CN111467975A - Separation membrane and preparation method and application thereof - Google Patents
Separation membrane and preparation method and application thereof Download PDFInfo
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- CN111467975A CN111467975A CN202010174185.3A CN202010174185A CN111467975A CN 111467975 A CN111467975 A CN 111467975A CN 202010174185 A CN202010174185 A CN 202010174185A CN 111467975 A CN111467975 A CN 111467975A
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/08—Polysaccharides
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M1/00—Suction or pumping devices for medical purposes; Devices for carrying-off, for treatment of, or for carrying-over, body-liquids; Drainage systems
- A61M1/14—Dialysis systems; Artificial kidneys; Blood oxygenators ; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis
- A61M1/16—Dialysis systems; Artificial kidneys; Blood oxygenators ; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis with membranes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
- B01D53/228—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion characterised by specific membranes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0079—Manufacture of membranes comprising organic and inorganic components
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/08—Polysaccharides
- B01D71/10—Cellulose; Modified cellulose
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/48—Antimicrobial properties
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Heart & Thoracic Surgery (AREA)
- Life Sciences & Earth Sciences (AREA)
- Urology & Nephrology (AREA)
- Emergency Medicine (AREA)
- Biomedical Technology (AREA)
- Manufacturing & Machinery (AREA)
- Organic Chemistry (AREA)
- Water Supply & Treatment (AREA)
- Environmental & Geological Engineering (AREA)
- Hydrology & Water Resources (AREA)
- Vascular Medicine (AREA)
- Anesthesiology (AREA)
- Inorganic Chemistry (AREA)
- Hematology (AREA)
- Animal Behavior & Ethology (AREA)
- General Health & Medical Sciences (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention relates to a separation membrane and a preparation method and application thereof. The preparation method of the separation membrane comprises the following steps: dissolving degradable natural polymers to obtain a membrane casting solution, wherein the degradable natural polymers comprise one of chitosan, cellulose and chitin; dispersing the slow-release anti-degradation substance in the membrane casting solution to obtain a modified membrane casting solution, wherein the slow-release anti-degradation substance comprises one of silver nanoparticles, copper nanoparticles, thymol oil, ginger oil and clove essential oil; forming a film by using the modified film casting solution to obtain a liquid film; and carrying out phase inversion or phase separation on the liquid film to obtain the separation film. The raw materials used in the preparation method of the separation membrane have wide sources, the prepared separation membrane has little pollution to the environment, the separation performance of the separation membrane can be maintained in the using process, and the natural degradation performance of the separation membrane can be recovered after the service life of the separation membrane is reached.
Description
Technical Field
The invention relates to the field of membrane separation, in particular to a separation membrane and a preparation method and application thereof.
Background
The membrane separation technology is started in the last 60 th century, is rapidly developed in the last thirty years, is widely applied to various industries including water treatment, seawater desalination, gas separation, chemical production, food and beverage, medical treatment, energy storage and the like, and makes great contribution to improving the living level of people and promoting the development of national economy. The key point of the membrane separation technology is to prepare a high-performance separation membrane, namely, a high permeation flux is ensured while the target component is retained. At present, most separation membranes in domestic and foreign markets are prepared from chemical high polymer materials (such as polysulfone, polyethersulfone, polytetrafluoroethylene, polypropylene nitrile and the like) extracted and obtained based on non-renewable petrochemical resources. With the continuous increase of the demand of the separation membrane, the increasing exhaustion of petrochemical resources and the continuous rising of the price of crude oil in the world, the preparation and the continuous supply of the separation membrane using chemical macromolecules as raw materials are seriously influenced. Along with a series of unavoidable problems such as membrane pollution, membrane aging and the like, in order to ensure the treatment efficiency of membrane separation, the separation membrane needs to be replaced regularly, which further aggravates the consumption of chemical high polymer materials and non-renewable petrochemical resources, and simultaneously generates huge amounts of waste separation membranes. In addition to the shortage of production raw materials, the chemical polymer separation membrane is very easy to generate various solid, liquid and gas wastes which have great harm to the human health and the ecological environment in the production and preparation processes, and after the separation membrane reaches the service life, the process is very easy to cause the harm to the human health and the ecological environment no matter what treatment and disposal mode (such as decomposition, incineration, landfill and the like) is adopted. Even the chemical polymer separation membrane material after treatment still may cause continuous harm to human health and ecological environment, wherein the most typical example is the micro plastic problem which has received global attention in recent years, namely ecological ring pollution caused by various chemical polymer particles with particle size smaller than millimeter scale.
Disclosure of Invention
Therefore, there is a need for a method for preparing a separation membrane which has a wide source, causes less environmental pollution, and can maintain the separation performance of the separation membrane during use and recover the natural degradation performance after the service life is reached.
Furthermore, a separation membrane and the use of a separation membrane are provided.
A method of making a separation membrane comprising the steps of:
dissolving degradable natural polymers to obtain a membrane casting solution, wherein the degradable natural polymers comprise one of chitosan, cellulose and chitin;
dispersing a slow-release anti-degradation substance in the membrane casting solution to obtain a modified membrane casting solution, wherein the slow-release anti-degradation substance comprises one of silver nanoparticles, copper nanoparticles, thymol oil, ginger oil and clove essential oil;
forming a film by using the modified film casting solution to obtain a liquid film; and
and carrying out phase inversion or phase separation on the liquid film to obtain the separation film.
In one embodiment, the mass of the slow release anti-degradation substance is 0.1-5.0% of the mass of the degradable natural macromolecule.
In one embodiment, the thickness of the liquid film is 200 μm to 500 μm.
In one embodiment, the step of subjecting the liquid film to phase inversion or phase separation to obtain a separation membrane comprises: and placing the liquid membrane in a coagulating bath for standing and regenerating to obtain the separation membrane.
In one embodiment, the coagulation bath comprises at least one of water, ethanol, and dimethylacetamide.
In one embodiment, in the step of placing the liquid film in a coagulation bath for standing and regeneration, the temperature of the coagulation bath is-80 ℃ to 30 ℃.
In one embodiment, in the step of placing the liquid film in the coagulating bath for standing regeneration, the standing regeneration time is 1 min-24 h.
In one embodiment, the step of dissolving the degradable natural polymer to obtain the casting solution includes: dissolving lithium hydroxide, potassium hydroxide and urea in water, adding the degradable natural polymer, freezing and thawing for multiple times, and performing centrifugal defoaming to obtain the membrane casting solution.
In one embodiment, the freezing temperature is-80 ℃ to-20 ℃, and the time of each freezing is 30min to 24 h.
In one embodiment, the liquid membrane is a flat membrane, and the step of forming the membrane from the modified membrane casting solution comprises: casting the casting solution on a flat plate to form the liquid film; or, the liquid membrane is a hollow fiber membrane, and the step of forming the membrane from the modified membrane casting solution comprises the following steps: and spinning the casting solution through a central control fiber membrane spinning machine to obtain the liquid membrane.
In one embodiment, in the casting solution, the mass concentration of the degradable natural polymer is 3% to 8%.
The separation membrane prepared by the preparation method of the separation membrane.
The separation membrane is applied to water treatment, gas separation or medical dialysis.
The preparation method of the separation membrane takes degradable natural polymers as raw materials, the degradable natural polymers have wide sources and can be biologically degraded, the degradable natural polymers are dissolved to obtain membrane casting solution, then the slow-release anti-degradation substances are dispersed in the membrane casting solution to obtain modified membrane casting solution, and the separation membrane is obtained through membrane forming, phase inversion or phase separation. By the method, the separation membrane formed by degradable natural polymers can be doped with the slow-release anti-degradation substance, and the slow-release anti-degradation substance can kill various microorganisms and proteins with biodegradation efficacy, so that the separation membrane is not easily degraded by the microorganisms in the natural environment in the use process, and the degradable natural polymers in the separation membrane can be biodegraded after the anti-degradation substance reaches the service life. In addition, experiments prove that the permeation function, the interception function and the like of the separation membrane are hardly influenced by doping the slow-release degradation-resistant substances in the separation membrane. Therefore, the preparation method of the separation membrane can prepare the separation membrane which has wide sources and small environmental pollution, can maintain the separation performance in the use process, can recover the natural degradation performance after the service life is reached, and can be used in the fields of water treatment, gas separation, medical dialysis and the like.
Drawings
Fig. 1 is a process flow diagram of a method of manufacturing a separation membrane according to an embodiment;
FIG. 2 is a flow chart showing one of the preparation steps S130 and S140 in the process flow chart of the method for preparing the separation membrane shown in FIG. 1;
FIGS. 3-a and 3-b are photographs of a chitosan separation membrane of comparative example 1 and a modified chitosan separation membrane containing silver nanoparticles of example 1, respectively; FIGS. 3-c and 3-d are scanning electron microscope pictures of the chitosan separation film of comparative example 1 and the modified chitosan separation film containing silver nanoparticles of example 1, respectively; FIG. 3-e is a photograph of an X-ray spectrum of the modified chitosan separation membrane containing silver nanoparticles of example 1;
FIGS. 4-a and 4-b are graphs showing experimental results of bacteriostatic rings of the chitosan separation membrane of comparative example 1 and the modified chitosan separation membrane containing silver nanoparticles of example 1, respectively;
fig. 5 is a graph showing sterilization experimental results of the chitosan separation membrane of comparative example 1 and the modified chitosan separation membrane containing silver nanoparticles of example 1;
FIG. 6 is a graph showing the weight change of the chitosan separation membrane of comparative example 1 and the modified chitosan separation membrane containing silver nanoparticles of example 1 by lysozyme degradation for 5 days;
FIG. 7 is a graph showing changes in water flux before and after 5 days of lysozyme degradation of the chitosan separation membrane of comparative example 1 and the modified chitosan separation membrane containing silver nanoparticles of example 1;
FIG. 8 is a comparison graph of water flux of the chitosan separation membrane of comparative example 1 and the chitosan separation membrane of comparative example 2 having different thicknesses;
FIG. 9 is a graph showing a comparison of water fluxes of the chitosan separation membrane of comparative example 2 and the chitosan separation membranes obtained in comparative examples 3 and 4 in different component gel baths;
FIG. 10 is a graph showing a comparison of water fluxes of the chitosan separation membrane of comparative example 1 and the chitosan separation membrane obtained in comparative example 5 in different temperature gel baths;
fig. 11 is a graph showing the change in retention rate before and after 5 days of lysozyme degradation of the chitosan separation membrane of comparative example 1 and the modified chitosan separation membrane containing silver nanoparticles of example 1.
Detailed Description
In order that the invention may be more fully understood, reference will now be made to the following description taken in conjunction with the accompanying drawings. The detailed description sets forth the preferred embodiments of the invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
Referring to fig. 1, a method for preparing a separation membrane according to an embodiment includes the following steps:
step S110: dissolving degradable natural polymer to obtain casting solution, wherein the degradable natural polymer comprises one of chitosan, cellulose and chitin.
The degradable natural polymer has rich sources, can reduce the production cost by selecting different degradable natural polymers, optimize the structure of the separation membrane, improve the performance of the separation membrane and expand the application range of the separation membrane.
In one embodiment, the degradable natural polymer is chitosan. Chitosan is obtained from chitosan deacetylation. Chitin, also called chitin and chitin, is a natural polysaccharide extracted from the exoskeletons of crustaceans such as shrimp, crab and insects and higher fungi. It has wide source, rich reserves, quick regeneration, low cost, good biocompatibility and natural degradation. The chitosan obtained by deacetylation of chitin has good solubility and chemical activity while maintaining the advantages, is applied to the fields of food, medicine, biology, environment, cosmetics, packaging and the like, and has a very wide application prospect. At present, in the field of membrane separation, although a few reports of chitosan gas separation membranes exist, and chitosan is used as an antibacterial or hydrophilic material to be doped into various separation membranes, the preparation and application research of water treatment separation membranes using chitosan as a main material is still in the beginning and has a fresh smell.
Different from the traditional chemical high polymer material, the casting solution system formed by degradable natural high polymers such as chitosan and the like has unique physicochemical properties, and the film forming mechanism and the film forming process are more obviously different from the traditional chemical high polymer. How to regulate and control the secondary structure such as the aperture, the appearance and the like of the chitosan separation membrane by controlling the membrane forming condition so as to ensure that the chitosan separation membrane has excellent separation performance, and is a great difficult problem to be solved urgently in the field of membrane separation by using natural high polymer materials such as chitosan and the like.
In addition, although the environment-friendly and biodegradable properties are the advantages of natural polymer materials such as chitosan, considering that the separation membrane generally needs to have a certain service life and needs to maintain stable separation performance in a service period, how to regulate the degradation performance of the chitosan separation membrane to ensure that the chitosan separation membrane is not easily degraded in the use process and the natural degradation capability is recovered after the service life is reached is a difficult problem which must be solved before the chitosan separation membrane is put into practical application.
Based on the above reasons, through a large number of experiments, the inventor uses degradable natural polymers such as chitosan and the like as raw materials, firstly dissolves the raw materials to obtain a casting solution, and then dopes the slow-release anti-degradation substance in the subsequent steps, so that the degradable natural polymers are not degraded under the action of the slow-release anti-degradation substance within a certain service life to realize the separation performance.
The method for dissolving the degradable natural polymer comprises the following steps: alkali-urea dissolution, acetic acid solution dissolution, organic solution dissolution, ionic liquid dissolution, or the like.
Specifically, the step of dissolving the degradable natural polymer to obtain the casting solution comprises the following steps: dissolving lithium hydroxide, potassium hydroxide and urea in water, adding degradable natural polymer, freezing and thawing for multiple times, and performing centrifugal defoaming to obtain the casting solution.
Wherein the lithium hydroxide is added in the form of lithium hydroxide monohydrate. Specifically, the mass ratio of the lithium hydroxide monohydrate to the potassium hydroxide to the urea to the water is (8-12) to (5-7) to (6-8) to 77. The addition amount of the degradable natural polymer is 3-8% of the mass of the casting solution.
The freezing temperature is-80 ℃ to-20 ℃, and the time of each freezing is 30min to 24 h. In the step of centrifugal defoaming, the rotation speed of the centrifugation is 6000 rpm-15000 rpm. The centrifugation time is 10 min-30 min.
In one embodiment, step S110 is to hydrate lithium hydroxide monohydrate (L iOH H)2O), potassium hydroxide and urea in ultrapure water, wherein lithium hydroxide monohydrate (L iOH. H)2O), potassium hydroxide, urea and water in a mass ratio of 8: 7: 8: 77. After the natural polymer is completely dissolved, adding degradable natural polymer with the mass of 3-8% of that of the casting solution, uniformly stirring, freezing in a low-temperature refrigerator with the temperature of-80-20 ℃ for 30-24 h, thawing at room temperature, and stirring in an electric stirrer at the rotating speed of 500-700 rpm for 10 min; after multiple freezing and dissolving stirring, centrifuging for 10-30 min at 6000-15000 rpm in a centrifuge to remove bubbles in the solution, and obtaining the membrane casting solution.
Compared with other dissolving methods, the raw materials and the dissolving process used in the step of obtaining the casting solution by adopting a urea-alkali dissolving method are more environment-friendly, and solid-liquid-gas wastes which have obvious harm to human health and ecological environment are not easy to generate; and the separation membrane prepared by using the membrane casting solution obtained by the low-temperature freeze-thaw method has better mechanical property and physical and chemical properties. However, it should be emphasized that the dissolution method of the degradable natural polymer does not directly affect the control of the degradation performance of the subsequent separation membrane, that is, the preparation of the separation membrane provided by the present invention may still be achieved by using the casting solution obtained by other dissolution methods (such as acetic acid solution dissolution, organic solution dissolution, ionic liquid dissolution, and the like which are harmful to the environment). Therefore, it is understood that, in another embodiment, the casting solution may be obtained in step S110 by an acetic acid solution dissolution method, an organic solution dissolution method, an ionic liquid dissolution method, or the like.
Specifically, the method for dissolving chitosan by adopting acetic acid solution comprises the following steps: weighing a certain amount of chitosan powder, adding the chitosan powder into an acetic acid solution with the volume fraction of 1-2% (v/v) to obtain a membrane casting solution, and enabling the mass volume fraction of chitosan in the membrane casting solution to be 2-5% (w/v). After stirring at room temperature for 24 hours, the insoluble fraction was filtered off, and the casting solution was allowed to stand for a while to remove air bubbles.
The method for dissolving chitosan by adopting organic solution comprises the following steps: weighing a certain amount of chitosan powder, adding the chitosan powder into an organic solvent (such as dimethylacetamide), and adding a small amount of lithium chloride as an additive to obtain a casting solution, wherein the mass volume fraction of chitosan in the casting solution is 2-5% (w/v). After stirring at room temperature for 24 hours, the casting solution was allowed to stand for a period of time to remove air bubbles.
The method for dissolving chitosan by adopting ionic liquid comprises the following steps: weighing a certain amount of chitosan powder, adding the chitosan powder into the ionic liquid to obtain a membrane casting solution, wherein the mass volume fraction of chitosan in the membrane casting solution is 2-5% (w/v). After stirring at room temperature for 24 hours, the casting solution was allowed to stand for a period of time to remove air bubbles. Step S120: dispersing the slow-release anti-degradation substance in the membrane casting solution to obtain the modified membrane casting solution, wherein the slow-release anti-degradation substance comprises one of silver nanoparticles, copper nanoparticles, thymol oil, ginger oil and clove essential oil.
In one embodiment, step S120 is: and directly adding the slow-release anti-degradation substance into the membrane casting solution and uniformly dispersing. The slow-release anti-degradation substance has a killing effect on various microorganisms and proteins, and the slow-release anti-degradation substance which can kill various microorganisms and proteins and has a slow-release property is introduced into the grid structure of the separation membrane in a mode of directly doping the slow-release anti-degradation substance into the membrane casting solution. However, it should be emphasized that the separation membrane provided by the present invention can be obtained by other methods, such as in-situ reduction and grafting, and thus, in other embodiments, the sustained-release anti-degradation substance can be obtained by other methods, such as in-situ reduction and grafting, and then dispersed in the casting solution.
Compared with the in-situ reduction silver nanoparticles, the method for preparing the separation membrane by directly doping the nanoparticles in the membrane casting solution has the advantages of simple operation method, mild and controllable reaction conditions, good stability, low energy consumption and more contribution to industrial application.
Specifically, the mass of the slow-release anti-degradation substance is 0.1-5.0% of the mass of the degradable natural polymer. When the sustained-release degradation-resistant substance is a silver nanoparticle or a copper nanoparticle, the particle diameter of the silver nanoparticle or the copper nanoparticle is several nanometers to several hundred nanometers.
Because the nano particles formed by silver, copper and other elements have obvious antibacterial effect, the heavy metal toxicity can also denature and inactivate proteins such as enzyme and the like; the nano-particles formed by silver, copper and other elements have obvious antibacterial effect by simply regulating and controlling the particle size, surface groups and the like of the nano-particles, the antibacterial effect, the release rate and the like of the nano-particles can be flexibly changed, and the heavy metal toxicity of the nano-particles can also denature and inactivate proteins such as enzyme and the like; and the sterilization effect, the release rate and the like can be flexibly changed by simply regulating and controlling the particle size, the surface groups and the like.
Step S130: and forming a film by using the modified film casting solution to obtain a liquid film.
Specifically, the liquid membrane is a flat membrane, a hollow fiber membrane or a tubular membrane.
In one embodiment, the liquid membrane is a flat membrane, and step S130 includes: and casting the casting solution on a flat plate to form a liquid film. Specifically, step S130 is: and pouring the casting solution onto a flat plate, and then forming a liquid film on the flat plate by using a scraper. In one embodiment, an automatic film scraper is used in step S130. The thickness of the liquid film is 200-500 μm. In this embodiment, the thickness of the resulting liquid film can be adjusted by adjusting the height of the doctor blade. The casting solution can be uniformly distributed on the smooth flat plate through the steps to form a liquid film with a certain thickness. It is emphasized that, unlike films used for packaging materials and film coatings, the different liquid film thicknesses resulting from the doctor blade height setting will directly affect the thickness of the separation membrane produced, and thus significantly affect its separation performance (e.g. water flux and rejection rate, etc.).
In particular, the flat plate may be a glass plate.
In another embodiment, the liquid membrane is a hollow fiber membrane, and the step S130 includes: and spinning the casting solution through a hollow fiber membrane spinning machine to obtain a liquid membrane.
In yet another embodiment, the liquid membrane is a tubular membrane, and step S130 includes: casting the membrane-casting solution into the porous ceramic tube by using an air compressor, and allowing the membrane-casting solution to stay in the porous ceramic tube for a period of time (such as 5 minutes); and after the inner wall of the porous ceramic tube is attached with a liquid film, discharging the casting solution. When the liquid membrane is a tubular membrane, the support tube used is not limited to a porous ceramic tube, and may be another tube commonly used in the art.
Step S140: and carrying out phase inversion or phase separation on the liquid film to obtain the separation film.
In one embodiment, step S140 includes: and (4) placing the liquid membrane in a coagulating bath for standing and regeneration to obtain the separation membrane.
Specifically, the coagulation bath includes at least one of water, ethanol, and dimethylacetamide. The temperature of the coagulating bath is-80 ℃ to 30 ℃. The standing regeneration time is 1 min-24 h.
Experiments prove that the performance of the prepared separation membrane can be influenced to different degrees by different coagulation bath compositions, temperatures and standing times.
Referring to fig. 2, a preparation flow chart of step S130 and step S140. In other embodiments, the method of obtaining the separation membrane in step S140 may further employ a water vapor-induced phase separation method or the like. For example, in step S140, a water vapor-induced phase separation method is used, and step S140 includes: and (3) placing the liquid membrane in a closed container, introducing air with water vapor to keep the humidity in the container constant, and allowing the casting membrane liquid to absorb the water vapor and then to undergo phase separation to obtain the separation membrane. Specifically, the relative humidity is 10-50%.
The separation membrane obtained in the above steps S110 to S140 can be directly stored in various solutions including pure water, ethanol, dimethylacetamide, a mixed solution thereof, and the like during the use period, and a drying step is not required.
The preparation method of the separation membrane is mainly used for solving the problems that the raw materials are increasingly in short supply, the preparation process is high in harm and waste is not easy to dispose, which exist in the membrane separation field (the specific application of the separation membrane can cover multiple industries such as chemical industry, environmental protection, medicine, food and energy), and the like. The separation membrane prepared by the preparation method of the separation membrane is expected to greatly expand the raw material obtaining way and the preparation process of the separation membrane, and provide assistance for the research and development, production and application of the novel water treatment separation membrane and the sustainable development of society and environment.
The preparation method of the separation membrane at least has the following advantages:
(1) the preparation method of the separation membrane is characterized in that a slow-release anti-degradation substance with killing effect on various microorganisms, proteins with biodegradation effect and the like is doped into the separation membrane prepared from degradable natural high polymer materials, so that the preparation method of the environment-friendly separation membrane can maintain the separation performance of the separation membrane in the use process, can recover the natural degradation performance after the separation membrane reaches the service life, can quickly carry out natural degradation, can not be left in the environment for a long time, and is harmless to the environment.
(2) The degradable natural polymer separation membrane containing the slow-release degradation-resistant substances prepared by the preparation method of the separation membrane has excellent separation performance, the original permeability and interception performance of the separation membrane cannot be obviously influenced after the slow-release degradation-resistant substances are doped, and the slow-release degradation-resistant substances are continuously and slowly released in the use process of the separation membrane, so that the residual quantity is very small and is far lower than the level required by the world health organization or national standard, and secondary pollution to the environment cannot be caused. And the structure of the separation membrane can be optimized by changing the height of the scraper, the components of the coagulation bath, the temperature of the coagulation bath and other membrane forming conditions.
(3) The slow-release degradation-resistant substance used in the preparation method of the separation membrane has wide selection range and various regulation and control modes (such as changing the size, the type and the surface groups of nanoparticles, the pore structure of the separation membrane and the like), and is beneficial to the structure optimization of the prepared separation membrane.
(4) The raw materials adopted by the preparation method of the separation membrane are degradable and have wide sources of natural polymers, abundant reserves, quick regeneration, low cost and good biocompatibility, and other substances used in the preparation process of the membrane have low toxicity or even no toxicity, so that secondary pollution is not generated.
(5) The preparation method of the separation membrane is simple, strong in operability and easy for industrial production.
The separation membrane of an embodiment is produced by the production method of the separation membrane of the above embodiment. The separation membrane has excellent separation performance, the original permeability and interception performance of the separation membrane cannot be obviously influenced after the slow-release degradation-resistant substances are doped, and the separation membrane can be rapidly and naturally degraded after the service life is reached, cannot be stored in the environment for a long time and is harmless to the environment.
An embodiment of the separation membrane is applied to the field of water treatment, the field of chemical engineering or the field of medical treatment. In particular to the application of the separation membrane in water treatment, gas separation or medical dialysis. For example, the separation membrane can be applied to separation of pollutants and drinking water treatment in the field of water treatment, separation of different substance components (including gas separation) in the field of chemical engineering, separation processes (such as blood and urine dialysis) in the field of medical treatment, and the like.
The following are specific examples:
example 1
The separation membrane of the embodiment is a modified chitosan separation membrane containing silver nanoparticles, and the preparation process is as follows:
lithium hydroxide monohydrate (L iOH. H)2O), potassium hydroxide and urea in ultrapure water, wherein lithium hydroxide monohydrate (L iOH. H)2O), potassium hydroxide, urea and water in a mass ratio of 8: 7: 8: 77. After the chitosan is completely dissolved, adding silver nanoparticles accounting for 1% of the mass of the chitosan, performing ultrasonic treatment in an ultrasonic pot for 1 hour to fully disperse the silver nanoparticles in the solution, adding a certain amount of chitosan powder to enable the mass concentration of the chitosan in the casting solution to be 4%, and uniformly stirring. Then putting the chitosan into a low-temperature freezing refrigerator to be frozen at the temperature of minus 80 ℃, taking out the chitosan, stirring the chitosan by using an electric stirrer, repeating the stirring for 3 times until the chitosan powder is uniformly dissolved, and then centrifuging the chitosan powder for 12min at the rotating speed of 11000rpm at the temperature of freezing a centrifuge to be minus 5 ℃ to remove bubbles to obtain the modified chitosan casting solution. And (3) uniformly pouring the defoamed modified chitosan casting solution onto a glass plate of a coating experiment machine, uniformly pushing a scraper with the set height of 250 micrometers by using an automatic film scraping machine at a constant speed, so that a liquid film is uniformly distributed on the smooth plane of the casting solution, and placing the liquid film in alcohol at 20 ℃ for standing and regenerating for 1h to obtain the modified chitosan separation film. And finally, placing the modified chitosan separation membrane in ultrapure water for storage.
Example 2
The separation membrane of the present embodiment is a modified cellulose separation membrane containing thymol oil, and the preparation process is specifically as follows:
lithium hydroxide monohydrate (L iOH. H)2O) and urea in ultrapure water, wherein lithium hydroxide monohydrate (L iOH. H)2O), urea and water in a mass ratio of 8: 15: 77. After completely dissolving, adding 1% thymol oil of cellulose volume mass fraction, and performing ultrasonic treatment in ultrasonic pan for 1 hr to obtain thymol oil in solutionFully dispersing, adding a certain amount of cellulose powder to ensure that the mass fraction of cellulose in the membrane casting solution is 4%, and uniformly stirring. Then putting the mixture into a low-temperature freezing refrigerator to be frozen at the temperature of-50 ℃, taking out the mixture, stirring the mixture by using an electric stirrer, repeating the stirring for 3 times until the cellulose powder is uniformly dissolved, and then centrifuging the mixture for 15min at the rotation speed of 8000rpm at the temperature of freezing a centrifuge to be 5 ℃ for removing bubbles to obtain the modified cellulose casting solution. And (3) uniformly pouring the defoamed modified cellulose membrane casting solution onto a glass plate of a coating experiment machine, uniformly pushing a scraper with the set height of 250 micrometers by using an automatic membrane scraping machine at a constant speed, so that a liquid membrane is uniformly distributed on a smooth plane, and placing the liquid membrane in alcohol at the temperature of 20 ℃ for standing and regenerating for 1h to obtain the modified cellulose separation membrane. And finally, placing the modified cellulose separation membrane in ultrapure water for storage.
Example 3
The separation membrane of the embodiment is a modified chitin separation membrane containing clove essential oil, and the preparation process specifically comprises the following steps:
lithium hydroxide monohydrate (L iOH. H)2O) and urea in ultrapure water, wherein lithium hydroxide monohydrate (L iOH. H)2O), urea and water in a mass ratio of 8: 15: 77. After the chitin is completely dissolved, adding 1% by volume and mass of clove essential oil of chitin, performing ultrasonic treatment in an ultrasonic pot for 1 hour to fully disperse clove in the solution, adding a certain amount of chitin powder, and uniformly stirring to ensure that the mass concentration of the chitin in the casting solution is 4%. Then putting into a low-temperature freezing refrigerator for freezing at-20 ℃, taking out, stirring by using an electric stirrer, repeating for 3 times until the chitin powder is uniformly dissolved, and then centrifuging for 15min at 8000rpm at the temperature of freezing centrifuge-5 ℃ for removing bubbles to obtain the modified chitin casting solution. And (3) uniformly pouring the defoamed modified chitin membrane casting solution onto a glass plate of a coating experiment machine, uniformly pushing a scraper with the set height of 250 micrometers by using an automatic membrane scraping machine at a constant speed, uniformly distributing the membrane casting solution on a smooth plane to obtain a liquid membrane, and placing the liquid membrane in alcohol at 20 ℃ for standing and regenerating for 1h to obtain the modified chitin separation membrane. And finally, placing the modified chitin separation membrane in ultrapure water for storage.
Comparative example 1
The preparation process of the chitosan separation membrane of comparative example 1 is specifically as follows:
lithium hydroxide monohydrate (L iOH. H)2O), potassium hydroxide and urea in ultrapure water, wherein lithium hydroxide monohydrate (L iOH. H)2O), potassium hydroxide, urea and water in a mass ratio of 8: 7: 8: 77. After the chitosan is completely dissolved, adding a certain amount of chitosan powder to ensure that the mass concentration of the chitosan is 4%, and uniformly stirring. Then putting into a low-temperature freezing refrigerator for freezing at-80 ℃, taking out, stirring by using an electric stirrer, repeating for 3 times until the chitosan powder is uniformly dissolved, and then centrifuging for 12min at 11000rpm at the temperature of a freezing centrifuge-5 ℃ to remove bubbles to obtain the chitosan casting solution. And (3) uniformly pouring the defoamed chitosan casting solution onto a glass plate of a coating experiment machine, uniformly pushing a scraper with the set height of 250 micrometers by using an automatic film scraping machine at a constant speed, uniformly distributing the casting solution on a smooth plane to obtain a liquid film, and standing and regenerating the liquid film in alcohol at 20 ℃ for 1h to obtain the chitosan separation membrane. And finally, placing the chitosan separation membrane in ultrapure water for storage.
Comparative example 2
The preparation process of the chitosan separation membrane of comparative example 2 is specifically as follows:
lithium hydroxide monohydrate (L iOH. H)2O), potassium hydroxide and urea in ultrapure water, wherein lithium hydroxide monohydrate (L iOH. H)2O), potassium hydroxide, urea and water in a mass ratio of 8: 7: 8: 77. After the chitosan is completely dissolved, adding a certain amount of chitosan powder to ensure that the mass concentration of the chitosan is 4%, and uniformly stirring. Then putting into a low-temperature freezing refrigerator for freezing at-80 ℃, taking out, stirring by using an electric stirrer, repeating for 3 times until the chitosan powder is uniformly dissolved, and then centrifuging for 12min at 11000rpm at the temperature of a freezing centrifuge-5 ℃ to remove bubbles to obtain the chitosan casting solution. Uniformly pouring the defoamed chitosan casting solution on a glass plate of a coating experiment machine, uniformly pushing a scraper with the set height of 350 mu m by using an automatic film scraping machine at a constant speed to ensure that the casting solution is a liquid film uniformly distributed on a smooth plane, and standing and regenerating for 1h in alcohol at the temperature of 20 ℃ to obtain the chitosan separation membrane. And finally, placing the chitosan separation membrane in ultrapure water for storage.
Comparative example 3
The preparation process of the chitosan separation membrane of comparative example 3 is specifically as follows:
lithium hydroxide monohydrate (L iOH. H)2O), potassium hydroxide and urea in ultrapure water, wherein lithium hydroxide monohydrate (L iOH. H)2O), potassium hydroxide, urea and water in a mass ratio of 8: 7: 8: 77. After the chitosan is completely dissolved, adding a certain amount of chitosan powder to ensure that the mass concentration of the chitosan is 4%, and uniformly stirring. Then putting into a low-temperature freezing refrigerator for freezing at-80 ℃, taking out, stirring by using an electric stirrer, repeating for 3 times until the chitosan powder is uniformly dissolved, and then centrifuging for 12min at 11000rpm at the temperature of a freezing centrifuge-5 ℃ to remove bubbles to obtain the chitosan casting solution. And (3) uniformly pouring the defoamed chitosan casting solution onto a glass plate of a coating experiment machine, uniformly pushing a scraper with the set height of 350 mu m at a constant speed by using an automatic film scraping machine to ensure that the casting solution is a liquid film uniformly distributed on a smooth plane, and standing and regenerating for 1h in an alcohol/water mixture (the volume ratio is 1: 1) at the temperature of 20 ℃ to obtain the chitosan separation membrane. And finally, placing the chitosan separation membrane in ultrapure water for storage.
Comparative example 4
The preparation process of the chitosan separation membrane of comparative example 4 is specifically as follows:
lithium hydroxide monohydrate (L iOH. H)2O), potassium hydroxide and urea in ultrapure water, wherein lithium hydroxide monohydrate (L iOH. H)2O), potassium hydroxide, urea and water in a mass ratio of 8: 7: 8: 77. After the chitosan is completely dissolved, adding a certain amount of chitosan powder to ensure that the mass concentration of the chitosan is 4%, and uniformly stirring. Then putting into a low-temperature freezing refrigerator for freezing at-80 ℃, taking out, stirring by using an electric stirrer, repeating for 3 times until the chitosan powder is uniformly dissolved, and then centrifuging for 12min at 11000rpm at the temperature of a freezing centrifuge-5 ℃ to remove bubbles to obtain the chitosan casting solution. Uniformly pouring the defoamed chitosan casting solution on a glass plate of a coating experiment machine, and uniformly pushing a set height at a certain speed by using an automatic film scraping machineAnd (3) a scraper with the temperature of 350 mu m is used for enabling the casting solution to be a liquid film uniformly distributed on a smooth plane, and the liquid film is placed in pure water with the temperature of 20 ℃ for standing and regeneration for 1h to obtain the chitosan separation film. And finally, placing the chitosan separation membrane in ultrapure water for storage.
Comparative example 5
The preparation process of the chitosan separation membrane of comparative example 5 is specifically as follows:
lithium hydroxide monohydrate (L iOH. H)2O), potassium hydroxide and urea in ultrapure water, wherein lithium hydroxide monohydrate (L iOH. H)2O), potassium hydroxide, urea and water in a mass ratio of 8: 7: 8: 77. After the chitosan is completely dissolved, adding a certain amount of chitosan powder to ensure that the mass concentration of the chitosan is 4%, and uniformly stirring. Then putting into a low-temperature freezing refrigerator for freezing at-80 ℃, taking out, stirring by using an electric stirrer, repeating for 3 times until the chitosan powder is uniformly dissolved, and then centrifuging for 12min at 11000rpm at the temperature of a freezing centrifuge-5 ℃ to remove bubbles to obtain the chitosan casting solution. And (3) uniformly pouring the defoamed chitosan casting solution onto a glass plate of a coating experiment machine, uniformly pushing a scraper with the set height of 250 mu m at a constant speed by using an automatic film scraping machine to ensure that the casting solution is a liquid film uniformly distributed on a smooth plane, and standing and regenerating for 1h in alcohol at the temperature of-80 ℃ to obtain the chitosan separation membrane. And finally, placing the chitosan separation membrane in ultrapure water for storage.
The following are test sections:
test example 1: membrane Structure characterization
The separation membranes prepared in example 1 and comparative example 1 were cut into membranes of appropriate size, placed in a 50m L centrifuge tube containing 25m L t-butanol solution, replaced in a table-top constant temperature shaker (set at 30 ℃ C., rotational speed 100rpm) for 24 hours, taken out, put in liquid nitrogen for rapid freezing, then put in a freeze dryer for freeze-drying for 24 hours, cut or broken into appropriate size, and then Scanning Electron Microscope (SEM) was used to photograph structural images of membrane surface and cross-section.
The actual images of the membrane sheets after the above treatments in comparative example 1 and example 1 are shown in FIG. 3-a and FIG. 3-b, respectively, and the SEM images are shown in FIG. 3-c and FIG. 3-d, respectively. As can be seen from fig. 3-a and 3-b, the modified chitosan separation membrane containing Ag nanoparticles (i.e., example 1) had a darker color, dark gray, than the chitosan separation membrane containing no Ag nanoparticles (i.e., comparative example 1). As can be seen from FIGS. 3-c and 3-d, a small amount of nano-or micro-scale white particles are present on the surface of the modified chitosan separation membrane of example 1; as can be seen from the X-ray spectroscopy analysis of fig. 3-e, the main component of the particles is silver, so that the particles are presumed to be silver nanoparticles that are not uniformly dispersed and agglomerated. This result is a good demonstration of successful doping of silver nanoparticles in modified chitosan separation membranes (i.e., example 1).
Test example 2: contact antimicrobial experiments
(1) Cultivation of Escherichia coli
L B culture solution is prepared by placing 1L g ultrapure water, 10g tryptone, 5g yeast extract and 10g sodium chloride in a 1.2L blue-covered bottle, shaking to dissolve, placing in a high pressure steam sterilization pot, sterilizing at 121 deg.C for 20min, screwing the bottle cap after sterilization, sealing with Parafilm sealing film, storing in a low temperature storage box (4 deg.C), and using within 3 days to obtain L B culture solution.
L B solid culture medium is prepared by placing 1L g ultrapure water, 10g tryptone, 5g yeast extract, 10g sodium chloride and 20g agar powder in a 1.2L blue-covered bottle, shaking to dissolve, placing in an autoclave to sterilize at 121 ℃ for 20 minutes to obtain L B agar, placing the plastic culture medium to be used in an ultraclean bench, sterilizing for 30 minutes by using an ultraviolet lamp, screwing the blue-covered bottle into the ultraclean bench after the autoclave is finished, cooling to about 60 ℃, igniting an alcohol lamp to maximize the wind speed, taking the plastic culture medium, uniformly pouring L B agar in the plastic culture medium at one time near the alcohol lamp, wherein each culture medium contains about 15m L or about L B agar, after L B agar is completely solidified, sealing with a sealing film of Parafilm, inverting, storing in ice at 4 ℃, and using in 3 days to obtain L B solid culture medium.
And (2) recovering the strains, namely adding the Escherichia coli dry powder into 100m L L B culture solution, mixing L B liquid culture solution with the Escherichia coli strains and glycerol according to the volume ratio of 1: 3, putting the mixture into a 2m L centrifuge tube, and storing the mixture in a low-temperature refrigerator at (-20 ℃) for a long time to obtain the Escherichia coli stock solution.
And E.coli culture, namely putting 100m L L B culture solution into a conical flask, adding 100 mu L of E.coli stock solution, culturing in a shaking table (30 ℃, 100rpm), wherein the E.coli used in the experiment is bacteria in a logarithmic growth phase according to the experimental requirements of the E.coli, and according to a measured E.coli growth curve used in the experiment, the E.coli reaches the end of logarithmic growth after 12 hours, and after the E.coli grows in L B culture solution for 12 hours, putting L B culture solution containing the E.coli stock solution into a centrifuge tube, centrifuging for 10min under the condition of 10000rmp, separating the E.coli, pouring out the culture solution in the centrifuge tube, adding physiological saline with the mass concentration of 0.9%, storing in a low-temperature storage box (4 ℃) for later use within 24 hours, and obtaining the E.coli liquid.
(2) Contact inhibition test
In a super clean bench, a fan is turned on, an alcohol lamp is ignited, the escherichia coli liquid obtained in the escherichia coli culture step is diluted by 1000 times by using normal saline, after uniform mixing, escherichia coli diluent is obtained, 100 mu L escherichia coli diluent is taken by using a liquid transfer gun, 100 mu L escherichia coli diluent is uniformly coated on L B solid culture medium by using a coating rod in front of the alcohol lamp, the membranes prepared in example 1 and comparative example 1 are respectively cut into circular membranes with the diameter of 2.4cm, the cut membranes are flatly laid on L B solid culture medium which is fully coated with the escherichia coli diluent, 3 parallel samples are arranged on each membrane, and the growth condition of bacteria is observed after 24 hours of culture at room temperature.
The results of the experiment are shown in FIGS. 4-a and 4-b. It can be seen from the graph that the modified chitosan separation membrane containing silver nanoparticles in example 1 has a strong antibacterial ability compared to the chitosan separation membrane of comparative example 1. The chitosan separation membrane of comparative example 1 did not show a significant inhibition zone of E.coli under and around it, but densely distributed E.coli colonies, while the modified chitosan separation membrane containing silver nanoparticles formed a significant inhibition zone under and around it, and did not show a significant growth of E.coli colonies. Therefore, the modified chitosan separation membrane containing the silver nanoparticles has an obvious inhibition effect on growth and propagation of escherichia coli after being directly contacted with the escherichia coli, and can effectively inhibit formation of escherichia coli colonies.
Test example 3: immersion antimicrobial experiments
(1) Cultivation of Escherichia coli
The method was the same as in test example 2
(2) Immersion inhibition test
In a super clean bench, a fan is turned on, an alcohol lamp is ignited, the escherichia coli liquid obtained in the escherichia coli culture step is diluted by 10 times by using normal saline and then stored in a refrigerator at 4 ℃, the membranes prepared in the example 1 and the comparative example 1 are respectively cut into circular membranes with the diameter of 2.4cm, each membrane cut membrane is placed in a centrifugal tube with the diameter of 50m L, the escherichia coli liquid diluted by 10 times by 10m L is added, 3 parallel control samples are arranged on each membrane, the opening of the centrifugal tube is sealed by cotton, after the centrifugal tube is vibrated for 24 hours in a shaking table with the temperature of 30 ℃ and 100rmp, the escherichia coli liquid soaked with the membranes and a blank control sample are respectively diluted by 10410 times of5Multiple sum of 106And after doubling, taking 100 mu L diluted escherichia coli liquid, placing the escherichia coli liquid before an alcohol lamp on a L B solid culture medium with 100 mu L uniform escherichia coli liquid by using a coating rod, culturing for 24 hours at room temperature, selecting a culture medium with proper dilution times, counting the number of colonies, and calculating the bacterial concentration and the sterilization efficiency of the modified chitosan separation membrane containing the silver nanoparticles.
As shown in fig. 5, the survival rate of escherichia coli in the escherichia coli liquid diluted by 24h of the chitosan separation membrane of comparative example 1 was 95%, and the survival rate of escherichia coli in the escherichia coli liquid diluted by 24h of the modified chitosan separation membrane containing silver nanoparticles of example 1 was 64%. From experimental results, although the unmodified chitosan separation membrane from the comparative example 1 has a certain broad-spectrum antibacterial property on bacteria, under the experimental conditions, the killing rate of 24h of the unmodified chitosan separation membrane on escherichia coli is between 5% and 10%, and the requirement of complex biological environment in the actual water treatment process cannot be met; the modified chitosan separation membrane containing silver nanoparticles in the example 1 has an obvious inhibition effect on escherichia coli in an aqueous solution, and after the membrane is immersed in an escherichia coli diluent for 24 hours, the killing rate on the escherichia coli is about 40% -50%.
Test example 4: lysozyme degradation chitosan separation membrane and experiment of modified chitosan separation membrane containing silver nanoparticles
The separation membranes prepared in example 1 and comparative example 1 were cut into circular membranes of 2.4cm diameter, one for each 10 membranes, one (10) for each membrane was taken out, dried in an oven for 24h and weighed as the initial weight, then the remaining membranes were divided into five groups and placed in 5 centrifuge tubes of 50m L, respectively, 25m L1 mg/m L in water solution of lysozyme was added to each centrifuge tube, after degradation for 24h in a shaker at 30 ℃, 100rpm, the first group of samples of each membrane was taken out, dried in an oven for 24h and weighed, the remaining four groups of samples of each membrane were replaced with a new 25m L1 mg/m L in water solution of lysozyme, and degradation was continued in a shaker at 30 ℃, 100rpm for 24h, and the degradation of each membrane sample for 5 days (120h) was calculated in this way.
The experimental result is shown in fig. 6, in which the weight of the chitosan separation membrane of comparative example 1 and the modified chitosan separation membrane containing silver nanoparticles of example 1 was reduced by 14% and 4%, respectively, in an aqueous solution of lysozyme of 1mg/m L within 120h, it can be clearly seen that lysozyme has a significant degradation effect on the chitosan separation membrane of comparative example 1, while the modified chitosan separation membrane containing silver nanoparticles of example 1 has a significant inhibitory effect on the degradation of lysozyme, because there are many silver nanoparticles on the surface of the modified chitosan separation membrane containing silver nanoparticles, which have a significant inhibitory effect on the activity of lysozyme.
Test example 5: pure water flux determination
The separation membranes prepared in example 1, comparative example 2, comparative example 3, comparative example 4 and comparative example 5 were immersed in ultrapure water for 3 days, and the ultrapure water was replaced once a day, so that the solvent components in the casting solution and the coagulation bath solution remaining on the membranes in the preparation of the separation membranes were completely washed away without remaining. Three days later handleCutting the flaw-free membrane into proper size, placing into a membrane pool of a triple flat plate cross-flow filtering device, using ultrapure water as feed liquid, adjusting the pressure to 1bar and operating for 1h, measuring the volume (unit L) of the ultrapure water penetrating through the membrane in unit time after the pure water flux of the membrane is basically stable, and measuring the area (unit m) of the membrane to be measured2) Thus, pure water flux J, unit L/m, of the chitosan separation membranes of comparative examples 1 to 5 and the modified chitosan separation membrane containing silver nanoparticles of example 1 was calculated according to the following equation2H, pure water flux was measured 3 times per membrane, and the formula was J ═ V/(A × t)
Wherein J-pure water flux of the membrane (L/m)2·h)；
V-volume of ultrapure water per unit time that permeates the membrane (L);
a-area of diaphragm to be measured (m)2)；
t-time (h).
Then, 5-day degradation experiments were performed to evaluate the biodegradation performance of the separation membrane. In the 5-day degradation experiment, the separation membrane is soaked in an enzyme solution (the lysozyme solution is adopted in the invention) with degradation effect, and the biodegradation performance of the separation membrane is evaluated by accurately measuring the weight change of the separation membrane.
The method comprises the following specific conditions of soaking the prepared separation membrane for 3 days, cutting the separation membrane into disks with the diameter of 2.4cm and 60 disks, randomly dividing the 60 disks into 6 groups according to 10 disks, respectively placing the 6 groups of disks into 6 centrifuge tubes containing 20 mg/L lysozyme solution and 50m L lysozyme solution, placing the 6 centrifuge tubes into a constant temperature shaking table, oscillating at the temperature of 30 ℃ at the speed of 100rpm, randomly taking one centrifuge tube every 24 hours (namely 0h, 24h, 48h, 72h, 96h and 120h), taking out the separation membrane, repeatedly rinsing with deionized water, placing the centrifuge tube in an oven for drying, measuring the mass of the dried membrane with an isotope balance, replacing the lysozyme solution every 24 hours (keeping the concentration and the volume of the lysozyme solution unchanged) of the centrifuge tube which is not taken out of the constant temperature shaking table to maintain the biodegradation efficiency of the lysozyme solution on the separation membrane, and ensuring the reliability of the experiment results, wherein the degradation results of each separation membrane in 5 days are the average value of 3 times of independent repeated experiments, and the standard deviation of the experiment results is 3 times of repeated experiments.
The experimental results are shown in fig. 7, fig. 8, fig. 9 and fig. 10, respectively. As can be seen from fig. 7, the pure water fluxes of the separation membranes prepared in example 1 and comparative example 1 before the degradation were substantially the same, which indicates that the permeability of the chitosan separation membrane was not changed after the doping of the silver nanoparticles. After 5 days of degradation experiments, the pure water flux of the modified chitosan separation membrane containing silver nanoparticles prepared in example 1 is basically maintained, which shows that the modified chitosan separation membrane containing silver nanoparticles has good degradation resistance, while the pure water flux of the chitosan separation membrane in comparative example 1 is significantly increased, which shows that the structure of the chitosan separation membrane is damaged and the permeability of the membrane is changed.
As can be seen from FIG. 8, when the height of the spatula was increased from 250 μm to 350 μm, the pure water flux of the chitosan separation membrane was significantly increased from 4.4L MH to 6.4L MH, which indicates that the height of the spatula can change the structure of the chitosan separation membrane, and further affect the pure water flux of the chitosan separation membrane.
As can be seen from FIG. 9, the components of the coagulation bath have a significant influence on the pure water flux of the chitosan separation membrane, the pure water flux of the chitosan separation membrane is 6.4L MH when the coagulation bath is pure alcohol, the pure water flux of the chitosan separation membrane is 17.0L MH when the coagulation bath is an alcohol/water mixture (volume ratio 1: 1), and the pure water flux of the chitosan separation membrane is 27.8L MH. when the coagulation bath is pure water, which provides a basis for further optimizing the structures of the chitosan separation membrane and the modified chitosan containing the degradation-controlling substance.
As can be seen from FIG. 10, the coagulation bath temperature has a significant effect on the pure water flux of the chitosan separation membrane, when the coagulation bath temperature is 20 ℃, the pure water flux of the chitosan separation membrane is 4.4L MH, and when the coagulation bath temperature is-80 ℃, the pure water flux of the chitosan separation membrane is 16.7L MH., which provides a basis for further optimizing the structure of the chitosan separation membrane and the modified chitosan containing the sustained-release degradation controlling substance.
Test example 6: determination of the Retention Rate
The separation membranes prepared in example 1 and the corresponding separation membranes degraded for 5 days were cut to an appropriate size, placed in a membrane pool of a triple-plate cross-flow filtration apparatus, and the pressure was adjusted to 1bar and run for 1 hour using ultrapure water as a feed liquid, and after the pure water flux of the membranes was substantially stabilized, polystyrene microspheres with a concentration of 0.05 g/L and a particle size of 1 μm were used as a feed liquid, and the concentration of the polystyrene microspheres in the permeate was measured with an ultraviolet spectrophotometer to calculate the rejection rate of the membranes.
The calculation formula is as follows:
in the formula: r-retention rate of the membrane;
Cp-concentration of polystyrene microspheres in the feed solution (g/L);
Cf-concentration of polystyrene microspheres in permeate (g/L).
The experimental result is shown in fig. 11, and it can be seen from fig. 11 that the retention rates of the separation membranes prepared in example 1 and comparative example 1 before degradation are 96.0% and 97.4%, respectively, which are not very different, which indicates that the retention performance of the chitosan separation membrane is not significantly affected after doping silver nanoparticles. After 5 days of degradation experiments, the retention rate of the modified chitosan separation membrane containing silver nanoparticles prepared in example 1 is basically maintained, which shows that the modified chitosan separation membrane containing silver nanoparticles has good degradation resistance, while the retention rate of the chitosan separation membrane in comparative example 1 is reduced from 97.4% to 92.8%, which is obviously reduced, and meanwhile, as can be seen from fig. 6, the water flux of the separation membrane in comparative example 1 is obviously increased, which shows that the structure of the chitosan separation membrane in comparative example 1 is damaged, and the retention rate of the separation membrane is changed.
The experimental results all show that the separation membrane prepared in the embodiment 1 can overcome the problems of structural damage and separation performance reduction caused by easy degradation of a natural polymer membrane in the using process; the modified chitosan separation membrane containing silver nanoparticles obtained by the preparation method of the separation membrane of example 1 was significantly improved in degradation resistance and showed excellent separation performance.
It should be noted that, in the above test section, all the modified chitosan separation membranes containing silver nanoparticles prepared in example 1, and the modified natural polymer separation membranes containing other sustained-release degradation-resistant substances, such as thymol oil, ginger oil or clove essential oil, such as modified cellulose separation membrane, modified chitin separation membrane, etc., have the same effects, and are not described herein again.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A method for preparing a separation membrane, comprising the steps of:
dissolving degradable natural polymers to obtain a membrane casting solution, wherein the degradable natural polymers comprise one of chitosan, cellulose and chitin;
dispersing a slow-release anti-degradation substance in the membrane casting solution to obtain a modified membrane casting solution, wherein the slow-release anti-degradation substance comprises one of silver nanoparticles, copper nanoparticles, thymol oil, ginger oil and clove essential oil;
forming a film by using the modified film casting solution to obtain a liquid film; and
and carrying out phase inversion or phase separation on the liquid film to obtain the separation film.
2. The method for preparing a separation membrane according to claim 1, wherein the mass of the sustained-release anti-degradation substance is 0.1 to 5.0% of the mass of the degradable natural polymer; and/or the presence of a catalyst in the reaction mixture,
in the membrane casting solution, the mass concentration of the degradable natural macromolecules is 3-8%.
3. The method of producing a separation membrane according to claim 1, wherein the thickness of the liquid membrane is 200 μm to 500 μm.
4. The method of preparing a separation membrane according to claim 1, wherein the step of subjecting the liquid membrane to phase inversion or phase separation to obtain a separation membrane comprises: and placing the liquid membrane in a coagulating bath for standing and regenerating to obtain the separation membrane.
5. The method of manufacturing a separation membrane according to claim 4, wherein the coagulation bath includes at least one of water, ethanol, and dimethylacetamide; and/or the presence of a catalyst in the reaction mixture,
placing the liquid film in a coagulating bath for standing and regenerating, wherein the temperature of the coagulating bath is-80-30 ℃; and/or the presence of a catalyst in the reaction mixture,
and in the step of placing the liquid film in a coagulating bath for standing regeneration, the standing regeneration time is 1 min-24 h.
6. The method for preparing a separation membrane according to claim 1, wherein the step of dissolving the degradable natural polymer to obtain a membrane casting solution comprises: dissolving lithium hydroxide, potassium hydroxide and urea in water, adding the degradable natural polymer, freezing and thawing for multiple times, and performing centrifugal defoaming to obtain the membrane casting solution.
7. The method for preparing a separation membrane according to claim 6, wherein the freezing temperature is-80 ℃ to-20 ℃, and the time for each freezing is 30min to 24 h.
8. The method for preparing a separation membrane according to claim 1, wherein the liquid membrane is a flat membrane, and the step of forming the modified membrane casting solution into a membrane to obtain a liquid membrane comprises: casting the casting solution on a flat plate to form the liquid film; or, the liquid membrane is a hollow fiber membrane, and the step of forming the membrane from the modified membrane casting solution comprises the following steps: and spinning the casting solution through a hollow fiber membrane spinning machine to obtain the liquid membrane.
9. A separation membrane produced by the method for producing a separation membrane according to any one of claims 1 to 8.
10. Use of the separation membrane of claim 9 in water treatment, gas separation or medical dialysis.
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