Ion transmembrane hydration number testing method based on non-equilibrium thermodynamics

Abstract

The invention provides an ion transmembrane hydration number testing method based on non-equilibrium thermodynamics. The testing method comprises the following steps: clamping a membrane in an H-type electrolytic tank, and respectively filling different solutions at two sides of the membrane, so as to measure the potential difference at two sides of the membrane. Specifically, the electrolytic tank on one side is filled with a mixed solution containing salt and non-membrane neutral molecules, the electrolytic tank on the other side is only filled with a salt solution, and the salt concentrations on the two sides are the same. The potential difference between the two sides of the membrane is tested through an electrochemical workstation, mathematical fitting is conducted according to the change of the potential difference along with time, and therefore the relation between the potential difference and the ion transmembrane hydration number is obtained, and finally measurement of the ion transmembrane hydration number is achieved. The method can quantify the transmembrane hydration state of the ions, and is of great significance to research on an ion mass transfer mechanism, selective separation of the ions, physicochemical characteristics of the membrane and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of testing methods for ion transmembrane phenomena, and in particular to a testing method for ion transmembrane hydration number based on non-equilibrium thermodynamics. Background Art

[0002] The hydration number of an ion (i.e., the number of water molecules surrounding the ion) is important for understanding the ion transmembrane process, membrane selectivity, and the behavior of ions in solution. In many applications, such as membrane filtration, electrochemical desalination, and selective recovery of high-value metal ions, the interaction between ions and water molecules has an important influence on the performance of the system. In order to better understand these phenomena, it is crucial to accurately determine the hydration status of ions.

[0003] Traditional methods for testing ion hydration numbers mainly rely on femtosecond / mass spectrometry analysis and molecular simulation calculations, but these methods are complex and time-consuming and require relatively special experimental equipment and environments. Summary of the invention

[0004] To solve the above technical problems, the present invention provides a method for testing the ion transmembrane hydration number based on non-equilibrium thermodynamics. The present invention provides a method that combines the theory of non-equilibrium thermodynamics with electrochemical signal measurement technology, which can calculate the ion transmembrane hydration number by the change of the potential difference on both sides of the membrane under relatively simple experimental conditions, with high accuracy and practicality. This method is mainly used in the fields of membrane separation technology, electrochemical analysis, and ion hydration research, and provides an important theoretical basis for understanding the ion behavior during ion membrane passage.

[0005] The object of the present invention is to provide a method for testing the ion transmembrane hydration number based on non-equilibrium thermodynamics, comprising the following steps: The membrane is placed between a first electrolytic cell and a second electrolytic cell of an H-type electrolytic cell provided with a membrane clamp; injecting a mixed solution containing salt and neutral molecules that do not cross the membrane into the first electrolytic cell; injecting a salt solution having the same concentration as that in the first electrolytic cell into the second electrolytic cell; Two reference electrodes are provided and placed in Luggin capillaries containing saturated potassium chloride solution, respectively, and are placed in the first electrolytic cell and the second electrolytic cell, respectively; Connect to an electrochemical workstation to measure the potential difference across the membrane , and record the potential difference Changes over time ; The potential difference and Linear fitting was performed to obtain the relationship between the ion transmembrane potential difference and time, and the ion transmembrane hydration number was calculated according to the following formula: , in, is the potential difference across the membrane, n is the hydration number of the ion across the membrane, F is the Faraday constant, is the molar volume of water molecules, R is the gas constant, T is the thermodynamic temperature, c i is the concentration of membrane-intransitive neutral molecules in the mixed solution, S(c0) is the fitting coefficient, and t is the test time.

[0006] In some embodiments of the present invention, the membrane is a cation exchange membrane, an anion exchange membrane, a reverse osmosis membrane, a nanofiltration membrane, a microfiltration membrane or an ultrafiltration membrane.

[0007] In some embodiments of the present invention, the salt solution is one of LiCl, NaCl, KCl, KBr, KI, Na2SO4, MgCl2, and CaCl2 solutions.

[0008] In some embodiments of the present invention, the concentration of the salt solution is 0.01-1.00 mol / L.

[0009] In some embodiments of the present invention, the concentration of the salt solution is 0.01-0.1 mol / L. For example, it can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1 mol / L, etc., or any interval value between any two values.

[0010] In some embodiments of the present invention, the neutral molecules that do not cross the membrane are selected from one or more of glucose, sucrose and urea.

[0011] In some embodiments of the present invention, the concentration of membrane-independent neutral molecules in the mixed solution is 0.1-2.00 mol / L.

[0012] In some embodiments of the present invention, the concentration of membrane-independent neutral molecules in the mixed solution is 0.1-1.00 mol / L, and illustratively, it can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.00 mol / L, etc.

[0013] In some embodiments of the present invention, the reference electrode is an Ag / AgCl electrode or a calomel electrode.

[0014] The H-type electrolytic cell device used in the present invention comprises: an electrochemical workstation, a first electrolytic cell connected to the electrochemical workstation, and a second electrolytic cell, wherein the first electrolytic cell and the second electrolytic cell are arranged opposite to each other, and the electrolytic cell device further comprises a membrane clamp connecting the first electrolytic cell and the second electrolytic cell, wherein the membrane clamp is used to fix and clamp the membrane, a first Luggin capillary is arranged in the first electrolytic cell, and the tip of the first Luggin capillary extends from the first electrolytic cell and extends to the first side of the membrane clamp, and a second Luggin capillary is arranged in the second electrolytic cell, and the second Luggin capillary extends from the first electrolytic cell to the first side of the membrane clamp. The tip of the electrode extends from the second electrolytic cell and extends to the second side of the membrane clamp, the working electrode and the working sensing electrode extend into the first Luggin capillary, the first electrolytic cell is connected to the electrochemical workstation via the working electrode and the working sensing electrode, the reference electrode and the counter electrode extend into the second Luggin capillary, the second electrolytic cell is connected to the electrochemical workstation via the reference electrode and the counter electrode; the first electrolytic cell contains a mixed solution of salt and neutral molecules that do not pass through the membrane, and the second electrolytic cell contains a salt solution with the same concentration as that of the first electrolytic cell.

[0015] The above technical solution of the present invention has the following advantages compared with the prior art: This method uses an electrochemical workstation to monitor the potential difference changes on both sides of the membrane in real time, simplifies the experimental process, saves time and cost, and avoids the complex experimental conditions required by traditional methods. The present invention does not require complex pretreatment of samples, and directly obtains data through electrochemical measurements. It is easy to operate, has strong applicability, and has broad application prospects. It can be applied to membrane separation, electrochemical desalination, water treatment and other fields to help optimize membrane materials, improve battery performance and water treatment efficiency, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein: Figure 1 It is a schematic diagram of the electrochemical test ion transmembrane potential difference device of the present invention.

[0017] Figure 2 It is a fitting relationship diagram between the ion transmembrane potential difference and time in the present invention.

[0018] Figure 3 is Li in Examples 1 to 3 of the present invention + 、Na + , K + Test results across different membrane hydration numbers. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0020] Embodiment 1: This embodiment provides a method for determining the transmembrane hydration number of ions based on non-equilibrium thermodynamics, and the specific steps are as follows: (1) a commercial ASTOM CMX cation exchange membrane is sandwiched between two electrolytic cells of an H-type electrolytic cell (a conventional H-type electrolytic cell in the art) with a single-side electrolytic cell of 50 mL to form a first electrolytic cell and a second electrolytic cell; (2) adding a mixed solution of 0.1 mol / L LiCl solution and 1 mol / L glucose into the first electrolytic cell; adding 0.1 mol / L LiCl solution into the second electrolytic cell; (3) Place two Ag / AgCl electrodes in a Luggin capillary containing saturated potassium chloride solution, one on each side of the membrane; (4) Connect the working electrode clip and the working sensing electrode clip of the electrochemical workstation to the Ag / AgCl electrode of the first electrolytic cell, and connect the counter electrode clip and the reference electrode clip to the Ag / AgCl electrode of the second electrolytic cell (such as Figure 1 ), measure the potential difference between the two sides of the membrane, and record the change of the potential difference over time; (5) Through mathematical fitting, the relationship between the ion transmembrane potential difference and time is obtained , and the transmembrane hydration number of the ion is calculated based on the intercept of the relationship.

[0021] The schematic diagram of the device for testing the ion transmembrane potential difference in Example 1 is as follows Figure 1 As shown, the Li obtained in step (5) + The hydration number is about 6.01, and the results are as follows Figure 3 shown.

[0022] Embodiment 2: This embodiment provides a method for determining the transmembrane hydration number of ions based on non-equilibrium thermodynamics, and the specific steps are as follows: (1) A commercial Fumatech FKS-PET-75 cation exchange membrane was sandwiched between two electrolytic cells of an H-type electrolytic cell with a single-side electrolytic cell of 50 mL to form a first electrolytic cell and a second electrolytic cell; (2) adding a mixed solution of 0.1 mol / L NaCl solution and 1 mol / L glucose into the first electrolytic cell; adding 0.1 mol / L NaCl solution into the second electrolytic cell; (3) Place two Ag / AgCl electrodes in a Luggin capillary containing saturated potassium chloride solution, one on each side of the membrane; (4) Connect the working electrode clip and the working sensing electrode clip of the electrochemical workstation to the Ag / AgCl electrode of the first electrolytic cell, and connect the counter electrode clip and the reference electrode clip to the Ag / AgCl electrode of the second electrolytic cell (such as Figure 1 ), measure the potential difference between the two sides of the membrane, and record the change of the potential difference over time; (5) Through mathematical fitting, the relationship between the ion transmembrane potential difference and time is obtained , and the transmembrane hydration number of the ion is calculated based on the intercept of the relationship.

[0023] The schematic diagram of the device for testing the ion transmembrane potential difference in Example 1 is as follows Figure 1 As shown, the Na obtained in step (5) + The hydration number is about 4.86, and the results are as follows Figure 3 shown.

[0024] Embodiment 3: This embodiment provides a method for determining the transmembrane hydration number of ions based on non-equilibrium thermodynamics, and the specific steps are as follows: (1) A commercial Nafion 211 cation exchange membrane is sandwiched between two electrolytic cells of an H-type electrolytic cell with a single-side electrolytic cell of 50 mL to form a first electrolytic cell and a second electrolytic cell; (2) adding a mixed solution of 0.1 mol / L KCl solution and 1 mol / L glucose into the first electrolytic cell; adding 0.1 mol / L KCl solution into the second electrolytic cell; (3) Place two Ag / AgCl electrodes in a Luggin capillary containing saturated potassium chloride solution, one on each side of the membrane; (4) Connect the working electrode and the working sensing electrode of the electrochemical workstation to the Ag / AgCl electrode of the first electrolytic cell, and connect the counter electrode and the reference electrode to the Ag / AgCl electrode of the second electrolytic cell, measure the potential difference between the two sides of the membrane, and record the change of the potential difference over time; (5) Through mathematical fitting, the relationship between the ion transmembrane potential difference and time is obtained , and the transmembrane hydration number of the ion is calculated based on the intercept of the relationship.

[0025] The schematic diagram of the device for testing the ion transmembrane potential difference in Example 1 is as follows Figure 1 As shown, the K obtained in step (5) is + The hydration number is about 3.92, and the results are as follows Figure 3 shown.

[0026] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for testing the ion transmembrane hydration number based on non-equilibrium thermodynamics, characterized in that: The following steps are involved: The membrane is placed between a first electrolytic cell and a second electrolytic cell of an H-type electrolytic cell provided with a membrane clamp; injecting a mixed solution containing salt and neutral molecules that do not cross the membrane into the first electrolytic cell; injecting a salt solution having the same concentration as that in the first electrolytic cell into the second electrolytic cell; Two reference electrodes are provided and placed in Luggin capillaries containing saturated potassium chloride solution, respectively, and are placed in the first electrolytic cell and the second electrolytic cell, respectively; Connect to an electrochemical workstation to measure the potential difference across the membrane , and record the potential difference Changes over time ; The potential difference and Linear fitting was performed to obtain the relationship between the ion transmembrane potential difference and time, and the ion transmembrane hydration number was calculated according to the following formula: ， in, is the potential difference across the membrane, n is the hydration number of the ion across the membrane, F is the Faraday constant, is the molar volume of water molecules, R is the gas constant, T is the thermodynamic temperature, c i is the concentration of membrane-intransitive neutral molecules in the mixed solution, S(c0) is the fitting coefficient, and t is the test time.

2. A method for testing the ion transmembrane hydration number based on non-equilibrium thermodynamics according to claim 1, characterized in that: The membrane is a cation exchange membrane, an anion exchange membrane, a reverse osmosis membrane, a nanofiltration membrane, a microfiltration membrane, and an ultrafiltration membrane.

3. The method for testing the ion transmembrane hydration number based on non-equilibrium thermodynamics according to claim 1, characterized in that: The salt solution is one of LiCl, NaCl, KCl, KBr, KI, Na2SO4, MgCl2, and CaCl2 solutions.

4. The method for testing the ion transmembrane hydration number based on non-equilibrium thermodynamics according to claim 1, characterized in that: The concentration of the salt solution is 0.01-1.00 mol / L.

5. The method for testing the ion transmembrane hydration number based on non-equilibrium thermodynamics according to claim 4, characterized in that: The concentration of the salt solution is 0.01-0.1 mol / L.

6. The method for testing the ion transmembrane hydration number based on non-equilibrium thermodynamics according to claim 1, characterized in that: The neutral molecules that do not pass through the membrane are selected from one or more of glucose, sucrose and urea.

7. The method for testing the ion transmembrane hydration number based on non-equilibrium thermodynamics according to claim 1, characterized in that: The concentration of membrane-independent neutral molecules in the mixed solution is 0.1~2.00 mol / L.

8. The method for testing the ion transmembrane hydration number based on non-equilibrium thermodynamics according to claim 7, characterized in that: The concentration of membrane-independent neutral molecules in the mixed solution is 0.1~1.00 mol / L.

9. The method for testing the ion transmembrane hydration number based on non-equilibrium thermodynamics according to claim 1, characterized in that: The reference electrode is a Ag / AgCl electrode or a calomel electrode.

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