Loose nanofiltration membrane for salt-dye separation and preparation method thereof
By performing the interfacial polymerization of bispyridine derivatives and acid chloride monomers on the nanofiltration membrane, a polyamide selection layer is formed, which solves the problem of low separation efficiency of nanofiltration membrane flux and salt dyeing, and achieves high permeability flux and salt dyeing separation performance.
Patent Information
- Application Number
- CN202510297241.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-13
- Publication Date
- 2025-05-23
AI Technical Summary
The existing nanofiltration membranes have problems with low membrane flux and salt dye separation efficiency in the field of water treatment.
By interfacial polymerization of bispyridine derivatives and acyl chloride monomers on the surface of the base membrane, a polyamide selection layer was formed, and a loose nanofiltration membrane with high permeability flux and salt dye separation performance was prepared.
The permeability flux of the membrane and the efficiency of salt dye separation were improved. The flux of the nanofiltration membrane was 121.5~157.6 L m-² h-1 bar-1, the dye retention rate was 97.5~99.5%, and the salt retention rate was 4.0~15.2%.
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Abstract
Description
Technical Field
[0001] The invention belongs to the field of sewage treatment, and in particular relates to a loose nanofiltration membrane for salt-dye separation and a preparation method thereof. Background Art
[0002] The textile industry is one of the most important industries in the world, but it is also one of the industries with the largest wastewater discharge. Textile industry wastewater is an important issue that needs to be addressed urgently, because many dyes in textile wastewater are difficult to degrade, biotoxic, and even carcinogenic. If these wastewaters are not properly treated, they will cause serious harm to the ecosystem and human health, and cause a waste of resources (dyes and salts). In addition, in order to improve the quality and dyeing efficiency of textiles, inorganic salts such as NaCl and Na 2 SO 4 , inorganic salts (mainly sodium salts) are also widely used in the synthesis of dyes. Therefore, textile wastewater also contains a large amount of salts. If the dye / salt mixture can be accurately separated and recycled, it will be beneficial to the sustainable development of the environment.
[0003] Nanofiltration (NF) membrane technology is widely used in wastewater treatment due to its low cost and high separation efficiency. However, conventional NF membranes have a dense selective layer, which exhibits high rejection rates for both organic dyes and inorganic salts due to the synergistic effect of the Donan effect and size screening, making them unsuitable for effective separation of dyes and salts. For this problem, loose nanofiltration (LNF) membranes usually have a looser structure and larger pore size than conventional nanofiltration membranes, allowing inorganic salts to penetrate freely while still maintaining a high rejection rate for organic dyes. The hydrophilicity, thickness, surface charge and pore size of the selective layer are significantly dependent on the characteristics of the monomer. Therefore, choosing the right monomer helps to construct an LNF membrane for a specific application. Based on the problem that the permeation flux of traditional nanofiltration membranes is not high and salt and dye cannot be effectively separated, it is of great significance to invent a loose nanofiltration membrane with high permeation flux and high salt-dye separation performance. Summary of the invention
[0004] In view of the problems of low membrane flux and low salt-contamination separation efficiency of existing nanofiltration membranes in the field of water treatment, the present invention aims to provide a loose nanofiltration membrane for salt-contamination separation and a preparation method thereof.
[0005] To solve the above problems, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a loose nanofiltration membrane material, which is prepared by a method in which a bipyridine derivative and an acyl chloride monomer undergo an interfacial polymerization reaction on the surface of a substrate membrane to form a polyamide selection layer.
[0006] In the above technical solution, the bipyridine derivative has a structure shown in the following formula: .
[0007] The bipyridine derivative is obtained by reflux stirring reaction of 4-aminopyridine and 1,2-dibromoethane in acetonitrile, an organic solvent. The specific preparation method is as follows: 4-aminopyridine and 1,2-dibromoethane are added to acetonitrile, the reflux stirring time exceeds 12 hours, the reaction is stopped and cooled to room temperature, filtered, the solid is washed with acetonitrile and ether for 3 times each, and air-dried at 90°C to obtain a bipyridinium salt derivative. The molar ratio of 4-aminopyridine to 1,2-dibromoethane is 4-5:1, and the molar concentration of 4-aminopyridine in acetonitrile is 0.5-1 mol / L.
[0008] As a further improvement of the above technical solution, the base membrane includes a polyethersulfone membrane or a polysulfone membrane.
[0009] As a further improvement of the above technical solution, the acyl chloride monomer includes one or more of trimesoyl chloride, terephthaloyl chloride or isophthaloyl chloride.
[0010] The second aspect of the present invention provides a method for preparing the above-mentioned loose nanofiltration membrane material, comprising the following steps: (1) dissolving a bipyridinium salt derivative in water to obtain an aqueous phase; (2) dissolving the acyl chloride monomer in an organic solvent that is immiscible with water to obtain an organic phase; (3) The basement membrane is first immersed in the aqueous phase prepared in step (1) for a period of time, and then the solution is poured out to remove excess solution on the surface of the basement membrane. The basement membrane is then immersed in the organic phase prepared in step (2). An interfacial polymerization reaction occurs on the surface of the basement membrane, and a loose nanofiltration membrane is prepared. The basement membrane is then placed in ultrapure water.
[0011] As a further improvement of the above-mentioned method for preparing nanofiltration membrane materials, the concentration of the bipyridinium salt derivative in the aqueous solution, i.e., the aqueous phase, is 1.0% to 2.0% g / mL, w / v.
[0012] As a further improvement of the above-mentioned method for preparing nanofiltration membrane materials, the mass concentration of the acyl chloride monomer in the organic phase is 0.3% to 0.5% g / mL, w / v. The water-immiscible organic solvent is one or more of n-hexane, n-pentane or cyclohexane.
[0013] As a further improvement of the above-mentioned method for preparing nanofiltration membrane materials, the substrate membrane is immersed in the aqueous phase for 5 to 10 minutes, and is immersed in the organic phase solution for 30 s to 2 minutes for the interfacial polymerization reaction to occur.
[0014] In some specific embodiments of the present invention, the base membrane used is a polyethersulfone ultrafiltration membrane with a molecular weight cutoff of 20-30 kDa.
[0015] The third aspect of the present invention provides the above-mentioned loose nanofiltration membrane material for filtering and separating salt / dye, wherein the salt is an inorganic salt, such as sodium chloride, sodium sulfate and other inorganic sodium salts; and the dye is an organic dye, such as direct blue 71 and other azo dyes.
[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention firstly synthesizes a bipyridinium salt derivative and uses it as an aqueous phase monomer. Its molecular structure is more twisted and the non-coplanarity of the molecule is strong, which can increase the free volume of the separation layer and the looseness of the separation layer structure to improve the membrane permeability, and at the same time can improve the membrane's retention rate for dyes.
[0017] The present invention uses bipyridinium salt derivatives as aqueous phase monomers in the nanofiltration membrane preparation process, which can reduce the interfacial polymerization rate, thereby better regulating the degree of polymerization, increasing the free volume of the separation layer, increasing the looseness of the separation layer structure, and reducing the density of the membrane layer, thereby improving the permeation flux of the membrane and the efficiency of salt-stained separation.
[0018] The loose nanofiltration membrane material of the present invention, the loose nanofiltration membrane prepared by using the bipyridinium salt derivative as the aqueous phase, has good hydrophilicity and surface electronegativity, and exhibits excellent permeation flux and salt staining separation ability. The flux of the nanofiltration membrane is 121.5~157.6 L m - ² h -1 bar -1 The retention rate of dyes (direct blue 71) in salt-dyed wastewater is 97.5~99.5%, and the retention rate of salt (sodium sulfate) is 4.0~15.2%. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 This is the hydrogen spectrum of the bipyridinium salt derivative prepared in Example 1.
[0020] Figure 2 The surface morphology (a) and cross-sectional morphology (b) of the nanofiltration membrane prepared in Example 1. DETAILED DESCRIPTION
[0021] The present invention is further described below in conjunction with specific examples. Example 1
[0022] The preparation method of the loose nanofiltration membrane material in this example comprises the following steps: 1) Preparation of bipyridinium salt derivatives: 4-aminopyridine (5.916 g, 62.90 mmol) and 1,2-dibromoethane (2.657 g, 14.29 mmol) were added to 100 mL of acetonitrile, refluxed and stirred for 24 h, the reaction was stopped and cooled to room temperature, filtered, the solid was washed with acetonitrile and ether three times each, and dried at 90°C to obtain bipyridinium salt derivatives with a yield of 99.9%. The hydrogen spectrum of the bipyridinium salt derivative is shown in Figure 1 shown.
[0023] 2) Preparation of aqueous phase: dissolving a bipyridinium salt derivative (1.5% w / v) in an aqueous solution to obtain an aqueous solution of a bipyridinium salt derivative; 3) Preparation of organic phase: dissolving trimesoyl chloride in n-hexane, wherein the mass concentration of trimesoyl chloride is 0.3% w / v; 4) Preparation of nanofiltration membrane: First, immerse the surface of the polyethersulfone ultrafiltration membrane in the aqueous phase prepared in step 2) for 5 min, remove the excess solution, and then immerse it in the organic phase solution prepared in step 3) for 1 min to allow interfacial polymerization reaction to occur. Then, take out the membrane and place it in ultrapure water for later use. Figure 2 As shown in a, the surface has a certain degree of roughness, indicating that polyamide is formed on the surface of the base film; the cross-sectional morphology is as follows Figure 2 As shown in b, it can be clearly seen that there is a thin polyamide selective layer on the surface of the base film.
[0024] The water flux test was conducted on the loose nanofiltration membrane prepared above, and the membrane water flux was calculated according to Formula 1: Formula 1 Where P is the flux of the membrane, in L m - ² h -1 bar -1 ; V is the volume of the filtrate within a certain filtration time, in L; A is the effective membrane filtration area, in m 2 , T is the filtration time, unit is h; ΔP is the pressure applied during the filtration process, unit is bar.
[0025] The above nanofiltration membrane was used for the separation experiment of salt (sodium sulfate) and dye (direct blue 71). The solute retention rate was measured by a laboratory-scale cross-flow filtration device. The retention rates of dye (direct blue 71) and salt (sodium sulfate) were calculated according to the following formula 2: Formula 2 Among them, C p and C fIt indicates the solute (dye or salt) concentration of the permeate and feed solution. The results show that under the operating pressure of 2 bar, the membrane flux of the nanofiltration membrane is 140.6 L m - ² h -1 bar -1 The retention rate of dyes is 98.2%, and the retention rate of salts is 7.3%. Example 2
[0026] The preparation of the bipyridinium salt derivative in this example is the same as in Example 1, and the preparation method of the loose nanofiltration membrane material comprises the following steps: 1) Preparation of aqueous phase: dissolving a bipyridinium salt derivative (1.5% w / v) in an aqueous solution to obtain an aqueous solution of a bipyridinium salt derivative; 2) Preparation of organic phase: dissolving trimesoyl chloride in n-hexane, wherein the mass concentration of trimesoyl chloride is 0.5% w / v; 3) Preparation of nanofiltration membrane: First, immerse the surface of the polyethersulfone ultrafiltration membrane in the aqueous phase prepared in step 1) for 5 min, remove the excess solution, and then immerse it in the organic phase solution prepared in step 2) for 1 min to allow interfacial polymerization reaction to occur. Then, take out the membrane and store it in ultrapure water for later use.
[0027] The above nanofiltration membrane was subjected to membrane flux and salt staining separation tests. The test operation was basically the same as in Example 1. Under the condition of an operating pressure of 2 bar, the membrane flux of the nanofiltration membrane was 135.5 L m - ² h -1 bar -1 The retention rate of dyes is 99.0%, and the retention rate of salts is 13.4%. Example 3
[0028] The preparation of the bipyridinium salt derivative in this example is the same as in Example 1, and the preparation method of the loose nanofiltration membrane material comprises the following steps: The preparation method of the loose composite nanofiltration membrane material in this example comprises the following steps: 1) Preparation of aqueous phase: dissolving a bipyridinium salt derivative (1.5% w / v) in an aqueous solution to obtain a bipyridinium salt derivative aqueous solution; 2) Preparation of organic phase: dissolving trimesoyl chloride in n-hexane, wherein the mass concentration of trimesoyl chloride is 0.3% w / v; 3) Preparation of nanofiltration membrane: First, immerse the surface of the polyethersulfone ultrafiltration membrane in the aqueous phase prepared in step 1) for 5 min, remove the excess solution, and then immerse it in the organic phase solution prepared in step 2) for 2 min to allow interfacial polymerization reaction to occur. Then, take out the membrane and store it in ultrapure water for later use.
[0029] The above nanofiltration membrane was subjected to membrane flux and salt staining separation tests. The test operation was basically the same as in Example 1. Under the condition of an operating pressure of 2 bar, the membrane flux of the nanofiltration membrane was 138.0 L m - ² h -1 bar -1 The retention rate of dyes is 98.6%, and the retention rate of salts is 8.8%. Example 4
[0030] The preparation of the bipyridinium salt derivative in this example is the same as in Example 1, and the preparation method of the loose nanofiltration membrane material comprises the following steps: 1) Preparation of aqueous phase: dissolving a bipyridinium salt derivative (2.0% w / v) in an aqueous solution to obtain a bipyridinium salt derivative aqueous solution; 2) Preparation of organic phase: dissolving trimesoyl chloride in n-hexane, wherein the mass concentration of trimesoyl chloride is 0.3% w / v; 3) Preparation of nanofiltration membrane: First, immerse the surface of the polyethersulfone ultrafiltration membrane in the aqueous phase prepared in step 1) for 5 min, remove the excess solution, and then immerse it in the organic phase solution prepared in step 2) for 1 min to allow interfacial polymerization reaction to occur. Then, take out the membrane and store it in ultrapure water for later use.
[0031] The above nanofiltration membrane was subjected to membrane flux and salt staining separation tests. The test operation was basically the same as in Example 1. Under the condition of an operating pressure of 2 bar, the membrane flux of the nanofiltration membrane was 128.4 L m - ² h -1 bar -1 The retention rate of dyes is 98.7%, and the retention rate of salts is 10.6%.
[0032] Table 1 Comparison of material properties obtained in the examples .
[0033] The above is a schematic description of the invention and its implementation methods, which is not restrictive. Therefore, if a person skilled in the art is inspired by it and creatively designs a structure and implementation method similar to the technical solution without departing from the purpose of the invention, they should all fall within the scope of protection of this patent.
Claims
1. A loose nanofiltration membrane material, characterized in that: The nanofiltration membrane material is prepared by interfacial polymerization of a bipyridine derivative and an acyl chloride monomer on the surface of a substrate membrane; the bipyridine derivative has a structure shown in the following formula: 。 2. The loose nanofiltration membrane material according to claim 1, characterized in that The bipyridine derivative is prepared by the following method: 4-aminopyridine and 1,2-dibromoethane are added to acetonitrile, the reaction time is more than 12 hours under reflux stirring, the reaction is stopped, cooled to room temperature, filtered, washed, and dried to obtain the bipyridine salt derivative.
3. The loose nanofiltration membrane material according to claim 1, characterized in that: The base membrane comprises a polyethersulfone membrane or a polysulfone membrane.
4. The method for preparing the loose nanofiltration membrane material according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) dissolving a bipyridinium salt derivative in water to obtain an aqueous solution of the bipyridinium salt derivative, which is used as an aqueous phase; (2) dissolving an acyl chloride monomer in an organic solvent to obtain an acyl chloride monomer solution, which is used as an organic phase; (3) The basement membrane is first immersed in an aqueous phase and then immersed in an organic phase, and an interfacial polymerization reaction occurs on the surface of the basement membrane to obtain the loose nanofiltration membrane material.
5. The method for preparing a loose nanofiltration membrane material according to claim 4, characterized in that: The mass concentration of the bipyridinium salt derivative in the aqueous solution of the bipyridinium salt derivative is 1.0% to 2.0% g / mL.
6. The method for preparing a loose nanofiltration membrane material according to claim 4, characterized in that: The mass concentration of the acyl chloride monomer in the acyl chloride monomer solution is 0.3%-0.5% g / mL.
7. The method for preparing a loose nanofiltration membrane material according to claim 4, characterized in that: The basement membrane is immersed in the water phase for 5 to 10 minutes and in the organic phase for 30 seconds to 2 minutes.
8. The method for preparing a loose nanofiltration membrane material according to claim 4, characterized in that: The acyl chloride monomer is selected from one or more of trimesoyl chloride, terephthaloyl chloride or isophthaloyl chloride; the organic solvent is selected from one or more of n-hexane, n-pentane or cyclohexane.
9. The use of the loose nanofiltration membrane material according to any one of claims 1 to 3, characterized in that: The nanofiltration membrane material is used for filtering and separating salt / dye.
10. The use according to claim 9, characterized in that: The salt is an inorganic salt, and the dye is an organic dye.