Method for electrochemically degrading antibiotic by MWCNTs-P-NiCu single atom combined Ti / SnO2

Abstract

The present application belongs to the technical field of electrochemistry and environmental wastewater treatment, and discloses a method for electrochemically degrading antibiotics by MWCNTs-P-NiCu monatomic catalyst combined with Ti / SnO2. A MWCNTs-P-NiCu monatomic catalyst modified carbon felt electrode is prepared, and in the electrocatalytic reaction, the electrode surface promotes the generation of a large number of active free radicals ROS under the synergistic action of the interface electric field and the electron migration channel. The surface of the modified Ti / SnO2 anode is rich in lattice oxygen. The loss of lattice oxygen will form oxygen vacancies, which act as electron trapping centers or active sites, further enhancing the conductivity and catalytic performance of the material. The composite degradation system prepared by the present application can effectively degrade NOR wastewater, and the degradation rate and defluorination rate can reach 100% in 2-3 h. The degradation rate of TOC reaches 78% in 6 h. After 10 cycles, the degradation rate remains 89.0%, effectively reducing the toxicity of NOR.

Description

Technical Field

[0001] This invention belongs to the fields of electrochemical technology and environmental wastewater treatment technology, and relates to a method for electrochemical degradation of antibiotics using MWCNTs-P-NiCu single-atom combined Ti / SnO2. Background Technology

[0002] Norfloxacin (NOR) is a synthetic antibacterial drug primarily used for antibacterial and anti-inflammatory purposes. Global demand and usage of this antibacterial drug are exceptionally high, leading to significant environmental residues. As a pharmaceutical and personal care product, norfloxacin can also enter the environment through various pathways, causing cumulative effects. Currently, varying levels of norfloxacin have been detected in some water bodies, primarily surface water. Existing ecological and health risk studies indicate that long-term intake of trace levels of norfloxacin can induce heart disease, stroke, and weakened immunity. Because norfloxacin is non-biodegradable, traditional water treatment processes cannot completely degrade it. Therefore, more efficient, green, and environmentally friendly methods are needed to treat norfloxacin.

[0003] Currently, the main methods for treating norfloxacin include biological methods, adsorption methods, and advanced oxidation methods. Due to its high toxicity, which can kill most bacteria, biological methods have very low efficiency in treating NOR wastewater. Improper treatment of pollutants after enrichment and separation by adsorption methods can lead to secondary pollution, and the stability and selectivity of adsorbents also limit their application. Advanced oxidation technologies, including photocatalytic oxidation, Fenton oxidation, and ozone oxidation, have been widely studied and developed rapidly, but still suffer from low treatment efficiency and high cost. They also exhibit drawbacks such as low mass transfer efficiency and the generation of highly toxic intermediate products, which may increase the toxicity of the wastewater after the reaction. Electrochemical methods for wastewater treatment, on the other hand, offer advantages such as high efficiency and stability, no need for reagent addition, and no secondary pollution, making their application in wastewater treatment a research hotspot.

[0004] Existing patented degradation methods typically use modified anodes to oxidize and degrade antibiotics. While this method is relatively green and efficient, its degradation efficiency is relatively low. Methods using cathodes for degradation usually employ electro-Fenton degradation. Traditional electro-Fenton degradation has several limitations, requiring the use of Fe cycling and Fe reduction at the cathode. 3+ Fe 2+ ,Fe 2+This invention promotes the decomposition of H2O2 into ·OH, thereby oxidizing and degrading pollutants in the water system. However, this degradation method is limited by the need for Fe salt catalysis. For example, as mentioned in the patent "An Internal Aeration Electro-Fenton Device and Method for Treating Antibiotic Wastewater," the free iron in traditional electro-Fenton systems easily forms precipitates and iron sludge, affecting the removal efficiency, and the reaction needs to be strictly controlled at around 3. This patent uses a MWCNTs-P-NiCu single-atom catalyst modified with carbon felt to prepare the cathode. This catalyst effectively avoids the limitations of Fe salt catalysts and has a wider degradation pH range. The catalyst synthesis does not require a large amount of metal salt, resulting in lower preparation costs. It has broader applicability in the degradation of antibiotics. The technical method of this invention combines electrochemical reduction-oxidation degradation with oxidative-oxidation degradation. During the degradation process, the modified anode and free radicals in the system are used to oxidize the antibiotics, while the cathode catalyzes the generation of reducing hydrogen free radicals to replace the recalcitrant F element in the antibiotics. Compared with other antibiotic degradation methods, the combined degradation of norfloxacin using these two systems has lower energy consumption, faster reaction speed, is more environmentally friendly and efficient, and has better applicability. Summary of the Invention

[0005] This invention aims to address the problem of antibiotic-induced water pollution by designing a method for the electrochemical degradation of antibiotics using a phosphorus-doped NiCu bimetallic single-atom (MWCNTs-P-NiCu) co-modified Ti / SnO2 catalyst. This invention enhances the synergistic catalytic ability of the NiCu bimetallic single atom at the catalytic center by doping with phosphorus (P), which has high electronegativity and coordination capacity. This strengthens the effective interfacial electric field and promotes directional electron migration, forming a MWCNTs-P-NiCu bimetallic single-atom composite catalyst. The catalyst is loaded onto a carbon felt to prepare a MWCNTs-P-NiCu catalytic electrode. During the electrocatalytic reaction, the electrode surface promotes the generation of a large number of reactive free radicals (ROS) under the synergistic effect of the interfacial electric field and electron migration channels. The co-modified Ti / SnO2 anode surface is rich in lattice oxygen. The absence of lattice oxygen creates oxygen vacancies, which serve as electron trapping centers or active sites, further enhancing the conductivity and catalytic performance of the material. The composite degradation system prepared by this invention can effectively degrade NOR wastewater. The degradation rate and defluorination rate can reach 100% in 2-3 hours, and the TOC degradation rate can reach 78% in 6 hours. After 10 cycles, the degradation rate is maintained at more than 89.0%, which can effectively reduce NOR toxicity.

[0006] The technical solution of the present invention: A method for electrochemical degradation of antibiotics using MWCNTs-P-NiCu single-atom combined Ti / SnO2 comprises the following steps: (1) Using multi-walled carbon nanotubes (MWCNTs) as a carrier, melamine was used to dope them with N to provide anchoring points for single-atom metal loading. Melamine and MWCNTs were ground and mixed at a mass ratio of 2:1 to 3:1 for 10 to 15 minutes until homogeneous. The mixture was then heated in a tube muffle furnace under a nitrogen atmosphere at 5 °C / min. -1 The mixture was heated to 500-650 ℃ and calcined for 2-4 hours, then naturally cooled to room temperature to obtain MWCNTs-N; (2) Stabilize the MWCNTs-N structure; MWCNTs-N were added to a concentration of 0.5–1 mol·L⁻¹ -1 The N-doped structure was soaked in HCl solution for 20 min to remove unreacted impurities and surface oxides, thereby enhancing the stability of the structure. Then, it was filtered, washed repeatedly with deionized water and anhydrous ethanol until neutral, and dried at 60-70 °C to obtain structurally stable MWCNTs-N. (3) Impregnation of metal precursors; Take the MWCNTs-N obtained in step (2) and immerse it in a mixed aqueous solution of Ni(NO3)2 and Cu(NO3)2 with a molar ratio of 1:1, where the concentrations of both Ni(NO3)2 and Cu(NO3)2 are 2.70 mmol·L. -1 The mixture was sonicated at room temperature for 90 min; then dried at 60–70 °C to obtain MWCNTs-N, a metal nitrate precursor. (4) Preparation of N-doped bimetallic single-atom catalyst MWCNTs-N-NiCu; Melamine and MWCNTs-N, a precursor of metal nitrates, are ground and mixed at a mass ratio of 2:1 to 3:1 for 10 to 15 min. The mixture is then placed in a corundum ceramic boat and heated in a tube furnace under a nitrogen atmosphere at 5 °C / min. -1 Calcine at 550 °C for 2 hours, then at 5 °C·min -1 Calcine at 600-800 ℃ for 2 h; the product is treated with 0.5-1 mol·L⁻¹ -1 The catalyst was repeatedly washed and filtered with hydrochloric acid, deionized water and anhydrous ethanol, and dried at 60-70 °C to obtain the N-doped bimetallic single-atom catalyst MWCNTs-N-NiCu. (5) P-doped modified MWCNTs-P-NiCu; NaH2PO2 and MWCNTs-N-NiCu were ground and mixed at a mass ratio of 5:1 for 10–15 min, and then heated at 5 °C·min. -1 The temperature was raised to 350 °C and calcined for 2 h to achieve P element doping and regulate the coordination environment of metal active sites, yielding MWCNTs-P-NiCu; the calcination tail gas was 0.5–1 mol·L⁻¹. -1CuSO4 solution is used for absorption to prevent environmental pollution; (6) Preparation of film-forming modification solution; MWCNTs-P-NiCu were dispersed in a 1:1 ethanol / water mixture to prepare solutions with a mass concentration of 1–1.5 mg / mL. -1 The suspension was mixed with 5 wt% Nafion solution to make the final Nafion concentration in the system 0.075 wt%, and the mixture was ultrasonically dispersed to obtain the electrode modification solution. (7) Electrode preparation; A film-like modification solution was uniformly coated onto the surface of a carbon felt to obtain a loading of 0.15–1.5 mg·cm³. -2 The carbon felt electrode was modified with MWCNTs-P-NiCu single-atom catalyst and dried to obtain the MWCNTs-P-NiCu single-atom catalyst modified carbon felt electrode. (8) Degradation reaction; The degradation was performed using a three-electrode system, with a Ti / SNO2 electrode as the counter electrode, a carbon felt electrode modified with the prepared MWCNTs-P-NiCu single-atom catalyst as the working electrode, and a calomel electrode as the reference electrode. The distance between the working electrode and the counter electrode was 0.5 cm. The degradation was carried out using 0.05 mol·L⁻¹ -1 Na₂SO₄ is the electrolyte. The pH is adjusted to 3, and NOR is added to bring the initial concentration to 15 mg·L⁻¹. -1 Electrolysis was performed at room temperature and a constant voltage of -1.0 V (vs SCE) at a rate of 0.8–1 L / min. -1 Air is introduced at a flow rate of 60 r·min with magnetic stirring. -1 Electrochemical degradation occurs; (9) Analyze and detect NOR content; The concentration of NOR was determined by high performance liquid chromatography (HPLC). Samples were filtered through a membrane before being analyzed: UV detection wavelength 278 nm, column temperature 40 ℃, C18 column; mobile phase: methanol (phase A): 0.1% formic acid aqueous solution (phase B) = 3:7, flow rate 1 mL / min. -1 Binary pump isocratic elution.

[0007] The beneficial effects of this invention are as follows: The MWCNTs-P-NiCu single-atom catalyst prepared by this invention regulates the electronic structure of the support through phosphorus doping, enabling Ni and Cu single atoms to be uniformly dispersed on the surface of the MWCNTs support, forming abundant and highly efficient catalytic active sites. Simultaneously, a synergistic system of Ti / SnO2 anode and single-atom modified cathode is constructed. Oxidation occurs at the anode, and catalytic reduction occurs at the cathode, accelerating the degradation and transformation of antibiotics to produce highly oxidizing actives such as ·OH and O.2- The synergistic effect of these two factors results in a rapid degradation rate, achieving ideal treatment results in a short time, with a 100% degradation rate of NOR within 3 hours. The single-atom catalyst preparation process of this invention requires no complex equipment; calcination, ultrasonication, and drop coating are all conventional operations, facilitating large-scale production. The electrochemical treatment system parameters are easily adjustable, with good anode-cathode matching. Electrolysis time, voltage, and electrolyte concentration can be adjusted according to actual wastewater concentration and treatment requirements, adapting to different wastewater treatment scenarios. Electrolysis is performed in a constant voltage mode, with an applied voltage of -1.0V (vs SCE), resulting in low energy consumption. No large amounts of chemical reagents are required during treatment; only Na2SO4 is used as the supporting electrolyte, eliminating the need for large amounts of oxidants and causing no secondary pollution, thus meeting green environmental protection requirements. This invention is not only applicable to the treatment of norfloxacin wastewater but can also be extended to other recalcitrant quinolone antibiotic wastewater such as ciprofloxacin and levofloxacin. Furthermore, by adjusting the type and loading of single-atom metals, it can be adapted to the treatment of different types of recalcitrant organic wastewater, demonstrating broad application prospects. Attached Figure Description

[0008] Figure 1 These are morphology images of the prepared MWCNTs-P-NiCu single-atom materials, where (a) is a 200,000x MWCNTs-P-NiCu SEM characterization image; (b) is a 100,000x MWCNTs-P-NiCu SEM characterization image; and (c) is a 50,000x MWCNTs-P-NiCu SEM-EDS characterization image.

[0009] Figure 2 They are antibiotics degraded by different types of single-atom materials.

[0010] Figure 3 This describes the effect of different single-atom metal doping concentrations on degradation.

[0011] Figure 4 This describes the effect of different calcination temperatures on degradation.

[0012] Figure 5 This describes the effect of different amounts of single-atom modification on degradation.

[0013] Figure 6 This relates to the effect of electrolyte concentration on antibiotic degradation.

[0014] Figure 7 The effects of different applied voltages on antibiotic degradation are shown in (a) to investigate the degradation rate under different working potentials and (b) to show the energy consumption and electrical energy utilization rate of degradation under different working potentials.

[0015] Figure 8 This is a graph showing the results of the cyclic degradation of norfloxacin.

[0016] Figure 9These are Nyquist plots of different single-atom catalysts.

[0017] Figure 10 These are hydrogen evolution curves for different single-atom catalysts. Detailed Implementation

[0018] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0019] Example 1: Comparison of the effects of different types of single-atom catalysts; 1. Catalyst preparation; Using MWCNTs as a carrier, nitrogen doping was performed with melamine to provide anchoring sites for the metal single-atom loading. 3 g of melamine and 1 g of MWCNTs were ground and mixed for 10 min until homogeneous, and then heated in a nitrogen-atmospheric tube furnace at 5 °C·min. -1 The mixture was calcined at 550 °C for 2 h and then naturally cooled to room temperature to obtain MWCNTs-N. It was then repeatedly washed with HCl solution, deionized water, and anhydrous ethanol to obtain structurally stable MWCNTs-N.

[0020] (1) Preparation of MWCNTs-P-NiCu catalyst; Take 0.5 g of MWCNTs-N and immerse it in 100 mL of solution containing 2.70 mmol·L⁻¹. -1 Ni(NO3)2 and 2.70 mmol·L -1 The mixture was prepared by sonication at room temperature for 90 min in a mixed aqueous solution of Cu(NO3)2, followed by drying at 60 °C and then grinding and mixing with 1 g of melamine for 10 min. The mixture was then subjected to a nitrogen atmosphere in a tube furnace at 5 °C / min. -1 Calcination at 550 °C for 2 h, followed by calcination at 5 °C / min -1 The mixture was heated to 800 °C and calcined for 2 h to obtain MWCNTs-N-NiCu. Then, it was treated with 0.5 mol·L⁻¹... -1 The structure was stabilized by washing with HCl. 0.2 g of MWCNTs-N-NiCu was ground and mixed with 1 g of NaH2PO2 for 10 min, and then subjected to nitrogen atmosphere at 5 °C·min. -1 The mixture was heated to 350 °C and calcined for 2 h to obtain a black powder of MWCNTs-P-NiCu bimetallic single-atom catalyst.

[0021] (2) Preparation of MWCNTs-P-Ni catalyst; Take 0.5 g of MWCNTs-N and immerse it in 100 mL of 5.30 mmol·L⁻¹ solution. -1In Ni(NO3)2 solution, the mixture was sonicated at room temperature for 90 min, dried at 60 ℃, and then ground and mixed with 1 g of melamine for 10 min. After two-stage calcination at 550 ℃ and 800 ℃, MWCNTs-N-Ni was obtained. [The remaining text appears to be incomplete and requires further context.] -1 Wash with HCl. Grind and mix 0.2 g of MWCNTs-N-Ni with 1 g of NaH2PO2, and calcine at 350 ℃ for 2 h to obtain MWCNTs-P-Ni single-atom catalyst.

[0022] (3) Preparation of MWCNTs-P-Cu catalyst; Take 0.5 g of MWCNTs-N and immerse it in 100 mL of 5.40 mmol·L⁻¹ solution. -1 The catalyst was ultrasonically treated in Cu(NO3)2 solution at room temperature for 90 min, dried at 60 °C, and then ground and mixed with 1 g of melamine for 10 min. After two-stage calcination, MWCNTs-N-Cu was obtained, and stabilized by acid washing. 0.2 g of MWCNTs-N-Cu was ground and mixed with 1 g of NaH2PO2, and calcined at 350 °C for 2 h to obtain the MWCNTs-P-Cu single-atom catalyst.

[0023] (4) Preparation of MWCNTs-P catalyst; 0.2 g of MWCNTs-N was ground and mixed with 1 g of NaH2PO2 for 10 min, and then calcined at 350 °C for 2 h under a nitrogen atmosphere to obtain the MWCNTs-P control sample.

[0024] 2. Electrode preparation; Five catalysts, namely MWCNTs-P, MWCNTs-P-Ni, MWCNTs-P-Cu, MWCNTs-P-NiCu, and MWCNTs-N-NiCu, were dispersed in an ethanol / water (v / v = 1 / 1) mixed solvent to prepare a solution with a mass concentration of 1.5 mg·mL⁻¹. -1 A suspension was prepared by adding 5% Nafion solution to achieve a final Nafion concentration of 0.075% (w / v), followed by ultrasonic dispersion to obtain the electrode modification solution. The modification solution was then uniformly coated onto a 3 cm × 3 cm carbon felt using a pipette, with the catalyst loading controlled at 0.75 mg·cm³. -2 After drying, a series of single-atom catalyst-modified carbon felt electrodes were obtained.

[0025] 3. Electrochemical degradation test; A three-electrode system was used: a Ti / SnO2 electrode as the counter electrode, a single-atom catalyst-modified carbon felt electrode as the working electrode, and a calomel electrode as the reference electrode, with an electrode spacing of 0.5 cm. The electrode was tested in 40 mL at 0.05 mol·L⁻¹. -1 NOR was added to the Na₂SO₄ electrolyte solution at pH=3, and degradation was carried out at room temperature by applying a constant voltage of -1.0 V at a rate of 0.8 L·min⁻¹. -1 Air is introduced, and the magnetic stirring speed is 60 r·min. -1 .

[0026] 4. Electrochemical characterization; The carbon felt electrode was subjected to linear polarization curve testing in H2SO4 solution at pH=1 to compare hydrogen evolution behavior; the modification solution was drop-coated onto the surface of glassy carbon electrode GCE and electrochemical impedance spectroscopy (EIS) was performed in potassium ferricyanide solution to characterize conductivity and interfacial electron transfer capability.

[0027] 5. Results and Analysis; As shown in Figure 2, the NOR degradation performance of the MWCNTs-P-NiCu bimetallic single-atom catalyst is significantly better than that of the single-metal catalysts MWCNTs-P-Ni and MWCNTs-P-Cu, indicating a significant synergistic effect between Ni-Cu bimetals, which can accelerate interfacial electron transfer. Meanwhile, the degradation performance of MWCNTs-P-NiCu is much higher than that of MWCNTs-N-NiCu. This is because P has a higher electronegativity and coordination ability than N, which can enhance the interfacial electric field, optimize the coordination environment of the metal center, and further improve the synergistic catalytic activity of NiCu biatoms.

[0028] As shown in the polarization curves in Figure 10, P doping can effectively broaden the electrochemical reaction window, promote the generation of active hydrogen radicals ·H, and suppress the hydrogen evolution side reaction H2 evolution; NiCu bimetallic synergy significantly improves electrode conductivity and catalytic kinetics.

[0029] As shown in Figure 9, the AC impedance spectrum reveals that MWCNTs-P-NiCu exhibits the lowest charge transfer resistance, which is far superior to MWCNTs-N-NiCu and other comparative samples. This significantly accelerates electron transfer and improves the efficiency of the electrochemical reaction, thus verifying the excellent performance and feasibility of this catalyst in antibiotic degradation from an electrochemical mechanism perspective.

[0030] Example 2: Comparison of the effects of different concentrations of single atoms on antibiotic degradation; 1. Preparation of N-doped carbon nanotubes (MWCNTs-N); Using MWCNTs as a carrier, melamine was used to dope them with N, providing anchoring sites for single-atom metal loading. 3 g of melamine and 1 g of MWCNTs were ground and mixed in a mortar for 10 min until homogeneous. The mixture was then heated in a tube muffle furnace under a nitrogen atmosphere at 5 °C / min. -1 The mixture was calcined at 550 °C for 2 h and then naturally cooled to room temperature to obtain MWCNTs-N. It was then repeatedly washed with HCl solution, deionized water, and anhydrous ethanol to obtain structurally stable MWCNTs-N.

[0031] 2. Preparation of MWCNTs-P-NiCu catalysts with different metal doping amounts; Prepare a series of catalysts by mixing aqueous solutions of Ni(NO3)2 and Cu(NO3)2 at different concentrations with a molar ratio of 1:1, and then follow the steps below: (1) Doping amount is approximately 2.70 mmol·L -1 Take 0.5 g of MWCNTs-N and immerse it in 100 mL of solution containing 1.37 mmol·L⁻¹. -1 Ni(NO3)2 and 1.33 mmol·L -1 The mixture was ultrasonically soaked in a Cu(NO3)2 solution at room temperature for 90 min. After drying at 60 °C, it was ground and mixed with 1 g of melamine for 10 min, then transferred to a corundum ceramic boat and sterilized under a nitrogen atmosphere at 5 °C·min. -1 Calcine at 550 °C for 2 h, then at 5 °C·min -1 The mixture was calcined at 800 °C for 2 h to obtain MWCNTs-N-NiCu, and the structure was stabilized by washing with hydrochloric acid. 0.2 g of the above product was then ground and mixed with 1 g of NaH₂PO₂ for 10 min, and then heated at 5 °C·min under a nitrogen atmosphere. -1 Calcination at 350 °C for 2 h yielded a metal doping concentration of approximately 2.70 mmol·L⁻¹. -1 MWCNTs-P-NiCu black powder.

[0032] (2) Doping amount is approximately 5.40 mmol·L -1 Take 0.5 g of MWCNTs-N and immerse it in 100 mL of solution containing 2.70 mmol·L⁻¹. -1 Ni(NO3)2 and 2.70 mmol·L -1 In a mixed solution of Cu(NO3)2, the remaining steps of sonication, calcination, acid washing, and P doping were the same as above, yielding a metal doping amount of approximately 5.40 mmol·L⁻¹.-1 MWCNTs-P-NiCu black powder.

[0033] (3) Doping amount is approximately 11.00 mmol·L -1 Take 0.5 g of MWCNTs-N and immerse it in 100 mL of solution containing 5.40 mmol·L⁻¹. -1 Ni(NO3)2 and 5.40 mmol·L -1 In a mixed solution of Cu(NO3)2, the remaining steps were the same as above, yielding a metal doping amount of approximately 11.00 mmol·L⁻¹. -1 MWCNTs-P-NiCu black powder.

[0034] (4) Doping amount is approximately 22.00 mmol·L -1 Take 0.5 g of MWCNTs-N and immerse it in 100 mL of solution containing 10.95 mmol·L⁻¹. -1 Ni(NO3)2 and 10.66 mmol·L -1 In a mixed solution of Cu(NO3)2, the remaining steps were the same as above, yielding a metal doping amount of approximately 22.00 mmol·L⁻¹. -1 MWCNTs-P-NiCu black powder.

[0035] 3. Electrode preparation; The four MWCNTs-P-NiCu catalysts with different metal doping amounts were dispersed in ethanol / water (v / v=1 / 1) mixed solutions to prepare solutions with a mass concentration of 1.5 mg·mL⁻¹. -1 The modified solution was mixed with 5% Nafion solution to achieve a final Nafion concentration of 0.075% (w / v), and ultrasonically dispersed to obtain a series of film-like modified solutions. The modified solutions were then uniformly coated onto 3 cm × 3 cm carbon felt using a pipette, with the catalyst loading controlled at 0.75 mg·cm³. -2 After drying, MWCNTs-P-NiCu modified carbon felt electrodes with different metal doping amounts were obtained.

[0036] 4. Electrochemical degradation test; A three-electrode system was used: a Ti / SnO2 electrode as the counter electrode, modified carbon felt electrodes with different doping concentrations as the working electrodes, and a calomel electrode as the reference electrode, with an electrode spacing of 0.5 cm. The system was tested in 40 mL at 0.05 mol·L⁻¹. -1 Norfloxacin (NOR) was added to the Na2SO4 electrolyte solution (pH=3) to an initial concentration of 15 mg·L⁻¹.-1 Degradation was carried out at room temperature by applying a constant voltage of -1.0 V at a rate of 0.8 L·min⁻¹. -1 Air is introduced, and the magnetic stirring speed is 60 r·min. -1 The NOR concentration was detected using high-performance liquid chromatography during the degradation process.

[0037] 5. Results and Analysis; As shown in Figure 3, the catalytic degradation efficiency of NOR by MWCNTs-P-NiCu first increases and then tends to stabilize with increasing metal nitrate doping concentration. When the metal doping concentration is 5.40 mmol·L⁻¹, the efficiency remains stable. -1 At this point, the degradation efficiency reaches its peak, and further increasing the metal doping amount does not significantly improve the degradation effect. This is because excessive metal tends to aggregate on the carbon support surface, forming nanoclusters that block pores and reduce the number of single-atom active sites, leading to a decrease in catalytic activity.

[0038] Considering both degradation efficiency and atom utilization rate, this study selected 2.70 mmol·L⁻¹. -1 Ni(NO3)2 and 2.70 mmol·L -1 A Cu(NO3)2 molar ratio of 1:1 is used as the optimal metal precursor doping amount for subsequent preparation of MWCNTs-P-NiCu single-atom catalysts and electrochemical degradation applications.

[0039] Example 3: Comparison of the effects of single-atom pairs at different calcination temperatures on antibiotic degradation; 1. Preparation of N-doped carbon nanotubes (MWCNTs-N); Using MWCNTs as a carrier, melamine was used to dope them with N, providing anchoring sites for single-atom metal loading. 6 g of melamine and 2 g of MWCNTs were ground and mixed in a mortar for 10 min until homogeneous. The mixture was then heated in a tube muffle furnace under a nitrogen atmosphere at 5 °C / min. -1 The mixture was calcined at 550 °C for 2 h and then naturally cooled to room temperature to obtain MWCNTs-N. It was then repeatedly washed with HCl solution, deionized water, and anhydrous ethanol to obtain structurally stable MWCNTs-N.

[0040] 2. Preparation of MWCNTs-P-NiCu catalysts at different calcination temperatures; Take 0.5 g of structurally stable MWCNTs-N and immerse it in 100 mL of solution containing 2.70 mmol·L⁻¹ -1 Ni(NO3)2 and 2.70 mmol·L -1The mixture was ultrasonically soaked in a Cu(NO3)2 aqueous solution at a molar ratio of 1:1 for 90 min at room temperature. After drying at 60 °C, it was ground and mixed with 4 g of melamine for 10 min and then placed in a covered corundum ceramic boat.

[0041] Under a nitrogen atmosphere, at 5 °C·min -1 The samples were first calcined at 550 °C for 2 h, and then calcined again at 600 °C, 700 °C, and 800 °C for 2 h each, to obtain MWCNTs-N-NiCu with different second-stage calcination temperatures. The structures were stabilized by washing with hydrochloric acid.

[0042] Take 0.2 g of the above MWCNTs-N-NiCu and grind and mix with 1 g of NaH2PO2 for 10 min, and calcine at 350 ℃ for 2 h under a nitrogen atmosphere to obtain black powder of MWCNTs-P-NiCu single-atom catalyst calcined at 600 ℃, 700 ℃ and 800 ℃ respectively.

[0043] 3. Electrode preparation; The MWCNTs-P-NiCu catalysts prepared at different calcination temperatures were dispersed in ethanol / water (v / v=1 / 1) mixed solutions to prepare solutions with a mass concentration of 1.5 mg·mL⁻¹. -1 The modified solution was mixed with 5% Nafion solution to achieve a final Nafion concentration of 0.075% (w / v), and ultrasonically dispersed to obtain a film-like modified solution. The modified solution was then uniformly coated onto a 3 cm × 3 cm carbon felt using a pipette, with the catalyst loading controlled at 0.75 mg·cm³. -2 After drying, a series of single-atom catalyst-modified carbon felt electrodes were obtained.

[0044] 4. Electrochemical degradation test; A three-electrode system was used: a Ti / SnO2 electrode as the counter electrode, modified carbon felt electrodes calcined at different temperatures as working electrodes, and a calomel electrode as the reference electrode, with an electrode spacing of 0.5 cm. The electrode was tested at 40 mL and 0.05 mol·L⁻¹. -1 Add NOR to the Na2SO4 electrolyte solution at pH=3 to bring the initial concentration to 15 mg·L⁻¹. -1 Degradation was carried out at room temperature by applying a constant voltage of -1.0 V at a rate of 0.8 L / min. -1 Air is introduced, and the magnetic stirring speed is 60 r·min. -1 .

[0045] 5. Results and Analysis; As shown in Figure 4, the degradation performance of the catalyst for NOR gradually improves with increasing calcination temperature in the second stage. The MWCNTs-P-NiCu catalyst prepared at 800 ℃ exhibits the best catalytic degradation effect, indicating that this temperature is more conducive to the formation of highly dispersed NiCu bimetallic single-atom sites, optimizing the graphitization degree and coordination structure of the carbon support, thereby enhancing the electrochemical catalytic activity. Example 4: Comparison of the effects of different single-atom modification amounts on antibiotic degradation; 1. Preparation of N-doped carbon nanotubes (MWCNTs-N); Using MWCNTs as a carrier, nitrogen doping was performed on them with melamine to provide attachment sites for single-atom metal loading. 3 g of melamine and 1 g of MWCNTs were ground and mixed in a mortar for 10 min until homogeneous, and then placed in a tube muffle furnace under a nitrogen atmosphere at 5 °C·min. -1 The temperature was increased to 550 °C and calcined for 2 h, then naturally cooled to room temperature to prepare MWCNTs-N. Subsequently, the MWCNTs-N was repeatedly washed with HCl solution, deionized water, and anhydrous ethanol to obtain structurally stable MWCNTs-N.

[0046] 2. Preparation of MWCNTs-P-NiCu single-atom catalysts; Weigh 0.5 g of structurally stable MWCNTs-N and immerse it in 100 mL of solution containing 2.70 mmol·L⁻¹. -1 Ni(NO3)2 and 2.70 mmol·L -1 The mixture was ultrasonically soaked in a Cu(NO3)2 aqueous solution at a molar ratio of 1:1 at room temperature for 90 min. After stirring evenly, it was dried in a 60 ℃ oven, and then ground and mixed with 1 g of melamine in a mortar for 10 min. The mixture was then introduced into a corundum ceramic boat.

[0047] The corundum porcelain boat was placed in a tube muffle furnace under a nitrogen atmosphere and heated to 5 °C / min. -1 The mixture was calcined at 550 °C for 2 h, then further calcined at 800 °C for another 2 h to prepare MWCNTs-N-NiCu. The structure was stabilized by washing with hydrochloric acid. 0.2 g of MWCNTs-N-NiCu was weighed and ground with 1 g of NaH2PO2 for 10 min, then placed in a tube muffle furnace under a nitrogen atmosphere and calcined at 350 °C for 2 h to prepare a black powder of MWCNTs-P-NiCu single-atom catalyst.

[0048] 3. Preparation of electrodes modified with different loading amounts; The MWCNTs-P-NiCu catalyst prepared above was dispersed in an ethanol / water (V / V=1 / 1) mixed solution to prepare a solution with a mass concentration of 1.5 mg·mL⁻¹. -1 The modification solution was prepared by adding 5% Nafion DuPont film solution as an adhesive, controlling the final Nafion concentration in the system to be 0.075% (w / v), and then ultrasonically dispersing it evenly to form a film-like modification solution.

[0049] Different volumes of the film-like modification solution were transferred using a pipette and uniformly coated onto the surface of a 3 cm × 3 cm carbon felt to prepare catalysts with loadings of 0, 0.15, 0.45, 0.75, 1.2, and 1.5 mg·cm⁻¹. -2 A single-atom catalyst was used to modify a carbon felt electrode, which was then dried and used in subsequent degradation experiments.

[0050] 4. Electrochemical degradation test; The degradation experiment used a three-electrode system: a Ti / SnO2 electrode as the counter electrode, carbon felt electrodes modified with single-atom catalysts with different loadings as the working electrodes, and a calomel electrode as the reference electrode. The distance between the working electrode and the counter electrode was controlled to be 0.5 cm.

[0051] The electrolyte system consisted of 40 mL of 0.05 mol·L⁻¹ electrolyte. -1 The Na₂SO₄ solution has a pH of 3. NOR is added to bring the initial concentration to 15 mg·L⁻¹. -1 A constant voltage mode was used, with a voltage of -1.0 V applied to the working electrode, and the degradation reaction was carried out at room temperature. During the degradation process, a flow rate of 0.8 L / min was applied. -1 Air is introduced into the system at a flow rate of 60 r·min⁻¹, while a magnetic stirrer is used simultaneously. -1 The stirring speed is maintained at a constant rate.

[0052] 5. Results and Analysis; Depend on Figure 5 It can be seen that with the change of the loading of the MWCNTs-P-NiCu single-atom catalyst, its catalytic degradation performance for NOR shows a trend of first increasing and then decreasing. When the catalyst loading is 0.45 mg·cm³, the degradation performance is significantly improved. -2 When the loading is too low, the degradation effect is optimal; when the loading is too low, the number of catalytic active sites is insufficient, resulting in low degradation efficiency; when the loading is too high, the catalyst is prone to agglomeration on the carbon felt surface, which will not only block the electrode channels and hinder electron transfer and reactant diffusion, but also reduce the utilization rate of active sites, leading to a decline in degradation performance.

[0053] Example 5: Comparison of the effects of different electrolytes on the degradation of antibiotics; 1. Preparation of N-doped carbon nanotubes (MWCNTs-N); Using MWCNTs as a carrier, nitrogen doping was performed on them with melamine to provide attachment sites for single-atom metal loading. 3 g of melamine and 1 g of MWCNTs were ground and mixed in a mortar for 10 min until homogeneous, and then placed in a tube muffle furnace under a nitrogen atmosphere at 5 °C·min. -1 The temperature was increased to 550 °C and calcined for 2 h, then naturally cooled to room temperature to prepare MWCNTs-N. Subsequently, the MWCNTs-N was repeatedly washed with HCl solution, deionized water, and anhydrous ethanol to obtain structurally stable MWCNTs-N.

[0054] 2. Preparation of MWCNTs-P-NiCu single-atom catalysts; Weigh 0.5 g of structurally stable MWCNTs-N and immerse it in 100 mL of 2.70 mmol·L⁻¹ solution. -1 Ni(NO3)2 and 2.70 mmol·L -1 The mixture was continuously sonicated for 90 min in a beaker containing a Cu(NO3)2 molar ratio of 1:1 nitrate aqueous solution. After stirring evenly, it was dried in an oven at 60 ℃, and then ground and mixed with 1 g of melamine in a mortar for 10 min. The mixture was then introduced into a corundum ceramic boat.

[0055] The corundum porcelain boat was placed in a tube muffle furnace under a nitrogen atmosphere and heated to 5 °C / min. -1 The MWCNTs-N-NiCu was prepared by calcination at 550 °C for 2 h, followed by calcination at 800 °C for 2 h. The MWCNTs-N-NiCu was then washed with hydrochloric acid to stabilize its structure. 0.2 g of MWCNTs-N-NiCu was weighed, and 1 g of NaH2PO2 was added. The mixture was ground and mixed for 10 min, then placed in a tube muffle furnace under a nitrogen atmosphere and calcined at 350 °C for 2 h to prepare a black powder of MWCNTs-P-NiCu single-atom catalyst.

[0056] 3. Preparation of modified electrodes; The MWCNTs-P-NiCu prepared above was dispersed and dissolved in a solution of ethanol and water at a volume ratio of 1 / 1 (v / v = 1 / 1) to prepare a mass concentration of 1.5 mg·mL⁻¹. -1 The MWCNTs-P-NiCu modified solution was prepared by adding 5% Nafion DuPont film solution as an adhesive, controlling the final Nafion concentration in the system to be 0.075% (w / v), and ultrasonically dispersing it evenly to form a film-like modified solution.

[0057] 2.7 mL of the film-forming modification solution was pipetted onto a 3 cm × 3 cm carbon felt to prepare a film with a loading of 0.45 mg·cm⁻¹. -2 A single-atom catalyst was used to modify a carbon felt electrode, which was then dried and used in subsequent degradation experiments.

[0058] 4. Electrochemical degradation test; The degradation experiment used a three-electrode system: a Ti / SnO2 electrode as the counter electrode, a carbon felt electrode modified with the single-atom catalyst prepared above as the working electrode, and a calomel electrode as the reference electrode. The distance between the working electrode and the counter electrode was 0.5 cm.

[0059] At 40 mL and 0.05 mol·L⁻¹ respectively -1 Na₂SO₄, NaCl, CH₃COONa, and NaH₂PO₄ are electrolytes with pH=3. Norfloxacin (NOR) is added to bring the initial concentration to 15 mg·L⁻¹. -1 A constant voltage mode was used, with a voltage of -1.0 V applied to the working electrode, and the degradation reaction was carried out at room temperature. During the degradation process, a flow rate of 0.8 L / min was applied. -1 Air is introduced into the system at a flow rate of 60 r·min⁻¹, while a magnetic stirrer is used simultaneously. -1 The stirring speed is maintained at a constant rate.

[0060] 5. Results and Analysis; Depend on Figure 6 It was found that different electrolytes exhibited significantly different degradation effects on NOR: NaCl showed the best degradation effect, followed by Na₂SO₄. However, NaCl produces other byproducts, such as chlorine-containing compounds, during the degradation process, posing a safety hazard. Therefore, considering both experimental safety and degradation efficiency, this experiment selected 0.05 mol·L⁻¹ NOR. -1 Na2SO 44 As the optimal electrolyte.

[0061] Example 6: Comparison of the effects of different applied voltages on antibiotic degradation; 1. Preparation of N-doped carbon nanotubes (MWCNTs-N); Using MWCNTs as a carrier, nitrogen doping was performed on them with melamine to provide attachment sites for single-atom metal loading. 3 g of melamine and 1 g of MWCNTs were ground and mixed in a mortar for 10 min until homogeneous, and then placed in a tube muffle furnace under a nitrogen atmosphere at 5 °C·min. -1 The temperature was increased to 550 °C and calcined for 2 h, then naturally cooled to room temperature to prepare MWCNTs-N. Subsequently, the MWCNTs-N was repeatedly washed with HCl solution, deionized water, and anhydrous ethanol to obtain structurally stable MWCNTs-N.

[0062] 2. Preparation of MWCNTs-P-NiCu single-atom catalysts; Weigh 0.5 g of structurally stable MWCNTs-N and immerse it in 100 mL of solution containing 2.70 mmol·L⁻¹.-1 Ni(NO3)2 and 2.70 mmol·L -1 The mixture was continuously ultrasonically soaked in a Cu(NO3)2 nitrate aqueous solution with a molar ratio of 1:1 at room temperature for 90 min. After stirring evenly, it was dried in an oven at 60 ℃, and then ground and mixed with 1 g of melamine in a mortar for 10 min. The mixture was then introduced into a corundum ceramic boat.

[0063] The corundum porcelain boat was placed in a tube muffle furnace under a nitrogen atmosphere and heated to 5 °C / min. -1 The temperature was increased to 550 °C and calcined for 2 h, then increased to 800 °C and calcined for another 2 h to prepare MWCNTs-N-NiCu. The mixture was repeatedly washed with hydrochloric acid to stabilize its structure. 0.2 g of MWCNTs-N-NiCu was weighed, added to 1 g of NaH2PO2, and ground and mixed for 10 min. The mixture was then placed in a tube muffle furnace under a nitrogen atmosphere and calcined at 350 °C for 2 h to prepare a black powder of MWCNTs-P-NiCu single-atom catalyst.

[0064] 3. Preparation of modified electrodes; The MWCNTs-P-NiCu catalyst prepared above was dispersed in a mixed solution of ethanol / water with a volume ratio of v / v = 1 / 1 to prepare a solution with a mass concentration of 1.5 mg·mL⁻¹. -1 The MWCNTs-P-NiCu modified solution was prepared by adding 5% Nafion DuPont film solution as an adhesive, controlling the final Nafion concentration in the system to be 0.075% (w / v), and ultrasonically dispersing it evenly to form a film-like modified solution.

[0065] 2.7 mL of the film-forming modification solution was pipetted onto a 3 cm × 3 cm carbon felt surface to prepare a film with a loading of 0.45 mg·cm⁻¹. -2 A single-atom catalyst was used to modify a carbon felt electrode, which was then dried and used in subsequent degradation experiments.

[0066] 4. Electrochemical degradation test; The degradation experiment used a three-electrode system: a Ti / SnO2 electrode as the counter electrode, a carbon felt electrode modified with the single-atom catalyst prepared above as the working electrode, and a calomel electrode as the reference electrode. The distance between the working electrode and the counter electrode was 0.5 cm.

[0067] At 40 mL, pH=3, 0.05 mol·L⁻¹ -1 Na₂SO₄ is the electrolyte; NOR is added to bring the initial concentration to 15 mg·L⁻¹. -1A constant voltage mode was used, with three voltages of -0.8 V, -1.0 V, and -1.2 V applied to the working electrode, and the degradation reaction was carried out at room temperature. During the degradation process, a flow rate of 0.8 L / min was applied. -1 Air is introduced into the system at a flow rate of 60 r·min⁻¹, while a magnetic stirrer is used simultaneously. -1 The stirring speed is maintained at a constant rate.

[0068] 5. Results and Analysis; Depend on Figure 7 It is evident that the applied voltage has a significant impact on the degradation effect of NOR: the degradation rate of norfloxacin gradually increases with increasing applied voltage. However, energy utilization calculations show that the system achieves the highest energy utilization rate under the condition of -1.0 V, balancing degradation efficiency and energy economy. Therefore, this experiment selected the condition of -1.0 V for antibiotic degradation experiments.

[0069] Example 7: The effect of cyclic degradation on antibiotic degradation efficiency; 1. Preparation of N-doped carbon nanotubes (MWCNTs-N); Using MWCNTs as a carrier, nitrogen doping was performed on them with melamine to provide attachment sites for single-atom metal loading. 3 g of melamine and 1 g of MWCNTs were ground and mixed in a mortar for 10 min until homogeneous, and then placed in a tube muffle furnace under a nitrogen atmosphere at 5 °C·min. -1 The temperature was increased to 550 °C and calcined for 2 h, then naturally cooled to room temperature to prepare MWCNTs-N. Subsequently, the MWCNTs-N was repeatedly washed with HCl solution, deionized water, and anhydrous ethanol to obtain structurally stable MWCNTs-N.

[0070] 2. Preparation of MWCNTs-P-NiCu single-atom catalysts; Weigh 0.5 g of structurally stable MWCNTs-N and immerse it in 100 mL of solution containing 2.70 mmol·L⁻¹. -1 Ni(NO3)2 and 2.70 mmol·L -1 The mixture was continuously sonicated for 90 min in a beaker containing a Cu(NO3)2 molar ratio of 1:1 nitrate aqueous solution. After stirring evenly, it was dried in an oven at 60 ℃, and then ground and mixed with 1 g of melamine in a mortar for 10 min. The mixture was then introduced into a corundum ceramic boat.

[0071] The corundum porcelain boat was placed in a tube muffle furnace under a nitrogen atmosphere and heated to 5 °C / min. -1The temperature was increased to 550 °C and calcined for 2 h, then increased to 800 °C and calcined for 2 h to prepare MWCNTs-N-NiCu. The MWCNTs-N-NiCu was then washed with hydrochloric acid to stabilize its structure. 0.2 g of MWCNTs-N-NiCu was weighed, added to 1 g of NaH2PO2, and ground and mixed for 10 min. The mixture was then placed in a tube muffle furnace under a nitrogen atmosphere and calcined at 350 °C for 2 h to prepare a black powder of MWCNTs-P-NiCu single-atom catalyst.

[0072] 3. Preparation of modified electrodes; The MWCNTs-P-NiCu prepared above was dispersed and dissolved in a solution of ethanol and water at a volume ratio of v / v = 1 / 1 to prepare a solution with a mass concentration of 1.5 mg·mL⁻¹. -1 The MWCNTs-P-NiCu modified solution was prepared by adding 5% (w / v) Nafion DuPont film solution as an adhesive, controlling the final Nafion concentration in the system to be 0.075% (w / v), and ultrasonically dispersing it evenly to form a film-like modified solution.

[0073] 2.7 mL of the film-forming modification solution was pipetted onto a 3 cm × 3 cm carbon felt to prepare a film with a loading of 0.45 mg·cm⁻¹. -2 A single-atom catalyst was used to modify a carbon felt electrode, which was then dried and used for subsequent degradation stability testing.

[0074] 4. Electrochemical degradation stability test; The degradation experiment used a three-electrode system: a Ti / SnO2 electrode as the counter electrode, a carbon felt electrode modified with the single-atom catalyst prepared above as the working electrode, and a calomel electrode as the reference electrode. The distance between the working electrode and the counter electrode was 0.5 cm.

[0075] The electrolyte used is 40 mL, 0.05 mol·L⁻¹. -1 The Na2SO4 solution has a pH of 3. Norfloxacin (NOR) is added to bring the initial concentration to 15 mg·L⁻¹. -1 A constant voltage mode was used, with a voltage of -1.0 V applied to the working electrode, and the degradation reaction was carried out at room temperature. During the degradation process, a flow rate of 0.8 L·min⁻¹ was applied. -1 Air was introduced into the system at a flow rate of 60 r·min, and a magnetic stirrer was used to stir the air at a flow rate of 60 r·min. -1 The stirring speed is maintained at a constant rate.

[0076] Under optimal degradation conditions, a degradation experiment was conducted continuously for 30 hours and 10 cycles. During each degradation process, the degradation concentration of NOR was analyzed and detected by liquid chromatography, and the changes in degradation rate were recorded.

[0077] 5. Results and Analysis; Depend on Figure 8 It can be seen that, under optimal degradation conditions, the MWCNTs-P-NiCu single-atom catalyst maintains good catalytic stability after 10 cycles of degradation and continuous operation for 30 h, with the NOR degradation rate remaining above 89%. This result verifies that the MWCNTs-P-NiCu single-atom catalyst and the corresponding electrochemical degradation method prepared in this invention possess excellent stability and practicality, providing important support for their industrial application.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for the electrochemical degradation of antibiotics using MWCNTs-P-NiCu single-atom combined Ti / SnO2, characterized in that, The steps are as follows: (1) Using multi-walled carbon nanotubes (MWCNTs) as a carrier, melamine was used to dope them with N to provide anchoring sites for single-atom metal loading, thus obtaining MWCNTs-N. (2) Stabilize the MWCNTs-N structure; MWCNTs-N were soaked in HCl solution for 20 min to remove unreacted impurities and surface oxides, thereby enhancing the stability of the N-doped structure and obtaining structurally stable MWCNTs-N. (3) Impregnation of metal precursors; The MWCNTs-N obtained in step (2) was immersed in a mixed aqueous solution of Ni(NO3)2 and Cu(NO3)2 to obtain MWCNTs-N loaded with metal nitrate precursors; (4) Preparation of N-doped bimetallic single-atom catalyst MWCNTs-N-NiCu; Melamine and MWCNTs-N, a precursor of metal nitrates, are ground and mixed at a mass ratio of 2:1 to 3:1 for 10 to 15 min. The mixture is then placed in a corundum ceramic boat and heated in a tube furnace under a nitrogen atmosphere at 5 °C / min. -1 Calcine at 550 °C for 2 h, then at 5 °C·min -1 Calcine at 600-800 ℃ for 2 h; the product is treated with 0.5-1 mol·L⁻¹ -1 The catalyst was repeatedly washed and filtered with hydrochloric acid, deionized water and anhydrous ethanol, and dried at 60-70 °C to obtain the N-doped bimetallic single-atom catalyst MWCNTs-N-NiCu. (5) P-doped modified MWCNTs-P-NiCu; NaH2PO2 and MWCNTs-N-NiCu were ground and mixed at a mass ratio of 5:1 for 10–15 min, and then heated at 5 °C·min. -1 The temperature was raised to 350 °C and calcined for 2 h to achieve P element doping and regulate the coordination environment of metal active sites, yielding MWCNTs-P-NiCu; the calcination tail gas was 0.5–1 mol·L⁻¹. -1 CuSO4 solution is used for absorption to prevent environmental pollution; (6) Preparation of film-forming modification solution; MWCNTs-P-NiCu were dispersed in a 1:1 ethanol / water mixture to prepare a concentration of 1–1.5 mg / mL. -1 The suspension was mixed with 5 wt% Nafion solution to make the final Nafion concentration in the system 0.075 wt%, and the mixture was ultrasonically dispersed to obtain the electrode modification solution. (7) Electrode preparation; Preparation of carbon felt electrode modified with MWCNTs-P-NiCu single-atom catalyst; (8) Degradation reaction; Antibiotic degradation was carried out using a three-electrode system, with a Ti / SNO2 electrode as the counter electrode, a carbon felt electrode modified with the prepared MWCNTs-P-NiCu single-atom catalyst as the working electrode, and a calomel electrode as the reference electrode.

2. The method for electrochemical degradation of antibiotics using MWCNTs-P-NiCu single-atom combined Ti / SnO2 according to claim 1, characterized in that, The specific implementation process of step (1) is as follows: Melamine and MWCNTs were ground and mixed at a mass ratio of 2:1 to 3:1 for 10 to 15 minutes until homogeneous. The mixture was then heated in a tube muffle furnace under a nitrogen atmosphere at 5 °C / min. -1 The mixture was heated to 500-650 ℃ and calcined for 2-4 h, then naturally cooled to room temperature to obtain MWCNTs-N.

3. The method for electrochemical degradation of antibiotics using MWCNTs-P-NiCu single-atom combined Ti / SnO2 according to claim 1, characterized in that, The specific implementation process of step (2) is as follows: MWCNTs-N were added to a concentration of 0.5–1 mol·L⁻¹ -1 Immersion in HCl solution for 20 min removes unreacted impurities and surface oxides, enhancing the stability of the N-doped structure; The mixture was then filtered, washed repeatedly with deionized water and anhydrous ethanol until neutral, and dried at 60–70 °C to obtain structurally stable MWCNTs-N.

4. The method for electrochemical degradation of antibiotics using MWCNTs-P-NiCu single-atom combined Ti / SnO2 according to claim 1, characterized in that, The specific implementation process of step (3) is as follows: Take the MWCNTs-N obtained in step (2) and immerse it in a mixed aqueous solution of Ni(NO3)2 and Cu(NO3)2 with a molar ratio of 1:1, where the concentrations of both Ni(NO3)2 and Cu(NO3)2 are 2.70 mmol·L. -1 The mixture was sonicated at room temperature for 90 min, and then dried at 60–70 °C to obtain MWCNTs-N, which is a precursor of metal nitrate.

5. The method for electrochemical degradation of antibiotics using MWCNTs-P-NiCu single-atom combined Ti / SnO2 according to claim 1, characterized in that, The specific implementation process of step (7) is as follows: A film-like modification solution was uniformly coated onto the surface of a carbon felt to obtain a loading of 0.15–1.5 mg·cm³. -2 The carbon felt electrode was modified with MWCNTs-P-NiCu single-atom catalyst and dried to obtain the MWCNTs-P-NiCu single-atom catalyst modified carbon felt electrode.

6. The method for electrochemical degradation of antibiotics using MWCNTs-P-NiCu single-atom combined Ti / SnO2 according to claim 1, characterized in that, The specific implementation process of step (8) is as follows: The distance between the working electrode and the counter electrode is 0.5 cm; at 0.05 mol·L⁻¹ -1 Na₂SO₄ was used as the electrolyte. The pH was adjusted to 3, and the antibiotic NOR was added to bring the initial concentration to 15 mg·L⁻¹. -1 Electrolysis was performed at room temperature and a constant voltage of -1.0 V, at a rate of 0.8–1 L / min. -1 Air is introduced at a flow rate of 60 r·min with magnetic stirring. -1 Electrochemical degradation occurs.

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