Of Ultrasound On The Crystallization Mechanism Of Ammonium Tungstate Solution

The characteristics and applications of tungsten and ammonium paratungstate, and the effect of ultrasonic on chemical process were summarized. The effect of ultrasonic on the crystallization of ammonium tungstate aqueous solution has been investigated systematically based on these. The crystalline form, thermochemistry, crystalline particle and crystalline growth rate were discussed. Macro mechanism of the process of crystallization was analyzed.By evaporating and neutralizing of two ammonium tungstates with different density, crystals of ammonium paratungstate (NH4) 10W12O11 nH2O (n=11, 7, 5) were prepared with ultrasonic. Using XRD, TG, DTG and granularity analysis, the crystalline form was confirmed and researched. The results proved that the effect of ultrasonic on ammonium tungstate was in evidence. The crystalline forms were the same with ultrasonic and without ultrasonic, but impure apexes on the XRD patterns were less and value of d/A more tallied with literature with ultrasonic. Distributing of crystalline granularity became narrower and the crystal was more homogeneous. Ultrasonic shortened the formation time nucleus of crystal.Macro mechanism of the process of crystallization was discussed with thermodynamics and kinetics. Thermodynamics process was analyzed using balance and driving force of crystallization process. Kinetics process were studied using crystal creating, the rate of formation and grow of nucleus. Macro mechanism of the effect of ultrasonic on the crystallization of ammonium paratungstate from aqueous solution was also discussed.