Recovery of Waste Liquor from Tungsten Disulfide

To avoid resource wasting and environmental pollution, we need to emphasize the recovery of waste liquor from tungsten disulfide. It contains a certain amount of recyclable tungsten oxide and sodium sulfate.

Tungsten disulfide is often prepared from ammonium tetrathiotungstate in industry. In the preparation process, the raw material is firstly dissolved with HCl hydrochloric acid to form tungstic acid. Then tungstic acid is mixed with ammonia water to form ammonium tungstate. Next, ammonium tungstate is added to hydrogen sulfide to form tetrathiotungstate. Finally, tungsten disulfide is prepared by the reduction reaction of tetrathiotungstate by hydrogen in high temperature reflector. According to the data of a factory, the annual output of acid-dissolved filtrate was 450m³, about 500 g/m³ of tungsten oxide contained in it, together with 2.5 mol/L of HCl. Tungstic acid solution annual output was 1350 m³, containing a small amount of calcium ions. The sodium sulfate concentrate contains a fairly high concentration of sodium sulfate.

The tungsten oxide and sodium sulfate contained in the waste liquor of tungsten disulfide can be recycled. It is a waste of resources to discard them.

Tungsten oxide is yellow powder. Being insoluble in water, soluble in alkali and slightly soluble in acid, it is the most stable tungsten oxide. Its melting point is 1473°C, the boiling point is higher than 1750°C, and the relative density is 7.16°C.It is a kind of tungstate product with high production and life value. For example, it is used for the detection of harmful gases such as nitrogen dioxide and ammonia, for the production of metal tungsten products and tungsten alloy products, for the preparation of ammonium tungstate, etc.

Sodium sulfate is prepared by sulfate and sodium ions, being soluble in water and the aqueous solution is neutral. It has a high use value in industrial production, such as being used to produce sodium sulphide water glass and other chemical products in the chemical industry, being used as cooking agent in the paper industry, being used as auxiliary solvent in the glass industry, etc.

In addition, waste liquor from tungsten disulfide is acid solution. If discharged into water, it may cause environmental pollution:

1.Fish reproduction and development will be seriously affected.

2. Changes may occur in the aquatic ecosystem. Drinking acidic water regularly will lead to the acidic physical condition of human body. Acidic water will corrode the water distribution network.

Therefore, we must recycle the waste liquor from tungsten disulfide to turn waste into treasure:

1. Filtrate containing tungsten oxide can be recycled, made into CaWO₄ and returned as raw material.

2. HCl can be neutralized with alkaline waste liquid to treat sewage.

3. High concentration of NaSO₄ in sodium sulfate concentrate can be recovered by the condensing crystallizing. 

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