Method for sulfur-mediated biological treatment of copper-containing wastewater based on magnetic charcoal reinforcement

Abstract

The invention discloses a method for sulfur-mediated biological treatment of copper-containing wastewater based on magnetic charcoal reinforcement. According to the method, magnetic biochar with good magnetic response performance and high specific surface area is prepared and introduced into a sulfur-mediated anaerobic biological treatment system, and heavy metal ions and sulfate in the copper-containing wastewater are synergistically removed under the anaerobic condition. The magnetic biochar not only can quickly remove Cu < 2 + > in wastewater through adsorption, complexation and precipitation effects and reduce toxicity inhibition of the magnetic biochar on microorganisms, but also is beneficial to stable operation of a sulfur-mediated biological system to a certain extent as a microorganism attachment carrier. Experimental results show that under proper conditions, the method has high removal efficiency on Cu < 2 + > in wastewater, and has positive influence on the overall operation stability of the system. The process is stable in operation, low in energy consumption and small in secondary pollution risk, is suitable for efficient treatment of copper-containing industrial wastewater of printed circuit boards and the like, and has a good engineering application prospect.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology and relates to a method for sulfur-mediated biological treatment of copper-containing wastewater based on magnetic biochar enhancement. Background Technology

[0002] With the rapid development of the electronics and information industry, wastewater generated during the manufacturing of printed circuit boards (PCBs) has become a serious environmental problem. PCB wastewater often contains high concentrations of heavy metal ions (such as copper, nickel, and lead), complex organic additives, and high concentrations of sulfates, characterized by high toxicity, difficulty in degradation, and complex composition. Direct discharge without effective treatment will pose a serious threat to the ecological environment and human health. Heavy metals can not only accumulate in water bodies over long periods but also enter organisms through the food chain, damaging proteins and enzyme systems, leading to ecological imbalance and chronic poisoning. Simultaneously, the presence of organic pollutants and sulfates in the wastewater exacerbates the difficulty of wastewater treatment, making it difficult for traditional processes to simultaneously achieve both removal efficiency and environmental hazard prevention.

[0003] Currently, the main methods for treating PCB wastewater include chemical, physical, and biological methods. Chemical precipitation, electrochemical, and photocatalytic methods offer fast treatment speeds, but often require large amounts of chemical reagents, produce significant amounts of sludge as byproducts, pose a risk of secondary pollution, and have high operating costs. Physical methods such as adsorption and ion exchange have advantages in removal efficiency, but are limited by the high cost of adsorbent materials and difficulties in regeneration. Biological methods have gained widespread attention due to their low cost and environmental friendliness, but they are easily inhibited when treating wastewater with high concentrations of heavy metals, leading to a significant decrease in removal efficiency. Overall, a single method is insufficient to meet the synergistic treatment needs of multiple pollutants in PCB wastewater.

[0004] In recent years, the synergistic coupling of multiple treatment technologies has gradually become an important development direction for improving wastewater treatment efficiency. Among them, magnetic biochar, due to its large specific surface area, rich pore structure, and good adsorption performance, has shown great potential in the removal of heavy metals. Magnetic biochar can also be simply referred to as magnetic carbon. Through magnetic modification, biochar retains its adsorption performance while acquiring certain magnetic response characteristics, providing possibilities for subsequent solid-liquid separation and material utilization. In existing biological treatment systems, sulfur-mediated biological systems can convert sulfate into sulfides under anaerobic conditions through sulfate-reducing bacteria. While achieving energy metabolism and electron transfer, these systems can react with heavy metal ions to form insoluble sulfide precipitates, showing certain application potential in the treatment of wastewater containing copper and other heavy metals. Therefore, combining magnetic biochar with sulfur-mediated biological treatment processes can not only reduce the toxicity of heavy metal ions to microorganisms through efficient adsorption, but also provide abundant surface functional groups and pore structures as sites for microbial attachment and growth, thereby promoting the enrichment of functional flora and metabolic activities. This achieves the complementary advantages of physical adsorption and biological action, further improving pollutant removal efficiency and enhancing system stability, and providing a new technical approach for heavy metal wastewater treatment.

[0005] Chinese patent document CN 111389363 A discloses a magnetic biochar adsorbent material based on sulfate-reduced sludge, its preparation method, and its application. The sludge is sieved, washed, and dried before being combined with Fe-containing... 2+ / Fe 3+ Iron salt solutions are mixed and treated under alkaline conditions to obtain iron-containing sludge, which is then pyrolyzed under a protective atmosphere to produce magnetic biochar. This material can be used for the adsorption of heavy metals and / or dyes. However, this patent mainly focuses on the preparation of the adsorbent material and the evaluation of its adsorption application effect, belonging to the material adsorption route. Its technical solution does not involve the sulfur-mediated anaerobic biological treatment process system for copper-containing wastewater, nor does it provide the operating conditions and control indicators related to biological treatment (such as the system construction method under anaerobic reaction conditions, the addition method and dosage of magnetic biochar in the system, etc.). Therefore, when facing scenarios such as copper-containing wastewater that are more sensitive to biological processes and require the simultaneous consideration of sulfate conversion and metal synergistic removal, there is still a lack of understanding on how to achieve stable operation and synergistic removal at the process system level. Summary of the Invention

[0006] To overcome the problems of insufficient operational stability and heavy metal toxicity inhibition in existing copper-containing wastewater treatment processes, this invention provides a method for coupling a magnetic biochar-sulfur-mediated biological system. The key technical point is: under anaerobic sulfur-mediated reaction conditions, magnetic biochar with both magnetically responsive recyclable characteristics and iron oxide-loaded active sites is introduced, enabling it to simultaneously bear (1) Cu 2+(1) Adsorption / complexation / precipitation solidification to achieve detoxification buffering; (2) Microbial attachment and immobilization carrier and interfacial microenvironment regulation; (3) Auxiliary verification of changes in electron transfer-related components (EPS, CytC) in the system, thereby achieving synergistic improvement of copper-containing wastewater treatment effect and system stability under batch conditions. This invention provides a new technical approach for the biological treatment of copper and other heavy metal wastewater, and provides a new research direction for sulfate conversion and synergistic metal removal.

[0007] The objectives of this invention include the following aspects:

[0008] Firstly, a magnetic biochar with good magnetic response performance and high specific surface area is provided.

[0009] Secondly, a method for preparing the aforementioned magnetic biochar is provided.

[0010] Thirdly, a method for sulfur-mediated biological treatment of copper-containing wastewater based on magnetic biochar enhancement is provided.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for sulfur-mediated biological treatment of copper-containing wastewater based on magnetic biochar enhancement includes the following steps: (1) Preparation of magnetic biochar: After biochar is prepared by pyrolysis, magnetic modification is carried out by iron salt coprecipitation-heat treatment process to obtain magnetic biochar loaded with iron oxide; (2) Under anaerobic conditions, a sulfur-mediated biological treatment system is constructed, and the magnetic biochar is added to the sulfur-mediated biological treatment system; (3) Add copper-containing wastewater to the system for reaction treatment to achieve Cu 2+ The adsorption and solidification and the bioreduction of sulfate are used for synergistic removal.

[0012] Furthermore, in step (1), the specific steps for preparing magnetic biochar are as follows: S1: Take agricultural waste and pyrolyze it at 600~800℃ to obtain biochar; S2: Using Fe 3+ and Fe 2+ Magnetic modification was performed using a co-precipitation method followed by heat treatment to obtain a magnetic biochar precursor. S3: The magnetic biochar precursor is subjected to a secondary heat treatment at 600~800℃ to obtain magnetic biochar.

[0013] Further, step S1 specifically includes: taking agricultural waste (such as straw, livestock and poultry manure), drying it at 80~120℃ and then crushing it, placing it in a tube furnace, and pyrolyzing it at 600~800℃ for 2~4 hours (preferably 700℃, 3h) under nitrogen-filled and oxygen-limited conditions, grinding and sieving the obtained product to obtain biochar.

[0014] Furthermore, step S2 specifically includes: mixing FeCl3·6H2O and FeSO4·7H2O according to Fe 3+ Fe 2+ The magnetic biochar precursor was dissolved in ultrapure water at a mass ratio of 2:1, and the pH was adjusted to 9-11 by adding NaOH solution dropwise. After standing for 1-3 hours, the precipitate was separated by centrifugation, washed with ultrapure water until neutral, dried at 50-80℃ for 8-24 hours, and then sealed and stored to obtain the magnetic biochar precursor.

[0015] Furthermore, step S3 specifically includes: subjecting the magnetic biochar precursor to a second heat treatment under nitrogen-filled and oxygen-limited conditions, holding it at 600~800℃ for 1~3 hours, preferably 2 hours; grinding and sieving the product, and drying it to obtain magnetic biochar.

[0016] The magnetic biochar prepared by the above method has a pore size of approximately 3.7–16.0 nm (calculated at 4 V / A by BET), exhibits magnetic resonance properties, and has a high specific surface area (19–161 m²). 2 / g).

[0017] Furthermore, in step (2), in constructing the sulfur-mediated biological treatment system, sulfate is used as an electron acceptor under anaerobic conditions, and sulfate-reducing bacteria metabolize and generate sulfides.

[0018] Furthermore, in step (2), the dosage of the magnetic biochar is 1~8 g / L. More preferably, the dosage of the magnetic biochar is 1~5 g / L.

[0019] Furthermore, in step (3), the Cu in the copper-containing wastewater 2+ The initial concentration is 10~300 mg / L.

[0020] Furthermore, in step (3), the reaction treatment time is 12~120 h.

[0021] This invention employs a co-precipitation-pyrolysis coupled process to magnetically modify biochar obtained from agricultural waste, under alkaline conditions using Fe... 3+ with Fe 2+Fe3O4 and other iron oxide particles are co-precipitated and loaded onto the pores and surface of biochar. Subsequently, oxygen-limited heat treatment promotes the formation of iron oxide crystal phases and interfacial bonding, endowing the material with magnetic response and retaining porous structure and active sites.

[0022] This invention further provides the application of magnetic biochar in sulfur-mediated biological systems. Sulfur-mediated biological systems are a widely studied anaerobic biological treatment process that uses sulfate as an electron acceptor under anaerobic conditions to generate sulfides through the metabolism of sulfate-reducing bacteria.

[0023] The key technical point of this invention lies in introducing magnetic biochar into a sulfur-mediated biological treatment system, and utilizing magnetic biochar to treat Cu under anaerobic conditions. 2+ The adsorption / solidification effect reduces its biotoxicity and provides a carrier and interfacial environment for microorganisms to attach to, thereby promoting the stable operation of the sulfur-mediated system; at the same time, the measurement results of indicators such as EPS and CytC provide auxiliary explanations for the changes in the system state.

[0024] In this coupled system, adsorption and microbial metabolic processes work together to reduce the toxicity of heavy metals on the biological system and improve the operating state of the reaction system. Batch experiment results show that after the introduction of magnetic biochar, the system can start up quickly and maintain a relatively stable operating state. Compared with the control system without magnetic biochar, the removal of heavy metals shows a certain improvement trend.

[0025] Preferably, the magnetic biochar has magnetic response characteristics, making it feasible to separate and recycle it under an external magnetic field, thus providing possibilities for expanding the subsequent utilization of the material.

[0026] This invention prepares magnetic biochar with good magnetic response and high specific surface area, and introduces it into a sulfur-mediated anaerobic biological treatment system to achieve synergistic removal of heavy metal ions and sulfates from copper-containing wastewater under anaerobic conditions. The magnetic biochar rapidly removes Cu from wastewater through adsorption, complexation, and precipitation. 2+ This reduces the toxicity and inhibition of microorganisms, while also serving as a carrier for microbial attachment, which is beneficial to the stable operation of sulfur-mediated biological systems. Ultimately, this invention achieves a significant enhancement effect through the synergistic combination of magnetic biochar and sulfur-mediated biological systems, the dosage / ratio, and the operational organization.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The prepared magnetic biochar has magnetic response characteristics, which facilitates solid-liquid separation and material recycling.

[0028] (2) Magnetic biochar can participate in Cu 2+ Removes and promotes its solidification, reducing free Cu2+ Inhibiting the toxicity of sulfur-mediated systems is beneficial to the stable operation of the system.

[0029] (3) In the small-bottle batch experiment, EPS and CytC, etc., were different at different dosages and different Cu 2+ The differences observed under varying concentration conditions can be used to further explain the effects of magnetic biochar on extracellular components and system state.

[0030] (4) Experimental results show that, under suitable conditions, this method is effective for Cu in wastewater. 2+ The removal rate can reach 79.5%~98.0%, and it has a positive impact on the overall operational stability of the system. The process of this invention is stable in operation, has low energy consumption, and low risk of secondary pollution. It is suitable for the efficient treatment of copper-containing industrial wastewater such as that from printed circuit boards, and has good prospects for engineering applications. Attached Figure Description

[0031] Figure 1 Pig manure biochar for the effect of Cu in simulated copper-containing wastewater 2+ A diagram illustrating the removal process.

[0032] Figure 2 Pig manure biochar for the effect of Cu in simulated copper-containing wastewater 2+ A schematic diagram showing the change in adsorption capacity.

[0033] Figure 3 To investigate the effect of straw biochar on Cu in simulated copper-containing wastewater 2+ A diagram illustrating the removal process.

[0034] Figure 4 To investigate the effect of straw biochar on Cu in simulated copper-containing wastewater 2+ A schematic diagram showing the change in adsorption capacity.

[0035] Figure 5 Biochar for the removal of Cu from simulated copper-containing wastewater 2+ A schematic diagram of the adsorption kinetics curve.

[0036] Figure 6 Biological systems incorporating magnetic biochar under different addition levels were studied for their effects on Cu in simulated copper-containing wastewater. 2+ A diagram illustrating the removal process.

[0037] Figure 7 Biological systems in which magnetic biochar was introduced under different initial copper concentrations were used to study the effects of Cu in simulated copper-containing wastewater. 2+ A diagram illustrating the removal process.

[0038] Figure 8 Magnetic hysteresis curves (VSM) of magnetic biochar samples prepared at different temperatures.

[0039] Figure 9 Scanning electron microscope (SEM) images of unmodified biochar and magnetic biochar samples at different temperatures.

[0040] Figure 10 The XRD patterns of the Z-series samples before and after adsorption / reaction of magnetic biochar are shown.

[0041] Figure 11 The XRD patterns of J series samples before and after adsorption / reaction with magnetic biochar are shown.

[0042] Figure 12 The changes in EPS content and PN / PS in the system at 0 h and 72 h under different magnetic biochar dosages were investigated.

[0043] Figure 13 For different initial Cu 2+ Changes in EPS content and PN / PS ratio in the system at different concentrations at 0 h and 72 h.

[0044] Figure 14 The changes in cytochrome c content in the system at different magnetic biochar dosages at 0 h and 72 h were investigated.

[0045] Figure 15 For different initial Cu 2+ Changes in cytochrome c content at different concentrations at 0 h and 72 h. Detailed Implementation

[0046] The present invention will be further described below with reference to embodiments, but this should not be construed as limiting the invention, but rather as an exemplary description of certain embodiments of the invention. Those skilled in the art can combine features from different embodiments without contradiction.

[0047] This invention provides the application of magnetic biochar in the removal of heavy metal ions from copper-containing simulated wastewater.

[0048] This invention also provides the application of a magnetic biochar-enhanced sulfur-mediated biological system in the treatment of copper-containing wastewater.

[0049] In the preparation of magnetic biochar, the present invention first prepares a base biochar, then performs magnetic modification and secondary heat treatment at different temperatures to obtain magnetic biochar with both good pore structure and magnetic response characteristics.

[0050] Preferably, the raw materials are two types of agricultural waste: rice straw and pig manure. The pig manure is dried at 105°C before use, and the straw is treated according to the same pretreatment process.

[0051] Preferably, both types of pretreated biomass are pyrolyzed at 700°C for 3 hours under nitrogen-filled and oxygen-limited conditions to prepare unmodified biochar. The pyrolysis is carried out in a tube furnace. After the pyrolysis is completed, the product is ground, pulverized, and passed through a 100-mesh sieve, and then stored in a desiccator.

[0052] More preferably, given the initial fluctuations in the performance of the self-made biochar, in order to ensure batch-to-batch consistency of the materials, subsequent experiments used purchased biochar prepared with the same parameters as above (nitrogen conditions, 700℃, 3h), supplied by Henan Lize Environmental Protection Co., Ltd.

[0053] Preferably, the magnetic modification employs a co-precipitation-thermal decomposition coupling process: FeCl3·6H2O and FeSO4·7H2O are mixed according to Fe... 3+ Fe 2+ The co-precipitate was dissolved in an appropriate amount of ultrapure water at a mass ratio of 2:1. Biochar was added to make the carbon-to-iron ratio 2:1 and the carbon-to-water ratio 1g:10mL. NaOH solution was added dropwise to adjust the pH to 10.0 under constant temperature and stirring at 70℃. After stirring for 2 hours, the mixture was allowed to stand for 2 hours. The precipitate obtained by co-precipitation was separated by centrifugation, washed with ultrapure water until neutral, dried at 50-80℃ for 12 hours, and then sealed and stored to obtain the magnetic precursor.

[0054] Preferably, the magnetic precursor is subjected to a second heat treatment under nitrogen-filled and oxygen-limited conditions at temperatures of 600℃, 700℃, and 800℃, respectively, for 2 hours. After heat treatment, the product is ground and passed through a 100-mesh sieve, and then dried and stored to obtain magnetic biochar samples under different temperature systems.

[0055] Preferably, the samples are named as follows: unmodified pig manure biochar is designated as Z, and unmodified straw biochar is designated as J; pig manure-based magnetic biochar with secondary pyrolysis temperatures of 600℃, 700℃, and 800℃ is designated as ZC600, ZC700, and ZC800, respectively, and straw-based magnetic biochar is designated as JC600, JC700, and JC800, respectively.

[0056] Preferably, the magnetic biochar is characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), specific surface area analysis (BET), and vibrating sample magnetometer (VSM) to characterize its pore structure, surface functional groups, and magnetic properties.

[0057] Preferably, the initial Cu in the solution 2+ The concentration was 150 mg / L, and the sampling points were 12h, 24h, and 72h.

[0058] Batch experiments on biochar addition levels revealed that the initial Cu 2+At a concentration of 150 mg / L, the adsorption capacities of samples Z, ZC800, and J reached 32.7 mg / g, 33.9 mg / g, and 32.5 mg / g, respectively, when the addition amounts were 3 g / L and 5 g / L. The adsorption capacity of JC800 reached a maximum of 75.4 mg / g at 1 g / L. This indicates that there are differences in the appropriate dosage and adsorption performance of biochar of different types / modification conditions. The appropriate dosage can improve the adsorption capacity per unit mass.

[0059] In the adsorption isotherm experiment, with a dosage of 1 g / L and a reaction time of 12 h, under different initial concentrations (10, 20, 50, 80, 100, 200, 300 mg / L), ZC800 and JC800 reached their maximum equilibrium adsorption capacities of 91.9 mg / g and 124.6 mg / g, respectively, at 300 mg / L. The experimental data conformed to the Langmuir isotherm adsorption model, indicating that magnetic biochar still has a certain adsorption capacity under high concentration conditions. In the adsorption kinetics experiment, with an initial concentration of 150 mg / L, a dosage of 1 g / L, and a reaction time of 12 h, the results showed that all biochars basically reached adsorption equilibrium within 12 hours. The equilibrium adsorption capacity of JC800 (129.1 mg / g) was significantly higher than that of Z, J, and ZC800, and the fitting results conformed to the pseudo-second-order kinetic model, indicating that the adsorption process mainly exhibited chemisorption characteristics, accompanied by a certain degree of physisorption.

[0060] Regarding wastewater adsorption performance, the magnetic biochar provided by this invention is effective against heavy metal Cu. 2+ It exhibits good removal capacity; after adding magnetic biochar to copper-containing solutions, it can effectively reduce Cu in water. 2+ Concentration. For example... Figure 5 As shown.

[0061] Kinetic and isotherm model fitting revealed that the adsorption process conforms to the Langmuir isotherm adsorption model. The adsorption mechanism mainly includes ion exchange, surface complexation, and precipitation, accompanied by a certain degree of physical adsorption. The oxygen-containing functional groups on the surface of magnetic biochar undergo complexation reactions with metal ions, and the mineral components in the biochar react with the metal ions to form precipitates, thus achieving efficient removal. Figures 12-15 As shown.

[0062] Example 1: Preparation and Characterization of Magnetic Biochar This embodiment provides a method for preparing magnetic biochar: (1) Take agricultural waste (such as straw and livestock manure), dry it at 105°C and crush it. Place it in a tube furnace and pyrolyze it at 700°C for 3 hours under nitrogen-filled and oxygen-limited conditions to obtain unmodified biochar. After pyrolysis, grind the obtained product and pass it through a 100-mesh sieve. Then place it in a desiccator for storage.

[0063] (2) Mix FeCl3·6H2O and FeSO4·7H2O according to Fe 3+ Fe 2+ The carbon-iron ratio was dissolved in an appropriate amount of ultrapure water at a mass ratio of 2:1. Unmodified biochar was added to make the carbon-iron ratio 2:1 and the carbon-water ratio 1g:10mL. The mixture was stirred continuously at 70℃, and NaOH was added dropwise to adjust the pH to 10.0. After reacting for 2 h, the mixture was allowed to stand for 2 h. After the reaction was completed, the resulting product was centrifuged, washed with ultrapure water until neutral, dried at 50-80℃ for 12 h, and then sealed and stored to obtain the magnetic precursor.

[0064] (3) The magnetic precursor obtained in step (2) was subjected to secondary heat treatment at 600℃, 700℃ and 800℃ under nitrogen protection for 2 h. After heat treatment, the product was ground and passed through a 100-mesh sieve, and then dried and stored to obtain magnetic biochar samples under different temperature systems.

[0065] The magnetic biochar was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and vibrating sample magnetometer (VSM) to analyze its microstructure, crystal structure, surface functional group characteristics, and magnetic properties. Among them, the Z series is a series of magnetic biochar samples prepared from pig manure, and the J series is a series of magnetic biochar samples prepared from straw. Except for the different sources of raw materials, the other preparation steps are carried out according to steps (1) to (3) of this embodiment.

[0066] like Figure 8 As shown, the prepared magnetic biochar exhibits magnetic response characteristics. Figure 9 As shown, magnetic modification and heat treatment can alter the surface morphology of biochar and form a particle-loaded structure, which is beneficial for providing interfacial contact and adhesion sites. Combined with BET test results, the specific surface area of ​​the prepared material is approximately 19–161 m². 2 / g, with an average pore size of approximately 3.7–16.0 nm (calculated at 4V / A by BET), indicates that the material is predominantly mesoporous, which is beneficial for Cu. 2+ It diffuses into the pores and undergoes complexation or precipitation reactions with the active sites of surface functional groups. For example... Figure 10 , Figure 11As shown, the sample exhibits iron oxide-related crystalline phase characteristics; after interacting with the copper-containing system, copper-related phase characteristic peaks appear, indicating that the material not only undergoes adsorption during the reaction but may also participate in the Cu solidification process through surface complexation / co-precipitation, thereby supporting the stable operation of the copper-containing system.

[0067] Example 2: Adsorption experiment and condition optimization of magnetic biochar The magnetic biochar was added to simulated copper-containing wastewater to investigate its removal performance for heavy metal ions. The main steps were as follows: Weigh out 0.03, 0.09, 0.15, and 0.24 g of biochar samples at different addition amounts (1, 3, 5, and 8 g / L) into 50 mL centrifuge tubes, and add 30 mL of Cu at a concentration of 150 mg / L. 2+ Simulated copper-containing wastewater was subjected to oscillating adsorption at 200 r / min, with sampling intervals of 12 h, 24 h, and 72 h. 1 ml of each sample was filtered through a 0.45 µm membrane before Cu content was determined. 2+ Concentrations were set up in triplicate for each concentration. Representative samples Z, J, ZC800, and JC800 were selected. Within 72 h, JC800 showed higher adsorption capacity (75.4 mg / g) and higher equilibrium adsorption capacity (38.0 mg / g) at a dosage of 1 g / L, which was higher than other types of biochar samples at other dosages. The results are as follows. Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown.

[0068] Weigh biochar at the optimal addition amount (1 g / L) into a 50 mL centrifuge tube, and add Cu at different concentrations (10, 20, 50, 80, 100, 200, 300 mg / L). 2+ Simulated copper-containing wastewater was subjected to adsorption by shaking at 200 r / min. After 12 h, the sample was taken out, filtered through a 0.45 µm membrane, and the Cu content was measured. 2+ Concentrations were set up in triplicate for each concentration. At low concentrations (10, 20, 50, 80, 100 mg / L), JC800 was used to treat Cu... 2+ It exhibits a high removal level, maintaining a certain removal rate (38.7%) and a high adsorption capacity (124.6 mg / g) even at 300 mg / L.

[0069] Weigh biochar at the optimal addition amount (1 g / L) into a 50 mL centrifuge tube, and add 50 mL of 150 mg / L Cu. 2+Simulated copper-containing wastewater was subjected to adsorption at 200 r / min with shaking. Sampling times were 5, 10, 20, 30, 45, 60, 80, 100, 120, 150, 180, 240, 360, 540, and 720 min. After filtration through a 0.45 µm membrane, Cu content was measured. 2+ Concentrations were set up in triplicate for each concentration. The equilibrium adsorption capacity of JC800 under the experimental conditions reached 129.1 mg / g, which is higher than that of other types of biochar samples.

[0070] The above experimental results show that, under the conditions described in this study, the straw-based magnetic biochar JC800 prepared at 800℃, when added at a concentration of 1 g / L, effectively inhibits Cu oxidation. 2+ It exhibits good adsorption performance and reaches adsorption equilibrium relatively quickly. Through isotherm and kinetic fitting of the experimental data, the adsorption process conforms to the Langmuir isothermal adsorption model. The adsorption mechanism mainly involves ion exchange, surface complexation, and precipitation, accompanied by a certain degree of physical adsorption. Therefore, preferably, under the conditions of this embodiment, the optimal dosage of magnetic biochar is 1 g / L, and the type is rice straw magnetic biochar prepared by pyrolysis at 800℃.

[0071] Example 3: Magnetic biochar-enhanced sulfur-mediated biological system Using the superior magnetic biochar types obtained in Examples 1 and 2, a sulfur-mediated biological system enhanced with magnetic biochar was constructed. The construction and operation of this reaction system followed the conventional construction approach for sulfur-mediated sludge systems. Specifically, sulfate-reducing bacteria (SRB) sludge was used as inoculum. Simulated wastewater was prepared according to the specified composition and added to the reaction flask to establish an anaerobic environment. The system was then pre-cultured under constant temperature and shaking conditions to ensure a stable sulfate reduction metabolic state. Subsequently, magnetic biochar and Cu were added according to the experimental scheme described below. 2+ To investigate the impact of the introduction of magnetic biochar on the system operation and heavy metal removal process, relevant batch experiments were conducted, including the following steps: (1) Experiment on the effect of magnetic biochar addition amount on system operation: Weigh out 0.045, 0.135, and 0.225 g of magnetic biochar samples at different addition amounts (1, 3, and 5 g / L) into 50 mL centrifuge tubes, and add 45 mL of 1 g-VSS / L sulfate-reducing bacteria (SRB) sludge and 150 mg / L Cu. 2+Simulated copper-containing wastewater was subjected to oscillation adsorption at 200 r / min, and samples were taken at 0, 2, 4, 8, 12, 18, 24, 36, 48, and 72 h. Five groups were set up: a control group (only SRB sludge was added), a sterilized group (high-temperature sterilized SRB sludge was added), and a normal group (SRB sludge and magnetic biochar were added according to the specified dosage). Each experimental group had three parallel samples.

[0072] The composition of the bioreactor water used in this example is as follows: The composition per 1000 mL is: 1232 mg Na2SO4, 640.615 mg CH3COONa, 26 mg CaCl2, 37.95 mg MgCl2, 95.5 mg NH4Cl, 12.58 mg K2HPO4·3H2O, 3.6 mg KH2PO4, 5 mg FeCl3·6H2O, 0.5 mg H3BO3, 0.125 mg CuSO4, 0.2 mg KI, 0.625 mg MnSO4·H2O, 0.375 mg ZnSO4·7H2O, and 0.5 mg CoCl2·6H2O.

[0073] Because the reactor's water distribution system originally contained a phosphate buffer system, the introduction of Cu... 2+ It readily forms insoluble precipitates (such as Cu3(PO4)2, Cu(OH)2) with phosphate or hydroxide ions, leading to turbidity in the system. To avoid this effect, this embodiment replaces the original phosphate buffer system with one that does not react with Cu. 2+ Good's buffer solution (MOPS) that forms a precipitate is obtained by replacing 12.58 mg K2HPO4·3H2O and 3.6 mg KH2PO4 in the original water with 41.25 mg MOPS.

[0074] like Figure 6 As shown, at 72 h, the Cu concentrations in the 3 g / L and 5 g / L groups... 2+ The removal rate was 98.0%, and 79.5% in the 1 g / L group, both significantly higher than the 62.2% of the control group, representing increases of 36.8% and 17.3%, respectively. After deducting the influence of sludge self-adsorption, the magnetic biochar-sulfur-mediated biocoupling system with introduced magnetic biochar showed significant improvements in Cu... 2+ The removal process showed a certain improvement trend, and compared with the single biological system without the addition of magnetic biochar, Cu 2+ The removal effect has been improved.

[0075] (2) Cu 2+ Experiment on the effect of concentration on pollutant degradation: Weigh the magnetic biochar into a 50 mL centrifuge tube according to the optimal dosage, and add 45 mL of solution containing 50, 150, or 300 mg / L Cu. 2+ Simulated copper-containing wastewater containing 1 g-VSS / L SRB sludge was subjected to shaking adsorption at 200 r / min at 0, 2, 4, 8, 12, 18, 24, 36, 48, and 72 h. Three groups were set up with Cu concentrations of 50, 150, and 300 mg / L. 2+ For each concentration group, three parallel samples were set up.

[0076] like Figure 7 As shown, at 72 h, the removal rate was approximately 100% with an initial concentration of 50 mg / L, while it was 86.1% and 51.7% with concentrations of 150 mg / L and 300 mg / L, respectively. At different initial Cu... 2+ Under the given concentration conditions, the magnetic biochar-sulfur-mediated biocoupling system incorporating magnetic biochar maintained stable operation and, to some extent, reduced the Cu concentration in the system. 2+ The removal behavior varies with the initial Cu concentration. 2+ The changes in concentration showed corresponding differences.

[0077] (3) Auxiliary verification of electron transport related indicators (EPS and CytC) To further illustrate the role of magnetic biochar in enhancing sulfur-mediated biological systems, this example measured extracellular polymeric substances (EPS) and cytochrome c (CytC) under batch conditions in vials. The experiment included eight groups: five groups with varying dosages (no magnetic biochar, sterilized control, and groups with magnetic biochar at concentrations of 1 g / L, 3 g / L, and 5 g / L). The initial Cu content of each group was... 2+ The concentration was 150 mg / L for all groups; there were four groups of copper concentration gradient groups, with initial Cu... 2+ Concentrations of 0 mg / L, 50 mg / L, 150 mg / L, and 300 mg / L were used, with a magnetic biochar dosage of 1 g / L for each group. Parallel samples (preferably two parallel samples) were set up for each group, and samples were taken at 0 h and 72 h. The sludge mass was weighed after sampling, and the EPS and CytC results were normalized according to the sludge mass for inter-group comparisons.

[0078] like Figure 12 and Figure 13 As shown, EPS was characterized by protein (PN) and polysaccharide (PS), and the total EPS was expressed as PN+PS. The PN / PS ratio was calculated to reflect compositional differences. Under the condition of Cu=150 mg / L, the total EPS and PN / PS ratios of the systems with different dosages of magnetic biochar showed differences. At different initial Cu... 2+Under different concentration conditions, the EPS index showed corresponding differences with the intensity of copper stress. Furthermore, comparing 72 h with 0 h, it can be seen that the total EPS of some magnetic biochar groups showed a certain degree of maintenance or increase at 72 h, indicating that the introduction of magnetic biochar can affect the generation and composition of extracellular polymers in the system under copper stress, thereby affecting the extracellular microenvironment and interface state.

[0079] like Figure 14 and Figure 15 As shown, CytC at different dosages and different Cu concentrations between 0 h and 72 h... 2+ The concentrations showed varying degrees of change. To reduce the impact of initial differences on the comparison, the 72 h / 0 h ratio (retention rate) was used to characterize the relative changes in CytC; the results showed that the CytC retention rate differed under different conditions. Combining this with the comparison between the control group and the sterilized control group can help distinguish the contributions of biological processes and abiotic factors to the changes in the indicators. The combined results of EPS and CytC indicate that the introduction of magnetic biochar can affect the levels of components related to the extracellular microenvironment and electron transport in the system, thus providing supplementary explanation for the role of magnetic biochar in enhancing sulfur-mediated biological systems.

[0080] Further explanation: Under the conditions of this embodiment, a higher magnetic biochar dosage is not necessarily more beneficial. When the dosage increases to 5 g / L, on the one hand, the magnetic biochar particles may aggregate / cover the interface, resulting in limited mass transfer and altering microbial attachment and the extracellular microenvironment, thereby reducing the levels of EPS secretion and electron transport-related components. On the other hand, this invention normalizes the EPS and CytC results according to the sampled sediment mass (mg / g, nmol / g), and the magnetic biochar itself also occupies a certain proportion of solid mass. Under the same sediment mass, this will reduce the proportion of "sludge / biomass" per unit mass, thus making the normalized apparent values ​​of EPS and CytC lower. In summary, the system has an optimal dosage window (1~3 g / L), and excessively high dosages may lead to a weakening of the enhancement effect.

[0081] The experimental results from Examples 2 and 3 show that, under the conditions described in this embodiment, the removal process of copper ions in the system after the introduction of magnetic biochar shows a certain improvement trend. Figures 6-7 At 72 h, compared with the blank group, the Cu system with introduced magnetic biochar showed a higher concentration of Cu. 2+ The removal rate is higher. This improvement is not due to a single biological process or a single adsorption process, but is related to the combined effects of material adsorption / solidification and sulfur-mediated precipitation: on the one hand, magnetic biochar reduces free Cu in solution through adsorption / complexation / precipitation solidification. 2+ Level and buffer its biotoxicity ( Figures 10-11On the other hand, sulfides produced in sulfur-mediated systems can react with Cu. 2+ This further forms a relatively stable precipitate, thereby reducing copper migration and promoting removal; in addition, the response results of the system's EPS and CytC indicators ( Figures 12-15 The introduction of this material suggests that it can alter the stability of components related to the extracellular microenvironment and electron transport, providing an auxiliary explanation for the stable operation of the coupled system.

[0082] Compared with the control system without magnetic biochar, the magnetic biochar-sulfur-mediated biocoupling system showed certain advantages in start-up process and operational stability, and the copper ion removal behavior also showed an improved trend.

[0083] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for sulfur-mediated biological treatment of copper-containing wastewater based on magnetic biochar enhancement, characterized in that, Includes the following steps: (1) After pyrolysis to prepare biochar, magnetic modification is carried out by iron salt coprecipitation-heat treatment process to obtain magnetic biochar loaded with iron oxide; (2) Under anaerobic conditions, a sulfur-mediated biological treatment system is constructed, and the magnetic biochar is added to the sulfur-mediated biological treatment system; (3) Add copper-containing wastewater to the system for reaction treatment to achieve synergistic removal of heavy metal ions and sulfates from the copper-containing wastewater.

2. The method according to claim 1, characterized in that, Step (1) includes: S1: Take agricultural waste and pyrolyze it at 600~800℃ to obtain biochar; S2: Using Fe 3+ and Fe 2+ Magnetic modification was performed using a co-precipitation method followed by heat treatment to obtain a magnetic biochar precursor. S3: The magnetic biochar precursor is subjected to a secondary heat treatment at 600~800℃ to obtain magnetic biochar.

3. The method according to claim 2, characterized in that, Step S1 specifically includes: Agricultural waste is dried, crushed, and then pyrolyzed at 600-800℃ for 2-4 hours under nitrogen-filled and oxygen-limited conditions to obtain biochar.

4. The method according to claim 2, characterized in that, Step S2 specifically includes: FeCl3·6H2O and FeSO4·7H2O were processed according to Fe 3+ Fe 2+ The mixture was dissolved in water at a mass ratio of 2:1, the pH was adjusted to 9-11, stirred and allowed to stand, the resulting precipitate was separated by centrifugation, washed with water until neutral, and dried to obtain the magnetic biochar precursor.

5. The method according to claim 4, characterized in that, The stirring time in step S2 is 1-3 hours, and the standing time is 1-3 hours; the drying is carried out at 50-80℃ for 8-24 hours.

6. The method according to claim 2, characterized in that, Step S3 specifically includes: The magnetic biochar precursor was placed again under nitrogen-filled and oxygen-limited conditions and kept at 600-800℃ for 1-3 hours to obtain magnetic biochar.

7. The method according to claim 2, characterized in that, The obtained magnetic biochar has a pore size of 3.7–16.0 nm, exhibits magnetic response characteristics, and has a high specific surface area of ​​19–161 m². 2 / g.

8. The method according to claim 1, characterized in that, In step (2), the amount of magnetic biochar added is 1~8 g / L.

9. The method according to claim 1, characterized in that, In step (3), the Cu in the copper-containing wastewater 2+ The initial concentration was 10-300 mg / L, and the reaction time was 12-120 h.

10. The method according to any one of claims 1-9, characterized in that, This method for Cu in wastewater 2+ The removal efficiency is 79.5%~98.0%.

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