A reverse osmosis membrane with coral-like structure and its preparation method and application

Abstract

The present invention relates to the field of membrane separation technology, and in particular to a reverse osmosis membrane with a coral-like structure, and a preparation method and application thereof. The reverse osmosis membrane comprises a base membrane and a separation layer arranged in sequence; the microscopic morphology of the separation layer comprises a coral-like structure, a nodular structure and a blade-like structure. The reverse osmosis membrane with a coral-like structure can increase its effective surface area, increase water transmission channels, and reduce water transmission resistance, thereby significantly improving the water flux of the reverse osmosis membrane without reducing its salt retention rate.

Description

Technical Field

[0001] The invention relates to the technical field of membrane separation, and in particular to a reverse osmosis membrane with a coral-like structure and a preparation method and application thereof. Background Art

[0002] As a new and efficient chemical separation technology in contemporary times, membrane separation technology plays an important role in solving the water resource crisis. Reverse osmosis membrane is one of the important types of separation membranes used in water treatment processes. It has been widely used in seawater / brackish water desalination, ultrapure water preparation, wastewater treatment and other fields. The typical structure of a reverse osmosis membrane consists of a bottom layer of polyester non-woven fabric, an intermediate layer of polysulfone ultrafiltration membrane and an upper separation layer. It is generally believed that the separation layer determines the separation performance of the membrane and contributes most of the mass transfer resistance. Therefore, the optimization of the separation layer structure has always been a research hotspot. Under the premise of ensuring a high retention rate, increasing the flux is crucial to improving the efficiency of the reverse osmosis membrane process, reducing the cost of the reverse osmosis membrane process and expanding the application range of the reverse osmosis membrane.

[0003] The introduction of co-solvents into the organic phase is a commonly used method for optimizing the structure of reverse osmosis membranes. A typical reverse osmosis membrane is formed by the interfacial polymerization of trimesoyl chloride and m-phenylenediamine on the surface of polysulfone. During the formation of the reverse osmosis membrane, the interfacial polymerization reaction occurs on the organic phase side of the two-phase interface. The structure of the polyamide can be adjusted by adjusting the diffusion rate of m-phenylenediamine from the aqueous phase to the organic phase. The introduction of co-solvents into the organic phase enhances the miscibility between the aqueous phase and the organic phase, thereby promoting the diffusion rate of m-phenylenediamine monomers into the organic phase. Currently available organic phase co-solvents include ethyl acetate, γ-valerolactone, dimethyl carbonate, ethyl silicate, etc. (CN114950165A, CN111569675A, CN109985531A). The addition of these co-solvents causes the morphological characteristics of the separation layer of the reverse osmosis membrane to evolve from the typical tightly packed "nodular" structure to a larger "leaf-like" structure, thereby improving the water flux of the reverse osmosis membrane. However, these traditional co-solvents have limited effects on improving the water flux of reverse osmosis membranes, and further increasing their flux will lead to a decrease in salt retention. In order to significantly increase the water flux of reverse osmosis membranes without reducing their salt retention, it is necessary to further optimize the structure and preparation method of reverse osmosis membranes. Summary of the invention

[0004] The first object of the present invention is to provide a reverse osmosis membrane with a coral-like structure, which can significantly improve the water flux of the reverse osmosis membrane without reducing the salt retention rate.

[0005] The second object of the present invention is to provide a method for preparing a reverse osmosis membrane having a coral-like structure, which has simple steps and is easy to practice.

[0006] The third purpose of the present invention is to provide an application of a reverse osmosis membrane with a coral-like structure, which has broad application prospects.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A reverse osmosis membrane with a coral-like structure comprises a base membrane and a separation layer arranged in sequence; the microscopic morphology of the separation layer comprises a coral-like structure, a nodule-like structure and a blade-like structure; the separation layer is a polyamide layer formed by interfacial polymerization; the coral-like structure is formed by stacking multiple layers of spherical particles, the spherical particles have an outer diameter of 20-150nm, have a hollow or non-hollow structure, the wall thickness of the spherical particles is 10-60nm, and the apparent thickness of the coral-like structure is 20-1000nm.

[0009] The "coral-like" structure contained in the reverse osmosis membrane obtained by the present invention is formed by stacking multiple layers (≥2 layers) of spherical particles, the outer diameter of the spherical particles is 20-150nm, and they have a hollow or non-hollow structure. The wall thickness of the spherical particles (i.e., the intrinsic thickness of the "coral-like" structure) is 10-60nm, and the maximum apparent thickness of the "coral-like" structure is 20-1000nm. The coral-like structure of the reverse osmosis membrane of the present invention can increase the effective surface area of ​​the reverse osmosis membrane, increase the water transmission channel, and reduce the water transmission resistance, thereby significantly improving the water flux of the reverse osmosis membrane without reducing its salt retention rate.

[0010] Furthermore, the area of ​​the coral-like structure accounts for 0.001%-99.999% of the total surface area of ​​the separation membrane.

[0011] Furthermore, the area of ​​the coral-like structure accounts for 3%-80% of the total surface area of ​​the separation membrane.

[0012] The permeable membrane obtained by the present invention is a multi-structure, and the area of ​​the region containing the "coral-like" structure in the multi-structure accounts for 0.001% to 99.999% of the total surface area of ​​the separation membrane, preferably 3%-80%. In a preferred embodiment of the present invention, the area of ​​the region containing the "coral-like" structure accounts for 5%-60% of the total surface area of ​​the separation membrane.

[0013] The method for preparing the above-mentioned reverse osmosis membrane having a coral-like structure comprises the following steps:

[0014] The base film is immersed in an aqueous solution, and the residual solution on the surface is drained; then immersed in an organic solution for interfacial polymerization reaction, and the residual solution on the surface is drained and then heat treated;

[0015] The aqueous phase solution includes polyamine monomers and water; the organic phase solution includes polyacyl chloride monomers, alkane solvents, and co-solvents; the co-solvents are selected from one or two of ester compounds and ether compounds; the ester compounds all contain two or more ester functional groups and the carbon-oxygen ratio of the compound molecules is ≥2.5; the carbon-oxygen ratio of the ether compound molecules is ≥8. The organic phase solution of the present invention includes acyl chloride monomers, alkane solvents, and co-solvents. The use of alkane solvents and co-solvents can cause the obtained reverse osmosis membrane to have multiple structures of "coral-like", "leaf-like" and "nodular-like" at the same time.

[0016] Furthermore, the concentration of the co-solvent in the organic phase solution is 0.01-50wt%.

[0017] Through the above technical scheme, the proportion of the alkane solvent co-solvent is controlled and regulated, and the area of ​​the "coral-like" region in the separation layer accounts for 0.001% to 99.999% of the surface of the separation membrane, preferably 3%-80%. In a preferred embodiment of the present invention, the area of ​​the "coral-like" region accounts for 5%-60% of the surface of the separation membrane.

[0018] Further, the ester compound includes but is not limited to dibutyl oxalate, diisobutyl oxalate, dipentyl oxalate, diisopentyl oxalate, dibutyl malonate, diisobutyl malonate, dipentyl malonate, diisopentyl malonate, dibutyl succinate, diisobutyl succinate, dipentyl succinate, diisopentyl succinate, dibutyl fumarate, diisobutyl fumarate, dipentyl fumarate, diisopentyl fumarate, dibutyl maleate, diisobutyl maleate, dipentyl maleate, diisopentyl maleate, dipropyl glutarate, diisopropyl glutarate, dibutyl glutarate, diisobutyl glutarate, dipentyl glutarate, glutaric acid One or more of diisoamyl adipate, diethyl adipate, dipropyl adipate, diisopropyl adipate, dibutyl adipate, diisobutyl adipate, diamyl adipate, diisoamyl adipate, or one or more of the carbon chain isomers of the ester compounds; the ether compounds include but are not limited to one or more selected from phenyl ether, n-butyl phenyl ether, isobutyl phenyl ether, n-pentyl phenyl ether, isopentyl phenyl ether, n-hexyl phenyl ether, isohexyl phenyl ether, diphenyl ether, dibutyl ether, diisobutyl ether, diamyl ether, diisoamyl ether, dihexyl ether, diisohexyl ether, or one or more selected from the carbon chain isomers of the ether compounds.

[0019] Further, the concentration of the polyacyl chloride monomer in the organic phase solution is 0.01-5wt%; the polyacyl chloride monomer is selected from one or more of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, biphenyl dicarboxylic acid chloride, biphenyl trimoyl chloride, biphenyl tetracarboxylic acid chloride, naphthalene dicarboxylic acid chloride, naphthalene tricarboxylic acid chloride, naphthalene tetracarboxylic acid chloride, malonic acid chloride, succinic acid chloride, glutaric acid chloride, and adipic acid chloride; further, the concentration of the polyamine monomer in the aqueous phase solution is 0.5-5wt%; the polyamine monomer includes but is not limited to one or more selected from o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, diaminotoluene, ethylenediamine, propylenediamine, butylenediamine, diaminocyclohexane, and piperazine.

[0020] Furthermore, the interfacial polymerization reaction time is 1-300s; the heat treatment temperature is 40-150°C, and the heat treatment time is 0.1-10min.

[0021] Furthermore, the alkane solvent includes but is not limited to one or more selected from hexane, heptane, octane, nonane, decane, undecane, dodecane, Isopar C, Isopar E, Isopar G, Isopar H, Isopar L, and Isopar M; the base membrane is a porous membrane; the material of the porous membrane includes but is not limited to one selected from polysulfone, polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polyimide, polyetherimide, polyacrylonitrile, polyphenylene ether, polyphenylene sulfide, polyether ketone, and polyaryletherketone.

[0022] Furthermore, the aqueous solution also includes triethylamine and camphorsulfonic acid; the concentration of triethylamine in the aqueous solution is 0.5-3wt%, and the concentration of camphorsulfonic acid in the aqueous solution is 1-5wt%.

[0023] Application of the above reverse osmosis membrane with coral-like structure in the field of water treatment.

[0024] The beneficial technical effects of the present invention are:

[0025] 1. The present invention provides a reverse osmosis membrane with a coral-like structure, which has multiple structures of "coral-like", "leaf-like" and "nodular-like", wherein the "coral-like" structure is formed by stacking multiple layers (≥2 layers) of spherical particles, the outer diameter of the spherical particles is 20-150nm, and they have a hollow or non-hollow structure. The wall thickness of the spherical particles (i.e., the intrinsic thickness of the "coral-like" structure) is 10-60nm, and the apparent thickness of the "coral-like" structure is 20-1000nm. The area of ​​the "coral-like" structure accounts for 0.001%-99.999% of the total surface area of ​​the separation membrane. The coral-like structure of the reverse osmosis membrane can increase the effective surface area of ​​the reverse osmosis membrane, increase the water transmission channel, and reduce the water transmission resistance, thereby significantly improving the water flux of the reverse osmosis membrane without reducing its salt retention rate.

[0026] 2. The present invention provides a method for preparing the above-mentioned reverse osmosis membrane with a coral-like structure, wherein the organic phase solution used in the preparation process includes an acyl chloride monomer, an alkane solvent, and a co-solvent. The use of the alkane solvent and the co-solvent in combination can cause the prepared reverse osmosis membrane to have multiple structures of "coral-like", "leaf-like", and "nodular", and by adjusting the types and proportions of the alkane solvent and the co-solvent, the proportion of the area of ​​the "coral-like" structure in the total surface area of ​​the separation membrane can be adjusted.

[0027] 3. The preparation method of the coral-like reverse osmosis membrane of the present invention is simple and easy to mass produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The scanning electron microscope (SEM) images of the surface of the reverse osmosis membrane samples obtained in Comparative Example 1 and Examples 1-4 are shown; A0-4 correspond to Comparative Example 1 and Examples 1-4, respectively; Figure A in the figure is a SEM image magnified 1000 times, and Figures B and C in the figure are SEM images magnified 50000 times;

[0029] Figure 2 A1 and B1, A2 and B2, A3 and B3 are scanning electron microscope (SEM) images of the surface of the separation layer of the reverse osmosis membrane samples obtained in Comparative Example 1, Example 2, and Example 4, respectively, and transmission electron microscope (TEM) images of the cross-section; wherein the magnification of Figures A1-A3 is 50,000, and A1-A3 are the surface morphologies of the "nodular" structure, the "leaf-like" structure, and the "coral-like" structure, respectively; the magnification of Figures B1-B3 is 30,000, and B1-B3 are the cross-sectional morphologies of the "nodular" structure, the "leaf-like" structure, and the "coral-like" structure, respectively. DETAILED DESCRIPTION

[0030] The following is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or replacements can also be made, all of which should be deemed to belong to the protection scope of the present invention. The specific conditions not indicated in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, unless otherwise specified, are conventional products obtained through commercial channels.

[0031] Example

[0032] Example 1

[0033] This embodiment provides a reverse osmosis membrane with a coral-like structure, which includes a base membrane and a separation layer arranged in sequence; the microscopic morphology of the separation layer includes a coral-like structure, a nodule-like structure and a leaf-like structure.

[0034] This embodiment also provides a method for preparing the above-mentioned reverse osmosis membrane with a coral-like structure, and the specific preparation steps are as follows:

[0035] The polysulfone porous membrane was immersed in an aqueous solution for 10 seconds, and the residual solution on the surface was drained; then immersed in an organic solution for interfacial polymerization reaction for 10 seconds, and the residual solution on the surface was drained, and then the membrane was heat treated at 90°C for 8 minutes.

[0036] The aqueous phase solution is composed of 3wt% m-phenylenediamine, 1.9wt% triethylamine, 3.3wt% camphorsulfonic acid and water;

[0037] The organic phase solution consists of 0.21 wt % of trimesoyl chloride, 5 wt % of diisobutyl fumarate and Isopar G.

[0038] Example 2

[0039] This embodiment provides a reverse osmosis membrane with a coral-like structure, which includes a base membrane and a separation layer arranged in sequence; the microscopic morphology of the separation layer includes a coral-like structure, a nodule-like structure and a leaf-like structure.

[0040] This embodiment also provides a method for preparing the above-mentioned reverse osmosis membrane with a coral-like structure, and the specific preparation steps are as follows:

[0041] The polysulfone porous membrane was immersed in the aqueous solution for 10 seconds, and the residual solution on the surface was drained; then immersed in the organic solution for interfacial polymerization reaction for 20 seconds, and the residual solution on the surface was drained, and then the membrane was heat treated at 85°C for 6 minutes.

[0042] The aqueous phase solution is composed of 2wt% m-phenylenediamine, 1wt% triethylamine, 3wt% camphorsulfonic acid and water;

[0043] The organic phase solution consists of a mixture of 0.1 wt % of trimesoyl chloride and terephthaloyl chloride, 10 wt % of diisobutyl fumarate and Isopar L; the dosage ratio of trimesoyl chloride to terephthaloyl chloride is 5:1.

[0044] Example 3

[0045] This embodiment provides a reverse osmosis membrane with a coral-like structure, which includes a base membrane and a separation layer arranged in sequence; the microscopic morphology of the separation layer includes a coral-like structure, a nodule-like structure and a leaf-like structure.

[0046] This embodiment also provides a method for preparing the above-mentioned reverse osmosis membrane with a coral-like structure, and the specific preparation steps are as follows:

[0047] The polyethersulfone porous membrane is immersed in the aqueous solution for 10 seconds, and the residual solution on the surface is drained; then immersed in the organic solution for interfacial polymerization reaction for 30 seconds, the residual solution on the surface is drained, and then the membrane is heat treated at 95°C for 5 minutes. The aqueous solution is composed of a mixture of 4wt% m-phenylenediamine and o-phenylenediamine, 2wt% triethylamine, 4wt% camphorsulfonic acid and water, and the ratio of m-phenylenediamine to o-phenylenediamine is 5:1;

[0048] The organic phase solution consists of 0.3 wt % of trimesoyl chloride, 5 wt % of dibutyl fumarate and n-dodecane.

[0049] Example 4

[0050] This embodiment provides a reverse osmosis membrane with a coral-like structure, which includes a base membrane and a separation layer arranged in sequence; the microscopic morphology of the separation layer includes a coral-like structure, a nodule-like structure and a leaf-like structure.

[0051] This embodiment also provides a method for preparing the above-mentioned reverse osmosis membrane with a coral-like structure, and the specific preparation steps are as follows:

[0052] The polysulfone porous membrane was immersed in an aqueous solution for 10 seconds, and the residual solution on the surface was drained; then immersed in an organic solution for interfacial polymerization reaction for 10 seconds, and the residual solution on the surface was drained, and then the membrane was heat treated at 90°C for 6 minutes.

[0053] The aqueous phase solution is composed of 3wt% m-phenylenediamine, 1.9wt% triethylamine, 3.3wt% camphorsulfonic acid and water;

[0054] The organic phase solution consists of 0.21 wt % of trimesoyl chloride, 10 wt % of dibutyl fumarate and Isopar G.

[0055] Example 5

[0056] This embodiment provides a reverse osmosis membrane with a coral-like structure. The reverse osmosis membrane includes a base membrane and a separation layer arranged in sequence. The microscopic morphology of the separation layer includes a coral-like structure, a nodule-like structure and a leaf-like structure.

[0057] This embodiment also provides a method for preparing the above-mentioned reverse osmosis membrane with a coral-like structure, and the specific preparation steps are as follows:

[0058] The polysulfone porous membrane was immersed in an aqueous solution for 10 seconds, and the residual solution on the surface was drained; then immersed in an organic solution for interfacial polymerization reaction for 10 seconds, and the residual solution on the surface was drained, and then the membrane was heat treated at 90°C for 6 minutes.

[0059] The aqueous phase solution is composed of 3wt% m-phenylenediamine, 1.9wt% triethylamine, 3.3wt% camphorsulfonic acid and water;

[0060] The organic phase solution consists of 0.21 wt % of trimesoyl chloride, 4 wt % of dibutyl succinate and Isopar G.

[0061] Example 6

[0062] This embodiment provides a reverse osmosis membrane with a coral-like structure. The reverse osmosis membrane includes a base membrane and a separation layer arranged in sequence. The microscopic morphology of the separation layer includes a coral-like structure, a nodule-like structure and a leaf-like structure.

[0063] This embodiment also provides a method for preparing the above-mentioned reverse osmosis membrane with a coral-like structure, and the specific preparation steps are as follows:

[0064] The polysulfone porous membrane was immersed in an aqueous solution for 10 seconds, and the residual solution on the surface was drained; then immersed in an organic solution for interfacial polymerization reaction for 10 seconds, and the residual solution on the surface was drained, and then the membrane was heat treated at 90°C for 6 minutes.

[0065] The aqueous phase solution is composed of 3wt% m-phenylenediamine, 1.9wt% triethylamine, 3.3wt% camphorsulfonic acid and water;

[0066] The organic phase solution consists of 0.21 wt % of trimesoyl chloride, 4 wt % of phenethyl ether and Isopar G.

[0067] Example 7

[0068] This embodiment provides a reverse osmosis membrane with a coral-like structure. The reverse osmosis membrane includes a base membrane and a separation layer arranged in sequence. The microscopic morphology of the separation layer includes a coral-like structure, a nodule-like structure and a leaf-like structure.

[0069] This embodiment also provides a method for preparing the above-mentioned reverse osmosis membrane with a coral-like structure, and the specific preparation steps are as follows:

[0070] The polysulfone porous membrane was immersed in an aqueous solution for 10 seconds, and the residual solution on the surface was drained; then immersed in an organic solution for interfacial polymerization reaction for 10 seconds, and the residual solution on the surface was drained, and then the membrane was heat treated at 90°C for 6 minutes.

[0071] The aqueous phase solution is composed of 3wt% m-phenylenediamine, 1.9wt% triethylamine, 3.3wt% camphorsulfonic acid and water;

[0072] The organic phase solution consists of 0.21 wt % of trimesoyl chloride, 4 wt % of n-butylphenyl ether and Isopar G.

[0073] Comparative Example

[0074] Comparative Example 1

[0075] The difference between Comparative Example 1 and Example 1 is that the organic phase solution consists of 0.21 wt % of trimesoyl chloride and Isopar G, and the preparation conditions are consistent with those of Example 1.

[0076] Test example

[0077] Test Example 1

[0078] The surface morphology of the reverse osmosis membrane samples obtained in Comparative Example 1 and Examples 1-4 was observed using a field emission scanning electron microscope. Figure 1 shown.

[0079] Figure 1 The scanning electron microscope images of the surface of the reverse osmosis membrane samples obtained in Comparative Example 1 and Examples 1-4 are shown. A0-4 correspond to Comparative Example 1 and Examples 1-4, respectively. A in the figure is a SEM image magnified 1000 times, and B and C in the figure are SEM images magnified 50000 times.

[0080] observe Figure 1 It can be seen that Comparative Example 1 has a uniform, flat surface morphology (A0) at a magnification of 1000 times, and further magnification can observe nodular structures and a small amount of blade-like structures (B0 and C0). However, the reverse osmosis membrane samples obtained in Examples 1-4 can be observed to have non-uniform surface morphology, relatively flat areas, and irregular protruding areas (A1-4) at a magnification of 1000 times; when these two areas are further magnified to 50,000 times, "nodular" or "blade-like" structure (C1-4) areas and new "coral-like" structures (B1-4) can be observed respectively, and the "coral-like" structure areas have been marked with circles.

[0081] Test Example 2

[0082] The cross-sectional structures of the reverse osmosis membrane sample slices obtained in Comparative Example 1, Example 2 and Example 4 were observed using a transmission electron microscope, and the process was as follows:

[0083] Before testing, the reverse osmosis membrane samples obtained in Comparative Example 1, Example 2 and Example 4 were embedded with resin and cured at 60°C for 24 hours. Then, ultrathin sections were made using an ultrathin slicer. Finally, the obtained ultrathin section samples were placed on a special copper mesh for observation. Figure 2 shown.

[0084] Figure 2 A1 and B1, A2 and B2, A3 and B3 are scanning electron microscope (SEM) images of the surface of the separation layer of the reverse osmosis membrane samples obtained in Comparative Example 1, Example 2, and Example 4, respectively, and transmission electron microscope (TEM) images of the cross-section; wherein the magnification of Figures A1-A3 is 50,000, and A1-A3 are the surface morphologies of the "nodular" structure, the "leaf-like" structure, and the "coral-like" structure, respectively; the magnification of Figures B1-B3 is 30,000, and B1-B3 are the cross-sectional morphologies of the "nodular" structure, the "leaf-like" structure, and the "coral-like" structure, respectively.

[0085] Test Example 3

[0086] I. The cross-sectional structures of the reverse osmosis membrane sample slices obtained in Examples 1-7 and Comparative Example 1 were observed using a transmission electron microscope, and the TEM images with a magnification of 30,000 were selected. The biological intrinsic thickness and apparent thickness of the membrane structures obtained in Examples 1-7 and Comparative Example 1 were analyzed using Adobe Photoshop software. The specific steps are as follows: a. Scale>Measurement (pixels of the original scale length); b. Image>Analysis>Set measurement scale>Custom (pixel length, logical length and logical unit); c. Measure thickness (calculate the average and standard deviation of 5 groups), and the results are shown in Table 1;

[0087] II. The surfaces of the reverse osmosis membrane samples obtained in Examples 1-7 and Comparative Example 1 were observed using a field emission scanning electron microscope. The SEM image with a magnification of 1000 was selected, and the area of ​​the "coral-like structure" region was analyzed using Image J software. The specific steps were as follows: ①Image>Type>8-bit; ②Image>Adjust>Brightness / contrast; ③Process>Smooth (about 5 times); ④Adjust>Threshold (adjusted until all the "coral-like structures" were just included), that is, the area ratio of the "coral-like structure" region was obtained. The results are shown in Table 1.

[0088] Table 1

[0089]

[0090] It can be seen from Table 1 that the addition of co-solvent in the organic phase causes the separation layer to produce leaf-like and "coral-like" structures, and both the intrinsic thickness and apparent thickness of the polyamide layer are increased.

[0091] Test Example 4

[0092] The performance of the reverse osmosis membrane samples obtained in Examples 1-7 and Comparative Example 1 was tested. The feed liquid was a 32000 ppm sodium chloride aqueous solution. The membrane samples were pre-pressed at 25°C and 5.5 MPa for 3 h. The water flux and salt retention rate of each group of membrane samples were tested after 20 min. The results are shown in Table 2.

[0093] Table 2

[0094]

[0095] It can be seen from Table 2 that, compared with Comparative Example 1, the reverse osmosis membrane samples obtained in Examples 1-7 of the present invention significantly improve the water flux of the reverse osmosis membrane without reducing its NaCl retention rate.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. On the basis of the present invention, some modifications or replacements may be made thereto, but these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of protection claimed by the present invention.

Claims

1. A reverse osmosis membrane having a coral-like structure, characterized in that: It comprises a base film and a separation layer which are arranged in sequence; the separation layer is a polyamide layer formed by interfacial polymerization; the microscopic morphology of the separation layer comprises a coral-like structure, a nodular structure and a leaf-like structure; the coral-like structure is formed by stacking multiple layers of spherical particles, the outer diameter of the spherical particles is 20-150nm, the spherical particles have a hollow or non-hollow structure, the wall thickness of the spherical particles is 10-60nm, and the apparent thickness of the coral-like structure is 20-1000nm.

2. The reverse osmosis membrane having a coral-like structure according to claim 1, characterized in that: The area of ​​the coral-like structure accounts for 0.001%-99.999% of the total surface area of ​​the separation membrane.

3. The reverse osmosis membrane having a coral-like structure as claimed in claim 2, characterized in that: The area of ​​the coral-like structure accounts for 3%-80% of the total surface area of ​​the separation membrane.

4. A method for preparing a reverse osmosis membrane having a coral-like structure as claimed in claim 1, characterized in that: The following steps are involved: Immerse the basement membrane in the aqueous solution, take it out and drain the residual solution on the surface; Then immerse it in an organic phase solution to carry out interfacial polymerization reaction, drain the residual solution on the surface and then perform heat treatment; The aqueous phase solution includes polyamine monomers and water; the organic phase solution includes polyacyl chloride monomers, alkane solvents, and co-solvents; the co-solvents are selected from one or two of ester compounds and ether compounds; the ester compounds all contain two or more ester functional groups and the carbon-oxygen ratio of the compound molecules is ≥2.5; the carbon-oxygen ratio of the ether compound molecules is ≥8.

5. The method for preparing a reverse osmosis membrane having a coral-like structure according to claim 4, characterized in that: The concentration of the co-solvent in the organic phase solution is 0.01-50 wt %.

6. The method for preparing a reverse osmosis membrane having a coral-like structure according to claim 5, characterized in that: The ester compound is selected from dibutyl oxalate, diisobutyl oxalate, dipentyl oxalate, diisopentyl oxalate, dibutyl malonate, diisobutyl malonate, dipentyl malonate, diisopentyl malonate, dibutyl succinate, diisobutyl succinate, dipentyl succinate, diisopentyl succinate, dibutyl fumarate, diisobutyl fumarate, dipentyl fumarate, diisopentyl fumarate, dibutyl maleate, diisobutyl maleate, dipentyl maleate, diisopentyl maleate, dipropyl glutarate, diisopropyl glutarate, dibutyl glutarate, diisobutyl glutarate, dipentyl glutarate, diisopentyl glutarate, The invention relates to a novel ester compound selected from the group consisting of pentyl adipate, diethyl adipate, dipropyl adipate, diisopropyl adipate, dibutyl adipate, diisobutyl adipate, dipentyl adipate and diisopentyl adipate, or one or more carbon chain isomers of the ester compounds; the ether compound is selected from the group consisting of phenyl ether, n-butyl phenyl ether, isobutyl phenyl ether, n-pentyl phenyl ether, isopentyl phenyl ether, n-hexyl phenyl ether, isohexyl phenyl ether, diphenyl ether, dibutyl ether, diisobutyl ether, dipentyl ether, diisopentyl ether, dihexyl ether and diisohexyl ether, or one or more carbon chain isomers of the ether compounds.

7. The method for preparing a reverse osmosis membrane having a coral-like structure according to claim 4, characterized in that: The concentration of the polyacyl chloride monomer in the organic phase solution is 0.01-5wt%; the polyacyl chloride monomer is selected from one or more of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, biphenyl dicarboxylic acid chloride, biphenyl trimoyl chloride, biphenyl tetracarboxylic acid chloride, naphthalene dicarboxylic acid chloride, naphthalene tricarboxylic acid chloride, naphthalene tetracarboxylic acid chloride, malonic acid chloride, succinic acid chloride, glutaric acid chloride, and adipic acid chloride; the concentration of the polyamine monomer in the aqueous phase solution is 0.5-5wt%; the polyamine monomer is selected from one or more of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, diaminotoluene, ethylenediamine, propylenediamine, butylenediamine, diaminocyclohexane, and piperazine.

8. The method for preparing a reverse osmosis membrane having a coral-like structure according to claim 4, characterized in that: The interfacial polymerization reaction time is 1-300s; the heat treatment temperature is 40-150°C, and the heat treatment time is 0.1-10min.

9. The method for preparing a reverse osmosis membrane having a coral-like structure according to claim 4, characterized in that: The alkane solvent is selected from one or more of hexane, heptane, octane, nonane, decane, undecane, dodecane, Isopar C, Isopar E, Isopar G, Isopar H, Isopar L, and Isopar M; the base membrane is a porous membrane; the material of the porous membrane is selected from one of polysulfone, polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polyimide, polyetherimide, polyacrylonitrile, polyphenylene ether, polyphenylene sulfide, polyether ketone, and polyaryletherketone.

10. Use of the reverse osmosis membrane with a coral-like structure as claimed in claim 1 in the field of water treatment.

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