Ammonium Paratungstate as Raw Material for Preparing Ammonium Metatungstate 1/2

Ammonium metatungstate (AMT) is an important intermediate product of tungsten metallurgy, a white crystal or yellow powder which is easy to dissolve in water, but insoluble in alcohol. AMT can be used in preparing tungsten, alloy steel, fire proof fabric, etc. and also be used for ceramic industry. It’s also used in the manufacture of various petrochemical catalysts and other tungsten compounds which is the raw material of catalysts based on tungsten. There are many ways to generate AMT, such as tungstate, ion exchange, thermal decomposition method and so on. This paper, we would like to introduce some methods that preparing AMT base on material of ammonium metatungstate (APT).

Neutralization method – take APT and nitric acid as raw materials to generate AMT, the specific steps are as follows:
1. Add ionized water n and citric acid into APT to form a mixture that concentration of WO₃ 12% ~ 30%;
2. According to the ratio of APT: nitric acid equals to 1:20, adding nitric acid which the concentration is 3% to 5% into APT slurry;
3. Control solid-liquid ratio at 1: (3~4), and pH controlled in 2~4, heating and dissolve to make the relative density of the solution about 1.18~1.20. Then heated to 80~90℃, keep the temperature and pH value constantly, stir for 4h, aging for several hours;
4. Concentrate the solution until the WO₃  content is about 50%, filtering to remove the insoluble substance, and keep concentrating, then cooling down to 80℃ and drying get AMT.

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