Soil remediation agent for environmental pollution and preparation method thereof

Abstract

The invention discloses a soil remediation agent for environmental pollution and a preparation method thereof, and relates to the technical field of soil regeneration. The preparation method comprises the following steps: firstly, adding ferric sulfate and manganese sulfate into deionized water, stirring and dissolving to obtain a mixed salt solution; then preparing chitosan microspheres; adding the chitosan microspheres into a mixed salt solution for reaction to obtain a chitosan-loaded iron-manganese composite oxide; and finally, adding the chitosan-loaded iron-manganese composite oxide into an ethylenediamine tetraacetic acid disodium solution for reaction to obtain the soil remediation agent. As a special medicament material for heavy metal environmental pollution treatment, the soil remediation agent disclosed by the invention can be used for efficiently treating various heavy metals in soil, and is good in acid-alkali soil adaptability, so that soil regeneration is realized.

Description

Technical Field

[0001] The present invention relates to the field of soil regeneration technology, and belongs to patent classification number B09C1 / 08, specifically a soil remediation agent for environmental pollution and a preparation method thereof. Background Art

[0002] With the acceleration of industrialization and urbanization, heavy metal contamination has become a serious problem facing the soil environment worldwide. Efficient soil remediation technology has become a research hotspot in the current environmental field. As specialized agents for environmental pollution treatment, their performance and applicability directly impact the effectiveness of contaminated soil regeneration.

[0003] Currently, a wide variety of soil remediation agents are available on the market, but these agents generally have limitations. For one thing, most soil remediation agents only remediate a single heavy metal, making it difficult to effectively treat multiple heavy metal contaminants simultaneously. However, in real-world pollution scenarios, soils are often contaminated by a combination of heavy metals. Single-function remediation agents are unable to meet the remediation needs of complex contaminated soils, resulting in slow regeneration, low remediation efficiency, and difficulty achieving ideal remediation results.

[0004] On the other hand, existing soil remediation agents have poor adaptability to soil pH, making them difficult to use in both acidic and alkaline soil environments. Existing remediation agents used as specialized materials for environmental pollution treatment typically only function under specific acid-base conditions. In other acid-base environments, their remediation activity is significantly reduced, or even ineffective. This significantly limits their scope of application, leading to increased remediation costs and unstable regeneration of contaminated soils. Summary of the Invention

[0005] The present invention aims to provide a soil remediation agent for environmental pollution and a method for its preparation to address the technical problems raised by the aforementioned background art. The present soil remediation agent, as a specialized agent for treating heavy metal environmental pollution, can effectively treat a variety of heavy metals in the soil and exhibits good adaptability to both acidic and alkaline soils, thereby achieving soil regeneration.

[0006] To achieve the above object, the present invention provides the following technical solutions: A method for preparing a soil remediation agent for environmental pollution, comprising the following steps: S1. Add ferric sulfate and manganese sulfate to deionized water, stir and dissolve to obtain a mixed salt solution; S2, adding chitosan to an acetic acid solution, stirring and dissolving to obtain a chitosan solution, slowly adding the chitosan solution dropwise to an oil phase consisting of liquid paraffin and Span-80, stirring to form an emulsion, then adding glutaraldehyde crosslinking agent to the emulsion, heating and stirring to react, standing for stratification, washing and drying to obtain chitosan microspheres; S3, adding chitosan microspheres to the mixed salt solution, adjusting the pH to alkaline, stirring the solution for reaction, filtering, separating, washing, and drying to obtain chitosan-loaded iron-manganese composite oxide; S4. Add disodium EDTA into deionized water and stir to dissolve to obtain a disodium EDTA solution. Add chitosan-loaded iron-manganese composite oxide into the disodium EDTA solution, stir to react, filter, separate, wash and dry to obtain a soil remediation agent.

[0007] The reaction principle in the technical solution of the present invention is as follows: first, chitosan is protonated and dissolved in an acetic acid solution, and a liquid paraffin oil phase containing Span-80 is dropped into it to form an emulsion, which is cross-linked into microspheres by glutaraldehyde to construct a porous infrastructure containing active functional groups. Then, under alkaline conditions, ferric sulfate and manganese sulfate are hydrolyzed to form hydroxide precipitates, which are loaded on the chitosan microspheres to form iron-manganese composite oxides, which have both redox and adsorption properties. Finally, disodium ethylenediaminetetraacetic acid, due to the amino and carboxyl groups in the molecule, has a strong coordination ability with the nitrogen and oxygen atoms in these functional groups having lone pairs of electrons, and the Fe 3+ 、Mn 4+ A stable coordination bond is formed, whereby disodium EDTA is bound to the chitosan-loaded iron-manganese composite oxide, further enhancing the repair agent's ability to handle heavy metals.

[0008] The abundant amino and hydroxyl groups on the surface of chitosan microspheres can coordinate with heavy metal ions, such as lead and cadmium, 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. They can also utilize surface active sites to adsorb heavy metals. Disodium ethylenediaminetetraacetic acid forms stable chelates with zinc and nickel ions, reducing their mobility and bioavailability, achieving efficient treatment of different heavy metals.

[0009] Chitosan microspheres have acid-base buffering capabilities. Their amino and hydroxyl groups can neutralize acidity and mitigate alkalinity, respectively. Their porous structure can also adsorb acids and bases to regulate soil pH. Chelates formed by disodium ethylenediaminetetraacetic acid (EDTA) and heavy metals are stable at varying pH levels, and their fixation of heavy metals is unaffected by either acidic or alkaline environments. Iron-manganese composite oxides maintain stability and activity in both acidic and alkaline soils, regulating heavy metal concentrations through dissolution-precipitation in acidic soils and continuously exerting redox and adsorption activities in alkaline soils.

[0010] Preferably, in step S1, the mass ratio of ferric sulfate to manganese sulfate is 3:1-2.

[0011] Preferably, in step S2, the amount of glutaraldehyde cross-linking agent added is 3-5% of the mass of chitosan.

[0012] Preferably, in step S2, the heating temperature is 40-50° C. and the reaction time is 2-5 h.

[0013] Preferably, in step S3, the pH is adjusted to 9-10.

[0014] Preferably, in step S3, the stirring reaction time is 5-8 hours.

[0015] Preferably, in step S4, the mass ratio of the chitosan-loaded iron-manganese composite oxide to disodium ethylenediaminetetraacetic acid is 10:2-4.

[0016] In the technical solution of the present invention, as described above, disodium ethylenediaminetetraacetic acid forms a stable chelate with zinc ions, nickel ions and heavy metal ions, reducing their mobility and bioavailability. To achieve the above technical effects, a sufficient amount of disodium ethylenediaminetetraacetic acid must be combined with the chitosan-loaded iron-manganese composite oxide, because the present invention controls the mass ratio of the chitosan-loaded iron-manganese composite oxide to disodium ethylenediaminetetraacetic acid to be less than 10 / 2. As the amount of disodium ethylenediaminetetraacetic acid continues to increase to a certain amount, that is, the mass ratio of the chitosan-loaded iron-manganese composite oxide to disodium ethylenediaminetetraacetic acid is less than 10 / 4, the soil remediation agent will destroy the soil aggregate structure, the looseness of the soil will increase significantly, and the large pores in the soil will increase, causing the water and nutrients in the soil to easily and quickly seep and lose. Further research found that this is because calcium ions in the soil play a "cementing" role in maintaining the structure of soil aggregates. Excessive disodium ethylenediaminetetraacetic acid will chelate calcium ions, weakening the connection between soil particles and destroying the soil aggregate structure. Therefore, the present invention simultaneously controls the mass ratio of the chitosan-loaded iron-manganese composite oxide to disodium ethylenediaminetetraacetic acid to be greater than 10 / 4.

[0017] A soil remediation agent for environmental pollution is prepared by the above method.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This soil remediation agent achieves efficient treatment of various heavy metals through the synergistic action 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. Iron-manganese composite oxides can alter the valence state of heavy metals like mercury through redox reactions, partially volatilizing them and adsorbing them through surface active sites. Disodium ethylenediaminetetraacetic acid forms stable chelates with heavy metal ions such as zinc and nickel, reducing their mobility and bioavailability, thereby comprehensively treating multiple heavy metal contamination in the soil.

[0019] The various components of the remediation agent provide excellent acid-base adaptability. Chitosan microspheres have acid-base buffering capacity, with amino groups neutralizing acidity and hydroxyl groups mitigating alkalinity. Their porous structure also allows them to absorb acids and bases to regulate soil pH. The chelates formed by disodium EDTA and heavy metals are stable at varying pH values, without affecting their fixation. Iron-manganese composite oxides remain stable and active in both acidic and alkaline soils, regulating heavy metal concentrations through dissolution-precipitation in acidic soils and continuously exerting their redox and adsorption properties in alkaline soils.

[0020] By precisely controlling the mass ratio of chitosan-loaded iron-manganese composite oxide to disodium EDTA within a reasonable range, it is possible to ensure that disodium EDTA is sufficiently bound to the chitosan-loaded iron-manganese composite oxide to achieve effective treatment of heavy metals, while also avoiding problems such as excessive chelation of calcium ions in the soil by disodium EDTA, which could lead to the destruction of soil aggregate structure, loosening of the soil, and rapid loss of water and nutrients. DETAILED DESCRIPTION

[0021] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the implementation regulations described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0022] The main raw material specifications used in the present invention in the specific embodiment are as follows: 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°C), density 0.85-0.89 g / cm³, flash point ≥160°C; Span-80, HLB value 4.3, acid value ≤8 mg KOH / g, saponification value 140-160 mg KOH / g; disodium EDTA, purity ≥99%.

[0023] Example 1

[0024] Step S1: Weigh 6 g of ferric sulfate and 3.5 g of manganese sulfate into a beaker. Measure 300 mL of deionized water and pour it into the beaker. Place the beaker on a magnetic stirrer, turn on the stirring function, and stir at 300 rpm for 30 minutes until the ferric sulfate and manganese sulfate are completely dissolved, to obtain a mixed salt solution, which is set aside.

[0025] Step S2: Weigh 10 g of chitosan into a beaker, measure 200 mL 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 200 rpm for 2 hours to fully dissolve the chitosan, thereby obtaining a chitosan solution.

[0026] Add 500 mL of liquid paraffin and 20 mL of Span-80 into a beaker, and stir with an electric stirrer at a speed of 400 r / min for 10 minutes to mix them evenly to form an oil phase.

[0027] The prepared chitosan solution was slowly added dropwise to the oil phase through a separatory funnel at a dropping rate of 1 drop / second. During the addition process, an electric stirrer was continuously stirred at a speed of 400 r / min to form a stable emulsion.

[0028] After the chitosan solution was added dropwise, 0.45 g of glutaraldehyde crosslinker was added to the emulsion. The beaker was transferred to a constant temperature water bath, set to 45°C, and stirred at 300 rpm for 4 hours.

[0029] After the reaction is complete, the emulsion is transferred to a separatory funnel and allowed to stand for 2 hours to separate. The upper oil phase is discarded, and the lower product is washed three times with 50 mL of anhydrous ethanol each time to remove any residual oil and unreacted reagents. Finally, the product is transferred to a watch glass, placed in a vacuum drying oven, and dried at 50°C to constant weight to obtain chitosan microspheres.

[0030] Step S3: Add all the chitosan microspheres to the mixed salt solution and stir evenly 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 at 300 rpm and stir at room temperature for 7 hours.

[0031] After the reaction, the solid product was isolated by filtration using a Büchner funnel. The solid product was washed three times with 50 mL of deionized water each time to remove any residual solution. The washed product was placed in a vacuum drying oven and dried at 60°C to a constant weight to obtain the chitosan-supported iron-manganese composite oxide.

[0032] Step S4: Weigh 3.5 g of disodium EDTA into a beaker, add 400 mL of deionized water, place the beaker on a magnetic stirrer, and stir at 300 rpm for 15 minutes to completely dissolve the disodium EDTA, thereby obtaining a disodium EDTA solution.

[0033] Add 10 g of chitosan-supported iron-manganese composite oxide to the disodium ethylenediaminetetraacetic acid solution and stir evenly with a glass rod. Place the beaker on a magnetic stirrer and stir at 300 rpm for 4 hours.

[0034] After the reaction, the solid product was separated by suction filtration using a Büchner funnel. The solid product was washed three times with 50 mL of deionized water each time to remove any residual solution. The washed product was placed in a vacuum drying oven and dried at 60°C to a constant weight to obtain a soil remediation agent.

[0035] Example 2

[0036] Step S1: Weigh 6 g of ferric sulfate and 2.5 g of manganese sulfate into a beaker. Measure 300 mL of deionized water and pour it into the beaker. Place the beaker on a magnetic stirrer, turn on the stirring function, and stir at 300 rpm for 30 minutes until the ferric sulfate and manganese sulfate are completely dissolved, to obtain a mixed salt solution, which is set aside.

[0037] Step S2: Weigh 10 g of chitosan into a beaker, measure 200 mL 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 200 rpm for 2 hours to fully dissolve the chitosan, thereby obtaining a chitosan solution.

[0038] Add 500 mL of liquid paraffin and 20 mL of Span-80 into a beaker, and stir with an electric stirrer at a speed of 400 r / min for 10 minutes to mix them evenly to form an oil phase.

[0039] The prepared chitosan solution was slowly added dropwise to the oil phase through a separatory funnel at a dropping rate of 1 drop / second. During the addition process, an electric stirrer was continuously stirred at a speed of 400 r / min to form a stable emulsion.

[0040] After the chitosan solution was added dropwise, 0.35 g of glutaraldehyde crosslinker was added to the emulsion. The beaker was transferred to a constant temperature water bath, set to 45°C, and stirred at 300 rpm for 3 hours.

[0041] After the reaction is complete, the emulsion is transferred to a separatory funnel and allowed to stand for 2 hours to separate. The upper oil phase is discarded, and the lower product is washed three times with 50 mL of anhydrous ethanol each time to remove any residual oil and unreacted reagents. Finally, the product is transferred to a watch glass, placed in a vacuum drying oven, and dried at 50°C to constant weight to obtain chitosan microspheres.

[0042] Step S3: Add all the chitosan microspheres to the mixed salt solution and stir evenly 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 at 300 rpm and stir at room temperature for 6 hours.

[0043] After the reaction, the solid product was isolated by filtration using a Büchner funnel. The solid product was washed three times with 50 mL of deionized water each time to remove any residual solution. The washed product was placed in a vacuum drying oven and dried at 60°C to a constant weight to obtain the chitosan-supported iron-manganese composite oxide.

[0044] Step S4: Weigh 2.5 g of disodium EDTA into a beaker, add 400 mL of deionized water, place the beaker on a magnetic stirrer, and stir at 300 rpm for 15 minutes to completely dissolve the disodium EDTA, thereby obtaining a disodium EDTA solution.

[0045] Add 10 g of chitosan-supported iron-manganese composite oxide to the disodium ethylenediaminetetraacetic acid solution and stir evenly with a glass rod. Place the beaker on a magnetic stirrer and stir at 300 rpm for 4 hours.

[0046] After the reaction, the solid product was separated by suction filtration using a Büchner funnel. The solid product was washed three times with 50 mL of deionized water each time to remove any residual solution. The washed product was placed in a vacuum drying oven and dried at 60°C to a constant weight to obtain a soil remediation agent.

[0047] Example 3

[0048] Step S1: Weigh 6 g of ferric sulfate and 3 g of manganese sulfate into a beaker. Measure 300 mL of deionized water and pour it into the beaker. Place the beaker on a magnetic stirrer, turn on the stirring function, and stir at 300 rpm for 30 minutes until the ferric sulfate and manganese sulfate are completely dissolved, to obtain a mixed salt solution, which is set aside.

[0049] Step S2: Weigh 10 g of chitosan into a beaker, measure 200 mL 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 200 rpm for 2 hours to fully dissolve the chitosan, thereby obtaining a chitosan solution.

[0050] Add 500 mL of liquid paraffin and 20 mL of Span-80 into a beaker, and stir with an electric stirrer at a speed of 400 r / min for 10 minutes to mix them evenly to form an oil phase.

[0051] The prepared chitosan solution was slowly added dropwise to the oil phase through a separatory funnel at a dropping rate of 1 drop / second. During the addition process, an electric stirrer was continuously stirred at a speed of 400 r / min to form a stable emulsion.

[0052] After the chitosan solution was added dropwise, 0.4 g of glutaraldehyde crosslinker was added to the emulsion. The beaker was transferred to a constant temperature water bath, set to 45°C, and stirred at 300 r / min for 3.5 hours.

[0053] After the reaction is complete, the emulsion is transferred to a separatory funnel and allowed to stand for 2 hours to separate. The upper oil phase is discarded, and the lower product is washed three times with 50 mL of anhydrous ethanol each time to remove any residual oil and unreacted reagents. Finally, the product is transferred to a watch glass, placed in a vacuum drying oven, and dried at 50°C to constant weight to obtain chitosan microspheres.

[0054] Step S3: Add all the chitosan microspheres to the mixed salt solution and stir evenly 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 at 300 rpm and stir at room temperature for 6.5 hours.

[0055] After the reaction, the solid product was isolated by filtration using a Büchner funnel. The solid product was washed three times with 50 mL of deionized water each time to remove any residual solution. The washed product was placed in a vacuum drying oven and dried at 60°C to a constant weight to obtain the chitosan-supported iron-manganese composite oxide.

[0056] Step S4: Weigh 3 g of disodium EDTA into a beaker, add 400 mL of deionized water, place the beaker on a magnetic stirrer, and stir at 300 rpm for 15 minutes to completely dissolve the disodium EDTA, thereby obtaining a disodium EDTA solution.

[0057] Add 10 g of chitosan-supported iron-manganese composite oxide to the disodium ethylenediaminetetraacetic acid solution and stir evenly with a glass rod. Place the beaker on a magnetic stirrer and stir at 300 rpm for 4 hours.

[0058] After the reaction, the solid product was separated by suction filtration using a Büchner funnel. The solid product was washed three times with 50 mL of deionized water each time to remove any residual solution. The washed product was placed in a vacuum drying oven and dried at 60°C to a constant weight to obtain a soil remediation agent.

[0059] Example 4

[0060] Step S1: Weigh 6 g of ferric sulfate and 4 g of manganese sulfate into a beaker. Measure 300 mL of deionized water and pour it into the beaker. Place the beaker on a magnetic stirrer, turn on the stirring function, and stir at 300 rpm for 30 minutes until the ferric sulfate and manganese sulfate are completely dissolved, to obtain a mixed salt solution, which is set aside.

[0061] Step S2: Weigh 10 g of chitosan into a beaker, measure 200 mL 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 200 rpm for 2 hours to fully dissolve the chitosan, thereby obtaining a chitosan solution.

[0062] Add 500 mL of liquid paraffin and 20 mL of Span-80 into a beaker, and stir with an electric stirrer at a speed of 400 r / min for 10 minutes to mix them evenly to form an oil phase.

[0063] The prepared chitosan solution was slowly added dropwise to the oil phase through a separatory funnel at a dropping rate of 1 drop / second. During the addition process, an electric stirrer was continuously stirred at a speed of 400 r / min to form a stable emulsion.

[0064] After the chitosan solution was added dropwise, 0.5 g of glutaraldehyde crosslinker was added to the emulsion. The beaker was transferred to a constant temperature water bath, set to 50°C, and stirred at 300 r / min for 5 hours.

[0065] After the reaction is complete, the emulsion is transferred to a separatory funnel and allowed to stand for 2 hours to separate. The upper oil phase is discarded, and the lower product is washed three times with 50 mL of anhydrous ethanol each time to remove any residual oil and unreacted reagents. Finally, the product is transferred to a watch glass, placed in a vacuum drying oven, and dried at 50°C to constant weight to obtain chitosan microspheres.

[0066] Step S3: Add all the chitosan microspheres to the mixed salt solution and stir evenly 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 at 300 rpm and stir at room temperature for 8 hours.

[0067] After the reaction, the solid product was isolated by filtration using a Büchner funnel. The solid product was washed three times with 50 mL of deionized water each time to remove any residual solution. The washed product was placed in a vacuum drying oven and dried at 60°C to a constant weight to obtain the chitosan-supported iron-manganese composite oxide.

[0068] Step S4: Weigh 4 g of disodium EDTA into a beaker, add 400 mL of deionized water, place the beaker on a magnetic stirrer, and stir at 300 rpm for 15 minutes to completely dissolve the disodium EDTA, thereby obtaining a disodium EDTA solution.

[0069] Add 10 g of chitosan-supported iron-manganese composite oxide to the disodium ethylenediaminetetraacetic acid solution and stir evenly with a glass rod. Place the beaker on a magnetic stirrer and stir at 300 rpm for 4 hours.

[0070] After the reaction, the solid product was separated by suction filtration using a Büchner funnel. The solid product was washed three times with 50 mL of deionized water each time to remove any residual solution. The washed product was placed in a vacuum drying oven and dried at 60°C to a constant weight to obtain a soil remediation agent.

[0071] Example 5

[0072] Step S1: Weigh 6 g of ferric sulfate and 2 g of manganese sulfate into a beaker. Measure 300 mL of deionized water and pour it into the beaker. Place the beaker on a magnetic stirrer, turn on the stirring function, and stir at 300 rpm for 30 minutes until the ferric sulfate and manganese sulfate are completely dissolved, to obtain a mixed salt solution, which is set aside.

[0073] Step S2: Weigh 10 g of chitosan into a beaker, measure 200 mL 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 200 rpm for 2 hours to fully dissolve the chitosan, thereby obtaining a chitosan solution.

[0074] Add 500 mL of liquid paraffin and 20 mL of Span-80 into a beaker, and stir with an electric stirrer at a speed of 400 r / min for 10 minutes to mix them evenly to form an oil phase.

[0075] The prepared chitosan solution was slowly added dropwise to the oil phase through a separatory funnel at a dropping rate of 1 drop / second. During the addition process, an electric stirrer was continuously stirred at a speed of 400 r / min to form a stable emulsion.

[0076] After the chitosan solution was added dropwise, 0.3 g of glutaraldehyde crosslinker was added to the emulsion. The beaker was transferred to a constant temperature water bath, set to 40°C, and stirred at 300 rpm for 2 hours.

[0077] After the reaction is complete, the emulsion is transferred to a separatory funnel and allowed to stand for 2 hours to separate. The upper oil phase is discarded, and the lower product is washed three times with 50 mL of anhydrous ethanol each time to remove any residual oil and unreacted reagents. Finally, the product is transferred to a watch glass, placed in a vacuum drying oven, and dried at 50°C to constant weight to obtain chitosan microspheres.

[0078] Step S3: Add all the chitosan microspheres to the mixed salt solution and stir evenly 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 at 300 rpm and stir at room temperature for 5 hours.

[0079] After the reaction, the solid product was isolated by filtration using a Büchner funnel. The solid product was washed three times with 50 mL of deionized water each time to remove any residual solution. The washed product was placed in a vacuum drying oven and dried at 60°C to a constant weight to obtain the chitosan-supported iron-manganese composite oxide.

[0080] Step S4: Weigh 2 g of disodium EDTA into a beaker, add 400 mL of deionized water, place the beaker on a magnetic stirrer, and stir at 300 rpm for 15 minutes to completely dissolve the disodium EDTA, thereby obtaining a disodium EDTA solution.

[0081] Add 10 g of chitosan-supported iron-manganese composite oxide to the disodium ethylenediaminetetraacetic acid solution and stir evenly with a glass rod. Place the beaker on a magnetic stirrer and stir at 300 rpm for 4 hours.

[0082] After the reaction, the solid product was separated by suction filtration using a Büchner funnel. The solid product was washed three times with 50 mL of deionized water each time to remove any residual solution. The washed product was placed in a vacuum drying oven and dried at 60°C to a constant weight to obtain a soil remediation agent.

[0083] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the soil remediation agent is replaced by chitosan microspheres, and the preparation method of the chitosan microspheres is the same as that of Example 1.

[0084] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the soil remediation agent is replaced by chitosan-loaded iron-manganese composite oxide, and the preparation method of chitosan-loaded iron-manganese composite oxide is the same as that of Example 1.

[0085] Comparative Example 3 The difference between Comparative Example 3 and Example 4 is that the mass ratio of chitosan-supported iron-manganese composite oxide to disodium ethylenediaminetetraacetic acid is 10:5, and the other steps are the same.

[0086] Comparative Example 4 The difference between Comparative Example 4 and Example 4 is that the mass ratio of chitosan-supported iron-manganese composite oxide to disodium ethylenediaminetetraacetic acid is 10:6, and the other steps are the same.

[0087] Performance testing: Heavy metal removal performance test: Nine 100g portions of simulated heavy metal-contaminated soil (containing lead, cadmium, mercury, zinc, and nickel at concentrations of 100mg / kg, 50mg / kg, 20mg / kg, 80mg / kg, and 60mg / kg, respectively) were weighed and placed into nine 250mL beakers. 1g of the soil remediation agents prepared in Examples 1-5 and Comparative Examples 1-4 was added to each of the nine beakers. All beakers were placed on a constant-temperature oscillator and shaken at 25°C and 150 rpm for 48 hours. After the reaction, soil samples were collected and the lead, cadmium, mercury, zinc, and nickel contents in the soil were determined using atomic absorption spectrometry (AAS) and atomic fluorescence spectrometry (AFS). Heavy metal removal rates were calculated using the formula: Removal rate (%) = (initial content - post-reaction content) / initial content × 100%. The results are shown in Table 1.

[0088] Table 1:

[0089] Acid-base adaptability test: Prepare buffer solutions with pH values of 6 and 10, respectively. Take two 100g portions of contaminated soil containing 50mg / kg lead, and add 1g of the example to a beaker to prepare a soil remediation agent. Then, add 100mL of a pH 6 buffer solution to one portion of the soil and 100mL of a pH 10 buffer solution to the other portion of the soil. After stirring evenly, place the beaker on a constant temperature oscillator and oscillate at 25°C and 150r / min for 48 hours. After the reaction is complete, measure the lead content in the soil and compare the lead removal effect of the remediation agent under different pH conditions. The removal effect of cadmium, mercury, zinc, and nickel was also tested using the above method. The test results are shown in Table 2.

[0090] Table 2:

[0091] 3. Soil structure impact test: Take 4 portions of 200g uncontaminated soil and place them in 4 flower pots respectively, labeled A, B, C, D. A pot is not treated as a control, B pot is added with 2g of the soil remediation agent prepared in Example 4, C pot is added with 2g of the soil remediation agent prepared in Comparative Example 3, and D pot is added with 2g of the soil remediation agent prepared in Comparative Example 4. The flower pots are placed in a greenhouse, kept under the same watering and curing conditions, and cultivated for 30 days. After 30 days, soil samples from each pot are taken, and the soil particle size distribution is measured using the straw method. The soil aggregate stability index is calculated, and the changes in soil structure are compared. The higher the soil aggregate stability index, the better the soil structure stability. The test results are shown in Table 3.

[0092] Table 3:

[0093] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a soil remediation agent for environmental pollution, characterized in that: The following steps are involved: S1. Add ferric sulfate and manganese sulfate to deionized water, stir and dissolve to obtain a mixed salt solution; S2, adding chitosan to an acetic acid solution, stirring and dissolving to obtain a chitosan solution, slowly adding the chitosan solution dropwise to an oil phase consisting of liquid paraffin and Span-80, stirring to form an emulsion, then adding glutaraldehyde crosslinking agent to the emulsion, heating and stirring to react, standing for stratification, washing and drying to obtain chitosan microspheres; S3, adding chitosan microspheres to the mixed salt solution, adjusting the pH to alkaline, stirring the solution for reaction, filtering, separating, washing, and drying to obtain chitosan-loaded iron-manganese composite oxide; S4. Add disodium EDTA into deionized water and stir to dissolve to obtain a disodium EDTA solution. Add chitosan-loaded iron-manganese composite oxide into the disodium EDTA solution, stir to react, filter, separate, wash and dry to obtain a soil remediation agent.

2. The method for preparing a soil remediation agent for environmental pollution according to claim 1, characterized in that: In step S1, the mass ratio of ferric sulfate to manganese sulfate is 3:1-2.

3. The method for preparing a soil remediation agent for environmental pollution according to claim 1, characterized in that: In step S2, the amount of glutaraldehyde cross-linking agent added is 3-5% of the mass of chitosan.

4. 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° C. and the reaction time is 2-5 hours.

5. 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.

6. 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.

7. The method for preparing a soil remediation agent for environmental pollution according to claim 1, characterized in that: In the step S4, the mass ratio of the chitosan-loaded iron-manganese composite oxide to disodium ethylenediaminetetraacetic acid is 10:2-4.

8. A soil remediation agent for environmental pollution, characterized in that: The method is prepared by any one of claims 1 to 7.

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