Basic information of Ammonium metatungstate
Chinese name of Ammonium metatungstate
Ammonium metatungstate
English name of Ammonium metatungstate
Ammonium Metatungstate, AMT
CAS No. of Ammonium Metatungstate
12333-11-8
Molecular formula of Ammonium metatungstate
The common molecular formula is (NH₄)₆H₂W₁₂O₄₀-xH₂O, where x denotes the number of water molecules, which may be different according to the preparation conditions and purity
Molecular weight of ammonium metatungstate
2974.32000 (this is a common molecular weight value, the actual may vary due to the change of x value)
Physical state of ammonium metatungstate
White crystalline powder or slightly yellow
Physical Properties
Solubility of ammonium metatungstate
Soluble in water, insoluble in ethanol.
Solubility of ammonium metatungstate
Solubility in water is 303.9g/100gH₂O at 20℃.
The solubility increases with the increase of temperature
Chemical properties of ammonium metatungstate
Decomposition temperature of ammonium metatungstate
200-300℃: Remove all the water of crystallization and most of the ammonium ions.
300-350℃: phase transition occurs, forming stabilized tungsten oxide
500-550 ℃: there are still a small amount of ammonium root and binding water is not decomposed
Above 600℃: completely decomposed into tungsten trioxide (WO₃)
700 ℃ (holding time 2h): get hollow mesoporous tungsten trioxide balls
Uses of ammonium metatungstate
Industrial application of ammonium metatungstate
Used in the production of tungsten metal, alloy steel, fireproof fabrics, etc.
Raw material of ceramic industry
Manufacture of petrochemical catalysts and other tungsten compounds.
Production of high-purity tungsten products, such as tungsten wires, tubes and rods.
As a starting material for synthesizing other tungsten compounds.
Safety Information of Ammonium Metatungstate
Hazard class of Ammonium Metatungstate
Symbols of Ammonium Metatungstate
GHS05 GHS07
Signal word for ammonium metatungstate
Hazard
Hazard statements for ammonium metatungstate
H302 (harmful to skin), H318 (serious damage to eyes)
Warning statements for ammonium metatungstate
P280 (wear protective gloves), P305 + P351 + P338 (if in eyes, flush with plenty of water and seek medical attention)
Hazard Category Codes for Ammonium Metatungstate
R22 (Harmful if swallowed)
Safety instructions for ammonium metatungstate
S26 (In case of inadvertent eye contact, flush with water immediately and seek medical attention)
Hazard symbols for ammonium metatungstate
Xn (Harmful)
Main Preparation Processes of Ammonium Metatungstate
Solvent extraction of ammonium metatungstate
Ammonium tungstate solution is made up of organic extractant (such as di(2-ethylhexyl) phosphate (D₂EHPA) or tributyl phosphate (TBP)) and kerosene solvent to form an organic phase, which extracts ammonium ions in ammonium tungstate, reduces the pH value to 2～4, and generates ammonium metatungstate solution by boiling.
Ion exchange method of ammonium metatungstate
Ammonium paratungstate is used as raw material to prepare ammonium metatungstate by ion exchange method. Heating ammonium paratungstate at 130～140℃ for 1～8 hours, the product is adjusted to slurry, and boiled at 80～100℃ for 2～6 hours to produce ammonium metatungstate solution. Then concentrated and crystallized, filtered and separated, dried to get the product.
Electrodialysis of ammonium metatungstate
Taking ammonium tungstate or ammonium sec-tungstate as raw material, ammonium metatungstate is prepared by electrodialysis. Ammonium paratungstate is added to the anode chamber, when the current passes, the ammonium ion enters the cathode chamber through the anion exchange membrane, and the concentration of ammonium metatungstate increases in the anode chamber. Finally, the ammonium metatungstate solution is released from the cathode chamber, and then ammonium metatungstate is produced by treatment similar to the foregoing method.
Neutralization method of ammonium metatungstate (with ammonium sec-metatungstate and nitric acid as raw materials)
Ammonium metatungstate was prepared from ammonium sec-metatungstate and nitric acid. Add ammonium sec-metatungstate to deionized water and ammonium citrate to form a slurry containing WO₃ 12% to 30% concentration. According to ammonium paratungstate: nitric acid = 1:20 to add 3% to 5% of dilute nitric acid to ammonium paratungstate slurry, control the solid-liquid ratio of 1: (3 ~ 4), pH value of 2 ~ 4, heating and dissolution, so that the relative density of the solution up to 1.18 ~ 1.20, heated to 80 ~ 90 ℃, constant temperature and constant volume control of pH, stirring reaction for 4 hours, aging for a few hours, the clear liquid is concentrated to the content of WO ₃ in 50% or so, filtering! Remove insoluble material, the clear liquid continue to concentrate, cooling crystallization, to 80 ℃ drying system.
Tungstic acid method of ammonium metatungstate (dissolving tungstic acid with ammonia, adding acetic acid, and then adjusting the pH with dilute nitric acid)
Ammonium metatungstate was prepared by dissolving tungstic acid in ammonia followed by a series of operations. Dissolve tungstic acid with ammonia, add it into the deionized water containing boiling, heat up the ammonia under stirring to make pH=8, add acetic acid under the boiling condition of the solution, and then adjust the pH with dilute nitric acid from 2 to 4, continue to heat up and concentrate to the time when the relative density is 1.5 to 2, stop heating, cool down and filter. The filtrate is stirred with ethanol, filtered after settling, and the crystals are dried and crushed at 80℃ to obtain the product.
Thermal decomposition of ammonium metatungstate (with ammonium paratungstate as raw material, control the thermal decomposition temperature)
Take ammonium paratungstate as raw material, prepare ammonium metatungstate by thermal decomposition method. Ammonium paratungstate and a small amount of citric acid catalyst are fully mixed, put into the far-infrared rotary furnace, control the thermal decomposition temperature of 200 to 280 ℃, decomposition for about 1 hour. At this time, some ammonia and water are removed, and the weight loss rate of ammonium paratungstate is 5% to 6%. After the thermal decomposition of the product immediately into a slurry, make up the appropriate amount of ammonia, adjust the pH value in the range of 3 ~ 4, at 90 ℃ to cook the slurry. After evaporation and concentration to the ammonium metatungstate content of 50% can be sold as liquid products, when the evaporation and concentration to the original volume of 20% crystallization, filtration and separation, granulation of the product.
Packing and Storage of Ammonium Metatungstate
Conventional standard package of Ammonium Metatungstate
Inner plastic and outer iron drum, net weight 50kg or 25kg per drum.
Storage of Ammonium Metatungstate
It should be stored in dry and well-ventilated place, avoiding direct sunlight. Smoking and open flame should be prohibited in the storage area.
Hazards of Ammonium Metatungstate
Hazardous nature of ammonium metatungstate
Ammonium metatungstate has strong oxidizing and reducing properties, capable of causing fire and explosion. When encountering organic substances, reducing agents and combustible substances, ammonium metatungstate will cause combustion or explosion. It is irritating to skin and eyes, and may cause multiple organ damage by accidental ingestion or inhalation.
