High Purity Ammonium Metatungstate Recycle from Tungsten Oxide Waste

Some scholars have provided a tungsten oxide waste as a raw material for the preparation of ammonium metatungmate system solutions, the system includes: tungsten oxide waste leaching, tungsten oxide waste leachate filtration, tungsten oxide waste leachate filtration filtrate leaching, tungsten oxide waste leachate filtrate filtration, dilute metatungstate ammonia solution, dilute metatungstate ammonia solution filtration; dilute metatungstic acid ammonia solution leaching solution concentrated, concentrated ammonium metatungstate solution spray drying process.

The method comprises the following steps: taking tungsten oxide waste as raw material, ammonia leaching, ammonium tungstate solution into ammonium metatungstate solution, ammonium metatungstate solution concentration and spray drying to prepare ammonium metatungstate,

A)Tungsten oxide waste leaching: The tungsten oxide waste is slowly added to the stirred ammonia, while slowly flushed into liquid ammonia to control free ammonia 50 ~ 60g / L, the following reaction occurs: WO₃ + NH₄OH = (NH₄) ₂WO₄, when Solution WO₃ content reached 160 ~ 200g / L, boiling for 20 minutes or more, incubated for 2 hours, allowed to stand overnight, filtered to give ammonium tungstate solution.

B)Ammonium tungstate solution into ammonium metatungstate solution: ammonium tungstate solution is pumped into the reactor was heated to boiling, with 1:4 nitrate solution adjust the pH value to 4~5, when the solution is concentrated to the content of WO₃ is less than 30g/L, 2 hours, cool for 4 hours, the siphon supernatant, slow crystal 1:4 to adjust the pH value to 4~5 nitrate solution, to dissolve, standing overnight, filtered, diluted by ammonium metatungstate solution.

C)The ammonium tungstate solution is concentrated by spray drying, and the product of ammonium partial tungstate powder is prepared.

Compared with the prior art, the method directly makes the tungsten oxide waste into the ammonium metatungstate product with higher added value than the ammonium paratungstate, and omits the process of crystallizing the ammonium paratungstate after the ammonia leaching of the tungsten oxide waste material, without using a crystallization reaction kettle, reduce the investment in fixed equipment, reduce production costs, improve product recovery and economic benefits.

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