CN107537330B - Antibacterial thin-layer composite membrane and preparation method thereof - Google Patents
Antibacterial thin-layer composite membrane and preparation method thereof Download PDFInfo
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Abstract
The invention relates to an antibacterial thin-layer composite film and a preparation method thereof. The method comprises the steps of performing infiltration treatment on the surface of a functional layer of the thin-layer composite membrane by using carboxylated chitosan coating liquid, then performing drying treatment to obtain a carboxylated chitosan membrane positioned on the surface of the functional layer, performing infiltration treatment on the carboxylated chitosan membrane by using a salt solution corresponding to metal ions in the antibacterial nanoparticles and a cross-linking agent solution, and then performing heat treatment to obtain the antibacterial thin-layer composite membrane with a cross-linked structure. The preparation method of the antibacterial thin-layer composite membrane provided by the invention is simple, the production cost is low, and the prepared antibacterial thin-layer composite membrane has high water flux, good antibacterial performance and strong antibacterial durability, and has a good industrial production basis and a wide application prospect.
Description
Technical Field
The invention belongs to the technical field of thin-layer composite films, and particularly relates to an antibacterial thin-layer composite film and a preparation method thereof.
Background
The membrane separation technology is a novel separation technology, is widely applied to various fields of food, biology, environmental protection, medicine and the like, and has the advantages of high efficiency, energy conservation, environmental protection and the like. The thin-layer composite membrane is a separation membrane which takes a microporous membrane or an ultrafiltration membrane as a supporting basement membrane and a layer of extremely thin and compact homogeneous membrane as a functional separation layer compounded on the surface of the basement membrane. The extremely thin surface compact layer enables the thin-layer composite membrane to have better solute separation rate and water permeation rate, so the thin-layer composite membrane is widely applied to the nanofiltration and reverse osmosis separation processes. The thin-layer composite nanofiltration membrane and the composite reverse osmosis membrane are mainly prepared in an interfacial polymerization mode. US patent US4277344 discloses a process for the preparation of thin layer composite films by interfacial polymerization: firstly coating a polysulfone solution on a polyester non-woven fabric, preparing a supporting base membrane by a phase inversion method, then immersing the supporting base membrane into a diamine or polyamine aqueous solution, removing the redundant amine solution on the surface of the supporting base membrane, then immersing the supporting base membrane into an organic nonpolar solution of polyacyl chloride, carrying out interfacial polymerization reaction on amine and acyl chloride, forming a compact polyamide ultrathin active layer on the supporting base membrane, and finally washing or thermocuring to prepare the thin-layer composite nanofiltration membrane or the composite reverse osmosis membrane.
For a long time, the problem of membrane fouling is one of the main problems restricting the development and progress of thin-layer composite membrane separation technology, and the membrane fouling greatly reduces the separation performance and the service life of the thin-layer composite membrane. In order to improve the anti-pollution performance of the membrane, people usually adopt methods such as adsorption, grafting, coating and the like on the surface of the membrane to fix a functional monomer on the surface of an active separation layer of the thin-layer composite membrane to prepare the anti-pollution thin-layer composite membrane. In the Chinese patent CN101462024A, a PVA solution and a solution containing a cross-linking agent and a catalyst are sequentially coated on the surface of a polyamide compact layer, and then the PVA anti-pollution layer with high cross-linking degree is formed on the surface of the polyamide compact layer through high-temperature cross-linking, so that the water flux and the anti-pollution capacity of the reverse osmosis membrane are improved. In patent CN101450289A, a chitosan acetic acid aqueous solution with a cross-linking agent is coated on the surface of a composite reverse osmosis membrane to prepare the ultra-low pressure pollution-resistant composite reverse osmosis membrane. Patent CN103691328A grafts chitosan on the surface of the polyamide compact layer of the composite reverse osmosis membrane by applying a chemical treatment method, so that the hydrophilicity of the surface of the membrane is improved, and the pollution resistance of the surface of the membrane is further improved.
The microbial contamination (including bacteria and fungi) is one of the main causes of membrane contamination, and it is only critical to improve the antibacterial property of the membrane surface if the growth of bacteria, fungi and the like on the membrane surface cannot be effectively inhibited by the above work of improving the hydrophilicity of the membrane surface and changing the charge property of the membrane surface. Some inorganic nano particles such as nano particles of silver, copper, zinc and corresponding compounds thereof have good antibacterial performance, and the antibacterial performance of the surface of the film can be improved by introducing the inorganic nano particles into the thin-layer composite film, so that the pollution resistance of the thin-layer composite film is improved, and the service life of the film is prolonged. Chinese patent CN101874989A firstly prepares a polyamide thin-layer composite membrane on a polysulfone support layer by an interfacial polymerization method, and then adds a water-phase monomer solution of inorganic nanoparticles containing silver, copper, zinc and corresponding compounds on the polyamide surface layer to prepare a second polyamide surface layer containing antibacterial inorganic nanoparticles as an antibacterial functional layer. Chinese patent CN103480284A mixes nano silver particles and PVA solution and coats the mixture on the surface of a polyamide reverse osmosis membrane to obtain the pollution-resistant polyamide composite membrane.
Although the prior art can improve the antibacterial performance of the membrane surface, the method of adding the antibacterial metal nanoparticles directly introduces the antibacterial nanoparticles onto the surface of the thin-layer composite membrane to form an antibacterial composite layer, and the antibacterial nanoparticles are not synthesized on the coating layer in situ, so that the antibacterial inorganic nanoparticles attached to the membrane surface are likely to be quickly lost along with the use process of the membrane, and the durability of the antibacterial performance of the membrane surface is poor.
Therefore, there is a need to develop an antibacterial thin-layer composite film with better antibacterial property and durability and a preparation method thereof.
Disclosure of Invention
The technical problem to be solved by the invention is to provide an antibacterial thin-layer composite film and a preparation method thereof aiming at the defects of the prior art. The inventors of the present invention have conducted extensive and intensive experimental studies in the technical field of an antibacterial thin-layer composite membrane, and have found that an antibacterial thin-layer composite membrane of a crosslinked carboxylated chitosan membrane containing antibacterial nanoparticles on a functional layer can be obtained by coating a carboxylated chitosan aqueous solution on the functional layer of the thin-layer composite membrane, drying the carboxylated chitosan to form a film, bringing the film into contact with a salt solution corresponding to metal ions in nanoparticles having an antibacterial function, impregnating the film with a reductive crosslinking agent solution, and finally heat-treating the film. The nano particles are embedded in the cross-linked carboxylated chitosan film, so that the antimicrobial pollution resistance of the antibacterial thin-layer composite film is improved; meanwhile, on the basis of keeping the flux of the antibacterial thin-layer composite membrane equivalent, the salt rejection rate of the antibacterial thin-layer composite membrane can be improved.
To this end, the present invention provides, in a first aspect, an antibacterial thin-layer composite film comprising a thin-layer composite film composed of a support layer and a functional layer, and an antibacterial layer located on a surface of the functional layer of the thin-layer composite film; wherein the antibacterial layer is a cross-linked carboxylated chitosan film containing antibacterial nanoparticles; the crosslinking degree of the crosslinked carboxylated chitosan is 10-50%.
According to the invention, the thin-layer composite membrane comprises a composite nanofiltration membrane and/or a composite reverse osmosis membrane.
According to the present invention, the antibacterial nanoparticles include a metal simple substance and/or a metal oxide; the metal comprises silver and/or copper.
In some embodiments of the present invention, the antibacterial nanoparticles have a particle size of 10 to 60 nm.
In other embodiments of the present invention, the antibacterial nanoparticles in the antibacterial layer are 0.5 wt% to 5.0 wt%.
In a second aspect, the present invention provides a method for preparing an antibacterial thin-layer composite film according to the first aspect, comprising:
step A, coating the functional layer surface of the thin-layer composite membrane by using a carboxylated chitosan coating liquid, and then drying to obtain a carboxylated chitosan membrane positioned on the functional layer surface;
and step B, soaking the carboxylated chitosan membrane in a salt solution corresponding to metal ions in the antibacterial nano particles and a cross-linking agent solution, and then carrying out heat treatment to obtain the antibacterial thin-layer composite membrane.
According to the present invention, the carboxylation degree of carboxylated chitosan in the carboxylated chitosan coating liquid is 60% to 90%; the viscosity average molecular weight of the carboxylated chitosan in the carboxylated chitosan coating liquid is 1 to 100 ten thousand, and preferably 8 to 30 ten thousand. The carboxylation chitosan used in the invention is a derivative of natural high molecular chitosan, has good hydrophilicity, is easy to form a film and has broad-spectrum antibacterial activity.
According to the method of the present invention, the carboxylated chitosan coating liquid is an aqueous solution of carboxylated chitosan. In some embodiments of the invention, the carboxylated chitosan coating fluid has a mass concentration of 0.04 wt% to 0.3 wt%, preferably 0.12 wt% to 0.2 wt%.
According to the method of the present invention, in step a, the method of the coating treatment is not particularly limited, and an existing coating treatment method such as a blade coating method, a wire bar coating method, a brush coating method, or the like can be employed. It is easily understood that the coating liquid should be applied to the surface of the functional layer for a time ranging from 10 to 60 seconds, preferably from 20 to 40 seconds. The temperature of the drying treatment is 40-150 ℃, preferably 50-120 ℃; the drying time is 1-10min, preferably 3-6 min.
According to the method, in the step B, the salt solution corresponding to the metal ions in the antibacterial nanoparticles is an aqueous solution of the salt corresponding to the metal ions in the antibacterial nanoparticles. The mass concentration of the salt solution corresponding to the metal ions in the antibacterial nano particles is 0.5 wt% -5.0 wt%, and preferably 1.0 wt% -2.5 wt%.
In some embodiments of the present invention, the salt corresponding to the metal ion in the antibacterial nanoparticle includes one or more of silver nitrate, copper sulfate, copper chloride, cuprous sulfate, and cuprous nitrate.
According to the method of the invention, the crosslinker solution is an aqueous solution of a crosslinker. The mass concentration of the cross-linking agent solution is 0.05 wt% -0.4 wt%, and preferably 0.1 wt% -0.2 wt%.
According to the process of the invention, the crosslinking agent is a reducing crosslinking agent. The cross-linking agent plays a role in cross-linking the carboxylated chitosan coating on one hand, and reduces metal ions on the surface of the membrane into nano particles in situ on the other hand. In some embodiments of the invention, the reductive crosslinking agent comprises one or more of glutaraldehyde, succinaldehyde, adipaldehyde, glyoxal, dimethylglyoxal, dodecanal, and citral.
In some embodiments of the present invention, in step B, the time for the soaking treatment by the salt solution corresponding to the metal ions in the antibacterial nanoparticles is 1 to 10min, preferably 5 to 10 min.
In other embodiments of the present invention, in step B, the time for the soaking treatment by the crosslinking agent solution is 1-10min, preferably 3-6 min.
In some embodiments of the invention, in step B, the temperature of the heat treatment is in the range of 40 to 150 ℃, preferably 50 to 120 ℃.
In other embodiments of the present invention, in step B, the heat treatment time is 1-10min, preferably 3-6 min.
Unless otherwise specified, the term "water" as used herein refers to deionized water.
Unless otherwise specified, the composite nanofiltration membrane or the composite reverse osmosis membrane used for preparing the antibacterial thin-layer composite membrane is commercially available.
The inventor of the present invention has found that, the carboxylated chitosan membrane uniformly adsorbed with metal ions is treated by the reductive crosslinking agent, and the crosslinking action is generated to firmly adhere to the surface of the carboxylated chitosan membrane (namely, the coating layer), and at the same time, nano particles are generated in the inner part and the surface of the coating layer. The nano particles synthesized in situ on the coating layer are uniformly embedded and dispersed in the cross-linked carboxylated chitosan film with the antibacterial function (namely, the antibacterial layer), the activity of the antibacterial nano particles embedded in the cross-linked carboxylated chitosan film is very high, metal ions with the antibacterial effect can be slowly released, the nano particles are firmly combined with the cross-linked carboxylated chitosan film, the agglomeration phenomenon is not easy to occur, the nano particles are not easy to break away, the antibacterial performance can be better exerted by the nano particles, and the antibacterial performance of the thin-layer composite film is greatly improved and has more durability through the synergistic antibacterial effect with the cross-linked carboxylated chitosan.
The antibacterial layer, namely the cross-linked carboxylated chitosan film is thin, the thickness of the film is about hundreds of nanometers, and the carboxylated chitosan film is a hydrophilic high polymer material, so that the influence on the original water flux of the composite reverse osmosis membrane or the composite nanofiltration membrane is little; the salt rejection rate of the antibacterial thin-layer composite membrane is improved due to the cross-linked structure of the antibacterial layer, the defect that the antibacterial layer is easy to fall off is overcome, the functional layer thin layer of the thin-layer composite membrane is protected, the pollution resistance of the thin-layer composite membrane is improved, and the service life of the thin-layer composite membrane is prolonged.
The antibacterial thin-layer composite membrane and the preparation method thereof provided by the invention have the following advantages:
(1) the preparation method of the antibacterial thin-layer composite membrane provided by the invention is simple and low in production cost.
(2) The antibacterial thin-layer composite membrane provided by the invention has the advantages of thin antibacterial layer, strong hydrophilicity, little influence on the flux of the thin-layer composite membrane, high salt rejection rate, strong antimicrobial pollution performance and long service life.
(3) The antibacterial thin-layer composite membrane and the preparation method thereof provided by the invention have good industrial production basis and wide application prospect.
Detailed Description
In order that the present invention may be more readily understood, the following detailed description of the invention is given by way of example only, and is not intended to limit the scope of the invention.
The performance evaluation and evaluation method of the antibacterial thin-layer composite membrane comprises the following steps:
(1) evaluation of separation Performance:
the salt cut-off R is defined as: under certain operating pressure conditions, the salt concentration (C) of the feed liquidf) With the salt concentration (C) in the permeatep) The difference is divided by the feed solution salt concentration.
The water flux is defined as: the volume of water per membrane area per unit time that permeates under certain operating conditions is expressed in L/(m)2·h)。
The test operation conditions adopted by the composite nanofiltration membrane are as follows: the feed was a 500ppm aqueous solution of magnesium sulfate at an operating pressure of 87psi, an operating temperature of 25 deg.C and a pH of 7.0.
The test operation conditions adopted by the composite reverse osmosis membrane are as follows: the feed was 2000ppm aqueous sodium chloride, operating pressure was 225psi, operating temperature was 25 deg.C, and the pH of the aqueous solution was 7.0.
(2) And (3) quantitatively detecting the antibacterial effect:
the antimicrobial test standards were referenced to the American Association for textile chemical printing and dyeing (AATCC) 100-2004 test standard. Shearing the antibacterial thin-layer composite membrane into 40mm × 40mm samples, contacting the samples with 100 μ L of Escherichia coli (ATCC 25922) bacterial liquid, culturing at 37 deg.C in a constant temperature incubator for 30-120min, repeatedly washing the samples with 10mL of PBS buffer solution, taking washing liquid, diluting properly, and performing viable bacteria culture counting. Meanwhile, a comparison test is carried out on a common composite membrane (containing no antibacterial component). The sterilization rate was calculated as follows:
the bactericidal ratio (%) ((a-B)/a) × 100 (formula 2)
In the formula: a, the number of viable bacteria of a common composite membrane sample;
b, the viable count of the antibacterial composite membrane sample.
In order to test the antibacterial durability of the composite membrane, the prepared antibacterial thin-layer composite membrane is immediately tested for the bactericidal rate after the preparation is finished, and the bactericidal rate is recorded as bactericidal rate-1; and soaking the prepared antibacterial thin-layer composite membrane in deionized water, storing for three months at normal temperature, taking out, and testing the sterilization rate, wherein the sterilization rate is marked as sterilization rate-2.
(3) Detecting the content of the antibacterial nanoparticles:
the surface of the prepared antibacterial composite membrane is characterized by adopting an Apollo XP type X-ray energy spectrometer (EDS) produced by EDAX of America, so that the mass content of the antibacterial nano particles in the antibacterial layer is obtained, and the resolution of the energy spectrometer is required to be ensured to be 131eV in the testing process.
(4) And (3) detecting the crosslinking degree of the antibacterial layer:
the crosslinked carboxylated chitosan was uniformly coated on a glass plate by the same method as the film-forming step and process, and then removed by a blade.
Accurately weighing a certain mass of cross-linked carboxylated chitosan W1Placing in an extraction tube of a Soxhlet extractor, extracting with 200mL glacial acetic acid solution with concentration of 0.5 wt% for 24h, and oven drying to constant weight2Then, the degree of crosslinking is calculated by the following formula:
C＝W2/W1×100％ (formula 3)
Examples
Example 1
Coating a carboxylation chitosan (the carboxylation degree is 60 percent, and the viscosity-average molecular weight is 8 ten thousand) aqueous solution with the mass concentration of 0.04 wt% on the surface of a polyamide active layer of a composite nanofiltration membrane (Dow chemical NF90), removing the redundant carboxylation chitosan solution on the surface of the polyamide layer after the coating solution soaks the surface of the polyamide layer (namely a functional layer) for 10s, and drying the polyamide layer in an oven at the temperature of 120 ℃ for 1min and taking out the polyamide layer; and (2) contacting a copper chloride aqueous solution with the mass concentration of 2.5 wt% with the surface of the composite nanofiltration membrane carboxylated chitosan, removing the redundant copper chloride solution after the contact is carried out for 5min, then contacting the surface of the carboxylated chitosan treated by the copper chloride solution with a glutaraldehyde aqueous solution with the mass concentration of 0.05 wt% for 1min, removing the redundant glutaraldehyde solution, finally placing the carboxylated chitosan surface in a drying oven with the temperature of 120 ℃ for heat treatment for 1min, and taking out the carboxylated chitosan to obtain the antibacterial composite nanofiltration membrane. The performance of the prepared antibacterial composite nanofiltration membrane is evaluated, and the results are shown in table 1.
Example 2
Coating a carboxylated chitosan (carboxylation degree of 75% and viscosity-average molecular weight of 12 ten thousand) aqueous solution with the mass concentration of 0.12 wt% on the surface of a polyamide active layer of a composite nanofiltration membrane (Dow chemical NF90), soaking the surface of the polyamide active layer for 20s by using a coating solution, removing the redundant carboxylated chitosan solution on the surface of the polyamide active layer, drying the polyamide active layer in an oven at 100 ℃ for 3min, and taking out; and (2) contacting a copper chloride aqueous solution with the mass concentration of 2.5 wt% with the surface of the composite nanofiltration membrane carboxylated chitosan, removing the redundant copper chloride solution after contacting for 5min, then contacting the surface of the carboxylated chitosan treated by the copper chloride solution with a succinaldehyde aqueous solution with the mass concentration of 0.1 wt% for 3min, removing the redundant succinaldehyde solution, finally placing the carboxylated chitosan treated by the copper chloride solution in an oven with the temperature of 100 ℃ for heat treatment for 3min, and taking out the carboxylated chitosan to obtain the antibacterial composite nanofiltration membrane. The performance of the prepared antibacterial composite nanofiltration membrane is evaluated, and the results are shown in table 1.
Example 3
Coating a carboxylation chitosan (the carboxylation degree is 85%, the viscosity-average molecular weight is 20 ten thousand) aqueous solution with the mass concentration of 0.2 wt% on the surface of a polyamide active layer of a composite nanofiltration membrane (Dow chemical NF270), removing the redundant carboxylation chitosan solution on the surface of the polyamide layer after the coating solution soaks the surface of the polyamide layer for 40s, and drying the polyamide layer in an oven at the temperature of 80 ℃ for 6min and taking out the polyamide layer; and (2) contacting a copper chloride aqueous solution with the mass concentration of 2.5 wt% with the surface of the composite nanofiltration membrane carboxylated chitosan, removing the redundant copper chloride solution after the contact is carried out for 5min, then contacting the surface of the carboxylated chitosan treated by the copper chloride solution with an hexanedial aqueous solution with the mass concentration of 0.2 wt% for 6min, removing the redundant hexanedial solution, finally placing the carboxylated chitosan surface in an oven with the temperature of 80 ℃ for heat treatment for 6min, and taking out the carboxylated chitosan surface to obtain the antibacterial composite nanofiltration membrane. The performance of the prepared antibacterial composite nanofiltration membrane is evaluated, and the results are shown in table 1.
Example 4
Coating a carboxylation chitosan (the carboxylation degree is 90 percent, and the viscosity average molecular weight is 30 ten thousand) aqueous solution with the mass concentration of 0.3 wt% on the surface of a polyamide active layer of a composite nanofiltration membrane (Dow chemical NF270), removing the redundant carboxylation chitosan solution on the surface of the polyamide layer after the coating solution soaks the surface of the polyamide layer for 60s, and drying the polyamide layer in an oven at 50 ℃ for 10min and taking out the polyamide layer; and (2) contacting a copper chloride aqueous solution with the mass concentration of 2.5 wt% with the surface of the composite nanofiltration membrane carboxylated chitosan, removing the redundant copper chloride solution after the contact is carried out for 5min, then contacting the surface of the carboxylated chitosan treated by the copper chloride solution with a glyoxal aqueous solution with the mass concentration of 0.4 wt% for 10min, removing the redundant glyoxal solution, finally placing the carboxylated chitosan surface in a 50 ℃ oven for heat treatment for 10min, and taking out the carboxylated chitosan to obtain the antibacterial composite nanofiltration membrane. The performance of the prepared antibacterial composite nanofiltration membrane is evaluated, and the results are shown in table 1.
Comparative example 1
The performance of a commercial polyamide composite nanofiltration membrane (dow chemical NF90) which was not subjected to antibacterial modification was evaluated, and the results are shown in table 1.
Comparative example 2
The performance of a commercial polyamide composite nanofiltration membrane (dow chemical NF270) which was not subjected to antibacterial modification was evaluated, and the results are shown in table 1.
Comparative example 3
The preparation method of the antibacterial composite nanofiltration membrane is the same as that in example 1, except that the mass concentration of the carboxylated chitosan aqueous solution is 0.02 wt%.
Comparative example 4
The preparation method of the antibacterial composite nanofiltration membrane is the same as that in example 3, except that the mass concentration of the carboxylated chitosan aqueous solution is 0.35 wt%.
Example 5
Coating a carboxylation chitosan (carboxylation degree is 75%, viscosity-average molecular weight is 12 ten thousand) aqueous solution with the mass concentration of 0.2 wt% on the surface of a polyamide active layer of a composite reverse osmosis membrane (American Heideneng ESPA1), removing the redundant carboxylation chitosan solution on the surface of the polyamide layer after the polyamide layer is soaked in the coating solution for 10s, and drying the polyamide layer in an oven at 120 ℃ for 1min and taking out the polyamide layer; and (2) contacting a silver nitrate aqueous solution with the mass concentration of 0.5 wt% with the surface of the carboxylated chitosan of the composite reverse osmosis membrane, removing the redundant silver nitrate solution after the contact is carried out for 5min, then contacting the surface of the carboxylated chitosan treated by the silver nitrate solution with a dodecanal aqueous solution with the mass concentration of 0.05 wt% for 5min, removing the redundant dodecanal solution, and finally placing the carboxylated chitosan surface in an oven with the temperature of 120 ℃ for heat treatment for 1min and taking out the carboxylated chitosan surface to obtain the antibacterial composite reverse osmosis membrane. The performance of the prepared antibacterial composite reverse osmosis membrane was evaluated, and the results are shown in table 2.
Example 6
Coating a carboxylation chitosan (carboxylation degree is 75%, viscosity-average molecular weight is 12 ten thousand) aqueous solution with the mass concentration of 0.2 wt% on the surface of a polyamide active layer of a composite reverse osmosis membrane (American Heideneng ESPA1), removing the redundant carboxylation chitosan solution on the surface of the polyamide layer after the polyamide layer is soaked in the coating solution for 20s, and drying the polyamide layer in an oven at 100 ℃ for 3min and taking out the polyamide layer; and (2) contacting a silver nitrate aqueous solution with the mass concentration of 1.0 wt% with the surface of the carboxylated chitosan of the composite reverse osmosis membrane, removing the redundant silver nitrate solution after the contact is carried out for 5min, then contacting the surface of the carboxylated chitosan treated by the silver nitrate solution with a citral aqueous solution with the mass concentration of 0.1 wt% for 5min, removing the redundant citral solution, and finally, placing the carboxylated chitosan surface in an oven with the temperature of 100 ℃ for heat treatment for 3min and taking out the carboxylated chitosan to obtain the antibacterial composite reverse osmosis membrane. The performance of the prepared antibacterial composite reverse osmosis membrane was evaluated, and the results are shown in table 2.
Example 7
Coating a carboxylation chitosan (carboxylation degree is 75%, viscosity-average molecular weight is 12 ten thousand) aqueous solution with the mass concentration of 0.2 wt% on the surface of a polyamide active layer of a composite reverse osmosis membrane (American Heideneng ESPA2), removing the redundant carboxylation chitosan solution on the surface of the polyamide layer after the polyamide layer is soaked in the coating solution for 40s, and drying the polyamide layer in an oven at 80 ℃ for 6min and taking out; and (2) contacting a silver nitrate aqueous solution with the mass concentration of 2.5 wt% with the carboxylated chitosan surface of the composite reverse osmosis membrane, removing the redundant silver nitrate solution after the contact is carried out for 5min, then contacting the carboxylated chitosan surface treated by the silver nitrate solution with a dimethyl glyoxal aqueous solution with the mass concentration of 0.2 wt% for 5min, removing the redundant dimethyl glyoxal solution, finally placing the carboxylated chitosan surface in an oven with the temperature of 80 ℃ for heat treatment for 6min, and taking out the carboxylated chitosan surface to obtain the antibacterial composite reverse osmosis membrane. The performance of the prepared antibacterial composite reverse osmosis membrane was evaluated, and the results are shown in table 2.
Example 8
Coating a carboxylation chitosan (carboxylation degree is 75%, viscosity-average molecular weight is 12 ten thousand) aqueous solution with the mass concentration of 0.2 wt% on the surface of a polyamide active layer of a composite reverse osmosis membrane (American Heideneng ESPA2), removing the redundant carboxylation chitosan solution on the surface of the polyamide layer after the polyamide layer is soaked in the coating solution for 60s, and drying the polyamide layer in an oven at 50 ℃ for 10min and taking out the polyamide layer; and (2) contacting a silver nitrate aqueous solution with the mass concentration of 5.0 wt% with the carboxylated chitosan surface of the composite reverse osmosis membrane, removing the redundant silver nitrate solution after the contact is carried out for 5min, then contacting the carboxylated chitosan surface treated by the silver nitrate solution with an hexanedial aqueous solution with the mass concentration of 0.4 wt% for 5min, removing the redundant hexanedial solution, and finally, placing the carboxylated chitosan surface in a 50 ℃ oven for heat treatment for 10min and taking out the carboxylated chitosan surface to obtain the antibacterial composite reverse osmosis membrane. The performance of the prepared antibacterial composite reverse osmosis membrane was evaluated, and the results are shown in table 2.
Comparative example 5
The performance of a commercially available polyamide composite reverse osmosis membrane (U.S. Heideneng ESPA1) that was not antibacterial modified was evaluated and the results are shown in Table 2.
Comparative example 6
The performance of a commercially available polyamide composite reverse osmosis membrane (U.S. Heideneng ESPA2) that was not antibacterial modified was evaluated and the results are shown in Table 2.
Comparative example 7
The preparation method of the antibacterial composite reverse osmosis membrane is the same as that in example 6, except that the preparation method is not subjected to infiltration treatment by a metal ion salt solution.
Comparative example 8
The preparation method of the antibacterial composite reverse osmosis membrane is the same as that in example 8, except that the mass concentration of the metal ion salt solution is 6.0 wt%, and the mass concentration of the cross-linking agent solution is 0.6 wt%.
Example 9
Coating a carboxylation chitosan (carboxylation degree of 85%, viscosity-average molecular weight of 20 ten thousand) aqueous solution with the mass concentration of 0.2 wt% on the surface of a polyamide active layer of a composite reverse osmosis membrane (American Heideneng ESPA1), soaking the surface of the polyamide active layer for 20s by using a coating solution, removing the redundant carboxylation chitosan solution on the surface of the polyamide active layer, drying the polyamide active layer in an oven at 120 ℃ for 1min, and taking out the polyamide active layer; and (2) contacting a copper sulfate aqueous solution with the mass concentration of 2.5 wt% with the carboxylated chitosan surface of the composite reverse osmosis membrane for 1min, removing the redundant copper sulfate solution, then contacting the carboxylated chitosan surface treated by the copper sulfate solution with a glutaraldehyde aqueous solution with the mass concentration of 0.2 wt% for 5min, removing the redundant glutaraldehyde solution, finally placing the carboxylated chitosan surface in an oven with the temperature of 120 ℃ for heat treatment for 1min, and taking out the carboxylated chitosan surface to obtain the antibacterial composite reverse osmosis membrane. The performance of the prepared antibacterial composite reverse osmosis membrane was evaluated, and the results are shown in table 3.
Example 10
Coating a carboxylation chitosan (carboxylation degree of 85%, viscosity-average molecular weight of 20 ten thousand) aqueous solution with the mass concentration of 0.2 wt% on the surface of a polyamide active layer of a composite reverse osmosis membrane (American Heideneng ESPA1), removing the redundant carboxylation chitosan solution on the surface of the polyamide layer after the polyamide layer is soaked in the coating solution for 40s, and drying the polyamide layer in an oven at 100 ℃ for 3min and taking out the polyamide layer; and (2) contacting a copper sulfate aqueous solution with the mass concentration of 2.5 wt% with the carboxylated chitosan surface of the composite reverse osmosis membrane, removing the redundant copper sulfate solution after contacting for 5min, then contacting the carboxylated chitosan surface treated by the copper sulfate solution with a glutaraldehyde aqueous solution with the mass concentration of 0.2 wt% for 5min, removing the redundant glutaraldehyde solution, finally placing the carboxylated chitosan surface in an oven with the temperature of 100 ℃ for heat treatment for 3min, and taking out the carboxylated chitosan surface to obtain the antibacterial composite reverse osmosis membrane. The performance of the prepared antibacterial composite reverse osmosis membrane was evaluated, and the results are shown in table 3.
Example 11
Coating a carboxylation chitosan (carboxylation degree of 85%, viscosity-average molecular weight of 20 ten thousand) aqueous solution with the mass concentration of 0.2 wt% on the surface of a polyamide active layer of a composite reverse osmosis membrane (American Heideneng ESPA1), soaking the surface of the polyamide active layer for 60s by using a coating solution, removing the redundant carboxylation chitosan solution on the surface of the polyamide active layer, drying the polyamide active layer in an oven at 80 ℃ for 6min, and taking out the polyamide active layer; and (2) contacting a copper sulfate aqueous solution with the mass concentration of 2.5 wt% with the carboxylated chitosan surface of the composite reverse osmosis membrane, removing the redundant copper sulfate solution after the contact is carried out for 10min, then contacting the carboxylated chitosan surface treated by the copper sulfate solution with a glutaraldehyde aqueous solution with the mass concentration of 0.2 wt% for 5min, removing the redundant glutaraldehyde solution, finally, placing the carboxylated chitosan surface in an oven with the temperature of 80 ℃ for heat treatment for 6min, and taking out the carboxylated chitosan surface to obtain the antibacterial composite reverse osmosis membrane. The performance of the prepared antibacterial composite reverse osmosis membrane was evaluated, and the results are shown in table 3.
Comparative example 9
Coating a carboxylation chitosan (carboxylation degree of 85%, viscosity-average molecular weight of 20 ten thousand) aqueous solution with the mass concentration of 0.2 wt% on the surface of a polyamide active layer of a composite reverse osmosis membrane (American Heideneng ESPA1), soaking the surface of the polyamide active layer for 20s by using a coating solution, removing the redundant carboxylation chitosan solution on the surface of the polyamide active layer, drying the polyamide active layer in an oven at 100 ℃ for 3min, and taking out the polyamide active layer; and (2) contacting a copper sulfate aqueous solution with the mass concentration of 2.5 wt% with the surface of the carboxylated chitosan of the composite reverse osmosis membrane, removing the redundant copper sulfate solution after contacting for 0.5min, then contacting the surface of the carboxylated chitosan treated by the copper sulfate solution with a glutaraldehyde aqueous solution with the mass concentration of 0.2 wt% for 5min, removing the redundant glutaraldehyde solution, finally placing the carboxylated chitosan surface in an oven with the temperature of 100 ℃ for heat treatment for 3min, and taking out the carboxylated chitosan to obtain the antibacterial composite reverse osmosis membrane. The performance of the prepared antibacterial composite reverse osmosis membrane was evaluated, and the results are shown in table 3.
Comparative example 10
Coating a carboxylation chitosan (carboxylation degree of 85%, viscosity-average molecular weight of 20 ten thousand) aqueous solution with the mass concentration of 0.2 wt% on the surface of a polyamide active layer of a composite reverse osmosis membrane (American Heideneng ESPA1), removing the redundant carboxylation chitosan solution on the surface of the polyamide layer after the polyamide layer is soaked in the coating solution for 40s, and drying the polyamide layer in an oven at 100 ℃ for 3min and taking out the polyamide layer; and (2) contacting a copper sulfate aqueous solution with the mass concentration of 2.5 wt% with the carboxylated chitosan surface of the composite reverse osmosis membrane, removing the redundant copper sulfate solution after the contact is carried out for 12min, then contacting the carboxylated chitosan surface treated by the copper sulfate solution with a glutaraldehyde aqueous solution with the mass concentration of 0.2 wt% for 5min, removing the redundant glutaraldehyde solution, finally, placing the carboxylated chitosan surface in an oven with the temperature of 100 ℃ for heat treatment for 3min, and taking out the carboxylated chitosan surface to obtain the antibacterial composite reverse osmosis membrane. The performance of the prepared antibacterial composite reverse osmosis membrane was evaluated, and the results are shown in table 3.
TABLE 1
TABLE 2
TABLE 3
As can be seen from the data of examples 1-4 and comparative examples 1-4 in Table 1, under the condition that the mass concentration of the metal ion salt solution is not changed, the water flux of the prepared antibacterial composite nanofiltration membrane is less changed and the salt rejection rate is gradually increased compared with that of the composite nanofiltration membrane without treatment (comparative example 1 and comparative example 2) along with the increase of the mass concentration of the carboxylated chitosan aqueous solution; the mass content of the antibacterial nano particles is correspondingly increased, and the sterilization rate is gradually enhanced. The mass concentration of the carboxylated chitosan aqueous solution is too low (comparative example 3), so that the mass content of the antibacterial nano particles is too low, and further the sterilization rate is too low; too high mass concentration of the carboxylated chitosan aqueous solution (comparative example 4) causes great reduction in water flux and reduction in practical value.
As can be seen from the data of examples 5-8 and comparative examples 5-8 in Table 2, under the condition that the mass concentration of the carboxylated chitosan aqueous solution is not changed, the mass content of the antibacterial nano particles in the prepared antibacterial composite reverse osmosis membrane is correspondingly increased along with the increase of the mass concentration of the metal ion salt solution, and further, the sterilization rate is gradually enhanced. The composite reverse osmosis membrane (comparative example 7) which is not treated with the metal ion salt solution and is coated with only the crosslinked carboxylated chitosan has insignificant antibacterial effect; the composite reverse osmosis membrane (comparative example 8) treated with the metal ion salt solution with the mass concentration higher than 5.0 wt% has no obvious increase in the mass content of the antibacterial nanoparticles and no change in the sterilization rate, and thus the carboxylated chitosan is saturated in adsorbing the metal ions.
As can be seen from the data of examples 9-11 and comparative examples 9-10 in Table 3, under the condition that the mass concentration of the carboxylated chitosan aqueous solution and the metal ion salt solution is not changed, the mass content of the antibacterial nanoparticles in the prepared composite reverse osmosis membrane is correspondingly increased along with the increase of the contact time of the metal ion salt solution, and further, the sterilization rate is gradually enhanced. The short contact time of the metal ion salt solution (comparative example 9) can cause that the carboxylated chitosan is not ready to adsorb metal ions, the mass content of the antibacterial nano particles is very low, and the antibacterial effect is not obvious; the composite reverse osmosis membrane with the overlong contact time of the metal ion salt solution (comparative example 10) has the antibacterial nano particle mass content which is not obviously increased compared with the composite reverse osmosis membrane with the contact time of the metal ion salt solution of 10min (example 11), and the sterilization rate is not obviously changed.
As can be seen from the sterilization rate data of examples 1 to 11, the sterilization rate-2 of the antibacterial thin-layer composite film after being stored for three months at normal temperature is very small in difference from the sterilization rate-1 of the antibacterial thin-layer composite film just prepared, which fully proves that the antibacterial durability of the antibacterial thin-layer composite film prepared by the method of the present invention is strong.
It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.
Claims (20)
1. An antibacterial thin-layer composite film comprises a thin-layer composite film consisting of a supporting layer and a functional layer, and an antibacterial layer positioned on the surface of the functional layer of the thin-layer composite film;
wherein the antibacterial layer is a cross-linked carboxylated chitosan film containing antibacterial nanoparticles; the crosslinking degree of the crosslinked carboxylated chitosan is 10-50%;
the antibacterial thin-layer composite membrane is prepared by the following method:
step A, coating the functional layer surface of the thin-layer composite membrane by using a carboxylated chitosan coating liquid, and then drying to obtain a carboxylated chitosan membrane positioned on the functional layer surface; wherein the mass concentration of the carboxylated chitosan coating liquid is 0.04 wt% -0.3 wt%;
and step B, soaking the carboxylated chitosan membrane in a salt solution corresponding to metal ions in the antibacterial nano particles and a cross-linking agent solution, and then carrying out heat treatment to obtain the antibacterial thin-layer composite membrane.
2. The antibacterial thin composite membrane according to claim 1, wherein the thin composite membrane comprises a composite nanofiltration membrane and/or a composite reverse osmosis membrane.
3. The antibacterial thin-layer composite film according to claim 1, wherein the antibacterial nanoparticles comprise a metal simple substance and/or a metal oxide; the metal comprises silver and/or copper.
4. The antibacterial thin-layer composite film according to claim 1, wherein the antibacterial nanoparticles have a particle size of 10-60 nm.
5. The antibacterial thin-layer composite film according to any one of claims 1 to 4, wherein the antibacterial nanoparticles in the antibacterial layer are contained in an amount of 0.5 wt% to 5.0 wt%.
6. A method for preparing the antibacterial thin composite film according to any one of claims 1 to 5, comprising:
step A, coating the functional layer surface of the thin-layer composite membrane by using a carboxylated chitosan coating liquid, and then drying to obtain a carboxylated chitosan membrane positioned on the functional layer surface; wherein the mass concentration of the carboxylated chitosan coating liquid is 0.04 wt% -0.3 wt%;
and step B, soaking the carboxylated chitosan membrane in a salt solution corresponding to metal ions in the antibacterial nano particles and a cross-linking agent solution, and then carrying out heat treatment to obtain the antibacterial thin-layer composite membrane.
7. The method of claim 6, wherein the carboxylated chitosan coating fluid has a degree of carboxylation of 60% to 90%; the viscosity average molecular weight of the carboxylated chitosan in the carboxylated chitosan coating liquid is 1-100 ten thousand.
8. The method of claim 6, wherein the viscosity average molecular weight of the carboxylated chitosan in said carboxylated chitosan coating solution is between 8 and 30 ten thousand.
9. The method of claim 6, wherein the carboxylated chitosan coating fluid has a mass concentration of 0.12 wt% to 0.2 wt%.
10. The method according to any one of claims 6 to 9, wherein in step a, the coating treatment is carried out for a time of 10 to 60 s;
the temperature of the drying treatment is 40-150 ℃; the drying time is 1-10 min.
11. The method according to claim 10, wherein in step a, the coating process is carried out for a time of 20-40 s; the temperature of the drying treatment is 50-120 ℃; the drying time is 3-6 min.
12. The method according to any one of claims 6 to 9, wherein in the step B, the mass concentration of the salt solution corresponding to the metal ions in the antibacterial nanoparticles is 0.5 wt% to 5.0 wt%.
13. The method of claim 12, wherein in step B, the mass concentration of the salt solution corresponding to the metal ions in the antibacterial nanoparticles is 1.0 wt% to 2.5 wt%.
14. The method of claim 12, wherein in step B, the salt corresponding to the metal ion in the antimicrobial nanoparticles comprises one or more of silver nitrate, copper sulfate, cupric chloride, cuprous sulfate, and cuprous nitrate.
15. The method according to any one of claims 6 to 9, wherein the mass concentration of the crosslinking agent solution is 0.05 wt% to 0.4 wt%.
16. The method of claim 15, wherein the cross-linking agent solution has a mass concentration of 0.1 wt% to 0.2 wt%.
17. The method according to any one of claims 6 to 9, wherein the crosslinking agent is a reducing crosslinking agent.
18. The method of claim 17, wherein the reductive crosslinking agent comprises one or more of glutaraldehyde, succinaldehyde, adipaldehyde, glyoxal, dimethylglyoxal, dodecanal, and citral.
19. The method according to any one of claims 6 to 9, wherein in the step B, the time for the infiltration treatment by the salt solution corresponding to the metal ions in the antibacterial nanoparticles is 1-10 min; the time of the soaking treatment by the cross-linking agent solution is 1-10 min;
the temperature of the heat treatment is 40-150 ℃; the time of the heat treatment is 1-10 min.
20. The method as claimed in claim 19, wherein in step B, the soaking treatment time of the salt solution corresponding to the metal ions in the antibacterial nanoparticles is 5-10 min; the time of the soaking treatment by the cross-linking agent solution is 3-6 min;
the temperature of the heat treatment is 50-120 ℃; the time of the heat treatment is 3-6 min.
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