Waste lithium iron phosphate electrode material coupled metal organic framework derived composite catalyst and preparation and organic pollutant treatment application thereof

Abstract

The invention discloses a waste lithium iron phosphate electrode material coupled metal organic framework derived composite catalyst and preparation and organic pollutant treatment application thereof.The method comprises the steps that pretreated waste lithium iron phosphate electrode material (sLFP) powder and a zinc-based zeolite imidazole framework (ZIF-8) are mixed according to a specific mass ratio, high-temperature calcination is conducted in an inert atmosphere, and the metal organic framework derived composite catalyst is obtained; and tight coating and coupling of a ZIF-8-derived nitrogen-doped carbon skeleton on a LiFePO4 phase obtained by reconstruction after sLFP pyrolysis are realized, so that a novel composite catalyst with high specific surface area, excellent conductivity and rich active sites is obtained. According to the method, recycling high-added-value conversion of waste electrode materials is achieved, the degradation rate of a Fenton-like reaction system constructed by the obtained composite catalyst and peroxymonosulfate (PMS) in cooperation on refractory organic pollutants such as sulfamethoxazole (SMX) at the normal temperature reaches 98.5% or above, the excellent catalytic stability and the green integrated treatment advantage that waste is treated with waste are achieved, and the method is suitable for industrial production. Wide engineering application prospects are realized.

Description

Technical Field

[0001] This invention belongs to the field of environmental engineering and resource recycling technology, specifically relating to a composite catalyst derived from waste lithium iron phosphate electrode material coupled with a metal-organic framework, its preparation and application in the treatment of organic pollutants. Background Technology

[0002] In recent years, the rapid development of the new energy vehicle industry has driven a significant increase in the production of lithium-ion power batteries, resulting in a continuous rise in the amount of waste lithium iron phosphate batteries. Waste lithium iron phosphate batteries are rich in valuable metal resources such as lithium, iron, and phosphorus. If not properly recycled, they not only cause serious resource waste but also pose long-term potential risks to the ecological environment and human health due to the presence of toxic and harmful components such as electrolytes and organic binders. Therefore, the efficient, green recycling and high-value utilization of waste lithium iron phosphate electrode materials (sLFP) has become an important issue that urgently needs to be addressed.

[0003] Currently, the recycling pathways for waste lithium iron phosphate electrode materials mainly fall into two categories: direct remediation and hydrometallurgical recycling. Direct remediation aims to restore electrochemical performance, typically achieved by removing surface organic matter, replenishing missing elements, and repairing the crystal lattice structure. For example, some studies have reported that direct calcination at approximately 750℃ can effectively remove surface organic residues, but its ability to repair lithium-deficient lattices is limited, making it only suitable for structurally intact, relatively simple scrap materials. Other researchers have achieved capacity retention rates greater than 95% through hydrothermal / solid-phase lithium replenishment strategies, but these methods require high raw material purity and are time-consuming, making them unsuitable for the economical recycling of large-scale, complex waste materials. Hydrometallurgical recycling focuses on leaching and separating valuable metal ions, followed by regeneration and synthesis to obtain new materials. This technology is relatively mature in the selective extraction of lithium, with literature reporting recovery rates exceeding 99%. However, its inherent drawbacks include the need for large amounts of acid and alkali solutions, complex process steps, and the generation of large amounts of acidic and saline wastewater, increasing the burden of subsequent treatment and overall costs.

[0004] Existing patented technologies also have significant limitations. For example, patent CN112694074B proposes a method for recycling lithium iron phosphate waste and its application. This method requires multiple acid-base treatments, has a long process route, and high energy consumption, and cannot fundamentally solve the problems of environmental pollution and cost. Although patent CN118970256A has achieved the conversion of waste lithium iron phosphate cathode powder into high-performance water electrolysis anode catalyst, the resulting material has a thick and uneven surface coating, which easily causes pore blockage and a decrease in specific surface area, thus severely limiting its practical application and catalytic efficiency in the field of advanced catalysis.

[0005] Overall, existing recycling technologies are mostly concentrated in the "dismantling-leaching-separation-regeneration" model, which generally suffers from complex processes, high energy consumption, large reagent consumption, and secondary pollution. From a resource attribute perspective, most components in waste lithium iron phosphate batteries (such as iron, phosphorus, aluminum, and carbon) have relatively low added value in the traditional metallurgical sense. If only the recovery of metal elements is the goal, a large amount of energy and chemical reagents are often required, making it difficult to balance economic efficiency and environmental friendliness. Therefore, directly converting waste lithium iron phosphate electrode materials into other high-value-added, highly active functional materials is considered a more economical, energy-saving, and environmentally friendly innovative utilization strategy.

[0006] In the field of advanced treatment of organic pollutants, advanced oxidation processes (AOPs) are favored because they can generate sulfate radicals (SO4•-). - Strongly oxidizing reactive oxygen species (ROS), such as Fe, are widely used for the degradation and mineralization of recalcitrant organic pollutants. Among them, the transition metal / permonosulfate (PMS) system has attracted widespread attention due to its excellent catalytic efficiency. Previous studies have shown that Fe... 2+ The use of iron-containing electronic waste materials as heterogeneous activators for PMS activation has attracted increasing attention, offering a new approach for directly utilizing iron resources from spent lithium iron phosphate electrode materials for PMS activation. However, significant technological gaps remain: existing work rarely addresses significantly improving the specific surface area, exposed active sites, and cycle stability of spent lithium iron phosphate electrode materials by constructing special composite synergistic structures (such as coupling with metal-organic frameworks (MOFs)). In particular, systematic research on coupling spent lithium iron phosphate electrode materials with MOFs to obtain heterogeneous PMS catalysts with both ultra-high specific surface area and synergistic high activity is lacking.

[0007] In summary, there is an urgent need to develop a highly active composite catalytic material and its preparation method that can directly utilize the metal resources in waste lithium iron phosphate electrode materials, construct a closely synergistic structure with metal-organic frameworks, and possess high specific surface area, unexpectedly high catalytic activity, and excellent cycle stability. This would provide a new and green technological approach for the resource utilization of waste electrode materials and the in-depth treatment of organic pollution. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies in the recycling of waste lithium iron phosphate electrode materials, such as complex processes, high energy consumption, significant secondary pollution, low specific surface area of ​​the resulting catalytic materials, easy agglomeration of active components, and insufficient catalytic synergistic effect, this invention provides a composite catalyst for waste lithium iron phosphate electrode materials coupled with a metal-organic framework (MORF) derivative, its preparation, and its application in the treatment of organic pollutants. The core technical problem this invention aims to solve is: how to construct a tightly synergistic coupling structure between waste lithium iron phosphate electrode materials and ZIF-8 derivatives through a green and simplified process, thereby obtaining a PMS heterogeneous activated catalyst with unexpectedly high catalytic activity and excellent cycle stability.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: This invention first provides a composite catalyst derived from waste lithium iron phosphate electrode material coupled with a metal-organic framework. The composite catalyst comprises a core active component and a support framework. The core active component is LiFePO4 particles reconstructed from waste lithium iron phosphate electrode material after pyrolysis. The support framework is a nitrogen-doped porous carbon framework generated by the pyrolysis of a zinc-based zeolite imidazole framework (ZIF-8). The LiFePO4 particles are coated by the nitrogen-doped porous carbon framework and uniformly dispersed within its porous structure. The nitrogen-doped porous carbon framework is a continuous three-dimensional conductive network structure. Its coating effect on the LiFePO4 particles effectively inhibits the aggregation and abnormal grain growth of the LiFePO4 particles, and constructs a continuous conductive carbon network, promoting interfacial electron transfer.

[0010] Furthermore, the composite catalyst comprises Fe, P, Li, C, N, and O elements. The Fe, P, and Li elements are mainly derived from waste lithium iron phosphate cathode material; the C and N elements are mainly derived from the pyrolysis and carbonization of ZIF-8; the catalyst may also contain trace amounts of Zn, a component of ZIF-8. Elemental distribution testing results show that Fe, P, C, N, and O elements are uniformly distributed in the composite catalyst, and trace amounts of Zn are also uniformly dispersed in the nitrogen-doped porous carbon framework.

[0011] Furthermore, the specific surface area of ​​the composite catalyst is ≥500 m². 2 / g. The specific surface area of ​​the composite catalyst is significantly higher than that of the nitrogen-doped porous carbon framework obtained solely by ZIF-8 pyrolysis (specific surface area of ​​470–490 m²). 2 / g) and materials obtained solely from the pyrolysis of waste lithium iron phosphate electrode materials (specific surface area of ​​15-25 m²) 2 / g).

[0012] This invention also provides a method for preparing the composite catalyst derived from the waste lithium iron phosphate electrode material coupled with a metal-organic framework. The method is characterized by: firstly, pretreating the collected waste lithium iron phosphate electrode material to obtain a uniform powder; then, using zinc nitrate hexahydrate and 2-methylimidazole in methanol to self-assemble a zinc-based zeolite imidazole framework (ZIF-8); finally, mixing the waste electrode material powder with ZIF-8 and calcining it in a tube furnace under an inert atmosphere, thereby tightly coupling the waste electrode material with the nitrogen-doped carbon framework derived from ZIF-8, ultimately obtaining a structurally stable and highly active composite catalyst. Specifically, the method includes the following steps: Step 1: Pretreatment of waste lithium iron phosphate electrode materials: The collected waste lithium iron phosphate electrode materials were immersed in N-methylpyrrolidone (NMP) to remove the binder and residual electrolyte. They were then washed with deionized water and anhydrous ethanol in sequence, dried and pulverized to obtain lithium iron phosphate electrode material powder (mainly lithium iron phosphate LiFePO4 and its associated conductive carbon). Step 2, Preparation of ZIF-8: Zinc nitrate hexahydrate was dissolved in methanol to obtain solution A, and 2-methylimidazole was dissolved in methanol to obtain solution B. Solution A and solution B were mixed and stirred and aged at room temperature. The white precipitate was collected, washed with methanol and dried to obtain ZIF-8. Step 3, Compounding and Calcination: The ZIF-8 obtained in step 2 is mixed evenly with the lithium iron phosphate electrode material powder obtained in step 1, and placed in an inert atmosphere. The mixture is heated to 500-900℃ (preferably 780-820℃) at a heating rate of 5-10℃ / min, held at this temperature for 120-180 min, and then naturally cooled to obtain a composite catalyst derived from waste lithium iron phosphate electrode material coupled with a metal-organic framework. The mass ratio of ZIF-8 to waste lithium iron phosphate electrode material powder is 5-7:1.

[0013] As a preferred method, 2.322–6.966 g of zinc nitrate hexahydrate is dissolved in 180–360 mL of methanol to obtain solution A; 2.367–7.101 g of 2-methylimidazole is dissolved in 180–360 mL of methanol to obtain solution B; and the aging time at room temperature is 20–30 h.

[0014] Preferably, the drying conditions in steps 1 and 2 are: a drying temperature of 60-80℃ and a drying time of 6-12 h.

[0015] Preferably, in step 3, the inert gas used is argon or nitrogen.

[0016] This invention further provides an application of the composite catalyst, characterized in that: the composite catalyst is used as a heterogeneous catalyst to synergistically construct a Fenton-like reaction system with persulfate (PMS) for the degradation of organic pollutants in water. Specifically, the application method involves adding PMS and the composite catalyst to an aqueous solution of the organic pollutants to be treated, stirring the reaction at room temperature, and utilizing the composite catalyst to activate PMS to generate reactive oxygen species, thereby achieving efficient degradation and mineralization of the organic pollutants.

[0017] Furthermore, the organic pollutant is at least one of antibiotics, phenols, halogenated phenols, dyes, and endocrine disruptors, preferably sulfamethoxazole, bisphenol A, 2,4-dichlorophenol, etc.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The material structure design exhibits significant synergistic effects: This invention uses waste lithium iron phosphate electrodes as the source of metal active components, combining the high specific surface area and porous framework advantages of zinc-based zeolite imidazole framework (ZIF-8). Through in-situ pyrolysis, a tightly coupled structure of "LiFePO4 particles—ZIF-8 derived nitrogen-doped porous carbon framework" is constructed, allowing Fe, P, and other metal components to be uniformly anchored within the carbon framework. This effectively inhibits the aggregation and loss of metal active components, while providing continuous conductive pathways and abundant surface / interfacial active sites, significantly improving the specific surface area and PMS activation capacity. Under the same conditions, the degradation rate of sulfamethoxazole by this composite catalytic material can reach approximately 98.5% within 90 minutes, significantly better than materials obtained solely from ZIF-8 carbonization (approximately 61.1%) and materials obtained solely from waste lithium iron phosphate pyrolysis (approximately 58.3%), demonstrating significant nonlinear synergistic effects.

[0019] 2. The "waste-to-waste" application concept achieves high-value utilization of resources and in-depth treatment of organic pollutants: This invention breaks through the traditional approach of "single metal recovery" or "single pollutant treatment," directly converting Fe, P, and other metal resources in waste lithium iron phosphate electrodes into highly efficient PMS activation catalysts. This avoids the high energy consumption and secondary pollution caused by the multi-step acid-base leaching and complex separation processes of hydrometallurgy. The resulting composite catalytic material can efficiently degrade typical recalcitrant organic pollutants such as bisphenol A, 2,4-dichlorophenol (2,4-DCP), and sulfamethoxazole (SMX) in the PMS system, achieving an organic unity of "resource utilization of waste electrode materials" and "in-depth treatment of organic pollutants." It constructs a demonstrative "waste-to-waste" closed-loop utilization model, possessing significant environmental benefits and engineering application value.

[0020] 3. Simplified and environmentally friendly process with excellent potential for large-scale preparation: This invention employs a synergistic construction strategy of waste electrode materials and ZIF-8. During pyrolysis, ZIF-8 provides in-situ carbon and nitrogen sources, forming a porous nitrogen-doped carbon framework. The inherent lithium defects and residual carbon in the waste electrode materials facilitate the introduction of defect sites and optimization of the surface microenvironment, thereby further improving the activation efficiency of PMS and the degradation efficiency of organic pollutants. The entire preparation process requires only three steps: "pretreatment – ​​self-assembly – mixed calcination," eliminating the need for complex processes such as acid leaching, extraction, or reprecipitation. The raw materials are widely available, low-cost, energy-efficient, and environmentally friendly. The resulting catalytic material exhibits stable structure and excellent cycle performance, demonstrating good scalability and engineering application prospects. Attached Figure Description

[0021] Figure 1 This is a scanning electron microscope (SEM) image of the ZIF / sLFP-800 catalyst prepared in Example 1 of this invention.

[0022] Figure 2 The image shows the elemental mapping of N, C, P, O, Zn and Fe for the ZIF / sLFP-800 catalyst prepared in Example 1 of this invention.

[0023] Figure 3 The image shows the total elemental spectrum (Map SumSpectrum) of the ZIF / sLFP-800 catalyst prepared in Example 1 of this invention.

[0024] Figure 4 The figure shows the repeatability test results of the ZIF / sLFP-800 catalyst prepared in Example 1 of this invention in the degradation of sulfamethoxazole (SMX).

[0025] Figure 5 This is a comparison chart of the specific surface area (BET) of the ZIF / sLFP-800 catalyst prepared in Example 1 of the present invention with that of ZIF-800 and sLFP-800 obtained by pyrolysis of ZIF-8 and waste lithium iron phosphate electrode materials at 800℃.

[0026] Figure 6 This is a comparison chart of the degradation performance of sulfamethoxazole (SMX) by catalysts prepared at different carbonization temperatures in Example 2 of the present invention.

[0027] Figure 7 This is a comparison diagram of the degradation of sulfamethoxazole (SMX) by the ZIF / sLFP-800 catalyst prepared in Example 1 of the present invention in different oxidant systems.

[0028] Figure 8This is a comparison chart of the degradation performance of sulfamethoxazole (SMX) by the ZIF / sLFP-800 catalyst prepared in Example 1 of the present invention and the ZIF-800 and sLFP-800 catalysts prepared in Comparative Examples 1 and 2. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are specific operation methods and processes implemented within the framework of the technical solution disclosed in the present invention, and are intended to more clearly illustrate the technical concept, implementation details and technical effects of the present invention. However, they are not intended to limit the scope of protection of the present invention. Any equivalent modifications, substitutions or improvements made based on the core technical solution of the present invention should fall within the scope of protection of the present invention.

[0030] Example 1 (I) Preparation of composite catalysts derived from waste lithium iron phosphate electrode materials coupled with metal-organic frameworks Step 1: Separate the collected waste lithium iron phosphate batteries from the aluminum foil current collector. Take 500 mg of the separated waste lithium iron phosphate electrode material and soak it in 300 mL of NMP for 24 h to remove impurities such as binder and residual electrolyte. Then wash it several times with deionized water and anhydrous ethanol to remove residual impurities on the surface. Place the washed sample in a drying oven at 60℃ for 12 h to allow the surface ethanol to evaporate completely. After drying, pulverize to obtain lithium iron phosphate electrode material powder with uniform particle size for later use.

[0031] Step 2: Weigh 2.322 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O), dissolve it in 180 mL of methanol to prepare solution A. Weigh 2.367 g of 2-methylimidazole (C4H6N2), dissolve it in 180 mL of methanol to prepare solution B. Mix solution A and solution B, stir for 5 min, and then let it stand at room temperature for 24 h. After aging, collect the resulting white precipitate (ZIF-8) by centrifugation, wash it several times with methanol to remove unreacted substances and impurities, then dry it at 60 °C and lightly grind it to obtain ZIF-8.

[0032] Step 3: Weigh 300 mg of ZIF-8 powder prepared in Step 2 and mix it evenly with 50 mg of lithium iron phosphate electrode material powder obtained in Step 1. Place the mixture in a tube furnace and heat it from room temperature to 800℃ at a rate of 5℃ / min under N2 atmosphere, holding it at this temperature for 180 min. After the holding period, allow it to cool naturally to room temperature under N2 atmosphere to obtain the waste lithium iron phosphate electrode material coupled with a metal-organic framework-derived composite catalyst, denoted as ZIF / sLFP-800.

[0033] Figure 1The image shown is a scanning electron microscope (SEM) image of the ZIF / sLFP-800 prepared in this embodiment. It can be seen that the nitrogen-doped carbon network reconstructed after ZIF-8 pyrolysis is uniformly coated on the surface of the generated LiFePO4 particles, which hinders the excessive growth of particle crystals, thereby improving the pore structure and wettability, enhancing mass transfer and accessibility of active sites, and helping to improve the charge transfer efficiency in the catalytic process.

[0034] Figure 2 and Figure 3 The figures show the energy dispersive spectroscopy (EDS) elemental mapping and total elemental spectrum (MapSum Spectrum) distribution of the ZIF / sLFP-800 obtained in this embodiment. As can be seen from the figures, the composite catalyst mainly contains Fe, P, N, C, and O elements. A small amount of residual Zn element can also be observed in the elemental distribution diagram. Furthermore, the distribution of each element in the material is relatively uniform, indicating that the waste electrode material and the ZIF-8 derived nitrogen-doped carbon framework have achieved good coupling.

[0035] (II) Degradation Experiments of Organic Pollutants A 200 mL aqueous solution of 10 mg / L sulfamethoxazole (SMX) was placed in a 500 mL beaker, and 60 mg of oxidant PMS and 60 mg of catalyst ZIF / sLFP-800 were added. The reaction was carried out using a magnetic stirrer under a constant temperature water bath at 25°C. After the reaction started, 2 mL of the reaction solution was taken every 10 min, and the concentration of sulfamethoxazole in the solution was determined by high performance liquid chromatography (HPLC). The test results showed that the removal rate of sulfamethoxazole under the above conditions was as high as 98.5%.

[0036] The sulfamethoxazole degradation shown in this embodiment can be carried out at room temperature. The experiment aims to preliminarily evaluate the removal efficiency of sulfamethoxazole by the ZIF / sLFP-800 and PMS synergistic system. Room temperature conditions are representative and comparable, and can intuitively reflect the practical application potential of this catalytic system under conventional water treatment conditions.

[0037] After completing one degradation experiment, the ZIF / sLFP-800 catalyst was separated from the reaction system by filtration, thoroughly rinsed with deionized water and dried, and then subjected to sulfamethoxazole degradation experiment again under the same conditions to examine its recycling performance and repeatability.

[0038] Figure 4 The figure shows the reproducibility test results of sulfamethoxazole degradation using the ZIF / sLFP-800 catalyst. Figure 4 It can be seen that the prepared composite catalytic material still maintains a high degradation efficiency in five consecutive cycles, indicating that the catalyst has excellent stability and reusability, and its active components did not suffer significant loss or deactivation during multiple cycles.

[0039] Figure 5 This is a comparison of the specific surface area (BET) of the ZIF / sLFP-800 catalyst prepared in this example with that of similar materials. Figure 5 It can be seen that the specific surface area of ​​ZIF / sLFP-800 is 577.993 m². 2 / g, significantly higher than that of ZIF-800 (specific surface area of ​​479.568 m²) obtained solely from the pyrolysis of ZIF-8 at 800℃. 2 / g) and sLFP-800 (specific surface area of ​​17.855 m²) material obtained solely from the pyrolysis of waste lithium iron phosphate electrode material at 800℃. 2 The figure ( / g) indicates that by synergistic pyrolysis of waste electrode materials and ZIF-8, a composite catalytic material with high specific surface area and porous structure can be effectively constructed, providing a structural basis for exposing more active sites and improving PMS activation efficiency.

[0040] Example 2 The preparation method of the composite catalyst derived from waste lithium iron phosphate electrode material coupled with a metal-organic framework in this embodiment is basically the same as that of ZIF / sLFP-800 in Example 1, except for the calcination temperature in step 3. Specifically, the calcination temperatures were set to 500℃, 600℃, 700℃, and 900℃, respectively, while other conditions remained unchanged. The resulting samples were designated as ZIF / sLFP-500, ZIF / sLFP-600, ZIF / sLFP-700, and ZIF / sLFP-900, respectively. Following the method used in the degradation experiment of organic pollutants in Example 1, sulfamethoxazole degradation experiments were conducted using the composite catalysts prepared at the different calcination temperatures described above.

[0041] Figure 6 This is a comparison of the degradation performance of the composite catalysts obtained at different calcination temperatures for sulfamethoxazole. The test results show that the degradation efficiency of SMX exhibits a significant non-monotonic trend with the calcination temperature during catalyst preparation: the degradation efficiency of the catalyst calcined at 500℃ is 78.1%, at 600℃ it is 56.2%, at 700℃ it is 53.8%, at 800℃ it reaches 98.5%, while at 900℃ it decreases to 69.1%. This indicates that the ZIF / sLFP-800 composite catalyst prepared at 800℃ exhibits the best degradation performance, demonstrating that a suitable pyrolysis temperature plays a crucial role in the equilibrium pore structure, the degree of graphitization, and the exposure of active sites.

[0042] Figure 7 This is a comparison of the degradation efficiency of sulfamethoxazole by the ZIF / sLFP-800 catalyst under different oxidant systems. Figure 7It can be seen that in the PMS system, ZIF / sLFP-800 exhibits the highest degradation efficiency for SMX, reaching 98.5%; the degradation efficiency is 94.0% in the persulfate (PDS) system; 61.3% in the periodate (PI) system; and only 19.65% in the hydrogen peroxide (H2O2) system. The results indicate that this composite catalyst has the most significant activation effect on PMS and is preferentially suitable for PMS-based advanced oxidation processes.

[0043] Comparative Example 1 In this comparative example, catalyst ZIF-800 was prepared solely by pyrolysis of ZIF-8 at 800℃. The specific method was as follows: The ZIF-8 powder obtained in step 2 of Example 1 was placed in a tube furnace and heated from room temperature to 800°C at a rate of 5°C / min under a N2 atmosphere, and held at that temperature for 180 min. After the holding period, it was naturally cooled to room temperature under a N2 atmosphere to obtain ZIF-800.

[0044] The degradation experiment of sulfamethoxazole was carried out under the same conditions as in Example 1. The test results showed that the degradation rate of sulfamethoxazole by ZIF-800 was only 61.1%.

[0045] Comparative Example 2 In this comparative example, catalyst sLFP-800 was prepared solely from waste lithium iron phosphate electrode material via pyrolysis at 800℃. The specific method is as follows: The lithium iron phosphate electrode material powder obtained in step 1 of Example 1 was placed in a tube furnace and heated from room temperature to 800°C at a rate of 5°C / min under a N2 atmosphere, and held at that temperature for 180 min. After the holding period, it was naturally cooled to room temperature under a N2 atmosphere to obtain sLFP-800.

[0046] The degradation experiment of sulfamethoxazole was carried out under the same conditions as in Example 1. The test results showed that the degradation rate of sulfamethoxazole by sLFP-800 was only 58.3%.

[0047] Figure 8 This is a comparison chart showing the degradation performance of sulfamethoxazole by the catalysts prepared in Comparative Example 1, Comparative Example 2, and Example 1. Figure 8 It is evident that the degradation efficiency of ZIF / sLFP-800 within 90 min is as high as 98.5%, which is significantly better than that of ZIF-800 (61.1%) and sLFP-800 (58.3%). This fully demonstrates that the composite structure synergistically constructed by waste electrode materials and ZIF-8 has a significant synergistic effect on PMS activation and organic pollutant degradation.

[0048] The above embodiments are merely several specific implementations of the present invention. Although the processes and parameters are relatively specific and detailed, they should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, without departing from the core concept and spirit of the present invention, equivalent substitutions or adjustments can be made to the types and proportions of raw materials, calcination temperatures, times, and types of organic pollutants in the embodiments. Such equivalent modifications and improvements should all fall within the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A composite catalyst derived from waste lithium iron phosphate electrode material coupled with a metal-organic framework, characterized in that: The composite catalyst comprises a core active component and a support framework. The core active component is LiFePO4 particles reconstructed from waste lithium iron phosphate electrode materials after pyrolysis. The support framework is a nitrogen-doped porous carbon framework generated by the pyrolysis of zinc-based zeolite imidazole framework ZIF-8. The LiFePO4 particles are coated by the nitrogen-doped porous carbon framework and uniformly dispersed in its porous structure.

2. The composite catalyst derived from waste lithium iron phosphate electrode material coupled with a metal-organic framework according to claim 1, characterized in that: The composite catalyst has an elemental composition including Fe, P, Li, C, N, and O.

3. The composite catalyst derived from waste lithium iron phosphate electrode material coupled with a metal-organic framework according to claim 1, characterized in that: The specific surface area of ​​the composite catalyst is ≥500 m². 2 / g.

4. The composite catalyst derived from waste lithium iron phosphate electrode material coupled with a metal-organic framework according to claim 1, characterized in that: When preparing the composite catalyst, the mass ratio of ZIF-8 to waste lithium iron phosphate electrode material powder is 5 to 7:

1.

5. The composite catalyst derived from waste lithium iron phosphate electrode material coupled with a metal-organic framework according to claim 1, characterized in that: The temperature for pyrolysis of waste lithium iron phosphate electrode materials mixed with ZIF-8 is 500~900℃, and the holding time is 120~180 min.

6. A method for preparing the composite catalyst according to any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Pretreatment of waste lithium iron phosphate electrode materials: The collected waste lithium iron phosphate electrode material was immersed in N-methylpyrrolidone to remove the binder and residual electrolyte. Then it was washed with deionized water and anhydrous ethanol in sequence, dried and crushed to obtain lithium iron phosphate electrode material powder. Step 2, Preparation of ZIF-8: Zinc nitrate hexahydrate was dissolved in methanol to obtain solution A, and 2-methylimidazole was dissolved in methanol to obtain solution B. Solution A and solution B were mixed and stirred and aged at room temperature. The white precipitate was collected, washed with methanol and dried to obtain ZIF-8. Step 3, Compounding and Calcination: The ZIF-8 obtained in step 2 was mixed evenly with the lithium iron phosphate electrode material powder obtained in step 1, placed in an inert atmosphere, heated to 500~900℃, kept at that temperature for 120~180 min, and then naturally cooled to obtain a composite catalyst derived from waste lithium iron phosphate electrode material coupled with a metal-organic framework.

7. The preparation method according to claim 6, characterized in that, In step 2: 2.322~6.966 g of zinc nitrate hexahydrate was dissolved in 180~360 mL of methanol to obtain solution A; 2.367~7.101 g of 2-methylimidazole was dissolved in 180~360 mL of methanol to obtain solution B; the aging time at room temperature was 20~30 h.

8. The preparation method according to claim 6, characterized in that, In step 3, the inert gas used is argon or nitrogen, and the heating rate is 5-10℃ / min.

9. An application of the composite catalyst according to any one of claims 1 to 5 for the treatment of organic pollutants, characterized in that: The composite catalyst was used as a heterogeneous catalyst and synergistically with persulfate to construct a Fenton-like reaction system for the degradation of organic pollutants in water.

10. The application according to claim 9, characterized in that: The organic pollutant is at least one of antibiotics, phenols, halogenated phenols, dyes, and endocrine disruptors.

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