Iron modified sludge biochar electro-catalytic tangential flow membrane pack, preparation method and application thereof

Abstract

This invention relates to an iron-modified sludge biochar electrocatalytic tangential flow membrane coating, its preparation method, and its application. The preparation method includes: sequentially subjecting wastewater treatment plant residue sludge to mechanical screening for impurity removal, drying, anaerobic high-temperature pyrolysis, and ball milling to 0.5-2 μm to obtain modified sludge biochar; Fe... 2+ with Fe 3+ A mixture of multivalent iron ions is obtained by dissolving the iron ions in water at a molar ratio of 2-4:1; tannic acid is then added to this mixture to form a chelation system. This invention, through the preparation of a catalytic membrane pack and the continuous replenishment of electrons by an external electric field, enables the iron-modified sludge biochar electrocatalytic tangential flow membrane pack to possess both physical separation and carbon electrocatalytic degradation functions. This fundamentally solves the technical problems of existing ultrafiltration membrane packs, such as single function, severe membrane fouling, and low energy utilization, and overcomes the defects of easy pollutant deposition, achieving synergistic effects of separation and catalysis. It can be widely applied in scenarios such as advanced wastewater treatment.

Description

Technical Field

[0001] This invention relates to the field of in-situ catalytic oxidation of polycyclic aromatic hydrocarbons, specifically to an iron-modified sludge biochar electrocatalytic tangential flow membrane coating, its preparation method, and its application. Background Technology

[0002] Pollution from polycyclic aromatic hydrocarbons (PAHs) in water has become a pressing environmental issue. These pollutants accumulate in the environment, creating persistent pollution. Even at trace levels, their accumulation can accelerate the proliferation and spread of antibiotic resistance genes, posing potential risks to the ecological environment (Curr. Opin. Environ. Sci. Healthy., 2023, 32, 100437). Existing wastewater treatment processes, such as activated sludge processes, are inefficient at removing these recalcitrant substances, leading to the continuous release of PAHs into the environment at concentrations ranging from ng·L⁻¹ to mg·L⁻¹ (Environ. Pollut., 2024, 343, 123199). Therefore, finding an efficient method for removing PAHs from water is urgently needed.

[0003] Membrane separation technology, as a highly efficient and energy-saving separation and purification method, can effectively separate various impurities such as particles, dirt, and silt from water under pressure, showing extremely broad application prospects in the field of deep water purification. Among these components, the membrane pack, as the core carrier of the membrane separation module, directly affects the operating efficiency, treatment effect, and adaptability to application scenarios of the separation system due to its reasonable structural design and performance. Currently, the core membrane material used in existing membrane pack technologies is usually ultrafiltration membrane. Its working principle is mainly based on a pressure-driven physical sieving mechanism. Through the difference in membrane pore size, it achieves the retention of large molecules, colloids, bacteria, and other impurities in the solution, while allowing water, inorganic salts, and small organic molecules to permeate freely, playing an important role in conventional separation scenarios. However, in scenarios such as deep wastewater treatment where high separation precision and purification effects are required, existing ultrafiltration membrane packs have limitations such as single function, only physical retention, significant membrane fouling problems, short service life, low energy utilization, and difficulty in synergistic separation and catalysis, making it difficult to meet the application requirements of high-end purification and energy-efficient applications.

[0004] Advanced oxidation processes are renowned for their powerful oxidizing ability against polycyclic aromatic hydrocarbons (PAHs), enabling the mineralization of pollutants and thus eliminating their residues in the environment. To enhance the oxidizing potential of oxidants, external energy is typically applied to promote their efficient activation (Chem. Eng. J., 2025, 509, 161468). Biochar, due to its wide availability, simple preparation methods, large specific surface area, abundant surface functional groups, high carbon content, low mass transfer limitation, high electrical conductivity, high order, good thermal stability, and easily controllable surface physicochemical properties, is considered a green and environmentally friendly material with great application potential (Chem. Eng. J., 2018, 354, 941-976). However, the catalytic efficiency of raw biochar is relatively limited. Metal doping can enhance the activation efficiency of oxidants by altering the electronic structure through interaction with the carbon framework. Iron is considered an effective metal for modifying biochar due to its economic viability, environmental friendliness, and relatively low toxicity. The electrical conductivity of biochar can be further improved by adjusting the ratio of Fe(II) to Fe(III) (Appl. Catal. BEnviron., 2026, 387, 126469).

[0005] How to couple iron-based biochar advanced oxidation technology with existing membrane coating technology to overcome the problems of difficult catalyst recovery and decreased oxidant activation capacity due to electron loss on the biochar surface after use in wastewater treatment, while overcoming the defects of easy pollutant deposition in membrane coating technology, and thus improving the antifouling performance of the catalytic membrane, enhancing the membrane's self-cleaning ability, maintaining the long-term operation activity of the catalytic membrane, and enhancing its ability to resist interference from complex water matrices, has become an urgent problem to be solved. Summary of the Invention

[0006] This invention provides an iron-modified sludge biochar electrocatalytic tangential flow membrane pack, its preparation method, and its application. Using environmentally friendly metallic iron as the metal source, and based on principles such as environmentally friendly disposal, resource utilization, and synergistic selection of material properties, sludge is selected as the carbon source. By applying an electric field to the membrane pack, this invention aims to provide an iron-modified sludge biochar electrocatalytic membrane pack to solve the problems of poor catalytic oxidation stability, weak pollution resistance, and insufficient self-cleaning capacity of the catalytic membrane packs mentioned in the background art.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing an iron-modified sludge biochar electrocatalytic tangential flow membrane package includes the following steps: 1) Modified sludge biochar is obtained by sequentially subjecting the wastewater treatment plant's residual sludge to mechanical screening for impurity removal, drying treatment, anaerobic high-temperature pyrolysis, and ball milling to crush it to 0.5-2μm. 2) Fe 2+ with Fe 3+ The iron ions were dissolved in water at a molar ratio of 2 to 4:1 to obtain a mixed solution of multivalent iron ions; tannic acid was added to the mixed solution to form a chelation system; the chelation system was then mixed and reacted with modified sludge biochar and post-treated to obtain iron-modified sludge biochar. 3) Iron-modified sludge biochar and carbon nanotubes accounting for 2%-4% of its mass are dispersed in water to prepare a suspension; the suspension is loaded onto the surface of a membrane substrate by vacuum filtration to obtain a carbonaceous catalytic membrane. 4) The carbonaceous catalytic membrane and the flow guiding screen are stacked alternately to form a layered membrane package, which is then placed in a mold. Polyurethane is injected into its edges to cure and seal the edges, thus obtaining the carbonaceous catalytic membrane package. 5) A membrane housing I is placed on a carbonaceous catalytic membrane package to form an assembly unit, and multiple holes are drilled to form the inlet end, reflux end, permeation end and electrode penetration end of the assembly unit for purifying water. 6) Stack at least one assembly unit on membrane housing II and secure it; 7) After passing the titanium cathode electrode II and the titanium anode electrode I with the outer insulator through the electrode penetration ends of all assembly units, fix them to the membrane shell II to obtain the finished catalytic membrane package, namely the iron-modified sludge biochar electrocatalytic tangential flow membrane package.

[0008] Preferably, in step 1, the treatment conditions for the wastewater treatment plant's residual sludge include: Mechanical screening uses 100-200 mesh screens; The drying process employs a hot air fluidized bed suspension drying process. The anaerobic high-temperature pyrolysis temperature is 700-900℃, and the pyrolysis time is 3-6 h; and the protective gas for anaerobic high-temperature pyrolysis is nitrogen.

[0009] Preferably, in step 2, the conditions for obtaining iron-modified sludge biochar include: The volume of the aqueous solution is 100 mL; Fe 2+ FeSO4·7H2O was selected as the source, and the dosage was 207~415 mg. Fe 3+ FeCl3·6H2O was selected as the source, and the dosage was 100 mg. The dosage of tannic acid is 1 to 3 times the total molar amount of multivalent iron ions, i.e., 0.636 to 1.909 g; The dosage of modified sludge biochar is 5g; The chelation reaction temperature is 25~60℃, and the reaction time is 2~6h.

[0010] Preferably, in step 3, the carbon nanotubes are single-walled carbon nanotubes or multi-walled carbon nanotubes; the membrane substrate is a polyethersulfone ultrafiltration membrane with dimensions of 25cm × 8cm, and the effective area of ​​the polyethersulfone ultrafiltration membrane is 140cm². 2 .

[0011] Preferably, in step 3, the dosage of iron-modified sludge biochar is 51.2 mg, and the dosage of carbon nanotubes is 2 mg; the suspension is prepared by ultrasonic dispersion with an ultrasonic power of 100-300 W and an ultrasonic dispersion time of 30-60 min; the negative pressure of vacuum filtration is 0.05-0.09 MPa; and the loading of the iron-modified sludge biochar layer on the membrane substrate is 8 g·m³. -2 .

[0012] Preferably, in step 4, the mesh size of the flow guiding screen is 100-200 mesh; the permeable surface of the carbonaceous catalytic membrane is positioned facing the flow guiding screen; and the thickness of the layered membrane package is 5 cm.

[0013] The present invention also provides an iron-modified sludge biochar electrocatalytic tangential flow membrane package prepared by the preparation method of the above technical solution.

[0014] The present invention also provides an application of the iron-modified sludge biochar electrocatalytic tangential flow membrane prepared above in the degradation of polycyclic aromatic hydrocarbons in wastewater.

[0015] Preferably, the polycyclic aromatic hydrocarbons in the wastewater include one or more of tetracycline, geosmin, and sulfonamide antibiotics.

[0016] This invention also provides the application of iron-modified sludge biochar electrocatalytic tangential flow membrane coating in the degradation of polycyclic aromatic hydrocarbons in wastewater, the application comprising the following steps: A. Connect the electrodes of the iron-modified sludge biochar electrocatalytic tangential flow membrane package to a DC power supply, and then connect the inlet end and return end of the membrane shell I to the water inlet system, and the permeate end to the water outlet system. B. Adjust the wastewater quality parameters to achieve an initial concentration of polycyclic aromatic hydrocarbons (PAHs) of 0.5–2 mg / L. -1 pH value should be controlled within the range of 3 to 9; C. Add one or two oxidants, namely persulfate and peracetate, to the wastewater, wherein the concentration of the oxidant in the wastewater is 0.5~2mM; D. The cathode voltage of the iron-modified sludge biochar electrocatalytic tangential flow membrane package is controlled to be -0.1~0V using a DC power supply; E. Wastewater with added oxidant is pumped to the inlet end of membrane housing I via a peristaltic pump, allowing the wastewater to flow parallel to the surface of the carbonaceous catalytic membrane of the iron-modified sludge biochar electrocatalytic membrane package and then pass through the carbonaceous catalytic membrane; wherein, the flow rate of the wastewater flowing parallel to the surface of the carbonaceous catalytic membrane is 0.5~2 mL·min. -1 The hydraulic residence time of water flowing through the membrane is 1~5 minutes; During the wastewater permeate membrane process, the oxidant is activated through electrocatalysis, and at the same time, it is combined with the physical filtration and separation of the carbonaceous catalytic membrane to form a synergistic oxidation mechanism dominated by the non-free radical pathway, thereby simultaneously achieving the degradation of pollutants in wastewater and the purification of water.

[0017] By adopting the above technical solution, the beneficial effects achieved by the present invention are as follows: 1. By continuously replenishing electrons with an external electric field through the preparation of the catalytic membrane pack, the iron-modified sludge biochar electrocatalytic tangential flow membrane pack itself can have both physical separation and carbon electrocatalytic degradation functions. This fundamentally solves the technical problems of existing ultrafiltration membrane packs, such as single function, serious membrane fouling, and low energy utilization. It also overcomes the defect of easy pollutant deposition and achieves synergistic effect of separation and catalysis. It can be widely used in wastewater deep treatment and other scenarios, filling the technical gap in the industry of integrating electrocatalytic function and membrane pack structure.

[0018] 2. This invention uses sludge as a carbon source, making the biochar raw material inexpensive and easy to prepare, enabling environmentally friendly treatment and resource utilization of sludge; and with its three-dimensional structure and adjustable physicochemical properties, it can provide a structural basis for stacking and preparing membrane materials with sieving functions; at the same time, the permeability and barrier properties of the membrane can be precisely adjusted by adjusting the biochar loading.

[0019] 3. This invention chelates multivalent iron onto biochar with tannic acid, which can effectively improve the redox cycle rate of solid iron and avoid problems such as dosage loss of chelating agent and metal leaching.

[0020] 4. This invention applies an electric field to the membrane, which can effectively protect the cathode membrane from oxidative damage and reduce irreversible membrane fouling by means of electrorepulsion and free radical pathways.

[0021] 5. By introducing an electric field into the iron-modified sludge biochar electrocatalytic membrane pack, the cathode electrode rod can replenish the electrons consumed by the carbon layer during the activation of the oxidant, ensuring the continuous and stable activation of the oxidant by the carbon layer. This effectively guarantees the stability and continuity of the iron-modified sludge biochar electrocatalytic membrane pack's operation and significantly enhances the membrane's ability to resist interference from complex water matrices. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the preparation process of the modified sludge biochar of this invention.

[0023] Figure 2 This is a flowchart illustrating the preparation process of iron-modified sludge biochar according to the present invention.

[0024] Figure 3 This is a flowchart illustrating the preparation process of the carbonaceous catalytic membrane package of the present invention.

[0025] Figure 4 This is a flowchart illustrating the preparation process of the finished catalytic membrane package of this invention.

[0026] Figure 5 This is a schematic diagram of the assembly of the iron-modified sludge biochar electrocatalytic tangential flow membrane pack of the present invention during use.

[0027] Figure 6 Comparison of the effects of different loadings of iron-modified sludge biochar electrocatalytic tangential flow membrane activation on PS degradation of SMX.

[0028] Figure 7 Comparison of the effects of iron-modified sludge biochar electrocatalytic tangential flow membrane activation on the degradation of SMX by PS at different preparation temperatures.

[0029] Figure 8 This is a comparison of the effects of iron-modified sludge biochar electrocatalytic tangential flow membrane activation on the degradation of SMX by PS under different applied voltage conditions.

[0030] Figure 9 Comparison of the effects of iron-modified sludge biochar electrocatalytic tangential flow membrane pack on SMX removal under different PS dosage conditions.

[0031] Figure 10 Comparison of the effects of iron-modified sludge biochar electrocatalytic tangential flow membrane activating PS for the degradation of different pollutants. Detailed Implementation

[0032] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0033] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification. Example 1

[0034] like Figures 1-4 As shown, this invention provides an iron-modified sludge biochar electrocatalytic tangential flow membrane package and its preparation method, wherein the preparation method includes the following steps: 1) Modified sludge biochar is obtained by sequentially subjecting the wastewater treatment plant's residual sludge to mechanical screening for impurity removal, drying treatment, anaerobic high-temperature pyrolysis, and ball milling to crush it to 0.5-2μm. 2) Fe 2+ (i.e., FeII) and Fe 3+ (i.e., FeⅢ) is dissolved in water at a molar ratio of 2~4:1 to obtain a mixed solution of multivalent iron ions; tannic acid is added to the mixed solution to form a chelation system; the chelation system is then mixed and reacted with modified sludge biochar and post-treated to obtain iron-modified sludge biochar. 3) Iron-modified sludge biochar and carbon nanotubes accounting for 2%-4% of its mass are dispersed in water to prepare a suspension; the suspension is loaded onto the surface of a membrane substrate by vacuum filtration to obtain a carbonaceous catalytic membrane. 4) The carbonaceous catalytic membrane and the flow guiding screen are stacked alternately to form a layered membrane package, which is then placed in a mold. Polyurethane is injected into its edges for curing and sealing to obtain a carbonaceous catalytic membrane package 100. 5) A membrane housing I300 is placed on a carbonaceous catalytic membrane pack 100 to form an assembly unit, and multiple holes are drilled to form the inlet end 1, reflux end 2, permeation end 3 and electrode penetration end 4 of the water purification body of the assembly unit. 6) Stack at least one assembly unit on the membrane housing II200 and secure it; 7) After passing the titanium cathode electrode II and the titanium anode electrode I with the outer insulator through the electrode penetration end 4 of all assembly units, fix them to the membrane shell II200 to obtain the finished catalytic membrane package, namely the iron-modified sludge biochar electrocatalytic tangential flow membrane package.

[0035] like Figure 1 As shown, as a further step, in step 1, the treatment conditions for the wastewater treatment plant's residual sludge include: Mechanical screening uses 100-200 mesh screens to remove inorganic impurities from the residual sludge of sewage treatment plants; The drying process employs a hot air fluidized bed suspension drying process to dry the sludge after screening. The anaerobic high-temperature pyrolysis temperature is 700-900℃, and the pyrolysis time is 3-6 h; and the protective gas for anaerobic high-temperature pyrolysis is nitrogen.

[0036] In a preferred embodiment, the oxygen-free high-temperature pyrolysis temperature in step 1 is 900°C.

[0037] like Figure 2 As shown, as a further step, in step 2, the conditions for obtaining iron-modified sludge biochar include: The volume of the aqueous solution is 100 mL; Fe 2+(i.e., FeⅡ) uses FeSO4·7H2O as the source, and the dosage is 207~415mg; Fe 3+ (i.e., FeⅢ) uses FeCl3·6H2O as the source, and the dosage is 100mg; The dosage of tannic acid is 1 to 3 times the total molar amount of multivalent iron ions, i.e., 0.636 to 1.909 g (636 to 1909 mg). The dosage of modified sludge biochar is 5g; The chelation reaction temperature is 25~60℃, and the reaction time is 2~6h.

[0038] In step 2, the post-mixing treatment includes washing with deionized water and drying. Thus, the mixed reaction product, after washing with deionized water and drying, yields iron-modified sludge biochar.

[0039] In this step, the tannic acid-iron chelation site is used to accelerate the Fe... 2+ / Fe 3+ The oxidation-reduction cycle is enhanced, and the adsorption capacity of oxidants is improved, which promotes the fixation of multivalent iron ions on the surface of sludge biochar through the chelation of tannic acid, and finally iron-modified sludge biochar is obtained.

[0040] As a further step, in step 3, the dosage of iron-modified sludge biochar is 109 mg, the dosage of carbon nanotubes is 3 mg, and the volume of aqueous solution is 100 mL.

[0041] The carbon nanotubes are either single-walled or multi-walled; the membrane substrate is a 25cm × 8cm polyethersulfone ultrafiltration membrane, with an effective area of ​​140cm². 2 .

[0042] The calculation method for carbon material dosage, effective membrane area, and loading is as follows: Carbon material dosage = Effective membrane area × Loading = 0.014 m² 2 ×8g / m 2 =112 mg. Based on this, we can deduce in reverse: loading capacity = dosage / effective membrane area; effective membrane area = dosage / loading capacity.

[0043] As a further step, in step 3, the conditions for preparing the suspension include: preparation by ultrasonic dispersion, with an ultrasonic power of 100~300W and an ultrasonic dispersion time of 30~60min.

[0044] In a preferred embodiment, the ultrasonic power is 200W during the preparation of the suspension.

[0045] In step 3, the negative pressure of vacuum filtration is 0.05~0.09 MPa, used to control the loading of the iron-modified sludge biochar layer on the membrane substrate to be 8 g·m³. -2 .

[0046] like Figure 3 As shown, as a further step, in step 4, the mesh size of the flow guiding screen is 100~200 mesh and the size is 22cm×5cm; when the carbonaceous catalytic membrane and the flow guiding screen are stacked alternately, the permeable surface of the carbonaceous catalytic membrane is set facing the flow guiding screen; the thickness of the layered ("thousand-layer cake") membrane package formed by the alternating stacking of the carbonaceous catalytic membrane and the flow guiding screen is 5cm.

[0047] As a further step, in step 4, by injecting polyurethane into the edge of the laminated membrane package and allowing it to cure to form a sealing edge, side leakage at the edge of the laminated membrane package can be effectively prevented.

[0048] As a further step, in step 5, after drilling multiple holes in the assembly unit formed by placing a membrane shell I on a carbonaceous catalytic membrane package, the holes on the carbonaceous catalytic membrane package and the holes on the membrane shell I are precisely aligned so that each aligned hole forms the inlet end, reflux end, permeation end and electrode penetration end of the water purification body of the assembly unit.

[0049] The assembly unit has one liquid inlet and one reflux end; two through-ends; and two electrode penetration ends, one of which serves as the anode electrode penetration end and the other as the cathode electrode penetration end.

[0050] like Figure 4 As shown, as a further step, in step 6, an un-drilled membrane shell is selected as membrane shell II, i.e., the base; then at least one assembly unit is stacked on membrane shell II, such that the carbonaceous catalytic membrane pack of the bottom assembly unit is located between membrane shell II and membrane shell I, and the carbonaceous catalytic membrane pack of the adjacent assembly unit above is located between the adjacent membrane shells I above and below; wherein, the membrane shell I at the top of the stacked structure and the membrane shell II at the bottom can be fastened together by screw fixing.

[0051] As a further step, both membrane shell I and membrane shell II are made of acrylic sheets and have the same custom dimensions.

[0052] The present invention also proposes an iron-modified sludge biochar electrocatalytic tangential flow membrane package, which is an iron-modified sludge biochar electrocatalytic tangential flow membrane package prepared based on the above preparation method. Example 2

[0053] like Figure 5 As shown, this invention also proposes the application of iron-modified sludge biochar electrocatalytic tangential flow membrane coating in the degradation of polycyclic aromatic hydrocarbons in wastewater. This application includes the following steps: A. Connect the electrodes of the iron-modified sludge biochar electrocatalytic tangential flow membrane package to a DC power supply, and then connect the inlet end and return end of the membrane shell I to the water inlet system, and the permeate end to the water outlet system. Specifically, the titanium anode electrode I of the finished catalytic membrane pack is connected to the positive terminal of the power supply, and the titanium cathode electrode II is connected to the negative terminal of the power supply, thus realizing the electrical connection between the electrodes and the direct power supply; the liquid inlet end on the membrane shell I of the finished catalytic membrane pack is connected to the water inlet tank (water inlet system) through a hose and a peristaltic pump; the return end and permeate end of the finished catalytic membrane pack are respectively connected to the water inlet tank (water inlet system) and the water outlet tank (water outlet system) through hoses; thus, this assembly can obtain an iron-modified sludge biochar electrocatalytic tangential flow membrane pack with filtration and catalytic functions.

[0054] Among them, polycyclic aromatic hydrocarbons in the wastewater of the influent system include one or more of tetracycline, geosmin, and sulfonamide antibiotics; B. Adjust the wastewater quality parameters to achieve an initial concentration of polycyclic aromatic hydrocarbons (PAHs) of 0.5–2 mg / L. -1 pH value should be controlled within the range of 3 to 9; C. Add one or two oxidants, namely persulfate and peracetate, to the wastewater, wherein the concentration of the oxidant in the wastewater is 0.5~2mM; D. The cathode voltage of the iron-modified sludge biochar electrocatalytic tangential flow membrane is controlled to be -1.0~0V using a DC power supply; E. Wastewater is pumped to the inlet end of membrane housing I via a peristaltic pump, allowing it to flow parallel to the surface of the carbonaceous catalytic membrane of the iron-modified sludge biochar electrocatalytic membrane package and pass through the carbonaceous catalytic membrane; wherein the flow rate of the wastewater flowing parallel to the surface of the carbonaceous catalytic membrane is 0.5~2 mL·min. -1 The hydraulic residence time of water flowing through the membrane is 1~5 minutes; During the wastewater permeate membrane process, the oxidant is activated through electrocatalysis, and at the same time, it is combined with the physical filtration and separation of the carbonaceous catalytic membrane to form a synergistic oxidation mechanism dominated by the non-free radical pathway, thereby simultaneously achieving the degradation of pollutants in wastewater and the purification of water.

[0055] In this process, the wastewater circulates throughout the entire operation. When the wastewater enters the iron-modified sludge biochar electrocatalytic tangential flow membrane package, it propagates parallel to the surface of the carbonaceous catalytic membrane. Under the action of transmembrane pressure, some of it passes through the membrane pores and enters the permeate end. At the same time, the internal screen turbulence forms a flow that continuously washes the membrane surface, effectively inhibiting the accumulation of pollutants and achieving a stable and efficient filtration and separation effect.

[0056] In summary, this invention prepares an iron-modified sludge biochar catalytic membrane (i.e., a carbonaceous catalytic membrane) using a vacuum filtration method. This carbonaceous catalytic membrane is then alternately stacked and fixed with a flow-guiding screen to form a layered membrane package. This package is then assembled with electrode rods and a membrane shell to obtain the finished catalytic membrane package. By continuously supplying electrons to the membrane package through an external electric field, the iron-modified sludge biochar electroactive tangential flow membrane package can continuously and stably activate the oxidant and generate active oxygen components, thereby efficiently degrading target substances and natural organic components in the water, improving the membrane package's pollution resistance and catalytic oxidation efficiency.

[0057] Based on Example 2, this invention proposes a preferred embodiment, namely a method for the electrocatalytic tangential flow membrane encapsulation degradation of sulfamethoxazole using continuous flow iron-modified sludge biochar, the method comprising: Following the electrocatalytic tangential flow membrane encapsulation process for preparing iron-modified sludge biochar in Example 1, the anaerobic high-temperature pyrolysis temperature for obtaining the modified sludge biochar was 900°C; Fe... 2+ FeSO4·7H2O was selected as the source, and the dosage was 415 mg; Fe 3+ FeCl3·6H2O was selected as the biosource, with a dosage of 100 mg; tannic acid was added at a dosage of 0.636 g. When preparing the carbonaceous catalytic membrane, the loading of iron-modified sludge biochar on the polyethersulfone ultrafiltration membrane was controlled at 8 g·m³. -2 .

[0058] Furthermore, while the peristaltic pump draws the waste liquid to be treated to the inlet end of the iron-modified sludge biochar electrocatalytic tangential flow membrane pack, a continuous filtration method is used under an electric field controlled at -0.5V to draw the sulfamethoxazole solution containing persulfate into the iron-modified sludge biochar electrocatalytic tangential flow membrane pack for treatment. The concentration of sulfamethoxazole is 1 mg·L⁻¹. -1 The concentration of persulfate was 0.5 mM, the hydraulic retention time was 3 min, and the initial pH of sulfamethoxazole was 7.

[0059] like Figure 6 The experimental data show that, based on the preferred embodiment of Example 2, and using the same preparation conditions as that example, iron-modified sludge biochar electrocatalytic tangential flow membranes with different loadings were prepared; among them, the membranes with a loading of 4 g·m³ were prepared. -2 The membrane was set as Comparative Example 1, and a loading of 16 g·m was obtained. -2 The membrane packaging is set as Comparative Example 2. The difference between Comparative Examples 1-2 and the preferred embodiment of Example 2 lies in the different iron-modified sludge biochar loading.

[0060] As a further step, after continuous filtration for 10 hours in Comparative Example 1, Comparative Example 2, and Example 2, the loading was 4 g·m³. -2Comparative Example 1, with a loading capacity of 8 g·m -2 Example 2 and a loading of 16 g·m -2 The iron-modified sludge biochar electrocatalytic tangential flow membrane packs corresponding to Comparative Example 2 showed removal efficiencies of 70.8%, 91.0%, and 94.0% for SMX (sulfamethoxazole), respectively; among them, the loading was 8 g·m³. -2 With a loading capacity of 16 g·m -2 The iron-modified sludge biochar electrocatalytic membrane coating exhibits similar catalytic efficiency for SMX, but with a loading of 16 g·m³. -2 Due to its large loading capacity, the filtration performance of the iron-modified sludge biochar electrocatalytic tangential flow membrane is inevitably weaker than that of the 8 g·m³ membrane. -2 Therefore, considering both catalytic oxidation efficiency and filtration performance, the optimal loading rate for this invention is 8 g·m³. -2 .

[0061] like Figure 7 The experimental data show that, based on the preferred embodiment of Example 2, and using the same preparation conditions as that example, iron-modified sludge biochar electrocatalytic tangential flow membrane packs with different pyrolysis temperatures were prepared. Specifically, the membrane pack prepared at a pyrolysis temperature of 700℃ was designated as Comparative Example 3, and the membrane pack prepared at a loading temperature of 800℃ was designated as Comparative Example 4. The difference between Comparative Examples 3-4 and the preferred embodiment of Example 2 lies in the different pyrolysis temperatures of the modified sludge biochar.

[0062] As a further step, after continuous filtration for 10 hours in Comparative Examples 3, 4, and 2, the iron-modified sludge biochar electrocatalytic tangential flow membrane packages corresponding to Comparative Example 3 (pyrolysis temperature 700℃), Comparative Example 4 (pyrolysis temperature 800℃), and Example 2 (pyrolysis temperature 900℃) showed SMX (sulfamethoxazole) removal efficiencies of 50.6%, 66.1%, and 91.0%, respectively. The higher the pyrolysis temperature, the more thorough the carbonization of the biomass, which is beneficial for activating PS (persulfate) to degrade SMX (sulfamethoxazole). Therefore, the optimal pyrolysis temperature of this invention is 900℃.

[0063] like Figure 8 The experimental data show that, based on the preferred embodiment of Example 2, using the same application conditions, only the applied voltage was adjusted to examine the effect of different applied voltages on the processing effect. Specifically, the condition with an applied voltage of 0V was designated as Comparative Example 5, the condition with an applied voltage of -0.25V as Comparative Example 6, and the condition with an applied voltage of -1.0V as Comparative Example 7. The difference between Comparative Examples 5-7 and the preferred embodiment of Example 2 lies in the different applied voltages.

[0064] As a further step, after continuous filtration for 10 hours in Comparative Examples 5, 6, 7, and 2, the iron-modified sludge biochar electrocatalytic tangential flow membrane packs corresponding to Comparative Example 5 (0V), Comparative Example 6 (-0.25V), Comparative Example 2 (-0.5V), and Comparative Example 7 (-1.0V) showed removal efficiencies of 20.2%, 72.3%, 91.0%, and 96.0% for SMX (sulfamethoxazole), respectively. This indicates that the removal efficiency of SMX is significantly improved after applying an external electric field, demonstrating that the application of an external electric field... - It can effectively compensate for the electron loss of the iron-modified sludge biochar electrocatalytic tangential flow membrane during the activation of PS, thereby improving the removal efficiency of SMX; and the removal efficiency of SMX is similar when the applied electric field is -0.5V and -1.0V. Therefore, based on the consideration of operating cost, the optimal applied voltage of this invention can be controlled at around -0.5V or -0.5V.

[0065] like Figure 9 The experimental data show that, based on the preferred embodiment of Example 2, using the same application conditions, only the dosage of PS (persulfate) was increased to investigate the effect of different PS dosages on the treatment effect. Specifically, Comparative Example 8 was set with a PS dosage of 0 mM, Comparative Example 9 with a PS dosage of 0.25 mM, and Comparative Example 10 with a PS dosage of 1 mM. The difference between Comparative Examples 8-10 and the preferred embodiment of Example 2 lies in the different PS (persulfate) dosages.

[0066] Furthermore, after continuous filtration for 10 hours in Comparative Examples 8, 9, 10, and 2, the iron-modified sludge biochar electrocatalytic tangential flow membrane packs corresponding to the PS dosages of 0 mM (Comparative Example 8), 0.25 mM (Comparative Example 9), 0.5 mM (Comparative Example 2), and 1 mM (Comparative Example 10) showed SMX removal efficiencies of 10.1%, 60.1%, 91.0%, and 92.3%, respectively. This indicates that adsorption by iron-modified sludge biochar and reduction by the negative electrode alone are insufficient for effective SMX removal. Moreover, the SMX removal efficiency is similar when the PS dosage is 0.5 mM and 1 mM. Therefore, considering operating costs, the optimal PS dosage in this invention is controlled at 0.5 mM. Example 3

[0067] Based on Example 2, this invention proposes another preferred embodiment, namely a method for continuous flow iron-modified sludge biochar electrocatalytic tangential flow membrane degradation of tetracycline. The operating conditions of the method are the same as those of the preferred embodiment of Example 2. After continuous filtration for 10 hours, the tetracycline removal efficiency of this method is 92.6%. Example 4

[0068] Based on Example 2, this invention proposes another preferred embodiment, namely a method for continuous flow iron-modified sludge biochar electrocatalytic tangential flow membrane degradation of oxytetracycline. The operating conditions of the method are the same as those of the preferred embodiment of Example 2. After continuous filtration for 10 hours, the removal efficiency of oxytetracycline is 85.2%.

[0069] like Figure 10 As shown, Examples 3 and 4 are the effect data of the iron-modified sludge biochar electrocatalytic tangential flow membrane package activating PS to degrade tetracycline and oxytetracycline, respectively. Based on the same operating conditions as Example 2, after continuous filtration for 10 hours, the removal efficiencies of tetracycline and oxytetracycline were 92.6% and 85.2%, respectively. It can be seen that the iron-modified sludge biochar electrocatalytic tangential flow membrane package proposed in this invention has good universality in the degradation of organic pollutants.

[0070] In summary, the present invention has the following advantages: 1. In this invention, by using the prepared catalytic membrane pack in conjunction with an external electric field to continuously replenish electrons, the iron-modified sludge biochar electrocatalytic tangential flow membrane pack itself can have both physical separation and carbon electrocatalytic degradation functions. This fundamentally solves the technical problems of existing ultrafiltration membrane packs, such as single function, serious membrane fouling, and low energy utilization. It also overcomes the defect of easy pollutant deposition and achieves synergistic effect of separation and catalysis. It can be widely used in scenarios such as deep wastewater treatment and fills the technical gap in the industry of integrating electrocatalytic function and membrane pack structure.

[0071] 2. In this invention, sludge is used as a carbon source, which makes the biochar raw material low in cost and easy to prepare, and can realize the environmental protection treatment and resource utilization of sludge; and with its three-dimensional structure and adjustable physicochemical properties, it can provide a structural basis for stacking to prepare membrane materials with screening function; at the same time, the permeability and barrier properties of the membrane can be precisely adjusted by adjusting the biochar loading.

[0072] 3. This invention chelates multivalent iron onto biochar with tannic acid, which can effectively improve the redox cycle rate of solid iron and avoid problems such as chelating agent dosage loss and metal leaching.

[0073] 4. This invention applies an electric field to the membrane, which can effectively protect the cathode membrane from oxidative damage and reduce irreversible membrane fouling by means of electrorepulsion and free radical pathways.

[0074] 5. In this invention, by introducing an electric field into the iron-modified sludge biochar electrocatalytic membrane pack, the cathode electrode rod can replenish the electrons consumed by the carbon layer during the activation of the oxidant, ensuring the continuous and stable activation of the oxidant by the carbon layer, thereby effectively guaranteeing the stability and continuity of the operation of the iron-modified sludge biochar electrocatalytic membrane pack and greatly enhancing the ability of the catalytic membrane to resist interference from complex water matrix.

[0075] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0076] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing an iron-modified sludge biochar electrocatalytic tangential flow membrane, characterized in that, Includes the following steps: 1) Modified sludge biochar is obtained by sequentially subjecting the wastewater treatment plant's residual sludge to mechanical screening for impurity removal, drying treatment, anaerobic high-temperature pyrolysis, and ball milling to crush it to 0.5-2μm. 2) Fe 2+ with Fe 3+ The iron ions were dissolved in water at a molar ratio of 2 to 4:1 to obtain a mixed solution of multivalent iron ions; tannic acid was added to the mixed solution to form a chelation system; the chelation system was then mixed and reacted with modified sludge biochar and post-treated to obtain iron-modified sludge biochar. 3) Iron-modified sludge biochar and carbon nanotubes accounting for 2%-4% of its mass are dispersed in water to prepare a suspension; the suspension is loaded onto the surface of a membrane substrate by vacuum filtration to obtain a carbonaceous catalytic membrane. 4) The carbonaceous catalytic membrane and the flow guiding screen are stacked alternately to form a layered membrane package, which is then placed in a mold. Polyurethane is injected into its edges to cure and seal the edges, thus obtaining the carbonaceous catalytic membrane package. 5) A membrane housing I is placed on a carbonaceous catalytic membrane package to form an assembly unit, and multiple holes are drilled to form the inlet end, reflux end, permeation end and electrode penetration end of the assembly unit for purifying water. 6) Stack at least one assembly unit on membrane housing II and secure it; 7) After passing the titanium cathode electrode II and the titanium anode electrode I with the outer insulator through the electrode penetration ends of all assembly units, fix them to the membrane shell II to obtain the finished catalytic membrane package, namely the iron-modified sludge biochar electrocatalytic tangential flow membrane package.

2. The method for preparing the iron-modified sludge biochar electrocatalytic tangential flow membrane according to claim 1, characterized in that, In step 1, the treatment conditions for the wastewater treatment plant's residual sludge include: Mechanical screening uses 100-200 mesh screens; The drying process employs a hot air fluidized bed suspension drying process. The anaerobic high-temperature pyrolysis temperature is 700-900℃, and the pyrolysis time is 3-6 h; and the protective gas for anaerobic high-temperature pyrolysis is nitrogen.

3. The method for preparing the iron-modified sludge biochar electrocatalytic tangential flow membrane according to claim 1, characterized in that, In step 2, the conditions for obtaining iron-modified sludge biochar include: The volume of the aqueous solution is 100 mL; Fe 2+ FeSO4·7H2O was selected as the source, and the dosage was 207~415 mg. Fe 3+ FeCl3·6H2O was selected as the source, and the dosage was 100 mg. The dosage of tannic acid is 1 to 3 times the total molar amount of multivalent iron ions; The dosage of modified sludge biochar is 5g; The chelation reaction temperature is 25~60℃, and the reaction time is 2~6h.

4. The method for preparing the iron-modified sludge biochar electrocatalytic tangential flow membrane according to claim 1, characterized in that, In step 3, the carbon nanotubes are single-walled or multi-walled carbon nanotubes; the membrane substrate is a polyethersulfone ultrafiltration membrane with dimensions of 25cm × 8cm, and the effective area of ​​the polyethersulfone ultrafiltration membrane is 140cm². 2 .

5. The method for preparing the iron-modified sludge biochar electrocatalytic tangential flow membrane according to claim 4, characterized in that, In step 3, the dosage of iron-modified sludge biochar is 109 mg, and the dosage of carbon nanotubes is 3 mg; the suspension is prepared by ultrasonic dispersion with an ultrasonic power of 100-300 W and an ultrasonic dispersion time of 30-60 min; the negative pressure of vacuum filtration is 0.05-0.09 MPa to control the loading of the iron-modified sludge biochar layer on the membrane substrate to 8 g·m³. -2 .

6. The method for preparing the iron-modified sludge biochar electrocatalytic tangential flow membrane according to claim 1, characterized in that, In step 4, the mesh size of the flow guiding screen is 100-200 mesh; the permeable surface of the carbonaceous catalytic membrane is set facing the flow guiding screen; and the thickness of the stacked membrane package is 5 cm.

7. An iron-modified sludge biochar electrocatalytic tangential flow membrane pack prepared by the method described in any one of claims 1-6.

8. The application of the iron-modified sludge biochar electrocatalytic tangential flow membrane as described in claim 7 in the degradation of polycyclic aromatic hydrocarbons in wastewater.

9. The application according to claim 8, characterized in that, The polycyclic aromatic hydrocarbons in the wastewater include one or more of tetracycline, geosmin, and sulfonamide antibiotics.

10. The application according to claim 8, characterized in that, The application includes the following steps: A. Connect the electrodes of the iron-modified sludge biochar electrocatalytic tangential flow membrane package to a DC power supply, and then connect the inlet end and return end of the membrane shell I to the water inlet system, and the permeate end to the water outlet system. B. Adjust the wastewater quality parameters to achieve an initial concentration of polycyclic aromatic hydrocarbons (PAHs) of 0.5–2 mg / L. -1 pH value should be controlled within the range of 3 to 9; C. Add one or two oxidants, namely persulfate and peracetate, to the wastewater, wherein the concentration of the oxidant in the wastewater is 0.5~2mM; D. The cathode voltage of the iron-modified sludge biochar electrocatalytic tangential flow membrane is controlled to be -1.0~0V using a DC power supply; E. Wastewater is pumped to the inlet end of membrane housing I via a peristaltic pump, allowing it to flow parallel to the surface of the carbonaceous catalytic membrane of the iron-modified sludge biochar electrocatalytic membrane package and pass through the carbonaceous catalytic membrane; wherein the flow rate of the wastewater flowing parallel to the surface of the carbonaceous catalytic membrane is 0.5~2 mL·min. -1 The hydraulic residence time of water flowing through the membrane is 1~5 minutes; During the wastewater permeate membrane process, the oxidant is activated through electrocatalysis, and at the same time, it is combined with the physical filtration and separation of the carbonaceous catalytic membrane to form a synergistic oxidation mechanism dominated by the non-free radical pathway, thereby simultaneously achieving the degradation of pollutants in wastewater and the purification of water.

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