Mildew-proof hollow filter membrane with synergic targeted adsorption and physical wall breaking of nanowhiskers and preparation method of mildew-proof hollow filter membrane

Abstract

The invention belongs to the technical field of water treatment, and particularly relates to a mildew-proof hollow filtering membrane with synergism of targeted adsorption and physical wall breaking of nanowhiskers and a preparation method, the preparation method comprises the following steps: S1, dissolving chitosan in an acid solution to partially degrade a molecular chain of the chitosan, and stirring until the chitosan is dissolved to form a uniform chitosan solution; s2, immersing a hollow fiber base membrane into the chitosan solution in the S1, dropwise adding an alkaline solution to adjust the system to an alkaline condition, so that chitosan molecular chains are directionally arranged, and forming chitosan nanowhiskers on the surface of the hollow fiber base membrane; s3, placing the solution system in S2 in a crystallization container, and controlling conditions for cooling crystallization; s4, separating the crystallized hollow fiber base membrane from the solution to obtain the mildew-proof hollow filter membrane loaded with the chitosan nanowhiskers. According to the invention, the targeting adsorption function of chitosan is combined with the physical wall breaking function of nanowhiskers, so that the long-term reliability of the membrane material under a complex water quality condition is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fiber filtration membrane, and particularly relates to a mildew-proof hollow filtration membrane with targeted adsorption and nanowhisker physical wall breaking cooperation and a preparation method. BACKGROUND

[0002] Hollow fiber filtration membranes have been widely used in water treatment, biological medicine and other fields due to their high separation efficiency and compact structure characteristics. The existing technology mainly realizes the antibacterial function by surface grafting of antibacterial groups such as quaternary ammonium salt, metal nanoparticles, or introduction of photocatalytic materials such as TiO2, and there are also studies on using physical screening combined with charge repulsion to block microorganisms. However, in the face of smaller mold spores, the conventional membrane material is prone to biological fouling, and the conventional antibacterial agent is difficult to continuously inhibit the formation of mold biofilm.

[0003] The current mildew-proof technology has three limitations: first, physical cleaning cannot destroy the structure of the bacteria attached in the membrane holes, and the residues of chemical cleaning agents can easily cause secondary pollution; second, the supported antibacterial agent has a slow-release failure problem, the silver-based antibacterial agent has biological toxicity, and the photocatalytic material requires specific light conditions; third, the existing modification methods mainly focus on a single sterilization mechanism, and cannot simultaneously achieve targeted capture and structure destruction of mold, resulting in insufficient sterilization timeliness and thoroughness, especially for mold with formed biofilm. SUMMARY

[0004] The purpose of the present application is to overcome the deficiencies in the prior art, and to provide a hollow fiber filtration membrane with high efficiency adsorption and structure destruction functions for mold, which realizes targeted enrichment by surface modification of specific adsorption groups for mold, and destroys the mold cell wall / spore structure by using the physical puncture effect of nanowhiskers, so as to solve the problems of incomplete sterilization, chemical residues and insufficient antibiofilm ability in the conventional technology, and to avoid the dependence on chemical sterilizing agents or light conditions, thereby improving the long-term antibacterial property and environmental safety of the membrane material.

[0005] The technical scheme adopted by the present application to solve its technical problems is to provide a preparation method of a mildew-proof hollow filtration membrane with targeted adsorption and nanowhisker physical wall breaking cooperation, comprising the following steps: S1, dissolving chitosan in an acidic solution to partially degrade the chitosan molecular chain, and stirring to form a uniform chitosan solution; S2, immersing the hollow fiber base membrane in the chitosan solution of S1, and adding an alkaline solution to adjust the system to alkaline conditions, so that the chitosan molecular chain is arranged in a specific direction, and chitosan nanowhiskers are formed on the surface of the hollow fiber base membrane; S3, placing the solution system of S2 in a crystallization container, and controlling the conditions to perform cooling crystallization; S4, separating the crystallized hollow fiber base membrane from the solution to obtain a mildew-proof hollow filtration membrane loaded with chitosan nanowhiskers.

[0006] Further, the deacetylation degree of the chitosan in S1 is greater than or equal to 90%, the acid solution is an acetic acid solution, the concentration of the acid solution is 1-2% V / V, the stirring speed is 300-500 rpm, the chitosan concentration of the solution obtained in S1 is 2-5% wt, and the pH value is 2-3.

[0007] Further, the basic solution in S2 is a NaOH solution, the concentration of the basic solution is 5-10%, and the pH value of the solution is adjusted to 8-10 after the basic solution is added.

[0008] Further, the procedure of the temperature reduction and crystallization in S3 is as follows: under the condition of 50-100 RPM stirring, the temperature of the system is uniformly reduced to 25 DEG C at a rate of 0.3-0.8 DEG C / min after being adjusted to the alkaline condition, and the crystallization is carried out at 25 DEG C for 12-24 h.

[0009] Further, the vacuum filtration is used in S4, the vacuum pressure is 0.05-0.08 Mpa, and the filtration time is 18-22 min.

[0010] Further, the vacuum drying step is further included after S4.

[0011] Further, the vacuum drying temperature is 40-60 DEG C, and the drying time is 2-4 h.

[0012] The application further provides a mold-proof hollow filter membrane which is targeted to adsorption and physical wall breaking of nanowhiskers, comprising a hollow fiber membrane substrate and a functional layer loaded on the surface of the substrate; the functional layer is composed of chitosan molecular chains and chitosan nanowhiskers, the chitosan molecular chains are specifically adsorbed to mold through hydrogen bonds and electrostatic interaction, and the chitosan nanowhiskers have the structural characteristics of physically piercing mold cell walls or spores; the deacetylation degree of the chitosan is greater than 90%, the diameter of the chitosan nanowhiskers is 50-200 nm, and the length is 1-5 um.

[0013] Further, the material of the hollow fiber membrane substrate is polysulfone, polyether sulfone or polyvinylidene fluoride; and the pore size of the hollow fiber membrane substrate is 0.01-0.2 um.

[0014] The application has the following beneficial effects:

[0015] 1. The application combines the targeted adsorption function of chitosan with the physical wall breaking function of nanowhiskers, constructs a microstructure with capturing and destroying functions on the membrane surface, so that mold spores are quickly adsorbed and physically pierced as soon as they contact the membrane surface, thereby breaking through the limitation of the traditional single sterilization mechanism, realizing the efficient and durable mold-proof effect of the hollow fiber filter membrane, and improving the long-term reliability of the membrane material under complex water quality conditions.

[0016] 2. Compared with the prior art, the application does not need to rely on chemical fungicides or external light conditions, avoids the risks of chemical residues and biological toxicity, and reduces the operation cost caused by frequent replacement of filter components.

[0017] 3. The chitosan and the whisker thereof are both natural degradable polymer materials, can be completely biodegraded while achieving the antifungal function, meet the green environmental protection requirements, have mild preparation process conditions, simple process, good industrial application prospect, and provide a safe, efficient and sustainable antifungal solution for the fields of water treatment, biological medicine, food fermentation and the like. DETAILED DESCRIPTION

[0018] The technical solutions of the application will be described clearly and completely in combination with the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0019] Embodiment 1: 30 g of chitosan with a degree of deacetylation of 95% is added into 1000 mL of 1.5% acetic acid solution, stirred and dissolved at a speed of 400 rpm to form a uniform solution with a concentration of 3 wt%, and the pH is adjusted to 2.5 to partially degrade the molecular chain. A hollow fiber base film made of polysulfone material and having a pore size of 0.1 μm is immersed in the solution, 8% sodium hydroxide solution is added dropwise to the system until the pH is 9.0, and the chitosan is directionally arranged by immersing for 45 minutes. The system is transferred to a crystallization container, cooled to 25℃ at a rate of 0.5℃ / min, and crystallized for 18 hours under constant temperature and stirring at a speed of 70 rpm. The product is separated by vacuum filtration, the pressure is controlled to be 0.06 MPa, and the filtration is performed for 20 minutes. Finally, the product is vacuum dried at 50℃ for 3 hours to obtain an antifungal hollow filtration membrane with the functions of targeted adsorption and nanowhisker physical wall breaking.

[0020] Embodiment 2: 25 g of chitosan with a degree of deacetylation of 99% is added into 750 mL of 1% acetic acid solution, dissolved at a speed of 350 rpm to form a solution with a concentration of 3.3 wt%, and the pH is adjusted to 2.2. A polyether sulfone base film is immersed, 10% sodium hydroxide solution is added dropwise to the system until the pH is 10.0, and the chitosan is directionally arranged by immersing for 30 minutes. The system is cooled to 25℃ at a rate of 0.3℃ / min, and crystallized for 24 hours under stirring at a speed of 50 rpm. The product is separated by vacuum filtration, the pressure is controlled to be 0.05 MPa, and the filtration is performed for 22 minutes. The product is vacuum dried at 60℃ for 2 hours to obtain an antifungal hollow filtration membrane with the functions of targeted adsorption and nanowhisker physical wall breaking.

[0021] Example 3: Take the degree of deacetylation of 92% of chitosan 40g, 2% acetic acid solution 1200mL, dissolved into a concentration of 3.3wt% solution with 450rpm rotation speed, adjust the pH to 2.8. Immersed in polyvinylidene fluoride base film, drop 5% sodium hydroxide solution to pH 8.0, soak for 60 minutes. Cooling rate of 0.8℃ / min to 25℃, stirring under 100rpm for 12 hours. Vacuum filtration pressure of 0.08MPa, filtration for 18 minutes. 40℃ vacuum drying for 4 hours, get the moldproof hollow filter membrane which target adsorption and nanowhisker physical wall breaking synergy.

[0022] Example 4: Take the degree of deacetylation of 96% of chitosan 20g, 1.2% acetic acid solution 800mL, dissolved into a concentration of 2.5wt% solution with 300rpm rotation speed, adjust the pH to 2.0. Immersed in polysulfone base film, drop 7% sodium hydroxide solution to pH 8.5, soak for 50 minutes. Cooling rate of 0.4℃ / min to 25℃, stirring under 80rpm for 20 hours. Vacuum filtration pressure of 0.07MPa, filtration for 19 minutes. 55℃ vacuum drying for 2.5 hours, get the moldproof hollow filter membrane which target adsorption and nanowhisker physical wall breaking synergy.

[0023] Example 5: Take the degree of deacetylation of 98% of chitosan 35g, 1.8% acetic acid solution 900mL, dissolved into a concentration of 3.9wt% solution with 500rpm rotation speed, adjust the pH to 3.0. Immersed in polyethersulfone base film, drop 9% sodium hydroxide solution to pH 9.5, soak for 40 minutes. Cooling rate of 0.6℃ / min to 25℃, stirring under 90rpm for 15 hours. Vacuum filtration pressure of 0.065MPa, filtration for 21 minutes. 45℃ vacuum drying for 3.5 hours, get the moldproof hollow filter membrane which target adsorption and nanowhisker physical wall breaking synergy.

[0024] Example 6: Take the degree of deacetylation of 94% of chitosan 28g, 1.3% acetic acid solution 700mL, dissolved into a concentration of 4wt% solution with 380rpm rotation speed, adjust the pH to 2.3. Immersed in polyvinylidene fluoride base film, drop 6% sodium hydroxide solution to pH 8.8, soak for 55 minutes. Cooling rate of 0.7℃ / min to 25℃, stirring under 65rpm for 22 hours. Vacuum filtration pressure of 0.055MPa, filtration for 20 minutes. 52℃ vacuum drying for 2.2 hours, get the moldproof hollow filter membrane which target adsorption and nanowhisker physical wall breaking synergy.

[0025] Example 7: Take deacetylation degree of 97% of chitosan 32g, 1.7% acetic acid solution 850mL, dissolved into a concentration of 3.8wt% solution at a speed of 420rpm, adjust the pH to 2.6. Immersed in polysulfone base film, drop 8.5% sodium hydroxide solution to pH 9.2, soak for 35 minutes. Cooling rate of 0.45℃ / min to 25℃, stirring at 75rpm for 16 hours. Vacuum filtration pressure 0.075MPa, filtration for 18.5 minutes. Vacuum drying at 48℃ for 3.2 hours, get the targeted adsorption and nanowhisker physical wall breaking synergistic antifungal hollow filtration membrane.

[0026] Example 8: Take deacetylation degree of 93% of chitosan 45g, 2% acetic acid solution 1500mL, dissolved into a concentration of 3wt% solution at a speed of 480rpm, adjust the pH to 2.9. Immersed in polyether sulfone base film, drop 7.5% sodium hydroxide solution to pH 8.2, soak for 42 minutes. Cooling rate of 0.55℃ / min to 25℃, stirring at 85rpm for 14 hours. Vacuum filtration pressure 0.062MPa, filtration for 19.5 minutes. Vacuum drying at 58℃ for 2.8 hours, get the targeted adsorption and nanowhisker physical wall breaking synergistic antifungal hollow filtration membrane.

[0027] Table 1 is the performance test table of the targeted adsorption and nanowhisker physical wall breaking synergistic antifungal hollow filtration membrane prepared in example 1 to example 8.

[0028]

[0029] Table 1 data shows that the targeted adsorption and nanowhisker physical wall breaking synergistic antifungal hollow filtration membrane prepared in example 1 to 8, whether the base film material is polysulfone, polyether sulfone or polyvinylidene fluoride, the mold inhibition rate of aspergillus niger, penicillium, chaetomium globosum and other molds is more than 99%, the physical wall breaking effect is remarkable, the spore perforation rate and hypha collapse rate are high, and the strength retention rate can still reach more than 96.8% after 10 times of cleaning.

[0030] The present application combines the targeted adsorption function of chitosan with the physical wall breaking function of nanowhisker, breaks through the limitation of traditional single sterilization mechanism, realizes efficient and durable antifungal of hollow fiber filtration membrane, and improves the long-term reliability of membrane material under complex water quality conditions; without relying on chemical sterilizing agent or external light condition, avoiding chemical residue and biological toxicity risk, at the same time, reducing the operation cost caused by frequent replacement of filtration components; chitosan and whisker are natural degradable polymer materials, which meet the green environmental protection requirements, and the preparation process conditions are mild and simple, which is easy to scale production, and has good industrial application prospect in the fields of water treatment, biological medicine and food fermentation.

[0031] Although the present application has been described in detail with reference to the foregoing embodiments, the technical solutions recorded in the foregoing embodiments can be modified, or some of the technical features can be replaced by equivalent features, by those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a mildew-proof hollow filtration membrane with synergistic effects of targeted adsorption and nanowhisker physical wall breaking, characterized in that: The following steps are involved: S1. dissolving chitosan in an acidic solution to partially degrade the chitosan molecular chain, and stirring until the chitosan solution is dissolved to form a uniform chitosan solution; S2, immersing the hollow fiber base membrane in the chitosan solution of S1, and adding alkaline solution to adjust the system to alkaline conditions, so that the chitosan molecular chains are oriented and chitosan nanowhiskers are formed on the surface of the hollow fiber base membrane; S3, placing the solution system of S2 in a crystallization container, and controlling the conditions to perform cooling crystallization; S4. Separating the crystallized hollow fiber-based membrane from the solution to obtain a mildew-proof hollow filtration membrane loaded with chitosan nanowhiskers.

2. The method for preparing a mildew-proof hollow filtration membrane with coordinated targeted adsorption and nanowhisker physical wall breaking according to claim 1, characterized in that: The chitosan in S1 has a deacetylation degree of ≥90%, the acidic solution is an acetic acid solution, and the concentration of the acidic solution is 1-2% V / V; the stirring speed is 300-500 rpm; The chitosan concentration of the solution obtained in S1 is 2-5%wt and the pH value is 2-3.

3. The method for preparing a mildew-proof hollow filtration membrane with coordinated targeted adsorption and nanowhisker physical wall breaking according to claim 1, characterized in that: The alkaline solution in S2 is a NaOH solution, and the concentration of the alkaline solution is 5-10%; After adding alkaline solution, the pH of the solution was adjusted to 8-10.

4. The method for preparing a mildew-proof hollow filtration membrane with coordinated targeted adsorption and nanowhisker physical wall breaking according to claim 1, characterized in that: The procedure for cooling crystallization in S3 is as follows: under stirring at 50-100 RPM, after adjusting the system temperature to alkaline conditions, the temperature is uniformly cooled at a rate of 0.3-0.8°C / min to the crystallization temperature of 25°C, and crystallization is carried out at a constant temperature of 25°C for 12-24 hours.

5. The method for preparing a mildew-proof hollow filtration membrane with coordinated targeted adsorption and nanowhisker physical wall breaking according to claim 1, characterized in that: S4 separation adopts vacuum filtration method, the vacuum pressure is 0.05-0.08Mpa, and the filtration time is 18-22min.

6. The method for preparing a mildew-proof hollow filtration membrane with coordinated targeted adsorption and nanowhisker physical wall breaking according to claim 1, characterized in that: S4 also includes a vacuum drying step after separation.

7. The method for preparing a mildew-proof hollow filtration membrane with coordinated targeted adsorption and nanowhisker physical wall breaking according to claim 6, characterized in that: The vacuum drying temperature is 40-60° C., and the drying time is 2-4 hours.

8. A mildew-proof hollow filtration membrane prepared by the method according to any one of claims 1 to 7, characterized in that: The invention comprises a hollow fiber membrane substrate and a functional layer supported on the surface of the substrate; the functional layer is composed of chitosan molecular chains and chitosan nanowhiskers. The chitosan molecular chains specifically adsorb molds through hydrogen bonds and electrostatic effects, and the chitosan nanowhiskers have the structural characteristics of physically puncturing mold cell walls or spores. The deacetylation degree of chitosan is greater than 90%, and the diameter of the chitosan nanowhiskers is 50-200nm and the length is 1-5μm.

9. The mold-proof hollow filtration membrane with targeted adsorption and nanowhisker physical wall breaking according to claim 8, characterized in that: The hollow fiber membrane substrate is made of polysulfone, polyethersulfone or polyvinylidene fluoride; the pore size of the hollow fiber membrane substrate is 0.01-0.2 μm.

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