Preparation method of modified biochar

Abstract

The invention belongs to the technical field of wastewater treatment, and relates to a preparation method of modified biochar and application of the modified biochar in treatment of antibiotic wastewater by an anaerobic ammonia oxidation process. Garden and agricultural wastes are used as raw materials, an extracellular polymer EPS is loaded while the specific surface area of the biochar is increased through iron modification, adsorption sites and biological niches of the biochar are increased, growth attachment sites are provided for microorganisms, the biological activity and the microorganism aggregation capacity are enhanced, and the iron and EPS co-modified biochar is obtained. When the research on the adsorption performance and mechanism of common biochar BC, iron modified biochar Fe-coated BC and iron and EPS co-modified biochar EPS / Fe-coated BC on three antibiotics at the pyrolysis temperature of 300-700 DEG C shows that the specific surface area of co-modified biochar is greatly increased, and the specific anaerobic ammonia oxidation activity SAA is remarkably enhanced; the denitrification and antibiotic removal of anaerobic ammonium oxidation bacteria are synergistically enhanced. Meanwhile, compared with common biochar, the modified biochar is easy to recover, low in cost, long in acting duration and wide in application range. According to the method, the problems of low denitrification efficiency and low antibiotic removal efficiency of anaerobic ammonia oxidation treatment of antibiotic wastewater are solved, garden and agricultural wastes are reused, pollutants are removed, and the method has remarkable environmental and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a modified biochar, its preparation method, and its application in the anaerobic ammonia oxidation treatment of antibiotic wastewater. Background Technology

[0002] In recent years, antibiotics have been detected in large quantities in various water bodies, causing serious environmental pollution problems. Anaerobic ammonia oxidation (AAO) technology, as a low-carbon, high-efficiency, green, and economical nitrogen removal technology, has attracted much attention in the field of wastewater denitrification treatment. Its advantages include no need for aeration or external carbon sources, and almost no residual sludge production, making it suitable for treating various types of wastewater with high ammonia nitrogen and low carbon-to-nitrogen ratios, such as landfill leachate, anaerobic sludge digestion liquid, and antibiotic wastewater. However, the long generation time, long start-up time, and demanding growth conditions of anaerobic ammonia oxidizing bacteria, along with their sensitivity to environmental factors such as temperature, substrate concentration, heavy metals, and antibiotics, severely restrict the development and promotion of AAO technology. Antibiotics inhibit the activity of anaerobic ammonia oxidizing bacteria, leading to changes in their metabolic pathways and even cell death, seriously affecting the nitrogen removal efficiency of the AAO process. Therefore, improving the activity and metabolic level of anaerobic ammonia oxidizing bacteria and ensuring the long-term stable operation of AAO is crucial for achieving efficient nitrogen removal treatment of antibiotic wastewater.

[0003] Currently, biochar, clay minerals, activated carbon, nanomaterials, mineral materials, and magnetic materials are used in wastewater treatment, primarily for enhancing microbial activity and adsorbing pollutants. Biochar, in particular, is widely used due to its ease of preparation, readily available raw materials, and low cost. Furthermore, biochar modification can significantly improve its performance, including increasing specific surface area, porosity, and enhancing magnetism through metal modification. Biochar modification involves physical, chemical, and biological methods, but a single modification method has limited performance enhancement. Therefore, using multiple methods to modify biochar can produce better results. Currently, biochar modification typically shows good performance in adsorbing pollutants such as metal ions and antibiotics, but its effect on microorganisms in wastewater denitrification is limited. Therefore, it is necessary to combine multiple modification methods to synergistically enhance anaerobic ammonia-oxidizing bacteria denitrification and antibiotic removal. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing modified biochar. Modified biochar is then applied to an anaerobic ammonia oxidation process for treating antibiotic wastewater. The modified biochar possesses a higher specific surface area, abundant functional groups, and metabolic products that can be utilized by microorganisms. The modification not only enhances the biochar's adsorption capacity but also improves its anaerobic ammonia oxidation activity, synergistically enhancing denitrification efficiency and antibiotic removal efficacy in the anaerobic ammonia oxidation treatment of antibiotic wastewater.

[0005] The objective of this invention is achieved as follows: A method for preparing modified biochar, characterized by comprising the following steps: Step 1: Crush the biochar raw material, clean it, dry it, and pass it through a perforated sieve; Step 2: Add the biomass powder obtained in Step 1 to the iron ion solution. The volume ratio of biomass powder to iron solution is 1 / 12 to 1 / 8. Then mix thoroughly by mechanical stirring. Step 3: During the stirring process, the pH is controlled to be stable at 10.0±1.0 using NaOH solution; after sealing, the mixture is stirred continuously for a set time, then the solid is filtered through a membrane, and then washed continuously with deionized water until the pH of the filtrate is 7.0±0.5. The remaining solid is then dried at a set temperature. Step 4: Place the ceramic boat containing the solid obtained in step 3 into a tube furnace and purge with nitrogen to control anaerobic pyrolysis to prepare iron-modified biochar Fe@BC. Step 5: Extraction of crude extracellular polymeric substances (EPS). Take the sludge mixture into a centrifuge tube, centrifuge, discard the supernatant, add NaCl solution until the initial volume is reached, and heat at the set temperature; then centrifuge the sludge mixture, and finally collect the supernatant after centrifugation, filter it with a filter to obtain the EPS solution; the EPS solution is stored in an environment at a specific temperature before the experiment. Step 6: Soak the iron-modified biochar obtained in Step 4 in the EPS solution prepared in Step 5 for a set time, and change the EPS solution every day; obtain iron and EPS co-modified biochar Fe / EPS@BC, then air dry them for a period of time and store them at room temperature.

[0006] Further specified, the temperature of the blower dryer used in step 1 is 40℃~60℃, the drying time is 12~24 h, and the sieve used is a 40 mesh sieve. Further specifying, the iron ion solution in step 2 has the composition of FeCl2 + FeCl3, wherein Fe2+ + The concentration of Fe was 0.25 ± 0.05 mol / L. 3+ The concentration was 0.5 ± 0.05 mol / L, and the volume ratio of biomass powder to iron ion solution was 1:10.

[0007] Further restrictions are imposed: in step 4, the pyrolysis temperature is 300℃~700℃, the heating rate is 5~15℃ / min, and the reaction time is 2~3 h.

[0008] Further specifying, the sludge mixture in step 5 should be sludge from the biological reactor.

[0009] Further specifying that in step 5, the solution in which NaCl solution is added to the supernatant to the initial volume is heated at 70°C for 30 minutes.

[0010] Further restrictions were imposed, with the EPS solution concentration in step 5 set to 25~75 mg / L, and the EPS solution stored at -20℃ before the experiment.

[0011] Further specifying, in step 6, the iron-modified biochar needs to be soaked in EPS solution for 72 hours; the obtained iron and EPS co-modified biochar needs to be air-dried for 36 hours.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, Fe is loaded onto biochar and then pyrolyzed, resulting in Fe@BC with a significantly increased specific surface area and enhanced aromaticity, thus improving the electron transfer capacity of microorganisms. EPS is then loaded onto the Fe@BC surface to obtain EPS / Fe@BC. The abundant functional groups in EPS further enhance its adsorption effect; moreover, EPS contains various metabolites such as amino acids and sugars that can be utilized by microorganisms, enhancing their activity. EPS / Fe@BC promotes the absorption and utilization of Fe and metabolites by anaerobic ammonia oxidizing bacteria, increases their metabolic activity (SAA), and simultaneously enhances the denitrification efficiency and antibiotic removal efficiency of anaerobic ammonia oxidation in treating antibiotic wastewater. Furthermore, this material has advantages such as low cost, good stability, easy recycling, low pollution, excellent performance, and wide applicability, and can be widely used in anaerobic ammonia oxidation processes to treat various antibiotic-containing wastewaters, providing theoretical guidance for the practical engineering application of anaerobic ammonia oxidation processes. Attached Figure Description

[0013] 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 only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0014] Figure 1 This is a comparison of the anaerobic ammonia oxidation denitrification rates of BC, Fe@BC, and EPS / Fe@BC prepared in Examples 1-4 of this invention.

[0015] Figure 2 The graphs show the changes in SAA after adding BC, Fe@BC, and EPS / Fe@BC as described in Examples 1-4 of this invention.

[0016] Figure 3 The adsorption kinetic curves of BC, Fe@BC and EPS / Fe@BC prepared in Examples 1-4 of this invention for different antibiotics are shown.

[0017] Figure 4The adsorption isotherms of BC, Fe@BC and EPS / Fe@BC prepared in Examples 1-4 of this invention for different antibiotics are shown.

[0018] Figure 5 These are SEM images of BC, Fe@BC, and EPS / Fe@BC prepared in Examples 1-4 of the present invention.

[0019] Figure 6 Fourier transform infrared spectroscopy analysis of BC, Fe@BC and EPS / Fe@BC prepared in Examples 1-4 of this invention. Detailed Implementation

[0020] 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, and 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.

[0021] Example 1 Pine biomass raw material was crushed, cleaned, dried at 55℃, and passed through a 40-mesh sieve. A ceramic boat containing the biomass was placed in a tube furnace and pyrolyzed at 300, 500, and 700℃ for 2 hours, respectively, with a heating rate of 10℃ / min. Nitrogen gas was introduced to control anaerobic digestion, thus producing biochar. These were labeled BC-300, BC-500, and BC-700, respectively.

[0022] The biochar raw material was pulverized, cleaned, dried at 60℃, and passed through a 40-mesh sieve. The biomass was then added to a solution containing 0.75 mol / L iron ions (FeCl2 + FeCl3, Fe...). 2+ 0.25 mol / L, Fe 3+ The biomass powder (0.5 mol / L) was mixed with iron solution at a volume ratio of 1:10, and then thoroughly stirred by mechanical stirring. During stirring, the pH was maintained at 10.0 using NaOH solution. After 12 h of sealed stirring, the mixed solid was filtered through a 0.45 μm membrane and continuously washed with deionized water until the pH of the filtrate reached 7.0. The remaining solid was dried at 60 °C for 24 h. The biomass-filled ceramic boat was then placed in a tube furnace and pyrolyzed at 300, 500, and 700 °C for 2 h at a heating rate of 10 °C / min, respectively, with nitrogen gas introduced to control anaerobic digestion, thus preparing iron-modified biochar. These were labeled Fe@BC-300, Fe@BC-500, and Fe@BC-700, respectively.

[0023] Example 2 Pine biomass raw materials were crushed, cleaned, dried at 50℃, and passed through a 40-mesh sieve. The biomass was then added to a solution containing 0.75 mol / L iron ions (FeCl2 + FeCl3, Fe...). 2+ 0.25 mol / L, Fe 3+ The biomass powder (0.5 mol / L) and iron solution were mixed at a volume ratio of 1:10, and then thoroughly stirred mechanically. During stirring, the pH was maintained at 10.0 using NaOH solution. After continuous stirring in a sealed container for 12 h, the mixed solid was filtered through a 0.45 μm membrane and continuously washed with deionized water until the pH of the filtrate reached 7.0. The retained solid was dried at 50 °C for 24 h. The biomass-filled ceramic boats were then placed in a tube furnace and pyrolyzed at 300 °C for 2 h at a heating rate of 5 °C / min, with nitrogen purging to control anaerobic conditions, thus preparing iron-modified biochar. The iron-modified biochar was then soaked in fresh EPS solution at 33 °C for 72 h, with EPS concentrations set at 25, 50, and 75 mg / L, and the EPS solution was changed daily to obtain iron- and EPS-modified biochar. This was then air-dried for 36 h and stored at room temperature. They are labeled as 25EPS / Fe@BC-300, 50EPS / Fe@BC-300, and 75EPS / Fe@BC-300, respectively.

[0024] Example 3 Pine biomass raw materials were crushed, cleaned, dried at 40℃, and passed through a 40-mesh sieve. The biomass was then added to a solution containing 0.75 mol / L iron ions (FeCl2 + FeCl3, Fe...). 2+ 0.25 mol / L, Fe 3+ The biomass powder (0.5 mol / L) and iron solution were mixed at a volume ratio of 1:10, and then thoroughly stirred mechanically. During stirring, the pH was maintained at 10.0 using NaOH solution. After 12 h of continuous stirring in a sealed container, the mixed solid was filtered through a 0.45 μm membrane and continuously washed with deionized water until the pH of the filtrate reached 7.0. The retained solid was dried at 40 °C for 24 h. The biomass-filled ceramic boats were then placed in a tube furnace and pyrolyzed at 500 °C for 2 h at a heating rate of 15 °C / min, with nitrogen purging to control anaerobic conditions, thus preparing iron-modified biochar. The iron-modified biochar was then soaked in fresh EPS solution at 33 °C for 72 h, with EPS concentrations set at 25, 50, and 75 mg / L, and the EPS solution was changed daily to obtain iron- and EPS-modified biochar. This was then air-dried for 36 h and stored at room temperature. They are labeled as 25EPS / Fe@BC-500, 50EPS / Fe@BC-500, and 75EPS / Fe@BC-500, respectively.

[0025] Example 4 Pine biomass raw materials were crushed, cleaned, dried at 45℃, and passed through a 40-mesh sieve. The biomass was then added to a solution containing 0.75 mol / L iron ions (FeCl2 + FeCl3, Fe...). 2+ 0.25 mol / L, Fe 3+ The biomass powder (0.5 mol / L) was mixed with iron solution at a volume ratio of 1 / 10, and then thoroughly stirred mechanically. During stirring, the pH was maintained at 10.0 using NaOH solution. After continuous stirring in a sealed container for 12 h, the mixed solid was filtered through a 0.45 μm membrane and continuously washed with deionized water until the pH of the filtrate reached 7.0. The retained solid was dried at 45 °C for 24 h. The biomass-filled ceramic boat was then placed in a tube furnace and pyrolyzed at 700 °C for 2 h at a heating rate of 5 °C / min, with nitrogen purging to control anaerobic conditions, thus preparing iron-modified biochar. The iron-modified biochar was then soaked in fresh EPS solution at 33 °C for 72 h, with EPS concentrations set at 25, 50, and 75 mg / L, and the EPS solution was changed daily to obtain iron- and EPS-modified biochar. This was then air-dried for 36 h and stored at room temperature. They are labeled as 25EPS / Fe@BC-700, 50EPS / Fe@BC-700, and 75EPS / Fe@BC-700, respectively.

[0026] 1. Sequencing batch test of specific anaerobic ammonium oxidation activity The biochar prepared in Examples 1-4 was added to a 150 mL serum bottle at a concentration of 10 g / L, prepared with ammonium chloride and sodium nitrite, and NH4. + -N and NO2 - A solution with a concentration of 50 mg / L of nitrogen (SNA) was prepared, and 120 mL was added to a serum bottle. 50 mL of anaerobic ammonia oxidation biomass was then inoculated into the solution. The initial pH was adjusted to 7.5 using 1 mol / L hydrochloric acid or sodium hydroxide. Oxygen was removed using nitrogen, and a batch experiment was conducted in a constant-temperature shaker at 33°C and 180 rpm. 5 mL water samples were collected at 0.5, 1, 2, 3, and 3.5 h to determine the total nitrogen concentration in the water. The specific anaerobic ammonia oxidation activity (SAA) was calculated using the following formula.

[0027] Figure 1 To investigate the effect of different biochar types on the nitrogen removal rate of anaerobic ammonia oxidizing bacteria, it was found that biochar co-modified with iron and EPS significantly improved the nitrogen removal rate. In Example 3, the addition of 50 EPS / Fe@BC-700 resulted in the highest total nitrogen removal rate. Figure 2The changes in SAA after adding the biochar prepared in Examples 1-4 are shown, with the SAA of the Fe@BC-700 group being 117.46 mg N·g VSS. -1 ·d -1 The level was significantly higher than that of the control group (CK) at 82.33 mg N·g VSS. -1 ·d -1 The SAA level increased by 42.67%. The SAA of 50EPS / Fe@BC-300 was 109.44 mg N·g VSS. -1 ·d -1 Compared with the control group, the efficiency of biochar modified with iron and EPS was increased by 32.93%, which significantly improved the efficiency of anaerobic ammonia oxidation denitrification.

[0028] 2. Adsorption kinetics test Three antibiotic solutions were prepared using 0.01 mol / L CaCl2 solution as the background electrolyte: oxytetracycline (OTC), ciprofloxacin (CIP), and ceftiofur sodium (CFS), with initial concentrations of 5, 10, 20, 50, and 100 mg / L, respectively. 30 mL of each solution was placed in a 50 mL centrifuge tube, and 0.150 g of BC or modified BC was added. The mixture was shaken in a 33 ℃ water bath in the dark. The supernatant was collected at 0, 0.5, 1, 2, 4, 6, 8, 12, and 24 h, filtered through a 0.45 μm filter membrane, and the antibiotic concentrations were determined.

[0029] Figure 3 Adsorption kinetic fitting curves for OTC, CIP, and CFS by different modified biochars are shown. For OTC adsorption, the adsorption effects of several biochars are similar, with the maximum adsorption rate within 2 hours; while the maximum adsorption values ​​for CIP and CFS occur between 4 and 6 hours. In the initial stage of adsorption, there are many adsorption sites on the biochar, resulting in a rapid adsorption rate. However, as adsorption progresses, these sites are gradually occupied by antibiotics, and the adsorption rate begins to decrease. Comparing the adsorption performance of different biochars, Fe@BC-700 exhibits the largest adsorption capacity, indicating that iron-modified biochar forms more adsorption sites and has a better adsorption effect on antibiotics.

[0030] Table 1. Fitting parameters for the adsorption kinetic model of modified biochar for different antibiotics.

[0031] Table 1 shows that the pseudo-first-order kinetics better fits the adsorption of antibiotics by Fe@BC-700 biochar, indicating that the adsorption of antibiotics by Fe@BC-700 is mainly physical adsorption. This suggests that iron modification of biochar can create more adsorption sites. The pseudo-second-order kinetic equation better fits the adsorption of antibiotics by most biochars, thanks to the EPS loading. The pseudo-second-order kinetic model is based on the principle of chemisorption, which involves the formation of chemical bonds through electron exchange or sharing between the adsorbent and adsorbate. The adsorption process reflected by the pseudo-second-order kinetic model includes surface adsorption, external liquid film, and internal particle diffusion, thus suggesting that the adsorption of antibiotics by biochar involves multiple adsorption mechanisms. Furthermore, the Qe values ​​in Table 1 show that the modified biochar has better adsorption effects for OTC and CIP antibiotics; and the iron-modified Fe@BC-700 has significantly higher adsorption effects for the three antibiotics than other biochars, demonstrating superior adsorption performance.

[0032] 3. Isothermal adsorption test Three antibiotic wastewater solutions were prepared using 0.01 mol / L CaCl2 solution as the background electrolyte: OTC, CIP, and CFS, with initial concentrations of 5, 10, 20, 50, and 100 mg / L, respectively. 30 mL of each solution was placed in a 50 mL centrifuge tube, and 0.150 g of BC or modified BC was added. The tubes were shaken in a 33°C water bath in the dark until adsorption equilibrium was reached. 3 mL of the supernatant was then filtered through a 0.45 μm filter membrane, and the antibiotic concentration was determined.

[0033] The adsorption effects of different biochars on different antibiotics are shown in the figure. Figure 4 See Table 2. The Langmuir equation fits the adsorption isotherms of most biochar better, indicating that most biochar mainly exhibits monolayer homogeneous adsorption, especially EPS-modified biochar. Some biochar shows a better fit in the Freundlich equation, indicating multilayer heterogeneous surface adsorption.

[0034] Analysis revealed that the maximum adsorption capacity of OTC increased with increasing EPS loading concentration, while the maximum adsorption capacity of the modified biochar was more than twice that of the original. The adsorption capacity of biochar for CIP was significantly higher than that of OTC and CFS. Furthermore, the maximum adsorption capacity of 50EPS / Fe@BC-700 reached 46.389 mg·g⁻¹. －1Furthermore, the fitted adsorption capacity of EPS / Fe@BC-700 on OTC and CIP was significantly higher than that of BC-700 and Fe@BC-700. In the adsorption of OTC and CFS, the maximum adsorption capacity of iron-modified biochar was much lower than that of unmodified biochar, which is the opposite of the adsorption trend for OTC, indicating that metal modification is selective for antibiotic adsorption. The adsorption effect of biochar loaded with EPS increased significantly, and the improvement in the adsorption capacity of EPS for antibiotics was evident.

[0035] Table 2. Fitting parameters of the adsorption isotherm model for different antibiotics using modified biochar.

[0036] 4. Scanning electron microscopy analysis of modified biochar Biochar morphology characterization see Figure 5 BC-300 has a smooth surface and few pores, while BC-500 and BC-700 have increased pores and rougher surfaces. This indicates that increasing the pyrolysis temperature increases the specific surface area of ​​biochar and generates a large number of pores, which is beneficial for providing more adsorption sites. Iron-modified biochar Fe@BC-700 has significantly larger pore sizes, more pores, and a highly rough surface. This indicates that iron modification is beneficial for improving the adsorption performance of biochar. In contrast, 25EPS / Fe@BC-700, 50EPS / Fe@BC-700, and 75EPS / Fe@BC-700 biochar surfaces have a large number of small spherical polymers aggregated, resulting in smaller pore sizes. These micropores and the loaded EPS can provide a microenvironment for microorganisms, which is conducive to their growth and reproduction. Simultaneously, EPS has a large number of functional groups, enabling it to adsorb pollutants such as metal ions and antibiotics.

[0037] 5. Elemental analysis of biochar surface The main elements (C, N, H, S) of biochar were quantitatively analyzed using an elemental analyzer. O was calculated using the differential method, and H / C was the molar ratio of the elements, as shown in Table 3.

[0038] As the pyrolysis temperature increases, carbon (C) increases while hydrogen (H) decreases, and the H / C ratio decreases. However, after loading Fe, C decreases, H increases, and the H / C ratio remains low. C is related to the carbonization level of biochar; higher pyrolysis temperatures result in more complete carbonization. The lower C content after adding Fe indicates successful Fe loading on the biochar. H / C primarily reflects the aromaticity of biochar. The aromatic structure of biochar has strong adsorption properties, capable of adsorbing and fixing pollutants such as metal ions and antibiotics in water. A H / C ratio < 1 indicates stronger aromaticity. In BC, the H / C decreases with increasing temperature, indicating that BC-700 has stronger aromaticity and stability. The H / C ratio after loading EPS in Fe@BC is lower than that in Fe@BC-700, indicating that EPS helps improve the aromaticity of biochar. Furthermore, the C content in EPS / Fe@BC-700 is lower than that in Fe@BC-700, proving that EPS was successfully loaded. The decrease in H and O elements with increasing pyrolysis temperature is mainly due to the disappearance of some H and O functional groups as the temperature rises. However, the increase in H and O elements in the modified biochar indicates an increase in the functional groups of the modified biochar.

[0039] Table 3 Organic elemental analysis of biochar Biochar C（%） N（%） H（%） S（%） O（%） H / C BC-300 59.16 0.23 5.01 0.00 35.600 1.016 BC-500 78.15 0.21 3.10 0.00 18.540 0.476 BC-700 76.47 0.29 1.25 0.00 21.990 0.196 Fe@BC-700 53.89 0.16 1.80 0.051 44.099 0.401 25EPS / Fe@BC-700 44.76 0.21 1.37 0.00 53.660 0.367 50EPS / Fe@BC-700 45.08 0.23 1.45 0.046 53.194 0.386 75EPS / Fe@BC-700 46.62 0.19 1.57 0.0 51.620 0.404 6. Fourier Transform Infrared Spectroscopy (FTIR) Analysis The changes in functional groups before and after biochar modification were analyzed using FTIR. The results are shown in the figure. Figure 6 Biochar contains a large number of functional groups, mainly hydroxyl (-OH) and carbonyl (CH) groups. As the pyrolysis temperature increases, the number of functional groups in biochar gradually decreases. At 300℃~500℃, the H and O groups in biochar disappear, and deoxygenation and dehydrogenation mainly occur. When the temperature rises to 500℃~700℃, the C and O groups disappear, and carbonization and deoxygenation mainly occur.

[0040] Conversely, due to Fe and EPS modification, the functional groups of biochar undergo significant changes, with Fe-modified biochar exhibiting a new functional group, the Fe-O stretching vibration peak (554 cm⁻¹). -1 Furthermore, after EPS loading, some peak intensities increased, and some functional groups reappeared, including the -OH stretching vibration peak (1422 cm⁻¹). -1 CO stretching vibration peak (1194-1204 cm⁻¹) -1 Aromatic CH stretching vibration peak (780-790 cm⁻¹) -1 The above results indicate that EPS / Fe loading is beneficial to the increase of functional groups in biochar under high-temperature pyrolysis.

[0041] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0042] III. Conclusion Elemental analysis and scanning electron microscopy revealed successful loading of Fe and EPS onto the biochar. Fe modification increased the porosity of the biochar, and FTIR showed an increase in functional groups after modification. Sequencing batch experiments showed that biochar co-modified with iron and extracellular polymeric substances (EPS / Fe@BC) significantly improved anaerobic ammonium oxidation (ANAO) activity. Biochar prepared at a pyrolysis temperature of 700℃ performed significantly better than other components, with an ANAO activity increase of up to 22% compared to unmodified biochar. Comparison showed that an EPS content of 50±2 mg / L was the most effective among the three components, indicating that the optimal EPS loading concentration was 50±2 mg / L. The nitrogen removal trend after adding modified biochar showed that ANAO and denitrification worked together to improve nitrogen removal efficiency, indicating that iron and EPS can be utilized by microorganisms, potentially enhancing electron transfer capacity and biological activity, while also activating quorum sensing communication between ANAO bacteria and other bacterial communities.

[0043] In the adsorption kinetics experiments of antibiotics on biochar, it was found that the adsorption capacity increased with time, reaching a maximum value between 2 and 4 hours. In the adsorption experiments of OTC and CIP, the adsorption rate of modified biochar was significantly higher than that of ordinary biochar, indicating that biochar modification created more adsorption sites. This result was further confirmed by scanning electron microscopy images and fitting of a pseudo-second-order kinetic model. Simultaneously, the isothermal adsorption model showed that the maximum adsorption capacity of modified biochar was more than twice that of unmodified biochar, especially with a significantly enhanced adsorption capacity for CIP.

[0044] The modified biochar prepared in this application can significantly enhance the activity of anaerobic ammonia oxidizing bacteria, and at the same time has good antibiotic adsorption performance. It can synergistically enhance the denitrification and antibiotic removal efficiency of the anaerobic ammonia oxidation system. It is not difficult to predict the huge potential of modified biochar in the treatment of antibiotic wastewater by anaerobic ammonia oxidation.

[0045] The above description of the specific embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing modified biochar, characterized in that, Includes the following steps: Step 1: Crush the biochar raw material, clean it, dry it, and pass it through a perforated sieve; Step 2: Add the biomass powder obtained in Step 1 to the iron ion solution. The volume ratio of biomass powder to iron solution is 1 / 12 to 1 / 8. Then mix thoroughly by mechanical stirring. Step 3: During the stirring process, the pH is controlled to be stable at 10.0±1.0 using NaOH solution; after sealing, the mixture is stirred continuously for a set time, then the solid is filtered through a membrane, and then washed continuously with deionized water until the pH of the filtrate is 7.0±0.

5. The remaining solid is then dried at a set temperature. Step 4: Place the ceramic boat containing the solid obtained in step 3 into a tube furnace and purge with nitrogen to control anaerobic pyrolysis to prepare iron-modified biochar Fe@BC. Step 5: Extraction of crude extracellular polymeric substances (EPS). Take the sludge mixture into a centrifuge tube, centrifuge, discard the supernatant, add NaCl solution until the initial volume is reached, and heat at the set temperature; then centrifuge the sludge mixture, and finally collect the supernatant after centrifugation, filter it with a filter to obtain the EPS solution; the EPS solution is stored in an environment at a specific temperature before the experiment. Step 6: Soak the iron-modified biochar obtained in Step 4 in the EPS solution prepared in Step 5 for a set time, and change the EPS solution every day; obtain iron and EPS co-modified biochar Fe / EPS@BC, then air dry for a set time and store at room temperature.

2. The method for preparing modified biochar according to claim 1, characterized in that, The drying process in step 1 uses a blower dryer with a temperature of 40℃~60℃ and a drying time of 12~24 hours. The sieve used is a 40-mesh sieve.

3. The method for preparing modified biochar according to claim 1, characterized in that, The iron ion solution in step 2 consists of FeCl2 + FeCl3, where Fe... 2+ The concentration of Fe was 0.25 ± 0.05 mol / L. 3+ The concentration was 0.5 ± 0.05 mol / L, and the volume ratio of biomass powder to iron ion solution was 1:

10.

4. The method for preparing modified biochar according to claim 1, characterized in that, In step 4, the pyrolysis temperature is 300℃~700℃, the heating rate is 5~15℃ / min, and the reaction time is 2~3 h.

5. The method for preparing modified biochar according to claim 1, characterized in that, In step 5, the sludge mixture should be sludge from the biological reactor.

6. The method for preparing modified biochar according to claim 1, characterized in that, In step 5, the solution in which NaCl solution is added to the supernatant until the initial volume is reached is heated at 70°C for 30 minutes.

7. The method for preparing modified biochar according to claim 1, characterized in that, In step 5, the concentration of EPS solution was set to 25~75 mg / L, and the EPS solution was stored at -20℃ before the experiment.

8. The method for preparing modified biochar according to claim 1, characterized in that, In step 6, the iron-modified biochar needs to be soaked in EPS solution for 72 hours, and the obtained iron and EPS co-modified biochar needs to be air-dried for 36 hours.

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