A membrane cleaning method combining pretreatment with an organic scale inhibitor and the use of a cleaning agent

Abstract

The present invention relates to the field of wastewater treatment, and particularly to a membrane cleaning method combining organic scale inhibitor pretreatment and the use of a cleaning agent, comprising the following steps: S1. Using an organic pollutant solution and a reverse osmosis membrane scale inhibitor for mixing to perform cyclic membrane blocking on a reverse osmosis membrane element; S2. Sequentially using an acidic solution, a basic solution, and a membrane cleaning agent to clean the reverse osmosis membrane element; S3. Using clear water to wash the reverse osmosis membrane element. This combined cleaning method can effectively improve the cleaning efficiency, reduce membrane fouling, and extend the service life of the membrane. The protective layer formed through pretreatment can reduce the formation of dirt and lower the subsequent cleaning difficulty. The organic scale inhibitor and cleaning agent used in the present invention are specifically designed for organic pollutants and have stronger pertinence and cleaning effect.

Description

Technical Field

[0001] The present invention relates to the field of wastewater treatment, and particularly to a membrane cleaning method that combines pretreatment with an organic scale inhibitor and the use of a cleaning agent. Background Art

[0002] In the field of water treatment technology, especially in the application of membrane separation technology, the problem of membrane fouling has always been a key factor restricting its development and efficiency. Due to its high-efficiency separation and purification capabilities, membrane separation technology has been widely used under the background of increasingly strict water quality requirements in the process of industrialization and urbanization. However, during the treatment process, the membrane is prone to adsorption and deposition of various pollutants in water, resulting in a decrease in membrane flux and separation performance, thereby increasing operating costs and maintenance difficulties.

[0003] Traditional membrane cleaning methods are mainly divided into two categories: physical cleaning and chemical cleaning. Physical cleaning methods, such as isobaric hydraulic flushing, air-water mixing cleaning, hot water and pure water flushing, negative pressure reverse flushing, etc., mainly remove pollutants on the membrane surface through mechanical forces. However, physical cleaning has limited effects on stubborn pollutants and may cause damage to the membrane material. Chemical cleaning methods use specific chemical agents to react with pollutants on the membrane surface to achieve the purpose of cleaning. This method can effectively remove dirt and deposits on the membrane surface and restore the performance of the membrane. However, the selection and use of chemical cleaning agents need to be cautious to avoid corrosion of the membrane material or causing secondary pollution, and frequent chemical cleaning will damage the membrane and shorten its service life.

[0004] With the development of water treatment technology, the research on new water treatment technologies has become a hot topic. However, the problem of membrane fouling remains an urgent challenge that requires the development of new cleaning methods and technologies to improve the cleaning efficiency and service life of the membrane. In addition, with the increasing emphasis on environmental protection and sustainable development, the development of new and environmentally friendly cleaning agents and scale inhibitors has become the focus of research. These studies not only focus on cleaning effects but also consider the environmental impact and biodegradability of chemicals to achieve the effective utilization and protection of water resources. Summary of the Invention

[0005] To solve the problems in the background art, the present invention proposes a membrane cleaning method that combines pretreatment with an organic scale inhibitor and the use of a cleaning agent. This method first uses an organic scale inhibitor for pretreatment. By utilizing its unique molecular structure and chemical properties, a protective layer is formed on the membrane surface to effectively prevent the formation of a scale layer. Subsequently, a highly efficient cleaning agent is used for comprehensive cleaning, penetrating into the membrane pores, decomposing and removing stubborn dirt, while maintaining the integrity and performance of the membrane.

[0006] The technical solution adopted by the present invention to solve its technical problems is: to provide a membrane cleaning method that combines pretreatment with an organic scale inhibitor and the use of a cleaning agent, including the following steps:

[0007] S1. Use an organic pollutant solution and an anti-scaling agent for reverse osmosis membranes to mix and circulate to block the reverse osmosis membrane elements.

[0008] S2. Clean the reverse osmosis membrane elements successively with an acidic solution, an alkaline solution, and a membrane cleaning agent.

[0009] S3. Wash the reverse osmosis membrane elements with clean water.

[0010] Furthermore, the preparation of the new anti-scaling agent for reverse osmosis membranes includes the following steps:

[0011] A1: Raw material preparation step; Select dodecyl bis(hydroxyethyl)methyl ammonium chloride and deionized water as the raw materials for the anti-scaling agent.

[0012] A2: Anti-scaling agent preparation step; Add dodecyl bis(hydroxyethyl)methyl ammonium chloride and deionized water to the reaction kettle in sequence; Start stirring at room temperature, and the stirring time is 18 - 22 minutes; Gradually raise the temperature to 38°C - 42°C during stirring, and continue stirring at this temperature for 28 - 32 minutes; After stopping stirring, keep warm for 4 - 6 hours; Then cool to room temperature and place for 2 - 4 hours to obtain the finished product.

[0013] Furthermore, the new anti-scaling agent for reverse osmosis membranes includes the following raw materials in parts by weight:

[0014] Dodecyl bis(hydroxyethyl)methyl ammonium chloride: 32 - 36 parts;

[0015] Deionized water: 64 - 68 parts.

[0016] Furthermore, in the preparation step of the new anti-scaling agent for reverse osmosis membranes, the stirring speed is 300 - 500 r / min.

[0017] Furthermore, in step S1, the preparation of the organic pollutant solution includes: Weigh humic acid and dissolve it in a NaOH solution, filter it after water bath heating, and adjust the pH to neutral.

[0018] Among them, the concentration of the NaOH solution is 0.08 - 0.12 mol / L; The water bath temperature is 78 - 82°C; The heating time is 7.8 - 8.2 hours.

[0019] In step S1, the concentration of the organic pollutant solution is 2800 - 3200 ppm, the dosing concentration of the new anti-scaling agent for reverse osmosis membranes is 55 - 65 ppm, and the circulation time for blocking the membrane is 22 - 26 h.

[0020] Furthermore, in step S2, the acidic solution is HCl and / or citric acid; The concentration of the HCl and / or citric acid is 0.008 - 0.012 mol / L.

[0021] The alkaline solution is NaOH; the concentration of the NaOH is 0.008 - 0.012 mol / L;

[0022] In step S2, the dosing concentration of the membrane cleaning agent is 0.8 - 1.2%.

[0023] Furthermore, the preparation of the membrane cleaning agent includes the following steps:

[0024] B1: Prepare the raw materials of the membrane cleaning agent; select sodium tetraphosphate, sodium citrate, EDTA-2Na, sodium gluconate, and sodium dodecylbenzenesulfonate for standby;

[0025] B2: Prepare a stirrer, add sodium tetraphosphate, sodium citrate, EDTA-2Na, sodium gluconate, and sodium dodecylbenzenesulfonate during stirring, control the temperature between 20°C and 30°C, and stir for 18 - 22 min to obtain the finished cleaning agent.

[0026] Furthermore, the membrane cleaning agent includes the following raw materials by weight:

[0027] Sodium tetraphosphate: 49 parts - 53 parts;

[0028] Sodium citrate: 7 parts - 11 parts;

[0029] EDTA-2Na: 17 parts - 21 parts;

[0030] Sodium gluconate: 15 parts - 19 parts;

[0031] Sodium dodecylbenzenesulfonate: 2 parts - 6 parts.

[0032] The present invention also provides a membrane cleaning agent, including: sodium tetraphosphate; sodium citrate; EDTA-2Na; sodium gluconate; sodium dodecylbenzenesulfonate.

[0033] Furthermore, the membrane cleaning agent includes the following raw materials by weight:

[0034] Sodium tetraphosphate: 49 parts - 53 parts;

[0035] Sodium citrate: 7 parts - 11 parts;

[0036] EDTA-2Na: 17 parts - 21 parts;

[0037] Sodium gluconate: 15 parts - 19 parts;

[0038] Sodium dodecylbenzenesulfonate: 2 parts - 6 parts.

[0039] The beneficial effects of the present invention are:

[0040] (1) The present invention proposes a membrane cleaning method that combines organic scale inhibitor pretreatment with cleaning agent. This combined method can effectively improve cleaning efficiency, reduce membrane fouling, and extend the service life of the membrane. The protective layer formed by pretreatment can reduce the formation of scale and reduce the difficulty of subsequent cleaning. The organic scale inhibitor and cleaning agent used in the present invention are specially designed for organic pollutants and have stronger targeting and cleaning effect. In the experiment, after using the scale inhibitor pretreatment, the cleaning agent can more easily clean the membrane surface, while the cleaning effect is not good when the scale inhibitor is not used, which shows that the present invention can significantly improve the cleaning effect. Compared with traditional cleaning methods, the cleaning method of the present invention performs better in terms of cleaning efficiency and membrane performance recovery. It can not only effectively remove dirt and sediment on the membrane surface, but also reduce damage to the membrane material, thereby extending the service life of the membrane.

[0041] (2) The present invention also provides a novel cleaning agent, the research and development of which takes environmental protection and sustainability into consideration, thereby reducing the impact on the environment. The environmental friendliness of the cleaning agent is reflected in its biodegradability and low toxicity, which helps to achieve the effective utilization and protection of water resources. By using the cleaning method of the present invention, the frequency and amount of chemical cleaning agents used can be reduced, thereby reducing operating costs and reducing potential damage to membrane materials. This has significant economic and environmental benefits for industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is the SEM analysis diagram of Example 1;

[0043] Figure 2 This is the EDS analysis diagram of Example 1;

[0044] Figure 3 This is the SEM analysis diagram of Example 2;

[0045] Figure 4 This is the EDS analysis diagram of Example 2;

[0046] Figure 5 This is the SEM analysis diagram of Comparative Example 1;

[0047] Figure 6 This is the EDS analysis diagram of Comparative Example 1;

[0048] Figure 7 This is the SEM analysis diagram of Comparative Example 2;

[0049] Figure 8 This is the EDS analysis diagram of Comparative Example 2;

[0050] Figure 9 This is the SEM analysis diagram of Comparative Example 3;

[0051] Figure 10EDS analysis diagram of Comparative Example 3;

[0052] Figure 11 SEM analysis diagram of Comparative Example 4;

[0053] Figure 12 EDS analysis diagram of Comparative Example 4;

[0054] Figure 13 SEM analysis diagram of Comparative Example 5;

[0055] Figure 14 EDS analysis diagram of Comparative Example 5. Specific Embodiments

[0056] The technical solutions in the embodiments of the invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the invention. It can be understood that the specific embodiments described herein are only for explaining the present invention, rather than limiting the present invention. In addition, it should be noted that for the convenience of description, only some parts related to the present invention rather than all the structures are shown in the drawings.

[0057] Embodiment 1: A membrane cleaning method combining pretreatment with an organic scale inhibitor and the use of a cleaning agent, specifically including the following steps:

[0058] 1. Use a 2000 ppm sodium chloride solution to test and record the operating parameters of the membrane elements in the reverse osmosis device before fouling at a pressure of 15 bar, including the water production flow rate, the conductivity of the produced water, and the conductivity of the raw water, and then wash the membrane 3 times with clean water (20 min / time);

[0059] 2. Prepare an organic pollutant solution and a scale inhibitor;

[0060] The preparation method of the organic pollutant solution is as follows:

[0061] Weigh 21.0 g of humic acid and dissolve it in 7 L of 0.1 mol / L NaOH solution. After filtration through water bath heating, heat it in a water bath at 80 °C for 8 h, filter it through a 450-mesh filter, and adjust the filtrate to pH = 7 with a 1:1 HCl solution and then make up the volume to 7 L.

[0062] The preparation method of the new reverse osmosis membrane scale inhibitor is as follows:

[0063] S1: The raw material preparation step of the new reverse osmosis membrane scale inhibitor. First, prepare 34 parts by weight of dodecyl bis(hydroxyethyl)methyl ammonium chloride and 66 parts by weight of deionized water for standby;

[0064] S2: Preparation steps of the new reverse osmosis membrane scale inhibitor. First, prepare a reaction kettle, add dodecyl bis(hydroxyethyl)methyl ammonium chloride and deionized water into the reaction kettle in sequence. After stirring for 20 min, the stirring speed is 300 - 500 r / min, and the temperature is gradually raised to 40 °C, then stir for 30 min. After stopping stirring, keep warm for 4 - 6 h. After cooling to room temperature and standing for 2 - 4 h, the finished product is obtained. It is a colorless transparent liquid at normal temperature, without sediment and visible mechanical impurities.

[0065] 3. Mix the prepared 3000 ppm organic pollutant solution and 60 ppm new reverse osmosis membrane scale inhibitor, and then add them to the reverse osmosis device to circulate and block the membrane at 20 bar pressure for 24 h.

[0066] 4. Use 2000 ppm sodium chloride solution to test and record the operating parameters of the membrane element in the reverse osmosis device at 15 bar pressure, including the water production flow rate, as well as the conductivity of the produced water and the raw water, and then wash the membrane with clean water 3 times (20 min each time).

[0067] 5. Use 0.01 mol / L hydrochloric acid solution with pH = 2 to clean the reverse osmosis membrane element without pressure for 3 h;

[0068] Use 0.01 mol / L sodium hydroxide solution with pH = 12 to clean the reverse osmosis membrane element without pressure for 3 h;

[0069] The preparation method of the cleaning agent is as follows:

[0070] S1: Raw material preparation steps of the cleaning agent. Prepare 51 parts by weight of tetrasodium diphosphate, 9 parts by weight of sodium citrate, 19 parts by weight of EDTA - 2Na, 17 parts by weight of sodium gluconate and 4 parts by weight of sodium dodecylbenzenesulfonate for standby;

[0071] S2: Preparation steps of the cleaning agent. Add the prepared raw materials to a blender for stirring. The stirring speed is 30 - 50 r / min. During the stirring process, add the prepared raw materials and stir for 20 min. After stirring evenly, the finished product is obtained. It is a white powdery solid at normal temperature, without visible mechanical impurities;

[0072] Use 1% new cleaning agent with pH = 12 to clean the reverse osmosis membrane element without pressure for 6 h;

[0073] Use 2.5% new cleaning agent with pH = 12 to clean the reverse osmosis membrane element without pressure for 6 h.

[0074] 6. Use 2000 ppm sodium chloride solution to test and record the operating parameters of the membrane element in the reverse osmosis device at 15 bar pressure, including the water production flow rate, as well as the conductivity of the produced water and the raw water, and then wash the membrane with clean water 3 times (20 min each time).

[0075] Table 1 shows the EDS analysis results of Example 1.

[0076]

[0077] As Figure 1 and Figure 2 shown, when 60 ppm of the new reverse osmosis membrane scale inhibitor is added to the 3000 ppm humic acid solution, combined with the new cleaning agent and the cleaning agent method, the deposition of pollutants on the surface of the membrane sheet after 24 hours of fouling is significantly reduced, and the apparent concentration of C element drops to 29.57%. This result indicates that the membrane cleaning method combining organic scale inhibitor pretreatment and the use of cleaning agent can most effectively reduce the deposition of pollutants and achieve the best cleaning effect.

[0078] Example 2: The difference between Example 2 and Example 1 is that the membrane element is not cleaned with a cleaning agent.

[0079] Table 2 shows the EDS analysis results of Example 2.

[0080]

[0081] As Figure 3 and Figure 4 shown, when the membrane element is not cleaned with a cleaning agent, the deposition of pollutants on the surface of the membrane sheet after 24 hours of fouling is significantly reduced, and the apparent concentration of C element drops to 29.85%.

[0082] Example 3: The difference between Example 3 and Example 1 is that the membrane element is not cleaned with an alkaline solution and a cleaning agent.

[0083] Comparative Example 1: Using humic acid to circulate and foul the membrane element

[0084] 1. Test and record the operating parameters of the membrane element in the reverse osmosis device before fouling with a 2000 ppm sodium chloride solution at a pressure of 15 bar, including the water production flow rate, the conductivity of the produced water, and the conductivity of the raw water, and then wash the membrane 3 times with clean water (20 min / time);

[0085] 2. Prepare an organic pollutant solution;

[0086] The preparation method of the organic pollutant solution is as follows:

[0087] Weigh 21.0 g of humic acid and dissolve it in 7 L of 0.1 mol / L NaOH solution. After heating in a water bath and filtering, heat it in a water bath at 80 °C for 8 h, filter it with a 450-mesh filter, and adjust the filtrate to pH = 7 with 1:1 HCl solution and then make up the volume to 7 L.

[0088] 3. Add the prepared 3000 ppm organic pollutant solution to the reverse osmosis device and circulate and foul the membrane at a pressure of 20 bar for 24 h.

[0089] 4. Test and record the operating parameters of the membrane elements in the reverse osmosis device with a 2000 ppm sodium chloride solution at a pressure of 15 bar, including the product water flow rate, as well as the product water conductivity and the raw water conductivity, and then wash the membrane with clean water 3 times (20 min each time).

[0090] Table 3 shows the EDS analysis results of Comparative Example 1.

[0091]

[0092] As Figure 5 and Figure 6 shown, in a 3000 ppm humic acid solution, after 24 h of fouling, obvious pollutant deposits appeared on the surface of the RO membrane sheet, and the apparent concentration of C element was 76.19%.

[0093] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that no organic scale inhibitor is used during the cyclic membrane fouling.

[0094] Table 4 shows the EDS analysis results of Example and Comparative Example 2.

[0095]

[0096] As Figure 7 and Figure 8 shown, when no organic scale inhibitor pretreatment is used in a 3000 ppm humic acid solution and only the new cleaning agent and the cleaning agent method are used, the pollutant deposits on the surface of the membrane sheet after 24 h of fouling are reduced, and the apparent concentration of C element is 40.80%. This shows that the cleaning effect of using the new cleaning agent alone is relatively average and fails to achieve the best cleaning effect.

[0097] Comparative Example 3: Replace the organic scale inhibitor with a commercially available foreign brand A scale inhibitor. The commercially available foreign brand A scale inhibitor is polyacrylic acid.

[0098] 1. Test and record the operating parameters of the membrane elements in the reverse osmosis device before fouling with a 2000 ppm sodium chloride solution at a pressure of 15 bar, including the product water flow rate, as well as the product water conductivity and the raw water conductivity, and then wash the membrane with clean water 3 times (20 min each time);

[0099] 2. Prepare an organic pollutant solution;

[0100] The preparation method of the organic pollutant solution is as follows:

[0101] Weigh 21.0 g of humic acid and dissolve it in 7 L of 0.1 mol / L NaOH solution. After heating in a water bath and filtering, heat it in a water bath at 80 °C for 8 h, filter it with a 450-mesh filter, adjust the filtrate to pH = 7 with a 1:1 HCl solution, and then make up the volume to 7 L.

[0102] 3. Add the prepared 3000 ppm organic pollutant solution and 60 ppm of commercially available foreign brand A scale inhibitor to the reverse osmosis device and circulate to block the membrane at a pressure of 20 bar for 24 h. The commercially available foreign brand A scale inhibitor is polyacrylic acid.

[0103] 4. Use a 2000 ppm sodium chloride solution to test and record the operating parameters of the membrane elements in the reverse osmosis device at a pressure of 15 bar, including the water production flow rate, the conductivity of the produced water and the raw water, and then wash the membrane 3 times with clean water (20 min each time).

[0104] Table 5 shows the EDS analysis results of Comparative Example 3.

[0105]

[0106] As Figure 9 and Figure 10 shown, when 60 ppm of commercially available foreign brand A scale inhibitor is added to a 3000 ppm humic acid solution, after 24 h, the deposition of pollutants on the membrane surface decreases, and the apparent concentration of element C is 91.89%.

[0107] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that the novel reverse osmosis membrane scale inhibitor is replaced with a commercially available foreign brand A scale inhibitor. The commercially available foreign brand A scale inhibitor is polyacrylic acid.

[0108] Table 6 shows the EDS analysis results of Comparative Example 4.

[0109]

[0110] As Figure 11 and Figure 12 shown, when 60 ppm of commercially available foreign brand A scale inhibitor is added to a 3000 ppm humic acid solution and combined with the novel cleaning agent and the cleaning agent method, after 24 h of fouling, the deposition of pollutants on the membrane surface decreases, and the apparent concentration of element C is 55.58%. Compared with the novel reverse osmosis membrane scale inhibitor, its effect is slightly insufficient.

[0111] Comparative Example 5: 1. Use a 2000 ppm sodium chloride solution to test and record the operating parameters of the membrane elements in the reverse osmosis device before fouling, including the water production flow rate, the conductivity of the produced water and the raw water, and then wash the membrane 3 times with clean water (20 min each time);

[0112] 2. Prepare an organic pollutant solution;

[0113] The preparation method of the organic pollutant solution is as follows:

[0114] Weigh 21.0 g of humic acid and dissolve it in 7 L of 0.1 mol / L NaOH solution. After heating in a water bath and filtering, heat it in a water bath at 80 °C for 8 h, filter it with a 450-mesh filter screen, and adjust the filtrate to pH = 7 with 1:1 HCl solution and then make up the volume to 7 L.

[0115] 3. Add the prepared 3000 ppm organic pollutant solution and 60 ppm new reverse osmosis membrane scale inhibitor to the reverse osmosis device and circulate to block the membrane at a pressure of 20 bar for 24 h.

[0116] 4. Use 2000 ppm sodium chloride solution to test and record the operating parameters of the membrane elements in the reverse osmosis device at a pressure of 15 bar, including the water production flow rate, the conductivity of the produced water and the raw water, and then wash the membrane with clean water 3 times (20 min each time).

[0117] Table 7 shows the EDS analysis results of Comparative Example 5.

[0118]

[0119] As Figure 13 and Figure 14 shown, when 60 ppm of the new reverse osmosis membrane scale inhibitor is added to the 3000 ppm humic acid solution, after 24 h, the deposition of pollutants on the membrane surface is further reduced, and the apparent concentration of C element is 46.90%.

[0120] For Examples 1-2 and Comparative Examples 1-5, the operating parameters of the reverse osmosis membrane before and after cleaning were tested, and the test results are shown in Table 1 and Table 2:

[0121] Among them, the calculation method of the membrane flux recovery rate is as follows: First, calculate the membrane fluxes of the cleaned membrane and the original membrane according to the water production flow rate; then calculate the membrane flux recovery rate according to the ratio of the membrane fluxes of the cleaned membrane and the original membrane. The specific calculation formula is shown in Equation (1):

[0122] (1)

[0123] Table 8: Test results of the operating parameters of the reverse osmosis membrane after membrane blocking and after cleaning in Examples 1-3.

[0124]

[0125] Table 9: Test results of the operating parameters of the reverse osmosis membrane after membrane blocking and after cleaning in Comparative Examples 1-5.

[0126]

[0127] As can be seen from Table 8 and Table 9, for the reverse osmosis membrane severely fouled, only alkali cleaning is adopted. As shown in Example 3, the membrane flux can only be restored to 83.33%. However, after chemical cleaning with the cleaning agent and cleaning method of the present invention, the flux can be restored to more than 90%. For the reverse osmosis membrane severely fouled, whether or not a scale inhibitor is added, after chemical cleaning with the cleaning agent and cleaning method of the present invention, all operating parameters of the reverse osmosis membrane are significantly improved, mainly manifested in the increase in membrane flux recovery. However, after adding a commercially available foreign brand A scale inhibitor and then performing chemical cleaning with the cleaning agent and cleaning method of the present invention, as shown in Comparative Example 4, the flux is not restored. In Example 1, the membrane cleaning method using the scale inhibitor and cleaning agent of the present invention in combination shows the most obvious increase in membrane flux, and the flux is restored to more than 90%, indicating that the membrane cleaning method of the present invention combining organic scale inhibitor pretreatment and cleaning agent use has good application value.

[0128] The present invention has been described in detail above in combination with examples and comparative examples. However, the present invention is not limited to the above examples. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the gist of the present invention. The content not described in detail in the present invention can all adopt the prior art.

Claims

1. A membrane cleaning method that combines the pretreatment with an organic scale inhibitor and the use of a cleaning agent, characterized in that, It includes the following steps: S1. Use an organic pollutant solution and an anti-scaling agent for reverse osmosis membranes to mix and conduct cyclic membrane blocking on the reverse osmosis membrane element; S2. Use an acidic solution, an alkaline solution, and a membrane cleaning agent to clean the reverse osmosis membrane element in sequence; S3. Wash the reverse osmosis membrane element with clean water; Among them, the preparation of the anti-scaling agent for reverse osmosis membranes includes the following steps: A1: Raw material preparation step; Select dodecyl bis(hydroxyethyl)methyl ammonium chloride and deionized water as the raw materials for the anti-scaling agent; A2: Anti-scaling agent preparation step; Add dodecyl bis(hydroxyethyl)methyl ammonium chloride and deionized water into the reaction kettle in sequence; Start stirring at room temperature, and the stirring time is 18 - 22 minutes; Gradually heat up to 38°C - 42°C during the stirring process, and continue stirring at this temperature for 28 - 32 minutes; After stopping stirring, keep warm for 4 - 6 hours; Then cool to room temperature and place for 2 - 4 hours to obtain the finished product.

2. A membrane cleaning method that combines the pretreatment with an organic scale inhibitor and the use of a cleaning agent, characterized in that, The anti-scaling agent for reverse osmosis membranes includes the following raw materials by weight: Dodecyl bis(hydroxyethyl)methyl ammonium chloride: 32 - 36 parts; Deionized water: 64 - 68 parts.

3. According to the membrane cleaning method combining organic anti-scaling agent pretreatment and cleaning agent use described in claim 2, it is characterized in that: In the preparation step of the anti-scaling agent for reverse osmosis membranes, the stirring speed is 300 - 500 r / min.

4. A membrane cleaning method combining the pretreatment with an organic scale inhibitor and the use of a cleaning agent according to claim 1, characterized in that, S1. The preparation of the organic pollutant solution includes: Weigh humic acid, dissolve it in an alkaline solution, filter it after water bath heating, and adjust the pH to neutral; Among them, the concentration of the alkaline solution is 0.08 - 0.12 mol / L; The water bath temperature is 78 - 82°C; The heating time is 7.8 - 8.2 hours; The concentration of the organic pollutant solution is 2800 - 3200 ppm, the dosing concentration of the anti-scaling agent for reverse osmosis membranes is 55 - 65 ppm, and the cyclic membrane blocking time is 22 - 26 h.

5. According to the membrane cleaning method combining organic anti-scaling agent pretreatment and cleaning agent use described in claim 1, it is characterized in that: In S2, the acidic solution is HCl and / or citric acid; The concentration of HCl and / or citric acid is 0.008 - 0.012 mol / L; The alkaline solution is NaOH; The concentration of NaOH is 0.008 - 0.012 mol / L; In S2, the dosing concentration of the membrane cleaning agent is 0.8 - 1.2%.

6. A membrane cleaning method combining the pretreatment with an organic scale inhibitor and the use of a cleaning agent according to claim 1, characterized in that, The preparation of the membrane cleaning agent includes the following steps: B1: Prepare the raw materials for the membrane cleaning agent; Select sodium tripolyphosphate, sodium citrate, EDTA - 2Na, sodium gluconate, and sodium dodecylbenzenesulfonate for standby; B2: Prepare a stirrer, add sodium tripolyphosphate, sodium citrate, EDTA - 2Na, sodium gluconate, and sodium dodecylbenzenesulfonate during the stirring process, control the temperature between 20°C and 30°C, and stir for 18 - 22 min to obtain the finished cleaning agent.

7. A membrane cleaning method combining the pretreatment with an organic scale inhibitor and the use of a cleaning agent according to claim 6, characterized in that, The membrane cleaning agent includes the following raw materials by weight: Sodium tripolyphosphate: 49 - 53 parts; Sodium citrate: 7 - 11 parts; ​ ​ ​

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