KR102337164B1 - Excellent removing nitrate polyamide reverse osmosis membrane, Method of manufacturing the same and Membrane module comprising the same - Google Patents

Abstract

The present invention relates to a polyamide-based reverse osmosis membrane used in a household water purifier, wherein the conventional polyamide-based reverse osmosis membrane had a low nitrate removal rate under city water conditions containing a high concentration of hardness-inducing substances. The reverse osmosis membrane prepared by secondary coating with a specific amine compound has a relatively high surface negative charge concentration, that is, as the electrostatic attraction between the hardness-inducing material and the surface of the separation membrane is weakened, the surface accumulation of the hardness-inducing material is reduced. , to provide a reverse osmosis membrane having an excellent nitrate nitrogen removal rate, a method for manufacturing the same, and a membrane module including the reverse osmosis membrane.

Description

Polyamide-based reverse osmosis membrane having excellent nitrate nitrogen removal rate, manufacturing method thereof, and membrane module comprising the same

The present invention relates to a reverse osmosis membrane used in household water purifiers, and more particularly, a polyamide-based reverse osmosis membrane having an excellent nitrate nitrogen removal rate even under raw water conditions with a low surface negative charge and a high content of hardness-inducing substances, and manufacturing thereof It relates to a method and a separation membrane module including the same.

As a method of separating various components such as fine impurities and ions present in a liquid, there are generally evaporation methods, electrodialysis methods, microfiltration methods, ultrafiltration methods, reverse osmosis methods, and the like. Among them, the reverse osmosis method has advantages in that energy consumption is low, it is possible to construct a small as well as large-scale facility, and even monovalent ions in water can be removed.

In general, the separation membrane used in the reverse osmosis method includes a nano separation membrane or a reverse osmosis membrane. Among them, the reverse osmosis membrane consists of a support layer for maintaining mechanical strength and an active layer with selective permeability. Recently, aromatic polysulfone is used as a porous support layer, A reverse osmosis membrane composed of polyamide as an active layer is being developed and commercialized.

The manufacturing method of the reverse osmosis membrane includes a thin layer dispersion method, a dip coating method, a vapor deposition method, a Langmuir-Blodgett method, an interfacial polymerization method, and the like. There is an interfacial polymerization method disclosed by Cadotte).

As an example of the interfacial polymerization method, in U.S. Patent No. 4277344, an aromatic polyfunctional amine containing at least two primary amine substituents and an aromatic acyl halide having at least three acyl halide substituents are interfacially polymerized. An aromatic polyamide composite membrane was disclosed. However, in the reverse osmosis membrane obtained through the interfacial polymerization method of the present invention, an unreacted acyl halide substitution agent inevitably remains on the surface of the reverse osmosis membrane after the completion of the reaction, and the residual acyl halide substitution agent is hydrolyzed through a water washing process after interfacial polymerization. and the carboxylic acid group is changed to . This mechanism can be explained as the reason that the surface of a general polyamide reverse osmosis membrane becomes negatively charged. When the surface of the reverse osmosis membrane becomes negatively charged, in particular, when raw water containing a high concentration of divalent cation components is treated, it causes the accumulation of high divalent ions on the membrane surface through electrostatic attraction. And finally, there is a problem that the nitrate nitrogen removal rate is reduced, research to solve this problem is urged.

On the other hand, among the domestic reverse osmosis water purifier certification items, the nitrate nitrogen test condition contains a hardness-inducing substance at a level of about 600 ppm. As a result, the nitrate nitrogen removal rate is significantly reduced compared to the nitrate nitrogen alone test.

US Registered Patent No. 4277344 (Registration Date: July 7, 1981)

The present invention has been devised to solve the above problems, and by secondary coating treatment with a solution containing a specific amine compound, the accumulation of divalent cation hardness components on the surface of the separator is minimized, and a high concentration of hardness-inducing substances is included. An object of the present invention is to manufacture a polyamide-based reverse osmosis membrane that exhibits excellent nitrate nitrogen removal rate even in fresh water and a membrane module including the same.

In order to solve the above problems, the present invention is a porous support; and a polyamide layer formed on at least one side of the porous support. It provides a polyamide-based reverse osmosis membrane having an excellent nitrate nitrogen removal rate, and a method for manufacturing the same.

As a preferred embodiment of the present invention, the reverse osmosis membrane may have a surface charge of -30 to -10 mV at pH 6 to 8.

As a preferred embodiment of the present invention, the porous support is a non-woven fabric; and a porous polymer layer.

As a preferred embodiment of the present invention, the porous polymer layer may include at least one selected from a polysulfone resin, a polyethersulfone resin, a polyimide resin, a polypropylene resin, and a polyvinylidene fluoride resin.

As a preferred embodiment of the present invention, the porous support may have an average thickness of 100 to 500 μm and an average pore size of 1 to 500 nm.

As a preferred embodiment of the present invention, the polyamide layer may include a primary coating film formed by reacting a polyfunctional amine compound and a polyfunctional acid halogen compound; and a secondary coating film formed on the upper surface of the primary coating film.

As a preferred embodiment of the present invention, the secondary coating film may be a film formed by reacting a polyfunctional acid halogen compound and an amine compound.

As a preferred embodiment of the present invention, the amine compound may include a compound satisfying the following formula (1) or the following formula (2).

[Formula 1]

In Formula 1, R ¹ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkylene group having 2 to 5 carbon atoms.

[Formula 2]

In Formula 2, R ² is an alkylene group having 2 to 5 carbon atoms.

As a preferred embodiment of the present invention, the reverse osmosis membrane may have a removal rate of 70 to 85% of nitrate nitrogen with respect to potable water containing 500 to 700 ppm of a hardness-inducing substance and 15 to 45 ppm of nitrate nitrogen. have.

As a preferred embodiment of the present invention, the hardness-inducing material may include one or more materials selected from calcium and magnesium.

For another object of the present invention, a method for manufacturing a polyamide-based reverse osmosis membrane having an excellent nitrate nitrogen removal rate comprises: a first step of coating a porous support with a first solution containing a polyfunctional amine compound; A second step of coating the second solution containing the polyfunctional acid halogen compound on the porous support that has been performed in step 1; Step 3 of removing the excess solution by spraying air on the porous support that has been performed in Step 2; A fourth step of thermally crosslinking the porous support having performed step 3 at a high temperature to form a primary coating film on at least one surface of the porous support; A fifth step of forming a secondary coating film on the upper surface of the primary coating film by reacting a third solution containing 0.001 to 0.10 wt% of an amine compound on the surface of the primary coating film; and step 6 of removing the acid or unreacted material remaining on the surface of the secondary coating film.

As a preferred embodiment of the present invention, the first solution may contain 0.1 to 10.0 wt% of metaphenylenediamine, 0.006 to 6.6 wt% of an additive, and the remaining amount of water, and the additive is ethylhexanediol, tetramethylhexa It may include at least one selected from diamine and toluenesulfonic acid.

As a preferred embodiment of the present invention, the second solution may contain 0.005 to 5.0% by weight of the polyfunctional acid halogen compound and the remaining amount of the organic solvent.

As a preferred embodiment of the present invention, the polyfunctional acid halogen compound may include at least one selected from a polyfunctional acyl halide, a polyfunctional sulfonyl halide, and a polyfunctional isocyanate.

As a preferred embodiment of the present invention, the organic solvent may include one or more selected from halogenated hydrocarbons, cycloalkanes having 6 to 12 carbon atoms, alkanes having 6 to 12 carbon atoms, and freons.

As another object of the present invention, it is possible to manufacture a separation membrane module including the reverse osmosis membrane.

The present invention can provide a polyamide-based reverse osmosis membrane having a lower surface negative charge value than that of a conventional polyamide reverse osmosis membrane, and excellent nitrate nitrogen removal rate even in city water containing a high concentration of hardness-inducing substances, and a method for manufacturing the same, A separation membrane module including the reverse osmosis membrane may be manufactured and applied to a household water purifier.

1 is a graph showing the measurement of the surface charge value according to the pH of the polyamide-based reverse osmosis membrane prepared in Examples 1, 2, and 4 in a graph.

Hereinafter, the present invention will be described in more detail.

In the present specification, a polyamide-based reverse osmosis membrane having an excellent nitrate nitrogen removal rate and a manufacturing method thereof are provided.

First, the reverse osmosis membrane of the present invention includes a porous support; and a polyamide layer. The polyamide layer may be formed on at least one side of the porous support, preferably on one side of the porous support.

In addition, the porous support is a non-woven fabric; and a porous polymer layer.

On the other hand, the non-woven fabric may be used without limitation as long as the non-woven fabric has specifications that can be commonly used in the art, and may preferably be a non-woven fabric made of polyester, polyethylene, or polypropylene material. The thickness of the nonwoven fabric may be 30 to 300 μm, preferably 50 to 200 μm. If the thickness of the nonwoven fabric is out of the above range, there may be a problem in that the permeate flow rate decreases.

On the other hand, the porous polymer layer may be a porous polymer layer formed of a commonly used material, preferably polyester resin, polysulfone resin, polyethersulfone resin, polyimide resin, polypropylene resin, and polyvinylidene flow. It may be formed by including one or more selected from the group consisting of a ride resin, and the average thickness of the porous polymer layer is 10 to 200 μm, preferably 30 to 190 μm . If the average thickness of the porous polymer layer is out of the above range, the water permeability is lowered, and thus it may be difficult to increase the effect .

In addition, the average thickness of the porous support may be 100 ~ 500㎛, preferably 100 ~ 300㎛. If the average thickness is less than 100㎛, the physical strength of the separation membrane is low, there may be a problem of defects due to damage to the separation membrane in the post-processing process for element formation, and if it exceeds 400㎛, the water permeability is lowered and the separation membrane There may be a problem that the performance of the In addition, the average pore size of the porous support may be 1 ~ 500nm, preferably 10 ~ 450nm, more preferably 50 ~ 400nm. If the pores of the porous support exceed 500 nm, since the ultra-thin film is recessed into the pores, there may be a problem in that a desired flat sheet structure cannot be formed.

On the other hand, the polyamide layer is a primary coating film on the upper surface of the porous support; and a secondary coating film formed on the upper surface of the primary coating film. In this case, the first coating film may be a film formed by reacting a polyfunctional amine compound and a polyfunctional acid halogen compound, and the secondary coating film may be a film formed by reacting a polyfunctional acid halogen compound and an amine compound. If the secondary coating film is not formed, unreacted acyl halide remaining on the surface of the primary coating film may be hydrolyzed through a water washing process to change to a carboxylic acid, resulting in a lower surface charge (surface negative charge). value) may be a problem.

On the other hand, among the domestic reverse osmosis water purifier certification items, the nitrate nitrogen test condition is a condition that contains a hardness-inducing substance at a concentration of about 600 ppm. As a result, the nitrate nitrogen removal rate is significantly reduced compared to the nitrate nitrogen alone test.

The reverse osmosis membrane of the present invention has a hardness-inducing substance of 500 to 700 ppm, preferably 550 to 650 ppm, and nitrate nitrogen 15 to 45 ppm, preferably 20 to 40 ppm of nitrate nitrogen, which are the nitrate test conditions. With respect to the number of hours containing In this case, the hardness-inducing material may be a divalent cation, and may preferably include calcium and magnesium.

In addition, the reverse osmosis membrane may have a surface charge of -30 to -10 mV at pH 6 to 8, preferably -28 to -15 mV. When the surface charge is lower than -30 mV, a hardness material may be accumulated on the surface through electrostatic attraction, and there may be a problem in that the nitrate nitrogen removal rate under the hardness-inducing material is lowered.

As another object of the present invention, the method for preparing a polyamide-based reverse osmosis membrane having improved nitrate nitrogen removal rate includes a first step of coating a first solution containing a polyfunctional amine compound on a porous support; A second step of coating the second solution containing the polyfunctional acid halogen compound on the porous support that has been performed in step 1; Step 3 of removing the excess solution by spraying air on the porous support that has been performed in Step 2; A fourth step of thermally crosslinking the porous support having performed step 3 at a high temperature to form a primary coating film on at least one surface of the porous support; a fifth step of forming a secondary coating film on the upper surface of the primary coating film by reacting a third solution containing an amine compound on the surface of the primary coating film; and step 6 of removing the acid or unreacted material remaining on the surface of the secondary coating film.

The porous support of step 1 may be prepared by casting the porous polymer layer on the nonwoven fabric.

The first solution of step 1 may be prepared including metaphenyldiamine, an additive, and water. The metaphenyldiamine may be included in an amount of 0.1 to 10% by weight, preferably in an amount of 0.3 to 6% by weight, and more preferably in an amount of 0.3 to 3% by weight of the total weight of the aqueous solution. If it is out of the above range, there may be a problem of a sudden decrease in flow rate.

Meanwhile, the additive may include at least one selected from ethylhexanediol (EHD), tetramethylhexadiamine (TMHD) and toluenesulfonic acid (TSA), and preferably, the additive is EHD, TMHD and TSA. It may include two or more selected from among, more preferably, the additive may include three or more selected from EHD, TMHD, and TSA, even more preferably, the additive is each of EHD, TMHD and TSA 1: It can be included in a ratio of 5.5 ~ 6.5 : 6.0 ~ 1 : 5.7 ~ 6.3 : 6.8.

In addition, the additive may be included in an amount of 0.003 to 6.6% by weight, preferably 0.006 to 6.0% by weight, based on the total weight of the aqueous solution. Specifically, the ethylhexanediol may be included in an amount of 0.001 to 0.60 wt%, preferably 0.002 to 0.55 wt%, based on the total weight of the first solution. In addition, the tetramethylhexadiamine may be included in an amount of 0.001 to 3.0% by weight, preferably 0.002 to 2.5% by weight, based on the total weight of the first solution. In addition, the toluenesulfonic acid may be included in an amount of 0.001 to 3.0% by weight, preferably 0.002 to 2.5% by weight, based on the total weight of the first solution. If the content of the additive is out of the above range, there may be a problem in that the permeate flow rate is reduced or the degree of polymerization of polyamide is lowered, thereby reducing the salt removal rate.

Meanwhile, the water may be included in the remaining amount excluding metaphenyldiamine and additives in the total weight of the first solution.

The coating treatment of step 1 may be performed for 20 to 60 seconds, and preferably may be performed for 25 to 55 seconds. Additionally, as a method of coating the first solution on the porous support, various methods such as immersion, impregnation and coating may be used, and the excess solution after application is rolled, sponge, air knife or other suitable means to the support. can be removed from

The second solution of step 2 is a polyfunctional acid halogen compound; and organic solvents. The polyfunctional acid halogen compound may include at least one compound selected from among polyfunctional acyl halides, polyfunctional sulfonyl halides and polyfunctional isocyanates, and the polyfunctional acyl halides are essentially monomeric, aromatic, and polyfunctional acyl halides. It may be a halide. Specifically, the polyfunctional acid halogen compound may include at least one selected from trimesoyl chloride (TMC), isophthaloyl chloride (IPC), terephthaloyl chloride (TPC), and tricarboxylic acid halide, , preferably TMC, IPC, TPC, and may be a compound comprising two or more selected from tricarboxylic acid halide, more preferably, the polyfunctional acid halogen compound is TMC and IPC 1: 0.2 to 1: 0.4 In a ratio of, preferably, it may be a compound comprising a ratio of 1: 0.25 to 1: 0.35.

The air injection of step 3 is to spray air to the porous support performing step 2 at a pressure of 0.1 to 1.0 bar, preferably under a pressure of 0.3 to 0.8 bar, for 5 to 20 seconds, preferably 10 to 15 seconds Excess organic solution can be removed by spraying during

Drying the porous support from which the excess organic solution is removed in step 3 at room temperature for 60 to 120 seconds, preferably drying for 70 to 110 seconds may be further included.

The first coating film of step 4 may be formed by thermal crosslinking of the polyfunctional amine compound and the polyfunctional halogen compound and grafting, and finally due to the thermal crosslinking, the hardness-inducing material and the electrostatic charge on the surface of the separator By reducing the attractive force, it is possible to minimize the accumulation of substances causing hardness on the surface of the separator. The thermal crosslinking may be performed by treating the porous support that has been subjected to step 3 under 40 to 80° C., preferably at 50 to 70° C., for 30 seconds to 20 minutes, preferably 50 seconds to 10 minutes.

The secondary coating film of step 5 is formed by reacting the unreacted acid halogen compound and the amine compound, Specifically, the secondary coating film By lowering the negative surface charge value of the reverse osmosis membrane (by increasing the surface charge value), the charge-masking effect and charge-induced pore size expansion caused by the accumulation of divalent hardness components on the membrane surface can also be reduced.

The third solution in step 5 may contain 0.001 to 0.10 wt% of an amine compound, preferably 0.002 to 0.08 wt% of an amine compound, and the remainder of water. If the amine compound exceeds 0.10% by weight, the permeate flow rate and the salt removal rate are rapidly reduced, so there may be a problem of being unsuitable as a water purifier filter.

The secondary coating in step 5 may be performed by various methods such as impregnation and spray coating, and 0.001 to 0.10% by weight of an amine compound, preferably 0.002 to 0.08% by weight of an amine compound, and the remaining amount of water. It can be carried out by treating for seconds to 10 minutes, preferably for 20 seconds to 2 minutes.

Meanwhile, the amine compound may include a compound satisfying Formula 1 or Formula 2 below. If Chemical Formulas 1 and 2 are used simultaneously, there may be a problem in that the secondary coating film is not properly formed.

[Formula 1]

In Formula 1, R ¹ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or an alkylene group having 2 to 5 carbon atoms, preferably an alkyl group having 2 to 5 carbon atoms or an alkylene group having 2 to 5 carbon atoms, more preferably a carbon number It is a 3 to 5 alkyl group or an alkylene group having 3 to 5 carbon atoms.

[Formula 2]

In Formula 2, R ² is an alkylene group having 2 to 5 carbon atoms, preferably an alkylene group having 3 to 5 carbon atoms, and more preferably an alkylene group having 3 to 4 carbon atoms.

And, 0.1 to 0.3% by weight, preferably 0.2 to 0.3% by weight of the porous support subjected to step 5 in a solution containing sodium carbonate and the remaining amount of water for 1 to 3 hours, preferably for 2 to 3 hours A polyamide-based reverse osmosis membrane can be manufactured by immersion to remove acids or unreacted residues.

On the other hand, it is possible to manufacture a membrane module including the polyamide-based reverse osmosis membrane manufactured through the above-described manufacturing method.

In addition, it is possible to manufacture a reverse osmosis water purifier including the separation membrane module, and when designing the reverse osmosis water purifier system, the design margin of operating factors that directly affect the removal rate, such as operating pressure and recovery rate, is increased, resulting in more economical water purifier operating conditions setting becomes possible.

Although described with reference to the embodiments with respect to the present invention above, this is not merely limited to the examples to be construed as an embodiment of the invention, those skilled in the art belonging to embodiments of the invention the essential characteristics of the invention In the range that does not deviate, there will be many variations and applications that are not exemplified in the above. For example, each element that appears specifically in the implementation example of this invention is that it can be implemented by transforming it. And the differences related to these variations and applications should be interpreted as being included in the scope of this invention as stipulated in the appended claims.

[Example]

Preparation Example 1: Preparation of the first solution

A polyfunctional amine compound as metaphenylenediamine (meta-phenylenediamine, MPD) 1.1% by weight, ethyl hexanediol (ethyl-hexanediol) as an additive 0.2% by weight, tetramethyl hexanediamine (tetramethyl hexanediamine, TMHD) 1.2% by weight. A first solution was prepared by mixing 1.32 wt % of toluene sulfonic acid (TSA) and the remaining amount of water.

Preparation Example 2: Preparation of the second solution

A second solution comprising trimesoyl chloride (TMC) 0.1% by weight, isophthaloyl chloride (IPC) 0.03% by weight and the remainder of the cyclohexane solvent (organic solvent) was prepared as an acid halogen compound .

Preparation Example 3-1: Preparation of third solution

A third solution containing 0.003% by weight of the compound represented by the following Chemical Formula 1-1 and the remaining amount of water was prepared.

[Formula 1-1]

In Formula 1, R ¹ is an n-propylene group.

Preparation Example 3-2: Preparation of third solution

A third solution containing 0.05% by weight of the compound represented by the following Chemical Formula 2-1 and the remaining amount of water was prepared.

[Formula 2-1]

In Formula 2, R ² is an n-propylene group.

Preparation Example 3-3 ~ Preparation Example 3-6: Preparation of the third solution

Preparation Example 3-3 to Preparation Example 3-6 were prepared in the same manner as in Preparation Example 3-1 or Preparation Example 3-2, but with the content of the compound represented by Formula 1 or Formula 2 as shown in Table 1 below. .

Comparative Preparation Example 3-1 ~ Comparative Preparation Example 3-3: Preparation of the third solution

Prepared in the same manner as in Preparation Example 3-1 or Preparation Example 3-2, but with the content of the compound represented by Formula 1-1 or Formula 2-1 as shown in Table 1 below, Comparative Preparation Example 3-1 ~ comparison Preparation Example 3-3 was prepared.

preparation example
3-1 preparation example
3-2 preparation example
3-3 preparation example
3-4 preparation example
3-5 preparation example
3-6 Comparative preparation example
3-1 Comparative preparation example
3-2 Comparative preparation example
3-3 third solution
(weight%) Formula 1-1 0.003 - 0.001 0.10 - - 0.12 - 0.003 Formula 2-1 - 0.05 - - 0.001 0.10 - 0.12 0.05

Example 1: Preparation of polyamide-based reverse osmosis membrane

(1) A porous support having an average pore size of 20 to 30 nm was prepared by casting a polysulfone porous polymer layer having a thickness of 140 μm on one surface of a polyester nonwoven fabric having an average thickness of 100 μm.

(2) The porous support was immersed in the first solution prepared in Preparation Example 1 for 40 seconds.

(3) The porous support having performed step (2) was immersed in the second solution prepared in Preparation Example 2 for 60 seconds.

(4) (3) was performed by spraying air on the porous support for 10 seconds under a pressure of 0.5 bar to remove the excess solution.

(5) (4) The porous support was dried under 25 ℃ for 90 seconds.

(6) The porous support on which step (5) was performed was thermally cross-linked at 60° C. for 120 seconds to form a primary coating film on the upper surface of the porous support.

(7) (6) The porous support was treated with the third solution prepared in Preparation Example 3-1 by spraying for 20 seconds to form a secondary coating film on the upper surface of the primary coating film.

(8) (7) was immersed in a solution containing 0.2% by weight of sodium carbonate and the remaining amount of water for 2 hours to remove the acid or unreacted material remaining on the surface of the secondary coating film, and finally A polyamide-based reverse osmosis membrane was obtained.

Examples 2 to 6 and Comparative Examples 1 to Comparative Example 3: Preparation of polyamide-based reverse osmosis membrane

Prepared in the same manner as in Example 1, except that the first solution (Preparation Example 1), the second solution (Preparation Example 2) and the third solution (Preparation Example 3-1 to Preparation Example 3-6 and Comparative Preparation Example 3-1) Reverse osmosis membranes of Examples 2 to 6 and Comparative Examples 1 to 3 were prepared by using Comparative Preparation Example 3-3) under the conditions of Tables 2 to 3 below.

Comparative Example 4: Preparation of polyamide-based reverse osmosis membrane

It was prepared in the same manner as in Example 1, but as shown in Table 3 below, except for step (7), a separation membrane in which only the primary coating membrane was formed on one surface of the porous support was prepared.

Experimental Example 1: Surface charge measurement

The surface charge was analyzed by measuring the surface zeta potential of each of the reverse osmosis membranes prepared in Examples 1 to 6 and Comparative Examples 1 to 4 using a surface charge measuring device (Anton Paar's Electrokinetic Analyzer). The measured values are shown in Tables 2 to 3 and FIG. 1 below.

Experimental Example 2: Flow rate and salt removal rate evaluation

In order to evaluate the performance of the reverse osmosis membrane, the reverse osmosis membranes prepared in Examples 1 to 6 and Comparative Examples 1 to 4 were placed in an aqueous sodium chloride (NaCl) solution (pH 7) having a concentration of 200 ppm at a temperature of 25° C. And the permeate flow rate and salt removal rate were measured under a pressure condition of 60 psi, and the results are shown in Tables 2 to 3 below.

Experimental Example 3: Evaluation of nitrate nitrogen removal rate

In order to evaluate the performance of the reverse osmosis membrane, the reverse osmosis membranes prepared in Examples 1 to 6 and Comparative Examples 1 to 4 were prepared under a temperature of 25° C. Removal rate in nitrogen 30ppm) and nitrate nitrogen certification test The removal rate is measured under the raw water conditions (since water containing nitrate nitrogen 30ppm, total 600ppm of nitrate nitrogen 30ppm, hardness-inducing substances calcium and magnesium in a ratio of 5:1) Tables 2 to 3 are shown.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 first solution preparation example
One preparation example
One preparation example
One preparation example
One preparation example
One preparation example
One second solution Preparation Example 2 Preparation Example 2 Preparation Example 2 Preparation Example 2 Preparation Example 2 Preparation Example 2 third solution Preparation Example 3-1 Preparation example 3-2 Preparation example 3-3 Preparation example 3-4 preparation example
3-5 preparation example
3-6 Surface charge at pH 7 (mV) -24.3 -22.1 -26.4 -15.4 -30.0 -19.3 Flow (GFD) 28.9 29.6 29.5 25.1 30.1 28.6 My
thing
rate
(%) 200ppm NaCl 96.8 96.3 96.6 97.7 96.2 96.9 Nitrous Nitrogen 30ppm 94.9 95.1 94.0 97.1 94.6 96.1 Nitric acid nitrogen 30ppm and hardness-causing substances 600ppm 78.3 76.8 74.8 84.3 71.4 79.3

Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 first solution preparation example
One preparation example
One preparation example
One preparation example
One second solution preparation example
2 preparation example
2 preparation example
2 preparation example
2 third solution Comparative preparation example
3-1 Comparative preparation example
3-2 Comparative preparation example
3-3 - Surface charge at pH 7 (mV) -10.6 -16.9 -0.2 -39.7 Flow (GFD) 21.9 22.3 27.9 30.9 My
thing
rate
(%) 200ppm NaCl 89.1 88.4 94.2 96.0 Nitrous Nitrogen 30ppm 90.1 91.2 96.9 94.3 Nitric acid nitrogen 30ppm and hardness-inducing substances 600ppm 86.9 83.3 68.2 60.9

Looking at Tables 2 to 3, Examples 1 to 6 use the third solutions prepared in Preparation Examples 3-1 to 3-6, and all of the surface charge values are higher than -30 mV. , showed an excellent removal rate of more than 70% of nitrate nitrogen removal rate in city water containing hardness-inducing substances.

On the other hand, Comparative Example 1 uses Comparative Preparation Example 3-1 (third solution) prepared in excess of 0.10% by weight of the amine compound represented by Formula 1-1, and Example 4 (expressed in Formula 1-1) Compared with Preparation Example 3-4) prepared by including 0.10 wt% of the amine compound, the surface charge value is high, and thus the nitrate nitrogen removal rate under the hardness-inducing material is somewhat high. However, it was found that the flow rate and salt removal rate were significantly lowered to a level not suitable for a separator used in a water purifier, which caused problems such as pore clogging due to excessive inclusion of the amine compound represented by Formula 1-1 in the third solution. is judged to be

In addition, Comparative Example 2 uses Comparative Preparation Example 3-2 (third solution) prepared in excess of 0.10% by weight of the amine compound represented by Formula 2-1, and Example 6 (amine represented by Formula 2-1) Compared with Preparation Example 3-6) prepared by including 0.10 wt% of the compound, the surface charge value is high, and thus the nitrate nitrogen removal rate under the hardness-inducing material is somewhat high. However, it was found that the flow rate and salt removal rate were significantly lowered to a level not suitable for a separator used in a water purifier, which caused problems such as pore clogging because the amine compound represented by Formula 1-2 in the third solution was contained in excess. is judged to be

In Comparative Example 3, Comparative Preparation Example 3-3 (third solution) prepared using both the amine compound represented by Formula 1-1 and the amine compound represented by Formula 2-1 was used, and Example 1 ( When compared to Example 2 (using only one amine compound represented by Formula 1-1) and Example 2 (using only one amine compound represented by Formula 2-1), the surface charge value is very low, less than -30 mV, and thus the hardness It was also found that the removal rate of nitrate nitrogen under the triggering substances was significantly reduced. Through this, it was found that when using a mixture of Chemical Formulas 1-1 and 2-1, the secondary coating film was not properly formed.

In addition, Comparative Example 4 is a polyamide-based reverse osmosis membrane in which only the primary coating film is formed. Compared with Examples 1 to 6 in which the primary coating film and the secondary coating film are formed, the surface charge value is close to -40mV was very low, which is expected because unreacted acyl halide remaining on the surface of the primary coating film was changed to carboxylic acid after interfacial polymerization. In addition, as the surface charge value was very low at a level close to -40 mV, it was found that the nitrate nitrogen removal rate under the hardness-inducing material was remarkably low, less than 70%, which caused the hardness-inducing material on the membrane surface through electrostatic attraction. (divalent cations) are expected to accumulate.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims (10)

porous support; And a polyamide layer formed on at least one side of the porous support; a reverse osmosis membrane comprising a,
The polyamide layer may include a primary coating film formed by reacting a polyfunctional amine compound and a polyfunctional acid halogen compound; and a secondary coating film formed on the upper surface of the primary coating film;
The secondary coating film is a film formed by reacting the polyfunctional acid halogen compound of the primary coating film, and an amine compound represented by the following Chemical Formula 1 or Chemical Formula 2,
The polyfunctional acid halogen compound includes at least one selected from trimesoyl chloride (TMC), isophthaloyl chloride (IPC), terephthaloyl chloride (TPC), and tricarboxylic acid halide,
The secondary coating film is a coating film formed by coating and reacting on top of the primary coating film with a solution containing 0.002 to 0.10 wt% of the amine compound and the remaining amount of water,
The reverse osmosis membrane has a surface charge of -30 to -10 mV at pH 6 to 8, and for potable water containing 500 to 700 ppm of a hardness-inducing substance and 15 to 45 ppm of nitrate nitrogen, A polyamide-based reverse osmosis membrane having an excellent nitrate nitrogen removal rate, characterized in that the removal rate is 70 to 85%;
[Formula 1]

In Formula 1, R ¹ is an alkylene group having 3 to 5 carbon atoms,
[Formula 2]

In Formula 2, R ² is an alkylene group having 2 to 5 carbon atoms. According to claim 1, wherein the porous support is a non-woven fabric; and a porous polymer layer;
The porous polymer layer includes at least one selected from polysulfone resin, polyethersulfone resin, polyimide resin, polypropylene resin and polyvinylidene fluoride resin,
The porous support is a polyamide-based reverse osmosis membrane with an excellent nitrate nitrogen removal rate, characterized in that the average thickness of 100 ~ 500㎛ and the average pore size of 1 ~ 500nm. delete delete delete The polyamide-based reverse osmosis membrane having an excellent nitrate nitrogen removal rate according to claim 1, wherein the hardness-inducing material comprises at least one material selected from calcium and magnesium. A first step of coating the porous support with a first solution containing a polyfunctional amine compound;
A second step of coating the second solution containing the polyfunctional acid halogen compound on the porous support that has been performed in step 1;
Step 3 of removing the excess solution by spraying air on the porous support that has been performed in Step 2;
A fourth step of thermally crosslinking the porous support having performed step 3 at a high temperature to form a primary coating film on at least one surface of the porous support;
By applying and reacting a third solution containing 0.002 to 0.10% by weight of an amine compound represented by the following Chemical Formula 1 or Chemical Formula 2 and the remaining amount of water to the porous support having performed step 4 and reacting, the secondary coating film on the upper surface of the primary coating film 5 steps to form; and
6 step of removing the acid or unreacted material remaining on the surface of the secondary coating film;
The polyfunctional acid halogen compound of step 5 comprises at least one selected from trimesoyl chloride (TMC), isophthaloyl chloride (IPC), terephthaloyl chloride (TPC) and tricarboxylic acid halide A method for manufacturing a polyamide-based reverse osmosis membrane with excellent nitrate nitrogen removal rate:
[Formula 1]

In Formula 1, R ¹ is an alkylene group having 3 to 5 carbon atoms,
[Formula 2]

In Formula 2, R ² is an alkylene group having 2 to 5 carbon atoms. The method of claim 7, wherein the first solution comprises 0.1 to 10.0% by weight of metaphenylenediamine, 0.003 to 6.6% by weight of the additive and the remaining amount of water,
The additive is a method for producing a polyamide-based reverse osmosis membrane excellent in nitrate nitrogen removal rate, characterized in that it comprises at least one selected from ethylhexanediol, tetramethylhexadiamine and toluenesulfonic acid. The method according to claim 7, wherein the second solution contains 0.005 to 5.0% by weight of the polyfunctional acid halogen compound and the remaining amount of the organic solvent,
The organic solvent is a polyamide-based reverse osmosis membrane with excellent removal rate of nitrate nitrogen, characterized in that it contains at least one selected from halogenated hydrocarbons, cycloalkanes having 6 to 12 carbon atoms, alkanes having 6 to 12 carbon atoms, and freons. . A separation membrane module comprising the reverse osmosis membrane according to any one of claims 1, 2 and 6 selected from the group consisting of.

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