Neutral cleaning agent for reverse osmosis membrane organic dirt as well as preparation method and use method of neutral cleaning agent

Abstract

The invention provides a neutral cleaning agent for reverse osmosis membrane organic dirt as well as a preparation method and a use method of the neutral cleaning agent, and belongs to the technical field of cleaning agents. N, N-dimethylglycine, chlorobutane, DMF (Dimethyl Formamide), glyceryl monoisostearate, epoxypropane, 2-naphthylamine-3, 6, 8-trisulfonic acid and the like are mainly used for synthesis, and an excessive solvent is removed through reduced pressure distillation to obtain a hyperdispersant product. The dispersant is basically neutral, and is matched with isodecanol polyoxyethylene ether and water to form a slightly neutral cleaning agent solution, so that a strong acidic or strong alkaline system is not needed, the organic dirt on the reverse osmosis membrane can be quickly and efficiently cleaned and removed after heating, and the reverse osmosis membrane is hardly damaged; the cleaning agent can be used for cleaning the reverse osmosis membrane for a long time.

Description

Technical Field

[0001] The present invention belongs to the technical field of cleaning agents, and particularly relates to a neutral cleaning agent for organic fouling of reverse osmosis membranes, a preparation method thereof, and a usage method thereof. Background Art

[0002] A reverse osmosis membrane is an artificial semi-permeable membrane with certain characteristics made by simulating a biological semi-permeable membrane, and is the core component of reverse osmosis technology. The principle of reverse osmosis technology is that under the action of a pressure higher than the osmotic pressure of the solution, these substances and water are separated based on the fact that other substances cannot pass through the semi-permeable membrane. The membrane pore diameter of the reverse osmosis membrane is very small, so it can effectively remove dissolved salts, colloids, microorganisms, organic substances, etc. in water. The system has the advantages of good water quality, low energy consumption, no pollution, simple process, easy operation, etc. In recent years, it has been widely used in the field of water treatment. After the reverse osmosis device operates for a period of time, substances such as colloids, bacteria, organic substances, and inorganic scales will accumulate on the concentrated water side of the membrane, causing problems such as a decrease in the treatment efficiency of the reverse osmosis system, a reduction in the water output, and an increase in the pressure difference, thereby forming membrane fouling. Especially for the reverse osmosis treatment devices used in the fine chemical industry, due to the small amount of organic substances in the treated water, the organic fouling is more serious. The cost of directly replacing the membrane is too high, and the most common method is to clean the contaminated reverse osmosis membrane.

[0003] Currently, the commonly used method in the industry is to use a strong acid solution for cleaning. For example, in Chinese Patent CN109499382B, this cleaning method generally has a good effect on treating inorganic salt fouling such as carbonate fouling, but has a poor effect on organic fouling. At the same time, the acidic solution has a certain damage to the membrane structure, affecting the effect of the regenerated membrane. Another method is to use an alkali solution for cleaning, with a pH generally above 12. The alkali solution cleaning has a certain treatment effect on organic fouling, and it uses the decomposition effect of the alkali solution on organic substances for washing. However, it often requires a high concentration of the alkali solution, which causes relatively serious damage to the membrane itself and is difficult to be used as a good cleaning solution.

[0004] How to develop a cleaning system that can be used for reverse osmosis cleaning for a long time, not only has a good cleaning effect, but also has less damage to the reverse osmosis membrane itself for reverse osmosis membranes contaminated by organic fouling is the direction that the industry has been developing. This can significantly reduce the use cost of reverse osmosis membranes and promote the development of reverse osmosis membranes and the downstream fine chemical industry. Summary of the Invention

[0005] In view of the above problems, the present invention provides a neutral cleaning agent for organic fouling of reverse osmosis membranes, a preparation method and a use method thereof. The cleaning agent is mainly synthesized using N,N-dimethylglycine, chlorobutane, DMF, glycerol monoisostearate, propylene oxide, 2-naphthylamine-3,6,8-trisulfonic acid, etc., and the excessive solvent is removed by vacuum distillation to obtain a hyperdispersant product. Since the dispersant contains multiple sodium sulfonate groups in its own molecular structure, and also contains active amino groups and quaternary ammonium salt groups, the sodium sulfonate and active amino groups are beneficial to the dispersion and removal of organic fouling on the reverse osmosis membrane, and the quaternary ammonium salt can simultaneously carry out a bactericidal effect. The dispersant itself is basically neutral, and it is combined with isodecyl polyoxyethylene ether and water to form a neutral cleaning agent solution. There is no need to use a strong acid or strong alkaline system. After heating to 50-70 °C, the organic fouling on the reverse osmosis membrane can be efficiently cleaned and removed quickly. It is not only convenient to use and low in cost, but also does not require a strong acid or strong alkaline environment and hardly damages the reverse osmosis membrane.

[0006] One of the purposes of the present invention is to provide a neutral cleaning agent for organic fouling of reverse osmosis membranes.

[0007] Another purpose of the present invention is to provide a preparation method of the neutral cleaning agent for organic fouling of reverse osmosis membranes.

[0008] The third purpose of the present invention is to provide a use method of the neutral cleaning agent for organic fouling of reverse osmosis membranes.

[0009] In order to achieve the above purposes of the present invention, the following technical solutions are specifically adopted:

[0010] In the first aspect, the present invention provides a neutral cleaning agent for organic fouling of reverse osmosis membranes, and the neutral cleaning agent for organic fouling of reverse osmosis membranes is prepared from raw materials including the following molar parts:

[0011] 8-10 parts of N,N-dimethylglycine;

[0012] 8-9.5 parts of 1-chlorobutane;

[0013] 5-8 parts of N,N-dimethylformamide;

[0014] 9-12 parts of glycerol monoisostearate;

[0015] 60-65 parts of propylene oxide;

[0016] 8-11 parts of 2-naphthylamine-3,6,8-trisulfonic acid.

[0017] In some embodiments, the raw materials further include catalyst A and catalyst B. Catalyst A is potassium iodide, and its dosage is 0.05-0.08% of the mass of N,N-dimethylglycine; catalyst B is tetrabutyl titanate, and its dosage is 0.08-0.12% of the mass of glyceryl mono-isostearate.

[0018] Preferably, the raw materials further include an aqueous sodium hydroxide solution for neutralizing and salifying and adjusting the pH value of the system, and the mass fraction of the aqueous sodium hydroxide solution is 50-55%.

[0019] In some embodiments, the raw materials further include isodecyl polyoxyethylene ether and water.

[0020] An exemplary model of isodecyl polyoxyethylene ether is E-1005, which is purchased from Hai'an Petrochemical Factory, Jiangsu Province.

[0021] Typical but non-limiting molar amounts of N,N-dimethylglycine are, for example, 8, 9, 10 parts;

[0022] Typical but non-limiting molar amounts of 1-chlorobutane are, for example, 8, 8.5, 9, 9.5 parts;

[0023] Typical but non-limiting molar amounts of N,N-dimethylformamide (DMF) are, for example, 5, 6, 7, 8 parts;

[0024] Typical but non-limiting molar amounts of glyceryl mono-isostearate (mono-isostearate glyceride, CAS No. 66085-00-5) are, for example, 9, 10, 11, 12 parts.

[0025] Typical but non-limiting molar amounts of propylene oxide are, for example, 60, 61, 62, 63, 64, 65 parts.

[0026] Typical but non-limiting molar amounts of 2-naphthylamine-3,6,8-trisulfonic acid are, for example, 8, 9, 10, 11 parts.

[0027] The dosage of catalyst A is, for example, 0.05%, 0.06%, 0.07%, 0.08% of the mass of N,N-dimethylglycine; the dosage of catalyst B is, for example, 0.08%, 0.09%, 0.10%, 0.11%, 0.12% of the mass of glyceryl mono-isostearate.

[0028] In a second aspect, the present invention provides a method for preparing the above-mentioned neutral cleaning agent for organic fouling of reverse osmosis membranes, including the following steps:

[0029] A. Add the formulated amounts of N,N-dimethylformamide, N,N-dimethylglycine, 1-chlorobutane and catalyst A into reactor A, start stirring, and raise the temperature for quaternization reaction;

[0030] B. When the conversion rate of 1-chlorobutane reaches over 97%, pump the quaternary ammonium salt solution obtained in reactor A to the high-level tank for standby.

[0031] C. Add the formulated amount of glyceryl isostearate, propylene oxide and catalyst B to high-pressure reactor B. After sealing the high-pressure reactor, start stirring and raise the temperature to conduct a high-temperature and pressure-bearing chain extension polymerization reaction.

[0032] D. When the pressure in reactor B reaches atmospheric pressure, lower the temperature. Then add the formulated amount of 2-naphthylamine-3,6,8-trisulfonic acid and the quaternary ammonium salt solution obtained in step B to reactor B, and raise the temperature to conduct a graft chain extension reaction of sulfonate and quaternary ammonium salt. At the same time, start the vacuum system to conduct a high-temperature vacuum esterification reaction, and remove the N,N-dimethylformamide solvent in the reaction system during the reaction process.

[0033] E. Take a sample and detect it by liquid chromatography. When the conversion rate of 2-naphthylamine-3,6,8-trisulfonic acid reaches over 95%, release the vacuum system, lower the temperature, and then dropwise add an aqueous sodium hydroxide solution to conduct a neutralization salt formation reaction and pH adjustment. When the pH in the system reaches 7.0 - 7.5, stop the reaction to obtain a polymeric hyperdispersant product.

[0034] F. Then add isomeric decanol polyoxyethylene ether accounting for 2 - 3% of the mass of the polymeric hyperdispersant product. After mixing evenly, add deionized water to prepare an aqueous solution with a solid content of 60 - 65% to obtain a neutral cleaning agent product.

[0035] In some embodiments, in step A, the temperature is raised to 60 - 65 °C.

[0036] In some embodiments, in step C, the temperature is raised to 120 - 125 °C, and the reaction time is 2 - 3 h.

[0037] In some embodiments, in step D, the temperature is lowered to 70 - 80 °C; the temperature is raised to 105 - 110 °C, and the vacuum degree is -0.095 Mpa to -0.097 Mpa.

[0038] In some embodiments, in step E, the temperature is lowered to 40 - 45 °C, and the mass fraction of the aqueous sodium hydroxide solution is 50 - 55 wt%.

[0039] In a specific embodiment, the preparation method of the neutral cleaning agent for organic fouling of reverse osmosis membranes includes the following steps:

[0040] A. Add the formulated amount of N,N-dimethylformamide, N,N-dimethylglycine, 1-chlorobutane and catalyst A to reactor A. Start stirring and raise the temperature to 60 - 65 °C for heat preservation to conduct a quaternization reaction.

[0041] B. Use gas chromatography for sampling detection. When the conversion rate of 1-chlorobutane reaches over 97%, it indicates that the quaternization reaction is basically completed. At this time, pump the quaternary ammonium salt solution obtained in reactor A to the high-level tank for standby;

[0042] C. Add the formulated amount of glycerol mono-iso-stearate, propylene oxide and catalyst B to high-pressure reactor B. After sealing the high-pressure reactor, start stirring and heat up to 120 - 125 °C for high-temperature pressure-bearing chain extension polymerization reaction for 2 - 3 h;

[0043] D. Detect the pressure in reactor B. When the pressure in the reactor reaches the atmospheric pressure state, it indicates that the propylene oxide is basically polymerized. Cool down to 70 - 80 °C, then open the high-pressure kettle, add the formulated amount of 2-naphthylamine-3,6,8-trisulfonic acid and the quaternary ammonium salt solution from step B into reactor B, and heat up to 105 - 110 °C for the grafting reaction of sulfonate and quaternary ammonium salt. At the same time, start the vacuum system for high-temperature vacuum esterification reaction, and control the vacuum degree at -0.095 Mpa to -0.097 Mpa;

[0044] E. Use liquid chromatography for sampling detection of the content of 2-naphthylamine-3,6,8-trisulfonic acid. When the conversion rate of 2-naphthylamine-3,6,8-trisulfonic acid reaches over 95%, it indicates that the grafting reaction is basically completed. At this time, release the vacuum system, cool down to 40 - 45 °C, then dropwise add 50 - 55 wt% sodium hydroxide aqueous solution for neutralization salt formation reaction and pH adjustment. When the pH in the system reaches 7.0 - 7.5, it indicates that the neutralization salt formation reaction is basically completed, stop the reaction, and obtain the polymeric hyperdispersant product;

[0045] F. Then add isodecyl polyoxyethylene ether accounting for 2 - 3% of the mass of the polymeric hyperdispersant product. After mixing evenly, add deionized water to prepare an aqueous solution with a solid content of 60 - 65% to obtain a neutral cleaning agent product.

[0046] The neutral cleaning agent for organic fouling of the reverse osmosis membrane obtained in the present invention is a light yellow transparent viscous liquid, with a solid content of 60 - 65% and a pH of 7.0 - 7.5.

[0047] In the third aspect, the present invention provides a method for using the above-mentioned neutral cleaning agent for organic fouling of the reverse osmosis membrane, including the following steps:

[0048] Dilute the neutral cleaning agent to a solution with a mass fraction of 4 - 7%, heat it to 50 - 70 °C, then add it to the reverse osmosis membrane cleaning device contaminated with organic fouling for circulating cleaning. After cleaning, drain the cleaning solution, and then rinse the reverse osmosis membrane with deionized water.

[0049] Beneficial effects:

[0050] The cleaning agent of the present invention is mainly synthesized using N,N-dimethylglycine, chlorobutane, DMF, glycerol monoisostearate, propylene oxide, 2-naphthylamine-3,6,8-trisulfonic acid, etc., and the excessive solvent is removed by vacuum distillation to obtain the hyperdispersant product. Since the main chain of this dispersant is mainly polyisopropyl ether structure, it has good compatibility with organic dirt, and its molecular structure contains multiple sodium sulfonate groups, and also contains active amino groups and quaternary ammonium salt groups. The sodium sulfonate and active amino groups are beneficial to the dispersion and removal of organic dirt on the reverse osmosis membrane, and the quaternary ammonium salt can simultaneously perform a bactericidal effect. This dispersant is basically neutral by itself, and is combined with isodecyl alcohol polyoxyethylene ether with fast penetration ability and water to form a neutral cleaning agent solution. There is no need to use a strong acid or strong base system. After heating to 50-70 °C, the organic dirt on the reverse osmosis membrane can be efficiently cleaned and removed quickly. It is not only convenient to use and low in cost, but also does not require a strong acid or strong base environment and causes almost no damage to the reverse osmosis membrane.

[0051] The present invention has been described in detail above, but the above embodiments are essentially illustrative only and are not intended to limit the present invention. In addition, the present invention is not limited by any theory described in the foregoing prior art or the invention content or the following examples. Detailed implementation manners

[0052] The following further illustrates the present invention in conjunction with embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of the present invention claimed.

[0053] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the embodiments are all conventional raw materials, reagents, methods in the art.

[0054] Isodecyl alcohol polyoxyethylene ether, model E-1005, is purchased from Hai'an Petrochemical Factory, Jiangsu Province.

[0055] Example 1

[0056] A neutral cleaning agent for organic dirt on a reverse osmosis membrane, comprising the following raw materials in molar parts:

[0057] N,N-dimethylglycine 8 parts;

[0058] 1-chlorobutane 8 parts;

[0059] N,N-dimethylformamide 5 parts;

[0060] Glycerol monoisostearate 11 parts;

[0061] Propylene oxide 64 parts;

[0062] 2-naphthylamine-3,6,8-trisulfonic acid 8 parts;

[0063] Catalyst A (potassium iodide), with a dosage of 0.05% of the mass of N,N-dimethylglycine;

[0064] Catalyst B (tetrabutyl titanate), with a dosage of 0.09% of the mass of glyceryl mono-isostearate.

[0065] A method for preparing the above neutral cleaning agent for organic fouling of reverse osmosis membranes, comprising the following steps:

[0066] A. Add the formulated amounts of N,N-dimethylformamide, N,N-dimethylglycine, 1-chlorobutane and Catalyst A to Reactor A, start stirring, and raise the temperature to 65 °C for heat preservation for quaternization reaction;

[0067] B. Take a sample for gas chromatography detection. When the conversion rate of 1-chlorobutane reaches more than 97%, it indicates that the quaternization reaction is basically completed. At this time, pump the quaternary ammonium salt solution obtained in Reactor A to the high-level tank for standby;

[0068] C. Add the formulated amounts of glyceryl mono-isostearate, propylene oxide and Catalyst B to High-pressure Reactor B. After sealing the high-pressure reactor, start stirring and raise the temperature to 120 °C for high-temperature pressure-bearing chain extension polymerization reaction for 2 - 3 h;

[0069] D. Detect the pressure in Reactor B. When the pressure in the reactor reaches the atmospheric pressure state, it indicates that the propylene oxide is basically polymerized. Cool down to 75 °C, then open the high-pressure kettle, add the formulated amount of 2-naphthylamine-3,6,8-trisulfonic acid and the quaternary ammonium salt solution obtained in Step B to Reactor B, and raise the temperature to 110 °C for grafting reaction of sulfonate and quaternary ammonium salt. At the same time, start the vacuum system for high-temperature vacuum esterification reaction, and control the vacuum degree at -0.095 Mpa;

[0070] E. Take a sample for liquid chromatography detection of the content of 2-naphthylamine-3,6,8-trisulfonic acid. When the conversion rate of 2-naphthylamine-3,6,8-trisulfonic acid reaches more than 95%, it indicates that the grafting reaction is basically completed. At this time, release the vacuum system, cool down to 40 °C, then dropwise add 55 wt% sodium hydroxide solution for neutralization and salt formation reaction and pH adjustment. When the pH in the system reaches 7.1, it indicates that the neutralization and salt formation reaction is basically completed, stop the reaction, and obtain the polymeric hyperdispersant product;

[0071] F. Then add isodecyl polyoxyethylene ether accounting for 2% of the mass of the polymeric hyperdispersant product, stir and mix evenly, and then add deionized water to formulate it into an aqueous solution with a solid content of 62% to obtain the neutral cleaning agent product.

[0072] The neutral cleaning agent for organic fouling of reverse osmosis membranes prepared is a light yellow transparent viscous liquid, with a pH of 7.1 and a solid content of 62%.

[0073] Example 2

[0074] A neutral cleaning agent for organic fouling of reverse osmosis membranes, comprising raw materials in the following molar parts:

[0075] N,N-dimethylglycine 10 parts;

[0076] 1-chlorobutane 9.5 parts;

[0077] N,N-dimethylformamide 8 parts;

[0078] mono-isostearoyl glycerol 9 parts;

[0079] propylene oxide 63 parts;

[0080] 2-naphthylamine-3,6,8-trisulfonic acid 9 parts;

[0081] Catalyst A (potassium iodide), with a dosage of 0.08% of the mass of N,N-dimethylglycine;

[0082] Catalyst B (tetrabutyl titanate), with a dosage of 0.10% of the mass of mono-isostearoyl glycerol;

[0083] The dosage of isomeric decanol polyoxyethylene ether is 2.5% of the mass of the polymeric hyperdispersant.

[0084] The preparation method is the same as that of Example 1.

[0085] The neutral cleaning agent for organic fouling of reverse osmosis membranes prepared is a light yellow transparent viscous liquid, with a pH of 7.3 and a solid content of 63%.

[0086] Example 3

[0087] A neutral cleaning agent for organic fouling of reverse osmosis membranes, comprising raw materials in the following molar parts:

[0088] N,N-dimethylglycine 9 parts;

[0089] 1-chlorobutane 9 parts;

[0090] N,N-dimethylformamide 6 parts;

[0091] mono-isostearoyl glycerol 10 parts;

[0092] propylene oxide 60 parts;

[0093] 2-naphthylamine-3,6,8-trisulfonic acid 11 parts;

[0094] Catalyst A (potassium iodide), with a dosage of 0.06% of the mass of N,N-dimethylglycine;

[0095] Catalyst B (tetrabutyl titanate), with a dosage of 0.12% of the mass of mono-isostearoyl glycerol.

[0096] The dosage of isomeric decyl alcohol polyoxyethylene ether is 3% of the mass of the polymeric hyperdispersant.

[0097] The preparation method is the same as that of Example 1.

[0098] The neutral cleaning agent for organic fouling of the reverse osmosis membrane prepared is a light yellow transparent viscous liquid, with a pH of 7.2 and a solid content of 64%.

[0099] Example 4

[0100] A neutral cleaning agent for organic fouling of a reverse osmosis membrane, comprising raw materials in the following molar parts:

[0101] 8 parts of N,N-dimethylglycine;

[0102]

[0103] Catalyst A (potassium iodide), with a dosage of 0.07% of the mass of N,N-dimethylglycine;

[0104] Catalyst B (tetrabutyl titanate), with a dosage of 0.09% of the mass of glycerol monoisostearate.

[0105] The dosage of isomeric decyl alcohol polyoxyethylene ether is 2.7% of the mass of the polymeric hyperdispersant.

[0106] The preparation method is the same as that of Example 1.

[0107] The neutral cleaning agent for organic fouling of the reverse osmosis membrane prepared is a light yellow transparent viscous liquid, with a pH of 7.1 and a solid content of 61%.

[0108] Comparative Example 1

[0109] Strong acid detergent: Select Example 1 in CN201811625912.2, with a pH of 1.7.

[0110] Comparative Example 2

[0111] Strong alkaline detergent: A mixed solution of 20% sodium hydroxide + 5% sodium dodecylbenzenesulfonate, with the balance being deionized water, with a pH of 14.6.

[0112] Performance Test

[0113] Using the cleaning liquids of Examples 1-4 and Comparative Examples 1-2, dilute them with deionized water to a cleaning agent working solution with a mass fraction of 5%. Heat it to 55°C in a heater, then add it to the reverse osmosis membrane cleaning device contaminated with organic dirt, and circulate for cleaning for 2 hours. Then drain the cleaning liquid, and rinse the reverse osmosis membrane with deionized water for 15 minutes. Among them, the reverse osmosis membranes contaminated with organic dirt are of the same specification and all come from the sewage treatment link of the same company (Huangshan Huasu New Material Technology Co., Ltd.). The performance test results of the cleaned reverse osmosis membranes are shown in Table 1.

[0114] The desalination rate calculation formula is: [(inlet water conductivity - outlet water conductivity) / inlet water conductivity]×100%. Among them, the lower the outlet water conductivity, the lower the salt concentration in the outlet water and the better the water quality.

[0115] Table 1 Test results of Examples 1-4 and Comparative Examples 1-2

[0116]

[0117]

[0118] The results after continuous cleaning 10 times are shown in Table 2.

[0119] Table 2 Durability test results of Example 1 and Comparative Examples 1-2 (after continuous cleaning 10 times)

[0120]

[0121] As can be seen from Table 1, the neutral reverse osmosis membrane cleaning agent prepared by the present invention using a specific process and formula has a pH basically in a slightly neutral environment of 7-7.5. It has a better cleaning effect on organic dirt. After cleaning, the water outlet efficiency can be significantly improved, and the desalination rate of the reverse osmosis membrane after cleaning reaches more than 97%. The outlet water conductivity also decreases significantly, and the water quality is better. As can be seen from Table 2, after continuous cleaning 10 times with the product of Example 1 of the present invention, the water outlet efficiency of the reverse osmosis membrane is still good, with little change compared with the first cleaning. The outlet water conductivity is low, and the desalination rate is still above 97%. This shows that the slightly neutral reverse osmosis membrane cleaning agent product prepared by the present invention has almost no corrosion on the reverse osmosis membrane and has a better cleaning effect, especially suitable for cleaning reverse osmosis membrane devices contaminated with organic dirt.

[0122] Comparative Example 1 used a strongly acidic reverse osmosis membrane cleaning agent. Since the pH was basically around 1, it not only corroded the reverse osmosis membrane, but also had a general cleaning effect on organic fouling. As can be seen from Table 1, the standard water production of the reverse osmosis membrane after the first cleaning was not high, indicating that the organic fouling was not cleaned thoroughly, which affected the water production efficiency. However, the conductivity after cleaning was relatively large, indicating that it had a certain corrosion on the reverse osmosis membrane and was not suitable for cleaning the reverse osmosis membrane contaminated by organic fouling. In addition, as can be seen from Table 2, the reverse osmosis membrane was severely corroded after 10 consecutive cleanings, with a relatively large standardized water production, but the desalination rate had dropped below 90%, showing a significant decrease.

[0123] Comparative Example 2 used a strongly alkaline cleaning agent formulation with a pH reaching above 14.5, which was extremely alkaline. As can be seen from Table 1, the corrosion of the reverse osmosis membrane device was relatively severe during the first cleaning. Its cleaning effect on organic fouling was relatively good, and the standard water production of the reverse osmosis membrane after cleaning was also relatively high. However, the desalination rate decreased significantly. After the first cleaning, the desalination rate dropped below 97%, indicating that the reverse osmosis membrane had been slightly corroded. As can be seen from Table 2, the reverse osmosis membrane was severely corroded after 10 consecutive cleanings, with a relatively large water production, but the desalination rate could only reach about 87%, making it difficult to meet the application requirements.

[0124] The above embodiments are only used to illustrate the technical solutions of the present invention by way of example, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: within the scope of the spirit and essence defined by the claims of the present invention, the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be equivalently replaced; and these modifications or replacements are still within the scope defined by the claims of the present invention.

Claims

1. A neutral cleaning agent for organic dirt on reverse osmosis membranes, characterized in that: The neutral cleaning agent for organic dirt on reverse osmosis membrane is prepared from raw materials including the following molar fractions: 8-10 parts of N,N-dimethylglycine; 8-9.5 parts of 1-chlorobutane; 5-8 parts of N,N-dimethylformamide; 9-12 parts of glyceryl monoisostearate; Propylene oxide 60-65 parts; 2-naphthylamine-3,6,8-trisulfonic acid 8-11 parts.

2. The neutral cleaning agent for organic dirt on reverse osmosis membrane according to claim 1, characterized in that: The raw materials also include catalyst A and catalyst B. Catalyst A is potassium iodide, and its dosage is 0.05-0.08% of the mass of N,N-dimethylglycine; catalyst B is tetrabutyl titanate, and its dosage is 0.08-0.12% of the mass of glyceryl monoisostearate.

3. The neutral cleaning agent for organic dirt of reverse osmosis membrane according to claim 1, characterized in that: The raw materials also include isomeric decanol polyoxyethylene ether and water.

4. A method for preparing a neutral cleaning agent for organic dirt on a reverse osmosis membrane according to any one of claims 1 to 3, characterized in that: The following steps are involved: A. Add the formulated amount of N,N-dimethylformamide, N,N-dimethylglycine, 1-chlorobutane and catalyst A to the reactor A, start stirring, and heat up to carry out quaternization reaction; B. When the conversion rate of 1-chlorobutane reaches 97% or more, the quaternary ammonium salt solution obtained in the reaction kettle A is pumped to the high-level tank for standby use; C. Adding the formulated amount of glyceryl monoisostearate, propylene oxide and catalyst B into the autoclave B, sealing the autoclave, starting stirring and heating to carry out high-temperature pressure chain extension polymerization reaction; D. When the pressure in the reaction kettle B reaches normal pressure, the temperature is lowered, and then the formula amount of 2-naphthylamine-3,6,8-trisulfonic acid and the quaternary ammonium salt solution of step B are added to the reaction kettle B, and the temperature is raised to carry out the grafting chain extension reaction of the sulfonate and the quaternary ammonium salt, and at the same time, the vacuum system is started to carry out high-temperature vacuum esterification reaction, and the N,N-dimethylformamide solvent in the reaction system is removed during the reaction process; E. Take samples and test them by liquid chromatography. When the conversion rate of 2-naphthylamine-3,6,8-trisulfonic acid reaches more than 95%, release the vacuum system, cool it down, and then drop sodium hydroxide aqueous solution to neutralize and form salts. When the pH in the system reaches 7.0-7.5, stop the reaction to obtain a polymeric hyperdispersant product. F. Then add 2-3% of the mass of the polymeric hyperdispersant product isomeric decanol polyoxyethylene ether, mix evenly, and then add deionized water to prepare it into an aqueous solution with a solid content of 60-65% to obtain a neutral detergent product.

5. The preparation method according to claim 4, characterized in that: In step A, the temperature is raised to 60-65°C.

6. The preparation method according to claim 4, characterized in that: In step C, the temperature is raised to 120-125°C and the reaction time is 2-3h.

7. The preparation method according to claim 4, characterized in that: In step D, the temperature is lowered to 70-80°C; the temperature is raised to 105-110°C, and the vacuum degree is -0.095Mpa to -0.097Mpa.

8. The preparation method according to claim 4, characterized in that: In step E, the temperature is lowered to 40-45°C.

9. A method for using the neutral cleaning agent for organic dirt on a reverse osmosis membrane according to any one of claims 1 to 3, characterized in that: The following steps are involved: The neutral cleaning agent is diluted to a solution with a mass fraction of 4-7%, heated, and then added to a reverse osmosis membrane cleaning device contaminated by organic dirt for cyclic cleaning. After cleaning, the cleaning liquid is discharged and the reverse osmosis membrane is rinsed with deionized water.

10. The method of use according to claim 9, characterized in that: Heat to 50-70°C.

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