CN113477085A - Polyamide composite reverse osmosis membrane with high permselectivity and antibacterial property and preparation method thereof - Google Patents
Polyamide composite reverse osmosis membrane with high permselectivity and antibacterial property and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a polyamide composite reverse osmosis membrane with high selective permeability and antibacterial property and a preparation method thereof. The polyamide composite reverse osmosis membrane comprises a porous ultrafiltration membrane supporting layer, an aromatic polyamide layer and an antibacterial layer; the aromatic polyamide layer is covered on the porous ultrafiltration membrane supporting layer, the aromatic polyamide layer is doped with a nano material, and the part of the nano material exposed out of the polyamide layer is connected with the antibacterial material through a covalent bond to form the ultrathin antibacterial layer. The nano material adopted by the invention can improve the water flux of the membrane, provide grafting sites for grafting reaction, and chemically bond antibacterial functional groups on the surface of the membrane without changing the structure of the polyamide main body material; the silicon oxygen group in the silane coupling agent antibacterial material reacts with the hydroxyl group in the nano material, the silane coupling agent antibacterial material is grafted on the surface of the membrane, and the mixed matrix membrane is endowed with antibacterial performance, so that the reverse osmosis membrane with high selective permeability and antibacterial performance is obtained, and the membrane can be operated efficiently for a long time.
Description
Technical Field
The invention belongs to the technical field of water treatment membranes, and particularly relates to a polyamide composite reverse osmosis membrane with high selective permeability and antibacterial property and a preparation method thereof.
Background
The performance of the reverse osmosis membrane determines the operation cost of the seawater or brackish water desalination process, and is related to the popularization of the water treatment process by the reverse osmosis membrane method. At present, the aromatic polyamide composite reverse osmosis membrane is still the mainstream product in the reverse osmosis membrane field, but due to the nature of the aromatic polyamide material, the reverse osmosis membrane at present still has the problems of low selective permeability and easy microbial contamination. The initial selected permeability of the reverse osmosis membrane is determined by the properties of the membrane material, and in the using process, the biological pollution increases the transfer resistance of water, thereby further reducing the permeability of the membrane. In order to obtain a high-performance reverse osmosis membrane which is stable for a long period of time, the permeability and the biological contamination resistance of the reverse osmosis membrane should be simultaneously improved.
The appearance and development of the nano material create conditions for further development of the reverse osmosis membrane, and the nano material has great potential in the aspects of optimizing the membrane structure and improving the membrane permeability. Pure nano material doping can obviously improve the initial selective permeability of the reverse osmosis membrane, but most nano materials have no antibacterial property or insufficient antibacterial property, and the membrane separation performance is seriously reduced or even fails along with the microbial pollution of the membrane in the operation process. For example, CN111282452A provides a method for preparing a high-throughput mixed matrix reverse osmosis membrane, which comprises using a polysulfone ultrafiltration membrane as a base membrane, m-phenylenediamine as a water phase monomer, trimesoyl chloride as an organic phase monomer, aminated graphene oxide as an organic phase additive, and n-hexane as an organic phase solvent, and preparing the mixed matrix reverse osmosis membrane by an interfacial polymerization method; the aminated graphene oxide is used as an organic phase additive, the problem of dispersion of the graphene oxide in an organic phase is successfully solved, and the prepared mixed matrix reverse osmosis membrane has high flux and high salt desalination rate, and the hydrophilicity is improved to a certain extent; however, the patent does not provide a solution for the antibacterial property of the membrane surface, and the problem of bacterial pollution in the use process of the membrane still exists. For example, CN112516799A provides a preparation method of a mixed matrix reverse osmosis membrane, which introduces organic components by forming covalent bonds between palygorskite containing nano-silver and KH550 through a chemical grafting method, and adjusts the surface hydrophilicity and hydrophobicity and the charge characteristics to weaken the aggregation effect. In the process of preparing the reverse osmosis membrane by interfacial polymerization, a KH550 modified palygorskite/nano-silver material is doped into an aqueous phase solution, so that the membrane has good salt rejection rate and water flux capacity and strong anti-pollution performance; however, the reaction of the silane coupling agent with the nanomaterial in this patent is used to solve the problem of dispersibility of the nanomaterial and does not involve the problem of antibacterial properties.
In order to obtain a high-performance reverse osmosis membrane which is stable for a long time, the antibacterial performance of the membrane should be simultaneously given on the basis of improving the initial selective permeability by doping a nano material. The grafting of the antibacterial material on the surface of the membrane is an effective means for improving the antibacterial performance, however, in the commonly used grafting method, the antibacterial material reacts with the surface groups of the membrane to destroy the cross-linked structure of the polyamide material, so that the selective permeability is reduced. For example, CN112473398A provides a method for preparing a reverse osmosis membrane with high desalination and anti-pollution, which comprises a support layer and a polyamide functional layer attached on the support layer; the reverse osmosis membrane firstly adopts polyamine and polybasic acyl chloride to carry out interfacial polymerization reaction, a polyamide functional layer is prepared on a supporting layer, and then secondary interfacial polymerization is carried out on the polyamide functional layer by utilizing the polybasic acyl chloride remained on the surface of the membrane and an antibacterial material, so as to obtain the reverse osmosis membrane with high desalination and pollution resistance; according to the method, the residual polyacyl chloride on the surface of the polyamide matrix is bonded with the antibacterial material, so that the characteristics of the polyamide matrix material are changed, the polyamide matrix structure is compact, and the water flux is reduced.
In summary, the polyamide composite membranes of the prior art do not meet the requirement of high permselectivity and at the same time improve the antibacterial properties. Therefore, how to impart antibacterial properties to a polyamide composite reverse osmosis membrane under conditions that ensure high permselectivity is a problem to be further solved.
Disclosure of Invention
The invention aims to provide a polyamide composite reverse osmosis membrane with high selective permeability and antibacterial property and a preparation method thereof. The invention organically couples the nanometer material and the antibacterial material by grafting, solves the problems that the polyamide composite reverse osmosis membrane in the prior art is low in permselectivity and easy to be polluted by microorganisms, and has high permselectivity and antibacterial performance.
The invention provides a polyamide composite reverse osmosis membrane, which comprises a porous ultrafiltration membrane supporting layer, an aromatic polyamide layer and an antibacterial layer; the aromatic polyamide layer covers the porous ultrafiltration membrane supporting layer and comprises a nano material; the antibacterial layer is formed by connecting the nanometer material exposed outside the aromatic polyamide layer with the antibacterial material through a covalent bond. According to the invention, the nano material and the antibacterial material are grafted and organically coupled, so that the prepared polyamide composite reverse osmosis membrane has high selective permeability and antibacterial performance.
As a preferred embodiment of the present invention: the nano material is hydrotalcite, and is preferably Mg-Al-CO3Hydrotalcite.
As a preferred embodiment of the present invention: the antibacterial material is silane coupling agent antibacterial material, and preferably dimethyl octadecyl [3- (trimethoxysilyl) propyl group]Ammonium chloride, i.e. C26H58ClNO3Si。
As a preferred embodiment of the present invention: the porous ultrafiltration membrane support layer is a polysulfone ultrafiltration membrane, and the pore size distribution is concentrated in 10nm-100 nm.
The invention also provides a preparation method of the polyamide composite reverse osmosis membrane, which comprises the following steps: the method comprises the following steps: preparing an aromatic polyamide layer on a porous ultrafiltration membrane supporting layer, and doping a nano material in the aromatic polyamide layer to obtain a mixed matrix reverse osmosis membrane; step two: and connecting the nano material on the surface of the reverse osmosis membrane with the antibacterial material through a covalent bond to form an antibacterial layer, thereby obtaining the polyamide composite reverse osmosis membrane. In the first step, the aromatic polyamide layer is prepared on the porous ultrafiltration membrane supporting layer preferably by adopting an interfacial polymerization method. According to the invention, the nano material and the antibacterial material are grafted and organically coupled, so that the prepared polyamide composite reverse osmosis membrane has high selective permeability and antibacterial performance.
As a preferred embodiment of the present invention: the preparation method of the mixed matrix reverse osmosis membrane specifically comprises the following steps: contacting the surface of the porous ultrafiltration membrane support layer with an aqueous phase solution to remove redundant liquid on the surface; then contacting with organic phase solution dispersed with nano material to make water phase monomer and organic phase monomer react; and finally, carrying out heat treatment on the membrane to obtain the mixed matrix reverse osmosis membrane.
Further preferably, in the step one, before the porous ultrafiltration membrane supporting layer is contacted with the aqueous phase solution, soaking and washing the porous ultrafiltration membrane supporting layer in deionized water, and purging the porous ultrafiltration membrane supporting layer with nitrogen until no liquid drops exist on the surface; the reaction time is 45s-70 s; the heat treatment temperature is 60-90 ℃, and the heat treatment time is 4-8 min.
Further preferably, in the first step, the porous ultrafiltration membrane support layer is a polysulfone ultrafiltration membrane, and the pore size distribution is concentrated in the range of 10nm to 100 nm. The water phase monomer is aromatic diamine primary amine, preferably m-phenylenediamine; the organic phase monomer is polyfunctional acyl chloride, preferably triacyl chloride, and more preferably trimesoyl chloride; the solvent of the organic phase solution was n-hexane. That is, the aqueous phase solution is preferably a solution in which an aromatic polyamine and an additive are dissolved in deionized water, and the organic phase solution is preferably a solution in which a polyfunctional acid chloride is dissolved in n-hexane. The nano material is hydrotalcite, preferably Mg-Al-CO3Hydrotalcite.
Further preferably, in the step one, the water phase monomer accounts for 2wt% -3wt% of the water phase solution; the additive of the aqueous phase solution is a composite additive consisting of triethylamine and camphorsulfonic acid; the triethylamine accounts for 1 to 2 weight percent of the aqueous phase solution; the mass percentage of the camphorsulfonic acid in the aqueous phase solution is 2-4 wt%; the nano material accounts for 0.010-0.075 wt% of the organic phase solution; the mass percentage of the organic phase monomer occupying the organic phase solution is 0.06wt% -0.15 wt%.
As a preferred embodiment of the present invention: and connecting the nano material on the surface of the reverse osmosis membrane with the antibacterial material through a covalent bond to form an antibacterial layer. The method specifically comprises the following steps: carrying out contact standing reaction on a methanol solution of an antibacterial material and a reverse osmosis membrane with a mixed matrix, and cleaning after the reaction is finished; wherein the antibacterial material is a silane coupling agent antibacterial material, preferably dimethyl octadecyl [3- (trimethoxysilyl) propyl ] ammonium chloride; the mass percentage of the antibacterial material in the methanol solution of the antibacterial material is 0.02wt% -0.50wt%, and further 0.02wt% -0.06 wt%; the reaction temperature is 20-30 ℃, and the reaction time is 1-3 h.
The invention has at least the following beneficial effects: the reverse osmosis membrane with high permselectivity and antibacterial property is prepared by adopting hydrotalcite doping and silane coupling agent antibacterial material grafting, and has the characteristics of simple operation, environmental friendliness, low price and easiness in obtaining. The nano hydrotalcite material has through nano channel and is doped into polyamide base material to raise the water transferring rate and selective permeability of the membrane. Meanwhile, the exposed part provides a grafting site for the antibacterial material, so that the grafting reaction does not damage the structure of the polyamide matrix. According to the invention, through hydrotalcite doping and silane coupling agent antibacterial material graft coupling, a reverse osmosis membrane with high selective permeability and biological pollution resistance can be prepared, and the service life of the membrane is prolonged.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Detailed Description
The invention is further illustrated below with reference to specific embodiments. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, it should be understood that various changes and modifications of equivalent forms to the present invention can be made by those skilled in the art after reading the teaching of the present invention, and also fall within the scope of the present invention defined by the claims.
The invention provides a polyamide composite reverse osmosis membrane, which comprises a porous ultrafiltration membrane supporting layer, an aromatic polyamide layer and an ultrathin antibacterial layer; the aromatic polyamide layer is covered on the porous ultrafiltration membrane supporting layer, and the aromatic polyamide layer is doped with a nano material; the ultrathin antibacterial layer is formed by connecting the nanometer material exposed outside the aromatic polyamide layer with the antibacterial material through a covalent bond. The nano material adopted by the invention is doped in the aromatic polyamide layer, so that the water transfer rate of the membrane can be improved, and the selective permeability can be improved; meanwhile, the exposed part provides a grafting site for the antibacterial material, so that the grafting reaction does not damage the structure of the polyamide matrix; thereby leading the polyamide composite reverse osmosis membrane to have high selective permeability and biological pollution resistance.
The nano material adopted by the invention has a water channel effect and has a reactive group. According to the embodiment of the present invention, the kind of the nanomaterial is not particularly limited, and those skilled in the art can select the nanomaterial accordingly as needed, for example, hydrotalcite can be selected. In some embodiments of the invention, Mg-Al-CO is selected3The hydrotalcite is a nano material; Mg-Al-CO3The hydrotalcite nano material consists of a main laminated plate with positive charges and carbonate ions with negative charges among layers, the sheet diameter is between 110 and 250nm, and the thickness is between 30 and 50 nm. The antibacterial material adopted by the invention is an antibacterial material with a group bonded with the nano material. According to the embodiment of the present invention, the kind of the antibacterial material is not particularly limited, and those skilled in the art can select the antibacterial material according to the need, for example, the silane coupling agent type antibacterial material can be selected. In some embodiments of the invention, dimethyloctadecyl [3- (trimethoxysilyl) propyl ] is selected]Ammonium chloride (C)26H58ClNO3Si) is an antibacterial material. According to the embodiment of the present invention, the kind of the porous ultrafiltration membrane support layer used in the present invention is not particularly limited, and those skilled in the art can select the porous ultrafiltration membrane support layer accordingly according to the needs, for example, polysulfone ultrafiltration membrane can be selected, and the pore size distribution is concentrated in 10nm to 100 nm.
The invention provides a preparation method of a polyamide composite reverse osmosis membrane, which comprises the following steps.
The method comprises the following steps: preparation of mixed matrix reverse osmosis membrane
The method comprises the steps of preparing an aromatic polyamide layer on a porous ultrafiltration support layer by an interfacial polymerization method, and introducing a nano material into a polyamide matrix to obtain the mixed matrix reverse osmosis membrane. According to the embodiment of the invention, the method specifically comprises the following steps: contacting the surface of the porous ultrafiltration membrane support layer with an aqueous phase solution to remove redundant liquid on the surface; then contacting with organic phase solution dispersed with nano material to make water phase monomer and organic phase monomer react; and finally, carrying out heat treatment on the membrane to obtain the mixed matrix reverse osmosis membrane.
In some embodiments of the invention, the porous ultrafiltration membrane support layer is rinsed by soaking in deionized water and purged with nitrogen to the surface without droplets prior to contacting the porous ultrafiltration membrane support layer with the aqueous solution. The porous ultrafiltration membrane support layer is a polysulfone ultrafiltration membrane, and the pore size distribution is concentrated in 10nm-100 nm.
In some embodiments of the present invention, the aqueous solution used for interfacial polymerization is a solution of aqueous monomer aromatic polyamine and additives dissolved in water, wherein the aromatic polyamine is preferably m-phenylenediamine; the additive is preferably a composite additive consisting of triethylamine and camphorsulfonic acid. As a preferred embodiment, the water phase monomer accounts for 2-3 wt% of the water phase solution; the triethylamine accounts for 1 to 2 weight percent of the aqueous phase solution; the mass percentage of the camphorsulfonic acid in the aqueous phase solution is 2-4 wt%.
In some embodiments of the present invention, the organic phase solution used in the interfacial polymerization is a solution of a multifunctional acid chloride dissolved in an organic solvent, preferably trimesoyl chloride; the organic solvent is preferably an organic solvent, which is immiscible with water, which dissolves the multifunctional acid chloride without damaging the porous ultrafiltration membrane support layer, which is inert with respect to the polyamine and the multifunctional acid chloride, and is preferably n-hexane. The mass percentage of the organic phase monomer occupying the organic phase solution is 0.06wt% -0.15 wt%.
In some embodiments of the invention, the nanomaterial is a hydrotalcite, such as Mg-Al-CO3Hydrotalcite. The nano material accounts for 0.010-0.075 wt% of the organic phase solution. The invention adopts hydrotalcite nano-sheets to play double roles: on one hand, the water flux of the membrane is improved, and the reduction of the water flux generated by subsequent grafting is compensated; on the other hand, provides grafting sites for the grafting reaction, and antibacterial functional groups are chemically bonded on the surface of the membrane, andthe structure of the polyamide main body material is not changed.
In some embodiments of the invention, the time for the aqueous phase monomer to react with the organic phase monomer is from 45s to 70 s; the heat treatment temperature is 60-90 ℃, and the heat treatment time is 4-8 min.
Step two: grafting of antimicrobial materials
The method comprises the step of connecting a nano material on the surface of the mixed matrix reverse osmosis membrane with an antibacterial material through a covalent bond to form an ultrathin antibacterial layer, so as to obtain the antibacterial polyamide composite reverse osmosis membrane. According to the embodiment of the invention, the method specifically comprises the following steps: preparing a methanol solution of an antibacterial material, then contacting the surface of the reverse osmosis membrane with the methanol solution of the antibacterial material, standing for reaction, and finally cleaning the surface of the membrane to obtain the reverse osmosis membrane with high selective permeability and antibacterial property. The invention grafts the antibacterial material on the nano material to endow the membrane with antibacterial property. According to the invention, through the doping of the nano material and the graft coupling of the silane coupling agent antibacterial material, the reverse osmosis membrane with high selective permeability and biological pollution resistance can be prepared, and the service life of the membrane is prolonged.
In some embodiments of the invention, the antimicrobial material is a silane coupling agent-based antimicrobial material, such as dimethyloctadecyl [3- (trimethoxysilyl) propyl group]Ammonium chloride (C)26H58ClNO3Si); the mass percentage of the antibacterial material in the methanol solution of the antibacterial material is 0.02wt% -0.50wt%, and further 0.02wt% -0.06 wt%. The invention is based on dimethyloctadecyl [3- (trimethoxy) silylpropyl group]Reacting siloxy group in ammonium chloride with hydroxyl in nano hydrotalcite material to obtain dimethyl octadecyl [3- (trimethoxy) silicon propyl group]Ammonium chloride is grafted on the surface of the membrane to endow the mixed matrix membrane with antibacterial performance.
In some embodiments of the invention, the mixed matrix reverse osmosis membrane surface is contacted with the methanol solution of the antibacterial material and stands still for reaction at the temperature of 20-30 ℃ for 1-3 h.
The invention provides a preferable preparation method of a polyamide composite reverse osmosis membrane with high selective permeability and antibacterial property.
(1) Soaking and washing the porous ultrafiltration membrane supporting layer by using deionized water, and purging the surface of the membrane by using nitrogen until no liquid drops exist; contacting the surface of a porous ultrafiltration membrane supporting layer with an aqueous solution containing 2-3 wt% of m-phenylenediamine, 2-4 wt% of camphorsulfonic acid and 1-2 wt% of triethylamine, soaking and contacting for 30-60 s, and purging the surface of the membrane with nitrogen until no liquid drops exist.
(2) Mixing the dried membrane surface with trimesoyl chloride content of 0.06-0.15 wt% and Mg-Al-CO3Contacting an n-hexane organic phase solution with the hydrotalcite content of 0.010-0.075 wt%, standing for 45-70 s to cause m-phenylenediamine and trimesoyl chloride to generate interfacial polymerization, and placing the membrane in a blast oven at 60-90 ℃ to carry out heat treatment for 4-8 min to obtain the mixed matrix reverse osmosis membrane.
(3) Preparing a solution for grafting the surface of a mixed matrix reverse osmosis membrane, i.e. C26H58ClNO3A methanol solution with Si content of 0.02wt% to 0.50 wt%; and (3) contacting the mixed matrix reverse osmosis membrane with the solution at the temperature of 20-30 ℃ for 1-3 h, and washing with deionized water to obtain the reverse osmosis membrane with high selective permeability and antibacterial property.
The present invention will be further explained with reference to specific examples and comparative examples.
Comparative example 1
An unmodified polyamide composite reverse osmosis membrane is selected as a comparative example, and the preparation method comprises the following steps: soaking the porous ultrafiltration membrane supporting layer in deionized water, and purging the membrane surface with nitrogen until no liquid drops. Preparing an aqueous solution with the m-phenylenediamine content of 2wt%, the camphorsulfonic acid content of 2.3 wt% and the triethylamine content of 1.1 wt%, contacting the surface of the porous ultrafiltration membrane supporting layer with the aqueous solution for 60s, and purging the membrane surface with nitrogen until no liquid drops exist; preparing a normal hexane organic phase solution with 0.1 wt% of trimesoyl chloride, contacting the surface of the membrane with the organic phase solution for 60s, placing the membrane in an oven at 80 ℃ for heat treatment for 5min, and cleaning the surface with deionized water to obtain the unmodified polyamide composite reverse osmosis membrane.
Comparative example 2
The preparation method of the reverse osmosis membrane with the doped hydrotalcite mixed matrix is as follows: soaking a porous ultrafiltration membrane supporting layer in deionized water,the membrane surface was purged with nitrogen until no droplets were present. Preparing an aqueous solution with the m-phenylenediamine content of 2wt%, the camphorsulfonic acid content of 2.3 wt% and the triethylamine content of 1.1 wt%, contacting the surface of the porous ultrafiltration membrane supporting layer with the aqueous solution for 60s, and then purging the membrane surface with nitrogen until no liquid drops exist; 0.1 wt% of trimesoyl chloride and Mg-Al-CO are prepared3Contacting the surface of the diaphragm with an organic phase solution of n-hexane with the content of hydrotalcite of 0.025wt% for 60s, placing the diaphragm in an oven at 80 ℃ for heat treatment for 5min, contacting the membrane surface with methanol for 3h, and then washing with pure water.
Example 1
In this embodiment, the preparation method of the polyamide composite reverse osmosis membrane includes the steps of: soaking the porous ultrafiltration membrane supporting layer in deionized water, and purging the membrane surface with nitrogen until no liquid drops. Preparing an aqueous solution with the m-phenylenediamine content of 2wt%, the camphorsulfonic acid content of 2.3 wt% and the triethylamine content of 1.1 wt%, contacting the surface of the porous ultrafiltration membrane supporting layer with the aqueous solution for 60s, and then purging the membrane surface with nitrogen until no liquid drops exist; 0.1 wt% of trimesoyl chloride and Mg-Al-CO are prepared3Contacting the surface of the diaphragm with an n-hexane organic phase solution with hydrotalcite content of 0.025wt% for 60s, placing in an oven at 80 deg.C for heat treatment for 5min, and contacting the membrane surface with a solution containing C26H58ClNO3A0.02 wt% solution of Si in methanol was used for 3 hours, followed by rinsing with pure water.
Example 2
In this embodiment, the preparation method of the polyamide composite reverse osmosis membrane includes the steps of: soaking the porous ultrafiltration membrane supporting layer in deionized water, and purging the membrane surface with nitrogen until no liquid drops. Preparing an aqueous solution with the m-phenylenediamine content of 2wt%, the camphorsulfonic acid content of 2.3 wt% and the triethylamine content of 1.1 wt%, contacting the surface of the porous ultrafiltration membrane supporting layer with the aqueous solution for 60s, and then purging the membrane surface with nitrogen until no liquid drops exist; 0.1 wt% of trimesoyl chloride and Mg-Al-CO are prepared3Contacting the surface of the diaphragm with an n-hexane organic phase solution with hydrotalcite content of 0.025wt% for 60s, placing in an oven at 80 deg.C for heat treatment for 5min, and contacting the membrane surface with a solution containing C26H58ClNO3A0.06 wt% solution of Si in methanol was used for 3 hours, followed by rinsing with pure water.
Example 3
In this embodiment, the preparation method of the polyamide composite reverse osmosis membrane includes the steps of: soaking the porous ultrafiltration membrane supporting layer in deionized water, and purging the membrane surface with nitrogen until no liquid drops. Preparing an aqueous solution with the m-phenylenediamine content of 2wt%, the camphorsulfonic acid content of 2.3 wt% and the triethylamine content of 1.1 wt%, contacting the surface of the porous ultrafiltration membrane supporting layer with the aqueous solution for 60s, and then purging the membrane surface with nitrogen until no liquid drops exist; 0.1 wt% of trimesoyl chloride and Mg-Al-CO are prepared3Contacting the surface of the diaphragm with an n-hexane organic phase solution with hydrotalcite content of 0.025wt% for 60s, placing in an oven at 80 deg.C for heat treatment for 5min, and contacting the membrane surface with a solution containing C26H58ClNO3A0.10 wt% solution of Si in methanol was used for 3 hours, followed by rinsing with pure water.
Example 4
In this embodiment, the preparation method of the polyamide composite reverse osmosis membrane includes the steps of: soaking the porous ultrafiltration membrane supporting layer in deionized water, and purging the membrane surface with nitrogen until no liquid drops. Preparing an aqueous solution with the m-phenylenediamine content of 2wt%, the camphorsulfonic acid content of 2.3 wt% and the triethylamine content of 1.1 wt%, contacting the surface of the porous ultrafiltration membrane supporting layer with the aqueous solution for 60s, and then purging the membrane surface with nitrogen until no liquid drops exist; 0.1 wt% of trimesoyl chloride and Mg-Al-CO are prepared3Contacting the surface of the diaphragm with an n-hexane organic phase solution with hydrotalcite content of 0.025wt% for 60s, placing in an oven at 80 deg.C for heat treatment for 5min, and contacting the membrane surface with a solution containing C26H58ClNO3A0.50 wt% solution of Si in methanol was used for 3 hours, followed by rinsing with pure water.
The polyamide composite reverse osmosis membrane obtained in the example was tested for separation performance (water flux, salt rejection) and antibacterial property (bactericidal property), and compared with the data obtained in the comparative examples, which were obtained from the unmodified polyamide composite reverse osmosis membrane and the hydrotalcite-doped mixed matrix reverse osmosis membrane.
The detection method comprises the following steps:
(1) the water flux and salt rejection test methods were as follows: a cross-flow type membrane detection device is adopted, the inlet water is 2000ppm NaCl water solution, the operation pressure is 1.55MPa, the temperature is 25 ℃, and the water flux and the desalination rate of the membrane are tested after pre-pressing for 0.5 h.
(2) The sterilization rate test method comprises the following steps: culturing the strain in LB culture medium at 37 deg.C for 16h, and diluting to 10%6cfu/mL, applying 60 μ L of the bacterial liquid on the membrane surface, culturing at 37 ℃ in an incubator for 3h, washing the membrane surface with 9mL of physiological saline, adding 1mL of the washing liquid into nutrient agar, culturing at 37 ℃ in the incubator for 48h, counting the number of colonies by using a colony counter, and calculating the sterilization rate.
And (3) detection results:
(1) the measured water flux and salt rejection results are shown in table 1;
TABLE 1 Water flux and salt rejection results data
The reverse osmosis membranes obtained in examples 1 to 4 were compared with the reverse osmosis membrane of the comparative example in terms of water flux and salt rejection data, and the results are shown in Table 1. As can be seen from table 1, the water flux of comparative example 2, example 1 and example 2 was significantly increased and the salt rejection rate was slightly decreased but was not greatly changed with respect to the reverse osmosis membrane of comparative example 1. The results show that the selective permeability of the polyamide composite reverse osmosis membrane doped with hydrotalcite is obviously superior to that of the polyamide composite reverse osmosis membrane not doped with hydrotalcite.
(2) The measured sterilization rate result data are shown in table 2;
TABLE 2 Sterilization Rate results data
The sterilization rate data of the reverse osmosis membranes obtained in examples 1 to 4 were compared with those of the comparative example, and the results are shown in Table 2. As can be seen from Table 2, the sterilization rate of comparative example 1 is between 20-30%, which is caused by the natural death of bacteria; comparative example 2 the sterilization rate did not change significantly compared to comparative example 1. The results of examples 1 to 4, relative to comparative examples 1 to 2, show that the antibacterial performance of the polyamide composite reverse osmosis membrane grafted with the silane coupling agent-based antibacterial agent of the present invention is significantly superior to that of the polyamide composite reverse osmosis membrane that is not grafted, regardless of whether it is against gram-positive bacteria (Bacillus subtilis) or gram-negative bacteria (Escherichia coli).
In conclusion, the invention realizes the doping and surface grafting of the nano material of the reverse osmosis membrane under the condition of not damaging the original structure of the polyamide separation layer, and the obtained polyamide composite reverse osmosis membrane has high selective permeability and antibacterial property, which is a new breakthrough in the aspect of water treatment application of the composite reverse osmosis membrane and has very important theoretical and practical significance for effectively prolonging the service life of the membrane material.
The present invention has been described in detail with reference to the examples, but the present invention is only preferred examples of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention.
Claims (10)
1. A polyamide composite reverse osmosis membrane is characterized in that: comprises a porous ultrafiltration membrane supporting layer, an aromatic polyamide layer and an antibacterial layer; the aromatic polyamide layer covers the porous ultrafiltration membrane supporting layer, and comprises a nano material; the antibacterial layer is formed by connecting the nanometer material on the outer side of the aromatic polyamide layer with an antibacterial material through a covalent bond.
2. The polyamide composite reverse osmosis membrane of claim 1, wherein: the nano material is hydrotalcite, preferably Mg-Al-CO3Hydrotalcite.
3. The polyamide composite reverse osmosis membrane of claim 1, wherein: the antibacterial material is a silane coupling agent type antibacterial material, and is preferably dimethyl octadecyl [3- (trimethoxysilyl) propyl ] ammonium chloride.
4. The polyamide composite reverse osmosis membrane of claim 1, wherein: the porous ultrafiltration membrane supporting layer is a polysulfone ultrafiltration membrane, and the pore size distribution is concentrated in the range of 10nm-100 nm.
5. A preparation method of a polyamide composite reverse osmosis membrane is characterized by comprising the following steps: preparing an aromatic polyamide layer on a porous ultrafiltration membrane supporting layer, and doping a nano material in the aromatic polyamide layer to obtain a mixed matrix reverse osmosis membrane; and connecting the nano material on the surface of the reverse osmosis membrane with the antibacterial material through a covalent bond to form an antibacterial layer, thus obtaining the polyamide composite reverse osmosis membrane.
6. The method of preparing a polyamide composite reverse osmosis membrane according to claim 5, characterized in that: the preparation method of the mixed matrix reverse osmosis membrane comprises the following steps: contacting the surface of the porous ultrafiltration membrane supporting layer with an aqueous phase solution; then contacting with organic phase solution dispersed with nano material to make water phase monomer and organic phase monomer react; and finally, carrying out heat treatment to obtain the mixed matrix reverse osmosis membrane.
7. The method of preparing a polyamide composite reverse osmosis membrane according to claim 6, characterized in that: before the porous ultrafiltration membrane supporting layer is contacted with the aqueous phase solution, soaking and washing the porous ultrafiltration membrane supporting layer in water, and purging the porous ultrafiltration membrane supporting layer with nitrogen until no liquid drops exist on the surface; the reaction time is 45-70 s; the temperature of the heat treatment is 60-90 ℃, and the time of the heat treatment is 4-8 min.
8. The method of preparing a polyamide composite reverse osmosis membrane according to claim 6, characterized in that: the porous ultrafiltration membrane supporting layer is a polysulfone ultrafiltration membrane, and the pore size distribution is concentrated in the range of 10nm-100 nm; the water phase monomer is aromatic primary diamine, preferably m-phenylenediamine; the organic phase monomer is polyfunctional acyl chloride, preferably trimesoyl chloride; the solvent of the organic phase solution is n-hexane; the nano material is hydrotalcite, preferably Mg-Al-CO3Hydrotalcite.
9. The method of preparing a polyamide composite reverse osmosis membrane according to claim 6, characterized in that: the mass percentage of the aqueous phase monomer in the aqueous phase solution is 2-3 wt%; the additive of the aqueous phase solution is a composite additive consisting of triethylamine and camphorsulfonic acid; the triethylamine accounts for 1 to 2 weight percent of the aqueous phase solution; the mass percent of the camphorsulfonic acid in the aqueous phase solution is 2-4 wt%; the nano material accounts for 0.010-0.075 wt% of the organic phase solution; the organic phase monomer accounts for 0.06wt% -0.15wt% of the organic phase solution.
10. The method of preparing a polyamide composite reverse osmosis membrane according to claim 5, characterized in that: the method for forming the antibacterial layer by connecting the nanometer material on the surface of the reverse osmosis membrane with the antibacterial material through the covalent bond specifically comprises the following steps: carrying out contact standing reaction on a methanol solution of an antibacterial material and the mixed matrix reverse osmosis membrane, and cleaning after the reaction is finished; wherein the antibacterial material is a silane coupling agent antibacterial material, preferably dimethyl octadecyl [3- (trimethoxysilyl) propyl ] ammonium chloride; the mass percentage of the antibacterial material in the methanol solution of the antibacterial material is 0.02wt% -0.50 wt%; the reaction temperature is 20-30 ℃, and the reaction time is 1-3 h.
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