It can be separated and purified by diethyl ether extraction method to obtain the adduct of diethyl ether and metatungstic acid; it can also be prepared by the action of ammonium metatungstate solution and platinum chloric acid; it can be prepared by the action of sulfuric acid and barium metatungstate. Common traditional preparation methods are:
- Add the cationic resin to the sodium tungstate solution with a concentration of 2% at 80°C under constant stirring until the pH value of the solution is 2.5. After continuing to stir for 20 minutes, put the solution in a water bath for 2 hours, and then wash it with barium chloride Solution treatment, the slightly soluble part is filtered out to obtain the barium metatungstate filtrate, and then the barium metatungstate filtrate is recrystallized several times, and finally the solution is made again. The solution is exchanged by cationic resin, and the exchange liquid is heated in hot air Evaporate to obtain metatungstic acid crystals.
- Acidify the tungstate solution to a pH value of about 4.0, then maintain the pH value of the solution, age for 48 hours, add an appropriate amount of ether-12N sulfuric acid, and generate an oily metatungstate ether with a large specific gravity after shaking, and then The oil is dried rapidly to obtain crystalline metatungstic acid.
The above two methods have problems such as complex process, high production cost, low production capacity, poor product quality and large environmental pollution to varying degrees. For this reason, researchers with the patent number CN1066418C have developed a method for the preparation of H6 (H2W12O40) which is relatively simple in process, low in cost and less in environmental pollution, and is conducive to the industrial production of H6 (H2W12O40): dissociation of ammonium paratungstate powder at a temperature of 270°C to 350°C. Ammonium metatungstate, the dissociation time is 30-60 minutes, and then add deionized water to the obtained ammonium metatungstate powder for leaching, after stirring to obtain an emulsion, filter out the insoluble matter, and the filtrate is heated at 60-90°C Aging in a water bath for 4 to 24 hours, then filtering, and exchanging the filtrate with a cationic resin to obtain a H6 (H2W12O40) solution.
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