Remediation agent for chemically eroded polluted soil and application and use method of remediation agent

Abstract

The invention discloses a remediation agent for chemically eroded polluted soil and application and a use method thereof in the technical field of environmental governance and site remediation, the remediation agent provided by the invention can synchronously fix heavy metals in the soil, adsorb and decompose organic pollutants and resist various chemical corrosion, the leaching toxicity of the polluted soil is reduced, and meanwhile, the remediation effect is good. And the repairing agent is wide in raw material source, simple and convenient to prepare and environment-friendly, so that the purpose of treating pollution with waste is achieved, and remarkable economic, environmental and engineering benefits are created.

Description

Technical Field

[0001] This invention relates to the field of environmental remediation and site restoration technology, specifically to a remediation agent for chemically contaminated soil, its uses, and methods of application. Background Technology

[0002] The overall exceedance rate of soil pollution sites in my country is 16.1%, with a moderate to severe rate as high as 2.6%, involving various pollutants such as cadmium (Cr), zinc (Zn), copper (Cu), lead (Pb), polycyclic aromatic hydrocarbons (PAHs), and total petroleum hydrocarbons (TPHs). These pollutants can enter the human body through drinking water, dust, and other routes, causing serious health hazards. They can also disrupt the cementation between soil particles, affecting engineering mechanical properties. Organic matter-heavy metal complex pollution is prevalent in petrochemical, coking, and military production sites. Historically, these types of enterprises have been concentrated in my country's economically developed coastal areas, especially the Yangtze River Delta. Due to the high salt content of groundwater in coastal areas, coupled with the unregulated discharge of wastewater and waste liquid during production, the groundwater in these contaminated sites has high sulfate (SO4) levels. 2- ), chloride salts (Cl - ), carbonates (HCO3) - The concentrations of corrosive ions such as [insert ions here] are high. Therefore, sites contaminated with both organic matter and heavy metals still face the threat of chemical erosion by water bodies after remediation. However, current remediation technologies mainly focus on research into heavy metal-heavy metal and organic matter-organic complex pollution, with less attention paid to soils contaminated with both heavy metals and organic matter, especially those subjected to chemical erosion.

[0003] Solidification and stabilization technologies have a significantly higher application rate than other remediation technologies and are currently one of the hot research topics in the international environmental geotechnical field. However, conventional silicate cement-based solidifiers have many drawbacks, limiting their widespread application in sites with combined heavy metal and organic pollution: 1) Organic matter and high concentrations of heavy metals can severely inhibit cement hydration, hindering the development of solidified soil strength and affecting the solidification effect; 2) Organic pollutants are only encapsulated but not removed, so their re-migration and diffusion are highly likely. Furthermore, the precipitation of amphoteric hydroxides is the main mechanism for fixing heavy metals, and they are easily redissolved in acidic / alkaline environments; 3) CO2, Cl... - SO4 2- Complex environments such as erosion can cause damage to the internal structure of solidified soil, increasing the risk of pollutant re-dissolution; 4) The release of a large amount of heat during clinker hydration can cause the volatilization and diffusion of various organic substances such as petroleum ether, which can easily cause secondary pollution.

[0004] Chemical oxidation, as the mainstream technology for removing organic pollutants from soil, also has significant limitations: 1) It cannot effectively remove heavy metals coexisting in the soil, and may even promote the leaching risk of heavy metals, especially oxidized heavy metals, in the soil; 2) The mechanical properties of the remediated soil are not significantly improved, and there are remediation residues such as oxidants and by-products in the soil, so it cannot be directly used as a resource for construction soil such as roadbed / foundation; 3) The amount of oxidant used is large, and the in-situ injection control technology is difficult, resulting in high remediation costs. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a remediation agent for soil contaminated by chemical erosion, its uses and methods of application. The remediation agent can simultaneously fix heavy metals in the soil, adsorb and decompose organic pollutants, and resist various chemical corrosions. While reducing the leaching toxicity of contaminated soil, it improves its engineering mechanical properties. Moreover, the raw materials of the remediation agent are widely available, easy to prepare, and environmentally friendly, thereby achieving pollution control with waste and creating significant economic, environmental, and engineering benefits.

[0006] To achieve the above objectives, the present invention is implemented using the following technical solution: In a first aspect, the present invention provides a remediation agent for soil contaminated by chemical erosion, comprising the following components in parts by weight: 12-25 parts of neutral composite material and 75-90 parts of alkaline composite material; The neutral composite material is composed of 3.5 parts of modified aluminum ash and 6.5 parts of shell powder loaded with sodium percarbonate, wherein the particle size of the shell powder loaded with sodium percarbonate is less than or equal to 500 mesh. The alkaline composite material consists of 4 parts calcium carbide slag powder, 5 parts granulated blast furnace slag, 1 part roasted aluminum-magnesium hydrotalcite powder, 3 parts caustic sodium waste liquid, and 2 parts impurity-removed aluminum ash.

[0007] Furthermore, the preparation method of the modified aluminum ash includes: Industrial waste aluminum ash was ground through a 50-mesh sieve. Water was added, stirred, and filtered multiple times at a solid-liquid mass ratio of 1:5. Then, water was added at a solid-liquid mass ratio of 1:5, and concentrated hydrochloric acid was added dropwise until the HCl mass concentration of the solution was 1%. The mixture was stirred evenly to obtain a dilute hydrochloric acid suspension soaked with aluminum ash. After the dilute hydrochloric acid suspension containing aluminum ash was allowed to stand for 1 hour, it was rinsed with distilled water until the pH of the suspension was 7.0~7.5, thus obtaining the rinsed suspension. The rinsed suspension was dried, and the resulting solid was ground through a 100-mesh sieve to obtain the final modified aluminum ash. And / or, the method for preparing the sodium percarbonate-loaded shell powder includes: After crushing, cleaning and drying, shell powder A is ground using a planetary ball mill and passed through an ultrasonic vibrating screen to obtain shell powder B with a particle size of less than or equal to 500 mesh. Sodium carbonate, shell powder B and distilled water were weighed according to a mass ratio of 7:8:20 and mixed evenly to obtain a sodium carbonate-shell powder suspension. Sodium percarbonate stabilizer was added to a sodium carbonate-shell powder suspension at a temperature of 10~15℃ and mixed evenly to obtain solution A. The sodium percarbonate stabilizer was composed of sodium sulfite, magnesium chloride, isopropanol and triethanolamine in a mass ratio of 3:1:5:1, and the mass concentration of sodium percarbonate stabilizer was 2%. Add 30% hydrogen peroxide dropwise to solution A at a molar ratio of sodium carbonate to hydrogen peroxide of 1:1.8 over a period of ≥20 min with continuous stirring. After the addition is complete, continue stirring for 30 min and then let stand for at least 25 min to obtain solution B. Solution B was filtered under reduced pressure and washed repeatedly with ethanol. After being dried by vacuum, it was dried in a 60°C water bath and passed through an ultrasonic vibrating sieve to obtain the final shell powder loaded with sodium percarbonate.

[0008] Furthermore, the neutral composite material should be sealed and protected from light at 4°C before use.

[0009] Furthermore, the method for preparing the carbide slag powder includes: After being piled up, evaporated, and dehydrated, waste carbide slag is obtained as carbide slag blocks with a moisture content of 30-50%. The carbide slag blocks were cut into carbide slag particles with a particle size of less than 2 mm. The calcium carbide slag particles are dried to a moisture content of less than 2%, ground, and passed through a 0.075 mm sieve to obtain calcium carbide slag powder. And / or, the preparation method of the calcined aluminum magnesium hydrotalcite powder includes: The aluminum-magnesium hydrotalcite powder was calcined at 500℃ for 5 h, then cooled for 45 min, and then cooled to 20℃-30℃. It was then ground in a planetary ball mill and passed through a 100-mesh sieve to obtain the final calcined aluminum-magnesium hydrotalcite powder. And / or, the method for preparing the impurity-removed aluminum ash includes: Industrial waste aluminum ash was ground through a 50-mesh sieve, and water was added, stirred, and filtered multiple times at a solid-liquid mass ratio of 1:5. Then it was dried at 105℃ for 6 hours, and after being taken out, it was ground through a 100-mesh sieve to obtain the final aluminum ash with impurities removed.

[0010] Furthermore, the preparation method of the alkaline composite material includes: Dilute the caustic soda waste liquid to achieve a NaOH mass concentration of 4.8%. Then, add the impurity-removed aluminum ash to the diluted caustic soda waste liquid in multiple batches, stirring continuously during the process. After the addition is complete, continue stirring for 1 hour and then let it stand for 30 minutes to obtain an aluminum ash-caustic soda solution. Aluminum ash-caustic soda solution was dried at 150℃ for 12 h. The dried powder was then ground using a planetary ball mill and passed through a 100-mesh sieve to obtain alkaline aluminum material. The alkaline aluminum material, calcium carbide slag powder, granulated blast furnace slag, and calcined aluminum-magnesium hydrotalcite powder are mixed evenly to obtain the final alkaline composite material.

[0011] Secondly, the present invention provides the use of the aforementioned remediation agent for chemically contaminated soil for remediating chemically contaminated soil.

[0012] Furthermore, the dosage of the remediation agent is 1-40% of the dry weight of the contaminated soil, the concentration of heavy metals in the contaminated soil is ≤ 20000 mg / kg, the concentration of organic pollutants is ≤ 15000 mg / kg, and the concentration of erosion ions in the soil pore fluid and groundwater is ≤ 1.0 mol / L.

[0013] Thirdly, the present invention provides a method for using the remediation agent for chemically contaminated soil, wherein the remediation agent is used to remediate chemically contaminated soil, and the method includes: Add the neutral composite material from the remediation agent components to the contaminated soil, adjust the moisture content to the plastic limit moisture content of the contaminated soil, stir evenly, and cure in situ or ex-situ for 3 to 7 days to obtain the pre-treated contaminated soil. Add the alkaline composite material from the remediation agent to the pre-treated contaminated soil, adjust the moisture content, stir evenly, and cure in situ or ex-situ for more than 3 days to complete the remediation of the contaminated soil.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The remediation agent for chemically contaminated soil provided by this invention can simultaneously treat heavy metals and organic pollutants in contaminated soil. Shell powder in the remediation agent, as a biomass material, can capture and passivate heavy metals. The heavy metal carbonates it generates have a solubility one order of magnitude lower than heavy metal hydroxide precipitates and are natural adsorbents for petroleum and organochlorides. Sodium percarbonate loaded with shell powder can completely decompose organic pollutants in the soil under the catalytic action of iron minerals in the soil. Aluminum-magnesium hydrotalcite, as a novel and inexpensive adsorbent, forms a special layered structure and a larger specific surface area after calcination, enabling it to efficiently fix heavy metals through ion exchange, chelation, surface adsorption, and memory effect. It can also effectively adsorb organic pollutants such as trichlorophenol and pesticides, especially anionic pollutants. Furthermore, carbide slag stimulates the formation of a highly dense cementitious structure in the slag, further enhancing the effect on heavy metals and organic matter in the soil through surface adsorption, precipitation, complexation, and sealing.

[0015] The remediation agent for chemically contaminated soil provided by this invention has excellent soil-stabilizing properties. The carbide slag in the remediation agent can efficiently activate blast furnace slag, reacting to generate CSH and C3A3CSH. 32 The addition of cementing substances such as Al(OH)3 has a significantly better effect on improving soil strength than silicate cement. At the same time, the incorporation of ultrafine shell powder and calcined aluminum magnesium hydrotalcite can fill the tiny pores and cement the soil particles, thereby making the solidified soil denser and improving its mechanical properties such as strength.

[0016] The remediation agent for chemically contaminated soil provided by this invention exhibits good resistance to chemical erosion after remediation. The Ca(OH)2 in the carbide slag activates the slag components, forming a cementitious agent similar to slag cement, which is more effective than silicate cement in improving the SO4 resistance of the solidified body. 2- Cl - HCO3 2- Corrosion resistance; calcined hydrotalcite, as an intercalation material with strong interlayer anion exchange capacity, can effectively solidify various corrosive anions and slow down their migration and penetration. When incorporated into cement-based materials, it, along with calcium carbonate (the main component of shell powder), can significantly reduce the permeability of the solidified body and improve its corrosion resistance coefficient. The repair agent of this invention, through the sequential incorporation of neutral aluminum ash and alkaline aluminum ash, further enhances the fixation / inhibition effect on sulfate and chloride ions. It can generate hydrated aluminum sulfate complex ions with corrosive anions, thereby inhibiting the dissolution and release of anions. The effect is significantly better than the simple precipitation mechanism of ettringite.

[0017] The remediation agent for chemically contaminated soil provided by this invention can prevent secondary pollution, is environmentally friendly, and facilitates waste utilization and resource conservation. The acid-base reaction of calcium carbide slag-aluminum ash and the hydration reaction initiated by slag both produce relatively little heat, resulting in a gentle process that effectively prevents the volatilization and release of organic pollutants and reduces secondary pollution. Calcium carbide slag, blast furnace slag, and aluminum ash are all industrial wastes with significant impacts on the surrounding environment. Caustic soda waste liquid is a commonly used processing and washing agent in the aluminum products industry, but it is highly alkaline and difficult to treat harmlessly. Shells are common agricultural and fishery waste, while aluminum-magnesium hydrotalcite is a natural or synthetic mineral material that is inexpensive and readily available. Therefore, the remediation agent of this invention is environmentally friendly and can achieve waste-to-pollution treatment when used to remediate contaminated soil, significantly reducing remediation costs. Detailed Implementation

[0018] The present invention will now be further described. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0019] In this embodiment of the invention, the calcium carbide slag used was purchased from Jiangsu Changfei Acetylene Manufacturing Co., Ltd., with a pH value (soil-to-water ratio = 1:1) of 12.84 and a specific surface area of ​​24.66 m² as measured by a nitrogen adsorption analyzer. 2 ·g -1 The main chemical components and their mass percentages are: CaO 68.99%, SiO2 8.84%, Al2O3 2.16%, Fe2O3 0.15%, with particles smaller than 75 μm accounting for 71.8%.

[0020] The aluminum ash was purchased from Shandong Aluminum Industry, and its main components are 61.75% Al2O3, 24.20% SiO2, 7.78% Fe2O3 and 1.64% CaO.

[0021] The aluminum-magnesium hydrotalcite is an aluminum-magnesium carbonate root-type hydrotalcite (Mg-Al-CO3-LDHs) produced by Beijing Ailiwensen Technology Co., Ltd.

[0022] The shells were obtained from local seafood processing in Nanjing.

[0023] The caustic soda waste liquid contains 12% NaOH and 1.3% aluminum.

[0024] Granulated blast furnace slag was produced by a cement plant in Nanjing. It is a grayish-white powder with a specific surface area of ​​0.2564 m². 2 / g, alkalinity 1.871, pH 12.21 (water-to-soil ratio 1:1). The main elemental contents of Conch brand PC 32.5 composite silicate cement, as determined by X-ray fluorescence spectrometry, are: CaO 44.37%, SiO2 27.41%, and Al2O3 13.09%.

[0025] The soil sample, which was contaminated with a combination of heavy metals and organic matter, was taken from a ferroalloy plant in Nanjing. The moisture content was 18%, and the main pollutants in the soil were Pb 2740 mg / kg and total petroleum hydrocarbons (TPH) 1880 mg / kg. Example 1

[0026] This embodiment provides a remediation agent for soil contaminated by chemical erosion and its preparation method. The remediation agent comprises the following components in parts by weight: 10 parts of neutral composite material and 90 parts of alkaline composite material. The neutral composite material is composed of 3.5 parts of modified aluminum ash and 6.5 parts of shell powder loaded with sodium percarbonate, wherein the particle size of the shell powder loaded with sodium percarbonate is less than or equal to 500 mesh. The alkaline composite material consists of 4 parts calcium carbide slag powder, 5 parts granulated blast furnace slag, 1 part roasted aluminum-magnesium hydrotalcite powder, 3 parts caustic sodium waste liquid, and 2 parts impurity-removed aluminum ash.

[0027] The method for preparing the repair agent includes: 1. Preparation of modified aluminum ash: (1) Grind the collected industrial waste aluminum ash through a 50-mesh sieve, add water at a solid-liquid mass ratio of 1:5 and stir for 15 minutes, then filter out the water; (2) Repeat the above steps of adding water, stirring, and filtering out water three times; (3) Add water again at a solid-liquid mass ratio of 1:5, and add concentrated hydrochloric acid dropwise until the HCl mass concentration in the solution is 1%. Stir for 10 min to mix evenly and prepare a dilute hydrochloric acid suspension soaked with aluminum ash. (4) After the above suspension has been allowed to stand for 1 h, it is continuously rinsed with distilled water until the pH of the suspension reaches 7.0~7.5; (5) Place the above-washed suspension in a 105°C oven and dry it. Then grind the resulting aluminum ash powder through a 100-mesh sieve to prepare modified aluminum ash. 2. Preparation of ultrafine seashell powder loaded with sodium percarbonate: (1) The collected shell powder was crushed and washed with water, placed in a 300℃ drying oven for 6 hours, then ground with a planetary ball mill and passed through an ultrasonic vibrating screen to obtain ultrafine shell powder (≤500 mesh). (2) Weigh sodium carbonate, ultrafine shell powder and distilled water according to the solid-liquid mass ratio of 7:8:20, stir evenly to prepare sodium carbonate-shell powder suspension, and place the above suspension in an environment of 10~15℃. (3) Under the above temperature conditions, add sodium percarbonate stabilizer composed of sodium sulfite, magnesium chloride, isopropanol and triethanolamine in a mass ratio of 3:1:5:1 to the suspension. The mass concentration of the stabilizer is 2%. After the addition is completed, stir evenly with a glass rod. (4) Add 30% hydrogen peroxide dropwise to the solution at a ratio of sodium carbonate to hydrogen peroxide of 1:1.8. The dropwise addition time is ≥20 min, and the solution is stirred continuously. After the dropwise addition is completed, continue stirring for 30 min, and then let it stand for more than 25 min so that sodium percarbonate crystallizes and precipitates on the surface of the microstructure of ultrafine shell powder. (5) The above solution was filtered under reduced pressure and washed twice with ethanol, then dried under vacuum and placed in a 60°C water bath to dry, and then passed through an ultrasonic vibrating sieve to obtain the final ultrafine shell powder loaded with sodium percarbonate. 3. Preparation of neutral mixture: Modified aluminum ash and ultrafine seashell powder loaded with sodium percarbonate were dry-mixed evenly to obtain a neutral mixture, which was then placed in a sealed bag and refrigerated at 4°C in the dark.

[0028] 4. Preparation of carbide slag powder: (1) The waste carbide slag generated during industrial production is piled up, evaporated and dehydrated to obtain carbide slag blocks with a moisture content of 30-50%; (2) Then cut the carbide slag block into carbide slag particles, so that the diameter of the carbide slag particles is less than 2 mm; (3) Place the carbide slag particles in a perforated metal tray and put it in an oven at a temperature of 100-450°C. Introduce an airflow at a temperature of 100-250°C to make the final moisture content of the carbide slag particles less than 2%. (4) Grind the dried carbide slag and pass it through a 0.075 mm sieve to obtain carbide slag powder.

[0029] 5. Preparation of calcined aluminum-magnesium hydrotalcite powder: (1) Place aluminum-magnesium hydrotalcite powder in a muffle furnace and calcine it at 500℃ for 5 h; (2) After heating is stopped, the obtained product is cooled in a muffle furnace for 45 min; (3) Remove it from the muffle furnace, cool it indoors to 20℃-30℃, grind it with a planetary ball mill and pass it through a 100-mesh sieve to obtain the final calcined aluminum magnesium hydrotalcite powder.

[0030] 6. Preparation of impurity-removed aluminum ash: (1) Grind the collected industrial waste aluminum ash through a 50-mesh sieve, add water at a solid-liquid mass ratio of 1:5 and stir for 15 minutes, then filter out the water; (2) After repeating the above steps of adding water, stirring and filtering out water three times, place the above rinsed suspension in a 105°C oven and dry for 6 hours. (3) After the water is dried, the aluminum ash powder is ground through a 100-mesh sieve to prepare the final aluminum ash with impurities removed.

[0031] 7. Preparation of alkaline composite materials: (1) Weigh out 4 parts of carbide slag powder, 5 parts of granulated blast furnace slag, 1 part of roasted aluminum magnesium hydrotalcite powder, 3 parts of caustic sodium waste liquid and 2 parts of impurity-removed aluminum ash according to mass and set aside. (2) Dilute the caustic soda waste liquid to make its NaOH mass concentration reach 4.8%, and then pour the impurity-removed aluminum ash into the diluted caustic soda waste liquid in multiple batches, stirring while pouring; (3) After adding aluminum ash, continue stirring for 1 hour, then let it stand for 30 minutes; (4) The aluminum ash-caustic soda solution after standing is placed in an oven at 150°C and dried for 12 h. The powder obtained after drying is ground by a planetary ball mill and passed through a 100-mesh sieve to obtain alkaline aluminum material. (5) The obtained alkaline aluminum material is dry-mixed with the remaining weighed carbide slag powder, granulated blast furnace slag and roasted aluminum magnesium hydrotalcite powder to prepare the final alkaline composite material. Example 2

[0032] This embodiment provides a remediation agent for soil contaminated by chemical erosion and its preparation method. The remediation agent comprises the following components in parts by weight: 25 parts of neutral composite material and 75 parts of alkaline composite material. The neutral composite material is composed of 3.5 parts of modified aluminum ash and 6.5 parts of shell powder loaded with sodium percarbonate, wherein the particle size of the shell powder loaded with sodium percarbonate is less than or equal to 500 mesh. The alkaline composite material consists of 4 parts calcium carbide slag powder, 5 parts granulated blast furnace slag, 1 part roasted aluminum-magnesium hydrotalcite powder, 3 parts caustic sodium waste liquid, and 2 parts impurity-removed aluminum ash.

[0033] The preparation method of the repair agent is the same as in Example 1. Comparative Example 1

[0034] This comparative example provides a PC 32.5 composite silicate cement as a comparative repair agent.

[0035] The remediation methods for contaminated soil in eroded environments using the remediation agents provided in Examples 1 and 2 include the following steps: (1) The contaminated soil is crushed and screened, and then passed through a 2 mm sieve for later use; (2) Add the neutral composite material from the remediation agent components to the contaminated soil and adjust the moisture content to the plastic limit moisture content of the contaminated soil, and mechanically force-stir to mix evenly; (3) Curing the contaminated soil with added neutral composite material in situ or ex-situ for 3 days; (4) Then add the alkaline composite material in the new remediation agent to the contaminated soil, adjust the moisture content, and mechanically force-stir evenly; (5) Cur the contaminated soil in situ or ex-situ for more than 3 days after re-mixing; (6) Repair completed.

[0036] A comparative experiment was conducted by adjusting the dosage of the remediation agent provided in Example 1 or Example 2 relative to the contaminated soil. Experiments 1-4 were set up. At the same time, the PC 32.5 composite silicate cement provided in Comparative Example 1 was used to remediate the contaminated soil in the same eroded environment as a comparative experiment. The specific test parameters are shown in Table 1.

[0037] Table 1

[0038] Three-dimensional immersion tests with erosion ion chemical solutions were conducted on the original contaminated soil, as well as the remediated contaminated soil from Tests 1-4 and the control test. The test methods included: Preparation of Cl - SO4 2 -and HCO3 - An ionic chemical solution (pH=7.0, concentration of each anion is 1.0 mol / L). The test soil was soaked in the above-mentioned ionic chemical solution for 28 days (d). After the designed soaking time is reached, the solidified soil is removed, and its compressive strength change pattern is analyzed. The HJ / T299 leaching toxicity of the soil sample is tested.

[0039] The soil leaching toxicity test method was conducted in accordance with the "Solid Waste Leaching Toxicity Leaching Method: Sulfuric Acid and Nitric Acid Method" (HJT299-2007).

[0040] The data results of the three-dimensional immersion test of the erosion ion chemical solution are shown in Table 2.

[0041] Table 2

[0042] As can be seen from the table above: (1) Regarding unconfined compressive strength: the original soil was 115 kPa before soaking in the erosion ion chemical solution. The strengths of groups 1-4 before soaking (850, 687, 205, 1340 kPa) were all higher than those of the original soil. After soaking (960, 820, 184, 1457 kPa), except for a slight decrease in group 3, the others remained stable or increased. The comparative test group using PC 32.5 composite silicate cement as the curing agent had a much lower strength (298 kPa) after soaking than the test group, indicating that the newly developed remediation agent can effectively improve and maintain soil strength and resist chemical erosion.

[0043] (2) Regarding the leaching concentration of heavy metals (Pb): The Pb leaching concentration of the original soil before soaking in the erosion ion chemical solution was 7.23 mg / L. The Pb leaching concentrations of groups 1-3 after soaking (0.05, 0.85, 2.20 mg / L) were lower than those of the original soil. No Pb was detected in group 4. The Pb leaching concentration of the comparative test using PC 32.5 composite silicate cement as a curing agent increased after soaking. This indicates that the experimental group using the new remediation agent achieved effective fixation of Pb pollutants in the soil. The new remediation agent can reduce the leaching toxicity of Pb and improve its fixation ability under chemical erosion conditions.

[0044] (3) Regarding the total petroleum hydrocarbon leaching concentration and content: Before soaking in the erosion ion chemical solution, the total petroleum hydrocarbon leaching concentration of the original soil was 45 mg / L, and the total petroleum hydrocarbon content was 1880 mg / kg. After soaking in groups 1-3 of the test using the new remediation agent, the leaching concentration and content decreased, while no leaching was detected in group 4. The comparative test group using PC 32.5 composite silicate cement as the curing agent had a higher leaching concentration (41 mg / L) and total content (1644 mg / kg) after soaking, indicating that, unlike cement, the new remediation agent of this invention has an effective decomposition and removal effect on organic pollutants.

[0045] In summary, it can be seen that the novel remediation agent finally prepared by this invention for remediating chemically contaminated soil is suitable for the safe treatment of soils contaminated with both heavy metals and organic matter; it can effectively decompose organic pollutants in the soil, while simultaneously reducing the leaching toxicity of heavy metals and heavy metal organic pollutants in the soil; and it can still maintain a high remediation effect under the erosion of chemical solutions.

[0046] The embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A remediation agent for chemically contaminated soil, characterized in that, The components include the following parts by weight: 12-25 parts of neutral composite material and 75-90 parts of alkaline composite material; The neutral composite material is composed of 3.5 parts of modified aluminum ash and 6.5 parts of shell powder loaded with sodium percarbonate, wherein the particle size of the shell powder loaded with sodium percarbonate is less than or equal to 500 mesh. The alkaline composite material consists of 4 parts calcium carbide slag powder, 5 parts granulated blast furnace slag, 1 part roasted aluminum-magnesium hydrotalcite powder, 3 parts caustic sodium waste liquid, and 2 parts impurity-removed aluminum ash.

2. The remediation agent for chemically contaminated soil according to claim 1, characterized in that: The method for preparing the modified aluminum ash includes: Industrial waste aluminum ash was ground through a 50-mesh sieve. Water was added, stirred, and filtered multiple times at a solid-liquid mass ratio of 1:

5. Then, water was added at a solid-liquid mass ratio of 1:5, and concentrated hydrochloric acid was added dropwise until the HCl mass concentration of the solution was 1%. The mixture was stirred evenly to obtain a dilute hydrochloric acid suspension soaked with aluminum ash. After the dilute hydrochloric acid suspension containing aluminum ash was allowed to stand for 1 hour, it was rinsed with distilled water until the pH of the suspension was 7.0~7.5, thus obtaining the rinsed suspension. The rinsed suspension was dried, and the resulting solid was ground through a 100-mesh sieve to obtain the final modified aluminum ash. And / or, the method for preparing the sodium percarbonate-loaded shell powder includes: After crushing, cleaning and drying, shell powder A is ground using a planetary ball mill and passed through an ultrasonic vibrating screen to obtain shell powder B with a particle size of less than or equal to 500 mesh. Sodium carbonate, shell powder B and distilled water were weighed according to a mass ratio of 7:8:20 and mixed evenly to obtain a sodium carbonate-shell powder suspension. Sodium percarbonate stabilizer was added to a sodium carbonate-shell powder suspension at a temperature of 10~15℃ and mixed evenly to obtain solution A. The sodium percarbonate stabilizer was composed of sodium sulfite, magnesium chloride, isopropanol and triethanolamine in a mass ratio of 3:1:5:1, and the mass concentration of sodium percarbonate stabilizer was 2%. Add 30% hydrogen peroxide dropwise to solution A at a molar ratio of sodium carbonate to hydrogen peroxide of 1:1.8 over a period of ≥20 min with continuous stirring. After the addition is complete, continue stirring for 30 min and then let stand for at least 25 min to obtain solution B. Solution B was filtered under reduced pressure and washed repeatedly with ethanol. After being dried by vacuum, it was dried in a 60°C water bath and passed through an ultrasonic vibrating sieve to obtain the final shell powder loaded with sodium percarbonate.

3. The remediation agent for chemically contaminated soil according to claim 1, characterized in that: Before use, the neutral composite material should be sealed and stored in a light-proof environment at 4°C.

4. The remediation agent for chemically contaminated soil according to claim 1, characterized in that: The method for preparing the carbide slag powder includes: After being piled up, evaporated, and dehydrated, waste carbide slag is obtained as carbide slag blocks with a moisture content of 30-50%. The carbide slag blocks were cut into carbide slag particles with a particle size of less than 2 mm. The calcium carbide slag particles are dried to a moisture content of less than 2%, ground, and passed through a 0.075 mm sieve to obtain calcium carbide slag powder. And / or, the preparation method of the calcined aluminum magnesium hydrotalcite powder includes: The aluminum-magnesium hydrotalcite powder was calcined at 500℃ for 5 h, then cooled for 45 min, and then cooled to 20℃-30℃. It was then ground in a planetary ball mill and passed through a 100-mesh sieve to obtain the final calcined aluminum-magnesium hydrotalcite powder. And / or, the method for preparing the impurity-removed aluminum ash includes: Industrial waste aluminum ash was ground through a 50-mesh sieve, and water was added, stirred, and filtered multiple times at a solid-liquid mass ratio of 1:

5. Then it was dried at 105℃ for 6 hours, and after being taken out, it was ground through a 100-mesh sieve to obtain the final aluminum ash with impurities removed.

5. The remediation agent for chemically contaminated soil according to claim 4, characterized in that: The preparation method of the alkaline composite material includes: Dilute the caustic soda waste liquid to achieve a NaOH mass concentration of 4.8%. Then, add the impurity-removed aluminum ash to the diluted caustic soda waste liquid in multiple batches, stirring continuously during the process. After the addition is complete, continue stirring for 1 hour and then let it stand for 30 minutes to obtain an aluminum ash-caustic soda solution. Aluminum ash-caustic soda solution was dried at 150℃ for 12 h. The dried powder was then ground using a planetary ball mill and passed through a 100-mesh sieve to obtain alkaline aluminum material. The alkaline aluminum material, calcium carbide slag powder, granulated blast furnace slag, and calcined aluminum-magnesium hydrotalcite powder are mixed evenly to obtain the final alkaline composite material.

6. The use of a remediation agent for chemically contaminated soil as described in any one of claims 1-5 for remediating chemically contaminated soil.

7. The use according to claim 6, characterized in that: The remediation agent is added at a dosage of 1-40% of the dry weight of the contaminated soil. The concentration of heavy metals in the contaminated soil is ≤ 20,000 mg / kg, the concentration of organic pollutants is ≤ 15,000 mg / kg, and the concentration of erosion ions in the soil pore fluid and groundwater is ≤ 1.0 mol / L.

8. A method of using a remediation agent for chemically contaminated soil as described in any one of claims 1-5, wherein the remediation agent is used to remediate chemically contaminated soil, characterized in that, The method includes: Add the neutral composite material from the remediation agent components to the contaminated soil, adjust the moisture content to the plastic limit moisture content of the contaminated soil, stir evenly, and cure in situ or ex-situ for 3 to 7 days to obtain the pre-treated contaminated soil. Add the alkaline composite material from the remediation agent to the pre-treated contaminated soil, adjust the moisture content, stir evenly, and cure in situ or ex-situ for more than 3 days to complete the remediation of the contaminated soil.

Images