CN114272772A - Asymmetric PES (polyether sulfone) porous membrane for virus removal and preparation method thereof - Google Patents

Asymmetric PES (polyether sulfone) porous membrane for virus removal and preparation method thereof Download PDF

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CN114272772A
CN114272772A CN202111677367.3A CN202111677367A CN114272772A CN 114272772 A CN114272772 A CN 114272772A CN 202111677367 A CN202111677367 A CN 202111677367A CN 114272772 A CN114272772 A CN 114272772A
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membrane
porous
colloidal gold
porous membrane
thickness
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贾建东
卢红星
庞铁生
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Hangzhou Cobetter Filtration Equipment Co Ltd
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Hangzhou Cobetter Filtration Equipment Co Ltd
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Abstract

The invention provides an asymmetric PES porous membrane for virus removal and a preparation method thereof, wherein the porous membrane comprises a first porous surface, a second porous surface and a main body positioned between the first porous surface and the second porous surface, and a non-directional tortuous passage is formed in the main body; the porous membrane is a single layer membrane; PMI has an average pore diameter of 15-25nm, a porosity of 70-85% and a thickness of 40-150 μm; the part for trapping colloidal gold with the diameter of 20nm is a region which is 90-100% of the thickness of the main body from the first porous surface; the average pore diameter of the main body is continuously reduced in a gradient manner from the area close to the first porous surface to the area close to the second porous surface; the PES porous membrane is prepared by only one casting membrane liquid, is integrally formed, does not need to be compounded, and has a relatively simple preparation process; meanwhile, the prepared PES filter membrane has a strong interception effect on parvoviruses with the particle size of 20nm or more, and can obtain a high protein yield, so that the requirements of practical application are met.

Description

Asymmetric PES (polyether sulfone) porous membrane for virus removal and preparation method thereof
Technical Field
The invention relates to the technical field of membrane materials, in particular to an asymmetric PES porous membrane for virus removal and a preparation method thereof.
Background
The membrane technology is a new technology of modern high-efficiency separation, and compared with the traditional technologies of distillation, rectification and the like, the membrane technology has the advantages of high separation efficiency, low energy consumption, small occupied area and the like, and the core of the membrane separation technology is a separation membrane. Wherein the polymer filter membrane is a separation membrane which is prepared by taking an organic high molecular polymer as a raw material according to a certain process; wherein the polymer filter membrane can be subdivided into cellulose polymer filter membranes, polyamide polymer filter membranes, sulfone polymer filter membranes, polytetrafluoroethylene polymer filter membranes and the like according to different types of high molecular polymers; in addition, the membrane may be classified into a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane according to the pore size of the membrane.
In recent years, in addition to human blood-derived plasma fractionation preparations, countermeasures for improving virus safety are also required for biopharmaceuticals; therefore, pharmaceutical manufacturers have studied the introduction of a virus removal/inactivation step into the manufacturing process; the virus removal method in which filtration is performed using a virus removal membrane is an effective method for reducing viruses while not denaturing useful proteins.
For example, chinese patent CN1759924B (EMD millipore applications) discloses a multilayer composite ultrafiltration membrane (fig. 19 and 20) comprising at least one first porous membrane layer having a first face and an equivalent second face, and at least one second porous membrane layer having an equivalent first face and second face, the first layer being superimposed with a junction of the second layers and having a porosity junction transition region from the equivalent first face of the second layer to the equivalent second face of the first layer, wherein at least one of the layers is an asymmetric ultrafiltration membrane; the membrane structure formed by compounding has stronger interception effect on parvovirus, and can obtain higher protein yield, thereby meeting the requirements of practical application; however, there are problems that, firstly, since the filter membrane is a composite membrane, the pore size changes (decreases) abruptly during the transition from one layer to another, which easily results in a large range of particle sizes remaining at the interface of the layers produced by co-casting, and such particle loading at the layer boundary results in a loss of the service life of the filter, i.e., a great reduction in service life; and the composite membranes risk delamination/layer separation during pleating.
At the same time US20200238221a1 (siduris) also discloses a porous single layer polymer membrane having at least one major surface with a surface porosity of at least 40% and a total porosity of the polymer membrane of from 0.8 to 1.4 times the surface porosity of at least 40%; and the polymer film has an asymmetry factor of 1.5 to 10; the polymer film is a single-layer filter membrane, has good flux and long service life, and is mainly applied to filtering viruses, proteins or macromolecules; however, the average pore diameter of the polymer membrane is large, and only large-particle substances with the particle size of hundreds of nanometers can be intercepted, but parvovirus with the particle size of 20nm cannot be intercepted.
Further, chinese patent CN201580007740.0 (asahi chemical company application) also discloses a virus-removing membrane comprising cellulose for removing viruses from a protein-containing solution, the virus-removing membrane having: a first porous surface to which a solution containing a protein is supplied and a second side surface from which a permeated solution that has permeated the virus-removal membrane is discharged, the membrane having an average pore diameter of 13nm to 21 nm; the membrane has the advantages of high efficiency in virus interception and low protein adsorption rate, and meanwhile, the membrane is a single-layer membrane and does not have the defects of sudden pore size change and easy separation between membrane layers; however, this membrane also has certain disadvantages; the virus removal membrane is prepared by a cuprammonium method, namely, a membrane forming substance is added into a cuprammonium solution for various treatments, and the preparation method not only pollutes the environment, but also has extremely high danger and is easy to cause great harm to the life safety of research personnel; the prepared virus removing membrane is a hollow fiber membrane, and has low compressive strength and is easy to damage, so that the preparation processes of the virus removing membrane component and the filter thereof are relatively complex; in addition, the pressure resistance strength of the virus removing membrane is low, so that the pressure difference between the membrane before and after the membrane is small, the filtration speed is low, and the economic benefit per unit time is too low.
In view of the above, the development of virus-removing membranes is also limited to some extent by the presence of the above-mentioned problems.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide an asymmetric PES porous membrane for virus removal and a preparation method thereof, wherein the PES porous membrane is prepared by only one casting membrane solution, is integrally formed, does not need to be compounded, and has a relatively simple and safe preparation process; meanwhile, the prepared PES porous membrane has a strong virus interception effect, and can obtain a high protein yield, so that the requirements of practical application are met;
in order to achieve the purpose, the invention provides the following technical scheme: an asymmetric PES porous membrane for virus removal comprising a first porous surface, a second porous surface and a body located between the first porous surface and the second porous surface, the body having non-directional tortuous pathways therein, the porous membrane being a single layer membrane; the PMI average pore diameter of the porous membrane is 15-25 nm; the porosity of the porous membrane is 70-85%, and the thickness is 40-150 μm; the part for trapping colloidal gold with the diameter of 20nm is a region which is 90-100% of the thickness of the main body from the first porous surface; the average pore size of the body decreases in a continuous gradient from a region on the side close to the first porous surface to a region on the side close to the second porous surface.
The PES porous membrane is a single-layer membrane, namely, the PES porous membrane is integrally formed and does not undergo processes such as compounding and the like; the whole membrane is made of polyether sulfone (PES) which is a material, the material of each part is uniform, and no change exists in the material; only a change in the structure of the membrane in the structure of the body of the membrane; in contrast, the composite membrane, which protects the multilayer structure, has a sudden change in pore size during the transition from one layer to the other; the PES porous membrane has a non-oriented tortuous path in a main body, wherein the non-oriented tortuous path is a randomly oriented groove structure and/or a discretely distributed hole structure, and the non-oriented tortuous paths are communicated with each other; and the fibers forming the porous structure of the membrane are continuous, it is understood that "continuous" means that substantially all of the fibers are integrally connected to one another, e.g., integrally formed, without the need for additional adhesives or the like to interconnect them, and the network-like fibers cannot be separated from one another unless torn by an external force; at the same time, the continuous network-like fibers are interconnected with the first porous surface and the second porous surface;
and through observing the membrane main body structure, the continuous gradient reduction of the average pore diameter of the main body from the area close to one side of the first porous surface to the area close to one side of the second porous surface is also found, namely the average pore diameter of the membrane main body is gradually reduced without mutation, so that the PES porous membrane is integrally formed without processes such as compounding and the like; in one side area close to the first porous surface, the pore diameter of the inner pores is relatively larger, and the inner pores are mainly used for intercepting large-particle impurities in the fluid, so that the porous membrane has larger pollutant carrying capacity and faster flow speed; in the area close to one side of the second porous surface, the pore diameter of the inner pores is relatively small, and the inner pores are mainly used for intercepting fine particle impurities, such as parvovirus in protein, so that the PES porous membrane is ensured to have higher virus trapping capacity, and is particularly suitable for being used as a virus removal membrane;
the average pore size of the porous membrane is tested by a PMI pore size tester, the PMI average pore size of the porous membrane is 15-25nm, and the PES porous membrane is ensured to have a strong interception effect on nano-scale parvoviruses (even rat parvoviruses with the particle size of 20 nm) by a tortuous path of a main body structure and a certain thickness of the membrane, so that the requirement of practical application can be met, and the PES porous membrane is suitable for being used as a virus removal membrane;
the thickness of the film can be measured by using a scanning electron microscope to perform morphology characterization on the film structure, and then using computer software (such as Matlab, NIS-Elements and the like) or manually measuring and then calculating; of course, the skilled person can also obtain the above parameters by other measuring means, and the above measuring means is only used for reference; when the thickness of the film is too small, the mechanical strength of the film is low; meanwhile, as the filtering time is too short, effective filtering cannot be carried out; when the thickness of the membrane is too large, the filtration time is too long, and the time cost is too large; the thickness of the PES porous membrane is 40-150 mu m, so that the PES porous membrane has high mechanical strength, can be effectively filtered, and has high filtering efficiency, short filtering time and low time cost;
when the porosity of the membrane is too high, the tensile strength of the membrane is too low, the mechanical property of the membrane is poor, the industrial practical value is low, and the market demand cannot be met; when the porosity of the membrane is too low, on one hand, the flow rate of the membrane is influenced, so that the filtering speed of the membrane is low, the filtering time is long, and the time cost is high; on the other hand, the pollution capacity of the membrane is too low, the service life is too short, the membrane needs to be replaced in a short time, and the economic cost is greatly improved; the porosity of the porous membrane is 70-85%, so that the membrane not only has good tensile strength, but also has high filtering speed, high flow rate, high pollutant carrying capacity, long service life and low economic cost, and can retain more impurity particles;
the part for trapping colloidal gold with the diameter of 20nm is a region which is 90-100% of the thickness of the main body from the first porous surface; after the porous membrane retains the colloidal gold, the distribution result of the colloidal gold in the porous membrane can be tested according to the test method in the membrane for removing the virus in Chinese patent CN 105980038B: the section was cut out from the virus-removed porous membrane after the colloidal gold solution was filtered, and the luminance distribution at a plurality of sites in the section of the section stained with colloidal gold was measured by an optical microscope. Since colloidal gold absorbs light, the luminance shifts depending on the amount of capture of colloidal gold. The background noise can be removed from the luminance distribution as necessary. Then, a graph with the film thickness on the horizontal axis and the luminance on the vertical axis is prepared; thereby obtaining a region where colloids with a certain particle size are intercepted in the film thickness direction; (in the present invention, the first porous surface is 0% of the film thickness, and the second porous surface is 100% of the film thickness);
note that, in the measurement by an optical microscope, when the absolute value of the position of the region of the spectrum is 10% or less of the maximum value of the absolute value of the spectrum by subtracting the shift of the luminance obtained by measuring the luminance distribution from a constant (255), the capture of colloidal gold in the region can be considered to be within the range of error from the viewpoint of the virus removal ability of the virus-removed membrane;
it can also be understood that at some region positions in the film thickness direction, although a certain amount of colloidal gold is also present, it is low, and therefore this region is not considered as a region where colloidal gold is trapped, and this region is merely a region where some colloidal gold remains;
therefore, in the virus-removing membrane, it is preferable that the portion trapping colloidal gold having a diameter of 20nm, that is, the region where colloidal gold having a corresponding particle diameter is actually trapped, is continuously formed in the membrane thickness direction from the inside of the first-side surface to the inside of the second-side surface.
Herein, a first distance a from the first porous surface of the virus-removing porous membrane to a portion of the colloidal gold capture site closest to the first porous surface is measured in the thickness direction;
further, a second distance b from the first porous surface of the virus-free porous membrane to a portion of the colloidal gold-capturing site closest to the second porous surface is measured in the thickness direction;
next, a value a (expressed as a percentage of a/c) obtained by dividing the first distance a by the thickness c of the virus membrane and expressing the value a as a percentage is calculated at each of the plurality of sites, and an average value of the values a at the plurality of sites is calculated as a first arrival degree;
further, a value B (expressed as a percentage of B/c) obtained by dividing the second distance B by the thickness c of the virus membrane and expressing the value B as a percentage is calculated at each of the plurality of sites, and an average value of the values B at the plurality of sites is calculated as a second arrival degree; the part for intercepting the colloidal gold with the diameter of 20nm is A20-B20;
in addition, after the slice is cut out from the virus-removed porous membrane after filtering the colloidal gold solution, the gold element content analysis can be performed by an EDS spectrometer to obtain a corresponding gold content distribution part (distribution of gold content in the membrane thickness direction), so that a region where the colloid with a certain particle size is intercepted in the membrane thickness direction can be obtained; note that: as in fig. 8 (fig. 7), the region with a small peak on the left side of the figure (near the inlet surface) is only the region where the colloidal gold in the membrane remains, but not the region where the colloidal gold in the membrane is trapped; the region with large peaks at the right side of the figure is the region where the colloidal gold is actually intercepted; the region (region near the inlet surface) on the left side of the graph in fig. 10 (fig. 9) also has a peak, which is only the region where the colloidal gold in the membrane remains, and not the region where the colloidal gold in the membrane is retained; the region with large peaks at the right side of the figure is the region where the colloidal gold is actually intercepted;
after testing, the part for trapping colloidal gold with the diameter of 20nm is a region which is 90% -100% of the thickness of the main body from the first porous surface (the first porous surface is 0% of the thickness of the main body, and the second porous surface is 100% of the thickness of the main body), while the diameter of the currently known virus is about 20nm, which further proves that the porous membrane has high virus removal rate, and the virus removal region is mainly a region close to the second porous surface, and further proves that the pore diameter is reduced in a continuous gradient manner.
As a further improvement of the invention, the peak of the cut-off for colloidal gold with a cut-off diameter of 20nm is the region at 94% -98% of the thickness of the body from the first porous surface.
Tests show that the region for intercepting 20nm colloidal gold is mainly positioned on one side close to the second porous surface, the interception peak value is the place for intercepting the colloidal gold with the corresponding particle size most, if the interception peak value is too close to the second porous surface, the danger of virus leakage easily exists, namely the LRV of the porous membrane to the virus is too low to meet the actual requirement; and if the rejection peak is too far from the second porous surface, the flux of the porous membrane is greatly affected, resulting in too low a flux of the porous membrane; the interception peak value of the colloidal gold with the interception diameter of 20nm is an area which is 94% -98% of the thickness of the main body from the first porous surface, so that the porous membrane can efficiently intercept viruses and has higher flux.
After a section was cut out from the virus-removed porous membrane after filtering the 20nm colloidal gold solution, the section was examined by an optical microscope, and the darkest place of the brightness was found to be the cut-off peak; or after the EDS spectrometer is used for testing, the position of the wave crest is the interception peak value.
As a further improvement of the invention, the part for trapping the colloidal gold with the diameter of 30nm is a region which is 81-100% of the thickness of the main body from the first porous surface; the part for trapping the colloidal gold with the diameter of 50nm is a region which is 73-95% of the thickness of the main body from the first porous surface; when the particle size of the trapped colloidal gold is 30-50nm, the average trapped colloidal gold particle size variation gradient K1 of the main body along the thickness direction is 2-8 nm/mum; when the particle size of the trapped colloidal gold is 20-30nm, the average trapped colloidal gold particle size variation gradient K2 of the main body along the thickness direction is 1.4-5.6 nm/mum; k1, K2 is 1.2-1.8;
the average retained colloidal gold particle size variation gradient is the colloidal gold particle size variation value/the main body thickness for retaining the corresponding colloidal gold particle size.
The 30nm colloidal gold solution was filtered, and then the virus-removed porous membrane was sliced and measured by an optical microscope to prepare a graph having a film thickness on the horizontal axis and a luminance shift on the vertical axis; or testing by using an EDS (enhanced data System) energy spectrometer to obtain a distribution diagram of the gold content along with the film thickness; thereby obtaining the distribution area of the colloidal gold with the thickness of 30nm in the film thickness direction, and the colloidal gold with the thickness of 50nm is tested according to the method, thereby obtaining the distribution area of the colloidal gold with the thickness of 50nm in the film thickness direction;
here, the first distance a from the first porous surface of the virus-removing porous membrane to the portion of the colloidal gold-capturing site closest to the first porous surface is measured in the film thickness direction.
In addition, a second distance b from the first porous surface of the virus-free porous membrane to the portion of the colloidal gold-capturing site closest to the second porous surface was measured in the thickness direction.
Next, a value a (expressed as a percentage of a/c) obtained by dividing the first distance a by the thickness c of the virus membrane and expressing the value a as a percentage is calculated at each of the plurality of sites, and the average value of the values a at the plurality of sites is calculated as the first arrival degree.
Further, a value B (expressed as a percentage of B/c) obtained by dividing the second distance B by the thickness c of the virus membrane and expressing the value B as a percentage is calculated at each of the plurality of sites, and an average value of the values B at the plurality of sites is calculated as a second arrival degree; the part for intercepting the colloidal gold with the diameter of 30nm is A30-B30; the part for intercepting the colloidal gold with the diameter of 50nm is A50-B50;
because the average pore diameter of the main body is continuously reduced in a gradient manner from the area close to one side of the first porous surface to the area close to one side of the second porous surface, the average pore diameter can be continuously changed in the film thickness direction, namely, colloidal gold with different particle sizes can be intercepted in different main body areas, and the size of the film pore can be well reflected through the intercepted position of the colloidal gold in the main body; the average intercepted colloidal gold particle size change gradient refers to the amplitude of the intercepted colloidal gold particle size along with the change of the membrane thickness, and the larger the value of the average intercepted colloidal gold particle size change gradient is, the larger the amplitude of the change of the membrane diameter along with the change of the membrane thickness is;
the average intercepted colloidal gold particle size variation gradient is obtained by the ratio of the colloidal gold particle size variation value to the main body thickness intercepting the corresponding colloidal gold particle size;
when the particle size of the trapped colloidal gold is 20-30nm, the part trapping the colloidal gold with the diameter of 30nm is A30-B30; the part for intercepting the colloidal gold with the diameter of 20nm is A20-B20; when the variation gradient of the average intercepted colloidal gold particle size is calculated, the average value of the corresponding colloidal gold intercepting area is used for representing the whole area intercepted by the colloidal gold; namely, C30 represents the whole region where 30nm colloidal gold is trapped in the bulk structure of the film, and C30 ═ a30+ B30)/2;
the whole region of the membrane bulk structure where 20nm colloidal gold was trapped is represented by C20, and C20 ═ (a20+ B20)/2;
then the change value of the particle size of the colloidal gold is 30nm-20 nm-10 nm;
main body thickness for intercepting corresponding colloidal gold particle size: c20-30(C20-C30) C; when the particle diameter of the trapped colloidal gold is 20-30nm, the average particle diameter variation gradient K2 of the trapped colloidal gold along the thickness direction of the main body is 10nm/C20-30Mu m; calculated, K2 is 1.4-5.6 nm/mum; the value is small, which indicates that the change of the membrane pore diameter along with the membrane thickness is small in a region (a small pore region) on one side of the porous membrane close to the second porous surface, the region is a key region for intercepting viruses, and the change of the pore diameter along with the membrane thickness is small in the region, so that the whole porous membrane can be ensured to have high interception efficiency on various viruses (particularly parvoviruses with the particle size of 20 nm), and the requirement of practical application is met;
the part for intercepting the colloidal gold with the diameter of 50nm is A50-B50; the whole region of the membrane bulk structure where 50nm of colloidal gold was trapped is represented by C50, i.e., C50 ═ (a50+ B50)/2;
when the particle size of the trapped colloidal gold is 30-50nm, the particle size change value of the colloidal gold is 50-30 nm-20 nm; main body thickness for intercepting corresponding colloidal gold particle size: c30-50＝(C30-C50)*c
When the particle size of the trapped colloidal gold is 30-50nm, the average trapped colloidal gold particle size variation gradient K1 of the main body along the thickness direction is 20nm/C30-50Mu m; calculating K1 to be 2-8 nm/mum; and K1, K2 ═ 1.2 to 1.8;
the closer the ratio of K1 to K2 is to 1, the more the membrane aperture is proved to be changed along with the equal gradient of the membrane thickness; the ratio of K1 to K2 is closer to 1 in the invention, which shows that the pore diameter of the macroporous membrane slightly changes with the thickness of the membrane in the macroporous area of the porous membrane, which is favorable for leading the membrane to have larger flux; meanwhile, the aperture of the whole membrane is changed in a small gradient mode along with the thickness, the aperture of the membrane cannot be changed too fast, and overlarge holes do not exist (when the membrane has overlarge holes, the mechanical strength of the whole membrane is too low, the membrane is not pressure-resistant, and the membrane is easy to damage under the action of pressure); at the moment, the large pore area of the membrane can play a certain supporting role on the small pore area of the membrane, so that the whole membrane has good mechanical strength and pressure resistance and is not easy to damage under larger pressure; and can guarantee the high-efficient interception of membrane to the virus, the filter membrane still has faster flux, and has great stain receiving capacity.
As a further improvement of the invention, the thickness of the main body region for retaining colloidal gold with the diameter of 20-30nm is 8-28 μm, and the main body region is 81% -100% of the thickness of the main body region from the first porous surface.
Here, the first distance a from the first porous surface of the virus-removing porous membrane to the portion of the colloidal gold-capturing site closest to the first porous surface is measured in the film thickness direction. In addition, a second distance b from the first porous surface of the virus-free porous membrane to the portion of the colloidal gold-capturing site closest to the second porous surface was measured in the thickness direction. Next, a value a (expressed as a percentage of a/c) obtained by dividing the first distance a by the thickness c of the virus membrane and expressing the value a as a percentage is calculated at each of the plurality of sites, and the average value of the values a at the plurality of sites is calculated as the first arrival degree.
Further, a value B (expressed as a percentage of B/c) obtained by dividing the second distance B by the thickness c of the virus membrane and expressing the value B as a percentage is calculated at each of the plurality of sites, and an average value of the values B at the plurality of sites is calculated as a second arrival degree;
the part for intercepting the colloidal gold with the diameter of 20nm is A20-B20; the part for intercepting the colloidal gold with the diameter of 30nm is A30-B30;
the site for trapping colloidal gold with a diameter of 20-30nm is a30-B20 at the bulk thickness from the first porous surface, the site has a thickness of (B20-a30) × c, note that if the thicknesses of the two membranes are different, c is the average of the thicknesses of the two membranes;
tests show that the thickness of the main body region for intercepting the colloidal gold with the diameter of 20-30nm is 8-28 mu m, and the main body region is 81% -100% of the thickness of the main body from the first porous surface;
it is understood that the particle size of each parvovirus is generally 20-30nm, wherein the murine parvovirus is about 20nm, so that the part of the porous membrane for trapping 20-30nm colloidal gold is the part of the porous membrane for trapping each parvovirus; the thickness of the part can greatly influence the virus interception efficiency and the integral flow of the membrane; if the thickness of the part is too small, the interception efficiency of the whole membrane to various parvoviruses is too low to meet the requirements of practical application; the thickness of the part is too large, namely the small pore area in the porous membrane is too large, so that the flux of the membrane is greatly reduced, the filtration speed of the membrane is low, and the economic benefit of the membrane per unit time is reduced; in addition, when the pore diameter of the membrane pore is small (the porous membrane made of polyether sulfone still has a certain adsorption effect on protein), the membrane pore has a strong adsorption effect on protein, and when the thickness of the part is too large, the adsorption effect of the porous membrane on the protein is enhanced, so that the protein yield of the whole membrane is reduced; the part of the porous membrane for intercepting 20-30nm colloidal gold has proper thickness, so that the porous membrane has high efficiency of intercepting 20-30nm colloidal gold, has high flux, has low protein adsorption (high protein yield) for the porous membrane prepared by the PES membrane, and meets the requirement of time application.
As a further improvement of the invention, the thickness of the main body region for retaining colloidal gold with the diameter of 30-50nm is 11-37 μm, and the main body region is 73-100% of the thickness of the main body region from the first porous surface.
As a further improvement of the invention, the thickness of the body region for intercepting the colloidal gold with the diameter of 30-50nm is 1.25-1.7 of the thickness of the body region for intercepting the colloidal gold with the diameter of 20-30 nm.
Here, the first distance a from the first porous surface of the virus-removing porous membrane to the portion of the colloidal gold-capturing site closest to the first porous surface is measured in the film thickness direction.
In addition, a second distance b from the first porous surface of the virus-free porous membrane to the portion of the colloidal gold-capturing site closest to the second porous surface was measured in the thickness direction.
Next, a value a (expressed as a percentage of a/c) obtained by dividing the first distance a by the thickness c of the virus membrane and expressing the value a as a percentage is calculated at each of the plurality of sites, and the average value of the values a at the plurality of sites is calculated as the first arrival degree.
Further, a value B (expressed as a percentage of B/c) obtained by dividing the second distance B by the thickness c of the virus membrane and expressing the value B as a percentage is calculated at each of the plurality of sites, and an average value of the values B at the plurality of sites is calculated as a second arrival degree;
the part for intercepting the colloidal gold with the diameter of 30nm is A30-B30; the part for intercepting the colloidal gold with the diameter of 50nm is A50-B50;
the site for trapping colloidal gold with a diameter of 30-50nm is a50-B30 at the bulk thickness from the first porous surface, the site has a thickness of (B30-a50) × c, note that if the thicknesses of the two membranes are different, c is the average of the thicknesses of the two membranes;
tests show that the thickness of a main body region for intercepting colloidal gold with the diameter of 30-50nm is 11-37 mu m, and the main body region is 73-100% of the thickness of the main body from the first porous surface;
according to the fact that colloidal gold with different particle sizes is arranged at the corresponding position of the porous membrane, the PES porous membrane is an asymmetric membrane, and the pore diameter of a hole of the PES porous membrane can change along with the thickness; according to tests, the thickness of the main body region for intercepting the colloidal gold with the diameter of 30-50nm is 1.25-1.7 of the thickness of the main body region for intercepting the colloidal gold with the diameter of 20-30nm, so that the membrane pore diameter of the membrane is changed in a small gradient mode along with the change of the thickness, the membrane pore diameter is not changed too fast, and overlarge pores do not exist, so that the high-efficiency interception of the PES porous membrane to the viruses is further ensured, the filter membrane has higher flux and higher pollutant carrying capacity is also ensured.
As a further improvement of the invention, the thickness of the main body region for trapping colloidal gold with the diameter of more than 40nm is 35-130 μm, and the main body region is 0-87% of the thickness of the main body region from the first porous surface;
in the film thickness direction, a first distance a from the first porous surface of the virus-removing porous membrane to a portion of the colloidal gold-capturing site closest to the first porous surface is measured.
In addition, a second distance b from the first porous surface of the virus-free porous membrane to the portion of the colloidal gold-capturing site closest to the second porous surface was measured in the thickness direction.
Next, a value a (expressed as a percentage of a/c) obtained by dividing the first distance a by the thickness c of the virus membrane and expressing the value a as a percentage is calculated at each of the plurality of sites, and the average value of the values a at the plurality of sites is calculated as the first arrival degree.
Further, a value B (expressed as a percentage of B/c) obtained by dividing the second distance B by the thickness c of the virus membrane and expressing the value B as a percentage is calculated at each of the plurality of sites, and an average value of the values B at the plurality of sites is calculated as a second arrival degree; the part for intercepting the colloidal gold with the diameter of 40nm is A40-B40;
in the field of virus removal, when the membrane pores are smaller than or equal to 40nm generally, the membrane pores can have a certain interception effect on parvovirus, and when the membrane pores are larger than 40nm, the parvovirus cannot be captured and intercepted, so that large-particle substances in a fluid can be removed through the pores with the pore diameters, and the integral membrane is guaranteed to have good pollutant carrying capacity;
in the invention, the average value of the corresponding gold colloid retention area is used for representing the whole gold colloid retention area; namely, C40 represents the whole region where 40nm colloidal gold is trapped in the bulk structure of the film, and C40 ═ a40+ B40)/2;
the main body area for intercepting the colloidal gold with the diameter of more than 40nm is 0-C40, and the thickness is C40C; calculating to obtain a main body region with the interception diameter of more than 40nm, wherein the thickness of the main body region is 35-130 μm, and the main body region is a region which is 0-87% of the thickness of the main body from the first porous surface; in the porous film of the present invention, the region having a pore diameter of more than 40nm is large, that is, the thickness of the region is large; therefore, the porous membrane is ensured to have higher flow velocity, and can also play a sufficient role in intercepting large-particle impurities (such as large-particle-size viruses) without influencing the interception of subsequent parvoviruses; under the combined action of large aperture and high porosity, the membrane is guaranteed to have high flux, high filtering speed, low time cost, high pollutant carrying capacity and long service life.
The area (small hole area) with the membrane hole less than or equal to 40nm in the porous membrane can retain parvovirus to a certain extent; the area with the membrane pore less than or equal to 40nm has a certain thickness, and the membrane pore diameter in the area can be further reduced along with the membrane thickness, so that the porous membrane has high interception efficiency on parvovirus (20nm virus), and meanwhile, the thickness of the area is small, so that the membrane has high flux, high filtration speed and low time cost; meanwhile, the porous membrane is made of polyether sulfone materials, so that the porous membrane has good hydrophilicity and low protein adsorption, but still has certain protein adsorption (the smaller the pore diameter of the region is, the stronger the protein adsorption effect of the region is), and the thickness of the region is smaller under the condition of ensuring the interception efficiency, so that the protein adsorption can be further reduced, the low protein adsorption effect of the whole membrane is ensured, and the economic value is high.
As a further improvement of the invention, the body comprises first fibers and second fibers forming a porous structure, the first fibers being located on a side of the body adjacent to the first porous surface, the second fibers being located on a side of the body adjacent to the second porous surface; the first fibers and the second fibers are continuous in a thickness direction of the body; the first fibers are of a sheet-like structure; the second fibers are in a strip-shaped structure.
In the film body structure of the PES porous film provided by the invention, the fiber structure can be clearly seen to change along with the film thickness; the first fibers on one side close to the first porous surface are of a sheet-shaped structure, namely the first fibers of the sheet-shaped structure form a porous structure with larger pore diameter, and the first fibers of the sheet-shaped structure are of a sheet-like structure with certain thickness, certain area and possibly certain bending degree;
the second fibers on the side close to the second porous surface are in a strip-shaped structure, namely the second fibers in the strip-shaped structure form a porous structure with smaller pore diameter, and the second fibers in the strip-shaped structure are in a strip-shaped structure with certain length and certain width
The first fibers and the second fibers are continuous, which also indicates that the porous membrane is integrally formed and does not have a composite process; the fibers with different structures form porous structures with different pore sizes; the flaky fiber structure distribution can help fluid diffusion, and the interception effect of macropores is further improved; the porous structure formed by the second fibers with the strip-shaped structures has proper porosity and pore distribution, so that the whole membrane has higher flow rate, and meanwhile, the virus interception efficiency is high;
as a further development of the invention, the average diameter of the first fibers is greater than the average diameter of the second fibers, the average diameter of the second fibers being between 30 and 75 nm.
By observing the membrane main body structure, the average diameter of the first fibers is larger than that of the second fibers, because the holes close to one side of the first porous surface are relatively larger, and the holes formed by the thicker first fibers have stronger stability and are not easy to collapse or shrink, so that the stability of the flow rate of the fluid is ensured; meanwhile, the area formed by the first fibers with the sheet-shaped structure is more stable and pressure-resistant, and can play a certain role in supporting and protecting the area (small hole area) on one side close to the second porous surface; in addition, the average diameter of the second fiber is 30-75nm, so that the stability of the inner holes of one side area (small hole area) close to the second porous surface is ensured, and the parvovirus impurities can be well reserved; with the structure, the thick and thin first fibers and the thin and thick second fibers are beneficial to ensuring that the whole membrane has higher mechanical strength and filtration stability, and can be efficiently filtered for a long time; therefore, the PES porous membrane is particularly suitable for being applied to the field of virus removal;
the thickness degree of the fiber section can be regarded as the diameter of the fiber, and the average diameter of the second fiber in the invention can be calculated by using a scanning electron microscope to perform morphology characterization on the porous membrane section structure, and then using computer software (such as Matlab, NIS-Elements and the like) or manually to perform measurement; it will of course be appreciated that the above parameters may also be obtained by other measurement means by a person skilled in the art.
As a further improvement of the invention, the tensile strength of the porous membrane is 5-10MPa, and the elongation at break is 8-30%; the flux of the porous membrane is greater than 600L h-1*m-2@30 psi; the LRV of the porous membrane to 20nm colloidal gold is not less than 4; the protein yield of the porous membrane is not less than 98%.
Important indexes for evaluating the mechanical strength of the porous membrane are the tensile strength and the elongation at break of the porous membrane; under certain conditions, the greater the tensile strength of the porous film, the better the mechanical strength of the porous film is said to be; tensile strength refers to the ability of a film to withstand parallel stretching; when the film is tested under a certain condition, the film sample is acted by a tensile load until the film sample is damaged, and the tensile strength and the elongation at break of the film can be calculated according to the maximum tensile load corresponding to the damage of the film sample, the change of the size (length) of the film sample and the like; tensile strength, elongation at break, can be measured by a universal tensile tester, tensile strength testing methods are well known in the art, for example, tensile strength testing procedures are explained in detail in ASTM D790 or ISO 178; the tensile strength of the porous membrane is 5-10 MPa; the elongation at break is 8-30%, which shows that the porous membrane of the invention has larger tensile strength and elongation at break, better mechanical property and higher industrial practical value, and can completely meet the market demand.
The permeation flux is also called permeation rate, called flux for short, and refers to the amount of substance permeation of a porous membrane through a unit membrane area within a unit time under a certain working pressure in a separation process; the flux reflects the speed of the filtration; the higher the flux, the faster the filtration rate of the membrane; the PES porous membrane of the invention has a flux of more than 600L x h-1*m-2@30psi, its flux is great, indicates that the filtration rate of porous membrane is faster, when guaranteeing the entrapment efficiency, and the fluid can pass through the porous membrane fast, and the time cost is lower, and economic benefits is higher.
The virus trapped by the invention mainly aims at various viruses with the particle size of 20nm and above (such as mouse parvovirus, the particle size of which is about 20 nm); therefore, colloidal gold of 20nm is used as intercepted test particles, and after an interception test, the LRV of the PES porous membrane to the colloidal gold of 20nm is not lower than 4, namely the LRV of the PES porous membrane to various viruses is not lower than 4, which shows that the PES porous membrane has very high interception rate to the viruses, plays a role in sufficiently retaining virus impurities and meets the requirements of practical application; the yield of the protein of the PES porous membrane is not lower than 98 percent, which indicates that the effective substance protein in the fluid is not easy to be adsorbed on the membrane, on one hand, the membrane pores are not blocked, the porous membrane still has longer service life, on the other hand, the content change of the effective substance protein in the fluid is ensured to be very small, the protein is not basically lost, and the economic benefit is ensured; as a method for testing viral impurities, reference may be made to a membrane for removing viruses of patent-CN 105980037B-, a CN 101816898B-ultra-porous membrane and a method for preparing the same, a CN 1759924B-ultra-porous membrane and a method for preparing the same, and the like.
On the other hand, the invention also provides a preparation method of the asymmetric PES porous membrane for virus removal, which comprises the following steps:
s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; wherein the casting solution comprises the following substances in parts by weight: 15-25 parts of polyether sulfone; 55-90 parts of an organic solvent; 6-25 parts of polar additive;
s2: pre-separating the liquid film in air with temperature of 5-20 deg.C and relative humidity of 70-90% for 2-10 s;
s3: immersing the liquid film after pre-phase separation into a curing liquid along with the carrier for at least 20 seconds, wherein the curing liquid invades into the liquid film and gradually diffuses inwards, and then curing to form a porous film; the solidifying liquid comprises water and a penetrating additive, and the penetrating additive is a fluorine-containing hydrophilic substance.
As a further improvement of the present invention, the organic solvent is at least one of butyl lactate, dimethyl sulfoxide, dimethylformamide, caprolactam, methyl acetate, ethyl acetate, N-ethylpyrrolidone, dimethylacetamide and N-methylpyrrolidone; the polar additive is at least one of polyvinyl alcohol, polyethylene glycol, polyethyleneimine and polyvinylpyrrolidone.
As a further improvement of the invention, the content of the penetrating additive in the curing liquid is 30-60%; the fluorine-containing hydrophilic substance is hexafluoroisopropanol or trifluoroethanol; the temperature of the solidified liquid is 20-30 ℃.
When the PES porous membrane is prepared, membrane casting solution is prepared firstly, wherein the membrane casting solution comprises a membrane forming substance polyether sulfone (PES), an organic solvent (used for solvent polyether sulfone material) and a polar additive; the polar additive is at least one of polyvinyl alcohol, polyethylene glycol, polyethyleneimine and polyvinylpyrrolidone, and the substances can control the viscosity of the system and inhibit the formation of macropores (pores with overlarge pore diameters) in a liquid film in a phase separation process on one hand, and on the other hand, the substances have good hydrophilicity, so that a formed film has good hydrophilicity, and then the formed film has low protein adsorption, the protein yield is high, and the requirements of practical application are met; the existence of the organic solvent ensures that the whole system is uniform and stable; the organic solvent can act together with the curing solution, and the organic solvent is easy to dissolve in the curing solution during phase separation, so that the polyether sulfone is easier to precipitate, and the PES porous membrane with small pore diameter and gradient change is easy to form; preferably, the viscosity of the prepared casting solution is 5000-10000cps, and the viscosity of the casting solution can have great influence on the structure and the performance of the finally formed porous membrane, such as the pore diameter, the thickness, the flow rate and the like of the porous membrane; such viscosity setting ensures that the finally produced porous membrane has a proper thickness and obtains a desired pore size; the viscosity of the casting solution can be directly obtained by a viscometer; then, casting the casting solution on a carrier to form a liquid film; the casting solutions of the present invention may be cast manually (e.g., by pouring, casting, or spreading by hand on a casting surface) or automatically (e.g., poured or otherwise cast on a moving bed); a variety of apparatus known in the art can be used for casting. Casting equipment includes, for example, mechanical coaters, including doctor blades, or spray/pressurized systems. As is known in the art, a variety of casting speeds are suitable, such as casting speeds of about 2 to 6 feet per minute (fpm), and the like, as the case may be;
then the liquid film is put in the environment of low temperature and high humidity to carry out pre-phase separation (the low temperature and the high humidity are both beneficial to accelerating the phase separation of the liquid film), the low temperature is that the temperature is controlled to be 5-20 ℃, the high humidity is that the relative humidity is controlled to be 70-90%, meanwhile, by controlling the reality of the pre-phase separation, the pre-phase separation time is short and is controlled to be within 2-10s, preferably 4-8s, the purpose of the method is to carry out the rapid phase separation on one side of the liquid film close to the air, and as is known, the faster the phase separation is, the smaller the aperture of the formed hole is, so that a certain number of holes with extremely small aperture are easy to appear on one side of the liquid film close to the aperture;
after the pre-phase separation is finished, immersing the liquid film after the pre-phase separation into the curing liquid along with the carrier for at least 20 seconds, wherein the preferable time of the phase separation curing is 25-55 seconds, and the proper time of the phase separation curing can be beneficial to obtaining a porous film with ideal film aperture size under the combined action of the liquid film casting system; the curing liquid can invade into the liquid film and gradually diffuse inwards, and then the curing liquid is cured to form a porous film with the pore diameter changing along with the small gradient of the thickness; in the prior art, the curing liquid is generally water, the mutual solubility of water and an organic solvent is not high, and the phase separation speed is slow, so that the pore diameter of a hole formed at the later phase of phase separation is large, which can also be understood as that the average pore diameter of a large-pore area is large, the asymmetry of a porous membrane is too strong, and the pore diameter is too large along with the change of the thickness; in order to accelerate the phase separation speed, the curing liquid is regulated to comprise conventional water and also comprise a fluorine-containing hydrophilic substance serving as a penetrating additive, and the penetrating additive can greatly increase the speed of the curing liquid entering the liquid film, so that the penetrating speed of the curing liquid is increased, the integral phase separation speed of the film is ensured to be higher, large holes are not easy to appear, the integral asymmetry of the film is smaller, and the PES porous film with holes and small gradient and continuous change is easy to form; preferably fluorine-containing hydrophilic substance hexafluoroisopropanol or trifluoroethanol, wherein the temperature of the curing liquid is 20-30 ℃, and the content of the penetrating additive in the curing liquid is 30-60%; the curing solution can be quickly dissolved with an organic solvent, so that the polyether sulfone is quickly separated out from the organic solvent, and then a porous membrane with small gradient change of pore diameter is formed; the preparation process is relatively simple, environment-friendly, free of damage to experimenters and suitable for large-scale popularization.
The invention has the beneficial effects that: the asymmetric PES porous membrane for virus removal provided by the invention is a single-layer membrane; the PMI average pore diameter of the porous membrane is 15-25nm, the porosity is 70-85%, and the thickness is 40-150 μm; and the part for trapping colloidal gold with the diameter of 20nm is a region which is 90-100% of the thickness of the main body from the first porous surface; the average pore diameter of the PES porous membrane main body is continuously reduced in a gradient manner from a region close to the first porous surface to a region close to the second porous surface; the PES porous membrane is integrally prepared and formed only through one casting membrane liquid, and is not required to be compounded, so that the preparation process is relatively simple; meanwhile, the prepared PES porous membrane has a strong interception effect on parvovirus, can obtain high protein yield, has high flux and high filtering speed, and meets the requirements of practical application; is particularly suitable for the field of virus removal; in addition, the invention also provides a preparation method of the porous membrane, and the preparation method is convenient, quick and effective, simple to operate, green and environment-friendly, and suitable for large-scale popularization.
Drawings
FIG. 1 is a Scanning Electron Microscope (SEM) image of a longitudinal section of a PES porous membrane prepared in example 3, wherein the magnification is 700 ×;
FIG. 2 is a Scanning Electron Microscope (SEM) image of a longitudinal section close to a second porous surface of a PES porous membrane prepared in example 3, wherein the magnification is 50K ×;
FIG. 3 is a Scanning Electron Microscope (SEM) image of a longitudinal section close to the first porous surface of a PES porous membrane prepared in example 3, wherein the magnification is 20K ×;
FIG. 4 is a further enlarged Scanning Electron Microscope (SEM) photograph of a longitudinal section close to the first porous surface of the PES porous membrane prepared in example 1, wherein the magnification is 50K ×;
FIG. 5 is an EDS spectrum of gold content in a longitudinal section of the PES porous membrane prepared in example 2 after being retained by 20nm colloidal gold;
FIG. 6 is an EDS energy spectrum of gold content in a longitudinal section of the PES porous membrane prepared in example 2 after being retained by 20nm colloidal gold;
FIG. 7 is an EDS spectrum showing the gold content in a longitudinal section of the PES porous membrane prepared in example 1 after being retained by 30nm colloidal gold;
FIG. 8 is an EDS energy spectrum of gold content in a longitudinal section of the PES porous membrane prepared in example 1 after being retained by 30nm colloidal gold;
FIG. 9 is an EDS spectrum showing the gold content in a longitudinal section of the PES porous membrane prepared in example 1 after being retained by 50nm colloidal gold;
FIG. 10 is an EDS energy spectrum of gold content in a longitudinal section of the PES porous membrane prepared in example 1 after being retained by 50nm colloidal gold;
FIG. 11 is a Scanning Electron Microscope (SEM) image of a longitudinal section of the PES porous membrane prepared in example 2, after being retained by 20nm colloidal gold, at a magnification of 10K ×;
FIG. 12 is a Scanning Electron Microscope (SEM) image of a PES porous membrane prepared in example 2 after being retained by 20nm colloidal gold, with a longitudinal section taken at a magnification of 20K ×, further enlarged near the first porous surface;
FIG. 13 is a Scanning Electron Microscope (SEM) image of a longitudinal section of the PES porous membrane prepared in example 1 after being retained by 30nm colloidal gold, at a magnification of 10K ×;
FIG. 14 is a Scanning Electron Microscope (SEM) image of a PES porous membrane prepared in example 1 after being retained by 30nm colloidal gold, with a longitudinal section taken at 50K ×, further enlarged near the first porous surface;
FIG. 15 is a Scanning Electron Microscope (SEM) image of a longitudinal section of the PES porous membrane prepared in example 1 after being retained by 50nm colloidal gold, at a magnification of 20K ×;
FIG. 16 is a Scanning Electron Microscope (SEM) image of a PES porous membrane prepared in example 1 after being retained by 50nm colloidal gold, with a longitudinal section taken at 50K X, and further enlarged near the first porous surface;
FIG. 17 is a schematic diagram of a PES porous membrane flux test device of the invention;
FIG. 18 is a schematic diagram of a testing apparatus for testing the retention efficiency of a PES porous membrane according to the invention using colloidal gold;
FIG. 19 is a Scanning Electron Microscope (SEM) image of a cross section of a multilayer composite ultra-porous membrane prepared in patent CN 1759924B;
FIG. 20 is a schematic diagram of a compounding device in the preparation of a multilayer composite ultra-porous membrane according to patent CN 1759924B.
Detailed Description
In order to more clearly explain the overall concept of the present application, the following detailed description is given by way of example. In the following examples, raw materials and equipment for preparing a porous film were commercially available, unless otherwise specified. The structural morphology of the porous membrane is characterized by adopting a scanning electron microscope with the model number of S-5500 provided by Hitachi company.
Example 1a method for preparing an asymmetric PES porous membrane for virus removal, comprising the steps of:
s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; wherein the casting solution comprises the following substances in parts by weight: 15 parts of polyether sulfone; 60 parts of an organic solvent; 8 parts of polar additive; the organic solvent is dimethyl sulfoxide; the polar additive is polyvinylpyrrolidone;
s2: pre-separating the liquid film in air with the temperature of 6 ℃ and the relative humidity of 90% for 3 s;
s3: immersing the liquid film after pre-phase separation into a curing liquid along with the carrier for 25 seconds, wherein the curing liquid invades into the liquid film and gradually diffuses inwards, and then curing to form a porous film; the curing liquid comprises water and a penetrating additive, wherein the penetrating additive is fluorine-containing hydrophilic substance hexafluoroisopropanol; the content of the permeation additive in the curing liquid is 55 percent; the curing liquid temperature was 20 ℃.
Example 2 a method for preparing an asymmetric PES porous membrane for virus removal, comprising the steps of:
s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; wherein the casting solution comprises the following substances in parts by weight: 17 parts of polyether sulfone; 65 parts of an organic solvent; 10 parts of polar additive; the organic solvent is ethyl acetate; the polar additive is polyethylene glycol;
s2: pre-separating the liquid film in air with the temperature of 8 ℃ and the relative humidity of 86% for 4 s;
s3: immersing the liquid film after pre-phase separation into a curing liquid along with the carrier for 30 seconds, wherein the curing liquid invades into the liquid film and gradually diffuses inwards, and then curing to form a porous film; the curing liquid comprises water and a penetrating additive, and the penetrating additive is fluorine-containing hydrophilic substance trifluoroethanol; the content of the permeation additive in the curing liquid is 50 percent; the curing liquid temperature was 22 ℃.
Example 3 a method for preparing an asymmetric PES porous membrane for virus removal, comprising the steps of:
s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; wherein the casting solution comprises the following substances in parts by weight: 19 parts of polyether sulfone; 70 parts of an organic solvent; 12 parts of polar additive;
the organic solvent is caprolactam; the polar additive is polyethyleneimine;
s2: pre-separating the liquid film in air with the temperature of 10 ℃ and the relative humidity of 82% for 5 s;
s3: immersing the liquid film after pre-phase separation into a curing liquid along with the carrier for 35 seconds, wherein the curing liquid invades into the liquid film and gradually diffuses inwards, and then curing to form a porous film; the curing liquid comprises water and a penetrating additive, wherein the penetrating additive is fluorine-containing hydrophilic substance hexafluoroisopropanol; the content of the permeation additive in the curing liquid is 46 percent; the curing liquid temperature was 24 ℃.
Example 4 a method for preparing an asymmetric PES porous membrane for virus removal, comprising the steps of:
s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; wherein the casting solution comprises the following substances in parts by weight: 21 parts of polyether sulfone; 75 parts of an organic solvent; 14 parts of polar additive;
the organic solvent is N-ethyl pyrrolidone; the polar additive is polyvinyl alcohol;
s2: pre-separating the liquid film in air with the temperature of 12 ℃ and the relative humidity of 78% for 6 s;
s3: immersing the liquid film after pre-phase separation into a curing liquid along with the carrier for 40 seconds, wherein the curing liquid invades into the liquid film and gradually diffuses inwards, and then curing to form a porous film; the curing liquid comprises water and a penetrating additive, and the penetrating additive is fluorine-containing hydrophilic substance trifluoroethanol; the content of the penetrating additive in the curing liquid is 42%; the curing liquid temperature was 26 ℃.
Example 5 a method for preparing an asymmetric PES porous membrane for virus removal, comprising the steps of:
s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; wherein the casting solution comprises the following substances in parts by weight: 23 parts of polyether sulfone; 80 parts of an organic solvent; 18 parts of polar additive;
the organic solvent is dimethylacetamide; the polar additive is polyvinylpyrrolidone;
s2: pre-separating the liquid film in air with the temperature of 14 ℃ and the relative humidity of 74% for 7 s;
s3: immersing the liquid film after pre-phase separation into a curing liquid along with the carrier for 45 seconds, wherein the curing liquid invades into the liquid film and gradually diffuses inwards, and then curing to form a porous film; the curing liquid comprises water and a penetrating additive, wherein the penetrating additive is fluorine-containing hydrophilic substance hexafluoroisopropanol; the content of the penetrating additive in the curing liquid is 38 percent; the curing liquid temperature was 28 ℃.
Example 6 a method for preparing an asymmetric PES porous membrane for virus removal, comprising the steps of:
s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; wherein the casting solution comprises the following substances in parts by weight: 25 parts of polyether sulfone; 85 parts of an organic solvent; 20 parts of polar additive;
the organic solvent is butyl lactate; the polar additive is polyvinyl alcohol;
s2: pre-separating the liquid film in air with the temperature of 16 ℃ and the relative humidity of 70% for 8 s;
s3: immersing the liquid film after pre-phase separation into a curing liquid along with the carrier for 50 seconds, wherein the curing liquid invades into the liquid film and gradually diffuses inwards, and further curing to form a porous film; the curing liquid comprises water and a penetrating additive, and the penetrating additive is fluorine-containing hydrophilic substance trifluoroethanol; the content of the permeation additive in the curing liquid is 34 percent; the curing liquid temperature was 30 ℃.
Firstly, the method comprises the following steps: structural characterization
Carrying out morphology characterization on the film structure of the porous film obtained in each embodiment by using a scanning electron microscope, and then obtaining required data; the specific results are as follows:
table 1:
thickness/mum Porosity/% PMI mean pore diameter/nm
Example 1 67 74.1 16.8
Example 2 71 75.4 18.6
Example 3 85 76.2 20.7
Example 4 98 78.6 21.5
Example 5 114 80.3 22.1
Example 6 136 82.7 23.4
Table 2: when the colloidal gold with the diameter of 20nm is intercepted
Figure BDA0003452479700000241
TABLE 3
K1 units are nm/mum; k2 units are nm/. mu.m
Figure BDA0003452479700000242
TABLE 4
Figure BDA0003452479700000243
As can be seen from tables 1 to 4, the PES porous membranes prepared in the embodiments 1 to 6 of the invention all have ideal membrane structures, and the porous membranes are integrally formed into membranes without a composite process, so that the process preparation is simple; the PES porous membrane is an asymmetric membrane, the pore diameter of the membrane pore changes along with the small thickness in a gradient manner, no extra large pore exists, the efficient interception of the virus is ensured, the flux is high, and the PES porous membrane is suitable for being applied to the field of virus removal.
Characteristic features
The membrane flux is calculated as follows:
the formula for calculating the membrane flux (J) is: j ═ V/(T × a) formula wherein:
j- -Membrane flux Unit: l h-1*m-2
V- -sample volume (L); t- -sampling time (h); a- -effective area of film (m2)
The PES porous membrane separation performance in the invention is measured by adopting the following operating conditions: the feed liquid is deionized water, the operating pressure is 30psi, the operating temperature is 25 ℃, and the pH of the solution is 7; the throughput testing apparatus is shown in fig. 15;
tests show that the PES porous membranes prepared in the examples 1-6 of the invention have the flux of more than 600L x h-1*m-2@30psi, its flux is great, can satisfy the demand of practical application.
Further, the test method used in paragraph 114 of CN 201010154974.7-ultra porous membrane and its preparation method can be followed: performing a virus retention test:
the virus used is a murine parvovirus with a particle size of 20 nm;
after testing, the PES porous membranes prepared in examples 1-6 have an LRV of not less than 4 for virus impurities with a particle size of 20nm, thereby indicating that the PES porous membranes of the invention have sufficient retention effect on viruses with a particle size of 20nm and above; the protein yield of the PES porous membrane is not lower than 98 percent; therefore, the PES porous membrane is particularly suitable for being applied to the field of virus removal.
And (3) testing the filtering precision: testing the interception efficiency of the PES porous membrane obtained in each example; intercepting particles: colloidal gold experimental equipment with the particle size of 20 nm: a Tianjin Roots particle counter KB-3; preparation of the experiment: the experimental set-up was assembled as in fig. 16, ensuring the set-up was clean, and the set-up was rinsed with ultra-pure water; a porous membrane with a diameter of 47mm is taken and arranged in the butterfly filter, so that the air tightness of the assembled filter is ensured to be good.
The experimental steps are as follows: the challenge was poured into a tank, the butterfly filter was vented, pressurized to 10kPa, and a clean bottle was used to take the butterfly downstream filtrate.
The number of particles in the filtrate and stock solutions was measured using a particle counter.
Intercepting efficiency:
Figure BDA0003452479700000261
in the formula: eta-type-interception efficiency,%; n is0-number of particles in stock solution, average of 5 sets of counts;
n1-number of particles in filtrate, average of 5 groups of counts, one.
After the test, the porous membranes prepared in examples 1 to 6 were found to have a rejection efficiency of not less than 99.99% for colloidal gold of 20 nm.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.

Claims (13)

1. An asymmetric PES porous membrane for virus removal comprising a first porous surface, a second porous surface, and a body positioned between the first porous surface and the second porous surface, the body having a non-directional tortuous pathway therein, characterized in that: the porous membrane is a single layer membrane; the PMI average pore diameter of the porous membrane is 15-25 nm; the porosity of the porous membrane is 70-85%, and the thickness is 40-150 μm;
the part for trapping colloidal gold with the diameter of 20nm is a region which is 90-100% of the thickness of the main body from the first porous surface;
the average pore size of the body decreases in a continuous gradient from a region on the side close to the first porous surface to a region on the side close to the second porous surface.
2. The asymmetric PES porous membrane for virus removal according to claim 1, wherein: the peak cut-off for colloidal gold with a cut-off diameter of 20nm is the region from the first porous surface at 94% -98% of the thickness of the body.
3. The asymmetric PES porous membrane for virus removal according to claim 1, wherein: the part for trapping colloidal gold with the diameter of 30nm is a region which is 81-100% of the thickness of the main body from the first porous surface;
the part for trapping the colloidal gold with the diameter of 50nm is a region which is 73-95% of the thickness of the main body from the first porous surface;
when the particle size of the trapped colloidal gold is 30-50nm, the average trapped colloidal gold particle size variation gradient K1 of the main body along the thickness direction is 2-8 nm/mum;
when the particle size of the trapped colloidal gold is 20-30nm, the average trapped colloidal gold particle size variation gradient K2 of the main body along the thickness direction is 1.4-5.6 nm/mum;
K1:K2＝1.2-1.8；
the average retained colloidal gold particle size variation gradient is the colloidal gold particle size variation value/the main body thickness for retaining the corresponding colloidal gold particle size.
4. The asymmetric PES porous membrane for virus removal according to claim 1, wherein: the thickness of the body region for trapping colloidal gold with a diameter of 20-30nm is 8-28 μm, and is a region from the first porous surface at 81% -100% of the thickness of the body.
5. The asymmetric PES porous membrane for virus removal according to claim 1, wherein: the thickness of the body region for trapping colloidal gold with a diameter of 30-50nm is 11-37 μm, and the region is 73-100% of the thickness of the body from the first porous surface.
6. The asymmetric PES porous membrane for virus removal according to claim 1, wherein: the thickness of the main body area for intercepting the colloidal gold with the diameter of 30-50nm is 1.25-1.7 of the thickness of the main body area for intercepting the colloidal gold with the diameter of 20-30 nm.
7. The asymmetric PES porous membrane for virus removal according to claim 1, wherein: the thickness of the body region that retains colloidal gold having a diameter greater than 40nm is 35-130 μm, and is the region from the first porous surface at 0-87% of the thickness of the body.
8. The asymmetric PES porous membrane for virus removal according to claim 1, wherein: the body comprising first fibers and second fibers forming a porous structure, the first fibers being located on a side of the body adjacent the first porous surface and the second fibers being located on a side of the body adjacent the second porous surface; the first fibers and the second fibers are continuous in a thickness direction of the body; the first fibers are of a sheet-like structure; the second fibers are in a strip-shaped structure.
9. The asymmetric PES porous membrane for virus removal according to claim 8, wherein: the first fibers have an average diameter greater than an average diameter of the second fibers, and the second fibers have an average diameter of 30 to 75 nm.
10. The asymmetric PES porous membrane for virus removal according to claim 1, wherein: the tensile strength of the porous membrane is 5-10MPa, and the elongation at break is 8-30%;
the flux of the porous membrane is greater than 600L h-1*m-2@30psi；
The LRV of the porous membrane to 20nm colloidal gold is not less than 4;
the protein yield of the porous membrane is not less than 98%.
11. The method for preparing an asymmetric PES porous membrane for virus removal according to any one of claims 1 to 10, characterized by comprising the steps of:
s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; wherein the casting solution comprises the following substances in parts by weight: 15-25 parts of polyether sulfone; 55-90 parts of an organic solvent; 6-25 parts of polar additive;
s2: pre-separating the liquid film in air with temperature of 5-20 deg.C and relative humidity of 70-90% for 2-10 s;
s3: immersing the liquid film after pre-phase separation into a curing liquid along with the carrier for at least 20 seconds, wherein the curing liquid invades into the liquid film and gradually diffuses inwards, and then curing to form a porous film; the solidifying liquid comprises water and a penetrating additive, and the penetrating additive is a fluorine-containing hydrophilic substance.
12. The method of claim 11, wherein the organic solvent is at least one selected from butyl lactate, dimethylsulfoxide, dimethylformamide, caprolactam, methyl acetate, ethyl acetate, N-ethylpyrrolidone, dimethylacetamide, and N-methylpyrrolidone;
the polar additive is at least one of polyvinyl alcohol, polyethylene glycol, polyethyleneimine and polyvinylpyrrolidone.
13. The method for preparing the asymmetric PES porous membrane for removing viruses of claim 11, wherein the content of the penetration additive in the curing solution is 30-60%; the fluorine-containing hydrophilic substance is hexafluoroisopropanol or trifluoroethanol; the temperature of the solidified liquid is 20-30 ℃.
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