CN114669197B - Preparation method of modified polyamide composite membrane capable of resisting organic matter pollution and microbial adhesion - Google Patents

Preparation method of modified polyamide composite membrane capable of resisting organic matter pollution and microbial adhesion Download PDF

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CN114669197B
CN114669197B CN202210264502.XA CN202210264502A CN114669197B CN 114669197 B CN114669197 B CN 114669197B CN 202210264502 A CN202210264502 A CN 202210264502A CN 114669197 B CN114669197 B CN 114669197B
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王志宁
张娇娇
张娜
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Shandong University
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    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
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    • B01D69/125—In situ manufacturing by polymerisation, polycondensation, cross-linking or chemical reaction
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    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
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Abstract

The invention relates to a preparation method of a modified polyamide composite membrane resisting organic matter pollution and microorganism adhesion, which comprises the steps of firstly activating an original TFC membrane by using an activating solution, then performing first-step grafting modification by using PAMAM/PDA grafting solution, and finally performing grafting modification by using TOCNs grafting solution; greatly improves the hydrophilicity and the anti-fouling performance of the surface of the TFC membrane, and compared with the traditional modification method, the chemical grafting method ensures that the modified macromolecule has stronger stability and is not easy to fall off. The TOCN has strong hydrophilicity and excellent organic matter pollution resistance and bacterial adhesion performance, and the preparation method has the advantages of low cost, environmental friendliness and simple process.

Description

Preparation method of modified polyamide composite membrane capable of resisting organic matter pollution and microbial adhesion
Technical Field
The invention relates to a preparation method of a modified polyamide composite membrane for resisting organic matter pollution and microbial adhesion, belonging to the technical field of membrane preparation.
Background
Membrane separation technology has received a great deal of attention in the fields of food processing, sea water desalination and wastewater treatment. In particular, the preparation technology of the polyamide composite membrane (TFC) is relatively mature and has wide application. Although the separation performance of TFC membranes is greatly improved, the inherent surface properties (e.g., hydrophilicity, roughness, etc.) of the polyamide layer result in a membrane having a high tendency to membrane fouling, which can seriously affect the permeation performance of the membrane over long periods of time, and thus membrane fouling remains one of the major concerns for the wide application of TFC membranes. Therefore, further regulation or modification of the TFC membrane surface is required to alleviate and avoid adhesion and deposition of contaminants and microorganisms on the membrane surface, thereby providing long-term stable performance in practical applications.
The polyamide-amine (PAMAM) dendrimer has a radially symmetric hyperbranched structure and has more amine groups and a stable molecular structure on its dendrimer surface than other macromolecules, wherein the number of terminal amine groups in the PAMAM dendrimer increases exponentially with its algebra (2 n+2 N is tree-like macromolecular algebra). In addition, the abundant terminal amine groups are used as ideal active centers and grafted to the surface of the TFC membrane layer through chemical reaction, and more hydrophilic groups can improve the hydrophilicity of the membrane surface.
Cellulose Nanocrystals (CNC) are natural and environment-friendly nano materials with high biodegradability, high mechanical strength and low cost, and can be obtained from various renewable biomasses such as cotton and the like. CNC has excellent mechanical properties and has been demonstrated to increase the Young's modulus and elastic modulus of the nanocomposite. CNC a carboxylated nanocellulose (TOCN) obtained by tetramethyl piperidine-1-oxyl (TEMPO) oxidation treatment. The surface of TOCN has a large number of carboxyl (-COOH) groups, and therefore TOCN has high hydrophilicity. In addition, since the carboxyl groups of the TOCN fiber surface with high density are negatively charged in water, electrostatic repulsive force generated in water can effectively prevent aggregation of molecules, thereby forming a uniform dispersion. TOCN has the basic structure and characteristic of natural cellulose and the characteristic of nano material. As hydrophilic nanomaterials, TOCN can be used to improve the hydrophilicity, permeability and resistance to fouling of separation membranes.
At present, membrane pollution is an important problem in the membrane separation process, and due to natural organic pollutants and microorganisms with certain concentration in feed liquid, after the membrane is used for a period of time, the pollutants can adhere to the surface of the membrane, cause biological pollution and accumulation and the like, even block membrane holes, increase permeation resistance and reduce water flux, further cause the performances of membrane such as permeation separation property, stability and the like to be drastically reduced, increase operation cost and shorten the service life of the membrane. Thus for TFC membranes, the active layer of the membrane determines the overall permeability, selectivity and antifouling properties.
In order to improve the pollution resistance of TFC membranes, it has been reported that a hydrophilic pollution-resistant layer, such as CN1213985a, is coated on the surface of the TFC membrane by a surface coating method, PVA is coated on the surface of the reverse osmosis membrane, and the PVA has electric neutrality, and can inhibit electrostatic adsorption of charged pollutant in the feed solution; however, in the surface coating method, the applied hydrophilic anti-pollution layer and the TFC film active layer have no acting force of chemical bonds, and in the using process of the film material, the hydrophilic anti-pollution layer is gradually dissolved in water under the hydraulic shearing action of the feed liquid to fall off, and finally the effect of the protective layer is lost; CN104028118B also discloses a polyamide reverse osmosis membrane containing amphoteric sodium carboxymethyl cellulose complex, which is obtained by adding a zwitterionic polymer (prepared from an amphoteric cationic polymer and sodium carboxymethyl cellulose) as a modifier into an aqueous monomer solution, and embedding the zwitterionic polymer into the polyamide layer after interfacial polymerization. However, these TFC membranes still have drawbacks in terms of desalination rate and water production flux, and it is difficult to satisfy the requirements of high desalination rate, high flux, and good anti-contamination performance.
Therefore, there is a need to develop a modified polyamide composite membrane with strong anti-fouling capability and long service life.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a preparation method of a modified polyamide composite membrane for resisting organic matter pollution and microorganism adhesion.
The technical scheme of the invention is as follows:
the preparation method of the modified polyamide composite membrane for resisting organic matter pollution and microorganism adhesion comprises the following steps:
(1) TFC membrane activation
Contacting the activating solution with an active layer of the TFC membrane, soaking the active layer of the TFC membrane for 1-10h, pouring out the liquid on the surface of the membrane, naturally airing at room temperature, and thoroughly flushing the surface of the membrane with deionized water to obtain the activated TFC membrane;
(2) First step grafting modification
The PAMAM/PDA grafting liquid is contacted with the activated TFC membrane, the surface liquid of the membrane is poured out after soaking for 5-30min, the membrane is naturally dried at room temperature, and then the surface of the membrane is thoroughly washed by deionized water, so that the first step of grafting modification is completed;
(3) Second step of grafting modification
Pouring TOCNs grafting liquid on the surface of the membrane subjected to the first step grafting modification, soaking for 1-5h, pouring out the liquid on the surface of the membrane, and flushing the surface of the membrane with deionized water; obtaining the modified polyamide composite membrane with the functions of resisting organic pollution and microbial adhesion.
According to the invention, in the step (1), the activating solution is prepared by the following method:
dissolving sodium chloride (NaCl) and 2-morpholinoethanesulfonic acid (MES) in deionized water to prepare a buffer solution, adjusting the pH of the buffer solution to 4-7 by adopting 1M hydrochloric acid and 1M sodium hydroxide solution, dissolving carbodiimide (EDC) and N-hydroxysuccinimide (NHS) in the buffer solution, and uniformly mixing to obtain an activation solution.
Further preferably, the concentration of NaCl in the buffer is 0.1 to 1M and the concentration of 2-morpholinoethanesulfonic acid MES is 1 to 100mM.
Further preferably, the concentration of EDC in the activating solution is 2-6mM and the concentration of NHS is 1-100mM.
According to the invention, in the step (2), the PAMAM/PDA grafting solution is prepared by the following method:
dissolving Dopamine (DA) in Tris-HCl buffer solution, stirring for 5-10min to obtain Polydopamine (PDA) solution, mixing and stirring the PDA solution and PAMAM grafting solution for 1-3h to obtain PAMAM/PDA grafting solution.
Further preferably, the DA concentration by mass in the PDA solution is 0.1-2%, the Tris-HCl buffer solution concentration is 5-100 mmol/L, and the pH is 6-10.
Further preferably, the PAMAM grafting solution is a solution obtained by dissolving PAMAM in deionized water and stirring for 2-10h, and the mass concentration of the PAMAM grafting solution is 0.1-2%.
It is further preferred that the PDA solution and PAMAM grafting solution be mixed in a volume ratio of (1-2): 1-2.
According to the invention, in the step (3), the TOCNs grafting liquid is prepared according to the following method:
dissolving MES in deionized water to prepare MES buffer solution, and then dissolving EDC and NHS in the MES buffer solution to obtain mixed solution A; taking TOCN suspension, performing water bath ultrasonic treatment for 20-60min, then performing magnetic stirring for 30-60min, and mixing the mixed solution A with the TOCN suspension to obtain TOCNs grafting liquid.
More preferably, the MES buffer has a concentration of 50 to 400mM and a pH of 4 to 7.
Further preferably, the EDC concentration in the mixture A is 0.2 to 2mM and the NHS concentration is 0.2 to 5mM.
Further preferred, the TOCN suspension has a mass concentration of 0.1-2%.
Further preferably, the mixed solution A is mixed with TOCN suspension according to the volume ratio of (1-2), and the pH of TOCNs grafting liquid is 6-10.
The modified TFC membrane of the invention adopts an activating solution to activate an original TFC membrane, adopts PAMAM/PDA grafting solution to carry out first-step grafting modification, and adopts TOCNs grafting solution to carry out second-step grafting modification, thus obtaining the modified TFC membrane with strong anti-fouling capability; in the activating solution, the MES buffer solution keeps the reaction system at constant pH, EDC in the activating solution reacts with carboxyl to form an unstable acyl urea intermediate, and then reacts with NHS to form more stable ester;
in the preparation process of PAMAM/PDA grafting liquid, tris-HCl buffer solution enables the reaction system to maintain constant pH, and PAMAM and PDA are mixed to carry out Michael addition coupling reaction to form larger hydrophilic molecules, so that the PAMAM and PDA are prevented from entering membrane pores. In TOCNs grafting solution, MES buffer solution maintains the reaction system at constant pH, EDC in mixed solution A mainly reacts with carboxyl of TOCN to form acyl urea intermediate, and then reacts with NHS to form more stable ester, so that the reaction with amino is facilitated; in the first grafting modification, nucleophilic substitution is carried out on the terminal amino group of the PAMAM macromolecule and NHS ester to form an amide bond on the surface of the membrane. In the second step of grafting modification, nucleophilic substitution is carried out on TOCNs grafting liquid and the amino remained on the surface of the first step of modified membrane so as to successfully graft. Because TOCN contains a large amount of carboxyl and hydroxyl, the hydrophilicity of the surface of the TFC film is obviously increased, and the adhesion of the film to dirt and bacteria is greatly reduced, so that the organic matter pollution resistance and the bacterial adhesion resistance of the TFC film are improved.
The modified polyamide composite membrane capable of resisting organic matter pollution and microorganism adhesion is prepared by adopting the method.
Compared with the prior art, the modified polyamide composite membrane for resisting organic matter pollution and microbial adhesion has the following excellent effects:
1. the method comprises the steps of firstly activating an original TFC membrane by using an activating solution, then performing a first-step grafting modification by using PAMAM/PDA grafting solution, and finally performing a grafting modification by using TOCNs grafting solution; firstly, PAMAM with rich terminal amino groups is modified on the surface of a TFC membrane, grafting sites on the surface of the TFC membrane are increased, and then TOCN is grafted on the surface of the membrane through nucleophilic substitution, so that the hydrophilicity and the anti-fouling performance of the surface of the TFC membrane are greatly improved, and compared with the traditional modification method, the modified macromolecule has stronger stability and is not easy to fall off due to the chemical grafting method. And TOCN has strong hydrophilicity, so that the hydrophilicity of the surface of the TFC film is obviously increased, thereby reducing acting force between pollutants and the surface of the film, and thus, the modified TFC film with strong pollution resistance is obtained.
2. The invention adopts two-step grafting method which is realized by nucleophilic substitution chemical reaction, and compared with the traditional modification method, the modified macromolecule has stronger stability and is not easy to fall off due to the chemical grafting method. And the TFC film obtained after the modification has rich negative charges, thereby enhancing the surface electronegativity of the TFC film. Because most of pollutants and bacteria in the sewage are negatively charged, the pollutants and the bacteria are not easy to adhere and accumulate on the surface of the TFC membrane with strong electronegativity due to the action of electrostatic repulsive force, and the anti-fouling performance of the TFC membrane is obviously improved.
3. The modified TFC membrane prepared by the invention has excellent organic pollution resistance and antibacterial adhesion resistance, can effectively prevent organic pollutants and bacteria from adhering and accumulating on the surface of the membrane, and prolongs the service life of the membrane.
Drawings
FIG. 1 is an initial water contact angle of the original TFC membrane of example 1 with a TFC membrane after two-step graft modification.
Detailed Description
The present invention is further illustrated by the following examples, but the scope of the present invention is not limited thereto.
Carboxylated cellulose nanocrystals (TOCN) in the examples were supplied by the Sijin Wood-Elfin Biotechnology Co. The length of carboxylated cellulose nanocrystals (TOCN) provided by the company is 150-200 nm, and the diameter of the rod-shaped cellulose is below 100 nm.
Example 1:
the preparation process of modified polyamide composite film with the functions of resisting organic matter pollution and adhering microbe includes the following steps:
(1) Preparing an activating solution:
dissolving sodium chloride (NaCl) and 2-morpholinoethanesulfonic acid (MES) in deionized water to prepare a buffer solution, adjusting the pH of the buffer solution to 5.0 by adopting 1M hydrochloric acid (HCl) and 1M sodium hydroxide (NaOH) solution, dissolving carbodiimide (EDC) and N-hydroxysuccinimide (NHS) in the buffer solution, and uniformly mixing to obtain an activating solution;
the concentration of NaCl in the buffer is 0.5M, the concentration of MES is 10mM, the concentration of EDC in the activation solution is 4mM, and the concentration of NHS in the activation solution is 10mM;
(2) Preparation of grafting liquid:
PAMAM/PDA grafting fluid: 1wt% pamam solution and 1.2wt% pda solution in a volume ratio of 1:1, mixing to prepare PAMAM/PDA grafting liquid;
TOCNs grafting liquid: MES is weighed and dissolved in deionized water to prepare MES buffer solution with the concentration of 100mM, the pH value is regulated to 6.2, 72mg of EDC and 72mg of NHS are respectively weighed and dissolved in the MES buffer solution to obtain mixed solution A, the concentration of EDC in the mixed solution A is 1mM, the concentration of NHS in the mixed solution A is 1mM, 50ml of TOCN suspension is firstly subjected to water bath ultrasonic treatment for 20min, then magnetic stirring is carried out for 30min, and then the mixed solution A and the TOCN suspension are mixed according to the volume ratio of 1:1, mixing to obtain TOCNs grafting liquid, and then regulating the pH value to 7.2;
(3) TFC membrane activation
Fixing TFC membrane on a customized polytetrafluoroethylene membrane tool through a long tail clamp, protecting a supporting layer of the membrane, only modifying polyamide of an active layer, pouring an activation solution into the membrane tool to be in contact with the active layer of the membrane, pouring out liquid on the surface of the membrane after soaking for 1h, naturally airing at room temperature, thoroughly flushing the surface of the membrane with deionized water,
(4) First grafting step
Contacting PAMAM/PDA grafting liquid with an activated TFC membrane, soaking for 15min, pouring out liquid on the surface of the membrane, naturally airing at room temperature, and thoroughly flushing the surface of the membrane with deionized water to obtain the PAMAM/PDA membrane;
(5) Second grafting step
Pouring TOCNs grafting liquid into a PAMAM/PDA membrane, soaking for 2 hours, pouring out liquid on the surface of the membrane, thoroughly flushing the surface of the membrane with deionized water to obtain the PAMAM/PDA-TOCN membrane, and storing the PAMAM/PDA-TOCN membrane in deionized water at 4 ℃ for use.
Comparative example 1:
a preparation method of a modified polyamide composite membrane comprises the following steps:
(1) Preparing an activating solution:
dissolving sodium chloride (NaCl) and 2-morpholinoethanesulfonic acid (MES) in deionized water to prepare a buffer solution, adjusting the pH of the buffer solution to 5.0 by adopting 1M hydrochloric acid (HCl) and 1M sodium hydroxide (NaOH) solution, dissolving carbodiimide (EDC) and N-hydroxysuccinimide (NHS) in the buffer solution, and uniformly mixing to obtain an activating solution;
the concentration of NaCl in the buffer is 0.5M, the concentration of MES is 10mM, the concentration of EDC in the activation solution is 4mM, and the concentration of NHS in the activation solution is 10mM;
(2) Preparation of grafting liquid:
PAMAM grafting fluid: 0.5g PAMAM was dissolved in 99.5g deionized water and stirred for over 2 hours to form 0.5wt% PAMAM grafting solution.
(3) TFC membrane activation
The TFC membrane was fixed to a custom made polytetrafluoroethylene membrane by a long tail clip to protect the support layer of the membrane and only the active layer polyamide was modified. Pouring the activation solution in the step (1) into a membrane to be contacted with the membrane active layer, pouring out the liquid on the surface of the membrane after soaking for 1h, naturally airing at room temperature, and then thoroughly flushing the surface of the membrane by deionized water.
(4) Graft modification
And (3) contacting the PAMAM grafting liquid with the activated TFC membrane, soaking for 15min, pouring out the liquid on the surface of the membrane, naturally airing at room temperature, and thoroughly flushing the surface of the membrane with deionized water to obtain the PAMAM membrane.
Comparative example 2:
a preparation method of a modified polyamide composite membrane comprises the following steps:
(1) Preparing an activating solution:
dissolving sodium chloride (NaCl) and 2-morpholinoethanesulfonic acid (MES) in deionized water to prepare a buffer solution, adjusting the pH of the buffer solution to 5.0 by adopting 1M hydrochloric acid (HCl) and 1M sodium hydroxide (NaOH) solution, dissolving carbodiimide (EDC) and N-hydroxysuccinimide (NHS) in the buffer solution, and uniformly mixing to obtain an activating solution;
the concentration of NaCl in the buffer is 0.5M, the concentration of MES is 10mM, the concentration of EDC in the activation solution is 4mM, and the concentration of NHS in the activation solution is 10mM;
(2) Preparation of grafting liquid:
PAMAM/PDA grafting fluid: 1wt% pamam solution and 1.2wt% pda solution in a volume ratio of 1:1 are mixed to prepare PAMAM/PDA grafting liquid,
(3) TFC membrane activation
And fixing the TFC membrane on a customized polytetrafluoroethylene membrane through a long tail clamp, protecting a supporting layer of the membrane, only modifying polyamide of an active layer, pouring an activation solution into the membrane to be in contact with the active layer of the membrane, pouring out liquid on the surface of the membrane after soaking for 1h, naturally airing at room temperature, and thoroughly flushing the surface of the membrane with deionized water.
(4) Graft modification
Contacting PAMAM/PDA grafting liquid with the activated TFC membrane, soaking for 15min, pouring out the liquid on the surface of the membrane, naturally airing at room temperature, and thoroughly flushing the surface of the membrane with deionized water to obtain the PAMAM/PDA membrane;
application effect test
1. Changing the concentration of PDA solution in step (2) of comparative example 2 to make the concentration of PDA in PAMAM/PDA grafting solution be 0, 0.2, 0.4, 0.6 and 0.8wt% respectively, and finally obtaining different modified TFC membranes, namely: PAMAM membrane (comparative example 1), PAMAM/0.2% pda membrane, PAMAM/0.4% pda membrane, PAMAM/0.6% pda membrane, PAMAM/0.8% pda membrane, the original TFC membrane and the different modified TFC membranes were passed through a forward osmosis test device to test their basic split permeate properties.
The test method is as follows: the forward osmosis test device consists of two symmetrical rectangular membrane tanks, and the effective test area of the membrane component is 21cm 2 The feed solution uses 1L deionized water, the draw solution uses 1M NaCl solution, the temperature of the feed solution and the draw solution is kept at 25+/-0.5 ℃, the feed solution level faces the active layer of the TFC membrane, and the solution in the membrane pool and the solution storage tank circulate at a flow rate of 200mL/min through a peristaltic pump. After the TFC membrane is fixed on the membrane component, the instrument is operated for about 30 minutes, data are recorded after the operation is stable, a liquid storage tank for storing the drawing liquid is placed on an electronic balance, meanwhile, the conductivity of the feeding liquid is monitored by a conductivity meter, and the water flux and the reverse salt flux are calculated by automatically monitoring the mass change of the drawing liquid and the conductivity change of the feeding liquid. The water flux (J) of the original TFC membrane and the differently modified TFC membrane and the composite membrane of example 1 W LMH), reverse salt flux (J S gMH) and specific salt flux (J) S /J W ) The data are shown in table 1.
TABLE 1 Water flux, reverse salt flux and specific salt flux of original TFC Membrane and modified TFC Membrane
Figure BDA0003551105500000071
Figure BDA0003551105500000081
As can be seen from the above table, when the PAMAM-modified TFC membrane alone was used as the only one, the water flux was significantly reduced and the reverse salt was also significantly increased, and by changing the concentration of PDA in the PAMAM/PDA grafting solution in step (2) of comparative example 2, it can be seen that as the concentration of dopamine in the grafting solution was increased, the water flux and the reverse salt flux were gradually improved, and the concentration of PDA in the grafting solution was optimal at 0.6%, although the water flux was reduced compared to that of the original TFC membrane, the reverse salt flux and the specific salt flux were significantly lower than those of the original TFC membrane. The water flux of the PAMAM/PDA-TOCN membrane obtained by two-step grafting modification is equivalent to that of the original TFC membrane, and the reverse salt flux is obviously improved, so that the preparation method of the dendritic polyamide-cellulose nanocrystal modified polyamide composite membrane can effectively improve the separation performance of the membrane without sacrificing the permeability of the membrane.
2. Organic contamination test of the original TFC film and the modified TFC film of example 1
The test method is as follows: common organic pollutants are represented by Bovine Serum Albumin (BSA), humic Acid (HA) and Sodium Alginate (SA), respectively. Wherein the pollution experiment is mainly divided into four stages, a) an initial stabilization stage: deionized water is used as a feed liquid, 1M NaCl is used as a drawing liquid, and the running time is 2 hours; b) Pollution stage: the feed solution consists of 200mg/L BSA (SA or HA) organic pollutants, 20mM NaCl and 1mM NaHCO 3 Salt solution is composed, 1M NaCl is used as a drawing liquid, the circulating flow rate is 200mL/min, and the running time is 24h; c) And (3) cleaning: the feeding liquid and the drawing liquid are deionized water, the running time is 0.5h, and the circulating flow rate is 300mL/min; d) And (3) a recovery stage: consistent with the initial stabilization phase conditions. All the forward osmosis processes are that the active layer faces the feed liquid side, and the temperatures of the two sides are room temperature. ThenThe total flux reduction rate (FDR) and Flux Recovery Rate (FRR) were used to evaluate the fouling resistance of the modified TFC FO membranes, which is shown in table 2 for different contaminants:
TABLE 2 organic contamination resistance of TFC films
Figure BDA0003551105500000082
As can be seen from table 2, the PAMAM/PDA-TOCN membrane of the present invention has a lower water flux decline rate and a higher flux recovery rate for three different organic contaminants compared to the original TFC membrane, indicating that the dendritic polyamide-cellulose nanocrystal modified polyamide composite membrane prepared according to the present invention has excellent anti-fouling properties.
3. Antibacterial adhesion test of the original TFC membrane with the modified TFC membrane of example 1
The test method is as follows: staphylococcus aureus (ATCC 25923) was added to the sterilized LB broth and incubated on a constant temperature shaker (37 ℃,150 rpm) for 24h. Centrifuging the cultured Escherichia coli at 10000rpm for 10min, and diluting with sterilized 0.9% NaCl solution to a concentration of about 1.0X10 6 cfu/mL of bacterial suspension. Then, the membrane having an area of 2 cm. Times.2 cm was put into a conical flask containing the above-mentioned bacterial suspension, and incubated for 2 hours at 37℃in a constant temperature shaker. The membrane was then rinsed with 5ml of sterilized 0.9% NaCl solution and collected. 0.1mL of the collected solution was added to LB agar medium, and the mixture was spread uniformly with a spreading bar, and incubated at 37℃for 15 hours. The culture medium was taken out, colony counts were obtained by plate counting and the antibacterial adhesion rate was calculated, and the test results are shown in Table 3.
TABLE 3 antibacterial adhesion Properties of TFC films
Figure BDA0003551105500000091
As can be seen from the above table, compared with the original film, the antibacterial adhesion of the PAMAM/PDA-TOCN film of the invention is as high as 90.4%, because TOCN has strong hydrophilicity after two-step grafting, the hydrophilicity of the surface of the TFC film is obviously increased, and the adhesion of the film to dirt is very small, so that the modified film has excellent antibacterial adhesion performance, and can effectively inhibit the growth, propagation and accumulation of bacteria on the surface of the film.
Example 2:
the preparation method of the modified polyamide composite membrane for resisting organic matter pollution and microbial adhesion described in the embodiment 1 is different in that:
in the activating process of the TFC film in the step (3), the contact time of the activating solution and the surface of the film is 30min.
And (4) the contact time of the PAMAM/PDA grafting liquid and the surface of the film is 20min.
And (5) the contact time of the TOCNs grafting liquid and the surface of the membrane is 3h.
Example 3:
the preparation method of the modified polyamide composite membrane for resisting organic matter pollution and microbial adhesion described in the embodiment 1 is different in that:
in step (1), the concentration of NaCl in the buffer was 0.2M, MES was 8mM, EDC in the activation solution was 3mM, and NHS was 20mM.
Example 4:
the preparation method of the modified polyamide composite membrane for resisting organic matter pollution and microbial adhesion described in the embodiment 1 is different in that:
in step (1), the concentration of NaCl in the buffer was 1M, MES was 50mM, EDC in the activation solution was 6mM, and NHS was 50mM.
Example 5:
the preparation method of the modified polyamide composite membrane for resisting organic matter pollution and microbial adhesion described in the embodiment 1 is different in that:
in the step (2), 0.8wt% PAMAM solution and 0.8wt% PDA solution are mixed according to the volume ratio of 1:1 are mixed to prepare PAMAM/PDA grafting liquid.
Example 6:
the preparation method of the modified polyamide composite membrane for resisting organic matter pollution and microbial adhesion described in the embodiment 1 is different in that:
in the step (2), MES is weighed and dissolved in deionized water to prepare MES buffer solution with the concentration of 200mM, the pH value is adjusted to 6.2, EDC and NHS are respectively weighed and dissolved in the MES buffer solution to obtain a mixed solution A, wherein the concentration of EDC in the mixed solution A is 1.5mM, and the concentration of NHS in the mixed solution A is 2mM.

Claims (4)

1. The preparation method of the modified polyamide composite membrane for resisting organic matter pollution and microorganism adhesion comprises the following steps:
(1) Polyamide composite membrane (TFC) activation
Contacting the activation solution with an active layer of a polyamide composite membrane (TFC), soaking the polyamide active layer of the polyamide composite membrane (TFC), pouring out the surface liquid of the membrane after soaking for 1-10h, naturally airing at room temperature, and thoroughly flushing the surface of the membrane with deionized water to obtain the activated polyamide composite membrane (TFC);
the activating solution is prepared by the following steps:
dissolving sodium chloride (NaCl) and 2-morpholinoethanesulfonic acid (MES) in deionized water to prepare a buffer solution, adjusting the pH of the buffer solution to 4-7 by adopting 1M hydrochloric acid and 1M sodium hydroxide solution, dissolving carbodiimide (EDC) and N-hydroxysuccinimide (NHS) in the buffer solution, and uniformly mixing to obtain an activation solution;
(2) First step grafting modification
Contacting PAMAM/PDA grafting liquid with an activated polyamide composite membrane (TFC), soaking for 5-30min, pouring out the liquid on the surface of the membrane, naturally airing at room temperature, and thoroughly flushing the surface of the membrane with deionized water to complete the first-step grafting modification;
the PAMAM/PDA grafting liquid is prepared by the following steps:
dissolving Dopamine (DA) in Tris-HCl buffer solution, stirring for 5-10min to obtain Polydopamine (PDA) solution, mixing and stirring the PDA solution and PAMAM grafting solution for 1-3h to obtain PAMAM/PDA grafting solution;
the mass concentration of DA in the PDA solution is 0.1-2%, the concentration of Tris-HCl buffer solution is 5-100 mmol/L, and the pH is 6-10; the PAMAM grafting liquid is a solution obtained by dissolving PAMAM in deionized water and stirring 2-10h, and the mass concentration of the PAMAM grafting liquid is 0.1-2%; the volume ratio of the PDA solution to the PAMAM grafting solution is (1-2) to (1-2);
(3) Second step of grafting modification
Pouring TOCNs grafting liquid on the surface of the membrane subjected to the first step grafting modification, soaking 1-5h, pouring out the liquid on the surface of the membrane, and flushing the surface of the membrane with deionized water; obtaining the modified polyamide composite membrane resisting organic matter pollution and microorganism adhesion;
the TOCNs grafting liquid is prepared by the following steps:
dissolving MES in deionized water to prepare MES buffer solution, and then dissolving EDC and NHS in the MES buffer solution to obtain mixed solution A; taking carboxylated nano-cellulose suspension, performing water bath ultrasonic treatment for 20-60min, then performing magnetic stirring for 30-60min, and mixing the mixed solution A with the carboxylated nano-cellulose suspension to obtain TOCNs grafting solution;
MES buffer concentration is 50-400mM, pH is 4-7, EDC concentration in mixture A is 0.2-2mM, NHS concentration is 0.2-5mM.
2. The method according to claim 1, wherein the buffer has NaCl concentration of 0.1-1M, MES concentration of 1-100mM, EDC concentration of 2-6mM, and NHS concentration of 1-100mM.
3. The preparation method according to claim 1, wherein the TOCN suspension has a mass concentration of 0.1-2%, the mixed solution A and the TOCN suspension are mixed according to the volume ratio of (1-2): (1-2), and the TOCNs grafting liquid has a pH of 6-10.
4. A modified polyamide composite membrane resistant to organic contamination and microbial adhesion prepared by the method of claim 1.
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