A method and apparatus for treating soil to degrade perfluorinated compounds.

Abstract

This invention relates to the field of soil treatment, specifically to a method and apparatus for degrading perfluorinated compounds in soil. The apparatus includes a support base, with pillars fixedly connected to each of the four corners of the top of the support base. A mounting plate is fixedly connected to the top of each pillar. A quartz tube passes through and is fixedly connected to the mounting plate and the support base. An air inlet is fixedly connected to the bottom of the quartz tube. An air supply assembly is located on the right side of the support base, with its end connected to the air inlet. A disassembly assembly is connected to the top of the quartz tube, with a delivery pipe connected to its top. A purification cylinder is located at the rear end of the support base, with the end of the delivery pipe passing through and fixedly connected to the purification cylinder. A sealing groove is formed at the top of the purification cylinder. Through the filter screen at the bottom of the quartz tube, gas-solid contact is significantly enhanced and gas distribution is improved, overcoming the problem of insufficient penetration depth in traditional plasma treatment and achieving highly efficient degradation of perfluorinated compounds.

Description

Technical Field

[0001] This invention relates to the field of soil treatment technology, specifically to a method and apparatus for degrading perfluorinated compounds in soil. Background Technology

[0002] Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a group of synthetic fluorine compounds widely used in industrial, commercial, and military applications since the 1950s. Due to the high stability of the carbon-fluorine (CF) bond, PFAS exhibit significant resistance to thermal, chemical, and biodegradation, resulting in strong persistence in the environment, particularly in soil and groundwater. Typical long-chain PFAS, such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), are subject to strict regulation due to their toxicity and bioaccumulation. With the implementation of bans and restrictions, the industry has gradually shifted towards short-chain and novel alternatives. However, studies have shown that the concentrations of these alternatives in the environment are often comparable to or even higher than those of traditional PFAS, posing new ecological and health risks. As a major sink for PFAS and other persistent pollutants, the ecological risks in soil urgently need to be addressed.

[0003] Currently, common research methods for degrading perfluorinated compounds (PFAS) include adsorption immobilization, chemical oxidation / reduction, thermal treatment, and bioremediation. While adsorption techniques limit the mobility of PFAS, they do not chemically degrade pollutants. Chemical and thermal treatments can destroy PFAS, but may generate secondary wastewater or exhaust gas pollution. Bioremediation is environmentally friendly, but is typically slow and inefficient.

[0004] In recent years, plasma technology has become an important means of degrading emerging pollutants due to its ability to generate a large number of highly reactive species under ambient temperature conditions. Various plasma reactors have been successfully used for PFAS removal in water systems, but their application in soil remains very limited, often resulting in poor degradation efficiency due to insufficient penetration depth of reactive substances. To address this issue, fluidized bed plasma, by enhancing gas-solid contact and interfacial mass transfer, is considered a potential solution. Studies have shown that it achieves removal rates exceeding 88% for persistent organic pollutants such as atrazine, tetrachlorobiphenyl, hexachlorobenzene, and fluoropyridones.

[0005] Therefore, developing a green, safe, and efficient fluidized bed low-temperature plasma system for the remediation of PFAS-contaminated soil is of significant scientific importance and application value. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method and apparatus for degrading perfluorinated compounds in soil, solving the problem of insufficient penetration depth of traditional plasma and achieving efficient degradation of perfluorinated compounds.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method and apparatus for treating perfluorinated compounds in soil, comprising a support base, with pillars fixedly connected to the four corners of the top of the support base, an mounting plate fixedly connected to the top of each pillar, a quartz tube passing through and fixedly connected to the mounting plate and the support base, an air inlet cylinder fixedly connected to the bottom of the quartz tube, an air supply assembly disposed on the right side of the support base with its end connected to the air inlet cylinder, a disassembly assembly connected to the top of the quartz tube, a conveying pipe connected to the top of the disassembly assembly, a purification cylinder disposed at the rear end of the support base, with the end of the conveying pipe passing through and fixedly connected to the purification cylinder, a sealing groove formed at the top of the purification cylinder, and a [missing information - likely a design element or feature] on the top of the purification cylinder. The filter cartridge has a bottom set in a sealing groove. An installation block is fixedly connected to the outside of the filter cartridge. Slots are opened on both sides of the installation block. A first activated carbon layer is installed in the upper part of the filter cartridge. A second activated carbon layer is installed in the middle part of the filter cartridge. A polytetrafluoroethylene filter element layer is installed in the lower part of the filter cartridge. A locking assembly is installed on the outside of the purification cartridge. A modulation pulse is set on the left side of the support base. A high-voltage high-frequency AC power supply is set on the right side of the modulation pulse. An electrical detection system is set behind the modulation pulse. A stainless steel mesh is fixedly connected to the outside of the quartz tube. A filter screen is fixedly connected to the lower part of the quartz tube. A stainless steel thread is set in the quartz tube, and the stainless steel thread is set on the top of the filter screen.

[0008] Preferably, the disassembly assembly includes an air outlet cylinder, which is fixedly connected to the top of the quartz tube. A sealing sleeve is fixedly connected to the top of the air outlet cylinder. First locking blocks are fixedly connected to both sides of the air outlet cylinder. A first locking groove is formed on the inner side of the first locking block. A first locking ring is fixedly connected to both sides of the air outlet cylinder. A disassembly cylinder is provided at the top of the air outlet cylinder. An installation groove is formed at the bottom of the disassembly cylinder. Second locking blocks are fixedly connected to both sides of the disassembly cylinder. A second locking groove is formed on the inner side of the second locking block. A second locking ring is fixedly connected to both sides of the disassembly cylinder. The delivery pipe passes through and is fixedly connected to the top of the disassembly cylinder.

[0009] Preferably, the gas supply assembly includes a high-pressure gas cylinder, which is disposed outside the support base. A gas pipe is fixedly connected to the output end of the high-pressure gas cylinder, and a flow meter is installed outside the gas pipe. The end of the gas pipe passes through and is fixedly connected to the air inlet cylinder.

[0010] Preferably, the locking assembly includes a mounting base, the top of which has a limiting groove, a bidirectional threaded rod that passes through and is rotatably connected in the limiting groove, a knob that is fixedly connected to the end of the bidirectional threaded rod and is located outside the mounting base, and clamping blocks that are threadedly connected to both sides of the outer ring of the bidirectional threaded rod and are located on both sides of the mounting block.

[0011] Preferably, a uniformly distributed spring is fixedly connected inside the sealing groove, and a sealing ring is fixedly connected to the top of the spring.

[0012] Preferably, the sealing sleeve is disposed in the mounting groove, and a sealing ring is fixedly connected in the mounting groove.

[0013] Preferably, the second locking ring is disposed in the first locking groove, and the first locking ring is disposed in the second locking groove.

[0014] Preferably, the method for treating perfluorinated compounds in soil is characterized by comprising the following steps: S1, Preparation Stage First, place the soil contaminated with perfluorinated compounds into the quartz tube. Then, align the mounting groove at the bottom of the disassembly cylinder with the sealing sleeve at the top of the vent cylinder and insert it. Finally, rotate the disassembly cylinder clockwise so that the first locking ring is inserted into the second locking groove, and the second locking ring is inserted into the first locking groove, forming a cross-locking structure, thus completing the fixed installation of the disassembly cylinder.

[0015] S2, Ventilate the quartz tube When the high-pressure gas cylinder valve is opened, the gas is delivered to the air inlet tube through the gas pipe, and then passes through the filter screen into the quartz tube to form a specific reaction atmosphere. Soil particles are suspended and agitated under the drive of the airflow, which significantly increases the gas-solid interface contact area and improves the penetration depth of active species.

[0016] S3, Adjust parameters Next, set the frequency and pulse width of the modulation pulse power supply, and simultaneously adjust the voltage and current of the high-voltage high-frequency AC power supply to discharge.

[0017] S4, PFAS degradation Plasma generates a large number of high-energy electrons and active species under normal pressure. These active species can break the stable carbon-fluorine bonds of perfluorinated compounds, thus achieving effective degradation of PFAS in soil.

[0018] S5, Exhaust Gas Degradation Driven by the continuous gas supply from the gas supply component, the degradation exhaust gas inside the quartz tube rises into the disassembly cylinder, and is then transported to the purification cylinder through a delivery pipe fixed to the top of the disassembly cylinder. The exhaust gas first comes into contact with a sodium hydroxide solution in the purification cylinder. The sodium hydroxide solution neutralizes the acidic substances in the exhaust gas, producing harmless sodium fluoride and water, thus initially removing the highly corrosive components. After neutralization, the exhaust gas continues to rise into the filter cylinder, and finally passes through a polytetrafluoroethylene filter layer, a second activated carbon layer, and a first activated carbon layer before being discharged.

[0019] Working Principle: First, soil contaminated with perfluorinated compounds (20 mg / kg) is placed inside a quartz tube. Then, the mounting groove at the bottom of the disassembly cylinder is aligned with the sealing sleeve at the top of the outlet cylinder and inserted. Finally, the disassembly cylinder is rotated clockwise, causing the first locking ring to insert into the second locking groove, and simultaneously the second locking ring to insert into the first locking groove, forming a cross-locking structure and completing the fixed installation of the disassembly cylinder. Simultaneously, the high-pressure gas cylinder valve is opened, and gas is delivered through the gas pipe to the inlet cylinder, passing through the filter screen into the quartz tube to create a specific reaction atmosphere (gas flow rate into the quartz tube is 20 L / min). Soil particles are suspended and agitated under the airflow, significantly increasing the gas-solid interface contact area and improving the penetration depth of active species. The filter screen at the bottom of the quartz tube can hold soil particles and evenly distribute the airflow, ensuring uniform reaction. A flow meter outside the gas pipe monitors the gas flow rate in real time. Next, the frequency and pulse width of the modulation pulse power supply were set, and the voltage and current of the high-voltage high-frequency AC power supply were adjusted (the frequency of the modulation pulse power supply was 800Hz, the pulse width was 50, the voltage of the high-voltage high-frequency AC power supply was 80V, the current was 0.6A, and the reaction time was 100min) for discharge. The stainless steel mesh on the outside of the quartz tube and the stainless steel threads inside served as the high-voltage electrode and the grounding electrode, respectively, forming a stable dielectric barrier discharge zone. The discharge was transmitted through the quartz tube to the soil sample and the reaction gas, exciting the reaction gas to generate active groups with strong oxidizing or reducing properties (such as hydroxyl radicals and hydrogen radicals). These active groups reacted chemically with the perfluorinated compounds in the soil, breaking the carbon-fluorine bonds in the perfluorinated compound molecules and gradually degrading them into low-toxicity or non-toxic small molecule compounds. During the reaction, the electrical detection system monitored the operating parameters of the device in real time. The electrical monitoring system not only detected the input power but also connected to the modulation pulse power supply to form a closed-loop feedback control, automatically adjusting the output frequency and power according to changes in discharge current and discharge voltage, thereby optimizing energy consumption and maintaining stable system operation. Driven by the continuous gas supply from the gas supply component, the degradation exhaust gas inside the quartz tube rises into the disassembly cylinder, and is then transported to the purification cylinder through a delivery pipe fixed to the top of the disassembly cylinder. The exhaust gas first comes into contact with a sodium hydroxide solution in the purification cylinder. The sodium hydroxide solution neutralizes the acidic substances in the exhaust gas, producing harmless sodium fluoride and water, thus initially removing the highly corrosive components. After neutralization, the exhaust gas continues to rise into the filter cylinder, and finally passes through a polytetrafluoroethylene filter layer, a second activated carbon layer, and a first activated carbon layer before being discharged. To disassemble the filter cylinder, the knob on the outside of the purification cylinder is rotated sequentially, causing the bidirectional threaded rod to rotate. This bidirectional threaded rod drives two clamping blocks to move in opposite directions, at which point the clamping blocks are pulled out of the slots on both sides of the mounting block, allowing the filter cylinder to be disassembled and replaced.

[0020] This invention provides a method and apparatus for treating soil to degrade perfluorinated compounds. It has the following beneficial effects: 1. This invention significantly enhances gas-solid contact and improves gas distribution through a filter at the bottom of a quartz tube, overcoming the problem of insufficient penetration depth in traditional plasmas and achieving efficient degradation of perfluorinated compounds. Driven by a modulated pulse power supply, high-density plasma can be generated at relatively low average power, reducing ineffective energy consumption, avoiding electrode overheating, and improving system energy efficiency and stability. Furthermore, using air as the working gas eliminates the need for flammable gases such as methane, avoiding safety hazards and making it suitable for practical soil remediation applications.

[0021] 2. This invention allows for easy and quick installation and fixation of the disassembly cylinder through the disassembly components, facilitating the placement of contaminated soil into the quartz tube. Simultaneously, the sealing sleeve and sealing ring ensure airtightness. No chemical reagents are required during the degradation of soil pollutants. Furthermore, a tail gas collection unit is installed at the outlet to centrally collect and treat the tail gas generated during the discharge process, preventing secondary pollution and further enhancing environmental friendliness. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the disassembly component structure of the present invention; Figure 3 This is a sectional view of the filter cartridge and mounting base of the present invention; Figure 4 This is a cross-sectional view of the quartz tube of the present invention; Figure 5 The degradation rate of different perfluorinated compounds in soil from 0 to 100 min is shown in the figure when the initial concentration is 20 mg / kg, the discharge power is 25 W, the gas flow rate is 20 L / min, the pH is 7.2, and the soil moisture content is 3%. Figure 6 The graph shows the degradation rate of perfluorinated compounds with an initial concentration of 20 mg / kg in the soil from 0 to 100 min under the conditions of discharge power of 6 W-32 W, gas flow rate of 20 L / min, pH of 7.2, and soil moisture content of 3%. Figure 7 The graph shows the degradation rate of perfluorinated compounds with an initial concentration of 20 mg / kg in soil from 0 to 100 min when the soil moisture content is 0%-5%, the discharge power is 25 W, the gas flow rate is 20 L / min, and the pH is 7.2.

[0023] The components include: 1. Support base; 2. Column; 3. Mounting plate; 4. Quartz tube; 5. Air inlet cylinder; 6. High-pressure gas cylinder; 7. Gas pipe; 8. Flow meter; 9. Air outlet cylinder; 10. Sealing sleeve; 11. First locking block; 12. First locking groove; 13. First locking ring; 14. Disassembly cylinder; 15. Mounting groove; 16. Second locking block; 17. Second locking groove; 18. Second locking ring; 19. Sealing ring; 20. Purification cylinder; 21. Sealing groove; 22. Spring. 23. Spring; 24. Sealing ring; 25. Filter cartridge; 26. Mounting block; 27. Slot; 28. First activated carbon layer; 29. ​​Second activated carbon layer; 30. PTFE filter element layer; 31. Mounting base; 32. Limiting groove; 33. Bidirectional threaded rod; 34. Knob; 35. Clamping block; 36. Modulation pulse; 37. High voltage high frequency AC power supply; 38. Electrical detection system; 39. Stainless steel mesh; 40. Stainless steel thread; 41. Filter screen; 42. Conveying pipe. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Examples 1-3 adopted Figure 1-4The device shown is for treating perfluorinated compounds in soil. It includes a support base 1, which provides fixed support. Support columns 2 are fixedly connected to the four corners of the top of the support base 1, providing support as well. Mounting plates 3 are fixedly connected to the top of the support columns 2, providing support as well. A quartz tube 4 passes through and is fixedly connected to the support base 1. The quartz tube 4 has an inner diameter of 23 mm, a length of 260 mm, and a thickness of 2 mm. An air inlet cylinder 5 is fixedly connected to the bottom of the quartz tube 4. An air supply assembly is located on the right side of the support base 1, and its end is connected to the air inlet cylinder 5. A disassembly assembly is connected to the top of the quartz tube 4. The disassembly assembly is made of corrosion-resistant polytetrafluoroethylene (PTFE). A delivery pipe 41, also made of PTFE, is connected to the top of the disassembly assembly and is used to deliver exhaust gas. A purification cylinder 20, containing a sodium hydroxide solution, is located at the rear end of the support base 1. The end of the delivery pipe 41 is passed through and fixedly connected to the purification cylinder 20. A sealing groove 21 is opened at the top of the purification cylinder 20, which serves to position and seal the cylinder. A filter cylinder 24 is installed at the top of the purification cylinder 20, and a discharge port is opened at the top of the filter cylinder 24. The bottom of the filter cylinder 24 is placed in the sealing groove 21. An installation block 25 is fixedly connected to the outside of the filter cylinder 24. Slots 26 are opened on both sides of the installation block 25. A first activated carbon layer 27 is installed inside the filter cylinder 24. This layer is modified activated carbon (to enhance the adsorption capacity of PFAS). The modification method (simple and easy to operate) is to soak ordinary activated carbon in a 10% NaOH solution for 24 hours, dry it, and then use it. NaOH can activate the pores of activated carbon, increase the surface hydroxyl groups, and enhance the hydrophobic adsorption capacity of PFAS. A second activated carbon layer 28, made of ordinary granular activated carbon (industrial grade, 2-4mm particle size), is installed in the middle of the filter cartridge 24 to treat ozone. The activated carbon decomposes ozone through catalysis and simultaneously adsorbs some small-molecule organic fluorine, preventing ozone from oxidizing the PFAS adsorption sites in the upper layer. A polytetrafluoroethylene (PTFE) filter element layer 29 is installed at the bottom of the filter cartridge 24. PTFE is highly corrosion-resistant and has uniform pore size, intercepting fine soil dust and some large, undegraded molecules carried in the exhaust gas, preventing them from clogging subsequent adsorption layers. A locking assembly is installed on the outside of the purification cartridge 20. A modulation pulse 35 is located on the left side of the support base 1, and a high-voltage, high-frequency AC power supply 36 is located on the right side of the modulation pulse 35. The high-voltage, high-frequency AC power supply 36 is equipped with a modulation pulse 35 to adjust the discharge frequency and pulse width. The high-voltage, high-frequency AC power supply 36 has voltage and current detection interfaces, allowing connection of probes to test the power supply's input power. An electrical detection system 37 is installed after the modulation pulse 35. The high-voltage high-frequency AC power supply 36 is connected to the electrical monitoring system 37. The electrical monitoring system 37 includes a high-frequency current sensor connected in series with the output live wire (or neutral wire) of the high-voltage high-frequency AC power supply 36, which is used to collect the instantaneous current value in the power supply circuit in real time.High-voltage voltage sensor: Connected in parallel to the output terminal (between the live wire and neutral wire) of the high-voltage high-frequency AC power supply 36, used to collect instantaneous voltage values ​​in the power supply circuit. Data acquisition unit (DAQ): Connected to the current and voltage sensors, it converts the analog signals of "instantaneous current" and "instantaneous voltage" collected by the sensors into digital signals and transmits them to the core control unit. Core control unit (MCU / PLC): Built-in power calculation algorithm, receives the current and voltage digital signals transmitted by the data acquisition unit, calculates the input power in real time; it also has data storage and threshold comparison functions, can record historical power data, and compare it with the preset "normal power range". Electrical monitoring system 37 and modulation pulse power supply 35 form a closed-loop control, used to automatically adjust the output frequency and power according to the discharge current signal to achieve energy consumption optimization. A stainless steel mesh 38 is fixedly connected to the outside of the quartz tube 4. The stainless steel thread 38 has a diameter of 15 mm and the length of the stainless steel mesh is 150 mm, used as a high-voltage electrode. A filter screen 40 with a mesh count of 100 is fixedly connected to the lower part of the quartz tube 4. To support and prevent soil particle loss, the filter screen 40 at the bottom of the quartz tube 4 can hold soil particles and evenly distribute airflow to ensure reaction uniformity. A stainless steel thread 39 is provided inside the quartz tube 4 and is located at the top of the filter screen 40. The stainless steel thread 39 serves as a grounding electrode. The external stainless steel mesh 38 and the internal stainless steel thread 39 of the quartz tube 4 serve as the high-voltage electrode and the grounding electrode, respectively, forming a stable dielectric barrier discharge region.

[0026] The disassembly assembly includes an air outlet 9, which is fixedly connected to the top of the quartz tube 4. A sealing sleeve 10 is fixedly connected to the top of the air outlet 9. First locking blocks 11 are fixedly connected to both sides of the air outlet 9. A first locking groove 12 is opened on the inner side of the first locking block 11. A first locking ring 13 is fixedly connected to both sides of the air outlet 9. A disassembly cylinder 14 is provided at the top of the air outlet 9. An installation groove 15 is opened at the bottom of the disassembly cylinder 14. Second locking blocks 16 are fixedly connected to both sides of the disassembly cylinder 14. A second locking groove 17 is opened on the inner side of the second locking block 16. A second locking ring 18 is fixedly connected to both sides of the disassembly cylinder 14. A delivery pipe 41 passes through and is fixedly connected to the top of the disassembly cylinder 14.

[0027] The first locking ring 13 of the disassembly assembly is inserted into the second locking groove 17, and the second locking ring 18 is inserted into the first locking groove 12 to form a cross locking structure, thereby completing the fixed installation of the disassembly cylinder 14. The gas supply assembly includes a high-pressure gas cylinder 6, which is located outside the support base 1. A gas pipe 7 is fixedly connected to the output end of the high-pressure gas cylinder 6. A flow meter 8 is installed outside the gas pipe 7. The end of the gas pipe 7 passes through and is fixedly connected to the air inlet cylinder 5.

[0028] The air supply component enables air to be supplied into the quartz tube 4, while the soil particles are suspended and agitated under the airflow, which significantly increases the gas-solid interface contact area and improves the penetration depth of active species. The locking assembly includes a mounting base 30, with a limiting groove 31 on the top of the mounting base 30. A bidirectional threaded rod 32 is rotatably connected through the limiting groove 31. A knob 33 is fixedly connected to the end of the bidirectional threaded rod 32, and the knob 33 is located outside the mounting base 30. Clamping blocks 34 are threadedly connected to both sides of the outer ring of the bidirectional threaded rod 32, and the clamping blocks 34 are located on both sides of the mounting block 25.

[0029] When the bidirectional threaded rod 32 of the locking assembly rotates, it can drive the two clamping blocks 34 to move relative to each other or away from each other. The clamping blocks 34 are inserted into the slots 26 on both sides of the mounting block 25 to install the filter cartridge 24. A uniformly distributed spring 22 is fixedly connected inside the sealing groove 21, and a sealing ring 23 is fixedly connected to the top of the spring 22.

[0030] The sealing sleeve 10 is set in the mounting groove 15, and the sealing ring 19 is fixedly connected in the mounting groove 15.

[0031] The sealing ring 19 can improve the sealing performance of the air outlet 9 and the disassembly cylinder 14 after installation. The second locking ring 18 is disposed in the first locking groove 12, and the first locking ring 13 is disposed in the second locking groove 17.

[0032] The second locking ring 18 can be inserted into the first locking groove 12, and the first locking ring 13 can be inserted into the second locking groove 17, forming a cross-locking structure. This structure uses the contact surface between the locking ring and the locking groove to limit the displacement of the components, ensuring that there is no looseness after the air outlet 9 and the disassembly cylinder 14 are spliced ​​together; A method for treating soil to degrade perfluorinated compounds, characterized by comprising the following steps: S1, Preparation Stage First, soil contaminated with perfluorinated compounds is placed inside the quartz tube 4. Then, the mounting groove 15 at the bottom of the disassembly cylinder 14 is aligned with the sealing sleeve 10 at the top of the vent cylinder 9 and inserted. Finally, the disassembly cylinder 14 is rotated clockwise so that the first locking ring 13 is inserted into the second locking groove 17, and at the same time, the second locking ring 18 is inserted into the first locking groove 12, forming a cross-locking structure, thus completing the fixed installation of the disassembly cylinder 14.

[0033] S2, Ventilate the quartz tube When the valve of the high-pressure gas cylinder 6 is opened, the gas is delivered to the air inlet cylinder 5 through the gas pipe 7, and then passes through the filter screen 40 to introduce air into the quartz tube 4 to form a specific reaction atmosphere. The soil particles are in a suspended and agitated state under the drive of the airflow, which significantly increases the gas-solid interface contact area and improves the penetration depth of active species.

[0034] S3, Adjust parameters Next, set the frequency and pulse width of the modulation pulse 35 power supply, and simultaneously adjust the voltage and current of the high-voltage high-frequency AC power supply 36 to discharge.

[0035] S4, PFAS degradation Plasma generates a large number of high-energy electrons and active species such as •OH, O•, O3, and NO2• under normal pressure. These active species can break the stable carbon-fluorine bonds of perfluorinated compounds, thus achieving effective degradation of PFAS in soil.

[0036] S5, Exhaust Gas Degradation Driven by the continuous gas input from the gas supply component, the degradation exhaust gas in the quartz tube 4 rises into the disassembly cylinder 14, and is then transported to the purification cylinder 20 through the delivery pipe 41 fixed to the top of the disassembly cylinder 14. The exhaust gas first comes into contact with the sodium hydroxide solution in the purification cylinder 20. The sodium hydroxide solution neutralizes the acidic substances in the exhaust gas, generating harmless sodium fluoride and water, thus initially removing the highly corrosive components in the exhaust gas. After neutralization, the exhaust gas continues to rise into the filter cylinder 24, and finally is discharged after being filtered through the polytetrafluoroethylene filter layer 29, the second activated carbon layer 28, and the first activated carbon layer 27.

[0037] Example 1 Quartz sand was used to simulate the soil matrix in the experiment. A test soil sample with a perfluorinated compound concentration of 20 mg / kg was prepared. 20 g of the test soil was placed in a quartz tube 4. The discharge voltage was adjusted to 80 V, the discharge current to 0.6 A, and the reaction time to 100 min. The degradation rates of different types of perfluorinated compounds over time are shown in the figure. Figure 5 At a discharge power of 25 W, a gas flow rate of 20 L / min, a pH of 7.2, and a soil moisture content of 3%, the removal efficiencies of PFNA, PFOA, PFHpA, PFHxA, PFPeA, HFPO-TA, and HFPO-DA were 95%, 100%, 97%, 87.6%, 84%, 73%, and 99%, respectively.

[0038] Example 2 Quartz sand was used to simulate the soil matrix in the experiment. A test soil sample with a perfluorinated compound concentration of 20 mg / kg was prepared. 20 g of the test soil was placed in plasma reactor 2, and the discharge voltage was adjusted to 80 V, the discharge current to 0.6 A, and the reaction time to 100 min. The degradation rates of perfluorinated compounds at different discharge powers and time periods are shown in [Figure / Reference]. Figure 6 Under the conditions of a gas flow rate of 20 L / min, pH of 7.2, and soil moisture content of 3%, and a discharge power of 25 W, the removal efficiencies of PFOA, PFHxA, HFPO-TA, and HFPO-DA were 100%, 87.6%, 73%, and 99%, respectively.

[0039] Example 3 Quartz sand was used to simulate the soil matrix in the experiment. A test soil sample with a perfluorinated compound concentration of 20 mg / kg was prepared. 20 g of the test soil was placed in a quartz tube 4. The discharge voltage was adjusted to 80 V, the discharge current to 0.6 A, and the reaction time to 100 min. The degradation rate of perfluorinated compounds at different soil moisture contents and time periods is shown in the figure. Figure 7 Under the conditions of a gas flow rate of 20 L / min, pH of 7.2, discharge power of 25 W, and soil moisture content of 3% W, the removal efficiencies of PFOA, PFHxA, HFPO-TA, and HFPO-DA were 100%, 87.6%, 73%, and 99%, respectively.

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An apparatus for degrading perfluorinated compounds in soil, comprising a support base, characterized in that: Each of the four corners of the support base is fixedly connected to a pillar. A mounting plate is fixedly connected to the top of each pillar. A quartz tube passes through and is fixedly connected to the support base. An air inlet is fixedly connected to the bottom of the quartz tube. An air supply assembly is located on the right side of the support base, and its end is connected to the air inlet. A disassembly assembly is connected to the top of the quartz tube. A delivery pipe is connected to the top of the disassembly assembly. A purification cylinder is located at the rear end of the support base, and the end of the delivery pipe passes through and is fixedly connected to the purification cylinder. A sealing groove is formed at the top of the purification cylinder. A filter cylinder is located at the top of the purification cylinder, and its bottom is placed within the sealing groove. An installation block is fixedly connected to the outside, and slots are provided on both sides of the installation block. A first activated carbon layer is installed in the upper part of the filter cylinder, a second activated carbon layer is installed in the middle part of the filter cylinder, a polytetrafluoroethylene filter element layer is installed in the lower part of the filter cylinder, a locking assembly is installed on the outside of the purification cylinder, a modulation pulse is provided on the left side of the support base, a high voltage high frequency AC power supply is provided on the right side of the modulation pulse, an electrical detection system is provided behind the modulation pulse, a stainless steel mesh is fixedly connected to the outside of the quartz tube, a filter screen is fixedly connected to the lower part of the quartz tube, and a stainless steel thread is provided inside the quartz tube, with the stainless steel thread located at the top of the filter screen. The disassembly assembly includes an air outlet cylinder, which is fixedly connected to the top of a quartz tube. A sealing sleeve is fixedly connected to the top of the air outlet cylinder. First locking blocks are fixedly connected to both sides of the air outlet cylinder. A first locking groove is formed on the inner side of the first locking block. A first locking ring is fixedly connected to both sides of the air outlet cylinder. A disassembly cylinder is provided at the top of the air outlet cylinder. An installation groove is formed at the bottom of the disassembly cylinder. Second locking blocks are fixedly connected to both sides of the disassembly cylinder. A second locking groove is formed on the inner side of the second locking block. A second locking ring is fixedly connected to both sides of the disassembly cylinder. The delivery pipe passes through and is fixedly connected to the top of the disassembly cylinder. The gas supply assembly includes a high-pressure gas cylinder, which is located outside the support base. A gas pipe is fixedly connected to the output end of the high-pressure gas cylinder. A flow meter is installed outside the gas pipe. The end of the gas pipe passes through and is fixedly connected to the air inlet cylinder. The locking assembly includes a mounting base with a limiting groove on the top. A bidirectional threaded rod is rotatably connected through the limiting groove. A knob is fixedly connected to the end of the bidirectional threaded rod and is located outside the mounting base. Clamping blocks are threaded to both sides of the outer ring of the bidirectional threaded rod and are located on both sides of the mounting block.

2. The apparatus for degrading perfluorinated compounds in soil according to claim 1, characterized in that: A uniformly distributed spring is fixedly connected inside the sealing groove, and a sealing ring is fixedly connected to the top of the spring.

3. The apparatus for degrading perfluorinated compounds in soil according to claim 1, characterized in that: The sealing sleeve is installed in the mounting groove, and a sealing ring is fixedly connected in the mounting groove.

4. The apparatus for degrading perfluorinated compounds in soil according to claim 1, characterized in that: The second locking ring is disposed in the first locking groove, and the first locking ring is disposed in the second locking groove.

5. A method for treating soil to degrade perfluorinated compounds according to any one of claims 1-4, characterized in that: Includes the following steps: S1, Preparation Stage First, place the soil contaminated with perfluorinated compounds into the quartz tube. Then, align the mounting groove at the bottom of the disassembly cylinder with the sealing sleeve at the top of the vent cylinder and insert it. Finally, rotate the disassembly cylinder clockwise so that the first locking ring is inserted into the second locking groove, and at the same time, the second locking ring is inserted into the first locking groove, forming a cross-locking structure, thus completing the fixed installation of the disassembly cylinder. S2, Ventilate the quartz tube When the high-pressure gas cylinder valve is opened, the gas is delivered to the air inlet cylinder through the gas pipe, and then passes through the filter screen into the quartz tube to form a specific reaction atmosphere. Soil particles are in a suspended and agitated state under the drive of airflow, which significantly increases the gas-solid interface contact area and improves the penetration depth of active species. S3, Adjust parameters Next, set the frequency and pulse width of the modulation pulse power supply, and simultaneously adjust the voltage and current of the high-voltage high-frequency AC power supply to discharge; S4, PFAS degradation Plasma generates a large number of high-energy electrons and active species under normal pressure. These active species can break the stable carbon-fluorine bonds of perfluorinated compounds, thus achieving effective degradation of PFAS in soil. S5, Exhaust Gas Degradation Driven by the continuous gas input from the gas supply component, the degradation exhaust gas inside the quartz tube enters the disassembly cylinder from the top. It is then transported to the purification cylinder through a delivery pipe fixed to the top of the disassembly cylinder. The exhaust gas first comes into contact with the sodium hydroxide solution in the purification cylinder. The sodium hydroxide solution neutralizes the acidic substances in the exhaust gas, generating harmless sodium fluoride and water, thus initially removing the highly corrosive components from the exhaust gas. The neutralized exhaust gas continues to enter the filter cylinder from the top and is finally discharged after being filtered through the polytetrafluoroethylene filter layer, the second activated carbon layer, and the first activated carbon layer.

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