Method and apparatus for determining ion transmembrane energy barrier of separation membrane under electric driving condition

Abstract

The application discloses a kind of method and device for determining the energy barrier of single ion across membrane under electric driving condition in the field of membrane separation and electrochemical analysis technology, including in the high concentration salt solution and low concentration salt solution with concentration difference, install the separation membrane to be measured, constitute the mass transfer system across membrane.The application can make different ions respectively permeate the separation membrane under the action of applied electric field, so as to realize the quantitative determination of the energy barrier of single ion across membrane, can directly quantify the energy barrier of single ion across membrane, and effectively separate the ion response signal under the electric field driving, avoid the interference of polarization effect and coexisting ion, can obtain the real, independent single ion migration behavior across membrane.

Description

Technical Field

[0001] This invention relates to the field of membrane separation and electrochemical analysis technology, specifically a method and apparatus for determining the transmembrane energy barrier of single ions in a membrane under electro-driven conditions. Background Technology

[0002] Electro-driven separation membranes (such as anion / cation exchange membranes, reverse osmosis membranes, and nanofiltration membranes) play a crucial role in water purification, salt recovery, and electrochemical energy systems. An applied electric field can drive ion migration, enabling selective separation. However, ion transmembrane transport behavior involves the coupling of multiple factors, including hydration structure, charge repulsion, membrane pore size distribution, and interfacial potential. This means that traditional characterization methods typically only provide overall ion transport efficiency or macroscopic conductivity information, making it difficult to distinguish the transmembrane mass transfer resistance of different ions.

[0003] Existing technologies often rely on macroscopic indicators such as transmembrane conductivity, membrane resistance, and electroosmotic flow to infer membrane selectivity, which cannot directly quantify the transmembrane energy barrier of a single ion. Furthermore, factors such as ion coexistence effects, concentration gradients, and interfacial potential distributions can all interfere with the test results, making it impossible to accurately characterize the transmembrane dynamics of the target ion. Summary of the Invention

[0004] The purpose of this invention is to provide a method and apparatus for determining the transmembrane energy barrier of a single ion in a separated membrane under electrically driven conditions, so as to solve the problem mentioned above that the transmembrane energy barrier of a single ion cannot be directly quantified, and that factors such as ion coexistence effect, concentration gradient, and interface potential distribution can interfere with the test results, resulting in the inaccurate characterization of the transmembrane kinetics of the target ion.

[0005] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for determining the transmembrane energy barrier of a single ion in a separated membrane under electrically driven conditions, comprising the following steps: In a high-concentration salt solution and a low-concentration salt solution with a concentration difference, the separation membrane to be tested is installed to form a transmembrane mass transfer system. Linear sweep voltammetry was performed on the transmembrane mass transfer system using a four-electrode system to obtain the current-potential curve, and the membrane potential ΔE was obtained from the current-potential curve. m Based on the membrane potential ΔE m The concentration difference between high-concentration and low-concentration salt solutions was used, and the ion transport numbers were calculated by fitting the Nernst equation, where the ion transport numbers included the positive ion transport numbers. and negative ion transport number ; The temperature of the transmembrane mass transfer system is adjusted, and linear scanning voltammetry is performed on the transmembrane mass transfer system at different preset temperatures based on a four-electrode system to obtain current-potential curves at different preset temperatures. The ionic conductivity G at each preset temperature is obtained by linear fitting of the current-potential difference curves at different preset temperatures. Based on the ion transport number and the ionic conductivity G at each preset temperature, the single-ion transmembrane energy barrier of the target ion is calculated by linear fitting using the Arrhenius equation. .

[0006] As a further aspect of the present invention: the concentration ratio of the low-concentration salt solution to the high-concentration salt solution is in the range of 1:1 to 1:100; The cations in the low-concentration salt solution and the high-concentration salt solution are Li. + Na + K + 、Rb + Cs + NH4 + Ca 2+ Mg 2 + Ba 2+ Cu 2+ Zn 2+ Ag + Co 2+ Mn 2+ Fe 2+ Cr 3+ And Al 3+ At least one of them; The cation in the low-concentration salt solution and the high-concentration salt solution is F. - Cl - ,Br - I - SO4 2- SO3 2- NO3 - NO2 - PO4 3- CO3 2- and ClO4 - At least one of them.

[0007] As a further aspect of the present invention: a linear sweep voltammetry test is performed on the transmembrane mass transfer system based on a four-electrode system to obtain a current-potential curve, and the membrane potential ΔE is obtained from the current-potential curve. m Based on the membrane potential ΔE m The concentration difference between high-concentration and low-concentration salt solutions was used to calculate the ion transport number based on the Nernst equation, including: The membrane potential ΔE is obtained from the intercept of the current-potential curve on the potential axis. m Ion transport numbers were calculated based on Nernst equation fitting. ; Among them, C h The electrolyte concentration of a high-concentration salt solution is C. l Let R be the electrolyte concentration of the low-concentration salt solution, T be the absolute temperature, and F be the Faraday constant. It is the transference number of the positive ion. The transport number of negative ions is denoted as , where . + =1.

[0008] As a further aspect of the present invention: the single-ion transmembrane energy barrier E of the target ion is calculated by linear fitting based on the ion transport number and the ion conductivity G at each preset temperature using the Arrhenius equation. P ,include; The ionic conductivity G was obtained at each preset temperature, and the transmembrane energy barrier was calculated based on the Arrhenius equation. ; ; Where G is the overall ionic conductivity. Where is the ion transport number, and T is the absolute temperature. R is the pre-exponential factor, and R is the gas constant; The preset temperature range is 5℃ to 65℃.

[0009] As a further aspect of the present invention: the Arrhenius equation is linearly fitted, wherein the correlation coefficient of the linear fit is not less than 0.95.

[0010] As a further aspect of the present invention: the operating voltage of the linear scanning voltammetry test is -200mV to 200mV, and the scanning rate is 0.01mV / s to 50mV / s.

[0011] In a second aspect, the present invention provides an apparatus for measuring the transmembrane energy barrier of a single ion in a separated membrane under electrically driven conditions, comprising: The test body has a centrally connected channel, and a separation membrane is installed in the channel to divide the test body into a high-concentration chamber and a low-concentration chamber. The four-electrode system includes a working electrode and a recording electrode disposed in the high-concentration chamber, and a counter electrode and a reference electrode disposed in the low-concentration chamber. The high-concentration chamber and the low-concentration chamber are each provided with an independent quartz capillary tube, and the recording electrode and the reference electrode are both disposed inside the quartz capillary tube. A signal control and acquisition system includes an electrochemical workstation, wherein a first signal terminal of the electrochemical workstation is connected to a working electrode and a recording electrode, and a second signal terminal of the electrochemical workstation is connected to a counter electrode and a reference electrode; A constant temperature circulation system is located on the outside of the test body. A circulating fluid flows within the constant temperature system, and the circulating fluid is used for constant temperature heating of the high concentration chamber and the low concentration chamber.

[0012] As a further aspect of the present invention: the constant temperature circulation system includes a first circulation chamber and a second circulation chamber. The first circulation chamber is disposed on the outer wall of the high concentration chamber, and the second circulation chamber is disposed on the outer wall of the low concentration chamber. The upper and lower ends of the first and second circulation chambers are connected to a circulating water bath channel. The circulating water bath channel is connected to a circulating water bath pump through a pipe. The circulating water bath pump is used to drive the constant temperature fluid to flow from bottom to top into the first and second circulation chambers. The flow rate of the constant temperature fluid is in the range of 0.1 L / min to 10 L / min.

[0013] As a further aspect of the present invention: a support frame is detachably installed inside the channel, and a separation membrane is installed on the support frame, the separation membrane having a thickness of 50nm~10000nm.

[0014] As a further embodiment of the present invention: the quartz capillary is an L-shaped sand core salt bridge or an L-shaped Lukin capillary, and the distance between the bottom elbow outlet of the quartz capillary and the separation membrane is 1mm~2mm. Both the working electrode and the counter electrode are made of sheet-shaped platinum electrodes or sheet-shaped titanium electrodes.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention is based on a four-electrode electrochemical system. It uses linear scanning voltammetry to test the transmembrane mass transfer system, obtaining the current-potential characteristics of the ion transmembrane process. Based on the membrane potential ΔEm and the ion concentration difference, the ion transport number is calculated using the Nernst equation, and the ionic conductivity of cations and / or anions is calculated using linear fitting. The single-ion transmembrane energy barrier of the target ion is calculated using linear fitting based on the Arrhenius equation. Under the action of an external electric field, different ions are allowed to pass through the separation membrane separately, thus achieving quantitative determination of the single-ion transmembrane energy barrier. This invention can directly quantify the transmembrane energy barrier of a single ion. By constructing a four-electrode system and using linear scanning voltammetry, the ion response signal driven by the electric field is effectively separated, avoiding interference from polarization effects and coexisting ions. This results in obtaining true and independent single-ion transmembrane migration behavior. Factors such as ion coexistence effects, concentration gradients, and interfacial potential distribution do not participate in the calculation of the single-ion transmembrane energy barrier, thus avoiding their interference with the test results. This allows for accurate characterization of the target ion transmembrane kinetics and provides good performance.

[0016] 2. This invention, through a circulating water bath channel within the device, ensures consistent temperatures on both sides of the separation membrane, significantly reducing the impact of temperature fluctuations on test results. Simultaneously, Arrhenius fitting of conductivity data across multiple temperature zones ensures the reliability and accuracy of transmembrane energy barrier calculations. A detachable support frame is installed within the channel, upon which the separation membrane is mounted. The support frame facilitates rapid membrane replacement. This invention has broad material applicability and can reveal the intrinsic mechanism of transmembrane mass transfer. By quantitatively characterizing the transmembrane energy barriers of different ions, the roles of factors such as membrane pore size, charge distribution, and interfacial energy barriers in selective ion mass transfer can be clarified. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the method flow of the present invention; Figure 2 A schematic diagram of the device structure provided by the present invention. Figure 3 A schematic diagram illustrating the determination of the ion transference number of sodium ions in sodium chloride via a cation exchange membrane using the method of Example 2 provided by the present invention; Figure 4 A schematic diagram illustrating the method for determining the transmembrane energy barrier of a cation exchange membrane for sodium ions in sodium chloride, as provided in Example 2 of this invention. Figure 5 A schematic diagram illustrating the determination of the ion transport number of chloride ions in sodium chloride by the method of Example 3 provided by the present invention; Figure 6 A schematic diagram illustrating the method for determining the transmembrane energy barrier of anion exchange membrane for chloride ions in sodium chloride, as provided in Example 3 of this invention.

[0018] In the diagram: 1. High concentration chamber; 2. Low concentration chamber; 3. Working electrode; 4. Recording electrode; 5. Counter electrode; 6. Reference electrode; 7. Circulating water bath channel; 8. Separation membrane; 9. Quartz capillary; 10. Circulating water bath pump. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example: Please see Figure 1 This embodiment provides a method for determining the transmembrane energy barrier of a single ion in a separation membrane under electrically driven conditions, comprising the following steps: S1: Install the separation membrane 8 to be tested in a high-concentration salt solution and a low-concentration salt solution with a concentration difference to form a transmembrane mass transfer system. S2: Linear sweep voltammetry was performed on the transmembrane mass transfer system using a four-electrode system to obtain the current-potential curve, and the membrane potential ΔE was obtained from the current-potential curve. m Based on membrane potential ΔE m The concentration difference between high-concentration and low-concentration salt solutions was used, and the ion transport numbers were calculated by fitting the Nernst equation, where the ion transport numbers included the positive ion transport numbers. and negative ion transport number ; S3: Adjust the temperature of the transmembrane mass transfer system, perform linear scanning voltammetry tests on the transmembrane mass transfer system at different preset temperatures based on the four-electrode system, obtain the current-potential curves at different preset temperatures, and obtain the ionic conductivity G at each preset temperature by linear fitting of the current-potential difference curves at different preset temperatures. S4: Based on the ion transport number and the ion conductivity G at each preset temperature, the single-ion transmembrane energy barrier of the target ion is calculated by performing linear fitting based on the Arrhenius equation. .

[0021] Furthermore, by adjusting the temperature, solution concentration, and electrochemical conditions, repeated tests can be performed on transmembrane mass transfer systems composed of different ion systems and different membrane materials. A correlation model between membrane selectivity, ion mass transfer resistance, and transmembrane energy barrier can be established, providing a basis for membrane material design and ion selectivity control.

[0022] The Nernst equation is an important formula in electrochemistry, used to describe the relationship between electrode potential and factors such as reactant concentration and temperature. This equation describes the relationship between electrode potential and the concentrations of reactants and products in solution, and is one of the fundamental equations in electrochemistry. Using this equation, changes in electrode potential under different conditions can be calculated, thus providing a theoretical basis for studying ion migration behavior.

[0023] The Arrhenius equation is an empirical formula describing the relationship between chemical reaction rates and temperature. This equation allows analysis of the influence of temperature on chemical reaction rates, thereby revealing the thermodynamic characteristics of ion transmembrane mass transfer. In practical applications, fitting the Arrhenius equation with experimental data can effectively obtain activation energy parameters related to ion migration, providing important quantitative evidence for understanding transmembrane mass transfer mechanisms.

[0024] The separation membrane 8 is selected from ion exchange membranes, polyamide membranes, or other self-made separation membranes. These membranes have different properties and applications, and can be selected and applied according to actual needs. Ion exchange membranes typically possess good selectivity and high ion conductivity, making them suitable for efficient separation processes of specific ions. Polyamide membranes are known for their excellent mechanical strength and chemical stability, maintaining stable performance even in harsh environments. Self-made separation membranes can be customized according to specific experimental or process requirements to meet separation needs under special conditions. The selection of these membrane materials directly affects the separation efficiency and system stability; therefore, in practical applications, multiple factors need to be considered comprehensively to determine the optimal solution.

[0025] Specifically, this invention is based on a four-electrode electrochemical system, using linear sweep voltammetry to test the transmembrane mass transfer system, obtaining the current-potential characteristics of the ion transmembrane process, and based on the membrane potential ΔE. m The concentration difference of the ions is used, and the ion transport number is calculated by fitting the Nernst equation. The ionic conductivity G of the cations and / or anions is calculated by combining linear fitting. The single-ion transmembrane energy barrier of the target ion is calculated by linear fitting according to the Arrhenius equation. Under the action of an external electric field, different ions are allowed to pass through the separation membrane, thereby realizing the quantitative determination of the transmembrane energy barrier of a single ion, which can directly quantify the transmembrane energy barrier of a single ion.

[0026] This invention effectively separates the ion response signal driven by the electric field by constructing a four-electrode system and using linear scanning voltammetry, avoiding the interference of polarization effects and coexisting ions. This results in obtaining real and independent single-ion transmembrane migration behavior. Factors such as ion coexistence effects, concentration gradients, and interface potential distribution do not participate in the calculation of the single-ion transmembrane energy barrier, thus avoiding their interference with the test results. This allows for accurate characterization of the target ion transmembrane dynamics and provides good performance.

[0027] The method of this invention can accurately resolve the mass transfer differences of different ions within the membrane, providing new experimental strategies and theoretical basis for revealing and regulating the transmembrane mass transfer mechanism of membrane materials.

[0028] In this embodiment, the concentration ratio of the low-concentration salt solution to the high-concentration salt solution ranges from 1:1 to 1:100; The cations in low-concentration and high-concentration salt solutions are Li + Na + K + 、Rb + Cs + NH4 + Ca 2+ Mg 2+ Ba 2 + Cu2+ Zn 2+ Ag + Co 2+ Mn 2+ Fe 2+ Cr 3+ And Al 3+ At least one of them; The cations in low-concentration salt solutions and high-concentration salt solutions are F. - Cl - ,Br - I - SO4 2- SO3 2- NO3 - NO2 - PO4 3- CO3 2- and ClO4 - At least one of them.

[0029] Specifically, by adjusting the concentration ratio of low-concentration salt solution to high-concentration salt solution, the mass transfer behavior of ions during transmembrane processes can be effectively controlled. During the experiment, different combinations of cations and anions can be selected to simulate transmembrane mass transfer conditions under various practical application scenarios. This not only improves the flexibility of the test but also provides a reliable experimental means for analyzing the ion mass transfer mechanism in complex systems.

[0030] In this embodiment, a linear sweep voltammetry test is performed on the transmembrane mass transfer system using a four-electrode system to obtain a current-potential curve, and the membrane potential ΔE is obtained from the current-potential curve. m Based on membrane potential ΔE m The concentration difference between high-concentration and low-concentration salt solutions was used to calculate the ion transport number based on the Nernst equation, including: The membrane potential ΔE is obtained from the intercept of the current-potential curve on the potential axis. m Ion transport numbers were calculated based on Nernst equation fitting. ; Among them, C h The electrolyte concentration of a high-concentration salt solution is C. l Let R be the electrolyte concentration of the low-concentration salt solution, T be the absolute temperature, and F be the Faraday constant. It is the transference number of the positive ion. The transport number of negative ions is denoted as , where . + =1.

[0031] Specifically, the current-potential curve obtained through linear sweep voltammetry can intuitively reflect the electrochemical characteristics of the transmembrane mass transfer system. In practice, it is necessary to ensure the stability of the concentration gradient between high-concentration and low-concentration salt solutions and to strictly control the experimental temperature to reduce the interference of external factors on the results. Furthermore, to improve measurement accuracy, appropriate scan rates and electrode materials should be selected to ensure the reliability and repeatability of the current-potential curve.

[0032] In this embodiment, based on the ion transport number and the ion conductivity G at each preset temperature, the single-ion transmembrane energy barrier E of the target ion is calculated by linear fitting using the Arrhenius equation. P ,include; The ionic conductivity G was obtained at each preset temperature, and the transmembrane energy barrier was calculated based on the Arrhenius equation. ; ; Where G is the overall ionic conductivity. Where is the ion transport number, and T is the absolute temperature. R is the pre-exponential factor, and R is the gas constant; The preset temperature range is 5℃ to 65℃.

[0033] Specifically, by measuring ionic conductivity at different preset temperatures, the influence of temperature on ion transmembrane behavior can be further analyzed. During the experiment, it is necessary to ensure the consistency of test conditions for each test to reduce the introduction of systematic errors. By performing linear regression analysis on the data, the single-ion transmembrane energy barrier of the target ion can be obtained.

[0034] In this embodiment, the Arrhenius equation is linearly fitted, and the correlation coefficient of the linear fit is not less than 0.95.

[0035] Specifically, a fitting correlation coefficient of not less than 0.95 reflects a high degree of agreement between the experimental data and the theoretical model of the Arrhenius equation. This indicates that the target ion single-ion transmembrane energy barrier results obtained by fitting the equation are highly reliable, reducing errors caused by data discrepancies or model mismatches, and ensuring the accuracy of the thermodynamic characteristics analysis during ion transmembrane mass transfer.

[0036] In this embodiment, the operating voltage of the linear scanning voltammetry test is -200mV to 200mV, and the scanning rate is 0.01mV / s to 50mV / s.

[0037] Specifically, by adjusting the working voltage and scan rate of the linear scan voltammetry test, the redox behavior characteristics of target ions on the electrode surface can be effectively captured. The working voltage setting should be optimized in combination with the electrochemical window of the specific system to ensure the stability and repeatability of the measurement signal.

[0038] Please see Figure 2 This invention provides an apparatus for determining the transmembrane energy barrier of a single ion in a separation membrane under electrically driven conditions, comprising: The test body has a centrally connected channel, and a separation membrane 8 is installed in the channel. The separation membrane 8 is used to divide the test body into a high-concentration chamber 1 and a low-concentration chamber 2. The test body is made of glass or quartz material. The four-electrode system includes a working electrode 3 and a recording electrode 4 disposed in the high-concentration chamber 1, and a counter electrode 5 and a reference electrode 6 disposed in the low-concentration chamber 2. Independent quartz capillary tubes 9 are respectively disposed in the high-concentration chamber 1 and the low-concentration chamber 2, and the recording electrode 4 and the reference electrode 6 are both disposed in the quartz capillary tubes 9. The signal control and acquisition system includes an electrochemical workstation, the first signal terminal of which is connected to the working electrode 3 and the recording electrode 4, and the second signal terminal of which is connected to the counter electrode 5 and the reference electrode 6. The constant temperature circulation system is located on the outside of the test body. The circulating fluid in the constant temperature system is used for constant temperature heating of the high concentration chamber 1 and the low concentration chamber 2.

[0039] Specifically, a high-concentration salt solution is placed in the high-concentration chamber 1 and a low-concentration salt solution is placed in the low-concentration chamber 2 within the test module. By controlling the output of a specific voltage signal from the electrochemical workstation, ions undergo directional migration across the separation membrane 8. Recording electrode 4 and reference electrode 6 are used to monitor the potential changes in the high-concentration chamber 1 and low-concentration chamber 2, respectively, thereby obtaining accurate potential difference data. The quartz capillary 9 effectively reduces the interference of ion diffusion in the solution on the measurement results, ensuring data accuracy. Furthermore, the isothermal circulation system maintains a stable test environment temperature, avoiding measurement errors caused by temperature fluctuations. Simultaneously, by adjusting the temperature of the circulating fluid, the transmembrane migration behavior of ions under different temperature conditions can be further studied.

[0040] In this embodiment, as Figure 2As shown, the constant temperature circulation system includes a first circulation chamber and a second circulation chamber. The first circulation chamber is located on the outer wall of the high concentration chamber 1, and the second circulation chamber is located on the outer wall of the low concentration chamber 2. The upper and lower ends of the first and second circulation chambers are connected to the circulating water bath channel 7. The circulating water bath channel 7 is connected to the circulating water bath pump 10 through a pipe. The circulating water bath pump 10 is used to drive the constant temperature fluid to flow into the first and second circulation chambers from bottom to top. The flow rate of the constant temperature fluid is in the range of 0.1 L / min to 10 L / min.

[0041] Specifically, the circulating water bath pump 10 is equipped with an intelligent control system, which can precisely adjust the flow rate according to experimental requirements, thereby achieving precise control of the test environment temperature. The circulating water bath pump 10 is connected to the corresponding circulating water bath channel 7 through a pipeline, so that the water bath fluid forms a stable temperature field between the first and second circulation chambers, ensuring the temperature consistency between the high concentration chamber 1 and the low concentration chamber 2.

[0042] In this embodiment (not shown in the figure), a support frame is detachably installed in the channel, and a separation membrane 8 is installed on the support frame. The thickness of the separation membrane 8 is 50nm~10000nm.

[0043] Specifically, the support frame facilitates quick replacement of the separation membrane 8 to meet the needs of different experimental conditions. Users can select separation membranes 8 with different pore sizes and materials according to the test objectives to achieve the best separation effect.

[0044] In this embodiment, as Figure 2 As shown, the quartz capillary 9 is an L-shaped sand core salt bridge or an L-shaped Luggin capillary. The distance between the bottom elbow outlet of the quartz capillary 9 and the separation membrane 8 is 1mm~2mm. The quartz capillary 9 is made of quartz glass. Hydrolysis of the working electrode 3 and the counter electrode 5 should be avoided during the test. Both the working electrode 3 and the counter electrode 5 should be sheet-shaped platinum electrodes or sheet-shaped titanium electrodes.

[0045] Specifically, the quartz capillary tube 9 can effectively reduce the resistance of liquid phase mass transfer while ensuring the stability of ion migration path. Its L-shaped structure design not only facilitates installation and operation but also avoids measurement errors caused by fluid impact. The precise distance between the bottom elbow outlet and the separation membrane 8 ensures the uniformity of the ion diffusion layer, thereby improving the accuracy and repeatability of test results, reducing the interference of the external environment on the experiment, and providing a reliable guarantee for long-term stable operation.

[0046] The circulating water bath channel 7 in the device ensures consistent temperature across the separation membrane, significantly reducing the impact of temperature fluctuations on test results. Simultaneously, Arrhenius fitting using conductivity data from multiple temperature zones ensures the reliability and accuracy of transmembrane energy barrier calculations. A detachable support frame is installed within the channel, upon which the separation membrane 8 is mounted. The support frame facilitates quick replacement of the separation membrane 8, demonstrating the invention's broad material applicability. This device and method can be used to test nanofiltration membranes, reverse osmosis membranes, anion and cation exchange membranes, and other self-made membrane materials, adapting to studies of single-ion transmembrane behavior under different membrane structures and surface charge characteristics. This invention reveals the intrinsic mechanism of transmembrane mass transfer. By quantitatively characterizing the transmembrane energy barriers of different ions, the roles of membrane pore size, charge distribution, and interfacial energy barriers in selective ion mass transfer can be clarified, thereby establishing a microscopic mechanism model for the source of ion selectivity. This invention provides a theoretical basis for the structural design and performance optimization of membrane materials. By establishing a quantitative relationship between membrane structure parameters, surface charge characteristics, and single-ion transmembrane energy barriers, the design of highly selective and high-flux membrane materials can be guided, promoting the development of membrane technology in water treatment and energy separation.

[0047] Example 1: like Figure 2 As shown, this embodiment provides an apparatus for measuring the transmembrane energy barrier of a single ion in a separation membrane under electrically driven conditions, comprising: a high-concentration chamber 1: a first chamber for holding a high-concentration solution to be tested, wherein a working electrode 3 and a recording electrode 4 are inserted; and a low-concentration chamber 2: a second chamber for holding a low-concentration solution, wherein a counter electrode 5 and a reference electrode 6 are inserted.

[0048] Both the working electrode 3 and the counter electrode 5 are 3cm × 3cm platinum sheets, placed outside the high and low concentration chambers respectively. The recording electrode 4 and the reference electrode 6 are both Ag / AgCl electrodes, each placed inside an independent quartz sand core salt bridge (quartz capillary 9). The salt bridge is filled with a 3M KCl solution to ensure stable electrode interface potential. The outlet of the quartz capillary 9 is kept at the same horizontal level as the center of the separation membrane, thereby eliminating the additional potential caused by the gravity liquid level difference and improving the accuracy and repeatability of the measurement.

[0049] Example 2: Using a high-concentration salt solution as the sodium chloride solution, with a sodium chloride concentration of 100 mM, and subsequent concentrations of 10 mM, 20 mM, and 50 mM, corresponding to concentration gradients of 10:1, 5:1, and 2:1, as an example, the method for determining the transmembrane energy barrier of Na+ ions in a cation exchange membrane is as follows: (1) In the four-electrode system, the current-potential relationship curve of ions across the membrane was determined by linear sweep voltammetry. Under the set concentration gradient (the high-concentration chamber ratio sodium chloride concentration was 100 mM, and the low-concentration chamber ratio solution concentrations were 10 mM, 20 mM, and 50 mM, respectively, forming concentration gradients of 10:1, 5:1, and 2:1), the membrane potential (ΔEm) obtained by LSV was the intercept of the IV curve on the voltage axis (i.e., the voltage value when the current is zero). Subsequently, with Linear fitting was performed with ΔEm as the x-axis and ΔEm as the y-axis to obtain the sodium ion transport number ( ); (1) The experimental fitting results are as follows Figure 3 As shown, the sodium ion transference number is 0.98, indicating that the membrane has high selectivity for Na+.

[0050] (2) Continue to use LSV to determine the current-potential curves at different temperatures and obtain the single-ion conductivity G. Using the Arrhenius equation: (2) Where G is the overall ionic conductivity, t+ is the ion transport number, T is the absolute temperature, B+ is the pre-exponential factor, and R is the gas constant.

[0051] With 1 / T as the x-axis, Perform linear fitting on the ordinate (e.g.) Figure 4 As shown in the figure, the transmembrane energy barrier of sodium ions was obtained from the slope. The results show that the transmembrane energy barrier of sodium ions is 38.5 kJ / mol.

[0052] Example 3: Using a high-concentration salt solution as the KCl solution, with KCl concentrations of 100 mM, and subsequent concentrations of 10 mM, 20 mM, and 50 mM, forming concentration gradients of 10:1, 5:1, and 2:1 respectively, the method for determining the chloride ion transmembrane energy barrier of anion exchange membranes is described below. (1) The KCl concentration in the high-concentration chamber was 100 mM, and the low-concentration chambers were 10, 20, and 50 mM, respectively. The LSV curve was measured according to the method in Example 2, and the membrane potential ΔEm was obtained. The transport number was obtained by linear fitting. The formula is as follows; (1) The fitting results are as follows Figure 5 As shown, chloride ion transport number 0.95.

[0053] (2) The single-ion conductivity at different temperatures was measured using the same method as in Example 2, and fitted using the Arrhenius equation: (2) With 1 / T as the x-axis, A linear fit is performed on the ordinate to calculate the chloride ion transmembrane energy barrier (e.g., ...). Figure 6 (As shown). Figure 6 The fitting results show that the transmembrane energy barrier of chloride ions is 87.75 kJ / mol.

[0054] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for determining the transmembrane energy barrier of a single ion in a separated membrane under electrically driven conditions, characterized in that, Includes the following steps: In a high-concentration salt solution and a low-concentration salt solution with a concentration difference, the separation membrane to be tested is installed to form a transmembrane mass transfer system. Linear sweep voltammetry was performed on the transmembrane mass transfer system using a four-electrode system to obtain the current-potential curve, and the membrane potential ΔE was obtained from the current-potential curve. m Based on the membrane potential ΔE m The concentration difference between high-concentration and low-concentration salt solutions was used, and the ion transport numbers were calculated by fitting the Nernst equation, where the ion transport numbers included the positive ion transport numbers. and negative ion transport number ; The temperature of the transmembrane mass transfer system is adjusted, and linear scanning voltammetry is performed on the transmembrane mass transfer system at different preset temperatures based on a four-electrode system to obtain current-potential curves at different preset temperatures. The ionic conductivity G at each preset temperature is obtained by linear fitting of the current-potential difference curves at different preset temperatures. Based on the ion transport number and the ionic conductivity G at each preset temperature, the single-ion transmembrane energy barrier of the target ion is calculated by linear fitting using the Arrhenius equation. .

2. The method for determining the transmembrane energy barrier of a single ion in a separated membrane under electrically driven conditions according to claim 1, characterized in that, The concentration ratio of the low-concentration salt solution to the high-concentration salt solution is in the range of 1:1 to 1:100; The cations in the low-concentration salt solution and the high-concentration salt solution are Li. + Na + K + 、Rb + Cs + NH4 + Ca 2+ Mg 2+ Ba 2 + Cu 2+ Zn 2+ Ag + Co 2+ Mn 2+ Fe 2+ Cr 3+ And Al 3+ At least one of them; The cation in the low-concentration salt solution and the high-concentration salt solution is F. - Cl - ,Br - I - SO4 2- SO3 2- NO3 - NO2 - PO4 3- CO3 2- and ClO4 - At least one of them.

3. The method for determining the transmembrane energy barrier of a single ion in a separated membrane under electrically driven conditions according to claim 2, characterized in that, A linear sweep voltammetry test was performed on the transmembrane mass transfer system using a four-electrode system to obtain a current-potential curve, and the membrane potential ΔE was obtained from the current-potential curve. m Based on the membrane potential ΔE m The concentration difference between high-concentration and low-concentration salt solutions was used to calculate the ion transport number based on the Nernst equation, including: The membrane potential ΔE is obtained from the intercept of the current-potential curve on the potential axis. m Ion transport numbers were calculated based on Nernst equation fitting. ； Among them, C h The electrolyte concentration of a high-concentration salt solution is C. l Let R be the electrolyte concentration of the low-concentration salt solution, T be the absolute temperature, and F be the Faraday constant. It is the transference number of the positive ion. The transport number of negative ions is denoted as , where . + =1.

4. The method for determining the transmembrane energy barrier of a single ion in a separated membrane under electrically driven conditions according to claim 3, characterized in that, The single-ion transmembrane energy barrier E of the target ion is calculated by linear fitting based on the ion transport number and the ion conductivity G at each preset temperature using the Arrhenius equation. P ,include; The ionic conductivity G was obtained at each preset temperature, and the transmembrane energy barrier was calculated based on the Arrhenius equation. ; ； Where G is the overall ionic conductivity. Where is the ion transport number, and T is the absolute temperature. R is the pre-exponential factor, and R is the gas constant; The preset temperature range is 5℃ to 65℃.

5. The method for determining the transmembrane energy barrier of a single ion in a separated membrane under electrically driven conditions according to claim 4, characterized in that, The Arrhenius equation is linearly fitted, and the correlation coefficient of the linear fit is not less than 0.

95.

6. The method for determining the transmembrane energy barrier of a single ion in a separated membrane under electrically driven conditions according to claim 5, characterized in that, The operating voltage of the linear scanning voltammetry test is -200mV to 200mV, and the scanning rate is 0.01mV / s to 50mV / s.

7. An apparatus for determining the transmembrane energy barrier of a single ion in a separated membrane under electrically driven conditions, applied to the method for determining the transmembrane energy barrier of a single ion in a separated membrane under electrically driven conditions as described in any one of claims 1-6, characterized in that, include: The test body has a centrally connected channel, and a separation membrane (8) is installed in the channel. The separation membrane (8) is used to divide the test body into a high-concentration chamber (1) and a low-concentration chamber (2). The four-electrode system includes a working electrode (3) and a recording electrode (4) disposed in the high-concentration chamber (1), and a counter electrode (5) and a reference electrode (6) disposed in the low-concentration chamber (2). The high-concentration chamber (1) and the low-concentration chamber (2) are respectively provided with independent quartz capillary tubes (9), and the recording electrode (4) and the reference electrode (6) are both disposed in the quartz capillary tubes (9). The signal control and acquisition system includes an electrochemical workstation, wherein the first signal terminal of the electrochemical workstation is connected to the working electrode (3) and the recording electrode (4), and the second signal terminal of the electrochemical workstation is connected to the counter electrode (5) and the reference electrode (6). A constant temperature circulation system is set on the outside of the test body, and a circulating fluid flows inside the constant temperature system. The circulating fluid is used for constant temperature heating of the high concentration chamber (1) and the low concentration chamber (2).

8. The apparatus for determining the transmembrane energy barrier of a single ion in a separated membrane under electrically driven conditions according to claim 7, characterized in that, The constant temperature circulation system includes a first circulation chamber and a second circulation chamber. The first circulation chamber is located on the outer wall of the high concentration chamber (1), and the second circulation chamber is located on the outer wall of the low concentration chamber (2). The upper and lower ends of the first and second circulation chambers are connected to a circulating water bath channel (7). The circulating water bath channel (7) is connected to a circulating water bath pump (10) through a pipe. The circulating water bath pump (10) is used to drive the constant temperature fluid to flow from bottom to top into the first and second circulation chambers. The flow rate of the constant temperature fluid is in the range of 0.1 L / min to 10 L / min.

9. The apparatus for determining the transmembrane energy barrier of a single ion in a separated membrane under electrically driven conditions, as described in claim 8, is characterized in that... A support frame is detachably installed inside the channel, and a separation membrane (8) is installed on the support frame. The thickness of the separation membrane (8) is 50nm~10000nm.

10. The apparatus for determining the transmembrane energy barrier of a single ion in a separated membrane under electrically driven conditions, as described in claim 9, is characterized in that... The quartz capillary (9) is an L-shaped sand core salt bridge or an L-shaped Lukin capillary, and the distance between the bottom elbow outlet of the quartz capillary (9) and the separation membrane (8) is 1mm~2mm. Both the working electrode (3) and the counter electrode (5) are made of sheet-shaped platinum electrodes or sheet-shaped titanium electrodes.

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