A high-temperature self-circulation iron-based slow-release catalyst, a preparation method and application thereof

Abstract

The present application relates to the technical field of advanced oxidation technology and environmental functional material, and specifically discloses a high-temperature self-circulation iron-based slow-release catalyst as well as a preparation method and application thereof.The catalyst comprises, from inside to outside, a substrate layer, an iron slow-release layer and a protective layer;the substrate layer is a high-temperature-resistant porous ceramic framework with a spinel structure;the iron slow-release layer is an Fe 0 @amorphous Fe2O3 core-shell structure microcapsule; and the protective layer is an oxygen vacancy-rich CuO-CoO electron-mediated functional layer.The preparation method is simple in process, mild in condition and easy to scale up.The prepared catalyst can efficiently and durably activate persulfate or hydrogen peroxide under medium-high temperature conditions, and especially exhibits optimal activation performance for peroxymonosulfate (PDS).The present application provides an efficient, stable and environmentally friendly new-type catalytic material and technical solution for long-acting and deep treatment of high-concentration and refractory industrial wastewater.

Description

Technical Field

[0001] This invention belongs to the field of advanced oxidation technologies (AOPs) and environmental functional materials, specifically relating to a catalyst for activating peroxides to degrade organic pollutants, particularly a sandwich-structured iron-based slow-release catalyst with high-temperature self-circulation function, its preparation method, and its application. Background Technology

[0002] Advanced oxidation technologies (AOPs) have become a research hotspot in water treatment due to their ability to generate strong oxidizing free radicals, which can effectively degrade recalcitrant organic pollutants. Among them, those based on sulfate free radicals (SO4·) are particularly promising. - AOPs (autogenous radicals) exhibit a broader application prospect than traditional hydroxyl radical (·OH) technology due to their advantages such as longer free radical lifetime, wider pH applicable window, and insensitivity to complex water background disturbances. Persulfates (PDS, PMS) and hydrogen peroxide (H2O2) are commonly used oxidants, but their own oxidation capacity is limited and they require catalyst activation.

[0003] Currently, catalysts used to activate the aforementioned oxidants are mainly divided into two categories: homogeneous and heterogeneous. Among them, homogeneous Fenton and Fenton-like technologies (such as Fe) 2+ While the PMS system possesses excellent catalytic activity, it suffers from three inherent and unavoidable drawbacks: First, its applicable pH range is limited, with the optimal reaction pH typically only between 2 and 4. In actual wastewater treatment, frequent pH adjustments are necessary, increasing operational complexity and significantly raising treatment costs. Second, it easily triggers secondary pollution from iron sludge, and the Fe produced during the reaction... 3+ Under near-neutral conditions, a large amount of iron-containing sludge (i.e., iron sludge) will be formed, which will not only cause catalyst loss, but also bring secondary pollution problems, and the subsequent sludge treatment is difficult; thirdly, the catalyst is difficult to reuse, homogeneous iron ions need to be consumed at once, and the recovery is difficult, which directly leads to high treatment costs.

[0004] To overcome these challenges, heterogeneous iron-based catalysts (such as iron oxides and supported iron catalysts) have become a research hotspot and have attracted widespread attention. However, the practical application of existing heterogeneous catalysts still faces three core challenges: first, the active components are easily dissolved and deactivated. During the reaction, active iron species (Fe... 2 ⁺ / Fe 3 (⁺) It easily detaches and dissolves from the catalyst framework, which not only leads to rapid decline in catalyst activity (i.e., deactivation), but also, to some extent, reproduces the inherent drawbacks of homogeneous systems. Secondly, Fe... 3 + / Fe 2 + The cycle efficiency is relatively low. In heterogeneous catalytic reactions, Fe... 3+ To Fe 2+The transformation rate of the active iron species usually becomes the limiting factor of the reaction, and the insufficient electron transfer efficiency further leads to the blocked catalytic cycle, which ultimately weakens the long-term degradation performance of the catalyst. Thirdly, the high-temperature adaptability is poor. The temperature of many industrial wastewater (such as refining and coking wastewater) is relatively high (usually 60-90 DEG C), and the activity component of the conventional heterogeneous catalytic material not only intensifies the dissolution phenomenon, but also is easy to be damaged and unstable, and finally the service life of the catalyst is greatly shortened. SUMMARY

[0005] In order to solve the technical problems of the prior art, the application provides a sandwich structure iron-based slow-release catalyst with high-temperature self-circulation function and a preparation method and application thereof. The catalyst realizes the accurate regulation of the release kinetics of the active iron species and the efficient circulation between the solid and liquid phases through the unique microstructure design, and fundamentally solves the bottleneck problems of the homogeneous catalyst and the heterogeneous catalyst in the application. The application is used for the mineralization of actual industrial wastewater, and the mineralization removal rate of the petroleum chemical wastewater, the steel coking wastewater and the printing and dyeing wastewater can reach more than 70%.

[0006] The core of the catalyst lies in the innovative sandwich type microstructure design of the "matrix layer-iron slow-release layer-protection layer". The structure realizes the accurate regulation of the release kinetics of the active iron species (such as Fe 2 + / Fe 3 +) through the interface engineering at the molecular level. The matrix layer provides mechanical support for the catalyst and serves as the initial iron source; the iron slow-release layer controls the slow and continuous release of the iron ions at high temperature through the chemical bonding and physical binding; and the outermost protection layer effectively avoids the rapid dissolution and invalid loss of the active component, and guarantees the long-acting and stability of the catalytic reaction. The unique high-temperature self-circulation characteristic realizes the dynamic circulation and efficient regeneration of the active iron center between the surface of the solid catalyst and the liquid reaction system, and fundamentally solves the bottleneck problems of the narrow pH application range, the secondary pollution of iron sludge, the difficult reuse of the catalyst and the like in the homogeneous Fenton / Fenton-like technology.

[0007] In order to achieve the above object, the application adopts the following technical scheme:

[0008] The first object of the application is to provide a high-temperature self-circulation iron-based slow-release catalyst, which comprises a matrix layer, an iron slow-release layer and a protection layer arranged in sequence from inside to outside; the matrix layer is a high-temperature resistant porous ceramic skeleton with a spinel structure; the iron slow-release layer is a Fe 0 @amorphous Fe2O3 core-shell structure microcapsule loaded on the matrix layer, which is used for controlling the slow and continuous release of the iron ions at high temperature and maintaining Fe 3+ / Fe 2+Cycle; the protective layer is a CuO-CoO electron-mediated functional layer rich in oxygen vacancies, used to prevent the ineffective loss of active iron species and accelerate electron transfer.

[0009] In some embodiments of the present invention, the substrate layer is made of porous magnesium aluminum spinel (MgAl2O4) microspheres with a particle size of 50-100 μm, a pore size of 50±10 nm, and a specific surface area of ​​not less than 80 m². 2 / g.

[0010] In some embodiments of the present invention, the Fe 0 @Amorphous Fe2O3 core-shell structured microcapsules with Fe 0 The core is composed of Fe2O3 layers obtained through gradient calcination, which form the outer shell.

[0011] In some embodiments of the present invention, the molar ratio of Cu to Co in the CuO-CoO electron-mediated functional layer is (0.8-1.2):1.

[0012] A second objective of this invention is to provide a method for preparing the aforementioned high-temperature self-circulating iron-based slow-release catalyst, comprising the following steps:

[0013] (1) Mix magnesium source, aluminum source and trivalent iron source in water-ethanol mixed solvent, add complexing agent, heat and stir to obtain sol;

[0014] (2) The sol obtained in step (1) is spray-dried and granulated to obtain porous precursor microspheres;

[0015] (3) The porous precursor microspheres obtained in step (2) are subjected to gradient calcination in an oxygen atmosphere to selectively oxidize the iron species on the surface to form Fe. 0 @Amorphous Fe2O3 core-shell microcapsules were used to transform the matrix material into a magnesium aluminum spinel structure, resulting in microspheres;

[0016] (4) Using vapor deposition technology, copper and cobalt elements are introduced onto the surface of the microspheres obtained in step (3), and then the microspheres are heated and activated in a reducing atmosphere to form a CuO-CoO electron-mediated functional layer on the surface of the microspheres, thereby obtaining the high-temperature self-circulating iron-based slow-release catalyst.

[0017] In some embodiments of the present invention, in step (1), the molar ratio of Mg:Al:Fe is (0.8-1.2):(0.8-1.2):(0.2-0.8).

[0018] The molar ratio of the complexing agent to the metal ions is (1.2-1.8):1;

[0019] The heating and stirring temperature is 50-70℃;

[0020] The magnesium source, aluminum source, and ferric source are independently selected from one or more of nitrates, sulfates, or chlorides;

[0021] The complexing agent is citric acid;

[0022] The volume ratio of water to ethanol in the water-ethanol mixed solvent is (1:1) to (3:1).

[0023] The sol has a viscosity of 80-90 cP and a pH value of 3.0-5.0.

[0024] In some embodiments of the present invention, in step (2), the inlet temperature of the spray dryer is 180-220°C, the outlet temperature is ≤90°C, and the atomization pressure is 0.2-0.4 MPa.

[0025] In some embodiments of the present invention, in step (3), the volume fraction of oxygen in the oxygen atmosphere is 0.1%-1%;

[0026] The gradient calcination procedure is as follows: first, hold at 180-220℃ for 20-40 minutes, then raise the temperature to 750-850℃ at a rate of 3-8℃ / min and hold for 1-3 hours.

[0027] In some embodiments of the present invention, in step (4), the copper element is derived from one or more of copper acetylacetone, acetylacetone metal compound, and hexafluoroacetylacetone metal compound, and the deposition temperature of the copper element is 160-200℃.

[0028] Furthermore, this includes copper β-diketone complexes such as copper acetylacetonate and copper hexafluoroacetylacetonate.

[0029] The cobalt element is derived from one or more of cobalt acetylacetonate, acetylacetonate metal compounds, and hexafluoroacetylacetonate metal compounds, and the deposition temperature of the cobalt element is 140-160℃;

[0030] Furthermore, this includes β-diketone complexes of cobalt, such as cobalt acetylacetonate and bis(hexafluoroacetylacetonate)cobalt.

[0031] The total deposition time for copper and cobalt is 30-60 minutes;

[0032] The molar ratio of copper to cobalt is (0.8-1.2):1;

[0033] The reducing atmosphere is a mixture of hydrogen and an inert gas, wherein the hydrogen component is 5%-15%.

[0034] The heating activation treatment temperature is 350-450℃, and the time is 1-3 hours.

[0035] A third objective of this invention is to provide the application of the aforementioned high-temperature self-circulating iron-based slow-release catalyst in the catalytic degradation of organic pollutants in water by heated activated oxidants.

[0036] In some embodiments of the present invention, the temperature for heating activation is 50-90°C, and the oxidant is selected from persulfate or hydrogen peroxide; the present invention removes organic pollutants by mineralizing and degrading recalcitrant organic matter in wastewater.

[0037] In some embodiments of the present invention, the oxidant is preferably persulfate (PDS, PMS).

[0038] The mass concentration ratio of the oxidant, the high-temperature self-circulating iron-based slow-release catalyst and the organic pollutant is (50-1000):(30-600):(25-60).

[0039] The wastewater originates from petrochemical, steel coking, and printing and dyeing industries.

[0040] This invention presents a high-temperature self-circulating sandwich-structured iron-based slow-release catalyst. The core of this catalyst lies in its innovative "matrix layer - iron slow-release layer - protective layer" sandwich-like microstructure design. The matrix layer provides stable mechanical support for the entire catalyst and serves as the initial iron source for the iron slow-release layer. The iron slow-release layer, through chemical bonding and physical confinement, controls the slow and continuous release of iron ions at high temperatures, utilizing the core Fe... 0 The reducing property of Fe is maintained 3+ / Fe 2+ The core-shell structure is formed through in-situ gradient calcination of the matrix layer surface, resulting in a highly efficient catalytic cycle. The protective layer prevents the rapid dissolution and ineffective loss of internal active iron species, while also serving as an electron transport channel to significantly accelerate interfacial electron transfer rates, ensuring the long-term effectiveness and stability of the catalytic reaction.

[0041] Beneficial effects and technical advantages of the present invention

[0042] Compared with existing technologies, the sandwich-structured iron-based slow-release catalyst, its preparation method, and its application provided by this invention have the following significant advantages and beneficial effects:

[0043] 1. Innovative Sandwich Structure Design: This invention achieves functional separation and synergy through a progressive design of "matrix layer - iron slow-release layer - protective layer". The matrix layer provides support, the slow-release layer precisely controls release, and the protective layer prevents loss and accelerates mass transfer. The three layers work together to resolve the contradiction between activity, stability, and long-lasting effect.

[0044] 2. This invention achieves precise slow release and efficient recycling of iron ions: a unique Fe... 0@Amorphous Fe2O3 core-shell structure slowly and continuously releases Fe through physicochemical processes at high temperatures. 2+ / Fe 3+ This avoids an initial explosive dissolution. The Fe core... 0 It can act as a built-in reducing agent to convert the generated Fe 3+ Instantaneous reduction to Fe 2 ⁺, achieving high-temperature self-circulation (Fe) on the catalyst surface. 3+ / Fe 2+ (Circulation), which greatly improves the utilization efficiency of iron atoms and the persistence of the reaction.

[0045] 3. Excellent electron transport capability: The outermost CuO-CoO functional layer of this invention is rich in oxygen vacancies and has excellent electron-mediating capability. It can greatly accelerate the transfer rate of interfacial electrons from oxidants or contaminants to Fe species inside the catalyst, further enhancing the Fe... 3+ The reduction process breaks the rate-limiting step of the reaction.

[0046] 4. Excellent high-temperature stability and anti-leakage properties: The protective layer of this invention effectively isolates the internal active components from direct contact with external water, greatly inhibiting the ineffective dissolution and loss of iron species at high temperatures. The robust spinel matrix ensures the structural stability of the catalyst under high-temperature conditions, making it particularly suitable for treating medium- and high-temperature industrial wastewater.

[0047] 5. Broad-spectrum degradation ability and high mineralization rate: This catalytic system can efficiently activate persulfate to produce SO4· - It is dominated by a variety of active oxygen species, which show excellent degradation effects on a variety of recalcitrant organic compounds (such as phenols, dyes, polycyclic aromatic hydrocarbons, etc.). The TOC mineralization rate of typical industrial wastewater can reach more than 70%, achieving deep purification.

[0048] 6. Environmentally friendly and economical: It fundamentally avoids secondary pollution from iron sludge, and the catalyst can be reused for a long time, reducing operating costs. The preparation method is simple, the conditions are mild, and it is easy to scale up production, showing broad prospects for industrial application. Attached Figure Description

[0049] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0050] Figure 1 This invention relates to the preparation of the iron-based slow-release catalyst obtained in the embodiments of the present invention and its application in actual wastewater.

[0051] Figure 2 These are the test results of the iron-based slow-release catalyst obtained in the embodiments of the present invention in practical water applications to evaluate its wide pH range applicability;

[0052] Figure 3 This is a diagram of the long-term stability testing device for the iron-based slow-release catalyst obtained in the embodiments of the present invention;

[0053] Figure 4 This is a test and evaluation of the long-term stability of the iron-based slow-release catalyst obtained in the embodiments of the present invention;

[0054] Figure 5 The results are the evaluation results of the active species sustained release of the iron-based sustained-release catalyst obtained in Example 1 of the invention. Detailed Implementation

[0055] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0056] Example 1

[0057] This embodiment provides a method for preparing an iron-based slow-release catalyst and its application in practical water.

[0058] I. Catalyst Preparation:

[0059] (1) Weigh magnesium nitrate, aluminum nitrate and ferric nitrate nonahydrate according to the Mg:Al:Fe molar ratio of 1.0:1.0:0.5, dissolve them in a mixed solvent of water and ethanol in a volume ratio of 2:1 to obtain a mixed solution.

[0060] (2) Add citric acid complexing agent to the mixed solution obtained in step (1), and the total molar ratio of citric acid to metal ions is 1.5:1. Stir at 60°C for 4 hours to form a homogeneous sol with a viscosity of about 85 cP and a pH of 4.0.

[0061] (3) Spray dry the sol obtained in step (2) to granulate it, control the inlet temperature to be 200℃, the atomization pressure to be 0.3 MPa, and the outlet temperature to be 85℃, to obtain porous precursor microspheres.

[0062] (4) The porous precursor microspheres obtained in step (3) were placed in a tube furnace and subjected to gradient calcination in a mixed atmosphere of argon and oxygen (0.5% O2 volume fraction); wherein the gradient calcination conditions were as follows: first, the temperature was held at 200℃ for 30 minutes, then the temperature was increased to 800℃ at a rate of 5℃ / min and held for 2 hours, and after natural cooling, Fe-loaded microspheres were obtained. 0 @Amorphous Fe2O3 core-shell structured magnesium aluminum spinel-based microspheres, with a particle size of 60 μm, a pore size of 52 nm, and a specific surface area of ​​56 m². 2 / g.

[0063] (5) Using a dual-source vapor deposition system, the microspheres obtained in step (4) were exposed to copper acetylacetone vapor at 180°C for 30 minutes, and then exposed to cobalt acetylacetone vapor at 150°C for 30 minutes, controlling the total deposition molar ratio of Cu to Co to be 1:1.

[0064] (6) Finally, the deposited microspheres were heat-treated at 400°C for 2 hours in a 10% H2 / Ar mixed atmosphere and then naturally cooled to obtain the sandwich structure iron-based slow-release catalyst.

[0065] II. Application of catalysts:

[0066] (1) Take a certain petrochemical wastewater (TOC = 105 mg / L), dyeing and printing wastewater (TOC = 98 mg / L) and iron and steel coking wastewater (TOC = 110 mg / L), and adjust the water temperature to 70℃.

[0067] (2) The sandwich-structured iron-based slow-release catalyst obtained in this invention was added to the wastewater to a concentration of 50 mg / L, and sodium persulfate (PDS) was added to a concentration of 20 mM. At the same time, three blank experiments (without catalyst) were set up. The reaction was carried out at 70℃ and 180 rpm for 120 minutes.

[0068] (3) The test results show that the TOC removal rates of petrochemical wastewater, dyeing and printing wastewater, and iron and steel coking wastewater are 78.5%, 73.2%, and 75.6%, respectively, demonstrating excellent mineralization capabilities. In contrast, the TOC removal rates of thermal activation alone (without catalyst addition) are only 32.1%, 31.6%, and 33.5%. Specific implementation effect diagrams are shown below. Figure 1 As shown.

[0069] Example 2

[0070] This embodiment provides a test to evaluate the wide pH range applicability of the sandwich-structured iron-based slow-release catalyst in practical water applications, as detailed below:

[0071] Petrochemical wastewater, identical to that in the previous example, was used. The initial pH was adjusted to 3.0, 5.0, 7.8 (raw water), and 9.0, respectively, using dilute H₂SO₄ or NaOH solution. At 70°C, 50 mg / L of the sandwich-structured iron-based slow-release catalyst and 20 mM of PDS were added, and the reaction was allowed to proceed for 120 minutes. Samples were taken at 0, 30, 60, 90, and 120 minutes to detect TOC. The experimental results are shown in [Figure number missing]. Figure 2The test results showed that the TOC removal rates were 76.8%, 77.5%, 78.5%, and 72.3% under pH conditions of 3.0, 5.0, 7.8 (raw water), and 9.0, respectively. This demonstrates that the catalyst of this invention can maintain high efficiency and stable catalytic performance under acidic, neutral, and weakly alkaline conditions, and its pH applicable range is much wider than that of traditional Fenton technology.

[0072] Example 3

[0073] This embodiment provides a long-term stability test for an iron-based slow-release catalyst, as detailed below:

[0074] (1) Reference Figure 3 A continuous flow reactor (reactor volume 300 mL) was constructed to treat actual petrochemical wastewater with a TOC of 105 mg / L (pH=7.8). The flow rate was controlled at 2.5 mL / min, and the reaction temperature was 70℃. PDS was continuously added at the inlet to maintain its concentration in the reactor at 20 mM, and 0.2 g of the catalyst obtained in Example 1 was added at one time (equivalent to an initial concentration of ~16.7 g / L, but the actual effective concentration in the cycle is similar to that in the batch experiment).

[0075] (2) The system was run continuously for 72 hours, and the TOC of the effluent was measured at intervals. The experimental results are shown in […]. Figure 4 The results showed that after the system stabilized, the TOC removal rate could be maintained between 68% and 72%, and there were no signs of catalyst deactivation, demonstrating the excellent long-term stability and engineering application potential of this invention.

[0076] Comparative Example 1

[0077] This comparative example provides a catalyst without a protective layer (a conventional iron-based material, without a deposited CuO-CoO protective layer):

[0078] The catalyst preparation method is similar to that in Example 1, except that steps (5) and (6) are missing, resulting in a comparative catalyst with only a matrix layer and an iron slow-release layer.

[0079] The same petrochemical wastewater was treated under the exact same application conditions as in Example 3 (70°C, catalyst 50 mg / L, PDS 20 mM, pH=7.8, reaction time 120 min). The experimental results are shown below. Figure 4 The test results showed that the initial TOC removal rate was high, but the final rate was only 55.2%. During the reaction, obvious turbid yellow iron leaching was observed, indicating severe loss of active components. Compared with Example 1 (78.5%) (clear appearance), the performance difference was significant, demonstrating the crucial role of the protective layer in preventing the loss of active components and maintaining long-term stability.

[0080] Comparative Example 2

[0081] This comparative example provides a traditional homogeneous Fenton process, as shown below:

[0082] The same petrochemical wastewater as in Example 1 was used, and its pH was adjusted to 3.0 with concentrated sulfuric acid. FeSO4·7H2O was added as a catalyst at a dosage of 200 mg / L (based on Fe). 2+ The mixture was prepared by adding H2O2 as an oxidant at a mass ratio of 1:2 (COD:H2O2 = 720 mg / L). The reaction was carried out at 25°C and 180 rpm for 120 minutes. After the reaction, the pH of the system was adjusted back to neutral with NaOH solution, and iron sludge was precipitated by sedimentation. The TOC of the supernatant was measured, showing a removal rate of 42.3%. However, a large amount of iron-containing sludge requiring further treatment was generated. This comparative example fully exposes the problems of traditional Fenton technology, such as narrow pH applicability, secondary pollution from iron sludge, and limited treatment efficiency, highlighting the comprehensive advantages of this invention.

[0083] Iron slow-release experiment

[0084] The iron-based slow-release catalyst obtained in Example 1 was subjected to a slow-release experiment, as detailed below: 20 mM PDS and 50 mg / L of the iron-based slow-release catalyst were added to petrochemical wastewater with a TOC of 105 mg / L to evaluate its mineralization effect on TOC, and the iron dissolution on the catalyst surface was monitored simultaneously. The results are as follows: Figure 5 As shown, the catalyst continuously released Fe during the 60-hour experiment. 2+ The concentration remained consistently low, within the range of 0.4-2.2 mg / L. This was due to Fe... 2+ It is a key active species in the thermally activated PDS process, and its stable release and conversion effectively ensure the continuous removal of TOC. Figure 4 This demonstrates that the catalyst possesses excellent and stable iron-releasing performance.

[0085] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A high-temperature self-circulating iron-based slow-release catalyst, characterized in that, The structure comprises, from the inside out, a matrix layer, an iron-releasing layer, and a protective layer; the matrix layer is a high-temperature resistant porous ceramic framework with a spinel structure; the iron-releasing layer is Fe supported on the matrix layer. 0 @Amorphous Fe2O3 core-shell structured microcapsules; the protective layer is a CuO-CoO electron-mediated functional layer rich in oxygen vacancies.

2. The high-temperature self-circulating iron-based slow-release catalyst according to claim 1, characterized in that, The substrate layer is made of porous magnesium aluminum spinel (MgAl2O4) microspheres with a particle size of 50-100 μm, a pore size of 50±10 nm, and a specific surface area of ​​not less than 80 m². 2 / g.

3. The high-temperature self-circulating iron-based slow-release catalyst according to claim 1, characterized in that, The Fe 0 @Amorphous Fe2O3 core-shell structured microcapsules with Fe 0 The core is composed of Fe2O3 layers obtained through gradient calcination, which form the outer shell.

4. The high-temperature self-circulating iron-based slow-release catalyst according to claim 1, characterized in that, In the CuO-CoO electron-mediated functional layer, the molar ratio of Cu to Co is (0.8-1.2):

1.

5. A method for preparing a high-temperature self-circulating iron-based slow-release catalyst as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Mix magnesium source, aluminum source and trivalent iron source in water-ethanol mixed solvent, add complexing agent, heat and stir to obtain sol; (2) The sol obtained in step (1) is spray-dried and granulated to obtain porous precursor microspheres; (3) The porous precursor microspheres obtained in step (2) are subjected to gradient calcination in an oxygen atmosphere to selectively oxidize the iron species on the surface to form Fe. 0 @Amorphous Fe2O3 core-shell microcapsules were used to obtain microspheres; (4) Using vapor deposition technology, copper and cobalt elements are introduced onto the surface of the microspheres obtained in step (3), and then the microspheres are heated and activated in a reducing atmosphere to form a CuO-CoO electron-mediated functional layer on the surface of the microspheres, thereby obtaining the high-temperature self-circulating iron-based slow-release catalyst.

6. The preparation method according to claim 5, characterized in that, In step (1), the molar ratio of Mg:Al:Fe is (0.8-1.2):(0.8-1.2):(0.2-0.8). The total molar ratio of the complexing agent to the metal ions is (1.2-1.8):1; The heating and stirring temperature is 50-70℃; The magnesium source, aluminum source, and ferric source are independently selected from one or more of nitrates, sulfates, or chlorides; The complexing agent is citric acid; The volume ratio of water to ethanol in the water-ethanol mixed solvent is (1:1) to (3:1). The sol has a viscosity of 80-90 cP and a pH value of 3.0-5.

0.

7. The preparation method according to claim 5, characterized in that, In step (2), the inlet temperature of the spray dryer is 180-220℃, the outlet temperature is ≤90℃, and the atomization pressure is 0.2-0.4 MPa.

8. The preparation method according to claim 5, characterized in that, In step (3), the volume fraction of oxygen in the oxygen atmosphere is 0.1%-1%; The gradient calcination procedure is as follows: first, hold at 180-220℃ for 20-40 minutes, then raise the temperature to 750-850℃ at a rate of 3-8℃ / min and hold for 1-3 hours.

9. The preparation method according to claim 5, characterized in that, In step (4), the copper element is derived from one or more of acetylacetone metal compounds and hexafluoroacetylacetone metal compounds, and the deposition temperature of the copper element is 160-200℃. The cobalt element is derived from one or more of acetylacetone metal compounds and hexafluoroacetylacetone metal compounds, and the deposition temperature of the cobalt element is 140-160℃. The total deposition time for copper and cobalt is 30-60 minutes; The molar ratio of copper to cobalt is (0.8-1.2):1; The reducing atmosphere is a mixture of hydrogen and an inert gas, wherein the hydrogen component is 5%-15%. The heating activation treatment temperature is 350-450℃, and the time is 1-3 hours.

10. The application of a high-temperature self-circulating iron-based slow-release catalyst as described in any one of claims 1-4 in the catalytic degradation of organic pollutants in water by a heated oxidant.

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