Microwave assisted synthesis of ZnO-TiO2 and its visible light catalytic denitrification activity

Abstract

Comparing the composite TiO2 prepared by hydrothermal sol gel method and microwave-assisted sol gel method, the microwave-assisted sol gel method with shorter time and better crystallinity was finally used to prepare ZnO-TiO2 materials with different composite ratios. The specific surface area, pore volume and pore size of ZnO-TiO2 composite are significantly larger than those of TiO2. The surface acidity of ZnO-TiO2 composite is stronger. The band structure is conducive to the efficient separation of electrons and holes, and the catalytic reduction activity and selectivity are stronger. The best composite ratio of ZnO and TiO2 is optimized to be 0.2 through photocatalytic denitration experiments. For NOx with an initial concentration of 6.83 mg/m3, under the light source condition irradiated by 65 W energy-saving lamp, the visible photocatalytic removal efficiency is as high as 85%. When the NOx concentration is increased to 13.67 mg/m3 and the ammonia nitrogen ratio is 1:1, the denitration efficiency is as high as 96%, which is 43% higher than that of pure TiO2. According to mechanism analysis, the whole reaction can be divided into adsorption and photocatalysis. Adsorption is the speed control step of the reaction. NO is oxidized to NO2 under the action of adsorbed oxygen, and photogenerated electrons can further reduce NO2 to N2. After NH3 is introduced, NH3 and photogenerated electrons work together to improve NOx removal efficiency.