Iron-based metal-organic complex catalysts, their preparation methods, and methods for removing ofloxacin from water.

Abstract

This invention belongs to the field of wastewater treatment and new materials technology. It discloses an iron-based metal-organic complex catalyst, its preparation method, and a method for removing ofloxacin from water. The catalyst is a six-coordinated black powder with an amorphous nanoscale sheet structure and micron-sized clusters, prepared using ellagic acid (EA) with an electron-rich structure as a ligand and iron atoms as the coordinating metal. The surface pore size distribution is mainly mesoporous. This iron-based metal-organic complex (FeMOCs) material provides an efficient catalytic interface and sufficient microscopic space for the rapid and effective reaction between the oxidant persulfate and ofloxacin in water. It has an adsorption-degradation synergistic effect and is named EFE-150 catalyst. This catalyst is synthesized by a solvothermal method and applied to the efficient removal of ofloxacin from water by catalytic PDS. It has the characteristics of rapid onset, self-sustaining, and low cost, which can meet the needs of large-scale promotion and application.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment and new materials technology, specifically relating to an iron-based metal-organic complex catalyst, its preparation method, and a method for removing ofloxacin from water. Background Technology

[0002] Ofloxacin (OFL) belongs to the fluoroquinolone (FQ) class of antibiotics. It is a broad-spectrum antibiotic widely used in the prevention and treatment of related diseases in humans and animals due to its low cost and broad applicability. However, the high electronegativity, chemical stability, and resistance to microbial degradation of the fluorine atoms in its structure make it prone to bioaccumulation and amplification in the environment through the food chain, leading to disruptions in the structure and function of ecosystems. The continuous accumulation of OFL and its resistance genes in humans can also cause tendinitis, central nervous system disorders, gastrointestinal dysfunction, and long-term effects on the immune system. Therefore, ofloxacin (OFL) in water bodies, as a typical fluoroquinolone antibiotic, poses a high ecological risk; its residues may lead to the spread of microbial resistance and ecotoxicity. Given the serious threat that OFL poses to both the ecological environment and human health, seeking economical, efficient, low-cost, and sustainable OFL treatment methods and technologies is of great significance.

[0003] In recent years, methods for OFL removal have been extensively studied, including physical, chemical, and biological methods. Physical methods utilize the surface activity or porous structure of adsorbents to capture OFL through physical adsorption, chemical adsorption, or ion exchange. However, once adsorption is saturated, these methods become ineffective, requiring a continuous supply of large amounts of adsorbent, such as magnetic Fe3O4@C nanocomposites. This approach is slow and costly. Chemical methods, compared to physical and biological methods, offer advantages such as faster removal speed, more thorough removal, and complete decomposition of pollutants. Advanced oxidation processes (AOPs) typically use ultraviolet radiation or semiconductor / metal / carbonaceous catalysts to catalyze oxidants such as hydrogen peroxide and persulfate, generating reactive oxygen species (ROS) with strong oxidizing capabilities, such as hydroxyl radicals (HO•) and sulfate radicals (SO4•). - •, superoxide radicals (O2) - • Degradation of pollutants. In recent years, advanced oxidation processes based on sulfate radicals (SR-AOP) have become one of the research hotspots in the environmental field. SR-AOP mainly generates SO4 by exciting persulfates (PS), including permonosulfate (PMS) and perdisulfate (PDS). - • Strongly oxidizing ROS, which further mineralize pollutants into H2O and CO2. SO4 -Similar to HO•, it has a high standard oxidation potential (E0=2.5 ​​V-3.1 V) and a long half-life (30-40 μs), and is extremely mild in its requirements for system pH, so it can oxidize and degrade pollutants under a relatively wide range of pH conditions.

[0004] However, the catalytic effect of PS is usually affected by various factors such as the catalytic method. Its catalytic effect is unstable, the degradation rate is slow, and a continuous supply of catalyst and oxidant is required to sustain the degradation reaction, necessitating large quantities. Furthermore, its applicable pH range is narrow (typically 2-4). When using catalytic materials such as metal oxides, defects such as material agglomeration, metal ion leakage, and poor structural stability occur. Using carbon-based materials can mediate the generation of singlet oxygen (…). 1 While PDS (Polydioxanone) catalytic activity is limited by metal oxide catalytic sites, making it difficult to accelerate the PDS catalytic rate through electron transfer. Using thermal activation or UV activation requires continuous external energy input and produces only one type of ROS, limiting pollutant degradation. Other multi-metallic materials and complex carbon-based materials can enhance PDS catalytic activity, but their preparation processes are complex, raw material costs are high, and they often have poor biocompatibility, making it difficult to achieve self-sustaining and environmentally friendly reaction systems. Traditional FeMOCs are based on iron ions (Fe... 2+ / Fe 3+ Porous crystalline materials, which are formed by coordination of metal nodes with organic ligands (such as carboxylic acids, imidazoles, etc.), have the advantages of high specific surface area (500~3000 m² / g), tunable pore structure and catalytic activity of metal sites. They are widely used in catalysis, adsorption, energy and other fields. However, they also have problems such as high cost, difficulty in engineering and poor environmental compatibility.

[0005] For example, CN105923738A discloses a method for treating organic wastewater using a metal-organic framework (MOF) for highly efficient catalytic activation of persulfate or bisulfate. This method uses MOF materials as catalysts, leveraging the high active sites and strong catalytic activity of MOFs to catalytically activate persulfate or bisulfate at room temperature, generating sulfate radicals to degrade organic pollutants in the wastewater. The key feature is the use of hexagonal rod-shaped morphology with a specific surface area of ​​10-30 m² / g. 2 The metal-organic framework material MIL-88A, at a concentration of / g, is used to achieve short catalytic time, good persistence, and high degradation efficiency of organic pollutants over a wide pH range. However, experimental data from its examples show that its degradation onset rate is slow, requiring a large amount of activated material (oxidant), the reaction system is not self-sustaining, and the removal rate within 30 minutes does not exceed 30%. It lacks selectivity for organic pollutants and cannot specifically improve the removal efficiency and effectiveness of OFL in water, easily leading to secondary pollution.

[0006] CN118047474A discloses another highly efficient method for activating peroxymonosulfate to degrade ofofloxacin. This method utilizes a degradation catalytic material based on an accordion-shaped Mxenes support, containing both Mn and N active sites, to activate peroxymonosulfate. The synergistic effect of the co-catalytic action of the Mn and N active sites enhances the activation efficiency of peroxymonosulfate, thereby achieving the degradation of ofofloxacin in water. According to the experimental data described in its examples, this degradation catalytic material Mn-U... 2.5 @MXenes 1.0 The adsorption and removal rate of ofloxacin in the peroxymonosulfate system was 21.45% within 10 min, and the amount of both catalyst and oxidant added was relatively large, so the reaction system could not be self-supporting.

[0007] In summary, existing materials and treatment processes for OFL removal from water generally suffer from problems such as high material costs, long onset times, slow degradation rates, and the inability of the reaction system to support itself. Furthermore, the raw materials for catalyst preparation are expensive, the preparation process is cumbersome, and the amount of activated materials such as persulfate required is large, resulting in complex treatment processes. Ultimately, the overall system solution suffers from shortcomings such as slow onset, high cost, and low efficiency, failing to meet the industry's demand for rapid onset, low cost, simple process, high efficiency, and no secondary pollution in the removal and treatment of large quantities of ofloxacin wastewater. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to propose an iron-based metal-organic complex catalyst, its preparation method, and a method for removing ofloxacin from water. Through simultaneous improvements to the catalyst components, ratios, and processes, a six-coordinate, nanoscale sheet-like iron-based metal-organic complex catalyst (FeMOCs) material, EFE-150, is prepared, exhibiting micron-scale cluster aggregation. Its electron-rich functional groups provide sufficient electrons to fully activate persulfate PDS. Based on the synergistic effect of adsorption and degradation, it has a short onset time, rapid degradation rate, and the reaction system can achieve self-support through electron supply and transfer. After adsorption saturation, it can release catalytic sites and restore adsorption capacity through degradation. This results in a catalytic degradation system with low material consumption, low cost, high efficiency, and a simple process without secondary pollution, meeting the industrial demand for efficient removal of large quantities of ofloxacin wastewater.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] An iron-based metal-organic complex catalyst is characterized by using ellagic acid (EA) with an electron-rich structure as a ligand and iron atoms as the coordinating metal to prepare a six-coordinated black powder with an amorphous nanoscale sheet structure and exhibiting micron-scale cluster aggregation. The surface pore size distribution is mainly mesoporous. It catalyzes the rapid and efficient reaction of the oxidant persulfate (PDS) with ofloxacin (OFL) in water and has an adsorption-degradation synergistic effect. This iron-based metal-organic complex FeMOC material is named EFE-150 catalyst.

[0011] The EFE-150 catalyst exhibits an amorphous, stacked sheet-like structure at the nanoscale, with an overall cluster-like appearance. Each sheet has an average thickness of 30 nm and a specific surface area of ​​35 m². 2 / g, with a surface pore size of 4.5 nm, C, O and Fe elements are uniformly distributed in the plate-like structure without enrichment, and the nitrogen adsorption-desorption curve shows the characteristics of type II adsorption isotherm and has H3 type hysteresis loop.

[0012] A method for preparing the aforementioned iron-based metal-organic complex catalyst involves using ellagic acid EA, which has an electron-rich structure, as a ligand and iron atoms as the coordinating metal, to synthesize a six-coordinated black powder with a nanoscale sheet-like structure and exhibiting micron-scale cluster aggregation by a solvothermal method. This powder is the iron-based metal-organic complex catalyst EFE-150.

[0013] A method for removing ofloxacin from water involves activating persulfate PDS oxidant with the aforementioned iron-based metal-organic complex catalyst EFE-150 to enhance the degradation of ofloxacin in the water. Specifically, an appropriate amount of persulfate PDS oxidant and a pre-prepared EFE-150 catalyst are sequentially added to wastewater containing ofloxacin pollutants. EFE-150 provides a sufficient catalytic interface and microscopic space for the rapid and efficient reaction between persulfate PDS and ofloxacin (OFL), accelerating the degradation rate. Under the synergistic effect of adsorption and degradation, it continuously promotes the adsorption-oxidation degradation process of OFL, increases the reaction rate of the system, and reduces the amount of catalyst and oxidant used in the system.

[0014] Compared with existing technologies, the present invention has the following advantages and effects:

[0015] 1. The iron-based metal-organic complex catalyst, its preparation method, and its application in removing ofloxacin from water provided by this invention, through simultaneous improvement of components, ratios, and processes, prepares an iron-based metal-organic complex catalyst (FeMOCs material) EFE-150 with a six-coordinate, nanoscale sheet-like structure, exhibiting micron-scale cluster aggregation. It possesses a synergistic adsorption-degradation effect, balancing high active electron quantity, high iron ion carrying capacity, and high catalytic efficiency. It also maintains an appropriate main pore size to improve targeting. The electron-rich functional groups of this catalyst can provide sufficient electrons to fully activate persulfate, resulting in a short onset time, fast degradation rate, and a self-supporting reaction system. After adsorption saturation, it can release catalytic sites through degradation to restore adsorption capacity. This makes the catalytic degradation system require less material, has low cost, high efficiency, and a simple process with no secondary pollution, meeting the industrial demand for efficient removal of large quantities of ofloxacin wastewater.

[0016] 2. The iron-based metal-organic complex catalyst and its preparation method provided by this invention utilize commonly used organic ligands EA and coordinating metal Fe, both of which possess good biocompatibility and can construct an environmentally friendly catalytic system. The EFE-150 catalyst has a six-coordinate rigid structure and multiple hydroxyl (-OH) and lactone rings. The ligand structure contains a large number of delocalized electrons, significantly enhancing electron supply and transfer capabilities, effectively reducing energy loss during PDS catalysis, enhancing PDS utilization efficiency, and significantly reducing the amount of EFE-150 catalyst and PDS used in the degradation system. Furthermore, the catalyst material possesses excellent structural rigidity, and the catalytic sites are not easily deactivated, thus exhibiting good reusability and further saving economic costs. This is of great significance for the reduction and treatment of organic pollutant wastewater. The iron-based metal-organic complex catalyst uses inexpensive raw materials, has a simple preparation method, a controllable preparation process, and is easy to industrialize.

[0017] 3. The iron-based metal-organic complex material provided by this invention can efficiently catalyze the degradation of OFL in water by PDS. Sufficient PDS can be catalyzed by adding a small amount of EFE-150 catalyst. It has a short onset time and fast degradation rate, achieving an OFL degradation rate of over 85% within 30 minutes and a OFL removal rate of up to 91% within one hour. Furthermore, it maintains a removal efficiency of over 80% under different temperatures, acidic to weakly alkaline environments, and background interference. The degradation efficiency remains high for different actual water bodies, making it widely applicable to various OFL treatment environments.

[0018] 4. The organic ligand ellagic acid (EA) used in this invention is a natural polyphenol compound. Its molecular structure consists of a benzene ring, a hydroxyl group (-OH), and a lactone ring, exhibiting strong antioxidant and anti-inflammatory properties and good biocompatibility. The structural characteristics of EA give it π-conjugation rigidity and a large number of delocalized electrons, providing strong coordination ability with metal ions. After sufficient chelation with iron ions, it can form a metal-iron-organic complex with tunable pore structure and abundant active sites. Therefore, this invention combines the highly catalytic transition metal iron with the electron-rich EA to form the EFE-150 catalyst, which has a synergistic effect. The large number of delocalized electrons in EA can significantly enhance the catalytic ability of the iron sites, especially in the catalytic degradation of organic pollutants (OFL) by persulfate (PDS). It exhibits strong targeting, fast treatment speed, high efficiency, low cost, and simple process for the degradation of OFL in water, making it easy to scale up and apply.

[0019] 5. The method for removing ofloxacin from water provided by the present invention is based on the synergistic effect of the EFE-150 catalyst and oxidant in the system. EFE-150 provides sufficient catalytic interface and microspace for the rapid and efficient reaction of persulfate PDS and ofloxacin OFL, thereby accelerating the degradation rate. Under the synergistic effect of adsorption and degradation, it continuously promotes the adsorption-oxidation degradation process of OFL. When the adsorption is saturated, the catalytic sites and adsorption sites are released through degradation, the adsorption capacity is restored, the reaction rate of the system is improved, and the amount of catalyst and oxidant used in the system is reduced. Attached Figure Description

[0020] Figure 1 A schematic diagram illustrating the preparation method of EFE-150 prepared according to an embodiment of the present invention;

[0021] Figure 2 SEM and EDS mapping images of EFE-150 prepared for embodiments of the present invention, wherein (a) is a SEM image and EDS mapping image of EFE-150 at the nanoscale, and (b) is a SEM image of EFE-150 at the micrometer scale.

[0022] Figure 3 XRD images of EFE-150 prepared for embodiments of the present invention;

[0023] Figure 4 FT-IR images of EFE-150 prepared for embodiments of the present invention;

[0024] Figure 5The nitrogen adsorption-desorption curve and BJH pore size distribution image of EFE-150 prepared for the embodiments of the present invention are shown in (a) and (b).

[0025] Figure 6 ESI-MS image of EFE-150 prepared for an embodiment of the present invention;

[0026] Figure 7 Images show the effects of EFE-150 prepared in this embodiment of the invention on the degradation of OFL. Among them, (a) is a comparison image of the OFL degradation effect of different reaction systems, (b) is a schematic image of the effect of EFE-150 addition amount on OFL degradation effect, (c) is a schematic image of the effect of PDS addition amount on OFL degradation effect, (d) is a schematic image of the effect of reaction temperature on OFL degradation effect, (e) is a schematic image of the effect of initial pH value on OFL degradation effect, (f) is a schematic image of the effect of different background interferences on OFL degradation effect, (g) is a schematic image of the effect of different actual water bodies on OFL degradation effect, and (h) is an image of EFE-150 catalyzing PDS degradation of OFL for reuse.

[0027] Figure 8 XPS images of EFE-150 before and after reaction prepared for an embodiment of the present invention;

[0028] Figure 9 These are electrochemical images of the reaction system in which EFE-150 participated in the embodiment of the present invention, where (a) is an OCP image, (b) is an It curve image, and (c) is an LSV image. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0030] Basic Implementation

[0031] This embodiment provides an iron-based metal-organic complex catalyst, which is a six-coordinated black powder with an amorphous nanoscale sheet structure and micron-scale cluster aggregation, prepared using ellagic acid EA with an electron-rich structure as a ligand and iron atoms as the coordinating metal. The surface pore size distribution is mainly mesoporous. It can provide an efficient catalytic interface and sufficient microscopic space for the rapid and powerful reaction of the oxidant persulfate PDS with ofloxacin OFL in water. It has an adsorption-degradation synergistic effect and is named EFE-150 catalyst.

[0032] The EFE-150 catalyst exhibits an amorphous, stacked sheet-like structure at the nanoscale, with an overall cluster-like appearance. Each sheet has an average thickness of 30 nm and a specific surface area of ​​35 m². 2 / g, with a surface pore size of 4.5 nm, C, O and Fe elements are uniformly distributed in the plate-like structure without enrichment, and the nitrogen adsorption-desorption curve shows the characteristics of type II adsorption isotherm and has H3 type hysteresis loop.

[0033] The adsorption-degradation synergistic effect of the EFE-150 catalyst is based on its nanoscale sheet-like FeMOCs structure. The EA ligand possesses a large number of delocalized π electrons, which are extensively delocalized within the polycyclic planar structure of EA, forming multiple electrostatic minimum points. These points efficiently adsorb OFL through π-π interactions and electrostatic interactions, reducing the interaction distance with active free radicals and increasing the contact frequency. The multiple hydroxyl and lactone rings in the EA polycyclic planar structure provide sufficient electrons to a large number of iron-based catalytic sites, rapidly restoring their catalytic activity. Combined with carbon-based catalytic sites possessing delocalized electrons, these sites efficiently catalyze the generation of a large number of active free radicals from PDS, leading to rapid OFL degradation through the synergistic effect of adsorption and oxidation. After OFL degradation, the previously occupied adsorption sites are re-exposed, restoring the adsorption activity of the EFE-150 catalyst and continuously driving the adsorption-oxidation degradation process of OFL, thereby increasing the reaction rate of the system.

[0034] The EFE-150 catalyst has a six-coordinate rigid structure and multiple hydroxyl (-OH) and lactone rings. It has a large amount of iron ions loaded and the ligand structure contains a large number of delocalized electrons, which can significantly enhance the electron supply and transfer capabilities, effectively reduce the energy loss in the PDS catalysis process, enhance the PDS utilization efficiency, and significantly reduce the amount of EFE-150 catalyst and PDS used in the degradation system.

[0035] A method for preparing the aforementioned iron-based metal-organic complex catalyst involves using ellagic acid EA, which has an electron-rich structure, as a ligand and iron atoms as the coordinating metal, to synthesize a six-coordinated black powder with a nanoscale sheet-like structure and exhibiting micron-scale cluster aggregation, namely the iron-based metal-organic complex catalyst EFE-150, via a solvothermal method. The specific steps include:

[0036] S1: Preparation of raw materials

[0037] FeCl3·6H2O and ellagic acid EA were prepared separately.

[0038] S2: Deprotonation reaction

[0039] N,N-dimethylformamide (DMF) was added to a reaction vessel, followed by FeCl3·6H2O and EA in a predetermined molar ratio. The mixture was sonicated to completely dissolve and disperse the EA. Formic acid was then added to deprotonate the EA and enhance its coordination ability, resulting in a mixed solution. The molar ratio of FeCl3·6H2O to EA was 1:3, and the concentration of FeCl3·6H2O ranged from 0.5 mmol to 1.5 mmol.

[0040] S3: Heating reaction

[0041] Place the above mixed solution in an oven and heat it to 120-180 ℃ for 24-72 hours. Then turn off the oven and allow it to cool naturally to room temperature. The preferred reaction temperature is 150 ℃ and the reaction time is 24 hours.

[0042] S4: Centrifugal drying

[0043] The product obtained in step S3 was collected by centrifugation and washed several times with DMF and isopropanol, respectively. Then it was placed in a vacuum drying oven and dried at 100 °C to remove the solvent, resulting in a black powder material, namely the iron-based metal-organic complex catalyst EFE-150, which was placed in a dry container for later use.

[0044] A method for removing ofloxacin from water involves using the aforementioned iron-based metal-organic complex catalyst EFE-150 to activate persulfate PDS oxidant, thereby enhancing the degradation of ofloxacin in the water. Specifically, an appropriate amount of persulfate PDS oxidant and the pre-prepared EFE-150 catalyst are sequentially added to wastewater containing ofloxacin pollutants. EFE-150 provides a sufficient catalytic interface and microscopic space for the rapid and efficient reaction between persulfate PDS and ofloxacin (OFL), accelerating the degradation rate. Under the synergistic effect of adsorption and degradation, it continuously promotes the adsorption-oxidative degradation process of OFL, increasing the reaction rate of the system and reducing the amount of catalyst and oxidant used in the system. The method includes the following steps:

[0045] A-1: Detection of OFL concentration in water;

[0046] A-2: Calculate the required amounts of EFE-150 catalyst and PDS oxidant, and add them to an appropriate amount of water to prepare a stock solution; for OFL wastewater treatment with a concentration not exceeding 25 mg / L, the concentration range of both catalyst and oxidant is 0.125-0.5 g / L; the specific concentration and amount can be adjusted according to actual needs.

[0047] A-3: Add the stock solution to the wastewater and stir. The EFE-150 catalyst and PDS oxidant will continuously promote the rapid degradation of OFL in the water through the adsorption-degradation synergistic effect. At this time, the EFE-150 catalyst will rapidly catalyze PDS to produce a variety of active oxides ROS. Combined with the catalyst's own electron transfer ability, a large number of free radicals and non-free radicals will be generated to efficiently remove OFL from the water.

[0048] A-4: Sample and test the water at regular intervals until the set removal rate or reaction endpoint is reached.

[0049] Tests showed that the EFE-150 catalyst and PDS oxidant, through an adsorption-degradation synergistic effect, achieved a degradation rate of over 85% for OFL within 30 minutes and over 90% within 60 minutes, while also exhibiting good reusability. The removal method and catalytic material provided in this invention are environmentally friendly, highly efficient, and low-cost, meeting the needs of large-scale application and rapidly achieving a degradation rate of over 90%.

[0050] The catalyst and removal method provided in this embodiment, through comprehensive selection of relevant synthesis parameters for iron-based metal-organic complexes, selects a target material with a six-coordinate structure. To obtain a high iron ion carrying capacity and to ensure the material possesses a large number of delocalized electrons to supplement iron ion catalytic activity, ellagic acid (EA), containing multiple electron-rich groups and capable of suppressing metal aggregation during synthesis, is specifically chosen as the ligand. The synergistic effect between the material's microstructure, components, and distribution positions leads to better material synthesis and stronger electron transfer. In this embodiment, DMF is selected as the organic solvent environment for the reaction, and the reaction temperature is set at 150°C to reduce hydration interference. Based on the six-coordinate characteristics of the transition metal Fe and considering hydration, the molar ratio of Fe centers to EA ligands is designed to be 1:3. Formic acid is added to adjust the pH of the system to a weakly acidic environment to deprotonate some phenolic hydroxyl groups, promoting the coordination process and increasing yield. The synthesis process designed in this embodiment aims to form a specific microstructure for the catalyst by controlling the component concentration and process parameters. This allows the EA ligand, which has a large number of delocalized electrons, to fully coordinate with iron ions, thereby transferring electrons to iron ions and maintaining its high catalytic activity. The EA ligand itself can also provide a large number of carbon-based catalytic sites through delocalized π electrons and enhance the adsorption of OFL through π-π interactions. Its non-planar six-coordinate structure can form a relatively large mesoporous pore size distribution, which can effectively promote the full contact between OFL in water and oxidative free radicals in the system, thereby improving the onset time and degradation efficiency of OFL degradation.

[0051] The following is in conjunction with the appendix Figures 1 to 9 Based on the basic embodiment, specific selections are made, and several specific embodiments are described in detail.

[0052] Example 1

[0053] This embodiment provides an iron-based metal-organic complex catalyst, its preparation method, and its application in removing ofloxacin from water (an efficient method for removing ofloxacin from water). Based on the basic embodiment, it specifically prepares a nano-scale catalyst, EFE-150 black powder.

[0054] For the method of preparing nanoscale EFE-150 materials, please refer to [link / reference]. Figure 1 It is prepared by a solvothermal method using commercially available reagent FeCl3·6H2O and ellagic acid (EA), specifically through the following steps:

[0055] FeCl3·6H2O was added to a 100mL reactor containing 40mL DMF and sonicated until completely dissolved. Then, EA was added and sonicated until completely dispersed. An appropriate amount of formic acid was added to the mixture to deprotonate EA to facilitate the coordination reaction. The reactor was then sealed and placed in a forced-air drying oven and heated at 150 °C for 24 h. After heating, the reactor was removed and cooled to room temperature. The solid material was then washed several times by centrifugation with DMF and isopropanol and placed in a vacuum drying oven and heated at 100 °C for 12 h.

[0056] The molar ratio of FeCl3·6H2O to EA is 1:3; the concentration of FeCl3·6H2O is 0.5 mmol, and the concentration of EA is 1.5 mmol; the volume of formic acid solution added is 2.5 mL; in other embodiments, the concentration of FeCl3·6H2O can also be selected as 1 mmol or 1.5 mmol, and the concentration of EA is adjusted accordingly.

[0057] Example 2

[0058] This embodiment investigates the morphology, elemental distribution, carbon-based structure, functional group and coordination characteristics, specific surface area and overall structure of the EFE-150 catalyst material prepared in Example 1 using SEM-EDS, XRD, FT-IR, BET and ESI-MS.

[0059] First, the morphology and elemental distribution of EFE-150 prepared in Example 1 were investigated using SEM-EDS characterization. See [link to SEM-EDS]. Figure 2 Figure (a) shows an amorphous sheet-like structure at the nanoscale; see also... Figure 2 Figure (b) shows that at the micrometer scale, the sheet-like structure of the material exhibits a clear tendency to aggregate into clusters, while the overall structure remains amorphous. EDS mapping images indicate that C, O, and Fe elements are uniformly distributed in the EFE-150 structure, without any elemental enrichment.

[0060] See Figure 3 The carbon-based structure of EFE-150 was studied by XRD characterization. EFE-150 exhibits an amorphous amorphous structure. The obvious diffraction peak at 43.6° can be attributed to the (101) crystal plane of the carbon-based structure. The presence of the diffraction peak proves that there is a certain graphitization structure in the carbon-based structure of EFE-150. However, the diffraction peak is broadened but not sharp, confirming that it is still an amorphous amorphous structure.

[0061] FT-IR images from EFE-150 ( Figure 4Different vibrational modes of its ligand EA can be observed in multiple structures, including the stretching vibration of the CC / C=C / C=O structure, the bending vibration of the -OH structure, and the presence of coordinate bonds, i.e., the stretching vibration of Fe-O. The results verify the presence of multiple functional groups belonging to EA and metallic coordinate bonds in the EFE-150 structure, which can preliminarily determine its structural characteristics.

[0062] In addition, the BET surface area and pore size distribution of EFE-150 were determined by nitrogen adsorption-desorption experiments. The results are shown below. Figure 5 Figures (a) and (b) show that the specific surface area and main pore size of the EFE-150 material are 35 μm. 2 / g and 4.5 nm indicate that the material is a nanoscale mesoporous material. The nitrogen adsorption-desorption curve shows the characteristics of a type II adsorption isotherm and has an H3 type hysteresis loop, indicating that the EFE-150 material has a large overall pore size structure.

[0063] See appendix Figure 6 To further confirm the structural characteristics of the EFE-150 catalyst, this embodiment performs high-resolution mass spectrometry (ESI-MS) testing on the EFE-150 material. By consulting existing literature on the coordination characteristics of trivalent iron and tannic acid-based organic compounds, it is initially assumed to be a six-coordinate structure with a theoretical molecular weight of 956. Combining the mass-to-charge ratio (m / z) and peak intensity analysis in the MS image, its molecular ion peak is located at m / z = 485.28317. Considering that the detection solvent is deionized water, and that the functional group characteristics and pore structure of EFE-150 may allow for water molecule adsorption, its theoretical molecular ion peak should be m / z = 487, which is consistent with the molecular peak located in the MS image. Secondly, a deprotonated ellagic acid structure (C1) was detected in the fragment ion peak. 14 H5O8 (m / z=300.99933). The above test results further verify that the EFE-150 material has a six-coordinate structure.

[0064] Example 3

[0065] This embodiment applies the EFE-150 material prepared in Example 1 to the efficient removal of ofloxacin from water. Based on the concentration of OFL in the water, a corresponding proportion of the catalyst EFE-150 material and oxidant PDS are added. Utilizing the morphology and physicochemical properties of this material, PDS is rapidly catalyzed to generate various ROS that attack OFL, thereby degrading OFL in the water and achieving efficient removal of OFL to obtain ideal removal efficiency and effect. The specific operation is as follows:

[0066] A-1: Detection of OFL concentration in water;

[0067] A-2: Calculate the required amounts of EFE-150 catalyst and PDS oxidant, and add them to an appropriate amount of water to prepare a high-concentration stock solution; the concentration range of catalyst and oxidant in the stock solution is usually 0.125-0.5 g / L, and can be further adjusted according to the actual situation;

[0068] A-3: Add the stock solution to the wastewater and stir. The two work together to rapidly degrade OFL in the water. The EFE-150 catalyst rapidly catalyzes PDS to produce various ROS. Combined with its own electron transfer ability, it can efficiently remove OFL from the water through free radical and non-free radical pathways.

[0069] A-4: Sample and test the water at regular intervals until the set removal rate or reaction endpoint is reached, then stop stirring.

[0070] This embodiment uses a preliminary experimental method to evaluate the degradation effect of EFE-150 on OFL. The preliminary experiment included an EFE-150-catalyzed PDS group, an organic ligand EA-catalyzed PDS group, and Fe... 2+ The PDS catalytic group investigated the degradation effect of OFL in different systems. In addition, EFE-150 material alone and PDS alone were set up as control groups to investigate the adsorption performance of the materials and the ability of PDS to directly generate ROS.

[0071] The preliminary experimental procedure was as follows: 10 mL of 25 mg / L OFL solution was added to a 20 mL sample vial. Then, 5 mg of oxidant PDS and 5 mg of catalyst EFE-150 were added to the sample vial. The sample vial was placed in a constant temperature shaking incubator and reacted at 160 rpm and 30℃ for 2 h. The OFL concentration was measured periodically. In addition, the EA-catalyzed PDS group and Fe... 2+ The dosage of the relevant reagents for the PDS catalytic group, the control group with only EFE-150 material, and the control group with only PDS are the same as those mentioned above (converted by the amount of the same substance).

[0072] Preliminary experimental results are as follows Figure 7 As shown in (a), adding only EFE-150 material exhibits good OFL adsorption and removal effects, while adding only PDS shows some OFL removal effect, but the removal process exhibits certain fluctuations. In different catalytic systems, the EA-catalyzed PDS group did not produce OFL removal effects, indicating that this ligand does not have the ability to catalyze PDS to generate ROS and degrade OFL on its own; Fe 2+The catalytic PDS group did not show any OFL removal effect in the first 15 minutes, but then OFL was steadily removed, reaching a 50% OFL removal rate within 2 hours. The EFE-150 catalytic PDS group, on the other hand, showed excellent OFL removal efficiency, removing 80% of OFL contaminants within 5 minutes and reaching a 91% OFL removal rate within 2 hours. Compared with adding only EFE-150 material, the catalytic system showed a significant improvement in both reaction rate and removal effect.

[0073] Further single-factor influence studies were conducted using the preliminary experimental reaction parameters as a reference. With other reaction parameters fixed, the effects of different EFE-150 addition amounts, PDS addition amounts, reaction temperatures, initial pH values, background interference, and real water bodies on the degradation of OFL by the EFE-150-catalyzed PDS system and the reusability of the materials were tested.

[0074] First, the effect of EFE-150 dosage on OFL removal efficiency was investigated. In this factorial study, the OFL concentration was 25 mg / L, the PDS dosage was fixed at 0.5 g / L, and the EFE-150 dosage was set at 0.125, 0.25, 0.375, and 0.5 g / L. Figure 7 As shown in (b), the removal efficiencies of different addition amounts within 5 min of the reaction were 68.9%, 86.4%, 83.1%, and 73.0%, respectively. The overall removal efficiency showed a trend of first increasing and then decreasing with the increase of catalyst addition. Within 2 h of the reaction, the removal efficiencies were 85.1%, 80.2%, 73.4%, and 69.6%, respectively, showing a gradual decreasing trend with the increase of catalyst addition. It can be seen that this catalyst can achieve a relatively ideal OFL removal effect with a relatively small addition amount, and increasing the amount of catalyst added does not necessarily improve the removal efficiency.

[0075] like Figure 7 As shown in (c), in the study of the effect of PDS addition amount, with an OFL concentration of 25 mg / L and a fixed EFE-150 addition amount of 0.125 g / L, OFL removal experiments were conducted with PDS addition amounts of 0.125, 0.25, 0.375, and 0.5 g / L. The OFL removal rates within 5 min were 61.6%, 67.1%, 71.7%, and 78.8%, respectively, and the OFL removal rates within 2 h were 81.6%, 86.8%, 88.4%, and 90.2%, respectively. The OFL removal efficiency generally increased with increasing PDS concentration, and the increasing trend gradually slowed down. It can be seen that the EFE-150 material has a high PDS catalytic efficiency and can catalyze several times the amount of PDS added.

[0076] To investigate the OFL removal capacity of EFE-150 material under different environmental conditions, a single-factor experiment was conducted with reaction temperature as the factor. The OFL concentration was set at 25 mg / L, the EFE-150 catalyst dosage was 0.125 g / L, and the PDS dosage was 0.5 g / L. The OFL removal efficiency of the reaction system at temperatures of 25℃, 35℃, and 45℃ was then examined. Figure 7 As shown in Figure (d), the OFL removal rates within 5 min were 63.3%, 79.7%, and 82.6%, respectively, and the OFL removal rates within 2 h were 86.7%, 94.1%, and 96.3%, respectively. The OFL removal effect increased with increasing reaction temperature.

[0077] Subsequently, OFL removal experiments were conducted at different initial pH values. The OFL concentration was set at 25 mg / L, the catalyst EFE-150 addition amount was 0.125 g / L, and the PDS addition amount was 0.5 g / L. The OFL removal efficiency of the reaction system under pH conditions of 3, 5, 7, 9, and 11 was investigated. Figure 7 As shown in Figure (e), the OFL removal rates within 5 min were 63.3%, 57.9%, 56.5%, 69.2%, and 0%, respectively, and the OFL removal rates within 2 h were 81.1%, 74.8%, 84.7%, 84.0%, and 28.6%, respectively. The EFE-150 catalytic PDS system maintained an OFL removal efficiency of over 80% under strongly acidic, neutral, and weakly alkaline environments, and still showed an OFL removal rate of about 75% under weakly acidic conditions, indicating that the catalytic material has excellent chemical stability and environmental adaptability.

[0078] To further investigate the interference of background substances during OFL removal, the OFL concentration was set at 25 mg / L, the catalyst EFE-150 dosage was 0.125 g / L, and the PDS dosage was 0.5 g / L. The Cl... - H2PO4 - HPO4 2- NO3 2- SO3 2- Interference from humic acid (HA) was also investigated. Three concentration gradients were set for each interfering substance: anion concentrations of 0.25 mM, 0.5 mM, and 0.75 mM, and HA concentrations of 2.5 mg / L, 5 mg / L, and 7.5 mg / L. Figure 7 As shown in Figure (f), OFL maintained a removal efficiency of over 78% under various background interference conditions, with anions maintaining a removal efficiency of over 80%.

[0079] Based on the preliminary experimental results, further experiments were conducted to investigate the degradation performance of the EFE-150 catalyst-PDS system on real water systems, including lake water, mineral water, river water, and leachate. The OFL concentration was set at 25 mg / L, the EFE-150 catalyst dosage at 0.125 g / L, and the PDS dosage at 0.5 g / L. The degradation system was prepared using real water samples. Figure 7 As shown in Figure (g), the OFL removal rates within 5 min were 79.1%, 85.0%, 80.4%, and 72.3%, respectively, and the OFL removal rates within 2 h were 90.1%, 90.4%, 87.8%, and 83.8%, respectively. It can be seen that the EFE-150 catalytic PDS system can exhibit excellent OFL removal efficiency in various water environments.

[0080] The reusability of EFE-150 is as follows: Figure 7 As shown in (h), the OFL concentration was set at 25 mg / L, the catalyst EFE-150 addition amount was 0.125 g / L, and the PDS addition amount was 0.5 g / L. After the first degradation experiment, the catalyst was recovered and could be reused five times. The OFL removal rates of EFE-150 in the five reuse experiments were 86.8%, 86.8%, 83.8%, 80.3%, and 79.4% respectively, demonstrating that the catalyst material has good reusability.

[0081] Example 4

[0082] Based on Example 3, this embodiment selects EFE-150 catalyst materials before and after the reaction for photoelectron spectroscopy (XPS) detection, specifically including the following steps:

[0083] B1. XPS detection of EFE-150 material before and after reaction

[0084] XPS analysis was performed on the EFE-150 material before and after the reaction. By comparing the changes in fine peak division and shift of each element before and after the reaction, the reaction mechanism was determined and the reaction performance was explored. The specific operation was as follows:

[0085] B1-1: Place the prepared EFE-150 material in a vacuum drying oven and dry it at 100℃ for 12 h, then seal it for later use.

[0086] B1-2: Weigh out sufficient EFE-150 material according to the optimal reagent addition ratio in Example 3 and react it. After the reaction, collect the EFE-150 catalyst material through a vacuum filter, wash it several times with deionized water, place it in a forced-air drying oven and dry it at 100°C for 12 hours, then seal it for later use.

[0087] In this embodiment, as Figure 8As shown in Figure (a), XPS analysis of the EFE-150 catalyst before the reaction revealed multiple structural features of ligand EA, including CC / C=C, COC, and OC=O, as well as the metal coordination characteristic Fe-O of EFE-150, consistent with the results of FT-IR and ESI-MS, further clarifying the structural characteristics of EFE-150. XPS analysis of EFE-150 after the reaction showed the same structural characteristics as before the reaction, but the binding energies of the orbital peaks for each element showed significant shifts. See [link to figure]. Figure 8 In Figure (b), the binding energy of the C 1s spectrum peaks increases, its electron cloud density decreases, and a π-π* shake-up peak is generated, further indicating that delocalized electrons in the carbon-based structure of EFE-150 participate in the electron transfer process; as shown in Figure (b). Figure 8 As shown in Figure (c), the binding energies of the O 1s spectra all show a decreasing state, indicating that oxygen-containing structures participate in the PDS catalytic process as active sites; as Figure 8 As shown in Figure (d), the binding energy of the Fe 2p spectrum is significantly lower than that of other elements, indicating that Fe in the EFE-150 material exists in different valence states and participates in the catalytic PDS process as a core catalytic site. XPS results show that the EFE-150 material possesses multiple catalytic sites, can catalyze the generation of ROS from PDS, and its carbon-based structure has good electron transfer capabilities, thus enabling the degradation of pollutants through electron transfer pathways.

[0088] Example 5

[0089] This embodiment further investigated the electron transfer capability of the EFE-150-catalyzed PDS system by evaluating the electrochemical characteristics of the reaction system involving EFE-150. The detection items included open circuit potential (OCP), current-time curve (I-tcurve), and linear voltammetry scan curve (LSV). The specific steps included:

[0090] C. Electrochemical detection of the reaction system involving EFE-150 material

[0091] Electrochemical detection of OCP, I-tcurve, and LSV was performed on three systems: EFE-150 material, EFE-150 and PDS, and EFE-150 catalyzing PDS degradation of OFL. The specific procedures were as follows:

[0092] C-1: A three-electrode system was prepared in an electrochemical workstation for relevant detection. The working electrode was made of EFE-150, the counter electrode was a platinum sheet, and the reference electrode was an Hg / HgCl electrode. 0.1 M Na2SO4 solution was used as the electrolyte.

[0093] C-2: Prepare an OCP test solution with a total volume of 100 mL. Add a few milligrams of PDS at 200 s and a few milligrams of OFL powder at 400 s.

[0094] C-3: Prepare an It curve test solution with a total volume of 100 mL. Add a few milligrams of PDS at 120 s and a few milligrams of OFL powder at 240 s.

[0095] C-4: The total volume of the LSV test solution was 100 mL. Three systems were prepared: a pure electrolyte solution, a solution containing a certain concentration of PDS, and a mixed solution containing a certain concentration of PDS and OFL. The scanning voltage range was -0.5 to 1.5 V (relative to the reference electrode), and the scanning rate was 5 mV / s.

[0096] In embodiments of the present invention, such as Figure 9 As shown in Figure (a), the addition of PDS to the working electrode system modified with EFE-150 material caused the OCP to surge, while the addition of OFL caused the OCP to drop sharply and then stabilize. Figure 9 Figure (b) shows the It Curve curve, indicating that the current decreases after adding PDS to the EFE-150 modified working electrode system, while the current increases sharply after further adding OFL. The LSV curve shows that the EFE-150 modified working electrode system exhibits the most significant current enhancement characteristic after adding PDS. Furthermore, when PDS and OFL are present simultaneously, the current enhancement is slightly less than that of the PDS solution. Figure 9 Figure (c) shows the EFE-150-catalyzed PDS degradation of OFL system. Significant voltage and current changes were observed in the electrochemical tests, indicating that the addition of OFL consumed the metastable PDS intermediates adsorbed on the EFE-150 material through electron transfer. This confirms the existence of a non-radical degradation pathway dominated by electron transfer, further demonstrating the high efficiency of EFE-150 material in catalyzing the removal of OFL from PDS.

[0097] The efficient method for removing OFL from water and the iron-based metal-organic complex provided in the above embodiments of the present invention utilize an EFE-150 catalyst with a rigid, six-coordinate, electron-rich structure. The required raw materials are inexpensive and readily available, the preparation process is simple, and it can catalyze the generation of various ROS from PDS. Combined with electron transfer processes, it efficiently removes OFL through both free radical and non-free radical pathways, achieving a degradation rate of over 85% within 30 minutes and over 90% within 60 minutes. It also exhibits good reusability; the material demonstrates excellent reusability, and for materials with decreased catalytic activity, simple deionized water washing after recovery is sufficient to restore catalytic activity. This method is environmentally friendly, highly efficient, low-cost, and produces no secondary pollution, meeting the needs for large-scale, widespread application and has broad application prospects in the field of wastewater treatment.

[0098] It should be particularly noted that other technical solutions obtained by specifically selecting from the components, proportions, and process parameters described in this invention can all achieve the technical effects of this invention, and therefore will not be listed one by one. Furthermore, other technical solutions obtained by using similar components, solvents, and processes as described in this invention are included within the protection scope of this invention.

[0099] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art can make many possible variations and modifications to the technical solution of the present invention using the methods and techniques disclosed above, or modify it into equivalent embodiments with equivalent changes, without departing from the scope of the present invention. All equivalent changes made to the components, proportions, and processes of the present invention should be covered within the protection scope of the present invention.

Claims

1. An iron-based metal-organic complex catalyst, characterized in that, It is a six-coordinated black powder with an amorphous nanoscale sheet structure and micron-scale cluster aggregation, prepared by using ellagic acid EA with a rich electron structure as a ligand and iron atoms as coordinating metal. The surface pore size distribution is mainly mesoporous, and it has an adsorption-degradation synergistic effect. It is an iron-based metal-organic complex FeMOC material that catalyzes the rapid and efficient reaction between the oxidant persulfate PDS and ofloxacin OFL in water. It is named EFE-150 catalyst. The EFE-150 catalyst exhibits an amorphous, stacked sheet-like structure at the nanoscale, with an overall cluster-like appearance. Each sheet has an average thickness of 30 nm and a specific surface area of ​​35 m². 2 / g, the main pore size on the surface is 4.5 nm, C, O and Fe elements are uniformly distributed in the plate-like structure without enrichment, the nitrogen adsorption-desorption curve shows the characteristics of type II adsorption isotherm and has H3 type hysteresis loop. The iron-based metal-organic complex catalyst is prepared by a solvothermal synthesis method, specifically including the following steps: S1: Preparation of raw materials FeCl3·6H2O and ellagic acid EA were prepared separately. S2: Deprotonation reaction N,N-dimethylformamide (DMF) was added to the reaction vessel, and then FeCl3·6H2O and EA were added in sequence according to a set molar ratio. The mixture was sonicated to completely dissolve and disperse the EA. Formic acid was then added to deprotonate the EA, resulting in a mixed solution. S3: Heating reaction Place the above mixed solution in an oven and heat it to 120-180 ℃ for 24-72 hours. Then turn off the oven and allow it to cool naturally to room temperature. S4: Centrifugal drying The product obtained in step S3 was collected by centrifugation and washed several times with DMF and isopropanol, respectively. Then it was placed in a vacuum drying oven and dried at 100 °C to remove the solvent, resulting in a black powder material, namely the iron-based metal-organic complex catalyst EFE-150, which was placed in a dry container for later use.

2. The iron-based metal-organic complex catalyst according to claim 1, characterized in that, The adsorption-degradation synergistic effect of the EFE-150 catalyst is based on its nanoscale sheet-like FeMOCs structure. The EA ligand possesses a large number of delocalized π electrons, which are extensively delocalized in the polycyclic planar structure of EA, forming multiple electrostatic minimum points. These points efficiently adsorb OFL through π-π interactions and electrostatic interactions. The multiple hydroxyl and lactone rings in the polycyclic planar structure of EA provide sufficient electrons to a large number of iron-based catalytic sites, enabling them to quickly restore catalytic activity. Combined with carbon-based catalytic sites possessing delocalized electrons, OFL is rapidly degraded through the synergistic effect of adsorption and oxidation. After OFL is degraded, the previously occupied adsorption sites are re-exposed, and the EFE-150 catalyst regains its adsorption activity.

3. The iron-based metal-organic complex catalyst according to claim 1, characterized in that, In step S2, the molar ratio of FeCl3·6H2O to EA is 1:3; The reaction temperature in step S3 is 150°C, and the reaction time is 24 hours.

4. A method for removing ofloxacin from water, characterized in that, The method employs the iron-based metal-organic complex catalyst EFE-150 as described in any one of claims 1 to 3 to activate persulfate PDS oxidant to enhance the degradation of ofloxacin in water. Specifically, persulfate PDS oxidant and pre-prepared EFE-150 catalyst are sequentially added to wastewater containing ofloxacin pollutants. EFE-150 catalyzes the rapid and efficient reaction between persulfate PDS and ofloxacin (OFL), and under the synergistic effect of adsorption and degradation, it continuously promotes the adsorption-oxidation degradation process of OFL, increases the reaction rate of the system, and reduces the amount of catalyst and oxidant used in the system.

5. The method for removing ofloxacin from water according to claim 4, characterized in that, Specifically, it includes the following steps: A-1: Detection of OFL concentration in water; A-2: Calculate the required amounts of EFE-150 catalyst and PDS oxidant, and add them to an appropriate amount of water to prepare a stock solution; A-3: Add the stock solution to the wastewater and stir. The EFE-150 catalyst and PDS oxidant will continuously promote the rapid degradation of OFL in the water through the adsorption-degradation synergistic effect. At this time, the EFE-150 catalyst will rapidly catalyze PDS to produce a variety of active oxides ROS. Combined with the catalyst's own electron transfer ability, OFL in the water will be efficiently removed. A-4: Sample and test the water at regular intervals until the set removal rate is achieved.

6. The method for removing ofloxacin from water according to claim 5, characterized in that, It includes the following steps: In step A-2, for the treatment of OFL wastewater with a concentration of 25 mg / L, the concentration range of both the catalyst and the oxidant is 0.125-0.5 g / L.

7. The method for removing ofloxacin from water according to claim 5, characterized in that, It includes the following steps: In step A-3, the EFE-150 catalyst and PDS oxidant achieve a degradation rate of over 85% for OFL within 30 minutes and over 90% for OFL within 60 minutes.

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