Neutralization method with secondary ammonium metatungstate and Nitrate As the raw material purchase ammonium metatungstate: secondary ammonium metatungstate deionized water and Ammonium citrate With WO312- ~ 30- concentration of slurry. According to =1:20: nitrate ammonium paratungstate by adding 3- ~ 5- of dilute nitric acid to ammonium paratungstate slurry, control ratio of solid to liquid 1: (3 ~ 4), the Ph value of 2 ~ 4, heating and dissolving solution, the relative density of 1.18 ~ 1.20, heating to 80 ~ 90 ℃, constant temperature and constant volume control Ph value, the stirring reaction for 4H hours, aging, concentrating the supernatant to WO3 content is about 50-, filtration to remove insoluble, liquid concentration, cooling crystallization, continue to 80 ℃ drying.
Tungstic Acid Dissolving Method
Method using ammonia tungstate tungstic acid dissolved, add a boil Deionized water In the stirring, heating by ammonia, Ph=8, in the boiling solution by adding acetic acid, and then use the Dilute nitric acid The Ph value is adjusted to 2 ~ 4, continuing heating concentrated to a relative density of 1.5 ~ 2, stop heating, cooling and filtering. The filtrate is added with Ethanol Stir, settlement after filtration, crystal at 80 ℃ drying, pulverizing to obtain the product.
Thermal Decomposition Method
The thermal decomposition of ammonium paratungstate by preparing ammonium metatungstate: ammonium paratungstate and a small amount of citric acid catalyst after mixing into the far infrared, rotary furnace, controlled thermal decomposition temperature 200 ～ 280 ℃, decomposition of about 1 h. The removal of ammonia and water, ammonium paratungstate weightlessness rate was 5- ~ 6-. The thermal decomposition products immediately after the slurry, adding proper amount of ammonia, Ph value is adjusted in the 3 to 4 range, at 90 ℃ digestion slurry. After evaporation to ammonium metatungstate content of 50- can be used as a liquid product to sell, crystallization, when the evaporation to the original volume of 20- filtering and separating, granulating product. Also can be evaporated and concentrated liquid product is prepared by spray drying. As of 45- ~ 50- ammonium metatungstate by high-speed centrifugal rotary spray dryer, imports of hot air temperature 250 ～ 300 ℃, outlet temperature 90 ～ 95 ℃, the obtained product is a spherical crystal, particle size is 200 mesh accounted for 95%, free water <1.5-.
Solvent Rxtraction Method
Solvent extraction using ammonium tungstate solution by organic extractant phosphoric acid two (2- ethylhexyl) ester (D2EHPA) or phosphoric acid butyl ester three (TBP) and kerosene solvent composition of organic phase, the ammonium ion extraction ammonium tungstate in, the Ph value to 2 ~ 4, the boiled solution generates ammonium metatungstate solution. Concentration and crystallization, filtration, drying products.
Ion Exchange Method
Ion exchange method Ammonium paratungstate by using ion exchange resin, preparation of ammonium metatungstate: at 130 ~ 140 ℃ heating ammonium paratungstate from 1 to 8 h, the resultant tune into a paste, to 80 ~ 100 ℃ boiling for 2 ~ 6 h, generates ammonium metatungstate solution. Concentrating crystallization, filtration, drying to obtain the product. The electrodialysis method using ammonium tungstate and ammonium paratungstate as raw materials by electrodialysis with ammonium metatungstate: ammonium paratungstate into an anode chamber, when the electric current passes through, the ammonium ion by anion exchange membrane into the cathode chamber, the anode chamber ammonium metatungstate concentration increase. Finally from the cathode chamber released ammonium metatungstate solution, according to the above method of treatment of ammonium metatungstate.