Ammonium Paratungstate Preparation with Low Pollution

In the existing technology, the industrial preparation methods of APT are mainly acid, caustic soda or soda decomposition method, and ion exchange or extraction after evaporation and crystallization, the overall evaluation, the existing methods are not used or semi circular circulation process system, must set a waste water outlet, the water pollution can not be completely eradicated.

Recently, a scholar from Central South University has invented a system for preparing ammonium paratungstate from tungsten mineral raw materials. Its process is short, its solution can be recycled and environmental pollution is almost eradicated, low cost and easy to industrialization. The cost of this approach is not high, and it has the potential to be universal. The methods include the following steps:

1.The raw materials and ingredients of tungsten minerals are fined, and the raw materials are prepared by mixing.

2.Roasting raw material, getting clinker, and crushing and grinding the clinker;

3.By ammonium carbonate, ammonium carbonate, ammonium bicarbonate, ammonium carbonate and ammonium tungstate, ammonium carbonate, ammonium carbonate and ammonia -CO₂ -CO₂, ammonia ammonium carbonate, ammonium carbonate and ammonium hydrogen carbonate and ammonium tungstate, ammonium carbonate and ammonium hydrogen carbonate and ammonium tungstate -CO₂, ammonium carbonate - ammonia - ammonium tungstate, carbonate ammonium ammonium tungstate -CO₂, ammonium carbonate - ammonia - ammonium tungstate -CO₂ clinker leaching system;

4.Leaching slurry by solid-liquid separation and slag washing, to obtain the crude ammonium tungstate solution and leaching slag, leaching slag as part of step 1) of raw ingredients return configuration, the remaining part of storage;

5.Purification of ammonium tungstate solution;

6.After purification, APT was precipitated by evaporation crystallization, and ammonia and carbon dioxide gas were obtained at the same time.

7.The slurry after crystallization is liquid-solid separated, the crystalline mother liquor and solid phase are obtained, and the solid phase is washed by water and / or ammonium salt solution. After drying, APT products are obtained after washing. The crystallization mother liquor is returned to step 3) together with the ammonia gas and carbon dioxide obtained in step 6), and the leaching of the clinker is circulated after replenishing the lost ammonium carbonate (which can be replaced by ammonium bicarbonate or ammonia water and CO₂).

This method only slightly changed the traditional process, and did not increase the investment of equipment. The APT produced by the method can also achieve the ideal purity, which has great potential for development.

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