Deep Purification and Impurity Removal Process of Ammonium Tungstate Solution

Ammonium paratungstate is an important intermediate product in tungsten hydrometallurgical process. The production process of tungsten concentrate decomposition-ammonium paratungstate mainly includes ore decomposition, transformation to obtain crude ammonium tungstate solution, impurity removal from crude ammonium tungstate solution, crystallization to obtain ammonium paratungstate and crystallization mother liquor, recycling of crystallization mother liquor, etc.

Among them, the crude ammonium tungstate solution obtained by transformation needs to be purified because it contains impurities of P, As and Si. The classical purification and impurity removal method is to add magnesium chloride in ammonium tungstate solution quantitatively to form magnesium salt precipitation, keep Mg=0.1g/l or so to form a balance with phosphorus, then add solid silicic acid into the filtrate to remove excess magnesium ions, and the solution should be stored for more than 48 hours, but this process is difficult to ensure that both phosphorus and magnesium can be purified up to standard, resulting in low purity of ammonium tungstate solution. The quality of final crystalline products and the primary yield of crystallization rate are affected.

In view of the existing technical problems, some scholars have proposed a process of deep purification and impurity removal of ammonium tungstate solution. The process is as follows:

Step (1): The crude ammonium tungstate solution obtained by ore decomposition is added with magnesium chloride to obtain magnesium salt precipitation and filtration precipitation. The magnesium chloride content in the filtrate should be more than 0.25g/l.

Step (2): The filtrate enters D850, D750, D851 or D751 resin for adsorption, and collects the purified ammonium tungstate solution.

On the one hand, by screening the addition amount of magnesium chloride, the impurities P, As and Si can be precipitated completely, and the excessive introduction of magnesium impurities can be controlled, which brings convenience to the purification process of step (2). On the other hand, D850, D750, D851 or D751 resins can adsorb magnesium ions in the solution very well, which has the effect of removing magnesium, thus overcoming the complexity of the existing magnesium removal process. And the defect of incomplete magnesium removal. Compared with the existing technology of impurity removal and purification process, the above method is simple to operate, does not occupy extra production time, and can effectively reduce costs.

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