KR20110098499A - Reverse osmosis membrane containing carbon nanotube and method for preparing thereof - Google Patents

Abstract

The present invention relates to a reverse osmosis membrane having a carbon nanotube inserted therein, and more particularly, to a reverse osmosis membrane having improved chlorine resistance of a reverse osmosis membrane active layer by inserting carbon nanotubes in the manufacture of a reverse osmosis membrane for seawater desalination, and a method of manufacturing the same. will be. According to the present invention, by adding a carbon nanotube to an aqueous polymer electrolyte solution to prepare a reverse osmosis membrane including a polymer electrolyte-based multilayer thin film self-assembly active layer, it is possible to provide a reverse osmosis membrane having low chemical resistance, particularly chlorine resistance, which is a weak point of a conventional reverse osmosis membrane. have. Thus improved chlorine resistance reverse osmosis membrane can be usefully used as a reverse osmosis membrane for seawater desalination.

Description

Reverse Osmosis Membrane Containing Carbon Nanotube and Method for Preparing Thereof}

The present invention relates to a reverse osmosis membrane having a carbon nanotube inserted therein, and more particularly, to a reverse osmosis membrane having improved chlorine resistance of the reverse osmosis membrane active layer by inserting carbon nanotubes during the preparation of the reverse osmosis membrane.

The reverse osmosis membrane consists of an active layer to remove salts in seawater and a support layer to support the active layer to withstand high pressure operating conditions. In 1960, UCLA's Loeb and Sourirajan developed the first reverse osmosis membrane using cellulose acetate, which was cheaper in production and easy to process, but weak in physical properties, resulting in narrow conditions for use and vulnerability to contamination. As a result of continued development, the mainstream of the currently commercially available reverse osmosis membrane is formed by polymerizing aromatic polyamide series, especially m-phenylene diamine and trimesoyl chloride. A composite membrane composed of an active layer and a porous polysulfone support layer supporting the same has been used.

However, this type of reverse osmosis membrane has a problem of low permeation rate due to the low porosity peculiar to the polyamide active layer and a bond that is susceptible to oxidation by chlorine ions. This has a shortened problem. This problem was not solved even in the reverse osmosis membrane through the conventional multilayer thin film self-assembly method. The polyamide amine hydrochloride (PAH) and polyacrylic acid (PAA), which are the raw materials used in this method, are the same amide bond as the polyamide membrane. Because. Therefore, there is a need to improve the conventional method in order to increase the durability against chlorine ions.

Multilayer thin films made using a method called multilayer thin film self-assembly can improve the function of thin films by inserting a separate material into each layer having a nanometer-class thickness as well as various lamination methods and stackable materials. Because of this, various researches are being conducted around the world that apply these properties, and the scope is also limited to membranes, anti-reflection films, biosensors, micropatterning, and photonic crystals. ) And so on.

The study of the multilayer thin film produced by the self-assembly method was first started by Decher et al. Of Mainz University in 1991. Subsequently, the substrate and material were immersed in a polyallylamine hydrochloride aqueous solution for a predetermined time by substituting a negative charge for a glass substrate. Induces adsorption through electrostatic attraction between the cells and gently washes them to drop the weakly adsorbed polyarylamine hydrochloride (PAH), followed by aqueous solution of poly (sodium styrene sulfonate) (PSS) By repeating the process of immersing the PSS again, the process was developed to produce a multilayer thin film. Later, in 1998, Max Planck Institute's Mohwald et al. Demonstrated a significant expansion of this new technology's range of applications by laminating multi-layered thin films on colloidal particles and removing colloids to produce hollow silica-polymer structures. More than thousands of papers are published annually in this field.

Under the technical background as described above, the present inventors have made efforts to develop reverse osmosis membranes having enhanced chlorine resistance. As a result, the present inventors have confirmed that chlorine resistance is enhanced by introducing self-assembled thin films incorporating carbon nanotubes into the reverse osmosis membranes, and have completed the present invention. .

As a result, an object of the present invention is to provide a reverse osmosis membrane having enhanced chlorine resistance by providing a self-assembled thin film in which carbon nanotubes are inserted as an active layer.

Another object of the present invention is to provide a method for enhancing chlorine resistance by providing a self-assembled thin film inserted into a polymer electrolyte layer as a carbon nanotube in the production of a reverse osmosis membrane.

According to an aspect of the present invention to achieve the above object, an active layer in which carbon nanotubes are inserted into a self-assembled thin film made of a combination of a cationic polymer electrolyte layer and an anionic polymer electrolyte layer; And a reverse osmosis membrane having improved chlorine resistance having a support layer made of a porous support.

According to one embodiment of the reverse osmosis membrane according to the present invention, the carbon nanotubes may be inserted into the anionic polymer electrolyte layer.

According to one embodiment of the reverse osmosis membrane according to the present invention, the porous support may be a polysulfone ultrafiltration membrane.

According to one embodiment of the reverse osmosis membrane according to the present invention, the porous support may be an ultrafiltration membrane having a pore of 0.001 ~ 0.01 μm.

According to one embodiment of the reverse osmosis membrane according to the present invention, the cationic polymer electrolyte may be polyaryl arylamine, and the anionic polymer electrolyte may be polyacrylic acid.

According to one embodiment of the reverse osmosis membrane according to the present invention, the carbon nanotubes may be multi-walled carbon nanotubes.

According to one embodiment of the reverse osmosis membrane according to the present invention, the carbon nanotubes may be surface modified with carboxylic acid.

According to one embodiment of the reverse osmosis membrane according to the present invention, the self-assembled thin film may be a multilayer self-assembled thin film.

According to another aspect of the invention, preparing a porous support; Anion treating the surface of the porous support; The anion-treated porous support is immersed in an aqueous cationic polymer electrolyte solution so that the cationic polymer electrolyte is adsorbed, and the porous support on which the cationic polymer electrolyte is adsorbed is immersed in an anionic polymer electrolyte solution containing carbon nanotubes. To form an active layer; There is provided a method for producing a reverse osmosis membrane comprising the step of heating the porous support formed on the surface of the active layer.

According to one embodiment of the reverse osmosis membrane manufacturing method according to the present invention, the step of forming the active layer may be repeated two or more times to adjust the thickness of the active layer.

According to one embodiment of the reverse osmosis membrane manufacturing method according to the present invention, the step of forming the active layer may be performed repeatedly 10 to 20 times.

According to one embodiment of the reverse osmosis membrane production method according to the invention, the porous support may be a polysulfone ultrafiltration membrane.

According to one embodiment of the reverse osmosis membrane production method according to the present invention, the anion surface treatment of the porous support consisting of a polysulfone ultrafiltration membrane may be performed using a sulfonation reaction or ozone plasma treatment.

According to one embodiment of the reverse osmosis membrane manufacturing method according to the invention, the porous support may be an ultrafiltration membrane having a pore of 0.001 ~ 0.01 ㎛.

According to one embodiment of the reverse osmosis membrane manufacturing method according to the present invention, the cationic polymer electrolyte aqueous solution may be an aqueous polyaryl arylamine solution.

According to one embodiment of the reverse osmosis membrane manufacturing method according to the present invention, the anionic polymer electrolyte aqueous solution may be a polyacrylic acid aqueous solution.

According to one embodiment of the reverse osmosis membrane manufacturing method according to the present invention, the step of heating the porous support formed on the surface of the active layer may be performed for 1 to 3 hours at 150 ℃ to 200 ℃.

According to the present invention, by adding a carbon nanotube to an aqueous polymer electrolyte solution to prepare a reverse osmosis membrane including a polymer electrolyte-based multilayer thin film self-assembly active layer, it is possible to provide a reverse osmosis membrane having low chemical resistance, particularly chlorine resistance, which is a weak point of a conventional reverse osmosis membrane. have. As such, the reverse osmosis membrane having improved chlorine resistance may be usefully used as a reverse osmosis membrane for seawater desalination.

Reverse osmosis membrane with improved chlorine resistance is resistant to the attack of chlorine ions and has the advantage that performance does not occur even after prolonged use for longer periods of time immediately after manufacture, and this advantage can improve the salt removal efficiency of the reverse osmosis membrane, The high strength, which is the characteristic of carbon nanotubes, is applied to the reverse osmosis membrane, so that the active layer can be maintained for a long time even under high pressure operating conditions. Therefore, the permeation flow rate can be expected to be increased by increasing the permeation rate.

FIG. 1 is a process chart for forming an activated layer of a reverse osmosis membrane made of an electrolyte polymer multilayer thin film in which carbon nanotubes are inserted on a surface of a polysulfone ultrafiltration (UF) membrane that is a supporting layer.
2 shows the FT-IR spectra before and after the modification of the multi-walled carbon nanotubes to the carboxylic acid.
3 shows the thickness of the MWCNTs / polymer electrolyte multilayer film with increased number of bilayers deposited on the support.
Figure 4 shows the thermal analysis results for confirming the thermal stability of the reverse osmosis membrane prepared in Example 1.
FIG. 5 shows the salt removal and transmission rates of (MWCNTs-PAA / PAH) n multilayers containing 1 wt% MWCNTs with 10, 15, and 20 bilayers in (a), (b), and (c), respectively. This graph shows over time.
6 shows the salt removal rate of reverse osmosis (RO) membranes before and after treatment with NaOCl solution.

The present invention provides a reverse osmosis membrane having improved chlorine resistance by inserting carbon nanotubes in a process of manufacturing a thin film by a self-assembly method and a method of manufacturing the same.

Since carbon nanotubes were discovered in 1991 by 飯 島 澄 男, carbon nanotubes have received extraordinary attention from academia due to the combination of strength over diamond, extremely large diameter-to-length ratio, and chemically inert properties. IBM's Bethune and others discovered single-walled carbon nanotubes, which attracted new attention for their electrical properties, opening the door for device applications. In 1998, Wagner et al. Of the Weizmann Institute of Science reported that polymers containing carbon nanotubes showed significantly improved physical properties compared to general polymers, and research using composite materials of polymers and carbon nanotubes was activated.

Hereinafter, a process of manufacturing a reverse osmosis membrane in which carbon nanotubes are inserted according to the present invention will be described in detail with reference to the accompanying drawings.

The manufacturing process of the reverse osmosis membrane active layer according to the present invention will be described with reference to FIG. 1. FIG. 1 is a process diagram for forming an activated layer of a reverse osmosis membrane made of an electrolyte polymer multilayer thin film in which carbon nanotubes are inserted on a surface of a polysulfone ultrafiltration (UF) membrane that is a supporting layer.

First, prepare a porous support. The ultrafiltration membrane is not particularly limited as the porous support, but in one embodiment of the present invention, a polysulfone ultrafiltration membrane was used.

In addition, it is preferable to use a porous support having a pore in the range of 0.001 ~ 0.01 ㎛, which has a problem that the permeate flow rate is reduced when the pore size is less than 0.001 ㎛, the strength for supporting the active layer when more than 0.01 ㎛ It is because of difficulty in formation.

Next, anion is treated on the surface of the porous support prepared as described above so that the polymer electrolyte can be adsorbed on the surface through the electrostatic attraction. Anion surface treatment of the porous support made of a polysulfone ultrafiltration membrane used in one embodiment of the present invention can be carried out using a sulfonation reaction or ozone plasma treatment. The sulfonation reaction may be carried out by precipitation of a polysulfone ultrafiltration membrane in an aqueous 0.5 mol sulfuric acid solution to generate sulfone functional groups (-SO ₃ ) on the surface through heating at 130 ° C. for 60 minutes, and ozone plasma treatment. May be performed in a manner of inducing negative charge through ozone plasma treatment for 3 seconds on 1 cm of surface.

Then, the anionic treated porous support is immersed in a cationic polyelectrolyte aqueous solution so that the cationic polymer electrolyte is adsorbed, and the porous support on which the cationic polymer electrolyte is adsorbed is anionic polymer electrolyte solution containing carbon nanotubes. Immersion treatment to form an active layer. The process of forming the active layer may be repeated two or more times to process the cationic polymer electrolyte and the anionic polymer electrolyte, the thickness of the active layer can be adjusted according to the number of times repeated.

In one embodiment of the present invention it is preferable to repeat the active layer forming step 10 to 20 times to be used as a reverse osmosis membrane. This is because if the active layer forming step is repeated less than 10 times, the thickness of the active layer is too thin to secure a salt removal rate, and if the active layer is repeated more than 20 times, the active layer thickness is too thick and thus the permeate flow rate is reduced.

Materials used in preparing the active layer using the multilayer thin film self-assembly method on the anionic surface-treated porous support are as follows. The anionic polyelectrolyte solution may be a solution in which 0.1 weight percent of surface modified carbon nanotubes are dissolved in 0.1 weight percent polyacrylic acid aqueous solution titrated at pH 3-4, and the cationic polyelectrolyte solution is titrated at pH 7-8. A weight percent polyaryl hydrochloride aqueous solution is used. According to the hydrogen ion concentration of each solution, the amount of charge carried by the polymer electrolyte in the solution may be controlled, and accordingly, the thickness of the stack may be controlled due to the change of polymer conformation.

In addition, carbon nanotubes are mixed with an acid solution mixed with nitric acid and sulfuric acid in a weight ratio of 3: 1, heated at 70 ° C. for 24 hours, diluted with distilled water, and filtered to use a carboxyl surface-modified product. It is preferable to use carbon nanotubes having a surface modified with a carboxyl group because they have excellent solubility in anionic polyelectrolyte aqueous solution and easy bond formation with the cationic polyelectrolyte aqueous solution compared to general carbon nanotubes.

In addition, since multi-walled carbon nanotubes are easy to mass-produce, cost can be reduced compared to the use of single-walled carbon nanotubes, and physical properties are better than single-walled carbon nanotubes, so it is preferable to use multi-walled carbon nanotubes. Do.

The active layer formed through the above process is a state in which the cationic polymer layer and the anionic polymer layer are bonded by electrostatic attraction. The porous support on which the active layer is formed is heat treated to convert this electrostatic attraction into stronger chemical bonds. Through heat treatment, the bond due to the electrostatic attraction between the cationic polymer and the cationic polymer is converted into crosslinking between the cationic polyelectrolyte and the anionic polyelectrolyte, which can be used as a more robust reverse osmosis membrane. The heat treatment may be performed by heating the porous support on which the active layer is formed at 150 ° C. to 200 ° C. for 1 to 3 hours. Since heat treatment is for forming an amide bond by mutual coupling of a carboxyl group and an amine group, it is preferable to process at 150 degreeC or more and 200 degrees C or less high temperature.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, these Examples are only for illustrating the present invention, and the scope of the present invention will not be construed as being limited by these Examples.

Example  1: Preparation of Reverse Osmosis Membrane with Active Layer

end. Preparation of the ingredients

Polyacrylic acid (PAA) (Polysciences, Mw = 100,000 g / mol) was used as an anionic polymer electrolyte to prepare a reverse osmosis membrane having a multi-layer self-assembled thin film in which carbon nanotubes were inserted as an active layer. Poly (allylamine hydrochloride (PAH) (Aldrich, Mn = 56,000 g / mol) (Aldrich, Mw = 200,000 to 350,000 g / mol) is used as the polymer electrolyte. As a porous support, an asymmetric porous polysulfone membrane (Trisep, UE50, 100,000 g / mol) was used, and multi-walled carbon nanotubes (MWCNTs) were 9 12 nm in average diameter and length from single CNTs, respectively. And 10 15 mm were purchased and used.

I. Multiwall  Surface Modification of Carbon Nanotubes and Preparation of Polymer Electrolyte Solution

In order to use the multi-walled carbon nanotubes of the self-assembled thin film, the multi-walled carbon nanotubes were carboxylated. Multi-walled carbon nanotubes were diffused into a mixed solution of 1 MH ₂ SO ₄ and 1 M HNO ₃ (3: 1 volume ratio) and refluxed at 70 ° C. overnight (about 24 hours). Multi-walled carbon nanotubes were separated by centrifugation at 10,000 rpm for 10 minutes and sonicated with deionized water. This process was repeated at least three times. Then, the obtained carboxylated multi-walled carbon nanotubes were dried under vacuum for 12 hours.

The presence of carboxylic acid in the multi-walled carbon nanotubes prepared through the above process was analyzed by Fourier Transform Infrared (FT-IR) spectroscopy. FT-IR spectra were used with a FTIR-200 spectrometer (JASCO) with a CaF ₂ window. Figure 2 shows the FT-IR spectrum before and after the modification of the multi-walled carbon nanotubes to carboxylic acid. There was no specific peak before the modification except for the presence of aromatic carbon in the MWCNTs, but after treatment with a mixture of H ₂ SO ₄ and HNO ₃ showed several peaks due to the carboxylation of MWCNTs. Carbonyl group (1703 cm ⁻¹ , -C═O of COOH), carboxyl group (1568 cm ⁻¹ , -COO ⁻ ) in the FT-IR spectrum of FIG. 2, and OH groups of carboxylic acids at 2500 to 3500 cm ⁻¹ The presence of a broad peak was found.

The carboxyl surface-modified carbon nanotubes were mixed with 1 wt% of an anionic PAA solution at 1.0 mg / mL (0.1 wt%) at a pH of 3-4 and sonicated for 3 hours. The cationic PAH solution was also adjusted to a concentration of 1.0 mg / mL (0.1 wt%) titrated to pH 7-8, and the pH of the anionic PAA / MWCNTs and cationic PAH solution was prepared by adjusting 0.1 M HCl and NaOH.

All. Multiwall  Carbon nanotube ( MWCNT ) / Polymer electrolyte ( MWCNT Of PE ) Active layer formation

Polysulfone ultrafiltration membranes were prepared as porous supports and treated with 0.5 MH ₂ SO ₄ solution at 80 ° C. for 30 minutes. Thereafter, the treated support was first immersed in cationic polyallylamine hydrochloride (PAH) solution for 10 minutes to form self-assembled multi-walled carbon nanotubes / electrolyte (MWCNTs / PE) multilayer and each with deionized water. After washing twice for 1 minute, it was dried with mild nitrogen air. Next, the porous support coated with the cationic polymer electrolyte was immersed in an anionic MWCNTs / PAA aqueous solution for 10 minutes to allow the anionic MWCNTs / PAA to be adsorbed, washed with deionized water and air dried. This process was repeated until the desired number of bilayers were obtained. In addition, in order to impose chemical crosslinking between the cationic PAH and the anionic MWNTs / PAA layers (MWCNTs-PAA / PAH) _n (n is repeated recovery of the bilayer) the multilayer film is heated to 180 ° C. under vacuum for 1 hour. A reverse osmosis membrane was prepared having an active layer into which a tube was inserted.

The thickness of the (MWCNTs-PAA / PAH) _n multilayer film formed on the porous support was measured by ellipsometry (Gaertner Scientific Corp, L2W15S830) using 632.8 nm He-Ne laser light. (MWCNTs-PAA / PAH) _n Multi-layer surface properties were analyzed using a field emission-scanning electron microscopy (FE-SEM, Hitachi, S-4300).

3 shows the thickness of the MWCNTs / polymer electrolyte multilayer film with increased number of bilayers deposited on the support. MWCNTs / polymer electrolyte multilayers were deposited under conditions of pH 7.5 for PAH and pH 3.5 for MECNTs / PAA. In this case, the film thickness was increased from 2 nm to 280 nm for 10 bilayers for one bilayer showing a typical exponential increase in the deposition of self-assembled multilayer films of multilayered polymer electrolytes.

After treating the H ₂ SO ₄ solution to impose a negative charge on the polysulfone ultrafiltration membrane, MWCNTs / PE multilayers (MWCNTs-PAA / PAH) _n having 10, 15 and 20 bilayers were prepared. The (MWCNTs-PAA / PAH) n multilayer film was heated under vacuum at 180 ° C. for 1 hour to impart amide crosslinking between the MWCNTs-PAA / PAH layers as described above. 2B shows SEM images of cross-sectional views of crosslinked (MWCNTs-PAA / PAH) _n multilayers with bilayers of 10, 15 and 20. FIG. (MWCNTs-PAA / PAH) The thicknesses of the _n multilayers were 200 nm, 250 nm, and 310 nm, respectively. Film thickness was significantly reduced due to the dense crosslinked structure due to heat treatment.

Example  2: reverse osmosis membrane Thermal stability  Confirm

Thermal analysis was performed by TGA-Q50 (TA) to determine the presence of multi-walled carbon nanotubes in the (MWCNTs-PAA / PAH) _n multilayer and its thermal stability. In this case, a selective layer, (MWCNTs-PAA / PAH) _n multilayer powder was rubbed with a doctor blade. TGA is a N ₂ at a heating rate of 10 ℃ / min in the range of room temperature to 1000 ℃ The cleaning gas was set.

4 shows the results of the thermal analysis. Pure MWCNTs were thermally stable up to 750 ° C. and slightly (<20%) decomposed above. In contrast, the (PAH / PAA) _n membrane shows a rapid decrease in the temperature range of 420 ° C. to 510 ° C. This is due to the thermal decomposition of (PAH / PAA) _n multilayers. In addition, the membrane shows a continuous decrease from 200 ° C to 420 ° C with small bumps, due to the decomposition of the remaining solvent in the multilayer or the low molecular weight portion of the polysulfone ultrafiltration membrane that forms the support layer. This property is similar to that of (MWCNTs-PAA / PAH) _n multilayers. However, it shows a significant change in the thermal decomposition in the range of 420 ~ 510 ℃. For (MWCNTs-PAA / PAH) _n multilayers, it can be clearly seen that pyrolysis was significantly delayed and continued to about 750 ° C.

These results show that MWCNTs are well introduced into the multilayer and that the thermal stability of (MWCNTs-PAA / PAH) _n multilayer is also improved due to the addition of a small amount of MWCNTs, as shown in FIG. 4 (MWCNTs -PAA / PAH) _n Multilayer thermal stability appears to be due to strong electrostatic interactions and covalent bonds between the carboxylated MWCNTs and the polymer electrolyte (eg PAA and PAH) matrices.

Example  3: Reverse osmosis performance of reverse osmosis membrane

(MWCNTs-PAA / PAH) Reverse osmosis (RO) performance of _n multilayers was measured using a well-known self-made reverse osmosis test system. Reverse osmosis performance was located in the pressure chamber (effective area of the membrane cell = 13.85 cm ² pressure = 15.5 bar). The rate of feed water and the concentration of ionic salts (NaCl) were 333 L / m ² h and 2000 ppm at room temperature, respectively. The bottom part of the cell was provided with a permeate outlet. Ion concentration of the discharge solution was measured using an ionic conductivity meter (EUTECH, PC650). The salt removal rate and permeate flow rate of the reverse osmosis membrane were calculated according to the following equations.

(1)

(One)

(2)

(2)

(Salt rejection is the salt rejection rate, permeate conductance is permeation conductivity, feed conductance is injection conductivity, permeate flux is permeation rate, permeate is permeation rate, membrane is membrane and time is time.)

5 shows salt removal rates and permeation rates of (MWCNTs-PAA / PAH) _n multilayers containing 1 wt% MWCNTs with 10, 15, and 20 bilayers in (a), (b), and (c), respectively. Shown over time. After about 60 minutes of operation, the salt removal rate and permeation rate were stabilized and all the membranes showed similar performance regardless of the number of bilayers. In this case, the salt removal rate and permeation rate of each of the (MWCNTs-PAA / PAH) _n multilayers containing 1 wt% of MWCNTs were 90.4% for n = 10 and 2.6 L / m ² h, 89.6 for n = 15. 91.2% and 2.1 L / m ² h for% and 3.6 L / m ² h and n = 20. On the other hand, when preparing a multi-layer (MWCNTs-PAA / PAH) ₅ with five bilayers, the salt removal rate was about 50-60%, indicating that it was too thin to function as a reverse osmosis membrane. Therefore, it was found that 10 bilayers are the optimal structure having the lowest number of bilayers in _n multilayers (MWCNTs-PAA / PAH) when considering reverse osmosis performance.

Example  4: reverse osmosis membrane Chlorine Tolerance  Confirm

In order to confirm the chemical resistance to chlorine of the reverse osmosis membrane prepared in Example 1, a nanocomposite (MWCNTs-PAA / PAH) n multilayer was immersed in 3,000 ppm sodium hypochlorite (NaOCl) solution for 4 hours, and then the membrane was deionized water. Wash and compare the salt removal rate. (MWCNTs-PAA / PAH) _n Polyamide reverse osmosis membranes were prepared by interfacial polymerization of 1,3-benzenediamine and trimesoyl chloride to quantitatively compare the chemical resistance of multiple layers. It is well known that the conventional polyamide reverse osmosis membrane has a weak resistance to chlorine. When the amide bond is exposed to chlorine, the NH bond is easily chlorinated and oxidized due to hydrolysis with water to form a quinone structure. The reaction breaks down the amide network of the reverse osmosis membrane in a chain manner. Thus, chlorination of the polyamide membrane causes serious defects and significantly reduces the salt removal rate.

In the reverse osmosis membrane prepared in Example 1, the binding of the inorganic MWCNT is improved not only thermal stability but also chemical resistance due to the electrostatic interaction and covalent bonding between the MWCNTs and the polymer matrix. 6 shows the salt removal rate of reverse osmosis (RO) membranes before and after treatment with NaOCl solution. The salt removal rate for the polyamide membrane was reduced by 21.8% (98.3% to 76.5%) by chlorination. However, the (MWCNTs-PAA / PAH) _n multilayers had 16.2% (90.4% to 74.2%), 15.2% (89.6% to 74.4%), and 9.9% (91.2%) for n = 10, 15, and 20, respectively. At 82.4%).

Since the reduction in salt removal rate is the main cause of defects in the membrane structure, the chemical resistance to chlorine is closely related to the relative amount of reduction in salt removal rate after chlorination. Therefore, it can be seen that the (MWCNTs-PAA / PAH) _n multilayer had better chemical resistance to chlorine than the polyamide membrane, and the number of bilayers reduced the reduction of the salt removal rate after chlorination. Therefore, it can be seen that the optimal structure among the reverse osmosis membranes prepared in Example 1 was ₂₀ multilayers having better chlorine resistance (MWCNTs-PAA / PAH) while showing reverse osmosis performance similar to those of 10 and 15 bilayers.

The specific parts of the present invention have been described in detail above, and it is apparent to those skilled in the art that such specific descriptions are merely preferred embodiments, and thus the scope of the present invention is not limited thereto. something to do. It is therefore intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims (17)

An active layer in which carbon nanotubes are inserted into a self-assembled thin film made of a combination of a cationic polymer electrolyte layer and an anionic polymer electrolyte layer; And
Reverse osmosis membrane with improved chlorine resistance having a support layer made of a porous support.
The reverse osmosis membrane according to claim 1, wherein the carbon nanotubes are inserted into the anionic polymer electrolyte layer.
The reverse osmosis membrane of claim 1, wherein the porous support is a polysulfone ultrafiltration membrane.
The reverse osmosis membrane according to claim 1, wherein the porous support is an ultrafiltration membrane having pores of 0.001 to 0.01 µm.
The reverse osmosis membrane according to claim 1, wherein the cationic polymer electrolyte is polyaryl arylamine, and the anionic polymer electrolyte is polyacrylic acid.
The reverse osmosis membrane according to claim 1, wherein the carbon nanotubes are multi-walled carbon nanotubes.
The reverse osmosis membrane according to claim 1, wherein the carbon nanotubes are surface-modified with carboxylic acid.
The reverse osmosis membrane of claim 1, wherein the self-assembling thin film is a multilayer self-assembling thin film.
In the method for producing a reverse osmosis membrane having a porous support formed on the surface of the active layer,
Preparing a porous support;
Anion treating the surface of the porous support;
The anionic-treated porous support is immersed in an aqueous cationic polymer electrolyte solution so that the cationic polymer electrolyte is adsorbed, and the porous support on which the cationic polymer electrolyte is adsorbed is immersed in an anionic polymer electrolyte solution containing carbon nanotubes. To form an active layer; And
Heat-treating the porous support formed on the surface of the active layer
Method for producing a reverse osmosis membrane comprising a.
The method of claim 9, wherein the forming of the active layer is repeated two or more times to adjust the thickness of the active layer.
The method of claim 10, wherein the forming of the active layer is repeated 10 to 20 times.
The method of claim 9, wherein the porous support is a polysulfone ultrafiltration membrane.
The method for producing a reverse osmosis membrane according to claim 12, wherein the anion surface treatment of the porous support made of the polysulfone ultrafiltration membrane is performed using a sulfonation reaction or an ozone plasma treatment method.
The method of claim 9, wherein the porous support is a method for producing a reverse osmosis membrane, characterized in that the ultrafiltration membrane having a pore of 0.001 ~ 0.01 ㎛.
10. The method of claim 9, wherein the cationic polyelectrolyte aqueous solution is a polyaryl arylamine aqueous solution.
The method of claim 9, wherein the anionic polyelectrolyte aqueous solution is a polyacrylic acid aqueous solution.
The method of claim 9, wherein the heat treatment of the porous support on the surface of the active layer is performed at 150 ° C. to 200 ° C. for 1 to 3 hours.

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