Ammonium Metatungstate Preparation from Tungsten Oxide Waste

Ammonium metatungstate is an important tungsten-containing compound. It is mainly used to produce various petrochemical catalysts and other tungsten compounds. It is the main raw material of tungsten-based catalysts in refineries. With the development of petroleum refining and petrochemical industries, the amount of ammonium metatungstate is increasing.

Some researchers tried to prepare ammonium metatungstate from tungsten oxide waste. The process includes ammonia leaching step, acid leaching step, concentration step and spray step. After ammonia leaching of tungsten oxide waste, acid leaching step was directly implemented. After concentration, ammonium metatungstate products were directly obtained by spray drying. The specific operation is as follows:

A)Leaching of tungsten oxide waste: adding tungsten oxide waste slowly into ammonia water with agitation, and slowly flushing into liquid ammonia to control free ammonia 50-60 g/L. When the content of WO₃ reaches 160-200 g/L, boiling stirring for more than 20 minutes, holding reaction for 2 hours, standing overnight, filtering, ammonium tungstate solution can be obtained.

B)The solution of ammonium tungstate is converted into ammonium metatungstate solution: the obtained solution is pumped into the reactor and heated to boil, and the pH value of the solution is adjusted to 4-5 by 1:4 nitric acid. When the concentration of the solution is less than 30 g/L, the solution is kept for 2 hours and cooled for 4 hours, the siphon supernatant is cooled for 4-5 by 1:4 nitric acid, and the crystallization is slowly adjusted to the pH value of the solution by 1:4 nitric acid until it dissolves, stays overnight and filters. To dilute ammonium metatungstate solution.

C)Ammonium metatungstate powder was prepared by concentrated spray drying of dilute ammonium metatungstate solution.

Compared with the traditional process, the new process of ammonium metatungstate is simpler, and the obtained product has less impurities, high purity, low energy consumption and low cost.

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