Graphite composite electrode for antibiotic degradation and preparation method and application thereof
By constructing a porous structure on the surface of graphite sheets and loading nickel-iron oxide nanoparticles, a graphite composite electrode was prepared, which solved the problems of low catalytic activity and poor stability of existing electrode materials, and achieved efficient electrocatalytic degradation of antibiotic wastewater.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANDONG JIANZHU UNIV
- Filing Date
- 2026-06-08
- Publication Date
- 2026-07-10
AI Technical Summary
Existing electrode materials suffer from low catalytic activity, high cost, or poor stability in antibiotic wastewater treatment, making it difficult to achieve efficient degradation.
A graphite composite electrode was prepared by using graphite sheets as a substrate, constructing a porous structure through KOH etching, and uniformly loading nickel-iron oxide nanoparticles onto the graphite surface using a liquid-phase reduction method.
It achieves highly efficient electrocatalytic degradation of antibiotics, with high catalytic activity, low cost and stable structure, and is suitable for the degradation of various antibiotics.
Smart Images
Figure CN122355423A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of environmental treatment materials, and more particularly to a graphite composite electrode for antibiotic degradation, its preparation method, and its application. Background Technology
[0002] Antibiotics, as a typical emerging pollutant, produce wastewater characterized by poor biodegradability, high chemical oxygen demand, high biotoxicity, and difficulty in degradation. Current traditional treatment methods, such as adsorption, biological methods, and chemical oxidation, suffer from low efficiency, high cost, and the potential for secondary pollution. Compared to these methods, advanced electrochemical oxidation technology is considered an effective means of deep treatment of antibiotics due to its mild reaction conditions, lack of external oxidant requirements, and low energy consumption. Electrode materials, as the core of electrocatalytic reactions, directly influence the application of electrocatalytic oxidation technology in antibiotic wastewater treatment due to their catalytic activity, stability, and cost. Currently used electrode materials exhibit a significant performance-cost trade-off: noble metal electrodes (such as platinum, iridium, and ruthenium-based materials) have high catalytic activity but are expensive, hindering large-scale application; iron-based electrodes are inexpensive but have poor stability, easily corroding or passivating during electrocatalysis, affecting long-term performance; boron-doped diamond, while possessing excellent mineralization capabilities, has complex preparation processes and high costs, limiting its practical application. Graphite electrodes have high conductivity and excellent corrosion resistance, and are inexpensive, but their catalytic activity for antibiotics is relatively low. Summary of the Invention
[0003] This invention provides a graphite composite electrode for antibiotic degradation, its preparation method and application, which has a simple preparation process, low cost, high catalytic activity and stable structure.
[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a method for preparing a graphite composite electrode for antibiotic degradation, comprising the following steps: (1) Using a graphite sheet as the anode and a conductive material as the cathode, and an alkaline electrolyte as the etching medium, the graphite sheet is electrochemically etched under constant current conditions to obtain an etched graphite sheet. (2) The etched graphite sheet is immersed in a mixed solution containing nickel salt, ferrous salt and complexing agent, and then an aqueous solution of alkaline regulator and a water dispersion of reducing agent are added to react and obtain a graphite composite electrode.
[0005] Preferably, the alkaline electrolyte comprises a KOH solution; The concentration of the KOH solution is 0.5~3 mol / L; The conductive material includes platinum; The current density for the electrochemical etching is 20~100 mA / cm². 2The etching time is 10~60 minutes.
[0006] Preferably, in the mixed solution, the concentration of nickel in the nickel salt is 20-40 mmol / L, the concentration of iron in the ferrous salt is 10-20 mmol / L, and the concentration of the complexing agent is 20-40 mmol / L.
[0007] Preferably, the ratio of the etched graphite sheet to the mixed solution is 4-8 cm⁻¹. 2 30-80 mL.
[0008] Preferably, the nickel salt includes one or more of nickel chloride, nickel nitrate, or nickel sulfate; The ferrous salt includes one or more of ferrous sulfate, ferrous chloride, or ferrous nitrate.
[0009] Preferably, the ratio of the etched graphite sheet to the alkaline conditioning agent aqueous solution is 4-8 cm⁻¹. 2 : 1.0-2.5 mL; the concentration of the alkaline regulator aqueous solution is 2~4 M; The ratio of the etched graphite sheet to the reducing agent aqueous dispersion is 4-8 cm⁻¹. 2 0.5-1.5 mL; The concentration of the reducing agent aqueous dispersion is 75~85wt%.
[0010] Preferably, the complexing agent comprises sodium citrate; The reducing agent in the aqueous dispersion of the reducing agent includes hydrazine hydrate; The alkaline regulator in the aqueous solution includes NaOH.
[0011] Preferably, the reaction temperature is 60~100℃ and the reaction time is 0.5~4h.
[0012] A second aspect of the present invention also provides a graphite composite electrode for antibiotic degradation, wherein the graphite composite electrode is prepared by the above-described preparation method.
[0013] A second aspect of the present invention also provides the application of the above-mentioned graphite composite electrode for antibiotic degradation in the electrocatalytic degradation of antibiotics.
[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention uses graphite sheets as a substrate, constructs a porous structure on its surface by KOH etching, and then uniformly loads nickel-iron oxide nanoparticles onto the graphite surface using a liquid-phase reduction method to prepare a graphite composite electrode. Experimental results show that the graphite composite electrode can achieve highly efficient electrocatalytic degradation of various antibiotics. Attached Figure Description
[0015] The above and other objects, features, and advantages of the invention will be apparent from the following description of preferred embodiments illustrating the gist of the invention and its use, and the accompanying drawings, in which: Figure 1 This is a schematic diagram of the preparation process of the graphite composite electrode in this invention.
[0016] Figure 2 The images show the characterization of the etched graphite sheet and graphite composite electrode in Example 1, where (a) is a scanning electron microscope (SEM) image of the etched graphite sheet, (b) is a SEM image of the graphite composite electrode, (c) is a transmission electron microscope (TEM) image of the graphite composite electrode, and (d) is a high-resolution TEM image of the graphite composite electrode.
[0017] Figure 3 The image shows the elemental mapping of the graphite composite electrode in Example 1, where (a) is a transmission electron microscope image, (b) shows the carbon element distribution, (c) shows the nickel element distribution, (d) shows the iron element distribution, and (e) shows the oxygen element distribution.
[0018] Figure 4 The image shows the XPS spectrum of the graphite composite electrode in Example 1.
[0019] Figure 5 The image shows the high-resolution XPS spectrum of the C1s of the graphite composite electrode in Example 1.
[0020] Figure 6 This is a high-resolution XPS spectrum of the Ni 2p of the graphite composite electrode in Example 1.
[0021] Figure 7 This is a high-resolution XPS spectrum of Fe 2p in the graphite composite electrode of Example 1.
[0022] Figure 8 The image shows the high-resolution XPS spectrum of the graphite composite electrode in Example 1 at 1s.
[0023] Figure 9 This is an X-ray diffraction image of the graphite composite electrode in Example 1.
[0024] Figure 10 The graphite sheet electrode is used to perform electrocatalytic degradation of levofloxacin at different etching current densities.
[0025] Figure 11 The effect of different sodium sulfate concentrations on the degradation rate of levofloxacin.
[0026] Figure 12 The effect of different initial concentrations on the degradation rate of levofloxacin.
[0027] Figure 13The effect of different current densities on the degradation rate of levofloxacin.
[0028] Figure 14 The effect of solution pH on the degradation rate of levofloxacin.
[0029] Figure 15 The curve shows the degradation rate of levofloxacin over time. Figure 16 According to Figure 15 The obtained first-order reaction kinetic equation fitting curve.
[0030] Figure 17 The degradation rate curve of levofloxacin after adding 2 M tert-butanol (TBA) and methanol (CH3OH) as scavenging agents to the levofloxacin solution is shown.
[0031] Figure 18 The electron paramagnetic resonance spectrum is shown for 5,5-dimethyl-1-pyrrolline-N-oxide (DMPO) as the trapping agent.
[0032] Figure 19 The curve shows the change in the degradation rate of levofloxacin with the number of degradation cycles.
[0033] Figure 20 This is a scanning electron microscope image of the graphite composite electrode after five degradation cycles.
[0034] Figure 21 This study aims to identify a possible pathway for the electrocatalytic degradation of levofloxacin based on the results of liquid chromatography-mass spectrometry (LC-MS).
[0035] Figure 22 The degradation rate of tetracycline (TC), sulfamethazine (MTZ), and metronidazole (SMT) by the graphite composite electrode is shown. Detailed Implementation
[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. The embodiments of this application are only examples, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0037] Example 1 The preparation process of the graphite composite electrode is illustrated in the schematic diagram below. Figure 1 As shown, it includes the following steps: (1) KOH etching Using 1 M KOH as the electrolyte, a graphite sheet as the anode, and a platinum sheet as the cathode, at 75 mA / cm 2 The graphite sheet was etched at a current density for 30 minutes. After the etching was completed, many micro- and nano-pores were formed on the graphite surface.
[0038] (2) Nickel-iron oxide loading The etched graphite sheet was immersed in a mixed solution of 33 mM nickel chloride, 15 mM ferrous sulfate, and 30 mM sodium citrate (the ratio of the etched graphite sheet to the mixed solution was 5 cm³). 2 Add 50 mL of 3M NaOH aqueous solution and 1 mL of 80 wt% hydrazine hydrate aqueous dispersion. React at 80 °C for 1 h. After the reaction is complete, nickel-iron oxide composite material can be deposited on the surface of the graphite sheet to obtain a graphite composite electrode.
[0039] Performance testing 1. Characterization Figure 2 The images show the characterization of the etched graphite sheet and graphite composite electrode in Example 1, where (a) is a scanning electron microscope (SEM) image of the etched graphite sheet, (b) is a SEM image of the graphite composite electrode, (c) is a transmission electron microscope (TEM) image of the graphite composite electrode, and (d) is a high-resolution TEM image of the graphite composite electrode.
[0040] Depend on Figure 2 It can be seen that the surface of the etched graphite sheet has a large number of micro and nano pores, the surface of the graphite composite electrode is loaded with a large number of nickel-iron oxide nanoparticles, and the lattice stripes of the Ni(111) crystal plane can be clearly seen in the graphite composite electrode, with a lattice spacing of about 0.204 nm.
[0041] Figure 3 The image shows the elemental mapping of the graphite composite electrode in Example 1, where (a) is a transmission electron microscope image, (b) shows the carbon element distribution, (c) shows the nickel element distribution, (d) shows the iron element distribution, and (e) shows the oxygen element distribution.
[0042] Depend on Figure 3 It can be seen that nickel, iron, and oxygen elements are all uniformly distributed on the surface of the graphite sheet in the graphite composite electrode.
[0043] Figure 4 The image shows the XPS spectrum of the graphite composite electrode in Example 1. Figure 4 It is known that graphite composite electrodes contain carbon, nickel, iron, and oxygen elements.
[0044] Figure 5 This is a high-resolution XPS spectrum of the C1s chromatogram of the graphite composite electrode in Example 1. Figure 5 It can be seen that C-C bonds and COOH bonds exist on the surface of the graphite sheet.
[0045] Figure 6 This is a high-resolution XPS spectrum of the Ni 2p layer of the graphite composite electrode in Example 1. Figure 6 It can be seen that nickel mainly exists in the +2 oxidation state.
[0046] Figure 7This is a high-resolution XPS spectrum of Fe 2p in the graphite composite electrode of Example 1. Figure 7 It is known that iron mainly exists in the +3 oxidation state.
[0047] Figure 8 This is the high-resolution XPS spectrum of the graphite composite electrode in Example 1 at 1s. Figure 8 It can be seen that the oxygen element on the surface of the graphite sheet has OH bonds and COC bonds.
[0048] Figure 9 This is an X-ray diffraction image of the graphite composite electrode in Example 1. Figure 9 It can be seen that the main components of the nanoparticles loaded on the graphite sheet surface are Ni, Fe3O4 and Fe2O3.
[0049] (2) Degradation performance First, an antibiotic aqueous solution was prepared using sodium sulfate as the electrolyte. Then, the antibiotic was degraded using an electrochemical workstation with a graphite composite electrode as the anode and a graphite sheet as the cathode in constant current mode.
[0050] Figure 10 The graphs show the electrocatalytic degradation efficiency of levofloxacin by graphite sheet electrodes at different etching current densities. It can be seen that the degradation rate of levofloxacin by the graphite electrode significantly increases with increasing current density. This is likely because higher current densities can form a more developed porous structure on the graphite surface, thereby increasing the specific surface area and providing more active sites.
[0051] Figure 11 The effect of different sodium sulfate concentrations on the degradation rate of levofloxacin was investigated. It can be seen that as the sodium sulfate concentration increased from 0.05 M to 0.1 M, the degradation rate of levofloxacin increased from 91.5% to 100%. Then, as the sodium sulfate concentration gradually increased to 0.4 M, the degradation rate of levofloxacin gradually decreased to 91.3%. This is because an appropriate amount of SO42-... 2- Sulfate radicals can be generated at the anode, enhancing the oxidative degradation of levofloxacin. However, when the sodium sulfate concentration is too high, excess SO4... 2- It may shield the active sites on the surface of the graphite composite electrode, hindering the generation of ·OH, thereby leading to a decrease in the degradation efficiency of levofloxacin.
[0052] Figure 12The effect of different initial concentrations on the degradation rate of levofloxacin was investigated. It can be seen that as the initial concentration of levofloxacin increased from 20 mg / L to 50 mg / L, the degradation rate gradually decreased from 100% to 59.3%. This is because at lower initial concentrations, the active species are sufficient for efficient degradation. However, with increasing initial concentration, the number of active species available for distribution per levofloxacin molecule decreases, leading to a decline in degradation efficiency.
[0053] Figure 13 The effect of different current densities on the degradation rate of levofloxacin is shown. It can be seen that as the current density increases from 12.5 mA / cm², the degradation rate of levofloxacin decreases. 2 Increased to 75 mA / cm 2 The degradation rate of levofloxacin gradually increased from 86.9% to 100%. We believe that the increase in current density can enhance the electron transfer rate on the electrode surface, promote the generation of free radicals (such as ·OH), and thus accelerate the oxidative degradation of levofloxacin.
[0054] Figure 14 The effect of solution pH on the degradation rate of levofloxacin was investigated. It can be seen that when the pH of the levofloxacin solution increased from 3 to 5, the degradation rate increased from 90.1% to 100%. Then, as the pH continued to increase to 9, the degradation rate gradually decreased to 91.5%. When the pH of the levofloxacin solution continued to increase to 10, the degradation rate increased to 100% again. This indicates that acidic conditions are beneficial for suppressing the oxygen evolution side reaction, improving current efficiency, and allowing more free radicals to participate in the degradation reaction; under moderately alkaline conditions, free radical generation is inhibited; under strongly alkaline conditions, certain free radicals (such as SO4·) are inhibited. 2- The degradation rate rebounded as the substance still exhibited high activity.
[0055] Figure 15 The curve shows the degradation rate of levofloxacin over time. Figure 16 According to Figure 15 The obtained first-order reaction kinetic equation fitting curve shows that the equation can well describe the degradation process of levofloxacin, indicating that its degradation process conforms to first-order reaction kinetics, and the reaction rate is controlled by the generation of active free radicals and the surface adsorption process.
[0056] Figure 17The degradation rate curves of levofloxacin after adding 2 M tert-butanol (TBA) and methanol (CH3OH) as scavenging agents to the levofloxacin solution are shown. It can be seen that after 120 min, the degradation rate of levofloxacin was 100% without the addition of scavenging agents; after adding tert-butanol and methanol, the degradation rates of levofloxacin decreased to 18.7% and 39.7%, respectively. Since tert-butanol can inhibit hydroxyl radicals, and methanol can inhibit sulfate radicals, both hydroxyl and sulfate radicals are active free radicals, but hydroxyl radicals play a dominant role in the degradation process.
[0057] Figure 18 The image shows the electron paramagnetic resonance spectrum of 5,5-dimethyl-1-pyrrolline-N-oxide (DMPO) as a scavenger. It can be seen that hydroxyl and sulfate reactive free radicals are indeed present in the solution during the degradation of levofloxacin.
[0058] Figure 19 The graph shows the degradation rate of levofloxacin as a function of the number of degradation cycles. It can be seen that after five degradation cycles, the degradation rate of levofloxacin is still as high as 81.9%, indicating that the graphite composite electrode has good reusability.
[0059] Figure 20 This is a scanning electron microscope image of the graphite composite electrode after five degradation cycles. It can be seen that the nickel-iron oxide composite nanoparticles are still loaded on the graphite sheet surface, demonstrating that the graphite composite electrode possesses excellent structural and compositional stability.
[0060] Figure 21 This study describes the possible pathways for the electrocatalytic degradation of levofloxacin, inferred from the results of liquid chromatography-mass spectrometry (LC-MS). In pathway I, the carboxyl, methyl, and fluorine atoms are substituted with hydroxyl groups to generate P1, followed by a piperazine reaction to generate P2. After the piperazine group is removed, the amino group on the benzene ring remains, generating P3. Oxygen in the ketone group and tertiary amine acts as a hydrogen bond acceptor, forming hydroxyl and secondary amino groups, respectively. In pathway II, LEVO is attacked by •OH, losing its carboxyl group to generate compound P5. P5 then loses a fluorine atom to generate compound P6. Next, P6 loses a methyl group, yielding compound P7. In pathway III, LEVO is attacked by reactive oxygen species, undergoing decarboxylation, demethylation, and hydroxylation to generate intermediate P8, which is then gradually degraded into smaller molecules P9 and P10. In pathway IV, the piperazine ring of LEVO is opened and completely removed to generate P11, followed by a defluorination reaction to generate P12. In pathway V, P11 is degraded to P13 through deamination and decarboxylation, and its oxazine ring opens to form P14. Finally, the intermediates P4, P7, P10, P12 and P14 continue to cleave and separate, mineralizing into CO2 and H2O.
[0061] Figure 22The graphite composite electrode represents the degradation rates of tetracycline (TC), sulfamethazine (MTZ), and metronidazole (SMT). As can be seen, the degradation rates of tetracycline, sulfamethazine, and metronidazole by the composite electrode are 100%, 97.8%, and 98.6%, respectively. This demonstrates the versatility of the graphite composite electrode for the degradation of various antibiotics.
[0062] Although preferred embodiments of the invention have been shown and described, it is conceivable that those skilled in the art can devise various modifications to the invention within the spirit and scope of the appended claims.
Claims
1. A method for preparing a graphite composite electrode for antibiotic degradation, characterized in that, Includes the following steps: (1) Using a graphite sheet as the anode and a conductive material as the cathode, and an alkaline electrolyte as the etching medium, the graphite sheet is electrochemically etched under constant current conditions to obtain the etched graphite sheet. (2) The etched graphite sheet is immersed in a mixed solution containing nickel salt, ferrous salt and complexing agent, and then an aqueous solution of alkaline regulator and a water dispersion of reducing agent are added to react and obtain a graphite composite electrode.
2. The preparation method according to claim 1, characterized in that, The alkaline electrolyte includes a KOH solution; The concentration of the KOH solution is 0.5~3 mol / L; The conductive material includes platinum; The current density for the electrochemical etching is 20~100 mA / cm². 2 The etching time is 10~60 minutes.
3. The preparation method according to claim 1, characterized in that, In the mixed solution, the concentration of nickel in the nickel salt is 20-40 mmol / L, the concentration of iron in the ferrous salt is 10-20 mmol / L, and the concentration of the complexing agent is 20-40 mmol / L.
4. The preparation method according to claim 1, characterized in that, The ratio of the etched graphite sheet to the mixed solution is 4-8 cm⁻¹. 2 30-80mL.
5. The preparation method according to claim 1, characterized in that, The nickel salt includes one or more of nickel chloride, nickel nitrate, or nickel sulfate; The ferrous salt includes one or more of ferrous sulfate, ferrous chloride, or ferrous nitrate.
6. The preparation method according to claim 1, characterized in that, The ratio of the etched graphite sheet to the alkaline conditioning aqueous solution is 4-8 cm⁻¹. 2 1.0-2.5 mL; The concentration of the alkaline regulator aqueous solution is 2~4M; The ratio of the etched graphite sheet to the reducing agent aqueous dispersion is 4-8 cm⁻¹. 2 0.5-1.5 mL; The concentration of the reducing agent aqueous dispersion is 75~85wt%.
7. The preparation method according to claim 1, characterized in that, The complexing agent includes sodium citrate; The reducing agent in the aqueous dispersion of the reducing agent includes hydrazine hydrate; The alkaline regulator in the aqueous solution includes NaOH.
8. The preparation method according to claim 1, characterized in that, The reaction temperature is 60~100℃, and the reaction time is 0.5~4h.
9. A graphite composite electrode for antibiotic degradation, characterized in that, The graphite composite electrode is prepared by the preparation method described in any one of claims 1 to 8.
10. The application of the graphite composite electrode for antibiotic degradation as described in claim 9 in the electrocatalytic degradation of antibiotics.