A method for efficiently removing heavy metals in soil

Abstract

The application discloses a kind of efficient removal methods of heavy metal in soil, including sample collection, sample pretreatment, preparation supramolecular cage, heavy metal capture, material screening and the like steps, the mercury, lead, cadmium and the like heavy metal in soil are captured by supramolecular cage, and the magnetic carrier after capturing heavy metal is removed by magnetic separation mode, process flow cycle is shorter, heavy metal removal efficiency is higher, there is no nanoparticle residual risk, and avoid the long-term leaching risk of apatite, bentonite and the like curing agent in traditional stabilization technology, environmental friendliness is stronger, especially suitable for industrial site, mining area and the like compound pollution scene, provide the innovative technical path of generalization for soil remediation.

Description

Technical Field

[0001] This invention relates to the field of soil heavy metal treatment technology, and in particular to a highly efficient method for removing heavy metals from soil. Background Technology

[0002] Heavy metals in soil is a complex environmental issue involving both natural processes and human activities. Natural processes include bedrock weathering, volcanic eruptions, and sedimentary cycles, while human activities include industrial emissions, agricultural inputs, mining, and electronic waste.

[0003] Heavy metals, especially mercury, lead, and cadmium, are difficult to degrade naturally after entering the soil. Long-term accumulation can lead to a decline in soil fertility, affect the activity of soil microorganisms, and have an impact on the ecological environment, plant growth, and soil animals. Furthermore, through the bioaccumulation effect in the food chain, they can also pose a potential threat to human health. Therefore, soil heavy metal decomposition is an issue that the agricultural sector must address.

[0004] Currently, the main methods for mitigating heavy metals in soil include: physical measures (soil replacement, electrokinetic remediation), chemical passivation (biochar modification, phosphate degradation), bioremediation (hyperaccumulating plants, microbial enhancement), and combined remediation (plant-mycorrhizal therapy, chemical-biological combination). With advancements in technology, cutting-edge technologies such as nanomaterial remediation and gene editing have emerged in recent years. However, all of these technologies have some drawbacks. For example, physical measures have long cycles and low efficiency, chemical passivation carries a high risk of drug residue, and nanoremediation also carries the risk of nanoparticle residue.

[0005] This application presents a highly efficient method for removing heavy metals such as mercury, lead, and cadmium from soil, based on supramolecular cage technology. A supramolecular cage is a molecular aggregate formed by non-covalent interactions (such as hydrogen bonds, electrostatic interactions, hydrophobic interactions, and van der Waals forces) between two or more molecules. Supramolecular cages possess a unique cavity structure that can dynamically change to enhance their affinity for specific molecules, exhibiting superior recognition and encapsulation capabilities for specific guest molecules. Summary of the Invention

[0006] To achieve the above objectives, this invention discloses a highly efficient method for removing heavy metals from soil, comprising the following steps:

[0007] S1 - Sample Collection: Take an appropriate amount of soil and sieve it to filter out large stones, soil clods and debris, and keep soil samples that meet the size requirements.

[0008] S2 - Sample Pretreatment: Place the collected soil sample in the test tray, add appropriate amounts of citric acid and tartaric acid to activate the heavy metal ions in the soil, and adjust the moisture content to 10-15%;

[0009] S3-Preparation of supramolecular cages: Cucurbita[8]urea is used as the main structure, and thiols, phosphate esters, carboxylic acid / amino high affinity groups are grafted onto its cage wall and covalently connected with Fe3O4@SiO2 to form a supramolecular cage complex;

[0010] S4 - Heavy Metal Capture: Add an appropriate amount of supramolecular cage complex to the test tray and let it stand for 4-6 hours to allow the supramolecular cage complex to react with the sample, thereby capturing Hg in the soil sample. 2+ Pb 2+ Cd 2+ Ions are captured;

[0011] S5 - Material Screening: After the reaction is completed, the material is placed in a vacuum drying oven for drying. After drying, a permanent magnet drum is used to recover the carrier after capturing heavy metal ions. The remaining material is the soil after heavy metal removal.

[0012] Furthermore, in step S1, the mesh size of the sieve used for sieving is 5-8 mm.

[0013] Furthermore, in step S2, the molar concentration of citric acid is 0.1-0.2M, the pH value is 3.5-3.8, and the concentration of tartaric acid is 45-50%.

[0014] Furthermore, in step S2, the ratio of citric acid to tartaric acid is 2:1.

[0015] Furthermore, the specific steps for preparing the supramolecular cage in step S3 are as follows:

[0016] S31: Cucurbita[8] ureathiolation modification

[0017] Cucurbit[8]urea and 3-mercaptopropyltrimethoxysilane were refluxed in DMF at a temperature of 150-160℃ for 2-3 hours, and each cucurbit[8]urea was grafted with 8 -SH groups.

[0018] S32: Introduction of phosphate ester groups

[0019] Thiolized cucurbit[8]urea was coupled with trichloroethyl phosphate under EDC / NHS catalysis, introducing 4 -PO4 groups into each cucurbit[8]urea. 3- Group;

[0020] S33: Carboxylic acid / amino bifunctionalization

[0021] The remaining hydroxyl groups of thiolated cucurbit[8]urea were reacted with ethylenediaminetetraacetic acid anhydride to form an EDTA-cucurbit[8]urea complex;

[0022] S34: Magnetic Composite Assembly

[0023] Thiolized cucurbit[8]urea was covalently bonded to the Fe3O4@SiO2 surface by aminosilane to form a cucurbit[8]urea-SH / PO4 / EDTA@Fe3O4 composite.

[0024] Furthermore, in step S4, the -SH group is applied to Hg. 2+ Captured via Hg-S bond binding, -PO4 3- Groups utilizing Pb 2+ With -PO4 3- The strong coordination ability of Pb 2+ Capture occurs through the -COOH and -NH2 groups on Cd. 2+ The trapping process is carried out to form a stable Cd-O / N pentagonal structure.

[0025] Furthermore, in step S5, the drying temperature of the vacuum drying oven is 60-65℃, and the drying time is 0.5-1h.

[0026] Furthermore, in step S5, the rotational speed of the permanent magnet drum is set to 40-50 r / min, and the material is screened 2-3 times.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] This invention captures heavy metals such as mercury, lead, and cadmium in soil using supramolecular cages and removes the magnetic carriers after capturing the heavy metals using magnetic separation. The process has a short cycle time, high heavy metal removal efficiency, no risk of nanoparticle residue, and avoids the long-term leaching risk of solidifying agents such as apatite and bentonite in traditional stabilization technologies. It is highly environmentally friendly and particularly suitable for complex pollution scenarios such as industrial sites and mining areas, providing a scalable and innovative technical path for soil remediation. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0030] Example 1:

[0031] The efficient method for removing heavy metals from soil in this embodiment includes the following steps:

[0032] S1 - Sample Collection: Take an appropriate amount of soil and sieve it to filter out large stones, clods of soil, weeds, plastic film and other debris, and keep soil samples that meet the size requirements; the sieve used for sieving has a mesh size of 5mm.

[0033] S2 - Sample Pretreatment: Place the collected soil sample in the test tray, add appropriate amounts of citric acid and tartaric acid to activate the heavy metal ions in the soil, and adjust the moisture content to 10%; the test tray is a round or square glass or ceramic vessel, the molar concentration of citric acid used is 0.1M, the pH value is 3.8, the concentration of tartaric acid is 50%, and the addition ratio of citric acid to tartaric acid is 2:1.

[0034] Citric acid and tartaric acid are added by spraying, which allows them to penetrate the soil more fully and evenly. Whether to spray water depends on the soil moisture. The soil moisture content is measured by a handheld soil moisture meter to ensure that the moisture content is 10%.

[0035] Heavy metals in soil typically exist as metal ions. The acidic anions in citric acid and tartaric acid can form complexes with metal cations, thus increasing the concentration of Hg in the soil. 2+ Pb 2+ Cd 2+ The dissolution rate reaches over 95%, providing a basic guarantee for the subsequent removal of heavy metal ions.

[0036] S3-Preparation of supramolecular cages: Cucurbita[8]urea is used as the main structure, and thiols, phosphate esters, and carboxylic acid / amino high-affinity groups are grafted onto its cage walls and covalently linked with Fe3O4@SiO2 to form a supramolecular cage complex; the specific preparation steps of the supramolecular cage complex are as follows:

[0037] S31: Cucurbita[8] ureathiolation modification

[0038] Cucurbit[8]urea was refluxed with 3-mercaptopropyltrimethoxysilane in DMF at a reaction temperature of 150°C for 3 hours, and each cucurbit[8]urea was grafted with 8 -SH groups.

[0039] Cucurbita[8]urea is a supramolecular compound with a hollow gourd-shaped structure consisting of eight nitrogen-oxygen heterocyclic rings (C3H3NO). Due to its unique cavity structure, it can form stable host-guest complexes with suitable molecules, and therefore can be used for molecular recognition and separation.

[0040] 3-Mercaptopropyltrimethoxysilane is a sulfur-containing silane compound containing one active organic thiol group (-SH) and three hydrolyzable methoxy groups (CH3O-), with each nitrogen-oxygen heterocycle coupled to an organic thiol group (-SH), thereby forming cucurbita urea with eight -SH groups [8].

[0041] DMF is N,N-dimethylformamide, which has good solubility for a variety of organic and inorganic compounds. Here it is used as a reaction solvent for cucurbit[8]urea and 3-mercaptopropyltrimethoxysilane.

[0042] S32: Introduction of phosphate ester groups

[0043] Thiolized cucurbit[8]urea was coupled with trichloroethyl phosphate under EDC / NHS catalysis, introducing 4 -PO4 groups into each cucurbit[8]urea. 3- Group; among which, EDC / NHS is a commonly used coupling method in the chemical field, which can convert the phosphate ion (-PO4) of trichloroethyl phosphate. 3- ) is separated and coupled with thiolized cucurbit[8]urea.

[0044] S33: Carboxylic acid / amino bifunctionalization

[0045] The remaining hydroxyl group (-OH) of thiolated cucurbit[8]urea is reacted with ethylenediaminetetraacetic acid (EDTA) via an anhydride reaction to form an EDTA-cucurbit[8]urea complex. Specifically, an ester and an amide are generated during the anhydride reaction, and EDTA is attached to the hydroxyl group (-OH) of cucurbit[8]urea via an ester bond or an amide bond to form a stable covalent bond.

[0046] Since each ethylenediaminetetraacetic acid molecule requires the consumption of one hydroxyl group (-OH) and the removal of one water molecule (H2O), the resulting EDTA-cucurbita[8]urea complex has two reaction pathways:

[0047] (1) If each thiolized cucurbit[8]urea is grafted with one molecule of ethylenediaminetetraacetic acid, then the reaction equation is:

[0048] C 48 H 48 N 32 O 16 + C 10 H 16 N₂O₈-H₂O → C 58 H 62 N 34 O 23 ‌

[0049] (2) If four ethylenediaminetetraacetic acid molecules are grafted (for example, modified at the four hydroxyl sites of cucurbit[8]urea), the reaction equation is:

[0050] C 48 H 48 N 32 O 16 + 4 (C) 10 H 16 N₂O₈)⁻⁴H₂O → C 88 H 100 N 40 O 44

[0051] S34: Magnetic Composite Assembly

[0052] Thiolized cucurbit[8]urea was covalently bonded to the Fe3O4@SiO2 surface by aminosilane to form a cucurbit[8]urea-SH / PO4 / EDTA@Fe3O4 composite. TEM showed that the coating thickness of the composite was 5 nm.

[0053] S4 - Heavy Metal Capture: An appropriate amount of supramolecular cage complex was added to the test tray and allowed to stand for 4 hours to allow the supramolecular cage complex to react with the sample, thereby capturing Hg from the soil sample. 2+ Pb 2+ Cd 2+ Ions are captured.

[0054] Among them, the -SH group is associated with Hg 2+ Captured via Hg-S bond binding, -PO4 3- Groups utilizing Pb 2+ With -PO4 3- The strong coordination ability of Pb 2+ Capture occurs through the -COOH and -NH2 groups on Cd. 2+ The trapping process is carried out to form a stable Cd-O / N pentagonal structure.

[0055] S5 - Material Screening: After the reaction is completed, the material is placed in a vacuum drying oven for drying. After drying, a permanent magnet drum is used to recover the carrier after capturing heavy metal ions. The remaining material is the soil after heavy metal removal.

[0056] The vacuum drying oven has a drying temperature of 60℃ and a drying time of 0.5h; the permanent magnet drum has a rotation speed of 40r / min and the material is screened 3 times.

[0057] Example 2:

[0058] The efficient method for removing heavy metals from soil in this embodiment includes the following steps:

[0059] S1 - Sample Collection: Take an appropriate amount of soil and sieve it to filter out large stones, clods of soil, weeds, plastic film and other debris, and keep soil samples that meet the size requirements; the sieve used for sieving has a mesh size of 6mm.

[0060] S2 - Sample Pretreatment: Place the collected soil sample in the test tray, add appropriate amounts of citric acid and tartaric acid to activate the heavy metal ions in the soil, and adjust the moisture content to 12%; the test tray is a round or square glass or ceramic vessel, the molar concentration of citric acid used is 0.15M, the pH value is 3.6, the concentration of tartaric acid is 48%, and the addition ratio of citric acid to tartaric acid is 2:1.

[0061] Citric acid and tartaric acid are added by spraying, which allows them to penetrate the soil more fully and evenly. Whether to spray water depends on the soil moisture. The soil moisture content is measured by a handheld soil moisture meter to ensure that the moisture content is 12%.

[0062] Heavy metals in soil typically exist as metal ions. The acidic anions in citric acid and tartaric acid can form complexes with metal cations, thus increasing the concentration of Hg in the soil. 2+ Pb 2+ Cd 2+ The dissolution rate reaches over 95%, providing a basic guarantee for the subsequent removal of heavy metal ions.

[0063] S3-Preparation of supramolecular cages: Cucurbita[8]urea is used as the main structure, and thiols, phosphate esters, and carboxylic acid / amino high-affinity groups are grafted onto its cage walls and covalently linked with Fe3O4@SiO2 to form a supramolecular cage complex; the specific preparation steps of the supramolecular cage complex are as follows:

[0064] S31: Cucurbita[8] ureathiolation modification

[0065] Cucurbit[8]urea was refluxed with 3-mercaptopropyltrimethoxysilane in DMF at a reaction temperature of 155°C for 2.5 h, and each cucurbit[8]urea was grafted with 8 -SH groups.

[0066] Cucurbita[8]urea is a supramolecular compound with a hollow gourd-shaped structure consisting of eight nitrogen-oxygen heterocyclic rings (C3H3NO). Due to its unique cavity structure, it can form stable host-guest complexes with suitable molecules, and therefore can be used for molecular recognition and separation.

[0067] 3-Mercaptopropyltrimethoxysilane is a sulfur-containing silane compound containing one active organic thiol group (-SH) and three hydrolyzable methoxy groups (CH3O-), with each nitrogen-oxygen heterocycle coupled to an organic thiol group (-SH), thereby forming cucurbita urea with eight -SH groups [8].

[0068] DMF is N,N-dimethylformamide, which has good solubility for a variety of organic and inorganic compounds. Here it is used as a reaction solvent for cucurbit[8]urea and 3-mercaptopropyltrimethoxysilane.

[0069] S32: Introduction of phosphate ester groups

[0070] Thiolized cucurbit[8]urea was coupled with trichloroethyl phosphate under EDC / NHS catalysis, introducing 4 -PO4 groups into each cucurbit[8]urea. 3-Group; among which, EDC / NHS is a commonly used coupling method in the chemical field, which can convert the phosphate ion (-PO4) of trichloroethyl phosphate. 3- ) is separated and coupled with thiolized cucurbit[8]urea.

[0071] S33: Carboxylic acid / amino bifunctionalization

[0072] The remaining hydroxyl group (-OH) of thiolated cucurbit[8]urea is reacted with ethylenediaminetetraacetic acid (EDTA) via an anhydride reaction to form an EDTA-cucurbit[8]urea complex. Specifically, an ester and an amide are generated during the anhydride reaction, and EDTA is attached to the hydroxyl group (-OH) of cucurbit[8]urea via an ester bond or an amide bond to form a stable covalent bond.

[0073] Since each ethylenediaminetetraacetic acid molecule requires the consumption of one hydroxyl group (-OH) and the removal of one water molecule (H2O), the resulting EDTA-cucurbita[8]urea complex has two reaction pathways:

[0074] (1) If each thiolized cucurbit[8]urea is grafted with one molecule of ethylenediaminetetraacetic acid, then the reaction equation is:

[0075] C 48 H 48 N 32 O 16 + C 10 H 16 N₂O₈-H₂O → C 58 H 62 N 34 O 23 ‌

[0076] (2) If four ethylenediaminetetraacetic acid molecules are grafted (for example, modified at the four hydroxyl sites of cucurbit[8]urea), the reaction equation is:

[0077] C 48 H 48 N 32 O 16 + 4 (C) 10 H 16 N₂O₈)⁻⁴H₂O → C 88 H 100 N 40 O 44

[0078] S34: Magnetic Composite Assembly

[0079] Thiolized cucurbit[8]urea was covalently bonded to the Fe3O4@SiO2 surface by aminosilane to form a cucurbit[8]urea-SH / PO4 / EDTA@Fe3O4 composite. TEM showed that the coating thickness of the composite was 6 nm.

[0080] S4 - Heavy Metal Capture: An appropriate amount of supramolecular cage complex is added to the test tray and allowed to stand for 5 hours to allow the supramolecular cage complex to react with the sample, thereby capturing Hg from the soil sample. 2+ Pb 2+ Cd 2+ Ions are captured.

[0081] Among them, the -SH group is associated with Hg 2+ Captured via Hg-S bond binding, -PO4 3- Groups utilizing Pb 2+ With -PO4 3- The strong coordination ability of Pb 2+ Capture occurs through the -COOH and -NH2 groups on Cd. 2+ The trapping process is carried out to form a stable Cd-O / N pentagonal structure.

[0082] S5 - Material Screening: After the reaction is completed, the material is placed in a vacuum drying oven for drying. After drying, a permanent magnet drum is used to recover the carrier after capturing heavy metal ions. The remaining material is the soil after heavy metal removal.

[0083] The vacuum drying oven has a drying temperature of 62℃ and a drying time of 0.8h; the permanent magnet drum has a rotation speed of 42r / min and the material is screened 3 times.

[0084] Example 3:

[0085] The efficient method for removing heavy metals from soil in this embodiment includes the following steps:

[0086] S1 - Sample Collection: Take an appropriate amount of soil and sieve it to filter out large stones, clods of soil, weeds, plastic film and other debris, and keep soil samples that meet the size requirements; the sieve used for sieving has an 8mm mesh size.

[0087] S2 - Sample Pretreatment: Place the collected soil sample in the test tray, add appropriate amounts of citric acid and tartaric acid to activate the heavy metal ions in the soil, and adjust the moisture content to 15%; the test tray is a round or square glass or ceramic vessel, the molar concentration of citric acid used is 0.2M, the pH value is 3.5, the concentration of tartaric acid is 45%, and the addition ratio of citric acid to tartaric acid is 2:1.

[0088] Citric acid and tartaric acid are added by spraying, which allows them to penetrate the soil more fully and evenly. Whether to spray water depends on the soil moisture. The soil moisture content is measured by a handheld soil moisture meter to ensure that the moisture content is 15%.

[0089] Heavy metals in soil typically exist as metal ions. The acidic anions in citric acid and tartaric acid can form complexes with metal cations, thus increasing the concentration of Hg in the soil. 2+ Pb 2+ Cd 2+ The dissolution rate reaches over 95%, providing a basic guarantee for the subsequent removal of heavy metal ions.

[0090] S3-Preparation of supramolecular cages: Cucurbita[8]urea is used as the main structure, and thiols, phosphate esters, and carboxylic acid / amino high-affinity groups are grafted onto its cage walls and covalently linked with Fe3O4@SiO2 to form a supramolecular cage complex; the specific preparation steps of the supramolecular cage complex are as follows:

[0091] S31: Cucurbita[8] ureathiolation modification

[0092] Cucurbit[8]urea was refluxed with 3-mercaptopropyltrimethoxysilane in DMF at a reaction temperature of 160°C for 2 hours, and each cucurbit[8]urea was grafted with 8 -SH groups.

[0093] Cucurbita[8]urea is a supramolecular compound with a hollow gourd-shaped structure consisting of eight nitrogen-oxygen heterocyclic rings (C3H3NO). Due to its unique cavity structure, it can form stable host-guest complexes with suitable molecules, and therefore can be used for molecular recognition and separation.

[0094] 3-Mercaptopropyltrimethoxysilane is a sulfur-containing silane compound containing one active organic thiol group (-SH) and three hydrolyzable methoxy groups (CH3O-), with each nitrogen-oxygen heterocycle coupled to an organic thiol group (-SH), thereby forming cucurbita urea with eight -SH groups [8].

[0095] DMF is N,N-dimethylformamide, which has good solubility for a variety of organic and inorganic compounds. Here it is used as a reaction solvent for cucurbit[8]urea and 3-mercaptopropyltrimethoxysilane.

[0096] S32: Introduction of phosphate ester groups

[0097] Thiolized cucurbit[8]urea was coupled with trichloroethyl phosphate under EDC / NHS catalysis, introducing 4 -PO4 groups into each cucurbit[8]urea. 3-Group; among which, EDC / NHS is a commonly used coupling method in the chemical field, which can convert the phosphate ion (-PO4) of trichloroethyl phosphate. 3- ) is separated and coupled with thiolized cucurbit[8]urea.

[0098] S33: Carboxylic acid / amino bifunctionalization

[0099] The remaining hydroxyl group (-OH) of thiolated cucurbit[8]urea is reacted with ethylenediaminetetraacetic acid (EDTA) via an anhydride reaction to form an EDTA-cucurbit[8]urea complex. Specifically, an ester and an amide are generated during the anhydride reaction, and EDTA is attached to the hydroxyl group (-OH) of cucurbit[8]urea via an ester bond or an amide bond to form a stable covalent bond.

[0100] Since each ethylenediaminetetraacetic acid molecule requires the consumption of one hydroxyl group (-OH) and the removal of one water molecule (H2O), the resulting EDTA-cucurbita[8]urea complex has two reaction pathways:

[0101] (1) If each thiolized cucurbit[8]urea is grafted with one molecule of ethylenediaminetetraacetic acid, then the reaction equation is:

[0102] C 48 H 48 N 32 O 16 + C 10 H 16 N₂O₈-H₂O → C 58 H 62 N 34 O 23 ‌

[0103] (2) If four ethylenediaminetetraacetic acid molecules are grafted (for example, modified at the four hydroxyl sites of cucurbit[8]urea), the reaction equation is:

[0104] C 48 H 48 N 32 O 16 + 4 (C) 10 H 16 N₂O₈)⁻⁴H₂O → C 88 H 100 N 40 O 44

[0105] S34: Magnetic Composite Assembly

[0106] Thiolized cucurbit[8]urea was covalently bonded to the Fe3O4@SiO2 surface by aminosilane to form a cucurbit[8]urea-SH / PO4 / EDTA@Fe3O4 composite. TEM showed that the coating thickness of the composite was 6 nm.

[0107] S4 - Heavy Metal Capture: An appropriate amount of supramolecular cage complex was added to the test tray and allowed to stand for 4 hours to allow the supramolecular cage complex to react with the sample, thereby capturing Hg from the soil sample. 2+ Pb 2+ Cd 2+ Ions are captured.

[0108] Among them, the -SH group is associated with Hg 2+ Captured via Hg-S bond binding, -PO4 3- Groups utilizing Pb 2+ With -PO4 3- The strong coordination ability of Pb 2+ Capture occurs through the -COOH and -NH2 groups on Cd. 2+ The trapping process is carried out to form a stable Cd-O / N pentagonal structure.

[0109] S5 - Material Screening: After the reaction is completed, the material is placed in a vacuum drying oven for drying. After drying, a permanent magnet drum is used to recover the carrier after capturing heavy metal ions. The remaining material is the soil after heavy metal removal.

[0110] The vacuum drying oven has a drying temperature of 65℃ and a drying time of 1 hour; the permanent magnet drum has a rotation speed of 45 r / min and the material is screened twice.

[0111] The above embodiments were subjected to a control experiment in a laboratory environment with constant temperature (25℃) and constant humidity (40%). The specific experimental structure is shown in the table below:

[0112] Group supramolecular cage addition amount reaction time <![CDATA[Hg 2+ Removal rate <![CDATA[Pb 2+ Removal rate <![CDATA[Cd 2+ Removal rate Example 1 10 mg / g soil 6h 98.3% 98.5% 98.8% Example 2 12 mg / g soil 6h 96.7% 96.9% 97.0% Example 3 15mg / g soil 6h 95.5% 95.7% 96.1%

[0113] The above comparative experiments show that, using this method, the removal rate of heavy metal ions in the soil is over 95%, including Hg. 2+ The removal rate was over 98.3%, Pb 2+ The removal rate was over 96.7% for Cd. 2+ The removal rate is over 95.5%, the process cycle is short, the heavy metal removal efficiency is high, there is no risk of nanoparticle residue, and it avoids the long-term leaching risk of solidifying agents such as apatite and bentonite in traditional stabilization technologies. It is highly environmentally friendly and is especially suitable for complex pollution scenarios such as industrial sites and mining areas, providing a scalable and innovative technical path for soil remediation.

[0114] Furthermore, the screened magnetic carrier can be desorbed to remove Hg. 2+ Pb 2+ Cd 2+ By recycling, the resource recovery and utilization of heavy metals can be achieved, which helps to reduce costs.

[0115] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them; when the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope claimed by the present invention.

Claims

1. A method for efficiently removing heavy metals from soil, characterized in that, Includes the following steps: S1 - Sample Collection: Take an appropriate amount of soil and sieve it to filter out large stones, soil clods and debris, and keep soil samples that meet the size requirements. S2 - Sample Pretreatment: Place the collected soil sample in the test tray, add appropriate amounts of citric acid and tartaric acid to activate the heavy metal ions in the soil, and adjust the moisture content to 10-15%; S3-Preparation of supramolecular cages: Cucurbita[8]urea is used as the main structure, and thiols, phosphate esters, carboxylic acid / amino high affinity groups are grafted onto its cage wall and covalently connected with Fe3O4@SiO2 to form a supramolecular cage complex; S4 - Heavy Metal Capture: Add an appropriate amount of supramolecular cage complex to the test tray and let it stand for 4-6 hours to allow the supramolecular cage complex to react with the sample, thereby capturing Hg in the soil sample. 2+ Pb 2+ Cd 2+ Ions are captured; S5 - Material Screening: After the reaction is completed, the material is placed in a vacuum drying oven for drying. After drying, a permanent magnet drum is used to recover the carrier after capturing heavy metal ions. The remaining material is the soil after heavy metal removal. The specific steps for preparing the supramolecular cage in step S3 are as follows: S31: Cucurbita[8] ureathiolation modification Cucurbit[8]urea and 3-mercaptopropyltrimethoxysilane were refluxed in DMF at a temperature of 150-160℃ for 2-3 hours, and each cucurbit[8]urea was grafted with 8 -SH groups. S32: Introduction of phosphate ester groups Thiolized cucurbit[8]urea was coupled with trichloroethyl phosphate under EDC / NHS catalysis, introducing 4 -PO4 groups into each cucurbit[8]urea. 3- Group; S33: Carboxylic acid / amino bifunctionalization The remaining hydroxyl groups of thiolated cucurbit[8]urea were reacted with ethylenediaminetetraacetic acid anhydride to form an EDTA-cucurbit[8]urea complex; S34: Magnetic Composite Assembly Thiolized cucurbit[8]urea was covalently bonded to the Fe3O4@SiO2 surface by aminosilane to form a cucurbit[8]urea-SH / PO4 / EDTA@Fe3O4 composite.

2. The method for efficient removal of heavy metals from soil according to claim 1, characterized in that: In step S1, the mesh size of the sieve used for sieving is 5-8 mm.

3. The method for efficient removal of heavy metals from soil according to claim 1, characterized in that: In step S2, the molar concentration of citric acid is 0.1-0.2M, the pH value is 3.5-3.8, and the concentration of tartaric acid is 45-50%.

4. The method for efficient removal of heavy metals from soil according to claim 1, characterized in that: In step S2, the ratio of citric acid to tartaric acid is 2:

1.

5. The method for efficient removal of heavy metals from soil according to claim 1, characterized in that: In step S4, the -SH group is applied to Hg. 2+ Captured via Hg-S bond binding, -PO4 3- Groups utilizing Pb 2+ With -PO4 3- The strong coordination ability of Pb 2+ Capture occurs through the -COOH and -NH2 groups on Cd. 2+ The trapping process is carried out to form a stable Cd-O / N pentagonal structure.

6. The method for efficient removal of heavy metals from soil according to claim 1, characterized in that: In step S5, the drying temperature of the vacuum drying oven is 60-65℃, and the drying time is 0.5-1h.

7. The method for efficient removal of heavy metals from soil according to claim 1, characterized in that: In step S5, the rotational speed of the permanent magnet drum is set to 40-50 r / min, and the material is screened 2-3 times.