A sulfur-deficient iron disulfide catalyst, its preparation method and application

Abstract

This invention discloses a sulfur-deficient iron disulfide catalyst, its preparation method, and its applications. The catalyst is prepared by a hydrothermal reaction of an NH2-MIL-101(Fe) precursor with a sulfur source. This catalyst possesses abundant sulfur vacancies, numerous active sites, high catalytic activity, and strong cycle stability. It can be used as an electro-Fenton catalyst for the efficient degradation of antibiotics. Its preparation method is simple, low-cost, and suitable for industrial production.

Description

Technical Field

[0001] This invention relates to an iron disulfide catalyst, specifically an iron disulfide catalyst with sulfur defects, and also to its preparation method and application, belonging to the field of catalyst preparation and environmental remediation technology. Background Technology

[0002] Electro-Fenton (EF) technology offers several advantages, including no need for external chemical oxidants, low energy consumption, a comfortable operating environment with minimal maintenance, and low sludge production. The specific reaction mechanism is as follows: First, oxygen on the cathode electrode surface undergoes an in-situ electrochemical synthesis of H2O2 via oxygen reduction through a two-electron transfer pathway. Subsequently, under specific pH conditions, H2O2 is catalytically decomposed into •OH by iron(II) ions in the solution (E° = 2.8 V vs HE). Finally, the large amount of •OH oxidizes and decomposes pollutants into small-molecule intermediates and harmless inorganic molecules (CO2, H2O, etc.). Compared to Fenton technology, EF technology, due to the introduction of current or voltage, offers significant improvements in application and degradation efficiency: 1) Electro-Fenton technology can generate H2O2 in situ, reducing the cost and safety risks associated with H2O2 during storage and transportation; 2) Electro-Fenton technology can largely achieve the recycling of Fe element valence states, reducing the amount of iron salts used and lowering sludge production during the reaction process; 3) Electro-Fenton technology can efficiently degrade pollutants under neutral or even alkaline conditions, adapting to the complex pH environment of actual wastewater, reducing acid-base adjustment steps, lowering operating costs, and reducing the burden of subsequent neutralization treatment; 4) Electro-Fenton technology continuously generates H2O2 through electrolysis, resulting in a more stable free radical concentration, faster degradation rate, and more thorough mineralization; 5) Electro-Fenton technology has a high degree of automation, enabling the formation of an integrated intelligent control system.

[0003] In electro-Fenton technology, the technique of directly adding iron salts as catalysts is usually referred to as homogeneous electro-Fenton technology. This type of technology has abundant interfacial mass transfer channels, a faster rate of active substance generation, and higher pollutant decomposition efficiency. However, research shows that there are many factors restricting the development of homogeneous electro-Fenton technology. On the one hand, since the Fenton reaction usually occurs under acidic conditions, it is necessary to adjust the pH of the raw water and neutralize the effluent. On the other hand, dissolved Fe... 2+Unable to be recycled and reused, these substances are discharged along with the sludge formed during the reaction, leading to resource waste and potential environmental risks, and may even cause secondary pollution of soil or water. To address the technical bottlenecks in homogeneous electro-Fenton technology, research has found that various solid-phase catalysts can be used instead of iron salts as catalytic materials, hence the term heterogeneous electro-Fenton technology. On the one hand, some heterogeneous catalysts maintain high activity under neutral conditions, eliminating the need for frequent pH adjustments. On the other hand, pollutant molecules in water can be adsorbed onto the catalyst surface, directly contacting the active sites (Fe(II)) on the material surface to form localized reaction zones, reducing the competitive consumption of free radicals by anions in the water. In heterogeneous electro-Fenton technology, catalyst process design becomes crucial for achieving a highly efficient and stable heterogeneous electro-Fenton process. However, most of the developed catalysts still suffer from drawbacks such as: 1) weak performance; 2) low stability and potential environmental risks; 3) poor pH adaptability; and 4) complex manufacturing methods and high costs.

[0004] Therefore, providing a novel composite catalyst with good catalytic performance, strong anti-interference ability, low preparation cost, and environmental friendliness for heterogeneous electro-Fenton reaction systems is of great significance for the efficient and thorough removal of antibiotics from wastewater. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the first objective of this invention is to provide an iron disulfide catalyst with sulfur defects. This iron disulfide catalyst possesses abundant sulfur vacancies, numerous catalytically active sites, excellent catalytic performance, and strong cycle stability.

[0006] A second objective of this invention is to provide a method for preparing an iron disulfide catalyst with sulfur defects. This method is simple, inexpensive, and suitable for industrial production.

[0007] A third objective of this invention is to provide an application of an iron disulfide catalyst with sulfur defects. This iron disulfide catalyst can efficiently electrocatalyze the degradation of antibiotics, exhibiting high catalytic degradation efficiency and no secondary pollution, thus showing promising application prospects.

[0008] To achieve the above-mentioned technical objectives, the present invention provides a method for preparing an iron disulfide catalyst with sulfur defects, which involves mixing an NH2-MIL-101(Fe) precursor with a sulfur source and water and carrying out a hydrothermal reaction to obtain the catalyst.

[0009] The iron disulfide catalyst of this invention is an iron disulfide (FeS2) particle derived from MOFs with abundant sulfur defects (vacancies, SVs). Using MOFs as a sacrificial template and introducing sulfur elements, sulfur vacancies (SVs) are constructed in the FeS2 crystal through a hydrothermal reaction. The introduction of SVs can adjust the charge density distribution of Fe active centers and promote the redox cycle reaction of Fe elements in a heterogeneous electro-Fenton reaction system. The defect structure not only enhances the electron transfer ability of the catalyst, but also improves the adsorption and activation efficiency of hydrogen peroxide through the vacancy effect, thereby significantly improving the catalytic efficiency.

[0010] As a preferred embodiment, the molar ratio of iron in the NH2-MIL-101(Fe) precursor to sulfur in the sulfur source is 1:13~26.4, and a more preferred Fe / S molar ratio is 1:16~23. Controlling the amounts of precursor and sulfur source within appropriate ranges is beneficial to improving the catalytic performance of the material. However, too low a sulfur source amount can lead to a reduction in sulfur vacancies, resulting in a relative decrease in catalytic performance, while too high a sulfur source amount will reduce the purity of the target iron disulfide phase, thus also resulting in a relative decrease in catalytic performance.

[0011] As a preferred embodiment, the concentration of the NH2-MIL-101(Fe) precursor is 2~10 g / L.

[0012] As a preferred embodiment, the sulfur source includes at least one of thiourea, thioacetamide, and sulfur powder. When the sulfur source is thiourea, the preferred mass ratio of NH2-MIL-101(Fe) precursor to thiourea is 1:4 to 8, and more preferably 1:5 to 7.

[0013] As a preferred embodiment, the hydrothermal reaction conditions are: temperature 160~180℃, time 24~30h. Controlling the hydrothermal reaction temperature within a suitable range can improve the catalytic performance of the material. However, excessively high hydrothermal reaction temperatures can lead to the collapse of the precursor structure or even damage to the integrity of the crystal structure, while excessively low temperatures can prevent the precursor from being fully converted, resulting in insufficient sulfur vacancy formation and affecting the crystallinity, stability, and conductivity of the material.

[0014] As a preferred embodiment, the NH2-MIL-101(Fe) precursor is prepared by a solvothermal reaction of iron salt and 2-aminoterephthalic acid.

[0015] As a preferred embodiment, the molar ratio of the iron salt to 2-aminoterephthalic acid is 1:1 to 1.2.

[0016] As a preferred embodiment, the molar concentration of the iron salt is 200-250 mM.

[0017] As a preferred embodiment, the molar concentration of the 2-aminoterephthalic acid is 200-300 mM.

[0018] As a preferred embodiment, the conditions for the solvothermal reaction are: temperature of 160~180℃ and time of 24~30h.

[0019] This invention also provides a sulfur-deficient iron disulfide catalyst, which is prepared by the above method. This catalyst possesses abundant active sites and sulfur vacancies, exhibiting excellent catalytic performance and strong cycle stability.

[0020] As a preferred embodiment, the particle size of the iron disulfide catalyst with sulfur defects is 8~10 μm.

[0021] As a preferred option, it is used as an electro-Fenton catalyst for the electrocatalytic oxidation degradation of antibiotics.

[0022] As a preferred option, it is used as an electro-Fenton catalyst for the electrocatalytic oxidation of antibiotics.

[0023] During the electrocatalytic degradation of antibiotics, H2O2 can be continuously generated in situ, reducing the cost and safety risks associated with H2O2 during storage and transportation. The lower H2O2 concentration effectively avoids side reactions detrimental to pollutant degradation. Furthermore, the H2O2 generation rate can be controlled by adjusting the current during the electrocatalytic process, thus optimizing the balance between cost control and pollutant removal. The generated H2O2 rapidly undergoes a Fenton-like reaction with Fe(II) / Fe(III) on the surface of the sulfur-deficient iron disulfide catalyst (SVs-FeS2) added to the solution, generating •OH and •O2. - The presence of active substances such as •O2H and sulfur vacancies (SVs) significantly enhances the catalyst's adsorption and decomposition capabilities for H2O2. Furthermore, the strongly reducing sulfur provides electrons for the formation of Fe(II), which promotes the Fe(II) / Fe(III) redox cycle, thereby generating more abundant •OH and •O2. - Content; in addition, oxygen can undergo a single-electron reduction reaction to generate •O2 after gaining an electron on the surface of the polarized SVs-FeS2 catalyst. - Meanwhile, •O2 − It can be further converted into singlet oxygen ( 1 O2 (reaction formulas 1-7). Unlike conventional advanced oxidation systems, this system contains multiple active substance transformation pathways and generates a rich variety of active substances, enabling efficient removal of pollutants and degradation products with different characteristics.

[0024] O2+ e - → O2 -(1);

[0025] H2O2 + Fe 2+ → Fe 3+ +•OH+OH - (2);

[0026] Fe 3+ +H₂O₂ → Fe 2+ +•O2 - +2H + (3);

[0027] Fe 3+ +e - → Fe 2+ (4);

[0028] •OH+H2O2 →•O2H+H2O (5);

[0029] •O2H→•O2 - +H + (6);

[0030] •O2 - → 1 O2 (7).

[0031] As a preferred embodiment, the amount of the sulfur-deficient iron disulfide catalyst added is 0.1~0.2 g / L of antibiotic-containing wastewater.

[0032] As a preferred embodiment, the initial concentration of the antibiotic does not exceed 20 mg / L.

[0033] As a preferred embodiment, the initial pH of the reaction system during the electrocatalytic degradation of antibiotics is 5-7.

[0034] As a preferred embodiment, the current for the electrocatalytic degradation of antibiotics is 45-70 mA, more preferably 50-60 mA.

[0035] As a preferred embodiment, the system for electrocatalytic degradation of antibiotics contains H2PO4. - This invention involves adding H2PO4 to antibiotic-containing wastewater. - This can improve the degradation efficiency of antibiotics, due to the presence of H2PO4 in the reaction system. - By altering the electronic structure of the catalyst through coordination, the activation energy of the reaction between Fe and H2O2 is lowered, thereby accelerating the generation rate of free radicals.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) The iron disulfide catalyst with sulfur defects in this invention has abundant active sites and sulfur vacancies, which can greatly improve the catalytic performance of the material. At the same time, it has excellent cycle stability, can adapt to weak acid to neutral environment, and has a long cycle life.

[0038] (2) When the iron disulfide catalyst in this invention is used as an electro-Fenton catalyst for the electrocatalytic degradation of antibiotics, the antibiotic degradation rate is high and the degradation rate is fast, which significantly improves the electrocatalytic degradation efficiency.

[0039] (3) The catalyst preparation method is simple, low cost, energy-saving and environmentally friendly, and suitable for industrial production. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0041] Figure 1 The images show SEM images of the NH2-MIL-101(Fe) precursor and SVs-FeS2 catalyst in Example 1 of this invention, as well as TEM images and EDS elemental mapping diagrams of the SVs-FeS2 catalyst.

[0042] Figure 2 The image shows the XRD patterns of the SVs-FeS2 catalyst and the NH2-MIL-101(Fe) precursor in Example 1 of this invention.

[0043] Figure 3 The image shows the XPS spectrum of the SVs-FeS2 catalyst in Example 1 of this invention.

[0044] Figure 4 The image shows the EPR spectrum of the SVs-FeS2 catalyst in Example 1 of this invention.

[0045] Figure 5 This is a comparison of the removal effects of different systems on tetracycline (TC) in Example 2 of the present invention.

[0046] Figure 6 This paper compares the removal efficiency of the SVs-FeS2 catalyst of the present invention for the electrocatalytic degradation of tetracycline under different pH conditions.

[0047] Figure 7The effect of different current intensities on the catalytic effect of the SVs-FeS2 electro-Fenton system of the present invention is shown in (a) for the removal rate of tetracycline in wastewater under different current intensities and (b) for the amount of H2O2 generated in the electro-Fenton system under different current intensities.

[0048] Figure 8 The effect of different inorganic ions on the catalytic effect of the SVs-FeS2 electro-Fenton system of this invention.

[0049] Figure 9 This invention compares the removal efficiency of the SVs-FeS2 catalyst after four cycles for the electrocatalytic degradation of tetracycline.

[0050] Figure 10 The effect of the SVs-FeS2 catalyst prepared in Example 7 of this invention on the electrocatalytic degradation of tetracycline removal. Detailed Implementation

[0051] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Example 1

[0053] A method for preparing an iron disulfide catalyst (SVs-FeS2) with sulfur defects includes the following steps:

[0054] S1. Using NN dimethylformamide (DMF) as solvent, ferric chloride hexahydrate and 2-aminoterephthalic acid were kneaded into DMF to prepare a 200 mM ferric chloride solution and a 200 mM 2-aminoterephthalic acid mixed solution. The mixed solution was transferred to a 200 mL reaction vessel and heated in an oven at a constant temperature of 180°C for 24 h. The product was washed multiple times with anhydrous ethanol, filtered, and vacuum dried to obtain NH2-MIL-101(Fe).

[0055] S2. Take 1g of NH2-MIL-101(Fe) obtained in step S1 and 6g of thiourea and add it to 100 mL of ultrapure water. Sonicate for 20 minutes to mix evenly. Transfer the resulting mixture to a 200 mL reaction vessel and heat it in an oven at 180°C for 24 h. After washing and filtering with deionized water several times and vacuum drying, sulfur vacancy-iron disulfide is obtained, denoted as SVs-FeS2, with a particle size of 8μm to 10μm.

[0056] The NH2-MIL-101(Fe) and SVs-FeS2 obtained in steps S1 and S2 of this embodiment were observed by scanning electron microscopy and transmission electron microscopy, and the results are as follows: Figure 1 As shown. Figure 1 The NH2-MIL-101(Fe) precursor shown in (a) exhibits typical octahedral-hexagonal bipyramidal composite morphology. Figure 1 The SVs-FeS2 catalyst shown in (b) did not retain the original morphology of the NH2-MIL-101(Fe) precursor, but formed irregular spherical particles with a diameter of 8 μm to 10 μm. This may be because the organic ligand skeleton is less supported at the lower synthesis temperature, and the derivatives are difficult to maintain their original morphology, resulting in mutual intercalation and the formation of spherical particles. Figure 1 The transmission electron microscopy image shown in (c) reveals distinct lattice fringes in the SVs-FeS2 catalyst. Calculations using DigitalMicrograph software show a lattice spacing of 0.271 nm, consistent with the (200) crystal plane of FeS2. Figure 1 As shown in (d, e, f, g), the elemental mapping images obtained by scanning electron microscopy (SEM) and the data in Table 1 indicate that the SVs-FeS2 catalyst of this invention mainly includes Fe, S, and C elements.

[0057]

[0058] X-ray diffraction analysis was performed on the NH2-MIL-101(Fe) and SVs-FeS2 obtained in steps S1 and S2 of this embodiment. The results are as follows: Figure 2 As shown: After derivatization, all characteristic peaks of NH2-MIL-101(Fe) were not retained on the derivative; the SVs-FeS2 catalyst showed obvious diffraction peaks near 28.4°, 32.9°, 37.0°, 40.6°, 47.3°, and 56.1°, which are basically consistent with the standard card (PDF #71-0053) of cubic iron disulfide (FeS2), indicating that the catalyst material of this invention is FeS2, and no diffraction peaks corresponding to other substances were observed, indicating that the synthesized catalyst material has excellent crystallinity and no alloys are present.

[0059] The NH2-MIL-101(Fe) and SVs-FeS2 obtained in steps S1 and S2 of this embodiment were analyzed by X-ray photoelectron spectroscopy (XPS). The results are shown in the figure. Figure 3 ,from Figure 3 The full-spectrum XPS spectrum (a) clearly shows two peaks with binding energies of approximately 163 eV and 707 eV in the sample, corresponding to S 2p and Fe 2p, respectively. This indicates that iron and sulfur elements are present in the SVs-FeS2-6 catalyst. Figure 3The Fe 2p plot of the SVs-FeS2 catalyst in (b) clearly separates two main spectral regions, corresponding to 707.5 eV (Fe(II)-S 2p3 / 2) and 709.3 eV (Fe 2+ 2p3 / 2) and 720.2 eV (Fe(II)-S 2p1 / 2), 722.3 eV (Fe 2+ 2p1 / 2); Figure 3 The orbital energy spectrum of (c)S 2p also allows for a complete analysis of two main spectral regions. The characteristic peak at 162.8 eV is attributed to Fe-S in the FeS2 lattice, while the characteristic peaks at 163.8 eV and 164.9 eV reveal the presence of S 2p3 / 2 and S 2p1 / 2 (mainly incompletely reacted CSC structures) in the SVs-FeS2-6 catalyst. The characteristic peak at 168.9 eV is mainly due to C-SO formed by oxidation of the SVs-FeS2-6 catalyst surface in air. x -C structure formed.

[0060] Figure 4 The image shows the electron paramagnetic resonance (EPR) spectrum of the SVs-FeS2 catalyst prepared in this embodiment. A significant isotropic resonance signal can be observed in the EPR spectrum of the SVs-FeS2 catalyst. This phenomenon is due to the trapping of electrons at certain defects, resulting in localized transitions of unpaired electrons at these defect sites. This characteristic g-factor value closely matches the defect characteristics of sulfur, indicating that the material forms abundant sulfur vacancies (SVs). The defect structure not only enhances the electron transport capacity of the catalyst but also improves the adsorption and activation efficiency of H2O2 in advanced oxidation systems through the vacancy effect. Furthermore, the introduction of SVs can promote the redox cycle of Fe in heterogeneous electro-Fenton reaction systems by adjusting the charge density distribution of Fe active centers, thereby improving the degradation efficiency of pollutants.

[0061] Example 2

[0062] The SVs-FeS2 prepared in Example 1 of this invention is used for the electrocatalytic degradation and removal of tetracycline (TC) from water, specifically including the following steps:

[0063] Take 1L of tetracycline solution with a concentration of 20mg / L, add 0.2g of SVs-FeS2 and antibiotic wastewater, mix them together, and add 0.05mM anhydrous sodium sulfate (Na2SO4) as electrolyte. Use platinum (Pt) electrodes and carbon felt as anode and cathode, fix the positive and negative electrodes in parallel in the reaction device, and ensure that the distance between the electrode surfaces is 2.0 cm. Connect a galvanometer (controlled with a constant current of 50 mA) and carry out the electro-Fenton reaction at room temperature to complete the degradation of tetracycline.

[0064] Control group 1: Take 1L of tetracycline solution with a concentration of 20mg / L, add 0.2g of NH2-MIL-101(Fe) and antibiotic wastewater, add 0.05mM anhydrous sodium sulfate (Na2SO4), fix the positive and negative electrodes in parallel in the reaction device, ensure that the distance between the electrode surfaces is 2.0 cm, connect a galvanometer (50 mA constant current), and carry out the electro-Fenton reaction at room temperature to complete the degradation of tetracycline.

[0065] Control group 2: Take 1L of tetracycline solution with a concentration of 20mg / L, mix 0.2g of SVs-FeS2 with antibiotic wastewater, and add 0.05mM anhydrous sodium sulfate (Na2SO4). The adsorption reaction of tetracycline by SVs-FeS2 is carried out at room temperature.

[0066] Control group 3: Take a 1L tetracycline solution with a concentration of 20mg / L, mix 0.2g NH2-MIL-101(Fe) with antibiotic wastewater, and add 0.05 mM anhydrous sodium sulfate (Na2SO4). The adsorption reaction of tetracycline by NH2-MIL-101(Fe) is carried out at room temperature.

[0067] Control group 4: Take 1L of tetracycline solution with a concentration of 20mg / L, add 0.05mM anhydrous sodium sulfate (Na2SO4), fix the positive and negative electrodes in parallel in the reaction device, ensure that the distance between the electrode surfaces is 2.0 cm, connect the galvanometer (50 mA constant current), and carry out a simple electro-Fenton reaction at room temperature to complete the degradation of tetracycline.

[0068] Samples were taken from the reaction system at 5 min, 10 min, 15 min, 20 min, 25 min, and 30 min of reaction. The tetracycline content in the solution was determined by high performance liquid chromatography (HPLC). The measurement results are shown in the figure. Figure 5 .Depend on Figure 5It is evident that neither SVs-FeS2 adsorption nor NH2-MIL-101(Fe) adsorption significantly removed tetracycline from wastewater in this invention. The SVs-FeS2 electro-Fenton system showed significantly better removal efficiency for tetracycline from wastewater than other electro-Fenton systems. Specifically, the SVs-FeS2 electro-Fenton system of this invention achieved a 100% removal rate of tetracycline from wastewater after 30 minutes of reaction. Therefore, the SVs-FeS2 of this invention exhibits excellent EF catalytic performance, significantly superior to NH2-MIL-101(Fe). This is because the H2O2 generated at the electrode rapidly undergoes a Fenton-like reaction with the Fe(II) / Fe(III) on the surface of the SVs-FeS2 catalyst added to the solution, generating •OH and •O2. - The presence of active substances such as •O2H significantly promotes the adsorption and decomposition capabilities of the SVs-FeS2 catalyst for H2O2. Furthermore, the strong reducing sulfur provides electrons for the formation of Fe(II), which can promote the Fe(II) / Fe(III) redox cycle, thereby generating more abundant •OH and •O2. - Content; in addition, oxygen can undergo a single-electron reduction reaction to generate •O2 after gaining an electron on the surface of the polarized SVs-FeS2 catalyst. - Meanwhile, •O2 - It can be further converted into singlet oxygen ( 1 O2), and the heterogeneous electro-Fenton system constructed in this way can efficiently generate oxidative active substances to degrade tetracycline.

[0069] Example 3

[0070] The removal effect of SVs-FeS2 of the present invention on tetracycline in water under different pH conditions was investigated. The removal of tetracycline (TC) from water using SVs-FeS2 prepared in Example 1 included the following steps:

[0071] Take 5 portions of tetracycline solution with a volume of 1L and a concentration of 20mg / L, add 0.2g of SVs-FeS2 prepared in Example 1 to each portion, and add 0.05mM anhydrous sodium sulfate (Na2SO4). After mixing evenly, adjust the initial pH value of 4 portions of the mixture to 3, 5, 7 and 9 respectively. Fix the positive and negative electrodes in parallel in the reaction device, ensuring that the distance between the electrode surfaces is 2.0 cm. Connect a galvanometer (50 mA constant current) and carry out an electro-Fenton reaction at room temperature to complete the degradation of tetracycline.

[0072] Samples were taken from the reaction system after 5, 10, 15, 20, 25, and 30 minutes of electro-Fenton reaction. The tetracycline content in the solution was determined by high-performance liquid chromatography (HPLC). The measurement results are shown in the figure. Figure 6 .like Figure 6 As shown, the degradation rate of the SVs-FeS2 catalyst in the electro-Fenton reaction system exhibits a trend of first increasing and then decreasing with increasing solution pH. At pH values ​​of 5, 7, and under natural conditions (i.e., without adjusting the solution's pH), the degradation rates reach 92.3%, 95.1%, and 100%, respectively. When pH values ​​are 3 and 9, the TC removal rate decreases significantly. This is because the SVs-FeS2 catalyst is unstable under excessively acidic or alkaline conditions, and Fe... 2+ Partial passivation reduces the removal rate of TC. Therefore, the SVs-FeS2 electro-Fenton system of this invention achieves the best catalytic effect under neutral or weakly acidic pH conditions.

[0073] Example 4

[0074] The removal effect of SVs-FeS2 of the present invention on tetracycline under different current intensities was investigated. The removal of tetracycline (TC) from water using SVs-FeS2 prepared in Example 1 included the following steps:

[0075] Take 8 1L tetracycline solutions with a concentration of 20 mg / L, add 0.2g SVs-FeS2 and antibiotic wastewater to each, and add 0.05 mM anhydrous sodium sulfate (Na2SO4) to each. Fix the positive and negative electrodes in parallel in the reaction apparatus, ensuring that the distance between the electrode surfaces is 2.0 cm. Connect a galvanometer and control the current magnitude to 10mA, 20mA, 30mA, 40mA, 50mA, 60mA, 70mA, and 80mA respectively. Carry out the electro-Fenton reaction at room temperature to complete the degradation of tetracycline.

[0076] Samples were taken from the reaction system after 5, 10, 15, 20, 25, and 30 minutes of electro-Fenton reaction. The tetracycline content in the solution was determined by high-performance liquid chromatography (HPLC), and the H₂O₂ content generated during the reaction was determined by iodometric titration. The measurement results are shown in the figure. Figure 7 .from Figure 7 (a) It can be seen that as the applied current increases, the degradation rate of TC first increases and then decreases, with the degradation rate reaching its optimal value when the current is 50 mA; from Figure 7 (b) It can be seen that as the current value increases, the amount of H2O2 contained in the system gradually decreases. This is because as the current intensity increases, the Fe element in the SVs-FeS2 catalyst in the system is reduced to Fe by the cathode. 3+ The rate gradually increases, maintaining Fe 2+The cycle promotes the continuous generation of free radicals, thereby improving the catalytic degradation efficiency. However, when the current intensity increases to a certain extent, the selectivity of the carbon felt electrode for two electron ORR gradually decreases, affecting the hydrogen peroxide generation rate, resulting in insufficient H2O2 supply in the system, and ultimately causing the reaction rate to decay.

[0077] Example 5

[0078] The removal effect of SVs-FeS2 of the present invention on tetracycline in water containing different inorganic ions was investigated. The removal of tetracycline (TC) from water using SVs-FeS2 prepared in Example 1 included the following steps:

[0079] Five 1L tetracycline solutions with a concentration of 20mg / L were taken. One solution was used as a control, and the other five were respectively added with 10 mmol of NaCl, NaHCO3, KH2PO4, NaNO3, and humic acid (HA). 0.2g of SVs-FeS2 prepared in Example 1 was added to each system, along with 0.05 mM anhydrous sodium sulfate (Na2SO4). After mixing thoroughly, the positive and negative electrodes were fixed parallel to each other in the reaction apparatus, ensuring a distance of 2.0 cm between the electrode surfaces. A galvanometer (50 mA constant current) was connected, and an electro-Fenton reaction was carried out at room temperature to complete the degradation of tetracycline.

[0080] Samples were taken from the reaction system after 5, 10, 15, 20, 25, and 30 minutes of electro-Fenton reaction. The tetracycline content in the solution was determined by high-performance liquid chromatography (HPLC). The measurement results are shown in the figure. Figure 8 .like Figure 8 As shown, Cl - HCO3 - NO3 - The effects of HA on the removal of tetracycline by the SVs-FeS2 electro-Fenton system differ to varying degrees. This is because these substances react with the active free radicals generated by the electro-Fenton system to produce less active free radicals, thereby reducing the content of the effective active substances in the reaction. Conversely, 10 mM H2PO4... - The presence of H2PO4 in the system promoted the degradation of tetracycline, which is due to the presence of H2PO4 in the reaction system. - By altering the electronic structure of the catalyst through coordination, the activation energy of the reaction between Fe and H2O2 is lowered, thereby accelerating the generation rate of free radicals.

[0081] Example 6

[0082] To investigate the recycling performance of SVs-FeS2 of the present invention, the SVs-FeS2 prepared in Example 1 was used to remove tetracycline (TC) from water, including the following steps:

[0083] A 1L tetracycline solution with a concentration of 20 mg / L was taken, and 0.2g of SVs-FeS2 prepared in Example 1 was added, along with 0.05 mM anhydrous sodium sulfate (Na2SO4). The positive and negative electrodes were fixed parallel to each other in the reaction apparatus, ensuring a distance of 2.0 cm between the electrode surfaces. A galvanometer (50 mA constant current) was connected, and an electro-Fenton reaction was carried out at room temperature to complete the degradation of tetracycline. After the degradation reaction was completed, the recovered catalyst was collected by filtration, dried under vacuum, and reused in the next catalytic degradation experiment. This cycle was repeated four times.

[0084] Samples were taken from the reaction system after 5, 10, 15, 20, 25, and 30 minutes of electro-Fenton reaction. The tetracycline content in the solution was determined by high-performance liquid chromatography (HPLC). The measurement results are shown in the figure. Figure 9 As shown in the figure, SVs-FeS2 exhibits good cycling stability. After the fourth cycle, the degradation efficiency of the SVs-FeS2 catalyst can still reach 87.1%.

[0085] In summary, the SVs-FeS2 electro-Fenton system of this invention exhibits good removal efficiency for tetracycline in water. Under the conditions of SVs-FeS2 iron concentration of 0.2 g / L and current intensity of 50 mA, the removal rate of tetracycline at a concentration of 20 mg / L can reach 100% within 30 minutes. This invention utilizes the SVs-FeS2 electro-Fenton system to effectively degrade antibiotics in a weakly acidic to neutral pH range under anion coexistence conditions. It offers advantages such as good treatment effect, simple operation, low cost, and no need for oxidant addition, while avoiding the disadvantage of secondary pollution caused by the precipitation of transition metal ions.

[0086] Example 7

[0087] The SVs-FeS2 catalyst was prepared using the method of Example 1, except that the mass ratio of NH2-MIL-101(Fe) precursor to thiourea was controlled to be 1:4, 1:5, 1:7, and 1:8, respectively. The resulting catalysts were denoted as SVs-FeS2-4, SVs-FeS2-5, SVs-FeS2-7, and SVs-FeS2-8, respectively.

[0088] Catalytic degradation experiments of tetracycline were conducted using the above-mentioned catalysts according to the method in Example 2. The results are shown in [Figure 2]. Figure 10 ,in, Figure 10The SVs-FeS2-6 in the figure is the catalyst prepared in Example 1. As can be seen from the figure, the appropriate amount of precursor and sulfur source (iron / sulfur molar ratio) can obtain the best-performing SVs-FeS2 catalyst, which enables the tetracycline degradation rate to reach 80% or more.

[0089] Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an iron disulfide catalyst with sulfur defects, characterized in that: The NH2-MIL-101(Fe) precursor is obtained by mixing it with a sulfur source and water and carrying out a hydrothermal reaction.

2. The method for preparing a sulfur-deficient iron disulfide catalyst according to claim 1, characterized in that: The molar ratio of iron in the NH2-MIL-101(Fe) precursor to sulfur in the sulfur source is 1:13~26.

4.

3. A method for preparing a sulfur-deficient iron disulfide catalyst according to claim 1 or 2, characterized in that: The concentration of the NH2-MIL-101(Fe) precursor is 2~10 g / L; The sulfur source includes at least one of thiourea, thioacetamide, and sulfur powder.

4. The method for preparing an iron disulfide catalyst with sulfur defects according to claim 1, characterized in that: The conditions for the hydrothermal reaction are: temperature 160~180℃, time 24~30h.

5. The method for preparing an iron disulfide catalyst with sulfur defects according to claim 1, characterized in that: The NH2-MIL-101(Fe) precursor is prepared by a solvothermal reaction of iron salt and 2-aminoterephthalic acid.

6. The method for preparing a sulfur-deficient iron disulfide catalyst according to claim 5, characterized in that: The molar ratio of the iron salt to 2-aminoterephthalic acid is 1:1 to 1.2; The molar concentration of the iron salt is 200~250 mM; The molar concentration of the 2-aminoterephthalic acid is 200~300mM.

7. An iron disulfide catalyst with sulfur defects, characterized in that: Prepared by the method described in any one of claims 1 to 6.

8. The iron disulfide catalyst with sulfur defects according to claim 7, characterized in that: The sulfur-deficient iron disulfide catalyst has a particle size of 8~10 μm.

9. The application of the iron disulfide catalyst with sulfur defects as described in claim 7 or 8, characterized in that: It is used as an electro-Fenton catalyst for the electrocatalytic oxidation degradation of antibiotics.

10. The application of the iron disulfide catalyst with sulfur defects according to claim 9, characterized in that: The amount of the sulfur-deficient iron disulfide catalyst added is 0.1~0.2 g / L of antibiotic-containing wastewater; The initial concentration of the antibiotic shall not exceed 20 mg / L; The initial pH value of the reaction system during the electrocatalytic degradation of antibiotics is 5-7; The current for the electrocatalytic degradation of antibiotics is 45~70mA; The system for electrocatalytic degradation of antibiotics contains H2PO4. - .

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