A method for preparing and applying A-site reconstructed perovskite oxide

Abstract

This invention discloses an A-site reconstruction method for perovskite oxides, its preparation method, and its applications, relating to the field of catalyst technology. The perovskite oxide is a LaCoO3 / La(OH)3 composite, with La(OH)3 nanoparticles uniformly embedded on the LaCoO3 surface. By reconstructing the A-sites of the perovskite oxide through alkoxide hydrolysis, the inactive A-sites of the perovskite oxide are transformed into active centers, significantly improving catalytic activity and providing new insights for future material design and research on heterogeneous AOPs.

Description

Technical Field

[0001] This invention relates to the field of perovskite catalyst technology, and in particular to an A-site reconstructed perovskite oxide, its preparation method, and its application. Background Technology

[0002] Antibiotics are a class of drugs that kill or inhibit bacteria and are widely used to treat infectious diseases in humans and animals. However, due to the overuse and abuse of antibiotics, drug-resistant bacteria have emerged rapidly worldwide, severely impairing their effectiveness. Antibiotics have also been identified as high-risk substances in global risk assessments of thousands of micropollutants. Because treatment plants are insufficient to completely remove antibiotics, they still enter the aquatic environment, highlighting the urgent need for advanced treatment processes to effectively remove them.

[0003] Advanced oxidation processes (AOPs) have developed into a powerful technology for degrading recalcitrant organic pollutants by utilizing reactive oxygen species (ROSs). These free radicals, such as SO42-, are key components. − It has a strong oxidizing ability. Like 1 Non-free radicals like O2 exhibit high tolerance to various inorganic ions and organic compounds. SO4• − and 1 O2 generation typically originates from the activation of persulfate monosulfate (PMS) or persulfate disulfate (PDS) using various transition metal-based activators. Notably, cobalt-based catalysts exhibit excellent PMS / PS activation performance, which is attributed to the Co... 2+ The specific 3d band structure of perovskite oxides is crucial. Among these catalysts, cobalt-based perovskite oxides have emerged as rising stars in multi-metal catalysts due to their high design flexibility, tunable surface properties, and stability. However, it has been reported that the A-site of perovskite oxides does not directly participate in the catalytic reaction. Furthermore, perovskite oxides themselves have a relatively small specific surface area, limiting the exposure of the catalytically active B-site. Currently, doping, defect manipulation, interface engineering, and nanoengineering are widely used to improve the catalytic activity of perovskite oxides, while research on A-site modification of perovskite oxides is limited. Summary of the Invention

[0004] In view of this, the purpose of this invention is to address the shortcomings of the prior art by providing an A-site reconstruction method for perovskite oxides. This method involves reconstructing the A-site of perovskite oxides through alkoxide hydrolysis, transforming the inactive A-site of the perovskite oxide into an active center, significantly improving catalytic activity, and providing new ideas for future material design and research on heterogeneous AOPs.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A site-reconstructed perovskite oxide, wherein the perovskite oxide is a LaCoO3 / La(OH)3 composite, and the La(OH)3 nanoparticles are uniformly embedded in the LaCoO3 surface.

[0007] A method for preparing A-site reconstructed perovskite oxide includes the following steps:

[0008] (1) Add LaCoO3 to the solvent of glycerol and isopropanol while stirring;

[0009] (2) Then the above solution is transferred to an autoclave and heated at 180°C for 0.5-4 h to form lanthanum alkoxy as a precursor of La(OH)3;

[0010] (3) Wash with ethanol and distilled water in sequence, disperse in deionized water, then transfer the suspension to an autoclave, heat at 160°C for 0.5-6 hours, cool to room temperature, wash the precipitate and dry.

[0011] Furthermore, in step (1), the ratio of LaCoO3, glycerol and isopropanol is 0.3g: 15-25mL: 55-65mL.

[0012] Furthermore, the LaCoO3 is prepared by the following steps:

[0013] (1) Add La(NO3)3 and Co(NO3)2 to deionized water, stir magnetically for 0.5-1 hours, and then add EDTA and citric acid to the above solution. The molar ratio of La(NO3)3, Co(NO3)2, EDTA and citric acid is 1:1:2:4.

[0014] (2) Stir the solution vigorously and heat it to 90°C in a water bath. Evaporate the mixture until a purple gel is obtained and dry it for 12 hours.

[0015] (3) Grind and calcine the obtained brown sponge-like solid to obtain the product;

[0016] Furthermore, the calcination in step (3) is divided into two stages, with each stage lasting 5°C for 1 minute. -1 Heat to 200°C and calcine for 1 hour, then reduce temperature by 10°C / min. -1 Calcine at 900℃ for 6 hours.

[0017] Application of an A-site reconstituted perovskite oxide in the catalytic degradation of ENR.

[0018] Furthermore, the application conditions are: ENR concentration is...

[0019] 10 mg·L -1 The catalyst dosage was 0.1 g·L.-1 The dosage of [PMS] is 0.05-0.3 g·L. -1 The temperature is 295-310k.

[0020] Furthermore, the application conditions are: ENR concentration of 10 mg·L⁻¹. -1 The catalyst dosage was 0.1 g·L. -1 The dosage of [PMS] was 0.2 g·L. -1 The temperature is 300K.

[0021] Furthermore, the A-site reconstructed perovskite oxide was loaded onto a PVDF substrate to prepare a catalytic membrane for the catalytic degradation of ENR. The ENR solution was degraded by passing through the catalytic membrane under external pressure.

[0022] Furthermore, the catalyst loading is 5-10 mg, and the flux is 26.45-264.52 L / (m²). 2 h).

[0023] The beneficial effects of this invention are:

[0024] 1. This application develops an A-site reconstructed perovskite oxide LaCoO3 / La(OH)3 composite, wherein the (210) crystal plane of La(OH)3 is in close contact with LaCoO3 to form a heterojunction, and La(OH)3 nanoparticles are uniformly embedded in the surface of LaCoO3, with a weight ratio of LaCoO3 to La(OH)3 of 7-9:1.

[0025] 2. This application reconstructs the A-site of perovskite oxides through alkoxide hydrolysis. First, a sponge-like LC (LaCoO3) is prepared by sol-gel method. Then, glycerol and isopropanol are added, and the mixture is first alcoholized under high temperature and high pressure. The lanthanum alkoxy is formed through solvothermal reaction as a precursor of La(OH)3. Then, hydrolysis is carried out at high temperature and high pressure, so that La(OH)3 can slowly grow onto the surface of LaCoO3 through hydrolysis, thereby realizing the modification and reconstruction of the A-site of perovskite oxides. The preparation process is simple and can be easily realized for large-scale application.

[0026] A-site reconstruction increases the specific surface area of ​​the catalyst, thereby increasing its adsorption of target pollutants; A-site reconstruction alters the electronic structure of LC, enhancing the electronic activity of the La-f orbitals, and the formation of Co-O-La bridging bonds provides a channel for electrons to transfer from LC to La(OH)3, improving the conductivity of the material; the inactive La sites of perovskite oxides are transformed into active centers, increasing the variety of active sites; La and Co sites together serve as active sites for PMS activation; compared with LC with a single Co active site, LC24 exhibits 4.5 times higher PMS activation capacity and ENR degradation efficiency.

[0027] 3. The prepared product was characterized by XRD. During the surface reconstruction process, La(OH)3 gradually formed on the LC surface. FTIR results indicated that lanthanide alkoxides may have formed during the reaction. SEM characterization showed that nanoparticles aggregated on the product surface during the reconstruction of the A site, and La(OH)3 was regenerated on the LC surface with increasing ethanolation time. TEM clearly observed the interface structure, with LC24 showing obvious lattice diffraction fringes, indicating the formation of a heterojunction structure. Furthermore, Rietveld X-ray diffraction analysis showed that the ratio of LC to La(OH)3 in LC24 was 89.04% and 10.96%, respectively. After the A site reconstruction, the BET specific surface area of ​​LC24 increased from 2.5698 m² / g to 13.1377 m² / g, a significant increase in specific surface area, resulting in more exposed active sites and further enhancing the catalytic reaction. XPS analysis revealed electron redistribution and strong interfacial interactions between La(OH)3 and LC. The reconstructed La(OH)3 in LC24 showed... 2+ The proportion of total La increased to 60.00%, meaning that reconstructing the A site of LC24 can regulate the electronic structure of LC and enhance the electronic activity of the La-f orbitals.

[0028] 4. The mechanism of perovskite oxide reconstruction at site A in this application for catalytic degradation of ENR is as follows: PMS adsorbed on the heterogeneous interface of LC24 is activated to SO4• − and 1 The piperazine and quinolone rings of O2, ENR are susceptible to electrophilic attack, initially being attacked by SO4• through electron transfer and electrophilic addition, respectively. − and 1 O2 attack, and gradually decomposes into smaller molecules (CO2, H2O, NO3). - and F - ).

[0029] 5. In the application experiment, LC26 (alcoholization time 2h, hydrolysis time 6h) achieved a degradation efficiency of 99.89% (kJ) for ENR within 6 minutes. obs =0.754min -1 It exhibits high catalytic activity.

[0030] 6. Furthermore, this application also constructs an LC24 micro-catalytic membrane reactor, using vacuum assistance to tightly stack the catalyst on a PVDF membrane, forming complex channels to provide localized space for ENR degradation. The k-value of the LC24 membrane / PMS system... obs The value reached 441.34 min. -1 Compared to the traditional heterogeneous LC24 / PMS system (0.702 min), -1The efficiency was four orders of magnitude higher, and under conditions of catalyst loading of 10 mg and water flux of 26.45 LMH, the LC24 membrane / PMS system degraded 96.26% of enrofloxacin. The rapid activation of PMS in the membrane channel and the near-complete degradation of ENR were achieved within a short retention time of 9.67 ms. After 12 hours of continuous operation, the efficiency of ENR decomposition remained above 96.26%, and the system was highly stable.

[0031] This study not only provides new design guidance for regulating the active sites of catalytic materials through structural reconstruction, but also broadens the application of perovskite oxide-based catalytic membrane reactors in environmental remediation. Attached Figure Description

[0032] Figure 1 : Schematic diagram of LC and LC24 synthesis (a), XRD pattern of LC prepared in Example 1 and XRD patterns of oxides prepared with different alcoholization times at 4h hydrolysis time (b), FTIR spectra of different materials (c); XRD Rietveld pattern of LC24 (d); HR-TEM image of LC24 (e); EDS image of LC24 (f); Nitrogen adsorption and desorption isotherms of LC and LC24 (g).

[0033] Figure 2 High-resolution spectra of La 3d (a), Co 2p (b), and O 1s (c) in LC and LC24, and DOS plots of La(OH)3 (d), LC (e), and LC24 (f).

[0034] Figure 3 Oxides prepared at different alcoholysis times (a, hydrolysis time of 4 h) and different hydrolysis times (b, alcoholysis time of 2 h) and their LC degradation curves for ENR; k-values ​​of ENR degradation at different alcoholysis and hydrolysis times. obs Value (c); Degradation curves of ENR at different PMS doses in LC / PMS (d) and LC24 / PMS (e) systems; k in LC / PMS and LC24 / PMS systems with different PMS concentrations. obs Value (f); degradation curves of ENR and apparent activation energy (i) of LC / PMS (g) and LC24 / PMS (h) in the system at different temperatures. Conditions: ENR = 10 mg / L, catalyst = 0.1 g / L, PMS = 0.2 g / L, initial pH = 6.65, T = 27°C.

[0035] Figure 4: Schematic diagram of catalytic membrane reactor (a); Degradation of ENR in LC24 membrane / PMS system under different catalyst loading and flux (b); Absorbance of PMS in LC24 membrane / PMS system at different reaction times (c); Continuous degradation curve of ENR in LC24 membrane / PMS system (d); Effect of inorganic ions on ENR degradation in LC24 membrane / PMS system (e); Adsorption energy of PMS on LC (f); Adsorption energy of PMS on LC24 (g).

[0036] Figure 5 XRD patterns of oxides prepared at different hydrolysis times (2 h): alcoholysis time.

[0037] Figure 6 XRD patterns of La(OH)3, Co3O4 and LC-AS.

[0038] Figure 7 SEM images of (a) LC, (b) al0.5, (c) al2, (d) al4, and (e) al6.

[0039] Figure 8 SEM images of: (a) LC, (b) hy0.5, (c) hy2, (d) hy4, (e) hy6, (f) La(OH)3, and (g) Co3O4.

[0040] Figure 9 TEM image of LC24.

[0041] Figure 10 High-resolution XPS images of LC and LC24.

[0042] Figure 11 Electron density difference diagram at the LaCoO3 / La(OH)3 interface; dark yellow and cyan areas represent charge accumulation and depletion, respectively.

[0043] Figure 12 Adsorption curves of NER by LC, LC24, and La(OH)3.

[0044] Figure 13 Degradation curves of NER in different reaction systems, where: [enrofloxacin] = 10 mg·L⁻¹ -1 [catalyst] = 0.1 g·L -1 [PMS] = 0.2 g·L -1 , initial pH = 6.65, T = 27 ℃.

[0045] Figure 14 First-order kinetic fitting curves of ENR degradation by LC at different alcoholization times.

[0046] Figure 15 First-order kinetic fitting curves of LC degradation of ENR at different hydrolysis times.

[0047] Figure 16 First-order kinetic fitting curves of ENR degradation in LC / PMS systems with different PMS doses.

[0048] Figure 17 First-order kinetic fitting curves of ENR degradation in LC24 / PMS systems with different PMS doses.

[0049] Figure 18 First-order kinetic fitting curves of ENR degradation by LC / PMS at different temperatures.

[0050] Figure 19 First-order kinetic fitting curves of ENR degradation in the LC24 / PMS system at different temperatures.

[0051] Figure 20 kJ at different temperatures in LC / PMS and LC24 / PMS systems obs value.

[0052] Figure 21 : Absorbance of PMS in LC / PMS systems with different reaction times.

[0053] Figure 22 Activation rate of PMS in LC / PMS and LC24 / PMS systems.

[0054] Figure 23 : Absorbance of PMS in the LC24 / PMS system at different reaction times.

[0055] Figure 24 First-order kinetic fitting curve of ENR degradation in LC24 membrane / PMS system.

[0056] Figure 25 Activation rate curves of PMS in LC24 / PMS and LC24 membrane / PMS systems.

[0057] Figure 26 XRD patterns of LC24 before and after use.

[0058] Figure 27 High-resolution XPS graphs before and after using LC24.

[0059] Figure 28 The effect of inorganic ions on ENR degradation in the LC24 / PMS system.

[0060] Figure 29 Degradation curves of ENR in a lanthanum-based catalyst reaction system.

[0061] Figure 30 : Absorbance of PMS in the La(OH)3 / PMS system at different reaction times.

[0062] Figure 31 Activation rate curve of PMS in La(OH)3 / PMS system.

[0063] Figure 32 pH change curves in La(OH)3 / PMS, LC24 / PMS and LC / PMS systems. Detailed Implementation

[0064] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the following embodiments, the prepared LaCoO3 is abbreviated as LC, and LCxy refers to oxides prepared with different alcoholysis times (x) and different hydrolysis times (y). The A-site reconstructed perovskite oxide LaCoO3 / La(OH)3 complex prepared in Example 1 is abbreviated as LC24. The product prepared in Example 3 that only underwent an alcoholysis process is abbreviated as LC-SA. Example 1

[0065] A type of A-site reconstructed perovskite oxide, a LaCoO3 / La(OH)3 composite, wherein La(OH)3 nanoparticles are uniformly embedded on the LaCoO3 surface, is prepared by the following steps:

[0066] (1) Add 0.3g LaCoO3 to a solvent containing 20mL glycerol and 60mL isopropanol for 0.5 hours with stirring;

[0067] (2) Then the above solution is transferred to an autoclave and heated at 180°C for 2 hours (alcoholization) to form lanthanum alkoxy as a precursor of La(OH)3 through a solvothermal reaction;

[0068] (3) Wash the sample three times with ethanol and distilled water in sequence, and finally disperse it in 30 mL of deionized water; then transfer the suspension to an autoclave and heat it at 160 °C for 4 hours (hydrolysis). During the hydrothermal process, La(OH)3 can slowly grow to the surface of LaCoO3 through hydrolysis. After cooling to room temperature, wash the precipitate and dry it to obtain LC24.

[0069] The above-mentioned LaCoO3 was prepared by the following steps (see...) Figure 1 a):

[0070] (1) Add 6 mmol La(NO3)3 and 6 mmol Co(NO3)2 to a beaker containing 50 mL of deionized water, stir magnetically for 0.5 hours, and then add 12 mmol EDTA and 24 mmol citric acid to the above solution;

[0071] (2) Stir the solution vigorously and heat it to 90°C in a water bath. Evaporate the mixture until a purple gel is obtained. Immediately dry it in a drying oven at 130°C for 12 hours.

[0072] (3) Grind the obtained brown sponge-like solid and calcine it in two stages: calcine at 200℃ for 1 hour (5℃ min). −1 Then, it was calcined in ambient air at 900°C for 6 hours (10°C min). -1 ), to obtain LC(LaCoO3).

[0073] Examples 2-5

[0074] The hydrolysis time in step (3) is 4 hours, and the alcoholysis time in step (2) is adjusted to 0.5 hours (al0.5).

[0075] 2h (al2), 4h (a4), 6h (al6), and other processes are the same as in Example 1.

[0076] Examples 6-9

[0077] The alcoholization time in step (2) is 2 hours, and the hydrolysis time in step (3) is adjusted to hy0.5, hy2, hy4, and hy6 respectively. Other processes are the same as in Example 1.

[0078] Comparative Example 1

[0079] The steps for preparing LC-SA are as follows:

[0080] (1) Add 0.3g LaCoO3 to a solvent containing 20mL glycerol and 60mL isopropanol for 0.5 hours with stirring;

[0081] (2) Then the above solution was transferred to an autoclave, heated at 180°C for 2 hours, the precipitate was washed and dried to obtain LC-SA.

[0082] LC-SA is a product prepared by treating LC with glycerol and isopropanol under high temperature and high pressure, followed by direct washing and drying, without further hydrolysis.

[0083] Comparative Example 2

[0084] Preparation of La(OH)3: Replace 0.3g LaCoO3 in Example 1 with 0.3g La(NO3)3, and keep other processes unchanged. The product prepared is La(OH)3.

[0085] I. Performance Testing

[0086] 1. XRD characterization

[0087] X-ray diffraction (XRD) pattern Figure 1 b) indicates that the LC prepared in Example 1 has good crystallinity, which is consistent with LaCoO3 (JCPDS No. 84-0848). The main diffraction peaks at 2θ = 23.235, 32.886, 33.298 and 47.501° correspond to the (110), (-110), (112) and (220) crystal planes, respectively.

[0088] Examples 2-5 investigated the effect of different alcoholysis times on the LC structure, with a hydrolysis time of 4 hours. Figure 1 As shown in b, 0.5 hours had the least effect on the LC crystal structure. Extending the reaction time to 2 hours (al2), a new set of diffraction peaks (JCPDS number 83-2034) associated with La(OH)3 were observed at 15.616, 27.220, 27.970, and 39.425°, attributed to the (100), (110), (101), and (201) crystal planes, respectively. With increasing reaction time to 4 hours (al4), the intensity of the La(OH)3 diffraction peaks increased. Furthermore, additional peaks corresponding to Co3O4 (JCPDS number 76-1802) began to appear at 36.266° and 36.840°. After 6 hours (al6), the intensity of the characteristic diffraction peaks of La(OH)3 and Co3O4 further increased, while the characteristic peaks of LC weakened with increasing reaction time. Given that the La-O bond is weaker than the Co-O bond, under high temperature, high pressure, and weakly acidic conditions of the alcohol, the La-O chain preferentially breaks to form a lanthanide alkoxide, which then hydrolyzes to lanthanum hydroxide. As the reaction time increases, the La-O bonds on the surface are rebuilt, while the Co-O octahedral structure retained by LC forms Co3O4.

[0089] Meanwhile, Examples 6-9 investigated the effects of different hydrothermal times on the LC structure, such as... Figure 5 As shown, when the alcoholysis time is fixed at 2 hours, the hydrothermal time (hy0.5-hy6) affects the formation of La(OH)3. The trend is that the La(OH)3 content gradually increases, becoming relatively stable after 4 hours. The XRD spectra of pure La(OH)3 and Co3O4 are shown below. Figure 6 As shown in the figure. These XRD results indicate that La(OH)3 and Co3O4 gradually form on the LC surface during the surface reconstruction process.

[0090] 2. FTIR detection

[0091] FTIR is used to track the reconstruction process at site A. Figure 1c). 3430 cm -1 and 1636 cm -1 The bands at 560 cm⁻¹ can be attributed to the OH vibrations of adsorbed water on the surfaces of samples LC, LC₂⁴, LC-AS, and La(OH)₃. LC, LC₂⁴, and LC-SA show bands at 560 cm⁻¹. -1 The band structure observed at 3320 cm⁻¹ is characteristic of the Co-O stretching vibration mode. The AS solution at 3320 cm⁻¹... -1 The peak of the OH stretching vibration of alcohol is shown at 2924 cm⁻¹. -1 The peak of the symmetric stretching vibration of CH3 is located at 1457 cm⁻¹. -1 The bending vibration peak of CH3 at 1120 cm⁻¹, and at 1120 cm⁻¹ -1 The corresponding CO stretching vibration is observed. LC-AS, which is the result of alcoholysis only, inherits most of the characteristic peaks of AS (2924 cm⁻¹). -1 1457cm -1 1120 cm -1 The results indicate a strong interaction between the alcohol and LC. A similar interaction was also observed at 1408 cm⁻¹ in LC₂⁴ and La(OH)₃. -1 The presence of a CO stretching vibration peak at this location is likely due to the interaction between surface La(OH)3 and atmospheric CO2. These FTIR results suggest that lanthanide alkoxides may be formed during the reaction.

[0092] 3. SEM characterization

[0093] Figure 7 Scanning electron microscopy (SEM) revealed that LC exhibited good dispersibility, with particle sizes of 300-500 nm, smooth surfaces, and a bean-like morphology. The surface of sample al0.5 became rough, likely due to the breaking of La-O bonds. The generation of nanoparticles with an average size of approximately 100 nm was observed on the surface of sample al2, attributed to the reconstruction of A sites. Sample al4 showed a high degree of nanoparticle aggregation on its surface. Nevertheless, the original bean-like appearance of LC was preserved. In sample al6, further alcoholysis led to the appearance of nanosheets interspersed with nanoparticles. For these samples hy0.5-hy6, SEM images (…) Figure 8 As can be seen, both the surface roughness and the number of surface nanoparticles in the LC surface have increased. For example... Figure 8 As shown in f and 8g, SEM images reveal that the original La(OH)3 and Co3O4 possess nanoparticle and nanosheet structures, respectively. These SEM results are consistent with XRD analysis, showing that La(OH)3 and Co3O4 are successively regenerated on the LC surface with increasing alcoholysis time.

[0094] 4. X-ray diffraction Rietveld full spectrum fitting analysis, HR-TEM, and specific surface area detection

[0095] XRD full-spectrum fitting was used to accurately determine the content of each phase in LC24. The LaCoO3 / La(OH)3 polycrystalline material was refined using the R-3cH and P63 / m space group models. The refinement results for LC24 are shown below. Figure 1 As shown in d and Table 1, the sample fit is very high (Rwp=3.34%, Rp=2.4%, χ²). 2 =2.14). These results indicate that the ratio of LC to La(OH)3 in LC24 is 89.04% and 10.96% (i.e., 8.12:1). The interface structure can be clearly observed by transmission electron microscopy (TEM) images. Figure 9 High-resolution TEM (HR-TEM) images show that LC24 exhibits distinct lattice diffraction fringes. Figure 1 e), the lattice distance of 0.2140 nm corresponds to the (210) crystal plane of La(OH)3, and the (210) crystal plane of La(OH)3 is in close contact with LaCoO3 to form a heterojunction. In addition, energy dispersive spectroscopy (EDS) mapping was performed, revealing that the distribution of La, Co and O elements is uniform. Figure 1 f). Furthermore, after reconstruction at site A, LC24 exhibited a type III isotherm with a hysteresis loop, and the BET specific surface area increased from 2.5698 m² / g in LC to 13.1377 m² / g (f). Figure 1 g). An increase in specific surface area means enhanced adsorption properties and more exposed active sites.

[0096] Table 1. Rietveld X-ray diffraction analysis of LC24

[0097]

[0098] 5. XPS detection

[0099] The surface elemental composition and chemical state of LC and LC24 were investigated using X-ray photoelectron spectroscopy (XPS). The coexistence of La, Co, and O elements in LC and LC24 was also studied. Figure 10 As shown. In the high-resolution La 3d spectrum, the two pairs of peaks in LC correspond to La... 2+ 834.07 eV and 850.67 eV and La 3+ At 837.74 eV and 854.36 eV ( Figure 2 a). In Figure 2 In the high-resolution Co 2p spectrum of b, the peaks at 780.03 eV and 795.15 eV correspond to Co 3+The peaks at 782.01 eV and 790.67 eV correspond to Co. 2+ In high-resolution O 1s spectra ( Figure 2 c), the peaks at 529.02 eV, 531.35 eV, and 532.56 eV were designated as lattice oxygen (O). I ), high oxygen species (O II ) and surface-adsorbed oxygen species (O III Importantly, it was found that through normalization, Co 2+ / (Co) 3+ +Co 2+ The ratio was LC (31.05%) > LC24 (28.88%). In LC24, La... 2+ The proportion relative to total La increased to 60.00% (LC (52.81%)). The results indicate that there is electron redistribution and strong interfacial interaction between La(OH)3 and LC.

[0100] To elucidate interfacial interactions, the charge density distribution at the LC24 interface was investigated using DFT calculations. The Fermi level intersects with the total density of states of La(OH)3, LC, and LC24, indicating that all compositions retain metallic properties. (The text then abruptly shifts to a seemingly unrelated topic about La(OH)3, charge density distribution, and its relationship to La(OH)3.) Figure 2 d) and LC ( Figure 2 Compared to e), LC24 ( Figure 2 The increased total density of states (DOS) intensity (f) leads to an increase in the number of conductive charge carriers in the composite material. Therefore, the interfacial properties effectively improve the conductivity of LC24. A systematic analysis of the projected density of states (PDOS) was performed to assess the changes in energy states. For the original La(OH)3 and LC, the band gap between the La-f and Op orbitals indicates weak interactions between the La-O bonds. In contrast, the La-f orbitals in LC24 are close to the Fermi level, while the band gap gradually disappears. Therefore, the La-f and Co-p orbitals overlap with the Op orbitals, forming La-O-Co bridging bonds, providing a channel for interfacial electron transfer. Charge transfer was quantified using charge density difference and Bader topological analysis. Figure 11 In the image, the charge accumulation region is depicted in yellow, and the charge depletion region in cyan, indicating a significant redistribution of electrons at the interface after LC24 formation. Measurements show that 0.165e... - Transfer from each LC primitive cell to La(OH)3 resulted in electron accumulation on La(OH)3. The calculated results were consistent with XPS analysis, which showed that La(OH)3 was reconstituted after LC24 reconstruction. 2+The content increases. Therefore, reconstructing the A-site of LC24 can modulate the electronic structure of LC and enhance the electronic activity of the La-f orbitals. The formation of the Co-O-La bridging bond provides a channel for electrons to transfer from LC to La(OH)3, thereby improving the conductivity of the material.

[0101] II. Application Experiment 1

[0102] 10 mg of enrofloxacin (ENR) was dissolved in 1 L of deionized water to prepare an enrofloxacin solution. 50 mL of this solution was measured and placed in a three-necked round-bottom container. 5 mg of catalyst was then added, and the mixture was mechanically stirred for 30 minutes to establish adsorption-desorption equilibrium. Subsequently, 200 μL of 50 g / L PMS was added to initiate the reaction. At regular intervals, 1 mL of the suspension was taken out and immediately mixed with 100 μL of methanol pre-filled into centrifuge tubes to quench any potential reactions. The catalyst was filtered through a 0.22 μm nylon membrane, and the filtrate was collected in a sample vial. The initial pH of the reaction system was approximately 6.65, which was subsequently adjusted by adding diluted KOH and H₂SO₄. The used catalyst was recovered by filtration, washing, and drying. C₀ (mg / L) and C₂SO₄ were also discussed. t (mg / L) represent the initial and reaction time t ENR concentrations, respectively; k obs (min -1 ) is the reaction rate constant; t (min) is the reaction time.

[0103] Compared with LC (13.25%), LC24 and La(OH)3 showed better adsorption performance for ENR, with adsorption capacities of 20.22% and 19.69%, respectively. Figure 12 This enhanced performance is attributed to the excellent adsorption capacity of La(OH)3. Figure 13 The results showed that only 4.77% of ENR was decomposed by PMS, while LC achieved a 69.20% removal rate of ENR within 8 minutes. Figure 3 The effect of alcoholization time on degradation performance was studied. As the alcoholization time increased, the degradation performance first increased and then decreased. Figure 3 a), corresponding k obs The values ​​exhibit a volcanic-like variation. Figure 3 c and Figure 14 When the alcoholysis time is set to 2 hours, the optimal degradation efficiency is 98.71% (kJ / L). obs =0.702 min -1 This is attributed to the in-situ reconstruction of La(OH)3 on the LC surface. Pure La(OH)3 was shown to participate in the degradation of ENR by PMS activation, with a degradation efficiency of 91.96%. Figure 13However, after 1 minute of reaction, the power of pure La(OH)3 was significantly insufficient. Due to the formation of Co3O4, the degradation efficiency decreased with increasing alcoholysis time. Co3O4 ( Figure 13 The inherent activity of ENR was 13.61%, lower than that of La(OH)3, and its formation significantly masked other active sites. With increasing hydrolysis time, the degradation performance of ENR gradually increased from 82.36% to 99.89%. Figure 3 b) It reaches a stable state after 4 hours, k obs The value increased from 0.199 to 0.754 min. -1 This is consistent with the effect of hydrolysis time on the surface La(OH)3 content. Figure 3 c and Figure 15 Considering cost and performance, the optimal alcoholysis and hydrolysis times are 2 hours and 4 hours, respectively, and the product prepared is LC24.

[0104] The catalytic activity of LC and LC24 was systematically studied under different PMS dosages and temperatures. Increasing the PMS dosage from 0.05 g / L to 0.30 g / L improved the degradation efficiency of the LC / PMS system, increasing it from 41.69% to 82.05%. Figure 3 d). This growth is accompanied by k obs The value increased accordingly, from 0.09 to 0.214 min. -1 ( Figure 3 f and Figure 16 Under similar conditions, the degradation efficiency of the LC24 / PMS system significantly increased from 82.34% to 99.65%. Figure 3 e), k obs The value increased from 0.362 to 0.897 min. -1 ( Figure 3 f and Figure 17 Compared to LC, the reaction kinetics of LC24 were improved by 3.6-4.5 times, indicating that A-site reconstruction in LC effectively improved the mass transfer efficiency of the heterogeneous interface. Activation energy (Ea) is also an important factor in characterizing chemical reaction kinetics. External heating (295-310 K) improved the degradation efficiency of LC / PMS and LC24 / PMS systems to varying degrees. Figure 3 gh). k of the LC / PMS system obs The value increased from 0.085 to 0.338 min. -1 ( Figure 17-20 Parallel increases were observed in the LC24 / PMS reaction system, increasing from 0.361 to 1.382 min. -1 By fitting k at different temperatures obs The value determines (Ea). For example... Figure 3As shown in h, the Ea value of LC24 is 65.709 kJ / mol, which is lower than that of LC (69.247 kJ / mol), indicating a lower energy barrier and easier reaction completion. The difference in ENR elimination between the LC / PMS and LC24 / PMS systems is related to the activation ability of PMS. In the LC / PMS system, the PMS concentration changes the least before and after the reaction ( Figure 21 The activation rate of PMS was only 12.83%. Figure 22 In contrast, the PMS concentration in the LC24 / PMS system changed significantly ( Figure 23 Of these, 57.31% of the PMS were activated. Therefore, the enhanced activation of the PMS is the reason for the rapid degradation of the ENR in the LC24 / PMS system.

[0105] III. Application Experiment Two

[0106] Design a micro catalytic membrane reactor (see...) Figure 4 a) Vacuum-assisted packing of the catalyst onto the PVDF membrane creates complex channels, providing localized spaces for ENR degradation. Since the pollutant solution does not readily pass through the catalytic membrane spontaneously, external gas pressure is used to force the solution through and regulate its flux. The specific operation method is as follows:

[0107] LC24 was dispersed in 20 mL of distilled water and continuously sonicated for 1 hour. Under vacuum conditions, the solution was directly filtered onto a PVDF substrate (47 mm diameter, 0.45 μm pore size) to prepare an LC24 catalytic membrane. The membrane was then supported by a stainless steel grid and sealed within a micro-integrated stainless steel support. The complete catalytic membrane reactor consisted of an air compressor, pressure regulator, reservoir, and catalytic membrane support connected in series (see [link to documentation]). Figure 4 a). ENR and PMS water flowed through the catalytic membrane under gas pressure, and Table 2 lists the relevant experimental parameters.

[0108] Flux through the LC24 membrane: J=V q / (S m ×T), J ((L / (m 2 h)), LMH) represent flux; Vq(L) is the volume of the filtered solution; Sm(m 2 ) represents the effective filtration area of ​​the membrane; T(h) is the permeation time.

[0109] Calculate the retention time (t, ms) in the LC membrane: t = (3600V) m ×m) / (J×S m ), where V m (cm) 3 / g) is the pore volume of LC24, m(g) is the total mass of catalyst supported, J(LMH) is the water flux, and S m(m) 2 ) is the effective membrane filtration area, and T(h) is the permeation time.

[0110] Table 3 lists the retention times of ENR solution through catalytic membranes with different catalyst loadings and fluxes.

[0111] Table 2. Experimental parameters of the reactor

[0112]

[0113] Table 3. Retention time of ENR solution through catalytic membranes with different catalyst loadings and fluxes

[0114]

[0115] The solution flux was adjusted within the range of 26.45-264.52 LMH. Figure 4 As shown in b, the degradation efficiency of ENR is positively correlated with the catalyst loading (ENR concentration 10 mg / L). A catalytic membrane with a catalyst loading of 5 mg operating at a flux of 26.45 LMH showed an ENR degradation efficiency of 89% and a retention time of 4.84 ms (Table 3). Notably, the k... obs The value reached 441.34 min. -1 ( Figure 24 ), compared to the traditional heterogeneous LC24 / PMS system (0.702 min), -1 The efficiency was four orders of magnitude higher, indicating that the catalytic membrane had a stronger ability to degrade ENR. Under conditions of a catalyst loading of 10 mg and a water flux of 26.45 LMH, the LC24 membrane / PMS system degraded 96.26% of enrofloxacin. Rapid activation of PMS in the membrane channels and near-complete degradation of ENR were achieved within a short retention time of 9.67 ms. Furthermore, the activation rate of PMS in the LC24 membrane / PMS system reached 58.30%. Figure 4 c and Figure 25 The results showed that the local space of the catalytic membrane can improve mass transfer efficiency and free radical utilization. After 12 hours of continuous operation, the efficiency of ENR decomposition remained above 96.26%. Figure 4 d). Therefore, the LC24 membrane / PMS system exhibits stable and efficient performance in the degradation of ENR. Meanwhile, the XRD spectrum of the reacted LC24 membrane showed characteristic peaks for LC and La(OH)3, with no other peaks detected. Figure 26 XPS measurements of the reaction LC24 showed a decrease in the intensity of the characteristic peaks for La, Co, and O, while the intensity of the C peak significantly increased. This is attributed to the adsorption of ENR or its intermediates on the surface of the reaction LC24. Figure 27These findings indicate that LC24 has a robust structure.

[0116] IV. Interference Experiment

[0117] The effect of inorganic ions in actual wastewater on the LC24 membrane / PMS system was simulated. Figure 4 As shown in e, add NO3 - H2PO4 - and Cl - There was no significant effect on the LC24 membrane / PMS system. Instead, HCO3 was found... - The presence of (4-20 mM) significantly hindered the degradation of ENR, reducing removal efficiency by 41.96% to 26.98%. This finding is consistent with the established interference effect of inorganic ions on conventional suspension systems. Figure 28 This phenomenon is related to HCO3. - It can attack SO4• − It also generates less reactive carbonate free radicals (HCO3•, CO3•). − This is related to the fact that the LC24 membrane / PMS system has a certain resistance to inorganic ions.

[0118] V. Mechanism Research

[0119] Identifying active sites on the catalyst surface. It has been reported that the B-site of perovskite oxides often acts as the main active site, while the A-site does not directly participate in the catalytic reaction. However, after A-site reconstruction, LC24 was found to significantly enhance the degradation of ENR, thus necessitating an investigation into the role of La(OH)3. La(OH)3 is commonly used as an adsorbent for the recovery of phosphates from aquatic environments, and compared to LC, it exhibits superior adsorption performance for ENR. Figure 13 This enhanced adsorption of La(OH)3 contributes to improving the catalytic performance of LC24. For example... Figure 29 As shown, La 3+ The degradation performance of the / PMS system for ENR is consistent with that of the PMS-only system, indicating that La 3+ It does not activate PMS. However, in the La2O3 / PMS and La(OH)3 / PMS systems, the degradation efficiencies of ENR were 35.38% and 91.96%, respectively. This finding indicates that lanthanum oxide / hydroxide can promote the activation of PMS, thereby degrading ENR, wherein La(OH)3 can activate 17.92% of the PMS in the reaction system (…). Figures 30-31In particular, the initial pH of the La(OH)3 dispersion in ENR solution was 7.40, higher than that of LC (pH 6.43) and LC24 (pH 6.65). When PMS was added to initiate the reaction, the pH values ​​of the La(OH)3 / PMS, LC / PMS, and LC24 / PMS systems stabilized at approximately 5.50, 3.70, and 4.00, respectively. Figure 32 It has been reported that alkalis are used as novel activators for PMS. The excellent degradation performance of La(OH)3 is also attributed to its alkaline effect. In summary, La(OH)3 not only promotes the adsorption of ENR but also plays a role in the activation of PMS. Refined XRD analysis showed that when LC and La(OH)3 were physically mixed, the degradation efficiency was 49.69%, lower than that of the LC24 / PMS system. The enhanced catalytic performance of LC24 is related to the formation of a heterojunction with strong interactions and electron transfer between Co-O-La covalent bonds.

[0120] To gain a deeper understanding of the catalytic mechanism of PMS activation at the LC24 interface, DFT calculations were used to evaluate the adsorption energy. Three potential adsorption sites were considered: the top sites at the La, Co, and O positions. After structural optimization, the two oxygen atoms on the PMS are consistently adsorbed at the Co-Co bridge site of the LC, with an adsorption energy of -2.22 eV. Figure 4 f). Similarly, after structural optimization, the two oxygen atoms on the PMS are always adsorbed at the La-Co bridging site of LC24, resulting in a significantly stronger adsorption energy of -4.06 eV ( Figure 4 (g). This indicates that La and O sites are not stable adsorption sites for PMS on LC, while Co-Co bridging sites are stable. In contrast, the optimal adsorption site for LC24 is the La-Co bridging site. The results show that the heterojunction formed by LC and La(OH)3 provides more stable adsorption for PMS, and that both La and Co sites act as active sites for LC24.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing A-site reconstructed perovskite oxide, characterized in that: Includes the following steps: (1) Add LaCoO3 to the solvent of glycerol and isopropanol while stirring; (2) Then the above solution is transferred to an autoclave and heated at 180°C for 0.5-4 h to form lanthanum alkoxy as a precursor of La(OH)3; (3) Wash with ethanol and distilled water in sequence, disperse in deionized water, then transfer the suspension to an autoclave, heat at 160°C for 0.5-6 h, cool to room temperature, wash the precipitate and dry; The perovskite oxide is a LaCoO3 / La(OH)3 composite. The (210) crystal plane of La(OH)3 is in close contact with LaCoO3 to form a heterojunction. La(OH)3 nanoparticles are uniformly embedded in the surface of LaCoO3. The weight ratio of LaCoO3 to La(OH)3 is 7-9:

1.

2. The method for preparing A-site reconstructed perovskite oxide according to claim 1, characterized in that: In step (1), the ratio of LaCoO3, glycerol and isopropanol is 0.3g: 15-25mL: 55-65mL.

3. The method for preparing A-site reconstructed perovskite oxide according to claim 1, characterized in that: The LaCoO3 is prepared by the following steps: (1) Add La(NO3)3 and Co(NO3)2 to deionized water, stir magnetically for 0.5-1 hours, and then add EDTA and citric acid to the above solution. The molar ratio of La(NO3)3, Co(NO3)2, EDTA and citric acid is 1:1:2:

4. (2) Stir the solution vigorously and heat it to 90°C in a water bath. Evaporate the mixture until a purple gel is obtained and dry it for 12 hours. (3) Grind and calcine the obtained brown sponge-like solid to obtain the product.

4. The method for preparing A-site reconstructed perovskite oxide according to claim 3, characterized in that: The calcination in step (3) is divided into two stages, at 5℃·min -1 Heat to 200℃ and calcine for 1 hour, then calcine at 10℃·min. -1 Calcine at 900℃ for 6 hours.

5. The application of the A-site reconstituted perovskite oxide prepared by the preparation method of claim 1 as a catalyst in the catalytic degradation of ENR.

6. The application according to claim 5, characterized in that: Application conditions: ENR concentration was [value missing]. 10 mg·L -1 The catalyst dosage was 0.1 g·L. -1 The dosage of PMS is 0.05-0.3 g·L. -1 The temperature is 295-310K.

7. The application according to claim 6, characterized in that: Application conditions: ENR concentration was [value missing]. 10 mg·L -1 The catalyst dosage was 0.1 g·L. -1 The PMS dosage was 0.2 g·L⁻¹. -1 The temperature is 300K.

8. The application according to claim 5, characterized in that: A-site reconstructed perovskite oxide was loaded onto a PVDF substrate to prepare a catalytic membrane for the catalytic degradation of ENR. The ENR solution was degraded by passing through the catalytic membrane under external pressure.

9. The application according to claim 8, characterized in that: The catalyst loading is 5-10 mg, and the flux is 26.45-264.52 L / (m²). 2 ·h).

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