Preparing Ammonium Paratungstate from Worn-Out Tungsten Oxide
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 k