Electrochemical adsorption treatment method and device for perchlorate wastewater

Abstract

This invention provides a method and apparatus for electrochemical adsorption treatment of perchlorate wastewater, comprising: conveying a fluidized carbon-based electrode slurry to the anode and cathode chambers of the electrochemical adsorption treatment apparatus, and then returning it to the electrode slurry storage tank to form a circulating flow; simultaneously, perchlorate wastewater and concentrate are respectively input into the desalination chamber and concentration chamber, and under the drive of a DC electric field, ions in the wastewater are forced to migrate in a directional manner, thereby achieving the removal of perchlorate ions in the aqueous phase, ensuring that the perchlorate wastewater meets discharge standards, and the treatment process is highly efficient and low-cost. The electrochemical adsorption treatment apparatus disclosed in this invention includes modules such as a cathode end plate, a cathode current collector, a first cation exchange membrane, a desalination chamber partition, an anion exchange membrane, a concentration chamber partition, a second cation exchange membrane, an anode current collector, and an anode end plate. Its equipment has low cost, high desalination rate, and low energy consumption, and has great application prospects in the treatment of perchlorate wastewater.

Description

Technical Field

[0001] This invention belongs to the field of perchlorate wastewater treatment technology, and particularly relates to an electrochemical adsorption treatment method and apparatus for perchlorate wastewater based on a fluidized carbon-based flow electrode. Background Technology

[0002] Perchlorates are a class of salts containing perchlorate ions (ClO4). - Perchlorate is an inorganic compound that exhibits strong oxidizing properties under high temperature and acidic conditions, and is widely used in aerospace, blasting, and fireworks industries. However, industrial wastewater containing perchlorate poses a significant threat to the ecological environment and human health. Perchlorate is highly water-soluble and can rapidly migrate through surface runoff and groundwater circulation systems, entering the human body through the food chain. Numerous studies have shown that perchlorate has been detected in drinking water, milk, vegetables, and meat. ClO4 - Similar in structure to iodide ions, it may competitively inhibit the thyroid gland's absorption of iodine, leading to thyroid dysfunction, especially affecting pregnant women and children.

[0003] Currently, perchlorate wastewater treatment technology is developing rapidly, resulting in various treatment methods, including membrane filtration, ion exchange, chemical (or electrochemical) reduction, adsorption, and biological reduction. While traditional membrane filtration technologies such as reverse osmosis, nanofiltration, and ultrafiltration have some removal effect on perchlorate, as perchlorate accumulates, the charge on the membrane surface becomes more negative, and the diffusion rate of perchlorate decreases significantly with increasing pH. Perchlorate wastewater generally contains other impurities (such as Cl-). - SO4 2- NO3 - (etc.) In ion exchange and chemisorption processes, there is an ion competition effect, where impurities will occupy corresponding chemical sites, severely affecting the removal of ClO4 by ion exchange resins or adsorbents. - Performance. Chemical reduction is a promising new technology that can remove harmful ClO4. - Reduced to harmless Cl - But ClO4 - Its unique tetrahedral structure and high redox potential (E0 = 1.39 V) give it strong chemical stability, making it considered an inert electrolyte in electrochemistry. Therefore, the chemical reduction of ClO4... - The reaction rate is slow, generally requiring the use of precious metal catalysts to accelerate the reduction process, which increases costs to some extent. In actual wastewater, ClO4... -Low or even trace concentrations of perchlorate wastewater are detrimental to the bioreduction process, resulting in insufficient nutrient supply for microbial growth and decreased microbial activity. Furthermore, industrial wastewater typically has high salinity, which is also unfavorable for microbial growth. Existing perchlorate wastewater treatment technologies generally suffer from low efficiency or high cost, significantly limiting their large-scale application.

[0004] Therefore, there is an urgent need for a treatment method that can efficiently and cost-effectively remove perchlorate under complex water quality conditions, especially a perchlorate removal technology that can avoid ion competition effects, does not require precious metal catalysts, and is unaffected by wastewater pH and salinity. Summary of the Invention

[0005] The main objective of this invention is to provide an electrochemical adsorption treatment method and apparatus for perchlorate wastewater. The method uses a DC electric field as the driving force to force ions in the wastewater to migrate in a specific direction and store them in the double layer of a carbon-based electrode, thereby achieving the removal of perchlorate ions in the aqueous phase, ensuring that the perchlorate wastewater meets the discharge standards, and the treatment process is highly efficient and low in cost.

[0006] To achieve the above objectives, the present invention provides an electrochemical adsorption treatment method for perchlorate wastewater, comprising the following steps: S1. Activated carbon, electrolyte and deionized water are mixed at room temperature to prepare a fluidized carbon-based electrode slurry; S2. The fluidized carbon-based electrode slurry is transported to the anode and cathode chambers of the electrochemical adsorption treatment device and then returned to the electrode slurry storage tank to form a circulating flow. At the same time, perchlorate wastewater and concentrate are respectively input into the desalination chamber and the concentration chamber. Driven by the DC electric field, perchlorate ions in the perchlorate wastewater pass through the anion exchange membrane into the concentrate, and cations in the perchlorate wastewater pass through the first cation exchange membrane into the cathode slurry. Meanwhile, cations in the anode slurry pass through the second cation exchange membrane into the concentrate to maintain charge balance, thereby achieving the enrichment of perchlorate. In the electrochemical adsorption treatment device, a cathode chamber is formed between the cathode current collector and the first cation exchange membrane, a desalination chamber is formed between the first cation exchange membrane and the anion exchange membrane, a concentration chamber is formed between the anion exchange membrane and the second cation exchange membrane, and an anode chamber is formed between the second cation exchange membrane and the anode current collector.

[0007] Further, in step S1, the mass ratio of activated carbon, electrolyte, and deionized water is (10-20):(0.2-0.8):(100-200). The activated carbon is one or more of nanoparticle carbon, capacitor activated carbon, and biochar. The electrolyte is one or more of sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate.

[0008] Furthermore, in step S1, the mixing method is magnetic stirring, with a stirring speed of 600-1000 r / min and a stirring time of 12-24 h.

[0009] Further, in step S2, the mass concentration of the perchlorate wastewater is 100–500 mg / L; The concentrate is a perchlorate solution with a concentration of 100–500 mg / mL.

[0010] Furthermore, in step S2, the flow rate of the fluidized carbon-based electrode slurry is 50–150 mL / min; The flow rates of both the concentrate and the desalination solution in the desalination chamber are 100–200 mL / min.

[0011] Furthermore, in step S2, the DC electric field is in constant voltage mode, with a voltage of 0.9 to 1.8V.

[0012] Furthermore, in step S2, the surfaces of the anode current collector and the cathode current collector are respectively provided with 4 to 8 parallel serpentine flow channels, and the depth of the serpentine flow channels is 0.5 to 2.5 mm.

[0013] Furthermore, in step S2, both the anode current collector and the cathode current collector are metal folded mesh current collectors. The metal folded mesh current collector is disposed in the grooves on the working surfaces of the anode and cathode end plates, and its placement angle in the grooves is 0 to 90°.

[0014] Furthermore, the metal folded mesh current collector has a mesh count of 30 to 120, a thickness of 1 to 2 mm, and a corrugation interval of 1 to 2.5 mm.

[0015] The present invention also provides an electrochemical adsorption treatment device for perchlorate wastewater, comprising, in sequence, a cathode end plate, a cathode sealing gasket, a cathode current collector, a first cation exchange membrane, a desalination chamber partition, an anion exchange membrane, a concentration chamber partition, a second cation exchange membrane, an anode current collector, an anode sealing gasket, and an anode end plate; The lower part of the cathode end plate is provided with a slurry input channel, a desalination liquid input channel and a concentrate input channel, which run through the entire desalination device; the upper part of the cathode end plate is provided with a slurry output channel, a desalination liquid output channel and a concentrate output channel, which run through the entire desalination device. The slurry input channel is connected to the electrode slurry storage tank via a slurry peristaltic pump. The slurry input channel passes through the cathode current collector, each membrane layer between the cathode current collector and the anode current collector, and the anode current collector in sequence, and then connects to the slurry output channel. The slurry output channel is connected to the electrode slurry storage tank. The desalination liquid input channel and the concentrate input channel are connected to the desalination liquid storage tank and the concentrate storage tank respectively by a multi-channel brine peristaltic pump; the desalination liquid input channel passes through the cathode current collector, the first cation exchange membrane and connects to the desalination chamber, then passes through the anion exchange membrane, the second cation exchange membrane and the anode current collector in sequence, and then connects to the desalination liquid output channel, which is connected to the desalination liquid storage tank; the concentrate input channel passes through the anode current collector, the second cation exchange membrane and connects to the concentration chamber, then passes through the anion exchange membrane, the first cation exchange membrane and the cathode current collector in sequence, and then connects to the concentrate output channel, which is connected to the concentrate storage tank.

[0016] Furthermore, both the desalination chamber partition and the concentration chamber partition are partition mesh with a thickness of 1–2.55 mm and a mesh size of 40–100 mesh. The mesh shape of the partition mesh is one of square holes, round holes, or diamond holes; The partition mesh is made of one of polyethylene, polypropylene, and titanium.

[0017] The technical effects of this invention are as follows: 1. The method of the present invention uses a "desalination-concentration" synergistic fluidized carbon-based electrode capacitor deionization device to electrochemically adsorb and treat perchlorate wastewater, realizing the simultaneous removal and concentration of perchlorate. At the same time, the number of cations in the electrode slurry in the cathode current collector is continuously increasing, while the number of cations in the electrode slurry in the anode current collector is continuously decreasing, thereby stabilizing the composition of the electrode slurry, which is conducive to long-term continuous operation and reduces operating costs.

[0018] 2. The electrochemical adsorption treatment method of the present invention effectively avoids the entry of perchlorate ions into the fluidized carbon-based electrode slurry system by migrating cations between wastewater, electrode slurry and concentrate (i.e., by utilizing ion selective migration), thereby preventing the problem of carbon particle oxidation failure under acidic conditions.

[0019] 3. The metal folded mesh current collector of the present invention has a three-dimensional structure, which greatly increases the effective contact area between the current collector and the electrode slurry compared with the planar structure of titanium mesh and woven mesh, which is conducive to enhancing charge transfer efficiency. The metal folded mesh current collector has high mechanical strength, which facilitates later equipment maintenance. The folded structure is simple to process and easy to scale up. It has the advantage of being lightweight compared to graphite plate current collectors. The metal folded mesh current collector is placed at a certain angle in the end plate groove, which intersects with the slurry flow direction, improves the dispersion of the electrode slurry velocity field, and is conducive to high-frequency collision between electrode particles and mesh wires, thereby enhancing the electron transfer process to carbon electrode particles and improving desalination efficiency.

[0020] 4. The electrochemical perchlorate wastewater treatment method of this invention has wide adaptability, is less affected by water quality fluctuations, and is basically unaffected by ambient temperature. Compared with existing traditional technologies, it has higher treatment efficiency, lower energy consumption and equipment investment costs. Combined with the subsequent resource recovery and disposal of concentrated liquid, it can effectively avoid secondary pollution problems. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the electrochemical adsorption treatment device for perchlorate wastewater according to an embodiment of the present invention; Figure 2 This is a front view of a male or female end plate with a groove provided in an embodiment of the present invention. Figure 3 This is a top view of the metal folded mesh current collector according to an embodiment of the present invention; Figure 4 This is a side view of a metal folded mesh current collector according to an embodiment of the present invention, wherein D is the thickness of the metal folded mesh current collector and L is the corrugation spacing of the metal folded mesh current collector; Figure 5 This is a graph showing the change in conductivity of the desalination solution under different voltages in Example 1 of the present invention; Figure 6 This is a graph showing the change in desalination liquid current under different voltages in Embodiment 1 of the present invention; Figure 7 This is a graph showing the change in conductivity of the desalination liquid under different carbon contents in Example 2 of the present invention; Figure 8 This is a graph showing the change in desalination liquid current under different carbon contents in Example 2 of the present invention; Figure 9 This is a graph showing the change in conductivity of the desalination solution under different electrolyte concentrations in Example 3 of the present invention; Figure 10 This is a graph showing the change in desalination liquid current under different electrolyte concentrations in Example 3 of the present invention.

[0023] Reference numerals: 1. Fastening nut; 2. Cathode end plate; 3. Cathode sealing gasket; 4. Cathode current collector; 5. First cation exchange membrane; 6. Desalination chamber partition; 7. Anion exchange membrane; 8. Concentration chamber partition; 9. Second cation exchange membrane; 10. Anode current collector; 11. Anode sealing gasket; 12. Anode end plate; 13. Fastening bolt. Detailed Implementation

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

[0025] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0026] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of this invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to those described, used, or made of materials in the embodiments of this invention.

[0027] Conventional electrochemical reduction treatment of perchlorate involves reducing perchlorate ions to chloride ions under an electric field. This is a chemical reaction process involving a change in the state of matter. Perchlorate ions have a tetrahedral structure and strong structural stability; therefore, the activation energy required for the chemical reaction is relatively high, resulting in a slow reaction rate, typically requiring a catalyst to accelerate the process. In this invention, a DC electric field drives the perchlorate ions to migrate towards the anode and store them in the electric double layer of the flowing electrode, thus separating them from the wastewater. When the flowing electrode containing perchlorate ions enters the cathode, the perchlorate ions are released into the enrichment solution. This process is a capacitive deionization process, which can also be understood as an electric field-driven adsorption process. It does not involve a change in the state of matter; the perchlorate ions remain in their original form. Since there is no redox reaction, no metal catalyst is needed.

[0028] like Figure 1 As shown, the electrochemical adsorption treatment method for perchlorate wastewater provided by the present invention includes the following steps: S1. Activated carbon, electrolyte, and deionized water in a mass ratio of (10–20):(0.2–0.8):(100–200) are magnetically stirred at room temperature at a stirring speed of 600–1000 r / min for 12–24 h to obtain a fluidized carbon-based electrode slurry. In a specific embodiment, the stirring speed is 800 r / min and the stirring time is 1.5 h during the slurry preparation process.

[0029] In this invention, the activated carbon is one or more of nanoparticle carbon, capacitor activated carbon, and biochar; the electrolyte is one or more of sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate.

[0030] S2. Desalination and purification: The fluidized carbon-based electrode slurry prepared above is transported to the slurry inlet of the electrochemical adsorption treatment device by a slurry peristaltic pump and flows into the slurry input channel at the bottom of the device (i.e., the electrochemical adsorption treatment device). The bottom slurry input channel passes through the intermediate membrane stack (i.e., the first cation exchange membrane 5, the anion exchange membrane 7, and the second cation exchange membrane 9) and connects the anode chamber and the cathode chamber at both ends. After the electrode slurry (i.e., the fluidized carbon-based electrode slurry in this invention) flows through the anode chamber and the cathode chamber at both ends, it is mixed in the slurry output channel at the top of the device and flows out from the slurry outlet at the top, returning to the electrode slurry storage tank to form a circulating flow.

[0031] Meanwhile, a multi-channel brine peristaltic pump delivers perchlorate wastewater and concentrate to the desalination inlet channel and concentrate inlet channel, respectively, and then into the desalination chamber and concentration chamber. Driven by a DC electric field, perchlorate ions (if the wastewater contains other anions, they will also pass through the anion exchange membrane 7 to be removed in the concentrate) pass through the anion exchange membrane 7 into the concentrate. Cations in the perchlorate wastewater pass through the first cation exchange membrane 5 into the cathode slurry. The concentrate continuously receives perchlorate ions from the perchlorate wastewater, while cations in the anode slurry pass through the second cation exchange membrane 9 into the concentrate (i.e., the concentration chamber) to maintain charge balance in the concentrate. Perchlorate is continuously enriched in the concentrate. When the enriched solution (i.e., the enriched perchlorate solution) reaches a certain concentration factor, it needs to be discharged from the system and processed in subsequent processes. After replacing with new concentrate, the unit continues to operate.

[0032] The processing method of the present invention is an intermittent operation mode. The desalination liquid needs to be continuously circulated in the device to slowly realize the desalination process until the conductivity or concentration in the desalination liquid storage tank drops to a specified value (5-100 μS / cm) before being discharged.

[0033] In this invention, the mass concentration of perchlorate wastewater is 100–500 mg / L; the concentrate is a perchlorate solution with a concentration of 100–500 mg / mL. The perchlorate wastewater is the raw water to be treated containing perchlorate.

[0034] In this invention, the flow rate of the fluidized carbon-based electrode slurry is 50–150 mL / min, which ensures sufficient collisions between carbon particles and efficient charge transfer, achieving a highly efficient, orderly, and stable slurry flow state. If the flow rate of the electrode slurry is too low, the slurry flows slowly, resulting in insufficient collisions between carbon particles and low charge transfer efficiency; if the flow rate of the electrode slurry is too high, it will increase the pressure inside the flow channel, causing the slurry to overflow and unable to flow in an orderly manner.

[0035] The flow rates of the concentrate and the desalination liquid in the desalination chamber are both 100-200 mL / min, which ensures that the residence time of perchlorate wastewater in the device is appropriate, adjusts the free diffusion rate of ions in the perchlorate wastewater, and improves the removal rate of perchlorate ions.

[0036] In this invention, the DC electric field is in constant voltage mode or constant current mode, and the voltage is 0.9 to 1.8V, which can be 0.9V, 1.0V, 1.1V, 1.2V, 1.3V, 1.4V, 1.5V, 1.6V, 1.7V, or 1.8V. Preferably, the voltage is 1.2V.

[0037] like Figure 1 As shown, the electrochemical adsorption treatment device for perchlorate wastewater provided by the present invention includes, in sequence, a cathode end plate 2, a cathode sealing gasket 3, a cathode current collector 4, a first cation exchange membrane 5, a desalination chamber partition 6, an anion exchange membrane 7, a concentration chamber partition 8, a second cation exchange membrane 9, an anode current collector 10, an anode sealing gasket 11, and an anode end plate 12. Furthermore, all components of the device have through holes around their edges for installing fastening bolts 13, which are then used to secure the device together with fastening nuts 1. A cathode chamber is formed between the cathode current collector 4 and the first cation exchange membrane 5; a desalination chamber is formed between the first cation exchange membrane 5 and the anion exchange membrane 7; a concentration chamber is formed between the anion exchange membrane 7 and the second cation exchange membrane 9; and an anode chamber is formed between the second cation exchange membrane 9 and the anode current collector 10.

[0038] The lower part of the cathode end plate 2 is provided with a slurry input channel, a desalination liquid input channel and a concentrate input channel, which run through the entire desalination device; the upper part of the cathode end plate 2 is provided with a slurry output channel, a desalination liquid output channel and a concentrate output channel, which run through the entire desalination device.

[0039] The slurry input channel is connected to the electrode slurry storage tank via a slurry peristaltic pump. The slurry input channel passes through the cathode current collector 4, the first cation exchange membrane 5, the anion exchange membrane 7, the second cation exchange membrane 9, and the anode current collector 10 in sequence, and then connects to the slurry output channel, which is connected to the electrode slurry storage tank.

[0040] The desalination liquid inlet channel and the concentrate inlet channel are connected to the desalination liquid storage tank and the concentrate storage tank respectively by a multi-channel brine peristaltic pump. The desalination liquid inlet channel passes through the cathode current collector 4 and the first cation exchange membrane 5 to connect with the desalination chamber, then sequentially passes through the anion exchange membrane 7, the second cation exchange membrane 9, and the anode current collector 10 before connecting with the desalination liquid outlet channel, which is connected to the desalination liquid storage tank. The concentrate inlet channel passes through the anode current collector 10 and the second cation exchange membrane 9 to connect with the concentration chamber, then sequentially passes through the anion exchange membrane 7, the second cation exchange membrane 9, and the cathode current collector 4 before connecting with the concentrate outlet channel, which is connected to the concentrate storage tank.

[0041] In this invention, the surfaces of the anode current collector 10 and the cathode current collector 4 are each provided with 4 to 8 parallel (i.e., parallel arrangement) serpentine flow channels, with a depth of 0.5 to 2.5 mm. This multi-channel parallel flow design allows for uniform distribution of the inlet slurry flow rate, resulting in a more uniform pressure distribution within the flow channels, reducing the area of ​​the "dead zone" where the flow velocity is zero, and helping to enhance the charge transfer process in the electrode slurry, thereby improving desalination performance. In contrast, traditional serpentine flow channels are single-track, and due to their longer length, flow resistance increases, making it easier to form "dead zones" at bends. Furthermore, a single track is not suitable for expansion.

[0042] In this invention, both the anode current collector 10 and the cathode current collector 4 are metal folded mesh current collectors (e.g., Figure 3 As shown, the metal folded mesh current collector has a continuous folded structure, including multiple folded units connected sequentially along a first direction. Specifically, the continuous folded structure of the present invention is as follows: adjacent folded units are connected by a common fold line; the main outline of the folded unit is triangular and has a wave crest protruding in a direction away from the common fold line. This folded structure has good continuity, good stability, and low manufacturing difficulty. If a rectangular structure is used, the processing is relatively difficult and deformation is easy to occur; wherein, the top of the wave crest is constructed as a vertex structure, and the vertex structure is configured as either a sharp vertex or an arc-shaped transition portion to form a sawtooth or wave-shaped three-dimensional outline in the folded or unfolded state.

[0043] like Figure 2As shown, the metal folded mesh current collectors are installed in the grooves on the working surfaces of the anode end plate 12 and the cathode end plate 2 (both the grooves on the anode end plate 12 and the cathode end plate 2 contain metal folded mesh current collectors), with a groove depth of 1–3 mm. The working surface of the anode end plate 12 refers to the side that contacts the anode current collector 10; the working surface of the cathode end plate 2 refers to the side that contacts the cathode current collector 4. It is noteworthy that the center lines of the two grooves coincide with the center lines of their respective end plates. If they do not coincide, the metal folded mesh current collectors cannot correspond to the desalination chamber and the concentration chamber, affecting the efficiency of perchlorate removal.

[0044] In this invention, the metal folded mesh current collector is placed at an angle of 0–90° in the groove. This ensures that the metal folded mesh current collector intersects with the slurry flow direction, improving the dispersion of the electrode slurry velocity field. This facilitates high-frequency collisions between electrode particles and the mesh wires, thereby enhancing the electron transfer process to the carbon electrode particles and improving desalination efficiency. It is worth noting that the placement angle of the metal folded mesh current collector in the groove refers to the angle between the corrugated direction of the metal folded mesh current collector and the flow direction of the fluidized electrode slurry.

[0045] In a specific embodiment of the present invention, a dispersive water distribution trough is provided at the bottom of the groove, the depth of the dispersive water distribution trough is 1 to 3 mm, and multiple water flow channels are provided at the top of the dispersive water distribution trough, the width of the water flow channels is 1 to 2 mm, so as to distribute the initial flow rate of the electrode slurry and enable the slurry to be evenly dispersed into the groove.

[0046] like Figure 4 As shown, D represents the thickness of the metal folded mesh current collector, and L represents the corrugation spacing of the metal folded mesh current collector. In this invention, the mesh count of the metal folded mesh current collector is 30–120 meshes, the thickness is 1–2 mm, and the corrugation spacing is 1–2.5 mm. This ensures that the metal folded mesh current collector is easy to process, the electrode slurry flows smoothly, and carbon particle deposition is less likely to occur. If the mesh count of the metal folded mesh current collector is less than 30 meshes, the wires are too thick, making it impossible to process the folded structure. If the mesh count is too high, the mesh size is too small. An excessively small mesh size greatly increases the flow resistance of the electrode slurry in the metal current collector, easily leading to clogging problems. The thickness of the metal folded mesh current collector depends on the corrugation spacing. An excessively large spacing will cause a significant increase in the overall thickness of the metal folded mesh, increasing the depth of the slurry flow area, resulting in a slower slurry flow rate and making carbon particle deposition more likely.

[0047] In this invention, both the desalination chamber partition 6 and the concentration chamber partition 8 are partition meshes with a thickness of 1–2.55 mm and a mesh size of 40–100 mesh. The mesh shape is one of square, round, or diamond-shaped holes; the material is one of polyethylene, polypropylene, or titanium. If the partition mesh is too thick, the internal resistance of the device will be high, and an excessively large compartment will cause sluggish brine flow, hindering ion diffusion. If the partition mesh is too thin, the brine (i.e., perchlorate wastewater) flow space will be small, increasing internal pressure and potentially causing membrane displacement and deformation, possibly leading to cross-contamination between different solutions. The mesh size is mainly used to control the turbulence during water flow. This invention uses a 40–100 mesh mesh, which is beneficial for enhancing the free diffusion of ions.

[0048] A concentrated liquid flow channel is provided at the bottom of the concentration chamber partition 8, and the concentrated liquid flow channel is connected to the concentrated liquid inlet of the anode plate 12 through a concentrated liquid pipe; a desalination liquid flow channel is provided at the bottom of the desalination chamber partition 6, and the desalination liquid flow channel is connected to the desalination liquid inlet of the cathode plate 2 through a desalination liquid pipe.

[0049] The specific operating steps of the electrochemical adsorption treatment method for perchlorate wastewater of the present invention are as follows: (1) Place the prepared concentrate and electrode slurry into the corresponding storage tanks and start stirring; place the conductivity meter probes into the desalination tank and the concentrate tank respectively to detect and record the conductivity changes.

[0050] (2) Connect the storage tank, the transfer pump, and the inlet of the FCDI device (i.e., the electrochemical adsorption treatment device of the present invention) in sequence using the pump pipe. Connect the outlet of the FCDI device to the corresponding storage tank through the pump pipe. Turn on the transfer pump. After each solution forms a circulating flow, record the conductivity of the desalted solution and the concentrated solution as the initial value.

[0051] (3) Apply voltage to the FCDI device in constant voltage electric field mode through DC power supply, and the desalination process begins. The voltage and current curves are automatically recorded by software.

[0052] (4) After running for a certain period of time, turn off the power and record the conductivity of the desalination solution and the concentrate as the final conductivity value. The electrochemical adsorption treatment method and apparatus for perchlorate wastewater of the present invention will be described below with reference to specific embodiments.

[0053] Example 1 The electrochemical adsorption treatment method for perchlorate wastewater is as follows: The perchlorate wastewater is desalinated using the aforementioned electrochemical adsorption treatment device, and the experiment is conducted according to the operating steps described above. During operation, a multi-channel brine peristaltic pump is used to transport the perchlorate wastewater and concentrate to the desalination liquid input channel and the concentrate input channel, respectively, and then into the desalination chamber and the concentration chamber, respectively. Driven by a DC electric field, perchlorate ions in the perchlorate wastewater pass through the anion exchange membrane 7 into the concentrate, while cations in the perchlorate wastewater pass through the first cation exchange membrane 5 into the cathode slurry. The concentrate continuously receives perchlorate ions from the perchlorate wastewater, while cations in the anode slurry pass through the second cation exchange membrane 9 into the concentrate to maintain charge balance in the concentrate, thus continuously enriching perchlorate in the concentrate. The cathode current collector 4 and the anode current collector 10 are both 4-channel graphite current collectors with a channel width of 2 mm and a depth of 1 mm; the partition mesh is made of polyethylene with a thickness of 2 mm and a mesh size of 40 mesh.

[0054] With the power switched on, the device entered the working state. Different voltages of 0.8V, 1.0V, 1.2V, 1.4V, and 1.6V were applied to test the removal performance of perchlorate. The fluidized carbon-based electrode slurry contained 10wt% carbon (i.e., activated carbon for supercapacitors that has passed through a 2000-mesh sieve), and the amount of sodium chloride electrolyte added was 0.1wt%. The initial concentration of potassium perchlorate was 500mg / L. The flow rates of the desalination solution (i.e., the initial concentration of potassium perchlorate solution, which was the same in the following examples and comparative examples), the electrode slurry, and the concentrate were all 100ml / min. The operating time was 1 hour.

[0055] like Figure 5 The figure shown is a graph illustrating the variation trend of the conductivity of the desalination solution over time under different voltages; as shown... Figure 6 The figure shows the trend of desalination liquid current over time under different voltages; Table 1 below shows the statistics of perchlorate removal rate, average desalination rate, charge efficiency, and molar energy consumption under different voltages. Figures 5-6 As shown in Table 1, the desalination rate and average desalination speed increase with increasing applied voltage, but the charge efficiency decreases and the desalination energy consumption increases continuously. The desalination energy consumption at 1.2V is 2.15 times that at 0.8V, indicating that applying too high a voltage is not conducive to the low-energy removal of perchlorate, and high voltage easily triggers the electrolysis reaction of water. Therefore, applying a voltage of 1.2V is the optimal choice, which is lower than the electrolysis potential of water.

[0056] Table 1. Statistics of desalination performance indicators under different voltages Example 2 Compared to Example 1, this example tested the perchlorate removal performance by setting electrode slurries with different carbon contents (i.e., activated carbon for supercapacitors that has passed through a 2000-mesh sieve): 5wt%, 10wt%, 15wt%, 20wt%, and 25wt%. The electrolyte sodium chloride added to the electrode slurry was 0.1wt%; the applied voltage was 1.2V; the initial potassium perchlorate concentration was 500mg / L; the flow rates of the desalination solution, electrode slurry, and concentrate were all 100ml / min; and the running time was 1h.

[0057] like Figure 7 The figure shown is a graph illustrating the change in conductivity of the desalination solution over time under different carbon contents; as shown... Figure 8 The figure shows the trend of desalination liquid current over time under different carbon contents; Table 2 below shows the statistics of perchlorate removal rate, average desalination rate, charge efficiency, and molar energy consumption under different voltages. Figures 7-8 As shown in Table 2, carbon content is one of the key parameters affecting perchlorate removal. The electrode slurry prepared with 5% wt activated carbon showed insufficient desalination performance, with a desalination rate of only 76.7%. As the carbon content increased, the desalination rate also increased. At a carbon content of 15% wt, the desalination rate reached 92.9%, with high charge efficiency and low operating energy consumption. When the carbon content increased further, the desalination rate showed a downward trend. Excessive carbon content is not conducive to the desalination process because the viscosity of the slurry with high carbon content increases, the rheological properties of the slurry decrease, and flow channel blockage is likely to occur, thereby weakening the desalination process.

[0058] Table 2. Statistics of desalination performance indicators under different voltages Example 3 Compared to Example 1, this example tested the perchlorate removal performance by setting different amounts of electrolyte NaCl: 0.06wt%, 0.08wt%, 0.1wt%, 0.12wt%, and 0.14wt%. The electrode slurry contained 10% carbon (i.e., activated carbon for supercapacitors that has passed through a 2000-mesh sieve); the initial potassium perchlorate concentration was 500 mg / L; the applied voltage was 1.2V; the flow rates of the desalination solution, electrode slurry, and concentrate were all 100 ml / min; and the running time was 1 hour.

[0059] like Figure 9 As shown in the figure, the conductivity of the desalination solution changes over time under different electrolyte concentrations; Figure 10The figure shows the trend of desalination liquid current over time under different electrolyte concentrations; Table 3 below shows the statistics of perchlorate removal rate, average desalination rate, charge efficiency, and molar energy consumption under different NaCl electrolyte concentrations. Figures 9-10 As shown in Table 3, adding electrolytes such as NaCl to the electrode slurry helps to improve the conductivity of the slurry. This example demonstrates that the NaCl concentration in the electrode slurry within the range of 600–1400 mg / L does not have a significant impact on the desalination performance. Considering the overall cost, a NaCl electrolyte concentration of 1000 mg / L in the slurry is more suitable.

[0060] Table 3. Statistical analysis of desalination performance indicators under different NaCl electrolyte concentrations. Example 4 Compared to Example 1, this example uses a traditional serpentine flow channel collector, a parallel 4-channel (i.e., four parallel serpentine flow channels) collector, and a 40-mesh titanium metal folded mesh collector (wherein the titanium metal folded mesh collector is placed at a 45° angle in the groove, the groove depth is 2 mm, the depth of the dispersion tank is 2 mm, the width of the water flow channel is 1 mm, the thickness of the titanium metal folded mesh collector is 2 mm, and the corrugation interval is 2.5 mm) to test the perchlorate removal performance. The electrode slurry contains 10% carbon (i.e., supercapacitor activated carbon that has passed through a 2000-mesh sieve), the NaCl electrolyte concentration is 1000 mg / L, the initial potassium perchlorate concentration is 500 mg / L, the applied voltage is 1.2 V, the flow rates of the desalination solution, electrode slurry, and concentrate are all 100 ml / min, and the running time is 1 h.

[0061] Table 4 shows the statistics of perchlorate removal rate, average desalination rate, charge efficiency, and molar energy consumption for different collectors. The results in Table 4 indicate that the parallel 4-channel design and titanium folded mesh of this invention provide the best desalination rate and average desalination rate when used as the collector.

[0062] Table 4. Statistics on desalination performance of different collectors Example 5 Compared to Example 1, this example tested the perchlorate removal performance by setting different initial perchlorate concentrations: 117.35 mg / L and 808.97 mg / L. The electrode slurry contained 10% carbon (i.e., activated carbon for supercapacitors that has passed through a 2000-mesh sieve); the electrolyte sodium chloride concentration in the slurry was 1000 mg / L; the applied voltage was 1.2 V; the flow rates of the desalination solution, electrode slurry, and concentrate were all 100 ml / min; and the running time was 2.5 h.

[0063] Table 5 shows the statistics of perchlorate removal rate, average desalination rate, charge efficiency, and molar energy consumption under different initial perchlorate concentrations. The results in Table 5 indicate that the treatment method of this invention is applicable to the adsorption treatment of perchlorate wastewater of different concentrations, and exhibits high desalination efficiency.

[0064] Table 5. Statistical analysis of desalination performance indicators under different initial perchlorate concentrations. Comparative Example 1 Compared to Example 1, the cathode and anode current collectors in this comparative example are both 40-mesh titanium folded mesh current collectors. The titanium folded mesh current collector is placed at a 45° angle in the groove, the groove depth is 2 mm, the depth of the dispersion tank is 2 mm, the water flow channel width is 1 mm, the mesh size of the titanium folded mesh current collector is 50 mesh, and the thickness is 2 mm. The perchlorate removal performance was tested by setting corrugation intervals of 5.5 mm and 7.5 mm. The electrode slurry contained 10% carbon (i.e., supercapacitor activated carbon that has passed through a 2000-mesh sieve), the NaCl electrolyte concentration was 1000 mg / L, the initial potassium perchlorate concentration was 500 mg / L, the applied voltage was 1.2 V, the flow rates of the desalination solution, electrode slurry, and concentrate were all 100 ml / min, and the operating time was 1 h.

[0065] Table 6 shows the statistics of perchlorate removal rate, average desalination rate, charge efficiency, and molar energy consumption under different corrugation intervals. The results in Table 6 show that when the corrugation interval is greater than 2.5 mm, the perchlorate removal performance decreases significantly. Excessively high corrugation intervals reduce the effective collision probability between the electrode slurry and the metal mesh to some extent, weakening the efficiency of charge transfer from the current collector to the slurry.

[0066] Table 6. Statistical analysis of desalination performance indicators under different corrugation intervals Comparative Example 2 Compared to Example 1, the cathode and anode current collectors in this comparative example are both 40-mesh titanium folded mesh current collectors. The titanium folded mesh current collector is placed at a 45° angle in the groove, the groove depth is 2 mm, the depth of the dispersion tank is 2 mm, the water flow channel width is 1 mm, the thickness of the titanium folded mesh current collector is 2 mm, and the corrugation interval is 2.5 mm. The perchlorate removal performance was tested by setting the metal folded mesh mesh numbers to 150 mesh and 200 mesh. The electrode slurry contained 10% carbon (i.e., supercapacitor activated carbon that has passed through a 2000-mesh sieve), the NaCl electrolyte concentration was 1000 mg / L, the initial potassium perchlorate concentration was 500 mg / L, the applied voltage was 1.2 V, the flow rates of the desalination solution, electrode slurry, and concentrate were all 100 ml / min, and the operating time was 1 h.

[0067] Table 7 shows the statistics of perchlorate removal rate, average desalination rate, charge efficiency, and molar energy consumption under different metal folded mesh counts. The results in Table 7 indicate that the mesh count of the metal folded mesh should not be too high. A higher mesh count means smaller mesh sizes, which increases the resistance to slurry flow within the mesh, hindering high-frequency collisions between the slurry and the mesh wires and impeding charge conduction.

[0068] Table 7. Statistics of desalination performance indicators at different mesh sizes The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for electrochemical adsorption treatment of perchlorate wastewater, characterized in that, Includes the following steps: S1. Activated carbon, electrolyte and deionized water are mixed at room temperature to prepare a fluidized carbon-based electrode slurry; S2. The fluidized carbon-based electrode slurry is transported to the anode and cathode chambers of the electrochemical adsorption treatment device and then returned to the electrode slurry storage tank to form a circulating flow. At the same time, perchlorate wastewater and concentrate are respectively input into the desalination chamber and the concentration chamber. Driven by the DC electric field, perchlorate ions in the perchlorate wastewater pass through the anion exchange membrane into the concentrate, and cations in the perchlorate wastewater pass through the first cation exchange membrane into the cathode slurry. Meanwhile, cations in the anode slurry pass through the second cation exchange membrane into the concentrate to maintain charge balance, thereby achieving the enrichment of perchlorate. In the electrochemical adsorption treatment device, a cathode chamber is formed between the cathode current collector and the first cation exchange membrane, a desalination chamber is formed between the first cation exchange membrane and the anion exchange membrane, a concentration chamber is formed between the anion exchange membrane and the second cation exchange membrane, and an anode chamber is formed between the second cation exchange membrane and the anode current collector.

2. The electrochemical adsorption treatment method of perchlorate wastewater according to claim 1, characterized in that, In step S1, the mass ratio of activated carbon, electrolyte, and deionized water is (10-20):(0.2-0.8):(100-200). The activated carbon is one or more of nanoparticle carbon, capacitor activated carbon, and biochar. The electrolyte is one or more of sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate.

3. The electrochemical adsorption treatment method of perchlorate wastewater according to claim 1, characterized in that, In step S1, the mixing method is magnetic stirring, with a stirring speed of 600-1000 r / min and a stirring time of 12-24 h.

4. The electrochemical adsorption treatment method of perchlorate wastewater according to claim 1, characterized in that, In step S2, the mass concentration of the perchlorate wastewater is 100–500 mg / L; The concentrate is a perchlorate solution with a concentration of 100–500 mg / mL.

5. The electrochemical adsorption treatment method for perchlorate wastewater according to claim 1, characterized in that, In step S2, the DC electric field is in constant voltage mode, with a voltage of 0.9 to 1.8V.

6. The electrochemical adsorption treatment method for perchlorate wastewater according to claim 1, characterized in that, In step S2, the surfaces of the anode current collector and the cathode current collector are respectively provided with 4 to 8 parallel serpentine flow channels, and the depth of the serpentine flow channels is 0.5 to 2.5 mm.

7. The electrochemical adsorption treatment method for perchlorate wastewater according to claim 1, characterized in that, In step S2, both the anode current collector and the cathode current collector are metal folded mesh current collectors. The metal folded mesh current collector is set in the groove of the working surface of the anode end plate and the cathode end plate, and its placement angle in the groove is 0 to 90°.

8. The electrochemical adsorption treatment method for perchlorate wastewater according to claim 7, characterized in that, The metal folded mesh current collector has a mesh count of 30 to 120, a thickness of 1 to 2 mm, and a corrugation interval of 1 to 2.5 mm.

9. An electrochemical adsorption treatment device for perchlorate wastewater, characterized in that, It includes, in sequence, a cathode end plate, a cathode sealing gasket, a cathode current collector, a first cation exchange membrane, a desalination chamber partition, an anion exchange membrane, a concentration chamber partition, a second cation exchange membrane, an anode current collector, an anode sealing gasket, and an anode end plate; The lower part of the cathode end plate is provided with a slurry input channel, a desalination liquid input channel and a concentrate input channel, which run through the entire desalination device; the upper part of the cathode end plate is provided with a slurry output channel, a desalination liquid output channel and a concentrate output channel, which run through the entire desalination device. The slurry input channel is connected to the electrode slurry storage tank via a slurry peristaltic pump. The slurry input channel passes through the cathode current collector, each membrane layer between the cathode current collector and the anode current collector, and the anode current collector in sequence, and then connects to the slurry output channel. The slurry output channel is connected to the electrode slurry storage tank. The desalination liquid input channel and the concentrate input channel are respectively connected to the desalination liquid storage tank and the concentrate storage tank via a multi-channel brine peristaltic pump. The desalination liquid input channel passes through the cathode current collector and the first cation exchange membrane to connect with the desalination chamber, and then sequentially passes through the anion exchange membrane, the second cation exchange membrane, and the anode current collector before connecting with the desalination liquid output channel, which is connected with the desalination liquid storage tank. The concentrate input channel passes through the anode current collector and the second cation exchange membrane to connect with the concentration chamber, and then sequentially passes through the anion exchange membrane, the first cation exchange membrane, and the cathode current collector before connecting with the concentrate output channel, which is connected with the concentrate storage tank.

10. The electrochemical adsorption treatment device for perchlorate wastewater according to claim 9, characterized in that, The partitions of the desalination chamber and the concentration chamber are both partition meshes, with a thickness of 1 to 2.55 mm and a mesh size of 40 to 100 meshes. The mesh shape of the partition mesh is one of square holes, round holes, or diamond holes; The partition mesh is made of one of polyethylene, polypropylene, and titanium.

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