Quorum sensing inhibitor modified ultrafiltration membrane as well as preparation method and application thereof

Abstract

The invention discloses a quorum sensing inhibitor modified ultrafiltration membrane as well as a preparation method and application thereof, a hydrophilic monomer is grafted on the surface of the membrane by utilizing ultraviolet light, the modified membrane is prepared through reaction of quorum sensing inhibitor amino and carboxyl of the hydrophilic monomer, and the prepared membrane can relieve biological pollution. The modification method comprises the following steps: soaking a polyethersulfone ultrafiltration membrane in an absolute ethyl alcohol solution containing a photoinitiator benzophenone (BP), then removing a redundant ethyl alcohol solution, exposing the polyethersulfone ultrafiltration membrane under ultraviolet rays, irradiating for a certain time, and drying in air; immersing the membrane in a maleic anhydride (MAH) aqueous solution for a period of time, and then irradiating under ultraviolet light; immersing the membrane grafted with the MAH monomer into an aqueous solution containing EDC and NHS, stirring to activate carboxyl of the monomer, adding a quorum sensing inhibitor 2-amino-6-fluorobenzoic acid (6F-ABA) into the solution, and stirring to graft the quorum sensing inhibitor 2-amino-6-fluorobenzoic acid (6F-ABA) on the surface of the membrane. The hydrophilicity and electronegativity of the prepared modified membrane are improved, and the modified membrane has good biological pollution resistance.

Description

Technical Field

[0001] The present invention relates to a quorum sensing inhibitor-modified ultrafiltration membrane, a preparation method thereof and an application thereof, and in particular to a preparation method of a high-performance anti-biofouling water treatment membrane. The present invention belongs to the fields of membrane technology for water treatment and anti-biofouling of membranes. Background Art

[0002] Membrane technology has the advantages of good water production quality, low energy consumption, small reactor size, etc., and has become a key technology for solving the global water shortage problem. However, membrane fouling problems such as inorganic fouling, organic fouling, colloidal fouling and biofouling increase the operation and maintenance costs, reduce the membrane separation performance and the membrane service life. Among them, biofouling caused by microbial proliferation and metabolic secretion accounts for more than 50% of the membrane fouling, and the secreted extracellular polymeric substances (EPS) are difficult to clean, which is the main bottleneck restricting the application of membranes. Biofouling is a dynamic process of biofilm formation, including cell transport, deposition and adhesion, EPS generation, and cell growth and proliferation. Traditional disinfection technologies will induce the generation of chlorine-resistant bacteria and cytoplasmic leakage, and to a certain extent promote the formation of biofilms. Even if 99% of the microorganisms in the water are removed by pretreatment, the remaining microorganisms can still adhere to the membrane surface, regenerate and form biofilms.

[0003] Quorum sensing (QS) is a system that transmits information between cells with signal molecules as carriers. When the concentration of signal molecules in the extracellular environment reaches a certain threshold, they bind to QS receptor proteins, triggering the expression of a series of genes related to EPS synthesis, directly affecting the synthesis and secretion of EPS by regulating the microbial signal pathway, and mediating the adhesion between microorganisms to form dense microbial aggregates. Quorum sensing inhibitors (QSI) interfere with the microbial QS system by inhibiting the synthesis of signal molecules, competitively binding to signal molecule receptors, etc., thereby inhibiting the formation of biofilms. Compared with other bacteriostatic agents, QSI inhibits the proliferation of microorganisms without killing microorganisms and destroying cell structures, and can effectively reduce the generation of chlorine-resistant bacteria. Developing QSI anti-fouling modified membranes, by interfering with the microbial QS system, including pathways such as N-acyl homoserine lactone (AHL), 2-heptyl-3-hydroxy-4(1H)-quinolone (PQS), etc., inhibiting the concentration of signal molecules, and then effectively controlling microbial proliferation and EPS secretion, is an effective strategy to alleviate biofouling on the membrane surface.

[0004] The present invention innovatively grafts QSI onto the surface of ultrafiltration membranes through hydrophilic monomers to prepare anti-biofouling composite membranes and applies them to water treatment systems. 2-Amino-6-fluorobenzoic acid (6F-ABA) used in the present invention has stable structural properties and is an effective QSI. It competes with anthranilic acid to bind to the PqsA protein, thereby inhibiting the synthesis of PQS signaling molecules. Using benzophenone (BP) as a photoinitiator, maleic anhydride (MAH) is grafted onto the surface of polyethersulfone (PES) membranes under ultraviolet light irradiation. The carboxyl group of MAH reacts with the amino group of 6F-ABA to graft it onto the membrane surface to form stable covalent bonds. MAH is used as an excellent membrane surface grafting monomer with hydrophilicity to further improve the anti-biofouling performance of the membrane. Summary of the Invention

[0005] The object of the present invention is to address the biofouling problem of ultrafiltration membranes in existing water treatment systems. Based on the interference of quorum sensing inhibitors on biofilm formation, through ultraviolet grafting method, the quorum sensing inhibitor 2-amino-6-fluorobenzoic acid (6F-ABA) is innovatively grafted onto the surface of ultrafiltration membranes to prepare a novel anti-biofouling membrane. The specific operation steps are as follows:

[0006] The ultrafiltration membrane is immersed in an anhydrous ethanol solution containing the photoinitiator benzophenone (BP) for a period of time and then taken out. After removing the excess ethanol solution, the membrane is exposed to ultraviolet light for a certain time and dried in air; the membrane is immersed in an aqueous solution of hydrophilic grafting monomer for a period of time, and then irradiated with ultraviolet light for a certain time. The membrane grafted with hydrophilic monomer is immersed in an aqueous solution containing 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) and stirred to activate the carboxyl group of the monomer; the quorum sensing inhibitor is added to the solution and stirred at room temperature for a certain time, and the prepared modified membrane is stored in deionized water.

[0007] Furthermore, the types of ultrafiltration membranes can be polysulfone, polyethersulfone membranes, etc.

[0008] Furthermore, the concentration of the photoinitiator BP solution is 1-10 mM, the immersion time of the ultrafiltration membrane in the BP solution is 60-120 min, and the ultraviolet light irradiation time is 5-20 min.

[0009] Furthermore, the hydrophilic grafting monomer is one of maleic anhydride and acrylic acid, and its addition amount is preferably 20-60 g / L.

[0010] Furthermore, the immersion time of the ultrafiltration membrane in the aqueous solution of hydrophilic grafting monomer is 5-20 min, and the ultraviolet light irradiation time is 5-20 min.

[0011] Further, the quorum sensing inhibitor is one of quorum sensing inhibitors containing amino functional groups such as methyl anthranilate (MA) and 2-amino-6-fluorobenzoic acid (6F-ABA), and its addition amount is preferably 10-40 mM.

[0012] Further, the concentration of the EDC is 1-3 mM, the concentration of the NHS is 1-10 mM, and the stirring time is 5-15 min to activate the carboxyl groups of the monomers.

[0013] Further, the stirring time for the reaction of the quorum sensing inhibitor is 12-36 h, so that the carboxyl groups of the hydrophilic monomers and the amino groups of the quorum sensing inhibitor fully react to graft it on the membrane surface.

[0014] The ultrafiltration membrane modified by the quorum sensing inhibitor is used to alleviate the biofouling on the membrane surface. To investigate the performance of the membrane, the prepared modified membrane is placed in a cross-flow filtration system for testing, and the membrane flux change and the content of EPS components on the membrane surface are investigated.

[0015] The advantages of the quorum sensing inhibitor modified membrane in the present invention are as follows: The quorum sensing inhibitor loaded on the membrane surface effectively inhibits the synthesis of the PQS signal molecule of the bacterial community, inhibits the growth of microorganisms and reduces the secretion of EPS on the membrane surface, and effectively improves the anti-biofouling performance of the ultrafiltration membrane in the water treatment system. This membrane can be directly applied to membrane treatment equipment without adding special structures such as a dedicated chemical dosing tank, saving space and cost. Description of the Drawings

[0016] Att Figure 1 are the scanning electron microscope SEM morphology diagrams of the PES membrane (a), the MAH(UV) membrane (b) and the example (c). Att Figure 2 are the membrane flux change diagrams of the PES membrane, the MAH(UV) membrane and Example 1 in the dynamic filtration mediated by Pseudomonas aeruginosa. Att Figure 3 are the membrane flux change diagrams of the PES membrane and Example 2 in the dynamic filtration of actual secondary effluent. Detailed Embodiments

[0017] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without any creative work fall within the scope of protection of the present invention.

[0018] Example 1

[0019] (1) Commercial PES and PVP powders were first dried at 60 °C for 24 h to remove moisture. While continuously stirring, PVP and PES powders were dissolved in NMP to prepare a casting solution. The casting solution consisted of 16% PES, 4% PVP, and 80% NMP.

[0020] (2) The casting solution was stirred at 60 °C for 12 h to mix evenly and then left to stand for 12 h to remove bubbles.

[0021] (3) The casting solution was poured onto a non-woven fabric laid on the surface of a smooth glass plate and spread with a 200-μm doctor blade. The membrane was immediately immersed in deionized water, and after phase inversion, a PES ultrafiltration membrane was obtained. The membrane was soaked in pure water for more than 72 h to remove the residual NMP solvent. Its SEM morphology is as Figure 1 (a) shown.

[0022] (4) After the PES ultrafiltration membrane was soaked in an anhydrous ethanol solution containing 3 mM photoinitiator BP for 60 min, the excess ethanol solution was removed to ensure the uniform distribution of BP molecules on the membrane surface. The membrane was exposed to ultraviolet light for 5 min and dried in air for 5 min.

[0023] (5) The membrane was immersed in a 60 g / L maleic anhydride aqueous solution for 10 min and then irradiated with ultraviolet light for 10 min to prepare a MAH(UV)-modified membrane. Its SEM morphology is as Figure 1 (b) shown.

[0024] (6) The membrane grafted with MAH was immersed in an aqueous solution of EDC (2 mM) and NHS (5 mM) and stirred for 15 min to activate the carboxyl group of MAH. 40 mM quorum sensing inhibitor 6F-ABA was added to the solution and stirred at room temperature for 24 h to allow the amino group of 6F-ABA to fully react with the carboxyl group of MAH, preparing a MAH(UV)-QSI modified membrane. Its SEM morphology of the upper surface is as Figure 1 (c) shown.

[0025] (7) The prepared MAH(UV)-QSI modified membrane was subjected to a biofouling test in a cross-flow filtration system. The membrane was run with ultrapure water at a pressure of 0.4 Mpa until the flux was stable, and then a dynamic filtration experiment of Pseudomonas aeruginosa-mediated biofouling was carried out at an operating pressure of 0.2 Mpa. The bacterial concentration was 10 7 CFU / mL. The membrane flux was monitored online by a balance and a computer. After the dynamic filtration experiment, the components of the biofilm on the membrane surface were analyzed. The change in membrane flux during dynamic filtration is as Figure 2 shown.

[0026] Example 2

[0027] Based on the modification method in Example 1, the difference is only in step (7), where the influent water in the dynamic biofouling filtration experiment is the actual secondary effluent filtered by a 0.45 μm filter membrane. The change in membrane flux during its dynamic filtration is as Figure 3 shown.

[0028] The test data of the modified MAH(UV)-QSI membrane, MAH(UV) membrane and the original PES membrane in the example are shown in Table 1. The data in the table show that compared with the original membrane, the contact angle of the MAH(UV) membrane and the example decreases, and the Zeta potential increases, indicating that the hydrophilicity and electronegativity of the QSI-modified membrane increase. However, the graft modification on the membrane surface may block the pores of the PES membrane, resulting in a slight decrease in water flux.

[0029] Table 1

[0030]

[0031] Figure 1 For the scanning electron microscope analysis results, it shows the successful loading of QSI on the membrane surface.

[0032] Figure 2 It reveals the changes in the normalized membrane flux of the original membrane, MAH(UV) membrane and Example 1 in the dynamic biofouling filtration experiment mediated by Pseudomonas aeruginosa. In the 12-hour dynamic filtration experiment, the flux of the original PES ultrafiltration membrane decreased by 81%, indicating serious biofouling. Compared with the original membrane, the final fluxes of the MAH(UV) membrane and the example decreased by 70% and 46% respectively, alleviating the membrane flux decline by 11% and 35% respectively, indicating that the example significantly improved the anti-biofouling ability of the membrane in dynamic filtration.

[0033] Table 2 illustrates the changes in the EPS (protein, polysaccharide, eDNA) of the membrane surface fouling layer. Compared with the original membrane, Example 1 has an obvious inhibitory effect on the EPS components. The contents of protein, polysaccharide and eDNA on the surface of the fouled original membrane are 279 μg / cm 2 , 40 μg / cm 2 , 86 ng / cm 2 respectively, indicating that protein is the main component of EPS on the fouled membrane surface. The contents of the three EPS components on the surface of the MAH(UV) membrane decreased by 18 - 32%. The MAH(UV) membrane improves hydrophilicity and negative charge, which can reduce the adhesion of microorganisms and nutrients, and reduce the EPS content on the membrane surface, thereby slightly alleviating the decline of membrane flux. Example 1 reduced the contents of protein, polysaccharide and eDNA on the fouled membrane surface by 67%, 52% and 76% respectively. Example 1 has high hydrophilicity and negative charge. At the same time, the quorum sensing interference effect of QSI on microorganisms will also reduce the EPS content on the fouled membrane surface, thus significantly alleviating the decline of membrane flux.

[0034] Table 2

[0035]

[0036] Figure 3 It reveals the changes in the normalized membrane flux of the original membrane and Example 2 in the actual secondary effluent dynamic filtration experiment. During the 100-h dynamic filtration experiment, the flux of the original PES ultrafiltration membrane decreased by 90%, indicating serious biological fouling. Compared with the original membrane, the final flux of Example 2 decreased by 63%, and the decrease in membrane flux was alleviated by 27%, indicating that Example 2 significantly improved the anti-biological fouling ability of the membrane in the actual secondary effluent dynamic filtration.

[0037] Table 3 illustrates the changes in the EPS (protein, polysaccharide, eDNA) of the fouling layer on the membrane surface. Compared with the original membrane, Example 2 has an obvious inhibitory effect on the EPS components. After fouling, the contents of protein, polysaccharide, and eDNA on the surface of the original membrane were 114 μg / cm 2 、37 μg / cm 2 、39 ng / cm 2 , indicating that protein is the main component of EPS on the fouled membrane surface. Example 2 reduced the contents of protein, polysaccharide, and eDNA on the fouled membrane surface by 42.97%, 40.4%, and 51.0% respectively. Example 2 has high hydrophilicity and negative charge. At the same time, the quorum sensing interference effect of QSI on microorganisms will also reduce the EPS content on the fouled membrane surface, thus significantly alleviating the decrease in membrane flux in the actual secondary effluent dynamic filtration.

[0038] Table 3

[0039]

[0040] It should be noted that the above embodiments are exemplary and should not be construed as limitations of the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A quorum sensing inhibitor-modified ultrafiltration membrane, its preparation method and application, characterized in that, It includes the following steps: (1) Hydrophilic monomer grafting The ultrafiltration membrane is immersed in an absolute ethanol solution containing the photoinitiator benzophenone (BP) for a period of time and then taken out. After removing the excess ethanol solution, the membrane is exposed to ultraviolet light for a certain time and dried in air. The membrane is immersed in an aqueous solution of the hydrophilic grafting monomer for a period of time and then irradiated with ultraviolet light for a certain time. (2) Preparation of quorum sensing inhibitor-modified ultrafiltration membrane The membrane grafted with the hydrophilic monomer is immersed in an aqueous solution containing 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) and stirred to activate the carboxyl group of the monomer. The quorum sensing inhibitor is added to the solution and stirred at room temperature for a certain time. The prepared modified membrane is stored in deionized water. In the present invention, the quorum sensing inhibitor-modified ultrafiltration membrane can be used to alleviate membrane surface biofouling and has broad application prospects.

2. The preparation method according to claim 1, characterized in that In step (1), the types of ultrafiltration membranes include polysulfone, polyethersulfone membranes, etc.

3. The preparation method according to claim 1, wherein In step (1), the concentration of the photoinitiator BP solution is 1-10 mM.

4. The preparation method according to claim 1, characterized in that In step (1), the immersion time of the ultrafiltration membrane in the BP solution is 60-120 min, and the ultraviolet light irradiation time is 5-20 min.

5. The preparation method according to claim 1, characterized in that In step (1), the hydrophilic grafting monomer is one of maleic anhydride and acrylic acid. Preferably, its addition amount is 20-60 g / L.

6. The preparation method according to claim 1, characterized in that In step (1), the immersion time of the ultrafiltration membrane in the aqueous solution of the hydrophilic grafting monomer is 5-20 min, and the ultraviolet light irradiation time is 5-20 min.

7. The preparation method according to claim 1, characterized in that In step (2), the concentration of EDC is 1-3 mM, the concentration of NHS is 1-10 mM, and the stirring time is 5-15 min to activate the carboxyl group of the monomer.

8. The preparation method according to claim 1, wherein The quorum sensing inhibitor in step (2) is one of quorum sensing inhibitors containing amino functional groups such as methyl anthranilate (MA) and 2-amino-6-fluorobenzoic acid (6F-ABA); preferably, its addition amount is 10-40 mM.

9. The preparation method according to claim 1, wherein In step (2), the stirring time is 12-36 h to allow the carboxyl group of the hydrophilic monomer to fully react with the amino group of the quorum sensing inhibitor and graft it onto the membrane surface.

10. Use of the quorum sensing inhibitor-modified ultrafiltration membrane according to any one of claims 1-9, characterized in that, This membrane is used to alleviate membrane surface biofouling.

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