Iron-nitrogen co-doped carbon material for phenol adsorption and catalytic degradation, and preparation method and application thereof

Abstract

This invention discloses an iron-nitrogen co-doped carbon material for the adsorption and catalytic degradation of phenol, its preparation method, and its applications. The preparation method includes the following steps: using grapefruit peel as raw material, the material undergoes oxidation, pre-amidation, metal-organic framework loading, inert atmosphere calcination, and activation to obtain the iron-nitrogen co-doped carbon material. This method is economical and environmentally friendly. The prepared material has a hierarchical pore structure and a nitrogen-rich structure, with a specific surface area of ​​365.35 m² / g. The pore size matches the phenol molecule, resulting in rapid mass transfer. The iron-nitrogen co-doped carbon material can achieve a saturated adsorption capacity of 186.6 mg / g for phenol and can catalytically degrade phenol through its stable Fe-N active sites, realizing integrated "adsorption-degradation" and avoiding secondary treatment. The material has a stable structure, is resistant to acids and alkalis, and maintains a high adsorption capacity even after multiple cycles, making it suitable for the efficient treatment of phenol-containing wastewater.

Description

Technical Field

[0001] This invention relates to the field of functional materials for adsorption and catalytic degradation, and in particular to an iron-nitrogen co-doped carbon material for the adsorption and catalytic degradation of phenol, its preparation method, and its application. Background Technology

[0002] With the rapid pace of industrialization and urbanization, industries such as petrochemicals, pharmaceuticals, dyes, pesticides, resins, and coal chemicals have developed rapidly, resulting in the discharge of large amounts of phenol-containing wastewater into the environment and causing serious water pollution problems. Phenolic compounds are a typical class of organic pollutants, characterized by high toxicity, difficulty in degradation, and easy accumulation. Phenol, as one of the most basic and widely used phenolic substances, is widely found in wastewater from oil refining, coking, papermaking, synthetic resin, and pharmaceutical industries. It has significant irritant and toxic effects on human skin, eyes, and central nervous system. Long-term exposure can cause headaches, difficulty breathing, and even organ damage, and it has been listed as one of the key controlled organic pollutants.

[0003] Currently, the main technologies for treating phenol wastewater include adsorption, chemical oxidation, biodegradation, electrochemical oxidation, ozone oxidation, and photocatalysis. Among these, adsorption is considered one of the most promising methods for industrial application due to its advantages such as simple operation, high treatment efficiency, low secondary pollution, and wide applicability. However, traditional adsorption materials such as activated carbon, molecular sieves, and resins have problems such as limited adsorption capacity, poor selectivity, insufficient regeneration performance, and high cost, making it difficult to meet the requirements for efficient removal of phenol from high-concentration or complex systems.

[0004] In recent years, metal-organic frameworks (MOFs) have attracted widespread attention in the field of organic pollutant adsorption due to their advantages such as large specific surface area, tunable pore structure, and abundant active sites. For example, MOF materials such as the MIL series and UiO series have shown certain advantages in adsorbing phenolic compounds, but they generally suffer from problems such as insufficient water stability, easy pulverization, high cost, and limited practical applications.

[0005] On the other hand, relying solely on adsorption technology is insufficient for the complete removal of phenol; further treatment is still required after adsorption saturation. Therefore, combining adsorption with catalytic degradation is considered a more promising solution. Transition metals, represented by iron, are widely used in Fenton or Fenton-like reactions for the catalytic oxidative degradation of organic pollutants due to their variable valence state, strong redox capabilities, and low cost. However, traditional Fenton systems suffer from drawbacks such as a narrow pH range, easy loss of iron ions, and severe secondary pollution, limiting their practical application.

[0006] In recent years, researchers have increasingly combined metals with carbon materials to construct metal-nitrogen co-doped carbon-based materials (M–N–C) to improve the dispersion and stability of metal active sites, thereby enhancing their catalytic performance. These materials combine the excellent conductivity, stability, and porous structure of carbon materials with the catalytic ability of metal active centers, showing promising application potential in the degradation of organic pollutants. However, existing M–N–C materials mostly use commercial carbon sources, resulting in high preparation costs, complex processes, and significant environmental burdens. Furthermore, their adsorption capacity for small-molecule phenols such as phenol remains limited.

[0007] Biomass materials, as a widely available, renewable, and inexpensive natural resource, have been increasingly incorporated into the construction of functional materials in recent years. Fruit peels, straw, and sawdust, among other biomass materials, are rich in oxygen-containing functional groups such as hydroxyl and carboxyl groups, exhibiting excellent chemical modifiability and making them ideal precursors for preparing biomass-derived carbon materials. However, existing biomass-derived carbon materials often suffer from underdeveloped pore structures, insufficient active sites, and limited functionality, making it difficult to simultaneously achieve both efficient adsorption and catalytic degradation.

[0008] Therefore, how to construct a composite material with both high efficiency in phenol adsorption and excellent catalytic degradation performance using low-cost biomass as raw material and through reasonable structural design and chemical modification, so as to achieve integrated "adsorption-degradation" treatment of phenol, remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] This invention provides an iron-nitrogen co-doped carbon material for phenol adsorption and catalytic degradation, its preparation method, and its application, to overcome the above-mentioned problems.

[0010] To achieve the above objectives, the technical solution of the present invention is as follows: This invention provides a method for preparing an iron-nitrogen co-doped carbon material for phenol adsorption and catalytic degradation, comprising the following steps: Step 1: Cut the biomass grapefruit peel into pieces, clean it alternately with deionized water and anhydrous ethanol using ultrasonic cleaning, and then freeze-dry it; immerse the cleaned grapefruit peel in an oxidizing agent solution, heat it in a water bath, and quench the reaction with anhydrous ethanol after the reaction is completed. Wash the resulting solid with deionized water and freeze-dry it to obtain oxidized grapefruit peel. Step 2: Place the oxidized grapefruit peel in the first solvent and heat it in a water bath at 60°C for 4-12 hours to achieve the pre-amidation reaction and obtain the pre-amidated product; Step 3: Pour the second solvent into the preamidated product and hydrothermally react at 90~150℃ for 2~48 hours. The resulting product is washed several times with N,N-dimethylformamide solvent and ethanol and dried to obtain grapefruit peel supported by metal-organic framework. Step 4: Place the grapefruit peel loaded with the metal-organic framework in a tube furnace and calcine it under an inert atmosphere. After calcination, wash the resulting solid several times with anhydrous ethanol and then dry it to obtain the grapefruit-derived metal-organic framework carbon material. Step 5: The metal-organic framework grapefruit-derived carbon material is immersed in an activation solution, dried, and then heated and activated in an inert atmosphere in a tube furnace. After activation, the resulting solid is washed with anhydrous ethanol until the pH is neutral, and then dried to obtain the iron-nitrogen co-doped carbon material used for phenol adsorption and catalytic degradation.

[0011] Furthermore, in step one, the oxidant solution is a 10% H2O2 and 0.5 mmol / L FeSO4 solution, and is adjusted to an acidic condition of pH=3~5 with H2SO4.

[0012] Furthermore, in step two, the first solvent is obtained by dissolving 2-aminoterephthalic acid in N,N-dimethylformamide solvent and stirring. The molar ratio of grapefruit peel to 2-aminoterephthalic acid is 1 g: 2-4 mmol; preferably 1 g: 3 mmol.

[0013] Furthermore, in step three, the second solvent is prepared by dissolving ferric chloride hexahydrate in tetrahydrofuran solvent and mixing and stirring, wherein the molar ratio of ferric chloride hexahydrate to 2-aminoterephthalic acid is (0.5~3):1; preferably 1.25:1.

[0014] Furthermore, in step five, the activation solution is a KOH solution, and the mass ratio of the metal-organic framework grapefruit-derived carbon material to KOH is 1:(1~5), preferably 1:3.

[0015] Furthermore, in step four, the calcination temperature is 400~800℃, and the calcination time is 2~4h.

[0016] Furthermore, in step five, the activation temperature is 400~800℃, and the activation time is 2~4h.

[0017] In another aspect, the present invention provides an iron-nitrogen co-doped carbon material for the adsorption and catalytic degradation of phenol, prepared according to the preparation method described above.

[0018] In another aspect, this invention provides the application of an iron-nitrogen co-doped carbon material for phenol adsorption in an absorption solution of phenol. During the absorption of phenol from the solution, the iron-nitrogen co-doped carbon material acts as an adsorbent; the pH of the solution containing phenol is 3-13; the concentration of phenol in the solution is 10-500 mg / L; the amount of iron-nitrogen co-doped carbon material added is 10-45 mg, preferably 30 mg; the temperature is 25-55℃, preferably 55℃; and the time is 10 min-48 h.

[0019] In another aspect, this invention provides the application of the iron-nitrogen co-doped carbon material for phenol adsorption in the degradation of phenol. During the degradation of phenol, the iron-nitrogen co-doped carbon material acts as a catalyst, and H2O2 is added to the degradation solution. The concentration of H2O2 added is 15-45 mL / L, the initial concentration of phenol in the degradation solution is 10-500 mg / L, the amount of iron-nitrogen co-doped carbon material added is 10-40 mg, the temperature is 25-55℃, preferably 55℃, and the time is 10 min-6 h.

[0020] The beneficial effects of this invention are: I. This method uses biomass grapefruit peel as a matrix and constructs iron-nitrogen co-doped porous carbon materials through steps such as oxidation modification, pre-amidation, metal-organic framework loading and calcination activation. It makes full use of the advantages of biomass resources, such as wide availability, low cost and high renewability, and achieves precise construction of functional structure while reducing the material preparation cost. It has significant economic and environmental benefits. II. This method introduces carboxyl groups onto the biomass framework and increases nitrogen doping content through pre-amidation, constructing a nitrogen-rich structure and a hierarchical porous system. This significantly enhances the hydrogen bonding, electrostatic interactions, and π–π interactions of phenol, achieving efficient enrichment and stable adsorption of phenol. The saturated adsorption capacity of the material prepared by this invention for phenol can reach 186.6 mg / g, which is significantly better than existing ordinary activated carbon and some MOF-type adsorbents, solving the problem of low phenol adsorption capacity in existing technologies. III. This method utilizes a metal-organic framework derivatization strategy to construct stable and dispersed Fe–N active sites in situ within a carbon matrix, avoiding the problems of metal particle aggregation and loss, and improving the utilization and stability of the metal active centers. The resulting iron-nitrogen structure can serve as a highly efficient catalytic active center, initiating Fenton-like reactions or peroxidation reactions under mild conditions to achieve rapid activation and bond-breaking degradation of phenol. IV. This method integrates adsorption enrichment and catalytic degradation functions into the same material system. During the adsorption stage, phenol is efficiently enriched on the material surface and within the pores. In the catalytic stage, the enriched phenol undergoes in-situ conversion, avoiding the need for secondary treatment after saturation of traditional adsorption materials. This achieves an integrated adsorption-degradation treatment pathway. Experimental results show that the material of this invention can completely degrade phenol, significantly improving the thoroughness and efficiency of phenol removal.

[0021] V. The iron-nitrogen co-doped carbon material prepared by this method has the advantages of stable structure, acid and alkali resistance, and good recyclability. It can still maintain a high adsorption capacity after multiple cycles, which solves the problems of easy deactivation and poor reusability of some existing adsorption materials, and has good prospects for engineering applications.

[0022] VI. The specific surface area of ​​the material prepared by this method reaches 365.35 m². 2 With an average pore size of 3.39 nm, which is well matched to the diameter of phenol molecules, the presence of both micropores and mesopores results in low mass transfer resistance, which facilitates the rapid entry of phenol molecules into the pores and their full contact with the active sites. This significantly improves the adsorption rate and catalytic reaction kinetics, making it suitable for the efficient treatment of high-concentration phenol wastewater and complex aquatic environments. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 SEM image of the iron-nitrogen co-doped carbon material prepared in an embodiment of the present invention; Figure 2 Here is a characterization diagram of the pore structure of the iron-nitrogen co-doped carbon material prepared in an embodiment of the present invention, wherein... Figure 2 a is the N2 adsorption-desorption curve. Figure 2 b is the aperture distribution diagram; Figure 3 The figures shown are characterization diagrams of the composition and thermal stability of the iron-nitrogen co-doped carbon material prepared in the embodiments of the present invention. Figure 3 a is the FT-IR spectrum. Figure 3 b is the thermogravimetric (TG) curve; Figure 4 The above are characterization diagrams of the adsorption and recycling performance of the iron-nitrogen co-doped carbon material prepared in the embodiments of the present invention. Figure 4 a represents the dynamic adsorption curves under different material dosages. Figure 4 b is the dynamic adsorption curve at different initial phenol concentrations. Figure 4 c shows the dynamic adsorption curves at different temperatures, and d shows the Zeta potentials of the material and phenol at different pH values. Figure 4 e is a bar chart showing the saturated adsorption capacity of the material at different pH values. Figure 4 f is a bar chart of the cyclic adsorption efficiency of the material when using different eluents; Figure 5 The figure shows the characterization of the catalytic degradation performance of the iron-nitrogen co-doped carbon material prepared in the embodiments of the present invention. Figure 5 a represents the dynamic degradation curves under different material dosages. Figure 5 b is the dynamic degradation curve at different initial phenol concentrations. Figure 5c represents the dynamic degradation curves under different H2O2 addition concentrations. Figure 5 d represents the dynamic degradation curves at different temperatures; Figure 6 The graph shows the intensity variation of the absorption spectrum of the iron-nitrogen co-doped carbon material prepared in this embodiment of the invention when the mass is 15 mg, the initial concentration of phenol is 100 mg / L, and the concentration of H2O2 added is 25 mL / L. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example: The preparation method of the iron-nitrogen co-doped carbon material for phenol adsorption and catalytic degradation in this embodiment is carried out according to the following steps: S1: Carboxylation modification of grapefruit peel Fresh grapefruit peel was thoroughly washed with deionized water to remove surface impurities, dried, and cut into 2×2 cm pieces. These pieces were then placed in an oxidizing agent solution for carboxylation modification. The oxidizing agent solution was a mixture of 10% H2O2 and 0.5 mmol / L FeSO4, and the solution was adjusted to acidic conditions (pH=3) using H2SO4. After stirring at room temperature or 60 °C for 6 h, the peel was repeatedly washed with deionized water until neutral, and then freeze-dried to obtain oxidized grapefruit peel. S2: Preamidation modification of grapefruit peel The oxidized grapefruit peel obtained in step S1 was placed in a 2-aminoterephthalic acid solution and heated in a water bath to achieve pre-amidation modification of the grapefruit peel surface. The 2-aminoterephthalic acid solution was prepared by dissolving 2-aminoterephthalic acid in N,N-dimethylformamide (DMF) and stirring. The ratio of grapefruit peel to 2-aminoterephthalic acid was 1 g : 3 mmol. The reaction temperature was controlled at 90 °C, and the reaction time was 6 h. After the reaction, the peel was washed with deionized water and ethanol and dried to obtain the pre-amidated grapefruit peel. S3: In-situ growth load of MIL-101-NH2(Fe) The pre-amidated grapefruit peel obtained in step S2 was dispersed in a ferric chloride hexahydrate solution, mixed thoroughly, and then transferred to a polytetrafluoroethylene-lined hydrothermal reactor for hydrothermal reaction to synthesize and load MIL-101-NH2(Fe) on the grapefruit peel surface in situ. The ferric chloride hexahydrate solution was prepared by dissolving FeCl3·6H2O in tetrahydrofuran (THF), with a molar ratio of FeCl3·6H2O to 2-aminoterephthalic acid of 1.25:1. The hydrothermal reaction temperature was 120℃, and the reaction time was 12 h. After the reaction, the grapefruit peel was washed with DMF and ethanol and dried to obtain a metal-organic framework-loaded grapefruit peel.

[0027] S4: Calcination and carbonization treatment The grapefruit peel loaded with the metal-organic framework obtained in step S3 was placed in a tube furnace and calcined under a N2 protective atmosphere. The heating rate was 5℃ / min, the calcination temperature was controlled at 800℃, and the temperature was held for 2 hours. After naturally cooling to room temperature, the grapefruit-derived metal-organic framework carbon material was obtained.

[0028] S5: Alkali activation treatment (pore structure regulation and active site exposure) The metal-organic framework (MOF) grapefruit-derived carbon material obtained in step S4 was immersed in a KOH activation solution, wherein the mass ratio of MOF grapefruit-derived carbon material to KOH was 1:3. After stirring and immersion for 12 hours, the material was removed, dried, and then calcined again in a tube furnace at 800°C for 2 hours under a nitrogen atmosphere. After calcination, the material was repeatedly washed with dilute hydrochloric acid and deionized water until neutral. After drying, the iron-nitrogen co-doped biomass-derived carbon material was finally obtained, which is used for the adsorption and catalytic degradation of phenol.

[0029] (1) SEM image analysis of iron-nitrogen co-doped biomass-derived carbon materials This invention characterizes the basic structure of iron-nitrogen co-doped biomass-derived carbon materials using scanning electron microscopy (SEM). The surface morphology and structure of the iron-nitrogen co-doped biomass-derived carbon materials were observed at the 20 μm, 1 μm, and 200 nm scales using SEM.

[0030] like Figure 1 As shown, the iron-nitrogen co-doped biomass-derived carbon material prepared by this invention exhibits a three-dimensional network morphology combining a hierarchical porous structure and nanosheets. Under low magnification, it can be observed that the material as a whole maintains the original honeycomb-like three-dimensional interconnected porous framework structure of biomass, with uniform pore distribution and continuous pore walls, which is conducive to the rapid diffusion and mass transfer of target pollutants in solution into the interior of the material.

[0031] Under medium magnification, a large number of hollow tubular channel structures can be seen inside the material. These structures are derived from the retention and reconstruction of the biomass vascular bundles. The surface of the tube wall is rough and uniformly distributed with fine granular protrusions, indicating that the metal components are well anchored on the carbon skeleton surface, which is conducive to the stable existence of subsequent catalytic active centers.

[0032] Under high magnification, it can be further observed that the material surface is covered with a large number of wrinkled nanosheet structures. The nanosheets are stacked in an interlaced manner to form flower-shaped clusters, creating a rich microporous and mesoporous structure, which significantly increases the specific surface area and the degree of exposure of active sites of the material.

[0033] The synergistic effect of the hierarchical porous structure and the nanosheet structure enables the material of this invention to simultaneously possess excellent mass transfer performance, high specific surface area, and abundant Fe–N active sites, thereby exhibiting good adsorption capacity and catalytic activity in the adsorption and catalytic degradation of phenol organic pollutants.

[0034] (2) Analysis of N2 adsorption-desorption curves and pore size distribution of iron-nitrogen co-doped biomass-derived carbon materials As can be seen from the nitrogen adsorption-desorption test, such as Figure 2 As shown in Figure a, the isothermal adsorption curves of the iron-nitrogen co-doped biomass-derived carbon material prepared in this invention exhibit a combination of Type I and Type IV characteristics, indicating that it simultaneously constructs microporous and mesoporous structures, forming a stable hierarchical porous system. The rapid adsorption characteristics in the low relative pressure region indicate that the material is rich in micropores. This microporous structure provides a large number of high-energy adsorption sites for phenol molecules, which is crucial for achieving a high specific surface area (365.35 m²). 2 The key structural basis for high adsorption capacity ( / g) and high adsorption capacity; the obvious hysteresis loops appearing in the medium-to-high relative pressure region indicate the existence of a continuous mesoporous structure in the material. For example... Figure 2 As shown in b, the BJH pore size distribution results further confirm that the mesopores are mainly concentrated in the range of approximately 3.39 nm. The hierarchical pore structure described above has a clear causal relationship with the high-efficiency phenol adsorption performance, and is one of the key technical features of the material of this invention that enables high adsorption capacity and rapid kinetic behavior.

[0035] (3) Analysis of the infrared spectrum of iron-nitrogen co-doped biomass-derived carbon materials The iron-nitrogen co-doped carbon material obtained in Example 1 for phenol adsorption and catalytic degradation was characterized by Fourier transform infrared spectroscopy. The resulting infrared spectrum is shown in the figure below. Figure 3 As shown in a. From Figure 3 a shows that at 3487 cm -1 A distinct –OH stretching vibration absorption peak appears at 1640 cm⁻¹, indicating the introduction of abundant hydroxyl functional groups on the material surface; -1and 1620cm -1 The presence of characteristic absorption peaks for C=O and C=C / C=N at 1382 cm⁻¹ indicates the formation of an aromatic carbon framework structure and the successful introduction of a nitrogen-containing structure, achieving nitrogen doping. -1 The absorption peak at 540 cm⁻¹ is attributed to the C–N stretching vibration, further confirming the successful incorporation of nitrogen into the carbon framework. Furthermore, at 540 cm⁻¹... -1 and 520 cm -1 Characteristic vibrational peaks of Fe–O and Fe–N can be observed at this point, indicating that iron forms a stable coordination structure with oxygen and nitrogen. After KOH activation treatment, the original low-frequency vibrational peaks merge and converge towards approximately 470 cm⁻¹. -1 The displacement indicates that the iron coordination environment has been restructured, forming a more homogeneous and stable Fe–N group. x Active sites. The above results demonstrate that this invention successfully constructed an iron-nitrogen co-doped carbon material structure rich in hydroxyl groups, nitrogen-rich functional groups, and a stable Fe–N structure, providing a structural basis for the efficient adsorption and catalytic degradation of phenol.

[0036] (4) Thermogravimetric analysis of iron-nitrogen co-doped biomass-derived carbon materials The thermal stability of the iron-nitrogen co-doped carbon material prepared in this embodiment was characterized by thermogravimetric analysis (TGA), and the obtained thermogravimetric curves are shown below. Figure 3 As shown in figure b, the iron-nitrogen co-doped carbon material maintains a high residual mass even at higher temperatures, indicating good thermal stability. This demonstrates that the nitrogen-doped conjugated carbon framework structure formed after metal-organic framework derivatization and amidation modification effectively enhances the material's thermal stability. Simultaneously, a significant thermogravimetric process occurs in the 325–478℃ temperature range, indicating the introduction of numerous oxygen-containing functional groups on the material surface, which decompose during heating. The introduction of these oxygen-containing functional groups enhances the hydrogen bonding interaction between the material and phenol molecules, providing a favorable structural basis for the efficient adsorption of phenol.

[0037] Example 2: Adsorption performance test and results of iron-nitrogen co-doped biomass-derived carbon materials The iron-nitrogen co-doped carbon material prepared in Example 1 for the adsorption and catalytic degradation of phenol was used to adsorb phenol. The specific experimental procedure is as follows: Step 1: Prepare phenol solutions with concentrations of 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, 70 mg / L, 80 mg / L, 90 mg / L, 100 mg / L, 200 mg / L, 300 mg / L, 400 mg / L, and 500 mg / L, respectively. Measure the liquid chromatography of the above phenol solutions and record the peak area of ​​the standard solution at an emission wavelength of 270 nm. Plot a linear relationship between phenol concentration and response value with peak area as the ordinate and phenol concentration as the abscissa. Step 2: Take the test solution containing phenol and measure the response peak area at an emission wavelength of 270 nm. The peak area is recorded as S0. Step 3: Find the phenol concentration corresponding to S0 on the standard curve and record it as the initial phenol concentration c0 in the test solution; Step 4: Add a mass of m iron-nitrogen co-doped carbon material for phenol adsorption to a volume V of the phenol-containing test solution. Adsorb for 48 hours. During the adsorption process, filter out the iron-nitrogen co-doped carbon material using a disposable syringe and needle filter. Perform chromatographic detection on the filtrate at an emission wavelength of 270 nm and record the response peak area S. t ; Step 5: Find the curve with respect to S on the standard curve. t The corresponding phenol concentration is denoted as c, the concentration of phenol at time t. t ; Step 6: According to formula q t =V(c0-c t The adsorption capacity of phenol by the iron-nitrogen co-doped carbon material used for phenol adsorption is calculated as q / m, where q t q e The values ​​represent the time t and equilibrium adsorption capacity of phenol by the iron-nitrogen co-doped carbon material used for phenol adsorption, in mg / g; V represents the volume of the phenol-containing test solution in step four, in L; c0 represents the initial concentration in step three, in mg / L; ct represents the equilibrium concentration of phenol in step five, in mg / L; and m represents the mass of the iron-nitrogen co-doped carbon material used for phenol adsorption in step four, in g.

[0038] (1) Dynamic adsorption test of iron-nitrogen co-doped carbon material at different feed masses 1. Prepare a phenol solution with a concentration of 100 mg / L (pH=7). Take 1.5 mL of the phenol solution and measure the peak area of ​​the phenol solution in liquid chromatography at an excitation wavelength of 270 nm. Record it as S0. Determine the corresponding initial concentration of phenol c0 through the standard curve. 2. Add 10 mg, 15 mg, 25 mg, 35 mg and 45 mg of iron-nitrogen co-doped carbon material to the phenol solution respectively, disperse evenly and place in a constant temperature shaker at 25℃; take samples once after stirring for 10 min, 20 min, 30 min, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 12 h, 24 h and 48 h respectively, filter with a 25 μm filter membrane to remove the iron-nitrogen co-doped carbon material used for phenol adsorption, and obtain phenol solutions with different adsorption times; III. For the determination of phenol solution by liquid chromatography, using 270 nm as the excitation wavelength, the peak area of ​​the phenol solution is measured and denoted as S. t The initial phenol concentration c was determined using a standard curve. t ; IV. Calculate the adsorption capacity of the iron-nitrogen co-doped carbon material for phenol adsorption using the formula in step 6, in mg / g. Obtain the dynamic adsorption curves of the iron-nitrogen co-doped carbon material at different dosage masses, as shown below. Figure 4 As shown in Figure a, when the adsorbent mass increases from 10 mg to 30 mg, the adsorption capacity Q per unit mass increases. e The increase from 168.67 to 199.72 mg / g indicates that more active sites are involved in adsorption. However, when further increased to 40 mg, Q... e The concentration dropped to 180.98 mg / g, indicating that the solute in the system was nearly completely adsorbed. Excess adsorbent reduced the amount of solute allocated per unit mass. Lower dosages provide ample active sites and a large concentration gradient, which is beneficial for adsorption. Conversely, higher dosages reduce the amount of solute allocated to each unit of adsorbent, leading to a decrease in Q. e decline.

[0039] (2) Dynamic adsorption test of iron-nitrogen co-doped carbon material at different initial phenol concentrations 1. Prepare phenol solutions with concentrations of 50 mg / L, 100 mg / L, 200 mg / L, 300 mg / L, 400 mg / L, and 500 mg / L (pH=7). Take 1.5 mL of phenol solution and measure the peak area of ​​the phenol solution in liquid chromatography at an excitation wavelength of 270 nm. Record this peak area as S0. Determine the corresponding initial concentration of phenol, c0, through a standard curve. 2. Add 15 mg of iron-nitrogen co-doped carbon material to the phenol solution, disperse it evenly, and place it in a constant temperature shaker at 25℃. Take samples after stirring for 10 min, 20 min, 30 min, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 12 h, 24 h, and 48 h, respectively. Filter the solution with a 25 μm filter membrane to remove the iron-nitrogen co-doped carbon material used for phenol adsorption, and obtain phenol solutions with different adsorption times. III. For the determination of phenol solution by liquid chromatography, using 270 nm as the excitation wavelength, the peak area of ​​the phenol solution is measured and denoted as S. t The initial phenol concentration c was determined using a standard curve. t ; 4. Calculate the adsorption capacity of the iron-nitrogen co-doped carbon material for phenol adsorption according to the formula in step 6, in mg / g, and obtain the dynamic adsorption curves of the iron-nitrogen co-doped carbon material at different initial phenol concentrations. Figure 4 b. Adsorption kinetics curves of the iron-nitrogen co-doped biomass-derived carbon material prepared in this invention under different initial concentrations of phenol solution (50–500 mg / L). As shown in the figure, under all initial concentrations, the material exhibits rapid adsorption and high saturation adsorption capacity for phenol. The adsorption rate is relatively fast in the initial stage of the reaction, then gradually slows down and reaches adsorption equilibrium, indicating that the material has good mass transfer performance and stable adsorption behavior. With the increase of the initial phenol concentration, the saturation adsorption capacity of the material increases significantly, reaching over 400 mg / g at 500 mg / L, demonstrating excellent carrying capacity and indicating that the material of this invention can meet the treatment requirements of phenol wastewater of different concentrations.

[0040] (3) Dynamic adsorption test of iron-nitrogen co-doped carbon materials at different temperatures 1. Prepare a phenol solution with a concentration of 100 mg / L (pH=7). Take 1.5 mL of the phenol solution and measure the peak area of ​​the phenol solution in liquid chromatography at an excitation wavelength of 270 nm. Record it as S0. Determine the corresponding initial concentration of phenol c0 through the standard curve. 2. Add 15 mg of iron-nitrogen co-doped carbon material to the phenol solution, disperse it evenly, and place it in a constant temperature shaker at 25℃, 35℃, 45℃, and 55℃ respectively; take samples after stirring for 10 min, 20 min, 30 min, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 12 h, 24 h, and 48 h respectively, filter the solution with a 25 μm filter membrane to remove the iron-nitrogen co-doped carbon material used for phenol adsorption, and obtain phenol solutions with different adsorption times; III. For the determination of phenol solution by liquid chromatography, using 270 nm as the excitation wavelength, the peak area of ​​the phenol solution is measured and denoted as S. t The initial phenol concentration c was determined using a standard curve. t ; IV. Calculate the adsorption capacity of the iron-nitrogen co-doped carbon material for phenol adsorption using the formula in step 6, in mg / g, and obtain the dynamic adsorption curves of the iron-nitrogen co-doped carbon material at different temperatures. Figure 4c represents the adsorption kinetics curves of phenol on the iron-nitrogen co-doped biomass-derived carbon material of this invention under different temperature conditions. Figure 4 As shown in c, within the temperature range of 25–55 ℃, the adsorption process of phenol by the material exhibits a two-stage characteristic: rapid initial adsorption followed by a slow approach to equilibrium. This indicates that the material possesses good mass transfer performance and stable adsorption behavior. As the temperature increases from 25 ℃ to 55 ℃, the adsorption rate of phenol significantly accelerates, and the equilibrium adsorption capacity increases significantly. Specifically, the equilibrium adsorption capacity of phenol reaches 297.3 mg / g at 55 ℃, while it is approximately 186.6 mg / g at 25 ℃. This indicates that the adsorption of phenol by the material of this invention is an endothermic adsorption process, and the increase in temperature facilitates the entry of phenol molecules into the pores and their interaction with the active sites.

[0041] To further characterize the thermodynamic properties of the adsorption process of phenol by the iron-nitrogen co-doped biomass-derived carbon material of the present invention, the standard Gibbs free energy change (ΔG°), standard enthalpy change (ΔH°), and standard entropy change (ΔS°) of the adsorption process were calculated and analyzed based on the adsorption equilibrium data under different temperature conditions.

[0042] 1. Calculation of the standard Gibbs free energy change ΔG° The standard Gibbs free energy change ΔG° during the phenol adsorption process is given by the formula ΔG° = RTlnK is calculated. Where R is the gas constant, taken as 8.314 J·mol⁻¹. -1 ·K -1 T represents the thermodynamic temperature of the adsorption system, in K; K is the adsorption equilibrium constant, obtained by fitting an adsorption isotherm model. The ΔG° values ​​under different temperature conditions are calculated using the above formula to determine the spontaneity of the adsorption process.

[0043] 2. Calculation of standard enthalpy change ΔH° The standard enthalpy change ΔH° of the phenol adsorption process is calculated based on the Van't Hoff equation, expressed as lnK = ΔH° / RT+ΔS° / R. A linear fit is performed using lnK against 1 / T, and ΔH° is calculated based on the slope of the fitted line, thus determining whether the adsorption process is endothermic or exothermic.

[0044] 3. Calculation of standard entropy change ΔS° In the Van't Hoff linear relationship described above, the standard entropy change ΔS° is calculated based on the intercept of the fitted straight line, with the formula ΔS° = R × intercept. The numerical change of ΔS° is used to characterize the change in the disorder of the system during adsorption.

[0045] The results show that the standard enthalpy change ΔH° for phenol adsorption by the material of this invention is positive (approximately 25.5 kJ / mol), indicating that the adsorption process requires energy absorption, which is beneficial for overcoming the hydration energy of phenol in aqueous solution and promoting its migration into the pores; the standard entropy change ΔS° is positive (approximately 110 J·mol). -1 ·K -1 This indicates that the increased disorder at the solid-liquid interface during adsorption is beneficial to the adsorption process; the standard Gibbs free energy change ΔG° is negative in the range of 25–55 °C (approximately...). 7.3 to The adsorption efficiency (10.6 kJ / mol) decreased further with increasing temperature, indicating that the adsorption process can proceed spontaneously under various temperature conditions, and that higher temperature conditions are more favorable for phenol adsorption. These results demonstrate that the iron-nitrogen co-doped carbon material of this invention is suitable for the efficient treatment of phenol wastewater under different temperature conditions.

[0046] (3) Phenol adsorption test of iron-nitrogen co-doped carbon material at different pH values 1. Prepare a phenol solution with a concentration of 100 mg / L. Adjust the pH of the phenol solution using NaOH solution and HCl solution respectively, and measure the pH of the solution using a pH meter. Prepare phenol solutions with pH values ​​of 3, 5, 7, 9, 11, and 13 respectively. Take 1.5 mL of phenol solution, and measure the peak area of ​​the phenol solution in liquid chromatography at an excitation wavelength of 270 nm, denoted as S0. Determine the corresponding initial phenol concentration c0 using a standard curve. 2. Add 15 mg of iron-nitrogen co-doped carbon material to the phenol solution, disperse it evenly, and place it in a constant temperature shaker at 25℃. Take samples after stirring for 10 min, 20 min, 30 min, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 12 h, 24 h and 48 h respectively, filter the solution with a 25 μm filter membrane to remove the iron-nitrogen co-doped carbon material used for phenol adsorption, and obtain phenol solutions with different adsorption times. III. For the determination of phenol solution by liquid chromatography, using 270 nm as the excitation wavelength, the peak area of ​​the phenol solution is measured and denoted as S. t The initial phenol concentration c was determined using a standard curve. t ; 4. Calculate the adsorption capacity of the iron-nitrogen co-doped carbon material for phenol adsorption according to the formula in step 6, in mg / g, and obtain the dynamic adsorption curves of the iron-nitrogen co-doped carbon material at different pH values. Figure 4 d represents the dynamic adsorption curves of the iron-nitrogen co-doped carbon material at different pH values. It can be seen that as the pH increases from 3 to 5–7, Q… eThe adsorption capacity increased to a maximum of 186.8 mg / g, indicating that neutral phenol was effectively captured by π–π interactions and hydrogen bonds. Combined with the zeta potential diagram of phenol and iron-nitrogen co-doped carbon materials, it can be seen that when the pH is close to or higher than the pKa of phenol (≈9.9), phenol ionizes into phenoxide anions, and the adsorption capacity decreases significantly (pH=9, pH=11), but still maintains a good adsorption capacity (125~141 mg / g).

[0047] (4) Cyclic adsorption test of p-phenol on iron-nitrogen co-doped carbon materials 1. Prepare a phenol solution with a concentration of 100 mg / L. Take 1.5 mL of phenol solution and measure the peak area of ​​the phenol solution in liquid chromatography at an excitation wavelength of 270 nm. Record it as S0. Determine the corresponding initial concentration of phenol c0 through the standard curve. 2. Add 15 mg of iron-nitrogen co-doped carbon material to the phenol solution, disperse it evenly, and place it in a constant temperature shaker at 25℃. After shaking for 48 h, take a sample once, filter it with a 25 μm filter membrane to remove the iron-nitrogen co-doped carbon material used for phenol adsorption, and obtain phenol solutions that have reached the saturated adsorption state. 3. The filtered iron-nitrogen co-doped carbon material was eluted using ethanol, methanol, and acetonitrile as eluents through filter paper and a funnel, respectively. After drying, the material was subjected to the next round of adsorption experiments. The "adsorption-elution" cycle was repeated to obtain phenol solutions with different adsorption cycles.

[0048] IV. For the determination of phenol solution by liquid chromatography, using 270 nm as the excitation wavelength, measure the peak area of ​​the phenol solution and record it as S. n The initial phenol concentration c was determined using a standard curve. n ; 5. Calculate the adsorption capacity of the iron-nitrogen co-doped carbon material for phenol adsorption according to the formula in step 6, in mg / g, and obtain the reusability of the iron-nitrogen co-doped carbon material under different cycles of adsorption. Figure 4 f is the phenol cyclic adsorption efficiency diagram of the iron-nitrogen co-doped carbon material. It can be seen that in the phenol adsorption cycle regeneration experiment, the overall elution performance is: methanol > ethanol > acetonitrile. After methanol elution, the adsorption efficiency is still above 85%.

[0049] Example 3: Catalytic Degradation Tests and Results of Iron-Nitrogen Co-doped Biomass-Derived Carbon Materials The iron-nitrogen co-doped carbon material prepared in the examples for the adsorption and catalytic degradation of phenol was used to degrade phenol. The specific experimental procedure is as follows: Step 1: Calibration of the phenol standard curve Phenol solutions with concentrations of 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, 70 mg / L, 80 mg / L, 90 mg / L, 100 mg / L, 200 mg / L, 300 mg / L, 400 mg / L, and 500 mg / L were prepared respectively. The liquid chromatography of the above phenol solutions was measured respectively, and the peak area of ​​the standard solution at the emission wavelength of 270 nm was recorded. A linear relationship graph of phenol concentration and response value was plotted with peak area as the ordinate and phenol concentration as the abscissa. Step 2: Determination of the concentration of the solution to be tested Take the test solution containing phenol and measure the response peak area when the emission wavelength is 270 nm. Record the peak area as S0. Find the phenol concentration corresponding to S0 on the standard curve and record it as the initial concentration of phenol in the test solution c0. Step 3: Construction of the catalytic reaction system A mass of m iron-nitrogen co-doped carbon material was added as a catalyst to a phenol-containing test solution of volume V, and a hydrogen peroxide solution of volume V1 was added as an oxidant. After mixing evenly, the solution was placed in a constant temperature shaker and the catalytic reaction was carried out under the set temperature conditions. The reaction start time was recorded as t = 0.

[0050] Step 4: Sampling and Detection of the Reaction Process As the reaction proceeds to t1, t2, t3...t n At different time points, a certain volume of reaction solution was taken and filtered using a disposable syringe and a needle filter to remove the iron-nitrogen co-doped carbon material, and the filtrate was collected. The obtained filtrate was subjected to chromatographic or ultraviolet detection at a wavelength of 270 nm, and the response peak area S at each time point was recorded. t .

[0051] Step 5: Calculation of phenol concentration during the reaction Find the value of S at each time point on the standard curve. t The corresponding phenol concentration is denoted as c. t , where c t This represents the remaining concentration of phenol in the solution at time t.

[0052] Step 6: Calculation of phenol degradation rate According to the formula η=c t / c0, calculate the catalytic degradation rate of phenol by the iron-nitrogen co-doped carbon material: Where η represents the degradation rate of phenol; c0 represents the initial concentration of phenol measured in step two, in mg / L; c t This indicates the remaining concentration of phenol at time t in step five, in mg / L.

[0053] (1) Phenol degradation test when iron-nitrogen co-doped biomass-derived carbon materials were added at different masses The experiment was conducted according to the following steps: 1. Prepare a phenol solution with a concentration of 100 mg / L; 2. Add 10 mg, 15 mg, 20 mg, 30 mg and 40 mg of iron-nitrogen co-doped carbon material to the phenol solution respectively, disperse evenly and place in a constant temperature shaker at 25℃ for 48 h to reach adsorption saturation. Take 1.5 mL of phenol solution and measure the peak area of ​​the phenol solution in liquid chromatography with 270 nm as the excitation wavelength, and record it as S0. Determine the corresponding initial concentration of phenol c0 through the standard curve.

[0054] 3. Add H2O2 solution to the adsorption-saturated system to make the H2O2 concentration in the system 25 mL / L. Place the system in a constant temperature shaker at 25℃ and shake for 10 min, 20 min, 30 min, 40 min, 50 min, 1 h, 2 h, 3 h, 4 h, 5 h and 6 h. Filter the solution with a 25 μm filter membrane to remove the iron-nitrogen co-doped carbon material used for phenol degradation, and obtain phenol solutions with different degradation times. IV. For the determination of phenol solution by liquid chromatography, using 270 nm as the excitation wavelength, measure the peak area of ​​the phenol solution and record it as S. t The initial phenol concentration c was determined using a standard curve. t ; 5. Calculate the adsorption capacity of the iron-nitrogen co-doped carbon material for phenol adsorption according to the formula in step 6, and obtain the dynamic degradation curves of the iron-nitrogen co-doped carbon material at different dosage masses, such as... Figure 5 As shown in Figure a, under the same reaction conditions, as the dosage of iron-nitrogen co-doped carbon material increased from 10 mg to 40 mg, the degradation rate and removal efficiency of phenol significantly improved, and the C / C ratio decreased more rapidly over time. This indicates that increasing the catalyst dosage can effectively increase the number of active sites in the system, promote the generation of active species, and thus accelerate the oxidative degradation process of phenol. The spectrum when the dosage of iron-nitrogen co-doped biomass-derived carbon material is 15 mg is shown in Figure a. Figure 6 As shown.

[0055] (2) Phenol degradation test of iron-nitrogen co-doped biomass-derived carbon materials at different initial phenol concentrations 1. Prepare phenol solutions with concentrations of 50 mg / L, 100 mg / L, 150 mg / L, 200 mg / L, and 300 mg / L; 2. Add 15 mg of iron-nitrogen co-doped carbon material to the phenol solution, disperse it evenly, and place it in a constant temperature shaker at 25℃ for 48 h to reach adsorption saturation. Take 1.5 mL of phenol solution, use 270 nm as the excitation wavelength, and measure the peak area of ​​the phenol solution in liquid chromatography, which is recorded as S0. Determine the corresponding initial concentration of phenol c0 through the standard curve. 3. Add H2O2 solution to the adsorption-saturated system to make the H2O2 concentration in the system 25 mL / L. Place the system in a constant temperature shaker at 25℃ and shake for 10 min, 20 min, 30 min, 40 min, 50 min, 1 h, 2 h, 3 h, 4 h, 5 h and 6 h. Filter the solution with a 25 μm filter membrane to remove the iron-nitrogen co-doped carbon material used for phenol degradation, and obtain phenol solutions with different degradation times. IV. For the determination of phenol solution by liquid chromatography, using 270 nm as the excitation wavelength, measure the peak area of ​​the phenol solution and record it as S. t The initial phenol concentration c was determined using a standard curve. t ; 5. Calculate the adsorption capacity of the iron-nitrogen co-doped carbon material for phenol adsorption using the formula in step 6, in mg / g. Obtain the dynamic degradation curves of the iron-nitrogen co-doped carbon material at different initial phenol concentrations, as shown below. Figure 5 As shown in b, under the same catalyst dosage, as the initial phenol concentration increased from 50 mg / L to 150 mg / L, the degradation rate of phenol gradually increased. This indicates that in the low to medium concentration range, the increase in the number of phenol molecules increases the probability of effective collisions with the active sites on the surface of the iron-nitrogen co-doped carbon material, thereby enhancing the mass transfer driving force, promoting the adsorption, enrichment, and activation bond-breaking reactions of phenol molecules, and improving the overall degradation kinetic rate.

[0056] When the initial concentration of phenol was further increased to 300 mg / L, the rate of degradation slowed down and even showed a downward trend. This indicates that the active sites tend to be saturated under excessively high concentration conditions, and the reactive oxygen species generated in the system are relatively insufficient, resulting in a decrease in the proportion of phenol molecules participating in the reaction per unit time, which in turn limits the continuous degradation of phenol.

[0057] (3) Phenol degradation test of iron-nitrogen co-doped biomass-derived carbon materials at different H2O2 addition concentrations 1. Prepare phenol solutions with a concentration of 100 mg / L; 2. Add 15 mg of iron-nitrogen co-doped carbon material prepared in the example to the phenol solution, disperse it evenly, and place it in a constant temperature shaker at 25°C for 48 h to reach adsorption saturation. Take 1.5 mL of phenol solution, use 270 nm as the excitation wavelength, and measure the peak area of ​​the phenol solution in liquid chromatography, which is recorded as S0. Determine the corresponding initial concentration of phenol c0 through the standard curve.

[0058] 3. Add H2O2 solution to the adsorption-saturated system to make the H2O2 concentrations in the system 15 mL / L, 25 mL / L, 35 mL / L, and 45 mL / L, respectively. Place the system in a constant temperature shaker at 25℃ and shake for 10 min, 20 min, 30 min, 40 min, 50 min, 1 h, 2 h, 3 h, 4 h, 5 h, and 6 h. Filter the solution with a 25 μm filter membrane to remove the iron-nitrogen co-doped carbon material used for phenol degradation, and obtain phenol solutions with different degradation times. IV. For the determination of phenol solution by liquid chromatography, using 270 nm as the excitation wavelength, measure the peak area of ​​the phenol solution and record it as S. t The initial phenol concentration c was determined using a standard curve. t ; 5. Calculate the adsorption capacity of the iron-nitrogen co-doped carbon material for phenol adsorption using the formula in step 6, in mg / g. Obtain the dynamic degradation curves of the iron-nitrogen co-doped carbon material at different initial phenol concentrations, as shown below. Figure 5 As shown in c, the catalytic degradation performance of phenol by the iron-nitrogen co-doped carbon material of this invention is significantly affected by the amount of H2O2 added. From Figure 5 c shows that when the H2O2 dosage is 25 mL·L - The system exhibited relatively balanced and stable degradation performance. In the initial stage of the reaction (0–100 min), the phenol concentration decreased rapidly over time, indicating that an appropriate amount of H2O2 could effectively activate and generate reactive oxygen species such as •OH under the action of the Fe–N–C catalytic sites, thereby promoting the rapid oxidative degradation of phenol molecules. With the extension of reaction time (>200 min), the phenol concentration continued to decrease and tended to stabilize, indicating that the system could maintain continuous oxidative capacity under these conditions, achieving efficient removal of phenol. Furthermore, with the increase of H2O2 dosage, the phenol degradation rate accelerated and the removal rate improved. In the initial stage of the reaction (0–100 min), the system with a higher H2O2 dosage (35–45 mL / L) had a faster degradation rate; in the middle and later stages of the reaction (>200 min), the system with a low dosage (15 mL / L) had higher phenol residue, while the system with a high dosage could fully degrade phenol. The results indicate that the H2O2 dosage is a key parameter affecting the phenol removal efficiency, and the degradation effect can be optimized by adjusting its dosage.

[0059] (4) Phenol degradation test of iron-nitrogen co-doped biomass-derived carbon materials at different temperatures 1. Prepare phenol solutions with a concentration of 100 mg / L; 2. Add 15 mg of iron-nitrogen co-doped carbon material to the phenol solution, disperse it evenly, and place it in a constant temperature shaker at 25℃ for 48 h to reach adsorption saturation. Take 1.5 mL of phenol solution, use 270 nm as the excitation wavelength, and measure the peak area of ​​the phenol solution in liquid chromatography, which is recorded as S0. Determine the corresponding initial concentration of phenol c0 through the standard curve.

[0060] 3. Add H2O2 solution to the adsorption-saturated system to make the H2O2 concentration in the system 25 mL / L. Place the system in a constant temperature shaker at 25℃, 35℃, 45℃ and 55℃ and shake for 10 min, 20 min, 30 min, 40 min, 50 min, 1 h, 2 h, 3 h, 4 h, 5 h and 6 h respectively. Filter the solution with a 25 μm filter membrane to remove the iron-nitrogen co-doped carbon material used for phenol degradation, and obtain phenol solutions with different degradation times. IV. For the determination of phenol solution by liquid chromatography, using 270 nm as the excitation wavelength, measure the peak area of ​​the phenol solution and record it as S. t The initial phenol concentration c was determined using a standard curve. t ; 5. Calculate the adsorption capacity of the iron-nitrogen co-doped carbon material for phenol adsorption using the formula in step 6, in mg / g. Obtain the dynamic degradation curves of the iron-nitrogen co-doped carbon material at different initial phenol concentrations, as shown below. Figure 5As shown in Figure d, under different temperatures (25℃, 35℃, 45℃, and 55℃), during the catalytic degradation of phenol by the iron-nitrogen co-doped carbon material of this invention, the normalized concentration of phenol (C / C0) continuously decreased with reaction time, and the removal rate of phenol significantly accelerated with increasing temperature. At a reaction temperature of 35℃, the phenol degradation rate was significantly higher than at 25℃, and the system showed a rapid concentration decrease trend in the early stages of the reaction, indicating that moderate heating is beneficial for promoting the activation of H2O2 at the Fe–N–C catalytic sites, thereby increasing the generation rate of reactive oxygen species such as •OH. At 45℃, the phenol degradation rate was further enhanced, and the C / C0 decreased more rapidly throughout the reaction, indicating that higher temperatures can further accelerate the reaction kinetics, improve the free radical generation efficiency, and increase the oxidation rate of phenol molecules. At 55℃, phenol was nearly completely removed within approximately 200 min; while at 25℃, the time required to achieve the same removal effect was significantly prolonged (approximately 500–700 min). The above results indicate that the catalytic degradation of phenol by the material of the present invention is a temperature-promoted reaction, and increasing the reaction temperature is beneficial to improving the degradation rate and removal efficiency of phenol.

[0061] Increasing the temperature helps to accelerate the bond-breaking reaction and mineralization process of phenol molecules; at the same time, increasing the temperature can lower the apparent activation energy of the reaction system, increase the reaction kinetic constant, and further promote the efficient degradation of phenol.

[0062] In summary, this invention utilizes biomass grapefruit peel as a matrix and constructs an iron-nitrogen co-doped porous carbon material through steps such as oxidative modification, pre-amidation, in-situ growth of metal-organic frameworks, and calcination activation. This achieves the synergistic construction of a hierarchical porous structure, nitrogen-rich functional groups, and Fe–N active sites. The material exhibits significant hydrogen bonding, π–π interactions, and electrostatic adsorption capabilities for phenol, with a saturated adsorption capacity reaching 186.6 mg / g. It can also achieve complete catalytic degradation of phenol under mild conditions, establishing an integrated adsorption-degradation treatment pathway. The prepared material is structurally stable, acid and alkali resistant, and exhibits excellent recyclability. It combines the advantages of low cost, biomass renewability, and high treatment efficiency, making it suitable for the efficient removal of phenol and phenolic wastewater, and demonstrating promising engineering application prospects.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an iron-nitrogen co-doped carbon material for the adsorption and catalytic degradation of phenol, characterized in that, Includes the following steps: Step 1: Immerse the cleaned grapefruit peel in an oxidizing agent solution, heat in a water bath, and quench the reaction with anhydrous ethanol after the reaction is complete. Wash the resulting solid with deionized water and freeze-dry to obtain oxidized grapefruit peel. Step 2: Place the oxidized grapefruit peel in the first solvent and heat it in a water bath at 60°C for 4-12 hours to achieve the pre-amidation reaction and obtain the pre-amidated product; Step 3: Pour the second solvent into the preamidated product and hydrothermally react at 90~150℃ for 2~48 hours. Wash the obtained product with N,N-dimethylformamide solvent and ethanol and dry it to obtain grapefruit peel supported by metal-organic framework. Step 4: The grapefruit peel loaded with the metal-organic framework is calcined under an inert atmosphere. After calcination, the resulting solid is washed with anhydrous ethanol and dried to obtain a grapefruit-derived metal-organic framework carbon material. Step 5: Immerse the metal-organic framework grapefruit-derived carbon material in an activation solution, dry it, and then heat it under an inert atmosphere for activation. After activation, wash the resulting solid with anhydrous ethanol until the pH is neutral, and then dry it to obtain the iron-nitrogen co-doped carbon material used for phenol adsorption and catalytic degradation.

2. The preparation method according to claim 1, characterized in that, In step one, the oxidant solution is a 10% H2O2 and 0.5 mmol / L FeSO4 solution, and the pH is adjusted to acidic conditions of 3-5 using H2SO4.

3. The preparation method according to claim 1, characterized in that, In step two, the first solvent is obtained by dissolving 2-aminoterephthalic acid in N,N-dimethylformamide solvent and stirring. The molar ratio of grapefruit peel to 2-aminoterephthalic acid is 1 g: 2~4 mmol.

4. The preparation method according to claim 1, characterized in that, In step three, the second solvent is prepared by dissolving ferric chloride hexahydrate in tetrahydrofuran solvent and mixing and stirring, wherein the molar ratio of ferric chloride hexahydrate to 2-aminoterephthalic acid is (0.5~3):

1.

5. The preparation method according to claim 1, characterized in that, In step five, the activation solution is a KOH solution, and the mass ratio of the metal-organic framework grapefruit-derived carbon material to KOH is 1:(1~5).

6. The preparation method according to claim 1, characterized in that, In step four, the calcination temperature is 400~800℃ and the calcination time is 2~4h.

7. The preparation method according to claim 5, characterized in that, In step five, the activation temperature is 400~800℃ and the activation time is 2~4h.

8. An iron-nitrogen co-doped carbon material for the adsorption and catalytic degradation of phenol, prepared by the method according to claim 1.

9. The application of the iron-nitrogen co-doped carbon material for phenol adsorption as described in claim 8 in the absorption solution of phenol, characterized in that, In the process of absorbing phenol from the solution, the iron-nitrogen co-doped carbon material adsorbed by the phenol serves as the adsorbent.

10. The application of the iron-nitrogen co-doped carbon material for phenol adsorption as described in claim 8 in the degradation of phenol, characterized in that, In the process of phenol degradation, the iron-nitrogen co-doped carbon material produced by phenol degradation serves as a catalyst.

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