CN110433662A - A kind of preparation method of membrane distillation super-amphiphobic PS membrane - Google Patents

Abstract

The invention discloses a simple and efficient method for preparing a super-amphiphobic polysulfone membrane, and relates to the field of membrane separation. In the present invention, a traditional solvent-induced phase inversion method is first used to prepare a polysulfone membrane with an interpenetrating network pore structure, and the interpenetrating network pores form a "recessed angle structure" on the surface of the membrane. Then, uniformly distributed silica nanoparticles are generated in situ on the walls of the interpenetrating network pores by a step-by-step sol-gel method to provide a certain nanoscale rough structure for the polysulfone membrane. Finally, a layer of low surface energy fluorosilane compound film is coated on the surface of the roughened polysulfone membrane to obtain a super-amphiphobic polysulfone membrane, which realizes double anti-wetting properties to water droplets and organic droplets, and the contact angle of water droplets can reach more than 150° , The contact angle of n-hexane can reach more than 65°. When the prepared super-amphiphobic polysulfone membrane is used in the membrane distillation process, it has a salt rejection rate of more than 99.5% and strong anti-wetting stability.

Description

A kind of preparation method of super amphiphobic polysulfone membrane for membrane distillation

technical field

The invention relates to a method for preparing a separation membrane used in a membrane distillation process, in particular to a method for preparing a super-amphiphobic membrane.

Background technique

At present, my country's water resources are relatively poor, and the per capita per mu is relatively small, especially in the northern coastal areas and islands. The problem of water resource shortage is becoming increasingly prominent. In order to alleviate the crisis of water resources, my country actively develops and utilizes unconventional water resources such as seawater while vigorously saving water. As a stable water resource increment technology, seawater desalination has gradually become an important supplement and strategic reserve of water resources. Actively developing the seawater desalination industry is of great significance to alleviate the shortage of water resources in my country's coastal water-scarce areas and islands, rationally optimize the water use structure, and promote the sustainable use of water resources.

Reverse osmosis is currently a membrane desalination technology widely used in seawater desalination. However, reverse osmosis is not an ideal choice for treating high-salinity wastewater. It faces great challenges in treating high-salt water because of the operating pressure required to overcome the osmotic pressure of high-salt water. Far beyond the limit of the reverse osmosis membrane, and the salinity of the wastewater is far beyond the limit of the reverse osmosis operation. Membrane distillation has been developed as the most promising alternative to reverse osmosis due to its unique advantages, including resistance to high-concentration brine and low operating pressure. Membrane distillation is a process in which heated seawater is evaporated through a porous membrane, and the evaporated steam is condensed on the other side of the membrane. The hydrophobic membrane acts as an interface between the liquid and the steam. The pore size of the membrane used for distillation is much larger than that of water molecules and salt ions, up to several microns, which can separate water molecules and salt ions from each other under the drive of temperature difference.

In recent years, the research on membrane distillation technology has become more and more extensive. At first, an important problem faced by the membrane distillation process is that there is no membrane specially prepared for membrane distillation. The structure and material properties of the commonly used membranes are difficult to meet the needs of the distillation process. . Later, considering the key issue of membrane wettability, the hydrophobicity of the membrane used in the distillation process was considered to be of great significance. Therefore, many scholars began to consider applying hydrophobic surfaces or even superhydrophobic surfaces to membrane distillation. There are many plants and animals in nature with superhydrophobic properties and self-cleaning functions on their surfaces. Inspired by it, many scholars have proposed different methods to construct super-hydrophobic surfaces, and summarized the necessary conditions for the preparation of super-hydrophobic surfaces. When preparing superhydrophobic surfaces, constructing rough surfaces and using low surface energy substances for modification are two indispensable conditions. The methods commonly used to prepare superhydrophobic membranes include electrospinning, coating, phase inversion and plasma technology. With the expansion of the application field of membrane distillation, the separated components are no longer a simple brine solution, and often contain some organic solvents. Therefore, although superhydrophobic membranes have excellent hydrophobic properties, most superhydrophobic surfaces are easily wetted by organic liquids. Including oils, alkanes and alcohols etc. When superhydrophobic surfaces are exposed to the environment of organic pollutants, their wetting resistance may be compromised, which eventually leads to the loss of self-cleaning ability and severe fouling. Therefore, the development of a membrane (superamphiphobic membrane) that has anti-wetting properties against both water droplets and low surface tension organic droplets has become the research direction of many researchers. It is difficult to achieve superamphiphobicity only by constructing a general rough structure and modifying it with low surface energy substances, and the construction of the reentrant structure plays an important role in it. However, the concave angle structure is a special structure with a wide top and a narrow bottom, which is difficult to obtain. The template method and laser etching reported in the literature can construct the concave angle structure, but it is not suitable for the surface of the polymer separation membrane. The Chinese invention patent with the application number 201710958054.2 discloses a method of preparing a superhydrophobic and oleophobic composite membrane by electrospinning the membrane and secondly spraying and modifying the surface of the membrane. However, the preparation process includes the preparation of nano-silica sol solution, the preparation of cellulose acetate solution, the preparation of electrospinning precursor solution, the hydrophobic modification of nano-silica sol solution, modification and modification. Spraying solution after curing, electrospinning method to prepare composite film, and surface modification two-step spraying method. The process of this method is too complicated, the steps are too cumbersome, and it takes a long time. Moreover, the electrospinning method is not a conventional method for preparing separation membranes, and is not suitable for large-scale preparation of separation membranes.

Contents of the invention

The object of the present invention is to provide a method for preparing a super-amphiphobic membrane with a simple preparation process and short time-consuming to solve the above-mentioned problems. This method adopts the phase inversion method to prepare the polymer membrane, constructs the concave angle structure through the special membrane pore structure formed in the phase inversion process, and further improves the surface roughness of the membrane matrix through the construction of nanoparticles and uses low surface energy substances for modification. Finally, a superamphiphobic membrane with anti-wetting properties to both water and organic liquids was obtained.

To achieve the above object, the technical solution adopted in the present invention is:

A preparation method of super amphiphobic polysulfone membrane for membrane distillation:

(1) Preparation of polysulfone membrane with interpenetrating network pore structure: add polysulfone particles, porogen and organic solvent into a round bottom flask according to a certain mass fraction, and stir through an oil bath stirring heater at a certain temperature and rotation speed , until a homogeneous solution is formed, and then stand at constant temperature for defoaming. After defoaming, cast the casting solution on a glass plate, spread the casting solution with a scraper to form a primary film, put the primary film into the coagulation bath quickly and steadily, and induce polysulfone gel to solidify through the exchange of solvent and non-solvent film forming.

(2) Construction of the nano-scale rough structure on the surface of the film: a certain volume fraction of tetraethyl silicate and absolute ethanol are stirred into a uniform mixed solution, which is recorded as liquid A; The water and ethanol were stirred into a uniform mixed solution, which was recorded as liquid B. The polysulfone-based membrane obtained in step (1) is immersed in liquid A and liquid B for a certain period of time in sequence, and uniform silica nanoparticles are grown in situ on the pore wall of the polysulfone membrane through hydrolysis and condensation reaction.

(3) Low surface energy modification of the membrane surface: soak the polysulfone matrix membrane with nanoscale rough structure obtained in step (2) in a mixed solution of low surface energy small molecules/absolute ethanol to make the low surface energy small Molecules are evenly coated on the surface of polysulfone membrane, and then put into an oven with a certain temperature for a period of time, so that the hydrolysis and condensation reaction occurs between small molecules with low surface energy and between small molecules with low surface energy and silicon dioxide , forming a cross-linked low surface energy thin layer on the surface of the membrane. The preparation of the super-amphiphobic polysulfone membrane can be realized through the above steps.

Preferably, in the above step 1, the mass fraction of the polysulfone particles used is 8-20, the mass fraction of the porogen is 2-7, and the mass fraction of the organic solvent is 73-90, and the organic solvent used is preferably One of N-methylpyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, 1,4-dioxane, chloroform, dichloromethane or a mixture of any two , the porogen used is one or more of polyethylene glycol, polyoxyethylene and polyvinylpyrrolidone, the weight average molecular weight of polyethylene glycol used is preferably 3000kD～8000kD, and the weight average molecular weight of polyoxyethylene used is preferably The weight average molecular weight of the polyvinylpyrrolidone used is preferably ^{5×10 4 kD} to 1.3× ^{10 6 kD} .

Preferably, in the above step 1, the heating temperature is 45°C-85°C, the heating time is 4-20h, the stirring speed is 200-450rpm, the glass plate includes a smooth glass plate and a rough glass plate, and the The coagulation bath is a double coagulation bath, the first coagulation bath is a mixed solution of water and an organic solvent, the second coagulation bath is deionized water, and the organic solvent and water volume ratio in the first coagulation bath is 0:10～9 : 1, the organic solvent in the first coagulation bath is preferably N-methylpyrrolidone, dimethylsulfoxide, dimethylacetamide, dimethylformamide, 1,4-dioxane, ethanol, One of n-propanol, isopropanol and n-butanol or a mixture of any two, the immersion time in the first coagulation bath is 5-50s.

Preferably, in the above step (1), the size of the interpenetrating network pore structure is 0.05 μm˜8 μm.

Preferably, in the above step (2), the volume fraction of ethyl orthosilicate in the liquid A is 10-50%, and the soaking time in the liquid A is 1.5-8h; the volume fraction of ammonia water in the liquid B is 15-45% , soaking time in liquid B is 20-100min, and the size of the silicon dioxide is preferably 20nm-600nm. .

Preferably, in the above step (3), the low surface energy small molecule is heptadecafluorodecyltrimethoxysilane (FAS), heptadecafluorodecyltriethoxysilane (FOTS), perfluorooctyl One of trichlorosilane (PFTS), perfluorodecyltrichlorosilane, and stearic acid, in the mixed solution of low surface energy small molecules/absolute ethanol, the volume fraction of low surface energy small molecules in the mixed solution 1 to 14%, placed in the oven for 0.5 to 8 hours, and the temperature of the oven is 35°C to 85°C.

Application of the super-amphiphobic polysulfone membrane in membrane distillation technology.

Advantage and beneficial effect that the present invention has:

(1) The present invention uses the interpenetrating network pore structure that is easy to obtain in the classic non-solvent-induced phase inversion process to construct a reentrant angle structure, and adopts the in-situ growth of silica particles to ensure the stability of silica nanoparticles in the membrane matrix Existence, low surface energy small molecules undergo polycondensation reaction with silanol on the surface of the membrane after hydrolysis to form a stable low surface energy thin layer. The preparation process is simple and easy to operate, does not require expensive equipment, and can complete large-scale membrane preparation in a short time.

(2) The film matrix material used in the present invention is polysulfone, which has excellent mechanical properties, high strength, high rigidity, and can maintain excellent mechanical properties at high temperatures, and has excellent oxidation resistance, hydrolysis resistance, and thermal stability In addition, polysulfone materials also have excellent mechanical properties, electrical properties, and food hygiene, and are one of the most widely used membrane materials.

(3) The super-amphiphobic polysulfone membrane prepared by the present invention has double anti-wetting properties to water droplets and organic droplets, especially to n-hexane with a very low surface tension. The feed liquid containing organic liquid droplets has stable anti-wetting properties.

Description of drawings

FIG. 1 is a scanning electron micrograph of the polysulfone membrane prepared in Comparative Example 1.

FIG. 2 is a diagram of the contact angle of the polysulfone membrane prepared in Comparative Example 1. FIG.

3 is a scanning electron micrograph of the polysulfone membrane prepared in Comparative Example 2.

FIG. 4 is a diagram of the contact angle of the polysulfone membrane prepared in Comparative Example 2.

FIG. 5 is a scanning electron micrograph of the polysulfone membrane prepared in Comparative Example 3.

6 is a diagram of the contact angle of the polysulfone membrane prepared in Comparative Example 3.

FIG. 7 is a scanning electron micrograph of roughened and modified by fluorination in Example 3. FIG.

FIG. 8 is a diagram of the contact angle measurement results of the super-amphiphobic polysulfone membrane in Example 3. FIG.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and through specific embodiments. It should be understood that the following examples are used to illustrate the present invention rather than limit its protection scope.

Comparative example 1:

Add 16 parts by mass of polysulfone particles, 4 parts by mass of polyvinylpyrrolidone (weight-average molecular weight: 1.3×10 ⁶ kD) and 80 parts by mass of dimethylformamide into a round-bottomed flask, heat at 80°C and dissolve at 400 rpm 10h until a homogeneous solution is formed, and then stand at constant temperature for defoaming. After defoaming, cast the casting solution on a rough glass plate, spread the casting solution with a scraper to form a primary film, and quickly and stably put the primary film into dimethylformamide/water (volume ratio 4:6) to mix After 15s in the solution, it was transferred into deionized water, and the polysulfone gel was induced to solidify and form a film through the sufficient exchange of solvent and non-solvent. It can be seen from Figure 1 that a polysulfone membrane with an interpenetrating network concave angle structure has been successfully constructed. The size of the interpenetrating network pores is about 5 μm. Used in membrane distillation process.

Comparative example 2:

Add 16 parts by mass of polysulfone particles, 4 parts by mass of polyvinylpyrrolidone (weight-average molecular weight: 1.3×10 ⁶ kD) and 80 parts by mass of dimethylformamide into a round-bottomed flask, heat at 80°C and dissolve at 400 rpm 10h until a homogeneous solution is formed, and then stand at constant temperature for defoaming. After defoaming, cast the casting solution on a rough glass plate, spread the casting solution with a scraper to form a primary film, and quickly and stably put the primary film into dimethylformamide/water (volume ratio 4:6) After 15s in the mixed solution, it was transferred into deionized water, and the polysulfone gel was induced to solidify to form a film through sufficient exchange of solvent and non-solvent, and an interpenetrating network of pores with a pore size of about 5 μm could be obtained.

Ethyl orthosilicate and absolute ethanol were stirred into a uniform mixed solution (volume fraction of ethyl orthosilicate was 30%), which was recorded as liquid A; ammonia water and absolute ethanol were stirred into a uniform mixed solution ( Ammonia water volume fraction is 20%), is recorded as B liquid. Soak the obtained polysulfone-based membrane in A solution for 4 hours and in B solution for 50 minutes respectively, and in situ grow uniform carbon dioxide particles with a particle size of about 200 nm on the pore wall of the polysulfone membrane through hydrolysis and condensation reaction. Silicon particles (Figure 2). A polysulfone membrane with surface nanoscale rough structure modification was obtained. The water droplet contact angle of the membrane is 0°, which is super-hydrophilic and super-lipophilic, and cannot be used in the membrane distillation process.

Comparative example 3:

Add 16 parts by mass of polysulfone particles and 84 parts by mass of dimethylformamide into a round-bottomed flask, heat at 80°C and dissolve at 400 rpm for 10 hours until a homogeneous solution is formed, and then stand at constant temperature for defoaming. After defoaming, the casting solution is cast on a rough glass plate to form a primary film, and the primary film is quickly and steadily placed in deionized water, and the polysulfone gel is induced to solidify and form a film through the full exchange of solvent and non-solvent. An asymmetric structure polysulfone-based membrane with a dense skin layer and a finger-like pore support layer can be obtained.

Ethyl orthosilicate and absolute ethanol were stirred into a uniform mixed solution (volume fraction of ethyl orthosilicate 30%), which was recorded as liquid A; ammonia water and absolute ethanol were stirred into a uniform mixed solution (ammonia water volume fraction 20%), denoted as B liquid. Soak the obtained polysulfone-based membrane in A solution for 2 hours and in B solution for 25 minutes in order, and grow uniform carbon dioxide particles with a particle size of about 100 nm on the pore wall of the polysulfone membrane through hydrolysis and condensation reaction. silicon particles. A polysulfone membrane whose surface is completely covered by nano-silica particles is obtained.

The film is soaked in a mixed solution of heptadecafluorodecyltriethoxysilane/absolute ethanol, and the volume fraction of heptadecafluorodecyltriethoxysilane in the mixed solution is 2%, so that small molecules with low surface energy Evenly coated on the surface of the polysulfone membrane, and then placed in an oven at 85°C for 0.5h to allow hydrolysis and condensation reactions to form a cross-linked low surface energy thin layer on the surface of the membrane. The polysulfone membrane obtained through the above steps has a water droplet contact angle of 128°, a hexanediol contact angle of 52°, a hexadecane contact angle of 0°, and a n-hexane contact angle of 0°. When applied to the membrane distillation process, the salt interception rate can reach 99.30%, the water vapor flux is 10L/m ² h, and the surface of the membrane begins to wet after 0.5h of stable operation.

Example 1:

Add 8 parts by mass of polysulfone particles, 2 parts by mass of polyoxyethylene (weight-average molecular weight: 1.0×10 ⁵ kD) and 90 parts by mass of dimethyl sulfoxide into a round-bottomed flask, heat at 55°C and dissolve at 200 rpm 4h until a homogeneous solution is formed, and then stand at constant temperature for defoaming. After degassing, cast the casting solution on a rough glass plate, spread the casting solution with a scraper to form a primary film, and quickly and stably put the primary film into the mixture of isopropanol/water (volume ratio 9:1) After 40s, it was moved into deionized water, and the polysulfone gel was induced to solidify into a film through sufficient exchange of solvent and non-solvent, and an interpenetrating network of pores with a pore size of about 8 μm could be obtained.

Ethyl orthosilicate and absolute ethanol were stirred into a uniform mixed solution (volume fraction of ethyl orthosilicate was 50%), which was recorded as liquid A; ammonia water and absolute ethanol were stirred into a uniform mixed solution ( Ammonia water volume fraction 45%), denoted as B liquid. The obtained polysulfone-based membrane was soaked in solution A for 1.5 h and in solution B for 100 min respectively in sequence, and uniform bismuth particles with a particle size of about 600 nm were grown in situ on the pore wall of the polysulfone membrane through hydrolysis and condensation reaction. Silicon oxide nanoparticles. A polysulfone membrane with surface nanoscale rough structure modification was obtained.

Soak the membrane in a mixed solution of heptadecafluorodecyltriethoxysilane/absolute ethanol, and the volume fraction of heptadecafluorodecyltriethoxysilane in the mixed solution is 1%, so that small molecules with low surface energy Evenly coated on the surface of the polysulfone membrane, and then put it in an oven at 85°C for 0.5h, hydrolysis and polycondensation can occur between small molecules with low surface energy, and small molecules with low surface energy may also be hydrolyzed and followed by silicon dioxide. The silanol polycondensation reaction forms a cross-linked low surface energy thin layer on the surface of the film. Through the above steps, a quasi-superamphiphobic polysulfone membrane is obtained. The contact angle of water droplet is 145°, the contact angle of hexanediol is 132°, the contact angle of hexadecane is 95°, and the contact angle of n-hexane is 40°. The efficiency can reach 99.50%, the water vapor flux is 50L/m ² h, and the surface of the membrane begins to wet after 2 hours of stable operation.

Example 2:

Add 10 parts by mass of polysulfone particles, 7 parts by mass of polyethylene glycol (weight-average molecular weight of 8000kD) and 83 parts by mass of dichloromethane/dimethylacetamide mixture (ratio of mass parts to numbers 60:40) into the circle In a bottom flask, dissolve at a heating temperature of 45°C and a rotating speed of 250rpm for 6h until a homogeneous solution is formed, and then stand at constant temperature for defoaming. After defoaming, cast the casting solution on a smooth glass plate, spread the casting solution with a scraper to form a primary film, and quickly and stably put the primary film into the mixture of n-propanol/water (volume ratio 7:3) After 50s, it was moved into deionized water, and the polysulfone gel was induced to solidify into a film through sufficient exchange of solvent and non-solvent, and an interpenetrating network of pores with a pore size of about 2 μm could be obtained.

Ethyl orthosilicate and absolute ethanol were stirred into a uniform mixed solution (volume fraction of ethyl orthosilicate was 30%), which was recorded as liquid A; ammonia water and absolute ethanol were stirred into a uniform mixed solution ( Ammonia water volume fraction is 20%), is recorded as B liquid. Soak the obtained polysulfone-based membrane in A solution for 6 hours and in B solution for 80 minutes respectively, and in situ grow uniform carbon dioxide particles with a particle size of about 150 nm on the pore wall of the polysulfone membrane through hydrolysis and condensation reaction. Silicon nanoparticles. A polysulfone membrane with surface nanoscale rough structure modification was obtained.

This film is soaked in the mixed solution of stearic acid/dehydrated alcohol, and the volume fraction of stearic acid in the mixed solution is 8%, so that the low surface energy small molecules are evenly coated on the surface of the polysulfone film, and then its Put it in an oven at 50°C for 6 hours to cause hydrolysis and condensation reaction to form a cross-linked low surface energy thin layer on the surface of the film. Through the above steps, a super amphiphobic polysulfone membrane is obtained. The contact angle of water droplet is 155°, the contact angle of hexanediol is 152°, the contact angle of hexadecane is 125°, and the contact angle of n-hexane is 75°. It can reach 99.87%, the water vapor flux is 25L/m ² h, and the surface of the membrane begins to wet after 3.5 hours of stable operation.

Example 3:

Add 16 parts by mass of polysulfone particles, 4 parts by mass of polyvinylpyrrolidone (weight-average molecular weight: 1.3× ¹⁰⁶ kD) and 80 parts by mass of dimethylformamide into a round-bottomed flask, heat at 80°C and dissolve at 200 rpm 10h until a homogeneous solution is formed, and then stand at constant temperature for defoaming. After defoaming, cast the casting solution on a rough glass plate, spread the casting solution with a scraper to form a primary film, and quickly and stably put the primary film into dimethylformamide/water (volume ratio 4:6) to mix After 15 seconds in the solution, move it into deionized water, and through the sufficient exchange of solvent and non-solvent, polysulfone gel is induced to solidify and form a film, and an interpenetrating network of pores with a pore size of about 5 μm can be obtained.

Ethyl orthosilicate and absolute ethanol were stirred into a uniform mixed solution (volume fraction of ethyl orthosilicate was 30%), which was recorded as liquid A; ammonia water and absolute ethanol were stirred into a uniform mixed solution ( The volume of ammonia water is fractionally 20%), which is referred to as liquid B. Soak the obtained polysulfone-based membrane in A solution for 4 hours and in B solution for 50 minutes respectively, and in situ grow uniform carbon dioxide particles with a particle size of about 200 nm on the pore wall of the polysulfone membrane through hydrolysis and condensation reaction. Silicon nanoparticles. A polysulfone membrane with surface nanoscale rough structure modification was obtained.

The film is soaked in the mixed solution of heptadecafluorodecyltrimethoxysilane/absolute ethanol, and the volume fraction of heptadecafluorodecyltrimethoxysilane in the mixed solution is 10%, so that the small molecules with low surface energy It is coated on the surface of polysulfone membrane, and then placed in an oven at 70°C for 30 minutes to cause hydrolysis and condensation reaction to form a cross-linked low surface energy thin layer on the surface of the membrane. The super-amphiphobic polysulfone membrane was obtained through the above steps. It can be seen from Figure 5 that a layer of fluorosilane was attached to the surface of the membrane. Its water droplet contact angle is 154°, hexanediol contact angle is 150°, hexadecane contact angle is 121°, n-hexane contact angle is 67°, the salt interception rate can reach 99.95% when it is applied in the membrane distillation process, and the water vapor flux is 20.5L /m ² h, the surface of the membrane began to wet after 4 hours of stable operation.

Example 4:

Add 20 parts by mass of polysulfone particles, 7 parts by mass of polyvinylpyrrolidone (weight-average molecular weight of ⁵ ×104 kD) and 73 parts by mass of dimethylacetamide into a round-bottomed flask, heat at 85°C and dissolve at 450rpm 20h until a homogeneous solution is formed, and then stand at constant temperature for defoaming. After degassing, cast the casting solution on a rough glass plate, spread the casting solution with a scraper to form a primary film, and quickly and stably put the primary film into the mixture of n-butanol/water (volume ratio 2:8) After 15s, it was moved into deionized water, and the polysulfone gel was induced to solidify into a film through sufficient exchange of solvent and non-solvent, and an interpenetrating network of pores with a pore size of about 0.5 μm could be obtained. .

Ethyl orthosilicate and absolute ethanol were stirred into a uniform mixed solution (volume fraction of ethyl orthosilicate was 10%), which was recorded as liquid A; ammonia water and absolute ethanol were stirred into a uniform mixed solution ( Ammonia water volume fraction is 15%), is recorded as B liquid. Soak the obtained polysulfone-based membrane in A solution for 2 hours and in B solution for 30 minutes respectively, and in situ grow uniform carbon dioxide particles with a particle size of about 60 nm on the pore wall of the polysulfone membrane through hydrolysis and condensation reaction. Silicon nanoparticles. A polysulfone membrane with surface nanoscale rough structure modification was obtained.

Soak the film in a mixed solution of perfluorooctyltrichlorosilane/absolute ethanol, the volume fraction of perfluorooctyltrichlorosilane in the mixed solution is 14%, so that small molecules with low surface energy are evenly coated on poly The surface of the sulfone membrane was then placed in an oven at 35°C for 8 hours to allow hydrolysis and condensation reactions to form a cross-linked low surface energy thin layer on the surface of the membrane. Through the above steps, the super amphiphobic polysulfone membrane is obtained. The contact angle of water droplet is 160°, the contact angle of hexanediol is 149°, the contact angle of hexadecane is 80°, and the contact angle of n-hexane is 10°. It can reach 99.99%, the water vapor flux is 5L/m ² h, and the surface of the membrane begins to wet after 1 hour of stable operation.

Example 5:

Add 18 parts by mass of polysulfone particles, 6 parts by mass of polyoxyethylene (weight-average molecular weight: 1.5×10 ⁴ kD) and 86 parts by mass of dimethylformamide into a round-bottomed flask, heat at 60°C and dissolve at 300 rpm 12h until a homogeneous solution is formed, and then stand at constant temperature for defoaming. After degassing, cast the casting solution on a rough glass plate, spread the casting solution with a scraper to form a primary film, and put the primary film into dimethylformamide/isopropanol/water (volume fraction ratio 6 :2:2) After 30s in the mixed solution, move it into deionized water, and through the sufficient exchange of solvent and non-solvent, polysulfone gel is induced to solidify and form a film, and an interpenetrating network of pores with a pore size of about 4 μm can be obtained.

Ethyl orthosilicate and absolute ethanol were stirred into a uniform mixed solution (volume fraction of ethyl orthosilicate was 40%), which was recorded as liquid A; ammonia water and absolute ethanol were stirred into a uniform mixed solution ( Ammonia water volume fraction is 30%), is recorded as B liquid. Soak the obtained polysulfone-based membranes in A solution for 5 hours and in B solution for 60 minutes in sequence, and in situ grow uniform carbon dioxide particles with a particle size of about 300 nm on the pore wall of the polysulfone membrane through hydrolysis and condensation reaction. Silicon nanoparticles. A polysulfone membrane with surface nanoscale rough structure modification was obtained.

Soak the membrane in a mixed solution of perfluorodecyltrichlorosilane/absolute ethanol. The volume fraction of perfluorodecyltrichlorosilane in the mixed solution is 14%, so that small molecules with low surface energy can be evenly coated on poly The surface of the sulfone membrane is then placed in an oven at 60°C for 5 hours to allow hydrolysis and condensation reactions to form a cross-linked low surface energy thin layer on the surface of the membrane. Through the above steps, a super amphiphobic polysulfone membrane is obtained. The contact angle of water droplet is 160°, the contact angle of hexanediol is 156°, the contact angle of hexadecane is 130°, and the contact angle of n-hexane is 90°. It can reach 99.91%, the water vapor flux is 25L/m ² h, and the surface of the membrane begins to wet after 4 hours of stable operation.

Embodiment 6:

Add 14 parts by mass of polysulfone particles, 6 parts by mass of polyethylene glycol (weight-average molecular weight: 3000kD) and 90 parts by mass of N-methylpyrrolidone into a round-bottomed flask, heat at 70°C and dissolve at 300rpm for 10h until the Homogeneous solution, then stand at constant temperature for defoaming. After degassing, cast the casting solution on a rough glass plate, spread the casting solution with a scraper to form a primary film, put the primary film into deionized water quickly and steadily, and induce polysulfone to coagulate through the full exchange of solvent and non-solvent. The glue is cured to form a film, and the interpenetrating network pores with a pore size of about 0.05 μm can be obtained.

Ethyl orthosilicate and absolute ethanol were stirred into a uniform mixed solution (volume fraction of ethyl orthosilicate was 30%), which was recorded as liquid A; ammonia water and absolute ethanol were stirred into a uniform mixed solution ( Ammonia water volume fraction is 40%), is recorded as B liquid. Soak the obtained polysulfone-based membrane in A liquid for 1.5 h and in B liquid for 20 min in sequence, and in situ grow uniform bismuth particles with a particle size of about 20 nm on the pore wall of the polysulfone membrane through hydrolysis and condensation reaction. Silicon oxide nanoparticles. A polysulfone membrane with surface nanoscale rough structure modification was obtained.

Soak the membrane in a mixed solution of perfluorodecyltrichlorosilane/absolute ethanol. The volume fraction of perfluorodecyltrichlorosilane in the mixed solution is 12%, so that small molecules with low surface energy can be evenly coated on poly The surface of the sulfone membrane was then placed in an oven at 55°C for 6 hours to cause hydrolysis and condensation reactions to form a cross-linked low surface energy thin layer on the surface of the membrane. Through the above steps, a quasi-superamphiphobic polysulfone membrane is obtained. The contact angle of water droplet is 140°, the contact angle of hexanediol is 130°, the contact angle of hexadecane is 80°, and the contact angle of n-hexane is 10°. The efficiency can reach 99.98%, the water vapor flux is 2L/m ² h, and the surface of the membrane begins to wet after 1.5 hours of stable operation.

Claims (7)

1. a kind of membrane distillation preparation method of super-amphiphobic PS membrane, which is characterized in that comprising the following three steps: preparation has The PS membrane of interpenetrating networks pore structure；The building of film surface nanoscale rough structure；Film surface low-surface-energy is modified, specifically:

(1) preparation has the PS membrane of interpenetrating networks pore structure: by the polysulfones particle of certain mass number, pore-foaming agent and organic Solvent is added in round-bottomed flask, is stirred under certain temperature and revolving speed by oil bath agitating and heating device, until homogeneous phase solution is formed, Then constant temperature standing and defoaming, after deaeration, casting solution casting forms primary membrane on a glass, and primary membrane is smoothly put into rapidly In coagulating bath, by the exchange of solvent and non-solvent, polysulfones gel solidification film forming is induced；

(2) building of film surface nanoscale rough structure: the ethyl orthosilicate of certain volume number and dehydrated alcohol is agitated At uniform mixed solution, it is denoted as A liquid；It is again that the ammonium hydroxide of certain volume number is agitated molten at uniformly mixing with dehydrated alcohol Liquid is denoted as B liquid, polysulfones basement membrane obtained in step (1) is successively impregnated the regular hour in A liquid and B liquid, through hydrolytic condensation Reaction growth in situ on PS membrane fenestra wall goes out uniform nano SiO 2 particle；

(3) film surface low-surface-energy is modified: the polysulfones basement membrane obtained in step (1) with nanoscale rough structure is immersed in In low-surface-energy small molecule/dehydrated alcohol mixed solution, low-surface-energy small molecule is made to be uniformly coated on the surface of PS membrane, A period of time in the baking oven with certain temperature is put it into later, brings it about hydrolysis-condensation reaction, forms one in film surface The low-surface-energy thin layer of layer crosslinking.

2. the membrane distillation according to claim 1 preparation method of super-amphiphobic PS membrane, which is characterized in that in step (1) The mass fraction of the polysulfones particle is 8~20, and the mass fraction of pore-foaming agent is 2~7, and the mass fraction of organic solvent is 73 ~90, the organic solvent is N-Methyl pyrrolidone, dimethyl sulfoxide, dimethyl acetamide, dimethylformamide, Isosorbide-5-Nitrae- One of dioxane, chloroform, methylene chloride or any two kinds of mixed liquor, the pore-foaming agent are polyethylene glycol, gather One of ethylene oxide and polyvinylpyrrolidone are a variety of, the weight average molecular weight of polyethylene glycol used be 3000kD~ 8000kD, the polyoxyethylated weight average molecular weight are 1.5 × 10⁴KD~1 × 10⁵KD, the polyvinylpyrrolidone Weight average molecular weight is 5 × 10⁴KD~1.3 × 10⁶kD。

3. the membrane distillation according to claim 1 preparation method of super-amphiphobic PS membrane, which is characterized in that in step (1) The heating temperature is 45 DEG C~85 DEG C, and heating time is 4~20h, and mixing speed is 200~450rpm, the glass Plate is smooth glass plate or abrasive glass plate, and the coagulating bath is dual-bath coagulation, and the first coagulating bath is water and organic solvent Mixed liquor, the second gelation are deionized water, and organic solvent and water volume ratio are 0:10~9:1 in first coagulating bath, The organic solvent is N-Methyl pyrrolidone, dimethyl sulfoxide, dimethyl acetamide, dimethylformamide, Isosorbide-5-Nitrae-dioxy One of six rings, ethyl alcohol, normal propyl alcohol, isopropanol, n-butanol or any two kinds of mixed liquors, when immersion in the first coagulating bath Between be 5~50s.

4. the membrane distillation according to claim 1 preparation method of super-amphiphobic PS membrane, which is characterized in that in step (1) The size of the interpenetrating networks pore structure is 0.05 μm~8 μm.

5. the building of step 2) film surface silica nanometer coarse structure according to claim 1, which is characterized in that institute Ethyl orthosilicate volume fraction is 10~50% in the A liquid stated, and soaking time is 1.5~8h in A liquid；Ammonium hydroxide volume in B liquid Score is 15~45%, and soaking time is 20~100min in B liquid.

6. the building of step 2) film surface silica nanometer coarse structure according to claim 1, which is characterized in that institute The size for the silica stated is 200nm~600nm.

7. step 3) film surface low-surface-energy according to claim 1 is modified, the low-surface-energy small molecule is 17 Fluorine ruthenium trimethoxysilane, heptadecafluorodecyl triethoxysilane, cross fluorine octyltrichlorosilane, perfluoro decyl trichlorosilane, One of stearic acid, in low-surface-energy small molecule/dehydrated alcohol mixed solution, low-surface-energy is small in mixed solution Molecular volume score is 1~14%, and standing time is 0.5~8h in an oven, and oven temperature is 35 DEG C~85 DEG C.