Covalence-coordination synergistic induced waste reverse osmosis membrane micro-nano damage in-situ repair method

Abstract

The invention relates to a covalence-coordination synergistic induced waste reverse osmosis membrane micro-nano damage in-situ repair method. The repairing agent comprises plant polyphenol, polyamine and metal ions. The repairing method comprises the following steps: providing a filtering device, and arranging the waste reverse osmosis membrane in the filtering device; the method comprises the following steps: preparing a plant polyphenol solution, a polyamine solution and a metal ion solution, mixing the plant polyphenol solution and the polyamine solution, and carrying out pressure filtration under the original cross-flow pressure filtration working condition; and then adding the solution into the filtering device, and carrying out pressure filtration to obtain the repaired reverse osmosis membrane. According to the method, the service life of the waste reverse osmosis membrane can be remarkably prolonged, the traditional mode that the membrane is damaged and discarded is broken, the negative environmental influence of treating and disposing the waste membrane is reduced, the economic burden generated by frequently replacing a new membrane of an enterprise is relieved, the repairing process is simple and convenient to operate, easy to implement and low in cost, and green and low-carbon development of a reverse osmosis membrane separation technology is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of membrane separation, and in particular to a method for in-situ repairing of micro-nano damaged waste reverse osmosis membranes by covalent-coordination synergistic induction. Background Art

[0002] Reverse osmosis membrane separation is an important technology for seawater desalination, deep treatment of sewage and wastewater, and purification of drinking water. It can achieve selective separation between water / pollutants, water / salt and other substances. According to statistics, the global reverse osmosis membrane separation market will reach US$1.2 billion in 2023. However, in actual application, chemical erosion, physical wear, high pressure stress, etc. may cause damage to the membrane structure, resulting in deterioration of membrane separation performance and decreased water quality. At this time, a new membrane must be replaced to maintain the normal operation of the process. It is reported that the service life of a reverse osmosis membrane is usually 1-3 years, and the price of each reverse osmosis membrane is between 4,000 and 10,000 yuan (8040 components, ~37m 2 The membrane area is large, and the frequent replacement of new membranes imposes a heavy economic burden on enterprises. In addition, when the reverse osmosis membrane reaches the end of its life, it is mainly disposed of by incineration and landfill, which has a serious negative impact on the environment. Therefore, if the abandoned reverse osmosis membrane can be repaired in situ, thereby extending the service life of the membrane material, it will contribute to the green and low-carbon development of membrane separation technology.

[0003] The reverse osmosis membrane consists of a non-woven fabric layer, a polysulfone porous support layer, and a polyamide layer from bottom to top. The polyamide layer is the main structure of the reverse osmosis membrane for selective separation. It is reported that micro-nano damage to the polyamide layer is the main cause of reverse osmosis membrane failure and deterioration of water quality. Therefore, the key to restoring the performance of the reverse osmosis membrane lies in how to repair the micro-nano damage of the polyamide layer without disassembling the membrane assembly. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for in-situ repair of micro-nano damage of waste reverse osmosis membranes induced by covalent-coordination synergistic induced damage. The method is simple to operate, can effectively extend the service life of the reverse osmosis membrane, reduce the negative impact of waste membrane treatment and disposal on the environment, and reduce the economic expenditure of frequent replacement of new membranes and treatment and disposal of waste membranes.

[0005] The first object of the present invention is to provide an in-situ repair agent for micro-nano damage of discarded reverse osmosis membranes, comprising plant polyphenols, polyamines and metal ions; the metal ions comprise one or more of ferric chloride, vanadium chloride, gadolinium chloride or chromium chloride.

[0006] In some embodiments of the present invention, the plant polyphenols are selected from one or more of tannic acid, proanthocyanidins, kaempferol and catechins.

[0007] In some embodiments of the present invention, the concentration of the plant polyphenols is 1.2-3.6 mmol / L, and the pH value is 8-8.5.

[0008] In some embodiments of the present invention, the polyamine is selected from one or more of polyethyleneimine, diethylenetriamine and tetraethylenepentamine.

[0009] In some embodiments of the present invention, the concentration of the polyamine is 0.5-1.0 g / L; the pH value is 8-8.5.

[0010] In some embodiments of the present invention, the concentration of the metal ions is 0.24-24 mmol / L.

[0011] In some embodiments of the present invention, the volume ratio of the plant polyphenol solution to the polyamine solution is (3:1) to (5:1).

[0012] The second object of the present invention is to provide a covalent-coordinated synergistically induced in situ repair method, comprising the following steps:

[0013] (1) providing a cross-flow filtration device, and placing a waste reverse osmosis membrane in the cross-flow filtration device;

[0014] (2) preparing a plant polyphenol solution, a polyamine solution and a metal ion solution, mixing the plant polyphenol solution and the polyamine solution, and performing pressure filtration under the original cross-flow pressure filtration conditions;

[0015] (3) Then, a metal ion solution is added to the cross-flow filtration device and filtered under pressure to obtain a repaired reverse osmosis membrane.

[0016] In some embodiments of the present invention, in step (2), the conditions for pressure filtration are: pressure of 6 to 16 bar, running for 5 to 10 minutes. The volume ratio of the metal ion solution to the plant polyphenol solution is 1:1. The cross-flow filtration device used in the present invention is a conventional device in the art.

[0017] In some embodiments of the present invention, in step (3), the conditions for pressure filtration are: pressure of 6 to 16 bar, and operation time of 5 to 10 min.

[0018] In the present invention, a method for in-situ repair of micro-nano damage of discarded reverse osmosis membranes induced by covalent-coordination synergistic is proposed, and the reverse osmosis membrane with deteriorated separation performance is repaired to a level of performance equivalent to that of a new membrane under the original cross-flow filtration working conditions. Specifically, without disassembling the membrane components, plant polyphenols and polyamines are firstly used to undergo covalent cross-linking reaction to form a macromolecular network repair agent, and the damaged part of the membrane is blocked by strong convection under the original cross-flow filtration working conditions; then, the filtered metal ion solution undergoes coordination reaction with the macromolecular substances on the membrane surface to further form a dense structure, which plays a role in selectively intercepting solutes, while ensuring that the repaired membrane has good water permeability.

[0019] The above technical solution of the present invention has the following advantages compared with the prior art:

[0020] (1) It breaks the traditional linear model that reverse osmosis membranes are discarded when they are damaged, and proposes a new technology for the regeneration of reverse osmosis membranes at the end of their life, which extends the service life of membrane materials and reduces the economic expenditure of enterprises caused by frequent replacement of new membranes.

[0021] (2) The process of the present invention is simple to operate, easy to implement, low-cost, and environmentally friendly, and has practical application significance. It provides an effective solution to the problem of end-of-life membrane treatment and disposal, and contributes to the green and low-carbon development of membrane wastewater treatment technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0023] Figure 1 The data graphs are for water permeability and sodium chloride rejection rate of comparative example 1 and three reverse osmosis membranes with different degrees of damage, which prove that the separation performance of commercial reverse osmosis membranes damaged to different degrees deteriorates, the membrane water permeability gradient increases, and the sodium chloride rejection gradient decreases.

[0024] Figure 2 The data graphs of water permeability and sodium chloride rejection rate of Comparative Example 1, Example 1, Example 2 and Example 3 prove that after in-situ repair induced by plant polyphenol-polyamine-metal covalent coordination synergistic induced, the reverse osmosis membrane with deteriorated separation performance is repaired to a sodium chloride salt rejection rate equivalent to that of a new membrane, while ensuring that the repaired membrane has good water permeability.

[0025] Figure 3 It is a data graph of water / sodium chloride selective separation of Comparative Example 1, Example 1, Example 2, and Example 3, proving that after in-situ repair induced by plant polyphenol-polyamine-metal covalent coordination synergistic induced, the water / salt selective separation performance of the optimal group of repaired membranes is better than that of the new membrane. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0027] Example 1, Example 2, Example 3

[0028] Three reverse osmosis membranes with different degrees of damage (corresponding to the damaged commercial membranes of Comparative Example 1, Comparative Example 2 and Comparative Example 3, respectively) were placed in a cross-flow filtration device, and a mixed solution of tannic acid (2.4 mmol / L, pH=8-8.5) and polyethyleneimine (1.0 g / L, pH=8-8.5) with a volume ratio of 5:1 was added to the feed tank. After filtering at 16 bar for 10 minutes, the mixed solution in the device was discharged, and then 7.2 mmol / L ferric chloride solution was added to the feed tank, and filtered at 16 bar for 10 minutes to obtain a repaired reverse osmosis membrane.

[0029] Laboratory performance testing of reverse osmosis membranes

[0030] At a constant temperature of 25°C, the repaired reverse osmosis membrane was subjected to cross-flow filtration at 16 bar through a cross-flow reverse osmosis device. After the membrane was stabilized by pre-pressure filtration, the sodium chloride retention rate of the membrane was tested with 2000 mg / L NaCl solution as the influent. The effective area of ​​the membrane was 19.0 cm 2 .

[0031] Comparative Example 1

[0032] Comparative Example 1 corresponds to an undamaged commercial reverse osmosis membrane.

[0033] Comparative Example 2, Comparative Example 3, Comparative Example 4

[0034] Comparative Examples 2, 3 and 4 are commercial reverse osmosis membranes that have been damaged to varying degrees.

[0035] Comparative Example 5

[0036] The same as Example 1, except that the addition of polyethyleneimine is missing.

[0037] Test Example 1

[0038] The performance of the commercial reverse osmosis membrane (Comparative Example 1) and the three reverse osmosis membranes with different damage degrees (Comparative Example 2, Comparative Example 3, Comparative Example 4) were tested. Figure 1 The results show that the water permeability of Comparative Example 1 is 3.9 L / (m 2 ·h·bar), the salt retention rate is 96.7%, and the water permeability of Comparative Examples 2, 3, and 4 is 8.8 L / (m 2·h·bar)、11.4L / (m 2 ·h·bar)、12.5L / (m 2 ·h·bar), and the sodium chloride salt retention rates were 93.6%, 85.3% and 78.2% respectively.

[0039] Test Example 2

[0040] The reverse osmosis filtration test results show that ( Figure 2 ), after covalent-coordination synergistic induction in situ repair, the salt retention performance of Example 1 was 96.9%, and the water permeability was 4.6 L / (m 2 ·h·bar), the salt retention and water permeability are better than those of comparative example 1, and the water / sodium chloride selective separation performance of embodiment 1 is 2.22bar, which is better than the water / sodium chloride selective separation performance of comparative example 1 of 2.18bar; the salt retention performance of embodiment 2 is 93.6%, and the water permeability is 4.9L / (m 2 ·h·bar), the salt retention was restored to more than 95% of that in comparative example 1, and the water permeability was better than that in comparative example 1; the salt retention performance of Example 3 was 91.6%, and the water permeability was 4.9 L / (m 2 ·h·bar), the salt retention was restored to about 95% of that in Comparative Example 1, and the water permeability was better than that in Comparative Example 1.

[0041] Test Example 3

[0042] The comparative example 6 lacking polyethyleneimine was tested, and the results showed that the salt retention performance of the comparative example 6 was 97.5%, and the water permeability was 2.8 L / (m 2 ·h·bar), the salt rejection is comparable to that of the new membrane, but the water permeability is much lower than that of Example 1.

[0043] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. An in-situ repair agent for micro-nano damage of discarded reverse osmosis membranes, characterized in that: It comprises plant polyphenols, polyamines and metal ions; the metal ions comprise one or more of ferric chloride, vanadium chloride, gadolinium chloride or chromium chloride.

2. The waste reverse osmosis membrane micro-nano damage in-situ repairing agent according to claim 1, characterized in that: The plant polyphenols are selected from one or more of tannic acid, proanthocyanidins, kaempferol and catechins.

3. The waste reverse osmosis membrane micro-nano damage in-situ repairing agent according to claim 1, characterized in that: The concentration of the plant polyphenols is 1.2-3.6 mmol / L, and the pH value is 8-8.

5.

4. The waste reverse osmosis membrane micro-nano damage in-situ repairing agent according to claim 1, characterized in that: The polyamine is selected from one or more of polyethyleneimine, diethylenetriamine and tetraethylenepentamine.

5. The waste reverse osmosis membrane micro-nano damage in-situ repairing agent according to claim 1, characterized in that: The concentration of the polyamine is 0.5-1.0 g / L; the pH value is 8-8.

5.

6. The in-situ repair agent for micro-nano damage of waste reverse osmosis membrane according to claim 1, characterized in that: The concentration of the metal ions is 0.24-24 mmol / L.

7. The in-situ repair agent for micro-nano damage of waste reverse osmosis membrane according to claim 1, characterized in that: The volume ratio of the plant polyphenol solution to the polyamine solution is (3:1) to (5:1); the volume ratio of the metal ion solution to the plant polyphenol solution is 1:

1.

8. A covalent-coordination synergistically induced in situ repair method, characterized in that: A method for in-situ repair of an abandoned reverse osmosis membrane using the in-situ repair agent for micro-nano damage of an abandoned reverse osmosis membrane according to any one of claims 1 to 7 comprises the following steps: (1) providing a cross-flow filtration device, and disposing a waste reverse osmosis membrane in the cross-flow filtration device; (2) preparing a plant polyphenol solution, a polyamine solution and a metal ion solution, mixing the plant polyphenol solution and the polyamine solution, and then pressure filtering under the original cross-flow pressure filtration conditions; (3) Then, a metal ion solution is added to the cross-flow filtration device and filtered under pressure to obtain a repaired reverse osmosis membrane.

9. The covalent-coordination synergistically induced in situ repair method according to claim 8, characterized in that: In step (2), the conditions for pressure filtration are: pressure of 6 to 16 bar, and operation time of 5 to 10 minutes.

10. The covalent-coordination synergistically induced in situ repair method according to claim 8, characterized in that: In step (3), the conditions for pressure filtration are: pressure of 6 to 16 bar, and operation time of 5 to 10 minutes.

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