Cathode material for electrocatalytic degradation of tetracycline as well as preparation method and application of cathode material

Abstract

The invention discloses a cathode material for electrocatalytic degradation of tetracycline, and a preparation method and application thereof, wherein the cathode material is high in activation efficiency, reusable and small in secondary pollution. The preparation method of the cathode material for electrocatalytic degradation of tetracycline comprises the following steps: preparing a reaction solution, wherein the reaction solution contains zinc ions, iron ions, manganese ions, urea and ammonium fluoride; obtaining a carrier, wherein the carrier has a three-dimensional network structure; performing high-pressure heat treatment on the mixture of the carrier and the reaction liquid to generate a precursor containing the carrier; and calcining the precursor to obtain the cathode material containing the carrier. The cathode material for electrocatalytic degradation of tetracycline is prepared by the preparation method. The purification method of tetracycline in water adopts the cathode material prepared by the preparation method to perform electrocatalytic degradation treatment on a to-be-treated water body containing tetracycline.

Description

Technical Field

[0001] The present invention relates to the technical field of purifying tetracycline in water. Specifically, it relates to a cathode material for electrocatalytic degradation of tetracycline, its preparation method and application. Background Art

[0002] Tetracycline (TC) is one of the most widely used antibiotics in the world. It can treat respiratory infections, urinary tract infections, sexually transmitted diseases, etc. The abuse of drugs and personal care products has led to the discovery of tetracycline in aquatic environments, foods and other samples. If a large amount of tetracycline remains in the water environment, it will cause serious harm to the ecological balance of the water environment and human health. Therefore, it is very important to remove tetracycline. Commonly used removal methods include physical, chemical and biological methods, such as ultrafiltration, activated carbon adsorption and microbial treatment. However, these methods have deficiencies, including high cost, incomplete removal, secondary pollution and other problems.

[0003] In recent years, sulfate radical (SO4 ·- )-based advanced oxidation processes (AOPs) have received extensive attention due to their high efficiency, safety, stable removal effect, wide application range and low cost. Compared with ·OH generated by traditional AOPs, SO4 ·- has a longer half-life, a higher redox potential and a wider pH application range. PMS (peroxymonosulfate) is the main source of SO4 ·- . However, PMS itself cannot degrade pollutants alone and needs to be activated to generate active substances to degrade pollutants.

[0004] The main activation methods of PMS include catalytic activation method, ultraviolet activation method, thermal activation method, ultrasonic activation method, etc. Among them. The catalytic activation method is considered to be the most promising activation method because of its high controllability, high efficiency, mild conditions and easy operation. However, due to relatively low activity and long reaction time, the application of AOPs still cannot achieve the best degradation effect. Moreover, as the reaction progresses, the reversibility of the high-valent metal on the catalyst surface to the low-valent state is poor, resulting in the loss of reaction activity. In addition, the subsequent separation and recovery of the powdered catalyst are extremely difficult, and even increase the risk of secondary pollution. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a cathode material for electrocatalytic degradation of tetracycline with high activation efficiency, reusable and less secondary pollution, its preparation method and application. The technical solution is as follows:

[0006] A preparation method of a cathode material for electrocatalytic degradation of tetracycline, comprising the following steps:

[0007] Prepare a reaction solution, wherein the reaction solution contains zinc ions, iron ions, manganese ions, urea, ammonium fluoride;

[0008] Obtain a carrier, the carrier having a three-dimensional network structure;

[0009] Perform high-pressure heat treatment on the mixture of the carrier and the reaction solution to generate a precursor containing the carrier;

[0010] Perform calcination treatment on the precursor to obtain a cathode material containing the carrier.

[0011] As a further improvement of the above preparation method: The step of preparing the reaction solution includes: using a mixed solution of water and absolute ethanol as a solvent, adding soluble zinc salt, soluble iron salt, and soluble manganese salt, and continuing to add urea and ammonium fluoride after dissolution to obtain the reaction solution.

[0012] As a further improvement of the above preparation method: The volume ratio of water to absolute ethanol in the solvent is 1:1; the molar ratio of zinc ions, iron ions, and manganese ions in the reaction solution is 1:(0.25 - 0.75):(1.25 - 1.75); 4 - 6 mmol of zinc ions, 13 - 17 mmol of urea, and 10 - 15 mmol of ammonium fluoride are added to every 100 mL of the solvent.

[0013] As a further improvement of the above preparation method: The carrier is nickel foam, and nickel foam is washed successively with hydrochloric acid, absolute ethanol, and water before use.

[0014] As a further improvement of the above preparation method: The high-pressure heat treatment is carried out in a polytetrafluoroethylene reaction kettle, the reaction temperature is 80 - 100 °C, and the reaction duration is 6 - 10 hours.

[0015] As a further improvement of the above preparation method: The reaction temperature of the calcination treatment is 300 - 400 °C, and the reaction duration is 4 - 8 hours.

[0016] The cathode material for electrocatalytic degradation of tetracycline is prepared by the above preparation method.

[0017] The purification method of tetracycline in water is to perform electrocatalytic degradation treatment on the water to be treated containing tetracycline using the cathode material prepared by the above preparation method.

[0018] As a further improvement of the above purification method: It further includes the step of adding PMS to the water to be treated.

[0019] As a further improvement of the above purification method: It further includes the step of performing calcination treatment on the used cathode material and then reusing it for electrocatalytic degradation treatment.

[0020] It can be seen that the cathode material for electrocatalytic degradation of tetracycline, its preparation method and application of the present invention have the following advantages: First, the present invention introduces electrochemical activation, directly provides electrons to the high-valent metal, successfully establishes the redox cycle of the metal, significantly accelerates the electron transfer of the transition metal, and further improves the recycling performance. Second, the introduction of electrochemical activation can enhance the activation of PMS by the transition metal catalyst, thereby improving the degradation efficiency. Further, the present invention introduces a porous material with a three-dimensional network structure as a carrier, in-situ generates a ternary active material of zinc, iron and manganese on the pore surface of the carrier, and through calcination treatment, the active material is tightly combined with the carrier, greatly reducing the dissolution rate of the metal in the electrolytic water body, without secondary pollution, facilitating repeated use, and significantly improving the service life of the cathode material. In particular, the used cathode material can be regenerated by calcination treatment, facilitating repeated use, and also having good degradation efficiency for tetracycline during repeated use.

[0021] During the synthesis process, urea can form complexes with metal ions, control the release rate of metal ions, and thus help to precisely adjust the composition and morphology of the precursor. In addition, urea can also decompose during the high-temperature calcination process to generate gases (such as ammonia, carbon dioxide, etc.), which have an impact on the structure and porosity of substances during the synthesis process. Specifically, urea helps to form the porous structure of the material, improve the specific surface area and conductivity of the material.

[0022] Ammonium fluoride can provide fluoride ions, which helps to adjust the surface properties of the material or enhance the chemical stability of the material. Especially during high-temperature calcination, fluoride ions contribute to the phase stability of the material, and may have an impact on the structural stability and ion conduction performance of the electrode material. In addition, ammonium fluoride may also promote the dissolution and uniform distribution of metal ions, thus helping to synthesize high-quality cathode materials.

[0023] It can be seen that the cathode material for electrocatalytic degradation of tetracycline, its preparation method and application of the present invention are prepared by a simple preparation process to obtain a cathode material for electrocatalytic degradation of tetracycline with high activation efficiency, reusable and low secondary pollution, and have strong practicability.

[0024] The following further describes the present invention in conjunction with the drawings and specific embodiments. The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings constituting a part of the present invention are used to assist in understanding the present invention. The content provided in the drawings and the related descriptions in the present invention can be used to explain the present invention, but do not constitute an improper limitation to the present invention. In the drawings:

[0026] Figure 1For NF, ZnFe2O4 / NF, ZnMn2O4 / NF, and ZnFe 0.5 Mn 1.50 O4 / NF SEM images.

[0027] Figure 2 XRD patterns of cathode materials with different Zn / Fe / Mn molar ratios.

[0028] Figure 3 Electrochemical impedance spectra of cathode materials with different Zn / Fe / Mn molar ratios.

[0029] Figure 4 Degradation effect diagrams of TC by cathode materials with different Zn / Fe / Mn molar ratios.

[0030] Figure 5 For ZnFe 0.5 Mn 1.5 Degradation effect diagrams of TC by ZnFe

[0031] Figure 6 O4 / NF at different current densities. 0.5 Mn 1.5 Degradation effect diagrams of TC by ZnFe

[0032] Figure 7 O4 / NF at different PMS dosages. 0.5 Mn 1.5 Degradation effect diagrams of TC by ZnFe

[0033] Figure 8 O4 / NF at different pH values. 0.5 Mn 1.5 Recycling effect diagrams of ZnFe

[0034] Figure 9 O4 / NF. 0.5 Mn 1.5 Metal ion leaching evaluation diagrams of ZnFe Detailed implementation manners

[0035] The present invention will be clearly and completely described below with reference to the accompanying drawings. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. Before describing the present invention with reference to the accompanying drawings, it should be particularly noted that:

[0036] The technical solutions and technical features provided in each part including the following description can be combined with each other without conflict.

[0037] In addition, the embodiments of the present invention involved in the following description are generally only a part of the embodiments of the present invention, rather than all embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0038] Regarding the terms and units in the present invention. The terms "comprising", "having" and any variations thereof in the specification, claims and relevant parts of the present invention are intended to cover non-exclusive inclusion.

[0039] The specific implementation manner of the preparation method of the cathode material for electrocatalytic degradation of tetracycline in the present invention includes the following steps:

[0040] (1) Prepare a reaction solution, wherein the reaction solution contains zinc ions, iron ions, manganese ions, urea, and ammonium fluoride;

[0041] The steps for preparing the reaction solution include: using a mixed solution of water and absolute ethanol with a volume ratio of 1:1 as the solvent, adding Zn(SO4)2·7H2O, FeSO4·7H2O, and MnSO4·H2O, and after dissolution, continuing to add urea and ammonium fluoride, and mixing evenly to obtain the reaction solution; wherein, the molar ratio of zinc ions, iron ions, and manganese ions in the reaction solution is 1:(0.25 - 0.75):(1.25 - 1.75); 5 mmol of zinc ions, 15 mmol of urea, and 12.5 mmol of ammonium fluoride are added per 100 mL of the solvent.

[0042] (2) Obtain a carrier with dimensions of 2 cm × 1 cm × 1 cm. The carrier is nickel foam (NF) with a three-dimensional network structure, purchased from Taiyuan Liyuan Technology Co., Ltd. Before use, the nickel foam is washed successively with hydrochloric acid, absolute ethanol, and water.

[0043] (3) Load the mixture of the carrier and the reaction solution into a polytetrafluoroethylene reaction kettle for high-pressure heat treatment. The reaction temperature is 90 °C and the reaction duration is 8 hours to generate a precursor containing the carrier;

[0044] (4) Calcinate the precursor. The reaction temperature is 350 °C and the reaction duration is 6 hours to obtain the cathode material containing the carrier, denoted as ZnFe 2-x Mn x O4 / NF.

[0045] The specific implementation manner of the cathode material for electrocatalytic degradation of tetracycline in the present invention is prepared by the above preparation method.

[0046] The specific implementation of the purification method of tetracycline in water of the present invention is to prepare the cathode material by the above preparation method and perform electrocatalytic degradation treatment on the water body to be treated containing tetracycline. The water body to be treated contains TC and PMS. The used cathode material is calcined and can be reused for electrocatalytic degradation treatment.

[0047] To test the purification effect of the cathode material on TC, a 150 mL three-electrode single-chamber electrolytic cell was used as the EC reactor. Specifically: a platinum sheet (2 cm × 2 cm) and ZnFe 2-x Mn x O4 / NF were used as the counter electrode and the working electrode respectively. The two electrodes were inserted into the water body to be treated, and the distance between the two electrodes was 2 cm. A DC power supply was used for electrolysis. The water body to be treated contained TC, Na2SO4 (electrolyte) and PMS (oxidant). All experiments were carried out at a constant temperature, and the magnetic stirrer was operated at a speed of 500 r·min -1 . The absorbance of a 1.5 mL solution at λ = 354 nm was analyzed with a UV-visible spectrophotometer every once in a while.

[0048] The calculation expression of the degradation rate is: η = (1 - C t / C0) × 100, where η is the TC degradation rate, and C0 and C t are the initial concentration and the concentration at time t of TC respectively.

[0049] In the present invention, by adjusting the dosage of metal salts in the reaction solution, a series of cathode materials with different Zn / Fe / Mn molar ratios were prepared, which were respectively designated as ZnFe2O4 / NF, ZnFe 1.25 Mn 0.75 O4 / NF, ZnFe 1.00 Mn 1.00 O4 / NF, ZnFe 0.75 Mn 1.25 O4 / NF, ZnFe 0.5 Mn 1.50 O4 / NF, ZnFe 0.25 Mn 1.75 O4 / NF, ZnMn2O4 / NF. Among them, the ratio of the subscripts is the molar ratio of zinc ions, iron ions and manganese ions. For example, ZnFe 0.5 Mn 1.50 O4 / NF means that the molar ratio of zinc ions, iron ions and manganese ions in the reaction solution is 1:0.5:1.5.

[0050] Figure 1 SEM photos of NF, ZnFe2O4 / NF, ZnMn2O4 / NF and ZnFe 0.5 Mn 1.50 O4 / NF are shown in the figure. AsFigure 1 As shown in (a), the NF surface is smooth, presenting a continuous three-dimensional network structure, which is beneficial to the diffusion of electrolyte and the migration of ions, and is an ideal substrate for preparing composite materials. As Figure 1 shown in (b), the ZnFe2O4 particles dispersed on the surface of nickel foam form clusters with uniform size, and the presence of these particles helps to improve the electrochemical performance of the material. As Figure 1 shown in (c), the ZnMn2O4 nanosheets are densely distributed on the surface of the NF substrate, where the nanosheets are vertically arranged along the NF substrate with a thickness of about 100 nm, forming a highly ordered structure, which is beneficial to increasing the specific surface area of the material and thus enhancing its electrochemical activity. As Figure 1 shown in (d), the NF surface is uniformly covered with dense ZnFe 0.5 Mn 1.50 O4 nanosheets. Compared with the ZnMn2O4 nanosheets, the loading density of the ZnFe 0.5 Mn 1.50 O4 nanosheets has increased, indicating that the partial substitution of Mn during the preparation process may promote the reduction of the nanosheet size, and this structure is very beneficial to electron transport and ion diffusion.

[0051] Figure 2 are the XRD patterns of cathode materials with different Zn / Fe / Mn molar ratios. As Figure 2 shown, the XRD diffraction peaks of each sample are generally consistent with the standard card (PDF No.22-1012), indicating that the doping process does not cause changes in the crystal structure. No impurity peaks are found, indicating that the prepared cathode materials are pure materials.

[0052] Figure 3 are the electrochemical impedance spectra of cathode materials with different Zn / Fe / Mn molar ratios. As Figure 3 shown, the diameter of the semicircle in the EIS curve corresponds to the charge transfer resistance (Rct) between the electrolyte and the electrode. From Figure 3 the comparison of the Nyquist plots in, it can be seen that the order of the corresponding values of the charge transfer resistance in the low-frequency region in the figure is ZnFe 0.5 Mn 1.50 O4 / NF < ZnFe 0.75 Mn 1.25 O4 / NF < ZnFe 0.25 Mn 1.75 O4 / NF < ZnFe2O4 / NF < ZnFe 1.00 Mn 1.00 O4 / NF < ZnFe 1.25 Mn 0.75 O4 / NF < ZnMn2O4 / NF, indicating that ZnFe 0.5 Mn 1.50O4 / NF exhibits better charge transfer performance than other materials, which is beneficial to accelerating the approach of ions to the electrode material and shortening the diffusion path.

[0053] Figure 4 Degradation effect diagrams of TC by cathode materials with different Zn / Fe / Mn molar ratios. Among them, the water body to be treated is a mixed solution of 60 mL of TC (30 ppm), Na2SO4 (0.05 M), and PMS (1.0 mM), at room temperature, carried out under natural pH conditions, ZnFe 2-x Mn x O4 / NF as the cathode and a platinum sheet as the anode, with a current density of 2.5 mA / cm 2 , and the reaction time is 60 minutes. As Figure 4 shown, ZnFe 0.75 Mn 1.25 O4 / NF, ZnFe 0.5 Mn 1.5 O4 / NF, and ZnFe 0.25 Mn 1.75 O4 / NF all show good TC degradation rates. Therefore, the molar ratio of zinc ions, iron ions, and manganese ions in the reaction solution is preferably 1:(0.25 - 0.75):(1.25 - 1.75). Among them, the TC degradation rate of ZnFe 0.5 Mn 1.5 O4 / NF as the cathode is the highest (80.7%), and the degradation kinetic constant is 0.8119. When the Mn 2+ proportion further increases, the TC degradation rate decreases. Therefore, ZnFe 0.5 Mn 1.5 O4 / NF is selected as the cathode catalyst to investigate other conditions.

[0054] Figure 5 Degradation effect diagrams of TC by ZnFe 0.5 Mn 1.5 O4 / NF at different current densities. As Figure 5 shown, when the current density increases from 1.5 mA / cm 2 to 2.5 mA / cm 2 , the TC degradation rate increases by about 20%. This is because the electrons provided by the cathode can reduce the high-valent metal on the electrode surface to a low-valent metal, and then more effectively activate PMS to generate active free radicals. When the current density continues to increase, the TC degradation rate gradually decreases. It is speculated that side reactions may occur at the cathode to produce H - that competes with HSO5 + for electrons, resulting in a decrease in the generation of SO4 ·- . Considering the above, it is preferred to set the current density to 2.5 mA / cm 2 .

[0055] Figure 6 is ZnFe 0.5 Mn 1.5 Degradation effect diagram of TC by ZnFe Figure 6 Mn ·- O4 / NF at different PMS dosages. As

[0056] Figure 7 is ZnFe 0.5 Mn 1.5 O4 / NF at different pH values. As Figure 7 shown, when the initial pH of the water to be treated is equal to 3.03 or 6.97, the TC degradation rates are 68.4% and 72.1% respectively, but the TC degradation rate is the highest under natural pH (unadjusted pH) conditions, reaching 81.3%. When the pH is equal to 9.0 and 10.96, the TC degradation rate decreases, probably because hydroxides can react with SO4 ·- The greater the pH, the greater the concentration of hydroxide ions, and the more SO4 ·- is scavenged, then the shorter-lived ·OH becomes the main radical for degrading TC, thus reducing the TC degradation rate. Considering the above, it is preferred to carry out electrolysis under natural pH conditions.

[0057] Figure 8 is ZnFe 0.5 Mn 1.5 Recycling effect diagram of ZnFe Figure 8 Mn 0.5 Mn 1.5 O4 / NF can be recycled. As

[0058] Considering that the electrode releases metal ions during the degradation process, the amounts of Zn, Fe, and Mn in the water to be treated were measured after each cycle of electrolysis. Figure 9 is ZnFe 0.5 Mn 1.5 Evaluation diagram of metal ion dissolution of ZnFe Figure 9As shown, in the first cycle, the average concentrations of leached Zn, Fe, and Mn ions were 0.525, 0.19, and 0.11 mg / L, respectively. In subsequent cycles, the concentrations of leached ions gradually decreased.

[0059] The above describes the relevant content of the present invention. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. Based on the above content of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a cathode material for electrocatalytic degradation of tetracycline, characterized in that: The following steps are involved: preparing a reaction solution, wherein the reaction solution contains zinc ions, iron ions, manganese ions, urea, and ammonium fluoride; obtaining a carrier, wherein the carrier has a three-dimensional network structure; subjecting the mixture of the carrier and the reaction solution to high pressure heat treatment to generate a precursor containing the carrier; The precursor is calcined to obtain a cathode material containing a carrier.

2. The preparation method according to claim 1, characterized in that: The steps of preparing the reaction solution include: using a mixed solution of water and anhydrous ethanol as a solvent, adding soluble zinc salt, soluble iron salt and soluble manganese salt, and adding urea and ammonium fluoride after the salts are dissolved to obtain the reaction solution.

3. The preparation method according to claim 2, characterized in that: The volume ratio of water to anhydrous ethanol in the solvent is 1:1; the molar ratio of zinc ion, iron ion and manganese ion in the reaction solution is 1:(0.25-0.75):(1.25-1.75); 4-6 mmol zinc ion, 13-17 mmol urea and 10-15 mmol ammonium fluoride are added to every 100 mL of solvent.

4. The preparation method according to claim 1, characterized in that: The carrier is foamed nickel, which is washed with hydrochloric acid, anhydrous ethanol and water in sequence before use.

5. The preparation method according to claim 1, characterized in that: The high-pressure heat treatment is carried out in a polytetrafluoroethylene reactor, the reaction temperature is 80-100° C., and the reaction time is 6-10 hours.

6. The preparation method according to claim 1, characterized in that: The reaction temperature of the calcination treatment is 300-400° C., and the reaction time is 4-8 hours.

7. A cathode material for electrocatalytic degradation of tetracycline, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 6.

8. A method for purifying tetracycline in water, characterized in that: The cathode material is prepared by the preparation method described in any one of claims 1 to 6 and is used to perform electrocatalytic degradation treatment on a water body to be treated containing tetracycline.

9. The method for purifying tetracycline in water as claimed in claim 8, characterized in that: The method also includes the step of adding PMS to the water to be treated.

10. The method for purifying tetracycline in water as claimed in claim 8, characterized in that: The method also includes the steps of calcining the used cathode material and then reusing it for electrocatalytic degradation treatment.

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