CN115184417A - Thin film mass transfer performance evaluation instrument and method - Google Patents
Thin film mass transfer performance evaluation instrument and method Download PDFInfo
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Abstract
The invention provides a thin film mass transfer performance evaluation instrument and a method, wherein the evaluation instrument comprises a measuring pool, a temperature control system, a thin film to be characterized, a circulating pressurization system, a data integration acquisition system and a data processing system; the measuring cell is filled with solution; the measuring cell is arranged in the temperature control system; the film to be characterized is inserted into the measuring cell and divides the measuring cell into two independent left and right chambers; the circulating pressurization system is communicated with the measuring cell; the data integration acquisition system is used for acquiring basic electrochemical parameters of the film and the solution to be characterized in the left chamber and the right chamber; and the data processing system is used for calculating relevant parameters reflecting the film mass transfer performance to be represented according to a preset algorithm and finishing the output, display and storage of the relevant parameters. The mass transfer performance related parameter system and the mass transfer performance related parameter evaluation method of the integrated thin film material of the measuring instrument have the advantages of wide application range, high integration level, simplicity in operation and remarkable practicability and technical economy.
Description
Technical Field
The invention relates to the technical field of thin film material performance characterization, in particular to a thin film mass transfer performance evaluation instrument and a thin film mass transfer performance evaluation method.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
The membrane separation technology can effectively realize the high-efficiency interception or selective screening of target solutes, has the characteristics of good selectivity, simple operation, no secondary pollution and the like, and is widely applied to the fields of water treatment, battery manufacturing, chemical industry, food industry and the like. With the increasingly wide application of membrane separation technology, the characterization and evaluation of membrane mass transfer related performances such as ion interception/sieving/transmission performance, membrane integrity, membrane surface coating and deposition condition, membrane aging, membrane pollution degree and the like of thin film and composite membrane materials are also paid extensive attention.
In the existing thin film mass transfer performance evaluation and analysis method, the separation performance of the film is mostly reflected by macroscopic physical quantities such as film flux, film retention rate and the like, the detected and analyzed physical quantities are few and single in type, and the microscopic process related to the mass transfer behavior of the quantitative reaction film cannot be determined, and equipment for measuring microscopic physical properties in the thin film mass transfer process and an index system closely related to the film mass transfer process are not formed yet. On the other hand, the transmembrane mass transfer process of the solute is clear, the integrity, the aging degree, the surface coating deposition degree and the like of the membrane are represented, and the method has important significance for developing or upgrading the membrane material with better separation performance. Therefore, it is necessary to develop a technical method and a characterization instrument which are convenient for efficiently characterizing the transmembrane process of the solute and reflecting the mass transfer characteristics of the membrane material.
The electrochemical technology can be used for measuring basic indexes of the membrane material such as resistance, capacitance, potential, ion migration number and the like in a specific solution system, so that the physical quantities of the membrane material such as the thickness, zeta potential, solute transmembrane potential barrier and the like, which reflect the characteristics or mass transfer performance of the membrane material, can be further calculated. However, there is no standardized method for measuring the above physical quantities, and standardized and integrated instruments and equipment related to the characterization of membrane mass transfer performance are still under development.
Disclosure of Invention
Aiming at the material performance characterization requirements of the thin film and the problems in the prior art, the invention provides a thin film mass transfer performance evaluation instrument and a thin film mass transfer performance evaluation method, so as to effectively measure the physical quantity reflecting the film material characteristics or mass transfer performance.
The technical scheme of the invention is realized as follows:
the mass transfer performance evaluation instrument of the thin film comprises:
the measuring cell is filled with solution;
the temperature control system is used for adjusting the temperature of the solution in the measuring tank and stabilizing the temperature at a set value;
the thin film to be characterized is inserted into the measuring cell and divides the measuring cell into two independent left and right chambers;
the circulating pressurization system is communicated with the measuring pool and is used for providing pressure and cross flow conditions for the thin film to be characterized so as to simulate the actual operation conditions of the thin film to be characterized;
the data integration acquisition system is used for acquiring basic electrochemical parameters of the thin film and the solution to be characterized in the left chamber and the right chamber;
and the data processing system is used for receiving the information transmitted by the data integrated acquisition system, calculating relevant parameters reflecting the mass transfer performance of the film to be represented according to a preset algorithm, and finishing the output, display and storage of the relevant parameters.
Further optimize technical scheme, data integration collection system includes:
the working electrode and the counter electrode in the left chamber and the right chamber are platinum electrodes, the reference electrode is an Ag/AgCl electrode, and a two-electrode, three-electrode or four-electrode system can be adopted according to actual conditions;
the left side chamber and the right side chamber are respectively provided with a conductivity probe which is used for detecting the conductivity of the solution in the left side chamber or the right side chamber;
the temperature probes are respectively arranged in the left cavity and the right cavity and used for detecting the temperature of the solution in the left cavity or the right cavity;
and the data integration acquisition module is used for acquiring detection information of the electrode, the conductivity probe and the temperature probe and feeding the detection information back to the data processing system.
According to the further optimized technical scheme, magnetic stirring systems for uniformly stirring the solution are respectively arranged inside the left chamber and the right chamber; and an anti-collision baffle for preventing the magnetic stirrer from damaging the film to be characterized is arranged at the joint of the left cavity and the right cavity.
Further optimize technical scheme, circulating pressurization system includes:
the water storage tank is communicated with the measuring pool through a circulating pipeline to form a circulating system;
and the pressurizing pump is arranged on the circulating pipeline and used for providing pressure for the liquid flow in the measuring pool.
The method for evaluating the mass transfer performance of the thin film is carried out based on the thin film mass transfer performance evaluator, and comprises the following steps of:
s1, selecting a measurement mode in a data processing system;
s2, inputting the stirring speed of the magnetic stirring system, the temperature of the solution in the left chamber, the temperature of the solution in the right chamber, the concentration of the solution in the left chamber and the concentration of the solution in the right chamber according to the prompt of a software interface of the data processing system;
s3, starting measurement, collecting basic electrochemical parameters of the film and the solution to be characterized in the left chamber and the right chamber, and feeding the basic electrochemical parameters back to the data processing system;
s4, the data processing system calculates relevant parameters reflecting the film mass transfer performance to be represented according to a preset algorithm, and outputs, displays and stores the relevant parameters; the relevant parameters to be characterized for the film mass transfer performance comprise the membrane potential delta phi mbr Ion transport number t, membrane resistance R, membrane capacitance C, membrane conductivity G, and ion transmembrane potential E of the membrane p,± Salt transmembrane barrier E of thin film p,s Thickness h of film m Or a film zeta potential.
Further optimizing the technical scheme, the stepsS4, calculating the membrane potential delta phi of the membrane to be characterized mbr The algorithm of (1) adopts one of the following two algorithms:
measuring a transmembrane I-V curve through a data integration acquisition module in a data acquisition system in a linear volt-ampere scanning mode, and outputting and storing the intercept of the transverse axis of the obtained I-V curve;
or selecting an open circuit potential mode of a data integration acquisition module in the data acquisition system, inputting monitoring time, measuring and outputting and storing the open circuit potential through the data integration acquisition module.
In step S4, the calculation formula of the ion transport number t of the thin film to be characterized is as follows:
t - ＝1-t +
in the formula: delta phi mbr Is the membrane potential; r is an ideal gas constant; t is the temperature; f is a Faraday constant; c h /C l The solution concentration ratio of the left chamber and the right chamber of the measuring cell is measured; gamma ray h /γ l Representative solution temperature T and solution concentration C h And C l The ratio of the activity coefficients of the ions to be measured; t is t + Is the ion transport number of the cation, t - Is the ion transport number of the anion.
In step S4, the algorithm for the film resistance R and the film capacitance C of the film to be characterized is as follows:
selecting circuit elements according to the structural characteristics of the thin film to be characterized, establishing an equivalent circuit model, fitting and solving Nyquist data obtained by electrochemical impedance spectrum measurement, and outputting and storing the Nyquist data; importing the measured Nyquist data into supporting circuit simulation software, selecting a resistor R and a capacitor C element to carry out series and parallel connection to form a system circuit model, and further carrying out simulation calculation to obtain a membrane resistor R and a membrane capacitor C;
the impedance of the resistance R element is calculated by the formula:
Z R ＝R＝Z′ R ，Z″ R ＝0
the impedance of the capacitive C element is calculated as:
Z C ＝-j(1/ωC)，Z′ C ＝0，Z″ C ＝-1/(ωC)
in the formula: z' is an impedance real part; z' is an imaginary impedance component; omega is the frequency;
in step S4, a calculation formula of the membrane conductance G of the thin film to be characterized is as follows:
G＝1/R
in the formula: g is membrane conductivity; r is membrane resistance;
ion transmembrane potential barrier E of the film to be characterized p,± The calculation formula of (c) is:
in the formula: g is the membrane conductance, t ± Is the ion transport number of the cation/anion, T is the temperature, B ± Is constant, R is ideal gas constant, E p,± Is an ion transmembrane potential barrier;
salt transmembrane barrier E of the film to be characterized p,s The calculation formula of (2) is as follows:
in the formula: j is a unit of s Is the salt flux; (C) h -C l ) Is the difference in concentration of the solution in the left chamber and the right chamber; b s Is a constant, E p,s Is a salt transmembrane barrier; salt flux J s Expressed as the change in conductivity of the solution per unit time.
Further optimizing the technical scheme, in the step S4, the film thickness h of the film to be characterized m The calculation formula of (2) is as follows:
in the formula: c is the membrane capacitance, epsilon f Film dielectric coefficient,. Epsilon g Dielectric coefficient of air,. Epsilon 0 Is the vacuum dielectric constant, D is the electrode diameter, h is the electrode spacing, h m Is the film thickness;
film zeta potential of the film to be characterized:
in the formula: zeta is the zeta potential of the film, delta phi mbr Is the membrane potential, eta is the solution viscosity,
for solution conductivity, Δ P is transmembrane pressure difference/osmotic pressure, ε r Is the relative dielectric constant of the electrolyte, ε 0 Is the dielectric constant in vacuum.
By adopting the technical scheme, the invention has the beneficial effects that:
the invention provides a standardized and integrated instrument for characterizing the mass transfer performance of a thin film, which has the advantages of convenient operation, high integration level and good universality and provides an effective method and technical support for characterizing the mass transfer performance of the thin film.
Aiming at the thin film materials widely applied to the fields of water treatment, battery manufacturing, chemical industry, food industry and the like, the invention utilizes an electrochemical method to obtain a series of parameters related to the mass transfer performance of the thin film, and provides effective technical support for evaluating the difficulty of mass transfer of different solutes across the film and quantitatively comparing the mass transfer performance difference of different thin films.
The invention starts from the microcosmic physical property of interaction between different ions and the membrane interface, realizes the qualitative evaluation and quantitative characterization of the membrane mass transfer performance through the online detection, the rapid processing, the integrated analysis and the scientific calculation of the conventional parameters, provides a scientific, rapid, convenient and highly integrated test instrument and an index system for the characterization of the membrane material mass transfer performance, and is beneficial to promoting the development and the application of the membrane material and the membrane technology in multiple fields.
The indexes measured by the method can directly reflect the ion interception, screening and transmission performances, membrane integrity, the coating and deposition level of the membrane surface, membrane aging, membrane pollution conditions and the like of the thin film and the composite membrane material, and can realize comprehensive and systematic evaluation on the mass transfer performance of the thin film to be characterized.
The measuring instrument provided by the invention integrates the film material mass transfer performance related parameter system and the evaluation method, and has the advantages of wide application range, high integration level, simple operation, and obvious practicability and technical economy.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic diagram of the thin film mass transfer performance evaluation instrument according to the present invention;
FIG. 2 is a top view of a measuring cell in the thin film mass transfer performance evaluator of the present invention;
FIG. 3 is a schematic diagram of a circulating pressurization system in the thin film mass transfer performance evaluation instrument according to the present invention;
FIG. 4 is a diagram of a software background fitting calculation according to embodiment 1 of the present invention;
FIG. 5 is a diagram of a software background fitting calculation according to embodiment 2 of the present invention;
FIG. 6 is a diagram of a software background fitting calculation according to embodiment 3 of the present invention;
fig. 7 is a diagram of software background fitting calculation according to embodiment 4 of the present invention.
Wherein: 1. a measuring cell; 2. an electrode fixing hole; 3. a sampling hole; 4. a magnetic stirring system; 5. an anti-collision baffle plate; 6. a film to be characterized; 7. an accessory system interface; 8. a temperature probe; 9. a conductivity probe; 10. an electrode; 11. a data integration acquisition system; 12. a data processing system; 13. a temperature control system; 14. a water storage tank; 15. a circulation line; 16. a booster pump.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
The thin film mass transfer performance evaluation instrument is shown in fig. 1 to 3, and comprises a measuring cell 1, a temperature control system 13, a thin film 6 to be characterized, a circulating pressurization system, a data integration acquisition system 11 and a data processing system 12.
The measuring cell 1 is filled with solution, and the measuring cell 1 is in a rectangular box shape. The measuring cell 1 has good sealing property, insulating property and thermal conductivity so as to facilitate the normal operation of detection.
The measuring cell 1 is provided in the middle with a sample chamber for receiving a membrane 6 to be characterized. The film to be characterized can be drawn out of the sample groove, so that the evaluation instrument can meet the performance test of various films to be characterized.
The membrane 6 to be characterized divides the measuring cell 1 into two separate left and right chambers. The top of the left chamber and the right chamber are respectively provided with not less than 2 electrode fixing holes 2 and not less than 1 sampling hole 3.
The data integrated acquisition system 11 is used for acquiring basic electrochemical parameters of the thin film 6 to be characterized and the solution from the left side chamber and the right side chamber and outputting the basic electrochemical parameters to the data processing system. The data integrated acquisition system 11 comprises an electrode 10, a conductivity probe 9, a temperature probe 8 and a data integrated acquisition module.
The working electrode and the counter electrode in the data acquisition system are platinum electrodes, and the reference electrode is an Ag/AgCl electrode. A platinum electrode and an Ag/AgCl reference electrode are respectively arranged in the left chamber and the right chamber to form a two-electrode system, a three-electrode system or a four-electrode system.
Conductivity probes 9 are respectively arranged in the left chamber and the right chamber, and the conductivity probes 9 are used for detecting the conductivity of the solution in the left chamber or the right chamber.
Temperature probes 8 are respectively arranged in the left side cavity and the right side cavity, and the temperature probes 8 are used for detecting the temperature of the solution in the left side cavity or the right side cavity.
The data integration acquisition module is used for acquiring detection information of the electrode 10, the conductivity probe 9 and the temperature probe 8 and feeding back the detection information to the data processing system 12.
The bottom ends of the left side wall and the right side wall of the measuring cell 1 are respectively provided with an accessory system interface 7, and the measuring cell 1 is communicated with a circulating type pressurization system through the accessory system interfaces 7. The circulating pressurization system is an accessory system, is communicated with the measuring cell 1, and is used for enabling liquid in the measuring cell 1 to circularly flow and providing pressure and cross flow conditions for the thin film 6 to be characterized so as to simulate the actual operation conditions of the thin film 6 to be characterized.
The circulating pressurization system comprises a circulating module and a pressurization module. The circulation module comprises a water storage tank 14 and a circulation pipeline 15. The pressurizing module includes a pressurizing pump 16. The water storage tank 14 is communicated with the measuring cell 1 through a circulating pipeline 15 to form a circulating system. A pressure pump 16 is provided on the circulation line 15 for providing pressure to the liquid flow in the measuring cell 1.
The measuring cell 1 is entirely placed in a temperature control system 13, and the temperature control system 13 is used for adjusting and stabilizing the temperature of the solution in the measuring cell at a set value. The temperature regulating range of the temperature control system is between 10 and 60 ℃. The temperature control system 13 may be a temperature control system of the prior art.
The data processing system 12 comprises a computer and matched software, and the data processing system 12 is used for receiving information transmitted by the data integrated acquisition system 11, automatically processing basic electrochemical parameters input by the data acquisition system, calculating and reflecting relevant physical quantity values of the film mass transfer performance to be represented according to a preset algorithm, and finishing the output, display and storage of the relevant parameters.
In order to uniformly stir the solution in the left chamber and the right chamber and enable the mass transfer performance of the film to be more accurately evaluated, magnetic stirring systems are respectively arranged in the left chamber and the right chamber. The rotating speed of the magnetic stirring system at the bottom of the measuring tank can be 50-400 r/min.
Because of the magnetic stirrers are located the bottom of measuring cell 1, the liquid mobility that is located 1 bottom of measuring cell is stronger, if do not set up crashproof baffle 5, can cause the damage to the film. In order to avoid the damage of the magnetic stirrer to the film to be characterized, the anti-collision baffle 5 is arranged at the joint of the left cavity and the right cavity, the anti-collision baffle 5 can be separately arranged in two parts and is respectively positioned at the left side and the right side of the film 6 to be characterized, and further, when the magnetic stirrer rotates, liquid positioned at the bottom of the measuring pool 1 cannot impact the bottom of the film to be characterized.
The temperature control system, the data acquisition system, the data processing system and the circulating pressurization system are automatically controlled by software programs, and all the systems can independently operate. The software program comprises the control functions of a temperature control system, a data acquisition system, a data processing system and an accessory system and the functions of data acquisition, calculation and transmission.
In order to enable the mobile phone APP remote control system to have a remote control function, information transmission is carried out between the data acquisition system and the data processing system through the wireless transmission module, and the data processing system can also be communicated with the mobile phone APP in a wireless transmission mode.
The method for evaluating the mass transfer performance of the thin film is carried out based on a thin film mass transfer performance evaluation instrument and comprises the following steps:
s1, selecting a measurement mode in the matched software of the data processing system 12.
And S2, inputting the stirring speed of the magnetic stirring system, the temperature of the solution in the left chamber, the temperature of the solution in the right chamber, the concentration of the solution in the left chamber and the concentration of the solution in the right chamber according to the prompt of a software interface of the data processing system 12.
And S3, starting measurement, collecting basic electrochemical parameters of the film 6 to be represented and the solution in the left chamber and the right chamber, and feeding the basic electrochemical parameters back to the data processing system 12.
S4, the data processing system 12 calculates a reflection waiting list according to a preset algorithmThe related parameters of the film mass transfer performance are characterized, and the related parameters are output, displayed and stored; relevant parameters to be characterized for the mass transport properties of the membrane include the membrane potential Δ φ mbr Ion transport number t, membrane resistance R, membrane capacitance C, membrane conductivity G, and ion transmembrane potential E of the membrane p,± Salt transmembrane barrier of thin film E p,s Thickness h of film m Or a film zeta potential.
The data processing system calculates the membrane potential delta phi of the membrane to be characterized mbr The algorithm of (1) adopts one of the following two algorithms:
firstly, a transmembrane I-V curve is measured through a data integration acquisition module in a data acquisition system in a linear voltammetry scanning (LSV) mode, and the intercept of the transverse axis of the obtained I-V curve is output and stored. The value range of the LSV mode linear scanning voltage is-0.1V, and the voltage conversion step length is 0.001-0.01V/s.
Secondly, selecting an Open Circuit Potential (Open Circuit Potential) mode of a data integrated acquisition module in the data acquisition system, inputting monitoring time, preferably 300-1800 s, and measuring, outputting and storing the Open Circuit Potential.
The data processing system calculates the ion transport number t of the film to be characterized by the following equation:
t - ＝1-t +
in the formula: delta phi mbr Is the membrane potential; r is an ideal gas constant; t is the temperature; f is a Faraday constant; c h /C l The solution concentration ratio of the left chamber and the right chamber of the measuring cell is measured; gamma ray h /γ l Representative solution temperature T and solution concentration C h And C l The ratio of the activity coefficients of the ions to be measured; t is t + Is the ion transport number of the cation, t - The ion transport number of an anion. The ion migration number t is obtained by the matching software through a built-in algorithm based on the formula, and is output and stored.
The algorithm for the data processing system to obtain the membrane resistance R and the membrane capacitance C of the membrane to be characterized is as follows:
and selecting circuit elements according to the structural characteristics of the thin film to be represented, establishing an equivalent circuit model, and carrying out fitting solution on Nyquist data obtained by electrochemical impedance spectrum measurement, outputting and storing. The measurement voltage of the electrochemical impedance spectrum is set as the open-circuit voltage of the system, the amplitude is 5-20 mV, and the frequency range is set as 0.1-10 6 Hz. And importing the measured Nyquist data into supporting circuit simulation software, and selecting a resistor R and a capacitor C element to carry out series and parallel connection to form a system circuit model. According to the difference of the measurement system, the circuit model is different (for example, R (RC) model, namely, the measurement system is regarded as the parallel connection of solution resistance series membrane resistance and capacitance), the area of the electrode is input, and the membrane resistance R and the membrane capacitance C are obtained by clicking calculation.
The impedance of the resistance R element is calculated by the formula:
Z R ＝R＝Z′ R ，Z″ R ＝0
the impedance of the capacitive C element is calculated as:
Z C ＝-j(1/ωC)，Z′ C ＝0，Z″ C ＝-1/(ωC)
in the formula: z' is an impedance real part; z' is an imaginary impedance component; omega is frequency;
the data processing system finds the membrane conductance G of the membrane to be characterized by the following equation:
G＝1/R
in the formula: g is membrane conductivity; r is a membrane resistance. The membrane conductance G is obtained by the matched software through a built-in algorithm based on the formula, and is output and stored.
The data processing system obtains the ion transmembrane potential E of the film to be characterized by the following equation p,± ：
In the formula: g is the membrane conductivity, t ± Is the ion transport number of the cation/anion, T is the temperature, B ± Is constant, R is the ideal gas constant, E p,± Is a barrier for ions across the membrane. Ion transmembrane potential barrier E p,± And the matched software is used for solving, outputting and storing the result through a built-in algorithm based on the formula.
The data processing system calculates the salt transmembrane barrier E of the film to be characterized by the following equation p,s ：
In the formula: j is a unit of s Is the salt flux; (C) h -C l ) The concentration difference of the solution in the left chamber and the right chamber; b is s Is a constant, E p,s Is a salt transmembrane barrier; salt flux J s Expressed as the change in conductivity of the solution per unit time. Ion transmembrane potential barrier E p,s And the matched software is used for solving, outputting and storing the result through a built-in algorithm based on the formula.
The data processing system calculates the film thickness h of the film to be characterized by the following equation m ：
In the formula: c is a membrane capacitance,. Epsilon f Dielectric coefficient of film,. Epsilon g Dielectric coefficient of air,. Epsilon 0 Is the vacuum dielectric constant, D is the electrode diameter, h is the electrode spacing, h m Is the film thickness. Thickness h of the film m And the matched software is used for solving through a built-in algorithm based on the formula, outputting and storing.
The data processing system calculates the film zeta potential of the film to be characterized by the following equation:
in the formula: zeta is the zeta potential of the film, delta phi mbr Is the membrane potential, eta is the solution viscosity,
for solution conductivity, Δ P is transmembrane pressure difference/osmotic pressure, ε r Is the relative dielectric constant of the electrolyte,. Epsilon 0 Is the dielectric constant in vacuum. The zeta potential of the film is obtained by the matching software through a built-in algorithm based on the formula and is output and stored.
Example 1
The embodiment discloses a method for evaluating mass transfer performance of a thin film, which comprises the following steps:
membrane potential delta phi is selected in the matched software mbr And (4) measuring a mode.
According to the prompt of a software interface, the stirring speed of the magnetic stirring system is sequentially input to be 150r/min, the temperature of the solution input into the left cavity and the right cavity is 26 ℃, the input voltage conversion step length is 0.002V/s, and the concentration of the solution input into the left cavity and the concentration of the solution input into the right cavity are respectively 0.1M and 0.01M.
0.1M and 0.01M LiCl solutions were added to the left and right chambers, respectively.
Starting the measurement, namely directly reading the membrane potential delta phi of the membrane to be characterized in the solution environment mbr 0.0171V; the membrane potential delta phi is obtained by a software background based on a built-in algorithm of the equation mbr The fitting calculation chart of (2) is shown in fig. 4.
Example 2
The embodiment discloses a method for evaluating mass transfer performance of a thin film, which is different from the embodiment 1, and comprises the following steps:
and selecting an ion migration number t measurement mode in the matched software.
According to the prompt of a software interface, the stirring speed of the magnetic stirring system is input to be 180r/min, the temperature of the solution input into the left chamber and the right chamber is 26 ℃, and the concentration of the solution input into the left chamber and the right chamber is 0.1M and 0.1M, 0.1M and 0.05M, 0.1M and 0.025M, 0.1M and 0.01M in sequence.
Sequentially placing 0.1M LiCl solution and 0.1M LiCl solution, 0.1M LiCl solution and 0.05M LiCl solution, 0.1M LiCl solution and 0.025M LiCl solution, 0.1M LiCl solution and 0.01M LiCl solution in the left chamber and the right chamber, starting measurement, and finishing measurementAfter the solution is formed, the lithium ion transference number t of the film to be characterized in the solution environment can be directly read + 0.318435, chloride migration number t - Is 0.681565.
A fitting calculation graph of the ion migration number t obtained by the software background based on the built-in algorithm of the equation is shown in fig. 5.
Example 3
The embodiment discloses a method for evaluating mass transfer performance of a thin film, which is different from the embodiment 1, and comprises the following steps:
selecting ion transmembrane potential barrier E in matched software p,± And (4) measuring mode.
According to the prompt of a software interface, the stirring speed of the magnetic stirring system is input to be 160r/min, the input sampling temperature points are 23 ℃, 26 ℃, 29 ℃ and 33 ℃, and the solution concentrations of the left cavity and the right cavity are input to be 0.1M and 0.1M, 0.1M and 0.05M, 0.1M and 0.025M, 0.1M and 0.01M in sequence.
Sequentially placing 0.1M LiCl solution and 0.1M LiCl solution, 0.1M LiCl solution and 0.05M LiCl solution, 0.1M LiCl solution and 0.025M LiCl solution, 0.1M LiCl solution and 0.01M LiCl solution in the left chamber and the right chamber, starting measurement, and directly reading Li after all measurements are completed + And Cl - Transmembrane potential barriers E in the thin film to be characterized p,+ Is 2.26kcal mol -1 ，E p,- Is 2.93kcal mol -1 。
The software background obtains the ion transmembrane potential barrier E based on the built-in algorithm of the equation p,± The fitting calculation chart of (a) is shown in fig. 6.
Example 4
The embodiment discloses a method for evaluating mass transfer performance of a thin film, which is different from embodiment 1 and comprises the following steps:
salt transmembrane barrier E is selected in matched software p,s And (4) measuring mode.
According to the prompt of a software interface, the stirring speed of the magnetic stirring system is input to be 200r/min, the input sampling temperature points are 23 ℃, 26 ℃, 29 ℃ and 33 ℃, and the solution concentrations of the left chamber and the right chamber are input to be 0.1M and 0M in sequence.
0 was placed in each of the left and right chambers.1M NaCl solution and deionized water and starting measurement, and directly reading the transmembrane potential barrier E of NaCl in the film to be characterized after all measurements are finished p,s 4.03kcal mol -1 。
The software background obtains the salt transmembrane potential barrier E based on the built-in algorithm of the equation p,s The fitting calculation chart of (2) is shown in fig. 7.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. The film mass transfer performance evaluation instrument is characterized by comprising:
the measuring cell (1) is filled with solution;
the temperature control system (13), the measuring cell (1) is arranged in the temperature control system (13), and the temperature control system (13) is used for regulating the temperature of the solution in the measuring cell and stabilizing the temperature at a set value;
the film (6) to be characterized is inserted into the measuring cell (1) and divides the measuring cell (1) into two independent left and right chambers;
the circulating pressurization system is communicated with the measuring cell (1) and is used for providing pressure and cross flow conditions for the thin film (6) to be characterized so as to simulate the actual operation conditions of the thin film (6) to be characterized;
the data integration acquisition system (11) is used for acquiring basic electrochemical parameters of the thin film (6) to be characterized and the solution in the left chamber and the right chamber;
and the data processing system (12) is used for receiving the information transmitted by the data integrated acquisition system (11), calculating relevant parameters reflecting the mass transfer performance of the thin film to be represented according to a preset algorithm, and finishing the output, display and storage of the relevant parameters.
2. The thin film mass transfer performance evaluator of claim 1 wherein the data collection system (11) includes:
the working electrode and the counter electrode in the left chamber and the right chamber are platinum electrodes, the reference electrode is an Ag/AgCl electrode, and a two-electrode, three-electrode or four-electrode system can be adopted according to actual conditions;
the conductivity probe (9) is respectively arranged in the left side chamber and the right side chamber, and the conductivity probe (9) is used for detecting the conductivity of the solution in the left side chamber or the right side chamber;
the temperature probes (8) are respectively arranged in the left side cavity and the right side cavity, and the temperature probes (8) are used for detecting the temperature of the solution in the left side cavity or the right side cavity;
and the data integration acquisition module is used for acquiring detection information of the electrode (10), the conductivity probe (9) and the temperature probe (8) and feeding back the detection information to the data processing system (12).
3. The thin film mass transfer performance evaluator of claim 1 wherein magnetic stirring systems for uniformly stirring the solution are respectively disposed inside the left chamber and the right chamber; and an anti-collision baffle for preventing the magnetic stirrer from damaging the film to be characterized is arranged at the joint of the left cavity and the right cavity.
4. The thin film mass transfer performance evaluator of claim 1 wherein said cyclic pressurization system comprises:
the water storage tank (14) is communicated with the measuring pool (1) through a circulating pipeline (15) to form a circulating system;
and the pressurizing pump (16) is arranged on the circulating pipeline (15) and is used for providing pressure for the liquid flow in the measuring cell (1).
5. The thin film mass transfer performance evaluation method, which is performed based on the thin film mass transfer performance evaluation apparatus according to any one of claims 1 to 4, comprising the steps of:
s1, selecting a measurement mode in a data processing system (12);
s2, inputting the stirring speed of the magnetic stirring system, the temperature of the solution in the left chamber, the temperature of the solution in the right chamber, the concentration of the solution in the left chamber and the concentration of the solution in the right chamber according to the prompt of a software interface of the data processing system (12);
s3, starting measurement, collecting basic electrochemical parameters of the film (6) to be characterized and the solution in the left side chamber and the right side chamber, and feeding the basic electrochemical parameters back to the data processing system (12);
s4, the data processing system (12) calculates relevant parameters reflecting the film mass transfer performance to be represented according to a preset algorithm, and outputs, displays and stores the relevant parameters; the relevant parameters of the film mass transfer property to be characterized comprise the membrane potential delta phi mbr Ion transport number t, membrane resistance R, membrane capacitance C, membrane conductivity G, and ion transmembrane potential E of the membrane p,± Salt transmembrane barrier E of thin film p,s Thickness h of film m Or a film zeta potential.
6. The method for evaluating the mass transfer performance of a thin film according to claim 5, wherein in the step S4, the membrane potential Δ φ of the thin film to be characterized is calculated mbr The algorithm of (1) employs one of the following two algorithms:
measuring a transmembrane I-V curve through a data integration acquisition module in a data acquisition system in a linear volt-ampere scanning mode, and outputting and storing the intercept of the transverse axis of the obtained I-V curve;
or selecting an open circuit potential mode of a data integration acquisition module in the data acquisition system, inputting monitoring time, measuring and outputting and storing open circuit potential through the data integration acquisition module.
7. The method for evaluating mass transfer performance of a thin film according to claim 5, wherein in the step S4, the ion transfer number t of the thin film to be characterized is calculated according to the formula:
t - ＝1-t +
in the formula：Δφ mbr Is the membrane potential; r is an ideal gas constant; t is the temperature; f is a Faraday constant; c h /C l The solution concentration ratio of the left chamber and the right chamber of the measuring cell is measured; gamma ray h /γ l Representative solution temperature T and solution concentration C h And C l The ratio of the activity coefficients of the ions to be measured; t is t + Is the ion transport number of the cation, t - Is the ion transport number of the anion.
8. The method for evaluating the mass transfer performance of a thin film according to claim 5, wherein in the step S4, the algorithm for the membrane resistance R and the membrane capacitance C of the thin film to be characterized is as follows:
selecting circuit elements according to the structural characteristics of the thin film to be characterized, establishing an equivalent circuit model, fitting and solving Nyquist data obtained by electrochemical impedance spectrum measurement, and outputting and storing the Nyquist data; importing the measured Nyquist data into supporting circuit simulation software, selecting a resistor R and a capacitor C element to carry out series and parallel connection to form a system circuit model, and further carrying out simulation calculation to obtain a membrane resistor R and a membrane capacitor C;
the impedance of the resistance R element is calculated by the formula:
Z R ＝R＝Z′ R ，Z" R ＝0
the impedance of the capacitive C element is calculated as:
Z C ＝-j(1/ωC)，Z′ C ＝0，Z" C ＝-1/(ωC)
in the formula: z' is an impedance real part; z' is an imaginary impedance component; omega is the frequency;
9. the method for evaluating the mass transfer performance of a thin film according to claim 5, wherein in the step S4, the calculation formula of the membrane electrical conductivity G of the thin film to be characterized is as follows:
G＝1/R
in the formula: g is membrane conductance; r is membrane resistance;
detachment of the film to be characterisedTransmembrane potential barrier E p,± The calculation formula of (2) is as follows:
in the formula: g is the membrane conductivity, t ± Is the ion transport number of cation/anion, T is the temperature, B ± Is constant, R is ideal gas constant, E p,± Is an ion transmembrane potential barrier;
salt transmembrane barrier E of the film to be characterized p,s The calculation formula of (2) is as follows:
in the formula: j. the design is a square s Is the salt flux; (C) h -C l ) The concentration difference of the solution in the left chamber and the right chamber; b s Is a constant, E p,s Is a salt transmembrane barrier; salt flux J s Expressed as the change in conductivity of the solution per unit time.
10. The method for evaluating the mass transfer performance of a thin film according to claim 5, wherein in the step S4, the thickness h of the thin film to be characterized m The calculation formula of (2) is as follows:
in the formula: c is the membrane capacitance, epsilon f Dielectric coefficient of film,. Epsilon g Dielectric coefficient of air,. Epsilon 0 Is the vacuum dielectric constant, D is the electrode diameter, h is the electrode spacing, h m Is the film thickness;
film zeta potential of the film to be characterized:
in the formula: zeta is the zeta potential of the film, delta phi mbr Is the membrane potential, eta is the solution viscosity,
for solution conductivity, Δ P is transmembrane pressure difference/osmotic pressure, ε r Is the relative dielectric constant of the electrolyte, ε 0 Is the dielectric constant in vacuum.
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