Reverse osmosis composite membrane and its preparation method and application

Abstract

The present invention relates to a reverse osmosis composite membrane and its preparation method and application. The preparation method of the reverse osmosis composite membrane comprises the following steps: placing a sodium metaphosphate aqueous solution and a calcium chloride aqueous solution on the same surface of a support membrane in sequence, forming a gel layer through a first heat treatment, wherein the surface of the gel layer has a peak-valley structure, and the mass fraction of sodium metaphosphate in the sodium metaphosphate aqueous solution is W1, and the mass fraction of calcium chloride in the calcium chloride aqueous solution is W2, W2 ≥ 2W1; forming a polyamide separation layer on the surface of the gel layer away from the support membrane through interfacial polymerization; placing a copper chloride aqueous solution and an octadecylamine solution on the surface of the polyamide separation layer away from the gel layer in sequence, forming an anti-pollution layer through a second heat treatment, and obtaining a reverse osmosis composite membrane. The reverse osmosis composite membrane prepared by this preparation method can have high salt rejection rate, high water flux and high anti-pollution performance when used in water treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment membranes, in particular to a reverse osmosis composite membrane and a preparation method and application thereof. Background Art

[0002] To improve the anti-pollution property of reverse osmosis membranes, the traditional method is mainly to directly coat a hydrophilic anti-pollution layer on the surface of the reverse osmosis membrane. However, the anti-pollution layer formed by this method is not only easy to fall off during use, but also reduces the water flux of the reverse osmosis membrane, making it difficult for the reverse osmosis membrane to maintain high water flux while having high anti-pollution performance. Summary of the Invention

[0003] Based on this, it is necessary to provide a reverse osmosis composite membrane and its preparation method and application to address the above problems. The reverse osmosis composite membrane prepared by this preparation method can have high desalination rate, high water flux and high anti-pollution performance when used in water treatment.

[0004] A method for preparing a reverse osmosis composite membrane comprises the following steps:

[0005] placing a sodium metaphosphate aqueous solution and a calcium chloride aqueous solution on the same surface of a support membrane in sequence, and forming a gel layer through a first heat treatment, wherein the surface of the gel layer has a peak-valley structure, and the mass fraction of sodium metaphosphate in the sodium metaphosphate aqueous solution is W1, the mass fraction of calcium chloride in the calcium chloride aqueous solution is W2, and W2 ≥ 2W1;

[0006] forming a polyamide separation layer on the surface of the gel layer away from the support membrane by interfacial polymerization;

[0007] A copper chloride aqueous solution and an octadecylamine solution are sequentially placed on the surface of the polyamide separation layer away from the gel layer, and an anti-pollution layer is formed through a second heat treatment to obtain a reverse osmosis composite membrane.

[0008] In one embodiment, the mass fraction of sodium metaphosphate in the sodium metaphosphate aqueous solution is 0.1%-0.5%.

[0009] In one embodiment, the mass fraction of calcium chloride in the calcium chloride aqueous solution is 1%-2%.

[0010] In one embodiment, the temperature of the sodium metaphosphate aqueous solution is 30° C.-40° C.;

[0011] And / or, the temperature of the calcium chloride aqueous solution is 20°C-30°C.

[0012] In one embodiment, the mass fraction of copper chloride in the copper chloride aqueous solution is 0.2%-0.6%.

[0013] In one embodiment, the mass fraction of octadecylamine in the octadecylamine solution is 1%-1.5%.

[0014] In one embodiment, the temperature of the first heat treatment is 60°C-80°C, and the time of the first heat treatment is 1 min-5 min;

[0015] And / or, the temperature of the second heat treatment is 80° C.-100° C., and the time of the first heat treatment is 2 min-3 min.

[0016] In one embodiment, in the step of forming a polyamide separation layer on the surface of the gel layer away from the support membrane by interfacial polymerization, an aqueous phase solution and an oil phase solution are placed in sequence on the surface of the gel layer away from the support membrane, and then heat treated to form the polyamide separation layer, wherein the aqueous phase solution contains a polyamine and the oil phase solution contains a polyacyl chloride.

[0017] A reverse osmosis composite membrane prepared by adopting the reverse osmosis composite membrane preparation method.

[0018] An application of the reverse osmosis composite membrane in a water treatment device.

[0019] In the preparation method of the reverse osmosis composite membrane of the present invention, a sodium metaphosphate aqueous solution and a calcium chloride aqueous solution are sequentially placed on the same surface of a support membrane, and the mass ratio of sodium metaphosphate to calcium chloride is limited, so that a gel layer can be formed on the surface of the support membrane, and a Maragonni effect is generated in the process, so that the surface of the formed gel layer has a peak-valley structure; the presence of the peak-valley structure makes the polyamide separation layer formed on the surface of the gel layer have a larger specific surface area, which can effectively improve the water flux of the reverse osmosis composite membrane; at the same time, a copper chloride aqueous solution and an octadecylamine solution are sequentially placed on the surface of the polyamide separation layer, and a complex reaction is performed on the surface of the polyamide separation layer by copper chloride and octadecylamine. Compared with the anti-pollution layer formed by directly coating the surface of the reverse osmosis membrane, the anti-pollution layer can be firmly connected to the surface of the polyamide separation layer, is not easy to fall off during use, and has good anti-pollution performance; moreover, because octadecylamine itself has positive charge, the anti-pollution layer is weakly positively charged, which can effectively neutralize the charge on the surface of the polyamide separation layer, further improving the anti-pollution performance and water flux of the reverse osmosis composite membrane. Therefore, when the reverse osmosis composite membrane of the present invention is applied to water treatment, it can have the performances of high desalination rate, high water flux and high anti-pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 This is an electron microscope image of the reverse osmosis composite membrane prepared in Example 1 of the present invention;

[0022] Figure 2 This is an electron microscope image of the reverse osmosis composite membrane prepared in Comparative Example 1 of the present invention;

[0023] Figure 3 This is an electron microscope image of the reverse osmosis composite membrane prepared in Comparative Example 5 of the present invention. DETAILED DESCRIPTION

[0024] To facilitate understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the technical field of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments or embodiments and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, including any two related listed items, any more related listed items, or the combination of all related listed items.

[0026] After long and in-depth research, the applicant found that one of the main reasons why reverse osmosis membranes prepared by interfacial polymerization are easily contaminated during use is that the polyamide separation layer formed by the interfacial polymerization reaction is negatively charged, and during the interfacial polymerization reaction, unreacted acyl chloride groups will remain. The acyl chloride groups will hydrolyze to produce carboxyl groups, which are also negatively charged. As a result, the surface of the reverse osmosis membrane has a strong negative charge, which will adsorb positively charged pollutants, affecting the anti-pollution property of the reverse osmosis membrane. In addition, the pollutants will clog the reverse osmosis membrane, thereby affecting the water flux of the reverse osmosis membrane.

[0027] To this end, the present invention provides a method for preparing a reverse osmosis composite membrane, comprising the following steps:

[0028] S1, placing a sodium metaphosphate aqueous solution and a calcium chloride aqueous solution on the same surface of a support membrane in sequence, and forming a gel layer through a first heat treatment, wherein the surface of the gel layer has a peak-valley structure, and the mass fraction of sodium metaphosphate in the sodium metaphosphate aqueous solution is W1, and the mass fraction of calcium chloride in the calcium chloride aqueous solution is W2, W2 ≥ 2W1. It can be understood that in step S1, when the sodium metaphosphate aqueous solution and the calcium chloride aqueous solution come into contact, the sodium metaphosphate undergoes salting out under the action of calcium chloride to form a hydrogel having a three-dimensional network structure. In this process, since W2 ≥ 2W1, the surface tension of the calcium chloride aqueous solution on the surface of the support membrane is greater than the surface tension of the sodium metaphosphate aqueous solution, resulting in a Maracas effect, causing the surface of the formed gel layer to have a peak-valley structure. The presence of this peak-valley structure gives the gel layer a large specific surface area. Therefore, when the subsequent step S2 is performed, that is, when interfacial polymerization is performed on the gel layer, the water-oil interface has a large specific surface area, which in turn makes the polyamide separation layer formed by the interfacial polymerization reaction have a large specific surface area, thereby effectively improving the water flux of the reverse osmosis composite membrane.

[0029] It can be understood that, in the present invention, the peak-valley structure refers to an uneven structure, that is, the surface of the formed gel layer has an uneven structure.

[0030] Optionally, the mass fraction of sodium metaphosphate in the sodium metaphosphate aqueous solution is 0.1%-0.5%; the mass fraction of calcium chloride in the calcium chloride aqueous solution is 1%-2%. This configuration, by regulating the mass fraction of sodium metaphosphate in the sodium metaphosphate aqueous solution and the mass fraction of calcium chloride in the calcium chloride aqueous solution, facilitates the full reaction of sodium metaphosphate and calcium chloride to form a gel layer. It also allows for better regulation of the difference in surface tension between the sodium metaphosphate aqueous solution and the calcium chloride aqueous solution, facilitating the formation of a more uniform peak-valley structure, further increasing the specific surface area of ​​the polyamide separation layer, and improving the water flux of the reverse osmosis composite membrane.

[0031] Optionally, the temperature of the sodium metaphosphate aqueous solution is 30°C-40°C; the temperature of the calcium chloride aqueous solution is 20°C-30°C; such an arrangement, by controlling the temperature of the sodium metaphosphate aqueous solution and the temperature of the calcium chloride aqueous solution, is conducive, on the one hand, to the rapid formation of polyphosphate ions by the sodium metaphosphate aqueous solution and the cross-linking reaction with the calcium ions to form a hydrogel; on the other hand, it is conducive to the formation of a significant surface tension gradient between the sodium metaphosphate aqueous solution and the calcium chloride aqueous solution, better producing the Marragoni effect, better forming a peak-valley structure, further increasing the specific surface area of ​​the polyamide separation layer, and increasing the water flux of the reverse osmosis composite membrane; and before the first heat treatment is performed, the stability of the hydrogel can be effectively guaranteed.

[0032] Optionally, the temperature of the first heat treatment is 60° C.-80° C., and the time of the first heat treatment is 1 min-5 min. Such an arrangement is beneficial to improving the firmness and stability of the gel layer on the surface of the support membrane.

[0033] In one embodiment, the support membrane is selected from at least one of a polysulfone membrane, a polypropylene membrane or a polyacrylonitrile membrane, wherein polysulfone is cheap and readily available, simple to prepare, has good mechanical strength, good pressure resistance, stable chemical properties, is non-toxic, and can resist biodegradation. Therefore, the support membrane is preferably a polysulfone membrane.

[0034] S2, forming a polyamide separation layer on the surface of the gel layer away from the support membrane by interfacial polymerization.

[0035] Specifically, an aqueous solution and an oily solution are sequentially placed on the surface of the gel layer away from the support membrane, and then heat-treated to form the polyamide separation layer, wherein the aqueous solution contains polyamines and the oily solution contains polyacyl chlorides.

[0036] It can be understood that the polyamine and the polyacyl chloride form a polyamide separation layer through interfacial polymerization to ensure that the reverse osmosis composite membrane has a high salt rejection rate. At the same time, the polyamide separation layer is negatively charged. At the same time, there are unreacted acyl chloride groups on the surface of the polyamide separation layer, and the acyl chloride groups will be hydrolyzed to form carboxylate groups, which are negatively charged. Therefore, the surface of the polyamide separation layer formed on the surface of the gel layer is strongly negatively charged.

[0037] In one embodiment, the mass fraction of the polyamine in the aqueous phase solution is 1%-3%, and the mass fraction of the polyacyl chloride in the oil phase solution is 0.1%-0.5%. This configuration facilitates a sufficient reaction between the polyamine and the polyacyl chloride to form a relatively dense polyamide separation layer, which helps the reverse osmosis composite membrane maintain a high salt rejection rate.

[0038] Furthermore, the polyamine is selected from at least one of m-phenylenediamine, piperazine, p-phenylenediamine, and tetraethylenepentamine, preferably m-phenylenediamine; the polyacyl chloride is selected from at least one of trimesoyl chloride, isophthaloyl chloride, and terephthaloyl chloride, preferably trimesoyl chloride.

[0039] In order to better remove the hydrochloric acid generated by the interfacial polymerization reaction and ensure the forward polymerization reaction of the polyamine and the polyacyl chloride, in the present invention, the aqueous phase solution also includes an acid scavenger, and the mass fraction of the acid scavenger in the aqueous phase solution is 0.5%-2%.

[0040] Furthermore, the acid scavenger is selected from at least one of triethylamine, sodium hydroxide, potassium hydroxide, sodium carbonate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, potassium phosphate, and dipotassium hydrogen phosphate, preferably triethylamine.

[0041] In one embodiment, in the step of forming the polyamide separation layer through heat treatment, the heat treatment temperature is 75°C-100°C and the heat treatment time is 2-4 minutes. This configuration further ensures the integrity and uniformity of the cross-linking of the polyamide separation layer, further improving the salt rejection rate and water flux of the reverse osmosis composite membrane.

[0042] In one embodiment, the solvent of the oil phase solution is selected from an isoparaffin solvent, and the isoparaffin solvent is selected from at least one of Isopar-E, Isopar-G, and Isopar-L; the solvent of the aqueous phase solution is water.

[0043] S3, placing a copper chloride aqueous solution and an octadecylamine solution in sequence on the surface of the polyamide separation layer away from the gel layer, and performing a second heat treatment to form an anti-pollution layer to obtain a reverse osmosis composite membrane.

[0044] In step S3, when the copper chloride aqueous solution and the octadecylamine solution contact the surface of the polyamide separation layer, the octadecylamine solution will form a film on the surface of the polyamide separation layer, and the octadecylamine will react with the copper chloride to form an anti-pollution layer. Compared with the anti-pollution layer formed by directly coating the surface of the reverse osmosis membrane, the anti-pollution layer can be firmly connected to the surface of the polyamide separation layer, is not easy to fall off during use, and has good anti-pollution performance; moreover, since octadecylamine itself has a positive charge, the anti-pollution layer is weakly positively charged, which can effectively neutralize the negative charge on the surface of the polyamide separation layer formed in step S2, reduce the adsorption of charged pollutants, and further improve the anti-pollution performance and water flux of the reverse osmosis composite membrane.

[0045] In addition, it should be noted that, in the present invention, by controlling the order of adding the copper chloride aqueous solution and the octadecylamine solution, the copper chloride aqueous solution can be used to fully hydrolyze the acyl chloride groups remaining on the surface of the polyamide separation layer, thereby avoiding the reaction of octadecylamine with unreacted acyl chloride groups to cause the polyamide separation layer to be too dense, thereby reducing the water flux of the reverse osmosis membrane.

[0046] Therefore, when the reverse osmosis composite membrane of the present invention is applied to water treatment, it can have the performances of high desalination rate, high water flux and high anti-pollution.

[0047] Optionally, the mass fraction of copper chloride in the copper chloride aqueous solution is 0.2%-0.6%; the mass fraction of octadecylamine in the octadecylamine solution is 1%-1.5%; in this way, by regulating the mass fraction of copper chloride in the copper chloride aqueous solution and the mass fraction of octadecylamine in the octadecylamine solution, a complexation reaction can be fully carried out between copper chloride and octadecylamine to form a uniform and firm anti-pollution layer, thereby further improving the anti-pollution performance of the reverse osmosis composite membrane.

[0048] Optionally, the temperature of the second heat treatment is 80-100° C., and the time of the first heat treatment is 1-5 minutes. This configuration is conducive to forming a more uniform and firm anti-pollution layer, further improving the anti-pollution performance of the reverse osmosis composite membrane.

[0049] In one embodiment, the solvent in the octadecylamine solution is preferably an alcohol solvent.

[0050] The present invention also provides a reverse osmosis composite membrane prepared by the reverse osmosis composite membrane preparation method. When used in water treatment, the reverse osmosis composite membrane can have high desalination rate, high water flux and high anti-pollution performance.

[0051] In addition, the present invention also provides an application of the reverse osmosis composite membrane in a water treatment device.

[0052] In one embodiment, the water treatment device can be a purifier. When the reverse osmosis membrane is used in the water purifier, during the water purification process, the raw water to be purified enters from the separation layer of the reverse osmosis membrane, and the raw water passes through the reverse osmosis membrane under pressure to form pure water.

[0053] In one embodiment, the water treatment device may also be a seawater desalination device.

[0054] The reverse osmosis composite membrane, its preparation method, and application will be further described below by way of the following specific examples. However, those skilled in the art will appreciate that the following examples are intended only to illustrate the present invention and should not be construed as limiting the scope of the present invention. In the examples, where specific conditions are not specified, the procedures were carried out under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used where the manufacturer is not specified are commercially available conventional products.

[0055] Example 1

[0056] Metaphenylenediamine, triethylamine and water were uniformly mixed to prepare an aqueous phase solution, wherein the mass fraction of metaphenylenediamine in the aqueous phase solution was 1%, and the mass fraction of triethylamine was 0.5%. Trimesoyl chloride and an isoparaffin solvent (Isopar-L) were uniformly mixed to prepare an oil phase solution, wherein the mass fraction of trimesoyl chloride in the oil phase solution was 0.15%. Octadecylamine and ethanol were uniformly mixed to prepare an octadecylamine solution, wherein the mass fraction of octadecylamine in the octadecylamine solution was 1.2%.

[0057] The sodium metaphosphate aqueous solution is coated on the surface of the polysulfone support membrane, and the calcium chloride aqueous solution is coated after no obvious liquid droplets are formed on the surface. After standing for 60 seconds, the excess calcium chloride aqueous solution is poured out and placed in an 80°C oven for 3 minutes to form a gel layer with a peak-valley structure on the surface, wherein the mass fraction of sodium metaphosphate in the sodium metaphosphate aqueous solution is 0.3%, the temperature of the sodium metaphosphate aqueous solution is 35°C, the mass fraction of calcium chloride in the calcium chloride aqueous solution is 1.5%, and the temperature of the calcium chloride aqueous solution is 30°C; then the above aqueous phase solution is coated on the surface of the gel layer, and after standing for 60 seconds, the excess calcium chloride aqueous solution is poured out and placed in an 80°C oven for 3 minutes to form a gel layer with a peak-valley structure on the surface. Pour out the excess aqueous solution, blow dry the membrane surface with cold air, then apply the above oil phase solution to the same surface of the gel layer, let it stand for 30 seconds, then pour out the excess oil phase solution, drain it, and place it in an 80°C oven for 2 minutes to form a polyamide separation layer; apply a copper chloride aqueous solution on the surface of the polyamide separation layer, pour out the excess copper chloride aqueous solution, wherein the mass fraction of copper chloride in the copper chloride aqueous solution is 0.4%; then apply octadecylamine solution, let it stand for 30 seconds, then pour out the excess octadecylamine solution, and place it in a 90°C oven for 2 minutes to form an anti-pollution layer, and obtain the following: Figure 1 The reverse osmosis composite membrane shown.

[0058] Example 2

[0059] Metaphenylenediamine, triethylamine and water are uniformly mixed to prepare an aqueous phase solution, wherein the mass fraction of metaphenylenediamine in the aqueous phase solution is 1.5%, and the mass fraction of triethylamine is 1%. Trimesoyl chloride and an isoparaffin solvent (Isopar-L) are uniformly mixed to prepare an oil phase solution, wherein the mass fraction of trimesoyl chloride in the oil phase solution is 0.2%. Octadecylamine and ethanol are uniformly mixed to prepare an octadecylamine solution, wherein the mass fraction of octadecylamine in the octadecylamine solution is 1%.

[0060] The sodium metaphosphate aqueous solution is coated on the surface of the polysulfone support membrane, and the calcium chloride aqueous solution is coated after no obvious liquid droplets are left on the surface. After standing for 60 seconds, the excess calcium chloride aqueous solution is poured out, and the membrane is placed in a 60°C oven for 5 minutes to form a gel layer with a peak-valley structure on the surface, wherein the mass fraction of sodium metaphosphate in the sodium metaphosphate aqueous solution is 0.1%, the temperature of the sodium metaphosphate aqueous solution is 30°C, the mass fraction of calcium chloride in the calcium chloride aqueous solution is 1%, and the temperature of the calcium chloride aqueous solution is 20°C; then the above aqueous phase solution is coated on the surface of the gel layer, and after standing for 60 seconds, the excess calcium chloride aqueous solution is poured out. The membrane surface is dried with cold air, and then the oil phase solution is applied to the same surface of the gel layer. After standing for 30 seconds, the excess oil phase solution is poured out. After draining, the membrane is placed in a 90°C oven for 2 minutes to form a polyamide separation layer; a copper chloride aqueous solution is applied to the surface of the polyamide separation layer, and the excess copper chloride aqueous solution is poured out, wherein the mass fraction of copper chloride in the copper chloride aqueous solution is 0.2%; then an octadecylamine solution is applied, and after standing for 30 seconds, the excess octadecylamine solution is poured out. The membrane is placed in an 80°C oven for 3 minutes to form an anti-pollution layer to obtain a reverse osmosis composite membrane.

[0061] Example 3

[0062] Metaphenylenediamine, triethylamine and water are uniformly mixed to prepare an aqueous phase solution, wherein the mass fraction of metaphenylenediamine in the aqueous phase solution is 3% and the mass fraction of triethylamine is 2%; trimesoyl chloride and an isoparaffin solvent (Isopar-L) are uniformly mixed to prepare an oil phase solution, wherein the mass fraction of trimesoyl chloride in the oil phase solution is 0.4%; octadecylamine and ethanol are uniformly mixed to prepare an octadecylamine solution, wherein the mass fraction of octadecylamine in the octadecylamine solution is 1.5%.

[0063] The sodium metaphosphate aqueous solution is coated on the surface of the polysulfone support membrane, and the calcium chloride aqueous solution is coated after no obvious liquid droplets are left on the surface. After standing for 60 seconds, the excess calcium chloride aqueous solution is poured out, and the membrane is placed in a 40°C oven for 2 minutes to form a gel layer with a peak-valley structure on the surface, wherein the mass fraction of sodium metaphosphate in the sodium metaphosphate aqueous solution is 0.5%, the temperature of the sodium metaphosphate aqueous solution is 40°C, the mass fraction of calcium chloride in the calcium chloride aqueous solution is 2%, and the temperature of the calcium chloride aqueous solution is 30°C; then the above aqueous phase solution is coated on the surface of the gel layer, and after standing for 60 seconds, the excess calcium chloride aqueous solution is poured out. The membrane surface is dried with cold air, and then the oil phase solution is applied to the same surface of the gel layer. After standing for 30 seconds, the excess oil phase solution is poured out. After draining, the membrane is placed in a 90°C oven for 2 minutes to form a polyamide separation layer; a copper chloride aqueous solution is applied to the surface of the polyamide separation layer, and the excess copper chloride aqueous solution is poured out, wherein the mass fraction of copper chloride in the copper chloride aqueous solution is 0.6%; then an octadecylamine solution is applied, and after standing for 30 seconds, the excess octadecylamine solution is poured out. The membrane is placed in a 100°C oven for 1 minute to form an anti-pollution layer to obtain a reverse osmosis composite membrane.

[0064] Example 4

[0065] Compared with Example 1, Example 4 differs only in that the mass fraction of sodium metaphosphate in the sodium metaphosphate aqueous solution is 0.05%, and other conditions are the same to obtain a reverse osmosis composite membrane.

[0066] Example 5

[0067] Compared with Example 1, Example 5 differs only in that the mass fraction of sodium metaphosphate in the sodium metaphosphate aqueous solution is 1%, and other conditions are the same to obtain a reverse osmosis composite membrane.

[0068] Example 6

[0069] Compared with Example 1, Example 6 differs only in that the temperature of the sodium metaphosphate aqueous solution is 20° C., and other conditions are the same to obtain a reverse osmosis composite membrane.

[0070] Example 7

[0071] Compared with Example 1, Example 7 differs only in that the temperature of the sodium metaphosphate aqueous solution is 50° C., and other conditions are the same to obtain a reverse osmosis composite membrane.

[0072] Example 8

[0073] Compared with Example 1, Example 8 differs only in that the mass fraction of calcium chloride in the calcium chloride aqueous solution is 0.5%, and other conditions are the same to obtain a reverse osmosis composite membrane.

[0074] Example 9

[0075] Compared with Example 1, Example 9 differs only in that the mass fraction of calcium chloride in the calcium chloride aqueous solution is 3%, and other conditions are the same to obtain a reverse osmosis composite membrane.

[0076] Example 10

[0077] Compared with Example 1, Example 10 differs only in that the mass fraction of copper chloride in the copper chloride aqueous solution is 0.1%, and other conditions are the same to obtain a reverse osmosis composite membrane.

[0078] Example 11

[0079] Compared with Example 1, Example 11 differs only in that the mass fraction of copper chloride in the copper chloride aqueous solution is 0.8%, and other conditions are the same to obtain a reverse osmosis composite membrane.

[0080] Example 12

[0081] Compared with Example 1, Example 12 differs only in that the mass fraction of octadecylamine in the octadecylamine solution is 0.5%, and other conditions are the same to obtain a reverse osmosis composite membrane.

[0082] Example 13

[0083] Compared with Example 1, Example 13 differs only in that the mass fraction of octadecylamine in the octadecylamine solution is 3%, and other conditions are the same to obtain a reverse osmosis composite membrane.

[0084] Example 14

[0085] Compared with Example 1, Example 14 differs only in that the aqueous phase solution does not contain triethylamine, and the other conditions are the same to obtain a reverse osmosis composite membrane.

[0086] Comparative Example 1

[0087] Comparative Example 1 is compared with Example 1, except that the mass fraction of sodium metaphosphate in the sodium metaphosphate aqueous solution is 0.5%, the mass fraction of calcium chloride in the calcium chloride aqueous solution is 0.7%, and the other conditions are the same to obtain a reverse osmosis composite membrane.

[0088] Comparative Example 2

[0089] Comparative Example 2 is compared with Example 1, except that sodium metaphosphate, calcium chloride and water are evenly mixed to form a mixed solution, wherein the mass fraction of sodium metaphosphate in the mixed solution is 0.5%, the mass fraction of calcium chloride is 1.5%, and the temperature of the mixed solution is 30°C; the above-mentioned mixed solution is applied to the surface of the polysulfone support membrane, and after standing for 60 seconds, the excess mixed solution is poured out and placed in an 80°C oven for 3 minutes to form a gel layer; then the above-mentioned aqueous phase solution is applied to the surface of the gel layer away from the support membrane, and the other conditions are the same to obtain a reverse osmosis composite membrane.

[0090] Comparative Example 3

[0091] Comparative Example 3 is different from Example 1 only in that an octadecylamine solution is applied to the surface of the polyamide separation layer away from the gel layer, and the excess octadecylamine solution is poured out after standing for 30 seconds; then a copper chloride aqueous solution is applied, and the excess copper chloride aqueous solution is poured out, wherein the mass fraction of copper chloride in the copper chloride aqueous solution is 0.4%. The anti-pollution layer is formed in a 90°C oven for 2 minutes, and the other conditions are the same to obtain a reverse osmosis composite membrane.

[0092] Comparative Example 4

[0093] Comparative Example 4 differs from Example 1 only in that the step of applying a copper chloride aqueous solution to the surface of the polyamide separation layer away from the gel layer is omitted. That is, an octadecylamine solution is directly applied to the surface of the polyamide separation layer away from the gel layer, and the excess octadecylamine solution is poured out after standing for 30 seconds. The membrane is then placed in an oven at 90°C for 2 minutes to form an anti-pollution layer. The other conditions are the same to obtain a reverse osmosis composite membrane.

[0094] Comparative Example 5

[0095] Comparative Example 5 is different from Example 1 only in that it does not contain the step of forming a gel layer, that is, the above-mentioned aqueous phase solution is directly applied to the surface of the polysulfone support membrane, and the excess aqueous phase solution is poured out after standing for 60 seconds, and the membrane surface is blown dry with cold air. Then, the above-mentioned oil phase solution is applied to the same surface of the polysulfone support membrane, and the excess oil phase solution is poured out after standing for 30 seconds. After draining, it is placed in an 80°C oven for 2 minutes to form a polyamide separation layer; a copper chloride aqueous solution is applied to the surface of the polyamide separation layer, and the excess copper chloride aqueous solution is poured out, wherein the mass fraction of copper chloride in the copper chloride aqueous solution is 0.4%; then an octadecylamine solution is applied, and the excess octadecylamine solution is poured out after standing for 30 seconds. It is placed in a 90°C oven for 2 minutes to form an anti-pollution layer. The other conditions are the same to obtain a reverse osmosis composite membrane.

[0096] The reverse osmosis composite membranes prepared in Examples 1 to 14 and Comparative Examples 1 to 5 were subjected to performance tests. The test conditions were as follows: a test pressure of 1.55 MPa, a brine flow rate of 1.0 GPM, an ambient temperature of 25°C, a brine pH of 6.5-7.5, and a brine solution of 2000 ppm sodium chloride. The test results are shown in Table 1.

[0097] Table 1

[0098]

[0099] At the same time, the anti-pollution performance of the reverse osmosis composite membranes prepared in Examples 1 to 14 and Comparative Examples 1 to 5 was tested. The test conditions were as follows: the test pressure was 1.55 MPa, the brine flow rate was 1.0 GPM, the ambient temperature was 25°C, the brine pH value was 6.5-7.5, and the brine was 2000 ppm sodium chloride + 100 ppm sodium humate + 100 ppm bovine serum albumin as the inlet water condition. The anti-pollution performance test was carried out. After 100 hours of continuous operation, the membrane was cleaned and then the performance test was carried out under the inlet water condition of 2000 ppm sodium chloride in the brine. The test results are shown in Table 2.

[0100] Table 2

[0101]

[0102] It should be noted that in Tables 1 and 2, the membrane water flux (F) is calculated by the volume of water passing through the reverse osmosis composite membrane in a certain period of time, and the formula is: F=V / (A×T), where V is the volume of water passing through the reverse osmosis composite membrane per unit time, A is the effective membrane area, and T is time.

[0103] The retention rate (R) is calculated by the concentration of the feed liquid and the concentration of the permeate. The calculation formula is: R=(1-C1 / C0)×100%, where C1 is the concentration of the permeate and C0 is the concentration of the feed liquid.

[0104] The calculation formula of the water flux recovery rate is: (water flux of the reverse osmosis composite membrane after pollution / water flux of the initial reverse osmosis composite membrane) × 100%.

[0105] from Figure 1 It can be seen that the surface of the reverse osmosis composite membrane prepared in Example 1 still has relatively obvious blade-like protrusions even when having an anti-pollution layer, indicating that the surface of the formed gel layer has a peak-valley structure, which can effectively increase the specific surface area of ​​the reverse osmosis composite membrane. At the same time, the anti-pollution layer will not completely cover the morphology of the surface of the reverse osmosis composite membrane, and the anti-pollution layer is relatively thin, thereby not affecting the water flux of the reverse osmosis composite membrane.

[0106] from Figure 2 It can be seen that the mass fraction W1 of sodium metaphosphate in the sodium metaphosphate aqueous solution and the mass fraction W2 of calcium chloride in the calcium chloride aqueous solution in Comparative Example 1 do not satisfy W2≥2W1, resulting in the inability to form a clear peak-valley structure, which significantly reduces the protrusion area on the surface of the reverse osmosis composite membrane prepared in Comparative Example 1, and the protrusions are transformed from leaf-shaped to granular, resulting in a decrease in the specific surface area of ​​the reverse osmosis composite membrane.

[0107] from Figure 3 It can be seen that since Comparative Example 5 does not contain a gel layer with a peak-valley structure, the surface of the prepared reverse osmosis composite membrane is basically covered by the anti-pollution layer, and the anti-pollution layer is too thick, thereby affecting the water flux of the reverse osmosis composite membrane.

[0108] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0109] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a reverse osmosis composite membrane, characterized in that: The steps include: placing a sodium metaphosphate aqueous solution and a calcium chloride aqueous solution on the same surface of a support membrane in sequence, and forming a gel layer through a first heat treatment, wherein the surface of the gel layer has a peak-valley structure, and the mass fraction of sodium metaphosphate in the sodium metaphosphate aqueous solution is W1, the mass fraction of calcium chloride in the calcium chloride aqueous solution is W2, and W2 ≥ 2W1; forming a polyamide separation layer on the surface of the gel layer away from the support membrane by interfacial polymerization; A copper chloride aqueous solution and an octadecylamine solution are sequentially placed on the surface of the polyamide separation layer away from the gel layer, and an anti-pollution layer is formed by a second heat treatment to obtain a reverse osmosis composite membrane, wherein the anti-pollution layer is formed by a complex reaction between octadecylamine and copper chloride.

2. The method for preparing a reverse osmosis composite membrane according to claim 1, wherein The mass fraction of sodium metaphosphate in the sodium metaphosphate aqueous solution is 0.1%-0.5%.

3. The method for preparing a reverse osmosis composite membrane according to claim 1, wherein The mass fraction of calcium chloride in the calcium chloride aqueous solution is 1%-2%.

4. The method for preparing a reverse osmosis composite membrane according to claim 1, wherein The temperature of the sodium metaphosphate aqueous solution is 30°C-40°C; And / or, the temperature of the calcium chloride aqueous solution is 20°C-30°C.

5. The method for preparing a reverse osmosis composite membrane according to claim 1, wherein The mass fraction of copper chloride in the copper chloride aqueous solution is 0.2%-0.6%.

6. The method for preparing a reverse osmosis composite membrane according to claim 1, wherein The mass fraction of octadecylamine in the octadecylamine solution is 1%-1.5%.

7. The method for preparing a reverse osmosis composite membrane according to claim 1, wherein The temperature of the first heat treatment is 60°C-80°C, and the time of the first heat treatment is 1min-5min; And / or, the temperature of the second heat treatment is 80° C.-100° C., and the time of the first heat treatment is 2 min-3 min.

8. The method for preparing a reverse osmosis composite membrane according to any one of claims 1 to 7, characterized in that: In the step of forming a polyamide separation layer on the surface of the gel layer away from the support membrane by interfacial polymerization, an aqueous phase solution and an oil phase solution are placed in sequence on the surface of the gel layer away from the support membrane, and then heat-treated to form the polyamide separation layer, wherein the aqueous phase solution contains polyamine and the oil phase solution contains polyacyl chloride.

9. A reverse osmosis composite membrane prepared by the method for preparing a reverse osmosis composite membrane according to any one of claims 1 to 8.

10. Use of the reverse osmosis composite membrane according to claim 9 in a water treatment device.

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