CN106348322B - Method for preparing high-purity magnesium fluoride from magnesite - Google Patents

Abstract

The invention discloses a method for preparing high-purity magnesium fluoride from magnesite, which is characterized by comprising the following steps: 1) calcining magnesite to obtain light-burned magnesia powder; 2) adding light-burned magnesia ore powder into an ammonium salt solution, stirring to remove soluble calcium, and filtering to obtain a filter cake; the ammonium salt is one or more of ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium oxalate or ammonium acetate; 3) adding the obtained filter cake into an organic acid solution for reaction, and filtering the solution after the reaction is finished to obtain a leaching solution; the organic acid is one or more of formic acid, acetic acid, propionic acid, lactic acid, citric acid, glycolic acid, malonic acid, succinic acid or adipic acid; 4) adding hydrofluoric acid into the leaching solution to generate a precipitate, filtering, washing and drying to obtain the high-purity magnesium fluoride. The method has the advantages of wide raw material source, low cost and low equipment requirement, and can obtain high-purity magnesium fluoride by using cheap magnesite, thereby greatly reducing the production cost of the high-purity magnesium fluoride.

Description

Method for preparing high-purity magnesium fluoride from magnesite

technical field

The invention belongs to the technical field of mineral processing, and in particular relates to a method for preparing high-purity magnesium fluoride from magnesite.

Background technique

my country's magnesite resource reserves rank first in the world, accounting for one-third of the world's total reserves, mainly distributed in Liaoning, Hebei, Shandong and other provinces and cities. Magnesite has a wide range of uses and can be used in many fields such as refractory materials, ironmaking additives, magnesium oxychloride cement, flue gas desulfurization, acid wastewater treatment, etc. However, it is widely used in these industries and the product price is low. Magnesium fluoride is an important chemical raw material and optical material. High-purity magnesium fluoride has excellent optical properties, thermal stability and chemical stability, and is widely used in optical film materials, catalyst carriers, infrared optics, etc. High-end technology field.

At present, the process of preparing magnesium fluoride from magnesite is to crush and screen the magnesite and directly react with hydrofluoric acid. The magnesite contains calcium, silicon, iron, manganese, aluminum and other impurities and is brought into magnesium fluoride. , the product can only be used as an additive for electrolytic aluminum and magnesium. The production is simple and extensive, and the added value of the product is low.

Other preparation methods of high-purity magnesium fluoride include magnesium oxide preparation method, basic magnesium carbonate preparation method, and brine preparation method. The preparation method of magnesia and basic magnesium carbonate is to use high-purity magnesium oxide or basic magnesium carbonate as raw material to react with hydrogen fluoride to prepare magnesium fluoride, while the raw materials of high-purity magnesium oxide or basic magnesium carbonate are expensive and cost high. The brine preparation method uses ammonia water or ammonium bicarbonate as raw materials to prepare magnesium hydroxide or basic magnesium carbonate, and neutralizes it with hydrogen fluoride to obtain magnesium fluoride. The process needs to consume a large amount of ammonia water, and the precipitation of magnesium ions is not complete, so the cost is also high .

The method of patent application CN103214012A is that hydrogen fluoride gas reacts with high-purity magnesium oxide, magnesium carbonate, magnesium hydroxide or magnesium chloride to obtain high-purity magnesium fluoride through gas phase reaction. In this process, the cost of high-purity magnesium compound raw materials is relatively high, and the reaction temperature is 400 ~ 500 ℃, high corrosion resistance requirements for equipment, resulting in high investment costs. Patent applications CN105776260A and CN101100303A all have the same principle as the preparation of magnesium fluoride from brine, and the methods are that magnesium hydroxide is reacted with ammonia water to prepare magnesium hydroxide, and then magnesium hydroxide is reacted with hydrofluoric acid, dried and calcined to obtain high Pure magnesium fluoride, this method needs to consume a large amount of ammonia water, and the precipitation is not complete when magnesium ions prepare magnesium hydroxide, so the cost is higher. The current existing methods are costly in terms of raw material sources and equipment requirements.

Contents of the invention

The object of the present invention is to provide a method for preparing magnesium fluoride from magnesite with low cost, low energy consumption and high product purity in view of the above technical problems.

The technical solution adopted for achieving the above object is: a method for preparing high-purity magnesium fluoride from magnesite, comprising the steps of:

1) Calcining magnesite to obtain light-burned magnesia ore powder;

2) Take lightly burned magnesia ore powder, add it to the ammonium salt solution and stir to remove soluble calcium, filter to obtain a filter cake; the ammonium salt is one of ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium oxalate or ammonium acetate or more;

3) adding the filter cake obtained in step 2) into an organic acid solution for reaction, and filtering the solution after the reaction to obtain a leachate; the organic acid is formic acid, acetic acid, propionic acid, lactic acid, citric acid, glycolic acid, malonic acid, One or more of succinic acid or adipic acid;

4) adding hydrofluoric acid to the leaching solution obtained in step 3), generating a precipitate, filtering, washing, and drying to obtain high-purity magnesium fluoride.

The molar ratio of the ammonium salt to the CaO in the light-burned magnesia ore powder in the step 2) is: 50-2:1. The lightly burned powder obtained after calcination of magnesite can be analyzed by conventional techniques to obtain the content of CaO.

The reaction temperature of the step 3) is 50-100° C., and the time is 15-120 minutes.

The amount of the organic acid used in step 3) is determined by the carboxyl group contained in the organic acid, and the molar ratio of -COOH:MgO is 1:0.1-4.

The amount of hydrofluoric acid used in step 4) is determined according to the carboxyl group contained in the organic acid added in step 3), and the molar ratio of HF:-COOH is 0.2˜1.2:1.

The condition for calcining the magnesite in the step 1) is calcination at 800-1200° C. for 0.5-2 hours.

The beneficial effects of the invention are: wide sources of raw materials, low cost, low equipment requirements, high-purity magnesium fluoride can be obtained by using cheap magnesite, and the production cost of high-purity magnesium fluoride is greatly reduced. The organic acid used in the process of the invention can be recycled and reused, has low cost, low reaction temperature, low energy consumption and good economic value.

Description of drawings

Fig. 1 is the process flow chart of the inventive method.

Fig. 2 is the XRD spectrum of the magnesium fluoride product that the inventive method obtains.

detailed description

The specific implementation manner of the present invention will be described below in conjunction with the accompanying drawings.

As shown in Table 1, it is the chemical composition analysis result of the magnesite raw material used in the embodiment of the present invention. After the magnesite is calcined at high temperature, the weight loss is constant, the MgO content is 90%, and the calcium oxide content is 2.1%. This is calcined magnesite The amount of ore added and the ammonium salt used for calcium removal provide the basis.

Table 1. The used magnesite raw material chemical composition of the present invention

Prepare high-purity magnesium fluoride, operate according to the following steps (technical process of the present invention as shown in Figure 1):

1) Using the aforementioned magnesite as raw material, calcining at 800-1200°C for 0.5-2 hours to obtain light-burned magnesia mixture, and then crushing and sieving to obtain light-burned magnesia ore powder with a particle size of -200 mesh.

2) Take 1.1 kg of light-burned magnesia ore powder, add it to an ammonium salt solution, stir to remove soluble calcium, and filter to obtain a filter cake. The amount of ammonium salt added is determined according to the calcium oxide in the calcined light-burned magnesia ore powder. The ammonium salt can be excessive to remove the calcium in the ore powder, and the solubility of magnesium in the ammonium salt is very small at room temperature, so the magnesium oxide is still in the filter cake.

3) Add the filter cake to the organic acid solution, the reaction temperature is 50-100° C., and the time is 15-120 minutes. After the reaction is completed, the solution is filtered to obtain the leaching solution.

4) adding hydrofluoric acid to the leaching solution to generate a precipitate, filtering the generated precipitate, washing and drying to obtain high-purity magnesium fluoride. The obtained filtrate is an organic acid solution, which can be recycled.

Using different ammonium salts and organic acids, there are 9 examples in total, and the specific parameters in the preparation methods of different examples are shown in Table 2.

Table 2. Each step reaction parameter in embodiment 1～9

Note: The amount of ammonium salt, organic acid, and HF in the table refers to the mass of the solute added to the solution rather than the mass of the solution

Carry out XRD analysis to the magnesium fluoride obtained in Examples 1-9, the results are shown in Figure 2, compared with the standard card PDF#70-2269, the peaks are sharp, the symmetry is good, no miscellaneous peaks are seen, qualitatively indicating that the purity is very high .

The magnesium fluoride obtained in Examples 1-9 was analyzed by XRF, and the results are shown in Table 3. It can be seen that the magnesium fluoride prepared in each embodiment has high purity, magnesium fluoride content ≥ 99.90%, and few impurities.

Table 3. XRF composition analysis results of magnesium fluoride products

Claims (6)

1. a method for preparing high-purity magnesium fluoride from magnesite, is characterized in that, comprises the steps: 1) Calcining magnesite to obtain light-burned magnesia ore powder; 2) Take lightly burned magnesia ore powder, add it to the ammonium salt solution and stir to remove soluble calcium, filter to obtain a filter cake; the ammonium salt is one of ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium oxalate or ammonium acetate or more; 3) adding the filter cake obtained in step 2) into an organic acid solution for reaction, and filtering the solution after the reaction to obtain a leachate; the organic acid is formic acid, acetic acid, propionic acid, lactic acid, citric acid, glycolic acid, malonic acid, One or more of succinic acid or adipic acid; 4) adding hydrofluoric acid to the leaching solution obtained in step 3), generating a precipitate, filtering, washing, and drying to obtain high-purity magnesium fluoride. 2. the method for preparing high-purity magnesium fluoride from magnesite as claimed in claim 1 is characterized in that, the mol ratio of ammonium salt and CaO in light-burned magnesia ore powder in described step 2) is: 50～2 :1. 3. The method for preparing high-purity magnesium fluoride from magnesite as claimed in claim 1, characterized in that, the reaction temperature of the step 3) is 50-100°C, and the time is 15-120min. 4. the method for preparing high-purity magnesium fluoride from magnesite as claimed in claim 1 is characterized in that, step 3) in the usage amount of organic acid is determined by the contained carboxyl of organic acid, is-COOH:MgO The molar ratio is 1:0.1～4. 5. the method for preparing high-purity magnesium fluoride from magnesite as claimed in claim 1 is characterized in that, the usage amount of hydrofluoric acid in the described step 4) is according to the contained in the organic acid added in the step 3). The carboxyl group is determined, and the molar ratio of HF:-COOH is 0.2～1.2:1. 6. The method for preparing high-purity magnesium fluoride from magnesite as claimed in claim 1, characterized in that the condition for calcining magnesite in said step 1) is calcination at 800-1200°C for 0.5-2h.