CN213091444U - Quantitative evaluation device for pore diameter of porous membrane - Google Patents
Quantitative evaluation device for pore diameter of porous membrane Download PDFInfo
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- CN213091444U CN213091444U CN202021569680.6U CN202021569680U CN213091444U CN 213091444 U CN213091444 U CN 213091444U CN 202021569680 U CN202021569680 U CN 202021569680U CN 213091444 U CN213091444 U CN 213091444U
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Abstract
The utility model discloses a porous membrane aperture's quantitative evaluation device, the membrane pond divide into feed liquid side and infiltration side by the membrane material, the feed liquid side constitutes feed liquid circulation circuit through first gear pump and feed liquid groove, the infiltration side constitutes penetrant circulation circuit through second gear pump and infiltration liquid groove, at feed liquid groove and penetrant inslot set up conductivity meter and conductivity meter respectively, on the pipeline of infiltration side and feed liquid side front end, set up respectively on the pipeline that front end was arranged in to manometer and flowmeter, all install temperature control system on feed liquid circulation circuit and penetrant circulation circuit, electronic balance fixes in infiltration tank bottom. Which obtains the convective diffusion coefficient M of the membrane according to the convective permeability coefficientwGreatly reduce the testThe method has the advantages of reducing the dosage of the reagent, testing time and testing process, avoiding expensive evaluation devices, and having good application value in quantitative evaluation of the pore diameter of porous membranes such as ultrafiltration membranes, ultrafiltration type forward osmosis membranes and the like.
Description
Technical Field
The utility model belongs to the technical field of membrane parameter evaluation, concretely relates to porous membrane aperture's quantitative evaluation device.
Background
The method can accurately determine the pore size of the porous membrane, and has important guiding significance for the regulation and control and the application development of the porous membrane structure. Currently, a commonly used method for evaluating the pore size of a porous membrane is a molecular weight cut-off Method (MWCO). The method calculates the pore size of the porous membrane by measuring the retention rate of the porous membrane to a series of substances with different molecular weights. In order to obtain retention rate data, the MWCO method needs to determine a standard working curve of a standard substance in advance; in addition, in the case of unknown pore, the pore size must be estimated. Therefore, the MWCO method has the disadvantages of complicated operation steps, high time cost, large reagent consumption and large-scale instrument assistance. Therefore, it is important to find a more convenient and efficient method for evaluating the pore diameter of the porous membrane.
In the field of dense membranes, researchers have provided a dissolution-diffusion defect model to describe its permeation-selection mechanism, and demonstrated that the convective permeability coefficient of desalinized dense membranes can enable quantification of membrane surface defects. Based on this, the invention proposes to apply the convective permeability coefficient to the quantitative evaluation of the pore size of the porous membrane. The difference from the desalting membrane is that the defect condition of the surface of the porous membrane is evaluated by using macromolecular polyelectrolyte as solute of feed liquid, and the pore size of the porous membrane is quantified from the side. The method uses only a specific macromolecular polyelectrolyte and can achieve regeneration by simple filtration. Therefore, the method has important significance for green, simple and economical evaluation of membrane parameters.
SUMMERY OF THE UTILITY MODEL
The utility model provides a porous membrane aperture's quantitative evaluation device can quantify the aperture of porous membrane fast, simply, economically, has solved conventional molecular weight cut-off method complex operation, has consumeed reagent scheduling problem.
In order to achieve the above purpose, the utility model adopts the following technical scheme:
a quantitative evaluation device for the pore diameter of a porous membrane comprises a membrane pool, a material liquid tank, a permeating liquid tank, a first gear pump, a second gear pump, a first pressure gauge, a second pressure gauge, a first conductivity meter, a second conductivity meter, a first temperature control system, a second temperature control system and an electronic balance, wherein the membrane pool is divided into a material liquid side and a permeating side by a membrane material, the material liquid side forms a material liquid circulation loop with the material liquid tank through the first gear pump, the permeating side forms a permeating liquid circulation loop with the permeating liquid tank through the second gear pump, the first conductivity meter and the second conductivity meter are respectively arranged in the material liquid tank and the permeating liquid tank, the first pressure meter and the first flow meter are arranged on a pipeline at the front end of the material liquid side, the second pressure meter and the second flow meter are arranged on a pipeline at the front end of the permeating side, the first temperature control system is arranged on the material liquid circulation loop to ensure the temperature of the circulating material liquid to be constant, the temperature of the circulating penetrating fluid is ensured to be constant, the electronic balance is fixed at the bottom of the penetrating fluid tank, and the change of the mass of the solution in the penetrating fluid tank is monitored in real time.
The device for quantitatively evaluating the pore diameter of the porous membrane further comprises a control processing unit, wherein the control processing unit is respectively connected with a first gear pump, a second gear pump, a first pressure gauge, a second pressure gauge, a first conductivity meter, a second conductivity meter, a first temperature control system, a second temperature control system and an electronic balance, controls the work of the control processing unit, collects detection data in real time, and calculates the convective permeability coefficients L of membrane materials with different known molecular weight cut-off and membrane materials to be detecteddThen based on the molecular weight cut-off M of the known membrane materialwAnd convective permeability coefficient LdCalculating the molecular weight M of the trapped materialwAnd convective permeability coefficient LdLinear relation between the two, finally substituting the convection permeability coefficient of the membrane material to be measured into MwAnd LdThe convection diffusion coefficient M of the film material to be measured is obtainedw。
Furthermore, the quantitative evaluation device for the pore diameter of the porous membrane can also adopt an ultrafiltration cup for evaluation, and pressure control is realized through a pressure tank.
A quantitative evaluation method for pore diameter of a porous membrane specifically comprises the following steps:
(1) selecting a plurality of known membrane materials with different molecular weight cut-off and membrane materials to be detected, placing the membrane materials and the membrane materials into a membrane pool, introducing a macromolecular polyelectrolyte solution with a certain concentration into the feed liquid side of the membrane pool, communicating pure water with the permeation side, driving the solutions at the two sides to flow through a gear pump, and controlling the temperature of the macromolecular polyelectrolyte solution and the temperature of the pure water to be constant;
(2) emptying system bubbles, and after the temperature of the system is reached, regularly recording the lateral pressure, flow, volume, mass, concentration and other parameters of a feed liquid side and a permeation side at a certain temperature;
(3) after the operation pressure is changed, repeating the operation of the step (2);
(4) calculating the water flux J of different membrane materials according to the first formula and the second formulawAnd salt flux Js，
In the formula, piLowAnd piHiRespectively the osmotic pressure of the raw material liquid side and the draw liquid side; dsThe diffusion coefficient of the solute is 1.61X 10 when the solute is sodium chloride-9m2S; s is a membrane structure parameter
t, epsilon and tau are respectively the thickness, porosity and pore tortuosity of the membrane;
in the formula, beta is a van t hough coefficient; r is a molar gas constant; t is the absolute temperature; a is the permeability coefficient of pure water; b is the permeability coefficient of the solute;
(5) calculating the convection permeability coefficient L of the membrane materials with different known molecular weight cut-off and the membrane material to be measured according to the formula IIId，
In the formula, Cfeed,sThe initial concentration of the feed liquid;
(6) molecular weight cut-off M based on known membrane materialswAnd convective permeability coefficient LdCalculating the molecular weight M of the trapped materialwAnd convective permeability coefficient LdA linear relationship therebetween;
(7) substituting the convection permeability coefficient of the membrane material to be tested obtained in the step (5) into the convection permeability coefficient of the membrane material to be tested in the step (6)wAnd LdThe convection diffusion coefficient M of the film is further obtainedw。
Preferably, the porous membrane includes, but is not limited to, an ultrafiltration membrane, a forward osmosis porous composite membrane; the macromolecular polyelectrolyte includes, but is not limited to, an anionic polyelectrolyte represented by sodium poly (p-styrenesulfonate), a neutral polyelectrolyte represented by dextran, and a cationic polyelectrolyte represented by polyethyleneimine.
The pore diameter of the porous membrane is evaluated by using the convective permeability coefficient, and the method is obviously different from the conventional pore diameter evaluation method in that the pore diameter of the membrane is not directly measured, but the defect condition of the membrane is evaluated by using the convective permeability coefficient. The method is characterized in that a convection permeability coefficient concept in a dissolution-diffusion defect model theory for describing permeation-selectivity performance of a compact membrane is applied to assessment of the pore diameter or defect degree of the porous membrane for the first time, a certain macromolecular polyelectrolyte solution under a certain concentration is used as a raw material solution, and the convection diffusion coefficient of the porous membrane can be obtained by measuring the diffusion flux of electrolytes under different pressures and simple linear fitting.
Compared with the prior art, the utility model has the advantages of it is following: (1) the evaluation equipment is simple, and only a conventional measuring instrument is needed to realize data recording and measurement; (2) the operation steps are few, and only the mass change and the conductivity change under different pressures need to be measured; (3) the reagent dosage is less, only macromolecular polyelectrolyte is needed, and the porous membrane can be recycled, so that the porous membrane has excellent application value in the aspect of porous membrane pore size evaluation.
Description of the drawings:
FIG. 1 is a schematic diagram of the quantitative evaluation method of the pore diameter of the porous membrane of the present invention.
FIG. 2 is a structural diagram of the apparatus for quantitative evaluation of pore diameter of a porous membrane according to the present invention.
FIG. 3 is a graph of the convective permeability coefficient data fit for the porous membrane of example 1
FIG. 4 is a graph of data fit for the porous composite membrane of example 2
Detailed Description
The above-mentioned contents of the present invention are further described in detail by the following embodiments, but it should not be understood that the scope of the above-mentioned subject matter of the present invention is limited to the following embodiments, and all the technologies realized based on the above-mentioned contents of the present invention belong to the scope of the present invention.
Example 1
As shown in figure 2, a porous membrane aperture quantitative assessment device, including a membrane pool, a feed liquid tank 9, a permeate liquid tank 2, a first gear pump 10, a second gear pump 3, a first pressure gauge 8, a second pressure gauge 5, a first conductivity meter, a second conductivity meter, a first temperature control system 11, a second temperature control system 4 and an electronic balance 1, the membrane pool is divided into a feed liquid side 7 and a permeate side 6 by a membrane material, the feed liquid side 7 and the feed liquid tank 9 form a feed liquid circulation loop through the first gear pump 10, the permeate side 6 and the permeate liquid tank 2 form a permeate liquid circulation loop through the second gear pump 3, the feed liquid tank 9 and the permeate liquid tank 2 are respectively provided with the first conductivity meter and the second conductivity meter, the first pressure gauge 8 and a first flowmeter are arranged on a pipeline at the front end of the feed liquid side 7, the second pressure gauge 5 and a second flowmeter are arranged on a pipeline at the front end of the permeate side 6, the first temperature control system 11 is installed on the feed liquid circulation loop, the temperature of the circulating feed liquid is guaranteed to be constant, the second temperature control system 4 is installed on a penetrating liquid circulating loop to guarantee the temperature of the circulating penetrating liquid to be constant, the electronic balance 1 is arranged at the bottom of the feed liquid tank 9 or the bottom of the penetrating liquid tank 2 and used for measuring the change of the quality of the solution in the feed liquid tank 9 and the penetrating liquid tank 2, the macromolecular polyelectrolyte is introduced into the feed liquid side, and the pure water is introduced into the penetrating side.
The device for quantitatively evaluating the pore diameter of the porous membrane further comprises a control processing unit, wherein the control processing unit is respectively connected with a first gear pump 10, a second gear pump 3, a first pressure gauge 8, a second pressure gauge 5, a first conductivity meter, a second conductivity meter, a first temperature control system 11, a second temperature control system 4 and an electronic balance 1, controls the work of each part, collects detection data in real time, and collects the detection data according to a formula ICalculating the convection permeability coefficient L of the membrane material with known different molecular weight cut-off and the membrane material to be measureddThen based on the molecular weight cut-off M of the known membrane materialwAnd convective permeability coefficient LdCalculating the molecular weight M of the same material liquid and the membrane materialwAnd convective permeability coefficient LdLinear relation between the two, finally substituting the convection permeability coefficient of the membrane material to be measured into MwAnd LdThe convection diffusion coefficient M of the film material to be measured is obtainedw。
Furthermore, the quantitative evaluation device for the pore diameter of the porous membrane can also adopt an ultrafiltration cup for evaluation, and pressure control is realized through a pressure tank.
Ultrafiltration membranes (designated UF-1, UF-2, UF-3, UF-4) with nominal molecular weight cut-off of 9000, 20000, 29000, 67000 Da. Selecting sodium polyterephtylenesulfonate (concentration is 1g/L) with weight-average molecular weight of 70000Da as raw material liquid, and deionized water as penetrating fluid, and obtaining the ratio of salt flux to raw material liquid concentration (J) under different operation pressuress/Cfeed,s) As shown in table 1. Operating pressure is used as abscissa, and J is useds/Cfeed,sThe values are plotted on the ordinate (as shown in FIG. 3), and the convective permeability coefficients of different ultrafiltration membranes, UF-1, UF-2, UF-3 and UF-4, are determined by least squares method, corresponding to 1.683LMH/bar, 3.775LMH/bar, 4.497LMH/bar and 9.925LMH/bar, respectively. For molecular weight cut-off LdAnd convective diffusion coefficient MwBy performing a linear fit, it can be found that both conform to Ld＝0.1530MwWherein R is20.9893. Description of LdThe pore size of the porous membrane can be quantitatively evaluated.
TABLE 1 Ultrafiltration membranes J at different operating pressuress/Cfeed,sValue of
Example 2
Selecting a water-washed cellulose acetate membrane with the aperture of 2 microns as a basement membrane, and performing suction filtration on dopamine-modified multi-walled carbon nano on the surface of the basement membraneFiltering the rice tube dispersion solution with suction 1, 3, 4, 5ml (respectively marked as CNT-1, CNT-2, CNT-3, CNT-4), standing, oven drying, and measuring with molecular weight cut-off method to obtain molecular weight cut-off of 57000, 25000, 20000 and 10000Da respectively. In the same way, the ratio of the flux of the obtained salt to the concentration of the feed solution (Js/C) was tested at different operating pressuresfeed,s) As shown in table 2. Operating pressure is used as abscissa, and J is useds/Cfeed,sThe values are plotted on the ordinate (as shown in FIG. 4), and the convective permeability coefficients of different ultrafiltration membranes can be obtained by using the least square method, wherein PC-1, PC-2, PC-3 and PC-4 correspond to 5.413LMH/bar, 4.20LMH/bar, 3.83LMH/bar and 3.67LMH/bar, respectively. The molecular weight cut-off and the convection diffusion coefficient are subjected to linear fitting, and the two can be found to accord with Ld＝0.3851Mw+3.20, wherein R20.9774. Description of LdThe pore size of the porous composite membrane can be quantitatively evaluated.
Table 2 porous composite membranes J at different operating pressuress/Cfeed,sValue of
Claims (1)
1. A quantitative evaluation device for the pore diameter of a porous membrane is characterized by comprising a membrane pool, a material liquid tank, a permeation liquid tank, a first gear pump, a second gear pump, a first pressure gauge, a second pressure gauge, a first conductivity meter, a second conductivity meter, a first temperature control system, a second temperature control system and an electronic balance, wherein the membrane pool is divided into a material liquid side and a permeation side by membrane materials, the material liquid side forms a material liquid circulation loop with the material liquid tank through the first gear pump, the permeation side forms a permeation liquid circulation loop with the permeation liquid tank through the second gear pump, the first conductivity meter and the second conductivity meter are respectively arranged in the material liquid tank and the permeation liquid tank, the first pressure gauge and the first flow meter are arranged on a pipeline at the front end of the material liquid side, the second pressure gauge and the second flow meter are arranged on a pipeline at the front end of the permeation side, the first temperature control system is arranged on the material liquid circulation loop to ensure the temperature, the second temperature control system is arranged on the penetrating fluid circulating loop to ensure the temperature of the circulating penetrating fluid to be constant, and the electronic balance is fixed at the bottom of the penetrating fluid tank to monitor the change of the quality of the solution in the penetrating fluid tank in real time.
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| CN114965582A (en) * | 2022-01-06 | 2022-08-30 | 山东大学 | Method for measuring pore diameter and pore density of porous membrane |
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