Nanofiber composite membrane as well as preparation method and application thereof

Abstract

The invention belongs to the field of wastewater treatment, and particularly relates to a nanofiber composite membrane as well as a preparation method and application thereof. The nanofiber composite membrane comprises a nanofiber substrate, amine compounds, metal ions and optional auxiliaries, wherein the amine compounds and the metal ions are loaded on the nanofiber substrate. According to the nanofiber composite membrane provided by the invention, the nanofiber is used as the substrate material, and the amine compound and the metal ions are used for performing dual modification on the substrate material, so that the obtained nanofiber composite membrane can effectively remove pollutants in a water body, and is particularly suitable for removing pollutants such as COD (Chemical Oxygen Demand) and atrazine in the water body.

Description

Technical Field

[0001] The present invention belongs to the field of wastewater treatment, and particularly relates to a nanofiber composite membrane, a preparation method thereof, and an application thereof. Background Art

[0002] With the development of industrialization, natural water bodies are facing the pollution risks of organic matters, pesticides, antibiotics, and emerging pollutants. These pollutants are highly toxic and difficult to degrade, and are likely to remain in the soil and water bodies for a long time, and accumulate in organisms. They enter the human body or animals through the food chain and drinking water, causing adverse reactions or even diseases. Therefore, effectively removing these pollutants from water is of crucial significance for environmental protection and human health.

[0003] Water treatment filter materials are the core components in the water treatment process. According to the material and function, they mainly include physical filtration filter materials, adsorption filter materials, and biochemical filter materials. Among them, physical filtration filter materials are mainly used to intercept particulate impurities in water bodies. For example, filter cotton / magic carpet can intercept large particulate impurities such as fish feces and food residues; rattan cotton / fiber balls can intercept tiny particulate impurities. Adsorption filter materials usually have a porous structure, a high specific surface area, and strong adsorption ability, and can remove odors, pigments, organic matters, and some heavy metals. Specific examples of physical filtration filter materials include activated carbon, porous adsorption resins, etc. Biochemical filter materials are mainly used to cultivate nitrifying bacteria, and decompose harmful substances such as ammonia nitrogen in water through biological transformation, thereby stabilizing the water quality. Examples of biochemical filter materials include ceramic rings, bacterial houses, biochemical balls, quartz balls, etc. Among them, the porous structures of ceramic rings and bacterial houses can provide attachment spaces for nitrifying bacteria to help decompose harmful substances such as ammonia nitrogen and stabilize the water quality. Biochemical balls are plastic porous spheres, and the concave channel design on their surfaces can increase the dissolved oxygen content. Quartz balls have a high specific surface area and high nitrifying bacteria cultivation efficiency, and can quickly establish a stable nitrification system. However, the existing water treatment filter materials generally have the defects of limited pollutant removal effect or slow removal speed. Summary of the Invention

[0004] The first object of the present invention is to provide a nanofiber composite membrane capable of effectively removing pollutants in water bodies.

[0005] The second object of the present invention is to provide a preparation method of the nanofiber composite membrane.

[0006] The third object of the present invention is to provide the application of the above-mentioned nanofiber composite membrane in water treatment.

[0007] The nanofiber composite membrane provided by the present invention includes a nanofiber substrate, an amine compound and a metal ion loaded on the nanofiber substrate, and an optional auxiliary agent.

[0008] The preparation method of the nanofiber composite membrane provided by the present invention includes the following steps:

[0009] S1. Immerse the nanofibers in an amine compound solution, add a metal ion precursor solution under stirring conditions for an aging reaction, and then wash to obtain the loaded and modified nanofibers;

[0010] S2. Disperse the loaded and modified nanofibers, adhesive fibers, and optional additives in a solvent to obtain a fiber suspension;

[0011] S3. Subject the fiber suspension to vacuum dehydration and then drying to obtain the nanofiber composite membrane.

[0012] The nanofiber composite membrane provided by the present invention uses nanofibers as the base material, and the base material is doubly modified with an amine compound and metal ions. The obtained nanofiber composite membrane can effectively remove pollutants in water, and is particularly suitable for removing pollutants such as COD and atrazine in water. Presumably, the reasons may be as follows: on the one hand, nanofibers have a high specific surface area, which can provide a larger adsorption area and more binding sites, and can also increase the porosity of the composite membrane, thereby increasing the contact area between pollutants in water and the material and accelerating the reaction rate; on the other hand, the amine compound and metal ions can be stably immobilized on the nanofibers. The amine compound has a charge adsorption property, and the amino groups contained therein can capture negatively charged pollutants through charge adsorption, while the metal ions can decompose organic pollutants such as atrazine through complexation and catalytic action. In other words, the present invention degrades organic pollutants in wastewater from multiple dimensions, and these dimensions can effectively complement each other to produce a synergistic effect, thereby achieving the efficient removal of pollutants in wastewater. Specific embodiments

[0013] The nanofiber composite membrane provided by the present invention includes a nanofiber substrate and an amine compound, metal ions, and optional additives loaded on the nanofiber substrate. The nanofiber composite membrane has substances with charge adsorption and catalytic functions, and can simultaneously achieve charge adsorption-catalytic synergy. The amino groups capture negatively charged pollutants through charge adsorption, and the metal ions decompose organic substances such as atrazine through complexation and catalytic action, which can improve the adsorption rate and adsorption capacity of organic pollutants.

[0014] In the present invention, the filtration accuracy of the nanofiber composite membrane is preferably 0.5 to 5 μm, such as 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or any value therebetween. The porosity of the nanofiber composite membrane is preferably 70% to 90%, such as 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90% or any value therebetween. In addition, the thickness of the nanofiber composite membrane is preferably 0.5 mm to 2 mm, such as 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm or any value therebetween.

[0015] In the present invention, the nanofiber substrate contains nanofibers and adhesive fibers. Among them, the nanofibers have a high specific surface area, which can provide more adsorption area and binding sites, while increasing the porosity of the composite membrane, thereby increasing the contact area between the organic matter in the water body and the material, accelerating the reaction rate, and thus improving the ability of the material to remove organic matter. The nanofibers can be natural nanofibers, synthetic fibers, or a composite of both. Among them, the natural nanofibers can be exemplified by at least one of spider silk, silk, collagen fiber, and cellulose nanofiber. The synthetic fibers can be exemplified by at least one of nanofiber whiskers, regenerated fibers, tencel fibers, lyocell nanofibers, fibrillated fibers, bacterial cellulose, viscose fibers, glass fibers, and precipitated fibers and their functional fibers after physical and chemical modification treatments. From the perspective of easy availability of raw materials and cost reduction, the nanofibers are preferably selected from at least one of cellulose nanofibers, nanofiber whiskers, regenerated fibers, tencel fibers, lyocell nanofibers, fibrillated fibers, bacterial cellulose, viscose fibers, glass fibers, and precipitated fibers and their modified fibers. The diameter of the nanofibers is preferably 50 nm to 800 nm, such as 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm or any value therebetween. The specific surface area of the nanofibers is preferably 200 to 1800 m 2 / g, such as 200, 400, 600, 800, 1000, 1200, 1400, 1600, 1800 m 2 / g or any value therebetween. The adhesive fibers may be single-component low-melting-point fibers, may be composite-component fibers, or may be a composite of both. Among them, examples of the single-component low-melting-point fibers include at least one of polyvinyl alcohol (PVA), polyester (PET), polyethylene (PE), and polypropylene (PP). Examples of the composite-component fibers include polyolefin composite fibers and / or polyester composite fibers.

[0016] In a preferred embodiment, based on the total weight of the nanofiber composite membrane, the total content of the nanofibers, amine compounds, and metal ions is 50% to 92%, the content of the adhesive fibers is 3% to 25%, and the content of the auxiliary agent is 5% to 25%. At this time, each substance can play a better synergistic cooperation role and can more effectively remove pollutants in wastewater. Specifically, the total content of the nanofibers, amine compounds, and metal ions may be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92% or any value therebetween. The content of the adhesive fibers may be 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25% or any value therebetween. The content of the auxiliary agent may be 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25% or any value therebetween. Furthermore, the mass ratio of the nanofibers to the amine compounds is preferably (10 to 90):1, such as 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 55:1, 60:1, 65:1, 70:1, 75:1, 80:1, 85:1, 90:1 or any value therebetween. The molar ratio of the metal ions to the amine compounds is preferably (0.1 to 1):1, such as 0.1:1, 0.2:1, 0.4:1, 0.6:1, 0.8:1, 1:1 or any value therebetween.

[0017] In the present invention, the amine compound may be a lower aliphatic amine, a higher aliphatic amine, etc., and is preferably a polymer cationic polyamine salt. The number-average molecular weight of the polymer cationic polyamine salt is preferably 10,000 to 100,000, such as 10,000, 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, 80,000, 90,000, 100,000 or any value therebetween. When the amine compound is a polymer cationic polyamine with a number-average molecular weight of 10,000 to 100,000, it has the advantages of stable structure and stronger adhesion performance, and can endow the nanofiber composite membrane with better removal ability for pollutants in water. The reason is that the molecular chain segments with high degree of polymerization are long, the entanglement ability is stronger, and the viscosity is also larger. The improvement of the entanglement ability and viscosity is beneficial to the removal of pollutants in water. The polymer cationic polyamines include linear, branched, long-chain, double-long-chain, etc., and the groups contained therein may be primary amines, secondary amines and quaternary amines, etc. The polymer cationic polyamines may include at least one of poly (methacryloyloxyethyl trimethyl ammonium chloride), quaternized polyethylene glycol amine condensate, cationic polyacrylamide, quaternized collagen polypeptide, and poly (diallyldimethyl ammonium chloride).

[0018] In the present invention, the metal ion may be at least one of Group IVA metal ions, Group IVA metal ions, Group IVB metal ions, transition metal ions and rare earth metal ions. Among them, the Group IVA metal ions may include, for example, germanium ( / Ge 4+ ) and / or tin ( / Sn 4+ ). The Group IVA metal ions may include at least one of aluminum (Al + / Al 2+ / Al 3+ ), gallium (Ga 3+ ), indium (In + / In 2+ / In 3+ ). The Group IVB metal ions may include at least one of titanium (Ti 3+ / Ti 4+ ), zirconium (Zr 4+ ), hafnium (Hf 2+ / Hf 3+ / Hf 4+ ). The transition metal ions may include, for example, iron ions ( / Fe 3+ ), cobalt (Co 2+ / Co 3+ ), nickel ( / Ni 3+ ), copper (Cu + / Cu 2+ ), zinc (Zn2+ ) and at least one of silver (Ag). + ) and the rare earth metal ions may include, for example, lanthanum ions (La 3+ ), cerium ions (Ce 3+ / Ce 4+ ), and at least one of neodymium ions (Nd 3+ ). Particularly preferably, the metal ions are selected from at least one of iron, silver, aluminum, copper, titanium, zirconium, tin, cerium, and lanthanum. These preferred metal ions can endow the nanofiber composite membrane with better ability to remove pollutants.

[0019] In the present invention, the auxiliary agent is preferably selected from at least one of adsorbents, bacteriostatic agents, scale inhibitors, and adhesives. Among them, the adsorbents may include at least one of powdered activated carbon, granular activated carbon, silver-loaded activated carbon, etc.

[0020] The preparation method of the nanofiber composite membrane provided by the present invention includes the following steps:

[0021] S1. Immerse the nanofibers in an amine compound solution, add a metal ion precursor solution under stirring conditions for an aging reaction, and then wash to obtain loaded and modified nanofibers;

[0022] S2. Disperse the loaded and modified nanofibers, bonding fibers, and optionally auxiliary agents in a solvent to obtain a fiber suspension;

[0023] S3. Vacuum dehydrate and then dry the fiber suspension to obtain the nanofiber composite membrane.

[0024] In the present invention, in step S1, due to the special adsorption function exhibited by the nanofibers with their extremely large specific surface area and surface area / volume ratio, the nanofibers are impregnated and loaded for modification, so that substances with charge adsorption and catalytic functions are loaded on their active sites, showing excellent dual removal ability of adsorption and catalysis for organic substances. At the same time, a composite membrane with adjustable different filtration pore sizes is prepared to achieve efficient removal of organic substances from fluids. The conditions of the impregnation preferably include a temperature of 15°C to 45°C, such as 15°C, 18°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, or any value between them; and a time of 10 to 60 minutes, such as 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, or any value between them. Using the loaded and modified nanofibers, a dynamic adsorption composite membrane with different filtration precisions, high adsorption capacity, and fast adsorption rate can be prepared, and the preparation method is simple and convenient for large-scale production.

[0025] In the present invention, in step S1, the dosage of the metal ion precursor solution is preferably such that the pH value of the system is 5 to 8, such as 5, 5.5, 6, 6.5, 7, 7.5, 8 or any value therebetween.

[0026] In the present invention, in step S1, the conditions of the aging reaction preferably include a temperature of 15°C to 45°C, such as 15°C, 18°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C or any value therebetween; and a time of 7.5 h to 8.5 h, such as 7.5 h, 7.8 h, 8 h, 8.2 h, 8.5 h or any value therebetween.

[0027] In the present invention, in step S2, there is no particular limitation on the manner of dispersing the loaded modified nanofibers, the adhesive fibers and the optional additives in the solvent to obtain the fiber suspension. The loaded modified nanofibers, the adhesive fibers and the optional additives can be dispersed in the solvent in any order. Preferably, the loaded modified nanofibers and the optional additives are dispersed in solvent I to obtain a first slurry, the adhesive fibers are dispersed in solvent II to obtain a second slurry, and the first slurry and the second slurry are mixed evenly to obtain the fiber suspension. Both solvent I and solvent II are preferably water.

[0028] The present invention also provides the application of the nanofiber composite membrane in wastewater treatment.

[0029] The present invention will be described in detail below through examples.

[0030] Example 1

[0031] This example is used to illustrate the nanofiber composite membrane and its preparation method provided by the present invention.

[0032] S1. 100 g of bacterial cellulose nanofibers with an average fiber diameter of 200 nm were added to 1.5 L of a 1% wt poly (methacryloyloxyethyl trimethyl ammonium chloride) solution (number average molecular weight of 10,000), and stirred and dispersed at 30°C at a rotation speed of 500 r / min for 10 min. Then, a 10% wt iron chloride solution was gradually added during continuous stirring until the pH value of the system reached 8, and the reaction was stirred at room temperature for 7.5 h. The obtained reaction product was filtered and dried to obtain the loaded modified nanofibers. The mass ratio of the nanofibers to poly (methacryloyloxyethyl trimethyl ammonium chloride) in the loaded modified nanofibers is 40:1, and the molar ratio of iron ions to poly (methacryloyloxyethyl trimethyl ammonium chloride) is 0.3:1.

[0033] S2. Add an appropriate amount of water to the load-modified nanofibers and activated carbon powder, and quickly stir and disperse them evenly to obtain a first slurry with a concentration of 0.5% wt. Add an appropriate amount of water to polyvinyl alcohol (PVA, melting point 230°C), and quickly stir and disperse it evenly to obtain a second slurry with a concentration of 0.5% wt. Mix the first slurry and the second slurry evenly to obtain a fiber suspension. The mass ratio of the dry weight of the load-modified nanofibers, polyvinyl alcohol to the activated carbon powder in the fiber suspension is 65% wt: 20% wt: 15% wt.

[0034] S3. Place the above fiber suspension on a vacuum suction device, and obtain a wet composite membrane after vacuum dehydration. Then dry the wet composite membrane at 140°C to obtain an organic matter removal composite membrane with a filtration accuracy of 0.5 - 1 μm, a porosity of 85%, and a thickness of 0.8 mm.

[0035] Example 2

[0036] This example is used to illustrate the nanofiber composite membrane and its preparation method provided by the present invention.

[0037] S1. Add 100 g of bacterial cellulose nanofibers with an average fiber diameter of 600 nm to 1.5 L of a 5% wt poly(diallyldimethylammonium chloride) solution (number average molecular weight 20,000), and stir and disperse it evenly at a rotation speed of 500 r / min at 20°C for 10 min. Then gradually add a 10% wt aluminum chloride solution during continuous stirring until the pH value of the system is 5, and stir and react at room temperature for 8.5 h. Filter and dry the obtained reaction product to obtain load-modified nanofibers. The mass ratio of nanofibers to poly(diallyldimethylammonium chloride) in the load-modified nanofibers is 50:1, and the molar ratio of aluminum ions to poly(diallyldimethylammonium chloride) is 0.3:1.

[0038] S2. Add an appropriate amount of water to the load-modified nanofibers and activated carbon powder, and quickly stir and disperse them evenly to obtain a first slurry with a concentration of 0.5% wt. Add an appropriate amount of water to polyethylene (PE, melting point 130°C), and quickly stir and disperse it evenly to obtain a second slurry with a concentration of 0.5% wt. Mix the first slurry and the second slurry evenly to obtain a fiber suspension. The mass ratio of the dry weight of the load-modified nanofibers, polyethylene to the activated carbon powder in the fiber suspension is 50% wt: 25% wt: 25% wt.

[0039] S3. Place the above fiber suspension on a vacuum suction device, and obtain a wet composite membrane after vacuum dehydration. Then dry the wet composite membrane at 140°C to obtain an organic matter removal composite membrane with a filtration accuracy of 4.5 - 5 μm, a porosity of 75%, and a thickness of 1.8 mm.

[0040] Example 3

[0041] This example is used to illustrate the nanofiber composite membrane and its preparation method provided by the present invention.

[0042] S1. Add 100 g of lyocell nanofibers with an average fiber diameter of 200 nm to 1.5 L of a 3% wt solution of poly(dimethyloctadecyl)[3-(trimethoxysilyl)propyl]ammonium chloride (number average molecular weight of 50,000), and stir and disperse thoroughly at a speed of 500 r / min at 40 °C for 60 min. Then, gradually add a 10% wt copper chloride solution during continuous stirring until the pH value of the system is 6.5, and stir and react at room temperature for 8 h. Filter the obtained reaction product and dry it to obtain the loaded modified nanofibers. The mass ratio of nanofibers to poly(dimethyloctadecyl)[3-(trimethoxysilyl)propyl]ammonium chloride in the loaded modified nanofibers is 30:1, and the molar ratio of copper ions to poly(dimethyloctadecyl)[3-(trimethoxysilyl)propyl]ammonium chloride is 0.5:1.

[0043] S2. Add an appropriate amount of water to the loaded modified nanofibers and activated carbon powder, and quickly stir and disperse evenly to obtain a first slurry with a concentration of 0.5% wt. Add an appropriate amount of water to polypropylene (PP, melting point of 165 °C), and quickly stir and disperse evenly to obtain a second slurry with a concentration of 0.5% wt. Mix the first slurry and the second slurry evenly to obtain a fiber suspension. The mass ratio of the dry weight of the loaded modified nanofibers, polypropylene, and activated carbon powder in the fiber suspension is 92% wt: 3% wt: 5% wt.

[0044] S3. Place the above fiber suspension on a vacuum suction device, obtain a wet composite membrane after vacuum dehydration, and then dry the wet composite membrane at 140 °C to obtain an organic matter removal composite membrane with a filtration accuracy of 0.5 - 1 μm, a porosity of 85%, and a thickness of 1 mm.

[0045] Example 4

[0046] This example is used to illustrate the nanofiber composite membrane and its preparation method provided by the present invention.

[0047] S1. Add 100 g of Lyocell nanofibers with an average fiber diameter of 600 nm to 1.5 L of a 5% wt solution of poly(dimethyloctadecyl)[3-(trimethoxysilyl)propyl]ammonium chloride (number average molecular weight of 50,000). Stir the mixture thoroughly at 500 r / min for 60 min at 30 °C. Then, gradually add a 10% wt silver nitrate solution during continuous stirring until the pH value of the system reaches 6.5. Stir and react at room temperature for 8 h. Filter and dry the resulting reaction product to obtain the loaded and modified nanofibers. The mass ratio of nanofibers to poly(dimethyloctadecyl)[3-(trimethoxysilyl)propyl]ammonium chloride in the loaded and modified nanofibers is 30:1, and the molar ratio of silver ions to poly(dimethyloctadecyl)[3-(trimethoxysilyl)propyl]ammonium chloride is 1:1.

[0048] S2. Add an appropriate amount of water to the loaded and modified nanofibers and activated carbon powder, and quickly stir and disperse them evenly to obtain a first slurry with a concentration of 0.5% wt. Add an appropriate amount of water to polyvinyl alcohol (PVA, melting point of 230 °C), and quickly stir and disperse it evenly to obtain a second slurry with a concentration of 0.5% wt. Mix the first slurry and the second slurry evenly to obtain a fiber suspension. The mass ratio of the dry weight of the loaded and modified nanofibers, polyvinyl alcohol to the activated carbon powder in the fiber suspension is 65% wt:20% wt:15% wt.

[0049] S3. Place the above fiber suspension on a vacuum suction device, and obtain a wet composite membrane after vacuum dehydration. Then dry the wet composite membrane at 140 °C to obtain an organic matter removal composite membrane with a filtration accuracy of 3 - 3.5 μm, a porosity of 65%, and a thickness of 1.2 mm.

[0050] Example 5

[0051] Prepare the nanofiber composite membrane according to the method of Example 1, except that the ferric chloride solution is replaced with a titanium chloride solution of the same concentration and the same dosage, and the other conditions are the same as those in Example 1. Obtain a nanofiber composite membrane with a filtration accuracy of 0.5 - 1 μm, a porosity of 86%, and a thickness of 1 mm.

[0052] Example 6

[0053] Prepare the nanofiber composite membrane according to the method of Example 1, except that the ferric chloride solution is replaced with a zirconium chloride solution of the same concentration and the same dosage, and the other conditions are the same as those in Example 1. Obtain a nanofiber composite membrane with a filtration accuracy of 0.5 - 1 μm, a porosity of 85%, and a thickness of 1 mm.

[0054] Example 7

[0055] The nanofiber composite membrane was prepared according to the method of Example 1, except that the iron chloride solution was replaced with a tin chloride solution having the same concentration and the same amount, and the remaining conditions were the same as those in Example 1, obtaining a nanofiber composite membrane with a filtration accuracy of 0.5 to 1 μm, a porosity of 84%, and a thickness of 1 mm.

[0056] Example 8

[0057] The nanofiber composite membrane was prepared according to the method of Example 1, except that the iron chloride solution was replaced with a cerium nitrate solution having the same concentration and the same amount, and the remaining conditions were the same as those in Example 1, obtaining a nanofiber composite membrane with a filtration accuracy of 0.5 to 1 μm, a porosity of 87%, and a thickness of 1 mm.

[0058] Example 9

[0059] The nanofiber composite membrane was prepared according to the method of Example 1, except that the iron chloride solution was replaced with a lanthanum nitrate solution having the same concentration and the same amount, and the remaining conditions were the same as those in Example 1, obtaining a nanofiber composite membrane with a filtration accuracy of 0.5 to 1 μm, a porosity of 85%, and a thickness of 1 mm.

[0060] Example 10

[0061] The nanofiber composite membrane was prepared according to the method of Example 1, except that the poly (methacryloyloxyethyl trimethyl ammonium chloride) solution (number average molecular weight of 10,000) was replaced with a poly (methacryloyloxyethyl trimethyl ammonium chloride) solution (number average molecular weight of 5,000) having the same concentration and the same amount, and the remaining conditions were the same as those in Example 1, obtaining a nanofiber composite membrane with a filtration accuracy of 0.5 to 1 μm, a porosity of 90%, and a thickness of 1 mm.

[0062] Comparative Example 1

[0063] The nanofiber composite membrane was prepared according to the method of Example 1, except that the iron chloride solution was replaced with a poly (methacryloyloxyethyl trimethyl ammonium chloride) solution having the same concentration and the same amount, and the remaining conditions were the same as those in Example 1, obtaining a nanofiber composite membrane.

[0064] Comparative Example 2

[0065] The nanofiber composite membrane was prepared according to the method of Example 1, except that the poly (methacryloyloxyethyl trimethyl ammonium chloride) solution was replaced with an iron chloride solution having the same concentration and the same amount, and the remaining conditions were the same as those in Example 1, obtaining a nanofiber composite membrane.

[0066] Test Example

[0067] The nanofiber composite membranes obtained from the above-mentioned examples and comparative examples were respectively cut into circular pieces with a membrane area of 0.01 square meters and sealed in a membrane testing device. The removal rates of chemical oxygen demand (COD) and atrazine were tested according to the following methods. The results are shown in Table 1.

[0068] (1) COD removal rate: According to the MOH "Hygienic Safety and Functional Evaluation Specification for Domestic Drinking Water Quality Processors - General Water Quality Processors", tannic acid was prepared into a tannic acid aqueous solution with a concentration of 15.0 ppm, and then 1 L of this tannic acid aqueous solution was used for a dynamic fluid rapid adsorption experiment with the above testing device. The COD before and after filtration was tested and the COD removal rate was calculated according to the following formula;

[0069] E(%) = (CODs - CODm) / CODs × 100%, where E represents the COD removal rate, CODs represents the initial COD value of the tannic acid solution, and CODm represents the COD value of the effluent after adsorption treatment.

[0070] (2) Atrazine removal rate: According to the NSF / ANSI 53-2023 "Drinking Water Treatment Units - Health Effects Standard", an atrazine stock solution with an atrazine concentration of 9 ppb was prepared, and then 1 L of this atrazine stock solution was used for a dynamic fluid rapid adsorption experiment with the above testing device. The atrazine content before and after filtration was tested and the atrazine removal rate was calculated according to the following formula;

[0071] F(%) = (ATRs - ATRm) / ATRs × 100%, where F represents the atrazine removal rate, ATRs represents the atrazine concentration in the atrazine stock solution, and ATRm represents the atrazine concentration in the effluent after adsorption treatment.

[0072] Table 1

[0073] Project COD Removal Rate (%) Atrazine Removal Rate (%) Example 1 90.20 98.88 Example 2 89.51 95.70 Example 3 91.72 98.91 Example 4 87.84 95.88 Example 5 88.70 96.23 Example 6 86.40 93.72 Example 7 84.53 90.77 Example 8 91.27 98.09 Example 9 89.34 97.53 Example 10 82.45 88.98 Comparative Example 1 45.63 52.37 Comparative Example 2 30.23 42.35

[0074] As can be seen from Table 1, the nanofiber composite membrane provided by the present invention has good removal ability for organic matter (COD) and atrazine, and can be used for water purification. From the comparison between Example 1 and Example 10, it can be seen that when the amine compound is a high-molecular cationic polyamine with a number-average molecular weight of 10,000 to 100,000, the nanofiber composite membrane can be given better removal ability for pollutants in water.

[0075] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and purposes of the present invention.

Claims

1. A nanofiber composite membrane, characterized in that, The nanofiber composite membrane includes a nanofiber substrate, an amine compound and metal ions loaded on the nanofiber substrate, and an optional auxiliary agent.

2. The nanofiber composite membrane according to claim 1, characterized in that, The filtration accuracy of the nanofiber composite membrane is 0.5 - 5 μm, the porosity is 70% - 90%, and the thickness is 0.5 mm - 2 mm.

3. The nanofiber composite membrane according to claim 1, wherein The nanofiber substrate contains nanofibers and adhesive fibers; Preferably, based on the total weight of the nanofiber composite membrane, the total content of the nanofibers, amine compound and metal ions is 50% - 92%, the content of the adhesive fibers is 3% - 25%, and the content of the auxiliary agent is 5% - 25%; Preferably, the mass ratio of the nanofibers to the amine compound is (10 - 90):1; Preferably, the molar ratio of the metal ions to the amine compound is (0.1 - 1):

1.

4. The nanofiber composite membrane according to claim 3, wherein The nanofibers are selected from at least one of cellulose nanofibers, nanofiber whiskers, regenerated fibers, tencel fibers, lyocell nanofibers, fibrillated fibers, bacterial cellulose, viscose fibers, glass fibers, precipitated fibers and their modified fibers; Preferably, the adhesive fibers are single-component low-melting-point fibers and / or composite-component fibers; preferably, the single-component low-melting-point fibers are selected from at least one of polyvinyl alcohol, polyester, polyethylene and polypropylene; preferably, the composite-component fibers are polyolefin composite fibers and / or polyester composite fibers; Preferably, the amine compound is a cationic polyamine salt with a number-average molecular weight of 10,000 - 100,000; Preferably, the metal ions are selected from at least one of iron, silver, aluminum, copper, titanium, zirconium, tin, cerium and lanthanum; Preferably, the auxiliary agent is selected from at least one of adsorbents, bacteriostatic agents, scale inhibitors and adhesives.

5. The preparation method of the nanofiber composite membrane according to any one of claims 1 to 4, characterized in that, This method includes the following steps: S1. Immerse the nanofibers in an amine compound solution, add a metal ion precursor solution under stirring conditions for an aging reaction, and then wash to obtain load-modified nanofibers; S2. Disperse the load-modified nanofibers, adhesive fibers and an optional auxiliary agent in a solvent to obtain a fiber suspension; S3. Vacuum dehydrate and dry the fiber suspension to obtain the nanofiber composite membrane.

6. The preparation method of the nanofiber composite membrane according to claim 5, wherein In step S1, the conditions for the immersion include a temperature of 15°C - 45°C and a time of 10 - 60 min.

7. The preparation method of the nanofiber composite membrane according to claim 5, wherein, In step S1, the dosage of the metal ion precursor solution is such that the pH value of the system is 5 - 8.

8. The preparation method of the nanofiber composite membrane according to claim 5, characterized in that, In step S1, the conditions for the aging reaction include a temperature of 15°C - 45°C and a time of 7.5 h - 8.5 h.

9. The preparation method of the nanofiber composite membrane according to claim 5, characterized in that, In step S2, the method of dispersing the load-modified nanofibers, adhesive fibers and an optional auxiliary agent in a solvent to obtain a fiber suspension includes dispersing the load-modified nanofibers and an optional auxiliary agent in solvent I to obtain a first slurry, dispersing the adhesive fibers in solvent II to obtain a second slurry, and mixing the first slurry and the second slurry evenly to obtain a fiber suspension.

10. Application of the nanofiber composite membrane according to any one of claims 1 - 4 in wastewater treatment.