TA-Fe 3+ Composite separation membranes, their preparation methods and applications

Abstract

The application provides a TA-Fe 3+ The application provides a composite separation membrane, a preparation method and application thereof, and a TA-Fe 3+ The preparation method of the composite separation membrane comprises the following steps: applying a polyphenolic compound, a non-ionic surfactant and trivalent iron ions to at least one side of a porous base film in a solution state to obtain a to-be-processed membrane; and performing rinsing and drying on the to-be-processed membrane to obtain a TA-Fe 3+ The application provides a composite separation membrane, a preparation method and application thereof, and a TA-Fe 3+ The composite separation membrane comprises a porous base film and a separation layer arranged on at least one side of the porous base film, the separation layer comprises a polyphenolic compound and trivalent iron ions chelated in the polyphenolic compound, and the separation layer comprises a plurality of pore structures. The preparation method is low in cost, environmentally friendly, simple in process flow and especially suitable for industrial production. The TA-Fe 3+ The composite separation membrane has good anti-pollution capacity, good dye interception rate and high salt permeation rate.

Description

Technical Field

[0001] This invention belongs to the field of dye / salt separation technology, and specifically relates to a TA-Fe 3+ Composite separation membranes, their preparation methods, and applications. Background Technology

[0002] Among numerous separation technologies, nanofiltration (NF), as a pressure-driven membrane separation technology, exhibits great application potential in dye desalination due to its unique pore size sieving (pore size approximately 0.5-2 nm) and Donnan charge repulsion effect. An ideal dye-salt separation nanofiltration membrane should possess the dual characteristics of "high dye rejection rate" and "high salt permeability," while allowing inorganic salt ions (especially NaCl and Na₂SO₄) to permeate as much as possible, thereby achieving dye concentration and purification as well as salt recovery and reuse.

[0003] However, traditional commercial nanofiltration membranes are mostly "dense" composite membranes, designed primarily for water softening or retaining polyvalent salts. These membranes have a high salt rejection rate, leading to significant salt retention when treating dyeing and printing wastewater, making effective separation of dyes and salts impossible. This not only causes a sharp increase in osmotic pressure on the concentration side, resulting in a significant decrease in membrane flux, but also exacerbates concentration polarization and membrane fouling, severely impacting the effective separation of dyes and salts and operational stability.

[0004] In recent years, nanofiltration membranes prepared using the interfacial coordination method based on metal-polyphenol networks (MPNs) have attracted widespread attention due to their environmental friendliness and mild operating conditions. However, with the increasing demands for dye and salt treatment in industrial applications, the membrane separation efficiency of existing technologies still needs further improvement. Developing composite separation membranes with higher permeability and separation efficiency to meet the more stringent and complex needs of dyeing and printing wastewater treatment remains a pressing technical challenge. Summary of the Invention

[0005] This application provides a TA-Fe 3+ Composite separation membrane, its preparation method and application, this TA-Fe 3+ The composite separation membrane combines excellent antifouling ability, good dye rejection rate, and high salt permeability. The preparation method is low-cost, environmentally friendly, and has a simple process flow, making it particularly suitable for industrial production.

[0006] Firstly, embodiments of this application provide a TA-Fe 3+ The method for preparing a composite separation membrane includes the following steps: A polyphenolic compound, a nonionic surfactant, and ferric ions are applied to at least one side of a porous membrane in solution to obtain the membrane to be treated. The membrane to be treated was rinsed and dried to obtain TA-Fe. 3+ Composite separation membrane, TA-Fe 3+ The composite separation membrane includes a porous base membrane and a separation layer disposed on at least one side of the porous base membrane. The separation layer includes a polyphenolic compound and ferric ions chelated in the polyphenolic compound. The separation layer includes multiple pore structures.

[0007] In some embodiments, a polyphenolic compound, a nonionic surfactant, and ferric ions are applied to at least one side of a porous base membrane in solution to obtain a membrane to be treated, comprising: Provide a first solution comprising polyphenolic compounds and nonionic surfactants; Provide a second solution containing ferric ions; The first solution and the second solution are sequentially applied to at least one side of the porous base membrane to obtain the membrane to be treated.

[0008] In some embodiments, the solvent in the solution is water.

[0009] In some embodiments, the nonionic surfactant includes one or more of polysorbate-80, polysorbate-60, polysorbate-40, polysorbate-20, sorbitan monooleate, and sorbitan monostearate.

[0010] In some embodiments, the nonionic surfactant has a mass concentration of 0.006 to 0.018 g / L in the first solution.

[0011] In some embodiments, the mass concentration of the polyphenolic compound in the first solution is 0.004 to 0.012 g / L.

[0012] In some embodiments, the mass concentration of the ferric ions in the second solution is 1.0 to 2.0 g / L.

[0013] In some embodiments, the polyphenolic compounds include one or more of gallic acid, tannic acid, pyrogallic acid, anthocyanins, catechins, and protocatechuic acid.

[0014] In some embodiments, the thickness of the separation layer is 10~500 nm.

[0015] In some embodiments, the porous base membrane includes one or more of polyethersulfone, polyvinylidene fluoride, polyamide, polytetrafluoroethylene, and polyethersulfone.

[0016] In some embodiments, the thickness of the porous base film is 10~300 nm.

[0017] Secondly, embodiments of this application provide TA-Fe3+ The composite separation membrane was prepared by a specific method.

[0018] Thirdly, the TA-Fe prepared by the method in the first aspect 3+ Composite separation membrane or TA-Fe from the second aspect 3+ Application of composite separation membranes in dye / salt separation.

[0019] Compared with the prior art, this application has at least the following beneficial effects: The preparation method of this application embodiment uses a nonionic surfactant to regulate the chelation of ferric ions by polyphenolic compounds to prepare TA-Fe. 3+ In the composite separation membrane, the separation layer contains ferric ions that interact with polyphenolic compounds, enhancing the TA-Fe... 3+ Hydrophilicity of composite separation membrane, TA-Fe 3+ The composite separation membrane exhibits a negative potential in a solution with a pH of 7, which is beneficial for repelling negatively charged dye molecules and improving its antifouling ability. The pore structure in the separation layer can retain molecules with a molecular weight greater than 800 Da, indicating a small pore size that allows the passage of smaller monovalent salts, such as TA-Fe... 3+ The composite separation membrane has good permeation flux and can achieve efficient separation of macromolecular dyes and small molecule salts. For example, the rejection rate of dyes such as tetrachlorotetraiodofluorescein, Direct Red 80, and Alsin Blue is ≥80%, while the rejection rate of monovalent salts such as NaCl is <5%.

[0020] TA-Fe of this application embodiment 3+ A method for preparing composite separation membranes is presented, which is low-cost, environmentally friendly, requires no complex and expensive equipment, and has a simple process flow, making it suitable for TA-Fe... 3+ Industrial production of composite separation membranes.

[0021] In addition, TA-Fe 3+ The porous base membrane and separation layer in the composite separation membrane enable TA-Fe 3+ The composite separation membrane has good mechanical stability and mechanical strength, which facilitates TA-Fe 3+ The long-term use of composite separation membranes in industrial applications.

[0022] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other objects, features and advantages of the present invention more obvious and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0024] Figure 1 The TA-Fe shown is an embodiment of this application. 3+ Scanning electron microscope image of the composite separation membrane surface; Figure 2 The TA-Fe shown is an embodiment of this application. 3+ A schematic diagram of the preparation method of the composite separation membrane; Figure 3 The TA-Fe shown is an embodiment of this application and a comparative example. 3+ The effect of composite separation membrane on the rejection rates of Direct Red 80 and Alcian Blue at different Tween 80 concentrations; Figure 4 The TA-Fe shown is an embodiment of this application and a comparative example. 3+ The effect of composite separation membrane on NaCl rejection rate at different Tween 80 concentrations; Figure 5 The TA-Fe shown is an embodiment of this application. 3+ Infrared spectrum of the composite separation membrane; Figure 6 The TA-Fe shown is an embodiment of this application. 3+ Zeta potential diagram of composite separation membrane at pH 7. Detailed Implementation

[0025] The TA-Fe of this application is hereby disclosed in detail with appropriate reference to the accompanying drawings. 3+ Embodiments of composite separation membranes, their preparation methods, and applications are described. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0026] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0027] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0028] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0029] Unless otherwise specified, in this application, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0030] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0031] Unless otherwise stated, the test temperature for all parameters mentioned in this application is 25°C.

[0032] Firstly, embodiments of this application provide a TA-Fe 3+The method for preparing a composite separation membrane includes the following steps: step 100 and step 200.

[0033] Step 100: Apply polyphenolic compounds, nonionic surfactants, and ferric ions to at least one side of a porous base membrane in solution to obtain the membrane to be treated. In this step, polyphenolic compounds can chelate with ferric ions, resulting in a chelation reaction that forms a dense TA-Fe group. 3+ Metal-phenol network, forming TA-Fe 3+ The separation layer of the combined separation membrane, in this state, contains multiple surfactants and solvents.

[0034] Step 200: The membrane to be treated is rinsed and dried to obtain the TA-Fe. 3+ Composite separation membrane, wherein the TA-Fe 3+ The composite separation membrane includes a porous base membrane and a separation layer disposed on at least one side of the porous base membrane. The separation layer includes a polyphenolic compound and ferric ions chelated in the polyphenolic compound. The separation layer includes a plurality of pore structures.

[0035] In this step, rinsing the membrane to be treated removes nonionic surfactants; drying removes the solvent, forming a stable product, namely TA-Fe. 3+ Composite separation membrane. The separation layer is generated in situ on one side of the porous base membrane.

[0036] Compared to existing technologies, such as tannic acid-iron self-assembled membranes, which suffer from difficulties in pore size control and the inability to simultaneously achieve selectivity and permeability, this application's embodiments introduce a nonionic surfactant, such as polysorbate-80, during the preparation process. This surfactant then reacts with ferric ions in solution via an interfacial coordination reaction, forming an ultrathin separation layer on a porous base membrane. The nonionic surfactant acts as a dynamic template and regulator during the interfacial reaction, effectively refining and homogenizing the pore size of the separation layer, optimizing the hydrophilicity of the membrane surface, and significantly improving the dye / salt separation selectivity. It exhibits a high rejection rate (≥80%) for dyes with a molecular weight ≥800 Da, and a rejection rate of less than 5% for monovalent salts (such as NaCl). Furthermore, the TA-Fe prepared by this method... 3+ The pure water flux of the composite separation membrane decreased less compared to the flux of the membrane without the addition of nonionic surfactants.

[0037] The preparation method described in this application is simple, the reaction process is mild, the cost is low, it is environmentally friendly, it does not require complex and expensive equipment, and the process flow is simple, making it suitable for TA-Fe 3+ Industrial production of composite separation membranes.

[0038] See Figure 1As shown, the TA-Fe provided by the present invention 3+ The preparation method of the composite separation membrane can be carried out according to the main steps.

[0039] In some embodiments, step 100, which involves applying a polyphenolic compound, a nonionic surfactant, and ferric ions to at least one side of a porous base membrane in solution to obtain a membrane to be treated, includes: Provide a first solution comprising polyphenolic compounds and nonionic surfactants; Provide a second solution containing ferric ions; The first solution and the second solution are sequentially applied to at least one side of the porous base membrane to obtain the membrane to be treated.

[0040] In some embodiments, the solvent in the solution is water. This facilitates the formation of a separation layer with small and uniform pore size in the solvent, which is beneficial for subsequent TA-Fe... 3+ Composite separation membranes enable the selective separation of macromolecular dyes.

[0041] In some embodiments, the first solution and the second solution are sequentially applied to at least one side of a porous base membrane to obtain a membrane to be treated, comprising: The first solution is applied to at least one side of the porous base membrane to remove at least a portion of the solvent; The second solution is applied to the same side on which the first solution was applied to remove at least part of the solvent, resulting in a membrane to be treated.

[0042] In some embodiments, step 200 involves rinsing and drying the membrane to be treated to obtain the TA-Fe. 3+ A composite separation membrane includes rinsing the membrane to be treated with an aqueous solution, optionally at least once.

[0043] In some embodiments, in step 200, the drying temperature is 50~70℃ and the drying time is 2~10min; optionally, the drying temperature can be any value among 50℃, 52℃, 54℃, 56℃, 58℃, 60℃, 62℃, 64℃, 66℃, 68℃, 70℃ or a range of any two of the above values; optionally, the drying time can be any value among 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min or a range of any two of the above values.

[0044] In some embodiments, the nonionic surfactant includes one or more of polysorbate-80 (i.e., Tween 80), polysorbate-60 (i.e., Tween 60), polysorbate-40 (i.e., Tween 40), polysorbate-20 (i.e., Tween 20), sorbitan monooleate (i.e., Span 80), and sorbitan monostearate (i.e., Span 60). These types of nonionic surfactants can act as dynamic templates and regulators during interfacial reactions, effectively refining and homogenizing the pore size of the separation layer, optimizing the hydrophilicity of the membrane surface, and significantly improving the selectivity for dye / salt separation.

[0045] In some embodiments, the mass concentration of the nonionic surfactant in the first solution is 0.006 to 0.018 g / L, optionally 0.008 to 0.012 g / L; optionally, the mass concentration of the nonionic surfactant in the first solution can be any value among 0.006 g / L, 0.007 g / L, 0.008 g / L, 0.009 g / L, 0.010 g / L, 0.011 g / L, 0.012 g / L, 0.013 g / L, 0.014 g / L, 0.015 g / L, 0.016 g / L, 0.017 g / L, and 0.018 g / L, or a range consisting of any two of the above values.

[0046] In some embodiments, the mass concentration of the polyphenolic compound in the first solution is 0.004 to 0.012 g / L; optionally, the mass concentration of the polyphenolic compound in the first solution can be any value from 0.004 g / L, 0.005 g / L, 0.006 g / L, 0.007 g / L, 0.008 g / L, 0.009 g / L, 0.010 g / L, 0.011 g / L, 0.012 g / L, or a range consisting of any two of the above values.

[0047] In some embodiments, the mass concentration of ferric ions in the second solution is 1.0 to 2.0 g / L; optionally, the mass concentration of ferric ions in the second solution can be any value from 1.0 g / L, 1.1 g / L, 1.2 g / L, 1.3 g / L, 1.4 g / L, 1.5 g / L, 1.6 g / L, 1.7 g / L, 1.8 g / L, 1.9 g / L, 2.0 g / L, or a range consisting of any two of the above values.

[0048] In some embodiments, the porous structure can retain molecules with a molecular weight of 800 Da or higher.

[0049] Optionally, the porous structure can retain compounds with molecular weights of 800 Da, 850 Da, 900 Da, 950 Da, 1000 Da, and 1100 Da or higher. This is beneficial for increasing the retention rate of compounds with molecular weights of 800 Da or higher, while keeping the retention rate of monovalent salts such as NaCl at a low level.

[0050] In some embodiments, the polyphenolic compounds include one or more of gallic acid, tannic acid, pyrogallic acid, anthocyanins, catechins, and protocatechuic acid. Therefore, the pore size between the polyphenolic compounds and the ferric ions forming the separation layer is smaller and more uniform, which is beneficial for optimizing the hydrophilicity of the membrane surface, improving antifouling ability, and achieving efficient separation of large molecular dyes and small molecular salts.

[0051] In some embodiments, the thickness of the separation layer is 10-500 nm. This is advantageous for TA-Fe... 3+ Composite separation membranes possess excellent mechanical stability, high permeation flux, and the ability to efficiently separate macromolecular dyes and small molecule salts.

[0052] In some embodiments, the porous base membrane comprises one or more of polyethersulfone, polyvinylidene fluoride, polyamide, polytetrafluoroethylene, and polyethersulfone. This is advantageous for TA-Fe... 3+ Composite separation membranes possess both good mechanical stability, mechanical strength, and permeation flux.

[0053] In some embodiments, the thickness of the porous base film is 10-300 nm. Optionally, the thickness of the porous base film can be any value from 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, and 300 nm, or a range of any two of the above values. This further enhances the TA-Fe... 3+ Composite separation membranes possess both good mechanical stability, mechanical strength, and permeation flux.

[0054] In some embodiments, the TA-Fe 3+ The composite separation membrane achieves a rejection rate of greater than or equal to 97% when filtering Alsin Blue; the TA-Fe 3+The composite separation membrane filtration has a rejection rate of greater than or equal to 98% at direct red 80; the TA-Fe 3+ The composite separation membrane has a rejection rate of less than 5% for monovalent salts with a molecular weight ≤100 Da. This is beneficial for the efficient separation of large molecular dyes and small molecular salts, enabling the concentration and classification of dye-containing wastewater.

[0055] In addition, TA-Fe 3+ The composite separation membrane also has a low rejection rate for divalent salts with a molecular weight ≤200 Da.

[0056] Secondly, embodiments of this application provide a TA-Fe 3+ The composite separation membrane is prepared by the method described in the first aspect.

[0057] According to this embodiment, TA-Fe 3+ In the separation layer of the composite separation membrane, the combined action of ferric ions and polyphenolic compounds enhances the TA-Fe... 3+ Hydrophilicity of composite separation membranes; TA-Fe 3+ The composite separation membrane exhibits a negative potential in a solution with a pH of 7, which is beneficial for repelling negatively charged dye molecules and improving its antifouling ability. The pore structure in the separation layer can retain substances with a molecular weight greater than 800 Da, indicating a small pore size that allows the passage of smaller monovalent salts, such as TA-Fe... 3+ The composite separation membrane has good permeation flux and can achieve efficient separation of macromolecular dyes and small molecule salts. For example, the rejection rate of dyes such as tetrachlorotetraiodofluorescein, Direct Red 80, and Alsin Blue is ≥80%, while the rejection rate of monovalent salts such as NaCl is <5%.

[0058] TA-Fe 3+ The porous base membrane and separation layer in the composite separation membrane enable TA-Fe 3+ The composite separation membrane has good mechanical stability and mechanical strength, which facilitates TA-Fe 3+ The long-term use of composite separation membranes in industrial applications.

[0059] Thirdly, regarding the first aspect, TA-Fe 3+ Composite separation membrane or TA-Fe prepared by the second method 3+ Application of composite separation membranes in dye / salt separation.

[0060] Example Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are all conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or through existing methods; unless otherwise specified, the amounts of experimental reagents used are the amounts used in conventional experimental operations; unless otherwise specified, the experimental methods are conventional methods. It should be further noted that the following description is merely exemplary and not a specific limitation of the present invention. Example 1 This application provides TA-Fe 3+ The method for preparing a composite separation membrane includes the following steps: (1) Add 1L of deionized water to a clean beaker and dissolve polysorbate-80 (Tween 80) in the deionized water to obtain a Tween 80 solution with a mass concentration of 0.010 g / L. Weigh 0.3g of tannic acid (TA) and dissolve it in 50ml of the previously prepared Tween 80 solution. Stir with a magnetic stirrer for 10min to obtain a TA solution with a Tween 80 mass concentration of 0.010 g / L.

[0061] (2) Weigh 0.363g of FeCl3•6H2O and dissolve it in 50ml of deionized water. Stir evenly with a magnetic stirrer to obtain a 1.5 g / L ferric ion solution, i.e. FeCl3 solution, for later use.

[0062] (3) Pretreatment of porous support substrate membrane: Soak commercial polyethersulfone (PES) membrane in deionized water for 2 hours, then replace the deionized water and soak for 24 hours to remove impurities from the commercial membrane.

[0063] (4) Place the above-mentioned porous base membrane, commercial polyethersulfone membrane (PES membrane), on a glass plate. Gently wipe the water droplets on the membrane surface with a paper towel. When no obvious water droplets are visible on the membrane surface, press the edge of the membrane with a filter cup and mark the position of the filter cup on the membrane surface. Add 3 ml of TA solution to the surface of the PES membrane, let it stand for 1 min, and then remove the excess solution. Add 3 ml of FeCl3 solution to the surface of the PES membrane, keep it for 1 min, and then remove the excess solution to obtain the membrane to be treated.

[0064] (5) Soak the membrane to be treated in deionized water for 5 minutes, then heat-treat it in an oven at 60°C for 5 minutes. Finally, place the prepared TA-Fe... 3+ The composite separation membrane was stored in deionized water at 4℃ until use.

[0065] Example 2 The difference between this embodiment and Example 1 is that the nonionic surfactant added to the TA solution is sorbitan monooleate (i.e., Span 80), and the steps include: (1) Add 1L of deionized water to a clean beaker and dissolve sorbitan monooleate (i.e., Span 80) in the deionized water to obtain Span 80 with a mass concentration of 0.01 g / L. Weigh 0.3g of tannic acid (TA) and dissolve it in 50ml of the previously prepared Span 80 solution. Stir with a magnetic stirrer for 10min to obtain a TA solution with a mass concentration of 0.010 g / L of Span 80.

[0066] (2) Weigh 0.363g of FeCl3•6H2O and dissolve it in 50ml of deionized water. Stir evenly with a magnetic stirrer to obtain a 1.5 g / L ferric ion solution, i.e. FeCl3 solution, for later use.

[0067] (3) Pretreatment of porous support substrate membrane: Soak commercial polyethersulfone (PES) membrane in deionized water for 2 hours, then replace the deionized water and soak for 24 hours to remove impurities from the commercial membrane.

[0068] (4) Place the above-mentioned porous base membrane, commercial polyethersulfone membrane (PES membrane), on a glass plate. Gently wipe the water droplets on the membrane surface with a paper towel. When no obvious water droplets are visible on the membrane surface, press the edge of the membrane with a filter cup and mark the position of the filter cup on the membrane surface. Add 3 ml of TA solution to the surface of the PES membrane, let it stand for 1 min, and then remove the excess solution. Add 3 ml of FeCl3 solution to the surface of the PES membrane, keep it for 1 min, and then remove the excess solution to obtain the membrane to be treated.

[0069] (5) Soak the membrane to be treated in deionized water for 5 minutes, then heat-treat it in an oven at 60°C for 5 minutes. Finally, place the prepared TA-Fe... 3+ The composite separation membrane was stored in deionized water at 4℃ until use.

[0070] Example 3 The difference between this embodiment and Example 1 is that the nonionic surfactant added to the TA solution is polysorbate-60 (Tween 60), and the steps include: (1) Add 1L of deionized water to a clean beaker and dissolve polysorbate-60 (Tween 60) in the deionized water to obtain a Tween 60 solution with a mass concentration of 0.010 g / L. Weigh tannic acid (TA) and dissolve it in 50ml of the previously prepared Tween 60 solution. Stir with a magnetic stirrer for 10min to obtain a TA solution with a Tween 60 mass concentration of 0.010 g / L.

[0071] (2) Weigh 0.363g of FeCl3•6H2O and dissolve it in 50ml of deionized water. Stir evenly with a magnetic stirrer to obtain a 1.5 g / L ferric ion solution, i.e. FeCl3 solution, for later use.

[0072] (3) Pretreatment of porous support substrate membrane: Soak commercial polyethersulfone (PES) membrane in deionized water for 2 hours, then replace the deionized water and soak for 24 hours to remove impurities from the commercial membrane.

[0073] (4) Place the above-mentioned porous base membrane, commercial polyethersulfone membrane (PES membrane), on a glass plate. Gently wipe the water droplets on the membrane surface with a paper towel. When no obvious water droplets are visible on the membrane surface, press the edge of the membrane with a filter cup and mark the position of the filter cup on the membrane surface. Add 3 ml of TA solution to the surface of the PES membrane, let it stand for 1 min, and then remove the excess solution. Add 3 ml of FeCl3 solution to the surface of the PES membrane, keep it for 1 min, and then remove the excess solution to obtain the membrane to be treated.

[0074] (5) Soak the membrane to be treated in deionized water for 5 minutes, then heat-treat it in an oven at 60°C for 5 minutes. Finally, prepare the TA-Fe... 3+ The composite separation membrane was stored in deionized water at 4℃ until use.

[0075] Example 4 The difference between this embodiment and Embodiment 1 is that the TA solution is converted into anthocyanin (ANC) solution, which includes the following steps: (1) Add 1L of deionized water to a clean beaker and dissolve polysorbate-80 (Tween 80) in the deionized water to obtain a Tween 80 with a mass concentration of 0.010 g / L. Weigh anthocyanins (ANC) and dissolve them in 50ml of the previously prepared Tween 80 solution. Stir with a magnetic stirrer for 10min to obtain an ANC solution with a Tween 80 mass concentration of 0.010 g / L.

[0076] (2) Weigh 0.363g of FeCl3•6H2O and dissolve it in 50ml of deionized water. Stir evenly with a magnetic stirrer to obtain a 1.5 g / L ferric ion solution, i.e. FeCl3 solution, for later use.

[0077] (3) Pretreatment of porous support substrate membrane: Soak commercial polyethersulfone (PES) membrane in deionized water for 2 hours, then replace the deionized water and soak for 24 hours to remove impurities from the commercial membrane.

[0078] (4) Place the above-mentioned porous base membrane, commercial polyethersulfone membrane (PES membrane), on a glass plate. Gently wipe the water droplets on the membrane surface with a paper towel. When no obvious water droplets are visible on the membrane surface, press the edge of the membrane with a filter cup and mark the position of the filter cup on the membrane surface. Add 3 ml of TA solution to the surface of the PES membrane, let it stand for 1 min, and then remove the excess solution. Add 3 ml of FeCl3 solution to the surface of the PES membrane, keep it for 1 min, and then remove the excess solution to obtain the membrane to be treated.

[0079] (5) Immerse the membrane in deionized water for 5 minutes, then heat-treat it in an oven at 60°C for 5 minutes. Finally, place the prepared ANC-Fe... 3+ The composite separation membrane was stored in deionized water at 4℃ until use.

[0080] Comparative Example 1 The difference between this comparative example and Example 1 is that Tween 80 was not added to the TA solution. The mass concentration of tannic acid in the TA solution is the same as in Example 1.

[0081] Performance testing 1. In order to investigate TA-Fe 3+ The morphological changes on the surface of the composite separation membrane, and the effect on the TA-Fe obtained in Example 1. 3+ The composite separation membrane was subjected to scanning electron microscopy (SEM) testing, and the results are as follows: Figure 2 As shown, TA-Fe 3+ The composite separation membrane has a small and uniformly distributed pore structure on its surface.

[0082] 2. Dye / Salt Separation Experiment: Tetrachlorotetraiodofluorescein solution, Direct Red 80 solution, and Alcian Blue solution were prepared separately. 1 g / L NaCl was dissolved in aqueous solutions containing tetrachlorotetraiodofluorescein, Direct Red 80, and Alcian Blue, respectively, to obtain these solutions. Specifically, in the tetrachlorotetraiodofluorescein solution, the mass concentration of tetrachlorotetraiodofluorescein was 0.02 g / L, and the mass concentration of NaCl was 1 g / L; in the Direct Red 80 solution, the mass concentration of Direct Red 80 was 0.02 g / L, and the mass concentration of NaCl was 1 g / L; in the Alcian Blue solution, the mass concentration of Alcian Blue was 0.02 g / L, and the mass concentration of NaCl was 1 g / L.

[0083] Using the TA-Fe obtained above 3+ The composite separation membrane was used to filter mixed solutions of these dyes and sodium chloride to evaluate TA-Fe. 3+Selective separation performance of the composite separation membrane for dyes / salts. Tests were conducted using nitrogen cylinders at a pressure of 0.1 bar. Filtration was initiated and water flux data were recorded. Each test was initially stabilized at 1 bar for 30 minutes before data collection. TA-Fe prepared using the examples or comparative examples respectively 3+ The composite separation membrane was used to filter tetrachlorotetraiodofluorescein solution, Direct Red 80 solution, and Alcian Blue solution, respectively. The rejection rates at different concentrations were recorded, and the average value of multiple parallel experiments was taken as the final result. The test results are as follows: Figure 3 As shown in the figure and Table 1.

[0084] TA-Fe prepared in Examples 1-3 3+ When the composite separation membrane was used to filter Alcian Blue (AB), the retention rates of Alcian Blue were 97.6%, 99.2%, and 98.8%, respectively; the TA-Fe prepared in Comparative Example 1... 3+ When the composite separation membrane was used to filter Alcian Blue, the retention rate of Alcian Blue was 53.5%. TA-Fe prepared in Examples 1-3 3+ When the composite separation membrane filtered Alcian Blue solution, the NaCl rejection rates were 3.98%, 4.63%, and 4.45%, respectively; the TA-Fe prepared in Comparative Example 1... 3+ When the composite separation membrane filters Alsin Blue, the rejection rate for NaCl is 3.71%.

[0085] TA-Fe prepared in Examples 1-3 3+ When the composite separation membrane was used to filter Direct Red 80 (DR-80), the rejection rates of Direct Red 80 were 98.6%, 99.3%, and 99.1%, respectively; the TA-Fe prepared in Comparative Example 1... 3+ When the composite separation membrane filters Direct Red 80, the rejection rate of Direct Red 80 is 15.2%.

[0086] TA-Fe prepared in Example 4 3+ When the composite separation membrane filters tetrachlorotetraiodofluorescein, the rejection rate of tetrachlorotetraiodofluorescein is 86.6%.

[0087] 3. The TA-Fe prepared in Example 1 was analyzed using Fourier transform infrared spectroscopy (FTIR). 3+ The structure and chemical composition of the composite separation membrane were systematically studied. Test results are as follows: Figure 5 As shown, by observation Figure 5 It can be seen that 3600~3100cm 1 The broad peak at 751 cm⁻¹ is due to the large number of phenolic hydroxyl groups in TA. 1 The peak originates from the out-of-plane bending of the CH group of the phenyl group. Furthermore, at 1700 cm⁻¹... 1 The absorption peak is generated by the skeletal vibration of the benzene ring in the TA molecule, which indicates that it has good hydrophilicity and stability.

[0088] 4. TA-Fe 3+ Determination of pure water flux of composite separation membrane: All filtration experiments in this experiment used dead-end filtration devices, and the effective membrane area was 44 × 10⁻⁶. -4 m 2 All filtration experiments were conducted at room temperature, at 2 bar (N). 2 ) Use pure water to dissolve TA-Fe 3+ The composite separation membrane was pre-pressed for 0.5 hours to achieve a stable flux, and then TA-Fe was calculated using pure water. 3+ The permeation flux P of the composite separation membrane is calculated using the following formula: J1=V / (A*Δt) In the formula, A, Δt, and V represent the effective membrane filtration area (m²). 2 ), infiltration time (h) and infiltration volume (J1).

[0089] 5. TA-Fe 3+ Method for determining the permeate flux of the composite separation membrane: The permeate flux of the prepared membrane was tested using a standard dead-end filtration apparatus equipped with a nitrogen cylinder, a digital balance, and a computer. The mass of the filtrate at different times was recorded by an electronic balance connected to the computer. The permeate flux J2 was calculated using the following formula: J = V / (A * P * t) In the formula, A is the effective membrane area (m²). 2 V is the permeate volume (L), t is the permeate time (h), and P is the permeate pressure (bar).

[0090] 6. Membrane surface wettability: Testing instrument: Contact angle measuring instrument.

[0091] Test conditions: room temperature environment, to TA-Fe 3+ Add 2 μL of deionized water droplets to the surface of the composite separation membrane.

[0092] Test method: Each TA-Fe tablet 3+ The composite separation membrane was tested at five different locations, and the average value was taken as the TA-Fe... 3+ Water contact angle data for composite separation membranes.

[0093] 7. TA-Fe 3+ Flow potential method for detecting TA-Fe using composite separation membranes 3+ The Zeta potential of the composite separation membrane at pH=7 is determined by the following steps: Step 1: Sample preparation and assembly: The assembled TA-Fe...3+ The first step involves placing the composite separation membrane sample into the measurement cell, ensuring a seal to prevent short circuits. The second step uses a background electrolyte solution (typically 1 mM or 10 mM KCl solution) as the test solution. The solution circulates within the system to wet the membrane surface and establish a stable electrical double layer. The third step involves pH adjustment and scanning, which follows a preset program, scanning from acidic (e.g., pH 3) to alkaline (e.g., pH 10), stopping and collecting data at each pH point (including pH 7), ultimately plotting the data as a curve. The fourth step involves data acquisition and calculation. At a steady state of pH 7, the instrument performs the following operations: Pressurization: Pressure is applied to the sample cell using a pneumatic pump (typically between 1500-3000 mbar), causing the solution to flow over the membrane surface at different rates. Measurement: The generated flow potential is detected by high-sensitivity Ag / AgCl electrodes or platinum electrodes located at both ends of the flow channel. Calculation: The instrument software automatically calculates the Zeta potential value at pH 7 based on the measured flow potential, flow current, and the solution's conductivity, temperature, and viscosity. Test results are as follows Figure 6 As shown, by observation Figure 6 It can be seen that the average Zeta potential at pH=7 is -55.43 (mV). The negatively charged membrane can effectively repel negatively charged dyes while allowing smaller salt ions to pass through.

[0094] Table 1

[0095] As can be seen from the test results in Table 1 above, compared with the comparative example, the TA-Fe prepared in Examples 1-3 of this application... 3+ The composite separation membrane exhibits a high rejection rate for large molecules like dyes and a low rejection rate for small molecules like NaCl, which is beneficial for the concentration and separation of dyes / salts. Meanwhile, the TA-Fe obtained in Examples 1-3 of this application... 3+ The composite separation membrane exhibits excellent water contact angle, pure water flux, and permeate flux, indicating that the TA-Fe... 3+ Composite separation membranes have good hydrophilicity, which is beneficial for filtering and separating aqueous solutions of dyes and salts, such as waste dye water.

[0096] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A TA-Fe 3+ A method for preparing a composite separation membrane, characterized in that, Includes the following steps: A polyphenolic compound, a nonionic surfactant, and ferric ions are applied to at least one side of a porous membrane in solution to obtain the membrane to be treated. The membrane to be treated is rinsed and dried to obtain the TA-Fe. 3+ Composite separation membrane, wherein the TA-Fe 3+ The composite separation membrane includes a porous base membrane and a separation layer disposed on at least one side of the porous base membrane. The separation layer includes the polyphenolic compound and ferric ions chelated in the polyphenolic compound. The separation layer includes a plurality of pore structures.

2. The preparation method according to claim 1, characterized in that, The process of applying polyphenolic compounds, nonionic surfactants, and ferric ions in solution to at least one side of a porous base membrane to obtain a membrane to be treated includes: Provide a first solution comprising polyphenolic compounds and nonionic surfactants; Provide a second solution containing ferric ions; The first solution and the second solution are sequentially applied to at least one side of the porous base membrane to obtain the membrane to be treated.

3. The preparation method according to claim 2, characterized in that, The preparation method satisfies one or more of the following conditions: (1) The mass concentration of the nonionic surfactant in the first solution is 0.006 to 0.018 g / L; (2) The mass concentration of the polyphenolic compound in the first solution is 0.004 to 0.012 g / L; (3) The mass concentration of the ferric ions in the second solution is 1.0 to 2.0 g / L.

4. The TA-Fe according to any one of claims 1 to 3 3+ Composite separation membrane, characterized in that, The nonionic surfactant includes one or more of polysorbate-80, polysorbate-60, polysorbate-40, polysorbate-20, sorbitan monooleate, and sorbitan monostearate.

5. The TA-Fe according to any one of claims 1 to 3 3+ Composite separation membrane, characterized in that, The polyphenolic compounds include one or more of gallic acid, tannic acid, pyrogallic acid, anthocyanins, catechins, and protocatechuic acid.

6. The TA-Fe according to any one of claims 1 to 3 3+ Composite separation membrane, characterized in that, The thickness of the separation layer is 10~500nm.

7. TA-Fe according to any one of claims 1 to 3 3+ Composite separation membrane, characterized in that, The porous base membrane includes one or more of polyethersulfone, polyvinylidene fluoride, polyamide, polytetrafluoroethylene, and polyethersulfone.

8. TA-Fe according to any one of claims 1 to 3 3+ Composite separation membrane, characterized in that, The thickness of the porous base film is 10~300nm.

9. A TA-Fe 3+ Composite separation membrane, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

10. The TA-Fe prepared by the preparation method according to any one of claims 1 to 8 3+ Composite separation membrane or the TA-Fe as described in claim 9 3+ Application of composite separation membranes in dye / salt separation.

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