The production technology of Ammonium Metatungstate mainly includes the following methods:
Solvent extraction method
Principle: Ammonium tungstate solution is composed of organic phase with organic extractant (such as di(2-ethylhexyl) phosphate (D₂EHPA) or tributyl phosphate (TBP)) and kerosene solvent to extract ammonium ions from ammonium tungstate, so that the Ph value is reduced to 2~4, and ammonium metatungstate solution is generated by boiling and decomposition.
Steps: Including extraction, boiling, concentration and crystallization, filtration and separation, drying and other steps, the final product of ammonium metatungstate.
Ion exchange method
Raw material: taking ammonium paratungstate as raw material, heating ammonium paratungstate under specific temperature (such as 130~140℃) for a period of time (1~8 hours), adjusting the generated product into slurry, and boiling under certain temperature (such as 80~100℃) for 2~6 hours to generate ammonium metatungstate solution. Finally, the product is obtained by concentration and crystallization, filtration and separation, drying and other steps.
Electrodialysis
Principle: taking ammonium tungstate or ammonium sec-tungstate as raw material, prepare ammonium metatungstate through electrodialysis process.
Process: Ammonium paratungstate is added to the anode chamber, when the current passes through, ammonium ions enter the cathode chamber through the anion exchange membrane, and the concentration of ammonium metatungstate in the anode chamber increases. The ammonium metatungstate solution is released from the cathode chamber and subsequently processed as described above to obtain ammonium metatungstate.
Neutralization method
Ammonium sec-metatungstate and nitric acid are used as raw materials. Add ammonium sec-metatungstate to deionized water and ammonium citrate to form a slurry, add dilute nitric acid according to a certain proportion, control the solid-liquid ratio and Ph value, heat to dissolve and stir the reaction for a certain period of time, and then carry out the steps of aging, filtration, concentration, cooling, crystallization and drying to obtain ammonium metatungstate.
Tungstic acid method
Raw material: tungstic acid.
Process: Dissolve tungstic acid with ammonia, add it into boiling deionized water, heat up ammonia and adjust the Ph value, continue to heat and concentrate, then cool and filter, add ethanol and stir well, filter after settling, and then dry the final crystals at 80℃ and crush them to get the product.
Thermal decomposition method
Raw material: ammonium paratungstate.
Process: Mix ammonium paratungstate and a small amount of citric acid catalyst, put it into pyrolysis equipment (such as rotary furnace), decompose it at a specific temperature (such as 200～280℃), and control the decomposition time. The product after decomposition is treated to produce ammonium metatungstate.
The above methods have their own characteristics and are suitable for different production conditions and needs. In actual production, suitable production technology can be selected according to the source of raw materials, equipment conditions, product quality requirements and other factors. At the same time, various production techniques need to strictly control the operating parameters, such as temperature, pH value, stirring speed, etc., to ensure product quality and production efficiency.
More details of ammonium metatungstate product, please visit website: http://ammonium-metatungstate.com/
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