A soil pollution remediation agent and a remediation method thereof

Abstract

This application discloses a contaminated soil remediation agent and its remediation method, belonging to the field of contaminated soil remediation. The contaminated soil remediation agent comprises a first component and a second component, with a weight ratio of 1.8–2.5:1. The first component is phosphonate-functionalized magnetic mesoporous carbon; the second component contains a protein-polysaccharide complex. This remediation agent, with its phosphonate-functionalized magnetic mesoporous carbon, solves the problem of solid-solid separation. Furthermore, it works synergistically with the protein-polysaccharide complex, achieving a good soil remediation effect.

Description

Technical Field

[0001] This application relates to a contaminated soil remediation agent and a remediation method thereof, belonging to the field of contaminated soil remediation. Background Technology

[0002] With the continuous development and demand for nuclear fuel, nuclear weapons, and nuclear power plants, the mining of uranium mines has been intensified. This has led to the problem of uranium contamination in mine soil. Uranium-contaminated soil is mainly found in tailings ponds and surrounding farmland. Uranium contamination is extremely harmful to the ecological environment. Once it enters the ecosystem, uranium cannot be biodegraded or deposited by common means, and it will continuously produce radioactive pollution in the surrounding area, causing uncontrollable damage to agricultural systems. Uranium can accumulate in organisms, enter the food chain cycle, enrich itself within the food chain, and eventually enter the human body, posing a potential threat to human health.

[0003] In response to the severe situation of soil pollution, a series of remediation technologies have been developed both domestically and internationally. These can be broadly categorized into chemical remediation, physical remediation, and bioremediation. Adsorption, as a representative of chemical remediation, boasts high pollutant removal efficiency, a simple process, and relatively low cost. Adding adsorbents to contaminated soil for chemical cleaning can achieve good results, but it also presents the problem of secondary pollution. After adsorption, the adsorbed material cannot be completely separated from the soil, requiring the addition of more flocculants to achieve separation. Summary of the Invention

[0004] The purpose of this invention is to provide a contaminated soil remediation agent and a remediation method thereof. The remediation agent has phosphonate-functionalized magnetic mesoporous carbon, which can solve the problem of solid-solid separation. It also works synergistically with protein-polysaccharide complexes to achieve good soil remediation results.

[0005] To achieve the above objectives, the present invention provides the following technical solution: According to one aspect of this application, a contaminated soil remediation agent is provided, comprising a first component and a second component, wherein the weight ratio of the first component and the second component is 1.8 to 2.5:1; The first component is phosphonate-functionalized magnetic mesoporous carbon; The second component contains a protein-polysaccharide complex.

[0006] Optionally, the method for preparing the phosphonate-functionalized magnetic mesoporous carbon includes: Magnetic mesoporous carbon was added to an organophosphonic acid solution (50% aqueous solution) and stirred at 100-300 rpm for 1-3 hours. After stirring, the mixture was filtered, washed, and dried (in an oven at 100°C for 8 hours) to obtain phosphonate-functionalized magnetic mesoporous carbon. The weight ratio of the magnetic mesoporous carbon to the organophosphonic acid is 15-17:600-700.

[0007] Optionally, the organophosphonic acid includes one or more of aminotrimethylenephosphonic acid, aminotrimethylphosphonic acid, and ethylenediaminetetramethylphosphonic acid.

[0008] Optionally, the second component is a protein-polysaccharide complex and / or a protein-polysaccharide complex modified with magnetic mesoporous carbon.

[0009] Optionally, the method for preparing the protein-polysaccharide complex modified magnetic mesoporous carbon includes: The protein-polysaccharide complex was added to a sodium hydroxide solution (7%), and then a cross-linking agent was added. The resulting mixture was stirred at 20-30°C (150 r·min-1) for 5-7 h. Then, magnetic mesoporous carbon was added, and stirring was continued for 4-6 h. After washing and drying, the protein-polysaccharide complex modified magnetic mesoporous carbon was obtained. The weight ratio of the protein-polysaccharide complex to the magnetic mesoporous carbon is 1.5 to 3:1. The weight ratio of the protein-polysaccharide complex to the cross-linking agent is 1:0.8 to 0.95.

[0010] Optionally, the crosslinking agent is epichlorohydrin and / or epichlorohydrin.

[0011] Optionally, the protein-polysaccharide complex is prepared by the following method: S1. Wash the seaweed with water, dry it at room temperature, crush it and sieve it to obtain seaweed particles with a particle size of 0.25-0.5 mm; S2. Add chloroform to a Soxhlet extractor to extract seaweed particles for 15-18 hours to remove lipid-pigment complexes and obtain defatted seaweed. S3. The defatted seaweed was extracted sequentially with hydrochloric acid (0.1 mol / L) and sodium carbonate solution (1.5%) to remove water-soluble substances and alginate. After washing with water, residual bound components were removed and the product composition was made uniform. The product was then freeze-dried to obtain a protein-polysaccharide complex.

[0012] Optionally, the seaweed is any one of kelp, Sargassum, and Sargassum fusiforme.

[0013] Optionally, the method for preparing the magnetic mesoporous carbon includes: Mesoporous carbon was added to an ethanol solution containing anhydrous ferric chloride and stirred at 50–70°C until the solvent evaporated. After drying, the resulting powder was moistened with ethylene glycol and placed in a nitrogen atmosphere for heat treatment at 500–600°C for 0.8–1.2 h to obtain magnetic mesoporous carbon. The weight ratio of the mesoporous carbon to anhydrous ferric chloride is 1:1.2 to 2.

[0014] According to another aspect of this application, a method for remediation using the above-described contaminated soil remediation agent is provided, comprising: The first component was thoroughly mixed with the uranium-contaminated soil. Two days later, the second component was added and mixed evenly. During this period, the soil moisture content was maintained at 55-65%. After the soil remediation was completed, deionized water was introduced into the mixture of remediation agent and contaminated soil at a solid-liquid ratio of 1:1.2-1.8. After thorough mixing, the mixture was separated and recycled using the magnetic force applied by a magnet. The amount of the remediation agent added is 13-17% of the contaminated soil. The weight ratio of the first component to the second component is 1.8 to 2.5:1.

[0015] In this application, "room temperature" refers to 20–30°C.

[0016] All percentages in this application are weight percentages.

[0017] The beneficial effects of this application include, but are not limited to: 1. According to the contaminated soil remediation agent and method of this application, the adsorbent is combined with a magnetic core, which not only solves the problem of solid-solid separation but also achieves high adsorption efficiency and is recyclable. Specifically, the coupling effect of phosphonate-functionalized magnetic mesoporous carbon and the protein-polysaccharide complex first utilizes the phosphonate-functionalized magnetic mesoporous carbon to remove a large amount of [UO2]. 2+ Then, it undergoes deep purification via a protein-polysaccharide complex, resulting in high remediation efficiency and excellent effects. The protein-polysaccharide complex, when used directly, can firmly immobilize some uranyl ions. Coating the surface of magnetic mesoporous carbon with the protein-polysaccharide complex retains its high specific surface area and magnetic responsiveness while also endowing it with biocompatibility and additional functional groups, thus better achieving soil remediation and solid-solid separation.

[0018] 2. According to the contaminated soil remediation agent and remediation method of this application, the first component, phosphonate-functionalized magnetic mesoporous carbon, has advantages such as large adsorption capacity, magnetic separation capability, and environmental friendliness. After grafting phosphonate groups onto the magnetic mesoporous carbon, [UO2]... 2+ The ability to form UOP bonds with P=O groups over a wider pH range, and to form shared electron pairs with nitrogen atoms, indicates that uranium adsorption is caused by the synergistic effect of nitrogen and phosphonic acid functional groups, both of which jointly promote [UO2]. 2+ Stable complexes are formed on the surface of phosphonate-functionalized magnetic mesoporous carbon.

[0019] 3. According to the contaminated soil remediation agent and method of this application, the protein-polysaccharide complex has the advantages of being degradable and recyclable, possesses a mesoporous structure with both amorphous and crystalline forms, and is rich in a large number of active functional groups (-OH, -COOH, and -NH2) that can serve as adsorption sites. Hydrogen bonds are formed between the hydroxyl groups and uranyl ions, and the positively charged uranyl ions interact electrostatically with the negatively charged sites on the surface of the protein-polysaccharide complex, [UO2]. 2+ It forms a bidentate complex with the carboxyl group, thus exhibiting significant adsorption activity. Detailed Implementation

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] Unless otherwise specified in the examples, the procedures shall be performed under standard conditions or conditions recommended by the manufacturer. Raw materials or instruments whose manufacturers are not specified are all commercially available products.

[0022] The following methods for preparing mesoporous carbon include: First, prepare solution A: Add 0.22g resorcinol, 0.12g melamine, and 0.32g formaldehyde to 20mL of deionized water and stir well; prepare solution B: Add 0.36g Pluronic F127 (EO) 106 PO 70 EO 106 The granules were added to 40 mL of deionized water and stirred until completely dissolved. Then, solution B was added to solution A, and the mixture was stirred for 2 hours. The mixture was then placed in a hydrothermal reactor and hydrothermally heated at 130 °C for 10 hours. After cooling to room temperature, the mixture was washed to obtain melamine-phenolic resin balls, which were dried at 60 °C, ground, and calcined at 700 °C for 2 hours under anaerobic conditions with a heating rate of 4 °C / min to obtain mesoporous carbon.

[0023] The method for preparing magnetic mesoporous carbon involved in the following embodiments of this application includes: Mesoporous carbon was added to an ethanol solution containing anhydrous ferric chloride (97%) and stirred at 60°C until the solvent evaporated. After drying, the resulting powder was moistened with ethylene glycol and placed in a nitrogen atmosphere for heat treatment at 550°C for 1 hour to obtain magnetic mesoporous carbon. The weight ratio of the mesoporous carbon to anhydrous ferric chloride was 1:1.5.

[0024] Example 1: Preparation of phosphonate-functionalized magnetic mesoporous carbon Methods for preparing phosphonate-functionalized magnetic mesoporous carbon include: Magnetic mesoporous carbon was added to an aminotrimethylene phosphonic acid solution (50% aqueous solution) at a weight ratio of 16:650. The mixture was stirred at 200 rpm for 2 hours. After stirring, the mixture was filtered, washed, and dried (in an oven at 100°C for 8 hours) to obtain phosphonate-functionalized magnetic mesoporous carbon 1#.

[0025] Phosphonate-functionalized magnetic mesoporous carbons 2#-3# and comparative phosphonate-functionalized magnetic mesoporous carbons D1#-D3# were prepared according to the above method. The differences in the preparation methods are shown in Table 1.

[0026] Table 1

[0027] Example 2 Preparation of protein-polysaccharide complex The protein-polysaccharide complex was prepared by the following method: S1. Wash the kelp with water, dry it at room temperature, crush it and sieve it to obtain kelp particles with a particle size of 0.25-0.5 mm; S2. Add chloroform to a Soxhlet extractor to extract kelp particles for 16 hours to obtain defatted kelp. S3. The defatted kelp was extracted sequentially with 0.1 mol / L hydrochloric acid and 1.5% sodium carbonate solution, washed with water, and freeze-dried to obtain protein-polysaccharide complex 4#.

[0028] Protein-polysaccharide complexes 5#-6# and comparative protein-polysaccharide complexes D4#-D6# were prepared according to the above method. The differences in preparation methods are shown in Table 2.

[0029] Table 2

[0030] Example 3: Preparation of Magnetic Mesoporous Carbon Modified by Protein-Polysaccharide Complex Methods for preparing protein-polysaccharide complex-modified magnetic mesoporous carbon include: The protein-polysaccharide complex 4# prepared in Example 2 was added to a sodium hydroxide solution (7%), followed by epichlorohydrin. The weight ratio of the protein-polysaccharide complex to epichlorohydrin was 1:0.9. The resulting mixture was stirred at 25°C (150 r·min). -1After reacting for 6 hours, magnetic mesoporous carbon was added. The weight ratio of the protein-polysaccharide complex to the magnetic mesoporous carbon was 2:1. The mixture was stirred for another 5 hours, washed, and dried to obtain protein-polysaccharide complex modified magnetic mesoporous carbon #7. The protein-polysaccharide complex-modified magnetic mesoporous carbons 8#-9# and the comparative protein-polysaccharide complex-modified magnetic mesoporous carbons D7#-D10# were prepared according to the above method. The differences in the preparation methods are shown in Table 3.

[0031] Table 3

[0032] Example 4: Contaminated Soil Remediation Agent A contaminated soil remediation agent includes a first component and a second component, wherein the weight ratio of the first component and the second component is 2:1; The first component is the 1# phosphonate-functionalized magnetic mesoporous carbon prepared in Example 1; The second component is magnetic mesoporous carbon modified with the 7# protein-polysaccharide complex prepared in Example 3.

[0033] Example 5: Preparation of Contaminated Soil Remediation Agent A contaminated soil remediation agent comprises a first component and a second component, wherein the weight ratio of the first component and the second component is 1.8:1; The first component is the 2# phosphonate-functionalized magnetic mesoporous carbon prepared in Example 1; The second component is the protein-polysaccharide complex #4 prepared in Example 2.

[0034] Example 6 Preparation of Contaminated Soil Remediation Agent A contaminated soil remediation agent includes a first component and a second component, wherein the weight ratio of the first component and the second component is 2.5:1; The first component is the 3# phosphonate-functionalized magnetic mesoporous carbon prepared in Example 1; The second component is magnetic mesoporous carbon modified with the 9# protein-polysaccharide complex prepared in Example 3.

[0035] Example 7: Remediation Method for Contaminated Soil A method for remediating contaminated soil, comprising: The first component was thoroughly mixed with the uranium-contaminated soil. Two days later, the second component was added and mixed evenly. The weight ratio of the first component to the second component was 2:1. During this period, the soil moisture content was kept at 60%. After the soil remediation was completed, deionized water was introduced into the mixture of the remediation agent of Example 4 and the contaminated soil at a solid-liquid ratio of 1:1.5. The amount of remediation agent added in Example 4 was 15% of the contaminated soil. After thorough mixing, the mixture was separated and recovered using the magnetic force applied by a magnet.

[0036] Example 8: Remediation Method for Contaminated Soil A method for remediating contaminated soil, comprising: The first component was thoroughly mixed with the uranium-contaminated soil. Two days later, the second component was added and mixed evenly. The weight ratio of the first component to the second component was 1.8:1. During this period, the soil moisture content was kept at 55%. After the soil remediation was completed, deionized water was introduced into the mixture of the remediation agent of Example 5 and the contaminated soil at a solid-liquid ratio of 1:1.2. The amount of remediation agent added in Example 5 was 13% of the contaminated soil. After thorough mixing, the mixture was separated and recovered using the magnetic force applied by a magnet.

[0037] Example 9: Remediation Method for Contaminated Soil A method for remediating contaminated soil, comprising: The first component was thoroughly mixed with the uranium-contaminated soil. Two days later, the second component was added and mixed evenly. The weight ratio of the first component to the second component was 2.5:1. During this period, the soil moisture content was kept at 65%. After the soil remediation was completed, deionized water was introduced into the mixture of the remediation agent and soil in Example 6 at a solid-liquid ratio of 1:1.8. The amount of remediation agent added in Example 6 was 17% of the contaminated soil. After thorough mixing, the mixture was separated and recovered using the magnetic force applied by a magnet.

[0038] Comparative Example 1 The difference from Example 7 is that the amount of remediation agent added in Example 4 is 5% of the contaminated soil.

[0039] Comparative Example 2 The difference from Example 7 is that the weight ratio of the first component and the second component is 1:1.

[0040] Comparative Example 3 The difference from Example 7 is that the repair agent does not contain a second component and consists only of the first component.

[0041] Comparative Example 4 The difference from Example 7 is that the first component is replaced with magnetic mesoporous carbon that has not been functionalized with phosphonates.

[0042] Comparative Example 5 The difference from Example 7 is that after the repair is completed, no magnetic force is applied for separation and recycling, and natural settling is used for 30 minutes.

[0043] Test case 1. Evaluation of the remediation effect of contaminated soil remediation agents Contaminated soil samples were taken from the vicinity of a uranium tailings dam. The main indicators were: total uranium content of 185.6 mg / kg and pH of 5.8. Based on the Soil Environmental Quality Standard GB 15618-2018, using uranium removal rate and magnetic recovery rate of the remediation agent as evaluation indicators, the effects of the remediation agent and method of this invention on the treated soil were described. The results are shown in Table 4.

[0044] Table 4

[0045] As shown in Table 4, the uranium removal rate of contaminated soil treated with the remediation agents and methods described in Examples 7-9 all reached over 92%, significantly reducing the uranium content in the soil after remediation. Furthermore, the magnetic recovery rate of the remediation agent was over 95%, achieving both efficient remediation and effective separation. Comparative Examples 1-4 indicate that when parameters such as the amount of remediation agent added, the component ratio, and functional modifications deviate from the scope of this application or when key components are omitted, the uranium removal rate decreases significantly. Comparative Example 5 shows that without magnetic separation, the recovery rate is extremely low, failing to solve the solid-solid separation problem.

[0046] 2. Evaluation of the effectiveness of the first component in contaminated soil remediation To further illustrate the effects of the 1#-3# phosphonate-functionalized magnetic mesoporous carbon of this application and the comparative 1#-3# phosphonate-functionalized magnetic mesoporous carbon D1#-D3#, the same remediation method as in Example 7 (only the first component was replaced, the second component was fixed as 7#, the total amount of remediation agent added was 15%, and the weight ratio of the first component to the second component was 2:1) was used to treat the same contaminated soil. The results are shown in Table 5.

[0047] Table 5

[0048] As shown in Table 5, the first components 1#-3# prepared using the parameters within the preferred range of this application exhibit significantly better uranium content and removal rate in the remediated soil compared to the control 1#-2# (parameter deviation), and also have a higher magnetic recovery rate. The poor removal effect of the control 3# (phytic acid modified) demonstrates that the type of organophosphonic acid and the functionalization process are crucial to adsorption performance.

[0049] 3. Evaluation of the effectiveness of the second component in contaminated soil remediation To further illustrate the effects of the second components 4#-9# of this application and the second components D4#-D10# of the comparative 4#-10#, the same remediation method as in Example 7 was used to treat the same contaminated soil (only the second component was replaced, the first component was fixed as 1#, the total amount of remediation agent added was 15%, and the weight ratio of the first component to the second component was 2:1). The results are shown in Table 6.

[0050] Table 6

[0051] As shown in Table 6, the protein-polysaccharide complexes (4#-6#) and their modified magnetic mesoporous carbon (7#-9#) prepared using the method of this application, as the second component, all achieved excellent remediation effects. Among them, the modified samples (7#-9#) exhibited the best remediation efficiency and recovery rate due to the synergistic effect of both biomass functional groups and magnetic nuclei. Comparison of the data for 4#-10# indicates that seaweed extraction process parameters, cross-linking reaction conditions, and raw material selection all significantly affect the performance of the second component; deviations from the scope of protection of this application will lead to a significant decrease in the remediation effect.

[0052] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A contaminated soil remediation agent, characterized in that, It includes a first component and a second component, and the weight ratio of the first component to the second component is 1.8 to 2.5:1; The first component is phosphonate-functionalized magnetic mesoporous carbon; The second component contains a protein-polysaccharide complex.

2. The contaminated soil remediation agent according to claim 1, characterized in that, The method for preparing the phosphonate-functionalized magnetic mesoporous carbon includes: Magnetic mesoporous carbon was added to an organophosphonic acid solution and stirred at 100–300 rpm for 1–3 hours. After stirring, the mixture was filtered, washed, and dried to obtain phosphonate-functionalized magnetic mesoporous carbon. The weight ratio of the magnetic mesoporous carbon to the organophosphonic acid is 15-17:600-700.

3. The contaminated soil remediation agent according to claim 2, characterized in that, The organophosphonic acid includes one or more of aminotrimethylenephosphonic acid, aminotrimethylphosphonic acid, and ethylenediaminetetramethylphosphonic acid.

4. The contaminated soil remediation agent according to claim 1, characterized in that, The second component is a protein-polysaccharide complex and / or a protein-polysaccharide complex modified with magnetic mesoporous carbon.

5. The contaminated soil remediation agent according to claim 4, characterized in that, The method for preparing the protein-polysaccharide complex modified magnetic mesoporous carbon includes: The protein-polysaccharide complex was added to a sodium hydroxide solution, and then a cross-linking agent was added. The resulting mixture was stirred at 20-30°C for 5-7 hours. Then, magnetic mesoporous carbon was added, and stirring was continued for 4-6 hours. After washing and drying, the protein-polysaccharide complex-modified magnetic mesoporous carbon was obtained. The weight ratio of the protein-polysaccharide complex to the magnetic mesoporous carbon is 1.5 to 3:

1. The weight ratio of the protein-polysaccharide complex to the cross-linking agent is 1:0.8 to 0.

95.

6. The contaminated soil remediation agent according to claim 5, characterized in that, The crosslinking agent is epichlorohydrin and / or epichlorohydrin.

7. The contaminated soil remediation agent according to claim 5, characterized in that, The protein-polysaccharide complex was prepared by the following method: S1. Wash the seaweed with water, dry it at room temperature, crush it and sieve it to obtain seaweed particles with a particle size of 0.25-0.5 mm; S2. Add chloroform to a Soxhlet extractor to extract seaweed particles for 15-18 hours to obtain defatted seaweed. S3. The defatted seaweed was extracted sequentially with hydrochloric acid and sodium carbonate solution, washed with water, and freeze-dried to obtain a protein-polysaccharide complex.

8. The contaminated soil remediation agent according to claim 7, characterized in that, The seaweed is any one of kelp, Sargassum, and Sargassum fusiforme.

9. The contaminated soil remediation agent according to any one of claims 1 to 8, characterized in that, The method for preparing the magnetic mesoporous carbon includes: Mesoporous carbon was added to an ethanol solution containing anhydrous ferric chloride and stirred at 50–70°C until the solvent evaporated. After drying, the resulting powder was moistened with ethylene glycol and placed in an inert atmosphere for heat treatment at 500–600°C for 0.8–1.2 h to obtain magnetic mesoporous carbon. The weight ratio of the mesoporous carbon to anhydrous ferric chloride is 1:1.2 to 2.

10. A method for remediating contaminated soil using the soil remediation agent according to claim 9, characterized in that, include: The first component was thoroughly mixed with the uranium-contaminated soil. Two days later, the second component was added and mixed evenly. During this period, the soil moisture content was maintained at 55-65%. After the soil remediation was completed, deionized water was introduced into the mixture of remediation agent and contaminated soil at a solid-liquid ratio of 1:1.2-1.

8. After thorough mixing, the mixture was separated and recycled using the magnetic force applied by a magnet. The amount of the remediation agent added is 13-17% of the contaminated soil. The weight ratio of the first component to the second component is 1.8 to 2.5:1.

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