Preparation of Bismuth Tungstate / Titanium Composite Photocatalyst

With the development of photocatalytic technology, it has characterized the mild reaction conditions, thorough degradation, clean and environmental protection in environmental purification, and gradually become one of the hot technologies in the field of pollution control. Bi₂WO₆ has become a hot research focus in the field of visible light photocatalysis because of its high visible light activity.

The preparation methods of bismuth tungstate are co precipitation, hydrothermal method and organic settlement. These methods can control the particle size of Bi₂WO₆ powder and improve the photocatalytic efficiency. However, there is still a gap between the oxidation and photocatalytic efficiency of Bi₂WO₆ and the mature TiO₂ system, but these methods are easy to improve.

The recombination of photogenerated carriers in the transmission process is the main reason why the photocatalytic efficiency of bismuth tungstate is not high, and the composite photocatalyst can effectively prevent the recombination probability of photoelectron and hole during the photocatalytic process, and effectively improve the photocatalytic efficiency and the utilization of solar light. In the preparation process, the combination of TiO₂ and Bi₂WO₆ is an effective way to improve performance.

According to the preparation of bismuth tungstate / Ti Composite Photocatalytic Membrane 98wt.% Bi₂WO₆ 2wt.%TiO₂ proportion, the specific steps are as follows:

1.Preparation of bismuth tungstate. The 0.970g Bi (NO₃) ₃ • 5H₂O and 0.330g Na₂WO₄ / 2H₂O were dissolved in 20mL ethylene glycol respectively with the chemical stoichiometry. The clarified solution was obtained after mixing the two kinds of solutions, and then transferred to the kettle and heated for 16 hours at 160 ℃. After the reaction is finished, the obtained products are dried for 4 hours at 60 degrees Celsius after centrifugation and washing. The obtained 0.98g Bi₂WO₆ powder was dispersed uniformly in TiO₂ precursor fluid prepared from butyl titanate.

2.Preparation of titanium dioxide precursor fluid. The ethanol solution of butyl titanate was prepared by adding 1 volume of butyl titanate into 10 volume ethanol. Then 1 volume stabilizers were added, and the light yellow transparent solution was stirred by strong stirring. Then two volume pure water was slowly dripped and stirred with a strong stirring. A transparent solution will be placed at 24h at constant temperature for 25 days, then homogeneous TiO₂ precursor fluid can be obtained.

3.Synthesis. The clean stainless steel mesh was immersed in the TiO₂ precursor solution dissolved in Bi₂WO₆, and the composite photocatalytic membrane was prepared by dip coating. After the drying, the number of pulls was repeated until the catalyst was loaded with 20 gm−2, and finally calcined at 500 ℃ for 4 h to obtain a Bi₂WO₆ composite photocatalyst film loaded with stainless steel wire mesh.

In order to study the performance of the composite photocatalytic membrane used in sewage treatment, photocatalytic degradation of RhB dye under visible light was carried out. Using the properties of RhB photocatalytic degradation of decolorization, the UV / visible absorption spectrum was used to measure the absorbance of 553nm in the solution to observe the change of color of the solution, and then the decolorization rate was obtained. In the process of degradation of RhB by visible light irradiation, the absorbance of RhB solution in the Bi₂WO₆ composite photocatalyst film varies with time, and the degradation rate of RhB solution is 99.5% and the performance is excellent after 30 minutes of light illumination.

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