An asymmetric inverse opal-like structure microfiltration membrane and a preparation method thereof
By preparing asymmetric inverse opal-like microfiltration membranes, the contradiction between pore size uniformity and permeability of microfiltration membranes was resolved, improving the porosity and permeability of the microfiltration membranes, making them suitable for water treatment and other fields.
Patent Information
- Application Number
- CN202310733536.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-20
- Publication Date
- 2025-11-25
- Estimated Expiration
- 2043-06-20
AI Technical Summary
Existing microfiltration membranes present a contradiction between pore size uniformity and permeability in terms of structure and performance, making it difficult to achieve both high efficiency retention and good permeability simultaneously, especially in water treatment applications.
Using SiO2 microspheres as templates, an asymmetric inverse opal-like structure microfiltration membrane was prepared by organic solvent treatment and hydrofluoric acid etching, forming a microfiltration membrane with an asymmetric structure, wherein the lower layer is an ordered inverse opal-like structure and the upper layer is a disordered structure with three-dimensional through pores.
It achieves uniform pore size distribution while improving membrane porosity and permeability, enhancing the separation performance of microfiltration membranes, and showing remarkable effects, especially in water treatment.
Smart Images
Figure CN116603402B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of novel separation membrane materials, and in particular to an asymmetric inverse opal-like microfiltration membrane and its preparation method. Background Technology
[0002] Wastewater treatment is a current research hotspot. Membrane separation technology has attracted much attention due to its advantages such as environmental friendliness, low energy consumption, high separation accuracy, and ease of operation. Among them, microfiltration membranes have excellent solid-liquid separation performance and are widely used in food processing (Gan, Howell et al. 2001), biomedicine (van Reis and Zydney 2007), and industrial production (Leiviskä, Rämö et al. 2009). However, microfiltration membranes still face many challenges in terms of structure, performance, and manufacturing.
[0003] The separation performance of microfiltration membranes depends on characteristics such as pore size distribution, porosity, and pore structure. Microfiltration membranes with uniformly distributed pore structures can allow particles of specific sizes to pass through while achieving high-efficiency retention of target substances and maintaining good permeability. Brans et al. (2006) prepared filter membranes with controllable and regularly distributed pore structures, exhibiting good permeability, retention, and antifouling properties. Therefore, the preparation of microfiltration membranes with highly ordered structures has great potential in improving separation membrane performance and has attracted the attention of scholars worldwide.
[0004] In recent years, various methods for preparing porous membranes have been developed, such as the template method (Pietsch, Gindy et al. 2009, Xu, Sun et al. 2015), the phase inversion method (Luo, Young et al. 2003, Yin, Goldovsky et al. 2013), and the breath mapping method (Bai, Du et al. 2013). Inverse opal (IO) is a typical photonic crystal, exhibiting a highly ordered, three-dimensionally interconnected microporous structure, and has been widely used in medicine (Xia, Shang et al. 2020, Wang, Sun et al. 2022) and photocatalysis (Bakos, Karajz et al. 2020, Chen, Wang et al. 2021). Some studies have prepared microfiltration membranes with IO-like structures using a template method (He, Fan et al. 2023). First, polymeric colloidal microspheres are regularly arranged into crystals. Then, by sacrificing the colloidal microspheres as a template, an IO-like structure is obtained, resulting in a microfiltration membrane with a controllable microstructure and uniform pore size, which is beneficial for high-precision separation. However, the membranes prepared by this method have a uniform overall pore size. To ensure high retention performance, the pore size is generally small, inevitably sacrificing some permeability, and is often unsuitable for use as microfiltration membranes in water treatment (Yu, Luo et al. 2018). Summary of the Invention
[0005] To address the aforementioned technical problems, this invention provides an asymmetric inverse opal-like microfiltration membrane and its preparation method. The microfiltration membrane not only possesses Io-like structural characteristics, such as uniform pore size distribution which facilitates precise separation, but also has the advantages of high porosity and good permeability due to its three-dimensional through-pore structure.
[0006] To achieve the above objectives, the present invention is implemented according to the following technical solution:
[0007] The first objective of this invention is to provide a method for preparing an asymmetric, anti-opal-structured microfiltration membrane, comprising the following steps:
[0008] S1. Disperse SiO2 microspheres with an organic solvent to obtain a SiO2 microsphere dispersion. Add 8wt%-15wt% of polymer to the SiO2 microsphere dispersion and mix evenly to obtain a casting solution. Cast the casting solution onto a glass plate and cure it in an oven at a constant temperature of 80℃ until the organic solvent evaporates to obtain a polymer / SiO2 microsphere composite film.
[0009] S2. Fix the glass plate with the polymer / SiO2 microsphere composite film facing upward in the mold, and treat the upper surface of the polymer / SiO2 microsphere composite film with organic solvent for 15 s-180 s to obtain an asymmetric polymer / SiO2 microsphere composite film.
[0010] S3. Immerse the asymmetric polymer / SiO2 microsphere composite membrane in hydrofluoric acid solution to remove the SiO2 microspheres, and obtain an asymmetric inverse opal structure microfiltration membrane.
[0011] Furthermore, the organic solvent in steps S1 and S2 is one of N,N-dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide.
[0012] Furthermore, the particle size of the SiO2 microspheres in step S1 is between 180 nm and 800 nm.
[0013] Furthermore, the polymer in step S1 is one of polyvinylidene fluoride, polyethersulfone, and polysulfone.
[0014] Furthermore, the concentration of hydrofluoric acid in step S3 is 2 wt%-10 wt%, and the hydrofluoric acid treatment time is 2 h-10 h.
[0015] The second objective of this invention is to provide an asymmetric inverse opal structure microfiltration membrane prepared by the above method, wherein the lower layer of the asymmetric inverse opal structure microfiltration membrane is an ordered layer with an inverse opal structure, and the upper layer is a disordered layer with a three-dimensional through-pore structure.
[0016] Compared with existing technologies, the present invention has a simple preparation process, short manufacturing cycle, and low energy consumption. It prepares an inverse opal-structured microfiltration membrane by sacrificing SiO2 microsphere templates, and further treats one side of the opal-structured membrane surface with organic solvents to form a one-sided disordered structure, thus preparing an asymmetric inverse opal-structured microfiltration membrane. The microfiltration membrane prepared in this way has both an ordered layer structure with uniform pore size distribution and high retention capacity, and a disordered layer with high porosity and high permeability, avoiding the permeability of the inverse opal-structured sacrificial membrane, and has good application prospects in the field of solid-liquid separation. Attached Figure Description
[0017] Figure 1 The cross-sectional morphology of the N,N-dimethylformamide-treated membrane obtained in Example 1 after 30 s is shown.
[0018] Figure 2 The cross-sectional morphology of the N,N-dimethylformamide-treated membrane obtained in Example 2 after 60 s is shown.
[0019] Figure 3 The cross-sectional morphology of the N,N-dimethylformamide-treated membrane obtained in Example 3 after 90 s is shown.
[0020] Figure 4 The cross-sectional morphology of the N,N-dimethylformamide-treated membrane obtained in Example 4 after 150 s. Detailed Implementation
[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.
[0022] Example 1
[0023] (1) 20 wt% of SiO2 microspheres with a diameter of 494 nm were dispersed with N,N-dimethylformamide to obtain a SiO2 microsphere dispersion. 10 wt% of polyvinylidene fluoride was added to the SiO2 microsphere dispersion to obtain a casting solution. The casting solution was poured onto the surface of a glass plate and cured in an 80°C constant temperature oven until the organic solvent evaporated to obtain a polymer / SiO2 microsphere composite film.
[0024] (2) Fix the glass plate with the polymer / SiO2 microsphere composite film facing upward in the mold, and treat the upper surface of the polymer / SiO2 microsphere composite film with N,N-dimethylformamide for 30 s to obtain an asymmetric polymer / SiO2 microsphere composite film.
[0025] (3) The asymmetric polymer / SiO2 microsphere composite membrane was immersed in 4 wt% hydrofluoric acid solution for 4 h to remove the SiO2 microspheres and obtain an asymmetric inverse opal structure microfiltration membrane.
[0026] Depend on Figure 1 It can be seen that the cross-section of the microfiltration membrane exhibits a distinct asymmetric structure. The lower layer of the asymmetric inverse opal microfiltration membrane is an ordered layer with an inverse opal structure, while the upper layer is a disordered layer with a three-dimensional through-pore structure.
[0027] The separation performance of the microfiltration membrane was tested using dead-end filtration. At a pressure of 0.1 MPa, the pure water flux was 1452 L / m³. 2 h; The feed solution is an aqueous suspension of SiO2 microspheres (size distribution in 180-494 nm), with a 100% rejection rate for SiO2 microspheres.
[0028] Example 2
[0029] (1) 20 wt% of SiO2 microspheres with a diameter of 494 nm were dispersed with N,N-dimethylformamide to obtain a SiO2 microsphere dispersion. 10 wt% of polyvinylidene fluoride was added to the SiO2 microsphere dispersion to obtain a casting solution. The casting solution was poured onto the surface of a glass plate and cured in an 80°C constant temperature oven until the organic solvent evaporated to obtain a polymer / SiO2 microsphere composite film.
[0030] (2) Fix the glass plate with the polymer / SiO2 microsphere composite film facing upward in the mold, and treat the upper surface of the polymer / SiO2 microsphere composite film with N,N-dimethylformamide for 60 s to obtain an asymmetric polymer / SiO2 microsphere composite film;
[0031] (3) The asymmetric polymer / SiO2 microsphere composite membrane was immersed in a 4 wt% hydrofluoric acid solution for 4 h to remove the SiO2 microspheres, thus obtaining an asymmetric inverse opal-like microfiltration membrane. The treatment time of the membrane surface with N,N-dimethylformamide was changed to 60 s. Figure 2 It can be seen that, compared Figure 1 The disordered layer structure of the microfiltration membrane becomes thicker, while the ordered layer structure becomes thinner.
[0032] Example 3
[0033] (1) 20 wt% of SiO2 microspheres with a diameter of 494 nm were dispersed with N,N-dimethylformamide to obtain a SiO2 microsphere dispersion. 10 wt% of polyvinylidene fluoride was added to the SiO2 microsphere dispersion to obtain a casting solution. The casting solution was poured onto the surface of a glass plate and cured in an 80°C constant temperature oven until the organic solvent evaporated to obtain a polymer / SiO2 microsphere composite film.
[0034] (2) Fix the glass plate with the polymer / SiO2 microsphere composite film facing upward in the mold, and treat the upper surface of the polymer / SiO2 microsphere composite film with N,N-dimethylformamide for 90 s to obtain an asymmetric polymer / SiO2 microsphere composite film.
[0035] (3) The asymmetric polymer / SiO2 microsphere composite membrane was immersed in a 4 wt% hydrofluoric acid solution for 4 h to remove the SiO2 microspheres, thus obtaining an asymmetric inverse opal-like microfiltration membrane. The treatment time of the membrane surface with N,N-dimethylformamide was changed to 90 s. Figure 3 It can be seen that, compared Figure 1 The disordered layer structure of the microfiltration membrane becomes thicker, while the ordered layer structure becomes thinner.
[0036] Example 4
[0037] (1) 20 wt% of SiO2 microspheres with a diameter of 494 nm were dispersed with N,N-dimethylformamide to obtain a SiO2 microsphere dispersion. 10 wt% of polyvinylidene fluoride was added to the SiO2 microsphere dispersion to obtain a casting solution. The casting solution was poured onto the surface of a glass plate and cured in an 80°C constant temperature oven until the organic solvent evaporated to obtain a polymer / SiO2 microsphere composite film.
[0038] (2) Fix the glass plate with the polymer / SiO2 microsphere composite film facing upward in the mold, and treat the upper surface of the polymer / SiO2 microsphere composite film with N,N-dimethylformamide for 150 s to obtain an asymmetric polymer / SiO2 microsphere composite film.
[0039] (3) The asymmetric polymer / SiO2 microsphere composite membrane was immersed in a 4 wt% hydrofluoric acid solution for 4 h to remove the SiO2 microspheres, thus obtaining an asymmetric inverse opal-like microfiltration membrane. The treatment time of the membrane surface with N,N-dimethylformamide was changed to 150 s. Figure 4 It can be seen that, compared Figure 1 The disordered layer structure of the microfiltration membrane becomes thicker, while the ordered layer structure becomes thinner.
[0040] Example 5
[0041] (1) 20 wt% of SiO2 microspheres with a diameter of 180 nm were dispersed with N,N-dimethylformamide to obtain a SiO2 microsphere dispersion. 10 wt% of polyvinylidene fluoride was added to the SiO2 microsphere dispersion to prepare a casting solution. The casting solution was cast onto a glass plate and cured in an 80°C constant temperature oven until the organic solvent evaporated to prepare a polymer / SiO2 microsphere composite film.
[0042] (2) Fix the glass plate with the polymer / SiO2 microsphere composite film facing upward in the mold, and treat the upper surface of the polymer / SiO2 microsphere composite film with N,N-dimethylformamide for 90 s to obtain an asymmetric polymer / SiO2 microsphere composite film.
[0043] (3) The asymmetric polymer / SiO2 microsphere composite membrane was immersed in 4 wt% hydrofluoric acid solution for 4 h to remove the SiO2 microspheres and obtain an asymmetric inverse opal structure microfiltration membrane.
[0044] Example 6
[0045] (1) 20 wt% of SiO2 microspheres with a diameter of 282 nm were dispersed with N,N-dimethylformamide to obtain a SiO2 microsphere dispersion. 10 wt% of polyvinylidene fluoride was added to the SiO2 microsphere dispersion to prepare a casting solution. The casting solution was cast onto a glass plate and cured in an 80°C constant temperature oven until the organic solvent evaporated to prepare a polymer / SiO2 microsphere composite film.
[0046] (2) Fix the glass plate with the polymer / SiO2 microsphere composite film facing upward in the mold, and treat the upper surface of the polymer / SiO2 microsphere composite film with N,N-dimethylformamide for 90 s to obtain an asymmetric polymer / SiO2 microsphere composite film.
[0047] (3) The asymmetric polymer / SiO2 microsphere composite membrane was immersed in 4 wt% hydrofluoric acid solution for 4 h to remove the SiO2 microspheres and obtain an asymmetric inverse opal structure microfiltration membrane.
[0048] Example 7
[0049] (1) 20 wt% of SiO2 microspheres with a diameter of 340 nm were dispersed with N,N-dimethylformamide to obtain a SiO2 microsphere dispersion. 10 wt% of polyvinylidene fluoride was added to the SiO2 microsphere dispersion to prepare a casting solution. The casting solution was cast onto a glass plate and cured in an 80°C constant temperature oven until the organic solvent evaporated to prepare a polymer / SiO2 microsphere composite film.
[0050] (2) Fix the glass plate with the polymer / SiO2 microsphere composite film facing upward in the mold, and treat the upper surface of the polymer / SiO2 microsphere composite film with N,N-dimethylformamide for 90 s to obtain an asymmetric polymer / SiO2 microsphere composite film.
[0051] (3) The asymmetric polymer / SiO2 microsphere composite membrane was immersed in 4 wt% hydrofluoric acid solution for 4 h to remove the SiO2 microspheres and obtain an asymmetric inverse opal structure microfiltration membrane.
[0052] The porosity of the asymmetric inverse opal structure microfiltration membranes prepared in Examples 1-7 were tested respectively, and the separation performance of the asymmetric inverse opal structure microfiltration membranes prepared in Examples 1-7 was tested using dead-end filtration. The pure water flux and the SiO2 microsphere rejection rate were tested at 0.1 MPa pressure. For comparison, the inverse opal structure microfiltration membrane prepared by He et al. (2023) using the sacrificial template method has a uniformly distributed pore structure and also exhibits good rejection performance for SiO2 microspheres, with a pure water flux reaching a maximum of 1146 L / m³. 2 h; Wang et al. (2010) designed a reverse colloidal crystal microfiltration membrane with uniform pore size, which showed good flow splitting performance, but the actual porosity was only 50-60%. The test results are shown in Table 1.
[0053] Table 1
[0054]
[0055] As shown in Table 1, uniform pore size is one of the ideal characteristics of microfiltration membranes, and optimizing membrane preparation methods is crucial for improving the performance of microfiltration membranes (such as porosity and water flux).
[0056] In summary, Examples 1-4 of this invention, by treating one side of the membrane surface with N,N-dimethylformamide, were able to prepare microfiltration membranes with an asymmetric inverse opal-like structure. Compared with microfiltration membranes with uniform pore size, this invention significantly increases the membrane porosity, improves the pure water flux of the microfiltration membrane, and has good retention performance.
[0057] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.
Claims
1. A method for preparing an asymmetric inverse opal microfiltration membrane, characterized by, The method comprises the following steps: S1, dispersing SiO2 microspheres with an organic solvent to obtain a SiO2 microsphere dispersion liquid, adding 8 wt%-15 wt% of a polymer to the SiO2 microsphere dispersion liquid, and uniformly mixing to obtain a casting solution; pouring the casting solution on a glass plate, and curing in an 80°C constant temperature oven until the organic solvent volatilizes to obtain a polymer / SiO2 microsphere composite membrane; the organic solvent is one of N,N-dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide; the particle size of the SiO2 microspheres is between 180 nm and 800 nm; S2, fixing the glass plate with the polymer / SiO2 microsphere composite membrane upwards in a mold, treating the upper surface of the polymer / SiO2 microsphere composite membrane with an organic solvent for 15 s-180 s to obtain an asymmetric polymer / SiO2 microsphere composite membrane; the organic solvent is one of N,N-dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide; the polymer is one of polyvinylidene fluoride, polyether sulfone, and polysulfone; S3, immersing the asymmetric polymer / SiO2 microsphere composite membrane in a hydrofluoric acid solution to remove the SiO2 microspheres to obtain an asymmetric inverse opal-like structure microfiltration membrane.
2. The method of claim 1, wherein the asymmetric inverse opal microfiltration membrane is prepared by the steps of: The concentration of the hydrofluoric acid in the step S3 is 2 wt%-10 wt%, and the hydrofluoric acid treatment time is 2 h-10 h.
3. An asymmetric inverse opal microfiltration membrane prepared by the method of claim 1 or 2, wherein: The lower layer of the asymmetric inverse opal-like structure microfiltration membrane is an ordered layer with an inverse opal-like structure, and the upper layer is a disordered layer with a three-dimensional through-hole structure.