Efficient microwave-assisted soil remediation device and method based on online feedback

Abstract

This invention discloses a highly efficient microwave-assisted oxidation soil remediation device and method based on online feedback. The device utilizes an online monitoring and control system to detect the properties of contaminated soil and adjusts the reaction conditions according to these properties, controlling the addition of oxidizing agents and microwave reaction parameters. By employing microwave activation of persulfate, it achieves the remediation of organically contaminated soil with minimal oxidizing agent dosage, lowest energy consumption, and fastest speed.

Description

Technical Field

[0001] This invention belongs to the field of soil remediation technology, and relates to a soil remediation device and method based on online feedback and efficient microwave synergistic oxidation. Background Technology

[0002] In recent years, with the adjustment of urban industrial structure and the advancement of industrialization, the soil environment has been plagued by organic pollution problems, especially the large number of relocated sites that urgently need treatment. These relocated sites include pharmaceutical factories, coking plants, and oil refineries, which leave behind many recalcitrant organic pollutants, such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and organic pesticides. These pollutants are persistent, difficult to treat, and highly toxic, seriously affecting human health and production activities. Therefore, the remediation of recalcitrant organic polluted sites is urgent, and a simple and efficient soil remediation technology needs to be found.

[0003] Persulfate advanced oxidation is a commonly used technique for treating polycyclic aromatic hydrocarbons (PAHs) in soil. Compared to other oxidants, persulfate has a wider range of application conditions, no pH limitations, and low activation requirements, making it increasingly important in research. The key to the effectiveness of persulfate in soil remediation lies in an effective activation mechanism, which is also a current research hotspot. Common activation methods include thermal activation, transition metal activation, and alkali activation. Thermal activation is simple to operate but has low efficiency and energy utilization. Transition metal activation and alkali activation can alter the physicochemical properties of the soil. Developing efficient and simple activation methods is currently a research focus. Microwave activation of persulfate has attracted widespread attention due to its broad selectivity, fast reaction speed, and low energy consumption. As an electromagnetic wave, microwaves selectively and irreversibly absorb energy from polar molecules when penetrating a medium, causing a rapid increase in temperature and vibration of the dipole bonds in polar molecules. Microwave activation of persulfate can maintain the system temperature and induce persulfate molecule vibration, breaking the O-O bonds and generating ·OH and ·OH radicals with oxidizing properties.

[0004] Currently, microwave-activated persulfate remediation of organically contaminated soil is mostly still in the laboratory stage and is rarely applied to the on-site remediation of actual contaminated soil. Summary of the Invention

[0005] The purpose of this invention is to provide a highly efficient microwave-assisted oxidation soil remediation device and method based on online feedback. This device uses microwave activation of persulfate, utilizes online intelligent monitoring to add oxidizing agents, and controls soil moisture content, achieving the remediation of organically contaminated soil with minimal oxidizing agent dosage, lowest energy consumption, and fastest speed.

[0006] The technical solution for achieving the objective of this invention is as follows:

[0007] A high-efficiency microwave-assisted oxidation soil remediation device based on online feedback includes a feeding conveyor belt 3, a material stirring device 5, a stirring drive motor 7, an oxidant dosing device 4, an online monitoring and control device 1, a reaction conveyor belt 12, and a microwave reaction cavity 10. Above the feeding conveyor belt 3 is a detection probe 2 for online monitoring of characteristic pollutant types, pollutant concentrations, soil pH, and moisture content in the soil, and the detection probe 2 is connected to the online monitoring and control device 1. The end of the feeding conveyor belt 3 is connected to the material stirring device 5, and a stirring rod 14 is located at the center of the cavity of the material stirring device 5, and the stirring rod 14 is connected to a stirring... The blades 6 are driven by the stirring drive motor 7; the material stirring device 5 is a cavity with a movable panel on the top for opening or closing, and a discharge port 8 with a movable panel on the bottom for opening or closing; the oxidizing agent dosing device 4 is located above the material stirring device 5; the reaction conveyor belt 12 is located below the material stirring device 5; the online monitoring and control device 1 is connected to the stirring drive motor 7, the oxidizing agent dosing device 4, the reaction conveyor belt 12 and the microwave reaction cavity 10; the microwave reaction cavity 10 is equipped with a microwave source 11 and a temperature detection device 13; there is an adjustable soil thickness baffle 9 at the connection between the microwave reaction cavity 10 and the reaction conveyor belt 12.

[0008] Furthermore, the stirring rod is connected to two stirring blades 6 at different angles.

[0009] Furthermore, the microwave reaction cavity 10 is equipped with three microwave sources 11.

[0010] Furthermore, the inner wall of the microwave reaction cavity 10 is a resonant cavity with a frequency of 2.45Hz, and the middle is a heat insulation layer.

[0011] A highly efficient microwave-assisted oxidation soil remediation method based on online feedback is described below:

[0012] Using the aforementioned soil remediation device, the crushed and screened soil enters the feeding conveyor belt 3. The soil is monitored by the detection probe 2, which tracks the type and concentration of characteristic pollutants, soil pH, and moisture content. The soil then enters the material mixing device 5. The online monitoring and control device 1 sets the concentration and dosage of the oxidant based on the monitored soil data and feeds this information back to the oxidant dosing device 4. The oxidant is then added to the material mixing device 5. The stirring drive motor 7 drives the stirring rod 14 to rotate the stirring blades 6, ensuring thorough mixing of the soil and oxidant. The mixture is then sent from the discharge port 8 below the material mixing device 5 to the reaction conveyor belt 12. The conveyor belt speed is controlled by the online monitoring and control device 1, which sets the dwell time. After passing through the baffle 9, the soil reaches the set thickness and then enters the microwave reaction chamber 10. The power of the microwave source 11 is controlled by the online monitoring and control device 1. The remediated soil, after microwave irradiation, is discharged from the end of the microwave reaction chamber 10, achieving efficient remediation of contaminated soil.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] (1) The soil remediation device based on online feedback of the present invention can determine the type of characteristic pollutants, pollutant concentration, soil pH and moisture content in the soil by monitoring soil properties, thereby setting the conditions of the oxidant added during the reaction. The experimental conditions, including moisture content, reaction time, reaction temperature, microwave power, etc., can be automatically set by the control device. The device can automatically adjust the operating conditions of the device through online monitoring and control, thereby reducing the experimental cost.

[0015] (2) This invention utilizes microwave heating and the vibration of molecular bonds to activate persulfate, generating ROS with oxidizing properties, which can quickly remove pollutants from the soil.

[0016] (3) The present invention utilizes a material mixing device to achieve full mixing of contaminated soil and oxidizing agent, ensuring that pollutants and ROS are in full contact. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a highly efficient microwave-assisted oxidation soil remediation device based on online feedback;

[0018] Figure 2 These are images showing the removal effects of different pollutants;

[0019] Figure 3 The figures show the changes in pyrene removal rate under different temperatures and persulfate concentrations in a laboratory microwave oven. (a) shows the effect of microwave activation of persulfate to remove pyrene at different temperatures, (b) shows the effect of microwave activation of persulfate to remove pyrene at different persulfate concentrations, (c) shows the pseudo-first-order kinetic coefficients at different temperatures, and (d) shows the pseudo-first-order kinetic coefficients at different persulfate concentrations.

[0020] In the diagram: 1. Online monitoring and control device; 2. Detection probe; 3. Feeding conveyor belt; 4. Oxidizing agent dosing device; 5. Material stirring device; 6. Stirring blades; 7. Stirring drive motor; 8. Discharge port; 9. Baffle; 10. Microwave reaction chamber; 11. Microwave source; 12. Reaction conveyor belt; 13. Temperature detection device; 14. Stirring rod. Detailed Implementation

[0021] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0022] like Figure 1As shown, the high-efficiency microwave synergistic oxidation soil remediation device based on online feedback includes a feeding conveyor belt 3, a material stirring device 5, a stirring drive motor 7, an oxidant dosing device 4, an online monitoring and control device 1, a reaction conveyor belt 12, and a microwave reaction cavity 10. Above the feeding conveyor belt 3 is a detection probe 2 for online monitoring of characteristic pollutant types, pollutant concentrations, soil pH, and moisture content in the soil, and the detection probe 2 is connected to the online monitoring and control device 1. The end of the feeding conveyor belt 3 is connected to the material stirring device 5, and a stirring rod 14 is located at the center of the cavity of the material stirring device 5, and the stirring rod 14 is connected to... The stirring blades 6 are driven by the stirring drive motor 7; the material stirring device 5 is a cavity with a movable panel on the top for opening or closing, and a discharge port 8 with a movable panel on the bottom for opening or closing; the oxidizing agent dosing device 4 is located above the material stirring device 5; the reaction conveyor belt 12 is located below the material stirring device 5; the online monitoring and control device 1 is connected to the stirring drive motor 7, the oxidizing agent dosing device 4, the reaction conveyor belt 12 and the microwave reaction cavity 10; the microwave reaction cavity 10 is equipped with a microwave source 11 and a temperature detection device 13; there is an adjustable soil thickness baffle 9 at the connection between the microwave reaction cavity 10 and the reaction conveyor belt 12.

[0023] A highly efficient microwave-assisted oxidation soil remediation method based on online feedback is described below:

[0024] Using the aforementioned soil remediation device, the crushed and screened soil enters the feeding conveyor belt 3. The soil is monitored by the detection probe 2, which tracks the type and concentration of characteristic pollutants, soil pH, and moisture content. The soil then enters the material mixing device 5. The online monitoring and control device 1 sets the concentration and dosage of the oxidant based on the monitored soil data and feeds this information back to the oxidant dosing device 4. The oxidant is then added to the material mixing device 5. The stirring drive motor 7 drives the stirring rod 14 to rotate the stirring blades 6, ensuring thorough mixing of the soil and oxidant. The mixture is then sent from the discharge port 8 below the material mixing device 5 to the reaction conveyor belt 12. The conveyor belt speed is controlled by the online monitoring and control device 1, which sets the dwell time. After passing through the baffle 9, the soil reaches the set thickness and then enters the microwave reaction chamber 10. The power of the microwave source 11 is controlled by the online monitoring and control device 1. The remediated soil, after microwave irradiation, is discharged from the end of the microwave reaction chamber 10, achieving efficient remediation of contaminated soil.

[0025] The online monitoring and control device of this invention is embedded with an experimental database for laboratory microwave-assisted oxidation soil remediation. The detection probe 2 detects characteristic pollutants, pollutant concentrations, soil moisture content, soil pH and other properties in the soil, and feeds them back to the online monitoring and control device. It automatically obtains parameters such as the dosage of oxidant, experimental retention time, soil moisture content, microwave power and soil layer thickness required to achieve the target parameters, and then adjusts the operating parameters of the stirring drive motor, oxidant dosing device, reaction conveyor belt and microwave reaction cavity.

[0026] In the above method, the concentration of the oxidizing agent is configured by the oxidizing agent dosing device, and the oxidizing agent can be a persulfate such as sodium persulfate.

[0027] In the above method, the experimental retention time is determined by the transfer speed of the reaction conveyor belt.

[0028] In the above method, the soil moisture content is controlled by an oxidant dosing device. The dosage of the oxidant is adjusted according to the monitored initial soil moisture content to achieve the purpose of controlling the moisture content.

[0029] In the above method, the microwave power and soil layer thickness are controlled by the microwave reaction cavity. There is an adjustable baffle at the contact point between the microwave reaction cavity and the reaction conveyor belt, and the soil layer thickness is controlled by adjusting the angle.

[0030] In the above method, the end of the feeding conveyor belt is connected to the material mixing device, which can transport the contaminated soil to the material mixing device.

[0031] In the above method, the reaction conveyor belt is located below the material mixing device to receive soil that is fully mixed with the oxidizing agent.

[0032] In the above method, the microwave reaction cavity contains three microwave sources with a frequency of 2.45 Hz, the inner wall of the cavity is a resonant cavity, and the middle is a heat insulation layer.

[0033] The online monitoring and control device of this invention incorporates an experimental database for laboratory microwave-assisted oxidation soil remediation. The laboratory experiments utilize a microwave reactor. By altering characteristics such as the type and concentration of pollutants in the soil, soil moisture content, and soil pH, and adjusting experimental conditions such as oxidant concentration, retention time, and reaction temperature, the optimal removal conditions are explored, providing data support for the online monitoring and control device 1.

[0034] The specific steps of the laboratory experiment are as follows:

[0035] (1) Prepare air-dried soil, then prepare contaminated soil contaminated with characteristic pollutants, and extract and detect the concentration of characteristic pollutants;

[0036] (2) Place a quantitative amount of soil contaminated with characteristic pollutants in a ceramic evaporating dish, add an oxidizing agent solution to the contaminated soil, maintain a quantitative moisture content, stir evenly, and then transfer it to a microwave reactor for microwave heating reaction.

[0037] (3) After the reaction is completed, the characteristic pollutants in the soil are extracted with organic solvents and the remaining concentration is detected.

[0038] Before the reaction begins, contaminated soils with different pollutants are prepared, and the pollutant removal effect is tested under the same conditions to collect characteristic pollutant removal data.

[0039] Figure 2 This study investigated the removal efficiency of naphthalene and pyrene under microwave conditions of 400W, reaction temperature of 80℃, persulfate concentration of 1M, and moisture content of 20%. Under the same pollutant mass concentration, naphthalene with two benzene rings showed better removal efficiency than pyrene with four benzene rings. The characteristics of pollutants in the soil affect all operating conditions; for example, naphthalene can achieve the set treatment effect with a shorter residence time.

[0040] Before the reaction begins, the microwave reaction temperature is set, and data on the effect of reaction temperature on pollutant removal efficiency is collected.

[0041] Figure 3 Figure a shows the degradation effect of pyrene in soil by microwave synergistic oxidation at different temperatures. The results indicate that increasing the temperature improves the degradation effect of pyrene, with the best degradation effect observed at 80℃. Therefore, the pollutant removal effect can also be controlled by adjusting the microwave power.

[0042] Before the reaction begins, the persulfate concentration is adjusted, and data on the effect of oxidant content on pollutant removal efficiency are collected.

[0043] Figure 3 b shows the effect of different persulfate concentrations on the removal rate of pyrene in soil. Higher concentrations result in faster reaction rates and better removal. Different persulfate concentrations (0.5M, 1M, and 2M) all achieved removal rates exceeding 80% after 30 minutes. Increasing the persulfate concentration further increased the reaction rate; at a 2M persulfate concentration, the removal rate reached 77.3% after 5 minutes, already achieving 90% of the final removal rate, while lower concentrations required 10 minutes. Therefore, controlling the persulfate concentration not only affects the removal efficiency but also the retention time.

[0044] This invention provides an online monitoring method for soil remediation. By monitoring the properties of contaminated soil online and automatically adjusting operating conditions, it achieves highly efficient and automated remediation of recalcitrant organic contaminated soil.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A soil remediation device based on online feedback and highly efficient microwave synergistic oxidation, characterized in that, The system includes a feeding conveyor belt 3, a material mixing device 5, a mixing drive motor 7, an oxidant dosing device 4, an online monitoring and control device 1, a reaction conveyor belt 12, and a microwave reaction cavity 10. Above the feeding conveyor belt 3 is a detection probe 2 for online monitoring of characteristic pollutant types, pollutant concentrations, soil pH, and moisture content in the soil, and the detection probe 2 is connected to the online monitoring and control device 1. The end of the feeding conveyor belt 3 is connected to the material mixing device 5, and a mixing rod 14 is located at the center of the cavity of the material mixing device 5, with the mixing rod 14 connected to mixing blades 6, and driven by a mixing drive motor.

7. Drive; Material mixing device 5 is a cavity with a movable panel on the top for opening or closing, and a discharge port 8 with a movable panel on the bottom for opening or closing; Oxidizing agent dosing device 4 is located above material mixing device 5; Reaction conveyor belt 12 is located below material mixing device 5; Online monitoring and control device 1 connects mixing drive motor 7, oxidizing agent dosing device 4, reaction conveyor belt 12 and microwave reaction cavity 10; Microwave source 11 is provided in microwave reaction cavity 10, and temperature detection device 13 is provided; There is a baffle 9 at the connection between microwave reaction cavity 10 and reaction conveyor belt 12 that can adjust soil thickness.

2. The soil remediation device according to claim 1, characterized in that, The stirring rod connects two stirring blades at different angles.

3. The soil remediation device according to claim 1, characterized in that, The microwave reaction cavity 10 is equipped with three microwave sources 11.

4. The soil remediation device according to claim 1, characterized in that, The inner wall of the microwave reaction cavity 10 is a resonant cavity with a frequency of 2.45Hz, and the middle is a heat insulation layer.

5. A highly efficient microwave-assisted oxidation soil remediation method based on online feedback, as detailed below: Using the soil remediation device described in any one of claims 1 to 4, the soil, after being crushed and screened, enters the feeding conveyor belt 3. The soil is monitored by the detection probe 2 for characteristic pollutant types, pollutant concentrations, soil pH, and moisture content. It then enters the material mixing device 5. The online monitoring and control device 1 sets the concentration and dosage of the oxidant based on the monitored soil data and feeds this information back to the oxidant dosing device 4. The oxidant is then added to the material mixing device 5. The stirring drive motor 7 drives the stirring rod 14 to control the rotation of the stirring blades 6, ensuring thorough mixing of the soil and oxidant. The mixture is then sent from the discharge port 8 below the material mixing device 5 to the reaction conveyor belt 12. The conveyor belt speed is controlled by the online monitoring and control device 1, which sets the residence time. After passing through the baffle 9, the soil reaches the set thickness and then enters the microwave reaction chamber 10. The power of the microwave source 11 is controlled by the online monitoring and control device 1. The remediated soil, after microwave irradiation, is discharged from the end of the microwave reaction chamber 10, achieving efficient remediation of contaminated soil.

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