Negative carbon modified clay-based salt-tolerant anti-seepage material and preparation method thereof

Abstract

The invention discloses a preparation method of a negative carbon modified clay-based salt-tolerant anti-seepage material, which comprises the following steps: grinding natural bentonite, washing with water to remove coarse particles, adding into a NaCl solution for sodium treatment, washing, and drying to obtain sodium bentonite powder; dispersing the obtained sodium bentonite powder in deionized water, carrying out shearing dispersion to realize lamella stripping, and carrying out centrifugal treatment to remove undispersed large particles so as to obtain highly dispersed nanosheet liquid; dissolving organic amine in the nanosheet liquid, adjusting the pH value to 8.5-9.0, heating to 60-80 DEG C, carrying out intercalation reaction for 4-24 hours, washing, and drying to obtain organic amine modified bentonite; the organic amine modified bentonite is mixed with water to obtain wet soil, the wet soil is placed in a fixed bed adsorber, CO2 gas is introduced, and the organic amine modified bentonite fully adsorbs CO2; and carrying out compression molding on the modified bentonite after adsorbing CO2 according to a set compaction degree to obtain the negative carbon modified clay-based salt-tolerant anti-seepage material.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of environmental engineering and material technology, and specifically relates to a clay-based salt-resistant anti-seepage material. BACKGROUND

[0002] Bentonite is a kind of layered silicate mineral, which is widely used in anti-seepage systems in solid waste landfills, tailings ponds and other solid waste landfills due to its good swelling property, ion exchange capacity and ultra-low permeability. Its rich adsorption capacity and low cost make it an ideal choice for clay-based anti-seepage materials. However, under the action of high salt environment (such as landfill leachate, tailings seepage), the swelling property and pore sealing ability of bentonite are significantly reduced, resulting in a significant increase in its permeability coefficient and weakening of its anti-seepage function, thereby seriously affecting its long-term service performance.

[0003] Studies have shown that when bentonite is exposed to an environment containing high concentrations of multivalent salt ions, particle flocculation and microstructure damage are likely to occur, causing pore expansion and anti-seepage interface failure, making it difficult to meet the requirements of long-term safe operation of solid waste landfills. To improve its salt resistance, a variety of modification methods have been proposed, such as adding inorganic salt regulators, polymer composites or cationic surface modifiers. These methods can alleviate the impact of high salt on bentonite to some extent, but their effectiveness is limited and they cannot fundamentally solve the problem of interface stability under the combined action of high salt and multiple ions, and they cannot endow the material with carbon capture or emission reduction function.

[0004] At the same time, bentonite and its main component mineral montmorillonite have important potential in the field of carbon dioxide capture and mineralization sequestration due to their rich interlayer structure and specific surface area. The adsorption of natural montmorillonite on CO2 is mainly physical adsorption, with limited adsorption capacity, and due to its strong hydrophilicity, it is difficult to effectively interact with nonpolar CO2. To improve its adsorption performance, organic amines (such as quaternary ammonium salts, fatty amines, imidazoles) are usually used for interlayer organic modification. After modification, CO2 active sites can be introduced, the specific surface area and pore structure can be adjusted, and the chemical adsorption capacity can be significantly enhanced. However, such adsorbents are mostly reversible adsorption, and CO2 can be desorbed under certain conditions, which cannot achieve long-term fixation and cannot meet the stability requirements of carbon sequestration. Therefore, relying solely on the anti-seepage function of bentonite or the CO2 adsorption function of montmorillonite cannot meet the dual requirements of interface stability and carbon emission reduction capacity of anti-seepage materials in high salt environment. SUMMARY

[0005] The application aims to provide a carbon-negative modified clay-based salt-resistant anti-seepage material and a preparation method thereof, which can realize permanent mineralization and fixation of CO2 by using multivalent cations in a high-salt environment, block the pores of the material itself, and enhance the structural stability, effectively solving the technical problem that traditional bentonite is easy to fail in a high-salt environment, and significantly improving the anti-seepage performance and durability of the material in a high-salt environment.

[0006] To achieve the above-mentioned purpose, the technical scheme is as follows: The application aims to provide a carbon-negative modified clay-based salt-resistant anti-seepage material and a preparation method thereof, which can realize permanent mineralization and fixation of CO2 by using multivalent cations in a high-salt environment, block the pores of the material itself, and enhance the structural stability, effectively solving the technical problem that traditional bentonite is easy to fail in a high-salt environment, and significantly improving the anti-seepage performance and durability of the material in a high-salt environment. (1) The natural bentonite is ground and washed to remove coarse particles, and then added into a NaCl solution for sodium treatment, and after washing and drying, a sodium-based bentonite powder is obtained; (2) The obtained sodium-based bentonite powder is dispersed in deionized water, and shear dispersion is performed to realize sheet layer peeling, and centrifugal treatment is performed to remove undispersed large particles, and a highly dispersed nanosheet liquid is obtained; (3) An organic amine is dissolved in the nanosheet liquid, the pH is adjusted to 8.5-9.0, the temperature is raised to 60-80℃, and intercalation reaction is performed for 4-24 hours, and after washing and drying, an organic amine modified bentonite is obtained; (4) The organic amine modified bentonite is mixed with water to obtain wet soil, and CO2 gas is introduced into a fixed bed adsorber to make the organic amine modified bentonite fully adsorb CO2; (5) The modified bentonite after adsorbing CO2 is pressed into a shape according to a set compaction degree, and a carbon-negative modified clay-based salt-resistant anti-seepage material is obtained.

[0007] According to the above scheme, the concentration of the NaCl solution for sodium treatment in step 1 is 0.5-1.0 mol / L, the temperature is 40-60℃, and the stirring time is 2-4 hours.

[0008] According to the above scheme, the drying temperature in step 1 is 60-80℃, the drying time is 8-12 hours, and after drying, the material is ground and passed through a 200-mesh sieve.

[0009] According to the above scheme, the mass ratio of the sodium-based bentonite powder to deionized water in step 2 is 1: (50-100).

[0010] According to the above scheme, after shear dispersion in step 2, ultrasonic treatment is performed for 10-60 minutes to promote sheet layer peeling.

[0011] According to the above scheme, a polar solvent is added to the obtained nanosheet liquid in step 2 to improve the dispersion effect.

[0012] According to the above scheme, the organic amine in step 3 is one or a combination of triethylenetetramine, ethylenediamine, diethylenetriamine, and dodecylamine.

[0013] According to the above scheme, step 3 adds the organic amine in an amount of 1-3 times the cation exchange capacity (CEC) of bentonite; a dispersing aid is also added, and the temperature is raised to 40-60 DEG C to improve the dissolution efficiency.

[0014] According to the above scheme, step 3 is assisted by ultrasound to improve the efficiency of the intercalation reaction. After the reaction is completed, the mixture is allowed to stand for more than 12 hours.

[0015] According to the above scheme, the wet soil in step 4 has a water content of about 5-10 wt%.

[0016] According to the above scheme, the temperature of the fixed bed in step 4 is 25-40 DEG C, and the adsorption time is 1-3 hours.

[0017] According to the above scheme, the amount of carbon fixed in the organic amine modified bentonite obtained in step 4 is 2-8 wt%.

[0018] The present application also provides a carbon-negative modified clay-based salt-tolerant impermeable material prepared by the above method. The application also provides the use of the carbon-negative modified clay-based salt-tolerant impermeable material as an impermeable layer for a landfill.

[0019] The present application proposes a synergistic mechanism based on "organic intercalation-CO2 adsorption-mineralization precipitation-interfacial self-repairing", and constructs a carbon-negative clay-based impermeable interface material, which significantly improves the structural stability and impermeability of bentonite in a high-salt environment; and realizes the conversion and long-term storage of CO2 into stable carbonate form. First, the natural bentonite is modified into sodium-based bentonite. Because the interlayer structure of sodium-based bentonite is peeled off under the combined action of mechanical force and ultrasound, its large specific surface area is unfolded, providing space conditions for the subsequent modification of the bentonite interface by organic amine. Through a cation exchange reaction, triethylenetetramine (TETA) is grafted onto the interface of the bentonite layer structure, which improves the chemical adsorption capacity of the material for CO2 by introducing abundant amine groups; at the same time, by controlling the degree of cation exchange reaction, the interlayer spacing and hydrophilicity are adjusted to retain certain swelling properties and maintain the impermeability characteristics. In a high-salt environment or landfill leachate, multivalent cations (such as Ca 2+ , Mg 2+ ) participate in the mineralization reaction. The reaction takes place in the limited space between the layers of bentonite. Due to the confinement effect, the interlayer space promotes the formation of small crystal nuclei, and the slow seepage speed of the landfill leachate is conducive to the formation of nanoscale CaCO3 and other precipitates. The generation of nanoscale calcium carbonate crystals in the interlayer or micropores in situ seals the micropores, significantly reducing the permeability; it can realize the "self-sealing-self-repairing" effect, enhance the salt-tolerant sealing performance of the material as an impermeable material; at the same time, it can realize long-term carbon stable storage, avoiding the leakage risk of geological and marine storage. In addition, the generated nanoscale calcium carbonate enhances the skeleton structure through physical cementation, improves the interfacial damage resistance, and endows the material with long-term structural stability and anti-scouring ability.

[0020] The present application has the following advantages over the prior art: Significantly enhance the CO2 adsorption capacity of bentonite, and give it a negative carbon function. The use of water-soluble organic amine (such as TETA) and PEG for intercalation modification significantly improves the chemical adsorption capacity of bentonite for CO2; the intercalation forms an ordered structure, stabilizes the amine group sites, improves the adsorption selectivity and immobilization efficiency, and realizes the integrated negative carbon process of CO2 capture-mineralization-sequestration; after adsorbing CO2, nanoscale CaCO3 can be induced to form in the pores or interlayers, realizing long-term carbon fixation, and having good green carbon sequestration potential.

[0021] Improve the structural stability and anti-permeation ability of the material in a high-salt environment. The nanoscale carbonates (such as CaCO3, MgCO3) formed during the CO2 mineralization process cement the bentonite layers, enhancing their mechanical strength and interface stability; the multivalent cations in the high-salt waste liquid react with CO2 to form a precipitate, which in-situ blocks the seepage channels in the pores, forming a micro "self-healing" effect, and improving the low permeability and structural stability of the material in a high-salt environment; the organic intercalation modification controls the interlayer space, retains part of the swelling and dispersibility, so that it still has good sealing performance in wet applications.

[0022] Multiple synergistic functions, green process, and wide applicability. The process is simple, can be carried out in water, has mild reaction conditions, and uses low-cost raw materials, making it suitable for large-scale and engineering applications; the modified bentonite does not need to be treated with additional sand to meet the strength requirements, making it easy to construct; effectively utilizes the discharged CO2 and mixed ion leachate, realizes the resource utilization of solid waste, and reduces environmental pollution; the finished product can be widely used in landfill sites, tailings ponds, saline-alkali soils, and other environmental engineering scenarios that require long-term salt-tolerant and anti-permeation.

[0023] The present application synergistically improves the performance of clay-based anti-permeation systems from three dimensions: material interface structure regulation, efficient CO2 adsorption and conversion, and high-salt environment adaptation, has the functional characteristics of "carbon sequestration, anti-permeation, and strength improvement", and takes into account environmental friendliness and engineering feasibility, making it have broad prospects for popularization. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 : Schematic diagram of bentonite layer peeling.

[0025] Figure 2 : Schematic diagram of bentonite layer surface grafting organic amine.

[0026] Figure 3 : Schematic diagram of the present application generating nanoscale calcium carbonate precipitate in a high-salt solution. DETAILED DESCRIPTION

[0027] The following examples further illustrate the technical solutions of the present application, but are not intended to limit the scope of protection of the present application.

[0028] DETAILED DESCRIPTION provides a carbon-negative modified clay-based salt-tolerant impermeable material: I. Preparation of uniform ion sodium-based bentonite: (1) Bentonite pretreatment: Take natural bentonite (such as 100 g), grind and sieve (<200 mesh) to improve the reactivity; if there are more impurities, first wash with water and settle to remove coarse particles and sand particles, discard the supernatant, and take the fine particles. (2) Sodium treatment: Prepare a NaCl solution (sodium agent), weigh an appropriate amount of NaCl and dissolve in a certain amount of deionized water to prepare a NaCl solution with a concentration of 0.5 mol / L; add bentonite to the NaCl solution, stir at 40-60°C for 2-4 hours (can be extended to 12 hours to improve exchange efficiency), promote the exchange of exchangeable Ca 2+ , Mg 2+ , etc. in the montmorillonite mineral to Na + . Stand for 24 hours to complete the sodium ion exchange and grading settlement. (3) Washing and drying: wash with deionized water 3-5 times until the filtrate is close to neutral, and ensure that the excess Na + is removed; put the wet bentonite sample into a drying oven and dry at 60-80°C for 8-12 hours; grind and pass through a 200 mesh sieve after drying to obtain a uniform sodium-based bentonite powder.

[0029] II. Dispersing and exfoliating sodium-based bentonite to expand the interlayer spacing: (1) Preparation of suspension: Add sodium-based bentonite to deionized water at a ratio of 1:50, stir to form a uniform suspension; (2) High-energy dispersion and exfoliation: Use a high-speed shear disperser to exfoliate the interlayer structure by strong mechanical force; then use an ultrasonic cleaner or a probe-type ultrasonic instrument for 10-60 minutes to promote the exfoliation of the lamella; (3) Centrifugal removal of large particles: Put the dispersed suspension into a centrifuge to remove large particles that have not been dispersed, and obtain a highly dispersed nanosheet liquid. To improve the dispersion effect, a small amount of polar solvent (such as ethanol, dimethyl sulfoxide DMSO, etc.) that is compatible with sodium-based montmorillonite can be added to the aqueous solution and heated and stirred to reduce the interlayer force and facilitate the separation of the lamella. The schematic diagram of the exfoliation of bentonite lamella is shown in FIG. Figure 1 .

[0030] III. Organic amine intercalation modification to construct CO2-active interface: (1) Preparation of organic amine solution: Dissolve triethylenetetramine (TETA) or other organic amines in a solution prepared by the above method to obtain highly dispersed nanosheet liquid, according to 1-3 times the CEC (cation exchange capacity) of bentonite. Heat to 40-60℃ to improve solubility, and dissolve by magnetic stirring. Add 2-4 g / L polyethylene glycol (PEG-200) as a dispersant, and adjust the pH to 8.5-9.0 with 0.1 mol / L NaOH to promote amine protonation (-NH4+). 3+ (2) Intercalation reaction via cation exchange: The above-mentioned dispersed bentonite nanosheet liquid and organic amine mixture are stirred at 60-80℃ for 4-24 hours, and ultrasound can be used to improve the intercalation efficiency; let stand for 12 hours to age, so that the organic amine can fully react with the exchangeable cation Na between the montmorillonite sheets. + Exchange occurs, and the amines are uniformly grafted onto the surface of the bentonite sheets. (3) Washing and drying: Wash 3-5 times with an ethanol-water (1:1) mixture to remove unreacted amines and impurities. Dry at 60-80℃, or vacuum drying if available. Grind and sieve (<200 mesh) to obtain organic amine-modified bentonite. See attached diagram for a schematic diagram of organic amine grafting onto the surface of bentonite sheets. Figure 2 As shown.

[0031] IV. CO2 Adsorption and Carbon Negation Treatment: (1) Pre-hydration treatment: The dried organic amine modified bentonite is pre-hydrated to prepare wet soil with a water content of about 10%, which can achieve the maximum adsorption performance of CO2. (2) CO2 adsorption reaction: The wet soil is placed in a fixed bed adsorber, and pure CO2 gas (≥99.5%, flow rate 50-100 mL / min) is introduced and reacted at 25-40℃ for 1-3 hours. This allows the bentonite surface and organic amine groups to fully adsorb CO2, and the amount of negative carbon fixed can reach 2-8 wt%.

[0032] V. Interfacial sedimentation enhancement during the formation and operation of the seepage barrier layer: (1) Compaction molding: The modified bentonite after adsorbing CO2 is pressed into shape according to the set compaction degree. The resulting carbon-modified clay-based salt-resistant seepage-proof material adsorbs a large amount of CO2 during the preparation process. Under the action of high-salt leachate (such as landfill leachate), the Ca in the liquid 2+ Mg 2+ Isovalent cations react with HCO3 generated after CO2 adsorption in modified bentonite - / CO3 2-Reaction, in-situ formation of CaCO3, MgCO3 and other nano precipitates. These precipitates limit the growth of the interlamellar structure and the pores, effectively blocking the microchannels, enhancing the interface stability and salt tolerance, thus realizing the integration of "CO2 adsorption-mineralization-blocking", and improving the long-term anti-seepage and carbon sequestration functions of the material. Because nano calcium carbonate will be generated during the CO2 mineralization process, the interlamellar structure of the cemented bentonite will be significantly enhanced, the mechanical properties of the anti-seepage material will be significantly enhanced, and the strength of the formed material will be improved. The mechanical properties and micro-compactness of the formed material are good. The schematic diagram of the negative carbon modified clay-based salt-tolerant anti-seepage material generating nano calcium carbonate precipitates in a high salt solution is shown in FIG. 1. Figure 3

[0033] Example 1 (1) Take 100 g of natural bentonite, grind and sieve 200 mesh, wash with water and settle to remove coarse particles and sand particles, discard the supernatant, and take the fine particles. A 0.5 mol / L NaCl solution is prepared, and the bentonite is added to the NaCl solution, stirred at 50°C for 3 hours, and left to stand for 24 hours to complete the sodium ion exchange and classification settlement. Wash with deionized water until the filtrate is nearly neutral, dry in a drying oven, grind and sieve 200 mesh, and obtain a uniform sodium-based bentonite powder.

[0034] (2) The obtained sodium-based bentonite is added to deionized water at a ratio of 1:50, stirred to form a uniform suspension, and then a high-speed shearing disperser is used to separate the interlamellar structure, and then an ultrasonic cleaning machine or a probe-type ultrasonic instrument is used for treatment for 60 minutes to promote the separation of the lamella; the dispersed suspension is placed in a centrifuge to remove large particles that have not been dispersed, and a highly dispersed nanosheet liquid is obtained.

[0035] (3) According to 3 times the amount of CEC of bentonite, triethylenetetramine is dissolved in the above highly dispersed nanosheet liquid, heated to 60°C, 4 g / L polyethylene glycol is added as a dispersing agent, the pH is adjusted to 8.5 with 0.1 mol / L NaOH, and the temperature is raised to 70°C, and the reaction is stirred for 12 hours, and then left to stand for 12 hours to age, washed with an ethanol / water (1:1) mixture, vacuum dried, ground and sieved 200 mesh, and an organic amine modified bentonite is obtained.

[0036] (4) The above dried organic amine modified bentonite is pre-hydrated to prepare a wet soil with a water content of 10%, placed in a fixed bed adsorber, and pure CO2 gas (≥99.5%, flow rate 100 mL / min) is introduced, and the reaction is carried out at 40°C for 2 hours to allow the surface of the bentonite and the organic amine groups to fully adsorb CO2.

[0037] (5) The modified bentonite after adsorbing CO2 is compacted according to the set compaction degree to form a negative carbon modified clay-based salt-tolerant anti-seepage material.

[0038] ​Comparative Example 1 The steps (1), (2), (3) of Example 1 were repeated, and the obtained organic amine modified bentonite was pre-hydrated to prepare wet soil with a water content of 10%, and then was pressed to form a clay-based impermeable interface material according to the set compaction degree.

[0039] The impermeable materials prepared in Example 1 and Comparative Example 1 were applied in a simulated high-salt environment, and the salt-resistant impermeability was detected. The impermeable layer was pressed to form a thickness of 10 mm with a compaction degree of 90%; the simulated percolate (high-salt aqueous solution) was Na + = 3000 mg / L, Ca 2+ = 800 mg / L, Mg 2+ = 500 mg / L; the water head pressure was 30 cm, and the temperature was room temperature 25℃; the penetration coefficient test method was the equal water head method, and the continuous immersion penetration was 30 days, and the test results are shown in Table 1.

[0040] Table 1

[0041] The penetration coefficient of Example 1 slightly decreased in the high-salt environment, indicating that the adsorbed CO2 continued to have in-situ CaCO3 / MgCO3 precipitation reaction under the action of the percolate, plugging the micropores of the layer structure, effectively enhancing the impermeability; Comparative Example 1 was not treated by CO2 adsorption, and lacked precipitation reaction, resulting in significant changes in the microstructure under the action of high salt, resulting in the appearance of large pores, which increased the penetration coefficient by two orders of magnitude.

[0042] The impermeable layer samples above which were continuously immersed in the high-salt environment for 30 days were sampled and tested for mechanical properties. The test method was the unconfined compressive strength test and the direct shear strength test (four-pair shear instrument, normal consolidation condition), and the samples were tested under the same compaction degree, and the test results are shown in Table 2.

[0043] Table 2

[0044] The adsorbed CO2 in Example 1 formed carbonate precipitates, cementing the layers and pores, significantly improving the compressive strength and cohesion. Its structure is more compact and stable, and can withstand higher compression and shear load, especially suitable for long-term buried, load environment impermeable sealing structure.

Claims

1. A method for preparing a carbon-negative modified clay-based salt-tolerant impermeable material, characterized by The method comprises the following steps: (1) grinding natural bentonite, washing to remove coarse particles, adding NaCl solution for sodium treatment, washing and drying to obtain sodium-based bentonite powder; (2) dispersing the obtained sodium-based bentonite powder in deionized water, shearing and dispersing to achieve sheet layer peeling, removing undispersed large particles by centrifugal treatment, and obtaining a highly dispersed nanosheet liquid; (3) dissolving an organic amine in the nanosheet liquid, adjusting the pH to 8.5-9.0, and heating to 60-80℃ for intercalation reaction for 4-24 hours, washing and drying to obtain organic amine modified bentonite; (4) mixing the organic amine modified bentonite with water to obtain wet soil, and passing CO2 gas into a fixed bed adsorber to allow the organic amine modified bentonite to fully adsorb CO2; (5) pressing the modified bentonite after adsorbing CO2 into a certain compactness to obtain a carbon-negative modified clay-based salt-resistant impermeable material.

2. The preparation method of the carbon-modified clay-based salt-resistant seepage-proof material as described in claim 1, characterized in that... In step 1, the concentration of the NaCl solution for sodium treatment is 0.5-1.0 mol / L, the temperature is 40-60℃, and the stirring time is 2-4 hours.

3. The preparation method of the carbon-modified clay-based salt-resistant seepage-proof material as described in claim 1, characterized in that... In step 1, the drying temperature is 60-80℃, the drying time is 8-12 hours, and after drying, grinding and passing through a 200 mesh sieve.

4. The preparation method of the carbon-modified clay-based salt-resistant seepage-proof material as described in claim 1, characterized in that... In step 2, the mass ratio of sodium-based bentonite powder to deionized water is 1: (50-100).

5. The preparation method of the carbon-modified clay-based salt-resistant seepage-proof material as described in claim 1, characterized in that... After shearing and dispersing in step 2, ultrasonic treatment is used for 10-60 minutes to promote sheet layer peeling.

6. The method of claim 1, wherein the carbon-modified clay-based salt-tolerant impermeable material is prepared by the steps of: a) mixing a clay with a carbon source; b) heating the mixture to a temperature of 500- 1000°C; c) cooling the mixture to room temperature; and d) washing the mixture with water. In step 2, a polar solvent is added to the obtained nanosheet liquid to improve the dispersion effect.

7. The method of claim 1, wherein the carbon-modified clay-based salt-tolerant impermeable material is prepared by the steps of: a) mixing the clay with the carbon source; b) heating the mixture to a temperature of 500- 1000°C; c) cooling the mixture to room temperature; and d) washing the mixture with water. In step 3, the organic amine is one or any combination of triethylenetetramine, ethylenediamine, diethylenetriamine, and dodecylamine.

8. The preparation method of the carbon-modified clay-based salt-resistant seepage-proof material as described in claim 1, characterized in that... In step 3, the organic amine is added in an amount of 1-3 times the cation exchange capacity of the bentonite; a dispersing aid is also added, and the temperature is raised to 40-60℃ to improve the dissolution efficiency.

9. The preparation method of the carbon-modified clay-based salt-resistant seepage-proof material as described in claim 1, characterized in that... In step 3, ultrasonic waves are used to assist the intercalation reaction to improve the efficiency, and after the reaction is completed, the mixture is allowed to stand for more than 12 hours.

10. The preparation method of the carbon-modified clay-based salt-resistant seepage-proof material as described in claim 1, characterized in that... In step 4, the moisture content of the wet soil is 5-10 wt%.

11. The preparation method of the carbon-modified clay-based salt-resistant seepage-proof material as described in claim 1, characterized in that... In step 4, the fixed bed adsorption temperature is 25-40℃, and the adsorption time is 1-3 hours.

12. The preparation method of the carbon-modified clay-based salt-resistant seepage-proof material as described in claim 1, characterized in that... In step 4, the carbon fixation amount of the organic amine modified bentonite is 2-8 wt%.

13. A carbon-negative modified clay-based salt-resistant impermeable material prepared by the method of any one of claims 1-12.

14. The use of the carbon-negative modified clay-based salt-resistant impermeable material of claim 13 as an impermeable layer for a landfill.

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