An apparatus for filtering charged particles using electrokinetic

Abstract

An apparatus for filtering charged particles using electrohydrodynamics is disclosed. The apparatus includes a main channel into which a fluid containing charged particles is introduced and flows, a first electrode disposed to allow fluid flow within the main channel, and an ion exchange membrane disposed downstream of the first electrode and having a plurality of pores into which the fluid filtered of the charged particles is discharged.

Description

Technology Field

[0001] The present invention relates to a filtration device, and more specifically, to a filtration device utilizing electrohydrodynamics. More specifically, and not limited thereto, to an electrohydrodynamic-assisted filtration technology for rapidly and efficiently removing charged particles, such as microplastics, from water. Background Technology

[0003] Water treatment is considered very important across a wide range of fields, including the treatment of sewage and industrial wastewater. While the substances to be filtered contained in the fluids being treated possess various properties, filtration of charged particles may be required as one of them. Plastics can be exemplified as a typical charged particle to be filtered.

[0004] In recent years, plastic pollution has become one of the major environmental issues, and related concerns are growing. As plastic use continues to increase, annual global plastic production currently stands at approximately 400 million tons and is expected to reach about 800 million tons by 2050. The problem is that plastic does not decompose. Because it takes at least decades to hundreds of years to completely break down, used plastic continues to accumulate in ecosystems. Meanwhile, discarded plastic waste breaks down into various forms of small fragments through mechanical or chemical processes; fragments smaller than 5 mm are called microplastics (MP). Due to their chemical stability, microplastics flow into the entire aquatic environment, including rivers and oceans, and remain floating in the water for extended periods. As a result, not only aquatic life but also humans and animals are inevitably exposed to MP, increasing ecological and environmental risks.

[0005] Furthermore, due to their high specific surface area and hydrophobicity, MP can easily adsorb organic chemical pollutants such as bacteria, heavy metals, and compounds; therefore, if humans ingest contaminated MP through the food chain, it can have harmful effects on human health. In particular, extremely small plastic fragments smaller than 1 μm, known as nanoplastics (NP), can enter cells or tissues, cause inflammation, and adversely affect cellular activity.

[0006] Among various engineered separation and decomposition technologies, membrane filtration (MF) is currently considered a promising strategy for successfully removing MP from underwater environments. Based on size exclusion mechanisms, MP of various sizes can be effectively removed via MF simply by adjusting the pore size of the membrane filter. Recent studies indicate that MF demonstrates effective MP removal performance compared to conventional water treatment processes (e.g., rapid sand filtration, dissolved air filtration, oxidation ditch methods, etc.). Various types of membranes have been developed for MP removal as effective alternatives to conventional polymer membranes.

[0007] However, despite the excellent removal performance of MP, MF presents a problem in that it is not suitable for reliable industrial applications due to the inherent trade-off between removal efficiency and flow rate. Generally, when a pressure of several bar is applied to a membrane filter with an average pore size of about 1 μm, hundreds of liters per liter -2 h -1 A flow rate is achieved. However, if a membrane filter with a finer pore size is used to separate finer particles, the pressure drop across the membrane becomes more severe, requiring significantly higher energy consumption to achieve the same level of flow rate.

[0008] Along with the trade-off between removal efficiency and flow rate, membrane fouling is an unavoidable challenge in MF. Membrane fouling causes a significant reduction in flow rate and affects the quality of the water produced, ultimately leading to various economic and operational problems. Furthermore, since fiber-type MP, the most dominant form of MP present in the aquatic environment, penetrates longitudinally into the small gaps or pores of the membrane filter, it is difficult to remove fiber-type MP using MF.

[0009] Therefore, in order to completely eliminate MP in an underwater environment, a practical approach capable of solving these problems is required. Prior art literature

[0011] Korean Patent Publication No. 10-2023-0037519 ("Filtering device and filtration method for continuously treating wastewater without backwashing process", Seyoung ENP Co., Ltd.) The problem to be solved

[0012] One objective of the present invention to solve the aforementioned problems is to provide an electrohydrodynamic charged particle filtration device that can filter out substances that are difficult to remove in conventional membrane filtration methods, such as those having a fine size or fiber shape, by filtering charged particles using electrohydrodynamics, and can solve the problem of membrane fouling.

[0013] Another objective of the present invention to solve the aforementioned problems is to provide a charged particle filtration device using electrohydrodynamics that can achieve high removal efficiency for the material to be filtered by using electrohydrodynamics for filtration, while preventing excessive energy consumption for reducing or maintaining the flow rate.

[0014] However, the problem to be solved by the present invention is not limited thereto and may be expanded in various ways without departing from the spirit and scope of the present invention. means of solving the problem

[0016] A charged particle filtration device according to one embodiment of the present invention for achieving the aforementioned purpose is a device for filtering charged particles using electrohydrodynamics, and may include: a main channel into which a fluid containing charged particles is introduced and flows; a first electrode disposed to allow fluid flow inside the main channel; and an ion exchange membrane disposed downstream of the first electrode and having a plurality of pores into which the fluid in which the charged particles have been filtered is discharged.

[0017] According to one aspect, the first electrode and the ion exchange membrane may be configured to generate an electric field between the first electrode and the ion exchange membrane.

[0018] According to one aspect, a polarity different from that of the charged particle to be filtered is applied to the first electrode, and the ion exchange membrane is an ion exchange membrane for ions with a polarity different from that of the charged particle to be filtered, and a second electrode with the same polarity as that of the charged particle to be filtered may be connected to the ion exchange membrane.

[0019] According to one aspect, an ion depletion region may be formed in the upstream direction of the ion exchange membrane to block the movement of charged particles into the pores of the ion exchange membrane.

[0020] According to one aspect, the ion depletion region may be formed based on ion concentration polarization (ICP).

[0021] According to one aspect, the first electrode may include an additional ion exchange membrane having a plurality of pores that allow fluid flow.

[0022] According to one aspect, the ion depletion region may allow an electrophoretic force to act on the charged particle.

[0023] According to one aspect, the charged particles may be configured to move in a direction different from the flow of the fluid according to the drag force and the electrophoretic force according to the flow of the fluid.

[0024] According to one aspect, the ion depletion region may be configured to include sub-ion depletion regions corresponding to each of the plurality of pores provided in the ion exchange membrane, and to have a fluid flow direction cross-sectional area greater than or equal to a predetermined first area by having the plurality of sub-ion depletion regions.

[0025] According to one aspect, the charged particle filtration device may further include a porous layer disposed upstream of the ion exchange membrane inside the main channel and configured to filter particles of a predetermined first size or larger among the particles contained in the fluid.

[0026] According to one aspect, the porous layer may limit the electric convection induced in the ion depletion region to a predetermined size or smaller, thereby allowing the ion depletion region to have a fluid flow direction cross-sectional area greater than or equal to a predetermined second area.

[0027] According to one aspect, the electric convection may be induced by electroosmotic instability.

[0028] According to one aspect, the electric convection may include three-dimensional helical vortex pairs.

[0029] According to one aspect, the porous layer may be formed of polyester microfibers.

[0030] According to one aspect, it may further include a dome-shaped cap configured to fix the porous layer while allowing fluid flow.

[0031] According to one aspect, the dome-shaped cap can cause the ion depletion region to have a convex shape by bending the upper boundary of the porous layer.

[0032] According to one aspect, the filtration efficiency of the charged particle filtration device may vary depending on at least one of the flow rate of the fluid passing through the filtration device, the voltage applied to the first electrode and the ion exchange membrane, the zeta potential of the charged particle, or the type of the charged particle.

[0033] According to one aspect, the charged particle filtration device can be used to filter a fluid that has passed through a reverse osmosis-based filtration device.

[0034] According to one aspect, it may further include a branch channel configured to branch off from the main channel upstream of the ion exchange membrane and discharge the charged particles.

[0035] According to one aspect, the charged particles can be transported to the branch channel by the resultant force of the electrophoretic force of the ion depletion region formed upstream of the ion exchange membrane and the drag force due to the fluid flow. Effects of the invention

[0037] The disclosed technology may have the following effects. However, this does not mean that a specific embodiment must include all of the following effects or only the following effects; therefore, the scope of the rights of the disclosed technology should not be understood as being limited by this.

[0038] According to the electrohydrodynamic charged particle filtration device of one embodiment of the present invention described above, by filtering charged particles using electrohydrodynamics, it is possible to filter out substances that are difficult to remove in conventional membrane filtration methods, such as those having a fine size or fiber shape, and has the advantage of solving membrane fouling problems.

[0039] In addition, by utilizing electrohydraulics for filtration, high removal efficiency for the substances to be filtered can be achieved while preventing a reduction in flow rate or excessive energy consumption required to maintain the flow rate. Brief explanation of the drawing

[0041] Figure 1 is a schematic diagram of an electrohydrodynamic assisted filtration system for removing charged particles from a fluid. Figure 2 shows the dynamic relationship of charged particles located at the edge and center of the main channel, respectively. Figure 3 is a schematic diagram showing the formation of ion depletion regions in an ion exchange membrane alone and in a combination of an ion exchange membrane and a porous layer. FIG. 4 illustrates a model experimental apparatus for a filtration device according to one embodiment of the present invention. Figure 5 is an exploded view of the configuration showing the arrangement of the main device components. Fig. 6 is a side view of the experimental apparatus of Fig. 4. Figure 7 shows an ion exchange membrane with a microhole array and a porous layer covered with a dome-shaped cap. Figure 8 shows the assembled experimental apparatus. Figure 9 shows a comparison of microplastic removal performance between mathematical analysis and experimental results. Figure 10 illustrates three different filtration conditions distinguished by the voltage-flow rate relationship. Figure 11 shows photographs and microscopic images of the feed and filtrate of sampled PE microspheres according to voltage change, and the removal efficiency of PE microspheres according to voltage. Figure 12 shows photographs and microscopic images of the feed and filtrate of sampled PE microspheres according to changes in flow rate, and the removal efficiency of PE microspheres according to flow rate. Figure 13 shows the particle size distribution of the feed and filtrate of PE microspheres according to voltage change. Figure 14 shows the particle size distribution of the feed and filtrate of PE microspheres according to changes in flow rate. Figure 15 shows photographs and microscopic images of the feed and filtrate under various pH conditions according to voltage change, and the removal efficiency of PS microspheres under various pH conditions according to voltage. Figure 16 shows photographs and microscopic images of the feed and filtrate under various pH conditions according to changes in flow rate, and the removal efficiency of PS microspheres under various pH conditions according to flow rate. Figure 17 shows photographs and microscopic images of the feed and filtrate for sampled PE, PS, and PP microspheres according to voltage change, and the removal efficiency of PE, PS, and PP microspheres according to voltage. Figure 18 shows photographs and microscopic images of the feed and filtrate for sampled PE, PS, and PP microspheres according to changes in flow rate, and the removal efficiency of PE, PS, and PP microspheres according to flow rate. Figure 19 shows photographs and microscopic images of the feed and filtrate for sampled PEST, acrylic, and nylon clumps according to voltage change, and the removal efficiency of PEST, acrylic, and nylon clumps according to voltage. Figure 20 shows photographs and microscopic images of the feed and filtrate for sampled PEST, acrylic, and nylon clumps according to changes in flow rate, and the removal efficiency of PEST, acrylic, and nylon clumps according to flow rate. Specific details for implementing the invention

[0042] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail.

[0043] However, this is not intended to limit the invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0044] Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. Such terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[0045] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0046] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to specify the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0047] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0048] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings. In order to facilitate an overall understanding of the present invention, the same reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0050] outline

[0051] Hereinafter, for the convenience of explanation, microplastics may be used as the standard for examples of charged particles in this description; however, it will be readily understood by those skilled in the art that the subject of filtration according to the technical concept of the present invention is not limited to plastics and any charged particle may be the subject of filtration.

[0053] Among engineered decomposition and separation methods for removing charged particles, such as microplastics (MP), in underwater environments, membrane filtration (MF), based on a size exclusion mechanism, has demonstrated the potential to effectively process charged particles of various sizes ranging from sub-microns to several millimeters. However, questions have been raised regarding its practical applicability due to the trade-off between inherent efficiency and flow rate, as well as issues with MF related to membrane fouling.

[0055] Indefinitely but more specifically, the present invention provides a method for removing charged particles by integrating electrohydrodynamic support into physical filtration, thereby overcoming the trade-off between the fundamental filtration efficiency and flow rate of MF and being free from membrane fouling-related problems. A filtration method according to one aspect of the present invention is based on electrohydrodynamic control of charged particles based on ion concentration polarization (ICP) and can effectively block the downstream movement of charged particles by inducing an electric force barrier in a fluid channel system.

[0056] Since small charged particles that pass through a physical filter grid are electrically screened, the trade-off between efficiency and flow rate is significantly mitigated in electrohydrodynamic-assisted filtration systems, enabling high removal efficiencies of over 99.9% and a flow rate of 10,000 L / m³ without the use of microfilters. -2 h -1 The flow rate can be achieved simultaneously. Since the filtration mechanism according to one aspect relies entirely on the electrophoretic mobility of charged particles, consistent filtration performance can be realized for the same type of charged particles regardless of size, shape, and chemical composition. In addition, due to the nature of the force-based charged particle filtration mechanism, it is not affected by the concentration of charged particles.

[0058] Below, the theoretical background of the filtration method using a scalable electrohydrodynamic system according to one aspect of the present invention is described in detail. The basic operating principle of the system according to one aspect of the present invention is explained through a parameter study for specific control variables (voltage and flow rate). As examples of charged particles, polyethylene microspheres of various sizes ranging from hundreds of nanometers to hundreds of micrometers are used in the parameter study to thoroughly verify the filtration mechanism according to the embodiments of the present invention. Subsequently, the effect of the electrophoretic mobility of charged particles on system performance is explained. In addition, the filtration performance of the system according to one aspect of the present invention is systematically evaluated for various types and forms of MP most frequently found in underwater environments. Three types of MP (polyethylene, PE; polystyrene, PS; polypropylene, PP) and three types of fiber MP (polyester, PEST; acrylic, nylon) were adopted as exemplary model MPs.

[0060] Electrohydraulic auxiliary filtration system

[0061] FIG. 1 is a schematic diagram of an electrohydrodynamic assisted filtration system for removing charged particles from a fluid. Hereinafter, the filtration system may also be referred to as a "filtration device." Hereinafter, the operating principle of an electrohydrodynamic assisted filtration system according to one aspect of the present invention will be explained in more detail with reference to FIG. 1.

[0062] The inventors of this invention devised an electrohydrodynamic-based filtration system based on the fact that charged particles, such as microplastics, actually possess a surface charge when suspended in an electrolyte. The system may be implemented as a hybrid filter system that assists electrohydrodynamics in physical filtration. As illustrated in FIG. 1, a system according to one embodiment may be composed of a main channel (100) and buffer channels (110, 120), and a first electrode (210) and an ion exchange membrane (220) may be disposed in the main channel (100). The first electrode (210) and the ion exchange membrane (220) may generate an electric field by allowing current between the first electrode and the ion exchange membrane.

[0063] In addition, more specifically, as illustrated exemplarily in FIG. 1, a filtration device (1000) utilizing electrokinetics may be provided according to one embodiment of the present invention. A fluid (10) containing charged particles, such as microplastics, may be introduced into the inlet of a buffer channel (110), and a fluid (90) in which the charged particles have been filtered may be discharged through a main channel (100) and through the outlet of a buffer channel (120). According to one aspect, the main channel (100) may represent a main filtration path in which the fluid containing charged particles is introduced and the fluid (90) in which the charged particles have been filtered is discharged. That is, the main channel (100) may provide a path in which the fluid containing charged particles is introduced and flows.

[0064] Inside the main channel (100), a first electrode (210) and an ion exchange membrane (220) may be included to allow fluid flow. The ion exchange membrane (220) may be configured to have a plurality of pores (221) through which fluid in which charged particles have been filtered is discharged, which are positioned downstream of the first electrode (210).

[0065] As described above, the first electrode (210) may be arranged to allow fluid flow. For example, as illustrated exemplarily in FIG. 1 or FIG. 5, the first electrode (210) may allow fluid flow by having a flat plate shape and having a plurality of pores (211) into which a fluid containing charged particles is introduced. Additionally, according to one aspect, such a first electrode may be an ion exchange membrane having a plurality of pores (211) that allow fluid flow. For example, the first electrode (210) formed as an ion exchange membrane in this description may be referred to as an "additional ion exchange membrane (210)" to distinguish it from the ion exchange membrane (220). However, it should be understood that the first electrode (210) according to the present description is not limited to such a flat electrode or ion exchange membrane, and any shape that can form an electric field opposite the ion exchange membrane (220) while allowing fluid flow inside the main channel, such as a rod shape or a mesh shape, may be adopted.

[0066] Referring again to FIG. 1, the ion exchange membrane (220) is positioned downstream of the first electrode (210), and the ion exchange membrane (220) may be provided with a plurality of pores (221) through which fluid with filtered charged particles is discharged. For example, microholes (211) may be formed in the first electrode (210) and microholes (221) may be formed in the ion exchange membrane (220) to facilitate fluid flow within the main channel. The first electrode (210) and the ion exchange membrane (220) may be configured to physically allow fluid flow within the main channel (100) while simultaneously generating current flow between the first electrode (210) and the ion exchange membrane (220).

[0067] A branch channel (900) may be introduced in the middle of the main channel (100) for the purpose of continuously discharging charged particles ejected from the electric force barrier to minimize the accumulation of charged particles in the physical filter (400). Filtered charged particles may be discharged through the outlets (30-1, 30-2) of the branch channel (900). According to one aspect, the branch channel (900) may be configured to branch off from the main channel (100) between the first electrode (210) and the ion exchange membrane (220) to discharge charged particles. According to one aspect, the charged particles may be transported to the branch channel (900) by an ion depletion region (300) formed upstream of the ion exchange membrane (220), which will be described in detail below. According to one aspect, the branch channel (900) may represent a path through which filtered charged particles are discharged branched off from the main channel (100).

[0068] According to one embodiment of the present invention, a polarity different from that of the charged particle to be filtered is applied to the first electrode (210), and the ion exchange membrane (220) is an ion exchange membrane for ions with a polarity different from that of the charged particle to be filtered, and the ion exchange membrane (220) may be configured to be connected to a second electrode with the same polarity as that of the charged particle to be filtered. That is, the polarity of the voltage applied to the first electrode (210) and the ion exchange membrane (220), respectively, and / or the type of the ion exchange membrane (220), such as a cation exchange membrane or an anion exchange membrane, may be determined according to the polarity of the charged particle to be filtered.

[0069] FIG. 1 illustrates a polarity connection relationship for negatively charged microplastics as a non-limiting example. According to one embodiment for filtration of charged particles having a negative charge, such as microplastics, as illustrated in FIG. 1, a positive electrode may be applied to a first electrode (210), and a negative electrode may be connected to an ion exchange membrane (220). That is, the first electrode (210) may be an electrode to which a positive electrode is applied, or may be formed of an electrode material connected to a positive electrode, and the negative electrode may be connected to an ion exchange membrane (220) on the downstream side, and the ion exchange membrane (220) may be a cation exchange membrane (CEM). According to one aspect, the first electrode (210) may also be a cation exchange membrane (CEM) having a plurality of microholes (211), but it should be noted that it is not limited thereto. The inlet and outlet of the main channel (100) and the branch channel (900) can be electrically floating. In this configuration, ion concentration polarization (ICP) occurs on both sides of the ion exchange membrane due to the difference in ion mobility between the bulk solution and the nanochannel. As a result, an ion depletion region (300) can be formed in the upstream direction of the ion exchange membrane (220), in other words, in the direction toward the anode of the ion exchange membrane (220). That is, the ion depletion region can be formed based on ion concentration polarization.

[0070] An ion depletion region, which has almost no ions, is considered to have electrical resistance and acts as an electric force barrier that prevents the movement of ions. Thus, the ion depletion region (300) can block charged particles, such as microplastics, from moving into the pores (221) of the ion exchange membrane (220). More specifically, the ion depletion region (300) can cause an electrophoretic force to act on charged particles, such as microplastics. Thus, the charged particles can move in a direction different from the fluid flow due to the drag force and electrophoretic force along the fluid flow.

[0071] The transport behavior of charged particles in a fluid is governed by Stokes' law because the particle Reynolds number is very low (Re p ≪ 1). For example, when considering a spherical charged particle of anion, drag force and electrophoretic force mainly act on the charged particle, and the velocity component among these is given by the following mathematical formula.

[0073]

[0074]

[0075] Here, ρ is the particle density, ρ0 is the fluid density, V is the particle volume, g is the acceleration due to gravity, m is the particle mass, η is the fluid kinematic viscosity, and r is the Stokes radius of the particle. Also, ε0 is the permittivity of free space, and ε r ε is the relative permittivity, ζ is the zeta potential, and E is the electric field. Here, it can be assumed that the drag velocity is equal to the fluid velocity.

[0076]

[0078] Here, Q is the flow velocity and A is the cross-sectional area of ​​the channel. Relaxation time (τ) of micrometer-sized particles in a fluid p ~10-4 -10 -2 Since the time interval (seconds) is very short, it can be assumed that the drag velocity is equal to the fluid velocity. Consequently, a charged particle approaching the ion depletion region has a forward drag velocity component, a drag velocity component in the direction of the branching channel, and a reverse electrophoretic velocity component (its direction is perpendicular to the tangent of the ion depletion region boundary).

[0079] According to one aspect of the present invention, a slightly convex ion depletion region (300) as shown in FIG. 1 is induced so that the direction of the electrophoretic velocity is formed obliquely to the direction of the drag velocity, thereby setting the direction of the resulting velocity to be in contact with the ion depletion region. As a result, charged particles moving toward the center of the main channel (100) continuously slide toward the branch channel (900) before entering the physical filter (400), thereby mitigating the accumulation of charged particles in the filter and enabling stable and long-term system operation. FIG. 2 shows the dynamic relationship between a charged particle (1a) located at the edge of the main channel and a charged particle (1b) located in the center.

[0080] For example, charged particles such as microplastics can exhibit rotational and lateral motions as well as inertial motion because they actually have arbitrary shapes such as plates, rods, and discs. However, this type of particle motion is ~10 1 -10 2 Since it is mainly observed at high particle Reynolds numbers, it can be ignored in systems according to the embodiments of this description that exhibit low particle Reynolds numbers.

[0082] Electrohydrodynamic systems, which offer the advantage of easily and accurately manipulating microparticles, can be used in various microfluidic field diagnostic applications. However, unfortunately, due to two fundamental upscaling issues, the channel size of electrohydrodynamic systems has been limited to the microscale, preventing their application in environmental applications requiring high capacity.

[0083] The first problem is generating an electric field (ion depletion region) of uniform direction and intensity across the entire width of the channel. In typical microfluidic H-type electrohydrodynamic systems, the channel size is limited to several hundred micrometers because the ion depletion region cannot be extended uniformly beyond the millimeter scale across the channel width. Consequently, while the direction of drag velocity and electrophoretic velocity is completely opposite in microchannels, it becomes oblique or even perpendicular in wide channels, leading to a problem of reduced filtration efficiency.

[0084] According to one aspect of the present invention, such problems can be overcome by introducing an ion exchange membrane having microholes. For example, the ion depletion region (300) according to one aspect may be configured to have a fluid flow direction cross-sectional area greater than a predetermined first area by including sub-ion depletion regions corresponding to each of the plurality of pores (221) provided in the ion exchange membrane (220). More specifically, the ion exchange membrane having microholes may act as a parallel microchannel connected by nanochannels, and local ion depletion regions generated in each microchannel may be combined to form an ion depletion region that is uniformly extended in a uniform direction across the entire channel width. Thus, unlike conventional microfluidic electrohydrodynamic systems where the channel size was limited to hundreds of micrometers, the ion exchange membrane having microholes according to one aspect of the present invention may be configured so that the ion depletion region (300) has a fluid flow direction cross-sectional area greater than a predetermined first area, for example, a fluid flow direction cross-sectional area greater than a milliscale.

[0085] The second problem is to suppress electric convection (e.g., helical vortex pairs) induced by electroosmotic instability (EOI), which hinders the formation of a well-dispersed electric force barrier in a wide channel. FIG. 3 is a schematic diagram showing the formation of ion depletion regions in an ion exchange membrane alone and in an ion exchange membrane-porous layer combination, respectively. As the channel size increases, an excessive current is transmitted by the EOI, which can generate active electric convection near the ion exchange membrane. In a filtration device according to one aspect of the present invention, if the porous layer (400) is not provided (300a), charged particles entering through helical vortex pairs generated near the ion exchange membrane with microholes can travel along the streamlines and leak through the membrane due to electric convective drag as shown in FIG. 3. According to one aspect of the present invention, the above problem can be solved by introducing a porous layer that acts as a physical filter to filter out materials having a relatively large size, such as large plastic pieces. According to one aspect of the present invention, in addition to the configuration for filtration using electrohydrodynamics, a porous layer (400) capable of performing the role of a physical filter may be further provided. If the porous layer (400) is larger than the pores of the porous layer (400), it can perform filtration of not only charged particles but also particles without charge. Furthermore, as described below, it can also perform the role of suppressing electric convection in the ion depletion region (300) for electrohydrodynamic-based filtration.

[0086] For example, a filtration device according to one embodiment of the present invention may further comprise a porous layer (400) disposed upstream of an ion exchange membrane (220) and configured to filter particles of a predetermined first size or larger among the particles contained in the fluid. In the present invention, the porous layer may be referred to as a 'microstructure'. The porous layer or microstructure (400) disposed upstream of the ion exchange membrane (220) may restrict electric convection to a micro-scale shape so that the overcurrent mechanism is converted from EOI to electroosmotic flow (see 300b in FIG. 3). In this way, a uniform and stable ion depletion region can be realized even within a wide channel of centi-scale or larger. That is, the porous layer (400) according to one aspect of the present invention may limit the electric convection induced in the ion depletion region to a predetermined size or smaller, so that the ion depletion region has a fluid flow direction cross-sectional area greater than or equal to a predetermined second area. Here, the second area may have any value and may be the same as or different from the first area. For example, the second area may mean a large area greater than or equal to the centimeter scale. According to one aspect, the porous layer (400) may be formed of polyester microfiber, but is not limited thereto.

[0088] Examples

[0089] FIG. 4 illustrates a model experimental apparatus for a filtration device according to one embodiment of the present invention, FIG. 5 is an exploded view of the configuration showing the arrangement of major device components, and FIG. 6 is a side view of the experimental apparatus of FIG. 4. The configuration of the experimental apparatus for a filtration device according to one aspect of the present invention is described in detail through FIG. 4 to FIG. 6.

[0090] The device may largely consist of an upper frame (510) and a lower frame (540) containing electrode buffer channels, and an intermediate frame (530) containing branch channels. A single hole, for example, with a diameter of 1 cm, may be formed in the center of each frame, and this hole may be assembled to form a main channel. A first electrode (210) and an ion exchange membrane (220) are located between the intermediate frame (530) and the upper frame (510) / lower frame (540) and have a plurality of voids (211, 221). The first electrode (210) and the ion exchange membrane (220) allow fluid flow while allowing current to flow, thereby preventing potential damage to the main channel due to byproducts of the electrode reaction. An elastic silicone gasket (521, 523, 525) may be laminated with the first electrode (210) to prevent fluid leakage between contact surfaces during device operation. For example, a plurality of silicone gaskets (521, 523, 525) may be provided between the upper frame (510) and the middle frame (530). For example, the first electrode (210) may be placed in the middle silicone gasket (523), but is not limited thereto.

[0091] FIG. 7 illustrates an ion exchange membrane having a microhole array and a porous layer covered with a dome-shaped cap. For the movement of charged particles and a uniform flow distribution of the main channel, microholes (211, 221) with a diameter of, for example, 400 μm may be densely formed in the first electrode (210) and / or the ion exchange membrane (220). A porous layer (400) or microstructure, which may be composed of, for example, PEST microfibers, may be installed in the central hole of the intermediate frame (530) to filter out relatively large particles while simultaneously suppressing electric convection to a predetermined level or lower.

[0092] According to one aspect, a dome-shaped cap (410) configured to secure the porous layer (400) while allowing fluid flow may be disposed upstream of the porous layer (400). For example, the dome-shaped cap (410) may have a plurality of openings to allow fluid flow. According to one aspect, the upper boundary of the porous layer (400) may be formed slightly rounded using the dome-shaped cap (410) to induce a convex ion depletion region. More specifically, the dome-shaped cap (410) may cause the ion depletion region (300) to have a convex shape by bending the upper boundary of the porous layer (400). FIG. 8 shows an assembled experimental apparatus. The device components may be assembled, for example, by simple screw fastening, as shown in FIG. 8.

[0094] Experimental Example 1 - Investigation of MP Filtration Behavior According to the Relationship Between Voltage and Flow Rate

[0095] Figure 9 shows a comparison of microplastic removal performance between mathematical analysis and experimental results. Below, the removal performance of microplastics is described as an example of charged particles. However, it should be noted that the filtration target according to this description is not limited to microplastics.

[0096] The equilibrium point where the drag velocity and the electrophoretic velocity cancel each other out is illustrated in Fig. 9. As previously mentioned, a plastic piece entering an ion depletion region induced in a simple linear channel system possesses a forward drag velocity and a reverse electrophoretic velocity. The piece stops near the boundary of the ion depletion region where the two velocity components cancel each other out; this is called the equilibrium point. Based on the equilibrium point, if the drag velocity is dominant, the piece moves downward, and if the electrophoretic velocity is dominant, it moves upward. Therefore, the equilibrium point serves as a reference point for theoretically predicting the filtration behavior of MP (Micro Plastic). By setting Equations 2 and 3 to be identical, a simple linear relationship between voltage and flow velocity, indicated by the equilibrium point line in the plot shown in Fig. 9, is confirmed. Theoretically, based on this line, the region above the line is the non-filtration region (u) where MP passes through the electric barrier. drag > u ep ) and the lower region is a filtering region that achieves a removal efficiency of over 99.9% (at the boundary of the ion depletion region u drag = u ep ) is. Experimental results of MP filtration under various voltage-current conditions were obtained and displayed overlaid on a plot. Experimental conditions showing a removal efficiency of 99.9% or higher were indicated by circle symbols, and other conditions were indicated by cross symbols. The overlaid experimental results show a significant correlation with the mathematical analysis, which indicates that the hybrid filtration mechanism according to the embodiment of this description operated normally.

[0097] Figure 10 illustrates three different filtration conditions distinguished by the voltage-velocity relationship. Referring to Figure 10, three filtration conditions (conditions 1 to 3) distinguished by the voltage-velocity relationship are illustrated. When the electrophoretic velocity is relatively dominant compared to the drag velocity (condition 1, 1010), most of the MP is bounced off the outer boundary of the porous layer and electrohydrodynamically filtered, while some MP remains in the porous layer.

[0098] When the flow rate is slightly increased, the equilibrium point appears in the center of the porous layer (Condition 2, 1020). Under these conditions, large plastic pieces are physically filtered by the porous layer grid, while small plastic pieces that pass through the grid are electrohydrodynamically trapped at the equilibrium point. Since MP cannot pass through the electric barrier, a near-perfect removal efficiency of 100% is achieved in Conditions 1 and 2. As the flow rate increases further and the drag velocity overwhelms the electrophoretic velocity (Condition 3, 1030), the equilibrium point no longer appears in the porous layer, and the ion depletion region is suppressed near the cation exchange membrane (CEM)-electrolyte interface. Large plastic pieces are still physically filtered, but small plastic pieces penetrate the electric barrier and flow into the filtrate, resulting in lower removal efficiency.

[0099] Figure 11 shows photographs and microscopic images of the feed and filtrate of sampled PE microspheres according to voltage change, and the removal efficiency of PE microspheres according to voltage. Additionally, Figure 12 shows photographs and microscopic images of the feed and filtrate of sampled PE microspheres according to flow rate change, and the removal efficiency of PE microspheres according to flow rate. The scale bars in the photographs and microscopic images represent 6 mm and 500 μm, respectively, and the photograph inserted into the graph in Figure 12 is at 6,000 L m⁻¹. -2 h -1(Condition 1), 8,000 L m -2 h -1 (Condition 2), 12,000 L m -2 h -1 (Condition 3) shows various patterns of PE microsphere accumulation in the microstructure at the flow rate, and the scale bar indicates 4 mm.

[0100] Figure 11 shows the filtration performance of MP as a function of voltage, and Figure 12 shows the filtration performance of MP as a function of flow rate.

[0101] In Fig. 11, it can be seen that a removal efficiency of 27.6% is achieved even without the application of voltage, which is attributed entirely to the physical filtration of large particles and a few small particles. The effect of physical filtration is the same even under conditions where voltage is applied, supported by microscopic images of the filtrate showing the absence of large particles. 8,000 L m² -2 h -1 As the voltage increases at a constant flow rate, the electro-hydraulic support gradually increases, and the removal efficiency increases, reaching over 99.9% under voltage conditions of 150 V or higher.

[0102] In contrast, as shown in Fig. 12, removal efficiency decreases as the flow rate increases at a constant voltage of 200 V. A removal efficiency of 99.9% or higher is achieved at a maximum of 10,000 L / m³. -2 h -1 It is confirmed under flow velocity conditions of , and the flow velocity is 12,000 L m -2 h -1 and 14,000 L m -2 h -1 As it increases, they decrease to 88.7% and 76.0%, respectively. The aforementioned conditions 1 to 3 can be distinguished by the particle accumulation distribution in the porous layer formed during system operation. As can be seen in the inset image of Fig. 12, the particles are mainly 6,000 L m⁻¹ -2 h -1While it accumulates on the top surface of the porous layer at a flow rate, the accumulation area is 8,000 L m² -2 h -1 It extends to deeper locations at the flow velocity. This distribution behavior corresponds to Conditions 1 and 2 in Fig. 10, and consequently, the point of transition from Condition 1 to Condition 2 is 6,000 L m⁻¹. -2 h -1 At 8,000 L m -2 h -1 It can be expected to exist at a specific flow rate between them. The critical flow rate for the transition from Condition 2, where MP begins to pass through the electric barrier, to Condition 3 is 10,000 L / m³, where removal efficiency begins to decrease. -2 h -1 It can be easily inferred from this.

[0103] Meanwhile, Figure 12 illustrates photographs and microscopic images of the filtrate under various flow rate conditions. As with the filtrate under various voltage conditions, no large particles were observed due to physical filtration. The particle size distribution of PE microspheres in the filtrate under various voltage and flow rate conditions is shown in Figures 13 and 14, respectively. Specifically, Figure 13 shows the particle size distribution of PE microspheres in the feed and filtrate according to voltage changes, and Figure 14 shows the particle size distribution of PE microspheres in the feed and filtrate according to flow rate changes. Here, it was confirmed that particles with various size distributions were evenly dispersed in the feed. On the other hand, particles with a size distribution of 250-300 μm could not be observed in the plot, which is presumed to be because their number (or concentration) is lower than the analytical detection limit. With physical filtration (0V) alone, all particles larger than 50 μm were removed, and the proportion of particles larger than tens of micrometers was also significantly reduced. Under voltage conditions of 25 V, the proportion of particles with a size distribution of 20 to 45 μm decreased, while the proportion of particles smaller than 10 μm increased, which is presumed to be due to the assistance of electrohydrodynamics. As the voltage increased, the proportion of relatively large particles decreased, and the proportion of small particles increased. This pattern of change may be due to the fact that the zeta potential for the same type of particle is proportional to particle size. In particular, for voltage conditions of 150 V or higher, where a removal efficiency of over 99.9% was confirmed, the baseline for the distribution was expressed as 0 because both filtrates contained a number of particles below the analytical detection limit. For the same reason, 4,000–10,000 L m³ -2 h -1 The distribution for flow velocity conditions was represented by a zero baseline. As the flow velocity increased, the proportion of small particles decreased and the proportion of relatively large particles increased, which showed a pattern opposite to the change in distribution with increasing voltage.

[0105] Experimental Example 2 - Effect of Zeta Potential on MP Removal Performance

[0106] To clarify the electrohydrodynamic-assisted filtration mechanism based on the electrophoretic mobility of MP, the filtration performance of the filtration system according to this description was investigated for the same type of MP with different zeta potentials under various pH conditions. In these experiments, three specific pH conditions of 4, 7, and 10 were selected to maintain the electrolyte concentration of the buffer at a constant level between 0.1 mM and 1 mM. Additionally, negatively charged PS microspheres with a diameter of 6 μm were used within the corresponding pH range, and the zeta potentials of the buffers at pH 4, 7, and 10 were -5.95 ± 0.47, -28.5 ± 0.50, and -31.7 ± 0.58 mV, respectively. The MP concentration of each sample was set to 0.2 g / L.

[0107] Figure 15 shows photographs and microscopic images of the feed and filtrate under various pH conditions according to voltage change, and the removal efficiency of PS microspheres under various pH conditions according to voltage. Figure 16 shows photographs and microscopic images of the feed and filtrate under various pH conditions according to flow rate change, and the removal efficiency of PS microspheres under various pH conditions according to flow rate. Specifically, photographs and microscopic images of the PS microsphere feed and filtrate at various pH conditions (pH 4, 7, 10) sampled in voltage control and flow rate control studies are shown. The scale bars in the photographs and images represent 6 mm and 250 μm, respectively. Hereinafter, the effect of zeta potential on MP removal performance will be explained with reference to Figures 15 and 16.

[0108] First, Figures 15 and 16 show photographs and microscopic images of the filtrate under various pH conditions according to changes in voltage and flow rate. The pattern of decreasing or increasing concentration of MP in the filtrate as voltage and flow rate increase demonstrates that the system experienced repulsive electrophoretic forces regardless of pH conditions, based on the fact that MP carries a negative charge when suspended in a buffer. As theoretically predicted, different filtration behaviors are observed in MP with different zeta potentials because the degree of electrohydrodynamic assistance depends entirely on the magnitude of the electrophoretic mobility of MP. The distribution of removal efficiency, clearly distinguished according to the zeta potential of MP, can be confirmed in Figures 15 and 16. As shown in Equation 2, since the electrophoretic velocity is proportional to the electric field and zeta potential of MP, the same degree of voltage change results in a larger velocity change in MP with a higher zeta potential. Therefore, considering the characteristics of the electrohydrodynamic assistance filtration mechanism, the zeta potential can be seen to have a positive correlation with the removal efficiency. For MP in pH 4 buffer, which has the smallest zeta potential, the removal efficiency gradually increases with increasing voltage, reaching 97.8% at 200 V. The removal efficiency of MP in pH 7 buffer is similar to that of MP in pH 4 buffer at 25 V, but increases more steeply with increasing voltage, reaching a peak (>99.9%) at 150 V. The steepest slope is observed in the removal efficiency curve of MP in pH 10 buffer, which has the largest zeta potential. Consequently, it reaches its peak first at 100 V. Meanwhile, testing the same MP revealed almost no difference in the effect of physical filtration under all pH conditions, with the removal efficiencies of MP in pH 4, 7, and 10 buffers being 13.5%, 12.7%, and 13.8%, respectively. The pattern of change in removal efficiency with varying flow rates was primarily influenced by the magnitude of the electrophoretic mobility of MP.The magnitude of the electrophoretic velocity changes in proportion to the zeta potential of MP. As the flow rate increases, MP with the smallest zeta potential enters Condition 3 first and begins to leak downstream. However, unlike the case of voltage change, the flow rate does not significantly affect the rate of change in removal efficiency and, as it is a variable independent of the electrophoretic velocity, merely determines the onset of MP leakage. The removal efficiency of MP in pH 4 buffer is 4,000 L / m. -2 h -1 Exceeding 99.9% only at the flow velocity and the flow velocity is 16,000 L m -2 h -1 While it decreases by 46.3% as it increases, the removal efficiency of MP in pH 7 and 10 buffers is 14,000 L m⁻³ -2 h -1 It maintains a stagnant state up to the flow rate. Based on the aforementioned assumption, it can be confirmed that there is no close relationship between the rate of decrease in removal efficiency and the zeta potential of MP. The fact that the same critical flow rate was confirmed at MP in pH 7 and 10 buffers with different zeta potentials is consistent with 2,000 L m⁻¹ in this study. -2 h -1 It is presumed to be due to the large change in flow rate. Therefore, in reality, 14,000 L m³ for the MP of pH 7 and 10 buffers -2 h -1 At 16,000 L m -2 h -1It is presumed that distinct critical flow rates exist between them, and for MP in a pH 7 buffer with a low zeta potential, it is expected to be slightly lower than that of MP in a pH 10 buffer. In this experiment, the effect of the electrophoretic properties of MP on filtration performance in a hybrid filtration system was demonstrated through experimental verification. The experimental results showed that the operating conditions exhibiting optimal removal efficiency depend on the zeta potential of MP. In this regard, appropriately adjusting the zeta potential of MP can help achieve faster and more effective MP removal in the filtration system according to one aspect of this description.

[0110] Experimental Example 3 - Filtration performance for various types of MP

[0111] The filtration performance of the filtration system according to this description was evaluated for the three types of MP (PE, PS, PP) most frequently found in aquatic environments. In each feed, PE microspheres with a diameter of 10–45 μm, PS microspheres with a diameter of 20 μm, and PP fragments with a diameter of 25–85 μm were uniformly dispersed in a 1 mM NaCl electrolyte at a concentration of 0.2 g / L. The zeta potentials of the PE microspheres, PS microspheres, and PP fragments were -12.5 ± 0.79, -25.7 ± 0.82, and -6.29 ± 0.98 mV, respectively.

[0112] Figure 17 shows photographs and microscopic images of the feed and filtrate for sampled PE, PS, and PP microspheres according to voltage change, and the removal efficiency of PE, PS, and PP microspheres according to voltage. Figure 18 shows photographs and microscopic images of the feed and filtrate for sampled PE, PS, and PP microspheres according to flow rate change, and the removal efficiency of PE, PS, and PP microspheres according to flow rate. The scale bars in the photographs and images are 6 mm and 500 μm, respectively. Hereinafter, the filtration performance for various types of MP will be described with reference to Figures 17 and 18.

[0113] The filtration behavior of each type of MP according to changes in voltage and flow rate is classified according to the magnitude of the zeta potential of the MP, as shown in Figs. 17 and 18. PS microspheres with the largest zeta potential were not visually observed in the filtrate under voltage conditions of 100 V or higher, and 16,000 L m -2 h -1 Leakage into the filtrate began at the flow rate. On the other hand, the PP piece with the smallest zeta potential was observed in the filtrate even at a maximum voltage of 150 V and 10,000 L m -2 h -1Under the above flow rate conditions, they were introduced into the filtrate. The removal efficiency distribution corresponding to microscopic observation is illustrated in Figures 17 and 18, confirming the highest and lowest rates of increase in removal efficiency for PS microspheres and PP fragments, respectively, as the voltage increases. Therefore, the higher the zeta potential, the lower the voltage at which the removal efficiency curve reaches its peak. The effect of physical filtration was greatest in PP fragments (58.4%), followed by PE microspheres (35.7%) and PS microspheres (17.6%), which is presumed to be due to differences in the average size distribution. The critical flow rates for PP fragments, PE microspheres, and PS microspheres were 8,000, 10,000, and 14,000 L / m³, respectively. -2 h -1 It exhibits a proportional relationship with the zeta potential. The removal efficiency of PE microspheres, PS microspheres, and PP fragments is at a flow rate of 16,000 L / m -2 h -1 As the value increases, it decreases to 55.0%, 79.6%, and 74.6%, respectively. In particular, it can be seen that the rate of decrease in removal efficiency for PP fragments is lower compared to other MPs, which appears to be due to the high physical filtration effect. The results of this experiment demonstrate that the MP removal performance is not significantly related to the type of MP but depends on the zeta potential of the MP. In the hybrid filtration method, when voltage and flow rate are properly balanced, PE, PS, and PP—the most dominant types of MP present in the aquatic environment—can all be effectively removed with a removal efficiency of over 99.9%. Considering the unique electrohydrodynamic assisted filtration mechanism, it should be understood that the filtration device according to the embodiments of this description can be applied not only to the MP investigated in this experiment but also to any other type of charged MP.

[0115] Experimental Example 4 - Microfiber Removal

[0116] Microfibers, which are primarily dispersed during the washing of synthetic fibers, are the most dominant form of MP present in the aquatic environment and are crucial for the successful treatment of MP. Since microfibers penetrate longitudinally through narrow grids or small pores, membrane and filter-based methods, such as membrane bioreactors, disc filters, and reverse osmosis, have had some difficulty in completely removing fiber MP. Fundamentally, the hybrid filtration method according to the embodiments of this invention does not cause leakage of this type of fiber MP because the electric force barrier operates consistently regardless of the form of MP, relying solely on electrophoretic mobility. Therefore, according to one aspect, the hybrid filtration device according to one aspect of this invention may be used to re-filter fluids that have passed through a reverse osmosis-based filtration device. To verify this, the filtration performance of the filtration system according to one aspect of this invention was evaluated for the most common fiber MPs (PEST, acrylic, nylon) in the aquatic environment. PEST, acrylic, and nylon flocks with diameters of 10–30 μm and lengths of 250 μm were used as model fiber MPs and were uniformly dispersed in a 1 mM NaCl electrolyte at a concentration of 0.2 g / L. The zeta potentials of the PEST, acrylic, and nylon flocks were -9.94 ± 0.18, -3.24 ± 0.61, and -7.60 ± 0.26 mV, respectively.

[0117] FIG. 19 shows photographs and microscopic images of the feed and filtrate for sampled PEST, acrylic, and nylon clumps according to voltage change, and the removal efficiency of PEST, acrylic, and nylon clumps according to voltage, and FIG. 20 shows photographs and microscopic images of the feed and filtrate for sampled PEST, acrylic, and nylon clumps according to flow rate change, and the removal efficiency of PEST, acrylic, and nylon clumps according to flow rate. The removal of microfibers in a filtration system according to one aspect of the present invention will be described in more detail below with reference to FIG. 19 and FIG. 20. The scale bars in the photographs and images represent 6 mm and 1 mm, respectively.

[0118] Figures 19 and 20 show photographs and microscopic images of the filtrate of PEST, acrylic, and nylon clumps according to changes in voltage and flow rate. A significant number of fibers and fragments smaller than tens of micrometers originating from fiber MP clumps were distributed in the feed and filtrate. When no voltage was applied, most clumps were removed through physical filtration because the effective pore size of the porous layer (82.6 ± 0.21 μm) was much smaller than the average size of the clumps (length 250 μm), but most microfibers passed through the filter grid and entered the filtrate. As the voltage increased, the electric force barrier blocked their movement, causing the number of leaked microfibers to gradually decrease. Conversely, as the flow rate increased, microfibers could pass through the electric force barrier, resulting in reduced removal efficiency.

[0119] Figures 19 and 20 show the distribution of removal efficiency varying with voltage and flow rate. Due to the clumps that account for the majority of the sample mass suspended in the feed, high removal efficiencies of 97.3–98.0% were achieved in all types of fiber MP without applied voltage. Since the average size of each type of fiber MP was similar, the physical filtration effect was nearly identical. The change in removal efficiency with increasing voltage depends mainly on the zeta potential of the MP. At a voltage of 200 V, the removal efficiency of PEST and nylon clumps, which have a relatively high zeta potential, exceeded 99.9%, whereas the removal efficiency of acrylic clumps, which have a low zeta potential, was only 99.0%. Similarly, the pattern of change in removal efficiency with increasing flow rate also differed depending on the zeta potential of the MP. For PEST and nylon clumps, the removal efficiency was 8,000 L / m³ -2 h -1 It was found to be over 99.9% up to the flow velocity of 16,000 L m -2 h -1 At the flow velocities, it was confirmed that there was a slight decrease to 99.0% and 98.3%, respectively. In the case of the acrylic bundle, Condition 3 was already 4,000 L m -2 h -1 It is dominant in flow velocity, and the flow velocity is 16,000 L m -2 h -1 As it increases, the removal efficiency decreases to 97.3%. As mentioned above, the low removal efficiency caused by the low zeta potential can be resolved by increasing the zeta potential of the MP through the adjustment of the sample's pH conditions. In conclusion, electrohydrodynamic support effectively prevented the leakage of small plastic fibers, allowing for the successful removal of fiber MP. Furthermore, this experiment once again demonstrated the unique characteristics of the hybrid filtration mechanism, in which the filtration system according to one embodiment of this description exhibits consistent filtration performance regardless of the shape of the MP.

[0121] As described above, the filtration efficiency of the charged particle filtration device according to one embodiment of the present invention may vary depending on at least one of the flow rate of the fluid passing through the filtration device, the voltage applied to the first electrode and the ion exchange membrane, the zeta potential of the charged particle, or the type of the charged particle.

[0122] In this regard, the present invention discloses a high-efficiency, high-speed, scalable filtration system for removing charged particles, such as microplastics, from wastewater by integrating electrohydrodynamic assistance into physical filtration. By inducing an electric force barrier in the physical filtration system, the downstream movement of charged particles passing through the filter grid is prevented, thereby significantly mitigating the trade-off between intrinsic efficiency and flow rate. Through electrohydrodynamic assistance, a high removal efficiency of over 99.9% for charged particles and a flow rate of 10,000 L / m³ were achieved without applying high pressure, even when using a filter with an average pore size of tens of micrometers. -2 h -1 It was possible to achieve a flow rate. Experimental results demonstrated that the filtration performance of the filtration mechanism according to one embodiment of the present invention relies solely on the electrophoretic properties of the charged particles, and can successfully process them regardless of the type, size, shape, or chemical composition of the charged particles.

[0123] Due to the characteristics of the electrophoresis-based filtration mechanism, the method according to one aspect of the present invention exhibited consistent filtration behavior even at various charged particle concentrations, and no clogging of filter pores occurred during device operation. These unique characteristics differentiate the method according to the embodiments of the present invention from conventional MF technology, which has inconsistent filtration performance and inevitable membrane fouling issues.

[0125] Experimental conditions

[0126] Preparation of artificial MP solution

[0127] The artificial MP solutions used in the filtration experiments were prepared by dispersing a single type of MP in deionized water (DI). For the study of the core operating parameters of the hybrid filtration system, feeds containing PE microspheres (Cospheric LLC, USA) with four size ranges of diameter were used: 0.2–10 μm, 10–45 μm, 95–115 μm, and 250–300 μm. The MP concentration for each size range was the same at 0.1 g / L (total MP concentration: 0.4 g / L). In another study, samples containing MP of a single size range were used, and the MP concentration for each sample was the same at 0.2 g / L. To determine the effect of the zeta potential of MP on the filtration behavior of the proposed system, the feeds used in the study were prepared by dispersing 6 μm diameter PS microspheres (Polysciences, USA) in buffers under various pH conditions (pH 4, 7, 10). In the study evaluating the filtration performance of the proposed system for various types of MP, PE microspheres (diameter: 10–45 μm), PS microspheres (diameter: 20 μm), and PP flakes (diameter: 25–85 μm) (Polysciences, USA) were selected as model types of MP. To demonstrate the efficacy of the proposed system for fiber MP, PEST (diameter: 10–30 μm), acrylic (diameter: 19–25 μm), and nylon bundles (diameter: 10–20 μm) (Goonvean Fibres ltd, UK) were tested. Their lengths were identical at 250 μm. To obtain a stable aqueous suspension of MP, the nonionic surfactant Tween 20 (Cospheric LLC, USA) was added to the artificial MP solution at a concentration of 0.1% w / v. In addition, to induce electrohydrodynamic phenomena in the system, sodium chloride (NaCl, Sigma-Aldrich, USA) was used to adjust the electrolyte concentration of the artificial MP solution to 1 mM.To determine the effect of the zeta potential of MP on the filtration behavior of the proposed system, the pH of the buffer used in the study was adjusted with hydrochloric acid (HCl, Sigma-Aldrich, USA) and sodium hydroxide (NaOH, Sigma-Aldrich, USA).

[0129] Fabrication of a Scalable Electro-Hydraulic Auxiliary Filtration Device

[0130] For experiments on the filtration device described in this document, a scalable electrohydrodynamic-assisted filtration device based on simple assembly was designed. The top, bottom, and middle frames of the device, including the main channel, buffer channel, and branch channel, were fabricated by 3D printing (Object3500 using Vero transparent material from Stratasys, USA). 1 mm thick carbon paper electrodes were cut into ring shapes using a paper punch, inserted into the slots of the upper and lower frames, and secured using silver conductive epoxy adhesive (MG Chemicals 8330, MG Chemicals, Canada). Titanium wires were firmly attached to the carbon paper electrodes for DC electrical application. Microholes in the CEM were prepared through a simple drilling process. A microhole array with holes of 400 μm diameter and a hole spacing of 500 μm was formed on a commercial CEM (Fumasep, FTCM-E, Germany) using a desktop engraver (DE-3 desktop engraver, Roland DF, Japan). After forming the microhole array, the CEM was cut into a circular shape using a paper punch. A silicone gasket to prevent fluid leakage was prepared by cutting a 0.5 mm thick silicone sheet (HSW, Korea) using a laser cutter (Universal Laser System, USA). The main channel of the mid-frame was densely filled with a porous layer (PEST microfiber, Huvis, Korea) and then covered with a 3D-printed dome-shaped cap to induce a convex ion depletion region. Finally, all device components were aligned as shown in Fig. 5 and assembled by securing them with screws. Tube connectors (Harvard Devices, USA) were installed at the inlet and outlet of the frame to control the fluid flow of the device.

[0132] Filtration experiment

[0133] The experimental procedure for the electrohydraulic auxiliary filtration system is as follows.

[0134] Prior to the experiment, the CEM was immersed in DI water for 5 minutes to ensure smooth current flow between the main channel and the buffer channel. The feed reservoir and buffer reservoir were connected to the respective inlets of the main and buffer channels via silicone tubes (Colfarmer, USA), and 0.3 M sodium sulfate (Na2SO4, Samchully, Korea) was used as the electrode buffer. A Luer-Lok syringe (BD Luer-Lok, BD, USA) was connected to the tube connectors mounted on the outlets of the main and branch channels via silicone tubes, and a specific withdrawal flow rate was applied to the outlets using a syringe pump (PHD 2000, Harvard Instruments, USA). A constant DC electric field was applied to the working electrode using a source measuring device (B2902A, Keysight, USA). To obtain a reliable filtrate unaffected by MP leakage occurring before the formation of the electric force barrier, the feed solution was introduced prior to the formation of the ion depletion region. First, the main channel was filled with 1 mM NaCl that did not contain MP. Then, to prevent downstream movement of MP, the outlets of the main channel and branch channel were sealed to maintain negative pressure, and a feed reservoir was connected to the inlet of the main channel. In this state, electricity was applied to the system to induce an ion depletion region near the cathode-side CEM, after which fluid flow was allowed. The filtrate collected in the Luerlock syringe connected to the outlets of the main channel and branch channel was gently extracted into a conical tube.

[0136] Determination and Characterization of MP

[0137] Microscopic and infrared methods have been widely used to quantify and characterize MP in underwater environments due to their high reliability, but they are cumbersome and time-consuming when analyzing numerous and complex samples. In this study, since the artificial MP solutions used in each experiment consisted of a single type of MP, a weighting method was adopted instead of these methods to measure the removal efficiency in an electrohydrodynamic-assisted filtration system. The detailed experimental procedure is as follows. First, the feed solution and filtrate were filtered using a 0.22 μm hydrophilic membrane filter (Millipore, USA). Then, the recovered membrane filter was covered with aluminum foil to prevent the entry of foreign substances and dried in a vacuum drying oven at 60°C for 24 hours. Since each sample and filtrate contained very small amounts of MP, the mass of the membrane filter was measured using a 5-digit high-precision balance (MS105, METTLER TOLEDO, USA) capable of readings up to 0.01 mg. The mass of MP was calculated by subtracting the mass of the pure membrane filter from the mass of the membrane filter in which MP was accumulated. The removal efficiency in electrohydrodynamic-assisted filtration was calculated by the following Equation 4.

[0139]

[0140] Here m F is the mass of MP in the sample and m fε₀ is the mass of MP₀ in the filtrate. All experiments were performed twice, and the average value of the two samples was recorded. The morphology of the porous layer was observed using a multifocal optical microscope (BX53M, Olympus, Japan) and a scanning electron microscope (SU6600, Hitachi, Japan), and the average pore size was calculated using ImageJ software (NIH, Bethesda, Maryland, USA). Digital microscope images of the samples and filtrate were acquired using an inverse fluorescence microscope (IX71, Olympus, Japan) and microscope imaging software (cellSens, Olympus, Japan). The particle size distribution of PE microspheres was analyzed using a laser diffraction particle size analyzer (LS 13 320, Beckman Coulter, USA). The zeta potential of MP₀ was measured using a zeta potential and particle size analyzer (ELSZ-2000, Otsuka Electronics, Japan).

[0142] Although the invention has been described above with reference to the drawings and embodiments, this does not mean that the scope of protection of the present invention is limited by the drawings or embodiments, and those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the spirit and scope of the invention as described in the following claims.

[0143] Although the present invention described above is explained based on a series of functional blocks, it is not limited by the aforementioned embodiments and attached drawings, and it will be obvious to those skilled in the art that various substitutions, modifications, and changes are possible within the scope of the technical concept of the present invention.

[0144] The combination of the aforementioned embodiments is not limited to the aforementioned embodiments, and various forms of combinations in addition to the aforementioned embodiments may be provided as needed for implementation and / or implementation.

[0145] In the aforementioned embodiments, methods are described based on flowcharts as a series of steps or blocks; however, the present invention is not limited to the order of the steps, and some steps may occur in a different order or simultaneously with other steps as described above. Furthermore, those skilled in the art will understand that the steps shown in the flowcharts are not exclusive, that other steps may be included, or that one or more steps of the flowcharts may be omitted without affecting the scope of the present invention.

[0146] The foregoing embodiments include examples of various aspects. While it is not possible to describe all possible combinations for representing various aspects, those skilled in the art will recognize that other combinations are possible. Accordingly, the present invention shall be deemed to include all other substitutions, modifications, and changes falling within the scope of the following claims. Explanation of the symbols

[0148] 100 : Main Channel 210: First electrode 220: Cation exchange membrane 300: Ion depletion zone 400: Porous layer 410: Dome-shaped cap

Claims

Claim 1 A device for filtering charged particles using electrohydrodynamics, comprising: a main channel into which a fluid containing charged particles is introduced and flows; a first electrode disposed within the main channel to allow fluid flow; and an ion exchange membrane disposed downstream of the first electrode and having a plurality of pores into which the fluid in which the charged particles have been filtered is discharged. A charged particle filtration device comprising: a first electrode and an ion exchange membrane, wherein the first electrode and the ion exchange membrane generate an electric field between the first electrode and the ion exchange membrane, wherein a polarity different from that of the charged particle to be filtered is applied to the first electrode, wherein the ion exchange membrane is an ion exchange membrane for ions with a polarity different from that of the charged particle to be filtered, wherein a second electrode having the same polarity as that of the charged particle to be filtered is connected to the ion exchange membrane, wherein an ion depletion region is formed in the upstream direction of the ion exchange membrane to block the charged particle from moving into the pores of the ion exchange membrane, wherein the ion depletion region includes sub-ion depletion regions corresponding to each of the plurality of pores provided in the ion exchange membrane, and is configured to have a fluid flow direction cross-sectional area greater than or equal to a predetermined first area by having the plurality of sub-ion depletion regions. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 A charged particle filtration device according to claim 1, wherein the ion depletion region is formed based on ion concentration polarization (ICP). Claim 6 A charged particle filtration device according to claim 1, wherein the first electrode comprises an additional ion exchange membrane having a plurality of pores that allow fluid flow. Claim 7 A charged particle filtration device according to claim 1, wherein the ion depletion region allows an electrophoretic force to act on the charged particle. Claim 8 A charged particle filtration device according to claim 7, wherein the charged particles move in a direction different from the flow of the fluid according to the drag force according to the flow of the fluid and the electrophoretic force. Claim 9 delete Claim 10 A charged particle filtration device according to claim 1, further comprising: a porous layer disposed upstream of the ion exchange membrane inside the main channel and configured to filter particles of a predetermined first size or larger among the particles contained in the fluid. Claim 11 A charged particle filtration device according to claim 10, wherein the porous layer limits the electric convection induced in the ion depletion region to a predetermined size or less, so that the ion depletion region has a fluid flow direction cross-sectional area greater than or equal to a predetermined second area. Claim 12 In claim 11, the electric convection is induced by electroosmotic instability, in a charged particle filtration device. Claim 13 In claim 11, the electric convection comprises three-dimensional helical vortex pairs, a charged particle filtration device. Claim 14 In claim 10, the porous layer is formed of polyester microfiber, a charged particle filtration device. Claim 15 A charged particle filtration device according to claim 10, further comprising a dome-shaped cap configured to fix the porous layer while allowing fluid flow. Claim 16 In claim 15, the dome-shaped cap causes the ion depletion region to have a convex shape by bending the upper boundary of the porous layer, a charged particle filtration device. Claim 17 A charged particle filtration device according to claim 1, wherein the filtration efficiency of the charged particle filtration device varies according to at least one of the flow rate of the fluid passing through the filtration device, the voltage applied to the first electrode and the ion exchange membrane, the zeta potential of the charged particle, or the type of the charged particle. Claim 18 In claim 1, the charged particle filtration device is a charged particle filtration device used to re-filter a fluid that has passed through a reverse osmosis-based filtration device. Claim 19 A charged particle filtration device according to claim 1, further comprising: a branch channel configured to branch off from the main channel upstream of the ion exchange membrane so as to discharge the charged particles. Claim 20 A charged particle filtration device according to claim 19, wherein the charged particles are transported to the branch channel by the resultant force of the electrophoretic force of the ion depletion region formed upstream of the ion exchange membrane and the drag force due to the fluid flow.

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