Recycle Ammonium Paratungstate from Tungsten Residue

In traditional ammonium paratungstate (APT) producing method, add tungsten into hydrochloride solution to remove impurities. Main impurities in tungsten residue are phosphoric ion, magnesium ion, ferro ion and potassium ion. 

Under 50~60℃, phosphorus ion and potassium ion can not be separated out. Affected by magnesium ion and ferro ion, during filtration process, tungsten residue will become block.

To oxidize tungsten residue fully, it needs secondary crushing first. But there are too many impurities, after oxidizing, the obtained tungsten oxide content is still very low. So traditional producing method is complex and will cause raw material waste, thus output is very low. So to shorten recycle process and increase APT output is a matter needs to be improved.

Researchers have done some trials to recycle APT from tungsten residue, steps are as follows:

1. Doping tungsten residue in acid under 95~110℃ to obtain liquid and solid matters mixture.

2. Separate liquid and solid matters under 80~90℃ to obtain tungsten residue.

3. Add tungsten residue from the last step into drying furnace under 600~700℃, and then conducting natural oxidization to obtain tungsten oxide. Add tungsten oxide into reaction furnace with accessories, under 105~120℃, stirring for 6~7 hours to obtain coarse ammonium tungstate solution.

4. Purifying coarse ammonium tungstate solution into refined ammonium tungstate solution.

5. Evaporative crystallization the obtained refined sodium tungstate solution to obtain APT.

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