Reverse osmosis composite membrane as well as preparation method and application thereof

Abstract

The invention relates to a reverse osmosis composite membrane and a preparation method and application thereof.The preparation method of the reverse osmosis composite membrane comprises the following steps that a sodium metaphosphate aqueous solution and a calcium chloride aqueous solution are sequentially placed on the same surface of a supporting membrane, a gel layer is formed through first heat treatment, and the surface of the gel layer is provided with a peak valley structure; 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 is larger than or equal to 2W1; forming a polyamide separation layer on the surface, away from the supporting membrane, of the gel layer through interfacial polymerization; a copper chloride aqueous solution and an octadecylamine solution are sequentially placed on the surface, away from the gel layer, of the polyamide separation layer, an anti-pollution layer is formed through second heat treatment, and the reverse osmosis composite membrane is obtained. When the reverse osmosis composite membrane prepared by the preparation method is applied to water treatment, the reverse osmosis composite membrane has high desalination rate, high water flux and high pollution resistance.

Description

Technical Field

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

[0002] To improve the anti-fouling property of reverse osmosis membranes, traditional methods mainly involve directly coating a hydrophilic anti-fouling layer on the surface of reverse osmosis membranes. However, during use, the anti-fouling layer formed by this method is not only prone to detachment but also causes a decrease in the water flux of the reverse osmosis membrane, making it difficult for the reverse osmosis membrane to have both high water flux and high anti-fouling performance simultaneously. Summary of the Invention

[0003] Based on this, to address the above problems, it is necessary to provide a reverse osmosis composite membrane, a preparation method thereof, and an application thereof. When the reverse osmosis composite membrane prepared by this preparation method is applied to water treatment, it can have the properties of high salt rejection rate, high water flux, and high anti-fouling performance.

[0004] A preparation method of a reverse osmosis composite membrane includes the following steps:

[0005] Sequentially place an aqueous sodium metaphosphate solution and an aqueous calcium chloride solution on the same surface of a support membrane, and form a gel layer through a first heat treatment. Among them, the surface of the gel layer has a peak-valley structure, and the mass fraction of sodium metaphosphate in the aqueous sodium metaphosphate solution is W1, and the mass fraction of calcium chloride in the aqueous calcium chloride solution is W2, where W2 ≥ 2W1;

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

[0007] Sequentially place an aqueous copper chloride solution and an octadecylamine solution on the surface of the polyamide separation layer away from the gel layer, and form an anti-fouling layer through a second heat treatment to obtain a reverse osmosis composite membrane.

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

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

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

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

[0012] In one embodiment, the mass fraction of copper chloride in the aqueous copper chloride 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 solution and an oil-phase solution are sequentially placed on the surface of the gel layer away from the support membrane, and then the polyamide separation layer is formed through heat treatment, wherein the aqueous solution contains polyamine and the oil-phase solution contains polyacyl chloride.

[0017] A reverse osmosis composite membrane prepared by the preparation method of the reverse osmosis composite membrane described above.

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

[0019] In the preparation method of the reverse osmosis composite membrane of the present invention, by sequentially placing an aqueous solution of sodium metaphosphate and an aqueous solution of calcium chloride on the same surface of the support membrane and defining the mass ratio of sodium metaphosphate to calcium chloride, a gel layer can be formed on the surface of the support membrane, and the Marangoni effect is generated during this process, so that the surface of the formed gel layer has a peak-valley structure; the existence of this peak-valley structure enables the polyamide separation layer formed on the surface of the gel layer to have a large specific surface area, which can effectively improve the water flux of the reverse osmosis composite membrane; at the same time, by sequentially placing an aqueous solution of copper chloride and an octadecylamine solution on the surface of the polyamide separation layer, a pollution-resistant layer is formed by the complexation reaction of copper chloride and octadecylamine on the surface of the polyamide separation layer. Compared with the pollution-resistant layer directly coated on the surface of the reverse osmosis membrane, this pollution-resistant layer can be firmly connected to the surface of the polyamide separation layer and is not easy to fall off during use, and has good pollution-resistant performance; moreover, since octadecylamine itself has a positive charge, the pollution-resistant layer is weakly positively charged, which can effectively neutralize the charge on the surface of the polyamide separation layer and further improve the pollution-resistant 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 properties of high desalination rate, high water flux and high pollution resistance. Description of the Drawings

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0021] Figure 1 Electron micrograph of the reverse osmosis composite membrane prepared in Example 1 of the present invention;

[0022] Figure 2 Electron micrograph of the reverse osmosis composite membrane prepared in Comparative Example 1 of the present invention;

[0023] Figure 3 Electron micrograph of the reverse osmosis composite membrane prepared in Comparative Example 5 of the present invention. Detailed Description of the Invention

[0024] To facilitate the 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 commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the description of the present invention in this specification are only for the purpose of describing specific embodiments or examples and are not intended to limit the present invention. The optional range 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 the related listed items. The any and all combinations include any two related listed items, any more related listed items, or all related listed items.

[0026] After long-term and in-depth research, the applicant found that for a reverse osmosis membrane prepared by interfacial polymerization reaction, a main reason for its easy contamination during use is that: the polyamide separation layer formed by the interfacial polymerization reaction is negatively charged, and during the interfacial polymerization reaction, there are also unreacted acyl chloride groups, and the acyl chloride groups will hydrolyze to produce carboxyl groups, and the carboxyl groups are also negatively charged, resulting in a strong negative charge on the surface of the reverse osmosis membrane, which will adsorb positively charged pollutants, affecting the anti-fouling property of the reverse osmosis membrane, and the pollutants will also block the reverse osmosis membrane, thereby affecting the water flux of the reverse osmosis membrane.

[0027] Therefore, the preparation method of the reverse osmosis composite membrane provided by the present invention includes the following steps:

[0028] S1. Place the sodium metaphosphate aqueous solution and the calcium chloride aqueous solution on the same surface of the support membrane in sequence, and form a gel layer through the first heat treatment. Among them, 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, where 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, sodium metaphosphate undergoes salting out under the action of calcium chloride to form a hydrogel with a three-dimensional network structure. In this process, due to W2≥2W1, the surface tension of the calcium chloride aqueous solution on the surface of the support membrane is greater than that of the sodium metaphosphate aqueous solution, generating the Marangoni effect, making the surface of the formed gel layer have a peak-valley structure. The existence of this peak-valley structure makes the gel layer have a large specific surface area. Therefore, when performing the subsequent step S2, that is, when interfacial polymerization is carried out on the gel layer, the water-oil interface has a large specific surface area, and then the polyamide separation layer formed by the interfacial polymerization reaction has 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%. With such settings, 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, it is beneficial for sodium metaphosphate and calcium chloride to fully react to form a gel layer, and at the same time, it can better regulate the difference in surface tension between the sodium metaphosphate aqueous solution and the calcium chloride aqueous solution, which is beneficial for forming 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; with such settings, by controlling the temperature of the sodium metaphosphate aqueous solution and the temperature of the calcium chloride aqueous solution, on the one hand, it is beneficial for sodium metaphosphate to quickly form polyphosphate ions and cross-link with calcium ions to form a hydrogel; on the other hand, it is beneficial for the sodium metaphosphate aqueous solution and the calcium chloride aqueous solution to form an obvious surface tension gradient, better generate the Marangoni effect, better form a peak-valley structure, further increase the specific surface area of the polyamide separation layer, and improve the water flux of the reverse osmosis composite membrane; moreover, it can effectively ensure the stability of the hydrogel before the first heat treatment.

[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 setting is beneficial to improving the firm 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 polysulfone membrane, polypropylene membrane or polyacrylonitrile membrane. Among them, polysulfone is inexpensive and easily available, the film-making process is simple, it has good mechanical strength, good anti-compaction performance, stable chemical properties, is non-toxic, and can resist biodegradation. Therefore, the support membrane is preferably a polysulfone membrane.

[0034] S2. A polyamide separation layer is formed on the surface of the gel layer away from the support membrane through interfacial polymerization.

[0035] Specifically, an aqueous solution and an oil-phase solution are sequentially placed on the surface of the gel layer away from the support membrane, and then the polyamide separation layer is formed through heat treatment. Among them, the aqueous solution contains polyamine, and the oil-phase solution contains polyacyl chloride.

[0036] It can be understood that polyamine and polyacyl chloride form a polyamide separation layer through an interfacial polymerization reaction to ensure that the reverse osmosis composite membrane has a high desalination rate. At the same time, the polyamide separation layer is negatively charged, and there are still unreacted acyl chloride groups on the surface of the polyamide separation layer, and the acyl chloride groups will hydrolyze to form carboxylate ions, 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 polyamine in the aqueous solution is 1% - 3%, and the mass fraction of polyacyl chloride in the oil-phase solution is 0.1% - 0.5%. Such setting is beneficial to enabling sufficient reaction between polyamine and polyacyl chloride to form a relatively dense polyamide separation layer, and is beneficial to the reverse osmosis composite membrane maintaining a high desalination rate.

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

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

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

[0041] In one embodiment, in the step of forming the polyamide separation layer by heat treatment, the temperature of the heat treatment is 75°C - 100°C, and the time of the heat treatment is 2 min - 4 min. With such settings, the integrity and uniformity of the cross-linking of the polyamide separation layer can be further ensured, and the salt rejection rate and water flux of the reverse osmosis composite membrane can be further improved.

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

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

[0044] In step S3, when the copper chloride aqueous solution and the octadecylamine solution come into contact on the surface of the polyamide separation layer, the octadecylamine solution will form a film on the surface of the polyamide separation layer, and octadecylamine will undergo a complexation reaction with copper chloride to form an anti-fouling layer. Compared with the anti-fouling layer formed by directly coating on the surface of the reverse osmosis membrane, this anti-fouling 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-fouling performance; moreover, since octadecylamine itself has a positive charge, the anti-fouling layer shows a weak positive charge, 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-fouling 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 addition sequence of the copper chloride aqueous solution and the octadecylamine solution, the remaining acyl chloride groups on the surface of the polyamide separation layer can be fully hydrolyzed by the copper chloride aqueous solution, thereby avoiding the situation that octadecylamine reacts with the unreacted acyl chloride groups, resulting in the polyamide separation layer being too dense and the water flux of the reverse osmosis membrane decreasing.

[0046] Therefore, when the reverse osmosis composite membrane of the present invention is applied to water treatment, it can have the properties of high salt rejection rate, high water flux, and high anti-fouling performance.

[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%; with such settings, by regulating the mass fraction of copper chloride in the copper chloride aqueous solution and the mass fraction of octadecylamine in the octadecylamine solution, the complexation reaction between copper chloride and octadecylamine can occur sufficiently, forming a uniform and firm anti-fouling layer, and further improving the anti-fouling performance of the reverse osmosis composite membrane.

[0048] Optionally, the temperature of the second heat treatment is 80°C - 100°C, and the time of the first heat treatment is 1 min - 5 min. Such settings are beneficial to better form a 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] Meanwhile, the present invention also provides a reverse osmosis composite membrane prepared by using the preparation method of the reverse osmosis composite membrane described above. When this reverse osmosis composite membrane is applied to water treatment, it can have the properties of 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 described above in a water treatment device.

[0052] In one embodiment, the water treatment device can be a purifier. When the reverse osmosis membrane is applied to a 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 forms pure water by passing through the reverse osmosis membrane under the action of pressure.

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

[0054] Hereinafter, the reverse osmosis composite membrane, its preparation method, and application will be further described through the following specific examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the examples, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0055] Example 1

[0056] Mix m-phenylenediamine, triethylamine, and water evenly to prepare an aqueous solution. Among them, in the aqueous solution, the mass fraction of m-phenylenediamine is 1%, and the mass fraction of triethylamine is 0.5%; mix trimellitic acid chloride and isoparaffin solvent (Isopar-L) evenly to prepare an oil phase solution. Among them, in the oil phase solution, the mass fraction of trimellitic acid chloride is 0.15%; mix octadecylamine and ethanol evenly to prepare an octadecylamine solution. Among them, in the octadecylamine solution, the mass fraction of octadecylamine is 1.2%.

[0057] Apply an aqueous solution of sodium metaphosphate to the surface of a polysulfone support membrane. After there are no obvious liquid beads on the surface, apply an aqueous solution of calcium chloride. After standing for 60 s, pour out the excess aqueous calcium chloride solution, and place it in an 80 °C oven for 3 min to form a gel layer with a peak-valley structure on the surface. Among them, the mass fraction of sodium metaphosphate in the aqueous sodium metaphosphate solution is 0.3%, the temperature of the aqueous sodium metaphosphate solution is 35 °C, the mass fraction of calcium chloride in the aqueous calcium chloride solution is 1.5%, and the temperature of the aqueous calcium chloride solution is 30 °C; then apply the above aqueous solution to the surface of the gel layer, after standing for 60 s, pour out the excess aqueous solution, dry the membrane surface with cold air, then apply the above oil phase solution to the same surface of the gel layer, after standing for 30 s, pour out the excess oil phase solution, drain it, and place it in an 80 °C oven for 2 min to form a polyamide separation layer; apply an aqueous solution of copper chloride to the surface of the polyamide separation layer, pour out the excess aqueous copper chloride solution, among which, the mass fraction of copper chloride in the aqueous copper chloride solution is 0.4%; then apply an octadecylamine solution, after standing for 30 s, pour out the excess octadecylamine solution, and place it in a 90 °C oven for 2 min to form an anti-fouling layer, obtaining the reverse osmosis composite membrane as Figure 1 shown.

[0058] Example 2

[0059] Mix m-phenylenediamine, triethylamine, and water evenly to prepare an aqueous solution. Among them, in the aqueous solution, the mass fraction of m-phenylenediamine is 1.5% and the mass fraction of triethylamine is 1%; mix trimesoyl chloride and an isoparaffin solvent (Isopar-L) evenly to prepare an oil phase solution. Among them, the mass fraction of trimesoyl chloride in the oil phase solution is 0.2%; mix octadecylamine and ethanol evenly to prepare an octadecylamine solution. Among them, the mass fraction of octadecylamine in the octadecylamine solution is 1%.

[0060] Apply an aqueous solution of sodium metaphosphate to the surface of the polysulfone support membrane. After there are no obvious liquid beads on the surface, apply an aqueous solution of calcium chloride. After standing for 60 s, pour out the excess aqueous solution of calcium chloride, and place it in an oven at 60 °C for 5 min to form a gel layer with a peak-valley structure on the surface. Among them, the mass fraction of sodium metaphosphate in the aqueous solution of sodium metaphosphate is 0.1%, the temperature of the aqueous solution of sodium metaphosphate is 30 °C, the mass fraction of calcium chloride in the aqueous solution of calcium chloride is 1%, and the temperature of the aqueous solution of calcium chloride is 20 °C; then apply the above aqueous solution to the surface of the gel layer, after standing for 60 s, pour out the excess aqueous solution, dry the membrane surface with cold air, and then apply the above oil phase solution to the same surface of the gel layer. After standing for 30 s, pour out the excess oil phase solution, drain it, and place it in an oven at 90 °C for 2 min to form a polyamide separation layer; apply an aqueous solution of copper chloride to the surface of the polyamide separation layer, pour out the excess aqueous solution of copper chloride, among which, the mass fraction of copper chloride in the aqueous solution of copper chloride is 0.2%; then apply an octadecylamine solution, after standing for 30 s, pour out the excess octadecylamine solution, and place it in an oven at 80 °C for 3 min to form an anti-fouling layer, obtaining a reverse osmosis composite membrane.

[0061] Example 3

[0062] Mix m-phenylenediamine, triethylamine and water evenly to prepare an aqueous solution. Among them, in the aqueous solution, the mass fraction of m-phenylenediamine is 3%, and the mass fraction of triethylamine is 2%; mix trimesoyl chloride and isoparaffin solvent (Isopar-L) evenly to prepare an oil phase solution. Among them, the mass fraction of trimesoyl chloride in the oil phase solution is 0.4%; mix octadecylamine and ethanol evenly to prepare an octadecylamine solution. Among them, the mass fraction of octadecylamine in the octadecylamine solution is 1.5%.

[0063] Apply an aqueous solution of sodium metaphosphate to the surface of the polysulfone support membrane. After there are no obvious liquid beads on the surface, apply an aqueous solution of calcium chloride. After standing for 60 s, pour out the excess aqueous solution of calcium chloride, and place it in an oven at 40 °C for 2 min to form a gel layer with a peak-valley structure on the surface. Among them, the mass fraction of sodium metaphosphate in the aqueous solution of sodium metaphosphate is 0.5%, the temperature of the aqueous solution of sodium metaphosphate is 40 °C, the mass fraction of calcium chloride in the aqueous solution of calcium chloride is 2%, and the temperature of the aqueous solution of calcium chloride is 30 °C; then apply the above aqueous solution to the surface of the gel layer, after standing for 60 s, pour out the excess aqueous solution, dry the membrane surface with cold air, and then apply the above oil phase solution to the same surface of the gel layer. After standing for 30 s, pour out the excess oil phase solution, drain it, and place it in an oven at 90 °C for 2 min to form a polyamide separation layer; apply an aqueous solution of copper chloride to the surface of the polyamide separation layer, pour out the excess aqueous solution of copper chloride, among which, the mass fraction of copper chloride in the aqueous solution of copper chloride is 0.6%; then apply an octadecylamine solution, after standing for 30 s, pour out the excess octadecylamine solution, and place it in an oven at 100 °C for 1 min to form an anti-fouling layer, obtaining a reverse osmosis composite membrane.

[0064] Example 4

[0065] Example 4 is different from Example 1 only in that the mass fraction of sodium metaphosphate in the aqueous sodium metaphosphate solution is 0.05%, and the remaining conditions are the same, obtaining a reverse osmosis composite membrane.

[0066] Example 5

[0067] Example 5 is different from Example 1 only in that the mass fraction of sodium metaphosphate in the aqueous sodium metaphosphate solution is 1%, and the remaining conditions are the same, obtaining a reverse osmosis composite membrane.

[0068] Example 6

[0069] Example 6 is different from Example 1 only in that the temperature of the aqueous sodium metaphosphate solution is 20 °C, and the remaining conditions are the same, obtaining a reverse osmosis composite membrane.

[0070] Example 7

[0071] Example 7 is different from Example 1 only in that the temperature of the aqueous sodium metaphosphate solution is 50 °C, and the remaining conditions are the same, obtaining a reverse osmosis composite membrane.

[0072] Example 8

[0073] Example 8 is different from Example 1 only in that the mass fraction of calcium chloride in the aqueous calcium chloride solution is 0.5%, and the remaining conditions are the same, obtaining a reverse osmosis composite membrane.

[0074] Example 9

[0075] Example 9 is different from Example 1 only in that the mass fraction of calcium chloride in the aqueous calcium chloride solution is 3%, and the remaining conditions are the same, obtaining a reverse osmosis composite membrane.

[0076] Example 10

[0077] Example 10 is different from Example 1 only in that the mass fraction of copper chloride in the aqueous copper chloride solution is 0.1%, and the remaining conditions are the same, obtaining a reverse osmosis composite membrane.

[0078] Example 11

[0079] Example 11 is different from Example 1 only in that the mass fraction of copper chloride in the aqueous copper chloride solution is 0.8%, and the remaining conditions are the same, obtaining a reverse osmosis composite membrane.

[0080] Example 12

[0081] Example 12 is different from Example 1 only in that the mass fraction of octadecylamine in the octadecylamine solution is 0.5%, and the rest of the conditions are the same, obtaining a reverse osmosis composite membrane.

[0082] Example 13

[0083] Example 13 is different from Example 1 only in that the mass fraction of octadecylamine in the octadecylamine solution is 3%, and the rest of the conditions are the same, obtaining a reverse osmosis composite membrane.

[0084] Example 14

[0085] Example 14 is different from Example 1 only in that the aqueous solution does not contain triethylamine, and the rest of the conditions are the same, obtaining a reverse osmosis composite membrane.

[0086] Comparative Example 1

[0087] Comparative Example 1 is different from Example 1 only in that the mass fraction of sodium metaphosphate in the sodium metaphosphate aqueous solution is 0.5%, and the mass fraction of calcium chloride in the calcium chloride aqueous solution is 0.7%, and the rest of the conditions are the same, obtaining a reverse osmosis composite membrane.

[0088] Comparative Example 2

[0089] Comparative Example 2 is different from Example 1 only in that sodium metaphosphate, calcium chloride and water are mixed evenly to prepare 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 mixed solution is coated on the surface of the polysulfone support membrane, and after standing for 60 s, the excess mixed solution is poured off, and then placed in an 80°C oven for 3 min to form a gel layer; then the above aqueous solution is coated on the surface of the gel layer away from the support membrane, and the rest of the conditions are the same, obtaining 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 coated on the surface of the polyamide separation layer away from the gel layer, and after standing for 30 s, the excess octadecylamine solution is poured off; then a copper chloride aqueous solution is coated and the excess copper chloride aqueous solution is poured off, wherein the mass fraction of copper chloride in the copper chloride aqueous solution is 0.4%, and it is placed in a 90°C oven for 2 min to form an anti-fouling layer, and the rest of the conditions are the same, obtaining a reverse osmosis composite membrane.

[0092] Comparative Example 4

[0093] Comparative Example 4 is different from Example 1 only in that it does not include the step of coating the surface of the polyamide separation layer away from the gel layer with an aqueous copper chloride solution. That is, an octadecylamine solution is directly coated on the surface of the polyamide separation layer away from the gel layer. After standing for 30 s, the excess octadecylamine solution is poured out; then it is placed in an oven at 90 °C for 2 min to form an anti-fouling layer. The other conditions are the same, and a reverse osmosis composite membrane is obtained.

[0094] Comparative Example 5

[0095] Comparative Example 5 is different from Example 1 only in that it does not include the step of forming a gel layer. That is, the above aqueous solution is directly coated on the surface of the polysulfone support membrane. After standing for 60 s, the excess aqueous solution is poured out, and the membrane surface is dried with cold air. Then the above oil phase solution is coated on the same surface of the polysulfone support membrane. After standing for 30 s, the excess oil phase solution is poured out. After draining, it is placed in an oven at 80 °C for 2 min to form a polyamide separation layer; an aqueous copper chloride solution is coated on the surface of the polyamide separation layer, and the excess aqueous copper chloride solution is poured out, where the mass fraction of copper chloride in the aqueous copper chloride solution is 0.4%; then an octadecylamine solution is coated again. After standing for 30 s, the excess octadecylamine solution is poured out, and it is placed in an oven at 90 °C for 2 min to form an anti-fouling layer. The other conditions are the same, and a reverse osmosis composite membrane is obtained.

[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: the test pressure was 1.55 MPa, the concentrated water flow rate was 1.0 GPM, the ambient temperature was 25 °C, the pH value of the concentrated water was 6.5 - 7.5, the concentrated water was a 2000 ppm sodium chloride aqueous solution, and the test results are shown in Table 1.

[0097] Table 1

[0098]

[0099] Meanwhile, the anti-fouling 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: the test pressure was 1.55 MPa, the concentrated water flow rate was 1.0 GPM, the ambient temperature was 25 °C, the pH value of the concentrated water was 6.5 - 7.5, and the anti-fouling performance test was carried out under the condition that the concentrated water was 2000 ppm sodium chloride + 100 ppm sodium humate + 100 ppm bovine serum albumin as the feed water. After continuous operation for 100 h, the membrane was cleaned, and then the performance test was carried out under the condition that the concentrated water was 2000 ppm sodium chloride as the feed water. The test results are shown in Table 2.

[0100] Table 2

[0101]

[0102] It should be noted that in Tables 1 to 2, the membrane water flux (F) is calculated by the volume of water passing through the reverse osmosis composite membrane within a certain 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 the time.

[0103] The rejection rate (R) is calculated from 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 for the water flux recovery rate is: (the water flux of the contaminated reverse osmosis composite membrane / the water flux of the initial reverse osmosis composite membrane)×100%.

[0105] From Figure 1 it can be seen that when the surface of the reverse osmosis composite membrane prepared in Example 1 has an anti-fouling layer, there are still relatively obvious blade-like protrusions, 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-fouling layer does not completely cover the surface morphology of the reverse osmosis composite membrane, and the anti-fouling layer is relatively thin, so it will not affect the water flux of the reverse osmosis composite membrane.

[0106] From Figure 2 it can be seen that in Comparative Example 1, 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 do not satisfy W2≥2W1, resulting in the inability to form an obvious 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 also transform from blade-like 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 there is no gel layer with a peak-valley structure in Comparative Example 5, the surface of the prepared reverse osmosis composite membrane is basically covered by the anti-fouling layer, and the anti-fouling layer is too thick, thus affecting the water flux of the reverse osmosis composite membrane.

[0108] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0109] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for preparing a reverse osmosis composite membrane, characterized in that, It includes the following steps: The sodium metaphosphate aqueous solution and the calcium chloride aqueous solution are successively placed on the same surface of the support membrane, and a gel layer is formed through the first heat treatment. Among them, 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, and W2≥2W1; A polyamide separation layer is formed on the surface of the gel layer far from the support membrane through interfacial polymerization; The copper chloride aqueous solution and the octadecylamine solution are successively placed on the surface of the polyamide separation layer far from the gel layer, and an anti-fouling layer is formed through the second heat treatment to obtain a reverse osmosis composite membrane.

2. The preparation method of the reverse osmosis composite membrane according to claim 1, characterized in that, The mass fraction of sodium metaphosphate in the sodium metaphosphate aqueous solution is 0.1%-0.5%.

3. The preparation method of the reverse osmosis composite membrane according to claim 1, characterized in that, The mass fraction of calcium chloride in the calcium chloride aqueous solution is 1%-2%.

4. The preparation method of the reverse osmosis composite membrane according to claim 1, characterized in that, 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 preparation method of the reverse osmosis composite membrane according to claim 1, characterized in that, The mass fraction of copper chloride in the copper chloride aqueous solution is 0.2%-0.6%.

6. The preparation method of the reverse osmosis composite membrane according to claim 1, characterized in that, The mass fraction of octadecylamine in the octadecylamine solution is 1%-1.5%.

7. The preparation method of the 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 1 min - 5 min; 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 far from the support membrane through interfacial polymerization, the aqueous solution and the oil-phase solution are successively placed on the surface of the gel layer far from the support membrane, and then the polyamide separation layer is formed through heat treatment. Among them, the aqueous solution contains polyamine, and the oil-phase solution contains polyacyl chloride.

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

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

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