Calcium-iron complex oxide ozone catalyst, method for preparing the same, and use thereof

Abstract

The application provides a calcium-iron composite oxide ozone catalyst and a preparation method and application thereof, and belongs to the technical field of catalyst preparation and water treatment. The preparation method of the calcium-iron composite oxide ozone catalyst comprises the following steps: adding a complexing regulator into a calcium-iron mixed salt solution, adjusting the pH of the mixed system to be acidic to obtain a calcium-iron precursor solution; adding a composite precipitant solution into the calcium-iron precursor solution, adjusting the pH of the mixed system to be alkaline to perform a co-precipitation reaction to obtain a co-precipitation precursor; performing a crystallization reaction on the co-precipitation precursor; after the crystallization reaction is completed, the precipitate is collected after cooling and standing; the precipitate is washed and dried to obtain a calcium-iron precursor powder; the calcium-iron precursor powder is mixed with a pyrolysis type defect regulator and then is subjected to staged calcination to obtain the calcium-iron composite oxide ozone catalyst; and the composite precipitant comprises a hydroxyl group main precipitant and a carbonate auxiliary precipitant.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation and water treatment technology, and particularly relates to a calcium-iron composite oxide ozone catalyst, its preparation method and application. Background Technology

[0002] Ozone catalytic oxidation technology, as a rapidly developing advanced wastewater treatment technology, introduces a catalyst into the ozone system to promote ozone decomposition and generate highly reactive hydroxyl radicals (·OH), thereby achieving efficient mineralization and removal of recalcitrant organic pollutants. This treatment technology has advantages such as strong oxidation capacity and no secondary pollution, and has broad application prospects in the treatment of industrial wastewater such as dyeing and printing wastewater, pharmaceutical wastewater, and coking wastewater.

[0003] Currently, ozone catalysts are mainly divided into two categories: homogeneous catalysts and heterogeneous catalysts. While homogeneous catalysts (such as metal ion solutions) possess high catalytic activity, they suffer from problems such as difficulty in catalyst recovery and the potential for secondary pollution. Heterogeneous catalysts mainly include metal oxides (such as manganese dioxide (MnO2), titanium dioxide (TiO2), and ferric oxide (Fe2O3), supported noble metals (such as platinum / alumina (Pt / Al2O3) and ruthenium / cerium oxide (Ru / CeO2),) and composite metal oxide catalysts.

[0004] Iron (Fe)-based materials have attracted increasing attention in the field of catalysis due to their wide availability, low cost, and environmental friendliness. Fe sites possess moderate adsorption energy for ozone (O3) molecules, effectively capturing and activating O3 in solution, and also effectively promoting the generation of hydroxyl radicals. Calcium (Ca), as an alkaline earth metal, has alkaline sites that promote the chemisorption of O3, making O3 more easily decomposed on the catalyst surface, thus overcoming the limitation of single-metal oxide surfaces having only one acid-base affinity.

[0005] However, existing calcium-iron-based ozone catalysts face the problem of calcium ion leaching in practical applications. During wastewater treatment, especially under acidic conditions, calcium ions easily dissolve and enter the water body, leading not only to the loss of active components and a decline in catalytic performance of the calcium-iron-based catalyst, but also to increased water hardness, affecting subsequent treatment processes. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a calcium-iron composite oxide ozone catalyst, its preparation method, and its application, aiming to at least partially solve the above-mentioned technical problems. The technical solution provided by this invention is as follows.

[0007] As a first aspect of the present invention, a method for preparing a calcium-iron composite oxide ozone catalyst is provided, comprising: adding a complexing regulator to a calcium-iron mixed salt solution and adjusting the pH of the mixed system to acidic to obtain a calcium-iron precursor solution; adding a composite precipitant solution to the calcium-iron precursor solution and adjusting the pH of the mixed system to alkaline to carry out a coprecipitation reaction to obtain a coprecipitated precursor; subjecting the coprecipitated precursor to a crystallization reaction; after the crystallization reaction is completed, cooling and settling are performed to collect the precipitate; the precipitate is washed and dried to obtain a calcium-iron precursor powder; the calcium-iron precursor powder is mixed with a pyrolysis-type defect regulator and then calcined in stages to obtain a calcium-iron composite oxide ozone catalyst; wherein the composite precipitant includes a hydroxide primary precipitant and a carbonate auxiliary precipitant.

[0008] As a second aspect of the present invention, a calcium-iron composite oxide ozone catalyst is provided, which is prepared by the above-described method for preparing the calcium-iron composite oxide ozone catalyst, wherein the calcium-iron composite oxide is Ca2Fe2O5.

[0009] As a third aspect of the present invention, an application of a calcium-iron composite oxide ozone catalyst in the catalytic degradation of organic pollutants by ozone is provided.

[0010] Based on the above technical solution, the calcium-iron composite oxide ozone catalyst, its preparation method, and its application provided by the present invention have at least one of the following beneficial effects:

[0011] (1) In this invention, a complexing regulator is added to the calcium-iron mixed salt solution and the pH of the mixed system is adjusted to acidity, on the one hand to regulate the calcium ion concentration (Ca). 2+ ) and ferric ions (Fe 3+ The coordination state of ) reduces the amount of Ca in the subsequent coprecipitation reaction. 2+ with Fe 3+ The difference in precipitation rate, on the other hand, ensures that the metals in the calcium-iron precursor solution are in an ionic state. A composite precipitant solution is added to the calcium-iron precursor solution. The hydroxide ion primary precipitant adjusts the pH of the mixture to alkaline and promotes the hydrolysis and co-precipitation reaction of the calcium-iron precursor solution, while the carbonate ion auxiliary precipitant reduces the calcium content through reversible coordination with calcium and iron ions and slow-release precipitation. 2+ with Fe 3+The difference in precipitation rate inhibits localized rapid nucleation and particle agglomeration. After adding the composite precipitant solution, the crystallization reaction promotes the nucleation of the co-precipitated precursor and the uniform growth of crystals, ensuring sufficient dispersion of calcium and iron elements and avoiding the formation of an independent calcium phase or elemental segregation due to differences in precipitation rate. After the crystallization reaction is completed, the obtained precipitate is washed and dried to obtain calcium-iron precursor powder. Subsequently, the calcium-iron precursor powder is mixed with a pyrolysis-type defect regulator and calcined in stages, causing the calcium-iron precursor powder to undergo solid-phase rearrangement and form a Ca2Fe2O5 dominant crystalline phase and a continuous calcium-oxygen-iron (Ca-O-Fe) bonded network structure. Thus, the calcium-iron composite oxide ozone catalyst (referred to as Ca2Fe2O5 catalyst) obtained by the present invention through complexation regulator regulation, co-precipitation reaction, crystallization reaction, and calcination treatment possesses a stable Ca-O-Fe bonded network structure, uniformly distributed oxygen vacancies, and open channels, which improves the ozone adsorption and activation efficiency while inhibiting calcium ion leaching.

[0012] (2) In this invention, the Ca2Fe2O5 catalyst is prepared by co-precipitation combined with crystallization reaction and calcination process. The raw materials used in this invention are all common water-soluble calcium and iron sources. The raw materials are widely available and easy to obtain. No organic solvents or surfactants are required, and no complex equipment is needed. It has the advantages of simple preparation process, mild operating conditions, short preparation cycle and easy scale-up production.

[0013] (3) In this invention, the Ca2Fe2O5 catalyst does not contain precious metals, toxic heavy metals or harmful organic components. The raw material composition and preparation process are green and environmentally friendly. After use, it will not introduce additional pollutants into the water body. Attached Figure Description

[0014] Figure 1 The X-ray diffraction (XRD) images are of the Ca2Fe2O5 catalysts in Examples 1 and 2 of this invention.

[0015] Figure 2 The images are scanning electron microscope (SEM) images of the calcium-iron precursor powder in Example 1 of the present invention at different magnifications.

[0016] Figure 3 The images show SEM images of different Ca2Fe2O5 catalysts of the present invention at different magnifications, where (a) is the S1 catalyst in Example 1 and (b) is the S2 catalyst in Example 2.

[0017] Figure 4 This is a graph showing the adsorption-desorption test results of the calcium-iron precursor powder before calcination in Example 1 of the present invention.

[0018] Figure 5This is a graph showing the adsorption-desorption test results of the Ca2Fe2O5 catalyst in Example 1 of this invention;

[0019] Figure 6 The images show the SEM-EDS-Mapping spectra of different Ca2Fe2O5 catalysts of the present invention, where (a) is the S1 catalyst in Example 1 and (b) is the S2 catalyst in Example 2.

[0020] Figure 7 The Fourier transform infrared (FTIR) spectra of different catalysts of this invention are shown below.

[0021] Figure 8 The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of the Ca2Fe2O5 catalyst in Example 1 of this invention, where (a) represents calcium (Ca), (b) represents iron (Fe), and (c) represents oxygen (O).

[0022] Figure 9 The above are electron paramagnetic resonance (EPR) images of the Ca2Fe2O5 catalysts in Examples 1 and 2 of this invention.

[0023] Figure 10 This is a diagram showing the effect of atrazine (ATZ) degradation in Application Example 1 of the present invention;

[0024] Figure 11 This is a diagram showing the effect of calcium-iron precursor powder and Ca2Fe2O5 catalyst on the degradation of atrazine in Example 1 of the present invention;

[0025] Figure 12 This is a diagram showing the effect of oxalic acid (OA) degradation in Application Example 2 of the present invention;

[0026] Figure 13 This is a diagram showing the degradation effect of actual wastewater in Application Example 3 of the present invention;

[0027] Figure 14 The figure shows the test results of the cyclic stability experiment in Application Example 4 of this invention. Detailed Implementation

[0028] In the process of implementing the concept of this invention, it was found that calcium-based or calcium-iron-based ozone catalysts generally suffer from calcium ion leaching during wastewater treatment. This not only causes the loss of active components and a decrease in catalytic performance in calcium-based or calcium-iron-based ozone catalysts, but also leads to an increase in water hardness, affecting subsequent treatment work.

[0029] To address the calcium ion leaching problem in calcium-based or calcium-iron-based ozone catalysts, methods such as calcination and surface coating have been proposed to improve their structural stability. However, calcium ion leaching persists during long-term operation. Related technologies also propose using the sol-gel method to prepare perovskite catalysts, which improves structural stability, but the preparation process is complex and costly, and the catalytic activity needs further improvement.

[0030] Therefore, there is an urgent need to develop a calcium-based or calcium-iron-based ozone catalyst that has higher catalytic activity, a more stable structure, and is suitable for large-scale preparation.

[0031] To address this issue, this invention proposes a co-precipitation method combined with crystallization and calcination processes to prepare a calcium-iron composite oxide ozone catalyst (referred to as Ca2Fe2O5 catalyst). In the Ca2Fe2O5 catalyst, the iron (Fe) sites possess moderate ozone adsorption energy, serving as catalytic active centers that effectively activate ozone while providing the main redox sites required for ozone decomposition. Calcium, on the other hand, inhibits calcium ion dissolution by forming a calcium-oxygen-iron (Ca-O-Fe) bonded network structure and induces lattice distortion using its ionic radius difference, constructing abundant oxygen vacancies at the interface. These oxygen vacancies, in conjunction with the Fe sites, promote the adsorption and activation of ozone molecules. Thus, this invention prepares a Ca2Fe2O5 catalyst with a stable Ca-O-Fe bonded network structure and abundant oxygen vacancies. This Ca2Fe2O5 catalyst effectively inhibits calcium ion leaching and exhibits both higher catalytic activity and structural stability. More importantly, the preparation process is simple and inexpensive. The Ca2Fe2O5 catalyst of this invention can be widely applied to the ozone catalytic oxidation treatment of recalcitrant industrial wastewater from dyeing, pharmaceutical, and coking industries.

[0032] Specifically, as a first aspect of the present invention, a method for preparing a calcium-iron composite oxide ozone catalyst is provided, comprising: step (1) to step (6).

[0033] Step (1): Add a complexing regulator to the calcium-iron mixed salt solution and adjust the pH of the mixed system to acidic to obtain a calcium-iron precursor solution.

[0034] Step (2): Add a composite precipitant solution to the calcium-iron precursor solution to adjust the pH of the mixed system to alkaline for coprecipitation reaction to obtain the coprecipitation precursor. The composite precipitant includes hydroxide ion main precipitant and carbonate ion auxiliary precipitant.

[0035] Step (3): The coprecipitated precursor is subjected to a crystallization reaction.

[0036] Step (4): After the crystallization reaction is completed, the precipitate is collected after cooling and standing.

[0037] Step (5): After washing and drying, the precipitate is used to obtain calcium-iron precursor powder.

[0038] Step (6): After mixing the calcium-iron precursor powder with the pyrolysis-type defect modifier, the mixture is calcined in stages to obtain the calcium-iron composite oxide ozone catalyst.

[0039] In this invention, a complexing regulator is added to a calcium-iron mixed salt solution and the pH of the mixture is adjusted to acidity, thereby regulating the calcium content. 2+ and Fe 3+ The coordination state of Ca reduces the amount of Ca in subsequent coprecipitation reactions. 2+ with Fe 3+ The difference in precipitation rate, on the other hand, ensures that the metal in the calcium-iron precursor solution is in an ionic state. A composite precipitant solution is added to the calcium-iron precursor solution. The hydroxide ion primary precipitant is used to adjust the pH of the mixed system to alkalinity and promote the hydrolysis co-precipitation reaction of the calcium-iron precursor solution, while the carbonate ion auxiliary precipitant reduces the difference in precipitation rate between calcium and iron ions through reversible coordination and slow-release precipitation, inhibiting local rapid nucleation and particle agglomeration. After the addition of the composite precipitant solution, a crystallization reaction promotes the nucleation of the co-precipitated precursor, uniform crystal growth, and ensures sufficient dispersion of calcium and iron elements, avoiding the formation of an independent calcium phase or elemental segregation due to differences in precipitation rate. After the crystallization reaction is completed, the obtained precipitate is washed and dried. The resulting calcium-iron precursor powder is mixed with a pyrolysis-type defect regulator and calcined in stages, causing the calcium-iron precursor powder to undergo solid-phase rearrangement and form a Ca2Fe2O5 dominant crystalline phase and a continuous Ca-O-Fe bonded network structure. Thus, the Ca2Fe2O5 catalyst obtained by the present invention through complexation regulator regulation, co-precipitation reaction, crystallization reaction, and calcination treatment possesses a stable Ca-O-Fe bonded network structure, uniformly distributed oxygen vacancy defects, and open pore structure, which improves ozone adsorption and activation efficiency while inhibiting calcium ion leaching.

[0040] The following describes steps (1) to (6) in detail with reference to specific implementation methods.

[0041] Step (1) Preparation of calcium-iron precursor solution

[0042] The calcium-iron mixed salt solution is prepared by dissolving calcium and iron sources in water at a calcium-iron molar ratio of 4-6:5 (i.e., 0.8-1.2).

[0043] The calcium source can be selected from one or more of calcium nitrate (Ca(NO3)2), calcium chloride (CaCl2), and calcium acetate, with calcium nitrate being preferred. Other water-soluble calcium sources can also be used, and are not limited in detail here. The iron source can be selected from one or more of ferric nitrate (Fe(NO3)3), ferric chloride (FeCl3), ferric sulfate, and ferric nitrate nonahydrate (Fe(NO3)3·9H2O), with ferric nitrate nonahydrate being preferred. Other water-soluble iron sources can also be used, and are not limited in detail here.

[0044] For example, preparing a calcium-iron mixed salt solution includes: dissolving 5 mmol-20 mmol of calcium source and 5 mmol-20 mmol of iron source in 80 mL-200 mL of deionized water at a calcium-iron molar ratio of 4-6:5 (i.e., 0.8-1.2), and stirring at 300 rpm-800 rpm for 20 min-60 min at room temperature (20-30°C) to obtain the calcium-iron mixed salt solution. More preferably, dissolving 10 mmol of calcium source and 10 mmol of iron source in 80 mL-200 mL of deionized water at the calcium-iron molar ratio, and stirring at 300 rpm-800 rpm for 20 min-60 min at room temperature (20-30°C) to obtain the calcium-iron mixed salt solution.

[0045] Furthermore, a complexing regulator is added to the calcium-iron mixed salt solution prepared above to adjust the Ca2+ content. 2+ and Fe 3+ The coordination state of Fe inhibits 3+ During the subsequent addition of the composite precipitant solution, localized rapid hydrolysis occurs, thereby reducing the Ca2+ content. 2+ with Fe 3+ Differences in precipitation rate. The complexing regulator of the present invention is selected from one or more of citric acid, ethylenediaminetetraacetic acid, urea and glucose. The molar ratio of the aforementioned complexing regulator to the total amount of calcium and iron metal ions in the calcium-iron mixed salt solution is (0.01-0.50):1, for example, it can be 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, preferably (0.05-0.20):1.

[0046] Furthermore, after adding a complexing regulator to the aforementioned calcium-iron mixed salt solution, the pH of the mixed system is adjusted to 1.5-4.0 (acidic), and the mixture is stirred at 25-60℃ for 20-120 minutes to obtain a clear, homogeneous and stable calcium-iron precursor solution.

[0047] Thus, in step (1) of the present invention, by controlling the calcium-iron molar ratio and the mixing conditions of the calcium-iron mixed salt solution and the complexing regulator, the calcium and iron elements are kept uniformly dispersed before the co-precipitation reaction, laying the foundation for the subsequent formation of the Ca2Fe2O5 dominant crystalline phase and the continuous Ca-O-Fe bonded network structure through crystallization reaction and calcination treatment. By controlling the calcium-iron molar ratio, the generation of independent calcium phase and iron oxide impurity phase can be reduced, and conditions are created for the uniform formation of oxygen vacancies in the calcium-iron lattice, taking into account both the construction of ozone activation sites and the structural stability of the calcium component.

[0048] Step (2) Coprecipitation reaction to prepare coprecipitate precursor

[0049] The composite precipitant solution is prepared by dissolving a hydroxide primary precipitant and a carbonate secondary precipitant in water at a specific molar ratio. The hydroxide primary precipitant is selected from at least one of sodium hydroxide (NaOH), potassium hydroxide (KOH), and ammonia (NH3·H2O), preferably sodium hydroxide. The carbonate secondary precipitant is selected from at least one of sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3). The hydroxide primary precipitant is used to adjust the pH of the mixed system to alkaline and promote the hydrolysis and co-precipitation reaction of the calcium-iron precursor solution. The carbonate secondary precipitant, through reversible coordination with calcium and iron ions and slow-release precipitation, reduces the difference in precipitation rates between calcium and iron ions, inhibits local rapid nucleation and particle agglomeration, and promotes uniform co-deposition of calcium and iron elements. Furthermore, the carbonate and / or bicarbonate ions in the co-precipitate precursor decompose and release gases during subsequent calcination, forming open channels and promoting the construction of the Ca2Fe2O5 crystal phase and oxygen vacancies, thereby enhancing the mass transfer, adsorption, and activation processes of ozone within the Ca2Fe2O5 catalyst.

[0050] For example, a method for preparing a composite precipitant solution includes: weighing a hydroxide primary precipitant and a carbonate auxiliary precipitant, dissolving them together in deionized water to form a composite precipitant solution; or dissolving the hydroxide primary precipitant and the carbonate auxiliary precipitant separately in water, and then mixing the two to obtain a composite precipitant solution.

[0051] The molar ratio of the hydroxide ion primary precipitant and the carbonate ion auxiliary precipitant is (1-20):1, for example, it can be 1:1, 5:1, 8:1, 10:1, 12:1, 15:1, 18:1, 20:1, etc., preferably (3-10):1, more preferably (4-6):1.

[0052] For example, taking sodium hydroxide and sodium carbonate as examples, the preparation of a composite precipitant solution includes: dissolving 40mmol-100mmol of sodium hydroxide and 5mmol-40mmol of sodium carbonate in 80mL-200mL of deionized water, stirring at 300rpm-800rpm for 15min-30min at room temperature until completely dissolved, forming a clear alkaline solution, which is the composite precipitant solution.

[0053] In this invention, the composite precipitant contains hydroxide ions (OH-). - The concentration of carbonate (CO3) is 0.3 mol / L to 2.0 mol / L, for example, it can be 0.3 mol / L, 0.5 mol / L, 0.8 mol / L, 1.0 mol / L, 1.3 mol / L, 1.5 mol / L, 1.8 mol / L, 2.0 mol / L, etc., or any value within this range, preferably 0.5-1.2 mol / L. 2- ) and bicarbonate (HCO3) - The total concentration of the catalyst is 0.02-0.5 mol / L, for example, it can be 0.02 mol / L, 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.30 mol / L, 0.35 mol / L, 0.40 mol / L, 0.45 mol / L, 0.50 mol / L, etc., or any value within this range, preferably 0.05-0.2 mol / L. In this invention, the hydroxide concentration affects the metal hydrolysis nucleation rate; the carbonate concentration affects the porosity of the Ca2Fe2O5 catalyst.

[0054] Furthermore, the calcium-iron precursor solution prepared above is placed in a reaction vessel equipped with an online temperature and pH monitoring device. Under continuous mechanical stirring, a composite precipitant solution is added to the calcium-iron precursor solution to adjust the pH of the mixture to alkaline and carry out a coprecipitation reaction to obtain a coprecipitated precursor. The composite precipitant solution can be added to the calcium-iron precursor solution by dripping or by continuous pumping with a constant flow pump for the coprecipitation reaction. The temperature of the coprecipitation reaction is 20℃-40℃, which helps to improve the formation rate of the coprecipitated precursor.

[0055] The composite precipitant solution is added to the calcium-iron precursor solution at a rate of 0.2 mL / min to 5 mL / min, for example, 0.2 mL / min, 0.5 mL / min, 1.0 mL / min, 1.5 mL / min, 2.0 mL / min, 3.0 mL / min, 4.0 mL / min, 5.0 mL / min, or any value within this range. Preferably, the composite precipitant solution is added to the calcium-iron precursor solution at a rate of 1 mL / min to 5 mL / min. By controlling the addition rate, controlled hydrolysis, nucleation, and co-precipitation reactions of calcium and iron ions are achieved. As the composite precipitant solution is added, the pH of the mixed system is adjusted to alkalinity, which is 8-13, for example, any value among 8, 9, 10, 11, 12, and 13.

[0056] In some embodiments, the composite precipitant solution can be added in batches according to the co-precipitation reaction process, so that calcium and iron elements can be uniformly nucleated, and calcium-containing species can be deposited and grown simultaneously on the surface of ferrohydroxyl crystal nuclei.

[0057] In some embodiments, during the initial stage, the temperature of the mixing system is controlled at 20-40°C, and a composite precipitant solution is added (dropwise or continuously pumped) to the calcium-iron precursor solution at a rate of 0.2 mL / min-2.0 mL / min to raise the pH of the mixing system to 8-9 and maintain this pH for 10-60 min, thereby obtaining homogeneous calcium-iron co-precipitated crystal nuclei. Subsequently, during the growth stage, the composite precipitant solution is added to the calcium-iron precursor solution at a rate of 1 mL / min-5 mL / min to further raise the pH of the mixing system to 10-13 and maintain this pH for 30-120 min. Preferably, the addition is done at a uniform rate during both the initial and growth stages to ensure more uniform crystal phase formation.

[0058] Thus, this invention controls the addition rate of the composite precipitant solution through pH feedback, keeping the pH fluctuation of the reaction system within a set value of ±0.2, avoiding excessively high local alkali concentration that could cause rapid aggregation of iron species or the formation of independent calcium phases, and promoting the synchronous deposition and growth of calcium-containing species on the surface of ferrooxyhydroxyl crystal nuclei.

[0059] Step (3) Crystallization reaction

[0060] In this invention, after the composite precipitant solution is added, stirring is continued at 600 rpm to 1800 rpm for 0.5 h to 2 h, and a crystallization reaction is carried out at 60 to 90 °C. Preferably, the crystallization reaction is carried out at 80 °C for 2 h to promote the uniform growth of the co-precipitated precursor and the full dispersion of calcium and iron elements.

[0061] In some embodiments, the crystallization reaction of the present invention preferably adopts a gradient temperature-increasing crystallization reaction, which first crystallizes at 60℃-70℃ for 0.5h-2h to further hydrolyze and rearrange the complexed calcium and iron species; then, the temperature is raised to 75℃-90℃ and the crystallization reaction continues at this temperature for 1h-6h to promote the formation of the Ca-O-Fe bonded network structure.

[0062] More preferably, the gradient temperature crystallization reaction involves first crystallizing at 65°C for 1 hour, then increasing the temperature to 80°C at a rate of 0.5-2°C / min and continuing the crystallization reaction for 2-4 hours.

[0063] Thus, this invention controls the nucleation and crystal growth processes of calcium-iron precursors through staged pH regulation and crystallization reaction (preferably gradient temperature crystallization reaction), thereby reducing the calcium content of calcium precursors. 2+ with Fe 3+ The elemental segregation caused by the difference in hydrolysis precipitation rate causes calcium species to be preferentially fixed in the coprecipitation precursor in the form of a Ca-O-Fe bonded network structure, rather than forming an easily soluble independent calcium phase.

[0064] Step (4) Collect the sediment

[0065] After the crystallization reaction in step (3) is completed, the suspension obtained in step (3) is cooled to 20℃-30℃ at a cooling rate of 0.5℃ / min-2℃ / min and left to stand for 0.5h-4h, so that the incompletely combined calcium and iron species can be further deposited on the surface of the coprecipitate precursor. Then, the precipitate is collected by centrifugation or filtration to obtain the precipitate.

[0066] Step (5) Obtain calcium-iron precursor powder

[0067] The precipitate obtained in step (4) is washed using a gradient washing method. For example, it is washed 2-4 times alternately with deionized water at 40℃-70℃ and anhydrous ethanol to remove pores and residual ions (such as sodium ions) from the precipitate. + ), potassium ions (K) + ), chloride ions (Cl) - ), nitrate ions (NO3) - (e.g., free complexes). Subsequently, the sample was washed 2-5 times with deionized water at 20℃-30℃, followed by centrifugation at 4000rpm-8000rpm for 5-10 minutes each time. The washing and centrifugation process was repeated until the pH of the washing solution reached 6.5-7.5 and the conductivity was below 100μS / cm. Gradient washing effectively removed free salts while avoiding damage to the Ca-O-Fe bonded network structure from harsh washing.

[0068] After gradient washing is completed, the obtained precipitate is placed in an oven at 50℃-120℃ and dried for 12h-24h to obtain calcium-iron precursor powder. Preferably, the precipitate is dried using staged hot air drying. During drying, it is first dried at 50℃-70℃ for 4h-12h, and then dried at 80℃-120℃ for 6h-18h to obtain calcium-iron precursor powder.

[0069] Step (6) Preparation of calcium-iron composite oxide ozone catalyst

[0070] The calcium-iron precursor powder obtained in step (5) is mechanically ground and mixed with a pyrolysis-type defect modifier to obtain a mixture. The pyrolysis-type defect modifier is selected from any one of urea, melamine, and activated carbon, and its mass is 1%-30% of the mass of the calcium-iron precursor powder. For example, it can be 1%, 5%, 10%, 15%, 20%, 25%, 30%, or any value within this range, preferably 5%-20%. The mechanical grinding method can be ball milling, wet milling, etc. When using ball milling, the ball-to-material mass ratio is (2-20):1, the rotation speed is 100rpm-500rpm, and the milling time is 0.5h-6h. When using wet milling, ethanol or isopropanol is used as the dispersion medium, and the mixture is dried at 40℃-80℃ after grinding.

[0071] After grinding, the resulting mixture is placed in an alumina crucible and calcined in stages under air, oxygen, or an inert atmosphere to obtain a calcium-iron composite oxide ozone catalyst. In this invention, the staged calcination includes: first, a first-stage calcination under a first atmosphere, followed by a second-stage calcination under a second atmosphere. The first atmosphere is nitrogen. The first-stage calcination involves heating to 250℃-450℃ at a rate of 1℃ / min-5℃ / min and holding for 0.5h-3h to allow the pyrolysis-type defect regulator to decompose slowly, preventing rapid decomposition that could cause particle sintering or pore collapse. The second atmosphere is air. The second-stage calcination involves heating to 600℃-800℃ at a rate of 2℃ / min-10℃ / min and holding for 2h-8h to allow the calcium-iron precursor powder to undergo solid-phase rearrangement and form a Ca2Fe2O5 dominant crystalline phase and a continuous Ca-O-Fe bonded network structure.

[0072] Finally, under the first protective atmosphere, the sample was cooled to room temperature at a rate of 0.5-5℃ / min to suppress excessive oxidation of oxygen vacancies during the cooling process. The resulting sample was washed 2-5 times with deionized water and anhydrous ethanol, respectively, and then dried again at 60℃-100℃ for 6-12 hours to obtain a brownish-red calcium-iron composite oxide ozone catalyst, namely Ca2Fe2O5 catalyst.

[0073] Thus, in step (6), the present invention avoids insufficient oxygen vacancy concentration caused by single high-temperature (600-800℃) air calcination through staged atmosphere control, and also avoids excessive oxygen deficiency in the calcium-iron lattice and destruction of the Ca-O-Fe bond network structure caused by continuous strong reducing atmosphere. The resulting Ca2Fe2O5 catalyst has a stable Ca-O-Fe bond network structure, uniformly distributed oxygen vacancies, and open pore structure, which improves ozone adsorption and activation efficiency and inhibits calcium leaching.

[0074] As a second aspect of the present invention, a calcium-iron composite oxide ozone catalyst prepared by the above preparation method is provided, wherein the calcium-iron composite oxide is Ca2Fe2O5.

[0075] In this invention, the Ca2Fe2O5 catalyst prepared by the above method possesses abundant oxygen vacancies and ozone adsorption energy, enabling it to efficiently activate ozone and promote ozone decomposition to generate hydroxyl radicals (·OH), thereby achieving pollutant degradation. Calcium in the Ca2Fe2O5 catalyst inhibits calcium ion dissolution by forming a Ca-O-Fe bonded network structure, thus improving the structural stability of the Ca2Fe2O5 catalyst.

[0076] As a third aspect of the present invention, the application of calcium-iron composite oxide ozone catalyst in the catalytic ozone degradation of organic pollutants is provided.

[0077] In this invention, the Ca2Fe2O5 catalyst has abundant oxygen vacancies and iron active sites, which can efficiently degrade organic pollutants by adsorbing, activating and promoting the decomposition of ozone to generate hydroxyl radicals.

[0078] In some implementations, the organic pollutants include atrazine, oxalic acid, etc.

[0079] The present invention will be further illustrated below through specific embodiments, related test experiments, and accompanying drawings. In the following detailed description, numerous specific details are set forth to provide a comprehensive understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict. All instruments, consumables, and reagents used in the following embodiments are commercially available unless otherwise specified.

[0080] Example 1

[0081] This embodiment 1 provides a method for preparing a calcium-iron composite oxide ozone catalyst, including: steps (1) to (6).

[0082] Step (1) Prepare a calcium and iron mixed salt solution

[0083] Dissolve 10 mmol of Ca(NO3)2 and 10 mmol of Fe(NO3)3·9H2O in 100 mL of deionized water, add 2 mmol of citric acid, and stir at 600 rpm for 30 min at 50 °C to allow Ca to dissolve. 2+ Fe 3+ After fully coagulating with the complexing regulator, the solution is stirred until clear to obtain a calcium-iron mixed salt solution.

[0084] Step (2) Preparation of composite precipitant solution

[0085] Dissolve 60 mmol sodium hydroxide (NaOH) and 10 mmol sodium carbonate (Na2CO3) in 100 mL of deionized water and stir until the solution is clear to obtain a composite precipitant solution.

[0086] Step (3) pH adjustment

[0087] Under stirring conditions of 1200 rpm, the composite precipitant solution was slowly poured into the calcium-iron mixed salt solution at a rate of 1 mL / min to raise the pH of the mixed system to 8.0 and maintain it for 30 min; then the composite precipitant solution was added again at a rate of 2 mL / min to raise the pH of the mixed system to 11.5, and the pH of the mixed system was stabilized at 11.5 ± 0.2 by feedback from the pH online monitoring device.

[0088] Step (4) Crystallization reaction

[0089] After the composite precipitant solution was added dropwise, stirring was continued for 1 hour. Then, the temperature of the mixture was raised from room temperature to 65°C and crystallization reaction was carried out for 1 hour. Subsequently, stirring was continued at 1500 rpm and the temperature was raised to 80°C for water bath heating for 2 hours.

[0090] Step (5) Preparation of calcium-iron precursor powder

[0091] After the crystallization reaction was completed, the sample was washed 2-3 times alternately with deionized water and anhydrous ethanol until the pH of the washing solution was 7.0±0.2 and the conductivity of the washing solution was less than 80 μS / cm. Then, it was centrifuged several times at 6000 rpm. Finally, it was vacuum dried at 50℃ for 6 h, and then the temperature was raised to 80℃ for another 12 h to obtain a loose and porous calcium-iron precursor powder, labeled S1-1.

[0092] Step (6) Preparation of calcium-iron composite oxide ozone catalyst

[0093] After grinding the dried calcium-iron precursor powder from step (5) with urea (10 wt%), the temperature was increased to 350°C at 2°C / min and held for 1 h under a nitrogen atmosphere; then the temperature was switched to air, increased to 650°C at 5°C / min and held for 5 h; finally, the temperature was reduced to room temperature at 2°C / min under nitrogen protection. The obtained sample was washed three times with deionized water and anhydrous ethanol to obtain a brown Ca2Fe2O5 catalyst, labeled as S1.

[0094] Example 2

[0095] Example 2 prepared the Ca2Fe2O5 catalyst using the same method as in Example 1, except that in step (1), 5 mmol of Ca(NO3)2 and 10 mmol of Fe(NO3)3·9H2O were dissolved in 100 mL of deionized water and stirred until the solution was clear. The prepared Ca2Fe2O5 catalyst was labeled as S2.

[0096] Example 3

[0097] Example 3 uses the same method as Example 1 to prepare the Ca2Fe2O5 catalyst, except that in step (1), 10 mmol of CaCl2 and 5 mmol of FeCl3 are dissolved in 100 mL of deionized water and stirred until the solution is clear. The prepared Ca2Fe2O5 catalyst is labeled as S3.

[0098] Comparative Example 1

[0099] Comparative Example 1 prepared an ozone catalyst using the same method as in Example 1, except that in step (1), 10 mmol of CaCl2 was dissolved in 100 mL of deionized water and stirred until the solution was clear. The prepared ozone catalyst was labeled S4.

[0100] Comparative Example 2

[0101] Comparative Example 2 prepared an ozone catalyst using the same method as in Example 1, except that in step (1), 10 mmol of Fe(NO3)3·9H2O was dissolved in 100 mL of deionized water and stirred until the solution was clear. The prepared ozone catalyst was labeled S5.

[0102] The ion leaching of the Ca2Fe2O5 catalysts in Examples 1-3 was analyzed using ICP-OES (inductively coupled plasma atomic emission spectrometry), and the specific test results are shown in Table 1.

[0103] Table 1. ICP-OES Test Results

[0104]

[0105] As shown in Table 1, the catalysts in Examples 1 and 2 of this invention have low ion leaching amounts, demonstrating that the catalysts prepared by this invention have good stability.

[0106] Furthermore, the catalysts synthesized in the examples were characterized and tested using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR).

[0107] Figure 1 The images show the X-ray diffraction (XRD) analysis of the Ca2Fe2O5 catalysts in Examples 1 and 2 of this invention.

[0108] like Figure 1 As shown, the active components of the Ca2Fe2O5 catalysts in Examples 1-2 of this invention have obvious perovskite-like structures.

[0109] Figure 2 The images are scanning electron microscope (SEM) images of the calcium-iron precursor powder in Example 1 of this invention at different magnifications.

[0110] like Figure 2 As shown, before calcination, the calcium-iron precursor powder (i.e., S1-1) was in a blocky and agglomerated state, and no obvious channels were observed.

[0111] Figure 3 The images are SEM images of different Ca2Fe2O5 catalysts of the present invention at different magnifications, wherein (a) is the S1 catalyst in Example 1 and (b) is the S2 catalyst in Example 2.

[0112] like Figure 3 As shown, the Ca2Fe2O5 catalysts in Examples 1 and 2 have a plate-like structure with open channels formed between the layers, exhibiting a distinct layered porous structure and open, dispersed microstructure, increasing the exposed surface area and promoting ozone diffusion and interfacial contact. Furthermore, from Figure 3 and Figure 2 The comparison shows that adding pyrolysis-type defect modifiers and mixing and calcining calcium-iron precursor powder helps to form a plate-like Ca2Fe2O5 catalyst, increasing the exposed area.

[0113] Furthermore, adsorption-desorption tests were performed on the calcium-iron precursor powder (S1-1) before calcination and the Ca2Fe2O5 catalyst (i.e., S1 catalyst) formed after calcination in Example 1 using a surface area and porosity analyzer (BET) to analyze the specific surface area and pore size of both. Specific test results are as follows: Figures 4-5 As shown.

[0114] Figure 4This is a graph showing the adsorption-desorption test results of the calcium-iron precursor powder before calcination in Example 1 of the present invention. Figure 5 The graph shows the adsorption-desorption test results of the Ca2Fe2O5 catalyst in Example 1 of this invention.

[0115] like Figure 4 As shown, the specific surface area of ​​the calcium-iron precursor powder before calcination is 16.6922 m². 2 / g, with an average pore size of 12.7292nm. After calcination of calcium-iron precursor powder mixed with urea, as... Figure 5 As shown, the specific surface area of ​​the Ca2Fe2O5 catalyst (i.e., the S1 catalyst) in Example 1 is 94.4427 m². 2 / g, with an average pore size of 8.9038nm.

[0116] Furthermore, the elemental composition of the Ca2Fe2O5 catalysts synthesized in Examples 1 and 2 was analyzed by energy dispersive spectroscopy (EDS-Mapping) using SEM. Specific results are as follows: Figure 6 As shown.

[0117] Figure 6 The images show the SEM-EDS-Mapping spectra of different Ca2Fe2O5 catalysts of the present invention, where (a) is the S1 catalyst in Example 1 and (b) is the S2 catalyst in Example 2.

[0118] like Figure 6 As shown, the S1 catalyst in Example 1 exhibits a better elemental distribution effect.

[0119] Furthermore, FTIR and XPS were used to analyze the structure, functional groups, and elemental valence states of the Ca2Fe2O5 catalysts in Examples 1 and 2. Specific analytical results are as follows: Figures 7-8 As shown.

[0120] Figure 7 The images show the Fourier transform infrared (FTIR) spectra of different catalysts used in this invention.

[0121] like Figure 7 As shown, at 604cm -1 The appearance of a new peak in the displacement indicates non-equivalent Fe-O / Ca-O vibrations and oxygen vacancies, 455 cm⁻¹. -1 Displacement indicates a change in the metal-oxygen framework, Fe 3+ / Fe 2+ The distribution changes, and the Ca-O-Fe bonded network structure promotes the formation of oxygen vacancies. 879cm -1 Displacement indicates a change in the covalent strength of Fe-O-Fe, which directly corresponds to a higher ozone activation capacity (easier electron transfer), 580-620 cm⁻¹. -1The displacement corresponds to the Fe-O stretching vibration induced by oxygen vacancies.

[0122] Figure 8 The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of the Ca2Fe2O5 catalyst in Example 1 of this invention, where (a) represents calcium (Ca), (b) represents iron (Fe), and (c) represents oxygen (O).

[0123] like Figure 8 As shown, XPS was used to analyze the metal composition of the Ca2Fe2O5 catalyst in Example 1, and the signals of calcium, iron, and oxygen were analyzed. The 2p 3 / 2 binding energy of Ca is 346.142 eV, and the 2p 1 / 2 binding energy of Ca is 349.677 eV, indicating good stability. Furthermore, this Ca2Fe2O5 catalyst contains sufficient Fe... 2+ Reduction activation of O3 also yields a significant amount of Fe. 3+ To maintain the continuity of the oxygen cycle. Furthermore, the Ca2Fe2O5 catalyst in Example 1 also contains lattice oxygen (O2). latt ) and adsorbed oxygen (O ads ).

[0124] Furthermore, the oxygen vacancies contained in the Ca2Fe2O5 catalysts in Examples 1 and 2 were tested, and the specific test results are as follows: Figure 9 As shown.

[0125] Figure 9 The images show the electron paramagnetic resonance (EPR) diagrams of the Ca2Fe2O5 catalysts in Examples 1 and 2 of this invention.

[0126] like Figure 9 As shown, the Ca2Fe2O5 catalyst in Example 1 has a richer number of oxygen vacancies than the Ca2Fe2O5 catalyst in Example 2.

[0127] Application Example 1

[0128] Step (1): Using pure oxygen as the gas source, O3 is generated by an ozone generator. The O3 concentration is measured in real time using an ozone concentration detector and the ozone concentration is controlled at 30 mg / L. At the same time, the ozone flow rate is maintained at 100 mL / min using a gas flow meter.

[0129] Step (2): The generated O3 is passed into a mixed aqueous solution of catalyst and pollutant. The reaction is carried out in a 250 mL beaker at a temperature of 25 ± 2 °C.

[0130] Step (3): Selecting atrazine (ATZ) as the organic pollutant: Prepare 200 mL of 10 mg / L atrazine solution and add it to the ozone reaction column. Add 0.04 g of catalysts S1, S2, S3, S4, and S5 from the examples and comparative examples, and a control without catalyst (Blank), to the solution. Then, purge O3 into the solution and take samples at fixed time intervals. Add ascorbic acid to stop the reaction, filter through a 0.22 μm filter membrane, and test the concentration of the pollutant using high performance liquid chromatography (HPLC). The specific test results are as follows: Figure 10 As shown.

[0131] Figure 10 This is a diagram showing the effect of atrazine (ATZ) degradation in Application Example 1 of the present invention.

[0132] like Figure 10 As shown, the addition of the Ca2Fe2O5 catalysts synthesized in Examples 1-3 significantly improved the efficiency of atrazine degradation in the ozone system. Among them, the S1 catalyst of Example 1 exhibited the best ozone catalytic activation performance, while the S4 catalyst in Comparative Example 1 and the S5 catalyst in Comparative Example 2 showed no significant effect in catalyzing the degradation of atrazine by ozone. The reason for this is that the S1 catalyst in Example 1 has a suitable calcium-iron ratio, a relatively uniform Ca-O-Fe lattice network, and abundant oxygen vacancies, which can synergistically promote ozone adsorption and activation. The S4 catalyst with a single calcium component lacks effective iron redox active sites, while the S5 catalyst with a single iron component lacks lattice regulation caused by calcium and the Ca-O-Fe synergistic structure, thus resulting in a weaker catalytic effect.

[0133] Furthermore, the effects of the calcium-iron precursor powder before calcination and the Ca2Fe2O5 catalyst formed after calcination in the ozone system on the degradation of atrazine were compared. Specific test results are as follows: Figure 11 As shown.

[0134] Figure 11 This is a diagram showing the effect of calcium-iron precursor powder and Ca2Fe2O5 catalyst on the degradation of atrazine in Example 1 of the present invention.

[0135] like Figure 11 As shown, after calcining the pyrolysis-type defect modifier mixed with calcium-iron precursor powder (i.e., S1-1), the obtained S1 catalyst has a layered structure, and the layers form a layered porous structure with obvious open channels and an open and loose microstructure, which increases the exposed surface area, promotes ozone diffusion and interfacial contact, and thus improves the degradation efficiency of atrazine.

[0136] Application Example 2

[0137] The organic pollutant was degraded using the same method as in Application Example 1, except that the organic pollutant was oxalic acid (OA). Specifically, 200 mL of a 10 mg / L oxalic acid solution was prepared and added to a beaker. 0.04 g of each of the S1, S2, S3, S4, and S5 samples provided in the examples and comparative examples, and a control without catalyst, were added to the solution. O3 was then bubbled into the solution, and samples were taken at fixed time intervals. After the reaction was stopped by adding ascorbic acid, the solution was filtered through a 0.22 μm filter membrane, and the concentration of the pollutant was tested using high-performance liquid chromatography (HPLC). The specific test results are shown below. Figure 12 As shown.

[0138] Figure 12 This is a diagram showing the effect of oxalic acid (OA) degradation in Application Example 2 of the present invention.

[0139] like Figure 12 As shown, ozone itself has almost no degradation effect on oxalic acid (OA). Among them, the S1 catalyst in Example 1 has the best ozone catalytic activation and OA degradation performance, while the S4 catalyst in Comparative Example 1 and the S5 catalyst in Comparative Example 2 have no obvious effect on catalytic ozone degradation of OA.

[0140] Application Example 3

[0141] Organic pollutants were degraded using the same method as in Application Example 1, except that actual wastewater (initial chemical oxygen demand (COD) of 225 mg / L) was selected as the pollutant. 200 mL of the actual wastewater was added to the ozone reaction column, and 0.1 g of S1 provided in Example 1 was added to the solution. With no catalyst added as a control, O3 was bubbled into the reaction column. Samples were taken at fixed time intervals, filtered through a 0.22 μm filter membrane, and the COD of the reaction solution was tested using a rapid digestion method. Specific test results are shown below. Figure 13 As shown.

[0142] Figure 13 This is a diagram showing the degradation effect of actual wastewater in Application Example 3 of the present invention.

[0143] like Figure 13 As shown, the addition of catalyst S1 in Example 1 can significantly improve the ability of ozone to degrade COD in actual wastewater.

[0144] Application Example 4: Cyclic Stability Experiment

[0145] Application Example 4 uses the same method as Application Example 1 to degrade organic pollutants, but the difference is that it also includes step (4): after each pollutant degradation reaction is completed, the catalyst is collected, washed with deionized water 3 times, and dried at 80°C to obtain the catalyst after the reaction.

[0146] Repeat steps (3) and (4) to obtain the degradation curve of catalyst S1 in Example 1 after 5 cycles. The specific results are as follows: Figure 14 As shown.

[0147] Figure 14 The figure shows the test results of the cyclic stability experiment in Application Example 4 of this invention.

[0148] like Figure 14 As shown, the S1 catalyst can complete the catalytic degradation of atrazine (ATZ) in half an hour under ozone conditions, and the degradation rate still exceeds 95% after 5 cycles. This result indicates that the Ca2Fe2O5 catalyst provided by this invention has excellent stability in ozone catalytic oxidation of water treatment.

[0149] In summary, the Ca2Fe2O5 catalyst prepared by this invention possesses abundant oxygen vacancy defects, enabling it to efficiently promote ozone decomposition and generate hydroxyl radicals (·OH). Experiments on the degradation of organic pollutants show that, under the same reaction conditions, the Ca2Fe2O5 catalyst of this invention achieves a removal rate of over 99% and a COD removal rate of over 80% for simulated atrazine wastewater, demonstrating the outstanding ozone catalytic oxidation performance of this catalyst.

[0150] In the crystal structure of the Ca2Fe2O5 catalyst of this invention, there is a strong chemical bond between calcium and iron elements, and the active components of Ca and Fe are not easily lost. After being reused 5 times, the removal rate of atrazine in simulated wastewater remains above 95%, indicating that the Ca2Fe2O5 catalyst has a stable structure, excellent long-term operational stability and reusability, and can effectively reduce the catalyst replacement cost in practical applications.

[0151] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a calcium-iron composite oxide ozone catalyst, characterized in that, include: A complexing regulator was added to a calcium-iron mixed salt solution, and the pH of the mixed system was adjusted to acidity to obtain a calcium-iron precursor solution. A composite precipitant solution is added to the calcium-iron precursor solution to adjust the pH of the mixed system to alkaline for coprecipitation reaction, thereby obtaining the coprecipitated precursor. The coprecipitated precursor is subjected to a crystallization reaction; After the crystallization reaction is completed, the precipitate is collected after cooling and settling. The precipitate was washed and dried to obtain calcium-iron precursor powder; The calcium-iron precursor powder was mixed with a pyrolysis-type defect modifier and then calcined in stages to obtain the calcium-iron composite oxide ozone catalyst. The composite precipitant includes a hydroxide ion primary precipitant and a carbonate ion secondary precipitant.

2. The preparation method according to claim 1, characterized in that: The calcium-iron mixed salt solution is prepared by dissolving and mixing a calcium source and an iron source in water at a calcium-iron molar ratio of 4-6:

5. The acidity has a pH of 1.5-4.

0.

3. The preparation method according to claim 1, characterized in that: The composite precipitant solution is prepared by dissolving the hydroxide ion primary precipitant and the carbonate ion auxiliary precipitant in water at a molar ratio of 1-20:

1. The hydroxide ion precipitant is selected from at least one of sodium hydroxide, potassium hydroxide, and ammonia water; The carbonate-assisted precipitant is selected from at least one of sodium carbonate and sodium bicarbonate.

4. The preparation method according to claim 1, characterized in that: The temperature of the coprecipitation reaction is 20-40℃, the rate at which the composite precipitant solution is added to the calcium-iron precursor solution is 0.2-5 mL / min, and the alkaline pH is 8-13. The crystallization reaction is carried out at 60-90℃. The composite precipitant solution is added to the calcium-iron precursor solution by dripping or by continuous pumping with a constant flow pump.

5. The preparation method according to claim 4, characterized in that: In the initial stage, the composite precipitant solution is added to the calcium-iron precursor solution at a rate of 0.2 mL / min-2.0 mL / min to raise the pH of the mixed system to 8-9 and maintain it for 10 min-60 min. During the growth phase, the composite precipitant solution is added to the calcium-iron precursor solution at a rate of 1 mL / min-5 mL / min to further raise the pH of the mixed system to 10-13 and maintain it for 30 min-120 min.

6. The preparation method according to claim 5, characterized in that: The crystallization reaction is a gradient temperature crystallization reaction, which involves first crystallizing at 60℃-70℃ for 0.5h-2h, and then raising the temperature to 75℃-90℃ to continue the crystallization reaction for 1h-6h.

7. The preparation method according to claim 1, characterized in that: The complexing regulator is selected from any one of citric acid, ethylenediaminetetraacetic acid, urea and glucose, and the molar ratio of the complexing regulator to the total amount of calcium and iron metal ions in the calcium-iron mixed salt solution is 0.01-0.50:1; The pyrolysis-type defect modifier is selected from any one of urea, melamine, and activated carbon. The mass of the pyrolysis-type defect modifier is 1%-30% of the mass of the calcium-iron precursor powder.

8. The preparation method according to claim 7, characterized in that: The staged calcination includes: First, a first-stage calcination is carried out under a first atmosphere, followed by a second-stage calcination under a second atmosphere; and Cooled to room temperature under the first atmosphere; Wherein, the first atmosphere is nitrogen and the second atmosphere is air; The first stage of calcination involves heating the temperature to 250℃-450℃ at a rate of 1℃ / min-5℃ / min and holding it at that temperature for 0.5h-3h. The second stage of calcination involves heating the temperature to 600℃-800℃ at a rate of 2℃ / min-10℃ / min and holding it at that temperature for 2h-8h.

9. A calcium-iron composite oxide ozone catalyst, characterized in that, The calcium-iron composite oxide is prepared by any one of claims 1-8, wherein the calcium-iron composite oxide is Ca2Fe2O5.

10. The application of the calcium-iron composite oxide ozone catalyst as described in claim 9 in the catalytic ozone degradation of organic pollutants.

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