There are various preparation methods for ammonium metatungstate reagent, the following are several major preparation methods and their brief introduction:
- Solvent extraction of ammonium metatungstate reagent
Overview of solvent extraction method of ammonium metatungstate reagent
Ammonium tungstate solution is made up of organic extractant (such as di(2-ethylhexyl) phosphate (D₂EHPA) or tributyl phosphate (TBP)) and kerosene solvent to form an organic phase, which extracts ammonium ions from ammonium tungstate, and reduces the pH value to 2~4. Subsequently, ammonium metatungstate solution is generated through boiling, and then the product is made up through the steps of concentration and crystallization, filtration, separation and drying, etc. The product can be used to produce ammonium tungstate reagent.
Advantages of Ammonium Metatungstate Reagent Solvent Extraction Method
This method can extract and purify ammonium metatungstate efficiently, and is suitable for large-scale industrial production.
- Ammonium metatungstate reagent ion exchange method
Process overview of ammonium metatungstate reagent ion exchange method
Ammonium paratungstate is used as raw material to prepare ammonium metatungstate by ion exchange method. Specific steps include heating ammonium paratungstate at 130～140℃ for 1～8 hours, mixing the product into slurry, and boiling at 80～100℃ for 2～6 hours to produce ammonium metatungstate solution. Finally, the product is made through the steps of concentration and crystallization, filtration and separation and drying.
Advantages of Ammonium Metatungstate Reagent Ion Exchange Method
This method is relatively simple to operate and can prepare high purity ammonium metatungstate.
- Thermal degradation of ammonium metatungstate reagent
Overview of the process of thermal degradation of ammonium metatungstate reagent
Thermal degradation method is the mainstream process for the production of ammonium metatungstate in industry at present. By controlling the roasting temperature of ammonium paratungstate and the partial pressure of ammonia and water vapor, the method causes its thermal decomposition to produce water-soluble ammonium metatungstate. Then through the steps of hydration, concentration and cooling crystallization, ammonium metatungstate solid is obtained.
Advantages of thermal degradation method of ammonium metatungstate reagent
The method adopts the direct degradation of ammonium paratungstate, the product purity is high, but the thermal degradation conditions are more demanding, need to accurately control the temperature to prevent over-firing or under-firing.
- Ammonium metatungstate reagent neutralization method
Process overview of ammonium metatungstate reagent neutralization method
Neutralization method is a simple and economical preparation method. Ammonium metatungstate is produced by reacting wet ammonium paratungstate with acidic solution such as nitric acid, controlling the pH value of the solution in a suitable range, and going through the steps of boiling, filtering, concentration and drying.
Advantages of Ammonium Metatungstate Reagent Neutralization Method
The method is easy to operate, low cost, suitable for small-scale production or laboratory preparation.
- Electrodialysis of ammonium metatungstate reagent
Overview of the process of electrodialysis of ammonium metatungstate reagent
Electrodialysis is a method of separating electrolytes from water under the action of DC electric field by utilizing the permeability selectivity of ion exchange membrane. Ammonium paratungstate is added to the anode chamber, and when the current passes through, the ammonium ions enter the cathode chamber through the anion exchange membrane, and the concentration of ammonium metatungstate increases in the anode chamber. Finally, ammonium metatungstate solution is released from the cathode chamber, and ammonium metatungstate is produced by treatment as described above.
Advantages of electrodialysis method of ammonium metatungstate reagent
This method can separate and purify ammonium metatungstate with high efficiency and less pollution to the environment.
There are various preparation methods of ammonium metatungstate reagent, each with its own advantages and disadvantages and scope of application. When choosing the preparation method, it needs to be considered comprehensively according to the actual production demand, raw material source, equipment conditions and other factors.
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