Rapid Phosphorus Removal by Ammonium Tungstate Solution

In China, NaOH⁺ phosphate is generally used to decompose scheelite or wolframite in tungsten smelting. Although the subsequent ion exchange process can remove most of the phosphorus, if the decomposition of sodium tungstate solution contains too much residual phosphorus, the concentration of phosphorus in ammonium tungstate solution obtained by ion exchange desorption is often higher than that of technical requirements, resulting in excessive phosphorus in ammonium paratungstate (APT).

Some scholars have proposed an effective method to remove the trace phosphorus rapidly and effectively in ammonium tungstate solution. The main steps are:

1. In the NH₃ content is usually 1.5 ~ 2.0mol / l ion exchange desorption of ammonium tungstate solution, at room temperature directly added chromium acetate, under the conditions of the reaction for a certain reaction time, so that the solution of phosphorus in the form of phosphorus that is generated amorphous chromium phosphate particles precipitated.

2. The solubility of chromium phosphate increases with the increase of pH, the pH must be increased in the chromium before the solution of chromium phosphate filtration separation. Because amorphous chromium phosphate particles are difficult to filter, they are removed by filtration and resin adsorption.

3. Adjust the pH value to remove chromium. Add excess chromium acetate to phosphorus in the ammonium tungstate solution. Before the conventional removal of molybdenum, increase the pH to make the residual chromium acetate to form solid particles of chromium hydroxide for precipitation and removal.

4. Chromium-molybdenum coprecipitation method, remove the ammonium tungstate mixed solution of chromium hydroxide precipitation, in order to obtain purified ammonium tungstate solution. Therefore, by this method, it is possible to efficiently remove the chromium hydroxide solid which is difficult to flocculate and precipitate, while removing molybdenum.

5. The ammonium tungstate solution after purification is evaporated and crystallized, and the products of ultra pure ammonium paratungstate with low phosphorus and chromium content are obtained.

The method for rapidly removing trace phosphorus in ammonium tungstate solution can efficiently and cost-effectively reduce the phosphorus content in the ammonium tungstate solution and further crystallize the ultrapure APT, thereby having high industrial value.

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