Ultrasonic Technology Effect on Ammonium Paratungstate Crystallization

Ammonium paratungstate ultrasonic technology is a technology that works in conjunction with ammonium paratungstate crystals. Ultrasound is a kind of sound wave whose frequency is between 10kHz-10MHz and whose wavelength is in the range of 10cm-0.015cm. Because ultrasonic has beam-like light and similar light propagation characteristics, it is a mechanical vibration wave that easily accumulates energy.

Ultrasonic technology to enhance the process of ammonium paratungstate to promote the role of ultrasound is introduced by ultrasonic cavitation effect, mechanical effects and thermal effects, rather than ultrasound directly on the material ammonium paratungstate.

Ultrasound technology mainly affects the induction period, the formation of nuclei and the crystallization rate in the crystallization process of ammonium paratungstate solution, the specific impact is as follows:

1.The crystallization induction period: the mechanical effect of ultrasonic effect can greatly enhance the stirring intensity, while the thermal effect can make the solution viscosity decreases, reducing the energy barrier required for nucleation, thus shortening the crystallization induction period effect. Some scholars have analyzed the influence of the introduction of ultrasonic wave on the crystallization in the saturated NH4Cl aqueous solution. The results showed that the initial crystallization time after ultrasonic treatment was 55 s shortened than that without ultrasonic treatment, and the crystallization start time could be accelerated whether ultrasonic power was increased or ultrasonic treatment time was extended. Under the action of ultrasonic wave, ammonium paratungstate solution showed that the induction period of ammonium paratungstate crystallization was shortened, the nuclei were precipitated rapidly, the nucleation rate increased by 2.74 times, the growth rate of crystal slowed down by 40.9% and the particle size decreased from 200μm to 100μm.

2.The impact of crystal nucleation: Ultrasound technology can not only shorten the crystallization induction period, but also significantly promote the nucleation. In particular, the second nucleation, when the ultrasonic power is relatively large, you can also play the role of seeds added. Ultrasonic treatment often yields good results for crystallization reactions that are difficult to nucleate or that are difficult to nucleate at low concentrations.

3.The impact on the crystallization reaction rate: the crystallization reaction rate and solution temperature, stirring intensity, the composition of the solution. Research shows that ultrasonic technology can significantly speed up the crystallization reaction rate. Some scholars in the mechanism of ammonium molybdate crystallization found that ultrasonic treatment can significantly enhance the crystallization reaction rate. In the reaction system that produces beta-type ammonium tetramolybdate, it takes about two days to crystallize under conventional conditions to produce ammonium tetramolybdate. The introduction of sonication only takes about 10min to complete the reaction, and the occurrence of a crystalline transition.

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