Supramolecular coordination framework membrane, method of making and use thereof

Abstract

The present application relates to the technical field of antibiotic-containing wastewater treatment, and particularly relates to a supramolecular coordination framework membrane, a preparation method and application thereof. By precisely coordinating organic ligands with metal ions in metal precursors, SCCs with specific pore sizes and surface characteristics are constructed, the pore sizes of which are matched with the sizes of antibiotic molecules to achieve efficient interception, and the porous structure of the SCCs guarantees high water flux, the SCCs being supramolecular coordination complexes; by regulating the composition of membrane surface functional groups, the membrane is endowed with antibiofouling properties. The supramolecular coordination framework membrane provided by the present application can solve the key problems such as the difficulty in balancing interception rate and flux and poor anti-fouling properties of traditional membrane materials, and provides a new technical solution for efficient purification of antibiotic-containing wastewater.

Description

Technical Field

[0001] This invention relates to the field of antibiotic-containing wastewater treatment technology, and in particular to a supramolecular coordination framework membrane, its preparation method, and its application. Background Technology

[0002] With the rapid development of the pharmaceutical industry and the widespread use of antibiotics in medical treatment, animal husbandry, and other fields, large amounts of antibiotics are discharged into the environment in their original form or as metabolites through incomplete metabolism and improper disposal, forming complex antibiotic-containing wastewater. This type of wastewater not only has high antibiotic residue concentrations but also exhibits significant biotoxicity and recalcitrant degradation. Direct discharge of such wastewater can cause soil pollution, eutrophication, and disruption of the balance of aquatic and terrestrial ecosystems. Furthermore, it can induce aquatic microorganisms to produce antibiotic resistance genes, fostering the growth of drug-resistant bacteria. These resistant bacteria accumulate and spread through drinking water and the food chain, posing a potential risk to human health.

[0003] Currently, the main methods for treating antibiotic-containing wastewater include biodegradation, chemical oxidation, and membrane separation. Among them, membrane separation has become one of the mainstream technologies for treating antibiotic-containing wastewater due to its advantages such as simple operation, no secondary pollution, and stable treatment efficiency. Its core relies on the retention effect of membrane modules such as ultrafiltration and reverse osmosis to separate antibiotic molecules from the water, thereby purifying the wastewater.

[0004] However, existing membrane materials in membrane separation technologies suffer from numerous problems, which limit their large-scale application and the improvement of treatment efficiency. These problems mainly manifest in the following aspects:

[0005] 1. Traditional ultrafiltration membranes have large pore sizes and low rejection rates for small molecule antibiotics, making it difficult to achieve deep removal of antibiotics. The treated water may still contain residual antibiotics exceeding the standard.

[0006] Second, although reverse osmosis membranes can significantly improve the antibiotic rejection rate, especially the rejection rate of small molecule antibiotics, they have the problem of low water flux, resulting in low treatment efficiency and difficulty in meeting the capacity requirements of large-scale wastewater treatment.

[0007] Third, both ultrafiltration membranes and reverse osmosis membranes share the common problem of weak resistance to biofouling. Microorganisms in antibiotic-containing wastewater can easily attach to and multiply on the membrane surface, forming a biofilm, which leads to serious membrane fouling. This not only further reduces membrane flux and retention efficiency, but also shortens the membrane's lifespan, increases the cost of replacing membrane modules, and raises the overall treatment cost.

[0008] Therefore, how to provide a suitable membrane separation technology to solve the problems existing in the current membrane materials is a technical problem that urgently needs to be solved. Summary of the Invention

[0009] The present invention aims to at least solve one of the technical problems existing in the related art. Therefore, the first objective of the present invention is to provide a method for preparing a supramolecular coordination framework membrane; the second objective of the present invention is to provide a supramolecular coordination framework membrane; and the third objective of the present invention is to provide an application of the supramolecular coordination framework membrane.

[0010] To achieve the first objective, the technical solution adopted by this invention is as follows:

[0011] A method for preparing a supramolecular coordination framework membrane includes the following steps:

[0012] S100, prepare organic ligand solutions and metal precursor solutions respectively;

[0013] The structural formula of the organic ligand is shown below:

[0014] ;

[0015] The structural formula of the metal precursor is shown below:

[0016] ;

[0017] The concentrations of the organic ligand solution and the metal precursor solution are both 0.01–0.1 mol / L;

[0018] S200: After mixing the organic ligand solution and the metal precursor solution, stir the reaction for 30-60 min to form an SCCs solution through coordination-driven self-assembly.

[0019] SCCs are supramolecular coordination complexes, with the following structural formula:

[0020] ;

[0021] S300. The SCCs solution is coated onto the substrate surface using a drop-coating method, and a supramolecular coordination framework membrane is formed on the substrate surface by evaporation.

[0022] The substrate is selected from porous anodic aluminum oxide substrate, and the pore size of the porous anodic aluminum oxide is 50nm to 200nm;

[0023] The evaporation treatment temperature is 70℃~90℃, and the time is 3h~5h.

[0024] Furthermore, in step S100, the solvents for both the organic ligand solution and the metal precursor solution are selected from a mixed solvent of ethanol and water.

[0025] Furthermore, in the mixed solvent of ethanol and water, the volume ratio of ethanol to water is 1:1.

[0026] Further, in step S200, the organic ligand solution and the metal precursor solution are mixed in equal volumes.

[0027] Furthermore, in step S200, the reaction is carried out with stirring at a temperature of 25°C to 35°C.

[0028] Furthermore, in step S200, the stirring speed is 200 rpm to 600 rpm.

[0029] Furthermore, in step S300, the thickness of the supramolecular coordination framework membrane is 210 nm to 990 nm.

[0030] To achieve the second objective, the technical solution adopted by this invention is as follows:

[0031] A supramolecular coordination framework membrane is prepared using any of the above-described methods for preparing supramolecular coordination framework membranes.

[0032] To achieve the third objective, the technical solution adopted by this invention is as follows:

[0033] An application of a supramolecular coordination framework membrane for treating antibiotic-containing wastewater.

[0034] Furthermore, the antibiotics include one or more of tetracycline, cefoperazone, erythromycin, and bacitracin.

[0035] The above-described one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0036] This invention provides a supramolecular coordination framework membrane, its preparation method, and its application. By precisely coordinating organic ligands with metal ions in a metal precursor, SCCs with specific pore sizes and surface properties are constructed. These pore sizes match the size of antibiotic molecules, enabling efficient retention. Simultaneously, the porous structure of the SCCs ensures high water flux. Furthermore, by controlling the composition of functional groups on the membrane surface, the membrane is endowed with anti-biofouling properties. This supramolecular coordination framework membrane solves key problems of traditional membrane materials, such as the difficulty in balancing retention rate and flux, and poor antifouling resistance, providing a new technical solution for the efficient purification of antibiotic-containing wastewater.

[0037] Specifically, its advantages are mainly reflected in the following aspects:

[0038] I. Excellent resistance to biofouling, extending membrane lifespan and reducing operation and maintenance costs. The supramolecular coordination complexes (SCCs) in SFM consist of a stable coordination structure formed by a platinum-based metal precursor and an organic ligand containing a pyridine group, endowing the membrane surface with good antibacterial activity. Experimental results show that after co-culturing SFM with E. coli for 24 hours, no colonies formed on the membrane surface. This characteristic effectively inhibits the attachment and reproduction of microorganisms on the membrane surface, reducing biofouling.

[0039] Second, the method is simple to operate, environmentally friendly, and has resource recycling value. The purification method for antibiotic-containing wastewater uses a dead-end filtration device, with mild operating pressure and temperature. It does not require complex equipment or energy investment, is compatible with the modification and upgrading of existing wastewater treatment systems, and does not require the addition of toxic or harmful chemical reagents, thus avoiding secondary pollution.

[0040] Third, strong structural stability. Through evaporation-induced self-assembly, the SCCs functional layers uniformly cover and anchor onto the surface of the porous anodic alumina (AAO) substrate, forming a continuous and defect-free film. The SCCs are tightly bonded to the substrate, and the SCCs themselves have a stable spatial structure, while the honeycomb porous structure of the AAO substrate provides them with good mechanical support.

[0041] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0042] Figure 1 The hydrogen nuclear magnetic resonance of SCCs provided in Embodiment 1 of this invention ( 1 ¹H NMR spectrum.

[0043] Figure 2 The image is an AAO scanning electron microscope (SEM) image provided in Embodiment 1 of the present invention, with a scale bar of 100 nm.

[0044] Figure 3 This is a SEM image of the surface of the supramolecular coordination framework membrane (SFM membrane) provided in Embodiment 1 of the present invention.

[0045] Figure 4 This is an SEM image of the cross-section of the SFM membrane provided in Embodiment 1 of the present invention.

[0046] Figure 5 This is the energy dispersive X-ray (EDS) elemental distribution map of the SFM film provided in Embodiment 1 of the present invention.

[0047] Figure 6 This is an atomic force microscope (AFM) three-dimensional morphology image of the SFM film provided in Embodiment 1 of the present invention.

[0048] Figure 7 This is a three-dimensional and two-dimensional superimposed image of the SFM film obtained by fluorescence / confocal laser scanning microscopy (CLSM) according to Embodiment 1 of the present invention, with a scale bar of 100 μm.

[0049] Figure 8 This is a bar chart showing the retention of different antibiotics by the SFM membrane provided in Embodiment 2 of the present invention.

[0050] Figure 9 This is a bar chart showing the flux of the SFM membrane for different antibiotics provided in Embodiment 3 of the present invention.

[0051] Figure 10 This is a diagram illustrating the colony formation of the SFM membrane and AAO substrate provided in Embodiment 4 of the present invention.

[0052] Figure 11 This is a bar chart showing the antibacterial activity and colony count of the SFM membrane provided in Example 4 of the present invention. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The following embodiments are used to illustrate this invention, but cannot be used to limit the scope of this invention.

[0054] In the following embodiments, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available, unless otherwise specified, and are carried out in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions.

[0055] Example 1

[0056] The process for preparing supramolecular coordination framework membranes is as follows:

[0057] I. Preparation of organic ligand solution: Prepare organic ligand solution... 1 mmol was dissolved in a mixed solvent of ethanol and water (volume ratio 1:1) (10 mL) to obtain an organic ligand solution with a concentration of 0.1 mol / L.

[0058] II. Preparation of metal precursor solution: The trans-di(triethylphosphine)bis(trifluoromethanesulfonate)platin(II)butyne complex The metal precursor solution was dissolved in a mixed solvent of ethanol and water (volume ratio of 1:1) (10 mL) to obtain a concentration of 0.1 mol / L.

[0059] III. Synthesis of SCCs, with the structural formula shown below:

[0060] ;

[0061] The aforementioned organic ligand solution and metal precursor solution were mixed at a volume ratio of 1:1. Then, the mixture was stirred at 500–600 r / min for 30–60 min at room temperature (approximately 25°C) to form SCCs in the reaction solution through coordination-driven self-assembly. 1 1H NMR spectrum (using CDCl3 as solvent), such as Figure 1 As shown in the figure, the spectrum shows clear peak splitting and symmetrical peak shape, indicating that SCCs have a highly homogeneous chemical environment and that the coordination self-assembly reaction is directional and complete.

[0062] IV. Pretreatment of AAO (pore size 50-200nm) substrates.

[0063] The AAO substrate was ultrasonically cleaned with anhydrous ethanol for 15–30 min to remove surface impurities, and then dried at 80°C for 2 h to obtain the pretreated AAO. Its SEM image is shown below. Figure 2 As shown.

[0064] V. Preparation of supramolecular coordination framework membranes.

[0065] The aforementioned reaction solution containing SCCs (0.2 mL) was uniformly coated onto the pretreated AAO substrate surface. Subsequently, the coated substrate was rapidly placed in an electric thermostatic oven preheated to 70–90 °C and evaporated at a constant temperature for 4 hours, allowing the SCCs to self-assemble and anchor on the substrate surface (rapid evaporation of ethanol and water caused local supersaturation, driving the SCCs to oriented assemblies at the gas-liquid-solid interface and deposit on the AAO pores and surface), forming a continuous film layer. Subsequently, the composite membrane was naturally cooled to room temperature, and the residual reagents on the surface were rinsed with deionized water. After drying, a supramolecular coordination framework membrane was obtained, denoted as the SFM membrane.

[0066] Scanning electron microscope (SEM) images of the SFM film surface, such as Figure 3 As shown in the figure, it can be seen that the SCCs functional layer is uniformly covered and anchored on the surface of the AAO substrate, forming a continuous and defect-free film layer without local exposure or voids. This result indicates that the SCCs are uniformly bonded to the substrate.

[0067] The scale bar of Figure A is 200 nm, and the scale bar of Figure B is 5 μm.

[0068] SEM images of the cross-section of the SFM membrane, such as Figure 4 As shown in the figure, a uniform SCCs coating with a thickness of 380 nm is formed on the surface of the AAO substrate.

[0069] EDS elemental distribution diagram of SFM film, as shown Figure 5 As shown in the figure, we can see that: the Al element signal is concentrated in the lower half of the image and is continuously and uniformly distributed; the S element signal is mainly distributed in the upper half; the Pt element is uniformly distributed overall; and the P element is mainly distributed in the upper half.

[0070] AFM three-dimensional morphology image of SFM membrane, as shown Figure 6 As shown in the figure, the surface exhibits a dense, uniform structure with small bumps / granules, without large cracks or holes.

[0071] Three-dimensional morphology and two-dimensional overlay images of SFM film obtained by fluorescence / confocal laser scanning microscopy (CLSM), as follows: Figure 7 As shown in the figure, the SCCs functional layer is uniformly dispersed on the surface of the SFM membrane, the fluorescence signal is concentrated on the membrane surface, and there are no SCCs distributed inside the membrane, which proves that the functional layer is a surface-loaded structure.

[0072] Example 2

[0073] A series of antibiotics of different sizes, including tetracycline (TC), cefoperazone (CP), erythromycin (EM), and bacitracin (BT), were selected to evaluate the retention of SFM membranes. The procedure is as follows:

[0074] Prepare aqueous solutions containing TC, CP, EM and BT respectively, with a concentration of 30 ppm, and adjust the pH to neutral (pH 7.0).

[0075] Cut the SFM membrane to 10cm. 2The membrane was installed in a dead-end filter device, sealed to ensure no leakage. An aqueous solution of one antibiotic was injected into the feed tank to remove air bubbles. The nitrogen pressure was adjusted to 2 bar, and the temperature was controlled at approximately 25°C. Filtration began (each batch was filtered for 10 minutes, continuous operation was possible; every 10 minutes of filtration was followed by a 3-minute backwash with deionized water to maintain high water flux and separation performance). The permeate from the first 3 minutes was discarded, and the permeate from the following 7 minutes was collected (the permeate was collected in the permeate device; antibiotic residue was tested and found to be ≤0.5 ppm, meeting discharge standards or allowing for recycling; the antibiotic-rich retentate was collected for subsequent antibiotic recovery or further deep degradation, achieving the dual goals of wastewater purification and resource recovery). The absorbance of the feed solution and permeate was measured using a UV-Vis spectrophotometer, and the concentration was calculated using a standard curve. The rejection rate was obtained using R=(Cf-Cp) / Cf, where Cf and Cp are the feed concentration and permeate concentration, respectively. The steps were repeated with different antibiotics, with each experiment performed three times in parallel. The average value was taken, and the results are shown in the table below.

[0076]

[0077] Based on the data provided in the table above, plot a bar chart of the retention rates of different antibiotics, such as... Figure 8 As shown in the figure. The results showed that SFM exhibited high retention efficiency for four different sizes of antibiotics, with the retention rate increasing with the increase of antibiotic molecule size. The parallel experiments showed small deviations and good performance stability. The antibiotic retention rates of TC, CP, EM and BT were approximately 95.2%, 97.5%, 98.1% and 99.5%, respectively.

[0078] Example 3

[0079] A series of antibiotics of different sizes, including tetracycline (TC), cefoperazone (CP), erythromycin (EM), and bacitracin (BT), were selected to evaluate the flux of SFM. The procedure is as follows:

[0080] Prepare aqueous solutions containing TC, CP, EM and BT respectively, with a concentration of 30 ppm, and adjust the pH to neutral (pH 7.0).

[0081] Cut the SFM membrane to 10cm. 2The membrane module of the dead-end filtration unit is installed to ensure a good seal and no leakage. Deionized water is injected into the unit, the pressure is adjusted to 2 bar, and the unit is run for 10 minutes. The pressure stability and sealing of the unit are checked, and the water is drained after confirmation. A TC aqueous solution is injected into the feed tank to remove air bubbles from the tank and pipeline. The temperature is adjusted to 25℃, the pressure is maintained at 2 bar, filtration is started, and timing begins simultaneously. The permeate is discarded after the first 5 minutes. Starting from the 6th minute, permeate is collected every 5 minutes, weighed, and the time is recorded. This is repeated 5 times (including the 25-minute filtration process after covering). After each antibiotic solution test, the membrane surface is backwashed with deionized water for 10 minutes, then forward filtered with deionized water for 15 minutes to remove residual antibiotics from the membrane surface and ensure no cross-contamination in subsequent tests. The flux of four antibiotic solutions (TC, CP, EM, and BT) is tested sequentially using the formula F = V / (A×t×P), where F is in L·m³. -2 ·h -1 ·bar -1 The unit of V is L, and the unit of A is m. 2 The units of t are h, and the unit of P is bar, representing flux, volume of permeate solution, effective membrane area, operating time, and transmembrane pressure, respectively (with consistent experimental conditions for each group). Where A = 0.001 m 2 P=2 bar, t=1 h, V and flux are shown in the table below:

[0082]

[0083] Based on the data in the table above, plot the flux of different antibiotics using bar charts, such as... Figure 9 As shown, the results indicate that the SFM membrane exhibits a significant advantage in high flux during the treatment of the four types of antibiotic-containing wastewater, and has the potential to meet the needs of large-scale and high-efficiency wastewater treatment in practice. At the same time, it has a synergistic effect with the retention performance, thereby achieving the dual goals of high flux and high retention.

[0084] Example 4

[0085] The testing procedure for the antibacterial properties of the SFM membrane is as follows:

[0086] Cut the SFM membrane and the bare porous anodic aluminum oxide (AAO) substrate into 1cm × 1cm pieces respectively, place them in sterile petri dishes, and add 10g of each. -3 Add CFU / mL (0.1mL) of E. coli bacterial suspension, ensuring uniform coverage of the membrane surface. Then, add an appropriate amount of LB medium to the petri dish and incubate at 37℃ for 24 hours. After incubation, observe and count the colony forming units (CFU) on both membrane surfaces. The results are as follows: Figure 10As shown in the figure, no colonies were found after 24 hours of SFM treatment compared to the bare substrate. This result indicates that the SFM membrane has significant antibacterial activity, which is beneficial for preventing microbial contamination in practical applications.

[0087] A bar chart showing the antibacterial properties of SFM membranes, as shown. Figure 11 As shown in the figure, the antibacterial activity rate of the SFM membrane exceeds 90%, corresponding to a colony count of 0 CFU, indicating that the SFM membrane has a strong killing / inhibiting effect on the test bacteria (such as Escherichia coli).

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a supramolecular coordination framework film, characterized by, Includes the following steps: S100, prepare organic ligand solutions and metal precursor solutions respectively; The structural formula of the organic ligand is shown below: ； The structural formula of the metal precursor is shown below: ； The concentrations of the organic ligand solution and the metal precursor solution are both 0.01–0.1 mol / L; S200: After mixing the organic ligand solution and the metal precursor solution, stir the reaction for 30-60 min to form an SCCs solution through coordination-driven self-assembly. SCCs are supramolecular coordination complexes, with the following structural formula: ； S300. The SCCs solution is coated onto the substrate surface using a drop-coating method, and a supramolecular coordination framework membrane is formed on the substrate surface by evaporation. The substrate is selected from porous anodic aluminum oxide substrate, and the pore size of the porous anodic aluminum oxide is 50nm to 200nm; The evaporation treatment temperature is 70℃~90℃, and the time is 3h~5h; The supramolecular coordination complexes (SCCs) in SFM consist of a stable coordination structure formed by a platinum-based metal precursor and an organic ligand containing a pyridine group, which endows the membrane surface with good antibacterial activity. SFM stands for supramolecular coordination framework membrane; Through evaporation-induced self-assembly, the functional layers of SCCs are uniformly covered and anchored on the surface of the porous anodic aluminum oxide substrate, forming a continuous and defect-free film. The SCCs are tightly bonded to the substrate, and the SCCs themselves have a stable spatial structure. The honeycomb porous structure of the porous anodic aluminum oxide substrate provides them with good mechanical support.

2. The method for preparing a supramolecular coordination framework membrane as described in claim 1, characterized in that, In step S100, the solvents for both the organic ligand solution and the metal precursor solution are selected from a mixed solvent of ethanol and water.

3. The method of claim 2, wherein the supermolecular coordination framework film is prepared by a method comprising: In a mixed solvent of ethanol and water, the volume ratio of ethanol to water is 1:

1.

4. The method for preparing a supramolecular coordination framework membrane as described in claim 1, characterized in that, In step S200, the organic ligand solution and the metal precursor solution are mixed in equal volumes.

5. The method for preparing a supramolecular coordination framework membrane as described in claim 1, characterized in that, In step S200, the reaction is carried out with stirring at a temperature of 25℃~35℃.

6. The method of claim 1, wherein the supramolecular coordination framework film is prepared by a method comprising: In step S200, the stirring speed is 200 rpm to 600 rpm.

7. The method for preparing a supramolecular coordination framework membrane as described in claim 1, characterized in that, In step S300, the thickness of the supramolecular coordination framework membrane is 210 nm to 990 nm.

8. A supramolecular coordination framework membrane, characterized in that, It is prepared using the method for preparing supramolecular coordination framework membranes as described in any one of claims 1 to 7.

9. Use of a supramolecular coordination framework membrane, characterized in that The supramolecular coordination framework membrane as described in claim 8 is used to treat antibiotic-containing wastewater.

10. Use of a supramolecular coordination framework membrane according to claim 9, wherein The antibiotics include one or more of tetracycline, cefoperazone, erythromycin, and bacitracin.

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