A soil remediation agent for environmental pollution and a method for preparing the same

Abstract

The application discloses a kind of soil remediation agent for environmental pollution and preparation method thereof, and relates to the technical field of soil regeneration.The preparation method comprises the following steps: first, iron sulfate and manganese sulfate are added to deionized water, stirred and dissolved to obtain a mixed salt solution;Then, chitosan microspheres are prepared;Chitosan microspheres are then added to the mixed salt solution for reaction to obtain chitosan-loaded iron-manganese composite oxides;Finally, chitosan-loaded iron-manganese composite oxides are added to a disodium ethylenediaminetetraacetate solution for reaction to obtain a soil remediation agent.The soil remediation agent is a special agent material for heavy metal environmental pollution treatment, can efficiently treat various heavy metals in soil, and has good adaptability to acidic and alkaline soils, thereby achieving soil regeneration.

Description

Technical Field

[0001] This invention relates to the field of soil regeneration technology, belonging to patent classification number B09C1 / 08, specifically to a soil remediation agent for environmental pollution and its preparation method. Background Technology

[0002] With the acceleration of industrialization and urbanization, heavy metal pollution has become a serious problem facing soil environments worldwide. Efficient soil remediation technologies have become a research hotspot in the environmental field, and the performance and applicability of specialized agents for environmental pollution treatment directly affect the effectiveness of contaminated soil regeneration.

[0003] Currently, there are many types of soil remediation agents on the market; however, these agents generally have some limitations. On the one hand, most soil remediation agents only have a remediation effect on a single heavy metal, making it difficult to effectively treat multiple heavy metal pollutants simultaneously. However, in actual pollution scenarios, soil is often contaminated with multiple heavy metals, and single-function remediation agents cannot meet the remediation needs of complex polluted soils, resulting in slow soil regeneration processes, low remediation efficiency, and difficulty in achieving ideal remediation results.

[0004] On the other hand, existing soil remediation agents have poor adaptability to soil pH levels, making them difficult to apply simultaneously to acidic and alkaline soil environments. Existing remediation agents, intended specifically for environmental pollution treatment, typically only function under specific acidic or alkaline conditions. In other acidic or alkaline environments, their remediation activity significantly decreases or even becomes ineffective, greatly limiting their application scope, leading to increased remediation costs and unstable soil regeneration results. Summary of the Invention

[0005] The purpose of this invention is to provide a soil remediation agent for environmental pollution and its preparation method, thereby solving the technical problems mentioned in the background section. This soil remediation agent, as a specialized agent for treating heavy metal environmental pollution, can efficiently treat various heavy metals in soil and exhibits good adaptability to acidic and alkaline soils, thus achieving soil regeneration.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a soil remediation agent for environmental pollution includes the following steps:

[0008] S1. Add ferric sulfate and manganese sulfate to deionized water, stir to dissolve, and obtain a mixed salt solution;

[0009] S2. Chitosan is added to acetic acid solution and stirred to dissolve, resulting in a chitosan solution. The chitosan solution is then slowly added dropwise to an oil phase composed of liquid paraffin and Span-80, and stirred to form an emulsion. Glutaraldehyde crosslinking agent is then added to the emulsion, and the mixture is heated and stirred to react. After standing and layering, washing, and drying, chitosan microspheres are obtained.

[0010] S3. Add chitosan microspheres to a mixed salt solution, adjust the pH to alkaline, stir the reaction, and after filtration, separation, washing and drying, obtain chitosan-supported iron-manganese composite oxides.

[0011] S4. Disodium ethylenediaminetetraacetate was added to deionized water and stirred to dissolve, resulting in a disodium ethylenediaminetetraacetate solution. Chitosan-loaded iron-manganese composite oxide was added to the disodium ethylenediaminetetraacetate solution and stirred to react. After filtration, separation, washing and drying, the soil remediation agent was obtained.

[0012] The reaction principle in this invention is as follows: First, chitosan is protonated and dissolved in acetic acid solution, and a liquid paraffin oil phase containing Span-80 is added dropwise to form an emulsion. This emulsion is then cross-linked with glutaraldehyde to form microspheres, constructing a porous framework containing active functional groups. Then, under alkaline conditions, ferric sulfate and manganese sulfate hydrolyze to generate hydroxide precipitates, which are loaded onto the chitosan microspheres to form an iron-manganese composite oxide, possessing both redox and adsorption properties. Finally, disodium ethylenediaminetetraacetate, with its amino and carboxyl groups, possesses strong coordination ability due to the lone pair electrons in the nitrogen and oxygen atoms of these functional groups. It interacts with the iron-manganese composite oxide surface, where Fe... 3+ Mn 4+ Stable coordination bonds are formed, allowing disodium ethylenediaminetetraacetate to bind to chitosan-supported iron-manganese composite oxides, further enhancing the remediation agent's ability to treat heavy metals.

[0013] The abundant amino and hydroxyl groups on the surface of chitosan microspheres can coordinate with heavy metal ions, such as lead and cadmium ions, for adsorption. Iron-manganese composite oxides can alter the valence state of heavy metals through redox reactions, such as partially oxidizing mercury ions to elemental mercury for volatilization, and can also adsorb heavy metals using surface active sites. Disodium ethylenediaminetetraacetate forms stable chelates with zinc and nickel ions, reducing their migration and bioavailability, thus achieving efficient treatment of various heavy metals.

[0014] Chitosan microspheres possess acid-base buffering capacity; their amino and hydroxyl groups can neutralize acidity and alleviate alkalinity, respectively, while their porous structure can adsorb acids and alkalis to regulate soil pH. The chelates formed by disodium ethylenediaminetetraacetate and heavy metals exhibit good stability at different pH levels; neither acidic nor alkaline environments affect their heavy metal fixation. Iron-manganese composite oxides maintain stability and activity in both acidic and alkaline soils. In acidic soils, they regulate heavy metal concentration through dissolution-precipitation, while in alkaline soils, they continuously exert redox and adsorption effects.

[0015] Preferably, in step S1, the mass ratio of ferric sulfate to manganese sulfate is 3:1-2.

[0016] Preferably, in step S2, the amount of glutaraldehyde crosslinking agent added is 3-5% of the mass of chitosan.

[0017] Preferably, in step S2, the heating temperature is 40-50℃ and the reaction time is 2-5h.

[0018] Preferably, in step S3, the pH is adjusted to 9-10.

[0019] Preferably, in step S3, the stirring reaction time is 5-8 hours.

[0020] Preferably, in step S4, the mass ratio of chitosan-supported iron-manganese composite oxide to disodium ethylenediaminetetraacetate is 10:2-4.

[0021] In the technical solution of this invention, as described above, disodium ethylenediaminetetraacetate (EDTA) forms stable chelates with zinc ions, nickel ions, and other heavy metal ions, reducing their migration and bioavailability. To achieve the above technical effects, sufficient disodium ethylenediaminetetraacetate must be bound to the chitosan-supported iron-manganese composite oxide. Therefore, this invention controls the mass ratio of chitosan-supported iron-manganese composite oxide to disodium ethylenediaminetetraacetate to be less than 10 / 2. As the amount of disodium ethylenediaminetetraacetate continues to increase to a certain level, i.e., the mass ratio of chitosan-supported iron-manganese composite oxide to disodium ethylenediaminetetraacetate is less than 10 / 4, the soil remediation agent will destroy the soil aggregate structure, significantly increasing soil looseness and macropores, leading to rapid infiltration and loss of soil moisture and nutrients. Further research revealed that this is because calcium ions in the soil play a "cementing" role in maintaining the soil aggregate structure. Excessive disodium ethylenediaminetetraacetate chelates calcium ions, weakening the connection between soil particles and destroying the soil aggregate structure. Therefore, the present invention simultaneously controls the mass ratio of chitosan-supported iron-manganese composite oxide to disodium ethylenediaminetetraacetate to be greater than 10 / 4.

[0022] A soil remediation agent for environmental pollution is prepared by the method described above.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] This soil remediation agent achieves efficient treatment of various heavy metals through the synergistic effect of multiple components. The amino and hydroxyl groups on the surface of chitosan microspheres can coordinate and adsorb heavy metal ions such as lead and cadmium; the iron-manganese composite oxide can change the valence state of heavy metals such as mercury through redox reactions, causing partial volatilization, and adsorb heavy metals through surface active sites; disodium ethylenediaminetetraacetate can form stable chelates with heavy metal ions such as zinc and nickel, reducing their mobility and bioavailability, thereby comprehensively treating multiple heavy metal pollutions in the soil.

[0025] The components of the remediation agent give it good acid-base adaptability. Chitosan microspheres have acid-base buffering capacity, with amino groups neutralizing acidity and hydroxyl groups alleviating alkalinity. Their porous structure can also adsorb acids and alkalis to regulate soil pH. The chelate formed by disodium ethylenediaminetetraacetate and heavy metals has good stability at different pH levels and does not affect the fixation of heavy metals. The iron-manganese composite oxide remains stable and active in both acidic and alkaline soils. In acidic soils, it regulates the concentration of heavy metals through dissolution-precipitation, and in alkaline soils, it continuously exerts redox and adsorption effects.

[0026] By precisely controlling the mass ratio of chitosan-supported iron-manganese composite oxide to disodium EDTA within a reasonable range, it is possible to ensure that sufficient disodium EDTA binds to the chitosan-supported iron-manganese composite oxide, achieving effective treatment of heavy metals, while avoiding problems such as the destruction of soil aggregate structure, soil loosening, and rapid loss of water and nutrients caused by excessive chelation of calcium ions in the soil by disodium EDTA. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] In specific embodiments, the main raw material specifications used in this invention are as follows:

[0029] Ferric sulfate, purity ≥99% (analytical grade), Fe content ≥20%; Manganese sulfate, purity ≥98%, Mn content ≥31%; Chitosan, degree of deacetylation ≥85%; Liquid paraffin, viscosity 15-30 mPa·s (25℃), density 0.85-0.89 g / cm³, flash point ≥160℃; Span-80, HLB value 4.3, acid value ≤8 mg KOH / g, saponification value 140-160 mg KOH / g; Disodium ethylenediaminetetraacetate, purity ≥99%.

[0030] Example 1

[0031] Step S1: Weigh 6g of ferric sulfate and 3.5g of manganese sulfate and place them in a beaker. Measure 300mL of deionized water and pour it into the beaker. Place the beaker on a magnetic stirrer, turn on the stirring function, and stir at 300r / min for 30 minutes until the ferric sulfate and manganese sulfate are completely dissolved, obtaining a mixed salt solution for later use.

[0032] Step S2: Weigh 10g of chitosan and place it in a beaker. Measure 200mL of 2% acetic acid solution and slowly pour it into the beaker containing the chitosan. Place the beaker on a magnetic stirrer and stir at 200r / min for 2 hours to fully dissolve the chitosan and obtain a chitosan solution.

[0033] Add 500 mL of liquid paraffin and 20 mL of Span-80 to a beaker, and stir with an electric stirrer at 400 rpm for 10 minutes to mix them evenly and form an oil phase.

[0034] The prepared chitosan solution was slowly added dropwise to the oil phase through a separatory funnel at a rate of 1 drop / second. During the addition process, the mixture was continuously stirred with an electric stirrer at a speed of 400 r / min to form a stable emulsion.

[0035] After the chitosan solution has been added dropwise, add 0.45g of glutaraldehyde crosslinking agent to the emulsion. Transfer the beaker to a constant temperature water bath, set the temperature to 45℃, turn on the stirring function, and heat and stir at 300r / min for 4 hours.

[0036] After the reaction was complete, the emulsion was transferred to a separatory funnel and allowed to stand for 2 hours to separate into layers. The upper oil phase was discarded, and the lower product was washed three times with 50 mL of anhydrous ethanol each time to remove residual oil phase and unreacted reagents. Finally, the product was transferred to a petri dish and placed in a vacuum drying oven at 50 °C to constant weight to obtain chitosan microspheres.

[0037] Step S3: Add all the chitosan microspheres to the mixed salt solution and stir thoroughly with a glass rod. Slowly add sodium hydroxide solution to the solution to adjust the pH to 9.5. Place the beaker on a magnetic stirrer, set the stirring speed to 300 rpm, and stir the reaction at room temperature for 7 hours.

[0038] After the reaction was complete, the solid product was separated by suction filtration through a Buchner funnel. The solid product was washed three times with deionized water, using 50 mL of water each time, to remove residual solution. The washed product was placed in a vacuum drying oven and dried at 60°C to constant weight to obtain chitosan-supported iron-manganese composite oxide.

[0039] Step S4: Weigh 3.5g of disodium ethylenediaminetetraacetate and place it in a beaker. Add 400mL of deionized water. Place the beaker on a magnetic stirrer and stir at 300r / min for 15 minutes to completely dissolve the disodium ethylenediaminetetraacetate, obtaining a disodium ethylenediaminetetraacetate solution.

[0040] Add 10g of chitosan-supported iron-manganese composite oxide to a solution of disodium ethylenediaminetetraacetate and stir until homogeneous with a glass rod. Place the beaker on a magnetic stirrer and stir the reaction at 300 rpm for 4 hours.

[0041] After the reaction was complete, the solid product was separated by suction filtration through a Buchner funnel. The solid product was washed three times with 50 mL of deionized water each time to remove residual solution. The washed product was then placed in a vacuum drying oven and dried at 60°C to constant weight to obtain the soil remediation agent.

[0042] Example 2

[0043] Step S1: Weigh 6g of ferric sulfate and 2.5g of manganese sulfate and place them in a beaker. Measure 300mL of deionized water and pour it into the beaker. Place the beaker on a magnetic stirrer, turn on the stirring function, and stir at 300r / min for 30 minutes until the ferric sulfate and manganese sulfate are completely dissolved, obtaining a mixed salt solution for later use.

[0044] Step S2: Weigh 10g of chitosan and place it in a beaker. Measure 200mL of 2% acetic acid solution and slowly pour it into the beaker containing the chitosan. Place the beaker on a magnetic stirrer and stir at 200r / min for 2 hours to fully dissolve the chitosan and obtain a chitosan solution.

[0045] Add 500 mL of liquid paraffin and 20 mL of Span-80 to a beaker, and stir with an electric stirrer at 400 rpm for 10 minutes to mix them evenly and form an oil phase.

[0046] The prepared chitosan solution was slowly added dropwise to the oil phase through a separatory funnel at a rate of 1 drop / second. During the addition process, the mixture was continuously stirred with an electric stirrer at a speed of 400 r / min to form a stable emulsion.

[0047] After the chitosan solution has been added dropwise, add 0.35g of glutaraldehyde crosslinking agent to the emulsion. Transfer the beaker to a constant temperature water bath, set the temperature to 45℃, turn on the stirring function, and heat and stir at 300r / min for 3 hours.

[0048] After the reaction was complete, the emulsion was transferred to a separatory funnel and allowed to stand for 2 hours to separate into layers. The upper oil phase was discarded, and the lower product was washed three times with 50 mL of anhydrous ethanol each time to remove residual oil phase and unreacted reagents. Finally, the product was transferred to a petri dish and placed in a vacuum drying oven at 50 °C to constant weight to obtain chitosan microspheres.

[0049] Step S3: Add all the chitosan microspheres to the mixed salt solution and stir thoroughly with a glass rod. Slowly add sodium hydroxide solution to the solution to adjust the pH to 9.5. Place the beaker on a magnetic stirrer, set the stirring speed to 300 rpm, and stir the reaction at room temperature for 6 hours.

[0050] After the reaction was complete, the solid product was separated by suction filtration through a Buchner funnel. The solid product was washed three times with deionized water, using 50 mL of water each time, to remove residual solution. The washed product was placed in a vacuum drying oven and dried at 60°C to constant weight to obtain chitosan-supported iron-manganese composite oxide.

[0051] Step S4: Weigh 2.5g of disodium ethylenediaminetetraacetate and place it in a beaker. Add 400mL of deionized water. Place the beaker on a magnetic stirrer and stir at 300r / min for 15 minutes to completely dissolve the disodium ethylenediaminetetraacetate, obtaining a disodium ethylenediaminetetraacetate solution.

[0052] Add 10g of chitosan-supported iron-manganese composite oxide to a solution of disodium ethylenediaminetetraacetate and stir until homogeneous with a glass rod. Place the beaker on a magnetic stirrer and stir the reaction at 300 rpm for 4 hours.

[0053] After the reaction was complete, the solid product was separated by suction filtration through a Buchner funnel. The solid product was washed three times with 50 mL of deionized water each time to remove residual solution. The washed product was then placed in a vacuum drying oven and dried at 60°C to constant weight to obtain the soil remediation agent.

[0054] Example 3

[0055] Step S1: Weigh 6g of ferric sulfate and 3g of manganese sulfate and place them in a beaker. Measure 300mL of deionized water and pour it into the beaker. Place the beaker on a magnetic stirrer, turn on the stirring function, and stir at 300r / min for 30 minutes until the ferric sulfate and manganese sulfate are completely dissolved, obtaining a mixed salt solution for later use.

[0056] Step S2: Weigh 10g of chitosan and place it in a beaker. Measure 200mL of 2% acetic acid solution and slowly pour it into the beaker containing the chitosan. Place the beaker on a magnetic stirrer and stir at 200r / min for 2 hours to fully dissolve the chitosan and obtain a chitosan solution.

[0057] Add 500 mL of liquid paraffin and 20 mL of Span-80 to a beaker, and stir with an electric stirrer at 400 rpm for 10 minutes to mix them evenly and form an oil phase.

[0058] The prepared chitosan solution was slowly added dropwise to the oil phase through a separatory funnel at a rate of 1 drop / second. During the addition process, the mixture was continuously stirred with an electric stirrer at a speed of 400 r / min to form a stable emulsion.

[0059] After the chitosan solution has been added dropwise, add 0.4g of glutaraldehyde crosslinking agent to the emulsion. Transfer the beaker to a constant temperature water bath, set the temperature to 45℃, turn on the stirring function, and heat and stir at 300r / min for 3.5 hours.

[0060] After the reaction was complete, the emulsion was transferred to a separatory funnel and allowed to stand for 2 hours to separate into layers. The upper oil phase was discarded, and the lower product was washed three times with 50 mL of anhydrous ethanol each time to remove residual oil phase and unreacted reagents. Finally, the product was transferred to a petri dish and placed in a vacuum drying oven at 50 °C to constant weight to obtain chitosan microspheres.

[0061] Step S3: Add all the chitosan microspheres to the mixed salt solution and stir thoroughly with a glass rod. Slowly add sodium hydroxide solution to the solution to adjust the pH to 9.5. Place the beaker on a magnetic stirrer, set the stirring speed to 300 rpm, and stir the reaction at room temperature for 6.5 hours.

[0062] After the reaction was complete, the solid product was separated by suction filtration through a Buchner funnel. The solid product was washed three times with deionized water, using 50 mL of water each time, to remove residual solution. The washed product was placed in a vacuum drying oven and dried at 60°C to constant weight to obtain chitosan-supported iron-manganese composite oxide.

[0063] Step S4: Weigh 3g of disodium ethylenediaminetetraacetate and place it in a beaker. Add 400mL of deionized water. Place the beaker on a magnetic stirrer and stir at 300r / min for 15 minutes to completely dissolve the disodium ethylenediaminetetraacetate, obtaining a disodium ethylenediaminetetraacetate solution.

[0064] Add 10g of chitosan-supported iron-manganese composite oxide to a solution of disodium ethylenediaminetetraacetate and stir until homogeneous with a glass rod. Place the beaker on a magnetic stirrer and stir the reaction at 300 rpm for 4 hours.

[0065] After the reaction was complete, the solid product was separated by suction filtration through a Buchner funnel. The solid product was washed three times with 50 mL of deionized water each time to remove residual solution. The washed product was then placed in a vacuum drying oven and dried at 60°C to constant weight to obtain the soil remediation agent.

[0066] Example 4

[0067] Step S1: Weigh 6g of ferric sulfate and 4g of manganese sulfate and place them in a beaker. Measure 300mL of deionized water and pour it into the beaker. Place the beaker on a magnetic stirrer, turn on the stirring function, and stir at 300r / min for 30 minutes until the ferric sulfate and manganese sulfate are completely dissolved, obtaining a mixed salt solution for later use.

[0068] Step S2: Weigh 10g of chitosan and place it in a beaker. Measure 200mL of 2% acetic acid solution and slowly pour it into the beaker containing the chitosan. Place the beaker on a magnetic stirrer and stir at 200r / min for 2 hours to fully dissolve the chitosan and obtain a chitosan solution.

[0069] Add 500 mL of liquid paraffin and 20 mL of Span-80 to a beaker, and stir with an electric stirrer at 400 rpm for 10 minutes to mix them evenly and form an oil phase.

[0070] The prepared chitosan solution was slowly added dropwise to the oil phase through a separatory funnel at a rate of 1 drop / second. During the addition process, the mixture was continuously stirred with an electric stirrer at a speed of 400 r / min to form a stable emulsion.

[0071] After the chitosan solution has been added dropwise, add 0.5g of glutaraldehyde crosslinking agent to the emulsion. Transfer the beaker to a constant temperature water bath, set the temperature to 50℃, turn on the stirring function, and heat and stir at 300r / min for 5 hours.

[0072] After the reaction was complete, the emulsion was transferred to a separatory funnel and allowed to stand for 2 hours to separate into layers. The upper oil phase was discarded, and the lower product was washed three times with 50 mL of anhydrous ethanol each time to remove residual oil phase and unreacted reagents. Finally, the product was transferred to a petri dish and placed in a vacuum drying oven at 50 °C to constant weight to obtain chitosan microspheres.

[0073] Step S3: Add all the chitosan microspheres to the mixed salt solution and stir thoroughly with a glass rod. Slowly add sodium hydroxide solution to the solution to adjust the pH to 10. Place the beaker on a magnetic stirrer, set the stirring speed to 300 rpm, and stir the reaction at room temperature for 8 hours.

[0074] After the reaction was complete, the solid product was separated by suction filtration through a Buchner funnel. The solid product was washed three times with deionized water, using 50 mL of water each time, to remove residual solution. The washed product was placed in a vacuum drying oven and dried at 60°C to constant weight to obtain chitosan-supported iron-manganese composite oxide.

[0075] Step S4: Weigh 4g of disodium ethylenediaminetetraacetate and place it in a beaker. Add 400mL of deionized water. Place the beaker on a magnetic stirrer and stir at 300r / min for 15 minutes to completely dissolve the disodium ethylenediaminetetraacetate, obtaining a disodium ethylenediaminetetraacetate solution.

[0076] Add 10g of chitosan-supported iron-manganese composite oxide to a solution of disodium ethylenediaminetetraacetate and stir until homogeneous with a glass rod. Place the beaker on a magnetic stirrer and stir the reaction at 300 rpm for 4 hours.

[0077] After the reaction was complete, the solid product was separated by suction filtration through a Buchner funnel. The solid product was washed three times with 50 mL of deionized water each time to remove residual solution. The washed product was then placed in a vacuum drying oven and dried at 60°C to constant weight to obtain the soil remediation agent.

[0078] Example 5

[0079] Step S1: Weigh 6g of ferric sulfate and 2g of manganese sulfate and place them in a beaker. Measure 300mL of deionized water and pour it into the beaker. Place the beaker on a magnetic stirrer, turn on the stirring function, and stir at 300r / min for 30 minutes until the ferric sulfate and manganese sulfate are completely dissolved, obtaining a mixed salt solution for later use.

[0080] Step S2: Weigh 10g of chitosan and place it in a beaker. Measure 200mL of 2% acetic acid solution and slowly pour it into the beaker containing the chitosan. Place the beaker on a magnetic stirrer and stir at 200r / min for 2 hours to fully dissolve the chitosan and obtain a chitosan solution.

[0081] Add 500 mL of liquid paraffin and 20 mL of Span-80 to a beaker, and stir with an electric stirrer at 400 rpm for 10 minutes to mix them evenly and form an oil phase.

[0082] The prepared chitosan solution was slowly added dropwise to the oil phase through a separatory funnel at a rate of 1 drop / second. During the addition process, the mixture was continuously stirred with an electric stirrer at a speed of 400 r / min to form a stable emulsion.

[0083] After the chitosan solution has been added dropwise, add 0.3g of glutaraldehyde crosslinking agent to the emulsion. Transfer the beaker to a constant temperature water bath, set the temperature to 40℃, turn on the stirring function, and heat and stir at 300r / min for 2 hours.

[0084] After the reaction was complete, the emulsion was transferred to a separatory funnel and allowed to stand for 2 hours to separate into layers. The upper oil phase was discarded, and the lower product was washed three times with 50 mL of anhydrous ethanol each time to remove residual oil phase and unreacted reagents. Finally, the product was transferred to a petri dish and placed in a vacuum drying oven at 50 °C to constant weight to obtain chitosan microspheres.

[0085] Step S3: Add all the chitosan microspheres to the mixed salt solution and stir thoroughly with a glass rod. Slowly add sodium hydroxide solution to the solution to adjust the pH to 9. Place the beaker on a magnetic stirrer, set the stirring speed to 300 rpm, and stir the reaction at room temperature for 5 hours.

[0086] After the reaction was complete, the solid product was separated by suction filtration through a Buchner funnel. The solid product was washed three times with deionized water, using 50 mL of water each time, to remove residual solution. The washed product was placed in a vacuum drying oven and dried at 60°C to constant weight to obtain chitosan-supported iron-manganese composite oxide.

[0087] Step S4: Weigh 2g of disodium ethylenediaminetetraacetate and place it in a beaker. Add 400mL of deionized water. Place the beaker on a magnetic stirrer and stir at 300r / min for 15 minutes to completely dissolve the disodium ethylenediaminetetraacetate, obtaining a disodium ethylenediaminetetraacetate solution.

[0088] Add 10g of chitosan-supported iron-manganese composite oxide to a solution of disodium ethylenediaminetetraacetate and stir until homogeneous with a glass rod. Place the beaker on a magnetic stirrer and stir the reaction at 300 rpm for 4 hours.

[0089] After the reaction was complete, the solid product was separated by suction filtration through a Buchner funnel. The solid product was washed three times with 50 mL of deionized water each time to remove residual solution. The washed product was then placed in a vacuum drying oven and dried at 60°C to constant weight to obtain the soil remediation agent.

[0090] Comparative Example 1

[0091] The difference between Comparative Example 1 and Example 1 is that the soil remediation agent is replaced with chitosan microspheres, and the preparation method of chitosan microspheres is the same as that of Example 1.

[0092] Comparative Example 2

[0093] The difference between Comparative Example 2 and Example 1 is that the soil remediation agent is replaced with chitosan-supported iron-manganese composite oxide, and the preparation method of chitosan-supported iron-manganese composite oxide is the same as that of Example 1.

[0094] Comparative Example 3

[0095] The difference between Comparative Example 3 and Example 4 is that the mass ratio of chitosan-supported iron-manganese composite oxide to disodium ethylenediaminetetraacetate is 10:5, while the other steps are the same.

[0096] Comparative Example 4

[0097] The difference between Comparative Example 4 and Example 4 is that the mass ratio of chitosan-supported iron-manganese composite oxide to disodium ethylenediaminetetraacetate is 10:6, while the other steps are the same.

[0098] Performance testing:

[0099] Heavy metal removal performance test:

[0100] Nine 100g portions of simulated heavy metal contaminated soil (containing lead, cadmium, mercury, zinc, and nickel, with concentrations of 100mg / kg, 50mg / kg, 20mg / kg, 80mg / kg, and 60mg / kg, respectively) were weighed and placed in nine 250mL beakers. 1g of the soil remediation agent prepared in Examples 1-5 and Comparative Examples 1-4 was added to each of the nine beakers sequentially. All beakers were placed on a constant-temperature shaker and shaken at 25℃ and 150r / min for 48 hours. After the reaction, soil samples were taken, and the contents of lead, cadmium, mercury, zinc, and nickel in the soil were determined using atomic absorption spectrometry (AAS) and atomic fluorescence spectrometry (AFS). The heavy metal removal rate was calculated using the formula: Removal rate (%) = (Initial content - Content after reaction) / Initial content × 100%. The calculation results are shown in Table 1.

[0101] Table 1:

[0102]

[0103] Acid-base adaptability test:

[0104] Buffer solutions with pH values ​​of 6 and 10 were prepared separately. Two 100g portions of contaminated soil containing 50mg / kg of lead were taken, and 1g of the soil remediation agent prepared in the example was added to each beaker. Then, 100mL of pH 6 buffer solution was added to one portion of soil, and 100mL of pH 10 buffer solution was added to the other portion. After thorough mixing, the beakers were placed on a constant-temperature shaker and the reaction was carried out at 25℃ and 150r / min for 48 hours. After the reaction, the lead content in the soil was measured, and the lead removal effect of the remediation agent under different pH conditions was compared. The removal effects on cadmium, mercury, zinc, and nickel were also tested using the same method. The test results are shown in Table 2.

[0105] Table 2:

[0106]

[0107] 3. Soil structure impact test:

[0108] Four 200g portions of uncontaminated soil were placed in four flowerpots, labeled A, B, C, and D. Pot A served as a control, untreated. Pot B received 2g of the soil remediation agent prepared in Example 4, Pot C received 2g of the soil remediation agent prepared in Comparative Example 3, and Pot D received 2g of the soil remediation agent prepared in Comparative Example 4. The flowerpots were placed in a greenhouse under identical watering and care conditions for 30 days. After 30 days, soil samples were taken from each pot, and the soil particle size distribution was determined using the pipette method. The soil aggregate stability index was calculated, and the changes in soil structure were compared. A higher soil aggregate stability index indicates better soil structural stability. The test results are shown in Table 3.

[0109] Table 3:

[0110]

[0111] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a soil remediation agent for environmental pollution, characterized in that, Includes the following steps: S1. Add ferric sulfate and manganese sulfate to deionized water, with a mass ratio of ferric sulfate to manganese sulfate of 3:1-2. Stir to dissolve and obtain a mixed salt solution. S2. Chitosan is added to acetic acid solution and stirred to dissolve, resulting in a chitosan solution. The chitosan solution is then slowly added dropwise to an oil phase composed of liquid paraffin and Span-80, and stirred to form an emulsion. Glutaraldehyde crosslinking agent is then added to the emulsion at a rate of 3-5% of the chitosan mass. The mixture is heated and stirred to react. After standing and separating, washing, and drying, chitosan microspheres are obtained. S3. Add chitosan microspheres to a mixed salt solution, adjust the pH to alkaline, stir the reaction, and after filtration, separation, washing and drying, obtain chitosan-supported iron-manganese composite oxides. S4. Disodium ethylenediaminetetraacetate was added to deionized water and stirred to dissolve, resulting in a disodium ethylenediaminetetraacetate solution. Chitosan-supported iron-manganese composite oxide was added to the disodium ethylenediaminetetraacetate solution, with a mass ratio of chitosan-supported iron-manganese composite oxide to disodium ethylenediaminetetraacetate of 10:2-4. The mixture was stirred and reacted. After filtration, separation, washing, and drying, the soil remediation agent was obtained.

2. The method for preparing a soil remediation agent for environmental pollution according to claim 1, characterized in that, In step S2, the heating temperature is 40-50℃ and the reaction time is 2-5h.

3. The method for preparing a soil remediation agent for environmental pollution according to claim 1, characterized in that, In step S3, the pH is adjusted to 9-10.

4. The method for preparing a soil remediation agent for environmental pollution according to claim 1, characterized in that, In step S3, the stirring reaction time is 5-8 hours.

5. A soil remediation agent for environmental pollution, characterized in that, It is prepared by the method described in any one of claims 1-4.

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