Anti-pollution reverse osmosis membrane and preparation method thereof

Abstract

The invention belongs to the field of separation membranes, and particularly relates to an anti-pollution reverse osmosis membrane and a preparation method thereof. The reverse osmosis membrane provided by the invention comprises a non-woven fabric layer, a porous support layer and a modified polyamide separation layer which are in contact in sequence, the modified polyamide separation layer is prepared by performing interfacial polymerization reaction on a water-phase solution and an oil-phase solution on the porous supporting layer to form a polyamide separation layer and then coating the polyamide separation layer with a modification solution; the water phase solution contains a polyamine monomer and aminated nano SiO2, the oil phase solution contains a polyacyl halide monomer, and the modified liquid contains a covalent organic framework material prepared from 2, 4, 6-tri (4-aminophenyl)-1, 3, 5-triazine and 1, 3, 5-trialdehyde phloroglucinol. The reverse osmosis membrane is modified by aminated nano SiO2 and a specific covalent organic framework material, so that the pollution resistance, acid resistance and oxidation resistance of the reverse osmosis membrane are effectively improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of separation membranes, and particularly relates to an anti-fouling reverse osmosis membrane and a preparation method thereof. BACKGROUND

[0002] With the rapid growth of population, the world is facing problems such as water resource shortage, water resource pollution and water resource abuse, and therefore there is an urgent requirement for developing environmentally friendly and excellent performance membrane technology and improving the utilization rate of water resources. The traditional polyamide reverse osmosis membrane has a trade-off effect, which hinders the further development of the reverse osmosis membrane. Therefore, it is of great significance to develop a new type of reverse osmosis membrane.

[0003] Patent No. CN 114452845 A discloses an anti-fouling reverse osmosis membrane and a preparation method and application thereof. The patent forms a loose network structure through polymerization reaction of polyvinyl alcohol and polyacyl chloride. On one hand, the network structure can act as a water molecule channel, maintaining the water flux of the reverse osmosis membrane. On the other hand, during the heat treatment process, the network structure can act as a template for crosslinking reaction, so that the growth direction of the crosslinking reaction is perpendicular to the surface of the reverse osmosis membrane and along the gap of the network structure. This not only reduces the crosslinking density of polyvinyl alcohol and glutaraldehyde, further maintaining the water flux of the reverse osmosis membrane, but also improves the thickness of the anti-fouling layer, and further improves the anti-fouling performance. However, the reverse osmosis membrane modification method based on crosslinking reaction has a limited performance improvement effect on the membrane material, and exploring a more effective reverse osmosis membrane modification method has become a research hotspot in the field. SUMMARY

[0004] Therefore, the purpose of the present application is to provide an anti-fouling reverse osmosis membrane and a preparation method thereof. The present application uses amino-functionalized nano-SiO2 and a specific covalent organic framework material to modify the reverse osmosis membrane, effectively improving the anti-fouling, acid-resistant and oxidation-resistant performance of the reverse osmosis membrane.

[0005] The present application provides an anti-fouling reverse osmosis membrane, which comprises a non-woven fabric layer, a porous support layer and a modified polyamide separation layer in sequence.

[0006] The modified polyamide separation layer is formed by interfacial polymerization reaction of an aqueous solution and an oil solution on the porous support layer, and then coated with a modification liquid. The aqueous solution contains polyamine monomers and amino-functionalized nano-SiO2, the oil solution contains polyacyl halide monomers, and the modification liquid contains a covalent organic framework material made of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 1,3,5-triformylphloroglucinol.

[0007] Preferably, the polyamine monomer is one or more of m-phenylenediamine, ethylenediamine, propylenediamine, butylenediamine, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, and piperazine.

[0008] Preferably, the amino-functionalized nano-SiO2 has a particle size of 10-50 nm and a specific surface area of 100-200 m 2 / g.

[0009] Preferably, the amino-functionalized nano-SiO2 has a particle size of 10-50 nm and a specific surface area of 100-200 m

[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, dodecyl methyl benzyl ammonium bromide, benzyl dimethyl phenyl ammonium chloride, and benzyl trimethyl ammonium chloride.

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

[0013] Preferably, the polyacyl halide monomer is one or more of trimesoyl chloride, terephthaloyl chloride, phthaloyl chloride, isophthaloyl chloride, diphenic acid chloride, and benzenedisulfonyl chloride.

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

[0015] The present application provides a method for preparing the anti-fouling reverse osmosis membrane described in the above technical solution, comprising the following steps:

[0016] a) coating a casting solution to one side surface of a non-woven fabric layer, and then performing phase inversion solidification in water to obtain a base membrane; the front surface of the base membrane is a porous support layer, and the back surface is a non-woven fabric layer;

[0017] b) coating an aqueous solution to the front surface of the base membrane, and then drying to a water phase surface dryness of the base membrane;

[0018] c) coating an oil phase solution to the front surface of the water phase surface dryness base membrane, and then performing heat curing treatment to form a polyamide separation layer;

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

[0020] Compared to the prior art, the present invention provides an anti-pollution reverse osmosis membrane and its preparation method. The reverse osmosis membrane provided by the present invention comprises a non-woven fabric layer, a porous support layer, and a modified polyamide separation layer, which are sequentially contacted. The modified polyamide separation layer is formed by interfacial polymerization of an aqueous solution and an oily solution on the porous support layer to form a polyamide separation layer, which is then coated with a modifying liquid. The aqueous solution contains a polyamine monomer and amino-modified nano-SiO2, the oily solution contains a polyacyl halide monomer, 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. The present invention modifies the surface of the polyamide separation layer of the reverse osmosis membrane by reacting acyl groups with amino groups in ammoniated 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 (abbreviated as TAPT-TP COF). This achieves co-modification of the reverse osmosis membrane with nano-SiO2 and TAPT-TP COF, thereby improving the flux and salt rejection rate of the reverse osmosis membrane to a certain extent and giving the reverse osmosis membrane excellent anti-fouling, acid resistance, and antioxidant capabilities. The present invention can effectively improve the overall performance of the reverse osmosis membrane and extend the service life of the reverse osmosis membrane, and has good market prospects. DETAILED DESCRIPTION

[0021] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. 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 making any creative efforts are within the scope of protection of the present invention.

[0022] The invention provides an anti-pollution reverse osmosis membrane, which comprises a non-woven fabric layer, a porous supporting layer and a modified polyamide separation layer which are in contact with each other in sequence.

[0023] In the reverse osmosis membrane provided by the present invention, the thickness of the non-woven fabric layer is preferably 70-150 μm, specifically 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm or 150 μm; the air permeability of the non-woven fabric layer is preferably 1-3 cm 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 solidifying a casting solution on the surface of a non-woven fabric layer; the components of the casting solution preferably include sulfonated polysulfone and an organic solvent; the brand of the sulfonated polysulfone is preferably S2010G6, and the above-mentioned brand of sulfonated polysulfone is provided by BASF of 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 oily solution on a porous support layer to form a polyamide separation layer, and then coated with a modifying liquid; wherein the aqueous solution contains a polyamine monomer, amino-modified nano-SiO2 and water, the oily solution contains a polyacyl halide monomer 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 of m-phenylenediamine, ethylenediamine, propylenediamine, butylenediamine, p-phenylenediamine, o-phenylenediamine, mesitylenetriamine and piperazine; the content of the polyamine monomer in the aqueous solution is preferably 0.5 to 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%;

[0027] Preferably, the particle size of the amino-functionalized nano-SiO2 in the aqueous solution for forming the modified polyamide separation layer is 10-50 nm, and more specifically, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm. Preferably, the specific surface area of the amino-functionalized nano-SiO2 is 100-200 m2 / g, and more specifically, 100 m2 / g, 110 m2 / g, 120 m2 / g, 130 m2 / g, 140 m2 / g, 150 m2 / g, 160 m2 / g, 170 m2 / g, 180 m2 / g, 190 m2 / g or 200 m2 / g. Preferably, the content of the amino-functionalized nano-SiO2 in the aqueous solution is 0.025-0.25 wt%, and more specifically, 0.025 wt%, 0.05 wt%, 0.075 wt%, 0.1 wt%, 0.125 wt%, 0.15 wt%, 0.175 wt%, 0.2 wt%, 0.225 wt% or 0.25 wt%. 2 2 2 2 2 2 2 2 2 2 2 2 Preferably, the content of the amino-functionalized nano-SiO2 in the aqueous solution is 0.025-0.25 wt%, and more specifically, 0.025 wt%, 0.05 wt%, 0.075 wt%, 0.1 wt%, 0.125 wt%, 0.15 wt%, 0.175 wt%, 0.2 wt%, 0.225 wt% or 0.25 wt%.

[0028] Preferably, the aqueous solution for forming the modified polyamide separation layer further comprises 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, dodecyl methyl benzyl ammonium bromide, benzyl dimethyl phenyl ammonium chloride and benzyl trimethyl ammonium chloride. Preferably, the content of the surfactant in the aqueous solution is 0.05-0.5 wt%, and more specifically, 0.05 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt% or 0.5 wt%. Preferably, the non-aqueous polar solvent is one or more of dimethyl sulfoxide, ethanol, methanol, acetonitrile, dimethyl formamide, citric acid, oxalic acid and sodium hypochlorite. Preferably, the content of the non-aqueous polar solvent in the aqueous solution is 0.5-5 wt%, and more specifically, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 2.68 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt% or 5 wt%.

[0029] ​​​​​​​​​​​In the reverse osmosis membrane provided by the application, the polybasic acid halide monomer in the oil phase solution used for forming the modified polyamide separation layer is preferably one or more of trimesic acid chloride, terephthalic acid chloride, phthalic acid chloride, isophthalic acid chloride, diphenic acid chloride and benzenedisulfonyl chloride; the content of the polybasic acid halide monomer in the oil phase solution is preferably 0.05-0.5wt%, and can be 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 application, the solvent oil in the oil phase solution used for forming 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 the application, the covalent organic framework material in the modification liquid used for forming the modified polyamide separation layer is made of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 1,3,5-triformylphloroglucinol, and the mass ratio of the 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to the 1,3,5-triformylphloroglucinol is preferably (0.5-2):1, and can be 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 content of the covalent organic framework material in the modification liquid is preferably 0.025-0.25wt%, and can be 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 application, the solvent in the modification liquid used for forming the modified polyamide separation layer is preferably mesitylene and / or 1,4-dioxane; and the volume ratio of the mesitylene to the 1,4-dioxane is preferably 1:(0.5-2), and can be 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 the application, the pH value of the modification liquid used for forming the modified polyamide separation layer is preferably 5.5-6.5, and can be 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4 or 6.5. In the application, the pH value of the modification liquid can be regulated by adding a pH regulator to the modification liquid, and the pH regulator includes but is not limited to citric acid.

[0034] In the reverse osmosis membrane provided by the application, the coating amount of the covalent organic framework material in the modification liquid used for forming the modified polyamide separation layer on the surface of the membrane sheet is preferably 0.025-0.25 g / m 2 , and can be 0.025 g / m 2 , 0.05 g / m 2 , 0.075 g / m 2 , 0.1 g / m 2 , 0.125 g / m 2 , 0.15 g / m 2 , 0.175 g / m 2 , 0.2 g / m 2 , 0.225 g / m 2 or 0.25 g / m 2 .

[0035] The application further provides a preparation method of the anti-pollution reverse osmosis membrane, which comprises the following steps:

[0036] a) coating a casting solution to one side surface of a non-woven fabric layer, and then performing phase inversion solidification in water to obtain a base membrane; the front surface of the base membrane is a porous support layer, and the back surface is a non-woven fabric layer;

[0037] b) coating an aqueous phase solution to the front surface of the base membrane, and then drying to water phase surface dryness of the base membrane;

[0038] c) coating an oil phase solution to the front surface of the water phase surface dryness base membrane, and then performing heat curing treatment to form a polyamide separation layer;

[0039] d) coating a modification liquid to the surface of the polyamide separation layer to form a modified polyamide separation layer, and thus obtaining the anti-pollution reverse osmosis membrane.

[0040] In the preparation method provided by the application, in step a), the thickness of the non-woven fabric layer is preferably 70-150 μm, and can be 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm or 150 μm; and the air permeability of the non-woven fabric layer is preferably 1-3 cm 3 / cm 2 / s, and can be 1 cm 3 / cm 2 / s, 1.2 cm 3 / cm 2 / s, 1.5 cm 3 / cm 2 / s, 1.7 cm 3 / cm 2 / s, 2 cm 3 / cm 2 / s, 2.3 cm 3 / cm 2 / s, 2.5 cm 3 / cm 2 / s, 2.7 cm 3 / cm 2 / s or 3 cm 3 / cm 2 / s.

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

[0042] In the preparation method provided by the application, in step a), the temperature of the phase inversion solidification is preferably 10-25℃, and specifically can be 10℃, 11℃, 12℃, 13℃, 14℃, 15℃, 16℃, 17℃, 18℃, 19℃, 20℃, 21℃, 22℃, 23℃, 24℃ or 25℃; and the time of the phase inversion solidification is preferably 1-5 min, and specifically can be 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min or 5 min.

[0043] In the preparation method provided by the application, in step a), after the phase inversion solidification is completed, the obtained base film is preferably cleaned.

[0044] In the preparation method provided by the present invention, in step b), the aqueous phase solution contains a polyamine monomer, amino-modified nano-SiO2 and water; the polyamine monomer is preferably one or more of m-phenylenediamine, ethylenediamine, propylenediamine, butylenediamine, p-phenylenediamine, o-phenylenediamine, s-phenylenediamine and piperazine; the content of the polyamine monomer in the aqueous phase 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%; the particle size of the amino-modified nano-SiO2 is preferably 10-50nm, specifically 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm or 50nm; the specific surface area of ​​the amino-modified nano-SiO2 is preferably 100-200m 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 amino 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 application, in step b), the aqueous phase 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, dodecyl methyl benzyl ammonium bromide, benzyl dimethyl phenyl ammonium chloride, and benzyl trimethyl ammonium chloride; the content of the surfactant in the aqueous phase solution is preferably 0.05-0.5 wt%, and specifically can be 0.05 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt% or 0.5 wt%; the non-aqueous polar solvent is preferably one or more of dimethyl sulfoxide, ethanol, methanol, acetonitrile, dimethyl formamide, citric acid, oxalic acid and sodium hypochlorite; the content of the non-aqueous polar solvent in the aqueous phase solution is preferably 0.5-5 wt%, and specifically can be 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 2.68 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt% or 5 wt%.

[0046] In the preparation method provided by the application, the specific process of step b) preferably includes: immersing the front surface of the base film into the aqueous phase solution for a period of time, and then taking out and drying to the aqueous phase surface dryness of the base film; wherein the time of the immersion is preferably 10-30 s, and specifically can be 10 s, 12 s, 15 s, 17 s, 20 s, 23 s, 25 s, 27 s or 30 s; the drying temperature is preferably 40-60℃, and specifically can be 40℃, 42℃, 45℃, 47℃, 50℃, 52℃, 55℃, 57℃ or 60℃.

[0047] In the preparation method provided by the application, in step c), the oil phase solution contains a polybasic acid halide monomer and a solvent oil; the polybasic acid halide monomer is preferably one or more of trimesoyl chloride, terephthaloyl chloride, phthaloyl chloride, isophthaloyl chloride, diphenyl dicarboxylic acid chloride and benzene disulfonyl chloride; the content of the polybasic acid halide monomer in the oil phase solution is preferably 0.05-0.5 wt%, and specifically can be 0.05 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt% or 0.5 wt%; the solvent oil is preferably one or more of Isopar G, Isopar L and n-hexane.

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

[0049] In the preparation method provided by the application, in step d), the modification liquid contains a covalent organic framework material made of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 1,3,5-triformylphloroglucinol and a solvent; the mass ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to 1,3,5-triformylphloroglucinol used for preparing the covalent organic framework material is preferably (0.5-2):1, and can be 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 content of the covalent organic framework material in the modification liquid is preferably 0.025-0.25wt%, and can be 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; and the volume ratio of the mesitylene to 1,4-dioxane is preferably 1:(0.5-2), and can be 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 the application, in step d), the covalent organic framework material in the modification liquid is preferably prepared according to the following steps: 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 1,3,5-trialdehyde phloroglucinol are mixed and reacted in a solvent under anaerobic conditions to obtain a covalent organic framework material; wherein the anaerobic condition is preferably a nitrogen-filled environment; the mass ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to 1,3,5-trialdehyde phloroglucinol is preferably (0.5-2):1, and specifically can be 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, and the volume ratio of mesitylene to 1,4-dioxane is preferably (0.5-2):1, and specifically can be 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 is preferably 100-150°C, and specifically can be 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C or 150°C; the reaction time is preferably 24-72h, and specifically can be 24h, 30h, 36h, 42h, 48h, 54h, 60h, 66h or 72h; and the reaction product is preferably dried after the reaction.

[0051] In the preparation method provided by the application, in step d), the coating amount of the covalent organic framework material in the modification liquid on the surface of the film piece is preferably 0.025-0.25g / m 2 , and specifically 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 scheme provided by the application realizes the co-modification of the nano-SiO2 and the TAPT-TP COF on the reverse osmosis membrane, improves the flux and desalination rate of the reverse osmosis membrane to a certain extent, and enables the reverse osmosis membrane to have excellent anti-pollution, acid resistance and oxidation resistance. The technical scheme provided by the application can effectively improve the overall performance of the reverse osmosis membrane, prolong the service life of the reverse osmosis membrane, and has good market prospects.

[0053] For a clearer understanding, the following examples and comparative examples are described in detail below. In the following examples of the application, unless otherwise specified, all operations are carried out at room temperature and under normal pressure.

[0054] Example 1

[0055] A preparation method of an anti-pollution reverse osmosis membrane is as follows:

[0056] 1) Preparation of casting solution: the components include 16wt% of sulfonated polysulfone (Germany BASF, S2010G6), and the balance is N,N-dimethylformamide.

[0057] 2) Preparation of support layer: the casting solution is coated on one side surface of non-woven fabric (thickness 140μm, air permeability 1.5cm 3 / cm 2 / s), then immersed in ionized water for phase inversion, and then cleaned to obtain a porous support layer formed on the surface of the non-woven fabric; wherein the phase inversion temperature is 17℃; the phase inversion time is 2min.

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

[0059] 4) Preparation of oil phase solution: the components include 0.25wt% of multifunctional acyl halide (trimesoyl chloride), and the balance is solvent oil (Isopar G).

[0060] 5) Preparation of polyamide separation layer: the above support layer is immersed in the aqueous phase solution for 20 s, and after taking out, it is dried at 50°C until the aqueous phase of the film is dry to the touch; then, the oil phase solution is coated on the front side of the film, and then placed in a 60°C oven for heat curing treatment for 2 min to form a polyamide separation layer, thereby obtaining a 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-triformylphloroglucinol (TP) are added to a mixed solvent of mesitylene and 1,4-dioxane (volume ratio 1:1) in a mass ratio of 1:1, heated and reacted under a nitrogen atmosphere, the reaction temperature is 120°C, and the reaction time is 48 h. After the reaction is completed, the product is dried to obtain a covalent organic framework material TAPT-TP COF.

[0062] 7) Preparation of modification liquid: the components include 0.05wt% of TAPT-TP COF, and the rest is solvent (mesitylene and 1,4-dioxane, volume ratio 1:1), and citric acid is used to adjust the pH to 6.

[0063] 8) Modification treatment: the modification liquid is coated on the front side of the nascent polyamide reverse osmosis membrane, and the coating amount of TAPT-TP COF is about 0.05g / m 2 , thereby obtaining an anti-pollution reverse osmosis membrane.

[0064] Example 2

[0065] A method for preparing an anti-pollution reverse osmosis membrane, which is different from example 1 only in that the content of amino-functionalized nano-SiO2 in the aqueous phase solution is 0.075wt%, the content of TAPT-TP COF in the modification liquid is 0.075wt%, and the coating amount of TAPT-TP COF is about 0.075g / m 2 .

[0066] Example 3

[0067] A method for preparing an anti-pollution reverse osmosis membrane, which is different from example 1 only in that the content of amino-functionalized nano-SiO2 in the aqueous phase solution is 0.1wt%, the content of TAPT-TP COF in the modification liquid is 0.1wt%, and the coating amount of TAPT-TP COF is about 0.1g / m 2 .

[0068] Example 4

[0069] A preparation method of an anti-pollution reverse osmosis membrane, which is only different from example 1 in that the content of the amino-nano-SiO2 in the aqueous solution is 0.2wt%, the content of the TAPT-TP COF in the modification solution is 0.2wt%, and the coating amount of the TAPT-TP COF is about 0.2g / m 2 .

[0070] Comparative example 1

[0071] A preparation method of an anti-pollution reverse osmosis membrane, which is only different from example 2 in that no amino-nano-SiO2 is added in the aqueous solution.

[0072] Comparative example 2

[0073] A preparation method of an anti-pollution reverse osmosis membrane, which is only different from example 2 in that the covalent organic framework material in the modification solution is replaced by TPB-DVA-COF; and the preparation process of the TPB-DVA-COF is as follows:

[0074] 1,3,5-tris(4-aminophenyl)benzene-1,4-dialdehyde (TPB) and 2,5-divinylbenzene (DVA) are added to a mixed solvent of mesitylene and 1,4-dioxane (volume ratio 1:1) in a mass ratio of 1:1, and heated to react under a nitrogen atmosphere, with a reaction temperature of 120℃ and a reaction time of 48h. After the reaction is completed, the product is dried to obtain the covalent organic framework material TPB-DVA-COF.

[0075] Comparative example 3

[0076] A preparation method of an anti-pollution reverse osmosis membrane, which is only different from example 2 in that the amino-nano-SiO2 added in the aqueous solution is replaced by nano-SiO2, and steps 6) to 8) are not performed.

[0077] Comparative example 4

[0078] A preparation method of an anti-pollution reverse osmosis membrane, which is only different from example 2 in that the covalent organic framework material in the modification solution is replaced by TAM-TPH-COF; and the preparation process of the TAM-TPH-COF is as follows:

[0079] Tetrakis(4-aminophenyl)methane (TAM) and terephthaldehyde (TPH) are added to a mixed solvent of mesitylene and 1,4-dioxane (volume ratio 1:1) in a mass ratio of 1:1, and heated to react under a nitrogen atmosphere, with a reaction temperature of 120℃ and a reaction time of 48h. After the reaction is completed, the product is dried to obtain the covalent organic framework material TAM-TPH-COF.

[0080] Performance evaluation

[0081] (I) Membrane basic performance evaluation:

[0082] The reverse osmosis membranes obtained in the above examples and comparative examples were subjected to basic performance testing on a standard membrane testing platform, and the results are shown in Table 1:

[0083] Table 1: Membrane flux and desalination rate test results

[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] Wherein:

[0086] The flux F is calculated as follows:

[0087] ;

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

[0089] The desalination rate R is calculated as follows:

[0090] ;

[0091] C0 is the concentration of NaCl in the raw solution, C1 is the concentration of NaCl in the permeate.

[0092] From the membrane basic performance, the flux of the membranes of Example 1, Example 2 and Example 3 is proportional to the COFs and the amount of added nano-SiO2, but if the amount is excessive, the flux will actually decrease. During the interfacial polymerization reaction, heat and gas are generated, and a large amount of agglomerated SiO2 nanoparticles at high concentrations hinder the release of heat and gas; on the other hand, a high load of nanoparticles will inhibit the diffusion speed of MPD to the oil phase solution. These two factors will affect the generation speed and crosslinking degree of the polyamide functional layer. Secondly, large nodules are formed on the membrane surface, and the separation layer thickness increases due to the agglomeration of nanosheets. The comparative examples without adding amino-functionalized nano-SiO2 and pure nano-SiO2 can show that amino-functionalized nano-SiO2 is optimal for improving the performance of reverse osmosis membranes. Secondly, by comparing without adding COFs, it can be shown that the introduction of COFs improves the flux and desalination of the membrane to a certain extent and solves the trade-off effect.

[0093] (II) Anti-fouling ability evaluation:

[0094] The test is carried out under the conditions of 15.5 bar pressure, 25±0.4℃, using 2000 mg / L NaCl aqueous solution and 400 mg / L contaminant aqueous solution (bovine serum albumin, humic acid, etc.). First, the performance of the membrane is stabilized, and the flux is measured under the condition of 1h 2000 mg / L NaCl as the test liquid, which is recorded as J0; then 400 mg / L contaminant is added to 2000 mg / L NaCl, and the flux is measured under the condition of 8h test liquid, which is recorded as Jt; the RO water is washed for 15 min for 3 times, and then the recovery flux is tested, which is recorded as Jwc; finally, PDR and PRR are calculated, wherein PDR (permeance decline rate) is the permeation decline rate after continuous filtration of the sewage solution, and PRR (permeance recovery rate) is the corresponding permeation recovery rate after physical washing, and the calculation formula is as follows:

[0095] ;

[0096] .

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

[0098] Table 2 Test results of the anti-pollution ability of the membrane sheet

[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] With the gradual accumulation of the contaminant, the transport resistance of the leachate gradually increases. From the above results, the performance of Example 2 is the best. The anti-pollution ability is related to the steric hindrance of COFs, and COFs can effectively reduce the accumulation of contaminants on the polyamide layer, and the flux of the reverse osmosis membrane modified by COFs is improved to a certain extent. Secondly, the functional monomer is grafted on the surface of the composite membrane, which can effectively improve the hydrophilicity of the membrane surface, increase the smoothness of the membrane surface, and increase the steric hindrance, thereby improving the anti-pollution ability of the composite membrane.

[0101] (Three) Acid resistance experiment:

[0102] To verify the acid resistance of the membrane sheet prepared by the application, a pH=2 hydrochloric acid solution is prepared, heated and maintained at 40±0.5℃, and then the membrane sheet is soaked for 24h, and then tested under the conditions of 15.5 bar pressure, pH=7.5, 25±0.4℃. The experimental results are shown in Table 3:

[0103] Table 3 Test results of the acid resistance of the membrane sheet

[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 F / GFD after acidification treatment 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] From the above results, grafting the functional groups with negative charge on the membrane surface can increase the number of negative charges on the membrane surface to a certain extent, thereby improving the rejection rate of the composite membrane to the negatively charged pollutants and ions. In addition, the surface grafting modification can also effectively improve the chlorine resistance of the composite membrane, and the COFs can be better combined with the polyamide layer, and the steric hindrance is greater, and it is more difficult to be attacked by hydrated protons.

[0106] (IV) Antioxidant experiment:

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

[0108] Table 4 Test results of the anti-oxidation ability 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 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] From the above experiments, the flux and the attenuation of desalination of Example 2 after HClO immersion are the lowest, because the COFs selected in this example have abundant N-H groups, which can be used as a sacrificial unit for free chlorine ion attack, thereby significantly improving the oxidation resistance of the modified reverse osmosis membrane. Secondly, the nano-SiO2@COF is modified on the surface of the polyamide composite membrane, and the modification layer can prevent the hydrolysis of the amide group on the membrane surface and the attack of the N-H bond by active chlorine by enhancing the hydrogen bond interaction between molecules, thereby proving that the modification method of the embodiment of the present application can effectively improve the chlorine resistance of the membrane.

[0111] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled persons in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. An anti-pollution reverse osmosis membrane, characterized in that: It comprises a non-woven fabric layer, a porous support layer and a modified polyamide separation layer that are in contact with each other in sequence; The modified polyamide separation layer is formed by interfacial polymerization of an aqueous solution and an oily solution on a porous support layer to form a polyamide separation layer, and then coated with a modifying liquid; the aqueous solution contains a polyamine monomer and amino-modified nano-SiO2, the oily solution contains a polyacyl halide monomer, 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.

2. The anti-pollution reverse osmosis membrane according to claim 1, characterized in that: The polyamine monomer is one or more of m-phenylenediamine, ethylenediamine, propylenediamine, butylenediamine, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine and piperazine.

3. The anti-pollution reverse osmosis membrane according to claim 1, characterized in that The particle size of the amino-silicon dioxide is 10-50 nm, and the specific surface area is 100-200 m 2 / g.

4. The anti-pollution reverse osmosis membrane according to claim 1, characterized in that The content of the amino-type nano-SiO2 in the aqueous solution is 0.025-0.25 wt%.

5. The anti-pollution reverse osmosis membrane according to claim 1, characterized in that: The aqueous phase solution also contains a surfactant and / or a non-aqueous polar solvent.

6. The anti-pollution reverse osmosis membrane according to claim 5, characterized in that: The surfactant is one or more of sodium lauryl sulfate, alkyl sulfonate, dodecylmethylbenzylammonium bromide, benzyldimethylphenylammonium chloride and benzyltrimethylammonium chloride.

7. The anti-pollution reverse osmosis membrane according to claim 5, characterized in that: The non-aqueous polar solvent is one or more of dimethyl sulfoxide, ethanol, methanol, acetonitrile, dimethylformamide, citric acid, oxalic acid and sodium hypochlorite.

8. The anti-pollution reverse osmosis membrane according to claim 1, characterized in that: The polyvalent acyl halide monomer is one or more of trimesoyl chloride, terephthaloyl chloride, phthaloyl chloride, isophthaloyl chloride, biphenyl dichloride and benzene disulfonyl chloride.

9. The anti-pollution reverse osmosis membrane according to claim 1, characterized in that: The content of the covalent organic framework material in the modified solution is 0.025-0.25 wt %.

10. A method for preparing an anti-pollution reverse osmosis membrane according to any one of claims 1 to 9, characterized in that: The following steps are involved: a) applying a casting solution to one side of a non-woven fabric layer, and then performing phase inversion curing 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 non-woven fabric layer; b) coating an aqueous solution on the front surface of the base film, and then drying until the aqueous solution on the surface of the base film is dry; c) coating an oil phase solution on the front surface of the base film on which the aqueous phase has dried, and then performing a heat curing treatment to form a polyamide separation layer; d) coating a modification liquid on the surface of the polyamide separation layer to form a modified polyamide separation layer, thereby obtaining an anti-fouling reverse osmosis membrane.