Plasma Electrolytic Oxidation to Prepare Tungsten Trioxide(WO3)

With the rapid development of modern industry, a large amount of industrial wastewater, such as untreated or untreated, is directly discharged into the natural world, causing enormous pollution damage to the environment and seriously affecting human health. Photocatalysis refers to the fact that when the visible light is irradiated onto the semiconductor powder in the aqueous solution, the dye molecules are decomposed into CO2, H2O and the like which are harmless to the environment.

The use of semiconductor materials as a catalyst for industrial wastewater treatment has the characteristics of high treatment rate and low energy consumption. Among various photocatalysts, tungsten trioxide (WO3) has the advantages of low band gap energy (about 2.7 eV), large specific surface area, high surface activity and high photostability. It is a semiconductor photocatalyst with potential after TiO2.

The preparation methods of the conventional nano WO3 include a vapor phase method, a solid phase method, and a liquid phase method. The gas phase method has the disadvantages of high equipment, high cost and complicated operation, which is not conducive to industrial production; when the solid phase method is decomposed, some toxic gases are easily generated, which have adverse effects on the environment; in the liquid phase method, there are mainly sol-gel method and precipitation. Law, microemulsion method, etc. The sol-gel method has disadvantages such as high cost of raw materials and long synthesis cycle; the precipitation method has disadvantages such as difficulty in removing impurities and easy agglomeration; while the microemulsion method consumes a large amount of surfactants and has a large capacity, is difficult to remove, and has high cost.

In order to improve efficiency and reduce costs, some scholars use plasma electrolytic oxidation for photocatalyst research. Plasma electrolytic oxidation is also called micro-arc oxidation. This technology is widely used in the surface modification of valve metals (such as Al, Mg, Ti, Zr, etc.) and its alloys: it forms a ceramic oxide film with wear resistance, corrosion resistance and biocompatibility on the metal surface. The use of the technology to synthesize micro-nano tungsten trioxide powder has the advantages of high yield, simple operation, time and labor saving, and the main processes include:

1) Pretreatment of pure aluminum samples:

The industrial pure aluminum sample is cut into a sample of size 20×10 mm, the copper wire is connected with the sample, and the sample is sealed with epoxy resin. After the resin is cured, the SiC sandpaper of 600#, 1000#, 2000# is sequentially polished and polished. Sample. Rinse with tap water, ultrasonically wash with alcohol, rinse several times with deionized water, and blow dry.

2) Preparation of electrolyte:

The composition of the electrolytic solution is: per 1000 mL of deionized water: Na2WO4•2H2O: 10 g;

3) Micro-arc oxidation power supply parameter setting:

Constant current AC pulse mode, positive current density: 50A/dm2, negative current density: 0, frequency: 100Hz, positive and negative duty cycles are: 20%.

4) Preparation of the micro-nano WO3 powder:

A pure aluminum sample was used as an anode, and a steel plate was used as a cathode. The electrolyte was placed in an electrolyte and connected to a wire. The magnet was placed in the electrolyte and placed on a magnetic stirrer for stirring. The electrolyte is cooled with a circulating cooling system to ensure that the system is at a constant temperature of 20 °C. Set the power parameters, turn on the power, after 1h, turn off the power, take out the sample, pour out the electrolyte, leave the electrolyte for a few hours, pour off the supernatant, rinse the precipitate several times with deionized water, and dry, finally Obtained tungsten trioxide.

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