A magnesium-doped co3o4 spinel catalytic membrane and a preparation method and application thereof

Abstract

The application relates to a magnesium-doped Co3O4 spinel catalytic membrane and a preparation method and application thereof. The preparation method takes ion exchange-calcination-vacuum filtration as a basic process, takes nano Co3O4 spinel as a matrix, takes magnesium acetate tetrahydrate as a Mg dopant, prepares the magnesium-doped Co3O4 spinel through ion exchange and high-temperature calcination, and further synthesizes the magnesium-doped Co3O4 spinel catalytic membrane through a vacuum filtration process. The preparation method has the characteristics of simple process, strong operability, short preparation period, low cost and easy industrial production.

Description

Technical Field

[0001] This invention relates to a Mg-doped Co3O4 spinel catalytic membrane, its preparation method and application, belonging to the technical field of catalytic membrane material preparation. Background Technology

[0002] Currently, the residue of emerging pollutants from pharmaceuticals and personal care products (PPCPs) in the environment is becoming increasingly serious. Antibiotic pollutants, in particular, are widely accumulated in surface water environments due to their extensive use and persistent degradation, posing a serious threat to ecosystems and human health. Therefore, developing efficient antibiotic pollutant treatment technologies is crucial for solving current water pollution problems. Compared with traditional wastewater treatment technologies, persulfate activation technology offers advantages such as low energy consumption, simple operation, high efficiency, mild reaction conditions, and a wide treatment range, making it a promising technology for practical application. However, at present, it still faces challenges such as difficult catalyst recovery, slow mass transfer efficiency, and incomplete pollutant mineralization.

[0003] Some researchers in this field are dedicated to the development of catalytic membranes, such as graphene membranes, metal oxide nanosheet membranes, and organic polymer membranes. However, these catalytic membrane materials suffer from high manufacturing costs, complex preparation processes, and poor durability.

[0004] Cobalt tetroxide spinel (Co3O4), a metal oxide with excellent reactivity to persulfate, is particularly suitable for constructing catalytic membranes to remove organic pollutants due to its simple preparation process, low cost, high chemical stability, and high catalytic efficiency. It is a promising catalytic membrane material. The Co sites in Co3O4 serve as reaction sites, activating persulfate into active species by donating electrons. Ma et al. [1] Hollow spherical Co3O4 was designed and prepared. It was found that morphology control enabled the full exposure of active sites on the Co3O4 surface, thereby leading to efficient degradation of organic pollutants. (Li et al.) [2] By doping Al into Co3O4, the change in the coordination atoms of the active sites optimizes the electron distribution on the catalyst surface.

[0005] However, Co3O4 catalytic membranes still have the following drawbacks in practical applications: (1) The continuous accumulation of high-valence Co(III) will greatly reduce the catalytic activity of Co3O4, so the redox cycle of Co sites has become the rate-limiting step; (2) Co leaching still exists in practical applications, and the environmental risks it causes cannot be ignored; (3) Commonly used modification methods are relatively complicated and do not have industrial production capabilities.

[0006] It can be seen that the Co3O4 catalytic membrane has superior performance in the application of persulfate activation, but the traditional Co3O4 still has defects such as low catalytic activity, poor stability and complex preparation process. Therefore, it is of great significance to develop a Co3O4 catalytic membrane with simple preparation process, low cost, high catalytic activity and high stability, which can promote the application of persulfate activation process in water environment treatment. SUMMARY

[0007] In view of the above problems, the purpose of the present application is to provide a Mg-doped Co3O4 spinel catalytic membrane and its preparation method and application.

[0008] In one aspect, the present application provides a Mg-doped Co3O4 spinel catalytic material, the composition structure general formula of which is Mg x -Co3O4. The x is the molar ratio of Mg and Co.

[0009] In another aspect, the present application provides a preparation method of Mg-doped Co3O4 spinel catalytic membrane, which is based on ion exchange-calcination-vacuum filtration method, taking Co3O4 spinel as the matrix and taking magnesium acetate tetrahydrate as the Mg source as the dopant, to prepare Mg-doped Co3O4 spinel through ion exchange and high-temperature calcination, and then taking polyether sulfone membrane (PES) as the substrate to synthesize Mg x -Co3O4@PES through vacuum filtration process.

[0010] The purpose of the present application can be achieved by the following technical solutions:

[0011] A preparation method of Mg-doped Co3O4 spinel, comprising the following steps:

[0012] 1) A certain amount of Co3O4 spinel and magnesium acetate tetrahydrate are sequentially added into a certain amount of deionized water, and mechanical stirring is carried out for 20-60 min to obtain a mixed solution;

[0013] 2) The mixed solution is added into a 150 mL hydrothermal reaction kettle, and after reaction at 120-200℃ for 6-12 h, the obtained product is collected by centrifugation and washed thoroughly, and vacuum drying at 60℃ for 6-12 h obtains a precursor;

[0014] 3) The precursor is placed in a ceramic crucible with a lid, and is placed in a tube furnace, nitrogen is introduced, and the temperature is raised to a certain temperature and kept for 4-6 h, and then naturally cooled to obtain Mg x -Co3O4.

[0015] As a preferred embodiment of the present application, the amount of Co3O4 in step 1) is 0.5-2 g / L, and the concentration of magnesium acetate tetrahydrate is 0.04-0.16 mM.

[0016] As a preferred embodiment of the present application, the temperature of the deionized water in step 1) is 30-60℃.

[0017] As a preferred embodiment of the present application, the temperature of the hydrothermal reaction in step 2) is 120-200℃, and the hydrothermal reaction time is 6-12h.

[0018] As a preferred embodiment of the present application, the vacuum drying time in step 2) is 6-12h.

[0019] As a preferred embodiment of the present application, the calcination temperature in step 3) is 300-800℃, and the holding time is 4-6h.

[0020] As a preferred embodiment of the present application, the temperature rising rate of the tube furnace in step 3) is 2-10℃ / min.

[0021] The Mg-doped Co3O4 spinel prepared by the preparation method of the present application.

[0022] The Mg-doped Co3O4 spinel of the present application is used in the preparation of a catalyst for activated degradation of antibiotics in water by persulfate; the catalyst for activated degradation of antibiotics in water by persulfate is preferably a Mg-doped Co3O4 spinel catalytic membrane; further preferably a Mg-doped Co3O4 spinel catalytic membrane with polyether sulfone membrane as the substrate.

[0023] A preparation method of a Mg-doped Co3O4 spinel catalytic membrane, first, the Mg-doped Co3O4 spinel prepared by the preparation method of the present application is prepared. x -Co3O4; then the Mg x -Co3O4 is added to a certain amount of deionized water, ultrasonic dispersion, with PES membrane as the substrate, the suspension is vacuum filtered and dried to obtain a Mg x -Co3O4@PES catalytic membrane.

[0024] As a preferred embodiment of the present application, the concentration of the Mg x -Co3O4 is 0.2-0.6g / L.

[0025] As a preferred embodiment of the present application, the temperature of the deionized water is 20-40℃.

[0026] As a preferred embodiment of the present application, the ultrasonic dispersion time is 20-80min.

[0027] A Mg-doped Co3O4 spinel catalytic membrane prepared by the above-mentioned preparation method of the present application is used for activated removal of antibiotics in water by persulfate.

[0028] The antibiotics in the water are norfloxacin.

[0029] The concentration of antibiotics in the water is 5–20 mg / L.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] This invention discloses a magnesium-doped Co3O4 spinel catalytic membrane. The preparation method utilizes ion exchange, calcination, and vacuum filtration as the basic process to synthesize the Mg-doped Co3O4 spinel catalytic membrane using Co3O4 spinel as the matrix. The preparation method of this invention is characterized by its simplicity, high operability, short preparation cycle, high yield, and ease of industrial production. Furthermore, this invention utilizes Mg doping to achieve electron polarization distribution on the catalyst surface (…). Figure 1 ,2), creating abundant electron-rich Co centers; the constructed catalytic membrane optimizes the exposure of active sites and mass transfer behavior in the reaction ( Figure 3 ,4); Enhanced exposure of active sites, specific surface area, and reaction mass transfer efficiency promote SO4· during peroxymonosulfate (PMS) activation. - , ·OH and 1 The generation of O2 active species effectively improves the removal efficiency of norfloxacin. Figure 5 ,6). Attached Figure Description

[0032] Figure 1 Mg prepared in Example 1 0.02 -DFT plot of Co3O4

[0033] a: Differential charge of Co3O4 adsorbed on PMS; b: Mg 0.02 -Co3O4 adsorption energy for PMS.

[0034] After Mg doping, electronic polarization was clearly observed around the Co sites, creating a large number of electron-rich Co centers. Figure 2 Mg prepared in Example 1 0.02 XPS plot of Co3O4.

[0035] After Mg doping, the Co(II) content in the Co 2p spectrum increased significantly, and the Co peak shifted to a lower binding energy, indicating the generation of electron-rich Co centers.

[0036] Figure 3 Mg prepared in Example 1 0.02 Cross-sectional SEM image of Co3O4@PES

[0037] a: 100μm; b: 1μm; c: elemental mapping;

[0038] Mg 0.02The cross section of Co3O4@PES is a porous structure with a large number of nanoparticle stacks, which is conducive to the exposure of active sites and reaction mass transfer.

[0039] Figure 4 Mg 0.02 BET graph of Co3O4@PES.

[0040] Mg 0.02 The pores of Co3O4@PES are concentrated in the nanoscale, and the nanopores can optimize the reaction mass transfer efficiency.

[0041] Figure 5 Mg 0.02 Norfloxacin removal efficiency graph of Co3O4@PES / PMS.

[0042] Mg 0.02 The Co3O4@PES / PMS system achieves super-fast removal of norfloxacin.

[0043] Figure 6 EPR graph of different systems

[0044] a: SO4· - and ·OH signals of different systems; b: O2 signals of different systems 1

[0045] Mg 0.02 The Co3O4@PES / PMS system presents a stronger EPR signal, indicating that it generates more abundant SO4· - , ·OH and O2. 1 DETAILED DESCRIPTION

[0046] The application will be further described in conjunction with specific examples, but the scope of protection of the application is not limited thereto.

[0047] Example 1

[0048] Take 100 mL of deionized water, and then add 0.2 g of Co3O4 spinel and 0.048 mM of magnesium acetate tetrahydrate, and mechanically stir at 30℃ for 30 min. Then put the mixture into a 150 mL hydrothermal reactor, and centrifuge the product collected after 6h reaction at 120℃ and wash with deionized water and ethanol. Vacuum dry at 60℃ for 6h to obtain the precursor. Put the precursor into a ceramic crucible with a lid and place it in a tube furnace, and pass nitrogen, heat to 500℃ at 5℃ / min, and keep for 4h, and then naturally cool to obtain Mg 0.02 -Co3O4. Put 0.04 g of Mg 0.02 ​​Co3O4 was added to 100 mL of deionized water at 20 °C and ultrasonically dispersed for 30 min. A PES membrane was used as the substrate, and the suspension was vacuum filtered and dried at 40 °C for 1 h to obtain Mg 0.02 Co3O4@PES catalytic membrane.

[0049] The Mg 0.02 The Co3O4@PES catalytic membrane was used to activate PMS to degrade norfloxacin (NFX), the PMS concentration was 0.8 mM, the NFX concentration was 10 mg / L, the temperature was 20 °C, the pH was 7, and the membrane pressure was 0.4 bar. After 30 min of filtration, the removal efficiency of NFX reached 98.3%.

[0050] Example 2

[0051] Take 100 mL of deionized water, and then add 0.1 g of Co3O4 spinel and 0.096 mM of magnesium acetate tetrahydrate, and mechanically stir at 40 °C for 20 min. Then put the mixture into a 150 mL hydrothermal reactor, centrifuge the product obtained after 8 h of reaction at 160 °C, and wash it with deionized water and ethanol. Vacuum dry at 60 °C for 7 h to obtain the precursor. Place the precursor in a ceramic crucible with a lid and place it in a tube furnace, introduce nitrogen, and heat to 400 °C at a rate of 8 °C / min, and keep it at this temperature for 5 h. After natural cooling, Mg 0.08 Co3O4. Add 0.03 g of Mg 0.08 Co3O4 was added to 100 mL of deionized water at 30 °C and ultrasonically dispersed for 50 min. A PES membrane was used as the substrate, and the suspension was vacuum filtered and dried at 40 °C for 1 h to obtain Mg 0.08 Co3O4@PES catalytic membrane.

[0052] The Mg 0.08 The Co3O4@PES catalytic membrane was used to activate PMS to degrade norfloxacin (NFX), the PMS concentration was 1.2 mM, the NFX concentration was 5 mg / L, the temperature was 20 °C, the pH was 7, and the membrane pressure was 0.6 bar. After 30 min of filtration, the removal efficiency of NFX reached 96.4%.

[0053] Example 3

[0054] Take 100 mL of deionized water, and then add 0.2 g of Co3O4 spinel and 0.144 mM of magnesium acetate tetrahydrate, and mechanically stir at 60 °C for 60 min. Then put the mixture into a 150 mL hydrothermal reactor, centrifuge the product obtained after 10 h of reaction at 200 °C, and wash it with deionized water and ethanol. Vacuum dry at 60 °C for 10 h to obtain the precursor. Place the precursor in a ceramic crucible with a lid and place it in a tube furnace, introduce nitrogen, and heat to 800 °C at a rate of 10 °C / min, and keep it at this temperature for 4 h. After natural cooling, Mg0.06 -Co3O4. 0.02 g Mg 0.06 -Co3O4was added into 100 mL deionized water at 40 °C and ultrasonically dispersed for 60 min. The suspension was vacuum filtered with PES membrane as substrate and dried at 40 °C for 1 h to obtain Mg 0.06 -Co3O4@PES catalytic membrane.

[0055] The Mg 0.06 -Co3O4@PES catalytic membrane was used to activate PMS to degrade norfloxacin (NFX), the PMS concentration was 1.6 mM, the NFX concentration was 20 mg / L, the temperature was 25 °C, the pH was 7, and the membrane pressure was 0.5 bar. After 30 min of filtration, the removal efficiency of NFX reached 97.2%.

[0056] Example 4

[0057] Take 100 mL deionized water, add 0.1 g of Co3O4 spinel and 0.144 mM of magnesium acetate tetrahydrate in turn, and mechanically stir at 30 °C for 20 min. Then put the mixture into a 150 mL hydrothermal reactor, centrifuge the product obtained after reaction at 140 °C for 6 h and wash with deionized water and ethanol. Vacuum dry at 60 °C for 12 h to obtain the precursor. Put the precursor in a covered ceramic crucible and place it in a tube furnace, pass nitrogen, heat to 600 °C at a rate of 5 °C / min and keep for 5 h, and then naturally cool to obtain Mg 0.12 -Co3O4. 0.06 g Mg 0.12 -Co3O4was added into 100 mL deionized water at 20 °C and ultrasonically dispersed for 40 min. The suspension was vacuum filtered with PES membrane as substrate and dried at 40 °C for 1 h to obtain Mg 0.12 -Co3O4@PES catalytic membrane.

[0058] The Mg 0.12 -Co3O4@PES catalytic membrane was used to activate PMS to degrade norfloxacin (NFX), the PMS concentration was 1.0 mM, the NFX concentration was 10 mg / L, the temperature was 20 °C, the pH was 7, and the membrane pressure was 0.6 bar. After 30 min of filtration, the removal efficiency of NFX reached 94.1%.

Claims

1. The application of Mg-doped Co3O4 spinel in the persulfate-activated degradation of antibiotics in water, characterized in that, The preparation method of the Mg-doped Co3O4 spinel includes the following steps: 1) A certain mass of Co3O4 spinel and magnesium acetate tetrahydrate are added sequentially to a certain amount of deionized water and mechanically stirred for 20-60 min to obtain a mixed solution; wherein, the amount of Co3O4 is 0.5-2 g / L, the concentration of magnesium acetate tetrahydrate is 0.04-0.16 mM, and the temperature of deionized water is 30-60℃. 2) Add the mixture to a 150 mL hydrothermal reactor, react at 120-200℃ for 6-12 h, centrifuge to collect the product, wash thoroughly, and vacuum dry at 60℃ for 6-12 h to obtain the precursor; 3) Place the precursor in a covered ceramic crucible and then in a tube furnace. Purge with nitrogen, heat to a certain temperature, and hold for 4-6 hours. After natural cooling, Mg is obtained. x -Co3O4.

2. The application according to claim 1, characterized in that... In step 2), the mixture accounts for 50% to 75% (V / V) of the total volume of the inner liner of the hydrothermal reactor; the hydrothermal reaction temperature is 120 to 200℃, the hydrothermal reaction time is 6 to 12 h, and the vacuum drying time is 6 to 12 h.

3. The application according to claim 1, characterized in that... In step 3), the calcination temperature is 300~800℃, the holding time is 4~6 h, and the heating temperature of the tube furnace is 2~10℃ / min.

4. The application of a Mg-doped Co3O4 spinel catalytic membrane in the persulfate-activated degradation of antibiotics in water, characterized in that, The preparation method of the Mg-doped Co3O4 spinel catalytic film includes the following steps: 1) A certain mass of Co3O4 spinel and magnesium acetate tetrahydrate are added sequentially to a certain amount of deionized water and mechanically stirred for 20-60 min to obtain a mixed solution; wherein, the amount of Co3O4 is 0.5-2 g / L, the concentration of magnesium acetate tetrahydrate is 0.04-0.16 mM, and the temperature of deionized water is 30-60℃. 2) Add the mixture to a 150 mL hydrothermal reactor, react at 120-200℃ for 6-12 h, centrifuge to collect the product, wash thoroughly, and vacuum dry at 60℃ for 6-12 h to obtain the precursor; 3) Place the precursor in a covered ceramic crucible and then in a tube furnace. Purge with nitrogen, heat to a certain temperature, and hold for 4-6 hours. After natural cooling, Mg is obtained. x -Co3O 4； 4) Add Mg x -Co3O4 is added to a certain amount of deionized water, Mg x -Co3O4 concentration was 0.2~0.6 g / L, ultrasonically dispersed, and the suspension was vacuum filtered and dried using a PES membrane as a substrate to obtain Mg. x -Co3O4@PES catalytic membrane.

5. The application according to claim 4, characterized in that, The temperature of the deionized water is 20~40℃, and the ultrasonic dispersion time is 20~80 min.

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