A method for modulating ultrafiltration membrane performance by controlling the micellar transition of amphiphilic block copolymers
By controlling the micellar transition of amphiphilic block copolymers to regulate ultrafiltration membrane performance, the energy consumption and cost problems caused by high-temperature coagulation baths have been solved, thereby optimizing membrane performance and simplifying industrial production.
Patent Information
- Application Number
- CN202411147823.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-21
- Publication Date
- 2025-10-28
- Estimated Expiration
- 2044-08-21
AI Technical Summary
Existing technologies for preparing ultrafiltration membranes increase the pore size and permeability by raising the coagulation bath temperature, which leads to increased energy consumption and preparation costs, and also places high demands on equipment management.
Ultrafiltration membrane performance can be modulated by controlling the micellar transition of amphiphilic block copolymers, including changing the gel bath temperature, the ratio of hydrophilic to hydrophobic segments in the block copolymer, molecular weight and concentration, and avoiding the use of high-temperature coagulation baths, thereby optimizing membrane performance.
It optimizes membrane permeation performance at room temperature, reduces energy consumption and preparation costs, simplifies operation, and is suitable for industrial production.
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Figure CN118846831B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of membrane technology, and more specifically to a method for regulating the performance of ultrafiltration membranes by controlling the micelle transition of amphiphilic block copolymers. Background Technology
[0002] Ultrafiltration (UF) technology, as a leading membrane separation technology, has the characteristics of high efficiency, safety, and economy, and has been widely used in the purification of drinking water and biological products and the reuse of wastewater in the food, pharmaceutical, and paper industries. Non-solvent-induced phase separation (NIPS) is one of the most commonly used technologies for preparing ultrafiltration membranes. Factors affecting membrane structure and performance during membrane formation include: (1) the composition of the casting solution, such as the properties and concentration of polymers, the types of solvents and additives, and the content of additives; (2) the conditions for flat sheet membrane casting or hollow fiber spinning, such as the composition and temperature of the coagulation bath, the composition of the pore suspension, the air gap, and the winding speed. Amphiphilic block copolymers have attracted much attention as additives for improving membrane performance. Among them, Pluronic is an amphiphilic block copolymer additive commonly used in the industry for preparing ultrafiltration membranes, which is composed of polyoxyethylene (PEO), polyoxypropylene (PPO), and polyoxyethylene (PEO) triblocks. The journal *Journal of Membrane Science* (2008, 318, 405) introduced Pluronic F127 as a multifunctional additive that effectively increases membrane pore size and hydrophilicity, while significantly reducing the total fouling index and irreversible fouling index. *Sep. Purif. Technol.* (2015, 150, 21) reported that Pluronic F127, as an additive for PES hollow fiber ultrafiltration membranes, significantly improves the membrane's water permeability and antifouling properties. Both of these studies demonstrate that Pluronic is an excellent pore-forming agent and surface modifier in the preparation of asymmetric ultrafiltration membranes using the NIPS method. Furthermore, due to its amphiphilic nature, Pluronic undergoes a transition from unimolecular to micellar transition at certain concentrations or temperatures; this is known as concentration-induced or thermo-induced micellar transition. Moreover, Pluronic with a higher proportion of hydrophobic segments is more prone to micellar transition when the external environment changes. The journal *Membr. Sci.* (2008, 318, 405) reported that in a polyethersulfone (PES) / N,N-dimethylformamide (DMF) membrane system, Pluronic F127 molecules self-assemble into spherical micelles with a core / shell structure. During gelation in water, these Pluronic micelles dissolve and occupy spaces in the membrane, forming pores, thereby increasing the pore size and permeability of the PES ultrafiltration membrane.
[0003] Among various strategies for controlling membrane structure and performance, coagulation bath temperature is a crucial parameter. It is generally believed that increasing the coagulation bath temperature accelerates the exchange rate between solvent and non-solvent, promoting phase separation and resulting in a more porous membrane structure. The journal *Applied Polymer Science* (J. Appl. Polym. Sci., 2008, 110, 1656) investigated the effect of coagulation bath temperature on the membrane formation mechanism and morphology of a cast membrane system based on polyvinylidene fluoride (PVDF) / N,N-dimethylacetamide (DMAc). As the coagulation bath temperature increased, liquid-liquid separation caused by solvent and non-solvent exchange kinetics accelerated, thus increasing the membrane pore size. *Ind. Eng. Chem. Res.* (Ind. Eng. Chem. Res., 2010, 49, 4858) reported the effect of coagulation bath temperature on membrane separation performance when preparing polyethersulfone (PES) ultrafiltration membranes using the NIPS method: with increasing coagulation bath temperature, the pure water flux of the membrane significantly increased. Therefore, in the NIPS method for preparing ultrafiltration membranes, increasing the coagulation bath temperature can improve the membrane's pore size, porosity, and permeate flux. However, to improve membrane porosity and achieve higher permeate performance, relying solely on coagulation bath temperature as an adjustment method often requires a higher coagulation bath temperature during the preparation process. This inevitably leads to increased membrane preparation costs (increased energy consumption) and places higher demands on equipment management. Summary of the Invention
[0004] To overcome the shortcomings of existing technologies, this invention provides a method for regulating the performance of ultrafiltration membranes by controlling the micellar transition of amphiphilic block copolymers, the technical solution of which is as follows:
[0005] A method for regulating the performance of an ultrafiltration membrane by controlling the micellar transition of an amphiphilic block copolymer includes the following steps:
[0006] (1) Preparation of ultrafiltration membrane with amphiphilic block copolymer as additive: 12% to 30% of polymer and 0.1% to 5% of amphiphilic block copolymer are dissolved in their good solvent by mass percentage, and heated and stirred to obtain a homogeneous casting solution; after degassing the prepared casting solution, it is placed on the substrate, flows and spreads; the substrate coated with the casting solution is immersed in gel bath water to solidify and obtain ultrafiltration membrane;
[0007] (2) The structure and performance of ultrafiltration membranes are controlled by controlling the micellar transition behavior of the amphiphilic block copolymer in step (1): The means of controlling the micellar transition behavior of the amphiphilic block copolymer include changing the gel bath temperature, changing the ratio of hydrophilic and hydrophobic segments of the amphiphilic block copolymer, changing the molecular weight of the amphiphilic block copolymer, and changing the concentration of the amphiphilic block copolymer.
[0008] Further, the polymer in step (1) includes polyethersulfone (PES), polysulfone (PSf), polyphenylene ether (PPO), polyvinylidene fluoride (PVDF), polyethersulfone ketone (PESK), and polyether ether ketone (PEEK).
[0009] Further, the amphiphilic block copolymer in step (1) is a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer.
[0010] Further, the good solvent in step (1) is one or more of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO).
[0011] Furthermore, the substrate types in step (1) include non-woven fabric, glass plate, metal lens and mixed paper.
[0012] Furthermore, the micellar transition behavior of the amphiphilic block copolymer in step (2) is based on the thermoinduced micellar transition effect of the amphiphilic block copolymer.
[0013] Furthermore, the thermoinduced micelle transition effect arises from the change in gel bath temperature, with the temperature range set to 20-45°C when controlling the membrane flux. o C, the pure water flux of the membrane reaches its maximum value in this temperature range, at which point the membrane pore size is at its maximum.
[0014] Furthermore, based on a baseline casting system with an amphiphilic block copolymer hydrophilic-hydrophobic block ratio of 7:3, a molecular weight of 11,000 Da, a concentration of 1 wt%, and a polymer concentration of 16 wt%-20 wt%, the coagulation bath temperature range was set to 23-27°C when adjusting the membrane flux. o C, the pure water flux of the membrane reaches its maximum value in this temperature range, at which point the membrane pore size is at its maximum.
[0015] Furthermore, based on the aforementioned benchmark casting system, increasing the proportion of hydrophilic segments in the amphiphilic block copolymer and / or decreasing its molecular weight weakens the thermally induced micelle transition effect, shifting the membrane flux extremum to the high-temperature region. When controlling the membrane flux, the coagulation bath temperature range is set to 28-40°C. o C, the pure water flux of the membrane reaches its maximum value in this temperature range, at which point the membrane pore size is at its maximum.
[0016] Furthermore, based on the aforementioned baseline casting system, increasing the concentration of the amphiphilic block copolymer weakens its thermally induced micelle transition effect, shifting the membrane flux extremum to the high-temperature region. When controlling the membrane flux, the coagulation bath temperature range is set to 28-40°C. o C, the pure water flux of the membrane reaches its maximum value in this temperature range, at which point the membrane pore size is at its maximum.
[0017] Compared with the prior art, the present invention has the following main advantages:
[0018] 1. The invention provides a method for regulating ultrafiltration membrane performance by controlling the micellar transition of amphiphilic block copolymers. It uses comprehensive technical means to optimize membrane permeation performance in a room-temperature coagulation bath, avoiding the use of high coagulation bath temperatures, reducing energy consumption, lowering preparation costs, and alleviating the pressure of equipment management.
[0019] 2. The operation method of this invention is simple, the conditions are mild, the ultrafiltration membrane has a wide range of adjustable properties, and it has a good industrial production foundation and broad application prospects. Attached Figure Description
[0020] Figure 1 For Example 1 of the present invention, the coagulation bath temperature (CBT) is set from 25°C. o C increased to 45 o At C, the pure water flux and the rejection rate of 0.5 g / L bovine serum albumin of the PES / Pluronic F127 (1%) ultrafiltration membrane (operating pressure 0.2 MPa).
[0021] Figure 2 For Example 2 of the present invention, the coagulation bath temperature (CBT) is set from 25°C. o C increased to 45 o At temperature C, the pure water flux and the rejection rate of 0.5 g / L bovine serum albumin by the PES / Pluronic F68 ultrafiltration membrane (operating pressure 0.2 MPa).
[0022] Figure 3 For Example 3 of the present invention, the coagulation bath temperature (CBT) is set from 25°C. o C increased to 45 o At temperature C, the pure water flux and the rejection rate of 0.5 g / L bovine serum albumin by the PES / Pluronic P123 ultrafiltration membrane (operating pressure 0.2 MPa).
[0023] Figure 4 For Example 4 of this invention, the coagulation bath temperature (CBT) is set from 25°C. o C increased to 40 o At C, the pure water flux and the rejection rate of 0.5 g / L bovine serum albumin of the PES / Pluronic F127 (3%) ultrafiltration membrane (operating pressure 0.2 MPa). Detailed Implementation
[0024] The technical solution of the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. Of course, the following embodiments are not intended to limit the present invention, but are intended to illustrate the invention. Example 1
[0025] (1) Preparation of ultrafiltration membrane: 18% polyethersulfone (PES) and 1% Pluronic F127 were dissolved in 81% N,N-dimethylacetamide (DMAc) by mass percentage, and the solution was heated to 80 °C. o After heating and stirring at C, a homogeneous casting solution was obtained. After degassing the prepared casting solution, it was placed on a clean glass plate, flowed and spread into a thin layer with a thickness of about 150 μm. The glass plate coated with the casting solution was immersed in a gel bath for 10 minutes and then solidified to obtain an ultrafiltration membrane.
[0026] (2) Regulation of ultrafiltration membrane performance: Change the coagulation bath temperature from 25°C o C to 45 o C, the obtained ultrafiltration membrane pure water flux (0.2 MPa) and bovine serum albumin (BSA) rejection rate are as follows: Figure 1 As shown.
[0027] The Pluronic F127 molecule has a polyoxyethylene (PEO) to polypropylene (PPO) block ratio (i.e., hydrophilic-hydrophobic block ratio) of 7:3 and a molecular weight of 11,000 Da. From Figure 1 It can be observed that when the coagulation bath temperature is 25... o At temperature C, the pure water flux of the PES ultrafiltration membrane is at its maximum, reaching 632 L / m³. 2 h (0.2MPa); at this point, the membrane pore size is also the largest, estimated to be approximately 17.7 nm according to the Guerout–Elford–Ferry equation; under this condition, the BSA rejection rate is the lowest, approximately 93%. Example 2
[0028] (1) Preparation of ultrafiltration membrane: 18% polyethersulfone (PES) and 1% Pluronic F68 were dissolved in 81% N,N-dimethylacetamide (DMAc) by mass percentage, and the solution was heated to 80 °C. o After heating and stirring at C, a homogeneous casting solution was obtained. After degassing the prepared casting solution, it was placed on a clean glass plate, flowed and spread into a thin layer with a thickness of about 150 μm. The glass plate coated with the casting solution was immersed in a gel bath for 10 minutes and then solidified to obtain an ultrafiltration membrane.
[0029] (2) Regulation of ultrafiltration membrane performance: Change the coagulation bath temperature from 25°C o C to 45 o C, the obtained ultrafiltration membrane pure water flux (0.2 MPa) and bovine serum albumin (BSA) rejection rate are as follows: Figure 2 As shown.
[0030] The Pluronic F68 molecule has a PEO to PPO block ratio (i.e., hydrophilic-hydrophobic block ratio) of 8:2 and a molecular weight of 7,957 Da. Compared to the ultrafiltration membrane regulated by Pluronic F127 in Example 1, the maximum pure water flux of the ultrafiltration membrane in this example shifts to the high-temperature region. This is related to the increased proportion of hydrophilic segments and decreased molecular weight of Pluronic F68, leading to a weakened micellar transition effect. Figure 2 It can be observed that when the coagulation bath temperature is 30... o At temperature C, the pure water flux of the PES ultrafiltration membrane is at its maximum, reaching 1391 L / m³. 2 h (0.2MPa); at this point, the membrane pore size is also the largest, estimated to be approximately 33.5 nm according to the Guerout–Elford–Ferry equation; under this condition, the BSA rejection rate is the lowest, approximately 64%. Example 3
[0031] (1) Preparation of ultrafiltration membrane: 18% PES and 1% Pluronic P123 were dissolved in 79% N,N-dimethylacetamide (DMAc) by mass percentage, and the solution was heated to 80 °C. o After heating and stirring at C, a homogeneous casting solution was obtained. After degassing the prepared casting solution, it was placed on a clean glass plate, flowed and spread into a thin layer with a thickness of about 150 μm. The glass plate coated with the casting solution was immersed in a gel bath for 10 minutes and then solidified to obtain an ultrafiltration membrane.
[0032] (2) Regulation of ultrafiltration membrane performance: Change the coagulation bath temperature from 25°C o C to 45 o C, the obtained ultrafiltration membrane pure water flux (0.2 MPa) and bovine serum albumin (BSA) rejection rate are as follows: Figure 3 As shown.
[0033] The Pluronic P123 molecule has a PEO to PPO block ratio (i.e., hydrophilic-hydrophobic block ratio) of 3:7 and a molecular weight of 5,800 Da. Compared to the ultrafiltration membrane regulated by Pluronic F127 in Example 1, the maximum pure water flux of the ultrafiltration membrane in this example shifts towards the high-temperature region. Although the hydrophilic segment ratio of Pluronic P123 is reduced compared to Pluronic F127, its molecular weight is significantly reduced, resulting in a much greater effect of shifting towards the high-temperature region than the effect of shifting towards the low-temperature region due to the reduced hydrophilic segment ratio. Therefore, the maximum pure water flux of the ultrafiltration membrane ultimately shifts towards the high-temperature region. Figure 3 It can be observed that when the coagulation bath temperature is 40... oAt temperature C, the PES ultrafiltration membrane exhibits the highest pure water flux, reaching 817 L / m²h (0.2 MPa); the membrane pore size is also the largest at this temperature, estimated to be approximately 23.3 nm according to the Guerout–Elford–Ferry equation; under this condition, the BSA rejection rate is the lowest, at approximately 48%. Example 4
[0034] (1) Preparation of ultrafiltration membrane: 18% polyethersulfone (PES) and 3% Pluronic F127 were dissolved in 79% N,N-dimethylacetamide (DMAc) by mass percentage, and the solution was heated to 80 °C. o After heating and stirring at C, a homogeneous casting solution was obtained. After degassing the prepared casting solution, it was placed on a clean glass plate, flowed and spread into a thin layer with a thickness of about 150 μm. The glass plate coated with the casting solution was immersed in a gel bath for 10 minutes and then solidified to obtain an ultrafiltration membrane.
[0035] (2) Regulation of ultrafiltration membrane performance: Change the coagulation bath temperature from 25°C o C to 40 o C, the obtained ultrafiltration membrane pure water flux (0.2 MPa) and bovine serum albumin (BSA) rejection rate are as follows: Figure 4 As shown.
[0036] from Figure 4 It can be observed that when the coagulation bath temperature is 30... o At temperature C, the pure water flux of the PES ultrafiltration membrane is at its maximum, reaching 914 L / m³. 2 h (0.2 MPa); at this point, the membrane pore size is also at its maximum, estimated to be approximately 20.5 nm according to the Guerout–Elford–Ferry equation; under this condition, the BSA rejection rate is the lowest, approximately 83%. Compared to the ultrafiltration membrane with 1% Pluronic F127 content in Example 1, the maximum pure water flux shifts to the high-temperature region, which is related to the weakening of the micelle effect due to the increased Pluronic F127 concentration.
Claims
1. A method for regulating the performance of an ultrafiltration membrane by controlling the micellar transition of an amphiphilic block copolymer, characterized in that, Includes the following steps: (1) Preparation of ultrafiltration membrane with amphiphilic block copolymer as additive: 12% to 30% of polymer and 0.1% to 5% of amphiphilic block copolymer are dissolved in their good solvent by mass percentage, and heated and stirred to obtain a homogeneous casting solution; after degassing the prepared casting solution, it is placed on the substrate, flows and spreads; the substrate coated with the casting solution is immersed in gel bath water to solidify and obtain ultrafiltration membrane; (2) The structure and performance of ultrafiltration membranes are controlled by controlling the micellar transition behavior of the amphiphilic block copolymer in step (1): The means of controlling the micellar transition behavior of the amphiphilic block copolymer include changing the gel bath temperature, changing the ratio of hydrophilic and hydrophobic segments of the amphiphilic block copolymer, changing the molecular weight of the amphiphilic block copolymer, and changing the concentration of the amphiphilic block copolymer. The micellar transition behavior of the amphiphilic block copolymer in step (2) is based on the thermoinduced micellar transition effect of the amphiphilic block copolymer; The thermoinduced micelle transition effect arises from changes in the gel bath temperature, with the temperature range set to 20-45°C when controlling the membrane flux. o C, the pure water flux of the membrane reaches its maximum value in this temperature range, at which point the membrane pore size is the largest; Based on a baseline casting system using an amphiphilic block copolymer with a hydrophilic-hydrophobic block ratio of 7:3, a molecular weight of 11,000 Da, a concentration of 1 wt%, and a polymer concentration of 16 wt%–20 wt%, the coagulation bath temperature range was set to 23–27°C when adjusting the membrane flux. o C, the pure water flux of the membrane reaches its maximum value in this temperature range, at which point the membrane pore size is the largest; Based on the aforementioned benchmark casting system, increasing the proportion of hydrophilic segments in the amphiphilic block copolymer and / or decreasing its molecular weight weakens the thermally induced micelle transition effect, shifting the membrane flux extremum to the high-temperature region. When controlling membrane flux, the coagulation bath temperature range is set to 28-40°C. o C, the pure water flux of the membrane reaches its maximum value in this temperature range, at which point the membrane pore size is the largest; Based on the aforementioned benchmark casting system, increasing the concentration of the amphiphilic block copolymer weakens its thermally induced micelle transition effect and shifts the membrane flux extremum to the high-temperature region. When controlling the membrane flux, the coagulation bath temperature range is set to 28-40°C. o C, the pure water flux of the membrane reaches its maximum value in this temperature range, at which point the membrane pore size is at its maximum.
2. The method for regulating ultrafiltration membrane performance by controlling the micellar transition of amphiphilic block copolymers according to claim 1, characterized in that, The polymers in step (1) include polyethersulfone, polysulfone, polyphenylene ether, polyvinylidene fluoride, polyethersulfone ketone and polyetherether ketone.
3. The method for regulating ultrafiltration membrane performance by controlling the micellar transition of amphiphilic block copolymers according to claim 1, characterized in that, The amphiphilic block copolymer in step (1) is a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer.
4. The method for regulating ultrafiltration membrane performance by controlling the micellar transition of amphiphilic block copolymers according to claim 1, characterized in that, The good solvent in step (1) is one or more of N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.
5. The method for regulating ultrafiltration membrane performance by controlling the micellar transition of amphiphilic block copolymers according to claim 1, characterized in that, The types of substrates used in step (1) include nonwoven fabric, glass plate, metal lens and mixed paper.