Preparing Ammonium Paratungstate from Worn-Out Tungsten Oxide 2/2

4) Vacuum filtration or pressing leaching, and translate the ammonium tungstate solution in a storage tank for 10~30 hours.
3. Preparation of ammonium paratungstate
1) Outlet the ammonium tungstate solution into a reaction kettle, heating to boiling, and then insulation for evaporating and concentrating till large numbers of APT crystal come into being;
2) Stop heating when the solution proportion dropped down to I.08~I.05, cooling the temperature below to 90℃ with stirring; then filtering the solution together with the APT crystal into the vacuum filtration or centrifugal, and washing with water for 3~4 times;
3) drying at the temperature of 80-130℃;
4) Cooling down and screening with 80 mesh sieve, inspecting, packaging, then we get ammonium paratungstate.

Advantages about this way to prepare ammonium paratungstate from the warn-out tungsten oxide are like bellows:
1. Save a lot of extra caustic soda, sodium carbonate and hydrochloric acid, thus reduce the cost;
2. Simplify the process to shorten the production cycle;
3. Strong acid and alkali do not used in the reaction process; therefore, the environmental costs have been reduced;
4. Save energy and pollutants discharging has been reduced.

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