Fe-doped sludge biochar as well as preparation method and application thereof

Abstract

The invention discloses a preparation method of Fe-doped sludge-based biochar, which comprises the following steps: step 1, weighing biochemical sludge, grinding, sieving with a 20-mesh sieve, drying at 105 DEG C for 6 hours, taking out the sludge, grinding again, and sieving with a 60-mesh sieve to obtain biochemical sludge powder; step 2, mixing the biochemical sludge powder with an activating agent, weighing 3.00 g of the biochemical sludge powder each time, the addition amount of the activating agent being 2-10% of the mass of the sludge, and the activating agent being one or more of FeCl3 and FeSO4; and 3, transferring the mixed sample into a crucible, putting the crucible into a tubular furnace, heating to 500-750 DEG C at a heating rate of 5 DEG C / min, keeping the temperature for 60-240 minutes, naturally cooling, and taking out to obtain the Fe-doped sludge biochar which is used as a particle electrode to be applied to the electro-Fenton degradation of the wine brewing wastewater. The Fe-doped biochar is prepared by taking biochemical sludge as a raw material and is used as a three-dimensional electro-Fenton system particle electrode for efficiently degrading the wine brewing wastewater, and the COD removal rate reaches 70.98%.

Description

Technical Field

[0001] This invention relates to, and in particular to, an iron-doped sludge biochar, its preparation method, and its application. Background Technology

[0002] As one of my country's traditional pillar industries, the brewing industry generates a large amount of brewing wastewater during production. This wastewater is extremely complex, containing not only high concentrations of organic matter (such as fermentation residues of sugars, alcohols, and organic acids) and a large amount of suspended solids (such as lees and grain residues), but also strong acidity / alkalinity and high nutrient load (high nitrogen and phosphorus content). Producing 1 ton of baijiu (Chinese liquor) can generate 12-20 tons of this type of wastewater. If discharged directly without effective treatment, it will cause serious pollution to water bodies, soil, and other ecosystems. Therefore, the efficient treatment of brewing wastewater is a key challenge for the sustainable development of the industry.

[0003] Currently, the main technologies for treating brewing wastewater include physical, chemical, biological, and combined methods, but all have significant limitations: Physical methods (such as coagulation, centrifugation, and adsorption) can only remove suspended solids and colloidal substances through solid-liquid separation, with weak degradation effects on dissolved organic matter. They are usually only used as pretreatment methods and cannot consistently meet emission standards. Chemical methods (such as oxidation-reduction and chemical precipitation) require the addition of large amounts of chemical reagents, which is not only costly but also prone to secondary pollution due to reagent residues or reaction byproducts. Furthermore, the traditional Fenton process requires continuous addition of H2O2, posing safety risks during transportation and storage, and the reaction conditions (such as pH) are stringent and difficult to control. Biological methods (such as anaerobic digestion and aerobic aeration) rely on microbial metabolism to degrade organic matter, but the high concentration of alcohol and complex components in brewing wastewater easily inhibit microbial activity, and microorganisms are sensitive to environmental conditions such as temperature and pH, leading to unstable treatment efficiency.

[0004] Meanwhile, biochemical sludge generated during wastewater treatment is another environmental problem that urgently needs to be addressed. Biochemical sludge is a mixture formed during the biological treatment stage, containing large amounts of organic matter, microorganisms, and moisture. It is produced in large quantities and is prone to breeding pathogens. Traditional disposal methods (such as landfill and incineration) not only occupy land resources but may also cause secondary pollution due to the leakage of heavy metals and toxic substances. Pyrolysis of biochemical sludge to produce biochar can both reduce and render the sludge harmless, and transform it into high-value functional materials, aligning with the circular economy concept of "treating waste with waste."

[0005] Three-dimensional electro-Fenton technology, as an important branch of advanced oxidation technology, can significantly improve the electrode specific surface area and mass transfer efficiency by introducing particle electrodes into the traditional electro-Fenton system, thereby enhancing the generation of ·OH free radicals and thus efficiently degrading recalcitrant organic compounds. However, existing three-dimensional electro-Fenton technologies still have shortcomings: the catalytic activity of traditional particle electrodes (such as activated carbon and graphite) is limited, and Fe needs to be continuously added during the electro-Fenton reaction.2+ It is prone to producing iron sludge; at the same time, there is a lack of research on the specific treatment of brewing wastewater, especially the lack of exploration of the application of biochemical sludge-based materials as particle electrodes.

[0006] In summary, existing brewing wastewater treatment technologies struggle to balance efficiency, cost, and environmental friendliness, while the resource utilization of biochemical sludge still requires expanding into high-value application scenarios. Therefore, developing a technology to prepare Fe-doped biochar from biochemical sludge and apply it as a high-efficiency particle electrode in a three-dimensional electro-Fenton system can not only solve the brewing wastewater treatment problem but also realize the resource utilization of biochemical sludge, which has significant theoretical and practical implications. Summary of the Invention

[0007] The present invention aims to provide Fe-doped sludge biochar, its preparation method and application, in order to solve the problems existing in the treatment of brewing wastewater.

[0008] This solution includes an Fe-coated sludge biochar, which uses biochemical sludge as raw material. The biochemical sludge undergoes pyrolysis to form a porous biochar matrix. The biochar is loaded with Fe, and the Fe is distributed as Fe... 2+ Fe 3+ It exists in the form of biochar on the surface and in the pores.

[0009] Furthermore, the Fe element originates from one or more activators among FeCl3 and FeSO4.

[0010] A method for preparing Fe-doped sludge biochar includes the following steps:

[0011] Step 1: Pretreatment of biochemical sludge. Weigh and grind the biochemical sludge, pass it through a 20-mesh sieve, and then dry it at 105℃ for 6 hours. After taking out the sludge, grind it again and pass it through a 60-mesh sieve to obtain biochemical sludge powder. Seal and dry it for storage.

[0012] Step 2: Mix the biochemical sludge powder with the activator. The amount of activator added is 2-10% of the sludge mass.

[0013] Step 3: Transfer the mixed sample to a crucible and place it in a tube furnace. Heat the sample to 500-750°C at a heating rate of 5°C / min and hold for 60-240 min. After natural cooling, remove the sample, wash it with deionized water until neutral, and dry it at 105°C to obtain Fe-doped sludge biochar.

[0014] Application of Fe-doped sludge biochar in the degradation of organic matter in brewing wastewater.

[0015] Furthermore, the Fe-doped sludge biochar is used as a particle electrode in a three-dimensional electro-Fenton system to degrade organic matter in brewing wastewater.

[0016] An application of Fe-infused sludge biochar in degrading organic matter in brewing wastewater includes the following steps:

[0017] Step A: Take the brewing wastewater, let it settle naturally for 48 hours, then filter it with gauze or cotton cloth, and keep the filtrate for later use;

[0018] Step B: Construct a three-dimensional electro-Fenton system. Add filtrate to the electrolytic cell, adjust the pH to 4 with 10% H2SO4, and add 3-15 g / L of biochar as the particle electrode. Use a stainless steel plate as the cathode and a ruthenium-iridium-titanium plate as the anode. Connect the air pump outlet pipe to the vicinity of the cathode plate to pump air in for aeration. Adjust the DC stable voltage to achieve a current density of 16 mA / cm². 2 The degradation time is 30-180 min, and the magnetic stirrer speed is 1100 rpm.

[0019] Furthermore, in step B, 12 g / L of biochar is added as a particle electrode.

[0020] The working principle and beneficial effects of this scheme: This invention has the following advantages: (1) Fe-doped biochar is prepared using biochemical sludge as raw material, which transforms waste into functional materials with catalytic activity, avoiding the harm to the environment caused by direct discharge of sludge, and reducing the land occupation and cost of sludge disposal. (2) Biochemical sludge is rich in organic matter and minerals. Through pyrolysis and activation treatment, its carbon components are converted into biochar with a high porosity structure. Fe elements are loaded with activators to form active sites, so that the potential resources in the sludge can be fully utilized, which meets the development needs of the circular economy. (3) The biochar prepared with FeSO4 as activator is less affected by the reaction conditions in terms of morphology and structure. It is more stable than biochar activated with FeCl3 and can maintain catalytic performance in multiple cycles, reducing the material loss cost in practical applications. (4) It can effectively reduce the organic pollution load of brewing wastewater and meet the requirements of subsequent treatment or discharge standards.

[0021] Compared with existing technologies: (1) Compared with physical methods (which are only used as pretreatment and cannot consistently meet standards), the present invention can deeply degrade dissolved organic matter and fundamentally reduce the degree of wastewater pollution.

[0022] (2) Compared with traditional chemical methods (which require the addition of a large amount of reagents, are costly and are prone to secondary pollution), the three-dimensional electro-Fenton system can generate H2O2 in situ through electrochemical action, reducing the amount of reagents added, lowering costs and avoiding secondary pollution; at the same time, Fe elements are stably loaded on the surface of biochar, reducing the generation of iron sludge.

[0023] (3) Compared with biological methods (which are sensitive to environmental conditions and difficult to control), this invention can operate stably by adjusting parameters such as current density and pH, and is not significantly affected by the complex components of brewing wastewater (such as high concentration of organic matter and pH fluctuations), making it more widely applicable. Attached Figure Description

[0024] Figure 1 XPS full spectrum of biological carbon and XPS plots of major elements;

[0025] Figure 2 XRD pattern of biocarbon;

[0026] Figure 3 FT-IR plot of biocarbon;

[0027] Figure 4 SEM image of the bio-carbon;

[0028] Figure 5 This is a particle size distribution diagram of biochar particles;

[0029] Figure 6 The effect of reaction temperature on biochar preparation is shown in Figure a, XRD pattern, FT-IR pattern, and SEM images c-e.

[0030] Figure 7 The effect of reaction time on biochar preparation is shown in Figure a, XRD pattern, FT-IR pattern, and SEM images c-e.

[0031] Figure 8 The effect of different particle electrode addition amounts on COD removal rate of brewing wastewater at different times. Detailed Implementation

[0032] The following detailed explanation illustrates the specific implementation methods:

[0033] Example:

[0034] A method for preparing Fe-doped sludge biochar includes the following steps:

[0035] Step 1: Pretreatment of biochemical sludge. Weigh and grind the biochemical sludge, pass it through a 20-mesh sieve, and then dry it at 105℃ for 6 hours. After removing the sludge, grind it again and pass it through a 60-mesh sieve to obtain biochemical sludge powder, which is then sealed and dried for storage.

[0036] Step 2: Mix the biochemical sludge powder with the activator. Weigh 3.00g of biochemical sludge powder each time. The activator is FeSO4 at 10% of the sludge mass.

[0037] Step 3: Transfer the mixed sample to a crucible and place it in a tube furnace. Heat the sample to 750°C at a heating rate of 5°C / min and hold for 180 min. After natural cooling, remove the sample to obtain Fe-doped sludge biochar.

[0038] The effect of activators on biochar production

[0039] XPS analysis was performed on the elemental composition of the biocarbon material, and the results are as follows: Figure 1 (a~d): Figure 1 (a) is the full XPS spectrum of biocarbons prepared without the addition of any activator. Figure 1 (b) is the XPS full spectrum after adding FeSO4 and FeCl3. Figure 1 (c) is a diagram of C1s biochar prepared from FeSO4. Figure 1 (d) is a diagram of Fe2p of biogenic carbon prepared from FeSO4.

[0040] The comparison showed that XPS added characteristic peaks for Fe, indicating that Fe has been loaded onto the surface of sludge biochar. Figure 1 As shown in (c), the C1s spectrum exhibits a characteristic peak at 287.68 eV, due to the effect of OC=O; a characteristic peak appears at 286.28 eV, due to the effect of CO; and a characteristic peak appears at 288.8 eV, due to the effect of CC. In addition, characteristic peaks for Fe2p, O1s, and Si2p elements appear in the spectrum, indicating that Fe, O, and Si may undergo certain reactions during pyrolysis, causing them to combine and exist in different compound forms. Figure 1 (d) It can be seen that the Fe2p peak is convolved into three peaks: Fe2p1 / 2 (711.28 eV), Fe2p3 / 2 (724.18 eV), and a satellite peak. Among them, 711.78 eV and 723.68 eV represent Fe(II), and 715.88 eV and 725.98 eV represent Fe(III). 2+ and Fe 3+ Therefore, Fe ions successfully exist in multiple forms on the surface of bio-carbon, which can promote the catalytic oxidation reaction in the three-dimensional electro-Fenton reaction process.

[0041] The structure of biochar was analyzed by XRD, and the results are as follows: Figure 2 XRD patterns of biochar prepared from 10% FeSO4, 5% FeCl3, and 2% FeCl3 at 750 °C are shown. The XRD results show a very strong peak at 2θ = 26.624°, which corresponds to the (011) crystal plane and is attributed to SiO2. At 2θ = 38.1°, 54.936°, and 70.178°, the peaks correspond to the (112), (004), and (312) crystal planes of Fe2O3, respectively. At 2θ = 36.941° (311), 49.414° (102), 29.455° (221), and 60.695° (104), the peaks correspond to Fe3O4, Fe, FeSiO3, and FeO, respectively, consistent with the XPS results.

[0042] FT-IR analysis was performed on the biocarbon material to further analyze its structural composition, and the results are as follows: Figure 3 (a~c): The results show that when the activator is FeSO4, the FT-IR characteristic peaks of the prepared Fe-doped biochar materials are basically similar. When the activator is FeCl3, the FT-IR characteristic peaks of biochar prepared with different addition amounts show different morphologies. This indicates that the concentration of the activator has an effect on the functional groups on the surface of the prepared biochar, and may change the structure and type of functional groups on the surface of biochar.

[0043] SEM analysis was performed on it, and the results are as follows: Figure 4 (a-j): SEM images of sludge biochar prepared at a calcination temperature of 750℃, a calcination time of 240 min, and with FeCl3 and FeSO4 as activators at concentrations of 10%, 8%, 5%, 2%, and 0%, respectively. The results show that the sludge biochar prepared without activator is porous and crystalline, with large pores, an uneven structure, and a relatively rough surface. The pore structure of the activated sludge biochar decreases slightly with increasing activator dosage. This is because the activator is also pyrolyzed and carbonized during the preparation of Fe-doped biochar; the carbonized activator is adsorbed onto the biochar surface as granular crystals. Since the adsorbate must pass through the pores before reaching the adsorption sites on the adsorbent surface, the surface porosity of the biochar decreases slightly. Figure 4 The morphological characteristics of (i), (g), and (f) are network, sheet-like, and flocculent, respectively, indicating that the activator FeCl3 has a significant impact on the structure of the prepared biochar; while Figure 4 The surfaces of (a) and (b) are covered with spherical particles, which may be due to the activator filling the pores of the biochar. Combined with XPS and XRD results, this indicates that Fe has successfully combined with the biochar to form an Fe-doped sludge biochar composite material, which can provide sufficient Fe for the three-dimensional electro-Fenton system. 2+ This ensures that the degradation experiment is carried out efficiently.

[0044] The particle size distribution was measured using a laser particle size analyzer, and the results are as follows: Figure 5 (a) and (b) show the particle size distribution of biochar particles prepared with different amounts of activators (FeCl3, FeSO4). Figure 5 As shown in (a), the average particle size of biochar particles slightly increased when the activator (FeCl3) addition amount was 2% and 5%. The particle size distribution at 5% addition showed a bimodal shape, while at 8% and 10% addition, the distribution showed a stable "normal distribution". The data are shown in Table 1. The average particle size was 191.349 μm, 90% of the particles had a diameter of 369.989 μm, and 10% of the particles had a diameter of 92.356 μm.

[0045] Table 1. Particle size distribution of biochar prepared with different types and concentrations of activators (A-1 to 5: 10%, 8%, 5%, 2%, 0% FeCl3; B-1 to 5: 10%, 8%, 5%, 2%, 0% FeSO4)

[0046]

[0047]

[0048] Effect of reaction temperature on biochar preparation

[0049] Figure 6 (a) XRD analysis showed that when 2θ = 26.624° (011), 29.455° (221), 36.941° (311), 38.100° (112) and 70.178° (312), 49.414° (102), 42.826° (111), 60.695° (104) are the diffraction peak crystal plane data of SiO2, FeSiO3, Fe3O4, Fe2O3, Fe and FeO, respectively. This indicates that Fe, O and Si exist in the biocarbon material in the form of compounds, which is basically consistent with the XRD results. Figure 6 (b) FT-IR spectra of biochar prepared at different temperatures; results are shown at 3732 cm⁻¹. 1 1709cm- 1 and 918cm- 1 The absorption peaks at these locations are attributed to stretching vibrations of -OH, C=C, and C=O, respectively, while the absorption peaks at 675 cm⁻¹ are due to these vibrations. 1 This is attributed to Fe-O. Comparison of SEM images revealed that as the temperature increased, the pores of the biochar material decreased slightly, and granular solids gradually appeared on the surface and between the pores of the biochar.

[0050] like Figure 7 (a) XRD analysis results show that when 2θ = 26.624°(011), 29.455°(221), 36.941°(311), 38.100°(112), 54.936°(004), 49.414°(102) and 42.826°(111), 60.695°(104) are the diffraction peak crystal plane data of SiO2, FeSiO3, Fe3O4, Fe2O3, Fe and FeO, respectively. Fe, O and Si exist in biocarbon materials in multiple forms; in FT-IR ( Figure 7 (b) In the analysis, the absorption peak is at 3244 cm⁻¹. 1 1573cm- 1 and 1058cm- 1 The strong absorption peaks at these locations are caused by the effects of -OH, C=C, and C=O, respectively, while the peak at 477 cm⁻¹ is the largest.1 568cm- 1 This is because the stretching transformation of Fe-O further confirms the existence of Fe, O, and Si composite substances.

[0051] Figure 7 (c-e) represent SEM images of biochar prepared at 750℃ for 60, 120, and 180 min, respectively. Comparison shows that the surface porosity of biochar prepared at 120 min is significantly smaller than that prepared at 60 and 180 min, with particulate matter adsorbed onto the particle surface, resulting in a layered pore structure. As the reaction time increases to 180 min, the porosity increases again, and the degree of crystallization is higher than that of biochar prepared at 60 and 120 min. Compared to 60 min, the biochar prepared at 180 min shows clearly visible partial crystallization of particulate matter on the pore surface, indicating that the activator has been converted into compounds and loaded onto the surface of the biochar material during the pyrolysis reaction. Therefore, 180 min is the optimal condition for this group.

[0052] Fe-infused biochar was prepared from biochemical sludge using different types and amounts of activators at the same temperature and time, and the data parameters were analyzed. The results are discussed below:

[0053] (1) Analysis of the effect of activators on biochar preparation:

[0054] XRD analysis revealed the presence of compounds containing SiO2, Fe2O3, Fe3O4, FeO, FeSiO3, and various Fe, O, and Si elements in the biochar material. The XRD pattern of biochar prepared with 10% FeSO4 showed richer and more prominent compound diffraction peaks compared to biochar prepared with 2% and 5% FeCl3, indicating a higher degree of crystallinity.

[0055] XPS analysis results indicate that Fe is in the form of Fe 2+ Fe 3+ The presence of Fe in three forms indicates that Fe has been successfully loaded onto the surface of the sludge biochar.

[0056] FT-IR analysis showed that when the activator was FeSO4, the FT-IR characteristic peaks of the prepared Fe-doped biochar materials were basically similar, indicating that FeSO4 had little effect on the functional groups on the surface of sludge biochar. When the activator was FeCl3, the FT-IR characteristic peaks at different addition concentrations showed different morphologies, indicating that the addition concentration of the activator affected the functional groups on the surface of the prepared biochar, and may have changed the structure and types of functional groups on the surface of biochar.

[0057] SEM characterization and analysis revealed that biochar materials prepared by adding FeCl3 as an activator at certain concentration gradients to the raw materials exhibited different structural characteristics, indicating that FeCl3 has a significant impact on the structure of the prepared biochar. However, when FeSO4 was used as the activator, the biochar material exhibited a relatively stable structure and could be added as a particle electrode to a three-dimensional electro-Fenton system.

[0058] (2) Effect of reaction temperature on biochar preparation:

[0059] XRD analysis results showed that SiO2, Fe2O3, Fe3O4, FeO, FeSiO3 and various compounds of Fe, O and Si elements were present in the biochar.

[0060] FT-IR analysis results showed that the infrared absorption peaks at reaction temperatures of 500, 600 and 700 °C were similar, with the same absorption peaks appearing in all cases. This indicates that the reaction temperature has little effect on the functional groups on the surface of the prepared biochar.

[0061] SEM analysis results show that as the temperature increases, the pore size of the biochar material decreases slightly but not significantly. Granular solids gradually appear on the surface of the biochar and between the pores, indicating that the activator has been successfully loaded onto the surface of the biochar.

[0062] (3) Effect of reaction time on biochar preparation:

[0063] XRD analysis showed that the biochar contained SiO2, Fe2O3, Fe3O4, FeO, and FeSiO3.

[0064] FT-IR analysis results showed that the infrared absorption peaks at reaction times of 60, 120 and 180 were similar, and the types of functional groups they represented were also the same. This indicates that the reaction time has little effect on the functional groups represented by the prepared biochar.

[0065] SEM analysis results show that as the reaction time increases, the porosity of biochar first decreases and then increases. At 60 min, many particulate materials appear on the surface of biochar, the porosity decreases significantly and shows a layered stacking state. When the reaction time is 180 min, the porosity increases again, and the particulate materials aggregate into small agglomerate structures loaded on the surface of biochar. This will be beneficial to the degradation of brewing wastewater. Therefore, 180 min is the optimal reaction time.

[0066] The application of Fe-doped sludge biomass in the degradation of brewing wastewater involves adding Fe-doped sludge biochar as a three-dimensional particle electrode to a three-dimensional electro-Fenton system, including the following steps:

[0067] Step A: Take 20L of brewing wastewater, let it settle naturally for 48 hours, then filter it with gauze and cotton, and keep the filtrate for later use;

[0068] Step B: Construct a three-dimensional electro-Fenton system. Adjust the pH of the electrolytic cell filtrate to 4 using 10% H2SO4. Add 12 g / L of biochar as the particle electrode. Use a stainless steel plate as the cathode and a ruthenium-iridium-titanium plate as the anode. Connect the air pump outlet pipe near the cathode plate to pump air in for aeration. Adjust the DC stable voltage to achieve a current density of 16 mA / cm². 2 The degradation time was 120 minutes, and the magnetic stirrer speed was 1100 rpm.

[0069] Effect of electrode addition amount on degradation efficiency:

[0070] Fe-doped sludge biochar was added to a three-dimensional electro-Fenton system at concentrations of 3, 6, 9, 12, and 15 g / L as particle electrodes, with all other factors remaining the same. The effect of electrode addition on COD removal rate was studied, and the results are as follows: Figure 8 As shown in the figure, when the particle addition amount is 12 g / L, the COD removal rate at different time points is higher than that at other addition amounts, and the COD removal rate also increases with time, reaching a maximum of 70.98% at 120 min. Therefore, the particle electrode addition amount of 12 g / L is the optimal parameter. When the particle addition amount is 15 g / L, the COD removal rate decreases significantly compared to 12 g / L. This may be because excessive particle electrodes accumulating in the system can cause current short circuits, reducing degradation efficiency. During the experiment, many biochar particles were observed to deposit at the bottom of the electrolyzer, which verifies the above hypothesis. When the particle electrode addition amount is 3, 9, and 15 g / L, the COD removal rate generally increases with time, but decreases between 60 and 90 min. This may be because the rotors in the electrolyzer stick together, preventing the water from rotating, resulting in insufficient degradation and a decrease in COD removal rate.

[0071] in conclusion:

[0072] Based on the analysis of the above test data, the optimal conditions for preparing Fe-doped sludge biochar are: 10% FeSO4 as the activator, 750℃ as the reaction temperature, and 180 min as the reaction time.

[0073] The experiment investigated the degradation efficiency of Fe-doped sludge biochar in brewing wastewater in a three-dimensional electro-Fenton system. The effects of particle electrode dosage and degradation time on the degradation efficiency were studied using COD removal rate as an indicator. Results showed that at pH 4 and a current density of 16 mA / cm², the degradation efficiency was optimal. 2 When the particle electrode addition amount is 12 g / L and the degradation time is 120 min, the COD removal rate reaches 70.98%.

[0074] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A type of Fe-doped sludge biochar, characterized in that: Using biochemical sludge as raw material, the biochemical sludge is pyrolyzed to form a porous biochar matrix; the biochar is loaded with Fe element, and the Fe element is in the form of Fe. 2+ Fe 3+ It exists in the form of biochar on the surface and in the pores.

2. The Fe-doped sludge biochar according to claim 1, characterized in that: The Fe element originates from one or more activators, such as FeCl3 and FeSO4.

3. The method for preparing Fe-doped sludge biochar according to claim 2, characterized in that: Including the following steps: Step 1: Pretreatment of biochemical sludge. Weigh and grind the biochemical sludge, pass it through a 20-mesh sieve, and then dry it at 105℃ for 6 hours. After taking out the sludge, grind it again and pass it through a 60-mesh sieve to obtain biochemical sludge powder. Seal and dry it for storage. Step 2: Mix the biochemical sludge powder with the activator. The amount of activator added is 2-10% of the sludge mass. Step 3: Transfer the mixed sample to a crucible and place it in a tube furnace. Heat the sample to 500-750°C at a heating rate of 5°C / min and hold for 60-240 min. After natural cooling, remove the sample, wash it with deionized water until neutral, and dry it at 105°C to obtain Fe-doped sludge biochar.

4. The application of Fe-doped sludge biochar according to claim 1 or 3 in the degradation of organic matter in brewing wastewater.

5. The application of Fe-doped sludge biochar according to claim 4, characterized in that: The Fe-doped sludge biochar is used as a particle electrode in a three-dimensional electro-Fenton system to degrade organic matter in brewing wastewater.

6. The application of Fe-coated sludge biochar according to claim 5, characterized in that: The degradation of organic matter in brewing wastewater includes the following steps: Step A: Take the brewing wastewater, let it settle naturally for 48 hours, then filter it with gauze or cotton cloth, and keep the filtrate for later use; Step B: Construct a three-dimensional electro-Fenton system. Add filtrate to the electrolytic cell, adjust the pH to 4 with 10% H2SO4, and add 3-15 g / L of biochar as the particle electrode. Use a stainless steel plate as the cathode and a ruthenium-iridium-titanium plate as the anode. Connect the air pump outlet pipe to the vicinity of the cathode plate to pump air in for aeration. Adjust the DC stable voltage to achieve a current density of 16 mA / cm². 2 The degradation time is 30-180 min, and the magnetic stirrer speed is 1100 rpm.

7. The application of Fe-doped sludge biochar according to claim 6, characterized in that: In step B, 12 g / L of biochar was added as a particle electrode.

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