A solidifying agent for solidifying heavy metal cadmium contaminated soil, a preparation method and application thereof

Abstract

This invention discloses a solidifying agent for solidifying cadmium-contaminated soil, comprising slag, red mud, carbide slag, and phosphogypsum. The mass ratio of red mud to slag is 1:(0.5-2), and the amounts of carbide slag and phosphogypsum are 10%-20% of the total mass of red mud and slag. Red mud can serve as an auxiliary cementing material for slag, while carbide slag and phosphogypsum can effectively activate the red mud and slag, thereby achieving a better solidification effect. The preparation method of this invention is simple, convenient, low-cost, and has good performance. The prepared environmentally friendly solidifying agent is a completely solid waste-based solidifying agent, unlike existing cement-based and lime-based solidifying agents. This environmentally friendly solidifying agent can replace the use of traditional solidifying agents such as cement and lime, reducing production costs, energy consumption, and carbon emissions. Furthermore, it not only serves as a way to reuse solid wastes such as red mud, avoiding the environmental risks associated with accumulation, but also as a highly efficient, economical, and environmentally friendly new solidifying agent for remediating cadmium-contaminated soil.

Description

Technical Field

[0001] This invention belongs to the field of environmental geotechnical engineering technology and relates to solidifying agents, specifically a novel solidifying agent for contaminated soil used under different concentrations of cadmium pollution and its preparation method. Background Technology

[0002] Recently, soil pollution has intensified due to improper wastewater discharge, indiscriminate disposal of industrial solid waste, irrational use of pesticides and fertilizers, fossil fuel combustion, and mining activities. This serious soil pollution poses a significant threat to human health, food safety, and the sustainability of the ecological environment. According to the "National Soil Pollution Status Survey Bulletin," cadmium is the most prominent inorganic pollutant exceeding standards in soil. Related studies show that cadmium can accumulate in the human body over a long period and can invade various tissues and organs, potentially causing cadmium poisoning-related lesions. Therefore, there is an urgent need to find economical and efficient remediation methods to treat cadmium-contaminated soil. Solidification / stabilization technology is widely used in contaminated site remediation due to its significant advantages in terms of contaminated soil type, remediation cost, technical reliability, long-term remediation effect, and site reuse. Cement-based and lime-based solidification agents are the most commonly used solidification agents. However, the poor effectiveness of cement and lime in treating soils with high concentrations of heavy metals, coupled with their high carbon emissions and pollution during production, necessitates the search for alternatives.

[0003] In recent years, the generation of large amounts of industrial solid waste has not only occupied land but also posed significant environmental risks. Many researchers have developed solidifying agents using industrial solid waste. However, most of these agents still contain high-cost, high-carbon-emission, and high-energy-consuming products such as cement, lime, and sodium hydroxide. Therefore, developing a novel, highly efficient solidifying agent composed entirely of industrial solid waste offers significant economic, environmental, and social benefits. Blast furnace slag has been widely used for the treatment of contaminated soil and has proven effective. However, with the continuous improvement of solid waste resource utilization, the price of blast furnace slag is rising, and its extensive use leads to a continuous increase in the cost of solidifying contaminated soil. Therefore, selecting low-cost solid waste with potential activity is particularly important. Red mud slag-based cementitious materials are gradually gaining popularity. Because they possess excellent strength and durability after activation, as well as good safety, they are considered a potential high-performance cementitious material. Summary of the Invention

[0004] One of the objectives of this invention is to provide a novel solidifying agent for solidifying soil contaminated with heavy metal cadmium. While remediating the heavy metal contaminated soil, the solidified soil can meet the conditions for use as a building material, such as foundation fill, thereby realizing the resource utilization of contaminated soil and industrial solid waste.

[0005] The second objective of this invention is to provide a new approach to the treatment and reuse of industrial solid waste, in response to the call for green and sustainable remediation.

[0006] This invention is achieved using the following technical solution:

[0007] A solidifying agent for solidifying soil contaminated with heavy metal cadmium includes red mud, slag, carbide slag, and phosphogypsum; wherein the mass ratio of red mud to slag is 1:(0.5-2), and the amount of carbide slag and phosphogypsum is 10%-20% of the total mass of the solidifying agent.

[0008] Further preferably, both the phosphogypsum and carbide slag are industrial waste residues; wherein, the carbide slag is mainly composed of calcium oxide and calcium hydroxide, and can be used as an alkaline activator; the phosphogypsum is mainly composed of calcium sulfate, and can be used as a sulfate activator. The particle size of the red mud, carbide slag, and phosphogypsum powder is 200 mesh. Red mud can be used as an auxiliary cementing material for slag, and carbide slag and phosphogypsum can effectively activate the red mud and slag, thereby achieving a better solidification effect.

[0009] More preferably, the mass ratio of red mud to slag is 1:2, and the amounts of carbide slag and phosphogypsum are 10% and 15% of the total mass of the curing agent, respectively.

[0010] More preferably, the slag is blast furnace slag with a surface area of ​​450 m². 2 / kg of S95 grade slag.

[0011] The preparation method of the above-mentioned solidifying agent for solidifying cadmium-contaminated soil is as follows: red mud, carbide slag, and phosphogypsum are dried at 105℃ and passed through a 200-mesh sieve; the slag selected has a surface area of ​​450m². 2 / kg of S95 grade slag was dried and set aside. The components were weighed according to the proportion and poured into a dry material mixing pot. The mixture was stirred evenly for 5 minutes to obtain the RAS curing agent.

[0012] The application method of the above-mentioned solidifying agent for solidifying heavy metal cadmium contaminated soil is as follows: add RAS solidifying agent to heavy metal cadmium contaminated soil, add water to make the total moisture content reach 19%, stir and place it in a mold to form solidified soil, after demolding the solidified soil, put it into a polyethylene sealed bag and transfer it to a standard curing box for curing under standard conditions.

[0013] Specifically, to ensure the consistency and reproducibility of the properties and pollution characteristics of cadmium-contaminated soil, this study adopted a method for artificially preparing cadmium-contaminated soil. The method for using RAS solidification agent for cadmium-contaminated soil treatment is as follows: a certain amount of Cd... 2+ The pollutant dissolved in distilled water to obtain a product containing Cd. 2+ The contaminated solution, after cleaning and drying the soil, is passed through a 10-mesh sieve for later use; then the solution containing the designed Cd content is prepared. 2 +The contaminated solution was added to clean soil, stirred evenly for 10 minutes, sealed, and aged in a cool place for 10 days to obtain artificially produced Cd of different grades. 2+ For soil contaminated with Cd, weigh out the RAS solidifying agent (10%–20% of the dry soil mass), add an appropriate amount of water to achieve a total moisture content of 19% (optimal moisture content), and evenly fill the mixed solidified soil into a stainless steel cylindrical mold with a diameter of 50 mm and a height of 100 mm in three layers. After each layer is filled, manually vibrate the mold to remove air bubbles from the sample. Then, use a hydraulic jack to statically compress the contaminated or solidified soil to a height of 50 mm. Use the matching hydraulic jack demolding device to remove the compacted contaminated or solidified soil sample to obtain a cylindrical soil sample with the designed dry density (95% of the maximum dry density). After demolding, place the soil sample in a polyethylene sealed bag (to prevent moisture loss) and transfer it to a standard curing chamber (relative humidity 95%, temperature 20℃) for curing periods of 7 days, 14 days, and 28 days. 2+ The content of Cd in contaminated soil is less than 0.25% (preferably Cd in contaminated soil). 2+ The content of [unspecified substance] is 0.04%. According to experimental verification, the solidified soil after 14 days of curing can be used as roadbed fill or foundation fill.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] 1. The principle of preparing the RAS curing agent in this invention is as follows: Red mud and slag powder, under the activation of carbide slag and phosphogypsum powder, can form C-(A)-SH cementitious materials and ettringite with good mechanical behavior. With increasing curing age, the amount of C-(A)-SH cementitious materials and ettringite produced during the reaction increases, thus increasing the strength of the RAS-cured soil. Heavy metal Cd 2+ Cd can be fixed in these gel pores by electrostatic adsorption, or it can be encapsulated by the gel during gel formation. 2+ C-(A)-SH cementitious materials and ettringite readily undergo ion exchange reactions, thus being immobilized. Chemical adsorption and chemical precipitation also make significant contributions to the solidification and stabilization of heavy metals, such as Cd. 2+ It readily complexes with the surface of hydroxylated hydrated products, forming insoluble hydroxide precipitates. Phosphogypsum contains PO4. 3- Able to Cd 2+ It has a good stabilizing effect because PO3-4 can react with Cd. 2+ It forms stable heavy metal compound precipitates. For example, cadmium hydroxyphosphate (Cd₅(PO₄)₃OH), Ksp = 10. -64.62 And cadmium phosphate Cd5(PO4), Ksp=10 -32.6These stable compounds enable effective treatment of heavy metal ions. Furthermore, the C-(A)-SH cementitious material and ettringite formed by the RAS reaction have a large specific surface area, which is beneficial for the treatment of Cd. 2+ It has good adsorption properties and reduces the leaching of heavy metal ions.

[0016] 2. The RAS curing agent prepared by this invention is an environmentally friendly curing agent that effectively cures the polluting heavy metal Cd through the synergistic effect of multiple industrial solid wastes. 2+ This aligns with the concept of green and sustainable restoration.

[0017] 3. The RAS curing agent prepared by this invention can meet the strength requirements of 0.36MPa for roadbed fill and 0.68MPa for foundation fill after 14 days of curing. At the same time, the toxicity leaching concentration is lower than the national safety limit (1mg / L), which is conducive to the secondary development and application of the cured soil, such as its use as foundation fill or roadbed fill.

[0018] 4. The RAS curing agent prepared by this invention has similar performance to existing curing agents such as cement and lime, and has better economic benefits and environmental friendliness.

[0019] This invention is rationally designed, using slag as raw material, red mud as an auxiliary cementing material for slag, and phosphogypsum and carbide slag, both solid wastes, as activators to prepare a novel environmentally friendly curing agent. Furthermore, it is the first time that the prepared RAS curing agent has been used for Cd... 2+ The curing process overcomes the limitations of existing curing agents, such as high energy consumption, high pollution, and high cost, and has great practical application and promotion value. Attached Figure Description

[0020] Figure 1 This indicates that Example 1 contains Cd. 2+ Cd in contaminated soil 2+ The effects of the content of [specific ingredient] on the strength of RAS-stabilized soil at curing ages of 7d, 14d, and 28d, respectively.

[0021] Figure 2 This indicates that Example 1 contains Cd. 2+ Cd in contaminated soil 2+ The content of Cd in RAS-stabilized soil at curing ages of 7d, 14d, and 28d was respectively compared with that in the samples. 2+ The effects of leaching.

[0022] Figure 3 This indicates that Example 1 contains Cd. 2+ Cd in contaminated soil 2+ The effects of the content of each on the micromineral structure of RAS-stabilized soil.

[0023] Figure 4 This indicates that Example 5 contains Cd.2+ Different initial Cd in contaminated soil 2+ The effects of the content of each ingredient on the strength of RAS-cured soil with different RAS curing agent dosages.

[0024] Figure 5 This indicates that Example 5 contains Cd. 2+ Different initial Cd in contaminated soil 2+ The content of Cd in RAS-cured soil with different RAS curing agent dosages was respectively affected. 2+ The effects of leaching.

[0025] Figure 6 This represents the different initial concentrations of Cd in Examples 1-4 and Comparative Examples 1-2. 2+ The effect on the compressive strength of solidified soil.

[0026] Figure 7 This represents the different initial concentrations of Cd in Examples 1-4 and Comparative Examples 1-2. 2+ Cd in solidified soil 2+ The effect of leaching concentration. Detailed Implementation

[0027] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0028] The soil was taken from a construction site in Taiyuan City, Shanxi Province. The red mud was provided by an aluminum plant in Shanxi. The slag, carbide slag, and phosphogypsum powder were purchased from a solid waste recycling company. The main chemical components and contents are shown in Table 1.

[0029] Table 1. Main chemical components and contents (%) of soil, red mud, slag, carbide slag, and phosphogypsum powder

[0030]

[0031] The RAS curing agent of this invention includes red mud, slag, carbide slag, and phosphogypsum; the optimal ratio of the four components was obtained through orthogonal experiments, as shown in Table 2.

[0032] Table 2

[0033]

[0034] Table 2 shows that when the ratio of red mud to slag is 1:2, carbide slag and phosphogypsum account for 10% and 15% of the total solidifier, respectively. Therefore, red mud and slag account for 25% and 50% of the total solidifier, respectively. The solidified soil exhibits high strength and meets the safety limits for Cd. 2+ Leaching concentration (<1 mg / L).

[0035] Example 1 This example is used for Cd 2+ The RAS solidification agent for contaminated soil treatment consists of red mud, slag, carbide slag, and phosphogypsum powder.

[0036] In this embodiment, the particle size of the red mud, carbide slag, and phosphogypsum powder is all 200 mesh. The slag has a surface area of ​​450 m². 2 / kg of S95 grade slag. Then, according to the mass ratio of red mud to slag of 1:2, the dosage of carbide slag and phosphogypsum is 10% and 15% of the total mass of the curing agent, respectively, and the mixture is stirred evenly to obtain RAS curing agent.

[0037] The above is used for Cd 2+ The preparation and application method of RAS solidification agent for contaminated soil treatment includes the following steps:

[0038] Red mud, carbide slag and phosphogypsum powder were mixed and stirred evenly for 5 minutes to obtain RAS curing agent.

[0039] Specific applications: Clean soil is dried and then sieved through a 10-mesh sieve for later use; different concentrations of heavy metal Cd(NO3)2 are dissolved in distilled water to obtain Cd-containing... 2+ The contaminated solution contains Cd 2+ Add the contaminated solution to clean soil and mix thoroughly. Referencing the cadmium risk management control values ​​for secondary construction land, design the Cd... 2+ Pollution concentrations of 0, 2, 5, and 15 times the control value represent clean, lightly, moderately, and heavily polluted soil, respectively. For ease of comparison, the Cd concentration in the soil was set to... 2+ The contents of the pollutants were 0%, 0.04%, 0.1%, and 0.25%, respectively, and then aged for 10 days in a sealed, cool environment. A 10% RAS curing agent (referring to the amount of RAS curing agent added to the contaminated soil, e.g., 10g of curing agent for 100g of contaminated soil) was added to different Cd concentrations. 2+ In contaminated soil, add an appropriate amount of water to achieve an overall moisture content of 19% (optimal moisture content). Evenly fill the mixed, solidified soil into a 50mm diameter, 100mm high stainless steel cylindrical mold, filling in three layers. After each layer, manually vibrate the mold to remove air bubbles. Then, use a hydraulic jack to statically compress the contaminated or solidified soil to a height of 50mm. Use the matching hydraulic jack demolding device to remove the compacted contaminated or solidified soil sample, obtaining a cylindrical soil sample with the designed dry density (95% of maximum dry density). After demolding, place the soil sample in a polyethylene sealed bag (to prevent moisture loss) and transfer it to a standard curing chamber (95% relative humidity, 20℃). Curing ages are 7 days, 14 days, and 28 days, followed by strength and Cd testing. 2+ Leaching concentration and other tests.

[0040] (1) Unconfined compressive strength tests were conducted on RAS solidified soil after curing for 7 days, 14 days and 28 days, respectively. The test standard was ASTM D4219.

[0041] Experimental Procedure: The experimental equipment used was a YHS-229WJ-50kN microcomputer-controlled electronic universal testing machine, with the axial strain rate controlled at 1 mm / min. The experimental results are as follows: Figure 1 As shown.

[0042] With Cd in contaminated soil 2+ With increasing content, the compressive strength of RAS-stabilized soil first increases and then decreases, such as Figure 1 shown. When containing Cd 2+ Cd in contaminated soil 2+ When the content is 0.04%, the RAS-stabilized soil exhibits the highest strength at curing ages of 7d, 14d, and 28d, and it also contains Cd. 2+ The compressive strength of the RAS-stabilized soil was significantly higher than the USEPA recommended value of 0.35 MPa. Furthermore, the Cd-containing soil... 2+ The compressive strength of RAS-stabilized soil increases with increasing curing time, such as Figure 1 As shown.

[0043] (2) Toxicity leaching tests were conducted on RAS solidified soil cured at room temperature (25℃) for 7 days, 14 days and 28 days respectively. The test standard was HJ / T299—2007.

[0044] Experimental Procedure: After strength tests were conducted on RAS-cured soil samples at 7, 14, and 28 days of curing, toxicity leaching tests were immediately performed on soil blocks inside the broken samples. The tests were conducted according to the methods and procedures specified in the "Solid Waste Leaching Toxicity Leaching Method: Sulfuric Acid and Nitric Acid Method" (HJ / T299—2007). The concentration of metals in the filtrate was determined using inductively coupled plasma mass spectrometry (ICP-MS). The test results are shown below. Figure 2 And Table 2.

[0045] The tests used Class IV standards from the "Identification Standard for Hazardous Waste" (GB 5085.3—2007) and the "Groundwater Quality Standard" (GB / T14848—2017) as the leaching toxicity identification standards. (Cd) 2+ Leaching concentration and Cd 2+ The initial doping amount is related to Cd. 2+ The leaching concentration varies with the initial added Cd 2+ The content is constantly increasing. Moreover, Cd... 2+ After 14 days of curing, the leaching concentration met the safety limit (1 mg / L) for hazardous solid waste treatment. Figure 2 As shown. Furthermore, with increasing maintenance age, Cd... 2+ The leaching concentration decreased. After 28 days of curing, the Cd concentration in the solidified / stabilized soil decreased. 2+The leaching concentration was 0.02–0.69 mg / L, close to the Class IV groundwater quality standard in China (0.01 mg / L). Figure 2 As shown. Therefore, the proposed RAS curing agent is effective against Cd. 2+ It has a good stabilizing effect.

[0046] (3) XRD experiments were conducted on RAS-stabilized soils with different initial Cd contents.

[0047] Experimental Procedure: The experimental equipment used was an XPert Pro X-ray diffractometer with Cu Kα radiation, an accelerating voltage of 40 kV, a measurement angle of 8–60°, and a step size of 0.01°. Powder X-ray diffraction analysis was performed on the samples. The soil samples were ground into powder in an agate grinding bowl for analysis. The experimental results are as follows: Figure 3 As shown. The intensity of the characteristic peaks of Cd(OH)2, C-(A)-SH and AFt in the XRD pattern is related to that of Cd. 2+ There is a clear correlation between content and concentration. Low Cd content 2+ A small amount of Cd(OH)2 with cementing properties will be generated, promoting the increase of the strength of the solidified soil, while a high Cd content... 2+ Excessive Cd(OH)₂ will be generated and adsorbed on the surface of the curing agent particles, thereby inhibiting the formation of hydration products. Therefore, Cd 2+ The lower the Cd content, the lower the porosity and the stronger the compressive strength of the solidified soil. This is achieved through physical encapsulation, complexation precipitation, electrostatic adsorption, and ion exchange. 2+ The quantity is also greater, resulting in higher chemical stability of cadmium (Cd). 2 + The leaching concentration is even lower. For example... Figure 3 As shown.

[0048] Example 2 follows the same preparation and curing process as Example 1, except that the mass ratio of red mud to slag is 1:2, and no carbide slag or phosphogypsum powder is added. The total amount of curing agent is 10% (relative to the dry soil mass). Strength and Cd are measured after 28 days of curing. 2+ Leaching concentration test.

[0049] Example 3 follows the same preparation and curing process as Example 1, except that the mass ratio of red mud to slag is 1:2, the amount of calcium carbide slag added is 10% of the total mass of the curing agent, and no phosphogypsum powder is added. The preparation and curing process is the same as in Example 1, with a total curing agent content of 10% (relative to dry soil mass). Strength and Cd are measured after 28 days of curing. 2+ Leaching concentration test.

[0050] Example 4 follows the same preparation and curing process as Example 1, except that the mass ratio of red mud to slag is 1:2, the phosphogypsum content is 10% of the total mass of the curing agent, and no carbide slag powder is added. The preparation and curing process is the same as in Example 1, with a total curing agent content of 10% (relative to dry soil mass). Strength and Cd are measured after 28 days of curing. 2+ Leaching concentration test.

[0051] Comparative Example 1: No curing agent was added; only the heavy metal contaminated soil sample from Example 1 was used. Subsequent sample preparation methods were the same as in Example 1. After 28 days of curing, strength and Cd were measured. 2+ Leaching concentration test.

[0052] Comparative Example 2 followed the same preparation and curing procedures as Example 1, except that the curing agent was #42.5 ordinary Portland cement. Subsequent sample preparation methods were the same as in Example 1, with a total curing agent dosage of 10% (relative to dry soil mass). Strength and Cd were measured after 28 days of curing. 2+ Leaching concentration and other tests were conducted. Experimental results are shown below. Figure 6 and Figure 7 .

[0053] Depend on Figure 6 , 7 It can be seen that the combined solidification of cadmium-contaminated soil by red mud and slag is less effective without an activator; the effect of a single activator is not as good as the combined activation of two solidifiers; when phosphogypsum and carbide slag are added simultaneously as activators in appropriate proportions, the four solid wastes exert a synergistic effect, resulting in solidified soil with better mechanical properties and lower Cd content. 2+ Leaching concentration.

[0054] Example 5: The preparation and curing processes of the curing agent were the same as in Example 1, except that the total dosage of the curing agent was 15% and 20% (relative to dry soil mass), respectively. Subsequent sample preparation methods were the same as in Example 1. After curing for 28 days, strength and Cd were measured. 2+ Leaching concentration test. Experimental results are shown below. Figure 4 and Figure 5 .

[0055] Depend on Figure 4 , 5 It can be seen that the strength of solidified soil is directly proportional to the amount of solidifying agent, Cd 2+ The leaching concentration is inversely proportional to the amount of curing agent. When the curing agent dosage is 20%, the strength of the cured soil is 3.07–4.74 MPa, far exceeding the 0.35 MPa required for roadbed fill. (Cd) 2+ The leaching concentration is 0.006–0.106 mg / L, which meets or is close to the Class IV groundwater quality standard in China (0.01 mg / L).

[0056] Table 3 Environmental and Economic Analysis of RAS Curing Agents

[0057]

[0058] As can be seen from Table 3, Examples 1-5, and Comparative Examples 1-2, the novel RAS curing agent of this invention is worth promoting. Compared with the most common cement curing agent, the curing performance of the RAS curing agent is similar, but the RAS curing agent has better economy and environmental friendliness. The strength of RAS-cured soil is directly proportional to the RAS curing agent dosage and curing age. 2+ Leaching concentration is inversely proportional to RAS curing agent dosage and curing age; low cadmium content promotes the increase of solidified soil strength, while higher cadmium content... 2+ The content can hinder the formation of hydration products.

[0059] The preparation method of this invention is simple, convenient, low-cost, and has good performance. Furthermore, the prepared RAS curing agent is an all-solid-waste-based environmentally friendly curing agent, unlike existing cement-based and lime-based curing agents. This novel RAS curing agent can replace traditional curing agents such as cement and lime, reducing production costs, energy consumption, and carbon emissions. This invention not only serves as a way to reuse solid wastes such as red mud, avoiding the environmental risks associated with accumulation, but also as a highly efficient, economical, and environmentally friendly new curing agent for remediating heavy metal cadmium pollution.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for applying a solidifying agent to solidify soil contaminated with heavy metal cadmium, characterized in that: The curing agent is composed of red mud, slag, carbide slag, and phosphogypsum; the mass ratio of red mud to slag is 1:2, and the amounts of carbide slag and phosphogypsum are 10% and 15% of the total mass of the curing agent, respectively. When applying the solution, add the solidifying agent to the cadmium-contaminated soil. The amount of solidifying agent added is 10% to 20% of the mass of the contaminated soil. The amount of Cd in the contaminated soil... 2+ The content is 0.04% to 0.25%. Water is added to make the total moisture content reach 19%. After stirring, it is placed in a mold and compacted in layers to form solidified soil. After the solidified soil is demolded, it is placed in a polyethylene sealed bag and transferred to a standard curing box for curing under standard conditions.

2. The application method of the solidifying agent for solidifying cadmium-contaminated soil according to claim 1, characterized in that: Slag selected S95 grade slag with a specific surface area of 450 m 2 / kg.

3. The application method of the solidifying agent for solidifying cadmium-contaminated soil according to claim 1, characterized in that: Red mud, carbide slag, and phosphogypsum were dried at 105℃ and then sieved. The slag is selected S95 grade slag with a specific surface area of 450 m 2 / kg, and is dried for standby. Each component is weighed according to the proportion and poured into a dry material stirring pot, uniformly stirred for 5 min, and a solidifying agent is obtained.

4. The application method of the solidifying agent for solidifying cadmium-contaminated soil according to claim 3, characterized in that: The standard maintenance conditions are 95% relative humidity and 20℃.

5. The application method of the solidifying agent for solidifying cadmium-contaminated soil according to claim 4, characterized in that: The solidified soil after 14 days of curing is used as roadbed fill or foundation fill.

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