Preparation of Secondary Ammonium Tungstate With High Purity Using Two-step Ion Exchange Method

The present invention relates to the preparation of secondary ammonium tungstate with high purity using two-step ion exchange method.

Firstly, the tungsten is absorbed from an alkaline solution by the porous strong alkaline negative ion exchange resin and the desorption solution is acidized to PH 2.5-4. Then,the tungsten is absorbed again by the acrylic acid type weak alkaline negative ion exchange resin and is desorbed by ammonia water. The secondary ammonium tungstate with high purity is obtained by evaporating and crystallizing the desorption solution.During the desorption by ammonia water, an ion exchange column with a drainage tube in the interface between resin layers is used. It can rapidly evade the secondary ammonium tungsten crystalline region with PH 6-8 so as to avoid the separation of crystal and to realize the desorption by fixed bed ammonia water. The density of WO3 in the desorption solution may reach 250-300 g/1. The said process can remove P,As, Si and other impurities, purify molybdenum as well. What's more, its tungsten recovery is up to 99%.

APT


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