A regenerant and a regeneration method for regenerating waste and old roll type reverse osmosis membrane by nanofiltration

Abstract

The application discloses a kind of regeneration agent and regeneration method for waste roll type reverse osmosis membrane nanofiltration regeneration, belong to separation membrane repair regeneration technical field.The regeneration agent includes alkaline cleaning solution, surface etching solution, adhesive removal liquid, modifier 1 and modifier 2.The regeneration method uses waste roll type reverse osmosis membrane as raw material, using the above-mentioned regeneration agent, sequentially through chemical cleaning, surface etching, adhesive removal and surface chemical modification treatment, obtain regeneration nanofiltration flat membrane.Through test, the separation performance of the regenerated membrane is well recovered, and also has good alkali resistance and anti-pollution performance.The regeneration agent and regeneration method in the application, on the one hand, improve the functional value of membrane material, on the other hand, make up for the poor alkali resistance of traditional polyamide membrane, and the cost of preparing alkali-resistant membrane in existing technology is higher, and the process is more complicated.

Description

Technical Field

[0001] This invention belongs to the field of membrane repair and regeneration technology, specifically relating to a regenerator and regeneration method for nanofiltration regeneration of waste spiral wound reverse osmosis membranes. Background Technology

[0002] Polyamide reverse osmosis membranes, currently the most widely used reverse osmosis membrane material, mainly consist of a porous support (such as polyethersulfone or polysulfone) and a polyamide desalination layer (also known as an active separation layer or active functional layer). The polyamide desalination layer, as the core functional layer, plays a crucial role in retaining salts and separating impurities. This layer is often prepared using interfacial polymerization technology, where diamine monomers (such as m-phenylenediamine) in the aqueous phase and acyl chloride monomers (such as trimesoyl chloride) in the organic phase react rapidly at the interface to form a dense polyamide network. Depending on the application, the polyamide reverse osmosis membrane can also be wound with a flow guide net onto a central tube to form a spiral wound membrane element, achieving the separation of water molecules from dissolved salts, organic matter, and other impurities within a small space.

[0003] Traditional spiral-wound reverse osmosis membranes face obsolescence after performance degradation, but their polyamide functional layer still retains over 60% of active sites. Therefore, efficient regeneration technology for spent reverse osmosis membranes has attracted significant attention due to its economic value. For example, Chinese invention patent application CN 120268239A discloses a method for downgrading and regenerating spent reverse osmosis membranes. This method uses plasma to etch the polymer layer on the surface of the spent reverse osmosis membrane, employing physical and chemical synergistic etching through ions or free radicals generated by low-voltage discharge to convert the reverse osmosis membrane into a nanofiltration or ultrafiltration membrane. However, this downgrading regeneration reduces the membrane's usability to some extent. Other research has attempted same-level regeneration and repair of the membrane. For instance, Chinese invention patent application CN 111974222A discloses an integrated method for regenerating and repairing industrial waste reverse osmosis membranes. This method involves disassembly, washing, oxidation, desalination, drying, soaking, spraying with a glycerol solution, and then manually rewinding the membrane to repair and recycle the waste reverse osmosis membrane. However, this same-level regeneration process can only restore the membrane's retention performance and cannot increase the functional value of the original membrane.

[0004] Traditional polyamide membranes exhibit poor stability in alkaline environments because their core chemical bond—the amide bond (-CO-NH-)—is prone to alkali-catalyzed hydrolysis, leading to polymer chain breakage and membrane structure destruction, thus limiting their application in alkaline wastewater. Furthermore, alkali-resistant polyamide membranes are expensive to produce. For example, Chinese invention patent application CN 115554865A discloses an interpenetrating network polyamide membrane, its preparation method, and its application. This method involves reacting polyetheramine, bisphenol, and formaldehyde to generate a polyamine monomer containing benzoxazine structural units. A polyamide separation layer is formed through interfacial polymerization, and benzoxazine ring-opening polymerization is completed under heating conditions to form an interpenetrating network polyamide membrane, thereby improving its acid, alkali, and chlorine resistance. However, this preparation process is overly complex and costly, limiting its large-scale application. Summary of the Invention

[0005] On the one hand, existing technologies for regenerating or repairing spent spiral-wound reverse osmosis membranes using either downgrading or same-level regeneration fail to fully restore the membrane's separation performance, reducing its usability. While the latter restores separation performance, it only restores the membrane's original function and fails to impart new properties. On the other hand, existing polyamide membranes exhibit poor stability in alkaline environments, while the production cost of alkali-resistant polyamide membranes is excessively high. To address these issues, this invention provides a regenerator and method for nanofiltration regeneration of spent spiral-wound reverse osmosis membranes. The regenerator comprises an alkaline cleaning solution, a surface etching solution, an adhesive removal solution, and modifiers 1 and 2. By sequentially chemically cleaning, surface etching, adhesive removal, and surface chemical modification of the spent spiral-wound reverse osmosis membrane using the regenerator, a regenerated nanofiltration flat sheet membrane is obtained. This process restores membrane separation performance while imparting alkali resistance and antifouling properties to the membrane material, comprehensively enhancing its functional value. Simultaneously, it overcomes the shortcomings of traditional polyamide membranes (poor alkali resistance) and the high cost and cumbersome process of preparing existing alkali-resistant membranes.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a regenerator for nanofiltration regeneration of spent spiral wound reverse osmosis membranes, the regenerator comprising modifier 1 and modifier 2, wherein:

[0008] Modifier 1 comprises a composite solution of ammonium fluoride, a polyamide-amine dendritic polymer, and an organic amine, wherein the content of ammonium fluoride is 1-20 wt%; the content of the polyamide-amine dendritic polymer is 0.25-7.5 wt%; and the content of the organic amine is 0.25-7.5 wt%.

[0009] Modifier 2 comprises a hexane solution containing acrylate and 5-isocyanate isopeptidyl chloride, wherein the content of acrylate is 0.05~3wt% and the content of 5-isocyanate isopeptidyl chloride is 0.1~3wt%.

[0010] Furthermore, the aforementioned organic amines include 1,3-propanediamine and / or triethylenetetramine.

[0011] Furthermore, the aforementioned acrylates include hexafluorobutyl acrylate and / or dodecafluoroheptyl acrylate.

[0012] Furthermore, the molecular weight of the above-mentioned polyamide-amine dendritic polymer is 10,000 to 15,000.

[0013] Furthermore, the aforementioned regenerator also includes an alkaline cleaning solution, a surface etching solution, and an adhesive removal solution, wherein:

[0014] An alkaline cleaning solution includes an alkaline cleaning agent and / or an alkaline cleaning aid, wherein the alkaline cleaning agent includes any one of sodium bicarbonate, sodium carbonate, and sodium hydroxide, with a content of 1.25~37.5 wt%; and the alkaline cleaning aid includes any one of sodium silicate, sodium metasilicate, and sodium tripolyphosphate, with a content of 1.25~37.5 wt%.

[0015] The surface etching solution comprises a composite solution of sodium dodecylbenzenesulfonate and polyepoxysuccinic acid, wherein the content of sodium dodecylbenzenesulfonate is 1-6 wt%; and the content of polyepoxysuccinic acid is 1-6 wt%.

[0016] Adhesive removal solution, comprising a mixed solution of propylene glycol methyl ether and n-butanol, wherein the volume ratio of propylene glycol methyl ether to n-butanol is 3:1 to 1:3.

[0017] The present invention also provides a method for nanofiltration regeneration of spent spiral wound reverse osmosis membranes using the above-mentioned regenerant, the method comprising the following steps:

[0018] S1. Peel, cut, and scrub the waste spiral wound membrane element to obtain a complete membrane sheet. It should be noted that the peeling and cutting process in this step produces a flat membrane sheet, which allows the surface and base layers of the membrane sheet to fully contact the cleaning solution in the subsequent chemical cleaning process, thus improving the cleaning efficiency.

[0019] S2. The membrane in S1 is chemically cleaned using the alkaline cleaning solution described above. It should be noted that this step utilizes the alkaline components and surfactants contained in the alkaline cleaning agent to promote the hydrolysis reaction of organic and biological pollutants (ester compounds, proteins, polysaccharides, etc.) on the membrane surface in an alkaline environment, converting them into small molecules that are easy to wash off. The alkaline cleaning aid plays a role in dispersing pollutants and inhibiting corrosion.

[0020] S3. Use the above-mentioned surface etching solution to etch the film after cleaning in S2. It should be noted that this step creates pores on the film surface by etching to form a functional microstructure, which provides a stronger mechanical anchoring and chemical bonding basis for subsequent chemical modification of the film interface.

[0021] S4. The adhesive on the surface of the etched membrane in S3 is removed using the above-mentioned adhesive removal solution. It should be noted that in traditional processes, adhesives are used to maintain the integrity and good performance of the membrane in order to ensure the tight bonding between reverse osmosis membrane materials and the stability of the structure. This step utilizes the polar permeation effect of propylene glycol methyl ether containing ether bonds and hydroxyl groups in the adhesive removal solution (penetrating the gaps between the polymer chains of the adhesive, breaking hydrogen bonds and van der Waals forces, and having strong dissolving power for its polar functional groups) in conjunction with the non-polar swelling effect of n-butanol (long-chain alkyl groups insert into the hydrophobic region of the adhesive, causing the polymer chains to relax and expand, reducing cohesion, and promoting overall peeling) to achieve accelerated dissolution of the adhesive and thoroughly remove residual adhesive from the membrane surface to ensure effective adhesion of the subsequent interface modification layer.

[0022] S5. The membrane after adhesive removal in S4 is first immersed using the above-mentioned modifier 1. It should be noted that ammonium fluoride is selected as the modifier in membrane preparation in this step. Its advantages are: 1) Formation of a protective layer: Ammonium fluoride may participate in the construction of fluoride conversion membrane on the membrane surface, forming a fluorine-containing protective layer, preventing pollutants or corrosive media from contacting the substrate, and extending the service life of the membrane; 2) Electrostatic control: Fluoride ions (F - 1) High electronegativity can directionally regulate the charge distribution on the membrane surface, enhance the selective sieving of charged ions, and improve the separation performance of the membrane; 2) Structural reinforcement: Fluoride ions may interact with amino or amide groups in the polyamide chain, increasing the degree of crosslinking of the membrane, improving mechanical strength and chemical stability, and enhancing the durability of the membrane; 3) Antifouling: Fluorine has low surface energy and high hydrophobicity, making the membrane surface more hydrophobic, reducing the adsorption of hydrophilic organic pollutants, and improving the membrane's antifouling properties; In this modifier, ammonium fluoride is also used in combination with amines. The purpose is to utilize the surface polymerization process of amines and acyl chlorides in subsequent modifier 2 to uniformly introduce ammonium fluoride into the membrane surface in the form of hydrogen bonds, so as to avoid defects in the modified layer;

[0023] S6. The membrane sheet soaked in the first soaking in S5 is then soaked a second time using the above-mentioned modifier 2. The membrane sheet is then removed, subjected to ultraviolet irradiation and drying treatment to obtain a regenerated nanofiltration flat sheet membrane. It should be noted that in this step, acrylate and 5-isocyanate isopeptidyl chloride are selected as modifier 2, which undergo a polymerization reaction with modifier 1. The amine reacts with the acyl chloride to form an amide polymer to ensure the membrane's separation properties. The polyamide-amine dendritic polymer reacts with the acrylate to form a graft copolymer. By utilizing the synergistic effect of the protonation / deprotonation behavior of the amino groups on the surface of the polyamide-amine dendritic polymer and the dissociation state change of the carboxyl groups of the acrylate, the stimulation responsiveness (including pH responsiveness) of the membrane surface is achieved. Finally, a biocompatible, hydrophilic, and chemically stable crosslinked polymer is obtained, which improves the chemical stability, antifouling properties, and permeate flux of the membrane material, while also enabling it to meet the separation requirements in harsh environments (including strong alkaline systems). The ultraviolet irradiation in this step can enhance the above polymerization reaction, further improving the crosslinking degree, alkali resistance, and antifouling performance of the above chemically modified membrane.

[0024] Furthermore, the chemical cleaning time is 1 to 24 hours.

[0025] Furthermore, the surface etching time is 1~24 h.

[0026] Furthermore, the removal time of the above adhesive is 1~24 h.

[0027] Furthermore, the duration of the first soaking is 1 to 24 hours.

[0028] Furthermore, the second soaking time is 1 to 60 minutes. It should be noted that the present invention does not specify the amount of alkaline cleaning solution, surface etching solution, adhesive removal solution, modifier 1 and modifier 2 used in chemical cleaning, surface etching, adhesive removal and surface chemical modification treatment. In actual operation, it is sufficient to ensure that the amount of the above reagents at least covers the film.

[0029] Furthermore, the above chemical cleaning process also includes soaking in deionized water.

[0030] Furthermore, the above-mentioned surface etching process also includes immersion in deionized water after completion.

[0031] Furthermore, the process of removing the adhesive also includes soaking in deionized water.

[0032] Furthermore, the above-mentioned ultraviolet irradiation uses an ultraviolet lamp with a wavelength of 350~420 nm and irradiates for 1~6 hours.

[0033] Furthermore, the above drying process is carried out in an oven at 80~100℃ for 1~2 hours.

[0034] The present invention also provides a regenerated nanofiltration sheet membrane prepared using the above-described regenerator or the above-described method.

[0035] The present invention also provides the application of the above-mentioned regenerated nanofiltration sheet membrane in water treatment.

[0036] Compared with the prior art, the advantages of this invention are as follows:

[0037] (1) The present invention provides a regenerator and regeneration method for nanofiltration regeneration of waste spiral reverse osmosis membranes. First, the alkaline cleaning solution in the regenerator decomposes organic and biological pollutants on the membrane surface to remove residual pollutants. Then, the surface etching solution is used to etch and construct pores on the membrane surface, providing a stronger mechanical anchoring and chemical bonding basis for subsequent membrane interface polymerization repair (chemical modification). Next, the adhesive removal solution is used to thoroughly remove any residual adhesives on the membrane, ensuring effective adhesion of the subsequent modification layer. Then, ammonium fluoride and amines are used as modifier 1, utilizing the electrostatic regulation, structural strengthening, and antifouling properties of fluoride to give the membrane superior chemical stability, permeate flux, and antifouling performance. Finally, polyamide-amine dendritic polymer and acrylate are used as modifier 2, and the polymerization reaction between modifier 1 and modifier 2 generates a biocompatible, hydrophilic, and chemically stable cross-linked polymer, achieving membrane interface reconstruction. Verification shows that the membrane after regeneration has well restored separation performance, while also possessing good alkali resistance and antifouling performance, comprehensively improving the functional value of the membrane.

[0038] (2) The present invention provides a regenerator and regeneration method for nanofiltration regeneration of waste spiral reverse osmosis membranes. The waste reverse osmosis membrane elements are used as raw materials. The whole regeneration process is economical and green, effectively reducing the preparation cost of alkali-resistant membranes and making up for the defect of poor alkali resistance of traditional polyamide membranes. Attached Figure Description

[0039] Figure 1 These are electron micrographs of the film surface before and after chemical modification in Example 2 of the present invention, where a) before chemical modification; b) after chemical modification.

[0040] Figure 2 This is an electron microscope scan of the cross-section of the chemically modified membrane in Example 2 of the present invention. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments.

[0042] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the term "and / or" as used in this invention includes any and all combinations of one or more of the associated listed items.

[0043] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0044] As used in this invention, the term "about" is used to provide flexibility and imprecision associated with a given term, measure, or value. Those skilled in the art can readily determine the degree of flexibility for a particular variable.

[0045] As used in this invention, the term "at least one of..." is intended to be synonymous with "one or more of...". For example, "at least one of A, B, and C" explicitly includes only A, only B, only C, and combinations thereof.

[0046] Concentration, amount, and other numerical data may be presented in a range format in this invention. It should be understood that such a range format is used only for convenience and brevity and should be flexibly interpreted to include not only the values ​​explicitly stated as the limits of the range, but also all individual values ​​or subranges covered within the range, as if each value and subrange were explicitly stated. For example, a numerical range of about 1 to about 4.5 should be interpreted to include not only the explicitly stated limits of 1 to 4.5, but also individual numbers (such as 2, 3, 4) and subranges (such as 1 to 3, 2 to 4, etc.). The same principle applies to ranges that describe only a single value, such as "less than about 4.5," which should be interpreted to include all the aforementioned values ​​and ranges. Furthermore, this interpretation should apply regardless of the breadth of the range or feature described.

[0047] The reagents used in the embodiments of this invention are as follows:

[0048] Sodium carbonate: ≥99%;

[0049] Sodium silicate: analytical grade (AR);

[0050] Sodium bicarbonate: ≥99%;

[0051] Sodium dodecylbenzenesulfonate: ≥95%;

[0052] Polyepoxysuccinic acid: ≥97%;

[0053] Propylene glycol methyl ether: ≥99%;

[0054] n-Butanol: ≥99%;

[0055] Ammonium fluoride: ≥98%;

[0056] 1,3-Propanediamine: ≥98%;

[0057] 5-Isocyanate isopeptidyl chloride: ≥99%;

[0058] Hexafluorobutyl acrylate: ≥99%;

[0059] Sodium hydroxide: ≥98%;

[0060] Triethylenetetramine: ≥97%;

[0061] Dodecafluoroheptyl acrylate: ≥97%.

[0062] Example 1

[0063] This embodiment provides a regenerator, regeneration method, and regenerated nanofiltration sheet membrane A1 for the nanofiltration regeneration of waste spiral wound reverse osmosis membranes.

[0064] The regenerant comprises the following components:

[0065] The alkaline cleaning solution includes an alkaline cleaning agent and an alkaline cleaning aid. The alkaline cleaning agent is sodium carbonate, with a content of 15 wt%; the alkaline cleaning aid is sodium silicate, with a content of 15 wt%.

[0066] The surface etching solution is a composite solution of sodium dodecylbenzenesulfonate and polyepoxysuccinic acid; the content of both sodium dodecylbenzenesulfonate and polyepoxysuccinic acid is 3wt%.

[0067] The adhesive removal solution is a mixed solution of propylene glycol methyl ether and n-butanol; the volume ratio of propylene glycol methyl ether to n-butanol is 3:1.

[0068] Modifier 1 is a composite solution of ammonium fluoride, polyamide-amine dendritic polymer (PAMAM G4; molecular weight 14000), and organic amine; the content of ammonium fluoride is 10 wt%; the organic amine is 1,3-propanediamine, and the content of both polyamide-amine dendritic polymer and 1,3-propanediamine is 1 wt%.

[0069] Modifier 2 is a hexane solution containing acrylate and 5-isocyanate isopeptidyl chloride; the acrylate is hexafluorobutyl acrylate with a content of 0.17 wt%; the content of 5-isocyanate isopeptidyl chloride is 0.33 wt%.

[0070] The waste roll membrane material used in this embodiment comes from the leachate treatment section of a waste incineration plant.

[0071] The specific regeneration method includes the following steps:

[0072] S1. Peel, cut, and scrub the waste spiral membrane element to obtain a complete membrane sheet;

[0073] S2. The membrane in S1 is chemically cleaned using the alkaline cleaning solution described above.

[0074] S3. Use the above-mentioned surface etching solution to etch the surface of the film cleaned in S2;

[0075] S4. Use the above-mentioned adhesive removal solution to remove the surface adhesive of the etched film in S3;

[0076] S5. The membrane after adhesive removal in S4 is first soaked with the above-mentioned modifier 1.

[0077] S6. The membrane sheet soaked for the first time in S5 is soaked a second time using the above-mentioned modifier 2; then the membrane sheet is taken out and subjected to ultraviolet irradiation and drying treatment to obtain regenerated nanofiltration flat sheet membrane A1.

[0078] In S2, the amount of alkaline cleaning solution used must at least submerge the membrane; the chemical cleaning time is 24 hours; after cleaning, the membrane is soaked in deionized water to remove any residual alkaline cleaning solution.

[0079] In S3, the amount of surface etching solution used must at least submerge the film; the surface etching time is 24 hours; after completion, the film is soaked in deionized water to remove any residual surface etching solution.

[0080] The amount of adhesive removal solution used in S4 should at least submerge the membrane; the treatment time is 24 hours; after completion, the membrane should be soaked in deionized water to remove any residual adhesive removal solution.

[0081] In S5, the amount of modifier 1 should at least submerge the membrane, and the first soaking time should be 4 hours.

[0082] In S6, the amount of modifier 2 should at least submerge the film, and the second immersion time should be 1 min; ultraviolet irradiation should be carried out using an ultraviolet lamp (GHX) with a wavelength of 365 nm and a power of 15 W for 6 h; drying treatment should be carried out in an oven at 80℃ for 1 h.

[0083] Example 2

[0084] This embodiment provides a regenerator, regeneration method, and regeneration of nanofiltration sheet membrane A2 for the nanofiltration regeneration of waste spiral wound reverse osmosis membrane.

[0085] The regenerant comprises the following components:

[0086] The alkaline cleaning solution, unlike Example 1, only includes an alkaline cleaning agent; it is sodium hydroxide, with a content of 10 wt%.

[0087] The surface etching solution differs from Example 1 in that the content of sodium dodecylbenzenesulfonate is increased from 3 wt% to 5 wt%, while the content of polyepoxysuccinic acid remains unchanged.

[0088] The adhesive removal liquid differs from Example 1 in that the volume ratio of propylene glycol methyl ether to n-butanol is adjusted from 3:1 to 2:1.

[0089] Modifier 1 differs from Example 1 in that the organic amine is changed from 1,3-propanediamine to triethylenetetramine, and the content of both the polyamide-amine dendritic polymer and triethylenetetramine is 4 wt%.

[0090] Modifier 2 differs from Example 1 in that the content of hexafluorobutyl acrylate is adjusted from 0.17wt% to 1.33wt%, and the content of 5-isocyanate isopeptidyl chloride is adjusted from 0.33wt% to 2.67wt%.

[0091] The waste roll membrane material used in this embodiment is from the same source as in Embodiment 1;

[0092] The specific regeneration method follows the same steps as in Example 1, except that the reagents used in each step are adjusted accordingly as described above; the processing time for each step is also changed, including:

[0093] The duration of chemical cleaning, surface etching, and adhesive removal has been reduced from 24 hours to 1 hour.

[0094] The first soaking time has been adjusted from 4 hours to 8 hours;

[0095] The second soaking time was adjusted from 1 min to 10 min; the ultraviolet lamp irradiation time was adjusted from 6 h to 2 h; other treatments were the same as in Example 1.

[0096] The structure of the prepared membrane material was further observed using scanning electron microscopy, and the results are as follows: Figures 1-2 As shown, where Figure 1 The images show the membrane surface structure before (a) and after (b) chemical modification with the modifier. It can be seen that after chemical modification, the membrane surface exhibits typical peak and trough morphology, which confirms that the chemical polymerization reaction was successfully achieved on the membrane material surface. The modified membrane surface structure is continuous, and no macropores or defects visible to the naked eye were observed, which further confirms that a complete and dense polyamide crosslinked network structure was formed in the active separation layer. Figure 2 The cross-sectional structure of the membrane after chemical modification with the modifier shows that the bottom support membrane exhibits typical asymmetric structural features. This gradually loosening structural change can effectively disperse pressure and prevent membrane structure rupture during high-pressure operation. After chemical modification, a dense and smooth active separation layer (active functional layer) has been successfully formed on the top of the support membrane.

[0097] Example 3

[0098] This embodiment provides a regenerator, regeneration method, and regeneration of nanofiltration sheet membrane A3 for the nanofiltration regeneration of waste spiral wound reverse osmosis membrane.

[0099] The regenerant comprises the following components:

[0100] The alkaline cleaning solution, unlike Example 1, consists only of an alkaline cleaning agent; it is sodium carbonate, with a content of 20 wt%.

[0101] The surface etching solution differs from Example 1 in that the content of polyepoxysuccinic acid is increased from 3 wt% to 5 wt%, while the content of sodium dodecylbenzenesulfonate remains unchanged.

[0102] Adhesive removal solution, same as in Example 1;

[0103] Modifier 1, differing from Example 1, has the following changes: the content of ammonium fluoride is adjusted from 10 wt% to 6 wt%; the content of polyamide-amine dendritic polymer is adjusted from 1 wt% to 3.33 wt%; and the content of 1,3-propanediamine is adjusted from 1 wt% to 1.67 wt%.

[0104] Modifier 2, which differs from Example 1, is dodecafluoroheptyl acrylate with a content of 0.07wt%, and the content of 5-isocyanate isopeptidyl chloride is adjusted from 0.33wt% to 0.13wt%.

[0105] The waste roll membrane material used in this embodiment is from the same source as in Embodiment 1;

[0106] The specific regeneration method follows the same steps as in Example 1, except that the reagents used in each step are adjusted accordingly as described above; the processing time for each step is also changed, including:

[0107] The duration of chemical cleaning, surface etching, and adhesive removal has been reduced from 24 hours to 5 hours.

[0108] The first soaking time was adjusted from 4 hours to 1 hour;

[0109] The second soaking time was adjusted from 1 min to 20 min; the ultraviolet lamp irradiation time was adjusted from 6 h to 1.5 h; other treatments were the same as in Example 1.

[0110] Example 4

[0111] This embodiment provides a regenerator, regeneration method, and regenerated nanofiltration sheet membrane A4 for the nanofiltration regeneration of waste spiral wound reverse osmosis membranes.

[0112] The regenerant comprises the following components:

[0113] The alkaline cleaning solution, unlike Example 1, only includes an alkaline cleaning agent; it is sodium bicarbonate, with a content of 15 wt%.

[0114] The surface etching solution differs from Example 1 in that the content of sodium dodecylbenzenesulfonate is increased from 3 wt% to 5 wt%, while the content of polyepoxysuccinic acid remains unchanged.

[0115] Adhesive removal solution, same as in Example 1;

[0116] Modifier 1, differing from Example 1, has its ammonium fluoride content adjusted from 10 wt% to 8 wt%; its organic amine changed from 1,3-propanediamine to triethylenetetramine; and both the polyamide-amine dendritic polymer and triethylenetetramine content are 4 wt%.

[0117] Modifier 2, which differs from Example 1, is acrylate dodecyl fluoroheptyl acrylate with a content of 0.67 wt%, and 5-isocyanate isopeptidyl chloride is adjusted from 0.33 wt% to 1.33 wt%.

[0118] The waste roll membrane material used in this embodiment is from the same source as in Embodiment 1;

[0119] The specific regeneration method follows the same steps as in Example 1, except that the reagents used in each step are adjusted accordingly as described above; the processing time for each step is also changed, including:

[0120] The duration of chemical cleaning, surface etching, and adhesive removal has been reduced from 24 hours to 10 hours.

[0121] The initial soaking time was adjusted from 4 hours to 24 hours.

[0122] The second soaking time was adjusted from 1 min to 30 min; the ultraviolet lamp irradiation time was adjusted from 6 h to 1 h; other treatments were the same as in Example 1.

[0123] Example 5

[0124] This embodiment provides a regenerator, regeneration method, and regenerated nanofiltration sheet membrane A5 for the nanofiltration regeneration of waste spiral wound reverse osmosis membranes.

[0125] The regenerant comprises the following components:

[0126] The alkaline cleaning solution includes an alkaline cleaning agent and an alkaline cleaning aid. The alkaline cleaning agent is sodium hydroxide, with a content of 5 wt%; the alkaline cleaning aid is sodium silicate, with a content of 5 wt%.

[0127] The surface etching solution differs from Example 1 in that the content of sodium dodecylbenzenesulfonate is increased from 3 wt% to 5 wt%, while the content of polyepoxysuccinic acid remains unchanged.

[0128] Adhesive removal solution, same as in Example 1;

[0129] Modifier 1, unlike Example 1, has its content of both the polyamide-amine dendritic polymer and 1,3-propanediamine adjusted from 1 wt% to 4 wt%.

[0130] Modifier 2 differs from Example 1 in that the content of hexafluorobutyl acrylate is adjusted from 0.17wt% to 0.33wt%, and the content of 5-isocyanate isopeptidyl chloride is adjusted from 0.33wt% to 0.67wt%.

[0131] The waste roll membrane material used in this embodiment is from the same source as in Embodiment 1;

[0132] The specific regeneration method follows the same steps as in Example 1, except that the reagents used in each step are adjusted accordingly as described above; the processing time for each step is also changed, including:

[0133] The duration of chemical cleaning, surface etching, and adhesive removal has been reduced from 24 hours to 1 hour.

[0134] The first soaking time was adjusted from 4 hours to 12 hours;

[0135] The second soaking time was adjusted from 1 minute to 12 minutes; all other treatments were the same as in Example 1.

[0136] Example 6

[0137] This embodiment provides performance tests of the regenerated nanofiltration flat sheet membranes A1-A5 in Embodiments 1-5.

[0138] This embodiment simultaneously tested the relevant performance of the waste spiral wound reverse osmosis membranes from the above embodiments, denoted as group A0. The specific testing process is as follows:

[0139] 1) Osmosis flux in alkaline environments

[0140] First, the membrane sample to be tested was pre-pressurized with deionized water at 4 bar for at least 30 minutes until the permeate flux stabilized. Then, at room temperature, the transmembrane pressure was adjusted and controlled at 10 bar, and the membrane permeate flux was tested using a 10% sodium hydroxide solution. The specific calculation formula is as follows:

[0141] ,

[0142] Where J is the membrane permeation flux (L / m 2 V is the volume of filtrate (L), and A is the effective area of ​​the membrane (m²). 2 T is the filtration time (h), and P is the filtration pressure (bar).

[0143] 2) Retention rate in alkaline environments

[0144] As mentioned above, the membrane sample was first pre-pressurized with deionized water at 4 bar for at least 30 minutes until the flux stabilized. Then, a 1000 ppm sodium sulfate solution was prepared, and the pH of the solution was adjusted to 12 using sodium hydroxide solution. At room temperature, the transmembrane pressure was adjusted and controlled at 10 bar, and the membrane's rejection rate for sodium sulfate was tested. The specific calculation formula is as follows:

[0145] ,

[0146] Where R is the retention rate (%), C p C is the permeate concentration (ppm). f The feed concentration is expressed in ppm.

[0147] The results are shown in Table 1:

[0148] Table 1

[0149]

[0150] It can be seen that the A0 fouling of the waste spiral wound membrane before regeneration was severe, with a permeation flux of only 20 L / m. 2 At 0.64 h·bar, membrane performance deteriorated severely, with a rejection rate of only 70%. After repair and regeneration treatments such as chemical cleaning and chemical modification, membrane performance was significantly improved, with the permeate flux reaching a maximum of 52 L / m³ in alkaline environments. 2 •h·bar; The rejection rate of sodium sulfate in an alkaline environment can reach up to 96%. This indicates that the regeneration method effectively restores the membrane's separation performance and also provides a certain degree of alkali resistance, enabling it to maintain good separation performance even under alkaline conditions.

[0151] Example 7

[0152] This embodiment provides an alkali resistance stability test for regenerated nanofiltration flat sheet membranes.

[0153] In this embodiment, the regenerated nanofiltration flat sheet membrane A2 from Example 2 was selected as a representative, and its alkali resistance stability was tested. Specifically, the testing process for permeate flux and rejection rate in an alkaline environment was the same as in Example 6, except that the test duration was extended to 36 hours to observe the stability of membrane separation performance under long-term alkaline conditions.

[0154] Results analysis: After 36 hours of continuous testing, the permeation flux of membrane A2 remained stable at 43 L / m. 2 The fluctuation range is strictly controlled within ±0.5 L / m at approximately h·bar. 2 Within h·bar, this excellent stability exhibited in an alkaline environment fully demonstrates the chemical stability of the regenerated membrane material structure. Throughout the entire testing period, the A2 rejection rate of the membrane remained consistently high at 95.8% to 96.3%, with a fluctuation range of 0.5%, confirming its good stability in separation performance under alkaline conditions.

[0155] Example 8

[0156] This embodiment provides an antifouling performance test for regenerated nanofiltration flat sheet membranes.

[0157] Similar to Example 7, using the regenerated nanofiltration sheet membrane A2 from Example 2 as a representative, bovine serum albumin was used as an organic pollutant model to test the antifouling performance of the membrane material. Specifically, the membrane was first filtered for 90 min at 4 bar pressure using a 0.1 g / L bovine serum albumin solution, followed by rinsing with deionized water for 30 min. This process was repeated for two cycles, and the membrane permeate flux was tested (using the same method as the permeate flux determination in Example 6).

[0158] Results analysis: The permeation flux of membrane A2 was measured to be stable at 34 L / m². 2 Approximately h·bar, compared to the initial permeation flux of 43 L / m² for membrane A2 measured in Example 2. 2 The permeate flux recovery rate is around 79%, which confirms that the membrane material can achieve the removal of pollutants on the membrane surface and membrane regeneration by simple deionized water washing during the circulating filtration process, indicating that it has good antifouling performance.

Claims

1. A regenerant for nanofiltration regeneration of spent spiral wound reverse osmosis membranes, characterized in that, The regenerant includes modifier 1 and modifier 2, wherein: Modifier 1 comprises a composite solution of ammonium fluoride, a polyamide-amine dendritic polymer, and an organic amine, wherein the content of ammonium fluoride is 1-20 wt%; the content of the polyamide-amine dendritic polymer is 0.25-7.5 wt%; and the content of the organic amine is 0.25-7.5 wt%. Modifier 2 comprises a hexane solution containing acrylate and 5-isocyanate isopeptidyl chloride, wherein the content of acrylate is 0.05~3wt%; and the content of 5-isocyanate isopeptidyl chloride is 0.1~3wt%. The regenerator also includes an alkaline cleaning solution, a surface etching solution, and an adhesive removal solution, wherein: An alkaline cleaning solution includes an alkaline cleaning agent and / or an alkaline cleaning aid, wherein the alkaline cleaning agent includes any one of sodium bicarbonate, sodium carbonate, and sodium hydroxide, with a content of 1.25~37.5 wt%; and the alkaline cleaning aid includes any one of sodium silicate, sodium metasilicate, and sodium tripolyphosphate, with a content of 1.25~37.5 wt%. The surface etching solution comprises a composite solution of sodium dodecylbenzenesulfonate and polyepoxysuccinic acid, wherein the content of sodium dodecylbenzenesulfonate is 1-6 wt%; and the content of polyepoxysuccinic acid is 1-6 wt%. Adhesive removal solution, comprising a mixed solution of propylene glycol methyl ether and n-butanol, wherein the volume ratio of propylene glycol methyl ether to n-butanol is 3:1 to 1:

3.

2. The regenerant according to claim 1, characterized in that, The organic amines include 1,3-propanediamine and / or triethylenetetramine.

3. The regenerant according to claim 1 or 2, characterized in that, The acrylates include hexafluorobutyl acrylate and / or dodecafluoroheptyl acrylate.

4. The regenerant according to claim 3, characterized in that, The polyamide-amine dendritic polymer has a molecular weight of 10,000 to 15,000.

5. A method for nanofiltration regeneration of spent spiral wound reverse osmosis membranes, characterized in that, The method includes regeneration using the regenerant according to claim 4, comprising the following steps: S1. Peel, cut, and scrub the waste spiral membrane element to obtain a complete membrane sheet; S2. The membrane in S1 is chemically cleaned using the alkaline cleaning solution. S3. Use the surface etching solution to etch the surface of the film cleaned in S2; S4. Use the adhesive removal solution to remove the surface adhesive of the etched film in S3; S5. The membrane after adhesive removal in S4 is first soaked with the modifier 1. S6. The membrane sheet soaked for the first time in S5 is soaked a second time using the modifier 2; then the membrane sheet is taken out and subjected to ultraviolet irradiation and drying treatment to obtain a regenerated nanofiltration flat sheet membrane.

6. The method according to claim 5, characterized in that, The chemical cleaning duration is 1-24 hours; and / or The surface etching time is 1~24 h; and / or The adhesive removal time is 1-24 h; and / or The first soaking time is 1-24 hours; and / or The second soaking time is 1 to 60 minutes.

7. The method according to claim 6, characterized in that, The ultraviolet irradiation is performed using an ultraviolet lamp with a wavelength of 350~420 nm for 1~6 hours; and / or The drying process involves drying in an oven at 80-100℃ for 1-2 hours.

8. A regenerated nanofiltration sheet membrane prepared by the method according to any one of claims 5-7.

9. The application of the regenerated nanofiltration sheet membrane according to claim 8 in water treatment.

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