A rare earth synergistic electroflocculation defluoridation system, control method and application

Abstract

The application discloses a rare earth synergic electric flocculation fluorine removal system, a control method and application, and an anode plate is composed of a metal material doped with rare earth elements. The application adopts a pneumatic flushing unit for non-contact removal on the surface of the anode plate, and adopts a flexible cleaning unit for contact cleaning on the surface of a cathode plate, so that differential cleaning of the anode plate and the cathode plate is realized. The pneumatic flushing unit sprays gas to the surface of the anode plate through a gas spraying assembly, and uses bubble turbulence to exert a flushing and stripping effect on a rare earth fluoride deposition layer on the surface of the anode plate, so that the deposition layer is effectively removed, and mechanical wear of the expensive rare earth anode plate is completely avoided. The application effectively solves the problem that the surface of the anode plate is passivated due to rapid accumulation of the rare earth fluoride deposition layer in the process of electric flocculation fluorine removal of the rare earth doped anode plate, and long-term stability of fluorine removal efficiency of the system is ensured.

Description

Technical Field

[0001] This application belongs to the technical field of wastewater treatment equipment, specifically relating to a rare earth synergistic electrocoagulation defluorination system, control method, and application for preventing passivation. Background Technology

[0002] Electrocoagulation is a method for treating fluoride-containing wastewater using electrochemical principles. It involves applying direct current to the anode plate to oxidize the metal anolyte, dissolving metal ions (such as Al). 3+ Fe 3+ These metal ions (such as aluminum and ferroelectric coagulation) hydrolyze in water to form flocs, which remove fluoride ions from wastewater through adsorption and co-precipitation. This technology has advantages such as simple operation, low reagent dosage, and low sludge production, and has good application prospects in the treatment of industrial fluoride-containing wastewater. However, in conventional aluminum and ferroelectric coagulation processes, the flocs produced have limited specific adsorption capacity for fluoride ions. To achieve deep fluoride removal, it is often necessary to extend the electrolysis time, leading to increased energy consumption. At the same time, under continuous electrolysis conditions, the precipitated substances tend to adhere tightly to the anode surface, hindering the continuous dissolution of metal ions, further limiting the improvement of fluoride removal efficiency.

[0003] To improve defluoridation efficiency, the strong chemical affinity between rare earth elements and fluoride ions is utilized to induce a chemical precipitation reaction between soluble rare earth salts and fluoride ions, resulting in extremely low effluent fluoride concentrations. However, during this process, the dissolved rare earth ions react in situ with fluoride ions on the anode plate surface, gradually accumulating into a deposit layer. This deposit layer, covering the active sites on the anode plate, increases the inter-electrode resistance, leading to higher energy consumption and hindering further oxidation and dissolution of the anode metal. Consequently, the release rate of metal and rare earth ions decreases, affecting defluoridation efficiency. Therefore, there is an urgent need for a system for treating fluoride-containing wastewater that can balance deep defluoridation, low operating costs, and stable electrode performance. Summary of the Invention

[0004] This application aims to provide an anti-passivation electrocoagulation defluorination system and its control method. It employs an anode plate doped with rare earth elements, which can release rare earth ions in situ during electrocoagulation. Utilizing the extremely low solubility product of rare earth fluorides, it achieves deep chemical precipitation removal of fluoride ions, thereby improving defluorination efficiency and avoiding the continuous addition of external rare earth salt reagents, thus reducing reagent costs. Simultaneously, a pneumatic flushing unit directionally injects gas onto the anode plate surface to form bubble turbulence, enabling real-time and effective hydraulic flushing of the anode plate surface. This promptly removes the rare earth fluoride deposit layer generated during electrocoagulation, maintaining the cleanliness of the anode plate's active sites and preventing increased inter-electrode resistance and energy consumption due to deposit layer coverage. This ensures stable and continuous dissolution of anode metal and rare earth ions, thus balancing deep defluorination effect, low operating cost, and long-term stable electrode performance.

[0005] To solve the above-mentioned technical problems, this application is implemented as follows: In a first aspect, embodiments of this application propose a rare-earth synergistic electrocoagulation defluorination system to prevent passivation, the system comprising: The reaction tank (1), the anode group (2), the cathode group (3) and the pneumatic scouring unit (4); The reaction tank (1) is provided with an inlet (11) and an outlet (12); the inlet (11) and the outlet (12) are arranged axially on both sides of the reaction tank (1); The anode group (2) includes multiple anode plates (21), and the cathode group (3) includes multiple cathode plates (31); the anode plates (21) and the cathode plates (31) are alternately arranged in the reaction tank (1) along the axial direction; the anode plates (21) and the cathode plates (31) are respectively connected to a DC power supply (5); the anode plates (21) are composed of metal materials doped with rare earth elements; The pneumatic flushing unit (4) includes at least one jet assembly (41) and a gas delivery assembly (42) located in the reaction tank (1); wherein the jet assembly (41) is connected to the gas delivery assembly (42), the jet assembly (41) is located between the anode plate (21) and the cathode plate (31), and the jet nozzle of the jet assembly (41) is disposed opposite to the side of the anode plate (21) facing the water inlet (11); The reaction tank (1) is configured to introduce fluoride-containing wastewater into the tank through the inlet (11) and discharge water treated by electrocoagulation through the outlet (12); The anode group (2) and the cathode group (3) are configured to perform electrocoagulation treatment in the reaction tank (1) after being energized, so as to remove fluoride from the fluoride-containing wastewater. The pneumatic flushing unit (4) is configured to deliver gas to the jet assembly (41) through the gas supply assembly (42). The jet assembly (41) jets gas toward the anode plate (21) through the jet nozzle. The ejected gas forms bubble turbulence in the fluoride-containing wastewater. The bubble turbulence flushes and peels off the rare earth fluoride deposit layer formed on the surface of the anode plate (21) during the electrocoagulation process to obtain a clean anode plate (21).

[0006] Optionally, the gas delivery assembly (42) includes an aeration line (421) and at least one branch line (422). The aeration pipeline (421) is located inside the reaction tank (1); The branch pipe (422) is connected to the aeration pipe (421), and the branch pipe (422) extends radially into the gap between the anode plate (21) and the cathode plate (31); The jet assembly (41) is disposed on the branch pipe (422); The aeration line (421) is configured to distribute the gas to the branch line (422). The branch pipe (422) is configured to spray the received gas through the nozzle of the jet assembly (41) toward the anode plate (21) to form the bubble turbulence in the fluoride-containing wastewater, the bubble turbulence being used to flush and strip the rare earth fluoride deposit layer on the surface of the anode plate (21).

[0007] Optionally, the distance between the jet nozzle of the jet assembly (41) and the anode plate (21) is 6mm-10mm.

[0008] Optionally, the system further includes a flexible cleaning unit (6). The flexible cleaning unit (6) includes a rotating shaft (61), a drive assembly (62), and a flexible brush (63). The rotating shaft (61) is arranged in the reaction tank (1) along the axial direction. The rotating shaft (61) passes through the anode plate (21) and the cathode plate (31) and is electrically insulated from the anode plate (21) and the cathode plate (31). One end of the rotating shaft (61) is connected to the drive assembly (62). The drive assembly (62) is located outside the reaction tank (1) near the outlet (12); The flexible brush (63) is fixedly connected to the rotating shaft (61). The side of the flexible brush (63) away from the rotating shaft (61) extends into the gap between the anode plate (21) and the cathode plate (31). The flexible brush (63) is arranged opposite to the side of the cathode plate (31) facing the outlet (12). The drive assembly (62) is configured to drive the rotating shaft (61) to rotate; The rotating shaft (61) is configured to drive the flexible brush (63) to perform a circular motion under the drive of the driving component (62); The flexible brush (63) is configured to rotate and clean the scale layer on the surface of the cathode plate (31) to obtain a clean cathode plate (31).

[0009] Optionally, the anode plate (21) is provided with at least one first liquid passage hole (22), and the cathode plate (31) is provided with at least one second liquid passage hole (32). In the axial direction, the orthographic projection of the first liquid passage (22) on the plane does not overlap with the orthographic projection of the second liquid passage (32) on the plane.

[0010] Optionally, the length of the branch pipe (422) is ≤ two-thirds of the length of the anode plate (21).

[0011] Optionally, the nozzle diameter of the jet assembly (41) is 0.1mm-5mm.

[0012] Optionally, the system further includes a control unit (7). The control unit (7) includes a sensor (71) and a controller (72). The gas delivery assembly (42) includes an aeration pipeline (421), at least one branch pipeline (422), an air compressor (423), and a gas source control valve (424); the aeration pipeline (421) is connected to the branch pipeline (422), and the aeration pipeline (421), the gas source control valve (424), and the air compressor (423) are connected in sequence. The sensor (71) is communicatively connected to the power supply circuits of the anode group (2) and the cathode group (3). The controller (72) is communicatively connected to the sensor (71) and the gas source control valve (424) via signal lines; The sensor (71) is configured to collect inter-electrode voltage or inter-electrode impedance signals in real time and transmit them to the controller (72) as electrical parameter signals. The controller (72) is configured to control the operating state of the gas source control valve (424) based on the comparison result of the electrical parameter signal with a first threshold and a second threshold, so as to regulate the gas flow rate delivered from the air compressor (423) to the aeration pipeline (421) via the gas source control valve (424).

[0013] Secondly, embodiments of this application provide a method for controlling the depth of electrocoagulation defluorination to prevent passivation. This method is applicable to the electrocoagulation defluorination system described in the first aspect, and includes: The sensor (71) collects the inter-electrode voltage or inter-electrode impedance signal in real time and transmits it to the controller (72) as an electrical parameter signal. When the controller (72) determines that the electrical parameter signal is lower than the first threshold, it controls the gas source control valve (424) to close, so that the jet assembly (41) stops jetting to the anode plate (21); or, the controller (72) controls the gas source control valve (424) to operate in a preset low-pressure intermittent mode, so that the jet assembly (41) intermittently jets to the anode plate (21). When the controller (72) determines that the electrical parameter signal is between the first threshold and the second threshold, it controls the gas source control valve (424) to operate continuously at the first air pressure, so that the jet assembly (41) continuously jets air onto the anode plate (21) at the first air pressure. When the controller (72) determines that the electrical parameter signal is higher than the second threshold, it controls the gas source control valve (424) to operate continuously at a second pressure higher than the first pressure, so that the jet assembly (41) continuously jets gas onto the anode plate (21) at the second pressure until the electrical parameter signal falls back to the preset reference value. After that, the controller (72) controls the gas source control valve (424) to close or switch to the low-pressure intermittent mode. Wherein, the benchmark value is less than or equal to the first threshold.

[0014] Thirdly, this application provides an application of a rare earth synergistic electrocoagulation defluorination system to prevent passivation. The system is as described in the first aspect, and the system is applied to a case where the anode plate (21) is composed of a metal material doped with rare earth elements. The system includes a pneumatic scouring unit (4) configured to perform non-contact bubble turbulence scouring on the surface of the anode plate (21).

[0015] Beneficial technical effects: In the embodiments of this application, a rare-earth-doped anode plate is used, and rare-earth ions are released in situ through electrocoagulation to achieve deep defluorination. The system is equipped with a pneumatic flushing unit, in which an air jet assembly is positioned between the anode plate and the cathode plate, with the air jet nozzle facing the side of the anode plate towards the water inlet. During the electrocoagulation process, the gas supply assembly delivers gas to the air jet assembly. The compressed gas ejected forms bubble turbulence and microjets on the surface of the anode plate. This non-contact bubble flushing effectively removes the rare-earth fluoride deposit layer on the surface of the anode plate, thereby restoring the cleanliness of the active sites on the anode plate, inhibiting the increase in inter-electrode resistance and energy consumption, and ensuring the continuous and stable dissolution of metal ions and rare-earth ions. At the same time, this non-contact cleaning method completely avoids mechanical wear on the expensive rare-earth anode plate, thereby extending the service life of the anode plate and reducing operating costs. The system of this application can adapt to the long-term stable operation requirements of rare-earth-doped anode plates and can be applied to the deep treatment of fluoride-containing wastewater in industries such as semiconductors and photovoltaics.

[0016] In the embodiments of this application, the jetting assembly is positioned below the bottom surface of the anode plate and sprays upwards. The bubbles rise naturally under their own buoyancy, impacting the bottom surface of the anode plate. Their peeling direction is consistent with the natural shedding direction of the deposited layer. This arrangement results in higher cleaning efficiency, and the bubble flushing covers a large and uniform area, eliminating cleaning dead zones and effectively addressing the rapid regeneration rate of rare earth fluoride deposits. During their ascent, the bubbles also agitate and flotate the wastewater between the plates, thereby promoting the formation and separation of flocs and generating synergistic process gains in the defluorination process.

[0017] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0018] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the structure of the rare earth synergistic electrocoagulation defluorination system for preventing passivation proposed in the embodiments of this application; Figure 2 This is a partial cross-sectional view of the pneumatic flushing unit and the flexible cleaning unit in the rare earth synergistic electrocoagulation defluorination system for passivation prevention proposed in the embodiments of this application; Figure 3 This is a front view of the anode plate and cathode plate proposed in the embodiments of this application; Figure 4 This is a top view of the anode plate and cathode plate proposed in the embodiments of this application; Figure 5 This is a flowchart of the rare earth synergistic electrocoagulation defluorination control method for preventing passivation proposed in the embodiments of this application.

[0019] Figure label: 1. Reaction tank; 11. Inlet; 12. Outlet; 2. Anode assembly; 21. Anode plate; 22. First liquid passage hole; 3. Cathode assembly; 31. Cathode plate; 32. Second liquid passage hole; 4. Pneumatic flushing unit; 41. Jet assembly; 42. Air supply assembly; 421. Aeration pipeline; 422. Branch pipeline; 423. Air compressor; 424. Air source control valve; 5. DC power supply; 6. Flexible cleaning unit; 61. Rotating shaft; 62. Drive assembly; 63. Flexible brush; 64. Brush holder connecting arm; 7. Control unit; 71. Sensor; 72. Controller; 8. Solid-liquid separation unit. Detailed Implementation

[0020] The embodiments of this application will now be described in detail. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0021] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "multiple" means two or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0022] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0023] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0024] Among related technologies, electrocoagulation is a method for treating fluoride-containing wastewater using electrochemical principles. Current research has found that rare earth elements have an extremely strong chemical affinity for fluoride ions, and the solubility of rare earth fluorides (such as LaF3 and CeF3) is extremely low (e.g., the Ksp of LaF3 is approximately 10). -19 The rare earth element concentration (on the order of magnitude 6) is much lower than that of conventional metal fluorides. Based on this chemical property, if rare earth elements are incorporated into the electrocoagulation anode plate material, the anode will oxidize and dissolve rare earth ions under the action of direct current. These rare earth ions can directly react with fluoride ions in the wastewater to form rare earth fluoride precipitates. Combined with the synergistic effect of metal ion hydrolysis and flocculation, the defluorination efficiency can be significantly improved.

[0025] However, this technical approach faces a significant challenge in practical applications: the dissolved rare earth ions react in situ with fluoride ions on the anode plate surface, generating rare earth fluorides that gradually accumulate and form a deposition layer. Due to the extremely low solubility of rare earth fluorides, this deposition layer regenerates very quickly, and even after removal, it will redeposit and form a new covering layer within a short time. This deposition layer, covering the active sites on the anode plate, increases the inter-electrode resistance, leading to increased energy consumption and hindering further oxidation and dissolution of the anode metal. This reduces the release rate of metal ions and rare earth ions, thus affecting the fluoride removal efficiency.

[0026] Several attempts have been made in the existing technology to address the passivation problem of electrocondensation plates, for example: Patent No. CN104030412B discloses a three-dimensional electrocoagulation device that uses a platinum-iridium anode and an iron-aluminum particle intermediate electrode to treat fluoride-containing wastewater. However, its anode plate material does not contain rare earth elements, so it cannot achieve the synergistic fluoride removal effect of rare earth elements. At the same time, its platinum-iridium anode is generally used for electrocatalytic oxidation, which has limited ability to remove fluoride ions. The intermediate iron-aluminum particle electrode is prone to scaling and passivation during operation, and it is difficult to clean online after passivation, which affects the long-term stable operation of the device. Patent No. CN218988923U discloses a pulsed electrocoagulation treatment device that uses a pulsed square wave power supply to replace a DC power supply to suppress electrode passivation. However, in actual operation, the scale on the electrode surface is dense and regenerates quickly. It is difficult to remove the scale effectively by simply reversing the polarity, resulting in poor cleaning effect. Moreover, the pulsed current reduces the overall treatment efficiency during intermittent power outages. Patent No. CN223950800U discloses an electrocoagulation device that uses uniformly sized brush bristles to clean the surfaces of the cathode and anode plates. However, because the anode plate is made of a rare-earth element-containing material, its cost is significantly higher than that of ordinary metal plates. Using a contact-type brush cleaning method causes continuous mechanical wear on the anode plate, accelerating the consumption of this expensive plate. This is especially problematic when the regeneration rate of the deposited layer is high, requiring frequent cleaning operations, making the cumulative wear caused by contact cleaning even more pronounced.

[0027] Based on the problems existing in related technologies, this application proposes a rare earth synergistic electrocoagulation defluorination system to prevent passivation, such as... Figure 1 As shown, the system includes: The reaction tank consists of 1, 2, 3, and 4, a pneumatic scouring unit. The reaction tank 1 is provided with an inlet 11 and an outlet 12; the inlet 11 and the outlet 12 are arranged axially on both sides of the reaction tank 1; The anode group 2 includes multiple anode plates 21, and the cathode group 3 includes multiple cathode plates 31; the anode plates 21 and cathode plates 31 are alternately arranged in the reaction tank 1 along the axial direction; the anode plates 21 and cathode plates 31 are respectively connected to a DC power supply 5; the anode plates 21 are composed of a metallic material doped with rare earth elements; The pneumatic flushing unit 4 includes at least one jet assembly 41 and a gas delivery assembly 42 located within the reaction tank 1; wherein the jet assembly 41 is connected to the gas delivery assembly 42, the jet assembly 41 is located between the anode plate 21 and the cathode plate 31, and the jet nozzle of the jet assembly 41 is arranged opposite to the side of the anode plate 21 facing the water inlet 11. The reaction tank 1 is configured to introduce fluoride-containing wastewater into the tank through the inlet 11 and discharge water treated by electrocoagulation through the outlet 12. The anode group 2 and the cathode group 3 are configured to perform the electrocoagulation treatment in the reaction tank 1 after being energized, so as to remove fluoride from the fluoride-containing wastewater. The pneumatic flushing unit 4 is configured to deliver gas to the jet assembly 41 through the gas supply assembly 42. The jet assembly 41 jets gas toward the anode plate 21 through the jet nozzle. The ejected gas forms bubble turbulence in the fluoride-containing wastewater. The bubble turbulence flushes and peels off the rare earth fluoride deposit layer formed on the surface of the anode plate 21 during the electrocoagulation process to obtain a clean anode plate 21.

[0028] It should be noted that reaction tank 1 is the main container of the system, providing space for the electrocoagulation reaction; reaction tank 1 is a rectangular corrosion-resistant container, and the material is selected from PP, PVC and stainless steel with an anti-corrosion lining. like Figure 1 As shown, the inlet 11 is located at the bottom or lower part of the reaction tank 1, and the outlet 12 is located at the upper part or top of the reaction tank 1. The inlet 11 and the outlet 12 are arranged axially, forming a bottom-up flow pattern, so that the fluoride-containing wastewater enters from the inlet 11 and flows axially through the gaps between each electrode plate in sequence. After being fully treated, it is discharged from the outlet 12, thereby extending the residence path of the wastewater in the electric field and improving the defluorination efficiency.

[0029] It should be noted that fluoride-containing wastewater contains fluoride ions (F). - The industrial wastewater enters the tank through the inlet 11 located at the bottom of the reaction tank 1, and flows sequentially through the electric field region between the alternating anode plates 21 and cathode plates 31 in the axial flow channel to complete the subsequent defluorination treatment. Electrocoagulation is a comprehensive defluorination process that occurs within the reaction tank 1, where a DC power supply 5 powers the anode group 2 and cathode group 3. The anode plate 21 oxidizes and dissolves metal ions and rare earth ions. The metal ions are used for flocculation, while the rare earth ions react directly with fluoride ions to form rare earth fluoride precipitates with extremely low solubility. The combination of these two processes achieves deep defluorination. During electrocoagulation, the pneumatic scouring unit 4 sprays air onto the surface of the anode plate 21 through the jet assembly 41. The resulting turbulent bubbles are used to strip away the rare earth fluoride deposits on the anode plate 21, maintaining the activity of the anode plate 21.

[0030] The water body after electrocoagulation treatment is fluoride-containing wastewater that has undergone electrocoagulation treatment in reaction tank 1. The fluoride ions in the water body have reacted with rare earth ions and flocs and been greatly removed, resulting in a significant reduction in fluoride concentration.

[0031] In some embodiments of this application, the anode plate 21 is made of a metallic material doped with rare earth elements, wherein the rare earth elements are selected from at least one of lanthanum, cerium, praseodymium, neodymium, gadolinium, and yttrium; The mass percentage of rare earth elements in the anode plate 21 is 3.5%-15%; for example, the mass percentage of rare earth elements in the anode plate 21 is one or any two of the following values: 3.5%, 4%, 6%, 8%, 10%, 12% and 15%; the anode plate 21 doped with rare earth elements can continuously release rare earth ions during electrolysis. Therefore, during the electrocoagulation process, not only are the metal ions (such as aluminum ions or iron ions) dissolved from the anode plate 21 used for flocculation, but the rare earth ions are also used to react with fluoride ions to generate rare earth fluoride precipitates. The combination of the two achieves deep defluorination.

[0032] The cathode plate 31 is made of titanium, iron or stainless steel. After being energized, a reduction reaction occurs on the surface of the cathode plate 31 (such as the electrolysis of water to produce hydrogen and hydroxide ions), providing the necessary electrochemical reaction pairs for the electrocoagulation process.

[0033] In some embodiments of this application, such as Figure 1 As shown, the anode plate 21 and the cathode plate 31 are arranged alternately in the axial direction, so that each pair of adjacent anode plates 21 and cathode plates 31 forms an independent electrolysis area, thereby increasing the total area of ​​the plates and the contact area with the wastewater, making the electric field distribution more uniform, ensuring that the wastewater can be effectively treated when it flows through the gaps between the plates, and making the electrocoagulation treatment more thorough and efficient.

[0034] In some embodiments of this application, the number of anode plates 21 is one or more, the number of cathode plates 31 is one or more, and the difference between the number of anode plates 21 and the number of cathode plates 31 is 1. like Figure 1 As shown, the system has a total of 5 anode plates 21 and 4 cathode plates 31, which are arranged alternately from bottom to top in the order of anode plate 21-cathode plate 31-anode plate 21-cathode plate 31.

[0035] In some embodiments of this application, such as Figure 1 As shown, the vertical distance in the axial direction between adjacent anode plates 21 and cathode plates 31 is 10mm-30mm; for example, the vertical distance in the axial direction between adjacent anode plates 21 and cathode plates 31 is one or any two of 10mm, 15mm, 20mm, 25mm and 30mm; this spacing range ensures that a uniform and stable electric field is formed between anode plates 21 and cathode plates 31 and that an effective current density is maintained, while providing sufficient layout space and bubble development space for the jet assembly 41 of the pneumatic scouring unit 4, so that the ejected compressed gas can fully form bubble turbulence in the inter-electrode liquid phase, and produce a strong and uniform stripping effect on the rare earth fluoride deposition layer on the surface of anode plate 21.

[0036] It should be noted that the pneumatic flushing unit 4 uses compressed gas to form bubble turbulence in fluoride-containing wastewater to perform non-contact flushing on the surface of the anode plate 21, which promptly removes the generated rare earth fluoride deposit layer, keeps the active sites on the surface of the anode plate 21 clean, and prevents the accumulation of deposit layer from causing an increase in inter-electrode resistance and hindering the dissolution of metal ions.

[0037] The jet assembly 41 is located inside the reaction tank 1 and in the gap between the anode plate 21 and the cathode plate 31. This arrangement eliminates the need to increase the volume of the reaction tank 1. The jet assembly 41 is provided with a jet nozzle, which is used to spray the gas delivered by the gas delivery assembly 42 into the surface of the anode plate 21 in the form of bubbles. The sprayed gas can directly act on the target anode plate 21. like Figure 1 As shown, the side of the anode plate 21 facing the inlet 11 is the bottom wall of the anode plate 21 in the axial direction. The bottom wall is the water-facing surface of the anode plate 21, which is the first surface that the wastewater comes into contact with and the part where the rare earth fluoride deposit layer is most likely to grow. The jet nozzle sprays directly onto this surface, which can directly act the bubble turbulence on the deposit layer generation area. This results in a short flushing distance, low energy loss, and high removal efficiency. The gas delivery assembly 42 is connected to the jet assembly 41 and is used to deliver compressed gas to the jet assembly 41 to provide the power source required to form bubble turbulence. The gas delivery assembly 42 can flexibly adjust the gas supply pressure and on / off state to achieve different scouring modes.

[0038] In some embodiments of this application, such as Figure 1 and Figure 2 As shown, the gas delivery assembly 42 includes an aeration pipe 421 and at least one branch pipe 422; The aeration pipe 421 is located inside the reaction tank 1; The branch pipe 422 is connected to the aeration pipe 421, and the branch pipe 422 extends radially into the gap between the anode plate 21 and the cathode plate 31; The jet assembly 41 is disposed on the branch pipe 422; The aeration pipe 421 is configured to distribute the gas to the branch pipe 422; The branch pipe 422 is configured to spray the received gas through the nozzle of the jet assembly 41 toward the anode plate 21 to form the bubble turbulence in the fluoride-containing wastewater. The bubble turbulence is used to flush and strip the rare earth fluoride deposit layer on the surface of the anode plate 21.

[0039] It should be noted that, as Figure 1As shown, the aeration pipe 421 is installed inside the reaction tank 1 and is installed vertically along the left inner wall of the reaction tank 1; the aeration pipe 421 is the main channel for gas distribution. like Figure 1 As shown, the bottom end of the aeration pipe 421 passes through the tank wall and is connected to the external air source control valve 424. The air source control valve 424 is connected to one end of the aeration pipe 421 and the air compressor 423. In specific implementation, the aeration pipeline 421 collects the compressed gas input from the air compressor 423 via the air source control valve 424 and distributes it to the branch pipelines 422 connected to it. In this embodiment, the aeration pipeline 421 is set inside the tank to shorten the gas delivery distance from the air source to the jet assembly 41, thereby reducing the pressure loss along the way. At the same time, it facilitates the pipeline layout inside the tank, making the overall structure compact. In some embodiments of this application, such as Figure 1 As shown, the number of branch pipes 422 is at least one; specifically, the number of branch pipes 422 corresponds one-to-one with the number of anode plates 21; the branch pipe 422 is the final stage delivery channel, which transmits the received gas to the jet assembly 41 installed on the branch pipe 422, realizing the synchronous gas supply from a single gas source to multiple jet assemblies 41, and ensuring the consistency of the scouring conditions of each anode plate 21 in the tank. After branch pipe 422 is led out from aeration pipe 421, it extends radially into the gap between anode plate 21 and cathode plate 31, so that branch pipe 422 extends into the gap between the plates from the side wall or bottom of reaction tank 1, and the radial extension line of branch pipe 422 does not intersect with the radial extension line of anode plate 21; branch pipe 422 delivers gas to the vicinity of the surface of anode plate 21 to provide gas source for jet assembly 41. The direction of branch pipe 422 and alternating arrangement of anode plate 21 and cathode plate 31 does not interfere with each other in space and does not affect the uniformity of electric field of the plates; The jet assembly 41 is in fluid communication with the branch pipe 422, and there may be one or more jet assemblies 41; like Figure 2 As shown, multiple jet components 41 are arranged at intervals along the length of the branch pipe 422 to cover different areas of the surface of the anode plate 21, so that the scouring range is comprehensive and without dead angles. like Figure 2 As shown, the number and spacing of the jet assembly 41 on the same branch pipe 422 are determined according to the area of ​​the anode plate 21; for example, in the embodiment of this application, three jet assemblies 41 are provided on each branch pipe 422, and the jet nozzles of the jet assembly 41 face the bottom surface of the upper anode plate 21.

[0040] In practice, compressed air is ejected upwards from each jet assembly 41 via aeration pipes 421 and branch pipes 422, forming dense bubble turbulence in the fluoride-containing wastewater. The bubbles at the jet nozzles possess high initial kinetic energy, impacting the bottom surface of the anode plate 21 directly above. The turbulent shear force generated during the bubble's ascent further strips the deposited layer surface. Since the rare earth fluoride deposited layer is a chemical precipitation product deposited on the metal surface of the anode plate 21, its adhesion to the substrate is significantly weaker than that of in-situ grown oxide films (such as Al2O3), making it a weakly adherent deposit. The scouring force generated by the bubble turbulence effectively strips it from the bottom surface of the anode plate 21. After being ejected from the jet nozzles, the bubbles naturally diffuse outwards during their ascent, even... Figure 1 In this configuration, the jet assembly 41 is only arranged in the left side region of the anode plate 21, and the rising and diffusing bubbles can also have a scouring and covering effect on the middle and right side regions of the anode plate 21. Furthermore, as... Figure 1 As shown, since the bottom layer of the electrode plate is the anode plate 21, after the bubbles rise, they pass through the entire gap area between the electrode plates, which can produce a continuous scouring effect on the bottom surface of each layer of anode plate 21.

[0041] In this embodiment, the gas supply assembly 42 is configured as an aeration pipe 421 and at least one branch pipe 422, with the branch pipe 422 extending radially into the gap between the anode plate 21 and the cathode plate 31. This allows the jetting assembly 41 to be positioned near the inter-electrode region of the anode plate 21. After being distributed via the branch pipe 422, the gas is directly sprayed onto the surface of the anode plate 21 through the jet nozzle, forming bubble turbulence in the fluoride-containing wastewater. This structure is designed to concentrate the flushing airflow on the location where the rare earth fluoride deposit layer is formed, resulting in a short flushing path and minimal energy loss, achieving efficient and directional stripping of the deposit layer on the surface of the anode plate 21. Simultaneously, the aeration pipe 421 distributes the gas to each branch pipe 422, ensuring the uniformity and synchronization of the gas supply from multiple jetting assemblies 41. This ensures that the surface of each anode plate 21 is effectively flushed, avoiding uneven inter-electrode resistance and decreased current efficiency caused by localized deposit layer residue. This maintains the long-term stability of the overall defluorination efficiency of the system and further reduces the risk of increased energy consumption due to deposit layer accumulation.

[0042] In some embodiments of this application, such as Figure 1 and Figure 2 As shown, the length of the branch pipe 422 is less than two-thirds of the length of the anode plate 21.

[0043] It should be noted that the radial extension length of the branch pipe 422 shall not exceed two-thirds of the length of the anode plate 21; like Figure 1 and Figure 2As shown, the branch pipe 422 extends from one side of the inner wall of the reaction tank 1 toward the middle of the electrode gap. The starting end is fixedly connected to the aeration pipe 421, and the main body of the pipe extends into the electrode gap, with the extension direction pointing to the middle of the gap. The extension length does not exceed two-thirds of the dimension of the anode plate 21 in the extension direction (i.e., the width of the anode plate 21). The purpose is to ensure that the end of the branch pipe 422 does not reach the inner wall on the other side of the tank, but terminates in the middle of the outer region of the electrode gap, leaving space between the end and the inner wall on the opposite side. This arrangement allows the jet assembly 41 to be placed near the main area where the deposition layer is generated on the surface of the anode plate 21 without spanning the entire gap. This allows the bubble turbulence to effectively cover the core working area on the surface of the anode plate 21. At the same time, the pipe-free space reserved between the end of the pipe and the inner wall on the opposite side ensures smooth flow of gas-liquid two-phase flow and bubble diffusion in the gap, avoiding obstruction of water and air flow by the pipe across its entire width.

[0044] In some embodiments of this application, the distance between the jet nozzle of the jet assembly 41 and the anode plate 21 is 6mm-10mm.

[0045] It should be noted that this distance refers to the vertical straight-line distance between the outlet end face of the jet nozzle and the surface of the anode plate 21 facing the jet nozzle; For example, the distance between the jet nozzle of the jet assembly 41 and the anode plate 21 is a value within the range of one or both of 6 mm, 7 mm, 8 mm, 9 mm and 10 mm. In this embodiment, the distance between the jet nozzle and the anode plate 21 is set to 6mm-10mm to ensure that the turbulent bubbles formed by the gas ejected from the jet nozzle in the fluoride-containing wastewater have a greater scouring intensity when they reach the surface of the anode plate 21. This distance allows the bubble jet to fully develop into a highly turbulent gas-liquid two-phase flow while avoiding excessive energy attenuation due to excessive distance. This results in a strong and concentrated stripping effect on the rare earth fluoride deposit layer regenerated on the surface of the anode plate 21, effectively breaking through the deposit layer coverage and promptly restoring the active sites of the anode plate 21.

[0046] In some embodiments of this application, the nozzle diameter of the jet assembly 41 is 0.1mm-5mm.

[0047] It should be noted that the jet nozzle is the outlet channel on the jet assembly 41 used for jetting gas; like Figure 2 As shown, the jet nozzle is opened on the jet assembly 41, which is set on the branch pipe 422. The branch pipe 422 extends radially into the gap between the anode plate 21 and the cathode plate 31, so the jet nozzle is in the inter-electrode gap liquid phase environment. For example, the nozzle diameter of the jet assembly 41 is a range of one or any two of 0.1 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm and 5 mm; In practice, when the nozzle diameter is less than 0.1mm, the gas channel is too narrow and the gas resistance is extremely high under liquid back pressure conditions. It is necessary to significantly increase the gas supply pressure to form an effective jet. Moreover, the airflow is too thin to form a turbulent bubble group with sufficient scouring intensity in the wastewater, resulting in insufficient cleaning ability. When the nozzle diameter is greater than 5 mm, the gas phase gathers into a large gas cloud at the nozzle. After leaving the nozzle, the bubbles formed are too large and the number is reduced. The bubbles rise quickly, but the specific area and turbulent shear strength acting on the surface of the anode plate 21 are reduced, the peeling ability of rare earth fluoride deposits is reduced, and large bubbles are prone to gas blockage in the inter-electrode gap, affecting the effective reaction area of ​​the electrode plate.

[0048] Therefore, the aperture range of 0.1mm-5mm set in this application allows the gas to form a dense cluster of small-sized bubbles in the liquid phase, which has sufficient kinetic energy to enable the turbulent flow of the formed bubbles to fully act on the high regeneration rate rare earth fluoride deposition layer generated on the surface of the anode plate 21, thereby achieving efficient and uniform non-contact scouring and stripping.

[0049] In some embodiments of this application, such as Figure 1 and Figure 3 As shown, the anode plate 21 is provided with at least one first liquid passage hole 22, and the cathode plate 31 is provided with at least one second liquid passage hole 32; In the axial direction, the orthographic projection of the first liquid passage 22 on the plane does not overlap with the orthographic projection of the second liquid passage 32 on the plane.

[0050] It should be noted that the first liquid passage 22 is a through hole opened on the anode plate 21, and there may be one or more of them; The first liquid passage 22 extends along the thickness direction of the anode plate 21, allowing liquid on both sides of the anode plate 21 to flow through the hole; during the electrocoagulation process, wastewater can pass through the anode plate 21 via the first liquid passage 22. The first liquid passage 22 can be set at any position on the surface of the anode plate 21; for example Figure 1 As shown in the embodiment of this application, the first liquid passage hole 22 is located on the side of the anode plate 21 away from the aeration pipe 421 and the branch pipe 422. This allows the water flow through the channel of the anode plate 21 to be spatially separated from the air supply side, avoiding water flow short circuit or bubble bypass caused by the proximity of the jet assembly 41 and the first liquid passage hole 22. This ensures that the wastewater flows fully in the gap between the plates and is flushed by bubbles before flowing out through the opposite channel.

[0051] like Figure 1As shown, in the axial direction, the first liquid passage hole 22 on each anode plate 21 can be aligned or not aligned; when the first liquid passage hole 22 is not aligned, it is still necessary to ensure that the orthographic projections of the first liquid passage hole 22 and the second liquid passage hole 32 on the plane do not overlap. The second liquid passage 32 is a through hole opened on the cathode plate 31, and there are one or more of them; The second liquid passage 32 extends along the thickness direction of the cathode plate 31 and has the same function as the first liquid passage 22. The second liquid passage 32 allows water and air bubbles to flow from one side of the cathode plate 31 through the hole to the other side. like Figure 1 As shown, the second liquid passage 32 is located on the side of the cathode plate near the aeration pipe 421; so that the water flow after fully reacting and scouring through the gap between the plates is discharged from the side near the gas source, and cooperates with the first liquid passage 22 on the anode plate 21 away from the aeration pipe to form a meandering flow path from the gas supply side to the opposite side and then back, thereby enhancing the deflection effect and flow field uniformity in the gap between the plates.

[0052] like Figure 1 As shown, in the axial direction, the second liquid passage holes 32 on each cathode plate 31 can be aligned or not aligned; when the second liquid passage holes 32 are not aligned, it is still necessary to ensure that the orthographic projections of the first liquid passage hole 22 and the second liquid passage hole 32 on the plane do not overlap. like Figure 4 As shown, in this embodiment of the application, four first liquid passage holes 22 are opened on the anode plate 21, and the four first liquid passage holes 22 are opened side by side on one side of the anode plate 21; four second liquid passage holes 32 are opened on the cathode plate 31, and the four second liquid passage holes 32 are opened side by side on one side of the cathode plate 31.

[0053] In some embodiments of this application, such as Figure 3 and Figure 4 As shown, the first liquid passage 22 and the second liquid passage 32 can be circular, elliptical or arc-shaped; The axial direction is the main direction of the flow of fluoride-containing wastewater within reaction tank 1; Orthographic projection refers to the pattern obtained by projecting the liquid passage holes on the anode plate 21 and the cathode plate 31 perpendicularly onto the same reference plane along the axial direction. "No overlap" means that on the projection plane, the projection area of ​​the first liquid passage 22 and the projection area of ​​the second liquid passage 32 do not overlap at all, and the two are arranged in an alternating manner in space.

[0054] In this embodiment, the projection of the first liquid passage 22 onto the plane of the anode plate 21 does not overlap with the projection of the second liquid passage 32 onto the plane of the cathode plate 31. This ensures that after wastewater enters the reaction tank 1 from the inlet 11, it cannot rise directly vertically through all the electrodes. Instead, it must flow horizontally through the gaps between the electrodes before passing through either the first or second liquid passage 22 to enter the gap between the next electrode layer. This repeated flow creates a baffled channel. The baffled channel extends the contact time and path between the wastewater and the electrodes, improving the completeness of the electrocoagulation reaction.

[0055] In practice, the upward flow of bubbles generated by the pneumatic flushing unit 4 and the meandering water flow in the baffle channel work together to enhance the ability to carry and remove debris from the stripped deposit layer, prevent debris from depositing in the gap between the electrodes and causing secondary blockage, further maintain the long-term cleanliness of the active surface of the anode plate 21, suppress the increase of inter-electrode resistance, ensure the continuous and stable dissolution of metal ions and rare earth ions, and achieve long-term efficient and stable operation of the system.

[0056] In practice, the number and position of the jet assembly 41 are independent of the first liquid passage 22 and / or the second liquid passage 32. The first liquid passage 22 and the second liquid passage 32 are functional holes used to form a wastewater baffle channel, and the jet assembly 41 is a cleaning element used for pneumatic flushing. Their functions, numbers and layouts are independent of each other.

[0057] In some embodiments of this application, such as Figure 1 and Figure 2 As shown, the system also includes a flexible cleaning unit 6; The flexible cleaning unit 6 includes a rotating shaft 61, a drive assembly 62, and a flexible brush 63; The rotating shaft 61 is disposed in the reaction tank 1 along the axial direction. The rotating shaft 61 passes through the anode plate 21 and the cathode plate 31 and is electrically insulated from the anode plate 21 and the cathode plate 31. One end of the rotating shaft 61 is connected to the drive assembly 62. The drive assembly 62 is located outside the reaction tank 1 near the outlet 12; The flexible brush 63 is fixedly connected to the rotating shaft 61. The side of the flexible brush 63 away from the rotating shaft 61 extends into the gap between the anode plate 21 and the cathode plate 31. The flexible brush 63 is arranged opposite to the side of the cathode plate 31 facing the outlet 12. The drive component 62 is configured to drive the rotating shaft 61 to rotate; The rotating shaft 61 is configured to drive the flexible brush 63 to perform a circular motion under the drive of the driving component 62. The flexible brush 63 is configured to rotate and clean the scale layer on the surface of the cathode plate 31 to obtain a clean cathode plate 31.

[0058] It should be noted that the flexible cleaning unit 6 is used to remove the scale layer on the surface of the cathode plate 31. The flexible cleaning unit 6 works in conjunction with the pneumatic flushing unit 4 to perform differentiated cleaning treatments on the cathode plate 31 and the anode plate 21 respectively. Among them, the rotating shaft 61 is the main transmission shaft, which is set inside the tank along the axial direction of the reaction tank 1 and vertically passes through the central through holes of all anode plates 21 and cathode plates 31. The rotating shaft 61 is electrically insulated from each electrode plate to ensure that the electrochemical process of the electrode plates is not affected when rotating. One end of the rotating shaft 61 extends to the outside of the reaction tank 1 near the outlet 12 and is connected to the drive assembly 62 to receive rotational driving force. Under the drive of the drive assembly 62, the rotating shaft 61 moves in a circular motion around its own axis to provide rotational sweeping power for the flexible brush 63 fixedly installed on it. The drive assembly 62 is a power source and is located outside the reaction tank 1 near the outlet 12. The drive assembly 62 is connected to one end of the rotating shaft 61 and is configured to drive the rotating shaft 61 to rotate continuously around its axis. The drive assembly 62 can be a rotating drive device such as a motor. Its external installation method facilitates maintenance and repair, and does not occupy the effective volume inside the reaction tank 1, nor does it affect the water flow and the electric field distribution of the electrode plates. The flexible brush 63 is a cleaning actuator that acts directly on the surface of the cathode plate 31; like Figure 2 As shown in the embodiment of this application, the flexible cleaning unit 6 further includes a brush holder connecting arm 64, the two ends of which are fixedly connected to the rotating shaft 61 and the flexible brush 63, respectively. Specifically, the brush holder connecting arm 64 is a rigid rod that extends horizontally outward from the rotating shaft 61 and is fixedly installed on the rotating shaft 61 at a height corresponding to the top surface of each cathode plate 31; the flexible brush 63 is installed at the end of the brush holder connecting arm 64 or distributed along the arm, with the bristles facing downward and the ends of the bristles contacting or slightly pressing the top surface of the cathode plate 31. The brush holder connecting arm 64 is only positioned at the height of the top surface of the corresponding cathode plate 31, and not at the height of the bottom surface of the corresponding anode plate 21. The cleaning of the bottom surface of the anode plate 21 is entirely handled by the pneumatic flushing unit 4. The rotating sweeping area of ​​the brush holder connecting arm 64 mainly covers the radial range from the center of the rotating shaft 61 to the edge of the cathode plate 31, and is spatially separate from the branch pipe 422 of the pneumatic flushing unit 4. Branch pipe 422 extends from the inner wall of one side of the reaction tank 1 toward the middle of the gap between the electrodes, and its end terminates in the outer part of the middle of the gap; the flexible brush 63 and the brush holder connecting arm 64 move in a circular motion from the center of the electrode to the opposite side under the drive of the rotating shaft 61. The two do not interfere with each other in spatial layout. The two cleaning mechanisms operate independently and each completes the differentiated cleaning tasks of the anode plate 21 and the cathode plate 31. The bristles of the flexible brush 63 are made of flexible materials such as nylon or polypropylene, with a bristle diameter ranging from 0.2mm to 0.5mm and a bristle length ranging from 8mm to 15mm. The bristles of this material and size have sufficient flexibility and cleaning power to effectively remove the hydroxide soft scale layer and bubble traces on the surface of the cathode plate 31, while avoiding scratches or wear on the cathode substrate.

[0059] In this embodiment, a flexible cleaning unit 6 is provided, with a rotating shaft 61 passing through the central through hole of each electrode plate and maintaining electrical insulation. The drive assembly 62 is externally placed at the outlet 12 of the tank. The rotating shaft 61 drives the flexible brush 63 to perform a circumferential sweeping motion on the top surface of the cathode plate 31, achieving full-coverage contact cleaning. This promptly removes the hydroxide scale layer generated on the cathode surface due to electrocoagulation reaction, restores the active surface of the cathode, and inhibits the increase in inter-electrode resistance and the decrease in current efficiency caused by cathode scaling.

[0060] In some embodiments of this application, such as Figure 1 As shown, the first liquid passage 22 and the second liquid passage 32 are respectively located on opposite sides of the rotating shaft. In this case, the first liquid passage 22 on the anode plate 21 and the second liquid passage 32 on the cathode plate 31 are spatially separated by the rotating shaft, and their axial projections do not overlap. This structure prevents wastewater from flowing in a straight axial direction through the gap between the electrodes, forcing it to flow around the rotating shaft in a circuitous manner, thus forming a baffled channel. This prolongs the contact time and reaction path between the fluoride-containing wastewater and the electrodes, improving the efficiency of electrocoagulation and fluoride removal.

[0061] In some embodiments of this application, such as Figure 1 As shown, the system also includes a control unit 7; The control unit 7 includes a sensor 71 and a controller 72; The gas delivery assembly 42 includes an aeration pipeline 421, at least one branch pipeline 422, an air compressor 423, and a gas source control valve 424; the aeration pipeline 421 is connected to the branch pipeline 422, and the aeration pipeline 421, the gas source control valve 424, and the air compressor 423 are connected in sequence. The sensor 71 is communicatively connected to the power supply circuits of the anode group 2 and the cathode group 3. The controller 72 is communicatively connected to the sensor 71 and the gas source control valve 424 via signal lines; The sensor 71 is configured to collect inter-electrode voltage or inter-electrode impedance signals in real time and transmit them to the controller 72 as electrical parameter signals. The controller 72 is configured to control the operating state of the gas source control valve 424 based on the comparison result of the electrical parameter signal with a first threshold and a second threshold, so as to regulate the gas flow rate delivered from the air compressor 423 to the aeration pipeline 421 via the gas source control valve 424.

[0062] It should be noted that the control unit 7 is an intelligent control module that realizes the automated operation of the pneumatic flushing unit 4. It consists of two parts: sensor 71 and controller 72. By monitoring the electrical parameters of the electrocoagulation process in real time, it automatically adjusts the intensity of pneumatic flushing, so that the system can dynamically adjust the jet cleaning force according to the degree of accumulation of the deposited layer on the surface of the anode plate 21, so as to achieve the operation goal of flushing on demand and saving energy and reducing consumption.

[0063] Sensor 71 is an electrical parameter signal acquisition device that establishes a communication connection with the power supply circuit of anode group 2 and cathode group 3, and can monitor the electrical parameters in the power supply circuit in real time. The inter-electrode voltage or inter-electrode impedance signal acquired by sensor 71 is directly related to the cumulative thickness of the rare earth fluoride deposition layer on the surface of anode plate 21. When the deposition layer thickens, the inter-electrode resistance increases, which is reflected as a voltage increase or a current decrease in constant current or constant voltage mode. Therefore, this electrical parameter signal can be used as a quantitative basis for judging the degree of deposition layer accumulation and triggering the scouring action.

[0064] The controller 72 is connected to the sensor 71 and the gas source control valve 424 via signal lines. After receiving the electrical parameter signal transmitted by the sensor 71, the controller 72 compares it with the preset first threshold and second threshold. Based on the comparison result, the controller outputs a control command to the gas source control valve 424 to adjust the valve's operating state, thereby changing the gas flow rate to the aeration pipeline 421 and achieving different levels of scouring intensity output. The first threshold and the second threshold constitute a three-level control range, including: when it is below the first threshold, it indicates that the accumulation of the deposit layer is slight; when it is above the second threshold, it indicates that the accumulation of the deposit layer is severe; and when it is between the two, it is a moderate accumulation state. The controller 72 outputs a differentiated control mode of shut-off / low pressure intermittent, first pressure continuous, and second pressure continuous accordingly.

[0065] Air compressor 423 is the air source device of air delivery assembly 42, used to generate compressed gas; the outlet end of air compressor 423 is connected to the inlet end of air source control valve 424, and the compressed gas is delivered to aeration pipeline 421 after being regulated by air source control valve 424. Air compressor 423, aeration pipeline 421 and air source control valve 424 are connected in sequence to form a complete gas delivery and distribution chain.

[0066] The gas source control valve 424 is connected in series between the air compressor 423 and the aeration pipeline 421. The gas source control valve 424 is connected to the controller 72 via a signal line, receives the command signal from the controller 72, and adjusts the opening degree or on / off mode of the valve according to the command, thereby controlling the gas flow rate delivered from the air compressor 423 to the aeration pipeline 421 through the gas source control valve 424. In this embodiment, the operating states of the air source control valve 424 include closed, low-pressure intermittent mode, first air pressure continuous mode and second air pressure continuous mode, which correspond to different scouring intensity levels.

[0067] This embodiment of the application, by setting a control unit 7 consisting of a sensor 71 and a controller 72 in the system, enables the pneumatic scouring unit 4 to have adaptive adjustment capability based on the degree of rare earth fluoride deposition on the surface of the anode plate 21. The sensor 71 collects inter-electrode voltage or inter-electrode impedance signals in real time as electrical parameter signals characterizing the accumulation state of the deposition layer. The controller 72 automatically controls the air source control valve 424 to switch different operating modes based on the comparison results of the electrical parameter signals with a first threshold and a second threshold, and adjusts the gas flow rate delivered from the air compressor 423 to the aeration pipeline 421 and the jet assembly 41, so as to realize the on-demand control of the scouring intensity. When the deposit layer is slight, the system reduces or stops jetting to save compressed air energy. When the deposit layer worsens, the system automatically increases the jetting pressure to enhance the bubble turbulence stripping ability, promptly removes the rare earth fluoride deposit layer with a high regeneration rate, restores the cleanliness of the active sites of the anode plate 21, achieves a balance between flushing energy consumption and scale removal effect, inhibits the increase in inter-electrode resistance and energy consumption caused by deposit layer coverage, ensures the continuous and stable dissolution of metal ions and rare earth ions, enables the system to maintain deep defluorination efficiency with the lowest compressed air consumption during long-term continuous operation, and extends the service life of the anode plate 21.

[0068] In some embodiments of this application, such as Figure 1 As shown, the system also includes a solid-liquid separation unit 8; The solid-liquid separation unit 8 is connected to the water outlet 12; The solid-liquid separation unit 8 is configured to separate the water discharged from the outlet 12 after electrocoagulation treatment to obtain a clear aqueous solution.

[0069] It should be noted that the solid-liquid separation unit 8 is connected to the outlet 12 of the reaction tank 1 through a pipeline, and receives the water discharged from the outlet 12 after electrocoagulation treatment. The water discharged from outlet 12 contains not only hydroxide flocs and rare earth fluoride precipitates generated during the electrocoagulation process, but also rare earth fluoride deposit debris that has been stripped from the surface of anode plate 21 by the pneumatic flushing unit 4 and discharged with the water flow and rising air bubbles. The solid-liquid separation unit 8 is used to separate these suspended solids from the water to obtain a clear aqueous solution that can be reused or meets discharge standards.

[0070] In some embodiments of this application, the solid-liquid separation unit 8 may be an air flotation tank, a sedimentation tank, or a membrane separation device, and the specific selection may be determined according to the treatment scale and water quality requirements.

[0071] This embodiment of the application adds a solid-liquid separation unit 8 downstream of the outlet 12 to effectively separate the suspended solids generated and peeled off in the electrocoagulation reaction tank 1, including hydroxide flocs, rare earth fluoride precipitates, and sediment debris, which are discharged with the water flow and rising bubbles, to obtain a clear aqueous solution. This achieves the final transfer and removal of pollutants from the aqueous phase, avoiding the accumulation of debris in the tank or its re-attachment to the electrode surface, thus ensuring the long-term effectiveness of the electrode cleaning effect.

[0072] In summary, the system provided in this application provides differentiated cleaning for the anode plate 21 and the cathode plate 31. For the rapidly regenerating rare earth fluoride deposits on the surface of the anode plate 21, a non-contact cleaning process is used with a pneumatic scouring assembly. The scouring and peeling action is applied through the turbulent flow of compressed gas bubbles and micro-jet jets in the liquid phase. Since this deposit is a chemical precipitation product, its adhesion to the metal substrate is weaker than that of the anodic oxide film, allowing for effective peeling by pneumatic scouring. This completely avoids mechanical wear on the expensive rare earth anode plate 21, thereby extending its service life and reducing operating costs. For the hydroxide soft scale layer on the surface of the cathode plate 31, a flexible brush 63 is used for contact cleaning, effectively removing the scale while avoiding damage to the cathode substrate.

[0073] The nozzles of the pneumatic flushing assembly are positioned below the bottom of the anode plate 21 and spray upwards. Bubbles rise naturally under buoyancy, impacting the bottom surface of the anode plate 21. The peeling direction is consistent with the flushing direction, resulting in high cleaning efficiency and a large, uniform bubble coverage area. This eliminates cleaning dead zones caused by insufficient contact in mechanical cleaning components, effectively addressing the rapid regeneration rate of the deposited layer. Branch pipes 422 of the pneumatic flushing assembly extend from the inner wall of one side of the reaction tank 1, spatially independent of the rotating shaft 61 located at the center of the electrode plate. The two cleaning mechanisms operate independently without affecting each other. During their ascent, the bubbles also agitate and flotate the wastewater between the electrode plates, promoting floc formation and flotation separation, thus generating synergistic process gains for the defluorination process. Meanwhile, the staggered first liquid passage hole 22 and second liquid passage hole 32 on the electrode plate form a baffle channel, which prolongs the contact time and path between the wastewater and the electrode plate and improves the electrocoagulation defluorination efficiency. The upward flow of bubbles generated by pneumatic flushing and the meandering water flow in the baffle channel work together to enhance the ability to carry and discharge the debris of the stripped deposit layer and prevent the debris from depositing in the gap between the electrode plates.

[0074] The system provided in this application embodiment maintains a defluorination efficiency of over 92% after 72 hours of continuous operation, while the comparative system using a uniform flexible brush 63 has a defluorination efficiency of 58% after 48 hours of operation and is forced to shut down, and obvious mechanical wear marks appear on the surface of the anode plate 21.

[0075] This application also provides a rare earth synergistic electrocoagulation defluorination control method to prevent passivation, such as... Figure 5 As shown, the control method includes: Step S1: Sensor 71 collects the inter-electrode voltage or inter-electrode impedance signal in real time and transmits it to controller 72 as an electrical parameter signal; Step S2: When the controller 72 determines that the electrical parameter signal is lower than the first threshold, it controls the gas source control valve 424 to close, so that the jet assembly 41 stops jetting gas to the anode plate 21; or, the controller 72 controls the gas source control valve 424 to operate in a preset low-pressure intermittent mode, so that the jet assembly 41 intermittently jets gas to the anode plate 21. Step S3: When the controller 72 determines that the electrical parameter signal is between the first threshold and the second threshold, it controls the gas source control valve 424 to operate continuously at the first air pressure, so that the jet assembly 41 continuously jets air onto the anode plate 21 at the first air pressure. Step S4: When the controller 72 determines that the electrical parameter signal is higher than the second threshold, it controls the gas source control valve 424 to operate continuously at a second pressure higher than the first pressure, so that the jet assembly 41 continuously jets gas onto the anode plate 21 at the second pressure until the electrical parameter signal falls back to the preset reference value. After that, the controller 72 controls the gas source control valve 424 to close or switch to the low-pressure intermittent mode. Wherein, the benchmark value is less than or equal to the first threshold.

[0076] It should be noted that the method judges the degree of accumulation of rare earth fluoride deposits on the surface of anode plate 21 by real-time monitoring of the electrical parameter signals of the power supply circuits of anode group 2 and cathode group 3. Based on the degree of deposition, it can not only automatically adjust the jet mode of pneumatic scouring unit 4, but also adjust the rotation speed of flexible cleaning unit 6 at the same time, so as to achieve dynamic matching between cleaning intensity and surface condition of electrode plate, thereby minimizing cleaning energy consumption and equipment wear while ensuring continuous cleanliness of electrode plate. Sensor 71 is communicatively connected to the power supply circuits of anode group 2 and cathode group 3. During system operation, it collects inter-electrode voltage or inter-electrode impedance signals in real time as electrical parameter signals and transmits them to controller 72. These electrical parameter signals can directly reflect the accumulation state of the deposited layer on the surface of anode plate 21. For example, the thickening of the deposited layer leads to an increase in inter-electrode resistance, which manifests as an increase in inter-electrode voltage or inter-electrode impedance under the condition that the power supply mode remains unchanged. Therefore, the electrical parameter signals serve as a quantitative basis for judging the surface activity and deposition degree of the electrode plates.

[0077] The reference value is defined as V0, which is the reference value of inter-electrode voltage or impedance recorded after the system has been running stably for the first time. In the initial stage of system commissioning, the surface of anode plate 21 is clean and free of deposits, and the inter-electrode electrical parameters are in the optimal state. The stable value collected at this time is the reference value V0. The reference value serves as the reference baseline for subsequent judgment of the degree of deposition. All thresholds in the control method are set proportionally based on the reference value V0 to adapt to the differences in reference parameters caused by different water quality conditions and water temperature changes. The intervals between the first and second thresholds correspond to three states: good surface activity, light deposition, and heavy deposition, respectively. Specifically: The first threshold is approximately 1.10 times the baseline value V0, and the second threshold is approximately 1.20 times the baseline value V0. If the electrical parameter signal is below the first threshold, it indicates that the deposition layer has not yet formed significantly; if it is between the first and second thresholds, it indicates that a light deposition layer has been formed; if it is above the second threshold, it indicates that a heavy deposition layer has been formed. The controller 72 outputs different control commands according to the range in which the electrical parameter signal falls.

[0078] In specific implementation, when the controller 72 determines that the electrical parameter signal is below the first threshold, it indicates that the surface activity of the anode plate 21 is good and the accumulation of rare earth fluoride deposits is slight. At this time, the controller 72 controls the gas source control valve 424 to close, so that the jet assembly 41 stops jetting to the anode plate 21 to save compressed air energy consumption; or controls the gas source control valve 424 to operate in a preset low-pressure intermittent mode, that is, to operate briefly at a lower jet pressure every long period of time to preventively maintain the cleanliness of the electrode plate surface; at the same time, the controller 72 also controls the drive assembly 62 to stop or only operate at a low-speed inspection speed, so that the flexible brush 63 is in a stationary or low-speed sweeping state to reduce mechanical wear and drive energy consumption; When the controller 72 determines that the electrical parameter signal is between the first threshold and the second threshold, it indicates that a light rare earth fluoride deposit has been formed on the surface of the anode plate 21, which needs to be removed by moderate rinsing. At this time, the controller 72 controls the gas source control valve 424 to operate continuously at the first air pressure, so that the jet assembly 41 continuously jets air onto the anode plate 21 at the first air pressure, providing a medium-intensity bubble turbulence to peel off the light deposit layer. At the same time, the controller 72 also controls the drive assembly 62 to operate at the first speed, so that the flexible brush 63 cleans the surface of the cathode plate 31 at a moderate sweeping speed, removing the hydroxide scale layer that is generated on the cathode plate 31 at this time. When the controller 72 determines that the electrical parameter signal is higher than the second threshold, it indicates that a heavy rare earth fluoride deposit has been formed on the surface of the anode plate 21, the inter-electrode resistance has increased significantly, and the dissolution of metal ions and rare earth ions has been significantly suppressed. At this time, the controller 72 controls the gas source control valve 424 to operate continuously at a second gas pressure higher than the first gas pressure, so that the jet assembly 41 continuously jets gas onto the anode plate 21 at the second gas pressure, providing high-intensity bubble turbulence to forcefully peel off the dense deposit layer. At the same time, the controller 72 also controls the drive assembly 62 to operate at a second speed higher than the first speed, so that the flexible brush 63 performs enhanced cleaning on the surface of the cathode plate 31 at a higher speed, and simultaneously removes the cathode scale layer that has increased due to the heavy deposition condition. After the second high-intensity flushing, the controller 72 detects that the electrical parameter signal has fallen back to the preset recovery condition, such as within 1.05 times the reference value V0. It then determines that the deposit layer has been effectively removed and the surface activity of the electrode plate has been basically restored. At this time, the controller 72 controls the system to return to the idle state, that is, controls the air source control valve 424 to close or operate in low-pressure intermittent mode, and controls the drive component 62 to stop or operate in low-speed inspection mode. This avoids excessive cleaning that would cause energy waste and equipment wear, and achieves the closed-loop control goal of cleaning on demand and saving energy.

[0079] This application embodiment establishes a closed-loop control method based on electrical parameter feedback, enabling the system to automatically adjust the cleaning intensity according to the actual accumulation degree of rare earth fluoride deposits on the surface of the anode plate 21. This achieves intelligent management of plate cleaning, giving the system the ability to dynamically match cleaning energy consumption and descaling effect according to the real-time status of the plates. It avoids the waste of compressed air caused by over-cleaning in fixed-sequence flushing modes and the deposition deterioration caused by untimely cleaning. During long-term continuous operation, it maintains the continuous cleanliness of the active sites of the anode plate 21 with the lowest comprehensive energy consumption, inhibits the increase of inter-electrode resistance, ensures the stable and efficient dissolution of metal ions and rare earth ions, and achieves long-term stability of deep defluorination efficiency, significant reduction of operating power consumption, and effective extension of the service life of the anode and cathode plates 21.

[0080] This application also provides an application of a rare earth synergistic electrocoagulation defluorination system to prevent passivation, wherein the system is applied when the anode plate 21 is composed of a metal material doped with rare earth elements; The system includes a pneumatic scouring unit 4, which is configured to perform non-contact bubble turbulence scouring on the surface of the anode plate 21.

[0081] The application provided in this application addresses the situation where the anode plate is composed of metal materials doped with rare earth elements. By configuring a pneumatic flushing unit to perform non-contact bubble turbulence flushing on the surface of the anode plate, the rare earth fluoride deposit layer can be promptly stripped off during the electrocoagulation defluorination process. This avoids electrode passivation and increased inter-electrode resistance caused by the deposit layer covering, and eliminates the risk of rare earth anode plate wear caused by mechanical contact, thereby extending the service life of the anode plate and ensuring long-term stable operation of the system in the deep treatment of fluoride-containing wastewater.

[0082] To enable those skilled in the art to better understand this application, the following embodiments are provided to illustrate in detail a rare earth synergistic electrocoagulation defluorination system, control method, and application for preventing passivation provided in this application.

[0083] Example 1 Example 1 provides a rare earth synergistic electrocoagulation defluorination system with passivation prevention. The specific parameters of each component are as follows: Reaction tank 1: PP material cuboid structure, effective volume 50L, internal dimensions 400mm×300mm×500mm (length×width×height); bottom inlet 11, top outlet 12, outlet 12 connects to air flotation tank (solid-liquid separation unit 8).

[0084] The electrode assembly consists of 5 anode plates 21 and 4 cathode plates 31, arranged alternately horizontally. The plate dimensions are 250mm × 200mm × 3mm, with a spacing of 15mm between plates. The anode plates 21 are made of aluminum alloy doped with 8% lanthanum (La) (Al-8La), and the cathode plates 31 are made of 316L stainless steel. Each plate has a 25mm diameter through-hole for the rotating shaft 61 to pass through. The plates are connected to a 36V DC power supply 5 via wiring, with an operating current density of 150A / m. 2 .

[0085] Pneumatic flushing unit 4: The aeration main pipe has an outer diameter of 12mm and is made of 316L stainless steel. It is installed vertically along the inner left side of the reaction tank 1. Five branch pipes 422 (corresponding to five anode plates 21) branch from the aeration main pipe. Each branch pipe 422 has an outer diameter of 8mm and extends horizontally from the left side wall into the gap between the anode plates. The extension length is about 130mm (about 65% of the 200mm width of the anode plate), and does not extend to the central through hole area of ​​the anode plate. Each branch pipe 422 is equipped with three nozzles. The nozzle nozzle has a nozzle orifice diameter of 1.5mm and the nozzle outlet is set directly upward, 8mm away from the bottom surface of the anode plate 21. The air compressor 423 has a rated power of 0.55kW and a maximum output air pressure of 0.3MPa. The air source control valve 424 adopts an SMC series solenoid valve. During system operation, the pneumatic flushing unit 4 operates periodically at an air pressure of 0.10MPa (a cycle of 10min operation followed by 20min interval).

[0086] Cathode cleaning assembly: The rotating shaft 61 has a diameter of 20mm and is made of 316L stainless steel. It is vertically installed on the central axis of the reaction tank 1 and passes through the central through hole of all the cathode plates. A set of brush holder connecting arms 64 and nylon flexible brushes 63 (brush diameter 0.3mm, brush length 10mm) are installed at the height corresponding to the top surface of each of the four cathode plates 31. The brush holder connecting arms 64 extend radially from the rotating shaft 61 by about 90mm, and the flexible brushes 63 are distributed along the arm and contact the top surface of the cathode plates 31.

[0087] Drive component 62: a three-phase asynchronous motor (rated power 0.25kW) is installed on the top cover, driving the shaft 61 to rotate at a speed of 80rpm. The flexible brush 63 starts and stops synchronously with the pneumatic flushing unit 4.

[0088] Treatment target: Simulated fluoride-containing wastewater, with an initial fluoride ion concentration of 10 mg / L, pH adjusted to 6.5, and water temperature of 25℃.

[0089] The above components are arranged as follows Figure 1 Assemble the system according to the shown system structure diagram, and then start running it. The results are as follows: the system composed of the above components ran continuously for 72 hours, and the concentration of fluoride ions in the water was measured every 4 hours.

[0090] During the initial operation (0-8 hours), the effluent fluoride concentration remained stable at 0.5-0.7 mg / L, with a fluoride removal efficiency of 93%-95%. After 72 hours of operation, the effluent fluoride concentration was 0.80 mg / L, with a fluoride removal efficiency of 92%. After 72 hours, the plates were disassembled and inspected. The surface of the anode plate 21 showed no obvious deposits or mechanical wear marks; the surface of the cathode plate 31 showed no scratches.

[0091] Example 2 The difference between Example 2 and Example 1 lies in the materials of the anode plate 21 and the flexible brush 63, and the operating current density of the DC power supply 5 is 200A / m. 2 The structural components of the remaining systems are the same, specifically including: Anode plate 21 is made of an iron alloy (Fe-5Ce-3La) doped with 5% cerium (Ce) and 3% lanthanum (La), with a total rare earth content of 8%. Cathode plate 31 is made of titanium.

[0092] Flexible brush 63: Polypropylene (PP) bristles, 0.4 mm in diameter.

[0093] The treatment object of Example 2 is different from that of Example 1. The treatment object of Example 2 is: actual industrial fluoride-containing wastewater (from the pickling wastewater of a rare earth smelting enterprise), with an initial fluoride ion concentration of 25 mg / L, pH adjusted to 5.5, and water temperature of 30℃.

[0094] The above components are arranged as follows Figure 1 Assemble the system according to the shown system structure diagram, and then start operation. The operating results are as follows: After 72 hours of continuous operation, the effluent fluoride concentration was 1.1-1.4 mg / L in the initial stage, with a defluoridation efficiency of 94.4%-95.6%. After 72 hours of operation, the effluent fluoride concentration was 1.7 mg / L, with a defluoridation efficiency of 93.2%. After 72 hours, the electrode plates were disassembled and inspected. The anode plate 21 had only a very thin layer of residual deposits (less than 0.05 mm thick) on its surface, and no wear marks were found. The cathode plate 31 was undamaged.

[0095] Example 3 The difference between Example 3 and Example 1 is the addition of a first liquid passage 22 and a second liquid passage 32; the remaining structures are the same, specifically including: Four arc-shaped first liquid passage holes 22 are opened on each anode plate 21, and four arc-shaped second liquid passage holes 32 are opened on each cathode plate 31. The width of the first liquid passage hole 22 and the second liquid passage hole 32 is 15mm and the arc length is 60mm. The first liquid passage holes 22 and the second liquid passage holes 32 of adjacent upper and lower plates are staggered by 180 degrees in the horizontal projection. That is, when the first liquid passage hole 22 or the second liquid passage hole 32 of the upper plate is located on the left, the first liquid passage hole 22 or the second liquid passage hole 32 of the lower plate is located on the right.

[0096] The treatment object in Example 3 was the same as in Example 1, which was simulated fluoride-containing wastewater with an initial fluoride ion concentration of 10 mg / L and a pH of 6.5.

[0097] The above components are arranged as follows Figure 1 Assemble the system according to the shown system structure diagram, and then start operation. The results are as follows: the system composed of the above components ran continuously for 72 hours. Initially, the effluent fluoride concentration was 0.3-0.5 mg / L, with a defluorination efficiency of 95%-97%. After 72 hours of operation, the effluent fluoride concentration was 0.60 mg / L, with a defluorination efficiency of 94%. Compared to Example 1 (without the first liquid passage 22 and the second liquid passage 32), the initial defluorination efficiency increased by approximately 2 percentage points, and the defluorination efficiency increased by 2 percentage points after 72 hours, indicating that the baffle channel formed by the first liquid passage 22 and the second liquid passage 32 effectively extended the contact time between the wastewater and the electrode plates. Furthermore, the synergistic effect of the rising bubble flow and the baffled water flow resulted in almost no visible debris residue remaining in the gaps between the electrode plates.

[0098] Comparative Examples 1-2 are set up based on Examples 1-3, specifically including: Comparative Example 1 The system structure of Comparative Example 1 is basically the same as that of Example 1, with the only difference being: Comparative Example 1 does not have a pneumatic scouring unit 4. The same nylon flexible brush 63 of the same specification is installed on the bottom surface of the corresponding anode plate 21 and the top surface of the cathode plate 31. That is, the anode plate 21 is also cleaned by contact flexible brush 63. The other parameters are exactly the same as those in Example 1.

[0099] The operating results were as follows: In the initial stage of operation (0-8 hours), the effluent fluoride concentration was 0.6-0.9 mg / L, with a defluorination efficiency of 91%-94%, similar to Example 1. However, starting from 16 hours of operation, the effluent fluoride concentration began to rise significantly. After 24 hours of operation, the effluent fluoride concentration rose to 2.5 mg / L, and the defluorination efficiency dropped to 75%. After 48 hours of operation, the effluent fluoride concentration rose to 4.2 mg / L, and the defluorination efficiency dropped to 58%, forcing the system to be shut down.

[0100] The above results are due to the following: Although the bonding force between the rare earth fluoride deposit and the substrate of the anode plate 21 is weak, the flexible brush 63 can partially remove the deposit in the initial stage. However, due to the extremely fast regeneration rate of the deposit (the solubility of rare earth fluorides is extremely low), the cleaning frequency and coverage uniformity of the flexible brush 63 are insufficient to cope with the high-speed regeneration of the deposit. As the operating time increases, the deposit gradually accumulates and thickens. After 48 hours, the electrode plates were disassembled and inspected. The surface of the anode plate 21 was covered with a white deposit layer with a thickness of approximately 0.6-1.0 mm (XRD analysis confirmed that the main component was LaF3). In addition, obvious brush scratches were visible on the surface of the anode plate 21, indicating that contact cleaning caused significant mechanical wear to the rare earth anode plate 21. The surface of the cathode plate 31 remained clean and intact.

[0101] Comparative Example 2 Comparative Example 2 used a conventional electrocoagulation device, in which the anode plate 21 was made of ordinary aluminum alloy (without rare earth doping), and the cathode plate 31 was made of stainless steel; there was no cleaning mechanism. The size, quantity, spacing of the electrodes, and parameters of the reaction tank 1 were the same as in Example 1. The operating current density of the DC power supply 5 was 150 A / m. 2 .

[0102] Comparative Example 2 uses the same treatment as Example 1, which is simulated fluoride-containing wastewater with an initial fluoride ion concentration of 10 mg / L and a pH of 6.5.

[0103] The operating results were as follows: Initially, the effluent fluoride concentration was 2.5-3.0 mg / L, with a defluoridation efficiency of 70%-75%. After 24 hours of operation, the effluent fluoride concentration rose to 3.8 mg / L, and the defluoridation efficiency decreased to 62%. After 48 hours of operation, the effluent fluoride concentration rose to 5.2 mg / L, and the defluoridation efficiency decreased to 48%.

[0104] Table 1 below summarizes the defluorination efficiency of Examples 1-3 and Comparative Examples 1-2 at different operating time points, as shown in Table 1: Table 1. Defluorination efficiency of Examples 1-3 and Comparative Examples 1-2 at different operating time points

[0105] It can be seen that, compared with Comparative Example 1, the initial defluorination efficiency of both is similar. However, after 24 hours of operation, the defluorination efficiency of Comparative Example 1 drops sharply to 75%, and after 48 hours it drops to 58%, forcing a shutdown. In contrast, Example 1 still maintains a defluorination efficiency of 92% after 72 hours. This indicates that although the single adhesion of the rare earth fluoride deposit is weak, its regeneration rate is extremely fast, and the uniform size of the flexible brush is insufficient to cope with the cleaning frequency and coverage uniformity, leading to the gradual accumulation of the deposit. The pneumatic rinsing method of this application achieves large-area uniform rinsing with bubble turbulence, which can effectively cope with the high-speed regeneration of the deposit. At the same time, obvious brush scratches appeared on the surface of the anode plate in Comparative Example 1, confirming the wear problem of contact cleaning on the rare earth anode plate, while the surface of the anode plate in Example 1 showed no wear marks.

[0106] Comparing Example 1 and Comparative Example 2, the initial defluorination efficiency of the rare earth-doped anode plate (94%) was much higher than that of the ordinary aluminum alloy anode plate (72.5%), which confirms the significant advantage of the synergistic defluorination effect of rare earth elements.

[0107] Compared to Example 1, Example 3 shows that the baffle channel (a structure composed of a first liquid passage and a second liquid passage) further improved the initial defluorination efficiency from 94% to 96%, and the 72-hour defluorination efficiency from 92% to 94%, confirming the positive effect of the baffle channel in extending the contact time. The synergistic effect of the bubble rising flow and the baffle water flow made the debris discharge more thorough.

[0108] In summary, compared with traditional electrocoagulation systems, the system provided in this application not only has higher defluorination efficiency and lower reagent costs, but also provides real-time and effective hydraulic flushing of the anode plate surface to promptly remove the rare earth fluoride deposits generated during electrocoagulation, maintaining the cleanliness of the active sites on the anode plate and preventing increased inter-electrode resistance and energy consumption due to deposit coverage. This ensures the stable and continuous dissolution of anode metal and rare earth ions. Furthermore, it can perform contact cleaning of the cathode plate surface, promptly removing the soft hydroxide scale layer and restoring cathode activity, thus achieving a balance between deep defluorination, lower operating costs, and long-term stable performance of the anode and cathode plates.

[0109] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0110] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A rare-earth synergistic electrocoagulation defluorination system with passivation prevention, characterized in that, The system includes: The reaction tank (1), the anode group (2), the cathode group (3) and the pneumatic scouring unit (4); The reaction tank (1) is provided with an inlet (11) and an outlet (12); the inlet (11) and the outlet (12) are arranged axially on both sides of the reaction tank (1); The anode group (2) includes multiple anode plates (21), and the cathode group (3) includes multiple cathode plates (31); the anode plates (21) and the cathode plates (31) are alternately arranged in the reaction tank (1) along the axial direction; the anode plates (21) and the cathode plates (31) are respectively connected to a DC power supply (5); the anode plates (21) are composed of metal materials doped with rare earth elements; The pneumatic flushing unit (4) includes at least one jet assembly (41) and a gas delivery assembly (42) located in the reaction tank (1); wherein the jet assembly (41) is connected to the gas delivery assembly (42), the jet assembly (41) is located between the anode plate (21) and the cathode plate (31), and the jet nozzle of the jet assembly (41) is disposed opposite to the side of the anode plate (21) facing the water inlet (11); The reaction tank (1) is configured to introduce fluoride-containing wastewater into the tank through the inlet (11) and discharge water treated by electrocoagulation through the outlet (12); The anode group (2) and the cathode group (3) are configured to perform electrocoagulation treatment in the reaction tank (1) after being energized, so as to remove fluoride from the fluoride-containing wastewater. The pneumatic flushing unit (4) is configured to deliver gas to the jet assembly (41) through the gas supply assembly (42). The jet assembly (41) jets gas toward the anode plate (21) through the jet nozzle. The ejected gas forms bubble turbulence in the fluoride-containing wastewater. The bubble turbulence flushes and peels off the rare earth fluoride deposit layer formed on the surface of the anode plate (21) during the electrocoagulation process to obtain a clean anode plate (21).

2. The rare earth synergistic electrocoagulation defluorination system for preventing passivation according to claim 1, characterized in that, The gas delivery assembly (42) includes an aeration line (421) and at least one branch line (422). The aeration pipeline (421) is located inside the reaction tank (1); The branch pipe (422) is connected to the aeration pipe (421), and the branch pipe (422) extends radially into the gap between the anode plate (21) and the cathode plate (31); The jet assembly (41) is disposed on the branch pipe (422); The aeration line (421) is configured to distribute the gas to the branch line (422). The branch pipe (422) is configured to spray the received gas through the nozzle of the jet assembly (41) toward the anode plate (21) to form the bubble turbulence in the fluoride-containing wastewater, the bubble turbulence being used to flush and strip the rare earth fluoride deposit layer on the surface of the anode plate (21).

3. The passivation-resistant rare earth synergistic electrocoagulation defluorination system according to claim 1 or 2, characterized in that, The distance between the jet nozzle of the jet assembly (41) and the anode plate (21) is 6mm-10mm.

4. The rare earth synergistic electrocoagulation defluorination system for preventing passivation according to claim 1, characterized in that, The system also includes a flexible cleaning unit (6); The flexible cleaning unit (6) includes a rotating shaft (61), a drive assembly (62), and a flexible brush (63). The rotating shaft (61) is arranged in the reaction tank (1) along the axial direction. The rotating shaft (61) passes through the anode plate (21) and the cathode plate (31) and is electrically insulated from the anode plate (21) and the cathode plate (31). One end of the rotating shaft (61) is connected to the drive assembly (62). The drive assembly (62) is located outside the reaction tank (1) near the outlet (12); The flexible brush (63) is fixedly connected to the rotating shaft (61). The side of the flexible brush (63) away from the rotating shaft (61) extends into the gap between the anode plate (21) and the cathode plate (31). The flexible brush (63) is arranged opposite to the side of the cathode plate (31) facing the outlet (12). The drive assembly (62) is configured to drive the rotating shaft (61) to rotate; The rotating shaft (61) is configured to drive the flexible brush (63) to perform a circular motion under the drive of the driving component (62); The flexible brush (63) is configured to rotate and clean the scale layer on the surface of the cathode plate (31) to obtain a clean cathode plate (31).

5. The rare earth synergistic electrocoagulation defluorination system for preventing passivation according to claim 1, characterized in that, The anode plate (21) is provided with at least one first liquid passage hole (22), and the cathode plate (31) is provided with at least one second liquid passage hole (32). In the axial direction, the orthographic projection of the first liquid passage (22) on the plane does not overlap with the orthographic projection of the second liquid passage (32) on the plane.

6. The rare earth synergistic electrocoagulation defluorination system for preventing passivation according to claim 2, characterized in that, The length of the branch pipe (422) is less than two-thirds of the length of the anode plate (21).

7. The rare earth synergistic electrocoagulation defluorination system for preventing passivation according to claim 1 or 2, characterized in that, The nozzle diameter of the jet assembly (41) is 0.1mm-5mm.

8. The rare earth synergistic electrocoagulation defluorination system for preventing passivation according to claim 1, characterized in that, The system also includes a control unit (7); The control unit (7) includes a sensor (71) and a controller (72). The gas delivery assembly (42) includes an aeration pipeline (421), at least one branch pipeline (422), an air compressor (423), and a gas source control valve (424); the aeration pipeline (421) is connected to the branch pipeline (422), and the aeration pipeline (421), the gas source control valve (424), and the air compressor (423) are connected in sequence. The sensor (71) is communicatively connected to the power supply circuits of the anode group (2) and the cathode group (3). The controller (72) is communicatively connected to the sensor (71) and the gas source control valve (424) via signal lines; The sensor (71) is configured to collect inter-electrode voltage or inter-electrode impedance signals in real time and transmit them to the controller (72) as electrical parameter signals. The controller (72) is configured to control the operating state of the gas source control valve (424) based on the comparison result of the electrical parameter signal with a first threshold and a second threshold, so as to regulate the gas flow rate delivered from the air compressor (423) to the aeration pipeline (421) via the gas source control valve (424).

9. A rare-earth synergistic electrocoagulation defluorination control method for preventing passivation, characterized in that, The control method is applicable to the passivation-resistant rare earth synergistic electrocoagulation defluorination system according to any one of claims 1-8, and the control method includes: The sensor (71) collects the inter-electrode voltage or inter-electrode impedance signal in real time and transmits it to the controller (72) as an electrical parameter signal. When the controller (72) determines that the electrical parameter signal is lower than the first threshold, it controls the gas source control valve (424) to close, so that the jet assembly (41) stops jetting to the anode plate (21); or, the controller (72) controls the gas source control valve (424) to operate in a preset low-pressure intermittent mode, so that the jet assembly (41) intermittently jets to the anode plate (21). When the controller (72) determines that the electrical parameter signal is between the first threshold and the second threshold, it controls the gas source control valve (424) to operate continuously at the first air pressure, so that the jet assembly (41) continuously jets air onto the anode plate (21) at the first air pressure. When the controller (72) determines that the electrical parameter signal is higher than the second threshold, it controls the gas source control valve (424) to operate continuously at a second pressure higher than the first pressure, so that the jet assembly (41) continuously jets gas onto the anode plate (21) at the second pressure until the electrical parameter signal falls back to the preset reference value. After that, the controller (72) controls the gas source control valve (424) to close or switch to the low-pressure intermittent mode. Wherein, the benchmark value is less than or equal to the first threshold.

10. The application of a rare-earth synergistic electrocoagulation defluorination system with passivation prevention, characterized in that, The system is as described in any one of claims 1-8, and the system is applied to a case where the anode plate (21) is composed of a metallic material doped with rare earth elements; The system includes a pneumatic scouring unit (4) configured to perform non-contact bubble turbulence scouring on the surface of the anode plate (21).

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