Environment-friendly bentonite composite material and preparation method thereof

Abstract

The present application relates to bentonite composite material technical field, specifically to an environment-friendly bentonite composite material and a preparation method thereof, comprising the following components: sodium-based bentonite, modified montmorillonite, composite microspheres. 2+ When invading, the sodium carboxymethyl cellulose adsorbed between the layers of the modified montmorillonite delays the diffusion rate of Ca 2+ to the interlayer, at the same time, the outer γ-PGA / Ca 2+ crosslinking coating of the composite microspheres releases the internal Na + and sodium polyphosphate, and the polyphosphate and PDA-EDTA together chelate and fix Ca 2+ . The Na + released by the composite microspheres is captured by the crown ether of the modified montmorillonite with high selectivity, and the Na + supplements the interlayer. The PDA-EDTA coating can enhance the interface stability, form an interface anchoring between the outer surface of the modified montmorillonite and the sodium carboxymethyl cellulose segment, and prevent the sodium carboxymethyl cellulose segment from falling off under the flushing of the seepage fluid.

Description

Technical Field

[0001] This invention belongs to the field of bentonite composite material technology, specifically an environmentally friendly bentonite composite material and its preparation method. Background Technology

[0002] Bentonite composite waterproof blankets are geosynthetic seepage-proof materials composed of sodium-based bentonite particles and geotextiles. They are widely used in sanitary landfills, mine tailings ponds, reservoirs, and underground engineering seepage prevention. Their waterproofing mechanism relies on the Na+ interlayer in the sodium-based montmorillonite. + High degree of hydration and expansion.

[0003] However, when bentonite composite waterproofing blankets come into contact with high concentrations of Ca... 2+ Mg 2+ When leachate containing divalent cations (such as landfill leachate, coal combustion by-product leachate, and mine acidic wastewater), interlayer Na + The replacement of montmorillonite with high-valence cations through cation exchange leads to a sudden contraction of the interlayer spacing, loss of montmorillonite's swelling capacity, and a sharp increase in the permeability coefficient. Simultaneously, after ion exchange, the expansion and sealing pressure of montmorillonite on the needle-punched fiber bundles in the bentonite composite waterproofing blanket geotextile decreases, creating preferential seepage channels around the fiber bundles and further exacerbating the increase in permeability. Ultimately, this results in a significant deterioration of the seepage prevention performance of the bentonite composite waterproofing blanket. Summary of the Invention

[0004] (1) Technical problems to be solved

[0005] The purpose of this invention is to provide an environmentally friendly bentonite composite material and its preparation method, so as to solve the problem of high concentration Ca 2+ In chemically corrosive environments, existing sodium-based bentonite is affected by Na... + by Ca 2+ The problem of significant deterioration in impermeability caused by replacement.

[0006] (2) Technical solution

[0007] To achieve the above objectives, on the one hand, the present invention provides an environmentally friendly bentonite composite material, comprising the following components in parts by weight: 70-80 parts of sodium-based bentonite, 15-22 parts of modified montmorillonite, and 4-8 parts of composite microspheres;

[0008] The modified montmorillonite is based on crown ether-grafted sodium carboxymethyl cellulose-montmorillonite, with a PDA-EDTA coating deposited on its surface;

[0009] The composite microspheres are Na + Pre-saturated covalently cross-linked sodium alginate microspheres encapsulated with sodium polyphosphate, with the outermost layer coated with γ-PGA / Ca 2+ Cross-linked coated composite microspheres.

[0010] Furthermore, the PDA-EDTA coating accounts for 22-30% of the total mass of the modified montmorillonite.

[0011] Furthermore, the preparation method of the modified montmorillonite includes the following steps:

[0012] S11. Add sodium montmorillonite to deionized water, stir to disperse, heat and continue stirring, let stand and cool to obtain swollen sodium montmorillonite;

[0013] S12. Dissolve sodium carboxymethyl cellulose in deionized water, slowly add it to the swollen sodium montmorillonite, adjust the pH with NaOH, stir the reaction, dialysis the resulting reaction solution, freeze dry it to obtain sodium carboxymethyl cellulose-sodium montmorillonite;

[0014] S13. Disperse sodium carboxymethyl cellulose-sodium montmorillonite in MES buffer to obtain a suspension. Dissolve EDC·HCl and NHS in MES buffer and add them to the suspension. Stir to activate. Add PBS buffer to adjust the pH to obtain an activated solution. Dissolve amino-15-crown ether-5 in PBS buffer and slowly add it dropwise to the activated solution. Stir to react. Add hydroxylamine hydrochloride. Wash the obtained product and freeze-dry to obtain crown ether-grafted sodium carboxymethyl cellulose-montmorillonite.

[0015] S14. Dissolve EDTA in MES buffer with stirring to obtain an EDTA solution. Dissolve EDC·HCl and NHS in MES buffer respectively, and add them to the EDTA solution sequentially. Stir to activate. After activation, add PBS buffer to obtain an activated solution. Add ethylenediamine to PBS buffer, adjust the pH with HCl, and slowly add it dropwise to the activated solution while stirring. After the reaction is complete, add hydroxylamine hydrochloride and stir. The resulting reaction solution is purified by dialysis and freeze-dried to obtain EDTA-EA.

[0016] S15. Dopamine hydrochloride and EDTA-EA were mixed and dissolved in deionized water and stirred until completely dissolved to obtain a mixed solution; crown ether-grafted sodium carboxymethyl cellulose-montmorillonite was ultrasonically dispersed in deionized water, NaOH was added to adjust the pH, the mixed solution was added, the mixture was stirred at room temperature, allowed to stand for self-polymerization, the obtained product was centrifuged, washed with deionized water, and freeze-dried to obtain modified montmorillonite.

[0017] Furthermore, the mass ratio of sodium carboxymethyl cellulose to sodium montmorillonite is 3:10; the mass ratio of aminated 15-crown ether-5 to sodium carboxymethyl cellulose-sodium montmorillonite is 0.75:1.

[0018] Furthermore, the preparation method of the composite microspheres includes the following steps:

[0019] S21. Dissolve sodium alginate in deionized water, add sodium periodate under light-protected conditions, stir the reaction, add ethylene glycol to terminate the reaction, stir, dialyze the product in deionized water, freeze dry to obtain oxidized sodium alginate.

[0020] S22. Dissolve sodium polyphosphate in deionized water, add sodium alginate oxide, heat and stir to dissolve, let stand to degas, and obtain the core liquid; add Span 80 to liquid paraffin, stir to premix, slowly add the core liquid, stir to emulsify, and obtain the emulsion;

[0021] S23. Dissolve adipic acid dihydrazide in deionized water and slowly add it dropwise to the emulsion. Add HCl to adjust the pH, stir the reaction at room temperature, collect the microspheres by centrifugation, and wash them successively with n-hexane, anhydrous ethanol, and deionized water to obtain microspheres.

[0022] S24. Dissolve γ-PGA in deionized water, adjust the pH with NaOH, add microspheres, disperse by ultrasonication, stir to adsorb, add CaCl2 solution, collect microspheres by centrifugation, wash with deionized water to obtain coated microspheres;

[0023] S25. Immerse the coated microspheres in NaCl solution at room temperature, remove them and rinse quickly with deionized water, then air dry at room temperature and vacuum dry to obtain composite microspheres.

[0024] Furthermore, the microspheres coated in S25 are immersed in NaCl solution for 10-12 hours to ensure that the Na+ inside the composite microspheres is absorbed. + saturation.

[0025] On the other hand, based on the same inventive concept, the present invention also provides a method for preparing an environmentally friendly bentonite composite material, applicable to the aforementioned environmentally friendly bentonite composite material, comprising the following steps:

[0026] S1. Sodium-based bentonite, modified montmorillonite, and composite microspheres are mixed, homogenized by low-speed ball milling, and sieved to obtain bentonite composite material.

[0027] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0028] 1. When Ca 2+ During intrusion, sodium carboxymethyl cellulose adsorbed between the modified montmorillonite layers maintains the interlayer Na... + While occupying the site, an electrostatic barrier is established to delay Ca2+ degradation. 2+ Diffusion rate into the interlayer; simultaneously, when external Ca 2+ As the concentration continues to increase, the polyphosphate group in the core of the composite microspheres affects Ca2+. 2+ The high affinity of Ca forms a chemical driving force, enabling Ca to form a chemical force. 2+ Continuously migrating towards the kernel, gradually consuming γ-PGA / Ca 2+The cross-linking points of the coating cause the network to swell and eventually rupture locally, releasing the internally stored Na. + Together with sodium polyphosphate, polyphosphate ions and coated PDA-EDTA, they chelate and immobilize Ca. 2+ .

[0029] 2. Crown ethers first competitively capture Na in solution. + Subsequently, Na+ was driven by concentration gradient and Donnan effect. + To enrich the interlayer, the anionic environment of the interlayer CMC provides additional electrostatic stabilization, ultimately Na + Desorbed from crown ether sites and migrated back into the interlayer.

[0030] 3. The PDA-EDTA coating enhances interfacial stability, forming an interfacial anchor between the modified montmorillonite outer surface and the sodium carboxymethyl cellulose chains, preventing the sodium carboxymethyl cellulose chains from detaching under permeate flushing. Simultaneously, EDTA also enhances the interfacial stability of Na+. + The coordination stability constant of Na is extremely low, therefore Na + It can easily migrate through the PDA-EDTA coating into the interlayer, while Ca 2+ It is then chelated and fixed to the coating by EDTA, thereby achieving the control of Ca. 2+ Selective interception and Na + The freedom to pass. Attached Figure Description

[0031] Figure 1 This refers to the bentonite composite material prepared in Example 1 of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1: This example discloses an environmentally friendly bentonite composite material, comprising the following components in parts by weight: 80 parts sodium-based bentonite, 22 parts modified montmorillonite, and 8 parts composite microspheres;

[0034] The modified montmorillonite is based on crown ether-grafted sodium carboxymethyl cellulose-montmorillonite, with a PDA-EDTA coating deposited on its surface;

[0035] The composite microspheres are Na + Pre-saturated covalently cross-linked sodium alginate microspheres encapsulated with sodium polyphosphate, with the outermost layer coated with γ-PGA / Ca 2+ Cross-linked coated composite microspheres.

[0036] The PDA-EDTA coating accounts for 22% of the total mass of the modified montmorillonite.

[0037] It should be noted that, according to thermogravimetric analysis (TGA), the actual deposition mass of PDA-EDTA on the surface of modified montmorillonite under the above conditions accounts for approximately 22% of the total mass of modified montmorillonite. The mass ratio of PDA-EDTA in the coating is controlled by the amount of material fed and the reaction time, and ranges from 22% to 30%.

[0038] The preparation method of the modified montmorillonite includes the following steps:

[0039] S11. Add 10g of sodium montmorillonite to 400mL of deionized water, stir and disperse at room temperature for 30min, raise the temperature to 60℃, continue stirring for 2h to allow the interlayer to swell fully, and let it stand to cool to obtain swollen sodium montmorillonite;

[0040] S12. Dissolve 3g of sodium carboxymethyl cellulose in 100mL of deionized water, slowly add it to the swollen sodium montmorillonite, adjust the pH to 7.0±0.2 with 0.1M NaOH, stir the reaction at 60℃ for 4h, purify the resulting reaction solution by dialyzing in deionized water for 24h, freeze-dry at -50℃ for 48h to obtain sodium carboxymethyl cellulose-sodium montmorillonite;

[0041] S13. Disperse 2g of sodium carboxymethyl cellulose-sodium montmorillonite in 100mL of LME buffer to obtain a suspension. Dissolve 0.96g of EDC·HCl and 0.58g of NHS in 10mL of LME buffer and add them to the suspension. Stir at room temperature for 15min to activate. Add PBS buffer to adjust the pH to 7.4 to obtain the activated solution. Dissolve 1.5g of amino-15-crown ether-5 in 20mL of PBS buffer and slowly add it dropwise to the activated solution. Stir at room temperature for 12h. Add hydroxylamine hydrochloride to a final concentration of 10mM and stir for 15min to quench residual NHS esters. Wash the obtained product with deionized water and freeze-dry to obtain crown ether-grafted sodium carboxymethyl cellulose-montmorillonite.

[0042] S14. Dissolve 0.88g EDTA in 30mL MES buffer to obtain an EDTA solution. Dissolve 0.58g EDC·HCl and 0.35g NHS in 5mL MES buffer respectively, and add them sequentially to the EDTA solution. Stir to activate. After activation, add 20mL PBS buffer to obtain an activation solution. Add 0.9g ethylenediamine to 10mL PBS buffer, adjust the pH to 7.0~7.5 with 0.1M HCl, and slowly add it dropwise to the activation solution. Maintain the pH at 7.0~7.5 with 0.1M HCl. Stir magnetically at room temperature for 4h. After the reaction, add hydroxylamine hydrochloride to a final concentration of 20mM, stir for 15min, and dialyze the resulting reaction solution for purification. Freeze-dry to obtain EDTA-EA.

[0043] S15. Mix 0.4g dopamine hydrochloride and 0.56g EDTA-EA in 5mL of deionized water and stir until completely dissolved to obtain a mixed solution; ultrasonically disperse 2g crown ether-grafted sodium carboxymethyl cellulose-montmorillonite in 200mL of deionized water, add 0.1M NaOH to adjust the pH to 8.5±0.1, add the mixed solution, stir and mix at room temperature, let stand for self-polymerization for 24h, centrifuge the obtained product, wash with deionized water, freeze dry at -50℃ for 48h to obtain modified montmorillonite.

[0044] It should be noted that both EDTA and crown ether are covalently anchored to the surface of montmorillonite, and are not in a free state.

[0045] The mass ratio of sodium carboxymethyl cellulose to sodium montmorillonite is 3:10; the mass ratio of aminated 15-crown ether-5 to sodium carboxymethyl cellulose-sodium montmorillonite is 0.75:1.

[0046] The preparation method of the composite microspheres includes the following steps:

[0047] S21. Dissolve 5g of sodium alginate in 250mL of deionized water, add 2.16g of sodium periodate under light-protected conditions, stir the reaction at room temperature for 4h, add 1mL of ethylene glycol to terminate the reaction, stir for 30min, dialyze the product in deionized water for 72h, freeze dry to obtain oxidized sodium alginate.

[0048] S22. Dissolve 1.5g sodium polyphosphate in 100mL deionized water, add 4g sodium alginate oxide, heat to 50℃ and stir to dissolve, let stand to degas for 30min to obtain the core solution; add 3mL Span 80 to 300mL liquid paraffin and stir to premix for 5min; slowly add the core solution and stir at 800rpm to emulsify for 20min to obtain the emulsion;

[0049] S23. Dissolve 1.94 g of adipic dihydrazide in 10 mL of deionized water and slowly add it dropwise to the emulsion. Add 0.1 M HCl to adjust the pH to 5.0-5.5. Stir the reaction at room temperature for 4 h. Collect the microspheres by centrifugation and wash them successively with n-hexane, anhydrous ethanol and deionized water to obtain microspheres.

[0050] S24. Dissolve 0.8 g γ-PGA in 50 mL of deionized water, adjust the pH to 6.5 with 0.1 M NaOH, add microspheres, sonicate to disperse, and stir at room temperature for 2 h for adsorption; add 10 mL of 50 mM CaCl2 solution to form γ-PGA / Ca on the surface of the microspheres. 2+ Cross-linked coating, centrifugation to collect microspheres, washing with deionized water to obtain coated microspheres;

[0051] S25. Immerse the coated microspheres in 0.15M NaCl solution and soak at room temperature for 12 hours to allow the NaCl to settle. + The material is pre-saturated by penetrating into the core of the microspheres. After being removed, it is quickly rinsed with deionized water, air-dried at room temperature for 2 hours, and then vacuum-dried at 40°C for 24 hours to obtain composite microspheres.

[0052] The microspheres coated in S25 were immersed in NaCl solution for 12 hours to ensure that the Na+ inside the composite microspheres was absorbed. + saturation.

[0053] The preparation method of the aforementioned environmentally friendly bentonite composite material includes the following steps:

[0054] S1. Sodium-based bentonite, modified montmorillonite, and composite microspheres are mixed, homogenized by low-speed ball milling, and sieved to obtain bentonite composite material.

[0055] It should be noted that, as Figure 1 The image shows the bentonite composite material prepared in Example 1 of this invention. Bentonite composite waterproof blankets can be prepared using either the needle-punching method or the needle-punching coating method. It should be noted that the bentonite composite material of this invention contains composite microspheres, thus differing from the preparation of ordinary bentonite waterproof blankets. During the ball milling stage, low-speed ball milling (≤30 rpm) is required, and the time should not be too long, preferably 15-20 minutes. The speed of the spiral disperser blades should be lower than the conventional bentonite laying speed, ≤60 rpm. The needle-punching density should not be too high, and it is recommended to control it at 20-30 needles / cm. 2 The needle is a conical fine needle to avoid the thick needle directly piercing the microsphere and causing damage.

[0056] Example 2: This example is based on Example 1, but differs from Example 1 in that it discloses an environmentally friendly bentonite composite material, comprising the following components in parts by weight: 75 parts sodium-based bentonite, 19 parts modified montmorillonite, and 6 parts composite microspheres.

[0057] The other components and preparation methods are the same as in Example 1.

[0058] Example 3: This example is based on Example 1, but differs from Example 1 in that it discloses an environmentally friendly bentonite composite material, comprising the following components in parts by weight: 70 parts sodium-based bentonite, 15 parts modified montmorillonite, and 4 parts composite microspheres;

[0059] The other components and preparation methods are the same as in Example 1.

[0060] Example 4: This example is based on Example 1, but differs from Example 1 in that the mass of the PDA-EDTA coating in this example accounts for 30% of the total mass of the modified montmorillonite.

[0061] The other components and preparation methods are the same as in Example 1.

[0062] Comparative Example 1: This comparative example is based on Example 1, but differs from Example 1 in that the modified montmorillonite in this comparative example is not grafted with crown ether.

[0063] The preparation method of the modified montmorillonite includes the following steps:

[0064] S11. Add 10g of sodium montmorillonite to 400mL of deionized water, stir and disperse at room temperature for 30min, raise the temperature to 60℃, continue stirring for 2h to allow the interlayer to swell fully, and let it stand to cool to obtain swollen sodium montmorillonite;

[0065] S12. Dissolve 3g of sodium carboxymethyl cellulose in 100mL of deionized water, slowly add it to the swollen sodium montmorillonite, adjust the pH to 7.0±0.2 with 0.1M NaOH, stir the reaction at 60℃ for 4h, purify the resulting reaction solution by dialyzing in deionized water for 24h, freeze-dry at -50℃ for 48h to obtain sodium carboxymethyl cellulose-sodium montmorillonite;

[0066] S13. Dissolve 0.88g EDTA in 30mL MES buffer to obtain an EDTA solution. Dissolve 0.58g EDC·HCl and 0.35g NHS in 5mL MES buffer respectively, and add them sequentially to the EDTA solution. Stir to activate. After activation, add 20mL PBS buffer to obtain an activated solution. Add 0.9g ethylenediamine to 10mL PBS buffer, adjust the pH to 7.0~7.5 with 0.1M HCl, and slowly add it dropwise to the activated solution. Maintain the pH at 7.0~7.5 with 0.1M HCl. Stir magnetically at room temperature for 4h. After the reaction, add hydroxylamine hydrochloride to a final concentration of 20mM, stir for 15min, and dialyze the resulting reaction solution for purification. Freeze-dry to obtain EDTA-EA.

[0067] S14. Mix 0.4g dopamine hydrochloride and 0.56g EDTA-EA in 5mL of deionized water and stir until completely dissolved to obtain a mixed solution; ultrasonically disperse 2g sodium carboxymethyl cellulose-montmorillonite in 200mL of deionized water, add 0.1M NaOH to adjust the pH to 8.5±0.1, add the mixed solution, stir and mix at room temperature, let stand for self-polymerization for 24h, centrifuge the obtained product, wash with deionized water, freeze dry at -50℃ for 48h to obtain modified montmorillonite.

[0068] Comparative Example 2: This comparative example is based on Example 1, but differs from Example 1 in that the modified montmorillonite in this comparative example does not contain sodium carboxymethyl cellulose.

[0069] The preparation method of the modified montmorillonite includes the following steps:

[0070] S11. Disperse 2g of sodium montmorillonite in 100mL of deionized water, add 0.5g of chloroacetic acid, adjust the pH to 10 with NaOH, stir at 60℃ for 4h, centrifuge and wash the product, freeze-dry to obtain surface carboxylated montmorillonite; disperse 2g of surface carboxylated montmorillonite in 100mL of MES buffer to obtain a suspension, dissolve 0.96g of EDC·HCl and 0.58g of NHS in 10mL of MES buffer, add to the suspension, stir at room temperature for 15min, adjust the pH to 7.4 with PBS buffer to obtain an activation solution; dissolve 1.5g of amino-15-crown ether-5 in 20mL of PBS buffer, slowly add to the activation solution, stir at room temperature for 12h, add hydroxylamine hydrochloride to a final concentration of 10mM, stir for 15min to quench residual NHS esters, wash the obtained product with deionized water, freeze-dry to obtain crown ether-grafted montmorillonite;

[0071] S12. Dissolve 0.88g EDTA in 30mL MES buffer to obtain an EDTA solution. Dissolve 0.58g EDC·HCl and 0.35g NHS in 5mL MES buffer respectively, and add them sequentially to the EDTA solution. Stir to activate. After activation, add 20mL PBS buffer to obtain the activation solution. Add 0.9g ethylenediamine to 10mL PBS buffer, adjust the pH to 7.0~7.5 with 0.1M HCl, and slowly add it dropwise to the activation solution. Maintain the pH at 7.0~7.5 with 0.1M HCl. Stir magnetically at room temperature for 4h. After the reaction, add hydroxylamine hydrochloride to a final concentration of 20mM, stir for 15min, and dialyze the resulting reaction solution for purification. Freeze-dry to obtain EDTA-EA.

[0072] S13. Mix 0.4g dopamine hydrochloride and 0.56g EDTA-EA in 5mL deionized water and stir until completely dissolved to obtain a mixed solution; ultrasonically disperse 2g crown ether-grafted montmorillonite in 200mL deionized water, add 0.1M NaOH to adjust the pH to 8.5±0.1, add the mixed solution, stir and mix at room temperature, let stand for self-polymerization for 24h, centrifuge the obtained product, wash with deionized water, freeze-dry at -50℃ for 48h to obtain modified montmorillonite.

[0073] The other components and preparation methods are the same as in Example 1.

[0074] Comparative Example 3: This comparative example is based on Example 1, but differs from Example 1 in that the modified montmorillonite surface described in this comparative example does not have a PDA-EDTA coating deposited on it.

[0075] The preparation method of the modified montmorillonite includes the following steps:

[0076] S11. Add 10g of sodium montmorillonite to 400mL of deionized water, stir and disperse at room temperature for 30min, raise the temperature to 60℃, continue stirring for 2h to allow the interlayer to swell fully, and let it stand to cool to obtain swollen sodium montmorillonite;

[0077] S12. Dissolve 3g of sodium carboxymethyl cellulose in 100mL of deionized water, slowly add it to the swollen sodium montmorillonite, adjust the pH to 7.0±0.2 with 0.1M NaOH, stir the reaction at 60℃ for 4h, purify the resulting reaction solution by dialyzing in deionized water for 24h, freeze-dry at -50℃ for 48h to obtain sodium carboxymethyl cellulose-sodium montmorillonite;

[0078] S13. Disperse 2g of sodium carboxymethyl cellulose-sodium montmorillonite in 100mL LME ES buffer to obtain a suspension. Dissolve 0.96g of EDC·HCl and 0.58g of NHS in 10mL LME ES buffer and add them to the suspension. Stir and activate at room temperature for 15min. Add PBS buffer to adjust the pH to 7.4 to obtain the activated solution. Dissolve 1.5g of amino-15-crown ether-5 in 20mL PBS buffer and slowly add it dropwise to the activated solution. Stir and react at room temperature for 12h. Add hydroxylamine hydrochloride to a final concentration of 10mM and stir for 15min to quench the residual NHS ester. Wash the obtained product with deionized water and freeze-dry to obtain modified montmorillonite.

[0079] The other components and preparation methods are the same as in Example 1.

[0080] Comparative Example 4: This comparative example is based on Example 1, but differs from Example 1 in that the composite microspheres described in this comparative example do not contain sodium polyphosphate.

[0081] The preparation method of the composite microspheres includes the following steps:

[0082] S21. Dissolve 5g of sodium alginate in 250mL of deionized water, add 2.16g of sodium periodate under light-protected conditions, stir the reaction at room temperature for 4h, add 1mL of ethylene glycol to terminate the reaction, stir for 30min, dialyze the product in deionized water for 72h, freeze dry to obtain oxidized sodium alginate.

[0083] S22. Dissolve 4g of sodium alginate in 100mL of deionized water, heat to 50℃ and stir to dissolve, let stand to degas for 30min to obtain the core solution; add 3mL of Span 80 to 300mL of liquid paraffin and stir to premix for 5min; slowly add the core solution and stir at 800rpm to emulsify for 20min to obtain the emulsion.

[0084] S23. Dissolve 1.94 g of adipic dihydrazide in 10 mL of deionized water and slowly add it dropwise to the emulsion. Add 0.1 M HCl to adjust the pH to 5.0-5.5. Stir the reaction at room temperature for 4 h. Collect the microspheres by centrifugation and wash them successively with n-hexane, anhydrous ethanol and deionized water to obtain microspheres.

[0085] S24. Dissolve 0.8 g γ-PGA in 50 mL of deionized water, adjust the pH to 6.5 with 0.1 M NaOH, add microspheres, sonicate to disperse, and stir at room temperature for 2 h for adsorption; add 10 mL of 50 mM CaCl2 solution to form γ-PGA / Ca on the surface of the microspheres. 2+ Cross-linked coating, centrifugation to collect microspheres, washing with deionized water to obtain coated microspheres;

[0086] S25. Immerse the coated microspheres in 0.15M NaCl solution and soak at room temperature for 12 hours to allow the NaCl to settle. + The material is pre-saturated by penetrating into the core of the microspheres. After being removed, it is quickly rinsed with deionized water, air-dried at room temperature for 2 hours, and then vacuum-dried at 40°C for 24 hours to obtain composite microspheres.

[0087] The other components and preparation methods are the same as in Example 1.

[0088] Comparative Example 5: This comparative example differs from Example 1 in that the composite microspheres described in this example are not externally coated with γ-PGA / Ca. 2+ Cross-linked coating.

[0089] The preparation method of the composite microspheres includes the following steps:

[0090] S21. Dissolve 5g of sodium alginate in 250mL of deionized water, add 2.16g of sodium periodate under light-protected conditions, stir the reaction at room temperature for 4h, add 1mL of ethylene glycol to terminate the reaction, stir for 30min, dialyze the product in deionized water for 72h, freeze dry to obtain oxidized sodium alginate.

[0091] S22. Dissolve 1.5g sodium polyphosphate in 100mL deionized water, add 4g sodium alginate oxide, heat to 50℃ and stir to dissolve, let stand to degas for 30min to obtain the core solution; add 3mL Span 80 to 300mL liquid paraffin and stir to premix for 5min; slowly add the core solution and stir at 800rpm to emulsify for 20min to obtain the emulsion;

[0092] S23. Dissolve 1.94 g of adipic dihydrazide in 10 mL of deionized water and slowly add it dropwise to the emulsion. Add 0.1 M HCl to adjust the pH to 5.0-5.5. Stir the reaction at room temperature for 4 h. Collect the microspheres by centrifugation and wash them successively with n-hexane, anhydrous ethanol and deionized water to obtain microspheres.

[0093] S24. Immerse the microspheres in 0.15M NaCl solution and soak at room temperature for 12 hours to allow the NaCl to settle. + The material is pre-saturated by penetrating into the core of the microspheres. After being removed, it is quickly rinsed with deionized water, air-dried at room temperature for 2 hours, and then vacuum-dried at 40°C for 24 hours to obtain composite microspheres.

[0094] The other components and preparation methods are the same as in Example 1.

[0095] Comparative Example 6: This comparative example differs from Example 1 in that the composite microspheres described in this comparative example are not subjected to Na treatment. + Pre-saturation treatment.

[0096] S21. Dissolve 5g of sodium alginate in 250mL of deionized water, add 2.16g of sodium periodate under light-protected conditions, stir the reaction at room temperature for 4h, add 1mL of ethylene glycol to terminate the reaction, stir for 30min, dialyze the product in deionized water for 72h, freeze dry to obtain oxidized sodium alginate.

[0097] S22. Dissolve 1.5g sodium polyphosphate in 100mL deionized water, add 4g sodium alginate oxide, heat to 50℃ and stir to dissolve, let stand to degas for 30min to obtain the core solution; add 3mL Span 80 to 300mL liquid paraffin and stir to premix for 5min; slowly add the core solution and stir at 800rpm to emulsify for 20min to obtain the emulsion;

[0098] S23. Dissolve 1.94 g of adipic dihydrazide in 10 mL of deionized water and slowly add it dropwise to the emulsion. Add 0.1 M HCl to adjust the pH to 5.0-5.5. Stir the reaction at room temperature for 4 h. Collect the microspheres by centrifugation and wash them successively with n-hexane, anhydrous ethanol and deionized water to obtain microspheres.

[0099] S24. Dissolve 0.8 g γ-PGA in 50 mL of deionized water, adjust the pH to 6.5 with 0.1 M NaOH, add microspheres, sonicate to disperse, and stir at room temperature for 2 h for adsorption; add 10 mL of 50 mM CaCl2 solution to form γ-PGA / Ca on the surface of the microspheres. 2+ Cross-linked coating, centrifugation to collect microspheres, washing with deionized water to obtain coated microspheres;

[0100] The other components and preparation methods are the same as in Example 1.

[0101] Comparative Example 7: This comparative example is based on Example 1, but unlike Example 1, this comparative example does not add modified montmorillonite and composite microspheres.

[0102] The other components and preparation methods are the same as in Example 1.

[0103] Experimental verification:

[0104] Experiment 1: Na + Supplement and Ca 2+ Interception test:

[0105] Weigh 1g of each bentonite composite material and add 25mL of 1mol / L NH4Cl solution. Extract by shaking for 24h (25℃, 150rpm) to fully displace all exchangeable cations in the interlayer. Centrifuge and filter the supernatant through a 0.45μm filter membrane. ICP-OES is used to determine the Na+ content. + Concentration, calculate the initial exchangeable Na in each group of samples. + Total amount (mmol / g), calculated as the average of three parallel determinations. Separately, 1g of each sample was added to 100mL of 50mmol / L CaCl2 solution (simulating the main erosive ionic strength of landfill leachate) and placed in a constant temperature shaking incubator (25℃, 150rpm) for continuous shaking and soaking. On day 28, the sample was removed and immediately centrifuged (5000rpm, 10min), discarding the supernatant. The solid-phase sample was then extracted again with 25mL of 1mol / L NH4Cl solution for 24h, centrifuged, filtered, and the residual exchangeable Na was determined by ICP-OES. + Quantity. Calculate Na. + Retention rate.

[0106] Supernatant was collected synchronously at each sampling time point, and residual Ca in the supernatant was determined by ICP-OES. 2+ Concentration. Control group: Initial Ca addition 2+ Quantity, calculate the effect of solid sample on Ca 2+ The cumulative fixed amount (mmol / g).

[0107] Table 1: Na + Supplement and Ca 2+ Interception test results:

[0108]

[0109] Na + Supplement and Ca 2+ The interception test results are shown in Table 1. In Example 1, the Na+ retention rate was higher than 70% after 28 days of erosion, significantly better than that of Comparative Example 7 (pure sodium-based bentonite). The retention rates of Comparative Examples 1 and 2 decreased significantly, demonstrating the synergistic effect of the "crown ether capture-CMC directional transfer" relay mechanism. The retention rate of Comparative Example 3 decreased due to the easy detachment of CMC segments. The fixation amount in Example 1 reached over 2.00 mmol / g on day 28, while the Ca+ retention rates in Comparative Examples 3 and 4 (without sodium polyphosphate) were significantly lower. 2+ The amount of calcium fixed was significantly lower than in the example, demonstrating that PDA-EDTA chelation and polyphosphate precipitation synergistically chelated and fixed Ca. 2+ The effect is remarkable.

[0110] Experiment 2:

[0111] (1) Permeability test: The bentonite composite powders of each group were tested at a concentration of 1.0 g / cm³. 2 The material is evenly applied to a 100mm diameter permeability test apparatus, with a layer of geotextile (needle-punched nonwoven fabric, 100g / m²) laid on top and bottom. 2 The leachate was pre-hydrated for 24 hours under a confining pressure of 50 kPa and an effective stress of 25 kPa. A simulated landfill leachate (main components: 50 mmol / L CaCl2, 10 mmol / L MgCl2, 5 mmol / L NaCl, pH 6.5 ± 0.2) was prepared as the chemically corrosive leachate. Deionized water was used as a control leachate. At an osmotic pressure difference of 20 kPa and a test temperature of 25 ± 1℃, the test was continued until a stable permeability coefficient was achieved (change in value <10% for three consecutive measurements). The permeability coefficient k (m / s) at each stage was recorded.

[0112] (2) Determination of free expansion rate: Weigh 2g of each group of bentonite composite powder (passed through a 200-mesh sieve) and slowly add it in batches to the surface of a 100mL graduated cylinder containing 100mL of test solution (deionized water and simulated permeate, respectively). It is advisable to add no more than 0.1g each time. After each addition, wait for complete sedimentation before adding the next batch. After all the additions are made, let it stand for 24 hours and read the expansion volume (mL / 2g).

[0113] Table 2: Permeability and Free Expansion Rate Tests:

[0114]

[0115] The test results of permeability and free expansion rate are shown in Table 2. In Example 1, the ratio of the permeability coefficient in the simulated permeate to that in deionized water was <2.5, while in Comparative Example 7, the ratio was >15, indicating that its anti-seepage performance failed. This proves that the composite material of the present invention is susceptible to high concentrations of Ca. 2+ It exhibits excellent chemical durability. In the examples, the free swelling rate retention rate in simulated permeate was ≥70%, far superior to Comparative Example 7, verifying the chemical durability of the composite material prepared by this invention in Ca... 2+ The expansion performance was effectively protected in the environment. The expansion retention rate decreased to varying degrees in each comparative example after the absence of a single functional component.

[0116] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An environmentally friendly bentonite composite material, characterized in that, It includes the following components in parts by weight: 70-80 parts sodium bentonite, 15-22 parts modified montmorillonite, and 4-8 parts composite microspheres; The modified montmorillonite is based on crown ether-grafted sodium carboxymethyl cellulose-montmorillonite, with a PDA-EDTA coating deposited on its surface; The composite microspheres are Na + Pre-saturated covalently cross-linked sodium alginate microspheres encapsulated with sodium polyphosphate, with the outermost layer coated with γ-PGA / Ca 2+ Cross-linked coated composite microspheres.

2. The environmentally friendly bentonite composite material according to claim 1, characterized in that, The PDA-EDTA coating accounts for 22-30% of the total mass of the modified montmorillonite.

3. The environmentally friendly bentonite composite material according to claim 1, characterized in that, The preparation method of the modified montmorillonite includes the following steps: S11. Add sodium montmorillonite to deionized water, stir to disperse, heat and continue stirring, let stand and cool to obtain swollen sodium montmorillonite; S12. Dissolve sodium carboxymethyl cellulose in deionized water, slowly add it to the swollen sodium montmorillonite, adjust the pH with NaOH, stir the reaction, dialysis the resulting reaction solution, freeze dry it to obtain sodium carboxymethyl cellulose-sodium montmorillonite; S13. Disperse sodium carboxymethyl cellulose-sodium montmorillonite in MES buffer to obtain a suspension. Dissolve EDC·HCl and NHS in MES buffer and add them to the suspension. Stir to activate. Add PBS buffer to adjust the pH to obtain an activated solution. Dissolve amino-15-crown ether-5 in PBS buffer and slowly add it dropwise to the activated solution. Stir to react. Add hydroxylamine hydrochloride. Wash the obtained product and freeze-dry to obtain crown ether-grafted sodium carboxymethyl cellulose-montmorillonite. S14. Dissolve EDTA in MES buffer with stirring to obtain an EDTA solution. Dissolve EDC·HCl and NHS in MES buffer respectively, and add them to the EDTA solution sequentially. Stir to activate. After activation, add PBS buffer to obtain an activated solution. Add ethylenediamine to PBS buffer, adjust the pH with HCl, and slowly add it dropwise to the activated solution while stirring. After the reaction is complete, add hydroxylamine hydrochloride and stir. The resulting reaction solution is purified by dialysis and freeze-dried to obtain EDTA-EA. S15. Dopamine hydrochloride and EDTA-EA were mixed and dissolved in deionized water and stirred until completely dissolved to obtain a mixed solution; crown ether-grafted sodium carboxymethyl cellulose-montmorillonite was ultrasonically dispersed in deionized water, NaOH was added to adjust the pH, the mixed solution was added, the mixture was stirred at room temperature, allowed to stand for self-polymerization, the obtained product was centrifuged, washed with deionized water, and freeze-dried to obtain modified montmorillonite.

4. The environmentally friendly bentonite composite material according to claim 3, characterized in that, The mass ratio of sodium carboxymethyl cellulose to sodium montmorillonite is 3:10; the mass ratio of aminated 15-crown ether-5 to sodium carboxymethyl cellulose-sodium montmorillonite is 0.75:

1.

5. The environmentally friendly bentonite composite material according to claim 1, characterized in that, The preparation method of the composite microspheres includes the following steps: S21. Dissolve sodium alginate in deionized water, add sodium periodate under light-protected conditions, stir the reaction, add ethylene glycol to terminate the reaction, stir, dialyze the product in deionized water, freeze dry to obtain oxidized sodium alginate. S22. Dissolve sodium polyphosphate in deionized water, add sodium alginate oxide, heat and stir to dissolve, let stand to degas, and obtain the core liquid; add Span 80 to liquid paraffin, stir to premix, slowly add the core liquid, stir to emulsify, and obtain the emulsion; S23. Dissolve adipic acid dihydrazide in deionized water and slowly add it dropwise to the emulsion. Add HCl to adjust the pH, stir the reaction at room temperature, collect the microspheres by centrifugation, and wash them successively with n-hexane, anhydrous ethanol, and deionized water to obtain microspheres. S24. Dissolve γ-PGA in deionized water, adjust the pH with NaOH, add microspheres, disperse by ultrasonication, stir to adsorb, add CaCl2 solution, collect microspheres by centrifugation, wash with deionized water to obtain coated microspheres; S25. Immerse the coated microspheres in NaCl solution at room temperature, remove them and rinse quickly with deionized water, then air dry at room temperature and vacuum dry to obtain composite microspheres.

6. The environmentally friendly bentonite composite material according to claim 5, characterized in that, The microspheres coated in S25 are immersed in NaCl solution for 10-12 hours to ensure that the Na+ inside the composite microspheres is absorbed. + saturation.

7. A method for preparing an environmentally friendly bentonite composite material, applied to the preparation of an environmentally friendly bentonite composite material as described in any one of claims 1 to 6, characterized in that, The method includes the following steps: S1. Sodium-based bentonite, modified montmorillonite, and composite microspheres are mixed, homogenized by low-speed ball milling, and sieved to obtain bentonite composite material.

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