The Phase Transformation Of Nano TiO₂ Induced By Nano MnO₂/Mn₃O₄ And Its Photocatalytic Activity

Manganese dioxide is closely related to the iron manganese oxides minerals catalyst of earth supergene environment,its self-assembly controllable preparation and?mineral?catalytic oxidation property still has the research value.Titanium dioxide?TiO₂?nanocrystal recognised as the representative of the semiconductor optical catalyst has been further research in recent years.Studying the controllable preparation and regulatory mechanism of multiphase orderly?mineral?composite of manganese oxide and titanium oxide nanocrystal and photocatalytic performance of this?mineral?materials which has theoretical instruction significance in environmental mineralogy to understand the manganese oxide and titanium oxide in soil and water environment by simulating the similar self-assembly function existed in the supergene minerals from the point of environment mineral materials.In this study,The best preparation conditions of MnO₂ nano film and Mn⁴⁺doped TiO₂nano film using the self-assembly method based on the silica substrate are explored?The crystal growth of Mn3O4-TiO2 nano composite film and the regulation function of rutile TiO₂ inducted by MnO₂/Mn₃O₄ are analyzed.The morphology structure of MnO₂ nano film,Mn₃O₄-TiO₂ nano composite film and Mn⁴⁺doped TiO₂ nano film are characterized and their photocatalytic properties are studied.the main research work of this paper are as follows:MnO₂ nano film is sheet structure with the thickness of 100 nm approximately,the nano grains are in the 5-10 nm size range which give priority to alpha MnO₂crystal shape.The removal rate of 40 mL 10 mg/L phenol is 50.93%for 12 h by the MnO₂ nano film.While it does not show up higher oxidation ability to degradate 1mg/L rhodamine B under the simulated natural light condition.The crystal type of the MnO₂ nano film changes in low temperature TiCl₄-HCl aqueous system,?-MnO₂ reduces to thetetragonal crystal system hausmannite Mn₃O₄ which controls the crystallization of rutile TiO₂.Mn₃O₄ becomes the impurity of deep subband energy levels of TiO₂ which accelerate the recombination of photoinduced electron-hole pairs,so the decoloration rate of 1 mg/L rhodamine B by the Mn₃O₄-TiO₂ nano composite film for 5 h is lower than the TiO₂ nano film under the same condition.The grain of Mn⁴⁺doped TiO₂ nano film is mainly anatase phase with the size of 5 to 25 nm and trace amount of Mn⁴⁺replace Ti⁴⁺into the cell of nano TiO₂ after Mn⁴⁺doping.The photocatalytic activity of the Mn⁴⁺doped TiO₂ nano film affected by the initial pH of 5 mg/L thiamphenicol solution and the amount of doping Mn⁴⁺of this film are studied.The degradation rate of thiamphenicol solution by this film is better in a weak alkaline environment than strong alkaline and acid environment.With the amount of Mn⁴⁺doping in the cells of TiO₂ increasing,the absorption sideband of TiO₂ nano film blue shifts gradually which means that the Mn⁴⁺doped nano TiO₂ is helpful to enhance the utilization of light energy in natural light.The Mn⁴⁺doped TiO₂ nano film has good reutilization efficiency,the degradation rate of thiamphenicol solution is reduced to 10.74%after using nine times.