| In order to solve the current environmental crisis which we faced, many methods and measures have been studied. Photocatalytic oxidation technology have a broad application value in the field of sewage disposal, especially in terms of the dyeing wastewater treatment because it has many features, such as well sewage treatment effect, energy conservation and simple operation. As a new type of visible-light active photocatalyst of BiVO4, whose virtues are narrow energy band gap, simple technics equipment, no toxicity and chemical stability. However, pure BiVO4 as photocatalyst have three big flaws. Firstly, BiV04 is limited to visible light catalytic activity for its higher recombination rate of electronic-hole and weak adsorption performance. Secondly, photoeatalytic oxidation degradation of organic pollutant is usually tested on BiVO4 suspension in aqueous solutions, so the catalysts are hard to separate and recycle, and easy to bring secondary pollution. Thirdly, the photocatalytic reaction of BiVO4 belongs to free radical reaction, so it can not degraded preferentially those high toxicity and low concentrations of organic contaminants in multicomponent of sewage. This paper aimed at solving the above problems of BiVO4. The major work includes the following aspects:(1)The BiVO4 photocatalytic materials are prepared by hydrothermal synthesis method with Bi(NO3)3-5H2O and NH4VO3 as the main raw materials, (NH2)2CO as template. The photocatalytic activity of BiVO4 is evaluated by degradating RhB in the different experimental conditions, such as addition of the template agent content, value of pH, reaction time and reaction temperature by orthogonal test. And the stability of BiV04 photocatalytic materials is studied. The results show that the optimal conditions for preparation BiVO4 are as follows:value of pH is 5, molar ratio of raw material and template is 1:0.8, reaction time is 24h and reaction temperature is 120 ℃. When the reaction time of photocatalysis is 150min, dosage of BiVO4 is 0.04g, the degradation rate of RhB with concentration of 4mg/L can reach above 98%.(2)The BiOCl/BiVO4 composite photocatalysts are prepared by the hydrothermal solvothermal method. The crystalline structures, morphologies and optical properties of the photocatalysts are characterized by XRD, SEM and UV-Vis DRS. The photocatalytic activity and adsorptive property of BiOCl/BiVO4 samples are investigated. The result shows that the degradation rate reached 98% of RhB after irradiation for 50 min when the mass fraction of BiOCl is 15 percent in composite photocatalyst, which is as 4.2 times as pure BiVO4 under the same photocatalytic experimental condition. Furthermore, the composite sample also shows superior adsorption capacity that is as 3.8 times as pure BiVO4 under the dark condition. BiOCl/BiVO4 has high stability, and after the catalyst is used 3 times, the degradation rate of RhB still reached 95%. Moreover, photocatalytic reaction ofBiOCl/BiVO4 belongs to a first-order reaction.(3)The effective magnetic and photocatalytic activity of Y-Fe2O3/BiOCl/BiVO4 photocatalysts are prepared for the problem that BiVO4 hard to separate and easy to bring secondary pollution after light- catalyzed reaction. The samples are characterized by XRD, SEM and VSM, and photocatalytic activity of samples are evaluated by photocatalytic degradation experiment. The magnetic photocatalyst particles are separated and recovered easily by using magnetic separation. Photocatalytic experiment results show that although the activity of photocatalyst will decline, the decline is not large when y-Fe2O3 is doped. The optimal supported fraction of y-Fe2O3 is 15 percent, and the degradation rate of RhB could reach 90% when the reaction time of photocatalysis is 60min. The samples can be easily separated from reaction system by the external magnetic field.(4) For the problem that BiVO4 can not degraded preferentially those high toxicity and low concentrations of organic contaminants in multicomponent of sewage. In this paper, the molecule imprinted photocatalysts(MIP-y-Fe2O3/BiOCl/BiVO4) are prepared by surface polymerization method with neutral red as template molecule, y-Fe2O3/BiOCl/BiVO4 as carrier, methacrylic acid as functional monomer, ethylene glycol dimethyl acrylic ester as cross-linking agent, and a series of characterization and catalytic properties of samples are studied. The experimental results show that the saturation magnetization of the samples is 6.37emu/g, so it can separated and recovered using magnetic separation. No matter for one-component degradable material degradation or multicomponent mixture material, the target molecules of neutral red could be degraded preferentially. |
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