A reverse osmosis membrane composite pollution cleaning agent and a preparation method thereof

Abstract

The present application relates to the technical field of cleaning agent, in particular to a kind of reverse osmosis membrane composite pollution cleaning agent and preparation method thereof, the cleaning agent is 100% by mass, comprising: sodium hydroxide 0.8~1.2%, sodium carbonate 1.5~2.5%, sodium fluoride 0.2~0.5%, sodium citrate 1.5~3%, chelating agent 2~4%, surfactant 1.15~2.4%, dispersant 0.5~1.0%, corrosion inhibitor 0.2~0.45%, the rest is water;Chelating agent includes diethylene triamine pentaacetic acid pentasodium and glutamic acid diacetic acid tetrasodium;Surfactant includes fatty alcohol polyoxyethylene ether, alkyl glycoside and cocobetaine.The cleaning agent provided by the present application has high removal capacity for silicon scale and organic composite pollutants through the synergistic effect of multiple components, and the membrane flux recovery rate is high;At the same time, the cleaning condition is mild, does not destroy the desalination layer structure of reverse osmosis membrane, and has little effect on the performance of membrane.

Description

Technical Field

[0001] This invention relates to the field of cleaning agent technology, and in particular to a reverse osmosis membrane composite fouling cleaning agent and its preparation method. Background Technology

[0002] Reverse osmosis membrane cleaning agents are chemicals specifically designed for cleaning reverse osmosis membranes. They remove various contaminants such as silica scale, organic matter, microorganisms, and particulate deposits from the membrane surface and adhering to the membrane, thereby restoring membrane performance and extending its service life. Their main function is to improve the permeate flow rate and desalination rate of the reverse osmosis membrane.

[0003] However, existing reverse osmosis membrane cleaning agents still have significant shortcomings in practical applications: On the one hand, for complex fouling conditions where silica scale and organic matter coexist, traditional cleaning agents often require multiple steps of alternating acid and alkali cleaning, resulting in lengthy cleaning cycles and low cleaning efficiency; on the other hand, in pursuit of short-term membrane flux recovery, some cleaning agents use excessively high pH conditions or highly corrosive components, causing irreversible chemical and physical damage to the core desalination layer of the reverse osmosis polyamide during long-term cleaning, significantly shortening the service life of the membrane element and imposing high replacement costs on enterprises. Particularly noteworthy is that for heavily fouled membrane elements, even increasing the dosage and number of cleaning cycles with existing cleaning agents is insufficient to restore membrane flux to ideal levels.

[0004] Therefore, developing a composite fouling cleaning agent that combines high cleaning efficiency, excellent membrane flux recovery rate, and no damage to the core desalination layer of the reverse osmosis membrane has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a reverse osmosis membrane composite fouling cleaning agent and its preparation method. This cleaning agent can simultaneously and efficiently remove silica scale and organic composite pollutants, while ensuring a high membrane flux recovery rate and reducing damage to the reverse osmosis membrane structure.

[0006] To achieve the above objectives, the present invention provides a reverse osmosis membrane composite fouling cleaning agent, comprising, by weight 100%,: Sodium hydroxide 0.8%~1.2%, sodium carbonate 1.5%~2.5%, sodium fluoride 0.2%~0.5%, sodium citrate 1.5%~3%, chelating agent 2%~4%, surfactant 1.15%~2.4%, dispersant 0.5%~1.0%, corrosion inhibitor 0.2%~0.45%, the remainder being water; The chelating agents include pentasodium diethylenetriaminepentaacetate and tetrasodium diglutamate; The surfactants include fatty alcohol polyoxyethylene ethers, alkyl glycosides, and cocoyl betaine.

[0007] Preferably, the reverse osmosis membrane composite fouling cleaning agent, by weight, comprises: 0.9%~1.1% sodium hydroxide, 1.8%~2.2% sodium carbonate, 0.3%~0.4% sodium fluoride, 2%~2.5% sodium citrate, 2.5%~3% chelating agent, 1.5%~2% surfactant, 0.7%~0.8% dispersant, 0.3%~0.4% corrosion inhibitor, with the remainder being water.

[0008] In this invention, the mass ratio of the pentasodium diethylenetriaminepentaacetate and the tetrasodium diglutamate is 1.5~2.5:0.5~1.5, preferably 1.8~2:0.7~1.

[0009] In this invention, the mass ratio of the fatty alcohol polyoxyethylene ether, alkyl glycoside and cocoyl betaine is 0.8~1.5:0.3~0.8:0.05~0.1, preferably 1~1.2:0.44~0.71:0.06~0.09.

[0010] In this invention, the dispersant comprises sodium polyacrylate, and the corrosion inhibitor comprises sodium silicate and benzotriazole.

[0011] In this invention, the mass ratio of sodium silicate to benzotriazole is 0.15~0.3:0.05~0.15, preferably 0.2~0.28:0.1~0.12.

[0012] This invention also provides a method for preparing the above-mentioned reverse osmosis membrane composite fouling cleaning agent, comprising the following steps: S1. Mix sodium hydroxide, sodium carbonate, sodium citrate, chelating agent and water to obtain mixture A; S2. Add surfactant to mixture A, stir, then add dispersant and benzotriazole to obtain mixture B; S3. Sodium fluoride is mixed with the remaining water and added to mixture B, followed by sodium silicate, to obtain a reverse osmosis membrane composite fouling cleaning agent.

[0013] In this invention, step S1 specifically includes: placing sodium hydroxide and sodium carbonate in water, stirring to obtain an alkaline solution, then adding sodium citrate, pentasodium diethylenetriaminepentaacetate, and tetrasodium diglutamate to the alkaline solution, and continuing to stir for 15-20 minutes to obtain mixture A. The stirring temperature is 40-45°C, preferably 42-44°C, the stirring speed is 150-300 rpm, preferably 200-250 rpm, and the stirring time is 10-15 minutes, preferably 12-13 minutes; the mass of the water accounts for 75%-80% of the total mass of the water.

[0014] In this invention, step S2 specifically includes: after lowering the system temperature to 30-35°C, adding fatty alcohol polyoxyethylene ether, alkyl glycoside, and cocoyl betaine, stirring to obtain a surfactant mixture, then adding sodium polyacrylate and benzotriazole, and continuing stirring for 10-20 minutes to obtain mixture B. The stirring temperature is 30-35°C, preferably 32-33°C, the stirring speed is 150-300 rpm, preferably 200-250 rpm, and the stirring time is 10-15 minutes, preferably 12-13 minutes.

[0015] In this invention, step S3 specifically includes: mixing sodium fluoride with the remaining water to obtain an aqueous sodium fluoride solution; adding the aqueous sodium fluoride solution dropwise to mixture B; subsequently adding sodium silicate; and continuing stirring for 20-30 minutes to obtain a reverse osmosis membrane composite fouling cleaning agent. The mixing speed is 150-300 rpm, preferably 200-250 rpm; the temperature is 50-55℃, preferably 52-53℃; and the time is 5-8 minutes, preferably 6-7 minutes. The dropwise addition time is 15-25 minutes, preferably 20-22 minutes.

[0016] The present invention has the following beneficial effects: This invention provides a reverse osmosis membrane composite fouling cleaning agent, comprising, by weight (100%): 0.8%~1.2% sodium hydroxide, 1.5%~2.5% sodium carbonate, 0.2%~0.5% sodium fluoride, 1.5%~3% sodium citrate, 2%~4% chelating agent, 1.15%~2.4% surfactant, 0.5%~1.0% dispersant, 0.2%~0.45% corrosion inhibitor, with the remainder being water; the chelating agent includes pentasodium diethylenetriaminepentaacetate and tetrasodium diglutamate; the surfactant includes fatty alcohol polyoxyethylene ether, alkyl glycoside, and cocoyl betaine.

[0017] This invention utilizes the reaction of fluoride ions provided by sodium fluoride with silica in silica scale to generate soluble fluorosilicic acid complexes. Combined with the strong complexing effect of sodium diethylenetriaminepentaacetate and sodium citrate on polyvalent metal ions such as iron, aluminum, calcium, and magnesium, the metal silicate framework structure is destroyed, achieving deep dissolution and stable dispersion of silica scale. At the same time, the mild alkaline environment constructed by sodium hydroxide and sodium carbonate causes organic pollutants to swell, hydrolyze, and saponify. Fatty alcohol polyoxyethylene ethers and alkyl glycosides synergistically penetrate, emulsify, and strip the organic pollutant layer, while coconut oil betaine further solubilizes and assists in the stripping of biofilm pollutants.

[0018] The chelating agent of this invention is a compound of pentasodium diethylenetriaminepentaacetate and tetrasodium glutamate diacetate. Pentasodium diethylenetriaminepentaacetate has an extremely strong chelating ability for high-valence metal ions such as iron, aluminum, and copper, effectively disintegrating the skeletal structure of dense metal silicates such as iron silicate and aluminum silicate. Tetrasodium glutamate diacetate exhibits excellent chelating effect on alkaline earth metals such as calcium and magnesium, and remains stable over a wide pH range. The two work synergistically to achieve coverage of multiple metal ions. After chelating and dissolving metal ions from the scale, a dispersant is used to maintain the dissolved state and prevent redeposition, loosening the silica scale structure and facilitating the penetration and dissolution of silica by alkaline solutions and fluoride ions, thus improving overall cleaning efficiency.

[0019] The surfactants used in this invention are a compound of fatty alcohol polyoxyethylene ether, alkyl glycoside, and cocoyl betaine. Fatty alcohol polyoxyethylene ether has strong penetrating power and can penetrate deep into scale. Alkyl glycoside has a stripping effect on polysaccharide biofilms and humic acids. Cocoyl betaine is an amphoteric surfactant with strong solubilizing ability and also has foam-stabilizing and bactericidal effects. The three surfactants have complementary detergency spectra, covering various organic pollutants such as oils, proteins, and biofilms. All three are resistant to hard water and maintain excellent detergency performance even in high-hardness concentrated water environments. Overall, the surfactants are mild, low in toxicity, and environmentally friendly.

[0020] The reverse osmosis membrane composite fouling cleaning agent provided by this invention has a high efficiency in removing silica scale and organic composite fouling through the synergistic effect of multiple components, and a high membrane flux recovery rate; at the same time, the cleaning conditions are mild, do not damage the desalination layer structure of the reverse osmosis membrane, and have little impact on membrane performance.

[0021] The present invention further specifies that the dispersant includes sodium polyacrylate; sodium polyacrylate utilizes the electrostatic repulsion of carboxyl groups and the steric hindrance effect of polymer chains to stably suspend detached contaminants in the cleaning solution, effectively preventing them from re-aggregating and depositing on the membrane surface and in the membrane pores, and avoiding secondary pollution during the cleaning process; at the same time, sodium polyacrylate works synergistically with chelating agents to inhibit the regeneration of metal silicate precipitates by chelated metal ions when locally supersaturated, thus maintaining the cleanliness of the cleaning solution.

[0022] This invention further specifies that the corrosion inhibitor includes sodium silicate and benzotriazole. Sodium silicate forms a nano-scale silica hydrated colloidal thin layer under alkaline conditions, which has a certain physical barrier effect on the diffusion of hydroxide ions into the deep layer of the polyamide membrane, thereby reducing the risk of excessive corrosion of the desalination layer by the alkaline cleaning environment. At the same time, sodium silicate forms a silicate passivation film on the stainless steel surface to prevent corrosion of metal equipment by fluorine-containing alkaline cleaning solution. Benzotriazole can form a dense passivation protective film on the surface of stainless steel pipelines and metal parts of the cleaning system to prevent corrosion of metal equipment by alkaline fluorine-containing cleaning solution. After the synergistic effect of sodium silicate and benzotriazole, they form protective barriers on the surface of membrane elements and stainless steel pipelines, respectively, ensuring efficient cleaning while taking into account the structural integrity of membrane elements and the corrosion resistance of metal equipment, thus comprehensively ensuring the safety and reliability of the cleaning process.

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0024] Figure 1 These are graphs showing the scale dissolution rate test results of Examples 1-4 and Comparative Examples 1-7 of the present invention; Figure 2 These are graphs showing the test results of desalination rate and membrane flux recovery rate in Examples 1-4 and Comparative Examples 1-7 of the present invention; in, Figure 2 In the figure, 'a' represents the membrane flux recovery rate test result. Figure 2 In the figure, b represents the result of the desalination rate test. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0026] Example 1 This embodiment provides a reverse osmosis membrane composite fouling cleaning agent, which, by weight (100%), consists of the following components: Sodium hydroxide 0.8%, sodium carbonate 1.5%, sodium fluoride 0.2%, sodium citrate 1.5%, pentasodium diethylenetriaminepentaacetate 1.5%, tetrasodium diglutamate diacetate 0.5%, fatty alcohol polyoxyethylene ether 0.8%, alkyl glycoside 0.3%, cocobetaine 0.05%, sodium polyacrylate 0.5%, sodium silicate 0.15%, benzotriazole 0.05%, with the remainder being water.

[0027] The preparation process of the above-mentioned reverse osmosis membrane composite fouling cleaning agent is as follows: S1. Sodium hydroxide and sodium carbonate are placed in water (75% of the total mass of water) and stirred at 150 rpm for 15 min at 40°C to obtain an alkaline solution. Then, sodium citrate, pentasodium diethylenetriaminepentaacetate and tetrasodium diglutamate are added to the alkaline solution and stirred for another 15 min to obtain mixture A.

[0028] S2. After the system temperature is lowered to 30℃, fatty alcohol polyoxyethylene ether, alkyl glycoside and cocoyl betaine are added. The mixture is stirred at 150 rpm for 15 min to obtain a surfactant mixture. Then sodium polyacrylate and benzotriazole are added and stirred for another 20 min to obtain mixture B.

[0029] S3. Sodium fluoride and the remaining water are mixed at 50°C and 150 rpm for 8 minutes to obtain an aqueous solution of sodium fluoride. The aqueous solution of sodium fluoride is added dropwise to the mixture B (dropwise addition time 15 minutes), followed by the addition of sodium silicate, and stirring is continued for 20 minutes.

[0030] Example 2 This embodiment provides a reverse osmosis membrane composite fouling cleaning agent, which, by weight (100%), consists of the following components: Sodium hydroxide 1.2%, sodium carbonate 2.5%, sodium fluoride 0.5%, sodium citrate 3%, pentasodium diethylenetriaminepentaacetate 2.5%, tetrasodium diglutamate diacetate 1.5%, fatty alcohol polyoxyethylene ether 1.5%, alkyl glycoside 0.8%, cocobetaine 0.1%, sodium polyacrylate 1.0%, sodium silicate 0.3%, benzotriazole 0.15%, with the remainder being water.

[0031] The preparation process of the above-mentioned reverse osmosis membrane composite fouling cleaning agent is as follows: S1. Sodium hydroxide and sodium carbonate are placed in water (75% of the total mass of water) and stirred at 300 rpm for 10 min at 45°C to obtain an alkaline solution. Then, sodium citrate, pentasodium diethylenetriaminepentaacetate and tetrasodium diglutamate are added to the alkaline solution and stirred for another 20 min to obtain mixture A.

[0032] S2. After the system temperature is lowered to 35℃, fatty alcohol polyoxyethylene ether, alkyl glycoside and cocoyl betaine are added. The mixture is stirred at 300 rpm for 10 min to obtain a surfactant mixture. Then sodium polyacrylate and benzotriazole are added and stirred for another 10 min to obtain mixture B.

[0033] S3. Sodium fluoride and the remaining water are mixed at 55°C and 300 rpm for 5 min to obtain an aqueous solution of sodium fluoride. The aqueous solution of sodium fluoride is added dropwise to the mixture B (dropwise addition time 25 min), followed by the addition of sodium silicate, and stirring is continued for 20 min.

[0034] Example 3 This embodiment provides a reverse osmosis membrane composite fouling cleaning agent, which, by weight (100%), consists of the following components: Sodium hydroxide 0.9%, sodium carbonate 1.8%, sodium fluoride 0.3%, sodium citrate 2%, pentasodium diethylenetriaminepentaacetate 1.8%, tetrasodium diglutamate diacetate 0.7%, fatty alcohol polyoxyethylene ether 1%, alkyl glycoside 0.44%, cocobetaine 0.06%, sodium polyacrylate 0.7%, sodium silicate 0.2%, benzotriazole 0.1%, with the remainder being water.

[0035] The preparation process of the above-mentioned reverse osmosis membrane composite fouling cleaning agent is as follows: S1. Sodium hydroxide and sodium carbonate are placed in water (80% of the total mass of water) and stirred at 200 rpm for 13 min at 42℃ to obtain an alkaline solution. Then, sodium citrate, pentasodium diethylenetriaminepentaacetate and tetrasodium diglutamate are added to the alkaline solution and stirred for another 20 min to obtain mixture A.

[0036] S2. After the system temperature is lowered to 32℃, fatty alcohol polyoxyethylene ether, alkyl glycoside and cocoyl betaine are added. The mixture is stirred at 200 rpm for 12 min to obtain a surfactant mixture. Then sodium polyacrylate and benzotriazole are added and the mixture is stirred for another 20 min to obtain mixture B.

[0037] S3. Sodium fluoride and the remaining water are mixed at 52°C and 250 rpm for 6 minutes to obtain an aqueous solution of sodium fluoride. The aqueous solution of sodium fluoride is added dropwise to the mixture B (dropwise addition time 20 minutes), followed by the addition of sodium silicate, and stirring is continued for 30 minutes.

[0038] Example 4 This embodiment provides a reverse osmosis membrane composite fouling cleaning agent, which, by weight (100%), consists of the following components: Sodium hydroxide 1.1%, sodium carbonate 2.2%, sodium fluoride 0.4%, sodium citrate 2.5%, pentasodium diethylenetriaminepentaacetate 2%, tetrasodium diglutamate diacetate 1%, fatty alcohol polyoxyethylene ether 1.2%, alkyl glycoside 0.71%, cocobetaine 0.09%, sodium polyacrylate 0.8%, sodium silicate 0.28%, benzotriazole 0.12%, with the remainder being water.

[0039] The preparation process of the above-mentioned reverse osmosis membrane composite fouling cleaning agent is as follows: S1. Sodium hydroxide and sodium carbonate are placed in water (80% of the total mass of water) and stirred at 250 rpm for 12 min at 44℃ to obtain an alkaline solution. Then, sodium citrate, pentasodium diethylenetriaminepentaacetate and tetrasodium diglutamate are added to the alkaline solution and stirred for another 10 min to obtain mixture A.

[0040] S2. After the system temperature is lowered to 33℃, fatty alcohol polyoxyethylene ether, alkyl glycoside and cocoyl betaine are added. The mixture is stirred at 250 rpm for 13 min to obtain a surfactant mixture. Then sodium polyacrylate and benzotriazole are added and the mixture is stirred for another 20 min to obtain mixture B.

[0041] S3. Sodium fluoride and the remaining water are mixed at 53°C and 200 rpm for 7 min to obtain an aqueous solution of sodium fluoride. The aqueous solution of sodium fluoride is added dropwise to the mixture B (dropwise addition time 22 min), followed by the addition of sodium silicate, and stirring is continued for 30 min.

[0042] Comparative Example 1 This comparative example provides a reverse osmosis membrane composite fouling cleaning agent, which has a composition that is basically the same as that of Example 1, except that it does not contain diethylenetriaminepentaacetic acid pentasodium.

[0043] Comparative Example 2 This comparative example provides a reverse osmosis membrane composite fouling cleaning agent, which has a composition that is basically the same as that of Example 1, except that it does not contain tetrasodium diacetate of glutamate.

[0044] Comparative Example 3 This comparative example provides a reverse osmosis membrane composite fouling cleaning agent, which has the same composition as Example 1, except that it does not contain fatty alcohol polyoxyethylene ether.

[0045] Comparative Example 4 This comparative example provides a reverse osmosis membrane composite fouling cleaning agent, which has basically the same composition as Example 1, except that no alkyl glycosides are added.

[0046] Comparative Example 5 This comparative example provides a reverse osmosis membrane composite fouling cleaning agent, which has basically the same composition as Example 1, except that sodium silicate is not added.

[0047] Comparative Example 6 This comparative example provides a reverse osmosis membrane composite fouling cleaning agent, which has basically the same composition as Example 1, except that benzotriazole is not added.

[0048] Comparative Example 7 This comparative example provides a reverse osmosis membrane composite fouling cleaning agent, which has basically the same composition as Example 1, except that sodium fluoride is not added.

[0049] Performance testing: Take 50 mL of the reverse osmosis membrane composite fouling cleaning agent prepared in Examples 1-4 and Comparative Examples 1-7 and add them to three-necked flasks respectively. Adjust the pH to 10.5±0.2, and after maintaining the temperature at 30±0.2℃, add 5 g of calcium sulfate crystals to each flask, denoted as m1. After stirring at the constant temperature for 4 h, filter, and dry the filter cake in a vacuum drying oven to constant weight, denoted as m3. Calculate the scale dissolution rate. The results are shown in Table 1 and... Figure 1 .

[0050] .

[0051] Where m1 is the mass of calcium sulfate crystals (5g); m2 is the mass of filter paper; and m3 is the mass of filter cake and filter paper after drying.

[0052] Table 1 Scale Dissolution Rate Test Results

[0053] From Table 1 and Figure 1 It can be seen that the scale dissolution rate of Examples 1-4 all reached over 90%, with Example 2 having the highest rate at 96.8%, indicating that the cleaning agent provided by the present invention has excellent dissolution ability for inorganic salt scale. The results of Comparative Examples 1 and 2 show that diethylenetriaminepentaacetic acid pentasodium and glutamic acid diacetic acid tetrasodium have a synergistic chelating effect, which can improve the scale dissolution effect.

[0054] The pH of the reverse osmosis membrane composite fouling cleaning agent prepared in Examples 1-4 and Comparative Examples 1-7 was adjusted to 10.5±0.2, and then added to the reverse osmosis membrane treatment device (BW30-400 model reverse osmosis system membrane element). The temperature was adjusted to 32°C, and after cleaning for 1.5 hours, the cleaning solution was drained, and the reverse osmosis membrane was rinsed with deionized water for 20 minutes.

[0055] Raw water was treated using reverse osmosis membrane treatment units before and after cleaning. The conductivity of the feed water and product water was measured to calculate the desalination rate and membrane flux recovery rate. The results are shown in Table 2 and... Figure 2 .

[0056] ; Table 2. Test results of desalination rate and membrane flux recovery rate

[0057] From Table 2 and Figure 2 It can be seen that the water flux was significantly restored after cleaning in Examples 1-4, indicating that the cleaning agent of the present invention has excellent cleaning effect on organosilicon complex fouling, and the membrane performance was well restored after cleaning. The desalination rate remained stable within a narrow range before and after cleaning and among the groups, indicating that the cleaning agent of the present invention effectively restored the membrane flux without causing structural damage such as swelling or hydrolysis to the membrane structure, and had little impact on the long-term operational safety of the membrane element. The water flux recovery rate of Comparative Example 1 (without diethylenetriaminepentaacetic acid pentasodium) and Comparative Example 7 (without sodium fluoride) decreased significantly, proving that diethylenetriaminepentaacetic acid pentasodium and sodium fluoride are the key components in this formulation for removing complex fouling, and play a role by chelating and disintegrating the metal silicate framework and dissolving silica scale by fluorine complexation, respectively.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A reverse osmosis membrane composite fouling cleaning agent, characterized in that, Based on 100% quality, it includes: Sodium hydroxide 0.8%~1.2%, sodium carbonate 1.5%~2.5%, sodium fluoride 0.2%~0.5%, sodium citrate 1.5%~3%, chelating agent 2%~4%, surfactant 1.15%~2.4%, dispersant 0.5%~1.0%, corrosion inhibitor 0.2%~0.45%, the remainder being water; The chelating agents include pentasodium diethylenetriaminepentaacetate and tetrasodium diglutamate; The surfactants include fatty alcohol polyoxyethylene ethers, alkyl glycosides, and cocoyl betaine.

2. The reverse osmosis membrane composite fouling cleaning agent according to claim 1, characterized in that, Based on 100% quality, it includes: Sodium hydroxide 0.9%~1.1%, sodium carbonate 1.8%~2.2%, sodium fluoride 0.3%~0.4%, sodium citrate 2%~2.5%, chelating agent 2.5%~3%, surfactant 1.5%~2%, dispersant 0.7%~0.8%, corrosion inhibitor 0.3%~0.4%, and the remainder is water.

3. The reverse osmosis membrane composite fouling cleaning agent according to claim 1, characterized in that, The mass ratio of the diethylenetriaminepentaacetic acid pentasodium and the glutamic acid diacetic acid tetrasodium is 1.5~2.5:0.5~1.

5.

4. The reverse osmosis membrane composite fouling cleaning agent according to claim 1, characterized in that, The mass ratio of the fatty alcohol polyoxyethylene ether, alkyl glycoside and cocoyl betaine is 0.8~1.5:0.3~0.8:0.05~0.

1.

5. The reverse osmosis membrane composite fouling cleaning agent according to claim 1, characterized in that, The dispersant includes sodium polyacrylate, and the corrosion inhibitor includes sodium silicate and benzotriazole.

6. The reverse osmosis membrane composite fouling cleaning agent according to claim 5, characterized in that, The mass ratio of sodium silicate to benzotriazole is 0.15~0.3:0.05~0.

15.

7. A method for preparing a reverse osmosis membrane composite fouling cleaning agent according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Mix sodium hydroxide, sodium carbonate, sodium citrate, chelating agent and water to obtain mixture A; S2. Add surfactant to mixture A, stir, then add sodium polyacrylate and benzotriazole to obtain mixture B; S3. Sodium fluoride is mixed with the remaining water and added to mixture B, followed by sodium silicate, to obtain a reverse osmosis membrane composite fouling cleaning agent.

8. The preparation method according to claim 7, characterized in that, The water described in S1 accounts for 75% to 80% of the total water mass.

9. The preparation method according to claim 7, characterized in that, The stirring temperature in S2 is 30~35℃, the stirring time is 10~15min, and the stirring speed is 150~300rpm.

10. The preparation method according to claim 7, characterized in that, The mixing speed described in S3 is 150~300 rpm, the temperature is 50~55℃, and the time is 5~8 min.

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