Preparation method and application of a co-doped perovskite catalyst

Abstract

The application provides a preparation method and application of a co-doped perovskite catalyst, and comprises the following steps: preparing aluminum pillared montmorillonite by performing pillaring modification on sodium-based montmorillonite; and simultaneously loading Bi 0.95 Ce 0.05 Fe 0.5 Co 0.5 O3 prepared from bismuth nitrate, cerium nitrate, iron nitrate and cobalt nitrate into the aluminum pillared montmorillonite by adopting a one-step sol-gel method to prepare a co-doped perovskite catalyst Bi 0.95 Ce 0.05 Fe 0.5 Co 0.5 O3 / Mt with high catalytic activity. The catalyst prepared by the application has good degradation effect on methyl orange, methylene blue, tetracycline and other several kinds of wastewater, has less active metal dissolution, has small secondary pollution, is an environment-friendly, low-cost, high-stability and catalytic-activity catalyst, and has important significance for expanding the application of the perovskite catalyst in the wet catalytic hydrogen peroxide oxidation technology.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and relates to the modification of perovskite catalysts, specifically to a method for preparing and applying a co-doped perovskite catalyst. Background Technology

[0002] In recent years, the accelerated pace of industrialization has propelled rapid economic and social development. However, all industries rely on water, resulting in the generation of large quantities of industrial wastewater, such as dyeing and printing wastewater, pharmaceutical wastewater, and coking wastewater. Industrial wastewater is characterized by its high toxicity, strong toxicity, and difficulty in complete degradation. If not properly treated, it can seriously threaten human health. Therefore, the proper treatment of all types of industrial wastewater is crucial.

[0003] Montmorillonite, also known as montmorillonite or microcrystalline kaolinite, is a silicate clay with platy crystals. Its lamellae are composed of silicon-oxygen tetrahedra and aluminum-oxygen octahedra, and its chemical formula is (Al,Mg)₂[SiO₂]. 10 Montmorillonite (OH)₂·nH₂O) is widely distributed in nature, inexpensive, readily available, and easily exchanged with other materials, making it suitable as a catalyst support material. Because exchangeable cations exist between the layers of montmorillonite, polycations formed during the hydrolysis of metal oxides can be used to exchange with these interlayer cations. After high-temperature calcination, the polycations dehydrate and become stable metal oxide columns, increasing the interlayer spacing while maintaining the basic structure of montmorillonite, thus resulting in a larger specific surface area and more active sites.

[0004] Perovskite is a general term for a class of metal oxides with the molecular formula ABO3. A is usually an alkaline earth metal or rare earth metal, primarily responsible for stabilizing the overall structure of the perovskite, while B is usually a transition metal and is the main component affecting catalytic activity. Taking advantage of its stable and tunable structure, perovskite catalysts can be modified by doping with other elements, introducing oxygen vacancies and lattice defects to further enhance their activity and stability.

[0005] Perovskite is typically used directly as a catalyst. However, as the reaction proceeds, the active components easily dissolve, leading to secondary pollution and reduced reusability. Furthermore, the small specific surface area of ​​perovskite limits the number of active sites it can provide, thus slowing down the catalytic reaction. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing co-doped perovskite catalysts and their applications, thereby solving the technical problem that perovskite catalysts in the existing technology are difficult to balance catalytic performance and environmental performance.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A method for preparing a co-doped perovskite catalyst, the method comprising the following steps:

[0009] Step 1: Add sodium montmorillonite powder (Na-Mt) to aluminum chloride solution and stir continuously with magnetic force to obtain mixture A.

[0010] Step 2: Heat and stir the mixture A, then add polyethylene glycol first, followed by sodium hydroxide solution to obtain mixture B.

[0011] Step 3: Continue heating and stirring the mixture B, sonicate it, and age it at room temperature to obtain the layered liquid C.

[0012] Step 4: Discard the supernatant of the layered liquid C, and then centrifuge, wash, dry, grind and calcine in sequence to obtain aluminum-pillared montmorillonite (Al-Mt).

[0013] Step 5: Dissolve bismuth nitrate, cerium nitrate, ferric nitrate, cobalt nitrate and citric acid in ethylene glycol monomethyl ether, add dilute nitric acid and ethylene glycol, stir and mix evenly and sonicate to obtain mixture D.

[0014] Step 6: Place the mixture D in a water bath, stir and add aluminum-supported montmorillonite, and continue stirring until a dark red sol E is formed.

[0015] Step 7: Dry and grind sol E, then calcine it in a muffle furnace at 600℃ for 5 hours to obtain the co-doped perovskite catalyst Bi. 0.95 Ce 0.05 Fe 0.5 Co 0.5 O3 / Mt.

[0016] The present invention also has the following technical features:

[0017] In step 1, preferably, the volume and concentration of the aluminum chloride solution corresponding to 3g of sodium montmorillonite powder in the mixed solution A is 80mL, 0.4mol·L⁻¹. -1 The stirring time is 20 minutes.

[0018] In step 2, the preferred preparation conditions for the mixture B include: a water bath temperature of 70°C, a stirring time of 20 min, and for every 5 mL of polyethylene glycol added, the corresponding amount and concentration of sodium hydroxide solution added is 192 mL (0.4 mol·L⁻¹). -1 The drop rate was 3 mL / min.

[0019] In step 3, the preferred preparation conditions for the layered liquid C include: water bath temperature of 70°C, stirring time of 60 min, ultrasonic power of 100 W, ultrasonic time of 20 min, and aging time of 24 h.

[0020] In step 4, the preferred method for preparing the aluminum-pillared montmorillonite specifically includes: alternately washing the precipitate with distilled water and anhydrous ethanol until Cl-free. - Dry at 70℃ for 12 hours, grind to 80-100 mesh, and calcine at 400℃ in a muffle furnace for 2 hours.

[0021] In step 5, the preferred method for preparing the mixture D specifically includes: a molar ratio of bismuth nitrate, cerium nitrate, ferric nitrate, and cobalt nitrate of 1:(0.17–0.18):(0.58–0.59):(0.58–0.59); 10 mL of ethylene glycol monomethyl ether; 15 μL of dilute nitric acid; and 0.1 mol·L⁻¹... -1 Add 5 mL of ethylene glycol, stir at room temperature for 10 min, and sonicate at 100 W for 10 min.

[0022] In step 6, the preferred preparation conditions for sol E include: a mass ratio of perovskite active component to aluminum pillared montmorillonite of 1:(2.9-3.1), a water bath temperature of 80°C, and a water bath time of 1.5-2.5 h.

[0023] In step 7, the preferred preparation conditions for the co-doped perovskite catalyst Bi0.95Ce0.05Fe0.5Co0.5O3 / Mt include: drying temperature 90℃, drying time 24h, and grinding time 10min.

[0024] The present invention also protects the application of co-doped perovskite catalysts prepared by the method described above for wastewater treatment.

[0025] Preferably, the wastewater is one or a mixture of more than one of methyl orange wastewater, tetracycline wastewater, phenol wastewater, and methylene blue wastewater.

[0026] Preferably, the dosage of co-doped perovskite catalyst per 100 mL of wastewater is 0.05 g, the reaction temperature is 70 °C, the wastewater concentration is 50 mg / L, the pH is 3.0, the amount of 30% hydrogen peroxide added is 6.6 mmol / L, and the reaction time is 2.5 h.

[0027] Compared with the prior art, the present invention has the following technical effects:

[0028] (I) This invention employs a one-step sol-gel method to load the perovskite active components onto aluminum-pillared montmorillonite while forming a gel, thereby improving catalytic performance and inhibiting the dissolution of active metals. This results in a novel perovskite mineralizer that is environmentally friendly, highly catalytically active, and inexpensive, and has significant application value for the degradation of wastewater.

[0029] (II) The co-doped perovskite catalyst prepared by this invention has shown good stability in practical applications, and its magnetic properties facilitate recovery.

[0030] (III) The co-doped perovskite catalyst prepared by this invention is applied to the catalytic wet peroxide oxidation technology to degrade wastewater such as methyl orange, which expands the application of perovskite catalysts in wastewater treatment. The whole experimental process is green, economical, safe and efficient, and has certain feasibility.

[0031] (IV) The catalyst prepared by this invention has a good degradation effect on several types of wastewater such as methyl orange, methylene blue, and tetracycline. It also has less active metal leaching and less secondary pollution. It is an environmentally friendly, low-cost, highly stable and catalytically active catalyst, which is of great significance for expanding the application of perovskite catalysts in wet catalytic hydrogen peroxide oxidation technology. Attached Figure Description

[0032] Figure 1 The images are scanning electron microscope (SEM) images of the co-doped perovskite catalysts synthesized in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0033] Figure 2 The X-ray diffraction patterns are those of the co-doped perovskite catalysts synthesized in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0034] Figure 3 This is the X-ray photoelectron spectrum of the co-doped perovskite catalyst synthesized in Example 1 of the present invention.

[0035] Figure 4 The N2 physical adsorption / desorption isotherms are shown for the co-doped perovskite catalysts synthesized in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0036] Figure 5 This is a cyclic experiment diagram of the degradation of methyl orange by the co-doped perovskite catalyst synthesized in Example 1.

[0037] Figure 6 The image shows the hysteresis loop of the co-doped perovskite catalyst synthesized in Example 1.

[0038] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0039] It should be noted that, unless otherwise specified, all raw materials used in this invention are those known in the prior art.

[0040] The sol-gel method refers to the process of uniformly mixing chemically active compounds in a liquid phase and subjecting them to hydrolysis and condensation reactions to form a stable sol system. After aging, the colloidal particles slowly polymerize to form a three-dimensional network structure gel. Following drying and sintering for solidification, a molecular-level material is finally prepared. In this invention, specifically, it refers to the process of dissolving bismuth nitrate, cerium nitrate, ferric nitrate, and cobalt nitrate under water bath heating conditions, using ethylene glycol monomethyl ether and ethylene glycol as solvents, to prepare a catalyst material.

[0041] The technical concept of this invention is as follows: Aluminum-pillared montmorillonite (Al-Mt) is prepared by pillaring modification of sodium-based montmorillonite (Na-Mt). Then, a one-step sol-gel method is used to prepare the perovskite active component Bi from bismuth nitrate (Bi(NO3)3·5H2O), cerium nitrate (Ce(NO3)3·6H2O), ferric nitrate (Fe(NO3)3·9H2O), and cobalt nitrate (Co(NO3)2·6H2O). 0.95 Ce 0.05 Fe 0.5 Co 0.5 O3 was simultaneously loaded onto Al-Mt during gelation to prepare a highly catalytically active co-doped perovskite catalyst, Bi. 0.95 Ce 0.05 Fe 0.5 Co 0.5 O3 / Mt.

[0042] Following the above technical solutions, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0043] Example 1:

[0044] This embodiment provides a method for preparing a co-doped perovskite catalyst, which includes the following steps:

[0045] Step 1: Add 3g of sodium montmorillonite powder (Na-Mt) to 80mL of 0.4mol·L⁻¹ -1 Mixture A is obtained by continuously stirring the aluminum chloride solution with magnetic force for 20 minutes.

[0046] Step 2: Heat mixture A in a water bath at 70°C and stir for 20 minutes. Then, add 5 mL of polyethylene glycol first, followed by slowly adding 192 mL of 0.4 mol·L⁻¹. -1 Sodium hydroxide solution was used to obtain mixture B.

[0047] In this embodiment, the preferred polyethylene glycol is commercially available polyethylene glycol 400, also known as Polyethylene Glycol 400 or PEG400, which has a number average molecular weight of 400.

[0048] Step 3: Continue to heat the mixture B in a water bath and stir it magnetically, then sonicate it at 100W for 20 minutes and age it at room temperature for 24 hours to obtain the layered liquid C.

[0049] Step 4: Discard the supernatant of the stratified liquid C, wash the precipitate 6 times alternately with distilled water and anhydrous ethanol, dry it in an oven at 70℃ for 12 hours, grind it to 80-100 mesh, and calcine it in a muffle furnace at 400℃ for 2 hours to obtain aluminum pillared montmorillonite (Al-Mt).

[0050] Step 5: Dissolve bismuth nitrate, cerium nitrate, ferric nitrate, cobalt nitrate, and citric acid in 10 mL of ethylene glycol monomethyl ether at a molar ratio of 1:(0.17–0.18):(0.58–0.59):(0.58–0.59). Then, add 15 μL of 0.1 mol·L⁻¹ solution sequentially. -1 Add dilute nitric acid and 5 mL of ethylene glycol, stir magnetically for 10 min, and then sonicate at 100 W for 10 min to obtain mixture D.

[0051] Step 6: Place the mixture D in an 80℃ water bath, stir magnetically and add a certain amount of Al-Mt so that the mass ratio of the perovskite active component to the aluminum pillared montmorillonite is 1:(2.9~3.1). Continue stirring until a dark red sol E is formed.

[0052] Step 7: Dry sol E in an oven at 90℃ for 24 hours, then grind for 10 minutes, and calcine in a muffle furnace at 600℃ for 5 hours to obtain the co-doped perovskite catalyst Bi. 0.95 Ce 0.05 Fe 0.5 Co 0.5 O3 / Mt.

[0053] Example 2:

[0054] This embodiment describes the application of a co-doped perovskite catalyst in the treatment of methyl orange wastewater. The specific process is as follows.

[0055] 100 mL of wastewater with a concentration of 50 mg / L and 0.05 g of catalyst were added to a flask, and the pH was adjusted using NaOH solution and dilute H2SO4 solution. The flask was placed in a magnetically stirred water bath, and the temperature was adjusted to a suitable level. The mixture was magnetically stirred for 30 min to reach adsorption equilibrium. Then, H2O2 solution was added, and the COD and absorbance values ​​were recorded from this point onwards. During the reaction, samples were taken at different times using an all-glass syringe and filtered to determine the COD and Fe content of the wastewater. 3+ Data such as dissolution rate.

[0056] The catalytic performance of the prepared co-doped perovskite catalyst was tested, and the results showed that the degradation rate of methyl orange reached 99.79% and the COD removal rate reached 76.01%.

[0057] Example 3:

[0058] This embodiment provides an application of a co-doped perovskite catalyst for treating tetracycline wastewater.

[0059] In this embodiment, the co-doped perovskite catalyst was prepared using the preparation method of the co-doped perovskite catalyst given in Example 1.

[0060] In this embodiment, the pH was 3, the concentration of tetracycline wastewater was 50 mg / L, the reaction time was 150 min, and other implementation steps and drug dosages were the same as in Example 2.

[0061] Catalytic performance experiments were conducted on the co-doped perovskite catalyst, and the results showed that the degradation rate of tetracycline reached 87.8% and the COD removal rate was 66.43%.

[0062] Example 4:

[0063] This embodiment provides an application of a co-doped perovskite catalyst for treating phenol wastewater.

[0064] In this embodiment, the co-doped perovskite catalyst was prepared using the preparation method of the co-doped perovskite catalyst given in Example 1.

[0065] In this embodiment, the pH is 3, the concentration of phenol wastewater is 50 mg / L, the reaction time is 150 min, and other implementation steps and reagent dosages are the same as in Example 2.

[0066] Catalytic performance experiments were conducted on the co-doped perovskite catalyst, and the results showed that the degradation rate of phenol reached 91.95% and the COD removal rate was 71.85%.

[0067] Example 5:

[0068] This embodiment provides an application of a co-doped perovskite catalyst for treating methylene blue wastewater.

[0069] In this embodiment, the co-doped perovskite catalyst was prepared using the preparation method of the co-doped perovskite catalyst given in Example 1.

[0070] In this embodiment, the pH is 3, the concentration of methylene blue wastewater is 50 mg / L, the reaction time is 150 min, and other implementation steps and reagent dosages are the same as in Example 2.

[0071] The catalytic performance of the prepared co-doped perovskite catalyst was tested, and the results showed that the degradation rate of methylene blue reached 99.86% and the COD removal rate was 78.63%.

[0072] Comparative Example 1:

[0073] This comparative example provides a method for preparing a catalyst, which is basically the same as the method in Example 1, except that the calcination temperature in step 7 is 500°C in this comparative example.

[0074] The catalyst prepared in this comparative example was used to treat methyl orange wastewater. The catalyst prepared in this comparative example was subjected to essentially the same catalytic performance experiments as in Example 2. The results showed that the methyl orange degradation rate was 99.06%, and the COD removal rate was 60.52%.

[0075] Comparative Example 2:

[0076] This comparative example provides a method for preparing a catalyst, which is basically the same as the method in Example 1, except that the calcination temperature in step 7 is 550°C in this comparative example.

[0077] The catalyst prepared in this comparative example was used to treat methyl orange wastewater. The catalyst prepared in this comparative example was subjected to essentially the same catalytic performance experiments as in Example 1. The results showed that the methyl orange degradation rate was 99.65%, and the COD removal rate was 66.75%.

[0078] Comparative Example 3:

[0079] This comparative example provides a method for preparing a catalyst, which is basically the same as the method in Example 1, except that the calcination temperature in step 7 is 650°C in this comparative example.

[0080] The catalyst prepared in this comparative example was used to treat methyl orange wastewater. The catalyst prepared in this comparative example was subjected to essentially the same catalytic performance experiments as in Example 1. The results showed that the methyl orange degradation rate was 99.89%, and the COD removal rate was 62.98%.

[0081] Performance testing:

[0082] The co-doped perovskite catalysts prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were subjected to BET testing (specific surface area testing), and the structural parameters obtained are shown in Table 1.

[0083] Table 1 Structural parameters of catalysts at different calcination temperatures

[0084]

[0085] Table 1 shows that calcination temperature has a significant impact on the structural properties of the catalyst. When the temperature is below 600℃, the specific surface area and total pore volume of the catalyst are directly proportional to the calcination temperature. This is because calcination promotes the formation and growth of crystal phases and can also regulate the pore structure and specific surface area of ​​the catalyst. However, this process needs to be carried out at a certain temperature; too low a temperature is not conducive to the formation of the catalyst's pore structure. When the calcination temperature is increased to 650℃, all structural parameters decrease significantly, possibly because the excessively high calcination temperature causes sintering of the active components and destroys the catalyst's pore structure. A larger specific surface area of ​​the catalyst is beneficial to the dispersion of the active components. The catalyst prepared in Example 1 has the largest specific surface area, reaching 91.46 m². 2 ·g -1 Furthermore, its total pore volume and average pore size are both larger than those of other samples, which is beneficial to improving its catalytic performance.

[0086] The results of the catalytic performance test are listed in Table 2.

[0087] Table 2. Degradation effects and performance of catalysts at different calcination temperatures on methyl orange.

[0088]

[0089]

[0090] Table 2 shows that the calcination temperature of the catalyst affects the degradation efficiency of methyl orange and Fe. 3+ Dissolution rate. When the calcination temperature is too low, BiFeO3 and Bi... 25 FeO 40 The active components have very low crystallinity, and the crystalline phase has not yet fully formed; conversely, excessively high calcination temperatures will damage the pore structure of the catalyst, reducing active sites and thus affecting catalytic performance. Furthermore, related studies have confirmed that the high volatility of Bi at high temperatures generates more oxygen vacancies, which helps improve catalytic performance. Fe can be observed... 3+ The amount of dissolution is inversely proportional to the calcination temperature, which is related to the sintering of the active components at high temperatures. Mild sintering helps control the dissolution of the active components, but high-temperature sintering will destroy the structure of the catalyst, causing the catalytic activity to drop sharply and be difficult to recover.

[0091] Figure 1SEM images of the co-doped perovskite catalysts prepared in Examples 1, 1, 2, and 3 show significant differences in morphology at different calcination temperatures. At 500°C, the perovskite active components were almost completely loaded onto the Al-Mt surface, but the distribution was uneven and the particle size varied. With increasing calcination temperature, the arrangement of the active components gradually became more regular, with spherical particles being the dominant type. At 600°C, the perovskite active components were arranged more regularly, forming a rich pore structure, which may be beneficial for pollutant degradation. Furthermore, the active components were relatively dispersed, and a small number of rod-shaped active components appeared. This may be because Ce doping optimized the morphology of the active components and effectively suppressed agglomeration, enhancing catalyst stability. When the calcination temperature was further increased, the pore structure on the catalyst surface decreased, and obvious sintering of the active component particles was observed. This leads to structural degradation of the catalyst and a reduction in catalytic activity.

[0092] To investigate the effect of calcination temperature on the crystal phase structure of the catalyst, XRD tests were performed on the co-doped perovskite catalysts prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively. The results are as follows: Figure 2 As shown, with increasing calcination temperature, the crystallinity of the characteristic peaks of BiFeO3 gradually increased. This is because excessively low temperatures are unfavorable for the formation and development of the BiFeO3 crystal phase. The diffraction peaks located at 2θ = 24.7° and 27.7° belong to BiFeO3, respectively. 25 FeO 40 Characteristic peaks of (220), (310) crystal planes, Bi 25 FeO 40 It is a product of Bi volatilization and lattice distortion, possessing the ability to activate H2O2. When the calcination temperature is above 500℃, its crystal phase integrity and crystallinity gradually increase, which is beneficial to enhancing catalytic activity. When the calcination temperature reaches 650℃, the crystallinity of the characteristic peaks of the montmorillonite (001) crystal plane decreases, and the peak shapes change. This may be due to the excessively high calcination temperature damaging the layered structure of montmorillonite. In addition, it was observed that the catalyst calcined at 650℃ produced more impurity peaks, so this temperature may not be suitable for catalyst calcination.

[0093] Figure 3 The image shows the XPS plot of the co-doped perovskite catalyst prepared in Example 1. From... Figure 3In (a) of the sample, characteristic peaks of Bi, Ce, Fe, and Co were observed in the catalyst sample prepared in Example 1, but these were not found in the full-spectrum Al-Mt, indicating successful loading of the perovskite active component. Characteristic peaks of C1s were observed in both samples, which is because C was the base element used in the test, and the samples may have adsorbed a certain amount of CO2.

[0094] Figure 3 (b) shows the peak fitting spectra of the O1s orbitals for the two samples. In the O1s spectrum of Al-Mt, the characteristic peaks at 531.58 eV and 532.5 eV belong to Si-O and Al-O bonds, respectively, corresponding to the SiO2 tetrahedron and Al2O3 octahedron in the layered structure of montmorillonite, indicating that the pillaring did not change the basic structure of montmorillonite. In the O1s spectrum of the catalyst sample prepared in Example 1, the characteristic peak at 529.88 eV belongs to lattice oxygen, and the characteristic peak at 531.69 eV is an oxygen vacancy in the sample. Compared with the Al-Mt spectrum, the characteristic peaks of the O1s orbitals of the sample showed a trend towards lower binding energies, and the peak area increased significantly, indicating that there are more active oxygen species in the sample, which is one of the main reasons for the high catalytic activity of the catalyst. Figure 3 (c) in the figure is the peak fitting diagram of Bi element in the catalyst sample prepared in Example 1. The characteristic peaks at 159.18 eV and 164.43 eV correspond to Bi4f, respectively. 7 / 2 and Bi4f 5 / 2 The orbital, and the approximately 5.3 eV difference between the two peaks, indicate that Bi is mainly distributed as Bi. 3+ It exists in the form of. Figure 3 (d) in the figure is the peak fitting diagram of Ce3d in the catalyst sample prepared in Example 1. 3 / 2 and Ce3d 5 / 2 The multiple spin states of the orbital are denoted by u and v, where u2 and v2 belong to Ce. 3+ The rest are Ce 4+ The characteristic peak of Ce. 3+ The presence of these elements disrupts the charge balance, leading to the formation of more oxygen vacancies and lattice defects on the catalyst surface. These structures can be considered as active sites, which greatly contribute to improving catalytic performance. Figure 3 (e) in the figure is the peak fitting diagram of Fe2p in the catalyst sample prepared in Example 1. Fe2p peaks were observed at 723.83 eV and 710.55 eV, respectively. 1 / 2 and Fe2p 3 / 2 The characteristic peaks of the spin orbitals show a binding energy difference of approximately 13.3 eV between the two peaks, and no Fe is fitted at 708.44 eV. 2+ The characteristic peaks indicate that Fe is the main component present in the sample. 3 +. Figure 3 (f) in the figure is the peak fitting spectrum of Co2p in the catalyst sample prepared in Example 1. The two main characteristic peaks at 795.53 eV and 780.63 eV correspond to Co2p. 1 / 2 and Co2p 3 / 2 Orbit, Co 3+ The characteristic peaks are located at 795.53 eV and 780.63 eV, respectively, and the characteristic peak at 782.88 eV indicates that Co 2+ The presence of [something] is also noted. Furthermore, a strong satellite peak was observed at 786.13 eV, which may be related to lattice defects in the sample.

[0095] To investigate the effect of calcination temperature on the structural properties of the catalyst, BET tests were performed on the co-doped perovskite catalysts prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of this invention. The results are as follows: Figure 4 As shown. According to IUPAC classification, the N2 physical adsorption / desorption isotherms of each sample belong to Type IV and exhibit an H3 hysteresis loop, a common characteristic of plate-like or granular materials, indicating the presence of mesopores. With increasing P / P0, the adsorption capacity rises rapidly, but no saturation adsorption plateau is observed, suggesting the possible presence of a slit-like structure and an irregular pore structure. Typically, in desorption curves, a significant decreasing trend in adsorption capacity is observed when P / P0 is below 0.5, a characteristic of montmorillonite materials. This characteristic disappears when the calcination temperature reaches 650℃, possibly due to the excessively high calcination temperature damaging the montmorillonite structure.

[0096] Figure 5 This is a cyclic experiment diagram showing the degradation of methyl orange wastewater by the co-doped perovskite catalyst prepared in Example 1 of this invention. In this invention, Fe... 3+ and Co 3+ The stability of the catalyst is evaluated by the amount of Fe dissolved in five cycles. 3+ The leaching levels were all below 0.3 mg / L, which complies with my country's regulations on iron ion content in drinking water being less than 0.3 mg / L (GB5749-2006). 3+ The dissolution rate decreased significantly with increasing reaction number, then stabilized, with an average dissolution rate of 0.4835 mg / L after five reactions. After five cycles, the degradation rate and COD removal rate reached 94.13% and 66.59%, respectively, indicating that the catalyst has high catalytic activity and good reusability. The slight decrease in degradation effect is likely mainly due to the dissolution of active metals, which reduces the number of active sites on the catalyst surface.

[0097] Figure 6The image shows the hysteresis loop of the co-doped perovskite catalyst prepared in Example 1 of this invention. For heterogeneous catalysts, recycling is a crucial step, and utilizing the catalyst's magnetic properties to recover the sample is a convenient method. The hysteresis loop of the sample prepared in Example 1 is shown below. Figure 6 As shown, the sample was fully magnetized when the external magnetic field strength reached 20 kOe, with a saturation magnetization (Ms) of 1.947 emu / g, exhibiting paramagnetism and easy magnetic recovery after the reaction. Unlike pure BiFeO3, the co-doped perovskite catalyst prepared in this invention showed obvious hysteresis loops, with a coercivity (Hc) of 297 Oe, indicating that Ce and Co doping further enhanced the paramagnetism of the material, which may be due to the enhanced magnetism of the sample caused by the coupling between metal ions. Figure 6 The illustration shows that the catalyst is well dispersed in the reaction system and can be rapidly enriched under the action of an external magnetic field, making recovery convenient and practical.

Claims

1. An application of co-doped perovskite catalysts for wastewater treatment; characterized in that, The co-doped perovskite catalyst is a Bi co-doped perovskite catalyst for the catalytic wet hydroperoxide oxidation degradation of wastewater. 0.95 Ce 0.05 Fe 0.5 Co 0.5 O3 / Mt; The wastewater is one or more of the following: methyl orange wastewater, tetracycline wastewater, phenol wastewater, and methylene blue wastewater; The dosage of co-doped perovskite catalyst per 100 mL of wastewater is 0.05 g, the reaction temperature is 70 °C, the wastewater concentration is 50 mg / L, the pH is 3.0, the amount of 30% hydrogen peroxide added is 6.6 mmol / L, and the reaction time is 2.5 h. The preparation method of the co-doped perovskite catalyst includes the following steps: Step 1: Add sodium montmorillonite powder to aluminum chloride solution and stir continuously with magnetic force to obtain mixture A; Step 2: Heat and stir mixture A, then add polyethylene glycol first, followed by sodium hydroxide solution to obtain mixture B; Step 3: Continue heating and stirring the mixture B, sonicate it, and age it at room temperature to obtain the layered liquid C; Step 4: Discard the supernatant of the layered liquid C, and then centrifuge, wash, dry, grind and calcine in sequence to obtain aluminum column-supported montmorillonite. Step 5: Dissolve bismuth nitrate, cerium nitrate, ferric nitrate, cobalt nitrate and citric acid in ethylene glycol monomethyl ether, add dilute nitric acid and ethylene glycol, stir and mix evenly and sonicate to obtain mixture D; Step 6: Place the mixture D in a water bath, stir and add aluminum-supported montmorillonite, and continue stirring until a dark red sol E is formed; Step 7: Dry and grind sol E, then calcine it in a muffle furnace at 600°C for 5 hours to obtain the co-doped perovskite catalyst.

2. The application as described in claim 1, characterized in that, In step 1, in the mixture A, the volume and concentration of the aluminum chloride solution corresponding to 3g of sodium montmorillonite powder are 80mL, 0.4mol·L⁻¹. -1 The stirring time is 20 minutes.

3. The application as described in claim 1, characterized in that, In step 2, the preparation conditions for mixture B include: water bath temperature 70℃, stirring time 20 min, and for every 5 mL of polyethylene glycol added, the corresponding amount and concentration of sodium hydroxide solution added is 192 mL (0.4 mol·L⁻¹). -1 The drop rate was 3 mL / min.

4. The application as described in claim 1, characterized in that, In step 3, the preparation conditions of the layered liquid C include: water bath temperature of 70°C, stirring time of 60 min, ultrasonic power of 100 W, ultrasonic time of 20 min, and aging time of 24 h.

5. The application as described in claim 1, characterized in that, In step 4, the preparation method of the aluminum pillared montmorillonite specifically includes: washing the precipitate alternately with distilled water and anhydrous ethanol until no Cl is present. - Dry at 70℃ for 12 hours, grind to 80-100 mesh, and calcine at 400℃ in a muffle furnace for 2 hours.

6. The application as described in claim 1, characterized in that, In step 5, the preparation method of the mixture D specifically includes: the molar ratio of bismuth nitrate, cerium nitrate, ferric nitrate, and cobalt nitrate is 1:(0.17~0.18):(0.58~0.59):(0.58~0.59); the amount of ethylene glycol monomethyl ether used is 10 mL; the amount and concentration of dilute nitric acid used are 15 μL; and the concentration is 0.1 mol·L⁻¹. -1 Add 5 mL of ethylene glycol, stir at room temperature for 10 min, and sonicate at 100 W for 10 min.

7. The application as described in claim 1, characterized in that, In step 6, the preparation conditions of sol E include: a mass ratio of perovskite active component to aluminum pillared montmorillonite of 1:(2.9~3.1), a water bath temperature of 80℃, and a water bath time of 1.5-2.5h.

8. The application as described in claim 1, characterized in that, In step 7, the preparation conditions for the co-doped perovskite catalyst include: drying temperature of 90°C, drying time of 24 h, and grinding time of 10 min.

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