Preparation of ammonium paratungstate by two step ion exchange method is a process of preparing high-purity APT by twice ion exchanges.
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Preparation of High-purity Ammonium Paratungstate by Two Step Ion Exchange Method
Step One: Absorb tungsten by porous strongly basic anion exchange resin from alkaline solution, and then acidify the pH value of solution to 2.5-4 by desorption solution;
Step Two. Absorb tungsten by using acrylic type weakly basic anion exchange resin, and then desorb W with ammonia water, finally get high purity ammonium paratungstate by evaporation crystallization.
For desorbing W with ammonia water, use an ion exchange column equipped with a drain tube at the interface of the resin layer to quickly avoid the pH 6-8 ammonium paratungstate crystallization area, prevent crystal precipitation, and realize fixed desorbing process. The concentration of tungsten trioxide in desorption solution can reach 250-300 g/L. This process has a good purification effect on impurities such as phosphorus, arsenic, silicon and tin, and also has a certain purification effect on molybdenum. The recovery rate of tungsten can reach 99%.
