Targeted repair method of polyamide desalination membrane assembly

Abstract

According to the targeted repair method for the polyamide desalination membrane assembly, the defects of the polyamide desalination membrane assembly caused by membrane stress / strain caused by manufacturing, chemical reagent corrosion and operation modes and damage caused by extreme operation conditions can be effectively repaired. The iron ions are enriched at the defects on the surface of the polyamide membrane under the complexing action of the iron ions and functional groups such as carboxyl, the aromatic amine substances are selectively and targeted enriched at the defects of the polyamide membrane under the complexing action of the iron ions and the introduced functional aromatic amine substances, and then the iron ions and hydrogen peroxide react to generate hydroxyl free radicals, so that the defects of the polyamide membrane are enriched. And initiating oxidative polymerization of aromatic amine substances to form a polymer to fill defects, and synchronously carrying out bonding reaction with terminal amino groups on the surface of the membrane. The method can effectively recover the desalting capacity of the polyamide desalting membrane assembly, the repaired membrane assembly is good in performance stability, and the method has the advantages of being simple, efficient and the like.

Description

Technical Field

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

[0002] The global shortage of freshwater resources has become a problem of great concern to the world. Population growth, industrialization, urbanization and climate change have exacerbated the world's freshwater crisis. In the past few decades, the scarcity of freshwater resources is threatening the sustainable development of human society due to the steady growth of demand. Therefore, humans urgently need to increase the supply of freshwater resources through efficient and energy-saving water purification methods to solve this increasingly serious global dilemma. From a thermodynamic point of view, the currently used desalination technologies can be basically divided into thermal separation technology and membrane separation technology. Thermal separation technology is usually limited by high energy consumption, high investment cost and high operating cost. In contrast, membrane separation technology does not require additional energy to drive the phase change of water, and has the advantages of low energy consumption, simple operation process and no greenhouse gas emissions. Therefore, membrane separation technology has a broader application prospect and has received more extensive attention.

[0003] As the most precise water separation membrane, polyamide membrane can effectively separate water from ions in water. However, defects caused by improper process control during the production process, degradation of the separation layer caused by corrosion of chemical reagents (acid-base hydrolysis, sodium hypochlorite residue, etc.) during long-term operation, membrane aging (high-temperature decomposition, performance degradation caused by changes in membrane surface stress caused by operating conditions, etc.), and scratches on the membrane surface by particles in the influent water can all lead to a decrease in the desalination capacity of the polyamide membrane, resulting in a significant decrease in the quality of the effluent during water treatment, and the need for frequent replacement of polyamide membrane components, 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 components.

[0004] In existing solutions, polyamide membrane components are removed from treatment facilities for replacement or repair, which not only affects the operation of the system, but also increases the cost of replacement. If a cheap in-situ repair method can be used to reconstruct and repair the defects or damaged points of the separation layer, restore its filtration performance and solute retention performance, and extend the service life of the polyamide membrane, 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 in-situ repair of membrane components.

[0005] The existing method is to repair the defects of the polyamide membrane surface by depositing organic polymer on the surface of the polyamide membrane. This method has certain defects when used. During the implementation process, the deposits are physically adsorbed on the membrane surface, the adhesion of the deposits on the membrane surface is not strong, and the stability of the repaired polyamide membrane is not high. Therefore, a new process is proposed to solve the shortcomings of the existing method. 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 components that can solve the problem of decreased separation performance, especially decreased desalination capacity, caused by defects on the membrane surface during long-term use of polyamide membrane components, thereby ensuring the water quality of the effluent from the polyamide desalination membrane components and saving operating costs, and having practicality and wide application.

[0007] 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 percent 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, pressurizing and circulating the cleaned polyamide membrane assembly with the modified solution A, and draining the modified solution 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, the modified solution is drained after a certain period of time, and then the membrane assembly is cleaned with a citric acid aqueous solution of a certain concentration by pressure circulation soaking and cleaning, and then the membrane assembly is cleaned with pure water;

[0014] S6. At room temperature, the membrane components treated with the modified solution B are subjected to cyclic pressurized soaking treatment with the modified solution C. After a certain period of time, the modified solution is drained, and then the membrane components are cleaned by pressurized cyclic soaking with a certain concentration of citric acid aqueous solution, and then the membrane components are 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 immersion 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 immersion 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 membrane stress / strain caused by manufacturing, chemical reagent corrosion, operation mode and damage caused by extreme conditions of the polyamide membrane; the complexation of iron ions with functional groups such as carboxyl groups is used to realize the enrichment of iron ions at defects and play a molecular target role, and the selective enrichment of aromatic amine substances at polyamide membrane defects is realized by the complexation of iron ions with the introduced functional aromatic amine substances, and then the hydroxyl radicals generated by the reaction of iron ions with hydrogen peroxide are used to induce the oxidative polymerization of aromatic amine substances to form polymers and fill the defects, and the polymers are generated while bonding with the terminal amino groups on the membrane surface. This method can not only effectively repair the membrane surface defects to restore the desalination capacity of the polyamide membrane, but also give the repaired membrane better stability by bonding with the membrane surface, and finally 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 inlet water of the polyamide device. There is no need to replace the inlet water 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 repair agent for targeted repair of polyamide desalination membrane components 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 to aggregate 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, and covalent bonding on the membrane surface is achieved by reacting with the amino groups on the membrane surface. While effectively restoring the desalination capacity of the polyamide membrane, it gives the repaired membrane better stability, ultimately achieving in situ repair of the polyamide membrane assembly. DETAILED DESCRIPTION

[0030] Polyamide desalination membrane assembly: The EM-RO-1812-75 household polyamide desalination membrane assembly purchased from the market was soaked in 20-30°C pure water for 30 minutes, and then rinsed with pure water for use.

[0031] Simulated performance-degraded polyamide desalination membrane components: The polyamide desalination membrane components were 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 components 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% hydrogen peroxide aqueous solution in pure water to prepare 0.5%-2% modified solution B, wherein the pH value of solution B ranges from 3 to 7.

[0034] Prepare modified solution C: dissolve a certain amount of aromatic amine substance in pure water to prepare modified solution C with a mass percentage concentration of 0.02%-0.1%. The aromatic amine substance 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 and soaked in the modified solution A for 5-10 minutes at 0.05-0.15MPa, and the modified solution is drained after a certain period of time.

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

[0037] Membrane components are circulated and soaked in modified solution C: At room temperature and 0.05-0.15MPa, the membrane components treated with modified solution B are circulated and pressurized and soaked in modified solution C for 10-30 minutes, and then the modified solution is drained. After that, the membrane components are cleaned by pressurized circulated soaking with a certain concentration of citric acid aqueous solution, and then the membrane components are cleaned with pure water.

[0038] The desalination rate (R) and water production (F) of the polyamide desalination membrane module are tested below.

[0039] The desalination rate and water production test of the polyamide desalination membrane module: a cross-flow experiment was used, with a 0.05% mass percent NaCl aqueous solution as the feed liquid, and the test was conducted under the conditions of 0.4MPa, 25°C, and pH 7.0±0.2. The results are shown in Table 1 below, showing 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% mass percent NaCl aqueous solution as the feed liquid; tested under 0.4MPa, 25°C, pH 7.0±0.2 conditions, the desalination rate of the repaired polyamide desalination membrane components was higher than 95%, and the component flux could be maintained at more than 90% of the new component. 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 protection scope of the present invention is not limited thereto. Any changes or substitutions that are not conceived through creative work should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope 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, dissolving a certain amount of 30% by mass percent 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; 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, pressurizing and circulating the cleaned polyamide membrane assembly with the modified solution A, and draining the modified solution after a certain period of time; S5. At room temperature, the membrane assembly treated with the modified solution A is subjected to a cyclic pressurized soaking treatment with the modified solution B; S6. At room temperature, the membrane components treated with the modified solution B are subjected to cyclic pressurized soaking treatment with the modified solution C. After a certain period of time, the modified solution is drained, and then the membrane components are cleaned by pressurized cyclic soaking with a certain concentration of citric acid aqueous solution, and then the membrane components are 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, ferrous nitrate and the like.

3. The targeted repair method of 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 ranges from 3 to 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, sulfonamide and the like.

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 of 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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