Research Of Novel MnO₂ Nanocompositcs Synthesis And Its Performance Of Organic Pollutant Catalytic Ozonation In Water

The demand for fresh water is increasing with the growth in world population,and obtaining an adequate supply of clean water has likely been the challenge for many countries.To solve this problem,using water from unconventional sources is the best method from economic point of view.To make wastewater reuse safety,all the pollutants presented at wastewater should be removed completely.Ozone is used widely in water treatment technology because of its powerful oxidation.However,it has been reported,in most cases,the ozonation can not completely degrade organic compound and sometimes produce toxic intermediates.In such cases,the efficiency of oxidation can be improved by employing ozone together with transition metal oxides as catalysts.As a new and the most promising development in the research of advanced oxidation water treatment,heterogeneous catalytic ozonation has been attracting the increasing interest due to its potentially higher effectiveness in the degradation,and mineralization of refractory organic pollutants and lower negative effect on water quality.The catalytic efficiency of transition metal oxides is decided by their physical and chemical properties.Physical properties include surface area and surface charge.The main chemical properties include chemical stability,and active surface sites.Among many transition metal oxide catalysts,MnO₂ shows excellent catalytic activity as the heterogeneous catalysts in degrading the organic pollutants in aqueous solution.In this thesis,we report the synthsis,characterization and heterogeneous catalytic ozonation of nano-MnO₂ and its nanocomposite for water treatment.The main points were summarized as follows:（1）We report the synthsis,characterization and heterogeneous catalytic ozonation ofα-MnO₂ andβ-MnO₂ for elimination of bisphenol-A in waster water in the precence of ozone.The results indicate that theα-MnO₂ andβ-MnO₂ can remove the bisphenol-A in waster water efficiently.（2）A novel nanocomposite composed of three-dimensional（3D）sea urchin-like-MnO₂ nanoarchitectures and reduced graphene oxide was synthetised,it was used as catalyst for the elimination of BPA in water by ozonation.The catalyst were well characterized by SEM,TEM,XRD,and Raman spectra.The nanocomposite was found to be a highly efficient catalyst to eliminate BPA from water in the presence of ozone.（3）We report unique three-dimensional（3D）flower-like nanoarchitectures composed ofβ-MnO₂ and reduced graphene oxide（RGO）for catalytic ozonation of dichloroacetic acid（DCAA）from drinking water.The catalytic results show that the 3Dβ-MnO₂/RGO nanocomposites can be used as efficient and stable ozonation catalysts to eliminate DCAA from water.（4）We report the synthsis,charateration and the the nanocomposites of MnO₂ and Bi₂O₃ and its heterogeneous photocatalytic ozonation for elimination of bisphenol-A in waste water.（5）The increasing of pH,temperature and dose of catalysis accelerated the elimination of organic pollutants in water by catalytic ozonation.（6）The intermedi of catalytic and photocatalytic ozonation were detected by GC-MS,the pathways of BPA and DCAA degradation by the ozonation were speculated.