Method for strengthening migration and arrangement of metal type nanoparticles in aquifer medium

Abstract

The invention provides a method for strengthening migration and arrangement of metal type nano particles in an aquifer medium. Comprising the following steps: constructing a mesoporous silica coating layer on the surface of a metal type nano particle, then dispersing the metal type nano particle in water, and performing dispersion treatment to obtain a particle suspension; and injecting the particle turbid liquid into the aquifer medium to be treated, so that the nano particles are migrated and dispersed into pore channels of the aquifer medium. The metal nanoparticles are coated with the mesoporous silica, and the coating layer is used as a physical barrier, so that particle aggregation is effectively inhibited, and long-time stable dispersion of the metal nanoparticles in a system is ensured; meanwhile, contact with porous media is reduced, and the migration performance is remarkably improved. In addition, the mesoporous structure on the coating layer can expose active sites of the inner core metal type nanoparticles, so that the material is endowed with reaction capacity. According to the method, the catalytic function is reserved while long-distance migration of the metal type nanoparticles is achieved, and the mesoporous silica is environmentally friendly and free of secondary pollution risks.

Description

Technical Field

[0001] This invention relates to the field of environmental engineering technology, and more specifically, to a method for enhancing the migration and deployment of metallic nanoparticles in aquifer media. Background Technology

[0002] With socio-economic development and population growth, the widespread use of various organic materials in industrial and agricultural production and daily life has led to increasingly severe soil and groundwater pollution problems. Among these, the remediation of recalcitrant organic pollutants such as chlorinated hydrocarbons, petroleum hydrocarbons, and polycyclic aromatic hydrocarbons is particularly challenging. Numerous studies have confirmed that metallic nanoparticles (such as zero-valent iron (nZVI), iron(III) oxide (nFe3O4), and titanium dioxide (nTiO2) exhibit great application potential in in-situ groundwater remediation technologies based on in-situ chemical reduction (ISCR) or in-situ chemical oxidation (ISCO) principles due to their high reactivity. By injecting metallic nanoparticles into aquifers, an in-situ active reaction zone can be formed in the polluted area, achieving highly efficient degradation of pollutants.

[0003] However, the engineering application effectiveness of this technology largely depends on the migration and deployment capabilities of nanoparticles in the aquifer medium. Metallic nanoparticles have a large specific surface area and high surface energy, making them prone to aggregation in aqueous environments, forming large aggregates. These aggregates are easily adsorbed or trapped by physical sieving, gravity settling, or electrostatic / van der Waals forces with the medium surface when passing through the complex and narrow pores of the aquifer. This results in a large amount of injected nanoparticles depositing in a limited area near the injection well, making it difficult for them to effectively migrate to the distant target contaminated area and form a sufficiently large active reaction zone, severely limiting remediation efficiency and practical application effectiveness.

[0004] To improve the migration properties of nanomaterials, existing technologies often employ surface modification methods, such as coating nanoparticles with surfactants or polymers to alter their surface charge or hydrophobicity, thereby reducing interactions between particles and with the medium. However, these modification methods primarily rely on the physical adsorption or weak chemical interaction of the modifier on the particle surface. Their stability is significantly affected by environmental conditions (such as pH and ionic strength), and they are prone to desorption or inactivation in complex groundwater environments, leading to decreased dispersion stability of nanoparticles and limited and unreliable enhancement of migration capabilities. Furthermore, some industrial surfactants or polymers themselves pose environmental risks and may cause secondary pollution.

[0005] Therefore, there is an urgent need in this field for a new method that can fundamentally improve the dispersion stability of metallic nanoparticles in aqueous environments and ensure their efficient and stable migration and deployment capabilities in aquifer media, so as to overcome the inherent defects of existing surface modification technologies and promote the widespread application of in-situ reaction zone technology of nanomaterials in actual site remediation. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides a method for enhancing the migration and deployment of metallic nanoparticles in aquifer media. It utilizes mesoporous silica as a physical barrier and stabilizing layer between metallic nanoparticles and aquifer media, which can effectively prevent the aggregation of nanoparticles and significantly weaken their adverse interactions with the surface of the medium, thereby achieving long-distance, stable migration and efficient deployment of nanoparticles in complex groundwater environments.

[0007] This invention provides a method for enhancing the migration and deployment of metallic nanoparticles in an aqueous aquifer medium, the method comprising the following steps: Step S1: Construct a mesoporous silica coating layer on the surface of the metal nanoparticles to obtain mesoporous silica-coated metal nanoparticles. Step S2: Disperse the mesoporous silica-coated metal nanoparticles in water and obtain a particle suspension after dispersion treatment. Step S3: Inject the particle suspension into the aquifer medium to be treated, so that the nanoparticles migrate and disperse into the pores of the aquifer medium.

[0008] Compared with existing technologies, this invention provides a stable and environmentally friendly physical barrier for metallic nanoparticles by constructing a mesoporous silica coating layer. This coating layer effectively inhibits the aggregation of nanoparticles in aqueous environments and significantly weakens their adverse interactions with the surface of aquifer media, thus fundamentally solving the technical bottlenecks of traditional metallic nanoparticles, such as easy deposition and short migration distance. This method not only significantly improves the migration and dispersion capabilities of nanoparticles in complex pores, ensuring the effective construction of in-situ reaction zones, but also avoids the use of easily degraded and environmentally risky surface modifiers, providing a reliable technical path for efficient and stable in-situ remediation of groundwater pollution.

[0009] In one possible implementation, in step S1, the metallic nanoparticles are selected from one of Fe3O4, TiO2, CeO2, CuO, Al2O3 and zero-valent iron, and the average spherical particle size distribution of the metallic nanoparticles is 5-1000 nm.

[0010] Compared with existing technologies, this invention clarifies the applicable range of highly active nanomaterials and their core physical dimensions. The selected materials all possess intrinsic activity in degrading pollutants, and by controlling their particle size within a specific range, it is ensured that the nanoparticles, while having a high reactive surface area, also have an overall size that facilitates smooth migration within the pores of the aquifer after subsequent coating treatment. This avoids coating difficulties or migration resistance caused by initial particle sizes that are too large or too small.

[0011] In one possible implementation, in step S1, the thickness of the mesoporous silica coating layer is 1-100 nm, and the mesopore diameter is 1-20 nm.

[0012] Compared with existing technologies, this invention defines the key structural parameters of the coating layer. A suitable thickness provides an effective physical barrier for the core nanoparticles, significantly inhibiting aggregation; simultaneously, the specific mesoporous pore size ensures that the coating layer protects the core without completely blocking its contact with contaminants, allowing reactants and products to diffuse freely, thereby enhancing mobility while maximizing the preservation of the reactivity of the core material.

[0013] In one possible implementation, step S1 is performed as follows: Step S11: Dissolve CTAB in water, add metallic nanoparticles, and then perform ultrasonic treatment; Step S12: Under alkaline conditions, TEOS is added dropwise, and a suspension is obtained after hydrolysis-condensation reaction. The suspension is then subjected to centrifugation, washing, drying and calcination treatments to obtain mesoporous silica-coated metal nanoparticles.

[0014] Compared with existing technologies, this invention provides a mature and controllable synthetic route. Using CTAB (hexadecyltrimethylammonium bromide) as a template agent to guide the hydrolytic condensation of TEOS (tetraethyl orthosilicate), a well-structured mesoporous silica layer can be formed in situ on the surface of nanoparticles. This method is stable, reproducible, and allows for effective control of the coating thickness and pore structure, laying the foundation for the mass production of core-shell structured materials with consistent performance.

[0015] In one possible implementation, the ultrasonic treatment time in step S11 is 40-50 minutes. Setting a sufficient ultrasonic treatment time aims to fully disperse the metallic nanoparticles and template agent in the solution during the initial stage, breaking down their original aggregates. This is a crucial prerequisite for the subsequent formation of a uniform and complete mesoporous silica coating layer, directly determining the quality and monodispersity of the final core-shell structured nanomaterial.

[0016] In one possible implementation, the parameters for the hydrolysis-condensation reaction in step S12 are as follows: temperature 28-32°C, time 8-9h; In step S12, the drying parameters are as follows: temperature is 35-45℃, and time is 23-25h; In step S12, the parameters for calcination are as follows: temperature is 380-420℃, and time is 1.5-2.5h.

[0017] Compared with existing technologies, this invention ensures that TEOS can be hydrolyzed and condensed smoothly and fully on the surface of nanoparticles by precisely controlling the reaction temperature and time, forming a stable silicon-oxygen network. Subsequent gentle drying avoids structural collapse, while calcination at a specific temperature completely removes the organic template agent, exposes the mesoporous channels, and further enhances the chemical stability and mechanical strength of the coating layer.

[0018] In one possible implementation, the mass concentration of the mesoporous silica-coated metallic nanoparticles in the particle suspension of step S2 is 50-5000 mg / L. This concentration balances injection efficiency and migration performance: too low a concentration results in low repair efficiency and poor economics; too high a concentration can easily lead to increased interparticle interactions, causing premature deposition or even pore blockage during migration. This range ensures that the suspension has both high loading capacity and maintains long-term dispersion stability.

[0019] In one possible implementation, in step S3, the pore water flow rate of the particle suspension in the aquifer medium is not less than 0.7 cm / min. Maintaining a pore water flow rate not less than a specific value can provide sufficient kinetic energy to overcome the adsorption energy barrier between the nanoparticles and the medium surface, promoting their migration to the far field. This effectively avoids premature deposition and local blockage of particles in the near-end region of the injection well, ensuring the extension range of the reaction zone.

[0020] In one possible implementation, in step S3, the aquifer medium has a porous or fractured structure and a permeability coefficient greater than 0.1 m / day. Requiring the medium to have a certain porosity or fractured structure and a minimum permeability coefficient ensures that the suspension possesses basic injectability and migration pathways. This definition excludes dense, low-permeability formations, thereby ensuring that the injected nanoparticles can effectively enter and migrate through the target remediation zone under hydraulic drive.

[0021] More specifically, in step S3, an in-situ injection well system is used to inject a suspension of mesoporous silica-coated metal nanoparticles into the aquifer medium to be treated. The mesoporous silica-coated metal nanoparticles migrate and diffuse in the pores of the medium. More than 20% of the total mass of nanoparticles injected at one time migrate to an area 15 cm away from the injection well in the aquifer medium.

[0022] The beneficial effects of this invention are as follows: 1. This invention coats metallic nanoparticles with mesoporous silica. The coating layer acts as a physical barrier, effectively inhibiting particle aggregation and ensuring their stable dispersion in the system for a long time; at the same time, it reduces contact with porous media, significantly improving migration performance. In addition, the mesoporous structure on the coating layer exposes the active sites of the core metallic nanoparticles, endowing the material with reactivity.

[0023] 2. After the mesoporous silica-coated metal nanoparticle dispersion is injected, the mesoporous silica, as an environmentally friendly material, does not participate in the pollutant removal reaction, thus avoiding the occurrence of side reactions. At the same time, it has biocompatibility and non-toxic properties, completely avoiding the risk of secondary pollution and ensuring the environmental safety of the technology implementation.

[0024] 3. The method of the present invention overcomes the inherent defects of traditional surface modification methods, and realizes long-distance material migration while ensuring the catalytic activity of metallic nanomaterials. It is applicable to the in-situ reaction zone repair technology of underground aquifers based on metallic nanoparticles. Attached Figure Description

[0025] Figure 1 The images show a morphological comparison of the five metal nanoparticle suspensions (nTiO2, nCeO2, nCuO, nAl2O3, nFe3O4) before and after coating. Figure 2 Sedimentation curves of five types of metal nanoparticle suspensions and corresponding silica-coated suspensions are shown. Figure 3 Schematic diagram of the nanoparticle migration experimental setup; Figure 4 A morphological diagram of a natural medium; Figure 5 Transmission curves of five types of metallic nanoparticle suspensions and corresponding silica-coated suspensions in quartz sand columns; Figure 6 This is a photograph of a porous media column after the migration process of a suspension of nFe3O4 and silica coating. Detailed Implementation

[0026] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the present invention.

[0027] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0028] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0029] The following description, based on specific embodiments, further illustrates the invention. Notably, the raw materials used in these specific embodiments are as follows: Nano-titanium dioxide (nTiO2, 5-10 nm, anatase, hydrophilic) was purchased from Aladdin Reagent (Shanghai) Co., Ltd., with a purity of 98%.

[0030] Nano-cerium dioxide (nCeO2, 20 nm) was purchased from Aladdin Reagent (Shanghai) Co., Ltd., with a purity of 99.95%.

[0031] The cetyltrimethylammonium bromide (CTAB) was purchased from Aladdin Reagent (Shanghai) Co., Ltd., with a purity of 99%.

[0032] Tetraethyl orthosilicate (TEOS) was purchased from Aladdin Reagent (Shanghai) Co., Ltd., with a purity greater than 99%.

[0033] Ammonia solution (25%~28%) was purchased from Aladdin Reagent (Shanghai) Co., Ltd., with a purity of GR.

[0034] Nano-alumina (nAl2O3, γ-crystal) was purchased from Maclean (Shanghai) Co., Ltd., with a purity of 99.99%.

[0035] Nano-sized copper oxide (nCuO, spherical, 40 nm) was purchased from Maclean (Shanghai) Co., Ltd., with a purity of 99.95%.

[0036] Nano-iron oxide (nFe3O4, 20 nm) was purchased from Maclean (Shanghai) Co., Ltd., with a purity of 99.99%.

[0037] Anhydrous ethanol was purchased from Beijing Sinopharm Chemical Reagent Co., Ltd., with a purity of AR. Example 1: 1) Dissolve 0.1g CTAB in 100 mL of deionized water, add 0.1g of nano-metallic nanoparticles (nAl2O3 was used in this example), and sonicate for 40 minutes; 2) After two centrifugation washes, disperse in 100 ml of a mixture of deionized water / anhydrous ethanol (volume ratio 1:4), add 1 mL of ammonia water, then add 1 mL of TEOS dropwise, and react at 30°C for 8 hours; then centrifuge the prepared suspension, wash twice with ethanol and deionized water, and then vacuum dry at 40°C for 24 hours.

[0038] 3) The sample was calcined at 400 degrees Celsius for 2 hours to obtain mesoporous silica-coated metallic nanoparticles.

[0039] Example 2 1) Dissolve 0.1g CTAB in 100 mL of deionized water, add 0.1g of nano-metallic nanoparticles (nFe3O4 was used in this example), and sonicate for 40 minutes; 2) After two centrifugation washes, disperse in 100 ml of a mixture of deionized water / anhydrous ethanol (volume ratio 1:4), add 1 mL of ammonia water, then add 1 mL of TEOS dropwise, and react at 30°C for 8 hours; then centrifuge the prepared suspension, wash twice with ethanol and deionized water, and then vacuum dry at 40°C for 24 hours.

[0040] 3) The sample was calcined at 400 degrees Celsius for 2 hours to obtain mesoporous silica-coated metallic nanoparticles.

[0041] Example 3 1) Dissolve 0.1g CTAB in 100 mL of deionized water, add 0.1g of nano-metallic nanoparticles (nCeO2 was used in this example), and sonicate for 40 minutes; 2) After two centrifugation washes, disperse in 100 ml of a mixture of deionized water / anhydrous ethanol (volume ratio 1:4), add 1 mL of ammonia water, then add 1 mL of TEOS dropwise, and react at 30°C for 8 hours; then centrifuge the prepared suspension, wash twice with ethanol and deionized water, and then vacuum dry at 40°C for 24 hours.

[0042] 3) The sample was calcined at 400 degrees Celsius for 2 hours to obtain mesoporous silica-coated metallic nanoparticles.

[0043] Example 4 1) Dissolve 0.1g CTAB in 100 mL of deionized water, add 0.1g of nano-metallic nanoparticles (nCuO is used in this example), and sonicate for 40 minutes; 2) After two centrifugation washes, disperse in 100 ml of a mixture of deionized water / anhydrous ethanol (volume ratio 1:4), add 1 mL of ammonia water, then add 1 mL of TEOS dropwise, and react at 30°C for 8 hours; then centrifuge the prepared suspension, wash twice with ethanol and deionized water, and then vacuum dry at 40°C for 24 hours.

[0044] 3) The sample was calcined at 400 degrees Celsius for 2 hours to obtain mesoporous silica-coated metallic nanoparticles.

[0045] Example 5 1) Dissolve 0.1g CTAB in 100 mL of deionized water, add 0.1g of nano-metallic nanoparticles (nTiO2 was used in this example), and sonicate for 40 minutes; 2) After two centrifugation washes, disperse in 100 ml of a mixture of deionized water / anhydrous ethanol (volume ratio 1:4), add 1 mL of ammonia water, then add 1 mL of TEOS dropwise, and react at 30°C for 8 hours; then centrifuge the prepared suspension, wash twice with ethanol and deionized water, and then vacuum dry at 40°C for 24 hours.

[0046] 3) The sample was calcined at 400 degrees Celsius for 2 hours to obtain mesoporous silica-coated metallic nanoparticles.

[0047] Figure 1 The morphology comparisons of five types of metallic nanoparticles (nAl2O3, nFe3O4, nCeO2, nCuO, and nTiO2) before and after coating in Examples 1-5 are shown. Wherein a represents nTiO2, b represents nTiO2 coating, c represents nCeO2, d represents nCeO2 coating, e represents nCuO, f represents nCuO coating, g represents nAl2O3, h represents nAl2O3 coating, i represents nFe3O4, and j represents nFe3O4 coating.

[0048] from Figure 1 Transmission electron microscopy (TEM) analysis showed that all samples successfully achieved mesoporous silica coating, exhibiting a clear core-shell structure; obvious interface boundaries were visible at the edges of the coating.

[0049] Example 6: 1) Weigh 0.025g of nAl2O3 and the mesoporous silica-coated nAl2O3 prepared in Example 1 and disperse them in 250mL of simulated groundwater. Stir evenly and sonicate for 30 minutes to obtain a 100 mg / L suspension.

[0050] 2) Immediately after the suspension is prepared, a sedimentation kinetic experiment is conducted. The suspension is transferred to a quartz cuvette, and the absorbance is measured over time at the corresponding wavelength using an ultraviolet spectrophotometer. The relationship between relative absorbance (the ratio of absorbance at different times to the initial absorbance, A / A0) and time is plotted as a sedimentation curve.

[0051] Example 7 1) Weigh 0.025g of nFe3O4 and the mesoporous silica-coated nFe3O4 prepared in Example 2, dissolve them in 250mL of simulated groundwater, stir evenly, and sonicate for 30 minutes to obtain a 100 mg / L suspension.

[0052] 2) Immediately after the suspension is prepared, a sedimentation kinetic experiment is conducted. The suspension is transferred to a quartz cuvette, and the absorbance is measured over time at the corresponding wavelength using an ultraviolet spectrophotometer. The relationship between relative absorbance (the ratio of absorbance at different times to the initial absorbance, A / A0) and time is plotted as a sedimentation curve.

[0053] Example 8 1) Weigh 0.025g of nCeO2 and the mesoporous silica-coated nCeO2 prepared in Example 3, dissolve them in 250mL of simulated groundwater, stir evenly, and sonicate for 30 minutes to obtain a 100 mg / L suspension.

[0054] 2) Immediately after the suspension is prepared, a sedimentation kinetic experiment is conducted. The suspension is transferred to a quartz cuvette, and the absorbance is measured over time at the corresponding wavelength using an ultraviolet spectrophotometer. The relationship between relative absorbance (the ratio of absorbance at different times to the initial absorbance, A / A0) and time is plotted as a sedimentation curve.

[0055] Example 9 1) Weigh 0.025g of nCuO and the mesoporous silica-coated nCuO prepared in Example 4 and dissolve them in 250mL of simulated groundwater. Stir well and sonicate for 30 minutes to obtain a 100 mg / L suspension.

[0056] 2) Immediately after the suspension is prepared, a sedimentation kinetic experiment is conducted. The suspension is transferred to a quartz cuvette, and the absorbance is measured over time at the corresponding wavelength using an ultraviolet spectrophotometer. The relationship between relative absorbance (the ratio of absorbance at different times to the initial absorbance, A / A0) and time is plotted as a sedimentation curve.

[0057] Example 10 1) Weigh 0.025g of nTiO2 and the mesoporous silica-coated nTiO2 prepared in Example 5, dissolve them in 250mL of simulated groundwater, stir evenly, and sonicate for 30 minutes to obtain a 100 mg / L suspension.

[0058] 2) Immediately after the suspension is prepared, a sedimentation kinetic experiment is conducted. The suspension is transferred to a quartz cuvette, and the absorbance is measured over time at the corresponding wavelength using an ultraviolet spectrophotometer. The relationship between relative absorbance (the ratio of absorbance at different times to the initial absorbance, A / A0) and time is plotted as a sedimentation curve.

[0059] Figure 2 This paper presents a comparison of the sedimentation behavior of five metallic nanoparticles (nAl₂O₃, nFe₃O₄, nCeO₂, nCuO, and nTiO₂) and their silica coatings in simulated groundwater at a concentration of 100 mg / L. Experimental data show that, except for nTiO₂, the silica-coated nanoparticle systems all exhibited a slower absorbance decay trend, indicating improved dispersion stability. Among them, nAl₂O₃ and nFe₃O₄ showed the most significant improvement, with 10% of the particles remaining unsedimented after 12 hours of settling (A / A₀ = 0.1). The dispersion stability of nCeO₂ and nCuO was enhanced by 10% and 3%, respectively (A / A₀ values ​​at 12 h increased by 0.1 and 0.03 compared to the uncoated state). These results indicate that mesoporous silica coating can improve the colloidal stability of metallic nanoparticles in aqueous media. Application Examples like Figure 3 and Figure 4 As shown, the migration experimental setup consists of three parts: an injection device, a mesoporous medium column, and an effluent collection device. The injection device includes a sample vial and a valveless fluid pump for flow control. A 2cm inner diameter, 15cm long glass-stainless steel column is uniformly filled with porous natural quartz sand (0.4-0.5 mm medium sand) using a dry packing method. After compaction, carbon dioxide gas is introduced into the quartz sand column to remove air. A simulated groundwater solution, degassed by heating, is pumped from the bottom of the quartz sand column using a valveless fluid pump until the sand column is saturated (the column maintains a constant weight). The pore volume of the quartz sand is determined using the water displacement method. The porosity of the quartz sand is calculated as "porosity = pore volume / column packing volume," and is approximately 0.40.

[0060] Weigh 0.025 g of sample powder (metal nanoparticles and their silica coatings from Examples 1-5) and dissolve them in 250 mL of simulated groundwater. Stir well and sonicate for 30 min to obtain a suspension with a mass concentration of 100 mg / L.

[0061] Upon completion of the suspension preparation, a one-dimensional column dynamic experiment was immediately conducted. The suspension was injected into the quartz sand column as the influent using a valveless fluid pump, with a pore water flow rate of 7.0 cm / min. After an injection volume of approximately 5 PVs, the influent was immediately switched to simulated groundwater. Effluent samples at different time points were analyzed using a UV spectrophotometer to obtain the relative concentration of the sample in the effluent (characterized by the ratio of the effluent sample concentration C to the initial sample concentration C0, C / C0), and breakthrough curves were plotted. Transmission rate is a parameter used to quantitatively evaluate the migration ability of nanoparticles in porous media. By performing mass balance calculations on the nanoparticles entering and exiting the simulated column, the migration ratio of particles in the porous media can be studied.

[0062] in C 0 and C t These are the injected and effluent concentrations (mg / L) of the particles and tracers, respectively. t and t 0 These represent the injection time and the total experiment time (in minutes), respectively. V in and V out These represent the volumes of the inflow and outflow fluids, respectively.

[0063] Figure 5 This study compares the migration performance of five metallic nanoparticles and their silica-coated forms from Examples 1-5 at a pore water flow rate of 7.0 cm / min in a quartz sand column. Experimental data show that mesoporous silica coating significantly improves the migration ability of nanoparticles in porous media: 1) According to... Figure 5 Calculations showed that the transmittance of the nAl2O3 and nFe3O4 coated samples reached 88.8% and 21.4%, respectively, while the uncoated samples were completely trapped (0% transmittance). Figure 6As shown, nFe3O4, due to its poor migration performance, forms a dark black deposit at the column inlet, causing blockage; however, mesoporous silica coating effectively improves the migration performance of nFe3O4, enabling it to achieve uniform distribution throughout the quartz sand column. 2) The penetration rates of other materials are significantly improved: nTiO2 increased from 46.7% to 89.1%, nCeO2 from 7.1% to 52.0%, and nCuO from 15.9% to 34.7%. These results confirm that mesoporous silica coating can effectively improve the migration of metallic nanoparticles in porous media. It is particularly noteworthy that for nAl2O3 and nFe3O4, this invention achieves a qualitative leap in migration performance: their behavior in porous media changes from "unmigratable" (0% penetration rate) before coating to "effectively migrating" (penetration rates of 88.8% and 21.4%, respectively) after coating, fully demonstrating the significant progress of this invention.

[0064] Therefore, the mesoporous silica coating method of this invention can improve the dispersion stability of metallic nanoparticles in simulated groundwater and their migration in porous natural quartz sand media, overcoming the problems of easy aggregation of metallic nanoparticles, poor dispersion and migration in soil and groundwater, and reduced application performance. This invention, using mesoporous silica to coat metallic nanoparticles, overcomes the high environmental risks associated with existing technologies using industrial chemical products, and is suitable for the treatment of contaminated groundwater using in-situ reactive zone remediation technology based on metallic nanoparticles.

[0065] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A method of enhancing the migration and placement of metal-type nanoparticles in an aqueous layer medium, characterized by, The method comprises the following steps: Step S1, constructing a mesoporous silica coating layer on the surface of metal type nanoparticles to obtain mesoporous silica coated metal type nanoparticles; Step S2, dispersing the mesoporous silica coated metal type nanoparticles in water after dispersion treatment to obtain a particle suspension; Step S3, injecting the particle suspension into the water-bearing layer medium to be treated, so that the nanoparticles migrate and disperse into the pore channels of the water-bearing layer medium.

2. The method of claim 1, wherein, In step S1, the metal type nanoparticles are selected from one of Fe3O4, TiO2, CeO2, CuO, Al2O3 and zero-valent iron, and the average spheroidization particle size distribution of the metal type nanoparticles is 5-1000 nm.

3. The method of claim 1, wherein, In step S1, the thickness of the mesoporous silica coating layer is 1-100 nm, and the mesoporous pore size is 1-20 nm.

4. The method of claim 1, wherein, The specific operation of step S1 is as follows: Step S11, dissolve CTAB in water, then add metal type nanoparticles, and then perform ultrasonic treatment; Step S12, under alkaline conditions, add TEOS dropwise, obtain a suspension by hydrolysis-polycondensation reaction, and then sequentially perform centrifugal treatment, washing treatment, drying treatment and calcination treatment on the suspension to obtain mesoporous silica coated metal type nanoparticles.

5. The method of claim 4, wherein, In step S11, the ultrasonic treatment time is 40-50 min.

6. The method of claim 4, wherein, In step S12, the hydrolysis-polycondensation reaction parameters are as follows: temperature is 28-32℃, time is 8-9h; In step S12, the drying treatment parameters are as follows: temperature is 35-45℃, time is 23-25h; In step S12, the calcination treatment parameters are as follows: temperature is 380-420℃, time is 1.5-2.5h.

7. The method of claim 1, wherein, In the particle suspension of step S2, the mass concentration of mesoporous silica coated metal type nanoparticles is 50-5000 mg / L.

8. The method of claim 1, wherein, In step S3, the pore water flow rate of the particle suspension in the water-bearing layer medium is not less than 0.7 cm / min.

9. The method of claim 1, wherein, In step S3, the water-bearing layer medium has pore or fracture structure, and the permeability coefficient is greater than 0.1 meter / day.

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