阅读说明：本技术 一种反渗透膜清洗剂及反渗透膜清洗方法 (Reverse osmosis membrane cleaning agent and reverse osmosis membrane cleaning method ) 是由 杨敏 雷成 韦驾 江明 唐先荣 唐志成 唐顺 陈华斌 兰元宵 于 2021-09-26 设计创作，主要内容包括：本发明公开了一种反渗透膜清洗剂及反渗透膜清洗方法,反渗透膜清洗剂包括碱性反渗透膜清洗剂和/或酸性反渗透膜清洗剂；碱性反渗透膜清洗剂包括金属螯合剂、亚硫酸钠、氢氧化钠和非离子表面活性剂；酸性反渗透膜清洗剂包括柠檬酸、氨水、酸性pH调节剂和抑菌剂。本发明采用物理清洗和化学清洗相结合的方法,对大部分反渗透膜污染物质有明显清洗效果,能有效提高反渗透膜通量及截留性能,延长反渗透膜使用寿命。(The invention discloses a reverse osmosis membrane cleaning agent and a reverse osmosis membrane cleaning method, wherein the reverse osmosis membrane cleaning agent comprises an alkaline reverse osmosis membrane cleaning agent and/or an acidic reverse osmosis membrane cleaning agent; the alkaline reverse osmosis membrane cleaning agent comprises a metal chelating agent, sodium sulfite, sodium hydroxide and a nonionic surfactant; the acidic reverse osmosis membrane cleaning agent comprises citric acid, ammonia water, an acidic pH regulator and a bacteriostatic agent. The method combines physical cleaning and chemical cleaning, has obvious cleaning effect on most of reverse osmosis membrane pollutants, can effectively improve the flux and interception performance of the reverse osmosis membrane, and prolongs the service life of the reverse osmosis membrane.)

1. A reverse osmosis membrane cleaning agent is characterized in that: the reverse osmosis membrane cleaning agent comprises an alkaline reverse osmosis membrane cleaning agent and/or an acidic reverse osmosis membrane cleaning agent; the alkaline reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

3.6-5.6% of metal chelating agent, 1.5-2.5% of sodium sulfite, 3.5-5.5% of sodium hydroxide, 3.5-5.5% of nonionic surfactant and the balance of solvent;

the acidic reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

10-25% of citric acid, 1.5-3.5% of ammonia water, 0.1-0.3% of acidic pH regulator, 0.05-0.1% of bacteriostatic agent and the balance of solvent.

2. A reverse osmosis membrane cleaning agent according to claim 1, wherein: the nonionic surfactant is at least one of alkyl glycoside, fatty alcohol-polyoxyethylene ether and sodium alkyl benzene sulfonate.

3. A reverse osmosis membrane cleaning agent according to claim 2, wherein: the nonionic surfactant is formed by mixing alkyl glycoside and fatty alcohol-polyoxyethylene ether according to the mass ratio of 3-5: 2.

4. A reverse osmosis membrane cleaning agent according to claim 2, wherein: the sodium alkyl benzene sulfonate is sodium dodecyl benzene sulfonate or sodium hexadecyl sulfonate.

5. A reverse osmosis membrane cleaning agent according to claim 1, wherein: the metal chelating agent is at least one of diethylenetriamine pentaacetic acid pentasodium, ethylene diamine tetraacetic acid tetrasodium and ethylene diamine tetraacetic acid disodium.

6. A reverse osmosis membrane cleaning agent according to claim 5, wherein: the metal chelating agent is prepared by mixing tetrasodium ethylenediamine tetraacetate and pentasodium diethylenetriamine pentaacetate according to the mass ratio of 1.2-4: 1.

7. A reverse osmosis membrane cleaning agent according to claim 1, wherein: the pH value of the alkaline reverse osmosis membrane cleaning agent is 10-13.5; the pH value of the acidic reverse osmosis membrane cleaning agent is 1.5-3.5.

8. A reverse osmosis membrane cleaning agent according to claim 1, wherein: the solvent is reverse osmosis system produced water, distilled water or industrial fresh water.

9. A method for cleaning reverse osmosis polluted by inorganic matters by using the reverse osmosis membrane cleaning agent as claimed in any one of claims 1 to 8, which is characterized by comprising the following steps: firstly, injecting an acidic reverse osmosis membrane cleaning agent into the polluted side of the reverse osmosis membrane, soaking for 0.5-4 h, then applying pressure of 2-7 bar to a reverse osmosis system, carrying out cyclic cleaning for 10-30min, and emptying the acidic cleaning solution after acid cleaning is finished; then, flushing with reverse osmosis system produced water, distilled water or industrial fresh water for 10-30min, emptying flushing water after the flushing is finished, and then cleaning with an alkaline reverse osmosis membrane cleaning agent, wherein the cleaning process is the same as the primary acid cleaning process; finally, washing the polluted side of the reverse osmosis membrane by using water produced by a reverse osmosis system, distilled water or industrial fresh water, and emptying washing water after washing for 10-30min to finish the washing of the reverse osmosis membrane; the temperature of the acidic reverse osmosis membrane cleaning agent and the alkaline reverse osmosis membrane cleaning agent is 30-38 ℃.

10. A method for cleaning reverse osmosis polluted by organic matters by using the reverse osmosis membrane cleaning agent as claimed in any one of claims 1 to 8, which is characterized by comprising the following steps: firstly, injecting an alkaline reverse osmosis membrane cleaning agent into the polluted side of the reverse osmosis membrane, soaking for 4-12 h, then applying pressure of 2-7 bar to water on the water production side of the reverse osmosis membrane, and carrying out cyclic cleaning for 10-30 min; emptying the alkaline cleaning solution after the alkaline cleaning is finished; then, flushing with reverse osmosis system produced water, distilled water or industrial fresh water for 10-30min, emptying flushing water after the flushing is finished, and then cleaning with an acidic reverse osmosis membrane cleaning agent, wherein the cleaning process is the same as the first alkali cleaning process; finally, washing the polluted side of the reverse osmosis membrane by using water produced by a reverse osmosis system, distilled water or industrial fresh water, and emptying washing water after washing for 10-30min to finish the washing of the reverse osmosis membrane; the temperature of the alkaline reverse osmosis membrane cleaning agent and the acidic reverse osmosis membrane cleaning agent is 30-38 ℃.

Technical Field

The invention relates to a cleaning agent, in particular to a reverse osmosis membrane cleaning agent and a reverse osmosis membrane cleaning method.

Background

At present, most of the treatment of the percolate of the old landfill is a two-stage DTRO membrane process, and the two-stage reverse osmosis membrane treatment of the percolate of the landfill forms a nearly finished process system after long-term development. The landfill leachate is characterized by mainly comprising the following steps: the pollutant has complex components, high content of organic matters and suspended matters, and putrefactive odor emitted by ammonia nitrogen, hydrogen sulfide gas and the like. In the operation of the system, the pollution of the membrane is a very troublesome problem, the membrane pollution can cause the great reduction of the removal rate and the membrane flux of the reverse osmosis device, and simultaneously, the operation pressure of each section is increased, so that the operation and operation cost is high, and the normal operation of the membrane system and the service life of the membrane are seriously influenced.

The reverse osmosis membrane pollution can be divided into reversible pollutants and irreversible pollutants, and in the practical use of the reverse osmosis membrane, the membrane flux is rapidly attenuated in a short time, the membrane pollution phenomenon is very serious, and the irreversible pollution of the membrane is very easy to cause if the reverse osmosis membrane is not cleaned in time. Membrane cleaning is closely related to membrane fouling. Aiming at the reverse osmosis membrane separation process of different inlet water, when a cleaning agent and a cleaning method are determined, not only the pollution reason and the pollution property of the cleaning agent and the cleaning method need to be researched, but also the economical efficiency of the cleaning method and the negative influence of the cleaning method on the membrane performance need to be considered. The reverse osmosis membrane is mainly polluted by three categories of organic matters, inorganic matters and microorganisms, and different optimal cleaning processes exist corresponding to different forms of pollution.

In the two-stage DTRO process, the pretreatment adopts coagulating sedimentation, microfiltration or ultrafiltration to remove most of organic matters and suspended matters; meanwhile, sulfuric acid is usually added in the pretreatment process to adjust the pH value, at the moment, ammoniacal nitrogen reacts with the added sulfuric acid to be converted into ammonium salt, and the ammonium salt is intercepted on the concentrated solution side through a primary DTRO membrane; meanwhile, the landfill leachate contains a large amount of heavy metal substances, after membrane concentration in the operation process, the concentration of the heavy metal substances in a concentrated solution is increased, when a scale inhibitor/dispersant adding system fails or an acid pH adjusting system fails, the pH of feed water is increased, and at the moment, the heavy metal substances are easily deposited to cause the pollution of a primary DTRO membrane; in addition, the solubility of the hydrogen sulfide gas dissolved in the water produced by the primary DTRO membrane is reduced along with the reduction of pH, the dissociated gas is increased, most organic matters, ammonia nitrogen, chromaticity and suspended matters are removed from the water produced by the primary DTRO membrane, and a small amount of gases such as hydrogen sulfide, carbon dioxide, oxygen and the like penetrate through the water produced and enter the secondary membrane system, and in the circulating concentration process of the secondary membrane system, the hydrogen sulfide is oxidized into elemental sulfur to be separated out and attached to the surface of the membrane, so that the pollution is caused to the secondary RO membrane.

Currently, the membrane pollution mainly comprises the following substances:

(1) calcium carbonate scale. Calcium carbonate scale is a mineral scale. When the feed water pH increases due to a failure of the scale inhibitor/dispersant addition system or a failure of the acid pH adjustment system, there is a possibility that calcium carbonate scale may be deposited.

(2) Sulfate scale. Before the landfill leachate enters a reverse osmosis system, the pH value of the landfill leachate is adjusted by adding sulfuric acid, so that the risk of sulfate scale is generated, and the sulfate scale is a permanent hard substance which is more difficult to remove than calcium carbonate scale.

(3) A metal oxide. Metal oxides and hydroxides contaminate the metal with iron, zinc, manganese, copper, aluminum, and the like. The formation of such scale is caused by the use of iron or aluminum coagulant aids in the pretreatment filtration system, in addition to scale formed by oxidation of the metal species present in the leachate itself, which may be corrosion products of the plant piping, vessels, or the like;

(4) the silica gel layer fouled. Silica gel scale is very difficult to remove due to the supersaturation of soluble silicon upon concentration and the polymers.

(5) And (3) colloid. Colloids are particles of inorganic or organic and inorganic compounds suspended in water that do not settle by their own weight. Colloids generally contain one or more of the following major components, such as: iron, aluminum, silicon, sulfur, or organic.

(6) Non-soluble natural organic contaminants. The insoluble natural organic pollutants are usually caused by the decomposition of nutrients in surface water or deep well water, the chemical mechanism of organic pollution is complex, and the main organic components are humic acid or fulvic acid.

(7) Organic deposits. Organic deposits are formed from bacterial slime, fungi, mold, etc., and such contaminants are difficult to remove.

Disclosure of Invention

Aiming at the problems of various membrane pollution forms and the existing membrane cleaning process, the invention provides a reverse osmosis membrane cleaning agent to solve the problem of poor cleaning effect of the existing reverse osmosis membrane cleaning agent.

In order to achieve the purpose, the invention adopts the technical scheme that: providing a reverse osmosis membrane cleaning agent, wherein the reverse osmosis membrane cleaning agent comprises an alkaline reverse osmosis membrane cleaning agent and/or an acidic reverse osmosis membrane cleaning agent; the alkaline reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

3.6-5.6% of metal chelating agent, 1.5-2.5% of sodium sulfite, 3.5-5.5% of sodium hydroxide, 3.5-5.5% of nonionic surfactant and the balance of solvent;

the acidic reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

10-25% of citric acid, 1.5-3.5% of ammonia water, 0.1-0.3% of acidic pH regulator, 0.05-0.1% of bacteriostatic agent and the balance of solvent.

On the basis of the technical scheme, the invention can be further improved as follows.

Further, the nonionic surfactant is at least one of alkyl glycoside, fatty alcohol-polyoxyethylene ether and sodium alkyl benzene sulfonate.

Further, the nonionic surfactant is formed by mixing alkyl glycoside and fatty alcohol-polyoxyethylene ether according to the mass ratio of 3-5: 2.

Further, the sodium alkyl benzene sulfonate is sodium dodecyl benzene sulfonate or sodium hexadecyl sulfonate.

Further, the metal chelating agent is at least one of diethylenetriamine pentaacetic acid pentasodium, ethylenediamine tetraacetic acid tetrasodium and ethylenediamine tetraacetic acid disodium.

Further, the metal chelating agent is prepared by mixing tetrasodium ethylenediamine tetraacetate and pentasodium diethylenetriamine pentaacetate according to the mass ratio of 1.2-4: 1.

Further, the pH value of the alkaline reverse osmosis membrane cleaning agent is 10-13.5; the pH value of the acidic reverse osmosis membrane cleaning agent is 1.5-3.5.

Further, the solvent is reverse osmosis system produced water, distilled water or industrial fresh water.

Further, the bacteriostatic agent is an isothiazolinone solution with the mass concentration of 0.05-0.1%.

The alkaline reverse osmosis membrane cleaning agent and the acidic reverse osmosis membrane cleaning agent in the reverse osmosis membrane cleaning agent are stored separately, and the two types of membrane cleaning agents can be used independently or alternatively. When the pollutants of the reverse osmosis membrane are mainly inorganic substances, the cleaning method of the reverse osmosis membrane comprises the following steps:

firstly, injecting an acidic reverse osmosis membrane cleaning agent into the polluted side of the reverse osmosis membrane, soaking for 0.5-4 h, then applying pressure of 2-7 bar to a reverse osmosis system, carrying out cyclic cleaning for 10-30min, and emptying the acidic cleaning solution after acid cleaning is finished; then, flushing with reverse osmosis system produced water, distilled water or industrial fresh water for 10-30min, emptying flushing water after the flushing is finished, and then cleaning with an alkaline reverse osmosis membrane cleaning agent, wherein the cleaning process is the same as the primary acid cleaning process; finally, washing the polluted side of the reverse osmosis membrane by using water produced by a reverse osmosis system, distilled water or industrial fresh water, and emptying washing water after washing for 10-30min to finish the washing of the reverse osmosis membrane; the temperature of the acidic reverse osmosis membrane cleaning agent and the alkaline reverse osmosis membrane cleaning agent is 30-38 ℃.

When the pollutants of the reverse osmosis membrane are mainly organic matters, the cleaning method of the reverse osmosis membrane comprises the following steps:

firstly, injecting an alkaline reverse osmosis membrane cleaning agent into the polluted side of the reverse osmosis membrane, soaking for 4-12 h, then applying pressure of 2-7 bar to water on the water production side of the reverse osmosis membrane, and carrying out cyclic cleaning for 10-30 min; emptying the alkaline cleaning solution after the alkaline cleaning is finished; then, flushing with reverse osmosis system produced water, distilled water or industrial fresh water for 10-30min, emptying flushing water after the flushing is finished, and then cleaning with an acidic reverse osmosis membrane cleaning agent, wherein the cleaning process is the same as the first alkali cleaning process; finally, washing the polluted side of the reverse osmosis membrane by using water produced by a reverse osmosis system, distilled water or industrial fresh water, and emptying washing water after washing for 10-30min to finish the washing of the reverse osmosis membrane; the temperature of the alkaline reverse osmosis membrane cleaning agent and the acidic reverse osmosis membrane cleaning agent is 30-38 ℃.

The invention has the beneficial effects that:

1. the reverse osmosis membrane cleaning agent comprises an acidic cleaning agent and an alkaline cleaning agent. Wherein the acidic cleaning agent cleans carbonate dirt and dirt blockage caused by most metal oxides on the surface of the membrane element through chemical reaction under the condition that the pH value is 1.5-3.5; the alkaline cleaning agent removes organic pollutants such as polyacrylamide under the condition that the pH value is 10-13.5 by utilizing the synergistic effect of a surfactant, a complexing agent, a penetrating agent and the like, can effectively remove organic pollutants such as humic acids and polyacrylamide on a reverse osmosis membrane, and can strip microbial mucosa and other organic pollutants wrapped by polyacrylamide.

2. The salt in the reverse osmosis membrane cleaning agent is used for adjusting the osmotic pressure of the cleaning agent. In the cleaning process, the salt concentration of the cleaning agent side is far greater than that of the water production side, sufficient purified water is supplied to the water production side of the reverse osmosis membrane, certain pressure is combined, the purified water on the water production side of the osmosis membrane permeates the membrane and permeates and flows to the cleaning side, the reverse osmosis membrane is different from the original reverse osmosis, and the process is forward osmosis. Through forward osmosis, water flows through the membrane, so that dirt on the surface of the membrane is physically washed, and a stripping effect is achieved. The cleaning agent can effectively elute pollutants attached to the permeable membrane, and the running flux and the differential pressure of the reverse osmosis membrane can be recovered to the level before pollution after cleaning.

3. The oxidative free chlorine or the combined chlorine in the pollutants can generate irreversible oxidative damage to the permeable membrane, so that the filtering performance and the service life of the permeable membrane are obviously reduced. According to the invention, sodium sulfite is added into the alkaline reverse osmosis membrane cleaning agent, and the sodium sulfite can rapidly react with free chlorine in a short time, so that oxidative free chlorine or combined chlorine in a system is eliminated, further, the potential oxidation hazard is eliminated, and the service life of the membrane is prolonged. Meanwhile, the existence of sodium sulfite can effectively improve the stability of the cleaning agent.

4. Acidic reverse osmosis membrane cleanerThe lotion contains citric acid which is a weak acid and can ionize H⁺Ionized H⁺Can react with metal oxide or metal hydroxide in the landfill leachate to generate water and free metal ions, and can effectively eliminate dirt. The acidic reverse osmosis membrane cleaning agent also contains ammonia water which can ionize NH₄ ⁺The ammonium citrate is combined with citric acid to generate ammonium citrate, and the ammonium citrate is easy to form a soluble complex with metal ions with high valence (such as iron ions) to play a role in removing the dirt of metal oxides or metal hydroxides. In addition, the citric acid and the ammonia water in the acidic reverse osmosis membrane cleaning agent are weak acid and weak base, so that the corrosivity is low, and the comprehensive performance of the membrane cannot be influenced.

5. The method combines physical cleaning and chemical cleaning, has obvious cleaning effect on most of reverse osmosis membrane pollutants, can effectively improve the flux and interception performance of the reverse osmosis membrane, and prolongs the service life of the reverse osmosis membrane.

Detailed Description

The following examples are provided to illustrate specific embodiments of the present invention.

Example 1

A reverse osmosis membrane cleaning agent comprises an alkaline reverse osmosis membrane cleaning agent and an acidic reverse osmosis membrane cleaning agent which are stored independently of each other. The alkaline reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

4% of metal chelating agent, 2% of sodium sulfite, 4% of sodium hydroxide, 4% of nonionic surfactant and the balance of distilled water; wherein the metal chelating agent is formed by mixing tetrasodium ethylene diamine tetraacetate and pentasodium diethylenetriamine pentaacetate according to the mass ratio of 2: 1; the nonionic surfactant is formed by mixing alkyl glycoside (APG0810) and fatty alcohol-polyoxyethylene ether (AEO-9) according to the mass ratio of 2: 1;

the acidic reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

20% of citric acid, 3% of ammonia water, 0.2% of acidic pH regulator, 0.1% of bacteriostatic agent and the balance of distilled water; wherein the acidic pH regulator is phosphoric acid, and the bacteriostatic agent is isothiazolinone solution with mass concentration of 0.1%.

Example 2

A reverse osmosis membrane cleaning agent comprises an alkaline reverse osmosis membrane cleaning agent and an acidic reverse osmosis membrane cleaning agent which are stored independently of each other. The alkaline reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

3.6% of metal chelating agent, 2.5% of sodium sulfite, 3.5% of sodium hydroxide and 5.5% of nonionic surfactant, and the balance being industrial fresh water; wherein the metal chelating agent is formed by mixing tetrasodium ethylene diamine tetraacetate and pentasodium diethylenetriamine pentaacetate according to the mass ratio of 2: 1; the nonionic surfactant is sodium dodecyl benzene sulfonate;

the acidic reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

10% of citric acid, 1.5% of ammonia water, 0.1% of acidic pH regulator and 0.3% of bacteriostatic agent, and the balance being industrial fresh water; wherein the acidic pH regulator is phosphoric acid, and the bacteriostatic agent is isothiazolinone solution with mass concentration of 0.05%.

Example 3

A reverse osmosis membrane cleaning agent comprises an alkaline reverse osmosis membrane cleaning agent and an acidic reverse osmosis membrane cleaning agent which are stored independently of each other. The alkaline reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

5.6% of metal chelating agent, 1.5% of sodium sulfite, 5.5% of sodium hydroxide and 3.5% of nonionic surfactant, and the balance being water produced by a reverse osmosis system; wherein the metal chelating agent is disodium ethylene diamine tetraacetate; the nonionic surfactant is formed by mixing alkyl glycoside (APG0810) and fatty alcohol-polyoxyethylene ether (AEO-9) according to the mass ratio of 2: 1;

the acidic reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

25% of citric acid, 3.5% of ammonia water, 0.1% of acidic pH regulator and 0.1% of bacteriostatic agent, and the balance is reverse osmosis system produced water; wherein the acidic pH regulator is phosphoric acid, and the bacteriostatic agent is isothiazolinone solution with mass concentration of 0.1%.

Comparative example 1

A reverse osmosis membrane cleaning agent comprises an alkaline reverse osmosis membrane cleaning agent and an acidic reverse osmosis membrane cleaning agent which are stored independently of each other. The alkaline reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

4% of metal chelating agent, 2% of sodium sulfate, 4% of sodium hydroxide, 4% of nonionic surfactant and the balance of distilled water; wherein the metal chelating agent is formed by mixing tetrasodium ethylene diamine tetraacetate and pentasodium diethylenetriamine pentaacetate according to the mass ratio of 2: 1; the nonionic surfactant is formed by mixing alkyl glycoside (APG0810) and fatty alcohol-polyoxyethylene ether (AEO-9) according to the mass ratio of 2: 1;

the acidic reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

20% of citric acid, 3% of ammonia water, 0.2% of acidic pH regulator, 0.1% of bacteriostatic agent and the balance of distilled water; wherein the acidic pH regulator is phosphoric acid, and the bacteriostatic agent is isothiazolinone solution with mass concentration of 0.1%.

Comparative example 2

A reverse osmosis membrane cleaning agent comprises an alkaline reverse osmosis membrane cleaning agent and an acidic reverse osmosis membrane cleaning agent which are stored independently of each other. The alkaline reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

4% of metal chelating agent, 4% of sodium hydroxide, 4% of nonionic surfactant and the balance of distilled water; wherein the metal chelating agent is formed by mixing tetrasodium ethylene diamine tetraacetate and pentasodium diethylenetriamine pentaacetate according to the mass ratio of 2: 1; the nonionic surfactant is formed by mixing alkyl glycoside (APG0810) and fatty alcohol-polyoxyethylene ether (AEO-9) according to the mass ratio of 2: 1;

the acidic reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

20% of citric acid, 3% of ammonia water, 0.2% of acidic pH regulator, 0.1% of bacteriostatic agent and the balance of distilled water; wherein the acidic pH regulator is phosphoric acid, and the bacteriostatic agent is isothiazolinone solution with mass concentration of 0.1%.

Comparative example 3

A reverse osmosis membrane cleaning agent comprises an alkaline reverse osmosis membrane cleaning agent and an acidic reverse osmosis membrane cleaning agent which are stored independently of each other. The alkaline reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

4% of metal chelating agent, 2% of sodium sulfite, 4% of sodium hydroxide, 4% of nonionic surfactant and the balance of distilled water; wherein the metal chelating agent is formed by mixing tetrasodium ethylene diamine tetraacetate and pentasodium diethylenetriamine pentaacetate according to the mass ratio of 2: 1; the nonionic surfactant is formed by mixing alkyl glycoside (APG0810) and fatty alcohol-polyoxyethylene ether (AEO-9) according to the mass ratio of 2: 1;

the acidic reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

20% of citric acid, 3% of ammonium chloride, 0.2% of acidic pH regulator, 0.1% of bacteriostatic agent and the balance of distilled water; wherein the acidic pH regulator is phosphoric acid, and the bacteriostatic agent is isothiazolinone solution with mass concentration of 0.1%.

Comparative example 4

A reverse osmosis membrane cleaning agent comprises an alkaline reverse osmosis membrane cleaning agent and an acidic reverse osmosis membrane cleaning agent which are stored independently of each other. The alkaline reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

4% of metal chelating agent, 2% of sodium sulfite, 4% of sodium hydroxide, 4% of nonionic surfactant and the balance of distilled water; wherein the metal chelating agent is formed by mixing tetrasodium ethylene diamine tetraacetate and pentasodium diethylenetriamine pentaacetate according to the mass ratio of 2: 1; the nonionic surfactant is formed by mixing alkyl glycoside (APG0810) and fatty alcohol-polyoxyethylene ether (AEO-9) according to the mass ratio of 2: 1;

the acidic reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

20% of citric acid, 0.2% of acidic pH regulator, 0.1% of bacteriostatic agent and the balance of distilled water; wherein the acidic pH regulator is phosphoric acid, and the bacteriostatic agent is isothiazolinone solution with mass concentration of 0.1%.

Comparative example 5

A reverse osmosis membrane cleaning agent comprises an alkaline reverse osmosis membrane cleaning agent and an acidic reverse osmosis membrane cleaning agent which are stored independently of each other. The alkaline reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

4% of metal chelating agent, 4% of sodium hydroxide, 4% of nonionic surfactant and the balance of distilled water; wherein the metal chelating agent is formed by mixing tetrasodium ethylene diamine tetraacetate and pentasodium diethylenetriamine pentaacetate according to the mass ratio of 2: 1; the nonionic surfactant is formed by mixing alkyl glycoside (APG0810) and fatty alcohol-polyoxyethylene ether (AEO-9) according to the mass ratio of 2: 1;

the acidic reverse osmosis membrane cleaning agent comprises the following components in percentage by mass:

20% of citric acid, 0.2% of acidic pH regulator, 0.1% of bacteriostatic agent and the balance of distilled water; wherein the acidic pH regulator is phosphoric acid, and the bacteriostatic agent is isothiazolinone solution with mass concentration of 0.1%.

Examples of the experiments

1. Reverse osmosis membranes for the construction of organic pollutants

Selecting a Dow reverse osmosis membrane element BW30-400FR as an experimental membrane, preparing a salt solution with the total salt content of 4000mg/L by using sodium chloride and purified water as raw water at the temperature of 25 ℃, and controlling the water inlet pressure to be 8-10bar and the water inlet flow to be 1m³Perh, when the membrane element normally runs, the produced water is 0.71m³The water and salt content is 6 mg/L. Adding anionic polyacrylamide (with a molecular weight of 1200 ten thousand and a concentration of 5mg/L) into raw water, and after running for 2 hours, increasing the water inlet pressure to 12-15bar and the water inlet flow to 1m³H, 0.3m of produced water³The salt content of the produced water is 35mg/L, and the parameter change shows that the membrane is polluted, wherein the salt rejection rate is slightly reduced, and the water production flux is reduced by about 57 percent.

2. Construction of inorganic contaminated reverse osmosis membranes

Selecting a Dow reverse osmosis membrane element BW30-400FR as an experimental membrane, and preparing an aqueous solution containing calcium chloride and sodium carbonate by using purified water at the temperature of 25 ℃, wherein the concentrations of the calcium chloride and the sodium carbonate in the aqueous solution are both 10 ppm; sodium chloride was then added to the solution so that the total salt content of the solution was 4000 mg/L. The solution is used as raw water, the water inlet pressure is controlled to be 8-10bar, and the water inlet flow is controlled to be 1m³Perh, when the membrane element normally runs, the produced water is 0.72m³H, the content of produced water and salt is 7 mg/L. Using the solution as a sourceAdding water, adding anionic polyacrylamide (molecular weight 1200 ten thousand, Taihe water treatment Co., Ltd.) into raw water, controlling the concentration at 10mg/L, operating for 2 hours, increasing the water inlet pressure to 12-15bar, and changing the water inlet flow to 1m³H, 0.27m of produced water³The salt content of the produced water is 63mg/L, and the parameter change shows that the membrane is polluted, wherein the salt rejection rate is slightly reduced, and the water production flux is reduced by 62 percent.

3. Cleaning reverse osmosis membrane polluted by organic matters

The reverse osmosis membrane cleaning agent in the embodiments 1 to 3 and the comparative examples 1 to 5 is respectively used for cleaning reverse osmosis membranes polluted by organic matters, and the cleaning method comprises the following steps:

firstly, injecting an alkaline reverse osmosis membrane cleaning agent into the polluted side of the reverse osmosis membrane, soaking for about 10 hours, then applying 3-6bar pressure to water on the water production side of the reverse osmosis membrane, and circularly cleaning for 15 min; emptying alkaline cleaning liquid after alkaline cleaning; then, washing the water by using water produced by a reverse osmosis system, distilled water or industrial fresh water for 10-30min, emptying the washing water after the washing is finished, and then washing the water by using an acidic reverse osmosis membrane cleaning agent, wherein the washing process is the same as the first alkali washing process; finally, washing the polluted side of the reverse osmosis membrane by using water produced by a reverse osmosis system, distilled water or industrial fresh water, and emptying washing water after washing for 10-30min to finish the washing of the reverse osmosis membrane; the temperature of the alkaline reverse osmosis membrane cleaning agent and the acidic reverse osmosis membrane cleaning agent is about 35 ℃.

After cleaning, the performance of the membrane element after cleaning is tested under the standard conditions of 25 ℃, water inlet pressure of 8-10bar and sodium chloride content in raw water of 4000mg/L, and the test results are shown in Table 1.

TABLE 1 reverse osmosis membrane cleaning Effect of organic contamination

4. Cleaning reverse osmosis membrane polluted by inorganic matters

The reverse osmosis membrane cleaning agents in examples 1 to 3 and comparative examples 1 to 5 were used to clean the reverse osmosis membranes contaminated with inorganic substances, and the cleaning methods were as follows:

firstly, injecting an acidic reverse osmosis membrane cleaning agent into the polluted side of the reverse osmosis membrane, soaking for 4 hours, then applying 3-6bar pressure to water on the water production side of the reverse osmosis membrane, and carrying out circulating cleaning for 150 min; emptying the acid cleaning solution after the acid cleaning is finished; then, washing the water by using the produced water of the reverse osmosis system, distilled water or industrial fresh water for 10-30min, emptying the washing water, and then cleaning by using an alkaline reverse osmosis membrane cleaning agent, wherein the cleaning process is the same as the primary acid cleaning process; finally, washing the polluted side of the reverse osmosis membrane by using water produced by a reverse osmosis system, distilled water or industrial fresh water, and emptying washing water after washing for 10-30min to finish the washing of the reverse osmosis membrane; the temperature of the acidic reverse osmosis membrane cleaning agent and the alkaline reverse osmosis membrane cleaning agent is about 35 ℃.

After continuous cleaning, the performance of the cleaned membrane element is tested under the standard conditions of 25 ℃, water inlet pressure of 8-10bar and sodium chloride content in raw water of 4000mg/L, and the test results are shown in Table 2.

TABLE 2 cleaning effect of inorganic contaminated reverse osmosis membrane

	Water inflow (1 m)3/h)	Produce water (t/h)	Produced Water salt content (mg/L)	Membrane flux recovery rate
					Example one	1	0.67	12	93.06％
Example two	1	0.68	12	94.44％
					EXAMPLE III	1	0.67	11	93.06％
Comparative example 1	1	0.58	17	80.56％
					Comparative example No. two	1	0.57	17	79.17％
Comparative example No. three	1	0.54	16	75.00％
					Comparative example No. four	1	0.53	15	73.61％
Comparative example five	1	0.50	21	69.44％

While the present invention has been described in detail with reference to the embodiments, it should not be construed as limited to the scope of the patent. Various modifications and changes may be made by those skilled in the art without inventive step within the scope of the appended claims.