Adding Carbon Dioxide to Produce Ammonium Paratungstate

There are two steps in the production of Ammonium paratungstate (APT) which are Preparation of pure ammonium tungstate solution and Crystallization of ammonium paratungstate. And ways to prepare pure ammonium tungstate are as follows: ion exchange, solvent extraction and classical method. A simple method which can be used in the process of alkali recycle, and using carbon dioxide reacts with sodium-ammonium salt solution to prepare ammonium paratungstate directly is put forward in this paper.

Steps like bellows:
1. Adding ammonia or ammonium salts or solution to sodium-ammonium salt solution of tungsten trioxide concentration about 15~450g/L;
2. Adding carbon dioxide to sodium-ammonium salt solution, and heating the temperature up to 20~100℃, then keep for  1~72 hours to generate ammonium paratungstate crystal slurry;
3. Separate the slurry, the solution after separation return to the tungsten concentrate decomposition process;
4. Using ammonium solution to wash the solid obtained in step 3 at temperature 20~100℃, then washed with water, and then get ammonium paratungstate.

The advantages are like bellows:
1. Realize the goal of Alkali circulation to reduce the environmental pollution in the process of tungsten metallurgy;
2. Alkali neutralization and ammonium paratungstate crystallization complete in one step which simplify the processing;
3. Low energy consumption and investment.

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