Method for preparing hydrated calcium silicate through deep defluorination of fluorine-silicon slag

Abstract

The invention discloses a method for preparing hydrated calcium silicate through deep defluorination of fluorosilicon slag. Fluorine silicon slag is used as a raw material, high-purity silicon dioxide gel is prepared after deep defluorination, and then hydrated calcium silicate is prepared by using the high-purity silicon dioxide gel as a raw material. The method disclosed by the invention is simple in process, low in cost, high in purity, relatively high in reaction efficiency and more sufficient in reaction, more importantly, high-valued reutilization of the fluorosilicon slag is realized, and the problems of stockpiling waste and environmental pollution of the fluorosilicon slag are solved.

Description

Technical Field

[0001] This invention relates to a method for preparing hydrated calcium silicate, and more particularly to a method for preparing hydrated calcium silicate by deep defluorination of fluorosilicone slag. 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] Calcium silicate hydrate is a hydrated calcium silicate mineral, typically possessing two different structures: calcium silicate hydrate type 11 and calcium silicate hydrate type 14. This substance was first discovered on the Isle of Mar in Scotland in 1880. As a major product of cement hydration, accounting for approximately 50%-60% of all hydration products, it is the primary gel phase in concrete.

[0005] In traditional cement hydration processes, the hydration reaction proceeds relatively slowly due to a lack of sufficient nucleation sites. However, when hydrated calcium silicate powder is introduced into the cement paste, these powder particles can act as additional nucleation sites, promoting the formation of more hydration products. This increased number of nucleation sites significantly improves the speed and efficiency of the hydration reaction.

[0006] Furthermore, the addition of hydrated calcium silicate powder can improve the overall performance of cement paste. Due to its smaller particle size and higher specific surface area, hydrated calcium silicate powder can be better dispersed in cement paste, thereby improving the uniformity and stability of the paste. This not only helps to improve the early strength of concrete but also enhances its long-term properties, such as durability and crack resistance.

[0007] Therefore, by introducing hydrated calcium silicate powder as seed crystals, the hydration process of cement can be significantly accelerated, early strength can be improved, and the overall performance of concrete can be enhanced.

[0008] There are various traditional methods for preparing calcium silicate hydrate, mainly hydrothermal methods, solution reaction methods, and solid-phase reaction methods. These methods usually use high-purity commercially available calcium and silicon sources, which is costly. In order to reduce costs and promote the utilization of industrial by-products, there is an increasing amount of research on using industrial by-products such as fly ash and white mud as raw materials to prepare calcium silicate hydrate. However, although there are many such studies, the basic idea is to process industrial by-products to provide the calcium and / or silicon required for calcium silicate hydrate, and then prepare calcium silicate hydrate through reaction.

[0009] The applicant's research found that the main problems with current industrial by-product methods are that the calcium and / or silicon sources obtained from industrial by-product treatment are mostly solid-solid reactions when participating in the reaction, resulting in low reaction efficiency and incomplete reaction. In addition, since fluorine is contained in fluorosilicone slag, it will hinder the formation of hydrated calcium silicate. Therefore, there are currently no reports on the preparation of hydrated calcium silicate using fluorosilicone slag.

[0010] The purpose of this invention is to provide a method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate. The method of this invention is simple, low-cost, produces high purity, and has high reaction efficiency and more complete reaction. More importantly, it enables the high-value reuse of fluorosilicone slag, solving the problems of slag storage waste and environmental pollution.

[0011] A method for preparing hydrated calcium silicate by deep defluorination of fluorosilicone slag involves using fluorosilicone slag as raw material, preparing high-purity silica gel after deep defluorination, and then using the high-purity silica gel as raw material to prepare hydrated calcium silicate.

[0012] Preferably, the aforementioned method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate comprises the following specific steps: S1. Dissolve the fluorosilicone slag in sodium hydroxide solution to obtain solution A; S2. Add dilute sulfuric acid to solution A and react until a gel is obtained. Then filter to obtain the filtrate and high-purity silica gel. S3. Dissolve the high-purity silica gel in sodium hydroxide solution, then add calcium hydroxide to react. Filter and dry the reaction product to obtain hydrated calcium silicate.

[0013] Preferably, in the aforementioned method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate, the concentration of the sodium hydroxide solution in step S1 is 80-100 g / L.

[0014] Preferably, in the aforementioned method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate, the concentration of the fluorosilicone slag in solution A in step S1 is 80-120 g / L.

[0015] Preferably, in the aforementioned method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate, in step S1, the dissolution is carried out by heating and stirring at 90-100°C for 0.5-3 hours.

[0016] Preferably, in the aforementioned method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate, after adding dilute sulfuric acid to solution A in S2, the pH value of solution A is 9-10.

[0017] Preferably, in the aforementioned method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate, the concentration of the sodium hydroxide solution in S3 is 20-40 g / L; and the mass ratio of silica gel to sodium hydroxide is 28-32:1.

[0018] Preferably, in the aforementioned method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate, in step S3, after adding calcium hydroxide, the Ca / Si molar ratio in the solution is 1:1.

[0019] Preferably, in the aforementioned method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate, in step S3, after adding calcium hydroxide, the reaction is carried out at 100-140℃ for 5-15 hours.

[0020] Preferably, in the aforementioned method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate, in step S3, the drying is performed under vacuum conditions at 30-50°C.

[0021] 1. This invention uses fluorosilicone slag as raw material to prepare hydrated calcium silicate, realizing the waste reuse of fluorosilicone slag and solving the problems of fluorosilicone slag storage waste and environmental pollution.

[0022] 2. The preparation process of the hydrated calcium silicate of the present invention is simple and conducive to industrial implementation.

[0023] 3. The hydrated calcium silicate of the present invention has a low preparation cost and a good market prospect.

[0024] 4. The present invention prepares hydrated calcium silicate using fluorosilicone slag as raw material while avoiding the influence of fluorine on hydrated calcium silicate, thus realizing the process route for preparing hydrated calcium silicate using fluorosilicone slag as raw material.

[0025] 5. The calcium silicate hydrate of the present invention is prepared from the intermediate high-purity silica gel as raw material, and has the advantages of high purity, complete reaction and high reaction efficiency.

[0026] In summary, the method of the present invention is simple, low-cost, high-purity, and has high reaction efficiency and more complete reaction. More importantly, it realizes the high-value reuse of fluorosilicone slag, solving the problems of fluorosilicone slag storage waste and environmental pollution. Attached Figure Description

[0027] Appendix Figure 1 The XRD pattern of the calcium silicate hydrate synthesized in this invention is shown. Appendix Figure 2 This is a SEM image of the hydrated calcium silicate synthesized in this invention. Detailed Implementation

[0028] 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.

[0029] The chemical composition of the fluorosilicone slag used in the following embodiments of the present invention is shown in the table below: Embodiments of the present invention Example 1

[0030] The specific steps of the method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate are as follows: S1. Dissolve fluorosilicone slag in a sodium hydroxide solution with a concentration of 90 g / L, heat and stir at 950℃ for 2 h 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, and react until a gel is obtained. Then filter to obtain the filtrate and high-purity silica gel. S3. Then, dissolve the high-purity silica gel in a sodium hydroxide solution with a concentration of 30 g / L, control the mass ratio of silica gel to sodium hydroxide to be 30:1, and then add calcium hydroxide according to the Ca / Si molar ratio of 1:1. React at 120℃ for 10 h, filter the reaction product, and dry it under vacuum at 40℃ to obtain hydrated calcium silicate. Example 2

[0031] The specific steps of the method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate are as follows: S1. Dissolve fluorosilicone slag in a sodium hydroxide solution with a concentration of 80 g / L, heat and stir at 90°C for 3 h to obtain solution A, wherein the concentration of fluorosilicone slag is 80 g / L; S2. Add dilute sulfuric acid to solution A until the pH value is 9, and react until a gel is obtained. Then filter to obtain the filtrate and high-purity silica gel. S3. Dissolve the high-purity silica gel in a sodium hydroxide solution with a concentration of 20 g / L, and control the mass ratio of silica gel to sodium hydroxide to be 28:1. Then add calcium hydroxide according to the Ca / Si molar ratio of 1:1, react at 100℃ for 15 h, filter the reaction product, and dry it under vacuum at 30℃ to obtain hydrated calcium silicate. Example 3

[0032] The specific steps of the method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate are as follows: S1. Dissolve fluorosilicone slag in a sodium hydroxide solution with a concentration of 100 g / L, 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, and react until a gel is obtained. Then filter to obtain the filtrate and high-purity silica gel. S3. Dissolve the high-purity silica gel in a sodium hydroxide solution with a concentration of 40 g / L, and control the mass ratio of silica gel to sodium hydroxide to be 32:1. Then add calcium hydroxide at a Ca / Si molar ratio of 1:1, react at 140℃ for 5 h, filter the reaction product, and dry it under vacuum at 50℃ to obtain hydrated calcium silicate. Example 4

[0033] The specific steps of the method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate are as follows: S1. Dissolve fluorosilicone slag in a sodium hydroxide solution with a concentration of 85 g / L, heat and stir at 90°C for 2.5 h to obtain solution A, in which the concentration of fluorosilicone slag is 90 g / L; S2. Add dilute sulfuric acid to solution A until the pH value is 9, and react until a gel is obtained. Then filter to obtain the filtrate and high-purity silica gel. S3. Dissolve the high-purity silica gel in a sodium hydroxide solution with a concentration of 25 g / L, and control the mass ratio of silica gel to sodium hydroxide to be 29:1. Then add calcium hydroxide at a Ca / Si molar ratio of 1:1, react at 110℃ for 12 h, filter the reaction product, and dry it under vacuum at 35℃ to obtain hydrated calcium silicate. Example 5

[0034] The specific steps of the method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate are as follows: S1. Dissolve fluorosilicone slag in a sodium hydroxide solution with a concentration of 95 g / L, heat and stir at 100°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, and react until a gel is obtained. Then filter to obtain the filtrate and high-purity silica gel. S3. Dissolve the high-purity silica gel in a sodium hydroxide solution with a concentration of 35 g / L, and control the mass ratio of silica gel to sodium hydroxide to be 31:1. Then add calcium hydroxide according to the Ca / Si molar ratio of 1:1, react at 130℃ for 8 hours, filter the reaction product, and dry it under vacuum at 45℃ to obtain calcium silicate hydrate.

[0035] Experimental Example The hydrated calcium silicate synthesized in Examples 1-5 was added to cement at a dosage of 5%, and its effect on cement strength was tested. The aforementioned cement mixture was poured into molds, cured at 20°C and 95% humidity for 1 day, and then molded and demolded. The compressive strength of the resulting specimens was measured after demolding. The results are shown in the table below: serial number 1d 3d 7d 28d Blank group 4.33 12.88 27.96 42.81 Example 1 7.88 26.33 31.64 42.78 Example 2 7.35 18.69 25.09 39.08 Example 3 8.74 24.67 32.93 42.41 Example 4 8.84 20.00 27.43 49.00 Example 5 8.21 23.81 29.24 41.42 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 deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate, characterized in that: The process involves using fluorosilicone slag as raw material, undergoing deep defluorination to prepare high-purity silica gel, and then using the high-purity silica gel as raw material to prepare hydrated calcium silicate.

2. The method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate according to claim 1, characterized in that, The specific steps of the method are as follows: S1. Dissolve the fluorosilicone slag in sodium hydroxide solution to obtain solution A; S2. Add dilute sulfuric acid to solution A and react until a gel is obtained. Then filter to obtain the filtrate and high-purity silica gel. S3. Dissolve the high-purity silica gel in sodium hydroxide solution, then add calcium hydroxide to react. Filter and dry the reaction product to obtain hydrated calcium silicate.

3. The method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate according to claim 2, characterized in that: The concentration of the sodium hydroxide solution in step S1 is 80-100 g / L.

4. The method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate according to claim 2, characterized in that: The concentration of the fluorosilicone slag in solution A in step S1 is 80-120 g / L.

5. The method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate according to claim 2, characterized in that: In step S1, the dissolution is carried out by heating and stirring at 90-100°C for 0.5-3 hours.

6. The method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate according to claim 2, characterized in that: After adding dilute sulfuric acid to solution A of S2, the pH value of solution A is 9-10.

7. The method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate according to claim 2, characterized in that: The concentration of the sodium hydroxide solution in S3 is 20-40 g / L; the mass ratio of silica gel to sodium hydroxide is 28-32:

1.

8. The method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate according to claim 2, characterized in that: In S3, after adding calcium hydroxide, the Ca / Si molar ratio in the solution is 1:

1.

9. The method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate according to claim 2, characterized in that: In step S3, after adding calcium hydroxide, the reaction is carried out at 100-140℃ for 5-15 hours.

10. The method for deep defluorination of fluorosilicone slag to prepare hydrated calcium silicate according to claim 2, characterized in that: In S3, the drying is performed under vacuum conditions at 30-50°C.

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