An anode material for ammonium oxidation under low-concentration chloride ion conditions and a preparation method thereof

Abstract

The application relates to the technical field of ammonium oxidation, and discloses an anode material for ammonium oxidation under a low-concentration chloride ion condition and a preparation method thereof.The anode material takes manganese dioxide as a carrier and is loaded with monatomic silver, and the loading amount of the monatomic silver is less than 0.1 wt%.In the preparation process, first, constant current density electrodeposition is carried out to prepare a MnO2 / platinum-coated titanium mesh; then, a wet chemical immersion method is used to load Ag on the MnO2 substrate; finally, high-temperature air atmosphere calcination is carried out to prepare a monatomic Ag / MnO2 anode material.The application utilizes the acid resistance of MnO2 itself and the strong metal carrier interaction between metal Ag and MnO2 to realize stable and continuous electrolysis operation; and Ag and MnO2 realize the enrichment of low-concentration chloride ions at the anode interface through chemical affinity and physical adsorption, thereby realizing the efficient generation of active chlorine under the condition of low-concentration chloride ions.

Description

Technical Field

[0001] This invention relates to the field of ammonium oxidation technology, specifically to an anode material for ammonium oxidation under low-concentration chloride ion conditions and its preparation method. Background Technology

[0002] In recent decades, the removal of ammonia nitrogen from wastewater has received widespread attention due to environmental problems associated with the excessive discharge of this critical nutrient, including eutrophication of receiving water bodies, unpleasant odors from decaying organisms, and complications related to water supply disinfection. Electrochemical advanced oxidation (EAOP) processes have emerged as a promising method for ammonia removal, offering advantages such as minimal secondary waste generation, ease of automation, versatility, and safety. EAOP has been reported to effectively treat ammonia-containing wastewater from tanneries, power plants, municipal sources, and landfills.

[0003] Ammonia (ammonium ions (NH4+)) + NH3 (or deprotonated NH3) can be removed by: (i) direct anodic oxidation and / or (ii) indirect oxidation mediated by electrically generated active chlorine. In the direct oxidation pathway, NH3 is first adsorbed onto the anode surface and then decomposed due to anodic electron transfer, primarily into harmless nitrogen gas, as shown in equation (1): 2NH3 + 6OH →N2 + 6H2O + 6e ……(1) However, direct ammonia oxidation requires adjusting the wastewater pH to a level greater than NH4+. + The pKa value of the / NH3 acid-base pair (i.e., pH > 9.25), because NH4 + Direct oxidation at the anode is not possible. Furthermore, the low reaction rate and high cost of the electrode (typically platinum) limit the practical application of this technology.

[0004] More commonly used is indirect oxidation, which utilizes in-situ generation of active chlorine at the anode to oxidize ammonia into nitrogen gas. If sufficient chloride ions are present in the wastewater stream, this method is faster, more efficient, and more cost-effective than direct oxidation. The overall reaction for N2 production is as follows: 2Cl →Cl2+2e ……(2) Cl₂ + H₂O → HClO + H₂ + +Cl ……(3) 2NH4 + +3HClO→N2+3H2O+5H+3Cl ……(4) The anode material strongly influences the Cl content in the chlorine evolution reaction (CER). EC oxidation process (ECl / Cl2 =1.25 V vs. SHE), because there are some competing side reactions during anodic oxidation, such as the formation of hydroxyl radicals from water oxidation (2.8 V vs. SHE) and oxygen evolution reaction (OER, 1.23 V vs. SHE). Inactive anodes based on SnO2, PbO2, and boron-doped diamond (BDD) have high OER overpotentials and have been shown to have excellent current efficiency for the generation of hydroxyl radicals. However, SnO2 and PbO2 anodes have poor conductivity and stability, and the generation of active chlorine on BDD is greatly reduced, because in contrast, size-stabilized electrodes (DSA) based on noble metal oxides (such as RuO2 and IrO2) exhibit higher chlorine evolution activity, although they are generally less efficient at generating hydroxyl radicals. In the literature reviewed, the main electrodes used for ammonia chlorination emission reduction are RuO2, IrO2, and their composites composed of active DSA anodes, while research on inactive SnO2 or PbO2 anodes, conductive carbon-based graphite and BDD, noble metal and other metal anodes is relatively limited.

[0005] Currently, the limitations and drawbacks of electrochemically active chloride-mediated ammonium oxidation technology are mainly as follows: (1) Dependence on precious metals leads to high basic costs As the core component for active chlorine generation, the material cost of the anode directly determines its techno-economic viability, and current mainstream solutions face significant cost pressures. Existing high-efficiency chlorine-evolving anodes commonly employ coatings with noble metal oxides such as Ru and Ir. For example, the Ti / RuO2-IrO2 anode exhibits excellent active chlorine generation capabilities in electrochemical active chlorine generation systems, increasing ammonium ion removal rates to 99.91%. However, the market prices of Ru and Ir are as high as tens of thousands of yuan per kilogram, and the utilization rate of noble metals during coating preparation is only 30%-50%. Even if the optimized Ti / IrO2-RuO2-SiO2 anode reduces the molar proportion of noble metals to 30%, its raw material cost is still 4-6 times that of traditional Pb alloy anodes.

[0006] (2) Physicochemical failure of anodic coating The active coating is prone to dissolution, exfoliation, and crystal transformation: After 50 cycles of operation under acidic conditions, the Ti / SnO2-Sb anode exhibits a significant "mud crack" structure on its surface, with a Sb element loss rate of up to 31%, leading to an increase in the chlorine evolution potential of 0.24 V; even with the relatively stable Ti / RuO2-IrO2 anode, the Ru element dissolution can reach 0.08 mg. L 1After 180 days, the catalytic activity decreased by 47%. High temperature and high current density accelerate failure; the electrode life is shortened by 62% at 45℃ compared to room temperature.

[0007] (3) The oxidation efficiency drops sharply at low chloride ion concentrations, limiting its adaptability. Chloride ions are the only precursor to reactive chlorine, and their concentration directly affects reaction kinetics. Technical performance is significantly reduced in low-chlorine environments: when Cl... Concentration below 500 mg L 1 At this time, the competition between the oxygen evolution reaction (OER) and the chlorine evolution reaction (CER) on the anolyte surface intensifies. Due to the potential difference between the two being only 0.1-0.2 V, the OER dominates. Experiments show that Cl... - Concentration from 0.2 mol L 1 Reduced to 0.01 mol L - At ¹, the ammonia nitrogen removal rate of the RuO2-SnO2-Sb / Ti anode decreased from 95.18% to 41.2%, and the total nitrogen removal rate decreased by 53 percentage points simultaneously. In the electrochemical system, when the Cl in the water... - When the concentration is insufficient, even with a 4V voltage applied, the contribution rate of active chlorine is still less than 15%. Typical water bodies such as municipal wastewater and surface water contain high levels of Cl. The concentration is usually 20-200 mg L 1 This is far below the optimal reaction concentration (1000 mg). L 1 (Above). To meet the reaction requirements, additional electrolytes such as NaCl need to be added, which increases the treatment cost by 1.2-2.5 yuan / ton and produces high-salt byproducts, violating the concept of "green treatment". Even with the use of a sequential redox mode to regulate the microenvironment, the ammonia removal rate under low-chlorine conditions is still less than 1.5 times, far lower than the 2.38 times of the high-chlorine system.

[0008] Therefore, developing economical, efficient, stable, and suitable anode materials for actual low-chlorine water bodies is crucial for promoting the further application of electrochemically active chlorine-mediated ammonia oxidation. Summary of the Invention

[0009] This invention aims to provide an anode material and its preparation method for ammonium ion oxidation under low-concentration chloride ion conditions, in order to solve the problem in the prior art where the anode material is used for ammonium ion oxidation in water with low concentration chloride ions. - The problem is that the ammonia removal rate from ammonium oxidation is not ideal when the concentration is insufficient.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: an anode material for ammonium ion oxidation under low concentration chloride ion conditions, using manganese dioxide as a carrier and loading single-atom silver, wherein the loading amount of single-atom silver is <0.1 wt%.

[0011] Preferably, as an improvement, a method for preparing an anode material for ammonium ion oxidation under low-concentration chloride ion conditions is characterized by comprising the following steps: S1, MnO2 electrodeposition: Using a platinum-plated titanium mesh as the anode and a nickel sheet as the cathode, the electrolyte system was a mixed solution of MnSO4 and NaCl. MnO2 samples were obtained by constant current density electrodeposition. S2, Single-atom silver loading: The MnO2 sample prepared in step S1 is immersed in silver nitrate aqueous solution, and then dried after impurity removal; S3. Calcination: The electrode sample that has been dried in step S2 is calcined at a high temperature of 380~420℃ for 1~2 h. After naturally cooling to room temperature, the preparation of single-atom silver-supported MnO2 anode material is completed.

[0012] Preferably, as an improvement, in step S1, the current density is 2.5~15 mA / cm². 2 The electrolysis time is 1~10min.

[0013] Preferably, as an improvement, in step S1, the mixed solution contains 1~3 mM MnSO4 and 30~60 mM NaCl.

[0014] Preferably, as an improvement, the soaking time in step S2 is 5 to 15 minutes.

[0015] Preferably, as an improvement, in step S2, the impurity removal method is rinsing with deionized water.

[0016] Preferably, as an improvement, in step S3, the heating rate is 5~15℃ / min.

[0017] Preferably, as an improvement, in step S3, the calcination process is carried out in an air atmosphere.

[0018] The principle and advantages of this scheme are as follows: In practical applications, this technical scheme addresses the high cost of traditional anode materials in existing technologies by selecting inexpensive and readily available manganese metal as the main support material and using a small amount of precious silver for doping modification, significantly reducing the preparation cost of anode materials and greatly improving the economic benefits and industrial application potential of this technology. Utilizing the strong metal-support interaction (SMSI) formed between single-atom Ag and the MnO2 support, on the one hand, the electronic structure of Ag can be optimized, providing a favorable electronic environment for the generation of active chlorine, thereby improving the electrochemical production performance of active chlorine; on the other hand, this strong interaction can effectively suppress electrolysis. During the process, the migration and aggregation of Ag atoms ensure the stability of its catalytic active center. At the same time, MnO2 itself has excellent acid resistance, which can resist the corrosion of the material by the acidic environment formed at the anode interface during electrolysis, further ensuring the structural and performance stability of the anode during long-term electrolysis. The unique layered structure of the MnO2 support can construct chloride ion transport channels, and Ag atoms have a very high affinity for chloride ions. The synergistic effect of the two can significantly promote the enrichment of chloride ions at the anode interface under low chloride ion concentration conditions. The effective enrichment of chloride ions provides sufficient reactants for subsequent oxidation reactions, thereby ensuring the efficient generation of active chlorine in low-chlorine water.

[0019] Regarding the synergistic optimization of the preparation process, this technical solution adopts a three-step method of "electrodeposition-wet chemical loading-high temperature calcination" to synthesize Ag / MnO2 anode materials. Through the synergistic control of electrodeposition time and calcination conditions, this process has advantages such as low cost of metal raw materials, simple and controllable operation process, and no need for complex precision equipment, and has certain potential for large-scale production. In terms of performance adaptability, existing anode materials often result in low active chlorine yield in low-chloride water bodies due to insufficient chloride ion supply. However, the Ag / MnO2 prepared by this invention can effectively solve the problem of limited chloride ion mass transfer under low-chloride conditions due to the synergistic enrichment effect of MnO2 layered structure and Ag atoms, and achieve high-efficiency production of active chlorine. In terms of performance stability, existing anode materials are prone to the loss of precious metal active components or carrier corrosion. However, this invention, through the strong metal-carrier interaction between single-atom Ag and MnO2, not only ensures the structural stability of Ag active centers and MnO2 carrier, but also further improves electrochemical activity through electronic structure optimization, achieving a dual improvement in "activity-stability".

[0020] During the technical solution development phase, the inventors' team initially attempted to directly deposit MnO2 onto a titanium mesh for electrochemical active chlorine generation under low-chlorine conditions, but this proved largely ineffective, and the deposited MnO2 was prone to detachment. Subsequently, a thin layer of platinum was sputtered onto the titanium mesh before MnO2 deposition, achieving stable and efficient active chlorine generation under low-chlorine conditions. Furthermore, they attempted to replace metallic Ir, but its activity was inferior to Ag-modified MnO2, and the results fell short of expectations.

[0021] In summary, the beneficial effects of this technical solution are as follows: 1. Significantly improved economic efficiency: Since silver metal is loaded onto the surface of the MnO2 support in an atomically dispersed state, the utilization rate of the precious metal can be maximized, achieving high-efficiency utilization; at the same time, the silver loading in this material is low (Ag<0.1 wt%), which further reduces the material preparation cost and highlights its cost advantage. 2. Synergistic Enhancement of Electrochemical Activity and Stability: In terms of activity, a strong metal-support interaction (SMSI) exists between the atomically dispersed noble metal silver and the MnO2 support. This interaction effectively optimizes the electronic structure of silver, thereby promoting the electrochemical production of active chlorine. In terms of stability, MnO2 itself is an acid-resistant metal oxide, which can effectively resist the corrosion and damage to the material caused by the acidic interface environment formed during the electrolysis process, ensuring the long-term stable operation of the Ag / MnO2 anode material. In addition, single-atom silver, through incorporation into the MnO2 lattice, forms a fully coordinated structure with the surrounding oxygen atoms, further stabilizing and fixing the silver atoms, ensuring the structural stability of the noble metal catalytic center in the electrochemical production of active chlorine. 3. Adaptable to low chloride ion concentration water environments: The MnO2 carrier has a unique interlayer structure, which can significantly promote the mass transfer process of chloride ions near the anode interface under low chloride ion concentration conditions, thereby improving the generation efficiency of active chlorine by effectively enriching chloride ions; at the same time, the silver metal center has a strong affinity for chloride ions, which can further accelerate the diffusion and enrichment process of chloride ions to the anode interface, thereby optimizing the generation performance of active chlorine in low chloride water. Attached Figure Description

[0022] Figure 1 The results of active chlorine generation and ammonia nitrogen removal in Example 1 of this invention are shown.

[0023] Figure 2 The results of active chlorine generation and ammonia nitrogen removal are shown in Comparative Example 1 of this invention.

[0024] Figure 3 The X-ray diffraction spectral data for Ag / MnO2 of this invention are shown below.

[0025] Figure 4 This is a scanning electron microscope for Ag / MnO2 according to the present invention.

[0026] Figure 5 This is a comparison of the linear scanning voltammetric curves of Embodiment 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0027] The following detailed description provides further details on specific embodiments, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art; the experimental methods used are all conventional methods; and the materials and reagents used are all commercially available.

[0028] Overview of the plan: An anode material for ammonium ion oxidation under low-concentration chloride ion conditions, using manganese dioxide (MnO2) as a carrier and loaded with single-atom silver.

[0029] A method for preparing an anode material for ammonium ion oxidation under low chloride ion conditions includes the following steps: S1, MnO2 electrodeposition steps: A platinum-plated titanium mesh is used as the anode, a nickel sheet as the cathode, and the electrolyte system is a mixed solution containing 1~3 mM MnSO4 and 30~60 mM NaCl. The current density is controlled at 2.5~15 mA / cm². 2 The electrolysis time is set to 1~10 min; S2, Single Atom Silver Loading Step: Immerse the MnO2 sample prepared in step S1 in 0.1 mM silver nitrate aqueous solution for 10 min. After removal, rinse repeatedly with deionized water until there are no residual impurities on the surface, and then dry. S3. Calcination in air atmosphere: Place the dried electrode sample from step S2 into a muffle furnace for high-temperature calcination. Set the heating rate to 5~15℃ / min, the calcination temperature to 380~420℃, and the holding time to 2 h. After the muffle furnace cools naturally to room temperature, the preparation of the single-atom silver-supported MnO2 anode material (Ag / MnO2) is complete.

[0030] Example 1 A method for preparing an anode material for ammonium ion oxidation under low chloride ion conditions includes the following steps: S1, MnO2 electrodeposition steps: A platinum-titanium coated mesh was used as the anode, a nickel sheet as the cathode, and the electrolyte system was a mixed solution containing 2 mM MnSO4 and 50 mM NaCl. The current density was controlled at 2.5 mA / cm². 2 The electrolysis time is set to 5 min; S2, Single Atom Silver Loading Step: Immerse the MnO2 sample prepared in step S1 in 0.1 mM silver nitrate aqueous solution for 10 min. After removal, rinse repeatedly with deionized water until there are no residual impurities on the surface, and then dry. S3. Calcination in air atmosphere: Place the dried electrode sample from step S2 into a muffle furnace for high-temperature calcination. Set the heating rate to 5℃ / min, the calcination temperature to 400℃, and the holding time to 2 h. After the muffle furnace cools naturally to room temperature, the preparation of the single-atom silver-supported MnO2 anode material (Ag / MnO2) is complete.

[0031] Generation of active chlorine and removal of ammonia nitrogen under different current densities in Ag / MnO2 The electrochemical production of active chlorine was determined using a conventional two-electrode method. Ag / MnO2 was used as the anode, a stainless steel sheet as the cathode, and the electrolyte was 0.1 M Na2SO4 + 5 mM NaCl. The mixture was stirred at 400 rpm for 0.5 h. The results are as follows: Figure 1 As shown, the Ag / MnO2 anode exhibits excellent active chlorine electrochemical generation capability at current densities of 2.5, 5, 7.5, and 10 mA / cm². 2 Under the given conditions, 54, 75, 59, and 40 mg / L Cl2 were produced, respectively. When 5 mM NH4+ was used... 4+ In the presence of the electrolysis solution and at an electrolysis time of 2 h, at current densities of 2.5, 5, 7.5, and 10 mA / cm², 2 Under the given conditions, ammonia nitrogen removal efficiencies of 80%, 100%, 100%, and 98% were achieved, respectively.

[0032] Comparative Example 1 Under the same operating parameters and electrolyte composition as in the examples, conventional commercially available iridium-silver electrode plates (MMO plates) and commercially available iridium-silver meshes (MMO meshes) at 2.5, 5, 7.5, and 10 mA / cm 2 At the specified current densities, electrolysis for 0.5 h only produces 0, 2.5, 5.5, and 10.2 mg / L Cl2 and 0, 3, 7.4, and 12.1 mg / L Cl2, respectively. Simultaneously, at 5 mM NH4+... 4+ In the presence of the present, only extremely low ammonia nitrogen removal efficiency can be achieved after 2 hours of electrolysis, highlighting the superiority of Ag / MnO2 in the example ( Figure 2 ).

[0033] Comparative Example 2 The difference between this comparative example and Example 1 is that the noble metal loaded in this comparative example is Ir, and the loading amount is 0.4 wt%.

[0034] Comparative Example 3 The difference between this comparative example and Example 1 is that the loading of single-atom silver in this comparative example is 5 wt%.

[0035] Comparative Example 4 The difference between this comparative example and Example 1 is that the calcination temperature in this comparative example is 450°C.

[0036] Comparative Example 5 The difference between this comparative example and Example 1 is that the calcination temperature in this comparative example is 350°C.

[0037] Comparative Example 6 The difference between this comparative example and Example 1 is that the heating rate in this comparative example is 10°C / min.

[0038] Experimental Example 1 X-ray diffraction and scanning electron microscopy analyses were performed on the Ag / MnO2 prepared in Example 1, and the results are as follows: Figure 3-4 As shown in the figure. The results indicate that the characteristic diffraction peaks of MnO2 are clear and have high intensity, with no obvious impurity peaks, indicating that the MnO2 support prepared by electrodeposition + calcination process has a complete crystal structure and has been successfully deposited on the platinum-titanium mesh substrate, providing a stable structural basis for subsequent chloride ion enrichment and catalytic reactions. Figure 4 The results show that the MnO2 support exhibits a clear layered microstructure, the Ag / MnO2 coating surface is uniform without obvious particle agglomeration, and the material surface has no obvious impurity morphology.

[0039] Experiment Example 2 Linear sweep voltammetry was performed on the Ag / MnO2 prepared in Example 1 and Comparative Example 1. The test method was in accordance with GB / T 20042.6-2024. The test results are as follows. Figure 5 As shown. The Ag / MnO2 electrode in Example 1 has a lower onset potential for the chlorine evolution reaction, indicating that under low chlorine conditions, this electrode can trigger the Cl reaction at a lower potential. - Oxidation to generate Cl2 leads to superior kinetics in the chlorine evolution reaction (CER). Simultaneously, the higher onset potential of the oxygen evolution reaction effectively suppresses the OER side reaction under low-chlorine conditions (where OER easily competes with and dominates CER), achieving selective enhancement of CER. At the same potential, the current density of the Ag / MnO2 electrode is significantly higher than that of the commercially available MMO plate / grid in Comparative Example 1, indicating stronger electrochemical activity and higher charge transfer efficiency, providing an electrochemical basis for the efficient generation of active chlorine.

[0040] Experimental Example 3 Functional tests were conducted on the above embodiments and comparative examples. The test indicators were the generation of active chlorine and the removal of ammonia nitrogen. The test results are as follows: Table 1 shows that: Example 1 is the baseline scheme, and the key design points are MnO2 support + <0.1 wt% single atom Ag, platinum-plated titanium mesh substrate, calcination at 400℃, and heating rate of 5℃ / min. In Table 1, the values ​​range from 2.5 to 10 mA / cm². 2 At the given current density, the active chlorine production was 40–75 mg / L, and the ammonia nitrogen removal rate was 5–7.5 mA / cm². 2Reaching 100%, 2.5 and 10 mA / cm 2 These figures, reaching 80% and 98% respectively, validate the synergistic advantages of the core design: the low loading of single-atom Ag ensures atomic-level dispersion, forming a strong metal-support interaction with MnO2 and optimizing the chlorine production electron environment; the layered structure of MnO2 and Ag's interaction with Cl... - The high affinity enables Cl under low chlorine conditions - Enrichment; the platinum-plated titanium mesh substrate ensured the stability of MnO2 deposition, while the process parameters guaranteed optimal material crystal structure and Ag dispersion. Comparative Example 1 used a commercially available iridium-silver MMO plate / mesh without MnO2 support and a single-atom Ag design; its active chlorine generation was almost zero at various current densities, and the highest ammonia nitrogen removal rate was only 13.5%. Comparative Example 2 replaced the modified metal, but the active chlorine generation and ammonia nitrogen removal rate decreased significantly. Comparative Example 3 increased the Ag loading to 5%, and its active chlorine generation and ammonia nitrogen removal rate were almost zero. This was because the high loading caused Ag atoms to agglomerate, losing the advantage of single-atom dispersion, and the strong metal-support interaction disappeared. Comparative Examples 4-6 showed that calcination conditions and heating rates had a key impact on material properties.

[0041] Table 1

[0042] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. An anode material for ammonium ion oxidation under low chloride ion conditions, characterized in that: Manganese dioxide was used as a carrier to support single-atom silver, with the loading amount of single-atom silver being <0.1 wt%.

2. The method for preparing an anode material for ammonium ion oxidation under low chloride ion conditions according to claim 1, characterized in that, Includes the following steps: S1, MnO2 electrodeposition: A platinum-plated titanium mesh was used as the anode, a nickel sheet as the cathode, and the electrolyte system was a mixed solution of MnSO4 and NaCl. After electrolysis, MnO2 samples were obtained. S2, Single-atom silver loading: The MnO2 sample prepared in step S1 is immersed in silver nitrate aqueous solution, and then dried after impurity removal; S3. Calcination: The electrode sample that has been dried in step S2 is calcined at a high temperature of 380~420℃ for 1~2 h. After naturally cooling to room temperature, the preparation of single-atom silver-supported MnO2 anode material is completed.

3. A method for preparing an anode material for ammonium ion oxidation under low-concentration chloride ion conditions according to claim 2, characterized in that: In step S1, the current density is 2.5~15 mA / cm². 2 The electrolysis time is 1~10 min.

4. A method for preparing an anode material for ammonium ion oxidation under low chloride ion conditions according to claim 3, characterized in that: In step S1, the mixed solution contains 1~3 mM MnSO4 and 30~60 mM NaCl.

5. A method for preparing an anode material for ammonium ion oxidation under low chloride ion conditions according to claim 4, characterized in that: In step S2, the soaking time is 5~15 min.

6. The method for preparing an anode material for ammonium ion oxidation under low-concentration chloride ion conditions according to claim 5, characterized in that: In step S2, the impurity removal method is rinsing with deionized water.

7. The method for preparing an anode material for ammonium ion oxidation under low-concentration chloride ion conditions according to claim 6, characterized in that: In step S3, the heating rate is 5~15℃ / min.

8. The method for preparing an anode material for ammonium ion oxidation under low-concentration chloride ion conditions according to claim 7, characterized in that: In step S3, the calcination process is carried out in an air atmosphere.

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