Mg atomically dispersed doped mnO2 nanowires and applications thereof

Abstract

The application belongs to the technical field of sewage treatment, and particularly relates to a kind of surface rich Mg atomic level dispersion doped MnO2 Nanowire and its application.The application provides a kind of rich Mg atomic level dispersion doped MnO2 Nanowire material, which is prepared by the double strategy of pre-adsorption and in-situ complexation of organic complexing agent combined with calcination to remove organic complexing agent.In the material, Mg is anchored in the MnO2 surface lattice in-situ, achieving high-density atomic-level dispersion of Mg on the surface of nanowire.At the same time, the low-valence Mg enriched on the surface is directionally induced to generate a large number of oxygen vacancies (OV) in the adjacent position through charge compensation effect, successfully constructing Mg-O-Mn and Mg-OV-Mn synergistic catalytic interface.Benefiting from the above characteristics, the surface rich Mg atomic level dispersion doped MnO2 nanowire material prepared by the application has excellent catalytic ozone oxidation activity and high-efficiency degradation capacity for organic pollutants in sewage.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology. More specifically, it relates to a surface-rich MnO2 nanowire with atomically dispersed Mg doping and its applications. Background Technology

[0002] Heterogeneous catalytic ozone oxidation technology promotes the decomposition of ozone through solid catalysts to generate reactive oxygen species (ROS), especially highly oxidizing hydroxyl radicals (·OH), which is an effective means of treating wastewater containing organic pollutants.

[0003] Currently, activated carbon-supported catalysts are widely used in heterogeneous catalytic ozone oxidation, with manganese oxides (such as MnO2) and magnesium oxides (MgO) being common active components. Among them, MnO2 nanowires with a one-dimensional tunnel structure exhibit good catalytic potential due to their high aspect ratio and specific surface area. However, the catalytic activity of pure-phase MnO2 nanowires is still limited by their slow electron transport rate and insufficient ozone activation ability, restricting further improvement of their catalytic activity. Magnesium oxide, as an ozone catalyst, also suffers from the problem of limited active sites.

[0004] To address the aforementioned issues, existing research has attempted to combine manganese and magnesium oxides to enhance catalytic ozone oxidation performance. For example, Chinese patent application CN114931963A proposes an N-doped manganese-magnesium binary oxide strategy, which modulates the acid-base properties of the catalyst through single-atom nitrogen doping to improve its catalytic ozone activity. Furthermore, Zhu Yaxiong (Zhu Yaxiong, Li Zhipeng, Wang Weiye, et al. Deep ozone catalytic oxidation treatment of dyeing and printing wastewater using MnO2-MgO / AC catalyst [J]. Water Treatment Technology, 2017, 43(11): 121-123, 128.) et al. loaded manganese-magnesium bimetallic oxides onto activated carbon particles for deep ozone catalytic oxidation treatment of dyeing and printing wastewater. All of these existing technologies involve macroscopic or micron-level physical composites or loading of Mg with MnO2 in the form of oxides (MgO). This simple composite method cannot fully utilize the regulatory effect of Mg doping on the electronic structure of MnO2, limiting further improvement in its catalytic effect.

[0005] Therefore, there is an urgent need to develop a novel MnO2 nanowire-based material to overcome the defects of poor Mg species dispersion and low utilization of active sites in existing MnO2 nanowire-based composite catalysts. This is of great practical significance for promoting the practical application of high-performance catalytic ozone oxidation catalysts in wastewater treatment. Summary of the Invention

[0006] This invention addresses the problems of poor Mg species dispersion, low utilization of active sites, and insufficient catalytic ozone oxidation activity in existing MnO2 nanowire-based composite catalysts, aiming to provide a MnO2 nanowire material with surface-rich Mg atomic-level dispersed doping.

[0007] A second objective of this invention is to provide the application of the MnO2 nanowire material with Mg-rich atomic-level dispersed doping on its surface in the catalytic ozone oxidation degradation of organic pollutants in wastewater.

[0008] The above-mentioned objective of this invention is achieved through the following technical solution: This invention provides a surface-rich MnO2 nanowire material with atomically dispersed Mg doping, prepared by the following steps: S1: Dissolve potassium permanganate and divalent manganese salt in water, carry out hydrothermal reaction at 120~180 ℃, and then perform post-treatment to obtain MnO2 nanowires; S2: Take the MnO2 nanowires obtained in step S1 and disperse them with an organic complexing agent in water to obtain an MnO2 nanowire dispersion; S3: Mix the MnO2 nanowire dispersion obtained in step S2 with magnesium salt, carry out a complexation reaction, and then perform post-processing to obtain the precursor; S4: The precursor obtained in step S3 is placed in an air atmosphere and calcined at 400~500 ℃ to obtain MnO2 nanowire material with Mg atomic-level dispersed doping on the surface. The organic complexing agent is selected from at least one of citric acid, malic acid, and disodium ethylenediaminetetraacetate. The molar ratio of the magnesium salt to the organic complexing agent is 1:(1.7~2). The molar ratio of the MnO2 nanowires to the magnesium salt is (5~14):1.

[0009] Preferably, in step S1, the molar ratio of potassium permanganate to divalent manganese salt is 1:(1~2).

[0010] Preferably, in step S1, the divalent manganese salt is selected from at least one of sulfate, nitrate, and chloride.

[0011] Preferably, in step S1, the molar volume ratio of potassium permanganate to water is (10~15) mmol:70mL.

[0012] Preferably, in step S1, the hydrothermal reaction takes 10-14 hours.

[0013] Preferably, in step S1, the post-processing includes washing and drying.

[0014] More preferably, in step S1, the washing is performed by washing with water and ethanol in sequence.

[0015] Optionally, in step S1, the washing process involves first washing with water three times, and then washing with ethanol once.

[0016] More preferably, in step S1, the drying is carried out at 60~100 ℃, specifically 80 ℃.

[0017] Preferably, in step S2, the molar volume ratio of the MnO2 nanowires to water is (5~14) mmol:100 mL.

[0018] Preferably, in step S3, the magnesium salt is selected from at least one of nitrates and acetates.

[0019] Preferably, in step S3, the pH of the complexation reaction is 4-6.

[0020] Preferably, in step S3, the temperature of the complexation reaction is 60~80 °C.

[0021] Preferably, in step S3, the post-processing includes drying and grinding.

[0022] More preferably, in step S3, the drying is carried out at 60~100 ℃, specifically 80 ℃.

[0023] Furthermore, the grinding is performed until there are no obvious lumps.

[0024] Preferably, in step S4, the calcination time is 1 to 3 hours.

[0025] Preferably, in step S4, the heating rate of the calcination is 3~7 °C / min.

[0026] Furthermore, in step S4, the calcination process also includes cooling.

[0027] Furthermore, the cooling is cooling to room temperature.

[0028] The present invention also provides the application of the MnO2 nanowire material with Mg-rich atomic-level dispersed doping on its surface in the catalytic ozone oxidation degradation of organic pollutants in wastewater.

[0029] Furthermore, the catalytic ozone oxidation degradation into MnO2 nanowires with Mg-rich atomic-level dispersed doping can catalyze the generation of highly reactive hydroxyl radicals (·OH) and / or singlet oxygen from ozone. 1 Highly reactive oxygen species such as O2 are used to achieve efficient and thorough degradation of organic pollutants in water.

[0030] Preferably, the organic pollutant includes one or more of acetaminophen, methylene blue, bisphenol A, and amoxicillin.

[0031] The present invention has the following beneficial effects: This invention provides a Mg-rich, atomically dispersed MnO2 nanowire material, prepared through a dual strategy of pre-adsorption and in-situ complexation of organic complexing agents combined with calcination removal of the organic complexing agents. In this material, Mg is in-situ anchored within the MnO2 surface lattice, achieving high-density, atomically dispersed Mg doping on the nanowire surface. Simultaneously, the surface-enriched low-valence Mg induces a large number of oxygen vacancies (OVs) at nearby sites through charge compensation effects, successfully constructing Mg-O-Mn and Mg-OV-Mn synergistic catalytic interfaces. Benefiting from these characteristics, the Mg-rich, atomically dispersed MnO2 nanowire material prepared by this invention exhibits excellent catalytic ozone oxidation activity and highly efficient degradation capabilities for organic pollutants in wastewater. Attached Figure Description

[0032] Figure 1 The X-ray diffraction patterns are shown for the MnO2 nanowire material with Mg-rich atomic-level dispersed doping obtained in Example 1, the MnO2 nanowire material obtained in Comparative Example 1, and the magnesium oxide nanomaterial obtained in Comparative Example 2.

[0033] Figure 2 This is a scanning electron microscope image of the MnO2 nanowire material with atomically dispersed Mg doping on its surface obtained in Example 1.

[0034] Figure 3 The image shows the scanning transmission electron microscope-X-ray energy dispersive spectral distribution (STEM-EDS Mapping) analysis results of the MnO2 nanowire material with Mg-rich atomic-level dispersed doping obtained in Example 1. In the image, "HAADF" refers to the high-angle annular dark field mode, Mg is marked in yellow, O is marked in green, and Mn is marked in red.

[0035] Figure 4 This is a diagram showing the results of high-resolution transmission electron microscopy (HRTEM) analysis, in which... Figure 4 Figure A in the figure shows the high-resolution transmission electron microscopy (HRTEM) analysis results of the MnO2 nanowire material with atomically dispersed Mg doping on the surface obtained in Example 1. Figure 4 Figure B in the figure shows the high-resolution transmission electron microscopy (HRTEM) analysis results of the MnO2 nanowire material obtained in Comparative Example 1.

[0036] Figure 5 The figures show the X-ray photoelectron spectroscopy (XPS) analysis results of the MnO2 nanowire material with atomically dispersed Mg doping obtained in Example 1 and the MnO2 nanowire material obtained in Comparative Example 1. Figure 5Figure A in the figure shows the Mn 2p spectrum of the MnO2 nanowire material with atomically dispersed Mg doping on the surface obtained in Example 1. Figure 5 Figure B in the figure shows the Mg 1s spectrum of the MnO2 nanowire material with atomically dispersed Mg doping on the surface obtained in Example 1. Figure 5 Figure C in the diagram shows the Mn 2p spectrum of the MnO2 nanowire material obtained in Comparative Example 1. Figure 5 Figure D in the diagram is the Mg 1s spectrum of the MnO2 nanowire material obtained in Comparative Example 1.

[0037] Figure 6 The images show the electron paramagnetic resonance (EPR) maps of the MnO2 nanowire material with Mg-rich atomic-level dispersed doping obtained in Example 1 and the MnO2 nanowire material obtained in Comparative Example 1. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0039] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0040] Example 1: A surface-rich MnO2 nanowire material with atomically dispersed Mg doping The MnO2 nanowire material with Mg-rich atomic-level dispersed doping on its surface is prepared by the following steps: (1) Dissolve 1.9 g (12.02 mmol) of potassium permanganate (KMnO4) and 3.0 g (17.75 mmol) of manganese sulfate monohydrate (MnSO4·H2O) in 70 mL of deionized water, stir for 20 min to mix thoroughly, transfer to a polytetrafluoroethylene liner, place in a stainless steel autoclave, seal, and hydrothermally heat at 150 ℃ for 12 h. After naturally cooling to room temperature (25 ℃), centrifuge the product, wash it 4 times with deionized water and ethanol, wash it 3 times with deionized water, and wash it 4 times with ethanol. Dry it overnight in an oven at 80 ℃ to obtain MnO2 nanowires; In this step, the molar ratio of KMnO4 to MnSO4·H2O is 2:3.

[0041] (2) Take 0.5 g (5.75 mmol) of MnO2 nanowires obtained in step (1) and disperse them in 100 mL of deionized water. Add 0.4 g (2.08 mmol) of citric acid and stir to pre-adsorb citric acid onto the surface of MnO2 nanowires to obtain MnO2 nanowire dispersion.

[0042] (3) Add 0.275 g (1.07 mmol) of magnesium nitrate hexahydrate (Mg(NO3)2·6H2O) to the MnO2 nanowire dispersion obtained in step (2), adjust the pH of the solution to 5.0 with ammonia, and carry out a complexation reaction at 80 °C. Use citric acid to simultaneously complex Mn and Mg to form an Mn-citric acid-Mg complex layer in situ on the surface of the nanowires. Transfer to an 80 °C oven for further drying, grind until there are no obvious lumps, and obtain the precursor; In this step, the molar ratio of MnO2 nanowires to Mg(NO3)2·6H2O is 5.4:1; The molar ratio of Mg(NO3)2·6H2O to citric acid is 1:1.9.

[0043] (4) Take the precursor obtained in step (3), calcine it at 450 °C for 2 h at a heating rate of 5 °C / min in air atmosphere, and then cool it to room temperature (25 °C) to obtain MnO2 nanowire material with Mg-rich atomic-level dispersed doping on the surface, named Mg-MnO2.

[0044] Example 2: A MnO2 nanowire material with surface rich in Mg atomically dispersed doping The difference from Example 1 is that the molar ratio of Mg(NO3)2·6H2O to citric acid is 1:1.75, while the remaining steps and parameters remain unchanged. The MnO2 nanowire material with surface-rich Mg atomically dispersed doping is prepared by the following steps: (1) Dissolve 1.9 g (12.02 mmol) of KMnO4 and 3.0 g (17.75 mmol) of MnSO4·H2O in 70 mL of deionized water, stir for 20 min to mix thoroughly, transfer to a polytetrafluoroethylene liner, place in a stainless steel autoclave, seal, and hydrothermally heat at 150 ℃ for 12 h. After naturally cooling to room temperature (25 ℃), centrifuge the product, wash it 4 times with deionized water and ethanol, wash it 3 times with deionized water, and wash it 4 times with ethanol. Dry it overnight in an oven at 80 ℃ to obtain MnO2 nanowires; In this step, the molar ratio of KMnO4 to MnSO4·H2O is 2:3.

[0045] (2) Take 0.5 g (5.75 mmol) of the MnO2 nanowires in step (1) and disperse them in 100 mL of deionized water. Add 0.36 g (1.87 mmol) of citric acid and stir to pre-adsorb the citric acid onto the surface of the MnO2 nanowires to obtain the MnO2 nanowire dispersion.

[0046] (3) Add 0.275 g (1.07 mmol) of Mg(NO3)2·6H2O to the MnO2 nanowire dispersion obtained in step (2), adjust the pH of the solution to 5.0 with ammonia water, carry out the complexation reaction at 80 ℃, use citric acid to simultaneously complex Mn and Mg, and form an Mn-citric acid-Mg complex layer in situ on the surface of the nanowires, transfer to an 80 ℃ oven for further drying, grind until there are no obvious lumps, and obtain the precursor; In this step, the molar ratio of MnO2 nanowires to Mg(NO3)2·6H2O is 5.4:1; The molar ratio of Mg(NO3)2·6H2O to citric acid is 1:1.75.

[0047] (4) Take the precursor obtained in step (3), calcine it at 450 °C for 2 h at a heating rate of 5 °C / min in air atmosphere, and then cool it to room temperature (25 °C) to obtain MnO2 nanowire material with Mg-rich atomic-level dispersed doping on the surface.

[0048] Example 3: A surface-rich MnO2 nanowire material with atomically dispersed Mg doping The difference from Example 1 is that the molar ratio of MnO2 nanowires to Mg(NO3)2·6H2O is 13.4:1, while the remaining steps and parameters remain unchanged. The MnO2 nanowire material with atomically dispersed Mg doping on its surface is prepared by the following steps: (1) Dissolve 1.9 g (12.02 mmol) of KMnO4 and 3.0 g (17.75 mmol) of MnSO4·H2O in 70 mL of deionized water, stir for 20 min to mix thoroughly, transfer to a polytetrafluoroethylene liner, place in a stainless steel autoclave, seal, and hydrothermally heat at 150 ℃ for 12 h. After naturally cooling to room temperature (25 ℃), centrifuge the product, wash it 4 times with deionized water and ethanol, wash it 3 times with deionized water, and wash it 4 times with ethanol. Dry it overnight in an oven at 80 ℃ to obtain MnO2 nanowires; In this step, the molar ratio of KMnO4 to MnSO4·H2O is 2:3.

[0049] (2) Take 0.5 g (5.75 mmol) of MnO2 nanowires obtained in step (1) and disperse them in 100 mL of deionized water. Add 0.16 g (0.83 mmol) of citric acid and stir to pre-adsorb citric acid onto the surface of MnO2 nanowires to obtain MnO2 nanowire dispersion.

[0050] (3) Add 0.11 g (0.43 mmol) of Mg(NO3)2·6H2O to the MnO2 nanowire dispersion obtained in step (2), adjust the pH of the solution to 5.0 with ammonia water, carry out the complexation reaction at 80℃, use citric acid to simultaneously complex Mn and Mg, and form an Mn-citric acid-Mg complex layer in situ on the surface of the nanowires, transfer to an 80℃ oven for further drying, grind until there are no obvious lumps, and obtain the precursor; In this step, the molar ratio of MnO2 nanowires to Mg(NO3)2·6H2O is 13.4:1; The molar ratio of Mg(NO3)2·6H2O to citric acid is 1:1.9.

[0051] (4) Take the precursor obtained in step (3), calcine it at 450 °C for 2 h at a heating rate of 5 °C / min in air atmosphere, and then cool it to room temperature (25 °C) to obtain MnO2 nanowire material with Mg-rich atomic-level dispersed doping on the surface.

[0052] Example 4: A MnO2 nanowire material with surface rich in Mg atomically dispersed doping The difference from Example 1 is that citric acid is replaced with an equimolar amount of DL-malic acid, while the remaining steps and parameters remain unchanged. The MnO2 nanowire material with atomically dispersed Mg doping on its surface is prepared by the following steps: (1) Dissolve 1.9 g (12.02 mmol) of KMnO4 and 3.0 g (17.75 mmol) of MnSO4·H2O in 70 mL of deionized water, stir for 20 min to mix thoroughly, transfer to a polytetrafluoroethylene liner, place in a stainless steel autoclave, seal, and hydrothermally heat at 150 ℃ for 12 h. After naturally cooling to room temperature (25 ℃), centrifuge the product, wash it 4 times with deionized water and ethanol, wash it 3 times with deionized water, and wash it 4 times with ethanol. Dry it overnight in an oven at 80 ℃ to obtain MnO2 nanowires; In this step, the molar ratio of KMnO4 to MnSO4·H2O is 2:3.

[0053] (2) Take 0.5 g (5.75 mmol) of MnO2 nanowires obtained in step (1) and disperse them in 100 mL of deionized water. Add 0.275 g (2.05 mmol) of DL-malic acid and stir to pre-adsorb DL-malic acid onto the surface of MnO2 nanowires to obtain MnO2 nanowire dispersion.

[0054] (3) Add 0.275 g (1.07 mmol) of magnesium nitrate Mg(NO3)2·6H2O to the MnO2 nanowire dispersion obtained in step (2), adjust the pH of the solution to 5.0 with ammonia water, and carry out a complexation reaction at 80 ℃. DL-malic acid is used to simultaneously complex Mn and Mg to form an Mn-malic acid-Mg complex layer in situ on the surface of the nanowires. Transfer to an 80 ℃ oven for further drying, grind until there are no obvious lumps, and obtain the precursor; In this step, the molar ratio of MnO2 nanowires to Mg(NO3)2·6H2O is 5.4:1; The molar ratio of Mg(NO3)2·6H2O to DL-malic acid is 1:1.9.

[0055] (4) Take the precursor obtained in step (3), calcine it at 450 °C for 2 h at a heating rate of 5 °C / min in air atmosphere, and then cool it to room temperature (25 °C) to obtain MnO2 nanowire material with Mg-rich atomic-level dispersed doping on the surface.

[0056] Example 5: A MnO2 nanowire material with surface rich in Mg atomically dispersed doping The difference from Example 1 is that citric acid is replaced with an equimolar amount of disodium ethylenediaminetetraacetate, while the remaining steps and parameters remain unchanged. The MnO2 nanowire material with a surface rich in Mg atoms-level dispersed doping is prepared by the following steps: (1) Dissolve 1.9 g (12.02 mmol) of KMnO4 and 3.0 g (17.75 mmol) of MnSO4·H2O in 70 mL of deionized water, stir for 20 min to mix thoroughly, transfer to a polytetrafluoroethylene liner, place in a stainless steel autoclave, seal, and hydrothermally heat at 150 ℃ for 12 h. After naturally cooling to room temperature (25 ℃), centrifuge the product, wash it 4 times with deionized water and ethanol, wash it 3 times with deionized water, and wash it 4 times with ethanol. Dry it overnight in an oven at 80 ℃ to obtain MnO2 nanowires; In this step, the molar ratio of KMnO4 to MnSO4·H2O is 2:3.

[0057] (2) Disperse 0.5 g (5.75 mmol) of the MnO2 nanowires obtained in step (1) in 100 mL of deionized water, and add 0.775 g (2.08 mmol) of disodium ethylenediaminetetraacetate dihydrate (C 10 H 14 (N2O8Na2·2H2O), stirring to pre-adsorb disodium ethylenediaminetetraacetate onto the surface of MnO2 nanowires, resulting in a MnO2 nanowire dispersion; (3) Add 0.275 g (1.07 mmol) of magnesium nitrate Mg(NO3)2·6H2O to the MnO2 nanowire dispersion obtained in step (2), adjust the pH of the solution to 5.0 with ammonia water, carry out the complexation reaction at 80 ℃, use disodium ethylenediaminetetraacetate to simultaneously complex Mn and Mg, form Mn-EDTA-Mg complex layer in situ on the nanowire surface, transfer to an 80 ℃ oven for further drying, grind until there are no obvious lumps, and obtain the precursor; In this step, the molar ratio of MnO2 nanowires to Mg(NO3)2·6H2O is 5.4:1; The molar ratio of Mg(NO3)2·6H2O to disodium ethylenediaminetetraacetate is 1:1.9.

[0058] (4) Take the precursor obtained in step (3), calcine it at 450 °C for 2 h at a heating rate of 5 °C / min in air atmosphere, and then cool it to room temperature (25 °C) to obtain MnO2 nanowire material with Mg-rich atomic-level dispersed doping on the surface.

[0059] Comparative Example 1: A MnO2 nanowire material The difference from Example 1 is that Mg(NO3)2·6H2O was not added, while the remaining steps and parameters remained unchanged. The MnO2 nanowire material (MnO2) was prepared by the following steps: (1) Dissolve 1.9 g (12.02 mmol) of KMnO4 and 3.0 g (17.75 mmol) of MnSO4·H2O in 70 mL of deionized water, stir for 20 min to mix thoroughly, transfer to a polytetrafluoroethylene liner, place in a stainless steel autoclave, seal, and hydrothermally heat at 150 ℃ for 12 h. After naturally cooling to room temperature (25 ℃), centrifuge the product, wash it 4 times with deionized water and ethanol, wash it 3 times with deionized water, and wash it 4 times with ethanol. Dry it overnight in an oven at 80 ℃ to obtain MnO2 nanowires; In this step, the molar ratio of KMnO4 to MnSO4·H2O is 2:3.

[0060] (2) Take 0.5 g (5.75 mmol) of MnO2 nanowires obtained in step (1) and disperse them in 100 mL of deionized water. Add 0.4 g (2.08 mmol) of citric acid and stir to pre-adsorb citric acid onto the surface of MnO2 nanowires to obtain MnO2 nanowire dispersion.

[0061] (3) Add ammonia to the MnO2 nanowire dispersion obtained in step (2), adjust the pH of the solution to 5.0, carry out the complexation reaction at 80 °C, transfer to an 80 °C oven for further drying, grind until there are no obvious lumps, and obtain the precursor.

[0062] (4) Take the precursor obtained in step (3), calcine it at 450 °C for 2 h in air at a heating rate of 5 °C / min, and then cool it to room temperature (25 °C) to obtain MnO2 nanowire material, which is named MnO2.

[0063] Comparative Example 2: A magnesium oxide nanomaterial The difference from Example 1 is that, without the MnO2 nanowire substrate, the magnesium oxide nanomaterial (MgO) is prepared by the following steps: (1) Dissolve 0.275 g (1.07 mmol) Mg(NO3)2·6H2O and 0.2 g (1.04 mmol) citric acid in 20 mL of deionized water to obtain a magnesium precursor solution; since there is no MnO2 nanowire substrate in this comparative example, the mass of citric acid added is half that of Example 1; In this step, the molar ratio of Mg(NO3)2·6H2O to citric acid is 1:1.

[0064] (2) Add ammonia to the magnesium precursor solution obtained in step (1) to adjust the pH of the solution to 5.0, carry out the complexation reaction at 80 °C, transfer to an 80 °C oven for further drying, grind until there are no obvious lumps, and obtain the precursor.

[0065] (3) Take the precursor obtained in step (2), calcine it at 450 °C for 2 hours in air at a heating rate of 5 °C / min, and then cool it to room temperature (25 °C) to obtain magnesium oxide nanomaterials, named MgO.

[0066] Comparative Example 3: A magnesium oxide-supported MnO2 nanomaterial This comparative example uses an impregnation method to achieve magnesium doping. The difference from Example 1 is that citric acid was not added, while the remaining steps and parameters remain unchanged. The magnesium oxide-supported MnO2 nanomaterial (MgO / MnO2) is prepared using the following steps: (1) Dissolve 1.9 g (12.02 mmol) of KMnO4 and 3.0 g (17.75 mmol) of MnSO4·H2O in 70 mL of deionized water, stir for 20 min to mix thoroughly, transfer to a polytetrafluoroethylene liner, place in a stainless steel autoclave, seal, and hydrothermally heat at 150 ℃ for 12 h. After naturally cooling to room temperature (25 ℃), centrifuge the product, wash it 4 times with deionized water and ethanol, wash it 3 times with deionized water, and wash it 4 times with ethanol. Dry it overnight in an oven at 80 ℃ to obtain MnO2 nanowires; In this step, the molar ratio of KMnO4 to MnSO4·H2O is 2:3.

[0067] (2) Disperse 0.5 g (5.75 mmol) of the MnO2 nanowires obtained in step (1) in 100 mL of deionized water to obtain a MnO2 nanowire dispersion.

[0068] (3) Add 0.275 g (1.07 mmol) of magnesium nitrate Mg(NO3)2·6H2O to the MnO2 nanowire dispersion obtained in step (2), adjust the pH of the solution to 5.0 with ammonia water, carry out the adsorption reaction at 80℃, transfer to an 80℃ oven for further drying, grind until there are no obvious lumps, and obtain the precursor; In this step, the molar ratio of MnO2 nanowires to Mg(NO3)2·6H2O is 5.4:1.

[0069] (4) Take the precursor obtained in step (3), calcine it at 450 °C for 2 h in air at a heating rate of 5 °C / min, and then cool it to room temperature (25 °C) to obtain magnesium oxide supported MnO2 nanomaterials, named MgO / MnO2.

[0070] Comparative Example 4: A Mg-doped MnO2 nanomaterial This comparative example uses a co-precipitation method to achieve magnesium doping. The Mg-doped MnO2 nanomaterials are prepared by the following steps: (1) Dissolve 1.34 mL of 50% (w / v, 5.76 mmol, density 1.54 g / mL) Mn(NO3)2 and 0.275 g (1.07 mmol) Mg(NO3)2·6H2O in 100 mL of deionized water to obtain a precursor solution; In this step, the molar ratio of Mn(NO3)2 to Mg(NO3)2·6H2O is 5.4:1.

[0071] (2) Add 0.3 g (7.5 mmol) NaOH to the precursor solution obtained in step (1) and carry out a coprecipitation reaction at 80 °C. Then wash with deionized water and ethanol 4 times in sequence, wash with deionized water 3 times, wash with ethanol 4 times, dry in an oven at 80 °C overnight, grind until there are no obvious lumps, and obtain the precursor.

[0072] (3) Take the precursor obtained in step (2), calcine it at 450 °C for 2 h at a heating rate of 5 °C / min in air atmosphere, and then cool it to room temperature (25 °C) to obtain Mg-doped MnO2 nanomaterials.

[0073] Experimental Example 1: Morphological Characterization 1. X-ray diffraction (XRD) analysis X-ray diffraction (XRD) analysis was performed on the MnO2 nanowire material with Mg-rich atomic-level dispersed doping obtained in Example 1, the MnO2 nanowire material obtained in Comparative Example 1, and the magnesium oxide nanomaterial obtained in Comparative Example 2.

[0074] Experimental results are as follows Figure 1 As shown, the MnO2 nanowire material with surface-rich Mg atomic-level dispersed doping prepared in Example 1 exhibited diffraction peaks corresponding to the standard card peaks (PDF#29-1020) of MnO2 nanowires in its XRD pattern, and no characteristic peaks of MgO (standard card peak is PDF#45-0946) were observed. This indicates that Mg did not aggregate into clusters on the MnO2 surface as an independent oxide, but rather existed in a highly dispersed state in the sample. Further observation revealed that, compared with the MnO2 nanowire material obtained in Comparative Example 1, the diffraction peak positions of the MnO2 nanowire material with surface-rich Mg atomic-level dispersed doping obtained in Example 1 were slightly shifted towards lower angles, indicating that Mg was not physically mixed in MnO2, but rather integrated into the crystal lattice structure.

[0075] 2. Scanning electron microscopy (SEM) analysis Scanning electron microscopy (SEM) analysis was performed on the MnO2 nanowire material with atomically dispersed Mg doping obtained in Example 1. The results are as follows: Figure 2 As shown, the MnO2 nanowires with surface-rich Mg atomic-level dispersed doping prepared in Example 1 exhibit a uniform nanowire morphology.

[0076] 3. Scanning transmission electron microscopy analysis (1) Scanning transmission electron microscopy-X-ray energy distribution mapping analysis The surface-rich Mg-atomic-level dispersed doped MnO2 nanowire material obtained in Example 1 was analyzed by scanning transmission electron microscopy-X-ray energy distribution mapping (STEM-EDS Mapping). In the scanning transmission electron microscopy (STEM) mode, high-angle annular dark field (HAADF) images and X-ray energy distribution mapping (EDS Mapping) data were acquired simultaneously.

[0077] Experimental results are as follows Figure 3As shown, in the high-angle annular dark-field (HAADF) image, the MnO2 nanowires with Mg-rich atomically dispersed doping exhibit a uniform one-dimensional nanowire morphology, with a diameter of approximately 20–25 nm. In the X-ray energy dispersive spectroscopy (EDS) elemental analysis image, Mg, O, and Mn are marked in yellow, green, and red, respectively. The Mn and O signals uniformly cover the entire nanowire region, forming the main framework of the nanowire; the Mg signal is also uniformly distributed throughout the area covered by the nanowire, and highly overlaps with the signal distributions of Mn and O. No local segregation or clustering of Mg was observed, indicating that Mg is uniformly distributed at the nanowire scale, and no large-scale macroscopic phase separation has occurred.

[0078] (2) High-resolution transmission electron microscopy (HRTEM) analysis The MnO2 nanowire material with surface-rich Mg atomic-level dispersed doping obtained in Example 1 and the MnO2 nanowire material obtained in Comparative Example 1 were analyzed by high-resolution transmission electron microscopy (HRTEM).

[0079] Experimental results are as follows Figure 4 As shown, Example 1 ( Figure 4 The MnO2 nanowire material (Mg-doped sample) with surface-rich Mg atomic-level dispersed doping obtained in Figure A has a lattice fringe spacing of 0.300 nm, while Comparative Example 1 ( Figure 4 The lattice fringe spacing of the MnO2 nanowire material (pure phase material) obtained in Figure B of Example 1 is 0.248 nm, indicating that Mg has entered the MnO2 lattice in the surface-rich Mg-atomic-level dispersed doped MnO2 nanowire material obtained in Example 1. This significant increase in interplanar spacing is directly attributed to the successful substitution of Mn by Mg in the MnO2 lattice. 4+ The presence of Mg at specific lattice sites triggers localized lattice expansion. These results indicate that Mg does not exist as an amorphous phase or surface-adsorbed clusters, but rather as an atomically dispersed element within the MnO2 lattice, achieving surface-enriched atomic-level doping.

[0080] 4. X-ray photoelectron spectroscopy (XPS) analysis X-ray photoelectron spectroscopy (XPS) was used to analyze the MnO2 nanowire material with Mg-rich atomic-level dispersed doping obtained in Example 1 and the MnO2 nanowire material obtained in Comparative Example 1.

[0081] Experimental results are as follows Figure 5 As shown, the Mn 2p spectrum of the surface-rich Mg-atomically dispersed doped MnO2 nanowire material obtained in Example 1 is shown. Figure 5 In Figure A, Mn 3+ The characteristic peak area of ​​Mn increased significantly.3+ / Mn 4+ The proportion increased significantly. This indicates that low-valent Mg... 2+ When doped with MnO2, the charge compensation effect promotes the doping of neighboring MnO2 to maintain the charge balance of the system. 4+ Partially reduced to Mn 3+ This also induces the generation of a large number of oxygen vacancies (OV), and Mn ions near these oxygen vacancies tend to exist in a lower valence state. Surface Mn 3+ The increased content promotes the adsorption and activation of ozone molecules. Furthermore, a strong characteristic signal peak appeared in the Mg 1s binding energy region ( Figure 5 Figure B in the diagram, combined with the absence of MgO diffraction peaks in XRD and the elemental distribution map in the STEM-EDS image showing uniform Mg distribution on the nanowire surface, further confirms that Mg has been successfully doped and enriched on the MnO2 nanowire surface, rather than existing as an independent MgO phase. The enrichment of Mg on the surface fully exposes the active sites, which is beneficial for the efficient catalytic ozone oxidation reaction. The Mn 2p spectrum of pure MnO2 (…) Figure 5 (Figure C in the image) After peak fitting, it mainly consists of Mn 4+ The characteristic peaks were dominant, and no signal peaks were detected in the Mg 1s binding energy region. Figure 5 The D-image in the figure confirms that the surface does not contain Mg. Based on the combined XPS analysis results, this invention successfully achieved atomic-level doping enrichment of Mg on the surface of MnO2 nanowires, and induced surface Mn doping through charge compensation effect. 3+ The increased content and the generation of a large number of oxygen vacancies (OV) construct a synergistic catalytic interface between Mg-O-Mn and Mg-OV-Mn, providing a structural basis for the catalyst's excellent ozone activation ability.

[0082] 5. Electron paramagnetic resonance (EPR) analysis Electron paramagnetic resonance (EPR) analysis was performed on the MnO2 nanowire material with surface rich Mg atomic-level dispersed doping obtained in Example 1 and the MnO2 nanowire material obtained in Comparative Example 1.

[0083] Experimental results are as follows Figure 6 As shown, the MnO2 nanowire material obtained in Comparative Example 1 exhibits only a very weak signal within the magnetic field range, indicating a very low oxygen vacancy concentration. In contrast, the MnO2 nanowire material with surface-rich Mg atomically dispersed doping obtained in Example 1 shows an extremely high-intensity and significantly broadened EPR signal peak near approximately 3300 G, indicating that Mg doping induces a high concentration of oxygen vacancies in the MnO2 lattice through charge compensation, thereby successfully constructing a Mg-O-Mn and Mg-OV-Mn synergistic catalytic interface.

[0084] The MnO2 nanowires with surface-rich Mg atomic-level dispersed doping obtained in Examples 2 to 5 have similar properties to the MnO2 nanowires with surface-rich Mg atomic-level dispersed doping obtained in Example 1, and will not be described again.

[0085] Experimental Example 2: Evaluation of Ozone Catalytic Degradation Effect 1. Experimental Methods The surface-rich Mg-doped MnO2 nanowires obtained in Examples 1-5, the MnO2 nanowires obtained in Comparative Example 1, the magnesium oxide nanomaterials prepared in Comparative Example 2, the magnesium oxide-supported MnO2 nanomaterials obtained in Comparative Example 3, and the Mg-doped MnO2 nanomaterials obtained in Comparative Example 4 were used as catalysts. Acetaminophen (PCT) was used as a simulated pollutant. 100.0 mL of 20.0 mg / L PCT wastewater and 0.03 g of each of the above catalysts were added to the reactor. Ozone at a concentration of 1.0 mg / L was continuously bubbled into the water using an ozone generator at a flow rate of 150 mL / min, and the gaseous ozone concentration was continuously monitored using an online ozone analyzer. Unreacted ozone at the reactor outlet was quenched with a 2% (w / v) potassium iodide solution. After 15 min of reaction, samples were taken. The ozone in the solution was stripped with N2, and the concentration of acetaminophen in the filtrate was immediately determined by high performance liquid chromatography (HPLC). The removal rate was calculated, and the group without catalyst was used as a blank control. Each experiment was repeated 3 times, and the average value was taken as the final result.

[0086] The experimental results are shown in Table 1.

[0087] Table 1. Degradation effect of different materials on PCT

[0088] Note: The same letters indicate that there is no significant difference between the two, while different letters indicate that there is a significant difference between the two.

[0089] As shown in Table 1, the MnO2 nanowire materials with surface-rich Mg atomic-level dispersed doping prepared in Examples 1 to 5 are significantly better than those in the comparative examples.

[0090] Experimental Example 3: Evaluation of Ozone Catalytic Degradation Effect The MnO2 nanowire materials with Mg-rich atomic-level dispersed doping obtained in Examples 1-5 exhibit comparable catalytic activity. To verify their universality for different organic pollutants, the nanowire material obtained in Example 1 was used as a representative sample in this experiment.

[0091] Using the surface-doped MnO2 nanowires rich in Mg atoms dispersed in Example 1 as a representative catalyst, methylene blue (MB), bisphenol A (BPA), and amoxicillin (AMOX) were selected as representative pollutants for ozone catalytic degradation experiments. The experimental conditions were as follows: 100.0 mL of wastewater containing 20.0 mg / L of pollutants and 0.03 g of catalyst were added to the reactor. Ozone at a concentration of 1.0 mg / L was continuously bubbled into the water using an ozone generator at a flow rate of 150 mL / min. After reacting for 15 min, samples were taken, and the pollutant concentration was determined using high-performance liquid chromatography (HPLC). The degradation rate was calculated. Each experiment was repeated three times, and the average value was taken as the final result.

[0092] The experimental results are shown in Table 2.

[0093] Table 2 Degradation effects on different pollutants

[0094] As shown in Table 2, the MnO2 nanowire material with Mg-rich atomic-level dispersed doping obtained in Example 1 exhibits good catalytic degradation efficiency for organic pollutants with different structural characteristics, confirming that the MnO2 nanowire material with Mg-rich atomic-level dispersed doping provided by the present invention has good substrate universality in the field of wastewater treatment.

[0095] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A surface-doped MnO2 nanowire material rich in Mg atoms at a dispersed level, characterized in that, The preparation process includes the following steps: S1: Dissolve potassium permanganate and divalent manganese salt in water, carry out hydrothermal reaction at 120~180 ℃, and then perform post-treatment to obtain MnO2 nanowires; S2: Take the MnO2 nanowires obtained in step S1 and disperse them with an organic complexing agent in water to obtain an MnO2 nanowire dispersion; S3: Mix the MnO2 nanowire dispersion obtained in step S2 with magnesium salt, carry out a complexation reaction, and then perform post-processing to obtain the precursor; S4: The precursor obtained in step S3 is placed in an air atmosphere and calcined at 400~500 ℃ to obtain MnO2 nanowire material with Mg atomic-level dispersed doping on the surface. The organic complexing agent is selected from at least one of citric acid, malic acid, and disodium ethylenediaminetetraacetate. The molar ratio of the magnesium salt to the organic complexing agent is 1:(1.7~2). The molar ratio of the MnO2 nanowires to the magnesium salt is (5~14):

1.

2. The MnO2 nanowire material with surface-rich Mg atomic-level dispersed doping as described in claim 1, characterized in that, The molar ratio of potassium permanganate to divalent manganese salt is 1:(1~2).

3. The MnO2 nanowire material with surface-rich Mg atomic-level dispersed doping as described in claim 1, characterized in that, The divalent manganese salt is selected from at least one of sulfate, nitrate, and chloride.

4. The MnO2 nanowire material with surface-rich Mg atomic-level dispersed doping as described in claim 1, characterized in that, The magnesium salt is selected from at least one of nitrates and acetates.

5. The MnO2 nanowire material with surface-rich Mg atomic-level dispersed doping as described in claim 1, characterized in that, The hydrothermal reaction takes 10-14 hours.

6. The MnO2 nanowire material with surface-rich Mg atomic-level dispersed doping as described in claim 1, characterized in that, The calcination time is 1 to 3 hours.

7. The MnO2 nanowire material with surface-rich Mg atomic-level dispersed doping as described in claim 1, characterized in that, The temperature of the complexation reaction is 60~80 ℃.

8. The MnO2 nanowire material with surface-rich Mg atomic-level dispersed doping as described in claim 1, characterized in that, The pH of the complexation reaction is 4-6.

9. The application of the surface-rich Mg-atomic-level dispersed doped MnO2 nanowire material according to any one of claims 1 to 8 in the catalytic ozone oxidation degradation of organic pollutants in wastewater.

10. The application as described in claim 9, characterized in that, The organic pollutants include one or more of acetaminophen, methylene blue, bisphenol A, and amoxicillin.

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