Method for regenerating waste roll type reverse osmosis membrane into acid-resistant reverse osmosis membrane, acid-resistant reverse osmosis membrane and application of acid-resistant reverse osmosis membrane

Abstract

The invention provides a method for regenerating a waste spiral-wound reverse osmosis membrane into an acid-resistant reverse osmosis membrane, the acid-resistant reverse osmosis membrane and application of the acid-resistant reverse osmosis membrane, and relates to the technical field of membrane materials. The method comprises the following steps: sequentially soaking the waste roll-type reverse osmosis membrane element with a mixed solution and a trimesoyl chloride solution; the mixed solution is composed of sodium fluoride, organic amine and deionized water, and the trimesoyl chloride solution is composed of trimesoyl chloride and normal hexane; sequentially carrying out post-curing treatment and drying treatment on the soaked reverse osmosis membrane element; and performing crosslinking treatment on the dried reverse osmosis membrane element to obtain the acid-resistant reverse osmosis membrane. According to the invention, the waste roll-type reverse osmosis membrane is used as a base material, sodium fluoride is used as a modifier, hydrogen bonds in sodium fluoride are mixed with organic amine, then the mixture and trimesoyl chloride are subjected to interfacial polymerization reaction, and the surface of the existing waste roll-type reverse osmosis membrane is modified; the acid resistance, the pollution resistance, the permeation flux and the separation performance of the reverse osmosis membrane are effectively improved.

Description

Technical Field

[0001] This application relates to the field of membrane material technology, specifically to a method for regenerating waste spiral wound reverse osmosis membranes into acid-resistant reverse osmosis membranes, the acid-resistant reverse osmosis membranes and their applications. Background Technology

[0002] In recent years, membrane technology has played a wide role in the field of water treatment. Among them, membrane separation technology is a simple, fast, efficient, selective, economical and energy-saving new technology, and is currently widely used in many fields such as water treatment, hydrometallurgy, biochemical industry, pharmaceutical industry, food industry and environmental protection.

[0003] Reverse osmosis membrane technology, as a type of membrane separation technology, utilizes a semi-permeable membrane (reverse osmosis membrane). Driven by external pressure higher than the osmotic pressure of the solution, solvent molecules (water) in the solution (usually water) are forced to permeate through the membrane, while solute molecules (such as salts, ions, organic matter, etc.) and suspended solids are almost completely retained, thus achieving a highly efficient separation of solvent and solute. This technology has been widely used in seawater and brackish water desalination, wastewater treatment and resource utilization, bioproduct separation, environmental engineering, food, and pharmaceutical fields, and has achieved significant economic and social benefits.

[0004] Reverse osmosis membrane technology, with its high efficiency and energy saving, has significant advantages in treating high-concentration brine. However, its application in treating acidic wastewater remains limited, primarily due to the need for reverse osmosis membranes to possess excellent acid resistance and fouling resistance. Existing commercial polyamide reverse osmosis membranes are prone to amide bond hydrolysis in fluorosilicic acid solutions with a pH < 2, leading to a desalination rate decrease of over 40%. Traditional membranes are also susceptible to acid degradation. - With a retention rate of only 70%-85%, it cannot meet the needs of industrial-grade fluorine recovery (for F... - (The rejection rate needs to be greater than 99%). The molecular size of fluorosilicic acid (about 0.6 nm) is close to that of the membrane pore size. Existing membranes lack specific recognition sites. Fluorosilicic acid can destroy reverse osmosis membranes through a triple action of chemical erosion by fluoride ions, corrosion by decomposition products, and physical damage by silica scale.

[0005] Currently, there are few reports on mature acid-resistant reverse osmosis membranes on the market, and there are no commercially available fluorosilicic acid-resistant reverse osmosis membranes in China; most are still in the laboratory stage. Furthermore, current acid-resistant reverse osmosis membranes also face problems such as easy material corrosion, low flux, and susceptibility to fouling. Therefore, there is an urgent need to develop a reverse osmosis membrane with high flux, excellent acid resistance, and antifouling properties to meet the needs of resource-based treatment of industrial wastewater containing fluorine-containing superacids. Traditional spiral wound membranes are mostly disposed of through landfill after decommissioning, but their polyamide functional layer still retains more than 60% of its active sites. Existing patent CN202321243736.2 attempts to directly cut and modify the membrane, but this cannot solve the problems of low membrane performance and irreversible interface fouling. Summary of the Invention

[0006] To solve the above-mentioned technical problems, or at least partially solve them, this application provides a method for regenerating waste spiral wound reverse osmosis membranes into acid-resistant reverse osmosis membranes through physical dismantling and chemical modification, the acid-resistant reverse osmosis membranes and their applications. This method achieves precise upgrading of the membrane structure through in-situ polymerization technology.

[0007] The first aspect of this application provides a method for regenerating a spent spiral wound reverse osmosis membrane into an acid-resistant reverse osmosis membrane, comprising the following steps: Waste spiral wound reverse osmosis membrane elements are sequentially soaked in a mixed solution and a trimesoyl chloride solution; the mixed solution consists of sodium fluoride, organic amine and deionized water, and the trimesoyl chloride solution consists of trimesoyl chloride and n-hexane; After soaking, the reverse osmosis membrane elements are subjected to post-curing and drying treatments in sequence. Acid-resistant reverse osmosis membranes are obtained by crosslinking dried reverse osmosis membrane elements with glutaraldehyde vapor.

[0008] Preferably, the mass ratio of sodium fluoride to organic amine is 1:5 to 1:1.

[0009] Preferably, the concentration of sodium fluoride in the mixed solution is 1-10 wt%.

[0010] Preferably, the concentration of organic amines in the mixed solution is 0.1-10 wt%.

[0011] Preferably, the organic amine is one or more of ethylenediamine, m-phenylenediamine, triethylenetetramine, and p-toluenesulfonamide.

[0012] Preferably, the method for preparing the mixed solution specifically includes: mixing sodium fluoride and organic amine, adding the mixed material to deionized water and stirring until uniform, thereby obtaining the mixed solution; The preparation method of the trimesoyl chloride solution specifically includes: adding trimesoyl chloride to n-hexane and stirring to dissolve it, thereby obtaining a trimesoyl chloride solution; the concentration of trimesoyl chloride in n-hexane is 0.2-5 wt%.

[0013] Preferably, the glutaraldehyde vapor concentration is 0.1-1 wt%, and the crosslinking time is 1-3 h.

[0014] Preferably, the soaking time of the waste spiral reverse osmosis membrane element in the mixed solution is 1-24 hours, and the soaking time of the soaked reverse osmosis membrane element in the trimesoyl chloride solution is 1-30 minutes; the drying treatment temperature is 80°C and the time is 1 hour.

[0015] According to a second aspect of this application, an acid-resistant reverse osmosis membrane is provided, which is prepared by regenerating a waste spiral wound reverse osmosis membrane into an acid-resistant reverse osmosis membrane as described in any of the preceding claims.

[0016] According to a third aspect of this application, the application of the acid-resistant reverse osmosis membrane as described above in the treatment of fluoride-containing superacid industrial wastewater is provided.

[0017] The beneficial effects of this application are as follows: This application provides a method for regenerating spent spiral-wound reverse osmosis membranes into acid-resistant reverse osmosis membranes. The method uses spent spiral-wound reverse osmosis membrane elements as the substrate and sodium fluoride as a modifier. The sodium fluoride is mixed with an organic amine via hydrogen bonds and then subjected to interfacial polymerization with trimesoyl chloride to modify the surface of the existing spent spiral-wound reverse osmosis membrane. This process produces an acid-resistant, anti-fouling, and high-performance interfacial polymer layer, giving the reverse osmosis membrane surface high acid resistance. Particularly in fluorosilicic acid systems, the acid-resistant reverse osmosis membrane prepared in this application exhibits stable separation performance. Furthermore, this acid-resistant reverse osmosis membrane also possesses high anti-fouling properties, high permeate flux, and high separation performance. Fluoride ions, through the synergistic effects of electrostatic regulation, structural enhancement, and catalytic film formation, achieve a dual improvement in membrane separation performance and durability, making them particularly suitable for separation requirements in harsh environments (such as fluorine-containing superacid systems). In the process of introducing sodium fluoride into spent spiral-wound reverse osmosis membrane elements, interfacial polymerization of amines and trimesoyl chloride is utilized. Sodium fluoride is uniformly introduced onto the surface of the spent spiral-wound reverse osmosis membrane elements via hydrogen bonds, while the polymer formed by the amines and trimesoyl chloride further increases the membrane's stability. Furthermore, glutaraldehyde vapor is used for the first time to modify acid-resistant reverse osmosis membranes. It reacts with excess amine groups on the membrane surface after interfacial polymerization to generate cross-linked polymers based on imine bonds (Schiff base structure), further enhancing the acid resistance, stability, and antifouling properties of the reverse osmosis membrane.

[0018] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of what is pointed out in the written description, claims, and drawings. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1SEM images of the reverse osmosis membrane before and after sodium fluoride modification provided in Example 5 of this application, wherein a is the SEM image of the reverse osmosis membrane before sodium fluoride modification, and b is the SEM image of the reverse osmosis membrane after sodium fluoride modification. Figure 2 This is a cross-sectional view of the sodium fluoride-modified reverse osmosis membrane provided in Example 5 of this application. Detailed Implementation

[0020] In the process of developing this application, the applicant discovered that there are currently no commercially available fluorosilicic acid resistant reverse osmosis membranes in China, and most are still in the laboratory stage. Moreover, current acid-resistant reverse osmosis membranes face problems such as easy material corrosion, low flux, and easy contamination.

[0021] To address the aforementioned problems, this application provides a method for regenerating spent spiral-wound reverse osmosis membranes into acid-resistant reverse osmosis membranes, the acid-resistant reverse osmosis membrane itself, and its applications. To make the objectives, technical solutions, and advantages of this application clearer, the following embodiments, in conjunction with the appendix, are provided. Figure 1 and 2 The embodiments of this application will be further described in detail below. It should be understood that the specific embodiments described herein are only for explaining this application and are not intended to limit this application.

[0022] Unless otherwise specified, the reagents and materials used in the examples are commercially available; the test methods used in the following examples are conventional methods in the art.

[0023] The amount of raw materials added and the reaction conditions in Examples 1 to 5 are shown in Table 1 below.

[0024] The method for regenerating waste spiral wound reverse osmosis membranes into acid-resistant reverse osmosis membranes in Embodiments 1 to 5 of this application includes the following steps: S10. The spent spiral wound reverse osmosis membrane elements are sequentially soaked in a mixed solution and a trimesoyl chloride solution, specifically including: S101. Prepare a mixed solution, specifically by mixing sodium fluoride and an organic amine in a mass ratio of 1:5 to 1:1, adding the mixture to deionized water and stirring until homogeneous to obtain a mixed solution; wherein the concentration of sodium fluoride in the mixed solution is 1-10 wt%, the concentration of the organic amine in the mixed solution is 0.1-10 wt%, and the organic amine is one or more of ethylenediamine, m-phenylenediamine, triethylenetetramine, and p-toluenesulfonamide; S102. Prepare a trimesoyl chloride solution, specifically by adding trimesoyl chloride to n-hexane and stirring to dissolve it, thereby obtaining a trimesoyl chloride solution; wherein the concentration of trimesoyl chloride in n-hexane is 0.2-5 wt%. S103. Immerse the waste spiral reverse osmosis membrane element in the mixed solution for the first soaking; wherein the first soaking time is 1-24 hours; in specific implementation, the waste spiral reverse osmosis membrane element is a waste 3013 type spiral reverse osmosis membrane (Zezhixing-400G) from a household water purifier, effectively realizing the resource utilization of waste reverse osmosis membrane. S104. Immerse the reverse osmosis membrane element after the first soaking in a pyromellitic methyl chloride solution for a second soaking; wherein the second soaking time is 1-30 min. S20. After the second soaking, the reverse osmosis membrane element (i.e., the soaked reverse osmosis membrane element) is post-cured at 60°C for 7 minutes, and the post-cured reverse osmosis membrane is dried at 80°C for 1 hour. S30. The dried reverse osmosis membrane is cross-linked with 0.1-1wt% glutaraldehyde vapor for 1-3 hours to obtain an acid-resistant reverse osmosis membrane.

[0025] This application provides a method for regenerating spent spiral-wound reverse osmosis membranes into acid-resistant reverse osmosis membranes. The method uses spent spiral-wound reverse osmosis membrane elements as the substrate and sodium fluoride as a modifier. The sodium fluoride is mixed with an organic amine via hydrogen bonds and then subjected to interfacial polymerization with trimesoyl chloride to modify the surface of the existing spent spiral-wound reverse osmosis membrane. This process produces an acid-resistant, anti-fouling, and high-performance interfacial polymer layer, giving the reverse osmosis membrane surface high acid resistance. Particularly in fluorosilicic acid systems, the acid-resistant reverse osmosis membrane prepared in this application exhibits stable separation performance. Furthermore, this acid-resistant reverse osmosis membrane also possesses high anti-fouling properties, high permeate flux, and high separation performance. Fluoride ions, through the synergistic effects of electrostatic regulation, structural enhancement, and catalytic film formation, achieve a dual improvement in membrane separation performance and durability, making them particularly suitable for separation requirements in harsh environments (such as fluorine-containing superacid systems). In the process of introducing sodium fluoride into spent spiral-wound reverse osmosis membrane elements, interfacial polymerization of amines and trimesoyl chloride is utilized. Sodium fluoride is uniformly introduced onto the surface of the spent spiral-wound reverse osmosis membrane elements via hydrogen bonds. Simultaneously, the polymer formed by the amines and trimesoyl chloride further increases the membrane's stability and acid resistance. Furthermore, glutaraldehyde vapor is used for the first time to modify acid-resistant reverse osmosis membranes. It reacts with excess amine groups on the membrane surface after interfacial polymerization to generate cross-linked polymers based on imine bonds (Schiff base structure), further enhancing the reverse osmosis membrane's acid resistance, stability, and antifouling properties.

[0026] Sodium fluoride, as a modifier in membrane preparation, mainly improves membrane performance through the following mechanisms: 1. Enhancing the chemical stability of the membrane: Modifying the membrane surface with sodium fluoride can form a fluoride protective layer, effectively resisting the erosion of strong acids, strong alkalis, or corrosive substances. For example, in reverse osmosis membrane applications, this protective layer can significantly reduce the hydrolytic damage of polyamide membranes by fluorosilicic acid, maintaining the integrity of the membrane structure; 2. Optimizing surface charge and separation selectivity: Sodium fluoride ionization generates F... - Adsorbed onto the membrane surface, it increases the negative charge density of the membrane surface, thus enhancing the adhesion to anionic pollutants (such as [SiF6] in fluorosilicic acid). 2- Sodium fluoride exhibits several advantages: First, it enhances the electrostatic repulsion effect, improving the rejection rate. It can fill membrane pores or form an ultra-thin coating, refining the effective pore size and enhancing the screening ability for small molecule pollutants. Second, it improves corrosion resistance and wear resistance. On the surface of metal-based membranes (such as aluminum alloys), sodium fluoride participates in the construction of fluoride conversion membranes (such as iron fluoride), blocking corrosive media from contacting the substrate conversion membrane through a physical barrier effect, while simultaneously increasing surface hardness and reducing membrane wear caused by fluid shear. Third, it assists in film formation and functional modification. When used in combination with amines, it ensures that sodium fluoride is uniformly dispersed on the membrane surface during interfacial polymerization, avoiding defects in the modified layer.

[0027]

[0028] To demonstrate the beneficial effects of the acid-resistant reverse osmosis membrane prepared using the method of this application, relevant tests were conducted on the acid-resistant reverse osmosis membranes prepared in Examples 1 to 5.

[0029] This application characterized the reverse osmosis membranes before and after sodium fluoride modification in Example 5 using scanning electron microscopy (SEM), such as... Figure 1 and Figure 2 As shown in the figure, the surface of the reverse osmosis membrane before sodium fluoride modification is a typical polyamide composite membrane material structure. After modification, the surface of the reverse osmosis membrane becomes rough, with granular and starfish-like structures appearing. This indicates that the modification of the reverse osmosis membrane has an effect on the surface of the reverse osmosis membrane, thereby causing changes in the separation performance and acid resistance of the reverse osmosis membrane.

[0030] This application also tested the fluorosilicic acid permeate flux, acid resistance, and antifouling properties of the acid-resistant reverse osmosis membranes prepared in Examples 1 to 5. Specifically, the water flux of the acid-resistant reverse osmosis membranes prepared in Examples 1 to 5 was tested; the acid-resistant reverse osmosis membranes prepared in Examples 1 to 5 were placed in a sodium sulfate solution with a pH of 0.8 (the pH of the sodium sulfate solution was adjusted with fluorosilicic acid), and the retention performance of each acid-resistant reverse osmosis membrane was tested; the acid-resistant reverse osmosis membranes prepared in Examples 1 to 5 were fouled using a bovine serum albumin solution with a mass concentration of 1 g / L (i.e., each acid-resistant reverse osmosis membrane was immersed in the bovine serum albumin solution for 48 h), and the water flux of each fouled acid-resistant reverse osmosis membrane was tested. The results are shown in Table 2.

[0031]

[0032] As shown in Table 2, the acid-resistant reverse osmosis membrane prepared in this application exhibits good rejection rate after immersion treatment in sodium sulfate solution (pH=0.8) treated with fluorosilicic acid, indicating that the acid-resistant reverse osmosis membrane prepared in this application has good acid resistance and is suitable for the treatment and resource recovery of industrial wastewater containing fluorine and superacids. The acid-resistant reverse osmosis membrane prepared in this application also exhibits good flux before and after the use of bovine serum albumin, proving that the acid-resistant reverse osmosis membrane prepared in this application has good antifouling properties.

[0033] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0034] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for regenerating a waste and old spiral reverse osmosis membrane into an acid-resistant reverse osmosis membrane, characterized in that, The method comprises the following steps: The waste spiral reverse osmosis membrane element is sequentially soaked by a mixed solution and a trimesoyl chloride solution; the mixed solution is composed of sodium fluoride, organic amine and deionized water, and the trimesoyl chloride solution is composed of trimesoyl chloride and n-hexane; The reverse osmosis membrane element after soaking is sequentially subjected to post-curing treatment and drying treatment; The reverse osmosis membrane element after drying is subjected to cross-linking treatment by glutaraldehyde vapor to obtain an acid-resistant reverse osmosis membrane.

2. The method for regenerating waste spiral wound reverse osmosis membranes into acid-resistant reverse osmosis membranes according to claim 1, characterized in that, The mass ratio of sodium fluoride to organic amine is 1:5-1:

1.

3. The method for regenerating waste spiral wound reverse osmosis membranes into acid-resistant reverse osmosis membranes according to claim 1, characterized in that, The concentration of sodium fluoride in the mixed solution is 1-10 wt%.

4. The method of claim 1, wherein the acid-resistant reverse osmosis membrane is regenerated from the waste and old roll-type reverse osmosis membrane. The concentration of organic amine in the mixed solution is 0.1-10 wt%.

5. The method of claim 1, wherein the acid-resistant reverse osmosis membrane is regenerated from the waste and old roll-type reverse osmosis membrane. The organic amine is one or more of ethylenediamine, m-phenylenediamine, triethylenetetramine and p-toluenesulfonamide.

6. The method of claim 1, wherein the acid-resistant reverse osmosis membrane is regenerated from the waste and old roll-type reverse osmosis membrane. The preparation method of the mixed solution specifically comprises: Sodium fluoride and organic amine are mixed, and the mixed material is added to deionized water for stirring, and the mixed solution is obtained after uniform stirring. The preparation method of the trimesoyl chloride solution specifically comprises: Trimesoyl chloride is added to n-hexane for stirring and dissolving to obtain a trimesoyl chloride solution; the concentration of trimesoyl chloride in n-hexane is 0.2-5 wt%.

7. The method of claim 1, wherein the acid-resistant reverse osmosis membrane is regenerated from the waste and old roll-type reverse osmosis membrane. The concentration of glutaraldehyde vapor is 0.1-1 wt%, and the cross-linking time is 1-3 h.

8. The method of claim 1, wherein the acid-resistant reverse osmosis membrane is regenerated from the waste and old roll-type reverse osmosis membrane. The soaking time of the waste spiral reverse osmosis membrane element by the mixed solution is 1-24 h, and the soaking time of the reverse osmosis membrane element after soaking by the trimesoyl chloride solution is 1-30 min. The drying temperature is 80℃, and the drying time is 1 h.

9. An acid-resistant reverse osmosis membrane, characterized by, The acid-resistant reverse osmosis membrane is prepared by the method for regenerating a waste spiral reverse osmosis membrane into an acid-resistant reverse osmosis membrane according to any one of claims 1-8.

10. The acid-resistant reverse osmosis membrane according to claim 9 is applied to treatment of fluorine-containing superacid industrial wastewater.

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