“Three Wastes” Pollution in Tungsten Disulfide Preparation

“Three wastes” pollution produced in the preparation of tungsten disulfide, harming the human health and environment. They are tungsten-containing residue, acid-containing liquor and hydrogen sulfide together with other gases. They deserve our attention.

Waste liquor, waste gases and solid wastes---collectively called “three wastes”---are three main types of industrial pollution. In tungsten disulfide process, tungsten-containing residue, acid-containing liquor, together with hydrogen sulfide and other gases constitute “three wastes” pollution.

Tungsten disulfide is often prepared from ammonium tetrathiotungstate. The preparation process is as follows:

raw materials (solution containing tungsten or artificial calcium tungstate) →ingredients →acid dissolution →ammonia neutralization →vulcanization →reduction →crushing →compression →tungsten disulfide products.

The raw material is firstly dissolved with HCl hydrochloric acid to form tungstic acid (H₂WO₄). Then tungstic acid is mixed with ammonia water to form ammonium tungstate [(NH₄)₂WO₄]. Next, ammonium tungstate is added to hydrogen sulfide (H₂S) to form tetrathiotungstate [(NH4)2WS4]. Finally, tungsten disulfide is prepared by the reduction reaction of tetrathiotungstate by hydrogen in high temperature reflector.

With the example of a plant, the following is “three wastes” pollution in tungsten disulfide preparation.

1. Solid wastes：tungsten-containing residue

The plant’s annual output of ammonia dissolved filter residue was 8.58 t, and 0.79 t of WO₃; the annual concentrated filter residue was 14.28 t, about 9.28 t of WO₃. The waste residue contains a certain amount of versatile WO₃. The tungsten-containing residue are versatile and recyclable material. If it is discarded, it will be a waste of resource.

2.Waste liquor: acid-containing liquor

The plant’s annual output of acid-soluble filtrate was 450 m³, containing 500 g/m³ WO₃ and 2.5 mol/L HCl. And tungsten acid solution annual output was 1350m³, containing a small amount of calcium ions. If it is poured into the clean water, the acid-containing liquor will cause the pollution.

3.Waste gases: hydrogen sulfide and other gases

Harmful gas H₂S, HCl, NH₃ and other gases were discharged in the preparation of tungsten disulfide. If released into the atmosphere, the exotic H₂S will do harm to the human health and environment.

With the continuous development economy, people should attach importance to “three wastes” pollution produced in tungsten disulfide preparation, so as to ensure the production safety and environmental health.

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