The Construction And Properties Of Hierarchical MnO₂ Composites

In recent years,the problem of water pollution has become increasingly serious,and the important substances causing water pollution in China are organic pollutants that are difficult to degrade.Organic pollutants are characterized by"carcinogenicity,teratogenicity,mutagenicity"and high toxicity,which are enriched and pose a serious threat to the entire ecosystem.Therefore,it is necessary to develop an effective strategy to completely remove organic pollutants from water.Although MnO₂-based materials can degrade organic pollutants efficiently under the premise of introducing oxidants,the presence of degradation intermediates is often found in water bodies,and it is difficult to achieve the ideal goal of complete mineralization.Therefore,the structure modification of the catalyst is carried out by adding other carriers:the hollow SiO₂or TiO₂ is used as the carrier to construct the MnO₂ catalytic system with hollow structure,and on this basis,the structure,morphology and photocatalytic properties of the catalyst are further studied.Preparation of hollow SiO₂/MnO₂ composites is using cationic polystyrene?CPS?as template,electrostatic pre-assembly on the surface to precipitate SiO₂,removing CPS at high temperature to form SiO₂ hollow microspheres,and then using hollow SiO₂ as template,Manganese nitrate is the manganese source,and the SiO₂/MnO₂ precursor is obtained by pyrolysis.Finally,the hollow SiO₂/MnO₂ composite is prepared by high temperature calcination.The prepared SiO₂/MnO₂ can not only effectively improve the dispersibility of MnO₂ due to the presence of internal hollow porous SiO₂,but also facilitate the diffusion of the substrate.Therefore,in the experiments for degrading phenol and tetracycline,the corresponding degradation rates were increased by 62%and 9%,respectively,compared with commercial MnO₂.Design and synthesis of hollow TiO₂/MnO₂ composites:Although the introduction of hollow SiO₂ can effectively improve the ability of MnO₂ to degrade organic pollutants,hollow SiO₂ itself does not contribute to the degradation of organic pollutants,resulting in limited performance.Therefore,we replaced SiO₂ as a hollow carrier of MnO₂,introduced photocatalysis into MnO₂ composite,and integrated photocatalytic and chemical oxidation activities to prepare a highly efficient TiO₂/MnO₂ composite.In the process of degradation of organic pollutants,the prepared catalyst can fully exert the synergistic effect of TiO₂ and MnO₂,and realize the rapid oxidative degradation of phenol in the first stage and the photomineralization process of residual phenol and its intermediates in the second stage.The ideal target for complete mineralization of phenol.Study on the structure-effect relationship between the structure and morphology of TiO₂/MnO₂ composites and their degradation pollutants:In order to understand the relationship between the structure and properties of the prepared TiO₂/MnO₂ composites in the degradation of organic pollutants,we have studied the shell thickness of TiO₂,the ratio of manganese dioxide and the influence of preparation methods on its properties,and summarized TiO₂.The structure and morphology of MnO₂ composites affect the degradation of phenol,revealing the degradation mechanism of fully mineralized phenol.In summary,the introduction of a hollow support can effectively improve the ability of MnO₂ to degrade organic pollutants,especially by combining photocatalysis of TiO₂ with chemical oxidation of MnO₂ to achieve the goal of complete mineralization of phenol.The development of this research can provide an experimental reference for the construction of composite materials with two or more components.