Method for recovering high-purity fluorine and silicon from fluorine-silicon slag and co-producing low-alkali fluorine-free accelerator

Abstract

The invention discloses a method for recovering high-purity fluorine and silicon from fluorine-silicon slag and co-producing a low-alkali fluorine-free accelerator, which comprises the following steps: S1, dissolving the fluorine-silicon slag in a sodium hydroxide solution to obtain a solution A; s2, adding dilute sulphuric acid into the solution A, reacting until gel is obtained, and filtering to obtain filtrate A and high-purity silicon dioxide gel; s3, adding calcium sulfate and EDTA (Ethylene Diamine Tetraacetic Acid) into the filtrate A, stirring and reacting, and filtering after the reaction is finished to obtain calcium fluoride and filtrate B; and S4, taking clear water, heating, carrying out heat preservation, then adding aluminum sulfate, lithium sulfate, diethanol amine and the filtrate B obtained in S3, continuously stirring until the aluminum sulfate is completely dissolved, then adding hydrated magnesium silicate, continuously carrying out heat preservation stirring, and obtaining the low-alkali fluorine-free accelerator after stirring is finished. The method is simple in process and easy to implement industrially, and fluoride and silicon oxide obtained through separation are high in purity and beneficial to follow-up extension application; more importantly, high-value recycling of the fluorosilicon slag is achieved, and the problems of stockpiling waste and environmental pollution of the fluorosilicon slag are solved.

Description

A method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent in parallel. Technical Field

[0001] This invention relates to a method for preparing hydrated calcium silicate, and more particularly to a method for recovering high-purity fluorine and silicon from fluorosilicone slag to produce a low-alkali, fluorine-free quick-setting agent. Background Technology

[0002] With the imminent depletion of fluorite resources—the primary raw material for anhydrous hydrogen fluoride production—the method of producing anhydrous hydrogen fluoride using fluorosilicic acid, a byproduct of phosphate fertilizer production, as a raw material is gaining increasing attention. This method can not only effectively alleviate the shortage of fluorite resources but also reduce production costs and improve economic efficiency to some extent. However, the process of producing anhydrous hydrogen fluoride using fluorosilicic acid as a raw material generates a large amount of fluorinated silica slag byproducts. If these fluorinated silica slags are not effectively treated and utilized, they will cause serious environmental pollution and further hinder the healthy and sustainable development of the anhydrous hydrogen fluoride industry.

[0003] Therefore, how to efficiently recover and reuse the useful components in fluorosilicon slag, especially silicon and fluorine, has become a major problem that urgently needs to be solved. To address this challenge, numerous researchers and enterprises have invested significant effort in related research. They hope to find more environmentally friendly and economically feasible solutions through technological innovation to achieve the effective recovery and comprehensive utilization of silicon and fluorine resources in fluorosilicon slag. This is not only of great significance for protecting the ecological environment, but also can bring new economic growth points to enterprises and promote the transformation of the entire industrial chain towards a green and low-carbon direction. In short, exploring a scientific, rational, economical, and efficient fluorosilicon slag treatment technology system will be key to promoting the sustainable and healthy development of the anhydrous hydrogen fluoride industry.

[0004] Current research indicates that methods for recovering fluorine and silicon from fluorosilicone slag mainly include chemical precipitation, adsorption, and membrane separation. However, adsorption and membrane separation are relatively expensive and primarily target the removal of ultra-low concentrations of fluorine. Therefore, chemical precipitation remains the mainstream method, which involves reacting chemical reagents with fluorine in the solution to obtain fluorinated precipitates, thus achieving the separation and removal of fluorine and silicon.

[0005] Chemical precipitation is mainly based on calcium salt precipitation. Calcium salt is added to a sodium fluorosilicate solution to form calcium fluoride precipitate, thereby separating fluoride. However, this method easily produces calcium silicate precipitate, resulting in low purity of calcium fluoride and affecting the subsequent use of fluoride.

[0006] In addition, chemical precipitation processes generate a large amount of waste liquid, the treatment of which increases the cost for production enterprises. Furthermore, the waste liquid contains a large number of valuable components. How to reduce the treatment cost of the waste liquid and promote its recycling and reuse is also a problem that researchers in this field need to consider.

[0007] Therefore, the main technical objective of this invention is to efficiently and accurately separate fluorine and silicon from fluorosilicone slag and to directly utilize the waste liquid.

[0008] The purpose of this invention is to provide a method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing a low-alkali, fluorine-free quick-setting agent in parallel. The method of this invention is simple, easy to implement industrially, and yields high-purity fluorides and silicon oxides, which are beneficial for their subsequent applications. More importantly, it realizes the high-value reuse of fluorosilicone slag, solving the problems of slag storage waste and environmental pollution.

[0009] A method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing a low-alkali, fluorine-free quick-setting agent includes the following steps: S1. Dissolving fluorosilicone slag in sodium hydroxide solution to obtain solution A; S2. Adding dilute sulfuric acid to solution A and reacting for 7-10 minutes to obtain a gel, which is then filtered to obtain filtrate A and high-purity silica gel; S3. Adding calcium sulfate and EDTA to filtrate A and stirring to react, then filtering after the reaction is complete to obtain calcium fluoride and filtrate B; S4. Heating and keeping the water warm, then adding aluminum sulfate, lithium sulfate, diethanolamine and filtrate B from S3, and stirring continuously until the aluminum sulfate is completely dissolved, then adding hydrated magnesium silicate, and continuing to keep warm and stir, until the low-alkali, fluorine-free quick-setting agent is obtained after stirring.

[0010] In the aforementioned method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent, the concentration of the sodium hydroxide solution in step S1 is 80-100 g / L.

[0011] In the aforementioned method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent in parallel, the concentration of the fluorosilicone slag in solution A in step S1 is 80-120 g / L.

[0012] In the aforementioned method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent, in step S1, the dissolution is carried out by heating and stirring at 90-100°C for 0.5-3 hours.

[0013] In the aforementioned method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent, after adding dilute sulfuric acid to solution A in S2, the pH value of solution A is 9-10.

[0014] In the aforementioned method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent in parallel, when calcium sulfate is added in step S3, the Ca / F molar ratio is 1:2.

[0015] In the aforementioned method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent, when EDTA is added in step S3, the molar ratio of EDTA to calcium ions in calcium sulfate is 1:1.

[0016] In the aforementioned method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent in parallel, the reaction time described in S3 is 20-30 hours.

[0017] In the aforementioned method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent, the heat preservation temperature in step S4 is 40-60℃.

[0018] In the aforementioned method for recovering high-purity fluorine and silicon from fluorosilicon slag and producing low-alkali, fluorine-free quick-setting agent, in step S4, the Na in the low-alkali, fluorine-free quick-setting agent... + The mass concentration is <1%.

[0019] 1. This invention uses fluorosilicone slag as raw material and separates and recovers valuable elements such as fluorine and silicon from it, realizing the waste reuse of fluorosilicone slag and solving the problems of fluorosilicone slag storage waste and environmental pollution.

[0020] 2. The process for recovering and separating fluorine and silicon in this invention is simple and easy to implement industrially.

[0021] 3. This invention achieves efficient separation of fluorine and silicon by first obtaining silica gel and then precipitating and separating fluorine in solution. The obtained silicon oxides and fluorides have the advantage of high purity, which is beneficial for their subsequent extended applications.

[0022] 4. The process of the present invention not only separates and recovers fluorine and silicon, but also reuses the waste liquid, eliminating the need for waste liquid treatment, reducing the burden on production enterprises, and reducing resource waste.

[0023] In summary, the method of this invention is simple and easy to implement industrially, and the fluorides and silicon oxides obtained by separation are of high purity, which is conducive to their subsequent extended applications. More importantly, it realizes the high-value reuse of fluorosilicone slag and solves the problems of fluorosilicone slag storage waste and environmental pollution. Attached Figure Description

[0024] Figure 1 shows the XRD pattern of the calcium fluoride recovered in this invention.

[0025] Figure 2 shows the XRD pattern of the silica gel recovered in this invention. Detailed Implementation

[0026] The present invention will be further described below with reference to embodiments, but these embodiments are not intended to limit the scope of the invention.

[0027] Embodiment 1 of the present invention

[0028] A method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing a low-alkali, fluorine-free quick-setting agent in parallel is described below: S1. Dissolve the fluorosilicone slag in a 90 g / L sodium hydroxide solution, heat and stir at 95°C for 2 hours to obtain solution A, in which the concentration of fluorosilicone slag is 100 g / L; S2. Add dilute sulfuric acid to solution A until the pH value is 9.5, react for 7 minutes until gel is obtained, then filter to obtain filtrate A and high-purity silica gel; S3. Add calcium sulfate to filtrate A at a Ca / F molar ratio of 1:2, and simultaneously add EDTA, and stir to react for 24 hours. After the reaction is completed, filter to obtain calcium fluoride and filtrate B; S4. Heat water to 50°C and keep warm, then add 300 g aluminum sulfate, 5 g lithium sulfate, 50 g diethanolamine and 50 g filtrate B, and continue stirring until the aluminum sulfate is completely dissolved. Then add 6 g hydrated magnesium silicate, and continue stirring and keeping warm for 2 hours. After stirring, a low-alkali, fluorine-free quick-setting agent is obtained. Example 2

[0029] A method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing a low-alkali, fluorine-free quick-setting agent in parallel is described below: S1. Dissolve the fluorosilicone slag in an 80 g / L sodium hydroxide solution, heat and stir at 90°C for 3 hours to obtain solution A, in which the concentration of fluorosilicone slag is 80 g / L; S2. Add dilute sulfuric acid to solution A until the pH value is 9, react for 10 minutes until gel is obtained, then filter to obtain filtrate A and high-purity silica gel; S3. Add calcium sulfate to filtrate A at a Ca / F molar ratio of 1:2, and simultaneously add EDTA, and stir to react for 20 hours. After the reaction is completed, filter to obtain calcium fluoride and filtrate B; S4. Heat water to 40°C and keep warm, then add 250 g aluminum sulfate, 2 g lithium sulfate, 40 g diethanolamine and 40 g filtrate B, and continue stirring until the aluminum sulfate is completely dissolved. Then add 4 g hydrated magnesium silicate, and continue stirring and keeping warm for 1 hour. After stirring, a low-alkali, fluorine-free quick-setting agent is obtained. Example 3

[0030] The method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing a low-alkali, fluorine-free quick-setting agent in parallel is as follows: S1. Dissolve the fluorosilicone slag in a 100 g / L sodium hydroxide solution, heat and stir at 100°C for 0.5 h to obtain solution A, in which the concentration of fluorosilicone slag is 120 g / L; S2. Add dilute sulfuric acid to solution A until the pH value is 10, react for 8 min until gel is obtained, and then filter to obtain filtrate A and high-purity silica gel; S3. Add calcium sulfate to filtrate A at a Ca / F molar ratio of 1:2, and add EDTA at the same time, and stir and react for 30 h. After the reaction is completed, filter to obtain calcium fluoride and filtrate B; S4. Heat water to 60°C and keep it warm, then add 350 g aluminum sulfate, 8 g lithium sulfate, 60 g diethanolamine and 60 g filtrate B, and continue stirring until the aluminum sulfate is completely dissolved. Then add 8 g hydrated magnesium silicate, and continue to keep it warm and stir for 3 h. After stirring, a low-alkali, fluorine-free quick-setting agent is obtained. Example 4

[0031] A method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing a low-alkali, fluorine-free quick-setting agent is described below: S1. Dissolve the fluorosilicone slag in an 85 g / L sodium hydroxide solution, heat and stir at 92°C for 2.5 h to obtain solution A, where the concentration of the fluorosilicone slag is 90 g / L; S2. Add dilute sulfuric acid to solution A until the pH reaches 9, react for 9 min until gel is obtained, then filter to obtain filtrate A and high-purity silica gel; S3. Add calcium sulfate to filtrate A at a Ca / F molar ratio of 1:2, simultaneously add EDTA, and stir for 22 h. After the reaction, filter to obtain calcium fluoride and filtrate B; S4. Heat water to 45°C and maintain the temperature, then add 280 g aluminum sulfate, 4 g lithium sulfate, 45 g diethanolamine, and 45 g filtrate B, and continue stirring until the aluminum sulfate is completely dissolved. Then add 5 g hydrated magnesium silicate and continue stirring for 1 h. After stirring, a low-alkali, fluorine-free quick-setting agent is obtained. Example 5

[0032] The method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing a low-alkali, fluorine-free quick-setting agent in parallel is as follows: S1. Dissolve the fluorosilicone slag in a 95 g / L sodium hydroxide solution, heat and stir at 95°C for 1 h to obtain solution A, in which the concentration of fluorosilicone slag is 110 g / L; S2. Add dilute sulfuric acid to solution A until the pH value is 10, react for 7 min until gel is obtained, then filter to obtain filtrate A and high-purity silica gel; S3. Add calcium sulfate to filtrate A at a Ca / F molar ratio of 1:2, and add EDTA at the same time, stir and react for 28 h, filter after the reaction is completed to obtain calcium fluoride and filtrate B; S4. Heat water to 55°C and keep it warm, then add 320 g aluminum sulfate, 7 g lithium sulfate, 55 g diethanolamine and 55 g filtrate B, and continue stirring until the aluminum sulfate is completely dissolved, then add 7 g hydrated magnesium silicate, and continue to keep warm and stir for 3 h, after stirring, a low-alkali, fluorine-free quick-setting agent is obtained.

[0033] In this experiment, the low-alkali, fluorine-free liquid accelerator synthesized in Examples 1-5 was added to cement at an 8% dosage to test its effect on cement strength. The test method followed standard GB / T 35159-2017. The mixture was poured into molds and cured at 20℃ and 95% humidity for 1 day before molding and demolding. The compressive strength of the resulting specimens was measured after demolding. The results are shown in the table below: Example 1: 9.37; Example 2: 9.59; Example 3: 9.59; Example 4: 9.14; Example 5: 9.98; Example 6: 9.98; Example 7: 9.41; Example 8: 9.39; Example 9: 9.41; Example 1: 9.39; Example 2: 9.39; Example 3: 9.19; Example 4: 9.12; Example 5: 9.41; Example 6: 9.35; Example 7: 9.22; Example 8: 9.12; Example 9: 9.41; Example 9: 9.35; Example 1: 9.37; Example 1: 9.39; Example 2: 9.39; Example 3: 9.22; Example 4: 9.39; Example 5: 9.41; Example 6: 9.39; Example 7: 9.39; Example 8: 9.39; Example 9: 9.22; Example 5: 9.35; Example 9: 9.22; Example 5: 9.35; Example 9: 9.41; Example 1: 9.39; Example 1: 9.39; Example 2: 9.39; Example 3: 9.22; Example 5: 9.39; Example 9: 9 The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent in parallel, characterized in that, The steps include: S1. Dissolving fluorosilicone slag in sodium hydroxide solution to obtain solution A; S2. Add dilute sulfuric acid to solution A and react for 7-10 minutes to obtain a gel. Filter the gel to obtain filtrate A and high-purity silica gel. S3. Add calcium sulfate and EDTA to filtrate A and stir to react. After the reaction is complete, filter to obtain calcium fluoride and filtrate B. S4. Heat and keep warm water, then add aluminum sulfate, lithium sulfate, diethanolamine and filtrate B from S3. Stir continuously until the aluminum sulfate is completely dissolved. Then add hydrated magnesium silicate and continue stirring while keeping warm. After stirring, a low-alkali, fluorine-free quick-setting agent is obtained.

2. The method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent according to claim 1, characterized in that: The concentration of the sodium hydroxide solution in step S1 is 80-100 g / L.

3. The method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent according to claim 1, characterized in that: The concentration of the fluorosilicone slag in solution A in step S1 is 80-120 g / L.

4. The method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent according to claim 1, characterized in that: In step S1, the dissolution is carried out by heating and stirring at 90-100°C for 0.5-3 hours.

5. The method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent according to claim 1, characterized in that: After adding dilute sulfuric acid to solution A of S2, the pH value of solution A is 9-10.

6. The method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent according to claim 1, characterized in that: When calcium sulfate is added to S3, the Ca / F molar ratio is 1:

2.

7. The method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent according to claim 1, characterized in that: When EDTA is added to S3, the molar ratio of EDTA to calcium ions in calcium sulfate is 1:

1.

8. The method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent according to claim 1, characterized in that: The reaction time described in S3 is 20-30 hours.

9. The method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent according to claim 1, characterized in that: In S4, the heat preservation temperature is 40-60℃.

10. The method for recovering high-purity fluorine and silicon from fluorosilicone slag and producing low-alkali, fluorine-free quick-setting agent according to claim 1, characterized in that: In S4, the Na in the low-alkali, fluorine-free quick-setting agent + The mass concentration is <1%.

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