Ammonium Paratungstate Recycle from Waste Tungsten Oxide

Waste tungsten oxide including unqualified blue tungsten oxide and tungsten trioxide. Ammonium tungstate includes ammonium tungstate solution, ammonium paratungstate, ammonium metatungstate etc.

Some scholars have proposed a process that is simpler, more environmentally friendly, and more efficient than the conventional process. It is possible to use waste tungsten to recycle ammonium paratungstate. The process is as follows:

Waste tungsten oxide treatment capacity: 300kg tungsten trioxide, 150kg blue tungsten oxide, and 450kg mixed tungsten oxide after mixing.

Ammonia concentration: dilute the concentrated ammonia water to make dilute ammonia water containing 14% ammonia.

The weight of waste tungsten oxide/dilute ammonia volume was 321 g/l.

1310 liters of dilute aqueous ammonia was added to a 2000-liter enamel high-pressure reactor, 450 kg of tungsten oxide was mixed, 185 liters of industrial-grade hydrogen peroxide solution was added, and the kettle cover was closed. The kettle was heated slowly under stirring to raise the temperature to a steam pressure of 4 to 6kg/cm2, boil for 110 minutes, stop heating, cool to 35°C, adjust free ammonia concentration to 3.8% with ammonia and water, tungsten trioxide concentration 276 g/l. The ammonium tungstate solution cooled to normal temperature was suction-filtered through a stainless steel vacuum filter, and the filtrate was transferred to a storage tank of ammonium tungstate solution and placed for 24 hours.

Ammonium tungstate solution was discharged from the outlet 20cm above the bottom of the sedation tank and transferred to a liter evaporating crystallization kettle with a capacity of 2000 liters. The mixture was heated to boiling, and concentrated by evaporation. A large amount of white ammonium paratungstate crystals precipitated, and the solution specific gravity decreased to 1.06. Heating, stirring and cooling to 80°C, the solution together with ammonium paratungstate crystals into a stainless steel vacuum suction filter, washed with water 3 to 4 times.

The crystals of the washed ammonium paratungstate are filtered and placed in a drying cabinet with a stainless steel charging basin, with loading thickness of 3 to 5cm and dried at 100 to 130°C. After passing through the 80-mesh sieve after cooling. The ammonium paratungstate is formed after inspection and packaging.

This waste tungsten recycling method greatly saves auxiliary raw materials and energy, reduces environmental pollution, and reduces production costs in the process. The ammonium paratungstate may also be further processed to produce ammonium metatungstate.

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