Lanthanum-doped composite catalyst as well as preparation method and application thereof

Abstract

The invention provides a lanthanum-doped composite catalyst and a preparation method and application thereof, and belongs to the technical field of catalyst preparation and pollutant degradation, and the preparation method of the lanthanum-doped composite catalyst comprises the following steps: uniformly mixing solid raw materials including urea, oxalic acid and a lanthanum source to obtain a solid mixture; and calcining the solid mixture in an inert atmosphere to obtain the lanthanum-doped composite catalyst.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation and pollutant degradation technology, and particularly relates to a lanthanum-doped composite catalyst, its preparation method and application. Background Technology

[0002] In recent years, with the rapid development of the pharmaceutical and cleaning industries, pharmaceutical and personal care products (PPCPs) have gradually come into people's view as a new type of pollutant. These substances are continuously introduced into the environment, causing water pollution problems to become increasingly prominent. Therefore, how to efficiently treat wastewater containing PPCPs has become an urgent task.

[0003] Current nitrogen-carbon catalysts are widely used, but they suffer from problems such as metal ion leaching, susceptibility to environmental pH, and limited ability to remove PPCPs in ozone (O3) systems. There is still room for improvement in the performance of nitrogen-carbon catalysts. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a lanthanum-doped composite catalyst, its preparation method, and its applications, aiming to at least partially solve the above-mentioned technical problems. The technical solution provided by this invention is as follows.

[0005] As a first aspect of the present invention, a method for preparing a lanthanum-doped composite catalyst is provided, comprising: uniformly mixing a solid raw material including urea, oxalic acid and a lanthanum source to obtain a solid mixture; and calcining the solid mixture under an inert atmosphere to obtain a lanthanum-doped composite catalyst.

[0006] As a second aspect of the present invention, a lanthanum-doped composite catalyst prepared by the above preparation method is provided, comprising: a support, and lanthanum oxycarbonate supported on the support; wherein the support is nitrogen-doped carbon or carbon nitride.

[0007] As a third aspect of the present invention, an application of the above-described lanthanum-doped composite catalyst in the degradation of pollutants is provided.

[0008] Based on the above technical solution, the lanthanum-doped composite catalyst, its preparation method, and its application provided by this invention have at least one of the following beneficial effects:

[0009] (1) In this invention, urea, oxalic acid, and lanthanum source are mixed by simple mechanical mixing to obtain a solid mixture, and the solid mixture is calcined under an inert atmosphere to obtain a lanthanum-doped composite catalyst with a lanthanum oxycarbonate (La2CO5) structure. The method for preparing this lanthanum-doped composite catalyst in this invention is relatively simple, the process is controllable, and the catalytic performance of the obtained lanthanum-doped composite catalyst is stable. The overall cost is low, and it is easy to achieve mass production.

[0010] (2) In this invention, the lanthanum-doped composite catalyst has a mesoporous structure and a special La2CO5 structure. It can generate more hydroxyl sites by adsorbing water in the environment, thereby effectively improving the catalytic ability of the lanthanum-doped composite catalyst and enabling the rapid degradation of pollutants. Attached Figure Description

[0011] Figure 1 The image shows a scanning electron microscope (SEM) image and elemental distribution diagram of the nitrogen-carbon-based lanthanum (La2CO5-NC-600) catalyst in Example 1 of this invention.

[0012] Figure 2 This is a graph showing the effect of different catalysts on the degradation of DEET pollutants in Test Example 1 of this invention;

[0013] Figure 3 This is a graph showing the effect of different catalysts on the degradation of DEET pollutants in Test Example 2 of this invention;

[0014] Figure 4 This is a graph showing the degradation effect of different catalysts on DEET pollutants in Test Example 3 of this invention;

[0015] Figure 5 This is a test graph showing the cycle stability of the La2CO5-NC-600 catalyst in Test Example 4 of this invention;

[0016] Figure 6 This is a graph showing the effect of metal ion leaching on the La2CO5-NC-600 catalyst in the cycle stability test of Test Example 4 of the present invention;

[0017] Figure 7 This is a graph showing the effect of the La2CO5-NC-600 catalyst on the degradation of DEET pollutants at different pH levels in Test Example 5 of this invention;

[0018] Figure 8 Adsorption pore size diagrams for different materials;

[0019] Figure 9 X-ray diffraction patterns of different materials;

[0020] Figure 10 The image shows the SEM image of the carbon nitride catalyst in Comparative Example 1. Detailed Implementation

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough 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. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0022] Nitrogen-carbon materials, or carbonitriding materials, are polymeric materials composed of carbon and nitrogen. Currently, thermal polymerization is commonly used to prepare nitrogen-carbon materials or carbonitriding materials. However, the resulting nitrogen-carbon materials or carbonitriding materials usually suffer from problems such as low specific area, poor metal loading and dispersion, and insufficient stability, which cannot improve the catalytic performance of nitrogen-carbon materials or carbonitriding materials, resulting in poor degradation effect of PPCPs.

[0023] Perozonation is an advanced oxidation technology that rapidly removes organic matter from water without secondary pollution by generating highly oxidizing hydroxyl radicals (·OH). However, the relatively slow ·OH generation rate reduces the removal rate of pollutants, making it difficult to remove pollutants quickly and effectively.

[0024] To address the aforementioned problems, this invention introduces the rare earth metal lanthanum (La) and prepares a lanthanum-doped composite catalyst (La₂CO₅-NC-600) with a unique structure by controlling the synthesis conditions. Finally, by combining this catalyst with advanced oxidation technologies, rapid degradation of organic pollutants can be achieved.

[0025] Specifically, as a first aspect of the present invention, a method for preparing a lanthanum-doped composite catalyst is provided, comprising: uniformly mixing solid raw materials including urea, oxalic acid and a lanthanum source to obtain a solid mixture; and calcining the solid mixture under an inert atmosphere to obtain a lanthanum-doped composite catalyst.

[0026] Urea, oxalic acid, and a lanthanum source are mixed mechanically to obtain a solid mixture. This solid mixture is then calcined under an inert atmosphere to obtain a lanthanum-doped composite catalyst with a lanthanum oxycarbonate (La₂CO₅ or La₂O₂CO₃) structure. The method for preparing this lanthanum-doped composite catalyst is relatively simple, the process is controllable, and the resulting lanthanum-doped composite catalyst exhibits stable catalytic performance, has low overall cost, and is easily scalable for mass production.

[0027] According to embodiments of the present invention, the mass ratio of urea to oxalic acid is 5:2-9:4, for example, 5:2, 5:3, 5:4, 6:2, 6:4, 7:2, 7:3, 8:2, 9:4, etc.; the lanthanum source is selected from lanthanum chloride heptahydrate (LaCl3·7H2O), lanthanum carbonate, or lanthanum acetate; the amount of lanthanum source added is 0.25-1 mmol, for example, 0.25 mmol, 0.5 mmol, 0.75 mmol, 1.0 mmol, etc. Urea is the main carbon and nitrogen source for nitrogen-carbon or carbon nitride carriers, and the addition of oxalic acid, in addition to acting as a metal anchoring agent, also provides a partial carbon source.

[0028] According to an embodiment of the present invention, urea, oxalic acid, and lanthanum source can be mechanically mixed, such as by ball milling or grinding, and the mixing time can be 30 min to 1 h, preferably 30 min.

[0029] According to an embodiment of the present invention, the calcination temperature is 550-650℃, for example 550℃, 600℃, 650℃, etc.; the calcination time is 2h-4h, for example 2h, 2.5h, 3h, 3.5h, 4h.

[0030] In the embodiments of this invention, the lanthanum source forms a unique La₂CO₅ structure during calcination, thereby exposing more active sites. Appropriate doping with rare earth metal La can effectively improve the catalytic activity of the composite catalyst, enabling rapid degradation of pollutants. By controlling the calcination temperature, lanthanum-doped composite catalysts with different supports can be obtained. For example, supports obtained below 600°C are mainly carbon nitride, with La₂CO₅ doped in their structure. Supports obtained by calcination at 600-650°C are mainly nitrogen-doped carbon, with La₂CO₅ doped in their structure.

[0031] As a second aspect of the present invention, a lanthanum-doped composite catalyst prepared by the above-described preparation method is provided, comprising: a support, and lanthanum oxycarbonate supported on the support; wherein the support is nitrogen-doped carbon or carbon nitride. In other words, the composite catalyst comprises a nitrogen-doped carbon support and lanthanum oxycarbonate supported on a nitrogen-doped carbon support; or a carbon nitride support and lanthanum oxycarbonate supported on a carbon nitride support. Wherein, when the support is nitrogen-doped carbon, no distinct characteristic peaks of carbon nitride appear in its X-ray diffraction pattern, and the nitrogen content is relatively low.

[0032] In embodiments of the present invention, the lanthanum-doped composite catalyst possesses unique La2CO5 crystals, exposing more active sites, and the lanthanum is uniformly dispersed in the support (nitrogen-doped carbon), which enhances the removal of pollutants. Furthermore, the catalyst has a mesoporous structure, which accelerates the diffusion and mass transfer of reactants (such as O3 and pollutants), improving the catalytic reaction kinetics.

[0033] According to embodiments of the present invention, the lanthanum-doped composite catalyst of the present invention is a nitrogen-doped carbon substrate with a plate-like structure, wherein La₂CO₅ has a spherical structure and is supported on the nitrogen-doped carbon substrate, and it has obvious lattice fringes. The presence of the spherical framework structure gives the composite catalyst excellent mechanical strength, making it less prone to structural collapse during long-term catalytic reactions, and the porous structure can buffer the dissolution of La metal, ensuring the activity of the catalyst.

[0034] As a third aspect of the invention, the application of lanthanum-doped composite catalysts in the degradation of pollutants is provided.

[0035] In the embodiments of the present invention, during the degradation of pollutants, the composite catalyst can enable La2CO5 to form surface hydroxyl groups with water adsorbed on the surface, thereby stabilizing the active La and preventing La from dissolving or deactivating. As a result, the composite catalyst can achieve rapid degradation of pollutants while maintaining a high degradation rate.

[0036] Specifically, the application of lanthanum-doped composite catalysts in the degradation of pollutants includes: introducing ozone (O3) into pollutants and adding lanthanum-doped composite catalysts to carry out catalytic reactions to degrade pollutants.

[0037] In embodiments of the present invention, O3 can directly oxidize pollutants or decompose to generate reactive oxide species (ROS) such as hydroxyl radicals (·OH) to degrade pollutants. However, the reaction rate is slow, and the generation of ·OH requires alkaline conditions or catalyst initiation, resulting in high cost and low ·OH yield, thus affecting the degradation effect. Using the lanthanum-doped composite catalyst of the present invention as a catalyst for pollutant degradation, the catalyst utilizes the combined effect of La2CO5 reacting with water adsorbed on the surface to generate more surface hydroxyl groups, and the electron-rich ability of the -C=O on the catalyst surface to achieve ·O2 degradation. - The rapid generation of active species such as ·OH enables the rapid removal of pollutants from water without causing secondary pollution.

[0038] According to an embodiment of the present invention, the ozone concentration is 5.8±1 mg / L; the lanthanum-doped composite catalyst is suitable for pH 3-9, such as acidic or alkaline water bodies, and has a wide range of applications, not limited by the pH of the water body.

[0039] According to embodiments of the present invention, the contaminant includes DEET, and the present invention also applies to other contaminants, which will not be described in detail here.

[0040] The following will use the degradation process of DEET as an example to briefly describe the reaction mechanism in the degradation process.

[0041] Specifically, the presence of La2CO5 promotes the formation of abundant -OH groups at the La sites, thereby accelerating the activation of O3 and the formation of •OH and... The transfer of water is particularly significant. Specifically, the adsorption of water by La2CO5 on the catalyst surface promotes the formation of abundant -OH groups (i.e., La2CO5-OH) at the La sites, which can react with O3 to form La2CO5-O2. - and , It further decomposes into ·OH. Furthermore, the -C=O sites on the catalyst surface can directly catalyze the decomposition of O3. O3 reacts with H2O at the -C=O sites on the catalyst surface and further dissociates to produce… and Subsequently, It reacts with another O3 molecule to produce ·OH. And O2. It is evident that the advanced oxidation system of this invention primarily utilizes the generation of ·OH. The benzene ring and carboxylic acid groups of DEET are susceptible to attack by electrophilic free radicals such as ·OH, initiating ring-opening or decarboxylation reactions; among these, O3 preferentially oxidizes double bonds or electron-rich regions (such as the benzene ring), while ·OH can indiscriminately attack organic matter, thoroughly mineralizing intermediate products and reducing the accumulation of toxic byproducts.

[0042] The reaction process involved in this invention is as follows:

[0043]

[0044] The specific technical solutions and beneficial effects of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] Example 1

[0046] Step S1: Prepare a solid mixture: Grind and mix 10g of urea, 4g of oxalic acid and 0.278g of lanthanum chloride heptahydrate (LaCl3·7H2O, 0.75mmol) thoroughly in a mortar.

[0047] Step S2: The solid mixture is loaded into a crucible and placed in a tube furnace. Under a nitrogen atmosphere, the temperature is increased to 600°C at a heating rate of 5°C / min, and calcined at this temperature for 4 hours to obtain a composite catalyst (La2CO5-NC-600 or La2CO5-NC-0.75) with nitrogen-doped carbon as the substrate (referred to as nitrogen-carbon substrate) and lanthanum-doped nitrogen-carbon substrate.

[0048] The La2CO5-NC-600 catalyst prepared in Example 1 was characterized using scanning electron microscopy (SEM), and the test results are as follows: Figure 1 As shown.

[0049] Figure 1The image shows a scanning electron microscope (SEM) image and elemental distribution diagram of the nitrogen-carbon-based lanthanum (La2CO5-NC-600) catalyst in Example 1 of this invention.

[0050] like Figure 1 As shown, the La2CO5-NC-600 catalyst exhibits a sheet-like structure with La2CO5 microspheres supported on it, and the four elements La, C, N, and O are uniformly distributed in the La2CO5-NC-600 material.

[0051] Example 2

[0052] The nitrogen-carbon-based lanthanum catalyst was prepared using the same method as in Example 1. The difference from Example 1 is that in step S2, the amount of LaCl3·7H2O added was 0.25 mmol, resulting in a nitrogen-doped carbon substrate with a sheet-like structure (i.e., a nitrogen-carbon substrate). La2CO5 in the form of small spheres was supported on the nitrogen-carbon substrate, which is the nitrogen-carbon-based lanthanum catalyst, named La2CO5-NC-0.25.

[0053] Example 3

[0054] The nitrogen-carbon-based lanthanum catalyst was prepared using the same method as in Example 1. The difference from Example 1 is that in step S2, the amount of LaCl3·7H2O added was 0.5 mmol, and the nitrogen-carbon-based lanthanum catalyst was obtained and named La2CO5-NC-0.5.

[0055] Example 4

[0056] The nitrogen-carbon-based lanthanum catalyst was prepared using the same method as in Example 1. The difference from Example 1 is that in step S2, the amount of LaCl3·7H2O added was 1 mmol, and the nitrogen-carbon-based lanthanum catalyst was obtained and named La2CO5-NC-1.

[0057] Example 5

[0058] The nitrogen-carbon-based lanthanum catalyst was prepared using the same method as in Example 1. The difference from Example 1 is that in step S2, the calcination temperature was 550°C, resulting in a carbon-carbon-based lanthanum catalyst named La2CO5-CN-550 or La-CN-550.

[0059] Example 6

[0060] The nitrogen-carbon-based lanthanum catalyst was prepared using the same method as in Example 1. The difference from Example 1 is that in step S2, the calcination temperature was 650°C, and the nitrogen-carbon-based lanthanum catalyst was obtained and named La2CO5-NC-650.

[0061] Comparative Example 1

[0062] Step S1: Grind urea as a precursor for carbon-nitrogen carrier.

[0063] Step S2: The carbon-nitrogen precursor solid was loaded into a crucible and placed in a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 600℃ at a heating rate of 5℃ / min, and calcined at this temperature for 4 hours to obtain the carbon nitride catalyst, named CN. Its SEM image is shown below. Figure 10 As shown, it has a sheet-like structure.

[0064] Test Example 1

[0065] Degradation experiments were conducted using the La2CO5-NC-600 catalyst prepared in Example 1 and the NC catalyst prepared in Comparative Example 1. Specifically, four groups of DEET contaminants with an initial concentration of 10 mg / L were provided. Ozone at a concentration of 5.8 ± 1 mg / L was introduced into three of these groups of DEET contaminants. One group had 0.01 g / L of CN catalyst (O3 / CN) added to the ozone, another group had 0.01 g / L of La2CO5-NC-600 catalyst (O3 / La2CO5-NC-600) added, and the third group served as a blank (no catalyst added, only O3). In the group without ozone (i.e., only DEET contaminants), 0.01 g / L of La2CO5-NC-600 catalyst (La2CO5-NC-600) was added. The degradation reaction time for all four groups was 30 min. After the reaction, the concentration of DEET in the four solutions at different reaction times was measured. The specific test results are as follows: Figure 2 As shown.

[0066] Figure 2 This is a graph showing the effect of different catalysts on the degradation of DEET pollutants in Test Example 1 of the present invention.

[0067] like Figure 2 As shown, ozone alone has a degradation effect on pollutants; adding only the catalyst without introducing ozone (i.e., La2CO5-NC-600) does not have a degradation effect on pollutants, confirming that the catalyst has no adsorption effect on pollutants; the La2CO5-NC-600 catalyst prepared in Example 1 can completely degrade DEET under O3 conditions, which significantly improves the treatment efficiency of organic pollutants compared with other reaction conditions (such as O3 / CN), proving that the nitrogen-carbon-based lanthanum catalyst synergistic ozonation technology prepared in this invention can remove organic pollutants quickly and efficiently.

[0068] Test Example 2

[0069] The catalysts prepared in Examples 1-4 were used for degradation tests. Specifically, four groups of DEET contaminants with an initial concentration of 10 mg / L were provided. Ozone at a concentration of 5.8 ± 1 mg / L was introduced into each of the four groups of DEET contaminants, followed by the addition of 0.01 g / L of La₂CO₅-NC-0.25, La₂CO₅-NC-0.5, La₂CO₅-NC-0.75, and La₂CO₅-NC-1 catalysts, respectively. The reaction time for pollutant degradation was 30 min. After the reaction was completed, the concentration of ibuprofen in the four solutions was measured at different reaction times. The specific test results are as follows: Figure 3 As shown.

[0070] Figure 3 This is a graph showing the effect of different catalysts on the degradation of DEET pollutants in Test Example 2 of the present invention.

[0071] like Figure 3 As shown, the nitrogen-carbon-based lanthanum catalysts prepared in Examples 1 to 4 can all improve the degradation rate and degradation effect of DEET, and indicate that the La2CO5-NC-0.75 catalyst prepared with a lanthanum source addition of 0.75 mmol has a high degradation efficiency.

[0072] Test Example 3

[0073] The catalysts prepared in Examples 1 and 5-6 were subjected to degradation tests. Specifically, four groups of DEET contaminants with an initial concentration of 10 mg / L were provided. In one group, only ozone (O3) was introduced. In the other three groups of DEET contaminants, ozone at a dose of 5.8 ± 1 mg / L was introduced, and then 0.01 g / L of La2CO5-CN-550 (La-CN-550), La2CO5-NC-600 (La2CO5-NC-0.75), and La2CO5-NC-650 catalysts were added to them respectively. The degradation reaction of the contaminants lasted for 30 min. After the reaction was completed, the concentration of DEET in the four solutions at different reaction times was measured. The specific test results are as follows: Figure 4 As shown.

[0074] Figure 4 This is a graph showing the degradation effect of different catalysts on DEET pollutants in Test Example 3 of the present invention.

[0075] like Figure 4 As shown, the nitrogen-carbon-based lanthanum catalysts prepared in Examples 1, 5-6 can all improve the degradation rate and degradation effect of DEET. In particular, the La2CO5-NC-600 catalyst prepared at a calcination temperature of 600℃ has the highest degradation efficiency for DEET.

[0076] Test Example 4

[0077] The cyclic stability of the La2CO5-NC-600 catalyst prepared in Example 1 was tested. Specifically, five groups of DEET contaminants with an initial concentration of 10 mg / L were provided. Ozone at a concentration of 5.8 ± 1 mg / L was introduced into the solutions, and 0.01 g / L of La2CO5-NC-600 catalyst was added. The reaction time for pollutant degradation was 30 min. After the reaction was completed, the used La2CO5-NC-600 catalyst was collected, dried at 60 °C for 12 h, and reused. The regenerated catalyst was cycled five times, and the concentration of DEET in the five solutions was measured at different reaction times. The specific test results are as follows: Figures 5-6 As shown.

[0078] Figure 5 This is a cyclic stability test graph of the La2CO5-NC-600 catalyst in Test Example 4 of this invention. Figure 6 This is a graph showing the effect of metal ion leaching on the La2CO5-NC-600 catalyst in the cycle stability test of Test Example 4 of the present invention.

[0079] like Figures 5-6 As shown, after 5 cycles of testing, the La2CO5-NC-600 catalyst maintained a high degradation efficiency for DEET, with only a small amount of ion leaching, indicating that the nitrogen-carbon-based lanthanum catalyst prepared in this invention has high catalytic stability.

[0080] Test Example 5

[0081] The pH adaptability of the La2CO5-NC-600 catalyst prepared in Example 1 was tested over a wide pH range. Specifically, four groups of DEET contaminants with initial concentrations of 10 mg / L were provided at initial pH values ​​of 3, 5.5 (original solution), 7, and 9. Ozone at a dose of 5.8 ± 1 mg / L was introduced into each group, and 0.01 g / L of La2CO5-NC-600 catalyst was added. The reaction time for pollutant degradation was 30 min. After the reaction was completed, the concentration of DEET in the four groups of solutions under different initial pH conditions was measured. The specific test results are as follows: Figure 7 As shown.

[0082] Figure 7 This is a graph showing the effect of the La2CO5-NC-600 catalyst on the degradation of DEET pollutants at different pH levels in Test Example 5 of this invention.

[0083] like Figure 7 As shown, the La2CO5-NC-600 catalyst of the present invention exhibits good degradation effect on DEET pollutants under different pH conditions.

[0084] Figure 8 Adsorption pore size diagrams for different materials. Figure 9 X-ray diffraction patterns of different materials.

[0085] like Figure 8 As shown, N2 adsorption-desorption assays revealed that all catalysts (CN, La-CN-550, La2CO5-NC-600) exhibited type IV isotherms and H4 hysteresis loops, indicating that the materials possess mesoporous structures and irregular channels. Figure 9 As shown, carbon nitride (CN, i.e., g-C3N4) and La-CN-550 exhibit characteristic diffraction peaks at 13.0° and 27.4°, respectively, corresponding to the (100) and (002) crystal planes of g-C3N4, indicating that the calcined product at 550°C is mainly based on carbon nitride. After La doping, the characteristic peaks of carbon nitride decrease. When the temperature reaches 600°C and higher, the peaks belonging to carbon nitride disappear, and the diffraction peaks belonging to La2CO5 (PDF#23-0320) appear, located at 13.08° (002), 22.90° (101), 29.55° (103), 31.12° (110), 44.59° (200), and 54.37° (213), respectively, indicating that the matrix structure changes, and the product is based on nitrogen-doped carbon at this time.

[0086] 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 lanthanum-doped composite catalyst, comprising: The solid raw materials, including urea, oxalic acid and lanthanum source, are mixed evenly to obtain a solid mixture; The solid mixture was calcined under an inert atmosphere to obtain a lanthanum-doped composite catalyst.

2. The production method according to claim 1, wherein The mass ratio of urea to oxalic acid is 5:2-9:

4.

3. The production method according to claim 1, wherein The calcination temperature is 550-650℃, and the calcination time is 2h-4h.

4. The production method according to claim 1, wherein The lanthanum source is selected from lanthanum chloride heptahydrate, lanthanum carbonate, or lanthanum acetate. The amount of lanthanum source added is 0.25-1 mmol.

5. A lanthanum-doped composite catalyst prepared by the preparation method according to any one of claims 1-4, comprising: The support, and lanthanum oxycarbonate loaded on the support; The carrier is nitrogen-doped carbon or carbon nitride.

6. The application of the lanthanum-doped composite catalyst as described in claim 5 in the degradation of pollutants.

7. The application according to claim 6, comprising: Ozone is introduced into the pollutants, and the lanthanum-doped composite catalyst is added to carry out a catalytic reaction to degrade the pollutants.

8. Use according to claim 7, wherein, The concentration of ozone was 5.8 ± 1 mg / L; The lanthanum-doped composite catalyst is suitable for pH 3-9.

9. Use according to claim 8, wherein, The contaminants include DEET.

Images