Method for defluorination activation and resource recovery of fluorine-containing silicon slag

Abstract

This invention belongs to the field of resource utilization technology for waste residue from the phosphate fertilizer industry, specifically a method for defluorination, activation, and resource recovery of fluorinated silicon slag. The technical solution involves mixing and stirring the washed and drained fluorinated silicon slag with a non-complexing strong acid solution and a metal cation donor to form a homogeneous mixture. Then, the mixture is heated under stirring to activate the reaction. After the reaction, the mixture is cooled and separated into a solid phase of activated silicon slag and a liquid phase of fluorinated metal mother liquor. The activated silicon slag is used to prepare silicon-based materials, and the fluorinated metal mother liquor is used to prepare fluoride salts. Through the synergistic effect of the non-complexing strong acid and the metal cation, efficient removal of lattice fluorine and activation of the silicon slag are achieved. Simultaneously, the solid-phase silicon slag and liquid-phase fluorine resources are utilized at high value, achieving the effects of solid waste reduction, harmlessness, and full-component resource recovery.

Description

Technical Field

[0001] This invention belongs to the field of resource utilization technology for waste residue in the phosphate fertilizer industry, specifically a method for defluorination activation and resource recovery of fluorinated silicon slag. Background Technology

[0002] The industrial production of phosphate fertilizer generates a large amount of fluorinated silica slag as a byproduct. This waste slag is mainly composed of amorphous SiO2, water, and fluorine. Fluorine exists in two forms: free fluorine and lattice-bound fluorine. The total fluorine content is usually 8-12%, of which lattice-bound fluorine accounts for 40-50%. Lattice-bound fluorine is embedded in the amorphous silica lattice in the form of stable Si-F bonds. Conventional water washing and simple acid washing can only remove free fluorine and cannot effectively remove lattice fluorine, which has become the core technical bottleneck for the resource utilization of fluorinated silica slag.

[0003] In existing technologies, none of the relevant methods for treating fluorinated silicon slag have proposed a targeted approach to remove fluorine from the lattice. They only remove free fluorine through single-acid activation, resulting in a large amount of residual fluorine in the silicon slag. This leads to a persistently high fluorine content in the silicon slag, making it unsuitable as a raw material for the preparation of silicon-based materials, cryolite, and other industrial products, thus wasting valuable silicon and fluorine resources. Furthermore, the slag slowly releases fluoride ions during storage, causing fluoride pollution in soil and water bodies and increasing the environmental protection costs of solid waste treatment for phosphate fertilizer companies. For example, CN101428805B only removes fluorine and aluminum impurities through hydrochloric acid leaching and rinsing, which can only remove surface-attached fluorides and cannot remove lattice-bound fluorine. Moreover, the leaching reaction takes up to 72 hours, resulting in extremely low treatment efficiency. CN113461021A uses a sulfuric acid wet process to purify fluorinated silicon slag to prepare silica, but this method is only suitable for silicon slag produced by the fluorosilicic acid process for aluminum fluoride production. This method has narrow raw material compatibility and does not achieve the recovery and utilization of fluorine resources. It only extracts silicon dioxide, resulting in low resource utilization. CN118479487A requires the preparation of Fe3O4@SiO2 magnetic nanoparticles for defluorination, which involves a complex and costly process. The magnetic particles also easily introduce secondary impurities, making subsequent separation difficult. While CN120534976A achieves separate recovery of fluorine and silicon, it only removes free fluorine and has no effect on lattice fluorine. Furthermore, the sulfuric acid concentration has a significant impact on the fluorine recovery rate, the process parameter control window is narrow, and industrial stability is poor.

[0004] In summary, existing methods for treating fluorinated silicon slag generally lack a targeted approach to the removal of lattice fluorine, resulting in incomplete defluorination, lengthy processes, high costs, poor raw material compatibility, and the inability to simultaneously achieve high-value utilization of silicon and fluorine. These methods fail to meet the practical needs of the phosphate fertilizer industry for efficient, environmentally friendly, and high-value resource recovery of bulk fluorinated silicon slag. Therefore, there is an urgent need in this field for a defluorination activation and resource recovery method for fluorinated silicon slag that can efficiently and deeply remove lattice fluorine, employ a mild and simple process, allow flexible raw material selection, and enable the resource recovery of all silicon and fluorine components. Summary of the Invention

[0005] The purpose of this invention is to solve the aforementioned technical problems. Addressing the issues of incomplete lattice fluorine removal, low resource utilization, complex processes, and difficulty in industrialization in existing fluorine-containing silicon slag treatment processes, this invention provides a method for defluorination, activation, and resource recovery of fluorine-containing silicon slag. Through the synergistic effect of a non-complexing strong acid and metal cations, efficient lattice fluorine removal and silicon slag activation are achieved. Simultaneously, the solid-phase silicon slag and liquid-phase fluorine resources are utilized at high value, achieving the effects of solid waste reduction, harmlessness, and full-component resource recovery.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for defluorination activation and resource recovery of fluorinated silicon slag involves washing and draining the fluorinated silicon slag with water, mixing it with a non-complexing strong acid solution and a metal cation donor to form a mixed system, and heating it under stirring to carry out an activation reaction. After the reaction is completed, the system is cooled and the solid and liquid phases are separated to obtain a solid-phase activated silicon slag and a liquid-phase fluorinated metal mother liquor. The activated silicon slag is used to prepare silicon-based materials, and the fluorinated metal mother liquor is used to prepare fluoride salts.

[0007] Furthermore, a penetrant can be added to the mixed system to reduce the solid-liquid interfacial tension, promote the penetration of reactive ions into the silicon slag lattice, and improve the defluorination efficiency.

[0008] Furthermore, the non-complexing strong acid solution is selected from at least one of sulfuric acid, hydrochloric acid, and nitric acid with a mass concentration of 10-50%, and it will not undergo complexation or precipitation reactions with metal cations. The preferred mass ratio of the non-complexing strong acid solution to the fluorinated silica slag is (2:1)-(6:1).

[0009] Furthermore, the metal cation in the metal cation donor is selected from Al. 3+ Zr 4+ Ti 4+ At least one of them.

[0010] Furthermore, the Al 3+ The donor is at least one of aluminum nitrate, aluminum sulfate, aluminum oxide, and aluminum hydroxide; the Zr 4+ The donor is at least one of zirconium nitrate, zirconium oxychloride, and zirconium hydroxide; the Ti 4+ The donor is at least one of titanium nitrate, titanium sulfate, titanium dioxide, and titanium hydroxide.

[0011] Furthermore, the amount of metal cation donor added is based on the content of lattice fluorine in the fluorine-containing silicon slag, and is multiplied by a coefficient of 1.05 to 1.5 based on the stoichiometric ratio of the metal cation to the lattice fluorine to form fluoride.

[0012] Furthermore, the penetrant is a nonionic penetrant or an anionic penetrant.

[0013] Furthermore, the nonionic penetrant is one of fatty alcohol polyoxyethylene ether and penetrant T (sodium diisooctyl succinate sulfonate); the anionic penetrant is one of sodium dodecylbenzene sulfonate and sodium alkyl sulfonate.

[0014] Furthermore, the amount of the penetrant added is 0.1~1.0% of the mass of the fluorinated silica slag.

[0015] Furthermore, the composition of the fluorinated silicon slag by mass percentage is: SiO2 25~30%, water 65~70%, total fluorine 8~12%, of which lattice-bonded fluorine accounts for 40~50% of the total fluorine, and the impurity content is less than 0.3%, totaling 100%.

[0016] Furthermore, the heating activation reaction temperature is 75~120℃, and the constant temperature reaction time is 1~4 hours. The activation process targets the Si-F bond for directional treatment without destroying the overall lattice structure of amorphous silica. By weakening the Si-F bond with H+, metal cations and lattice fluorine are directionally combined to form metal fluorides. The penetrant promotes the penetration of the reaction system into the lattice interior, achieving complete removal of lattice-bound fluorine. Deep defluorination can be completed in a short time at mild medium and low temperatures, significantly improving efficiency and reducing energy consumption. Specifically, the process parameters can be controlled according to the lattice fluorine content in the silicon slag. If the lattice fluorine content in the silicon slag is high, the reaction temperature can be appropriately increased, the reaction time extended, or the amount of penetrant added can be increased; if the lattice fluorine content is low, the reaction temperature can be appropriately decreased, the reaction time shortened, and energy consumption reduced.

[0017] Furthermore, the stirring rate during the heating activation reaction is 200~500 r / min to ensure that the system is mixed evenly and the reaction is complete.

[0018] This invention first removes free fluorine from fluorinated silicon slag by washing with water. Then, the washed silicon slag is mixed with a non-complexing strong acid and a metal cation donor. The invention creatively utilizes the metal cations to combine with and remove lattice fluorine from amorphous silica under non-complexing acidic conditions. The H+ ions provided by the non-complexing strong acid mildly activate the lattice structure of amorphous silica, weakening the Si-F bond strength and placing the lattice fluorine in an easily detachable activated state. The metal cations in the system then undergo directional coordination with the activated lattice fluorine to form stable metal fluorides. This process completely breaks the Si-F bonds, achieving efficient removal of fluorine from the lattice through heating. Preferably, the metal cation donor is added at a stoichiometric coefficient of 1.05-1.5 to form the metal fluoride, avoiding fluorine residue in the lattice due to incomplete local reactions. The strong acid only provides an acidic environment for the system, and the metal cation donor only provides effective metal cations; neither reacts with other side effects. That is, the metal cation donor is a metal-containing compound that can provide the aforementioned cations and does not react with the acidic system. Preferably, the metal cation in the metal cation donor is selected from Al. 3+ Zr 4+ Ti 4+ One type of fluorine cation involves a donor including a salt, oxide, or hydroxide. These cations can form stable coordination compounds with fluorine, achieving directional capture of fluorine within the lattice. Based on this, the entire component is utilized through solid-liquid separation. The solid phase is amorphous silica, used to prepare silicon-based materials such as sodium silicate and silica. The liquid phase is a fluorine-containing metal mother liquor, used for fluorine-containing products. When Al is selected as the metal cation... 3+ At that time, the byproduct is cryolite; when Zr 4+ Ti 4+ The byproducts are corresponding metal fluoride salts (sodium fluorozirconate or sodium fluorotitanate), with a product purity of ≥90%, meeting the requirements of corresponding industrial applications. This expands the selection of raw materials and the product range, allowing for flexible selection based on the actual production system. The solid-liquid separation methods include, but are not limited to, filtration, centrifugation, or pressure filtration.

[0019] Furthermore, fluorinated silica slag, a byproduct of phosphate fertilizer production, typically exists as dense, amorphous aggregates with high surface energy. Conventional acidic solutions struggle to completely wet the encapsulated regions within these aggregates, preventing the encapsulated fluorine lattice from effectively contacting the metal cations (Al3+, Zr4+, Ti4+), creating "reaction dead zones." This invention introduces penetrants (such as fatty alcohol polyoxyethylene ethers, sodium alkyl sulfonates, etc.) that overcome the agglomeration effect and interfacial mass transfer resistance of fluorinated silica slag. These penetrants exhibit excellent surface activity and are preferably non-ionic or anionic. Their mechanism of action is as follows: reducing interfacial tension and enhancing wetting: significantly reducing the surface tension at the solid-liquid interface allows acidic metal salt solutions to rapidly penetrate into the gaps within the dense silica slag aggregates, eliminating gas film resistance at the solid-liquid interface. Promoting depolymerization and mass transfer: Combined with mechanical stirring, the penetrant helps disperse and depolymerize large silica slag agglomerates into fine particles, significantly increasing the effective contact area of ​​the solid-liquid reaction. This allows H+ and metal cations to uniformly and rapidly attack exposed Si-F bonds, thereby significantly improving the defluorination rate and depth, ensuring no dead zones in the reaction. The added penetrant reduces the solid-liquid interfacial tension, promoting the penetration of metal cations and H+ into the amorphous silica lattice, increasing the contact probability between fluorine and metal cations in the lattice, further improving the defluorination rate, reducing reagent consumption and reaction time, and lowering operating costs. Non-ionic penetrants (fatty alcohol polyoxyethylene ether, sodium diisooctyl succinate sulfonate) have good acid resistance and are suitable for high-concentration acidic systems, effectively promoting the entry of H+ and metal cations into the micropores of silica slag, making them the preferred option; anionic penetrants can be used with low-concentration acidic systems. The amount of the penetrant added is 0.1~1.0% of the mass of the fluorinated silica slag, more preferably 0.1~0.5%. Too much will form micelles or emulsions, generating a large amount of foam, which will hinder stirring and increase the difficulty of subsequent filtration. Too little will result in the solid-liquid interface gas film not being eliminated, and ions will not be able to penetrate into the micropores, leading to incomplete reaction, high fluorine residue in the crystal lattice, and unqualified product.

[0020] The solid amorphous silica obtained after solid-liquid separation can be flexibly selected to prepare sodium silicate or precipitated silica according to the needs of enterprises, and the corresponding reaction process parameters can be adjusted. Sodium source in the liquid phase fluorine-containing metal mother liquor can be sodium carbonate, sodium hydroxide, etc., to replace sodium fluoride, reduce raw material costs, and adjust the pH value to the corresponding range to obtain qualified fluoride salt products. Fluorine-containing metal mother liquor can also be concentrated and crystallized to recover metal fluorides, further improving resource utilization.

[0021] This invention utilizes a non-complexing strong acid with Al 3+ Zr 4+ Ti 4+The synergistic effect of metal cations, combined with a penetrant to enhance mass transfer, enables the deep removal of lattice-bound fluorine from fluorinated silica slag. This completely solves the problem of traditional processes that only remove free fluorine and are incomplete in defluorination. After treatment, the total fluorine content of the silica slag is reduced to below 2%, and the SiO2 purity is ≥90%. The process is mild, efficient, energy-saving, and the equipment is versatile and easily industrialized. Raw material selection is flexible, with no side reactions or secondary pollution. This process achieves high-value resource utilization of all components in the preparation of sodium silicate and silica from solid-phase silica slag, and cryolite, sodium fluorozirconate, and sodium fluorotitanate from liquid-phase mother liquor. It transforms solid waste from the phosphate fertilizer industry into high-value products, offering significant environmental and economic benefits. It has a wide range of applications and strong potential for widespread adoption. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of the present invention.

[0023] Figure 2 This is a graph showing the relationship between the penetrant and the fluorine content in the crystal lattice. Detailed Implementation

[0024] The process parameters of this invention are as follows: Fluorine-containing silicon slag composition: SiO2 25~30%, water 65~70%, total fluorine 8~12% (lattice-bound fluorine 40~50%), impurity content less than 0.3%, total 100%; Metal cation: Al 3 +、Zr 4 +、Ti 4 + (choose one or more); Metal cation donor addition factor: 1.05-1.5 × stoichiometric coefficient of metal fluoride produced (based on lattice fluorine content); Penetrant: Nonionic / anionic, addition amount 0.1~1.0% (based on the mass of fluorinated silica slag); Non-complexing strong acids: sulfuric acid, hydrochloric acid, nitric acid (optional), mass concentration 10~50%; Heating activation reaction conditions: temperature 75~120℃, time 1~4 hours, stirring speed 200~500r / min; Solid product specifications: Amorphous silica (SiO2) purity ≥90%, total fluorine content ≤2%, can be used to prepare qualified sodium silicate and silica; Liquid phase product specifications: Fluoride salt purity ≥90%, of which Al 3 The purity of cryolite prepared by the + system is ≥95%.

[0025] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. The scope of protection of the present invention is not limited to the selection of specific raw materials. All process adjustments based on the idea of ​​defluorination by combining metal cations with fluorine in amorphous silica lattice under non-complexing acidic conditions and the resource utilization of all components are within the scope of protection of the present invention. Unless otherwise specified, all percentages in the following embodiments are mass percentages, and all additives are commercially available.

[0026] General testing standards: After activation, the silicon slag is tested for residual fluorine in the crystal lattice, total fluorine content, and SiO2 purity; the mother liquor containing fluorine metals is tested for metal ion and fluoride ion content; sodium silicate, silica, and fluoride salt products are tested according to their respective industrial standards.

[0027] General raw materials: Fluorine-containing silicon slag is composed of 32% SiO2, 68% water, and 10% total fluorine (45% lattice-bound fluorine, with the molar amount of lattice fluorine calculated based on actual test values); sodium fluoride is used as the sodium source; and fatty alcohol polyoxyethylene ether is used as the penetrant.

[0028] Example 1 Fluorinated silicon slag was washed with deionized water to remove free fluorine and drained for later use. Aluminum nitrate nonahydrate (10g / 100g fluorinated silicon slag) was added to the washed silicon slag according to a stoichiometric coefficient of AlF3 generated from fluorine in the crystal lattice × 1.05, along with 0.5% (by weight of the fluorinated silicon slag) of a penetrant, fatty alcohol polyoxyethylene ether, and a 30% sulfuric acid solution (the mass ratio of sulfuric acid solution to fluorinated silicon slag was 3:1). The mixture was stirred at 300 rpm at room temperature to form a homogeneous mixture. The mixture was heated to 80°C and reacted at a constant temperature of 300 rpm for 2 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed, dried, and collected. Solid amorphous silica was collected along with a fluorinated aluminum mother liquor. The solid amorphous silica was added to a 30% sodium hydroxide solution and stirred at 85-100℃ for 2-4 hours. After the silica slag was completely dissolved, trace impurities were removed by pressure filtration, and the solution was concentrated to obtain liquid sodium silicate. Sodium fluoride was added to the fluorinated aluminum mother liquor to adjust the pH to 7-8, and the mixture was stirred for 1 hour. After precipitation, filtration, washing, and drying, cryolite was prepared. Test results showed that the fluorine in the activated silica slag lattice completely disappeared, the total fluorine decreased to 1.3%, the SiO2 purity was 92%, and the prepared sodium silicate met industrial-grade standards. The cryolite purity was 97.5%.

[0029] Example 2 The fluorinated silicon slag was washed with deionized water to remove free fluorine and drained for later use. Zirconium nitrate (12g / 100g of fluorinated silicon slag) was added to the washed silicon slag according to a stoichiometric coefficient of 1.2 for the formation of ZrF4 from lattice fluorine, along with 0.3% sodium dodecylbenzenesulfonate (by mass of the fluorinated silicon slag), and a 10% hydrochloric acid solution (hydrochloric acid solution to fluorinated silicon slag mass ratio of 2:1). The mixture was stirred at 200 r / min at room temperature to form a homogeneous mixture. The mixture was heated to 75℃ and reacted at a constant temperature of 200 r / min for 4 hours. After the reaction was completed, it was cooled to room temperature and centrifuged (30...). The silica was washed, dried, and the solid amorphous silica was collected along with the fluorinated zirconium mother liquor. The solid amorphous silica was reacted with hydrochloric acid to generate silicic acid, which was then precipitated, washed, dried, and pulverized to obtain precipitated silica. Sodium fluoride was added to the fluorinated zirconium mother liquor to adjust the pH to 6-7, and the mixture was stirred for 1.5 hours. The precipitate was then filtered, washed, and dried to prepare sodium fluorozirconate. The test results showed that the fluorine in the activated silica slag lattice was completely eliminated, the total fluorine was reduced to 1.4%, the SiO2 purity was 91%, and the prepared precipitated silica met the industrial grade standard. The sodium fluorozirconate purity was 92%, which met the requirements for industrial applications.

[0030] Example 3 Fluorine-containing silicon slag was washed with deionized water to remove free fluorine and drained for later use. Titanium sulfate (11 g / 100 g fluorine-containing silicon slag) was added to the washed silicon slag according to a stoichiometric coefficient of 1.3 for the formation of TiF4 from lattice fluorine, along with 0.8% (by weight of the fluorine-containing silicon slag) of penetrant T (sodium diisooctyl succinate sulfonate). A 50% nitric acid solution was then added (the mass ratio of hydrochloric acid solution to fluorine-containing silicon slag was 6:1). The mixture was stirred at 500 rpm at room temperature to form a homogeneous mixture. The mixture was heated to 120°C and reacted at a constant temperature of 500 rpm for 1 hour. After the reaction, the mixture was cooled to room temperature, filtered, washed, and... The solid amorphous silica was dried and collected, along with the fluorinated titanium mother liquor. The solid amorphous silica was mixed with sodium hydroxide solution and reacted under micro-pressure (0.2~0.4MPa) and 130℃ conditions. After dissolution, filtration, and concentration, sodium silicate product was obtained. Sodium fluoride was added to the fluorinated titanium mother liquor to adjust the pH value to 7~8. The mixture was stirred and reacted for 1 hour. After precipitation, filtration, washing, and drying, sodium fluorotitanate was prepared. The test results showed that the fluorine in the activated silica slag lattice was completely eliminated, the total fluorine was reduced to 1.5%, and the SiO2 purity was 90.5%. The prepared sodium silicate met the industrial grade standard. The sodium fluorotitanate purity was 91%, which met the requirements for industrial applications.

[0031] Example 4 The fluorinated silicon slag was washed with deionized water to remove free fluorine, and then drained for later use; according to the lattice fluorine content, Al 3+ Zr 4+Aluminum hydroxide and zirconium oxychloride were added to the washed silica slag in a 1:1 molar ratio (total addition amount was calculated as 1.5 times the stoichiometric coefficient of the generated fluoride). Then, a 20% sulfuric acid + hydrochloric acid mixed solution (volume ratio 1:1, mass ratio of the mixed solution to the fluorinated silica slag 5:1) was added. The mixture was stirred at 400 rpm at room temperature to form a homogeneous system. The system was heated to 95°C and reacted at a constant temperature of 400 rpm for 3 hours. After the reaction, the mixture was cooled to room temperature, filtered, washed, and dried to collect the solid amorphous silica. Fluorinated aluminum zirconium mother liquor was collected; solid amorphous silica was reacted with sulfuric acid to generate silicic acid, which was then precipitated, washed, dried, and pulverized to obtain precipitated silica; sodium fluoride was added to the fluorinated aluminum zirconium mother liquor to adjust the pH to 7-8, and the mixture was stirred for 2 hours. After precipitation, filtration, washing, and drying, a mixed fluoride salt (a mixture of cryolite and sodium fluorozirconate) was prepared; the test results showed that the fluorine in the activated silica slag lattice was completely eliminated, the total fluorine was reduced to 1.6%, the SiO2 purity was 91.5%, and the prepared precipitated silica met the industrial grade standard; the mixed fluoride salt had a purity of 93%, which met the requirements for industrial applications.

[0032] Comparative Example 1 Fluorinated silica slag was washed with deionized water to remove free fluoride and drained for later use. A 30% sulfuric acid solution (sulfuric acid to fluorinated silica slag mass ratio 3:1) was added to the washed silica slag without any metal cation donors, and the mixture was stirred at room temperature to form a homogeneous system. The mixture was heated to 80℃ and stirred for 2 hours. After the reaction, it was cooled to room temperature, filtered, washed, and dried, and the solid silica slag and fluorinated mother liquor were collected simultaneously. An attempt was made to use the solid silica slag to prepare sodium silicate and the fluorinated mother liquor to prepare cryolite. The results showed that the fluoride removal rate of the solid silica slag lattice was only 30%, the total fluoride decreased to 6.3%, and the SiO2 purity was 82%, making it impossible to prepare qualified sodium silicate. The fluorinated mother liquor had low fluoride ion content and no effective metal cations, making it impossible to prepare qualified cryolite. The cryolite purity was 88.9%, which did not meet GB / T standards. According to standard 22441-2008, the conclusion is that a single acidic + penetrant system cannot achieve efficient removal of lattice fluoride. The addition of metal cations is the core necessary condition for the removal of lattice fluoride, which verifies the uniqueness, effectiveness and inventiveness of the defluorination strategy of metal cations and acidic conditions in this invention. At the same time, without metal cations, it is impossible to achieve the full-component resource utilization of fluorinated silicon slag, further highlighting the advantages of the full-component utilization strategy of this invention.

[0033] Comparative Example 2 Wash the fluorinated silicon slag with deionized water to remove free fluorine, and drain it for later use. Add 0.5% (by weight) of a penetrant, fatty alcohol polyoxyethylene ether, containing fluorinated silica slag to the washed silica slag, without adding any metal cation donors. Then add a 30% sulfuric acid solution (the mass ratio of sulfuric acid solution to fluorinated silica slag is 3:1). Stir at 300 rpm at room temperature to form a homogeneous mixture. Heat the mixture to 80°C and maintain a constant temperature reaction at 300 rpm for 2 hours. After the reaction is complete, cool to room temperature, filter, wash, and dry. Collect the solid silica slag and the fluorinated mother liquor simultaneously. Add the solid silica slag to a 30% (by weight) sodium hydroxide solution. The reaction was carried out at a constant temperature of 85~100℃ for 2~4 hours with stirring. After the silica slag was completely dissolved, trace impurities were removed by pressure filtration and the product was concentrated to obtain liquid sodium silicate. Sodium fluoride was added to the fluorine-containing mother liquor to adjust the pH value to 7~8. The reaction was stirred for 1 hour, followed by precipitation, filtration, washing, and drying to attempt to prepare cryolite. The test results showed that the fluorine removal rate of the solid-phase silica slag lattice was only 30%, the total fluorine was reduced to 6.3%, and the SiO2 purity was 82%, which was insufficient to prepare qualified sodium silicate. There were no effective metal cations in the fluorine-containing mother liquor, which was insufficient to prepare qualified cryolite. The purity of the cryolite was only 88.9%, which did not meet the standard.

[0034] Comparative Example 3 Fluorine-containing silicon slag was washed with deionized water to remove free fluorine and drained for later use. Aluminum nitrate nonahydrate (10g / 100g fluorine-containing silicon slag) was added to the washed silicon slag at a stirring rate of 1.05 (based on the stoichiometric coefficient of AlF3 formation from fluorine in the crystal lattice) to form a homogeneous mixture. The mixture was heated to 80°C and maintained at this temperature. Sodium stearate (0.5% by weight of the fluorine-containing silicon slag) was added as a penetrant, followed by a 30% sulfuric acid solution (sulfuric acid solution to fluorine-containing silicon slag mass ratio of 3:1). The mixture was reacted at room temperature with a stirring rate of 300 rpm for 2 hours. After the reaction, it was cooled to room temperature, filtered, washed, and dried. The solid silicon slag and the fluorine-containing aluminum mother liquor were collected simultaneously. The solid silicon slag was then added to a 30% (w / w) solution of aluminum nitrate nonahydrate. In a sodium hydroxide solution, the reaction was carried out at a constant temperature of 85-100℃ for 2-4 hours with stirring. After the silica slag was completely dissolved, trace impurities were removed by pressure filtration, and the product was concentrated to obtain liquid sodium silicate. Sodium fluoride was added to the fluorine-containing aluminum mother liquor to adjust the pH to 7-8, and the reaction was stirred for 1 hour. After precipitation, filtration, washing, and drying, cryolite was prepared. The test results showed that the strong acid caused sodium stearate to precipitate out, and a large amount of lattice fluorine remained in the activated silica slag. The total fluorine decreased to 4.8%, and the SiO2 purity was 85.5%, making it impossible to prepare qualified sodium silicate. The purity of cryolite was only 92%, and it contained organic impurities, failing to meet industrial-grade standards. The conclusion is that in a strong acid system, an acid-resistant penetrant must be selected to effectively eliminate interfacial resistance and ensure deep removal of lattice fluorine.

[0035] Furthermore, Figure 2 The images show the Raman spectra of the original sample (blank sample) and the control sample (Example 1), with the values ​​at 800-900 cm⁻¹.-1 The peak at this point is a characteristic peak of the Si-F bond, which can reflect the change of lattice fluorine in the sample. The original sample is a silicon slag sample without Al source and penetrant added, while the control sample (Example 1) is a silicon slag sample with Al source and penetrant added. It can be seen from the figure that the addition of Al source and penetrant can effectively remove lattice fluorine in silicon slag.

Claims

1. A method for defluorination activation and resource recovery of fluorinated silicon slag, characterized in that, Fluorine-containing silicon slag is washed and drained, then mixed with a non-complexing strong acid solution and a metal cation donor to form a mixed system. The system is then heated and activated under stirring. After the reaction is completed, the system is cooled and the solid and liquid phases are separated to obtain a solid phase of activated silicon slag and a liquid phase of fluorine-containing metal mother liquor. The activated silicon slag is used to prepare silicon-based materials, and the fluorine-containing metal mother liquor is used to prepare fluoride salts.

2. The method for defluorination activation and resource recovery of fluorinated silicon slag as described in claim 1, characterized in that, The mixture also contains a penetrant.

3. The method for defluorination activation and resource recovery of fluorinated silicon slag as described in claim 1, characterized in that, The non-complexing strong acid solution is selected from at least one of sulfuric acid, hydrochloric acid, and nitric acid with a mass concentration of 10-50%.

4. The method for defluorination activation and resource recovery of fluorinated silicon slag as described in claim 3, characterized in that, The ratio of the amount of the non-complexing strong acid solution added to the mass ratio of the fluorinated silicon slag is 2:1 to 6:

1.

5. The method for defluorination activation and resource recovery of fluorinated silicon slag as described in claim 1, characterized in that, The metal cation donor is selected from Al. 3+ Zr 4+ Ti 4+ At least one of them.

6. The method for defluorination activation and resource recovery of fluorinated silicon slag as described in claim 5, characterized in that, Al 3 +The donor is at least one of aluminum nitrate, aluminum sulfate, aluminum oxide, and aluminum hydroxide; Zr 4 The donor is at least one of zirconium nitrate, zirconium oxychloride, and zirconium hydroxide; the Ti 4+ The donor is at least one of titanium nitrate, titanium sulfate, titanium dioxide, and titanium hydroxide.

7. The method for defluorination activation and resource recovery of fluorinated silicon slag as described in claim 5, characterized in that, The amount of metal cation donor added is based on the content of lattice fluorine in the fluorine-containing silicon slag, and is multiplied by a coefficient of 1.05 to 1.5 based on the stoichiometric ratio of the metal cation to the lattice fluorine to form fluoride.

8. The method for defluorination activation and resource recovery of fluorinated silicon slag as described in claim 2, characterized in that, The penetrant is a nonionic penetrant or an anionic penetrant.

9. The method for defluorination activation and resource recovery of fluorinated silicon slag as described in claim 8, characterized in that, The nonionic penetrant is one of penetrant fatty alcohol polyoxyethylene ether and penetrant T, and the anionic penetrant is one of sodium dodecylbenzene sulfonate and sodium alkyl sulfonate.

10. The method for defluorination activation and resource recovery of fluorinated silicon slag as described in claim 2, characterized in that, The amount of the penetrant added is 0.1~1.0% of the mass of the fluorinated silica slag.

11. The method for defluorination activation and resource recovery of fluorinated silicon slag as described in claim 1, characterized in that, The components of the fluorinated silicon slag, by mass percentage, are as follows: The composition is 25-30% SiO2, 65-70% water, and 8-12% total fluorine, of which 40-50% is lattice-bonded fluorine and the impurity content is less than 0.3%, totaling 100%.

12. The method for defluorination activation and resource recovery of fluorinated silicon slag as described in any one of claims 1-11, characterized in that, The heating activation reaction temperature is 75~120℃, and the reaction is carried out at a constant temperature for 1~4 hours.

13. The method for defluorination activation and resource recovery of fluorinated silicon slag as described in claim 12, characterized in that, The stirring rate is 200~500 r / min.

14. The method for defluorination activation and resource recovery of fluorinated silicon slag as described in any one of claims 1-11, characterized in that, The silicon-based material is sodium silicate or silica, and the fluoride salt is cryolite, sodium fluorozirconate, or sodium fluorotitanate.

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