”period,nitrogen-containing compounds were listed as the main control indicators.Catalytic ozone oxidation technology as a kind of advanced oxidation technology,can be placed on the back end as an advanced treatment process,so that the effluent reaches a certain standard of reuse water,to achieve the goal of sewage resources.The problems of catalyst loss,low ozone utilization,and high operating cost severely restrict the wide application of catalytic ozone oxidation technology.The development of a stable,efficient,long-life catalyst is the key to the large-scale application of catalytic ozone oxidation technology.The?-Al₂O₃-supported catalysts were prepared by co-impregnation method for different active components.By evaluating the NH₄⁺-N conversion rate and the selectivity of N₂,the oxidative decomposition of Mn-CuO_x/?-Al₂O₃ catalysts was optimized.Ammonia in water,and the catalyst preparation conditions were optimized.The results showed that the optimal preparation conditions were Mn?NO₃?₂ and Cu?NO₃?₂·3H₂O impregnating solution concentrations of 0.2 mol/L and 0.1 mol/L,the immersion time was 8 h,the calcination temperature was 500°C,and the calcination time was 6 h.The performance and stability of Mn-CuO_x/?-Al₂O₃ catalyst in degradation of ammonia in water were evaluated using NH₄Cl as the target pollutant.The results show that the catalyst can be used in water treatment for a long time.The reaction products were analyzed by GC and spectrophotometer.The main products of the reaction were N₂ and a small amount of NO₃^-?the N balance was close to 100%?.The effects of ozone concentration,catalyst addition amount,initial ammonia nitrogen concentration and initial pH on catalytic oxidation of ammonia-nitrogen by ozone were investigated.With the increase of ozone concentration and ammonia nitrogen concentration,the reaction rate increased,and the reaction rate of the catalyst increased accordingly.The increase of pH favored the removal of ammonia nitrogen.The simultaneous introduction of COD and ammonia nitrogen into the reaction demonstrated that catalyzed ozonation of Mn-CuOx/?-Al₂O₃ catalysts has the ability to remove both COD and ammonia nitrogen.The mechanism of catalysis of ozone oxidation by Mn-CuO_x/?-Al₂O₃ was discussed.The indirect and direct methods were used to prove that the main active material in the catalytic process is hydroxyl radical.