High-salt-rejection pollution-resistant polyamide reverse osmosis membrane and preparation method thereof

Abstract

The invention discloses a high-salt-rejection and pollution-resistant polyamide reverse osmosis membrane, which is characterized in that an aromatic cationic surfactant containing two benzene ring structures is adopted to regulate and control the interfacial polymerization reaction of a polyamine monomer and a polyacyl chloride monomer, and a high-salt-rejection and pollution-resistant polyamide functional layer is generated on a porous ultrafiltration base membrane. The effective specific surface area of the polyamide functional layer of the reverse osmosis membrane is gt; 1.2, the surface potential gt when the pH is equal to 7; -20 mV; the molecular weight cut-off of the polyamide reverse osmosis membrane is 1t; the molecular weight is 100Da, and the retention rate for 2000ppm of NaCl is gt; the anti-fouling coating has the advantages of good hydrophilicity and excellent anti-fouling performance. The preparation process of the polyamide reverse osmosis membrane is simple and efficient, and has industrial application potential. The polyamide reverse osmosis membrane can be used for purification and treatment of different types of water, and has important application value.

Description

Technical Field

[0001] The invention relates to the technical field of separation membrane materials, and in particular to a high-salt-cutoff and pollution-resistant polyamide reverse osmosis membrane and a preparation method thereof. Background Art

[0002] With the growth of population and the increasing demand for water resources in industry, the serious water shortage problem has become a major challenge affecting global sustainable development. Reverse osmosis membrane has become an important technical means to maximize the recycling of water resources due to its excellent monovalent salt retention performance. Among them, thin-layer composite polyamide membrane has become the most widely used type of reverse osmosis membrane due to its excellent separation selectivity and good chemical stability. However, in actual use, polyamide reverse osmosis membrane faces a trade-off effect between permeability and selectivity, and is prone to membrane fouling, which increases the operation and maintenance costs of the system. Therefore, the development of high permeability and selectivity and pollution-resistant reverse osmosis membranes is still the focus of current membrane research.

[0003] The published patents CN 114130218 A, CN 114570218 B, and CN 117160254 B use ionic surfactants to regulate the interfacial polymerization process to prepare polyamide reverse osmosis membranes, breaking the trade-off effect between the permselective performance and achieving the improvement of the permselective performance of the membrane. Among them, the polyamide reverse osmosis membrane prepared by using anionic surfactants to regulate interfacial polymerization is easily blocked by pollutants (especially positively charged pollutants) in the water body in practical applications, causing a significant attenuation of flux, requiring frequent cleaning and maintenance, and increasing the cost of membrane use. Compared with anionic surfactants, cationic surfactants can be embedded in the PA layer through electrostatic interactions, thereby improving the charge and hydrophilicity of the PA layer, and are expected to improve the anti-fouling performance of the reverse osmosis membrane. Therefore, it is of great value to develop a surfactant that can be stably embedded in the PA layer for regulating interfacial polymerization to prepare a high salt cutoff, hydrophilic and weakly charged anti-fouling reverse osmosis membrane.

[0004] Based on this, this patent invents a method for preparing a high salt interception and pollution resistant polyamide reverse osmosis membrane by regulating interfacial polymerization with an aromatic cationic surfactant containing two benzene ring structures. The cationic surfactant containing two benzene ring structures can not only improve the cross-linking degree of polyamide during the interfacial polymerization process, but also embed into polyamide more effectively, thereby significantly improving the interception rate of the reverse osmosis membrane and the hydrophilicity of the membrane surface (the water contact angle of the membrane surface is <70°). At the same time, it also greatly improves the surface potential of the reverse osmosis membrane in a neutral water environment and weakens the negative charge of the membrane (at pH = 7, the surface charge of the membrane is greater than -20mV), which has important innovation and practical application value. Summary of the invention

[0005] The invention provides a new method for preparing a high-salt-cutoff and pollution-resistant polyamide reverse osmosis membrane by regulating interfacial polymerization using an aromatic cationic surfactant containing two benzene ring structures.

[0006] To this end, the technical solution of the present invention is as follows:

[0007] 1. A high salt cut-off and pollution-resistant polyamide reverse osmosis membrane, characterized in that:

[0008] (1) The polyamide reverse osmosis membrane comprises a porous ultrafiltration base membrane and a polyamide dense functional layer;

[0009] (2) The effective specific surface area of ​​the polyamide functional layer is greater than 1.2, and the surface charge range at pH = 7 is greater than -20 mV;

[0010] (3) The molecular weight cut-off of the polyamide reverse osmosis membrane is less than 100 Da, and the rejection rate of 2000 ppm NaCl is greater than 99.50%.

[0011] 2. The method for preparing a high salt cut-off and pollution-resistant polyamide reverse osmosis membrane according to claim 1 is characterized in that an aromatic cationic surfactant containing two benzene ring structures is used to regulate the interfacial polymerization of polyamine monomers and polyacyl chloride monomers to form a polyamide reverse osmosis membrane on the surface of a porous ultrafiltration base membrane, characterized in that:

[0012] (1) The porous ultrafiltration base membrane used includes but is not limited to organic ultrafiltration membrane, inorganic ultrafiltration membrane, and metal ultrafiltration membrane with a pore size range of 5nm to 50nm.

[0013] (2) The polyamine monomers used include, but are not limited to, one or more of m-phenylenediamine, p-phenylenediamine, ethylenediamine, N-phenylethylenediamine, 1,3-diaminocyclohexane, and the like.

[0014] (3) The polyacyl chloride monomers used include, but are not limited to, one or more of aromatic polyacyl chlorides, aliphatic polyacyl chlorides, and alicyclic polyacyl chlorides; wherein the aromatic polyacyl chlorides include, but are not limited to, at least one of trimesoyl chloride and biphenyl dicarboxylic acid chloride; the aliphatic polyacyl chlorides include, but are not limited to, at least one of propanedioyl chloride and glutaryl chloride; and the alicyclic polyacyl chlorides include, but are not limited to, at least one of cyclopropanetricarboxylic acid chloride and cyclobutanetetracarboxylic acid chloride.

[0015] 3. The high salt cut-off and pollution-resistant polyamide reverse osmosis membrane according to claims 1 and 2, wherein the chemical structure of the aromatic cationic surfactant containing two benzene ring structures used to regulate interfacial polymerization is characterized in that it is composed of an aromatic cationic group containing two benzene ring structures and an anion, and at least one of R1, R2, and R3 is an alkyl chain with more than eight carbon atoms, and X is an anion group, including but not limited to sulfonate, chloride, bromide, etc.

[0016] Preferably, the aromatic cationic surfactant containing two benzene ring structures is composed of an aromatic cationic group and an anion, and has the following chemical structure:

[0017]

[0018] The aromatic cationic surfactant containing two benzene ring structures can be selected from at least one of, but not limited to, benzethonium chloride, benzethonium chloride, and the like.

[0019] 4. The method for preparing a high salt cut-off and pollution-resistant polyamide reverse osmosis membrane according to claims 1-3, characterized in that the preparation steps include:

[0020] S1, preparing an aqueous solution of 0.1wt.% to 5.0wt.% polyamine monomer and 0.1wt.% to 10.0wt.% aromatic cationic surfactant, immersing one side of the porous ultrafiltration base membrane in the aqueous solution for 0.5min to 5min, and then removing excess aqueous solution on the membrane surface with a rubber roller or an air knife;

[0021] S2, preparing an organic solution of 0.01wt.% to 5.00wt.% polyacid chloride, wherein the organic solvent used includes but is not limited to at least one of n-hexane, isoparaffin, n-nonane, and n-decane; uniformly coating the organic solution of 0.01wt.% to 5.00wt.% polyacid chloride on the surface of the base film coated with the aqueous monomer solution obtained in step S1 for 0.5min to 5min to form a thin layer of composite polyamide film;

[0022] S3, placing the thin layer composite polyamide membrane obtained in step S2 at 40°C to 180°C for thermal crosslinking for 1min to 10min, and finally obtaining a polyamide reverse osmosis membrane.

[0023] The preparation method can directly prepare a high salt cutoff and pollution-resistant polyamide reverse osmosis membrane by one-step interfacial polymerization. The method has the advantages of simple operation, short reaction time, good stability, and industrial preparation advantages. In step S1, the addition of an aromatic cationic surfactant to the aqueous monomer solution can greatly reduce the interfacial tension between the aqueous phase and the oil phase, thereby regulating the rate and concentration of the cross-interface diffusion of the amine / acyl chloride monomer into the oil / aqueous phase, thereby achieving the preparation of a high salt cutoff and pollution-resistant polyamide reverse osmosis membrane.

[0024] Preferably, the preparation method of the aqueous monomer solution in step S1 is: preparing a polyamine monomer aqueous solution with a mass fraction of 0.1wt.% to 5.0wt.%, and then adding 0.1wt.% to 10.0wt.% of an aromatic cationic surfactant to the polyamine monomer aqueous solution.

[0025] Preferably, in step S1, the aqueous monomer solution is coated on the upper surface of the porous ultrafiltration base membrane, and after waiting for 0.5 to 5 minutes, the excess aqueous monomer solution on the membrane is removed by a rubber roller or an air knife, and then step S2 can be performed.

[0026] Preferably, in step S2, the mass fraction of the polyacyl chloride in the organic mixed solution is 0.01 wt.% to 5.00 wt.%; the organic solvent used to prepare the organic mixed solution includes but is not limited to n-hexane, isoparaffin, and n-nonane.

[0027] Preferably, in step S2, after the surface of the aqueous solution coating layer is immersed in an organic mixed solution prepared by polyacyl chlorides for 0.5 min to 15 min, the membrane is taken out and left to stand for 1 min to wait for the organic solvent to evaporate, and then step S3 can be performed.

[0028] A high salt-cutting and pollution-resistant polyamide reverse osmosis membrane can be used in seawater desalination, industrial wastewater treatment, electronics and semiconductor manufacturing, biomedicine, chemical production and other fields.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) Compared with the reverse osmosis membranes reported in other literature and patents, the high salt cutoff and pollution-resistant polyamide reverse osmosis membrane developed in this application has the advantages of high salt cutoff and good pollution resistance. When used for actual water treatment, it can greatly reduce the cleaning cycle and operation and maintenance costs, extend the service life of the membrane, and reduce the cost of water treatment.

[0031] (2) The preparation method of the high salt cut-off and pollution-resistant polyamide reverse osmosis membrane applied for in this patent is a simple one-step interfacial polymerization method. Compared with the traditional graft coating modification method, this method not only shortens the preparation time and reduces the production cost, but also improves the comprehensive performance of the polyamide separation membrane, and has good industrial production application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A comparison diagram of the membrane surface Zeta potential curves of the polyamide reverse osmosis membrane prepared by the polyamide membrane of the present invention and the traditional polyamide membrane;

[0033] Figure 2 A comparison diagram of the water contact angle of the membrane surface of the polyamide reverse osmosis membrane prepared by the polyamide membrane of the present invention and the traditional polyamide membrane and the water contact angle of the membrane surface of the traditional polyamide membrane;

[0034] Figure 3 , Figure 4 , Figure 5 and Figure 6A comparison chart of the anti-fouling performance of the high-flux and high-retention anti-fouling polyamide composite membrane prepared by the polyamide membrane of the present invention and the traditional polyamide membrane;

[0035] Figure 7 and Figure 8 This is a comparison chart of the polyamide membrane of the present invention and the traditional polyamide membrane using X-ray photoelectron spectrometer (XPS) to detect the elements on the membrane surface, separate the N element peaks, and calculate the surfactant embedding amount. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the following embodiments are by no means intended to limit the present invention in any way.

[0037] Example 1

[0038] A method for preparing a high salt cut-off and pollution-resistant polyamide reverse osmosis membrane, which is prepared by the following steps:

[0039] S1, dissolving m-phenylenediamine in water to prepare a 2.0wt.% m-phenylenediamine aqueous solution; then, adding 1.0wt.% benzethonium chloride to the m-phenylenediamine aqueous solution, stirring and mixing evenly to obtain an aqueous monomer solution; immersing one side of a polysulfone ultrafiltration membrane in the aqueous monomer solution for 2 minutes, and removing excess aqueous monomer solution on the surface of the ultrafiltration base membrane with a rubber roller or an air knife;

[0040] S2, dissolving trimesoyl chloride in n-hexane to prepare a 0.1wt.% trimesoyl chloride organic solution, stirring and mixing to obtain an oil phase monomer solution; uniformly coating the oil phase monomer solution on the surface of the base film coated with the aqueous phase monomer solution obtained in step S1 for 1 minute, and placing it in the air for 2 minutes to allow the n-hexane to completely volatilize, thereby forming a thin layer of composite polyamide film;

[0041] S3, placing the thin layer composite polyamide membrane obtained in step S2 in a forced air drying oven, and thermally crosslinking at 60° C. for 5 minutes, to finally obtain a polyamide reverse osmosis membrane.

[0042] Example 2

[0043] A method for preparing a high salt-cutting and pollution-resistant polyamide reverse osmosis membrane is disclosed, which differs from Example 1 in that 1.0 wt. % of benzethonium chloride is replaced with 1.0 wt. % of benzethonium chloride.

[0044] Example 3

[0045] A method for preparing a high salt-cutting and pollution-resistant polyamide reverse osmosis membrane is disclosed, which is different from Example 1 in that 1.0 wt. % of benzethonium chloride is replaced with 2.0 wt. % of benzethonium chloride.

[0046] Example 4

[0047] A method for preparing a high salt cutoff and pollution resistant polyamide reverse osmosis membrane is different from Example 1 in that the thermal crosslinking condition is changed to thermal crosslinking at 60° C. for 10 minutes.

[0048] Example 5

[0049] A method for preparing a high salt-cutting and pollution-resistant polyamide reverse osmosis membrane is different from Example 1 in that the concentration of benzethonium chloride is increased to 10 wt.%.

[0050] Example 6

[0051] A method for preparing a high salt cutoff and pollution resistant polyamide reverse osmosis membrane is different from Example 1 in that the solvent n-hexane in the organic solution for preparing trimesoyl chloride is replaced by isomeric alkanes.

[0052] Example 7

[0053] A method for preparing a high salt-cutting and pollution-resistant polyamide reverse osmosis membrane is different from Example 1 in that the polysulfone membrane used as the porous ultrafiltration base membrane is replaced by a polyacrylonitrile membrane.

[0054] Example 8

[0055] A method for preparing a high salt cutoff and pollution resistant polyamide reverse osmosis membrane is different from Example 1 in that the polysulfone membrane used as the porous ultrafiltration base membrane is replaced by a polyethersulfone membrane.

[0056] Example 9

[0057] A method for preparing a high salt-cutting and pollution-resistant polyamide reverse osmosis membrane, which differs from Example 1 in that: the 2.0wt.% m-phenylenediamine aqueous solution prepared in step S1 is replaced by a 5.0wt.% m-phenylenediamine aqueous solution; and the n-hexane solution containing 0.1wt.% trimesoyl chloride is replaced by a n-hexane solution containing 5.0wt.% trimesoyl chloride.

[0058] Example 10

[0059] A method for preparing a high salt-cutting and pollution-resistant polyamide reverse osmosis membrane, which differs from Comparative Example 1 in that: the 2.0wt.% aqueous solution of m-phenylenediamine prepared in step S1 is replaced by a 2.0wt.% aqueous solution of p-phenylenediamine; and the n-hexane solution containing 0.1wt.% of trimesoyl chloride is replaced by a n-hexane solution containing 1.0wt.% of biphenyl dicarboxylic acid chloride.

[0060] Comparative Example 1

[0061] A polyamide reverse osmosis membrane prepared without surfactant regulation is prepared by the following steps:

[0062] S1, dissolving m-phenylenediamine in water to prepare a 2.0 wt.% m-phenylenediamine aqueous solution; immersing one side of a polysulfone ultrafiltration membrane in the m-phenylenediamine aqueous solution for 2 minutes, and removing excess m-phenylenediamine aqueous solution on the surface of the ultrafiltration base membrane using a rubber roller or an air knife;

[0063] S2, dissolving trimesoyl chloride in n-hexane to prepare a 0.1wt.% trimesoyl chloride organic solution, stirring and mixing to obtain an oil phase monomer solution; uniformly coating the oil phase monomer solution on the surface of the base film coated with the aqueous phase monomer solution obtained in step S1 for 1 minute, and placing it in the air for 2 minutes to allow the n-hexane to completely volatilize, thereby forming a thin layer of composite polyamide film;

[0064] S3: placing the thin layer composite polyamide membrane obtained in step S2 in a forced air drying oven at 60° C. for thermal crosslinking for 5 minutes, and finally obtaining a polyamide reverse osmosis membrane.

[0065] Comparative Example 2

[0066] A polyamide reverse osmosis membrane prepared by regulating a cationic surfactant containing only one benzene ring structure is prepared by the following steps:

[0067] S1, dissolving m-phenylenediamine in water to prepare a 2.0 wt. % m-phenylenediamine aqueous solution; then, adding 1.0 wt. % of a cationic surfactant benzalkonium chloride (BAC) to the m-phenylenediamine aqueous solution, stirring and mixing, to obtain an aqueous monomer solution; immersing one side of a polysulfone ultrafiltration membrane in the aqueous monomer solution for 2 minutes, and removing excess aqueous monomer solution on the surface of the ultrafiltration base membrane using a rubber roller or an air knife;

[0068] S2, dissolving trimesoyl chloride in n-hexane to prepare a 0.1wt.% trimesoyl chloride organic solution, stirring and mixing to obtain an oil phase monomer solution; uniformly coating the oil phase monomer solution on the surface of the base film coated with the aqueous phase monomer solution obtained in step S1 for 1 minute, and placing it in the air for 2 minutes to allow the n-hexane to completely volatilize, thereby forming a thin layer of composite polyamide film;

[0069] S3, placing the thin layer of composite polyamide membrane obtained by the treatment in step S2 in a forced air dryer at 180° C. for 2 minutes for thermal crosslinking, and finally obtaining a polyamide reverse osmosis membrane.

[0070] Performance Test:

[0071] (I) Membrane separation performance test:

[0072] The membrane separation performance was tested using a cross-flow test device; the separation performance test conditions were as follows: after pre-pressurization for 1 hour at 20 bar and 25°C, the prepared polyamide reverse osmosis membrane was used as a test membrane under conditions of 15 bar and 25°C to test its retention rate and permeation flux of 2000 ppm NaCl solution, with the flux unit being LMH / bar (liter / square meter / hour / bar).

[0073] The permeation flux was calculated by the following formula (1):

[0074]

[0075] In the formula, J w is the membrane permeation flux (LMH / bar), M is the mass of the permeate passing through the membrane (kg), and ρ is the density of the permeate (kg·m -3 ), E is the effective permeation area of ​​the membrane sample (m 2 ), t is the test time (h), and P is the test pressure (bar).

[0076] The NaCl concentration of the feed solution and the permeate was measured using a conductivity meter; the NaCl retention rate was calculated using formula (2):

[0077]

[0078] Where R is the salt retention rate of the membrane sample (%), C p is the NaCl concentration of the permeate (mg / L), C f is the NaCl concentration of the feed solution (mg / L).

[0079] At least three parallel samples were tested for each membrane sample, and the average value and error range of the test results were calculated.

[0080] The specific test results are shown in Table 1 below.

[0081] Table 1: Permeation selectivity performance of polyamide reverse osmosis membrane

[0082]

[0083] From the test results in Table 1, we can see that:

[0084] (1) Compared with the polyamide reverse osmosis membrane prepared in comparative example 1 without adding an aromatic cationic surfactant, the polyamide reverse osmosis membranes prepared in Examples 1 to 10 have effectively improved retention rates while maintaining the water permeability coefficient. Specifically, compared with the retention rate of 98.23% in comparative example 1, the retention rates of Examples 1 to 10 are all improved to more than 99.50%.

[0085] (2) Compared with the cationic surfactant containing only one benzene ring structure in Comparative Example 2, the polyamide reverse osmosis membrane obtained by regulating the use of aromatic cationic surfactants in the present application has a higher retention rate and a weaker electronegativity on the membrane surface. Examples 1 to 10 have better retention performance than Control Examples 1 to 2, which further illustrates that the aromatic cationic surfactant used in the present invention has a better effect on improving the NaCl retention performance of the RO membrane.

[0086] Furthermore, the selective permeability of the high salt cutoff polyamide reverse osmosis membrane prepared by the method of this patent is higher than the selective permeability of the polyamide reverse osmosis membrane prepared by introducing other non-aromatic cationic surfactants reported so far. The performance comparison with the latest literature reports is shown in Table 2 below.

[0087] Table 2: Comparison of permeation selectivity of polyamide reverse osmosis membranes

[0088] Use of other surfactant types Permeability coefficient NaCl retention rate Ref Tween80 0.72 99.60 [1] Sodium dodecyl trimethyl sulfate (SDS) 1.80 98.20 [2] Dodecyltrimethylammonium bromide (DTAB) 3.84 98.50 [3] Benzethonium chloride (BEC) 2.94 99.50 Self-Test

[0089] (II) Membrane surface electrical properties

[0090] The solid surface Zeta potential analyzer was used to characterize the potential change on the surface of the polyamide reverse osmosis membrane. According to the test, the polyamide reverse osmosis membrane prepared in Examples 1 to 10 maintained a surface Zeta potential change between -20mV and 25mV during the pH change from 10 to 3, showing good pH stability.

[0091] like Figure 3 The graph shows the comparison of the Zeta potential curves of the polyamide reverse osmosis membranes prepared in Example 1 and Comparative Example 2 of the present invention; it can be clearly seen from the graph that the Zeta potential of the polyamide reverse osmosis membrane of Example 1 changes from -25.28mV to 20.58mV during the pH change from 10 to 3, while the Zeta potential of the conventional polyamide membrane prepared in Comparative Example 1 changes from -30.98mV to 16.52mV during the pH change from 10 to 3. At pH = 7, the Zeta potential of the polyamide reverse osmosis membrane of Example 1 is -15.36mV, while the Zeta potential of the conventional polyamide membrane is -31.23mV. In summary, the surface negative charge of the polyamide reverse osmosis membrane prepared by the aromatic cationic surfactant with two benzene ring structures is reduced, and the positive charge is significantly improved.

[0092] (III) Test on the embedded amount of cationic surfactants containing benzene ring structure

[0093] An X-ray photoelectron spectrometer is used to characterize the embedding of surfactants containing benzene ring structures in the polyamide layer, and the N element of Example 1, Example 2 and Comparative Example 1 is subjected to XPS peak separation. The third peak N3 of N1s appears at 402.2 eV in both Example 1 and Comparative Example 2. This peak is the N element peak in the quaternary ammonium group of benzethonium chloride and benzalkonium chloride, which can confirm the successful incorporation of benzethonium chloride and benzalkonium chloride. The peak area ratios of N3 in Example 1 and Comparative Example 2 are 6.68% and 3.35%, respectively. The embedding amount of benzethonium chloride in PA is higher than that of benzalkonium chloride, because benzethonium chloride contains more benzene ring structures, which make the benzethonium chloride and PA produce stronger π-π conjugation and cation-π interaction, etc., so that more benzethonium chloride is successfully embedded in the PA layer. In addition, the degree of crosslinking of the membrane is calculated by the XPS results. With the addition of benzethonium chloride and benzalkonium chloride, the cross-linking unit ratio (N2 / N1) increased from 7.08 to 9.56 and 10.62, respectively, so the formed polyamide network became denser, ultimately improving the retention performance.

[0094] (IV) Test of membrane anti-pollution performance:

[0095] The membrane anti-fouling performance was evaluated using positive charge model pollutant dodecyl trimethyl ammonium bromide (DTAB), negative charge model pollutant sodium dodecyl sulfate (SDS), electrically neutral model organic pollutant Tween 20, and inorganic model pollutant CaCl2+SA. These are typical representative examples of pollutants of different properties in the water system. Specifically, during the pollution test, DTAB, SDS, Tween20 and CaCl2+SA ​​were added to the 2000ppm NaCl solution respectively, and the concentrations of the above four pollutants were all 200ppm.

[0096] The normalized flux attenuation rate (%) and recovery rate of Examples 1-5 prepared by the interfacial polymerization process regulated by an aromatic cationic surfactant and the unmodified comparative example 1 were evaluated.

[0097] The specific steps for determining the flux decay rate are as follows: 1) Under the conditions of 15 bar and a cross-flow velocity of 14 cm / s, the RO system is pre-pressurized for 60 minutes using a feed aqueous solution containing 2000 ppm of NaCl to determine the baseline permeate flux and salt retention rate; 2) 200 ppm of the aforementioned model pollutant is added to the aforementioned supply aqueous solution, and the RO system is operated under the same conditions as step 1) until the volume of the permeate is 200 mL; 3) The polyamide composite reverse osmosis membrane is cleaned more than 3 times with deionized water at a water circulation flow rate of 3 L / min, with each cycle lasting 10 minutes; 4) The permeate flux and salt retention rate are measured again using a feed aqueous solution containing 2000 mg / L of NaCl.

[0098] The calculation formula of Flux attenuation rate is as follows:

[0099] Flux reduction rate (%) = [1-(permeation flux of step 2) / permeation flux of step 1)] × 100%;

[0100] Flux recovery rate (%) = (permeation flux in step 4) / permeation flux in step 1)) × 100%.

[0101] The specific test results are shown in Table 3 below.

[0102] Table 3: Anti-fouling performance of polyamide reverse osmosis membrane

[0103]

[0104] From the test results in Table 3, it can be seen that the flux attenuation rates of the four model pollutants in Examples 1-4 are lower than those in Comparative Example 1, and the flux recovery rates are higher than those in Comparative Example 1. It can be seen that the polyamide reverse osmosis membrane prepared by using an aromatic cationic surfactant with two benzene ring structures exhibits excellent pollution resistance to common pollutants in water bodies.

[0105] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high salt cut-off and pollution-resistant polyamide reverse osmosis membrane, characterized in that: (1) The polyamide reverse osmosis membrane comprises a porous ultrafiltration base membrane and a polyamide dense functional layer; (2) The effective specific surface area of ​​the polyamide functional layer is greater than 1.2, and the surface charge range at pH = 7 is greater than -20 mV; (3) The molecular weight cut-off of the polyamide reverse osmosis membrane is less than 100 Da, and the rejection rate of 2000 ppm NaCl is greater than 99.50%.

2. The method for preparing a high salt cut-off pollution-resistant polyamide reverse osmosis membrane according to claim 1, characterized in that: An aromatic cationic surfactant containing two benzene ring structures is used to regulate the interfacial polymerization of polyamine monomers and polyacyl chloride monomers to form a polyamide reverse osmosis membrane on the surface of a porous ultrafiltration base membrane, characterized in that: (1) The porous ultrafiltration base membrane used includes but is not limited to organic ultrafiltration membrane, inorganic ultrafiltration membrane, and metal ultrafiltration membrane with a pore size range of 5nm to 50nm. (2) The polyamine monomers used include, but are not limited to, one or more of m-phenylenediamine, p-phenylenediamine, ethylenediamine, N-phenylethylenediamine, 1,3-diaminocyclohexane, and the like. (3) The polyacyl chloride monomers used include, but are not limited to, one or more of aromatic polyacyl chlorides, aliphatic polyacyl chlorides, and alicyclic polyacyl chlorides; wherein the aromatic polyacyl chlorides include, but are not limited to, at least one of trimesoyl chloride and biphenyl dicarboxylic acid chloride; the aliphatic polyacyl chlorides include, but are not limited to, at least one of propanedioyl chloride and glutaryl chloride; and the alicyclic polyacyl chlorides include, but are not limited to, at least one of cyclopropanetricarboxylic acid chloride and cyclobutanetetracarboxylic acid chloride.

3. A method for preparing a high salt cut-off and pollution-resistant polyamide reverse osmosis membrane according to claim 1 and a high salt cut-off and pollution-resistant polyamide reverse osmosis membrane according to claim 2, wherein the chemical structure of the aromatic cationic surfactant containing two benzene ring structures used to regulate interfacial polymerization is characterized in that it is composed of an aromatic cationic group containing two benzene ring structures and an anion, and at least one of R1, R2, and R3 is an alkyl chain with more than eight carbon atoms, and X is an anion group, including but not limited to sulfonate, chloride, bromide, etc. Preferably, the aromatic cationic surfactant containing two benzene ring structures is composed of an aromatic cationic group and an anion, and has the following chemical structure: The aromatic cationic surfactant containing two benzene ring structures can be selected from at least one of, but not limited to, benzethonium chloride, benzethonium chloride, and the like.

4. A high salt cut-off and pollution-resistant polyamide reverse osmosis membrane and a preparation method thereof according to claims 1-3, characterized in that: The preparation steps include: S1, preparing an aqueous solution of 0.1wt.% to 5.0wt.% polyamine monomer and 0.1wt.% to 10.0wt.% aromatic cationic surfactant, immersing one side of the porous ultrafiltration base membrane in the aqueous solution for 0.5min to 5min, and then removing excess aqueous solution on the membrane surface with a rubber roller or an air knife; S2, preparing an organic solution of 0.01wt.% to 5.00wt.% polyacid chloride, wherein the organic solvent used includes but is not limited to at least one of n-hexane, isoparaffin, n-nonane, and n-decane; uniformly coating the organic solution of 0.01wt.% to 5.00wt.% polyacid chloride on the surface of the base film coated with the aqueous monomer solution obtained in step S1 for 0.5min to 5min to form a thin layer of composite polyamide film; S3, placing the thin layer composite polyamide membrane obtained in step S2 at 40°C to 180°C for thermal crosslinking for 1min to 10min, and finally obtaining a polyamide reverse osmosis membrane.

5. The high salt cut-off and pollution-resistant polyamide reverse osmosis membrane and the preparation method thereof according to claims 1-4 can be applied to seawater desalination, brackish water desalination, industrial wastewater treatment, water purification and purification, biomedicine, chemical production and other fields.

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