Preparation method of composite membrane for tetracycline wastewater treatment

Abstract

The invention relates to the technical field of antibiotic wastewater treatment, and particularly discloses a preparation method of a composite membrane for tetracycline wastewater treatment, which comprises the following steps: adding 1-vinyl imidazole and equimolar bromo-n-hexane into a three-necked flask, carrying out stirring reaction, cooling to room temperature after the stirring reaction is completed, filtering, washing, and drying to obtain the composite membrane for tetracycline wastewater treatment. Washing with ethyl acetate to obtain a product I, and drying the product I in a vacuum drying oven to obtain yellow viscous ionic liquid 1-hexyl-3-vinyl imidazole bromide; and preparing imidazole polyionic liquid from the product I, and preparing the polyionic liquid composite membrane from the obtained polyionic liquid through a phase inversion method. The prepared imidazole polyion liquid composite membrane removes tetracycline in wastewater through physical barrier, chemical adsorption or synergistic effect; compared with the prior art, the polyion liquid composite membrane prepared by the method disclosed by the invention combines the characteristics of the ionic liquid and the polymer, and shows good hydrophilicity, thermal stability, pollution resistance, mechanical property and separation property.

Description

Technical Field

[0001] This invention belongs to the field of antibiotic wastewater treatment technology, specifically relating to a method for preparing a composite membrane for tetracycline wastewater treatment. Background Technology

[0002] Antibiotics are drugs used to treat various bacterial or pathogenic microbial infections. However, with the increasing demand for antibiotics and the prominent problem of overuse, they accumulate and enrich in various environments and organisms, inducing the evolution and spread of drug-resistant genes in microbial communities, thus posing a potential threat to human health and the ecological environment. Tetracycline (TC) is a commonly used broad-spectrum antibiotic, widely used in livestock and aquaculture due to its strong inhibitory effects on Gram-positive bacteria, chlamydia, mycoplasma, etc., and its low cost. The discharge of pharmaceutical wastewater, livestock manure, and domestic sewage has led to the detection of tetracycline in groundwater, surface water, and other aquatic environments, thus posing potential ecological risks. The current pollution situation presents a severe picture of widespread distribution across multiple media and significant ecological and health risks. Due to its concentrated pollution sources, large dosage, good water solubility, stable structure, and difficulty in treatment in water, tetracycline persists in groundwater, surface water, rivers, and wastewater, making water pollution a particularly prominent issue. The mainstream treatment methods for antibiotic-contaminated wastewater include adsorption, chemical oxidation, photocatalytic degradation, and electrochemical degradation. Among these, adsorption is considered the preferred solution for wastewater treatment due to its simple operation and low cost. Currently, various high-capacity adsorbents such as metal oxides and metal-organic frameworks are difficult to apply in practice due to their poor separation and mechanical properties. Membrane materials, as adsorbents, exhibit excellent separation and mechanical properties, which can make up for the shortcomings of traditional particulate adsorbents. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a composite membrane for tetracycline wastewater treatment, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a composite membrane for tetracycline wastewater treatment includes the following steps: S1. Add 1-vinylimidazolium and an equimolar amount of n-hexane bromide to a three-necked flask and stir to react. After the reaction is complete, cool to room temperature and wash with ethyl acetate to obtain product one. Dry product one in a vacuum drying oven to obtain a yellow viscous ionic liquid 1-hexyl-3-vinylimidazolium bromide. S2. Dissolve the above ionic liquid 1-hexyl-3-vinylimidazolium bromide in methanol, then add ethylene glycol dimethacrylate (EDGMA) and azobisisobutyronitrile (AIBN), and heat under reflux to react. After the reaction is completed, cool to room temperature, and wash with methanol to obtain product two. Dry product two in a vacuum drying oven to obtain poly(1-hexyl-3-vinylimidazolium bromide) (P[HVIM][Br]). S3. Poly(1-hexyl-3-vinylimidazolium bromide) (P[HVIM][Br]) is uniformly dispersed in N,N-dimethylformamide (DMF), and polyvinylidene fluoride (PVDF) is added to obtain a mixture. The mixture is continuously stirred until a homogeneous solution is formed, and then allowed to stand at room temperature to remove air bubbles. A certain volume of the mixed solution is then cast onto a glass plate, and the shape of the membrane is fixed using a circular mold. The glass plate is then immersed in deionized water to induce a phase inversion. Finally, the membrane is peeled off from the glass plate to obtain a polyionic liquid composite membrane, which is a composite membrane for tetracycline wastewater treatment, prepared by the phase inversion method.

[0005] Preferably, the 1-vinylimidazole in S1 is 0.10 mol, and the molar ratio of 1-vinylimidazole to n-hexane bromide is 1:1.

[0006] Preferably, the temperature of the stirring reaction in S1 is 70°C and the reaction time is 2 hours.

[0007] Preferably, the washing of product one in step S1 is performed three times, and the drying temperature of the vacuum drying oven in step S1 is 65°C, and the drying time is 12 hours.

[0008] Preferably, in S2, the mass of the ionic liquid 1-hexyl-3-vinylimidazolium bromide is 2.61 g, the volume of methanol is 30 mL, the mass of ethylene glycol dimethacrylate (EDGMA) is 1.42 g, and the mass of azobisisobutyronitrile (AIBN) is 0.05 g.

[0009] Preferably, the heating reflux temperature in S2 is 80°C and the time is 2 hours; the washing product II is washed three times in S2; and the drying temperature of the vacuum drying oven in S2 is 70°C and the drying time is 12 hours.

[0010] Preferably, the molar ratio of ionic liquid 1-hexyl-3-vinylimidazolium bromide solution, ethylene glycol dimethacrylate (EDGMA), and azobisisobutyronitrile (AIBN) in S2 is 33:24:1.

[0011] Preferably, in S3, the mass of poly(1-hexyl-3-vinylimidazolium bromide) is 0.30 g, the mass of N,N-dimethylformamide (DMF) is 15 g, and the mass of polyvinylidene fluoride (PVDF) is 1 g.

[0012] Preferably, the mixing time of the mixture in S3 is 4 hours, the standing time at room temperature is 12 hours, and the diameter of the circular mold is 6 cm.

[0013] Preferably, the molar ratio of poly(1-hexyl-3-vinylimidazolium bromide):N,N-dimethylformamide (DMF):polyvinylidene fluoride (PVDF) in S3 is 0.3:15:1.

[0014] Compared with the prior art, the beneficial effects of the present invention are: The imidazole-based polyionic liquid composite membrane prepared by this invention is a nitrogen-containing heterocyclic compound with a membrane surface exhibiting strong hydrophilicity. This membrane combines the advantages of adsorption and membrane filtration, removing tetracycline from wastewater through physical barrier, chemical adsorption, or synergistic effect. Compared with the prior art, the polyionic liquid composite membrane prepared by this invention combines the characteristics of ionic liquids and polymers, exhibiting good hydrophilicity, thermal stability, antifouling properties, mechanical properties, and separation performance. Attached Figure Description

[0015] Figure 1 The figure shows the performance test results of the polyionic liquid composite membrane prepared in this invention.

[0016] Figure 2 The diagram shows the optimized performance of the polyionic liquid composite membrane prepared in this invention for removing tetracycline from water. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example: A method for preparing a composite membrane for tetracycline wastewater treatment includes the following steps: Step 1: Add 0.10 mol of 1-vinylimidazolium and an equimolar amount of n-hexane bromide to a three-necked flask, stir at 70 °C for 2 h, cool to room temperature after the reaction is complete, and wash three times with ethyl acetate to obtain product 1. Dry product 1 in a vacuum drying oven at 65 °C for 12 h to obtain a yellow viscous ionic liquid 1-hexyl-3-vinylimidazolium bromide ([HVIM][Br]). Step 2: Dissolve 2.61 g of ionic liquid 1-hexyl-3-vinylimidazolium bromide ([HVIM][Br]) in 30 mL of methanol, then add 1.42 g of ethylene glycol dimethacrylate (EDGMA) and 0.05 g of azobisisobutyronitrile (AIBN), and heat under reflux at 80 °C for 24 h. After the reaction is complete, cool to room temperature and wash three times with methanol to obtain product 2. Dry product 2 in a vacuum drying oven at 70 °C for 12 h to obtain poly(1-hexyl-3-vinylimidazolium bromide) (P[HVIM][Br]). Step 3: Take 0.30g of poly(1-hexyl-3-vinylimidazolium bromide) (P[HVIM][Br]) and uniformly disperse it in 15g of N,N-dimethylformamide (DMF). Then add 1g of polyvinylidene fluoride (PVDF) to obtain a mixture. Stir the mixture for 4 hours until a homogeneous solution is formed. Let it stand at room temperature for 12 hours to remove air bubbles. Then take a certain volume of the mixed solution and cast it onto a glass plate. Use a circular mold with a diameter of 6cm to fix the shape of the membrane. Immerse the glass plate in deionized water to induce a phase inversion. Finally, peel the membrane off the glass plate to obtain polyionic liquid composite membranes (PILMs). Polyionic liquid composite membranes (PILMs) combine the characteristics of ionic liquids and polymers, exhibiting good structural tunability, thermal stability, mechanical properties, and separation performance.

[0019] The surface contact angle of the composite membrane was further determined using a contact angle analyzer to assess its hydrophilicity / hydrophobicity. An automated specific surface area and pore size analyzer was used to analyze the pore structure type of the composite membrane surface. The zeta potential of PILMs at different pH values ​​was measured using a flow potentiometer to analyze their surface charge. Thermogravimetric analysis was used to continuously measure the mass change of the composite membrane with temperature to determine its thermal stability.

[0020] A schematic diagram of the contact angles of PILMs is shown below. Figure 1 As shown in figure a, the average contact angle of three random points on the PILMs surface is 67.4°. This indicates that the PILMs exhibit good hydrophilicity, which may be due to the strong electrostatic interaction between the polyionic liquid-induced membrane and water.

[0021] like Figure 1 As shown in b, the nitrogen adsorption / desorption curves of PILMs exhibit a significant hysteresis loop, and the pore type belongs to type IV-H3 (IUPAC classification), indicating the presence of irregular mesopores in the PILMs. Furthermore, the specific surface area of ​​the PILMs is 309.871 m². 2 / g, pore volume is 0.975 cm³ 3 / g, with a pore size of 16.233nm. This indicates that PILMs belong to ultrafiltration membranes, and their excellent specific surface area and pore volume are beneficial for achieving high removal efficiency and high stability in the process of pollutant removal.

[0022] The surface charge of PILMs was analyzed by measuring their Zeta potentials at different pH values. Figure 1 As shown in c, PILMs carry a positive charge in the pH range of 3.00-7.40 due to the presence of a large number of imidazole cations, while PILMs carry a negative charge when pH>7.40 due to the deprotonation of the PILMs membrane surface.

[0023] PILMs exhibit three distinct phases of weightlessness (e.g. Figure 1 d). The initial weight loss occurred between 28.12 and 357.04 °C, mainly attributed to the evaporation of trace amounts of water and DMF in the material. The second weight loss stage, from 356.40 to 580.83 °C, was primarily related to the decomposition of PVDF and the P[HVIM][Br]imidazolium ring. The final, third stage of weight loss, characterized by degradation at high temperatures (581.47–821.32 °C), was attributed to the collapse of the material framework. These results demonstrate that PILMs exhibit excellent thermal stability.

[0024] Furthermore, a classic dynamic adsorption method combined with high-performance liquid chromatography (HPLC) was used to separate and remove tetracycline from wastewater. The working mode is to drive the wastewater through polyionic liquid composite membranes (PILMs) under pressure, thereby achieving the separation and concentration of tetracycline. This mode has the advantages of simple operation, easy scale-up, and no need to recover the adsorbent from the solution, making it easier to achieve industrialization. Under optimal experimental conditions, the removal rate of tetracycline by polyionic liquid composite membranes (PILMs) reached 87.0%.

[0025] It should be noted that the amount of poly(1-hexyl-3-vinylimidazolium bromide) (P[HVIM][Br]) added has the following effect: Theoretically, increasing the relative mass of poly(1-hexyl-3-vinylimidazolium bromide) (P[HVIM][Br]) provides more active sites for TC removal; with the increase of poly(1-hexyl-3-vinylimidazolium bromide) (P[HVIM][Br]), the TC removal efficiency initially increases, and then reaches an equilibrium (e.g., ...). Figure 2 a) The improvement in removal efficiency is related to the increase in TC active sites on PILMs due to the increase in poly(1-hexyl-3-vinylimidazolium bromide) (P[HVIM][Br]). Subsequently, when the amount of poly(1-hexyl-3-vinylimidazolium bromide) (P[HVIM][Br]) added reaches 0.30 g, the TC removal efficiency reaches equilibrium, and more poly(1-hexyl-3-vinylimidazolium bromide) (P[HVIM][Br]) actually hinders TC molecules from reaching the active sites. Therefore, the amount of poly(1-hexyl-3-vinylimidazolium bromide) (P[HVIM][Br]) added is selected to be 0.30 g.

[0026] Effect of the volume of the casting solution: The film thickness is affected by the volume of the casting solution. Circular PILMs with a diameter of 6 cm are prepared by casting 1.0 - 5.0 mL of the casting solution; as Figure 2 shown in b, as the volume of the casting solution increases, the removal efficiency also increases, which is related to the increase in the active sites of TC in PILMs; when the volume of the casting solution increases to 3.0 mL, the removal efficiency reaches a balanced state because the active sites of PILMs are sufficient to meet the demand at this time; therefore, 3.0 mL of the casting solution is selected for subsequent experiments to prepare circular PILMs.

[0027] Effect of the injection concentration: The injection concentration affects the removal efficiency of PILMs; as Figure 2 shown in c, when the injection concentration is lower than 6.0 mg / mL, the removal efficiency always remains above 85.0%; as the injection concentration continues to increase, the removal efficiency begins to decline. The injection concentration is positively correlated with the number of TC molecules in the injection solution. Initially, TC molecules will quickly occupy the active sites on PILMs, hindering the continued interaction between PILMs and TC molecules, resulting in a decrease in the removal efficiency of TC.

[0028] Effect of the injection volume: The TC removal efficiency is affected by the filtration volume; as Figure 2 shown in d, when the injection concentration is 6.0 mg / mL, as the injection volume increases, the TC removal efficiency gradually decreases (the removal efficiency can remain above 87.0% for 40.0 mL of the TC solution), which is because as the injection volume increases, the active sites on PILMs are gradually occupied by TC molecules, weakening the interaction between PILMs and TC molecules.

[0029] Effect of the pump speed: The pump speed determines the rate at which the TC solution passes through PILMs, thus affecting the removal efficiency; as Figure 2 shown in e, as the pump speed increases, the TC removal efficiency gradually decreases. When the pump speed is lower than 4 r / min, the removal efficiency can remain above 87.0%; at higher fluxes, the residence time of TC molecules on PILMs is shortened, resulting in a reduced interaction time between the two, thus reducing the removal efficiency.

[0030] Effect of pH: The pH value of the solution affects the form of substances; the effect of PILMs on the removal efficiency of TC is studied within the range of pH 3.00 - 12.00; TC has three isoelectric points (pH = 3.32, 7.78, and 9.85); the results are as follows Figure 2 shown in f: (1) When pH = 3.00, TC exists in the cationic form (<pH 3.32), PILMs are positively charged, and there is a repulsive force between the two, resulting in a low removal efficiency; (2) Within the pH range of 5.00 - 7.00, the binding mechanism between amphoteric TC (3.32 < pH < 7.78) and positively charged PILMs may be electrostatic interaction; (3) When pH > 7.00, amino anionic TC (7.78 < pH < 9.85) and anionic TC ( <ph>9.85) There is a repulsive force between the TC and negatively charged PILMs, which leads to a decrease in TC removal efficiency. Therefore, the optimal pH of the solution is 7.00.

[0031] Effect of temperature: The effect of temperature on TC removal efficiency was studied within the range of 0-50℃; experiments showed that temperature had no significant effect on removal efficiency. The reason why temperature has no effect on removal efficiency may be due to the limitation of TC transfer to the membrane surface.

[0032] in conclusion: The polyionic liquid / PVDF composite membrane material prepared by the method of the present invention has excellent mechanical properties, thermal stability, hydrophilicity and high flux. Its surface is rich in active sites, which can interact efficiently with target molecules, and it is suitable for the removal of tetracycline from wastewater.

[0033] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.< / ph>

Claims

1. A method for preparing a composite membrane for tetracycline wastewater treatment, characterized in that, Includes the following steps: S1. Add 1-vinylimidazolium and an equimolar amount of n-hexane bromide to a three-necked flask and stir to react. After the reaction is complete, cool to room temperature and wash with ethyl acetate to obtain product one. Dry product one in a vacuum drying oven to obtain a yellow viscous ionic liquid 1-hexyl-3-vinylimidazolium bromide. S2. Dissolve the above ionic liquid 1-hexyl-3-vinylimidazolium bromide in methanol, then add ethylene glycol dimethacrylate and azobisisobutyronitrile, and heat under reflux to react. After the reaction is completed, cool to room temperature, and wash with methanol to obtain product two. Dry product two in a vacuum drying oven to obtain poly(1-hexyl-3-vinylimidazolium bromide). S3. Disperse poly(1-hexyl-3-vinylimidazolium bromide) evenly in N,N-dimethylformamide, then add polyvinylidene fluoride to obtain a mixture. Continue stirring the mixture until a uniform solution is formed, and let it stand at room temperature to remove air bubbles. Then, take a certain volume of the mixed solution and cast it onto a glass plate. Fix the shape of the membrane with a circular mold, immerse the glass plate in deionized water to induce a phase inversion, and finally peel the membrane off the glass plate to obtain a polyionic liquid composite membrane.

2. The method for preparing a composite membrane for tetracycline wastewater treatment according to claim 1, characterized in that: The 1-vinylimidazole in S1 is 0.10 mol, and the molar ratio of 1-vinylimidazole to n-hexane bromide is 1:

1.

3. The method for preparing a composite membrane for tetracycline wastewater treatment according to claim 1, characterized in that: The stirring reaction in S1 is carried out at a temperature of 70°C for 2 hours.

4. The method for preparing a composite membrane for tetracycline wastewater treatment according to claim 1, characterized in that: The washing of product one in S1 is performed three times, and the drying temperature of the vacuum drying oven in S1 is 65°C, and the drying time is 12 hours.

5. The method for preparing a composite membrane for tetracycline wastewater treatment according to claim 1, characterized in that: The S2 contains 2.61 g of ionic liquid 1-hexyl-3-vinylimidazolium bromide, 30 mL of methanol, 1.42 g of ethylene glycol dimethacrylate, and 0.05 g of azobisisobutyronitrile.

6. The method for preparing a composite membrane for tetracycline wastewater treatment according to claim 1, characterized in that: The heating and reflux temperature in S2 is 80°C for 2 hours. The washing of product two in S2 is performed three times. The drying temperature of the vacuum drying oven in S2 is 70°C for 12 hours.

7. The method for preparing a composite membrane for tetracycline wastewater treatment according to claim 1, characterized in that: The molar ratio of ionic liquid 1-hexyl-3-vinylimidazolium bromide solution, ethylene glycol dimethacrylate, and azobisisobutyronitrile in S2 is 33:24:

1.

8. The method for preparing a composite membrane for tetracycline wastewater treatment according to claim 1, characterized in that: The mass of poly(1-hexyl-3-vinylimidazolium bromide) in S3 is 0.30 g, the mass of N,N-dimethylformamide is 15 g, and the mass of polyvinylidene fluoride is 1 g.

9. The method for preparing a composite membrane for treating tetracycline wastewater according to claim 1, characterized in that: The mixing time of the mixture in S3 is 4 hours, the standing time at room temperature is 12 hours, and the diameter of the circular mold is 6 cm.

10. The method for preparing a composite membrane for tetracycline wastewater treatment according to claim 1, characterized in that: The molar ratio of poly(1-hexyl-3-vinylimidazolium bromide):N,N-dimethylformamide:polyvinylidene fluoride in S3 is 0.3:15:1.

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