Neutralization method of ammonium tungstate hydrate preparation
Prepare ammonium metatungstate with ammonium sec-metatungstate and nitric acid as raw materials: add ammonium sec-metatungstate to deionized water and ammonium citrate to form a slurry with a concentration of 312%～30% WO3. 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 to dissolve, 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 the value of Ph, stirring reaction for 4h, aging for a few hours, the liquid is concentrated to the content of WO3 in the 50 percent or so, filtering! Remove insoluble material, the clear liquid continue to concentrate, cooling crystallization, to 80 ℃ drying system.
Ammonium tungstate hydrate preparation of tungstic acid method
Tungstic acid will be dissolved in ammonia, added to the deionized water containing boiling, heating under stirring by ammonia, so that Ph = 8, add acetic acid in the case of boiling solution, and then adjust the Ph value of 2 ~ 4 with dilute nitric acid, continue to heat and concentrate to the relative density of 1.5 ~ 2, stop heating, cooling and filtration. The filtrate was added with ethanol and stirred thoroughly, filtered after settling, and the crystals were dried and crushed at 80°C to obtain the product.
Thermal decomposition method for the preparation of ammonium tungstate hydrate
Ammonium paratungstate as raw material for the preparation of ammonium metatungstate: 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 ~ 280 ℃, decomposition for about 1 h. At this time, some ammonia and water are removed. 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, add 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 evaporation and concentration to the original volume of 20% crystallization, filtration and separation, granulation products. The evaporation concentrate can also be spray-dried to produce products. Such as 45% to 50% ammonium tungstate through the high-speed centrifugal rotary spray dryer, the inlet hot air temperature of 250-300 ℃, out of the tower temperature of 90-95 ℃, the products obtained for the spherical crystals, particle size of 200 mesh accounted for 95%, containing free water <1.5%.
Ammonium tungstate hydrate preparation solvent extraction method
Ammonium tungstate solution with organic extractant di(2-ethylhexyl) phosphate (D2EHPA) or tributyl phosphate (TBP) and kerosene solvent to form an organic phase, extract ammonium ions in ammonium tungstate, so that the Ph value is reduced to 2 ~ 4, after boiling to generate ammonium metatungstate solution. Concentration and crystallization, filtration and separation, drying to produce products.
Ammonium tungstate hydrate preparation ion exchange method
Taking ammonium paratungstate as raw material, ammonium metatungstate is prepared by ion exchange method: heating ammonium paratungstate at 130～140℃ for 1～8 h, adjusting the product into slurry, boiling at 80～100℃ for 2～6 h, generating ammonium metatungstate solution. Then it is concentrated and crystallized, filtered and separated, and dried to obtain the product. The electrodialysis method uses ammonium tungstate or ammonium sec-tungstate as raw material to prepare ammonium metatungstate by electrodialysis: ammonium sec-tungstate is added to the anode chamber, and when the current passes through, ammonium ions are fed into the cathode chamber through the anion-exchange membrane, and the concentration of ammonium metatungstate in the anode chamber increases. Finally, ammonium metatungstate solution is released from the cathode chamber, and ammonium metatungstate is produced by processing according to the above method.
Among the above preparation methods of ammonium tungstate hydrate, neutralization method, tungstic acid method and thermal decomposition method are the main methods for industrialized production in China.
More details of ammonium metatungstate product, please visit website: http://ammonium-metatungstate.com/
Please contact CHINATUNGSTEN for inquiry and order of ammonium metatungstate:
Email: sales@chinatungsten.com
Tel.: 86 592 5129595
