Sludge-based iron-nitrogen co-doped biochar material as well as preparation method and application thereof

Abstract

The invention provides iron-nitrogen co-doped sludge-based biochar as well as a preparation method and application thereof in pollutant degradation. The material takes municipal sludge as a carbon source, and is directly synthesized through a simple one-step pyrolysis method under the condition of no additional pretreatment, so that the energy consumption and the process complexity are reduced. Compared with a traditional method, by optimizing the proportion of the sludge, the iron source and the nitrogen source (the mass ratio is preferably 40: (1-2): (1-2)) and regulating and controlling the heating rate to 10 DEG C / min, the material has a spherical porous structure and rich iron-nitrogen coordination structures and pyridine nitrogen active sites. In a periodate system, the material shows excellent catalytic activity, and the removal rate of bisphenol A within 30 minutes is as high as 96.1%, which is far superior to that of similar non-doped materials and other iron-based catalysts. In addition, due to the surface adsorption characteristic of the material, BPA molecules are close to an active center, the reaction path is effectively shortened, and the generation of free radical and non-free radical oxidation pathways is synergistically promoted. The material has exclusive degradation adaptability to typical endocrine disruptors, and is suitable for industrial tail water, paper mill wastewater and other difficult-to-treat fields. According to the invention, resource utilization of municipal sludge is realized, and a green, economic, simple and efficient wastewater advanced treatment solution is provided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental catalysis and adsorption materials, and particularly relates to a sludge-based iron-nitrogen co-doped biochar material and a preparation method and application thereof. BACKGROUND

[0002] With the acceleration of urbanization, a large amount of residual sludge is generated in municipal wastewater treatment plants every day, and its treatment and disposal has become a problem to be solved in the environmental protection field. Traditional sludge treatment methods, such as landfill and incineration, not only face high costs and land occupation problems, but also may cause secondary pollution, which restricts the sustainable development of resource utilization. In recent years, sludge pyrolysis to prepare biochar has become an effective means that takes into account sludge reduction and resource utilization. Biochar generally has characteristics such as large specific surface area, rich pore structure, and many surface oxygen-containing functional groups, and is widely used in environmental remediation, wastewater purification, and soil improvement fields. Biochar materials mainly remove pollutants through adsorption mechanism in the treatment of organic pollutants, but after adsorption saturation, there are problems such as difficulty in regeneration and easy to cause secondary pollution. The single adsorption function has been difficult to meet the increasingly stringent water purification requirements.

[0003] In order to improve the environmental function of sludge-based biochar, researchers try to introduce transition metals (such as Fe) and non-metallic doping (such as N) into its structure to endow it with catalytic oxidation performance. Fe, as a typical Fenton catalyst, can generate free radicals when activating oxidizing agents such as periodate; and N doping can effectively adjust the electron distribution of carbon materials, introduce charge uneven regions, and enhance the π-π electron donor-acceptor interaction between them and aromatic pollutants, thereby improving the adsorption and catalytic performance. Existing research shows that Fe and N co-doping can synergistically improve the electrochemical performance and active site distribution of carbon materials, especially promoting the non-free radical activation pathway of periodate in the advanced oxidation process, generating 1 O2, high-valence metal species and electron transfer mechanism, thereby achieving efficient degradation of organic pollutants. In addition, the π-π electron donor-acceptor interaction, electrostatic interaction, hydrogen bonding and surface complexation together constitute the adsorption mechanism of pollutants.

[0004] Although iron-nitrogen co-doped carbon materials have great potential in the field of advanced oxidation catalysts, related research mainly focuses on high-purity carbon sources (such as graphite, metal organic frameworks), which has problems such as high cost, complex process, and resource waste. Using low-cost, rich in organic matter and mineral matter municipal sludge as raw material to construct iron-nitrogen co-doped multifunctional carbon materials with adsorption and catalytic capacity is a green, environmentally friendly and economically feasible technical path, which needs further research and promotion. SUMMARY

[0005] Therefore, the present application aims to provide a sludge-based iron-nitrogen co-doped biochar material (Fe@N-SBC) and a preparation method and application thereof.

[0006] To achieve the above-mentioned application purposes, the present application provides the following technical solutions.

[0007] The present application provides a preparation method of a sludge-based iron-nitrogen co-doped biochar material, comprising the following steps:

[0008] The dewatered sludge, the iron source and the nitrogen source are mixed to obtain a precursor mixture;

[0009] The precursor mixture is pyrolyzed and carbonized to obtain the sludge-based iron-nitrogen co-doped biochar material.

[0010] Preferably, the mass ratio of the dewatered sludge, the iron source and the nitrogen source is 40:1-2:1-2.

[0011] Preferably, the iron source comprises ferrous sulfate heptahydrate and / or ferric nitrate nonahydrate.

[0012] Preferably, the nitrogen source comprises ammonium chloride and / or urea.

[0013] Preferably, the pyrolysis and carbonization temperature is 550-950℃, and the time is 2h.

[0014] Preferably, the temperature rising rate from room temperature to the pyrolysis and carbonization temperature is 5-15℃ / min, and the temperature rising rate promotes the formation of an irregular porous structure of the material, and improves the specific surface area and the exposure rate of the reaction active sites.

[0015] Preferably, the pyrolysis and carbonization are carried out in a protective atmosphere.

[0016] The present application also provides the sludge-based iron-nitrogen co-doped biochar material prepared by the preparation method.

[0017] The present application also provides the application of the sludge-based iron-nitrogen co-doped biochar material in the field of organic pollutant degradation.

[0018] Preferably, the sludge-based iron-nitrogen co-doped biochar material and a periodate are used in combination for the degradation of bisphenol A.

[0019] The present application provides a preparation method of a sludge-based iron-nitrogen co-doped biochar material, comprising the following steps: mixing dewatered sludge, an iron source and a nitrogen source to obtain a precursor mixture; and pyrolyzing and carbonizing the precursor mixture to obtain the sludge-based iron-nitrogen co-doped biochar material.

[0020] Compared with the prior art, the application has the following advantages:

[0021] The raw material is widely sourced and environmentally friendly: using dewatered sludge from a municipal sewage treatment plant as a raw material, waste resource utilization is achieved, disposal costs are reduced, and the concept of sustainable development is met;

[0022] Dual-function synergistic removal mechanism: the prepared Fe@N-SBC material has high adsorption performance and high periodate activation capacity, and under the adsorption-catalysis synergistic effect, deep degradation of organic pollutants such as bisphenol A is achieved;

[0023] Rich catalytic active centers: the Fe-N x coordination structure, pyridine-type nitrogen and C=O in the material provide multiple active sites for periodic acid activation;

[0024] Optimized reaction path, complete degradation: pollutants are preferentially enriched on the surface of the carbon material, shortening the reaction path, improving the reaction efficiency with active oxygen species, and reducing energy consumption;

[0025] Stable material structure, strong reusability: after multiple cycles, it can still maintain high catalytic efficiency, and X-ray diffraction and X-ray photoelectron spectroscopy analysis confirm its structural stability;

[0026] Simple process, suitable for promotion: the material preparation steps are simple, the cost is low, and it is suitable for batch production and can be expanded to practical sewage treatment engineering applications.

[0027] In summary, the application improves the structure regulation and functional performance of sludge-based carbon materials through co-doping strategy, providing a new path for the green and efficient treatment of organic pollutants, and having significant environmental benefits and industrialization prospects.

[0028] The technical highlight of the application is that without additional introduction of a template or pore-forming agent, a sludge-derived biochar material with a sheet-like structure and hierarchical pores is achieved. In the prior art, silica, alumina, potassium hydroxide and other templates or activators are often used to construct specific pores or morphological structures, which not only increases the process complexity, but also may introduce secondary pollution. However, by adjusting the heating rate (5-15℃ / min) and raw material ratio (dewatered sludge: iron source: nitrogen source = 40:1-2:1-2), the application achieves spontaneous regulation of the microstructure in a one-step pyrolysis process, generating a Fe / N co-doped sludge carbon material with a sheet-like skeleton structure and a hierarchical pore system.

[0029] Such structure has the following advantages:

[0030] (1) The sheet-like structure is beneficial to uniform dispersion of the material, avoiding agglomeration and improving the stability and reusability of the catalyst;

[0031] (2) The hierarchical pore system (micro / meso / macropore synergy) effectively improves mass transfer efficiency and enhances the ability of reactants to enter the active center;

[0032] (3) The uniform distribution and exposure of active sites and functional groups contribute to the synergistic activation of free radical and non-free radical pathways.

[0033] Therefore, this invention not only avoids the use of non-environmentally friendly template agents, realizing a green and low-carbon synthesis route, but also achieves the controllable construction of highly active structures through precise control of heating process parameters, significantly improving the removal efficiency of target pollutants and demonstrating significant potential for environmental and engineering applications.

[0034] This invention also provides a sludge-based iron-nitrogen co-doped biochar material prepared by the preparation method described above. This invention uses sludge from urban wastewater treatment plants as a carbon source and introduces Fe and N elements in situ through pyrolysis to prepare a Fe@N-SBC catalytic material with high specific surface area, porous structure and abundant active sites. It can efficiently adsorb bisphenol A and catalyze its deep degradation in the presence of periodate through a synergistic mechanism of free radicals and non-free radicals. This catalyst has good stability, recyclability and wide pH adaptability, providing a new approach for the green and efficient removal of organic pollutants. Attached Figure Description

[0035] Figure 1 The images are scanning electron microscopes (SEMs) of Fe@N-SBC (a) and SBC (b) prepared in Example 3 at different magnifications.

[0036] Figure 2 X-ray diffraction patterns of Fe@N-SBC and related comparative materials;

[0037] Figure 3 The X-ray photoelectron spectroscopy spectrum of Fe@N-SBC is shown in full scan.

[0038] Figures 4 to 7 The high-resolution X-ray photoelectron spectra of C1s, N 1s, O 1s, and Fe 2p in Fe@N-SBC material are shown in sequence.

[0039] Figure 8 The mass ratio of dewatered sludge, iron source, and nitrogen source ( Figure 8 (a) and types of iron / nitrogen sources ( Figure 8 (b) and heating rate ( Figure 8 (c) Effect of bisphenol A removal on the sample;

[0040] Figure 9 For sludge-based iron-nitrogen co-doped biochar materials ( Figure 9 (a) and periodate ( Figure 9Amount of organic pollutants used in (b) and Figure 9 Figure of removal effect of bisphenol A in (c);

[0041] Figure 10 Figure of removal effect of bisphenol A by different catalytic systems (Fe@N-SBC, N-SBC, Fe-SBC, SBC, PI);

[0042] Figure 11 Degradation rate of bisphenol A under the condition of adding different radical quenchers;

[0043] Figure 12 Electron paramagnetic resonance spectrum of Fe@N-SBC / PI system. DETAILED DESCRIPTION

[0044] The application provides a preparation method of a sludge-based iron-nitrogen co-doped biochar material, comprising the following steps:

[0045] Mixing dewatered sludge, an iron source and a nitrogen source to obtain a precursor mixture;

[0046] Pyrolyzing and carbonizing the precursor mixture to obtain the sludge-based iron-nitrogen co-doped biochar material.

[0047] In the application, the raw materials used are commercially available products in the art unless otherwise specified.

[0048] The application mixes dewatered sludge, an iron source and a nitrogen source to obtain a precursor mixture.

[0049] In the application, the dewatered sludge is preferably obtained by dewatering sludge from a municipal sewage treatment plant, and the application does not have special limitations on the specific parameters of the dewatering, which can be achieved by using a scheme well known to those skilled in the art.

[0050] In the application, the mass ratio of the dewatered sludge, the iron source and the nitrogen source is preferably 40:2:1, 40:1:1 or 40:1:2.

[0051] In the application, the iron source preferably comprises ferrous sulfate heptahydrate and / or ferric nitrate nonahydrate.

[0052] In the application, the nitrogen source preferably comprises ammonium chloride and / or urea.

[0053] After the mixing is completed, the application preferably dries the obtained material to obtain the precursor mixture.

[0054] In the application, the temperature of the drying is preferably 105 DEG C, and the time is preferably 24 h to remove water.

[0055] After obtaining the precursor mixture, the sludge-based iron-nitrogen co-doped biochar material is obtained by pyrolysis carbonization of the precursor mixture.

[0056] In the present application, the temperature of the pyrolysis carbonization is preferably 550-950℃, and can be 550, 650, 750, 850 or 950℃, and the time is preferably 2h.

[0057] In the present application, the heating rate from room temperature to the temperature of the pyrolysis carbonization is preferably 5-15℃ / min, and can be 5, 10 or 15℃ / min.

[0058] In the present application, the pyrolysis carbonization is preferably carried out in a protective atmosphere, and the protective atmosphere is preferably nitrogen.

[0059] In the present application, the device for pyrolysis carbonization is preferably a controllable temperature tube furnace, and the nitrogen flow is preferably 150mL / min to ensure a good inert environment to prevent oxidation.

[0060] After the pyrolysis carbonization is completed, the obtained pyrolysis carbonization product is preferably naturally cooled to room temperature, and the product is taken out and sequentially washed, dried, crushed and sieved to obtain the Fe@N-SBC.

[0061] In the present application, the washing is preferably repeated washing with ultrapure water and anhydrous ethanol.

[0062] In the present application, the drying is preferably drying at 60℃ for 12h.

[0063] In the present application, the crushing is preferably ball milling, and then sieving through a 100 mesh sieve.

[0064] The present application also provides a sludge-based iron-nitrogen co-doped biochar material prepared by the preparation method of the above technical solution.

[0065] The present application also provides the application of the sludge-based iron-nitrogen co-doped biochar material in the field of organic pollutant degradation.

[0066] In the present application, the organic pollutants preferably include bisphenol A, and the sludge-based iron-nitrogen co-doped biochar material exhibits excellent synergistic adsorption-catalytic degradation performance, acting as an adsorbent and a catalyst.

[0067] In the present application, the sludge-based iron-nitrogen co-doped biochar material and periodate are preferably used synergistically for the degradation of bisphenol A.

[0068] In the present application, the periodate preferably includes sodium periodate.

[0069] In the present application, the dosage ratio of the sludge-based iron-nitrogen co-doped biochar material, periodate and organic pollutants is preferably (0.3-0.5 g):(0.1-1.0 mmol):(10-30 mg).

[0070] In the present application, the degradation temperature is preferably 25℃, and the time is preferably 0.5-1 h.

[0071] In the present application, the degradation is preferably carried out under stirring, and the stirring speed is preferably 350-500 rpm.

[0072] In the present application, the Fe@N-SBC is preferably added to the solution to be treated, and the solution of periodate is added under stirring to carry out the degradation.

[0073] In the specific embodiments of the present application, the concentration of the sludge-based iron-nitrogen co-doped biochar material in the solution during the degradation is preferably 0.3-0.5 g / L, the concentration of the periodate is preferably 0.1-1.0 mM, and the concentration of the organic pollutants is preferably 10-30 mg / L.

[0074] In the present application, the solution to be treated is preferably wastewater containing refractory organic pollutants.

[0075] During the degradation, Fe-N x promotes the activation of sodium periodate (PI) to generate ·OH, 1 O2, etc., thereby achieving efficient degradation of bisphenol A.

[0076] In the present application, the Fe@N-SBC still has good degradation ability after being used for four consecutive cycles, and has stable structure and is not prone to passivation or inactivation. It shows good tolerance to common anions (including Cl - , SO4 2- , HCO3 - , CO3 2- , etc.), is suitable for treatment of complex water bodies, can be widely used for efficient removal of refractory organic pollutants, and has advantages of resource utilization, low cost and environmental friendliness.

[0077] The technical solutions in the present application will be described clearly and completely below in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0078] Example 1:

[0079] In order to optimize the preparation conditions of Fe@N-SBC, the effects of the mass ratio of dewatered sludge, iron source and nitrogen source, the types of iron / nitrogen source and the heating rate on the degradation performance of bisphenol A (BPA) were systematically investigated (as shown in Table 1). Figure 8 In each group of experiments, the initial concentration of BPA was 20 mg / L, the dosage of Fe@N-SBC was 0.4 g / L, the concentration of PI was 0.5 mM, and the reaction was carried out at 25°C.

[0080] I. Effects of different raw material ratios

[0081] In this experiment, the mass ratio of dewatered sludge, iron source (ferrous sulfate heptahydrate) and nitrogen source (ammonium chloride) was set to 40:2:1, 40:1:1 and 40:1:2, respectively, and the prepared biochar catalyst was used for BPA degradation. The results showed that under the mass ratio of 40:2:1, the degradation efficiency of the catalyst was the highest, and after 30 min of reaction, the removal rate of BPA was 96.1%. In the 40:1:1 and 40:1:2 groups, the removal rates of BPA after 30 min were 71.4% and 82.8%, respectively, indicating that 40:2:1 was the optimal ratio. Therefore, the mass ratio described in the present application is preferably 40:2:1.

[0082] II. Effects of different iron sources and nitrogen sources

[0083] Based on the optimal ratio of 40:2:1, the effects of the types of iron source and nitrogen source on the catalytic performance were further investigated. Comparative experiments were conducted using ferrous sulfate heptahydrate and ammonium chloride, and iron nitrate nonahydrate and urea. It was found that the material prepared using ferrous sulfate heptahydrate / ammonium chloride had a BPA removal rate of 96.1% after 30 min, while the material prepared using iron nitrate nonahydrate / urea had a BPA removal rate of 51.9% under the same conditions, which was significantly lower than the former, indicating that ferrous sulfate heptahydrate and ammonium chloride as raw materials had better PI activation ability.

[0084] III. Effects of different heating rates

[0085] Under the conditions of a pyrolysis temperature of 850°C and a holding time of 2h, the effects of heating rate on the performance of the material were compared. The results showed that the material prepared at a heating rate of 10°C / min exhibited the best BPA degradation ability (BPA removal rate of 96.1% after 30 min), while the degradation effects were relatively weak at 5°C / min and 15°C / min (BPA removal rates were 88.5% and 57.0%, respectively). Therefore, the preferred heating rate is 10°C / min.

[0086] In summary, the optimal preparation parameters are as follows: the mass ratio of dewatered sludge, iron source and nitrogen source is 40:2:1, the iron source is ferrous sulfate heptahydrate, the nitrogen source is ammonium chloride, the temperature rising rate is 10℃ / min, the pyrolysis temperature range is 550-950℃, and the holding time is 2h. The above parameters and their variation ranges are verified in multiple experiments, ensuring that the material of the application has good PI activation performance and stable structural properties.

[0087] Example 2 (The sludge-based iron-nitrogen co-doped biochar material used in Example 2 is the sludge-based iron-nitrogen co-doped biochar material obtained under the optimal preparation parameters)

[0088] In order to optimize the reaction parameters in the experiment, the effect of the mass ratio of sludge-based iron-nitrogen co-doped biochar material, periodate and organic pollutants on the degradation performance of bisphenol A was systematically investigated (as shown in Figure 9

[0089] I. Effect of different catalyst dosages

[0090] In order to study the effect of Fe@N-SBC dosage on BPA removal efficiency, the catalyst dosage was set to 0.3g / L, 0.4g / L and 0.5g / L, the initial concentration of BPA was 20mg / L, the concentration of PI was 0.5mM, and the reaction temperature was 25℃.

[0091] The experimental results show that when the catalyst dosage is 0.4g / L, the BPA degradation effect is best, and the BPA removal rate reaches 96.1% after 30min. When the dosage is 0.3g / L, the BPA removal rate is 79.3%, and when the dosage is 0.5g / L, the BPA removal rate is 100%. However, at a dosage of 0.5g / L, BPA is almost completely removed after 10min of degradation reaction, indicating that appropriately increasing the catalyst dosage can improve the reaction efficiency, but too high a dosage may affect the catalytic performance due to agglomeration or saturation of adsorption sites. Therefore, the dosage of Fe@N-SBC is preferably 0.4g / L.

[0092] II. Effect of different PI concentrations on degradation performance

[0093] The PI concentration was set to 0.1mM, 0.5mM and 1mM, the initial concentration of BPA was fixed at 20mg / L, and the dosage of Fe@N-SBC was 0.4g / L.

[0094] ​The results show that the system exhibits the optimal degradation effect when the PI concentration is 0.5 mM, and the BPA removal rate is 96.1% within 30 min; when the PI concentration is 0.1 mM, the amount of active species generated in the system is insufficient, and the BPA removal rate is only 85.1%; and when the PI concentration is 1 mM, a slight inhibition occurs, and the BPA removal rate is 92.8%, which may be due to self-quenching of high-concentration PI or enhancement of side reactions. Therefore, the PI concentration is preferably 0.5 mM.

[0095] III. Influence of different initial concentrations of BPA

[0096] The influence of BPA initial concentrations of 10 mg / L, 20 mg / L and 30 mg / L on the degradation efficiency was investigated, and the catalyst dosage was fixed at 0.4 g / L and the PI concentration was 0.5 mM.

[0097] The experimental results show that when the BPA concentration is 20 mg / L, the system can completely degrade BPA within 30 min; when the concentration is 10 mg / L, BPA can be completely removed within 10 min; and when the concentration is 30 mg / L, the degradation rate is significantly reduced, and the BPA concentration is 88.7% after 30 min. This indicates that when the BPA concentration is too high, the active sites on the surface of the catalyst may tend to be saturated, resulting in a decrease in reaction efficiency. Therefore, the BPA treatment concentration is preferably 20 mg / L.

[0098] Example 3

[0099] 60 g of dehydrated sludge was weighed and added to a mixed solution prepared by dissolving 3 g of ferrous sulfate heptahydrate and 1.5 g of ammonium chloride in 100 mL of deionized water, and the resulting mixed system was magnetically stirred at room temperature for 12 h. The mixture was dried in a constant temperature oven at 105°C until the weight was constant, then ground into fine powder and sieved through a 100 mesh sieve (particle size <0.074 mm) for use, to obtain a precursor mixture.

[0100] The precursor mixture was weighed and placed in an alumina crucible and placed in a tube furnace, and pyrolysis carbonization was carried out at 550, 650, 750, 850 and 950°C, respectively, under the protection of nitrogen gas (150 mL / min) at a heating rate of 10°C / min for 2 h, and then naturally cooled to room temperature. Then, ultrapure water and anhydrous ethanol were used for repeated washing, 60°C drying for 12 h, then ball milling, and then sieving through a 100 mesh sieve, to obtain the final product Fe@N-SBC.

[0101] The preparation conditions of the comparative sample were consistent with the above, and only one of ferrous sulfate heptahydrate (named N-SBC), ammonium chloride (named Fe-SBC) or both (named SBC) was removed from the raw material, which was used for subsequent performance comparison.

[0102] All samples were sealed and stored in dry glass bottles for later use.

[0103] Figure 1 For Fe@N-SBC ( Figure 1 (a) and SBC ( Figure 1 Scanning electron microscopy (SEM) images of the material at different magnifications (b) show that the Fe@N-SBC surface exhibits a more pronounced lamellar and quasi-lamellar porous structure with higher roughness. Compared to the more flat and dense SBC, it has a larger specific surface area and more exposed active sites. This structural feature helps improve the material's adsorption performance and PI activation efficiency, thereby enhancing its ability to remove organic pollutants. The results indicate that the introduction of Fe and N effectively regulates the microstructure of the carbon material, which is beneficial for improving its environmental application performance.

[0104] Figure 2 X-ray diffraction patterns of Fe@N-SBC and related comparative materials are shown for analysis of their crystal structure. It can be observed that all samples exhibit distinct diffraction peaks at 26.71° and 44.29°, corresponding to the (002) and (101) crystal planes of pyrolyzed graphitic carbon (PDF#99-0057). Furthermore, diffraction peaks at 16.55°, 28.02°, 33.80°, 40.91°, 42.95°, and 47.38° also appear in the Fe@N-SBC samples. These peaks can be attributed to C3N4 (PDF#87-1523), indicating that N doping promotes the formation of the C3N4 structure. The diffraction peaks at 20.86°, 30.02°, 33.82°, 43.60°, 52.98°, and 54.18° indicate the typical crystal planes of Fe2O3 (PDF#40-1139). Furthermore, characteristic peaks of Fe3O4 (PDF#72-2303) are also observed at angles of 35.33°, 43.60°, 47.38°, 52.98°, 70.92°, and 73.92°, confirming that during pyrolysis, the iron source is partially converted into a coexisting phase of Fe2O3 and Fe3O4.

[0105] Figure 3 The X-ray photoelectron spectroscopy full scan spectrum of Fe@N-SBC material shows that its surface elemental composition is mainly C (68.21%), N (3.38%), O (28.13%) and Fe (0.28%), with almost no change before and after the reaction, indicating that its structure has good stability. Figures 4 to 7 High-resolution XPS spectra of C 1s, N 1s, O 1s, and Fe 2p of Fe@N-SBC material were further presented. Figure 4Three main peaks were observed in the C1s spectrum of Fe@N-SBC, corresponding to C-C / C=C (284.80 eV), C-N / C-O (285.79 eV) and C=O (288.70 eV), respectively. Figure 6 In the O1s spectrum of Fe@N-SBC, characteristic peaks of C-O (532.10 eV), C=O (531.28 eV), Fe-O (530.29 eV) and -OH (533.37 eV) could be distinguished. Figure 5 In the N1s spectrum of Fe@N-SBC, pyridine N (397.84 eV), pyrrole N (398.59 eV), Fe-N x (399.44 eV), graphitic N (400.95 eV) and oxidized N (403.24 eV) were resolved, in which pyridine N was considered as an important site to form Fe-N x coordination structure. Figure 7 The Fe 2p spectrum of Fe@N-SBC showed Fe 3+ 2p3 / 2 and 2p1 / 2 main peaks at 711.00 eV and 724.22 eV, and satellite peaks at 719.59 eV and 732.95 eV; in addition, peaks at 714.69 eV and 727.84 eV were attributed to the presence of Fe 2+ species. The above results collectively confirmed the coexistence of Fe2O3 and Fe3O4, and Fe species might form Fe-N x active centers by coordination with pyridine N.

[0106] The above characterization results showed that Fe@N-SBC material possessed porous structure, graphitic carbon skeleton, abundant oxygen-containing and nitrogen-containing functional groups, and Fe-N x active sites, which could be used as an ideal catalyst for activating periodate and further degrading organic pollutants such as bisphenol A, and had good application potential.

[0107] Application Example

[0108] Unless otherwise specified, all degradation experiments in the present application were carried out in a 100 mL beaker. First, an appropriate amount of bisphenol A was accurately weighed using an electronic balance and dissolved in deionized water to prepare a BPA stock solution with a concentration of 100 mg / L, and diluted according to the experimental requirements before use. The experiment was carried out at room temperature (25±2℃), and the catalyst used was the prepared Fe@N-SBC and the comparative sample, and the initial addition amount was 0.40 g / L.

[0109] After adding the catalyst into 20 mL of BPA solution, a magnetic stirrer was used to stir at a speed of 350 rpm to make the catalyst uniformly dispersed in the reaction system. First, an adsorption equilibrium experiment was carried out for 30 min, and then 0.5 mM sodium periodate was added to the reaction system to start the catalytic oxidation reaction.

[0110] At specific time intervals (e.g., 1, 5, 10, 15, 20, 30 min), 1 mL of the reaction solution was taken using a 2.5 mL syringe and filtered through a 0.22 μm polytetrafluoroethylene (PTFE) membrane to remove particulate matter and catalyst residue. The filtrate was then immediately transferred to a high-performance liquid chromatography (HPLC) vial pre-filled with 100 μM dimethyl sulfoxide (DMSO) to terminate the reaction and facilitate subsequent quantitative analysis.

[0111] Figure 10 The results show the comparison of the degradation effects of different catalyst systems (Fe@N-SBC, N-SBC, Fe-SBC, SBC) on bisphenol A in the presence of PI. Figure 10 The inset shows the reaction rate constants for different catalyst systems. It can be seen that Fe@N-SBC exhibits the best degradation performance, far exceeding that of the undoped metal or nitrogen-based comparative materials. Although N-SBC and Fe-SBC can also partially activate PI to degrade BPA, their efficiency is significantly lower than that of Fe@N-SBC, indicating that the synergistic effect of Fe and N is crucial in improving catalytic activity. SBC exhibits almost no catalytic activity in this reaction, only showing some adsorption. Sodium periodate itself has virtually no removal effect on BPA. These results validate the significant advantage of Fe@N-SBC in the activation and degradation of BPA using sodium periodate.

[0112] To identify the active species for bisphenol A degradation in the Fe@N-SBC / PI system, a series of quenching experiments were conducted, such as... Figure 11 As shown, after adding 500 mM methanol (MeOH), the BPA degradation rate decreased to 85.0%, indicating that the contribution of ·OH was limited. In contrast, the addition of 20 mM furfuryl alcohol (FFA) significantly reduced the degradation rate. 1 O2 quencher significantly inhibited BPA degradation to 69.2%, and the degradation rate k decreased to 0.021 min. -1 ,show 1 O2 is one of the main oxide species. Control experiments excluded the direct consumption of PI by FFA. Furthermore, the addition of phenol reduced the BPA removal rate from 96.1% to 65.3%, confirming the presence of IO3. - The oxidation contribution. The above results indicate that this system mainly contributes through... 1 O2 and IO3 - Synergistically promotes BPA degradation.

[0113] To directly detect free radicals and non-free radical species that may be generated during the reaction, this invention further employs electron paramagnetic resonance spectroscopy, such as... Figure 12 As shown, Figure 12 (a) is a DMPO-·OH radical, (b) is a TEMP- 1O2. Using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a trapping agent, four-line spectrum signals were clearly observed, which were characteristic of DMPO-·OH adducts, indicating that ·OH radicals indeed existed in the system. At the same time, using p-methoxyphenyl-4-methylpiperazine-1-oxide (TEMP) as a probe, obvious three-line spectrum signals were obtained, confirming the existence of TEMP- 1 O2. These results indicate that the high efficiency of BPA degradation in the Fe@N-SBC / PI system is derived from the synergistic effect of the radical pathway (mainly ·OH) and the non-radical pathway (O2assisted). 1 O2. These results indicate that the high efficiency of BPA degradation in the Fe@N-SBC / PI system is derived from the synergistic effect of the radical pathway (mainly ·OH) and the non-radical pathway (O2assisted).

[0114] The above only describes the preferred embodiments of the present application, and does not limit the present application in any form. It should be noted that, for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing sludge-based iron-nitrogen co-doped biochar material, characterized in that, Includes the following steps: Dewatered sludge, iron source, and nitrogen source are mixed to obtain a precursor mixture; The precursor mixture is pyrolyzed and carbonized to obtain the sludge-based iron-nitrogen co-doped biochar material.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the dewatered sludge, iron source, and nitrogen source is 40:1~2:1~2.

3. The preparation method according to claim 1 or 2, characterized in that, The iron source includes ferrous sulfate heptahydrate and / or ferric nitrate nonahydrate.

4. The preparation method according to claim 1 or 2, characterized in that, The nitrogen source includes ammonium chloride and / or urea.

5. The preparation method according to claim 1, characterized in that, The pyrolysis carbonization temperature is 550~950℃, and the time is 2h.

6. The preparation method according to claim 1 or 5, characterized in that, The heating rate during the pyrolysis carbonization process is controlled at 5~15℃ / min. This heating rate promotes the formation of an irregular porous structure in the material, thereby increasing the specific surface area and the exposure rate of reactive sites.

7. The preparation method according to claim 1 or 5, characterized in that, The pyrolysis carbonization is carried out in a protective atmosphere.

8. The sludge-based iron-nitrogen co-doped biochar material prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the sludge-based iron-nitrogen co-doped biochar material according to claim 8 in the field of organic pollutant degradation.

10. The application according to claim 9, characterized in that, The sludge-based iron-nitrogen co-doped biochar material and periodate were used synergistically for the degradation of bisphenol A.

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