A targeted repair method for polyamide desalination membrane components

Abstract

The present invention provides a targeted repair method for a polyamide desalination membrane assembly, which can effectively repair defects of the polyamide desalination membrane assembly caused by membrane stress / strain due to manufacturing, chemical reagent corrosion, and operation mode, as well as damage caused by extreme operating conditions. By utilizing the complexation of iron ions with functional groups such as carboxyl groups, iron ions are enriched at defects on the membrane surface. By complexation of iron ions with introduced functional aromatic amine substances, selective targeted enrichment of aromatic amine substances at defects in the polyamide membrane is achieved. Hydroxyl radicals generated by the reaction of iron ions with hydrogen peroxide are then used to induce oxidative polymerization of aromatic amine substances to form polymers to fill defects, and simultaneously react with terminal amino groups on the membrane surface to form a bond. This method can effectively restore the desalination capacity of the polyamide desalination membrane assembly, and the repaired membrane assembly has good performance stability and is simple and efficient.

Description

Technical Field

[0001] The invention relates to a targeted repair method for a polyamide desalination membrane component. Background Art

[0002] Global freshwater shortages have become a major concern worldwide. Population growth, industrialization, urbanization, and climate change have exacerbated the global freshwater crisis. Over the past few decades, due to steadily increasing demand, the scarcity of freshwater resources is threatening the sustainable development of human society. Therefore, there is an urgent need to increase the supply of freshwater resources through efficient and energy-efficient water purification methods to address this increasingly serious global dilemma. From a thermodynamic perspective, currently used desalination technologies can be broadly categorized into thermal separation and membrane separation. Thermal separation technologies are generally limited by high energy consumption, high investment costs, and high operating costs. In contrast, membrane separation technologies do not require additional energy to drive the phase change of water and offer the advantages of low energy consumption, simple operation, and zero greenhouse gas emissions. Therefore, membrane separation technology offers broader application prospects and is attracting widespread attention.

[0003] As the most precise water separation membrane, polyamide membrane can effectively separate water from the ions in it. However, defects caused by improper process control during the production process, degradation of the separation layer caused by corrosion from chemical reagents (acid-base hydrolysis, sodium hypochlorite residue, etc.) during long-term operation, membrane aging (pyrolysis, performance degradation caused by changes in membrane surface stress due to operating conditions, etc.), and scratches on the membrane surface caused by particles in the influent water can all lead to a decrease in the desalination capacity of the polyamide membrane, resulting in a significant reduction in the effluent quality during water treatment. This requires frequent replacement of polyamide membrane modules, thus affecting the economic efficiency of polyamide membrane applications and becoming a technical problem that urgently needs to be solved in the long-term operation of polyamide desalination membrane modules.

[0004] In existing solutions, removing the polyamide membrane components from the treatment facility for replacement or repair not only affects the operation of the system, but also increases the replacement cost. If an inexpensive in-situ repair method can be used to reconstruct and repair the defects or damaged points of the separation layer, its filtration performance and solute retention performance can be restored, and the service life of the polyamide membrane can be extended, it will be of great significance for improving the water quality of the polyamide membrane effluent and saving operating costs. However, there is currently no better way to repair degraded polyamide membranes with reduced desalination due to defects, degradation or aging, especially the in-situ repair of membrane components.

[0005] Existing methods use organic polymers deposited on the surface of polyamide membranes to repair membrane defects. This method has certain drawbacks. During implementation, the deposits physically adsorb onto the membrane surface, resulting in weak adhesion and low stability of the repaired polyamide membrane. Therefore, a new process is proposed to address these shortcomings of existing methods. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a targeted repair method for polyamide desalination membrane assemblies that can solve the problem of defects on the membrane surface during long-term use of polyamide membrane assemblies, resulting in a decrease in separation performance, especially a decrease in desalination capacity, thereby ensuring the water quality of the effluent from the polyamide desalination membrane assemblies and saving operating costs, and having practicality and wide application.

[0007] In order to solve the above problems, the present invention adopts the following technical solutions:

[0008] A targeted repair method for a polyamide desalination membrane assembly comprises the following steps:

[0009] S1. Dissolve a certain amount of ferrous salt and a small amount of citric acid in pure water to prepare an aqueous solution of a certain concentration as modified solution A;

[0010] S2. Dissolving a certain amount of 30% by mass hydrogen peroxide aqueous solution in pure water to prepare a certain concentration of hydrogen peroxide aqueous solution, and adjusting the pH value with dilute hydrochloric acid to prepare a modified solution B;

[0011] S3, dissolving a certain amount of aromatic amine substance in pure water to prepare an aqueous solution of a certain concentration as modified solution C;

[0012] S4. At room temperature, the cleaned polyamide membrane assembly is subjected to pressurized cyclic soaking treatment with the modified solution A, and the modified solution is drained after a certain period of time;

[0013] S5. At room temperature, the membrane assembly treated with the modified solution A is subjected to a cyclic pressure soaking treatment with the modified solution B. After a certain period of time, the modified solution is drained, and then the membrane assembly is cleaned with a citric acid aqueous solution of a certain concentration by cyclic pressure soaking and cleaning, and then the membrane assembly is rinsed with pure water;

[0014] S6. At room temperature, the membrane assembly treated with the modified solution B is subjected to a circulating pressurized soaking treatment with the modified solution C. After a certain period of time, the modified solution is drained, and then the membrane assembly is cleaned with a certain concentration of citric acid aqueous solution by pressurized circulating soaking and cleaning, and then the membrane assembly is cleaned with pure water.

[0015] Preferably, the ferrous salt is one or more of ferrous chloride, ferrous sulfate, ferrous nitrate, etc.;

[0016] Preferably, the mass percentage concentration of the transition metal salt is 0.5%-2%;

[0017] Preferably, the mass percentage concentration of the hydrogen peroxide is 0.5%-2%;

[0018] Preferably, the pH value of the hydrogen peroxide solution is in the range of 3-7;

[0019] Preferably, the aromatic amine substance is one or more of p-aminobenzoic acid, m-phenylenediamine, sulfonamide, etc.;

[0020] Preferably, the mass percentage concentration of the aromatic amine is 0.02%-0.1%;

[0021] Preferably, the time for pressurized cyclic soaking treatment of the membrane assembly with the modified solution A is 5-10 minutes;

[0022] Preferably, the membrane assembly treated with the modified solution A is subjected to pressurized cyclic soaking treatment with the modified solution B for 10-30 minutes.

[0023] Preferably, the membrane assembly treated with the modified solution B is subjected to pressurized cyclic soaking treatment with the modified solution C for 10-30 minutes.

[0024] The beneficial effects of the present invention are:

[0025] 1. The targeted repair method of the polyamide desalination membrane assembly provided by the present invention can effectively repair the membrane surface defects formed by the damage caused by the membrane stress / strain and extreme conditions caused by the manufacture, chemical reagent corrosion, and operation mode of the polyamide membrane; the complexation of iron ions and functional groups such as carboxyl groups is utilized to realize the enrichment of iron ions at defects and play a molecular target role, and the complexation of iron ions with the functional aromatic amine substances introduced is used to realize the selective enrichment of aromatic amine substances at the defects of the polyamide membrane, and then the hydroxyl radicals produced by the reaction of iron ions with hydrogen peroxide are utilized to induce the oxidative polymerization of aromatic amine substances to form polymers and fill defects, and the polymer is generated while being bonded to the amino group on the membrane surface. This method can not only effectively repair the membrane surface defects and restore the desalination capacity of the polyamide membrane, but also give the repair membrane better stability by bonding with the membrane surface, and ultimately realize the effective repair of the polyamide desalination membrane assembly.

[0026] 2. When achieving targeted repair of polyamide membrane components, the repair agent is directly added to the water inlet of the polyamide device. There is no need to replace the water inlet of the polyamide device, disassemble the polyamide membrane components, or change the operating conditions of the polyamide device. The operation is simple and economical.

[0027] 3. The targeted repair agent for the polyamide desalination membrane assembly provided is cheap and readily available, and is suitable for a variety of polyamide membrane systems.

[0028] 4. It can repair the degraded performance of polyamide desalination membrane components, effectively extend the service life of polyamide desalination membrane components, reduce the waste of membrane components, reduce the impact of waste membrane components on the environment, and significantly reduce the economic cost of water treatment.

[0029] 5. Using transition metal ions as "anchor points", aromatic amine substances are targeted and aggregated at the defects on the surface of the polyamide membrane, and oxidative polymerization occurs under the action of hydroxyl radicals to form polymers, which repair the defects on the membrane surface in situ. Covalent bonding on the membrane surface is achieved by reacting with the amino groups on the membrane surface, effectively restoring the desalination capacity of the polyamide membrane while giving the repaired membrane better stability, ultimately achieving in situ repair of the polyamide membrane assembly. DETAILED DESCRIPTION

[0030] Polyamide desalination membrane assembly: Soak the EM-RO-1812-75 household polyamide desalination membrane assembly purchased from the market in 20-30°C pure water for 30 minutes, then rinse it with pure water and set aside.

[0031] Simulated performance-degraded polyamide desalination membrane assembly: The polyamide desalination membrane assembly was immersed in a sodium hypochlorite aqueous solution with a mass percentage concentration of 0.6% and a pH of 8 for 24 hours to 72 hours to obtain polyamide desalination membrane assemblies with different degrees of performance degradation.

[0032] Prepare modified solution A: dissolve a certain amount of ferrous salt and a small amount of citric acid in pure water to prepare a modified solution A with a mass percentage concentration of 0.5%-4%. The ferrous salt is one or more of ferrous chloride, ferrous sulfate, ferrous nitrate, etc.

[0033] Prepare modified solution B: dissolve a certain amount of 30% by mass hydrogen peroxide aqueous solution in pure water to prepare 0.5%-2% by mass modified solution B, wherein the pH value of solution B is in the range of 3-7.

[0034] Prepare modified solution C: dissolve a certain amount of aromatic amine in pure water to prepare modified solution C with a mass percentage concentration of 0.02%-0.1%. The aromatic amine is one or more of p-aminobenzoic acid, m-phenylenediamine, sulfonamide, etc.

[0035] The membrane assembly is circulated and soaked in the modified solution A: the cleaned deteriorated polyamide membrane assembly is pressurized and circulated with the modified solution A for 5-10 minutes at 0.05-0.15 MPa, and the modified solution is drained after a certain period of time.

[0036] The membrane assembly is circulated and soaked in the modified solution B: at room temperature and 0.05-0.15 MPa, the membrane assembly treated with the modified solution A and drained is circulated and pressurized and soaked in the modified solution B for 10-30 minutes, and then the modified solution is drained.

[0037] Circulating soaking of the membrane assembly in modified solution C: At room temperature and 0.05-0.15 MPa, circulate and pressurize the membrane assembly treated with modified solution B in modified solution C for 10-30 minutes. Drain the modified solution. Then, clean the membrane assembly with a citric acid solution of a certain concentration by pressurized circulatory soaking, and then rinse with pure water.

[0038] The following tests are conducted on the desalination rate (R) and water production (F) of the polyamide desalination membrane module.

[0039] The polyamide desalination membrane module's salt rejection and water yield were tested using a cross-flow test with a 0.05% NaCl aqueous solution as the feed solution at 0.4 MPa, 25°C, and a pH of 7.0±0.2. The results, shown in Table 1 below, demonstrate the separation performance of the polyamide desalination membrane module.

[0040] Table 1;

[0041]

[0042]

[0043] From the data in Table 1, it can be found that under appropriate conditions, the simulated deteriorated polyamide desalination membrane components were repaired in situ with targeted repair, using a 0.05% by mass concentration of NaCl aqueous solution as the feed liquid; tested under the conditions of 0.4 MPa, 25°C, and pH 7.0±0.2, the rejection rate of the repaired polyamide desalination membrane components was higher than 95%, and the component flux could be maintained at more than 90% of that of the new components. The desalination capacity of the membrane components was well restored, reflecting a good repair effect.

[0044] The above are only specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that are not conceived through creative work should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined in the claims.

Claims

1. A targeted repair method for a polyamide desalination membrane assembly, characterized in that: The steps include: S1. Dissolve a certain amount of ferrous salt and a small amount of citric acid in pure water to prepare an aqueous solution of a certain concentration as modified solution A; S2. Dissolve a certain amount of 30% by mass hydrogen peroxide aqueous solution in pure water to prepare a certain concentration of hydrogen peroxide aqueous solution, and adjust the pH value with dilute hydrochloric acid to prepare a modified solution B; S3, dissolving a certain amount of aromatic amine substance in pure water to prepare an aqueous solution of a certain concentration as modified solution C; S4. At room temperature, the cleaned polyamide membrane assembly is subjected to pressurized cyclic soaking treatment with the modified solution A, and the modified solution is drained after a certain period of time; S5. At room temperature, the membrane assembly treated with the modified solution A is subjected to a cyclic pressure soaking treatment with the modified solution B; S6. At room temperature, the membrane assembly treated with the modified solution B is subjected to a circulating pressurized soaking treatment with the modified solution C. After a certain period of time, the modified solution is drained, and then the membrane assembly is cleaned with a certain concentration of citric acid aqueous solution by pressurized circulating soaking and cleaning, and then the membrane assembly is cleaned with pure water.

2. The targeted repair method for a polyamide desalination membrane assembly according to claim 1, characterized in that: The ferrous salt is one or more of ferrous chloride, ferrous sulfate, and ferrous nitrate.

3. The targeted repair method for a polyamide desalination membrane assembly according to claim 1, characterized in that: The mass percentage concentration of the ferrous salt is 0.5%-2%.

4. The targeted repair method for a polyamide desalination membrane assembly according to claim 1, characterized in that: The mass percentage concentration of the hydrogen peroxide is 0.5%-2%.

5. The targeted repair method for a polyamide desalination membrane assembly according to claim 1, characterized in that: The pH value of the hydrogen peroxide solution is in the range of 3-7.

6. The targeted repair method for a polyamide desalination membrane assembly according to claim 1, characterized in that: The aromatic amine substance is one or more of p-aminobenzoic acid, m-phenylenediamine and sulfonamide.

7. The targeted repair method for a polyamide desalination membrane assembly according to claim 1, characterized in that: The mass percentage concentration of the aromatic amine is 0.02%-0.1%.

8. The targeted repair method for a polyamide desalination membrane assembly according to claim 1, characterized in that: In step S4, the membrane assembly is subjected to pressurized cyclic soaking treatment with the modified solution A for 5-10 minutes.

9. The targeted repair method for a polyamide desalination membrane assembly according to claim 1, characterized in that: In step S5, the membrane assembly treated with the modified solution A is subjected to a pressurized cyclic soaking treatment with the modified solution B for 10-30 minutes.

10. The targeted repair method for a polyamide desalination membrane assembly according to claim 1, characterized in that: In step S6, the membrane assembly treated with the modified solution B is subjected to a pressurized cyclic soaking treatment with the modified solution C for 10-30 minutes.

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