Bismuth Tungstate Preparation by Microemulsion Method
Bismuth tungstate (Bi2WO6) is an oxide with perovskite like structure, and is a typical n type semiconductor. Bismuth tungstate has become a new hot spot of photocatalysis because of its unique crystal structure.
The preparation methods of bismuth tungstate include solvothermal method, precipitation method, microemulsion method, hydrothermal method, etc.. Among them, microemulsion method is a new method for preparing ultrafine powders, which can be used to prepare nanometer bismuth tungstate, which is relatively simple and the powder morphology is easy to control.
Microemulsion refers to two mutually insoluble reaction solutions which form isotropic and thermodynamically stable emulsions under the influence of surfactants, the reactants are nucleated, agglomerated, agglomerated, crystallized and grown in tiny vacuoles and then treated at high temperatures (usually less than 240 degrees) to form nanoparticles.
Microemulsion can be divided into three types: water-in-oil and oil-in-water type, intermediate state, also known as positive phase microemulsion (O / W), reverse microemulsion (W / O) and double continuous phase microemulsion.
Some scholars have prepared Bi2Wo6 photocatalyst by microemulsion mediated hydrothermal method: The oil phase of n-butanol and cyclohexane is mixed with an aqueous phase consisting of dilute nitric acid solutions and Na2WO4 solutions, and the magnetic stirring for 15 minutes, forming precursor, adjust pH value, pour into the high pressure reactor, the hydrothermal reaction was carried out at a temperature of 180 °C for 24 hours, the product is naturally cooled to room temperature, and the product is dried at 80 °C by centrifugal separation and washing, and then Bi2WO6 photocatalyst is obtained.
Microemulsion is characterized by the formation of tiny reactors under the action of amphiphilic molecules of surfactant, which prevents the formation of agglomerated nanocrystals. Compared with other liquid phase methods, microemulsion method has the advantages of simple process, good product dispersion, and the surface active agent can be used to modify the surface of nanomaterials, the prepared bismuth tungstate has controllable particle size and uniform morphology, so the photocatalytic property of bismuth tungstate produced by microemulsion method is highly recognized.
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