A method for preparing a heavy metal chelating agent composite material

Abstract

The application discloses a preparation method of a heavy metal chelating agent composite material, and the method comprises the following steps: S1, montmorillonite is placed in a dilute acid solution for treatment, and then the montmorillonite is washed, dried, crushed, and ground to obtain montmorillonite powder; S2, polyvinyl acetate is dissolved in a solvent to obtain a blending liquid, the montmorillonite powder is added and stirred uniformly, then ionic monomers and an initiator are added and continuously stirred, and then polyvinylpyrrolidone is added and stirred uniformly; after the stirring is completed, the blending liquid is left to stand, and then the blending liquid is filtered; the obtained product is washed and dried to obtain a modified montmorillonite copolymer composite; S3, the modified montmorillonite is placed in a urea solution for heat treatment, and then the modified montmorillonite is filtered; the obtained product is sequentially washed, freeze-dried, and sieved to obtain the heavy metal chelating agent composite material. The chelating agent composite material can effectively remove heavy metal ions in polluted water.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal treatment technology, and more specifically, relates to a method for preparing a heavy metal chelating agent composite material. Background Technology

[0002] Heavy metal wastewater comes from a wide range of sources, primarily: leaching from waste rock dumps in the mining industry, washing of plated parts in the electroplating industry, pickling in steel mills and dust removal wastewater from non-ferrous metal smelting plants in the non-ferrous metal smelting industry, and fertilizer and pharmaceutical production in the chemical industry. Because heavy metal wastewater cannot be degraded by natural water bodies through self-purification, water bodies polluted by heavy metals are difficult to remediate. Furthermore, since heavy metals can damage proteins and other organic molecules in the human body, their accumulation after entering the body can lead to various diseases.

[0003] Currently, the main methods for treating heavy metal wastewater both domestically and internationally include chemical precipitation, bioflocculation, adsorption, and electrochemical methods. However, due to economic reasons, most regions still choose chelation precipitation as the primary technology for treating heavy metal wastewater. Heavy metal chelating agents utilize their unique functional groups to chelate with heavy metal ions in wastewater, forming insoluble or sparingly soluble chelated precipitates to remove heavy metal ions. Heavy metal chelating agents are suitable for treating wastewater containing heavy metal ions across a wide pH range and can generally chelate rapidly with various heavy metal ions in the wastewater simultaneously at room temperature, ensuring that the heavy metal ions in the wastewater meet discharge standards.

[0004] Therefore, developing high-performance novel heavy metal chelating agents remains the key to removing heavy metal ions. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and provide a method for preparing a heavy metal chelating agent composite material. The chelating agent composite material of this invention can effectively remove heavy metal ions from polluted water bodies.

[0006] The objective of this invention and the technical problem it solves are achieved by the following technical solutions.

[0007] One aspect of the present invention provides a method for preparing a heavy metal chelating agent composite material, the method comprising the following steps:

[0008] S1: Place montmorillonite in a dilute acid solution and stir for 10-20 minutes at 60-100°C. Then remove it and wash, dry, crush and grind it to obtain montmorillonite powder.

[0009] S2: Polyvinyl acetate is dissolved in a solvent to obtain a blend solution with a concentration of 30-50 wt%. The obtained montmorillonite powder is added to the blend solution and stirred evenly. Then, ionic monomers and initiators are added and stirred continuously at 50-70°C for 4-10 h. Subsequently, polyvinylpyrrolidone is added and stirred evenly. After stirring, the mixture is allowed to stand for 12-24 h. After filtration, the obtained product is washed and dried to obtain the modified montmorillonite copolymer composite.

[0010] S3: The obtained modified montmorillonite was placed in a 30-80 wt% urea solution and heat-treated at 100-150℃ for 20-30 min. After filtration, the obtained product was washed, freeze-dried and passed through an 80-200 mesh sieve to obtain a heavy metal chelating agent composite material.

[0011] In a preferred embodiment of the present invention, in step S1, the dilute acid solution is a dicarboxylic acid solution with a concentration between 20 and 40 wt%.

[0012] In a preferred embodiment of the present invention, the dicarboxylic acid is selected from one or a mixture of two or more of oxalic acid, malonic acid, succinic acid, adipic acid, maleic acid, trans-butenedioic acid, and methylene succinic acid.

[0013] In a preferred embodiment of the present invention, in step S2, the solvent is selected from any one of acetone, benzene, or chloroform.

[0014] In a preferred embodiment of the present invention, in step S2, the montmorillonite powder is added at a mass-to-volume ratio of 1g to 5-15mL with the blended liquid.

[0015] In a preferred embodiment of the present invention, in step S2, the ionic monomer is selected from any one of N,N-dimethyl-N-acrylamidopropyl-N-(2-carboxymethyl)-ammonium betaine, N,N-dimethyl-N-methacryloylethoxy-N-(3-sulfopropyl)-ammonium betaine, N,N-dimethyl-N-acryloylethoxy-N-(3-sulfopropyl)-ammonium betaine, and N,N-dimethyl-N-methacrylamidopropyl-N-(3-sulfopropyl)-ammonium betaine.

[0016] In a preferred embodiment of the present invention, in step S2, the initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisobutyramidoline hydrochloride, and azobisisobutyramidine hydrochloride.

[0017] In a preferred embodiment of the present invention, in step S2, the ionic monomer is added in an amount with a mass ratio of 1 to 3:1 to polyvinyl acetate.

[0018] In a preferred embodiment of the present invention, in step S2, the amount of initiator added is 0.12 to 0.7% of the mass of the ionic monomer.

[0019] In a preferred embodiment of the present invention, in step S2, the polyvinylpyrrolidone is added in a mass ratio of 0.01 to 0.03:1 to polyvinyl acetate.

[0020] In a preferred embodiment of the present invention, in step S3, the modified montmorillonite and urea solution are added at a mass-volume ratio of 1g:10-30mL.

[0021] Another aspect of the present invention provides an application of a heavy metal chelating agent composite material prepared according to the preparation method described above in the treatment of heavy metal wastewater.

[0022] By employing the above technical solution, the present invention has at least the following advantages:

[0023] This invention uses montmorillonite as raw material. After treatment with dicarboxylic acids, the content of metal ions such as aluminum and magnesium in montmorillonite is reduced, and the surface of montmorillonite is carboxylated. The montmorillonite is then pulverized and placed in a polyvinyl acetate solution. An amphoteric monomer and initiator are added to initiate a monomer polymerization reaction, yielding an amphoteric grafted modified polyvinyl acetate / montmorillonite composite. The addition of polyvinylpyrrolidone (PVP) acts as a stabilizer and coagulant, precipitating the product from the reaction system and maintaining its structural stability. Finally, the product is placed in a urea solution for heat treatment. At this treatment temperature, urea begins to decompose, releasing hydroxide and carbonate ions, resulting in hydroxylation of the product surface and a large number of negative charges. Therefore, the heavy metal chelating agent composite material of this invention can be used in the treatment of heavy metal wastewater. The negative charge on its surface binds to heavy metal cations in the wastewater, achieving the removal of heavy metal ions and thus improving water quality.

[0024] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below. Detailed Implementation

[0025] To make the technical means, creative features, achieved objectives, and effects of this invention readily understandable, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0026] Montmorillonite is a layered aluminosilicate mineral with the theoretical structural formula (1 / 2Ca, Na). 0.7 (Al, Mg, Fe)4(Si, Al)8O 20 (OH)₄·nH₂O, where Ca and Na are exchangeable cations. Montmorillonite is abundant in nature and inexpensive, and is currently used in many fields such as metallurgy, chemical industry, geological exploration, textiles, ceramics, medicine, environmental protection, and nanomaterials. Studies have shown that the addition of montmorillonite can effectively improve the strength, thermal stability, flame retardancy, barrier properties, and mechanical properties of various polymers. Therefore, in one aspect, this invention incorporates montmorillonite into the graft polymerization process of zwitterionic graft-modified polyvinyl acetate to form a zwitterionic graft-modified polyvinyl acetate / montmorillonite composite, resulting in a composite with excellent mechanical properties and stability; simultaneously, the polymer coating can reduce the release of metal ions, silicon, etc., from montmorillonite, thereby avoiding the impact of montmorillonite on water bodies. Under low-temperature conditions, urea solution is neutral. When the solution temperature exceeds 90°C, urea begins to decompose, producing hydroxide ions and carbonate ions. Therefore, in another aspect, the present invention further places the obtained complex in a urea solution for heat treatment. During the heat treatment, hydroxide ions and carbonate ions generated by urea can adhere to the surface of the complex, so that the product surface is hydroxylated and has a large number of negative charges. The environment system rich in negative charges is more likely to combine metal cations.

[0027] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0028] Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0029] Example 1:

[0030] A method for preparing a heavy metal chelating agent composite material, the method comprising the following steps:

[0031] S1: Montmorillonite was placed in a 30wt% oxalic acid solution and stirred at 80°C for 15 minutes. Then, it was taken out and washed, dried, crushed and ground in sequence to obtain montmorillonite powder.

[0032] S2: Polyvinyl acetate was dissolved in acetone to obtain a 40wt% blend. Montmorillonite powder was added to the blend at a mass-to-volume ratio of 1g:10mL and stirred until homogeneous. Then, N,N-dimethyl-N-acrylamidopropyl-N-(2-carboxymethyl)-ammonium betaine (added at a mass ratio of 2:1 to polyvinyl acetate) and azobisisobutyronitrile (added at 0.41% of the mass of N,N-dimethyl-N-acrylamidopropyl-N-(2-carboxymethyl)-ammonium betaine) were added and stirred continuously at 60°C for 7h. Subsequently, polyvinylpyrrolidone (added at a mass ratio of 0.02:1 to polyvinyl acetate) was added and stirred until homogeneous. After stirring, the mixture was allowed to stand for 18h, then filtered. The resulting product was washed and dried to obtain the modified montmorillonite copolymer composite.

[0033] S3: The modified montmorillonite was placed in a 55wt% urea solution at a mass-volume ratio of 1g:20mL and heat-treated at 125℃ for 25min. After filtration, the resulting product was washed, freeze-dried and passed through a 100-mesh sieve to obtain a heavy metal chelating agent composite material.

[0034] Example 2:

[0035] A method for preparing a heavy metal chelating agent composite material, the method comprising the following steps:

[0036] S1: Montmorillonite was placed in a 30wt% malonic acid solution and stirred at 60°C for 20 minutes. Then, it was taken out and washed, dried, crushed and ground in sequence to obtain montmorillonite powder.

[0037] S2: Polyvinyl acetate was dissolved in acetone to obtain a 30wt% blend. Montmorillonite powder was added to the blend at a mass-to-volume ratio of 1g:15mL and stirred until homogeneous. Then, N,N-dimethyl-N-methacryloylethoxy-N-(3-sulfopropyl)-ammonium betaine (added at a mass ratio of 1:1 to polyvinyl acetate) and azobisisobutyronitrile (added at 0.7% of the mass of N,N-dimethyl-N-methacryloylethoxy-N-(3-sulfopropyl)-ammonium betaine) were added and stirred continuously at 50°C for 10h. Subsequently, polyvinylpyrrolidone (added at a mass ratio of 0.01:1 to polyvinyl acetate) was added and stirred until homogeneous. After stirring, the mixture was allowed to stand for 24h, then filtered. The resulting product was washed and dried to obtain the modified montmorillonite copolymer composite.

[0038] S3: The modified montmorillonite was placed in an 80wt% urea solution at a mass-volume ratio of 1g:10mL and heat-treated at 100℃ for 30min. After filtration, the resulting product was washed, freeze-dried and passed through an 80-mesh sieve to obtain a heavy metal chelating agent composite material.

[0039] Example 3:

[0040] A method for preparing a heavy metal chelating agent composite material, the method comprising the following steps:

[0041] S1: Montmorillonite was placed in a 30wt% succinic acid solution and stirred at 100℃ for 10 minutes. Then, it was taken out and washed, dried, crushed and ground in sequence to obtain montmorillonite powder.

[0042] S2: Polyvinyl acetate was dissolved in acetone to obtain a 50wt% blend. Montmorillonite powder was added to the blend at a mass-to-volume ratio of 1g:5mL and stirred until homogeneous. Then, N,N-dimethyl-N-methacrylamidopropyl-N-(3-sulfopropyl)-ammonium betaine (added at a mass ratio of 3:1 to polyvinyl acetate) and azobisisobutyronitrile (added at 0.12% of the mass of N,N-dimethyl-N-methacrylamidopropyl-N-(3-sulfopropyl)-ammonium betaine) were added and stirred continuously at 70°C for 4 hours. Subsequently, polyvinylpyrrolidone (added at a mass ratio of 0.03:1 to polyvinyl acetate) was added and stirred until homogeneous. After stirring, the mixture was allowed to stand for 12 hours, then filtered. The resulting product was washed and dried to obtain the modified montmorillonite copolymer composite.

[0043] S3: The modified montmorillonite was placed in a 30wt% urea solution at a mass-volume ratio of 1g:10mL and heat-treated at 150℃ for 20min. After filtration, the resulting product was washed, freeze-dried and passed through a 200-mesh sieve to obtain a heavy metal chelating agent composite material.

[0044] Example 4:

[0045] A method for preparing a heavy metal chelating agent composite material, the method comprising the following steps:

[0046] S1: Montmorillonite was placed in a 30wt% adipic acid solution and stirred at 90°C for 12 minutes. Then, it was taken out and washed, dried, crushed and ground in sequence to obtain montmorillonite powder.

[0047] S2: Polyvinyl acetate was dissolved in acetone to obtain a 35wt% blend. Montmorillonite powder was added to the blend at a mass-to-volume ratio of 1g:10mL and stirred until homogeneous. Then, N,N-dimethyl-N-acryloylethoxy-N-(3-sulfopropyl)-ammonium betaine (added at a mass ratio of 1:1 to polyvinyl acetate) and azobisisobutyrazoline hydrochloride (added at 0.2% of the mass of N,N-dimethyl-N-acryloylethoxy-N-(3-sulfopropyl)-ammonium betaine) were added and stirred continuously at 55°C for 9 hours. Subsequently, polyvinylpyrrolidone (added at a mass ratio of 0.01:1 to polyvinyl acetate) was added and stirred until homogeneous. After stirring, the mixture was allowed to stand for 20 hours, then filtered. The resulting product was washed and dried to obtain the modified montmorillonite copolymer composite.

[0048] S3: The modified montmorillonite was placed in a 70wt% urea solution at a mass-volume ratio of 1g:15mL and heat-treated at 140℃ for 20min. After filtration, the resulting product was washed, freeze-dried and passed through a 150-mesh sieve to obtain a heavy metal chelating agent composite material.

[0049] Example 5:

[0050] A method for preparing a heavy metal chelating agent composite material, the method comprising the following steps:

[0051] S1: Montmorillonite was placed in a 30wt% maleic acid solution and stirred at 70°C for 16 minutes. Then, it was taken out and washed, dried, crushed and ground in sequence to obtain montmorillonite powder.

[0052] S2: Polyvinyl acetate was dissolved in acetone to obtain a blend solution with a concentration of 45 wt%. The obtained montmorillonite powder was added to the blend solution at a mass-to-volume ratio of 1 g: 5 mL and stirred evenly. Then, N,N-dimethyl-N-methacryloylethoxy-N-(3-sulfopropyl)-ammonium betaine (added at a mass ratio of 2:1 to polyvinyl acetate) and azobisisobutyramidine hydrochloride (added at 0.5% of the mass of N,N-dimethyl-N-methacryloylethoxy-N-(3-sulfopropyl)-ammonium betaine) were added and stirred continuously at 65°C for 5 h. Subsequently, polyvinylpyrrolidone (added at a mass ratio of 0.02:1 to polyvinyl acetate) was added and stirred evenly. After stirring, the mixture was allowed to stand for 16 h, then filtered, and the resulting product was washed and dried to obtain the modified montmorillonite copolymer composite.

[0053] S3: The modified montmorillonite was placed in a 60wt% urea solution at a mass-volume ratio of 1g:25mL and heat-treated at 110℃ for 25min. After filtration, the resulting product was washed, freeze-dried and passed through a 200-mesh sieve to obtain a heavy metal chelating agent composite material.

[0054] Example 6:

[0055] A method for preparing a heavy metal chelating agent composite material, the method comprising the following steps:

[0056] S1: Montmorillonite was placed in a 30wt% fumaric acid solution and stirred at 90°C for 18 minutes. Then, it was taken out and washed, dried, crushed and ground in sequence to obtain montmorillonite powder.

[0057] S2: Polyvinyl acetate was dissolved in acetone to obtain a 40wt% blend. Montmorillonite powder was added to the blend at a mass-to-volume ratio of 1g:10mL and stirred until homogeneous. Then, N,N-dimethyl-N-acrylamidopropyl-N-(2-carboxymethyl)-ammonium betaine (added at a mass ratio of 3:1 to polyvinyl acetate) and azobisisobutyronitrile (added at 0.6% of the mass of N,N-dimethyl-N-acrylamidopropyl-N-(2-carboxymethyl)-ammonium betaine) were added and stirred continuously at 55°C for 8 hours. Subsequently, polyvinylpyrrolidone (added at a mass ratio of 0.03:1 to polyvinyl acetate) was added and stirred until homogeneous. After stirring, the mixture was allowed to stand for 22 hours, then filtered. The resulting product was washed and dried to obtain the modified montmorillonite copolymer composite.

[0058] S3: The modified montmorillonite was placed in a 70wt% urea solution at a mass-volume ratio of 1g:20mL and heat-treated at 140℃ for 20min. After filtration, the resulting product was washed, freeze-dried and passed through a 100-mesh sieve to obtain a heavy metal chelating agent composite material.

[0059] Comparative Example 1:

[0060] A method for preparing a heavy metal chelating agent composite material, the method comprising the following steps:

[0061] S1: Montmorillonite was placed in a 30wt% oxalic acid solution and stirred at 80°C for 15 minutes. Then, it was taken out and washed, dried, crushed and ground in sequence to obtain montmorillonite powder.

[0062] S2: Polyvinyl acetate was dissolved in acetone to obtain a 40wt% blend. Montmorillonite powder was added to the blend at a mass-to-volume ratio of 1g:10mL and stirred until homogeneous. Then, N,N-dimethyl-N-acrylamidopropyl-N-(2-carboxymethyl)-ammonium betaine (added at a mass ratio of 2:1 to polyvinyl acetate) and azobisisobutyronitrile (added at 0.41% of the mass of N,N-dimethyl-N-acrylamidopropyl-N-(2-carboxymethyl)-ammonium betaine) were added and stirred continuously at 60°C for 7h. Subsequently, polyvinylpyrrolidone (added at a mass ratio of 0.02:1 to polyvinyl acetate) was added and stirred until homogeneous. After stirring, the mixture was allowed to stand for 18h, then filtered. The resulting product was washed and dried to obtain a modified montmorillonite copolymer composite, which was used as a metal chelating agent composite material.

[0063] Comparative Example 2:

[0064] A method for preparing a heavy metal chelating agent composite material, the method comprising the following steps:

[0065] S1: Polyvinyl acetate was dissolved in acetone to obtain a blend with a concentration of 40 wt%. Then, N,N-dimethyl-N-acrylamidopropyl-N-(2-carboxymethyl)-ammonium betaine (added at a mass ratio of 2:1 to polyvinyl acetate) and azobisisobutyronitrile (added at a mass ratio of 0.41% of N,N-dimethyl-N-acrylamidopropyl-N-(2-carboxymethyl)-ammonium betaine) were added and stirred continuously at 60°C for 7 h. Subsequently, polyvinylpyrrolidone (added at a mass ratio of 0.02:1 to polyvinyl acetate) was added and stirred evenly. After stirring, the mixture was allowed to stand for 18 h, then filtered. The resulting product was washed and dried to obtain the copolymer.

[0066] S2: The obtained copolymer was placed in a 55wt% urea solution at a mass-volume ratio of 1g:20mL and heat-treated at 125℃ for 25min. After filtration, the obtained product was washed, freeze-dried and passed through a 100-mesh sieve to obtain a heavy metal chelating agent composite material.

[0067] Comparative Example 3:

[0068] A method for preparing a heavy metal chelating agent composite material, the method comprising the following steps:

[0069] S1: Montmorillonite was placed in a 30wt% oxalic acid solution and stirred at 80°C for 15 minutes. Then, it was taken out and washed, dried, crushed and ground in sequence to obtain montmorillonite powder.

[0070] S2: The obtained montmorillonite powder was placed in a 55wt% urea solution at a mass-volume ratio of 1g:20mL and heat-treated at 125℃ for 25min. After filtration, the obtained product was washed, freeze-dried and passed through a 100-mesh sieve to obtain a heavy metal chelating agent composite material.

[0071] Comparative Example 4:

[0072] A method for preparing a heavy metal chelating agent composite material, the method comprising the following steps:

[0073] S1: Montmorillonite is washed, dried, crushed, and ground to obtain montmorillonite powder.

[0074] S2: Polyvinyl acetate was dissolved in acetone to obtain a 40wt% blend. The obtained montmorillonite powder was added to the blend at a mass-to-volume ratio of 1g:10mL and stirred evenly. Then, N,N-dimethyl-N-acrylamidopropyl-N-(2-carboxymethyl)-ammonium betaine (added at a mass ratio of 2:1 to polyvinyl acetate) and azobisisobutyronitrile (added at 0.41% of the mass of N,N-dimethyl-N-acrylamidopropyl-N-(2-carboxymethyl)-ammonium betaine) were added and stirred continuously at 60℃ for 7h. Subsequently, polyvinylpyrrolidone (added at a mass ratio of 0.02:1 to polyvinyl acetate) was added and stirred evenly. After stirring, the mixture was allowed to stand for 18h, then filtered. The resulting product was washed and dried to obtain modified montmorillonite.

[0075] S3: The modified montmorillonite was placed in a 55wt% urea solution at a mass-volume ratio of 1g:20mL and heat-treated at 125℃ for 25min. After filtration, the resulting product was washed, freeze-dried and passed through a 100-mesh sieve to obtain a heavy metal chelating agent composite material.

[0076] Experimental Example 1: Evaluation of the Removal Effect of Different Heavy Metal Chelating Agents on Heavy Metal Ions in Wastewater

[0077] The test water was collected from wastewater discharged from a mine in Hebei Province. Before treatment, the metal ion content of the wastewater was measured as follows: copper 125 mg / L, lead 13.6 mg / L, iron 352 mg / L, nickel 36 mg / L, and cadmium 4.6 mg / L. The wastewater sample was divided into 10 groups, each containing 200 mL. 8 mg of the heavy metal chelating agent composite materials from Examples 1-6 and Comparative Examples 1-4 of this invention were added to each group. The mixture was stirred at 200 rpm for 5 minutes. After stirring, the mixture was allowed to stand for 15 minutes. The supernatant was collected, and the heavy metal residue was detected using an atomic absorption spectrophotometer. The removal rate (%) of each heavy metal was calculated.

[0078] Metal removal rate = (concentration before treatment - concentration after treatment) / concentration before treatment × 100%;

[0079] The statistical results are shown in Table 1 below.

[0080] Table 1. Statistics on the removal rates of various metals

[0081] Group copper lead iron nickel cadmium Example 1 99.4 99.2 98.7 99.1 95.3 Example 2 99.2 99.4 98.2 98.5 95.1 Example 3 99.5 99.1 98.5 98.4 95.2 Example 4 99.3 99.5 98.9 98.1 94.9 Example 5 99.6 99.2 98.4 98.9 95.2 Example 6 99.2 99.3 98.2 98.6 95 Comparative Example 1 80.5 78.7 75.9 79.4 77.3 Comparative Example 2 89.3 88.9 86.7 87.2 84.1 Comparative Example 3 70.4 67.8 66.5 69.3 68.4 Comparative Example 4 97.2 97.1 96.5 96.9 93.2

[0082] As shown in Table 1, the heavy metal chelating agent composite material of the present invention can effectively remove heavy metal ions from wastewater, and the effect is significant. Compared with Comparative Examples 1-4, the heavy metal chelating agent composite materials of Examples 1-6 of the present invention show a significantly improved removal effect on metal ions. This result indicates that the treatment of montmorillonite with dicarboxylic acid has a slight impact on the heavy metal removal effect of the obtained product (corresponding to Comparative Example 4). The composite material without montmorillonite (Comparative Example 2), the composite material without urea heat treatment (Comparative Example 1), and the composite material without polymer addition (Comparative Example 3) all show significantly reduced heavy metal removal effects. Therefore, the preparation process of the heavy metal chelating agent composite material of the present invention is a whole; the absence of any step or any raw material will affect the effect of the final product.

[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the methods and techniques disclosed above without departing from the scope of the present invention to create equivalent embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a heavy metal sequestering agent composite material, characterized by, The method comprises the following steps: S1: stirring montmorillonite in a dilute acid solution at 60-100℃ for 10-20 min, then taking it out and sequentially washing, drying, crushing, grinding to obtain montmorillonite powder; S2: dissolving polyvinyl acetate in a solvent to obtain a blending solution with a concentration of 30-50wt%, adding the obtained montmorillonite powder into the blending solution and stirring uniformly, then adding ionic monomer and initiator and continuously stirring at 50-70℃ for 4-10 h, then adding polyvinylpyrrolidone and stirring uniformly, after the stirring is completed, standing for 12-24 h, then filtering, washing and drying the obtained product to obtain modified montmorillonite copolymer composite; S3: placing the obtained modified montmorillonite copolymer composite in a 30-80wt% urea solution and heat treating at 100-150℃ for 20-30 min, then filtering, sequentially washing, freeze-drying and passing through an 80-200 mesh sieve to obtain heavy metal chelating agent composite material; In step S1, the dilute acid solution is a dicarboxylic acid solution with a concentration of 20-40wt%.

2. The production method according to claim 1, characterized by, The dicarboxylic acid is selected from one or more than two kinds of mixture of oxalic acid, malonic acid, succinic acid, adipic acid, maleic acid, fumaric acid and methylene succinic acid.

3. The preparation method according to claim 1, characterized in that, In step S2, the solvent is selected from any one of acetone, benzene or chloroform.

4. The method of claim 1, wherein, In step S2, the montmorillonite powder is added in an amount of 1g:5-15mL of mass volume ratio with the blending solution.

5. The preparation method according to claim 1, characterized in that, In step S2, the ionic monomer is selected from any one of N,N-dimethyl-N-acrylamide propyl-N-(2-carboxymethyl)-ammonium betaine, N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl)-ammonium betaine, N,N-dimethyl-N-acryloxyethyl-N-(3-sulfopropyl)-ammonium betaine and N,N-dimethyl-N-methacrylamide propyl-N-(3-sulfopropyl)-ammonium betaine.

6. The method of claim 1, wherein, In step S2, the initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptyl nitrile, azobisisobutylimidazoline hydrochloride and azobisisobutyrimidamide hydrochloride.

7. The preparation method according to claim 1, characterized in that, In step S2, the ionic monomer is added in an amount of 1-3:1 of mass ratio with polyvinyl acetate; the amount of the initiator added is 0.12-0.7% of the mass of the ionic monomer.

8. The method of claim 1, wherein, In step S2, the polyvinylpyrrolidone is added in an amount of 0.01-0.03:1 of mass ratio with polyvinyl acetate.

9. Application of the heavy metal chelating agent composite material prepared by the preparation method according to any one of claims 1-8 in heavy metal wastewater treatment.