A multi-stage synergistic continuous treatment system and method for degrading fluorine-containing organic pollutants

Abstract

This invention discloses a multi-level synergistic continuous treatment system and method for degrading fluorinated organic pollutants, belonging to the field of water treatment technology. The system includes a plasma dual-frequency acoustic synergistic treatment module to convert PFAS into short-chain fluorocarbon intermediates; and an acoustic-electric synergistic advanced oxidation module to perform defluorination and mineralization on the short-chain fluorocarbon intermediates. The acoustic-electric synergistic advanced oxidation module includes a main tank, electrode components, opposing matrix ultrasonic units, and flow channel switching pipes. The electrode components are fixedly installed inside the main tank, and the opposing matrix ultrasonic units are symmetrically installed on two opposite sidewalls of the main tank with their ultrasonic emission direction pointing towards the electrode components. The outlet end of the flow channel switching pipe is connected to the main tank, and the inlet end is connected to the reactor. This invention achieves continuous treatment from long-chain to short-chain to complete defluorination and mineralization through the tiered synergy of plasma chain breaking, dual-frequency ultrasonic cavitation, and acoustic-electric coupling, significantly improving the degradation efficiency and operational stability of fluorinated organic pollutants.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a multi-level synergistic continuous treatment system and method for degrading fluorinated organic pollutants. Background Technology

[0002] Fluorinated organic pollutants such as perfluorinated and polyfluoroalkyl substances (PFAS) are extremely difficult to degrade in the natural environment and conventional water treatment processes due to the presence of highly energetic carbon-fluorine bonds (CF bonds) in their molecular structure. Therefore, they are known as permanent chemicals. Traditional wastewater treatment methods can only transfer the physical phase of these recalcitrant organic pollutants; they cannot achieve complete mineralization and detoxification of the final molecular structure, and are highly prone to causing secondary concentration pollution.

[0003] In recent years, advanced oxidation processes based on low-temperature plasma, sonochemical cavitation, and electrochemical oxidation have been gradually applied to the treatment of highly difficult and recalcitrant industrial wastewater. While existing technologies can exhibit long-chain structural conversion activity within specific reaction times under limited conditions in laboratory batch processing or simulated pure water systems, when these single-level treatment technologies are introduced into industrial continuous flow applications with high flow rates, complex matrices, and long-term stable operation requirements, the following technological gaps remain to be systematically addressed in terms of fluid dynamics integration and in-situ passivation prevention: First, existing processes, guided by continuous flow, fail to systematically consider the degradation kinetics of PFAS molecular chains and the dynamic evolution of physicochemical characteristics during multi-level series degradation. In actual water bodies, PFAS typically exist as long carbon chains, and single-level technologies often only cleave some long-chain molecules into medium- and short-chain substances (such as PFBA and PFBS). However, these derived short-chain products possess stronger hydrophilicity and higher chemical stability, readily retreating rapidly into deeper water and escaping the gas-liquid reaction interface. This results in continuous flow degradation reactions often being limited by the accumulation of products in the short-chain stage. Due to the lack of dynamic control over the process sequence in existing systems, it is difficult to guide the fluid to conform to the tiered degradation pattern of carbon chains from long to short, and then from short chains to complete defluorination and mineralization during continuous flow.

[0004] Secondly, the complex matrix in real industrial wastewater is prone to in-situ surface passivation and scaling at the reaction interface under continuous operation, which not only hinders the continuous mass transfer of heterogeneous catalytic reactions, but also leads to an increase in system energy consumption and operating impedance. Summary of the Invention

[0005] This invention provides a multi-level synergistic continuous treatment system and method for degrading fluorinated organic pollutants, which solves the problems of existing advanced oxidation processes in continuous flow treatment of fluorinated organic pollutants, such as difficulty in achieving stepwise degradation from long chain to short chain to complete defluorination and mineralization, easy accumulation of short chain products, easy passivation and scaling at the reaction interface, and lack of dynamic adjustment and convenient maintenance capabilities.

[0006] The objective of this invention can be achieved through the following technical solutions: A multi-level synergistic continuous treatment system for degrading fluorinated organic pollutants, characterized in that it comprises: A plasma dual-frequency acoustic wave co-processing module is used to convert PFAS into short-chain fluorocarbon intermediates. The plasma dual-frequency acoustic wave co-processing module includes a plasma reaction unit and a reactor. The plasma reaction unit is installed in the reactor. The plasma reaction unit breaks the carbon-fluorine bonds of long-chain PFAS molecules and reduces the proportion of macromolecules, causing them to degrade and convert into short-chain fluorocarbon intermediates. An acoustic-electric synergistic advanced oxidation module, connected to and located downstream of the plasma dual-frequency acoustic synergistic processing module, performs defluorination and mineralization on short-chain fluorocarbon intermediates. The acoustic-electric synergistic advanced oxidation module includes a main tank, electrode assemblies, opposing matrix ultrasonic units, and flow channel switching pipes. The electrode assemblies are fixedly disposed inside the main tank, and the opposing matrix ultrasonic units are symmetrically installed on two opposite sidewalls of the main tank with their ultrasonic emission direction pointing towards the electrode assemblies. The outlet end of the flow channel switching pipe is connected to the main tank, and the inlet end is connected to the reactor.

[0007] Preferably, the electrode assembly includes an insulating support frame and multiple parallel conductive electrode sheets, each of which is independently and detachably mounted on the insulating support frame; the mesh structure of the conductive electrode sheet is a diamond-shaped mesh structure formed by stretching a metal substrate, and the top of the conductive electrode sheet is provided with a wiring end, which is located on one side of the central axis of the conductive electrode sheet in a horizontal position.

[0008] Preferably, the conductive electrode sheet includes a first polar electrode and a second polar electrode; the materials of the first polar electrode and the second polar electrode are independently selected, and at least one of them includes an electrochemically active material with a high oxygen evolution potential; at least one of the first polar electrode and the second polar electrode is composed of a conductive substrate and an electrochemically active coating disposed on opposite surfaces of the conductive substrate.

[0009] Preferably, the opposing matrix ultrasonic unit includes two sets of protective chambers symmetrically arranged on opposite sidewalls of the main body tank. Each protective chamber is provided with multiple sets of ultrasonic transducers, and the vibration emission surface of any ultrasonic transducer is perpendicularly pointed to the plane of the parallel conductive electrode sheets.

[0010] Preferably, the plasma reaction unit includes a swirling induction shell, an axially adjustable hollow energy mandrel, and an axially adjustable expansion nozzle; the hollow energy mandrel and the expansion nozzle are threaded into the swirling induction shell to form an annular flow channel with adjustable swirl depth.

[0011] Preferably, the plasma reaction unit further includes a plasma generator, which is installed in the swirling induction housing; the plasma generator includes a power supply assembly and a reaction gas assembly; the power supply assembly is used to provide discharge energy, and the reaction gas assembly is used to provide reaction gas, which includes one of inert gases such as air, oxygen, and argon, or combinations thereof.

[0012] Preferably, the bottom of the main tank is provided with an inverted conical uniform water distribution area, and the top of the main tank is provided with bidirectional overflow collection tanks on both sides. The inner wall of the collection tank is provided with multiple V-shaped overflow ports, and the bottom height of the overflow ports is higher than the conductive electrode sheet and lower than the wiring end.

[0013] Preferably, the reactor includes a reactor body, a central partition assembly, a first ultrasonic component, and a second ultrasonic component; the central partition assembly is installed inside the reactor body and forms a first ultrasonic reaction zone between it and the inner wall of the reactor body; the central partition assembly includes a vertical tube and an expansion guide cover integrally connected to the bottom of the vertical tube; the vertical tube and the expansion guide cover are hollow inside, forming a second ultrasonic reaction zone; the first ultrasonic component is installed in the first ultrasonic reaction zone, and the second ultrasonic component is installed in the second ultrasonic reaction zone.

[0014] Preferably, the upper part of the reactor body is provided with at least one installation interface, the bottom of which is provided with a gas inlet and a sludge outlet, the top of the reactor body is provided with a closed top cover and a water collection tray, the closed top cover is provided with a gas collection chamber, and the gas collection chamber is connected to the gas inlet through a gas micronization device to form a gas circulation path.

[0015] A multi-level synergistic continuous treatment method for degrading fluorinated organic pollutants includes the following steps: S1, the fluid containing long-chain PFAS to be treated is introduced into the plasma reaction unit, high shear force is applied to the fluid to perform physical destabilization, and plasma is applied to the fluid to make the fluid and plasma come into contact with active substances, so as to perform preliminary oxidation treatment on the fluid and obtain oxidized fluid. S2, introduce the oxidizing fluid into the reactor, and apply the first high-frequency ultrasonic energy to the oxidizing fluid in the reactor to form a first cavitation reaction environment. In the first cavitation reaction environment, the oxidizing fluid undergoes physical chain breaking and preliminary oxidation to obtain the first processed fluid after chain breaking treatment. S3: Collect at least a portion of the gas generated in the first cavitation reaction environment of S2, and convert the collected gas into microbubbles, then reintroduce it into the reactor for recycling; the microbubbles form a gas-liquid mixture with the first processing fluid, and apply second low-frequency ultrasonic energy to the gas-liquid mixture to further oxidize the pollutants in the first processing fluid to obtain a short-chain fluorocarbon intermediate; S4, the short-chain fluorocarbon intermediate is introduced into the acoustic-electric synergistic advanced oxidation module and flows vertically upward into the region of the electrode assembly and the opposing matrix ultrasonic unit. The electrode assembly is energized to carry out an electrochemical oxidation reaction, while the opposing matrix ultrasonic unit emits ultrasonic waves to obtain a defluorinated mineralization fluid. The defluorinated mineralization fluid rises with the liquid level and is discharged.

[0016] The beneficial effects of this invention are as follows: 1. The plasma dual-frequency acoustic wave synergistic processing module of this invention utilizes high-energy plasma physical chain severing to break long-chain PFAS, significantly reducing the proportion of macromolecules; the downstream acoustic-electric synergistic advanced oxidation module uses the instantaneous coupling of ultrasonic cavitation and electrochemistry to generate high-concentration hydroxyl radicals and clean the electrodes in real time, achieving rapid mineralization and defluorination of short-chain intermediates. The two modules are sequentially connected and progressively advanced, thereby completing the efficient conversion from long chain to short chain to complete mineralization in a continuous flow, which not only avoids the accumulation of short-chain products but also significantly improves defluorination efficiency and operational stability.

[0017] The turbulent disturbances introduced by the previous stage are reshaped in situ into a stable vertical upflow by utilizing an inverted conical uniform water distribution zone. This vertical upflow, the diamond-shaped mesh structure of the conductive electrode plate itself, and the ultrasonic acoustic axes emitted laterally from both sides forcefully lock and construct a three-dimensional cross-coupled flow field in physical space. Attached Figure Description

[0018] Figure 1 A three-dimensional structural diagram of the multi-level collaborative continuous processing system provided by the present invention.

[0019] Figure 2 This is a schematic diagram of the main structure of the multi-level collaborative continuous processing system provided by the present invention.

[0020] Figure 3 This is a top view of the multi-level collaborative continuous processing system provided by the present invention.

[0021] Figure 4This is a rear view structural diagram of the multi-level cooperative continuous processing system provided by the present invention.

[0022] Figure 5 This is a right-side structural schematic diagram of the multi-level cooperative continuous processing system provided by the present invention.

[0023] Figure 6 This is a schematic diagram of the left-side structure of the multi-level collaborative continuous processing system provided by the present invention.

[0024] Figure 7 This is a bottom view of the multi-level collaborative continuous processing system provided by the present invention.

[0025] Figure 8 for Figure 3 A schematic diagram of the cross-sectional structure of AA.

[0026] Figure 9 for Figure 2 A schematic diagram of the cross-sectional structure of BB.

[0027] Figure 10 for Figure 2 A schematic diagram of the cross-sectional structure of CC.

[0028] Figure 11 This is a cross-sectional view of the plasma reaction unit.

[0029] Legend: 1. Plasma dual-frequency acoustic wave synergistic processing module; 2. Acoustic-electric synergistic advanced oxidation module; 3. Reactor body; 4. Installation interface; 5. Energy enhancement device; 51. Swirl-induced shell; 52. Hollow energy mandrel; 53. Expansion nozzle; 6. Plasma generator; 7. Water inlet; 8. Sealed top cover; 9. Gas collection chamber; 10. Water collection tray; 11. Gas inlet; 12. Sludge discharge port; 13. Vertical pipe; 14. Expansion guide hood; 15. First ultrasonic reaction zone; 16. First ultrasonic component; 17. Second ultrasonic... 18. Acoustic reaction zone; 19. Second ultrasonic component; 20. Outlet; 21. Main tank; 22. Shared flow channel opening; 23. Flow channel switching fitting; 24. Inverted cone-shaped uniform water distribution zone; 25. Electrode reaction zone; 26. Drain outlet; 27. Conductive electrode plate; 28. Insulating support frame; 29. ​​Wiring end; 30. Opposing matrix ultrasonic unit; 31. Ultrasonic transducer; 32. V-shaped overflow port; 33. Bidirectional overflow collection tank; 34. Swirl pretreatment zone; 35. Diameter reduction acceleration zone; 36. Confined reaction zone; 37. Expansion and refining zone. Detailed Implementation

[0030] The specific embodiments of the present invention will be further described in detail below with reference to the technical solution of the present invention. It should be noted that, as... Figures 1-11As shown, the present invention provides a multi-level synergistic continuous treatment system for degrading fluorinated organic pollutants, comprising an upstream plasma dual-frequency acoustic wave synergistic treatment module 1 and a downstream acoustic-electric synergistic advanced oxidation module 2. The two modules are connected by pipelines to form a continuous flow treatment multi-level synergistic cycle, wherein: The plasma dual-frequency acoustic wave co-processing module 1 includes a plasma reaction unit and a reactor. The plasma reaction unit is installed on the upper part of the reactor.

[0031] Raw water containing PFAS first enters the plasma reaction unit, where high-energy physical chain-breaking action preferentially breaks down long-chain PFAS. The mixture treated by the plasma reaction unit then enters the reactor, where long-chain PFAS are further broken down, and the proportion of large molecules continues to decrease. The resulting short-chain fluorocarbon intermediate fluid is collected in the reactor's water collection pan 10 and discharged from the water collection pan 10 to the acoustic-electric synergistic advanced oxidation module 2.

[0032] The short-chain fluorocarbon intermediate fluid discharged from the water collection tray 10 of the plasma dual-frequency acoustic wave co-processing module 1 is guided to the acoustic-electric co-processing advanced oxidation module 2 via the flow channel switching pipe 22. The acoustic-electric co-processing advanced oxidation module 2 includes a main tank 20, electrode components, opposing matrix ultrasonic units 29, and flow channel switching pipe 22. The inlet end of the flow channel switching pipe 22 is connected to the upstream reactor, and the outlet end is connected to the main tank 20. The flow channel switching pipe 22 is connected to a shared flow channel opening 21 located at the bottom of the inverted conical uniform water distribution zone 23 at the bottom of the main tank 20. In the water inlet state, the flow channel switching pipe 22 switches to the water inlet path, allowing the short-chain fluorocarbon intermediate fluid to be introduced upward into the inverted conical uniform water distribution zone 23 through the shared flow channel opening 21. The inverted conical uniform water distribution zone 23, with its bottom-to-top expanding geometry, can buffer the incoming kinetic energy, converting turbulent or deflected flow into uniform vertical upward laminar flow, and avoiding airlocks and dead zones in the electrode gaps.

[0033] The electrode assembly includes at least one set of anode plates and cathode plates. An external DC power supply applies an electric field of appropriate strength between the anode and cathode. Under the action of the electric field, a direct electron transfer reaction occurs on the anode surface: short-chain fluorocarbon intermediates are adsorbed and lose electrons, and their carbon-carbon and carbon-fluorine bonds gradually break; simultaneously, indirect free radical oxidation occurs, where water molecules or hydroxide ions adsorbed on the anode surface are oxidized into highly reactive hydroxyl radicals or other reactive oxygen species. These reactive substances form an oxidation reaction zone near the anode surface, actively attacking and breaking down the carbon chain structure of the short-chain fluorocarbon intermediates in the fluid. The hydroxyl radicals gradually convert the carbon-fluorine bonds into free fluoride ions, while simultaneously generating carbon dioxide and water.

[0034] On the cathode surface, oxygen reduction or hydrogen evolution reactions occur, producing trace amounts of hydrogen peroxide, which further assists the oxidative defluorination process. The opposing matrix ultrasonic unit 29 consists of multiple sets of ultrasonic transducers, installed on both sides of the main tank 20 in an opposing arrangement. The ultrasonic waves emitted by the opposing matrix ultrasonic unit 29 generate a violent cavitation effect in the reaction liquid: countless tiny cavitation bubbles release localized high temperatures and pressures upon instantaneous collapse, accompanied by shock waves and microjets. The cavitation effect directly destroys carbon-carbon and carbon-fluorine bonds in fluorocarbon molecules through high-temperature pyrolysis; on the other hand, it promotes the decomposition of water molecules to generate more hydroxyl radicals, compensating for the uneven distribution of hydroxyl radical concentration in the near-electrode region during electrochemical oxidation. Furthermore, the ultrasonic waves continuously clean the electrode surface, effectively suppressing electrode passivation caused by fluoride or carbonate deposition. Simultaneously, the acoustic flow effect enhances convective mass transfer within the reaction zone, continuously transporting short-chain fluorocarbon intermediates to the anode surface and its diffusion layer, avoiding local concentration depletion or dead zones in the flow field.

[0035] In summary, the plasma dual-frequency acoustic wave synergistic processing module 1 of this invention utilizes high-energy plasma physics to break down long-chain PFAS, significantly reducing the proportion of macromolecules. The downstream acoustic-electric synergistic advanced oxidation module 2 leverages the instantaneous coupling of ultrasonic cavitation and electrochemistry to generate high-concentration hydroxyl radicals and clean the electrodes in real time, achieving rapid mineralization and defluorination of short-chain intermediates. The two modules are sequentially connected and progressively advanced, thus completing the efficient conversion from long-chain to short-chain to complete mineralization in a continuous flow, avoiding the accumulation of short-chain products and significantly improving defluorination efficiency and operational stability.

[0036] Furthermore, the flow channel switching fitting 22 is a three-way pipe structure, including an inlet 7, an outlet 19, and a drain outlet. The inlet 7 connects to the outlet end of the collection tray 10, the outlet 19 connects to the shared flow channel opening 21, and the drain outlet is a normally closed interface or connected to an external sludge discharge pipe. The pipe is equipped with a switching valve, such as a ball valve or a directional valve, to selectively guide the water inlet path from the inlet 7 to the outlet 19, or to guide the sludge discharge path from the outlet 19 to the drain outlet. When the system needs to discharge sludge, the pipe is switched to the sludge discharge path, causing the bottom sediment to be discharged in reverse from the same shared flow channel opening 21, restoring water distribution stability.

[0037] In one embodiment, the electrode assembly includes multiple layers of parallel and arranged conductive electrode sheets 26 and an insulating support frame 27. Each conductive electrode sheet 26 is independently and detachably mounted on the insulating support frame 27. The conductive electrode sheets 26 adopt a diamond-shaped mesh structure formed by stretched metal, and have wiring terminals 28 at their top. The horizontal position of the wiring terminals 28 is offset to one side relative to the central axis of the conductive electrode sheet 26, that is, the wiring terminals 28 offset at the top of the conductive electrode sheet 26 are installed in a staggered manner, so that the wiring terminals 28 of adjacent electrodes are arranged in a staggered manner. All wiring terminals 28 are distributed in sections on both sides of the upper end of the entire electrode assembly to expand the wiring space and reduce the risk of short circuit. In addition, the system is also equipped with a monitoring and control system to collect electrical data such as voltage, current and impedance of each conductive electrode sheet 26 in real time. When a certain electrode sheet shows local passivation or impedance abnormality, the fault location can be identified, and the operator can check and assess whether the conductive electrode sheet 26 needs to be replaced.

[0038] Furthermore, the insulating support frame 27 has multiple parallel positioning slots on both sides for inserting conductive electrode plates 26. The spacing between the positioning slots is determined according to the specifications of the insulating support frame 27. The distance between adjacent conductive electrode plates 26 can be adjusted by replacing the insulating support frame 27 with one having a different positioning slot spacing, or by inserting removable spacers of different thicknesses into the same insulating support frame 27. When treating wastewater with high conductivity or high pollutant concentration, an insulating support frame 27 with a larger slot spacing is selected to increase the electrode gap, avoid short circuits, and improve flow channel unobstructedness. When it is necessary to improve the electrochemical oxidation efficiency, an insulating support frame 27 with a smaller slot spacing is selected to shorten the electrode gap, reduce ohmic voltage drop, and increase current density.

[0039] In one embodiment, the conductive electrode sheet 26 includes a plurality of first polarity electrodes and a plurality of second polarity electrodes. The materials of the first polarity electrodes and the second polarity electrodes are independently selected, and at least one of them includes an electrochemically active material with a high oxygen evolution potential, such as a titanium suboxide coated electrode (Ti4O7), a mixed metal oxide coated electrode (MMO), or a boron-doped diamond coated electrode (BDD). At least one of them is composed of a conductive substrate and an electrochemically active coating disposed on at least one surface of the conductive substrate. When the electrode assembly is energized, the surface of the high oxygen evolution potential material performs direct and indirect electrocatalytic deep oxidation and defluorination mineralization reactions on the flowing short-chain fluorine-containing intermediates.

[0040] One of the first polar electrode and the second polar electrode uses a high oxygen evolution potential active material to suppress the ineffective oxygen evolution side reaction of water during electrolysis and improve the utilization efficiency of electrical energy conversion into hydroxyl radicals.

[0041] In this embodiment, one of the first polar electrode and the second polar electrode adopts a composite molding structure with a metal conductive substrate inside. Both opposite plates of the substrate are sprayed with a solidified electrochemical active coating. While ensuring the overall conductivity of the electrode, the electrocatalytic performance is improved by the surface active coating. Combined with the cavitation effect formed by ultrasound in the reaction chamber, continuous descaling can be achieved, making the electrochemical active coating less likely to be covered and deactivated by dirt, which is conducive to maintaining the catalytic performance of the electrode for a long time.

[0042] In one embodiment, the opposing matrix ultrasonic unit 29, symmetrically arranged within the protective chambers on two opposite side walls of the main tank 20, includes multiple sets of ultrasonic transducers 30. The vibration emission surface of each ultrasonic transducer 30 is perpendicularly pointed to the plane of the parallel conductive electrode plates 26, allowing the acoustic axis of the ultrasonic transducer 30 to penetrate the rhomboid mesh structure of the conductive electrode plates 26 and point between adjacent conductive electrode plates 26. The operating frequency of the opposing matrix ultrasonic unit 29 is 20kHz to 50kHz. Ultrasonic energy directly acts on the mixture of the reaction liquid and the microbubbles generated by the electrolytic reaction, using the acoustic field energy to explode the microbubbles and excite the third-stage ultrasonic cavitation reaction. The shock waves and microjets generated by ultrasonic cavitation can in situ strip away the scale and passivation film deposited on the electrode surface. At the same time, the extreme microenvironment generated by the collapse of ultrasonic cavitation can in situ induce the generation of hydroxyl radicals, forming a synergistic effect with electrocatalytic anodic oxidation and accelerating the breaking of carbon-fluorine bonds in short-chain organic compounds.

[0043] The vertically upward laminar flow direction aligns with the natural rising direction of the byproduct microbubbles generated on the surface after the electrode is energized, forming a downstream carrying mechanism. This actively guides the bubbles upward with the rising flow, escaping from the electrode reaction zone 24 and preventing bubble accumulation in the parallel electrode gaps, which could lead to gas lock and interface passivation. Combined with the diamond-shaped mesh structure of the electrode sheet and the horizontally opposing ultrasonic acoustic axes on both sides, mass transfer is enhanced, and a stable heterogeneous catalytic reaction interface is maintained.

[0044] In one embodiment, the bottom of the main tank 20 is provided with an inverted conical uniform water distribution area 23, and the top of the main tank 20 is provided with bidirectional overflow collection tanks 32 on both sides. Multiple V-shaped overflow ports 31 are provided between adjacent inner wall panels. The bottom height of the V-shaped overflow ports 31 is physically anchored to ensure that the mesh reaction zone of the conductive electrode sheet 26 is completely submerged while the wiring end 28 is maintained in the dry protection zone to prevent leakage and corrosion. The defluorinated mineralized fluid obtained after treatment rises with the liquid level, passes through the V-shaped overflow ports 31 and falls into the bidirectional overflow collection tanks 32, and is discharged from the drain port 25.

[0045] Before entering the plasma dual-frequency acoustic synergistic treatment module 1, raw water containing high concentrations of PFAS preferably undergoes conventional pretreatment, including screen interception, flocculation sedimentation, or multi-media filtration, to remove suspended solids, settleable particles, and background chemical oxygen demand or total organic carbon that is easily consumed by conventional oxidants. Pretreatment can reduce the ineffective consumption of hydroxyl radicals generated by subsequent plasma and cavitation by conventional pollutants, allowing the oxidant to target PFAS molecules.

[0046] In one embodiment, the plasma reaction unit includes a swirling-inducing shell 51, an axially adjustable hollow energy mandrel 52, and an axially adjustable expansion nozzle 53. The swirling-inducing shell 51, the hollow energy mandrel 52, and the expansion nozzle 53 together constitute an energy enhancement device 5. The hollow energy mandrel 52 and the expansion nozzle 53 are threaded into the swirling-inducing shell 51, and together they form an annular flow channel with an adjustable engagement depth.

[0047] Specifically, the outer surface of the hollow energy mandrel 52 is provided with a first external thread, and the corresponding inner wall of the swirling induction housing 51 is provided with a first internal thread. The hollow energy mandrel 52 is screwed into the swirling induction housing 51 through the first external thread. The outer surface of the expansion nozzle 53 is provided with a second external thread, and the inner wall of the downstream section of the swirling induction housing 51 is provided with a second internal thread. The expansion nozzle 53 is also screwed into the swirling induction housing 51 through the second external thread. By changing the geometry of the annular flow channel, the flow cross-section and the volume of the confined reaction zone 35 are altered, thereby changing the pressure distribution of the fluid and adjusting the negative pressure intensity within the confined reaction zone 35.

[0048] The annular flow channel forms a confined flow path along the fluid flow direction, consisting of a swirling pretreatment zone 33, a narrowing acceleration zone 34, a confined reaction zone 35, and an expansion and refining zone 36 connected in sequence. The swirling pretreatment zone 33 is located between the hollow energy core 52 and the swirling induction shell 51, and is used to guide the incoming water to form a stable spiral downward swirling flow.

[0049] The narrowing acceleration zone 34, located downstream of the swirling pretreatment zone 33, gradually decreases in the radial radius of the annular channel 6, resulting in a continuous decrease in the fluid's cross-sectional area. The confined swirling film formed along the wall further thins during axial advancement, extending into the confined reaction zone 35. According to the law of conservation of angular momentum, the fluid's tangential velocity significantly increases, generating centripetal acceleration. This concentrates the fluid's kinetic energy, causing it to rotate against the wall. This pre-acceleration configuration ensures sufficient momentum-pressure differential when the fluid enters subsequent regions.

[0050] The restricted reaction zone 35 is located downstream of the narrowing acceleration zone 34. It is mainly affected by the acceleration effect of the narrowing acceleration zone 34. Due to the sudden narrowing of the throat section, a local negative pressure environment is formed, which triggers the liquid film to become unstable and break, and generates primary atomized droplets. The expansion and refining zone 36, located downstream of the confined reaction zone 35, is guided by the gradually increasing radial size of the expansion hollow channel, resulting in further turbulent collisions and secondary refinement, which continuously increases the surface area of ​​the droplets, thereby shortening the diffusion path between the active particles and the target substances in the fluid.

[0051] Driven by the influent power, the fluid to be treated tangentially enters the annular flow channel and flows sequentially through the vortex pretreatment zone 33, the narrowing acceleration zone 34, the confined reaction zone 35, and the expansion and refining zone 36. By varying the flow cross-section of the annular flow channel and the volume of the confined reaction zone 35, precise control can be achieved throughout the entire process of vortex establishment, gradual acceleration, throat flow, negative pressure atomization, and secondary refining of the fluid to be treated. This triggers flash atomization within the confined reaction zone 35, greatly increasing the contact area of ​​the liquid-phase wastewater and improving reaction efficiency.

[0052] Furthermore, the energy enhancement device 5 is preferably made of quartz or other inert materials. Quartz can exert optical penetration characteristics, so that the high-intensity ultraviolet light accompanying the discharge forms multi-path reflection in the flow channel, and produces a photoelectric synergistic effect with the active oxygen and nitrogen substances in the plasma jet.

[0053] In one embodiment, the plasma reaction unit includes a plasma generator 6, which is mounted on the swirling induction housing 51. The plasma generator 6 includes a power supply assembly and a reaction gas assembly. The power supply assembly preferably employs a nanosecond-level high-voltage pulsed power supply with a peak voltage of approximately 20–60 kV to generate high-density non-thermal plasma active material. The reaction gas assembly can provide compressed air, oxygen, argon, or a mixture thereof, depending on the operating conditions. After the gas enters the plasma reaction unit 3, it is ionized under the action of the high-voltage electric field emitted by the power supply assembly to form a highly active jet rich in ozone (O3), hydroxyl radicals (-OH), and superoxide ions. Subsequently, this highly active gaseous material, along with the fluid, is injected into the reactor body 1.

[0054] In one embodiment, the reactor includes a reactor body 3, a central partition assembly, a first ultrasonic component 16, and a second ultrasonic component 18. A gas-liquid mixture ejected from the outlet of the plasma reaction unit 3 is tangentially injected into the first ultrasonic reaction zone 15 within the reactor body 3. The first ultrasonic reaction zone 15 is located between the inner wall of the reactor body 3 and the outer wall of the central partition assembly, and is equipped with the first ultrasonic component 16. The first ultrasonic component 16 emits high-frequency ultrasonic waves of 100-300 kHz, inducing a first cavitation reaction in the gas-liquid mixture. The oxidizing substances generated by cavitation collapse further weaken the bond energy and partially oxidize the long-chain PFAS that have been loosened by the plasma. The fluid travels downward and is redirected by an expanding guide shroud 14 to flow upward into the second ultrasonic reaction zone 17 inside the vertical tube 13.

[0055] The central partition component includes a vertical tube 13 and an expansion guide cover 14 integrally connected to the bottom of the vertical tube 13; the vertical tube 13 and the expansion guide cover 14 are hollow inside, forming a second ultrasonic reaction zone 17. The gas overflowing during the reaction in the first ultrasonic reaction zone 15 is collected and reintroduced into the reactor body 3. The gas is then guided into the second ultrasonic reaction zone 17 by the expansion guide hood 14. The second ultrasonic reaction zone 17 is equipped with a second ultrasonic component 18, which emits low-frequency ultrasonic waves of 20-80 kHz. The low-frequency ultrasonic energy explodes the reintroduced microbubbles, generating a larger-scale second cavitation collapse effect, which performs deep chain breaking on the fluid, causing long-chain PFAS to be efficiently sheared and reducing the proportion of large molecules, forming a short-chain fluorocarbon intermediate fluid.

[0056] After undergoing multiple stages of reaction, the short-chain fluorocarbon intermediate fluid rises with the liquid level, passes through the overflow edge, falls into the top water collection pan 10, and is discharged from the outlet 19.

[0057] In summary, this embodiment utilizes plasma high-energy physical chain breaking to preferentially shear long-chain PFAS, and then combines high-frequency and low-frequency dual-frequency ultrasonic cavitation to achieve a stepped energy attack from physical shearing to deep chain breaking. At the same time, by using a gas collection and micro-recycling mechanism, the exhaust gas is converted into microbubbles and reintroduced into the low-frequency ultrasonic zone for detonation and to generate additional active substances, thereby effectively avoiding the excessive accumulation of short-chain intermediate products and improving energy utilization efficiency.

[0058] In one embodiment, the upper end of the reactor body 3 is provided with at least one mounting interface 4. The number of mounting interfaces 4 can be configured according to the processing scale; the bottom is provided with a gas inlet 11 and a sludge discharge port 12, and the top of the reactor body 3 is provided with a closed top cover 8 and a water collection tray 10. The closed top cover 8 is provided with a gas collection chamber 9, and the gas overflowing during the reaction in the first ultrasonic reaction zone 15 is collected upward into the gas collection chamber 9. The gas collection chamber 9 is connected to the gas inlet 11 through an external conduit to form a gas circulation path. The collected tail gas is atomized into microbubbles by a micronization device and then reintroduced into the reactor body 3.

[0059] A multi-level synergistic continuous treatment method for degrading fluorinated organic pollutants includes the following steps: S1, Plasma Physical Destabilization and Preliminary Oxidation: The raw water to be treated contains long-chain perfluorinated or polyfluoroalkyl substances (PFAS), which have stable molecular structures and extremely high carbon-fluorine bond energies. This step first introduces the fluid into the energy enhancement device 5, which has an annular flow channel composed of a swirling-induced shell 51, a hollow energy core 52, and an expanding nozzle 53. As the fluid passes through the narrow annular channel, it is subjected to intense high shear forces, stretching from a normal fluid state into an extremely thin film or high-speed jet state. This physical process disrupts the aggregation and charge bonds between PFAS molecules and colloids or particles in the water, i.e., physical destabilization, exposing more reaction sites. Simultaneously, the reactive gas in the plasma generator is ionized and excited, producing highly reactive substances such as high-energy electrons, ultraviolet light, ozone, and hydroxyl radicals. These reactive substances come into full contact with the fluid in the thin film state, initiating the preliminary oxidation and chain scission of the PFAS. This step breaks down some long-chain PFAS into relatively shorter molecules, while also partially removing hardness ions from the water that can cause scaling in downstream equipment, thus reducing the load on downstream treatment. The output is called an oxidizing fluid.

[0060] S2, High-frequency ultrasonic cavitation enhances chain breaking and preliminary oxidation; the oxidized fluid obtained in S1 is introduced into the first ultrasonic reaction zone 15. The first ultrasonic reaction zone 15 is equipped with a high-frequency first ultrasonic component 16. When the first ultrasonic component 16 propagates in the liquid, it generates periodic compression and stretching. Due to the presence of microbubbles generated by the aforementioned plasma reaction unit in the oxidized fluid, these bubbles are suspended in this zone as cavitation nuclei, significantly reducing the initiation threshold of acoustic cavitation. When the sound pressure is strong enough, a large number of tiny cavitation bubbles (cavitation nuclei) are formed inside the liquid. The bubbles grow in the negative pressure phase of the acoustic wave and rapidly implode in the positive pressure phase, i.e., the cavitation reaction environment. The collapse of the cavitation bubbles releases powerful shock waves and microjets, and generates local high temperature and high pressure, while simultaneously splitting water molecules to generate new hydroxyl radicals. In the cavitation reaction environment, the long-chain PFAS that have been loosened by plasma undergoes further physical shearing and bond energy weakening, achieving deeper chain breaking and partial oxidation. The fluid treated in S2 is the first treated fluid, and its molecular weight has been significantly reduced.

[0061] S3, Preparation for upflow guidance and gas recycling; After S2, the first processed fluid is driven downward to the bottom of the reactor by the liquid level difference and hydrodynamics, then bypasses the expansion guide shroud 14 and turns upward to enter the second ultrasonic reaction zone 17. The expansion guide shroud 14 plays the role of fluid deflection and guidance, so that the fluid forms a stable upflow in the second ultrasonic reaction zone 17.

[0062] S301, Gas-phase recycling and micronization: During the cavitation reaction in the first ultrasonic reaction zone 15, some unreacted or newly generated gases, such as unconsumed ozone and oxygen, will overflow from the liquid and rise into the sealed top cover 8 of the reactor, where they are captured by the gas collection chamber 9. Direct emission would result in energy waste and potential air pollution. Therefore, this step involves drawing out the exhaust gas and using a gas micronization device (e.g., a microporous aeration disc, a Venturi jet, or an ultrasonic aerator) to cut and disperse it into extremely small microbubbles. These microbubbles are then reinjected into the second ultrasonic reaction zone 17 through the gas inlet 11 at the bottom of the reactor body. This achieves the recycling and reuse of gaseous active substances, preventing the leakage of harmful gases.

[0063] In step S302, low-frequency ultrasound is used to synergistically enhance deep chain scission, generating short-chain fluorocarbon intermediates. Within the second ultrasonic reaction zone 17, reintroduced microbubbles are thoroughly mixed with the first treatment fluid, forming a gas-liquid mixture. Subsequently, the second ultrasonic component 18 applies 20-80kHz low-frequency ultrasound. Low-frequency ultrasound has stronger mechanical impact and cavitation intensity, easily bursting the microbubbles. The collapse of the bubbles releases stronger shock waves, shear forces, and free radicals, performing deep chain scission on the remaining medium- and long-chain PFAS in the first treatment fluid, minimizing the proportion of large molecules. After this step, the PFAS in the fluid has been efficiently converted into short-chain fluorocarbon intermediates with very small molecular weights (such as C2-C6 perfluorocarboxylic acids or sulfonic acids). As the liquid level rises, the short-chain fluorocarbon intermediates overflow from the top of the vertical tube 13 into the collection tray 10, ready for the next stage of treatment.

[0064] S4, downstream acoustic-electric synergistic defluorination and mineralization: Short-chain fluorocarbon intermediates discharged from the water collection pan 10 are introduced into the downstream main tank 20. First, they pass through an inverted conical uniform water distribution zone 23: This zone gradually expands from bottom to top, smoothly converting the turbulent kinetic energy of the incoming water into a vertically upward uniform laminar flow, eliminating flow deviation and dead zones, and ensuring the fluid enters the upper electrode reaction zone 24 at a balanced speed. Within the electrode reaction zone 24, multiple layers of parallel-arranged conductive electrode plates 26 are energized. Their surfaces, equipped with active materials possessing high oxygen evolution potential, directly and indirectly catalytically oxidize the short-chain fluorocarbon intermediates, achieving complete breakage of carbon-fluorine bonds and mineralization of fluoride ions. Simultaneously, symmetrically installed opposing matrix ultrasonic units 29 emit 20-50kHz ultrasonic waves towards the electrode plate plane. Their acoustic axes can penetrate the diamond-shaped mesh of the electrode plates, directly acting on the electrode surface. Ultrasonic cavitation breaks down microbubbles generated by electrolysis, preventing them from accumulating in the electrode gaps and forming gas locks. Furthermore, the cavitation shock waves in situ strip away any scale or passivation film that may have deposited on the electrode surface, and further generate free radicals that synergistically interact with electrochemical oxidation. The treated defluorinated mineralization fluid rises with the liquid level, passes through the V-shaped overflow port 31, falls into the bidirectional overflow collection tank 32, and is then discharged from the system.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A multi-order level synergistic continuous treatment system for degrading fluorine-containing organic pollutants, characterized in that, include: A plasma dual-frequency acoustic wave co-processing module is used to convert PFAS into short-chain fluorocarbon intermediates; The plasma dual-frequency acoustic wave synergistic processing module includes a plasma reaction unit and a reactor; the plasma reaction unit is installed in the reactor, and the plasma reaction unit breaks the carbon-fluorine bonds of long-chain PFAS molecules and reduces the proportion of macromolecules, causing them to degrade and transform into short-chain fluorocarbon intermediates. An acoustic-electric synergistic advanced oxidation module, connected to and located downstream of the plasma dual-frequency acoustic synergistic processing module, performs defluorination and mineralization on short-chain fluorocarbon intermediates. The acoustic-electric synergistic advanced oxidation module includes a main tank, electrode assemblies, opposing matrix ultrasonic units, and flow channel switching pipes. The electrode assemblies are fixedly disposed inside the main tank, and the opposing matrix ultrasonic units are symmetrically installed on two opposite sidewalls of the main tank with their ultrasonic emission direction pointing towards the electrode assemblies. The outlet end of the flow channel switching pipe is connected to the main tank, and the inlet end is connected to the reactor.

2. The multi-order level synergistic continuous treatment system for degrading fluorine-containing organic pollutants according to claim 1, characterized in that, The electrode assembly includes an insulating support frame and multiple parallel conductive electrode sheets. Each conductive electrode sheet is independently and detachably mounted on the insulating support frame. The mesh structure of the conductive electrode sheet is a diamond-shaped mesh structure formed by stretching a metal substrate. The top of the conductive electrode sheet is provided with a wiring end. In a horizontal position, the wiring end is located on one side of the central axis of the conductive electrode sheet.

3. The multi-level synergistic continuous treatment system for degrading fluorinated organic pollutants according to claim 2, characterized in that, The conductive electrode sheet includes a first polar electrode and a second polar electrode; the materials of the first polar electrode and the second polar electrode are independently selected, and at least one of them includes an electrochemically active material with a high oxygen evolution potential; at least one of the first polar electrode and the second polar electrode is composed of a conductive substrate and an electrochemically active coating disposed on the opposite surface of the conductive substrate.

4. The multi-order level synergistic continuous treatment system for degrading fluorine-containing organic pollutants according to claim 2, characterized in that, The opposing matrix ultrasonic unit includes two sets of protective chambers symmetrically arranged on opposite sidewalls of the main tank. Each protective chamber contains multiple sets of ultrasonic transducers, and the vibration emission surface of any ultrasonic transducer is perpendicularly pointed to the plane of the parallel conductive electrode sheets.

5. The multi-order level synergistic continuous treatment system for degrading fluorine-containing organic pollutants according to claim 1, characterized in that, The plasma reaction unit includes a swirling induction shell, an axially adjustable hollow energy mandrel, and an axially adjustable expansion nozzle; the hollow energy mandrel and the expansion nozzle are threaded into the swirling induction shell to form an annular flow channel with adjustable swirl depth.

6. A multi-order degradation system for synergistically and continuously treating fluorine-containing organic pollutants according to claim 5, characterized in that, The plasma reaction unit further includes a plasma generator, which is installed in the swirling induced housing. The plasma generator includes a power supply assembly and a reaction gas assembly. The power supply assembly is used to provide discharge energy, and the reaction gas assembly is used to provide reaction gas, which includes one of the following: air, oxygen, argon, or other inert gases or combinations thereof.

7. The multi-order level synergistic continuous treatment system for degrading fluorine-containing organic pollutants according to claim 2, characterized in that, The bottom of the main tank is provided with an inverted cone-shaped uniform water distribution area, and the top of the main tank is provided with bidirectional overflow collection tanks on both sides. The inner wall of the collection tank is provided with multiple V-shaped overflow ports. The bottom height of the overflow ports is higher than the conductive electrode sheet and lower than the wiring end.

8. The multi-order level synergistic continuous treatment system for degrading fluorine-containing organic pollutants according to claim 1, characterized in that, The reactor includes a reactor body, a central partition assembly, a first ultrasonic component, and a second ultrasonic component. The central partition assembly is installed inside the reactor body and forms a first ultrasonic reaction zone between itself and the inner wall of the reactor body. The central partition assembly includes a vertical tube and an expansion guide cover integrally connected to the bottom of the vertical tube. The vertical tube and the expansion guide cover are hollow inside, forming a second ultrasonic reaction zone. The first ultrasonic component is installed in the first ultrasonic reaction zone, and the second ultrasonic component is installed in the second ultrasonic reaction zone.

9. The multi-stage synergistic continuous treatment system for degrading fluorine-containing organic pollutants according to claim 8, characterized in that, The upper part of the reactor body is provided with at least one installation interface, and the bottom of the reactor body is provided with a gas inlet and a sludge outlet. The top of the reactor body is provided with a closed top cover and a water collection tray. The closed top cover is provided with a gas collection chamber. The gas collection chamber is connected to the gas inlet through a gas micronization device to form a gas circulation path.

10. A multi-level synergistic continuous treatment method for degrading fluorinated organic pollutants, applicable to the multi-level synergistic continuous treatment system for degrading fluorinated organic pollutants as described in any one of claims 1-9, characterized in that, Includes the following steps: S1, the fluid containing long-chain PFAS to be treated is introduced into the plasma reaction unit, high shear force is applied to the fluid to perform physical destabilization, and plasma is applied to the fluid to make the fluid and plasma come into contact with active substances, so as to perform preliminary oxidation treatment on the fluid and obtain oxidized fluid. S2, introduce the oxidizing fluid into the reactor, and apply the first high-frequency ultrasonic energy to the oxidizing fluid in the reactor to form a first cavitation reaction environment. In the first cavitation reaction environment, the oxidizing fluid undergoes physical chain breaking and preliminary oxidation to obtain the first processed fluid after chain breaking treatment. S3: Collect at least a portion of the gas generated in the first cavitation reaction environment of S2, and convert the collected gas into microbubbles, then reintroduce it into the reactor for recycling; the microbubbles form a gas-liquid mixture with the first processing fluid, and apply second low-frequency ultrasonic energy to the gas-liquid mixture to further oxidize the pollutants in the first processing fluid to obtain a short-chain fluorocarbon intermediate; S4, the short-chain fluorocarbon intermediate is introduced into the acoustic-electric synergistic advanced oxidation module and flows vertically upward into the region of the electrode assembly and the opposing matrix ultrasonic unit. The electrode assembly is energized to carry out an electrochemical oxidation reaction, while the opposing matrix ultrasonic unit emits ultrasonic waves to obtain a defluorinated mineralization fluid. The defluorinated mineralization fluid rises with the liquid level and is discharged.

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