Method for regenerating reverse osmosis membranes of waste brackish water of a thermal power plant

Abstract

The present application relates to a kind of thermal power plant waste brackish water reverse osmosis membrane regeneration method, comprising: the reverse osmosis membrane is chemically cleaned;Reverse osmosis membrane is repeatedly compacted by high hydraulic pressure waste brackish water reverse osmosis membrane piece;The reverse osmosis membrane after cleaning internal pollutants is modified.The beneficial effects of the present application are: the modified regeneration membrane obtained by the present application can effectively intercept small molecule organic matter and fluoride, and has partial salt separation performance and good stability, and has good practical engineering application prospect.

Description

Technical Field

[0001] This invention relates to the field of reverse osmosis membrane treatment technology, and more specifically, to a method for regenerating reverse osmosis membranes from waste brackish water from thermal power plants. Background Technology

[0002] In recent years, all-membrane water treatment technology has been increasingly used in thermal power plants, and brackish water reverse osmosis membranes are widely used for desalination in systems that use surface river water as raw water. However, reverse osmosis membranes are generally made of composite polyamide materials, and membrane fouling is unavoidable after a certain period of operation.

[0003] The rejection rate and filtration performance of discarded brackish water reverse osmosis membranes decrease, but their main structure remains intact. After proper regeneration, the regenerated reverse osmosis membranes can be downgraded for use depending on their performance. Brackish water reverse osmosis membranes used in thermal power plants are generally spiral-wound, composite polyamide membranes. The separation layer of these composite membranes is very thin, and improper regeneration methods can easily cause complete damage to the separation layer, rendering the reverse osmosis membrane completely ineffective. Furthermore, the finished membranes are industrially standardized and cannot be modified as precisely and conveniently as in a laboratory setting. Therefore, waste membrane regeneration is extremely difficult. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for regenerating reverse osmosis membranes in waste brackish water from thermal power plants, comprising:

[0005] S1. Chemically clean the reverse osmosis membrane; the reverse osmosis membrane is a discarded RO membrane sheet that has been repeatedly compacted under high hydraulic pressure;

[0006] S2. Modify the reverse osmosis membrane after cleaning internal contaminants, including:

[0007] S201. The reverse osmosis membrane is oxidized with a weak oxidant, and then the surface structure of the reverse osmosis membrane is modified with a polymeric surfactant; the concentration of the weak oxidant in the aqueous solution is 0.1-4%, and the concentration of the polymeric surfactant is 0.01-1%.

[0008] S202. Treat the reverse osmosis membrane with a strong oxidant; the concentration of the strong oxidant in the aqueous solution is 0.1-5%.

[0009] Preferably, in S201, the weak oxidant is one or a mixture of several of ammonium persulfate, potassium persulfate, and sodium persulfate; the polymeric activator is one or a mixture of several of polyvinyl alcohol, chitosan quaternary ammonium salt, polyvinylpyrrolidone, polyethyleneimine, and polyacrylamide; and in S202, the strong oxidant is one or a mixture of several of sodium hypochlorite, hydrogen peroxide, and potassium permanganate.

[0010] Preferably, in S201, the applicable temperature of the weak oxidant is ≤60℃.

[0011] Preferably, in S201, the weak oxidant is in a weakly acidic environment with a pH value ≤ 6.

[0012] Preferably, in S202, the strong oxidant is under strongly alkaline conditions with a pH value ≥ 9.

[0013] Preferably, in S201, the weak oxidant is potassium persulfate with a concentration range of 0.1-2%; and the polymeric activator is chitosan quaternary ammonium salt with a concentration range of 0.01%-0.5%.

[0014] Preferably, in S202, the strong oxidant is sodium hypochlorite, with a concentration range of 0.1-3%.

[0015] Preferably, in S201, the weak oxidant is in a weakly acidic environment with a pH value of 2 ≤ pH ≤ 6.

[0016] Preferably, the strong oxidant is under strongly alkaline conditions with a pH value ≥ 10.

[0017] Preferably, S1 and S2 are performed at room temperature.

[0018] The beneficial effects of this invention are: the regenerated membrane obtained by modification can effectively retain small molecule organic matter and fluorides, and has partial salt separation performance and good stability, and has good prospects for practical engineering applications, such as for circulating cooling water side filtration, first-stage reverse osmosis pre-desalination, concentrated water reverse osmosis, etc., making full use of its residual value and reducing enterprise production costs. Attached Figure Description

[0019] Figure 1 A flowchart of a method for regenerating reverse osmosis membranes in waste brackish water from a thermal power plant;

[0020] Figure 2 This is a flowchart illustrating the modification of a reverse osmosis membrane after cleaning internal contaminants. Detailed Implementation

[0021] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0022] Developing a method for regenerating waste brackish water membranes can not only bring good economic benefits but also reduce the environmental pressure on thermal power plants. To address the difficulty of regenerating reverse osmosis membranes in waste brackish water from thermal power plants, this invention focuses on the modified regeneration and reuse of waste BW reverse osmosis membranes replaced by thermal power plants. By adjusting the concentration, composition, pH value, and temperature of the modifying chemicals, the surface roughness of the reverse osmosis membrane is increased. This increases water flux while reducing the desalination rate, thus modifying the reverse osmosis membrane into a nanofiltration membrane with nanofiltration characteristics, making it suitable for application in relevant scenarios.

[0023] Specifically, this invention proposes a novel method for modifying and recycling reverse osmosis membranes, such as... Figure 1 and Figure 2 As shown, the reverse osmosis membrane is a discarded reverse osmosis membrane sheet that has been repeatedly compacted under high hydraulic pressure. The discarded reverse osmosis membrane is first chemically cleaned, and then modified after cleaning the internal contaminants.

[0024] The modification method is mainly carried out in two parts. The first part is to oxidize the reverse osmosis membrane with a certain concentration of weak oxidant, and then modify the surface structure of the reverse osmosis membrane by using polymer as an active agent, so as to provide good basic conditions for the next step of modification. The second part is to treat the reverse osmosis membrane with strong oxidant to further improve its water flux.

[0025] The modification principle of this invention is as follows: When the reverse osmosis membrane is treated with a weak oxidant, the amide group can be oxidized, and then the hydrogen bonds of the molecular chain segments are broken, forming pores on the membrane surface. Then, a polymeric surfactant is inserted to increase the roughness of the membrane surface. Further treatment of the reverse osmosis membrane with a strong oxidant can further hydrolyze the amide bonds of the amide layer, increase its water flux, reduce the desalination rate, and convert the reverse osmosis membrane into a nanofiltration membrane for use.

[0026] To better understand the above technical solution, the present invention will be described in detail below with reference to specific embodiments. The reverse osmosis membranes used in the following embodiments are based on waste brackish water (BW) reverse osmosis membranes replaced by thermal power plants, and research on their modification, regeneration, and reuse has been carried out. The waste membrane elements were first chemically cleaned and then disassembled, cut into approximately 8×8cm pieces. 2 Uniformly sized membranes; the cut membranes are soaked in deionized water and refrigerated at 4°C until use.

[0027] Example 1

[0028] Prepare solution A: a mixture of 1% potassium persulfate and 0.1% chitosan quaternary ammonium salt; prepare solution B: a 1% sodium hypochlorite solution. Completely immerse the membrane in solution A for static soaking, adjusting the pH to 4 during this process. After 60 minutes, remove the membrane and repeatedly rinse its surface with deionized water until the pH of the cleaning waste solution matches that of the deionized water. Then, place the membrane in solution B for 15 minutes, adjusting the pH to 10, and repeat the soaking and rinsing process as described above. The modified membrane remains immersed in deionized water and stored under cold for subsequent performance testing.

[0029] Example 2

[0030] Compared to Example 1, the concentration of potassium persulfate in solution A was adjusted to 0.8%, while the rest of the methods were the same as in Example 1.

[0031] Example 3

[0032] Compared to Example 1, the concentration of potassium persulfate in solution A was adjusted to 1.5%, while the rest of the methods were the same as in Example 1.

[0033] Example 4

[0034] Compared to Example 2, the concentration of sodium hypochlorite in solution B was adjusted to 1.5%, while the rest of the methods were the same as in Example 2.

[0035] Example 5,

[0036] Compared to Example 2, the concentration of sodium hypochlorite in solution B was adjusted to 2%, while the rest of the methods were the same as in Example 2.

[0037] Example 6

[0038] Compared to Example 1, the concentration of chitosan quaternary ammonium salt in solution A was adjusted to 0.05%, while the rest of the methods were the same as in Example 1.

[0039] Example 7

[0040] Compared to Example 1, the concentration of chitosan quaternary ammonium salt in solution A was adjusted to 0.15%, while the rest of the methods were the same as in Example 1.

[0041] Comparative Example 1

[0042] The membrane used in this comparative example is the waste BW reverse osmosis membrane used in Example 1, which was cleaned and placed in the refrigerator for later use.

[0043] Comparative Example 2

[0044] Compared to Example 1, the chitosan quaternary ammonium salt in solution A was removed, while the rest of the methods were the same as in Example 1.

[0045] Comparative Example 3

[0046] Compared to Example 1, the preparation of solution B was omitted, while the rest of the methods were the same as in Example 1.

[0047] Comparative Example 4

[0048] Compared to Example 1, the preparation of solution A was omitted, while the rest of the methods were the same as in Example 1.

[0049] Comparative Example 5

[0050] Compared to Example 1, the chitosan quaternary ammonium salt in solution A was removed, and solution B was omitted; all other methods were the same as in Example 1.

[0051] As shown in Table 1, the membrane obtained by the embodiments of this application has a large water flux.

[0052] Table 1

[0053]

[0054]

[0055] In summary, the regenerated membrane obtained by the present invention through modification can effectively retain small molecule organic matter and fluorides, and has partial salt separation performance and good performance stability, showing good prospects for practical engineering applications.

Claims

1. A method for regenerating a reverse osmosis membrane for waste brackish water of a thermal power plant, characterized in that, The application relates to a method for improving the performance of a reverse osmosis membrane. S1, chemically cleaning a reverse osmosis membrane; The reverse osmosis membrane is a waste brackish water reverse osmosis membrane piece compacted by repeated high hydraulic pressure; S2, modifying the reverse osmosis membrane after cleaning the internal pollutants, comprising: S201, oxidizing the reverse osmosis membrane by using a weak oxidant, and then modifying the surface structure of the reverse osmosis membrane by using a high-molecular active agent; the concentration of the weak oxidant in the aqueous solution is 0.1-4%, and the concentration of the high-molecular active agent is 0.01-1%; in S201, the weak oxidant is one or a mixture of several of ammonium persulfate, potassium persulfate and sodium persulfate; the high-molecular active agent is one or a mixture of several of polyvinyl alcohol, chitosan quaternary ammonium salt, polyvinylpyrrolidone, polyethyleneimine and polyacrylamide; S202, treating the reverse osmosis membrane by using a strong oxidant; the concentration of the strong oxidant in the aqueous solution is 0.1-5%; in S202, the strong oxidant is one or a mixture of several of sodium hypochlorite, hydrogen peroxide and potassium permanganate.

2. The method for regenerating a reverse osmosis membrane for waste brackish water of a thermal power plant according to claim 1, characterized in that, In S201, the weak oxidant is used at a temperature of <=60 DEG C.

3. The method for regenerating a reverse osmosis membrane for waste brackish water of a thermal power plant according to claim 2, characterized by, In S201, the weak oxidant is used in a weak acid environment with a pH value of <=6.

4. The method for regenerating a reverse osmosis membrane for waste brackish water of a thermal power plant according to claim 3, characterized by, In S202, the strong oxidant is used in a strong alkaline condition with a pH value of >=9.

5. The method for regenerating a reverse osmosis membrane for waste brackish water of a thermal power plant according to claim 1, characterized in that, In S201, the weak oxidant is potassium persulfate, and the concentration range is 0.1-2%; the high-molecular active agent is chitosan quaternary ammonium salt, and the concentration range is 0.01%-0.5%.

6. The method for regenerating a reverse osmosis membrane for waste brackish water of a thermal power plant according to claim 1, characterized in that, In S202, the strong oxidant is sodium hypochlorite, and the concentration range is 0.1-3%.

7. The method for regenerating a reverse osmosis membrane for waste brackish water of a thermal power plant according to claim 3, characterized by, In S201, the weak oxidant is used in a weak acid environment with a pH value of 2<=6.

8. The method for regenerating a reverse osmosis membrane for waste brackish water of a thermal power plant according to claim 4, characterized by, The strong oxidant is used in a strong alkaline condition with a pH value of >=10.

9. The method for regenerating a reverse osmosis membrane for waste brackish water of a thermal power plant according to any one of claims 1 to 8, characterized in that, S1 and S2 are carried out at room temperature.

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