Passivated zero-valent iron activation method, underground water remediation system, remediation method and application

Abstract

The invention belongs to the technical field of underground water remediation, and particularly relates to a passivated zero-valent iron activation method, an underground water remediation system, a remediation method and application. The activation method of the passivated zero-valent iron, provided by the invention, comprises the following steps: mixing and reacting a small molecule acid activation solution and the passivated zero-valent iron under the condition that the pH value is 5.0-7.0 to obtain activated zero-valent iron; micromolecular acid in the micromolecular acid activating solution is selected from citric acid and / or oxalic acid. According to the method, the passivated zero-valent iron in the underground water in-situ reaction zone is activated by using specific green natural small-molecule organic acids (citric acid and oxalic acid) in a specific pH environment, so that the stability and the long-term effect of a system for repairing the underground water by using the zero-valent iron are improved, and a low-cost in-situ activated passivated zero-valent iron in-situ reaction zone technology is constructed; the reduction degradation efficiency of pollutants can be improved, and the underground water composite pollutants can be efficiently removed in a long-acting manner.

Description

Technical Field

[0001] The present invention belongs to the technical field of groundwater remediation, and specifically relates to a passivated zero-valent iron activation method, a groundwater remediation system, a remediation method and an application thereof. Background Art

[0002] Groundwater is a vital component of water resources, and organic pollution is a common type of groundwater contamination. A variety of methods are available for groundwater pollution control. Traditional chemical oxidation techniques, such as persulfate advanced oxidation (ADO) for degrading toxic and recalcitrant organic pollutants, suffer from persulfate's sluggish decomposition, resulting in unstable treatment efficiency, high energy consumption, and high maintenance costs. Activated sodium persulfate, a broad-spectrum ADO technology, has become a popular ADO remediation agent for contaminated soil and groundwater. However, if the persulfate dosage and reaction conditions are not strictly controlled during treatment, this method can easily generate excessive free radicals and byproducts. Fenton reagents have a slow reaction rate, low H₂O₂ utilization, incomplete organic matter conversion, and potentially colored treated water, making them difficult to apply to drinking water treatment. Fenton-like methods suffer from low catalyst activity, a narrow pH operating range, and high cost of precious metal catalysts. Ozone oxidation suffers from issues of selective oxidation and incomplete mineralization, limiting its application for selective oxidation of organic matter and preventing its complete decomposition. Electrochemical methods consume high power, and their electrode materials, often precious metals, are costly. The use of photocatalytic degradation of organic pollutants in groundwater can deeply oxidize most organic pollutants. Under normal pressure, more than ten types of difficult-to-degrade organic matter can be photocatalytically decomposed into carbon dioxide and water. This method has the advantages of not causing secondary pollution, being inexpensive, and being stable in the aqueous phase. It has become a green environmental protection technology that has attracted much attention. However, photocatalysis requires an environment with light to provide energy. Bioremediation technology is a method of treating polluted water by changing environmental conditions to stimulate microbial growth and degrade target pollutants. In many cases, bioremediation is cheaper and more sustainable than other remediation alternatives, but it relies heavily on the growth conditions of the microorganisms and requires the addition of foreign substances to optimize the microbial conditions.

[0003] Zero-valent iron (ZVI), a highly effective reducing agent, has been widely used in the remediation of polluted environments, particularly groundwater pollution control, due to its strong reducing power, environmental friendliness, flexibility, high efficiency, and low cost. ZVI can be directly injected into heavily contaminated aquifers, forming a highly efficient in-situ reaction zone where it effectively degrades pollutants by leveraging its physicochemical properties. This ZVI in-situ reaction zone technology can be combined with other remediation techniques (such as bioremediation and electroremediation). Furthermore, it is not restricted by light conditions, making it particularly suitable for lightless environments such as groundwater. However, in practical applications, this technology also faces several challenges, the most significant of which is the passivation of the ZVI. During contact with groundwater, ZVI undergoes oxidation and becomes passivated. The resulting iron oxide or hydroxide precipitates coat the surface of the ZVI, preventing further contact between the ZVI and the pollutant, thereby reducing its reactivity and remediation efficiency. Therefore, how to solve the passivation problem of zero-valent iron and improve the remediation efficiency of zero-valent iron in-situ reaction zone technology is one of the current research hotspots in the field of groundwater pollution remediation. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect that the existing zero-valent iron is easily passivated during contact with groundwater, thereby reducing the reaction activity and repair efficiency of zero-valent iron, thereby providing a passivated zero-valent iron activation method, groundwater remediation system, remediation method and application.

[0005] The present invention provides a method for activating passivated zero-valent iron, comprising the following steps:

[0006] The small molecule acid activation solution and the passivated zero-valent iron are mixed and reacted at a pH of 5.0-7.0 to obtain activated zero-valent iron;

[0007] The small molecule acid in the small molecule acid activation solution is selected from citric acid and / or oxalic acid.

[0008] The present invention corresponds to different groundwater environmental conditions and types of pollutants, and can add activation solutions with different small molecule acid compound ratios. For example, when the groundwater environment pH is alkaline, oxalic acid activation solution with stronger acidity is used; if the groundwater environment pH is neutral or acidic, citric acid with weaker acidity can be used.

[0009] Definition of passivated zero-valent iron: As zero-valent iron degrades pollutants, its surface is oxidized to form an oxide layer, resulting in a decrease in activity. For example, the oxidation reaction produces Fe3O4 or FeOOH. This oxide film hinders direct contact between zero-valent iron and pollutants, thereby significantly reducing its reduction efficiency.

[0010] Zero-valent iron is easily passivated in practical applications, which limits its service life and efficiency and affects its actual repair effect.

[0011] Preferably, the ratio of the small molecule acid to the passivated zero-valent iron in the small molecule acid activation solution is (1-10):1, expressed in mmol:g;

[0012] Optionally, the ratio of the small molecule acid to the passivated zero-valent iron in the small molecule acid activation solution is 5:1, and the unit is mmol:g;

[0013] And / or, the solvent in the small molecule acid activation solution is selected from water.

[0014] The present invention does not impose any specific limitation on the mass concentration of the small molecule acid in the small molecule acid activation solution, as long as the ratio of the small molecule acid in the small molecule acid activation solution to the passivated zero-valent iron is within a specified range.

[0015] The present invention provides a groundwater remediation system based on the above-mentioned activation method of passivated zero-valent iron, the groundwater remediation system comprising:

[0016] An injection pipe with a plurality of permeable holes provided on its wall, which is extended to a target groundwater layer and injects nano-zero-valent iron into the groundwater layer;

[0017] A small molecule acid injection device connected to the injection pipeline;

[0018] A monitoring device, comprising an iron ion concentration monitoring unit and a gravity monitoring unit provided in the injection pipe;

[0019] a controller connected to the monitoring device and the small molecule acid injection device, and controlling the small molecule acid injection device to inject the small molecule acid activation solution into the injection pipe according to the iron ion concentration monitored by the iron ion concentration monitoring unit and the zero-valent iron mass concentration monitored by the gravity monitoring unit;

[0020] Preferably, the groundwater remediation system also includes a zero-valent iron injection device connected to the injection pipe, and the controller is connected to the zero-valent iron injection device to control the zero-valent iron injection device to inject zero-valent iron into the injection pipe according to the monitored iron ion concentration and zero-valent iron mass concentration.

[0021] Optionally, the iron ion concentration monitoring unit includes an iron ion concentration monitoring device. The present invention does not specifically limit the type of the iron ion concentration monitoring device, as long as it can achieve the purpose of monitoring the iron ion concentration in the water body, for example, it can be a commercially available iron ion water quality detector.

[0022] Optionally, the pollutant concentration monitoring unit can monitor target pollutants according to actual needs. The present invention does not specifically limit the types of pollutants. For example, they include but are not limited to phenols, chlorinated hydrocarbons, antibiotics, hormones, and heavy metals. The pollutant concentration monitoring unit includes a pollutant concentration monitoring device. The present invention does not specifically limit the type of pollutant concentration monitoring device. It can achieve the purpose of monitoring the concentration of pollutants in water bodies. For example, the pollutant concentration monitoring device can optionally include a sampling device and a detection device. After sampling with the sampling device, the pollutants are detected by the detection device (high-performance gas chromatograph (GC-MS) detects the concentration of phenols and chlorinated hydrocarbons in water quality; high-performance liquid chromatograph (LC-MS) detects the concentration of antibiotics and hormones, and flame atomic absorption spectrophotometer detects the concentration of heavy metal pollutants). It can also directly use the sensing device as a pollutant concentration monitoring device to detect the concentration of different pollutants. The pollutant concentration can be a mass concentration or a molar concentration. The present invention does not specifically limit it and can be determined based on the detection results of the actual monitoring device.

[0023] Iron ion concentration reflects the degree of zero-valent iron activation. Higher iron ion concentrations indicate greater activation effectiveness of the small-molecule acid. Higher concentrations of zero-valent iron and small-molecule acid increase the iron ion concentration. Experimental results indicate that 1g / L of zero-valent iron, when activated with 5mmol / L of small-molecule acid, typically produces 100-200mg / L of iron ions (total iron). Furthermore, higher concentrations of ferrous iron indicate greater activation effectiveness.

[0024] After zero-valent iron is activated by small molecule acids, it releases iron ions. Ferrous ions can reflect the activity of zero-valent iron: the higher the ferrous ion concentration, the higher the activation activity of zero-valent iron. Therefore, the iron ion concentration in the injection pipeline should be monitored. When the ferrous ion concentration near the injection pipeline is greater than 100 mg / L, the zero-valent iron activity is better.

[0025] Preferably, the monitoring device further comprises a pH monitoring unit provided on the injection pipe;

[0026] The controller controls the small molecule acid injection device to inject the pH regulator into the injection pipeline according to the pH value monitored by the pH monitoring unit.

[0027] Optionally, the gravity monitoring unit includes a gravity sensor.

[0028] Optionally, the pH monitoring unit includes a pH sensor, which includes but is not limited to a commercially available pH meter.

[0029] Preferably, the monitoring device comprises:

[0030] A monitoring pipe having a plurality of permeable holes formed in its wall, the monitoring pipe being arranged parallel to the injection pipe along the axial direction of the injection pipe on one side of the injection pipe; and / or the monitoring pipe being spaced 3-5 m apart from the injection pipe;

[0031] a pollutant concentration monitoring unit, provided on the monitoring pipeline, for monitoring pollutants in the groundwater layer;

[0032] The control unit is connected to the pollutant concentration monitoring unit, and controls the zero-valent iron injection device to inject zero-valent iron into the injection pipeline according to the pollutants in the groundwater layer monitored by the pollutant concentration monitoring unit;

[0033] Preferably, a sampling device is provided on one side of the monitoring pipe and / or injection pipe, and the sampling tube of the sampling device extends from one end to the other end of the monitoring pipe and / or injection pipe, and a sampling port is provided on the pipe wall of the sampling tube for sampling the groundwater layer.

[0034] Optionally, the iron ion concentration monitoring unit is provided in the injection pipeline;

[0035] And / or, the pollutant concentration monitoring unit is provided in the monitoring pipeline;

[0036] And / or, the pH monitoring unit is provided in the injection pipeline;

[0037] Alternatively, the gravity monitoring unit is installed in the injection pipeline. Because groundwater has a certain flow rate and comes into direct contact with zero-valent iron, it may carry away some iron-based materials with the water flow. Therefore, a gravity sensor and an iron ion concentration detector are installed below the injection pipeline. If the monitored iron ion concentration is low and the zero-valent iron quality is too low, it indicates that the zero-valent iron is almost depleted and requires additional zero-valent iron material.

[0038] Preferably, the injection pipeline is divided into at least two sections along the axial direction, each section of the injection pipeline is respectively provided with the monitoring device, and the small molecule acid injection device and / or the zero-valent iron injection device are respectively connected to each section of the pipeline;

[0039] Preferably, two adjacent sections of pipeline are connected.

[0040] Preferably, the injection pipeline is a segmented injection pipeline, which is used to inject nano zero-valent iron into different aquifers;

[0041] Preferably, the segmented injection pipeline includes three sections of injection pipelines, namely an upper injection pipeline, a middle injection pipeline, and a lower injection pipeline;

[0042] The small molecule acid injection device includes a small molecule acid injection conduit, which includes three injection ports, namely an upper injection port, a middle injection port, and a lower injection port; the small molecule acid activation solution and / or the pH adjuster are injected into the three injection pipes in the zero-valent iron injection device through the three injection ports of the small molecule acid injection conduit;

[0043] It can be understood that among the three injection ports of the small molecule acid injection catheter, the upper injection port is connected to the upper injection pipe of the segmented injection pipe, the middle injection port is connected to the middle injection pipe of the segmented injection pipe, and the lower injection port is connected to the lower injection pipe of the segmented injection pipe. The small molecule acid activation solution and / or pH adjuster are correspondingly injected into the three injection pipes through the three injection ports of the small molecule acid injection catheter.

[0044] Optionally, the monitoring pipeline includes a first monitoring pipeline and a second monitoring pipeline; the first monitoring pipeline is arranged along the axial direction of the injection pipeline and is parallel to the injection pipeline on one side of the injection pipeline; the second monitoring pipeline is arranged in the downstream direction of the injection pipeline and is spaced 3-5m apart from the injection pipeline;

[0045] The first of the monitoring pipes includes at least one sampling port for the concentration of pollutants in the water body;

[0046] Preferably, the first monitoring pipe in the monitoring pipe includes three sampling ports, which respectively correspond to the groundwater areas at the bottom ends of the three injection pipes, and are used to monitor the pollutant concentration in the water body of the groundwater areas at the bottom ends of the three injection pipes.

[0047] Preferably, the zero-valent iron injection device comprises a zero-valent iron injection conduit;

[0048] The upper injection pipe, the middle injection pipe, and the lower injection pipe are sequentially connected by a zero-valent iron injection pipe, and the zero-valent iron injection pipe connected to the upper injection pipe, the zero-valent iron injection pipe connected to the middle injection pipe, and the zero-valent iron injection pipe connected to the lower injection pipe are respectively provided with a pipe valve. The controller can control the amount of nano zero-valent iron injected into the injection pipes of different sections by controlling the pipe valves.

[0049] And / or, the walls of the upper injection pipe, the middle injection pipe, and the lower injection pipe have holes, which help the contaminated groundwater to fully contact the zero-valent iron system and prevent the zero-valent iron from being lost with the water flow;

[0050] Preferably, the pipe walls of the upper injection pipe, the middle injection pipe, and the lower injection pipe are provided with screens;

[0051] Preferably, a capsule for accommodating nano-zero-valent iron is provided in the injection pipe, a plurality of permeation holes are provided on the capsule wall of the capsule, and the zero-valent iron injection device is connected to the capsule for injecting zero-valent iron into the capsule;

[0052] Preferably, a stirring device is provided in the wrapping bag.

[0053] Optionally, the upper injection pipe, the middle injection pipe, and the lower injection pipe are equipped with a stirring device to promote rapid contact and fusion of the substances injected into the pipe; optionally, the stirring speed of the stirring device can be automatically controlled by a controller;

[0054] Optionally, a wrapping capsule is provided in the upper injection pipe, the middle injection pipe, and the lower injection pipe, the injected zero-valent iron is in the wrapping capsule, and a stirring device is provided in the wrapping capsule.

[0055] Optionally, gravity monitoring units are respectively provided at the bottom layer of the upper injection pipe, the bottom layer of the middle injection pipe, and the bottom layer of the lower injection pipe.

[0056] Zero-valent iron typically settles to the bottom of the injection pipe (or the bottom of the upper, middle, or lower injection pipe). A gravity monitoring unit (such as a gravity sensor) can be installed at the bottom of the injection pipe (or the bottom of the upper, middle, or lower injection pipe) to monitor the mass concentration of the zero-valent iron. Alternatively, during injection, the zero-valent iron can be placed in a capsule within the injection pipe. The capsule can be made of gauze or other containers with fine pores to prevent the zero-valent iron from being carried away by the water flow, allowing water to pass through without affecting the activation of the small molecule acid and the degradation of pollutants by the zero-valent iron. After a period of time, the capsule is removed from the injection pipe and the mass of the zero-valent iron is weighed to obtain the zero-valent iron mass concentration. The reduction in the mass of the zero-valent iron at this point is primarily due to the generation of iron ions after activation by the small molecule acid, rather than a reduction in loss.

[0057] The present invention provides a method for repairing groundwater using the above-mentioned groundwater repair system, which obtains the iron ion concentration and zero-valent iron mass concentration in the injection pipeline;

[0058] When the zero-valent iron mass concentration is greater than or equal to the target zero-valent iron mass concentration and the iron ion concentration is less than the target iron ion concentration, the small molecule acid activation solution is controlled to be injected into the injection pipe.

[0059] Preferably, the method further comprises obtaining the concentration of pollutants and the pH value in the injection pipeline;

[0060] When the zero-valent iron mass concentration is less than the zero-valent iron mass target concentration and the iron ion concentration is less than the iron ion target concentration, controlling the injection of zero-valent iron into the injection pipe;

[0061] When the zero-valent iron mass concentration is greater than or equal to the zero-valent iron mass target concentration, the iron ion concentration is greater than or equal to the iron ion target concentration, but the concentration of the pollutant is greater than or equal to the target concentration, controlling the zero-valent iron injection device to inject zero-valent iron into the injection pipe;

[0062] When the pH is lower than 5.0 or higher than 7.0, the small molecule acid injection device is controlled to inject a pH regulator into the injection pipe to adjust the pH to 5.0-7.0;

[0063] Preferably, the injection pipeline is divided into at least two sections along the axial direction, and small molecule acid and / or zero-valent iron and / or pH regulator are injected into different pipelines respectively according to the iron ion concentration, zero-valent iron mass, pH and pollutant concentration at different injection pipelines.

[0064] The present invention does not specifically limit the target concentration of zero-valent iron mass concentration, the target concentration of iron ion concentration, and the target concentration of pollutant concentration, which can be set according to actual needs or actual groundwater pollutant conditions.

[0065] Preferably, when the monitoring device detects that the mass concentration of zero-valent iron is lower than the target concentration and the iron ion concentration is lower than the target concentration, the controller controls the zero-valent iron injection device to inject an amount of nano-zero-valent iron into the injection pipe so that the mass concentration of zero-valent iron is greater than or equal to the target concentration;

[0066] When the monitoring device detects that the zero-valent iron mass concentration is not lower than the target concentration, but the iron ion concentration is lower than the target concentration, the controller controls the small molecule acid injection device to inject the small molecule acid activation liquid into the injection pipe in such an amount that the iron ion concentration is higher than or equal to the target concentration;

[0067] When the monitoring device detects that the zero-valent iron mass concentration is not lower than the target concentration and the iron ion concentration is not lower than the target concentration, but the concentration of the pollutant is higher than the target concentration, the controller controls the zero-valent iron injection device to inject an injection amount of nano-zero-valent iron into the injection pipe so that the concentration of the pollutant reaches below the target concentration;

[0068] Optionally, when the monitoring device detects that the pH in the water is lower than 5.0 or higher than 7.0, the controller controls the small molecule acid injection device to inject an injection amount of pH regulator into the injection pipe to adjust the pH to 5.0-7.0.

[0069] For example, the target concentration of zero-valent iron mass concentration can be selected to be 2-6 g / L, and the target concentration of iron ion concentration can be selected to be 50-200 mg / L.

[0070] Optionally, the pH regulator includes but is not limited to a hydrochloric acid aqueous solution or a sodium hydroxide aqueous solution. The concentration of the hydrochloric acid aqueous solution or the sodium hydroxide aqueous solution is usually 0.1-1 mol / L.

[0071] Preferably, when the monitoring device detects that the mass concentration of zero-valent iron is lower than 3 g / L and the iron ion concentration is lower than 100 mg / L, the controller controls the zero-valent iron injection device to inject an amount of nano-zero-valent iron into the injection pipe so that the mass concentration of zero-valent iron is greater than 3 g / L;

[0072] When the monitoring device detects that the mass concentration of zero-valent iron is not less than 3 g / L, but the iron ion concentration is less than 100 mg / L, the controller controls the small molecule acid injection device to inject the small molecule acid activation solution into the injection pipe in such an amount that the iron ion concentration is higher than 100 mg / L.

[0073] When the monitoring device detects that the zero-valent iron mass concentration is not less than 3g / L and the iron ion concentration is not less than 100mg / L, but the concentration of the pollutant is higher than the target concentration, the controller controls the zero-valent iron injection device to inject an amount of nano-zero-valent iron into the injection pipe so that the concentration of the pollutant reaches below the target concentration;

[0074] Optionally, when the monitoring device detects that the pH in the water is lower than 5.0 or higher than 7.0, the controller controls the small molecule acid injection device to inject an injection amount of pH regulator into the injection pipe to adjust the pH to 5.0-7.0.

[0075] Preferably, when the monitoring device detects that the zero-valent iron mass concentration in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe is lower than the target concentration and the iron ion concentration is lower than the target concentration, the controller controls the zero-valent iron injection device to inject an injection amount of nano-zero-valent iron into the corresponding upper injection pipe and / or the middle injection pipe and / or the lower injection pipe so that the zero-valent iron mass concentration is greater than or equal to the target concentration;

[0076] When the monitoring device detects that the mass concentration of zero-valent iron in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe is not lower than the target concentration, but the iron ion concentration is lower than the target concentration, the controller controls the small molecule acid injection device to inject the small molecule acid activation solution into the corresponding upper injection pipe and / or the middle injection pipe and / or the lower injection pipe so that the iron ion concentration is higher than or equal to the target concentration;

[0077] When the monitoring device detects that the zero-valent iron mass concentration in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe is not lower than the target concentration and the iron ion concentration is not lower than the target concentration, but the concentration of the pollutant is higher than the target concentration, the controller controls the zero-valent iron injection device to inject the nano-zero-valent iron into the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe in such an amount that the pollutant concentration reaches below the target concentration;

[0078] and / or, when the monitoring device detects that the pH of the water in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe is lower than 5.0 or higher than 7.0, the controller controls the small molecule acid injection device to inject an injection amount of the pH adjuster into the corresponding upper injection pipe and / or the middle injection pipe and / or the lower injection pipe to adjust the pH to 5.0-7.0;

[0079] And / or, when the monitoring device detects that the mass of the nano-zero-valent iron in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe is less than 1 / 2 of the initial mass, the controller controls the zero-valent iron injection device to inject an amount of nano-zero-valent iron into the injection pipe and / or the middle injection pipe and / or the lower injection pipe so that the nano-zero-valent iron in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe reaches the initial mass respectively.

[0080] Preferably, when the monitoring device detects that the zero-valent iron mass concentration in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe is lower than 3 g / L and the iron ion concentration is lower than 100 mg / L, the controller controls the zero-valent iron injection device to inject the nano-zero-valent iron into the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe so that the zero-valent iron mass concentration is greater than or equal to 3 g / L;

[0081] When the monitoring device detects that the mass concentration of zero-valent iron in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe is not less than 3 g / L, but the iron ion concentration is less than 100 mg / L, the controller controls the small molecule acid injection device to inject the small molecule acid activation solution into the corresponding upper injection pipe and / or the middle injection pipe and / or the lower injection pipe so that the iron ion concentration is greater than or equal to 100 mg / L;

[0082] When the monitoring device detects that the zero-valent iron mass concentration in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe is not less than 3 g / L and the iron ion concentration is not less than 100 mg / L, but the concentration of the pollutant is higher than the target concentration, the controller controls the zero-valent iron injection device to inject the nano-zero-valent iron into the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe in an amount such that the pollutant concentration reaches below the target concentration;

[0083] and / or, when the monitoring device detects that the pH of the water in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe is lower than 5.0 or higher than 7.0, the controller controls the small molecule acid injection device to inject an injection amount of the pH adjuster into the corresponding upper injection pipe and / or the middle injection pipe and / or the lower injection pipe to adjust the pH to 5.0-7.0;

[0084] And / or, when the monitoring device detects that the mass of the nano-zero-valent iron in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe is less than 1 / 2 of the initial mass, the controller controls the zero-valent iron injection device to inject an amount of nano-zero-valent iron into the injection pipe and / or the middle injection pipe and / or the lower injection pipe so that the nano-zero-valent iron in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe reaches the initial mass respectively.

[0085] The present invention also provides an application of the above-mentioned activation method for passivated zero-valent iron, the above-mentioned groundwater remediation system, or the above-mentioned method for remediating groundwater in groundwater remediation.

[0086] The technical solution of the present invention has the following advantages:

[0087] 1. The activation method for passivated zero-valent iron provided by the present invention comprises the following steps: mixing a small molecule acid activation solution with passivated zero-valent iron, reacting the mixture at a pH of 5.0-7.0 to obtain activated zero-valent iron; the small molecule acid in the small molecule acid activation solution is selected from citric acid and / or oxalic acid. The present invention utilizes specific green, natural small molecule organic acids (citric acid, oxalic acid) to activate the passivated zero-valent iron in an in-situ reaction zone of groundwater under a specific pH environment, thereby enhancing the reactivity of the zero-valent iron and improving the removal efficiency of pollutants in groundwater, particularly those that are difficult to degrade. This improves the stability and long-term effectiveness of zero-valent iron in remediating groundwater systems, constructing a low-cost in-situ activation and passivation zero-valent iron in-situ reaction zone technology, which can improve the reduction and degradation efficiency of pollutants and effectively and long-term remove complex pollutants in groundwater.

[0088] 2. The activation method for passivated zero-valent iron provided by the present invention can activate the zero-valent iron system multiple times. When the zero-valent iron activity decreases due to pollutant degradation, it can be reactivated by adding a small molecule acid, allowing the zero-valent iron material to be reused repeatedly, extending its service life and enabling long-term treatment of pollutants in groundwater. This allows the nano-zero-valent iron to persist and continuously reduce pollutants, enhancing pollutant removal. The method can also be designed to target multiple types of pollutants, including organic pollutants and heavy metals, for example, by promoting the reduction and degradation efficiency of organic pollutants and their complete mineralization. The activated nano-zero-valent iron has enhanced reducibility, enabling the treatment of a variety of complex groundwater pollutants.

[0089] 3. The activation method for passivated zero-valent iron provided by the present invention broadens the pH applicable range, has low energy consumption, is green and pollution-free, and also reduces dependence on precious metal catalysts and has low cost; it can also prevent the passivation of zero-valent iron.

[0090] 4. The present invention provides a groundwater remediation system based on the above-mentioned activation method of passivated zero-valent iron, the groundwater remediation system comprising: an injection pipe having a plurality of permeable holes formed in the pipe wall for extending to a target groundwater layer and injecting nano-zero-valent iron into the groundwater layer; a small molecule acid injection device connected to the injection pipe; a monitoring device including an iron ion concentration monitoring unit and a gravity monitoring unit provided in the injection pipe; and a controller connected to the monitoring device and the small molecule acid injection device, and controlling the small molecule acid injection device to inject a small molecule acid activation solution into the injection pipe according to the iron ion concentration monitored by the iron ion concentration monitoring unit and the zero-valent iron mass concentration monitored by the gravity monitoring unit. The system can detect the iron ion concentration and the zero-valent iron mass concentration in real time, and accurately control the injection amount of zero-valent iron and the small molecule acid activation solution through the feedback detection data, so that the passivation problem is promptly resolved during the zero-valent iron remediation process. The passivated zero-valent iron is activated by the system, and then the contaminants are continuously reduced for a long time, ensuring dynamic adjustment and efficient operation of the remediation process, and optimizing the groundwater remediation effect. Preferably, the groundwater remediation system further includes a zero-valent iron injection device connected to the injection pipeline, and a controller is connected to the zero-valent iron injection device, and controls the zero-valent iron injection device to inject zero-valent iron into the injection pipeline based on the monitored iron ion concentration and zero-valent iron mass concentration. The system can detect the iron ion concentration, pollutant concentration, and zero-valent iron mass concentration in real time, and accurately control the injection amount of zero-valent iron and small molecule acid activation solution through feedback detection data, so that the passivation problem during the zero-valent iron remediation of groundwater is promptly resolved. Through this system, the passivated zero-valent iron is activated, and the pollutants are continuously reduced over a long period of time. It also ensures the timely replenishment of lost zero-valent iron, maintains the content of active zero-valent iron, ensures the dynamic adjustment and efficient operation of the remediation process, and optimizes the groundwater remediation effect.

[0091] 5. The groundwater remediation system provided by the present invention, based on the activation method of passivated zero-valent iron, combines a monitoring device with a controller to provide an automated adjustment function, reduce manual intervention, and improve operational efficiency and safety. At the same time, the system can flexibly adjust the operating parameters of each system, such as the injection volume of zero-valent iron and the injection volume of small molecule acid activation solution, according to the groundwater pollution situation and remediation needs, and has strong adaptability and scalability. Combining the long-lasting effect of nano-zero-valent iron with the effective activation of small molecule acids, it can better ensure the continuity and stability of the remediation process, reducing maintenance frequency and remediation cycle.

[0092] 6. In the groundwater remediation system based on the above-described activation method for passivated zero-valent iron, the monitoring device further comprises a pH monitoring unit disposed on the injection pipeline; the controller controls the small molecule acid injection device to inject a pH adjuster into the injection pipeline based on the pH value monitored by the pH monitoring unit. The remediation system provided by the present invention, which also includes a pH monitoring unit and a device for injecting the pH adjuster into the injection pipeline, can be used to regulate and control the pH of groundwater within the activation area and is suitable for groundwater remediation in various regions.

[0093] 7. The present invention provides a groundwater remediation system based on the activation method of the above-mentioned passivated zero-valent iron, wherein the injection pipeline is divided into at least two injection pipelines along the axial direction, each injection pipeline is provided with the monitoring device, and the small molecule acid injection device and / or the zero-valent iron injection device is respectively connected to each injection pipeline; preferably, the two adjacent injection pipelines are connected. The injection pipeline of the present invention is divided into at least two injection pipelines along the axial direction, which can make the zero-valent iron evenly distributed in each layer of the underground aquifer, avoid gravity accumulation and affect the remediation efficiency of underground contaminated water, and improve the degradation rate of pollutants. The small molecule acid injection conduit in the small molecule acid injection device corresponds to the three injection ports included, and can independently adjust the injection of small molecule acid or pH regulator according to the pH of the environment in the three injection pipelines, different pollutant contents, and the lack of treatment raw materials.

[0094] 8. The present invention provides a method for remediating groundwater using the aforementioned groundwater remediation system. The method comprises obtaining the iron ion concentration and zero-valent iron mass concentration in the injection pipeline. When the zero-valent iron mass concentration is greater than or equal to the target zero-valent iron mass concentration and the iron ion concentration is less than the target iron ion concentration, a small-molecule acid activation solution is injected into the injection pipeline. This method automatically adjusts the amount of small-molecule acid injected based on the real-time detected iron ion and zero-valent iron mass concentration data, promptly activating the passivated zero-valent iron and enhancing its remediation activity.

[0095] 9. The method provided by the present invention for remediating groundwater using the above-mentioned groundwater remediation system further includes obtaining the pollutant concentration and the pH in the injection pipe; when the zero-valent iron mass concentration is less than the zero-valent iron mass target concentration and the iron ion concentration is less than the iron ion target concentration, controlling the injection of zero-valent iron into the injection pipe; when the zero-valent iron mass concentration is greater than or equal to the zero-valent iron mass target concentration, the iron ion concentration is greater than or equal to the iron ion target concentration, but the pollutant concentration is greater than or equal to the target concentration, controlling the zero-valent iron injection device to inject zero-valent iron into the injection pipe; the method automatically adjusts the injection amount of zero-valent iron and small molecule acid based on the real-time detected iron ion, zero-valent iron mass concentration and pollutant concentration data, timely activates the passivated zero-valent iron, improves the remediation activity of the zero-valent iron, and ensures the active iron content with remediation activity, and automatically adapts the adjustment mechanism to ensure the flexibility of the remediation process; the automated system controls the injection amount of zero-valent iron and small molecule acid, reduces manual operation and avoids human error; at the same time, according to the pollutant concentration distribution, such as in severely polluted areas, the working parameters are appropriately adjusted, and the zero-valent iron dosage is increased. The remediation strategy can be flexibly adjusted according to the needs of different polluted areas, which helps to efficiently treat different types of pollution.

[0096] When the pH is below 5.0 or above 7.0, the small molecule acid injection device is controlled to inject a pH adjuster into the injection pipe to adjust the pH to 5.0-7.0. Real-time monitoring of groundwater pH and the addition of pH adjusters when needed optimize the reaction environment for activating zero-valent iron and avoid the negative impact of excessively high or low pH on the remediation results. This method allows for precise remediation. By monitoring the area of ​​contamination, targeted adjustments to remediation strategies can be made, improving remediation efficiency and avoiding over- or under-remediation. It also avoids excessive use of chemicals and reduces negative impacts on the surrounding environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0097] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0098] Figure 1 Schematic diagram of the assembly structure of the groundwater remediation system of the present invention;

[0099] Figure 2 A schematic diagram of the internal structure of the groundwater remediation system of the present invention;

[0100] Figure 3 Schematic diagram of the distribution structure of the groundwater remediation system of the present invention in the underground aquifer;

[0101] Figure 4 Schematic diagram of the structure of the groundwater remediation system of the present invention;

[0102] Figure 5 Residual rate curves obtained from the tests of Examples 1-2 of the present invention and Comparative Examples 1-6;

[0103] Figure 6 Residual rate curves obtained from tests of Examples 3-4 of the present invention and Comparative Examples 7-9;

[0104] Figure 7 Residual rate curves obtained from tests of Examples 5-6 of the present invention and Comparative Examples 10-12;

[0105] Figure 8 Comparative data from a test experiment using the activation method for passivated zero-valent iron of the present invention to remediate contaminated groundwater at a complex contaminated site in Midong Industrial Park, Urumqi;

[0106] Figure numerals: 1-injection pipeline, 2-zero-valent iron injection device, 21-zero-valent iron injection conduit, 22-zero-valent iron storage tank, 3-small molecule acid injection device, 31-small molecule acid injection conduit, 32-small molecule acid storage tank, 41-iron ion concentration monitoring unit, 42-gravity monitoring unit, 43-first monitoring pipeline, 44-second monitoring pipeline, 431-sampling tube, 432-sampling port, 433-pollutant detection device, 33-pH adjuster storage tank, 11-upper injection pipeline, 12-middle injection pipeline, 13-lower injection pipeline, 311-upper injection port, 312-middle injection port, 313-lower injection port, 14-wrapping capsule, 15-stirring device. DETAILED DESCRIPTION

[0107] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0108] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0109] The following will be combined Figures 1 to 4 , the technical solution provided by the present invention is described in detail.

[0110] like Figure 1As shown, A represents the underground aeration zone, B represents the underground aquifer, and C represents the bottom plate of the underground aquifer. The groundwater remediation system provided by the present invention includes: an injection pipe 1, a plurality of permeable holes are opened on the pipe wall, which are used to extend to the target groundwater layer and inject nano zero-valent iron into the groundwater layer; a zero-valent iron injection device 2, which is connected to the injection pipe 1 and injects zero-valent iron into the injection pipe 1; the zero-valent iron injection device 2 includes a zero-valent iron injection conduit 21 and a zero-valent iron storage tank 22; a small molecule acid injection device 3, which is connected to the injection pipe 1 and injects a small molecule acid activation liquid into the injection pipe 1; the small molecule acid injection device 3 includes a small molecule acid injection conduit 31 and a small molecule acid storage tank 22. A storage tank 32; a monitoring device comprising an iron ion concentration monitoring unit 41 and a gravity monitoring unit 42; the iron ion concentration monitoring unit 41 is used to monitor the iron ion concentration in the water body and is disposed in the injection pipe 1; the gravity monitoring unit 42 is used to monitor the mass concentration of zero-valent iron and is disposed in the injection pipe 1, and the gravity monitoring unit 42 includes a gravity sensor; a controller connected to the monitoring device, the small molecule acid injection device 3, and the zero-valent iron injection device 2, and controls the small molecule acid injection device 3 to inject small molecule acid into the injection pipe 1 based on the iron ion concentration monitored by the iron ion concentration monitoring unit 41 of the monitoring device and the mass concentration of zero-valent iron monitored by the gravity monitoring unit 42. Furthermore, the controller of the groundwater remediation system is connected to the zero-valent iron injection device 2 and controls the zero-valent iron injection device 2 to inject zero-valent iron into the injection pipe 1 based on the monitored iron ion concentration and zero-valent iron mass concentration.

[0111] The monitoring device includes: a monitoring pipeline with a plurality of penetration holes provided in its wall, the monitoring pipeline being arranged parallel to the injection pipeline along the axis of the injection pipeline on one side of the injection pipeline; and / or the monitoring pipeline and the injection pipeline are spaced 3-5m apart; a pollutant concentration monitoring unit being provided on the monitoring pipeline for monitoring pollutants in the groundwater layer; a control unit being connected to the pollutant concentration monitoring unit, and controlling the zero-valent iron injection device to inject zero-valent iron into the injection pipeline according to the pollutants in the groundwater layer monitored by the pollutant concentration monitoring unit; further, a sampling device is provided on one side of the monitoring pipeline and / or the injection pipeline, and a sampling tube 431 of the sampling device extends from one end to the other end of the monitoring pipeline and / or the injection pipeline, and a sampling port 432 is provided on the wall of the sampling tube 431 for sampling the groundwater layer, and a pollutant detection device 433 is used for detection after sampling.

[0112] like Figure 1As shown, a monitoring pipeline has a plurality of permeable holes in its wall. The monitoring pipeline is arranged along the axis of the injection pipeline 1 and is a first monitoring pipeline arranged in parallel with the injection pipeline 1 on one side of the injection pipeline 1. The monitoring device also includes a pollutant concentration monitoring unit for monitoring the pollutant concentration in the water body. The pollutant concentration monitoring unit includes a first monitoring pipeline, and the first monitoring pipeline includes a sampling tube 431, a sampling port 432, and a pollutant detection device 433. The monitoring device also includes a pH monitoring unit for monitoring the pH value in the water body, for example, using a pH sensor. The pH detection unit is arranged in the injection pipeline 1 and is arranged at the same position as the iron ion concentration monitoring unit 41. The pH detection and iron ion concentration detection can be completed by one device together, or two different devices can be used for detection separately. The small molecule acid injection device 3 also includes a pH regulator storage tank 33. The small molecule acid injection device is also used to inject the pH regulator into the zero-valent iron injection device. The controller controls the small molecule acid injection device 3 to inject the pH regulator into the injection pipeline 1 according to the pH value monitored by the pH monitoring unit. The controller connected to the monitoring device, the small molecule acid injection device 3, and the zero-valent iron injection device 2 can control the small molecule acid injection device 3 to inject small molecule acid into the injection pipe 1, and / or control the small molecule acid injection device 3 to inject pH regulator into the injection pipe 1, and / or control the zero-valent iron injection device 2 to inject zero-valent iron into the injection pipe 1 according to the pollutant concentration, iron ion concentration, zero-valent iron mass concentration and pH value monitored by the monitoring device.

[0113] The injection pipeline of the present invention is divided into at least two sections along the axial direction, each section of the pipeline is respectively provided with the monitoring device, and the small molecule acid injection device and / or the zero-valent iron injection device is respectively connected to each section of the pipeline; preferably, two adjacent sections of the pipeline are connected.

[0114] like Figure 1 As shown, the injection pipeline 1 can be a one-stage injection pipeline; the injection pipeline 1 can also be a segmented injection pipeline, which is used to inject nano zero-valent iron into different aquifers, and the injection pipeline is divided into at least two segments; Figure 2As shown, the segmented injection pipeline includes three injection pipelines, namely an upper injection pipeline 11, a middle injection pipeline 12, and a lower injection pipeline 13; the upper injection pipeline 11, the middle injection pipeline 12, and the lower injection pipeline 13 are sequentially connected by a zero-valent iron injection conduit 21; the zero-valent iron injection conduit 21 connected to the upper injection pipeline 11, the zero-valent iron injection conduit 21 connected to the middle injection pipeline 12, and the zero-valent iron injection conduit 21 connected to the lower injection pipeline 13 are also respectively provided with conduit valves, and the controller can control the amount of nano zero-valent iron injected into the injection pipelines of different segments by controlling the conduit valves; the bottom layer of the upper injection pipeline 11, the bottom layer of the middle injection pipeline 12, and the bottom layer of the lower injection pipeline 13 are respectively provided with a gravity monitoring unit 42; the small molecule acid injection conduit can be a one-stage type or a segmented injection conduit with at least two sections; as shown Figure 2 As shown, the small molecule acid injection conduit includes three injection ports, namely, an upper injection port 311, a middle injection port 312, and a lower injection port 313; the small molecule acid activation solution and / or the pH adjuster are injected into the three injection pipes through the three injection ports of the small molecule acid injection conduit 31; at least one sampling port 432 is provided on the first monitoring pipe 43, as shown Figure 2 As shown, three sampling ports 432 are provided on the first monitoring pipeline, and pollutant detection is used to detect the changes in pollutants near the upper injection pipeline 11, the middle injection pipeline 12, and the lower injection pipeline 13 respectively.

[0115] like Figure 1 As shown, the walls of the upper injection pipe 11, the middle injection pipe 12, and the lower injection pipe 13 have holes, which help the contaminated groundwater to fully contact the zero-valent iron system and prevent the zero-valent iron from being lost with the water flow; preferably, the walls of the upper injection pipe 11, the middle injection pipe 12, and the lower injection pipe 13 are provided with screens. Figure 2 As shown, when zero-valent iron is injected into the injection pipe 1, the zero-valent iron is injected into the wrapping bag 14 in the injection pipe 1. The wrapping bag 14 can be made of gauze or other containers with fine holes, so that the zero-valent iron will not be carried away by the water flow, and the water can pass through without affecting the activation of small molecule acids and the degradation of pollutants by the zero-valent iron.

[0116] like Figure 2 As shown, the upper injection pipe 11, the middle injection pipe 12, and the lower injection pipe 13 may also be equipped with a stirring device 15. The number of stirring devices 15 can be set according to actual needs to promote rapid contact and fusion of the substances injected into the pipes. Optionally, the stirring speed of the stirring device 15 can be automatically controlled by a controller. It is understood that when a wrapping capsule 14 is provided in the injection pipe 1, the stirring device 15 can be provided inside the wrapping capsule 14.

[0117] like Figure 3As shown, A represents the underground vadose zone, B represents the underground aquifer, C represents the underground aquifer floor, a represents the groundwater flow direction, b represents the composite pollutant, and c represents the pollution plume. The groundwater remediation system of the present invention can be installed in multiple locations in the contaminated area to improve the removal of groundwater pollutants.

[0118] like Figure 3 As shown, the monitoring pipe in the groundwater remediation system of the present invention has a plurality of penetration holes on its wall. The monitoring pipe includes a first monitoring pipe 43 arranged along the axial direction of the injection pipe 1 and parallel to the injection pipe 1 on one side of the injection pipe 1; and a second monitoring pipe 44 spaced 3-5m apart from the injection pipe 1. Optionally, the second monitoring pipe 44 is arranged in the downstream direction of the injection pipe 1 to identify changes in pollutants in a larger area so as to comprehensively evaluate the remediation of underground sewage. The second monitoring pipe 44 can be a solid tubular device or in the form of a well.

[0119] The structural diagram of the groundwater remediation system of the present invention is as follows Figure 4 The iron ion concentration monitoring unit, zero-valent iron mass concentration monitoring unit, pollutant concentration monitoring unit, and pH monitoring unit in the monitoring device are connected to the controller, and the controller is connected to the small molecule acid activation solution injection system and the zero-valent iron injection device.

[0120] The method for repairing groundwater based on the above-mentioned groundwater repair system provided by the present invention includes obtaining iron ion concentration data, zero-valent iron mass concentration data, pollutant concentration data, and pH data according to the iron ion concentration monitoring unit, zero-valent iron mass concentration monitoring unit, pollutant concentration monitoring unit, and pH monitoring unit in the monitoring device, and then transmitting the data to a controller to control the injection amount of small molecule acid activation solution, the injection amount of zero-valent iron, and the injection amount of pH adjuster.

[0121] Specifically, the present invention provides a method for repairing groundwater based on the above-mentioned groundwater repair system, comprising the following steps:

[0122] Obtain the iron ion concentration and zero-valent iron mass concentration in the injection pipeline;

[0123] It also includes obtaining the concentration of pollutants and the pH value of the injection pipeline;

[0124] When the monitoring device detects that the mass concentration of zero-valent iron is lower than 3 g / L and the iron ion concentration is lower than 100 mg / L, the controller controls the zero-valent iron injection device to inject an amount of nano-zero-valent iron into the injection pipe so that the mass concentration of zero-valent iron is greater than 3 g / L;

[0125] When the monitoring device detects that the mass concentration of zero-valent iron is not less than 3 g / L, but the iron ion concentration is less than 100 mg / L, the controller controls the small molecule acid injection device to inject the small molecule acid activation solution into the injection pipe in such an amount that the iron ion concentration is higher than 100 mg / L.

[0126] When the monitoring device detects that the zero-valent iron mass concentration is not less than 3g / L and the iron ion concentration is not less than 100mg / L, but the concentration of the pollutant is higher than the target concentration, the controller controls the zero-valent iron injection device to inject an amount of nano-zero-valent iron into the injection pipe so that the concentration of the pollutant reaches below the target concentration;

[0127] Optionally, when the monitoring device detects that the pH in the water is lower than 5.0 or higher than 7.0, the controller controls the small molecule acid injection device to inject an injection amount of pH regulator into the injection pipe to adjust the pH to 5.0-7.0.

[0128] The present invention also provides a method for repairing groundwater based on the above-mentioned groundwater repair system, comprising: obtaining the iron ion concentration and the zero-valent iron mass concentration in each section of the injection pipeline;

[0129] It also includes obtaining the concentration of pollutants and the pH value of each section of the injection pipeline;

[0130] When the monitoring device detects that the zero-valent iron mass concentration in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe is lower than 3 g / L and the iron ion concentration is lower than 100 mg / L, the controller controls the zero-valent iron injection device to inject an amount of nano-zero-valent iron into the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe so that the zero-valent iron mass concentration is greater than 3 g / L;

[0131] When the monitoring device detects that the mass concentration of zero-valent iron in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe is not less than 3 g / L, but the iron ion concentration is less than 100 mg / L, the controller controls the small molecule acid injection device to inject the small molecule acid activation solution into the corresponding upper injection pipe and / or the middle injection pipe and / or the lower injection pipe so that the iron ion concentration is higher than 100 mg / L;

[0132] When the monitoring device detects that the zero-valent iron mass concentration in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe is not less than 3 g / L and the iron ion concentration is not less than 100 mg / L, but the concentration of the pollutant is higher than the target concentration, the controller controls the zero-valent iron injection device to inject the nano-zero-valent iron into the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe in an amount such that the pollutant concentration reaches below the target concentration;

[0133] and / or, when the monitoring device detects that the pH of the water in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe is lower than 5.0 or higher than 7.0, the controller controls the small molecule acid injection device to inject an injection amount of the pH adjuster into the corresponding upper injection pipe and / or the middle injection pipe and / or the lower injection pipe to adjust the pH to 5.0-7.0;

[0134] And / or, when the monitoring device detects that the mass of the nano-zero-valent iron in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe is less than 1 / 2 of the initial mass, the controller controls the zero-valent iron injection device to inject an amount of nano-zero-valent iron into the injection pipe and / or the middle injection pipe and / or the lower injection pipe so that the nano-zero-valent iron in the upper injection pipe and / or the middle injection pipe and / or the lower injection pipe reaches the initial mass respectively.

[0135] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0136] The examples and comparative examples of the present invention used simulated bottles to conduct simulation experiments on contaminated groundwater treatment. The simulated bottles were prepared by adding 100 mL of simulated contaminated groundwater solution (containing 20 mg / L trichloroethylene) to a 500 mL brown bottle with an initial pH of 7. Then, 0.1 g of passivated zero-valent iron was added to simulate the passivation of zero-valent iron during contact with groundwater.

[0137] Example 1

[0138] This embodiment provides a method for activating passivated zero-valent iron, comprising the following steps:

[0139] Add citric acid solution to the simulation bottle so that the ratio of citric acid to passivated zero-valent iron in the citric acid solution is 5:1, and the unit is mmol:g. Then use 1 mol / L HCl solution or NaOH solution to adjust the pH to 5.5, place it on a light-proof shaker at 180 rpm for activation reaction, and regularly sample and test the residual rate of trichloroethylene (that is, the post-reaction concentration of trichloroethylene / the initial concentration of trichloroethylene, recorded as C t / C0).

[0140] Example 2

[0141] This embodiment provides a method for activating passivated zero-valent iron, comprising the following steps:

[0142] Add citric acid solution to the simulation bottle so that the addition ratio of citric acid to passivated zero-valent iron in the citric acid solution is 5:1, the unit is mmol:g, and then use 1 mol / L HCl solution or NaOH solution to adjust the pH to 6.3. Place it on a light-proof shaker at 180 rpm for activation reaction, and take samples regularly to test the residual rate of trichloroethylene.

[0143] Example 3

[0144] This embodiment provides a method for activating passivated zero-valent iron, comprising the following steps:

[0145] Add oxalic acid solution to the simulation bottle so that the addition ratio of oxalic acid to passivated zero-valent iron in the oxalic acid solution is 5:1, the unit is mmol:g, and then use 1 mol / L HCl solution or NaOH solution to adjust the pH to 5.5. Place it on a light-proof shaker at 180 rpm for activation reaction, and take samples regularly to test the residual rate of trichloroethylene.

[0146] Example 4

[0147] This embodiment provides a method for activating passivated zero-valent iron, comprising the following steps:

[0148] Add oxalic acid solution to the simulation bottle so that the addition ratio of oxalic acid to passivated zero-valent iron in the oxalic acid solution is 5:1, and the unit is mmol:g. Then use 1 mol / L HCl solution or NaOH solution to adjust the pH to 6.3, place it on a light-proof shaker at 180 rpm for activation reaction, and take samples regularly to test the residual rate of trichloroethylene.

[0149] Comparative Example 1

[0150] This comparative example provides a method for activating passivated zero-valent iron, comprising the following steps:

[0151] Ascorbic acid solution was added to the simulation bottle so that the addition ratio of ascorbic acid to passivated zero-valent iron in the ascorbic acid solution was 5:1 (mmol:g). The pH was then adjusted to 6.3 using 1 mol / L HCl solution or NaOH solution. The solution was placed on a light-proof shaker at 180 rpm for activation reaction, and samples were taken regularly to test the residual rate of trichloroethylene.

[0152] Comparative Example 2

[0153] This comparative example provides a method for activating passivated zero-valent iron, comprising the following steps:

[0154] Add glutamate solution to the simulation bottle so that the ratio of glutamate to passivated zero-valent iron in the glutamate solution is 5:1, in units of mmol:g. Then use 1 mol / L HCl solution or NaOH solution to adjust the pH to 6.3, place it on a light-proof shaker at 180 rpm for activation reaction, and take samples regularly to test the residual rate of trichloroethylene.

[0155] Comparative Example 3

[0156] This comparative example provides a method for activating passivated zero-valent iron, comprising the following steps:

[0157] Add malic acid solution to the simulation bottle so that the addition ratio of malic acid to passivated zero-valent iron in the malic acid solution is 5:1, and the unit is mmol:g. Then, use 1 mol / L HCl solution or NaOH solution to adjust the pH to 6.3, place it on a light-proof shaker at 180 rpm for activation reaction, and take samples regularly to test the residual rate of trichloroethylene.

[0158] Comparative Example 4

[0159] This comparative example provides a method for activating passivated zero-valent iron, comprising the following steps:

[0160] Add tartaric acid solution to the simulation bottle so that the addition ratio of tartaric acid to passivated zero-valent iron in the tartaric acid solution is 5:1, the unit is mmol:g, and then use 1 mol / L HCl solution or NaOH solution to adjust the pH to 6.3. Place it on a light-proof shaker at 180 rpm for activation reaction, and take samples regularly to test the residual rate of trichloroethylene.

[0161] Comparative Example 5

[0162] This comparative example provides a method for activating passivated zero-valent iron, comprising the following steps:

[0163] Add lactic acid solution to the simulation bottle so that the addition ratio of lactic acid to passivated zero-valent iron in the lactic acid solution is 5:1, in units of mmol:g. Then use 1 mol / L HCl solution or NaOH solution to adjust the pH to 6.3, place it on a light-proof shaker at 180 rpm for activation reaction, and take samples regularly to test the residual rate of trichloroethylene.

[0164] Comparative Example 6

[0165] This comparative example provides a method for activating passivated zero-valent iron, comprising the following steps:

[0166] Add acetic acid solution to the simulation bottle so that the addition ratio of acetic acid to passivated zero-valent iron in the acetic acid solution is 5:1, and the unit is mmol:g. Then use 1 mol / L HCl solution or NaOH solution to adjust the pH to 6.3, place it on a light-proof shaker at 180 rpm for activation reaction, and take samples regularly to test the residual rate of trichloroethylene.

[0167] Comparative Example 7

[0168] This comparative example provides a method for activating passivated zero-valent iron, comprising the following steps:

[0169] Add citric acid solution to the simulation bottle so that the addition ratio of citric acid to passivated zero-valent iron in the citric acid solution is 5:1, and the unit is mmol:g. Then use 1 mol / L HCl solution or NaOH solution to adjust the pH to 2.5, place it on a light-proof shaker at 180 rpm for activation reaction, and take samples regularly to test the residual rate of trichloroethylene.

[0170] Comparative Example 8

[0171] This comparative example provides a method for activating passivated zero-valent iron, comprising the following steps:

[0172] Add citric acid solution to the simulation bottle so that the addition ratio of citric acid to passivated zero-valent iron in the citric acid solution is 5:1, and the unit is mmol:g. Then use 1 mol / L HCl solution or NaOH solution to adjust the pH to 3.8, place it on a light-proof shaker at 180 rpm for activation reaction, and take samples regularly to test the residual rate of trichloroethylene.

[0173] Comparative Example 9

[0174] This comparative example provides a method for activating passivated zero-valent iron, comprising the following steps:

[0175] Add citric acid solution to the simulation bottle so that the addition ratio of citric acid to passivated zero-valent iron in the citric acid solution is 5:1, and the unit is mmol:g. Then, use 1 mol / L HCl solution or NaOH solution to adjust the pH to 8.0, place it on a light-proof shaker at 180 rpm for activation reaction, and take samples regularly to test the residual rate of trichloroethylene.

[0176] Comparative Example 10

[0177] This comparative example provides a method for activating passivated zero-valent iron, comprising the following steps:

[0178] Add oxalic acid solution to the simulation bottle so that the addition ratio of oxalic acid to passivated zero-valent iron in the oxalic acid solution is 5:1, and the unit is mmol:g. Then use 1 mol / L HCl solution or NaOH solution to adjust the pH to 2.5, place it on a light-proof shaker at 180 rpm for activation reaction, and take samples regularly to test the residual rate of trichloroethylene.

[0179] Comparative Example 11

[0180] This comparative example provides a method for activating passivated zero-valent iron, comprising the following steps:

[0181] Add oxalic acid solution to the simulation bottle so that the addition ratio of oxalic acid to passivated zero-valent iron in the oxalic acid solution is 5:1, and the unit is mmol:g. Then use 1 mol / L HCl solution or NaOH solution to adjust the pH to 3.8, place it on a light-proof shaker at 180 rpm for activation reaction, and take samples regularly to test the residual rate of trichloroethylene.

[0182] Comparative Example 12

[0183] This comparative example provides a method for activating passivated zero-valent iron, comprising the following steps:

[0184] Add oxalic acid solution to the simulation bottle so that the addition ratio of oxalic acid to passivated zero-valent iron in the oxalic acid solution is 5:1, and the unit is mmol:g. Then, use 1 mol / L HCl solution or NaOH solution to adjust the pH to 8.0, place it on a light-proof shaker at 180 rpm for activation reaction, and take samples regularly to test the residual rate of trichloroethylene.

[0185] Test Example 1

[0186] The residual rates of trichloroethylene during the activation process of Examples 1-6 and Comparative Examples 1-12 were measured respectively. The residual rate curves obtained from the tests of Examples 2, 4 and Comparative Examples 1-6 are shown in FIG. Figure 5 As shown; the residual rate curves obtained from the tests of Examples 1-2 and Comparative Examples 7-9 are shown Figure 6 As shown; the residual rate curves obtained from the tests of Examples 3-4 and Comparative Examples 10-12 are shown Figure 7 The residual rates of trichloroethylene after activation for 24 hours in Examples 1-4 and Comparative Examples 1-12 are shown in Table 1.

[0187] Table 1

[0188]

[0189] The activation of passivated zero-valent iron can improve the degradation effect of trichloroethylene, so the activation effect of passivated zero-valent iron can be reflected by the residual rate of trichloroethylene. Figure 5As can be seen, after activation with various small-molecule acids, the degradation curves of the passivated zero-valent iron, which showed little degradation, all exhibited first-order kinetics. However, activation with citric acid and oxalic acid was most effective, degrading the majority of trichloroethylene, with the reaction nearly complete within 24 hours. Therefore, choosing citric acid or oxalic acid as activation solutions for passivated zero-valent iron significantly outperformed other small-molecule acids.

[0190] Depend on Figure 6 、 7 It can be seen that when the reaction pH is between 5.0-7.0, both small molecule acids can completely degrade trichloroethylene, while under acidic pH conditions, it cannot be completely degraded due to the corrosion of iron. In other words, adjusting the pH to between 5.0-7.0 (neutral) during the reaction can effectively promote the activation and passivation of zero-valent iron by natural small molecule organic acids, promoting the degradation of trichloroethylene. Moreover, the reaction pH = 5.0-7.0 just matches the pH of normal groundwater in most areas. Therefore, after adding the small molecule acid activation solution, the system pH is controlled between 5.0-7.0, which can completely degrade the pollutant without causing secondary pollution.

[0191] Test Example 2

[0192] To demonstrate the feasibility of the passivated zero-valent iron activation method for treating actual contaminated groundwater, a test experiment was conducted using an equal volume of contaminated groundwater sampled from a complex contaminated site in the Midong Industrial Park in Urumqi, replacing the simulated contaminated groundwater solution in a simulation bottle as test bottle 1. The groundwater at this site was severely contaminated, with a trichloroethylene concentration of approximately 20 mg / L, along with other organic pollutants and heavy metals. Due to the numerous contaminants, the passivated zero-valent iron content needed to be increased. 0.5g of passivated zero-valent iron was used to replace the 0.1g of passivated zero-valent iron in test bottle 1, creating test bottle 2.

[0193] After preparing the test bottle 1, add citric acid solution and oxalic acid solution to the test bottle 1 respectively, so that the ratio of citric acid in the citric acid solution (or oxalic acid in the oxalic acid solution) to the passivated zero-valent iron is 5:1, and the unit is mmol:g. Then use 1mol / L HCl solution or NaOH solution to adjust the pH to acidic (pH=3.0), neutral (pH=7.0) and alkaline (pH=9.0), respectively. Place it on a light-proof shaker at 180rpm for activation reaction, and test the residual rate of trichloroethylene after 24 hours. Similarly, the test bottle 1 with oxalic acid solution added is also adjusted to acidic (pH=3.0), neutral (pH=7.0) and alkaline (pH=9.0), and test the residual rate of trichloroethylene after 24 hours. The residual rate results are as follows: Figure 8 shown.

[0194] After preparing test bottle 2, add citric acid solution and oxalic acid solution to test bottle 2 respectively, so that the addition ratio of citric acid in the citric acid solution (or oxalic acid in the oxalic acid solution) to passivated zero-valent iron is 5:1, and the unit is mmol:g. Then use 1 mol / L HCl solution or NaOH solution to adjust the pH to acidic (pH = 3.0), neutral (pH = 7.0) and alkaline (pH = 9.0), respectively, and place it on a light-proof shaker at 180 rpm for activation reaction. Test the residual rate of trichloroethylene after 24 hours; similarly, the test bottle 2 with oxalic acid solution added is also adjusted to acidic (pH = 3.0), neutral (pH = 7.0) and alkaline (pH = 9.0), and test the residual rate of trichloroethylene after 24 hours. The residual rate results are as follows: Figure 8 shown.

[0195] Depend on Figure 8 It was found that trichloroethylene was almost completely degraded under both acidic and neutral conditions, while alkaline conditions showed less degradation. This indicates that this method can activate passivated zero-valent iron under both acidic and neutral conditions, and effectively degrades all other pollutants besides trichloroethylene. Therefore, this method is feasible for application to actual contaminated groundwater, and can still effectively degrade pollutants under neutral conditions without causing secondary contamination. Since this method involved sampling contaminated groundwater at an actual contaminated site, it has certain reference value.

[0196] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for activating passivated zero-valent iron, characterized in that: The following steps are involved: Mixing the small molecule acid activation solution with the passivated zero-valent iron and reacting them at a pH of 5.0-7.0 to obtain activated zero-valent iron; The small molecule acid in the small molecule acid activation solution is selected from citric acid and / or oxalic acid.

2. The activation method of passivated zero-valent iron according to claim 1, characterized in that: The ratio of the small molecule acid to the passivated zero-valent iron in the small molecule acid activation solution is (1-10):1, in units of mmol:g; And / or, the solvent in the small molecule acid activation solution is selected from water.

3. A groundwater remediation system based on the activation method of passivated zero-valent iron according to claim 1 or 2, characterized in that: The groundwater remediation system comprises: An injection pipe with a plurality of permeable holes provided on its wall, which is extended to a target groundwater layer and injects nano-zero-valent iron into the groundwater layer; A small molecule acid injection device connected to the injection pipeline; A monitoring device, comprising an iron ion concentration monitoring unit and a gravity monitoring unit provided in the injection pipe; a controller connected to the monitoring device and the small molecule acid injection device, and controlling the small molecule acid injection device to inject the small molecule acid activation solution into the injection pipe according to the iron ion concentration monitored by the iron ion concentration monitoring unit and the zero-valent iron mass concentration monitored by the gravity monitoring unit; Preferably, the groundwater remediation system also includes a zero-valent iron injection device connected to the injection pipe, and the controller is connected to the zero-valent iron injection device to control the zero-valent iron injection device to inject zero-valent iron into the injection pipe according to the monitored iron ion concentration and zero-valent iron mass concentration.

4. The groundwater remediation system according to claim 3, characterized in that: The monitoring device further comprises a pH monitoring unit provided on the injection pipe; The controller controls the small molecule acid injection device to inject the pH regulator into the injection pipeline according to the pH value monitored by the pH monitoring unit.

5. The groundwater remediation system according to claim 4, characterized in that: The monitoring device comprises: A monitoring pipe having a plurality of permeable holes formed in its wall, the monitoring pipe being arranged parallel to the injection pipe along the axial direction of the injection pipe on one side of the injection pipe; and / or the monitoring pipe being spaced 3-5 m apart from the injection pipe; a pollutant concentration monitoring unit, provided on the monitoring pipeline, for monitoring pollutants in the groundwater layer; The control unit is connected to the pollutant concentration monitoring unit, and controls the zero-valent iron injection device to inject zero-valent iron into the injection pipeline according to the pollutants in the groundwater layer monitored by the pollutant concentration monitoring unit; Preferably, a sampling device is provided on one side of the monitoring pipe and / or injection pipe, and the sampling tube of the sampling device extends from one end to the other end of the monitoring pipe and / or injection pipe, and a sampling port is provided on the pipe wall of the sampling tube for sampling the groundwater layer.

6. The groundwater remediation system according to any one of claims 3 to 5, characterized in that: The injection pipeline is divided into at least two sections along the axial direction, each section of the injection pipeline is provided with the monitoring device, and the small molecule acid injection device and / or the zero-valent iron injection device are respectively connected to each section of the pipeline; Preferably, two adjacent sections of pipeline are connected.

7. The groundwater remediation system according to any one of claims 3 to 5, characterized in that: A capsule for accommodating nano-zero-valent iron is provided in the injection pipe, and a plurality of permeation holes are provided on the capsule wall. The zero-valent iron injection device is connected to the capsule and is used to inject zero-valent iron into the capsule. Preferably, a stirring device is provided in the wrapping bag.

8. A method for repairing groundwater using the groundwater repair system according to any one of claims 3 to 7, characterized in that: Obtain the iron ion concentration and zero-valent iron mass concentration in the injection pipeline; When the zero-valent iron mass concentration is greater than or equal to the target zero-valent iron mass concentration and the iron ion concentration is less than the target iron ion concentration, the small molecule acid activation solution is controlled to be injected into the injection pipe.

9. The method for repairing groundwater by the groundwater repair system according to claim 8, characterized in that: It also includes obtaining the pollutant concentration and pH in the injection pipeline; When the zero-valent iron mass concentration is less than the zero-valent iron mass target concentration and the iron ion concentration is less than the iron ion target concentration, controlling the injection of zero-valent iron into the injection pipe; When the zero-valent iron mass concentration is greater than or equal to the zero-valent iron mass target concentration, the iron ion concentration is greater than or equal to the iron ion target concentration, but the concentration of the pollutant is greater than or equal to the target concentration, controlling the zero-valent iron injection device to inject zero-valent iron into the injection pipe; When the pH is lower than 5.0 or higher than 7.0, the small molecule acid injection device is controlled to inject a pH regulator into the injection pipe to adjust the pH to 5.0-7.0; Preferably, the injection pipeline is divided into at least two sections along the axial direction, and small molecule acid and / or zero-valent iron and / or pH regulator are injected into different pipelines respectively according to the iron ion concentration, zero-valent iron mass, pH and pollutant concentration at different injection pipelines.

10. Use of the activation method for passivated zero-valent iron according to claim 1 or 2, the groundwater remediation system according to any one of claims 3 to 7, or the method for remediating groundwater according to claim 8 or 9 in groundwater remediation.

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