Underground water remediation and activity monitoring system based on zero-valent iron-based nano material

Abstract

The invention relates to the technical field of environmental engineering, and particularly discloses an underground water remediation and activity monitoring system based on a zero-valent iron-based nano material, which comprises composite nano particles consisting of a zero-valent iron core, a ferrous sulfide / humic acid dynamic compensation layer and a temperature-sensitive polymer, through a crack self-adaptive regulation and control module driven by a sensor array and a temperature difference driving migration module based on an underground water temperature gradient, the system can realize automatic circulation of selective adsorption, desorption and degradation of pollutants under different temperature conditions through the combined action of a phase change behavior of a temperature-sensitive polymer and a dynamic compensation layer; the stability and the repair efficiency of the nanoparticles are improved; compared with a traditional scheme, the method has the advantages that on-demand response activity adjusting capacity and an accurate injection path guiding mechanism are achieved, the technical bottlenecks that in the groundwater heterogeneous environment, migration of a repairing agent is uncontrollable, and adsorption selectivity is poor are avoided, and good engineering adaptability and practical application prospects are achieved.

Description

Technical Field

[0001] The present invention relates to a groundwater remediation and activity monitoring system based on zero-valent iron-based nanomaterials, belonging to the technical field of environmental engineering. Background Art

[0002] Composite pollutants such as heavy metal ions and organochlorines are commonly present in groundwater. To achieve in-situ purification treatment, nano zero-valent iron is widely used in such environmental remediation due to its good reducibility and economy; its basic principle is to reduce pollutants to low-toxic or non-toxic forms through electron transfer, thereby achieving pollution removal.

[0003] However, current mainstream solutions still face several engineering limitations in scenarios where the complex structure of the aquifer and the types of pollutants are intertwined: 1. In a heterogeneous groundwater aquifer environment, nano zero-valent iron particles often preferentially migrate along high-permeability channels, and it is difficult for the remediation agent to be effectively distributed in low-permeability areas, resulting in pollution residues and affecting the overall remediation coverage rate; 2. Nano particles are easily oxidized and passivated in practical applications. Although the oxide layer formed on their surface inhibits electron supply, it has not been reasonably utilized, resulting in rapid accumulation of activity loss and limited service life; 3. In the face of the problem of diverse pollutant types, existing solutions usually need to be treated by batch and component addition. For example, heavy metals are treated first, and then materials that can adsorb organic pollutants are injected. This sequential path is complex and inefficient.

[0004] To alleviate the above problems, some technical solutions attempt to increase the treatment range and efficiency by increasing the dosage of the remediation agent, connecting an external power pumping system, or applying multiple functional particles for synergistic remediation. However, on the one hand, these remedial measures increase the system energy consumption and engineering costs, and on the other hand, it is difficult to achieve precise response control in a dynamic pollutant release environment; especially under the condition of lack of real-time feedback and spatial distribution recognition, the activity state of the remediation area is unpredictable, which in turn restricts the effective guidance of the particle migration path and subsequent regulation.

[0005] Currently, most mainstream remediation technologies are built on the logical chain of fixed dosage - single injection - periodic replacement. This path has certain practicality under conventional conditions, but when facing complex geological structures, significant temperature changes, or diverse coexistence of pollutants, the system still lacks the inherent adjustment ability to balance activity maintenance and migration control; this structural limitation has become the key bottleneck in the current optimization of groundwater remediation path technologies. Therefore, how to maintain the continuous activity of nanomaterials in the groundwater environment, synergistically remove composite pollutants, and finely regulate the migration path without introducing an external high-energy-consuming system has become the technical problem to be solved by the present invention. Summary of the Invention

[0006] The present invention provides a groundwater remediation and activity monitoring system based on zero-valent iron-based nanomaterials, and its main purpose is to solve the problems of rapid attenuation of nanomaterial activity, uncontrollable migration, and poor synergy in the treatment of multiple pollutants.

[0007] To achieve the above object, a groundwater remediation and activity monitoring system based on zero-valent iron-based nanomaterials provided by the present invention includes: Nano zero-valent iron composite particles, which are composed of a zero-valent iron core, a dynamic compensation layer coated outside the zero-valent iron core, and a thermosensitive polymer grafted on the surface of the dynamic compensation layer; the dynamic compensation layer contains iron sulfide and humic acid, and the mass ratio of satisfies the inequality: , wherein, represents the mass of iron sulfide participating in the construction of the dynamic compensation layer (unit: mg), represents the mass of humic acid participating in the reaction (unit: mg). The dynamic compensation layer can carry out in-situ reduction reaction with the oxidation layer in the aquifer and synergistically adsorb pollutants; the thermosensitive polymer is poly(N-isopropylacrylamide), and its grafting rate is 15% to 30%, which is used to switch between adsorbing hydrophobic organic pollutants and releasing hydrophobic organic pollutants to the surface of the zero-valent iron core for reduction degradation according to the change of environmental temperature, so as to realize the self-triggered cycle of selective adsorption, desorption and degradation of hydrophobic organic pollutants; A fracture self-adaptive regulation module, which obtains the redox gradient and dissolved oxygen distribution data of the groundwater body through a three-dimensional redox potential sensor array and a dissolved oxygen sensor array deployed at the boundary of the repair area, and inputs the data into a multi-modal activity mapping model to generate a three-dimensional heat map reflecting the activity of the repair area. The multi-modal activity mapping model is constructed based on three parameters of conductivity, redox potential and dissolved oxygen, and is used for activity prediction in both spatial and temporal dimensions, dynamically dividing the high-activity repair area and the low-activity repair area, and guiding the pulse injection strategy of nano zero-valent iron composite particles to achieve precise repair of pollutants in heterogeneous aquifers; A temperature difference-driven migration module, which sets up a micro thermoelectric power generation module at the upstream and downstream of the repair area, uses the limited temperature gradient naturally existing in the groundwater body to generate a weak directional current, and the weak directional current can drive the slow directional migration of nano zero-valent iron composite particles in the aquifer at the nanoscale, and combines with the aquifer temperature gradient to trigger the phase change of the thermosensitive polymer, and synergistically realizes the selective adsorption of pollutants and the spatial migration regulation of nanoparticles.

[0008] Preferably, the crystal form of iron sulfide in the dynamic compensation layer is mackinawite, and the crystal plane spacing of mackinawite , the crystal plane of the Mackinawite can form a hydrogen bond anchoring structure with the carboxyl group of humic acid, enhancing the stability of the dynamic compensation layer.

[0009] Preferably, the lower critical solution temperature of the thermosensitive polymer poly(N-isopropylacrylamide) is adjusted to 20 °C to 25 °C by acrylamide copolymerization modification to match the naturally occurring temperature difference in groundwater and optimize the adsorption and desorption performance of hydrophobic organic pollutants.

[0010] Preferably, the method for the multimodal activity mapping model to generate a heat map includes: mapping the redox potential value to the intensity of the red channel of the heat map, mapping the dissolved oxygen value to the intensity of the green channel of the heat map, mapping the conductivity value to the intensity of the blue channel of the heat map, and visualizing and displaying the activity attenuation degree and distribution in the groundwater remediation area by fusing the intensities of the red channel, green channel, and blue channel through the RGB color model.

[0011] Preferably, the nano zero-valent iron composite particles further include a conductive biochar layer, and a sulfur-doped silicon carbide support with a mesoporous structure is embedded on the surface of the conductive biochar layer. The pore size of the sulfur-doped silicon carbide support is 20 nm to 50 nm, and the porosity is greater than or equal to 70%, which is used to load the dormant spores of sulfate-reducing bacteria to form a microbial-electrochemical symbiotic interface.

[0012] Preferably, the dormant spores of sulfate-reducing bacteria are coated with an environment-responsive activation layer, which is composed of a pH-responsive polydopamine and a temperature-sensitive hydrogel copolymer. When the pH value of the groundwater environment is less than 6.5 and the temperature is greater than 25 °C, the environment-responsive activation layer shrinks and releases the sulfate-reducing bacteria spores, synchronously activating the iron sulfide dynamic compensation mechanism of the dynamic compensation layer.

[0013] Preferably, the sulfur-doped silicon carbide support serves as an electron shuttle directional channel to directionally transfer the electrons of hydrogen sulfide generated by the metabolism of sulfate-reducing bacteria to the zero-valent iron core, accelerating the reduction of ferric ions to ferrous ions in the zero-valent iron core and forming a symbiotic metabolic chain of electron donation by sulfate-reducing bacteria and electron consumption by zero-valent iron.

[0014] Preferably, molybdenum-doped iron sulfide nanosheets are further loaded on the surface of the sulfur-doped silicon carbide support. The mass percentage content of molybdenum in the molybdenum-doped iron sulfide is 0.5% to 1.2%, and the interlayer spacing of the molybdenum-doped iron sulfide nanosheets is 0.8 nm to 1.2 nm, forming a contradictory conversion catalytic layer for the directional conversion of hydrogen sulfide to polysulfide.

[0015] Preferably, carbon-coated iron oxide nanoparticles with a particle size of 10 nm to 20 nm are embedded inside the sulfur-doped silicon carbide support, and local thermal effects are generated by absorbing infrared bands with wavelengths greater than or equal to 800 nm in the groundwater environment to activate the catalytic activity of the contradictory conversion catalytic layer.

[0016] Preferably, an adsorption layer co - deposited by mesoporous silica and polypyrrole is constructed on the surface of the zero - valent iron core. The pore diameter of the mesoporous silica is 2 to 5 nanometers. The adsorption layer captures polysulfides through π - π interaction and triggers the spontaneous disproportionation reaction of polysulfides into elemental sulfur and electrons. The released electrons reach the zero - valent iron core, enhancing the reduction ability of the zero - valent iron core.

[0017] Compared with the problems of the background technology, the beneficial effects of the present invention are as follows: 1. The ferrous sulfide - humic acid dynamic compensation layer and the thermosensitive polymer form a dual interface for electron transfer and pollutant capture. When the environmental temperature triggers the phase change of the polymer, the exposure / contraction of its hydrophobic groups not only regulates the adsorption - desorption equilibrium of organic pollutants, but also enables the released pollutants to obtain continuous reduction ability on the surface of the zero - valent iron core through the directional electron transfer of the semiconductor characteristics in the compensation layer. This temperature - responsive self - triggering mechanism effectively solves the contradiction between adsorption site saturation and degradation activity attenuation in traditional technologies, and at the same time utilizes the natural temperature gradient of groundwater to achieve energy self - supply during the remediation process.

[0018] 2. The spatio - temporal prediction system constructed by the three - dimensional redox potential sensor array and the multi - modal activity mapping model can real - time analyze the distribution characteristics of electron donors / acceptors in the aquifer. By converting the electrochemical parameters into the color - space mapping of the heat map, the system can dynamically identify the electron depletion trend in the high - activity area and guide the temperature - difference - driven device to form an electron concentration gradient in specific permeation channels. This directional migration strategy based on the ambient background energy enables the nanoparticles to preferentially accumulate in the electron - demanding area, realizing the adaptive matching of remediation activity and migration path.

[0019] 3. The symbiotic system formed by sulfur - doped silicon carbide carriers and sulfate - reducing bacteria, through the semiconductor - mediated electron shuttle effect, converts the hydrogen sulfide metabolite regarded as an interference factor in traditional technologies into an electron donor for the zero - valent iron core. When the pH - responsive activation layer releases dormant spores, the sulfide produced by its metabolism not only replenishes the loss of ferrous sulfide in the dynamic compensation layer, but also triggers the disproportionation reaction to generate elemental sulfur and free electrons through the polysulfide conversion function of the molybdenum - doped catalytic layer. This biological - chemical cascade reaction constructs a self - sufficient electron cycle network, breaking through the technical bottleneck of mutual inhibition between biological and abiotic remediation processes in traditional technologies.

[0020] 4. The carbon-coated iron oxide nanoparticles absorb the infrared radiation in the groundwater environment to generate a local thermal effect, which activates the activity of the catalytic layer while triggering the shrinkage phase change of the thermosensitive polymer. This thermo-chemical coupling effect not only accelerates the desorption rate of pollutants, but also enhances the reduction ability of the zero-valent iron core by the released electrons. The system utilizes the natural distribution characteristics of geothermal energy to form a self-enhanced thermodynamic cycle in the pollutant enrichment area, achieving a dynamic balance between the remediation efficiency and the environmental energy supply. In addition, the adsorption layer formed by the co-deposition of mesoporous silica and polypyrrole selectively captures polysulfide intermediates through the pore size matching effect, and its π-π interaction and the spontaneous disproportionation reaction of sulfide form a spatially confined catalytic system. While consuming the blocking precipitate, this structure continuously releases electrons to the zero-valent iron core and forms a multi-level electron transfer network with the conductive biochar layer, realizing the synergistic design of this pore structure-electron channel, so that the remediation agent maintains stable permeability and reactivity under complex hydrogeological conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the working flow chart of the groundwater remediation and activity monitoring system of the present invention; Figure 2 is the composition diagram of the nano zero-valent iron composite particle structure and the regulation module of the present invention; Figure 3 is the working principle diagram of the multi-modal activity mapping model of the present invention.

[0022] The implementation, functional features and advantages of the present invention will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] An embodiment of the present application provides a groundwater remediation and activity monitoring system based on zero-valent iron-based nanomaterials, including: Nano zero-valent iron composite particles, which are composed of a zero-valent iron core, a dynamic compensation layer coated outside the zero-valent iron core, and a thermosensitive polymer grafted on the surface of the dynamic compensation layer; the dynamic compensation layer contains iron sulfide and humic acid, and the mass ratio of the iron sulfide to the humic acid satisfies the inequality: , wherein, represents the mass of iron sulfide participating in the construction of the dynamic compensation layer (unit: mg), denotes the mass of humic acid participating in the reaction (unit: mg). The dynamic compensation layer can carry out in-situ reduction reaction with the oxidation layer in the aquifer and synergistically adsorb pollutants; the thermosensitive polymer is poly(N-isopropylacrylamide) with a grafting rate of 15% to 30%, which is used to switch between adsorbing hydrophobic organic pollutants and releasing hydrophobic organic pollutants to the surface of the zero-valent iron core for reduction degradation according to the change of environmental temperature, so as to realize the self-triggered cycle of selective adsorption, desorption and degradation of hydrophobic organic pollutants; The fracture self-adaptive regulation module. The fracture self-adaptive regulation module obtains the redox gradient and dissolved oxygen distribution data of the groundwater body through a three-dimensional redox potential sensor array and a dissolved oxygen sensor array deployed at the boundary of the repair area, and inputs the data into a multi-modal activity mapping model to generate a three-dimensional heat map reflecting the activity of the repair area. The multi-modal activity mapping model is constructed based on three parameters: conductivity, redox potential and dissolved oxygen, and is used for activity prediction in both spatial and temporal dimensions, dynamically dividing the high-activity repair area and the low-activity repair area, and guiding the pulse injection strategy of nano zero-valent iron composite particles to achieve precise repair of pollutants in heterogeneous aquifers; The temperature difference-driven migration module. The temperature difference-driven migration module sets up a micro thermoelectric power generation module at the upstream and downstream of the repair area, uses the limited temperature gradient naturally existing in the groundwater body to generate a weak directional current, and the weak directional current can drive the slow directional migration of nano zero-valent iron composite particles in the aquifer at the nanoscale, and combines with the aquifer temperature gradient to trigger the phase change of the thermosensitive polymer, synergistically realizing the selective adsorption of pollutants and the spatial migration regulation of nanoparticles.

[0025] Preferably, the crystal form of iron sulfide in the dynamic compensation layer is mackinawite, and the interplanar spacing of mackinawite , and the crystal plane of mackinawite can form a hydrogen bond anchoring structure with the carboxyl group of humic acid, enhancing the stability of the dynamic compensation layer.

[0026] Preferably, the critical solution temperature of the thermosensitive polymer poly(N-isopropylacrylamide) is adjusted to 20 °C to 25 °C by acrylamide copolymer modification to match the naturally existing temperature difference in groundwater and optimize the adsorption and desorption performance of hydrophobic organic pollutants.

[0027] Preferably, the method for the multi-modal activity mapping model to generate a heat map includes: mapping the redox potential value to the intensity of the red channel of the heat map, mapping the dissolved oxygen value to the intensity of the green channel of the heat map, mapping the conductivity value to the intensity of the blue channel of the heat map, and visualizing the attenuation degree and distribution of the activity of the groundwater repair area by fusing the intensities of the red channel, green channel and blue channel through the RGB color model.

[0028] Preferably, the nano zero-valent iron composite particles further comprise a conductive biochar layer, and a sulfur-doped silicon carbide support with a mesoporous structure is embedded on the surface of the conductive biochar layer. The pore diameter of the sulfur-doped silicon carbide support is 20 to 50 nanometers, and the porosity is greater than or equal to 70%, which is used to load the dormant spores of sulfate-reducing bacteria to form a microbial-electrochemical symbiotic interface.

[0029] Preferably, the dormant spores of the sulfate-reducing bacteria are coated with an environment-responsive activation layer, which is composed of a pH-responsive polydopamine and a temperature-sensitive hydrogel copolymer. When the pH value of the groundwater environment is less than 6.5 and the temperature is greater than 25 °C, the environment-responsive activation layer shrinks and releases the spores of the sulfate-reducing bacteria, simultaneously activating the ferrous sulfide dynamic compensation mechanism of the dynamic compensation layer.

[0030] Preferably, the sulfur-doped silicon carbide support serves as an electron shuttle directional channel to directionally transfer the hydrogen sulfide electrons generated by the metabolism of sulfate-reducing bacteria to the zero-valent iron core, accelerating the reduction of ferric ions to ferrous ions in the zero-valent iron core, and forming a symbiotic metabolic chain in which sulfate-reducing bacteria supply electrons and zero-valent iron consumes electrons.

[0031] Preferably, molybdenum-doped ferrous sulfide nanosheets are further loaded on the surface of the sulfur-doped silicon carbide support. The mass percentage content of molybdenum in the molybdenum-doped ferrous sulfide is 0.5% to 1.2%, and the interlayer spacing of the molybdenum-doped ferrous sulfide nanosheets is 0.8 to 1.2 nanometers, forming a contradictory conversion catalytic layer for the directional conversion of hydrogen sulfide to polysulfide.

[0032] Preferably, carbon-coated iron oxide nanoparticles with a particle size of 10 to 20 nanometers are embedded inside the sulfur-doped silicon carbide support, and local thermal effects are generated by absorbing infrared bands with wavelengths greater than or equal to 800 nanometers in the groundwater environment to activate the catalytic activity of the contradictory conversion catalytic layer.

[0033] Preferably, an adsorption layer co-deposited by mesoporous silica and polypyrrole is constructed on the surface of the zero-valent iron core. The pore diameter of the mesoporous silica is 2 to 5 nanometers. The adsorption layer captures polysulfides through π-π interactions and triggers the spontaneous disproportionation reaction of polysulfides into elemental sulfur and electrons. The released electrons reach the zero-valent iron core, enhancing the reduction ability of the zero-valent iron core.

[0034] Meanwhile, since the natural temperature gradient of underground water bodies is usually relatively limited (about 5–8°C), in the design of the thermally-driven migration module of the present invention, instead of relying on high-energy thermal differences or macroscopic electric fields in the traditional sense, a micro thermoelectric power generation device is constructed by combining the scale characteristics of the nanoparticle system to form a micro-voltage direct current (voltage < 1V), which drives the surface-charged particles to achieve slow and directional migration, making this migration process operable within the particle size range of 20–50 nm, and synergistically linked with the thermosensitive response range (20–25°C) of poly N-isopropylacrylamide, capable of enhancing the adsorption and enrichment of pollutants in the low-temperature zone, releasing pollutants and exposing the iron core for reduction and degradation in the high-temperature zone, forming a synergistic linkage mechanism between the migration path and the reactive activity location. Based on this, the mechanism of thermally-driven migration of the present invention is established on the coupling of nanoscale physical mechanisms and environmentally responsive materials.

[0035] And during the particle preparation process, for example, zero-valent iron (Fe 0 ) particles with a particle size controlled at 40 nm are first dispersed in an ethanol-water mixed solution (volume ratio 1:1), and ultrasonic oscillation is used for 30 minutes to fully disperse them. Subsequently, a precursor solution of iron sulfide and a sodium humate solution containing are added dropwise, and the pH of the system is maintained at 6.8–7.2. By controlling the FeS:HA mass ratio within the range of 0.3–0.6, a dynamic compensation layer is promoted to form on the particle surface. The deposition reaction is carried out with stirring at room temperature for 4 hours. Subsequently, free impurities are removed by centrifugal washing. After the particles are dried, they are redispersed in an N-isopropylacrylamide (NIPAm) monomer solution, and a grafting reaction of the thermosensitive polymer is carried out by the free radical initiation polymerization method. The reaction temperature is set at 60°C and the duration is 4 hours. By adjusting the concentration of the initiator (APS) and the feeding ratio of the reaction monomers, the polymer grafting rate is controlled within 15%–30%. The finally obtained composite particles are stored by freeze-drying, and the structure and surface characteristics of the particles are characterized by the following means: FTIR is used to verify the binding of functional groups; Zeta potential analysis measures that the particles are stably dispersed (below -20 mV) under the condition of pH 6.5; TEM observes the uniformity of particle coating and the consistency of particle size; BET specific surface area test verifies the pore structure distribution; XRD confirms that the crystal form of FeS is mackinawite (d001 = 0.5 nm); the thermally-driven module, for example, adopts a bilateral symmetric layout method and is respectively installed in the upstream and downstream regions of the underground water body flow direction. The main structure of the module consists of a micro-thermocouple array (based on It consists of a thermoelectric conversion module (material) and a supporting boost micro-power controller. The encapsulation size of each module is 2 cm × 2 cm × 0.5 cm, with an IP68-level protection ability. The thermocouple is directly in contact with the underground medium. By measuring the average temperature difference (ΔT) between upstream and downstream, it is converted into a DC micro-electrical signal. Under simulated conditions, the average temperature difference between the shallow layer and the deep layer can be stably maintained at 6 - 8 °C. The output voltage of the module is 0.3 - 0.7 V, and the actual current does not exceed 5 μA. This weak directional current, through a charge shielding design, guides surface-charged particles with a particle size in the range of 20 - 50 nm to slowly migrate towards the low-temperature region. The average migration speed is about 0.8 μm / h, and the response delay is about 20 minutes. To enhance the system synergy, the module signals are synchronized and adjusted with the sensor array through low-frequency Bluetooth to ensure the consistency of the response path. And the sensor array is arranged in a grid pattern around the underground remediation area. The recommended side length of the grid is 5 meters. Three types of sensor units (oxidation-reduction potential ORP, dissolved oxygen DO, conductivity EC) are deployed at each node. Each type of parameter is independently collected by a three-dimensional probe. Each sensor array node can cover a remediation area of about 25 m³. The number of nodes can be adjusted according to the scale of the remediation site. The recommended basic deployment density is 16 - 25 measuring points per 100 m². The collection frequency is set at 5 minutes per time. The collected data is transmitted to the ground control terminal in real time through a low-power LoRa wireless module. The control terminal is equipped with a multi-modal activity mapping model and combines GIS positioning information for real-time zoning update. The pulse injection module receives the high-activity area priority injection strategy signal output by the control terminal and completes the local directional injection adjustment within a 30-minute window, so as to maximize the matching of the remediation agent injection path and the pollutant concentration hot spot. All of these belong to the extended implementation methods known to those of ordinary skill in the art.

[0036] Example 1: In this example, the mass ratio of iron sulfide (FeS) to humic acid (HA) in the dynamic compensation layer is set in the range of 0.3 to 0.6. The main basis is the optimization mechanism of the reduction-complexation synergistic reaction. In the groundwater environment, FeS mainly provides a fast electron transfer path, while humic acid has high hydrophilicity and multi-functional group adsorption ability. The combination of the two can effectively delay the formation of the oxide film on the surface of the zero-valent iron core and enhance the particle stability. When the mass ratio is lower than 0.3, the electron donor in the dynamic compensation layer is insufficient, affecting the reduction reaction rate; when it exceeds 0.6, the complexation reaction of humic acid dominates, inhibiting the reactive sulfur released in-situ by FeS, resulting in a decrease in the remediation efficiency.

[0037] The grafting rate of poly(N-isopropylacrylamide) is controlled between 15% and 30%. Its grafting degree directly affects the thermosensitive response interval and the swelling-shrinking degree of the polymer. When the grafting rate is insufficient, the phase transition response of the polymer is insensitive, resulting in ineffective adsorption-desorption switching. When the grafting rate is too high, it may cause an increase in the polymer chain density, reduce the permeability of pollutants, and hinder the transfer of target pollutants to the zero-valent iron core. The grafting rate is regulated by free radical-initiated solution polymerization. The specific grafting reaction can be continuously carried out in a 60°C water bath for 4 hours, and the grafting efficiency is verified by infrared spectroscopy.

[0038] In the migration control mechanism, the temperature difference-driven migration module utilizes the naturally existing temperature difference between the upstream and downstream of the underground aquifer (for example, the deep layer is stable at 16°C, and the shallow layer can reach 25°C affected by the surface heat flux) to form a temperature difference electric field, and combines with the micro thermoelectric power generation module to generate a directional microcurrent. Although the magnitude of this current is weak, in the composite particle system with a particle size of 20 - 50 nm, it can guide their directional migration to the low-temperature enrichment area. At the same time, this migration path is highly coordinated with the response interval of the thermosensitive polymer, that is, the polymer is in a hydrophobic aggregated state below 20°C, enhancing the adsorption ability for hydrophobic organic pollutants; while in the high-temperature area, it transforms into a hydrophilic diffusion state, which is conducive to releasing pollutants and exposing the iron core surface for reduction.

[0039] In the fracture self-adaptive regulation module, the sensor array real-time collects three parameters: redox potential (ORP), dissolved oxygen concentration (DO), and conductivity (EC), and establishes a three-dimensional active thermal map through a spatial mapping algorithm. Among them, ORP is mapped to the red channel, DO to the green channel, and EC to the blue channel. After normalizing the values of each parameter, they are fused according to the RGB model to form a thermal map distribution. This model can quickly generate a local active image at the processing end deployed on-site, guiding the particle injection nodes and injection time, and avoiding dose waste caused by blind injection. In specific engineering operations, the composite particles are prepared by liquid-phase co-deposition combined with surface grafting. First, the Fe0 particles are immersed in a solution containing FeS precursors and humic acid, and by adjusting the pH to the range of 6.8 - 7.2, FeS and humic acid are induced to form a stable dynamic compensation layer on the particle surface. Subsequently, poly(N-isopropylacrylamide) is grafted to form a thermosensitive response structure. The measurement of the Zeta potential on the particle surface shows that it presents a stable dispersion state at pH 6.5, which is suitable for the natural acid-base environment of groundwater.

[0040] Example 2: This example combines Figures 1 to 3 , to illustrate the groundwater remediation and activity monitoring system based on zero-valent iron-based nanomaterials. As Figure 1As shown, the process starts with a sensor array that continuously monitors environmental data and sends redox gradient and dissolved oxygen data to a multimodal activity mapping model. After receiving the data, the multimodal activity mapping model processes the data and generates a three-dimensional activity heat map. Subsequently, it dynamically divides high- and low-activity remediation areas and sends pulse injection strategy instructions to an injection strategy execution unit. After receiving the instructions, the injection strategy execution unit performs pulse injection into the target area. Finally, the nano zero-valent iron composite particles migrate and act in the groundwater to complete the remediation process.

[0041] As Figure 2 shown, the core of the nano zero-valent iron composite particles in the figure is a zero-valent iron core, which is wrapped by a dynamic compensation layer composed of iron sulfide / humic acid with a mass ratio of 1:0.3 to 1:0.6. Outside the dynamic compensation layer, there is also a temperature-sensitive polymer, namely poly(N-isopropylacrylamide), with a grafting rate of 15% to 30%. In addition, the figure also shows a fracture self-adaptive regulation module and a temperature difference-driven migration module. The fracture self-adaptive regulation module includes three-dimensional redox potential sensors, dissolved oxygen sensors, and a multimodal activity mapping model. The multimodal activity mapping model generates a three-dimensional heat map, and the temperature difference-driven migration module generates a directional current by a thermoelectric power generation module.

[0042] As Figure 3 shown, the sensor data input in the figure includes three-dimensional redox potential data, dissolved oxygen distribution data, and conductivity data. These data are provided to a multimodal activity mapping model, which includes the following aspects: parameters constructed based on conductivity, parameters constructed based on redox potential, parameters constructed based on dissolved oxygen, spatial and temporal two-dimensional activity prediction, and generation of a three-dimensional activity heat map. To generate the three-dimensional activity heat map, the model also performs a series of processes, including: mapping the potential to the red channel, mapping the dissolved oxygen to the green channel, mapping the conductivity to the blue channel, and performing RGB color model fusion; finally, the model generates an output, and the output content includes a three-dimensional activity heat map, the division result of high- and low-activity remediation areas, and pulse injection strategy guidance information.

[0043] Example 3: First, in the thermoelectric-driven migration module, the electric field strength formed by the natural temperature gradient between the upstream and downstream of the groundwater body is vulnerable to multiple factors in the aquifer. For example, factors such as changes in geological thermal conductivity and local disturbances may cause the drift of particle migration direction. Therefore, in the collaborative working system formed by the thermoelectric power generation module and the sensor array, the groundwater temperature gradient changes are fed back in real time through the sensor array to adjust the current output direction. In this path, the thermoelectric voltage is not quantitatively set, but a weak but continuous DC signal is used as the migration driving force to achieve slow-speed directional movement within the particle scale range. Combining with the phase change response window of the thermosensitive polymer, the adsorption capacity is automatically enhanced around the temperature threshold of 20 °C, thereby indirectly promoting the enrichment and reduction of pollutants in the low-temperature area. The working mechanism of this device is based on the principle of particle size control (20 - 50 nm) matching the pore size of the clay layer, avoiding the influence of the uncertainty of macroscopic-scale current control.

[0044] Secondly, in the multi-modal activity mapping model, the generation of the activity heat map is not a simple image superposition, but based on the three types of original data of redox potential (ORP), dissolved oxygen (DO), and electrical conductivity (EC) obtained by the sensor. After normalization processing, they are assigned to the three RGB channels to realize the visualization of the spatial distribution trend. In specific applications, ORP, DO, and EC are all collected by an in-situ deployed three-dimensional sensor array, and the data is updated at a minute-level time resolution. Combined with the GIS geographical grid system for coordinate registration, this model dynamically divides the remediation area by setting parameter fluctuation thresholds, rather than static area division. Even in the case of pollutant source migration or changes in groundwater flow velocity, it can still adjust the pulse injection area of nanoparticles in real time, thereby improving the response accuracy of the injection strategy.

[0045] In addition, in the microbial co-remediation module, the activation path of sulfate-reducing bacteria dormant spores clearly depends on the combined triggering conditions of pH value less than 6.5 and temperature higher than 25 °C in the groundwater environment. In actual deployment, the pH response layer is coated with a hydrogel structure of copolymerized polydopamine outside the biochar loading layer, which can disintegrate and release spores at a specific pH value. To avoid mis-triggering or premature release, the entire response layer preparation process uses a swelling - de-crosslinking - re-curing process to precisely control its disintegration time window. This module synergizes with the FeS reaction mechanism of the dynamic compensation layer, generates through microbial metabolism and forms a closed-loop enhancement chain with the Fe core electron transfer path, promoting the forward progress of the multivalent iron ion reduction reaction, and maintaining and enhancing the pollutant reduction ability from the mechanism level. The mass ratio formula:

[0046] , where and are the masses of ferrous sulfide and humic acid (in mg) that make up the dynamic compensation layer. This mass ratio is not fixedly set, but is preliminarily adjusted according to the oxidation pressure, pollutant concentration, and water body salinity in different groundwater environments. In specific operations, the redox potential and pH characteristic values in the remediation environment can be obtained through small-scale pre-simulation experiments, and the optimal range can be estimated by combining the FeS oxidation rate curve and the HA complexation ability. If humic acid is dominant, it can enhance the stable complexation of heavy metal pollutants, while if FeS is dominant, it is suitable for the system remediation mainly composed of halogenated organic compounds. These are all extended implementation methods known to those of ordinary skill in the art.

[0047] Example 4: When constructing the dynamic compensation layer in this example, the set range of the mass ratio between ferrous sulfide (FeS) and humic acid (HA) is: , wherein, represents the mass of ferrous sulfide participating in the construction of the dynamic compensation layer, represents the mass of humic acid participating in the reaction, and the unit is milligram (mg). This ratio is not statically set, but is obtained by adjusting parameters through simulating different groundwater environments (such as redox potential, pH value, and water body salinity) in the initial test stage. In specific operations, the titration-potential monitoring linkage method is used to synchronously measure the ORP and the HA complexation reaction rate curve, so as to screen the optimal ratio range and ensure good electron supply and complexation balance ability in actual remediation. The technical effect of this mass ratio lies not only in adjusting the release rate of FeS, but also in delaying the formation of the oxide film on the surface of the iron core through a synergistic mechanism, so as to maintain the electron transfer efficiency of the overall system. As a multi-functional organic complexing agent, humic acid can form a relatively stable surface complexing layer at an appropriate ratio, making FeS not easily agglomerate or precipitate, and improving the stable dispersion ability of the dynamic compensation layer in the aquifer medium.

[0048] Secondly, regarding the driving principle of the temperature difference-driven migration module, it does not rely on high-power electric fields or forced pumping systems in the traditional sense. Instead, it constructs a micro-electric field driving mechanism based on the naturally existing temperature difference in the underground aquifer. In a typical deployment scenario, the temperature of shallow groundwater is maintained between 20–25°C throughout the year due to the influence of solar radiation on the earth's surface, while the temperature in the deep region is relatively stable at around 16–18°C. An average temperature gradient of about 5–8°C is formed between the two. This temperature difference drives a low-voltage DC field (usually less than 1V) through an integrated micro-thermoelectric power generation module, which can form a directional migration trend in a composite particle system with a particle size of 20–50 nm. It should be noted that poly(N-isopropylacrylamide) in the composite particles exhibits significant phase change behavior in the range of 20–25°C, and its structure undergoes a hydrophobic / hydrophilic switch in this temperature range, driving the adsorption and release of pollutants to occur synergistically. Therefore, in the temperature difference-driven migration mechanism, it is not a single temperature gradient or current that plays a role, but a systematic cooperation combining particle size, electrophoretic response characteristics, and the polymer phase change window, enabling the particles to complete directional enrichment in the low-temperature region and trigger the desorption-degradation process of pollutants, achieving spatial coordination of the migration path and reaction sites.

[0049] Thirdly, to ensure the stability and credibility of the activity mapping results in the fracture adaptive regulation module, during the implementation process, normalization processing of three-component parameters of conductivity (EC), redox potential (ORP), and dissolved oxygen (DO) is adopted. A spatial distribution map is generated through the red-green-blue (RGB) three-channel intensity mapping algorithm of the heat map. The data collected by each sensor is updated at a minute-level time frequency and synchronously fed into the multi-modal activity mapping model. The red channel of the heat map reflects local redox activity, the green channel indicates the distribution of dissolved oxygen concentration, and the blue channel corresponds to the change in conductivity. By comparing the intensities of the color channels, not only can the spatial hot spots of pollutant release be identified, but the pulse injection strategy can also be updated in real time in the internal algorithm of the model to adapt to the changes in the dynamic groundwater flow environment. In terms of variable description, in the above model, EC, ORP, and DO represent the conductivity, redox potential (mV), and dissolved oxygen concentration (mg / L) in the groundwater per unit volume respectively. The normalization process uses a piecewise linear function to ensure the relative consistency of the sampled data in different geological regions in the spatial expression after standardization. This method avoids the phenomenon of full-map distortion caused by the deviation of a certain parameter interval and ensures the accuracy of the identification of the active remediation area and the formulation of the injection strategy, all of which are implementation methods known to those of ordinary skill in the art.

[0050] Finally, for the specific preparation process of the composite particles, to avoid parameter fluctuations caused by insufficient variable control, this embodiment uses a constant temperature water bath reaction to control the polymer grafting rate, with the target range controlled at 15–30%, the reaction time is 4 hours, and the reaction temperature is 60°C. The measured value of the surface Zeta potential of the obtained composite particles is maintained at -20 to -35 mV under the condition of pH 6.5, indicating that the system has good dispersibility and surface stability under natural groundwater conditions, can effectively adapt to the migration environment in the porous medium of the underground aquifer, and is not prone to agglomeration and deposition phenomena.

[0051] Example 5: In the dynamic compensation layer constituting the nano-zero-valent iron composite particles, the mass ratio of iron sulfide (FeS) to humic acid (HA) is determined to be in the range of , where represents the mass of iron sulfide participating in the construction of the dynamic compensation layer, with the unit of milligram (mg), and represents the mass of humic acid participating in the reaction, also with the unit of milligram (mg). Iron sulfide can provide continuous electron supplementation for the zero-valent iron core, delay its oxidation and passivation, and maintain its reduction activity; humic acid, with its rich functional groups such as carboxyl groups, can not only complex and adsorb pollutants in the water body, but also stabilize the dispersion state of iron sulfide on the particle surface and prevent its agglomeration. When the mass ratio is lower than 0.3, the content of iron sulfide is relatively insufficient, and the electron supply ability is limited, which may affect the overall reduction efficiency. On the contrary, when the mass ratio exceeds 0.6, the proportion of humic acid is too high, and its strong complexing effect may overly wrap iron sulfide, restricting its ability to in-situ release active sulfur, and instead reducing the effect of synergistic remediation; therefore, within this specific mass ratio range, the two can achieve an optimized balance of electron transfer and pollutant adsorption complexation, effectively improving the stability and remediation efficiency of the nanoparticles in the complex groundwater environment. In this structure, the iron sulfide in the dynamic compensation layer preferably has the marcasite crystal form, and its crystal plane spacing is , and this specific crystal plane structure helps to form a stable hydrogen bond anchoring with the carboxyl group of humic acid, further enhancing the structural stability and synergistic efficiency of the dynamic compensation layer.

[0052] Thermosensitive polymers usually use poly(N-isopropylacrylamide). By grafting onto the surface of the dynamic compensation layer, the nanoparticles are given the ability to respond to environmental temperature. The grafting rate is controlled within the range of 15% to 30%. The grafting density of the polymer directly affects its conformational change behavior at different temperatures, that is, the switching between the hydrophilic state and the hydrophobic state. Under the natural temperature gradient of groundwater, for example, from the relatively warm shallow layer to the lower temperature deep layer, the thermosensitive polymer will undergo corresponding phase changes. When the temperature is higher than its critical solution temperature, the polymer chains stretch into a hydrophilic state, which is conducive to the diffusion of pollutants to the zero-valent iron core for reduction degradation; when the temperature is lower than this temperature, the polymer chains contract into a hydrophobic state, enhancing the adsorption capacity for hydrophobic organic pollutants. By regulating the grafting rate of the polymer and copolymer modification, adjusting its critical solution temperature to match the groundwater temperature range (such as 20 degrees Celsius to 25 degrees Celsius), the automatic cycle of pollutant adsorption, desorption and zero-valent iron core reduction degradation can be achieved.

[0053] The fracture adaptive regulation module provides the entire system with the ability of environmental perception and intelligent decision-making. By deploying a three-dimensional redox potential sensor array and a dissolved oxygen sensor array at the boundary of the remediation area, the system can obtain real-time data on the redox gradient and dissolved oxygen distribution of the groundwater body. These environmental parameters are key indicators reflecting the chemical state and remediation activity of groundwater; the collected data is input into a multi-modal activity mapping model. This model is constructed based on three parameters: conductivity, redox potential, and dissolved oxygen, and can comprehensively analyze the complex information of the groundwater environment. The model processes these data to generate a three-dimensional heat map reflecting the activity of the remediation area. The method of generating the heat map can be to map the redox potential value to the intensity of the red channel of the heat map, map the dissolved oxygen value to the intensity of the green channel, map the conductivity value to the intensity of the blue channel, and then fuse them through the RGB color model, so as to visually visualize the attenuation degree and distribution of the activity in the remediation area; based on this heat map, the model can dynamically divide the high-activity remediation area and the low-activity remediation area, and guide the pulse injection strategy of nano zero-valent iron composite particles according to the real-time activity distribution. This strategy avoids blind large-dose injection and can accurately deliver the remediation agent to the area most in need of remediation, improving the remediation efficiency and coverage rate.

[0054] The temperature difference-driven migration module works in coordination with the response mechanism of the temperature-sensitive polymer, further enhancing the efficiency of the remediation system. This device utilizes the naturally existing temperature gradient between the upstream and downstream of the underground water body to generate a weak directional current through the thermoelectric power generation module. Although the magnitude of this directional current is not large, it is sufficient to drive the directional migration of nano zero-valent iron composite particles with a certain charge on the surface in the aquifer, causing them to accumulate in the low-temperature region. Exactly in the low-temperature region, the temperature-sensitive polymer is in a hydrophobic contracted state, which can enhance the adsorption of hydrophobic organic pollutants. When the particles migrate to the region with a higher temperature, the polymer turns into a hydrophilic extended state, releasing the pollutants to the surface of the zero-valent iron core for reduction and degradation. This organic combination of temperature difference-driven migration and thermosensitive phase transition realizes the directional transportation of nanoparticles and the enrichment and treatment of pollutants in specific regions, avoiding the problem of uncontrollable migration paths of remediation agents in traditional solutions, and all belong to the extended implementation methods known to those of ordinary skill in the art.

[0055] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A groundwater remediation and activity monitoring system based on zero-valent iron-based nanomaterials, characterized in that: include: The nano zero-valent iron composite particle is composed of a zero-valent iron core, a dynamic compensation layer coated outside the zero-valent iron core, and a temperature-sensitive polymer grafted on the surface of the dynamic compensation layer; the dynamic compensation layer contains ferrous sulfide and humic acid, and the mass ratio of ferrous sulfide to humic acid is Satisfies the inequality: ， in, represents the mass of ferrous sulfide involved in building the dynamic compensation layer, Indicates the mass of humic acid participating in the reaction. The dynamic compensation layer can undergo in-situ reduction reaction with the oxide layer in the aquifer and synergistically adsorb pollutants. The thermosensitive polymer is poly-N-isopropylacrylamide, with a grafting rate of 15% to 30%, which is used to switch between adsorbing hydrophobic organic pollutants and releasing hydrophobic organic pollutants to the surface of the zero-valent iron core for reduction and degradation according to changes in ambient temperature. A fracture adaptive control module, which obtains the redox gradient and dissolved oxygen distribution data of the groundwater body through a three-dimensional redox potential sensor array and a dissolved oxygen sensor array deployed at the boundary of the restoration area, and inputs the data into a multimodal activity mapping model to generate a three-dimensional heat map reflecting the activity of the restoration area. The multimodal activity mapping model is constructed based on three parameters: conductivity, redox potential, and dissolved oxygen. It is used to predict activity in both space and time, dynamically divide high-activity restoration areas and low-activity restoration areas, and guide the pulse injection strategy of nano zero-valent iron composite particles; A temperature difference driven migration module is provided with a micro temperature difference power generation module upstream and downstream of the restoration area, and uses the naturally existing limited temperature gradient of the groundwater body to generate a weak directional current. The weak directional current can drive the slow directional migration of nano zero-valent iron composite particles in the aquifer at the nanoscale, and trigger the phase change of the thermosensitive polymer in combination with the temperature gradient of the aquifer, thereby synergistically realizing the selective adsorption of pollutants and the spatial migration regulation of nanoparticles.

2. The groundwater remediation and activity monitoring system based on zero-valent iron-based nanomaterials according to claim 1 is characterized in that: The crystal form of the ferrous sulfide in the dynamic compensation layer is makinoite, and the interplanar spacing of makinoite is The crystal face of makinoite can form a hydrogen bond anchoring structure with the carboxyl group of humic acid.

3. The groundwater remediation and activity monitoring system based on zero-valent iron-based nanomaterials according to claim 1 is characterized in that: The critical solution temperature of the thermosensitive polymer poly (N-isopropylacrylamide) was adjusted to 20°C to 25°C through copolymerization modification of acrylamide to match the naturally occurring temperature differences in groundwater.

4. The groundwater remediation and activity monitoring system based on zero-valent iron-based nanomaterials according to claim 3 is characterized in that: The method for generating a heat map using the multimodal activity mapping model includes: mapping the redox potential value to the red channel intensity of the heat map, mapping the dissolved oxygen value to the green channel intensity of the heat map, mapping the conductivity value to the blue channel intensity of the heat map, fusing the intensities of the red channel, green channel and blue channel through the RGB color model, and visually displaying the activity attenuation degree and distribution of the groundwater remediation area.

5. The groundwater remediation and activity monitoring system based on zero-valent iron-based nanomaterials according to claim 1, characterized in that: The nano zero-valent iron composite particles further include a conductive biochar layer, the surface of which is embedded with a sulfur-doped silicon carbide carrier with a mesoporous structure. The pore size of the sulfur-doped silicon carbide carrier is 20 nanometers to 50 nanometers, and the porosity is greater than or equal to 70%. The conductive biochar layer is used to load dormant spores of sulfate-reducing bacteria to form a microbial-electrochemical symbiotic interface.

6. The groundwater remediation and activity monitoring system based on zero-valent iron-based nanomaterials according to claim 5, characterized in that: The dormant spores of sulfate-reducing bacteria are coated by an environmental response activation layer, which is composed of a pH-responsive polydopamine and a temperature-sensitive hydrogel copolymer. When the pH value of the groundwater environment is less than 6.5 and the temperature is greater than 25 degrees Celsius, the environmental response activation layer shrinks and releases the sulfate-reducing bacteria spores, and synchronously activates the ferrous sulfide dynamic compensation mechanism of the dynamic compensation layer.

7. The groundwater remediation and activity monitoring system based on zero-valent iron-based nanomaterials according to claim 5 or 6, characterized in that: The sulfur-doped silicon carbide carrier acts as a directional channel for electron shuttle, which directionally transfers hydrogen sulfide electrons produced by the metabolism of sulfate-reducing bacteria to the zero-valent iron core, accelerates the reduction of trivalent iron ions in the zero-valent iron core to divalent iron ions, and forms a symbiotic metabolic chain of sulfate-reducing bacteria supplying electrons and zero-valent iron consuming electrons.

8. The groundwater remediation and activity monitoring system based on zero-valent iron-based nanomaterials according to any one of claims 5 or 6, characterized in that: The surface of the sulfur-doped silicon carbide carrier is further loaded with molybdenum-doped ferrous sulfide nanosheets, the mass percentage of molybdenum in the molybdenum-doped ferrous sulfide is 0.5% to 1.2%, and the interlayer spacing of the molybdenum-doped ferrous sulfide nanosheets is 0.8 nanometers to 1.2 nanometers, forming a paradoxical conversion catalytic layer for the directional conversion of hydrogen sulfide to polysulfides.

9. The groundwater remediation and activity monitoring system based on zero-valent iron-based nanomaterials according to claim 8, characterized in that: Carbon-coated ferroferric oxide nanoparticles are embedded inside the sulfur-doped silicon carbide carrier. The particle size of the carbon-coated ferroferric oxide nanoparticles is 10 nanometers to 20 nanometers. They produce local thermal effects by absorbing infrared bands with wavelengths greater than or equal to 800 nanometers in the groundwater environment, thereby activating the catalytic activity of the contradiction conversion catalytic layer.

10. The groundwater remediation and activity monitoring system based on zero-valent iron-based nanomaterials according to claim 9, characterized in that: An adsorption layer co-deposited by mesoporous silica and polypyrrole is constructed on the surface of the zero-valent iron core. The pore size of the mesoporous silica is 2 to 5 nanometers. The adsorption layer captures polysulfides through π-π interaction and triggers the spontaneous disproportionation reaction of polysulfides into elemental sulfur and electrons.

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