Soft Scrap Containing Tungsten Used for Producing Ammonium Paratungstate

The two traditional ways for recycling soft scrap containing tungsten are as follows:
1.Turn the wastes into sodium tungstate solution by cooking with NaOH, crystallize sodium tungstate crystal; then dissolve the crystal in circulating mother liquor and rebuild sodium tungstate solution, extract tungsten and purify to get ammonium tungstate, get ammonium paratungstate by evaporation at last.

2.Recover by method of ion exchange. First of all, acidify the mother liquor (adjust pH), then adsorb tungsten in mother liquor by using ion exchange resin with weak alkali macroporous. To generate ammonium paratungstate, ammonium chloride and hydrolysis are used in ion exchange process to get sodium tungstate solution, and finally get ammonium paratungstate by evaporate.

For shorten the process and increasing the recovery rate of tungsten, reducing production cost and preventing the environment pollution, a new method to recycle was puts forward, the specific steps are like below:
1. Ammonia leaching with pressure: mix soft scrap containing tungsten which is produced in Tungsten Hydrometallurgy smelting process with dilute ammonia in the environment of 0.2~0.6MPa and 120~200℃ for 1~3 hours; the molar ratio of NH3 in dilute ammonia and WO₃ in soft scrap containing tungsten ratio is 2.5~4.5:1;
2. Filter to remove the slag: send the feed liquid generated in step 1 by leaching reaction into filter to remove slag;
3. Crystallization and separation: crystallize the solution which is obtained from step 2 in a evaporator at temperature 50~100℃ until the slurry density reach to1.02~1.10g/ml, finally we get APT crystal by solid-liquid separation.

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