Preparation And Photocatalytic Performance Study Of Calcined Hybrid Zn-Al Layered Double Hydroxide Material

The progress on the structure, properties, synthesis and application of layered double hydroxides (LDHs) was reviewed. LDHs were modified using two kinds of methods and the prepared samples were characterized and fully ananlyzed. Using degradation of methylene blue (MB) as an example, we discuss the condition of synthesis and degradation. The stability of catalysts and degradation mechanisms were investigated and proposed. The main contents are as follows:(1) Zn-Al-Bi mixed-metal oxide (Bi2O3-ZnAl/CLDH) has been successfully prepared by facile coprecipitation method and controllable calcination. The powder X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), Energy Dispersive X-Ray (EDX) and UV-vis diffuse reflectance spectra (UV-Vis) confirmed the structure of as-synthesized solids. The results reveal that calcination products obtained from LDHs precursor provide the heterostructure of mixed-metal oxide and can be illuminated under visible light.The photocatalytic activity of Bi2O3-ZnAl/CLDH was evaluated by the photodegradation of methylene blue (MB) under Xenon lamp simulating sunlight. Factors that may affect the photodegradation behavior were studied such as catalyst dose, calcination temperature, catalyst dose and pH. An efficient degradation (92%) was achieved under the condition of Al/Bi=2, calcination temperature500℃, catalyst dose0.5g and pH=7.0. The results showed that catalysts still had high catalytic activity after three times recycling. The possible mechanism was also discussed underlying the enhanced photocatalytic activity.(2) With the modified carbon nanotubes as the carrier, catalyst (ZnAl/CLDHs-CNTs doping Fe) doping with Fe was calcined under the production of N2. The surface structure, properties and composition of the catalyst were studied by XRD, TEM and UV-Vis characterization. The results demonstrated that distributing uniformly on CNTs, the calcination products from Zn-Al layered double hydroxides didn’t fall off from CNTs. The effect of the content of CNTs and Fe was investigated on the photocatalytic performance. Other factors such as dark adsorption, pH were also studied. The catalysts were recycled three times and the possible mechanism was proposed. The results showed that the calcined products exhibited best photoactivity at the quality of CNTs0.8g, molar ratio of Fe/Zn0.06. The catalytic efficiency can reach90%under the degradation condition of pH=7.0, catalyst dose0.4g.