Preparation And Photocatalytic Properties Of Layered Double Hydroxides (LDHs) Composites

Layerd double hydroxides（LDHs）is hydrotalcite layered compounds with a high photocatalytic activity,interlayer anionic exchangeability,the diversity of cation in the host layer,"memory effect" of calcined products and other characteristics,so that it is gradually valued in the photocatalytic field.In this paper,Zn-Al LDHs composites were prepared by coprecipitation or ion exchange method,the as-prepared composites were characterized by X-ray diffraction,Fourier transmission infrared spectroscory,UV-Vis diffuse reflectance spectra,scanning electron microscopy and Brunauer-Emmett-Teller surface area.Their photocatalytic activities were evaluated by degradation of organic dye.By changing the contents of Zn-Al LDHs,the BiOCl microspheres were combined with Zn-Al LDHs by coprecipitation method.The photocatalytic activity of the samples was evaluated by degradation of methyl orange.When the Zn-Al LDHs content is 19.5wt%,the BiOCl/Zn-Al LDHs composites can efficiently degrade methyl orange more than 95.5% under the UV light for 100 min.BiOC_lxBr_1-x was prepared by one-step hydrolysis and compounded with Zn-Al LDHs.The experimental results show that the addition of Br extends the optical response wavelength range of the material,when x = 0.5,the degradation rates of methylene orange and rhodamine B by BiOCl0.5Br0.5/Zn-Al LDHs were 99.2% and 98.9% under the visible light for 90 min,respectively,showing the excellent photocatalytic activity.With Zn-Al-NO₃ LDHs as precursors,WO42-was successfully inserted into Zn-Al LDHs by ion exchange,and further prepared Ag2WO4/Zn-Al LDHs composites.The experimental results show that the specific surface area of Ag2WO4/Zn-Al LDHs composites obtained by ion exchange was 30.21 cm2·g-1,and the degradation rate of rhodamine B was 96.1% under visible light in 30 min,indicating a higher catalytic performance.