Modified biochar material embedded with electroactive bacteria as well as preparation method and use method of modified biochar material

Abstract

The invention provides a modified biochar material embedded with electroactive bacteria as well as a preparation method and a use method of the modified biochar material. The preparation method comprises the following steps: S1, preparing modified biochar; s2, preparing an electroactive bacterium liquid, putting the modified biochar obtained in the step S1 into the electroactive bacterium liquid, and fully mixing, so that electroactive bacteria are uniformly adsorbed on the surface of the modified biochar; s3, adding the modified biochar uniformly adsorbed with the electroactive bacteria obtained in S2 into an embedding material solution, and fully and uniformly stirring to obtain a mixed solution; and S4, dropwise adding the mixed solution obtained in S3 into a cross-linking agent, so that the embedding material is cross-linked and cured on the surface of the modified biochar adsorbed with the electroactive bacteria, and washing and drying to obtain the modified biochar material embedded with the electroactive bacteria. The preparation method can provide a suitable growth environment and attachment surface for the electroactive bacteria, promote electron transfer between the electroactive bacteria and the external environment, accelerate the metabolic process of microorganisms, and further improve the degradation efficiency of pollutants such as antibiotics.

Description

Technical Field

[0001] The present invention belongs to the field of environmental science, and in particular relates to a modified biochar material for embedding electrically active bacteria, and a preparation method and a use method thereof. Background Art

[0002] Antibiotics, as indispensable agents, are widely used in modern medicine, animal husbandry, aquaculture, and other fields for the treatment and prevention of diseases, as well as for promoting animal growth. However, during the use of antibiotics, a large amount of unabsorbed antibiotics enters the surrounding water bodies with various types of wastewater discharge. Even extremely low concentrations of residual antibiotics in wastewater pose a potential threat to the ecological environment and human health. However, due to their complex and stable chemical structures, antibiotics are often difficult to decompose by microorganisms. Currently commonly used wastewater treatment processes, such as traditional biological treatment, are less than ideal due to the inherent antimicrobial activity of antibiotics.

[0003] Faced with the increasingly serious problem of antibiotic contamination in wastewater, numerous technologies have emerged. Physical adsorption, due to its simplicity and relatively low cost, became one of the earliest and most widely used methods. This technology primarily exploits the porous structure and surface properties of adsorbents to adsorb antibiotics from wastewater onto the adsorbent surface through physical adsorption, chemical adsorption, or ion exchange. However, physical adsorption has significant drawbacks. First, the adsorbents can easily reach saturation, requiring frequent replacement or regeneration, increasing treatment costs. Second, adsorption merely transfers the antibiotics from wastewater to the adsorbent, not truly degrading them. Saturated adsorbents must subsequently be properly disposed of to prevent potential secondary contamination. Advanced oxidation technologies, on the other hand, generate highly oxidizing free radicals to oxidize and decompose antibiotic molecules in wastewater into smaller molecules, or even mineralize them into carbon dioxide and water. However, practical application of advanced oxidation technologies also faces numerous challenges. The resulting active species lack selectivity and are not only reactive with antibiotics but also easily captured by the abundant dissolved organic and inorganic matter present in the water. This results in high reagent consumption and difficulty achieving efficient removal when treating trace amounts of antibiotics, making them less economical.

[0004] To address these challenges, numerous emerging technologies are emerging and being researched, offering new hope and direction for addressing antibiotic contamination in wastewater. Compared to physical adsorption and advanced oxidation technologies, constructed wetlands (CWs) are considered a superior option for antibiotic removal. However, existing CWs are often limited to practical applications for antibiotic removal, suffering from drawbacks such as large footprints, slow degradation rates, and toxic effects on the functional microbial communities within the CWs. Research has demonstrated that enhancing CWs with a novel bioelectrochemical coupled system (BES-CWs)—combining constructed wetlands with bioelectrochemical systems (BES-CWs)—can significantly improve the removal efficiency of emerging and conventional pollutants, such as COD, nitrogen, and phosphorus. The specialized microorganisms employed—electroactive bacteria—can exchange electrons with electrodes through direct electron transfer (mediated by electron carriers such as cytochromes) or indirect electron transfer (via electron shuttles), resulting in efficient degradation of antibiotics. These bacteria are environmentally friendly, exhibit long-lasting treatment effects, and avoid secondary pollution. Furthermore, under favorable conditions, the microorganisms can continuously reproduce and perform their degradation activities.

[0005] However, selecting the right carrier is crucial for electroactive bacteria to fully function in the antibiotic degradation process in constructed wetlands. Conventional carrier materials have drawbacks such as limited surface functional groups and reactivity, poor electron conductivity, and low capacitance, making it difficult for electroactive bacteria to effectively accumulate on their surfaces. Furthermore, it is difficult to achieve ideal adsorption properties while maintaining sufficient conductivity and catalytic activity. Therefore, improving the performance of fillers and imparting specific functional effects has become a pressing challenge in existing technologies. Summary of the Invention

[0006] To address these issues, the present invention provides a modified biochar material for encapsulating electroactive bacteria, as well as methods for its preparation and use. By pyrolyzing and modifying the biochar material, it provides a superior carrier for the electroactive bacteria, enhancing their ability to degrade antibiotic pollutants in water. The encapsulated biochar material can be used as an electrically enhanced filler in constructed wetlands, enabling the construction of superior bioelectrochemical coupling systems.

[0007] To achieve the above technical effects, the present invention provides a method for preparing a modified biochar material that embeds electroactive bacteria, comprising the following steps: S1: preparing modified biochar; S2: preparing an electroactive bacteria liquid, and placing the modified biochar obtained in S1 in the electroactive bacteria liquid and mixing thoroughly, so that the electroactive bacteria are evenly adsorbed on the surface of the modified biochar; S3: adding the modified biochar uniformly adsorbed with electroactive bacteria obtained in S2 to the embedding material solution, stirring thoroughly to obtain a mixed solution; S4: dropping the mixed solution obtained in S3 into a cross-linking agent, so that the embedding material is cross-linked and solidified on the surface of the modified biochar adsorbed with electroactive bacteria, and after washing and drying, obtaining a modified biochar material that embeds electroactive bacteria.

[0008] Optionally, the specific steps of preparing the modified biochar in step S1 include: S11: placing the biomass raw material in a quartz boat and transferring it to the insulation area of ​​the tube furnace; S12: evacuating the insulation area of ​​the tube furnace to a negative pressure of 0.1~1.0 kPa, then introducing nitrogen to a positive pressure of 102~105 kPa, and repeating the operation three or more times; S13: starting from room temperature, the tube furnace is heated at a rate of 8-15℃ / min to a first reaction temperature of 400℃-1000℃, heating at a constant temperature for 2-4h, and then cooling to room temperature to obtain a biochar material; S14: grinding the biochar material obtained in S13 and passing it through a 100-mesh sieve, and then mixing it in a 0.05-0.1 liter sieve at a ratio of 7-12 g:100 ml. mol / L FeCl3 and KMnO4 solutions, respectively, and stirred and soaked for 3-5 hours; S15: filtering, washing, and drying the biochar material obtained in S14 after stirring and soaking, and then heating it in a tube furnace at a second reaction temperature of 400-600°C for 2-4 hours to obtain modified biochar.

[0009] Optionally, the biomass raw material in S11 is one or more of crop straw such as rice straw, wheat straw, corn straw, agricultural waste such as rice husk, peanut shell, bagasse, coconut shell, walnut shell, wood processing waste such as sawdust and bark, bamboo waste, fruit tree branches, shrub branches and other forestry residues; preferably, the first reaction temperature in S13 is 1000°C; the mixing ratio of biochar material and FeCl3 and KMnO4 solution in S14 is 8 g:100 ml, and the molar concentration of FeCl3 and KMnO4 solution is 0.05 mol / L; the modification temperature in S15 is 450°C, and the modification time is 3 h.

[0010] Optionally, the filtering, washing, and drying of the stirred and soaked biochar material obtained in S14 in S15 specifically includes filtering the stirred and soaked biochar material with filter paper, repeatedly rinsing it with deionized water 3-5 times during the filtration process, and then drying the filtered and washed biochar material in an oven at 60-70° C. for 16-20 hours.

[0011] Optionally, the specific steps of preparing the electroactive bacterial liquid in S2 include: S21a: collecting the cultured electroactive bacteria by centrifugation; S22a: washing the electroactive bacteria collected by centrifugation in S21a with sterile physiological saline, and resuspending them in a certain volume of sterile water to obtain an electroactive bacterial liquid; wherein the electroactive bacteria are one or more species of Shewanella, Geobacter, Pseudomonas, Achromobacter, etc.

[0012] Optionally, in S4, the mixed solution obtained in S3 is dripped into a cross-linking agent using a dripping method or a spraying method; wherein the cross-linking agent is a sodium alginate-CaCl2 composite coupling agent.

[0013] Optionally, the washing and drying treatment in S4 specifically includes: washing the embedded, cross-linked and solidified modified biochar carrier multiple times with sterile water, and then drying the washed modified biochar carrier in a low temperature environment of 30-40°C for 12-16h.

[0014] A second aspect of the present invention provides a modified biochar material encapsulating electroactive bacteria, which is prepared by the preparation method. The modified biochar material encapsulating electroactive bacteria is used as a filler in artificial wetlands to achieve degradation and / or removal of antibiotics.

[0015] The third aspect of the present invention provides a method for using a modified biochar material encapsulating electroactive bacteria, comprising the following steps: s1: setting and fixing at least two layers of electrode plates in an artificial wetland reactor; s2: placing the modified biochar material encapsulating electroactive bacteria between adjacent layers of electrode plates in s1; s3: planting plants on the top of the artificial wetland reactor to form a combined effect of filler adsorption, plant absorption and microbial degradation, so as to achieve degradation and / or removal of antibiotics.

[0016] The beneficial effects of the present invention are: (1) Providing modified biochar materials provides a suitable growth environment and attachment surface for electroactive bacteria, promotes the attachment and growth of electroactive bacteria, increases the biomass and activity of electroactive bacteria on the filler surface, and is conducive to the formation of a stable biofilm, so as to more efficiently promote the electron transfer between electroactive bacteria and the external environment, accelerate the metabolic process of microorganisms, and thus improve the degradation efficiency of pollutants.

[0017] (2) Biochar-based materials were prepared from biomass by thermal cracking, and then modified with iron and manganese bimetallic surface loading. The biochar prepared by thermal cracking formed a graphite structure, which improved the electron transfer ability of the material. The iron and manganese oxide modification method improved the electron storage capacity, increased the specific surface area of ​​the biochar material, and developed a pore structure, which was conducive to the attachment and growth of electroactive microorganisms.

[0018] (3) By implanting electrodes as electron acceptors and electron donors, the problem of lack of electron acceptors and electron donors in traditional CWs is solved, which can accelerate the degradation of emerging pollutants, form a combined effect of filler adsorption, plant absorption and microbial degradation, and enhance the treatment effect of electrically enhanced artificial wetlands.

[0019] Those skilled in the art will understand that the purposes and advantages that can be achieved by the present invention are not limited to the above specific descriptions, and the above and other purposes that can be achieved by the present invention will be more clearly understood based on the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of this application, and do not constitute a limitation of the present invention.

[0021] Figure 1 Schematic diagram of a method for preparing a modified biochar material for embedding electroactive bacteria in an embodiment of the present invention; Figure 2 This is the SEM-EDS image of BC1000 in an embodiment of the present invention; Figure 3 The SEM-EDS image and Fe element distribution diagram of BC-Fe in the embodiment of the present invention; Figure 4 The SEM-EDS image and Mn element distribution diagram of BC-Mn in the embodiment of the present invention; Figure 5 The XPS spectra of BC1000, BC-Fe and BC-Mn in the embodiment of the present invention are shown in FIG. Figure 6 This is a comparison chart of the electrical conductivity of biochar at different pressures in an embodiment of the present invention; Figure 7 CV curve of biochar at a sweep speed of 20 m / s in an embodiment of the present invention; Figure 8 are the EDC and EAC values ​​of the biochar in the embodiment of the present invention; Figure 9 This is a comparison chart of the adsorption kinetics of BC1000, BC-Fe, and BC-Mn in the examples of the present invention; Figure 10 The degradation of SMX by Shewanella and mixed culture of Shewanella and biochar in the examples of the present invention; Figure 11 The removal efficiencies of SMX (a), OFL (b), and TC (c) in the effluent of different electrically enhanced constructed wetlands in the embodiments of the present invention are shown. DETAILED DESCRIPTION

[0022] In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and the accompanying drawings. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention. It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only the structures and / or processing steps closely related to the solutions according to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0023] It should be emphasized that the term "include / comprises" when used herein refers to the existence of features, elements, steps or components, but does not exclude the existence or addition of one or more other features, elements, steps or components.

[0024] Combined with attachment Figure 1 It can be seen that the first aspect of the embodiment of the present invention provides a method for preparing a modified biochar material that embeds electroactive bacteria, comprising the following steps: S1: preparing modified biochar; S2: preparing an electroactive bacteria liquid, and placing the modified biochar obtained in S1 in the electroactive bacteria liquid and mixing thoroughly so that the electroactive bacteria are evenly adsorbed on the surface of the modified biochar; S3: adding the modified biochar uniformly adsorbed with electroactive bacteria obtained in S2 to the embedding material solution, stirring thoroughly to obtain a mixed solution; S4: dropping the mixed solution obtained in S3 into a cross-linking agent to cross-link and solidify the embedding material on the surface of the modified biochar adsorbed with electroactive bacteria, and after washing and drying, obtaining a modified biochar material that embeds electroactive bacteria. It has been verified that the modified biochar material that embeds electroactive bacteria can achieve the purpose of efficiently degrading new pollutants in tail water. The characteristic that electroactive bacteria can directly transfer electrons without adding a medium or electron shuttle is used to construct a functional material with high conductivity and high capacitance as a biological carrier, and enhance the degradation effect of antibiotics by increasing the electron transfer efficiency of electroactive microorganisms in the microbial electrochemical system. The degradation effect of active bacteria on difficult-to-degrade new pollutants such as antibiotics is significantly better than that of conventional activated sludge mixed bacteria, and the addition of conductive fillers further enhances the degradation efficiency of electroactive bacteria on difficult-to-degrade pollutants by enhancing the activity of the electron transfer system of electroactive bacteria as well as the cytochrome c content and NADH enzyme content.

[0025] Optionally, the specific steps of preparing the modified biochar in step S1 include: S11: placing the biomass raw material in a quartz boat and transferring it to the insulation area of ​​the tube furnace; S12: evacuating the insulation area of ​​the tube furnace to a negative pressure of 0.1~1.0 kPa (corresponding to the gauge pressure of -101.2~-100.3 kPa), then introducing nitrogen to a positive pressure of 102~105 kPa (corresponding to the gauge pressure of 0.7~3.7 kPa), and repeating the operation three or more times; S13: starting from room temperature, the tube furnace is heated at a rate of 8-15℃ / min to a first reaction temperature of 400℃-1000℃, heated at a constant temperature for 2-4h, and then cooled to room temperature to obtain a biochar material; S14: grinding the biochar material obtained in S13 and passing it through a 100-mesh sieve, and then mixing it in a 0.05-0.1 liter of water at a ratio of 7-12 g:100 ml. mol / L FeCl3 and KMnO4 solutions, respectively, stirred and soaked for 3-5 hours; S15: filtering, washing, and drying the stirred and soaked biochar material obtained in S14, and then heating it in a tube furnace at a second reaction temperature of 400-600°C for 2-4 hours for modification to obtain modified biochar. Among them, the biochar prepared by thermal cracking forms a graphite structure, which improves the material's electron transfer capacity. The larger specific surface area and developed pore structure are conducive to the attachment and growth of electroactive microorganisms. At the same time, the iron and manganese oxide modification method improves the electron storage capacity. The biochar material modified with iron and manganese can promote the attachment and growth of electroactive bacteria, increase the biomass and activity of electroactive bacteria on the filler surface, and more efficiently promote electron transfer between the electroactive bacteria and the external environment, accelerate the metabolic process of the microorganisms, and thus improve the degradation efficiency of antibiotics.

[0026] Optionally, the biomass raw material in S11 is one or more of crop straw such as rice straw, wheat straw, and corn straw; agricultural waste such as rice husks, peanut shells, sugarcane bagasse, coconut shells, and walnut shells; wood processing waste such as sawdust and bark; and forestry residues such as bamboo waste, fruit tree branches, and shrub branches. Because biochar raw materials are widely available and readily available, they encompass almost all biomass resources. In addition to the examples given above, they also include various carbon-containing organic matter or industrial waste, agricultural and forestry waste, and the like with the same or similar material composition. Compared to some traditional functional materials, the raw material cost of biochar is negligible, which provides favorable conditions for its large-scale production and application.

[0027] Preferably, the first reaction temperature in S13 is 1000°C; in S14, the mixing ratio of the biochar material to the FeCl3 and KMnO4 solution is 8 g:100 ml, and the molar concentration of the FeCl3 and KMnO4 solution is 0.05 mol / L; the product is then filtered with filter paper, and deionized water is repeatedly used to rinse away metal ions during the filtration process; and in S15, the modification temperature is 450°C and the modification time is 3 hours. Since the biochar material (BC1000) prepared at 1000°C has the highest conductivity among the several temperature gradients, this is used as the basis for performance modification to obtain a material with both high conductivity and high capacitance.

[0028] Optionally, filtering, washing, and drying the stirred and soaked biochar material obtained in S14 in S15 specifically includes filtering the stirred and soaked biochar material with filter paper, repeatedly rinsing it with deionized water 3-5 times during the filtration process, and then drying the filtered and washed biochar material in an oven at 60-70°C for 16-20 hours. Preferably, the number of rinses is 5, the drying temperature is 60°C, and the drying time is 16 hours.

[0029] Optionally, the specific steps of preparing the electroactive bacterial liquid in S2 include: S21a: collecting the cultured electroactive bacteria by centrifugation; S22a: washing the electroactive bacteria collected by centrifugation in S21a with sterile physiological saline, and resuspending them in a certain volume of sterile water to obtain an electroactive bacterial liquid; wherein the electroactive bacteria are one or more species of Shewanella, Geobacter, Pseudomonas, Achromobacter, etc.

[0030] Optionally, in S4, the mixed solution obtained in S3 is dripped into a cross-linking agent using a dripping method or a spraying method, so that the embedding material is cross-linked and solidified on the surface of the biochar to form a biochar-based carrier that embeds the electroactive bacteria; wherein the cross-linking agent is a sodium alginate-CaCl2 composite linker.

[0031] Optionally, the washing and drying treatment in S4 specifically includes: washing the embedded, cross-linked and solidified modified biochar carrier with sterile water multiple times, and then drying the washed modified biochar carrier in a low temperature environment of 30-40°C for 12-16 hours to remove moisture and improve the stability and strength of the carrier, wherein the preferred low temperature environment temperature is 30°C and the drying treatment time is 16 hours.

[0032] A second aspect of an embodiment of the present invention provides a modified biochar material encapsulating electroactive bacteria, which is prepared by a preparation method. The modified biochar material encapsulating electroactive bacteria is used as a filler in an artificial wetland to achieve degradation and / or removal of antibiotics.

[0033] A third aspect of the present invention provides a method for using a modified biochar material encapsulating electroactive bacteria, comprising the following steps: s1: setting and securing at least two layers of electrode plates within a constructed wetland reactor; s2: placing the modified biochar material encapsulating electroactive bacteria between adjacent layers of electrode plates in s1; and s3: planting plants on top of the constructed wetland reactor to achieve a combined effect of filler adsorption, plant absorption, and microbial degradation, thereby degrading and / or removing antibiotics. This embodiment of the present invention utilizes enhancement methods such as matrix reinforcement and electrical coupling to improve conventional CWs. The original non-reactive matrix in the constructed wetland is replaced with a modified filler with a high surface area and excellent conductivity. Electrodes are then implanted, and the electroactive bacteria are fixed and grown in the constructed wetland through artificial cultivation and enrichment followed by embedding. By implanting electrodes as electron acceptors and electron donors, the lack of electron acceptors and electron donors in conventional CWs is addressed, accelerating the degradation of emerging pollutants. Replacing the matrix with a high electrical conductivity and capacitance enhances electron supply and transfer, thereby enhancing the degradation capacity of the electroactive bacteria. Experimental results show that the improved CWs significantly improve the removal efficiency of emerging pollutants and conventional pollutants. Compared with conventional biological systems, the bioelectrochemical coupling system provided by the present invention can increase the removal rate of difficult-to-degrade emerging pollutants by more than 60%.

[0034] The following is combined with Figure 2-11 The present invention will be further described in detail with reference to specific experimental data and charts by specific implementation examples. The following examples are only descriptive and not restrictive, and the scope of protection of the present invention cannot be limited thereto.

[0035] Example 1: Biochars (designated BC400, BC600, BC800, and BC1000) were prepared from coconut shells by pyrolysis at different temperatures (400°C, 600°C, 800°C, and 1000°C). The electrical conductivity of BC1000 increased significantly with increasing pyrolysis temperature. Therefore, BC1000 was modified with Fe and Mn, designated BC-Fe and BC-Mn, respectively. Elemental analysis of the modified biochars revealed carbon contents of 92.10% for BC-Fe and 91.32% for BC-Mn, respectively. Scanning electron microscopy (SEM)-energy dispersive spectrometer (EDS) analysis of the three biochars (BC1000, BC-Fe, and BC-Mn) revealed that the original biochar (BC1000) had numerous fine pores due to high-temperature sintering, resulting in a rough surface with irregular and uneven pore distribution. After metal modification, the surface of BC-Fe exhibited a flaky structure with pronounced pores, while the surface of BC-Mn became smoother and exhibited pore expansion. The specific surface area of ​​BC-Fe increased to 24.18 times that of the original biochar (BC1000), while the specific surface area of ​​BC-Mn increased to 21.79 times that of the original biochar (BC1000).

[0036] XPS analysis was performed on BC1000, BC-Fe, and BC-Mn. Figure 4 The O1s spectrum shows that BC1000 primarily forms C-O and C=O bonds. However, the modified BC-Fe adds Fe-OH bonds, and the BC-Mn adds Mn-O bonds.

[0037] The resistivity of biochar was measured by a four-probe resistivity meter, and the conductivity of modified biochar was measured. The results are as follows: Figure 5 The analysis found that the sintering temperature significantly improved the electrical conductivity of biochar.

[0038] The electron transfer capacity of biochar was determined by measuring the cyclic voltammetry curve, such as Figure 6 As shown in the figure, there are 6 types of biochar before and after modification, among which BC-Mn has the largest CV curve area, which means that its specific capacitance is larger and it can store more electrons.

[0039] The electron donating capacity (EDC) and electron accepting capacity (EAC) of biochar were calculated by measuring the It curves of different biochars. Figure 7 As shown in the figure, the EAC of BC1000, BC-Fe, and BC-Mn increases from low to high, and the EAC of all biochars is much stronger than that of EDC, indicating that they have stronger electron accepting ability.

[0040] The kinetic fitting results of SMX adsorption by three biochars, BC1000, BC-Fe and BC-Mn, are shown in Figure 2. Figure 8 As shown in the figure, the three biochars rapidly adsorbed SMX in the first 20 minutes of the adsorption process, and gradually reached adsorption equilibrium at 120 minutes. Comparison revealed that the modified biochar had a higher SMX removal rate.

[0041] In order to explore whether the prepared conductive filler has an enhancing effect on the degradation of antibiotics by the electroactive bacteria S. oneidensis MR-1, we first compared the differences in the degradation ability of S. oneidensis MR-1 and activated sludge mixed bacteria on antibiotics.

[0042] The results showed that within 24 hours, the two microorganisms had the highest removal efficiency for SMX, with S. oneidensis MR-1 achieving a removal rate of 22.31% for SMX, while the removal rate of sludge mixed bacteria was only 14.14%. At the same time, the adsorption of SMX by BC1000, BC-Fe, and BC-Mn in the culture medium was determined, as well as the degradation effect of SMX by the electroactive bacteria S. oneidensis MR-1 co-cultured with BC1000, BC-Fe, and BC-Mn. Figure 9 The results showed that the adsorption of SMX by BC1000, BC-Fe and BC-Mn reached saturation on the first day, and the adsorption effect was BC-Fe>BC-Mn>BC1000.

[0043] Co-culture of S. oneidensis MR-1 with BC1000, BC-Fe, and BC-Mn optimized SMX degradation, reaching removal rates of 42.03%, 45.50%, and 56.51% on the fifth day, respectively. These removal rates were significantly greater than the combined SMX degradation rate (22.31%) of S. oneidensis MR-1 cultured alone and the adsorption rate of biochar. Measurements of SMX adsorption by biochar and the effects of co-culture with Shewanella on SMX degradation revealed that the addition of conductive fillers, particularly BC-Fe and BC-Mn, enhanced the ETSA, cytochrome c, and NADH enzyme levels of Shewanella. These results demonstrate that the modified conductive fillers effectively promote SMX degradation by Shewanella.

[0044] Example 2: Four constructed wetlands were constructed, consisting of hollow stainless steel cuboids with a cross-sectional area of ​​30 cm × 30 cm and a height of 1 m: a microbial fuel cell constructed wetland (MFC-CW), an electrolysis constructed wetland with iron-modified biochar (EC-CW), a constructed wetland with biochar (CC-CW), and an unfortified constructed wetland (DF-CW). The MFC-CW, EC-CW, and CC-CW reactors were equipped with a set of electrode plates at the top and bottom of the reactor. Each set consisted of an acrylic frame and a graphite plate, with the graphite plates serving as the processed electrode assembly, spaced 10 cm apart. The MFC-CW and EC-CW reactors were filled with modified biochar embedded with electroactive bacteria between the electrodes, while the CC-CW reactor was filled with unmodified biochar, ensuring normal water flow. The MFC-CW reactor was connected to a 1000Ω resistor. The EC-CW reactor was connected to a DC power supply. The remainder of each reactor was filled with bioceramic aggregate. Iris sempervirens was planted on the reactor tops at a density of 45 plants / m². The influent COD, total phosphorus, ammonia nitrogen, and nitric nitrogen are prepared by sodium humate, potassium hydrogen phthalate, ammonium chloride, potassium dihydrogen phosphate, and potassium nitrate solution, and are configured with reference to the concentration of secondary effluent. At the same time, antibiotics are added, including ofloxacin (OFL), sulfamethoxazole (SMX), and tetracycline (TC), each with a concentration of 1μg / L.

[0045] The results of the embodiment show that the artificial wetland with added biochar filler has higher species richness and diversity. The microbial fuel cell artificial wetland doped with iron-modified biochar filler has the highest removal rate of SMX, reaching 84.4%, which is 20.6% higher than the control group (63.8%). EC-CW and CC-CW have the highest removal rate of OFL, both reaching 98.1%, which is 34.5% higher than the control group (63.6%). EC-CW has the highest removal rate of TC (91.5%), which is 14.7% higher than the control group (76.8%).

[0046] It was found that the electrically enhanced constructed wetland was significantly more efficient at removing antibiotics than the control. Antibiotic removal in constructed wetlands primarily involves adsorption by fillers, absorption by plants, and microbial degradation, with microbial degradation being the dominant process. Electrical enhancement can enhance the biodegradability of recalcitrant pollutants while promoting electron transfer in microorganisms, thereby accelerating antibiotic degradation.

[0047] This invention, based on constructed wetlands (CWs), is a sustainable technology applicable to various wastewater treatment processes due to its low cost, ease of operation, and resistance to shock loads. CWs can remove most environmental pollutants, such as suspended solids, pathogens, and nutrients, through physical, chemical, and biological interactions. They have also been shown to be effective in removing antibiotics and antibiotic resistance genes (ARGs). Compared to conventional, highly efficient bacteria, electroactive bacteria can not only utilize antibiotics as a carbon and energy source but also regulate their metabolic rate and electron transfer processes through an applied electric field, further enhancing degradation efficiency. However, in natural environments, the electron acceptors of electroactive bacteria are often unevenly distributed or have low concentrations. Under conventional culture conditions, without the artificial addition of specific electron acceptors or electron donors, electroactive bacteria struggle to compete with other microorganisms for carbon and energy sources.

[0048] To further improve its stability, adsorption properties, electrical conductivity, and catalytic activity, biochar is often modified, with metal modification being a common and effective method. Metal modification involves the introduction of metal elements or metal compounds onto the biochar surface to improve its performance or impart specific functions. Modified pyrolytic biochar-based materials often possess a larger specific surface area and a richer pore structure, enabling them to adsorb more pollutants and providing a favorable electron transfer pathway for electroactive bacteria. Compared to conventional carbon materials, these materials provide a suitable growth environment and attachment surface for electroactive bacteria, promoting their attachment and growth, increasing their biomass and activity on the filler surface, and facilitating the formation of a stable biofilm. They also more efficiently promote electron transfer between electroactive bacteria and the external environment, accelerating microbial metabolic processes and thereby improving pollutant degradation efficiency.

[0049] Conductive fillers play multiple key roles in the degradation of antibiotics in electrically enhanced constructed wetlands. Carbon materials are widely used due to their excellent electrical conductivity, enhanced stability when mixed with microbial inoculum, and enhanced surface area. Raw biochar materials have limited pore structure and surface functional groups, and may be susceptible to microbial decomposition and oxidation in the natural environment, leading to changes in their structure and properties.

[0050] The present invention proposes to modify biochar in order to further improve its stability, adsorption performance, electrical conductivity and catalytic activity. By introducing metal elements or metal compounds on the surface of biochar, the effect of improving performance or giving it specific functions is achieved. After modification, the pyrolytic biochar-based material has a larger specific surface area and rich pore structure, can adsorb more pollutants, and provides a good electron transfer channel for electroactive bacteria. Compared with ordinary carbon materials, it can provide a suitable growth environment and attachment surface for electroactive bacteria, promote the attachment and growth of electroactive bacteria, increase the biomass and activity of electroactive bacteria on the filler surface, and facilitate the formation of a stable biofilm. It can also more efficiently promote the transfer of electrons between electroactive bacteria and the external environment, accelerate the metabolic process of microorganisms, and thus improve the degradation efficiency of pollutants.

[0051] The modified biochar material for embedding electroactive bacteria provided by the present invention can intercept or adsorb antibiotics due to its own properties, and the microorganisms in the filler also have a certain degradation effect on the antibiotics. Due to the high surface area, high porosity and cation exchange capacity of biochar, the adsorption and degradation of pollutants can be enhanced. The preparation steps of the biochar and its metal modification of the present invention are relatively simple and do not require complex equipment and high investment. Compared with ordinary carbon materials, it can provide a suitable growth environment and attachment surface for electroactive bacteria, promote the attachment and growth of electroactive bacteria, increase the biomass and activity of electroactive bacteria on the filler surface, and facilitate the formation of a stable biofilm. It can also more efficiently promote the transfer of electrons between electroactive bacteria and the external environment, accelerate the metabolic process of microorganisms, and thus improve the degradation efficiency of pollutants.

[0052] The above specific description further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a modified biochar material for embedding electroactive bacteria, characterized in that: The steps include: S1: Preparation of modified biochar; S2: preparing an electroactive bacterial solution, and placing the modified biochar obtained in S1 into the electroactive bacterial solution and mixing thoroughly, so that the electroactive bacteria are evenly adsorbed on the surface of the modified biochar; S3: adding the modified biochar uniformly adsorbed with electroactive bacteria obtained in S2 to the embedding material solution, stirring thoroughly to obtain a mixed solution; S4: dropping the mixed solution obtained in S3 into a cross-linking agent to cross-link and solidify the embedded material on the surface of the modified biochar adsorbed with the electroactive bacteria, and washing and drying to obtain the modified biochar material embedding the electroactive bacteria.

2. The preparation method according to claim 1, characterized in that The specific steps of preparing modified biochar in step S1 include: S11: placing the biomass raw material in a quartz boat and transferring it into the insulation area of ​​the tube furnace; S12: Evacuate the insulation area of ​​the tube furnace to a negative pressure of 0.1-1.0 kPa, then introduce nitrogen to a positive pressure of 102-105 kPa, and repeat this operation three or more times; S13: heating the tubular furnace from room temperature to a first reaction temperature of 400°C to 1000°C at a heating rate of 8-15°C / min, heating at a constant temperature for 2-4 hours, and then cooling to room temperature to obtain a biochar material; S14: Grind the biochar obtained in S13 and pass it through a 100-mesh sieve, then stir and soak it in 0.05-0.1 mol / L FeCl3 and KMnO4 solutions at a ratio of 7-12 g:100 ml for 3-5 hours; S15: filtering, washing, and drying the stirred and soaked biochar material obtained in S14, and then heating the modified biochar material in a tube furnace at a second reaction temperature of 400-600° C. for 2-4 h to obtain modified biochar.

3. The preparation method according to claim 2, wherein: The biomass raw materials in S11 are one or more of crop straws such as rice straw, wheat straw, corn straw, agricultural wastes such as rice husks, peanut shells, sugarcane bagasse, coconut shells, walnut shells, wood processing wastes such as sawdust and bark, and forestry residues such as bamboo waste, fruit tree branches, and shrub branches.

4. The preparation method according to claim 2, wherein: The first reaction temperature in S13 is 1000° C. The mixing ratio of the biochar material and the FeCl3 and KMnO4 solutions in S14 is 8 g:100 ml, and the molar concentration of the FeCl3 and KMnO4 solutions is 0.05 mol / L; In the S15, the modification temperature is 450° C. and the modification time is 3 h.

5. The preparation method according to claim 2, characterized in that The filtering, washing and drying of the stirred and soaked biochar material obtained in S14 in S15 specifically includes: The stirred and soaked biochar material is filtered with filter paper and repeatedly rinsed with deionized water for 3-5 times during the filtration process. The filtered and washed biochar material is then placed in an oven and dried at 60-70°C for 16-20 hours.

6. The preparation method according to claim 1, characterized in that The specific steps of preparing the electroactive bacterial solution in S2 include: S21a: collecting the cultured electroactive bacteria by centrifugation; S22a: The electroactive bacteria collected by centrifugation in S21a are washed with sterile physiological saline and resuspended in a certain volume of sterile water to obtain an electroactive bacterial solution; The electroactive bacteria are one or more species of Shewanella, Geobacter, Pseudomonas, Achromobacter and the like.

7. The preparation method according to claim 1, wherein: In step S4, the mixed solution obtained in step S3 is dripped into the cross-linking agent using a dripping method or a spraying method; Wherein, the cross-linking agent is a sodium alginate-CaCl2 composite linking agent.

8. The preparation method according to claim 1, characterized in that The washing and drying process in S4 specifically includes: The embedded, cross-linked and solidified modified biochar carrier was washed multiple times with sterile water, and then the washed modified biochar carrier was dried at a low temperature of 30-40° C. for 12-16 hours.

9. A modified biochar material encapsulating electroactive bacteria, prepared by the method according to any one of claims 1 to 8, characterized in that: The modified biochar material embedding the electroactive bacteria is used as a filler in artificial wetlands to achieve degradation and / or removal of antibiotics.

10. A method for using the modified biochar material embedded with electroactive bacteria as claimed in claim 9, characterized in that: The steps include: s1: at least two layers of electrode plates are set and fixed in the artificial wetland reactor; s2: placing the modified biochar material encapsulating the electroactive bacteria between the electrode plates of adjacent layers in s1; s3: Plants are planted on top of the artificial wetland reactor to form a combined effect of filler adsorption, plant absorption and microbial degradation to achieve the degradation and / or removal of antibiotics.

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