Preparing Ammonium Paratungstate from Worn-Out Tungsten Oxide 1/2

Warn-out tungsten oxide including tungsten trioxide and blue tungsten oxide ect. which have been scrapped, and substandard thus must be reworked. This warn-out tungsten oxide which can not directly be used in tungsten smelting or other industries can be recycling. In this paper we will present a method for recovering ammonium paratungstate from warn-out tungsten oxide.



1. Handling the raw material
Screen the warn-out tungsten oxide by a 60~80 mesh sieve to remove caking tungsten oxide and mechanical inclusions; then the grinding caking tungsten oxide and also screen it;
2. Autoclaving with ammonia for preparing ammonium tungstate solution
1) Dilute the concentrated ammonia in deionized water or use water to absorb liquid ammonia, get ammonia with concentrate of 8~20%; and then formulating the slurry with stirring at the ratio that weight of tungsten oxide: volume of ammonia is 150~350g/L;
2) Add hydrogen peroxide when the material contains blue tungsten oxide, compress the kettle cover, heating to the pressure in the kettle is in the range of 4~l0kg/cm² with stirring; the reaction time supposed to be 60~180 minutes;
3) Stop heating and cooling down to room temperature (20~40℃) after finishing the reaction; check if the color of solution is blue or not, if so, supplemented with hydrogen peroxide until it disappear; adjust the concentration of ammonia in ammonium tungstate solution among 3~5% with ammonia or water, and the concentration of WO₃ is controlled among 120~350g/L;