High catalytic activity of Mo–Zn–Al–O catalyst for dye degradation: Effect of pH in the impregnation process
High catalytic activity of Mo–Zn–Al–O catalyst for dye degradation: Effect of pH in the impregnation process
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DOI：
10.1016/j.apcatb.2014.05.011
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发表时间：
2014-11
影响因子：
22.1
通讯作者：
Yang Li;Yin Xu;Xiao-ying Chen;Fei Ge;Runliang Zhu
中科院分区：
文献类型：
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作者：
Yang Li;Yin Xu;Xiao-ying Chen;Fei Ge;Runliang Zhu
考察了浸渍过程中pH值对共沉淀浸渍法制备的Mo-Zn-Al-O催化剂的物相、结构和催化性能的影响。用X射线衍射仪、紫外-可见漫反射光谱、傅里叶变换红外光谱、X射线光电子能谱和氮气吸附技术对材料进行了表征。在室温条件下，考察了Mo-Zn-Al-O催化剂对阳离子兰花X-BL的湿式氧化降解性能。建立了钼在水溶液中的形态与pH值的关系图。在碱性pH(pH=8)时，溶液中的主要阴离子是MoO42-−。HnMo7O24m−是由于H+和Mo7O246−的结合而使pH值下降8~4而形成的。当pH值低于4.0时，钼以H_2MoO_4的固体形式存在。有趣的是，在pH=7.0时制备的Mo-Zn-Al-O催化剂的表面织构值(SBET=99.9×m~2/g，Vp=0.083×cm~3/g)低于在pH=4.4时制备的Mo-Zn-Al-O催化剂(SBET=0.21.6×m~2/g，V_p=0.038×cm~3/g)。而在pH=0.7时制备的Mo-Zn-Al-O催化剂具有最高的催化活性，脱色率为94.6%，TOC脱色率为86.7%。这种最高的催化活性可以归因于特殊的Mo物种、特殊的晶相、四面体的Mo结构和高度分散的Mo。
The effect of pH in the impregnation process on the phase formation, structure and catalytic potential of Mo–Zn–Al–O catalysts synthesized by the co-precipitation and impregnation method was evaluated. The materials were characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy, Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy and N2adsorption technique. The catalytic efficiency of Mo–Zn–Al–O catalysts was evaluated with respect to the degradation of cationic orchid X-BL by wet air oxidation under room conditions. The speciation diagram of Mo species in aqueous solution as a function of pH value was established. At basic pH (pH > 8), MoO42−was the main anionic in the solution. HnMo7O24m−was formed with the decrease of pH values ranging from 8 to 4 due to the combination of H+and Mo7O246−. Molybdenum was present as solid of H2MoO4when pH value was below 4.0. Interestingly, the Mo–Zn–Al–O catalyst prepared under pH = 7 has lower surface texturing values (SBET= 9.9 m2/g andVp= 0.083 cm3/g) than the Mo–Zn–Al–O catalyst prepared under pH = 4 (SBET= 21.6 m2/g andVp= 0.038 cm3/g). However, the Mo–Zn–Al–O catalysts prepared under pH = 7 shows the highest catalytic activity with 94.6% of decolorization and 86.7% of TOC removal efficiency. This highest catalytic activity can be contributed to special Mo species, special crystalline phases, tetrahedral Mo structure and highly dispersed Mo.