Bismuth Tungstate Photocatalyst Preparation by Sol-gel Method

Photocatalysis can effectively convert light energy into chemical energy. Bi₂WO₆, as a new visible light-responsive photocatalytic material, has a narrow band gap (2.7eV), good photocatalytic activity under ultraviolet and visible light, and can effectively degrade organic pollutants in wastewater.

Bismuth tungstate is usually synthesized by solid-phase sintering: oxides or salts containing Bi and W elements are mechanically mixed and sintered directly at about 1000 degrees. The disadvantage is that the process parameters are not easy to control. In addition, hydrothermal method is another commonly used method for preparing Bismuth tungstate photocatalytic materials, but it needs hydrothermal kettle to be used for subsequent spin coating and filling. The process compatibility is poor.

In view of the shortcomings of the existing technology, some scholars have prepared bismuth tungstate photocatalyst by sol-gel method. In the process of preparation, only one kind of rare earth chelating agent and less dosage can be used to solve these problems effectively.

1)Rare earth nitrate solution was obtained by dissolving Yb₂O₃ and Tm₂O₃ in nitric acid. Rare earth nitrate solution was treated by repeated operation of "drying-water dissolution" to obtain rare earth nitrate solution for reserve.

2)Ethylenediaminetetraacetic acid was stirred and dissolved in ammonia water to obtain EDTA ammonia solution for reserve.

3)Bismuth nitrate solution is obtained by dissolving bismuth nitrate in dilute nitric acid solution. The rare earth nitrate solution prepared by adding step 1 to bismuth nitrate solution is stirred to make it mix evenly, then EDTA ammonia solution prepared by step 2 is added to form transparent Bi-EDTA mixed solution by fully stirring.

4)Ammonium tungstate solution is obtained by dissolving ammonium tungstate in deionized water. The remaining step 2 is added to ammonium tungstate solution. The EDTA ammonia solution is prepared and stirred at constant temperature to form W-EDTA mixed solution.

5)W-EDTA mixture solution is added to the Bi-EDTA mixture by drop, and the pH of solution is adjusted to pH with ammonia and nitric acid. Then the mixture is heated at 70-90 degree constant temperature water bath to stir until the solution is clarified, and then the precursor of bismuth tungstate sol is dried at 80 OC to obtain xerogel.

6) The dry gel was crushed and then calcined at 350 OC to remove the organic matter, which was calcined at 450 degrees to prepare the rare earth ions doped bismuth tungstate nano powder.
The sol gel method was used to prepare bismuth tungstate precursor sol, and bismuth tungstate nanoparticles were prepared at 450 degree sintering. The prepared bismuth tungstate precursor sol can effectively increase the concentration of the sol due to the use of less chelating agent in the operation process. It can prepare the finished product of good quality and has very high compatibility. It can be directly used in the following advanced material preparation processes such as thin film spinning and opal photonic crystal template filling.

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