The preparation of ammonium metatungstate hydrate by solvent extraction is a relatively complex but efficient process, the following are the detailed steps and points:
- Preparation of raw materials
Ammonium tungstate solution: as the starting raw material, a certain concentration of ammonium tungstate solution needs to be prepared.
Second, solvent extraction process
Extractant selection
Commonly used organic extractants are di(2-ethylhexyl) phosphate (D2EHPA) or tributyl phosphate (TBP).
These extractants and kerosene solvent form an organic phase for extracting ammonium ions in ammonium tungstate solution.
Extraction operation
Ammonium tungstate solution is mixed with the organic phase (extractant + kerosene) to transfer ammonium ions from the aqueous phase to the organic phase by physical or chemical action.
This process causes the pH of the solution to drop to 2 to 4, which is one of the key conditions for generating ammonium metatungstate.
Extraction Stage Control
The entire extraction process may require several stages of mixing and clarification to ensure adequate extraction of the ammonium ions.
Box-type mixing clarifiers are commonly used to provide effective separation between the mixing and clarification stages.
III. Boiling to generate ammonium metatungstate solution
Cooking process
The solution after extraction (at this time the ammonium ion has been mostly extracted) needs to be further boiled to generate ammonium metatungstate solution. Cooking is usually carried out under specific temperature to ensure the complete generation of ammonium metatungstate.
- Subsequent treatment
Concentration and crystallization
Concentrate the boiled ammonium metatungstate solution to make it saturated, and then crystallize it by cooling.
During the crystallization process, ammonium metatungstate will be precipitated in the form of hydrate.
Separation by filtration
The crystallized ammonium metatungstate hydrate is separated from the mother liquor by filtration operation.
Drying
The filtered ammonium metatungstate hydrate is dried to remove residual water and solvent.
The dried product is the finished product of ammonium metatungstate hydrate.
- Precautions
Safety
Extractants such as D2EHPA and TBP are usually flammable, explosive and toxic, and safety regulations should be strictly observed during operation. Harmful gases and vapors may be generated during extraction and boiling, good ventilation should be ensured.
Equipment Selection
Selection of suitable extraction equipment and mixing clarifiers is essential to improve extraction efficiency and product quality.
Process Control
Strictly control the parameters such as pH, temperature and time of the extraction process to ensure the quality and stability of the product.
Through the above steps, ammonium metatungstate hydrate can be prepared efficiently. With the advantages of simple equipment, rapid operation and good separation effect, solvent extraction is one of the commonly used preparation methods in industrial production.
More details of ammonium metatungstate product, please visit website: http://ammonium-metatungstate.com/
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