The process of preparing ammonium metatungstate by thermal decomposition can be roughly divided into the following steps, and the following is the detailed process flow:
Raw material preparation
The main raw material is ammonium paratungstate (APT), to ensure the quality and purity of raw materials.
Thermal decomposition reaction
Put ammonium paratungstate into appropriate reaction vessel, such as far-infrared rotary furnace. Control the temperature of thermal decomposition, usually between 200~280°C, and the decomposition time is about 1 hour. This temperature range is favorable for ammonium paratungstate to lose part of its ammonium and water of crystallization, and to be converted into ammonium metatungstate which is easily soluble in water. During this process, ammonia escapes from the solid phase, promoting the reaction in the positive direction.
Product treatment
The product of the pyrolysis is removed, which at this point may be a mixture containing ammonium metatungstate. The pyrolysis product is dissolved in pre-heated water with a controlled solid-liquid ratio of about 1:7. During the dissolution process, the temperature was gradually increased to between 90 and 98°C. When the dissolution was nearly complete, an appropriate amount of 732 strongly acidic cation exchange resin was added and the pH was adjusted in the range of 3.5 to 4.5. At this temperature, hold the conversion for half an hour to make the reaction more complete. After clarification, it was filtered to remove insoluble matter and impurities to obtain a clear filtrate. The clear liquid is crystallized by evaporation and stirring or spraying method, and further concentrated and cooled to crystallize to obtain ammonium metatungstate crystals.
Drying and packaging
The obtained ammonium metatungstate crystals were dried at a suitable temperature (e.g. 50~60°C) to remove excess water. The dried ammonium metatungstate is packed according to the specification, usually in inner-plastic and outer-iron drums with a net weight of 50kg or 25kg per drum.
Quality Inspection
Conduct quality inspection on the prepared ammonium metatungstate to ensure that it meets the relevant standards and requirements.
Precautions
During the whole preparation process, parameters such as temperature, time and pH value need to be strictly controlled to ensure the quality and purity of the product. Operators need to wear appropriate protective equipment to avoid contact with hazardous substances. Through the above process, high quality Ammonium Metatungstate product can be prepared efficiently and stably.
More details of ammonium metatungstate product, please visit website: http://ammonium-metatungstate.com/
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