A functional catalyst supported on two-dimensional nanosheets of lanthanide fluorides, its preparation method and application

Abstract

This invention discloses a lanthanide fluoride two-dimensional nanosheet-supported functional catalyst, its preparation method, and its application, belonging to the field of catalyst technology. The catalyst comprises lanthanide fluoride two-dimensional nanosheets and metal active species supported on the surface and within the pores of the nanosheets. The two-dimensional supported catalyst synthesized by this invention exhibits a controllable pore structure, allowing the metal active species to not only be supported on the nanosheet surface but also penetrate into its pores. The active species are uniformly distributed on the surface, demonstrating high catalytic activity and stability as a catalyst for the heterogeneous Fenton oxidation degradation of phenol-simulated wastewater. Under an external light source, this two-dimensional catalyst, together with hydrogen peroxide, forms a photocatalytic synergistic Fenton oxidation system, which can efficiently remove organic pollutants from wastewater. The catalyst prepared by this invention is easily separated from wastewater and can be recycled.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and relates to a functional catalyst supported on two-dimensional nanosheets of lanthanide fluorides, its preparation method and application. Background Technology

[0002] With rapid industrialization and urbanization, organic pollutants in wastewater from human production and daily life have become a serious environmental problem, posing a potential threat to aquatic ecosystems and human health. Traditional wastewater treatment methods, such as biological treatment, physical filtration, and chemical precipitation, have limitations in treating organic pollutants, failing to completely degrade them or generating byproducts. Therefore, finding an efficient and sustainable method to treat organic pollutants in wastewater is crucial.

[0003] Heterogeneous Fenton technology, as a promising wastewater treatment method, boasts advantages such as simplicity, high efficiency, and ease of operation. It utilizes highly reactive hydroxyl radicals (·OH) to continuously and efficiently oxidize and degrade organic pollutants. In the development of heterogeneous Fenton catalysts, it was found that supported catalysts maintain their activity while improving stability, thereby extending catalyst lifespan. Two-dimensional materials, due to their large specific surface area and abundant unsaturated coordination atoms on their surface, are excellent candidates for novel catalyst supports.

[0004] Porosity is a crucial factor to consider when using two-dimensional materials as supports. Porous structures offer a larger specific surface area, increasing the contact area between the catalyst and organic pollutants in wastewater, thereby improving reaction efficiency. Furthermore, porous structures provide more active sites, enhancing the catalyst's reactivity. However, porous structures can lead to decreased catalyst stability, as the pore structure may introduce unstable sites or cause partial deactivation. Many two-dimensional materials have irregular shapes, constrained by non-uniform binding sites, and often lack the adjustability of specific variables, such as in-plane dimensions and pore size. This makes the preparation of two-dimensional materials with highly controllable pore structures as supports a significant technical challenge.

[0005] Therefore, developing highly efficient two-dimensional supported catalysts with controllable pore structures can optimize catalytic performance and provide a sustainable solution for heterogeneous Fenton catalysis in wastewater treatment. Summary of the Invention

[0006] In view of this, the present invention provides a lanthanide fluoride two-dimensional nanosheet supported functional catalyst, its preparation method and application.

[0007] A functional catalyst supported on lanthanide fluoride two-dimensional nanosheets includes lanthanide fluoride two-dimensional nanosheets and metal active species supported on the surface and pores of the two-dimensional nanosheets.

[0008] Furthermore, the average pore size of the above-mentioned two-dimensional nanosheets is 1–50 nm.

[0009] Furthermore, the mass ratio of metal active species to two-dimensional nanosheets in the above catalyst is 1% to 30%.

[0010] Furthermore, the metal active species in the above catalyst include one or both of the following: metal oxides or zero-valent nanoparticles of metal elements.

[0011] Furthermore, the aforementioned metallic elements include one or more transition metal elements.

[0012] Furthermore, the aforementioned transition metal elements include one or more of gold, silver, platinum, iron, copper, cobalt, nickel, manganese, or palladium.

[0013] This invention also provides a method for preparing the functional catalyst supported on lanthanide fluoride two-dimensional nanosheets as described above. When the metal active species is an oxide of a metal element, the catalyst is a lanthanide fluoride two-dimensional nanosheet supported metal oxide catalyst. The preparation method includes the following steps:

[0014] (1) Lanthanide fluoride two-dimensional nanosheets were added to a metal salt-ethanol solution and ultrasonically dispersed to obtain an impregnation solution of lanthanide fluoride two-dimensional nanosheets.

[0015] (2) Add ammonium bicarbonate to the impregnation solution and continuously stir magnetically at room temperature to carry out the precipitation reaction, and obtain a solution of lanthanide fluoride two-dimensional nanosheet supported metal oxide catalyst. After centrifugation, a solid product is obtained, which is washed several times with ethanol solution and deionized water, and then dried under vacuum to obtain lanthanide fluoride two-dimensional nanosheet supported metal oxide catalyst.

[0016] This invention also provides a method for preparing a functional catalyst supported on lanthanide fluoride two-dimensional nanosheets as described above. When the metal active species is a zero-valent metal nanoparticle, the catalyst is a zero-valent metal catalyst supported on lanthanide fluoride two-dimensional nanosheets. The preparation method includes the following steps:

[0017] (I) Under nitrogen protection, lanthanide fluoride two-dimensional nanosheets were added to a metal salt solution and ultrasonically dispersed to obtain an impregnation solution of lanthanide fluoride two-dimensional nanosheets.

[0018] (II) Under ice bath conditions, the prepared sodium borohydride solution was slowly added dropwise to the impregnation solution with stirring. The mixture was stirred continuously under ice bath conditions for more than 8 hours to carry out the reduction reaction and obtain a solution of lanthanide fluoride two-dimensional nanosheets supporting zero-valent metal catalyst. After centrifugation, a solid product was obtained, which was washed several times with deionized water, dried under vacuum, and then sealed and stored under nitrogen conditions.

[0019] Furthermore, the lanthanide fluoride two-dimensional nanosheets mentioned in step (1) or step (Ⅰ) are prepared by the following method, the specific steps of which are as follows:

[0020] (a) Adjust the initial pH of the water-soluble lanthanide metal salt solution to obtain a mixed solution;

[0021] (b) A fluoride-containing aqueous solution was added to the above mixture to cause a precipitation reaction, resulting in two-dimensional porous nanosheets of lanthanide fluorides.

[0022] Furthermore, in step (a), the concentration of the water-soluble lanthanide metal salt in the above mixture is 5 to 100 mg / mL, the initial pH range for adjustment is 3 to 10, and the water-soluble lanthanide metal salt includes one or more of the following: nitrates, ammonium chlorates, chlorides, and acetates of lanthanum, cerium, praseodymium, or neodymium.

[0023] Further, in step (b), the concentration of the above-mentioned fluoride-containing aqueous solution is 0.001 to 0.01 mg / mL, and the above-mentioned fluoride-containing aqueous solution and the above-mentioned mixed solution are mixed according to the molar ratio of fluorine to lanthanide metals of (0.1 to 10):1; the temperature of the above-mentioned precipitation reaction is room temperature, and the time is 12 h; the above-mentioned fluoride-containing aqueous solution includes one or more of the following: ammonium fluoride, sodium fluoride, potassium fluoride, potassium fluoroborate, potassium fluorosilicate, and tetrabutylammonium fluoride.

[0024] Furthermore, the amount of ammonium bicarbonate added in step (2) is selected according to the metal valence state in the metal salt-ethanol solution. When the metal valence state is +3, it is added according to a molar ratio of ammonium bicarbonate to metal salt of 3:1; when the metal valence state is +2, it is added according to a molar ratio of ammonium bicarbonate to metal salt of 2:1. The precipitation reaction temperature is at room temperature and the time is 8 hours. The vacuum drying temperature is 40-60℃ and the time is 10-12 hours.

[0025] Furthermore, in step (II), the concentration of the sodium borohydride solution is 1-5 g / L; the stirring speed is 1200 r / min and the dropping rate is maintained at 1 drop / s; the vacuum drying temperature is 40-60℃ and the time is 10-12 h.

[0026] This invention also provides the application of the above-mentioned lanthanide fluoride two-dimensional nanosheet supported functional catalyst or the lanthanide fluoride two-dimensional nanosheet supported functional catalyst prepared by the above method in heterogeneous Fenton catalysis, and its application in photocatalysis synergistic with Fenton catalysis under an external light source.

[0027] As can be seen from the above technical solutions, compared with the prior art, the present invention discloses a two-dimensional lanthanide fluoride nanosheet and its preparation method, as well as a functional catalyst supported on a two-dimensional lanthanide fluoride nanosheet and its preparation method and application, which have the following beneficial effects:

[0028] (1) The preparation process of the lanthanide fluoride two-dimensional nanosheets and their supported functional catalysts disclosed in this invention does not require the addition of templates or surfactants, has a wide range of applications, is simple to operate, is green, safe and pollution-free, and has low cost. Moreover, the prepared nanosheets all have good crystallinity and pore structure.

[0029] (2) The pore structure of the catalyst can be controlled by adjusting the initial pH of the solution to achieve optimal catalytic performance. Larger pore structures can accommodate metal active species, increase the contact area of ​​reactants, and thus improve catalytic activity.

[0030] (3) The prepared two-dimensional catalyst has the structural advantages of two-dimensional materials and porous materials. The introduction of the pore structure inhibits the stacking of single-layer or few-layer two-dimensional materials, increases the specific surface area of ​​the catalyst, provides more active sites, and increases the adsorption amount of reactants and the reaction rate.

[0031] (4) Compared with the comparative two-dimensional catalyst with a non-porous structure, this catalyst exhibits higher catalytic activity for heterogeneous Fenton oxidation of phenol under the same conditions. In addition, in the photocatalytic synergistic Fenton catalysis process, the porous structure can shorten the migration distance of charge carriers from the generation center to the active surface, thereby making it easier for electrons to migrate to the surface and minimizing the hole-electron recombination process.

[0032] (5) The prepared catalyst has good stability. The pore walls can protect the active sites of the catalyst and prevent them from being affected and damaged by the external environment.

[0033] (6) The catalyst is prepared by impregnation precipitation or in-situ reduction. The synthesis method is simple, economical, and can be produced on a large scale and used in actual sewage treatment processes.

[0034] This invention can further explore the structure-activity relationship between pore structure and catalytic activity, as well as the role mechanism of pore structure in two-dimensional catalysts. Attached Figure Description

[0035] Figure 1This is a high-magnification transmission scanning electron microscope image of the cerium fluoride nanosheets prepared in Example 1;

[0036] Figure 2 This is a high-magnification transmission scanning electron microscope image of the cerium fluoride nanosheet-supported iron oxide catalyst prepared in Example 1;

[0037] Figure 3 The pore size distribution curves are for the cerium fluoride nanosheets and the catalyst supported on iron oxide prepared in Example 1.

[0038] Figure 4 High-resolution Fe2p XPS spectrum of the cerium fluoride nanosheet-supported iron oxide catalyst prepared in Example 1;

[0039] Figure 5 The graph shows the heterogeneous Fenton catalytic performance of phenol prepared in Example 1 using cerium fluoride nanosheet-supported iron oxide catalyst.

[0040] Figure 6 The image shows the photocatalytic synergistic effect of Fenton's catalysis on methylene blue using the cerium fluoride nanosheet-supported iron oxide catalyst prepared in Example 6.

[0041] Figure 7 Scanning electron microscope image of zero-valent iron catalyst supported on two-dimensional cerium fluoride nanosheets in Example 9;

[0042] Figure 8 The graph shows the performance of the heterogeneous Fenton catalyst for phenol prepared as a graphene oxide-supported iron oxide catalyst in Comparative Example 1. Detailed Implementation

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] Example 1

[0045] Adjust the pH to 3 using 260 mL of ultrapure water, add 3.6 mmol of cerium acetate and stir to dissolve, obtaining a cerium acetate mixture. Add 100 mL of 0.0012 mg / mL sodium fluoride aqueous solution dropwise to the mixture, stir at room temperature for 12 h, collect by centrifugation, wash several times with deionized water, and dry in a freeze dryer to obtain cerium fluoride two-dimensional nanosheets. Dissolve 3.03 mg of ferric chloride hexahydrate in 50 mL of ethanol by stirring, add 0.1 g of the prepared cerium fluoride nanosheets to an iron salt-ethanol solution and ultrasonically disperse to obtain a dispersion. Add ammonium bicarbonate to the dispersion at a molar ratio of 3:1 to the iron salt, and stir continuously for 8 h to carry out the precipitation reaction. Collect by centrifugation, wash several times with ethanol and deionized water, and vacuum dry to obtain a porous cerium fluoride two-dimensional nanosheet supported iron oxide catalyst.

[0046] Figure 1 and Figure 2 High-magnification transmission electron microscopy (SEM) images of the prepared cerium fluoride nanosheets and the cerium fluoride nanosheet-supported iron oxide catalyst are shown. The surface morphology of the catalyst is not significantly different from that of the cerium fluoride nanosheets, indicating that the iron oxide loading has no significant effect on the surface morphology of the support. Both the support and the catalyst exhibit a porous two-dimensional nanosheet structure. Nitrogen adsorption-desorption tests were performed on the cerium fluoride nanosheets and the prepared catalyst, and the pore size distribution was calculated according to the BJH model. Figure 3 As shown, the results indicate that the average pore size of the nanosheets prepared in this embodiment is 31.86 nm, and the average pore size of the catalyst is 21.44 nm. The high-resolution Fe2p XPS spectrum of the catalyst prepared in this embodiment is shown below. Figure 4 As shown, iron in iron oxides exists in the form of ferric iron.

[0047] The catalyst and H₂O₂ were added to 50 mL of a phenol solution with a pH of 3 and a concentration of 100 mg / L, simulating wastewater. The catalyst dosage was 0.6 g / L, and the H₂O₂ concentration was 50 mM. The mixture was continuously stirred at room temperature, and samples were taken at equal time intervals to determine the phenol concentration. The catalytic degradation effect of the heterogeneous Fenton system on the simulated wastewater was investigated. Figure 5 As shown, when the mass ratio of iron oxide to cerium fluoride nanosheets is 1%, the removal rate of phenol is 95.5% in 40 min, and the first-order degradation rate constant is 0.09089 min.

[0048] Example 2

[0049] Adjust the pH to 7 using 260 mL of ultrapure water, add 3.6 mmol of cerium acetate and stir to dissolve, obtaining a cerium acetate mixture. Add 100 mL of 0.0012 mg / mL sodium fluoride aqueous solution dropwise to the mixture, stir at room temperature for 12 h, collect by centrifugation, wash several times with deionized water, and dry in a freeze dryer to obtain cerium fluoride two-dimensional nanosheets. Dissolve 3.03 mg of ferric chloride hexahydrate in 50 mL of ethanol by stirring, add 0.1 g of the prepared cerium fluoride nanosheets to an iron salt-ethanol solution and ultrasonically disperse to obtain a dispersion. Add ammonium bicarbonate to the dispersion at a molar ratio of 3:1 to the iron salt, and stir continuously for 8 h to carry out the precipitation reaction. Collect by centrifugation, wash several times with ethanol and deionized water, and vacuum dry to obtain a porous cerium fluoride two-dimensional nanosheet supported iron oxide catalyst.

[0050] Nitrogen adsorption-desorption tests were performed on cerium fluoride nanosheets and the prepared catalyst, and the pore size distribution was calculated according to the BJH model. The results showed that the average pore size of the nanosheets prepared in this embodiment was 15.72 nm, and the average pore size of the catalyst was 13.51 nm.

[0051] The catalyst and H₂O₂ were added to 50 mL of a phenol solution with a pH of 3 and a concentration of 100 mg / L, simulating wastewater. The catalyst dosage was 0.6 g / L, and the H₂O₂ concentration was 50 mM. The mixture was continuously stirred at room temperature, and samples were taken at equal time intervals to determine the phenol concentration. The catalytic degradation effect of the heterogeneous Fenton system on the simulated wastewater was investigated. The results showed that when the mass ratio of iron oxide to cerium fluoride nanosheets was 1%, the removal rate of phenol was 86.7% after 40 min.

[0052] Example 3

[0053] Adjust the pH to 7 using 260 mL of ultrapure water, add 3.6 mmol of cerium acetate and stir to dissolve, obtaining a cerium acetate mixture. Add 100 mL of 0.0012 mg / mL sodium fluoride aqueous solution dropwise to the mixture, stir at room temperature for 12 h, collect by centrifugation, wash several times with deionized water, and dry in a freeze dryer to obtain cerium fluoride two-dimensional nanosheets. Dissolve 1.98 mg of copper chloride dihydrate in 50 mL of ethanol by stirring, add 0.1 g of the prepared cerium fluoride nanosheets to a copper salt-ethanol solution and ultrasonically disperse to obtain a dispersion. Add ammonium bicarbonate to the dispersion at a molar ratio of 2:1 to copper salt, and stir continuously for 8 h to carry out the precipitation reaction. Collect by centrifugation, wash several times with ethanol and deionized water, and vacuum dry to obtain porous cerium fluoride two-dimensional nanosheets supporting copper oxide catalyst.

[0054] Nitrogen adsorption-desorption tests were performed on cerium fluoride nanosheets and the prepared catalyst, and the pore size distribution was calculated according to the BJH model. The results showed that the average pore size of the nanosheets prepared in this embodiment was 15.72 nm, and the average pore size of the catalyst was 12.67 nm.

[0055] The catalyst and H₂O₂ were added to 50 mL of a phenol solution with a pH of 3 and a concentration of 100 mg / L, simulating wastewater. The catalyst dosage was 0.6 g / L, and the H₂O₂ concentration was 50 mM. The mixture was continuously stirred at room temperature, and samples were taken at equal time intervals to determine the phenol concentration. The catalytic degradation effect of the heterogeneous Fenton system on the simulated wastewater was investigated. The results showed that when the mass ratio of copper oxide to cerium fluoride nanosheets was 1%, the phenol removal rate was 68.7% after 40 min.

[0056] Example 4

[0057] Adjust the pH to 7 using 260 mL of ultrapure water, add 3.6 mmol of neodymium acetate and stir to dissolve, obtaining a neodymium acetate mixture. Add 100 mL of 0.0012 mg / mL sodium fluoride aqueous solution dropwise to the mixture, stir at room temperature for 12 h, collect by centrifugation, wash several times with deionized water, and freeze dry to obtain neodymium fluoride two-dimensional nanosheets. Dissolve 3.03 mg of ferric chloride hexahydrate in 50 mL of ethanol by stirring, add 0.1 g of the prepared neodymium fluoride nanosheets to an iron salt-ethanol solution and ultrasonically disperse to obtain a dispersion. Add ammonium bicarbonate to the dispersion at a molar ratio of 3:1 to the iron salt, and stir continuously for 8 h to carry out the precipitation reaction. Collect by centrifugation, wash several times with ethanol and deionized water, and vacuum dry to obtain a porous neodymium fluoride two-dimensional nanosheet supported iron oxide catalyst.

[0058] Nitrogen adsorption-desorption tests were performed on the fluorinated nanosheets and the prepared catalyst, and the pore size distribution was calculated according to the BJH model. The results showed that the average pore size of the nanosheets prepared in this embodiment was 11.42 nm, and the average pore size of the catalyst was 10.57 nm.

[0059] The catalyst and H₂O₂ were added to 50 mL of a phenol solution with a pH of 3 and a concentration of 100 mg / L, simulating wastewater. The catalyst dosage was 0.6 g / L, and the H₂O₂ concentration was 50 mM. The mixture was continuously stirred at room temperature, and samples were taken at equal time intervals to determine the phenol concentration. The catalytic degradation effect of the heterogeneous Fenton system on the simulated wastewater was investigated. The results showed that when the mass ratio of iron oxide to neodymium fluoride nanosheets was 1%, the phenol removal rate was 82.7% after 40 min.

[0060] Example 5

[0061] Adjust the pH to 7 using 260 mL of ultrapure water, add 3.6 mmol of cerium acetate and stir to dissolve, obtaining a cerium acetate mixture. Add 100 mL of 0.0012 mg / mL sodium fluoride aqueous solution dropwise to the mixture, stir at room temperature for 12 h, collect by centrifugation, wash several times with deionized water, and dry in a freeze dryer to obtain cerium fluoride two-dimensional nanosheets. Dissolve 42.5 mg of ferric chloride hexahydrate in 50 mL of ethanol by stirring, add 0.1 g of the prepared cerium fluoride nanosheets to an iron salt-ethanol solution and ultrasonically disperse to obtain a dispersion. Add ammonium bicarbonate to the dispersion at a molar ratio of 3:1 to the iron salt, and stir continuously for 8 h to carry out the precipitation reaction. Collect by centrifugation, wash several times with ethanol and deionized water, and vacuum dry to obtain a porous cerium fluoride two-dimensional nanosheet supported iron oxide catalyst.

[0062] Nitrogen adsorption-desorption tests were performed on cerium fluoride nanosheets and the prepared catalyst, and the pore size distribution was calculated according to the BJH model. The results showed that the average pore size of the nanosheets prepared in this embodiment was 15.72 nm, and the average pore size of the catalyst was 16.83 nm.

[0063] The catalyst and H₂O₂ were added to 50 mL of a phenol solution (pH 2.5, concentration 150 mg / L) simulating wastewater. The catalyst dosage was 0.75 g / L, and the H₂O₂ concentration was 20 mM. A xenon lamp was used as the external light source to simulate visible light. The solution was continuously stirred at room temperature, and samples were taken at equal time intervals to determine the phenol concentration. The catalytic degradation effect of the photocatalytic synergistic Fenton system on the simulated wastewater was investigated. The results showed that when the mass ratio of iron oxide to cerium fluoride nanosheets was 14%, the phenol removal rate reached 95.9% after 5 min.

[0064] Example 6

[0065] Adjust the pH to 7 using 260 mL of ultrapure water, add 3.6 mmol of cerium acetate and stir to dissolve, obtaining a cerium acetate mixture. Add 100 mL of 0.0012 mg / mL sodium fluoride aqueous solution dropwise to the mixture, stir at room temperature for 12 h, collect by centrifugation, wash several times with deionized water, and dry in a freeze dryer to obtain cerium fluoride two-dimensional nanosheets. Dissolve 42.5 mg of ferric chloride hexahydrate in 50 mL of ethanol by stirring, add 0.1 g of cerium fluoride nanosheets to an iron salt-ethanol solution and ultrasonically disperse to obtain a dispersion. Add ammonium bicarbonate to the dispersion at a molar ratio of 3:1 to the iron salt, and stir continuously for 8 h to carry out the precipitation reaction. Collect by centrifugation, wash several times with ethanol and deionized water, and vacuum dry to obtain a porous cerium fluoride two-dimensional nanosheet supported iron oxide catalyst.

[0066] The catalyst and H₂O₂ were added to 50 mL of a 100 mg / L methylene blue (MB) solution (pH 2.5) to simulate dye wastewater. The catalyst dosage was 0.75 g / L, and the H₂O₂ concentration was 20 mM. A xenon lamp was used as the external light source to simulate visible light. The mixture was continuously stirred at room temperature, and samples were taken at equal time intervals to determine the MB concentration. The catalytic degradation effect of the photocatalytic synergistic Fenton system on the simulated wastewater was investigated. Figure 6 As shown, when the mass ratio of iron oxide to cerium fluoride nanosheets is 14%, the removal rate of MB can reach 100% after 30 minutes.

[0067] Example 7

[0068] Adjust the pH to 3 using 260 mL of ultrapure water, add 3.6 mmol of cerium acetate and stir to dissolve, obtaining a cerium acetate mixture. Add 100 mL of 0.0012 mg / mL sodium fluoride aqueous solution dropwise to the mixture, stir at room temperature for 12 h, collect by centrifugation, wash several times with deionized water, and dry in a freeze dryer to obtain cerium fluoride two-dimensional nanosheets. Add 3.03 mg of ferric chloride hexahydrate and 0.606 mg of copper chloride dihydrate to 50 mL of ethanol and stir to dissolve, obtaining an iron-copper salt-ethanol mixed solution. Add 0.1 g of the prepared cerium fluoride nanosheets to the iron-copper salt mixed solution and ultrasonically disperse to obtain a dispersion. Add ammonium bicarbonate to the dispersion at a molar ratio of 3:1 to the iron salt and 2:1 to the copper salt, and stir continuously for 8 h to carry out the precipitation reaction. Collect by centrifugation, wash several times with ethanol and deionized water, and vacuum dry to obtain a porous cerium fluoride two-dimensional nanosheet-supported iron-copper oxide catalyst.

[0069] The catalyst and H₂O₂ were added to 50 mL of a phenol solution (pH = 7, concentration 100 mg / L) simulating wastewater. The catalyst dosage was 0.6 g / L, and the H₂O₂ concentration was 50 mM. The mixture was continuously stirred at room temperature, and samples were taken at equal time intervals to determine the phenol concentration. The catalytic degradation effect of the heterogeneous Fenton system on the simulated wastewater was investigated. The results showed that when the mass ratio of iron oxide to copper oxide was 20%, the phenol removal rate was 60.3% after 60 min.

[0070] Example 8

[0071] Adjust the pH to 10 using 260 mL of ultrapure water, add 3.6 mmol of cerium acetate and stir to dissolve, obtaining a cerium acetate mixture. Add 100 mL of 0.0012 mg / mL sodium fluoride aqueous solution dropwise to the mixture, stir at room temperature for 12 h, collect by centrifugation, wash several times with deionized water, and dry in a freeze dryer to obtain cerium fluoride two-dimensional nanosheets. Dissolve 3.03 mg of ferric chloride hexahydrate in 50 mL of ethanol by stirring, add 0.1 g of the prepared cerium fluoride nanosheets to an iron salt-ethanol solution and ultrasonically disperse to obtain a dispersion. Add ammonium bicarbonate to the dispersion at a molar ratio of 3:1 to the iron salt, and stir continuously for 8 h to carry out the precipitation reaction. Collect by centrifugation, wash several times with ethanol and deionized water, and vacuum dry to obtain a porous cerium fluoride two-dimensional nanosheet supported iron oxide catalyst.

[0072] Nitrogen adsorption-desorption tests were performed on cerium fluoride nanosheets and the prepared catalyst, and the pore size distribution was calculated according to the BJH model. The results showed that the average pore size of the nanosheets prepared in this embodiment was 14.66 nm, and the average pore size of the catalyst was 15.72 nm.

[0073] The catalyst and H₂O₂ were added to 50 mL of a phenol solution with a pH of 3 and a concentration of 100 mg / L, simulating wastewater. The catalyst dosage was 0.6 g / L, and the H₂O₂ concentration was 50 mM. The mixture was continuously stirred at room temperature, and samples were taken at equal time intervals to determine the phenol concentration. The catalytic degradation effect of the heterogeneous Fenton system on the simulated wastewater was investigated. The results showed that when the mass ratio of iron oxide to cerium fluoride nanosheets was 1%, the phenol removal rate was 89.1% after 40 min.

[0074] Example 9

[0075] 260 mL of ultrapure water was used to adjust the pH to 7. 3.6 mmol of cerium acetate was added and stirred to dissolve, resulting in a cerium acetate mixture. 100 mL of 0.0012 mg / mL sodium fluoride aqueous solution was added dropwise to the mixture. The mixture was stirred at room temperature for 12 h. After centrifugation, the mixture was washed several times with deionized water and then dried in a freeze dryer to obtain cerium fluoride two-dimensional nanosheets. Under nitrogen protection, 4.83 mg of ferric chloride hexahydrate was added to 50 mL of deionized water and stirred to dissolve, obtaining an iron salt solution. 0.1 g of the prepared cerium fluoride nanosheets were added to the iron salt solution and ultrasonically dispersed to obtain a dispersion. Under ice bath conditions, 150 mL of 1 g / L sodium borohydride solution was added dropwise to the impregnation solution at a stirring speed of 1200 r / min, and stirring was continued under ice bath conditions for 10 h to carry out the reduction reaction, obtaining a solution of lanthanide fluoride two-dimensional nanosheets supporting zero-valent iron catalyst. The solid product was collected by centrifugation, washed several times with deionized water, and vacuum dried. The obtained cerium fluoride two-dimensional nanosheets supporting zero-valent iron catalyst was then sealed and stored under nitrogen conditions. Figure 7 This is a scanning electron microscope image of a zero-valent iron catalyst supported on two-dimensional cerium fluoride nanosheets.

[0076] The catalyst and H₂O₂ were added to 50 mL of a phenol solution with a pH of 3 and a concentration of 100 mg / L, simulating wastewater. The catalyst dosage was 0.6 g / L, and the H₂O₂ concentration was 50 mM. The mixture was continuously stirred at room temperature, and samples were taken at equal time intervals to determine the phenol concentration. The catalytic degradation effect of the heterogeneous Fenton system on the simulated wastewater was investigated. The results showed that when the mass ratio of zero-valent iron to cerium fluoride nanosheets was 1%, the removal rate of phenol was 95.3% within 30 min.

[0077] Example 10

[0078] 260 mL of ultrapure water was used to adjust the pH to 7. 3.6 mmol of cerium acetate was added and stirred to dissolve, resulting in a cerium acetate mixture. 100 mL of 0.0012 mg / mL sodium fluoride aqueous solution was added dropwise to the mixture. The mixture was stirred at room temperature for 12 h. After centrifugation, the mixture was washed several times with deionized water and then dried in a freeze dryer to obtain cerium fluoride two-dimensional nanosheets. Under nitrogen protection, 4.83 mg of ferric chloride hexahydrate and 0.53 mg of copper chloride dihydrate were added to 50 mL of deionized water and stirred to dissolve, obtaining a mixed solution of iron and copper salts. 0.1 g of the prepared cerium fluoride nanosheets were added to the mixed solution of iron and copper salts and ultrasonically dispersed to obtain a dispersion. Under ice bath conditions, 150 mL of 1.5 g / L sodium borohydride solution was added dropwise to the impregnation solution at a stirring speed of 1200 r / min, and stirring was continued under ice bath conditions for 10 h to carry out the reduction reaction, obtaining a solution of lanthanide fluoride two-dimensional nanosheets supporting zero-valent iron-copper catalyst. The solid product was collected by centrifugation, washed several times with deionized water, and vacuum dried. The obtained lanthanide fluoride two-dimensional nanosheets supporting zero-valent iron-copper catalyst was then sealed and stored under nitrogen conditions.

[0079] The catalyst and H₂O₂ were added to 50 mL of a phenol solution with a pH of 3 and a concentration of 100 mg / L, simulating wastewater. The catalyst dosage was 0.6 g / L, and the H₂O₂ concentration was 50 mM. The mixture was continuously stirred at room temperature, and samples were taken at equal time intervals to determine the phenol concentration. The catalytic degradation effect of the heterogeneous Fenton system on the simulated wastewater was investigated. The results showed that when the mass ratio of zero-valent copper to zero-valent iron was 20%, the phenol removal rate was 73.3% after 60 min.

[0080] Example 11

[0081] Adjust the pH to 7 using 260 mL of ultrapure water, add 3.6 mmol of cerium acetate and stir to dissolve, obtaining a cerium acetate mixture. Add 100 mL of 0.0012 mg / mL sodium fluoride aqueous solution dropwise to the mixture, stir at room temperature for 12 h, collect by centrifugation, wash several times with deionized water, and dry in a freeze dryer to obtain cerium fluoride two-dimensional nanosheets. Dissolve 60.7 mg of ferric chloride hexahydrate in 50 mL of ethanol by stirring, add 0.1 g of the prepared cerium fluoride nanosheets to an iron salt-ethanol solution and ultrasonically disperse to obtain a dispersion. Add ammonium bicarbonate to the dispersion at a molar ratio of 3:1 to the iron salt, and stir continuously for 8 h to carry out the precipitation reaction. Collect by centrifugation, wash several times with ethanol and deionized water, and vacuum dry to obtain a porous cerium fluoride two-dimensional nanosheet supported iron oxide catalyst.

[0082] The catalyst and H₂O₂ were added to 50 mL of a phenol solution with a pH of 3 and a concentration of 100 mg / L, simulating wastewater. The catalyst dosage was 0.6 g / L, and the H₂O₂ concentration was 50 mM. The mixture was continuously stirred at room temperature, and samples were taken at equal time intervals to determine the phenol concentration. The catalytic degradation effect of the heterogeneous Fenton system on the simulated wastewater was investigated. The results showed that when the mass ratio of iron oxide to cerium fluoride nanosheets was 20%, the removal rate of phenol was 87.6% after 40 min.

[0083] Comparative Example 1

[0084] 3.03 mg of ferric chloride hexahydrate was dissolved in 50 mL of ethanol by stirring. 0.1 g of graphene oxide nanosheets were added to the iron salt-ethanol solution and ultrasonically dispersed to obtain a dispersion. Ammonium bicarbonate was added to the dispersion at a molar ratio of 3:1 to the iron salt, and the mixture was stirred continuously for 8 hours to induce precipitation. The solution was collected by centrifugation, washed several times with ethanol and deionized water, and vacuum dried to obtain the graphene oxide nanosheet-supported iron oxide catalyst.

[0085] The catalyst and H₂O₂ were added to 50 mL of a phenol solution with a pH of 3 and a concentration of 100 mg / L, simulating wastewater. The catalyst dosage was 0.6 g / L, and the H₂O₂ concentration was 50 mM. The mixture was continuously stirred at room temperature, and samples were taken at equal time intervals to determine the phenol concentration. The catalytic degradation effect of the heterogeneous Fenton system on the simulated wastewater was investigated. Figure 8 As shown, when the mass ratio of iron oxide to graphene oxide nanosheets is 1%, the removal rate of phenol is 70.9% after 40 min.

[0086] Conclusion: Comparing Examples 1, 2, 4, and 8, under the same catalytic conditions and with a constant amount of active iron oxide species, porous fluoride two-dimensional nanosheets exhibit higher catalytic activity as a support than non-porous graphene oxide nanosheets. This fully demonstrates the superiority of porous fluoride nanosheets as a 2D catalyst support, and its pore structure has a significant impact on the catalytic performance of phenol degradation.

[0087] Comparative Example 2

[0088] 3.03 mg of ferric chloride hexahydrate was dissolved in 50 mL of ethanol by stirring. 0.1 g of graphitic carbon nitride nanosheets were added to the iron salt-ethanol solution and ultrasonically dispersed to obtain a dispersion. Ammonium bicarbonate was added to the dispersion at a molar ratio of 3:1 to the iron salt, and the mixture was stirred continuously for 8 h to induce precipitation. The solution was collected by centrifugation, washed several times with ethanol and deionized water, and vacuum dried to obtain the graphitic carbon nitride nanosheet-supported iron oxide catalyst.

[0089] Nitrogen adsorption-desorption tests were performed on the graphite carbon nitride nanosheets and the prepared catalyst, and the pore size distribution was calculated according to the BJH model. The results showed that the average pore size of the nanosheets prepared in this example was 23.26 nm, and the average pore size of the catalyst was 21.47 nm.

[0090] The catalyst and H₂O₂ were added to 50 mL of a phenol solution (pH = 3, concentration 100 mg / L) simulating wastewater. The catalyst dosage was 0.6 g / L, and the H₂O₂ concentration was 50 mM. The mixture was continuously stirred at room temperature, and samples were taken at equal time intervals to determine the phenol concentration. The catalytic degradation effect of the heterogeneous Fenton system on the simulated wastewater was investigated. The results showed that when the mass ratio of iron oxide to graphite carbon nitride nanosheets was 1%, the phenol removal rate was 89.4% after 40 min, and the first-order degradation rate constant was 0.04977 min. -1 .

[0091] Conclusion: Comparing the catalytic performance of porous graphitic carbon nitride and porous cerium fluoride nanosheets in Example 1 as catalyst supports, despite similar pore size and volume, cerium fluoride nanosheets showed significantly higher degradation efficiency for phenol than graphitic carbon nitride, with a first-order rate constant 1.83 times that of graphitic carbon nitride. This difference is attributed to the pore shape of the two-dimensional materials. Cerium fluoride nanosheets provide an ordered and regular pore shape, while the pore shape of graphitic carbon nitride is irregular and randomly distributed, leading to a lower average mass transfer rate within the catalyst and ultimately affecting its catalytic activity.

[0092] Comparative Example 3

[0093] Adjust the pH to 7 using 260 mL of ultrapure water, add 3.6 mmol of cerium acetate and stir to dissolve, obtaining a cerium acetate mixture. Add 100 mL of 0.0012 mg / mL sodium fluoride aqueous solution dropwise to the mixture, stir at room temperature for 12 h, collect by centrifugation, wash several times with deionized water, and freeze dry to obtain cerium fluoride two-dimensional nanosheets. Dissolve 151.85 mg of ferric chloride hexahydrate in 50 mL of ethanol by stirring, add 0.1 g of the prepared cerium fluoride nanosheets to an iron salt-ethanol solution and ultrasonically disperse to obtain a dispersion. Add ammonium bicarbonate to the dispersion at a molar ratio of 3:1 to the iron salt, and stir continuously for 8 h to carry out the precipitation reaction. Collect by centrifugation, wash several times with ethanol and deionized water, and vacuum dry to obtain a cerium fluoride porous two-dimensional nanosheet supported iron oxide catalyst.

[0094] The catalyst and H₂O₂ were added to 50 mL of a phenol solution with a pH of 3 and a concentration of 100 mg / L, simulating wastewater. The catalyst dosage was 0.6 g / L, and the H₂O₂ concentration was 50 mM. The mixture was continuously stirred at room temperature, and samples were taken at equal time intervals to determine the phenol concentration. The catalytic degradation effect of the heterogeneous Fenton system on the simulated wastewater was investigated. The results showed that when the mass ratio of iron oxide to cerium fluoride nanosheets was 50%, the phenol removal rate was 51.5% after 40 min.

[0095] Conclusion: When the mass ratio of metal active species to fluoride nanosheet support is between 1% and 30%, the removal rate of phenol can reach over 95% within 40 minutes. The metal active species are uniformly dispersed on the support, which improves the utilization rate of active sites and thus enhances catalytic activity. When the mass ratio of metal active species to fluoride nanosheet support exceeds 30%, the metal active species exhibit agglomeration, which prevents some active sites from being exposed, thereby reducing catalytic activity. Therefore, 1% to 30% is the optimal mass ratio of metal active species to support.

[0096] The description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A functional catalyst supported on two-dimensional nanosheets of lanthanide fluorides, characterized in that, The invention includes two-dimensional nanosheets of lanthanide fluorides and metal active species supported on the surface and pores of the two-dimensional nanosheets. The average pore size of the two-dimensional nanosheets is 1~50 nm; The active metal species in the catalyst include one or both of the following: oxides of metal elements or zero-valent nanoparticles of metal elements. The mass ratio of the metal active species to the lanthanide fluoride two-dimensional nanosheets is 1% to 30%. The metallic element includes one or more transition metal elements; The transition metal element includes one or both of iron and copper; When the metal active species is an oxide of a metal element, the catalyst is a lanthanide fluoride two-dimensional nanosheet supported metal oxide catalyst, and the preparation method includes the following steps: (1) Lanthanide fluoride two-dimensional nanosheets were added to a metal salt-ethanol solution and ultrasonically dispersed to obtain an impregnation solution of lanthanide fluoride two-dimensional nanosheets. (2) Add ammonium bicarbonate to the impregnation solution and continuously stir magnetically at room temperature to carry out precipitation reaction, and obtain a solution of lanthanide fluoride two-dimensional nanosheet supported metal oxide catalyst. After centrifugation, a solid product is obtained. The product is washed several times with ethanol solution and deionized water and then dried under vacuum to obtain lanthanide fluoride two-dimensional nanosheet supported metal oxide catalyst. When the metal active species is a zero-valent nanoparticle of a metal element, the catalyst is a zero-valent metal catalyst supported on two-dimensional nanosheets of lanthanide fluorides, and the preparation method includes the following steps: (I) Under nitrogen protection, lanthanide fluoride two-dimensional nanosheets were added to a metal salt solution and ultrasonically dispersed to obtain an impregnation solution of lanthanide fluoride two-dimensional nanosheets; (II) Under ice bath conditions, the prepared sodium borohydride solution was slowly added dropwise to the impregnation solution with stirring. The mixture was stirred continuously under ice bath conditions for more than 8 hours to carry out the reduction reaction and obtain a solution of lanthanide fluoride two-dimensional nanosheets supported on zero-valent metal catalyst. After centrifugation, a solid product was obtained, which was washed several times with deionized water and dried under vacuum. The obtained lanthanide fluoride two-dimensional nanosheets supported on zero-valent metal catalyst was then sealed and stored under nitrogen conditions. The lanthanide fluoride two-dimensional nanosheets described in step (1) or step (Ⅰ) are prepared by the following method, the specific steps of which are as follows: (a) Adjust the initial pH range of the water-soluble lanthanide metal salt solution to 3~10 to obtain a mixed solution; (b) A fluoride-containing aqueous solution is added to the mixture to cause a precipitation reaction, thereby obtaining lanthanide two-dimensional porous nanosheets.

2. The lanthanide fluoride two-dimensional nanosheet supported functional catalyst according to claim 1, characterized in that, The concentration of water-soluble lanthanide metal salt in the mixture in step (a) is 5 to 100 mg / mL, and the water-soluble lanthanide metal salt includes one or more of lanthanum, cerium, praseodymium or neodymium nitrates, chlorides, and acetates.

3. The lanthanide fluoride two-dimensional nanosheet supported functional catalyst according to claim 1, characterized in that, The concentration of the fluoride-containing aqueous solution in step (b) is 0.001–0.01 mg / mL, and the fluoride-containing aqueous solution and the mixed solution are mixed at a molar ratio of fluorine to lanthanide metals of (0.1–10):1; the precipitation reaction is carried out at room temperature for 12 hours; the fluoride-containing aqueous solution includes one or more of the following: ammonium fluoride, sodium fluoride, potassium fluoride, potassium fluoroborate, potassium fluorosilicate, and tetrabutylammonium fluoride.

4. The lanthanide fluoride two-dimensional nanosheet supported metal oxide catalyst according to claim 1, characterized in that, In step (2), the amount of ammonium bicarbonate added is selected according to the metal valence state in the metal salt-ethanol solution. When the metal valence state is +3, it is added according to a molar ratio of ammonium bicarbonate to metal salt of 3:1; when the metal valence state is +2, it is added according to a molar ratio of ammonium bicarbonate to metal salt of 2:

1. The precipitation reaction temperature is at room temperature and the time is 8 hours. The vacuum drying temperature is 40~60℃ and the time is 10~12 hours.

5. The lanthanide fluoride two-dimensional nanosheet supported zero-valent metal catalyst according to claim 1, characterized in that, In step (II), the concentration of sodium borohydride solution is 1-5 g / L; the stirring speed is 1200 r / min and the dropping rate is maintained at 1 drop / s; the vacuum drying temperature is 40-60℃ and the time is 10-12 h.

6. The application of the lanthanide fluoride two-dimensional nanosheet supported functional catalyst of claim 1 in heterogeneous Fenton catalysis.

7. The application of the lanthanide fluoride two-dimensional nanosheet supported functional catalyst of claim 1 in photocatalysis synergistic with Fenton catalysis under an external light source.

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