• 关键词：氨氮  臭氧  MgO  催化臭氧化  机制

• 基金项目：国家自然科学基金（No.51179099，E090301）；山西省重点研发计划项目（No.201603D321007）；山西省科技攻关项目（No.20140313003-3）；山西省留学回国人员科技活动择优资助项目（2014）；山西省回国留学人员科研资助项目（No.2015-004）

• 陈璐
• 山西大学环境与资源学院, 太原 030006

• 刘海龙
• 山西大学环境与资源学院, 太原 030006

• 吉力
• 山西大学环境与资源学院, 太原 030006

• 李焕峰
• 山西省环境监测中心站, 太原 030002

• 摘要：研究了低温条件下单独臭氧及MgO催化臭氧化降解水中氨氮的效率和特征，并对其反应机制分别进行了探讨.结果表明，pH是影响臭氧和催化臭氧化除氨的重要因素，不仅影响溶液中NH₃与NH₄⁺的比例和臭氧氧化氨氮的速率，还影响氧化产物种类，从而影响脱氮效果.10℃时，单独臭氧对水中氨氮的氧化降解效率随pH的升高而增大，pH≤9时整体降解效率不高，pH=9时仅为16.39%，而pH=10时达到41.77%.臭氧和·OH共同参与降解氨氮的过程.单独臭氧氧化氨氮生成氮气的选择性具有pH依赖性，并与Cl^-密切相关.pH低（≤9）时，氨氮多以NH₄⁺形态存在，O₃与Cl^-反应生成ClO_x^-（x=1、3），再氧化NH₄⁺，从而生成气态产物N₂或N₂O.MgO在低温条件下具有很强的催化臭氧化降解氨氮的能力且温度升高有利于反应的进行，0、10、20℃时，MgO催化臭氧化氨氮的效率分别为77.53%、80.17%、91.26%.此过程中，·OH参与反应的程度低，一部分氨氮降解依靠ClO_x^-氧化NH₄⁺，而氨氮降解的主要途径为O₃对NH₃的直接氧化.

• Abstract：The degradation efficiency and characteristics of ammonia in water by ozonation alone and ozonation catalyzed with MgO were studied under low temperature conditions. The reaction mechanisms were discussed, respectively. Results show that pH significantly influences the removal of ammonia by ozonation and catalytic ozonation, affecting not only the NH₃ over NH₄⁺ ratio in the solution but also the ozonation rate of ammonia as well as the types of oxidation products. At 10℃, the degradation efficiency of ammonia by ozonation alone increases with the increase of pH, which is relatively low at pH ≤ 9, only 16.39% at pH=9 while 41.77% at pH=10. Ammonia degradation is the result of direct molecular O₃ and ·OH attack. And the selectivity to gaseous products is pH dependent in the presence of Cl^-. At low pH(≤ 9), ammonia mainly exists in the form of NH₄⁺. ClO_x^- (x=1, 3) generated by the reaction of O₃ with Cl^- reacts with NH₄⁺ to produce gaseous products including N₂ or N₂O. MgO has a strong catalytic ability for ozonation to degrade ammonia at a low temperature, and the temperature increase helps to promote the degradation. 77.53%, 80.17% and 91.26% ammonia removal is gained at 0, 10 and 20℃, respectively. In the process, the contribution of ·OH to the ammonia removal is insignificant. The main degradation pathway for ammonia is direct ozone oxidation with the form of NH₃ and a part of ammonia is degraded by the reaction of ClO_x^- with NH₄⁺.

• Key words：ammonia  ozone  MgO  catalytic ozonation  mechanism

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