微波辅助合成ZnO-TiO_(2)及其可见光催化脱硝活性

Microwave assisted synthesis of ZnO-TiO_(2) and its visible light catalytic denitrification activity

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TiO_(2)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-TiO_(2)材料。ZnO-TiO_(2)复合材料比表面积和孔容孔径尺寸较TiO_(2)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TiO_(2)最佳复合比为0.2,对于初始质量浓度为6.83 mg/m^(3)的NO_(x),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%,NO_(x)质量浓度提高至13.67 mg/m^(3),在通入氨氮比为1:1的NH_(3)后,脱硝效率高达96%,比纯TiO_(2)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NO_(2),光生电子能够将NO_(2)进一步还原为N_(2),通入NH_(3)后,NH_(3)与光生电子共同作用,NO_(x)脱除效率得以提高。

Comparing the composite TiO_(2) 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-TiO_(2) materials with different composite ratios.The specific surface area,pore volume and pore size of ZnOTiO_(2) composite are significantly larger than those of TiO_(2).The surface acidity of ZnO-TiO_(2) 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 TiO_(2) is optimized to be 0.2 through photocatalytic denitration experiments.For NO_(x) with an initial concentration of 6.83 mg/m^(3),under the light source condition irradiated by 65 W energy-saving lamp,the visible photocatalytic removal efficiency is as high as 85%.When the NO_(x) concentration is increased to 13.67 mg/m^(3) and the ammonia nitrogen ratio is 1∶1,the denitration efficiency is as high as 96%,which is 43% higher than that of pure TiO_(2).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 NO_(2) under the action of adsorbed oxygen,and photogenerated electrons can further reduce NO_(2) to N2.After NH_(3) is introduced,NH_(3) and photogenerated electrons work together to improve NO_(x) removal efficiency.