A method for characterizing ion exchange membrane fouling and an online monitoring method

Abstract

The application discloses a method for characterizing ion exchange membrane pollution and an online monitoring method. The method for characterizing ion exchange membrane pollution comprises the following steps: S1, obtaining impedance data of the ion exchange membrane; S2, constructing an equivalent circuit model of the ion exchange membrane without pollution and the ion exchange membrane with pollution based on the obtained impedance data; S3, obtaining resistance data and capacitance data of the ion exchange membrane without pollution and the ion exchange membrane with pollution according to the equivalent circuit model; and S4, determining the pollution degree of the ion exchange membrane according to the resistance data and the capacitance data. The method for characterizing ion exchange membrane pollution can accurately detect the influence of a pollution layer on the ion exchange membrane on ion transport, and can test the impedance of the pollution membrane offline. The method for characterizing ion exchange membrane pollution can determine the degree of ion exchange membrane pollution.

Description

Technical Field

[0001] This invention relates to an electrochemical testing device and method, and particularly to a method for characterizing ion exchange membrane fouling and an online monitoring method, belonging to the field of electrochemical testing technology. Background Technology

[0002] The main methods for lithium extraction from salt lake brine include adsorption, extraction, nanofiltration, and electrodialysis. Among these, electrodialysis has advantages such as fewer operating parameters, ease of control, low energy consumption, low cost, no need for chemical reagents, minimal environmental impact, simple pretreatment, low equipment wear and tear, long lifespan, and high raw water recovery rate, making it one of the most widely used membrane technologies. Electrodialysis is a highly selective electro-membrane separation process that uses a potential difference as the driving force to transfer ions from one side of a membrane stack equipped with ion-selective exchange membranes to the other, thereby achieving the concentration and desalination of the feed solution. However, salt lake brine also contains a large amount of calcium and magnesium ions and other impurities. When treating this type of brine with electrodialysis, inorganic scaling of the ion exchange membrane is prone to occur, resulting in a decrease in desalination efficiency, affecting the stability of the electrodialysis system, and limiting the large-scale application of electrodialysis technology. Therefore, studying the fouling mechanism and prevention measures of ion exchange membranes during electrodialysis is of great significance. It can provide theoretical support for the widespread application of electrodialysis technology in lithium extraction from salt lake brine and provide a theoretical basis for solving membrane fouling. However, efficient characterization methods are needed to accurately analyze the fouling mechanism in order to study membrane fouling.

[0003] Currently commonly used methods for characterizing membrane fouling include:

[0004] Scanning electron microscopy (SEM) can provide high-resolution images of the microstructure of membrane surfaces and the morphology of contaminants, allowing for a direct observation of the type and distribution of contaminants.

[0005] Energy dispersive spectroscopy (EDS), combined with SEM, can determine the chemical composition of pollutants and provide qualitative and quantitative information for elemental analysis.

[0006] Contact angle measurement can assess changes in the hydrophilicity or hydrophobicity of the membrane surface, thereby indirectly reflecting the fouling status of the membrane surface.

[0007] Membrane surface conductivity measurement: Since contaminants usually affect the conductivity of membranes, the degree of membrane fouling can be indirectly assessed by measuring the change in conductivity on the membrane surface.

[0008] XRD and FTIR, etc.

[0009] Although these characterization methods can analyze the morphology and chemical composition of contaminants on the membrane surface, since the ion exchange membrane is always in a DC electric field during electrodialysis, the above-mentioned characterization methods cannot reflect the ion electromigration state at the membrane interface and inside in a timely manner, and it is difficult to detect the influence of the fouling layer on the ion exchange membrane on ion transport. At the same time, the above-mentioned characterization methods are limited in scope. Summary of the Invention

[0010] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method and online monitoring method for characterizing ion exchange membrane fouling, which can realize online monitoring of the fouling process and also perform impedance testing on ion exchange membranes with different types of fouling.

[0011] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0012] This invention discloses a method for characterizing ion exchange membrane fouling, comprising the following steps:

[0013] S1. Obtain the impedance data of the ion exchange membrane;

[0014] S2. Construct equivalent circuit models of contaminated and uncontaminated ion exchange membranes based on the obtained impedance data.

[0015] S3. Obtain the resistance and capacitance data of the uncontaminated and contaminated ion exchange membranes based on the equivalent circuit model.

[0016] S4. Determine the degree of fouling of the ion exchange membrane based on the resistance and capacitance data.

[0017] Furthermore, this method for characterizing ion exchange membrane fouling is based on an EIS testing device connected to an impedance analyzer. The impedance analyzer performs electrochemical impedance testing on the ion exchange membrane in the preset EIS testing device to obtain impedance data.

[0018] Furthermore, the equivalent circuit model includes an equivalent circuit model of a pure ion exchange membrane, which is a [R(RQ)(RQ)] model. The [R(RQ)(RQ)] model includes the equivalent resistance R of the electrolyte in the electrolytic cell of the EIS testing device. s The equivalent resistance R of the ion exchange membrane m The equivalent resistance R of the electric double layer of the ion exchange membrane edl and constant phase angle element Q edl The equivalent resistance R of the diffusion layer of the ion exchange membrane dbl and its constant phase angle element Q dbl The equivalent resistance R of the electrolyte solution s The equivalent resistance R of the ion exchange membrane mThe equivalent resistance R of the electric double layer of the ion exchange membrane edl The equivalent resistance R of the diffusion layer of the ion exchange membrane dbl The equivalent resistance R of the double layer of the ion exchange membrane in series edl Its constant phase angle element Q is connected in parallel, with an equivalent resistance R. edl It is connected in parallel with its constant phase angle element Q.

[0019] Furthermore, the equivalent circuit model includes an equivalent circuit model of the contaminated membrane, which is a [R(RQ)(RC)(RQ)] model. The [R(RQ)(RC)(RQ)] model is formed by connecting an equivalent resistance R in series with the [R(RQ)(RQ)] model. p R p Then parallel C p , where R p C is the equivalent resistance of the fouling layer of the fouling membrane. p The capacitance of the contamination layer of the contamination membrane.

[0020] The present invention also discloses an online monitoring method for characterizing ion exchange membrane fouling. The online monitoring method is based on an online monitoring device for ion exchange membrane fouling and includes the following steps: placing the ion exchange membrane to be tested into the online monitoring device, injecting a fouling agent solution into the online monitoring device, turning on the power switch, and monitoring the ion exchange membrane fouling process online.

[0021] Furthermore, the online monitoring device for ion exchange membrane contamination includes two or more compartments, with the ion exchange membrane to be tested placed between the two compartments. A salt bridge is provided in the two compartments, and an electrolyte solution is filled in the salt bridge. An electrode is provided in the electrolyte solution. Inert metal electrode plates are provided on the opposite sides of the two compartments, and electrode plates are provided on the sides of the two compartments at both ends.

[0022] Furthermore, the online monitoring device for ion exchange membrane fouling includes five compartments. The two middle compartments are equipped with salt bridges, which are filled with electrolyte solutions and contain electrodes. Inert metal electrode plates are provided on the opposite sides of the two compartments, and electrode plates are provided on the sides of the two end compartments.

[0023] Furthermore, the salt bridge is an L-shaped ceramic core salt bridge.

[0024] Furthermore, the electrode plate is embedded in the ends of the two compartments at both ends, the electrode plate is detachably connected to the compartments, and the electrode plate is an inert metal electrode plate.

[0025] Furthermore, each of the aforementioned compartments is equipped with a water inlet and a water outlet.

[0026] Compared with the prior art, the advantages of the present invention include:

[0027] 1) The present invention provides a method for characterizing ion exchange membrane fouling, which can accurately detect the influence of the fouling layer on the ion exchange membrane on ion transport and can test the impedance of the fouled membrane offline;

[0028] 2) The present invention provides a method for characterizing ion exchange membrane fouling, which can determine the degree of ion exchange membrane fouling;

[0029] 3) The present invention provides a method for characterizing ion exchange membrane fouling, which can more intuitively determine the degree of fouling of ion exchange membranes; the method for characterizing ion exchange membrane fouling of the present invention is simple, only requiring reasonable fitting to obtain the resistance value of the corresponding part, which can quantitatively measure the resistance value of the fouled layer, and the degree of fouling can be analyzed by comparing the magnitude and increase of the resistance value, without the need for a large amount of calculation to obtain the degree of fouling;

[0030] 4) The present invention provides an online monitoring method for characterizing ion exchange membrane fouling, which can monitor the electrochemical characteristics of the ion exchange membrane fouling process online. Attached Figure Description

[0031] Figure 1 This is a flowchart of the method for characterizing ion exchange membrane fouling provided by the present invention;

[0032] Figure 2 This is a schematic diagram of the structure of the four-electrode EIS testing device provided by the present invention;

[0033] Figure 3 This is a schematic diagram of the structure of the online monitoring device for ion exchange membrane fouling provided by the present invention;

[0034] Figure 4 Nyquist equivalent circuit fitting diagrams of electrochemical impedance spectra of contaminated cation exchange membranes under different conditions in the low frequency range (1000Hz-0.01Hz);

[0035] Figure 5 A schematic diagram of the [R(RQ)(RQ)] model provided by this invention;

[0036] Figure 6 A schematic diagram of the [R(RQ)(RC)(RQ)] model provided by this invention;

[0037] Figure 7a This is a graph fitted using the forward osmosis membrane characterization method in Comparative Example 1 of the present invention;

[0038] Figure 7b This is a graph fitted using the characterization method of the present invention in Comparative Example 1 of the present invention;

[0039] Explanation of reference numerals in the attached diagram: 1. Compartment; 2. Salt bridge; 3. Electrode plate; 4. Electrode; 5. Inlet; 6. Outlet; 7. Electrode sheet. Detailed Implementation

[0040] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate the technical solution, its implementation process, and its principles.

[0041] This invention discloses a method for characterizing ion exchange membrane fouling, the method comprising the following steps:

[0042] S1. Obtain the impedance data of the ion exchange membrane; the impedance data includes the resistance R between the ion exchange membrane and the electrolyte. m+s (i.e., the equivalent resistance R of the electrolyte) s Equivalent resistance R of ion exchange membrane m (sum of the two layers of the ion exchange membrane) and the resistance R of the double layer of the ion exchange membrane. edl The equivalent resistance R of the fouling layer of the fouling membrane p The equivalent resistance R of the diffusion layer of the ion exchange membrane dbl Ion exchange membranes include both contaminated and uncontaminated ion exchange membranes.

[0043] S2. Construct equivalent circuit models of contaminated and uncontaminated ion exchange membranes based on the obtained impedance data.

[0044] S3. Obtain the resistance and capacitance data of the uncontaminated and contaminated ion exchange membranes based on the equivalent circuit model.

[0045] S4. Determine the degree of fouling of the ion exchange membrane based on the resistance and capacitance data.

[0046] This method for characterizing ion exchange membrane fouling is based on a four-electrode EIS testing device. The device includes two compartments, with the ion exchange membrane to be tested placed between them. Each compartment contains an L-shaped ceramic core salt bridge filled with a 3.5 mol / L KCl solution. A silver chloride electrode is placed within the electrolyte solution, serving as a reference electrode and a sensing electrode for an electrochemical workstation. Ruthenium-plated titanium electrode plates are detachably embedded in the opposing surfaces of the two compartments, forming a cavity for holding the test solution.

[0047] Specifically, a method for characterizing ion exchange membrane fouling includes the following steps:

[0048] S1. Place the ion exchange membrane to be tested between the two compartments;

[0049] S2. Prepare the electrolyte solution and inject the prepared electrolyte solution into the two compartments;

[0050] S3. Connect one of the electrode plates to the counter electrode (CE) of the electrochemical workstation channel, and connect the reference electrode near this electrode plate to the reference electrode (RE) of the electrochemical workstation channel; connect the other electrode plate to the working electrode (WE) of the electrochemical workstation channel, and connect the reference electrode near this electrode plate to the sensing electrode (SE) of the electrochemical workstation channel.

[0051] S4. On the computer connected to the electrochemical workstation, open the EIS test project, set the test frequency to 1000Hz to 0.01Hz, set the AC voltage amplitude to 0.01V, and collect multiple impedance data.

[0052] S5. After the test is completed, collect the impedance data of the ion exchange membrane. Based on the collected impedance data, construct equivalent circuit models of the uncontaminated and contaminated cation exchange membranes. Obtain the resistance and capacitance values ​​of the uncontaminated and contaminated cation exchange membranes according to the equivalent circuit models.

[0053] The equivalent circuit model includes an equivalent circuit model of a pure ion exchange membrane (a pure ion exchange membrane is an uncontaminated ion exchange membrane). The equivalent circuit model of the pure ion exchange membrane is the [R(RQ)(RQ)] model, which includes the equivalent resistance R of the electrolyte in the compartment of the EIS test device. s The equivalent resistance R of the ion exchange membrane m The equivalent resistance R of the electric double layer of the ion exchange membrane edl and constant phase angle element Q edl The equivalent resistance R of the diffusion layer of the ion exchange membrane dbl and its constant phase angle element Q dbl， Q edl and Q dbl It's a component in the circuit; the corresponding data is only obtained after fitting the circuit. The equivalent resistance R of the electrolyte solution is also considered. s The equivalent resistance R of the ion exchange membrane m The equivalent resistance R of the electric double layer of the ion exchange membrane edl The equivalent resistance R of the diffusion layer of the ion exchange membrane dbl Series connection, equivalent resistance R edl and its constant phase angle element Q edl Parallel connection, equivalent resistance R edl and its constant phase angle element Q dblParallel connection. In this invention, the ion exchange membrane system is generally equivalent to a resistor. The [R(RQ)(RQ)] model in this invention involves fewer circuit elements and has a simpler connection method. This model can more accurately describe the circuit behavior of the ion exchange membrane.

[0054] In the contaminated membrane, the equivalent resistance R is connected in series in the [R(RQ)(RQ)] model. p R p Then parallel C p This forms the [R(RQ)(RC)(RQ)] model, where R p Cp is the equivalent resistance of the fouling layer of the fouling membrane, and Cp is the capacitance of the fouling layer of the fouling membrane.

[0055] Example 1:

[0056] This embodiment uses a Type 12 cation exchange membrane manufactured by Fuji and different concentrations of Ca. 2+ Different Ca 2+ The fouled membrane in the solution system was used as the test membrane. An EIS test was performed using a four-electrode EIS testing device, and relevant impedance data were collected to establish a model. The data was analyzed to obtain the electrochemical performance of the fouled membrane. The operation steps and data analysis are as follows:

[0057] (1) The ion exchange membrane (pure cation exchange membrane: CEM, membrane contaminated with 0.5 g / L CaCl2 solution: Ca) 2+ Membrane fouled by -0.5 gM, 2 g / L CaCl2 solution: Ca 2+ Membrane fouled by -2g-M, 0.5g / L CaSO4 solution: Ca 2+ -SO4 2- Membrane fouled by -0.5 gM, 0.9 g / L CaSO4 solution: Ca 2+ -SO4 2- -0.9 gM) is placed in an electrolytic cell, which is then divided into two electrolytic chambers. Ruthenium-plated titanium electrode plates are placed on both sides of each chamber as the working electrode and the counter electrode. Two saturated AgCl electrodes connected to an L-shaped ceramic core salt bridge are used as the reference electrode and the sensing electrode, respectively, and are symmetrically arranged on both sides of the ion exchange membrane. These four electrodes and the electrolytic cell constitute a four-electrode EIS testing device. The electrolytic cell is then filled with an electrolyte solution (1 g / L LiCl solution).

[0058] (2) Connect the EIS testing device to an impedance analyzer, and perform electrochemical impedance testing on the ion exchange membrane in the preset EIS device using the impedance analyzer to obtain the corresponding impedance data. Based on the impedance data, construct an equivalent circuit model of the ion exchange membrane to fit the impedance data diagram, as shown below. Figure 4The capacitance, resistance, and constant phase angle element data of the ion exchange membrane were obtained based on the equivalent circuit model, as shown in Table 1.

[0059] The impedance fitting diagrams and related impedance data of the membranes tested in the above embodiments are as follows: Figure 4 See Table 1.

[0060] Table 1. Results obtained based on different equivalent circuits Figure 4 The impedance spectrum fitting results shown

[0061]

[0062] Through the above embodiments, impedance testing of the diffusion layer and boundary layer of a contaminated ion exchange membrane was achieved, obtaining data on the influence of different contamination concentrations in different contamination systems on the migration resistance caused by ion migration in the membrane. The embodiments show that as the concentration of the contaminant increases, the resistance R of the contaminated membrane increases. m As the double-layer resistance R of the fouled membrane increases, eal With diffusion layer resistance R dbl The increased resistance of both membranes indicates that the increased resistance of the electric double layer and diffusion layer in contaminated cation exchange membranes hinders ion migration within these layers, reducing migration efficiency and leading to a decline in membrane desalination performance. This also indirectly suggests that contamination by CaCl2 and CaSO4 solutions primarily occurs on the membrane surface, altering its surface properties and rendering it ineffective as an ion exchange membrane, making ion migration pathways in solution more difficult and complex. Furthermore, at the same concentration of contaminated solution, CaSO4-contaminated cation exchange membranes exhibit higher membrane resistance values ​​and diffusion layer resistance R compared to CaCl2-contaminated membranes. dbl and contamination layer resistance R p This indicates that CaCl2 and CaSO4 cause different types and modes of fouling to cation exchange membranes. Membranes fouled by CaSO4 have a thicker diffusion layer, making ion migration more difficult, and the scale on the membrane has a stronger hindering effect on ion migration. This suggests that membranes fouled by CaCl2 and CaSO4 require different cleaning and repair methods, providing a theoretical basis for proposing repair methods for fouled membranes.

[0063] As can be seen from Table 1: R p and R m+s The higher the value, the more severe the fouling of the ion exchange membrane; R p and R m+s If the increase in value is slight compared to that of a pure membrane, it is judged as light contamination; if the increase is significant, it is judged as heavy contamination.

[0064] Comparative Example 1:

[0065] The ion exchange membrane to be tested was tested using a membrane fouling characterization method for forward osmosis membranes. This method includes: obtaining impedance data; constructing an equivalent circuit of the forward osmosis membrane using the impedance data; and wherein the equivalent circuit model includes the equivalent resistance R of the electrolyte in the preset electrolytic cell. s The equivalent capacitance C1 and equivalent resistance R of the forward osmosis membrane. m The inductance L1 of the forward osmosis membrane and the equivalent resistance R1 of the inductance, wherein the equivalent resistance R... s It is connected in series with the equivalent capacitance C1, and the equivalent capacitance C1 is connected in series with the equivalent resistance R. m In parallel, the inductor L1 and the equivalent resistance R1 are connected in series and then in parallel with the equivalent resistance R. m The two ends. The measured impedance data of the ion exchange membrane are then fitted using the equivalent circuit method in the membrane fouling characterization method for forward osmosis membranes, as shown below. Figure 7a The impedance data of the ion exchange membrane test were fitted using the equivalent circuit model in this application, as shown below. Figure 7b ,from Figure 7a It is evident that the characterization method for fouling of forward osmosis membranes cannot fit the test data of ion exchange membranes, nor can it accurately obtain data on the membrane, the double layer, and the diffusion layer. Therefore, the characterization method for forward osmosis membranes cannot be used to characterize ion exchange membranes.

[0066] In another aspect, the present invention provides an online monitoring method for characterizing ion exchange membrane fouling, the online monitoring method being based on an online monitoring device for ion exchange membrane fouling, comprising:

[0067] 1) Place the ion exchange membrane to be monitored between two separators with L-shaped ceramic core salt bridges, and place platinum electrode plates thereafter. Place the other ion exchange membranes in the order of electrodialysis.

[0068] 2) A silver chloride electrode is placed in an L-shaped ceramic core salt bridge. One silver chloride electrode is then connected to a reference electrode on a specific channel of a Princeton Applied Research electrochemical workstation. A platinum electrode adjacent to the silver chloride electrode is connected to the counter electrode of the channel. Another silver chloride electrode is connected to the sensing electrode (SE) on the same channel of the electrochemical workstation, and a platinum electrode adjacent to the silver chloride electrode is connected to the working electrode (WE) of the channel. Two ruthenium-plated titanium electrodes are connected to an external power source.

[0069] 3) Prepare the contaminant solution and inject it into the entire test apparatus using a peristaltic pump at a rate of 20 ml / min.

[0070] 4) After the solution fills the device, turn on the external power supply to provide an electric field for the entire device.

[0071] 5) Open the Chronopotentiometry test project on the computer connected to the electrochemical workstation. Ensure solution circulation throughout the process and monitor the change in membrane current during fouling.

[0072] In some embodiments, the online monitoring device for ion exchange membrane fouling includes two or more compartments, which can be four or five. The number of compartments is determined by the number of ion exchange membranes to be detected. The ion exchange membrane to be detected is placed between two compartments. A salt bridge is provided between the two compartments, and an electrolyte solution is filled within the salt bridge. An electrode is placed within the electrolyte solution. Inert metal electrode plates are provided on the opposite sides of the two compartments. Electrode plates are provided on the sides of the two compartments at both ends; these electrode plates serve as both compartment plates and electrode plates. Each compartment is provided with an inlet and an outlet to ensure the circulation of the solution during testing. This device can perform tests with or without the test solution circulating.

[0073] Example 2:

[0074] like Figure 3 As shown, the online monitoring device for ion exchange membrane fouling includes five compartments 1, two electrode plates 3, and two platinum electrode sheets 7, wherein the five compartments 1 and the two electrode plates 3 at both ends form a closed cavity. Two compartments 1 are equipped with detachable L-shaped ceramic core salt bridges 2, and silver chloride electrodes 4 are immersed in the L-shaped ceramic core salt bridges 2 filled with 3.5 mol / L KCl solution. The silver chloride electrodes 4 are connected to the reference electrode and the sensing electrode of the electrochemical workstation. The two platinum electrode sheets 7 are inserted into both sides of the compartments 1 with the L-shaped ceramic core salt bridges 2, and are connected to the working electrode and the counter electrode of the electrochemical workstation. Two ruthenium-plated titanium electrode plates 3 are detachably mounted on the opposite surfaces of the two compartments 1 at both ends. The ruthenium-plated titanium electrode plates 3 are connected to an external power source to provide DC power to the entire device. Each compartment 1 has dimensions of 60×60×30 mm, and each electrode plate 3 has dimensions of 40×40×3 mm. The device can accommodate two pairs of ion exchange membranes. One pair of ion exchange membranes is placed between two compartments 1 with L-shaped ceramic core salt bridges 2, and the other pair of ion exchange membranes is placed between two other adjacent compartments 1. In addition, each compartment 1 is provided with an inlet 5 and an outlet 6, and the solution is circulated through the inlet 5 and the outlet 6.

[0075] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for characterizing ion exchange membrane fouling, characterized in that, Includes the following steps: S1. Obtain the impedance data of the ion exchange membrane; S2. Construct equivalent circuit models of contaminated and uncontaminated ion exchange membranes based on the obtained impedance data. S3. Obtain the resistance and capacitance data of the uncontaminated and contaminated ion exchange membranes based on the equivalent circuit model. S4. Determine the degree of fouling of the ion exchange membrane based on the resistance and capacitance data; The equivalent circuit model includes an equivalent circuit model of a pure ion exchange membrane and an equivalent circuit model of a fouled membrane. The equivalent circuit model of the pure ion exchange membrane is the [R(RQ)(RQ)] model, which includes the equivalent resistance Rs of the electrolyte in the electrolytic cell of the EIS test device, the equivalent resistance Rm of the ion exchange membrane, the equivalent resistance Redl of the double layer of the ion exchange membrane and the constant phase angle element Qedl, the equivalent resistance Rdbl of the diffusion layer of the ion exchange membrane and its constant phase angle element Qdbl. The equivalent resistance Rs of the electrolyte solution, the equivalent resistance Rm of the ion exchange membrane, the equivalent resistance Redl of the double layer of the ion exchange membrane and the equivalent resistance Rdbl of the diffusion layer of the ion exchange membrane are connected in series, the equivalent resistance Redl of the double layer of the ion exchange membrane and its constant phase angle element Qedl are connected in parallel, and the equivalent resistance Rdbl and its constant phase angle element Qdbl are connected in parallel. The equivalent circuit model of the contamination membrane is the [R(RQ)(RC)(RQ)] model, which is an equivalent resistance Rp connected in series with the [R(RQ)(RQ)] model, and then Rp is connected in parallel with Cp, where Rp is the equivalent resistance of the contamination layer of the contamination membrane, and Cp is the capacitance of the contamination layer of the contamination membrane.

2. The method for characterizing ion exchange membrane fouling according to claim 1, characterized in that: The method for characterizing ion exchange membrane fouling is implemented based on an EIS testing device, which is connected to an impedance analyzer. The impedance analyzer performs electrochemical impedance testing on the ion exchange membrane in the preset EIS testing device to obtain impedance data.

3. An online monitoring method for characterizing ion exchange membrane fouling, characterized in that: The online monitoring method is implemented based on an online monitoring device for ion exchange membrane fouling. The online monitoring device for ion exchange membrane fouling includes two or more compartments. The number of compartments is set according to the number of ion exchange membranes to be detected. The ion exchange membrane to be detected is placed between the two compartments. A salt bridge is set in the two compartments. The salt bridge is filled with an electrolyte solution. An electrode is set in the electrolyte solution. Inert metal electrode plates are set on the back sides of the two compartments. Electrode plates are set on the sides of the two compartments at both ends. Furthermore, the online monitoring method includes placing the ion exchange membrane to be tested into an online monitoring device for ion exchange membrane fouling, injecting a fouling agent solution into the online monitoring device, and monitoring the ion exchange membrane fouling process online.

4. The online monitoring method for characterizing ion exchange membrane fouling according to claim 3, characterized in that: The online monitoring device for ion exchange membrane fouling includes five compartments. The two middle compartments are equipped with salt bridges, which are filled with electrolyte solutions and contain electrodes. Inert metal electrode plates are provided on the opposite sides of the two middle compartments, and electrode plates are provided on the sides of the two end compartments.

5. The online monitoring method for characterizing ion exchange membrane fouling according to claim 4, characterized in that: The salt bridge is an L-shaped ceramic core salt bridge.

6. The online monitoring method for characterizing ion exchange membrane fouling according to claim 4, characterized in that: The electrode plate is embedded in the ends of the two compartments at both ends, and the electrode plate is detachably connected to the compartments. The electrode plate is an inert metal electrode plate.

7. The online monitoring method for characterizing ion exchange membrane fouling according to claim 6, characterized in that: Each compartment is equipped with a water inlet and a water outlet.

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