Ultrafiltration system and ultrafiltration method with synergistic magnetic membrane

Abstract

The invention relates to a magnetic membrane synergetic ultrafiltration system and ultrafiltration method, and the system comprises a magnetic coupling unit and a membrane separation unit; the membrane separation unit comprises a membrane material, and soft magnetic composite particles are embedded in the membrane material; the magnetic coupling unit comprises a first magnetic field device and a second magnetic field device, the first magnetic field device is arranged adjacent to the water inlet end of the membrane separation unit, and the second magnetic field device is arranged adjacent to the backwashing end of the membrane separation unit. The device has the beneficial effects that the membrane material embedded with the soft magnetic composite particles and the magnetic coupling units separately arranged at the water inlet end and the backwashing end have a synergistic effect, so that precise control and efficient cleaning of the membrane pollution process are realized.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a magnetic membrane-assisted ultrafiltration system and ultrafiltration method. Background Technology

[0002] Membrane separation technologies (such as ultrafiltration, nanofiltration, and reverse osmosis) have become one of the core processes in water treatment due to their high separation efficiency and the fact that they do not require phase change. However, membrane fouling remains a bottleneck restricting their widespread application and stable operation. During filtration, large organic molecules in the water (such as proteins, polysaccharides, and humic substances) can cause membrane pore narrowing and blockage through adsorption and deposition, leading to an irreversible decrease in membrane flux and a significant increase in operating energy consumption. Although conventional backwashing procedures can restore membrane performance to some extent, their cleaning effect is limited for irreversible fouling caused by organic matter, often ultimately relying on costly chemical cleaning or membrane module replacement, which greatly increases the burden of operation and maintenance.

[0003] Currently, to alleviate membrane fouling, some novel field-effect technologies, such as magnetic fields, electric fields, and ultrasound, are coupled with membrane separation processes. These technologies aim to alter the structure of organic pollutants in water, thereby mitigating membrane fouling to some extent. Many researchers have improved the structure of different field effects to enhance the integration of specific membrane separation technologies. However, these technologies often suffer from limitations such as relying on a single field effect and insufficient application. A single magnetic field cannot adapt to dynamic changes in influent organic matter concentration and zeta potential, and it easily leads to cross-contamination of residual pollutants in the pipeline, ultimately resulting in incomplete backwashing. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a magnetic membrane synergistic ultrafiltration system and ultrafiltration method, which solves the technical problems of poor membrane fouling control and incomplete backwashing caused by the single field effect in the existing membrane separation system.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0008] In a first aspect, embodiments of the present invention provide a magnetic membrane-coordinated ultrafiltration system, comprising a magnetic coupling unit and a membrane separation unit;

[0009] The membrane separation unit includes a membrane material in which soft magnetic composite microparticles are embedded; the magnetic coupling unit includes a first magnetic field device and a second magnetic field device, the first magnetic field device being located near the inlet end of the membrane separation unit and the second magnetic field device being located near the backwash end of the membrane separation unit.

[0010] Soft magnetic composite microparticles are embedded within the membrane material, transforming the membrane from a passive filtration medium into an active functional material with magnetic response capabilities. Under the action of the first magnetic field device, the microparticles within the membrane are magnetized, forming a strong microscopic magnetic field gradient that continuously and actively captures flowing pollutants. This not only delays deep pore blockage and the formation of a surface filter cake layer, but also allows for easy switching between the membrane's capture and release states by simply turning the first magnetic field device on and off, matching the different operating conditions required for filtration and backwashing.

[0011] In a preferred embodiment of the present invention, the soft magnetic composite microparticles are FeCo-BN soft magnetic composite microparticles, the mass ratio of FeCo to BN is 1:0.5-2, and the particle size of the FeCo-BN soft magnetic composite microparticles is 0.1-2 μm.

[0012] The soft magnetic composite microparticles employ an FeCo-BN system, with a defined mass ratio of FeCo to BN of 1:0.5-2. FeCo provides extremely high saturation magnetization, laying the physical foundation for strong magnetic trapping. BN, as a chemically inert protective layer, fundamentally solves the problems of FeCo's easy corrosion and ion dissolution. The mass ratio balances magnetic properties and protective properties, ensuring that the film maintains both high magnetic function and long service life during long-term operation. If the ratio is lower than 1:0.5 (i.e., too little BN), the protective layer is incomplete and cannot effectively resist corrosion; if the ratio is higher than 1:2 (i.e., too much BN), the magnetic phase will be excessively diluted, leading to a significant decrease in magnetic responsiveness.

[0013] In a preferred embodiment of the present invention, the concentration of soft magnetic microparticles in the membrane material is 10-20 wt%.

[0014] The FeCo-BN soft magnetic composite microparticle concentration is 10-20wt%. This concentration range ensures that sufficiently dense magnetic interaction points can be formed within the membrane, while avoiding the problem of membrane matrix structure damage caused by excessive addition of inorganic microparticles and avoiding the negative impact of functional additions on the membrane matrix.

[0015] In a preferred embodiment of the present invention, the membrane material is a polysulfone or polyethersulfone ultrafiltration membrane with an asymmetric structure, which is integrally composed of a macroporous support layer and a thin dense separation layer.

[0016] The thickness of the macroporous support layer is 100-200 μm, and the thickness of the thin-layer dense separation layer is 0.1-1.0 μm.

[0017] Polysulfone (PSF) or polyethersulfone (PES) is chosen as the membrane substrate because it has good mechanical strength, heat resistance, chemical stability, and is easy to dop with inorganic nanoparticles (FeCo-BN), resulting in good compatibility.

[0018] A method for preparing a membrane material dispersed with FeCo-BN soft magnetic composite microparticles includes the following steps:

[0019] (1) Preparation of soft magnetic composite microparticles: According to the mass ratio of FeCo to BN of 1:0.5-2, weigh iron powder, cobalt powder and boron nitride powder, put the powder mixture and stainless steel grinding balls into a ball milling jar at a ball-material mass ratio of 20-25:1, add anhydrous ethanol, and use a planetary ball mill for ball milling. Wash the ball-milled slurry with anhydrous ethanol 3-5 times. After centrifugation, vacuum dry the solid product at 80-100℃ for 6-12 hours to obtain FeCo-BN soft magnetic composite microparticles with a particle size of 0.1-2μm.

[0020] Anhydrous ethanol, used as a process control agent, can prevent excessive cold welding of powder. The ball mill jar is sealed in a glove box to ensure that the entire ball milling process is carried out under the protection of inert argon gas, preventing the Fe and Co powders from being oxidized.

[0021] Preferably, the molar ratio of iron powder to cobalt powder is 1:1.

[0022] Preferably, the spindle speed of the planetary ball mill is 300-350 rpm, and the ball milling time is 20-25 hours;

[0023] The ball milling process employs a forward-pause-reverse rotation mode to help the powders mix and compound thoroughly.

[0024] (2) Preparation of casting solution: Dissolve polysulfone or polyethersulfone in N-methylpyrrolidone and dissolve for 3-4 hours under stirring conditions of 60-80℃ and 400-500rpm; add FeCo-BN soft magnetic composite microparticles obtained in step (1), disperse by ultrasonication, and continue stirring for 1-2 hours; add polyvinylpyrrolidone, stir until homogeneous, and let stand to degas for 24-36 hours to obtain casting solution.

[0025] (3) Film formation and post-treatment: Using a doctor blade coater, the casting solution obtained in step (2) is coated onto the substrate with a gap of 160-200 μm, and then immersed in a deionized water coagulation bath at 25°C to form a phase inversion film; the coagulated film is vacuum dried at 40-60°C for 12-15 hours, and then hot-pressed at 110-120°C and 0.4-0.5 MPa for 30-40 minutes to obtain a film material with FeCo-BN soft magnetic composite microparticles dispersed in it.

[0026] In a preferred embodiment of the present invention, the inlet end of the membrane separation unit is provided with an inlet pipe, and the first magnetic field device is covered on the outer wall of the inlet pipe; the backwash end of the membrane separation unit is provided with a backwash water pipe, and the second magnetic field device is covered on the outer wall of the backwash water pipe; the outlet end of the membrane separation unit is provided with an outlet pipe.

[0027] As a preferred embodiment of the present invention, the first magnetic field device includes a first-stage permanent magnet and a second-stage permanent magnet, wherein the magnetic field strength inside the second-stage permanent magnet is greater than the magnetic field strength inside the first-stage permanent magnet.

[0028] The first-stage permanent magnet is close to the end of the water to be treated, and the second-stage permanent magnet is close to the membrane separation unit. The water to be treated passes sequentially through the first-stage permanent magnet and the second-stage permanent magnet with increasing magnetic field strength.

[0029] The magnetic field strength of the first-stage permanent magnet is 2500-3000 Gs, and the magnetic field strength of the second-stage permanent magnet is 3500-4000 Gs.

[0030] A lower-intensity first-stage magnetic field pre-magnetizes and initially agglomerates pollutants in the feed water, increasing their particle size. Subsequently, a higher-intensity second-stage magnetic field applies a stronger magnetic force to the initially agglomerated pollutants, resulting in deeper magnetization and secondary agglomeration. This progressive magnetization treatment is more efficient than a single-intensity magnetic field and can adapt to pollutants with varying degrees of magnetization difficulty. After this gradient magnetic field pretreatment, colloids, suspended solids, and other pollutants in the water are magnetized and agglomerated into larger particles. The change in their physical morphology makes them more easily intercepted by the magnetic barrier on the membrane surface, rather than directly clogging the tiny membrane pores, thus significantly reducing the initial fouling load of the membrane unit.

[0031] In a preferred embodiment of the present invention, both the first-stage permanent magnet and the second-stage permanent magnet are tubular hollow permanent magnets, and the inner diameter of the hollow permanent magnet matches the outer diameter of the water inlet pipe.

[0032] In a preferred embodiment of the present invention, the second magnetic field device includes a coil wound around the outside of the backwash water pipe and a magnetized water generator connected to both ends of the coil; the winding density of the coil is 10-20 turns / cm.

[0033] In a preferred embodiment of the present invention, the ultrafiltration system further includes a monitoring device; the monitoring device is used to monitor the membrane flux and transmembrane pressure difference of the membrane separation unit.

[0034] A decrease in membrane flux (J) and an increase in transmembrane pressure (TMP) are the most direct and fundamental characteristics of membrane fouling. Real-time monitoring of these two key parameters allows for accurate assessment of the severity of membrane fouling. Backwashing is initiated when membrane flux drops to 70%-85% of its initial value or transmembrane pressure rises to 1.5-2 times its initial value. This avoids the drawbacks of traditional fixed-time backwashing, where premature backwashing wastes water and energy, while delayed backwashing can lead to irreversible fouling, difficult cleaning, and unrecoverable flux. By monitoring and performing backwashing at the optimal time, operating costs are minimized while ensuring membrane performance.

[0035] Secondly, embodiments of the present invention provide an ultrafiltration method using a magnetic membrane-coordinated ultrafiltration system, employing the magnetic membrane-coordinated ultrafiltration system of the first aspect, comprising the following steps:

[0036] S1: In the water pretreatment stage, the water to be treated flows through the first magnetic field device at the water inlet end, causing it to be subjected to a magnetic field.

[0037] S2: Membrane separation stage, the pretreated water flows into the membrane separation unit and undergoes ultrafiltration separation in the membrane material with a gradient distribution of soft magnetic composite particles to obtain purified water;

[0038] S3: Backwashing and regeneration stage. Backwash water flows through the second magnetic field device at the backwash end, causing the backwash water to be subjected to its magnetic field and backwashing the membrane separation unit.

[0039] (III) Beneficial Effects

[0040] The beneficial effects of this invention are as follows: The magnetic membrane synergistic ultrafiltration system and method of this invention achieve precise control and efficient cleaning of the membrane fouling process by synergistically combining membrane material embedded with soft magnetic composite microparticles with magnetic coupling units located at the inlet and backwash ends. At the inlet end, a first magnetic field device pre-treats the inlet water with magnetization, causing pollutants in the water to be pre-magnetized and micro-aggregated, altering their basic properties such as average particle size, potential, and hydrophilicity / hydrophobicity, thus reducing the initial fouling load for subsequent membrane separation from the source. In the membrane separation unit, the soft magnetic composite microparticles embedded in the membrane body form a magnetic barrier on the membrane surface and internal pores under the action of the magnetic field, actively capturing pollutants magnetically. The combination of the magnetic barrier and the magnetization pre-treatment of the inlet water constitutes a dual line of defense against pollutants, significantly slowing down the membrane fouling process, thereby maintaining higher membrane flux and more stable effluent quality. At the backwash end, the second magnetic field device activates the backwash water into magnetized water, which, together with the hydraulic flushing, creates a synergistic effect. This allows for more effective penetration, disturbance, stripping, and removal of stubborn contaminants from inside the membrane pores and on the membrane surface, significantly improving the efficiency of physical cleaning.

[0041] Because the soft magnetic composite microparticles are embedded within the membrane material, the membrane itself transforms from a passive filtration medium into an active functional material with magnetic response capabilities. Under the action of the first magnetic field, the microparticles within the membrane are magnetized, forming a strong microscopic magnetic field gradient that can continuously and actively capture flowing pollutants. This not only delays deep pore blockage and the formation of a surface filter cake layer, but also allows for switching between the membrane's capture and release states simply by turning the first magnetic field on and off, matching the different operating conditions required for filtration and backwashing.

[0042] Testing showed that the membrane flux recovery rate of this system can be increased from approximately 68% using traditional methods to over 95%. This demonstrates the high efficiency of the physical cleaning method, which significantly reduces the frequency and intensity of chemical cleaning, thereby extending membrane lifespan and fundamentally lowering system operation and maintenance costs. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the structure of a magnetic membrane-assisted ultrafiltration system according to the present invention.

[0044] [Explanation of Labels in the Attached Image]

[0045] 1: Water to be treated; 2: First-stage permanent magnet; 3: Second-stage permanent magnet; 4: Membrane separation unit; 5: Monitoring device; 6: Purified water; 7: Backwash water; 8: Coil; 9: Magnetized water generator. Detailed Implementation

[0046] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and that the scope of the present invention can be fully conveyed to those skilled in the art.

[0048] Example 1

[0049] like Figure 1 As shown, this embodiment provides a magnetic membrane synergistic ultrafiltration system, including a magnetic coupling unit, a membrane separation unit 4, and a monitoring device 5 for monitoring the membrane flux and transmembrane pressure difference of the membrane separation unit 4. The magnetic coupling unit includes a first magnetic field device and a second magnetic field device. The first magnetic field device is located near the inlet end of the membrane separation unit 4, and the second magnetic field device is located near the backwash end of the membrane separation unit 4. The inlet end of the membrane separation unit 4 has an inlet pipe, and the first magnetic field device covers the outer wall of the inlet pipe. The backwash end of the membrane separation unit 4 has a backwash water pipe, and the second magnetic field device covers the outer wall of the backwash water pipe. The outlet end of the membrane separation unit 4 has an outlet pipe.

[0050] Specifically, the first magnetic field device includes a first-stage permanent magnet 2 and a second-stage permanent magnet 3, with the magnetic field strength inside the second-stage permanent magnet 3 being greater than that inside the first-stage permanent magnet 2. The first-stage permanent magnet 2 is located near the water to be treated, and the second-stage permanent magnet 3 is located near the membrane separation unit 4. The water to be treated sequentially passes through the first-stage permanent magnet 2 and the second-stage permanent magnet 3, with increasing magnetic field strengths. The magnetic field strength of the first-stage permanent magnet 2 is 2500-3000 Gs, and the magnetic field strength of the second-stage permanent magnet 3 is 3500-4000 Gs. Both the first-stage permanent magnet 2 and the second-stage permanent magnet 3 are tubular hollow permanent magnets, and the inner diameter of the hollow permanent magnet matches the outer diameter of the inlet pipe. The hollow permanent magnets are made of sintered neodymium iron boron. The second magnetic field device includes a coil 8 wound around the outside of the backwash water 7 pipe and a magnetized water generator 9 connected to both ends of the coil 8. The winding density of the coil 8 is 10-20 turns / cm.

[0051] It should be noted that the opening and closing of the first magnetic field device in this invention does not refer to the disappearance of the magnetism of the permanent magnet itself, but rather to controlling whether its magnetic field can effectively act on the inlet channel of the membrane separation unit 4 through mechanical or electromagnetic means. The magnetic field can be switched on or off by changing the relative position of the permanent magnet and the inlet, or by introducing or removing magnetic shielding material in the magnetic field path.

[0052] The membrane separation unit 4 includes a membrane material in which FeCo-BN soft magnetic composite microparticles with a distribution concentration of 15wt% are embedded. The FeCo-BN soft magnetic composite microparticles have a particle size of 0.5μm and a mass ratio of FeCo to BN of 1:1.6. The membrane material is a polysulfone membrane.

[0053] This embodiment also provides an ultrafiltration method using a magnetic membrane-coordinated ultrafiltration system. The method involves filtering a solution using this magnetic membrane-coordinated ultrafiltration system, and includes the following steps:

[0054] S1: In the water pretreatment stage, the water to be treated flows through the first magnetic field device at the water inlet end, causing it to be subjected to a magnetic field.

[0055] The inlet pump and the first magnetic field device are turned on. The first magnetic field device is preferably a two-stage gradient permanent magnetic field. The water to be treated flows through the gradient magnetic field sequentially at a certain flow rate. When the water flows through the first stage of the weaker magnetic field, the paramagnetic pollutant particles in the water are initially magnetized and begin to slowly aggregate. The tiny particles collide to form smaller flocs. Subsequently, the water flows into the second stage of the stronger magnetic field, where the pollutants that have already been initially aggregated are subjected to a stronger magnetic force, and quickly complete deep magnetization and micro-aggregation.

[0056] S2: Membrane separation stage, the pretreated water flows into membrane separation unit 4, and ultrafiltration separation is carried out in the membrane material with soft magnetic composite microparticle gradient distribution to obtain purified water;

[0057] When the pre-magnetized pollutant flocs approach the membrane surface, they are attracted by the strong gradient magnetic field generated by the soft magnetic particles magnetized by the first magnetic field inside the membrane. They are actively and firmly captured on the membrane surface, forming a loose filter cake layer. For smaller particles that cannot be captured on the surface, when they enter the membrane pores with the water flow, they are adsorbed onto the inner wall of the pores by the continuous magnetic force of the magnetic particles distributed on the inner wall of the pores. This effectively delays the deep clogging of the membrane pores and obtains high-quality purified water.

[0058] The monitoring device 5 records the changes in membrane flux (J) and transmembrane pressure difference (TMP) in real time.

[0059] S3: Backwash regeneration stage, the backwash water flows through the second magnetic field device at the backwash end, so that the backwash water is subjected to its magnetic field and performs reverse rinsing on the membrane separation unit 4.

[0060] When monitoring device 5 detects that the membrane flux has dropped to 80% of the initial flux and / or the transmembrane pressure difference has risen to 1.8 times the initial value, the backwashing procedure is triggered. The system stops the feed pump and shuts down the first magnetic field device, causing the soft magnetic particles inside the membrane to demagnetize rapidly, releasing their magnetic capture function. The magnetic bond between the pollutants and the membrane is broken, and they are transformed into a physical attachment state. At the same time, the backwash pump and the second magnetic field device are turned on. The backwash water flows through the second magnetic field device at the backwash end and is activated into magnetized water by the magnetized water generator 9. The backwash water provides a strong reverse water force to flush the membrane surface and pores. Due to the change in its physicochemical properties, the magnetized water has stronger permeability and stripping ability, dispersing the pollutant clumps that have been flushed down.

[0061] Example 2

[0062] This embodiment provides a method for preparing a membrane material with FeCo-BN soft magnetic composite microparticles dispersed therein, the steps of which are as follows:

[0063] (1) Weigh iron powder, cobalt powder (calculated based on a Fe:Co molar ratio of 1:1), and boron nitride powder according to the FeCo:BN mass ratio. Place the weighed powder mixture and stainless steel grinding balls (ball-to-material mass ratio of 20:1) into a ball mill jar, and add an appropriate amount of anhydrous ethanol as a process control agent. Seal the ball mill jar in a glove box to ensure that the entire ball milling process is carried out under inert argon protection to prevent the Fe and Co powders from being oxidized.

[0064] (2) Fix the grinding jar on the planetary ball mill, wherein the ball mill parameters are: spindle speed of 350 rpm and grinding time of 25 hours;

[0065] It adopts a forward-pause-reverse operation mode to help the powder to be fully mixed and compounded.

[0066] (3) After ball milling, the obtained slurry was washed three times with anhydrous ethanol and the solid product was collected by centrifugation. The collected solid product was placed in a vacuum drying oven and vacuum dried at 80°C for 12 hours to obtain FeCo-BN soft magnetic composite microparticles with a particle size of 0.6 μm.

[0067] (4) According to the concentration requirements, accurately calculate the mass of each component and prepare a casting solution with a total mass of 100g. Dissolve polysulfone (PES) in N-methylpyrrolidone (NMP) and stir at 80℃ (500rpm) for 4h until completely dissolved. Add FeCo-BN soft magnetic composite microparticles, disperse by ultrasonication, and continue stirring for 2h. Finally, add polyvinylpyrrolidone (PVP K30), stir until homogeneous, and let stand to degas for 24h.

[0068] (5) Using a doctor blade coating machine, the degassed casting liquid is coated onto a clean glass plate. The doctor blade gap is set to 200 μm. The glass plate with the coated liquid film is horizontally immersed in a deionized water coagulation bath at 25°C. The coagulated film is dried in a vacuum drying oven at 60°C for 12 hours to remove residual solvent. It is then hot-pressed at 120°C and 0.5 MPa for 30 minutes to form a membrane material with FeCo-BN soft magnetic composite microparticles dispersed in it.

[0069] Example 3

[0070] This embodiment provides a magnetic membrane synergistic ultrafiltration system, which differs from Embodiment 1 in that: the mass ratio of FeCo to BN in the FeCo-BN soft magnetic composite particles is 1:1.5, the FeCo-BN concentration is 18wt%, and the membrane material is a polyethersulfone membrane.

[0071] Example 4

[0072] This embodiment provides a magnetic membrane synergistic ultrafiltration system, which differs from Embodiment 1 in that the mass ratio of FeCo to BN in the FeCo-BN soft magnetic composite particles is 1:1.3, and the FeCo-BN concentration is 10wt%.

[0073] Example 5

[0074] This embodiment provides a magnetic membrane synergistic ultrafiltration system, which differs from Embodiment 1 in that the mass ratio of FeCo to BN in the FeCo-BN soft magnetic composite particles is 1:0.8, and the FeCo-BN concentration is 15wt%.

[0075] Comparative Example 1

[0076] This embodiment provides a magnetic membrane-coordinated ultrafiltration system, which differs from Embodiment 1 in that the first magnetic field device only includes a first-stage permanent magnet 2, wherein the magnetic induction intensity of the first-stage permanent magnet 2 is 500-1500 Gs.

[0077] Comparative Example 2

[0078] This embodiment provides a magnetic membrane synergistic ultrafiltration system, which differs from Embodiment 1 in that the membrane material is a polyethersulfone membrane and does not embed soft magnetic composite microparticles.

[0079] Experimental verification

[0080] 1. Under the same influent turbidity (270-350 NTU), the water was pretreated using Example 1 (gradient magnetic field device) and Comparative Example 1 (single-stage permanent magnet). The characteristics of the magnetized water were measured using a Zeta potential analyzer and particle size change. The results are shown in Table 1.

[0081] Table 1. Changes in Zeta potential and particle size under different pretreatment conditions

[0082]

[0083] As shown in Table 1, the Zeta potential changes are as follows: In Example 1, the gradient magnetic field effectively reduces the absolute value of the pollutant surface potential through controllable magnetic force, weakening the electrostatic repulsion between particles, and significantly increasing it from -25mV to -12.5mV, promoting micro-agglomeration while avoiding excessive flocculation. In contrast, the Zeta potential under the single-intensity magnetic field (500-1500Gs) of Comparative Example 1 only changes from -25mV to -20.5mV, with a limited decrease in the absolute value of the potential, indicating that its ability to neutralize the surface charge of pollutants is weak and it is difficult to effectively overcome the electrostatic repulsion barrier between particles, resulting in poor pre-agglomeration effect.

[0084] Regarding particle size changes, the above conclusions were further confirmed. After pretreatment with the gradient magnetic field in Example 1, the volume average particle size of pollutants in the water increased from the initial 2.5 μm to 18.7 μm, forming magnetic flocs of moderate size and concentrated distribution. This gradually increasing magnetic field environment provided the optimal pathway for pollutants, achieving precise control over floc size. In contrast, the average particle size of pollutants after pretreatment in Comparative Example 1 only increased to 5.8 μm, and the particle size distribution range was wider. Its single magnetic field strength could not provide the gradual aggregation driving force, resulting in smaller floc size and looser structure, making it easier to penetrate the surface filter cake layer during the subsequent membrane separation stage, causing deep blockage of the membrane pores.

[0085] 2. Measure the membrane flux with different FeCo-BN ratios and concentrations.

[0086] To verify the synergistic effect of the ratio and concentration of soft magnetic composite microparticles on membrane separation performance, continuous filtration experiments were conducted on the membrane modules prepared in Examples 1-4 and Comparative Example 2 under the same influent water quality (turbidity 270-350 NTU), and their membrane flux was recorded. The results are shown in Table 2.

[0087] Table 2 Measurement results under different FeCo-BN ratios and concentrations

[0088]

[0089] As shown in Table 2, Example 1 is the optimal embodiment. In Example 1, the synergistic optimization of the mass ratio (1:1.6) and concentration (15wt%) of the FeCo-BN soft magnetic composite particles achieves the best balance in system performance. This indicates that Example 1 effectively slows down the membrane fouling process and extends the membrane module maintenance cycle while ensuring high throughput.

[0090] Comparing Example 1 with Examples 3 and 5, it can be seen that when the proportion of BN increases to 1.6 times, its high dielectric properties enhance the wettability of the membrane surface and reduce the adhesion of pollutants. Insufficient BN content cannot effectively disperse pollutants, and an excessively high FeCo ratio leads to an excessively strong magnetic dipole effect, forming a magnetic chain structure between particles and blocking the membrane pores.

[0091] A comparison of Examples 1 with Examples 3 and 4 shows that when the particle concentration is moderate, the magnetic response and dispersibility reach a balance. High concentration leads to particle aggregation, forming a local high magnetic response zone, which increases the flux decay rate. Too low a concentration leads to insufficient magnetic response, reduced pollutant retention efficiency, and the lowest stable flux.

[0092] Comparing Comparative Example 2 with Example 1, it can be seen that although Comparative Example 2 has the highest initial flux, the random deposition of pollutants leads to rapid contamination, and the stable flux is only 21.2 L / m²·h.

[0093] 3. After continuous operation, measure COD.

[0094] To comprehensively evaluate the continuous removal capacity of the magnetic membrane synergistic ultrafiltration system of the present invention for organic pollutants and the system stability in actual operation, after completing the above continuous filtration experiment, the chemical oxygen demand (COD) of the system influent and effluent water and the membrane surface flushing liquid was analyzed, and the results are shown in Table 3.

[0095] Table 3 Measurement results of COD content

[0096]

[0097] As shown in Table 3, Example 1 exhibits the best and most stable organic pollutant removal efficiency. The average COD removal rate reaches 92.5%, and the COD concentration in the flushing solution collected from the membrane surface after backwashing is as high as 580 mg / L. This demonstrates that the system intercepts and enriches a large amount of organic matter on the membrane surface, rather than allowing it to penetrate the membrane pores and deteriorate the effluent quality. By efficiently backwashing with magnetized water, the organic matter is concentrated and discharged, thereby restoring the membrane's original performance.

[0098] The COD removal rates of Examples 3 and 4 were 91.0% and 88.5%, respectively. The effluent quality of Example 5 fluctuated greatly, with an average COD of 52 mg / L and a removal rate of only 82.0%. Due to insufficient BN protection, FeCo corrosion may have catalyzed the decomposition of organic matter (producing small molecule organic matter that easily penetrates the membrane pores), resulting in a comprehensive decline in its ability to retain and enrich organic matter.

[0099] The COD removal rate of Comparative Example 1 was 83.8%. Its flushing solution COD concentration was 400 mg / L. This confirms that a weaker pretreatment magnetic field cannot form sufficiently large magnetic flocs, allowing some small molecules or colloidal organic matter to directly reach the membrane surface and cause deeper clogging, affecting both the effluent quality and the cleaning difficulty.

[0100] Comparative Example 2 performed the worst, with a COD removal rate of only 75.0%. Its flushing solution COD concentration was only 300 mg / L. This indicates that traditional ultrafiltration membranes primarily rely on sieving to remove organic matter; a large amount of organic matter cannot be effectively retained and permeates the membrane pores. Simultaneously, the fouling layer formed on the membrane surface is loose and easily partially washed away, failing to achieve efficient enrichment and centralized removal of pollutants.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A magnetic membrane-assisted ultrafiltration system, characterized in that, Includes a magnetic coupling unit and a membrane separation unit (4); The membrane separation unit (4) includes a membrane material in which soft magnetic composite microparticles are embedded. The magnetic coupling unit includes a first magnetic field device and a second magnetic field device. The first magnetic field device is located near the water inlet end of the membrane separation unit (4), and the second magnetic field device is located near the backwash end of the membrane separation unit (4).

2. The magnetic membrane-assisted ultrafiltration system as described in claim 1, characterized in that, The soft magnetic composite microparticles are FeCo-BN soft magnetic composite microparticles, with a mass ratio of FeCo to BN of 1:0.5-2, and a particle size of 0.1-2 μm.

3. The magnetic membrane-assisted ultrafiltration system as described in claim 2, characterized in that, The concentration of soft magnetic microparticles in the membrane material is 10-20 wt%.

4. The magnetic membrane-assisted ultrafiltration system as described in claim 1, characterized in that, The membrane material is a polysulfone or polyethersulfone ultrafiltration membrane with an asymmetric structure, which is integrally composed of a macroporous support layer and a thin dense separation layer. The thickness of the macroporous support layer is 100-200 μm, and the thickness of the thin-layer dense separation layer is 0.1-1.0 μm.

5. The magnetic membrane-assisted ultrafiltration system as described in claim 1, characterized in that, The membrane separation unit (4) has an inlet pipe at its inlet end, and the first magnetic field device covers the outer wall of the inlet pipe; the membrane separation unit (4) has a backwash pipe at its backwash end, and the second magnetic field device covers the outer wall of the backwash pipe; the membrane separation unit (4) has an outlet pipe at its outlet end.

6. The magnetic membrane-assisted ultrafiltration system as described in claim 5, characterized in that, The first magnetic field device includes a first-stage permanent magnet (2) and a second-stage permanent magnet (3), wherein the magnetic field strength inside the second-stage permanent magnet (3) is greater than the magnetic field strength inside the first-stage permanent magnet (2); The first-stage permanent magnet (2) is close to the end of the water to be treated, and the second-stage permanent magnet (3) is close to the membrane separation unit (4). The water to be treated passes through the first-stage permanent magnet (2) and the second-stage permanent magnet (3) with increasing magnetic field strength in sequence. The magnetic field strength of the first-stage permanent magnet (2) is 2500-3000Gs, and the magnetic field strength of the second-stage permanent magnet (3) is 3500-4000Gs.

7. The magnetic membrane-assisted ultrafiltration system as described in claim 6, characterized in that, The first-stage permanent magnet (2) and the second-stage permanent magnet (3) are both tubular hollow permanent magnets, and the inner diameter of the hollow permanent magnet matches the outer diameter of the water inlet pipe.

8. The magnetic membrane-assisted ultrafiltration system as described in claim 6, characterized in that, The second magnetic field device includes a coil (8) wound around the outside of the backwash water pipe and a magnetized water generator (9) connected to both ends of the coil (8). The winding density of the coil (8) is 10-20 turns / cm.

9. The magnetic membrane-assisted ultrafiltration system as described in claim 1, characterized in that, The ultrafiltration system also includes a monitoring device (5); The monitoring device (5) is used to monitor the membrane flux and transmembrane pressure difference of the membrane separation unit (4).

10. An ultrafiltration method for a magnetic membrane-coordinated ultrafiltration system, characterized in that, The ultrafiltration system employing the magnetic membrane synergy as described in any one of claims 1-9 includes the following steps: S1: In the water pretreatment stage, the water to be treated flows through the first magnetic field device at the water inlet end, causing it to be subjected to a magnetic field. S2: In the membrane separation stage, the pretreated water flows into the membrane separation unit (4) and undergoes ultrafiltration separation in the membrane material of soft magnetic composite microparticles to obtain purified water; S3: Backwashing and regeneration stage. Backwash water flows through the second magnetic field device at the backwash end, causing the backwash water to be subjected to its magnetic field and backwashing the membrane separation unit (4).

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