The principle of preparing ammonium metatungstate hydrate by ion exchange method can be clearly summarized as follows:
The ion exchange method takes ammonium tungstate solution or ammonium sec-tungstate as raw material, and exchanges H+ in the ion exchange resin with NH4+ in the solution to produce ammonium metatungstate hydrate. The key of this method is to control the parameters of pH, temperature and time of the reaction to realize the efficient conversion of ammonium tungstate to ammonium metatungstate.
Specific steps for the preparation of ammonium metatungstate hydrate by ion exchange method
Preparation of raw materials
Ammonium paratungstate is used as the main raw material to ensure that its purity and quantity meet the production requirements.
Ion exchange process
Use strong acid or weak acid H+ type cation resin as ion exchange medium.
Under the action of the resin, NH4+ in the solution is exchanged with H+ in the resin.
At a pH of about 3.5, H+ enters the solution while NH4+ is adsorbed by the resin.
Cooking and Conversion
The ion-exchanged solution is boiled at 98°C for 5 hours to convert the ammonium tungstate to a stable ammonium metatungstate solution.
Temperature and time control in this step are critical for the efficiency of the reaction and the quality of the product.
Evaporation and concentration
The ammonium metatungstate solution after boiling is evaporated and concentrated to increase the concentration of ammonium metatungstate in the solution.
Crystallization and Drying
The concentrated ammonium metatungstate solution is converted to ammonium metatungstate hydrate in solid form by cooling crystallization or spray drying.
The crystallization and drying process can be adjusted according to specific needs to obtain products of different purity and particle size.
Resin regeneration
Resin saturated with NH4+ can be recycled after regeneration process with hydrochloric acid solution.
The regeneration process of resin not only reduces the production cost, but also helps to protect the environment.
The preparation of ammonium metatungstate hydrate by ion exchange method realizes the exchange of NH4+ and H+ through ion exchange resin, and then the final product is obtained through the steps of boiling, evaporation and concentration, crystallization and drying. This method has the advantages of simple process, convenient control, avoiding the formation of APT, and not introducing new pollutants, but it also has the disadvantages of possibly generating a small amount of colloidal tungstic acid and increasing the number of operation steps. In practical application, it is necessary to consider various factors to choose the most suitable production method.
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
