| Recently, semiconductor-assisted photodegradation of organic wastewater as an eco-friendly technology has received special attention in the application of the solution of the energy and environmental problems. However, most of powder photocatalyst together easily, and is difficult to be removed from the solution. Besides, it has a small surface area and low absorbability with organic pollutants, which is not beneficial for the photocatalytic reaction. Layered double hydroxides (LDHs) was a kind of lamellar compound with anion exchange ability, the LDHs nanosheets can mix with other substances after delaminating, the use of the binding force between inorganic layer and insertosome can generate some new functional materials that are difficult to obtain through direct intercalation method. Herein, we assembled BiOCl and TiO2 on exfoliated ZnCr-LDHs nanosheets to synthesize ZnCr-Ex, BiOCl-ZnCr-Ex and TiO2-BiOCl-ZnCr-Ex composites for improving the photocatalytic activities of visible light-responsive supported photocatalysts. The morphology, structure and composition of supported photocatalysts were characterized by X-ray diffraction, Transmission electron microscopy, Fourier transform infrared spectroscopy, UV-Vis diffuse reflection spectroscopy and the Brunauer, Emmett, and Teller (BET) method. The photocatalytic performance of supported photocatalysts was evaluated by the photo-degradation of rhodamine B (RhB) in water under visible light. The structure-function relationship between the structure and photocatalytic activity of supported photocatalysts was discussed. Main results of this paper were as follows:(1) The ZnCr-Lac-LDH is synthesized by one-step method under N2 protection, and then put in the water oscillation for 48 h under 60℃ Hydrotalcite layers overcome electrostatic force with anion during the oscillation process, and so as to achieve the aim of exfoliation. The LDHs is showed delaminated into single layer structure from the characterization, and the layer board without damage. The ZnCr-Lac-LDH also be delaminated by microwave method by the use of its "internal heating" function. Therefore, the water stripping method can achieve the purpose of exfoliate hydrotalcite, and keep stripping state in the water for a long time.(2) With exfoliated ZnCr LDH as the support, BiOCl-ZnCr-Ex is synthetised. It can be seen that BiOCl-ZnCr-Ex exhibited enlarged surface area and stronger light absorption ability than pure BiOCl. BiOCl-ZnCr-Ex-3 exhibited the highest photocatalytic activity for the decolorization of RhB. After 80 min, pure BiOCl could degrade RhB by only 35.96%, while the BiOCl-ZnCr-Ex-3 composite can degrade RhB by 99.4%. The improved photoactivity of BiOCl-ZnCr-Ex is mainly attributed to the electrostatic interaction between BiOCl and ZnCr-Ex, this lead to the efficient separation rate of photoinduced electron-hole pairs.(3) Novel visible-light-driven heteroj unction photocatalysts (TiO2-BiOCl-ZnCr-Ex) composed by ZnCr-Ex, TiO2 and BiOCl is synthesized. The characterizations shown the surface area and light absorption ability of TiO2-BiOCl-ZnCr-Ex were improved, and ZnCr-Ex combined well with BiOCl. Under visible light irradiation, TiO2-BiOCl-ZnCr-Ex-4 exhibited the highest photocatalytic activity for the decolorization of RhB, which is 58.8-folds higher than that of pure TiO2,15.8-folds higher than that of pure BiOCl, and 2.17-folds higher than that of BiOCl-ZnCr-Ex-3. After three successive degradation of RhB, the photocatalytic activity of the TiO2-BiOCl-ZnCr-Ex-4 could degrade more than 90% of RhB after 30 min. Which also prove that TiO2-BiOCl-ZnCr-Ex-4 was a kind of excellent composite catalyst, and with good application prospect in the printing and dyeing wastewater treatment. |
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