A method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination
By introducing a complex of tannic acid and ferric chloride metal polyphenols into a vermiculite-based two-dimensional layered nanofiltration membrane, the interlayer spacing was controlled, solving the problem of balancing water permeability and selectivity in antibiotic/salt separation of nanofiltration membranes, and achieving efficient, green, and simple separation results.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DONGHUA UNIV
- Filing Date
- 2026-03-02
- Publication Date
- 2026-06-02
AI Technical Summary
Existing nanofiltration membranes struggle to balance high water permeability and high selectivity in antibiotic/salt separation. Traditional vermiculite two-dimensional membranes have few reports on this application, and existing materials exhibit low separation factors at high water permeability.
A metal polyphenol complex was formed by tannic acid and ferric chloride. By adjusting the interlayer spacing of vermiculite-based two-dimensional layered nanofiltration membrane and combining it with polyvinylidene fluoride microporous filter membrane, a stable vermiculite-based two-dimensional layered nanofiltration membrane was prepared. High-throughput and high-selectivity separation was achieved by utilizing its natural negative charge and adjustable interlayer channels.
It achieves high-purity water permeability and efficient salt/antibiotic separation, and is characterized by being green and environmentally friendly, simple to operate, and suitable for large-scale applications.
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Figure CN121755047B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of membrane separation technology and relates to a method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination. Background Technology
[0002] Membrane separation technology, with its high efficiency and environmental friendliness, eliminates the need for additional reagents, thus avoiding secondary pollution caused by chemical sludge at the source. It boasts high and stable separation efficiency, exhibiting excellent retention performance for small-molecule antibiotics. Its simple and controllable operation, minimal interference from environmental factors such as water quality and temperature, demonstrates significant advantages in antibiotic removal and desalination of water bodies, making it a promising sustainable water treatment solution. Antibiotic molecules are typically separated from water due to their size or charge difference with nanofiltration membranes, while inorganic salts such as NaCl and Na₂SO₄ can pass through the membrane. Traditional separation membranes often suffer from decreased selectivity with increased permeability, short lifespan, poor thermal stability, and poor corrosion resistance.
[0003] Natural vermiculite has attracted much attention due to its excellent thermal and chemical stability. It can be exfoliated into hydrophilic nanosheets. Two-dimensional vermiculite nanosheet films have shown unique advantages in achieving high-throughput and high-selectivity separation due to their natural negative charge, tunable interlayer channels and easily modifiable surface chemistry.
[0004] Currently, the main literature reports on the application of vermiculite two-dimensional membranes in nanofiltration membrane separation are as follows: 1. Metal ion intercalation for organic dye nanofiltration (Reference 1: Two-dimensional vermiculite nanolayer membrane for high-efficiency organic solvent nanofiltration, DOI: 10.1002 / adfm.202410635); 2. Blending with titanium dioxide nanoparticles for dye / salt separation (Reference 2: Vermiculite nanofiltration membrane with TiO2 nanoparticles as a multifunctional intercalating agent and its enhanced water purification performance, DOI: 10.1016 / 3. Lithium-magnesium separation is achieved by crosslinking vermiculite sheets with alumina pillars and doping with metal ions (Reference 3: Pillared layered vermiculite membrane with tunable monovalent / polyvalent ion selectivity, DOI: 10.1002 / adma.202417994); 4. Ion separation is achieved by crosslinking with diamine (Reference 4: Tunable ion transport based on self-supporting vermiculite membrane, DOI: 10.1021 / acsnano.2c05954). Due to the specific application environment of the materials and the low water permeability of the membranes, the above methods have resulted in few reports on the application of two-dimensional vermiculite membranes in antibiotic / salt separation. In contrast, other materials such as COF two-dimensional membranes and polyamide membranes have been extensively reported in the literature for antibiotic / salt separation.
[0005] For example, in reference 5 (Inorganic salt-regulated zwitterionic nanofiltration membranes for antibiotic / monovalent salt separation, DOI: 10.1016 / j.memsci.2022.121144), the water permeability of the ZNFMs membrane is 21.6 L / (m³). 2 The antibiotic retention rate was 97.5% (ERY), the NaCl retention rate was 8.5%, and the NaCl / ERY separation factor was 36.6.
[0006] In Reference 6 (N-oxide-linked zwitterionic polyamide nanofiltration membrane for high-efficiency antibiotic / salt separation, DOI: 10.1016 / j.memsci.2024.123249), the water permeability of the DTFC-3 membrane is 19.2 L / (m³). 2 (·h·bar), the separation factor of NaCl / ERY is 41.1.
[0007] In Reference 7 (Preparation of Covalent Organic Framework Membranes for Antibiotic Desalination Based on Green Scalable Interfacial Polymerization of Ionic Liquids, DOI: 10.1002 / anie.202316315), the water permeability of the TpPa-75-250-2 membrane is 48.09 L / (m²). 2 The antibiotic rejection rate (ADR) was 98.03% (h·bar), the NaCl rejection rate was 18.3%, and the NaCl / ADR separation factor was 41.8.
[0008] Reference 8 (Layer-by-layer self-assembly preparation of metal-doped covalent organic framework membranes for efficient antibiotic desalting, DOI: 10.1016 / j.desal.2025.118537) shows that the water permeability of the Fe-COF membrane is 33.5 L / (m²). 2 The antibiotic rejection rate was 99% (ADR), the NaCl rejection rate was <20%, and the NaCl / ADR separation factor was 116.
[0009] Reference 9 (Microstructure optimization of bio-based polyester nanofilms for antibiotic desalination via nanofiltration, DOI: 10.1126 / sciadv.adg6134) St 0.1 / TMC 0.1 The water permeability of the -3 membrane is 81.2 L / (m³). 2 The antibiotic rejection rate was 92% (TC), the NaCl rejection rate was <10%, and the NaCl / TC separation factor was 11.4.
[0010] In Reference 10 (Customized Nanofiltration Membrane Based on Surface Modification of Branched Quaternized Triethanolamine Assembly and Its Enhanced Antibiotic Desalination Performance, DOI: 10.1016 / j.memsci.2024.123364), the water permeability of the PA-BQTE membrane is 9.7 L / (m²). 2 The antibiotic rejection rate was 98% (TC), the NaCl rejection rate was 15%, and the NaCl / TC separation factor was 42.5.
[0011] In Reference 11 (Nanofiltration Membranes Grafted with Zwitterionic Triethanolamine for Sustainable Antibiotic Recovery, DOI: 10.1016 / j.memsci.2025.124684), the water permeability of the PA-ZTEA membrane is 20.3 L / (m²). 2 The antibiotic retention rate was 98.4% (ERY), the NaCl retention rate was <10%, and the NaCl / ERY separation factor was 58.4.
[0012] In Reference 12 (Using Post-treatment to Modulate the Microstructure of Znophilic Ion Nanofiltration Membranes for Antibiotic Desalination, DOI: 10.1016 / j.seppur.2024.127884), the water permeability of the ZNFM-EtOH membrane was 8.9 L / (m³). 2 The antibiotic rejection rate was 93.8% (OFL), the NaCl rejection rate was 12.2%, and the NaCl / OFL separation factor was 13.9.
[0013] In Reference 13 (Water activation treatment before microwave heating to enhance nanofiltration performance of antibiotic / sodium chloride separation, DOI: 10.1016 / j.memsci.2021.119285), the water permeability of the PA-H2O-Mw membrane was 29.9 L / (m³). 2 The antibiotic rejection rate was 95.6% (TC), the NaCl rejection rate was <7.1%, and the NaCl / TC separation factor was 21.1.
[0014] Reference 14 (High-throughput electrochemical stripping of two-dimensional covalent organic frameworks, DOI: 10.1021 / jacs.5c06026) shows that the TpPa-Nylon membrane has a TC antibiotic rejection rate of >90%, a NaCl rejection rate of <13%, and a NaCl / TC separation factor of 24.5.
[0015] Reference 15 (TFC membrane based on hydroxypropyl-β-cyclodextrin for efficient antibiotic desalting, DOI: 10.1016 / j.seppur.2023.123884) shows that TIHP-0.15 has a pure water permeability as high as 82.9 L / (m³). 2(·h·bar), but the TIHP-0.15 membrane had a 94.8% rejection rate for antibiotics (TC) and an 8.5% rejection rate for NaCl, with a NaCl / TC separation factor of only 18.
[0016] Reference 16 (Preparation of Polyamide Nanofilms by Non-Isothermal Controlled Interfacial Polymerization, DOI: 10.1002 / adfm.202313026) shows that the NIIP membrane exhibits a 99.49% rejection rate for antibiotics (ROX) and a 18.76% rejection rate for NaCl, with a NaCl / ROX separation factor of 159.3. The membrane demonstrates top-tier selectivity for antibiotic salt separation, but its water permeability is only 42.9 L / (m²). 2 ·h·bar).
[0017] The comparison of antibiotic / salt separation performance among different nanofiltration membranes reveals variations in membrane performance due to differences in antibiotic molecule size and charge. Very small pore sizes result in extremely high antibiotic rejection rates and a very high separation factor, but also extremely low water permeability. In salt / antibiotic separation applications, high water permeability comes at the cost of selectivity. Currently, membrane water permeability exceeds 80 L / (m²). 2 The permeability of membranes (·h·bar) is at an extremely high level; however, in existing technologies, the water permeability exceeds 80 L / (m²). 2 Nanofiltration membranes with a density of ·h·bar have antibiotic salt separation factors below 20, making it difficult to achieve a balance between excellent membrane water permeability and separation effect.
[0018] Therefore, it is of great significance to study a method for preparing vermiculite-based two-dimensional layered nanofiltration membranes for antibiotic desalination in order to solve the problems existing in the prior art. Summary of the Invention
[0019] The purpose of this invention is to solve the problems existing in the prior art and provide a method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination.
[0020] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0021] A method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalting includes the following steps:
[0022] (1) Dissolve tannic acid in Tris-HCl solution to obtain tannic acid solution, and at the same time dissolve ferric chloride hexahydrate in Tris-HCl solution to obtain ferric chloride solution;
[0023] (2) Stir the tannic acid solution obtained in step (1) and the ferric chloride solution at room temperature (25 °C) and adjust the pH of the mixed solution to 8.5 to obtain a metal polyphenol complex solution; at this pH, tannic acid is fully deprotonated and can form a stable tricoordinated metal polyphenol complex;
[0024] (3) Mix the metal polyphenol complex solution obtained in step (2) with the two-dimensional vermiculite nanosheet solution and then ultrasonicate at room temperature to obtain a uniformly dispersed mixed solution;
[0025] (4) Pour the mixed solution obtained in step (3) into a suction filtration device equipped with a polyvinylidene fluoride microporous membrane for suction filtration to obtain a wet membrane, and place the wet membrane in a vacuum drying oven for drying at room temperature to obtain a dry membrane;
[0026] (5) Immerse the dry membrane obtained in step (4) in a sodium hydroxide solution with a pH of 11 to obtain a wet vermiculite-based two-dimensional layered nanofiltration membrane; in an environment with a pH of 11, the free tannic acid in the membrane can be removed from the membrane. The reason for removing tannic acid is that a large amount of free tannic acid is between the membrane layers, and the tannic acid segments are relatively soft, which will cause poor membrane pressure stability during the test. Therefore, alkali treatment is used to remove the free tannic acid, and only the metal polyphenol complex of tannic acid and ferric chloride is retained, which can make the membrane structure more stable;
[0027] (6) Place the wet vermiculite-based two-dimensional layered nanofiltration membrane obtained in step (5) in a vacuum drying oven for drying at room temperature to obtain a dry vermiculite-based two-dimensional layered nanofiltration membrane, that is, the vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination.
[0028] The deprotonation of the phenolic hydroxyl group of tannic acid forms a phenolate anion that can coordinate with ferric ions to form a five-membered or six-membered ring chelate, and this chelate structure is very stable. Tannic acid and ferric chloride will form a mono-coordinated complex (pH < 3), a bi-coordinated complex (3 < pH < 6), and a tricoordinated complex (pH > 7) in different pH environments due to the different degrees of deprotonation of the phenolic hydroxyl group of tannic acid. The stability of the complex is poor under acidic conditions. As pH > 7, the degree of deprotonation of tannic acid is large, and it is very easy to form a stable tricoordinated complex with ferric ions. The pH of 8.5 is selected because at this pH, tannic acid is basically deprotonated, which can make it fully coordinate with Fe 3+ to form a stable tricoordinated complex.
[0029] The two-dimensional vermiculite nanosheet membrane shows unique advantages in achieving high-throughput and high-selectivity separation through its natural negative charge, adjustable interlayer channels, and easily modified surface chemistry. In this invention, the metal polyphenol complex formed by tannic acid and ferric chloride is introduced into the interlayer of the two-dimensional vermiculite nanosheet. The complex can not only form stable channels between the two-dimensional vermiculite membrane layers, but also prevent the two-dimensional vermiculite membrane from swelling and dispersing in water, thus solving the problem of poor water stability of the two-dimensional vermiculite membrane.
[0030] As a preferred technical solution:
[0031] In the preparation method of the vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination as described above, the concentration of tannic acid solution in step (1) is 1.2~2.4 mM and the concentration of ferric chloride solution is 0.1 mM;
[0032] In step (3), the concentration of the two-dimensional vermiculite nanosheet solution is 0.15 mg / mL.
[0033] The method described above for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination involves a molar ratio of tannic acid to ferric chloride of 12-24:1 and a mass ratio of tannic acid to two-dimensional vermiculite nanosheets of 680-1361:1. The interlayer spacing of the vermiculite-based two-dimensional layered nanofiltration membrane can be controlled by adjusting the molar ratio of tannic acid to ferric chloride. By adjusting the membrane pore size, the vermiculite-based two-dimensional layered nanofiltration composite membrane achieves both high-purity water permeability and efficient rapid separation of salts and antibiotics.
[0034] In the preparation method of the vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination as described above, the pore size of the polyvinylidene fluoride microporous membrane in step (4) is 0.22 μm.
[0035] The preparation process of the two-dimensional vermiculite nanosheet solution is as follows: A method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination, as described above.
[0036] (1) Add vermiculite to a saturated sodium chloride solution and stir continuously at 100°C for 24 h. After the reaction is complete, wash the collected precipitate three times with deionized water and anhydrous ethanol alternately.
[0037] (2) Add the product obtained in step (1) to the lithium chloride solution and stir continuously at 100°C for 24 h. After the reaction is completed, wash the collected precipitate three times with deionized water and anhydrous ethanol alternately.
[0038] (3) Disperse the product obtained in step (2) in deionized water and sonicate for 1 h. Centrifuge the suspension obtained by sonication and collect the supernatant, which is the two-dimensional vermiculite nanosheet solution.
[0039] Beneficial effects:
[0040] (1) The present invention provides a method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination. For the first time, a complex of tannic acid and ferric chloride metal polyphenols is introduced into the sub-nanometer space of the two-dimensional vermiculite membrane. The interlayer spacing of the two-dimensional vermiculite membrane can be continuously controlled. The operation is simple. The high efficiency of salt / antibiotic separation by the vermiculite-based two-dimensional layered nanofiltration membrane is achieved by adjusting the membrane pore size. At the same time, it has high purity water permeability.
[0041] (2) The present invention provides a method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalting. The experimental materials are green, natural and environmentally friendly, the experimental reaction conditions are mild and the preparation process is simple. At the same time, the vermiculite-based two-dimensional layered nanofiltration membrane has a high efficiency separation effect on salt / antibiotic mixtures. The preparation method has the prospect of large-scale application. Attached Figure Description
[0042] Figure 1 The images show surface and cross-sectional scanning electron microscope (SEM) images of the original two-dimensional vermiculite membrane in Comparative Example 1 and the vermiculite-based two-dimensional layered nanofiltration membrane in Example 5. (a) is a surface SEM image of the original two-dimensional vermiculite membrane in Comparative Example 1, (b) is a cross-sectional SEM image of the original two-dimensional vermiculite membrane in Comparative Example 1, (c) is a surface SEM image of the vermiculite-based two-dimensional layered nanofiltration membrane in Example 5, and (d) is a cross-sectional SEM image of the vermiculite-based two-dimensional layered nanofiltration membrane in Example 5.
[0043] Figure 2 X-ray diffraction patterns of the vermiculite-based two-dimensional layered nanofiltration membranes of Examples 1 and 5 of the present invention and the original two-dimensional vermiculite membrane of Comparative Example 1;
[0044] Figure 3 This is a comparison chart of the separation factors of sodium chloride / tetracycline for the vermiculite-based two-dimensional layered nanofiltration membranes of Examples 1 to 5 of the present invention;
[0045] Figure 4 This is a comparison chart of the separation factors of the vermiculite-based two-dimensional layered nanofiltration membrane of Example 5 of the present invention for four mixed solutions of sodium chloride / antibiotics: sodium chloride / doxorubicin, sodium chloride / tetracycline, sodium chloride / ofloxacin, and sodium chloride / norfloxacin. Detailed Implementation
[0046] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.
[0047] The testing / calculation methods involved in the performance indicators of this invention are as follows:
[0048] (1) Pure water permeability of vermiculite-based two-dimensional layered nanofiltration membrane:
[0049] The permeability (J) of a vermiculite-based two-dimensional layered nanofiltration membrane is calculated using the formula: J = V / (A × T × P), where V is the volume (L) of pure water permeating from the composite membrane within time T (h), and A is the effective membrane area (m²). 2 P is 1 (bar);
[0050] (2) Antibiotic retention rate: The formula for calculating the antibiotic retention rate (r1) is as follows: In the formula, C 01 C is the concentration of the antibiotic solution before filtration. p1 This refers to the concentration of the antibiotic solution after filtration; both are measured using Thermo Fisher Scientific's Evolution method. TM Measured by a One UV-Vis spectrophotometer;
[0051] (3) Salt rejection rate: The formula for calculating the salt rejection rate (r2) is as follows: In the formula, C 02 C is the concentration of the salt solution before filtration. p2 The concentrations are those of the filtered salt solution and were both measured using a Sartorius PB-10 pH meter.
[0052] (4) Separation factor: In the formula, r2 is the retention rate of the antibiotic salt mixture to the salt, measured using a Sartorius PB-10 pH meter, and r1 is the retention rate of the antibiotic in the antibiotic salt mixture aqueous solution, measured using a Thermo Fisher Evolution pH meter. TM Measured using a One UV-Vis spectrophotometer;
[0053] The antibiotic salt mixture solution contains 10 ppm of antibiotics and 1000 ppm of sodium chloride in water; the mass ratio of antibiotics to sodium chloride is 1:100.
[0054] (5) Scanning electron microscopy (SEM) test: The surface and cross-section of the original two-dimensional vermiculite membrane and the vermiculite-based two-dimensional layered nanofiltration membrane were observed using a field emission scanning electron microscope (SU8010, Hitachi, Japan).
[0055] (6) X-ray diffraction (XRD) test: The original two-dimensional vermiculite membrane and vermiculite-based two-dimensional layered nanofiltration membrane were analyzed using an X-ray diffractometer (Bruker D8, Germany).
[0056] The vermiculite used in this invention was purchased from Bid Pharmaceuticals, with a purity of 10 mesh, catalog number: BD01204388-25g, CAS number: 1318-00-9. Unless otherwise specified, all raw materials used in this invention are commercially available products well-known in the art.
[0057] Example 1
[0058] A method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalting, the specific steps of which are as follows:
[0059] (1) Tannic acid was dissolved in a Tris-HCl solution with pH=5 to obtain a tannic acid solution with a concentration of 1.2 mM, and ferric chloride hexahydrate was dissolved in a Tris-HCl solution with pH=5 to obtain a ferric chloride solution.
[0060] (2) The tannic acid solution from step (1) and the ferric chloride solution with a concentration of 0.1 mM were stirred at room temperature (25°C) and the pH of the mixed solution was adjusted to 8.5 to obtain a metal polyphenol complex solution.
[0061] The molar ratio of tannic acid to ferric chloride is 12:1.
[0062] (3) Preparation of two-dimensional vermiculite nanosheet solution:
[0063] (3.1) Add vermiculite to a saturated sodium chloride solution with a concentration of 5.44 M and stir continuously at 100 °C for 24 h. After the reaction is completed, wash the collected precipitate three times with deionized water and anhydrous ethanol alternately.
[0064] The ratio of vermiculite to saturated sodium chloride solution used is 1g:500mL;
[0065] (3.2) Add the product obtained in step (3.1) to a lithium chloride solution with a concentration of 4 M and stir continuously at 100°C for 24 h. After the reaction is completed, wash the collected precipitate three times alternately with deionized water and anhydrous ethanol.
[0066] The ratio of vermiculite to lithium chloride solution used was 1 g: 500 mL;
[0067] (3.3) Disperse the product obtained in step (3.2) in deionized water and sonicate for 1 h. Centrifuge the suspension obtained by sonication at 3500 rpm for 30 min and collect the supernatant, which is a two-dimensional vermiculite nanosheet solution with a concentration of 0.15 mg / mL.
[0068] (4) The metal polyphenol complex solution obtained in step (2) is mixed with the two-dimensional vermiculite nanosheet solution and then sonicated at room temperature for 15 min to obtain a uniformly dispersed mixed solution.
[0069] The mass ratio of tannic acid to two-dimensional vermiculite nanosheets is 680:1.
[0070] (5) Take 10 mL of the mixed solution obtained in step (4) and pour it into a filtration device containing a polyvinylidene fluoride microporous filter membrane with a pore size of 0.22 μm to filter and obtain a wet membrane. Place the wet membrane in a vacuum drying oven and dry it at room temperature to obtain a dry membrane.
[0071] (6) The dried membrane obtained in step (5) was soaked in a sodium hydroxide solution with a pH of 11 for 4 h to obtain a moist vermiculite-based two-dimensional layered nanofiltration membrane.
[0072] (7) Place the moist vermiculite-based two-dimensional layered nanofiltration membrane obtained in step (6) into a vacuum drying oven and dry at room temperature for 24 h to obtain a dried vermiculite-based two-dimensional layered nanofiltration membrane, which is a vermiculite-based two-dimensional layered nanofiltration membrane used for antibiotic desalting.
[0073] The final vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination has a water permeability of 86.28 L / (m²). 2 (·h·bar), sodium chloride retention rate was 22.65%, tetracycline retention rate was 96.93%, and the sodium chloride / tetracycline separation factor was 25.2.
[0074] Example 2
[0075] A method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalting, the specific steps of which are as follows:
[0076] (1) Dissolve tannic acid in a Tris-HCl solution with pH=5 to obtain a tannic acid solution with a concentration of 1.5 mM, and dissolve ferric chloride hexahydrate in a Tris-HCl solution with pH=5 to obtain a ferric chloride solution.
[0077] (2) The tannic acid solution from step (1) and the ferric chloride solution with a concentration of 0.1 mM were stirred at room temperature (25°C) and the pH of the mixed solution was adjusted to 8.5 to obtain a metal polyphenol complex solution.
[0078] The molar ratio of tannic acid to ferric chloride is 15:1.
[0079] (3) Preparation of two-dimensional vermiculite nanosheet solution:
[0080] (3.1) Add vermiculite to a saturated sodium chloride solution with a concentration of 5.44 M and stir continuously at 100 °C for 24 h. After the reaction is completed, wash the collected precipitate three times with deionized water and anhydrous ethanol alternately.
[0081] The ratio of vermiculite to saturated sodium chloride solution used was 1 g: 500 mL.
[0082] (3.2) Add the product obtained in step (3.1) to a lithium chloride solution with a concentration of 4 M and stir continuously at 100°C for 24 h. After the reaction is completed, wash the collected precipitate three times alternately with deionized water and anhydrous ethanol.
[0083] The ratio of vermiculite to lithium chloride solution used is 1g:500mL;
[0084] (3.3) Disperse the product obtained in step (3.2) in deionized water and sonicate for 1 h. Centrifuge the suspension obtained by sonication at 3500 rpm for 30 min and collect the supernatant, which is a two-dimensional vermiculite nanosheet solution with a concentration of 0.15 mg / mL.
[0085] (4) The metal polyphenol complex solution obtained in step (2) is mixed with the two-dimensional vermiculite nanosheet solution and then sonicated at room temperature for 15 min to obtain a uniformly dispersed mixed solution.
[0086] The mass ratio of tannic acid to two-dimensional vermiculite nanosheets is 851:1.
[0087] (5) Take 10 mL of the mixed solution obtained in step (4) and pour it into a filtration device containing a polyvinylidene fluoride microporous filter membrane with a pore size of 0.22 μm to filter and obtain a wet membrane. Place the wet membrane in a vacuum drying oven and dry it at room temperature to obtain a dry membrane.
[0088] (6) The dried membrane obtained in step (5) was soaked in a sodium hydroxide solution with a pH of 11 for 4 h to obtain a moist vermiculite-based two-dimensional layered nanofiltration membrane.
[0089] (7) Place the moist vermiculite-based two-dimensional layered nanofiltration membrane obtained in step (6) into a vacuum drying oven and dry at room temperature for 24 h to obtain a dried vermiculite-based two-dimensional layered nanofiltration membrane, which is a vermiculite-based two-dimensional layered nanofiltration membrane used for antibiotic desalting.
[0090] The final vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination has a water permeability of 88.45 L / (m²). 2 (·h·bar), sodium chloride retention rate was 22.12%, tetracycline retention rate was 96.90%, and sodium chloride / tetracycline separation factor was 25.12.
[0091] Example 3
[0092] A method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalting, the specific steps of which are as follows:
[0093] (1) Tannic acid was dissolved in a Tris-HCl solution with pH=5 to obtain a tannic acid solution with a concentration of 1.8 mM, and ferric chloride hexahydrate was dissolved in a Tris-HCl solution with pH=5 to obtain a ferric chloride solution.
[0094] (2) The tannic acid solution from step (1) and the ferric chloride solution with a concentration of 0.1 mM were stirred at room temperature (25°C) and the pH of the mixed solution was adjusted to 8.5 to obtain a metal polyphenol complex solution.
[0095] The molar ratio of tannic acid to ferric chloride is 18:1.
[0096] (3) Preparation of two-dimensional vermiculite nanosheet solution:
[0097] (3.1) Add vermiculite to a saturated sodium chloride solution with a concentration of 5.44 M and stir continuously at 100 °C for 24 h. After the reaction is completed, wash the collected precipitate three times with deionized water and anhydrous ethanol alternately.
[0098] The ratio of vermiculite to saturated sodium chloride solution used was 1 g: 500 mL.
[0099] (3.2) Add the product obtained in step (3.1) to a lithium chloride solution with a concentration of 4 M and stir continuously at 100°C for 24 h. After the reaction is completed, wash the collected precipitate three times alternately with deionized water and anhydrous ethanol.
[0100] The ratio of vermiculite to lithium chloride solution used was 1 g: 500 mL;
[0101] (3.3) Disperse the product obtained in step (3.2) in deionized water and sonicate for 1 h. Centrifuge the suspension obtained by sonication at 3500 rpm for 30 min and collect the supernatant, which is a two-dimensional vermiculite nanosheet solution with a concentration of 0.15 mg / mL.
[0102] (4) The metal polyphenol complex solution obtained in step (2) is mixed with the two-dimensional vermiculite nanosheet solution and then sonicated at room temperature for 15 min to obtain a uniformly dispersed mixed solution.
[0103] The mass ratio of tannic acid to two-dimensional vermiculite nanosheets is 1021:1.
[0104] (5) Take 10 mL of the mixed solution obtained in step (4) and pour it into a filtration device containing a polyvinylidene fluoride microporous filter membrane with a pore size of 0.22 μm to filter and obtain a wet membrane. Place the wet membrane in a vacuum drying oven and dry it at room temperature to obtain a dry membrane.
[0105] (6) The dried membrane obtained in step (5) was soaked in a sodium hydroxide solution with a pH of 11 for 4 hours to obtain a moist vermiculite-based two-dimensional layered nanofiltration membrane.
[0106] (7) Place the moist vermiculite-based two-dimensional layered nanofiltration membrane obtained in step (6) into a vacuum drying oven and dry at room temperature for 24 hours to obtain a dried vermiculite-based two-dimensional layered nanofiltration membrane, which is a vermiculite-based two-dimensional layered nanofiltration membrane used for antibiotic desalting.
[0107] The final vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination has a water permeability of 90.21 L / (m²). 2(·h·bar), sodium chloride retention rate was 22.43%, tetracycline retention rate was 96.85%, and sodium chloride / tetracycline separation factor was 24.63.
[0108] Example 4
[0109] A method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalting, the specific steps of which are as follows:
[0110] (1) Tannic acid was dissolved in a Tris-HCl solution with pH=5 to obtain a tannic acid solution with a concentration of 2.1 mM, and ferric chloride hexahydrate was dissolved in a Tris-HCl solution with pH=5 to obtain a ferric chloride solution.
[0111] (2) The tannic acid solution from step (1) and the ferric chloride solution with a concentration of 0.1 mM were stirred at room temperature (25°C) and the pH of the mixed solution was adjusted to 8.5 to obtain a metal polyphenol complex solution.
[0112] The molar ratio of tannic acid to ferric chloride is 21:1.
[0113] (3) Preparation of two-dimensional vermiculite nanosheet solution:
[0114] (3.1) Add vermiculite to a saturated sodium chloride solution with a concentration of 5.44 M and stir continuously at 100 °C for 24 h. After the reaction is completed, wash the collected precipitate three times with deionized water and anhydrous ethanol alternately.
[0115] The ratio of vermiculite to saturated sodium chloride solution used was 1 g: 500 mL.
[0116] (3.2) Add the product obtained in step (3.1) to a lithium chloride solution with a concentration of 4 M and stir continuously at 100°C for 24 h. After the reaction is completed, wash the collected precipitate three times alternately with deionized water and anhydrous ethanol.
[0117] The ratio of vermiculite to lithium chloride solution used was 1 g: 500 mL;
[0118] (3.3) Disperse the product obtained in step (3.2) in deionized water and sonicate for 1 h. Centrifuge the suspension obtained by sonication at 3500 rpm for 30 min and collect the supernatant, which is a two-dimensional vermiculite nanosheet solution with a concentration of 0.15 mg / mL.
[0119] (4) The metal polyphenol complex solution obtained in step (2) was mixed with the two-dimensional vermiculite nanosheet solution and then sonicated at room temperature for 15 min to obtain a uniformly dispersed mixed solution.
[0120] The mass ratio of tannic acid to two-dimensional vermiculite nanosheets is 1191:1.
[0121] (5) Take 10 mL of the mixed solution obtained in step (4) and pour it into a filtration device containing a polyvinylidene fluoride microporous filter membrane with a pore size of 0.22 μm to filter and obtain a wet membrane. Place the wet membrane in a vacuum drying oven and dry it at room temperature to obtain a dry membrane.
[0122] (6) The dried membrane obtained in step (5) was soaked in a sodium hydroxide solution with a pH of 11 for 4 h to obtain a moist vermiculite-based two-dimensional layered nanofiltration membrane.
[0123] (7) Place the moist vermiculite-based two-dimensional layered nanofiltration membrane obtained in step (6) into a vacuum drying oven and dry at room temperature for 24 h to obtain a dried vermiculite-based two-dimensional layered nanofiltration membrane, which is a vermiculite-based two-dimensional layered nanofiltration membrane used for antibiotic desalting.
[0124] The final vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination has a water permeability of 94.5 L / (m²). 2 (·h·bar), sodium chloride retention rate was 22.36%, tetracycline retention rate was 96.79%, and sodium chloride / tetracycline separation factor was 24.19.
[0125] Example 5
[0126] A method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalting, the specific steps of which are as follows:
[0127] (1) Tannic acid was dissolved in a Tris-HCl solution with pH=5 to obtain a tannic acid solution with a concentration of 2.4 mM, and ferric chloride hexahydrate was dissolved in a Tris-HCl solution with pH=5 to obtain a ferric chloride solution.
[0128] (2) The tannic acid solution from step (1) and the ferric chloride solution with a concentration of 0.1 mM were stirred at room temperature (25°C) and the pH of the mixed solution was adjusted to 8.5 to obtain a metal polyphenol complex solution.
[0129] The molar ratio of tannic acid to ferric chloride is 24:1.
[0130] (3) Preparation of two-dimensional vermiculite nanosheet solution:
[0131] (3.1) Add vermiculite to a saturated sodium chloride solution with a concentration of 5.44 M and stir continuously at 100 °C for 24 h. After the reaction is completed, wash the collected precipitate three times with deionized water and anhydrous ethanol alternately.
[0132] The ratio of vermiculite to saturated sodium chloride solution used was 1 g: 500 mL.
[0133] (3.2) Add the product obtained in step (3.1) to a lithium chloride solution with a concentration of 4 M and stir continuously at 100°C for 24 h. After the reaction is completed, wash the collected precipitate three times alternately with deionized water and anhydrous ethanol.
[0134] The ratio of vermiculite to lithium chloride solution used was 1 g: 500 mL;
[0135] (3.3) Disperse the product obtained in step (3.2) in deionized water and sonicate for 1 h. Centrifuge the suspension obtained by sonication at 3500 rpm for 30 min and collect the supernatant, which is a two-dimensional vermiculite nanosheet solution with a concentration of 0.15 mg / mL.
[0136] (4) The metal polyphenol complex solution obtained in step (2) is mixed with the two-dimensional vermiculite nanosheet solution and then sonicated at room temperature for 15 min to obtain a uniformly dispersed mixed solution.
[0137] The mass ratio of tannic acid to two-dimensional vermiculite nanosheets is 1361:1.
[0138] (5) Take 10 mL of the mixed solution obtained in step (4) and pour it into a filtration device containing a polyvinylidene fluoride microporous filter membrane with a pore size of 0.22 μm to filter and obtain a wet membrane. Place the wet membrane in a vacuum drying oven and dry it at room temperature to obtain a dry membrane.
[0139] (6) The dried membrane obtained in step (5) was soaked in a sodium hydroxide solution with a pH of 11 for 4 h to obtain a moist vermiculite-based two-dimensional layered nanofiltration membrane.
[0140] (7) Place the moist vermiculite-based two-dimensional layered nanofiltration membrane obtained in step (6) into a vacuum drying oven and dry at room temperature for 24 h to obtain a dried vermiculite-based two-dimensional layered nanofiltration membrane, which is a vermiculite-based two-dimensional layered nanofiltration membrane used for antibiotic desalting.
[0141] The final vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination has a water permeability of 102.13 L / (m²). 2 (·h·bar), sodium chloride retention rate was 22.5%, tetracycline retention rate was 96.7%, and sodium chloride / tetracycline separation factor was 23.48.
[0142] like Figure 4As shown, the vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination in Example 5 had separation factors of 97.38, 23.48, 17.44, and 16.2 for four sodium chloride / antibiotic mixed solutions: sodium chloride / doxorubicin, sodium chloride / tetracycline, sodium chloride / ofloxacin, and sodium chloride / norfloxacin, respectively. The vermiculite-based two-dimensional layered nanofiltration membrane exhibits excellent separation selectivity for sodium chloride / antibiotics while maintaining high-purity water permeability. In particular, for the sodium chloride / doxorubicin mixed solution, the rejection rate for doxorubicin was 99.2%, the rejection rate for sodium chloride was 22.1%, and the separation factor was as high as 97.38, demonstrating excellent salt / antibiotic separation selectivity.
[0143] Comparative Example 1
[0144] A method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane is basically the same as in Example 5, except that steps (1) and (2) are omitted. Correspondingly, the metal polyphenol complex solution is not added in step (4).
[0145] The final two-dimensional vermiculite membrane has a water permeability of 1.5 L / (m²). 2 ·h·bar).
[0146] Table 1
[0147]
[0148] The original two-dimensional vermiculite membrane in Comparative Example 1 had a water permeability of only 1.51 L / (m²). 2 The membrane water permeability was extremely low (·h·bar), but increased to 102.13 L / (m³) after the introduction of a metal polyphenol complex (Example 5) and vermiculite. 2 The increase in water permeability (·h·bar) is due to the introduction of the metal polyphenol complex, which increases the interlayer spacing of the membrane from 12.70 Å to 13.42 Å. This reduces the resistance to water molecule transport between membrane layers, increases the transport rate, significantly increases the membrane water permeability, and the membrane exhibits excellent separation performance, with a separation factor as high as 23.48 for sodium chloride / tetracycline mixed solution.
[0149] like Figure 1 Images (a) and (b) in the figure are scanning electron microscope (SEM) images of the surface and cross-section of the original two-dimensional vermiculite film in Comparative Example 1, respectively. Figure 1 (c) and (d) are scanning electron microscope images of the surface and cross-section of the vermiculite-based two-dimensional layered nanofiltration membrane used for antibiotic desalination in Example 5, respectively. After the introduction of the metal polyphenol complex, a clear complex morphology appeared on the membrane surface and the membrane thickness increased significantly, indicating that the complex was successfully combined with vermiculite. Combined with the changes in membrane interlayer spacing in Table 1, it shows that the metal polyphenol complex was successfully intercalated into the membrane interlayer, resulting in an increase in membrane thickness and membrane interlayer spacing.
[0150] Figure 2The X-ray diffraction curves are obtained from the original two-dimensional vermiculite membrane of Comparative Example 1 and the vermiculite-based two-dimensional layered nanofiltration membranes used for antibiotic desalination in Examples 1 and 5. Figure 2 It can be seen that the introduction of the metal polyphenol complex increases the interlayer spacing (compared to Comparative Example 1). As the molar ratio of tannic acid to ferric chloride gradually increases, the diffraction angle of the composite film decreases and the interlayer spacing increases. This is because the amount of tannic acid increases, which increases the size of the metal polyphenol complex and thus the interlayer spacing.
[0151] Comparing Examples 1-5 with Comparative Example 1, it can be seen that the vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination prepared by the present invention has a high rejection rate for tetracycline, exceeding 96%, and good permeability to monovalent sodium chloride. It also exhibits good sodium chloride / tetracycline selectivity and good pure water permeability.
[0152] like Figure 3 As shown, the separation factors of different vermiculite-based two-dimensional layered nanofiltration membranes for sodium chloride / tetracycline in Examples 1-5 are as follows: the larger the separation factor, the better the separation effect of the two substances. The separation factors of the vermiculite-based two-dimensional layered nanofiltration membranes for sodium chloride / tetracycline in Examples 1-5 are all greater than 23, which shows good separation selectivity.
Claims
1. A method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination, characterized in that... Includes the following steps: (1) Dissolve tannic acid in Tris-HCl solution to obtain tannic acid solution, and at the same time dissolve ferric chloride hexahydrate in Tris-HCl solution to obtain ferric chloride solution; (2) Stir the tannic acid solution and ferric chloride solution from step (1) at room temperature and adjust the pH of the mixed solution to 8.5 to obtain a metal polyphenol complex solution; the molar ratio of tannic acid to ferric chloride is 12~24:1; (3) The metal polyphenol complex solution obtained in step (2) is mixed with the two-dimensional vermiculite nanosheet solution and then ultrasonicated at room temperature to obtain a uniformly dispersed mixed solution; (4) Pour the mixed solution obtained in step (3) into a filtration device containing a polyvinylidene fluoride microporous filter membrane and filter it to obtain a wet membrane. Place the wet membrane in a vacuum drying oven and dry it at room temperature to obtain a dry membrane. (5) The dried membrane obtained in step (4) is soaked in NaOH solution with pH 11 to obtain a moist vermiculite-based two-dimensional layered nanofiltration membrane. (6) The moist vermiculite-based two-dimensional layered nanofiltration membrane obtained in step (5) is placed in a vacuum drying oven and dried at room temperature to obtain a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination.
2. The method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination according to claim 1, characterized in that, In step (1), the concentration of tannic acid solution is 1.2~2.4 mM, and the concentration of ferric chloride solution is 0.1 mM; In step (3), the concentration of the two-dimensional vermiculite nanosheet solution is 0.15 mg / mL.
3. The method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination according to claim 2, characterized in that, The mass ratio of tannic acid to two-dimensional vermiculite nanosheets is 680~1361:
1.
4. The method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination according to claim 1, characterized in that, In step (4), the pore size of the polyvinylidene fluoride microporous filter membrane is 0.22 μm.
5. The method for preparing a vermiculite-based two-dimensional layered nanofiltration membrane for antibiotic desalination according to claim 1, characterized in that, The preparation process of the two-dimensional vermiculite nanosheet solution is as follows: (1) Add vermiculite to a saturated sodium chloride solution and stir continuously at 100°C for 24 h. After the reaction is complete, wash the collected precipitate three times with deionized water and anhydrous ethanol alternately. (2) Add the product obtained in step (1) to the lithium chloride solution and stir continuously at 100°C for 24 h. After the reaction is completed, wash the collected precipitate three times with deionized water and anhydrous ethanol alternately. (3) Disperse the product obtained in step (2) in deionized water and sonicate for 1 h. Centrifuge the suspension obtained by sonication and collect the supernatant, which is the two-dimensional vermiculite nanosheet solution.