Preparation method and application of copper-manganese composite ferrite microwave catalyst capable of forming oxygen vacancies

Abstract

This invention belongs to the field of microwave catalysis, specifically relating to a method for preparing and applying a copper-manganese composite ferrite microwave catalyst capable of forming oxygen vacancies. The catalyst preparation method includes the following steps: (1) adding ferric chloride, copper chloride, and manganese chloride to deionized water to obtain a precursor aqueous solution, then adding urea and stirring; (2) adding sodium hydroxide aqueous solution dropwise to the precursor aqueous solution obtained in step (1) while stirring, adjusting the pH to 11-12 to obtain a suspension, and continuing stirring; (3) filtering, washing, and drying the suspension obtained in step (2) to obtain a solid substance; (4) grinding and sintering the solid substance obtained in step (3) to obtain the copper-manganese composite ferrite microwave catalyst. The preparation method of this invention has a simple process flow, short processing time, high safety, and better microwave catalytic activity and stability than manganese ferrite and copper ferrite alone.

Description

Technical Field

[0001] This invention belongs to the field of microwave catalysis technology, specifically relating to a method for preparing and applying a copper-manganese composite ferrite microwave catalyst capable of forming oxygen vacancies. Background Technology

[0002] Antibiotic residues in aquatic environments not only pollute water bodies but also lead to antimicrobial resistance, thereby damaging natural ecosystems and even threatening human health. Therefore, measures to address antibiotic residues in water are urgently needed. Among various technologies, microwave catalysis offers advantages such as short reaction time and high efficiency. Ferrates strongly absorb microwave radiation, generating "hot spots" on their surfaces to oxidize and decompose pollutants. Furthermore, under the thermal effect of microwaves, ferrates can generate various active groups while maintaining good stability, making them a research hotspot in the field of microwave catalysis. MnFe₂O₄, with its tetrahedral and octahedral structures, exhibits excellent microwave catalytic activity. Under microwave radiation, MnFe₂O₄ in aqueous solution can absorb microwave energy and generate numerous "hot spots" on its surface, where organic pollutants attached to these "hot spots" can be oxidized and decomposed. However, using ferrates as catalysts often has limitations, such as a tendency to agglomerate, poor dispersibility, and small specific surface area.

[0003] One method to improve the activity of single ferrite catalysts is through multi-component composite or doping, one function of which is to form oxygen vacancies, which can promote the generation of active species. Patent CN202110160476.1 discloses a method for preparing a cobalt ferrite photocatalyst containing oxygen vacancies, which exhibits good photocatalytic activity. However, no research has been reported on improving MnFe2O4 microwave catalysis technology to form oxygen vacancies. Currently, common methods for preparing ferrites include hydrothermal methods, solvothermal methods, microwave-assisted hydrothermal methods, sol-gel methods, microemulsion methods, and co-precipitation methods. Different preparation methods have a significant impact on the catalytic performance of ferrites. Patent CN202310806573.2 discloses a method for preparing lanthanum ferrite photocatalytic material, which uses a hydrothermal method. The metal salt used is nitrate, and the hydrothermal reaction time is 18-22 hours, which is time-consuming. Patent CN201810042672.7 discloses a method for preparing manganese ferrite magnetic nanorods, which obtains a precursor gel by igniting and burning a precursor solution, and then calcining the precursor gel to obtain manganese ferrite magnetic nanorods. The preparation process is complex and has a low safety factor. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing and applying a stable and catalytically active copper-manganese composite ferrite microwave catalyst capable of forming oxygen vacancies. This invention uses a highly efficient and rapid co-precipitation method to replace the traditional hydrothermal method for preparing copper-manganese composite ferrite microwave catalysts containing oxygen vacancies, thereby solving the problems of long catalyst synthesis time, low safety factor, and high economic cost in existing preparation methods.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a copper-manganese composite ferrite microwave catalyst, the method comprising the following steps:

[0007] (1) Ferric chloride, copper chloride, and manganese chloride are added to deionized water in a certain ratio to obtain a precursor aqueous solution. Urea is then added and stirred. In the precursor aqueous solution, the concentration of ferric chloride is 0.02-0.1 mol / L, the concentration of copper chloride is 0.0025-0.0375 mol / L, the concentration of manganese chloride is 0.0025-0.0375 mol / L, and the concentration of urea is 0.1-0.4 mol / L.

[0008] (2) Add sodium hydroxide aqueous solution dropwise to the precursor aqueous solution obtained in step (1) and stir, adjust the pH value to 11-12 to obtain a suspension, and continue stirring;

[0009] (3) The suspension obtained in step (2) is subjected to filtration, washing and drying to obtain a solid substance;

[0010] (4) Grind and sinter the solid material obtained in step (3) to obtain a copper-manganese composite ferrite microwave catalyst.

[0011] In the above technical solution, further, in step (1), the stirring time is 30 minutes.

[0012] In the above technical solution, further, in step (1), the ferric chloride, copper chloride, and manganese chloride are FeCl3·6H2O, CuCl2·2H2O, and MnCl2·4H2O, respectively.

[0013] In the above technical solution, further, in step (1), the molar ratio of ferric chloride and urea in the precursor aqueous solution is 4:1-15.

[0014] In the above technical solution, further, in step (2), the concentration of the sodium hydroxide aqueous solution is 0.1-1 mol / L.

[0015] In the above technical solution, further, in step (2), the stirring time is 30 minutes.

[0016] In the above technical solution, further, in step (3), the drying temperature is 60-90℃.

[0017] In the above technical solution, further, in step (4), the sintering temperature is 300-550℃ and the sintering time is 0.5-2h.

[0018] In another aspect, the present invention provides a copper-manganese composite ferrite microwave catalyst prepared by the above preparation method, wherein the molar ratio of iron, copper and manganese in the catalyst is 4:0.5:1.5-4:1.5:0.5.

[0019] In another aspect, the present invention provides an application of the above-mentioned copper-manganese composite ferrate microwave catalyst for the degradation of organic matter in wastewater.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. This invention uses Cu 2+ Doping with MnFe2O4, Cu 2+ Due to its small ionic radius, it can be incorporated into the MnFe₂O₄ lattice, affecting the distribution of tetrahedral and octahedral cations in ferrites. The presence of metals with different ionic radii in the MnFe₂O₄ spinel structure leads to defects and distortions, introducing oxygen vacancies. These oxygen vacancies can activate lattice oxygen, participate in catalytic reactions, and adsorb and degrade organic pollutants, thereby improving catalytic activity. Furthermore, they are beneficial to the formation of reactive oxygen species. Additionally, Cu doping... 2+ MnFe2O4 is chemically stable.

[0022] 2. The catalyst of this invention can be used for the degradation of organic matter in wastewater under microwave induction. No additional reagents such as hydrogen peroxide or persulfate are required in the wastewater, and the catalyst exhibits good stability.

[0023] 3. The microwave catalyst prepared by this invention, Cu under microwave irradiation 2+ Mn 2+ Fe 3+ The two molecules work synergistically to effectively degrade organic wastewater. Under microwave radiation, the degradation rate of tetracycline can reach 96.14% in 6 minutes.

[0024] 4. The preparation method of the present invention is simple to operate, takes a short time, is highly safe, and has low cost. Attached Figure Description

[0025] Figure 1 The image shows the XRD pattern of the copper-manganese composite ferrite microwave catalyst prepared in Example 1.

[0026] Figure 2Here is a SEM image of the copper-manganese composite ferrite microwave catalyst prepared in Example 1.

[0027] Figure 3 XPS spectra of the copper-manganese composite ferrite microwave catalyst prepared in Example 1: a is the full spectrum, b is the XPS spectrum of Cu, c is the XPS spectrum of Fe, d is the XPS spectrum of Mn, and e is the XPS spectrum of O.

[0028] Figure 4 This is a comparison of the microwave catalytic degradation activity of different metal element composite ferrate microwave catalysts prepared in Example 1 and Comparative Examples 1-4 for tetracycline degradation.

[0029] Figure 5 This is a comparison of the microwave catalytic degradation activity of the catalysts prepared in Example 1 and Comparative Examples 5-8 for tetracycline degradation.

[0030] Figure 6 The activity of the catalyst prepared in Example 1 in catalytic degradation of tetracycline after repeated use;

[0031] Figure 7 This is a comparison of the activity of the catalysts prepared in Example 1 and Comparative Examples 9-10 in the microwave catalytic degradation of tetracycline. Detailed Implementation

[0032] The technical solution of the present invention will be described in detail below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained commercially or prepared according to conventional methods known to those skilled in the art.

[0034] Example 1

[0035] (1) Using the co-precipitation method, 1.0812 g of ferric chloride, 0.17048 g of copper chloride, 0.19791 g of manganese chloride, and 0.9 g of urea were first dissolved in 100 mL of deionized water to obtain a precursor aqueous solution containing 0.04 mol / L ferric chloride, 0.01 mol / L copper chloride, 0.01 mol / L manganese chloride, and 0.15 mol / L urea.

[0036] (2) Add 1 mol / L sodium hydroxide solution dropwise to the precursor aqueous solution, adjust the pH value to 11-12, stir for 30 min to obtain a suspension;

[0037] (3) The obtained suspension was filtered, washed several times with deionized water and anhydrous ethanol, and dried in an oven at 60°C for 8 hours to obtain a solid substance.

[0038] (4) The obtained solid material was calcined in a muffle furnace at 450°C for 1 h to obtain a copper-manganese composite ferrite microwave catalyst with a Fe, Cu, and Mn molar ratio of 4:1:1, denoted as Cu. 0.5 Mn 0.5 Fe2O4.

[0039] Figure 1 The microwave catalyst Cu prepared in Example 1 0.5 Mn 0.5 XRD pattern of Fe2O4, from Figure 1 It can be seen that the diffraction peaks of the prepared products, copper-manganese bimetallic composite ferrates CuFe2O4 and MnFe2O4, correspond to JCPDS 77-0010 and JCPDS 73-1964, respectively. No other impurity peaks were found, and the sharp diffraction peaks prove that the prepared catalyst sample has good crystallinity.

[0040] Figure 2 The microwave catalyst Cu prepared in Example 1 0.5 Mn 0.5 SEM image of Fe2O4, from Figure 1 It can be seen that the prepared microwave catalyst Cu 0.5 Mn 0.5 Fe2O4 is composed of a large number of uniformly sized block structures and a small number of two-dimensional nanosheets. Its surface is rough and its interface structure is dense and orderly, which can provide more active sites and effectively absorb microwave energy.

[0041] Figure 3 The microwave catalyst Cu prepared in Example 1 0.5 Mn 0.5 XPS plot of Fe2O4, from Figure 3 It can be seen that the prepared sample contains Fe, Mn, Cu, and O elements, and the three main peaks in the O1s XPS image correspond to the lattice oxygen of the metal oxides (Fe-O, Mn-O, and Cu-O are represented by O). Latt The synthesized catalyst contained oxygen vacancies (OVs) and surface hydroxyl species (OH). Analysis of the data using Advantage software showed that the total peak area of ​​the three O element forms was 15978.96, with the characteristic peak area of ​​oxygen vacancies being 5425.79. Based on the peak area ratio (5425.79 / 15978.96), its content was calculated to be 33.95%.

[0042] Example 2

[0043] 0.1 g of Cu prepared in Example 1 was added to 100 mL of a 50 mg / L tetracycline solution. 0.5 Mn 0.5 After the Fe2O4 microwave catalyst reached adsorption equilibrium, it was placed in a microwave reactor, and the microwave power was set to 480W for 6 minutes.

[0044] The degradation rate of tetracycline wastewater over time is shown in the curve. Figure 4 As can be seen from the figure, the copper-manganese composite ferrite microwave catalyst exhibits significant advantages, with a faster reaction rate and a higher degradation rate.

[0045] Example 3

[0046] 0.1 g of Cu prepared in Example 1 was added to 100 mL of a 50 mg / L tetracycline solution. 0.5 Mn 0.5 After the Fe2O4 catalyst reached adsorption equilibrium, it was placed in a microwave reactor. The microwave power was set to 480W, and the microwave reaction was carried out for 6 minutes. The resulting Cu catalyst was then removed from the microwave reactor. 0.5 Mn 0.5 Fe₂O₄ was recovered, and 100 mL of a 50 mg / L tetracycline solution was reprocessed. This process was repeated four times. Results are shown below. Figure 7 After five microwave reactions lasting 6 minutes, the removal rates of tetracycline were 96.14%, 86.13%, 84.22%, 83.04%, and 80.77%, respectively, consistently remaining above 80%. These results indicate that Cu... 0.5 Mn 0.5 The Fe2O4 catalyst exhibits good stability.

[0047] Comparative Examples 1-4

[0048] Following the preparation method of Example 1, 0.17048 g of copper chloride was replaced with 0.1363 g of zinc chloride, 0.23973 g of cobalt chloride, 0.2033 g of magnesium chloride, and 0.24143 g of aluminum chloride, respectively, to prepare a composite ferrate microwave catalyst with a Fe, M, Mn molar ratio of 4:1:1, denoted as M. 0.5 Mn 0.2 Fe2O4, where M is Zn, Co, Mg, or Al.

[0049] 0.1 g of M prepared in Comparative Examples 1-4 was added to 100 mL of a 50 mg / L tetracycline solution. 0.5 Mn 0.5 After the Fe2O4 microwave catalyst reached adsorption equilibrium, it was placed in a microwave reactor, and the microwave power was set to 480W for 6 minutes. The degradation rate of tetracycline wastewater over time is shown in the figure. Figure 4As can be seen from the figure, the copper-manganese composite ferrite microwave catalyst exhibits significant advantages, with a faster reaction rate and a higher degradation rate.

[0050] Comparative Example 5

[0051] (1) Using the co-precipitation method, 2.703 g of ferric chloride, 0.17048 g of copper chloride, 0.79164 g of manganese chloride, and 2.4024 g of urea were first dissolved in 100 mL of deionized water to obtain a precursor aqueous solution containing 0.1 mol / L ferric chloride, 0.01 mol / L copper chloride, 0.04 mol / L manganese chloride, and 0.6 mol / L urea.

[0052] (2) Add 1 mol / L sodium hydroxide solution dropwise to the precursor aqueous solution, adjust the pH value to 11-12, stir for 30 min to obtain a suspension;

[0053] (3) The obtained suspension was filtered, washed several times with deionized water and anhydrous ethanol, and dried in an oven at 60°C for 8 hours to obtain a solid substance.

[0054] (4) The obtained solid material was calcined in a muffle furnace at 450°C for 1 h to obtain a copper-manganese composite ferrite microwave catalyst with a Fe, Cu, and Mn molar ratio of 10:1:4, denoted as Cu. 0.2 Mn 0.8 Fe2O4.

[0055] Comparative Example 6

[0056] (1) Using the co-precipitation method, 2.703 g of ferric chloride, 0.68192 g of copper chloride, 0.19791 g of manganese chloride, and 0.9 g of urea were first dissolved in 100 mL of deionized water to obtain a precursor aqueous solution containing 0.1 mol / L ferric chloride, 0.04 mol / L copper chloride, 0.01 mol / L manganese chloride, and 0.15 mol / L urea.

[0057] (2) Add 1 mol / L sodium hydroxide solution dropwise to the precursor aqueous solution, adjust the pH value to 11-12, stir for 30 min to obtain a suspension;

[0058] (3) The obtained suspension was filtered, washed several times with deionized water and anhydrous ethanol, and dried in an oven at 60°C for 8 hours to obtain a solid substance.

[0059] (4) The obtained solid material was calcined in a muffle furnace at 450°C for 1 hour. Finally, a copper-manganese composite ferrite microwave catalyst with a Fe, Cu, and Mn molar ratio of 10:4:1 was prepared, denoted as Cu. 0.8 Mn 0.2 Fe2O4.

[0060] Comparative Example 7

[0061] Preparation of a single MnFe2O4 microwave catalyst: The coprecipitation method was used. First, 0.5406 g of ferric chloride, 0.19791 g of manganese chloride, and 0.9 g of urea were dissolved in 100 mL of deionized water to obtain a precursor aqueous solution containing 0.02 mol / L ferric chloride, 0.01 mol / L manganese chloride, and 0.15 mol / L urea.

[0062] Add 1 mol / L sodium hydroxide solution dropwise to the precursor aqueous solution, adjust the pH value to 11-12, stir for 30 min to obtain a suspension;

[0063] The obtained suspension was filtered, washed several times with deionized water and anhydrous ethanol, and dried in an oven at 60°C to obtain a solid substance.

[0064] The obtained solid material was calcined in a muffle furnace at 450°C for 1 hour to prepare a catalyst with a Fe to Mn molar ratio of 2:1, denoted as MnFe2O4.

[0065] Comparative Example 8

[0066] Preparation of a single CuFe2O4 microwave catalyst: The coprecipitation method was adopted. First, 0.5406 g of ferric chloride, 0.17048 g of copper chloride, and 0.9 g of urea were dissolved in 100 mL of deionized water to obtain a precursor aqueous solution containing 0.02 mol / L ferric chloride, 0.01 mol / L copper chloride, and 0.15 mol / L urea.

[0067] Add 1 mol / L sodium hydroxide solution dropwise to the precursor aqueous solution, adjust the pH value to 11-12, stir for 30 min to obtain a suspension;

[0068] The obtained suspension was filtered, washed several times with deionized water and anhydrous ethanol, and dried in an oven at 60°C to obtain a solid substance.

[0069] The obtained solid material was calcined in a muffle furnace at 450°C for 1 hour to obtain a catalyst with a Fe to Cu molar ratio of 2:1, denoted as CuFe2O4.

[0070] 0.1 g of the catalyst prepared in Comparative Example 5-8 was added to 100 mL of a tetracycline solution with a concentration of 50 mg / L. After the adsorption reached equilibrium, the solution was placed in a microwave reactor, and the microwave power was set to 480 W. The microwave reaction was carried out for 6 min.

[0071] Figure 5 It is MnFe2O4, Cu 0.2 Mn 0.8 Fe2O4, Cu 0.5 Mn 0.5Fe2O4, Cu 0.8 Mn 0.2 The microwave catalytic degradation of tetracycline by five microwave catalysts, including Fe2O4 and CuFe2O4, under microwave irradiation is illustrated in the diagram. Figure 5 As shown, without the addition of a microwave catalyst, tetracycline hardly degrades under microwave irradiation alone, indicating that tetracycline is relatively stable and cannot directly absorb microwaves. After adding the catalyst, Cu... 0.5 Mn 0.5 Fe₂O₄ achieved a degradation efficiency of 96.14% for tetracycline, while Cu... 0.2 Mn 0.8 Fe2O4, Cu 0.8 Mn 0.2 The degradation efficiencies of Fe2O4, MnFe2O4, and CuFe2O4 for tetracycline were 65.26%, 54.92%, 76.11%, and 45.82%, respectively. Therefore, during catalyst preparation, the molar ratio of Fe, Cu, and Mn can be adjusted by controlling the dosage of ferric chloride, copper chloride, and manganese chloride, thereby improving the microwave catalytic performance.

[0072] Comparative Example 9

[0073] (1) Using the co-precipitation method, 1.5995g of ferric sulfate, 0.24969g of copper sulfate, 0.16902g of manganese sulfate, and 0.9g of urea were first dissolved in 100mL of deionized water to obtain a precursor aqueous solution containing 0.04mol / L ferric sulfate, 0.01mol / L copper sulfate, 0.01mol / L manganese sulfate, and 0.15mol / L urea;

[0074] (2) Add 1 mol / L sodium hydroxide solution dropwise to the aqueous solutions of the two precursors, adjust the pH value to 11-12, stir for 30 min, and obtain a suspension;

[0075] (3) The obtained suspension was filtered, washed several times with deionized water and anhydrous ethanol, and dried in an oven at 60°C for 8 hours to obtain a solid substance.

[0076] (4) The obtained solid material was calcined in a muffle furnace at 450°C for 1 hour to obtain catalysts with different metal salt raw materials and a Fe, Cu, Mn molar ratio of 4:1:1, denoted as Cu. 0.5 Mn 0.5 Fe2O4.

[0077] Comparative Example 10

[0078] (1) Using the coprecipitation method, 1.616 g of ferric nitrate, 0.24160 g of copper nitrate, 0.17895 g of manganese nitrate, and 0.9 g of urea were first dissolved in 100 mL of deionized water to obtain a precursor aqueous solution containing 0.04 mol / L ferric nitrate, 0.01 mol / L copper nitrate, 0.01 mol / L manganese nitrate, and 0.15 mol / L urea.

[0079] (2) Add 1 mol / L sodium hydroxide solution dropwise to the aqueous solutions of the two precursors, adjust the pH value to 11-12, stir for 30 min, and obtain a suspension;

[0080] (3) The obtained suspension was filtered, washed several times with deionized water and anhydrous ethanol, and dried in an oven at 60°C for 8 hours to obtain a solid substance.

[0081] (4) The obtained solid material was calcined in a muffle furnace at 450°C for 1 hour to obtain catalysts with different metal salt raw materials and a Fe, Cu, Mn molar ratio of 4:1:1, denoted as Cu. 0.5 Mn 0.5 Fe2O4.

[0082] Add 0.1 g of the catalyst prepared in Comparative Example 9-10 to 100 mL of a tetracycline solution with a concentration of 50 mg / L. After the adsorption reaches equilibrium, place the solution in a microwave reactor, set the microwave power to 480 W, and microwave the reaction for 6 min.

[0083] The degradation rate of tetracycline wastewater over time is shown in the curve. Figure 6 As can be seen from the figure, the microwave catalyst prepared using chloride salts as raw materials exhibits significant advantages, with a faster reaction rate and a higher degradation rate.

[0084] It should be noted that the above embodiments are merely preferred examples of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. Use of a copper-manganese complex ferrite microwave catalyst, characterized in that, It is applied to microwave-induced degradation of organic matter in wastewater; The method for preparing the catalyst includes the following steps: (1) Add ferric chloride, copper chloride and manganese chloride to deionized water to obtain a precursor aqueous solution, then add urea and stir. In the precursor aqueous solution, the concentration of ferric chloride is 0.02-0.1 mol / L, the concentration of copper chloride is 0.0025-0.0375 mol / L, the concentration of manganese chloride is 0.0025-0.0375 mol / L, and the concentration of urea is 0.1-0.4 mol / L. (2) Add sodium hydroxide aqueous solution dropwise to the precursor aqueous solution obtained in step (1) and stir, adjust the pH value to 11-12 to obtain a suspension, and continue stirring; (3) The suspension obtained in step (2) is subjected to filtration, washing and drying to obtain a solid substance; (4) Grind and sinter the solid material obtained in step (3) to obtain a copper-manganese composite ferrite microwave catalyst; In step (4), the sintering temperature is 300-550 ℃ and the sintering time is 0.5-2 h; The molar ratio of iron, copper, and manganese in the catalyst is 4:1:

1.

2. The application according to claim 1, characterized in that, In step (1), the stirring time is 30 min.

3. The application according to claim 1, characterized in that, In step (1), the molar ratio of ferric chloride to urea in the precursor aqueous solution is 4:1-15.

4. The application according to claim 1, characterized in that, In step (2), the concentration of the sodium hydroxide aqueous solution is 0.1-1 mol / L.

5. The application according to claim 1, characterized in that, In step (2), the stirring time is 30 min.

6. The application according to claim 1, characterized in that, In step (3), the drying temperature is 60-90℃.

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