A long-lasting reverse osmosis RO membrane filter material and its preparation method

Abstract

The present application relates to the field of reverse osmosis (RO) membranes, and more specifically, to a long-lasting reverse osmosis (RO) membrane filter material and a method for preparing the same. A long-lasting reverse osmosis (RO) membrane filter material is a polyamide reverse osmosis membrane grafted with a small molecule modifier, wherein the small molecule modifier is a mixture of one or more of L-O-phosphoserine, sodium alendronate, and 3-aminopropane sulfonic acid, and the polyamide reverse osmosis layer is further embedded with graphite-phase carbon nitride-titanium dioxide. The long-lasting reverse osmosis (RO) membrane filter material of the present application has both excellent resistance to silica scale and organic pollution, as well as high water flux and high desiliconization rate.

Description

Technical Field

[0001] The present invention relates to the field of reverse osmosis (RO) membranes, and more specifically, to a long-lasting reverse osmosis (RO) membrane filter material and a preparation method thereof. Background Art

[0002] Reverse osmosis (RO) membranes are artificially synthesized, semipermeable membranes with specific properties. They allow solvents to pass through, but prevent solutes from passing through. They are the core component of RO technology. RO membranes have extremely small pore sizes, ranging from 0.5 to 10 nm, effectively removing various contaminants from water, including microorganisms and salts, thereby purifying the water.

[0003] Polyamide reverse osmosis membranes are one of the mainstream RO membranes used in membrane-based water treatment, and aromatic polyamide membranes are the primary type of polyamide reverse osmosis membrane. The molecular chain backbone of aromatic polyamide membrane materials is composed of alternating benzene rings and amide groups. The presence of benzene rings restricts the inward rotation of the molecular chains within the system, while the presence of highly polar amide groups forms hydrogen bonds between the molecular chains, enhancing the interaction between the molecular chains. This, in turn, contributes to the aromatic polyamide reverse osmosis membrane's excellent permeability selectivity and stability.

[0004] However, although polyamide reverse osmosis membranes have the advantages of high water flux, high salt rejection rate, and high stability, they are still often affected by pollutants in the water. Among them, silica scale is one of the most difficult fouling to deal with in the reverse osmosis system. Once silica scale is formed, it will cause a serious decrease in membrane flux. The treatment of silica scale requires expensive chemical and mechanical cleaning. Therefore, there is an urgent need for a long-lasting reverse osmosis RO membrane with excellent anti-silicon scale performance. Summary of the Invention

[0005] In order to improve the defect of poor anti-silicon performance of conventional reverse osmosis RO membranes, the present application provides a long-lasting reverse osmosis RO membrane filter material and a preparation method thereof.

[0006] In the first aspect, the present application provides a long-lasting reverse osmosis (RO) membrane filter material, which adopts the following technical solution:

[0007] A long-lasting reverse osmosis (RO) membrane filter material is a polyamide reverse osmosis membrane grafted with a small molecule modifier, wherein the small molecule modifier is one or a mixture of LO-phosphoserine, sodium alendronate, and 3-aminopropane sulfonic acid, and graphite phase carbon nitride-titanium dioxide is also embedded in the polyamide reverse osmosis layer.

[0008] The scaling mechanism of silica on the membrane surface is complex. The main reason is that silica can spontaneously undergo condensation reactions, thereby producing silicic acid dimers, trimers, polymers and particles. These polysilicic acids usually deposit and grow on the membrane surface. At the same time, the deposition of colloidal silica also plays an important role in the formation of silica scale. At the same time, silica scale usually tends to form at the same time as other organic pollutants. Therefore, while improving the anti-silicon scale performance of the reverse osmosis membrane, it is also necessary to also maintain the anti-organic fouling performance of the reverse osmosis membrane.

[0009] In the present application, small molecules are grafted onto the acyl chloride groups and amino groups on the surface of the polyamide reverse osmosis membrane to graft LO-phosphoserine, sodium alendronate and 3-aminopropane sulfonic acid into the reverse osmosis membrane, thereby causing the surface of the prepared reverse osmosis membrane to carry more negative charges, thereby producing a stronger charge repulsion effect on negatively charged organic pollutants and negatively charged silicic acid molecules.

[0010] At the same time, small molecule grafting modification also promotes the formation of a hydration layer on the surface of the reverse osmosis membrane, thereby reducing the direct contact between the membrane surface and pollutants; in addition, small molecule grafting modification also makes the surface of the reverse osmosis membrane smoother, effectively reducing the specific surface area of ​​the reverse osmosis membrane, reducing the sites for pollutant attachment, and promoting the formation of a hydration layer, thereby further improving the reverse osmosis membrane's resistance to silica scale and organic pollution.

[0011] Among them, the reason for the smoother surface of the reverse osmosis membrane may be that the peak-valley structure on the surface of the reverse osmosis membrane is mainly formed during the interfacial polymerization process, and small molecule grafting modification can affect the structure of the membrane surface to a certain extent, that is, the density of the acyl chloride groups on the surface of the reverse osmosis membrane is greatly reduced, thereby affecting the cross-linking of the acyl chloride groups and amino groups during the heat treatment process, thereby showing a smoother reverse osmosis membrane surface.

[0012] The reason for the generation of the hydration layer and the formation of negative charge is that the small molecule grafting modification enables the reverse osmosis membrane surface to obtain a large number of hydrophilic groups, phosphate and sulfonate, which, combined with the smooth effect of the reverse osmosis membrane surface, effectively promotes the formation of the hydration layer; at the same time, phosphate and sulfonate have extremely strong negative electronegativity, thereby effectively promoting the generation of negative charge.

[0013] While improving the anti-silicon scale and anti-organic pollution performance of the reverse osmosis membrane, the water flux and desalination rate of the reverse osmosis membrane itself also need to be paid attention to, that is, the modification of the reverse osmosis membrane should not significantly reduce the water flux and desalination rate of the reverse osmosis membrane.

[0014] However, the grafting of small molecules also increases the density of the polyamide selective layer. Furthermore, to improve the desiliconization rate of the polyamide selective layer, the thickness of the polyamide selective layer must be increased, which in turn reduces the water permeability of the reverse osmosis membrane. Inspired by the high-speed transmembrane transport of water molecules in cell membranes, the applicants embedded water channel materials in the polyamide selective layer to improve its water permeability.

[0015] Graphitic carbon nitride is a two-dimensional graphene-like nanosheet structure. When combined with titanium dioxide to form a complex, the interlayer spacing between the nanosheets can serve as additional water channels. Furthermore, the layered network contains regularly distributed triangular nanopores and planar structural defects, which accelerate the rapid penetration of water molecules. Furthermore, as an amphiphilic polymer, graphitic carbon nitride possesses amphiphilic properties similar to those of phospholipid plug molecules, which makes the graphitic carbon nitride-titanium dioxide more compatible with the reverse osmosis membrane matrix, meaning that it is better dispersed within the reverse osmosis membrane matrix, further enhancing the water permeability of the reverse osmosis membrane.

[0016] Preferably, the small molecule modifier is a mixture of LO-phosphoserine, sodium alendronate and 3-aminopropane sulfonic acid.

[0017] Preferably, the content ratio of LO-phosphoserine, alendronate sodium and 3-aminopropane sulfonic acid is (1-2): (1-2): (2-4).

[0018] When the small molecule modifier is a mixture of LO-phosphoserine, sodium alendronate and 3-aminopropane sulfonic acid, and the content ratio of LO-phosphoserine, sodium alendronate and 3-aminopropane sulfonic acid is as mentioned above, the surface of the prepared long-term reverse osmosis RO membrane will be grafted with more hydrophilic phosphate and sulfonate groups, thereby further promoting the formation of a hydration layer and significantly improving the negative charge of the long-term reverse osmosis RO membrane, and further improving the smoothness of the surface of the long-term reverse osmosis RO membrane, thereby effectively improving the anti-silicon scale performance and anti-organic pollution performance of the long-term reverse osmosis RO membrane.

[0019] Preferably, the preparation method of the graphite phase carbon nitride-titanium dioxide is:

[0020] First, titanium sulfate is added to the graphene carbon nitride aqueous solution, followed by ultrasonication in an ice-water bath for 20-30 minutes. The mixture is then transferred to 50-70°C and stirred for 24 hours. The mixture is then washed with water until neutral, centrifuged with concentrated acid, and cooled to obtain graphite carbon nitride-titanium dioxide.

[0021] Preferably, the amount of the graphene carbon nitride aqueous solution added is 400-600 ml, the concentration of the graphene carbon nitride aqueous solution is 1 mg / ml, and the amount of the titanium sulfate added is 500-2500 mg.

[0022] In a second aspect, the present application provides a method for preparing a long-lasting reverse osmosis (RO) membrane filter material, which adopts the following technical solution:

[0023] A method for preparing a long-lasting reverse osmosis (RO) membrane filter material comprises the following steps:

[0024] S1. First, pour the aqueous solution onto the surface of the polysulfone-based membrane, let it stand for 30-40 seconds, and then pour it out. The aqueous solution contains graphite carbon nitride-titanium dioxide, m-phenylenediamine, sodium dodecylsulfonate and triethylamine;

[0025] S2, removing the aqueous phase solution on the surface of the polysulfone-based membrane, and then pouring the organic phase solution on the surface of the polysulfone-based membrane, standing for 30-40 seconds and then pouring it out, the organic phase solution is a solution of trimesoyl chloride in n-heptane;

[0026] S3. Use n-hexane to clean the surface of the polysulfone-based membrane, and pour the small molecule modifier aqueous solution on the surface of the polysulfone-based membrane, let it stand for 4-6 minutes, then pour out the modifier aqueous solution, and clean the surface of the polysulfone-based membrane with deionized water. Finally, transfer the polysulfone-based membrane to a temperature of 80-90°C for heat treatment for 4-6 minutes, and finally soak it in deionized water for 10-15 minutes, take it out and dry it to obtain a long-lasting reverse osmosis RO membrane filter material.

[0027] Preferably, in the aqueous solution of the small molecule modifier, the content of the small molecule modifier is 0.3-0.5 wt %, and in the organic phase solution, the content of the trimesoyl chloride is 0.1-0.2 wt %;

[0028] In the aqueous solution, the content of m-phenylenediamine is 2-4 wt %, and the content of graphite carbon nitride-titanium dioxide is 0.01-0.05 wt %.

[0029] Preferably, in the aqueous solution of the small molecule modifier, the content of the small molecule modifier is 0.4wt%, in the organic phase solution, the content of trimesoyl chloride is 0.15wt%; in the aqueous phase solution, the content of m-phenylenediamine is 3.2wt%, and the content of the graphite phase carbon nitride-titanium dioxide is 0.02wt%.

[0030] When the small molecule modifier, trimesoyl chloride, m-phenylenediamine and graphite phase carbon nitride-titanium dioxide are used in the above-mentioned contents, the prepared reverse osmosis membrane will have more balanced anti-silicon scale performance, anti-organic pollution performance, desiliconization rate and water flux.

[0031] Preferably, the aqueous phase solution contains 1-2 wt% triethylamine and 0.05-0.15 wt% sodium lauryl sulfate.

[0032] In summary, this application has the following beneficial effects:

[0033] 1. In the present application, LO-phosphoserine, sodium alendronate, and 3-aminopropane sulfonic acid are grafted into the reverse osmosis membrane by modifying the acyl chloride groups and amino groups on the surface of the polyamide reverse osmosis membrane with small molecules, thereby causing the surface of the prepared reverse osmosis membrane to carry more negative charges, thereby generating a stronger charge repulsion effect on negatively charged organic pollutants and negatively charged silicic acid molecules;

[0034] At the same time, small molecule grafting modification also promotes the formation of a hydration layer on the surface of the reverse osmosis membrane, thereby reducing the direct contact between the membrane surface and pollutants; in addition, small molecule grafting modification also makes the surface of the reverse osmosis membrane smoother, effectively reducing the specific surface area of ​​the reverse osmosis membrane, reducing the sites for pollutant attachment, and promoting the formation of a hydration layer, thereby further improving the reverse osmosis membrane's resistance to silica scale and organic pollution.

[0035] 2. Graphitic carbon nitride is a two-dimensional graphene-like nanosheet structure. When it forms a complex with titanium dioxide, the interlayer spacing between the nanosheets can serve as additional water channels, and there are regularly distributed triangular nanopores and planar structural defects on the layered network. These channels can accelerate the rapid penetration of water molecules. At the same time, as an amphiphilic polymer, graphitic carbon nitride has the amphiphilicity of phospholipid plug molecules, which makes graphitic carbon nitride-titanium dioxide more compatible with the reverse osmosis membrane matrix, that is, better dispersed in the reverse osmosis membrane matrix, thereby further improving the water permeability of the reverse osmosis membrane.

[0036] 3. When the small molecule modifier is a mixture of LO-phosphoserine, sodium alendronate and 3-aminopropane sulfonic acid, and the content ratio of LO-phosphoserine, sodium alendronate and 3-aminopropane sulfonic acid is as mentioned above, the surface of the prepared long-term reverse osmosis RO membrane will be grafted with more hydrophilic groups such as phosphate and sulfonate, thereby further promoting the formation of a hydration layer and significantly improving the negative charge of the long-term reverse osmosis RO membrane, and further improving the smoothness of the surface of the long-term reverse osmosis RO membrane, thereby effectively improving the anti-silicon scale performance and anti-organic pollution performance of the long-term reverse osmosis RO membrane. DETAILED DESCRIPTION

[0037] The present application is further described in detail below in conjunction with Examples 1 to 8 and Comparative Examples 1 and 2.

[0038] raw material

[0039] LO-phosphoserine, sodium alendronate, 3-aminopropane sulfonic acid, m-phenylenediamine, sodium dodecylsulfonate and triethylamine were purchased from Aladdin Reagent (China) Co., Ltd.; trimesoyl chloride was purchased from J&K (China) Technology Co., Ltd.; n-heptane was purchased from Tianjin Jiangtian Chemical Technology Co., Ltd.; graphene carbon nitride was purchased from Guangdong Yuanfeng Chemical Reagent Co., Ltd.; titanium sulfate was purchased from Xilong Chemical Co., Ltd.; the polysulfone-based membrane had a pore size of 9-12 nm from Times Wharton Company.

[0040] Example

[0041] Example 1

[0042] A long-lasting reverse osmosis (RO) membrane filter material is a polyamide reverse osmosis membrane grafted with a small molecule modifier; the small molecule modifier is a mixture of LO-phosphoserine, sodium alendronate, and 3-aminopropane sulfonic acid, and graphite phase carbon nitride-titanium dioxide is also embedded in the polyamide reverse osmosis layer.

[0043] The preparation method of long-lasting reverse osmosis RO membrane filter material comprises the following steps:

[0044] S1. First, pour the aqueous solution onto the surface of the polysulfone-based membrane, let it stand for 30 seconds and then pour it out. The aqueous solution contains graphite phase carbon nitride-titanium dioxide, m-phenylenediamine, sodium dodecylsulfonate and triethylamine;

[0045] In the aqueous solution, the content of m-phenylenediamine is 3.2 wt %, the content of graphite carbon nitride-titanium dioxide is 0.02 wt %, the content of triethylamine is 1.5 wt %, and the content of sodium dodecylsulfonate is 0.1 wt %;

[0046] S2, removing the aqueous phase solution on the surface of the polysulfone-based membrane, and then pouring the organic phase solution on the surface of the polysulfone-based membrane, standing for 30-40 seconds and then pouring it out, the organic phase solution is a n-heptane solution of trimesoyl chloride, and the content of trimesoyl chloride is 0.15wt%;

[0047] S3. Use n-hexane to clean the surface of the polysulfone-based membrane, and pour the small molecule modifier aqueous solution on the surface of the polysulfone-based membrane and let it stand for 4-6 minutes;

[0048] The small molecule modifier is a mixture of LO-phosphoserine, sodium alendronate and 3-aminopropane sulfonic acid, and the content ratio of LO-phosphoserine, sodium alendronate and 3-aminopropane sulfonic acid is 1:1:2;

[0049] Then, the modifier aqueous solution was poured out, and the surface of the polysulfone-based membrane was washed with deionized water. Finally, the polysulfone-based membrane was transferred to 80° C. for heat treatment for 5 minutes, and finally immersed in deionized water for 15 minutes, taken out and dried to obtain a long-lasting reverse osmosis RO membrane filter material.

[0050] Wherein, the preparation method of graphite phase carbon nitride-titanium dioxide is:

[0051] First, 1500 mg of titanium sulfate was added to 500 ml of a 1 mg / ml graphene carbon nitride aqueous solution. The mixture was then ultrasonicated in an ice-water bath for 30 minutes. The mixture was then transferred to 60°C and stirred for 24 hours. The mixture was then washed with water until neutral, centrifuged, and cooled in concentrated acid to obtain graphite carbon nitride-titanium dioxide.

[0052] Example 2

[0053] The difference from Example 1 is that the small molecule modifier is only LO-phosphoserine.

[0054] Example 3

[0055] The difference from Example 1 is that the small molecule modifier is only sodium alendronate.

[0056] Example 4

[0057] The difference from Example 1 is that the small molecule modifier is only 3-aminopropanesulfonic acid.

[0058] Example 5

[0059] The difference from Example 1 is that the content ratio of LO-phosphoserine, alendronate sodium and 3-aminopropane sulfonic acid is 1:2:4.

[0060] Example 6

[0061] The difference from Example 1 is that the content ratio of LO-phosphoserine, alendronate sodium and 3-aminopropane sulfonic acid is 2:1:2.

[0062] Example 7

[0063] The difference from Example 1 is that in the aqueous solution of the small molecule modifier, the content of the small molecule modifier is 0.3wt%, in the organic phase solution, the content of trimesoyl chloride is 0.2wt%; in the aqueous phase solution, the content of m-phenylenediamine is 2wt%, and the content of graphite phase carbon nitride-titanium dioxide is 0.01wt%.

[0064] Example 8

[0065] The difference from Example 1 is that in the aqueous solution of the small molecule modifier, the content of the small molecule modifier is 0.5wt%, in the organic phase solution, the content of trimesoyl chloride is 0.1wt%; in the aqueous phase solution, the content of m-phenylenediamine is 4wt%, and the content of graphite phase carbon nitride-titanium dioxide is 0.05wt%.

[0066] Comparative Example

[0067] Comparative Example 1

[0068] The difference from Example 1 is that no small molecule modifier is added.

[0069] Comparative Example 2

[0070] The difference from Example 1 is that graphite phase carbon nitride-titanium dioxide is no longer added.

[0071] Performance testing

[0072] 1. Anti-silicon scale and anti-organic pollution performance test

[0073] Sodium humate (HA) was selected as an organic pollutant model. The raw material solution contained 2000 mg / L NaCl, 500 mg / LMgCl2, 750 mg / L CaCl2, 340 mg / L Na2SiO3, and 10 mg / L HA. Three samples were then taken from Examples 1 to 8 and Comparative Example 1. The samples were pre-pressed at 1.7 MPa for 1.5 h, and then the raw material solution was introduced into the device. The process was carried out at 25°C and 1 L / min. The original permeation flux of the system was recorded, and the real-time pressure was also recorded and recorded as P0.

[0074] After continuously testing the flux for 24 hours, the raw material liquid was replaced with deionized water for cleaning at a cleaning flow rate of 1.2 L / min. After 90 minutes, the deionized water was replaced with the raw material liquid again, the system pressure was adjusted to P0, the real-time permeation flux was measured, and finally the flux decline rate was calculated.

[0075] Flux recovery rate = (original permeation flux - real-time permeation flux) / original permeation flux × 100%.

[0076] The test data are shown in Table 1.

[0077] Table 1 Test table of anti-silicon scale and anti-organic pollution performance of Example 1 to Example 8 and Comparative Example 1

[0078] Flux decline rate / % Flux decline rate / % Example 1 31％ Example 6 35％ Example 2 47％ Example 7 38％ Example 3 45％ Example 8 30％ Example 4 41％ Comparative Example 1 54％ Example 5 33％

[0079] 2. Permeation flux and desiliconization rate test

[0080] Three samples were taken from Example 1, Example 7-Example 8 and Comparative Example 2, respectively. Then, a 340 mg / L Na2SiO3 aqueous solution was used as the stock solution to be filtered. The permeation flux and desiliconization rate of the samples were tested through a cross-flow filter (Unite) at a pressure of 1.55 MPa. The test data are shown in Table 2.

[0081] Table 2 Permeation flux and desiliconization rate test table of Example 1, Examples 7-8 and Comparative Example 2

[0082] <![CDATA[Permeation flux (L·m -2 ·h -1 )]]> Desiliconization rate / % Example 1 86.71 97.9％ Example 7 83.67 98.1％ Example 8 87.98 97.6％ Comparative Example 2 62.19 98.3％

[0083] From Examples 1 to 4 and Comparative Example 1 in combination with Table 1, it can be seen that relative to Comparative Example 1, the flux reduction rates of Examples 1 to 4 are significantly reduced, which shows that the addition of small molecule modifiers can effectively improve the anti-silicon scale performance and anti-organic pollution performance of the reverse osmosis membrane.

[0084] The reason is that LO-phosphoserine, sodium alendronate and 3-aminopropane sulfonic acid are grafted into the reverse osmosis membrane through the acyl chloride groups and amino groups on the surface of the polyamide reverse osmosis membrane, thereby causing the surface of the prepared reverse osmosis membrane to carry more negative charges, thereby producing a stronger charge repulsion effect on negatively charged organic pollutants and negatively charged silicic acid molecules.

[0085] At the same time, small molecule grafting modification also promotes the formation of a hydration layer on the surface of the reverse osmosis membrane, thereby reducing the direct contact between the membrane surface and pollutants; in addition, small molecule grafting modification also makes the surface of the reverse osmosis membrane smoother, effectively reducing the specific surface area of ​​the reverse osmosis membrane, reducing the sites for pollutant attachment, and promoting the formation of a hydration layer, thereby further improving the reverse osmosis membrane's resistance to silica scale and organic pollution.

[0086] Among them, the reason for the smoother surface of the reverse osmosis membrane may be that the peak-valley structure on the surface of the reverse osmosis membrane is mainly formed during the interfacial polymerization process, and small molecule grafting modification can affect the structure of the membrane surface to a certain extent, that is, the density of the acyl chloride groups on the surface of the reverse osmosis membrane is greatly reduced, thereby affecting the cross-linking of the acyl chloride groups and amino groups during the heat treatment process, thereby showing a smoother reverse osmosis membrane surface.

[0087] The reason for the generation of the hydration layer and the formation of negative charge is that the small molecule grafting modification enables the reverse osmosis membrane surface to obtain a large number of hydrophilic groups, phosphate and sulfonate, which, combined with the smooth effect of the reverse osmosis membrane surface, effectively promotes the formation of the hydration layer; at the same time, phosphate and sulfonate have extremely strong negative electronegativity, thereby effectively promoting the generation of negative charge.

[0088] Compared with Example 1, the flux decrease rates of Examples 2 to 4 are slightly improved, which shows that compared with the addition of LO-phosphoserine, sodium alendronate or 3-aminopropane sulfonic acid alone, the mixed addition of LO-phosphoserine, sodium alendronate and 3-aminopropane sulfonic acid can further improve the anti-silicon scale and anti-organic pollution performance of the reverse osmosis membrane.

[0089] At the same time, referring to Example 1 and Example 5-Example 6 and combining with Table 1, it can be seen that compared with Example 1, the flux decrease rate of Example 5-Example 6 is also slightly improved. This shows that when LO-phosphoserine, sodium alendronate and 3-aminopropane sulfonic acid use the content ratio of Example 1, the prepared reverse osmosis membrane will have better resistance to silica scale and organic pollution.

[0090] The reason is that when the small molecule modifier is a mixture of LO-phosphoserine, sodium alendronate and 3-aminopropane sulfonic acid, and the LO-phosphoserine, sodium alendronate and 3-aminopropane sulfonic acid are used in the above-mentioned content ratio, the surface of the prepared long-term reverse osmosis RO membrane will be grafted with more hydrophilic groups such as phosphate and sulfonate, thereby further promoting the formation of a hydration layer and significantly improving the negative charge of the long-term reverse osmosis RO membrane, and further improving the smoothness of the surface of the long-term reverse osmosis RO membrane, thereby effectively improving the anti-silicon scale performance and anti-organic pollution performance of the long-term reverse osmosis RO membrane.

[0091] Referring to Example 1 and Comparative Example 2 and combining with Table 2, it can be seen that relative to Example 1, the permeation flux of Comparative Example 2 is significantly reduced, while the desiliconization rate is only slightly increased. This shows that the addition of graphite phase carbon nitride-titanium dioxide can effectively improve the water permeability of the reverse osmosis membrane without significantly affecting the desiliconization rate of the reverse osmosis membrane.

[0092] The reason is that the grafting modification of small molecules will also lead to an increase in the density of the polyamide selective layer. In addition, in order to increase the desiliconization rate of the polyamide selective layer, the thickness of the polyamide selective layer has to be increased, which in turn leads to a decrease in the water permeability of the reverse osmosis membrane.

[0093] Graphitic carbon nitride is a two-dimensional graphene-like nanosheet structure. When combined with titanium dioxide to form a complex, the interlayer spacing between the nanosheets can serve as additional water channels. Furthermore, the layered network contains regularly distributed triangular nanopores and planar structural defects, which accelerate the rapid penetration of water molecules. Furthermore, as an amphiphilic polymer, graphitic carbon nitride possesses amphiphilic properties similar to those of phospholipid plug molecules, which makes the graphitic carbon nitride-titanium dioxide more compatible with the reverse osmosis membrane matrix, meaning that it is better dispersed within the reverse osmosis membrane matrix, further enhancing the water permeability of the reverse osmosis membrane.

[0094] With reference to Example 1 and Example 7-Example 8 and in combination with Table 1-Table 2, it can be seen that, compared with Example 1, Examples 1-Example 8 are insufficient in flux reduction rate, permeation flux or desiliconization rate, that is, Example 1 has more balanced anti-silicon scale and anti-organic pollution performance, water permeability and desiliconization rate.

[0095] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A long-lasting reverse osmosis RO membrane filter material, characterized in that: The invention relates to a polyamide reverse osmosis membrane grafted with a small molecule modifier, wherein the small molecule modifier is one of LO-phosphoserine, sodium alendronate and 3-aminopropane sulfonic acid, or the content ratio of LO-phosphoserine, sodium alendronate and 3-aminopropane sulfonic acid is (1-2): (1-2): (2-4), and graphite phase carbon nitride-titanium dioxide is also embedded in the polyamide reverse osmosis layer; The preparation method of the graphite phase carbon nitride-titanium dioxide is: First, titanium sulfate is added to the graphene carbon nitride aqueous solution, followed by ultrasonication in an ice-water bath for 20-30 minutes, then transferred to 50-70°C and stirred for 24 hours, then washed with water until neutral, centrifuged with concentrated acid and cooled to obtain graphite phase carbon nitride-titanium dioxide; The addition amount of the graphene carbon nitride aqueous solution is 400-600 ml, the concentration of the graphene carbon nitride aqueous solution is 1 mg / ml, and the addition amount of the titanium sulfate is 500-2500 mg.

2. A method for preparing the long-lasting reverse osmosis RO membrane filter material according to claim 1, characterized in that: The following steps are involved: S1. First, pour the aqueous solution onto the surface of the polysulfone-based membrane, let it stand for 30-40 seconds, and then pour it out. The aqueous solution contains graphite carbon nitride-titanium dioxide, m-phenylenediamine, sodium dodecylsulfonate and triethylamine; S2, removing the aqueous phase solution on the surface of the polysulfone-based membrane, and then pouring the organic phase solution on the surface of the polysulfone-based membrane, standing for 30-40 seconds and then pouring it out, the organic phase solution is a solution of trimesoyl chloride in n-heptane; S3. Use n-hexane to clean the surface of the polysulfone-based membrane, and pour the small molecule modifier aqueous solution on the surface of the polysulfone-based membrane, let it stand for 4-6 minutes, then pour out the modifier aqueous solution, and clean the surface of the polysulfone-based membrane with deionized water. Finally, transfer the polysulfone-based membrane to a temperature of 80-90°C for heat treatment for 4-6 minutes, and finally soak it in deionized water for 10-15 minutes, take it out and dry it to obtain a long-lasting reverse osmosis RO membrane filter material.

3. The method for preparing a long-lasting reverse osmosis RO membrane filter material according to claim 2, wherein: In the aqueous solution of the small molecule modifier, the content of the small molecule modifier is 0.3-0.5wt%, in the organic phase solution, the content of trimesoyl chloride is 0.1-0.2wt%; in the aqueous phase solution, the content of m-phenylenediamine is 2-4wt%, and the content of the graphite phase carbon nitride-titanium dioxide is 0.01-0.05wt%.

4. The method for preparing a long-lasting reverse osmosis RO membrane filter material according to claim 3, wherein: In the aqueous solution of the small molecule modifier, the content of the small molecule modifier is 0.4 wt %, in the organic phase solution, the content of trimesoyl chloride is 0.15 wt %; in the aqueous phase solution, the content of m-phenylenediamine is 3.2 wt %, and the content of the graphite phase carbon nitride-titanium dioxide is 0.02 wt %.

5. The method for preparing a long-lasting reverse osmosis RO membrane filter material according to claim 4, wherein: In the aqueous phase solution, the content of triethylamine is 1-2 wt %, and the content of sodium dodecylsulfonate is 0.05-0.15 wt %.