CN114669197A - Preparation method of modified polyamide composite membrane capable of resisting organic pollution and microbial adhesion - Google Patents
Preparation method of modified polyamide composite membrane capable of resisting organic pollution and microbial adhesion Download PDFInfo
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Abstract
The invention relates to a preparation method of a modified polyamide composite membrane resisting organic pollution and microbial adhesion, which comprises the steps of firstly activating an original TFC membrane by using an activating solution, then carrying out first-step graft modification by using a PAMAM/PDA grafting solution, and finally carrying out graft modification by using a TOCNs grafting solution; 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 chemical grafting method ensures that the modified polymer has stronger stability and is not easy to fall off. And the TOCN has strong hydrophilicity and excellent organic pollution resistance and bacterial adhesion resistance, and the preparation method has the advantages of low cost, environmental friendliness and simple process.
Description
Technical Field
The invention relates to a preparation method of a modified polyamide composite membrane capable of resisting organic pollution and microbial adhesion, belonging to the technical field of membrane preparation.
Background
Membrane separation technology has received much attention in the fields of food processing, seawater 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 membrane has a high membrane fouling tendency due to the inherent surface properties (such as hydrophilicity, roughness, etc.) of the polyamide layer, and the membrane can severely affect the permeability of the membrane in long-term operation, so that membrane fouling remains one of the main concerns of TFC membranes in widespread use. Therefore, there is a need for further conditioning or modifying the surface of TFC membranes to mitigate and prevent the adhesion and deposition of contaminants and microorganisms on the membrane surface, so that the TFC membranes have long-term stable performance in practical applications.
The Polyamidoamine (PAMAM) dendrimer has a radial symmetric hyperbranched structure, and has more amine groups and stable molecular structures on the dendritic surface than other macromolecules, wherein the number of terminal amine groups in the PAMAM dendrimer exponentially increases with the generation number (2)n+2And n is the generation number of the dendrimer). In addition, abundant terminal amino is used as an ideal active center 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.
The Cellulose Nanocrystal (CNC) is a natural, environmentally-friendly, biodegradable, high-mechanical-strength and low-cost nanomaterial, and can be obtained from various renewable biomasses such as cotton. CNC has excellent mechanical properties and has been shown to improve the young's modulus and elastic modulus of nanocomposites. CNC is treated with tetramethylpiperidine-1-oxyl (TEMPO) to obtain a carboxylated nanocellulose (TOCN). Since a large number of carboxyl (-COOH) groups are present on the surface of TOCN, TOCN has high hydrophilicity. In addition, since the high density of carboxyl groups on the surface of the TOCN fiber is negatively charged in water, electrostatic repulsion generated in water can effectively prevent the molecules from aggregating, thereby forming a uniform dispersion. The TOCN has the basic structure and characteristics of natural cellulose and the characteristics of nano materials. As a hydrophilic nanomaterial, TOCN can be used to improve the hydrophilicity, permeability, and contamination resistance of a separation membrane.
At present, membrane pollution is an important problem in the membrane separation process, and natural organic pollutants and microorganisms with certain concentration are contained in feed liquid, so that after the membrane is used for a period of time, the pollutants can be adhered to the surface of the membrane, biologically polluted, accumulated and the like, even block membrane pores, increase the osmotic resistance, reduce the water flux, further cause the properties of the membrane such as osmotic separation performance, stability and the like to be sharply reduced, increase the 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 anti-fouling performance.
In order to improve the anti-pollution performance of the TFC membrane, a hydrophilic anti-pollution layer is coated on the surface of the TFC membrane by a surface coating method, for example, CN1213985A is coated on the surface of a reverse osmosis membrane and has neutral charge, so that the static adsorption of charged pollutants in feed liquid can be inhibited; in the surface coating method, the acting force of chemical bonds does not exist between the coated hydrophilic anti-pollution layer and the active layer of the TFC membrane, and the hydrophilic anti-pollution layer is gradually dissolved in water and falls off under the hydraulic shearing action of feed liquid in the use process of the membrane material, so that the function of a protective layer is finally lost; CN104028118B also discloses a polyamide reverse osmosis membrane containing amphoteric carboxymethyl cellulose sodium complex, which is prepared by adding amphoteric ionic polymer (prepared from amphoteric cationic polymer and sodium carboxymethyl cellulose) as modifier into aqueous monomer solution, and inlaying the amphoteric ionic polymer inside polyamide layer after interfacial polymerization. However, these TFC membranes are still insufficient in desalination rate and water flux, and it is difficult to satisfy high desalination rate and high flux, and at the same time, they have a requirement of good anti-pollution performance.
Therefore, it is necessary to develop a modified polyamide composite membrane with strong anti-fouling ability 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 capable of resisting organic pollution and microorganism adhesion.
The technical scheme of the invention is as follows:
a preparation method of a modified polyamide composite membrane for resisting organic pollution and microbial adhesion comprises the following steps:
(1) TFC membrane activation
Contacting the activated solution with the active layer of the TFC membrane, soaking the active layer of the TFC membrane, pouring out the liquid on the surface of the membrane after soaking for 1-10h, naturally drying at room temperature, and then thoroughly washing the surface of the membrane by deionized water to obtain the activated TFC membrane;
(2) first step graft modification
Contacting the PAMAM/PDA grafting solution with the activated TFC membrane, soaking for 5-30min, pouring out the liquid on the surface of the membrane, naturally drying at room temperature, and then thoroughly washing the surface of the membrane by deionized water to finish the first step of grafting modification;
(3) second step graft modification
Pouring the TOCNs grafting solution onto the surface of the membrane subjected to the grafting modification in the first step, soaking for 1-5h, pouring the liquid on the surface of the membrane, and washing the surface of the membrane with deionized water; obtaining the modified polyamide composite membrane with organic pollution resistance and microbial adhesion resistance.
Preferably, in step (1), the activating solution is prepared as follows:
dissolving sodium chloride (NaCl) and 2-morpholine ethanesulfonic acid (MES) in deionized water to prepare a buffer solution, adjusting the pH value 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 the activation solution.
Further preferably, the concentration of NaCl in the buffer solution is 0.1-1M, and the concentration of 2-morpholinoethanesulfonic acid MES is 1-100 mM.
Further preferably, the concentration of EDC is 2-6mM and the concentration of NHS is 1-100mM in the activation solution.
Preferably, in step (2), the PAMAM/PDA grafting solution is prepared as follows:
dissolving Dopamine (DA) in a Tris-HCl buffer solution, stirring for 5-10min to obtain a Polydopamine (PDA) solution, and mixing and stirring the PDA solution and the PAMAM grafting solution for 1-3h to obtain the PAMAM/PDA grafting solution.
Further preferably, 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 value is 6-10.
More 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%.
Further preferably, the volume ratio of the PDA solution to the PAMAM grafting solution is (1-2) to (1-2).
Preferably, in step (3), the TOCNs grafting solution is prepared as follows:
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; and (3) taking the TOCN suspension, performing water bath ultrasonic treatment for 20-60min, then performing magnetic stirring for 30-60min, and mixing the mixed solution A and the TOCN suspension to obtain the grafted solution of the TOCNs.
Further preferably, the concentration of the MES buffer is 50-400mM, and the pH is 4-7.
More preferably, the mixture A has an EDC concentration of 0.2-2mM and an NHS concentration of 0.2-5 mM.
Further preferably, the mass concentration of the TOCN suspension is 0.1 to 2%.
More preferably, the mixed solution A and the suspension liquid of the TOCN are mixed according to the volume ratio of (1-2) to (1-2), and the pH of the grafting liquid of the TOCNs is 6-10.
The modified TFC membrane of the invention firstly adopts activating liquid to activate the original TFC membrane, then adopts PAMAM/PDA grafting liquid to carry out first-step grafting modification, and finally adopts TOCNs grafting liquid to carry out second-step grafting modification, thus finally obtaining the modified TFC membrane with strong anti-fouling capability; in the activation solution, MES buffer solution maintains the reaction system at a constant pH, EDC in the activation solution reacts with carboxyl to form unstable acyl urea intermediate, and then reacts with NHS to form more stable ester;
In the preparation process of the PAMAM/PDA grafting solution, the Tris-HCl buffer solution enables the reaction system to be maintained at a constant pH value, and the PAMAM and the PDA are mixed to carry out Michael addition coupling reaction to form larger hydrophilic molecules, so that the PAMAM/PDA grafting solution is prevented from entering membrane pores. In the TOCNs grafting solution, MES buffer solution maintains the reaction system at a constant pH, and EDC in the mixed solution A mainly reacts with carboxyl of TOCN to form an acylurea intermediate and then reacts with NHS to form more stable ester, so that the reaction with amino is facilitated; in the first step of graft modification, the terminal amino group of the PAMAM macromolecule and NHS ester undergo nucleophilic substitution to form amido bond on the membrane surface. In the second step of grafting modification, the grafting solution of the TOCNs and the residual amino on the surface of the modified membrane in the first step are subjected to nucleophilic substitution so as to be successfully grafted. Because the TOCN contains a large amount of carboxyl and hydroxyl, the hydrophilicity of the surface of the TFC membrane is obviously increased, and the adhesion of the membrane to dirt and bacteria is greatly reduced, thereby improving the organic pollution resistance and the bacteria adhesion resistance of the TFC membrane.
A modified polyamide composite membrane resisting organic pollution and microbial adhesion is prepared by the method.
Compared with the prior art, the modified polyamide composite membrane for resisting organic 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 first-step grafting modification by using a PAMAM/PDA grafting solution, and finally performing grafting modification by using a TOCNs grafting solution; firstly, PAMAM with abundant 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 the TOCN has strong hydrophilicity, so that the hydrophilicity of the surface of the TFC membrane is obviously increased, and the acting force between pollutants and the surface of the membrane is reduced, thereby obtaining the modified TFC membrane with strong dirt resistance.
2. The invention adopts the two-step grafting method which is realized by the chemical reaction of nucleophilic substitution, compared with the traditional modification method, the chemical grafting method ensures that the modified polymer has stronger stability and is not easy to fall off. And the resulting TFC membrane after modification has an abundant negative charge, thereby enhancing the surface electronegativity of the TFC membrane. As most pollutants and bacteria in the sewage are negatively charged, the pollutants and the bacteria are not easy to adhere to and accumulate on the surface of the TFC membrane with strong electronegativity due to the electrostatic repulsion, 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 performance, can effectively prevent organic pollutants and bacteria from adhering and accumulating to the surface of the membrane, and prolongs the service life of the membrane.
Drawings
FIG. 1 is a graph of the initial water contact angle of the original TFC membrane of example 1 with a TFC membrane after two-step graft modification.
Detailed Description
The invention is further illustrated with reference to the following examples, without however limiting the scope of the invention.
The carboxylated cellulose nanocrystals (TOCN) in the examples were provided by trichoderma biotechnology limited, tianjin. The carboxylated cellulose nanocrystals (TOCN) provided by the same company are rod-like cellulose having a length of 150 to 200nm and a diameter of 100nm or less.
Example 1:
a preparation method of a modified polyamide composite membrane capable of resisting organic pollution and microbial adhesion comprises the following steps:
(1) preparation of an activation solution:
dissolving sodium chloride (NaCl) and 2-morpholine ethanesulfonic acid (MES) in deionized water to prepare a buffer solution, adjusting the pH value 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 activation solution;
NaCl concentration in buffer solution is 0.5M, MES is 10mM, EDC in activating solution is 4mM, NHS is 10 mM;
(2) preparation of a grafting solution:
PAMAM/PDA grafting solution: 1 wt% PAMAM solution and 1.2 wt% PDA solution in a volume ratio of 1: 1 mixing to prepare PAMAM/PDA grafting solution;
TOCNs grafting solution: weighing MES, dissolving in deionized water to obtain MES buffer solution with the concentration of 100mM, adjusting the pH value to 6.2, then weighing 72mg EDC and 72mg NHS, respectively, and dissolving in the MES buffer solution to obtain mixed solution A, wherein the concentration of EDC in the mixed solution A is 1mM, the concentration of NHS is 1mM, taking 50ml of TOCN suspension, firstly carrying out water bath ultrasonic treatment for 20min, then carrying out magnetic stirring for 30min, and then mixing the mixed solution A and the TOCN suspension according to the volume ratio of 1: 1 mixing to obtain a TOCNs grafting solution, and then adjusting the pH value to 7.2;
(3) TFC membrane activation
Fixing the TFC membrane on a customized polytetrafluoroethylene membrane through a long-tail clamp to protect a supporting layer of the membrane, modifying only polyamide of an active layer, pouring an activation solution into the membrane to contact with the active layer of the membrane, pouring liquid on the surface of the membrane after soaking for 1h, naturally drying at room temperature, then thoroughly washing the surface of the membrane with deionized water,
(4) first step grafting
Contacting the PAMAM/PDA grafting solution with an activated TFC membrane, soaking for 15min, pouring out the liquid on the surface of the membrane, naturally drying at room temperature, and then thoroughly washing the surface of the membrane by using deionized water to obtain the PAMAM/PDA membrane;
(5) Second step grafting
Pouring the grafting solution of the TOCNs into the PAMAM/PDA membrane, pouring the liquid on the surface of the membrane after soaking for 2h, also thoroughly washing the surface of the membrane with deionized water to obtain the PAMAM/PDA-TOCN membrane, and storing the PAMAM/PDA-TOCN membrane in the deionized water at 4 ℃ for use.
Comparative example 1:
a preparation method of a modified polyamide composite membrane comprises the following steps:
(1) preparation of an activation solution:
dissolving sodium chloride (NaCl) and 2-morpholine ethanesulfonic acid (MES) in deionized water to prepare a buffer solution, adjusting the pH value 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 activation solution;
the NaCl concentration in the buffer solution is 0.5M, the MES is 10mM, the EDC in the activation solution is 4mM, and the NHS is 10 mM;
(2) preparing a grafting solution:
PAMAM grafting solution: 0.5g PAMAM is dissolved in 99.5g deionized water and stirred for more than 2h to form 0.5 wt% PAMAM grafting solution.
(3) TFC membrane activation
And fixing the TFC membrane on a customized polytetrafluoroethylene membrane through a long tail clamp, so that a supporting layer of the membrane is protected, and only the polyamide of an active layer is modified. Pouring the activated solution in the step (1) into a membrane to contact with a membrane active layer, pouring out the liquid on the surface of the membrane after soaking for 1h, naturally drying at room temperature, and then thoroughly washing the surface of the membrane by deionized water.
(4) Graft modification
And (3) contacting the PAMAM grafting solution with the activated TFC membrane, soaking for 15min, pouring out the liquid on the surface of the membrane, naturally drying at room temperature, and then thoroughly washing the surface of the membrane by using deionized water to obtain the PAMAM membrane.
Comparative example 2:
a preparation method of a modified polyamide composite membrane comprises the following steps:
(1) preparation of an activation solution:
dissolving sodium chloride (NaCl) and 2-morpholine ethanesulfonic acid (MES) in deionized water to prepare a buffer solution, adjusting the pH value 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 activation solution;
the NaCl concentration in the buffer solution is 0.5M, the MES is 10mM, the EDC in the activation solution is 4mM, and the NHS is 10 mM;
(2) preparing a grafting solution:
PAMAM/PDA grafting solution: 1 wt% PAMAM solution and 1.2 wt% PDA solution in a volume ratio of 1: 1 mixing to prepare PAMAM/PDA grafting solution,
(3) TFC membrane activation
Fixing the TFC membrane on a customized polytetrafluoroethylene membrane through a long-tail clamp, protecting a supporting layer of the membrane, only modifying the polyamide of an active layer, pouring an activating solution into the membrane to contact with the active layer of the membrane, pouring liquid on the surface of the membrane after soaking for 1h, naturally drying the membrane at room temperature, and then thoroughly washing the surface of the membrane by deionized water.
(4) Graft modification
Contacting the PAMAM/PDA grafting solution with an activated TFC membrane, soaking for 15min, pouring out the liquid on the surface of the membrane, naturally drying at room temperature, and then thoroughly washing the surface of the membrane by using deionized water to obtain the PAMAM/PDA membrane;
test of application Effect
1. The concentration of the PDA solution in step (2) of comparative example 2 was changed to make the concentration of PDA in the PAMAM/PDA grafting solution 0, 0.2, 0.4, 0.6, 0.8 wt% respectively, and finally different modified TFC membranes were obtained, 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 unit to test their basic separation and permeation performance.
The test method is as follows: the forward osmosis testing device is composed of two symmetrical rectangular membrane tanks, and the effective testing area of the membrane component is 21cm2The feed liquid uses 1L of deionized water, the drawing liquid uses 1M NaCl solution, the temperature of the feed liquid and the drawing liquid is kept at 25 +/-0.5 ℃, the feed liquid faces to the active layer of the TFC membrane, and the solution in the membrane pool and the solution storage tank circulates at the 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 30min, data are recorded after the operation is stable, a liquid storage tank for storing the absorption liquid is placed on an electronic balance, 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 absorption liquid and the conductivity change of the feeding liquid. Water flux (J) of the original TFC membrane and the differently modified TFC membranes and the composite membrane of example 1 WLMH), reverse salt flux (J)SgMH) and specific salt flux (J)S/JW) The data are shown in table 1.
TABLE 1 Water flux, reverse salt flux, and specific salt flux for original TFC and modified TFC membranes
From the above table, it can be seen that the water flux is significantly decreased and the reverse salt is also significantly increased when only the PAMAM modified TFC membrane is present, compared to the original TFC membrane, 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 is increased, the water flux and the reverse salt flux are gradually improved, and the optimal concentration of PDA in the grafting solution is 0.6%, although the water flux is decreased compared to the water flux of the original TFC membrane, the reverse salt flux and the salt flux are significantly lower than those of the original TFC membrane. The water flux of the PAMAM/PDA-TOCN membrane obtained by the 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. The original TFC membrane and the modified TFC membrane of example 1 were subjected to organic contamination test
The test method is as follows: bovine Serum Albumin (BSA), Humic Acid (HA) and Sodium Alginate (SA) represent common organic contaminants, respectively. Wherein the contamination experiment is mainly divided into four stages, a) an initial stabilization stage: deionized water is used as a feeding liquid, 1M NaCl is used as an extraction liquid, and the running time is 2 hours; b) and (3) a pollution stage: the feed solution was composed of 200mg/L BSA (SA or HA) organic contaminant and 20mM NaCl and 1mM NaHCO 3Salt solution, 1M NaCl is used as an extraction solution, the circulation flow rate is 200mL/min, and the operation time is 24 h; c) a cleaning stage: the feed liquid and the drawing liquid are deionized water, the running time is 0.5h, and the circulating flow rate is 300 mL/min; d) and (3) a recovery phase: consistent with the initial stabilization phase conditions. All forward osmosis processes are performed in such a way that the active layer faces the feed liquid side, and the temperatures of both sides are room temperature. The fouling resistance of the modified TFC FO membranes was then evaluated by total flux reduction (FDR) and flux recovery (FRR) and is shown in table 2 for different contaminants:
TABLE 2 anti-organic fouling Performance of TFC membranes
As can be seen from table 2, the PAMAM/PDA-TOCN membrane of the present invention has a lower water flux reduction rate and a higher flux recovery rate for three different organic contaminants compared to the original TFC membrane, which indicates that the dendritic polyamide-cellulose nanocrystal modified polyamide composite membrane prepared by the present invention has excellent anti-contamination properties.
3. The original TFC membrane was subjected to an antibacterial adhesion test with the modified TFC membrane of example 1
The test method is as follows: adding Staphylococcus aureus (ATCC25923) to the sterilized LB broth, and placing in a constant temperature shaking table (37 deg.C)150rpm) for 24 h. Centrifuging the cultured Escherichia coli at 10000rpm for 10min, and diluting with sterilized 0.9% NaCl solution to obtain a solution with a concentration of about 1.0 × 10 6cfu/mL of bacterial suspension. Subsequently, a membrane having an area of 2 cm. times.2 cm was added to the conical flask containing the above bacterial suspension, and the mixture was cultured for 2 hours in a constant temperature shaker at 37 ℃. The membrane was then rinsed with 5ml of a 0.9% NaCl solution that was sterilized and collected. 0.1mL of the collected solution was added to LB agar medium, spread uniformly with a spreading bar, and cultured at 37 ℃ for 15 hours. The medium was removed, the number of colonies was obtained by plate counting and the antibacterial adhesion rate was calculated, and the test results are shown in table 3.
TABLE 3 antibacterial adhesion Performance of TFC membranes
As can be seen from the above table, the PAMAM/PDA-TOCN membrane of the present invention has an antibacterial adhesion of up to 90.4% compared to the original membrane, because after two-step grafting, the TOCN has strong hydrophilicity, which makes the hydrophilicity of the TFC membrane surface increase significantly, and makes the adhesion of the membrane to dirt small, therefore, the modified membrane has excellent antibacterial adhesion performance, and can effectively inhibit the growth, reproduction and accumulation of bacteria on the membrane surface.
Example 2:
the preparation method of the modified polyamide composite membrane with organic pollution resistance and microbial adhesion resistance as described in the example 1 is different in that:
and (4) in the TFC membrane activation process of the step (3), the contact time of the activation solution and the membrane surface is 30 min.
And (4) the contact time of the PAMAM/PDA grafting solution and the surface of the membrane is 20 min.
And (5) the contact time of the TOCNs grafting solution and the surface of the membrane is 3 h.
Example 3:
the difference from the preparation method of the modified polyamide composite membrane for resisting organic pollution and microorganism adhesion described in the example 1 is that:
in step (1), the buffer solution had a NaCl concentration of 0.2M, MES of 8mM, and the activation solution had EDC of 3mM and NHS of 20 mM.
Example 4:
the difference from the preparation method of the modified polyamide composite membrane for resisting organic pollution and microorganism adhesion described in the example 1 is that:
in step (1), the buffer solution had a NaCl concentration of 1M, a MES concentration of 50mM, an activation solution having EDC of 6mM and NHS of 50 mM.
Example 5:
the difference from the preparation method of the modified polyamide composite membrane for resisting organic pollution and microorganism adhesion described in the example 1 is that:
in the step (2), mixing a 0.8 wt% PAMAM solution and a 0.8 wt% PDA solution according to a volume ratio of 1: 1 to prepare PAMAM/PDA grafting solution.
Example 6:
the difference from the preparation method of the modified polyamide composite membrane for resisting organic pollution and microorganism adhesion described in the example 1 is that:
in the step (2), MES was weighed and dissolved in deionized water to prepare a 200mM MES buffer, the pH was adjusted to 6.2, and then EDC and NHS were weighed and dissolved in the MES buffer to obtain a mixture A, wherein the concentration of EDC and the concentration of NHS in the mixture A were 1.5mM and 2mM, respectively.
Claims (10)
1. A preparation method of a modified polyamide composite membrane with organic pollution resistance and microbial adhesion resistance comprises the following steps:
(1) TFC membrane activation
Contacting the activated solution with the active layer of the TFC membrane, soaking the polyamide active layer of the TFC membrane, pouring out the liquid on the surface of the membrane after soaking for 1-10h, naturally drying at room temperature, and then thoroughly washing the surface of the membrane by deionized water to obtain the activated TFC membrane;
(2) first step graft modification
Contacting the PAMAM/PDA grafting solution with the activated TFC membrane, soaking for 5-30min, pouring out the liquid on the surface of the membrane, naturally drying at room temperature, and then thoroughly washing the surface of the membrane by deionized water to finish the first step of grafting modification;
(3) second step graft modification
Pouring the TOCNs grafting solution onto the surface of the membrane subjected to the grafting modification in the first step, soaking for 1-5h, pouring the liquid on the surface of the membrane, and washing the surface of the membrane with deionized water; obtaining the modified polyamide composite membrane with organic pollution resistance and microbial adhesion resistance.
2. The method according to claim 1, wherein in the step (1), the activating solution is prepared as follows:
dissolving sodium chloride (NaCl) and 2-morpholine ethanesulfonic acid (MES) in deionized water to prepare a buffer solution, adjusting the pH value 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 the activation solution.
3. The method according to claim 2, wherein the buffer solution contains NaCl at a concentration of 0.1-1M and MES at a concentration of 1-100mM, and the activating solution contains EDC at a concentration of 2-6mM and NHS at a concentration of 1-100 mM.
4. The method according to claim 1, wherein in step (2), the PAMAM/PDA grafting solution is prepared as follows:
dissolving Dopamine (DA) in a Tris-HCl buffer solution, stirring for 5-10min to obtain a Polydopamine (PDA) solution, and mixing and stirring the PDA solution and the PAMAM grafting solution for 1-3h to obtain the PAMAM/PDA grafting solution.
5. The method according to claim 4, wherein 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 solution is 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%.
6. The method of claim 4, wherein the PDA solution and the PAMAM graft are mixed at a volume ratio of (1-2) to (1-2).
7. The method according to claim 1, wherein in step (3), the TOCNs grafting solution is prepared as follows:
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; and (3) taking the carboxylated nano-cellulose suspension, performing water bath ultrasound for 20-60min, then performing magnetic stirring for 30-60min, and mixing the mixed solution A and the carboxylated nano-cellulose suspension to obtain the TOCNs grafting solution.
8. The method according to claim 1, wherein the MES buffer has a concentration of 50 to 400mM, a pH of 4 to 7, the mixed solution A has a concentration of 0.2 to 2mM of EDC, and a concentration of 0.2 to 5mM of NHS.
9. The method of claim 1, wherein the weight concentration of the suspension of the TOCN is 0.1-2%, the mixture A is mixed with the suspension of the TOCN at a volume ratio of (1-2) to (1-2), and the pH of the grafting solution of the TOCNs is 6-10.
10. A modified polyamide composite membrane with resistance to organic pollution and microbial adhesion, which is prepared by the method of claim 1.
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