Characteristics and differences of the catalytic ozonation of methylene blue by δ-MnO2 and Mn3O4

Abstract

According to the characteristics and differences of manganese oxides in the catalytic treatment of dye wastewater, the catalytic capability and its influencing factors of δ-MnO2 and Mn3O4 two manganese oxides on the catalyzation of methylene blue wastewater were comparatively investigated, the adsorption characteristics of the catalysts and the effect of tert-butyl alcohol on the catalytic efficiency were explored, and the XRD, SEM, BET and FTIR methods were used to study the structural characteristics of the oxides to further reveal the mechanism of the difference in the catalytic performance of the two manganese oxides. The results show that both δ-MnO2 and Mn3O4 can improve the efficiency of the catalytic ozonation system significantly, and δ-MnO2 has higher catalytic activity, the removal rates of chroma and CODcr are 99.77% and 71.43%, respectively, and when pH=11, the dosage of catalyst is 2.4 g/L, and the mass concentration of ozone is 9.5 mg/L, the removal performance of δ-MnO2 is the best. Both of the oxides can promote the production of ·OH, but δ-MnO2 has larger specific surface area, more amount of surface hydroxyl groups and better adsorption performance, which has better catalytic effect than Mn3O4.

Keywords

• methylene blue
• manganese oxide
• catalytic ozonation
• decolorization
• codcr