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Title：How to treat industrial magnesium sulfate wastewater?
How to treat industrial magnesium sulfate wastewater? Generally, the treatment of industrial magnesium sulfate wastewater usually adopts the method of combining evaporation concentration with flash cooling crystallization and crystallization. He Cheng Xiaobian talked with you about how to treat industrial magnesium sulfate wastewater.
1、 Sources of industrial magnesium sulfate wastewater
In the development and application of rare earth, some rare earth alloy enterprises will produce a large amount of magnesium-containing wastewater in the production process. Most of this wastewater is magnesium sulfate solution. These wastewater cannot be discharged directly, and needs to be treated in a certain way.
2、 Treatment method of industrial magnesium sulfate wastewater
As an important industrial product, industrial magnesium sulfate has a wide range of uses in pharmaceutical, construction, agriculture and other fields. At present, the common resource treatment method of magnesium sulfate wastewater is crystallization. Generally, the magnesium sulfate in the wastewater is separated by crystallization through evaporation or cooling coupling to obtain magnesium sulfate crystal products and purified water.
Purified water is returned to the upstream process for reuse, and industrial grade magnesium sulfate crystal products are used in other fields to achieve zero discharge of magnesium sulfate wastewater.
3、 Difficulties in the treatment of industrial magnesium sulfate wastewater
Most industrial magnesium sulfate wastewater contains a small amount of calcium ions, which will have a great impact on the nucleation and crystal growth of magnesium sulfate, such as magnesium sulfate is not easy to precipitate, crystal product particles are too small, solution viscosity is too high, these problems have affected the difficulty of magnesium sulfate wastewater treatment and the improvement of crystal product quality.
At the same time, under different crystallization conditions, magnesium sulfate crystal products may exist in the form of 1, 2, 3, 4, 5, 6, 12 water and other hydrates. The particle size and crystal shape of magnesium sulfate crystal products in different hydrate forms are quite different, which brings great difficulties to subsequent centrifugal separation and recovery.
4、 Treatment of wastewater containing calcium magnesium sulfate
The solubility of magnesium sulfate increases first and then decreases with the increase of temperature. In the calcium magnesium sulfate system, the solubility of magnesium sulfate in calcium sulfate aqueous solution is lower than that in pure water due to the same ion effect.
For the crystallization process of magnesium sulfate solution, the conventional treatment method of magnesium sulfate wastewater is evaporation crystallization, and the high-temperature evaporation crystallization product is magnesium sulfate monohydrate. Due to the small crystal size of magnesium sulfate monohydrate and the high viscosity of crystal slurry, the crystallization products are not easy to separate.
In order to solve the problem of small crystal particles of magnesium sulfate monohydrate, Kang Jinghui placed magnesium sulfate monohydrate crystal in magnesium sulfate solution at room temperature, and converted magnesium sulfate monohydrate into magnesium sulfate heptahydrate.
Compared with pure magnesium sulfate solution, the crystallization process of calcium magnesium sulfate solution is quite different. The calcium magnesium sulfate solution is evaporated under normal pressure at 100 ℃. When the concentration of magnesium sulfate in the solution reaches a certain level, the evaporated concentrated solution appears as a thick solution or a solid-liquid mixture that is difficult to separate. It is basically impossible to separate and obtain magnesium sulfate crystal products. Due to the anti-solubility property of calcium sulfate, calcium sulfate is easy to scale on the heat exchange tube during the evaporation crystallization process, resulting in frequent cleaning of heat exchange equipment in the evaporation crystallization system.
The above is about the treatment of industrial magnesium sulfate wastewater and the treatment methods of magnesium sulfate wastewater containing calcium. I hope it can help you.
