Anti-pollution reverse osmosis membrane with adhesion resistance and antibacterial property and preparation method of anti-pollution reverse osmosis membrane

Abstract

The invention relates to an anti-pollution reverse osmosis membrane with adhesion resistance and antibacterial property and a preparation method thereof.The anti-pollution reverse osmosis membrane comprises a non-woven fabric supporting layer, a polysulfone-based membrane layer, a polyamide desalination layer and an anti-adhesion antibacterial coating which are sequentially arranged, the anti-adhesion antibacterial coating is a cross-linked PVA coating grafted with a bactericide, and the anti-adhesion antibacterial coating is a non-woven fabric layer. The bactericide is a guanidine salt bactericide. The preparation method comprises the following steps: immersing a polyamide separation layer of the polyamide reverse osmosis membrane into a PVA protection solution, taking out and drying, then immersing into an antibacterial solution, taking out and drying to form an anti-adhesion antibacterial coating, thereby obtaining the anti-pollution reverse osmosis membrane. According to the invention, anti-pollution of the reverse osmosis membrane is realized by combining anti-adhesion and contact sterilization mechanisms, and the conditions of pollutant adsorption and bacterial proliferation on the surface of the membrane are greatly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of reverse osmosis membrane preparation, and particularly relates to an anti-fouling reverse osmosis membrane with anti-adhesion and anti-bacterial properties and a preparation method thereof. BACKGROUND

[0002] Reverse osmosis (RO) technology is one of the core technologies in the fields of water treatment, seawater desalination and material separation today, and the performance of the reverse osmosis membrane, a core component, directly determines the separation efficiency and operation cost of the system. However, in actual operation, membrane fouling, especially biological fouling and organic fouling, is the primary bottleneck restricting the wide application and stable operation of reverse osmosis technology. The adsorption and deposition of pollutants on the membrane surface and the breeding of microorganisms can significantly cause the increase of system operating pressure, the decrease of water production flux and desalination rate, and the increase of chemical cleaning frequency and energy consumption, thereby shortening the service life of the membrane.

[0003] To cope with the problem of membrane fouling, two anti-fouling strategies have been mainly developed in the prior art: one is to improve the “anti-adhesion” of the membrane surface, and the other is to endow the membrane surface with “anti-bacterial property”.

[0004] The anti-adhesion strategy: it mainly modifies the membrane surface to construct an interface layer that is hydrophilic, smooth and electrically neutral, so as to reduce the interaction force between the pollutants and the membrane surface, making it difficult to adhere or easy to be washed away by water flow. Common methods include surface grafting or coating of polyethylene glycol (PEG), zwitterionic polymers (such as polysulfone betaine) and the like. However, this method can only passively prevent the adhesion of pollutants and cannot kill microorganisms in water. Once the protective layer is damaged or the cleaning cycle is improper, the residual microorganisms will still multiply to form a biofilm, causing irreversible pollution of the membrane.

[0005] The anti-bacterial strategy: it actively kills microorganisms contacting the membrane surface by loading bactericidal active substances (such as silver nanoparticles, quaternary ammonium salt, antibacterial peptide, etc.) on the membrane surface or in the membrane matrix. Although this strategy can effectively reduce the number of living bacteria, the killed bacteria, cell debris and other dead bacteria may still firmly adhere to the membrane surface, forming a dense pollution layer, which not only causes physical blockage, but also becomes the aggregation core of other organic and inorganic pollutants, thereby masking the bactericidal advantage, resulting in a rapid decline in membrane flux.

[0006] And the only functional strategy in the prior art is currently available. The pure anti-adhesion membrane cannot eliminate the threat of biological pollution, and the pure anti-bacterial membrane faces the problem of secondary pollution caused by dead bacteria residues. Therefore, both schemes have obvious limitations when applied alone, and it is difficult to achieve long-term and stable resistance to complex pollution systems.

[0007] Therefore, there is an urgent need in the art for a new reverse osmosis membrane that can combine the functions of "anti-adhesion" and "antibacterial" in an organic way. Through the synergistic effect of the two mechanisms, on the one hand, the number of microorganisms is actively reduced, and on the other hand, the adhesion of various pollutants (including dead bacteria) is passively prevented, thereby fundamentally improving the long-term anti-pollution performance and operation stability of the reverse osmosis membrane. SUMMARY

[0008] The present application aims to overcome the defects in the prior art and provides an anti-pollution reverse osmosis membrane with anti-adhesion and antibacterial properties and a preparation method thereof, which combines the "anti-adhesion" and "contact sterilization" mechanisms to achieve anti-pollution of the reverse osmosis membrane, greatly improving the conditions of pollutant adsorption and bacterial proliferation on the membrane surface.

[0009] To achieve the above-mentioned purpose, the technical solutions adopted by the present application are as follows:

[0010] An anti-pollution reverse osmosis membrane with anti-adhesion and antibacterial properties comprises a non-woven fabric support layer, a polysulfone-based membrane layer, a polyamide desalination layer, and an anti-adhesion and antibacterial coating layer arranged in sequence, wherein the anti-adhesion and antibacterial coating layer is a cross-linked PVA coating layer grafted with a bactericide, and the bactericide is a guanidine salt bactericide.

[0011] A preparation method of an anti-pollution reverse osmosis membrane with anti-adhesion and antibacterial properties comprises the following steps:

[0012] Step 1, preparation of a solution:

[0013] Preparation of a PVA protection solution: PVA is added to pure water and dissolved by heating. After the solution cools to room temperature, an acid is added to adjust the solution pH to 1.5-3.0. Then an aldehyde cross-linking agent is added to obtain the PVA protection solution.

[0014] Preparation of an antibacterial solution: a guanidine salt antibacterial agent is dissolved in water, and then a NaOH aqueous solution is added dropwise to adjust the solution pH to 7.0-9.0.

[0015] Step 2, preparation of an anti-adhesion and antibacterial coating layer: the polyamide separation layer of the polyamide reverse osmosis membrane is immersed in the PVA protection solution, then taken out and dried, and then immersed in the antibacterial solution, taken out and dried to form the anti-adhesion and antibacterial coating layer, thereby obtaining the anti-pollution reverse osmosis membrane.

[0016] As a further technical solution, in the PVA protection solution, the mass concentration of PVA is 0.1-1 %, and the mass concentration of the aldehyde cross-linking agent is 0.1-0.5 %.

[0017] As a further technical solution, the aldehyde cross-linking agent is one or more of glutaraldehyde, glyoxal, and dialdehyde polysaccharide.

[0018] As a further technical solution, the acid uses hydrochloric acid and / or sulfuric acid.

[0019] As a further technical solution, in the antibacterial solution, the mass concentration of guanidine salt antibacterial agent is 0.1-2wt%.

[0020] As a further technical solution, the guanidine salt antibacterial agent includes one or more of polyhexamethylene biguanide hydrochloride, dodecyl guanidine hydrochloride, polyhexamethylene guanidine hydrochloride, and triaminoguanidine hydrochloride.

[0021] As a further technical solution, in step 2, the immersion time of the polyamide separation layer in the PVA protection solution and the antibacterial solution is 15-25 seconds; the drying temperature is 55-65 degrees Celsius, and the drying time is 4-6 minutes.

[0022] As a further technical solution, the preparation method of the polyamide reverse osmosis membrane comprises the following steps: first, immersing a polysulfone-based membrane in a polyamine aqueous solution, then removing the excess solution on the surface, and then immersing it in a polyacyl chloride oil solution for interfacial polymerization reaction. After the reaction is completed, heat treatment is performed to form a polyamide separation layer, thereby preparing a polyamide reverse osmosis membrane.

[0023] As a further technical solution, the polyamine aqueous solution further includes a phase transfer catalyst and a surfactant.

[0024] As a further technical solution, in the polyamine aqueous solution, the mass concentration of polyamine is 0.5-5wt%, the mass concentration of the phase transfer catalyst is 0.2-2wt%, and the mass concentration of the surfactant is 0.05-0.2wt%.

[0025] As a further technical solution, the polyamine includes one or more of m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, piperazine, 1,4-cyclohexanediamine, and 1,2-ethylenediamine.

[0026] As a further technical solution, the phase transfer catalyst is one of camphor sulfonic acid-triethylamine salt, o-aminobenzoic acid-triethylamine salt, and m-aminobenzoic acid-triethylamine salt.

[0027] As a further technical solution, the surfactant is sodium dodecyl sulfate (SDS).

[0028] As a further technical solution, in the polyacyl chloride oil solution, the mass concentration of polyacyl chloride is 0.05-0.2wt%.

[0029] As a further technical solution, the solvent of the polyacyl chloride oil solution includes n-hexane, n-heptane, Isopar TM C, IsoparTM E, Isopar TM G, Isopar TM H, Isopar TM L, Isopar TM M one or more of.

[0030] As a further technical solution, the polybasic acid chloride includes one or more of trimesic acid chloride, isophthalic acid chloride, terephthalic acid chloride.

[0031] Compared with the prior art, the beneficial effects of the present application are that:

[0032] The PVA gel generated by crosslinking PVA with aldehyde crosslinking agent under acidic conditions is coated on the surface of the reverse osmosis membrane, the aldehyde groups left by the aldehyde crosslinking agent which does not completely participate in the reaction undergo nucleophilic addition-elimination reaction with the primary amino groups of the subsequent guanidine salt antibacterial agent under alkaline conditions to form Schiff base, thereby fixing the antibacterial agent on the surface of the crosslinked PVA coating, and a synergistic anti-pollution layer with both "anti-adhesion" and "antibacterial" functions is ingeniously constructed. This structure effectively overcomes the limitations of existing single functional modification technologies. Specifically, it has the following advantages:

[0033] 1. Synergistic anti-pollution, long-lasting: The dense crosslinked PVA layer can passively and effectively block the initial adhesion of pollutants such as proteins and colloids through its strong hydrophilicity and smooth surface; and the stably immobilized guanidine salt antibacterial agent can actively and continuously kill microorganisms contacting the membrane surface, thereby fundamentally inhibiting the formation of biofilms. This "anti-pollution + antibacterial" synergistic mechanism achieves all-round resistance to complex pollution systems, significantly improving the long-term stability and flux retention rate of the membrane.

[0034] 2. Functional integration, stable structure: The present application uses glutaraldehyde as a "bridge" to not only consolidate the stability of the PVA coating itself and prevent it from swelling and losing during long-term operation, but also to firmly anchor the guanidine salt antibacterial agent in the crosslinked network through interaction. The guanidine salt contact-type bactericide with broad-spectrum bactericidal properties, long-lasting bactericidal effect, and low toxicity is directly introduced onto the membrane surface, which has more persistent bactericidal effect and higher safety factor than release-type bactericides; thereby greatly solving the industry problems of easy elution and short service life of antibacterial agents, and ensuring the persistence of antibacterial effect.

[0035] 3. Simple process, easy to promote: The entire preparation process is based on mature coating and soaking processes, with mild conditions and simple operation, without the need for complex equipment, which is very suitable for technical upgrading and large-scale production based on existing reverse osmosis membrane production lines, and has high industrial application value. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1The scanning electron microscope diagram of the membrane after rinsing with water for 1 h;

[0037] In Figure 1 a: Example 1; b: Example 2; c: Example 3; d: Comparative Example 1; e: Comparative Example 2; f: Comparative Example 5. DETAILED DESCRIPTION

[0038] The technical solutions of the present application will be described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0039] The raw materials used in the present application are commercially available unless otherwise specified.

[0040] Example 1

[0041] A kind of anti-fouling reverse osmosis membrane with anti-adhesion and antibacterial property, its preparation method, comprising the following steps:

[0042] Step 1, preparation of solution:

[0043] 1) Preparation of polyamine aqueous solution: 20 g of m-phenylenediamine, 20 g of camphor sulfonic acid, 10 g of triethylamine and 2 g of SDS were weighed and added to 948 g of RO water. After stirring for 60 min, it was completely dissolved to form an RO membrane aqueous solution;

[0044] 2) Preparation of trimesoyl chloride oil phase solution: 2 g of trimesoyl chloride was weighed and added to 998 g of Isopar TM G oil phase, and after stirring for 60 min, it was completely dissolved to form an RO membrane oil phase solution;

[0045] 3) Preparation of PVA protective solution: 10 g of PVA was weighed and added to 990 g of hot water at 80℃. After stirring for 60 min under the condition of heating at 80℃, it was completely dissolved. After the solution was cooled to room temperature, hydrochloric acid solution was added dropwise until the pH value of the solution was 2±0.1. Finally, 1 g of glutaraldehyde was weighed and added dropwise to the PVA solution while stirring. After stirring for 30 min, a PVA protective solution was formed;

[0046] 4) Preparation of antibacterial solution: 5 g of polyhexamethylene biguanide hydrochloride was weighed and added to 995 g of water. After stirring for 60 min, it was completely dissolved. NaOH aqueous solution was added dropwise to adjust the pH to 8±0.1. The prepared antibacterial solution had a concentration of 0.5%.

[0047] Step 2, preparation of RO membrane: the polysulfone-based membrane is soaked in the polyamine aqueous solution for 20 s, then taken out, and the residual water on the membrane surface is blown dry with nitrogen. After that, the membrane is soaked in the trimesoyl chloride oil solution for 10 s. After the excess solution on the membrane surface is removed by a rubber roller, the polyamide separation layer is formed by heat treatment at 60℃ for 5 min in a blast drying oven, and the polyamide RO membrane is prepared.

[0048] Step 3, preparation of cross-linked PVA coating: the polyamide separation layer of the RO membrane is soaked in the PVA protective solution for 20 s, then taken out, and placed in a blast drying oven for heat treatment at 60℃ for 5 min. After that, the anti-adhesion cross-linked PVA coating is formed on the surface of the polyamide separation layer.

[0049] Step 4, conversion of the cross-linked PVA coating into an anti-adhesion and anti-bacterial coating: the polyamide separation layer coated with the anti-adhesion cross-linked PVA coating is soaked in the anti-bacterial solution for 20 s, then taken out, and placed in a blast drying oven for heat treatment at 60℃ for 5 min. After that, the cross-linked PVA coating is endowed with anti-bacterial function, and the anti-adhesion and anti-bacterial coating is formed, thereby obtaining the anti-pollution reverse osmosis membrane with both anti-adhesion and anti-bacterial properties.

[0050] Example 2

[0051] An anti-pollution reverse osmosis membrane with both anti-adhesion and anti-bacterial properties, and a preparation method thereof, including the following steps: the same as in Example 1, except that the amount of polyhexamethylene biguanide hydrochloride used in the preparation of the anti-bacterial solution is 10 g, and the amount of water used is 990 g; and the concentration of the prepared anti-bacterial solution is 1%.

[0052] Example 3

[0053] An anti-pollution reverse osmosis membrane with both anti-adhesion and anti-bacterial properties, and a preparation method thereof, including the following steps: the same as in Example 1, except that the amount of polyhexamethylene biguanide hydrochloride used in the preparation of the anti-bacterial solution is 15 g, and the amount of water used is 985 g; and the concentration of the prepared anti-bacterial solution is 1.5%.

[0054] Comparative Example 1

[0055] A reverse osmosis membrane, and a preparation method thereof, including the following steps: the same as in Example 1, except that no glutaraldehyde is used in the PVA protective solution.

[0056] Comparative Example 2

[0057] A reverse osmosis membrane, and a preparation method thereof, including the following steps: the same as in Example 1, except that Step 4 is omitted, and the anti-adhesion cross-linked PVA coating is not converted into an anti-adhesion and anti-bacterial coating.

[0058] Comparative Example 3

[0059] A reverse osmosis membrane, a preparation method thereof, comprising the following steps: same as example 1, except that formaldehyde is used to replace glutaraldehyde.

[0060] Comparative example 4

[0061] A reverse osmosis membrane, a preparation method thereof, comprising the following steps: same as example 1, except that dimethyl octadecyl [3- (trimethoxysilyl) propyl] ammonium chloride is used to replace the polyhexamethylene biguanide hydrochloride in example 1.

[0062] Comparative example 5

[0063] A reverse osmosis membrane, a preparation method thereof, comprising the following steps:

[0064] Step 1, preparation of a solution:

[0065] 1) Preparation of a polyamine aqueous solution: same as example 1;

[0066] 2) Preparation of a trimesoyl chloride oil phase solution: same as example 1;

[0067] 3) Preparation of an antibacterial coating solution: polyvinyl alcohol 0.5 parts by weight, antibacterial material dimethyl octadecyl [3- (trimethoxysilyl) propyl] ammonium chloride 0.1 parts by weight, formaldehyde 0.01 parts by weight, and deionized water 99.39 parts by weight are weighed;

[0068] First, the polyvinyl alcohol is dissolved in deionized water, then the antibacterial material and formaldehyde are added to the polyvinyl alcohol solution, the pH of the reaction system is adjusted to 1-2, and then stirred at 20-30°C for 1h and left to stand for 3-6h to obtain the antibacterial coating solution.

[0069] Step 2, preparation of a RO membrane: same as example 1.

[0070] Step 3, preparation of an antibacterial coating: the polyamide reverse osmosis membrane is immersed in the antibacterial coating solution, so that the polyamide reverse osmosis membrane is in contact with the antibacterial coating solution, the soaking time is 2min, and after taking out, it is heated treated in a blast oven at 60-100°C for 3-10min to obtain an antibacterial composite reverse osmosis membrane.

[0071] Comparative example 6

[0072] A reverse osmosis membrane, a preparation method thereof, comprising the following steps: same as example 1, except that steps 3-4 are omitted, and no antibacterial and anti-adhesion coating is provided on the surface of the polyamide reverse osmosis membrane.

[0073] Example 1: test of the anti-fouling and anti-adhesion performance of the membrane surface

[0074] 1. Using a cross-flow RO system, the reverse osmosis membranes prepared in each example and comparative example were tested as follows: 1500 ppm NaCl solution was filtered at 1 MPa, 25.0 ± 0.5 ℃ for 30 min, and the initial flux J0 of the membrane material was tested. Subsequently, 500 ppm bovine serum albumin (BSA) model pollutants were added, and then run for 8 h, the water flux of the membrane was tested and recorded as J t . Finally, the membrane was rinsed with deionized water at a high flow rate and a pressure of less than 3 bar for 30 min. The water flux of the membrane after cleaning was tested with 1500 ppm NaCl aqueous solution as the feed liquid, and was recorded as J C . The initial flux decay rate (FDR) and the flux recovery rate (FRR) were calculated according to the following formula, respectively.

[0075]

[0076]

[0077] The results of the membrane surface anti-pollution performance test are shown in Table 1.

[0078] Table 1

[0079]

[0080] From the data in Table 1, it can be seen that: 1) Examples 1-3 adopt the “glutaraldehyde cross-linked PVA + polyhexamethylene biguanide hydrochloride” synergistic coating design, and the performance indicators are balanced and excellent: in the bovine serum albumin pollution test, the flux decay rate of Examples 1-3 is the lowest (15.7%-19.3%), and after simple water washing, the flux recovery rate is the highest (94.4%-94.7%). This proves that the coating not only can effectively prevent the adhesion of pollutants (anti-adhesion of PVA gel), but also can inhibit the breeding of microorganisms (antibacterial property of guanidine salt), and the pollutants are not easy to reside on the surface and are easy to be physically washed away. The desalination rates of the three examples are all stable at an extremely high level of 99.48%-99.53%, which indicates that the introduction of the functional coating does not damage the core desalination ability of the reverse osmosis membrane. At the same time, the coating brings a certain amount of permeation resistance, resulting in an initial water flux (26.7-30.6 GFD) slightly lower than that of the comparative example without coating, but this is an acceptable and reasonable performance trade-off for introducing an anti-pollution layer.

[0081] 2) The flux decay rate of Comparative Example 1 (only PVA and antibacterial agent, without cross-linking and fixation) is as high as 55.8%, and the recovery rate is only 54.3%, which proves that without glutaraldehyde cross-linking and subsequent Schiff base fixation, the anti-adhesion layer and the antibacterial agent cannot be effectively anchored, and the entire coating structure is unstable, and the anti-pollution function is almost ineffective.

[0082] The anti-fouling performance (attenuation rate 22.5%, recovery rate 93.4%) of Comparative Example 2 (only cross-linked PVA layer) is significantly better than Comparative Example 1, but slightly inferior to Example 1. This confirms that the single "anti-adhesion" function has a certain effect, but combined with the "antibacterial" function, a more comprehensive protection can be formed (Example 1 attenuation rate 19.3%).

[0083] Comparative Example 3 (formaldehyde instead of glutaraldehyde): its performance (attenuation rate 34.8%, recovery rate 75.5%) is worse than Example 1, but better than Comparative Example 1, which verifies the universality of aldehyde cross-linking agent, and also indirectly suggests that glutaraldehyde, as a dialdehyde, may have more advantages in cross-linking efficiency or functionality for subsequent antibacterial agent reaction.

[0084] The anti-fouling performance of Comparative Example 4 (attenuation rate 26.7%, recovery rate 87.5%) and Comparative Example 5 (attenuation rate 37.4%, recovery rate 71.1%) is obviously inferior to Example 1. This strongly proves that the antibacterial effect of polyhexamethylene biguanide hydrochloride is better than that of organosilicon quaternary ammonium salt in this system. Especially Comparative Example 5 tries to simplify the process, but the effect is not good, which highlights the key of the preparation method of "step-by-step reaction and formation of covalent bond fixation".

[0085] Comparative Example 6 (no coating): its data (attenuation rate 65.6%, recovery rate 43.7%) is the worst in all groups, which indirectly proves the absolute necessity and great improvement effect of the anti-fouling coating design of the present application.

[0086] In summary, the present application forms an anti-adhesion gel layer by cross-linking PVA with glutaraldehyde, and covalently fixes the guanidine salt antibacterial agent by using its residual aldehyde group, and the synergistic effect of the dual-functional coating constructed by the two produces a "1+1>2" synergistic anti-fouling effect, which significantly reduces the flux attenuation during operation, while achieving a very high physical cleaning recovery rate. Among them, the step-by-step preparation method of "cross-linking and solidifying PVA gel layer first, and then fixing the antibacterial agent through Schiff base reaction under alkaline conditions" is the key to success, which is better than simple mixing coating (Comparative Example 5); and glutaraldehyde as a dual-functional cross-linking agent and polyhexamethylene biguanide hydrochloride as a covalently fixed antibacterial agent are confirmed as the preferred combination in this system, which has better comprehensive performance than formaldehyde and organosilicon quaternary ammonium salt and other alternative solutions.

[0087] Effect Example 2: Morphological characteristics

[0088] In order to explore the influence of the coating on the surface morphology of the RO membrane, and the firmness of the coating attached to the surface of the RO membrane separation layer, the products of Example 1 and Comparative Examples 1-2 and 5 were washed with deionized water at a high flow rate and a pressure lower than 3 bar for 1 h, and then dried, and the membrane pieces were characterized by scanning electron microscopy (SEM), and the results are shown in Figure 1 .

[0089] FromFigure 1 It can be seen that:

[0090] 1) The SEM images of Examples 1-3 show that the film surface is covered with a continuous, uniform and dense coating layer, the surface is smooth and flat, and no obvious cracks or peeling phenomena are observed; after high flow rate and low pressure flushing, the coating layer is still completely attached to the film surface, indicating that the cross-linked PVA gel layer is firmly combined with the film matrix, and no swelling phenomenon occurs.

[0091] 2) From the comparison of Example 1 and Comparative Example 1, it can be seen that: after flushing, the coating layer on the film surface almost completely peels off, the surface roughness increases, indicating that the uncross-linked PVA coating layer is easy to swell and separate from the film surface in water, and the adhesion is poor.

[0092] 3) From the comparison of Example 1 and Comparative Example 2, it can be seen that: the film surface of Comparative Example 2 presents a uniform and smooth morphology, similar to Example 1, indicating that the cross-linked PVA coating layer itself has good film-forming and covering properties, and the introduction of the antibacterial agent will not destroy the integrity of the coating layer. The coating layer remains intact after flushing, further confirming that the gel layer formed by cross-linking PVA with glutaraldehyde has excellent anti-water flushing performance.

[0093] 4) From the comparison of Example 1 and Comparative Example 5, it can be seen that: the SEM image of Comparative Example 5 shows that the coating layer on the film surface after flushing appears partial peeling, and some areas expose the underlying film, indicating that the coating layer prepared by one-step blending has poor structural uniformity and weak adhesion to the film matrix.

[0094] Example 3: Test of antibacterial performance of RO membrane

[0095] Using a cross-flow RO system, after filtering a 1500 ppm NaCl solution at 1 MPa, 25.0 ± 0.5 ℃ for 8 h, the antibacterial performance of the membrane sheets of each example and comparative example was tested according to the national standard GB / T 37206-2018 "Test method for antibacterial performance of organic separation membrane".

[0096] Take two sterile petri dishes, numbered A and B, and respectively take 0.4 mL of test bacterial suspension (Escherichia coli, inoculation bacterial liquid concentration is 10 6Add CFU / ml to a Petri dish. Using sterile forceps, pick up a circular membrane sample with a diameter of 20±1 mm and spread it evenly over the bacterial suspension in Petri dish A (the effective filtration surface of the membrane should be in contact), ensuring the bacterial suspension is evenly in contact with the membrane sample. Petri dish B serves as a blank control and does not contain a membrane sample. Simultaneously, place Petri dishes A and B in a constant temperature and humidity incubator at (36±1)℃ and a relative humidity of not less than 90% for 2 hours. After incubation, remove Petri dishes A and B and repeatedly elute the samples from both dishes and the membrane sample with 10 ml of phosphate buffer, mixing thoroughly. Using a 1 ml sterile pipette, pipette 1 ml of the eluent into a test tube containing 9 ml of phosphate buffer, mix thoroughly, and then pipette 1 ml into a test tube containing 9 ml of phosphate buffer, mix thoroughly, and repeat the operation to prepare a 10-fold serial dilution (approximately 4 to 5 serial dilutions may be performed as needed). Transfer 1 ml of the eluent and 10-fold serial dilutions to sterile Petri dishes. Pour in approximately 15 ml of melted (45±2)℃ plate counting agar. Gently shake the Petri dish to disperse the bacteria evenly. After cooling and solidification, invert the Petri dish and incubate at (36±1)℃ for 18 h. Remove the incubated Petri dishes and count the colonies according to the method specified in 6.3 of GB4789.2-2016, recording the count as N. A N B The antibacterial rate K of the sample is calculated using the following formula:

[0097]

[0098] Where N A The number of colonies after the test sample is in contact with the test bacteria and cultured, expressed in colony forming units (CFU); N B The number of colonies after culturing the blank test bacteria is expressed in colony forming units (CFU).

[0099] The antibacterial rate of the membrane is shown in Table 2.

[0100] Table 2

[0101]

[0102] From the data in Table 2, we can see that:

[0103] 1) A comparison of Example 1 and Comparative Examples 1-2 shows that both used a 0.5% PHMB solution for treatment, but Example 1 (with glutaraldehyde crosslinking) achieved an antibacterial rate as high as 54.46%, while Comparative Example 1 (without glutaraldehyde) had an antibacterial rate of -34.25%, and Comparative Example 2 (without antibacterial agent) had an antibacterial rate of -43.52%. The negative antibacterial rates of Comparative Examples 1-2 indicate that PHMB, which is simply physically adsorbed, is easily lost during 8 hours of water operation, and its residue may even become a nutrient source for microorganisms, exacerbating biofouling. This comparison demonstrates that glutaraldehyde, acting as a "molecular bridge," covalently grafts PHMB into the PVA network, which is an indispensable key step in overcoming antibacterial agent loss and achieving long-lasting antibacterial function.

[0104] 2) A comparison between Example 1 and Comparative Example 3 shows that Comparative Example 3 (formaldehyde replacing glutaraldehyde) had an antibacterial rate of -11.11%, which is unsatisfactory. This indicates that glutaraldehyde, as a dual-aldehyde crosslinking agent, may provide a better interface for subsequent antibacterial agent fixation through a more stable crosslinking network or more residual aldehyde groups.

[0105] 3) A comparison of Example 1 and Comparative Examples 4-5 shows that: Comparative Example 4 (quaternary ammonium salt replacing PHMB) has some antibacterial activity (24.54%), but its effect is far inferior to PHMB (54.46% in Example 1). This proves that PHMB, as a polyguanidine compound, has the ability to form multiple Schiff base bonds with aldehyde groups, giving it superior fixation efficiency and antibacterial performance in this system. The antibacterial rate of Comparative Example 5 (one-step blending method) is only 12.04%, far lower than Comparative Example 4 (24.54%), and incomparable to Example 1. This proves that simple physical blending cannot achieve effective fixation and stable exposure of antibacterial agents. The stepwise strategy of "first crosslinking to form a film, then bonding for fixation" is crucial for constructing a durable and efficient antibacterial surface.

[0106] Example 4: RO membrane separation performance test

[0107] A 1500 ppm NaCl solution was used as the feed solution, and the system temperature was maintained at 25.0 ± 0.5 ℃. The membrane was first pre-pressed at 1 MPa for 30 min, and then the mass and conductivity of the permeate were measured to calculate the water flux (J) and solute rejection ratio (R). Where V is the permeate volume; A is the effective filtration area of ​​the membrane cell; and t is the permeation time. P and C f These are the ionic conductivity in the permeate and feed solutions, respectively.

[0108]

[0109]

[0110] The membrane performance test results are shown in Table 3.

[0111] Table 3

[0112]

[0113] As shown in Table 3, the desalination rates (99.28%-99.42%) of the reverse osmosis membranes prepared in all embodiments remained at extremely high levels, and were superior to or equivalent to the unmodified blank membrane (Comparative Example 6, 98.13%) and other comparative examples. This indicates that the surface functional layer constructed in this invention did not damage the inherent density of the polyamide separation layer; on the contrary, the uniform and dense PVA gel layer may have played a good role in filling and repairing microscopic defects on the membrane surface, thereby endowing the membrane with new functions while ensuring or even slightly improving its core desalination performance.

[0114] The flux of the reverse osmosis membranes prepared in Examples 1-3 (26.7-30.6 GFD) was lower than that of the blank membrane (46.6 GFD), which is the expected result of introducing the hydrophilic gel coating. Although the flux of Examples 1-3 was slightly lower, the aforementioned robust coating structure and significant antibacterial properties were obtained. This demonstrates that the present invention successfully achieves a stable and strong antifouling function at the cost of controllable and limited flux, thus achieving an optimized balance between performance and function.

[0115] The embodiments described above are merely preferred embodiments of the present invention, and not an exhaustive list of all possible implementations of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A reverse osmosis membrane with both anti-adhesion and antibacterial properties, characterized in that, It includes a nonwoven support layer, a polysulfone-based film layer, a polyamide desalination layer, and an anti-adhesion and antibacterial coating arranged in sequence. The anti-adhesion and antibacterial coating is a cross-linked PVA coating grafted with a bactericide, and the bactericide is a guanidine salt bactericide.

2. A method for preparing an antifouling reverse osmosis membrane with both anti-adhesion and antibacterial properties, characterized in that, Includes the following steps: Step 1, Solution preparation: Preparation of PVA protective solution: PVA is added to pure water and heated to dissolve. After the solution is cooled to room temperature, an acid solution is added to adjust the pH to 1.5~3.

0. Then, an aldehyde crosslinking agent is added to obtain the PVA protective solution. Preparation of antibacterial solution: Dissolve guanidine salt antibacterial agent in water, then add NaOH aqueous solution dropwise to adjust the pH of the solution to 7.0~9.0; Step 2, Preparation of anti-adhesion and antibacterial coating: Immerse the polyamide separation layer of the polyamide reverse osmosis membrane in PVA protective solution, take it out and dry it, then immerse it in antibacterial solution, take it out and dry it to form an anti-adhesion and antibacterial coating, thus obtaining the anti-fouling reverse osmosis membrane.

3. The method for preparing an antifouling reverse osmosis membrane according to claim 2, characterized in that, In the PVA protective solution, the mass concentration of PVA is 0.1% to 1%, and the mass concentration of the aldehyde crosslinking agent is 0.1% to 0.5%. The aldehyde crosslinking agent is one or more of glutaraldehyde, glyoxal, and dialdehyde polysaccharide; The acid used is hydrochloric acid and / or sulfuric acid.

4. The method for preparing an antifouling reverse osmosis membrane with both anti-adhesion and antibacterial properties according to claim 2, characterized in that, The antibacterial solution contains guanidine salt antibacterial agents at a concentration of 0.1-2 wt%. The guanidine salt antibacterial agents include one or more of polyhexamethylene biguanide hydrochloride, dodecyl guanidine hydrochloride, polyhexamethylene guanidine hydrochloride, and triaminoguanidine hydrochloride.

5. The method for preparing an antifouling reverse osmosis membrane with both anti-adhesion and antibacterial properties according to claim 2, characterized in that, In step 2, the immersion time of the polyamide separation layer in the PVA protective solution and antibacterial solution is 15-25 seconds; the drying temperature is 55-65 degrees Celsius, and the drying time is 4-6 minutes.

6. The method for preparing an antifouling reverse osmosis membrane with both anti-adhesion and antibacterial properties according to claim 2, characterized in that, The method for preparing the polyamide reverse osmosis membrane includes: first, immersing a polysulfone-based membrane in a polyamine aqueous solution, then removing excess solution from the surface, and then immersing it in a polyacrylamide chloride oil solution for interfacial polymerization reaction. After the reaction is completed, heat treatment is performed to form a polyamide separation layer, thereby obtaining the polyamide reverse osmosis membrane.

7. The method for preparing an antifouling reverse osmosis membrane with both anti-adhesion and antibacterial properties according to claim 6, characterized in that, The polyamine aqueous solution also includes a phase transfer catalyst and a surfactant; In the aqueous polyamine solution, the mass concentration of the polyamine is 0.5 to 5 wt%, the mass concentration of the phase transfer catalyst is 0.2 to 2 wt%, and the mass concentration of the surfactant is 0.05 to 0.2 wt%.

8. The method for preparing an antifouling reverse osmosis membrane with both anti-adhesion and antibacterial properties according to claim 6, characterized in that, The polyamines include one or more of m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, piperazine, 1,4-cyclohexanediamine, and 1,2-ethylenediamine; The phase transfer catalyst is one of camphor sulfonic acid-triethylamine salt, anthranilic acid-triethylamine salt, and m-aminobenzoic acid-triethylamine salt; The surfactant is sodium dodecyl sulfate.

9. The method for preparing an antifouling reverse osmosis membrane with both anti-adhesion and antibacterial properties according to claim 6, characterized in that, In the polyacrylamide chloride oil phase solution, the mass concentration of the polyacrylamide chloride is 0.05 ~ 0.2 wt%; The solvents in the polyacrylamide chloride oil phase solution include n-hexane, n-heptane, and Isopar. TM C, Isopar TM E, Isopar TM G, Isopar TM H, Isopar TM L, Isopar TM One or more of M; The polyacrylic chlorides include one or more of pyromellitic trichloroisocyanurate, isophthaloyl chloride, and terephthaloyl chloride.

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