The process of preparing ammonium metatungstate hydrate using tungstic acid method can be clearly divided into the following steps, which are summarized with relevant figures and information:
- Preparation of raw materials
Main raw materials
Tungstic acid (WO₃) is used as the starting raw material.
Ammonia (NH₃-H₂O) as dissolving agent.
Acetic acid (CH₃COOH) and dilute nitric acid (HNO₃) were used as acid solutions for pH adjustment.
- Dissolving and adjusting pH
Dissolving tungstic acid
Dissolve tungstic acid with appropriate amount of ammonia and add it to the deionized water containing boiling water. Heat and chase the ammonia under stirring so that the pH of the solution reaches about 8.
Adjustment of pH
Add acetic acid slowly while the solution is boiling, and then adjust the pH to between 2 and 4 with dilute nitric acid.
Heating and concentration
Heating concentration
Continue to heat the solution for concentration. When the relative density of the solution reaches 1.5～2, stop heating.
Cooling, filtration and drying
Cooling filtration
The concentrated solution is cooled to room temperature and filtered. Add ethanol to the filtrate, stir well and settle, and filter again.
Drying
The crystals obtained by filtration were dried at 80°C to remove residual water and solvent. The dried crystals were pulverized to obtain ammonium metatungstate hydrate product.
- Product collection and inspection
Combined batch of products
Collect the dried and pulverized ammonium metatungstate hydrate products and make a batch.
Quality Inspection
Conduct quality inspection on the products, including purity, particle size, moisture content and other indicators to ensure that the products comply with the relevant standards.
Packing
Pack and store the qualified ammonium metatungstate hydrate products according to the market demand specification.
The process of preparing ammonium metatungstate hydrate by tungstic acid method includes the steps of raw material preparation, dissolving and adjusting pH value, heating and concentration, cooling, filtration and drying, as well as product collection and inspection. In this method, tungstic acid is dissolved by ammonia and the pH of the solution is adjusted, and then the product of ammonium metatungstate hydrate is finally obtained after heating, concentration and cooling filtration. During the whole process, attention needs to be paid to controlling the parameters such as dissolving temperature, pH value, conditions of heating and concentration as well as drying temperature to ensure the quality and stability of the product.
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