Preparation method and application of a composite modified biochar filler

Abstract

The application discloses a preparation method and application of a composite modified biochar filler, and the preparation method comprises the following steps: S1, pyrolysis treatment, S2, modification treatment, and S3, secondary calcination; the application is applied to a heavy metal-antibiotic cooperative removal system; the biochar filler prepared through the three-stage temperature control pyrolysis combined with the NH3 activation modification process has the characteristics of large specific surface area, high mechanical strength and excellent magnetic separation performance, and can effectively remove heavy metal-antibiotic composite pollution.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a method for preparing and applying a composite modified biochar packing material. Background Technology

[0002] With the rapid development of industry and livestock farming, the treatment of wastewater contaminated with heavy metals and antibiotics has become a major challenge in the water treatment field. my country's "GB18918-2002 Discharge Standard of Pollutants for Urban Wastewater Treatment Plants" and local standards in Beijing (such as DB11 / 307-2013) clearly stipulate that the emission limit for copper ions is ≤0.3 mg / L (Class A standard). The "List of Key Controlled New Pollutants" released by the Ministry of Ecology and Environment in 2023 included sulfonamide antibiotics in the limit control for the first time, specifying an emission limit of ≤0.1 mg / L. Under these strict control requirements, the treatment of this type of wastewater faces a dual technical bottleneck: firstly, Cu... 2+ There is a fundamental conflict between the adsorption removal and the reaction mechanism of antibiotic oxidative degradation. Secondly, high concentrations of Cl- (20-50 g / L) in aquaculture wastewater can poison catalytic active sites and interfere with material recovery, leading to a significant decrease in the stability of the treatment system.

[0003] Current modified biochar technology has systemic limitations: regarding the defect of single function, the magnetic rice husk biochar of patent CN105797693A has limitations in its ability to modify Pb. 2+ / Cd 2+ The adsorption capacity reaches 85 mg / g, but the specific surface area is only 110 m². 2 The biochar, with its low concentration of phosphate and lack of catalytically active sites, cannot degrade antibiotics. While the phosphoric acid-activated biochar in patent CN110327882A increases Zn / Cd adsorption rate by 20%, its compressive strength is only 4-6 MPa, and the breakage rate reaches 18% after two weeks of fixed-bed operation. The lack of synergistic treatment capability is evident in the fact that while Fenton oxidation can degrade sulfamethoxazole (half-life t1 / 2 ≈ 15 min, literature DOI: 10.1016 / j.watres.2022.118952), Cu... 2+ At concentrations >10 mg / L, the oxidant is ineffectively consumed by more than 30% due to the catalytic reaction. In engineering applications, traditional biochar has a particle size <100 μm and a bulk density of 0.2-0.5 g / cm³. 3 Under high-salt conditions, the magnetic recovery rate is <80%; although ceramic modification (patent CN116351395B) increases the compressive strength to ≥8MPa, the specific surface area is ≤150m². 2 / g, Cu 2+ The adsorption capacity is only 58.7 mg / g; magnetic nitrogen doping (patent CN114917943B) enhances catalytic activity (sulfonamide t1 / 2≈12 min), but the mechanical strength is only 3-5 MPa and the fluidized bed breakage rate is >25%.

[0004] The aforementioned technical defects reveal the core contradiction: a single modification method cannot simultaneously meet the four-dimensional performance requirements—①Cu 2+ The adsorption capacity is ≥120mg / g (100% higher than ceramic modification); ② Sulfonamide degradation half-life t1 / 2 ≤8min (87.5% higher than Fenton oxidation efficiency); ③ Compressive strength ≥8MPa (fluidized bed breakage rate <5%); ④ High salt content (Cl- = 50g / L), magnetic recovery rate ≥97% (0.5T magnetic field). In existing technologies, the contradictions between adsorption and catalytic activity, mechanical strength and specific surface area, and high salt stability and recovery efficiency remain unresolved. There is an urgent need to develop multifunctional composite biochar packing materials and intelligent synergistic systems to overcome the technical barriers to the separate removal of heavy metals and antibiotics. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of low treatment efficiency, insufficient material performance, complex process, and difficulty in adapting to specific concentration ranges of wastewater when treating wastewater with combined heavy metal and antibiotic pollution. This invention provides a composite modified biochar packing material, its preparation method, and its application.

[0006] The technical solution of this invention is: a method for preparing composite modified biochar filler, comprising the following steps:

[0007] S1, Pyrolysis treatment

[0008] First, agricultural and forestry waste and clay components are mixed at a weight ratio of 2:1. After being pressed into shape under a pressure of 10-15 MPa, the mixture is heated to 350-420℃ at a rate of 5-10℃ / min under nitrogen protection and held for 6-24 hours. Then, the temperature is raised to 550-600℃ at a rate of 10-15℃ / min and held for 6-24 hours. Finally, the temperature is raised to 700-780℃ at a rate of 15-20℃ / min. When the temperature reaches 700℃, NH3 is introduced at a flow rate of 0.5-1.5 L / min and held for 10-48 hours.

[0009] S2, Modification Treatment

[0010] The pyrolysis product was impregnated with an Fe-containing solution. 3+ In the modified solution of the compound, the pH of the modified solution was adjusted to 9.5-10.5 by pH adjuster, and electrodeposition was carried out at 45-55℃ for 20-40 min without electrodeposition.

[0011] S3, Secondary calcination

[0012] The deposited product is mixed with 5-10 wt% carboxymethyl cellulose and granulated to form particles with a particle size of 2-5 mm. The particles are then calcined for 1-3 h at a temperature of 600-800 °C under nitrogen protection at a rate of 5-20 °C / min to obtain the composite modified biochar filler.

[0013] Note: The filler prepared by the above method in this invention has a specific surface area ≥300m². 2 / g, compressive strength ≥8MPa, XRD pattern simultaneously shows graphite carbon (002) crystal plane (2θ=26.5°±0.5°), Fe3O4 characteristic peak (2θ=35.5°±0.5°) and kaolinite (001) crystal plane (2θ=12.5°±0.5°), saturation magnetization ≥20 emu / g, and XPS full spectrum analysis shows that the pyridine nitrogen content in the surface nitrogen species is ≥40%; it can simultaneously and efficiently adsorb heavy metal ions (Cu 2+ With an adsorption capacity ≥120mg / g and catalytic degradation of antibiotics (sulfonamide degradation half-life ≤8min), pollutants can be removed synergistically.

[0014] Furthermore, in S1, the agricultural and forestry waste is a mixture of corn stalks and sawdust in a mass ratio of 2-4:1, which is then crushed to a particle size of 50-100μm; the clay component is a mixture of kaolin and montmorillonite in a mass ratio of 7:3.

[0015] Note: Wood chips are rich in lignin, which mainly improves the pore structure and mechanical strength, and enhances the adsorption function of hydrophobic antibiotics. The ratio of corn stalks to wood chips can effectively balance porosity and strength, making it suitable for dynamic adsorption towers. The ratio of kaolin to montmorillonite can balance structural stability and catalytic activity, thereby improving the utilization rate of persulfate.

[0016] Further, in S2, the modified liquid is composed of 15-20 wt% ferric sulfate and 2-6 wt% polyethyleneimine with a molecular weight of 800-1000 Da in a mass ratio of 2.5-10:1;

[0017] Explanation: The advantages of using ferric iron as the modifying solution are twofold: firstly, it forms ferric hydroxide precipitate under alkaline conditions, which can simultaneously adsorb heavy metals and antibiotics; secondly, it avoids the ineffective consumption of persulfate by ferrous ions, reducing iron melting. The selection of ferric sulfate and polyethyleneimine as the modifying solution utilizes the properties of polyethyleneimine to stabilize Fe. 3+ Colloids, enhanced antibiotic adsorption, optimized pore structure; compared with single Fe 3+ Modification with polyethyleneimine increases the lifespan of the filler.

[0018] Furthermore, in S2, the pH adjuster is a sodium hydroxide solution with a mass concentration of 5-8 wt% or an ammonia solution with a mass concentration of 10-15 wt%.

[0019] Note: The above-mentioned regulator can effectively adjust the pH, thereby promoting Fe production. 3+ Electrostatic deposition and premature precipitation should be avoided.

[0020] On the other hand, the present invention also provides an application of composite modified biochar packing material in a heavy metal-antibiotic synergistic removal system.

[0021] The heavy metal-antibiotic synergistic removal system includes an upflow adsorption tower filled with the composite modified biochar packing material, a fluidized bed reactor connected in series with the upflow adsorption tower, the fluidized bed reactor being equipped with a persulfate dosing device and a magnetic separation device located at the end of the system; an ORP online monitoring instrument and a Cu2O2 monitoring instrument are installed at the outlet of the adsorption tower. 2+ Dual electrode control, when ORP > 200mV or Cu 2+ When the concentration is ≤1 mg / L, the persulfate dosing device of the fluidized bed will be automatically activated;

[0022] The volume ratio of the upflow adsorption tower to the fluidized bed reactor is 1:0.5-1.5; the empty bed contact time of the upflow adsorption tower is 10-45 min; the dosage of persulfate is 0.5-3 g / L; and the magnetic field strength in the magnetic separation device is 0.5-0.8 T.

[0023] Note: Through ORP and Cu 2+ The catalytic oxidation step is intelligently triggered by dual concentration signals, ensuring stable and reliable system operation.

[0024] Furthermore, the filling rate of the composite modified biological filler is ≥70-90%;

[0025] Note: The composite filler works best under the above filling conditions.

[0026] Furthermore, the application method is as follows:

[0027] Step 1: Test the wastewater for the presence of tetracycline antibiotics, copper ion concentration, and sulfonamide antibiotic concentration;

[0028] Step 2: When the wastewater contains tetracycline antibiotics and the copper ion concentration is <10 mg / L, and the sulfonamide antibiotic concentration is <5 mg / L, treat it as follows:

[0029] (1) Pass the wastewater into the upflow adsorption tower and control the empty bed contact time to be 10-15 min;

[0030] (2) Real-time monitoring of effluent indicators; when Cu in the effluent of the upflow adsorption tower... 2+ When the concentration is ≤1mg / L or ORP>200mV, the effluent should be immediately introduced into the fluidized bed reactor;

[0031] (3) Add 0.5-1 g / L persulfate and 0.05-0.1 g / L Fe to the fluidized bed reactor. 2+ Initiate the oxidation catalytic reaction;

[0032] (4) Finally, the process is completed after being processed by a magnetic separation device with a magnetic field strength of 0.5-0.8T for 1-5 minutes.

[0033] When the wastewater contains tetracycline antibiotics and the copper ion concentration is 10-100 mg / L, and the sulfonamide antibiotic concentration is 5-50 mg / L, adjust the hollow bed contact time in (1) to 15-30 min; at the same time, add 1-2 g / L of persulfate and 0.1-0.3 g / L of Fe to the fluidized bed reactor in (3). 2+ The oxidation catalytic reaction is initiated; the remaining steps remain unchanged.

[0034] When the wastewater contains tetracycline antibiotics and the copper ion concentration is >100 mg / L, and the sulfonamide antibiotic concentration is >50 mg / L, adjust the hollow bed contact time in (1) to 30-45 min; at the same time, add 2-3 g / L of persulfate and 0.3-0.5 g / L of Fe to the fluidized bed reactor in (3). 2+ The oxidation catalytic reaction is initiated; the remaining steps remain unchanged.

[0035] When the wastewater contains only sulfonamides and persulfates, without tetracycline antibiotics, Fe... 2+ With the addition ratio kept constant, the oxidation reaction can proceed through the Fe3O4 surface of the packing material. 4 / The synergistic catalysis of pyridine nitrogen enables efficient degradation;

[0036] When wastewater contains tetracycline antibiotics, but Cu 2+ When the concentrations of the antibiotics and sulfonamides fall within the ranges of different protocols, the combination should be implemented: the empty bed contact time should be based on Cu. 2+ Concentration selection; persulfate and Fe 2+ The dosage should be selected based on the concentration of sulfonamide antibiotics; the oxidation triggering step should be based on the ORP / Cu ratio of the corresponding adsorption step. 2+ Threshold selection; the separation and detection steps shall be performed in accordance with the emission indicators of the corresponding scheme for the oxidation step;

[0037] Note: Based on the concentration characteristics of heavy metals and antibiotics in the wastewater, a graded treatment scheme is adopted, using ORP and Cu... 2+ The dual-signal intelligent triggering of the catalytic oxidation step ensures stable and reliable system operation, demonstrating significant technical advantages and application prospects in industrial and aquaculture wastewater treatment.

[0038] Furthermore, the magnetic separation device also has a packing regeneration module at the end. After processing, the composite modified biochar packing is taken out. First, 0.1-0.5 mol / L HCl solution is added to the composite modified biochar packing at a solid-liquid ratio of 5 mL:1 g. The packing is shaken for 25-30 min at a temperature of 22-25℃ and a shaking speed of 120-150 rpm. Then, 0.1 mol / L NaOH solution and 10% ethanol are added. The packing is treated for 15-20 min at a temperature of 45-50℃, an ultrasonic frequency of 35-40 kHz, and an ultrasonic power of 90-100 W. Finally, the composite modified biochar packing is immersed in a FeCl3 and CoCl2 solution with a total concentration of 0.1 mol / L. Electrodeposition is performed for 25-30 min at a pH of 9.5 and a temperature of 50-55℃ to obtain the regenerated composite modified biochar packing.

[0039] Note: After long-term operation in a heavy metal-antibiotic synergistic removal system, biochar packing may face the following problems: adsorption saturation, Cu... 2+ Pollutants such as tetracycline occupy active sites (e.g., oxygen-containing functional groups, Fe...). 3+ Loading sites); pore blockage, degradation intermediates of organic pollutants (such as sulfonamides) block micropores; loss of magnetic components, partial dissolution of CoFe2O4 in acidic or high-salt environments; the above methods can utilize acid washing to desorb heavy metals and alkali washing to desorb organic matter to restore the porosity of the composite modified biochar filler. Finally, FeCl3 and CoCl2 solutions are used to replenish the magnetic components, and low-temperature thermal activation is used to repair carbon skeleton defects and restore surface functional groups for reuse.

[0040] Furthermore, the molar ratio of FeCl3 to CoCl2 is 2:1;

[0041] Note: When Fe:Co < 2:1, Co3O4 is formed, which has weak magnetism; when Fe:Co > 2:1, α-Fe2O3 remains, which is diamagnetic and interferes with separation.

[0042] The beneficial effects of this invention are:

[0043] (1) This invention innovatively combines clay ceramicization and nitrogen-doped magnetic dual modification technology to develop composite biochar with gradient pore structure. It adopts a preparation process that combines staged pyrolysis and low-temperature electroless deposition, and designs an "adsorption-catalytic oxidation" combined system and intelligent operation method to achieve efficient synergistic treatment of heavy metal-antibiotic composite pollutant wastewater with a specific concentration range. It has the advantages of excellent material properties, simple preparation process, stable system operation and strong anti-interference ability, and provides a new solution for the treatment of heavy metal-antibiotic composite pollutant wastewater.

[0044] (2) The biochar packing material prepared by the present invention through a three-stage temperature-controlled pyrolysis combined with NH3 activation modification process has the characteristics of large specific surface area, high mechanical strength and excellent magnetic separation performance. Moreover, the preparation process is simple and controllable and easy to scale up production. The surface of the packing material is rich in pyridine nitrogen active sites (accounting for ≥40%) and Fe3O4 catalytic components, which can simultaneously and efficiently adsorb heavy metal ions and catalytically degrade antibiotics, thereby achieving synergistic removal of pollutants. Detailed Implementation

[0045] The present invention will now be described in more detail with reference to specific embodiments, so as to better demonstrate the advantages of the present invention.

[0046] Example 1: A method for preparing a composite modified biochar packing material, comprising the following steps:

[0047] S1, Pyrolysis treatment

[0048] First, agricultural and forestry waste and clay components are mixed at a weight ratio of 2:1. After being pressed into shape under a pressure of 13 MPa, the mixture is heated to 385°C at a rate of 7°C / min and held for 15 hours under nitrogen protection. Then, the temperature is increased to 575°C at a rate of 13°C / min and held for 15 hours. Finally, the temperature is increased to 740°C at a rate of 18°C / min. When the temperature reaches 700°C, NH3 is introduced at a flow rate of 1 L / min and held for 30 hours. In S1, the agricultural and forestry waste is a mixture of corn stalks and sawdust at a mass ratio of 3:1, which is then crushed to a particle size of 50-100 μm. The clay component is a mixture of kaolin and montmorillonite at a mass ratio of 7:3.

[0049] S2, Modification Treatment

[0050] The pyrolysis product was impregnated with an Fe-containing solution. 3+ In the modified solution of the compound, the pH of the modified solution was adjusted to 10 by a pH adjuster, and electrodeposition was performed at 50°C for 30 min without electrodeposition. In S2, the modified solution was composed of 18 wt% ferric sulfate and 4 wt% polyethyleneimine with a molecular weight of 900 Da in a mass ratio of 6:1. In S2, the pH adjuster was ammonia water with a mass concentration of 13 wt%.

[0051] S3, Secondary calcination

[0052] The deposited product was mixed with 8 wt% carboxymethyl cellulose and granulated to form particles with a particle size of 4 mm. The particles were then calcined for 2 hours at 700 °C at a rate of 15 °C / min under nitrogen protection to obtain the composite modified biochar filler.

[0053] Based on the above-mentioned application of a composite modified biochar packing material, it is applied in a heavy metal-antibiotic synergistic removal system;

[0054] The heavy metal-antibiotic synergistic removal system includes an upflow adsorption tower filled with composite modified biochar packing, a fluidized bed reactor connected in series with the upflow adsorption tower, a persulfate dosing device and a magnetic separation device located at the end of the system; an ORP online monitoring instrument and a Cu2O2 monitoring instrument are installed at the outlet of the adsorption tower. 2+ Dual electrode control, when ORP is 201mV or Cu 2+ When the concentration is 1 mg / L, the persulfate dosing device of the fluidized bed is automatically started;

[0055] The volume ratio of the upflow adsorption tower to the fluidized bed reactor is 1:1.

[0056] The application method is as follows:

[0057] Step 1: Detect the presence of tetracycline antibiotics, copper ion concentration, and sulfonamide antibiotic concentration in the wastewater; in this embodiment, the influent water quality measured contains: Cu 2+ =50mg / L, sulfonamides =25mg / L, pH=6.8;

[0058] Step 2: Process as follows: The filling rate of the composite modified biological packing is 85%;

[0059] (1) The wastewater is fed into the upflow adsorption tower and the empty bed contact time is controlled to be 20 min;

[0060] (2) Real-time monitoring of effluent indicators; when Cu in the effluent of the upflow adsorption tower... 2+ When the concentration is 1 mg / L or the ORP is 201 mV, the effluent should be immediately introduced into the fluidized bed reactor.

[0061] (3) Add 1.5 g / L persulfate and 0.2 g / L Fe to the fluidized bed reactor. 2+ Initiate the oxidation catalytic reaction;

[0062] (4) Finally, the process is completed after being processed by a magnetic separation device with a magnetic field strength of 0.6T for 3 minutes.

[0063] Example 2: Unlike Example 1, in S1, after being pressed and molded under 10 MPa pressure, the temperature is raised to 350°C at a rate of 5°C / min under nitrogen protection and held for 6 hours. Then, the temperature is raised to 550°C at a rate of 10°C / min and held for 6 hours. Finally, the temperature is raised to 700°C at a rate of 15°C / min. When the temperature reaches 700°C, NH3 with a flow rate of 0.5 L / min is introduced and the temperature is held for 10 hours.

[0064] Example 3: Unlike Example 1, in S1, after being pressed and molded under 15 MPa pressure, the temperature is raised to 420°C at a rate of 10°C / min under nitrogen protection and held for 24 hours. Then, the temperature is raised to 600°C at a rate of 15°C / min and held for 24 hours. Finally, the temperature is raised to 780°C at a rate of 20°C / min. When the temperature reaches 700°C, NH3 with a flow rate of 1.5 L / min is introduced and the temperature is held for 48 hours.

[0065] Example 4: Unlike Example 1, in S1, the agricultural and forestry waste is a mixture of corn stalks and wood chips in a mass ratio of 2:1, which is then crushed into a mixture with a particle size of 50-100μm.

[0066] Example 5: Unlike Example 1, in S1, the agricultural and forestry waste is a mixture of corn stalks and sawdust in a mass ratio of 4:1, which is then crushed into a mixture with a particle size of 50-100μm.

[0067] Example 6: Unlike Example 1, in S2, the pH of the modified solution was adjusted to 9.5 by a pH adjuster, and electrodeposition was performed at 45°C for 20 minutes.

[0068] Example 7: Unlike Example 1, in S2, the pH of the modified solution was adjusted to 10.5 by a pH adjuster, and electrodeposition was performed at 55°C for 40 minutes.

[0069] Example 8: Unlike Example 1, in S2, the modified solution is composed of 15 wt% ferric sulfate and 2 wt% polyethyleneimine with a molecular weight of 800 Da in a mass ratio of 2.5:1.

[0070] Example 9: Unlike Example 1, in S2, the modified solution is composed of 20 wt% ferric sulfate and 6 wt% polyethyleneimine with a molecular weight of 1000 Da in a mass ratio of 10:1.

[0071] Example 10: Unlike Example 1, in S2, the pH adjuster is ammonia water with a mass concentration of 10 wt%.

[0072] Example 11: Unlike Example 1, in S2, the pH adjuster is a sodium hydroxide solution with a mass concentration of 8 wt%.

[0073] Example 12: Unlike Example 1, in S3, the deposited product was mixed with 5 wt% carboxymethyl cellulose and granulated to form particles with a particle size of 2 mm. The particles were then calcined for 1 hour at 600 °C under nitrogen protection at a rate of 5 °C / min to obtain a composite modified biochar filler.

[0074] Example 13: Unlike Example 1, in S3, the deposited product was mixed with 10 wt% carboxymethyl cellulose and granulated to form particles with a particle size of 5 mm. The particles were then calcined for 3 hours at 800 °C under nitrogen protection at a rate of 20 °C / min to obtain a composite modified biochar filler.

[0075] Example 14: Unlike Example 1, the composite modified biological filler was processed as follows: the filling rate was 70%;

[0076] (1) The wastewater is fed into the upflow adsorption tower and the empty bed contact time is controlled to be 15 min;

[0077] (2) Real-time monitoring of effluent indicators; when Cu in the effluent of the upflow adsorption tower... 2+ When the concentration is 1 mg / L or the ORP is 201 mV, the effluent should be immediately introduced into the fluidized bed reactor.

[0078] (3) Add 1 g / L persulfate and 0.1 g / L Fe to the fluidized bed reactor. 2+ Initiate the oxidation catalytic reaction;

[0079] (4) Finally, the process is completed after being processed by a magnetic separation device with a magnetic field strength of 0.5T for 1 minute.

[0080] Example 15: Unlike Example 1, the composite modified biological filler was processed as follows: the filling rate was 90%;

[0081] (1) The wastewater is fed into the upflow adsorption tower and the empty bed contact time is controlled to be 30 min;

[0082] (2) Real-time monitoring of effluent indicators; when Cu in the effluent of the upflow adsorption tower... 2+ When the concentration is 1 mg / L or the ORP is 201 mV, the effluent should be immediately introduced into the fluidized bed reactor.

[0083] (3) Add 2 g / L persulfate and 0.3 g / L Fe to the fluidized bed reactor. 2+ Initiate the oxidation catalytic reaction;

[0084] (4) Finally, the process is completed after 5 minutes of treatment by a magnetic separation device with a magnetic field strength of 0.8T.

[0085] Example 16: Unlike Example 1, the magnetic separation device also has a packing regeneration module at the end. After processing, the composite modified biochar packing is taken out. First, 0.3 mol / L HCl solution is added to the composite modified biochar packing at a solid-liquid ratio of 5 mL:1 g. The packing is shaken for 28 min at 24°C and 135 rpm. Then, 0.1 mol / L NaOH solution and 10% ethanol are added. The packing is treated for 18 min at 48°C, 38 kHz ultrasonic frequency, and 95 W ultrasonic power. Finally, the composite modified biochar packing is immersed in a FeCl3 and CoCl2 solution with a total concentration of 0.1 mol / L. Electrodeposition is carried out for 28 min at pH 9.5 and 53°C to obtain the regenerated composite modified biochar packing. The molar ratio of FeCl3 to CoCl2 is 2:1.

[0086] Example 17: Unlike Example 16, 0.1 mol / L HCl solution was first added to the composite modified biochar filler at a solid-liquid ratio of 5 mL: 1 g, and the mixture was shaken for 25 min at a temperature of 22°C and a shaking speed of 120 rpm.

[0087] Example 18: Unlike Example 16, 0.5 mol / L HCl solution was first added to the composite modified biochar filler at a solid-liquid ratio of 5 mL: 1 g, and the mixture was shaken for 30 min at 25°C and a shaking speed of 150 rpm.

[0088] Example 19: Unlike Example 16, a 0.1 mol / L NaOH solution and a 10% ethanol solution were then added, and the mixture was treated for 15 min at a temperature of 45°C, an ultrasonic frequency of 35 kHz, and an ultrasonic power of 90 W.

[0089] Example 20: Unlike Example 16, a 0.1 mol / L NaOH solution and a 10% ethanol solution were then added, and the mixture was treated for 20 min at a temperature of 50°C, an ultrasonic frequency of 40 kHz, and an ultrasonic power of 100 W.

[0090] Example 21: Unlike Example 16, the composite modified biochar filler was finally immersed in a FeCl3 and CoCl2 solution with a total concentration of 0.1 mol / L, and electrodeposited for 25 min at pH 9.5 and 50°C to obtain the regenerated composite modified biochar filler.

[0091] Example 22: Unlike Example 16, the composite modified biochar filler was finally immersed in a FeCl3 and CoCl2 solution with a total concentration of 0.1 mol / L, and electrodeposited for 30 min at pH 9.5 and 55°C to obtain the regenerated composite modified biochar filler.

[0092] Experimental Example 1: Investigating the effects of various parameters in the treatment method on the heavy metal-antibiotic removal efficiency of the composite modified biochar packing.

[0093] Examples 1, 14, and 15 were compared to verify the effect of parameter differences in the composite modified biochar packing material on the treatment effect under different schemes. The results are as follows:

[0094] Table 1. Removal efficacy of composite modified biochar packing materials obtained in Examples 1, 14-15 for heavy metals and antibiotics.

[0095] Example 14 0.295 0.048 Example 1 0.283 0.0482 Example 15 0.275 0.049

[0096] Conclusion: Testing showed that the composite modified biochar packing material, through adjustments to differentiated parameters (contact time, reagent dosage, and packing filling rate), could achieve "Cu" results under various pollution scenarios. 2+ The effluent targets of "≤0.3 mg / L for sulfonamides and ≤0.05 mg / L for sulfuramides" were used to verify the multi-scenario adaptability of the composite modified biochar packing material, and to improve the overall effluent Cu content. 2+ The concentrations of sulfonamides in the effluent and the concentration of sulfonamides in the effluent show that Example 1 has the optimal parameters.

[0097] 2. Investigating the effect of pyrolysis treatment on the removal efficiency of heavy metals and antibiotics by composite modified biochar packing. Table 2 shows the removal efficiency of heavy metals and antibiotics by the composite modified biochar packing obtained in Examples 1-9 and Control Examples 1-Control Examples 3.

[0098]

[0099]

[0100] Comparative Example 1: Unlike Example 1, during the pyrolysis process, the temperature was increased to 740°C at a rate of 7°C / min under nitrogen protection. When the temperature reached 700°C, NH3 was introduced at a flow rate of 1L / min and the temperature was maintained for 30 hours.

[0101] Comparative Example 2: Unlike Example 1, the agricultural and forestry waste does not contain sawdust.

[0102] Comparative Example 3: Unlike Example 1, the modified liquid does not contain polyethyleneimine.

[0103] Conclusion: A comparison of Examples 1, 2-3, and Control Example 1 shows that direct heating negatively impacts the removal of heavy metals and antibiotics from the composite modified biochar filler. This is mainly because gradient heating promotes the stepwise decomposition of biomass components through staged pyrolysis: the low-temperature stage (385℃) degrades hemicellulose, forming an initial pore framework; the medium-temperature stage (575℃) promotes lignin carbonization, expanding the mesopore structure; and the high-temperature stage (740℃) completes graphitization and introduces nitrogen-containing functional groups under an NH3 atmosphere. In contrast, direct heating to 740℃ in the control example leads to the instantaneous escape of volatiles, causing pore collapse and a decrease in specific surface area. When NH3 is introduced at 700℃, the abundant pores formed by gradient heating can adsorb more NH3 molecules, generating active sites such as pyridine nitrogen / pyrrole nitrogen. Direct heating results in insufficient pore development and a decrease in nitrogen doping efficiency.

[0104] Cu 2+ Desorption depends on pore-based physical adsorption and chelation by nitrogen-containing functional groups. Reduced pore size leads to decreased adsorption capacity. Degradation of sulfonamides requires Fe. 3+ / Nitrogen co-catalytic activation of persulfate, direct heating to Fe 3+ The load has decreased;

[0105] A comparison of Examples 1, 4, and 5 with Control Example 2 reveals that the absence of sawdust in agricultural and forestry waste negatively impacts the heavy metal and antibiotic removal efficiency of the composite modified biochar filler. This is primarily because sawdust is rich in lignin, which forms a graphitized microcrystalline structure during high-temperature pyrolysis (740℃), enhancing the mechanical strength and pore stability of the biochar. Without sawdust, the pyrolysis products dominated by corn stalks are predominantly cellulose-derived pores, reducing the proportion of mesopores and thus decreasing the adsorption capacity. Furthermore, the aromatic carbon structure generated from sawdust pyrolysis is more readily reacted with NH3 to form pyridine nitrogen / pyrrole nitrogen functional groups, enhancing the adsorption capacity for Cu. 2+ The chelating ability of Fe was improved; while the nitrogen doping efficiency of control example 2 was reduced, affecting the density of active sites for heavy metal adsorption; at the same time, the hierarchical porosity derived from wood chips could optimize Fe 3+ Dispersibility, Fe when free of sawdust 3+ It easily aggregates, reducing the efficiency of catalytic activation of persulfate; Cu 2+ Removal depends on pore-based physical adsorption and chelation with nitrogen functional groups. Decreased porosity and functional groups lead to reduced adsorption capacity. Sulfonamide degradation requires Fe... 3+ / Persulfate system catalysis, Fe 3+ Aggregation reduces the degradation efficiency of sulfonamides;

[0106] A comparison of Examples 1, 8, and 9 with Control Example 3 shows that the absence of polyethyleneimine in the modified solution negatively impacts the removal efficiency of heavy metals and antibiotics by the composite modified biochar filler. This is mainly because the amine groups (-NH2) of PEI stabilize and fix Fe through coordination bonds.3+ The absence of PEI ions leads to a large amount of Fe in the modified solution. 3+ Unable to be effectively loaded onto the surface of biochar, forming free or aggregated ineffective iron components; PEI is protonated at pH=10 to form -NH3. + Positive charge imparts a positive charge to biochar, enhancing the electrostatic adsorption of anionic pollutants (such as sulfonamides); its absence weakens the electrostatic adsorption effect; simultaneously, PEI-Fe... 3+ The complex, acting as an electron transfer medium, can activate persulfate to generate reactive oxygen species (·OH / SO4·). - ); Without PEI, the amount of free radicals generated decreases, and the oxidative degradation efficiency of sulfonamides is sharply reduced; Cu 2+ Removing PEI-dependent amino chelation reduces the density of metal binding sites, leading to a decrease in adsorption capacity; sulfonamide degradation requires PEI-Fe... 3+ Composite catalytic system, Fe alone 3+ The catalytic efficiency decreases, which in turn reduces the degradation efficiency of sulfonamides.

[0107] 3. Investigate the effect of packing regeneration on the heavy metal and antibiotic removal efficiency of composite modified biochar packing.

[0108] Table 3 shows the removal efficacy of the composite modified biochar packing materials obtained in Examples 1, 16-22, and Comparative Examples 4-6 for heavy metal and antibiotic removal.

[0109] Example 1 0.283 0.0482 Example 16 0.226 0.035 Example 17 0.229 0.037 Example 18 0.231 0.035 Example 19 0.228 0.036 Example 20 0.230 0.036 Example 21 0.229 0.038 Example 22 0.228 0.037 Compare with Example 4 0.281 0.0477 Compare with Example 5 0.26 0.048 Compare with Example 6 0.279 0.048

[0110] Comparative Example 4: Unlike Example 16, the HCl treatment step is missing.

[0111] Comparative Example 5: Unlike Example 16, the combined treatment of NaOH solution and ethanol was omitted.

[0112] Comparative Example 6: Unlike Example 16, the loading step of FeCl3 and CoCl2 solutions is missing.

[0113] Conclusion: A comparison of Examples 1 and 16-24 shows that the added packing regeneration module has a positive effect on improving the removal of heavy metals and antibiotics from the composite modified biochar packing. This is mainly because HCl cleaning can effectively remove heavy metal precipitates (such as Cu) accumulated on the packing surface. 2+ (or iron oxides), restoring pore structure and specific surface area; subsequent NaOH / ethanol treatment, through hydrolysis and ultrasonic removal of organic dirt (such as sulfonamide residues), increases the exposure rate of functional groups (such as carboxyl and hydroxyl groups) on the biochar surface by ≥25%, enhancing the protection of Cu. 2+The chelating ability; an electrodeposition process in which FeCl3 / CoCl2 solution is immersed in the solution to form uniformly loaded Fe-Co bimetallic nanoparticles (particle size <100nm) at pH 9.5 and 50-55℃. 2+ As a persulfate activation promoter, with Fe 3+ Synergistic reduction of free radicals (·OH / SO4·) - The formation of an energy barrier improves the oxidative degradation efficiency of sulfonamides, thereby optimizing Cu. 2+ The removal effect of sulfonamides; and the regeneration process through acid-alkali-ethanol treatment can eliminate biofilm blockage and inorganic scaling on the packing surface; the loaded Fe-Co nanoparticles form a stable oxide layer in a high pH environment, avoiding deactivation of active sites and ensuring that the system maintains a high removal rate during continuous operation; and the comparison of Examples 16-24 shows that Example 16 is the optimal solution.

[0114] A comparison of Examples 16-18 and Control Example 4 shows that the absence of the HCl treatment step negatively impacts the removal of heavy metals and antibiotics from the composite modified biochar packing. This is mainly because HCl cleaning dissolves Cu(OH)2 colloids and carbonate precipitates (such as CuCO3) formed in an alkaline environment, restoring the specific surface area of ​​the biochar. Without this step, the precipitate coverage increases, shielding Fe / Co active sites and leaving residual Cu... 2+ Fe3+ with subsequent load + / Co 2+ Competition for persulfate activation sites weakens bimetallic catalytic activity; undisturbed inorganic precipitates adsorb sulfonamide organic compounds, forming a complex fouling layer that hinders the ·OH / SO4· - Free radicals contact the target pollutant; residual Cu 2+ Consume reduction electrons (Fe) in the system 3+ →Fe 2+ The conversion requires electrons, which terminates the free radical chain reaction, thereby yielding water Cu. 2+ Concentrations of sulfonamides in the effluent and concentrations in the effluent have rebounded.

[0115] A comparison of Examples 16, 19-20, and Comparative Example 5 reveals that the absence of the combined treatment with NaOH solution and ethanol negatively impacts the heavy metal and antibiotic removal efficiency of the composite modified biochar packing. This is primarily because the core function of the NaOH / ethanol combined treatment is to remove residual sulfonamide organic matter after acid washing. The absence of this step leads to the formation of a dense organic film from the unremoved sulfonamides, which covers the subsequently loaded Fe / Co active sites, hindering free radical generation. Furthermore, the NaOH / ethanol treatment enhances heavy metal adsorption capacity through dual activation; the absence of this step results in pore blockage and Cu... 2+The probability of contact with active sites decreases, leading to a decline in adsorption capacity. Furthermore, the alkaline washing step provides an optimized interfacial environment for the Fe / Co loading; its absence results in the aggregation of the loaded Fe / Co nanoparticles, catalyzing the formation of SO4·4·4 from persulfate. - The efficiency decreased;

[0116] A comparison of Examples 16, 21-22, and Control Example 6 shows that the absence of the loading step involving FeCl3 and CoCl2 solutions negatively impacts the heavy metal-antibiotic removal efficiency of the composite modified biochar packing material. This is mainly because Fe... 3+ With Co 2+ Synergistically lowers the activation barrier of persulfate (PMS) and promotes the ·OH / SO4· - Free radical generation (rate increased by 5.27 times). Without it, sulfonamides rely solely on physical adsorption, resulting in a sharp drop in degradation rate; Fe 3+ With Cu 2+ Competitive substitution occurs (Fe) 3+ +Cu 2+ →Fe 2+ +Cu 3+ ), enhance Cu 2+ Immobilization; simultaneously, at pH=9.5, the Fe / Co oxide surface is positively charged, strongly adsorbing Cu. 2+ When unloaded, the electrostatic adsorption capacity is weakened; and the lack of magnetic responsiveness imparted to the filler by Fe / Co leads to an increase in filler loss rate and insufficient system retention.

Claims

1. A method for preparing a composite modified biochar filler, characterized in that, Includes the following steps: S1, Pyrolysis treatment First, agricultural and forestry waste and clay components are mixed at a weight ratio of 2:

1. After being pressed into shape under a pressure of 10-15 MPa, the mixture is heated to 350-420℃ at a rate of 5-10℃ / min under nitrogen protection and held for 6-24 hours. Then, the temperature is raised to 550-600℃ at a rate of 10-15℃ / min and held for 6-24 hours. Finally, the temperature is raised to 700-780℃ at a rate of 15-20℃ / min. When the temperature reaches 700℃, NH3 is introduced at a flow rate of 0.5-1.5 L / min and held for 10-48 hours. S2, Modification Treatment The pyrolysis product was impregnated with an Fe-containing solution. 3+ The compound is placed in a modified solution, and the pH of the modified solution is adjusted to 9.5-10.5 by a pH adjuster. Electrodeposition is carried out at 45-55℃ for 20-40 min. The modified solution is composed of 15-20 wt% ferric sulfate and 2-6 wt% polyethyleneimine with a molecular weight of 800-1000 Da in a mass ratio of 2.5-10:

1. S3, Secondary calcination The deposited product is mixed with 5-10 wt% carboxymethyl cellulose and granulated to form particles with a particle size of 2-5 mm. The particles are then calcined for 1-3 h at a temperature of 5-20 °C / min to 600-800 °C to obtain the composite modified biochar filler. S4, Application This technology is applied to a heavy metal-antibiotic synergistic removal system. The system includes an upflow adsorption tower filled with the composite modified biochar packing material, a fluidized bed reactor connected in series with the upflow adsorption tower, the fluidized bed reactor being equipped with a persulfate dosing device and a magnetic separation device located at the end of the system; an ORP online monitoring instrument and a Cu2O2 monitoring device are installed at the adsorption tower outlet. 2+ Dual electrode control, when ORP > 200 mV or Cu 2+ When the concentration is ≤1 mg / L, the persulfate dosing device of the fluidized bed will be automatically activated.

2. The method for preparing a composite modified biochar filler as described in claim 1, characterized in that, In S1, the agricultural and forestry waste is a mixture of corn stalks and sawdust mixed in a mass ratio of 2-4:1 and then crushed to a particle size of 50-100μm; the clay component is a mixture of kaolin and montmorillonite mixed in a mass ratio of 7:

3.

3. The method for preparing a composite modified biochar filler as described in claim 1, characterized in that, In S2, the pH adjuster is a sodium hydroxide solution with a mass concentration of 5-8 wt% or an ammonia solution with a mass concentration of 10-15 wt%.

4. The method for preparing a composite modified biochar filler as described in claim 1, characterized in that, In S4, the volume ratio of the upflow adsorption tower to the fluidized bed reactor is 1:0.5-1.5; the empty bed contact time of the upflow adsorption tower is 10-45 min; the dosage of persulfate is 0.5-3 g / L; and the magnetic field strength in the magnetic separation device is 0.5-0.8 T.

5. The method for preparing a composite modified biochar filler as described in claim 1, characterized in that, In S4, the filling rate of the composite modified biochar filler is ≥70-90%.

6. The method for preparing a composite modified biochar filler as described in claim 1, characterized in that, In S4, the method of application is as follows: Step 1: Test the wastewater for the presence of tetracycline antibiotics, copper ion concentration, and sulfonamide antibiotic concentration; Step 2: When the wastewater contains tetracycline antibiotics and the copper ion concentration is <10 mg / L, and the sulfonamide antibiotic concentration is <5 mg / L, treat it as follows: (1) Pass the wastewater into the upflow adsorption tower and control the empty bed contact time to be 10-15 min; (2) Monitor effluent indicators in real time. When Cu in the effluent of the upflow adsorption tower... 2+ When the concentration is ≤1mg / L or ORP>200mV, the effluent should be immediately introduced into the fluidized bed reactor; (3) Add 0.5-1 g / L persulfate and 0.05-0.1 g / L Fe to the fluidized bed reactor. 2+ Initiate the oxidation catalytic reaction; (4) Finally, the process is completed after being processed by a magnetic separation device with a magnetic field strength of 0.5-0.8T for 1-5 minutes. When the wastewater contains tetracycline antibiotics and the copper ion concentration is 10-100 mg / L, and the sulfonamide antibiotic concentration is 5-50 mg / L, adjust the hollow bed contact time in (1) to 15-30 min; at the same time, add 1-2 g / L of persulfate and 0.1-0.3 g / L of Fe to the fluidized bed reactor in (3). 2+ The oxidation catalytic reaction is initiated; the remaining steps remain unchanged. When the wastewater contains tetracycline antibiotics and the copper ion concentration is >100 mg / L, and the sulfonamide antibiotic concentration is >50 mg / L, adjust the hollow bed contact time in (1) to 30-45 min; at the same time, add 2-3 g / L of persulfate and 0.3-0.5 g / L of Fe to the fluidized bed reactor in (3). 2+ The oxidation catalytic reaction is initiated; the remaining steps remain unchanged.

7. The method for preparing a composite modified biochar filler as described in claim 1, characterized in that, In S4, the magnetic separation device also has a packing regeneration module at the end. After processing, the composite modified biochar packing is taken out. First, 0.1-0.5 mol / L HCl solution is added to the composite modified biochar packing at a solid-liquid ratio of 5 mL:1 g. The packing is shaken for 25-30 min at a temperature of 22-25℃ and a shaking speed of 120-150 rpm. Then, 0.1 mol / L NaOH solution and 10% ethanol are added. The packing is treated for 15-20 min at a temperature of 45-50℃, an ultrasonic frequency of 35-40 kHz, and an ultrasonic power of 90-100 W. Finally, the composite modified biochar packing is immersed in a FeCl3 and CoCl2 solution with a total concentration of 0.1 mol / L. Electrodeposition is performed for 25-30 min at a pH of 9.5 and a temperature of 50-55℃ to obtain the regenerated composite modified biochar packing.

8. The method for preparing a composite modified biochar filler as described in claim 7, characterized in that, The molar ratio of FeCl3 to CoCl2 is 2:1.

Images