Microwave assisted synthesis of ZnO-TiO2 and its visible light catalytic denitrification activity
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摘要: 通过对比水热溶胶凝胶法与微波辅助溶胶凝胶法制备的复合TiO2的光催化性能,最终采用耗时较短且结晶度更好的微波辅助溶胶凝胶法制备了不同复合比例的ZnO-TiO2材料。ZnO-TiO2复合材料比表面积和孔容孔径尺寸较TiO2材料均有明显增大,表面酸性更强,能带结构有利于电子空穴的高效分离,催化还原活性与选择性更强。经光催化脱硝实验优化出ZnO与TiO2最佳复合比为0.2,对于初始质量浓度为6.83 mg/m3的NOx,在65 W节能灯照射的光源条件下,可见光催化脱除效率高达85%,NOx质量浓度提高至13.67 mg/m3,在通入氨氮比为1∶1的NH3后,脱硝效率高达96%,比纯TiO2的提高43%,质量浓度适用范围较前期研究拓宽近六倍。机理分析认为,整个反应可分成吸附与光催化两个部分,其中,吸附是该反应的速控步骤,NO在吸附氧的作用下被氧化为NO2,光生电子能够将NO2进一步还原为N2,通入NH3后,NH3与光生电子共同作用,NOx脱除效率得以提高。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.
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Key words:
- ZnO-TiO2 /
- denitration /
- visible light catalysis
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表 1 不同样品的BET分析
Table 1 Bet analysis parameters of different samples
Sample type Specific surface area /(m2·g−1) Average aperture /nm Pore volume /(cm3·g−1) TiO2 (Microwave method) 89.54 20.87 0.19 TiO2 (Hydrothermal method) 92.10 21.09 0.25 ZnO (Microwave method) 90.54 17.00 0.13 0.2-ZnO-TiO2 126.42 25.88 0.33 -
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