Preparation method and application of ZIF-67 coated protruding graphite nanosheet single atom catalyst

Abstract

A preparation method and application of a ZIF-67 coated protruding graphite nanosheet single-atom catalyst, which relates to a preparation method and application of a catalyst. The purpose of the present invention is to solve the negative impact of the charge transport performance of existing catalysts, the low carrier concentration and the poor carrier migration efficiency. The present invention uses mesoporous expanded graphite and ZIF-67 as precursors to develop a new single-atom cobalt catalyst anchored on a three-dimensional porous carbon material; the ZIF-67 coated protruding graphite nanosheet single-atom catalyst prepared by the present invention introduces cobalt atoms in the protrusions formed by EG to increase the carrier concentration and significantly improve the carrier mobility. A ZIF-67 coated protruding graphite nanosheet single-atom catalyst is used to catalyze the degradation of micropollutants in water by persulfate, and has a good removal effect on levofloxacin antibiotics, reactive yellow dyes, carbamazepine, bisphenol A, rhodamine B, etc.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a catalyst. Background Art

[0002] The increased surface energy of isolated metal atoms facilitates their migration and aggregation, forming metal clusters. Metal clusters, due to their aggregation, alter the electronic structure and distribution of active sites, thereby reducing the catalytic performance of the catalyst. Current research has found that supporting single metal atoms on specific substrates is an effective method to mitigate atomic aggregation and stabilize individual metal atoms. However, how to bind single metal atoms to a fixed substrate and ensure unimpeded medium transport remains an urgent challenge. Currently, molecular channels within porous materials such as molecular sieves and metal-organic frameworks (MOFs) act as "cages" to confine the migration of metal atoms. The confinement within nanoporous materials allows precise control of the metal coordination environment, electronic properties, and the size and distribution of metal atoms, contributing to improved selectivity and catalytic performance. However, the relatively small pore size restricts the diffusion and encapsulation of larger organic molecules within the internal pore network, particularly persistent macromolecular organic pollutants in wastewater, which severely affects mass transfer efficiency during the catalytic process. Therefore, to optimize catalytic performance, it is necessary to explore effective material synthesis methods that can both enhance carrier mobility and mass transfer efficiency while increasing the accessibility of metal sites during the catalytic process. The advanced oxidation treatment process of persistent organic pollutants in wastewater also urgently needs an efficient catalyst with good catalytic effect in real wastewater. Summary of the Invention

[0003] The purpose of the present invention is to solve the negative impact of the charge transport performance of existing catalysts, the low carrier concentration and the poor carrier migration efficiency, and to provide a preparation method and application of ZIF-67 coated protruded graphite nanosheet single atom catalyst.

[0004] A method for preparing a ZIF-67-coated protruding graphite nanosheet single-atom catalyst is specifically completed by the following steps:

[0005] 1. Preparation of expanded graphite:

[0006] ①, ammonium persulfate and concentrated sulfuric acid are mixed evenly, then natural flake graphite is added, and then stirred at room temperature for a period of time to obtain natural flake graphite slurry; the natural flake graphite slurry is allowed to stand at room temperature for a period of time, then washed with distilled water, and vacuum dried to obtain expandable graphite with a worm-like structure;

[0007] ② Transfer the expandable graphite with a worm-like structure to a porcelain boat, then place it in the temperature zone of a tube furnace, introduce nitrogen, heat the expandable graphite with a worm-like structure to 600°C, and keep it at 600°C for a period of time to obtain expanded graphite;

[0008] 2. Preparation of ZIF-67-x@EG composite materials:

[0009] ① Add expanded graphite and polyvinyl pyrrolidone to methanol and stir for a period of time to obtain solution A;

[0010] ②. Add Co(NO3)2·6H2O to methanol and stir for a while to obtain solution B;

[0011] ③. Add 2-methylimidazole to methanol and stir for a while to obtain solution C;

[0012] ④. Add solution B and solution C to solution A, and stir magnetically at room temperature for a period of time to obtain a mixture; transfer the mixture to an autoclave lined with polytetrafluoroethylene, heat it to 110°C, perform a hydrothermal reaction at 110°C for a period of time, and then cool it to room temperature to obtain a reaction product;

[0013] ⑤. Centrifugally washing the reaction product with anhydrous ethanol as a cleaning agent, collecting the solid matter after centrifugation, and drying the solid matter to obtain a washed solid product;

[0014] ⑥. The cleaned solid product was transferred to a tubular furnace, and then heated to 600°C under a nitrogen atmosphere, and carbonized at 600°C for a period of time to obtain a ZIF-67-coated protruding graphite nanosheet single-atom catalyst.

[0015] A ZIF-67-coated protruded graphene nanosheet single-atom catalyst was used to catalyze the degradation of micropollutants in water by persulfate.

[0016] Beneficial effects of the present invention:

[0017] (1) The present invention uses mesoporous expanded graphite (EG) and ZIF-67 as precursors to develop a new single-atom cobalt catalyst anchored on a three-dimensional porous carbon material (ZIF-67-x@EG);

[0018] (2) The ZIF-67 coated protrusion graphite nanosheet single atom catalyst prepared by the present invention can increase the carrier concentration and significantly improve the carrier mobility by introducing cobalt atoms into the protrusions formed by EG;

[0019] (3) The ZIF-67-coated protruding graphite nanosheet single-atom catalyst (ZIF-67-x@EG catalyst) prepared by the present invention has a mesoporous structure, which improves the carrier mobility and mass transfer efficiency, and improves the accessibility of metal sites during the catalytic process, and has a significant catalytic oxidation effect on a variety of dyes;

[0020] (4) Cobalt atoms can expand pores, generate mesopores, and optimize electron transfer pathways; the deformation of the protrusions increases the carrier concentration exponentially, and due to the introduction of cobalt atoms, the carrier mobility is significantly improved;

[0021] (5) The ZIF-67-x@EG catalyst prepared by the present invention was used in combination with persulfate, and the removal efficiency of levofloxacin (24 mg / L, 48 mg / L) within 10 min was as high as 95%, and the removal efficiency of levofloxacin (72 mg / L) within 10 min was as high as over 77%;

[0022] (6) The ZIF-67-x@EG catalyst prepared by the present invention has a good removal effect on levofloxacin antibiotics, reactive yellow dyes, carbamazepine, bisphenol A, rhodamine B, etc.

[0023] The present invention can obtain a ZIF-67 coated protruding graphite nanosheet single atom catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a scanning electron micrograph of ZIF-67-1@EG prepared in step 2 (6) of Example 1;

[0025] Figure 2 TEM image of ZIF-67-1@EG prepared in step 2 (6) of Example 1;

[0026] Figure 3 HETEM image of ZIF-67-1@EG prepared in step 2 (6) of Example 1;

[0027] Figure 4 This is the HAADF diagram of ZIF-67-1@EG prepared in step 2 (6) of Example 1;

[0028] Figure 5 for Figure 1 EDX element mapping of the selected area;

[0029] Figure 6 This is the XANES pattern of ZIF-67-1@EG prepared in step 2 (6) of Example 1;

[0030] Figure 7 FT k3-weighted EXAFS diagram of ZIF-67-1@EG prepared in step 2 (6) of Example 1;

[0031] Figure 8 This is the XPS spectrum of ZIF-67-1@EG prepared in step 2 (6) of Example 1;

[0032] Figure 9This is the N2 adsorption-desorption isotherm of ZIF-67-1@EG prepared in step 2 (6) of Example 1;

[0033] Figure 10 The effect diagram of levofloxacin degradation in application tests 1 to 7;

[0034] Figure 11 The degradation kinetics of levofloxacin were investigated using experiments 1 to 7;

[0035] Figure 12 To investigate the degradation kinetics of high-concentration levofloxacin using experiments 1 to 7;

[0036] Figure 13 is the degradation kinetics under the conditions of inorganic anions and humic acid;

[0037] Figure 14 To investigate the degradation kinetics of different pollutants in the application test 8;

[0038] Figure 15 This is a diagram showing the effect of reusing the ZIF-67 coated protruding graphite nanosheet single atom catalyst prepared in Example 1 to degrade levofloxacin. In the figure, "Used" means the used catalyst, "Re-calcined" means the re-calcined catalyst, and "1" means the re-calcined catalyst. st For first time use, 2 nd For the second use, 3 rd For the third use, 4 th For the fourth use, 5 th This is the fifth use. DETAILED DESCRIPTION

[0039] The following examples further illustrate the present invention, but should not be construed as limiting the present invention. Without departing from the essence of the present invention, modifications and substitutions made to the methods, steps or conditions of the present invention are within the scope of the present invention.

[0040] Specific embodiment 1: This embodiment is a method for preparing a ZIF-67 coated protruding graphite nanosheet single atom catalyst, which is specifically completed by the following steps:

[0041] 1. Preparation of expanded graphite:

[0042] ①, ammonium persulfate and concentrated sulfuric acid are mixed evenly, then natural flake graphite is added, and then stirred at room temperature for a period of time to obtain natural flake graphite slurry; the natural flake graphite slurry is allowed to stand at room temperature for a period of time, then washed with distilled water, and vacuum dried to obtain expandable graphite with a worm-like structure;

[0043] ② Transfer the expandable graphite with a worm-like structure to a porcelain boat, then place it in the temperature zone of a tube furnace, introduce nitrogen, heat the expandable graphite with a worm-like structure to 600°C, and keep it at 600°C for a period of time to obtain expanded graphite;

[0044] 2. Preparation of ZIF-67-x@EG composite materials:

[0045] ① Add expanded graphite and polyvinyl pyrrolidone to methanol and stir for a period of time to obtain solution A;

[0046] ②. Add Co(NO3)2·6H2O to methanol and stir for a while to obtain solution B;

[0047] ③. Add 2-methylimidazole to methanol and stir for a while to obtain solution C;

[0048] ④. Add solution B and solution C to solution A, and stir magnetically at room temperature for a period of time to obtain a mixture; transfer the mixture to an autoclave lined with polytetrafluoroethylene, heat it to 110°C, perform a hydrothermal reaction at 110°C for a period of time, and then cool it to room temperature to obtain a reaction product;

[0049] ⑤. Centrifugally washing the reaction product with anhydrous ethanol as a cleaning agent, collecting the solid matter after centrifugation, and drying the solid matter to obtain a washed solid product;

[0050] ⑥. The cleaned solid product was transferred to a tubular furnace, and then heated to 600°C under a nitrogen atmosphere, and carbonized at 600°C for a period of time to obtain a ZIF-67-coated protruding graphite nanosheet single-atom catalyst.

[0051] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the natural flake graphite described in step 1 (1) is 2H-phase nano-scale graphite flakes with a particle diameter of 100 nm to 800 nm and 50 to 60 carbon atoms; the mass-to-volume ratio of ammonium persulfate, natural flake graphite, and concentrated sulfuric acid described in step 1 (1) is (1 g to 5 g): (4 g to 20 g): (1 mL to 4 mL). Other steps are the same as those in specific embodiment 1.

[0052] Specific embodiment 3: This embodiment differs from either specific embodiment 1 or 2 in that: in step 1 (1), stirring at room temperature is performed for 5 to 10 minutes; in step 1 (1), distilled water is used to wash the mixture until it is neutral; in step 1 (1), the natural flake graphite slurry is allowed to stand at room temperature for 20 to 24 hours; and the vacuum drying temperature in step 1 (1) is 70 to 80°C, and the vacuum drying time is 10 to 12 hours. Other steps are the same as those in specific embodiments 1 or 2.

[0053] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that: the heating rate described in step 1 (2) is 5°C / min to 10°C / min; the holding time at 600°C in step 1 (2) is 2h to 4h; the mass ratio of expanded graphite and polyvinyl pyrrolidone described in step 2 (1) is (1g to 5g): (0.1g to 0.5g); the volume ratio of the total mass of expanded graphite and polyvinyl pyrrolidone described in step 2 (1) to methanol is (0.5g to 1.5g): 25mL; the mass ratio of Co(NO3)2·6H2O described in step 2 (2) to methanol is (0.5g to 1.23g): 25mL; the mass ratio of 2-methylimidazole described in step 2 (3) to methanol is (0.5g to 1.23g): 25mL; and the stirring time described in steps 2 (1), (2) and (3) is 5min to 10min. The other steps are the same as specific embodiments 1 to 3.

[0054] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that: the volume ratio of solution B, solution C, and solution A in step 2 (4) is 1:1:1; the heating rate in step 2 (4) is 5°C / min to 10°C / min; the cooling rate in step 2 (4) is 1°C / min to 8°C / min; the magnetic stirring speed in step 2 (4) at room temperature is 150 to 200 r / min, and the magnetic stirring time is 20 to 40 minutes; and the hydrothermal reaction time at 110°C in step 2 (4) is 10 to 12 hours. Other steps are the same as specific embodiments 1 to 4.

[0055] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that: in step 2 (5), the reaction product is centrifuged and cleaned using anhydrous ethanol as a cleaning agent until the liquid no longer has a noticeable purple color; the centrifugal cleaning speed in step 2 (5) is 5000 r / min, and each centrifugal cleaning time is 5 to 10 minutes; the drying temperature in step 2 (5) is 70°C to 90°C, and the drying time is 10 to 14 hours; the carbonization time at 600°C in step 2 (6) is 2 to 3 hours; and the heating rate in step 2 (6) is 5 to 10°C / min. The other steps are the same as specific embodiments 1 to 5.

[0056] Specific embodiment seven: This embodiment is a ZIF-67 coated protruding graphite nanosheet single atom catalyst used to catalyze the degradation of micropollutants in water with persulfate.

[0057] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the micropollutant is one or a mixture of levofloxacin antibiotics, carbamazepine, bisphenol A, rhodamine B, and a reactive yellow dye. The other steps are the same as specific embodiments 1 to 7.

[0058] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that the persulfate is peroxymonosulfate, peroxydisulfate or sulfite. The other steps are the same as those of specific embodiments 1 to 8.

[0059] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that a ZIF-67-coated protruding graphite nanosheet single-atom catalyst is used to catalyze the degradation of micropollutants in water by persulfate, which is specifically accomplished by the following steps:

[0060] ZIF-67 coated protruding graphite nanosheet single atom catalyst and persulfate were added to wastewater containing micropollutants and degraded for a period of time to obtain water free of micropollutants.

[0061] The dosage of the ZIF-67 coated protruding graphite nanosheet single atom catalyst is 0.1 g / L to 0.8 g / L, and the dosage of the persulfate is 0.1 g / L to 0.8 g / L;

[0062] The concentration of micropollutants in the wastewater containing micropollutants is 12 mg / L to 72 mg / L;

[0063] The degradation time is 10 to 60 minutes. The other steps are the same as those in the first to ninth embodiments.

[0064] The following examples are used to verify the beneficial effects of the present invention:

[0065] Example 1: A method for preparing a ZIF-67 coated protruding graphite nanosheet single atom catalyst is specifically completed by the following steps:

[0066] 1. Preparation of expanded graphite:

[0067] ①, 5g of ammonium persulfate and 3mL of concentrated sulfuric acid (mass fraction of 98%) were mixed evenly, and then 5g of natural flake graphite was added, and then stirred at room temperature for 5min to obtain a natural flake graphite slurry; the natural flake graphite slurry was allowed to stand at room temperature for 24h, and then centrifuged and washed with distilled water until neutral, and then vacuum dried at 77°C for 12h to obtain expandable graphite with a worm-like structure;

[0068] The natural flake graphite described in step 1① is a 2H phase nano-flake graphite sheet with a particle diameter of 100nm to 800nm ​​and 50 to 60 layers of carbon atoms;

[0069] ② Transfer the expandable graphite with a worm-like structure to a porcelain boat, place it in the temperature zone of a tube furnace, introduce nitrogen, heat the expandable graphite with a worm-like structure to 600°C, and keep it at 600°C for 2 hours to obtain expanded graphite;

[0070] The heating rate in step 1 (2) is 5°C / min;

[0071] 2. Preparation of ZIF-67-x@EG composite materials:

[0072] ① Add 1.0 g of expanded graphite and 0.5 g of polyvinyl pyrrolidone to 25 mL of methanol and stir for 10 min to obtain solution A;

[0073] ②. Add 1.23 g of Co(NO3)2·6H2O to 25 mL of methanol and stir for 10 min to obtain solution B.

[0074] ③. Add 1.23 g of 2-methylimidazole to 25 mL of methanol and stir for 10 min to obtain solution C;

[0075] ④. Solution B and solution C were added to solution A, and the mixture was magnetically stirred at room temperature for 30 minutes at a speed of 200 r / min to obtain a mixture; the mixture was transferred to an autoclave lined with polytetrafluoroethylene, heated to 110°C, and hydrothermally reacted at 110°C for 12 hours, and then cooled to room temperature to obtain a reaction product;

[0076] The volume ratio of solution B, solution C and solution A described in step 2 (4) is 1:1:1;

[0077] The heating rate in step 2 (4) is 5°C / min;

[0078] The cooling rate in step 2 (4) is 3°C / min;

[0079] ⑤. The reaction product is centrifuged and washed with anhydrous ethanol until the liquid has no obvious purple color, and then the solid matter after centrifugation is collected and dried to obtain a washed solid product;

[0080] The centrifugal washing speed in step 2 (5) is 5000 r / min, and the time of each centrifugal washing is 5 min;

[0081] The drying temperature in step 2 (5) is 80°C and the drying time is 10 hours;

[0082] ⑥ The cleaned solid product was transferred to a tube furnace, then heated to 600°C under a nitrogen atmosphere and carbonized at 600°C for 2 h to obtain a ZIF-67-coated protruding graphene nanosheet single-atom catalyst, denoted as ZIF-67-0.5@EG catalyst.

[0083] The heating rate described in step 2 (6) is 5°C / min.

[0084] Example 2: This example differs from Example 1 in that, in step 2 (2), 2.46 g of Co(NO₃)₂·6H₂O was added to 25 mL of methanol and stirred for 10 minutes to obtain Solution B; in step 2 (3), 2.46 g of 2-methylimidazole was added to 25 mL of methanol and stirred for 10 minutes to obtain Solution C; and the ZIF-67-coated protruding graphite nanosheet single-atom catalyst obtained in step 2 (6) was designated as ZIF-67-1@EG catalyst. All other steps and parameters were the same as in Example 1.

[0085] Example 3: This example differs from Example 1 in that, in step 2 (2), 3.69 g of Co(NO₃)₂·6H₂O was added to 25 mL of methanol and stirred for 10 minutes to obtain Solution B; in step 2 (3), 3.69 g of 2-methylimidazole was added to 25 mL of methanol and stirred for 10 minutes to obtain Solution C; and the ZIF-67-coated protruding graphite nanosheet single-atom catalyst obtained in step 2 (6) was designated as ZIF-67-1.5@EG catalyst. All other steps and parameters were the same as in Example 1.

[0086] Example 4: This example differs from Example 1 in that, in step 2 (2), 4.92 g of Co(NO₃)₂·6H₂O was added to 25 mL of methanol and stirred for 10 minutes to obtain Solution B; in step 2 (3), 4.92 g of 2-methylimidazole was added to 25 mL of methanol and stirred for 10 minutes to obtain Solution C; and the ZIF-67-coated protruding graphite nanosheet single-atom catalyst obtained in step 2 (6) was designated as ZIF-67-2@EG catalyst. All other steps and parameters were the same as in Example 1.

[0087] Figure 1 This is a scanning electron micrograph of ZIF-67-1@EG prepared in step 2 (6) of Example 1;

[0088] from Figure 1It can be seen that after loading ZIF-67, the smooth wrinkled surface of expanded graphite (EG) with multi-layer curled flakes becomes rough and presents a fluffy porous structure, which effectively increases the contact area between ZIF-67 nanoparticles and the substrate surface, and ultimately enhances their dispersion. This compact structure can shorten the carrier transmission distance, provide excellent electron transport performance, and expose the catalytic surface area, thereby increasing the accessibility of active sites and ultimately improving the catalytic performance.

[0089] Figure 2 TEM image of ZIF-67-1@EG prepared in step 2 (6) of Example 1;

[0090] Figure 3 HETEM image of ZIF-67-1@EG prepared in step 2 (6) of Example 1;

[0091] from Figure 3 It can be seen that at an interlayer spacing of 0.295 nm, the (102) planes of carbon graphite are observed to match the lattice fringes. Correspondingly, the interlayer spacings of 0.252 nm and 0.295 nm correspond to the (203) and (204) planes of Co.

[0092] Figure 4 This is the HAADF diagram of ZIF-67-1@EG prepared in step 2 (6) of Example 1;

[0093] from Figure 4 Reflects that a single Co atom is smaller than The metals are uniformly dispersed within a radius of 1.5 Å, and no metal clusters are detected on the surface of ZIF-67-1@EG.

[0094] Figure 5 for Figure 1 EDX element mapping of the selected area;

[0095] Figure 5 The uniform distribution of C, N, O and Co was confirmed.

[0096] Figure 6 This is the XANES pattern of ZIF-67-1@EG prepared in step 2 (6) of Example 1;

[0097] from Figure 6 It can be seen that the absorption edge of ZIF-67-1@EG is located between Co foil and CoO, indicating that the valence state of the Co atom is between 0 and +2, and a single Co atom is coordinated with four pyridinic nitrogen atoms to form a Co-N4 site.

[0098] Figure 7 FT k3-weighted EXAFS diagram of ZIF-67-1@EG prepared in step 2 (6) of Example 1;

[0099] from Figure 7 It can be seen that in There is a main peak at , which is caused by Co-N coordination scattering.

[0100] Figure 8 This is the XPS spectrum of ZIF-67-1@EG prepared in step 2 (6) of Example 1;

[0101] from Figure 8 It can be seen that Co, O, C, and N elements exist in the ZIF-67-x@EG composite material.

[0102] Figure 9 This is the N2 adsorption-desorption isotherm of ZIF-67-1@EG prepared in step 2 (6) of Example 1;

[0103] from Figure 9 It can be seen that the specific surface area of ​​ZIF-67-x@EG is 16.26m 2 / g, BJH pore volume is 0.089dm 3 / g, and the average pore diameter is 21.94nm.

[0104] Application Test 1: Under natural light conditions, natural flake graphite (NG) and potassium permonosulfate (PMS) were added to wastewater containing levofloxacin (LEVO) at a pH of 3.8, and then degraded under stirring for 0 to 45 minutes to obtain wastewater free of levofloxacin (LEVO);

[0105] The addition amount of the natural flake graphite is 0.4 g / L, and the addition amount of potassium permonosulfate (PMS) is 0.4 g / L;

[0106] The concentration of levofloxacin LEVO in the wastewater containing levofloxacin LEVO is 24 mg / L.

[0107] Application Test 2: Under natural light, nitrogen-doped flake graphite (NG@N) (1 g of graphite nanosheets and 5 g of urea were thoroughly ground, placed in a magnetic boat, and pyrolyzed in a tube furnace at 600°C for 4 hours under a nitrogen atmosphere. After the system cooled, it was removed for later use) and potassium permonosulfate (PMS) were added to wastewater containing levofloxacin (LEVO) at a pH of 3.8. The mixture was then degraded under stirring for 0 to 45 minutes to obtain wastewater free of levofloxacin (LEVO).

[0108] The addition amount of the nitrogen-doped flake graphite (NG@N) is 0.4 g / L, and the addition amount of potassium permonosulfate (PMS) is 0.4 g / L;

[0109] The concentration of levofloxacin LEVO in the wastewater containing levofloxacin LEVO is 24 mg / L.

[0110] Application Test 3: Under natural light conditions, expanded graphite (EG) catalyst and potassium permonosulfate (PMS) were added to wastewater containing levofloxacin (LEVO) at a pH of 3.8, and then degraded for 0 to 45 minutes under stirring to obtain wastewater free of levofloxacin (LEVO);

[0111] The added amount of the expanded graphite catalyst is 0.4 g / L, and the added amount of potassium permonosulfate (PMS) is 0.4 g / L;

[0112] The concentration of levofloxacin LEVO in the wastewater containing levofloxacin LEVO is 24 mg / L.

[0113] Application Test 4: Under natural light conditions, a nitrogen-doped expanded graphite (EG@N) catalyst (1 g of the expanded graphite nanosheets EG prepared in Example 1 and 5 g of urea were thoroughly ground, placed in a magnetic boat, placed in a tube furnace, and pyrolyzed at 600°C for 4 hours under a nitrogen atmosphere. After the system cooled, it was removed for later use) and potassium permonosulfate (PMS) were added to wastewater containing levofloxacin (LEVO) at a pH of 3.8, and then degraded under stirring for 0 to 45 minutes to obtain wastewater from which levofloxacin (LEVO) had been removed.

[0114] The added amount of the expanded graphite catalyst is 0.4 g / L, and the added amount of potassium permonosulfate (PMS) is 0.4 g / L;

[0115] The concentration of levofloxacin LEVO in the wastewater containing levofloxacin LEVO is 24 mg / L.

[0116] Application Test 5: Under natural light conditions, ZIF-67-doped flake graphite (ZIF-67 / NG) catalyst and potassium permonosulfate (PMS) were added to wastewater containing levofloxacin (LEVO) at a pH of 3.8. The wastewater was then degraded under stirring for 0 to 45 minutes to obtain levofloxacin-free wastewater.

[0117] The addition amount of the ZIF-67 doped flake graphite (ZIF-67 / NG) catalyst is 0.4 g / L, and the addition amount of potassium permonosulfate (PMS) is 0.4 g / L;

[0118] The concentration of levofloxacin LEVO in the wastewater containing levofloxacin LEVO is 24 mg / L;

[0119] The preparation method of the ZIF-67 doped flake graphite (ZIF-67 / NG) catalyst is specifically completed according to the following steps:

[0120] ① Add 1.0 g of natural flake graphite (NG) and 0.5 g of polyvinyl pyrrolidone to 25 mL of methanol and stir for 10 min to obtain solution A;

[0121] ②. Add 1.23 g of Co(NO3)2·6H2O to 25 mL of methanol and stir for 10 min to obtain solution B.

[0122] ③. Add 1.23 g of 2-methylimidazole to 25 mL of methanol and stir for 10 min to obtain solution C;

[0123] ④. Solution B and solution C were added to solution A, and the mixture was magnetically stirred at room temperature for 30 minutes at a speed of 200 r / min to obtain a mixture; the mixture was transferred to an autoclave lined with polytetrafluoroethylene, heated to 110°C, and hydrothermally reacted at 110°C for 12 hours, and then cooled to room temperature to obtain a reaction product;

[0124] The volume ratio of solution B, solution C and solution A described in step ④ is 1:1:1;

[0125] The heating rate in step ④ is 5°C / min;

[0126] The cooling rate in step ④ is 3°C / min;

[0127] ⑤. The reaction product is centrifuged and washed with anhydrous ethanol until the liquid has no obvious purple color, and then the solid matter after centrifugation is collected and dried to obtain a washed solid product;

[0128] The centrifugal washing speed in step ⑤ is 5000 r / min, and the time of each centrifugal washing is 5 min;

[0129] The drying temperature in step ⑤ is 80° C. and the drying time is 10 h;

[0130] ⑥ The cleaned solid product was transferred to a tube furnace, and then heated to 600°C under a nitrogen atmosphere and carbonized at 600°C for 2 h to obtain a ZIF-67-doped flake graphite (ZIF-67 / NG) catalyst;

[0131] The heating rate in step ⑥ is 5°C / min.

[0132] Application Test 6: Under natural light conditions, the ZIF-67-coated convex graphite nanosheet single-atom catalysts (ZIF-67-x@EG) prepared in Examples 1 to 4 and potassium monopersulfate (PMS) were respectively added to the wastewater containing levofloxacin (LEVO) with a pH value of 3.8, and then degraded for 0 min to 45 min under stirring conditions to obtain wastewater with levofloxacin (LEVO) removed;

[0133] The addition amount of the ZIF-67-coated convex graphite nanosheet single-atom catalyst (ZIF-67-x@EG) is 0.4 g / L, and the addition amount of potassium monopersulfate (PMS) is 0.4 g / L;

[0134] The concentration of levofloxacin (LEVO) in the wastewater containing levofloxacin (LEVO) is 24 mg / L.

[0135] Application Test 7: Under natural light conditions, potassium monopersulfate (PMS) was added to the wastewater containing levofloxacin (LEVO) with a pH value of 3.8, and then degraded for 0 min to 45 min under stirring conditions to obtain wastewater with levofloxacin (LEVO) removed;

[0136] The addition amount of the potassium monopersulfate (PMS) is 0.4 g / L;

[0137] The concentration of levofloxacin (LEVO) in the wastewater containing levofloxacin (LEVO) is 24 mg / L.

[0138] Figure 10 is the effect diagram of the degradation of levofloxacin in Application Tests 1 to 7;

[0139] From Figure 10 it can be seen that in the absence of potassium monopersulfate (PMS), the static adsorption efficiencies of EG, EG@N, and ZIF-67-x@EG for LEVO are 8.05%, 20.6, and 11.13 - 18.34% respectively; only introducing PMS into the reaction system, even after 30 min, only 6.56% of LEVO is removed from the PMS system.

[0140] Figure 11 is the degradation kinetics of the degradation of levofloxacin in Application Tests 1 to 7;

[0141] From Figure 11 it can be seen that the order of the pseudo-first-order rate constants (k obs ) of different catalysts is ZIF-67-0.5@EG < ZIF-67-1.5@EG < ZIF-67-2@EG < ZIF-67-1@EG. Among them, the k obs value of ZIF-67-1@EG is the highest, which is 0.196 min-1 , respectively ZIF-67-0.5@EG(0.077min -1 ) and ZIF-67-1.5@EG(0.084min -1 ) are 2.55 times and 2.33 times of .

[0142] Figure 12 To investigate the degradation kinetics of high-concentration levofloxacin using experiments 1 to 7;

[0143] from Figure 12 It can be seen that the removal efficiency of ZIF-67-1@EG catalyst for 48 mg / L and 72 mg / L LEVO within 10 min is 90.63% and 51.98%, respectively.

[0144] Figure 13 is the degradation kinetics under the conditions of inorganic anions and humic acid;

[0145] from Figure 13 It can be seen that Cl - and NO3 - The inhibitory effect on the catalytic system is significant, and H2PO4 - and humic acid (HA) had a smaller effect.

[0146] Application Test 8: Degradation of different pollutants using the ZIF-67-coated protruding graphite nanosheet single-atom catalyst prepared in Example 1 was carried out in the following steps:

[0147] The ZIF-67-coated protruding graphite nanosheet single-atom catalyst and potassium permonosulfate (PMS) prepared in Example 1 were added to wastewater containing micropollutants at a pH of 3.8, and then degraded for 0 min to 120 min under stirring to obtain wastewater from which micropollutants were removed;

[0148] The addition amount of the ZIF-67 coated protruding graphite nanosheet single atom catalyst is 0.4 g / L, and the addition amount of potassium permonosulfate (PMS) is 0.4 g / L;

[0149] The concentrations of rhodamine B (RhB), carbamazepine (CBZ), reactive yellow (YR), bisphenol A (BPA) and levofloxacin (LEVO) in the wastewater containing micropollutants are all 24 mg / L.

[0150] Figure 14 To investigate the degradation kinetics of different pollutants in the application test 8;

[0151] from Figure 14It can be seen that the ZIF-67-1@EG / PMS system completely removed rhodamine B (RhB), carbamazepine (CBZ), reactive yellow (YR), bisphenol A (BPA) and levofloxacin (LEVO) within 10 minutes, and the removal efficiency of BPA was 62.14% within 30 minutes. The removal rate of RhB was about 100% within 1 minute, and the removal rate of k obs 1.93 minutes -1 .

[0152] The ZIF-67 coated protruding graphite nanosheet single atom catalyst prepared in Example 1 was reused to degrade levofloxacin. Figure 15 As shown;

[0153] Figure 15 This is a diagram showing the effect of reusing the ZIF-67 coated protruding graphite nanosheet single atom catalyst prepared in Example 1 to degrade levofloxacin. In the figure, "Used" means the used catalyst, "Re-calcined" means the re-calcined catalyst, and "1" means the re-calcined catalyst. st For first time use, 2 nd For the second use, 3 rd For the third use, 4 th For the fourth use, 5 th For the fifth use;

[0154] from Figure 15 It can be seen that when using ZIF-67-1@EG catalyst, the removal rate of LEVO gradually decreased in five cycles. In the first cycle, the removal rate was 99.40%, and in the fifth cycle, the removal rate dropped to 42.86%, k obs From 0.030min -1 Down to 0.010min -1 After the first, third, and fifth cycles, the catalyst was washed three times with deionized water and then heated at 600°C in a nitrogen atmosphere for 2 hours to remove the intermediate products accumulated on the catalyst surface and restore its performance. The catalytic performance was then significantly restored, with LEVO removal rates reaching 80.05%, 75.49%, and 57.06% in the first, third, and fifth cycles, respectively.

Claims

1. A method for preparing a ZIF-67 coated protruding graphite nanosheet single atom catalyst, characterized in that The preparation method is specifically completed according to the following steps:

1. Preparation of expanded graphite: ①, ammonium persulfate and concentrated sulfuric acid are mixed evenly, then natural flake graphite is added, and then stirred at room temperature for a period of time to obtain natural flake graphite slurry; the natural flake graphite slurry is allowed to stand at room temperature for a period of time, then washed with distilled water, and vacuum dried to obtain expandable graphite with a worm-like structure; ② Transfer the expandable graphite with a worm-like structure to a porcelain boat, then place it in the temperature zone of a tube furnace, introduce nitrogen, heat the expandable graphite with a worm-like structure to 600°C, and keep it at 600°C for a period of time to obtain expanded graphite; 2. Preparation of ZIF-67-x@EG composite materials: ① Add expanded graphite and polyvinyl pyrrolidone to methanol and stir for a period of time to obtain solution A; ②. Add Co(NO3)2·6H2O to methanol and stir for a while to obtain solution B; ③. Add 2-methylimidazole to methanol and stir for a while to obtain solution C; ④. Add solution B and solution C to solution A, and stir magnetically at room temperature for a period of time to obtain a mixture; transfer the mixture to an autoclave lined with polytetrafluoroethylene, heat it to 110°C, perform a hydrothermal reaction at 110°C for a period of time, and then cool it to room temperature to obtain a reaction product; ⑤. Centrifugally washing the reaction product with anhydrous ethanol as a cleaning agent, collecting the solid matter after centrifugation, and drying the solid matter to obtain a washed solid product; ⑥. The cleaned solid product was transferred to a tubular furnace, and then heated to 600°C under a nitrogen atmosphere, and carbonized at 600°C for a period of time to obtain a ZIF-67-coated protruding graphite nanosheet single-atom catalyst.

2. The method for preparing a ZIF-67 coated protruding graphite nanosheet single atom catalyst according to claim 1, characterized in that The natural flake graphite described in step 1① is a 2H phase nano-flake graphite sheet with a particle diameter of 100nm to 800nm ​​and 50 to 60 layers of carbon atoms; the mass volume ratio of ammonium persulfate, natural flake graphite and concentrated sulfuric acid described in step 1① is (1g to 5g): (4g to 20g): (1mL to 4mL).

3. The method for preparing a ZIF-67 coated protrusion graphite nanosheet single atom catalyst according to claim 1, characterized in that The stirring time at room temperature in step 1① is 5min to 10min; distilled water is used to wash to neutrality in step 1①; the natural flake graphite slurry in step 1① is allowed to stand at room temperature for 20h to 24h; the vacuum drying temperature in step 1① is 70℃ to 80℃, and the vacuum drying time is 10h to 12h.

4. The method for preparing a ZIF-67 coated protruding graphite nanosheet single atom catalyst according to claim 1, characterized in that The heating rate described in step 1 ② is 5 ℃ / min ~ 10 ℃ / min; the holding time of step 1 ② at 600 ℃ is 2h ~ 4h; the mass ratio of the expanded graphite and polyvinyl pyrrolidone described in step 2 ① is (1g ~ 5g): (0.1 ~ 0.5g); the volume ratio of the total mass of the expanded graphite and polyvinyl pyrrolidone described in step 2 ① to methanol is (0.5g ~ 1.5g): 25mL; the mass ratio of Co (NO3) 2 · 6H2O described in step 2 ② to methanol is (0.5g ~ 1.23g): 25mL; the mass ratio of 2-methylimidazole described in step 2 ③ to methanol is (0.5g ~ 1.23g): 25mL; the stirring time described in steps 2 ①, ② and ③ is 5min ~ 10min.

5. The method for preparing a ZIF-67 coated protruding graphite nanosheet single atom catalyst according to claim 1, wherein The volume ratio of solution B, solution C and solution A described in step 2④ is 1:1:1; the heating rate described in step 2④ is 5℃ / min~10℃ / min; the cooling rate described in step 2④ is 1℃ / min~8℃ / min; the magnetic stirring speed at room temperature in step 2④ is 150r / min~200r / min, and the magnetic stirring time is 20min~40min; the hydrothermal reaction time at 110℃ in step 2④ is 10h~12h.

6. The method for preparing a ZIF-67 coated protruding graphite nanosheet single atom catalyst according to claim 1, characterized in that In step 2 (5), the reaction product is centrifuged and cleaned with anhydrous ethanol as a cleaning agent until the liquid has no obvious purple color; the centrifugal cleaning speed in step 2 (5) is 5000 r / min, and the time for each centrifugal cleaning is 5 min to 10 min; the drying temperature in step 2 (5) is 70°C to 90°C, and the drying time is 10 h to 14 h; the carbonization time at 600°C in step 2 (6) is 2 h to 3 h; the heating rate in step 2 (6) is 5°C / min to 10°C / min.

7. Application of a ZIF-67 coated protruding graphite nanosheet single atom catalyst prepared by the preparation method according to claim 1, characterized in that A ZIF-67-coated protruded graphene nanosheet single-atom catalyst was used to catalyze the degradation of micropollutants in water by persulfate.

8. The use of a ZIF-67 coated protruding graphite nanosheet single atom catalyst according to claim 7, characterized in that The micro-pollutants are one or a mixture of several of levofloxacin series antibiotics, carbamazepine, bisphenol A, rhodamine B and reactive yellow series dyes.

9. The use of a ZIF-67 coated protruding graphite nanosheet single atom catalyst according to claim 7, characterized in that The persulfate is peroxymonosulfate, peroxydisulfate or sulfite.

10. The use of a ZIF-67 coated protruding graphite nanosheet single atom catalyst according to claim 7, characterized in that A ZIF-67-coated protruding graphite nanosheet single-atom catalyst is used to catalyze the degradation of micropollutants in water using persulfate, specifically by following the steps below: ZIF-67 coated protruding graphite nanosheet single atom catalyst and persulfate were added to wastewater containing micropollutants and degraded for a period of time to obtain water free of micropollutants. The dosage of the ZIF-67 coated protruding graphite nanosheet single atom catalyst is 0.1 g / L to 0.8 g / L, and the dosage of the persulfate is 0.1 g / L to 0.8 g / L; The concentration of micropollutants in the wastewater containing micropollutants is 12 mg / L to 72 mg / L; The degradation time is 10 minutes to 60 minutes.

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