Anti-wetting Janus membrane as well as preparation method and application thereof
By interfacial polymerization modification of the surface of a hydrophobic microporous membrane to form polydopamine and polyamide layers, an anti-wetting Janus membrane was prepared, which solved the wetting problem of PVDF membranes when treating wastewater containing surfactants and maintained the desalination performance and flux of the membrane.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HENAN ACADEMY OF SCI CHEM RES INST CO LTD
- Filing Date
- 2024-11-11
- Publication Date
- 2026-05-12
AI Technical Summary
Existing membrane materials, such as PVDF membranes, are easily fouled by pollutants when treating wastewater containing surfactants, leading to wetting and loss of desalination capacity.
An anti-wetting Janus membrane was prepared by performing a first interfacial polymerization modification on the surface of a hydrophobic microporous membrane to form a polydopamine layer, followed by a second interfacial polymerization modification to form a dense polyamide hydrophilic layer.
The prepared anti-wetting Janus membrane exhibited good anti-wetting performance when treating wastewater containing surfactants, with no significant loss in membrane flux and maintaining good desalination capacity.
Smart Images
Figure CN122006493A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of membrane separation technology, and in particular to an anti-wetting Janus membrane, its preparation method, and its application. Background Technology
[0002] Membrane distillation (MD), as a novel desalination technology, has broad application prospects in the reduction and zero discharge of high-salinity wastewater. However, in practical applications, common membrane materials such as PVDF membranes are easily fouled by pollutants in the water, especially low surface energy pollutants (such as surfactants), which can easily cause membrane surface wetting and lead to the loss of desalination capacity. Summary of the Invention
[0003] In view of this, the purpose of this invention is to provide an anti-wetting Janus membrane, its preparation method, and its application. The anti-wetting Janus membrane prepared by this invention has excellent anti-fouling wettability, exhibits good anti-wetting performance when treating wastewater containing surfactants by membrane distillation, and the membrane flux does not show a significant loss compared to the original membrane.
[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0005] This invention provides a method for preparing an anti-wetting Janus membrane, comprising the following steps:
[0006] A hydrophobic microporous membrane was floated on the surface of a dopamine solution for first-interfacial polymerization modification to obtain a polydopamine-modified porous membrane.
[0007] The polydopamine-modified porous membrane was immersed in a pyromellitic methyl chloride solution for a second interfacial polymerization modification to obtain the anti-wetting Janus membrane.
[0008] Preferably, the hydrophobic microporous membrane is a PVDF membrane, and the pore size of the PVDF membrane is 0.1 to 0.4 μm.
[0009] Preferably, the dopamine solution is prepared by mixing dopamine hydrochloride, water, and ammonia.
[0010] Preferably, the concentration of dopamine hydrochloride in the dopamine solution is 0.1–2 g / L.
[0011] Preferably, the polymerization modification time of the first interface is 1 to 24 hours.
[0012] Preferably, the pyromellitic chloride solution is prepared by mixing pyromellitic chloride and an organic solvent, and the mass fraction of pyromellitic chloride in the pyromellitic chloride solution is 1-10%.
[0013] Preferably, the time for the second interface polymerization modification is 5s to 30min.
[0014] The present invention provides an anti-wetting Janus membrane prepared by the preparation method described above. The anti-wetting Janus membrane includes a hydrophobic porous substrate and a hydrophilic layer grafted onto one side surface of the hydrophobic porous substrate. The hydrophilic layer is a polyamide layer.
[0015] This invention provides the application of the anti-wetting Janus membrane described above in membrane distillation treatment of wastewater containing surfactants.
[0016] Preferably, the wastewater also includes salt.
[0017] This invention provides a method for preparing an anti-wetting Janus membrane, comprising the following steps: floating a hydrophobic microporous membrane on the surface of a dopamine solution for a first interfacial polymerization modification to obtain a polydopamine-modified porous membrane; immersing the polydopamine-modified porous membrane in a trimesoyl chloride solution for a second interfacial polymerization modification to obtain the anti-wetting Janus membrane. This invention first forms a strong adhesion layer on the surface of the hydrophobic microporous membrane by grafting a polydopamine layer onto the membrane surface; then, a dense polyamide hydrophilic surface layer is formed through interfacial polymerization of polydopamine and trimesoyl chloride. The anti-wetting Janus membrane prepared by this invention comprises a hydrophobic porous substrate and a hydrophilic layer (polyamide layer) grafted onto one side surface of the hydrophobic porous substrate. Because the surface hydrophilic layer is a dense hydrophilic film, organic molecules cannot penetrate the dense layer to contact the hydrophobic porous membrane, thus preventing the wetting of organic pollutants, especially surfactant molecules. At the same time, because the surface hydrophilic layer has good hydrophilicity, during membrane distillation treatment of wastewater, water will permeate through the hydrophilic layer and evaporate on the lower surface of the hydrophilic layer to form water vapor. Then, the water vapor passes through the hydrophobic porous membrane to achieve desalination and water purification. Compared with the unmodified hydrophobic porous membrane, the distance and resistance of water vapor transmission are not increased, so there is no significant loss in water flux.
[0018] The results of the examples show that the pure water flux of the anti-wetting Janus membrane prepared by the present invention is improved compared with the original membrane; when the membrane distillation treatment of wastewater containing surfactants is carried out, the anti-wetting Janus membrane exhibits good anti-wetting performance, and the flux of the membrane does not show a significant loss compared with the original membrane. Attached Figure Description
[0019] Figure 1 The image shown is a scanning electron microscope (SEM) image of the original PVDF film in the example.
[0020] Figure 2 Here is a cross-sectional scanning electron microscope image of the original PVDF film in the example;
[0021] Figure 3 This is a static water contact angle image of the original PVDF membrane in the embodiment;
[0022] Figure 4 The image shows a scanning electron microscope (SEM) image of the surface of the PA120-PVDF film obtained in Example 2.
[0023] Figure 5 This is a cross-sectional scanning electron microscope image of the PA120-PVDF film obtained in Example 2;
[0024] Figure 6 Images showing the static water contact angle of the PA120-PVDF membrane obtained in Example 2;
[0025] Figure 7 Pure water flux of the original PVDF membrane and the anti-wetting Janus membranes obtained in Examples 1-3;
[0026] Figure 8 Membrane distillation desalination performance of a pristine PVDF membrane for treating a 35 g / L NaCl solution containing the surfactant SDS;
[0027] Figure 9 The membrane distillation desalination performance of the PA120-PVDF membrane obtained in Example 2 for treating a 35 g / L NaCl solution containing the surfactant SDS is shown. Detailed Implementation
[0028] This invention provides a method for preparing an anti-wetting Janus membrane, comprising the following steps:
[0029] A hydrophobic microporous membrane was floated on the surface of a dopamine solution for first-interfacial polymerization modification to obtain a polydopamine-modified porous membrane.
[0030] The polydopamine-modified porous membrane was immersed in a pyromellitic methyl chloride solution for a second interfacial polymerization modification to obtain the anti-wetting Janus membrane.
[0031] Unless otherwise specified, all raw materials involved in this invention are commercially available products well known in the art.
[0032] In this invention, a hydrophobic microporous membrane is floated on the surface of a dopamine solution for first-interfacial polymerization modification to obtain a polydopamine-modified porous membrane.
[0033] In this invention, the hydrophobic microporous membrane is preferably a PVDF membrane, and the pore size of the PVDF membrane is preferably 0.1–0.4 μm. In this invention, the dopamine solution is preferably prepared by mixing dopamine hydrochloride, water, and ammonia, and the water is preferably deionized water. The preferred method for preparing the dopamine solution is to dissolve the dopamine hydrochloride in water to obtain an aqueous solution of dopamine hydrochloride; add ammonia to the aqueous solution of dopamine hydrochloride and stir to obtain the dopamine solution. In this invention, the concentration of dopamine hydrochloride in the dopamine solution is preferably 0.1–2 g / L, more preferably 1–2 g / L, and even more preferably 1.5–2 g / L; the mass fraction of the ammonia is preferably 10–25%, and the ratio of dopamine hydrochloride to ammonia is preferably 0.1 g: 100 μL.
[0034] In this invention, the preferred time for the first interfacial polymerization modification is 1–24 hours, more preferably 2–10 hours, and the first interfacial polymerization modification can be carried out at room temperature. In this invention, the first interfacial polymerization modification is a process of dopamine oxidative self-polymerization to form polydopamine. Polydopamine has very strong adhesive ability and can form a strong adhesion layer on the surface of a hydrophobic porous membrane, thereby facilitating the construction of a robust hydrophilic layer on the membrane surface. The ammonia water serves to assist the dopamine oxidative self-polymerization to form the adhesion layer.
[0035] After the first interfacial polymerization modification is completed, the resulting membrane material is preferably rinsed with deionized water and dried sequentially to obtain a polydopamine-modified porous membrane. In this invention, the drying temperature is preferably 60°C.
[0036] After obtaining the polydopamine-modified porous membrane, the present invention immerses the polydopamine-modified porous membrane in a pyromellitic chloride solution for a second interfacial polymerization modification to obtain the anti-wetting Janus membrane.
[0037] In this invention, the trimesoyl chloride solution is preferably a mixture of trimesoyl chloride (TMC) and an organic solvent, wherein the organic solvent is preferably n-hexane; the mass fraction of trimesoyl chloride in the trimesoyl chloride solution is preferably 1-10%, more preferably 1-5%.
[0038] In this invention, the preferred time for the second interfacial polymerization modification is 5s to 30min, which can be 60s, 120s, or 180s; the second interfacial polymerization modification can be carried out at room temperature. During the second interfacial polymerization modification process, polydopamine in the polydopamine-modified porous membrane undergoes interfacial polymerization with trimesoyl chloride to form a polyamide layer.
[0039] After the second interfacial polymerization modification is completed, the resulting membrane material is preferably washed and dried sequentially to obtain the anti-wetting Janus membrane. In this invention, the washing agent is preferably n-hexane; specifically, the resulting membrane material is transferred to n-hexane for washing. The purpose of washing is to remove unreacted trimesoyl chloride. In this invention, the drying is preferably oven drying.
[0040] The preparation method provided by this invention is simple, easy to operate, uses inexpensive and readily available modifiers, and has mild reaction conditions, making it suitable for large-scale production.
[0041] The present invention provides an anti-wetting Janus membrane prepared by the preparation method described above. The anti-wetting Janus membrane includes a hydrophobic porous substrate and a hydrophilic layer grafted onto one side surface of the hydrophobic porous substrate. The hydrophilic layer is a polyamide layer.
[0042] This invention provides the application of the anti-wetting Janus membrane described above in membrane distillation treatment of wastewater containing surfactants. In this invention, the concentration of the surfactant in the wastewater is preferably 0.1–0.4 mmol / L. In this invention, the wastewater also preferably includes salt, and the concentration of the salt is preferably 0–200 g / L. In this embodiment of the invention, the concentration of the salt in the wastewater is 35 g / L. In this embodiment of the invention, wastewater containing the surfactant sodium dodecyl sulfate (SDS) and the salt NaCl is used as an example. This invention does not impose special requirements on the method and conditions of the membrane distillation treatment; membrane distillation methods and conditions well known to those skilled in the art can be used.
[0043] In this invention, the anti-wetting Janus membrane has a porous hydrophobic substrate and a dense hydrophilic surface layer, and the dense hydrophilic layer on the membrane surface exhibits good hydrophilicity. When the anti-wetting Janus membrane is used for membrane distillation treatment of wastewater containing surfactants, it exhibits good anti-wetting performance, and the membrane flux does not show a significant loss compared to the original membrane.
[0044] To further illustrate the present invention, the anti-wetting Janus membrane, its preparation method, and its application provided by the present invention are described in detail below with reference to examples, but these should not be construed as limiting the scope of protection of the present invention.
[0045] In each embodiment, the PVDF membrane has a pore size of 0.22 μm and a thickness of 120 μm.
[0046] Example 1
[0047] The preparation steps of the anti-wetting Janus membrane are as follows:
[0048] Weigh 0.1 g of dopamine hydrochloride and dissolve it in 50 mL of deionized water. Add 100 μL of ammonia (25% by mass). After stirring, float the PVDF membrane on the surface of the solution for 2 h for modification. After the reaction, rinse with deionized water and dry in an oven at 60 °C. The modified membrane is a polydopamine-modified porous membrane, denoted as PDA-PVDF membrane.
[0049] The PDA-PVDF membrane was immersed in a hexane solution containing 1 wt% trimesoyl chloride (TMC) and reacted at room temperature for 60 s. The membrane was then transferred to hexane to remove unreacted TMC, dried in an oven, and stored. This is the anti-wetting Janus membrane, denoted as PA60-PVDF membrane.
[0050] Example 2
[0051] The preparation steps of the anti-wetting Janus membrane are as follows:
[0052] Weigh 0.1 g of dopamine hydrochloride and dissolve it in 50 mL of deionized water. Add 100 μL of ammonia (25% by mass). After stirring, float the PVDF membrane on the surface of the solution for 2 h for modification. After the reaction, rinse with deionized water and dry in an oven at 60 °C. The modified membrane is a polydopamine-modified porous membrane, denoted as PDA-PVDF membrane.
[0053] The PDA-PVDF membrane was immersed in a hexane solution containing 1 wt% TMC and reacted at room temperature for 120 s. The membrane was then transferred to hexane to remove unreacted TMC. After drying in an oven, it was stored and became the anti-wetting Janus membrane, denoted as PA120-PVDF membrane.
[0054] Example 3
[0055] The preparation steps of the anti-wetting Janus membrane are as follows:
[0056] Weigh 0.1 g of dopamine hydrochloride and dissolve it in 50 mL of deionized water. Add 100 μL of ammonia (25% by mass). After stirring, float the PVDF membrane on the surface of the solution for 2 h for modification. After the reaction, rinse with deionized water and dry in an oven at 60 °C. The modified membrane is a polydopamine-modified porous membrane, denoted as PDA-PVDF membrane.
[0057] The PDA-PVDF membrane was immersed in a hexane solution containing 1 wt% TMC and reacted at room temperature for 180 s. The membrane was then transferred to hexane to remove unreacted TMC. After drying in an oven, it was stored and became the anti-wetting Janus membrane, denoted as PA180-PVDF membrane.
[0058] Figure 1 These are scanning electron microscope (SEM) images of the surface of the PVDF film before modification (i.e., the original PVDF film). Figure 1As can be seen, the membrane surface has a smooth porous structure. Figure 2 Here are cross-sectional scanning electron microscope images of the PVDF film before modification. Figure 2 As can be seen, the membrane exhibits an irregular porous structure inside. Figure 3 The static water contact angle of the PVDF membrane before modification is 121°, indicating that the PVDF membrane surface has good hydrophobicity.
[0059] Figure 4 The image shows a scanning electron microscope (SEM) image of the surface of the PA120-PVDF film obtained in Example 2. Figure 4 It can be seen that the porous structure on the surface of the modified membrane is covered by a dense layer. Figure 5 This is a cross-sectional scanning electron microscope image of the PA120-PVDF film obtained in Example 2. Figure 5 It can be seen that there is a dense modified layer on the surface of the membrane. Figure 6 The static water contact angle of the PA120-PVDF membrane obtained in Example 2 is from... Figure 6 The modified membrane has a contact angle of 60°, indicating that the surface of the modified membrane has good hydrophilicity.
[0060] Membrane distillation experiment
[0061] The water flux and antiwetting properties of the original PVDF membrane and the antiwetting Janus membrane materials obtained in Examples 1, 2, and 3 were tested using pure water and a 35 g / L NaCl solution (containing 0.1, 0.2, 0.3, and 0.4 mmol / L sodium dodecyl sulfate surfactant (SDS)). The raw water temperature was 70 °C, the permeate temperature was 25 °C, the flow rate for both the raw water and permeate measurements was 14 L / h, and the effective membrane area was 15 square centimeters (membrane size 3 × 5 cm).
[0062] Figure 7 The pure water flux represents the original PVDF membrane and the anti-wetting Janus membranes obtained in Examples 1, 2, and 3. From... Figure 7 As can be seen from the results, the pure water flux of the antiwetting Janus membrane PA120-PVDF obtained in Example 2 is significantly improved compared to the original membrane, with an improvement of about 25%.
[0063] Figure 8 Membrane distillation desalination performance of a pristine PVDF membrane for treating a 35 g / L NaCl solution containing the surfactant SDS. Figure 8 As can be seen, when the SDS concentration increases to 0.3 mmol / L, the flux decreases sharply and the permeate conductivity increases rapidly, indicating that the membrane is wetted and loses its retention capacity.
[0064] Figure 9The membrane distillation desalination performance of the anti-wetting Janus membrane PA120-PVDF obtained in Example 2 was evaluated when treating a 35 g / L NaCl solution containing the surfactant SDS. From... Figure 9 As can be seen, the flux did not decrease sharply and the permeate-side conductivity did not increase significantly, indicating that the membrane obtained in Example 2 has excellent anti-wetting properties and desalination capabilities.
[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing an anti-wetting Janus membrane, characterized in that, Includes the following steps: A hydrophobic microporous membrane was floated on the surface of a dopamine solution for first-interfacial polymerization modification to obtain a polydopamine-modified porous membrane. The polydopamine-modified porous membrane was immersed in a pyromellitic methyl chloride solution for a second interfacial polymerization modification to obtain the anti-wetting Janus membrane.
2. The preparation method according to claim 1, characterized in that, The hydrophobic microporous membrane is a PVDF membrane with a pore size of 0.1–0.4 μm.
3. The preparation method according to claim 1, characterized in that, The dopamine solution is composed of dopamine hydrochloride, water, and ammonia.
4. The preparation method according to claim 3, characterized in that, The concentration of dopamine hydrochloride in the dopamine solution is 0.1–2 g / L.
5. The preparation method according to claim 1, 3, or 4, characterized in that, The time for the first interface aggregation modification is 1 to 24 hours.
6. The preparation method according to claim 1, characterized in that, The pyromellitic benzoyl chloride solution is prepared by mixing pyromellitic benzoyl chloride and an organic solvent, and the mass fraction of pyromellitic benzoyl chloride in the pyromellitic benzoyl chloride solution is 1-10%.
7. The preparation method according to claim 1 or 6, characterized in that, The time for the second interface polymerization modification is 5s to 30min.
8. The antiwetting Janus membrane prepared by the preparation method according to any one of claims 1 to 7, wherein the antiwetting Janus membrane comprises a hydrophobic porous substrate and a hydrophilic layer grafted onto one side surface of the hydrophobic porous substrate, wherein the hydrophilic layer is a polyamide layer.
9. The application of the anti-wetting Janus membrane of claim 8 in membrane distillation treatment of wastewater containing surfactants.
10. The application according to claim 9, characterized in that, The wastewater also contains salt.