Selective nanofiltration membrane as well as preparation method and application thereof

Abstract

The invention relates to a selective nanofiltration membrane as well as a preparation method and application thereof. The selective nanofiltration membrane comprises a support layer and a separation layer, the separation layer is obtained through interfacial polymerization of an oil-phase reactant and a water-phase reactant; the water-phase reactant comprises a negatively charged monomer and a positively charged monomer; the positively charged monomer comprises any one or a combination of at least two of polyvinylamine, polyethyleneimine, diethylenetriamine, water-soluble chitosan, quaternized polyethyleneimine, polyallylamine or triethylene tetramine. According to the method, monomers with different charges are added into a water phase, so that the nanofiltration membrane is wholly charged and neutral, the interception of sodium sulfate can be effectively reduced, the interception of antibiotics is increased, and the separation of the antibiotics and inorganic salts can be efficiently promoted.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite materials, and particularly relates to a selective nanofiltration membrane and a preparation method and application thereof. BACKGROUND

[0002] At present, a large amount of inorganic salts such as sodium chloride and sodium sulfate are generated in the acid-base neutralization reaction, salting-out process, solvent extraction and water washing process in the antibiotic production and purification process. In the production process of antibiotics, the subsequent processes such as separation, purification and refining account for 40%-60% of the cost. These subsequent treatments not only relate to the quality and cost of the product, but also directly affect the final yield of the product. If the green separation of inorganic salts can be realized in the antibiotic post-processing, the economic and social benefits of enterprises will be greatly improved, and the production capacity expansion of related enterprises will be facilitated. Therefore, it is necessary to develop a high-efficiency selective desalination technology for antibiotics.

[0003] The current antibiotic desalination methods mainly include ion exchange chromatography, solvent extraction / back extraction, electrodialysis and membrane separation technology. The solvent extraction / back extraction can realize desalination and concentration, and is maturely applied in industry, but a large amount of organic solvents are needed, and there are problems of solvent recovery, cost and environment; the ion exchange chromatography has large treatment capacity and high efficiency, but produces acid / alkali waste liquid, which is not conducive to the environment, and some antibiotics are charged, which need to be changed into uncharged state; the electrodialysis method has high desalination efficiency and can be operated continuously, and is suitable for large-volume samples. However, the equipment cost is high, and the operation is relatively complex.

[0004] The membrane separation technology has the advantages of simple operation, mild conditions and relatively low energy consumption, and can realize the desalination of monovalent salt and a certain degree of concentration at the same time, but there is currently a lack of nanofiltration membrane which can effectively separate divalent salt and antibiotic.

[0005] CN105126650A discloses a method for preparing a nanofiltration membrane for antibiotic desalination by surface cross-linking coating, which is prepared by surface cross-linking coating polyethyleneimine and gallic acid on the surface of a polyacrylonitrile-based membrane to prepare a nanofiltration membrane for separating antibiotics, thereby improving the separation selectivity of antibiotics / sodium chloride. However, the flux of the composite nanofiltration membrane is not ideal, which cannot break through the trade-off relationship between the flux and selectivity of the nanofiltration membrane, and the ability to selectively separate antibiotics and sodium sulfate is poor. CN116196778A discloses a surface-grafted small-molecule anti-pollution nanofiltration membrane and a preparation method and application thereof, which uses a certain proportion of small molecules 2-aminoethyl morpholine, and 2-aminoethyl morpholine is grafted on a polyamide film by a surface grafting method to prepare an anti-pollution nanofiltration separation membrane. The obtained nanofiltration membrane exhibits high rejection rate for sodium chloride and different antibiotics; can well achieve the effect of antibiotic desalination; and due to the introduction of 2-aminoethyl morpholine, the prepared polyamide nanofiltration membrane has good anti-pollution performance. However, the rejection rate of the composite nanofiltration membrane for divalent salt ions such as sodium sulfate is greater than 80%, which cannot effectively separate antibiotics and divalent inorganic salts.

[0006] Similar problems of poor flux and inability to separate antibiotics and sodium sulfate also exist in other disclosed antibiotic desalination nanofiltration membranes, such as the salt separation nanofiltration membranes disclosed in CN119386687A and CN118925510A.

[0007] Therefore, how to develop an antibiotic desalination nanofiltration membrane with high flux, high selectivity, and mainly for the separation of sodium sulfate and antibiotics is a problem to be solved in the field. SUMMARY

[0008] To solve the above technical problems, the purpose of the present application is to provide a selective nanofiltration membrane and a preparation method and application thereof. The selective nanofiltration membrane is used for separating antibiotics and sodium sulfate, and can solve the problems of poor separation effect and small flux in the separation of antibiotics and sodium sulfate by the current nanofiltration membrane.

[0009] To achieve this purpose, the present application adopts the following technical solutions:

[0010] In a first aspect, the present application provides a selective nanofiltration membrane, which comprises a support layer and a separation layer; the separation layer is obtained by interfacial polymerization of an oil phase reactant and an aqueous phase reactant; the aqueous phase reactant comprises a negatively charged monomer and a positively charged monomer; the positively charged monomer comprises any one or a combination of at least two of polyvinylamine, polyethyleneimine, diethylene triamine, water-soluble chitosan, quaternary ammonium polyethyleneimine, polyallylamine, or triethylene tetramine.

[0011] This invention addresses the problem of excessive negative charge and high sodium sulfate rejection rate in traditional nanofiltration membranes by selecting specific types of positively charged monomers. Compared to other monomers such as piperazine, the positively charged monomers protected in this invention have a large number of primary, secondary, and tertiary amine functional groups, which means more reaction sites and higher crosslinking density, resulting in a denser separation layer. Simultaneously, the amine functional groups carry more positive charges, which can balance the negative charges of sulfonic acid or carboxylic acid functional groups, achieving overall membrane charge neutrality.

[0012] Preferably, the negatively charged monomer includes a functional monomer containing a sulfonic acid functional group.

[0013] Preferably, the positively charged monomer includes amine compounds.

[0014] Preferably, the reactants also include surfactants.

[0015] Preferably, the surfactant is an anionic surfactant.

[0016] Preferably, the surfactant comprises any one or a combination of at least two of sodium dodecyl sulfonate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium hexadecyl sulfate, sodium hexadecyl sulfonate, sodium eicosyl sulfate, or dodecyl phosphate.

[0017] In this invention, the surfactant can form an oriented arrangement at the water / oil phase interface, thereby significantly reducing the interfacial tension between the two phases and facilitating the formation of a polyamide separation layer with controllable thickness. Compared to positively charged surfactants, negatively charged surfactants can attract amine monomers through electrostatic interactions, further promoting their diffusion into the oil phase and reacting with acyl chloride monomers to form a polyamide layer with a narrow pore size distribution.

[0018] Preferably, the support layer comprises a polymer porous layer and a nonwoven fabric layer stacked sequentially.

[0019] In this invention, the support layer can be a commercially available support layer that meets the specified requirements, or the support layer with the corresponding specified structure can be prepared using existing technology.

[0020] Preferably, the polymer porous layer comprises any one or a combination of at least two of the following: a polysulfone porous layer, a polyethersulfone porous layer, a polyacrylonitrile porous layer, a polyetherimide porous layer, a polytetrafluoroethylene or a polyethylene porous layer.

[0021] Preferably, the thickness of the polymer porous layer is 30-100 μm, for example, it can be 40 μm, 50 μm, 60 μm, 70 μm, 80 μm or 90 μm.

[0022] Preferably, the thickness of the nonwoven fabric layer is 50-200 μm, for example, it can be 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm or 180 μm.

[0023] Preferably, the thickness of the support layer is 100-300 μm, for example, it can be 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm or 280 μm, etc.

[0024] Preferably, the thickness of the separation layer is 0.05-5 μm, for example, it can be 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, 0.1 μm, 0.2 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or 4.5 μm, and more preferably 0.5-3 μm.

[0025] Preferably, the oil phase reactants comprise any one or a combination of at least two of the following: aromatic organic compounds containing at least two acyl halide functional groups, aliphatic organic compounds containing at least two acyl halide functional groups, or alicyclic organic compounds containing at least two acyl halide functional groups.

[0026] In this invention, the oil phase reactants can be commercially available products or compounds containing acyl halide functional groups obtained by reacting carboxylic acids and halogenated compounds.

[0027] Preferably, the oil phase reactants include any one or a combination of at least two of phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, trimesoyl chloride, methyl isophthaloyl diisocyanate, biphenyltriacyl chloride, 5-oxoformyl chloride-isophthaloyl chloride, or 5-isocyanate-isophthaloyl chloride.

[0028] Preferably, the mass ratio of the positively charged monomers in the oil phase reactant to those in the aqueous phase reactant is 1:(0.1-10); for example, it can be 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, or 1:9, etc.

[0029] Preferably, the negatively charged monomers in the aqueous reactants include any one or a combination of at least two of 2,2'-benzidine disulfonic acid, sodium 2,2'-benzidine disulfonic acid, 4,4'-diaminostilbene-2,2'-disulfonic acid, sodium 4,4'-diaminostilbene-2,2'-disulfonic acid, 5,6-diamino-1,3-naphthalene disulfonic acid, or sodium 5,6-diamino-1,3-naphthalene disulfonic acid.

[0030] In this invention, the negatively charged monomers all contain two amino functional groups and two sulfonic acid functional groups. The amino functional groups can undergo polymerization with the oil phase reactants to form a polyamide separation layer, while the sulfonic acid functional groups make the membrane negatively charged, balancing the positive charge of the amino functional groups and achieving overall neutrality of the membrane charge. Other negatively charged monomers, such as trimethylolpropanesulfonate, carry fewer sulfonic acid and amino functional groups, resulting in reduced density of the polyamide network and an inability to achieve overall neutrality of the charge.

[0031] Preferably, the mass ratio of positively charged monomers to negatively charged monomers in the aqueous reactant is 1:(0.1-10), for example, it can be 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 or 1:9, and more preferably 1:(0.1-5).

[0032] In this invention, an excessively high or low mass ratio of positively charged to negatively charged monomers in the aqueous phase reactants can lead to a charge imbalance, affecting the membrane charge and reducing the separation selectivity of sodium sulfate / antibiotics.

[0033] In a second aspect, the present invention provides a method for preparing a selective nanofiltration membrane as described in the first aspect, the method comprising the following steps:

[0034] The support layer is impregnated sequentially with aqueous and oil-phase reactant solutions to form a separation layer, thereby obtaining a selective nanofiltration membrane.

[0035] Preferably, the concentration of the surfactant in the reactant solution is 0.001wt%-0.5wt%, for example, it can be 0.005wt%, 0.01wt%, 0.02wt%, 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt%, 0.1wt%, 0.2wt%, 0.3wt%, or 0.4wt%, etc.

[0036] In this invention, if the surfactant concentration is too low, the aqueous phase will spread unevenly, the amine monomer supply will be unstable, and a defective polyamide layer with uneven thickness will be formed. If the surfactant concentration is too high, the surfactant molecules will exceed the critical micelle concentration and self-assemble in the aqueous phase to form micelles, generating loose polymer particles that deposit at the interface, forming a loose and rough skin.

[0037] Preferably, the concentration of the monomer in the aqueous reactant solution is 0.01wt%-0.5wt%, for example, it can be 0.02wt%, 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt%, 0.1wt%, 0.2wt%, 0.3wt%, or 0.4wt%, etc.

[0038] Preferably, the concentration of the solute in the oil phase reactant solution is 0.01wt%-0.5wt%, for example, it can be 0.02wt%, 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt%, 0.1wt%, 0.2wt%, 0.3wt%, or 0.4wt%, etc.

[0039] Preferably, the solvent of the aqueous reactant solution includes an aqueous solvent, and more preferably water.

[0040] Preferably, the time for the aqueous reactant solution to impregnate the support layer is 3-30 min, for example, 5 min, 10 min, 15 min, 20 min or 25 min.

[0041] Preferably, the solvent of the oil phase reactant solution includes a nonpolar solvent, more preferably any one or a combination of at least two of alkane, ether solvent, aromatic hydrocarbon or ester solvent, and even more preferably n-hexane.

[0042] Preferably, the impregnation time of the oil phase reactant solution into the support layer is 5-120 s, for example, it can be 6 s, 7 s, 8 s, 9 s, 10 s, 20 s, 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, 100 s or 110 s, etc.

[0043] Preferably, after the separation layer is formed, it is further subjected to drying and solvent soaking treatments in sequence.

[0044] In this invention, the drying method includes air drying, oven drying, and other drying methods commonly used in the art.

[0045] Preferably, the drying time is 60-600 s, for example, it can be 70 s, 80 s, 90 s, 100 s, 200 s, 300 s, 400 s or 500 s, etc.

[0046] Preferably, the solvent used for solvent immersion treatment includes any one or a combination of at least two of water, glycerin, polyethylene glycol, or ethanol.

[0047] Preferably, the solvent soaking time is 1-24 h, for example, it can be 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h or 22 h.

[0048] Thirdly, the present invention provides an application of the selective nanofiltration membrane as described in the first aspect, the application including the separation of organic matter and inorganic salts using the selective nanofiltration membrane, more preferably the separation of antibiotics and inorganic salts.

[0049] Compared with the prior art, the present invention has at least the following beneficial effects:

[0050] In this invention, a high-flux nanofiltration membrane for separating sodium sulfate / antibiotics is prepared by forming an interfacial polymer between oil-phase reactants and aqueous-phase reactants. By adding monomers with different charges to the aqueous phase, the nanofiltration membrane is made electrically neutral, which effectively reduces the retention of sodium sulfate while increasing the retention of antibiotics, thus efficiently promoting the separation of antibiotics and inorganic salts. Attached Figure Description

[0051] Figure 1 This is a surface photograph of the selective nanofiltration membrane obtained in Embodiment 1 of the present invention;

[0052] Figure 2 This is a cross-sectional photograph of the selective nanofiltration membrane obtained in Embodiment 1 of the present invention. Detailed Implementation

[0053] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0054] The following are some of the raw materials used in the embodiments and comparative examples of this invention:

[0055] The aqueous and oil phase reactant solutions and surfactants were all commercially available products, such as trimesoyl chloride (Sigma-Aldrich, CAS: 4422-95-1), polyethyleneimine (average Mw ~800, average Mn ~600), product number: P121256 (Aladdin, CAS: 25987-06-8), sodium dodecyl sulfate (Xilong Scientific, CAS: 151-21-3), etc.; and polyacrylonitrile ultrafiltration membrane (Sepro Membranes).

[0056] Example 1

[0057] This embodiment provides a selective nanofiltration membrane, which includes a support layer and a separation layer stacked sequentially; the separation layer is obtained by interfacial polymerization of oil-phase reactants and aqueous-phase reactants.

[0058] The aqueous reactants comprise polyethyleneimine and 4,4'-diaminostilbene-2,2'-disulfonic acid, and sodium dodecyl sulfate (a surfactant) in a mass ratio of 4:1; the mass concentration of the mixture of 4,4'-diaminostilbene-2,2'-disulfonic acid and polyethyleneimine in the aqueous reactant solution is 0.05 wt%, and the mass concentration of sodium dodecyl sulfate in the aqueous reactant solution is 0.008 wt%.

[0059] The oil phase reactant includes trimesoyl chloride, and the mass concentration of trimesoyl chloride in the oil phase reactant solution is 0.05 wt%.

[0060] The method for preparing the aqueous reactant solution includes the following steps:

[0061] 4,4'-diaminostilbene-2,2'-disulfonic acid and polyethyleneimine were dissolved separately in deionized water, and after complete dissolution, they were mixed in proportion. Sodium dodecyl sulfate, a surfactant, was added to obtain the aqueous reactant solution.

[0062] The preparation method of the oil phase reactant solution includes the following steps:

[0063] The pyromellitic chloride was dissolved in n-hexane in a certain proportion to obtain an oil phase reaction solution.

[0064] The method for preparing the selective nanofiltration membrane includes the following steps:

[0065] (1) Place the polyacrylonitrile ultrafiltration membrane support layer in a mold, immerse 20 mL of aqueous reaction solution on the support layer for 3 min; remove it and remove the surface moisture, then immerse the support layer in 20 mL of oil reaction solution for 30 s; remove it and dry it for 600 s to obtain the separation membrane.

[0066] (2) Then quickly immerse the separation membrane obtained in step (1) in deionized water for 12 h to obtain the selective nanofiltration membrane.

[0067] Figure 1 and Figure 2 The images shown are surface and cross-sectional photographs of the selective nanofiltration membrane obtained in Example 1 of this invention. Electron microscopy of the nanofiltration membrane surface reveals a dense and uniform spherical nodular structure, forming a dense separation layer. Electron microscopy of the nanofiltration membrane cross-section shows a separation layer with a thickness of 95 ± 5 nm on the base membrane.

[0068] Example 2

[0069] This embodiment provides a selective nanofiltration membrane, differing from Embodiment 1 only in that 4,4'-diaminostilbene-2,2'-disulfonic acid is replaced with the same mass of sodium 2,2'-benzidine disulfonate. The preparation method of the selective nanofiltration membrane is the same as that of Embodiment 1.

[0070] Example 3

[0071] This embodiment provides a selective nanofiltration membrane, differing from Embodiment 1 only in that the mass concentration of the mixture of 4,4'-diaminostilbene-2,2'-disulfonic acid and polyethyleneimine in the aqueous reactant solution is 0.07 wt%, and the mass ratio of polyethyleneimine to 4,4'-diaminostilbene-2,2'-disulfonic acid is 6:1. The preparation method of the selective nanofiltration membrane is the same as in Embodiment 1.

[0072] Example 4

[0073] This embodiment provides a selective nanofiltration membrane, which differs from Embodiment 1 only in that the surfactant is dodecyl phosphate.

[0074] Specifically, this embodiment provides a selective nanofiltration membrane, which includes a support layer and a separation layer stacked sequentially; the separation layer is obtained by interfacial polymerization of oil phase reactants and aqueous phase reactants.

[0075] The aqueous reactants comprise polyethyleneimine and 4,4'-diaminostilbene-2,2'-disulfonic acid in a mass ratio of 4:1; the mass concentration of the mixture of 4,4'-diaminostilbene-2,2'-disulfonic acid and polyethyleneimine in the aqueous reactant solution is 0.05 wt%.

[0076] The oil phase reactants include trimesoyl chloride and the surfactant dodecyl phosphate, wherein the mass concentration of trimesoyl chloride in the oil phase reactant solution is 0.05 wt%, and the concentration of dodecyl phosphate in the oil phase reactant solution is 0.15 g / L.

[0077] The method for preparing the aqueous reactant solution includes the following steps:

[0078] 4,4'-diaminostilbene-2,2'-disulfonic acid and polyethyleneimine were dissolved separately in deionized water, and then mixed in proportion after complete dissolution to obtain the aqueous reactant solution.

[0079] The preparation method of the oil phase reactant solution includes the following steps:

[0080] Pyrimethanol chloride was fully dissolved in n-hexane in a certain proportion, and the surfactant dodecyl phosphate was added to obtain an oil phase reaction solution.

[0081] The method for preparing the selective nanofiltration membrane includes the following steps:

[0082] (1) Place the polyacrylonitrile ultrafiltration membrane support layer in a mold, immerse 20 mL of aqueous reaction solution on the support layer for 3 min; remove it and remove the surface moisture, then immerse the support layer with 20 mL of oil reaction solution for 30 s; remove it and air dry for 600 s to obtain the separation membrane.

[0083] (2) Then quickly immerse the separation membrane obtained in step (1) in deionized water for 12 h to obtain the selective nanofiltration membrane.

[0084] Example 5

[0085] This embodiment provides a selective nanofiltration membrane, differing from Embodiment 1 only in that 4,4'-diaminostilbene-2,2'-disulfonic acid is replaced with the same mass of sodium 5,6-diamino-1,3-naphthalenedisulfonic acid. The preparation method of the selective nanofiltration membrane is the same as that of Embodiment 1.

[0086] Example 6

[0087] This embodiment provides a selective nanofiltration membrane, differing from Embodiment 1 only in that polyethyleneimine is replaced with the same mass of triethylenetetramine. The preparation method of the selective nanofiltration membrane is the same as that of Embodiment 1.

[0088] Example 7

[0089] This embodiment provides a selective nanofiltration membrane, differing from Embodiment 1 only in that sodium dodecyl sulfate is replaced with the same mass of sodium eicosyl sulfate. The preparation method of the selective nanofiltration membrane is the same as that of Embodiment 1.

[0090] Example 8

[0091] This comparative example provides a selective nanofiltration membrane, which differs from Example 1 only in that sodium dodecyl sulfate in the aqueous phase reactant is replaced with the same mass of dodecyl dimethyl benzyl ammonium chloride in the oil phase reactant.

[0092] Example 9

[0093] This comparative example provides a selective nanofiltration membrane, which differs from Example 1 only in that the aqueous phase reactants do not contain the surfactant sodium dodecyl sulfate.

[0094] Example 10

[0095] This embodiment provides a selective nanofiltration membrane, which differs from Embodiment 1 only in that 4,4'-diaminostilbene-2,2'-disulfonic acid is replaced with the same mass of sodium trihydroxymethylaminopropanesulfonate.

[0096] Comparative Example 1

[0097] This comparative example provides a selective nanofiltration membrane, which differs from Example 1 only in that the polyethyleneimine is replaced with the same mass of piperazine.

[0098] Comparative Example 2

[0099] This comparative example uses an MPDA / TMC membrane. Data are from the Journal of Membrane Science, Vol. 493, November 1, 2015, pp. 156-166.

[0100] Comparative Example 3

[0101] This comparative example uses a St / TMC TFCM membrane, and the data is from Science Advances, Volume 9, Issue 18, May 5, 2023.

[0102] Test methods

[0103] The selective nanofiltration membranes provided in the examples and comparative examples were tested for filtration of water, inorganic salts, negatively charged clindamycin phosphate (CLP), and positively charged bacitracin (BAC).

[0104] Selective nanofiltration membrane water flux and its retention performance for inorganic salts and antibiotics were tested in a low-pressure cross-flow apparatus (purchased from Hangzhou Saifei Membrane Separation Technology Co., Ltd.). The effective membrane area was 7 cm³. 2 The filtration process employs a full-circulation mode, operating at a cross-flow velocity of 50 L / H. The water flux is calculated using the following formula:

[0105]

[0106] Where P is the permeation flux (Lm)-2 h -1 bar -1 );V p A represents the volume (L) of permeate collected within time t; m Effective membrane area (m²) 2 ); t is the running time (h); TMP is the transmembrane pressure (bar).

[0107] The retention rates of inorganic salts and antibiotics are calculated using the following formula:

[0108]

[0109] Where C p and C r These represent the concentrations of the solute in the permeate and retentate, respectively: for inorganic salt solutions, the concentration ratio can be replaced by the conductivity ratio; for antibiotic solutions, the concentration ratio can be replaced by the ratio of carbon content from the TOC (Total Organic Carbon) analyzer.

[0110] Sodium sulfate and antibiotic separation factor are calculated using the following formula:

[0111]

[0112]

[0113] The above tests were conducted at 25°C, with an inorganic salt solution concentration of 1000 ppm and an antibiotic solution concentration of 500 ppm. The specific test results are shown in Table 1.

[0114] Table 1

[0115]

[0116] The test results show that:

[0117] (1) As can be seen from Examples 1-7, the present invention can improve the sodium sulfate / antibiotic selectivity of nanofiltration membrane while maintaining high water flux by selecting monomers and surfactants.

[0118] (2) By comparing Examples 1, 2 and 5, it can be seen that when the negatively charged monomer in the aqueous phase monomer is replaced, the separation performance of sodium sulfate / antibiotic will be affected.

[0119] (3) By comparing Examples 1 and 3, it can be seen that when the mass ratio of monomers in the aqueous phase of the antibiotic desalination nanofiltration membrane is 0.1-10, the increase of amine monomers will increase the selectivity for sodium sulfate / BAC and decrease the selectivity for sodium sulfate / CLP.

[0120] (4) By comparing Examples 1, 4 and 7, it can be seen that the changes in the surfactant all affect the separation performance of sodium sulfate / antibiotic in nanofiltration membrane;

[0121] (5) By comparing Example 1, Example 10 and Comparative Example 1, it can be seen that changing the type of aqueous monomer will affect the separation performance of sodium sulfate / antibiotic.

[0122] (6) By comparing Example 1 with Examples 8 and 9, it can be seen that using a positively charged surfactant or not adding a surfactant will reduce the separation performance of sodium sulfate / antibiotic.

[0123] (7) By comparing Examples 1-7 with Comparative Examples 2-3, it can be seen that the antibiotic desalination nanofiltration membrane has better performance in sodium sulfate / antibiotic separation than the nanofiltration membranes reported in previous literature.

[0124] In summary, this invention utilizes the monomers and surfactants protected by this patent to prepare a nanofiltration membrane exhibiting both high water flux and high selectivity for sodium sulfate / antibiotics. The method is simple to operate and suitable for industrial production. This invention regulates the diffusion rate of the aqueous monomer to the reaction interface, balancing the charge on the membrane to obtain a nanofiltration membrane that is nearly electrically neutral overall. This membrane has universal applicability for the separation of sodium sulfate / antibiotics and can achieve highly efficient desalination of antibiotics with different charges.

[0125] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A selective nanofiltration membrane, characterized in that, The selective nanofiltration membrane includes a support layer and a separation layer; The separation layer is obtained by interfacial polymerization of oil phase reactants and aqueous phase reactants; The aqueous phase reactants include negatively charged monomers and positively charged monomers; The positively charged monomers include any one or a combination of at least two of the following: polyethyleneamine, polyethyleneimine, diethylenetriamine, water-soluble chitosan, quaternized polyethyleneimine, polyallylamine, or triethylenetetramine.

2. The selective nanofiltration membrane according to claim 1, characterized in that, The reactants also include surfactants; Preferably, the surfactant is an anionic surfactant; Preferably, the surfactant comprises any one or a combination of at least two of sodium dodecyl sulfonate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium hexadecyl sulfate, sodium hexadecyl sulfonate, sodium eicosyl sulfate, or dodecyl phosphate.

3. The selective nanofiltration membrane according to claim 1 or 2, characterized in that, The support layer comprises a polymer porous layer and a non-woven fabric layer stacked sequentially; Preferably, the polymer porous layer comprises any one or a combination of at least two of the following: a polysulfone porous layer, a polyethersulfone porous layer, a polyacrylonitrile porous layer, a polyetherimide porous layer, a polytetrafluoroethylene or a polyethylene porous layer. Preferably, the thickness of the support layer is 100-300 μm.

4. The selective nanofiltration membrane according to any one of claims 1-3, characterized in that, The thickness of the separation layer is 0.05-5 μm, more preferably 0.5-3 μm.

5. The selective nanofiltration membrane according to any one of claims 1-4, characterized in that, The oil phase reactants include any one or a combination of at least two of the following: aromatic organic compounds containing at least two acyl halide functional groups, aliphatic organic compounds containing at least two acyl halide functional groups, or alicyclic organic compounds containing at least two acyl halide functional groups. Preferably, the oil phase reactants include any one or a combination of at least two of phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, trimesoyl chloride, methyl isophthaloyl diisocyanate, biphenyltriacyl chloride, 5-oxoformyl chloride-isophthaloyl chloride, or 5-isocyanate-isophthaloyl chloride; Preferably, the mass ratio of the positively charged monomers in the oil phase reactant to those in the aqueous phase reactant is 1:(0.1-10); Preferably, the negatively charged monomers in the aqueous reactants include any one or a combination of at least two of 2,2'-benzidine disulfonic acid, sodium 2,2'-benzidine disulfonic acid, 4,4'-diaminostilbene-2,2'-disulfonic acid, sodium 4,4'-diaminostilbene-2,2'-disulfonic acid, 5,6-diamino-1,3-naphthalene disulfonic acid, or sodium 5,6-diamino-1,3-naphthalene disulfonic acid. Preferably, the mass ratio of positively charged monomers to negatively charged monomers in the aqueous reactants is 1:(0.1-10), and more preferably 1:(0.1-5).

6. A method for preparing a selective nanofiltration membrane as described in any one of claims 1-5, characterized in that, The preparation method includes the following steps: The support layer is impregnated sequentially with aqueous and oil-phase reactant solutions to form a separation layer, thereby obtaining a selective nanofiltration membrane.

7. The preparation method according to claim 6, characterized in that, The concentration of surfactant in the aqueous reactant solution is 0.001 wt%-0.5 wt%. Preferably, the concentration of the monomer in the aqueous reactant solution is 0.01 wt%-0.5 wt%; Preferably, the concentration of the solute in the oil phase reactant solution is 0.01wt%-0.5wt%. Preferably, the aqueous reactant solution impregnates the support layer for 3-30 minutes.

8. The preparation method according to claim 6 or 7, characterized in that, The oil phase reactant solution impregnates the support layer for 5-120 seconds.

9. The preparation method according to any one of claims 6-8, characterized in that, After the separation layer is formed, it is then subjected to drying and solvent soaking treatments in sequence. Preferably, the drying time is 60-600 s; Preferably, the solvent used for solvent immersion treatment includes any one or a combination of at least two of water, glycerin, polyethylene glycol, or ethanol; Preferably, the solvent immersion treatment time is 1-24 h.

10. Use of a selective nanofiltration membrane as described in any one of claims 1-5, characterized in that, The applications include the separation of organic matter and inorganic salts using selective nanofiltration membranes, more preferably the separation of antibiotics and inorganic salts.

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