CN110433662B - Preparation method of super-amphiphobic polysulfone membrane for membrane distillation - Google Patents
Preparation method of super-amphiphobic polysulfone membrane for membrane distillation Download PDFInfo
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Abstract
The invention discloses a simple and efficient method for preparing a super-amphiphobic polysulfone membrane, and relates to the field of membrane separation. The invention firstly adopts the traditional solvent-induced phase inversion method to prepare the polysulfone membrane with the interpenetrating network pore structure, and the interpenetrating network pores form a 'reentrant structure' on the surface of the membrane. Then, uniformly distributed silicon dioxide nano particles are generated on the wall of the interpenetrating network hole in situ by a step-by-step sol-gel method, so that a certain nano coarse structure is provided for the polysulfone membrane. And finally, coating a layer of low-surface-energy fluorine silane compound film on the surface of the roughened polysulfone film to obtain the super-amphiphobic polysulfone film, so that the dual anti-wetting property of water drops and organic liquid drops is realized, the contact angle of the water drops can reach more than 150 degrees, and the contact angle of n-hexane can reach more than 65 degrees. The prepared super-amphiphobic polysulfone membrane has a salt rejection rate of more than 99.5% and stronger anti-wetting stability when applied to a membrane distillation process.
Description
Technical Field
The invention relates to a preparation method of a separation membrane used in a membrane distillation process, in particular to a preparation method of a super-amphiphobic membrane.
Background
At present, water resources in China are relatively poor, per mu is relatively small, and the problem of water resource shortage in coastal areas and islands in the north is increasingly prominent. In order to relieve the water resource crisis, China actively develops and utilizes unconventional water resources such as seawater and the like while saving water vigorously. Seawater desalination, as a stable water resource incremental technology, has gradually become an important supplement and strategic reserve of water resources. The seawater desalination industry is actively developed, and the method has very important significance for relieving the problem of water resource shortage in coastal water-deficient areas and islands in China, reasonably optimizing water use structures and promoting sustainable utilization of water resources.
Reverse osmosis is a membrane desalination technology widely used for sea water desalination at present, however, reverse osmosis is not an ideal choice for treating high salinity wastewater, and it faces a great challenge in treating high salinity wastewater because the operating pressure required to overcome the osmotic pressure of high salinity wastewater far exceeds the limit of reverse osmosis membrane, and the salinity of wastewater also far exceeds the limit of 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 concentrations of salt water and low operating pressures. Membrane distillation is a process in which heated seawater is evaporated through a porous membrane, the evaporated vapor condenses on the other side of the membrane, and a hydrophobic membrane acts as an interface between the liquid and the vapor. The membrane for distillation has a much larger pore diameter than water molecules and salt ions, up to several micrometers, and can separate the water molecules and the salt ions from each other under the drive of temperature difference.
In recent years, as research on membrane distillation technology has become more extensive, initially, an important problem faced by membrane distillation processes is that there is no membrane prepared specifically for membrane distillation, and the structure and material properties of commonly used membranes are difficult to meet the requirements of distillation processes. Later, considering the key issue of membrane wettability, the hydrophobicity of membranes used in distillation processes was considered to be of great significance, and many researchers began considering the application of hydrophobic and even superhydrophobic surfaces in membrane distillation. Many plant and animal surfaces in nature have superhydrophobic properties and self-cleaning functions. Inspired by it, many scholars have proposed different methods to construct superhydrophobic surfaces and concluded the necessary conditions for preparing superhydrophobic surfaces. When preparing the super hydrophobic surface, two conditions of constructing a rough surface and using a low surface energy substance for modification are indispensable. Common methods for preparing superhydrophobic films include electrospinning, coating, phase inversion, and plasma techniques. With the expansion of the application field of membrane distillation, the separation component is no longer a simple saline solution and often contains some organic solvents, so that most of the super-hydrophobic surfaces are easily wetted by organic liquids including oil, alkane, alcohol and the like, although the super-hydrophobic membrane has excellent hydrophobic performance. When superhydrophobic surfaces are exposed to an environment of organic contaminants, their anti-wettability may be compromised, eventually resulting in a loss of self-cleaning ability, resulting in severe fouling. Therefore, the development of a film (super-amphiphobic film) having both resistance to wetting by water droplets and low surface tension organic droplets has become the direction of research by many researchers. Super-amphiphobicity is difficult to achieve merely by constructing general roughness structures and modifying with low surface energy substances, and the construction of reentrant structures plays an important role therein. However, the reentrant corner structure is a special structure with a wide top and a narrow bottom, so that the acquisition difficulty is high, and the reentrant corner structure can be constructed by a template method, a laser etching method and other methods reported in the literature, but is not suitable for the surface of the polymer separation membrane. The Chinese patent with application number 201710958054.2 discloses a method for preparing a super-hydrophobic and oleophobic composite membrane by adopting an electrostatic spinning method to prepare a membrane and carrying out secondary spraying modification on the surface of the membrane, the method constructs a reentrant structure by mutual lapping of electrostatic spinning fibers, but the preparation process comprises the preparation of a nano-silica sol solution, the preparation of a cellulose acetate solution, the preparation of an electrostatic spinning precursor solution, the preparation of a hydrophobically modified nano-silica sol solution, a modified spraying solution, the preparation of a composite membrane by an electrostatic spinning method and a surface modification two-step spraying method, and the method has the disadvantages of too complex process, too complex steps and longer time consumption. Furthermore, the electrospinning method is not a conventional method for producing separation membranes, and is not suitable for large-scale production of separation membranes.
Disclosure of Invention
The invention aims to solve the problems and provides a preparation method of a super-amphiphobic membrane, which has simple preparation process and short time consumption. The method adopts a phase inversion method to prepare a polymer film, constructs a reentrant corner structure through a special film pore structure formed in the phase inversion process, further improves the roughness of the surface of a film substrate through the construction of nano particles, and uses a low surface energy substance to modify, thereby finally obtaining the super-amphiphobic film with anti-wetting property to water and organic liquid.
In order to achieve the purpose, the invention adopts the technical scheme that:
a preparation method of a super-amphiphobic polysulfone membrane for membrane distillation comprises the following steps:
(1) preparing a polysulfone membrane with an interpenetrating network pore structure: polysulfone particles, a pore-forming agent and an organic solvent are added into a round-bottom flask according to a certain mass portion, stirred by an oil bath stirring heater at a certain temperature and a certain rotating speed until a homogeneous solution is formed, and then kept stand at a constant temperature for defoaming. And after defoaming, casting the membrane casting solution on a glass plate, spreading the membrane casting solution by using a scraper to form a primary membrane, quickly and stably putting the primary membrane into a coagulating bath, and inducing polysulfone gel to be solidified into a membrane through exchange of a solvent and a non-solvent.
(2) Constructing a nano rough structure on the surface of the membrane: stirring a certain volume part of tetraethoxysilane and absolute ethyl alcohol into a uniform mixed solution, and recording the mixed solution as solution A; then a certain volume portion of ammonia water and absolute ethyl alcohol are stirred into a uniform mixed solution, which is recorded as solution B. And (2) sequentially soaking the polysulfone base membrane obtained in the step (1) in the solution A and the solution B for a certain time, and carrying out hydrolysis condensation reaction to grow uniform silicon dioxide nano-particles on the pore wall of the polysulfone base membrane in situ.
(3) Modifying the surface of the film with low surface energy: soaking the polysulfone substrate membrane with the nano-scale rough structure obtained in the step (2) in a mixed solution of low surface energy micromolecules/absolute ethyl alcohol to uniformly coat the low surface energy micromolecules on the surface of the polysulfone membrane, and then putting the polysulfone membrane into an oven with a certain temperature for a period of time to enable hydrolysis condensation reactions to occur among the low surface energy micromolecules and between the low surface energy micromolecules and silicon dioxide, so as to form 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 steps.
Preferably, in the step 1, the mass parts of the polysulfone particles, the pore-forming agent and the organic solvent are 8-20, 2-7 and 73-90 respectively, and the organic solvent is preferably N-methylpyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, 1, 4-dioxane, chlorohexine or the likeOne or a mixture of any two of chloroform and dichloromethane, the pore-foaming agent is one or more of polyethylene glycol, polyoxyethylene and polyvinylpyrrolidone, the weight-average molecular weight of the polyethylene glycol is preferably 3000 kD-8000 kD, and the weight-average molecular weight of the polyoxyethylene is preferably 1.5 × 104kD～1×105kD, the weight-average molecular weight of the polyvinylpyrrolidone used is preferably 5X 104kD～1.3×106kD。
Preferably, in the step 1, the heating temperature is 45-85 ℃, the heating time is 4-20 hours, the stirring speed is 200-450 rpm, the glass plate comprises a smooth glass plate and a rough glass plate, 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, the volume ratio of the organic solvent to the water in the first coagulation bath is 0: 10-9: 1, the organic solvent in the first coagulation bath is preferably one or two of N-methylpyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, 1, 4-dioxane, ethanol, N-propanol, isopropanol and N-butanol, and the soaking time in the first coagulation bath is 5-50 s.
Preferably, in the step (1), the size of the interpenetrating network pore structure is 0.05 μm to 8 μm.
Preferably, in the step (2), the volume fraction of the tetraethoxysilane in the solution A is 10-50%, and the soaking time in the solution A is 1.5-8 hours; the volume fraction of ammonia water in the solution B is 15-45%, the soaking time in the solution B is 20-100 min, and the size of the silicon dioxide is preferably 20-600 nm. .
Preferably, in the step (3), the low surface energy small molecule is one of heptadecafluorodecyltrimethoxysilane (FAS), heptadecafluorodecyltriethoxysilane (FOTS), per fluoro octyltrichlorosilane (PFTS), perfluorodecyltrichlorosilane and stearic acid, and in the mixed solution of the low surface energy small molecule and absolute ethyl alcohol, the volume fraction of the low surface energy small molecule in the mixed solution is 1-14%, the standing time in an oven is 0.5-8 h, and the oven temperature is 35-85 ℃.
The application of the super-amphiphobic polysulfone membrane in a membrane distillation technology.
The invention has the advantages and beneficial effects that:
(1) the method utilizes an interpenetrating network pore structure which is easily obtained in the process of a classical non-solvent induced phase inversion method to construct a reentrant angle structure, adopts the in-situ growth of silicon dioxide particles to ensure that the silicon dioxide nanoparticles exist stably on a membrane matrix, and ensures that low surface energy micromolecules are hydrolyzed and then have polycondensation reaction with silicon hydroxyl on silicon dioxide on the surface of the membrane to form a stable low surface energy thin layer, and the membrane layer and the polysulfone base membrane have good bonding property and are not easy to fall off. The preparation process is simple and easy to operate, expensive equipment is not needed, and large-scale membrane preparation can be completed in a short time.
(2) The film matrix material adopted by the invention is polysulfone, which has excellent mechanical property, high strength and large rigidity, can keep excellent mechanical property at high temperature, has excellent oxidation resistance, hydrolysis resistance, thermal stability and high-temperature melting stability, and in addition, the polysulfone material also has excellent mechanical property, electrical property and food sanitation property, thus being one of the most widely applied film materials.
(3) The super-amphiphobic polysulfone membrane prepared by the invention has double anti-wetting property on water drops and organic liquid drops, particularly has a contact angle of nearly 90 degrees on n-hexane with extremely low surface tension, and has stable anti-wetting property on feed liquid containing the organic liquid drops when being applied to a membrane distillation process.
Drawings
FIG. 1 is a scanning electron micrograph of a polysulfone film prepared in comparative example 1.
Fig. 2 is a contact angle graph of the polysulfone membrane prepared in comparative example 1.
FIG. 3 is a scanning electron micrograph of the polysulfone film prepared in comparative example 2.
Fig. 4 is a contact angle graph of the polysulfone membrane prepared in comparative example 2.
FIG. 5 is a scanning electron micrograph of the polysulfone film prepared in comparative example 3.
Fig. 6 is a contact angle graph of the polysulfone membrane prepared in comparative example 3.
FIG. 7 is a scanning electron micrograph of the roughened and fluorinated modified film of example 3.
FIG. 8 is a graph showing the results of measuring the contact angle of the super-amphiphobic polysulfone membrane in example 3.
Detailed Description
The invention is explained in further detail below by means of specific embodiments with reference to the drawings. It is to be understood that the following examples are intended to illustrate the invention and are not intended to limit its scope.
Comparative example 1:
16 parts by mass of polysulfone particles and 4 parts by mass of polyvinylpyrrolidone (weight-average molecular weight of 1.3X 10)6kD) and 80 parts by mass of dimethylformamide are added into a round-bottom flask, the mixture is dissolved for 10 hours at the heating temperature of 80 ℃ and the rotating speed of 400rpm until a homogeneous solution is formed, and then the mixture is kept stand at constant temperature for deaeration. And after defoaming, casting the membrane casting solution on a rough glass plate, spreading the membrane casting solution by using a scraper to form a primary membrane, quickly and stably placing the primary membrane into a dimethyl formamide/water (volume part ratio is 4:6) mixed solution for 15s, then transferring the primary membrane into deionized water, and inducing polysulfone gel to be cured into a membrane through full exchange of a solvent and a non-solvent. As can be seen from FIG. 1, the polysulfone membrane with interpenetrating network reentrant structure has been successfully constructed, the size of the interpenetrating network pores is about 5 μm, the water drop contact angle of the membrane is 0 DEG, the membrane is super-hydrophilic and super-lipophilic, and the membrane cannot be used in the membrane distillation process.
Comparative example 2:
16 parts by mass of polysulfone particles and 4 parts by mass of polyvinylpyrrolidone (weight-average molecular weight of 1.3X 10)6kD) and 80 parts by mass of dimethylformamide are added into a round-bottom flask, the mixture is dissolved for 10 hours at the heating temperature of 80 ℃ and the rotating speed of 400rpm until a homogeneous solution is formed, and then the mixture is kept stand at constant temperature for deaeration. And after defoaming, casting the membrane casting solution on a rough glass plate, spreading the membrane casting solution by using a scraper to form a primary membrane, quickly and stably placing the primary membrane into a dimethyl formamide/water (volume part ratio is 4:6) mixed solution for 15s, then transferring the primary membrane into deionized water, and inducing polysulfone gel to be cured into a membrane through full exchange of a solvent and a non-solvent, so as to obtain the interpenetrating network pores with the pore size of about 5 microns.
Stirring tetraethoxysilane and absolute ethyl alcohol to form a uniform mixed solution (the volume fraction of tetraethoxysilane is 30 percent) which is recorded as solution A; then, the ammonia water and the absolute ethyl alcohol are stirred into a uniform mixed solution (the volume fraction of the ammonia water is 20 percent), and the mixed solution is recorded as the solution B. And sequentially soaking the obtained polysulfone base membrane in the solution A for 4h and in the solution B for 50min, and carrying out hydrolysis condensation reaction to grow uniform silicon dioxide particles with the particle size of about 200nm on the pore wall of the polysulfone base membrane in situ (figure 2). Obtaining the polysulfone membrane with the surface modified by the nano-scale rough structure. The contact angle of the film drop is 0 degree, is super-hydrophilic and super-lipophilic, and can not be used in the film distillation process.
Comparative example 3:
adding 16 parts by mass of polysulfone particles and 84 parts by mass of dimethylformamide into a round-bottom flask, dissolving at the heating temperature of 80 ℃ and the rotating speed of 400rpm for 10 hours until a homogeneous solution is formed, and then standing at constant temperature for defoaming. And after defoaming, casting the membrane casting solution on a rough glass plate to form a primary membrane, quickly and stably putting the primary membrane into deionized water, and inducing polysulfone gel to be solidified into a membrane through full exchange of a solvent and a non-solvent. An asymmetric structure polysulfone based membrane with an integral skin layer and a finger-like pore support layer is obtained.
Stirring tetraethoxysilane and absolute ethyl alcohol to form a uniform mixed solution (volume fraction of tetraethoxysilane is 30 percent), and recording the mixed solution as solution A; then, the ammonia water and the absolute ethyl alcohol are stirred into a uniform mixed solution (the volume fraction of the ammonia water is 20 percent), and the mixed solution is recorded as the solution B. And sequentially soaking the obtained polysulfone base membrane in the solution A for 2h and in the solution B for 25min, and carrying out hydrolysis condensation reaction to grow uniform silicon dioxide particles with the particle size of about 100nm on the pore wall of the polysulfone base membrane in situ. Obtaining the polysulfone membrane with the membrane surface completely covered by the nano-silica particles.
Soaking the membrane in a mixed solution of heptadecafluorodecyltriethoxysilane and absolute ethyl alcohol, wherein the volume fraction of the heptadecafluorodecyltriethoxysilane in the mixed solution is 2 percent, so that low-surface-energy micromolecules are uniformly coated on the surface of the polysulfone membrane, and then putting the polysulfone membrane into an oven at 85 ℃ for 0.5h to perform hydrolytic condensation reaction, so that a cross-linked low-surface-energy thin layer is formed on the surface of the membrane. The polysulfone membrane obtained by the steps has a water drop contact angle of 128 degrees, a hexanediol contact angle of 52 degrees, a hexadecane contact angle of 0 degree and a normal hexane contact angle of 0 degree, and is applied to a membrane distillation processThe time salt rejection rate can reach 99.30 percent, and the water vapor flux is 10L/m2h, starting to wet the membrane surface after stable operation for 0.5 h.
Example 1:
8 parts by mass of polysulfone particles and 2 parts by mass of polyoxyethylene (weight average molecular weight 1.0X 10)5kD) and 90 parts by mass of dimethyl sulfoxide are added into a round-bottom flask, the mixture is dissolved for 4 hours at the heating temperature of 55 ℃ and the rotating speed of 200rpm until a homogeneous solution is formed, and then the mixture is kept stand at constant temperature for deaeration. And after defoaming, casting the membrane casting solution on a rough glass plate, spreading the membrane casting solution by using a scraper to form a primary membrane, quickly and stably placing the primary membrane into an isopropanol/water (volume part ratio is 9:1) mixed solution for 40s, then transferring the primary membrane into deionized water, and inducing polysulfone gel to be cured into a membrane through full exchange of a solvent and a non-solvent, so as to obtain the interpenetrating network pores with the pore size of about 8 mu m.
Stirring tetraethoxysilane and absolute ethyl alcohol to form a uniform mixed solution (the volume fraction of tetraethoxysilane is 50 percent), and recording the mixed solution as solution A; then, ammonia water and absolute ethyl alcohol were stirred to obtain a uniform mixed solution (ammonia water volume fraction: 45%), which was designated as solution B. And sequentially soaking the obtained polysulfone base membrane in the solution A for 1.5h and in the solution B for 100min, and carrying out hydrolysis condensation reaction to grow uniform silicon dioxide nanoparticles with the particle size of about 600nm on the pore wall of the polysulfone base membrane in situ. Obtaining the polysulfone membrane with the surface modified by the nano-scale rough structure.
The membrane is soaked in a mixed solution of heptadecafluorodecyltriethoxysilane and absolute ethyl alcohol, the volume fraction of the heptadecafluorodecyltriethoxysilane in the mixed solution is 1 percent, so that the low-surface-energy micromolecules are uniformly coated on the surface of the polysulfone membrane, and then the polysulfone membrane is placed in an oven at 85 ℃ for 0.5h, hydrolytic polycondensation can be carried out among the low-surface-energy micromolecules, the low-surface-energy micromolecules can also hydrolyze silicon hydroxyl on the silica to carry out polycondensation reaction, and a cross-linked low-surface-energy thin layer is formed on the surface of the membrane. The quasi-super-amphiphobic polysulfone membrane is obtained through the steps, the water drop contact angle is 145 degrees, the hexanediol contact angle is 132 degrees, the hexadecane contact angle is 95 degrees, the n-hexane contact angle is 40 degrees, the salt rejection rate can reach 99.50 percent when the quasi-super-amphiphobic polysulfone membrane is applied to the membrane distillation process, and the water vapor flux is 50L/m2h, film surface after stable operation for 2hWetting begins.
Example 2:
adding 10 parts by mass of polysulfone particles, 7 parts by mass of polyethylene glycol (with the weight-average molecular weight of 8000kD) and 83 parts by mass of dichloromethane/dimethylacetamide mixed solution (with the mass part ratio of 60: 40) into a round-bottom flask, dissolving for 6 hours at the heating temperature of 45 ℃ and the rotating speed of 250rpm until a homogeneous solution is formed, and then standing at constant temperature for defoaming. And after defoaming, casting the membrane casting solution on a smooth glass plate, spreading the membrane casting solution by using a scraper to form a primary membrane, quickly and stably placing the primary membrane into a mixed solution of n-propanol/water (the volume part ratio is 7:3) for 50s, then transferring the primary membrane into deionized water, and inducing polysulfone gel to be cured into a membrane through full exchange of a solvent and a non-solvent, so as to obtain the interpenetrating network pores with the pore size of about 2 microns.
Stirring tetraethoxysilane and absolute ethyl alcohol to form a uniform mixed solution (the volume fraction of tetraethoxysilane is 30 percent) which is recorded as solution A; then, the ammonia water and the absolute ethyl alcohol are stirred into a uniform mixed solution (the volume fraction of the ammonia water is 20 percent), and the mixed solution is recorded as the solution B. And sequentially soaking the obtained polysulfone base membrane in the solution A for 6 hours and in the solution B for 80min, and carrying out hydrolysis condensation reaction to grow uniform silicon dioxide nanoparticles with the particle size of about 150nm on the pore wall of the polysulfone base membrane in situ. Obtaining the polysulfone membrane with the surface modified by the nano-scale rough structure.
Soaking the membrane in a mixed solution of stearic acid/absolute ethyl alcohol, wherein the volume fraction of stearic acid in the mixed solution is 8%, so that low-surface-energy micromolecules are uniformly coated on the surface of the polysulfone membrane, and then putting the polysulfone membrane into a 50-DEG C oven for 6h to perform hydrolytic condensation reaction, so that a cross-linked low-surface-energy thin layer is formed on the surface of the membrane. The super-amphiphobic polysulfone membrane is obtained through the steps, the water drop contact angle is 155 degrees, the hexanediol contact angle is 152 degrees, the hexadecane contact angle is 125 degrees, the n-hexane contact angle is 75 degrees, the salt rejection rate can reach 99.87 percent when the super-amphiphobic polysulfone membrane is applied to the membrane distillation process, and the water vapor flux is 25L/m2h, starting to wet the membrane surface after stable operation for 3.5 h.
Example 3:
16 parts by mass of polysulfone particles and 4 parts by mass of polyvinylpyrrolidone (weight-average molecular weight of 1.3X 10)6kD) and 80 moleculesAdding a certain amount of dimethylformamide into a round-bottom flask, dissolving at the heating temperature of 80 ℃ and the rotating speed of 200rpm for 10 hours until a homogeneous solution is formed, and then standing at constant temperature for defoaming. And after defoaming, casting the membrane casting solution on a rough glass plate, spreading the membrane casting solution by using a scraper to form a primary membrane, quickly and stably placing the primary membrane into a dimethyl formamide/water (volume part ratio is 4:6) mixed solution for 15s, then transferring the primary membrane into deionized water, and inducing polysulfone gel to be cured into a membrane through full exchange of a solvent and a non-solvent, so as to obtain an interpenetrating network pore with the pore size of about 5 microns.
Stirring tetraethoxysilane and absolute ethyl alcohol to form a uniform mixed solution (the volume fraction of tetraethoxysilane is 30 percent) which is recorded as solution A; then, ammonia water and absolute ethyl alcohol are stirred into a uniform mixed solution (the volume of the ammonia water is 20 percent), and the mixed solution is recorded as solution B. And sequentially soaking the obtained polysulfone base membrane in the solution A for 4h and in the solution B for 50min, and carrying out hydrolysis condensation reaction to grow uniform silicon dioxide nanoparticles with the particle size of about 200nm on the pore wall of the polysulfone base membrane in situ. Obtaining the polysulfone membrane with the surface modified by the nano-scale rough structure.
Soaking the membrane in a mixed solution of heptadecafluorodecyltrimethoxysilane and absolute ethyl alcohol, wherein the volume fraction of the heptadecafluorodecyltrimethoxysilane in the mixed solution is 10%, so that low-surface-energy small molecules are uniformly coated on the surface of the polysulfone membrane, and then putting the polysulfone membrane into a 70-DEG C oven for 30min to perform hydrolytic condensation reaction, so that a cross-linked low-surface-energy thin layer is formed on the surface of the membrane. The super-amphiphobic polysulfone membrane is obtained through the steps, and as can be seen from fig. 5, a fluorosilane layer is attached to the surface of the membrane. The water drop contact angle is 154 degrees, the hexanediol contact angle is 150 degrees, the hexadecane contact angle is 121 degrees, the n-hexane contact angle is 67 degrees, the salt rejection rate can reach 99.95 percent when the method is applied to the membrane distillation process, and the water vapor flux is 20.5L/m2h, starting to wet the membrane surface after stable operation for 4 h.
Example 4:
20 parts by mass of polysulfone particles and 7 parts by mass of polyvinylpyrrolidone (weight-average molecular weight: 5X 10)4kD) and 73 parts by mass of dimethylacetamide are added into a round-bottom flask and dissolved for 20 hours at a heating temperature of 85 ℃ and a rotating speed of 450rpm until formationHomogeneous solution, and then standing at constant temperature for defoaming. And after defoaming, casting the membrane casting solution on a rough glass plate, spreading the membrane casting solution by using a scraper to form a primary membrane, quickly and stably placing the primary membrane into a mixed solution of n-butyl alcohol/water (the volume part ratio is 2:8) for 15s, then transferring the primary membrane into deionized water, and inducing polysulfone gel to be cured into a membrane through full exchange of a solvent and a non-solvent, so as to obtain an interpenetrating network pore with the pore size of about 0.5 mu m. .
Stirring tetraethoxysilane and absolute ethyl alcohol to form a uniform mixed solution (the volume fraction of tetraethoxysilane is 10 percent), and recording the mixed solution as solution A; then, the ammonia water and the absolute ethyl alcohol are stirred into a uniform mixed solution (the volume fraction of the ammonia water is 15 percent), and the mixed solution is recorded as the solution B. And respectively soaking the obtained polysulfone base membrane in the solution A for 2h and in the solution B for 30min in sequence, and carrying out hydrolysis condensation reaction to grow uniform silicon dioxide nanoparticles with the particle size of about 60nm on the pore wall of the polysulfone base membrane in situ. Obtaining the polysulfone membrane with the surface modified by the nano-scale rough structure.
Soaking the membrane in a mixed solution of perfluorooctyl trichlorosilane/absolute ethyl alcohol, wherein the volume fraction of the perfluorooctyl trichlorosilane in the mixed solution is 14 percent, so that low-surface-energy micromolecules are uniformly coated on the surface of the polysulfone membrane, and then putting the polysulfone membrane into a 35-DEG C oven for 8 hours to perform hydrolytic condensation reaction, so that a cross-linked low-surface-energy thin layer is formed on the surface of the membrane. The super-amphiphobic polysulfone membrane is obtained through the steps, the water drop contact angle of the super-amphiphobic polysulfone membrane is 160 degrees, the hexanediol contact angle of the super-amphiphobic polysulfone membrane is 149 degrees, the hexadecane contact angle of the super-amphiphobic polysulfone membrane is 80 degrees, the n-hexane contact angle of the super-amphiphobic polysulfone membrane is 10 degrees, the salt rejection rate can reach 99.99 percent when the super-amphiphobic polysulfone membrane is applied to a membrane distillation process, and the water vapor flux of the super-amphiphobic polysulfone membrane is 5L/m2h, starting to wet the membrane surface after stable operation for 1 h.
Example 5:
18 parts by mass of polysulfone particles and 6 parts by mass of polyoxyethylene (weight average molecular weight 1.5X 10)4kD) and 86 parts by mass of dimethylformamide are added into a round-bottom flask, the mixture is dissolved for 12 hours at the heating temperature of 60 ℃ and the rotating speed of 300rpm until a homogeneous solution is formed, and then the mixture is kept stand at constant temperature for deaeration. After defoaming, casting the casting solution on a rough glass plate, spreading the casting solution by a scraper to form a primary film, and quickly and stably putting the primary film into dimethylformamide/isopropanol/water (volume fraction)The mixed solution is moved into deionized water after 30 seconds in a ratio of 6:2:2), polysulfone gel is induced to be solidified into a film through full exchange of a solvent and a non-solvent, and interpenetrating network pores with the pore size of about 4 mu m can be obtained.
Stirring tetraethoxysilane and absolute ethyl alcohol to form a uniform mixed solution (the volume fraction of tetraethoxysilane is 40 percent), and recording the mixed solution as solution A; then, the ammonia water and the absolute ethyl alcohol are stirred into a uniform mixed solution (the volume fraction of the ammonia water is 30 percent), and the mixed solution is recorded as the solution B. And sequentially soaking the obtained polysulfone base membrane in the solution A for 5h and in the solution B for 60min, and carrying out hydrolysis condensation reaction to grow uniform silicon dioxide nanoparticles with the particle size of about 300nm on the pore wall of the polysulfone base membrane in situ. Obtaining the polysulfone membrane with the surface modified by the nano-scale rough structure.
Soaking the membrane in a mixed solution of perfluorodecyl trichlorosilane/absolute ethyl alcohol, wherein the volume fraction of the perfluorodecyl trichlorosilane in the mixed solution is 14%, so that low-surface-energy micromolecules are uniformly coated on the surface of the polysulfone membrane, and then putting the polysulfone membrane into a 60-DEG C oven for 5 hours to perform hydrolytic condensation reaction, so that a cross-linked low-surface-energy thin layer is formed on the surface of the membrane. The super-amphiphobic polysulfone membrane is obtained through the steps, the water drop contact angle is 160 degrees, the hexanediol contact angle is 156 degrees, the hexadecane contact angle is 130 degrees, the n-hexane contact angle is 90 degrees, the salt rejection rate can reach 99.91 percent when the super-amphiphobic polysulfone membrane is applied to the membrane distillation process, and the water vapor flux is 25L/m2h, starting to wet the membrane surface after stable operation for 4 h.
Example 6:
14 parts by mass of polysulfone particles, 6 parts by mass of polyethylene glycol (weight average molecular weight is 3000kD) and 90 parts by mass of N-methylpyrrolidone are added into a round-bottom flask, the materials are dissolved for 10 hours at the heating temperature of 70 ℃ and the rotating speed of 300rpm until a homogeneous solution is formed, and then the solution is kept at a constant temperature and is defoamed. And after defoaming, casting the membrane casting solution on a rough glass plate, spreading the membrane casting solution by using a scraper to form a primary membrane, quickly and stably putting the primary membrane into deionized water, and inducing polysulfone gel to be cured into a membrane through full exchange of a solvent and a non-solvent, so that interpenetrating network pores with the pore size of about 0.05 mu m can be obtained.
Stirring tetraethoxysilane and absolute ethyl alcohol to form a uniform mixed solution (the volume fraction of tetraethoxysilane is 30 percent) which is recorded as solution A; then, the ammonia water and the absolute ethyl alcohol are stirred into a uniform mixed solution (the volume fraction of the ammonia water is 40 percent), and the mixed solution is recorded as the solution B. And sequentially soaking the obtained polysulfone base membrane in the solution A for 1.5h and in the solution B for 20min respectively, and carrying out hydrolysis condensation reaction to grow uniform silicon dioxide nanoparticles with the particle size of about 20nm on the pore wall of the polysulfone base membrane in situ. Obtaining the polysulfone membrane with the surface modified by the nano-scale rough structure.
Soaking the membrane in a mixed solution of perfluorodecyl trichlorosilane/absolute ethyl alcohol, wherein the volume fraction of the perfluorodecyl trichlorosilane in the mixed solution is 12%, so that low-surface-energy micromolecules are uniformly coated on the surface of the polysulfone membrane, and then putting the polysulfone membrane into a 55-DEG C oven for 6h to perform hydrolytic condensation reaction, so that a cross-linked low-surface-energy thin layer is formed on the surface of the membrane. The quasi-super-amphiphobic polysulfone membrane is obtained through the steps, the water drop contact angle is 140 degrees, the hexanediol contact angle is 130 degrees, the hexadecane contact angle is 80 degrees, the n-hexane contact angle is 10 degrees, the salt rejection rate can reach 99.98 percent when the quasi-super-amphiphobic polysulfone membrane is applied to the membrane distillation process, and the water vapor flux is 2L/m2h, after stable operation for 1.5h, the membrane surface starts to wet.
Claims (5)
1. A preparation method of a super-amphiphobic polysulfone membrane for membrane distillation is characterized by comprising the following three steps:
(1) preparing a polysulfone membrane with an interpenetrating network pore structure: adding a certain mass part of polysulfone particles, a pore-forming agent and an organic solvent into a round-bottom flask, stirring by an oil bath stirring heater at a certain temperature and a certain rotating speed until a homogeneous solution is formed, standing and defoaming at a constant temperature, casting a membrane casting solution on a glass plate to form a primary membrane after defoaming, quickly and stably putting the primary membrane into a coagulating bath, and inducing polysulfone gel to be solidified into a membrane through exchange of the solvent and a non-solvent;
(2) constructing a nano rough structure on the surface of the membrane: stirring a certain volume part of tetraethoxysilane and absolute ethyl alcohol into a uniform mixed solution, and recording the mixed solution as solution A; stirring a certain volume part of ammonia water and absolute ethyl alcohol into a uniform mixed solution, recording the mixed solution as solution B, sequentially soaking the polysulfone base membrane obtained in the step (1) in the solution A and the solution B for a certain time, and carrying out hydrolysis condensation reaction to grow uniform silicon dioxide nanoparticles on the pore wall of the polysulfone base membrane in situ;
(3) modifying the surface of the film with low surface energy: soaking the polysulfone base membrane with the nanoscale rough structure obtained in the step (1) in a mixed solution of low-surface-energy micromolecules/absolute ethyl alcohol to uniformly coat the low-surface-energy micromolecules on the surface of the polysulfone membrane, and then putting the polysulfone base membrane into a drying oven with a certain temperature for a period of time to perform hydrolytic condensation reaction to form a cross-linked low-surface-energy thin layer on the surface of the membrane;
in the step (1), the mass parts of polysulfone particles in the homogeneous phase solution are 8-20, the mass parts of pore-forming agent is 2-7, the mass parts of organic solvent is 73-90, the organic solvent is one or a mixture of any two of N-methylpyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, 1, 4-dioxane, chloroform and dichloromethane, the pore-forming agent is one or more of polyethylene glycol, polyoxyethylene and polyvinylpyrrolidone, the weight-average molecular weight of the polyethylene glycol is 3000 kD-8000 kD, and the weight-average molecular weight of the polyoxyethylene is 1.5 x 104 kD ~ 1×105kD, said polyvinylpyrrolidone having a weight average molecular weight of 5X 104 kD ~ 1.3×106 kD;
In the step (1), the heating temperature is 45-85 ℃, the heating time is 4-20 hours, the stirring speed is 200-450 rpm, the glass plate is a smooth glass plate or a rough glass plate, 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, the volume ratio of the organic solvent to the water in the first coagulation bath is 0: 10-9: 1, the organic solvent is one or any two mixed solution of N-methylpyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, 1, 4-dioxane, ethanol, N-propanol, isopropanol and N-butanol, and the soaking time in the first coagulation bath is 5-50 s.
2. The method for preparing the super-amphiphobic polysulfone membrane for membrane distillation according to claim 1, wherein the size of the interpenetrating network pore structure in the step (1) is 0.05-8 μm.
3. The preparation method of the super-amphiphobic polysulfone membrane for membrane distillation according to claim 1, wherein the volume fraction of the tetraethoxysilane in the solution A is 10-50%, and the soaking time in the solution A is 1.5-8 h; the volume fraction of ammonia water in the liquid B is 15-45%, and the soaking time in the liquid B is 20-100 min.
4. The method for preparing the super-amphiphobic polysulfone membrane for membrane distillation according to claim 1, wherein the size of the silica is 200 nm-600 nm.
5. The preparation method of the super-amphiphobic polysulfone membrane for membrane distillation according to claim 1, wherein the low surface energy small molecule is one of heptadecafluorodecyltrimethoxysilane, heptadecafluorodecyltriethoxysilane, perfluorooctyltrichlorosilane, perfluorodecyltrichlorosilane and stearic acid, the volume fraction of the low surface energy small molecule in the mixed solution is 1-14% in the mixed solution of the low surface energy small molecule and absolute ethyl alcohol, the mixed solution is placed in an oven for 0.5-8 h, and the oven temperature is 35-85 ℃.
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