Preparation methods and applications of polysulfonamide and acid-resistant composite nanofiltration membranes

Abstract

This invention relates to the field of nanofiltration membrane technology, and discloses a method for preparing a polysulfonamide and an acid-resistant composite nanofiltration membrane, as well as its application. The method for preparing the polysulfonamide includes reacting polyethylene polyamine, polyethyleneimine, and polysulfonyl chloride in contact. The composite nanofiltration membrane includes a bottom layer, an intermediate support layer, and a separation layer, wherein the separation layer is separation layer A or separation layer B; separation layer A is made of polysulfonamide with metal ions chelated on its surface; separation layer B is obtained by reacting polyethylene polyamine, polyethyleneimine, and polysulfonyl chloride in contact. The composite nanofiltration membrane of this invention can improve the desalination rate and acid resistance of nanofiltration membranes when used in water treatment.

Description

Technical Field

[0001] This invention relates to the field of nanofiltration membrane technology, and more specifically to the preparation method and application of polysulfonamide and acid-resistant composite nanofiltration membranes. Background Technology

[0002] Nanofiltration is a pressure-driven membrane separation process that falls between reverse osmosis and ultrafiltration. Nanofiltration membranes have pore sizes ranging from a few nanometers. They are less effective at removing monovalent ions and organic compounds with molecular weights less than 200, but have higher removal rates for divalent or polyvalent ions and organic compounds with molecular weights between 200 and 500. Nanofiltration membranes can be widely used in freshwater softening, seawater softening, drinking water purification, water quality improvement, oil-water separation, wastewater treatment and recycling, as well as in the classification, purification, and concentration of chemical products such as dyes, antibiotics, peptides, and polysaccharides.

[0003] Currently, most commercial nanofiltration membranes use polysulfone ultrafiltration membranes as the support layer. In-situ interfacial polymerization of a polyamine aqueous phase and a polyacrylamide organic phase occurs on the surface of the ultrafiltration membrane, resulting in a composite nanofiltration membrane. Common aqueous monomers are piperazine or piperazine-substituted amines, and the organic phase is trimesoyl chloride or a polyfunctional acryl halide, as disclosed in patents US4769148 and US4859384. A large number of unreacted acrylamide groups hydrolyze into carboxylic acids, giving the nanofiltration membrane a negative charge. Utilizing this charge effect, the polypiperazine amide composite nanofiltration membrane exhibits a high rejection rate for high-valence anions and an adjustable rejection rate for monovalent anions. Furthermore, patents US4765897, US4812270, and US4824574 also provide a method for converting a polyamide composite reverse osmosis membrane into a nanofiltration membrane. However, due to the limitations of the material itself, traditional polyamide nanofiltration membranes will degrade under extreme pH conditions. Since the pH range for polyamide nanofiltration membranes is generally 2-11, they can only be used in neutral media or near-neutral weak acid or weak alkaline media.

[0004] In recent years, researchers have developed a variety of nanofiltration membranes, and many commercial products have emerged. In addition, many new materials, such as sulfonated polyetherketone and sulfonated polyethersulfone, have also been applied in the field of nanofiltration.

[0005] The literature "Sulfonated poly(etheretherketone) based composite membranes for nanofiltration of acidic and alkaline media, J.Membr.Sci., 381, 81-89, 2011" reports that sulfonated poly(etheretherketone) possesses acid resistance, and crosslinking further enhances its nanofiltration membrane properties, resulting in nanofiltration membranes with excellent retention performance. Moreover, the crosslinked poly(etheretherketone) material exhibits strong solvent resistance, enabling the separation of dyes in polar solvents such as isopropanol and acetone (Crosslinking of modified poly(etheretherketone) membranes for use in solvent-resistant nanofiltration, 447, 212-221, 2013).

[0006] The literature "Acid and Alkali Resistant High Temperature Nanofiltration Membrane HYDRACoRe70pHT for the Recovery of Alkali Waste from Sugar Industry, Membrane Science and Technology, 32, 11-15, 2006" reports that the commercially available sulfonated polyethersulfone composite nanofiltration membrane is the HYDRACoRe series developed by Nitto Denko Hydranautics Co., Ltd. It can be used in strong acid and strong alkali solutions and is widely used in the recovery of waste alkali.

[0007] Patents US5265734 and EP0392982(A3) report that the only nanofiltration membrane capable of long-term stable operation at pH 0-14 is the SelRO MPS34 developed by KOCH. It was originally developed by Israeli scientists and was first applied to pervaporation.

[0008] AMS has developed a composite nanofiltration membrane that is resistant to acid, alkali and solvent. Its separation layer material is polyamine (US9943811), which is prepared by interfacial polymerization of polyamines and cyanuric chloride or its derivatives.

[0009] The literature (Journal of Membrane Science 523(2017)487-496) and the literature (Journal of Membrane Science 478(2015)75-84) reported that a polyaniline separation layer was modified on a porous support layer by interfacial polymerization, and the composite membrane had strong permeation and separation stability in a medium environment with pH=0-14.

[0010] The literature (Journal of Membrane Science 572(2019)489-495) prepared polyvinylidene fluoride nanofiltration membrane material by phase inversion and post-treatment method, which has strong stability in strong acid and strong alkali environments.

[0011] The literature "Acid stable thin-film composite membrane for nanofiltration prepared from naphthalene-1,3,6-trisulfonylchloride (NTSC) and piperazine (PIP), J. Membr. Sci., 415-416, 122-131, 2012" reports that sulfonamide materials have strong acid resistance. Composite nanofiltration membranes obtained by interfacial polymerization of polysulfonyl chloride monomers and piperazine can maintain stable separation performance in a pH=0 environment. GE's acid-resistant nanofiltration membrane, Duracid NF1812C, has a three-layer composite structure. Its separation layer is made of polysulfonamide (patent number US7138058), which remains stable under 20% hydrochloric acid, sulfuric acid, and phosphoric acid conditions, and also remains stable at 70°C under 20% sulfuric acid concentration.

[0012] Although there are reports in the literature and patents regarding polysulfonamides as separation layers in acid-resistant nanofiltration membranes, the water flux and desalination rates of these membranes are relatively low due to limitations in their molecular structure. Therefore, developing polysulfonamide composite nanofiltration membranes with novel cross-linked structures to improve their water permeability and salt rejection properties for application in the treatment of acidic wastewater is of great significance. Summary of the Invention

[0013] The purpose of this invention is to overcome the problem of low water flux and desalination rate of nanofiltration membranes in the prior art when used to treat acidic water, and to provide a method for preparing polysulfonamide and an acid-resistant composite nanofiltration membrane and its application.

[0014] The first aspect of the present invention provides a method for preparing polysulfonamide, the method comprising reacting polyethylene polyamine, polyethyleneimine and polysulfonyl chloride in contact.

[0015] A second aspect of the present invention provides a polysulfonamide, which is a polysulfonamide prepared by the method described in the first aspect.

[0016] A third aspect of the present invention provides an acid-resistant composite nanofiltration membrane, the composite nanofiltration membrane comprising a bottom layer, an intermediate support layer and a separation layer, wherein the separation layer is separation layer A or separation layer B;

[0017] The material of the separation layer A is polysulfonamide with metal ions chelated on its surface;

[0018] The material of the separation layer B is the polysulfonamide described in the second aspect.

[0019] The fourth aspect of the present invention provides the application of the polysulfonamide described in the second aspect and the acid-resistant composite nanofiltration membrane described in the third aspect in water treatment.

[0020] (1) Chelating metal ions on polysulfonamide (separation layer A) can improve the desalination rate and acid resistance of nanofiltration membrane.

[0021] (2) Adding polyethylene polyamine during the preparation of polysulfonamide can improve the desalination rate and acid resistance of nanofiltration membrane.

[0022] (3) Chelating metal ions on polysulfonamide containing polyethylene polyamine monomers can further improve the desalination rate and acid resistance of nanofiltration membranes. Attached Figure Description

[0023] Figure 1 The image shows the EDS spectrum of the composite nanofiltration membrane prepared in Example 1. Detailed Implementation

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] The first aspect of the present invention provides a method for preparing polysulfonamide, the method comprising reacting polyethylene polyamine, polyethyleneimine and polysulfonyl chloride in contact.

[0026] According to the present invention, the molecular weight of the polyethyleneimine can be selected in a wide range. Preferably, the weight-average molecular weight of the polyethyleneimine is 1,000-100,000, more preferably 5,000-50,000. More preferably, the degree of branching of the polyethyleneimine is greater than 90%, more preferably 98-100%. "Degree of branching" is defined as the molar percentage of branched units.

[0027] According to the present invention, the molecular weight of the polyethylene polyamine can be selected in a wide range. Preferably, the weight-average molecular weight of the polyethylene polyamine is 100-10000, more preferably 200-2000, and even more preferably 200-400.

[0028] According to the present invention, the polyethylene polyamine has the structure shown in formula (1):

[0029]

[0030] Where x is an integer from 0 to 100, preferably an integer from 1 to 3; y is an integer from 0 to 50, preferably an integer from 1 to 3; 1 <x+y<150,1<x+y<6。

[0031] According to the present invention, the type of polysulfonyl chloride can be selected from a wide range. Preferably, the polysulfonyl chloride is a disulfonyl chloride having an aromatic ring and / or a trisulfonyl chloride having an aromatic ring, preferably at least one selected from 1,3-benzene disulfonyl chloride, 1,2-benzene disulfonyl chloride, 1,4-benzene disulfonyl chloride, 2,4-disulfonyl chloride methyltrimethylbenzene, biphenyl-4,4'-disulfonyl chloride, 4,5-dichloro-1,3-benzene disulfonyl chloride, 2,6-naphthalene disulfonyl chloride, 1,3-naphthalene disulfonyl chloride, 2,7-naphthalene disulfonyl chloride, 1,3,5-benzene trisulfonyl chloride, and 1,3,6-naphthalene trisulfonyl chloride. More preferably, it is at least one selected from 1,3-benzene disulfonyl chloride, 1,2-benzene disulfonyl chloride, 1,4-benzene disulfonyl chloride, and 1,3,5-benzene trisulfonyl chloride.

[0032] According to the present invention, the amounts of the polyethylene polyamine, polyethyleneimine, and polysulfonyl chloride can be selected within a wide range. However, in order to improve the acid resistance and desalination rate of polysulfonamide, preferably, the weight ratio of the sum of the weights of the polyethylene polyamine and polyethyleneimine to the weight ratio of the polysulfonyl chloride is 0.5-50:1, more preferably 3-10:1, and even more preferably 3.75-6.5:1.

[0033] According to the present invention, the amount of polyethylene polyamine and polyethyleneimine can be selected in a wide range, but in order to improve the acid resistance and desalination rate of polysulfonamide, the weight ratio of polyethylene polyamine to polyethyleneimine is preferably 0.1-10:1, more preferably 0.5-3.5:1.

[0034] According to the present invention, preferably, the reaction conditions include: a temperature of 40-150°C, more preferably 50-120°C, and a time of 0.5-20 min, more preferably 1-10 min.

[0035] According to the present invention, in order to further improve the acid resistance and desalination rate of polysulfonamide, preferably, the method further includes chelating the reaction products with metal ions.

[0036] According to the present invention, preferably, the chelation is performed by contacting the reaction product with a base, and then contacting it with a solution containing metal ions.

[0037] According to the present invention, preferably, the contact time with the alkali is 1-60 min, more preferably 5-30 min, and the temperature is 15-40°C.

[0038] According to the present invention, preferably, the alkali is an alkali metal hydroxide, more preferably sodium hydroxide and / or potassium hydroxide.

[0039] According to the present invention, preferably, the alkali is contacted with the reaction product in the form of an alkaline solution, the concentration of which is 0.05-2 wt%, preferably 0.1-1 wt%.

[0040] According to the present invention, preferably, the amount of the metal ion is 0.01-0.1g relative to each gram of reaction product.

[0041] According to the present invention, preferably, the metal ion is a metal ion of the third period and / or the fourth period, preferably Cu. 2+ Fe 3+ Zn 2+ Mg 2+ Ca 2+ Fe 2+ Mn 2+ Al 3+ Ni 2+ and Cr 3+ At least one of them, more preferably Cu 2+ and / or Fe 3 + .

[0042] According to the present invention, preferably, the metal ion may be provided by at least one of copper sulfate, copper chloride, ferrous sulfate, ferric chloride, magnesium sulfate, magnesium chloride, calcium chloride, zinc chloride, aluminum chloride, manganese chloride, nickel chloride, and chromium chloride, and more preferably by copper sulfate and / or ferric chloride.

[0043] According to the present invention, preferably, the concentration of the metal ion-containing solution is 0.1-10 wt%, more preferably 0.5-5 wt%.

[0044] According to the present invention, preferably, the contact time with the solution containing metal ions is 5-60 min, more preferably 10-30 min, and the temperature is 15-40°C.

[0045] According to the present invention, preferably, the reaction product is washed until neutral after contacting with an alkali, and then contacted with a solution containing metal ions.

[0046] A second aspect of the present invention provides a polysulfonamide, which is a polysulfonamide prepared by the method described in the first aspect.

[0047] In the present invention, when preparing polysulfonamide using binary sulfonyl chloride, polyethylenepolyamine, and polyethyleneimine, the obtained polysulfonamide may have the structures shown in Formula (1) and Formula (2), or may have the structures shown in Formula (1), Formula (2), and Formula (3).

[0048]

[0049]

[0050] R is an aromatic ring; M is a metal ion in the third and / or fourth period, preferably Cu 2+ 、Fe 3+ 、Zn 2+ 、Mg 2+ 、Ca 2+ 、Fe 2+ 、Mn 2+ 、Al 3+ 、Ni 2+ and Cr 3+ at least one of them, more preferably Cu 2+ and / or Fe 3+ ; n is an integer from 1 to 1000; x is an integer from 0 to 100, preferably an integer from 1 to 3; y is an integer from 0 to 50, preferably an integer from 1 to 3; 1 < x + y < 150, preferably 1 < x + y < 6.

[0051] The third aspect of the present invention provides a composite nanofiltration membrane with acid resistance, which includes a bottom layer, an intermediate support layer, and a separation layer. Among them, the separation layer is Separation Layer A or Separation Layer B;

[0052] The material of Separation Layer A is polysulfonamide surface-chelated with metal ions;

[0053] [[ID=4²]]The material of Separation Layer B is the polysulfonamide described in the second aspect.

[0054] According to the present invention, preferably, the metal ions in Separation Layer A are metal ions in the third and / or fourth period, preferably Cu 2+ 、Fe 3+ 、Zn 2+ 、Mg 2+ 、Ca 2+ 、Fe 2+ 、Mn 2+ 、Al 3+ 、Ni 2+ and Cr 3+ at least one of them, more preferably Cu 2+ and / or Fe 3+ .

[0055] According to the present invention, preferably, the content of metal ions on the surface of separation layer A is 0.01-1% by weight. The content of metal ions on the surface of separation layer A is obtained by EDS elemental analysis (test sample depth is about 20 nm).

[0056] According to the present invention, preferably, the content of metal ions on the surface of separation layer B is 0.01-1% by weight, more preferably 0.2-0.8% by weight. The content of metal ions on the surface of separation layer B is obtained by EDS elemental analysis (test sample depth is about 20 nm).

[0057] According to the present invention, the materials of the bottom layer and the support layer are not particularly limited, and can be made of various existing materials with certain strength that can be used for nanofiltration membranes or reverse osmosis membranes.

[0058] Preferably, the bottom layer is a non-woven fabric; more preferably, the non-woven fabric is made of at least one material selected from polyester, polyethylene, and polypropylene.

[0059] Preferably, the material of the support layer is selected from at least one of polyethersulfone, polysulfone, polyaryl ether, polybenzimidazole, polyetherketone, polyetheretherketone, polyacrylonitrile, polyvinylidene fluoride, and polyaryl etherketone.

[0060] According to the present invention, preferably, the support layer has a porous structure, the porosity of the support layer is 40%-60%, and the average pore size of the surface film is 5-20 nm.

[0061] According to the present invention, the thickness of the bottom layer, the support layer, and the separation layer is not particularly limited and can be a conventional choice in the art. However, in order to enable these three layers to play a better synergistic role and to enable the resulting composite nanofiltration membrane to better combine excellent acid resistance, high water flux, and desalination rate, preferably, the thickness of the bottom layer is 30-150 μm, more preferably 50-120 μm; the thickness of the support layer is 10-100 μm, more preferably 30-60 μm; and the thickness of the separation layer is 10-500 nm, more preferably 50-300 nm.

[0062] The present invention also provides a method for preparing the acid-resistant composite nanofiltration membrane described in the third aspect, the method comprising the following steps:

[0063] (1) Provide an underlying layer and prepare a support layer on one surface of the underlying layer;

[0064] (2) Prepare separation layer A or separation layer B on the other surface of the support layer;

[0065] Preparation of separation layer A: A polysulfonamide layer is prepared on the other surface of the support layer, and then metal ions are chelated;

[0066] Preparation of separation layer B: The other surface of the support layer is reacted with polyethylene polyamine, polyethyleneimine and polysulfonyl chloride.

[0067] According to the method for preparing an acid-resistant composite nanofiltration membrane of the present invention, the materials and thicknesses of the bottom layer, support layer and separation layer are as described in the third aspect and will not be repeated here.

[0068] According to the method for preparing an acid-resistant composite nanofiltration membrane of the present invention, the method for preparing a support layer on one surface of the substrate can be a conventional method in the art. Preferably, a phase inversion method is used, for example, a polymer solution of the support layer material can be coated on one surface of the substrate, and the support layer is obtained through phase inversion. More preferably, the phase inversion method includes: dissolving the polymer material of the support layer in a solvent to obtain a polymer solution with a concentration of 10-20% by weight, degassing at 20-40°C for 10-180 min; then coating the polymer solution onto the substrate to obtain an initial membrane, and then immersing the initial membrane in water at a temperature of 10-30°C for 10-60 min, and obtaining the support layer through phase inversion.

[0069] The solvent in the polymer solution can be at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide. The concentration of the polymer solution can be selected as needed.

[0070] According to the method for preparing an acid-resistant composite nanofiltration membrane according to the present invention, preferably, the method for preparing the separation layer A includes contacting another surface of the support layer with an aqueous phase containing polyethyleneimine, then contacting it with an organic phase containing polysulfonyl chloride, then reacting, and then chelating metal ions.

[0071] According to the method for preparing separation layer A according to the present invention, preferably, the concentration of polyethyleneimine in the aqueous phase containing polyethyleneimine is 0.2-10 wt%, more preferably 0.75-3 wt%.

[0072] According to the method for preparing separation layer A according to the present invention, preferably, the concentration of polysulfonyl chloride in the organic phase containing polysulfonyl chloride is 0.01-1 wt%, more preferably 0.1-0.5 wt%.

[0073] According to the method for preparing separation layer A according to the present invention, preferably, the weight ratio of polyethyleneimine to polysulfonyl chloride is 0.2-10:1.

[0074] According to the method for preparing separation layer A of the present invention, preferably, the contact time with the aqueous phase containing polyethyleneimine is 5-100s, more preferably 10-60s, and the temperature is 15-40℃.

[0075] According to the method for preparing separation layer A according to the present invention, preferably, the contact time with the organic phase containing polysulfonyl chloride is 10-200s, more preferably 20-120s, and the temperature is 15-40℃.

[0076] According to the method for preparing separation layer A according to the present invention, preferably, the reaction conditions include: a temperature of 40-150℃, more preferably 50-120℃, and a time of 0.5-20 min, more preferably 1-10 min.

[0077] According to the method for preparing separation layer A according to the present invention, preferably, the method of chelating metal ions can refer to the first aspect, and will not be repeated here.

[0078] According to the method for preparing an acid-resistant composite nanofiltration membrane of the present invention, preferably, the method for preparing the separation layer B includes contacting another surface of the support layer with an aqueous phase containing polyethylene polyamine and polyethyleneimine, then contacting it with an organic phase containing polysulfonyl chloride, and then reacting.

[0079] According to the method for preparing separation layer B of the present invention, preferably, in the aqueous phase containing polyethylene polyamine and polyethyleneimine, the concentration of polyethylene polyamine is 0.1-10 wt%, preferably 0.5-2.5 wt%; and the concentration of polyethyleneimine is 0.2-10 wt%, preferably 0.75-3 wt%.

[0080] According to the method for preparing separation layer B of the present invention, preferably, the concentration of polysulfonyl chloride in the organic phase containing polysulfonyl chloride is 0.01-1 wt%, more preferably 0.1-0.5 wt%.

[0081] According to the method for preparing separation layer B of the present invention, preferably, the contact time with the aqueous phase containing polyethylene polyamine and polyethyleneimine is 5-100s, more preferably 10-60s, and the temperature is 15-40℃.

[0082] According to the method for preparing separation layer B of the present invention, preferably, the contact time with the organic phase containing polysulfonyl chloride is 10-200s, more preferably 20-120s, and the temperature is 15-40℃.

[0083] According to the method for preparing separation layer B of the present invention, the reaction conditions and raw material amounts are as described in the first aspect, and will not be repeated here.

[0084] According to the method for preparing separation layer B of the present invention, preferably, the method for preparing separation layer B further includes chelating the reaction products with metal ions. The chelation method is as described in the first aspect and will not be repeated here.

[0085] According to the method for preparing separation layer A or separation layer B of the present invention, the type of organic solvent in the organic phase containing polysulfonyl chloride is not particularly limited, as long as it can dissolve the polysulfonyl chloride. Preferably, the solvent of the organic phase is at least one selected from n-hexane, dodecane, n-heptane and alkane solvent oil; more preferably, the alkane solvent oil is a mixture of isoparaffins, such as Isopar E, Isopar G, Isopar H, Isopar L, and Isopar M.

[0086] The fourth aspect of the present invention provides the application of the polysulfonamide described in the second aspect and the acid-resistant composite nanofiltration membrane described in the third aspect in water treatment.

[0087] The present invention will be described in detail below through embodiments. In the following embodiments and comparative examples,

[0088] (1) The water flux of the composite nanofiltration membrane was tested using the following method: The composite nanofiltration membrane was loaded into a membrane tank and pre-pressurized at 1.2 MPa for 0.5 h. The water permeation rate of the nanofiltration membrane was measured within 1 h at a pressure of 2.0 MPa and a temperature of 25 °C, and then calculated using the following formula:

[0089] J = Q / (A·t), where J is the water flux, Q is the water permeation rate (L), and A is the effective membrane area of ​​the composite nanofiltration membrane (m²). 2 ), where t is time (h).

[0090] (2) The desalination rate of the composite nanofiltration membrane was obtained by the following method: The composite nanofiltration membrane was loaded into the membrane tank and pre-pressed at 0.2 MPa for 0.5 h. The concentration changes of magnesium sulfate in the original aqueous solution with an initial concentration of 1000 ppm and the permeate were measured within 1 h at a pressure of 0.5 MPa and a temperature of 25 °C. The results were then calculated using the following formula:

[0091] R = (Cp - Cf) / Cp × 100%, where R is the desalination rate, Cp is the concentration of magnesium sulfate in the original solution, and Cf is the concentration of magnesium sulfate in the permeate.

[0092] (3) Acid resistance test of composite nanofiltration membrane: The composite nanofiltration membrane is immersed in an aqueous solution containing 20% ​​by mass H2SO4 for 2 months, and then the water flux and desalination rate of the composite nanofiltration membrane are tested.

[0093] Branched polyethyleneimine (weight average molecular weight of 25,000, degree of branching of 100%), polyethylene polyamine (structure as shown in formula (1), x is 2, y is 2, weight average molecular weight of 275), 1,3-benzene disulfonyl chloride, 2,4-disulfonyl chloride methyltrimethylbenzene, biphenyl-4,4'-disulfonyl chloride, 1,3-naphthalene disulfonyl chloride, 1,3,5-benzene trisulfonyl chloride, 1,3,6-naphthalene trisulfonyl chloride, etc. were all purchased from Bailingwei Technology Co., Ltd., and other chemical reagents were purchased from Sinopharm Chemical Reagent Co., Ltd.

[0094] Preparation Example

[0095] The support layer is prepared using a phase transformation method, and the specific steps are as follows:

[0096] A certain amount of polysulfone (weight-average molecular weight of 80,000) was dissolved in N,N-dimethylformamide to prepare a polysulfone solution with a concentration of 18% by weight. The solution was degassed at 25°C for 120 min. Then, the polysulfone solution was coated onto a 75 μm thick polyethylene nonwoven fabric (basis weight of 60 g / m²) using a doctor blade. 2 An initial membrane was obtained on the polyethylene nonwoven fabric and then immersed in water at 25°C for 60 minutes. This allowed the polysulfone layer on the surface of the polyethylene nonwoven fabric to undergo phase transformation into a porous membrane. Finally, after three water washes, a support layer with a total thickness of 115 μm was obtained. The support layer has a porous structure with a porosity of 50% and an average pore size of 10 nm on the surface membrane.

[0097] Example 1

[0098] The upper surface of the support layer in the preparation example was contacted with an aqueous solution containing 1 wt% polyethyleneimine and 0.5 wt% polyethylenepolyamine at 25°C for 60 s, and then drained. Next, the upper surface of the support layer was contacted with an Isopar E-type isoalkane solvent oil solution containing 0.4 wt% 1,3-benzenedisulfonyl chloride at 25°C for 60 s, and then drained. The membrane was then placed in an oven and heated at 70°C for 3 min to obtain a composite membrane. The thickness of the separation layer was measured to be 225 nm by scanning electron microscopy. The obtained composite membrane was immersed in a 1 wt% sodium hydroxide aqueous solution at 25°C for 5 min, and then rinsed with deionized water until neutral. The membrane was then immersed in an aqueous solution containing 2.5 wt% copper sulfate at 25°C for 10 min, and then immersed in deionized water to obtain a metal ion surface chelation crosslinking modified composite nanofiltration membrane N1.

[0099] The weight ratio of polyethyleneimine, polyethylene polyamine, and 1,3-benzene disulfonyl chloride is 1:0.5:0.4.

[0100] The amount of metal ions used is 0.07g per gram of separation layer.

[0101] EDS elemental analysis (test sample depth approximately 20 nm) showed that the metal ion content on the surface of the separation layer was approximately 0.6% by weight.

[0102] The obtained composite nanofiltration membrane N1 was soaked in water for 24 hours, and the water flux and the desalination rate of magnesium sulfate were measured. The results are shown in Table 1.

[0103] The composite nanofiltration membrane N1 was immersed in a 20% (w / w) H2SO4 aqueous solution for 2 months, and then the water flux and desalination rate of the composite nanofiltration membrane were tested. The results are shown in Table 1.

[0104] Figure 1 The image shows the EDS spectrum of the composite nanofiltration membrane prepared in Example 1. As can be seen from the image, copper is present on the membrane surface, confirming the occurrence of the chelation modification reaction.

[0105] Example 2

[0106] The upper surface of the support layer in the preparation example was contacted with an aqueous solution containing 0.5 wt% polyethyleneimine and 0.75 wt% polyethylenepolyamine at 25°C for 60 s, and then drained. Next, the upper surface of the support layer was contacted with an Isopar E-type isoalkane solvent oil solution containing 0.3 wt% 1,3-naphthalenedisulfonyl chloride at 25°C for 60 s, and then drained. The membrane was then placed in an oven and heated at 70°C for 3 min to obtain a composite membrane. Scanning electron microscopy measured the thickness of the separation layer to be 184 nm. The obtained composite membrane was immersed in a 0.1 wt% sodium hydroxide aqueous solution at 25°C for 30 min, and then rinsed with deionized water until neutral. The membrane was then immersed in an aqueous solution containing 0.5 wt% copper chloride at 25°C for 30 min, and then immersed in deionized water to obtain a metal ion surface chelate crosslinking modified composite nanofiltration membrane N2.

[0107] The weight ratio of polyethyleneimine, polyethylene polyamine, and 1,3-naphthalene disulfonyl chloride is 0.5:0.75:0.3.

[0108] The amount of metal ions used is 0.03g per gram of separation layer.

[0109] EDS elemental analysis (test sample depth approximately 20 nm) showed that the metal ion content on the surface of the separation layer was approximately 0.2% by weight.

[0110] The obtained composite nanofiltration membrane N2 was soaked in water for 24 hours, and the water flux and the desalination rate of magnesium sulfate were measured. The results are shown in Table 1.

[0111] The composite nanofiltration membrane N2 sheet was immersed in 20% H2SO4 aqueous solution for 2 months, and then the water flux and desalination rate of the composite nanofiltration membrane were tested. The results are shown in Table 1.

[0112] Example 3

[0113] The upper surface of the polysulfone support layer in the preparation example was contacted with an aqueous solution containing 0.75 wt% polyethyleneimine and 2.5 wt% polyethylenepolyamine at 25°C for 60 s, after which the solution was drained. Then, the upper surface of the support layer was contacted again with an Isopar E-type isoalkane solvent oil solution containing 0.5 wt% 1,3,5-benzenetrisulfonyl chloride at 25°C for 60 s, after which the solution was drained. The membrane was then placed in an oven and heated at 70°C for 3 min to obtain a composite membrane. The thickness of the separation layer was measured to be 267 nm by scanning electron microscopy. The obtained composite membrane was then immersed in a 0.5 wt% sodium hydroxide aqueous solution at 25°C for 10 min, and after removal, the membrane surface was rinsed with deionized water until neutral. The membrane was then immersed in an aqueous solution containing 5 wt% ferrous sulfate at 25°C for 10 min, and after removal, immersed in deionized water to obtain a metal ion surface chelation crosslinking modified composite nanofiltration membrane N3.

[0114] The weight ratio of polyethyleneimine, polyethylene polyamine, and 1,3,5-benzenetrisulfonyl chloride is 0.75:2.5:0.5.

[0115] The amount of metal ions used is 0.1g relative to each gram of separation layer.

[0116] EDS elemental analysis (test sample depth approximately 20 nm) showed that the metal ion content on the surface of the separation layer was approximately 0.8% by weight.

[0117] The obtained composite nanofiltration membrane N3 was soaked in water for 24 hours, and the water flux and the desalination rate of magnesium sulfate were measured. The results are shown in Table 1.

[0118] The composite nanofiltration membrane N3 was immersed in a 20% (w / w) H2SO4 aqueous solution for 2 months, and then the water flux and desalination rate of the composite nanofiltration membrane were tested. The results are shown in Table 1.

[0119] Example 4

[0120] The composite membrane was prepared according to the method in Example 1, except that 1,3,6-naphthalenetrisulfonyl chloride was used instead of 1,3-benzenedisulfonyl chloride to obtain composite membrane N4.

[0121] The obtained composite nanofiltration membrane N4 was soaked in water for 24 hours, and the water flux and the desalination rate of magnesium sulfate were measured. The results are shown in Table 1.

[0122] The composite nanofiltration membrane N4 was immersed in a 20% (w / w) H2SO4 aqueous solution for 2 months, and then the water flux and desalination rate of the composite nanofiltration membrane were tested. The results are shown in Table 1.

[0123] Example 5

[0124] The composite membrane was prepared according to the method of Example 1, except that 1,3-benzenedisulfonyl chloride was replaced with 2,4-disulfonyl chloride-trimethylbenzene to obtain composite membrane N5.

[0125] The obtained composite nanofiltration membrane N5 was soaked in water for 24 hours, and the water flux and desalination rate of magnesium sulfate were measured. The results are shown in Table 1.

[0126] The N5 composite nanofiltration membrane was immersed in a 20% (w / w) H2SO4 aqueous solution for 2 months, and then the water flux and desalination rate of the composite nanofiltration membrane were tested. The results are shown in Table 1.

[0127] Example 6

[0128] The composite membrane was prepared according to the method in Example 1, except that 1,3-benzenedisulfonyl chloride was replaced with biphenyl-4,4'-disulfonyl chloride to obtain composite membrane N6.

[0129] The obtained composite nanofiltration membrane N6 was soaked in water for 24 hours, and the water flux and the desalination rate of magnesium sulfate were measured. The results are shown in Table 1.

[0130] The N6 composite nanofiltration membrane was immersed in a 20% (w / w) H2SO4 aqueous solution for 2 months, and then the water flux and desalination rate of the composite nanofiltration membrane were tested. The results are shown in Table 1.

[0131] Example 7

[0132] The composite membrane was prepared according to the method in Example 1, except that ferric chloride was used instead of copper sulfate to obtain composite membrane N7.

[0133] The obtained composite nanofiltration membrane N7 was soaked in water for 24 hours, and the water flux and the desalination rate of magnesium sulfate were measured. The results are shown in Table 1.

[0134] The N7 composite nanofiltration membrane was immersed in a 20% (w / w) H2SO4 aqueous solution for 2 months, and then the water flux and desalination rate of the composite nanofiltration membrane were tested. The results are shown in Table 1.

[0135] Example 8

[0136] The upper surface of the support layer in the preparation example was contacted with an aqueous solution containing 1 wt% polyethyleneimine and 0.5 wt% polyethylenepolyamine at 25°C for 60 s, after which the solution was drained. Then, the upper surface of the support layer was contacted again with an Isopar E solution containing 0.4 wt% 1,3-benzenedisulfonyl chloride at 25°C for 60 s, after which the solution was drained. The membrane was then placed in an oven and heated at 70°C for 3 min to obtain the composite membrane N8. Scanning electron microscopy measured the thickness of the separation layer to be 225 nm.

[0137] The weight ratio of polyethyleneimine, polyethylene polyamine, and 1,3-benzene disulfonyl chloride is 1:0.5:0.4.

[0138] The obtained composite membrane N8 was soaked in water for 24 hours, and the water flux and the desalination rate of magnesium sulfate were measured. The results are shown in Table 1.

[0139] The composite nanofiltration membrane N8 was immersed in a 20% (w / w) H2SO4 aqueous solution for 2 months, and then the water flux and desalination rate of the composite nanofiltration membrane were tested. The results are shown in Table 1.

[0140] Example 9

[0141] The upper surface of the support layer in the preparation example was contacted with an aqueous solution containing 1 wt% polyethyleneimine at 25°C for 60 s, and then drained. Next, the upper surface of the support layer was contacted with an Isopar E-type isoalkane solvent oil solution containing 0.4 wt% 1,3-benzenedisulfonyl chloride at 25°C for 60 s, and then drained. The membrane was then placed in an oven and heated at 70°C for 3 min to obtain a composite membrane. Scanning electron microscopy measured the thickness of the separation layer to be 225 nm. The obtained composite membrane was then immersed in a 1 wt% sodium hydroxide aqueous solution at 25°C for 5 min, and after removal, the membrane surface was rinsed with deionized water until neutral. The membrane was then immersed in an aqueous solution containing 2.5 wt% copper sulfate at 25°C for 10 min, and after removal, immersed in deionized water to obtain a metal ion surface chelation crosslinking modified composite nanofiltration membrane N9.

[0142] The weight ratio of polyethyleneimine to 1,3-benzenesulfonyl chloride is 1:0.4.

[0143] The amount of metal ions used is 0.07g per gram of separation layer.

[0144] EDS elemental analysis (test sample depth approximately 20 nm) showed that the metal ion content on the surface of the separation layer was approximately 0.5% by weight.

[0145] The obtained composite nanofiltration membrane N9 was soaked in water for 24 hours, and the water flux and desalination rate of magnesium sulfate were measured. The results are shown in Table 1.

[0146] The N9 composite nanofiltration membrane was immersed in a 20% (w / w) H2SO4 aqueous solution for 2 months, and then the water flux and desalination rate of the composite nanofiltration membrane were tested. The results are shown in Table 1.

[0147] Example 10

[0148] The composite membrane was prepared according to the method in Example 1, except that "an aqueous solution containing 1% polyethyleneimine and 0.5% polyethylene polyamine" was replaced with "an aqueous solution containing 1% polyethyleneimine and 5% polyethylene polyamine" to obtain composite membrane N10.

[0149] The weight ratio of polyethyleneimine, polyethylene polyamine, and 1,3-benzene disulfonyl chloride is 1:5:0.4.

[0150] The obtained composite nanofiltration membrane N10 was soaked in water for 24 hours, and the water flux and the desalination rate of magnesium sulfate were measured. The results are shown in Table 1.

[0151] The composite nanofiltration membrane N10 was immersed in 20% H2SO4 aqueous solution for 2 months, and then the water flux and desalination rate of the composite nanofiltration membrane were tested. The results are shown in Table 1.

[0152] Example 11

[0153] The composite membrane was prepared according to the method in Example 1, except that "containing 2.5% copper sulfate aqueous solution" was replaced with "containing 5% copper sulfate aqueous solution", and composite membrane N11 was obtained.

[0154] The amount of metal ions used is 0.14g per gram of separation layer.

[0155] EDS elemental analysis (test sample depth approximately 20 nm) showed that the metal ion content on the surface of the separation layer was approximately 0.9% by weight.

[0156] The obtained composite nanofiltration membrane N11 was soaked in water for 24 hours, and the water flux and the desalination rate of magnesium sulfate were measured. The results are shown in Table 1.

[0157] The N11 composite nanofiltration membrane was immersed in a 20% (w / w) H2SO4 aqueous solution for 2 months, and then the water flux and desalination rate of the composite nanofiltration membrane were tested. The results are shown in Table 1.

[0158] Comparative Example 1

[0159] The nanofiltration membrane was prepared according to the method of Example 9, except that metal ion chelation was not performed, resulting in composite nanofiltration membrane D1. That is, the separation layer is a polysulfonamide layer formed from polyethyleneimine and 1,3-benzenedisulfonyl chloride.

[0160] Table 1

[0161]

[0162]

[0163] As shown in Table 1, compared with Comparative Example 1, the composite nanofiltration membrane provided by the present invention has a higher desalination rate and stronger acid resistance. Examples 1-7 of the present invention, using preferred embodiments, introduce polyethylene polyamines and metal ions into the separation layer, which can further improve the desalination rate and acid resistance. Particularly preferably, Examples 1, 3, and 7 of the present invention use polysulfonyl chlorides containing one phenyl group to obtain even higher desalination rates and stronger acid resistance.

[0164] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A composite nanofiltration membrane with acid resistance, characterized in that, The composite nanofiltration membrane includes a bottom layer, an intermediate support layer, and a separation layer, wherein the separation layer is separation layer A; The material of the separation layer A is polysulfonamide with metal ions chelated on its surface.

2. The composite nanofiltration membrane according to claim 1, wherein, The method for preparing the polysulfonamide includes reacting polyethylene polyamine, polyethyleneimine and polysulfonyl chloride in contact.

3. The composite nanofiltration membrane according to claim 2, wherein, The weight-average molecular weight of the polyethyleneimine is 1,000-100,000; And / or, the weight-average molecular weight of the polyethylene polyamine is 100-10000; And / or, the polysulfonyl chloride is a disulfonyl chloride having an aromatic ring and / or a trisulfonyl chloride having an aromatic ring; And / or, the weight ratio of the sum of the polyethylene polyamine and polyethyleneimine to the polysulfonyl chloride is 0.5-50:1; And / or, the weight ratio of the polyethylene polyamine to polyethyleneimine is 0.1-10:1; And / or, the reaction conditions include: a temperature of 40-150°C and a time of 0.5-20 min.

4. The composite nanofiltration membrane according to claim 2, wherein, The polysulfonamide with metal ions chelated on its surface is obtained by contacting the reaction product with an alkali, and then with a solution containing metal ions.

5. The composite nanofiltration membrane according to claim 4, wherein, The contact time with alkali is 1-60 minutes, and the temperature is 15-40℃; And / or, the base is an alkali metal hydroxide; And / or, the amount of metal ions used is 0.01-0.1 g relative to each gram of reaction product; And / or, the metal ion is a metal ion of the third period and / or the fourth period; And / or, the contact time with the solution containing metal ions is 5-60 min, and the temperature is 15-40℃.

6. The composite nanofiltration membrane according to claim 1, wherein, The bottom layer is non-woven fabric; And / or, the thickness of the bottom layer is 30-150 μm, the thickness of the support layer is 10-100 μm, and the thickness of the separation layer is 10-500 nm; And / or, the material of the support layer is selected from at least one of polyethersulfone, polysulfone, polyaryl ether, polybenzimidazole, polyetherketone, polyetheretherketone, polyacrylonitrile, polyvinylidene fluoride and polyaryl etherketone.

7. The application of the acid-resistant composite nanofiltration membrane according to any one of claims 1-6 in water treatment.

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