Abstract:

A series of MnO_x-CeO₂ mixed oxide catalysts were prepared by co-precipitation method and used for catalytic wet air oxidation of pesticide wastewater from imidacloprid production. These catalysts were characterized by BET, XRD, XPS. The relationships between the surface structure and catalytic activity, and the effect of the manganese content[i.e. the molar ratio of Mn/(Mn+Ce)] on catalytic activity were researched. BET and XRD data revealed that the particle size of catalyst with n(Mn)/n(Mn+Ce)=0.6 was the smallest, and specific surface area was the biggest in the series of catalysts. XRD and XPS techniques showed that the occurrence of significant interaction between Mn and Ce oxides, resulting in the evolution of textural, structural, oxidation state and the amount of chemisorbed oxygen with manganese content. The highest oxidation state of manganese oxide and the chemisorbed oxygen were present in the surface of MnO_x-CeO₂ mixed oxide catalyst at Mn/(Mn+Ce)=0.7. In the catalytic wet oxidation of pesticide wastewater from imidacloprid production, the most active catalyst was n(Mn)/n(Mn+Ce)=0.7. Using this catalyst, about 89.3%COD removal was attained at catalyst loading of 4 g/L, temperature of 190 ℃, partial pressure of oxygen of 1.6 MPa and influent pH 7.0 for 60 min.

Key words: Catalytic wet air oxidation, Pesticide wastewater, MnOx-CeO2, CeO2