Mn single-atom modified gamma-aluminum oxyhydroxide material, and preparation method and application thereof

Abstract

The application discloses a kind of Mn single-atom modified gamma-AlOOH materials and its preparation method and application, belong to high activity stability material preparation and ozone catalytic oxidation technical field.The Mn single-atom modified gamma-AlOOH material includes nanometer sheet gamma-AlOOH and manganese atom, and manganese atom replaces aluminum atom in gamma-AlOOH lattice.The application introduces Mn single atom in gamma-AlOOH, and obtains the Mn x / γ-AlOOH with local amorphous structure and enhanced oxygen vacancy, realizes the efficient removal of perfluorooctanoic acid, while maintaining excellent stability and extremely low ion leaching rate.The introduction of Mn atom breaks the original symmetry, induces local amorphization, increases the concentration of oxygen vacancy, improves the reaction activity and stability;The existence of Mn single atom also provides additional electron supplement way, promotes the activation of O3, prevents the excessive loss of electrons on metal site.

Description

Technical Field

[0001] This invention belongs to the field of high-activity and stable material preparation and ozone catalytic oxidation technology, specifically relating to a Mn single-atom modified γ-AlOOH material and its preparation method and application. Background Technology

[0002] Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are widely used in agricultural chemicals, electronics manufacturing, and food packaging due to their excellent hydrophobicity, oleophobicity, and high chemical stability. However, due to their persistent stability, they accumulate in the environment, posing a significant threat to ecological health. Catalytic ozonation based on heterogeneous catalysts has become an effective water purification method due to its strong oxidizing power, ease of operation, and environmental friendliness.

[0003] Existing catalytic ozonation systems for PFAS degradation face a bottleneck: catalytic activity and structural stability are difficult to balance, resulting in a performance trade-off. While traditional transition metal-based catalysts such as MnO2 possess good catalytic activity sufficient for PFAS degradation, they suffer from metal ion leaching during long-term catalytic reactions, leading to secondary metal pollution. Experimental data shows that after 15 hours of catalytic ozonation, approximately 10.44% of Mn (6683.3 μg / L) leach from MnO2, highlighting the significant metal leaching problem that has long been overlooked in current research. Although catalysts with low leaching characteristics, such as γ-AlOOH, significantly reduce aluminum ion leaching and avoid secondary pollution, their inherent catalytic activity is too low to meet the process requirements for efficient PFAS degradation. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a Mn single-atom modified γ-AlOOH material, its preparation method, and its application.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows.

[0006] In a first aspect, the present invention provides a Mn single-atom modified γ-AlOOH material comprising nanosheet γ-AlOOH and manganese atoms, wherein the manganese atoms replace aluminum atoms in the γ-AlOOH lattice.

[0007] Preferably, in the Mn single-atom modified γ-AlOOH material, the relative mass fraction of manganese is 0.5-3.5%, more preferably 2-2.5%, and even more preferably 2.2%.

[0008] A second aspect of the present invention provides a method for preparing the Mn single-atom modified γ-AlOOH material described in the first aspect, comprising: Aluminum source, urea and manganese source are dissolved in a solvent and subjected to a solvothermal reaction to obtain Mn single-atom modified γ-AlOOH material.

[0009] Preferably, the aluminum source includes aluminum nitrate, the manganese source includes manganese nitrate, and the solvent is water.

[0010] Preferably, the concentration of the aluminum source in the reaction system is 20-30 mmol·L⁻¹. -1 The preferred concentration is 28 mmol·L⁻¹. -1 The concentration of urea is 40-50 mmol·L⁻¹ -1 Preferably 50 mmol·L -1 The concentration of the manganese source was 0.1-2 mmol·L⁻¹. -1 Preferably 0.9 mmol·L -1 .

[0011] Preferably, the solvothermal reaction is carried out at a temperature of 140-180℃, more preferably 150℃, for a time of 12-36 h, more preferably 24 h.

[0012] Preferably, aluminum source, urea and manganese source are dissolved in water, and after complete dissolution, a hydrothermal reaction is carried out to obtain Mn single-atom modified γ-AlOOH material.

[0013] A third aspect of the present invention provides the application of γ-AlOOH or the Mn single-atom modified γ-AlOOH material described in the first aspect in the ozone-catalyzed oxidative degradation of perfluorooctanoic acid.

[0014] A fourth aspect of the present invention provides a method for the ozone-catalyzed oxidation degradation of perfluorooctanoic acid, comprising: The γ-AlOOH or the Mn single-atom modified γ-AlOOH material described in the first aspect is dispersed in a perfluorooctanoic acid solution and then catalytically degraded by introducing ozone.

[0015] Preferably, the concentration of perfluorooctanoic acid is 2-10 mg / L. -1 Preferably 2.5 mg L -1 .

[0016] Preferably, the amount of Mn single-atom modified γ-AlOOH material is 0.05-0.15 mg / mL, and more preferably 0.15 mg / mL.

[0017] Preferably, the catalytic degradation reaction time is 5-20 h, preferably 15 h, and the reaction is continuously stirred.

[0018] Preferably, the ozone introduction rate is 0.1-0.5 L / min, and more preferably 0.2 L / min.

[0019] The beneficial effects of this invention are as follows: This invention provides a Mn single-atom modified γ-AlOOH material, in which manganese atoms replace aluminum atoms in the γ-AlOOH lattice to achieve atomic-level dispersed doping. On one hand, the Mn atoms introduced by the lattice substitution break the original crystal structure symmetry of the support, inducing local amorphization and increasing the oxygen vacancy concentration. This not only exposes more catalytic active sites and promotes ozone adsorption and interfacial electron transfer to ozone, but also significantly enhances the catalytic activity for the ozonochemical degradation of PFAS. Simultaneously, the flexible microstructure resulting from amorphization enhances the catalyst's resistance to structural disturbances, improves stability, and effectively inhibits the excessive dissolution of metal components. On the other hand, the Mn single atoms embedded in the lattice construct additional electron replenishment pathways, effectively promoting ozone activation, preventing excessive electron loss from active metal sites, and ensuring the continuous and stable operation of the catalytic sites. Compared to pure γ-AlOOH, the Mn single-atom modified γ-AlOOH catalyst provided by this invention exhibits superior photocatalytic degradation ability of perfluorooctanoic acid (PFOA), and can efficiently degrade PFAS pollutants such as PFOA in water. At the same time, it overcomes the defect of secondary pollution caused by the large-scale leaching of metals in traditional transition metal catalysts, and takes into account both high catalytic activity and excellent structural stability, solving the technical problem that existing catalysts cannot achieve both activity and stability. It has good application potential in the field of PFAS polluted water treatment. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0021] Figure 1 The γ-AlOOH and Mn prepared in the embodiments of the present invention x X-ray diffraction pattern of γ-AlOOH material.

[0022] Figure 2 The γ-AlOOH(a) and Mn prepared in the embodiments of the present invention are x Scanning electron microscope images of / γ-AlOOH (x=0.8(b), 1.4(c), 2.2(d), 3.1(e)).

[0023] Figure 3 The Mn obtained in Example 4 of this invention 2.2 Low-magnification transmission electron microscopy (TEM) image (a) and high-magnification transmission electron microscopy (TEM) image (b) of γ-AlOOH.

[0024] Figure 4 The Mn obtained in Example 4 of this invention 2.2 Selected area electron diffraction pattern of / γ-AlOOH.

[0025] Figure 5The Mn obtained in the embodiments of the present invention 2.2 High-angle annular dark-field scanning transmission electron microscope image of / γ-AlOOH.

[0026] Figure 6 The γ-AlOOH and Mn prepared in the embodiments of the present invention x Energy dispersive X-ray elemental distribution spectrum of / γ-AlOOH.

[0027] Figure 7 The γ-AlOOH and Mn prepared in the embodiments of the present invention x Raman spectrum of / γ-AlOOH.

[0028] Figure 8 The γ-AlOOH and Mn prepared in the embodiments of the present invention 2.2 EPR spectrum of / γ-AlOOH.

[0029] Figure 9 The γ-AlOOH and Mn prepared in the examples 2.2 X-ray absorption spectrum (a) and extended X-ray absorption fine structure spectrum (b) of / γ-AlOOH.

[0030] Figure 10 The γ-AlOOH and Mn prepared in the examples 2.2 Degradation activity diagram of perfluorooctanoic acid (PFOA) with γ-AlOOH and ozone.

[0031] Figure 11 The γ-AlOOH and Mn prepared in the examples 2.2 Activity diagram of defluorination rate of perfluorooctanoic acid with γ-AlOOH and ozone.

[0032] Figure 12 The catalyst Mn prepared in Example 4 2.2 Cyclic stability test diagram of perfluorooctanoic acid degradation catalytically oxidized by γ-AlOOH.

[0033] Figure 13 The figures show the ion leaching diagrams of different catalysts prepared in the examples. Specifically, (a) shows the Al and Mn content in γ-AlOOH. 2.2 (a) shows the ion leaching diagrams of Al and Mn in γ-AlOOH, and (b) shows the ion leaching diagrams of Al in γ-AlOOH, Mn in MnO2, Fe in Fe2O3, and Co in Co3O4. Detailed Implementation

[0034] In response to the problems of water pollution caused by the overuse of perfluorooctanoic acid (PFOA), low efficiency of traditional ozone catalytic oxidation, and serious ion leaching issues, this invention proposes a Mn single-atom modified γ-AlOOH material, its preparation method, and its application.

[0035] In a typical embodiment of the present invention, a Mn single-atom modified γ-AlOOH material (Mn x / γ-AlOOH (x refers to the relative mass fraction of Mn) includes nanosheet-like γ-AlOOH and manganese atoms, with manganese atoms replacing aluminum atoms in the γ-AlOOH lattice.

[0036] To address the technical challenge of existing catalytic ozonation catalysts for PFAS degradation failing to simultaneously achieve high catalytic activity and excellent structural stability, and thus unable to effectively suppress metal ion leaching and avoid secondary pollution while ensuring pollutant degradation efficiency, this invention's research and analysis revealed that γ-AlOOH exhibits low metal ion leaching levels and a low risk of secondary pollution, but suffers from insufficient inherent catalytic activity; while traditional manganese-based catalysts, although possessing high catalytic activity, suffer from severe metal dissolution problems. To balance high catalytic activity and structural stability, single-atom catalysts (SACs) are widely recognized as an effective strategy for enhancing activity due to their unique electronic structure. In addition to improved activity, the engineering of SACs has been reported to influence the substrate's crystallization process and lead to localized amorphization. Amorphous materials have recently been reported to be more stable than their crystalline forms because their more flexible structures allow for easier self-regulation, making them more resistant to structural interference.

[0037] To address this issue, this invention utilizes SACs technology to achieve atomic-level dispersion of active metal atoms within the support lattice by replacing aluminum atoms in the γ-AlOOH lattice with Mn single atoms. The Mn atoms occupying lattice sites disrupt the original crystal structure symmetry of the support, inducing localized amorphization of the catalyst, increasing oxygen vacancy concentration, exposing more active sites, and promoting ozone adsorption and interfacial electron transfer. Simultaneously, the Mn single atoms can construct additional electron replenishment pathways, promoting ozone activation and preventing excessive electron loss at active sites. This synergistic effect of structural and electronic regulation significantly enhances the catalytic activity for PFAS degradation while simultaneously improving catalyst structural stability and inhibiting metal ion leaching. This overcomes the technical bottleneck of existing catalysts that struggle to simultaneously achieve catalytic activity and structural stability, enabling efficient and green degradation of PFAS pollutants in water.

[0038] In some embodiments of this implementation, the relative mass fraction of manganese in the Mn single-atom modified γ-AlOOH material is 0.5-3.5%, specifically 0.5%, 0.8%, 1%, 1.4%, 1.5%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.5%, or any range of two values; preferably 2-2.5%, more preferably 2.2%.

[0039] Understandably, the relative mass fraction of manganese has a significant impact on the microstructure and catalytic performance of catalysts. When the manganese content is too low, the number of Mn atoms that can replace aluminum atoms in the γ-AlOOH lattice is insufficient, making it difficult to fully disrupt crystal symmetry. This limits the effects of inducing local amorphization and generating oxygen vacancies, resulting in fewer electron transport channels, minimal improvement in ozone activation capacity, and a small increase in the catalyst's activity for PFAS degradation. When the manganese content is in the preferred range of 2-2.5% (optimal 2.2%), Mn atoms can efficiently embed into the γ-AlOOH lattice and replace aluminum atoms, fully inducing local amorphization of the support, obtaining abundant oxygen vacancies, and simultaneously constructing sufficient electron transport pathways to efficiently activate ozone, achieving optimal synergy between catalytic activity and structural stability. When the manganese content is too high, the excess manganese cannot exist in the form of single atoms in the lattice due to the limited number of substitution sites in the γ-AlOOH crystal lattice. It easily aggregates on the support surface to form manganese-based particles. This not only weakens the amorphization and oxygen vacancy regulation effects, reducing ozone activation efficiency, but also causes the aggregated manganese species to detach from the lattice, making them prone to metal ion leaching during the catalytic reaction, resulting in secondary pollution and a decline in the overall performance of the catalyst. Therefore, this invention limits the relative mass fraction of manganese to 0.5-3.5%.

[0040] In another typical embodiment of the present invention, a method for preparing the Mn single-atom modified γ-AlOOH material is provided, comprising: Aluminum source, urea and manganese source are dissolved in a solvent and subjected to a solvothermal reaction to obtain Mn single-atom modified γ-AlOOH material.

[0041] This invention employs an in-situ doping solvothermal preparation method. By introducing Mn single atoms into γ-AlOOH, a Mn / γ-AlOOH structure with a locally amorphous structure is obtained, achieving highly efficient removal of perfluorooctanoic acid (PFOA) while maintaining excellent stability and extremely low ion leaching. The introduction of Mn single atoms not only induces local amorphization in γ-AlOOH but also increases the oxygen vacancy concentration, both of which contribute to improved activity and stability. Furthermore, the presence of Mn single atoms provides an additional electron replenishment pathway, thereby promoting O3 activation and preventing excessive electron loss from metal sites. Moreover, this material has advantages such as a simple and controllable preparation method, environmental friendliness and non-polluting nature, and low cost and easy availability, making it highly valuable for applications.

[0042] In some embodiments of this implementation, the aluminum source includes, but is not limited to, aluminum nitrate; the manganese source includes, but is not limited to, manganese nitrate; and the solvent is water.

[0043] The solvent is water, and both the aluminum and manganese sources must be water-soluble materials. Specifically, the aluminum source includes, but is not limited to, any one of aluminum nitrate and aluminum chloride. Aluminum sulfate is not a preferred aluminum source because sulfate ions are difficult to completely remove and easily adsorb onto the material surface, interfering with the crystal structure, oxygen vacancies, and interfacial electron transport. The preferred aluminum source is aluminum nitrate. Aluminum nitrate anions are easily removed, which is more conducive to obtaining a clean surface structure and facilitates subsequent Mn atom lattice substitution doping.

[0044] The manganese salt includes, but is not limited to, any one of manganese nitrate, manganese chloride, and manganese acetate, preferably any one of manganese nitrate and manganese acetate, and more preferably manganese nitrate. Sulfate ions are easily adsorbed on the surface of γ-AlOOH, which hinders the insertion of manganese atoms into the crystal lattice to achieve aluminum atom substitution, and are not preferred manganese sources; chloride ions are easily retained at the material interface, affecting the oxygen vacancy concentration and electron transport efficiency, and are not preferred manganese sources; nitrate and acetate ions are easy to remove, which is conducive to the uniform dispersion of manganese atoms and the completion of crystal lattice substitution, and are more suitable as raw materials for preparation.

[0045] In some embodiments of this implementation, the concentration of the aluminum source in the reaction system is 20-30 mmol·L⁻¹. -1 Specifically, the values ​​can be 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 mmol·L. -1 Or any range consisting of two values, preferably 28 mmol·L -1 .

[0046] In some embodiments of this implementation, the concentration of urea in the reaction system is 40-50 mmol·L⁻¹. -1 Specifically, the values ​​can be 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 mmol·L. -1 Or any range consisting of two values, preferably 50 mmol·L -1 .

[0047] In some embodiments of this implementation, the concentration of the manganese source in the reaction system is 0.1-2 mmol·L⁻¹. -1 Specifically, the values ​​can be 0.1, 0.3, 0.5, 0.7, 0.9, 1, 1.2, 1.4, 1.5, 1.7, 1.8, or 2 mmol·L⁻¹. -1 or any range consisting of two values, preferably 0.9 mmol·L⁻¹. -1 .

[0048] In some embodiments of this implementation, the solvothermal reaction is carried out at a temperature of 140-180°C, specifically 140, 145, 150, 155, 160, 165, 170, 175, 180°C, or any range of two values, preferably 150°C; the reaction time is 12-36 h, specifically 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36 h, or any range of two values, preferably 24 h.

[0049] In some embodiments of this implementation, aluminum source, urea, and manganese source are dissolved in water, and after complete dissolution, a hydrothermal reaction is carried out to obtain Mn single-atom modified γ-AlOOH material. During the preparation process, by controlling the mass of the manganese salt, Mn single-atom modified γ-AlOOH materials with different manganese contents are obtained.

[0050] In some embodiments of this implementation, aluminum nitrate and urea are completely dissolved in an aqueous solution under stirring until the solution is clear and transparent, obtaining a mixed solution; manganese nitrate is completely dissolved in water under stirring until the solution is clear and transparent, obtaining a manganese nitrate solution; the manganese nitrate solution is slowly poured into the mixed solution and stirred evenly, and a hydrothermal reaction is carried out to obtain Mn single-atom modified γ-AlOOH material. This feeding method allows aluminum ions to be uniformly dispersed in the system beforehand. After the manganese nitrate solution is added, the manganese ions can be quickly diluted by the mother liquor, avoiding excessively high local manganese ion concentrations that could lead to hydrolysis and the formation of manganese oxide agglomerates. During the subsequent hydrothermal synthesis and growth of γ-AlOOH crystals, Mn atoms can simultaneously participate in lattice construction, making it easier to achieve Mn atom substitution for aluminum atoms in the γ-AlOOH lattice, which is beneficial for obtaining atomically dispersed Mn single-atom modified γ-AlOOH material. If the feeding order is changed, local enrichment is likely to occur, preferentially forming manganese group aggregates, making it difficult to achieve lattice substitution type single-atom modification.

[0051] In another typical embodiment of the present invention, an application of γ-AlOOH or the Mn single-atom modified γ-AlOOH material is provided in the ozone catalytic oxidation degradation of perfluorooctanoic acid.

[0052] Understandably, the γ-AlOOH is in nanosheet form, and its preparation method differs from that of Mn single-atom modified γ-AlOOH materials in that no manganese source is added.

[0053] In some embodiments of this implementation, the preparation method of the γ-AlOOH includes: dissolving an aluminum source and urea in water and carrying out a hydrothermal reaction to obtain the γ-AlOOH.

[0054] It should be noted that aluminum nitrate and urea need to be completely dissolved in the aqueous solution with stirring until the solution is clear and transparent.

[0055] In some embodiments of this implementation, the aluminum source is aluminum nitrate; the concentration of the aluminum source in the reaction system is 20-30 mmol·L⁻¹. -1 The preferred concentration is 28 mmol·L⁻¹. -1 The concentration of urea is 40-50 mmol·L⁻¹ -1 Preferably 50 mmol·L -1 The hydrothermal reaction is carried out at a temperature of 140-180℃, preferably 150℃, for a time of 12-36 h, preferably 24 h.

[0056] In another typical embodiment of the present invention, a method for ozone-catalyzed oxidation degradation of perfluorooctanoic acid is provided, comprising: γ-AlOOH or the Mn single-atom modified γ-AlOOH material described above is dispersed in a perfluorooctanoic acid solution, and ozone is introduced for catalytic degradation.

[0057] In some embodiments of this implementation, the concentration of perfluorooctanoic acid is 2-10 mg / L. -1 Specifically, the dosage can be 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10 mg / L. -1 Or a range consisting of any two values, preferably 2.5 mg / L. -1 .

[0058] In some embodiments of this implementation, the amount of γ-AlOOH or Mn single-atom modified γ-AlOOH material used is 0.05-0.15 mg / mL, specifically 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15 mg / mL, or any range of two values, preferably 0.15 mg / mL.

[0059] In some embodiments of this implementation, the catalytic degradation reaction time is 5-20 h, specifically 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 h, or any range of two values, preferably 15 h, and continuous stirring is carried out during the reaction.

[0060] In some embodiments of this implementation, γ-AlOOH or the Mn single-atom modified γ-AlOOH material is ultrasonically dispersed in a perfluorooctanoic acid solution.

[0061] In some embodiments of this implementation, the ozone introduction rate is 0.1-0.5 L / min, specifically 0.1, 0.2, 0.3, 0.4, 0.5 L / min, or any range of two numbers, preferably 0.2 L / min.

[0062] This invention introduces a single Mn atom into γ-AlOOH, resulting in Mn with a locally amorphous structure and enhanced oxygen vacancies. x / γ-AlOOH achieves highly efficient removal of perfluorooctanoic acid (PFOA) while maintaining excellent stability and extremely low ion leaching. Mn x The γ-AlOOH catalyst is formed by replacing Al atoms in the γ-AlOOH lattice with Mn. The introduction of Mn atoms breaks the original symmetry, induces local amorphization, increases the concentration of oxygen vacancies, and improves the reaction activity and stability. The presence of Mn single atoms also provides an additional electron replenishment pathway, thereby promoting the activation of O3 and preventing excessive loss of electrons on metal sites.

[0063] Compared to γ-AlOOH, Mn x / γ-AlOOH exhibits superior photocatalytic degradation ability of perfluorooctanoic acid, with Mn as the most significant component. 2.2 The γ-AlOOH catalyst showed the best performance. This is attributed to the localized amorphization and increased oxygen vacancies, which exposed more active sites on the catalyst, promoting O3 adsorption and electron transfer to O3. This indicates that this material has broad application prospects in reducing the hazards of perfluorinated compounds and purifying the environment.

[0064] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0065] The test materials used in the following examples are all conventional test materials in the art and can be purchased through commercial channels.

[0066] Example 1 This embodiment provides a method for preparing γ-AlOOH nanosheets, including the following steps: In standard procedure, 750 mg of aluminum nitrate (Al(NO3)3·9H2O) and 211 mg of urea (CO(NH2)2) were dissolved in 70 mL of water by ultrasonic treatment. The mixture was then placed in a 100 mL PTFE-lined autoclave and subsequently transferred to an oven at 150 °C for 24 hours. After natural cooling to room temperature, the powder was collected and washed several times with ethanol. Finally, the product was dried in an oven at 60 °C for 8 hours.

[0067] Example 2 This embodiment provides a Mn 2.2 The preparation method of γ-AlOOH catalyst includes the following steps: In standard procedure, 750 mg of aluminum nitrate (Al(NO3)3·9H2O) and 211 mg of urea (CO(NH2)2) were dissolved in 50 mL of water by ultrasonic treatment to obtain a mixed solution. 18.7 mg of manganese nitrate (Mn(NO3)2·6H2O) was dissolved in 20 mL of water and slowly added to the previous mixed solution, stirring until completely dissolved. The mixture was then placed in a 100 mL PTFE-lined autoclave, and subsequently transferred to an oven at 150 °C and maintained for 24 hours. After natural cooling to room temperature, the powder was collected and washed several times with ethanol. Finally, the product was dried in an oven at 60 °C for 8 hours.

[0068] Example 3 This embodiment provides a Mn x Preparation method of γ-AlOOH catalyst. Same as Example 2, except for the amount of manganese nitrate used. The amount of manganese nitrate (Mn(NO3)2·6H2O) used was 6.2 mg (Mn 0.8 / γ-AlOOH), 12.5 mg (Mn 1.4 / γ-AlOOH) and 25.0 mg (Mn 3.1 / γ-AlOOH).

[0069] Product analysis and performance testing: Mn 2.2 Morphology and phase analysis of γ-AlOOH catalyst: Mn prepared in the examples x The XRD pattern of the γ-AlOOH catalyst is shown below. Figure 1 As shown in the figure, it can be seen that with the increase of Mn content, Mn... x The (020) crystal plane peak of / γ-AlOOH gradually broadens and decreases in intensity, indicating that the introduction of a single manganese atom disrupts the symmetry of the γ-AlOOH crystal and induces a disordered state in the γ-AlOOH lattice.

[0070] γ-AlOOH and Mn prepared in the examples 2.2 SEM images of / γ-AlOOH are as follows: Figure 2 As shown, both exhibit a size of 300-600×250 nm. 2 Two-dimensional nanosheet structures with clean and smooth surfaces were prepared. Mn nanosheets with different Mn contents were also prepared. x / γ-AlOOH also exhibits a similar morphology. From Figure 3 Low-magnification transmission electron microscopy and high-resolution transmission electron microscopy can reveal Mn2.2 The surface of / γ-AlOOH exhibits distinct lattice striations and localized amorphous features.

[0071] Figure 4 The Mn prepared in Example 2 is shown. 2.2 Selected area electron diffraction (SED) patterns of / γ-AlOOH show clear electron diffraction spots and diffuse diffraction rings, indicating its polycrystalline nature and local amorphization.

[0072] Figure 5 The Mn prepared in Example 2 is shown. 2.2 The angular annular dark-field scanning transmission electron microscope (TEM) pattern of / γ-AlOOH shows a smooth surface and distinct isolated bright spots (Mn atoms), which further confirms the atomic-level distribution of Mn.

[0073] Figure 6 The Mn prepared in Example 2 is shown. 2.2 The positions and content distribution of Mn, Al, and O elements in / γ-AlOOH clearly show the role of Mn, Al, and O elements in Mn 2.2 Uniform distribution on γ-AlOOH nanosheets.

[0074] Figure 7 The γ-AlOOH and Mn prepared in the examples are shown. x The Raman spectrum of / γ-AlOOH, with the increase of the number of Mn single atoms, belongs to Al-O-Al (358 cm⁻¹). -1 Al-O (493 cm) -1 ) and Al-OH (671 cm -1 The peaks of the characteristic signal of Mn gradually broaden and weaken. This further confirms that Mn... x Local disordering of / γ-AlOOH.

[0075] Figure 8 The γ-AlOOH and Mn prepared in the examples are shown. 2.2 The ESR spectrum of / γ-AlOOH, compared with the original γ-AlOOH, shows that Mn 2.2 The oxygen vacancy signal of / γ-AlOOH was significantly enhanced, indicating an increase in oxygen vacancies in the latter due to Al substitution by Mn.

[0076] Figure 9 The γ-AlOOH and Mn prepared in the examples are shown. 2.2 The X-ray absorption spectrum of / γ-AlOOH proves that the average valence state of Mn is close to +3, and also proves the atomic-level distribution and position of Mn.

[0077] Example 4 This embodiment provides a method for the ozone-catalyzed oxidation degradation of perfluorooctanoic acid, including the following steps: 30 mg of catalyst (γ-AlOOH, Mn with different Mn contents) was used. x / γ-AlOOH) suspended in a solution at a concentration of 2.5 mg / L -1 The perfluorooctanoic acid (PFOA) solution was dispersed in 200 mL of aqueous solution at room temperature by magnetic stirring. During the ozone catalytic oxidation degradation process, O3 gas was introduced into the solution at a rate of 0.2 L / min. O3 was generated by compressed oxygen flowing through an ozone generator. 5 mL of the suspension was collected at regular intervals for further analysis. All collected suspensions were filtered through a 0.25 μm organic filter before analysis. The PFOA concentration was analyzed by high-performance liquid chromatography (HPLC) using a C18 column. The injection volume was 100 μL, and the measurement wavelength was 210 nm. Finally, F was quantitatively determined by ion chromatography. - The concentration was determined. Five cycles were conducted under the same conditions to verify the cyclic stability of the catalyst. After each test, the catalyst was centrifuged, washed multiple times with deionized water, and dried at 60°C for use in the next cycle.

[0078] The metal ions precipitated in the solution were determined by inductively coupled plasma mass spectrometry (ICP-MS) to obtain the ion leaching rate, which was used to further evaluate the stability of the catalyst, which is also an indicator of potential secondary metal contamination.

[0079] The γ-AlOOH and Mn with different Mn contents prepared in the examples x Comparative experiments on the catalytic degradation activity of perfluorooctanoic acid by γ-AlOOH are as follows: Figure 10-11 As shown. Where Mn 2.2 / γ-AlOOH exhibits the highest removal and defluorination rates due to the catalyst's suitable Mn content, localized amorphous structure, and enhanced oxygen vacancy concentration. Figure 12 Prove Mn 2.2 / γ-AlOOH catalysts exhibit good photocatalytic cycle stability.

[0080] Figure 13 The ion leaching diagrams of different catalysts (where the manganese oxide, iron oxide, and cobalt oxide used were purchased from Sinopharm Chemical Reagent Co., Ltd. and used directly without further treatment) demonstrate that Mn 2.2 / γ-AlOOH exhibits a low ion leaching rate, which is attributed to the local amorphization and increased oxygen vacancies resulting from the introduction of Mn. This enhances the catalyst's resistance to external disturbances. Furthermore, the presence of a single Mn atom provides an additional electron replenishment pathway, thereby promoting the activation of O3 and preventing excessive loss of electrons from metal sites.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A Mn single-atom modified γ-AlOOH material, characterized in that, It includes nanosheet-like γ-AlOOH and manganese atoms, with manganese atoms replacing aluminum atoms in the γ-AlOOH lattice.

2. The Mn single-atom modified γ-AlOOH material as described in claim 1, characterized in that, In the Mn single-atom modified γ-AlOOH material, the relative mass fraction of manganese is 0.5-3.5%, preferably 2-2.5%, and more preferably 2.2%.

3. A method for preparing the Mn single-atom modified γ-AlOOH material according to claim 1 or 2, characterized in that, include: Aluminum source, urea and manganese source are dissolved in a solvent and subjected to a solvothermal reaction to obtain Mn single-atom modified γ-AlOOH material.

4. The preparation method according to claim 3, characterized in that, The aluminum source includes aluminum nitrate, the manganese source includes manganese nitrate, and the solvent is water.

5. The preparation method according to claim 3, characterized in that, In the reaction system, the concentration of the aluminum source is 20-30 mmol·L⁻¹. -1 The preferred concentration is 28 mmol·L⁻¹. -1 The concentration of urea is 40-50 mmol·L⁻¹ -1 Preferably 50 mmol·L -1 The concentration of the manganese source was 0.1-2 mmol·L⁻¹. -1 Preferably 0.9 mmol·L -1 .

6. The preparation method according to claim 3, characterized in that, The solvothermal reaction is carried out at a temperature of 140-180℃, preferably 150℃, for a time of 12-36 h, preferably 24 h.

7. The preparation method according to claim 3, characterized in that, Aluminum source, urea and manganese source were dissolved in water, and after complete dissolution, a hydrothermal reaction was carried out to obtain Mn single-atom modified γ-AlOOH material.

8. The application of a γ-AlOO or the Mn single-atom modified γ-AlOOH material as described in claim 1 or 2 in the ozone-catalyzed oxidative degradation of perfluorooctanoic acid.

9. A method for ozone-catalyzed oxidation degradation of perfluorooctanoic acid, characterized in that, include: The γ-AlOOH or the Mn single-atom modified γ-AlOOH material as described in claim 1 or 2 is dispersed in a perfluorooctanoic acid solution and then catalytically degraded by introducing ozone.

10. The method as described in claim 9, characterized in that, The concentration of perfluorooctanoic acid is 2-10 mg / L. -1 Preferably 2.5 mg L -1 ; Preferably, the amount of γ-AlOOH or Mn single-atom modified γ-AlOOH material used is 0.05-0.15 mg / mL, and more preferably 0.15 mg / mL; Preferably, the catalytic degradation reaction time is 5-20 h, more preferably 15 h, and the reaction is continuously stirred during the reaction; Preferably, the ozone introduction rate is 0.1-0.5 L / min, and more preferably 0.2 L / min.

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