Chitosan-based electronic shuttle filler, preparation method and application thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WUHAN UNIV OF TECH
- Filing Date
- 2026-04-01
- Publication Date
- 2026-06-26
Smart Images
Figure CN122276971A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of microbial enhancement and wastewater treatment technology, and particularly relates to a chitosan-based electron shuttle packing material, its preparation method and application. Background Technology
[0002] Antibiotics are widely used globally in the medical, livestock, and aquaculture sectors, but they are biotoxic and can lead to the spread of antibiotic resistance genes. Wastewater discharge is the primary pathway for antibiotics to enter the natural environment. However, conventional wastewater treatment technologies (such as the traditional activated sludge process) have low antibiotic removal efficiency, and currently, there is a lack of technologies that can be efficiently applied to wastewater treatment and significantly improve antibiotic removal rates. Chemical methods (such as advanced oxidation processes) have high antibiotic removal rates, but they suffer from drawbacks such as high energy and chemical consumption, susceptibility to water quality and substrate interference, and the potential generation of byproducts such as bromate, making them difficult to widely apply in practical low-concentration antibiotic wastewater treatment projects. In actual wastewater treatment projects, biological treatment remains the mainstream method. However, this method is significantly affected by the type and concentration of antibiotics and water quality fluctuations, and under high-load inhibition conditions, it has limitations such as long start-up cycles, large land area requirements, and low removal efficiency.
[0003] Meanwhile, nitrogen removal is one of the core functions of wastewater treatment. However, existing conventional secondary biological treatment relies on nitrification-denitrification processes, requiring the addition of large amounts of carbon source reagents as electron donors. This not only increases the operating costs of wastewater treatment plants but also leads to additional carbon emissions. With increasingly stringent wastewater discharge standards, many regions require effluent to meet the Class IV surface water standard (total nitrogen ≤10 mg / L), forcing wastewater treatment plants to upgrade and further reduce total nitrogen emissions by adding advanced nitrogen removal units. However, conventional advanced nitrogen removal methods (such as post-denitrification filters) struggle to achieve the goal of "simultaneous advanced nitrogen removal and efficient antibiotic removal."
[0004] Against this backdrop, there is currently no mature wastewater treatment technology that can simultaneously and efficiently remove antibiotics and achieve deep denitrification. Summary of the Invention
[0005] In view of the shortcomings of the prior art, the primary objective of this invention is to provide a chitosan-based electron shuttle filler.
[0006] Another object of the present invention is to provide a method for preparing the above-mentioned chitosan-based electron shuttle filler.
[0007] Another object of the present invention is to provide the application of the above-mentioned chitosan-based electron shuttle filler.
[0008] The objective of this invention is achieved through the following technical solution: A chitosan-based electron shuttle filler includes a thermoplastic carrier and chitosan loaded thereon, wherein the active sites on the surface of the chitosan are chemically bonded to neutral red via a glutaraldehyde grafting reaction.
[0009] Preferably, the thermoplastic carrier is made of high-density polyethylene.
[0010] Preferably, the viscosity of the chitosan is 400~850 mPa. s.
[0011] The preparation method of the above-mentioned chitosan-based electron shuttle filler includes the following steps: S1. The thermoplastic carrier is mixed with chitosan powder, and after shaping, cooling, washing and drying, a chitosan-based carrier is obtained. S2. Mix glutaraldehyde solution and acetic acid solution to obtain a mixture, adjust the pH of the mixture to 2~3, add the chitosan-based carrier described in S1, stir at room temperature under light-protected conditions, and then wash to obtain chitosan-grafted glutaraldehyde filler. S3. Add the chitosan-grafted glutaraldehyde filler described in S2 to a neutral red aqueous solution, stir at room temperature under light-protected conditions, wash and dry to obtain the chitosan-based electron shuttle filler.
[0012] Preferably, the specific operation of the shaping in step S1 is as follows: after mixing the thermoplastic carrier and chitosan powder, heat at 130~160 ℃ for 30~40 min, so that the chitosan particles adhere to the surface of the thermoplastic carrier, thus completing the shaping.
[0013] Preferably, the loading rate of the chitosan powder on the thermoplastic carrier in step S1 is 20~35 wt%.
[0014] Preferably, the volume ratio of the glutaraldehyde solution to the acetic acid solution in step S2 is 20~10:1.
[0015] Preferably, the concentration of the glutaraldehyde solution in step S2 is 25-30 wt%; and the concentration of the acetic acid solution is 0.02-0.04 wt%.
[0016] Preferably, the volume fraction of the chitosan-based carrier in step S2 in the mixture is 20-30%.
[0017] Preferably, the stirring time at room temperature under light-protected conditions in step S2 is 24~48 h.
[0018] Preferably, the washing in step S2 refers to washing with ethanol and water in sequence, and repeating the process 2 to 3 times.
[0019] Preferably, the concentration of the neutral red aqueous solution in step S3 is 0.1~0.5 g / L.
[0020] Preferably, the stirring time at room temperature under light-protected conditions in step S3 is 24~48 h.
[0021] The above-mentioned chitosan-based electron shuttle packing material is used as a packing material in moving bed biofilm reactors (MBBRs) for wastewater treatment and antibiotic degradation.
[0022] Compared with the prior art, the beneficial effects of the present invention include: (1) A new process that couples denitrification and antibiotic degradation This invention proposes a method for electron transfer in denitrification and antibiotic degradation reactions mediated by an electron shuttle fixed on packing material. This promotes the use of recalcitrant organic carbon as an electron donor, while simultaneously enhancing nitrogen removal and antibiotic biodegradation, achieving the goal of "pollution reduction and carbon reduction, synergistic efficiency improvement." This process is highly suitable for upgrading and expanding existing wastewater treatment plants for post-denitrification deep treatment. It has minimal impact on existing secondary wastewater treatment processes and structures, minimizing the impact of shutdowns and production stoppages, and resulting in relatively low upgrade and expansion costs.
[0023] (2) Novel fixed electron shuttle packing material This invention employs a glutaraldehyde grafting reaction to immobilize soluble neutral red on chitosan (CTS) and prepare a chitosan-based electron shuttle carrier. The method for immobilizing the electron shuttle is simple and reliable, the packing material is recyclable, and carbon source agents can be continuously added, significantly reducing operating costs and carbon emissions. Furthermore, natural high-molecular-weight chitosan is abundant, with high content in food waste byproducts such as shrimp and crab shells, enabling waste recycling and improving economic and environmental benefits. Attached Figure Description
[0024] Figure 1 This is a schematic diagram illustrating the preparation and application route of the chitosan-based electron shuttle filler described in this invention.
[0025] Figure 2 This is a schematic diagram illustrating the preparation process of the chitosan-based electron shuttle filler described in this invention.
[0026] Figure 3 This is a photograph of the chitosan-based electron shuttle filler prepared in Example 1.
[0027] Figure 4 Microscopic image of the chitosan-based electron shuttle filler prepared in Example 1.
[0028] Figure 5 This is a comparison chart of the denitrification rates between the "conventional packing material + substrate + metronidazole" group and the "chitosan-based electron shuttle packing material + substrate + metronidazole" group.
[0029] Figure 6 The pseudo-first-order kinetic fitting curves for the degradation of metronidazole in four groups of packing materials are shown. Detailed Implementation
[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0031] Antibiotics are widely used in the global medical, livestock, and aquaculture sectors, but they are biotoxic and can lead to the spread of antibiotic resistance genes. Wastewater discharge is the primary pathway for antibiotics to enter the natural environment. Although conventional wastewater treatment technologies (such as the traditional activated sludge process) are currently the mainstream in engineering applications, their removal efficiency for antibiotics is low, making it difficult to meet increasingly stringent emission standards. In contrast, chemical methods (such as advanced oxidation processes) have high removal rates, but they suffer from drawbacks such as high energy and chemical consumption, susceptibility to water quality and substrate interference, and the potential generation of toxic byproducts such as bromate, making them difficult to widely promote in practical low-concentration antibiotic wastewater treatment projects.
[0032] Meanwhile, denitrification, a core function of wastewater treatment, relies on nitrification-denitrification processes in existing conventional secondary biological treatments. This requires the addition of large amounts of carbon source agents as electron donors, increasing operating costs and carbon emissions. Furthermore, conventional deep denitrification methods (such as post-denitrification filters) often struggle to simultaneously achieve both deep denitrification and efficient antibiotic removal when using ordinary packing materials. Fundamentally, antibiotics have stable chemical structures and antibacterial properties, and are often present in trace amounts (ng / L to μg / L) in wastewater. Whether used as substrates or screening agents, they are insufficient to support antibiotic-degrading bacteria in activated sludge or biofilms becoming dominant. This leads to limitations in existing biological systems under high-load inhibition conditions, including long start-up cycles, large footprints, and low removal efficiency. While introducing electron shuttles can enhance the efficiency of electron donor-acceptor biochemical reactions and lower the energy barrier for antibiotic bioconversion, thereby increasing denitrification and antibiotic biodegradation rates, traditional electron shuttles are mostly soluble substances that are easily lost with the effluent after being added to wastewater. This not only wastes resources but may also cause secondary pollution.
[0033] Therefore, there is currently a lack of mature wastewater treatment technology that can simultaneously achieve efficient removal of antibiotics and deep denitrification of wastewater while avoiding secondary pollution and high costs.
[0034] In view of this, the primary objective of the present invention is to provide a chitosan-based electron shuttle filler.
[0035] Another object of the present invention is to provide a method for preparing the above-mentioned chitosan-based electron shuttle filler.
[0036] Another object of the present invention is to provide the application of the above-mentioned chitosan-based electron shuttle filler.
[0037] The objective of this invention is achieved through the following technical solution: A chitosan-based electron shuttle filler includes a thermoplastic carrier and chitosan loaded thereon, wherein the active sites on the surface of the chitosan are chemically bonded to neutral red via a glutaraldehyde grafting reaction.
[0038] This invention utilizes a novel suspended packing material modified with chitosan-based electron shuttles (CTS@RMs) and applies this novel packing material in a moving bed biofilm reactor (MBBR) process to enhance wastewater denitrification and antibiotic degradation. The main principle is to use chitosan (CTS), a common natural polymer, to immobilize neutral red electron shuttles to create CTS@RMs, which are then fixed onto conventional plastic packing. Adding chitosan-based electron shuttle packing to the denitrification MBBR promotes the transfer of electrons from organic matter to nitrate nitrogen during denitrification, fully utilizing organic carbon in the wastewater and significantly reducing the need for external carbon sources for denitrification. It also further enhances the extracellular electron transfer mechanism of the biofilm on the packing, further promoting the degradation of new pollutants such as antibiotics, achieving simultaneous and efficient denitrification and antibiotic removal. The chitosan-based electron shuttle packing and electron shuttles used in this invention are retained in the MBBR process and can be used long-term in wastewater without frequent replacement or elution recovery treatment, reducing the operating costs of replenishing electron shuttles. In addition, the chitosan-based electron shuttle packing material used in this invention has a rough surface and well-developed pores, making it easy for biofilm to attach; the MBBR process used is easy to control in terms of operating conditions, and can be used as a pure membrane process or as a sludge-membrane mixing process with activated sludge. It is stable in operation and has strong resistance to shock loads.
[0039] Preferably, the thermoplastic carrier is made of high-density polyethylene.
[0040] In some embodiments of the present invention, high-density polyethylene is chosen as the carrier material for the following reasons: (1) Strong chemical stability: It is corrosion-resistant and aging-resistant, suitable for long-term immersion in sewage, and has good chemical stability during the modification process, so the functional material is not prone to adverse reactions with the substrate; (2) High mechanical strength: High-density polyethylene has good mechanical properties and is not easily damaged. The modified carrier maintains structural integrity during long-term operation; (3) Strong processability: It is easy to form through extrusion, injection molding and other processes, and is convenient to be compounded with modified materials and industrialized; (4) Low cost and high efficiency: Compared with other engineering plastics, it is moderately priced and suitable for large-scale application.
[0041] Preferably, the viscosity of the chitosan is 400~850 mPa. s.
[0042] In some embodiments of the present invention, selecting medium-viscosity chitosan can avoid the deformation problem of low viscosity and the tailing phenomenon of high viscosity; its mechanical strength is suitable to meet the pressure resistance requirements of practical applications, while maintaining appropriate toughness; its solubility is moderate, and it can more easily undergo cross-linking reaction with electron shuttles; it has good mass transfer performance, biodegradability and microbial adhesion; the raw materials are readily available, the cost is moderate, and the process is mature.
[0043] The preparation method of the above-mentioned chitosan-based electron shuttle filler includes the following steps: S1. The thermoplastic carrier is mixed with chitosan powder, and after shaping, cooling, washing and drying, a chitosan-based carrier is obtained. S2. Mix glutaraldehyde solution and acetic acid solution to obtain a mixture, adjust the pH of the mixture to 2~3, add the chitosan-based carrier described in S1, stir at room temperature under light-protected conditions, and then wash to obtain chitosan-grafted glutaraldehyde filler. S3. Add the chitosan-grafted glutaraldehyde filler described in S2 to a neutral red aqueous solution, stir at room temperature under light-protected conditions, wash and dry to obtain the chitosan-based electron shuttle filler.
[0044] In some embodiments of the present invention, in step S2, acetic acid serves to dissolve chitosan and provide acidic conditions. The key innovation lies in the cross-linking reaction between glutaraldehyde and chitosan at pH 2-3 (conventional conditions are pH 4.0-5.5). This is because under more acidic conditions, chitosan undergoes a higher degree of protonation, and the reaction between its amino group and the aldehyde group of glutaraldehyde is controlled, resulting in a moderate cross-linking density. This ensures the formation of a stable Schiff base with one end of the aldehyde group, preparing for the subsequent cross-linking of the amino group of neutral red with the other end of the aldehyde group. Both S2 and S3 are performed in the dark because glutaraldehyde and neutral red are prone to decomposition under light, thus maintaining the stability of the cross-linking agent and the electron shuttle.
[0045] Preferably, the specific operation of the shaping in step S1 is as follows: after mixing the thermoplastic carrier and chitosan powder, heat it at 130~160℃ for 30~40 min, so that the chitosan particles adhere to the surface of the thermoplastic carrier, and the shaping is completed.
[0046] In some embodiments of the present invention, the melting temperature of the thermoplastic carrier is typically in the range of 120~180 ℃. Choosing 130~160 ℃ is because the carrier is completely melted at this temperature, with moderate fluidity, and the chitosan particles can be uniformly dispersed and adhered to the surface. If the temperature is too high, the carrier will deform severely, and the chitosan will undergo thermal degradation, browning, or carbonization. If the temperature is too low, the carrier will partially melt, and the chitosan will not be able to adhere effectively, resulting in weak bonding force.
[0047] Preferably, the loading rate of the chitosan powder on the thermoplastic carrier in step S1 is 20~35 wt%.
[0048] In some embodiments of the present invention, at this loading rate, chitosan particles form a dense monolayer to several molecular layers covering the surface of the thermoplastic carrier, which ensures functional integrity and avoids interface defects caused by excessive accumulation.
[0049] Preferably, the volume ratio of the glutaraldehyde solution to the acetic acid solution in step S2 is 20~10:1.
[0050] Preferably, the concentration of the glutaraldehyde solution in step S2 is 25-30 wt%; and the concentration of the acetic acid solution is 0.02-0.04 wt%.
[0051] In some embodiments of the present invention, the ultimate goal of selecting the concentrations of glutaraldehyde and acetic acid is to: avoid excessive cross-linking (cross-linking is too fast and too dense at conventional pH 4.0~5.5); retain the aldehyde group at one end of glutaraldehyde for neutral red grafting in step S3; and form a three-dimensional network with "moderate cross-linking": which enhances mechanical strength while maintaining functional activity.
[0052] Preferably, the volume fraction of the chitosan-based carrier in step S2 in the mixture is 20-30%.
[0053] In some embodiments of the present invention, in the reaction vessel of step S2, solid carrier particles are dispersed in a liquid mixture to form a slurry or suspension reaction system. A filling rate of 20-30% places the chitosan-based carrier in the optimal range of "sufficient suspension without overcrowding," ensuring that each carrier particle can fully contact the mixture and achieve uniform crosslinking. When the filling rate is <15%, the particles tend to settle, requiring extremely high stirring speeds; however, when the filling rate is >35%, the particle collision frequency is too high, making them prone to agglomeration.
[0054] Preferably, the stirring time at room temperature under light-protected conditions in step S2 is 24~48 h.
[0055] In some embodiments of the present invention, the stirring time at room temperature under light-protected conditions in step S2 is 24-48 h, for example, it can be 24 h, 26 h, 28 h, 30 h, 32 h, 34 h, 36 h, 38 h, 40 h, 42 h, 44 h, 46 h, and 48 h, or any value between any two of the above. Chitosan undergoes protonation under acidic conditions and then crosslinks with glutaraldehyde; the reaction rate is moderately slow, requiring an extended reaction time of 24-48 h to achieve sufficient crosslinking. Reacting at room temperature reduces energy consumption, avoids the risk of thermal degradation and glutaraldehyde volatilization, and exhibits good batch-to-batch reproducibility due to smaller environmental temperature fluctuations.
[0056] Preferably, the washing in step S2 refers to washing with ethanol and water in sequence, and repeating the process 2 to 3 times.
[0057] Preferably, the concentration of the neutral red aqueous solution in step S3 is 0.1~0.5 g / L.
[0058] In some embodiments of the present invention, the concentration of the neutral red aqueous solution in step S3 is 0.1~0.5 g / L, for example, it can be 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L and 0.1 g / L and any two of the above values. This concentration can ensure that neutral red molecules form a monolayer or quasi-monolayer on the surface of chitosan, with an intermolecular spacing of 1~3 nm, which is within the effective range of electron tunneling effect (<5 nm). (1) Sufficient density: ensures that there are adjacent electron shuttles at the microbial-carrier interface, shortening the electron transfer distance; (2) Immobilization advantage: avoids the loss and dilution of free neutral red, and maintains a local high-concentration microenvironment; (3) Accessibility: the monolayer arrangement ensures that each neutral red molecule can contact the microorganism and electron acceptor in subsequent biofilm culture.
[0059] Preferably, the stirring time at room temperature under light-protected conditions in step S3 is 24~48 h.
[0060] The above-mentioned chitosan-based electron shuttle packing material is used as a packing material in moving bed biofilm reactors (MBBRs) for wastewater treatment and antibiotic degradation.
[0061] Example 1 A method for preparing a chitosan-based electron shuttle filler, the specific steps of which are as follows: S1. The preparation of the chitosan-based carrier was completed in "A device for preparing high-density polyethylene filler with immobilized functional particles" (Patent No.: ZL202321399862.7). The specific steps are as follows: the high-density polyethylene carrier is mixed with chitosan powder (molecular weight 5×10⁻⁶). 5 ~8×10 5 The mixture was mixed with Da and heated at 135 °C for 35 min to allow the chitosan particles to adhere to the surface of the thermoplastic carrier. The loading rate of the chitosan powder on the high-density polyethylene carrier was 35.04 wt%. After shaping, the chitosan-based carrier was obtained after cooling, washing and drying. S2. A 25 wt% glutaraldehyde solution and a 0.02 wt% acetic acid solution are mixed at a volume ratio of 20:1 to obtain a mixture. The pH of the mixture is adjusted to 3. The chitosan-based carrier described in S1 is added, with a volume fraction of 25% in the mixture. The mixture is stirred at room temperature for 48 hours in the dark and then washed to obtain chitosan-grafted glutaraldehyde filler. S3. Add the chitosan-grafted glutaraldehyde filler described in S2 to a neutral red aqueous solution with a concentration of 0.1 g / L, stir at room temperature for 24 hours under light-protected conditions, then wash and dry to obtain the chitosan-based electron shuttle filler.
[0062] Figure 4 Microscopic images of the chitosan-based electron shuttle filler prepared in Example 1. Figure 4 We can see that the rough morphology and porous structure of the chitosan-based electron shuttle filler prepared in Example 1 provide high-density physical sites for the attachment of microorganisms such as filamentous bacteria, which may lead to a significant increase in the activity of nitroreductase secreted by them.
[0063] Application example: Denitrifying sludge (derived from the anoxic section of an oxidation ditch in an urban wastewater treatment plant) was inoculated into the MBBR. During the start-up period, the suspended sludge MLSS was controlled at 300 mg / L. Chitosan-based electron shuttle packing material prepared in Example 1 was added at a filling rate of 40%, and dissolved oxygen (DO) was maintained at ≤0.5 mg / L. -1 Mechanical stirring is used to achieve a stable fluidized state in the packing material. In the initial stage of biofilm formation, the C / N ratio of the wastewater is 7-8, COD is not less than 150 mg / L, BOD is not less than 100 mg / L, and the hydraulic retention time (HRT) can be controlled at 12-24 hours until a brown biofilm forms on the surface of the packing material in 7-10 days, completing the biofilm formation start-up stage. After biofilm formation was complete and the MBBR reactor had been running stably for 60 days, chitosan-based electron shuttle packing and conventional packing were removed (both had biofilms; the biomass of the chitosan-based electron shuttle packing was 3.0 g / L, and the biofilm thickness was 380 μm; the biomass of the conventional packing was 1.84 g / L, and the biofilm thickness was 230 μm). Both packings showed good denitrification activity. The Chaol index of the chitosan-based electron shuttle packing (37.00) was slightly higher than that of the conventional packing (34.00), indicating higher species richness; the Shannon index (1.57 vs 1.18) and the Simpson index (0.32 vs 1.18) were also higher. (0.54) Further analysis shows that the chitosan-based electron shuttle packing exhibits superior and more evenly distributed microbial community diversity, with a lower concentration of dominant species. In contrast, conventional packing materials have a higher Simpson index, suggesting that a few dominant species may dominate their communities, leading to reduced overall diversity. This difference may stem from the biocompatibility of chitosan-based electron shuttle materials and their abundant internal functional groups, which promote electron transport and provide a more balanced growth environment for microorganisms. The abundance of Bacteroidota and Chloroflexota in the chitosan-based electron shuttle packing was 17% (each 17%). The concentrations of COD (16%) in chitosan-based electron shuttles were higher than those in conventional packing materials (4%, 10%), and Chloroflexota was reported to be a Gram-negative bacterium capable of utilizing complex organic matter, while Bacteroidota utilized aromatic compounds (such as benzoquinones) in humic acid as COD. This indicates that chitosan-based electron shuttle materials have the ability to enrich such functionalized bacteria, thereby promoting the removal of recalcitrant pollutants such as metronidazole by microorganisms. A batch denitrification degradation experiment was conducted to investigate the effect of chitosan-based electron shuttle immobilization on the denitrification efficiency of biofilms. The initial COD concentration was set at 150 mg / L, and the nitrate nitrogen (NO3) concentration was 16%. - The concentration of -N was 40 mg / L, the concentration of metronidazole was 400 μg / L, and the reaction time was 24 h.
[0064] The experiment consisted of four groups: (1) conventional packing material + substrate + metronidazole; (2) chitosan-based electron shuttle packing material + substrate + metronidazole; (3) sterilized conventional packing material + substrate + metronidazole; and (4) sterilized chitosan-based electron shuttle packing material + substrate + metronidazole. The packing material filling rate was 20%. After sampling, the packing material was rinsed three times with deionized water to remove residual substrate. The sterilized packing material group refers to the packing material that has been autoclaved for 4 hours to deactivate the biofilm. Each group of experiments had parallel samples.
[0065] The specific steps are as follows: (1) Add metronidazole solution dissolved in methanol to 8 200 mL serum bottles in 4 groups, and dry them in an oven at 40℃ for 4 hours to evaporate the methanol; (2) Add 100 mL of carbon source and nitrogen source to the bottle (the carbon source is 100 mg COD / L methanol and 50 mg COD / L potassium humate (simulating recalcitrant organic matter); the nitrogen source is nitrate nitrogen and 20 mg N / L sodium nitrate; 100 mL is the total amount of carbon source and nitrogen source), place it in a shaker and shake at room temperature for 24 h to allow metronidazole to dissolve completely; (3) Add the appropriate filler, quickly aerate with nitrogen for 15 min, then plug and seal with sealing film, and place on a shaker for reaction; (4) Samples were taken at 0, 0.5, 1, 2, 4, 8, 12, 24, and 48 h. 5 mL of sample was taken from 0 to 24 h to determine the concentrations of nitrate nitrogen, nitrite nitrogen, and metronidazole. 2 mL of sample was taken from 48 h to determine the concentration of metronidazole.
[0066] Results analysis: Figure 5 This is a comparison of denitrification rates between the "conventional packing material + substrate + metronidazole" group and the "chitosan-based electron shuttle packing material + substrate + metronidazole" group. Figure 5 We observed that the initial denitrification rate of the chitosan-based electron shuttle packing reached 16.3 ± 2.2 mgN / (L·h), approximately twice that of conventional packing (8.0 mgN / (L·h)); and its nitrate nitrogen degradation efficiency remained higher than that of conventional packing within 24 hours. This indicates that the electron shuttle possesses highly efficient electron transfer capabilities, rapidly transferring the reducing equivalents (NADH, H2) generated from COD oxidation to the denitrifying enzyme system, thereby significantly enhancing the denitrification process.
[0067] Figure 6 The pseudo-first-order kinetic fitting curves for metronidazole degradation in four groups of packing materials are shown. The sterilization group (conventional packing material and chitosan-based packing material) showed no removal effect on metronidazole, eliminating the interference of adsorption and proving that the degradation of metronidazole is entirely dependent on microbial activity. Kinetic analysis indicates that the pseudo-first-order reaction rate constant of the chitosan-based electron shuttle packing material... k (0.422±0.083 h) -1 ) and biomass-standardized reaction constant k bio (0.156 L·g) -1 ·h -1 All were significantly higher than conventional packing materials ( k =0.215±0.045 h -1 , k bio =0.117 L·g -1 ·h -1Therefore, chitosan-based electron shuttle fillers may promote microbial degradation of pollutants and may enrich highly efficient degrading bacterial communities. The polysaccharide structure of chitosan may act as an electron donor, directly participating in the reduction reaction of metronidazole nitro (-NO2). The electron shuttle acts as a bridge for electron transfer outside the cell, accelerating the transfer of electrons from COD to pollutants.
[0068] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A chitosan-based electron shuttle filler, characterized in that, It includes a thermoplastic carrier and chitosan loaded thereon, wherein the active sites on the surface of the chitosan are chemically bonded to neutral red via a glutaraldehyde grafting reaction.
2. The chitosan-based electron shuttle filler according to claim 1, characterized in that, The thermoplastic carrier is made of high-density polyethylene; and / or The viscosity of the chitosan is 400~850 mPa. s.
3. The method for preparing the chitosan-based electron shuttle filler according to any one of claims 1 to 2, characterized in that, Includes the following steps: S1. The thermoplastic carrier is mixed with chitosan powder, and after shaping, cooling, washing and drying, a chitosan-based carrier is obtained. S2. Mix glutaraldehyde solution and acetic acid solution to obtain a mixture, adjust the pH of the mixture to 2~3, add the chitosan-based carrier described in S1, stir at room temperature under light-protected conditions, and then wash to obtain chitosan-grafted glutaraldehyde filler. S3. Add the chitosan-grafted glutaraldehyde filler described in S2 to a neutral red aqueous solution, stir at room temperature under light-protected conditions, wash and dry to obtain the chitosan-based electron shuttle filler.
4. The method for preparing the chitosan-based electron shuttle filler according to claim 3, characterized in that, The specific operation of the shaping in step S1 is as follows: after mixing the thermoplastic carrier and chitosan powder, heat it at 130~160℃ for 30~40 minutes to make the chitosan particles adhere to the surface of the thermoplastic carrier, thus completing the shaping.
5. The method for preparing the chitosan-based electron shuttle filler according to claim 4, characterized in that, The loading rate of the chitosan powder on the thermoplastic carrier in step S1 is 20~35wt%.
6. The method for preparing the chitosan-based electron shuttle filler according to claim 3, characterized in that, The volume ratio of glutaraldehyde solution to acetic acid solution in step S2 is 20~10:1; and / or The concentration of the glutaraldehyde solution in step S2 is 25-30 wt%; and / or The concentration of the acetic acid solution is 0.02~0.04wt%.
7. The method for preparing the chitosan-based electron shuttle filler according to claim 3, characterized in that, The chitosan-based carrier in step S2 has a volume fraction of 20-30% in the mixture; and / or The stirring time at room temperature under light-protected conditions described in step S2 is 24~48h.
8. The method for preparing the chitosan-based electron shuttle filler according to claim 3, characterized in that, The washing described in step S2 refers to washing with ethanol and water in sequence, and repeating this process 2 to 3 times.
9. The method for preparing the chitosan-based electron shuttle filler according to claim 3, characterized in that, The concentration of the neutral red aqueous solution in step S3 is 0.1~0.5 g / L; and / or The stirring time at room temperature under light-protected conditions described in step S3 is 24~48h.
10. The application of the chitosan-based electron shuttle packing material according to any one of claims 1 to 2 as a moving bed biofilm reactor packing material in wastewater treatment and antibiotic degradation.