Contaminated soil remediation method by combining plant-microorganism symbiotic system with non-woven fabric

Abstract

The invention relates to the technical field of soil remediation, aims to solve the problems of low adsorption efficiency and secondary pollution risk in the existing bioremediation technology, and discloses a contaminated soil remediation method by combining a plant-microorganism symbiotic system with a non-woven fabric. The PLA / PBAT non-woven fabric is subjected to surface carboxylation treatment, and introduced carboxyl and ethylenediamine are condensed to form amido; acetylsulfydryl is grafted on humic acid, then carboxyl of the humic acid reacts with amino of the modified non-woven fabric, the modified humic acid is loaded to the non-woven fabric, and sulfydryl capable of reducing quinonyl of As and Cr and selectively chelating Cd and Pb is provided. After the modified non-woven fabric is buried, the root system of the sedum plumbizincicola absorbs the fixed-state heavy metal and the sulfenyl-chelated heavy metal, meanwhile, high-toxicity As and Cr are reduced by microorganisms, and the dual purposes of efficient removal of the heavy metal and ecological safety are achieved.

Description

Technical Field

[0001] This application relates to the technical field of soil remediation, and specifically relates to a method for remediating contaminated soil by using a plant-microbe symbiotic system combined with non-woven fabric. Background Art

[0002] The remediation technologies for heavy metal contaminated soil mainly include physical remediation, chemical remediation, and biological remediation. Physical remediation such as soil replacement method involves excavating contaminated soil and replacing it with uncontaminated soil, but it has high costs and is prone to damaging the soil structure. Chemical remediation changes the form of heavy metals by adding chemical reagents, such as solidification / stabilization technology, to convert heavy metals into forms that are not easily absorbed by plants, but there may be a risk of secondary pollution.

[0003] Phytoremediation in biological remediation uses the absorption and enrichment of plants on heavy metals to reduce the heavy metal content in soil, and has advantages such as environmental friendliness, but has deficiencies such as a long remediation cycle and limited remediation effect on highly contaminated soil. Microbial remediation is to repair soil by means of the adsorption and transformation of heavy metals by microorganisms. The combined technology of plants and microorganisms combines the advantages of both. Chinese Patent Application with Publication No. CN110653251A discloses a method for in-situ remediation of heavy metal contaminated soil by plant-microbe combination. This method uses a microbe-plant symbiotic system to accelerate the transformation and enrichment of heavy metals, enhance the enrichment and degradation of heavy metals by plants, and can adapt to various harsh soil environments to achieve the simultaneous removal of multiple heavy metals such as cadmium, chromium, copper, zinc, and lead. However, it relies on direct enrichment of plants and microorganisms, the adsorption efficiency is limited by biological activity, and the desorption of adsorbed heavy metals is synchronized with plant absorption, affecting the remediation effect. Summary of the Invention

[0004] In view of the deficiencies of the prior art, this application provides a method for remediating contaminated soil by using a plant-microbe symbiotic system combined with non-woven fabric. The PLA / PBAT non-woven fabric is surface carboxylated, and the introduced carboxyl groups are condensed with ethylenediamine to form amino groups; acetylthiol groups are grafted onto humic acid, and then through the reaction of the carboxyl groups of humic acid with the amino groups of the modified non-woven fabric, the modified humic acid is loaded onto the non-woven fabric, providing quinone groups capable of reducing As and Cr and thiol groups capable of selectively chelating Cd and Pb. After the modified non-woven fabric is buried, the roots of Sedum plumbizincicola penetrate the non-woven fabric to absorb fixed heavy metals, and at the same time, microorganisms reduce highly toxic As and Cr, achieving the dual goals of efficient heavy metal removal and ecological safety.

[0005] To achieve the above object, this application adopts the following technical solutions:

[0006] The present invention provides a method for remediating contaminated soil by using a plant-microbe symbiotic system combined with non-woven fabric, comprising the following steps:

[0007] S1. Surface carboxylation treatment, amidation treatment, and modified humic acid loading are successively performed on the PLA / PBAT non-woven fabric to obtain a modified non-woven fabric;

[0008] S2. The heavy metal contaminated soil is plowed, and the modified non-woven fabric is buried. After pre-inoculating Shewanella oneidensis MR-1 at the roots of Sedum plumbizincicola, it is planted in the heavy metal contaminated soil where the modified non-woven fabric is buried to form a treatment area to be repaired;

[0009] S3. The soil humidity is maintained by periodic irrigation, and after harvesting, the harvested Sedum plumbizincicola is subjected to harmless incineration treatment to complete soil remediation.

[0010] Beneficial technical effects:

[0011] In this application, carboxylation, amidation, and modified humic acid loading are carried out on the surface of the non-woven fabric. First, the PLA / PBAT non-woven fabric is subjected to surface carboxylation treatment to introduce carboxyl groups, and the carboxyl groups condense with ethylenediamine to form surface amino groups; the modified humic acid undergoes an esterification reaction between S-acetylmercapto succinic anhydride and the surface hydroxyl groups of humic acid, introducing acetylmercapto groups while retaining the original quinone groups of humic acid; among them, the quinone groups are conjugated groups and can serve as electron transfer mediators to promote Shewanella oneidensis MR-1 to reduce highly toxic As(V) and Cr(VI) to low-toxic valence states, reducing their mobility, while the mercapto groups gradually hydrolyze the acetylmercapto groups through esterases secreted by soil microorganisms, and the deacetylated sulfur groups are released, and the sulfur groups can chelate Cd 2+ and Pb 2 + , and the long-term removal effect is maintained through slow release. After the non-woven fabric loaded with modified humic acid is buried, the planted Sedum plumbizincicola, as a hyperaccumulator, the organic acids secreted by the roots accelerate the degradation of the non-woven fabric and reduce the mobility of heavy metals; at the same time, the organic acids desorb the sulfur groups from the chelated heavy metals, and then the heavy metals released are absorbed by the roots of Sedum plumbizincicola. Through the continuous processes of non-woven fabric adsorption, microbial reduction, plant enrichment, and non-woven fabric degradation, the efficient remediation of heavy metal contaminated soil is synergistically achieved. Description of the Drawings

[0012] Figure 1 It is a schematic diagram of a method for remediating contaminated soil using a plant-microbial symbiotic system combined with non-woven fabric provided by the present invention. Detailed Embodiments

[0013] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clear and understandable, the following will further elaborate on this application in combination with embodiments. However, this should not be construed as limiting the scope of this application to the following examples. Without departing from the above-mentioned method concept of this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of this application.

[0014] In this application, the terms used are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0015] In this application, the singular forms of "is", "or", "a", "any one" and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0016] In addition, if the terms "first" and "second" appear, they are only for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0017] Shewanella oneidensis MR-1 used in the present invention was purchased from Shanghai Jiachu Bioengineering Co., Ltd., and the product number is SHMCC(SHBCC)D25217.

[0018] The present invention provides a method for repairing contaminated soil by using a plant-microbial symbiotic system combined with non-woven fabric, which includes the following steps:

[0019] S1. The PLA / PBAT non-woven fabric is sequentially subjected to surface carboxylation treatment, amidation treatment and modified humic acid loading to obtain a modified non-woven fabric;

[0020] S2. The heavy metal contaminated soil is plowed, the modified non-woven fabric is buried, and Shewanella oneidensis MR-1 is pre-inoculated at the roots of Sedum plumbizincicola and then planted in the heavy metal contaminated soil where the modified non-woven fabric is buried to form a repair area to be repaired;

[0021] S3. The soil humidity is maintained by periodic irrigation, harvested, and the harvested Sedum plumbizincicola is subjected to harmless incineration treatment to complete the soil repair.

[0022] In a feasible implementation case, the mass ratio of PLA to PBAT in the PLA / PBAT non-woven fabric is 7:3; the molecular weight of PLA is 80,000-120,000 g / mol, and the molecular weight of PBAT is 60,000-100,000 g / mol.

[0023] Both PLA and PBAT have biodegradable properties. In natural environments, such as soil, compost, etc., they can be decomposed by microorganisms into carbon dioxide and water, reducing environmental pollution and having advantages in the environmental protection field.

[0024] In a feasible implementation scenario, the surface carboxylation treatment includes: treating the PLA / PBAT non-woven fabric in an alkaline alcohol solution. The alkaline alcohol solution includes sodium hydroxide with a concentration of 0.05 - 0.1 mol / L and a mixed solvent of ethanol / water with a volume ratio of (1 - 3):1. After reacting for 1 - 2 h, it is washed with deionized water, then immersed in a 0.1 - 0.5 mol / L hydrochloric acid solution and reacted for 0.5 - 1 h. After washing and drying, the surface carboxylated non-woven fabric is obtained. The reaction formula is as follows:

[0025]

[0026] Where m < n.

[0027] In a feasible implementation scenario, the amidation treatment includes: immersing the non-woven fabric that has undergone the surface carboxylation treatment in a tetrahydrofuran solution containing 3.0 - 3.4 mol / L of ethylenediamine and 0.6 - 1.0 mol / L of condensing agent HATU, and reacting under an inert atmosphere. The reaction equation is as follows:

[0028]

[0029] HATU catalyzes the condensation reaction of the carboxyl group of the surface carboxylated non-woven fabric with ethylenediamine to generate surface-grafted primary amino groups.

[0030] In a feasible implementation scenario, the preparation method of the modified humic acid includes: dissolving S-acetylmercapto succinic anhydride and humic acid in tetrahydrofuran, adding 4-dimethylaminopyridine, and reacting to obtain the modified humic acid. The molar ratio of S-acetylmercapto succinic anhydride, humic acid, and 4-dimethylaminopyridine is 1:(4 - 5):0.01, and the concentration of S-acetylmercapto succinic anhydride is 0.1 mol / L. The reaction equation is as follows:

[0031]

[0032] R-OH is humic acid.

[0033] Functional groups such as carboxyl, hydroxyl, carbonyl, quinone, and methoxy are attached to the humic acid macromolecule. The anhydride group of S-acetylmercaptosuccinic anhydride undergoes an esterification reaction with the hydroxyl group of humic acid, and after ring-opening, a carboxyl group is formed to obtain modified humic acid, retaining the acetylmercapto group of S-acetylmercaptosuccinic anhydride and the quinone group (C=O) of humic acid; the quinone group, as an electron conjugate group, can mediate the electron transfer of Shewanella oneidensis MR-1, reducing As(V) and Cr(VI) to low-toxic forms. The esterase secreted by microorganisms in the soil can gradually hydrolyze the acetyl group for deacetylation, slowly releasing the mercapto group and increasing the chelating ability for Cd 2+ and Pb 2+ in the soil. The slowly released sulfhydryl group enables the non-woven fabric to maintain a long-term effective heavy metal adsorption effect before the degradation is completed.

[0034] In a feasible implementation scenario, the modification humic acid loading includes: immersing the non-woven fabric after amidation treatment in a loading solution to obtain the modified non-woven fabric; the loading solution is a phosphate buffer solution containing modified humic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and N-hydroxysuccinimide, and the molar ratio of the modified humic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC), and N-hydroxysuccinimide (NHS) is (0.8 - 1.2):2:1; the concentration of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is 0.3 mol / L, and the reaction equation is as follows:

[0035]

[0036] The carboxyl group on the surface of the modified humic acid and the amino group on the surface of the non-woven fabric form an amide bond through the catalysis of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide, loading the modified humic acid onto the non-woven fabric.

[0037] In a feasible implementation scenario, the burial depth of the non-woven fabric is 10 - 20 cm.

[0038] In a feasible implementation scenario, the planting density of Sedum plumbizincicola is 15 - 25 plants / m 2 .

[0039] Sedum plumbizincicola is a hyperaccumulator that can absorb and accumulate heavy metals through its roots. During its growth, its roots secrete some organic substances, such as low-molecular-weight organic acids, sugars, proteins, etc. These secretions can react with heavy metals in the soil, such as complexation and chelation reactions, thereby reducing the mobility of heavy metals and reducing their potential harm to the surrounding environment and other organisms. The organic acids secreted by the roots of Sedum plumbizincicola can also accelerate the degradation of non-woven fabrics; at the same time, the organic acids desorb the sulfhydryl groups from the chelated heavy metals, and then the heavy metals released and absorbed by the roots of Sedum plumbizincicola cooperate with the non-woven fabrics to remove heavy metals.

[0040] In a feasible implementation case, the inoculation concentration of Shewanella oneidensis MR-1 ≥ 1×10 8 CFU / g.

[0041] Shewanella oneidensis MR-1 accelerates the degradation of non-woven fabrics by secreting esterase or lipase, and the small-molecule organic substances such as lactic acid released by the degradation provide a carbon source for microbial metabolism; the extracellular polymers produced by microbial metabolism combine with the modified humic acid loaded on the non-woven fabric, and its rich functional groups (such as sulfhydryl groups and carboxyl groups) enhance the chelation ability of Cd 2+ and Pb 2+ through coordination bonds and hydrophobic interactions; at the same time, Shewanella oneidensis MR-1 can use quinone groups for the electron transport chain to reduce the highly toxic As(V) and Cr(VI) to the low-toxic forms of As(III) and Cr(III); the redox gradient formed by quinone groups can also attract microorganisms to enrich on the surface, and significantly improve the reduction efficiency of As and Cr through the spatial aggregation effect; the engineered bacteria also secrete 2,6-pyridinedicarboxylic acid to promote the penetration of plant roots through the non-woven fabric and enhance the absorption of fixed heavy metals.

[0042] In a feasible implementation case, the periodic irrigation includes: irrigating once a week when growing for 0 - 3 months, and irrigating once every two weeks when growing for 3 - 6 months; the soil humidity is maintained between 30% and 40%.

[0043] In 0 - 3 months, the surface layer of the non-woven fabric is initially degraded, deacetylation proceeds slowly, adsorbing heavy metals and colonizing microorganisms; in 3 - 6 months: more than half of the degradation process, the sulfhydryl groups are fully activated, and the roots penetrate the non-woven fabric to directly absorb fixed heavy metals; the non-woven fabric is completely degraded.

[0044] The following will specifically describe a method for remediating contaminated soil by using a plant-microbial symbiotic system combined with non-woven fabrics provided by the present application in combination with different embodiments.

[0045] Example 1

[0046] AsFigure 1 As shown in Figure 1 , a method for repairing contaminated soil by using a plant-microorganism symbiotic system combined with non-woven fabric includes the following steps:

[0047] 1. Prepare a PLA / PBAT non-woven fabric with a mass ratio of PLA to PBAT of 7:3, where the molecular weight of PLA is 80,000 g / mol and the molecular weight of PBAT is 60,000 g / mol. Immerse the PLA / PBAT non-woven fabric in an ethanol / water solution of 0.05 mol / L sodium hydroxide with an ethanol / water volume ratio of 3:1, react at room temperature for 2 h, wash with deionized water, then immerse in a 0.1 mol / L hydrochloric acid solution, react for 1 h, and wash and dry with deionized water to obtain a surface carboxylated non-woven fabric;

[0048] 2. Immerse the surface carboxylated non-woven fabric in a DMF solution containing 3.0 mol / L ethylenediamine and 0.6 mol / L condensing agent HATU, react at 65 °C for 11 h under N2 protection, wash alternately with DMF and ethanol, and dry to obtain an amidated non-woven fabric;

[0049] 3. Dissolve S-acetylmercaptosuccinic anhydride, humic acid with a molecular weight of <500 Da, and 4-dimethylaminopyridine in tetrahydrofuran at a molar ratio of 1:4:0.01. The concentration of S-acetylmercaptosuccinic anhydride is 0.1 mol / L, stir and react at 65 °C for 6 h to obtain modified humic acid;

[0050] 4. Prepare a phosphate buffer solution with a molar ratio of potassium dihydrogen phosphate to disodium hydrogen phosphate of 1:50 and a total molar concentration of 0.1 mol / L. Add modified humic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and N-hydroxysuccinimide at a molar ratio of 0.8:2:1. The concentration of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is 0.3 mol / L, adjust the pH to 5.8 to obtain a loading solution; immerse the amidated non-woven fabric in the loading solution, react at 50 °C for 7 h, and dry to obtain a modified non-woven fabric;

[0051] 5. Plow the heavy metal-contaminated soil to a depth of 40 cm, bury the modified non-woven fabric 30 cm below the surface of the contaminated soil, irrigate the roots of Sedum plumbizincicola with a Shewanella oneidensis MR-1 bacterial solution with a concentration of 5×10 7 CFU / g, 50 mL of the bacterial solution per plant; then plant the Sedum plumbizincicola after root irrigation in the heavy metal-contaminated soil with the modified non-woven fabric evenly at a density of 15 plants / m 2 ;

[0052] 6. Irrigate once a week for 0 - 3 months after planting to keep the soil humidity at 30%, irrigate once every 2 weeks for 3 - 6 months, and harvest and incinerate the plants after 6 months to complete soil remediation.

[0053] Example 2

[0054] As Figure 1 shown, a method for remediating contaminated soil by using a plant-microorganism symbiotic system combined with non-woven fabric includes the following steps:

[0055] 1. Prepare a PLA / PBAT non-woven fabric with a mass ratio of PLA to PBAT of 7:3, where the molecular weight of PLA is 100,000 g / mol and the molecular weight of PBAT is 80,000 g / mol. Immerse the PLA / PBAT non-woven fabric in an ethanol / water solution of 0.08 mol / L sodium hydroxide with an ethanol / water volume ratio of 2:1, react at room temperature for 1.5 h, wash with deionized water, then immerse in a 0.3 mol / L hydrochloric acid solution, react for 0.5 h, and wash and dry with deionized water to obtain a surface carboxylated non-woven fabric;

[0056] 2. Immerse the surface carboxylated non-woven fabric in a DMF solution containing 3.2 mol / L ethylenediamine and 0.8 mol / L condensing agent HATU, react at 65 °C for 12 h under N2 protection, wash alternately with DMF and ethanol, and dry to obtain an amidated non-woven fabric;

[0057] 3. Dissolve S-acetylmercaptosuccinic anhydride, humic acid with a molecular weight <500 Da, and 4-dimethylaminopyridine in tetrahydrofuran at a molar ratio of 1:4.5:0.01. The concentration of S-acetylmercaptosuccinic anhydride is 0.1 mol / L, stir and react at 65 °C for 8 h to obtain modified humic acid;

[0058] 4. Prepare a phosphate buffer solution with a molar ratio of potassium dihydrogen phosphate to disodium hydrogen phosphate of 1:50 and a total molar concentration of 0.1 mol / L. Add modified humic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and N-hydroxysuccinimide at a molar ratio of 1:2:1. The concentration of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is 0.3 mol / L, adjust the pH to 5.6 to obtain a loading solution; immerse the amidated non-woven fabric in the loading solution, react at 45 °C for 8 h, and dry to obtain a modified non-woven fabric;

[0059] 5. Plow the heavy metal contaminated soil to a depth of 30 cm, bury the modified non-woven fabric 20 cm below the surface of the contaminated soil, irrigate the roots of Sedum plumbizincicola with a Shewanella oneidensis MR-1 bacterial solution with a concentration of 8×10 7 CFU / g, 50 mL of the bacterial solution per plant; then plant the Sedum plumbizincicola with irrigated roots in the heavy metal contaminated soil buried with the modified non-woven fabric at a density of 20 plants / m 2 evenly;

[0060] 6. Irrigate once a week for 0 - 3 months after planting, keep the soil humidity at 35%, irrigate once every two weeks for 3 - 6 months, harvest the plants and incinerate them after 6 months to complete soil remediation.

[0061] Example 3

[0062] As Figure 1 shown, a contaminated soil remediation method using a plant - microorganism symbiotic system combined with non - woven fabric includes the following steps:

[0063] 1. Prepare a PLA / PBAT non - woven fabric with a mass ratio of PLA to PBAT of 7:3, the molecular weight of PLA is 120000 g / mol, and the molecular weight of PBAT is 100000 g / mol. Immerse the PLA / PBAT non - woven fabric in an ethanol / water solution of 0.1 mol / L sodium hydroxide with an ethanol / water volume ratio of 1:1, react at room temperature for 1.5 h, wash with deionized water, then immerse it in a 0.5 mol / L hydrochloric acid solution, react for 0.5 h, and wash and dry with deionized water to obtain a surface - carboxylated non - woven fabric;

[0064] 2. Immerse the surface - carboxylated non - woven fabric in a DMF solution containing 3.4 mol / L ethylenediamine and 1.0 mol / L condensing agent HATU, react at 60 °C for 14 h under N2 protection, wash alternately with DMF and ethanol, and dry to obtain an amidated non - woven fabric;

[0065] 3. Dissolve S - acetylmercaptosuccinic anhydride, humic acid with a molecular weight < 500 Da, and 4 - dimethylaminopyridine in tetrahydrofuran in a molar ratio of 1:5:0.01, the concentration of S - acetylmercaptosuccinic anhydride is 0.1 mol / L, stir and react at 60 °C for 10 h to obtain modified humic acid;

[0066] 4. Prepare a phosphate buffer solution with a molar ratio of potassium dihydrogen phosphate to disodium hydrogen phosphate of 1:50 and a total molar concentration of 0.1 mol / L. Add modified humic acid, 1 - (3 - dimethylaminopropyl) - 3 - ethylcarbodiimide, and N - hydroxysuccinimide in a molar ratio of 1.0:2:1, the concentration of 1 - (3 - dimethylaminopropyl) - 3 - ethylcarbodiimide is 0.3 mol / L, adjust the pH to 5.8 to obtain a loading solution; immerse the amidated non - woven fabric in the loading solution, react at 40 °C for 8 h, and dry to obtain a modified non - woven fabric;

[0067] 5. Plow the heavy - metal - contaminated soil to a depth of 20 cm, bury the modified non - woven fabric 10 cm below the surface of the contaminated soil, irrigate Sedum plumbizincicola with a Shewanella oneidensis MR - 1 bacterial solution with a concentration of 1×10 8 CFU / g at 50 mL per plant; then plant the irrigated Sedum plumbizincicola in the heavy - metal - contaminated soil with the buried modified non - woven fabric at a density of 25 plants / m2 Uniform planting according to density;

[0068] Irrigate once a week for 0 - 3 months after planting, keep the soil humidity at 40%, irrigate once every two weeks for 3 - 6 months, harvest the plants and incinerate them after 6 months to complete soil remediation.

[0069] Comparative Example 1

[0070] A method for remediating contaminated soil by using a plant - microorganism symbiotic system combined with non - woven fabric, the steps and parameters are the same as those in Example 2, except that unmodified PLA / PBAT non - woven fabric is used.

[0071] Comparative Example 2

[0072] A method for remediating contaminated soil by using a plant - microorganism symbiotic system combined with non - woven fabric, the steps and parameters are the same as those in Example 2, except that amidation treatment is not carried out.

[0073] Comparative Example 3

[0074] A method for remediating contaminated soil by using a plant - microorganism symbiotic system combined with non - woven fabric, the steps and parameters are the same as those in Example 2, except that modification with humic acid is not carried out.

[0075] Comparative Example 4

[0076] A method for remediating contaminated soil by using a plant - microorganism symbiotic system combined with non - woven fabric, the steps and parameters are the same as those in Example 2, except that modified humic acid is not loaded.

[0077] Heavy metal removal rate test:

[0078] Prepare a mixed solution containing Cd(NO3)2, Cr(NO3)6, As(NO3)5 and Pb(NO3)2, with the concentrations of Cd, Cr, As and Pb being 500 mg / L, 1000 mg / L, 500 mg / L and 2000 mg / L respectively. Mix this mixed solution with clean soil at a mass ratio of 1:1, stir manually and then place it in a ventilated place to age naturally for 2 months to obtain self - made heavy metal - contaminated soil. Use the method for remediating contaminated soil by using a plant - microorganism symbiotic system combined with non - woven fabric provided by the present invention to test the self - made heavy metal - contaminated soil, and detect the heavy metal removal rates of the test soils of Examples 1 - 3 and Comparative Examples 1 - 4 after harvesting the ore - associated plants. The test results are shown in Table 1.

[0079] Table 1 Test results of soil heavy metal removal rate

[0080]

[0081] As can be seen from Table 1, in Example 1 - Example 3 of the present invention, the Cd removal rate from heavy metal - contaminated soil is ≥91%; the Cr removal rate is ≥86%; the As removal rate is ≥89%; the Pb removal rate is ≥89%, and it can effectively achieve the effect of repairing heavy metal - contaminated soil.

[0082] In Comparative Example 1, unmodified PLA / PBAT non - woven fabric was used, and the heavy metal removal rate was significantly lower than that of the examples. The Cd removal rate was only 25%, and the As removal rate was 20%. The unmodified non - woven fabric lacks carboxylation, amidation, and humic acid loading functions, and cannot fix or reduce heavy metals through chemical adsorption or electron transfer. It only relies on natural plant absorption and microbial metabolism, with extremely low adsorption efficiency, and it causes the inhibition of plant growth by heavy metal toxicity. In addition, the unmodified one cannot effectively load humic acid, resulting in limited reduction by Shewanella oneidensis MR - 1, and the heavy metal repair and removal effect is weak.

[0083] In Comparative Example 2, amidation treatment was not carried out, and carboxylation and modified humic acid loading were directly carried out. Its Cd and As removal rates were 58% and 53% respectively, which were significantly lower than those of the examples. Amidation treatment generates amino groups by catalyzing the reaction of carboxyl groups with ethylenediamine by HATU. The lack of amidation leads to insufficient amino group density on the surface of the non - woven fabric. Humic acid is only loaded by physical adsorption and is easily detached from the surface of the non - woven fabric, and cannot effectively contact the roots of Sedum plumbizincicola. After chelation, there is no desorption process, and the heavy metal removal effect is limited.

[0084] In Comparative Example 3, ordinary humic acid was used to replace modified humic acid, and its As and Cr removal rates were only 48% and 62% respectively, far lower than those of the examples. Unmodified humic acid lacks the slow - release function of mercapto groups grafted with S - acetylmercaptosuccinic anhydride and has insufficient long - term chelation function. At the same time, the quinone group content of ordinary humic acid is low, and it cannot effectively carry out electron transfer, resulting in a reduction in the efficiency of reducing As(V) and Cr(VI) to low - toxicity forms. In addition, unmodified humic acid cannot gradually release mercapto groups through esterase hydrolysis, resulting in a lag in the chelation of Cd 2+ and Pb 2+ and a rebound in the concentration of free heavy metals in the soil, and a decrease in the stability of the repair.

[0085] In Comparative Example 4, modified humic acid was not loaded on the non - woven fabric, and its As and Cr removal rates were the lowest (35%, 40%). The lack of loaded humic acid results in the lack of quinone groups (C = O) on the surface of the non - woven fabric, which cannot provide an electron transfer medium for Shewanella oneidensis MR - 1, and the reduction reactions of As(V) and Cr(VI) are inhibited. At the same time, the selective chelation function of mercapto groups is missing, resulting in Cd 2+ and Pb 2+The adsorption efficiency drops significantly (Cd removal rate is 45%). The remediation system relies on natural plant enrichment, and the efficiency is much lower than that of the embodiment.

[0086] The above results show and describe the basic principles, main features and advantages of the present application.

[0087] Those skilled in the art should understand that the present application is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present application. Without departing from the spirit and scope of the present application, the present application will have various changes and improvements, and these changes and improvements fall within the scope of the present application claimed. The scope of protection claimed by the present application is defined by the equivalents of the appended claims.

Claims

1. A method for remediating contaminated soil by using a plant-microorganism symbiotic system combined with non-woven fabric, characterized in that, It includes the following steps: S1. Subject the PLA / PBAT non-woven fabric to surface carboxylation treatment, amidation treatment, and modified humic acid loading in sequence to obtain a modified non-woven fabric; S2. Plow the heavy metal-contaminated soil, bury the modified non-woven fabric, irrigate the roots of Sedum plumbizincicola with the bacterial solution of Shewanella oneidensis MR-1, and plant it in the heavy metal-contaminated soil where the modified non-woven fabric is buried to form a zone to be repaired; S3. Maintain the soil humidity through periodic irrigation, harvest, and perform harmless incineration treatment on the harvested Sedum plumbizincicola to complete soil remediation.

2. The method for remediating contaminated soil by using a plant-microorganism symbiotic system combined with non-woven fabric according to claim 1, characterized in that, In the PLA / PBAT non-woven fabric, the mass ratio of PLA to PBAT is 7:3; the molecular weight of PLA is 80,000 - 120,000 g / mol, and the molecular weight of PBAT is 60,000 - 100,000 g / mol.

3. A method for remediating contaminated soil by using a plant-microorganism symbiotic system combined with non-woven fabric according to claim 1, characterized in that, The surface carboxylation treatment includes: treating the PLA / PBAT non-woven fabric in an alkaline alcohol solution, where the alkaline alcohol solution includes sodium hydroxide with a concentration of 0.05 - 0.1 mol / L and a mixed solvent of ethanol / water with a volume ratio of (1 - 3):

1. After reacting for 1 - 2 h, wash with deionized water, then immerse it in a 0.1 - 0.5 mol / L hydrochloric acid solution, react for 0.5 - 1 h, and wash and dry.

4. A contaminated soil remediation method using a plant-microbial symbiotic system combined with non-woven fabric according to claim 1, characterized in that The amidation treatment includes: immersing the non-woven fabric after the surface carboxylation treatment in a DMF solution containing 3.0 - 3.4 mol / L of ethylenediamine and 0.6 - 1.0 mol / L of condensing agent HATU, and reacting at 60 - 65 °C in a nitrogen atmosphere for 11 - 14 h.

5. A contaminated soil remediation method using a plant-microbial symbiotic system combined with non-woven fabric according to claim 1, characterized in that, The preparation method of the modified humic acid includes: dissolving S-acetylmercaptosuccinic anhydride and humic acid in tetrahydrofuran, adding 4-dimethylaminopyridine, and reacting at 60 - 65 °C for 6 - 10 h to obtain the modified humic acid; the molar ratio of S-acetylmercaptosuccinic anhydride, humic acid, and 4-dimethylaminopyridine is 1:(4 - 5):0.01, and the concentration of S-acetylmercaptosuccinic anhydride is 0.1 mol / L.

6. The method for remediating contaminated soil by using a plant-microorganism symbiotic system combined with non-woven fabric according to claim 1, wherein, The modified humic acid loading includes: immersing the non-woven fabric after the amidation treatment in a loading solution with a pH of 5.5 - 5.8, and reacting at 40 - 50 °C for 7 - 10 h to obtain the modified non-woven fabric; the loading solution is a phosphate buffer solution containing modified humic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and N-hydroxysuccinimide, and the molar ratio of modified humic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and N-hydroxysuccinimide is (0.8 - 1.2):2:1; the concentration of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is 0.3 mol / L.

7. A method for remediating contaminated soil by using a plant-microorganism symbiotic system combined with non-woven fabric according to claim 1, wherein, The plowing depth is 20 - 40 cm; the burial depth of the non-woven fabric is 10 - 30 cm.

8. A method for remediating contaminated soil by using a plant-microorganism symbiotic system combined with non-woven fabric according to claim 1, characterized in that, The planting density of Sedum plumbizincicola is 15 - 25 plants / m 2 .

9. A method for remediating contaminated soil by using a plant-microorganism symbiotic system combined with non-woven fabric according to claim 1, characterized in that The bacterial solution concentration of Shewanella oneidensis MR-1 is 5×10 7 ~1×10 8 CFU / g.

10. A method for remediating contaminated soil by using a plant-microbial symbiotic system combined with non-woven fabric according to claim 1, characterized in that, The periodic irrigation includes: irrigating once a week when planting for 0 - 3 months, and irrigating once every two weeks when planting for 3 - 6 months; the soil humidity is maintained at 30% - 40%.

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