A method for preparing a reverse osmosis membrane

Abstract

The present invention belongs to the field of separation membranes, and in particular to a method for preparing a reverse osmosis membrane, comprising the following steps: a) coating an aqueous phase solution containing a multifunctional amine on the surface of a support layer of a base membrane, and then coating an oil phase solution containing a multifunctional acyl halide, and then drying to form a polyamide separation layer on the surface of the support layer to obtain a nascent membrane; b) soaking the nascent membrane in an alkaline solution with a pH value of 9 to 12, and then rinsing to obtain a semi-finished membrane; c) coating a post-treatment solution containing polyvinyl alcohol, polydimethylsiloxane and an aminosilane coupling agent on the surface of the polyamide separation layer of the semi-finished membrane, and drying; d) soaking the membrane sheet treated in step c) in a 3-chloro-2-hydroxypropyltrimethylammonium chloride aqueous solution for quaternization reaction, and drying to obtain a reverse osmosis membrane. The reverse osmosis membrane prepared by the method of the present invention has good permeability, hydrophilicity, anti-fouling, antibacterial and scouring resistance.

Description

Technical Field

[0001] The invention belongs to the field of separation membranes, and in particular relates to a method for preparing a reverse osmosis membrane. Background Art

[0002] Reverse osmosis technology is a high-end water treatment technology that uses pressure to drive the separation of solutes and solvents. Most reverse osmosis membranes use ultrafiltration membranes as the support layer. They are composite membranes prepared by interfacial polymerization reaction between polyamines and polyacyl chlorides on the surface of the support layer. They have a high degree of cross-linking and a low free volume, and therefore exhibit good selectivity and better water flux performance.

[0003] Chinese patent CN1301586A discloses a polyamide reverse osmosis composite membrane and a method for manufacturing the same, which uses raw materials such as multifunctional amines and multifunctional acyl halides to perform interfacial polymerization on a support layer material to prepare a polyamide reverse osmosis composite membrane consisting of a support layer and a polyamide layer. However, in the actual water treatment process, due to the poor hydrophilicity of the polyamide layer, pollutants such as bacteria, viruses, organic matter and colloids in the water are easily adsorbed and precipitated on the surface and membrane pores of the reverse osmosis composite membrane, causing blockage of the membrane pores and membrane pollution, thereby causing the separation of the support layer and the polyamide layer in the reverse osmosis composite membrane, and ultimately causing the reverse osmosis composite membrane to have a poor filtration effect.

[0004] At present, membrane pollution has become one of the important factors restricting the development and promotion of reverse osmosis technology. How to solve the pollution problem of reverse osmosis membrane has become a research hotspot in this field. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for preparing a reverse osmosis membrane, wherein the reverse osmosis membrane prepared by the method has good permeability, hydrophilicity, anti-pollution, antibacterial and scour resistance.

[0006] The present invention provides a method for preparing a reverse osmosis membrane, comprising the following steps:

[0007] a) coating an aqueous solution containing a multifunctional amine on the surface of the support layer of the base film, and then coating an oily solution containing a multifunctional acyl halide, and then drying to form a polyamide separation layer on the surface of the support layer to obtain a primary green membrane;

[0008] In step a), the polyfunctional amine is one or more of m-phenylenediamine, ethylenediamine, propylenediamine, butylenediamine, hexylenediamine, N-(2-hydroxyethyl)ethylenediamine, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, diethylenetriamine, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, s-phenylenediamine, piperazine and 4-aminomethylpiperazine, and the content of the polyfunctional amine in the aqueous phase solution is 0.5-5wt%; the polyfunctional acyl halide is trimesoyl chloride, and the content of the polyfunctional acyl halide in the oil phase solution is 0.05-0.3wt%;

[0009] b) soaking the nascent membrane in an alkaline solution with a pH value of 9 to 12, and then rinsing it to obtain a semi-finished membrane;

[0010] In step b), the soaking temperature is 15-30°C and the soaking time is 1-5 minutes;

[0011] c) coating a post-treatment solution containing polyvinyl alcohol, polydimethylsiloxane and an aminosilane coupling agent on the surface of the polyamide separation layer of the semi-finished membrane, and drying;

[0012] d) The membrane sheet treated in step c) is immersed in an aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride to undergo quaternization reaction, and then dried to obtain a reverse osmosis membrane.

[0013] Preferably, in step b), the alkaline solution is an aqueous sodium hydroxide solution.

[0014] Preferably, in step b), the rinsing process specifically comprises: sequentially performing isopropanol aqueous solution initial washing, water washing, isopropanol aqueous solution re-washing, water washing and glycerol aqueous solution washing.

[0015] Preferably, the isopropanol concentration of the isopropanol aqueous solution in the initial washing is 1-5wt%, the washing temperature is 50-80°C, and the washing time is 2-10min;

[0016] The temperature of the initial water washing is 15-30°C and the time is 1-5 minutes;

[0017] The isopropanol concentration of the isopropanol aqueous solution for re-washing is 1-5wt%, the washing temperature is 50-80°C, and the washing time is 2-10min;

[0018] The temperature of the re-washing is 15-30°C and the time is 1-5 minutes;

[0019] The glycerol concentration of the glycerol aqueous solution for washing is 2-6 wt %, the washing temperature is 15-30° C., and the washing time is 2-10 min.

[0020] Preferably, in step c), the number average molecular weight of the polyvinyl alcohol is 150,000-300,000, and the number average molecular weight of the polydimethylsiloxane is 500-8,000.

[0021] Preferably, in step c), the aminosilane coupling agent is 3-aminopropyltriethoxysilane.

[0022] Preferably, in step c), the post-treatment solution has a polyvinyl alcohol content of 1 to 3 wt %, a polydimethylsiloxane content of 0.05 to 2 wt %, and an aminosilane coupling agent content of 0.01 to 1 wt %.

[0023] Preferably, in step c), the post-treatment solution further contains a surfactant.

[0024] Preferably, in step c), the surfactant is sodium dodecylbenzene sulfonate and / or sodium lauryl sulfate; and the content of the surfactant in the post-treatment solution is 0.05-2 wt %.

[0025] Preferably, in step d), the concentration of the 3-chloro-2-hydroxypropyltrimethylammonium chloride aqueous solution is 1-2 wt % and the pH value is 8-11.

[0026] Compared with the prior art, the present invention provides a method for preparing a reverse osmosis membrane, comprising the following steps: a) coating an aqueous solution containing a multifunctional amine on the surface of the support layer of the base membrane, and then coating an oil phase solution containing a multifunctional acyl halide, and then drying to form a polyamide separation layer on the surface of the support layer to obtain a nascent membrane; b) soaking the nascent membrane in an alkaline solution with a pH value of 9 to 12, and then rinsing to obtain a semi-finished membrane; c) coating a post-treatment solution containing polyvinyl alcohol, polydimethylsiloxane and aminosilane coupling agent on the surface of the polyamide separation layer of the semi-finished membrane, and drying; d) soaking the membrane sheet treated in step c) in an aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride for quaternization reaction, and drying to obtain a reverse osmosis membrane. The reverse osmosis membrane prepared by the method of the present invention has good permeability, hydrophilicity, anti-fouling, antibacterial and scouring resistance. More specifically, the key points and advantages of the preparation method are as follows:

[0027] (1) Soak the nascent reverse osmosis membrane in a strong alkaline solution. Under strong alkaline conditions, the hydroxide ions (OH -) can promote the hydrolysis of amide bonds (-CONH-) to generate corresponding carboxylates and amino groups. The carboxylates and amino groups generated by the hydrolysis reaction further react in an alkaline environment to generate new hydroxyl (-OH) groups. In this way, the original amide bond position is replaced by a hydroxyl group, which improves the hydrophilicity of the reverse osmosis membrane surface and enhances the anti-fouling performance of the membrane surface. At the same time, more reactive hydroxyl sites are obtained for the subsequent bonding of 3-chloro-2-hydroxypropyltrimethylammonium chloride.

[0028] (2) The polyamide separation layer of the reverse osmosis membrane is coated with a post-treatment solution containing polyvinyl alcohol (PVA), polydimethylsiloxane (PDMS) and aminosilane coupling agent. The aminosilane coupling agent first reacts with the silanol groups on the surface of PDMS to form a siloxane bond (Si-O-Si). While firmly anchoring the aminosilane coupling agent on the surface of PDMS, the surface of PDMS is aminoated. The amino groups anchored on the surface of PDMS can react with the hydroxyl groups in PVA to form hydrogen bonds or covalent bonds through dehydration condensation. The aminosilane coupling agent acts as a bridge between PVA and PDMS, enhancing the interaction between the two. This interaction involves both physical adsorption and chemical bonding, and PDMS itself has excellent flexibility and elasticity, which improves the mechanical properties, chemical resistance and erosion resistance of the membrane, thereby effectively alleviating the problem of decreased water flux and reduced separation performance of the membrane during water treatment.

[0029] (3) Soak the reverse osmosis membrane in an aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride for quaternization reaction. 3-chloro-2-hydroxypropyltrimethylammonium chloride has a positively charged nitrogen atom, which can be combined with the amino group on the PDMS surface through an ionic bond or a covalent bond; at the same time, the chlorine atom in 3-chloro-2-hydroxypropyltrimethylammonium chloride can undergo a nucleophilic substitution reaction with the amino group to form a stable covalent bond; in addition, 3-chloro-2-hydroxypropyltrimethylammonium chloride can undergo a grafting reaction with the active hydroxyl group on the surface of the reverse osmosis membrane to generate an ether bond. Under the combined action of the above three methods, the quaternary ammonium salt base with antibacterial activity bonded to the surface of the reverse osmosis membrane is more resistant to scouring and has a more lasting antibacterial effect. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The present invention provides a method for preparing a reverse osmosis membrane, comprising the following steps:

[0032] a) coating an aqueous solution containing a multifunctional amine on the surface of the support layer of the base film, and then coating an oily solution containing a multifunctional acyl halide, and then drying to form a polyamide separation layer on the surface of the support layer to obtain a primary green membrane;

[0033] b) soaking the nascent membrane in an alkaline solution with a pH value of 9 to 12, and then rinsing it to obtain a semi-finished membrane;

[0034] c) coating a post-treatment solution containing polyvinyl alcohol, polydimethylsiloxane and an aminosilane coupling agent on the surface of the polyamide separation layer of the semi-finished membrane, and drying;

[0035] d) The membrane sheet treated in step c) is immersed in an aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride to undergo quaternization reaction, and then dried to obtain a reverse osmosis membrane.

[0036] In the preparation method provided by the present invention, in step a), the base film comprises a non-woven fabric layer and a support layer composited on one side surface of the non-woven fabric layer, and the component of the support layer is preferably polysulfone.

[0037] In the preparation method provided by the present invention, in step a), the polyfunctional amine contained in the aqueous phase solution is one or more of m-phenylenediamine, ethylenediamine, propylenediamine, butylenediamine, hexylenediamine, N-(2-hydroxyethyl)ethylenediamine, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, diethylenetriamine, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, s-phenylenediamine, piperazine and 4-aminomethylpiperazine; the content of the polyfunctional amine in the aqueous phase solution is 0.5-5wt%, specifically 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%.

[0038] In the preparation method provided by the present invention, in step a), the aqueous phase solution preferably further contains a surfactant; the surfactant is preferably sodium dodecylbenzene sulfonate and / or sodium lauryl sulfate; the content of the surfactant in the aqueous phase solution is preferably 0.05-2wt%, specifically 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 1.2wt%, 1.5wt%, 1.7wt% or 2wt%.

[0039] In the preparation method provided by the present invention, in step a), the aqueous phase solution preferably further contains a polar solvent; the polar solvent is preferably dimethyl sulfoxide and / or N-methylpyrrolidone; the content of the polar solvent in the aqueous phase solution is preferably 3-10wt%, specifically 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, 9wt%, 9.5wt% or 10wt%.

[0040] In the preparation method provided by the present invention, in step a), the pH value of the aqueous phase solution is preferably 7-9. Controlling the pH value of the aqueous phase solution under the above conditions is conducive to the absorption of by-product hydrochloric acid molecules in the interfacial polymerization process and the formation of polyamide with a high degree of cross-linking. If the pH is too low or too high, the amide bonds are prone to hydrolysis, affecting the separation performance of the polyamide separation layer. In the present invention, the pH value of the aqueous phase solution is preferably regulated by an alkaline pH regulator, and the alkaline pH regulator is preferably NaOH.

[0041] In the preparation method provided by the present invention, in step a), the polyfunctional acyl halide contained in the oil phase solution is trimesoyl chloride; the content of the polyfunctional acyl halide in the oil phase solution is 0.05-0.3wt%, specifically 0.05wt%, 0.07wt%, 0.1wt%, 0.12wt%, 0.15wt%, 0.17wt%, 0.2wt%, 0.23wt%, 0.25wt%, 0.27wt% or 0.3wt%.

[0042] In the preparation method provided by the present invention, in step a), the oil phase solvent in the oil phase solution is preferably one or more of n-hexane, Isopar G and Isopar L.

[0043] In the preparation method provided by the present invention, in step a), the drying temperature is preferably 40-80°C, specifically 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C; the drying time is preferably 1-5 min, specifically 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min or 5 min.

[0044] In the preparation method provided by the present invention, in step b), the pH value of the alkaline solution can be specifically 9, 9.5, 10, 10.5, 11, 11.5 or 12; the alkaline solution is preferably an aqueous sodium hydroxide solution; the immersion temperature is 15-30°C, specifically 15°C, 20°C, 25°C or 30°C; the immersion time is 1-5min, specifically 1min, 1.5min, 2min, 2.5min, 3min, 3.5min, 4min, 4.5min or 5min.

[0045] In the preparation method provided by the present invention, in step b), the specific process of rinsing preferably includes: initial washing with isopropanol aqueous solution, initial water washing, re-washing with isopropanol aqueous solution, re-washing with water and washing with glycerol aqueous solution in sequence. wherein, the isopropanol concentration of the initial washing with the isopropanol aqueous solution is preferably 1-5wt%, specifically 3wt%, the washing temperature is preferably 50-80°C, specifically 60°C, and the washing time is preferably 2-10min, specifically 5min; the temperature of the initial water washing is preferably 15-30°C, specifically 20°C, and the time is preferably 1-5min, specifically 2min; the isopropanol concentration of the secondary washing with the isopropanol aqueous solution is preferably 1-5wt%, specifically 3wt%, the washing temperature is preferably 50-80°C, specifically 60°C, and the washing time is preferably 2-10min, specifically 5min; the temperature of the secondary water washing is preferably 15-30°C, specifically 20°C, and the time is preferably 1-5min, specifically 2min; the glycerol concentration of the glycerol aqueous solution washing is preferably 2-6wt%, specifically 3wt%, the washing temperature is preferably 15-30°C, specifically 25°C, and the washing time is preferably 2-10min, specifically 5min.

[0046] In the preparation method provided by the present invention, in step c), the number average molecular weight of the polyvinyl alcohol contained in the post-treatment solution is preferably 150,000-300,000, specifically 150,000, 160,000, 170,000, 180,000, 190,000, 200,000, 210,000, 220,000, 230,000, 240,000, 250,000, 260,000, 270,000, 280,000, 290,000 or 300,000; the content of the polyvinyl alcohol in the post-treatment solution is preferably 1-3wt%, specifically 1wt%, 1.2wt%, 1.5wt%, 1.7wt%, 2wt%, 2.3wt%, 2.5wt%, 2.7wt% or 3wt%.

[0047] In the preparation method provided by the present invention, in step c), the number average molecular weight of the polydimethylsiloxane contained in the post-treatment solution is preferably 500-8000, specifically 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500 or 8000; the content of the polydimethylsiloxane in the post-treatment solution is preferably 0.05-2wt%, specifically 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.7wt%, 1wt%, 1.2wt%, 1.5wt%, 1.7wt% or 2wt%.

[0048] In the preparation method provided by the present invention, in step c), the aminosilane coupling agent contained in the post-treatment solution is preferably 3-aminopropyltriethoxysilane (APTES); the content of the aminosilane coupling agent in the post-treatment solution is preferably 0.01-1wt%, specifically 0.01wt%, 0.02wt%, 0.05wt%, 0.07wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.7wt% or 1wt%.

[0049] In the preparation method provided by the present invention, in step c), the post-treatment solution preferably further contains a surfactant; the surfactant is preferably sodium dodecylbenzene sulfonate and / or sodium lauryl sulfate; the content of the surfactant in the post-treatment solution is preferably 0.05-2wt%, specifically 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.7wt%, 1wt%, 1.2wt%, 1.5wt%, 1.7wt% or 2wt%.

[0050] In the preparation method provided by the present invention, in step c), the contact time between the post-treatment solution and the surface of the polyamide separation layer is preferably 2 to 5 seconds, specifically 2 seconds, 3 seconds, 4 seconds or 5 seconds; and then the excess solution is removed.

[0051] In the preparation method provided by the present invention, in step c), the drying temperature is preferably 60-90°C, specifically 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C; the drying time is preferably 1-5 min, specifically 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min or 5 min.

[0052] In the preparation method provided by the present invention, in step d), the concentration of the 3-chloro-2-hydroxypropyltrimethylammonium chloride aqueous solution is preferably 1-2wt%, specifically 1wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt% or 2wt%; the pH value of the 3-chloro-2-hydroxypropyltrimethylammonium chloride aqueous solution is preferably 8-11, specifically 8, 8.5, 9, 9.5, 10, 10.5 or 11. In the present invention, the pH value of the 3-chloro-2-hydroxypropyltrimethylammonium chloride aqueous solution is preferably regulated by an alkaline pH regulator, and the alkaline pH regulator is preferably NaOH.

[0053] In the preparation method provided by the present invention, in step d), the temperature of the quaternization reaction is preferably 10-40°C, specifically 10°C, 15°C, 20°C, 25°C, 30°C, 35°C or 40°C; the time of the quaternization reaction is preferably 1-5 min, specifically 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min or 5 min.

[0054] In the preparation method provided by the present invention, in step d), the drying temperature is 60-90°C, specifically 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C; the drying time is preferably 2-8 min, specifically 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min or 8 min.

[0055] For the purpose of greater clarity, the present invention is described in detail with reference to the following examples and comparative examples.

[0056] Example 1

[0057] An aqueous solution is coated on the polysulfone support layer of the polysulfone non-woven composite base membrane, and then an oily solution is coated, and the mixture is dried at 60°C for 3 minutes to form a polyamide separation layer on the polysulfone support layer, thereby obtaining a nascent polyamide reverse osmosis membrane; wherein the aqueous solution comprises a base liquid and a pH regulator, the base liquid comprises the following components: 3wt% m-phenylenediamine, 1wt% sodium dodecylbenzene sulfonate, 8wt% dimethyl sulfoxide, and the remainder is deionized water, the pH regulator is NaOH, and the amount used is such that the pH value of the aqueous solution is 8; the oily solution comprises the following components: 0.1wt% trimesoyl chloride, and the remainder is n-hexane.

[0058] The obtained nascent polyamide reverse osmosis membrane was soaked in alkali solution, the alkali solution used was sodium hydroxide solution (pH=12), the soaking temperature was 25°C, and the soaking time was 4 minutes; then it was rinsed, and the specific rinsing steps included: first rinsing with 60°C isopropanol aqueous solution (concentration 3wt%) for 5 minutes, then rinsing with 20°C deionized water for 2 minutes, then rinsing with 60°C isopropanol aqueous solution (concentration 3wt%) for 5 minutes, then rinsing with 20°C deionized water for 2 minutes, and finally rinsing with 25°C glycerol aqueous solution (concentration 3wt%) for 5 minutes.

[0059] The post-treatment solution was coated on the surface of the polyamide separation layer of the obtained rinsed membrane for 3 seconds, the excess solution was removed, and the membrane was treated in an oven at 80°C for 2 minutes to obtain a PVA hydrophilic-modified PDMS surface amino composite membrane; wherein the raw material formula of the post-treatment solution was as follows: polyvinyl alcohol (PVA, number average molecular weight 200000) 1wt%, sodium dodecylbenzene sulfonate 1wt%, polydimethylsiloxane (PDMS, number average molecular weight 7000) 1wt%, 3-aminopropyltriethoxysilane 0.1wt%, and the balance was deionized water.

[0060] The obtained PVA hydrophilic modified PDMS surface amino composite membrane was immersed in a 3-chloro-2-hydroxypropyltrimethylammonium chloride aqueous solution (concentration 1.5wt%, pH=10, temperature 25°C) for 2 minutes for quaternization reaction, and then baked in an oven at 80°C for 6 minutes to obtain a hydrophilic modified antibacterial and anti-fouling reverse osmosis membrane.

[0061] Example 2

[0062] Refer to Example 1, the only difference is that the pH value of the alkaline solution immersion is adjusted to 10, the PVA content in the post-treatment solution is adjusted to 2wt%, the PDMS content is adjusted to 0.5wt%, and the concentration of the 3-chloro-2-hydroxypropyltrimethylammonium chloride aqueous solution is adjusted to 1wt%.

[0063] Example 3

[0064] Refer to Example 1, the only difference is that the pH value of the alkaline solution immersion is adjusted to 9, the PVA content in the post-treatment solution is adjusted to 3wt%, the PDMS content is adjusted to 2wt%, and the concentration of the 3-chloro-2-hydroxypropyltrimethylammonium chloride aqueous solution is adjusted to 2wt%.

[0065] Comparative Example 1

[0066] Refer to Example 1, the only difference is that no PDMS is added to the post-treatment solution.

[0067] Comparative Example 2

[0068] Refer to Example 1, the only difference is that the concentration of the 3-chloro-2-hydroxypropyltrimethylammonium chloride aqueous solution is adjusted to 0 wt %.

[0069] Comparative Example 3

[0070] Refer to Example 1, the only difference is that the alkali solution soaking is replaced by deionized water soaking.

[0071] Effect evaluation

[0072] The reverse osmosis membranes prepared in the above embodiments and comparative examples were respectively loaded into membrane pools, and the raw aqueous solution containing Escherichia coli was run for 0 min, 30 min, 4 h and 12 h at a pressure of 1.03 MP, a temperature of 25°C and a membrane surface flow rate of 1.1 GPM / min. After deionized water was run for 15 min at a pressure of 1.03 MP, a temperature of 25°C and a membrane surface flow rate of 1.1 GPM / min, 1500 ppm of sodium chloride aqueous solution was filtered at a pressure of 1.03 MP, a temperature of 25°C and a membrane surface flow rate of 1.1 GPM / min, and the volume of the permeate and the concentration of sodium chloride therein were measured.

[0073] The water permeation of the reverse osmosis membrane is calculated by the following formula:

[0074] J = Q / (A·t), where J is the water flux, Q is the water permeation (L), and A is the effective membrane area of ​​the composite nanofiltration membrane (m 2 ), t is time (h);

[0075] The salt rejection rate of the reverse osmosis membrane is calculated by the following formula:

[0076] R = (Cp-Cf) / Cp×100%, where R is the desalination rate, Cp is the concentration of sodium chloride in the raw solution, and Cf is the concentration of sodium chloride in the permeate.

[0077] The experimental results are shown in the following table:

[0078]

[0079] It can be seen from the above results that the reverse osmosis membrane provided by the present invention has excellent water flux, desalination rate and excellent anti-pollution and scour resistance, and the present invention is consistent with the existing conventional reverse osmosis membrane production line process, with little equipment modification, which is conducive to industrial production.

[0080] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a reverse osmosis membrane, characterized in that: The following steps are involved: a) coating an aqueous solution containing a multifunctional amine on the surface of the support layer of the base film, and then coating an oily solution containing a multifunctional acyl halide, and then drying to form a polyamide separation layer on the surface of the support layer to obtain a primary green membrane; In step a), the polyfunctional amine is one or more of m-phenylenediamine, ethylenediamine, propylenediamine, butylenediamine, hexylenediamine, N-(2-hydroxyethyl)ethylenediamine, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, diethylenetriamine, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, s-phenylenediamine, piperazine and 4-aminomethylpiperazine, and the content of the polyfunctional amine in the aqueous phase solution is 0.5-5wt%; the polyfunctional acyl halide is trimesoyl chloride, and the content of the polyfunctional acyl halide in the oil phase solution is 0.05-0.3wt%; b) soaking the nascent membrane in an alkaline solution with a pH value of 9 to 12, and then rinsing it to obtain a semi-finished membrane; In step b), the soaking temperature is 15-30°C and the soaking time is 1-5 minutes; c) coating a post-treatment solution containing polyvinyl alcohol, polydimethylsiloxane and an aminosilane coupling agent on the surface of the polyamide separation layer of the semi-finished membrane, and drying; d) soaking the membrane sheet treated in step c) in an aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride to carry out a quaternization reaction, and drying to obtain a reverse osmosis membrane; In step d), the pH value of the 3-chloro-2-hydroxypropyltrimethylammonium chloride aqueous solution is 8-11.

2. The preparation method according to claim 1, characterized in that: In step b), the alkaline solution is an aqueous sodium hydroxide solution.

3. The preparation method according to claim 1, characterized in that: In step b), the rinsing process specifically includes: initial washing with isopropanol aqueous solution, initial water washing, re-washing with isopropanol aqueous solution, re-washing with water and washing with glycerol aqueous solution in sequence.

4. The preparation method according to claim 3, characterized in that: The isopropanol concentration of the isopropanol aqueous solution for initial washing is 1-5wt%, the washing temperature is 50-80°C, and the washing time is 2-10min; The temperature of the initial water washing is 15-30°C and the time is 1-5 minutes; The isopropanol concentration of the isopropanol aqueous solution for re-washing is 1-5wt%, the washing temperature is 50-80°C, and the washing time is 2-10min; The temperature of the re-washing is 15-30°C and the time is 1-5 minutes; The glycerol concentration of the glycerol aqueous solution for washing is 2-6 wt %, the washing temperature is 15-30° C., and the washing time is 2-10 min.

5. The preparation method according to claim 1, characterized in that: In step c), the number average molecular weight of the polyvinyl alcohol is 150,000-300,000, and the number average molecular weight of the polydimethylsiloxane is 500-8,000.

6. The preparation method according to claim 1, characterized in that: In step c), the aminosilane coupling agent is 3-aminopropyltriethoxysilane.

7. The preparation method according to claim 1, characterized in that: In step c), the post-treatment solution has a polyvinyl alcohol content of 1-3 wt %, a polydimethylsiloxane content of 0.05-2 wt %, and an aminosilane coupling agent content of 0.01-1 wt %.

8. The preparation method according to claim 1, characterized in that: In step c), the post-treatment solution further contains a surfactant.

9. The preparation method according to claim 8, characterized in that: In step c), the surfactant is sodium dodecylbenzene sulfonate and / or sodium lauryl sulfate; the content of the surfactant in the post-treatment solution is 0.05-2wt%.

10. The preparation method according to claim 1, characterized in that: In step d), the concentration of the 3-chloro-2-hydroxypropyltrimethylammonium chloride aqueous solution is 1-2 wt %.

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