Platinum nanoparticle composite manganese dioxide / manganese cobaltate hollow microsphere water treatment catalyst and preparation method thereof
By loading Pt and MnO2 onto a MnCo2O4 support to prepare a composite catalyst, the problems of easy aggregation of noble metals and low activity of transition metals were solved, and the effect of efficient removal of tetracycline from water at room temperature was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TIANJIN POLYTECHNIC UNIV
- Filing Date
- 2024-01-08
- Publication Date
- 2026-06-23
AI Technical Summary
Existing precious metal catalysts are expensive and prone to aggregation. Transition metal catalysts alone are not effective at removing tetracycline at room temperature and have low catalytic activity, making it difficult to efficiently remove tetracycline from water in practical applications.
A composite catalyst of Pt and MnO2 was prepared by using hollow spherical MnCo2O4 as a support and then loading it onto the catalyst. The Pt/MnO2/MnCo2O4 catalyst was prepared by solvothermal method and calcination process, and its high specific surface area and uniform nanostructure were used to improve the catalytic activity.
It can efficiently catalyze the degradation of tetracycline in water at room temperature, with a catalytic efficiency of 86.7% within 90 minutes. After repeated use, it still maintains a removal rate of 79.5%, and Pt and MnO2 are uniformly dispersed and structurally stable.
Smart Images
Figure CN117884142B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a platinum nanoparticle composite manganese dioxide / manganese cobalt oxide hollow microsphere water treatment catalyst and its preparation method, belonging to the field of composite material technology. Background Technology
[0002] Currently, the excessive and improper use of tetracycline antibiotics has resulted in exceptionally high concentrations in aquatic environments, seriously threatening aquatic ecosystems and human health, necessitating the development of novel removal technologies. Among existing removal technologies, catalytic oxidation is widely used due to its mild reaction conditions and the fact that degradation products do not cause secondary pollution. Catalysts are broadly classified into two categories: noble metals (such as Pt and Au) and transition metals (such as MnO2 and TiO2). While Pt catalysts exhibit high activity, their high cost and tendency to agglomerate, affecting catalytic efficiency, limit their practical application when used alone. Although MnO2 catalysts alone show high removal efficiency for tetracyclines, they typically require high temperatures, and their removal performance at room temperature is poor.
[0003] To address the above problems, a composite catalyst is needed to efficiently catalyze the oxidative degradation of tetracycline at room temperature. Among semiconductor catalyst materials, spinel composite oxides and transition metal oxides (AB₂O₄) show great potential in the catalytic degradation of environmental pollutants. MnCo₂O₄, in particular, possesses excellent catalytic activity, high stability, and low cost, making it suitable as a catalyst for tetracycline degradation. However, using MnCo₂O₄ alone... o2 Compared with noble metals, O4 has lower catalytic activity, a lower surface oxygen / lattice oxygen ratio, and lower redox reaction activity. Therefore, this patent discloses a method for preparing Pt and MnO2 supported on hollow spherical MnCo2O4. This composite material has a higher surface oxygen / lattice oxygen ratio, higher electronic conductivity and stability, resulting in high catalytic activity of the composite catalyst. It can catalytically degrade tetracycline in polluted water at room temperature, and after repeated use, the Pt nanoparticles and MnO2 remain uniformly dispersed, the hollow spherical structure remains unchanged, and the catalytic efficiency can still be maintained. Summary of the Invention
[0004] In view of the shortcomings of existing technologies, the technical problems to be solved by this invention are that although noble metal catalysts have high catalytic activity, they are expensive and prone to agglomeration, which affects catalytic efficiency. The use of noble metal catalysts alone is limited in practical applications. The catalysts cannot be reused and have low removal capacity for tetracycline antibiotics.
[0005] To address the aforementioned technical problems, this invention proposes a hollow spherical composite catalyst material and its preparation method, which can catalytically degrade tetracycline antibiotics at room temperature and reduce the concentration of tetracycline.
[0006] This invention provides the following technical solution:
[0007] A hollow spherical composite catalyst, Pt / MnO2 / MnCo2O4, is disclosed. MnCo2O4 consists of hollow spheres with a spinel structure composed of manganese and cobalt dual transition metal oxides, with diameters ranging from 1 to 2 μm. These hollow microspheres are composed of numerous randomly distributed and interconnected nanosheets, creating a porous structure with cavities between adjacent nanosheets. The cavity diameter is 0.9–1 μm. Due to its open, layered structure, this catalyst exhibits a high specific surface area, providing more contact sites. These excellent properties make it a good catalyst and support material for catalytic oxidation. MnO2 particles and Pt nanoparticles are uniformly deposited and loaded on hollow microspheres. The MnO2 particles are irregularly shaped microspheres assembled from cross-linked ultrathin nanosheets through strong interparticle forces and high surface energy of small nuclei. They are uniformly attached to hollow spherical MnCo2O4 with a diameter of 95-105 nm. The Pt nanoparticles have a smaller particle size of 2-20 nm and are uniformly loaded on hollow spherical MnCo2O4 and MnO2.
[0008] The preparation method of hollow spherical composite catalyst Pt / MnO2 / MnCo2O4 involves loading Pt nanoparticles and MnO2 particles onto hollow spherical MnCo2O4. The specific preparation method includes the following steps:
[0009] Step 1: Preparation of MnCo2O4 support:
[0010] First, using Co(CH3COO)2·4H2O as the Co source and Mn(CH3COO)2·4H2O as the Mn source, dissolved in (CH2OH)2, with CH3COONa and CTAB as stabilizers, a template-free solvothermal method was used to prepare the MnCo2O4 precursor. Then, the prepared precursor solution was transferred to a stainless steel high-pressure reactor for heat treatment reaction. The dried precipitate was collected by filtration and finally transferred to a muffle furnace for air bath calcination and natural cooling to room temperature to obtain hollow spherical MnCo2O4.
[0011] Step 2, Preparation of MnO2 / MnCo2O4:
[0012] Using KMnO4 and MnSO4·H2O as manganese sources, a water bath heating and stirring reaction was carried out, followed by centrifugation, washing of the precipitate, and vacuum drying to obtain MnO2 / MnCo2O4;
[0013] Step 3: Preparation of Pt / MnO2 / MnCo2O4:
[0014] Using H2PtCl6·6H2O as the Pt source and NaBH4 as the reducing agent, Pt nanoparticles were synthesized in situ on the surface of MnO2 / MnCo2O4 with the addition of a small amount of 0.1 mol / L NaOH solution, thus preparing a Pt / MnO2 / MnCo2O4 hollow spherical composite catalyst.
[0015] In step one, the heat treatment temperature in the high-pressure reactor is 180°C, and the heating time is 10 hours.
[0016] In step one, the calcination in the muffle furnace involves heating to 350°C at a heating rate of 5°C / min, followed by holding at that temperature for 2 hours.
[0017] In step two, MnO2 is composed of irregularly shaped microspheres and small particles. It is a δ-MnO2 with a large interlayer spacing and a two-dimensional layered structure. Its growth first attaches along the edge and grows to a sufficiently large size, and then gradually increases and aggregates together to form a sheet-like microsphere structure, which is uniformly loaded on hollow spherical MnCo2O4.
[0018] In step two, the mass ratio of MnCo2O4 to KMnO4 and MnSO4·H2O can be controlled between 2.0:1 and 10:1, and the mass ratio of MnCo2O4 to δ-MnO2 can be controlled between 2.7:1 and 13.6:1.
[0019] In step three, the concentration of the H2PtCl6 solution is 0.09–0.10 mol / L, and the mass fraction of Pt in the resulting Pt / MnO2 / MnCo2O4 is controlled between 0.1 wt% and 2 wt%.
[0020] According to the present invention, the hollow spherical composite catalyst Pt / MnO2 / MnCo2O4 is used to catalytically degrade tetracycline in polluted water at room temperature. After repeated use, the Pt nanoparticles and δ-MnO2 remain uniformly dispersed, the hollow spherical structure remains unchanged, and the catalytic efficiency can still be maintained.
[0021] The present invention discloses the following technical effects:
[0022] (1) The platinum nanoparticle / manganese oxide composite hollow spherical manganese cobalt oxide catalyst (Pt / δ-MnO2 / MnCo2O4) synthesized in this invention has the characteristics of small pore size, high porosity, and large specific surface area. It is prepared by uniformly dispersing platinum nanoparticles and manganese oxide nanoparticles on hollow spherical MnCo2O4 prepared by a solvothermal method. The uniform loading of platinum nanoparticles and manganese oxide microspheres on the surface of MnCo2O4 results in a high specific surface area and porosity, providing more active sites to further enhance catalytic activity and improve catalytic degradation efficiency. It exhibits good catalytic performance for antibiotic removal in indoor environments. The preparation route of this invention is simple, and the reaction conditions are mild.
[0023] (2) The Pt / δ-MnO2 / MnCo2O4 hollow spherical composite catalyst material synthesized in this invention has a good removal capacity for antibiotics. In a TC solution with an initial concentration of 10 mg / L, it can achieve a degradation capacity of 86.7% for TC concentration solution within 90 min, which is greater than the catalytic effect of pure MnCo2O4 and δ-MnO2. The catalytic efficiency can still reach 79.5% after four cycles of use. The results show that the Pt / δ-MnO2 / MnCo2O4 hollow spherical composite catalyst has excellent TC catalytic activity and is a TC catalytic oxidation material with good application prospects.
[0024] (3) The reaction process of the present invention is highly controllable. By changing the reaction conditions and various experimental variables, different properties can be obtained as needed. Attached Figure Description
[0025] Figure 1 This is a scanning electron microscope image of the Pt / δ-MnO2 / MnCo2O4 hollow spherical catalyst prepared in Example 1 of this invention.
[0026] Figure 2 This is a field emission high-resolution transmission electron microscope image of the Pt / δ-MnO2 / MnCo2O4 hollow spherical catalyst prepared in Example 1 of the present invention. Detailed Implementation
[0027] Specific embodiments of the present invention are given below. These specific embodiments are only used to further illustrate the present invention in detail and do not limit the scope of protection of the claims of the present invention.
[0028] This invention provides a platinum nanoparticle / manganese oxide composite hollow spherical manganese cobalt oxide catalyst and its preparation method (hereinafter referred to as the method), which includes the following steps:
[0029] Step 1: Preparation of MnCo2O4 support:
[0030] First, using Co(CH3COO)2·4H2O as the Co source and Mn(CH3COO)2·4H2O as the Mn source, dissolved in (CH2OH)2, with CH3COONa and CTAB as stabilizers, a template-free solvothermal method was used to prepare the MnCo2O4 precursor. Then, the prepared precursor solution was transferred to a stainless steel high-pressure reactor for heat treatment reaction. The dried precipitate was collected by filtration and finally transferred to a muffle furnace for air bath calcination and natural cooling to room temperature to obtain hollow spherical MnCo2O4.
[0031] Step 2, Preparation of MnO2 / MnCo2O4:
[0032] Using KMnO4 and MnSO4·H2O as manganese sources, a water bath heating and stirring reaction was carried out, followed by centrifugation, washing of the precipitate, and vacuum drying to obtain MnO2 / MnCo2O4;
[0033] Step 3: Preparation of Pt / MnO2 / MnCo2O4:
[0034] Using H2PtCl6·6H2O as the Pt source and NaBH4 as the reducing agent, Pt nanoparticles were synthesized in situ on the surface of MnO2 / MnCo2O4 with the addition of a small amount of 0.1 mol / L NaOH solution, thus preparing a Pt / MnO2 / MnCo2O4 hollow spherical composite catalyst.
[0035] Furthermore, the hollow spherical manganese cobalt oxide (MnCo2O4) described in step one has a diameter of approximately 1-2 μm.
[0036] Furthermore, the hollow spherical manganese cobalt oxide (MnCo2O4) described in step one is a porous structure composed of a large number of randomly distributed and interconnected nanosheets, which generate many cavities between adjacent nanosheets, with a cavity diameter of 0.9 to 1 μm.
[0037] Furthermore, the heat treatment temperature in the high-pressure reactor described in step one is 180°C, and the heating time is 10 hours.
[0038] Furthermore, the calcination in the muffle furnace described in step one involves heating to 350°C at a heating rate of 5°C / min, and then holding at that temperature for 2 hours.
[0039] Furthermore, the MnO2 mentioned in step two is composed of some irregularly shaped microspheres and small particles. It is a δ-MnO2 with a large interlayer spacing and a two-dimensional layered structure. Its growth first attaches along the edge and grows to a sufficiently large size, and then gradually increases and aggregates together to form a sheet-like microsphere structure, which is uniformly loaded on hollow spherical MnCo2O4.
[0040] Furthermore, in step two, the mass ratio of MnCo2O4 to KMnO4 and MnSO4·H2O can be controlled between 2.0:1 and 10:1, and the mass ratio of MnCo2O4 to δ-MnO2 can be controlled between 2.7:1 and 13.6:1.
[0041] Furthermore, the concentration range of H2PtCl6·6H2O mentioned in step three is 0.09 to 0.10 mol / L, and the mass fraction of Pt in the obtained Pt / MnO2 / MnCo2O4 is controlled between 0.1 wt% and 2 wt%.
[0042] Furthermore, the Pt / δ-MnO2 / MnCo2O4 prepared through the above steps can catalytically degrade tetracycline in polluted water at room temperature. After repeated use, the Pt nanoparticles and δ-MnO2 remain uniformly dispersed, the hollow spherical structure remains unchanged, and the catalytic efficiency can still be maintained.
[0043] The catalytic performance analysis of the Pt / δ-MnO2 / MnCo2O4 composite catalyst is as follows: In a tetracycline pollutant solution with an initial concentration of 10 mg / L, different ratios of MnCo2O4 to δ-MnO2 and different mass fractions of Pt can effectively catalyze the degradation of tetracycline. The catalyst with 0.1 wt% Pt nanoparticles and a MnCo2O4 to δ-MnO2 ratio of 5:1 exhibits the best tetracycline catalytic effect, achieving a degradation rate of 86.7% within 90 min, representing a 44.8% increase in catalytic efficiency compared to pure hollow spherical MnCo2O4. Furthermore, after four cycles, the tetracycline removal rate remains at 79.5%, and the δ-MnO2 and Pt nanoparticles remain uniformly dispersed, with no significant change in the hollow spherical structure.
[0044] The morphology and structure characterization methods of the Pt / δ-MnO2 / MnCo2O4 hollow spherical composite catalyst were transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), X-ray photoelectron surface energy dispersive spectroscopy (XPS), and specific surface area analysis (BET).
[0045] Catalysis test: The absorbance of the tetracycline solution catalyzed by the catalyst was measured using a UV-Vis spectrophotometer.
[0046] Example 1
[0047] (1) Dissolve 1.1g Co(CH3COO)2·4H2O and 0.54g Mn(CH3COO)2·4H2O in a 100mL round-bottom flask containing 60mL ethylene glycol. Stir and mix at 30℃. Add 5g CH3COONa and 1.6g CTAB to the solution and stir vigorously for 30min. Then transfer the solution to a 100mL stainless steel high-pressure reactor lined with polytetrafluoroethylene and heat to 180℃. Hold at this temperature for 10h. After the experiment, allow it to cool naturally to room temperature. Collect the precipitate by filtration, wash it several times with ethanol, and dry it under vacuum. Finally, transfer the precursor prepared in this step to a muffle furnace and heat it to 350℃ at a heating rate of 5℃ / min. Hold the temperature for 2h and allow it to cool naturally to room temperature to obtain hollow spherical MnCo2O4.
[0048] (2) Take 5.0 g of KMnO4 and add it to a 100 mL round-bottom flask containing 200 mL of deionized water. Stir thoroughly until dissolved and clear. Then, add 9 g of MnSO4·H2O to the round-bottom flask and react in a water bath at 60 °C for 3 h. Finally, filter the obtained precipitate and wash it several times with deionized water. Dry it under vacuum at 80 °C for 24 h to obtain the δ-MnO2 catalyst.
[0049] (3) Take 0.2g of the MnCo2O4 powder prepared in step (1) above into a 50ml round-bottom flask containing 30mL of deionized water, and stir magnetically for 15min to disperse it evenly. After even dispersion, add a certain mass of KMnO4 and MnSO4·H2O (the molar ratio of MnCo2O4 and MnO2 is 5:1), heat and stir in a 60℃ water bath for 3h, transfer the precipitate generated after the reaction to a 50mL centrifuge tube, centrifuge at 10000r / min for 10min, wash with deionized water 4 times, transfer the material after the last centrifugation to a vacuum drying oven and vacuum dry at 25℃ for 12h to obtain MnCo2O4 loaded with MnO2.
[0050] (4) Dissolve 1g of chloroplatinic acid hexahydrate (H2PtCl6·6H2O) in 20mL of water to obtain a chloroplatinic acid solution with a concentration of 0.09654mol / L. Take 0.5g of MnCo2O4 powder loaded with MnO2 in step (3) above into a 50mL round-bottom flask, add 10mL of deionized water and stir magnetically for 15min to disperse it. Then measure 26.57μL of chloroplatinic acid solution (0.09654mol / L) and add it to the round-bottom flask by inserting a needle below the liquid surface. Seal and protect from light and stir magnetically for 12h. Finally, weigh 0.0189g of NaBH4 and 0.02g of NaOH into a 50mL beaker, add 5mL of deionized water, stir thoroughly to dissolve, and then quickly add it to the round-bottom flask. Seal and protect from light and stir for 30min. The above solution was centrifuged at 10000 r / min and washed four times with deionized water. Ultrasonic dispersion was performed for 10 min between each wash. After the final centrifugation, the supernatant was discarded, and the resulting product was dried in an oven at 80 °C for 8 h. This yielded MnCo2O4 loaded with Pt and MnO2.
[0051] The overall morphology of the obtained catalyst particles was analyzed using field emission scanning electron microscopy, such as... Figure 1 As shown, the composite catalyst is composed of a large number of randomly distributed and interconnected nanosheets, forming a porous structure with many cavities between adjacent nanosheets. The cavity diameter is 0.9–1 μm, and the cavities are uniformly distributed. The diameter of the hollow spheres is 1.7 μm.
[0052] High-resolution transmission electron microscopy images characterize the catalyst surface supported structure and the crystal form of nanoparticles, such as... Figure 2 As shown, δ-MnO2 particles and Pt nanoparticles are uniformly loaded on the surface of the micro-flower, with the diameter of the δ-MnO2 particles being 70.37 nm and the diameter of the Pt nanoparticles being 2.09 nm. The lattice fringes with interplanar spacing of 0.48 nm and 0.25 nm correspond to the (111) and (311) lattice planes of MnCo2O4, respectively. The interplanar spacing of 0.36 nm corresponds to the (002) plane of δ-MnO2. The interplanar spacing of 0.223 nm corresponds to the (111) lattice plane of metallic Pt. Loading δ-MnO2 and Pt nanoparticles on hollow spherical MnCo2O4 does not change the crystal structure of MnCo2O4.
[0053] Effect Experiment:
[0054] The prepared Pt / MnO2 / MnCo2O4 hollow spherical composite catalyst was tested for tetracycline catalysis at room temperature with an initial tetracycline pollutant concentration of 10 mg / L. The tetracycline removal rate was measured to be 86.7%, which proves that the platinum nanoparticle / manganese oxide composite hollow spherical manganese cobalt oxide catalyst of the present invention can efficiently remove low to medium concentrations of tetracycline in water.
[0055] Example 2
[0056] (1) Dissolve 1.1g Co(CH3COO)2·4H2O and 0.54g Mn(CH3COO)2·4H2O in a 100mL round-bottom flask containing 60mL ethylene glycol. Stir and mix at 30℃. Add 5g CH3COONa and 1.6g CTAB to the solution and stir vigorously for 30min. Then transfer the solution to a 100mL stainless steel high-pressure reactor lined with polytetrafluoroethylene and heat to 180℃. Hold at this temperature for 10h. After the experiment, allow it to cool naturally to room temperature. Collect the precipitate by filtration, wash it several times with ethanol, and dry it under vacuum. Finally, transfer the precursor prepared in this step to a muffle furnace and heat it to 350℃ at a heating rate of 5℃ / min. Hold the temperature for 2h and allow it to cool naturally to room temperature to obtain hollow spherical MnCo2O4.
[0057] (2) Take 5.0 g of KMnO4 and add it to a 100 mL round-bottom flask containing 200 mL of deionized water. Stir thoroughly until dissolved and clear. Then, add 9 g of MnSO4·H2O to the round-bottom flask and react in a water bath at 60 °C for 3 h. Finally, filter the obtained precipitate and wash it several times with deionized water. Dry it under vacuum at 80 °C for 24 h to obtain the δ-MnO2 catalyst.
[0058] (3) Take 0.2g of the MnCo2O4 powder prepared in step (1) above into a 50ml round-bottom flask containing 30mL of deionized water, and stir magnetically for 15min to disperse it evenly. After even dispersion, add a certain mass of KMnO4 and MnSO4·H2O (the molar ratio of MnCo2O4 and MnO2 is 5:2), heat and stir in a 60℃ water bath for 3h, transfer the precipitate generated after the reaction to a 50mL centrifuge tube, centrifuge at 10000r / min for 10min, wash with deionized water 4 times, transfer the material after the last centrifugation to a vacuum drying oven and vacuum dry at 25℃ for 12h to obtain MnCo2O4 loaded with MnO2.
[0059] (4) Dissolve 1g of chloroplatinic acid hexahydrate (H2PtCl6·6H2O) in 20mL of water to obtain a chloroplatinic acid solution with a concentration of 0.09654mol / L. Take 0.5g of MnCo2O4 powder loaded with MnO2 in step (3) above into a 50mL round-bottom flask, add 10mL of deionized water and stir magnetically for 15min to disperse it. Then measure 26.57μL of chloroplatinic acid solution (0.09654mol / L) and add it to the round-bottom flask by inserting a needle below the liquid surface. Seal and protect from light and stir magnetically for 12h. Finally, weigh 0.0189g of NaBH4 and 0.02g of NaOH into a 50mL beaker, add 5mL of deionized water, stir thoroughly to dissolve, and then quickly add it to the round-bottom flask. Seal and protect from light and stir for 30min. The above solution was centrifuged at 10000 r / min and washed four times with deionized water. Ultrasonic dispersion was performed for 10 min between each wash. After the final centrifugation, the supernatant was discarded, and the resulting product was dried in an oven at 80 °C for 8 h. This yielded MnCo2O4 loaded with Pt and MnO2.
[0060] Effect Experiment:
[0061] The prepared Pt / MnO2 / MnCo2O4 hollow spherical composite catalyst was tested for tetracycline catalysis at room temperature with an initial tetracycline pollutant concentration of 10 mg / L. The tetracycline removal rate was measured to be 79.9%, which proves that the platinum nanoparticle / manganese oxide composite hollow spherical manganese cobalt oxide catalyst of the present invention can efficiently remove low to medium concentrations of tetracycline from water.
[0062] Example 3
[0063] (1) Dissolve 1.1g Co(CH3COO)2·4H2O and 0.54g Mn(CH3COO)2·4H2O in a 100mL round-bottom flask containing 60mL ethylene glycol. Stir and mix at 30℃. Add 5g CH3COONa and 1.6g CTAB to the solution and stir vigorously for 30min. Then transfer the solution to a 100mL stainless steel high-pressure reactor lined with polytetrafluoroethylene and heat to 180℃. Hold at this temperature for 10h. After the experiment, allow it to cool naturally to room temperature. Collect the precipitate by filtration, wash it several times with ethanol, and dry it under vacuum. Finally, transfer the precursor prepared in this step to a muffle furnace and heat it to 350℃ at a heating rate of 5℃ / min. Hold the temperature for 2h and allow it to cool naturally to room temperature to obtain hollow spherical MnCo2O4.
[0064] (2) Take 5.0 g of KMnO4 and add it to a 100 mL round-bottom flask containing 200 mL of deionized water. Stir thoroughly until dissolved and clear. Then, add 9 g of MnSO4·H2O to the round-bottom flask and react in a water bath at 60 °C for 3 h. Finally, filter the obtained precipitate and wash it several times with deionized water. Dry it under vacuum at 80 °C for 24 h to obtain the δ-MnO2 catalyst.
[0065] (3) Take 0.2g of the MnCo2O4 powder prepared in step (1) above into a 50ml round-bottom flask containing 30mL of deionized water, and stir magnetically for 15min to disperse it evenly. After even dispersion, add a certain mass of KMnO4 and MnSO4·H2O (the molar ratio of MnCo2O4 and MnO2 is 2:1), heat and stir in a 60℃ water bath for 3h, transfer the precipitate generated after the reaction to a 50mL centrifuge tube, centrifuge at 10000r / min for 10min, wash with deionized water 4 times, transfer the material after the last centrifugation to a vacuum drying oven and vacuum dry at 25℃ for 12h to obtain MnCo2O4 loaded with MnO2.
[0066] (4) Dissolve 1g of chloroplatinic acid hexahydrate (H2PtCl6·6H2O) in 20mL of water to obtain a chloroplatinic acid solution with a concentration of 0.09654mol / L. Take 0.5g of MnCo2O4 powder loaded with MnO2 in step (3) above into a 50mL round-bottom flask, add 10mL of deionized water and stir magnetically for 15min to disperse it. Then measure 26.57μL of chloroplatinic acid solution (0.09654mol / L) and add it to the round-bottom flask by inserting a needle below the liquid surface. Seal and protect from light and stir magnetically for 12h. Finally, weigh 0.0189g of NaBH4 and 0.02g of NaOH into a 50mL beaker, add 5mL of deionized water, stir thoroughly to dissolve, and then quickly add it to the round-bottom flask. Seal and protect from light and stir for 30min. The above solution was centrifuged at 10000 r / min and washed four times with deionized water. Ultrasonic dispersion was performed for 10 min between each wash. After the final centrifugation, the supernatant was discarded, and the resulting product was dried in an oven at 80 °C for 8 h. This yielded MnCo2O4 loaded with Pt and MnO2.
[0067] Effect Experiment:
[0068] The prepared Pt / MnO2 / MnCo2O4 hollow spherical composite catalyst was tested for tetracycline catalysis at room temperature with an initial tetracycline pollutant concentration of 10 mg / L. The tetracycline removal rate was measured to be 71.9%, which proves that the platinum nanoparticle / manganese oxide composite hollow spherical manganese cobalt oxide catalyst of the present invention can efficiently remove low to medium concentrations of tetracycline from water.
[0069] Example 4
[0070] (1) Dissolve 1.1g Co(CH3COO)2·4H2O and 0.54g Mn(CH3COO)2·4H2O in a 100mL round-bottom flask containing 60mL ethylene glycol. Stir and mix at 30℃. Add 5g CH3COONa and 1.6g CTAB to the solution and stir vigorously for 30min. Then transfer the solution to a 100mL stainless steel high-pressure reactor lined with polytetrafluoroethylene and heat to 180℃. Hold at this temperature for 10h. After the experiment, allow it to cool naturally to room temperature. Collect the precipitate by filtration, wash it several times with ethanol, and dry it under vacuum. Finally, transfer the precursor prepared in this step to a muffle furnace and heat it to 350℃ at a heating rate of 5℃ / min. Hold the temperature for 2h and allow it to cool naturally to room temperature to obtain hollow spherical MnCo2O4.
[0071] (2) Take 5.0 g of KMnO4 and add it to a 100 mL round-bottom flask containing 200 mL of deionized water. Stir thoroughly until dissolved and clear. Then, add 9 g of MnSO4·H2O to the round-bottom flask and react in a water bath at 60 °C for 3 h. Finally, filter the obtained precipitate and wash it several times with deionized water. Dry it under vacuum at 80 °C for 24 h to obtain the δ-MnO2 catalyst.
[0072] (3) Take 0.2g of the MnCo2O4 powder prepared in step (1) above into a 50ml round-bottom flask containing 30mL of deionized water, and stir magnetically for 15min to disperse it evenly. After even dispersion, add a certain mass of KMnO4 and MnSO4·H2O (the molar ratio of MnCo2O4 and MnO2 is 1:1), heat and stir in a 60℃ water bath for 3h, transfer the precipitate generated after the reaction to a 50mL centrifuge tube, centrifuge at 10000r / min for 10min, wash with deionized water 4 times, transfer the material after the last centrifugation to a vacuum drying oven and vacuum dry at 25℃ for 12h to obtain MnCo2O4 loaded with MnO2.
[0073] (4) Dissolve 1g of chloroplatinic acid hexahydrate (H2PtCl6·6H2O) in 20mL of water to obtain a chloroplatinic acid solution with a concentration of 0.09654mol / L. Take 0.5g of MnCo2O4 powder loaded with MnO2 in step (3) above into a 50mL round-bottom flask, add 10mL of deionized water and stir magnetically for 15min to disperse it. Then measure 26.57μL of chloroplatinic acid solution (0.09654mol / L) and add it to the round-bottom flask by inserting a needle below the liquid surface. Seal and protect from light and stir magnetically for 12h. Finally, weigh 0.0189g of NaBH4 and 0.02g of NaOH into a 50mL beaker, add 5mL of deionized water, stir thoroughly to dissolve, and then quickly add it to the round-bottom flask. Seal and protect from light and stir for 30min. The above solution was centrifuged at 10000 r / min and washed four times with deionized water. Ultrasonic dispersion was performed for 10 min between each wash. After the final centrifugation, the supernatant was discarded, and the resulting product was dried in an oven at 80 °C for 8 h. This yielded MnCo2O4 loaded with Pt and MnO2.
[0074] Effect Experiment:
[0075] The prepared Pt / MnO2 / MnCo2O4 hollow spherical composite catalyst was tested for tetracycline catalysis at room temperature with an initial tetracycline pollutant concentration of 10 mg / L. The tetracycline removal rate was measured to be 57.3%, which proves that the platinum nanoparticle / manganese oxide composite hollow spherical manganese cobalt oxide catalyst of the present invention can remove low to medium concentrations of tetracycline in water.
[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of this application. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technical content disclosed in this invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of this invention.
Claims
1. A hollow spherical composite catalyst Pt / MnO2 / MnCo2O4 for catalytic degradation of tetracycline in polluted water at room temperature, characterized in that: MnCo2O4 is a hollow sphere with a spinel structure composed of manganese and cobalt dual transition metal oxides, with a diameter distribution of 1-2 μm. The hollow sphere is a porous structure composed of a large number of randomly distributed and interconnected nanosheets, creating many cavities between adjacent nanosheets. The cavity diameter is 0.9-1 μm. Due to its open layered structure, this structure has a high specific surface area and provides more contact sites. These excellent properties make it a good catalytic oxidation catalyst and support material. MnO2 particles and Pt nanoparticles are uniformly deposited and loaded on the hollow spheres. The MnO2 particles are irregularly shaped microspheres assembled from cross-linked ultrathin nanosheets through strong interparticle forces and high surface energy of small nuclei, and are uniformly attached to the hollow spherical MnCo2O4. The diameter of the MnO2 particles is 95-105 nm, and the particle size of the Pt nanoparticles is 2-20 nm, which are uniformly loaded on the hollow spherical MnCo2O4 and MnO2. The MnO2 is δ-MnO2; The hollow spherical composite catalyst Pt / MnO2 / MnCo2O4 is prepared by loading Pt nanoparticles and MnO2 particles onto hollow spherical MnCo2O4, and the preparation steps are as follows: Step 1: Preparation of MnCo2O4 support: First, using Co(CH3COO)2·4H2O as the Co source and Mn(CH3COO)2·4H2O as the Mn source, MnCo2O4 precursor was prepared by dissolving Co(CH3COO)2·4H2O in ethylene glycol and CH3COONa and CTAB as stabilizers via a template-free solvothermal method. Then, the prepared precursor solution was transferred to a stainless steel high-pressure reactor for heat treatment reaction. The dried precipitate was collected by filtration and finally transferred to a muffle furnace for air bath calcination and natural cooling to room temperature to obtain hollow spherical MnCo2O4. Step 2, Preparation of MnO2 / MnCo2O4: The MnCo2O4 support obtained in step one was subjected to a water bath heating and stirring reaction using KMnO4 and MnSO4·H2O as manganese sources. The mixture was then centrifuged, the precipitate was washed, and the mixture was vacuum dried to obtain MnO2 / MnCo2O4. Step 3: Preparation of Pt / MnO2 / MnCo2O4: Using H2PtCl6·6H2O as the Pt source and NaBH4 as the reducing agent, Pt nanoparticles were synthesized in situ on the surface of MnO2 / MnCo2O4 with the addition of a small amount of 0.1 mol / L NaOH solution, thus preparing a Pt / MnO2 / MnCo2O4 hollow spherical composite catalyst.
2. The hollow spherical composite catalyst Pt / MnO2 / MnCo2O4 according to claim 1, characterized in that: In step one, the heat treatment temperature in the high-pressure reactor is 180°C, and the heating time is 10 hours.
3. The hollow spherical composite catalyst Pt / MnO2 / MnCo2O4 according to claim 1, characterized in that: In step one, the calcination in the muffle furnace involves heating to 350°C at a heating rate of 5°C / min, followed by holding at that temperature for 2 hours.
4. The hollow spherical composite catalyst Pt / MnO2 / MnCo2O4 according to claim 1, characterized in that: In step two, the mass ratio of MnCo2O4 to KMnO4 and MnSO4·H2O is controlled to be between 2.0:1 and 10:1, and the mass ratio of MnCo2O4 to δ-MnO2 is controlled to be between 2.7:1 and 13.6:
1.
5. The application of the hollow spherical composite catalyst Pt / MnO2 / MnCo2O4 according to claim 1, characterized in that: The hollow spherical composite catalyst Pt / MnO2 / MnCo2O4 is used to catalyze the degradation of tetracycline in polluted water at room temperature. After repeated use, the Pt nanoparticles and δ-MnO2 remain uniformly dispersed, the hollow spherical structure remains unchanged, and the catalytic efficiency continues to be maintained.