A soil amendment additive based on slag aggregate and a preparation process thereof

Abstract

The application discloses a kind of soil improvement additive based on slag aggregate and preparation process thereof, belong to soil improvement technical field.First, slag aggregate is mixed with phosphoric acid solution, filtrate and solid are collected, to obtain acid-activated slag, then the collected filtrate is mixed with magnesium chloride hexahydrate, aluminium chloride hexahydrate and urea, and the pH is adjusted to obtain a hydrothermal reaction solution;The hydrothermal reaction solution and acid-activated slag are reacted, filtered to obtain slag@LDHs, solvent and cetyltrimethylammonium bromide are added, ammonia water and tetraethyl orthosilicate are added in sequence, and the mixture is stirred to obtain slag@LDHs@SiO2;Deionized water, ferrous sulfate heptahydrate and sodium citrate are mixed, and the pH is adjusted to obtain a plating solution.Finally, slag@LDHs@SiO2, plating solution and sodium hypophosphite are mixed and reacted to obtain a soil improvement additive.The soil improvement additive provided by the application can dynamically neutralize acidic soil, reduce nutrient loss and reduce heavy metal content in crops.

Description

Technical Field

[0001] This invention belongs to the field of soil improvement technology, specifically relating to a soil improvement additive based on slag aggregate and its preparation process. Background Technology

[0002] Environmentally friendly sand is the solid residue remaining after municipal solid waste incineration slag undergoes a series of processes such as crushing, screening, and mineral processing in a comprehensive treatment plant to extract valuable metals. Also known as "slag aggregate," its main chemical components are calcium oxide (CaO), silicon dioxide (SiO2), aluminum oxide (Al2O3), magnesium oxide (MgO), and small amounts of oxides of elements such as iron, manganese, and phosphorus. Slag aggregate is rich in calcium, magnesium, and silicon, medium-level elements essential for plant growth, as well as trace elements. Furthermore, the processed slag particles have a porous structure and a certain specific surface area. Currently, slag aggregate is widely used in road construction, engineering backfilling, and cement admixtures, achieving initial resource utilization. In agriculture, due to its content of medium-level elements such as calcium, magnesium, and silicon, and its alkaline properties, it is used directly or after simple processing as a soil conditioner to neutralize acidic soils and supplement mineral nutrients.

[0003] In agricultural production, various materials such as lime, gypsum, organic fertilizer, water-retaining agents, and passivating agents are commonly used to improve degraded soils. However, existing technologies have some drawbacks: First, they are functionally limited, with different materials often only addressing a single issue such as pH, structure, or heavy metals, making it difficult to synergistically solve systemic soil problems. Second, their effects are not lasting or contradictory; for example, lime adjusts pH but can easily cause compaction, and ordinary passivating agents may alter the soil's physicochemical properties. Moreover, most materials lack long-term slow-release capabilities, easily leading to nutrient loss or diminishing effectiveness. Finally, they lack responsiveness; the behavior of these materials in the soil is static, unable to adjust their functional release according to changes in the soil environment (such as pH fluctuations and alternating wet and dry periods).

[0004] Therefore, given the shortcomings of existing technologies, it is essential to propose a new soil amendment additive based on slag aggregate and its preparation process. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a soil amendment additive based on slag aggregate and its preparation process.

[0006] The first aspect of this invention is to provide a preparation process for a soil amendment additive based on slag aggregate, comprising the following steps: S1: The slag aggregate is mixed with phosphoric acid solution and reacted. The filtrate and solid are collected. The solid is washed to obtain acid-activated slag. S2: Mix the filtrate collected in S1 with magnesium chloride hexahydrate, aluminum chloride hexahydrate, and urea, and adjust the pH value to obtain a hydrothermal reaction solution. S3: Mix the hydrothermal reaction solution and acid-activated slag for reaction, and then filter and dry to obtain slag@LDHs; S4: Mix slag@LDHs, solvent and hexadecyltrimethylammonium bromide, add ammonia water and tetraethyl orthosilicate in sequence and stir to react. After the reaction is completed, filter, wash, dry and remove template agent to obtain slag@LDHs@SiO2; S5: Mix deionized water, ferrous sulfate heptahydrate and sodium citrate, and adjust the pH value to obtain the plating solution; S6: Under inert gas protection, slag@LDHs@SiO2, plating solution and sodium hypophosphite are mixed and reacted. After the reaction is completed, the mixture is filtered, washed and dried to obtain a soil amendment additive based on slag aggregate.

[0007] It should be noted that this invention first utilizes phosphoric acid to dissolve active metal ions such as calcium, magnesium, and aluminum from the surface of slag particles, forming micro-etchings and active sites on the surface. Subsequently, under hydrothermal conditions with an alkaline environment provided by urea, these dissolved ions, together with added magnesium and aluminum ions, crystallize and grow on the slag surface, forming strongly chemically bonded layered bimetallic hydroxide (LDH) sheets. Next, using the cationic surfactant hexadecyltrimethylammonium bromide as a template, tetraethyl orthosilicate is hydrolyzed and polycondensed to form an amorphous SiO2 network outside the LDH layers. After calcination to remove the template, a shell with interconnected mesopores is formed. Finally, in a weakly acidic electroless plating bath under nitrogen protection, sodium hypophosphite is used to decompose Fe... 2+ Reduced to Fe 0 Atoms grow at active sites on the surface of the SiO2 shell, forming well-dispersed zero-valent iron particles.

[0008] In some embodiments, the ratio of slag aggregate to phosphoric acid solution is 0.5-1.5g:4-6mL; the concentration of phosphoric acid solution is 0.45-0.55mol / L; and the particle size of slag aggregate is 0.5-2mm.

[0009] In some embodiments, the mass ratio of magnesium chloride hexahydrate to slag aggregate is 5.8-6.3:18-22; the mass ratio of magnesium chloride hexahydrate, aluminum chloride hexahydrate, and urea is 6-6.2:2.8-3.2:3.

[0010] In some embodiments, the mass ratio of slag@LDHs to hexadecyltrimethylammonium bromide is 48-52:0.5-2; the solvent is an aqueous ethanol solution with a volume fraction of 78-82%; the mass amount of the solvent is 4.5-5.5 times the sum of the masses of slag@LDHs and hexadecyltrimethylammonium bromide; the mass amount of ammonia is 9-12% of the mass of slag@LDHs; and the volume ratio of ammonia to tetraethyl orthosilicate is 0.5-1.5:1-3.

[0011] In some embodiments, the ratio of deionized water, ferrous sulfate heptahydrate, and sodium citrate is 500mL:6-8g:13-15g; the dissolved oxygen in the deionized water is <0.5ppm; and the ratio of slag@LDHs@SiO2, plating solution, and sodium hypophosphite is 1-3g:10-11mL:0.05-0.15g.

[0012] In some embodiments, in S1, the mixing reaction is carried out at 65-75°C for 1.5-2.5 hours, and the washing is performed 2-4 times with deionized water; in S2, the pH value is adjusted to 9-9.5.

[0013] In some embodiments, in S3, the mixing reaction is carried out by heating to 105-115°C at a rate of 2-4°C / min and holding the reaction at that temperature for 8-12 hours; the drying is carried out at 75-85°C for 10-14 hours.

[0014] In some embodiments, in S4, the stirring reaction time is 5-7 hours, the washing is performed with anhydrous ethanol 2-4 times, and the drying is carried out at 55-65°C for 5-7 hours; the template agent is removed by first heating to 145-155°C at a rate of 1-3°C / min, holding at that temperature for 55-65 minutes, then heating to 380-420°C at a rate of 1-2°C / min, holding at that temperature for 3.5-4.5 hours, and then naturally cooling after the holding period.

[0015] In some embodiments, in S5, the pH value is adjusted to 4.8-5.2; in S6, the mixing reaction is carried out at 55-65°C for 50-70 min, the washing is carried out by washing with deionized water 2-3 times and anhydrous ethanol 1-2 times, and the drying is carried out at 55-65°C and -0.09 to -0.12 MPa for 5-7 h.

[0016] The second aspect of the present invention is to provide a process for preparing a soil amendment additive based on slag aggregate to obtain the soil amendment additive based on slag aggregate.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: This invention creatively modifies slag aggregate. First, a layered bimetallic hydroxide (LDH) layer is grown in situ on the slag surface, giving it pH buffering and anion-controlled release capabilities. When it encounters soil acid, it dissolves and releases OH-. -It neutralizes acidity, continuously and stably adjusting strongly acidic soil to a suitable range for crops, and releases anionic nutrients such as phosphate and nitrate through ion exchange. Secondly, it is coated with a mesoporous SiO2 protective shell, which physically fixes nutrient molecules, prevents leaching, slows the dissolution of LDHs, and enhances its water absorption and fertilizer retention performance. Finally, zero-valent iron particles grow on the shell surface; their high specific surface area and reducing properties efficiently fix heavy metals. These zero-valent iron particles, through their strong reducing properties, release soluble heavy metal ions (such as Cd). 2+ Pb 2+ It is transformed into an insoluble form and fixed through surface complexation and precipitation, thereby reducing the heavy metal content of crops. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to specific embodiments.

[0019] Example 1 A soil amendment additive based on slag aggregate is prepared by the following steps: S1: Mix slag aggregate with phosphoric acid solution at a ratio of 1g:5mL, react at 70℃ for 2h, collect the filtrate and solid, and wash the solid three times with deionized water to obtain acid-activated slag; wherein, the concentration of phosphoric acid solution is 0.5mol / L; the particle size of slag aggregate is 0.5-2mm; S2: The filtrate collected in S1 is mixed with magnesium chloride hexahydrate, aluminum chloride hexahydrate, and urea in a mass ratio of 6.1:3:3, and the pH is adjusted to 9.3 to obtain a hydrothermal reaction solution; wherein the mass ratio of magnesium chloride hexahydrate to slag aggregate is 6.1:20. S3: Mix the hydrothermal reaction solution and acid-activated slag, heat to 110°C at a rate of 3°C / min, hold for 10 hours, filter after the reaction, and then dry at 80°C for 12 hours to obtain slag@LDHs. S4: Slag@LDHs, solvent, and hexadecyltrimethylammonium bromide were mixed, and ammonia water and tetraethyl orthosilicate were added sequentially in a volume ratio of 1:2. The mixture was stirred and reacted for 6 hours. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and dried at 60°C for 6 hours. Finally, the template agent was removed, and the temperature was increased to 150°C at a rate of 2°C / min and held for 60 minutes. Then, the temperature was increased to 400°C at a rate of 2°C / min and held for 4 hours. After the holding period, the mixture was allowed to cool naturally to obtain slag@LDHs@SiO2. The mass ratio of slag@LDHs to hexadecyltrimethylammonium bromide was 50:1.5. The solvent was an 80% (v / v) aqueous ethanol solution. The mass of the solvent was 5 times the sum of the masses of slag@LDHs and hexadecyltrimethylammonium bromide. The mass of ammonia water was 11% of the mass of slag@LDHs. S5: Mix deionized water, ferrous sulfate heptahydrate, and sodium citrate in a ratio of 500mL:7g:14g, adjust the pH to 5, and obtain the plating solution; wherein, the dissolved oxygen in the deionized water is <0.5ppm; S6: Under inert gas protection, slag@LDHs@SiO2, plating solution and sodium hypophosphite in a ratio of 2g:10mL:0.1g are mixed and reacted at 60℃ for 60min. After the reaction is completed, the mixture is filtered, washed 3 times with deionized water and 1 time with anhydrous ethanol, and finally dried at 60℃ and -0.01MPa for 6h to obtain the soil amendment additive based on slag aggregate.

[0020] Example 2 A soil amendment additive based on slag aggregate is prepared by the following steps: S1: Slag aggregate with a ratio of 1.5g:6mL is mixed with phosphoric acid solution and reacted at 75℃ for 2.5h. The filtrate and solid are collected. The solid is washed 4 times with deionized water to obtain acid-activated slag. The concentration of phosphoric acid solution is 0.55mol / L. The particle size of slag aggregate is 2mm. S2: The filtrate collected in S1 is mixed with magnesium chloride hexahydrate, aluminum chloride hexahydrate, and urea in a mass ratio of 6.2:3.2:3, and the pH is adjusted to 9.5 to obtain a hydrothermal reaction solution; wherein the mass ratio of magnesium chloride hexahydrate to slag aggregate is 6.3:22. S3: Mix the hydrothermal reaction solution and acid-activated slag, heat to 115°C at a rate of 4°C / min, hold for 8 hours, filter after the reaction, and then dry at 85°C for 14 hours to obtain slag@LDHs. S4: Slag@LDHs, solvent, and hexadecyltrimethylammonium bromide were mixed, and ammonia water and tetraethyl orthosilicate were added sequentially in a volume ratio of 1.5:3. The mixture was stirred and reacted for 7 hours. After the reaction was completed, the mixture was filtered, washed four times with anhydrous ethanol, and dried at 65°C for 7 hours. Finally, the template agent was removed, and the temperature was increased to 155°C at a rate of 3°C / min and held for 55-65 minutes. Then, the temperature was increased to 420°C at a rate of 2°C / min and held for 4.5 hours. After the holding period, the mixture was allowed to cool naturally to obtain slag@LDHs@SiO2. The mass ratio of slag@LDHs to hexadecyltrimethylammonium bromide was 52:2. The solvent was an 82% (v / v) aqueous ethanol solution. The mass of the solvent was 5.5 times the sum of the masses of slag@LDHs and hexadecyltrimethylammonium bromide. The mass of ammonia water was 12% of the mass of slag@LDHs. S5: Mix deionized water, ferrous sulfate heptahydrate, and sodium citrate in a ratio of 500mL:8g:15g, adjust the pH to 5.2, and obtain the plating solution; wherein, the dissolved oxygen in the deionized water is <0.5ppm; S6: Under inert gas protection, slag@LDHs@SiO2, plating solution and sodium hypophosphite in a ratio of 3g:11mL:0.15g are mixed and reacted at 65℃ for 70min. After the reaction is completed, the mixture is filtered, washed 3 times with deionized water and 2 times with anhydrous ethanol, and finally dried at 65℃ and -0.12MPa for 7h to obtain the soil amendment additive based on slag aggregate.

[0021] Example 3 A soil amendment additive based on slag aggregate is prepared by the following steps: S1: Slag aggregate with a ratio of 0.5g:4mL is mixed with phosphoric acid solution and reacted at 65℃ for 1.5h. The filtrate and solid are collected. The solid is washed twice with deionized water to obtain acid-activated slag. The concentration of phosphoric acid solution is 0.45mol / L. The particle size of slag aggregate is 0.5mm. S2: The filtrate collected in S1 is mixed with magnesium chloride hexahydrate, aluminum chloride hexahydrate, and urea in a mass ratio of 6:2.8:3, and the pH is adjusted to 9 to obtain a hydrothermal reaction solution; wherein the mass ratio of magnesium chloride hexahydrate to slag aggregate is 5.8:18. S3: Mix the hydrothermal reaction solution and acid-activated slag, heat to 105°C at a rate of 2°C / min, hold for 8 hours, filter after the reaction, and then dry at 75°C for 10 hours to obtain slag@LDHs. S4: Slag@LDHs, solvent, and hexadecyltrimethylammonium bromide were mixed, and ammonia water and tetraethyl orthosilicate were added sequentially in a volume ratio of 0.5:1. The mixture was stirred and reacted for 5 hours. After the reaction was completed, the mixture was filtered, washed twice with anhydrous ethanol, and dried at 55°C for 5 hours. Finally, the template agent was removed, and the temperature was increased to 145°C at a rate of 1°C / min and held for 55 minutes. Then, the temperature was increased to 380°C at a rate of 1°C / min and held for 3.5 hours. After the holding period, the mixture was allowed to cool naturally to obtain slag@LDHs@SiO2. The mass ratio of slag@LDHs to hexadecyltrimethylammonium bromide was 48:0.5. The solvent was a 78% (v / v) aqueous ethanol solution. The mass of the solvent was 4.5 times the sum of the masses of slag@LDHs and hexadecyltrimethylammonium bromide. The mass of ammonia water was 9% of the mass of slag@LDHs. S5: Mix deionized water, ferrous sulfate heptahydrate, and sodium citrate in a ratio of 500mL:6g:13g, adjust the pH to 4.8, and obtain the plating solution; wherein, the dissolved oxygen in the deionized water is <0.5ppm; S6: Under inert gas protection, slag@LDHs@SiO2, plating solution and sodium hypophosphite in a ratio of 1g:10mL:0.05g are mixed and reacted at 55℃ for 50min. After the reaction is completed, the mixture is filtered, washed twice with deionized water and once with anhydrous ethanol, and finally dried at 55℃ and -0.09Pa for 5h to obtain the soil amendment additive based on slag aggregate.

[0022] Example 4 A soil amendment additive based on slag aggregate is prepared by the following steps: S1: Slag aggregate with a ratio of 0.8g:4.5mL is mixed with phosphoric acid solution and reacted at 70℃ for 2.5h. The filtrate and solid are collected. The solid is washed 4 times with deionized water to obtain acid-activated slag. The concentration of phosphoric acid solution is 0.55mol / L. The particle size of slag aggregate is 1.5mm. S2: The filtrate collected in S1 is mixed with magnesium chloride hexahydrate, aluminum chloride hexahydrate, and urea in a mass ratio of 6.2:2.8:3, and the pH is adjusted to 9.2 to obtain a hydrothermal reaction solution; wherein the mass ratio of magnesium chloride hexahydrate to slag aggregate is 5.9:19. S3: Mix the hydrothermal reaction solution and acid-activated slag, heat to 15°C at a rate of 3°C / min, hold for 9 hours, filter after the reaction, and then dry at 80°C for 11 hours to obtain slag@LDHs. S4: Slag@LDHs, solvent, and hexadecyltrimethylammonium bromide were mixed, and ammonia water and tetraethyl orthosilicate were added sequentially in a volume ratio of 1:3. The mixture was stirred and reacted for 6.5 h. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and dried at 60 °C for 7 h. Finally, the template agent was removed, and the temperature was increased to 150 °C at a rate of 3 °C / min and held for 65 min. Then, the temperature was increased to 390 °C at a rate of 2 °C / min and held for 4 h. After the holding period, the mixture was allowed to cool naturally to obtain slag@LDHs@SiO2. The mass ratio of slag@LDHs to hexadecyltrimethylammonium bromide was 49:0.1. The solvent was a 79% (v / v) aqueous ethanol solution. The mass of the solvent was 5 times the sum of the masses of slag@LDHs and hexadecyltrimethylammonium bromide. The mass of ammonia water was 11% of the mass of slag@LDHs. S5: Mix deionized water, ferrous sulfate heptahydrate, and sodium citrate in a ratio of 500mL:6g:15g, adjust the pH to 5, and obtain the plating solution; wherein, the dissolved oxygen in the deionized water is <0.5ppm; S6: Under inert gas protection, slag@LDHs@SiO2, plating solution and sodium hypophosphite in a ratio of 3g:10mL:0.1g are mixed and reacted at 65℃ for 50min. After the reaction is completed, the mixture is filtered, washed twice with deionized water and twice with anhydrous ethanol, and finally dried at 65℃ and -0.1MPa for 7h to obtain the soil amendment additive based on slag aggregate.

[0023] Example 5 A soil amendment additive based on slag aggregate is prepared by the following steps: S1: Slag aggregate with a ratio of 1.5g:4mL is mixed with phosphoric acid solution and reacted at 65℃ for 2.5h. The filtrate and solid are collected. The solid is washed twice with deionized water to obtain acid-activated slag. The concentration of phosphoric acid solution is 0.55mol / L. The particle size of slag aggregate is 1.5mm. S2: The filtrate collected in S1 is mixed with magnesium chloride hexahydrate, aluminum chloride hexahydrate, and urea in a mass ratio of 6.1:3.1:3, and the pH is adjusted to 9.4 to obtain a hydrothermal reaction solution; wherein the mass ratio of magnesium chloride hexahydrate to slag aggregate is 6.2:21. S3: Mix the hydrothermal reaction solution and acid-activated slag, heat to 105°C at a rate of 3°C / min, hold for 11 hours, filter after the reaction, and then dry at 85°C for 14 hours to obtain slag@LDHs. S4: Slag@LDHs, solvent, and hexadecyltrimethylammonium bromide were mixed, and ammonia water and tetraethyl orthosilicate (volume ratio 1:1) were added sequentially. The mixture was stirred and reacted for 7 hours. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and dried at 65°C for 5 hours. Finally, the template agent was removed, and the temperature was increased to 150°C at a rate of 2°C / min and held for 65 minutes. Then, the temperature was increased to 410°C at a rate of 2°C / min and held for 4.5 hours. After the holding period, the mixture was allowed to cool naturally to obtain slag@LDHs@SiO2. The mass ratio of slag@LDHs to hexadecyltrimethylammonium bromide was 52:1. The solvent was an 81% (volume fraction) aqueous ethanol solution. The mass of the solvent was 5.5 times the sum of the masses of slag@LDHs and hexadecyltrimethylammonium bromide. The mass of ammonia water was 11% of the mass of slag@LDHs. S5: Mix deionized water, ferrous sulfate heptahydrate, and sodium citrate in a ratio of 500mL:8g:13g, adjust the pH to 5, and obtain the plating solution; wherein, the dissolved oxygen in the deionized water is <0.5ppm; S6: Under inert gas protection, slag@LDHs@SiO2, plating solution and sodium hypophosphite in a ratio of 1g:11mL:0.05g are mixed and reacted at 55℃ for 65min. After the reaction is completed, the mixture is filtered, washed 3 times with deionized water and 2 times with anhydrous ethanol, and finally dried at 55℃ and -0.12MPa for 7h to obtain the soil amendment additive based on slag aggregate.

[0024] Comparative Example 1 Unmodified raw slag was used as a soil amendment additive.

[0025] Comparative Example 2 It is basically the same as Example 1, except that S4-S6 are omitted, that is, slag@LDHs is used as a soil amendment additive.

[0026] Comparative Example 3 It is basically the same as Example 1, except that S5-S6 are omitted, that is, slag@LDHs@SiO2 is used as soil amendment additive.

[0027] Comparative Example 4 Unmodified raw slag, commercially purchased LDHs powder (source: Shandong Hongxing), mesoporous SiO2 powder (source: Jiangsu Xianfeng Nano), and nano iron powder (source: Ya'an Shijiaweier) were physically mixed according to the theoretical mass ratio of each component in the final product in Example 1.

[0028] The performance of the soil amendment additives prepared in Examples 1-5 and Comparative Examples 1-4 was tested, and the test results are shown in Tables 1-3.

[0029] pH buffering capacity and long-term performance test: 1g of sample was evenly mixed with 20g of standard acidic red soil with pH=4.0, and deionized water was added to 60% of field capacity. The mixture was placed in a constant temperature incubator at 25℃. The pH value of the soil suspension (soil-water ratio 1:2.5) was measured on days 1, 7, 30, and 60. The pH test results are shown in Table 1.

[0030] Nutrient slow-release performance test: 5g of sample was loaded into a glass column and covered with a measured amount of quartz sand. Simulated acid rain (pH=5.6) was used for intermittent leaching at a certain flow rate (e.g., 0.5 mL / min). Leachate was collected at different time points, and the Ca content was determined. 2+ Concentration and cumulative calcium ion release data are shown in Table 2.

[0031] Heavy metal passivation performance test: After mixing and culturing the sample with Cd-containing contaminated soil, the conversion rate of heavy metals from acid-extractable state to residual state was analyzed. The test results are shown in Table 3.

[0032] Table 1

[0033] Table 2

[0034] Table 3

[0035] As can be seen from Tables 1-3, the soil amendment additives based on slag aggregates prepared in Examples 1-5 of the present invention exhibit excellent performance in pH buffering, nutrient slow release, and metal passivation.

[0036] Based on the comparative data, it can be seen that Comparative Example 1 used unmodified raw slag, and the rapid dissolution of alkaline substances on its surface caused the pH value to drop continuously. The lack of slow-release capacity led to the rapid release of calcium ions, and it did not have the ability to passivate heavy metals. Comparative Example 2 used slag@LDHs. Due to the lack of a mesoporous SiO2 protective shell, it dissolved too quickly under the acidic soil environment and the action of microorganisms. In the middle and later stages, the pH buffering capacity decreased and the release of calcium ions was weak. Comparative Example 3 used slag@LDHs@SiO2. Due to the lack of zero-valent iron particles on the surface, it could not passivate heavy metals well.

[0037] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A preparation process for a soil amendment additive based on slag aggregate, characterized in that, Includes the following steps: S1: The slag aggregate is mixed with phosphoric acid solution and reacted. The filtrate and solid are collected. The solid is washed to obtain acid-activated slag. S2: Mix the filtrate collected in S1 with magnesium chloride hexahydrate, aluminum chloride hexahydrate, and urea, and adjust the pH value to obtain a hydrothermal reaction solution. S3: The hydrothermal reaction solution and the acid-activated slag are mixed and reacted, and then filtered and dried to obtain slag@LDHs; S4: The slag@LDHs, solvent and hexadecyltrimethylammonium bromide are mixed, and ammonia water and tetraethyl orthosilicate are added in sequence and stirred to react. After the reaction is completed, the mixture is filtered, washed, dried and the template agent is removed to obtain slag@LDHs@SiO2. S5: Mix deionized water, ferrous sulfate heptahydrate and sodium citrate, and adjust the pH value to obtain the plating solution; S6: Under inert gas protection, the slag@LDHs@SiO2, the plating solution and sodium hypophosphite are mixed and reacted. After the reaction is completed, the mixture is filtered, washed and dried to obtain the soil amendment additive based on slag aggregate.

2. The preparation process of the soil amendment additive based on slag aggregate according to claim 1, characterized in that, The ratio of the slag aggregate to the phosphoric acid solution is 0.5-1.5g:4-6mL; the concentration of the phosphoric acid solution is 0.45-0.55mol / L; and the particle size of the slag aggregate is 0.5-2mm.

3. The preparation process of the soil amendment additive based on slag aggregate according to claim 1, characterized in that, The mass ratio of magnesium chloride hexahydrate to the slag aggregate is 5.8-6.3:18-22; the mass ratio of magnesium chloride hexahydrate, aluminum chloride hexahydrate, and urea is 6-6.2:2.8-3.2:

3.

4. The preparation process of the soil amendment additive based on slag aggregate according to claim 1, characterized in that, The mass ratio of the slag@LDHs to the hexadecyltrimethylammonium bromide is 48-52:0.5-2; the solvent is an aqueous ethanol solution with a volume fraction of 78-82%; the mass amount of the solvent is 4.5-5.5 times the sum of the masses of the slag@LDHs and the hexadecyltrimethylammonium bromide; the mass amount of ammonia is 9-12% of the mass of the slag@LDHs; and the volume ratio of the ammonia to the tetraethyl orthosilicate is 0.5-1.5:1-3.

5. The preparation process of the soil amendment additive based on slag aggregate according to claim 1, characterized in that, The ratio of the amount of deionized water, the amount of ferrous sulfate heptahydrate, and the amount of sodium citrate is 500mL:6-8g:13-15g; the dissolved oxygen in the deionized water is <0.5ppm; the ratio of the amount of slag@LDHs@SiO2, the plating solution, and the amount of sodium hypophosphite is 1-3g:10-11mL:0.05-0.15g.

6. The preparation process of the soil amendment additive based on slag aggregate according to claim 1, characterized in that, In step S1, the mixing reaction is carried out at 65-75℃ for 1.5-2.5 hours, and the washing is performed 2-4 times with deionized water; in step S2, the pH value is adjusted to 9-9.

5.

7. The preparation process of the soil amendment additive based on slag aggregate according to claim 1, characterized in that, In S3, the mixing reaction is carried out by heating to 105-115℃ at a rate of 2-4℃ / min and holding the temperature for 8-12 hours; the drying is carried out at 75-85℃ for 10-14 hours.

8. The preparation process of the soil amendment additive based on slag aggregate according to claim 1, characterized in that, In step S4, the stirring reaction time is 5-7 hours, the washing is performed with anhydrous ethanol 2-4 times, and the drying is carried out at 55-65℃ for 5-7 hours. The template agent removal is carried out by first heating to 145-155℃ at a rate of 1-3℃ / min and holding for 55-65 minutes, then heating to 380-420℃ at a rate of 1-2℃ / min and holding for 3.5-4.5 hours, and then naturally cooling after the holding period.

9. The preparation process of the soil amendment additive based on slag aggregate according to claim 1, characterized in that, In step S5, the pH value is adjusted to 4.8-5.2; in step S6, the mixing reaction is carried out at 55-65℃ for 50-70 min, the washing is carried out by washing with deionized water 2-3 times and anhydrous ethanol 1-2 times, and the drying is carried out at 55-65℃ and -0.09 to -0.12 MPa for 5-7 h.

10. A soil amendment additive based on slag aggregate prepared by the preparation process of the soil amendment additive based on slag aggregate as described in any one of claims 1-9.

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