A method for reducing the content of fluosilicic acid in magnesium fluosilicate product

Abstract

The application discloses a method for reducing the content of fluosilicic acid in magnesium fluosilicate product, comprising the following steps: 1) analyzing and detecting the content of fluosilicic acid in magnesium fluosilicate crystals; 2) dissolving the magnesium fluosilicate crystals in a saturated magnesium fluosilicate solution to prepare a magnesium fluosilicate solution; and 3) adding a magnesium hydroxide solution into the magnesium fluosilicate solution in a magnesium fluosilicate cooling crystallization tank, and after sufficient reaction, the magnesium fluosilicate is obtained through cooling crystallization, centrifugal separation and drying; the method can reduce the content of fluosilicic acid in the finished product magnesium fluosilicate, and meanwhile, no new impurities are introduced.

Description

Technical Field

[0001] This invention relates to the field of magnesium fluorosilicate production technology, and in particular to a method for reducing the fluorosilicic acid content in magnesium fluorosilicate products. Background Technology

[0002] Magnesium fluorosilicate is widely used in construction, chemical, and materials industries, such as as a concrete reinforcing agent, concrete retarder, concrete surface antifreeze agent, rubber latex coagulant, preservative, and textile moth repellent. In addition, magnesium fluorosilicate can be used to treat permeable cement, manufacture sewage filter pipes, and as a flux, electroplating component, and welding electrode additive. In metal processing, it is used in aluminum and manganese foundries as a grain refiner and polishing agent for active fillers in resin-bonded abrasives. However, during the preparation of magnesium fluorosilicate, the dissolution of magnesium fluorosilicate crystals in water leads to partial dissolution. After the reaction, concentration is required, and the increased temperature during concentration causes the magnesium fluorosilicate to slowly decompose. However, magnesium fluorosilicate decomposes in solution at 70°C, producing magnesium fluoride and silicon tetrafluoride. Silicon tetrafluoride dissolves in water, producing fluorosilicic acid, silicon dioxide, and hydrofluoric acid. Thus, a certain amount of fluorosilicic acid will be present in the magnesium fluorosilicate product. If the concentration temperature is controlled too high, the material will be exposed to excessively high temperatures for a long time, which will lead to excessive fluorosilicic acid content in the magnesium fluorosilicate product, ultimately affecting the quality of the magnesium fluorosilicate product. On the other hand, if the concentration temperature is controlled too low, the concentration time will be slow and new impurities will be easily introduced, resulting in higher production time and process costs for manufacturing and processing companies. Summary of the Invention

[0003] To address the above problems, this invention provides a method for reducing the fluorosilicic acid content in magnesium fluorosilicate products.

[0004] The solution of the present invention is:

[0005] A method for reducing the fluorosilicic acid content in magnesium fluorosilicate products includes the following steps:

[0006] 1) Analyze and detect the fluorosilicic acid content in magnesium fluorosilicate crystals;

[0007] 2) Dissolve magnesium fluorosilicate crystals in a saturated magnesium fluorosilicate solution to prepare a magnesium fluorosilicate solution; the solid-liquid ratio of the magnesium fluorosilicate crystals to the saturated magnesium fluorosilicate solution is 1:3;

[0008] 3) In a magnesium fluorosilicate cooling crystallization tank, magnesium hydroxide solution is added to the magnesium fluorosilicate solution. After the reaction is complete, magnesium fluorosilicate is obtained by cooling crystallization, centrifugation, and drying.

[0009] As a preferred technical solution, the concentration of the magnesium hydroxide solution is 20% to 30%.

[0010] As a preferred technical solution, the amount of magnesium hydroxide solution fed into the cooling crystallization tank is 4.5% to 6.5% of the amount of magnesium fluorosilicate crystals fed.

[0011] As a preferred technical solution, the reaction temperature in the cooling crystallization tank in step 3) is 45℃~65℃.

[0012] As a preferred technical solution, water bath heating is used in the cooling crystallization tank in step 3).

[0013] As a preferred technical solution, the reaction time in the cooling crystallization tank in step 3) is >15 min.

[0014] As a preferred technical solution, the magnesium fluorosilicate crystals are prepared using the following steps:

[0015] S1. Neutralize fluorosilicic acid with magnesia and filter to obtain magnesium fluorosilicate filtrate;

[0016] S2. The magnesium fluorosilicate filtrate obtained in S1 is fed into a vacuum concentration system;

[0017] S3, until the density of the concentrated solution in S2 reaches 1.33 g / cm³. 3 ~1.36g / cm 3 Afterwards, it is placed in a cooling crystallization tank for cooling and crystallization, and then filtered to obtain magnesium fluorosilicate. After airflow drying and separation, magnesium fluorosilicate crystals are obtained; the filtrate obtained from filtration is returned to prepare a saturated magnesium fluorosilicate solution.

[0018] As a preferred technical solution, the concentration temperature in step S2 is controlled to be <70℃.

[0019] A method for reducing the fluorosilicic acid content in magnesium fluorosilicate products using the above-mentioned technical solution includes the following steps: 1) analyzing and detecting the fluorosilicic acid content in magnesium fluorosilicate crystals; 2) dissolving magnesium fluorosilicate crystals in a saturated magnesium fluorosilicate solution to prepare a magnesium fluorosilicate solution; wherein the solid-liquid ratio of the magnesium fluorosilicate crystals to the saturated magnesium fluorosilicate solution is 1:3; 3) adding magnesium hydroxide solution to the magnesium fluorosilicate solution in a magnesium fluorosilicate cooling crystallization tank, and after sufficient reaction, obtaining magnesium fluorosilicate by cooling crystallization, centrifugation, and drying.

[0020] Advantages of this invention:

[0021] 1. This invention uses magnesium hydroxide to neutralize the fluorosilicic acid in magnesium fluorosilicate, which not only reduces the fluorosilicic acid content in magnesium fluorosilicate, but also generates a small amount of magnesium fluorosilicate, thereby increasing the yield of magnesium fluorosilicate and avoiding the harm of introducing new byproducts.

[0022] 2. In this invention, magnesium fluorosilicate crystals are redissolved in a saturated magnesium fluorosilicate solution with a solid-liquid ratio of 1:3, instead of dissolving the magnesium fluorosilicate crystals in water. This is because using water would cause some of the magnesium fluorosilicate crystals to dissolve, and after the reaction, the solution would need to be concentrated again to obtain magnesium fluorosilicate crystals. If the temperature is raised again, the magnesium fluorosilicate dissolved in water would still slowly decompose, generating magnesium fluoride and silicon tetrafluoride. Silicon tetrafluoride dissolves in water to generate fluorosilicic acid, silicon dioxide, and hydrofluoric acid. Therefore, a saturated magnesium fluorosilicate solution is used for dissolution to ensure a fully reacted solid-liquid system, reducing the decomposition of magnesium fluorosilicate during the reaction. After the reaction, the product can be obtained by cooling, crystallizing, centrifuging, and drying.

[0023] 3. In this invention, the reaction of fluorosilicic acid and magnesium hydroxide in magnesium fluorosilicate solution is carried out in a cooling crystallization tank, which reduces material transfer. Appropriate stirring and water bath heating can be performed in the cooling crystallization tank to ensure the full reaction of fluorosilicic acid and magnesium hydroxide. Preferably, this invention reasonably controls the concentration and amount of magnesium hydroxide added to improve the uniformity of magnesium hydroxide dispersion in the industrial reaction system and improve the reaction efficiency.

[0024] 4. In the step of preparing magnesium fluorosilicate crystals in this invention, the filtrate obtained by centrifugation is returned to prepare a saturated magnesium fluorosilicate solution and placed in a cooling crystallization tank to dissolve the magnesium fluorosilicate crystals. At the same time, it can be used to cool the material, reduce the process cost of wastewater treatment, and improve resource utilization. Attached Figure Description

[0025] Figure 1 This is a process flow diagram of the present invention.

[0026] Figure 2 This is a process flow diagram for preparing magnesium fluorosilicate according to the present invention. Detailed Implementation

[0027] This invention provides a method for reducing the fluorosilicic acid content in magnesium fluorosilicate products.

[0028] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments. Example

[0029] A method for reducing the fluorosilicic acid content in magnesium fluorosilicate products includes the following steps:

[0030] 1) Analyze and detect the fluorosilicic acid content in magnesium fluorosilicate crystals;

[0031] 2) Dissolve magnesium fluorosilicate crystals in a saturated magnesium fluorosilicate solution to prepare a magnesium fluorosilicate solution;

[0032] 3) In a magnesium fluorosilicate cooling crystallization tank, magnesium hydroxide solution is added to the magnesium fluorosilicate solution. After the reaction is complete, magnesium fluorosilicate is obtained by cooling crystallization, centrifugation, and drying.

[0033] The concentration of the magnesium hydroxide solution is 20%–30%.

[0034] The amount of magnesium hydroxide solution fed into the cooling crystallization tank is 4.5% to 6.5% relative to the amount of magnesium fluorosilicate crystals fed.

[0035] In step 3), the reaction temperature in the cooling crystallization tank is 45℃~65℃;

[0036] In step 3), a water bath is used to raise the temperature in the cooling crystallization tank;

[0037] In step 3), the reaction time in the cooling crystallization tank is >15 min;

[0038] The magnesium fluorosilicate product is obtained by the following preparation steps:

[0039] (1) Neutralize fluorosilicic acid with magnesia and filter to obtain magnesium fluorosilicate filtrate;

[0040] (2) The magnesium fluorosilicate filtrate is pumped into a vacuum concentration system and the concentration temperature is controlled to be <70℃;

[0041] (3) When the density of the concentrated solution in step (2) reaches 1.33-1.36 g / cm³ 3 Afterwards, the solution is placed in a cooling crystallization tank for cooling and crystallization, and then filtered to obtain magnesium fluorosilicate. After airflow drying and separation, magnesium fluorosilicate product is obtained. The filtrate obtained from filtration is returned to prepare a saturated solution of magnesium fluorosilicate, which is used to dissolve magnesium fluorosilicate crystals in the cooling crystallization tank. Example

[0042] Magnesium fluorosilicate crystals were analyzed to determine their fluorosilicic acid content. Then, 150g of magnesium fluorosilicate crystals were dissolved in 350g of water to prepare a 30% magnesium fluorosilicate solution. A 2% magnesium hydroxide solution was added (relative to the amount of magnesium fluorosilicate crystals added). The reaction was carried out at 50℃ for 2 hours, during which time the pH of the solution was 1–1.5. The solution was filtered to obtain a magnesium fluorosilicate solution. This solution was then heated and concentrated, followed by cooling, crystallization, centrifugation, and drying to obtain the finished magnesium fluorosilicate product. (Note: This is for comparison product 1, and the fluorosilicic acid content in the magnesium fluorosilicate crystals was also determined.) Example

[0043] Magnesium fluorosilicate crystals were analyzed to determine their fluorosilicic acid content. Then, 150g of magnesium fluorosilicate crystals were dissolved in 450g of saturated magnesium fluorosilicate solution to prepare a magnesium fluorosilicate solution with a solid-liquid ratio of 1:3. 4.3% magnesium hydroxide solution was added (relative to the amount of magnesium fluorosilicate crystals added). The reaction was carried out at 50℃ in a water bath for 2 hours, at which point the pH of the solution was 0.5–1. After cooling, crystallization, centrifugation, and drying, the finished magnesium fluorosilicate product was obtained. (Note: This is for comparison product 2.) The fluorosilicic acid content in the magnesium fluorosilicate crystals was also determined. Example

[0044] 150g of magnesium fluorosilicate crystals from the same batch were dissolved in 450g of saturated magnesium fluorosilicate solution to prepare a magnesium fluorosilicate solution with a solid-liquid ratio of 1:3. 4.7% magnesium hydroxide solution was added (relative to the amount of magnesium fluorosilicate crystals fed). The reaction was carried out at a water bath temperature of 50℃ for 2 hours. At this time, the pH value of the solution was 1-1.5. After cooling, crystallization, centrifugation, and drying, the finished magnesium fluorosilicate product was obtained. It was noted as Comparative Product 3. The fluorosilicic acid content in the magnesium fluorosilicate crystals was also tested. Example

[0045] 150g of magnesium fluorosilicate crystals from the same batch were dissolved in 450g of saturated magnesium fluorosilicate solution to prepare a magnesium fluorosilicate solution with a solid-liquid ratio of 1:3. 5% magnesium hydroxide solution was added (relative to the amount of magnesium fluorosilicate crystals added). The reaction was carried out at a water bath temperature of 50℃ for 2 hours. At this time, the pH value of the solution was 1-1.5. After cooling, crystallization, centrifugation, and drying, the finished magnesium fluorosilicate product was obtained. It was noted as Comparative Product 4. The fluorosilicic acid content in the magnesium fluorosilicate crystals was also tested. Example

[0046] 150g of magnesium fluorosilicate crystals from the same batch were dissolved in 450g of saturated magnesium fluorosilicate solution to prepare a magnesium fluorosilicate solution with a solid-liquid ratio of 1:3. 5.6% magnesium hydroxide solution was added (relative to the amount of magnesium fluorosilicate crystals added). The reaction was carried out at a water bath temperature of 50℃ for 2 hours. At this time, the pH value of the solution was 1.5-2. After cooling, crystallization, centrifugation, and drying, the finished magnesium fluorosilicate product was obtained. It was noted as Comparative Product 5. The fluorosilicic acid content in the magnesium fluorosilicate crystals was also tested. Example

[0047] 150g of magnesium fluorosilicate crystals from the same batch were dissolved in 450g of saturated magnesium fluorosilicate solution to prepare a magnesium fluorosilicate solution with a solid-liquid ratio of 1:3. 6.5% magnesium hydroxide solution was added (relative to the amount of magnesium fluorosilicate crystals added). The reaction was carried out at a water bath temperature of 50℃ for 2 hours. At this time, the pH value of the solution was 1.8-1.9. After cooling, crystallization, centrifugation, and drying, the finished magnesium fluorosilicate product was obtained. It was noted as Comparative Product 6. The fluorosilicic acid content in the magnesium fluorosilicate crystals was also tested.

[0048] The indicators for products 1-6 are shown in Table 1 below.

[0049] Table 1:

[0050]

[0051] As shown in Table 1, this application, through continuous optimization, controls the amount of magnesium hydroxide added and adjusts the pH value of the solution to reduce the fluorosilicic acid content in magnesium fluorosilicate crystals under the premise of determining the solid-liquid system. The magnesium fluorosilicate product prepared according to the reaction conditions of Example 7 has the lowest fluorosilicic acid content, meeting the HG / T 2768-2009 "Industrial Magnesium Fluorosilicate" standard.

[0052] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for reducing the fluorosilicic acid content in magnesium fluorosilicate products, characterized in that, Includes the following steps: 1) Analyze and detect the fluorosilicic acid content in magnesium fluorosilicate crystals; 2) Dissolve magnesium fluorosilicate crystals in a saturated magnesium fluorosilicate solution to prepare a magnesium fluorosilicate solution; the solid-liquid ratio of the magnesium fluorosilicate crystals to the saturated magnesium fluorosilicate solution is 1:3; 3) In a magnesium fluorosilicate cooling crystallization tank, magnesium hydroxide solution is added to the magnesium fluorosilicate solution. After the reaction is complete, magnesium fluorosilicate is obtained by cooling crystallization, centrifugation, and drying.

2. The method for reducing the fluorosilicic acid content in magnesium fluorosilicate products as described in claim 1, characterized in that: The concentration of the magnesium hydroxide solution is 20% to 30%.

3. The method for reducing the fluorosilicic acid content in magnesium fluorosilicate products as described in claim 1, characterized in that: The amount of magnesium hydroxide solution fed into the cooling crystallization tank is 4.5% to 6.5% of the amount of magnesium fluorosilicate crystals fed.

4. The method for reducing the fluorosilicic acid content in magnesium fluorosilicate products as described in claim 1, characterized in that: The reaction temperature in the cooling crystallization tank in step 3) is 45℃~65℃.

5. The method for reducing the fluorosilicic acid content in magnesium fluorosilicate products as described in claim 1, characterized in that: In step 3), a water bath is used to raise the temperature in the cooling crystallization tank.

6. The method for reducing the fluorosilicic acid content in magnesium fluorosilicate products as described in claim 1, characterized in that: The reaction time in the cooling crystallization tank in step 3) is >15 min.

7. The method for reducing the fluorosilicic acid content in magnesium fluorosilicate products as described in claim 1, characterized in that, The magnesium fluorosilicate crystals are prepared using the following steps: S1. Neutralize fluorosilicic acid with magnesia and filter to obtain magnesium fluorosilicate filtrate; S2. The magnesium fluorosilicate filtrate obtained in S1 is fed into a vacuum concentration system; S3, until the density of the concentrated solution in S2 reaches 1.33 g / cm³. 3 ~1.36g / cm 3 Afterwards, it is placed in a cooling crystallization tank for cooling and crystallization, and then filtered to obtain magnesium fluorosilicate. After airflow drying and separation, magnesium fluorosilicate crystals are obtained; the filtrate obtained from filtration is returned to prepare a saturated magnesium fluorosilicate solution.

8. The method for reducing the fluorosilicic acid content in magnesium fluorosilicate products as described in claim 7, characterized in that: The concentration temperature controlled by S2 is <70℃.

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