Preparation, Characterization And Photocatalytic Properties Of BiVO₄

BiVO4 photocatalyst is concerned for it can response in the visible light and degrade the organic pollution. The monoclinic BiVO4 was prepared with Bi(NO3)3·5H2O and NH4VO3 as raw materials, EDTA as additive by the hydrothermal method. By investigating the preparation conditions of hydrothermal temperature, pH, hydrothermal time and EDTA amount through the degradation of methylene blue (MB), the appropriate condition of hydrothermal temperature of 170℃, pH of 7.0, hydrothermal time of 4h, EDTA amount of 3.0 mmol were gotten. The degradation rate of MB (5mg/L 100mL) reached 91.92% with 0.1000g of the prepared BiVO4 within 5h. The prepared BiVO4 were tested by the XRD, SEM, UV-vis analysis, and the factors of crystal, morphology and band gap (Eg) which affecting the performance of the catalysts were discussed.The orthogonal experiment were carried out according to the results of the single factors experiment. The optimal preparation conditions was:the hydrothermal temperature of 170℃, pH of 5.5, hydrothermal time of 4h and the EDTA amount 3.3 mmol. Catalyzed by the prepared perforated hollow polygon BiVO4, the discoloration rate of MB reached 92.20%. The four factors were ranged by the sort of degree of affecting the photocatalytic. The order was:hydro thermal temperature> EDTA amount> hydrothermal time> pH. The prepared conditions were optimized by variance analysis calculating: hydrothermal temperature of 180℃, hydrothermal time of 4h, pH of 7.5, the EDTA amount 3.3 mmol. The average decolorization rate of MB is 92.78% by the prepared BiVO4 for 3 repeated experiments. Compared with the optimal condition obtained in the orthogonal experiment, the decolorization rate of MB by the variance analysis conditions prepared BiVO4 was higher. The optimal preparation conditions was:the hydrothermal temperature of 180℃, hydrothermal time of 4h, pH of 7.5, EDTA amount of 3.3mmol. The reliability of the experiment was further evidenced by the SEM, XRD, UV-vis testing.On the basis of the optimal preparation conditions, the BiVO4 were modified by the mental ions and phthalocyanine compounds. The results showed that the monoclinic scheelite structure and the transparent hollow morphology of BiVO4 were not changed by the two modified methods. The modified catalysts were occurred different degrees of redshift in the visible range, and the absorption of visible light of the modified BiVO4 were enhanced than the unmodified BiVO4, so that the Eg of the modified BiVO4 were narrower. And the Eg of BiVO4 modified by the phthalocyanine compounds were narrower than the metal ions modified BiVO4. Wherein the Eg of BiVO4 samples modified by 0.20 wt% MnPc was as narrowest as 2.40 eV. And the decolonization rate of MB was maximum as 98.42%. The BiVO4 were modified by phthalocyanine compounds, and the method was simple and effect was obvious.