Abstract:The Mg/Mn composite metal oxide catalysts were prepared in method of homogeneous co-precipitation and their catalytic degradation on the low concentration of ammonium-nitrogen(NH4 -N) in the solution were investigated. The prepared catalysts were characterized by scanning electron microscopy (SEM) and nitrogen adsorption analysis, and the effects of preparation conditions on the microstructure, specific surface area and catalytic degradation on NH4 -N were studied. The mechanism of ammonia nitrogen degradation was discussed. The experimental results showed that the catalyst with Mg/Mn molar ratio of 8:2 calcined under 500 ℃ for 4 h have the higher catalytic activity and the best selectivity for the gaseous nitrogenous material. The catalyst has a flocculent structure, a fluffy and coarse surface, and the specific surface area is 31.8845 m2/g. The mechanism of Mg/Mn composite metal oxide catalytic ozonation for oxidizing NH4 -N from water was hydroxyl radicals produced by ozone’s decomposition.