Cathode catalyst and application thereof in norfloxacin wastewater treatment

Abstract

The application discloses a cathode catalyst and application thereof in norfloxacin wastewater treatment, and belongs to the technical field of wastewater treatment. A CoFePBA with a core-shell nanocage structure is prepared by adopting Prussian blue analogs (PBAs) as a precursor and by regulating the Co / Fe ratio, and the CoFePBA keeps the shape structure after being calcined under a N2 atmosphere at 400 DEG C, so that a new core-shell cube carbon (CSCC) is obtained. Then, MoSe2 is loaded by a hydrothermal method, and finally, a new cathode catalyst MoSe2 / CSCC is obtained, and the cathode catalyst is driven by electric current to activate PMS, so that the degradation efficiency of NOR in water is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a cathode catalyst and its application in norfloxacin wastewater treatment. Background Technology

[0002] Norfloxacin (NOR) is a third-generation quinolone antibiotic, characterized by its broad spectrum, high efficacy, and low toxicity, and is widely used in medical and aquaculture industries. In recent years, however, an increasing number of researchers have detected residual norfloxacin in water bodies. It can enter the bodies of humans and animals through drinking water or consuming aquatic products. Prolonged ingestion can lead to weakened immunity and drug resistance. Therefore, finding an efficient method to treat norfloxacin is of paramount importance.

[0003] In recent years, electrochemically activated persulfate (PMS) advanced oxidation technology has become an ideal choice for treating NOR wastewater due to its advantages such as being environmentally friendly, not generating secondary pollution, and being easy to adjust the reaction process—advantages not found in other activation methods. Electrochemical activation primarily relies on the cathode activation of PMS to generate persulfate radicals (SO42-). ·- Therefore, the cathode material is the key to the activation efficiency, and thus, the development of efficient cathode catalysts has become a research focus.

[0004] Prussian blue analogues (PBAs) are a class of Prussian blue compounds in which mixed-valence iron is replaced by other transition metals, such as Co and Ni ions. PBAs retain the classic crystal structure of PB while undergoing changes in metal substitution and interstitial modification. The diversity of the substitution metals and the multiple possibilities of alkali metal ions allow for effective control of electronic and ionic properties. Studies have shown that heterogeneous catalysts based on cobalt and iron exhibit excellent performance in activating PMS; therefore, PBAs show promise for treating NOR wastewater through PMS activation. However, different Co to Fe ratios exhibit varying catalytic efficiencies in PMS activation, and related research is currently limited.

[0005] Molybdenum diselenide (MoSe2) is a layered nanomaterial. A single-layer MoSe2 consists of two selenium atoms on the top and bottom layers, with a molybdenum atom layer in the middle. This structure results in strong covalent bonds between the layers. Multilayer MoSe2 is composed of several single-layer MoSe2 structures, with weak van der Waals forces between the layers. MoSe2 possesses high theoretical capacitance and the ability to mitigate volume expansion during potassium ion insertion / extraction processes. Currently, it is mainly used in the preparation of supercapacitors and anode materials for potassium-ion batteries.

[0006] However, there are very few reports on the use of PBAs and MoSe2 combined with PMS to treat NOR wastewater. Summary of the Invention

[0007] To address the aforementioned limitations of existing technologies, the present invention aims to provide a cathode catalyst and its application in norfloxacin wastewater treatment. This invention utilizes Prussian blue analogues (PBAs) as precursors, and prepares CoFePBA with a core-shell nanocage structure by controlling the Co-Fe ratio. After calcination at 400°C under a N2 atmosphere, its shape and structure are maintained, yielding a novel core-shell cube carbon (CSCC) material. Subsequently, MoSe2 is loaded via a hydrothermal method, ultimately obtaining a novel cathode catalyst, MoSe2 / CSCC. Current-driven activation of PMS significantly improves the degradation efficiency of NOR in water.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a cathode catalyst prepared by the following method:

[0010] (1) K3Fe(CN)6 and Co(NO3)2 were mixed evenly and then sealed and aged. Then, they were hydrothermally reacted at 70-90℃ for 20-28h. The product was washed and dried to prepare CoFePBA.

[0011] (2) CoFePBA was heated to 400℃ under a nitrogen atmosphere, calcined at a constant temperature, and annealed to prepare CSCC;

[0012] (3) Using CSCC, MoO3 and Se powder as raw materials, and alcohol, water and hydrazine hydrate as reaction solvents, the reaction was carried out at 180-220℃ for 10-14h. The product was washed and dried to prepare the cathode catalyst (MoSe2 / CSCC).

[0013] Preferably, in step (1), Co(NO3)2 and K3Fe(CN)6 are mixed at a mass ratio of 0.70:0.65.

[0014] Different ratios of Co to Fe can lead to changes in the morphology of PBA. This study found that when Co(NO3)2 and K3Fe(CN)6 are added at a mass ratio of 0.70:0.65, the prepared CoFePBA has a larger specific surface area and can provide more loading area for MoSe2.

[0015] Preferably, in step (1), the sealing aging treatment time is 24 hours.

[0016] Preferably, in step (2), the temperature is raised to 400°C at a heating rate of 2°C / min, calcined at a constant temperature for 2 hours, and then annealed at a rate of 2°C / min.

[0017] Preferably, in step (3), the ratio of the amount of CSCC, MoO3 and Se powder added is 1:1:1.

[0018] Preferably, in step (3), the volume ratio of alcohol, water and hydrazine hydrate is 15:10:5.

[0019] A second aspect of the present invention provides the application of the above-described cathode catalyst in the degradation of norfloxacin.

[0020] A third aspect of the present invention provides an electrochemical system for degrading norfloxacin, comprising: an anode, a cathode, and an electrolyte;

[0021] The anode is a graphite electrode;

[0022] The cathode is prepared by the following method:

[0023] The above cathode catalyst was mixed with carbon black, and then polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) were added and ground into a paste. The paste was then coated on both sides of graphite paper to prepare the cathode.

[0024] The electrolyte is 50 mM Na2SO4.

[0025] Preferably, the cathode catalyst and carbon black are mixed in a mass ratio of 2:1.

[0026] A fourth aspect of the present invention provides a method for degrading norfloxacin in wastewater using the above-described electrochemical system, comprising the following steps:

[0027] The cathode and anode are installed in an electrolytic cell containing electrolyte. Wastewater to be treated is added to the electrolytic cell, and PMS is added to adjust the pH of the system to 7. The current is controlled at 300-900mA to degrade norfloxacin in the wastewater.

[0028] Preferably, PMS is added to achieve a final concentration of 0.5 mM.

[0029] The beneficial effects of this invention are:

[0030] (1) The cathode catalyst (MoSe2 / CSCC) of the present invention has excellent redox ability and electron transfer ability. Compared with the use of MoSe2 alone and the use of CSCC alone, it has a synergistic effect in improving the redox ability and electron transfer ability of the catalyst.

[0031] (2) The cathode for preparing electrochemical reactions using the cathode catalyst (MoSe2 / CSCC) of the present invention can generate free radicals by activating PMS, thereby improving the catalytic oxidation performance of the cathode and achieving high efficiency in treating norfloxacin over a wide pH range. Attached Figure Description

[0032] Figure 1 : Cyclic voltammetry test diagram of the cathode catalyst prepared in this invention; Co:Fe in the diagram refers to the mass ratio of Co(NO3)2 to K3Fe(CN)6.

[0033] Figure 2 Chronoamperometry results of the cathode catalyst prepared in this invention.

[0034] Figure 3 SEM image of the cathode catalyst prepared in this invention.

[0035] Figure 4 Investigation into the ratio of cathode catalyst to carbon black.

[0036] Figure 5 : Examination of PMS dosage.

[0037] Figure 6 Investigation of the pH of the reaction.

[0038] Figure 7 Investigation of current parameters.

[0039] Figure 8 : Examination of cycle stability. Detailed Implementation

[0040] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0041] As mentioned earlier, the key to treating NOR wastewater by electrochemically activating PMS lies in the generation of persulfate radicals (SO4) through cathode activation of PMS. ·- Developing efficient cathode catalysts is a current research focus.

[0042] Based on this, the present invention uses Prussian blue analogues (PBAs) as precursors and prepares CoFePBA with a core-shell nanocage structure by adjusting the ratio of Co to Fe. After calcination at 400℃ in an N2 atmosphere, the shape and structure are maintained, resulting in a novel core-shell cube carbon material (CSCC). Subsequently, using CSCC, MoO3 and Se powder as reaction raw materials, and alcohol, water and hydrazine hydrate as reaction solvents, MoSe2 is grown in situ on the surface of CSCC by hydrothermal method, finally obtaining a novel cathode catalyst MoSe2 / CSCC.

[0043] In the preparation of the cathode catalyst MoSe2 / CSCC, this invention first adjusts the addition ratio of K3Fe(CN)6 and Co(NO3)2 to give the prepared CoFePBA a larger specific surface area. Then, by calcining CoFePBA, it is transformed into a porous carbon material, forming a MNC structure, which enhances its electron transport and catalytic ability. Pure MoSe2 will agglomerate and collapse, and cannot be uniformly loaded onto the CSCC surface. This invention, by adding MoO3 and Se powder for hydrothermal reaction, allows MoSe2 to grow in situ on the CSCC surface. Under appropriate growth ratios, collapse and agglomeration do not occur, which is beneficial to electron transport.

[0044] In the cathode catalyst prepared by this invention, MoSe2 nanosheets are uniformly attached to the surface of CSCC, forming a nanospherical structure. Electrochemical performance tests show that the MoSe2 / CSCC cathode catalyst of this invention exhibits excellent redox capabilities and electron transfer capabilities.

[0045] The cathode of the electrochemical reaction system is prepared by mixing and grinding the cathode catalyst of the present invention with carbon black (CB) and coating it on both sides of graphite paper. A graphite electrode is then used as the anode, and 50 mM Na₂SO₄ is used as the electrolyte to construct the electrochemical system. In the electrochemical system of the present invention, the activation of PMS by current-driven activation significantly improves the degradation efficiency of NOR in water.

[0046] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0047] The test materials used in the embodiments of the present invention, unless otherwise specified, are all conventional test materials in the art and can be purchased through commercial channels.

[0048] Example 1: Preparation and Condition Optimization of Cathode Catalyst

[0049] 1. Optimization of preparation conditions:

[0050] 4.0 g of PVP was dissolved in 40 mL of 0.1 M HCl solution. After uniform stirring, the solution was divided into two equal portions, A and B. A certain amount of K3Fe(CN)6 was added to 20 mL of solution A. A certain amount of Co(NO3)2 was added to 20 mL of solution B. At room temperature, solution A was poured into solution B, making the mass ratio of Co(NO3)2 to K3Fe(CN)6 0.70:0, 0.85:0.65, 0.70:0.65, 0.35:0.65, and 0:0.65, respectively. After stirring evenly, the solution was sealed and aged for 24 h. The aged solution was transferred to a reaction vessel and placed in an 80 °C oven for hydrothermal treatment for 24 h. After the reaction vessel cooled to room temperature, the product was washed three times with water and ethanol, and then dried in a 60 °C vacuum oven for 24 h to obtain a solid powder (CoFePBA). The solid powder was then placed in a tube furnace and heated to 400°C at a rate of 2°C / min, calcined at a constant temperature for 2 hours, and then annealed to room temperature at a rate of 2°C / min to obtain CSCC powder.

[0051] Subsequently, CSCC, MoO3, and Se powder were added to the polytetrafluoroethylene liner of the reactor in different ratios. When CSCC:MoSe2 = 1:1, the corresponding amount of CSCC, MoO3, and Se powder added was 30 mg; when CSCC:MoSe2 = 2:1, the corresponding amounts of CSCC, MoO3, and Se powder added were 30 mg, 15 mg, and 15 mg, respectively; when CSCC:MoSe2 = 1:2, the corresponding amounts of CSCC, MoO3, and Se powder added were 15 mg, 30 mg, and 30 mg, respectively; when CSCC:MoSe2 = 1:0, the corresponding amounts of CSCC, MoO3, and Se powder added were 30 mg, 0 mg, and 0 mg, respectively; and when CSCC:MoSe2 = 0:1, the corresponding amounts of CSCC, MoO3, and Se powder added were 0 mg, 30 mg, and 30 mg, respectively.

[0052] 15 mL of ethanol, 10 mL of water and 5 mL of hydrazine hydrate were added, and then the mixture was heated in an oven at 200 °C for 12 h. The product was then washed three times with water and ethanol to obtain the final material (MoSe2 / CSCC).

[0053] Cyclic voltammetry and chronoamperometry were performed on cathode catalysts (CSCC:MoSe2 = 1:1) prepared with different Co:Fe ratios (Co:Fe = 0.70:0, Co:Fe = 0.85:0.65, Co:Fe = 0.70:0.65, Co:Fe = 0.35:0.65, Co:Fe = 0:0.65) and cathode catalysts (CSCC:MoSe2 = 1:1, CSCC:MoSe2 = 1:0, CSCC:MoSe2 = 2:1, CSCC:MoSe2 = 1:1, CSCC:MoSe2 = 1:2, CSCC:MoSe2 = 0:1) (CSCC preparation with Co:Fe = 0.70:0.65). The results are as follows: Figure 1 and Figure 2 As shown.

[0054] Cyclic voltammetry (CV) results showed that the peak current was highest when the Co / Fe ratio was 0.70:0.65 and the CSCC:MoSe2 loading ratio was 1:1, indicating that the catalyst prepared under these conditions has stronger redox capabilities.

[0055] The chronoamperometry test was conducted under open-circuit voltage with 50 mM Na2SO4 as the electrolyte. The sampling interval was 0.1 s, the running time was 300 s, the sensitivity was 0.0001 A / V, and PMS with a final concentration of 0.5 mM was added at 100 s.

[0056] Under open-circuit voltage conditions, the current immediately increased after 0.5 mM PMS was added in 100 s, which proved that electron transfer occurred between the material and PMS. The greater the change in current, the stronger its electron transfer ability.

[0057] Depend on Figure 2 It can be seen that the timing current values ​​for Co / Fe ratios of 0.7:0, 0:0.65, and 0.7:0.65 are 0.38, 0.19, and 1.40 mA, respectively; and the timing current values ​​for CSCC:MoSe2=1:0, CSCC:MoSe2=0:1, and CSCC:MoSe2=1:1 are 0.48, 0.20, and 1.40 mA, respectively.

[0058] The results indicate that the optimal electron transfer capability is achieved when the Co / Fe ratio is 0.70:0.65 and the CSCC:MoSe2 loading ratio is 1:1. Compared with using MoSe2 or CSCC alone, it exhibits a synergistic effect in improving the redox capacity and electron transfer capability of the catalyst.

[0059] 2. Optimal preparation conditions:

[0060] The optimal preparation conditions for the cathode catalyst are:

[0061] 4.0 g of PVP was dissolved in 40 mL of 0.1 M HCl solution. After uniform stirring, the solution was divided into two equal portions, namely solution A and solution B. 65 mg of K3Fe(CN)6 was added to 20 mL of solution A. 70 mg of Co(NO3)2 was added to 20 mL of solution B. Solution A was poured into solution B at room temperature, stirred evenly, and then sealed and aged for 24 h. The aged solution was transferred to a reaction vessel and placed in an 80 °C oven for hydrothermal treatment for 24 h. After the reaction vessel cooled to room temperature, the product was washed three times with water and ethanol, and then dried in a 60 °C vacuum oven for 24 h to obtain solid powder (CoFePBA). Subsequently, the solid powder was placed in a tube furnace and calcined at 400 °C at a heating rate of 2 °C / min for 2 h, followed by annealing at 2 °C / min to room temperature to obtain CSCC powder.

[0062] Take 30 mg each of CSCC, MoO3, and Se powder, add them to the polytetrafluoroethylene liner of the reactor, and add 15 mL of alcohol, 10 mL of water, and 5 mL of hydrazine hydrate. Then place it in an oven and heat at 200 °C for 12 h. After washing the product three times with water and ethanol, the cathode catalyst (MoSe2 / CSCC) is obtained.

[0063] Scanning electron microscopy (SEM) analysis was performed on the cathode catalyst (MoSe2 / CSCC) prepared under optimal conditions, and the results are as follows: Figure 3 As shown, the results indicate that MoSe2 nanosheets are uniformly attached to the surface of CSCC and form a nanosphere structure.

[0064] Example 2: Construction of an electrochemical system for the degradation of norfloxacin and optimization of reaction conditions

[0065] 1. Cathode preparation:

[0066] The cathode catalyst (MoSe2 / CSCC, abbreviated as C) prepared under the optimal conditions in Example 1 was mixed with carbon black (CB) in a certain proportion (the mass of the mixture was 12 mg), and then ground thoroughly with 10 mg of polyvinylidene fluoride (PVDF) in a quartz mortar. Subsequently, 0.25 mL of N-methylpyrrolidone (NMP) was added dropwise, and the mixture was ground thoroughly until it became a thick paste. The paste was then applied to one side of a 2.5 cm × 2.5 cm graphite paper and allowed to air dry. The other side was coated in the same way to prepare the cathode.

[0067] 2. Construction of an electrochemical system for the degradation of norfloxacin:

[0068] A graphite electrode (2.5cm×2.5cm×1mm) was used as the anode, and the cathode prepared above was used as the cathode. The anode and cathode were placed in a 200mL glass electrolytic cell with an electrode spacing of 2cm and 50mM Na2SO4 as the electrolyte.

[0069] 3. Optimization of reaction conditions:

[0070] (1) The ratio of cathode catalyst to carbon black:

[0071] Different cathodes were prepared by mixing cathode catalyst (C) and carbon black (CB) at mass ratios of 0:1, 1:3, 1:2, 1:1, 2:1, 3:1, and 1:0. The degradation effect of different electrodes on NOR was investigated under the following conditions: current: 200 mA; electrolyte: 50 mM Na₂SO₄; PMS concentration: 0.5 mM; initial NOR concentration: 20 mg / L; pH: 7.

[0072] The results are as follows Figure 4 As shown, the ratio of catalyst MoSe2 / CSCC to carbon black affects the degradation of NOR. Due to its large specific surface area, carbon black can improve electrode stability while also increasing the contact area between the catalyst and PMS. The results indicate that the NOR degradation efficiency gradually increases with the increase of the catalyst MoSe2 / CSCC ratio. This is because the active sites of Se, Mo, Co, and Fe on the catalyst surface, as well as electron conversion, can activate PMS to produce SO4. ·- , 1 Active species such as O2 and ·OH are used to degrade NOR. The optimal ratio of catalyst to carbon black for NOR wastewater treatment is 2:1. Further increasing the catalyst ratio at this point reduces the NOR degradation efficiency, possibly because some active sites on the catalyst are occupied, reducing the number of available active sites for activation. Therefore, the optimal ratio of cathode catalyst to carbon black is 2:1.

[0073] (2) PMS dosage:

[0074] A cathode was prepared by mixing cathode catalyst (C) and carbon black (CB) at a mass ratio of 2:1. The degradation effects of different PMS concentrations (final concentrations after addition of 0.25 mM, 0.50 mM, 0.75 mM, and 1 mM) on NOR were investigated under the conditions of current: 300 mA, electrolyte: 50 mM Na2SO4, initial NOR concentration: 20 mg / L, and pH: 7.

[0075] The results are as follows Figure 5 As shown, when PMS is not added to the system, an electro-Fenton reaction occurs at the cathode to produce ·OH(O2 + 2H+). + +2e - →H₂O₂, O₂ + 2H₂O + 2e- →4OH - M 2+ +H₂O₂→M 3+ +·OH+OH - This leads to the degradation of NOR, and when PMS is added, SO42- is reduced as the PMS concentration increases. ·- The release of PMS increases accordingly, thus gradually increasing the NOR degradation rate. When the PMS dosage exceeds 0.5 mM, due to the limited number of cathode active sites and the quenching effect of unactivated PMS on different active species, This reduces the NOR degradation rate; therefore, the optimal PMS concentration in this system is 0.5 mM.

[0076] (3) pH:

[0077] A cathode was prepared by mixing cathode catalyst (C) and carbon black (CB) at a mass ratio of 2:1. The degradation effect of different pH values ​​(1, 3, 5, 7, 9, and 11) on NOR was investigated under the following conditions: current: 300 mA; electrolyte: 50 mM Na₂SO₄; PMS concentration: 0.5 mM; initial NOR concentration: 20 mg / L.

[0078] The results are as follows Figure 6 As shown, when pH < 3 (strong acid conditions), H + The H bonds formed between PMS and its OO groups give PMS a positive charge, hindering its interaction with Co(II) and Fe(II), thus resulting in a lower degradation rate at pH 1. At pH 11 (strongly alkaline conditions), PMS mainly exists as a binary ion (SO₅₅). 2- ) exists, and SO5 2- Its oxidizing power is lower than that of HSO5. - Furthermore, PMS exhibits high concentrations of OH- - In its presence, NOR is decomposed into sulfate ions and oxygen by non-free bases, thus reducing the degradation rate of NOR in a strongly alkaline environment. However, under both strongly acidic and strongly alkaline conditions, the NOR removal rate exceeds 90%, indicating that this electrode exhibits good NOR degradation performance over a wide pH range.

[0079] (4) Current:

[0080] A cathode was prepared by mixing cathode catalyst (C) and carbon black (CB) at a mass ratio of 2:1. The degradation effects of different current intensities (100mA, 200mA, 300mA, 500mA, 700mA, and 900mA) on NOR were investigated under the following conditions: electrolyte: 50mM Na₂SO₄; PMS concentration: 0.5mM; initial NOR concentration: 20mg / L; pH: 7.

[0081] The results are as follows Figure 7 As shown, the NOR degradation rate increases significantly with increasing current. When the current is ≥300mA, the NOR degradation rate exceeds 90%, and especially when the current is increased to 900mA, the NOR degradation rate reaches as high as 99.2%. The increase in current increases the yield of H2O2 at the cathode and simultaneously enhances the redox cycle of transition metal electron pairs in the catalyst, thereby activating PMS to generate a large number of active species and improving the NOR degradation rate.

[0082] (5) Cyclic stability:

[0083] A cathode was prepared by mixing cathode catalyst (C) and carbon black (CB) at a mass ratio of 2:1. The cycling stability of the cathode was tested under the following conditions: current: 300 mA, electrolyte: 50 mM Na2SO4, PMS concentration: 0.5 mM, initial NOR concentration: 20 mg / L, pH: 7.

[0084] The results are as follows Figure 8 As shown, the cathode underwent six cyclic degradation tests. After six cycles, the NOR degradation rate decreased by only 6.4%, indicating that the cathode has good cyclic stability.

[0085] In summary, the optimal reaction conditions for the degradation of norfloxacin using the above electrochemical system are:

[0086] The cathode catalyst (C) prepared in Example 1 was mixed with carbon black (CB) at a mass ratio of 2:1 to prepare the cathode. The final concentration of PMS added was 0.5 mM, the pH of the reaction system was 7.0, the current was 900 mA, and the electrolyte was 50 mM Na2SO4. Under optimal reaction conditions, the degradation rate of norfloxacin in wastewater was over 99.2%.

[0087] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. The application of a cathode catalyst in the degradation of norfloxacin, characterized in that, The cathode catalyst is prepared by the following method: (1) K3Fe(CN)6 and Co(NO3)2 were mixed evenly and then sealed and aged. Then, they were hydrothermally reacted at 70-90℃ for 20-28h. The product was washed and dried to prepare CoFePBA. (2) CoFePBA was heated to 400℃ under a nitrogen atmosphere, calcined at a constant temperature, and annealed to prepare CSCC; (3) Using CSCC, MoO3 and Se powder as reaction raw materials, and alcohol, water and hydrazine hydrate as reaction solvents, the reaction was carried out at 180-220℃ for 10-14h. The product was washed and dried to prepare a cathode catalyst. The cathode catalyst was activated by current driving to improve the degradation efficiency of norfloxacin in water. In step (1), Co(NO3)2 and K3Fe(CN)6 are mixed at a mass ratio of 0.70:0.65; In step (3), the mass ratio of CSCC, MoO3 and Se powder is 1:1:1; the volume ratio of alcohol, water and hydrazine hydrate is 15:10:

5.

2. The application according to claim 1, characterized in that, In step (2), the temperature is raised to 400℃ at a heating rate of 2℃ / min, calcined at a constant temperature for 2 hours, and then annealed at a rate of 2℃ / min.

3. An electrochemical system for degrading norfloxacin, characterized in that, include: Anode, cathode, and electrolyte; The anode is a graphite electrode; The cathode is prepared by the following method: The cathode catalyst of claim 1 was mixed with carbon black, and then polyvinylidene fluoride and N-methylpyrrolidone were added and ground into a paste. The paste was then coated on both sides of graphite paper to prepare a cathode. The cathode catalyst was activated by current-driven activation of PMS, which improved the degradation efficiency of norfloxacin in water. The electrolyte is 50 mM Na2SO4.

4. The electrochemical system according to claim 3, characterized in that, The cathode catalyst and carbon black are mixed at a mass ratio of 2:

1.

5. A method for degrading norfloxacin in wastewater using the electrochemical system described in claim 3 or 4, characterized in that, Includes the following steps: The cathode and anode are installed in an electrolytic cell containing electrolyte. Wastewater to be treated is added to the electrolytic cell, and PMS is added to adjust the pH of the system to 7. The current is controlled at 300-900mA to degrade norfloxacin in the wastewater.

6. The method according to claim 5, characterized in that, Add PMS to achieve a final concentration of 0.5 mM.

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