A carbon-based adsorption material for remediation of heavy metal contaminated soil

Abstract

The application relates to the technical field of materials, and discloses a carbon-based adsorption material for treating heavy metal contaminated soil, which is prepared by using surface functionalized activated carbon as a base material, using bentonite and fly ash as auxiliary materials, bonding through biomass guar gum, and then mixing and sintering. The carbon-based adsorption material is prepared by using surface functionalized activated carbon as the main substance of the adsorption material, using bentonite and fly ash as auxiliary materials, realizing adsorption enrichment of heavy metal ions in the soil through the ultrahigh specific surface area of the activated carbon and the bentonite, then performing chemical solidification of the heavy metal ions by using active groups in the structure of the surface functionalized macromolecular reagent, and forming an adsorption mode of adsorption first and then solidification, so that the prepared adsorption material has extremely strong adsorption capacity and does not cause secondary pollution.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and specifically to a carbon-based adsorbent material for treating soil contaminated with heavy metals. Background Technology

[0002] With the acceleration of industrialization, heavy metal pollution has become one of the most serious challenges facing soil environments globally. Heavy metals such as lead, cadmium, chromium, and mercury pose a significant threat to ecosystems and human health due to their difficulty in degradation, their tendency to accumulate in organisms, and their transmission along the food chain. Therefore, developing efficient and environmentally friendly technologies for remediating heavy metal-contaminated soil is particularly important. Among the many methods for remediating heavy metal-contaminated soil, carbon-based adsorbent materials have gradually become a research hotspot for treating heavy metal-contaminated soil due to their excellent adsorption performance, environmental friendliness, and renewability.

[0003] Carbon-based adsorbents mainly include activated carbon, biochar, graphene, and their derivatives. They possess characteristics such as large specific surface area, abundant pore structure, and diverse surface functional groups. These properties enable them to effectively adsorb and immobilize heavy metal ions in soil. Applying carbon-based adsorbents directly to contaminated soil allows for the capture of heavy metal ions through physical adsorption, reducing their migration and bioavailability in the soil. This method is widely used due to its ease of operation. However, most conventional carbon-based adsorbents can only immobilize heavy metal ions in pores through physical adsorption. This physical immobilization method is not very stable, easily causing secondary pollution, and has limited adsorption capacity. These shortcomings significantly limit the application of carbon-based adsorbents in heavy metal contaminated soil. Therefore, developing carbon-based adsorbents with strong stability and excellent adsorption performance is of great significance. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a carbon-based adsorbent material for treating heavy metal-contaminated soil.

[0006] (II) Technical Solution

[0007] A carbon-based adsorbent material for remediating heavy metal contaminated soil comprises the following raw materials measured in parts by weight:

[0008]

[0009] As a further aspect of the present invention, the preparation method of the carbon-based adsorbent material includes the following steps:

[0010] Step 1: According to the weight proportions, mechanically stir and mix the surface-functionalized activated carbon, bentonite, biomass adhesive, fly ash and paraffin wax evenly to form a slurry;

[0011] Step 2: Transfer the slurry to a mold, let it stand for 10-30 minutes, then extrude and shape it to form a blank. Next, place the blank in a sintering furnace and raise the temperature to 280-320℃ at a heating rate of 3-5℃ / min. After 1-3 hours, take it out and let it cool naturally. Then crush it and pass it through an 80-100 mesh sieve to obtain the carbon-based adsorbent material.

[0012] As a further aspect of the present invention, the specific preparation method of the surface-functionalized activated carbon includes the following steps:

[0013] Step S1: Immerse the doped activated carbon in concentrated nitric acid and acidify it at a temperature of 90-100℃ for 1-3 hours. Remove it, wash it until neutral, and then dry it to form acidified activated carbon.

[0014] Step S2: Add acidified activated carbon to tetrahydrofuran and sonicate for 20-30 minutes to form a uniform dispersion. Then add the composite catalyst to the dispersion and stir at room temperature for 1-2 hours. Next, add the surface-functionalized macromolecular reagent to the dispersion. After the addition is complete, continue stirring at room temperature for 4-8 hours. Discharge the material, separate the solids, wash and vacuum dry to obtain the surface-functionalized activated carbon.

[0015] In the above technical solution, the doped activated carbon is first acidified with concentrated nitric acid to generate active carboxyl substituents on its surface. Then, a composite catalyst is used to catalyze the carboxyl substituents to esterify and condense with the hydroxyl groups in the structure of the surface-functionalized macromolecular reagent, thereby modifying the activated carbon surface with surface-functionalized macromolecular reagents to obtain surface-functionalized activated carbon.

[0016] As a further aspect of the present invention, in step S1, the specific preparation method of the doped activated carbon includes the following steps:

[0017] Step SS1: Add gellan gum to N,N-dimethylformamide, stir and disperse evenly, then add isocyanate monomer and dibutyltin dilaurate, mix well, raise the temperature to 70-80℃, stir and keep warm for 6-12 hours, then stop heating, cool down and discharge the material to form cross-linked carbon precursor;

[0018] Step SS2: Grind and mix the cross-linked carbon precursor and potassium hydroxide evenly, then place it in a tube furnace for carbonization treatment. After the treatment, remove it, allow it to cool naturally, wash it until neutral, and dry it completely to obtain doped activated carbon.

[0019] As a further aspect of the present invention, in step SS1, the isocyanate monomer is any one of toluene diisocyanate, isophorone diisocyanate, or dicyclohexylmethane diisocyanate.

[0020] As a further aspect of the present invention, in step SS2, the carbonization process is carried out at a temperature of 700-750°C for 1-3 hours under nitrogen protection.

[0021] In the above technical solution, isocyanate monomers are used as crosslinking agents to crosslink gellan gum to form a crosslinked carbon precursor. The crosslinked gellan gum is used as a carbon source, and isocyanate monomers are used as a nitrogen source. After activation with potassium hydroxide to form pores, and then carbonization at high temperature, nitrogen-doped activated carbon can be obtained.

[0022] As a further embodiment of the present invention, in step S2, the composite catalyst is a mixture of dicyclohexylcarbodiimide and 4-dimethylaminopyridine in a mass ratio of 1:0.3-0.4.

[0023] As a further aspect of the present invention, in step S2, the specific preparation method of the surface-functionalized macromolecular reagent includes the following steps:

[0024] Step SSS1: Add 3,5-dihydroxybenzonitrile and ethylene glycol diglycidyl ether to toluene and stir until completely dissolved to form a homogeneous reaction solution. Then add boron trifluoride diethyl ether complex to the reaction solution, purge with nitrogen for protection, raise the temperature to 80-90℃, stir continuously, keep warm for 8-12 hours, and then discharge to obtain the macromolecular precursor.

[0025] Step SSS2: Mix a 1-2 mol / L hydroxylamine hydrochloride solution with a 0.4-0.6 mol / L sodium carbonate solution to form a homogeneous mixture. Then add the macromolecular precursor to the mixture, control the temperature at 70-80℃, stir for 4-6 hours, cool down and discharge the material. After washing and vacuum drying, the surface-functionalized macromolecular reagent can be obtained.

[0026] As a further aspect of the present invention, in step SSS1, the molar ratio of 3,5-dihydroxybenzonitrile and ethylene glycol diglycidyl ether is 1:0.8-0.9.

[0027] As a further aspect of the present invention, in step SSS2, the volume ratio of the hydroxylamine hydrochloride solution to the sodium carbonate solution is 1:1.

[0028] In the above technical solution, 3,5-dihydroxybenzonitrile and ethylene glycol diglycidyl ether are first used as polymerization monomers. Under the catalysis of boron trifluoride diethyl ether complex, the active hydroxyl and epoxy groups between them can undergo continuous ring-opening reactions, thereby forming block-linked macromolecular substances, i.e., macromolecular precursors. Then, hydroxylamine hydrochloride is used to convert the cyano groups in its structure into amylopectin groups, and finally, a surface-functionalized macromolecular reagent containing a large number of amylopectin groups in its structure is obtained.

[0029] (III) Beneficial Technical Effects

[0030] This invention prepares surface-functionalized activated carbon by modifying the surface of nitrogen-doped activated carbon with a surface-functionalized macromolecular reagent containing a large number of amine oxime groups. Firstly, the surface-functionalized macromolecular reagent contains a large number of unreacted hydroxyl groups, as well as numerous ether bonds and amine oxime groups. The active hydroxyl and amine oxime groups can chelate and coordinate with heavy metal ions in the soil, chemically adsorbing them. This chemical adsorption is relatively stable, preventing secondary pollution and increasing the adsorption capacity of the material. Secondly, nitrogen is used to dope the activated carbon; the lone pair electrons of nitrogen can also complex with heavy metal ions, further enhancing the adsorption effect of the activated carbon.

[0031] This invention uses surface-functionalized activated carbon as the main adsorbent material and bentonite and fly ash as auxiliary materials. Through the ultra-high specific surface area of ​​activated carbon and bentonite, heavy metal ions in the soil are adsorbed and enriched. Then, the active groups in the structure of the surface-functionalized macromolecular reagent are used to chemically immobilize the heavy metal ions, forming an adsorption-immobilization adsorption mode. This makes the prepared adsorbent material have extremely strong adsorption capacity and does not cause secondary pollution. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a scanning electron microscope image of doped activated carbon.

[0034] Figure 2 Infrared spectra of surface-functionalized macromolecular reagents. Detailed Implementation

[0035] To facilitate understanding of the present invention, a more complete description will be provided below. Preferred embodiments of the invention are given below. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0036] Preparation Example 1

[0037] Preparation of surface-functionalized activated carbon:

[0038] Step S1: Immerse the doped activated carbon in concentrated nitric acid and acidify it at 95°C for 2 hours. Remove it, wash it until neutral, and then dry it to form acidified activated carbon.

[0039] Step S2: Add 1.5g of acidified activated carbon to tetrahydrofuran and sonicate for 30min to form a uniform dispersion. Then add 0.5g of dicyclohexylcarbodiimide and 0.2g of 4-dimethylaminopyridine to the dispersion. Stir at room temperature for 1h, then add 4g of surface-functionalized macromolecular reagent to the dispersion. After the addition is complete, continue stirring at room temperature for 6h. Discharge the material, separate the solid, wash and vacuum dry to obtain surface-functionalized activated carbon.

[0040] The preparation method of doped activated carbon is as follows:

[0041] Step SS1: Add 3g of gellan gum to N,N-dimethylformamide, stir and disperse evenly, then add 0.6g of toluene-2,4-diisocyanate and 0.01g of dibutyltin dilaurate, mix well, raise the temperature to 75℃, stir and keep warm for 9h, then stop heating, cool down and discharge the material to form a cross-linked carbon precursor;

[0042] Step SS2: Grind and mix 1.8g of cross-linked carbon precursor and 7g of potassium hydroxide evenly, then place it in a tube furnace and carbonize it at a carbonization temperature of 750℃ for 2 hours under nitrogen protection. After the carbonization is completed, remove it and let it cool naturally. Wash it until it is neutral and dry it completely to obtain doped activated carbon.

[0043] Figure 1 The scanning electron microscope image of the doped activated carbon clearly shows that it has a rich pore structure, and the overall structure presents a honeycomb-like porous structure.

[0044] The specific preparation method of surface-functionalized macromolecular reagents includes the following steps:

[0045] Step SSS1: Add 0.3g of 3,5-dihydroxybenzonitrile and 0.32g of ethylene glycol diglycidyl ether to toluene and stir until completely dissolved to form a homogeneous reaction solution. Then add 0.01g of boron trifluoride diethyl ether complex to the reaction solution, purge with nitrogen gas for protection, raise the temperature to 85℃, stir continuously, keep warm for 9 hours, and then discharge to obtain the macromolecular precursor.

[0046] Step SSS2: Mix 20 mL of 1 mol / L hydroxylamine hydrochloride solution with 20 mL of 0.5 mol / L sodium carbonate solution to form a homogeneous mixture. Then add 1 g of macromolecular precursor to the mixture, control the temperature at 70℃, stir for 6 h, cool down and discharge the material. After washing and vacuum drying, the surface-functionalized macromolecular reagent can be obtained.

[0047] Figure 2 The infrared spectrum of the surface-functionalized macromolecular reagent shows that the value at 3439 cm⁻¹ is [missing information]. -1 The characteristic absorption peak appearing at 3301 cm⁻¹ is the NH absorption peak of the amine oxime group. -1 The characteristic absorption peak appearing at 3000–3100 cm⁻¹ is the characteristic absorption peak of hydroxyl groups. -1 The characteristic absorption peak appearing at 1654 cm⁻¹ is a characteristic absorption peak of the benzene ring skeleton. -1 The characteristic absorption peak appearing at 1096 cm⁻¹ is the characteristic C=N absorption peak of the amine oxime group. -1 The characteristic absorption peak appearing at this point is the characteristic absorption peak of the ether bond generated by the ring-opening reaction.

[0048] Example 1

[0049] A carbon-based adsorbent material for remediating heavy metal contaminated soil comprises the following raw materials measured in parts by weight:

[0050]

[0051] The preparation method of the carbon-based adsorbent material includes the following steps:

[0052] Step 1: According to the weight proportions, mechanically stir and mix the surface-functionalized activated carbon, bentonite, biomass adhesive, fly ash and paraffin wax evenly to form a slurry;

[0053] Step 2: Transfer the slurry into a mold, let it stand for 10 minutes, then extrude and shape it to form a blank. Next, place the blank in a sintering furnace and raise the temperature to 280℃ at a heating rate of 5℃ / min. After 3 hours, take it out, let it cool naturally, crush it, and pass it through an 80-mesh sieve to obtain the carbon-based adsorbent material.

[0054] The preparation method of surface-functionalized activated carbon is described in Preparation Example 1, and the same applies to the following examples.

[0055] Example 2

[0056] A carbon-based adsorbent material for remediating heavy metal contaminated soil comprises the following raw materials measured in parts by weight:

[0057]

[0058] The preparation method of the carbon-based adsorbent material includes the following steps:

[0059] Step 1: According to the weight proportions, mechanically stir and mix the surface-functionalized activated carbon, bentonite, biomass adhesive, fly ash and paraffin wax evenly to form a slurry;

[0060] Step 2: Transfer the slurry to a mold, let it stand for 20 minutes, then extrude and shape it to form a blank. Next, place the blank in a sintering furnace and raise the temperature to 300℃ at a heating rate of 5℃ / min. After 2 hours, take it out, let it cool naturally, crush it, and pass it through a 100-mesh sieve to obtain the carbon-based adsorbent material.

[0061] Example 3

[0062] A carbon-based adsorbent material for remediating heavy metal contaminated soil comprises the following raw materials measured in parts by weight:

[0063]

[0064] The preparation method of the carbon-based adsorbent material includes the following steps:

[0065] Step 1: According to the weight proportions, mechanically stir and mix the surface-functionalized activated carbon, bentonite, biomass adhesive, fly ash and paraffin wax evenly to form a slurry;

[0066] Step 2: Transfer the slurry into a mold, let it stand for 30 minutes, then extrude and shape it to form a blank. Next, place the blank in a sintering furnace and raise the temperature to 320℃ at a heating rate of 5℃ / min. After 1 hour, take it out and let it cool naturally. Then crush it and pass it through a 100-mesh sieve to obtain the carbon-based adsorbent material.

[0067] Comparative Example 1

[0068] A carbon-based adsorbent material for remediating heavy metal contaminated soil comprises the following raw materials measured in parts by weight:

[0069]

[0070] The preparation method of the carbon-based adsorbent material includes the following steps:

[0071] Step 1: According to the weight proportions, mechanically stir and mix the doped activated carbon, bentonite, biomass adhesive, fly ash and paraffin wax evenly to form a slurry;

[0072] Step 2: Transfer the slurry to a mold, let it stand for 20 minutes, then extrude and shape it to form a blank. Next, place the blank in a sintering furnace and raise the temperature to 300℃ at a heating rate of 5℃ / min. After 2 hours, take it out, let it cool naturally, crush it, and pass it through a 100-mesh sieve to obtain the carbon-based adsorbent material.

[0073] The preparation method of the doped activated carbon is shown in Preparation Example 1.

[0074] Comparative Example 2

[0075] A carbon-based adsorbent material for remediating heavy metal contaminated soil comprises the following raw materials measured in parts by weight:

[0076]

[0077] The preparation method of the carbon-based adsorbent material includes the following steps:

[0078] Step 1: According to the weight proportions, mechanically stir and mix commercially available activated carbon, bentonite, biomass adhesive, fly ash and paraffin wax evenly to form a slurry;

[0079] Step 2: Transfer the slurry to a mold, let it stand for 20 minutes, then extrude and shape it to form a blank. Next, place the blank in a sintering furnace and raise the temperature to 300℃ at a heating rate of 5℃ / min. After 2 hours, take it out, let it cool naturally, crush it, and pass it through a 100-mesh sieve to obtain the carbon-based adsorbent material.

[0080] The commercially available activated carbon was purchased from Anhui Xingheng Environmental Protection Technology Co., Ltd. as Grade A bamboo charcoal with a fixed carbon content of ≥90.0%.

[0081] Test case

[0082] Heavy metal contaminated soil was extracted, and after removing all impurities, it was pulverized through a 100-mesh sieve, mixed with water, and prepared into a 2L test sample with a soil solids content of 200g / L. Then, 10mL of 1mol / L hydrochloric acid solution was added to the test sample, stirred at room temperature for 2 hours, and allowed to stand for 30 minutes. The heavy metal ion content in the supernatant was measured and recorded as m. The test sample was then divided into 5 equal portions, and 1.5g of the carbon-based adsorbent material from Examples 1-3 and Comparative Examples 1-2 was added to each portion. After addition, the mixture was stirred continuously for 8 hours, allowed to stand for 30 minutes, and the heavy metal ion content in the supernatant was measured and recorded as M. The adsorption rate was calculated using the formula [(mM) / m]×100%. The test results are shown in the table below:

[0083]

[0084] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

[0085] Based on the preferred embodiments of the present invention, and through the above description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A carbon-based adsorbent material for remediating heavy metal-contaminated soil, characterized in that, It is made from the following raw materials measured in parts by weight: 25-35 parts of surface-functionalized activated carbon; 5-12 parts bentonite; 4-8 parts guar gum; 3-6 parts fly ash; 3-5 parts paraffin; The preparation method of the carbon-based adsorbent material includes the following steps: Step 1: According to the weight proportions, mechanically stir and mix the surface-functionalized activated carbon, bentonite, guar gum, fly ash and paraffin wax evenly to form a slurry; Step 2: Transfer the slurry into a mold, let it stand for 10-30 minutes, then extrude and shape it to form a blank. Next, place the blank in a sintering furnace and raise the temperature to 280-320℃ at a heating rate of 3-5℃ / min. After 1-3 hours, take it out and let it cool naturally. Then crush it and pass it through an 80-100 mesh sieve to obtain the carbon-based adsorbent material. The specific preparation method of the surface-functionalized activated carbon includes the following steps: Step S1: Immerse the doped activated carbon in concentrated nitric acid and acidify it at a temperature of 90-100℃ for 1-3 hours. Remove it, wash it until neutral, and then dry it to form acidified activated carbon. Step S2: Add acidified activated carbon to tetrahydrofuran and sonicate for 20-30 minutes to form a uniform dispersion. Then add the composite catalyst to the dispersion and stir at room temperature for 1-2 hours. Next, add the surface-functionalized macromolecular reagent to the dispersion. After the addition is complete, continue stirring at room temperature for 4-8 hours. Discharge the material, separate the solids, wash and vacuum dry to obtain the surface-functionalized activated carbon. The specific preparation method of the doped activated carbon includes the following steps: Step SS1: Add gellan gum to N,N-dimethylformamide, stir and disperse evenly, then add isocyanate monomer and dibutyltin dilaurate, mix well, raise the temperature to 70-80℃, stir and keep warm for 6-12 hours, then stop heating, cool down and discharge the material to form cross-linked carbon precursor; Step SS2: Grind and mix the cross-linked carbon precursor and potassium hydroxide evenly, then place it in a tube furnace for carbonization treatment. After the treatment, remove it, let it cool naturally, wash it until neutral, and dry it completely to obtain doped activated carbon. The specific preparation method of the surface-functionalized macromolecular reagent includes the following steps: Step SSS1: Add 3,5-dihydroxybenzonitrile and ethylene glycol diglycidyl ether to toluene and stir until completely dissolved to form a homogeneous reaction solution. Then add boron trifluoride diethyl ether complex to the reaction solution, purge with nitrogen for protection, raise the temperature to 80-90℃, stir continuously, keep warm for 8-12 hours, and then discharge to obtain the macromolecular precursor. Step SSS2: Mix a 1-2 mol / L hydroxylamine hydrochloride solution with a 0.4-0.6 mol / L sodium carbonate solution to form a homogeneous mixture. Then add the macromolecular precursor to the mixture, control the temperature at 70-80℃, stir for 4-6 hours, cool down and discharge the material. After washing and vacuum drying, the surface-functionalized macromolecular reagent can be obtained.

2. The carbon-based adsorbent material for remediating heavy metal contaminated soil according to claim 1, characterized in that, In step SS1, the isocyanate monomer is any one of toluene diisocyanate, isophorone diisocyanate, or dicyclohexylmethane diisocyanate.

3. The carbon-based adsorbent material for remediating heavy metal contaminated soil according to claim 1, characterized in that, In step SS2, the carbonization process is carried out at a temperature of 700-750℃ for 1-3 hours under nitrogen protection.

4. The carbon-based adsorbent material for remediating heavy metal contaminated soil according to claim 1, characterized in that, In step S2, the composite catalyst is a mixture of dicyclohexylcarbodiimide and 4-dimethylaminopyridine in a mass ratio of 1:0.3-0.

4.

5. The carbon-based adsorbent material for remediating heavy metal contaminated soil according to claim 1, characterized in that, In step SSS1, the molar ratio of 3,5-dihydroxybenzonitrile and ethylene glycol diglycidyl ether is 1:0.8-0.

9.

6. The carbon-based adsorbent material for remediating heavy metal contaminated soil according to claim 1, characterized in that, In step SSS2, the volume ratio of the hydroxylamine hydrochloride solution to the sodium carbonate solution is 1:1.

Images