Method for preparing polyamide polymer, polyamide nanoparticle, method for preparing reverse osmosis membrane, and reverse osmosis membrane prepared thereby

Abstract

The present disclosure relates to a method for preparing a polyamide polymer, a polyamide nanoparticle, a method for preparing a reverse osmosis membrane, and a reverse osmosis membrane prepared thereby. The method for preparing a polyamide polymer comprises polymerizing equimolar proportions of a polyamine monomer and a polyacyl chloride monomer. The polyamide nanoparticles are obtained by grinding a polyamide polymer obtained thereby. The method for preparing a reverse osmosis membrane comprises: curing a membrane casting solution on a supporting material to form a base membrane, wherein the membrane casting solution comprises a polymer, a polyhydroxy compound, and a solvent; and bringing the base membrane into contact with an aqueous phase solution and an oil phase solution in sequence, wherein the aqueous phase solution comprises polyamide nanoparticles and a polyamine monomer, and the oil phase solution comprises a polyacyl chloride monomer. The method for preparing a reverse osmosis membrane according to the present disclosure has a simple and easy technological process, facilitating commercial promotion and application. The prepared reverse osmosis membrane has both a high flux and a high desalination rate and solves the problems of poor compatibility of a nanoparticle intermediate layer with a base membrane and a functional layer and poor long-term stability.

Description

Preparation method of polyamide polymer and polyamide nanoparticles, preparation method of reverse osmosis membrane and reverse osmosis membrane prepared therefrom

[0001] Citation of Related Applications

[0002] This disclosure claims priority to invention patent application number 202311531742.2, filed in China on November 16, 2023, entitled “Method for preparing polyamide polymers and polyamide nanoparticles, method for preparing reverse osmosis membranes and reverse osmosis membranes prepared thereby”, and the entire contents of the patent application are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the technical field of water treatment membranes, more specifically to the technical field of reverse osmosis membranes, and in particular to a method for preparing a reverse osmosis membrane with high flux and high desalination rate and a reverse osmosis membrane prepared thereby. Background Art

[0004] Reverse osmosis (RO) technology, one of the most important and effective water purification technologies currently available, boasts high separation efficiency and low cost. It has been widely adopted in seawater desalination, brackish water desalination, reclaimed water reuse, and household water purification. The performance of RO membrane materials, the core of this technology, directly impacts the economic performance of water treatment technology. High flux and low energy consumption have always been key priorities in RO technology. With the continuous development of the market, low-pressure RO is poised to become a hot topic in RO membrane technology development.

[0005] Commercial reverse osmosis membranes are primarily polyamide composite membranes, consisting primarily of a non-woven fabric layer, a polysulfone support layer, and a polyamide functional layer. The flux of a reverse osmosis membrane is primarily determined by the performance of the functional layer, and research into the modification of the functional layer is currently the primary focus for improving the flux of reverse osmosis membranes. For example, by modifying the base membrane to prepare a small-pore, high-porosity ultrafiltration support layer, a high-flux composite reverse osmosis membrane can be indirectly obtained. By introducing small molecule additives into the aqueous or oil phase, the properties of the eutectic zone during interfacial polymerization can be altered to obtain high-flux reverse osmosis membranes with enhanced performance. By introducing a metal nano-intermediate layer to prepare an ultra-thin desalination layer, the lower water transport resistance of the ultra-thin desalination layer can be utilized to obtain high-flux reverse osmosis membranes.

[0006] Patent document CN112023731A discloses a method for preparing a high-flux, low-pressure reverse osmosis membrane. By constructing a layer of nano-silicon oxide particles as an intermediate layer on the surface of the base membrane, the nanoparticles' high hydrophilicity and porosity are leveraged to form a water permeation channel, enabling a high-flux reverse osmosis process under low-pressure drive conditions. This method, which effectively increases the porosity of the functional layer by introducing an inorganic nanoparticle intermediate layer between the polysulfone base membrane and the functional layer, suffers from poor compatibility with the polysulfone base membrane and the functional layer, as well as poor long-term stability.

[0007] Summary of the Invention

[0008] Problems to be solved by the invention

[0009] The purpose of the present disclosure is to solve the above-mentioned problems existing in the prior art and to provide a method for preparing a reverse osmosis membrane and a reverse osmosis membrane prepared thereby. The method is simple in process and the reverse osmosis membrane prepared thereby has both high flux and high desalination rate.

[0010] Solutions for solving problems

[0011] In order to achieve the above objectives, the inventors of the present invention have discovered through in-depth research that an ultrafiltration support layer with a surface rich in hydroxyl hydrophilic groups can be prepared by introducing polyhydroxy hydrophilic compounds into the casting liquid. Then, the ultrafiltration support layer is sequentially contacted with an aqueous solution and an oily solution containing polyamide nanoparticles to form a functional layer through an interfacial polymerization reaction, which enables the polyamide nanoparticles to be embedded in the functional layer, thereby solving the problems of poor compatibility and long-term stability of the nanoparticle intermediate layer with the base membrane and the functional layer in the prior art.

[0012] The ultrafiltration support layer, which is rich in hydroxyl hydrophilic groups on the surface, utilizes its more hydrogen bonding sites to increase the adsorption capacity of polyamide nanoparticles. Polyamide nanoparticles have a microporous structure and a large number of hydrophilic carboxyl groups, which improve the porosity and hydrophilicity of the functional layer and expand the number of water channels in the functional layer. At the same time, the good hydrophilicity of the nanoparticles themselves allows them to be evenly dispersed in the aqueous solution, which is conducive to the preparation of reverse osmosis membranes with excellent performance, including high flux and high desalination rate.

[0013] One aspect of the present disclosure relates to a method for preparing a polyamide polymer, wherein polyamine monomers and polyacyl chloride monomers are polymerized in an equimolar ratio.

[0014] The preparation method of the polyamide polymer described in the present disclosure, wherein the polyamine monomer is at least one of p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene and piperazine, and the polyacyl chloride monomer is at least one of phthaloyl chloride, biphenyl dichloride, oxalyl chloride, terephthaloyl chloride, trimesoyl chloride and isophthaloyl chloride.

[0015] Another aspect of the present disclosure relates to polyamide nanoparticles obtained by grinding a polyamide polymer prepared according to the method described in the present disclosure, wherein the polyamide nanoparticles have a particle size of 50-500 nm.

[0016] Another aspect of the present disclosure relates to a method for preparing a reverse osmosis membrane, comprising the following steps:

[0017] preparing a casting solution, and solidifying the casting solution on a supporting material to form a base film, wherein the casting solution comprises a polymer, a polyhydroxy compound, and a solvent;

[0018] The base film is sequentially immersed in an aqueous solution and an oily solution, wherein the aqueous solution contains polyamide nanoparticles prepared according to the method of the present disclosure and polyamine monomers, and the oily solution contains polyacyl chloride monomers;

[0019] After post-treatment and drying, a reverse osmosis membrane is obtained.

[0020] The preparation method disclosed herein, wherein the polymer is at least one of bisphenol A type polysulfone, polyarylsulfone, polyethersulfone, sulfonated polyethersulfone, polyimide, polyvinylidene fluoride and polyacrylonitrile; preferably, based on the total mass of the casting solution, the concentration of the polymer is 10-22%; preferably, the solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpyrrolidine and dimethyl sulfoxide; preferably, the supporting material is a non-woven fabric.

[0021] The preparation method disclosed herein, wherein the polyhydroxy compound is at least one of a cyclodextrin compound, a monosaccharide, a disaccharide, tannic acid and a polyol; preferably, based on the total mass of the casting solution, the concentration of the polyhydroxy compound is 0.01-3%; preferably, the cyclodextrin compound is at least one of α-cyclodextrin, β-cyclodextrin and hydroxypropyl-β-cyclodextrin, the monosaccharide is at least one of glucose, mannose and fructose, the disaccharide is at least one of sucrose, lactose and trehalose, and the polyol is at least one of ethylene glycol and glycerol.

[0022] In the preparation method disclosed herein, the concentration of the polyamide nanoparticles is 100-1000 ppm based on the total mass of the aqueous solution.

[0023] The preparation method disclosed herein, wherein the polyamine monomer is at least one of p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene and piperazine; preferably, based on the total mass of the aqueous solution, the concentration of the polyamine monomer is 1-5%; preferably, the aqueous solution further contains an acid binding agent.

[0024] The preparation method disclosed herein, wherein the polyacyl chloride monomer is at least one of phthaloyl chloride, biphenyl dichloride, oxalyl chloride, terephthaloyl chloride, trimesoyl chloride and isophthaloyl chloride; preferably, based on the total mass of the oil phase solution, the concentration of the polyacyl chloride monomer is 1-5%; preferably, the oil phase solution further contains an organic solvent; preferably, the organic solvent is at least one of n-hexane, cyclohexane, ethylcyclohexane, n-heptane, tetrahydrofuran, isoparaffins, chloroform, toluene and m-xylene.

[0025] Yet another aspect of the present disclosure relates to a reverse osmosis membrane prepared according to the preparation method of the present disclosure.

[0026] Effects of the Invention

[0027] The disclosed preparation method is simple and easy to implement, facilitating commercial application. The reverse osmosis membrane prepared using the disclosed method exhibits both high flux and high salt rejection, while also addressing the issues of poor compatibility and long-term stability of the nanoparticle intermediate layer with the base membrane and functional layer. DETAILED DESCRIPTION

[0028] Various exemplary embodiments, features, and aspects of the present disclosure are described in detail below. The word "exemplary" is used herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior or preferred over other embodiments.

[0029] In addition, numerous specific details are provided in the following detailed description to better illustrate the present disclosure. Those skilled in the art will appreciate that the present disclosure can be practiced without certain specific details. In other instances, methods, means, equipment, and steps well known to those skilled in the art are not described in detail in order to highlight the main points of the present disclosure.

[0030] Unless otherwise stated, the units used in this specification are international standard units, and the numerical values ​​and numerical ranges appearing in this disclosure should be understood to include the inevitable systematic errors in industrial production.

[0031] In this specification, the use of "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process.

[0032] In this specification, references to "some specific / preferred embodiments," "other specific / preferred embodiments," "embodiments," etc., mean that the specific elements (e.g., features, structures, properties, and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0033] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints A and B.

[0034] In this specification, when "normal temperature" or "room temperature" is used, the temperature may be 15-25°C.

[0035] The technical concept of the present invention is to prepare an ultrafiltration support layer with a surface rich in hydroxyl hydrophilic groups by introducing polyhydroxyl hydrophilic compounds into the casting liquid, and then sequentially contact the ultrafiltration support layer with an aqueous solution and an oily solution containing polyamide nanoparticles to form a functional layer through interfacial polymerization reaction, so that the polyamide nanoparticles can be embedded in the functional layer, thereby solving the problems of poor compatibility and long-term stability of the nanoparticle intermediate layer with the base membrane and the functional layer in the prior art.

[0036] The ultrafiltration support layer, which is rich in hydroxyl hydrophilic groups on the surface, utilizes its more hydrogen bonding sites to increase the adsorption capacity of polyamide nanoparticles. Polyamide nanoparticles have a microporous structure and a large number of hydrophilic carboxyl groups, which improve the porosity and hydrophilicity of the functional layer and expand the number of water channels in the functional layer. At the same time, the good hydrophilicity of the nanoparticles themselves allows them to be evenly dispersed in the aqueous solution, which is conducive to the preparation of reverse osmosis membranes with excellent performance, including high flux and high desalination rate.

[0037] The present disclosure provides a method for preparing a polyamide polymer, wherein polyamine monomers and polyacyl chloride monomers are polymerized in an equimolar ratio.

[0038] Preferably, the polyamine monomer is at least one of p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene and piperazine, and the polyacyl chloride monomer is at least one of phthaloyl chloride, biphenyl dichloride, oxalyl chloride, terephthaloyl chloride, trimesoyl chloride and isophthaloyl chloride.

[0039] As a non-limiting example, the method for preparing the polyamide polymer includes:

[0040] Dissolve a polyamine monomer and a polyacyl chloride monomer at a molar ratio of 1:1 in 50-100 ml of an organic solvent, add 1-10 ml of pyridine, and reflux under nitrogen for 1-30 minutes to form a precipitate. Wash the precipitate with acid, pure water, and an organic solvent, respectively, and finally dry it in an 80°C oven for 1-4 hours to obtain a polyamide polymer.

[0041] Preferably, the organic solvent is one or more of n-hexane, cyclohexane, ethylcyclohexane, n-heptane, tetrahydrofuran, isoparaffin, chloroform, toluene and m-xylene. The acid is one or more of hydrochloric acid, citric acid, malic acid and oxalic acid.

[0042] Finally, the polyamide polymer was ground into nanoparticles with a particle size of 50-500 nm using a sand mill.

[0043] The present disclosure provides polyamide nanoparticles obtained by grinding a polyamide polymer prepared by the method described in the present disclosure, wherein the polyamide nanoparticles have a particle size of 50-500 nm.

[0044] Preferably, the particle size of the polyamide nanoparticles is 50-450 nm, 50-400 nm, 50-350 nm, 50-300 nm, 50-250 nm, or 50-200 nm.

[0045] There is no particular limitation on the grinding equipment, and commonly used grinding equipment can be used, preferably a sand mill.

[0046] The present disclosure provides a method for preparing a reverse osmosis membrane, which comprises the following steps:

[0047] preparing a casting solution, and solidifying the casting solution on a supporting material to form a base film, wherein the casting solution comprises a polymer, a polyhydroxy compound, and a solvent;

[0048] The base film is sequentially immersed in an aqueous solution and an oily solution, wherein the aqueous solution contains polyamide nanoparticles prepared according to the method of the present disclosure and polyamine monomers, and the oily solution contains polyacyl chloride monomers;

[0049] After post-treatment and drying, a reverse osmosis membrane is obtained.

[0050] Preferably, the polymer is at least one of bisphenol A type polysulfone, polyarylsulfone, polyethersulfone, sulfonated polyethersulfone, polyimide, polyvinylidene fluoride and polyacrylonitrile.

[0051] Preferably, the concentration of the polymer is 10-22% based on the total mass of the casting solution.

[0052] There is no particular limitation on the solvent in the casting solution as long as it can fully dissolve the polymer. Preferably, the solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpyrrolidine and dimethyl sulfoxide.

[0053] There is no particular limitation on the supporting material. Preferably, the supporting material is a non-woven fabric, more preferably, polypropylene (PP) non-woven fabric, polyester (PET) non-woven fabric, acrylic (PAN) non-woven fabric, and polyvinyl chloride (PVC) non-woven fabric.

[0054] Preferably, the polyhydroxy compound is at least one of cyclodextrin compounds, monosaccharides, disaccharides, tannic acid and polyols.

[0055] Preferably, based on the total mass of the casting solution, the concentration of the polyol is 0.01-3%, more preferably 0.01-2.5%, 0.01-2.0%, 0.01-1.5%, or 0.01-1.0%.

[0056] Preferably, the cyclodextrin compound is at least one of α-cyclodextrin, β-cyclodextrin and hydroxypropyl-β-cyclodextrin, the monosaccharide is at least one of glucose, mannose and fructose, the disaccharide is at least one of sucrose, lactose and trehalose, and the polyol is at least one of ethylene glycol and glycerol.

[0057] The method for coating the casting solution on the nonwoven fabric is not particularly limited, and any coating method commonly used in the art may be used, such as casting, dip coating, blade coating, and spin coating, with blade coating being more preferred. After coating the nonwoven fabric, the nonwoven fabric is then immersed in a coagulation bath to solidify the casting solution into a film.

[0058] In the present disclosure, the method of forming the base film is not particularly limited, and the base film is preferably formed using a liquid-solid phase conversion method.

[0059] Preferably, based on the total mass of the aqueous solution, the concentration of the polyamide nanoparticles is 100-1000 ppm, more preferably 100-900 ppm, even more preferably 100-800 ppm, and even more preferably 100-700 ppm.

[0060] Preferably, the polyamine monomer is at least one of p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene and piperazine. More preferably, based on the total mass of the aqueous solution, the concentration of the polyamine monomer is 1-5%.

[0061] Preferably, the aqueous solution further comprises an acid binding agent, which adjusts the pH of the solution to a range of 9 to 12, thereby facilitating the interfacial polymerization reaction. More preferably, the acid binding agent is one or more of sodium hydroxide, potassium hydroxide, and triethylamine camphorsulfonate, and the concentration of the acid binding agent is 0.03-3% based on the total mass of the aqueous solution.

[0062] The contact time and temperature between the base film and the aqueous solution are not particularly limited, but are preferably kept in contact for 5 to 60 seconds within a temperature range of 20 to 30°C.

[0063] Preferably, the polyacyl chloride monomer is at least one of phthaloyl chloride, biphenyl dichloride, oxalyl chloride, terephthaloyl chloride, trimesoyl chloride and isophthaloyl chloride; more preferably, based on the total mass of the oil phase solution, the concentration of the polyacyl chloride monomer is 1-5%.

[0064] Preferably, the oil phase solution further comprises an organic solvent; preferably, the organic solvent is at least one of n-hexane, cyclohexane, ethylcyclohexane, n-heptane, tetrahydrofuran, isoparaffin, chloroform, toluene and m-xylene.

[0065] The contact time and temperature between the base film and the organic phase solution are not particularly limited, but are preferably kept in contact at a temperature within the range of 25 to 30° C. for 5 to 60 seconds.

[0066] Preferably, the post-treatment includes cleaning with an acid-containing aqueous solution, cleaning with pure water, and pore-preserving treatment.

[0067] More preferably, the acid comprises one or more of citric acid, malic acid, sodium bisulfate, hydrochloric acid, sulfurous acid and hypochlorous acid, and the concentration of the acid is 0.5-20% based on the total mass of the aqueous solution containing the acid.

[0068] Preferably, an aqueous solution containing 3-10 wt % of glycerol is used as the pore retaining agent.

[0069] Preferably, after the above post-treatment, drying is performed. There is no particular limitation on the drying time and drying temperature, which are usually 50-120° C. for 1-10 minutes.

[0070] The present disclosure also provides a reverse osmosis membrane prepared according to the above preparation method, which has both high flux and high desalination rate, and solves the problems of poor compatibility of the nanoparticle intermediate layer with the base membrane and the functional layer and poor long-term stability.

[0071] Example

[0072] The embodiments of the present disclosure will be described in detail below with reference to the examples. However, those skilled in the art will appreciate that the following examples are intended only to illustrate the present disclosure and should not be construed as limiting the scope of the present disclosure. Where specific conditions are not specified in the examples, the experiments were performed under conventional conditions or the conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments is not specified, all are commercially available conventional products.

[0073] Example 1

[0074] Preparation of basement membrane:

[0075] Tannic acid with a concentration of 0.1% and bisphenol A polysulfone with a concentration of 15% are added to N,N-dimethylformamide, heated and stirred at a temperature of 80°C until completely dissolved, and allowed to stand for degassing to obtain a casting solution; the casting solution is coated on a PET non-woven fabric and phase-converted in pure water to form a base membrane.

[0076] Preparation of polyamide nanoparticles:

[0077] 1 g of m-phenylenediamine monomer and 2.45 g of trimesoyl chloride at a molar ratio of 1:1 were dissolved in 100 ml of tetrahydrofuran, and 6 ml of pyridine was added thereto. The mixture was stirred and refluxed under nitrogen atmosphere for 20 minutes to form a precipitate.

[0078] The resulting product was washed three times with 1M hydrochloric acid, pure water, and tetrahydrofuran solvent, respectively, and finally dried in an oven at 80°C for 3 hours to obtain a polyamide polymer.

[0079] The polyamide polymer was ground into nanoparticles with a particle size of 100-200 nm using a sand mill.

[0080] Preparation of reverse osmosis membrane:

[0081] The polysulfone-based membrane was immersed in an aqueous solution containing 3.0 wt.% m-phenylenediamine and 0.04 wt.% sodium hydroxide for 20 seconds, wherein the aqueous solution also contained 100 ppm of polyamide nanoparticles that were evenly dispersed and exhibited a Tyndall effect, and surface water droplets were removed and removed. The membrane was then immersed in an oily solution containing 0.15 wt.% trimesoyl chloride in n-hexane for 20 seconds to form a polyamide functional layer. The membrane was then washed with an aqueous solution containing 7 wt.% citric acid for 1 minute and pure water for 30 seconds, and then immersed in an aqueous solution containing 5 wt.% glycerol for 30 seconds to maintain pores. The membrane was finally dried in an oven at 65°C for 3 minutes to obtain a reverse osmosis membrane 1.

[0082] Example 2

[0083] A reverse osmosis membrane 2 was obtained in the same manner as in Example 1 except that the concentration of the polyamide nanoparticles was changed to 200 ppm.

[0084] Example 3

[0085] A reverse osmosis membrane 3 was obtained in the same manner as in Example 1 except that the concentration of the polyamide nanoparticles was changed to 300 ppm.

[0086] Example 4

[0087] A reverse osmosis membrane 4 was obtained in the same manner as in Example 1 except that the concentration of the polyamide nanoparticles was changed to 400 ppm.

[0088] Example 5

[0089] Reverse osmosis membrane 5 was obtained in the same manner as in Example 1, except that the polyamide nanoparticles were prepared as follows: 1 g of piperazine and 1.37 g of trimesoyl chloride at a molar ratio of 1:1 were dissolved in 100 ml of tetrahydrofuran, and 6 ml of pyridine was added thereto. The mixture was stirred and refluxed under a nitrogen atmosphere for 20 min to form a precipitate.

[0090] Comparative Example 1

[0091] A reverse osmosis membrane 1 was prepared in the same manner as in Example 1 except that no polyamide nanoparticles were added.

[0092] Diaphragm performance test

[0093] Using a 1500 ppm NaCl aqueous solution as the feed liquid, the reverse osmosis membranes 1-5 obtained in Examples 1-5 and the comparative reverse osmosis membrane 1 obtained in Comparative Example 1 were tested for desalination rate (also known as retention rate) and flux at an operating pressure of 0.69 MPa and a temperature of 25°C. The results are shown in Table 1 below (concentrated water circulation).

[0094] Table 1

[0095] It can be seen from the experimental results in Table 1 that compared with the comparative reverse osmosis membrane 1 of the comparative example, the permeation flux of the reverse osmosis membranes 1-5 prepared by the method of the present invention in Examples 1-5 is greatly improved, while the rejection rate of monovalent salts remains basically unchanged at more than 98%.

[0096] The disclosed method, by embedding polyamide nanoparticles within the functional layer, advantageously promotes the generation of nanopores within the functional layer, providing more channels for water transport, thereby gradually increasing the membrane's permeation flux. Furthermore, the polyamide nanoparticles introduced into the functional layer can undergo re-crosslinking during the interfacial polymerization process, improving the compatibility between the polyamide nanoparticles and the functional layer and the crosslinking degree of the functional layer, thereby maintaining a high level of salt rejection.

[0097] It should be noted that, although the technical solutions of the present disclosure are described with specific examples, those skilled in the art will appreciate that the present disclosure should not be limited thereto.

[0098] While various embodiments of the present disclosure have been described above, the foregoing description is intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or technological improvements in the marketplace, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a polyamide polymer, It is characterized in that Polyamine monomers and polyacyl chloride monomers in equal molar ratios are polymerized.

2. The preparation method according to claim 1, wherein the polyamine monomer is at least one of p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene and piperazine, and the polyacyl chloride monomer is at least one of phthaloyl chloride, biphenyl dichloride, oxalyl chloride, terephthaloyl chloride, trimesoyl chloride and isophthaloyl chloride.

3. A polyamide nanoparticle obtained by grinding the polyamide polymer prepared according to the method of claim 1 or 2, wherein the particle size of the polyamide nanoparticle is 50-500 nm.

4. A method for preparing a reverse osmosis membrane, It is characterized in that The following steps are involved: Preparing a casting solution, and solidifying the casting solution on a supporting material to form a base film, wherein the casting solution comprises a polymer, a polyhydroxy compound and a solvent; The base film is immersed in an aqueous solution and an oily solution in sequence, wherein the aqueous solution comprises the polyamide nanoparticles according to claim 3 and polyamine monomers, and the oily solution comprises polyacyl chloride monomers; After post-treatment and drying, a reverse osmosis membrane is obtained.

5. The preparation method according to claim 4, wherein the polymer is at least one of bisphenol A type polysulfone, polyarylsulfone, polyethersulfone, sulfonated polyethersulfone, polyimide, polyvinylidene fluoride and polyacrylonitrile; preferably, based on the total mass of the casting solution, the concentration of the polymer is 10-22%; preferably, the solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpyrrolidine and dimethyl sulfoxide; preferably, the supporting material is a non-woven fabric.

6. The preparation method according to claim 4 or 5, wherein the polyhydroxy compound is at least one of cyclodextrin compounds, monosaccharides, disaccharides, tannic acid and polyols; preferably, based on the total mass of the casting solution, the concentration of the polyhydroxy compound is 0.01-3%; preferably, the cyclodextrin compound is at least one of α-cyclodextrin, β-cyclodextrin and hydroxypropyl-β-cyclodextrin, the monosaccharide is at least one of glucose, mannose and fructose, the disaccharide is at least one of sucrose, lactose and trehalose, and the polyol is at least one of ethylene glycol and glycerol.

7. The preparation method according to claim 4 or 5, wherein the concentration of the polyamide nanoparticles is 100-1000 ppm based on the total mass of the aqueous solution.

8. The preparation method according to claim 4 or 5, wherein the polyamine monomer is at least one of p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene and piperazine; preferably, based on the total mass of the aqueous solution, the concentration of the polyamine monomer is 1-5%; preferably, the aqueous solution further comprises an acid binding agent.

9. The preparation method according to claim 4 or 5, wherein the polyacyl chloride monomer is at least one of phthaloyl chloride, biphenyl dichloride, oxalyl chloride, terephthaloyl chloride, trimesoyl chloride and isophthaloyl chloride; preferably, based on the total mass of the oil phase solution, the concentration of the polyacyl chloride monomer is 1-5%; preferably, the oil phase solution further contains an organic solvent; preferably, the organic solvent is at least one of n-hexane, cyclohexane, ethylcyclohexane, n-heptane, tetrahydrofuran, isoparaffin, chloroform, toluene and m-xylene.

10. A reverse osmosis membrane obtained by the preparation method according to any one of claims 4 to 9.

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