Iron-loaded graphene fiber rod catalyst as well as preparation method and application thereof

Abstract

The invention relates to an iron-loaded graphene fiber rod catalyst as well as a preparation method and application thereof, and belongs to the technical field of water treatment. The preparation method comprises the following steps: calcining biomass to form a graphene-like structure carbon skeleton, carrying out surface modification on the graphene carbon skeleton to load iron nanoparticles on the surface, forming Fe-O-C or / and Fe-N-C bond bridge connection, taking metal iron as an active center, forming an electron-rich center by a Fe site, and forming an electron-deficient center around a graphene-like C site. The catalyst prepared by the method disclosed by the invention can effectively remove organic pollutants in water without adding extra energy and under natural conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to an iron-loaded graphene fiber rod catalyst and a preparation method and application thereof. Background Art

[0002] With the rapid advancement of modern industry, a large number of modern products such as plastics, pesticides, antibiotics, synthetic rubber, coatings, and food additives are discharged into water, leading to the emergence of emerging contaminants (ECs). High-molecular-weight polymers, due to their resistance to oxidation and biodegradation, remain in aquatic environments for long periods of time and can even enter the human body through the natural food chain, potentially causing health problems such as carcinogenesis, teratogenesis, and mutagenesis.

[0003] In recent years, heterogeneous Fenton catalysis has been optimized based on the Fenton oxidation method. Heterogeneous Fenton catalysis utilizes the redox reaction of a single metal to achieve electron transfer within the catalyst, allowing H₂O₂ to generate OH. This technology has achieved breakthrough progress in recent years, addressing the issues of low H₂O₂ utilization and poor stability that emerged in the early stages of heterogeneous Fenton catalyst research. However, since its inception, Fenton catalytic oxidation technology has faced challenges in H₂O₂ utilization.

[0004] Therefore, seeking a Fenton catalyst that does not rely on H2O2 has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art by providing an iron-loaded graphene fiber rod catalyst, its preparation method, and its application. The iron-loaded graphene fiber rod catalyst prepared by the present invention can effectively remove organic pollutants in water without the addition of additional energy (such as H2O2) and under natural conditions.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] In a first aspect, the present invention provides a method for preparing an iron-supported graphene fiber rod catalyst, the preparation method comprising the following steps:

[0008] (1) placing biomass in an alkaline solution for thermal reaction to obtain a solid product A, and drying and grinding the solid product A;

[0009] (2) dispersing the ground solid product A, the iron source, and melamine in an organic solvent to obtain a suspension A;

[0010] (3) adding dimethylimidazole and a zinc source to the organic solution to obtain a suspension B;

[0011] (4) mixing suspension A and suspension B to obtain suspension C;

[0012] (5) adding a nitrogen source to the suspension C and drying it to obtain a solid product B;

[0013] (6) grinding the solid product B and adding zinc chloride to obtain a solid product C;

[0014] (7) The solid product C is ground and calcined to obtain the iron-supported graphene fiber rod catalyst.

[0015] The present invention calcines biomass to form a graphene-like carbon skeleton. This graphene-like carbon skeleton is then surface-modified to load iron nanoparticles onto its surface, forming Fe-OC and / or Fe-NC bond bridges. The metallic iron serves as the active center, with the Fe sites forming electron-rich centers and electron-deficient centers surrounding the graphene-like C sites. Pollutants complex at the C active sites, transferring electrons to the material interface and subsequently being oxidized and decomposed. Oxygen then gains electrons at the Fe sites, undergoing a reduction reaction.

[0016] The present invention uses biomass as the carbon source of the catalyst, which is the main substance for constructing C active sites. Alkaline solution is used to pretreat the biomass, exposing its surface functional groups by removing the colloid on the biomass surface. The iron source is used to construct the electron-rich active sites of the catalyst, forming a polarization center with the C active sites at the material interface, which is beneficial to electron transport. Melamine, as a nitrogen source, can promote the formation of graphitic nitrogen in the catalyst, enhance conductivity and electron transfer rate; on the other hand, it forms Fe-N with Fe. x bond. Dimethylimidazole and zinc source are used to construct a metal-organic framework, and the porous carbon generated by biomass pyrolysis is used as a carrier to grow the metal-organic framework, thereby enhancing the stability and conductivity of the catalyst. The secondary added nitrogen source significantly regulates the nitrogen doping type, active site distribution and electronic structure of the catalyst during the synthesis of the catalyst, thereby affecting its catalytic activity and stability. Zinc chloride reacts with the carbon precursor at high temperature to dope Zn atoms into the carbon skeleton, forming Zn-NC or Zn-OC active sites, which significantly enhances the activity of the catalyst. In addition, ZnCl catalyzes the graphitization of carbon materials during calcination, reduces defect density and improves conductivity.

[0017] As a preferred embodiment of the first aspect, the mass ratio of the biomass to the alkaline solution in step (1) is: (2000-13000):(1-3). Preferably, the mass ratio of the biomass to the alkaline solution in step (1) is: 12500:3.

[0018] As a preferred embodiment of the first aspect, the concentration of the solute in the alkaline solution in step (1) is 15-25 ppm.

[0019] Biomass reacts in an alkaline solution for a period of time to achieve the effect of degumming and activating biomass surface functional groups. Excessive alkali can break the triple helix structure of collagen, resulting in excessive degradation of the organic carbon skeleton in biomass (such as fish scales), reducing the carbon source during subsequent carbonization, and reducing the carbon material yield. In addition, excessive degumming loosens the fiber network of biomass, reduces the micropore / mesoporous structure after carbonization, and reduces the specific surface area. Insufficient alkali can cause the collagen in the biomass that is not fully degummed to pyrolyze and generate amorphous carbon during carbonization, covering HAP (hydroxyapatite) active sites and reducing catalytic activity. At the same time, the collagen in the biomass that is not fully degummed can cover and reduce the surface -OH / -COOH sites, making it difficult for Fe metal to effectively anchor, resulting in uneven loading. Therefore, the present invention optimizes the mass ratio of biomass to alkaline solution. When it is (2000-13000): (1-3), especially 12500: 3, it has a better effect.

[0020] As a preferred embodiment of the first aspect, in step (1), the biomass comprises fish scales, egg shells and shrimp shells, preferably fish scales; and the alkaline solution is sodium hydroxide solution, potassium hydroxide solution or calcium hydroxide solution.

[0021] As a preferred embodiment of the first aspect, the thermal reaction temperature in step (1) is 110-130°C, and the reaction time is 30-60 minutes. Reaction at 110-130°C for 30-60 minutes completely removes the collagen in the biomass, retaining the HAP active sites, which is beneficial for subsequent metal loading and improves metal dispersion.

[0022] As a preferred embodiment of the first aspect, the step (1) of drying the solid product A specifically includes: a first-stage drying temperature of 60-80°C and a drying time of 12-24h; a second-stage drying temperature of 100-120°C and a drying time of 2-4h.

[0023] The present invention employs a staged drying process: in the first stage, excess water from the precursor is evaporated, and in the second stage, residual water (including bound water) is further removed, preventing pore collapse caused by steam explosion during subsequent high-temperature treatment. Furthermore, when the dried biomass is used as a catalyst support, the pore structure is more stable, facilitating the uniform penetration of the metal precursor.

[0024] As a preferred embodiment of the first aspect, the mass ratio of the solid product A, the iron source, and the melamine in step (2) is: (4-10):1:(4-10). Preferably, the mass ratio of the solid product A, the iron source, and the melamine in step (2) is: 10:1:10.

[0025] Solid product A is biomass activated by alkali. Too low an iron ratio will result in an insufficient number of Fe-N sites and poor catalytic activity, while too high an iron ratio will easily form large-sized Fe particles, clogging pores and reducing the specific surface area, which will also reduce catalytic activity. A too high mass ratio of solid product A to melamine will result in insufficient nitrogen doping, low graphitic nitrogen (graphitic-N) content, poor conductivity, and slow electron transfer rate; if its mass ratio is too low, excess melamine will be pyrolyzed to form a nitrogen-rich carbon layer, which may cover the Fe active sites. Mass ratio of iron source to melamine: Low Fe / N ratio causes melamine to react preferentially with the biomass carbon source, and Fe is difficult to form Fe-N x bond; high Fe / N ratio will affect Fe agglomeration, part of which exists in metallic state, reducing Fe-N x Therefore, the invention limits the mass ratio of solid product A, iron source and melamine to (4-10):1:(4-10), especially 10:1:10, which has a better effect.

[0026] As a preferred embodiment of the first aspect, the iron source in step (2) includes ferric chloride hexahydrate, ferrous chloride tetrahydrate, iron powder and ferric nitrate nonahydrate; preferably ferric chloride hexahydrate.

[0027] As a preferred embodiment of the first aspect, the mass of melamine in step (2) is 1-3 g.

[0028] As a preferred embodiment of the first aspect, the organic solvent in step (2) is anhydrous methanol, and the volume of anhydrous methanol used is 50-100 mL.

[0029] The present invention selects anhydrous methanol as the organic solvent. Experiments have shown that in the synthesis of ZIF-8 (zeolite imidazolate framework-8) of the present invention, methanol can dissolve Zn 2+ Salt and 2-methylimidazole promote coordination reactions; the rapid diffusion rate of molecules in methanol facilitates homogeneous nucleation and the formation of uniformly sized crystals. The catalytic effect decreases when other solvents are used.

[0030] As a preferred embodiment of the first aspect, the mass ratio of dimethylimidazole to the zinc source in step (3) is: (1-3):1; preferably, the mass ratio of dimethylimidazole to the zinc source in step (3) is: 2:1.

[0031] The present invention uses dimethylimidazole and zinc source to construct the metal organic framework. The ratio of the two directly determines the structural integrity, porosity and catalytic performance of the framework. If the ratio is too large, the ligands will compete for adsorption on the crystal surface, inhibiting grain growth and reducing thermal stability. If the ratio is insufficient, Zn 2+Incomplete coordination forms a defective structure or an amorphous phase, exposing open metal sites and reducing the specific surface area. Therefore, the present invention achieves better results by limiting the ratio of the two to within the above range.

[0032] As a preferred embodiment of the first aspect, the mass of dimethylimidazole in step (3) is 1-5 g.

[0033] As a preferred embodiment of the first aspect, the zinc source in step (3) includes zinc acetate, zinc nitrate hexahydrate, zinc chloride and zinc oxide, preferably zinc nitrate hexahydrate; the mass of the zinc source is 1-3 g.

[0034] As a preferred embodiment of the first aspect, the organic solvent in step (3) is anhydrous methanol, and the volume of methanol used is 10-30 mL.

[0035] As a preferred embodiment of the first aspect, in step (4), the mixing volume ratio of suspension A to suspension B is: (2-6): (1-2).

[0036] As a preferred embodiment of the first aspect, the mass ratio of the nitrogen source to the suspension C in step (5) is: (2-4): (1-2). As a preferred embodiment of the first aspect, the mass ratio of the nitrogen source to the suspension C in step (5) is: 3:2.

[0037] In the present invention, too low a content of secondary nitrogen doping will lead to Fe-N x Insufficient site density; excessive secondary nitrogen doping can reduce stability (nitrogen is easily lost); free nitrogen can cover metal sites (e.g., forming an inactive CNC layer); and excessive etching can lead to pore wall collapse and a decrease in specific surface area. Therefore, limiting the ratio of the two to within the above range achieves better results in this invention.

[0038] As a preferred embodiment of the first aspect, the nitrogen source in step (5) includes thiourea, urea and dicyandiamide, preferably urea; and the mass of the nitrogen source is 1-15 g.

[0039] As a preferred embodiment of the first aspect, the mass ratio of the solid product B to zinc chloride in step (6) is: (200-300):1.

[0040] As a preferred embodiment of the first aspect, the mass ratio of the solid product B to zinc chloride in step (6) is 250:1.

[0041] ZnCl reacts with the carbon precursor at high temperatures, doping Zn atoms into the carbon skeleton to form Zn-NC or Zn-OC active sites, significantly enhancing activity. Furthermore, ZnCl catalyzes the graphitization of the carbon material during calcination, reducing defect density and improving conductivity. Too little ZnCl can result in an insufficient number of Zn-N or Zn-O sites, resulting in poor catalytic activity. Excessive ZnCl leads to dominant semiconductor properties, hindering electron conduction and coating the metal particles.

[0042] As a preferred embodiment of the first aspect, the mass of zinc chloride in step (6) is 10-50 mg.

[0043] As a preferred embodiment of the first aspect, the calcination in step (7) specifically includes: calcining in a tubular furnace, a calcination temperature of 500-900°C, a calcination time of 30-180 min; and a calcination heating rate of 5°C / min.

[0044] In the second aspect, the present invention provides an iron-loaded graphene-like fiber rod catalyst prepared by the preparation method described in the first aspect. The catalyst has a graphene-like skeleton, and a plurality of iron nanoparticles are distributed on its surface, forming Fe-OC and / or Fe-NC bond bridge connections in the graphene-like structure.

[0045] The iron-supported graphene fiber rod catalyst prepared by the present invention is observed to be in the shape of a fiber rod through a scanning electron microscope (SEM), and many zero-valent iron nanoparticles are dispersed on the surface, accompanied by a small amount of chloroapatite.

[0046] In a third aspect, the present invention provides the use of the iron-loaded graphene fiber rod catalyst in degrading organic pollutants in wastewater.

[0047] As a preferred embodiment of the third aspect, the organic pollutants include bisphenol A (BPA), ciprofloxacin (CIP), ibuprofen (IBU), phenytoin (PHT), diphenhydramine (DP) and 2-chlorophenol (2-CP).

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] (1) The present invention uses biomass as raw material to prepare iron-loaded graphene-like catalysts, which have the advantages of low cost and excellent performance compared with catalysts previously prepared by artificially synthesizing high molecular weight polymer nanocomposites loaded with metals;

[0050] (2) The catalyst of the present invention can effectively remove organic pollutants in water without adding additional energy (such as H2O2) and under natural conditions;

[0051] (3) The catalyst of the present invention utilizes the internal Fe-π electrostatic force to transmit electrons at the interface, oxidizing and decomposing organic pollutants adsorbed on the catalyst surface, thereby reducing dissolved oxygen;

[0052] (4) The catalyst of the present invention does not dissolve metal during the reaction process, has good stability in the reaction process of removing organic pollutants, and does not produce solid foreign matter such as iron sludge, so no additional foreign matter removal device is required;

[0053] (5) The catalyst of the present invention is a solid catalyst that can be separated from water and is easy to recycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a scanning electron microscope (SEM) image of the Fe-FSC catalyst prepared in Example 2;

[0055] Figure 2 Transmission electron microscopy (TEM) images and high-resolution transmission electron microscopy (HR-TEM) images of the Fe-FSC catalyst prepared in Example 2, as well as a schematic diagram of elemental mapping analysis corresponding to the TEM images;

[0056] Figure 3 The XRD pattern of the Fe-FSC catalyst prepared in Example 2;

[0057] Figure 4 Schematic diagram of the Fe 2p XPS spectrum of the Fe-FSC catalyst prepared in Example 2;

[0058] Figure 5 This is a graph showing the evaluation results of the catalytic degradation activity of the Fe-FSC catalyst prepared in Example 2 for different organic pollutants;

[0059] Figure 6 This is a diagram showing the evaluation results of the recycling activity of the Fe-FSC catalyst prepared in Example 2 for the degradation of BPA. DETAILED DESCRIPTION

[0060] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0061] The information of the chemical substances of this invention is as follows:

[0062] Iron powder CAS number: 7439-89-6; melamine CAS number: 108-78-1; dimethylimidazole CAS number: 693-98-1; zinc nitrate hexahydrate CAS number: 10196-18-6; urea CAS number: 57-13-6; zinc chloride CAS number: 7646-85-7; ferric chloride hexahydrate CAS number: 10025-77-1; ferrous chloride tetrahydrate CAS number: 13478-10-9; eggshells were purchased from Ali Health Pharmacy Co., Ltd.; fish scales were purchased from Xianghe Seafood Co., Ltd.; shrimp shells were purchased from Fangnuoxiang Flagship Store Co., Ltd.; copper powder CAS number: 7440-50-8; thiourea CAS number: 62-56-6; pyrazole CAS number: 288-13-1; zinc powder CAS number: 7440-66-6.

[0063] Example 1

[0064] This embodiment provides a method for preparing an iron-supported graphene-like fiber rod catalyst, comprising the following steps:

[0065] (1) 2.5 g of eggshell was placed in 40 ml of 15 ppm sodium hydroxide solution and reacted in a 100°C water bath for 30 min to obtain solid product A; solid product A was repeatedly washed with deionized water, placed in an 80°C oven for 18 h, then placed in a 100°C oven for 4 h, and then ground uniformly;

[0066] Among them, the mass ratio of eggshell to sodium hydroxide solution is: 12500:3.

[0067] (2) The uniformly ground solid product A, 0.002 mol of iron powder, and 1 g of melamine were dispersed in 40 ml of anhydrous methanol solution and placed in a shaker for 6 h to obtain a suspension A;

[0068] The mass ratio of the solid product A, iron powder and melamine is 10:1:10.

[0069] (3) 3 g of dimethylimidazole and 1.5 g of zinc nitrate hexahydrate were added to 20 ml of anhydrous methanol and ultrasonicated to obtain suspension B;

[0070] The mass ratio of dimethylimidazole to zinc nitrate hexahydrate is 2:1.

[0071] (4) Suspension A and suspension B were mixed and stirred for 30 min to obtain suspension C;

[0072] The volume ratio of suspension A to suspension B is 2:1.

[0073] (5) 6 g of urea was added to suspension C, placed in a water bath at 80°C, stirred, and evaporated to dryness, and then placed in an oven at 80°C to dry to obtain solid product B;

[0074] The mass ratio of urea to suspension C is 3:2.

[0075] (6) Add 20 mg of zinc chloride to the evenly ground solid product B to obtain solid product C;

[0076] The mass ratio of the solid product B to zinc chloride is 250:1.

[0077] (7) The uniformly ground solid product C was placed in nitrogen gas and calcined in a tube furnace at a temperature of 800°C, a calcination time of 90 min, and a heating rate of 5°C / min. After natural cooling, the target catalyst was obtained by grinding and denoted as Fe-FSC catalyst.

[0078] (8) The cooled catalyst was washed alternately with deionized water and anhydrous ethanol for 3-4 times, and then vacuum dried at 60°C.

[0079] Example 2

[0080] This embodiment provides a method for preparing an iron-supported graphene-like fiber rod catalyst, comprising the following steps:

[0081] (1) 2.5 g of fish scales were placed in 40 ml of a 20 ppm sodium hydroxide solution and reacted in a 120°C water bath for 30 min to obtain a solid product A; the solid product A was repeatedly washed with deionized water, placed in an oven at 80°C for 18 h, then placed in an oven at 110°C for 2 h, and then ground uniformly;

[0082] Among them, the mass ratio of fish scales to sodium hydroxide solution is: 3125:1.

[0083] (2) The uniformly ground solid product A, 0.002 mol of ferric chloride hexahydrate, and 2 g of melamine were dispersed in 40 ml of anhydrous methanol solution and placed in a shaker for 6 h to obtain a suspension A;

[0084] The mass ratio of the solid product A, ferric chloride hexahydrate and melamine is 4:1:4.

[0085] (3) 3 g of dimethylimidazole and 1.5 g of zinc nitrate hexahydrate were added to 20 ml of anhydrous methanol and ultrasonicated to obtain suspension B;

[0086] The mass ratio of dimethylimidazole to zinc nitrate hexahydrate is 2:1.

[0087] (4) Suspension A and suspension B were mixed and stirred for 30 min to obtain suspension C;

[0088] The volume ratio of suspension A to suspension B is 2:1.

[0089] (5) 8 g of urea was added to suspension C, placed in a water bath at 80°C, stirred, and evaporated to dryness, and then placed in an oven at 60°C to dry to obtain solid product B;

[0090] The mass ratio of urea to suspension C is 2:1.

[0091] (6) Add 20 mg of zinc chloride to the evenly ground solid product B to obtain solid product C;

[0092] Wherein, the mass ratio of solid product B to zinc chloride is: 200:1.

[0093] (7) The uniformly ground solid product C was placed in nitrogen gas and calcined in a tube furnace at a calcination temperature of 900°C, a calcination time of 120 min, and a heating rate of 5°C / min. After natural cooling, the solid product C was ground to obtain the target catalyst;

[0094] (8) The cooled catalyst was washed alternately with deionized water and anhydrous ethanol for 3 to 4 times, and then vacuum dried at 60°C.

[0095] Example 3

[0096] This embodiment provides a method for preparing an iron-supported graphene-like fiber rod catalyst, comprising the following steps:

[0097] (1) 2.5 g of shrimp shells were placed in 40 ml of a 25 ppm sodium hydroxide solution and reacted in a 130°C water bath for 30 min to obtain a solid product A. The solid product A was repeatedly washed with deionized water, dried in a 60°C oven for 24 h, then dried in a 120°C oven for 2 h, and then ground uniformly.

[0098] The mass ratio of shrimp shell to sodium hydroxide solution is 2500:1.

[0099] (2) The uniformly ground solid product A, 0.002 mol of ferrous chloride tetrahydrate, and 2 g of melamine were dispersed in 50 ml of anhydrous methanol solution and placed in a shaker for 8 h to obtain a suspension A;

[0100] The mass ratio of the solid product A, ferrous chloride tetrahydrate and melamine is 5:1:5.

[0101] (3) 3 g of dimethylimidazole and 1.5 g of zinc nitrate hexahydrate were added to 20 ml of anhydrous methanol and ultrasonicated to obtain suspension B;

[0102] The mass ratio of dimethylimidazole to zinc nitrate hexahydrate is 2:1.

[0103] (4) Suspension A and suspension B were mixed and stirred for 30 min to obtain suspension C;

[0104] The volume ratio of suspension A to suspension B is 5:2.

[0105] (5) 8 g of urea was added to suspension C, placed in a water bath at 80°C, stirred, and evaporated to dryness, and then placed in an oven at 80°C to dry to obtain solid product B;

[0106] The mass ratio of urea to suspension C is 2:1.

[0107] (6) Add 20 mg of zinc chloride to the evenly ground solid product B to obtain solid product C;

[0108] The mass ratio of the solid product B to zinc chloride is 300:1.

[0109] (7) The uniformly ground solid product C was placed in nitrogen gas and calcined in a tube furnace at a calcination temperature of 700°C, a calcination time of 120 min, and a heating rate of 5°C / min. After natural cooling, the product was ground to obtain the target catalyst;

[0110] (8) The cooled catalyst was washed alternately with deionized water and anhydrous ethanol for 3 to 4 times, and then vacuum dried at 60°C.

[0111] Example 4

[0112] The difference between Example 4 and Example 1 is that in step (1), the mass ratio of eggshell to sodium hydroxide solution is 1000:1.

[0113] Example 5

[0114] The difference between Example 5 and Example 1 is that the staged drying method is not adopted in step (1). Specifically, the solid product A is repeatedly washed with deionized water, placed in an oven at 100° C. for 22 h, and then ground evenly.

[0115] Example 6

[0116] The difference between Example 6 and Example 1 is that in step (2), the mass ratio of solid product A, iron powder and melamine is 2:3:17.

[0117] Example 7

[0118] The difference between Example 7 and Example 1 is that in step (3), the mass ratio of dimethylimidazole to zinc nitrate hexahydrate is 5:1.

[0119] Example 8

[0120] The difference between Example 8 and Example 1 is that the mass ratio of urea to suspension C in step (5) is 5:1.

[0121] Example 9

[0122] The difference between Example 9 and Example 1 is that no secondary nitrogen doping is performed in step (5). Specifically, the suspension C is placed in a water bath at 80°C, stirred, and evaporated to dryness, and then placed in an oven at 80°C to dry to obtain a solid product B;

[0123] Example 10

[0124] The difference between Example 10 and Example 1 is that the urea in step (5) is replaced by an equal amount of melamine.

[0125] Example 11

[0126] The difference between Example 11 and Example 1 is that the mass ratio of solid product B to zinc chloride in step (6) is 400:1.

[0127] Comparative Example 1

[0128] The difference between Comparative Example 1 and Example 1 is that the egg shells in step (1) are replaced with an equal amount of calcium carbonate.

[0129] Comparative Example 2

[0130] The difference between Comparative Example 2 and Example 1 is that the iron powder in step (2) is replaced with an equal amount of copper powder.

[0131] Comparative Example 3

[0132] The difference between Comparative Example 3 and Example 1 is that the melamine in step (2) is replaced by an equal amount of thiourea.

[0133] Comparative Example 4

[0134] The difference between Comparative Example 4 and Example 1 is that the dimethylimidazole in step (3) is replaced by an equal amount of pyrazole.

[0135] Comparative Example 5

[0136] The difference between Comparative Example 5 and Example 1 is that the zinc chloride in step (6) is replaced by an equal amount of zinc powder.

[0137] Comparative Example 6

[0138] The difference between Comparative Example 6 and Example 1 is that anhydrous methanol is replaced with an equal amount of deionized water.

[0139] Comparative Example 7

[0140] The difference between Comparative Example 7 and Example 1 is that dimethylimidazole is missing in step (3), and the missing part is supplemented with an equal amount of water. The rest is the same as Example 1.

[0141] Comparative Example 8

[0142] The difference between Comparative Example 8 and Example 1 is that zinc nitrate hexahydrate is missing in step (3), and the missing part is supplemented with an equal amount of water. The rest is the same as Example 1.

[0143] Comparative Example 9

[0144] The difference between Comparative Example 9 and Example 1 is that zinc chloride is lacking in step (6), and the lacking part is supplemented with an equal amount of water. The rest is the same as Example 1.

[0145] Test Example 1: Testing the catalytic degradation performance of Fe-FSC catalyst

[0146] The Fe-FSC catalysts prepared in the examples and comparative examples were used to degrade organic pollutants in water. Specifically, 0.03 g of the prepared Fe-FSC catalyst was added to 50 mL of a 5 mg / L bisphenol A solution. The degradation reaction was initiated by continuous stirring at 35°C. Samples were taken within 120 minutes to measure the bisphenol A concentration. The results are shown in the following table:

[0147] Table 1

[0148]

[0149]

[0150] As shown in the above table, the Fe-FSC catalyst prepared by embodiment 1-3 has higher catalytic activity to organic pollutants. Embodiment 4 is due to the mass ratio of eggshell and sodium hydroxide solution not being within the scope of the present invention, embodiment 5 is due to not adopting the mode of segmented drying, affecting the structure of catalyst, embodiment 6 is due to the mass ratio of solid product A, iron powder and melamine not being within the scope of the present invention, embodiment 7 dimethylimidazole and the mass ratio of zinc nitrate hexahydrate not being within the scope of the present invention, embodiment 8 urea and the mass ratio of suspension C not being within the scope of the present invention, embodiment 9 step (5) does not carry out secondary nitrogen doping, embodiment 10 urea is changed into the melamine of equal amount, embodiment 11 is due to the mass ratio of solid product B and zinc chloride not being within the scope of the present invention, all weakened the performance of catalyst of the present invention. Comparative Examples 1-6, due to replacing the composition of catalyst of the present invention with other components, cause the catalytic performance of catalyst to reduce, comparative examples 7-9, due to lacking the composition of catalyst of the present invention, cause the catalytic performance of catalyst to reduce. It can be seen that the component for preparing Fe-FSC catalyst of the present invention has synergistic effect, if replacing and lacking one of them, then can destroy the structure of catalyst and thus affect catalytic activity.

[0151] Test Example 2: Testing the stability of Fe-FSC catalyst

[0152] The Fe-FSC catalysts prepared in the examples and comparative examples were used to degrade organic pollutants in water, respectively, and their stability was tested. The specific method included the following steps:

[0153] (1) 0.03 g of the Fe-FSC catalysts of the examples and comparative examples were added to 50 mL of a 5 mg / L bisphenol A solution and continuously stirred in a water bath at 35° C. to initiate the degradation reaction.

[0154] (2) After 2 h of reaction, the concentration of bisphenol A was measured;

[0155] (3) After the Fe-FSC catalyst in step (2) was separated and dried, the catalyst was taken and steps (1 to 3) were repeated 6 times. The results are shown in Table 2.

[0156] Table 2

[0157]

[0158]

[0159] As shown in the above table, the stability of the Fe-FSC catalyst obtained by embodiment 1-3 is better. Example 4 is due to the mass ratio of egg shell and sodium hydroxide solution not being within the scope of the present invention, embodiment 5 is due to not adopting the mode of segmented drying, affecting the structure of catalyst, embodiment 6 is due to the mass ratio of solid product A, iron powder and melamine not being within the scope of the present invention, embodiment 7 dimethylimidazole and zinc nitrate hexahydrate mass ratio not being within the scope of the present invention, embodiment 8 urea and the mass ratio of suspension C not being within the scope of the present invention, embodiment 9 step (5) is not carried out secondary nitrogen doping, embodiment 10 urea is changed into equal amount of melamine, embodiment 11 is due to the mass ratio of solid product B and zinc chloride not being within the scope of the present invention, all weakened the performance of catalyst of the present invention. Comparative Examples 1-6 are due to replacing the composition of catalyst of the present invention with other components, resulting in reduced stability of catalyst. Comparative Examples 7-9 are due to lacking the composition of catalyst of the present invention, resulting in reduced stability of catalyst. It can be seen that the component for preparing Fe-FSC catalyst of the present invention produces synergistic effect, if replaced and lacking one of them, the structure of catalyst can be destroyed so as to affect its stability.

[0160] Test Example 3: Characterization of Fe-FSC Catalyst

[0161] From Tables 1 and 2, it can be seen that the catalytic performance of the Fe-FSC catalyst prepared in Example 2 is the best, and characterization is carried out. The characterization results are as follows:

[0162] Depend on Figure 1 It can be seen that the catalyst of Example 2 has a fiber rod shape, and many nanoparticles are observed to be dispersed on the surface of the fiber rod.

[0163] Depend on Figure 2 From the TEM image, HR-TEM image and the element mapping analysis corresponding to the TEM image, it can be seen that many nanoparticles are highly dispersed on the surface of the fiber rods of the Fe-FSC catalyst in Example 1. Further high-resolution transmission electron microscopy and corresponding element mapping analysis can be determined that the fiber rods formed by biomass after calcination have a graphene-like structure, and zero-valent iron nanoparticles are highly dispersed on the surface, accompanied by a small amount of chloroapatite.

[0164] Depend on Figure 3 The XRD pattern analysis shows that in addition to the characteristic peak of chlorapatite, the Fe-FSC catalyst of Example 2 also has an obvious 002 crystal plane graphene-like structure characteristic peak at 26.2°, and the Fe 0 , Fe2O3, Fe3O4, Fe3C, Fe7C3.

[0165] Depend on Figure 4 The XPS spectrum of Fe 0 、Fe 2+ 、Fe 3+ existence.

[0166] The above results show that the structure of the Fe-FSC catalyst is a graphene-like structure supported by iron nanoparticles.

[0167] Test Example 4: The catalytic degradation performance and stability of the Fe-FSC catalyst prepared in Example 2 on other organic pollutants were tested. The specific steps are as follows:

[0168] 0.03 g of the prepared Fe-FSC catalyst was added into 50 mL of 5 mg / L bisphenol A solution, ciprofloxacin solution, ibuprofen solution, phenytoin solution, diphenhydramine solution and 2-chlorophenol solution, respectively. The degradation reaction was started by continuous stirring at 35 °C, and samples were taken at different time points to determine the pollutant concentration.

[0169] The results are as follows Figure 5 As shown in the figure, after 60 minutes of reaction, the Fe-FSC catalyst achieved almost 100% degradation of BPA and ICP. Within 120 minutes, the degradation rates of 2-CP, DP, PHT, and IBU were 83.4%, 77.4%, 56.0%, and 59.9%, respectively. The degradation of various organic pollutants was substantial within 120 minutes, demonstrating the Fe-FSC catalyst's strong catalytic activity and high adaptability to pollutants.

[0170] The results are as follows Figure 6As shown in the figure, it can be observed that the efficiency of the Fe-FSC catalyst in degrading bisphenol A did not decrease significantly after continuous cycling. In all six repeated experiments, the removal efficiency reached over 85%. These results fully demonstrate the stability advantage of the Fe-FSC catalyst in Example 2 and its applicability to the treatment of actual slightly polluted water bodies.

[0171] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing an iron-supported graphene fiber rod catalyst, characterized in that: The preparation method comprises the following steps: (1) placing biomass in an alkaline solution for thermal reaction to obtain a solid product A, and drying and grinding the solid product A; (2) dispersing the ground solid product A, the iron source, and melamine in an organic solvent to obtain a suspension A; (3) adding dimethylimidazole and a zinc source to the organic solution to obtain a suspension B; (4) mixing suspension A and suspension B to obtain suspension C; (5) adding a nitrogen source to the suspension C and drying it to obtain a solid product B; (6) grinding the solid product B and adding zinc chloride to obtain a solid product C; (7) The solid product C is ground and calcined to obtain the iron-supported graphene fiber rod catalyst.

2. The preparation method according to claim 1, wherein The mass ratio of biomass to alkaline solution in step (1) is: (2000-13000): (1-3).

3. The preparation method according to claim 1, wherein The step (1) of drying the solid product A specifically includes: a first stage drying temperature of 60-80°C and a drying time of 12-24 hours; a second stage drying temperature of 100-120°C and a drying time of 2-4 hours.

4. The preparation method according to claim 1, wherein In the step (2), the mass ratio of the solid product A, the iron source and the melamine is (4-10):1:(4-10).

5. The preparation method according to claim 1, wherein The mass ratio of dimethylimidazole to zinc source in step (3) is: (1-3):

1.

6. The preparation method according to claim 1, wherein The mass ratio of the nitrogen source to the suspension C in step (5) is: (2-3): (1-2).

7. The preparation method according to claim 1, wherein The mass ratio of the solid product B to zinc chloride in the step (6) is 250:

1.

8. The preparation method according to claim 1, wherein The calcination in step (7) specifically includes: a calcination temperature of 500-900° C. and a calcination time of 30-180 min.

9. A catalyst of iron-supported graphene-like fiber rods prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The catalyst uses a graphene-like structure as a skeleton, with a plurality of iron nanoparticles distributed on the surface thereof, and Fe-OC and / or Fe-NC bond bridges are formed in the graphene-like structure.

10. Use of the iron-supported graphene fiber rod catalyst according to claim 9 in degrading organic pollutants in wastewater.

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