There are mainly the following preparation methods for ammonium tungstate pentahydrate:
Reaction method of tungstic acid with ammonia
Tungstic acid is dissolved in an appropriate amount of water.
Ammonia is added slowly to produce a white solid.
This white solid is ammonium tungstate pentahydrate.
Hydrochloric acid decomposition of tungsten concentrate method
Solid tungstic acid and waste acid are prepared by decomposing tungsten concentrate with hydrochloric acid.
Tungstic acid is dissolved in ammonia to obtain ammonium tungstate solution.
The ammonium tungstate solution is evaporated and crystallized to prepare ammonium sec-tungstate, and then ammonium tungstate pentahydrate is prepared through the relevant reaction.
Reaction method between sodium tungstate and ammonium salt
Ammonium tungstate is prepared by reacting sodium tungstate and ammonium salt.
In the preparation process, some additives can be added to improve the purity and form of ammonium tungstate.
Further processing to get ammonium tungstate pentahydrate.
Reaction method between ammonium sulfate and tungstic acid
This is the commonly used method, and the specific reaction equation is H2WO4 + (NH4)2SO4 → (NH4)10(H2W12O42)-4H2O (please note that ammonium tungstate pentahydrate is not directly obtained here, but it can be obtained through the subsequent treatment).
Wolframite alkaline decomposition and ammonia action method
After wolframite is alkalized, calcium tungstate is synthesized with calcium chloride.
Ammonium tungstate is produced from calcium tungstate by further acid digestion and then interaction with ammonia.
Further processed to get ammonium tungstate pentahydrate.
During the preparation process, safe operation is required because although ammonium tungstate pentahydrate is generally regarded as a low-toxicity compound, it is still necessary to avoid contact with skin and inhalation of its dust. In addition, wastewater and waste residue that may be generated during the preparation process need to be properly disposed of in order to comply with environmental requirements.
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