A rotary detachable electrochemical treatment device

Abstract

The application discloses a rotary detachable electrochemical treatment device, and the core comprises a corrosion-resistant spiral electrode, a direct current, a rotatable cylindrical body with holes, a polycrystalline manganese carbon shuttle electrode material and a dynamic scattering system. The two electrodes are connected to the positive and negative poles of a direct current power supply, and an electric field is formed between the two electrodes. The side wall of the cylindrical body is provided with an anti-backflow inclined hole, and an electrode material hopper bin and an air compressor are arranged at the top of the cylindrical body. The material is uniformly scattered to the soil by air pressure driving. The device is externally integrated with spiral blades, which can stir the soil synchronously when the device rotates, so that the electrode pores are prevented from being blocked by particulate matter. After the repair is completed, the cylindrical body can be detached, and the electrode system is retained. When the device is operated, the electrode material is dynamically penetrated into the soil through the inclined hole, and the corrosion-resistant spiral electrode applies an electric field to drive the directional migration and reduction and fixation of heavy metal ions. Through the synergistic effect of rotary scattering and electric field, the application solves the technical problems of uneven repair, easy blockage and electrode deactivation of the static device, and is suitable for efficient in-situ repair of heavy metal contaminated soil.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical environmental remediation technology, specifically relating to a rotary removable electrochemical treatment device, which is particularly suitable for in-situ remediation of heavy metal contaminated soil. Background Technology

[0002] With the rapid development of industrialization and agricultural activities, soil heavy metal pollution has become an increasingly prominent problem. Heavy metals such as lead, cadmium, and chromium are difficult to degrade in soil and easily accumulate through the food chain, posing a serious threat to ecosystems and human health. Traditional remediation technologies, such as chemical stabilization and leaching, have drawbacks such as high risk of secondary pollution, long remediation cycles, or limited applicability, making them unsuitable for the remediation needs of complex contaminated sites.

[0003] Electrochemical remediation technology utilizes an electric field to drive the directional migration of heavy metal ions, combined with electrode reactions to achieve the reduction and fixation of pollutants, offering advantages such as high efficiency and strong controllability. However, existing electrochemical devices still face significant challenges in practical applications, including uneven electrode distribution, electrode passivation and clogging, and low material dispersion efficiency. The static layout of traditional fixed electrodes easily leads to uneven electric field intensity distribution, especially in heterogeneous soils, which can easily create remediation blind zones, affecting the overall treatment effect. Soil particles and colloidal substances easily deposit on the electrode surface, hindering ion conduction pathways and accelerating electrode corrosion, resulting in decreased system operational stability. The static spreading method of electrode materials (such as biochar) is prone to local aggregation due to differences in soil porosity, forming conductive short-circuit areas and reducing electric field utilization.

[0004] To address the aforementioned issues, existing technologies have attempted improvements using porous electrodes or mechanical vibration devices, but limitations remain. For example, poorly designed porous electrodes can lead to insufficient material permeability; while mechanical vibration can improve material dispersion, it can damage soil structure and exacerbate the risk of heavy metal migration. Furthermore, existing devices generally lack a dynamic synergistic mechanism between the electrode material and the soil, making it difficult to achieve continuous and efficient operation of the remediation process.

[0005] Therefore, there is an urgent need to develop an electrochemical device that can dynamically control material distribution, prevent electrode blockage, and optimize electric field distribution in order to overcome the shortcomings of existing technologies and improve the efficiency and reliability of heavy metal contaminated soil remediation. Summary of the Invention

[0006] This invention provides a rotary, removable electrochemical treatment device that solves problems such as uneven material distribution, electrode corrosion, and clogging in traditional electrochemical soil remediation, achieving efficient in-situ remediation and resource recovery of heavy metal contaminated soil. The technical solution of this invention is as follows:

[0007] In a first aspect, the present invention provides a rotary removable electrochemical treatment device for in-situ remediation of heavy metal contaminated soil. The device includes a corrosion-resistant spiral electrode, a DC power supply, a rotatable perforated cylinder, a polycrystalline manganese-carbon shuttle electrode material, a dynamic spreading system, and a removable structure.

[0008] The device features corrosion-resistant spiral electrodes with a titanium-based mixed metal oxide coating. These electrodes are connected to a DC power supply to create a uniform electric field. The spiral structure enhances ion migration efficiency and inhibits electrode passivation. A rotatable, perforated cylinder is coaxially positioned between the spiral electrodes. Its sidewalls are segmented into a lower rigid crushing section and a middle-upper flexible agitation section. The rigid section is equipped with spiral blades to crush the soil surface, while the flexible section features anti-backflow oblique holes and dynamically distributes polycrystalline manganese carbon material into the soil pores using centrifugal force. The elastic deformation of the flexible material achieves gentle agitation. A dynamic spreading system is integrated into the outer wall of the rotatable, perforated cylinder, which synchronously agitates the soil using spiral blades to prevent clogging. The modular, removable structure allows for the removal of the rotatable, perforated cylinder after repair, while retaining the electrodes in situ. This supports rapid disassembly and recyclability at multiple points, enabling efficient repair and resource-based remediation.

[0009] Optionally, the rotary removable electrochemical treatment device may further include a rotary main support, a crusher, an AC power supply, and an air compressor;

[0010] The rotating main support is coaxially connected to the perforated cylinder in the middle, and the crossbars on both sides fix the corrosion-resistant spiral electrodes to ensure stable electrode spacing and synchronous rotation. The crusher is set at the top of the funnel chamber and is used to pre-treat the material, filtering out particles that meet the porosity requirements through the sieve holes to prevent material from clogging the inclined holes. The positive and negative terminals of the AC power supply are respectively connected to the corrosion-resistant spiral electrodes, and it alternates with the DC power supply during the spreading stage to suppress the formation of a passivation layer on the electrode surface through the alternating electric field. The air compressor is set at the top of the rotatable perforated cylinder and applies controllable pressure to the polycrystalline manganese carbon material through the air pressure drive module. It works synergistically with the alternating AC / DC composite power supply to suppress electrode passivation while enhancing the material's penetration depth in highly compacted soil.

[0011] Optionally, the device has a rotation speed of 200 to 240 r / min, and the oblique holes on its sidewalls are at an angle of 45° to 60° to the direction of rotation, with a diameter range of 0.5 to 1 mm.

[0012] Optionally, the spacing between the corrosion-resistant spiral electrodes is 15–20 cm, and the applied current is 2–5 V / cm.

[0013] In a second aspect, the present invention provides a method for applying the aforementioned rotary removable electrochemical treatment device, comprising:

[0014] Step A1: The polycrystalline manganese-carbon shuttle electrode material is fed into the crusher through the feeding port;

[0015] Step A1: Within the treatment range of the device, the amount of polycrystalline manganese-carbon shuttle electrode material added is 5-10g per kilogram of the heavy metal contaminated soil.

[0016] The DC power supply is activated, creating a homogenized electric field on the corrosion-resistant spiral electrode. The rotating main support is then activated, causing the polycrystalline manganese-carbon shuttle electrode material to be uniformly dispersed in the heavy metal-contaminated soil. This process achieves oxidation-reduction treatment of heavy metal ions in the soil, forming heavy metal precipitates. The heavy metal precipitates are adsorbed into the pores of the polycrystalline manganese-carbon shuttle electrode material.

[0017] Optionally, the polycrystalline manganese-carbon shuttle electrode material is loaded into the funnel chamber, and the motor is started to drive the rotating main support.

[0018] Optionally, the application method further includes a method for preparing the corrosion-resistant spiral electrode, the preparation method of which is as follows:

[0019] Step B1: Sandblast the electrode surface to enhance the adhesion of the coating;

[0020] Step B2: Immerse the sandblasted electrode in the pickling solution, rinse with deionized water until neutral, and dry with nitrogen.

[0021] Step B3: Weigh RuCl3·xH2O, IrCl3·3H2O and Ti(OEt)4, dissolve them in a mixed solvent of n-butanol-acetylacetone, and stir magnetically to obtain a homogeneous coating solution;

[0022] Step B4: Apply the coating solution evenly to the electrode surface by brushing or spraying. The thickness of the wet film in a single application needs to be controlled. First, keep the temperature to evaporate the solvent and initially form an oxide skeleton. Then, raise the temperature and continue to keep the temperature to allow RuO2, IrO2 and TiO2 to form a solid solution structure. Repeat the coating-sintering process 3 times.

[0023] Optionally, in step B1, the alumina sand particles have a particle size of 80-120 mesh, the sandblasting pressure is 0.4-0.6 MPa, and the surface roughness Ra is controlled at 3.0-3.5 μm;

[0024] Optionally, in step B2, the pickling solution is preferably a 10wt% oxalic acid solution, the temperature is maintained at 80±2℃, and the treatment time is 20-30 min; or optionally, a 5-15wt% hydrochloric acid, sulfuric acid, or a mixed acid solution thereof (such as 10% HCl + 5% H2SO4) is used, and the treatment conditions are 50-70℃ and 10-40 min.

[0025] Optionally, in step B3, the molar percentage of Ru is 10%–30%, Ti is 60%–80%, Ir ≤ 10%, the mixture is magnetically stirred for 2–3 hours, the total metal ion concentration of the coating solution is 0.2–0.5 mol / L, and the pH value is adjusted to 1.5–2.5 (by adding nitric acid or ammonia).

[0026] Optionally, in step B4, the thickness of the single wet film is controlled at 10-15 μm, the temperature is maintained at 300-350℃ for 10-20 min, the temperature is raised to 450-520℃ and maintained for 1-2 h, the heating rate is 3-5℃ / min, the total coating thickness reaches 3-5 μm, and the density is ensured to be ≥95%.

[0027] Optionally, the application method further includes preparing the polycrystalline manganese-carbon composite shuttle electrode material, the preparation method of which is as follows:

[0028] Step C1, Pretreatment of biochar: The biochar is screened, washed and dried to obtain clean biochar;

[0029] Step C2: Place the pretreated biochar and manganese precursor in a beaker, add water to dissolve them, and then mix them ultrasonically to ensure full contact.

[0030] Step C3: Add potassium permanganate solution and ammonium sulfate solution in a certain molar ratio to the manganese precursor to the suspension in sequence, and stir the mixture at room temperature until it is completely dissolved.

[0031] Step C4: Transfer the mixed solution to a reaction vessel, hydrothermally heat it, and then allow it to cool naturally.

[0032] Step C5: Wash the reaction product repeatedly with deionized water and dry it in an oven to obtain polycrystalline manganese-carbon shuttle material.

[0033] Optionally, the biochar in step C1 can be bamboo charcoal, walnut charcoal, wood charcoal, etc., and the sieve mesh size is 4 to 7 mesh;

[0034] Optionally, in step C2, the amount of biochar is 1.5–2.5 g, the manganese precursor is manganese sulfate, the amount of deionized water added is 50–80 ml, the ultrasonic mixing time is 30–60 min, and the manganese sulfate content is 0.4–0.6 mol / L.

[0035] Optionally, in step C3, the molar ratio of the manganese precursor to potassium permanganate in the polycrystalline manganese-carbon shuttle material is 0.2 to 0.4, and the molar ratio of the manganese precursor to ammonium persulfate is 3.5 to 4.5.

[0036] Optionally, in step C3, the volumes of potassium permanganate solution and ammonium persulfate solution are 10-25 ml, the mixing speed is 200-240 r / min, and the time is 30-60 min.

[0037] Optionally, in step C4, the hydrothermal temperature and duration are as follows: 200℃ for 2-4 hours is the α-crystal dominance stage, promoting the formation of large-aperture tunnel structures; 140℃ for 8-12 hours is the β / γ crystal regulation stage, optimizing lattice stability and conductivity; and 120℃ for 2-4 hours is the δ-crystal modification stage, constructing a layered open structure.

[0038] Optionally, in step C5, the material is repeatedly washed with deionized water 4 to 5 times, and dried in an oven at a temperature of 60 to 80°C for 12 to 24 hours to obtain a polycrystalline manganese-carbon shuttle electrode material with an α-crystal MnO2 content of 40% to 60%, an γ-crystal MnO2 content of 10% to 15%, an δ-crystal MnO2 content of 25% to 40%, and an β-crystal MnO2 content of ≤5%.

[0039] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0040] (1) The rotary removable electrochemical treatment device provided by this invention achieves efficient remediation and long-term stable operation of heavy metal contaminated soil through dynamic spreading, synergy of polycrystalline materials and electric field, and anti-clogging and anti-corrosion mechanisms. When the device is started, the pretreated polycrystalline manganese-carbon shuttle electrode material is put into the funnel chamber. The rotating main support drives the perforated cylinder to run. Under the action of centrifugal force, the material permeates evenly into the soil pores through the anti-backflow inclined holes. The one-way opening design of the inclined holes effectively prevents backflow of soil particles. The outer spiral blades rotate synchronously, and the spiral blades on their surface agitate the soil particles, promote the diffusion of the material into the deeper layers, and peel off the attached particles on the electrode surface. The DC electric field drives the heavy metal ions to migrate directionally to the electrode surface, and fix them through electrostatic adsorption, thereby achieving stable remediation. In addition, it can accelerate charge transfer and combine with the porous framework of biochar to adsorb free ions, improve the redox performance, and thus achieve efficient remediation. In terms of the anti-clogging and anti-corrosion mechanism, the dynamic agitation of the spiral blades and the anti-backflow design of the inclined holes significantly reduce the pore blockage rate and eliminate the risk of secondary blockage throughout the process. In terms of corrosion protection, the surface of the spiral electrode is coated with a titanium-based mixed metal oxide and other anti-corrosion coatings, providing an efficient and sustainable solution for the remediation of heavy metal contaminated soil.

[0041] (2) The rotary removable electrochemical treatment device provided by this invention can significantly reduce reaction time and energy consumption. Specifically, through the design of chemical bonding synthesis of polycrystalline α / β / γ / δ-MnO2 and biochar, a composite remediation material with high activity, stability and charge transport capacity is constructed. Biochar is pretreated by 4-7 mesh sieve to form a porous framework, providing dispersion anchoring points for manganese oxides and inhibiting particle agglomeration; during the hydrothermal process, manganese sulfate and oxidant react synergistically at a molar ratio of 0.2-0.4, and the crystal ratio is controlled in stages: α-MnO2 is generated at 200℃, β-MnO2 and γ-MnO2 are induced to grow in combination at 140℃, and δ-MnO2 is stabilized at 120℃. The polycrystalline ordered-disordered composite structure achieves high redox performance, high porosity, specific surface area, and stability by synergistically combining the high active sites of the α-type crystal, the cycling stability of the β-type crystal, and the rapid charge transport characteristics of the γ / δ-type crystal, along with the π-π adsorption of biochar and the redox reaction of manganese oxides. This promotes the precipitation and separation of heavy metals. By using polycrystalline manganese-carbon shuttle electrode material as the core component of a three-dimensional particle electrode, combined with the synergistic effect of a corrosion-resistant spiral electrode and an alternating electric field, the remediation efficiency of heavy metal-contaminated soil is significantly improved. The three-dimensional particle electrode has different pore channels, providing a rapid diffusion path for heavy metal ions, shortening the diffusion distance of pollutants to the electrode surface; the dense Mn within the channels... 3+ / Mn 4+ Redox sites significantly increase the electron transfer rate. An alternating electric field excites microcurrents on the surface of the three-dimensional electrode, driving ions to accumulate directionally within the channels through electromagnetic effects. Simultaneously, periodic current reversal dynamically renews the active sites on the electrode surface, and combined with eddy current thermal effects to dissolve the passivation layer, the continuous operation time of the electrode is extended. The device reduces operating energy consumption and offers advantages in both efficient remediation and resource recycling.

[0042] (3) The rotary removable electrochemical treatment device provided by this invention has sustainable advantages after remediation, specifically: First, the device efficiently converts migratory heavy metals into a low-toxicity stable state through the synergistic effect of composite remediation materials and electric fields, significantly reducing environmental risks, and the remediated soil can be directly and safely utilized; Second, the rotary spreading system and alternating electric field design endow the device with anti-clogging performance and long-term operation capability, adapting to complex soil environments and requiring no frequent maintenance; Third, the remediation materials can be magnetically separated and recycled, and the enriched heavy metals can be extracted as resources, forming a closed-loop chain of remediation, recycling, and reuse. In addition, after the device is removed, only the electrodes are retained in situ to stabilize pollutants, avoiding secondary excavation disturbance, and no chemical additives are introduced throughout the process, resulting in excellent environmental compatibility.

[0043] In summary, this invention achieves efficient remediation and resource recovery of heavy metal contaminated soil through polycrystalline composite materials, synergistic electric field control, and resource recycling design, breaking through the bottlenecks of traditional technologies such as low efficiency, high cost, and high risk of secondary pollution. Attached Figure Description

[0044] The accompanying drawings, which constitute a part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0045] Figure 1 This is a schematic diagram of the structure of a rotary removable electrochemical treatment device according to Embodiment 1 of the present invention;

[0046] Figure 2 This is a schematic diagram showing the connection of a corrosion-resistant spiral electrode to a DC power supply and an AC power supply.

[0047] Figure 3 This is a partial view of the oblique hole on the side wall of a rotatable cylinder with a hole;

[0048] Figure 4 This is a top view of a rotatable cylinder with a hole;

[0049] Figure 5 The diagram shows the corrosion-resistant spiral electrode structure and corresponding electric field intensity distribution in Example 1 and Comparative Example 1. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0051] Example 1:

[0052] See Figures 1-4 A rotary removable electrochemical treatment device includes a corrosion-resistant spiral electrode 1 (such as titanium-plated ruthenium alloy, the alloy used conforming to the HG / T2471-2011 standard), a DC power supply 2, a rotatable perforated cylinder 3, a polycrystalline manganese-carbon shuttle electrode material 4, a dynamic spreading system 5, and a removable structure 6.

[0053] The corrosion-resistant spiral electrode 1 (spacing range of 15cm) has a titanium-based mixed metal oxide coating (RuO2:IrO2:TiO2 = 20:10:70) with a coating thickness controlled at 3μm. The corrosion-resistant spiral electrode 1 is rigidly connected to the positive and negative terminals of the DC power supply 2 to form a closed loop and establish a directional electric field in the soil. The rotatable perforated cylinder 3 (hole diameter of 0.5mm) has oblique holes on its sidewalls at a 45° angle to the direction of rotation, and its top is connected to a funnel chamber 3.1. Furthermore, the sidewall of the rotatable perforated cylinder 3 adopts a segmented composite structure design. Its lower rigid spiral blades 3.2 are made of high-strength alloy and are used to cut into and break the soil surface. The upper and middle sidewall spiral blades 3.3 are made of flexible and corrosion-resistant polymer material polyurethane. Through elastic deformation, they achieve gentle soil agitation, avoid excessive damage to the soil aggregate structure, and reduce rotational resistance. At the same time, small holes are arranged on the top to evenly spread polycrystalline manganese carbon material 4 into the soil pores through the inclined holes by rotational centrifugal force. Anti-clogging baffles 3.4 are provided on the holes. There are multiple polycrystalline manganese carbon shuttle electrode materials 4, which enter the rotatable perforated cylinder 3 through the funnel chamber 3.1. The lower rigid spiral blades and the upper and middle flexible and corrosion-resistant polyurethane material spiral blades of the dynamic spreading system 5 are integrated into the outer wall of the rotatable perforated cylinder 3 by welding, and the rotation synchronously agitates the soil. The removable structure 6 drives the rotatable perforated cylinder 3 to rotate in the opposite direction after repair, so as to achieve physical separation of the rotatable perforated cylinder 3 from the spiral electrode 1. When powered by the DC power supply 2, a stable electric field is formed between the spiral electrodes 1, driving the migration of heavy metals. The rotating perforated cylinder 3 allows the polycrystalline manganese-carbon shuttle electrode material 4 to be centrifugally spread through oblique holes and mixed with the spiral blades of the dynamic spreading system 5. During disassembly, the spiral electrodes 1 are separated by the threads of the removable structure 6, preserving the corrosion-resistant spiral electrodes 1 in situ to maintain a stable heavy metal morphology. The removable structure 6 adopts a modular quick-disassembly design, using bidirectional threaded connections and positioning slots to enable rapid disassembly and repeated deployment of the device at multiple points within the same contaminated area. After disassembly, the spiral electrodes 1 remain in situ to maintain a stable heavy metal morphology, and the rotating perforated cylinder 3 can be transferred to adjacent locations for reuse, eliminating the need for repeated soil excavation, significantly improving remediation efficiency and reducing construction costs.

[0054] The rotary removable electrochemical treatment device also includes a rotary main support 7, a crusher 8, an AC power supply 9, and an air compressor 10.

[0055] The rotating main support 7 serves as the core support structure, with its central shaft rigidly connected to the rotatable perforated cylinder 3 via coaxial alignment, secured with high-strength bolts to transmit rotational torque. The horizontal bars extending from both sides of the rotating main support 7 are mechanically connected to the top of the double-sided spiral electrodes 1 via bidirectional threads. After repair, reverse rotation drives the threads to disengage, physically separating the rotating main support 7 from the double-sided spiral electrodes 1, allowing the corrosion-resistant spiral electrodes 1 to remain in the soil for continued operation. A high-strength aluminum alloy slide rail is installed at the bottom of the crusher 8, matching the guide groove at the top of the funnel hopper 3.1, enabling quick installation via push-pull sliding. A spring lock is installed at the end of the slide rail, automatically locking after being pushed in to ensure operational stability. For disassembly, pressing the lock allows the crusher 8 to be pulled out along the slide rail for easy screen cleaning or blade replacement. Power transmission uses a built-in motor directly connected to the blade shaft, eliminating belt drive and reducing space occupation. The crusher 8 is fixed to the top of the funnel hopper, with an internal screen controlling material particle size and preventing clogging of the rotatable perforated cylinder 3. The AC power supply 9 is connected in parallel with electrode 1, and its positive and negative interfaces are connected to the reserved ports of the corrosion-resistant spiral electrode 1 via waterproof plugs, forming a complementary power supply with the DC power supply 2: when the DC electric field drives ion migration, the AC power supply periodically outputs pulse current, which vibrates and peels off surface deposits through the corrosion-resistant spiral electrode 1. The control module of the AC power supply 9 is integrated in the electrical box of the main support 7, and can switch between AC / DC modes. The device further integrates an air compressor 10, which is located at the top of the funnel chamber 3.1. It applies controllable pressure to the polycrystalline manganese carbon material 4 through a pneumatic drive module, and works synergistically with the AC / DC composite power supply to suppress electrode passivation while enhancing the material's penetration depth in dense soil.

[0056] A method of applying the aforementioned rotary removable electrochemical treatment device includes:

[0057] Step A1: The polycrystalline manganese-carbon shuttle electrode material is fed into the crusher 8 through the feeding port;

[0058] Step A2: Within the treatment range of the device, the amount of polycrystalline manganese-carbon shuttle electrode material 4 is controlled to be 5g per kilogram of heavy metal contaminated soil.

[0059] The DC power supply 2 is activated (voltage 5V / cm, time 30min), creating a homogenized electric field on the corrosion-resistant spiral electrodes 1 (spaced 15cm). The rotating main support 7 is then activated (rotation speed 200r / min), allowing the rotatable perforated cylinder 3 (pore diameter range 1mm) to distribute the polycrystalline manganese-carbon shuttle electrode material 4 evenly in the heavy metal-contaminated soil. This achieves oxidation-reduction treatment of heavy metal ions in the contaminated soil, forming heavy metal precipitates. The heavy metal precipitates are adsorbed into the pores of the polycrystalline manganese-carbon shuttle electrode material 4.

[0060] The application method also includes a method for preparing the corrosion-resistant spiral electrode 1, the preparation method of which is as follows:

[0061] Step B1: Sandblast the electrode surface to enhance the adhesion of the coating;

[0062] Step B2: Immerse the sandblasted electrode in the pickling solution, rinse with deionized water until neutral, and dry with nitrogen.

[0063] Step B3: Weigh RuCl3·xH2O, IrCl3·3H2O and Ti(OEt)4, dissolve them in a mixed solvent of n-butanol-acetylacetone, and stir magnetically to obtain a homogeneous coating solution;

[0064] Step B4: Apply the coating solution evenly to the electrode surface by brushing or spraying. The thickness of the wet film in a single application needs to be controlled. First, keep the temperature to evaporate the solvent and initially form an oxide skeleton. Then, raise the temperature and continue to keep the temperature to allow RuO2, IrO2 and TiO2 to form a solid solution structure. Repeat the coating-sintering process 3 times.

[0065] In step B1, the alumina sand particles are 100 mesh in size, the sandblasting pressure is 0.4–0.6 MPa, and the surface roughness Ra is controlled at 3.0 μm. In step B2, the pickling solution is preferably a 10 wt% oxalic acid solution, the temperature is maintained at 80 ± 2 °C, and the treatment time is 30 min; alternatively, 10 wt% hydrochloric acid is used, and the treatment conditions are 60 °C and 30 min. In step B3, the Ru:Ir:Ti molar ratio is 2:1:7, the mixture is magnetically stirred for 2 h, the total metal ion concentration of the coating solution is 0.3 mol / L, and the pH value is adjusted to 2 (by adding nitric acid or ammonia). In step B4, the thickness of the single wet film is controlled at 10 μm, the temperature is raised to 300 °C for 10 min, then raised to 500 °C and held for 2 h, the heating rate is 5 °C / min, and the total coating thickness reaches 5 μm, ensuring a density ≥95%.

[0066] The application method also includes preparing the polycrystalline manganese-carbon shuttle electrode material 4, the preparation method of which is as follows:

[0067] Step C1, Pretreatment of biochar: The bamboo charcoal is sieved, washed and dried to obtain clean bamboo charcoal;

[0068] Step C2: Take 2g of pretreated bamboo charcoal and manganese sulfate and place them in a beaker. Add 50ml of water to dissolve them and then sonicate for 60min to ensure full contact.

[0069] Step C3: Add potassium permanganate solution and ammonium persulfate solution in a certain proportion to the amount of manganese sulfate to the suspension in sequence, and stir the mixture at 240 r / min for 30 min at room temperature until it is completely dissolved.

[0070] Step C4: Transfer the mixed solution to a 100ml reaction vessel, hydrothermally heat it, and then allow it to cool naturally.

[0071] Step C5: Wash repeatedly with deionized water 4-5 times, and dry in an oven at 80℃ for 24 hours to obtain α / β / γ / δ crystalline polycrystalline manganese carbon shuttle electrode material.

[0072] In step C2, the manganese sulfate content is 0.6 mol / L; in step C3, the molar ratio of manganese precursor to potassium permanganate in the polycrystalline manganese-carbon shuttle material is 2:7, and the molar ratio of manganese precursor to ammonium persulfate is 4:1; in step C4, the hydrothermal temperature and duration are 4h at 200℃, 12h at 140℃, and 4h at 120℃, respectively, ultimately obtaining a polycrystalline manganese-carbon shuttle electrode material with 49% α-crystal MnO2, 13% γ-crystal MnO2, 34% δ-crystal MnO2, and 4% β-crystal MnO2.

[0073] Example 2:

[0074] Unlike Example 1:

[0075] The spacing between the corrosion-resistant spiral electrodes 1 is 1 cm;

[0076] The aperture range of the sieve holes on the sieve plate 7 is 0.8 mm.

[0077] Step C1, Pretreatment of biochar: The bamboo charcoal is sieved, washed and dried to obtain clean bamboo charcoal;

[0078] Step C2: Take 2g of pretreated bamboo charcoal and manganese sulfate and place them in a beaker. Add 50ml of water to dissolve them and then sonicate for 60min to ensure full contact.

[0079] Step C3: Add potassium permanganate solution and ammonium persulfate solution in a certain proportion to the amount of manganese sulfate to the suspension in sequence, and stir the mixture at 240 r / min for 30 min at room temperature until it is completely dissolved.

[0080] Step C4: Transfer the mixed solution to a 100ml reaction vessel, hydrothermally heat it, and then allow it to cool naturally.

[0081] Step C5: Wash repeatedly with deionized water 4-5 times, and dry in an oven at 80℃ for 24 hours to obtain α / β / γ / δ crystalline polycrystalline manganese carbon shuttle electrode material.

[0082] In step C2, the manganese sulfate content is 0.5 mol / L. In step C3, the molar ratio of manganese precursor to potassium permanganate in the polycrystalline manganese-carbon shuttle material is 1:3, and the molar ratio of manganese precursor to ammonium persulfate is 7:2. In step C4, the hydrothermal temperature and duration are 3 hours at 200℃, 8 hours at 140℃, and 3 hours at 120℃, respectively, ultimately obtaining a polycrystalline manganese-carbon shuttle electrode material with 53% α-crystal MnO2, 11% γ-crystal MnO2, 33% δ-crystal MnO2, and 3% β-crystal MnO2.

[0083] Example 3:

[0084] Unlike Example 1:

[0085] The spacing between the corrosion-resistant spiral electrodes 1 is 0.8 cm;

[0086] The aperture range of the sieve holes on the sieve plate 7 is 1 mm.

[0087] Step C1, Pretreatment of biochar: The bamboo charcoal is sieved, washed and dried to obtain clean bamboo charcoal.

[0088] Step C2: Take 2g of pretreated bamboo charcoal and manganese sulfate and place them in a beaker. Add 50ml of water to dissolve them and then sonicate for 60min to ensure full contact.

[0089] Step C3: Add potassium permanganate solution and ammonium persulfate solution in a certain proportion to the amount of manganese sulfate to the suspension in sequence, and stir the mixture at 240 r / min for 30 min at room temperature until it is completely dissolved.

[0090] Step C4: Transfer the mixed solution to a 100ml reaction vessel, hydrothermally heat it, and then allow it to cool naturally.

[0091] Step C5: Wash repeatedly with deionized water 4-5 times, and dry in an oven at 80℃ for 24 hours to obtain α / β / γ / δ crystalline polycrystalline manganese carbon shuttle electrode material.

[0092] In step C2, the manganese sulfate content is 0.4 mol / L. In step C3, the molar ratio of manganese precursor to potassium permanganate in the polycrystalline manganese-carbon shuttle material is 2:5, and the molar ratio of manganese precursor to ammonium persulfate is 8:3. In step C4, the hydrothermal temperature and reaction time are 4 h at 200℃, 10 h at 140℃, and 2 h at 120℃, respectively, to finally obtain a polycrystalline manganese-carbon shuttle electrode material with 58% α-crystal MnO2, 10% γ-crystal MnO2, 27% δ-crystal MnO2, and 5% β-crystal MnO2.

[0093] Comparative Example 1:

[0094] The difference from Example 1 is as follows: Figures 4-5 As shown, the spiral blades of the dynamic spreading system 5 are not installed outside the rotatable perforated cylinder 3.

[0095] Comparative Example 2:

[0096] The difference from Example 1 is that the titanium-based mixed metal oxide coating is replaced with a graphene coating in the preparation of the corrosion-resistant spiral electrode 1.

[0097] Comparative Example 3:

[0098] The difference from Example 1 is that potassium permanganate solution is not added in the preparation of polycrystalline manganese carbon shuttle electrode material 4.

[0099] Comparative Example 4:

[0100] The difference from Example 1 is that bamboo charcoal was replaced with walnut charcoal in the preparation of polycrystalline manganese carbon shuttle electrode material 4.

[0101] Comparative Example 5:

[0102] The difference from Example 1 is that polycrystalline manganese carbon shuttle electrode material 4 is not added.

[0103] Comparative Example 6:

[0104] The difference from Example 1 is that: no polycrystalline manganese carbon shuttle electrode material 4 is added and unmodified bamboo charcoal is added.

[0105] Comparative Example 7:

[0106] The difference from Example 1 is that no electric field is applied, that is, the DC power supply 2 and the AC power supply 9 are not started.

[0107] The heavy metal contaminated soil used in Examples 1-3 and Comparative Examples 1-7 of this invention were all artificially simulated heavy metal contaminated soil. The specific simulation details are as follows:

[0108] In simulated heavy metal contaminated soil, the Cr content was 100 mg / L and the Tl content was 100 μg / L.

[0109] Table 1. Concentrations and removal rates of Cr(VI) and Tl(I) after treatment

[0110]

[0111] Based on this study that validates the results, the following conclusions can be drawn:

[0112] Examples 1-3 of this invention significantly improve the removal efficiency of Cr(VI) and Tl(I) through the synergistic effect of polycrystalline manganese-carbon electrode material 4, rotary spreading system 5, DC power supply 2, and AC power supply 9. Examples 1-3 address the pain points of traditional technologies such as material deactivation, clogging, and uneven remediation through a triple synergy of dynamic spreading optimizing material dispersion, polycrystalline material enhancing redox activity, and alternating electric field suppressing electrode passivation, providing a highly efficient solution for Cr(VI) and Tl(I) contaminated soil.

[0113] A comparison of Example 1 and Comparative Example 1 shows that the dynamic spreading system 5 and the spiral blade design play a decisive role in the heavy metal removal efficiency and device stability. Example 1 uses a rotatable perforated cylinder and integrated external spiral blades to uniformly spread polycrystalline manganese carbon electrode material through centrifugal force. Simultaneously, the spiral blades agitate the soil at 200 r / min, breaking up agglomerates and preventing electrode clogging. Experimental data show that the removal rates of Cr(VI) and Tl(I) reached 96.52% and 91.31%, respectively. In contrast, Comparative Example 1 did not have spiral blades and relied solely on gravity to spread the material, resulting in material accumulation in the surface soil. Deeper pollutants could not effectively contact the electrodes, and the electrode pores experienced high clogging rates due to particle backflow, causing the removal rates of Cr(VI) and Tl(I) to plummet to 35.86% and 30.53%, respectively. Furthermore, the anti-backflow oblique hole design (45° opening direction) in Example 1 blocks the backflow of soil particles through rotational centrifugal force, while the comparative scheme, lacking this structure, experienced a 60% decrease in electric field strength due to electrode pore blockage after 30 minutes of operation. The results indicate that the spiral blade agitation and oblique hole anti-backflow design of the dynamic spreading system 5 are the core elements for improving material dispersion and maintaining electric field stability, directly determining the directional migration efficiency and remediation uniformity of heavy metal ions.

[0114] A comparison of Example 1 and Comparative Example 2 shows that in the fabrication process of the corrosion-resistant spiral electrode 1, replacing the titanium-based mixed metal oxide coating with a graphene coating significantly reduced the electrode's removal efficiency for Cr(VI) and Tl(I) contaminants. Table 1 shows that Example 1, using the titanium-based mixed metal oxide coating, achieved removal rates of 96.52% and 91.31% for Cr(VI) and Tl(I), respectively, while Comparative Example 2, using a graphene coating, saw these rates drop to 80.77% and 78.96%, representing reductions of 15.75% and 12.35%, respectively. This difference stems from the contrasting electrochemical properties of the two coatings. The titanium-based mixed metal oxide coating possesses a porous gradient structure and a high density of catalytically active sites, promoting the continuous generation of ·OH and the kinetics of pollutant oxidation reactions. While the graphene coating exhibits high conductivity, its two-dimensional layered structure limits the effective catalytic area, and surface functional groups (such as epoxy and carboxyl groups) are prone to protonation passivation during electrolysis, weakening the charge transfer efficiency of redox reactions. Furthermore, the interfacial bonding strength between graphene and the titanium matrix is ​​significantly lower than that of the titanium-based mixed metal oxide coating, making it susceptible to coating delamination under high-speed rotation of the helical electrode, further exacerbating performance degradation. In summary, the titanium-based mixed metal oxide coating outperforms the graphene coating in terms of catalytic activity, structural stability, and interfacial bonding.

[0115] A comparison of Example 1 and Comparative Example 3 shows that potassium permanganate plays a crucial regulatory role in the redox activity of Cr(VI) and Tl(I) in the synthesis of polycrystalline manganese-carbon electrode material 4. In Example 1, manganese sulfate was reacted with potassium permanganate via a staged hydrothermal method to generate an α / β / γ / δ-MnO2 polycrystalline composite structure. The α-MnO2 provides a highly active tunnel structure, while the δ-MnO2 forms layered adsorption sites, synergistically enhancing the reduction efficiency of Cr(VI) and the fixation capacity of Tl(I). In Comparative Example 2, without the addition of potassium permanganate, the material relied solely on the self-oxidation of manganese sulfate to generate a single β-MnO2 crystal form, resulting in a reduced specific surface area and removal rates of only 47.65% and 43.84% for Cr(VI) and Tl(I), respectively. Furthermore, the lack of potassium permanganate led to a deterioration in the material's conductivity. Experiments demonstrate that potassium permanganate, by regulating the crystal ratio and surface defect state density, is a core element in constructing a polycrystalline synergistic effect and achieving efficient heavy metal removal.

[0116] A comparison of Example 1 and Comparative Example 4 shows that the type of biochar has a significant impact on the adsorption performance and structural stability of the polycrystalline manganese carbon electrode material 4. Example 1 uses bamboo charcoal as a porous framework. Its unique fibrous pore structure provides uniformly dispersed anchoring sites for manganese oxides, and its surface oxygen-containing functional groups, such as carboxyl and hydroxyl groups, can efficiently adsorb Cr(VI) (96.52%) and Tl(I) (91.31%). In Comparative Example 3, after using walnut charcoal, the high lignin content resulted in a predominantly closed-pore pore structure after carbonization, leading to the agglomeration of manganese oxide particles and a decrease in the exposure rate of active sites. Simultaneously, the lower density of functional groups on the surface of walnut charcoal compared to bamboo charcoal weakens its electrostatic adsorption capacity for Tl(I), reducing the removal rates of Cr(VI) and Tl(I) to 64.95% and 64.42%, respectively. Furthermore, bamboo charcoal exhibits significantly better conductivity than walnut charcoal, accelerating the electron transfer rate in the electric field and further enhancing the reduction and fixation efficiency of heavy metal ions. Experiments show that the multi-level pores, high surface activity, and conductivity of bamboo charcoal are key to achieving efficient repair of polycrystalline materials.

[0117] A comparison of Example 1 and Comparative Example 5 shows that the presence of polycrystalline manganese carbon electrode material 4 is the core driving force for the efficient reduction and fixation of heavy metal ions. In Example 1, by adding polycrystalline manganese carbon material, the tunnel structure of its α-MnO2 and the layered pores of δ-MnO2 synergistically adsorb Cr(VI) and Tl(I). At the same time, the π-π conjugated framework of biochar enriches free heavy metal ions through electrostatic interaction, combined with Mn under the drive of an electric field. 3+ / Mn 4+ The rapid redox cycle of the sample achieved removal rates of 96.52% for Cr(VI) and 91.31% for Tl(I). In contrast, the polycrystalline manganese-carbon electrode material 4 (Comparative Example 4), relying solely on the electric field, lacked active sites. Cr(VI) accumulated on the electrode surface through electromigration but could not be effectively reduced, while Tl(I) remained largely in the soil pores due to insufficient adsorption capacity, resulting in a sharp drop in removal rates to 24.35% and 19.36% for Cr(VI) and Tl(I), respectively. This demonstrates that the polycrystalline manganese-carbon electrode material 4 significantly shortened the diffusion path of heavy metal ions and improved electron transfer efficiency through an adsorption-catalysis synergistic mechanism. This comparison proves that the absence of polycrystalline manganese-carbon material 4 leads to a substantial decrease in heavy metal remediation efficiency.

[0118] A comparison of Example 1 and Comparative Example 6 shows that the redox active sites of manganese oxide in the polycrystalline manganese-carbon electrode material 4 are the core of efficient heavy metal removal. Example 1 uses the polycrystalline manganese-carbon shuttle electrode material 4, whose manganese oxide lattice contains Mn... 3+ / Mn 4+The redox pair can directly reduce Cr(VI) to Cr(III) and form a stable Tl-O-Mn complex with Tl(I) through surface hydroxyl groups. In contrast, Comparative Example 5, using only unmodified bamboo charcoal, lacks catalytically active sites for manganese oxides. The reduction of Cr(VI) relies on indirect electron transfer driven by an electric field, and Tl(I) exhibits a high desorption rate due to the inability to form chemical bonds. Furthermore, the polycrystalline manganese-carbon shuttle electrode material 4 significantly enhances the electron migration rate in the electric field, resulting in a significantly higher concentration of heavy metal ions on the material surface. These results indicate that the polycrystalline manganese-carbon material, through a synergistic adsorption-catalysis-conductivity mechanism, overcomes the shortcomings of traditional biochar materials, such as low activity and poor selectivity, and is key to achieving efficient removal of Cr(VI) and Tl(I).

[0119] A comparison of Example 1 and Comparative Example 7 shows that the application of a DC / AC electric field is the core driving force for the directional migration of heavy metal ions and the activation of material activity. Example 1 uses alternating DC and AC electric fields to create a homogenized electric field between the spiral electrodes, driving Cr(VI) and Tl(I) to migrate towards the electrodes, while simultaneously activating Mn in the polycrystalline manganese-carbon material. 3+ / Mn 4+ Redox active sites were established to achieve deep reduction of Cr(VI) and stable fixation of Tl(I). In contrast, in Comparative Example 6, without an applied electric field, heavy metal ions diffused solely through the concentration gradient, and the active sites remained inert due to the lack of electric field polarization, resulting in a sharp drop in the removal rates of Cr(VI) and Tl(I) to 9.84% and 6.18%, respectively. These results indicate that the electric field not only accelerates heavy metal enrichment through electromigration but also enhances redox activity by regulating the surface charge distribution of the material; both are indispensable. Furthermore, the thermal effect of the alternating electric field (heating the electrode surface to 60-80°C in Example 1) can dissolve the passivation layer and promote material regeneration, whereas Comparative Example 6 lacked this mechanism and even became completely deactivated after 2 hours of continuous operation.

[0120] In summary, this invention achieves uniform penetration and soil agitation of polycrystalline manganese-carbon electrode material 4 through a rotary dynamic spreading system 5 (perforated cylinder + helical blades), combined with AC / DC electric field synergistic drive, significantly improving the removal efficiency of Cr(VI) and Tl(I). The polycrystalline manganese-carbon shuttle electrode material achieves rapid reduction and stable fixation of heavy metal ions through polycrystalline synergistic effect and biochar adsorption-catalysis coupling mechanism. The anti-backflow oblique hole design of the device controls the pore blockage rate to below 8%, and the eddy current thermal effect of the alternating electric field dissolves the passivation layer and achieves material regeneration. Compared with traditional technologies, this solution significantly shortens the remediation cycle and reduces operating energy consumption, combining the advantages of high-efficiency remediation, long-term stability, and resource recycling, making it suitable for in-situ remediation of complex soil environments.

[0121] Finally, it should be pointed out that the above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A rotary removable electrochemical treatment device for in-situ remediation of heavy metal contaminated soil, characterized in that, Includes corrosion-resistant spiral electrode (1), DC power supply (2), rotatable perforated cylinder (3), polycrystalline manganese-carbon shuttle electrode material (4), dynamic spreading system (5), modular removable structure (6). The device is equipped with a corrosion-resistant spiral electrode (1) with a titanium-based mixed metal oxide coating on its surface. It is connected to a DC power supply (2) to form a uniform electric field. The spiral structure enhances ion migration efficiency and inhibits electrode passivation. A rotatable perforated cylinder (3) is coaxially arranged between the spiral electrodes (1). Its sidewall is designed in sections as a lower rigid crushing section and a middle and upper flexible stirring section. The rigid section is equipped with spiral blades to crush the soil surface. The flexible section is equipped with anti-backflow oblique holes and dynamically spreads polycrystalline manganese carbon shuttle electrode material (4) to the soil pores through rotational centrifugal force. The elastic deformation of the flexible material achieves gentle stirring. The dynamic spreading system (5) is integrated into the outer wall of the rotatable perforated cylinder (3) and synchronously stirs the soil through spiral blades to prevent clogging. The modular removable structure (6) can be removed from the rotatable perforated cylinder (3) after repair and retain the original function of the electrode. It supports rapid disassembly and recycling at multiple points and achieves efficient repair and resource-based management. The rotatable perforated cylinder (3) has a rotation speed of 200~240 r / min, and the anti-backflow oblique hole on its sidewall forms an angle of 45°~60° with the rotation direction, with a hole diameter range of 0.5~1 mm; the spacing of the corrosion-resistant spiral electrode (1) ranges from 15~20 cm, and the voltage gradient ranges from 2~5 V / cm; in the polycrystalline manganese carbon shuttle electrode material (4), the proportion of α-crystal MnO2 is 40%~60%, γ-crystal MnO2 is 10%~15%, δ-crystal MnO2 is 25%~40%, and β-crystal MnO2 is ≤5%, and the total proportion of the four crystal forms of α, β, γ, and δ MnO2 is 100%.

2. The rotary removable electrochemical treatment device according to claim 1, characterized in that, It also includes a rotating main support (7), a crusher (8), an AC power supply (9), and an air compressor (10). The rotating main support (7) is coaxially connected to the rotatable perforated cylinder (3), and the crossbars on both sides fix the corrosion-resistant spiral electrode (1) to ensure the stability of the electrode spacing and the synchronicity of rotation; the crusher (8) is set at the upper end of the funnel chamber to pre-treat the material, filter out particles that meet the pore requirements through the sieve holes, and avoid the material from clogging the inclined holes; the positive and negative poles of the AC power supply (9) are respectively connected to the corrosion-resistant spiral electrode (1), and it runs alternately with the DC power supply (2) during the spreading stage, and suppresses the formation of the passivation layer on the electrode surface through the alternating electric field; the air compressor (10) is set at the top of the rotatable perforated cylinder (3), and applies controllable pressure to the polycrystalline manganese carbon shuttle electrode material (4) through air pressure drive to enhance the penetration depth of the material in high-density soil.

3. A method for applying the rotary removable electrochemical treatment device as described in any one of claims 1-2, characterized in that, include: Step A1: The polycrystalline manganese carbon shuttle electrode material (4) is fed into the feed port of the crusher (8); Step A2: According to the treatment range of the device, the amount of polycrystalline manganese-carbon shuttle electrode material (4) added per kilogram of heavy metal contaminated soil is controlled to be 5-10 g. The DC power supply (2) is turned on, so that the corrosion-resistant spiral electrode (1) forms a homogenized electric field; the rotating main support (7) is turned on, so that the polycrystalline manganese carbon shuttle electrode material (4) is uniformly dispersed in the heavy metal contaminated soil, so as to realize the oxidation-reduction treatment of heavy metal ions in the heavy metal contaminated soil and form heavy metal precipitate; the heavy metal precipitate is adsorbed in the pores of the polycrystalline manganese carbon shuttle electrode material (4).

4. The application method according to claim 3, characterized in that, The application method also includes preparing the corrosion-resistant spiral electrode (1), the preparation method of which is as follows: Step B1: Sandblast the electrode surface to enhance the adhesion of the coating; Step B2: Immerse the sandblasted electrode in the pickling solution, rinse with deionized water until neutral, and dry with nitrogen. Step B3: Weigh RuCl3·xH2O, IrCl3·3H2O and Ti(OEt)4, dissolve them in a mixed solvent of n-butanol-acetylacetone, and stir magnetically to obtain a homogeneous coating solution; Step B4: Apply the coating solution evenly to the electrode surface by brushing or spraying, controlling the thickness of the wet film in a single application; first, keep the temperature to evaporate the solvent and initially form an oxide skeleton; then raise the temperature and continue to keep the temperature to allow RuO2, IrO2 and TiO2 to form a solid solution structure; repeat the coating-sintering process 3 times.

5. The application method according to claim 4, characterized in that, In step B1, the alumina sand particles have a particle size of 80-120 mesh, the sandblasting pressure is 0.4-0.6 MPa, and the surface roughness Ra is controlled at 3.0-3.5 μm. In step B2, the pickling solution is a 10 wt% oxalic acid solution, the temperature is maintained at 80±2℃, and the treatment time is 20-30 min; or a 5-15 wt% hydrochloric acid solution, a 5-15 wt% sulfuric acid solution, or a mixed acid solution of hydrochloric acid and sulfuric acid is used, and the treatment conditions are 50-70℃ for 10-40 min. In step B3, the Ru molar ratio is 10%-30%, Ti is 60%-80%, Ir≤10%, magnetic stirring is performed for 2-3 h, the total metal ion concentration of the coating solution is 0.2-0.5 mol / L, and the pH value is adjusted to 1.5-2.

5. In step B4, the single wet film thickness is controlled at 10-15 μm, and the temperature is maintained at 300-350℃ for 10-20 minutes. Heat to 450-520℃ and hold for 1-2 hours at a rate of 3-5℃ / min. The total coating thickness should be 3-5 μm, ensuring a density of ≥95%.

6. The application method according to claim 5, characterized in that, The application method also includes the preparation of the polycrystalline manganese-carbon shuttle electrode material (4), the preparation method of which is as follows: Step C1, Pretreatment of biochar: The biochar is screened, washed and dried to obtain clean biochar; Step C2: Place the pretreated biochar and manganese precursor in a beaker, add water to dissolve them, and then mix them ultrasonically to ensure full contact. Step C3: Add potassium permanganate solution and ammonium persulfate solution to the suspension in the specified molar ratio with the manganese precursor, and stir the mixture at room temperature until completely dissolved. Step C4: Transfer the mixed solution to a reaction vessel, hydrothermally heat it, and then allow it to cool naturally. Step C5: Wash the reaction product repeatedly with deionized water and dry it in an oven to obtain polycrystalline manganese-carbon shuttle electrode material.

7. The application method according to claim 6, characterized in that, In step C1, the biochar is selected from bamboo charcoal, walnut charcoal, and wood charcoal, and the sieve mesh size is 4-7 mesh; in step C2, the amount of biochar is 1.5-2.5 g, the manganese precursor is manganese sulfate, the amount of deionized water added is 50-80 ml, the ultrasonic mixing time is 30-60 min, and the manganese sulfate content is 0.4-0.6 mol / L; in step C3, the molar ratio of manganese precursor to potassium permanganate in the polycrystalline manganese-carbon shuttle electrode material (4) is 0.2-0.4, the molar ratio of manganese precursor to ammonium persulfate is 3.5-4.5, the volumes of potassium permanganate solution and ammonium persulfate solution are 10-25 ml respectively, the mixing and stirring speed is 200-240 r / min, and the time is 30-60 min; in step C4, the hydrothermal temperature and time are as follows: reacting at 200℃ for 2-4 h to form the α-crystal dominant structure; reacting at 140℃ for 8-12 h. h, regulate the β / γ crystal form; react at 120℃ for 2~4 h to modify the δ crystal form; in step C5, wash repeatedly with deionized water 4~5 times, and dry in an oven at 60~80℃ for 12~24 h to obtain the polycrystalline manganese carbon shuttle electrode material (4).

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