An aerogel adsorption material for contaminated soil remediation, a preparation method and use thereof

Abstract

The application provides a kind of aerogel adsorption material for contaminated soil remediation, its preparation method and purposes, comprising: intercalation treatment is carried out to sodium-based montmorillonite to obtain intercalated montmorillonite; the intercalated montmorillonite is dispersed in deionized water, and under the conditions of stirring and heating, drop the ferric chloride solution, while drop the lye to adjust the pH value of the reaction system, then carry out standing aging, filtration, washing and drying, to obtain iron modified montmorillonite; the iron modified montmorillonite and nanocellulose solution are mixed, stirred and heated to obtain a composite sol, crosslinking agent and catalyst are added thereto, mixed, stirred and heated, then injected into a mold to carry out standing aging and heating curing, to obtain a composite gel, the composite gel is immersed in anhydrous ethanol, and freeze-dried to obtain the aerogel adsorption material. The aerogel adsorption material prepared by the application has excellent mechanical strength while retaining the high specific surface area of aerogel, and can efficiently fix various heavy metals through ion exchange, coordination and other effects.

Description

Technical Field

[0001] This invention belongs to the field of contaminated soil remediation technology, and relates to an aerogel adsorbent material for contaminated soil remediation, its preparation method and application. Background Technology

[0002] In recent years, with the rapid development of industrialization and urbanization, soil pollution has become increasingly serious, especially the accumulation of heavy metals and organic pollutants in the soil, which has posed a serious threat to the ecological environment and human health. Traditional soil remediation technologies, such as topsoil replacement and chemical leaching, have limitations such as complex operation, high cost, and the potential for secondary pollution, making it difficult to meet the needs of large-scale remediation with low environmental impact. Although adsorption methods have received widespread attention due to their high efficiency and ease of operation, conventional adsorption materials such as activated carbon and montmorillonite often have problems such as limited adsorption capacity, poor selectivity, and difficulty in regeneration, which limits their application in actual contaminated sites.

[0003] Against this backdrop, the development of high-performance adsorbent materials has become a research hotspot in the field of soil remediation. Aerogel materials, due to their ultra-high specific surface area, abundant pore structure, and tunable surface chemical properties, exhibit outstanding adsorption potential. However, the application of existing aerogel materials in soil remediation still faces many challenges: on the one hand, their poor mechanical properties and fragility make it difficult to maintain stability in complex soil environments; on the other hand, their limited functionality results in insufficient synergistic adsorption capacity for multiple pollutants in complex pollution systems. Furthermore, traditional aerogel preparation processes often involve complex steps, high costs, or toxic solvents, which are not conducive to large-scale production and environmentally friendly applications.

[0004] Therefore, there is an urgent need to develop an aerogel material that combines high adsorption performance, good mechanical strength and environmental adaptability, and to achieve its efficient application through green and low-cost preparation methods, so as to fill the gaps in the effectiveness and sustainability of existing soil remediation materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an aerogel adsorbent material for contaminated soil remediation, its preparation method, and its applications. The present invention prepares an aerogel adsorbent material that combines high adsorption capacity with a stable structure. While retaining the high specific surface area of ​​the aerogel, it also possesses excellent mechanical strength and achieves efficient fixation of various heavy metals through ion exchange, coordination, and other processes.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing an aerogel adsorbent material for contaminated soil remediation, the preparation method comprising:

[0008] (I) Intercalation treatment of sodium-based montmorillonite yields intercalated montmorillonite; the intercalated montmorillonite is dispersed in deionized water to obtain a montmorillonite suspension; under stirring and heating conditions, ferric chloride solution is added dropwise to the montmorillonite suspension, and alkali solution is added dropwise to adjust the pH value of the reaction system; then, the system is allowed to stand for aging, filtered, washed and dried to obtain iron-modified montmorillonite.

[0009] (II) Iron-modified montmorillonite and nanocellulose solution are mixed, stirred and heated to obtain a composite sol. A crosslinking agent and catalyst are added to it, and after mixing, stirring and heating, it is poured into a mold for static aging and heating curing to obtain a composite gel. The composite gel is immersed in anhydrous ethanol for solvent replacement and freeze-dried to obtain the aerogel adsorbent material.

[0010] This invention prepares an aerogel adsorbent material with both high adsorption capacity and stable structure. First, sodium-based montmorillonite is intercalated to expand the interlayer spacing. Then, under weakly alkaline conditions, amorphous iron oxides are loaded into the montmorillonite interlayers via ferric chloride hydrolysis. Subsequently, using nanocellulose as a three-dimensional network matrix, iron-modified montmorillonite is covalently linked through a crosslinking agent to form a stable porous structure. Solvent displacement and freeze-drying allow the aerogel to retain its high specific surface area while possessing excellent mechanical strength, achieving efficient fixation of various heavy metals.

[0011] In the preparation of iron-modified montmorillonite, sodium-based montmorillonite is first subjected to intercalation modification. Sodium ions between the layers of sodium-based montmorillonite are replaced by organic cations (hexadecyltrimethylammonium bromide), expanding the interlayer spacing. Subsequently, ferric chloride solution is added dropwise. In a weakly alkaline environment, iron ions hydrolyze between the layers of sodium-based montmorillonite to generate nano-sized iron hydroxide colloids. After static aging, the iron oxide crystal structure stabilizes, forming iron-modified montmorillonite with a high specific surface area. The iron-modified montmorillonite prepared by this invention combines the ion exchange capacity of sodium-based montmorillonite with the specific adsorption capacity of iron oxides for heavy metal ions. Montmorillonite itself has a layered structure and cation exchange capacity; its negative surface charge can adsorb heavy metal cations through electrostatic interactions. The intercalation treatment further expands the interlayer spacing of montmorillonite, prolonging the diffusion path of heavy metal ions within the material, thus extending the contact time and increasing the contact opportunities between heavy metal ions and iron oxides. The surface hydroxyl groups of iron compounds in situ loaded between montmorillonite layers can undergo coordination reactions with heavy metal ions to form surface complexes, which are then encapsulated and fixed through co-precipitation. The synergistic effect of montmorillonite and iron compounds enhances the adsorption and fixation effect of aerogel adsorbents on heavy metal ions.

[0012] In the preparation of the composite gel, a nanocellulose solution was used as a three-dimensional network matrix. Its abundant hydroxyl groups formed hydrogen bonds with the hydroxyl groups on the surface of iron-modified montmorillonite. The crosslinking agent, epichlorohydrin, under the action of an alkaline catalyst, underwent ring-opening and etherification with the hydroxyl groups of both the nanocellulose and iron-modified montmorillonite, forming a covalently crosslinked network. This chemical crosslinking significantly enhanced the mechanical strength of the gel skeleton. Subsequently, the composite gel was immersed in anhydrous ethanol for thorough solvent replacement, allowing the anhydrous ethanol to displace all the water in the composite gel. This ensured the integrity of the gel's pore structure during freeze-drying, preventing pore collapse caused by surface tension.

[0013] The aerogel adsorbent material prepared by this invention achieves efficient immobilization of heavy metal ions through the synergistic effect between iron-modified montmorillonite and the aerogel matrix. The aerogel matrix, formed by freeze-drying nanocellulose, has a three-dimensional porous structure, which can promote the transport and diffusion of heavy metal ions within the material. The iron-modified montmorillonite captures heavy metal cations through ion exchange between montmorillonite layers and utilizes the surface hydroxyl groups of the iron oxides loaded in its interlayer to coordinate with heavy metals. At the same time, it converts highly toxic hexavalent chromium into low-migration trivalent chromium through redox reactions, achieving efficient immobilization of various heavy metal ions such as Pb, Cd, As, and Cr, significantly reducing the migration of heavy metal ions in the soil. The aerogel adsorbent material prepared by this invention maintains a high adsorption capacity for heavy metal ions while also possessing excellent compressive strength and environmental stability, effectively overcoming the failure and desorption risks of traditional adsorbent materials in complex soil environments.

[0014] As a preferred technical solution of the present invention, in step (I), the operation steps of the sodium-based montmorillonite intercalation treatment include:

[0015] Sodium-based montmorillonite was dispersed in deionized water, mixed, stirred, and heated to obtain a montmorillonite dispersion. Under stirring and heating conditions, a hexadecyltrimethylammonium bromide solution was added dropwise to the montmorillonite dispersion. After all the solution was added, the mixture was stirred, heated, and then centrifuged, washed, and dried to obtain the intercalated montmorillonite.

[0016] As a preferred technical solution of the present invention, the temperature of mixing and heating the sodium-based montmorillonite in the deionized water is 60~70℃, for example, it can be 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, 66℃, 67℃, 68℃, 69℃ or 70℃, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0017] In some alternative instances, the sodium-based montmorillonite is mixed, stirred, and heated in the deionized water for 2 to 3 hours, for example, 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours, or 3.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0018] In some optional instances, the mixing and heating speed of the sodium montmorillonite in the deionized water is 600 to 800 rpm, for example, 600 rpm, 620 rpm, 640 rpm, 660 rpm, 680 rpm, 700 rpm, 720 rpm, 740 rpm, 760 rpm, 780 rpm or 800 rpm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0019] In some optional instances, the mass fraction of sodium montmorillonite in the montmorillonite dispersion is 4 to 6 wt%, for example, 4.0 wt%, 4.2 wt%, 4.4 wt%, 4.6 wt%, 4.8 wt%, 5.0 wt%, 5.2 wt%, 5.4 wt%, 5.6 wt%, 5.8 wt%, or 6.0 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0020] As a preferred technical solution of the present invention, the hexadecyltrimethylammonium bromide solution is added dropwise to the montmorillonite dispersion at a stirring speed of 600-800 rpm and a heating temperature of 75-85°C. The stirring speed can be 600 rpm, 620 rpm, 640 rpm, 660 rpm, 680 rpm, 700 rpm, 720 rpm, 740 rpm, 760 rpm, 780 rpm, or 800 rpm, and the heating temperature can be 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C, or 85°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] In some optional instances, the concentration of hexadecyltrimethylammonium bromide in the hexadecyltrimethylammonium bromide solution is 10 to 20 g / L, for example, it can be 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L or 20 g / L, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0022] In some alternative examples, the dropping rate of the hexadecyltrimethylammonium bromide solution is 1 to 2 mL / min, for example, 1.0 mL / min, 1.1 mL / min, 1.2 mL / min, 1.3 mL / min, 1.4 mL / min, 1.5 mL / min, 1.6 mL / min, 1.7 mL / min, 1.8 mL / min, 1.9 mL / min or 2.0 mL / min, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0023] In some alternative examples, the mass ratio of hexadecyltrimethylammonium bromide in the hexadecyltrimethylammonium bromide solution to sodium montmorillonite in the montmorillonite dispersion is (0.15~0.25):1, for example, it can be 0.15:1, 0.16:1, 0.17:1, 0.18:1, 0.19:1, 0.2:1, 0.21:1, 0.22:1, 0.23:1, 0.24:1 or 0.25:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0024] This invention specifically defines the mass ratio of hexadecyltrimethylammonium bromide (CTAB) in the hexadecyltrimethylammonium bromide solution to sodium montmorillonite in the montmorillonite dispersion as (0.15~0.25):1. The cationic groups of CTAB can replace sodium ions between montmorillonite layers through charge attraction, and its long alkyl chains extend in the interlayer domain to form a monolayer arrangement, thereby increasing the interlayer spacing of montmorillonite. This can fully open the interlayer channels to facilitate the subsequent loading of iron oxides, while avoiding excessive expansion that would lead to the loss of the lamellar structure.

[0025] When the amount of CTAB used is below the lower limit defined in this invention, the number of CTAB cations is insufficient to fully replace the sodium ions between the montmorillonite layers. This results in the montmorillonite sheets not being fully expanded, making it difficult for subsequent ferric chloride solution to penetrate the unexpanded interlayer spaces. Iron oxides are mainly deposited on the surface of the montmorillonite rather than between the layers, significantly reducing the density of active sites. Furthermore, the unexpanded, narrow sheets severely hinder the diffusion of heavy metal ions, especially significantly reducing the adsorption capacity for lead and cadmium, which have larger ionic radii.

[0026] When the amount of CTAB exceeds the upper limit defined in this invention, excessive CTAB causes the montmorillonite sheets to over-expand. At this point, the sheet structure is prone to curling and breakage under mechanical stirring, damaging the integrity of the montmorillonite sheet structure. Furthermore, the long alkyl chains of excessive CTAB densely cover the montmorillonite surface, forming a dense hydrophobic layer that hinders the movement of iron ions into the interlayer of montmorillonite. This results in iron oxides only forming on the outside of the montmorillonite and failing to be fixed within the interlayer. Without the fixing carrier within the montmorillonite interlayer, the iron oxides are easily detached and lost during subsequent processing and use, leading to a reduction in the number of effective adsorption sites and a decrease in the material's ability to fix and adsorb heavy metal ions.

[0027] In some optional instances, after all the hexadecyltrimethylammonium bromide solution is added dropwise, the mixture is stirred and heated for 12 to 14 hours, for example, 12 hours, 12.2 hours, 12.4 hours, 12.6 hours, 12.8 hours, 13 hours, 13.2 hours, 13.4 hours, 13.6 hours, 13.8 hours, or 14 hours, but not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0028] As a preferred technical solution of the present invention, in step (I), the mass fraction of intercalated montmorillonite in the montmorillonite suspension is 4~6wt%, for example, it can be 4.0wt%, 4.2wt%, 4.4wt%, 4.6wt%, 4.8wt%, 5.0wt%, 5.2wt%, 5.4wt%, 5.6wt%, 5.8wt%, or 6.0wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] In some optional instances, the ferric chloride solution is added dropwise to the montmorillonite suspension at a stirring speed of 500-600 rpm and a heating temperature of 55-65°C. The stirring speed can be 500 rpm, 510 rpm, 520 rpm, 530 rpm, 540 rpm, 550 rpm, 560 rpm, 570 rpm, 580 rpm, 590 rpm, or 600 rpm, and the heating temperature can be 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, or 65°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0030] In the preparation of iron-modified montmorillonite, ferric chloride solution was added dropwise to the montmorillonite suspension under heating and stirring conditions. The reaction solution was kept in a weakly alkaline environment by adding alkali solution. Under this pH condition, iron ions rapidly underwent hydrolysis, generating amorphous and weakly crystalline hydrated iron oxide (FeOOH), which was then in situ loaded onto the surface and interlayer of the montmorillonite. The entire reaction process is essentially a hydrolysis-condensation process.3+ First with OH - The monomer Fe(OH)3 is generated by combining. The Fe(OH)3 monomer is extremely unstable and will rapidly polymerize to form a polymer with a network structure. Finally, it is dehydrated to form an amorphous hydrated iron oxide with a high specific surface area and abundant surface functional groups. By loading the intercalated montmorillonite in situ between the layers, the agglomeration of hydrated iron oxide particles is avoided.

[0031] The adsorption and fixation effect of hydrated iron oxides on heavy metal ions is mainly reflected in:

[0032] On the one hand, hydrated iron oxides can undergo electrostatic adsorption with heavy metal ions. Hydrated iron oxides are amphoteric surface compounds with a surface rich in unsaturated oxygen atoms. These oxygen atoms combine with water molecules to form a large number of surface hydroxyl groups (≡Fe-OH). These surface hydroxyl groups can react with H+ in the soil. + or OH - The reaction results in the surface becoming charged, positively charged in acidic environments and negatively charged in alkaline environments. This variable charge capability allows it to adsorb heavy metal ions with opposite charges from the soil through electrostatic attraction.

[0033] On the other hand, hydrated iron oxides can undergo surface complexation with heavy metal ions. The hydroxyl groups abundant on the surface of iron oxides can act as ligands in contaminated soil, allowing heavy metal ions (such as Pb) to bind together. 2+ Cd 2+ Some hydrated molecules are removed, and they directly bind to the hydroxyl groups on the surface of iron oxides via coordinate bonds to form stable surface complexes (such as ≡Fe-OCd). + ≡Fe-OPb + (etc.), thus firmly fixing heavy metal ions on its surface. The binding strength is much higher than that of simple electrostatic adsorption, and the adsorbed heavy metal ions are difficult to desorb.

[0034] On the other hand, hydrated iron oxides can undergo redox reactions with heavy metal ions of variable valence states, such as arsenic and chromium, thus affecting As... 3+ And As 5+ Regarding Fe in iron-modified montmorillonite 3+ As can 3+ Oxidized to As 5+ To reduce its biotoxicity, oxidized As 5+ It can combine with hydroxyl groups (≡Fe-OH) on the surface of iron oxides through coordination to form stable surface complexes, and can also combine with Fe on the surface of iron oxides through co-precipitation. 3+ This combines to form insoluble iron arsenates (such as FeAsO4), thereby reducing the As content. 5+ It is fixed in the precipitate. For Cr 3+ and Cr 6+In contrast, iron oxides are doped with a small amount of Fe. 2+ It can contain highly toxic Cr 6 + Reduced to Cr, which is less toxic and has weaker migration properties. 3+ Cr 3+ It can combine with hydroxyl groups (≡Fe-OH) on the surface of iron oxides through coordination to form stable surface complexes, and can also combine with Fe on the surface of iron oxides through co-precipitation. 3+ This combines to form insoluble iron-chromium hydroxide complexes (such as FeCr(OH)6), thereby reducing Cr... 3+ It is fixed in the precipitate.

[0035] Through the above-mentioned multiple adsorption and fixation mechanisms, iron-modified montmorillonite can efficiently capture and stabilize various heavy metal ions with different properties, thereby significantly improving the overall adsorption performance of aerogel adsorption materials.

[0036] In some alternative examples, the ferric chloride solution consists of ferric chloride hexahydrate and deionized water.

[0037] In some alternative examples, the concentration of ferric chloride hexahydrate in the ferric chloride solution is 0.4 to 0.6 mol / L, for example, 0.4 mol / L, 0.42 mol / L, 0.44 mol / L, 0.46 mol / L, 0.48 mol / L, 0.5 mol / L, 0.52 mol / L, 0.54 mol / L, 0.56 mol / L, 0.58 mol / L or 0.6 mol / L, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0038] In some alternative examples, the dropping rate of the ferric chloride solution is 1 to 2 mL / min, for example, 1.0 mL / min, 1.1 mL / min, 1.2 mL / min, 1.3 mL / min, 1.4 mL / min, 1.5 mL / min, 1.6 mL / min, 1.7 mL / min, 1.8 mL / min, 1.9 mL / min or 2.0 mL / min, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0039] In some optional instances, the mass ratio of ferric chloride hexahydrate in the ferric chloride solution to intercalated montmorillonite in the montmorillonite suspension is (0.3~0.4):1, for example, it can be 0.3:1, 0.31:1, 0.32:1, 0.33:1, 0.34:1, 0.35:1, 0.36:1, 0.37:1, 0.38:1, 0.39:1 or 0.4:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0040] This invention specifically defines the mass ratio of ferric chloride hexahydrate in the ferric chloride solution to intercalated montmorillonite in the montmorillonite suspension as (0.3~0.4):1. Within this range, the iron ions provided by ferric chloride can fully penetrate into the interlamellae of the intercalated montmorillonite and hydrolyze under weakly alkaline conditions to generate amorphous iron hydroxyl oxides. These nanoscale iron oxides can be uniformly dispersed and anchored on the surface and interlamellae of montmorillonite, forming active sites with high specific surface area and abundant surface hydroxyl groups.

[0041] When the amount of ferric chloride hexahydrate is below the lower limit defined in this invention, the ferric hydroxide generated by hydrolysis is sparsely dispersed in the interlayer and surface of montmorillonite. The montmorillonite surface not covered by ferric hydroxide exposes a large number of siloxy groups, which easily compete with calcium and magnesium ions for adsorption in the soil environment, significantly reducing the adsorption and fixation effect on heavy metal ions. Furthermore, excessively low amounts of ferric hydroxide lead to a significant decrease in the adsorption capacity for pollutants such as arsenic and chromium.

[0042] When the amount of ferric chloride hexahydrate exceeds the upper limit defined in this invention, excess iron ions aggregate within the montmorillonite layers, forming large iron oxide aggregates whose size far exceeds the interlayer spacing of montmorillonite. This forces the montmorillonite layers apart, causing them to twist and break, thus disrupting the integrity of the montmorillonite's layered structure and affecting the material's mechanical strength. Furthermore, the iron oxide aggregates severely block the interlayer channels of montmorillonite, affecting the diffusion and migration of heavy metal ions and reducing the adsorption effect on heavy metal ions.

[0043] In some alternative instances, during the addition of the ferric chloride solution, the alkaline solution is added dropwise to the resulting mixture to control the pH of the mixture at 7 to 7.5, for example, 7.0, 7.05, 7.1, 7.15, 7.2, 7.25, 7.3, 7.35, 7.4, 7.45, or 7.5, but not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0044] In a weakly alkaline environment with a pH of 7-7.5, Fe 3+ Hydrolysis forms amorphous iron hydroxyl oxide, rather than highly crystalline goethite or hematite. Amorphous iron hydroxyl oxide has a higher specific surface area and a higher surface hydroxyl density, providing abundant adsorption sites. When the pH value is below 7, the hydrolysis of iron ions is incomplete, resulting in fewer and less dispersed iron hydroxyl oxides. When the pH value is above 7.5, highly crystalline iron oxides are more likely to form, with lower specific surface area and surface hydroxyl density.

[0045] In some alternative examples, the alkaline solution is a sodium hydroxide solution with a concentration of 1 to 2 mol / L, such as 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, or 2.0 mol / L, but not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0046] In some optional instances, after all the ferric chloride solution has been added dropwise, the resulting mixture is further mixed, stirred, and heated for 1 to 2 hours, for example, 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, or 2.0 h, but not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0047] In some optional instances, the static aging temperature is 60~70°C, for example, it can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C or 70°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0048] In some optional instances, the settling time is 10 to 15 hours, for example, 10 hours, 10.5 hours, 11 hours, 11.5 hours, 12 hours, 12.5 hours, 13 hours, 13.5 hours, 14 hours, 14.5 hours or 15 hours, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0049] In some optional instances, the drying temperature is 80-90°C, for example, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0050] In some optional instances, the drying time is 10 to 15 hours, for example, 10 hours, 10.5 hours, 11 hours, 11.5 hours, 12 hours, 12.5 hours, 13 hours, 13.5 hours, 14 hours, 14.5 hours or 15 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0051] As a preferred technical solution of the present invention, in step (II), the mass fraction of the nanocellulose solution is 1.5~2.5wt%, for example, it can be 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, 2.0wt%, 2.1wt%, 2.2wt%, 2.3wt%, 2.4wt% or 2.5wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] In some alternative examples, the mass ratio of the iron-modified montmorillonite to the nanocellulose solution is (0.22~0.25):1, for example, it can be 0.15:0.22:1, 0.155:0.225:1, 0.16:0.23:1, 0.165:0.235:1, 0.17:0.4:1, 0.175:0.45:1 or 0.18:0.5:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0053] This invention specifically limits the mass ratio of iron-modified montmorillonite to nanocellulose solution to (0.22~0.25):1. When the amount of iron-modified montmorillonite is within this range, the iron-modified montmorillonite can be uniformly dispersed in the three-dimensional network structure formed by nanocellulose. It will not block the pore structure of the aerogel matrix due to excessive amount, thus affecting the diffusion and transport of heavy metal ions, nor will it weaken the fixation and adsorption capacity of heavy metal ions due to insufficient amount.

[0054] When the amount of iron-modified montmorillonite used is below the lower limit specified in this invention, it affects the aerogel adsorbent material's ability to fix and adsorb heavy metal ions, and also makes the fixed heavy metal ions more susceptible to re-release when environmental conditions change. Simultaneously, insufficient montmorillonite sheets weaken the rigid support for the aerogel matrix, increasing the material's brittleness, reducing compressive strength, and decreasing toughness, making the aerogel adsorbent material prone to cracking under pressure.

[0055] When the amount of iron-modified montmorillonite exceeds the upper limit defined in this invention, the dense montmorillonite sheets stack up locally in the nanocellulose network, resulting in a reduction in the number of effective active sites available for binding heavy metal ions, thus affecting the fixation effect of the aerogel adsorbent material on heavy metal ions. Simultaneously, the aggregated montmorillonite agglomerates can block the pore structure of the aerogel matrix, hindering the diffusion and transport of heavy metal ions into the material. Furthermore, the montmorillonite agglomerates can cause stress concentration in the aerogel matrix, leading to a decrease in the compressive strength of the material and making it prone to fracture or collapse during use.

[0056] In some optional instances, the temperature at which the iron-modified montmorillonite and the nanocellulose solution are mixed and heated is 40-50°C, for example, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C or 50°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0057] In some optional instances, the mixing and heating time of the iron-modified montmorillonite and the nanocellulose solution is 2 to 4 hours, for example, 2.0 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, or 4.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0058] As a preferred technical solution of the present invention, in step (II), the crosslinking agent is epichlorohydrin.

[0059] In some optional instances, the mass of the crosslinking agent is 0.5 to 1 wt% of the mass of the composite sol, for example, it may be 0.5 wt%, 0.55 wt%, 0.6 wt%, 0.65 wt%, 0.7 wt%, 0.75 wt%, 0.8 wt%, 0.85 wt%, 0.9 wt%, 0.95 wt%, or 1 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0060] This invention specifically limits the mass of the crosslinking agent to 0.5~1wt% of the mass of the composite sol. When the amount of crosslinking agent is within this range, epichlorohydrin molecules can fully contact the surface hydroxyl groups of nanocellulose and iron-modified montmorillonite, and firmly connect through covalent bonds under alkaline catalytic conditions to form a crosslinked network structure with moderate density. This not only significantly improves the strength and toughness of the aerogel adsorbent material, but also retains a sufficient number of pore structures for the diffusion and transport of heavy metal ions.

[0061] When the amount of crosslinking agent is less than 0.5 wt%, the resulting aerogel adsorbent material has a loose structure, making it prone to plastic deformation and even cracking. Simultaneously, the loose gel structure cannot effectively fix and encapsulate the iron-modified montmorillonite, leading to its easy detachment and loss from the gel matrix during practical use. Furthermore, excessively low crosslinking density significantly increases the swelling rate of the final aerogel adsorbent material, causing it to lose its original shape due to excessive water absorption in liquid environments, resulting in poor dimensional stability.

[0062] When the amount of crosslinking agent exceeds 1 wt%, excessive crosslinking leads to a significant reduction in the toughness and elasticity of the aerogel adsorbent material, making it prone to brittle fracture under external force and reducing its impact resistance. At the same time, the excessively dense network structure severely compresses the pore volume inside the material, hindering the diffusion and transport of heavy metal ions within the material, thus preventing heavy metal ions from fully contacting the iron-modified montmorillonite.

[0063] In some alternative examples, the catalyst is sodium hydroxide.

[0064] In some optional instances, the mass of the catalyst is 0.2 to 0.5 wt% of the mass of the composite sol, for example, it may be 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, or 0.5 wt%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0065] In some optional instances, the temperature at which the composite sol, crosslinking agent, and catalyst are mixed, stirred, and heated is 45 to 55°C, for example, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51°C, 52°C, 53°C, 54°C, or 55°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0066] In some optional examples, the mixing, stirring, and heating time of the composite sol, crosslinking agent, and catalyst is 2 to 3 hours, for example, 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours, or 3.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0067] In the crosslinking process of the composite sol, epichlorohydrin acts as a crosslinking agent, reacting with the hydroxyl groups of nanocellulose and iron-modified montmorillonite under the catalysis of sodium hydroxide to form a three-dimensional network. In an alkaline environment, the hydroxyl groups on the surfaces of nanocellulose and iron-modified montmorillonite undergo deprotonation, forming nucleophilic oxygen anions. These oxygen anions attack the epoxy ring of epichlorohydrin, leading to ring opening and the formation of ether bonds. Simultaneously, a new hydroxyl group is generated at the ring-opening end of epichlorohydrin. The chloromethyl (-CH2-Cl) group at the other end of epichlorohydrin hydrolyzes in an alkaline environment, producing OH-. -The chloromethyl group undergoes a nucleophilic substitution reaction, where the chlorine atom is replaced by a hydroxyl group to form an alcohol hydroxyl group (-CH2-OH). Under alkaline conditions, the alcohol hydroxyl group can further deprotonate to form a new nucleophilic oxonium, which then attacks the epoxy ring of other epichlorohydrin molecules. Through continuous ring-opening and substitution, epichlorohydrin molecules covalently link the functional groups at the edges of nanocellulose and montmorillonite sheets via ether bonds, ultimately forming a covalently cross-linked network that significantly enhances the mechanical strength of the aerogel structure.

[0068] As a preferred technical solution of the present invention, in step (II), the time for static aging is 12 to 24 hours, for example, it can be 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours or 24 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0069] In some optional instances, the heat curing temperature is 60~80°C, for example, 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0070] In some optional instances, the heat curing time is 2 to 4 hours, for example, 2.0 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, or 4.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0071] In some optional instances, the composite gel is immersed in anhydrous ethanol, and the ethanol is replaced with fresh anhydrous ethanol every 6 to 8 hours for a total of 3 to 5 times.

[0072] In some optional instances, the freeze-drying temperature is -40 to -50°C, for example, -40°C, -41°C, -42°C, -43°C, -44°C, -45°C, -46°C, -47°C, -48°C, -49°C, or -50°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0073] In some optional instances, the freeze-drying time is 24 to 36 hours, for example, 24 hours, 25 hours, 26 hours, 27 hours, 28 hours, 29 hours, 30 hours, 31 hours, 32 hours, 33 hours, 34 hours, 35 hours, or 36 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0074] Secondly, the present invention provides an aerogel adsorbent material for remediation of contaminated soil prepared by the preparation method described in the first aspect.

[0075] Thirdly, the present invention provides an application of the aerogel adsorbent material for remediating contaminated soil as described in the second aspect, wherein the aerogel adsorbent material is used to remediate heavy metal contaminated soil.

[0076] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0077] This invention prepares an aerogel adsorbent material with both high adsorption capacity and stable structure. First, sodium-based montmorillonite is intercalated to expand the interlayer spacing. Then, under weakly alkaline conditions, amorphous iron oxides are loaded into the montmorillonite interlayers via ferric chloride hydrolysis. Subsequently, using nanocellulose as a three-dimensional network matrix, iron-modified montmorillonite is covalently linked through a crosslinking agent to form a stable porous structure. Solvent displacement and freeze-drying allow the aerogel to retain its high specific surface area while possessing excellent mechanical strength, achieving efficient fixation of various heavy metals. Attached Figure Description

[0078] Figure 1 The following is a process flow diagram of the preparation process of the aerogel adsorption material provided in Examples 1-13 of the present invention;

[0079] Figure 2 This is a scanning electron microscope image of the aerogel adsorbent material prepared in Example 1 of the present invention;

[0080] Figure 3 Infrared spectra of nanocellulose, iron-modified montmorillonite prepared in Example 1 of this invention, and aerogel adsorbent material. Detailed Implementation

[0081] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0082] Example 1

[0083] This embodiment provides a method for preparing aerogel adsorbent materials for contaminated soil remediation, such as... Figure 1 As shown, the preparation method specifically includes the following steps:

[0084] (1) Sodium montmorillonite was dispersed in deionized water and mixed and heated at 600 rpm and 60°C for 3 h to obtain a montmorillonite dispersion with a mass fraction of 4 wt%. A 10 g / L hexadecyltrimethylammonium bromide solution was added dropwise to the montmorillonite dispersion at a rate of 1 mL / min at a stirring speed of 600 rpm and a heating temperature of 75°C. The mass ratio of hexadecyltrimethylammonium bromide in the hexadecyltrimethylammonium bromide solution to sodium montmorillonite in the montmorillonite dispersion was 0.15:1. After all the hexadecyltrimethylammonium bromide solution was added, the mixture was mixed, stirred and heated for 14 h. Then, the mixture was centrifuged and the precipitate was washed repeatedly with deionized water until no bromide ions could be detected with silver nitrate solution. Finally, the mixture was dried at 80°C for 15 h to obtain intercalated montmorillonite.

[0085] (2) The intercalated montmorillonite was dispersed in deionized water to obtain a montmorillonite suspension with a mass fraction of 4 wt%. At a stirring speed of 500 rpm and a heating temperature of 55 ℃, a ferric chloride solution with a concentration of 0.4 mol / L was added dropwise to the montmorillonite suspension at a dropwise rate of 1 mL / min. The mass ratio of ferric chloride hexahydrate in the ferric chloride solution to intercalated montmorillonite in the montmorillonite suspension was 0.3:1. At the same time as adding the ferric chloride solution, a sodium hydroxide solution with a concentration of 1 mol / L was added dropwise to the mixture to control the pH value of the mixture at 7. After all the ferric chloride solution was added, the mixture was stirred and heated for 2 h to obtain the reaction product solution. The reaction product solution was placed at 60 ℃ and aged for 15 h. Then, it was centrifuged and the precipitate was repeatedly washed with deionized water until no chloride ions were detected by silver nitrate solution. Finally, it was dried at 80 ℃ for 15 h to obtain iron-modified montmorillonite.

[0086] (3) Iron-modified montmorillonite and a nanocellulose solution with a mass fraction of 1.5 wt% were mixed at a mass ratio of 0.22:1 and heated at 40°C for 4 hours to obtain a composite sol. Epichlorohydrin and sodium hydroxide were added to the composite sol, with the mass of epichlorohydrin being 0.5 wt% of the mass of the composite sol and the mass of sodium hydroxide being 0.2 wt% of the mass of the composite sol. The mixture was then heated at 45°C for 3 hours to obtain a gel precursor solution. The gel precursor solution was injected into a mold and aged at room temperature for 12 hours to obtain an intermediate gel. The intermediate gel was removed and heated at 60°C for 4 hours to obtain a composite gel. The composite gel was immersed in anhydrous ethanol for solvent replacement (anhydrous ethanol replaced the water in the composite gel). The anhydrous ethanol was replaced every 6 hours for a total of 5 times. Finally, the composite gel was freeze-dried at -40°C for 36 hours to obtain the aerogel adsorbent material.

[0087] Figure 2The image shows a scanning electron microscope (SEM) image of the aerogel adsorbent material prepared in this embodiment. As can be seen from the image, the aerogel adsorbent material exhibits a layered, stacked, porous, and interconnected microstructure. The layers and channels are interconnected without obvious closed pores. This is because, during the preparation process, a three-dimensional network is formed through sol-gel, combined with solvent displacement and freeze-drying, ultimately resulting in the pore structure shown in the image. The loose and porous structure endows the material with high porosity and specific surface area, while the interconnected pore structure promotes the diffusion and transport of heavy metal ions within the material, facilitating sufficient contact between heavy metal ions and iron-modified montmorillonite.

[0088] Figure 3 The figures show the infrared spectra of nanocellulose, the iron-modified montmorillonite prepared in this embodiment, and the aerogel adsorbent material. As can be seen from the figures, in the infrared curve of nanocellulose, the 3200~3600 cm⁻¹... -1 The characteristic peak at 2800~3000 cm⁻¹ is attributed to the OH stretching vibration, which originates from the intramolecular / intermolecular hydrogen bonds of cellulose molecules; -1 The characteristic peak at this point is attributed to the CH stretching vibration, originating from the CH bonds of saturated alkyl groups such as -CH2OH and -CH- on the glucose unit; 1000~1200 cm⁻¹ -1 The characteristic peak at 1300~1400 cm⁻¹ is attributed to the CO stretching vibration, which originates from the cellulose glycosidic bond (COC) and the hydroxyl group (C-OH); -1 The characteristic peak at this location is attributed to the CH bending vibration. In the infrared curve of iron-modified montmorillonite, the peak at 3200–3600 cm⁻¹ is... -1 The characteristic peak at 2800~3000 cm⁻¹ belongs to the OH stretching vibration, which originates from the HOH stretching of interlayer water in montmorillonite and the OH of hydrated hydroxyl groups; -1 The characteristic peak at 1400–1450 cm⁻¹ is attributed to the CH stretching vibration, which originates from the saturated CH bonds in the CTAB alkyl chain; -1 The characteristic peak at 1000~1100 cm⁻¹ belongs to the CN stretching vibration, which originates from the CN bond of the CTAB quaternary ammonium salt group. It is a new characteristic peak introduced after intercalation modification; -1 The characteristic peak at 500~700 cm⁻¹ belongs to the Si-O stretching vibration, which originates from the Si-O-Si bonds in the silicon-oxygen tetrahedral framework of montmorillonite; -1 The characteristic peak at 1600 cm⁻¹ belongs to the Fe-O stretching vibration, which originates from the Fe-O bonds in the iron oxide formed after the hydrolysis of FeCl₃; -1 The characteristic peak at this location is attributed to the OH bending vibration, which originates from the HOH bending of interlayer water. The presence of these functional groups indicates that the iron-modified montmorillonite prepared in this embodiment is derived from sodium-based montmorillonite through hexadecyltrimethylammonium bromide intercalation modification and Fe... 3+The loaded material contained a montmorillonite framework, CTAB quaternary ammonium salt, iron oxides, and interlayer water. In the infrared spectrum of the aerogel adsorbent material, the range was 3200–3600 cm⁻¹. -1 The characteristic peak at 2800~3000 cm⁻¹ belongs to the OH stretching vibration, which originates from the OH groups of nanocellulose, montmorillonite interlayer water, and hydrated hydroxyl groups of iron oxides; -1 The characteristic peak at 1000~1200 cm⁻¹ is attributed to the CH stretching vibration, which originates from the superposition of saturated CH₄ in nanocellulose and saturated CH₄ in CTAB alkyl chains; -1 The characteristic peak at 500-700 cm⁻¹ is attributed to the CO stretching vibration, which originates from the multiple superposition of glycosidic bonds in nanocellulose, Si-O in montmorillonite, and COC ether bonds formed by epichlorohydrin crosslinking; -1 The characteristic peak at 1400~1450 cm⁻¹ belongs to the Fe-O stretching vibration, which originates from the characteristic peak of iron oxides in iron-modified montmorillonite; -1 The characteristic peak at this location is attributed to the CN stretching vibration, which originates from the characteristic peak of the CTAB quaternary ammonium salt group in iron-modified montmorillonite.

[0089] Example 2

[0090] This embodiment provides a method for preparing aerogel adsorbent materials for contaminated soil remediation, such as... Figure 1 As shown, the preparation method specifically includes the following steps:

[0091] (1) Sodium montmorillonite was dispersed in deionized water and mixed and heated at 650 rpm and 62°C for 2.8 h to obtain a montmorillonite dispersion with a mass fraction of 4.5 wt%. A 12 g / L hexadecyltrimethylammonium bromide solution was added dropwise to the montmorillonite dispersion at a rate of 1.2 mL / min at a stirring speed of 650 rpm and a heating temperature of 78°C. The mass ratio of hexadecyltrimethylammonium bromide in the hexadecyltrimethylammonium bromide solution to sodium montmorillonite in the montmorillonite dispersion was 0.18:1. After all the hexadecyltrimethylammonium bromide solution was added, the mixture was mixed and heated for 13.5 h. Then, the mixture was centrifuged and the precipitate was washed repeatedly with deionized water until no bromide ions could be detected with silver nitrate solution. Finally, the mixture was dried at 82°C for 13 h to obtain intercalated montmorillonite.

[0092] (2) The intercalated montmorillonite was dispersed in deionized water to obtain a montmorillonite suspension with a mass fraction of 4.5 wt%. At a stirring speed of 520 rpm and a heating temperature of 58 ℃, a ferric chloride solution with a concentration of 0.45 mol / L was added dropwise to the montmorillonite suspension at a dropping rate of 1.2 mL / min. The mass ratio of ferric chloride hexahydrate in the ferric chloride solution to intercalated montmorillonite in the montmorillonite suspension was 0.32:1. At the same time as adding the ferric chloride solution, a sodium hydroxide solution with a concentration of 1.2 mol / L was added dropwise to the mixture to control the pH value of the mixture at 7.2. After all the ferric chloride solution was added, the mixture was stirred and heated for 1.8 h to obtain the reaction product solution. The reaction product solution was placed at 62 ℃ and aged for 13 h. Then, it was centrifuged and the precipitate was repeatedly washed with deionized water until no chloride ions were detected by silver nitrate solution. Finally, it was dried at 82 ℃ for 13 h to obtain iron-modified montmorillonite.

[0093] (3) Iron-modified montmorillonite and a nanocellulose solution with a mass fraction of 1.8 wt% were mixed at a mass ratio of 0.23:1 and heated at 42°C for 3.5 h to obtain a composite sol. Epichlorohydrin and sodium hydroxide were added to the composite sol, with the mass of epichlorohydrin being 0.6 wt% of the mass of the composite sol and the mass of sodium hydroxide being 0.3 wt% of the mass of the composite sol. The mixture was then heated at 48°C for 2.8 h to obtain a gel precursor solution. The gel precursor solution was injected into a mold and aged at room temperature for 15 h to obtain an intermediate gel. The intermediate gel was removed and heated at 65°C for 3.5 h to obtain a composite gel. The composite gel was immersed in anhydrous ethanol for solvent replacement (anhydrous ethanol replaced the water in the composite gel). The anhydrous ethanol was replaced every 6 h for a total of 5 times. Finally, the composite gel was freeze-dried at -42°C for 33 h to obtain the aerogel adsorbent material.

[0094] Example 3

[0095] This embodiment provides a method for preparing aerogel adsorbent materials for contaminated soil remediation, such as... Figure 1 As shown, the preparation method specifically includes the following steps:

[0096] (1) Sodium montmorillonite was dispersed in deionized water and mixed and heated at 700 rpm and 65°C for 2.5 h to obtain a montmorillonite dispersion with a mass fraction of 5 wt%. A 15 g / L hexadecyltrimethylammonium bromide solution was added dropwise to the montmorillonite dispersion at a rate of 1.5 mL / min at a stirring speed of 700 rpm and a heating temperature of 80°C. The mass ratio of hexadecyltrimethylammonium bromide in the hexadecyltrimethylammonium bromide solution to sodium montmorillonite in the montmorillonite dispersion was 0.2:1. After all the hexadecyltrimethylammonium bromide solution was added, the mixture was mixed and heated for 13 h. Then, the mixture was centrifuged and the precipitate was washed repeatedly with deionized water until no bromide ions could be detected by silver nitrate solution. Finally, the mixture was dried at 85°C for 12 h to obtain intercalated montmorillonite.

[0097] (2) The intercalated montmorillonite was dispersed in deionized water to obtain a montmorillonite suspension with a mass fraction of 5 wt%. At a stirring speed of 550 rpm and a heating temperature of 60 ℃, a ferric chloride solution with a concentration of 0.5 mol / L was added dropwise to the montmorillonite suspension at a dropping rate of 1.5 mL / min. The mass ratio of ferric chloride hexahydrate in the ferric chloride solution to intercalated montmorillonite in the montmorillonite suspension was 0.35:1. At the same time as adding the ferric chloride solution, a sodium hydroxide solution with a concentration of 1.5 mol / L was added dropwise to the mixture to control the pH value of the mixture at 7.3. After all the ferric chloride solution was added, the mixture was stirred and heated for 1.5 h to obtain the reaction product solution. The reaction product solution was placed at 65 ℃ and aged for 12 h. Then, it was centrifuged and the precipitate was repeatedly washed with deionized water until no chloride ions were detected by silver nitrate solution. Finally, it was dried at 85 ℃ for 12 h to obtain iron-modified montmorillonite.

[0098] (3) Iron-modified montmorillonite and a nanocellulose solution with a mass fraction of 2 wt% were mixed at a mass ratio of 0.23:1 and heated at 45°C for 3 hours to obtain a composite sol. Epichlorohydrin and sodium hydroxide were added to the composite sol, with the mass of epichlorohydrin being 0.7 wt% of the mass of the composite sol and the mass of sodium hydroxide being 0.3 wt% of the mass of the composite sol. The mixture was then heated at 50°C for 2.5 hours to obtain a gel precursor solution. The gel precursor solution was injected into a mold and aged at room temperature for 18 hours to obtain an intermediate gel. The intermediate gel was removed and heated at 70°C for 3 hours to obtain a composite gel. The composite gel was immersed in anhydrous ethanol for solvent replacement (anhydrous ethanol replaced the water in the composite gel). The anhydrous ethanol was replaced every 7 hours for a total of 4 times. Finally, the composite gel was freeze-dried at -45°C for 30 hours to obtain the aerogel adsorbent material.

[0099] Example 4

[0100] This embodiment provides a method for preparing aerogel adsorbent materials for contaminated soil remediation, such as... Figure 1 As shown, the preparation method specifically includes the following steps:

[0101] (1) Sodium-based montmorillonite was dispersed in deionized water and mixed and heated at 750 rpm and 68°C for 2.2 h to obtain a montmorillonite dispersion with a mass fraction of 5.5 wt%. At 750 rpm and 82°C, a hexadecyltrimethylammonium bromide solution with a concentration of 18 g / L was added dropwise to the montmorillonite dispersion at a rate of 1.8 mL / min. The mass ratio of hexadecyltrimethylammonium bromide in the hexadecyltrimethylammonium bromide solution to sodium-based montmorillonite in the montmorillonite dispersion was 0.22:1. After all the hexadecyltrimethylammonium bromide solution was added, the mixture was mixed and heated for 12.5 h. Then, the mixture was centrifuged and the precipitate was washed repeatedly with deionized water until no bromide ions could be detected with silver nitrate solution. Finally, the mixture was dried at 88°C for 11 h to obtain intercalated montmorillonite.

[0102] (2) The intercalated montmorillonite was dispersed in deionized water to obtain a montmorillonite suspension with a mass fraction of 5.5 wt%. At a stirring speed of 580 rpm and a heating temperature of 62 ℃, a ferric chloride solution with a concentration of 0.55 mol / L was added dropwise to the montmorillonite suspension at a dropping rate of 1.8 mL / min. The mass ratio of ferric chloride hexahydrate in the ferric chloride solution to intercalated montmorillonite in the montmorillonite suspension was 0.38:1. At the same time as adding the ferric chloride solution, a sodium hydroxide solution with a concentration of 1.8 mol / L was added dropwise to the mixture to control the pH value of the mixture at 7.4. After all the ferric chloride solution was added, the mixture was stirred and heated for 1.2 h to obtain the reaction product solution. The reaction product solution was placed at 68 ℃ and aged for 11 h. Then, it was centrifuged and the precipitate was repeatedly washed with deionized water until no chloride ions were detected by silver nitrate solution. Finally, it was dried at 88 ℃ for 11 h to obtain iron-modified montmorillonite.

[0103] (3) Iron-modified montmorillonite and a nanocellulose solution with a mass fraction of 2.2 wt% were mixed at a mass ratio of 0.24:1 and heated at 48°C for 2.5 h to obtain a composite sol. Epichlorohydrin and sodium hydroxide were added to the composite sol, with the mass of epichlorohydrin being 0.8 wt% of the mass of the composite sol and the mass of sodium hydroxide being 0.4 wt% of the mass of the composite sol. The mixture was then heated at 52°C for 2.2 h to obtain a gel precursor solution. The gel precursor solution was injected into a mold and aged at room temperature for 21 h to obtain an intermediate gel. The intermediate gel was removed and heated at 75°C for 2.5 h to obtain a composite gel. The composite gel was immersed in anhydrous ethanol for solvent replacement (anhydrous ethanol replaced the water in the composite gel). The anhydrous ethanol was replaced every 7 h for a total of 4 times. Finally, the composite gel was freeze-dried at -48°C for 27 h to obtain the aerogel adsorbent material.

[0104] Example 5

[0105] This embodiment provides a method for preparing aerogel adsorbent materials for contaminated soil remediation, such as... Figure 1 As shown, the preparation method specifically includes the following steps:

[0106] (1) Disperse sodium montmorillonite in deionized water and mix and heat at 800 rpm and 70°C for 2 h to obtain a montmorillonite dispersion with a mass fraction of 6 wt%. Add a 20 g / L hexadecyltrimethylammonium bromide solution to the montmorillonite dispersion at a dropping rate of 2 mL / min at 800 rpm and 85°C. The mass ratio of hexadecyltrimethylammonium bromide in the hexadecyltrimethylammonium bromide solution to sodium montmorillonite in the montmorillonite dispersion is 0.25:1. After all the hexadecyltrimethylammonium bromide solution has been added, continue mixing, stirring and heating for 12 h. Then, centrifuge and wash the precipitate repeatedly with deionized water until no bromide ions can be detected with silver nitrate solution. Finally, dry at 90°C for 10 h to obtain intercalated montmorillonite.

[0107] (2) The intercalated montmorillonite was dispersed in deionized water to obtain a montmorillonite suspension with a mass fraction of 6 wt%. At a stirring speed of 600 rpm and a heating temperature of 65 ℃, a ferric chloride solution with a concentration of 0.6 mol / L was added dropwise to the montmorillonite suspension at a dropping rate of 2 mL / min. The mass ratio of ferric chloride hexahydrate in the ferric chloride solution to intercalated montmorillonite in the montmorillonite suspension was 0.4:1. At the same time as adding the ferric chloride solution, a sodium hydroxide solution with a concentration of 2 mol / L was added dropwise to the mixture to control the pH value of the mixture at 7.5. After all the ferric chloride solution was added, the mixture was stirred and heated for 1 h to obtain the reaction product solution. The reaction product solution was placed at 70 ℃ and aged for 10 h. Then, it was centrifuged and the precipitate was repeatedly washed with deionized water until no chloride ions were detected by silver nitrate solution. Finally, it was dried at 90 ℃ for 10 h to obtain iron-modified montmorillonite.

[0108] (3) Iron-modified montmorillonite and a nanocellulose solution with a mass fraction of 2.5 wt% were mixed at a mass ratio of 0.25:1 and heated at 50°C for 2 hours to obtain a composite sol. Epichlorohydrin and sodium hydroxide were added to the composite sol, with the mass of epichlorohydrin being 1 wt% of the mass of the composite sol and the mass of sodium hydroxide being 0.5 wt% of the mass of the composite sol. The mixture was then heated at 55°C for 2 hours to obtain a gel precursor solution. The gel precursor solution was injected into a mold and aged at room temperature for 24 hours to obtain an intermediate gel. The intermediate gel was removed and heated at 80°C for 2 hours to obtain a composite gel. The composite gel was immersed in anhydrous ethanol for solvent replacement (anhydrous ethanol replaced the water in the composite gel). The anhydrous ethanol was replaced every 8 hours for a total of 3 times. Finally, the composite gel was freeze-dried at -50°C for 24 hours to obtain the aerogel adsorbent material.

[0109] Example 6

[0110] This embodiment provides a method for preparing an aerogel adsorbent material for remediation of contaminated soil. The difference from Example 1 is that the mass ratio of hexadecyltrimethylammonium bromide in the hexadecyltrimethylammonium bromide solution to sodium montmorillonite in the montmorillonite dispersion is adjusted to 0.1:1. Other operating steps and process parameters are exactly the same as in Example 1.

[0111] Example 7

[0112] This embodiment provides a method for preparing an aerogel adsorbent material for remediation of contaminated soil. The difference from Example 1 is that the mass ratio of hexadecyltrimethylammonium bromide in the hexadecyltrimethylammonium bromide solution to sodium montmorillonite in the montmorillonite dispersion is adjusted to 0.3:1. Other operating steps and process parameters are exactly the same as in Example 1.

[0113] Example 8

[0114] This embodiment provides a method for preparing aerogel adsorbent material for contaminated soil remediation. The difference from Embodiment 1 is that the mass ratio of ferric chloride hexahydrate in the ferric chloride solution to intercalated montmorillonite in the montmorillonite suspension is adjusted to 0.1:1. Other operating steps and process parameters are exactly the same as in Embodiment 1.

[0115] Example 9

[0116] This embodiment provides a method for preparing aerogel adsorbent material for contaminated soil remediation. The difference from Embodiment 1 is that the mass ratio of ferric chloride hexahydrate in the ferric chloride solution to intercalated montmorillonite in the montmorillonite suspension is adjusted to 0.5:1. Other operating steps and process parameters are exactly the same as in Embodiment 1.

[0117] Example 10

[0118] This embodiment provides a method for preparing an aerogel adsorbent material for contaminated soil remediation. The difference from Embodiment 1 is that the mass ratio of iron-modified montmorillonite and nanocellulose solution is adjusted to 0.2:1, while other operating steps and process parameters are exactly the same as in Embodiment 1.

[0119] Example 11

[0120] This embodiment provides a method for preparing an aerogel adsorbent material for remediation of contaminated soil. The difference from Embodiment 1 is that the mass ratio of iron-modified montmorillonite and nanocellulose solution is adjusted to 0.3:1, while other operating steps and process parameters are exactly the same as in Embodiment 1.

[0121] Example 12

[0122] This embodiment provides a method for preparing an aerogel adsorbent material for contaminated soil remediation. The difference from Embodiment 1 is that the mass of epichlorohydrin is adjusted to 0.1 wt% of the mass of the composite sol, while the other operating steps and process parameters are exactly the same as in Embodiment 1.

[0123] Example 13

[0124] This embodiment provides a method for preparing an aerogel adsorbent material for contaminated soil remediation. The difference from Embodiment 1 is that the mass of epichlorohydrin is adjusted to 1.5 wt% of the mass of the composite sol, while the other operating steps and process parameters are exactly the same as in Embodiment 1.

[0125] The heavy metal removal rate, leaching toxicity, and compressive strength of the aerogel adsorbent materials prepared in Examples 1-13 were tested. The specific test steps included:

[0126] (1) Heavy metal removal rate

[0127] Take clean soil (pH=6.5±0.5, organic matter content 2.5%), crush it through a 2mm sieve, and add Pb(NO3)2 solution (Pb 2+ ), Cd(NO3)2 solution (Cd 2+ ), NaAsO2 solution (As 3+ ), NaAsO3 solution (As 5+ K2Cr2O7 solution (Cr) 6+ ), regulating Pb in soil 2+ Concentration up to 800 mg / kg, Cd 2+ Concentration up to 80 mg / kg, As 3+ The concentration was up to 80 mg / kg, As 5+ The concentration was up to 80 mg / kg, Cr 6+ The concentration was increased to 50 mg / kg, and the soil was aged for 30 days (25℃) to age the heavy metals, thus obtaining simulated contaminated soil.

[0128] The aerogel adsorbent material prepared in the example was crushed into particles with a particle size of 5-10 mm. The crushed particles were added at 5 wt% of the mass of the simulated contaminated soil. The moisture content of the simulated contaminated soil was adjusted to 60% of the field capacity with deionized water. The soil was incubated in a constant temperature incubator (25±1℃, protected from light) and stirred regularly. On the 7th day, soil from a depth of 0-15 cm was taken, freeze-dried, ground and passed through a 100-mesh sieve. The soil was digested until clear using the EPA 3052 method (HCl-HNO3-HF microwave digestion). After cooling, the volume was adjusted to 50 mL and filtered through a 0.45 μm filter membrane. The filtrate was collected.

[0129] Pb in the filtrate was determined by inductively coupled plasma mass spectrometry. 2+ Concentration and Cd 2+ The concentration of As in the filtrate was determined by high performance liquid chromatography-inductively coupled plasma mass spectrometry. 3+ And As 5+ The concentration of Cr in the filtrate was determined by the diphenylcarbazide spectrophotometric method. 6+ The concentration.

[0130] The removal rate of various heavy metal ions is calculated using the following formula:

[0131]

[0132] Where C0 represents the initial concentration of various heavy metal ions in the simulated contaminated soil, C t The concentration of various heavy metal ions in the filtrate obtained after 7 days of treatment.

[0133] (2) Leaching toxicity

[0134] Dissolve 5.7 mL of glacial acetic acid in 500 mL of deionized water, add 64.3 mL of NaOH solution, and bring the volume to 1 L. Adjust the pH to 4.93 ± 0.05 to obtain the extractant. Crush the aerogel adsorbent material prepared in the example to particles ≤ 1 mm in diameter, dry at 105 °C to constant weight, place 5.0 g of the dried sample in a centrifuge tube, add 100 mL of the extractant at a solid-liquid ratio of 1:20, place on a vortex mixer, and continuously shake at 30 ± 2 rpm for 18 h. After shaking, let stand for 10 min, then vacuum filter using a 0.45 μm microporous membrane. Collect the filtrate, and determine the Pb content in the filtrate using inductively coupled plasma mass spectrometry. 2+ Concentration and Cd 2+ The concentration of As in the filtrate was determined by high performance liquid chromatography-inductively coupled plasma mass spectrometry. 3+ And As 5+ The concentration of Cr in the filtrate was determined by the diphenylcarbazide spectrophotometric method. 6+ The concentration.

[0135] (3) Compressive strength

[0136] The aerogel adsorbent material prepared in the examples was cut into cylindrical specimens with a diameter of 10 mm × 10 mm and dried at 105 °C to constant weight. The specimens were vertically fixed in a universal testing machine and subjected to vertical pressure at a loading rate of 1 mm / min. The load-displacement curves were collected in real time. Loading was stopped when the first through crack appeared in the specimen, and the peak load F was recorded. max (N). The compressive strength σ is calculated using the following formula. c (MPa):

[0137] σ c =F max / A

[0138] Where A is the area of ​​the specimen subjected to pressure (mm²) 2 ).

[0139] The test results are shown in Table 1.

[0140] Table 1

[0141]

[0142] The test data from Examples 1, 6, and 7 show that when the amount of CTAB is too low (Example 6), the intercalation effect on montmorillonite is weakened, the interlayer spacing of montmorillonite is not sufficiently increased, resulting in uneven and low iron oxide loading, a decrease in the removal rate of heavy metal ions, and a reduction in compressive strength due to insufficient interlayer support. When the amount of CTAB is too high (Example 7), although the interlayer spacing of montmorillonite is increased, the excessive CTAB long chains cover the surface of montmorillonite, hindering iron ions from entering the interlayer spacing. The resulting iron oxide aggregates block the pore structure of the aerogel matrix, leading to a decrease in the fixation and adsorption capacity for heavy metal ions.

[0143] The test data from Examples 1, 8, and 9 show that when the amount of ferric chloride hexahydrate is too low (Example 8), the amount of iron oxide generated is insufficient, the surface hydroxyl density is too low, and the ability to fix heavy metal ions decreases. When the amount of ferric chloride hexahydrate is too high (Example 9), excessive deposition of iron oxides causes agglomeration, blocking the interlayer channels of montmorillonite, resulting in a decrease in the removal rate of heavy metal ions. At the same time, the iron oxide agglomerates strongly expand the montmorillonite sheets, destroying the integrity of the montmorillonite sheet structure, resulting in a decrease in the compressive strength of the aerogel adsorbent material.

[0144] The test data from Examples 1, 10, and 11 show that when the amount of iron-modified montmorillonite is too low (Example 10), the removal rate of heavy metal ions decreases, and the leaching concentration increases. Simultaneously, insufficient iron-modified montmorillonite weakens the rigid support of the aerogel matrix, increasing the brittleness of the aerogel adsorbent material and reducing its compressive strength. When the amount of iron-modified montmorillonite is too high (Example 11), the montmorillonite sheets aggregate and block the pore structure of the aerogel matrix, hindering the diffusion and transport of heavy metal ions into the material, resulting in a decrease in the removal rate of heavy metal ions. Furthermore, the aggregates also cause stress concentration in the aerogel matrix, leading to a decrease in the compressive strength of the aerogel adsorbent material.

[0145] The test data from Examples 1, 12, and 13 show that when the amount of epichlorohydrin is too low (Example 12), the resulting aerogel adsorbent material has a loose structure, causing pore collapse during freeze-drying and a decrease in compressive strength. Simultaneously, the loose aerogel matrix cannot effectively fix and coat the iron-modified montmorillonite, leading to easy detachment of the iron-modified montmorillonite from the gel matrix during actual use, resulting in a reduced removal rate of heavy metal ions. When the amount of epichlorohydrin is too high (Example 13), excessive cross-linking results in excessively rigid gel with poor flexibility, making it prone to brittle fracture under external force and reducing compressive strength. Furthermore, the excessively dense gel structure severely compresses the pore volume within the material, hindering the diffusion and transport of heavy metal ions within the material, thus preventing the iron-modified montmorillonite loaded inside the material from fully functioning.

[0146] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing an aerogel adsorbent material for contaminated soil remediation, characterized by, The preparation method comprises: (I) intercalation treatment of sodium-based montmorillonite to obtain intercalated montmorillonite; the intercalated montmorillonite is dispersed in deionized water to obtain a montmorillonite suspension, under stirring and heating, an iron chloride solution is added dropwise into the montmorillonite suspension, the mass ratio of ferric chloride hexahydrate in the iron chloride solution to the intercalated montmorillonite in the montmorillonite suspension is (0.3-0.4):1, and an alkali solution is added dropwise to adjust the pH value of the reaction system, followed by standing and aging, filtration, washing and drying to obtain iron-modified montmorillonite; The operation steps of the intercalation treatment of the sodium-based montmorillonite comprise: The sodium-based montmorillonite is dispersed in deionized water, mixed, stirred and heated to obtain a montmorillonite dispersion; under stirring and heating, a cetyltrimethylammonium bromide solution is added dropwise into the montmorillonite dispersion, after all the cetyltrimethylammonium bromide solution is added dropwise, the mixture is continuously stirred and heated, and then the intercalated montmorillonite is obtained through centrifugal separation, washing and drying; The mass ratio of cetyltrimethylammonium bromide in the cetyltrimethylammonium bromide solution to the sodium-based montmorillonite in the montmorillonite dispersion is (0.15-0.25):1; (II) the iron-modified montmorillonite and a nanocellulose solution are mixed, stirred and heated to obtain a composite sol, the mass ratio of the iron-modified montmorillonite to the nanocellulose solution is (0.22-0.25):1, a crosslinking agent and a catalyst are added into the composite sol, the crosslinking agent is epichlorohydrin, and the mass of the crosslinking agent is 0.5-1 wt% of the mass of the composite sol, after mixed, stirred and heated, the composite sol is poured into a mold to stand and age and to be heated and cured to obtain a composite gel, the composite gel is immersed in anhydrous ethanol for solvent replacement, and then the aerogel adsorption material is obtained through freeze drying.

2. The production method according to claim 1, characterized by, The temperature of the mixed, stirred and heated sodium-based montmorillonite in the deionized water is 60-70℃; The time of the mixed, stirred and heated sodium-based montmorillonite in the deionized water is 2-3h; The mass fraction of the sodium-based montmorillonite in the montmorillonite dispersion is 4-6wt%.

3. The production method according to claim 1, characterized by, The cetyltrimethylammonium bromide solution is added dropwise into the montmorillonite dispersion under stirring at a stirring speed of 600-800rpm and heating at a temperature of 75-85℃; The concentration of cetyltrimethylammonium bromide in the cetyltrimethylammonium bromide solution is 10-20g / L; After all the cetyltrimethylammonium bromide solution is added dropwise, the mixture is continuously stirred and heated for 12-14h.

4. The method of claim 1, wherein, In step (I), the mass fraction of the intercalated montmorillonite in the montmorillonite suspension is 4-6wt%; The iron chloride solution is added dropwise into the montmorillonite suspension under stirring at a stirring speed of 500-600rpm and heating at a temperature of 55-65℃; The iron chloride solution is composed of ferric chloride hexahydrate and deionized water; The concentration of ferric chloride hexahydrate in the iron chloride solution is 0.4-0.6mol / L; During the addition of the iron chloride solution, the alkali solution is added dropwise into the formed mixture to control the pH value of the mixture to be 7-7.5; After all the iron chloride solution is added dropwise, the obtained mixture is continuously stirred and heated for 1-2h; The temperature of the static aging is 60-70℃; The time of the static aging is 10-15h.

5. The preparation method according to claim 1, characterized in that, In step (II), the mass fraction of the nanocellulose solution is 1.5-2.5wt%; The temperature of the mixing, stirring and heating of the iron modified montmorillonite and the nanocellulose solution is 40-50℃; The time of the mixing, stirring and heating of the iron modified montmorillonite and the nanocellulose solution is 2-4h.

6. The method of claim 1, wherein, In step (II), the catalyst is sodium hydroxide; The mass of the catalyst is 0.2-0.5wt% of the mass of the composite sol; The temperature of the mixing, stirring and heating of the composite sol, the crosslinking agent and the catalyst is 45-55℃; The time of the mixing, stirring and heating of the composite sol, the crosslinking agent and the catalyst is 2-3h.

7. The preparation method according to claim 1, characterized in that, In step (II), the time of the static aging is 12-24h; The temperature of the heating and solidification is 60-80℃; The time of the heating and solidification is 2-4h. The composite gel is immersed in anhydrous ethanol, and the anhydrous ethanol is replaced every 6-8h, and the replacement is performed 3-5 times in total; The temperature of the freeze drying is -40--50℃; The time of the freeze drying is 24-36h.

8. An aerogel adsorption material for repairing contaminated soil, which is prepared by the method of any one of claims 1-7.

9. Use of the aerogel adsorbent material for the remediation of contaminated soil according to claim 8, characterized in that, The aerogel adsorption material is used for repairing heavy metal contaminated soil.

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