Janus nanofiber membrane based on polysulfone material and preparation method and application thereof

Abstract

The application belongs to the technical field of oil-water separation, and particularly relates to a Janus nanofiber membrane based on a polysulfone material and a preparation method and application thereof. After the super-hydrophobic polysulfone nanofiber membrane is prepared, a super-thin hydrophilic layer is photo-grafted on one side of the super-hydrophobic polysulfone nanofiber membrane, in the oil-water separation process, a single channel of oil can be formed, a demulsification effect is achieved, the water removal rate is increased, and the water removal rate is high. The polysulfone nanofiber membrane with a silicon-containing hydrophobic structure is prepared by utilizing the different volatilization rates of tetrahydrofuran, a nitrogen-containing organic solvent and anhydrous ethanol, and the polysulfone nanofiber membrane has rich pore size structures; the polysulfone substrate is adopted, and the obtained membrane material has high strength; the Janus nanofiber membrane prepared by the application has a hydrophobic / hydrophilic structure, exhibits excellent stability, has high permeability, low long-term operation permeability attenuation and a long cleaning cycle.

Description

Technical Field

[0001] This invention belongs to the field of oil-water separation technology, specifically relating to a Janus nanofiber membrane based on polysulfone material, its preparation method, and its application. Background Technology

[0002] The large-scale discharge of oil-water mixtures from household and industrial production causes enormous economic losses and resource waste, seriously jeopardizing ecological balance and environmental safety. Traditional oil-water separation processes, such as gravity separation, centrifugal separation, electrostatic separation, and adsorption separation, suffer from low separation efficiency, high operating costs, and are prone to secondary pollution, and are gradually being replaced by emerging membrane separation technologies. Therefore, developing a super-wetting oil-water separation membrane material has become an urgent problem to be solved in the treatment of oil-water mixtures.

[0003] Janus membranes are separation membrane materials with significant differences in properties on both sides. These differences are usually manifested in the different chemical wetting properties on both sides of the membrane. Janus membranes can be used in fluid manipulation, mist collection, water collection, oil-water separation, and other applications.

[0004] Superhydrophobic surfaces exhibit excellent affinity for oil and opposite wettability to oil and aqueous phases, effectively removing water droplets from water-in-oil emulsions. Polysulfone is an important polymer material widely used in separation applications. Compared to traditional hydrophobic materials such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), it is inexpensive, has a high glass transition temperature, and good thermoplasticity, making it more suitable for long-term use at high temperatures. However, due to the inherent hydrophobicity of polysulfone, the resulting polysulfone membranes typically have low porosity, poor permeability, and low membrane flux, and are easily fouled by organic matter in the water. Surface modification of ultrafiltration / microfiltration membranes prepared by the traditional phase inversion method can improve the porosity, permeability, or membrane flux of the membrane material, but the phase inversion method has disadvantages such as consuming large amounts of solvent and requiring coagulation bath treatment. Furthermore, due to the single wettability of the separation membrane, the wettability of the separation membrane is prone to change during long-term oil-water separation, resulting in poor separation performance and further deterioration of permeability. Small amounts of dissolved water and water droplets with microemulsion-level particle size in the oil are difficult to remove, resulting in a low water removal rate. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a Janus nanofiber membrane based on polysulfone material, its preparation method, and its application. When the Janus nanofiber membrane prepared by this invention is used in an oil-water separation process, it achieves a high water removal rate.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing Janus nanofiber membranes based on polysulfone materials, comprising the following steps:

[0008] After coaxial electrospinning of the polysulfone solution and the hybrid modification solution, hot pressing and hydrolysis are performed sequentially to obtain a superhydrophobic polysulfone nanofiber membrane; the hybrid modification solution contains tetraethyl orthosilicate and a fluorosilane coupling agent;

[0009] After immersing one side of the superhydrophobic polysulfone nanofiber membrane in a mixture containing hydrophilic modified monomers and photoinitiators, it is then rinsed and irradiated with ultraviolet light in sequence to obtain the Janus nanofiber membrane based on polysulfone material.

[0010] Preferably, the polysulfone solution contains 5-20% polysulfone by mass.

[0011] Preferably, the solvent of the polysulfone solution is a mixture of a nitrogen-containing organic solvent and tetrahydrofuran, wherein the nitrogen-containing organic solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.

[0012] Preferably, the mass ratio of tetraethyl orthosilicate to fluorosilane coupling agent in the hybrid modified solution is 0.1 to 10:1.

[0013] Preferably, the sum of the mass fractions of tetraethyl orthosilicate and fluorosilane coupling agent in the hybrid modified solution is 2-10%.

[0014] Preferably, the solvent of the hybrid modified solution is a mixture of tetrahydrofuran and anhydrous ethanol.

[0015] Preferably, the conditions for coaxial electrospinning include: a voltage of 10–30 kV, an injection rate of 0.0001–0.01 mm / s, and a roller speed of 100–500 rpm.

[0016] Preferably, the hydrophilic modifying monomer includes one or more of sodium acrylate, acrylamide, sodium p-styrene sulfonate, and acrylic acid.

[0017] The present invention also provides a Janus nanofiber membrane based on polysulfone material obtained by the preparation method described above. The Janus nanofiber membrane includes a superhydrophobic polysulfone nanofiber membrane and a hydrophilic layer, wherein the hydrophilic layer is loaded on any side surface of the superhydrophobic polysulfone nanofiber membrane.

[0018] The present invention also provides the application of the above-mentioned Janus nanofiber membrane based on polysulfone material in oil-water separation.

[0019] This invention provides a method for preparing Janus nanofiber membranes based on polysulfone materials, comprising the following steps:

[0020] After coaxial electrospinning of the polysulfone solution and the hybrid modification solution, hot pressing and hydrolysis are performed sequentially to obtain a superhydrophobic polysulfone nanofiber membrane; the hybrid modification solution contains tetraethyl orthosilicate and a fluorosilane coupling agent;

[0021] After immersing one side of the superhydrophobic polysulfone nanofiber membrane in a mixture containing hydrophilic modified monomers and photoinitiators, it is then rinsed and irradiated with ultraviolet light in sequence to obtain the Janus nanofiber membrane based on polysulfone material.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] After preparing the superhydrophobic polysulfone nanofiber membrane, the present invention performs a single-sided optical grafting of an ultrathin hydrophilic layer onto the superhydrophobic polysulfone nanofiber membrane. During the oil-water separation process, a single oil channel can be formed, which plays a role in demulsification and increases the water removal rate.

[0024] Furthermore, this invention utilizes the different evaporation rates of tetrahydrofuran, nitrogen-containing organic solvents, and anhydrous ethanol during the electrospinning process to prepare a polysulfone nanofiber membrane with a silicon-containing hydrophobic structure. This membrane has a rich pore structure with a pore size of 0.1–2.0 μm. The polysulfone substrate used in this invention results in a Janus nanofiber membrane with excellent strength properties. The Janus nanofiber membrane prepared by this invention has hydrophobic / hydrophilic properties (one side hydrophobic and the other side hydrophilic), exhibiting excellent stability, high permeability, low permeability decay over long-term operation, and long cleaning cycle.

[0025] Data from the examples show that the Janus nanofiber membrane prepared by this invention has a permeability greater than 25000 L·m⁻² to various water-in-oil emulsions. -2 ·h -1 ·bar -1 The flux reduction rate of the n-octane-in-water emulsion was less than 8% after 5 hours, the flux recovery rate was more than 95%, the irreversible fouling rate was less than 3%, the flux reduction rate after 30 days was less than 10%, the cleaning cycle was more than 7 days, and the strength was more than 25 MPa. It has application potential in oil refining. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a microstructure diagram of the polyethersulfone Janus nanofiber membrane prepared in Example 1. Detailed Implementation

[0028] This invention provides a method for preparing Janus nanofiber membranes based on polysulfone materials, comprising the following steps:

[0029] After coaxial electrospinning of the polysulfone solution and the hybrid modification solution, hot pressing and hydrolysis are performed sequentially to obtain a superhydrophobic polysulfone nanofiber membrane; the hybrid modification solution contains tetraethyl orthosilicate and a fluorosilane coupling agent;

[0030] After immersing one side of the superhydrophobic polysulfone nanofiber membrane in a mixture containing hydrophilic modified monomers and photoinitiators, it is then rinsed and irradiated with ultraviolet light in sequence to obtain the Janus nanofiber membrane based on polysulfone material.

[0031] Unless otherwise specified, all materials and equipment used in this invention are commercially available products in the field.

[0032] This invention involves coaxial electrospinning of a polysulfone solution and a hybrid modification solution, followed by hot pressing and hydrolysis to obtain a superhydrophobic polysulfone nanofiber membrane; the hybrid modification solution contains tetraethyl orthosilicate and a fluorosilane coupling agent.

[0033] In this invention, the polysulfone in the polysulfone solution preferably includes one or more of bisphenol A type polysulfone, polyether sulfone, and polyphenylene sulfone.

[0034] In this invention, the mass fraction of polysulfone in the polysulfone solution is preferably 5-20%, more preferably 8-12%.

[0035] In this invention, the solvent of the polysulfone solution is preferably a mixture of a nitrogen-containing organic solvent and tetrahydrofuran (THF), wherein the volume ratio of the nitrogen-containing organic solvent to tetrahydrofuran in the mixture is preferably 1:1, and the nitrogen-containing organic solvent preferably includes one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), and N-methylpyrrolidone (NMP).

[0036] In this invention, the mass ratio of tetraethyl orthosilicate to fluorosilane coupling agent in the hybrid modified solution is preferably 0.1 to 10:1, more preferably 1 to 6:1, and even more preferably 5:1; the tetraethyl orthosilicate forms modified SiO2 nanoparticles, which together with the nanofibers constitute a nanofiber membrane; the fluorosilane coupling agent can reduce surface energy.

[0037] In this invention, the sum of the mass fractions of tetraethyl orthosilicate and fluorosilane coupling agent in the hybrid modified solution is preferably 2-10%, more preferably 5-8%.

[0038] In this invention, the solvent of the hybrid modified solution is preferably a mixture of tetrahydrofuran and anhydrous ethanol, and the volume ratio of tetrahydrofuran to anhydrous ethanol in the mixture is preferably 1:1. During the phase transformation process of solvent evaporation, the hybrid modified solution forms a hydrophobic nanostructure on the membrane surface, thereby increasing the hydrophobicity of the membrane.

[0039] In this invention, the volume ratio of the polysulfone solution and the hybrid modified solution during coaxial electrospinning is preferably 1:1.

[0040] In this invention, the conditions for coaxial electrospinning include: a voltage preferably of 10-30 kV, more preferably 22-25 kV; an injection rate preferably of 0.0001-0.01 mm / s, more preferably 0.0005 mm / s; and a roller speed preferably of 100-500 rpm, more preferably 250-400 rpm.

[0041] In this invention, the coaxial electrospinning time is preferably 8 to 10 hours.

[0042] In this invention, the temperature of the hot pressing is preferably 80-120°C, more preferably 100°C; the time is preferably 0.5-3h, more preferably 1-2h; the hot pressing can enhance the bonding force between fibers.

[0043] In this invention, the hydrolysis temperature is preferably 5-60°C, more preferably 30°C; the time is preferably 0.5-3h, more preferably 1-2h; the hydrolysis is preferably carried out in hydrochloric acid, the concentration of which is preferably 0.1mol / L; and the tetraethyl orthosilicate and fluorosilane coupling agent undergo hybrid crosslinking during the hydrolysis process.

[0044] In this invention, the thickness of the superhydrophobic polysulfone nanofiber membrane is preferably 20-200 μm, more preferably 150 μm.

[0045] After obtaining the superhydrophobic polysulfone nanofiber membrane, the present invention immerses any side surface of the superhydrophobic polysulfone nanofiber membrane in a mixture containing a hydrophilic modified monomer and a photoinitiator, and then rinses and irradiates it with ultraviolet light in sequence to obtain the Janus nanofiber membrane based on polysulfone material.

[0046] In this invention, the hydrophilic modifying monomer preferably includes one or more of sodium acrylate, acrylamide, sodium p-styrene sulfonate and acrylic acid, and the hydrophilic modifying monomer is a water-soluble monomer.

[0047] In this invention, the photoinitiator preferably includes 2,4,6-trimethylbenzoyl-diphenylphosphine oxide or benzophenone.

[0048] In this invention, the mass ratio of the hydrophilic modified monomer to the photoinitiator in the mixture containing the hydrophilic modified monomer and the photoinitiator is preferably 5 to 100:1, more preferably 10:1.

[0049] In this invention, the sum of the mass fractions of the hydrophilic modified monomer and the photoinitiator in the mixture containing the hydrophilic modified monomer and the photoinitiator is preferably 2 to 15%, more preferably 5 to 10%.

[0050] In this invention, the solvent of the mixture containing the hydrophilic modified monomer and the photoinitiator is preferably anhydrous ethanol.

[0051] In this invention, the soaking time is preferably 0.5 to 2 hours, more preferably 1 to 1.5 hours.

[0052] In this invention, the rinsing agent is preferably water.

[0053] In this invention, the wavelength of the ultraviolet light used for ultraviolet irradiation is preferably 40-400 nm, more preferably 200 nm; the irradiation time is preferably 20-200 min, more preferably 30 min; and the ultraviolet light initiates a polymerization reaction of the hydrophilic monomers during the ultraviolet irradiation process.

[0054] In this invention, any side surface of the superhydrophobic polysulfone nanofiber membrane is immersed in a mixture containing a hydrophilic modified monomer and a photoinitiator, and then rinsed and irradiated with ultraviolet light in sequence to form an ultrathin hydrophilic layer on the surface of the superhydrophobic polysulfone nanofiber membrane. The thickness of the ultrathin hydrophilic layer is preferably 10-200 nm.

[0055] The present invention also provides a Janus nanofiber membrane based on polysulfone material obtained by the preparation method described above. The Janus nanofiber membrane includes a superhydrophobic polysulfone nanofiber membrane and a hydrophilic layer, wherein the hydrophilic layer is loaded on any side surface of the superhydrophobic polysulfone nanofiber membrane.

[0056] The present invention also provides the application of the above-mentioned Janus nanofiber membrane based on polysulfone material in oil-water separation.

[0057] In this invention, the oil-water mixture preferably comprises n-hexane / water, n-octane / water, or soybean oil / water, and the oil-water mixture is preferably a water-in-oil emulsion.

[0058] The Janus nanofiber membrane prepared in this embodiment of the invention exhibits a permeability greater than 25000 L·m⁻² to various water-in-oil emulsions. -2 ·h -1 ·bar -1The flux reduction rate of the n-octane-in-water emulsion was less than 8% after 5 hours, the flux recovery rate was more than 95%, the irreversible fouling rate was less than 3%, the flux reduction rate after 30 days was less than 10%, the cleaning cycle was more than 7 days, and the strength was more than 25 MPa. It has application potential in oil refining.

[0059] To further illustrate the present invention, the Janus nanofiber membrane based on polysulfone material, its preparation method, and its application are described in detail below with reference to the accompanying drawings and embodiments. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0060] Example 1

[0061] A method for preparing a Janus oil-water refining membrane based on polysulfone material includes the following steps:

[0062] Step 1: Preparation of hybrid polysulfone nanofiber-based membranes:

[0063] Polyethersulfone (polysulfone) was dissolved in a solution with a DMF / THF volume ratio of 1:1 to obtain solution A, with a polyethersulfone mass fraction of 12%.

[0064] Tetraethyl orthosilicate and fluorosilane coupling agent were dissolved in a solution with a THF / anhydrous ethanol volume ratio of 1:1 at a mass ratio of 5:1 to obtain solution B, where the sum of the mass fractions of tetraethyl orthosilicate and fluorosilane coupling agent was 5%.

[0065] Solution A and solution B (volume ratio of solution A to solution B is 1:1) were coaxially electrospun. The electrospinning voltage was 22kV, the injection rate was 0.0005mm / s, the roller speed was 250rpm, and the coaxial electrospinning time was 10h.

[0066] The nanofibers obtained by coaxial electrospinning were subjected to hot pressing treatment, followed by hydrolysis treatment in 0.1 mol / L hydrochloric acid for 0.5 h. The hot pressing temperature was 100 ℃, the hot pressing time was 0.5 h, and the hydrolysis temperature was 30 ℃, to obtain a superhydrophobic polysulfone nanofiber membrane (hybrid polysulfone nanofiber base membrane).

[0067] Step 2: Preparation of the ultrathin hydrophilic layer:

[0068] Sodium acrylate (hydrophilic modified monomer) and benzophenone (photoinitiator) were dissolved in anhydrous ethanol to obtain solution C. The mass ratio of sodium acrylate to photoinitiator was 10:1, and the sum of the mass fractions of sodium acrylate and photoinitiator was 5%.

[0069] One side surface of the superhydrophobic polysulfone nanofiber membrane prepared in step one was immersed in solution C for 0.5 h. After removal, the surface was rinsed with water for 1 min and then subjected to ultraviolet irradiation with a wavelength of 200 nm for 30 min to obtain a Janus nanofiber membrane (polyethersulfone Janus oil-water refined membrane) based on polysulfone material, with a membrane thickness of 150 μm and a pore size of 0.5 μm.

[0070] Figure 1 The image shows the microstructure of the polyethersulfone Janus nanofiber membrane prepared in Example 1. It can be seen that the Janus nanofiber membrane is composed of nanoparticles (modified SiO2) and nanofibers, with obvious micro-nano structure, which endows the separation membrane with excellent separation performance.

[0071] Example 2

[0072] The difference between Example 2 and Example 1 is that: in step one, polysulfone is replaced with polyphenylene sulfone, with a mass fraction of 12%; the mass ratio of tetraethyl orthosilicate to fluorosilane coupling agent is 6:1, and the sum of their mass fractions is 8%; the remaining steps are the same as in Example 1.

[0073] Example 3

[0074] The difference between Example 3 and Example 1 is that the hydrophilic modified monomer in step two is replaced with sodium p-styrene sulfonate, with a mass ratio of 10:1 to the photoinitiator, and the sum of their mass fractions is 5%; the remaining steps are the same as in Example 1.

[0075] Comparative Example 1

[0076] Commercial PTFE hydrophobic filter membrane with an average pore size of 0.22 μm is used.

[0077] Comparative Example 2

[0078] The difference between Comparative Example 2 and Example 1 is that tetraethyl orthosilicate and fluorosilane coupling agent are not added in step one.

[0079] Comparative Example 3

[0080] The difference between Comparative Example 3 and Example 1 is that step two, the preparation of the ultrathin hydrophilic layer, is not performed.

[0081] Comparative Example 4

[0082] The difference between Comparative Example 4 and Example 1 is that the polysulfone in step one is replaced with polyvinylidene fluoride.

[0083] The membranes of Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests, and the results are shown in Table 1.

[0084] Table 1. Performance data of the membranes in Examples 1-3 and Comparative Examples 1-4.

[0085]

[0086] As can be seen from Table 1, the Janus nanofiber membrane prepared in the embodiments of the present invention has excellent oil-water separation performance. The soybean oil / water flux is more than 100 times that of the commercial PTFE hydrophobic filter membrane, and the dehydration rate is high. In contrast, the dehydration rate of the membranes without fluorination treatment and hydrophilic modification is significantly lower than that of the embodiments. The membrane prepared using polyvinylidene fluoride as the main material has significantly lower strength than the polysulfone Janus nanofiber membrane of the embodiments.

[0087] The Janus nanofiber membrane prepared in this embodiment of the invention exhibits a permeability greater than 25000 L·m⁻² to various water-in-oil emulsions. -2 ·h -1 ·bar -1 The flux reduction rate of the n-octane-in-water emulsion was less than 8% after 5 hours, the flux recovery rate was more than 95%, the irreversible fouling rate was less than 3%, the flux reduction rate after 30 days was less than 10%, the cleaning cycle was more than 7 days, and the strength was more than 25 MPa. It has application potential in oil refining.

[0088] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a Janus nanofiber membrane based on a polysulfone material, characterized by, The method comprises the following steps: After coaxial electrospinning of a polysulfone solution and a hybrid modification solution, heat pressing and hydrolysis are sequentially performed to obtain a super-hydrophobic polysulfone nanofiber membrane; the hybrid modification solution contains tetraethyl orthosilicate and a fluorosilane coupling agent, and the solvent of the hybrid modification solution is a mixture of tetrahydrofuran and anhydrous ethanol; the solvent of the polysulfone solution is a mixture of a nitrogen-containing organic solvent and tetrahydrofuran; After immersing any one side surface of the super-hydrophobic polysulfone nanofiber membrane in a mixture containing a hydrophilic modification monomer and a photoinitiator, rinsing and ultraviolet irradiation are sequentially performed to obtain the Janus nanofiber membrane based on the polysulfone material.

2. The production method according to claim 1, characterized by, The mass fraction of the polysulfone in the polysulfone solution is 5-20%.

3. The production method according to claim 1 or 2, characterized by, The nitrogen-containing organic solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.

4. The production method according to claim 1, characterized by, The mass ratio of the tetraethyl orthosilicate to the fluorosilane coupling agent in the hybrid modification solution is 0.1-10:

1.

5. The production method according to claim 1 or 4, characterized by, The sum of the mass fractions of the tetraethyl orthosilicate and the fluorosilane coupling agent in the hybrid modification solution is 2-10%.

6. The method of claim 1, wherein, The conditions of the coaxial electrospinning include a voltage of 10-30 kV, an injection rate of 0.0001-0.01 mm / s and a drum rotation speed of 100-500 rpm.

7. The preparation method according to claim 1, characterized in that, The hydrophilic modification monomer includes one or more of sodium acrylate, acrylamide, sodium p-styrenesulfonate and acrylic acid.

8. The Janus nanofiber membrane based on a polysulfone material obtained by the production method according to any one of claims 1 to 7, characterized in that, The Janus nanofiber membrane includes a super-hydrophobic polysulfone nanofiber membrane and a hydrophilic layer, and the hydrophilic layer is loaded on any one side surface of the super-hydrophobic polysulfone nanofiber membrane.

9. Application of the Janus nanofiber membrane based on the polysulfone material in claim 8 to oil-water separation.

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