Phosphorus-fluorine curing agent for phosphogypsum and preparation method thereof

Abstract

This invention relates to a novel phosphorus-fluorine curing agent for phosphogypsum and its preparation method, belonging to the technical field of industrial solid waste treatment and resource utilization. The curing agent of this invention comprises slag powder, anhydrous sodium sulfate, water glass, water, sodium hydroxide, and a Fe3O4@SiO2@Zr-Al bimetallic oxide stabilizer. The Fe3O4@SiO2@Zr-Al bimetallic oxide stabilizer has a core-shell structure, with magnetic iron oxide particles as the core, and an amorphous silica protective layer and an active layer sequentially coating the surface of the magnetic iron oxide particles. The active layer is an amorphous, porous network structure of zirconium-aluminum bimetallic oxide. The preparation method of the curing agent of this invention is simple, mild, and easy to industrialize. The main raw material is industrial solid waste slag, achieving "waste treatment with waste," with a small amount of agent added and low overall treatment cost.

Description

Technical Field

[0001] This invention relates to the field of industrial solid waste treatment and resource utilization technology, and in particular to a phosphorus-fluorine solidification agent for phosphogypsum and its preparation method. Background Technology

[0002] Phosphogypsum typically contains harmful impurities such as residual phosphorus, fluorine, heavy metals, and organic matter. Current treatment methods for phosphogypsum mainly include: (i) Washing: High energy consumption, generates large amounts of wastewater, high cost, and cannot completely remove impurities. (ii) Neutralization: Commonly uses alkaline materials such as lime and cement to neutralize its acidity and solidify some impurities, but suffers from poor stability of the solidifying agent, poor long-term effects, excessive addition leading to large volume expansion, and a tendency for "redissolution" (the fixed phosphorus and fluorine dissolve again over time). (iii) High-temperature calcination: Extremely high energy consumption, prohibitively high cost, and unsuitable for large-scale applications.

[0003] Traditional curing agents used in existing technologies (such as ordinary silicate cement and lime) mainly rely on the physical encapsulation of hydration products and precipitation reactions in an alkaline environment. They have weak specific chelating ability for phosphorus and fluorine, resulting in low curing efficiency. Furthermore, phosphorus and fluorine ions can severely hinder the hydration process of cement, leading to slow strength development or even failure to solidify the cured body.

[0004] Therefore, there is an urgent need to develop a curing agent that is efficient, stable, low-cost, and capable of specifically chemically binding phosphorus and fluorine impurities. Summary of the Invention

[0005] To address the above technical problems, this invention provides a phosphorus-fluoride curing agent for phosphogypsum and its preparation method. This invention, by adding a Fe3O4@SiO2@Zr-Al bimetallic oxide stabilizer, utilizes multiple mechanisms such as chemical adsorption, complexation precipitation, and physical coating to remove soluble, highly mobile harmful fluorine (F) from phosphogypsum. - ) and phosphorus (mainly H2PO4) - / HPO4 2- It can be transformed into stable, insoluble compounds (such as zirconium fluoride, aluminum fluoride, zirconium phosphate, and aluminum phosphate) or inner surface complexes, thereby "locking" it in the solid phase and preventing it from being released when rainwater leaches or environmental conditions change, thus preventing secondary pollution.

[0006] The first objective of this invention is to provide a phosphorus-fluorine curing agent for phosphogypsum, which, by mass parts, is composed of the following raw materials: 300-500 parts of slag powder, 10-20 parts of anhydrous sodium sulfate, 150-200 parts of water glass, 10-20 parts of sodium hydroxide, 50-200 parts of Fe3O4@SiO2@Zr-Al bimetallic oxide stabilizer, and 400-800 parts of water;

[0007] The Fe3O4@SiO2@Zr-Al bimetallic oxide stabilizer has a core-shell structure, with magnetic iron oxide grains as the core, and an amorphous silicon dioxide protective layer and an active layer sequentially wrapped around the surface of the magnetic iron oxide grains.

[0008] The active layer is an amorphous, porous network structure of zirconium-aluminum bimetallic oxide; the surface of the amorphous silica protective layer contains Si-OH bonds, which are connected to the active layer by chemical bonds.

[0009] In some embodiments of the present invention, the Fe3O4@SiO2@Zr-Al bimetallic oxide stabilizer is prepared by the following method:

[0010] A magnetic iron oxide nanoparticle dispersion is provided;

[0011] Tetraethyl orthosilicate solution was added to the magnetic iron oxide nanoparticle dispersion and reacted to form a protective layer of silicon dioxide on the surface of the magnetic iron oxide nanoparticles, thus obtaining Fe3O4@SiO2 composite particles. The Fe3O4@SiO2 composite particle dispersion was obtained by resuspending the particles in water.

[0012] Zirconium and aluminum sources were dissolved in water to obtain a mixed metal salt solution. Under vigorous stirring, the mixed metal salt solution was added dropwise to the Fe3O4@SiO2 composite particle dispersion. Then, ammonia solution was added dropwise as a precipitant while controlling the solution to be alkaline. The reaction was carried out under heating to form an amorphous zirconium-aluminum hydroxide gel layer on the surface of the composite particles. The product was separated using a magnet, washed and dried to obtain the precursor powder.

[0013] The obtained precursor powder was heated and calcined to obtain the Fe3O4@SiO2@Zr-Al bimetallic oxide stabilizer.

[0014] In some embodiments of the present invention, the concentration of the magnetic iron oxide nanoparticle dispersion is 15~25wt%; for example, it can be 15, 20, 25wt%, or any value between any two values.

[0015] The concentration of the tetraethyl orthosilicate solution is 5~10wt%, and can be, for example, 5, 6, 7, 8, 9, 10wt%, or any value between any two values.

[0016] In some embodiments of the present invention, the reaction conditions for adding tetraethyl orthosilicate solution to the magnetic iron oxide nanoparticle dispersion and carrying out the reaction are: temperature 25~30℃, time 3~5h;

[0017] The concentration of the Fe3O4@SiO2 composite particle dispersion is 10~30 mg / ml, and can be, for example, 10, 15, 20, 25, 30 mg / ml, or any value between any two values.

[0018] In some embodiments of the present invention, the zirconium source is selected from zirconium oxychloride;

[0019] The aluminum source is selected from one or more of aluminum nitrate, aluminum chloride, or aluminum sulfate, and more preferably aluminum nitrate.

[0020] In some embodiments of the present invention, the molar ratio of the zirconium source to the aluminum source is 1:(1~2), which can be exemplarily 1:1, 1:2, 1:1.5, or any value between any two values;

[0021] The concentration of the ammonia solution is 25~28 wt%, for example, it can be 55, 26, 27 or 28, or any value between any two values.

[0022] The pH of an alkaline solution is 9-10; the pH should not be too high or too low. When pH < 9, precipitation may be incomplete, especially with Al(OH)3. When pH > 10, the amphoteric Al(OH)3 will begin to dissolve, forming [Al(OH)4]. - (This disrupts the product structure).

[0023] In some embodiments of the present invention, the heating reaction is carried out at a temperature of 60-80°C for a time of 3-6 hours.

[0024] The heating and calcination temperature is 400~550℃, and can be, for example, 400, 450, 500, 550℃, or any value between any two values; the time is 2~4 hours, and can be, for example, 2, 2.5, 3, 3.5, 4 hours, or any value between any two values; the calcination temperature of this invention should not be too high or too low. When the temperature is too high (>550℃), Fe3O4 will be oxidized into weakly magnetic γ-Fe2O3, or even non-magnetic α-Fe2O3. When the temperature is too low, the SiO2 layer undergoes uncontrolled sintering with the metal oxide, the zirconium-aluminum oxide crystallinity is too high, the specific surface area decreases, and the number of adsorption active sites decreases.

[0025] A second objective of this invention is to provide a method for preparing the aforementioned phosphorus-fluorine curing agent, comprising the following steps:

[0026] The slag powder and anhydrous sodium sulfate are mixed evenly to obtain a dry mixture;

[0027] Water glass and sodium hydroxide are fully dissolved and hydrolyzed in water to obtain an alkaline activation solution;

[0028] The obtained alkaline activation solution was added to the dry mixture and stirred evenly. Then, Fe3O4@SiO2@Zr-Al bimetallic oxide stabilizer was added and stirred and mixed step by step to obtain a slurry. The slurry was heated and allowed to stand for aging to obtain the phosphorus-fluorine curing agent.

[0029] In some embodiments of the present invention, the conditions for heating and static aging are: temperature of 50~60°C, aging for 20~30 hours.

[0030] In some embodiments of the present invention, the stirring is performed in stages: first, stirring is carried out at a speed of 450-500 rpm for 10-12 minutes, then the speed is adjusted to 250-300 rpm for 10-12 minutes, and finally stirring is carried out at a speed of 100-150 rpm for 15-25 minutes. Because the material has a high solid content and high viscosity, a staged stirring method is needed to achieve uniform dispersion of the material.

[0031] In this invention, combining the two to form a bimetallic oxide overcomes the shortcomings of single alumina (narrow pH range, limited adsorption capacity) or zirconium oxide (high cost, poor formability), achieving synergistic effects and obtaining superior adsorption performance. The SiO2 layer surface is rich in silanol groups (-Si-OH). Similarly, the zirconium and aluminum precursors hydrolyze in aqueous solution to generate hydrated metal hydroxides, with their surfaces filled with metal hydroxyl groups (-M-OH, M = Zr or Al). During the preparation process (especially when heating or adjusting pH), the -Si-OH on the SiO2 surface undergoes a dehydration condensation reaction with the -M-OH of the zirconium-aluminum precursor, forming strong covalent bonds. Metal ions (such as Zr...) 4+ Al 3+ ) is a typical Lewis acid (electron docking acceptor), while the oxygen atoms on the SiO2 surface (especially in the deprotonated -Si-O) - The sites are Lewis bases (electron pair donors), and therefore, coordinate bonds can form between them. Under specific pH conditions during preparation (e.g., 9–10), the negatively charged SiO2 surface electrostatically attracts positively charged zirconium-aluminum hydrolysates, enriching them on the SiO2 surface and creating favorable conditions for subsequent chemical bonding.

[0032] The technical solution of the present invention has the following advantages compared with the prior art:

[0033] This invention provides a reagent for efficiently and stably chemically solidifying soluble phosphorus and fluorine in phosphogypsum, achieving a high solidification rate (target >90%) and good long-term stability. Furthermore, the preparation method of the solidifying reagent is simple, mild, and easy to industrialize, using industrial solid waste slag as the main raw material, thus realizing "waste-to-waste treatment." The reagent dosage is low, resulting in low overall treatment costs. This invention also provides an application method for this reagent, achieving the harmless treatment of phosphogypsum and laying the foundation for its safe storage or resource utilization as a building material raw material.

[0034] This invention utilizes a highly efficient curing core component, a "phosphorus-fluorine specific stabilizer," which forms a stable compound with extremely low solubility (such as fluorapatite) with P and F ions, achieving chemical bonding and fixation rather than simple physical encapsulation. This results in curing efficiency far exceeding that of traditional agents and effectively prevents "re-dissolution."

[0035] This invention utilizes Fe3O4, an excellent magnetic material, as its core to give the entire composite material superparamagnetism. After stabilizing the phosphogypsum, the stabilizer can be easily separated from the treatment system using an external magnetic field, enabling catalyst recovery and reuse. This significantly reduces processing costs and prevents the stabilizer itself from becoming new solid waste. It also has a certain adsorption capacity for fluorine phosphorus, assisting in the fixation of fluorine phosphorus in the active layer. Since the Fe3O4 magnetic core is very unstable in acidic environments (phosphogypsum is typically acidic), it is prone to dissolution and corrosion, leading to magnetic degradation. This invention, by setting a SiO2 protective layer, isolates the magnetic core from the external environment, greatly improving the chemical stability and acid resistance of the entire material. Simultaneously, the SiO2 layer forms a porous, high-specific-surface-area mesoporous structure, providing a large attachment area for the loading of the active component Zr / Al oxide in the outer active layer, preventing its aggregation and exposing more active sites. Through chemical bonding, the internal magnetic core and the outer active component are firmly connected together. In this invention, the oxides or hydroxides of zirconium and aluminum possess high specific surface areas and are rich in hydroxyl groups. These hydroxyl groups are active sites for surface complexation reactions; the hydroxyl groups on the metal (Zr / Al) surface can react with phosphate ions (H2PO4) in the solution. - HPO4 2- A ligand exchange reaction occurs, forming a stable inner surface complex. This is a strong, irreversible chemisorption. Simultaneously, Zr... 4+ And Al 3+ Both are strong Lewis acids, capable of reacting with phosphate ions to form insoluble zirconium phosphate and aluminum phosphate precipitates, permanently fixing phosphorus; similar to their effect on phosphorus, they can adsorb phosphorus through surface complexation. - Furthermore, it forms insoluble precipitates such as zirconium fluoride, aluminum fluoride, or more complex fluoride-oxygen metal compounds, thereby achieving fluorine fixation. Attached Figure Description

[0036] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0037] Figure 1 This is a schematic diagram of the structure of the magnetic iron oxide-supported zirconium-aluminum bimetallic oxide stabilizer obtained in Example 1 of the present invention; wherein, 1, iron oxide grains, 2, amorphous silicon dioxide protective layer, and 3, zirconium-aluminum bimetallic oxide active layer.

[0038] Figure 2 This is a TEM image of the magnetic iron tetroxide-supported zirconium-aluminum bimetallic oxide stabilizer obtained in Example 1 of the present invention. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0040] Example 1

[0041] This invention provides a method for preparing a phosphorus-fluorine curing agent for phosphogypsum, as detailed below:

[0042] 500g of dried, ball-milled S95 grade slag powder was uniformly mixed with 15g of anhydrous sodium sulfate to avoid clumping, resulting in a dry mixture. 200g of water glass (modulus 2.4) and 15g of sodium hydroxide were pre-dissolved and hydrolyzed in 500ml of water for 1 hour to form a homogeneous and active alkaline activation solution. The obtained alkaline activation solution was added to the dry mixture and stirred evenly. Then, 100g of magnetic iron tetroxide-supported zirconium-aluminum bimetallic oxide stabilizer was added, and the mixture was stirred in stages: first, it was stirred at 500rpm for 10 minutes, then the speed was adjusted to 300rpm for 10 minutes, and finally stirred at 100rpm for 20 minutes to obtain a slurry. After discharge, the slurry was sealed and aged at 50℃ for 24 hours to obtain the phosphorus-fluorine curing agent.

[0043] The magnetic iron tetroxide-supported zirconium-aluminum bimetallic oxide stabilizer was prepared by the following method:

[0044] 1. Mix 3.22g of ferric chloride (FeCl3·6H2O) and 2.72g of ferrous sulfate (FeSO4·7H2O) in 30ml of deionized water to obtain a mixed solution; under a nitrogen atmosphere, add 10ml of 25wt% ammonia solution to the mixed solution and react at 60℃ for 40 minutes. The solution turns black rapidly, indicating the formation of Fe3O4 nanoparticles. Separate the product using a magnet and wash it three times with deionized water and ethanol to obtain magnetic nanoparticles (MNPs).

[0045] 2. The magnetic nanoparticles (MNPs) obtained in step 1 were redispersed in ethanol to obtain a 20 wt% magnetic nanoparticle dispersion. Under slow stirring, a 5 wt% TEOS ethanol solution was added at 45 drops / min. The reaction was carried out at room temperature for 4 hours, followed by magnetic separation. The magnetically separated solid phase was washed three times with ethanol and deionized water to obtain Fe3O4@SiO2 composite particles.

[0046] 3. The Fe3O4@SiO2 composite particles obtained in step 2 were uniformly dispersed in 100 ml of deionized water to obtain a 20 mg / ml Fe3O4@SiO2 composite particle dispersion. 3.2 g of zirconium oxychloride and 1.9 g of aluminum nitrate were dissolved in 200 mL of deionized water and magnetically stirred for 30 minutes until completely dissolved, yielding a mixed metal salt solution. Under vigorous stirring, the mixed metal salt solution was slowly added dropwise to the Fe3O4@SiO2 composite particle dispersion. Then, 10 ml of 25 wt% dilute ammonia solution was slowly added dropwise as a precipitant to adjust the pH of the system to 9.0. The mixture was heated and stirred at 70 °C for 4 hours to allow the hydrolysis and condensation reactions to proceed fully, forming an amorphous Zr / Al hydroxide gel layer on the surface of the magnetic particles. After the reaction was complete, the product was separated using a magnet, thoroughly washed with water and ethanol, and dried overnight in an oven at 60 °C to obtain the precursor powder.

[0047] 4. The precursor powder obtained in step 3 was calcined in a muffle furnace at 450℃ for 3 hours, cooled to room temperature, washed three times with water and ethanol, and vacuum dried at 50℃ for 1 hour to obtain the Fe3O4@SiO2@Zr-Al bimetallic oxide stabilizer. The structure of the obtained final product was characterized, and the results are as follows: Figure 2 As shown, by Figure 2 It is known that the stabilizer obtained in this invention has a core-shell structure.

[0048] Comparative Example 1

[0049] Similar to Example 1, the difference is that step 3 in the preparation of the magnetic iron oxide-supported zirconium-aluminum bimetallic oxide stabilizer lacks zirconium oxychloride; otherwise, it is the same as Example 1.

[0050] Comparative Example 2

[0051] Similar to Example 1, the difference is that aluminum nitrate is missing in step 3 of the preparation of the magnetic iron oxide-supported zirconium-aluminum bimetallic oxide stabilizer; otherwise, it is the same as Example 1.

[0052] Comparative Example 3

[0053] Similar to Example 1, the difference is that the addition of the magnetic iron oxide-supported zirconium-aluminum bimetallic oxide stabilizer is missing.

[0054] Application Example 1

[0055] Application Process: Raw phosphogypsum residue from a phosphate chemical plant was taken, crushed, and dried to obtain pretreated raw phosphogypsum residue. The soluble phosphorus leaching concentration was measured to be 50 mg / L, and the fluoride leaching concentration was 100 mg / L. 1000 g of the pretreated phosphogypsum and 40 g of the phosphorus-fluoride curing agent obtained in Example 1 (ratio 25:1) or the curing agents obtained in Comparative Examples 1-3 were weighed and mixed separately, then placed in a mixer and dry-mixed for 8 minutes. Then, 260 ml of water was added, and the mixture was stirred for another 10 minutes to form a uniform slurry. The slurry was poured into a 30 mm × 30 mm × 150 mm mold, vibrated to compact, and the surface was smoothed. The slurry was cured for 28 days under standard curing conditions (temperature 20 ± 2°C, humidity ≥ 95%) to obtain harmlessly treated phosphogypsum. The leachate from the obtained harmlessly treated phosphogypsum was tested to obtain the curing rate of soluble phosphorus and soluble fluoride in the phosphogypsum. The experimental results are shown in Table 1.

[0056] Table 1

[0057]

[0058] As shown in Table 1, the curing agent obtained by this invention can achieve efficient curing of fluorine and phosphorus in the original phosphogypsum residue. Comparing Example 1 and Comparative Examples 1-3, it can be seen that, through the comparative examples, it is clear that both the magnetic iron oxide-supported zirconium-aluminum bimetallic oxide stabilizer and the bimetallic oxide are indispensable in the curing agent. Without either of the metal oxides, the curing effect of phosphorus and fluorine will be significantly reduced, further illustrating the crucial importance of the synergistic effect of the bimetallic oxide in the zirconium-aluminum bimetallic oxide.

[0059] Application Example 2

[0060] Regeneration and recycling of magnetic iron oxide-supported zirconium-aluminum bimetallic oxide stabilizers:

[0061] (1) 100g of harmlessly treated phosphogypsum obtained in Application Example 1 was crushed to obtain crushed stone blocks with a diameter of less than 1 cm. After that, it was vacuum dried at 90°C and then ball-milled. The powder was sieved to obtain 200 mesh powder. The obtained powder was dispersed in 200ml of water (0.5wt% sodium hexametaphosphate solution was added to prevent agglomeration and sedimentation) to obtain a dispersion. A strong magnet was slowly moved on the outer wall of a beaker to adsorb magnetic particles. Then, the non-magnetic slurry was poured out, and the collected magnetic material was rinsed with pure water. The obtained magnetic material was soaked in 0.5 mol / L sodium hydroxide solution for 1h, then soaked in 0.1 mol / L hydrochloric acid for 10min, and the regenerated stabilizer was repeatedly washed with deionized water until the washing solution was neutral to remove residual acid, alkali and soluble salt. Finally, it was dried at 80°C to obtain regenerated stabilizer powder.

[0062] (2) The obtained regenerated stabilizer powder was used to prepare a curing agent in the same way as in Example 1. The process was repeated twice, and the phosphorus / fluorine of the original phosphogypsum residue was cured. The experimental results are shown in Table 2.

[0063] Table 2

[0064]

[0065] Therefore, the stabilizer used in this invention can achieve good recycling and regeneration effects.

[0066] Application Example 3

[0067] The unconfined compressive strength of the phosphogypsum obtained by the harmless treatment according to Example 1 and Comparative Example 3 in Application Example 1 was tested, and the experimental results are shown in Table 3.

[0068] Table 3

[0069]

[0070] As can be seen from Table 3, the addition of the magnetic iron oxide-supported zirconium-aluminum bimetallic oxide stabilizer results in phosphogypsum with strong compressive strength.

[0071] Application Example 4

[0072] The phosphogypsum obtained from Application Example 1 was subjected to stability testing. The phosphogypsum was soaked in a 0.2 wt% hydrochloric acid solution. After six months, the content of soluble phosphorus and soluble fluorine in the leachate and the compressive strength were measured. The results are shown in Table 4.

[0073] Table 4

[0074]

[0075] As shown in Table 3, with the increase of time, phosphogypsum has a good phosphorus / fluorine curing effect in weakly acidic solution and maintains good compressive strength.

[0076] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A phosphorus-fluorine curing agent for phosphogypsum, characterized in that, By mass, it is composed of the following raw materials: 300-500 parts of slag powder, 10-20 parts of anhydrous sodium sulfate, 150-200 parts of water glass, 10-20 parts of sodium hydroxide, 50-200 parts of Fe3O4@SiO2@Zr-Al bimetallic oxide stabilizer and 400-800 parts of water. The Fe3O4@SiO2@Zr-Al bimetallic oxide stabilizer has a core-shell structure, with magnetic iron oxide grains as the core, and an amorphous silicon dioxide protective layer and an active layer sequentially wrapped around the surface of the magnetic iron oxide grains. The active layer is an amorphous, porous network structure of zirconium-aluminum bimetallic oxide. The amorphous silica protective layer contains Si-OH bonds on its surface, which are connected to the active layer by chemical bonds.

2. The phosphorus-fluorine curing agent according to claim 1, characterized in that, The Fe3O4@SiO2@Zr-Al bimetallic oxide stabilizer was prepared by the following method: A magnetic iron oxide nanoparticle dispersion is provided; Tetraethyl orthosilicate solution was added to the magnetic iron oxide nanoparticle dispersion and reacted to form a protective layer of silicon dioxide on the surface of the magnetic iron oxide nanoparticles, thus obtaining Fe3O4@SiO2 composite particles. The Fe3O4@SiO2 composite particle dispersion was obtained by resuspending the particles in water. Zirconium and aluminum sources were dissolved in water to obtain a mixed metal salt solution. Under stirring, the mixed metal salt solution was added dropwise to the Fe3O4@SiO2 composite particle dispersion. Then, ammonia solution was added dropwise as a precipitant while controlling the solution to be alkaline. The reaction was carried out under heating to form an amorphous zirconium-aluminum hydroxide gel layer on the surface of the composite particles. The product was separated using a magnet, washed and dried to obtain the precursor powder. The obtained precursor powder was heated and calcined to obtain the Fe3O4@SiO2@Zr-Al bimetallic oxide stabilizer. The zirconium source is selected from zirconium oxychloride; The aluminum source is selected from one or more of aluminum nitrate, aluminum chloride, or aluminum sulfate; Heating reaction: temperature 60~80℃, time 3~6h.

3. The phosphorus-fluorine curing agent according to claim 2, characterized in that, The concentration of the magnetic iron oxide nanoparticle dispersion is 15~25wt%; The concentration of the tetraethyl orthosilicate solution is 5~10wt%.

4. The phosphorus-fluorine curing agent according to claim 2, characterized in that, The reaction conditions for adding tetraethyl orthosilicate solution to the magnetic iron oxide nanoparticle dispersion and carrying out the reaction are: temperature 25~30℃, time 3~5h; The concentration of the Fe3O4@SiO2 composite particle dispersion is 10~30 mg / ml.

5. The phosphorus-fluorine curing agent according to claim 2, characterized in that, The molar ratio of the zirconium source to the aluminum source is 1:(1~2); The concentration of the ammonia solution is 25~28wt%.

6. The phosphorus-fluorine curing agent according to claim 2, characterized in that, The heating and roasting temperature is 400~550℃, and the time is 2~4 hours.

7. The method for preparing the phosphorus-fluorine curing agent according to any one of claims 1 to 6, characterized in that, Includes the following steps: The slag powder and anhydrous sodium sulfate are mixed evenly to obtain a dry mixture; Water glass and sodium hydroxide are fully dissolved and hydrolyzed in water to obtain an alkaline activation solution; The obtained alkaline activation solution was added to the dry mixture and stirred evenly. Then, Fe3O4@SiO2@Zr-Al bimetallic oxide stabilizer was added and stirred and mixed step by step to obtain a slurry. The slurry was heated and allowed to stand for aging to obtain the phosphorus-fluorine curing agent.

8. The preparation method according to claim 7, characterized in that, Conditions for heating and aging: temperature 50~60℃, aging time 20~30 hours.

9. The preparation method according to claim 7, characterized in that, Step-by-step mixing: First, mix at 450-500 rpm for 10-12 minutes, then adjust the speed to 250-300 rpm and mix for 10-12 minutes, and finally mix at 100-150 rpm for 15-25 minutes.

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