High-entropy metal oxide catalyst as well as preparation method and application thereof

Abstract

The invention relates to a high-entropy metal oxide catalyst and a preparation method and application thereof.The preparation method comprises the following steps that S1, ferric salt, cobalt salt, manganese salt, nickel salt, copper salt and organic alkaline matter are mixed to obtain a mixed solution, hydrothermal reaction is conducted, and a precursor is obtained; and S2, calcining the precursor at the temperature of 500-600 DEG C to obtain the high-entropy metal oxide catalyst. The high-entropy metal oxide catalyst uniformly doped with iron, cobalt, manganese, nickel and copper is prepared by adopting a hydrothermal reaction and calcination method, and the high-entropy metal oxide catalyst not only can efficiently catalyze ozone to remove antibiotics, but also can still keep an excellent antibiotic removal rate constant in a water body containing hetero ions and humic acid; and the anti-interference capability is excellent.

Description

Technical Field

[0001] This application relates to the field of catalyst technology, and in particular to a high-entropy metal oxide catalyst, its preparation method, and its application. Background Technology

[0002] With the widespread detection of emerging organic pollutants (ECs) in the environment, water pollution is facing new challenges. Antibiotic pollutants, especially sulfamethoxazole (SMX), have become a significant target for water environment management due to their widespread use, persistent degradation, and the risk of antibiotic resistance. Traditional water treatment technologies (such as activated carbon adsorption, membrane separation, and ultraviolet irradiation) often suffer from low efficiency, complex operation, and a tendency to cause secondary pollution in EC removal, making them unsuitable for practical water treatment needs. Ozone catalytic oxidation technology, however, can generate reactive oxygen species (such as •OH and •O) under mild conditions. 2- 1O 2 Ozone oxidation, including processes like mineralization, to achieve deep mineralization of organic pollutants, is considered a promising advanced oxidation technology. However, due to the high chemical stability of ozone molecules (O=O bond energy reaches 363 kJ / mol), its oxidation capacity is limited under catalytic conditions. Therefore, developing efficient catalysts to promote ozone activation is crucial for the application of this technology in practical water treatment processes.

[0003] Conventional single-metal oxide catalysts generally suffer from low ozone activation efficiency, limited conversion of reaction intermediates, and unstable catalytic lifetime, making it difficult to achieve stable and efficient pollutant removal in complex aquatic environments. For example, in aquaculture, large amounts of antibiotics are used to prevent fish from becoming infected. SMX that is not absorbed by the fish is directly released, resulting in high levels of SMX in aquaculture wastewater. Simultaneously, the wastewater also contains large amounts of heterogeneous ions (such as chloride ions and bicarbonate ions) and humic acid produced from the decomposition of organic matter. In actual advanced oxidation processes of wastewater, the reactive oxygen species decomposed by ozone are easily quenched by heterogeneous ions or humic acid in the water, leading to a decline in the degradation performance of the target pollutants.

[0004] In recent years, high-entropy metal oxides (HEOs) have shown great potential in environmental catalysis as a new class of multi-metal synergistic catalytic materials. Their unique high-entropy stable structure, abundant reaction sites, and tunable electronic structure endow them with excellent catalytic activity and stability. However, existing research on HEOs is mostly focused on gas-phase catalysis, and studies on their application in liquid-phase ozone degradation systems remain limited. Existing literature (doi: 10.1080 / 09593330.2023.2283054) reports a high-entropy metal oxide ((Mn) with a spinel structure... 0.2 Fe 0.2 Co 0.2 Ni 0.2 Cu 0.2 Ozone (3O4) catalyzes the production of reactive oxygen species from hydrogen peroxide during advanced oxidation processes, and combines this with photo-irradiation technology to degrade the antibiotic tetracycline hydrochloride (TC-HCl). However, it does not address the degradation performance of antibiotics using ozone as the reactive substance, nor does it address the issue of impurities in wastewater quenching the reactive oxygen species decomposed by ozone. Summary of the Invention

[0005] The primary objective of this invention is to overcome the problems that the efficiency of existing metal oxide catalysts in removing antibiotics by ozone still needs to be improved, and that ozone is easily quenched by impurities in water, and to provide a method for preparing a high-entropy metal oxide catalyst.

[0006] A further objective of this invention is to provide a high-entropy metal oxide catalyst.

[0007] Another object of the present invention is to provide the application of high-entropy metal oxide catalysts in ozone catalytic oxidation.

[0008] The above-mentioned objective of the present invention is achieved through the following technical solution: A method for preparing a high-entropy metal oxide catalyst includes the following steps: S1. Iron salts, cobalt salts, manganese salts, nickel salts, copper salts and organic alkaline substances are mixed to obtain a mixed solution, and a hydrothermal reaction is carried out to obtain a precursor; S2. The precursor is calcined at a temperature of 500~600℃ to obtain the high-entropy metal oxide catalyst.

[0009] The inventors of this invention have discovered that a high-entropy metal oxide catalyst uniformly doped with iron, cobalt, manganese, nickel, and copper can be prepared by using a hydrothermal reaction and calcination method. This high-entropy metal oxide catalyst can not only efficiently catalyze the removal of antibiotics by ozone, but also maintain an excellent rate constant for antibiotic removal in water containing impurities and humic acid, and has excellent anti-interference ability.

[0010] The principle is as follows: The high-entropy metal oxide catalyst of this invention has a hematite-type crystal structure, in which five metal elements are uniformly distributed, regulating the d-band center and band structure of the catalyst, thereby enhancing its adsorption and activation ability for ozone molecules, and thus improving the removal rate of antibiotics. Simultaneously, the surface of the high-entropy metal oxide catalyst of this invention is enriched with low-valence Fe and Co metals, which not only facilitates the electron transfer activation of ozone, promoting the decomposition of ozone into superoxide radicals and singlet oxygen, thereby improving the removal rate of antibiotics, but also weakens the adsorption competition of impurity ions in complex water bodies, enhancing its anti-interference ability.

[0011] Preferably, in step S1, the molar ratio of trivalent iron, divalent cobalt, divalent manganese, dimethyl nickel and divalent copper in the mixed solution is 1:1:1:1:1.

[0012] Preferably, in step S1, the total amount of trivalent iron, divalent cobalt, divalent manganese, dimethyl nickel and divalent copper in the mixed solution and the amount of organic alkaline substances are in a ratio of 1:(1.5~2.5).

[0013] Preferably, in step S1, the organic alkaline substance is at least one of urea, melamine, or dicyandiamide.

[0014] It should be understood that the organic alkaline substances used in this invention decompose into ammonia gas during hydrothermal reaction. Ammonia gas can adjust the pH of the solution to cause iron salts, cobalt salts, manganese salts, nickel salts, and copper salts to form precipitates.

[0015] Preferably, in step S1, the temperature of the hydrothermal reaction is 120~200℃.

[0016] Preferably, in step S1, the hydrothermal reaction takes 4 to 8 hours.

[0017] Preferably, in step S1, the mixing is carried out at 60~80°C.

[0018] Preferably, step S1 further includes washing and drying steps after the hydrothermal reaction.

[0019] More preferably, the reagent used for washing is at least one of water, ethanol, or methanol.

[0020] More preferably, the drying temperature is 50~70℃ and the time is 10~20 h.

[0021] More preferably, the drying is carried out in a vacuum environment.

[0022] Preferably, in step S1, the iron salt is at least one of FeCl3, Fe(NO3)3 or Fe2(SO4)3.

[0023] Preferably, in step S1, the cobalt salt is at least one of CoCl2, Co(NO3)2, or CoSO4·7H2O.

[0024] Preferably, in step S1, the manganese salt is at least one of MnCl2, Mn(NO3)2, or MnSO4·H2O.

[0025] Preferably, in step S1, the nickel salt is at least one of NiCl2, Ni(NO3)2·6H2O or NiSO4·6H2O.

[0026] Preferably, in step S1, the copper salt is at least one of CuCl2, Cu(NO3)2·3H2O or CuSO4·5H2O.

[0027] Preferably, in step S2, the calcination time is 1 to 3 hours.

[0028] Preferably, in step S2, the temperature is increased to the calcination temperature at a heating rate of 1~3℃ / min.

[0029] Preferably, in the high-entropy metal oxide catalyst, the content ratio of divalent iron to trivalent iron is (61~65):(35~39), the content ratio of divalent cobalt to trivalent cobalt is (60~65):(35~40), the content ratio of divalent manganese to trivalent manganese is (70~72.5):(27.5~30), the content ratio of divalent nickel to trivalent nickel is (30~40):(60~70), and the content ratio of monovalent copper to divalent copper is (0~10):(90~100).

[0030] Preferably, in the high-entropy metal oxide catalyst, the content ratio of lattice oxygen, oxygen vacancies and surface adsorbed oxygen is (74~76):(17.5~20):(4~8.5).

[0031] A high-entropy metal oxide catalyst is prepared by the above-described preparation method.

[0032] This invention also protects the application of the above-mentioned high-entropy metal oxide catalyst in ozone catalytic oxidation.

[0033] Preferably, the high-entropy metal oxide catalyst is used in the ozone catalytic oxidation degradation of antibiotics in wastewater.

[0034] More preferably, the wastewater contains Cl - SO4 2- NO 3- HCO 3- Or at least one of humic acids.

[0035] More preferably, the antibiotic is sulfamethoxazole.

[0036] More preferably, the wastewater is aquaculture wastewater.

[0037] Compared with the prior art, the beneficial effects of the present invention are: This invention prepares a high-entropy metal oxide catalyst uniformly doped with iron, cobalt, manganese, nickel, and copper metals by using a hydrothermal reaction and calcination method. This high-entropy metal oxide catalyst can not only efficiently catalyze the removal of antibiotics by ozone, but also maintain an excellent rate constant for antibiotic removal in water containing impurities and humic acid, and has excellent anti-interference ability. Attached Figure Description

[0038] Figure 1 Thermogravimetric analysis diagram of the precursor in step (1) of Example 1; Figure 2 The images show the XRD results of the high-entropy metal oxide catalyst in Example 1 and the comparative metal oxide catalysts in Examples 1-3. Figure 3 The figures show the transmission electron microscopy (TEM) and EDS results of the high-entropy metal oxide catalyst in Example 1; where, Figure 3 Figure A shows the results of transmission electron microscopy (TEM) testing. Figure 3 B is the result graph of the EDS test; Figure 4 The XPS test results are shown for the high-entropy metal oxide catalyst of Example 1 and the comparative metal oxide catalyst of Comparative Example 3. Figure 5 The graph shows the EPR test results of the high-entropy metal oxide catalyst in Example 1; where, Figure 5 A is for testing • O2 - The generated result image, Figure 5 B is for testing. 1 The result image generated by O2; Figure 6 The graph shows the removal rates of SMX by the high-entropy metal oxide catalyst of Example 1 and the comparative metal oxide catalysts of Examples 1-2. Figure 7 The graph shows the removal rates of SMX by the high-entropy metal oxide catalyst of Example 1 and the comparative metal oxide catalyst of Comparative Example 3. Figure 8 The graph shows the rate constant results for the removal of SMX by the high-entropy metal oxide catalyst of Example 1 in the presence of ozone in water containing different heteroions and humic acids. Detailed Implementation

[0039] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention.

[0040] Example 1 This embodiment provides a method for preparing a high-entropy metal oxide catalyst, including the following steps: (1) Dissolve 0.01 mol LFeCl3, 0.01 mol LCoCl2·2H2O, 0.01 mol LMnCl2, 0.01 mol NiCl2, and 0.01 mol LCuCl2 in deionized water, then add 0.1 mol urea and stir in an oil bath at 70°C to obtain a mixed solution. Transfer the mixed solution to a polytetrafluoroethylene-lined autoclave at a pressure of 1 MPa and carry out a hydrothermal reaction at 180°C for 6 h. After cooling to room temperature, wash three times with deionized water and then vacuum dry at 50°C for 12 h to obtain the precursor. (2) Calcine the precursor from step (1): In an air atmosphere, heat the temperature to 550°C at a rate of 1°C / min and hold for 1 h; cool naturally to obtain the high-entropy metal oxide catalyst.

[0041] Example 2 This embodiment provides a method for preparing a high-entropy metal oxide catalyst, which differs from Embodiment 1 in that the calcination temperature in step (2) is 600°C.

[0042] Example 3 This embodiment provides a method for preparing a high-entropy metal oxide catalyst, which differs from Embodiment 1 in that the calcination temperature in step (2) is 500°C.

[0043] Example 4 This embodiment provides a method for preparing a high-entropy metal oxide catalyst, which differs from Embodiment 1 in that the temperature of the hydrothermal reaction in step (1) is 120°C.

[0044] Example 5 This embodiment provides a method for preparing a high-entropy metal oxide catalyst, which differs from Embodiment 1 in that: in step (2), the temperature is increased to 550°C at a heating rate of 1°C / min and held for 3 hours.

[0045] Comparative Example 1 This comparative example provides a method for preparing a comparative metal oxide catalyst, which differs from Example 1 in that the calcination temperature in step (2) is 450°C.

[0046] Comparative Example 2 This comparative example provides a method for preparing a comparative metal oxide catalyst, which differs from Example 1 in that the calcination temperature in step (2) is 650°C.

[0047] Comparative Example 3 This comparative example provides a comparative metal oxide catalyst, wherein the comparative metal oxide catalyst is Fe2O3.

[0048] The preparation process of Fe2O3 in this comparative example is as follows: 0.05 mol of FeCl3 was dissolved in deionized water, and then 0.1 mol of urea was added. The mixture was stirred in an oil bath at 70°C to obtain a mixed solution. The mixed solution was transferred to a polytetrafluoroethylene-lined autoclave and subjected to a hydrothermal reaction at 180°C for 6 h. After cooling to room temperature, the mixture was washed three times with deionized water and then vacuum dried at 50°C for 12 h to obtain the precursor. Under air atmosphere, the precursor was heated to 550°C at a heating rate of 1°C / min and held at that temperature for 1 h. After natural cooling, Fe2O3 was obtained.

[0049] Comparative Example 4 This comparative example provides a comparative metal oxide catalyst, which is Co2O3.

[0050] The Co2O3 used in this comparative example was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0051] Comparative Example 5 This comparative example provides a comparative metal oxide catalyst, wherein the comparative metal oxide catalyst is MnO2.

[0052] The MnO2 used in this comparative example was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0053] Comparative Example 6 This comparative example provides a comparative metal oxide catalyst, wherein the comparative metal oxide catalyst is NiO.

[0054] The NiO used in this comparative example was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0055] Comparative Example 7 This comparative example provides a comparative metal oxide catalyst, wherein the comparative metal oxide catalyst is CuO.

[0056] The CuO used in this comparative example was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0057] Characterization and performance testing (1) Thermogravimetric test The precursor from step (1) of Example 1 was subjected to thermogravimetric analysis, and the results are as follows: Figure 1 As shown. From Figure 1It can be seen that the weight of the precursor drops to its lowest point at 444℃, and then begins to rise slightly after 561℃. This indicates that the precursor begins to crystallize at 444℃, and that the low-valence metal begins to be oxidized into the high-valence metal at 561℃.

[0058] (2) XRD test XRD tests were performed on the high-entropy metal oxide catalyst of Example 1 and the comparative metal oxide catalysts of Comparative Examples 1-3. Figure 2 As shown, the standard card PDF#97-018-4766 corresponds to Fe2O3. The high-entropy metal oxide catalyst of Example 1 is designated as "HEO-550", the comparative metal oxide catalyst of Comparative Example 2 is designated as "HEO-650", the comparative metal oxide catalyst of Comparative Example 1 is designated as "HEO-450", the comparative metal oxide catalyst of Comparative Example 2 is designated as "HEO-650", and the comparative metal oxide catalyst of Comparative Example 3 is designated as "Fe2O3".

[0059] from Figure 2 It can be seen that the crystal structure of the high-entropy metal oxide catalyst in Example 1 and the comparative metal oxide catalyst in Comparative Example 2 is the same as that of Fe2O3, which is a hematite-type crystal structure. The peak of the comparative metal oxide catalyst in Comparative Example 1 at a 2θ angle of approximately 35° does not completely correspond to the standard card, indicating that the comparative metal oxide catalyst in Comparative Example 1 has not completely formed the Fe2O3 crystal structure. The XRD test results of the high-entropy metal oxide catalysts in other examples are similar to those in Example 1.

[0060] (3) Transmission electron microscopy and EDS testing The high-entropy metal oxide catalyst from Example 1 was subjected to transmission electron microscopy (TEM) and EDS (Electron Spectroscopy) tests, and the results are as follows: Figure 3 As shown, Figure 3 Figure A shows the results of transmission electron microscopy (TEM) testing. Figure 3 B is the result graph of the EDS test. From Figure 3 It can be seen that the high-entropy metal oxide catalyst of Example 1 exhibits a hexahedral morphology, with the five metal elements uniformly distributed to form an entropy-stable structure. The transmission electron microscopy (TEM) and EDS results of the high-entropy metal oxide catalysts of other examples are similar to those of Example 1.

[0061] (4) XPS test XPS tests were performed on the high-entropy metal oxide catalyst of Example 1 and the comparative metal oxide catalyst of Comparative Example 3. The results are as follows: Figure 4 As shown in Table 1. Figure 4 The image shows the XPS test results for the high-entropy metal oxide catalyst in Example 1. (Refer to Table 1 and...) Figure 4It can be seen that, compared with Comparative Example 2, the ratio of low-valence metal content to high-valence metal content in Fe and Co on the surface of the high-entropy metal oxide catalyst in Example 1 is higher. The XPS test results of the high-entropy metal oxide catalysts in other examples are similar to those of Example 1.

[0062] Table 1. Percentage of chemical states of O, Fe, Co, Mn, Ni and Cu

[0063] (5) EPR test The high-entropy metal oxide catalyst from Example 1 was subjected to EPR testing, and the results are as follows: Figure 5 As shown, Figure 5 A is for testing • O2 - The generated result image, Figure 5 B is for testing. 1 The result image generated by O2. From Figure 5 It can be seen that the high-entropy metal oxide catalyst in Example 1 mainly generates •O2 when activating ozone. - and 1 O2. The EPR test results of the high-entropy metal oxide catalysts in other embodiments are similar to those in Example 1.

[0064] (6) Sulfamethoxazole (SMX) removal test High-purity oxygen (99.99%) was used as the gas source, and an ozone generator produced ozone at an inlet flow rate of 2 L / min. The ozone concentration was 1 mg / L. A dual-channel device (UV method) was used to detect the ozone concentration and introduce it into the reaction system. 10 mg / L SMX solution was added to the reaction system along with 100 mg / L of different catalysts (the high-entropy metal oxide catalyst of Example 1 was designated "HEO-550", the comparative metal oxide catalyst of Comparative Example 1 was designated "HEO-450", the comparative metal oxide catalyst of Comparative Example 2 was designated "HEO-650", and the comparative metal oxide catalysts of Comparative Examples 3-7 were designated "Fe2O3", "Co2O3", "MnO2", "NiO", and "CuO", respectively). After stirring for 30 minutes, ozone was introduced to start the reaction. A 1 mL sample was taken every 5 minutes, filtered through a 0.22 μm PES membrane, and the SMX concentration was determined by HPLC (mobile phase: methanol:water = 55:45, detection wavelength 270 nm). The results are shown in [Figure number missing]. Figures 6-7 As shown. Among them, Figure 6 The graph shows the removal rates of SMX by the high-entropy metal oxide catalyst of Example 1 and the comparative metal oxide catalysts of Examples 1-2. Figure 7The graph shows the removal rates of SMX by the high-entropy metal oxide catalyst of Example 1 and the comparative metal oxide catalyst of Comparative Example 3. Removal rate = (1 - C / C0) × 100% = , where "C" is the SMX concentration at different times and "C0" is the SMX concentration before the test.

[0065] from Figure 6 and 7 It can be seen that the removal rate of SMX by each catalyst gradually increases with time in the presence of ozone. When 30 min is reached, the removal rate of SMX by the high-entropy metal oxide catalyst in Example 1 is 79% in the presence of ozone. However, the removal rates of SMX by the comparative metal oxide catalysts in Examples 1 and 2 are 65% and 67% respectively in the presence of ozone after 30 min. This may be because the calcination temperature of Comparative Example 1 is too low, and the Fe2O3 crystal structure has not been fully formed, while the temperature of Comparative Example 2 is too high, resulting in a large proportion of high-valence Fe and Co metals in the comparative metal oxide catalyst. The removal rates of SMX by the comparative metal oxide catalysts in Examples 3 to 7 are 65%, 65%, 74%, 71%, and 64% respectively in the presence of ozone after 30 min. This may be because the single metal oxide has a single active site and limited electron transfer, resulting in low ozone activation efficiency and stability. The removal results of sulfamethoxazole by the high-entropy metal oxide catalysts in other examples are similar to those in Example 1.

[0066] (7) Resistance to interference from impure ions In the presence of different heteroions (Cl) - SO4 2- NO 3- HCO 3- The rate constant of the high-entropy metal oxide catalyst in Example 1 for removing SMX in the presence of ozone was tested in water containing humic acid (HA). The test procedure was as follows: High-purity oxygen (99.99%) was used as the gas source, and an ozone generator produced ozone at an inlet flow rate of 2 L / min and an ozone concentration of 1 mg / L. A dual-channel device (UV method) was used to detect the ozone concentration and introduce it into the reaction system. 10 mg / L SMX solution and 100 mg / L of the high-entropy metal oxide catalyst from Example 1 were added to the reaction system. Then, different test substances (NaCl, NaSO4, NaNO3, NaHCO3, HA) were added. After stirring for 30 minutes, ozone was introduced to start the reaction. 1 mL of sample was taken every 5 minutes, filtered through a 0.22 μm PES membrane, and the SMX concentration was determined by HPLC (mobile phase: methanol:water = 55:45, detection wavelength 270 nm). The degradation rate constant was obtained by fitting the degradation curve. The results are shown below. Figure 8 As shown.

[0067] from Figure 8 It can be seen that the rate constant for SMX removal remains essentially unchanged when different heteroions or humic acids are present. This indicates that the presence of different heteroions or humic acids in the water has little effect on the catalytic activation of ozone by the high-entropy metal oxide catalyst in Example 1, suggesting that the high-entropy metal oxide catalyst in Example 1 has the ability to resist heteroion interference. The test results of heteroion interference resistance of the high-entropy metal oxide catalysts in other examples are similar to those in Example 1.

[0068] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a high-entropy metal oxide catalyst, characterized in that, Includes the following steps: S1. Iron salts, cobalt salts, manganese salts, nickel salts, copper salts and organic alkaline substances are mixed to obtain a mixed solution, and a hydrothermal reaction is carried out to obtain a precursor; S2. The precursor is calcined at a temperature of 500~600℃ to obtain the high-entropy metal oxide catalyst.

2. The preparation method according to claim 1, characterized in that, In step S1, the molar ratio of trivalent iron, divalent cobalt, divalent manganese, dimethyl nickel and divalent copper in the mixed solution is 1:1:1:1:

1.

3. The preparation method according to claim 1, characterized in that, In step S1, the organic alkaline substance is at least one of urea, melamine, or dicyandiamide.

4. The preparation method according to claim 1, characterized in that, In step S1, the temperature of the hydrothermal reaction is 120~200℃.

5. The preparation method according to claim 1, characterized in that, In step S1, the hydrothermal reaction takes 4 to 8 hours.

6. The preparation method according to claim 1, characterized in that, In step S2, the calcination time is 1 to 3 hours.

7. The preparation method according to claim 1, characterized in that, In step S2, the temperature is increased to the calcination temperature at a heating rate of 1~3℃ / min.

8. A high-entropy metal oxide catalyst, characterized in that, It is prepared by any of the preparation methods described in claims 1 to 7.

9. The application of the high-entropy metal oxide catalyst according to claim 8 in ozone catalytic oxidation.

10. The application of the high-entropy metal oxide catalyst of claim 9 in the ozone catalytic oxidation degradation of antibiotics in wastewater.

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