Preparation Of ?-and ?-MnO₂ And Their Catalytic Ozonation Activity

China is a country with relatively lack of fresh water resources and a low per capita freshwater resource.Under such situation,the problem of water pollution in China is very serious.The massive use of chemical compounds such as industrial compounds,plant hormones,pesticides,drugs and cosmetics in human social life,and continuously discharging them into the water environment system through direct and indirect ways which has caused severe pollution on freshwater resources.Environmental endocrine disruptors(EDCs)and drugs and personal care products(PPCPs)are two major emerging pollutants.It is necessary to take some measures to prevent two emerging pollutants from causing greater damage to human health and ecosystems.Heterogeneous catalytic ozonation technology can effectively remove refractory organics in water.The preparation of highly active manganese dioxide catalyst is an important development direction for future heterogeneous catalytic ozonation technology for wastewater treatment.At present,?-MnO2 is considered as the best catalyst among various types of manganese dioxide.The report of a-MnO2 used as an ozone catalyst mainly determined which type of the organics it can oxide by catalyzing ozone and the catalytic mechanism.The material synthesis method basically adopted classical preparation process to obtain rod-like ?-MnO2.The researches about the preparation process of material to get a-MnO2 with a special microscopic morphology are not much.At the same time,?-MnO2 is a kind of catalyst with good catalytic properties,but there is a little report on the application of ?-MnO2 in heterogeneous catalytic ozonation technology.And the existing ?-MnO2 preparation process is generally complicated or the crystallinity of the prepared material is poor.In this paper,the hollow square structure ?-MnO2 with double-layer was prepared by using MnCO3 as template and petal-like ?-MnO2 with good crystallinity was prepared by one-step hydrothermal reaction using KMnO4 as the only raw material.The catalytic ozonation tests of bisphenol A and ibuprofen were done with the prepared material as catalyst.In the degradation experiments of bisphenol A and ibuprofen,the prepared materials showed good catalytic activity and the first 2 min of the reaction is a period of rapid progress of the catalytic reaction.Commercially y-MnO2 exhibited a certain catalytic activity in the degradation of bisphenol A,but its catalytic activity is much lower than the prepared material.However,?-MnO2 didn't exhibit catalytic activity in the degradation of ibuprofen,but rather the degradation of ibuprofen was inhibited.It showed that the main reason why the catalyst played a catalytic role depended on the effective interaction among the catalyst,ozone and organic molecules.Hydroxyl radicals are not the main active radicals during the catalytic reaction.