A fouling-resistant reverse osmosis membrane and its preparation method

Abstract

This invention belongs to the field of separation membranes, and particularly relates to an antifouling reverse osmosis membrane and its preparation method. The reverse osmosis membrane provided by this invention comprises a nonwoven fabric layer, a porous support layer, and a modified polyamide separation layer in sequential contact. The modified polyamide separation layer is formed by interfacial polymerization of an aqueous solution and an oil solution on the porous support layer, followed by coating with a modifying liquid. The aqueous solution contains polyamine monomers and aminated nano-SiO2, the oil solution contains polyacrylamide halogen monomers, and the modifying liquid contains a covalent organic framework material made of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 1,3,5-trialdehyde phloroglucinol. This invention uses aminated nano-SiO2 and a specific covalent organic framework material to jointly modify the reverse osmosis membrane, effectively improving the antifouling, acid resistance, and oxidation resistance of the reverse osmosis membrane.

Description

Technical Field

[0001] This invention belongs to the field of separation membranes, and particularly relates to an antifouling reverse osmosis membrane and its preparation method. Background Technology

[0002] Traditional polyamide reverse osmosis membranes suffer from a trade-off effect, hindering their further development. Therefore, developing novel reverse osmosis membranes is of great significance.

[0003] Patent CN 114452845 A discloses an antifouling reverse osmosis membrane, its preparation method, and its applications. This patent utilizes a polymerization reaction between polyvinyl alcohol and polyacrylamide chloride to form a loose network structure. This network structure serves two purposes: firstly, it acts as a water molecule channel, maintaining the water flux of the reverse osmosis membrane; secondly, during heat treatment, it acts as a template for cross-linking reactions, allowing the cross-linking growth direction to proceed perpendicular to the reverse osmosis membrane surface along the gaps in the network structure. This not only reduces the cross-linking density of polyvinyl alcohol and glutaraldehyde, further maintaining the water flux of the reverse osmosis membrane, but also increases the thickness of the antifouling layer, thereby improving antifouling performance. However, the performance improvement effect of reverse osmosis membrane modification based on cross-linking reactions is relatively limited. Exploring more effective reverse osmosis membrane modification methods has become a research hotspot in this field. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide an antifouling reverse osmosis membrane and its preparation method. This invention uses aminated nano-SiO2 and specific covalent organic framework materials to jointly modify the reverse osmosis membrane, which effectively improves the antifouling, acid resistance and antioxidant properties of the reverse osmosis membrane.

[0005] The present invention provides an antifouling reverse osmosis membrane, comprising a nonwoven fabric layer, a porous support layer and a modified polyamide separation layer in sequential contact;

[0006] The modified polyamide separation layer is formed by interfacial polymerization of an aqueous solution and an oil solution on a porous support layer, followed by coating with a modifying liquid. The aqueous solution contains polyamine monomers and aminated nano-SiO2, the oil solution contains polyacrylamide halogen monomers, and the modifying liquid contains a covalent organic framework material made of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 1,3,5-trialdehyde phloroglucinol.

[0007] Preferably, the polyamine monomer is one or more selected from m-phenylenediamine, ethylenediamine, propylenediamine, butanediamine, p-phenylenediamine, o-phenylenediamine, pyromellitic triamine, and piperazine.

[0008] Preferably, the amination-modified nano-SiO2 has a particle size of 10-50 nm and a specific surface area of ​​100-200 m².2 / g.

[0009] Preferably, the content of the aminated nano-SiO2 in the aqueous solution is 0.025~0.25wt%.

[0010] Preferably, the aqueous solution further contains a surfactant and / or a non-aqueous polar solvent.

[0011] Preferably, the surfactant is one or more of sodium dodecyl sulfate, alkyl sulfonate, dodecylmethylbenzylammonium bromide, benzyl dimethylphenylammonium chloride, and benzyl trimethylammonium chloride.

[0012] Preferably, the non-aqueous polar solvent is one or more selected from dimethyl sulfoxide, ethanol, methanol, acetonitrile, dimethylformamide, citric acid, oxalic acid, and sodium hypochlorite.

[0013] Preferably, the polyacrylamide monomer is one or more of pyromellitic trichloroethylene, terephthaloyl chloride, orthophthaloyl chloride, isophthaloyl chloride, biphenyl dichloroethylene, and benzene disulfonyl chloride.

[0014] Preferably, the content of the covalent organic framework material in the modified liquid is 0.025~0.25wt%.

[0015] This invention provides a method for preparing the antifouling reverse osmosis membrane described above, comprising the following steps:

[0016] a) The casting solution is coated onto one side of the nonwoven fabric layer, and then phase-inversion curing is performed in water to obtain a base film; the front side of the base film is a porous support layer and the back side is a nonwoven fabric layer.

[0017] b) Coat the front side of the base film with an aqueous solution, and then dry until the aqueous phase of the base film is surface dry;

[0018] c) Coat the surface of the aqueous base film with an oil phase solution, and then perform a heat curing treatment to form a polyamide separation layer;

[0019] d) Coat the surface of the polyamide separation layer with a modified liquid to form a modified polyamide separation layer, thereby obtaining an anti-fouling reverse osmosis membrane.

[0020] Compared with existing technologies, this invention provides an antifouling reverse osmosis membrane and its preparation method. The reverse osmosis membrane provided by this invention comprises a nonwoven fabric layer, a porous support layer, and a modified polyamide separation layer in sequential contact; the modified polyamide separation layer is formed by interfacial polymerization of an aqueous solution and an oil solution on the porous support layer to form a polyamide separation layer, followed by coating with a modifying liquid; the aqueous solution contains polyamine monomers and aminated nano-SiO2, the oil solution contains polyacrylamide halide monomers, and the modifying liquid contains a covalent organic framework material made of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 1,3,5-trialdehyde phloroglucinol. This invention modifies the surface of the polyamide separation layer of a reverse osmosis membrane by reacting acyl groups with amino groups in nano-SiO2 and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT)-1,3,5-trialdehyde phloroglucinol (TP) covalent organic framework (COF) material (hereinafter referred to as TAPT-TP COF). This achieves co-modification of the reverse osmosis membrane by nano-SiO2 and TAPT-TP COF, thereby improving the flux and desalination rate of the reverse osmosis membrane to a certain extent, and endowing the reverse osmosis membrane with excellent antifouling, acid resistance, and oxidation resistance. This invention can effectively improve the overall performance of the reverse osmosis membrane and extend its service life, and has good market prospects. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The present invention provides an antifouling reverse osmosis membrane, comprising a nonwoven fabric layer, a porous support layer and a modified polyamide separation layer in sequential contact.

[0023] In the reverse osmosis membrane provided by the present invention, the thickness of the nonwoven fabric layer is preferably 70~150μm, specifically 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm or 150μm; the air permeability of the nonwoven fabric layer is preferably 1~3cm. 3 / cm 2 / s, specifically 1cm 3 / cm 2 / s, 1.2cm 3 / cm 2 / s, 1.5cm 3 / cm 2 / s, 1.7cm3 / cm 2 / s、2cm 3 / cm 2 / s, 2.3cm 3 / cm 2 / s, 2.5cm 3 / cm 2 / s, 2.7cm 3 / cm 2 / s or 3cm 3 / cm 2 / s.

[0024] In the reverse osmosis membrane provided by the present invention, the porous support layer is preferably formed by curing a casting solution on the surface of a nonwoven fabric layer; the casting solution preferably includes sulfonated polysulfone and an organic solvent; the grade of the sulfonated polysulfone is preferably S2010G6, which is provided by BASF, Germany; the organic solvent includes, but is not limited to, N,N-dimethylformamide; the concentration of the sulfonated polysulfone in the casting solution is preferably 10~20wt%, specifically 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, or 20wt%.

[0025] In the reverse osmosis membrane provided by the present invention, the modified polyamide separation layer is formed by interfacial polymerization of an aqueous solution and an oil solution on a porous support layer to form a polyamide separation layer, and then coated with a modifying liquid; wherein, the aqueous solution contains polyamine monomers, aminated nano-SiO2 and water, the oil solution contains polyacrylamide halide monomers and solvent oil, and the modifying liquid contains a covalent organic framework material made of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 1,3,5-trialdehyde phloroglucinol and a solvent.

[0026] In the reverse osmosis membrane provided by the present invention, the polyamine monomer in the aqueous solution used to form the modified polyamide separation layer is preferably one or more selected from m-phenylenediamine, ethylenediamine, propylenediamine, butanediamine, p-phenylenediamine, o-phenylenediamine, pyromellitic triamine, and piperazine; the content of the polyamine monomer in the aqueous solution is preferably 0.5~5wt%, specifically 0.5wt%, 0.7wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%, 2.3wt%, 2.5wt%, 2.8wt%, 3wt%, 3.2wt%, 3.5wt%, 4wt%, 4.5wt%, or 5wt%.

[0027] In the reverse osmosis membrane provided by this invention, the particle size of the aminated nano-SiO2 in the aqueous solution used to form the modified polyamide separation layer is preferably 10-50 nm, specifically 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm; the specific surface area of ​​the aminated nano-SiO2 is preferably 100-200 m² / g. 2 / g, specifically 100m 2 / g、110m 2 / g、120m 2 / g、130m 2 / g, 140m 2 / g, 150m 2 / g、160m 2 / g、170m 2 / g、180m 2 / g、190m 2 / g or 200m 2 / g; the content of the aminated nano-SiO2 in the aqueous solution is preferably 0.025~0.25wt%, specifically 0.025wt%, 0.05wt%, 0.075wt%, 0.1wt%, 0.125wt%, 0.15wt%, 0.175wt%, 0.2wt%, 0.225wt% or 0.25wt%.

[0028] In the reverse osmosis membrane provided by the present invention, the aqueous solution used to form the modified polyamide separation layer preferably further contains a surfactant and / or a non-aqueous polar solvent; the surfactant includes, but is not limited to, one or more of sodium dodecyl sulfate, alkyl sulfonate, dodecylmethylbenzylammonium bromide, benzyl dimethylphenylammonium chloride, and benzyl trimethylammonium chloride; the content of the surfactant in the aqueous solution is preferably 0.05~0.5wt%, specifically 0.05wt%, 0.1wt%, 0.15wt%, 0.2wt%, or 0.25wt%. The non-aqueous polar solvent is preferably one or more of dimethyl sulfoxide, ethanol, methanol, acetonitrile, dimethylformamide, citric acid, oxalic acid, and sodium hypochlorite. The content of the non-aqueous polar solvent in the aqueous solution is preferably 0.5~5wt%, specifically 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 2.68wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, or 5wt%.

[0029] In the reverse osmosis membrane provided by the present invention, the polyacrylamide halide monomer in the oil phase solution used to form the modified polyamide separation layer is preferably one or more of pyromellitic trimethylolpropionate chloride, terephthaloyl chloride, orthophthaloyl chloride, isophthaloyl chloride, biphenyl dimethyl chloride, and benzene disulfonyl chloride; the content of the polyacrylamide halide monomer in the oil phase solution is preferably 0.05~0.5wt%, specifically 0.05wt%, 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, or 0.5wt%.

[0030] In the reverse osmosis membrane provided by the present invention, the solvent oil in the oil phase solution used to form the modified polyamide separation layer is preferably one or more of Isopar G, Isopar L and n-hexane.

[0031] In the reverse osmosis membrane provided by this invention, the covalent organic framework material in the modified liquid used to form the modified polyamide separation layer is made of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 1,3,5-trialdehyde phloroglucinol. The preferred mass ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to 1,3,5-trialdehyde phloroglucinol is (0.5~2):1, specifically 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, or 1:1. The ratios are 1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, or 2:1; the content of the covalent organic framework material in the modified solution is preferably 0.025~0.25wt%, specifically 0.025wt%, 0.05wt%, 0.075wt%, 0.1wt%, 0.125wt%, 0.15wt%, 0.175wt%, 0.2wt%, 0.225wt%, or 0.25wt%.

[0032] In the reverse osmosis membrane provided by the present invention, the solvent in the modified liquid used to form the modified polyamide separation layer is preferably mesitylene and / or 1,4-dioxane; the volume ratio of mesitylene and 1,4-dioxane is preferably 1:(0.5~2), specifically 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2.

[0033] In the reverse osmosis membrane provided by this invention, the pH value of the modifying solution used to form the modified polyamide separation layer is preferably 5.5 to 6.5, specifically 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4, or 6.5. In this invention, the pH value can be adjusted by adding a pH adjuster to the modified solution, and the pH adjuster includes, but is not limited to, citric acid.

[0034] In the reverse osmosis membrane provided by this invention, the coating amount of the covalent organic framework material in the modifying solution used to form the modified polyamide separation layer on the membrane surface is preferably 0.025~0.25 g / m². 2 Specifically, it can be 0.025g / m 2 0.05g / m 2 0.075g / m 2 0.1g / m 2 0.125g / m 2 0.15g / m 2 0.175g / m 2 0.2g / m 2 0.225g / m 2 Or 0.25g / m 2 .

[0035] This invention also provides a method for preparing an antifouling reverse osmosis membrane, comprising the following steps:

[0036] a) The casting solution is coated onto one side of the nonwoven fabric layer, and then phase-inversion curing is performed in water to obtain a base film; the front side of the base film is a porous support layer and the back side is a nonwoven fabric layer.

[0037] b) Coat the front side of the base film with an aqueous solution, and then dry until the aqueous phase of the base film is surface dry;

[0038] c) Coat the surface of the aqueous base film with an oil phase solution, and then perform a heat curing treatment to form a polyamide separation layer;

[0039] d) Coat the surface of the polyamide separation layer with a modified liquid to form a modified polyamide separation layer, thereby obtaining an anti-fouling reverse osmosis membrane.

[0040] In the preparation method provided by this invention, in step a), the thickness of the nonwoven fabric layer is preferably 70~150μm, specifically 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm or 150μm; the air permeability of the nonwoven fabric layer is preferably 1~3cm. 3 / cm 2 / s, specifically 1cm 3 / cm 2 / s, 1.2cm 3 / cm 2 / s, 1.5cm 3 / cm 2 / s, 1.7cm 3 / cm 2 / s、2cm 3 / cm 2 / s, 2.3cm 3 / cm 2 / s, 2.5cm 3 / cm 2 / s, 2.7cm 3 / cm 2 / s or 3cm 3 / cm 2 / s.

[0041] In the preparation method provided by the present invention, in step a), the casting solution preferably includes sulfonated polysulfone and an organic solvent; the grade of the sulfonated polysulfone is preferably S2010G6, which is provided by BASF, Germany; the organic solvent includes, but is not limited to, N,N-dimethylformamide; the concentration of the sulfonated polysulfone in the casting solution is preferably 10~20wt%, specifically 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, or 20wt%.

[0042] In the preparation method provided by the present invention, in step a), the phase transformation curing temperature is preferably 10~25℃, specifically 10℃, 11℃, 12℃, 13℃, 14℃, 15℃, 16℃, 17℃, 18℃, 19℃, 20℃, 21℃, 22℃, 23℃, 24℃ or 25℃; the phase transformation curing time is preferably 1~5min, specifically 1min, 1.5min, 2min, 2.5min, 3min, 3.5min, 4min, 4.5min or 5min.

[0043] In the preparation method provided by the present invention, in step a), after the phase transformation and curing are completed, it is preferable to clean the obtained base film.

[0044] In the preparation method provided by this invention, in step b), the aqueous solution contains a polyamine monomer, aminated nano-SiO2, and water; the polyamine monomer is preferably one or more selected from m-phenylenediamine, ethylenediamine, propylenediamine, butanediamine, p-phenylenediamine, o-phenylenediamine, pyromellitic triamine, and piperazine; the content of the polyamine monomer in the aqueous solution is preferably 0.5-5 wt%, specifically 0.5 wt%, 0.7 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, 2 wt%, 2.3 wt%, 2.5 wt%, 2.8 wt%, 3 wt%, 3.2 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%; the particle size of the aminated nano-SiO2 is preferably 10-50 nm, specifically 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm; the specific surface area of ​​the aminated nano-SiO2 is preferably 100-200 m² / g. 2 / g, specifically 100m 2 / g、110m 2 / g、120m 2 / g、130m 2 / g, 140m 2 / g, 150m 2 / g、160m 2 / g、170m 2 / g、180m 2 / g、190m 2 / g or 200m 2 / g; the content of the aminated nano-SiO2 in the aqueous solution is preferably 0.025~0.25wt%, specifically 0.025wt%, 0.05wt%, 0.075wt%, 0.1wt%, 0.125wt%, 0.15wt%, 0.175wt%, 0.2wt%, 0.225wt% or 0.25wt%.

[0045] In the preparation method provided by the present invention, in step b), the aqueous solution preferably further contains a surfactant and / or a non-aqueous polar solvent; the surfactant includes, but is not limited to, one or more of sodium dodecyl sulfate, alkyl sulfonate, dodecylmethylbenzylammonium bromide, benzyl dimethylphenylammonium chloride, and benzyl trimethylammonium chloride; the content of the surfactant in the aqueous solution is preferably 0.05~0.5wt%, specifically 0.05wt%, 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0. 3wt%, 0.35wt%, 0.4wt%, 0.45wt%, or 0.5wt%; the non-aqueous polar solvent is preferably one or more of dimethyl sulfoxide, ethanol, methanol, acetonitrile, dimethylformamide, citric acid, oxalic acid, and sodium hypochlorite; the content of the non-aqueous polar solvent in the aqueous solution is preferably 0.5~5wt%, specifically 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 2.68wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, or 5wt%.

[0046] In the preparation method provided by the present invention, the specific process of step b) preferably includes: immersing the front side of the base film in an aqueous solution and keeping it there for a period of time, then taking it out and drying it until the aqueous surface of the base film is dry; wherein, the keeping time is preferably 10~30s, specifically 10s, 12s, 15s, 17s, 20s, 23s, 25s, 27s or 30s; the drying temperature is preferably 40~60℃, specifically 40℃, 42℃, 45℃, 47℃, 50℃, 52℃, 55℃, 57℃ or 60℃.

[0047] In the preparation method provided by the present invention, in step c), the oil phase solution contains a polyacrylamide halide monomer and a solvent oil; the polyacrylamide halide monomer is preferably one or more of pyromellitic trimethylolpropionate chloride, terephthaloyl chloride, phthaloyl chloride, isophthaloyl chloride, biphenyl dimethyl chloride, and benzene disulfonyl chloride; the content of the polyacrylamide halide monomer in the oil phase solution is preferably 0.05~0.5wt%, specifically 0.05wt%, 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, or 0.5wt%; the solvent oil is preferably one or more of Isopar G, Isopar L, and n-hexane.

[0048] In the preparation method provided by the present invention, in step c), the temperature of the thermosetting treatment is preferably 40~80℃, specifically 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃; the time of the thermosetting treatment is preferably 1~5min, specifically 1min, 1.5min, 2min, 2.5min, 3min, 3.5min, 4min, 4.5min or 5min; during the thermosetting treatment, the aqueous phase solution and the oil phase solution undergo an interfacial polymerization reaction on the porous support layer to form a polyamide separation layer.

[0049] In the preparation method provided by this invention, in step d), the modified liquid contains a covalent organic framework material and a solvent made of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 1,3,5-trialdehyde phloroglucinol; the preferred mass ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to 1,3,5-trialdehyde phloroglucinol used in preparing the covalent organic framework material is (0.5~2):1, specifically 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1; the covalent organic framework material in the modification The content in the liquid is preferably 0.025~0.25wt%, specifically 0.025wt%, 0.05wt%, 0.075wt%, 0.1wt%, 0.125wt%, 0.15wt%, 0.175wt%, 0.2wt%, 0.225wt%, or 0.25wt%; the solvent is preferably mesitylene and / or 1,4-dioxane; the volume ratio of mesitylene to 1,4-dioxane is preferably 1:(0.5~2), specifically 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, or 1:2.

[0050] In the preparation method provided by this invention, in step d), the covalent organic framework material in the modified liquid is preferably prepared according to the following steps: under anaerobic conditions, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 1,3,5-trialdehyde-resorcinol are mixed and reacted in a solvent to obtain the covalent organic framework material; wherein, the anaerobic conditions are preferably a nitrogen-filled environment; the mass ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to 1,3,5-trialdehyde-resorcinol is preferably (0.5~2):1, specifically 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1; the solvent is preferably mesitylene. And / or 1,4-dioxane, wherein the volume ratio of mesitylene to 1,4-dioxane is preferably (0.5~2):1, specifically 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1; the reaction temperature The preferred temperature is 100~150℃, specifically 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃ or 150℃; the preferred reaction time is 24~72h, specifically 24h, 30h, 36h, 42h, 48h, 54h, 60h, 66h or 72h; after the reaction is completed, the reaction product is preferably dried.

[0051] In the preparation method provided by this invention, in step d), the coating amount of the covalent organic framework material in the modified liquid on the membrane surface is preferably 0.025~0.25 g / m. 2 Specifically, it can be 0.025g / m 2 0.05g / m 2 0.075g / m 2 0.1g / m 2 0.125g / m 2 0.15g / m 2 0.175g / m 2 0.2g / m 2 0.225g / m 2 Or 0.25g / m 2 .

[0052] The technical solution provided by this invention involves the reaction of acyl groups with amino groups in nano-SiO2 and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT)-1,3,5-trialdehyde phloroglucinol (TP) covalent organic framework (COFs) material (hereinafter referred to as TAPT-TPCOF). This process modifies the surface of the polyamide separation layer of the reverse osmosis membrane with nano-SiO2 and TAPT-TP COF, achieving co-modification of the reverse osmosis membrane. This improves the flux and desalination rate of the reverse osmosis membrane to a certain extent, and also endows the reverse osmosis membrane with excellent antifouling, acid resistance, and oxidation resistance. The technical solution provided by this invention can effectively improve the overall performance of the reverse osmosis membrane and extend its service life, showing promising market prospects.

[0053] For clarity, the following examples and comparative examples provide a detailed description. Unless otherwise specified, all embodiments of the present invention are carried out at room temperature and normal pressure.

[0054] Example 1

[0055] A method for preparing an antifouling reverse osmosis membrane is as follows:

[0056] 1) Formulation of casting solution: The composition includes 16wt% sulfonated polysulfone (BASF, Germany, S2010G6), with the balance being N,N-dimethylformamide.

[0057] 2) Preparation of the support layer: The casting solution was coated onto a nonwoven fabric (140 μm thick, 1.5 cm² air permeability). 3 / cm 2 The nonwoven fabric is formed by immersing a single-sided surface of the nonwoven fabric in ionized water for phase transformation, followed by cleaning, to obtain a porous support layer on the surface of the nonwoven fabric; wherein the phase transformation temperature is 17°C and the phase transformation time is 2 min.

[0058] 3) Preparation of the aqueous solution: The components include 1.8 wt% polyamine (m-phenylenediamine), 0.15 wt% surfactant (sodium dodecyl sulfate), 2.68% non-aqueous polar solvent (dimethyl sulfoxide), and 0.05 wt% aminated nano-SiO2 (particle size 20 nm, specific surface area 160 m²). 2 / g), the remainder is water.

[0059] 4) Preparation of oil phase solution: The composition includes 0.25 wt% of a polyfunctional acyl halide (pyromellitic trimethylol chloride), and the balance is solvent oil (Isopar G).

[0060] 5) Preparation of polyamide separation layer: Immerse the above support layer in aqueous solution for 20s, remove it and dry it at 50℃ until the aqueous phase of the membrane is dry; then, coat the front side of the membrane with oil solution, and then put it in a 60℃ oven for heat curing treatment for 2min to form polyamide separation layer, thus obtaining the nascent polyamide reverse osmosis membrane.

[0061] 6) Preparation of TAPT-TP COF: 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and 1,3,5-trialdehyde phloroglucinol (TP) were added to a mixed solvent of mesitylene and 1,4-dioxane (volume ratio 1:1) at a mass ratio of 1:1. The mixture was heated under a nitrogen atmosphere at a reaction temperature of 120℃ for 48 h. After the reaction was completed, the product was dried to obtain the covalent organic framework material TAPT-TP COF.

[0062] 7) Preparation of modified solution: The components include 0.05wt% TAPT-TP COF, and the balance is solvent (trimethylbenzene and 1,4-dioxane, volume ratio 1:1), and the pH is adjusted to 6 with citric acid.

[0063] 8) Modification treatment: A modification solution is coated onto the front side of the nascent polyamide reverse osmosis membrane. The coating of TAPT-TP COF is approximately 0.05 g / m². 2 This yields an anti-fouling reverse osmosis membrane.

[0064] Example 2

[0065] A method for preparing an antifouling reverse osmosis membrane differs from Example 1 only in that: the content of aminated nano-SiO2 in the aqueous solution is 0.075 wt%, the content of TAPT-TP COF in the modified solution is 0.075 wt%, and the coating of TAPT-TP COF is approximately 0.075 g / m³. 2 .

[0066] Example 3

[0067] A method for preparing an antifouling reverse osmosis membrane differs from Example 1 only in that: the content of aminated nano-SiO2 in the aqueous solution is 0.1 wt%, the content of TAPT-TP COF in the modified solution is 0.1 wt%, and the coating of TAPT-TP COF is approximately 0.1 g / m³. 2 .

[0068] Example 4

[0069] A method for preparing an antifouling reverse osmosis membrane differs from Example 1 only in that: the content of aminated nano-SiO2 in the aqueous solution is 0.2 wt%, the content of TAPT-TP COF in the modified solution is 0.2 wt%, and the coating of TAPT-TP COF is approximately 0.2 g / m³. 2 .

[0070] Comparative Example 1

[0071] A method for preparing an antifouling reverse osmosis membrane differs from Example 2 only in that: aminated nano-SiO2 is not added to the aqueous solution.

[0072] Comparative Example 2

[0073] A method for preparing an antifouling reverse osmosis membrane differs from Example 2 only in that the covalent organic framework material in the modified solution is replaced with TPB-DVA-COF; the preparation process of TPB-DVA-COF is as follows:

[0074] 1,3,5-tris(4-aminophenyl)benzene-1,4-dialdehyde (TPB) and 2,5-divinylbenzene (DVA) were added to a mixed solvent of mesitylene and 1,4-dioxane (volume ratio 1:1) at a mass ratio of 1:1. The mixture was heated under a nitrogen atmosphere at a temperature of 120°C for 48 hours. After the reaction was completed, the product was dried to obtain the covalent organic framework material TPB-DVA-COF.

[0075] Comparative Example 3

[0076] A method for preparing an antifouling reverse osmosis membrane differs from Example 2 only in that: the aminated nano-SiO2 added to the aqueous solution is replaced with nano-SiO2, and steps 6) to 8) are omitted.

[0077] Comparative Example 4

[0078] A method for preparing an antifouling reverse osmosis membrane differs from Example 2 only in that the covalent organic framework material in the modified solution is replaced with TAM-TPH-COF; the preparation process of TAM-TPH-COF is as follows:

[0079] Tetra(4-aminophenyl)methane (TAM) and terephthalaldehyde (TPH) were added to a mixed solvent of mesitylene and 1,4-dioxane (volume ratio 1:1) at a mass ratio of 1:1. The mixture was heated under a nitrogen atmosphere at a temperature of 120°C for 48 hours. After the reaction was completed, the product was dried to obtain the covalent organic framework material TAM-TPH-COF.

[0080] Performance Evaluation

[0081] (a) Evaluation of basic diaphragm performance:

[0082] The reverse osmosis membranes obtained in the above embodiments and comparative examples were subjected to basic performance tests on a standard membrane test bench. The results are shown in Table 1:

[0083] Table 1. Test results of membrane flux and desalination rate.

[0084] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Flux F / GFD 36.5 38.4 36.9 32.5 34.8 37.1 36.2 35.2 Desalination rate R / % 99.76 99.81 99.78 99.79 99.71 99.70 99.72 99.75

[0085] in:

[0086] The formula for calculating flux F is as follows:

[0087] ;

[0088] V is the permeate volume, S is the effective membrane area, and t is time.

[0089] The formula for calculating the desalination rate R is as follows:

[0090] ;

[0091] This represents the NaCl concentration in the original solution. This represents the NaCl concentration in the permeate.

[0092] From the perspective of basic membrane performance, the changes in membrane flux in Examples 1, 2, and 3 are directly proportional to the amount of COFs and nano-SiO2 added; however, excessive amounts will actually decrease the flux. During the interfacial polymerization reaction, the MPD and TMC reactions generate heat and gas. At high concentrations, the large agglomeration of SiO2 nanoparticles hinders the release of heat and gas. On the other hand, high-load nanoparticles inhibit the diffusion rate of MPD into the oil phase solution. Both of these factors affect the formation rate and crosslinking degree of the polyamide functional layer. Secondly, large nodules form on the membrane surface, and the agglomeration of nanosheets increases the thickness of the separation layer. Comparative examples using unaminated nano-SiO2 and pure nano-SiO2 show that aminated nano-SiO2 is optimal for improving the performance of the reverse osmosis membrane. Furthermore, compared to the absence of COFs, the introduction of COFs improves membrane flux and desalination to a certain extent, resolving the trade-off effect.

[0093] (II) Evaluation of pollution prevention capabilities:

[0094] The membrane was tested using a 2000 mg / L NaCl aqueous solution and a 400 mg / L pollutant aqueous solution (bovine serum albumin, humic acid, etc.) at 15.5 bar pressure and 25 ± 0.4 °C. First, the membrane performance was stabilized by measuring the flux (J0) over 1 hour with 2000 mg / L NaCl as the test solution. Then, 400 mg / L of pollutant was added to 2000 mg / L NaCl, and the flux was measured over 8 hours under this test solution condition (Jt). The membrane was then washed three times with RO water for 15 minutes each time, and the recovery flux (Jwc) was measured. Finally, the permeance decline rate (PDR) and permeance recovery rate (PRR) were calculated. The PDR is the rate of permeation decline after continuous filtration of the wastewater solution, and the PRR is the rate of permeance recovery after physical washing. The calculation formulas are as follows:

[0095] ;

[0096] .

[0097] The experimental results are shown in Table 2:

[0098] Table 2. Test results of the antifouling ability of the diaphragm.

[0099] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 PDR 21.4 20.6 23.8 24.6 25.6 25.9 26.4 22.7 PRR 39.4 50.6 46.4 48.9 47.4 36.8 35.4 33.3

[0100] As contaminants gradually accumulate, the transport resistance of the leachate gradually increases. Based on the above results, Example 2 exhibits the best performance. The antifouling ability is related to the steric hindrance of COFs; COFs can effectively reduce the accumulation of contaminants on the polyamide layer, and the flux of the COF-modified reverse osmosis membrane is improved to some extent. Furthermore, grafting functional monomers onto the composite membrane surface can effectively improve the hydrophilicity of the membrane surface, increase its smoothness, and increase steric hindrance, thereby enhancing the composite membrane's resistance to contaminants.

[0101] (III) Acid resistance test:

[0102] To verify the acid resistance of the membrane prepared in this invention, a hydrochloric acid solution with pH=2 was prepared, heated and maintained at 40±0.5℃, and the membrane was immersed for 24 hours. The membrane was then tested under conditions of 15.5 bar pressure, pH=7.5, and 25±0.4℃. The experimental results are shown in Table 3.

[0103] Table 3. Results of acid resistance test of the membrane.

[0104] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Initial flux F / GFD 36.5 38.4 36.9 32.5 34.8 37.1 36.2 35.2 Initial desalination rate R / % 99.76 99.81 99.78 99.79 99.71 99.70 99.72 99.75 Flux of F / GFD after acidification 30.1 33.2 29.8 23.5 26.4 28.8 26.5 28.4 Desalination rate R / % after acidification treatment 99.70 99.75 99.69 99.71 99.64 99.63 99.70 99.68

[0105] The results show that grafting negatively charged functional groups onto the membrane surface can increase the amount of negative charge on the membrane surface to a certain extent, thereby improving the retention rate of negatively charged pollutants and ions in the composite membrane. Furthermore, surface grafting modification can effectively improve the chlorine resistance of the composite membrane, allowing COFs to better bond with the polyamide layer. Due to its greater steric hindrance, it is less susceptible to attack by hydrated protons.

[0106] (iv) Antioxidant experiment:

[0107] The membrane was immersed in a 1000 mg / L HClO solution for 24 h and tested under the conditions of 15.5 bar pressure, pH=7.5, and 25±0.4℃. The experimental results are shown in Table 4.

[0108] Table 4. Results of the antioxidant capacity test of the membrane.

[0109] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Initial flux F / GFD 36.5 38.4 36.9 32.5 34.8 37.1 36.2 35.2 Initial desalination rate R / % 99.76 99.81 99.78 99.79 99.71 99.70 99.72 99.75 Flux of F / GFD after oxidation treatment 31.2 35.5 32.2 27.6 28.6 31.5 29.9 28.5 Desalination rate R / % after oxidation treatment 99.70 99.78 99.72 99.71 99.65 99.66 99.68 99.6

[0110] As shown in the above experiments, Example 2 exhibited the lowest flux and desalination decline after HClO immersion. This is because the COFs selected in this example have abundant NH groups, which can serve as sacrificial units against free chloride ion attack, significantly improving the antioxidant properties of the modified reverse osmosis membrane. Furthermore, modifying the polyamide composite membrane surface with nano-SiO2@COF enhances intermolecular hydrogen bonding, preventing the hydrolysis of amide groups and the attack of NH bonds by active chlorine. This demonstrates that the modification method of this invention can effectively improve the chlorine resistance of the membrane.

[0111] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A fouling-resistant reverse osmosis membrane, characterized in that, It includes a nonwoven fabric layer, a porous support layer, and a modified polyamide release layer that are in sequential contact; The modified polyamide separation layer is formed by interfacial polymerization of an aqueous solution and an oil solution on a porous support layer, followed by coating with a modifying liquid. The aqueous solution contains polyamine monomers, aminated nano-SiO2, surfactants, and non-aqueous polar solvents. The oil solution contains polyacrylamide halogen monomers. The modifying liquid contains a covalent organic framework material made of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 1,3,5-trialdehyde phloroglucinol. The polyamine monomer is m-phenylenediamine; the content of the polyamine monomer in the aqueous solution is 1.8 wt%; the particle size of the aminated nano-SiO2 is 20 nm, and the specific surface area is 160 m². 2 / g; the content of the aminated nano-SiO2 in the aqueous solution is 0.075wt%; the surfactant is sodium dodecyl sulfate; the content of the surfactant in the aqueous solution is 0.15wt%; the non-aqueous polar solvent is dimethyl sulfoxide; the content of the non-aqueous polar solvent in the aqueous solution is 2.68wt%; The polyacrylamide halide monomer is pyromellitic trimethylolpropionate chloride; the content of the polyacrylamide halide monomer in the oil phase solution is 0.25 wt%. The covalent organic framework material in the modification solution contains 0.075 wt%; the amount of covalent organic framework material in the modification solution coated on the membrane surface is 0.075 g / m². 2 .

2. A method for preparing the antifouling reverse osmosis membrane according to claim 1, characterized in that, Includes the following steps: a) The casting solution is coated onto one side of the nonwoven fabric layer, and then phase-inversion curing is performed in water to obtain a base film; the front side of the base film is a porous support layer and the back side is a nonwoven fabric layer. b) Coat the front side of the base film with an aqueous solution, and then dry until the aqueous phase of the base film is surface dry; c) Coat the surface of the aqueous base film with an oil phase solution, and then perform a heat curing treatment to form a polyamide separation layer; d) Coat the surface of the polyamide separation layer with a modified liquid to form a modified polyamide separation layer, thereby obtaining an anti-fouling reverse osmosis membrane.