Preparation method and system of modified reverse osmosis membrane element

Abstract

The invention discloses a preparation method and system of a modified reverse osmosis membrane element, and the method comprises the following steps: 1) washing a membrane element in a membrane shell, and removing a chemical agent or a residual solvent on the surface of the membrane element; 2) enabling the grafting solution to be in full contact with the first batch of membrane elements so as to carry out first-round grafting on the washed membrane elements; wherein the grafting solution comprises an activating agent, a stabilizing agent and a carboxyl source, the temperature of the grafting solution is 10-40 DEG C, and the grafting time is 0.5-6.0 h; and (3) taking out the first batch of membrane elements, putting the second batch of membrane elements into the grafting solution obtained in the step (2), supplementing the activating agent or the stabilizing agent, and carrying out second-round grafting. The reverse osmosis membrane element is subjected to multiple rounds of grafting, the carboxyl content on the surface of the membrane element is increased, the combining capacity of pollutants and the membrane surface is reduced, and the grafted reverse osmosis membrane element has high anti-pollution performance.

Description

Technical Field

[0001] The present invention relates to the field of membrane separation technology, and in particular to a method and system for preparing a modified reverse osmosis membrane element. Background Art

[0002] Among the many industrial wastewater treatment technologies, membrane separation technology has garnered widespread attention and is developing rapidly. Reverse osmosis membrane separation technology, with its low energy consumption, small footprint, and environmental friendliness, is widely used in seawater desalination, pure water production, and industrial wastewater treatment. However, RO membranes are susceptible to fouling during use, which reduces their flux and retention rate, further shortening their service life and increasing replacement costs. Currently, measures to combat membrane fouling in industrial wastewater treatment typically include pretreatment, adjusting operating parameters, using scale inhibitors, and membrane cleaning. While these methods have some effectiveness in preventing membrane fouling, in most cases, membrane fouling is unavoidable, and membrane elements still require frequent chemical cleaning. Modifying RO membranes to enhance their anti-fouling properties is an effective approach to preventing membrane surface contamination. However, much current research on anti-fouling RO membranes remains limited to the membrane sheet stage. Certain modified or grafted formulations are not commercially viable, and processes and systems for producing anti-fouling RO membrane elements are lacking.

[0003] CN 112827368 A discloses an anti-pollution reverse osmosis membrane and its preparation method. The membrane comprises a polyamide desalination layer surface modified with a fluorine-containing amine and a guanidine-containing compound. The polyamide desalination layer is first heat-treated, and then the desalination layer of the membrane is modified with the fluorine-containing amine and guanidine-containing compound. Because the modified membrane surface contains guanidine and fluorine, it can kill microorganisms deposited on the membrane surface, reducing the adhesion of pollutants and the subsequent deposition of pollutants. However, the fluorine on the membrane surface easily detaches from the reverse osmosis membrane surface, resulting in a short service life and a shorter duration of anti-pollution.

[0004] CN 114452845 A discloses an anti-pollution reverse osmosis membrane and its preparation method and application, comprising the following steps: first, preparing a polymer aqueous phase solution comprising polyvinyl alcohol, a dialdehyde cross-linking agent, and an inorganic acid; second, preparing an oil phase solution comprising polyacyl chloride, wherein the molar concentration of secondary hydroxyl groups in the polymer aqueous phase solution is greater than the molar concentration of acyl chloride groups in the oil phase solution; and finally, sequentially forming the polymer aqueous phase solution and the oil phase solution on the surface of the reverse osmosis membrane, and subjecting the membrane to heat treatment to form an anti-pollution layer, thereby obtaining the anti-pollution reverse osmosis membrane.

[0005] The above patent requires heat treatment of the reverse osmosis membrane, which increases the complexity and cost of membrane production. Although the reverse osmosis membrane can kill microorganisms to a certain extent, it cannot prevent the formation of pollutants on the membrane surface during the deep desalination process of reverse osmosis; and the research on the above anti-pollution reverse osmosis membrane is only at the membrane stage and cannot be used in industry. Summary of the Invention

[0006] In order to reduce the impact of membrane fouling on the life of reverse osmosis membranes and reduce the operating costs increased by control measures such as pretreatment and membrane cleaning, the present invention provides a method and system for preparing modified reverse osmosis membrane elements to accelerate the industrial application of anti-fouling reverse osmosis membrane elements.

[0007] To achieve the above-mentioned object of the invention, the first aspect of the present invention provides a method for preparing a modified reverse osmosis membrane element, comprising:

[0008] 1) Rinse the membrane elements in the membrane shell to remove chemicals or residual solvents on the surface of the membrane elements;

[0009] 2) fully contacting the grafting solution with the first batch of membrane elements for the first round of grafting on the flushed membrane elements; wherein the grafting solution includes an activator, a stabilizer, and a carboxyl source, the grafting solution temperature is 10-40° C., and the grafting time is 0.5 h-6.0 h;

[0010] 3) Taking out the first batch of membrane elements, placing the second batch of membrane elements in the grafting solution of step 2), and adding an activator or stabilizer to perform a second round of grafting.

[0011] Furthermore, the activator is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC), the stabilizer is N-hydroxysuccinimide (NHS), and the carboxyl source is polyacrylic acid (PAA).

[0012] Furthermore, the mass concentration of the 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) is 0.2-3.5%, the mass concentration of N-hydroxysuccinimide (NHS) is 0.10-3.0%, and the mass concentration of the polyacrylic acid (PAA) is 0.1-2.6%.

[0013] Furthermore, in step 2), making the grafting solution and the membrane element fully contact each other includes: placing the membrane element in the circulating grafting solution.

[0014] Furthermore, based on the volume of the grafting solution in step 2) being 100%, 0.01%-0.5% of an activator or 0.02-0.06% of a stabilizer is added in step 3).

[0015] Furthermore, the method further includes step 4), placing the Nth batch of membrane elements (N≧3) in the N-1th round grafting solution, and adding an activator or a carboxyl source to perform the Nth round of grafting.

[0016] Furthermore, after the second round of grafting in step 4) is completed, a new membrane element is replaced for the third round of grafting. Based on the volume of the second round of grafting solution as 100%, 0.1%-0.6% of an activator or 0.01-0.05% of a carboxyl source is added.

[0017] Furthermore, the method further comprises step 5), wherein the membrane element is flushed with a protective liquid after the grafting is completed.

[0018] Furthermore, the protective solution includes an organic solvent and a reducing agent; preferably, the organic solvent includes alcohol with a mass concentration of 0.1-1%, and the reducing agent includes sodium sulfite with a mass concentration of 0.05-1.5%.

[0019] Furthermore, the water flow rate of each membrane shell is adjusted to 0.02-1.55m 3 / h.

[0020] Furthermore, the number of membrane elements in each batch is 1-16.

[0021] Furthermore, the grafting solution temperature is 25-32°C, the grafting time is 1.5-3h, the mass concentration of EDC is 0.3-2.0%, the mass concentration of PAA is 0.4-1.5%, the mass concentration of NHS is 0.4-1.8%, and the water flow rate of each membrane shell is 0.1-1.0m 3 / h, the number of membrane elements is 4-16.

[0022] A second aspect of the present invention provides a modified reverse osmosis membrane element preparation system, comprising:

[0023] The membrane shell assembly comprises at least one membrane shell, wherein the membrane shell contains at least one membrane element.

[0024] Flushing liquid tank, used to provide flushing liquid to the inside of the membrane housing,

[0025] Grafting solution tank, used to provide grafting solution to the inside of the membrane shell,

[0026] Protective liquid tank, used to provide protective liquid to the inside of the membrane shell;

[0027] The liquid conveying device is connected between the flushing liquid box and the membrane shell to convey the flushing liquid into the membrane shell; or connected between the grafting solution box and the membrane shell to convey the grafting solution into the membrane shell; or connected between the protective liquid box and the membrane shell to convey the protective liquid into the membrane shell.

[0028] Furthermore, it also includes a filter connected between the flushing liquid box and the liquid conveying device for filtering the flushing liquid; or connected between the grafting solution box and the liquid conveying device for filtering the grafting solution; or connected between the protection liquid box and the membrane shell for filtering the protection liquid.

[0029] Furthermore, the liquid delivery device circulates and delivers the grafting solution into the membrane shell.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] The present invention directly grafts and modifies the reverse osmosis membrane element, and the prepared reverse osmosis membrane element can be directly used in engineering. At the same time, the carboxyl content on the surface of the membrane element is increased after modification by the method of the present invention, which can reduce the binding ability of pollutants to the membrane surface, so that the modified reverse osmosis membrane has stronger anti-pollution performance.

[0032] The present invention configures a grafting solution once and can graft multiple batches of membrane elements, effectively improving the utilization rate of chemical agents and reducing the grafting cost of reverse osmosis membrane elements.

[0033] The invention has a simple process flow, small floor space, low energy consumption, and the lowest preparation cost of the reverse osmosis membrane element is 30.3 yuan per element.

[0034] Other features and advantages of the present invention will be described in detail through the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 This is a process flow chart of a modified reverse osmosis membrane element preparation system.

[0037] The markings are as follows: flushing liquid tank 1, grafting solution tank 2, protection liquid tank 3, membrane shell group 4, liquid conveying device 5, filter 6. DETAILED DESCRIPTION

[0038] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0039] In the description of the present invention, it should be noted that the terms "center," "up," "down," "left," "right," "vertical," "horizontal," "inside," and "outside" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions.

[0040] Unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," and "fixed" should be interpreted broadly. For example, they may refer to fixed or removable connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0041] Most pollutants have low solubility in water. During reverse osmosis system operation, concentration polarization causes a significant concentration of pollutants on the membrane surface on the concentrate side. When saturation is reached, they deposit on the membrane surface. Some pollutants are difficult to effectively prevent or control through chemical cleaning, significantly reducing the service life of the reverse osmosis membrane.

[0042] In order to reduce the impact of membrane fouling on the life of reverse osmosis membranes, reduce the operating costs increased by control measures such as pretreatment and membrane cleaning, and accelerate the industrial application of anti-fouling reverse osmosis membrane elements, the present invention provides a method for preparing a modified reverse osmosis membrane element, comprising:

[0043] 1) Rinse the membrane elements in the membrane shell to remove chemicals or residual solvents on the surface of the membrane elements;

[0044] 2) fully contacting the grafting solution with the first batch of membrane elements for the first round of grafting on the flushed membrane elements; wherein the grafting solution includes an activator, a stabilizer, and a carboxyl source, the grafting solution temperature is 10-40° C., and the grafting time is 0.5 h-6.0 h;

[0045] 3) Taking out the first batch of membrane elements, placing the second batch of membrane elements in the grafting solution of step 2), and adding an activator or stabilizer to perform a second round of grafting.

[0046] In some examples, the grafting solution temperature is 15°C, 20°C, 25°C, 30°C, 35°C, etc., and the grafting time is 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, etc.

[0047] In some examples, the activator is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC), the stabilizer is N-hydroxysuccinimide (NHS), and the carboxyl source is polyacrylic acid (PAA). The above types of selection are suitable for use in industrial membrane elements.

[0048] In some examples, the mass concentration of the 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) is 0.2-3.5%, exemplarily 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, 2.2%, 2.5%, 2.8%, 3.0%, 3.2%, etc.; the mass concentration of N-hydroxysuccinimide (NHS) is 0.10-3.0%, exemplarily 0.2% %, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, 2.2%, 2.5%, 2.8%, etc.; the mass concentration of the polyacrylic acid (PAA) is 0.1-2.6%, illustratively 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, 2.2%, 2.5%, etc. Within the above mass concentration range, sufficient carboxyl groups can be grafted onto the surface of the reverse osmosis membrane without increasing the grafting cost due to waste of reagents.

[0049] In some examples, in step 2), allowing the grafting solution to fully contact the membrane element includes placing the membrane element in a circulating grafting solution.

[0050] In some examples, based on the grafting solution volume of step 2) being 100%, 0.01%-0.5% of an activator or 0.02-0.06% of a stabilizer is added in step 3). After one cycle of use, the activation level and stability of the carboxyl groups on the membrane surface decrease in the grafting solution. Supplementing one or both of these agents can increase the reaction kinetics between the carboxyl groups on the PAA and the amino groups on the membrane surface, thereby enhancing the stability of the carboxyl groups on the membrane surface.

[0051] In some examples, the method further includes step 4), placing the Nth batch of membrane elements (N≧3) in the N-1th round grafting solution, and adding an activator or a carboxyl source to perform the Nth round of grafting.

[0052] In some examples, after the second round of grafting in step 4) is completed, a new membrane element is replaced for a third round of grafting. Based on the volume of the second-round grafting solution as 100%, 0.1%-0.6% of an activator or 0.01-0.05% of a carboxyl source is added. Because the activation level and carboxyl content of the agents in the grafting solution decrease after two cycles of use, supplementing one of these agents can enhance the reaction kinetics between the carboxyl groups on the PAA and the amino groups on the membrane surface.

[0053] In some examples, the water flow rate of each membrane shell is adjusted to 0.02-1.55m 3 / h, exemplarily 0.05m 3 / h, 0.08m 3 / h, 0.1m 3 / h, 0.2m 3 / h, 0.3m 3 / h, 0.4m 3 / h, 0.5m 3 / h, 0.6m 3 / h, 0.7m 3 / h, 0.8m 3 / h, 0.9m 3 / h, 1.0m 3 / h, 1.2m 3 / h, 1.3m 3 / h, 1.4m 3 / h, 1.5m 3 / h, etc., to increase the grafting concentration of carboxyl groups on the surface of the reverse osmosis membrane.

[0054] In some examples, the number of membrane elements in each batch is 1-16.

[0055] The present invention further includes step 5), wherein the membrane element is rinsed with a protective liquid after the grafting is completed.

[0056] In some examples, the protective solution in step 3) includes an organic solvent and a reducing agent, such as 0.1-1% alcohol and 0.05-1.5% sodium sulfite. After grafting is completed, the protective solution is used to rinse the membrane element to remove residual grafting solution and protect the grafted carboxyl groups.

[0057] As a preferred example, the grafting solution temperature is 25-32°C, the grafting time is 1.5-3h, the mass concentration of EDC is 0.3-2.0%, the mass concentration of PAA is 0.4-1.5%, the mass concentration of NHS is 0.4-1.8%, and the water flow rate of each membrane shell is 0.1-1.0m 3 / h, and the number of membrane elements is 4-16. The optimal combination of the above parameters can maximize the grafting of carboxyl groups on the membrane surface, thus providing strong anti-fouling performance.

[0058] refer to Figure 1 On the other hand, the present invention provides a modified reverse osmosis membrane element preparation system, comprising:

[0059] The membrane shell group 4 comprises at least one membrane shell, wherein the membrane shell contains at least one membrane element.

[0060] Flushing liquid tank 1, used to provide flushing liquid to the inside of the membrane shell,

[0061] Grafting solution tank 2, used to provide grafting solution to the inside of the membrane shell,

[0062] The protective liquid tank 3 is used to provide protective liquid to the inside of the membrane shell.

[0063] The liquid conveying device 5 is connected between the flushing liquid box and the membrane shell to convey the flushing liquid into the membrane shell; or connected between the grafting solution box and the membrane shell to convey the grafting solution into the membrane shell; or connected between the protective liquid box and the membrane shell to convey the protective liquid into the membrane shell.

[0064] It is understandable that, in the present invention, before delivering the grafting solution into the interior of the membrane shell, the flushing liquid inside the membrane shell can be drained to avoid affecting the grafting effect.

[0065] Furthermore, it also includes a filter 6, which is connected between the flushing liquid tank and the liquid conveying device to filter impurities, particles and suspended matter in the flushing liquid; or connected between the grafting solution tank and the liquid conveying device to filter impurities, particles and suspended matter in the grafting solution; or connected between the protective liquid tank and the membrane shell to filter impurities, particles and suspended matter in the protective liquid.

[0066] Furthermore, the liquid delivery device circulates the grafting solution into the membrane shell, so that the membrane elements are fully in contact with the circulated grafting solution.

[0067] The following describes in detail the working process of a modified reverse osmosis membrane element preparation method and system of the present invention through examples.

[0068] Example 1: This example is to graft a single membrane element

[0069] 1. Use water tank 1 to flush the membrane elements in the system;

[0070] 2. The flushed membrane elements were tested before grafting. The test conditions were: 2000ppm NaCl, test pressure 1.55MPa, test temperature 25°C, test pH 7.0, and a single membrane element recovery rate of approximately 15%. The test results are shown in Table 1 below.

[0071] Table 1

[0072]

[0073] 3. Drain the flushing water in the system and prepare 131 L of grafting solution in water tank 2 with the following mass concentrations: EDC 0.15%, NHS 0.68%, and PAA 0.21%).

[0074] 4. The grafting solution is circulated in the system through the water pump, with a circulation flow rate of 10.3m 3 / h, and perform the first round of grafting on the flushed membrane elements;

[0075] 5. After 2.0 hours of the first round of grafting, replace the second batch of membrane elements and add 0.05% EDC for the second round of grafting;

[0076] 6. After 2 hours of the second round of grafting, the third batch of membrane elements were replaced and 0.13% PAA was added for the third round of grafting.

[0077] 7. Operation parameters of the three-round grafting process: grafting solution temperature 25.0℃, water production 0.06m 3 / h, grafting time is 2h;

[0078] 8. After grafting is completed, flush the system with a protective solution (0.2% alcohol and 0.8% sodium sulfite) to remove residual grafting solution and protect the grafted carboxyl groups;

[0079] 9. The grafted reverse osmosis membrane elements were tested after grafting under the following conditions: 2000 ppm NaCl, test pressure 1.55 MPa, test temperature 25°C, test pH 7.0, and a single membrane element recovery rate of approximately 15%. The test results are shown in Table 2.

[0080] Table 2

[0081]

[0082] 10. A test solution containing silicon pollutants was prepared and the grafted membranes and ungrafted membranes were tested under the same operating conditions. As shown in Table 3 below, the average flux reduction rate of the three grafted membranes was 17.0%, while the flux reduction rate of the ungrafted membrane was 30.4%. In comparison, the flux reduction rate of the grafted membrane was reduced by 43.4%, indicating significantly enhanced anti-pollution performance.

[0083] Table 3

[0084]

[0085] 11. Through cost calculation, the grafting cost of anti-pollution reverse osmosis membrane is 35.3 yuan per piece.

[0086] Data show that the present invention uses 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC), N-hydroxysuccinimide (NHS) as an activator and polyacrylic acid (PAA) to graft reverse osmosis membrane elements, and the anti-fouling performance of the grafted membrane is significantly enhanced. At the same time, the present invention can prepare a grafting solution once to achieve grafting of three batches of membranes, greatly reducing the grafting cost of the anti-fouling reverse osmosis membrane.

[0087] Example 2: This example is to graft four membrane elements (4 in each round)

[0088] 1. Use water tank 1 to flush the membrane elements in the system;

[0089] 2. The flushed membrane elements were tested before grafting. The test conditions were: 2000ppm NaCl, test pressure 1.55MPa, test temperature 25°C, test pH 7.0, and the recovery rate of a single membrane element was approximately 15%. The test results are shown in Table 4 below.

[0090] Table 4

[0091]

[0092]

[0093] 3. Drain the flushing water from the system and prepare 143 L of grafting solution with the following mass concentrations: EDC 0.05%, NHS 0.57%, and PAA 0.3%);

[0094] 4. The grafting solution is circulated in the system through the water pump, with a circulation flow rate of 13.8m 3 / h, graft the first round of membrane elements after flushing, and adjust the operating parameters of the system: grafting solution temperature 36℃, water production 0.73m 3 / h, grafting time is 3h;

[0095] 5. After 3 hours of the first round of grafting, the second batch of membrane elements were replaced and 0.04% NHS was added for the second round of grafting.

[0096] 6. After 3 hours of the second round of grafting, the third batch of membrane elements were replaced and 0.12% EDC was added for the third round of grafting.

[0097] 7. After grafting is completed, flush the system with protective solution (0.12% alcohol and 0.08% sodium sulfite);

[0098] 8. The flushed reverse osmosis membrane elements were tested under the following conditions: 2000ppm NaCl, test pressure 1.55MPa, test temperature 25°C, test pH 7.0, and a single membrane element recovery rate of approximately 15%. The test results are shown in Table 5 below.

[0099] Table 5

[0100]

[0101] 9. A test solution containing silicon pollutants was prepared and four grafted membranes and one ungrafted membrane were tested under the same operating conditions. As shown in the table below, the flux reduction rate of the grafted membrane in three rounds was 15.3-17.4%, while the flux reduction rate of the ungrafted membrane was 34.0%. In comparison, the flux reduction rate of the grafted membrane was reduced by 48.8-55.0%, indicating significantly enhanced anti-pollution performance.

[0102] Through cost calculation, the grafting cost of anti-pollution membrane is 30.6 yuan per piece.

[0103] Table 6

[0104]

[0105]

[0106] Comparative Example 1: This comparative example is a one-round grafting of four membrane modules.

[0107] 1. Use water tank 1 to flush the membrane components in the system;

[0108] 2. The flushed membrane elements were tested before grafting. The test conditions were: 2000ppm NaCl, test pressure 1.55MPa, test temperature 25°C, test pH 7, and a single membrane element recovery rate of approximately 15%. The test results are shown in Table 7 below.

[0109] Table 7

[0110]

[0111] 3. Drain the flushing water from the system and prepare 143 L of grafting solution with the following mass concentrations: EDC 0.15%, NHS 0.67%, and PAA 0.65%).

[0112] 4. The grafting solution is circulated in the system through the water pump, with a circulation flow rate of 12.9m 3 / h, graft the flushed membrane elements, and adjust the operating parameters of the system: grafting solution temperature 20℃, water production 0.40m 3 / h, grafting time is 2.0h;

[0113] 5. After grafting is completed, flush the system with protective solution (0.05% alcohol and 0.08% sodium sulfite);

[0114] 6. The grafted reverse osmosis membrane elements were tested after grafting. The test conditions were: 2000ppm NaCl, test pressure 1.55MPa, test temperature 25°C, test pH 7.0, and a single membrane element recovery rate of approximately 15%. The test results are shown in Table 8 below.

[0115] Table 8

[0116]

[0117]

[0118] 7. A test solution containing silicon pollutants was prepared, and four grafted membranes and one ungrafted membrane were tested under the same operating conditions. As shown in the table below, the average flux reduction rate of the grafted membrane was 16.7%, and the flux reduction rate of the ungrafted membrane was 34.1%. In comparison, the flux reduction rate of the grafted membrane was reduced by 51.0%, and the anti-pollution performance was significantly enhanced.

[0119] Table 9

[0120]

[0121] 8. Through cost calculation, the grafting cost of the anti-fouling membrane of this process is 45.1 yuan / branch, which is 32.1% higher than the cost of the three-round grafting process of the present invention.

[0122] Comparative Example 2

[0123] Similar to Example 2, except that no NHS or EDC was added in step 5 and no EDC or PAA was added in step 6. The effect data are shown in Table 10 below:

[0124] Table 10

[0125]

[0126] When no reagents were added in the second and third rounds, the anti-silicon scale performance test found that the flux decline rate of the membrane in the second and third rounds was large and the anti-pollution performance was poor.

[0127] Comparative Example 3

[0128] Similar to Example 2, except that PAA was added in step 5 and NHS was added in step 6. The effect data are shown in Table 11 below:

[0129] Table 11

[0130]

[0131] When PAA was added in the second round and NHS was added in the third round, the anti-silicon scale performance test found that the flux decline rate of the membrane in the second and third rounds was large and the anti-fouling performance was poor, indicating that the added agents did not work.

[0132] Obviously, the above embodiments of the present invention are merely examples for the purpose of illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not possible to enumerate all embodiments here. Any obvious variations or modifications arising from the technical solutions of the present invention are intended to fall within the spirit and scope of the present invention.

Claims

1. A method for preparing a modified reverse osmosis membrane element, characterized in that: include: 1) Rinse the membrane elements in the membrane shell to remove chemicals or residual solvents on the surface of the membrane elements; 2) fully contacting the grafting solution with the first batch of membrane elements for the first round of grafting on the flushed membrane elements; wherein the grafting solution includes an activator, a stabilizer, and a carboxyl source, the grafting solution temperature is 10-40° C., and the grafting time is 0.5 h-6.0 h; 3) Taking out the first batch of membrane elements, placing the second batch of membrane elements in the grafting solution of step 2), and adding an activator or stabilizer to perform a second round of grafting.

2. The method for preparing a reverse osmosis membrane element according to claim 1, wherein: The activator is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, the stabilizer is N-hydroxysuccinimide, and the carboxyl source is polyacrylic acid; Preferably, the mass concentration of the 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride is 0.2-3.5%, the mass concentration of N-hydroxysuccinimide is 0.10-3.0%, and the mass concentration of the polyacrylic acid is 0.1-2.6%.

3. The method for preparing a reverse osmosis membrane element according to claim 1, wherein: In step 2), the step of making the grafting solution and the membrane element fully contact each other includes: placing the membrane element in the circulating grafting solution.

4. The method for preparing a reverse osmosis membrane element according to any one of claims 1 to 3, characterized in that: Based on the volume of the grafting solution in step 2) being 100%, 0.01%-0.5% of an activator or 0.02-0.06% of a stabilizer is added in step 3).

5. The method for preparing a reverse osmosis membrane element according to any one of claims 1 to 4, characterized in that: The method further includes step 4), placing the Nth batch of membrane elements in the N-1th round grafting solution, and adding an activator or a carboxyl source to perform the Nth round of grafting, wherein N≧3.

6. The method for preparing a reverse osmosis membrane element according to claim 5, characterized in that: After the second round of grafting in step 4) is completed, a new membrane element is replaced for the third round of grafting. Based on the volume of the second round of grafting solution as 100%, 0.1%-0.6% of an activator or 0.01-0.05% of a carboxyl source is added.

7. The method for preparing a reverse osmosis membrane element according to any one of claims 1 to 6, characterized in that: The invention also includes step 5), after the grafting is completed, the membrane element is rinsed with a protective liquid; The protective solution includes an organic solvent and a reducing agent; preferably, the organic solvent includes 0.1-1% alcohol, and the reducing agent includes 0.05-1.5% sodium sulfite.

8. The method for preparing a reverse osmosis membrane element according to claim 1, wherein: Adjust the water flow rate of each membrane shell to 0.02-1.55m 3 / h; Preferably, the number of membrane elements in each batch is 1-16.

9. A modified reverse osmosis membrane element preparation system, characterized in that: include: The membrane shell assembly comprises at least one membrane shell, wherein the membrane shell contains at least one membrane element. Flushing liquid tank, used to provide flushing liquid to the inside of the membrane housing, Grafting solution tank, used to provide grafting solution to the inside of the membrane shell, Protective liquid tank, used to provide protective liquid to the inside of the membrane shell; The liquid conveying device is connected between the flushing liquid box and the membrane shell to convey the flushing liquid into the membrane shell; or connected between the grafting solution box and the membrane shell to convey the grafting solution into the membrane shell; or connected between the protective liquid box and the membrane shell to convey the protective liquid into the membrane shell.

10. The reverse osmosis membrane element preparation system according to claim 9, characterized in that: It also includes a filter connected between the flushing liquid tank and the liquid delivery device for filtering the flushing liquid; or connected between the grafting solution tank and the liquid delivery device for filtering the grafting solution; Or it is connected between the protective liquid tank and the membrane shell to filter the protective liquid; The liquid delivery device circulates and delivers the grafting solution into the membrane shell.

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