KR20140003296A - Hollow fiber type nanofiltration membrane and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a hollow fiber nanofiltration membrane and a manufacturing method thereof. More specifically the present invention provides a hollow fiber nanofiltration membrane with fouling resistance, chemical resistance, and high salt rejection rate by improving the degree of coupling of a polyamide layer by effectively coating the polyamide layer, and forming a firm and uniform coating layer.

Description

Hollow fiber type nanofiltration membrane and manufacturing method thereof

The present invention relates to a hollow fiber-type nano separator and a method for manufacturing the same, and more particularly, to a hollow fiber-type nano separator and a method for producing the same, which improves salt rejection and satisfies excellent permeation flux characteristics and chemical resistance.

The separation membrane is classified into a microfiltration membrane (MF), an ultrafiltration membrane (UF), a nano separation membrane (NF), or a reverse osmosis membrane (RO) according to the pore size. Among them, nanomembrane is usually defined as a membrane having the ability to separate a compound having a molecular weight of less than 1000.

More specifically, it is a membrane having a selective separation ability to a nanometer solute, having a high salt rejection ratio of 90% or more for divalent ions, and a relatively wide range of salt rejection rate of 40% or more for monovalent ions. It has a permeability of about 5 to 10 times larger than a reverse osmosis membrane using a polyfunctional aromatic amine.

In particular, the nano-membrane has a merit that the material such as geosmin, which is a typical tasteless substance, is removed, and water quality from which contaminants generated during water treatment such as nitrate nitrogen and trihalogen methane are removed can be produced.

Various studies have been conducted on polyamide composite membranes in order to improve the basic physical properties of membranes such as salt rejection, permeation flux, fouling resistance and chemical resistance.

In addition, the separation membrane may be in the form of a hollow fiber membrane, the hollow fiber membrane is a membrane having a hollow ring shape has an advantage that can increase the membrane area per unit volume of the module compared to the flat membrane. If the water treatment separator has a hollow fiber membrane structure, the membrane may be cleaned by backwashing to remove sediments by passing a clean liquid in a direction opposite to the filtration direction, air scrubbing for removing sediments by shaking the membrane by introducing air bubbles into the module Can be effectively used.

The properties required for nanofibers in the form of hollow fiber membranes include good mechanical strength to extend the service life affecting the driving ability, high water permeability associated with operating costs, and excellent salt rejection. In addition, chemical resistance, chemical resistance, heat resistance, and the like for chemical treatment are required as material characteristics.

However, the conventional hollow fiber nano-membrane has a problem in that the coating of the polyamide layer is difficult due to the use of a hydrophobic material to secure mechanical strength that can withstand pressure. Accordingly, there is a problem in that there is a limit in improving physical properties such as excellent salt rejection rate, permeate flow rate, fouling resistance and chemical resistance required for the nano separator.

The present invention has been made to solve the above problems, and by coating the polyamide layer on the hollow fiber-type nano-membrane more efficiently, excellent filtration efficiency that satisfies the excellent salt rejection rate, permeation flow rate, fouling resistance and chemical resistance at the same time The purpose is to provide a hollow fiber-type nano separator.

 In order to solve the above problems, the present invention,

(1) spinning a spinning solution containing a solvent and a hydrophobic polymer and a core solution for forming a hollow through a spinning nozzle to form a nano separator; (2) plasma-treating the surface of the separator to introduce hydrophilic radicals; (3) immersing the separator in an aqueous solution containing a polyfunctional amine and then contacting an organic solution containing a polyfunctional acid halogen compound to form a polyamide layer. Hollow fiber type NF (Nanofiltration) ) Provides a method for producing a membrane.

According to a preferred embodiment of the present invention, the solvent of step (1) is N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and dimethylacetamide (DMAc At least one selected from the group consisting of).

According to another preferred embodiment of the present invention, the polymer of step (1) is a polysulfone polymer, polyamide polymer, polyimide polymer, polyester polymer, olefin polymer, polybenzoimidazole polymer and poly At least one selected from the group consisting of vinylidene fluoride.

According to another preferred embodiment of the present invention, the core solution of step (1) may be a mixing ratio of the organic polar solvent (solvent A) and water (solvent B) is 4: 6 to 9: 1.

According to another preferred embodiment of the present invention, the organic polar solvent may be any one or more selected from the group consisting of dimethylacetamide, N-methyl-2-pyrrolidone and dimethylformamide.

According to another preferred embodiment of the present invention, the spinning nozzle of the step (1) is a multi-tubular spinning nozzle, and the spinning stock solution is discharged to the outer tube of the multi-tubular spinning nozzle, The core solution can be discharged.

According to another preferred embodiment of the present invention, the plasma surface treatment of the step (2) is ammonia (NH ₃ ), hydrogen sulfide (H ₂ S), oxygen (O ₂ ), nitrogen (N ₂ ), sulfuric acid (H Any one or more gases or liquids selected from the group consisting of ₂ SO ₄ ) and water (H ₂ O) can be used.

According to another preferred embodiment of the present invention, the plasma surface treatment of step (2) may be a discharge treatment for 10 to 600 seconds to 100 to 1000W.

The present invention is hollow; A supporting layer formed along the outer periphery of the hollow; And a polyamide layer formed along the outer circumference of the support layer, wherein the support layer forms a sponge like structure, and the support layer surface is hydrophilic surface-modified by plasma treatment. Provide a membrane.

In addition, the present invention is hollow; A supporting layer formed along the outer periphery of the hollow; And a polyamide layer formed along the outer circumference of the support layer, wherein the support layer has a contact angle of 45 ° or less and an initial wettability of 70% or more.

According to a preferred embodiment of the present invention, the support layer is composed of polysulfone polymer, polyamide polymer, polyimide polymer, polyester polymer, olefin polymer, polybenzoimidazole polymer and polyvinylidene fluoride It may include any one or more selected from the group to be.

According to another preferred embodiment of the present invention, the cross-sectional thickness of the support layer is 50 to 700um, the cross-sectional thickness of the polyamide layer may be 0.1 to 1um.

According to another preferred embodiment of the present invention, the average pore size of the support layer may be 0.01 to 0.1um.

According to another preferred embodiment of the present invention, the hydrophilic surface-modified support layer has a contact angle of 45 ° or less, and initial wettability may be 70% or more.

According to another preferred embodiment of the present invention, the divalent ion salt removal rate of the hollow fiber type NF membrane may be 95% or more.

The hollow fiber-type nano separator of the present invention coats the polyamide layer more efficiently, thereby increasing the bondability of the polyamide layer and forming a solid and uniform coating layer, thereby ensuring high fouling resistance and chemical resistance as well as high salt rejection rate. It is possible to provide a hollow fiber-type nano separator having.

1 is a cross-sectional view of a double tubular spinning nozzle for producing a hollow fiber nanomembrane according to the present invention.
Figure 2 is a cross-sectional view of the hollow fiber-type nano separator according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in more detail with reference to the accompanying drawings.

 As described above, the conventional hollow fiber-type nano separator has a problem in that the coating of the polyamide layer is difficult due to the use of a hydrophobic material to secure mechanical strength.

 Thus, the present invention comprises the steps of (1) spinning a spinning solution containing a solvent and a hydrophobic polymer and the core solution for forming a hollow through a spinning nozzle to form a nano separator; (2) plasma-treating the surface of the separator to introduce hydrophilic radicals; (3) immersing the separator in an aqueous solution containing a polyfunctional amine and then contacting an organic solution containing a polyfunctional acid halogen compound to form a polyamide layer. Hollow fiber type NF (Nanofiltration) By providing a method for producing a film, the above-mentioned problem was sought.

This increases the bondability of the polyamide layer and forms a solid and uniform polyamide coating layer, thereby ensuring fouling resistance and chemical resistance and satisfying high salt rejection.

In the step (1), the spinning solution containing the solvent and the hydrophobic polymer and the core solution for forming the hollow are spun through the spinning nozzle to form a nano separator.

The solvent is not particularly limited as long as the hydrophobic polymer can be uniformly dissolved and spun without forming a precipitate, and more preferably, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), and dimethyl. It may be in single or mixed form, such as sulfoxide (DMSO) or dimethylacetamide (DMAc).

If the temperature is lower than 20 ° C, the polymer may not be dissolved and the membrane may not be produced. If the temperature is higher than 90 ° C, the viscosity of the polymer solution may become too thin, and thus the membrane may be difficult to produce .

The hydrophobic polymer is not particularly limited as long as it can form a hollow fiber-type nano-membrane, but it is preferable to use a weight average molecular weight range of 65,000 to 150,000 in order to take into account mechanical strength, a preferred example is polysulfone-based It may be a single or mixed form of a polymer, a polyamide-based polymer, a polyimide-based polymer, a polyester-based polymer, an olefin-based polymer, a polybenzoimidazole polymer or a polyvinylidene fluoride.

The spinning stock solution may preferably include 10 to 40 parts by weight of the hydrophobic polymer with respect to 100 parts by weight of the solvent. If the polymer material is less than 10 parts by weight, the strength is lowered, the solution viscosity is difficult to manufacture a film, if it exceeds 40 parts by weight may affect the desired phase transition speed may not be able to form a pore structure.

The core solution serves to form the hollow fiber hollow, and can form an optimized pore structure and pore size of asymmetric porosity.

The core solution may be a mixture of an organic polar solvent (solvent A) and water (solvent B), and preferred examples of the organic polar solvent include dimethylacetamide, N-methyl-2-pyrrolidone, Dimethylformamide can be used.

The mixed solvent constituting the core solution is an organic polar solvent (solvent A): water (solvent B) when the composition ratio of 4: 6 to 9: 1, the average pore size of 0.01 to 0.1um sponge structure (Sponge like structure) An asymmetric porous membrane is observed.

In this case, when the ratio of the organic polar solvent is less than 4, the cross-section of the support layer of the finger like structure of the double layer is formed, and thus, the membrane may be damaged because it does not endure a certain level of internal pressure. Can be.

The spinning nozzle of step (1) may be a multi-tubular spinning nozzle, and FIG. 1 is a cross-sectional view of a double tubular spinning nozzle 5 for discharging spinning spinning solution. The spinning stock solution may be discharged to the outer tube 2 of the double tubular spinning nozzle 5, and the core solution may be simultaneously discharged to the double tubular spinning nozzle inner tube 1.

Hollow yarn of the present invention can adjust the thickness and the outer diameter / inner diameter ratio of the hollow fiber cross-section according to the feed rate (rpm) and the core solution inflow (cc / min) of the spinning solution, preferably the feed rate (rpm) ): The core solution inflow rate (cc / min) can be carried out at 12: 1 to 12: 6, more preferably 12: 3 to 12: 5 conditions.

The hollow shaped product emitted from the spinneret is exposed to air before it is immersed in the coagulation bath, and the pore structure of the hollow fiber can be optimized according to the length of the air gap.

Thus, the preferred air gap is 1 to 15 cm, more preferably 3 to 7 cm can be maintained. If the air gap length is less than 1 cm, the linear velocity of the spinning liquid discharged from the spinning nozzle is rapidly increased, so that the time for staying in the external coagulating solution is insufficient. If the interval between the coagulation liquid surface and the spinning nozzle is shortened, the reaction occurs before coagulation by the gases generated in the coagulation liquid surface, resulting in problems of deterioration of membrane properties and membrane strength. When the air gap exceeds 15 cm in length, it is not suitable because it is exposed to air for a long time and the hollow fiber skin layer is firmly formed and dense, thereby lowering the film properties, especially the flow rate.

After passing through the air gap is discharged or immersed in the external coagulation solution, the external coagulation solution is not particularly limited as long as it is possible to exchange material with the spinning stock solution, more preferably N-methylpyrrolidone, N in water or water Or a solution in which some glycol-based solvents such as N-dimethylacetamide, dimethyl sulfoxide, dimethylformamide or glycerol, polyethylene glycol, ethylene glycol, propylene glycol, diethylene glycol, and the like are partially mixed.

The temperature of the coagulation bath may be a temperature condition lower than the room temperature, more preferably maintained at 10 to 30 ℃, even more preferably 10 to 25 ℃ to promote the phase transition rate, it is possible to manufacture a hollow fiber membrane with optimized pore structure have.

In step (2), the surface of the separator is subjected to plasma surface treatment to introduce hydrophilic radicals.

Conventionally, due to the hydrophobic polymer which is a major constituent of the nano-membrane, the initial wettability is low, so that the aqueous solution of the amine is not easily penetrated when the selective layer is prepared by the polyamide interfacial polymerization, thereby effectively forming the polyamide layer on the surface of the nano-membrane. In the present invention, the degree of binding of the polyamide layer was improved by introducing a hydrophilic radical into the surface of the nano-membrane by performing plasma surface treatment.

By increasing the tendency of hydrophilization of the nano-membrane membrane, the initial wettability of the polyfunctional amine aqueous solution may be improved, and the penetration rate of the amine aqueous solution may be increased to increase the bond between the support layer and the polyamide layer. In addition, the porosity is lowered due to the plasma treatment may further improve the salt rejection rate of divalent ions.

The plasma surface treatment may be a gas or liquid containing nitrogen oxides and sulfur oxides capable of binding hydrophilic radicals such as amine radicals, hydroxyl group radicals or sulfonated radicals to the surface of the nano separator. More preferably, a gas or liquid such as ammonia (NH ₃ ), hydrogen sulfide (H ₂ S), oxygen (O ₂ ), nitrogen (N ₂ ), sulfuric acid (H ₂ SO ₄ ) or water (H ₂ O) may be used. And most preferably, hydrogen sulfide (H ₂ S) gas capable of binding sulfonated radicals which most effectively acts to improve the penetration of the aqueous amine solution.

The gases may be injected at a flow rate of 0.2 to 30 L / min, and inert gases such as hydrogen (H ₂ ) gas or helium (He) and argon (Ar) may be injected together as a carrier gas.

Such plasma surface treatment is preferably 100 to 1000W discharge treatment at a rate of 1 to 200mm / s at a temperature of 0 to 80 ℃, plasma surface treatment for 10 to 600 seconds.

As such, the hollow fiber treated with the plasma surface may have a contact angle of 45 ° or less, and initial wettability may be 70% or more.

In step (3), the separator is immersed in an aqueous solution containing a polyfunctional amine, and then contacted with an organic solution containing a polyfunctional acid halogen compound to form a polyamide layer.

 The polyamide layer of the present invention ensures fouling resistance and chemical resistance from the intrinsic properties of the material, and at the same time, a polyamide layer is formed on the skin layer of the hollow fiber membrane, so that the solutes are diffused by the diffusion of raw water solutions through the free volume between the polymer chains. As a mechanism to be removed, it is possible to secure a high salt removal rate up to monovalent ions or divalent ions.

In particular, the nano-membrane membrane of the present invention is a polyamide layer formed on the surface of the hollow fiber support of the present invention has a hollow fiber type having a flow rate of 10.37LMH / bar or more and a salt removal rate of divalent ions of 97.5% or more at a constant membrane area (15.7 cm ² ). Nano separators (NF) can be prepared.

Specifically, after the hollow fiber is immersed in an aqueous solution containing a polyfunctional amine such as metaphenyldiamine, paraphenyldiamine, orthophenyldiamine, piperazine or alkylated piperidine, polyfunctional acyl halide, polyfunctional sulfonyl An organic solution containing a polyfunctional acid halogen compound such as halide or polyfunctional isocyanate may be contacted to form a polyamide layer by interfacial polymerization between the compounds.

In addition, after the hydrophilic compound is further included in the aqueous solution containing the polyfunctional amine, an organic solution containing the polyfunctional acid halogen compound is contacted on the surface of the support layer to improve fouling resistance by interfacial polymerization between the compounds. Can be formed. At this time, the compound containing the hydrophilic group may be present in an amount of 0.001 to 8% by weight, more preferably 0.01 to 4% by weight in the aqueous solution.

The hydrophilic compound added to the aqueous solution containing the polyfunctional amine is a hydrophilic compound having at least any one hydrophilic functional group selected from the group consisting of hydroxyl group, sulfonate group, carbonyl group, trialkoxysilane group, anion group and tertiary amino group And more preferably a hydrophilic amino compound.

More specifically, preferred examples of the hydrophilic compound having a hydroxyl group include 1,3-diamino-2-propanol, ethanolamine, diethanolamine, 3-amino-1-propanol, 4-amino-1-butanol, 2 It may be any one or more selected from the group consisting of -amino-1-butanol.

Hydrophilic compounds having a carbonyl group are selected from the group consisting of aminoacetaldehyde dimethyl acetal, α-aminobutyrolactone, 3-aminobenzamide, 4-aminobenzamide and N- (3-aminopropyl) -2-pyrrolidinone It may be any one or more.

Further, the hydrophilic compound containing a trialkoxysilane group may be any one or more selected from the group consisting of (3-aminopropyl) triethoxysilane and (3-aminopropyl) trimethoxysilane.

Examples of the hydrophilic compound having an anion group include glycine, taurine, 3-amino-1-propenesulphonic acid, 4-amino-1-butenesulphonic acid, 2-aminoethyl hydrogen sulfate, 3-aminobenzenesulfonic acid, 3-amino-4-hydroxybenzenesulphonic acid, 4-aminobenzenesulphonic acid, 3-aminopropylphosphonic acid, 3-amino-4-hydroxybenzoic acid, 4-amino-3-hydroxybenzoic acid It may be any one or more selected from the group consisting of Ix acid, 6-aminohexenoxy acid, 3-aminobutanic acid, 4-amino-2-hydroxybutyric acid, 4-aminobutyric acid and glutamic acid have.

Examples of the hydrophilic compound having one or more tertiary amino groups include 3- (diethylamino) propylamine, 4- (2-aminoethyl) morpholine, 1- - diamino-N-methyldipropylamine and 1- (3-aminopropyl) imidazole.

In addition, A supporting layer formed along the outer periphery of the hollow; A polyamide layer is formed along the outer circumference of the support layer, wherein the support layer forms a sponge like structure, and the support layer surface is plasma-treated to provide a hydrophilic surface modified NF (Nanofiltration) film. do.

The surface of the hollow fiber type NF membrane support layer of the present invention has a contact angle of 45 ° or less, an initial wettability of 70% or more, and the hollow fiber type NF membrane may satisfy a 95% or more of divalent ion salt removal rate.

2 is a cross-sectional view of the hollow fiber-type NF film according to an embodiment of the present invention described in the center, the hollow fiber-type NF film 200 according to an embodiment of the present invention is hollow 210, the outer periphery of the hollow The support layer 220 is formed along the polyamide layer 230 is formed along the outer periphery of the support layer.

The outer diameter / inner diameter ratio of the hollow yarn is preferably 1.1 to 3.0, the cross-sectional thickness of the support layer 220 may be 50 to 700um and the cross-sectional thickness of the polyamide layer 230 may be 0.1 to 1 um.

At this time, more preferably, the ratio of the outer diameter / inner diameter of the hollow fiber is 1.1 to 2.0, and when the ratio is less than 1.1, the film is too thin and the strength is low. In addition, the polyamide layer 230 may have a thickness of 0.01 to 1 μm. When the polyamide layer 230 is less than 0.01 μm, the salt removing ability may be reduced to serve as a selection layer. There may be a problem that is too thick so that the flow rate is lowered.

The support layer 220 includes a hydrophobic polymer, and the hydrophobic polymer is not particularly limited as long as it can form a hollow fiber-type nanomembrane, but using a weight average molecular weight range of 65,000 to 150,000 in order to consider mechanical strength In one preferred embodiment, polysulfone polymer, polyamide polymer, polyimide polymer, polyester polymer, olefin polymer, polybenzoimidazole polymer or polyvinylidene fluoride may be used. Can be.

The support layer 220 may have pores of a sponge like structure, and an average pore size of the support layer may be 0.01 to 0.1 μm.

The surface of the support layer 220 has a contact angle of 45 ° or less, and the initial wettability may satisfy 70% or more.

 This is because as the support layer surface 220 is plasma treated, the surface is modified to be hydrophilic, thereby increasing the hydrophilization tendency, thereby reducing the contact angle and improving the initial wettability of the polyfunctional aqueous amine solution. Therefore, the penetration amount of the amine aqueous solution may be increased and the bonding degree between the support layer 220 and the polyamide layer 230 may be increased.

In addition, as the porosity is slightly reduced due to the plasma treatment, the divalent ion salt rejection rate is improved to 95% or more, thereby effectively removing divalent ions.

The hydrophilic surface modification of the support layer 220 uses a gas or liquid containing nitrogen oxides and sulfur oxides capable of binding a hydrophilic radical such as an amine radical, a hydroxyl group radical or a sulfonated radical to the surface of the support layer 220. Plasma treatment may be performed, more preferably ammonia (NH ₃ ), hydrogen sulfide (H ₂ S), oxygen (O ₂ ), nitrogen (N ₂ ), sulfuric acid (H ₂ SO ₄ ), water (H ₂ O), or the like. Gas or liquid can be used. Most preferably, hydrogen sulfide (H ₂ S) gas capable of binding sulfonated radicals which most effectively acts to improve the penetration of the aqueous amine solution can be used.

The polyamide layer 230 may be formed by interfacial polymerization by immersing in an aqueous solution containing a polyfunctional amine and then contacting an organic solution containing a polyfunctional acid halogen compound. The polyamide layer 230 ensures contamination resistance and chemical resistance from the intrinsic properties of the material, and at the same time, a polyamide layer is formed on the skin layer of the hollow fiber membrane, so that the solutes are diffused by the diffusion of raw water solutions through the free volume between the polymer chains. As a mechanism to be removed, it is possible to secure a high salt removal rate up to monovalent ions or divalent ions.

In particular, the nano-membrane of the present invention by the polyamide layer formed on the surface of the hollow fiber support of the present invention can satisfy the flow rate of 10.37LMH / bar or more, the salt removal rate of divalent 97.5% or more in a certain membrane area (15.7cm ² ) Can be.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples should not be construed as limiting the scope of the present invention, and should be construed to facilitate understanding of the present invention.

≪ Example 1 >

A spinning solution containing 22 parts by weight of polysulfone was prepared based on 100 parts by weight of solvent (DMF) to remove bubbles. The spinning stock solution was introduced into the outer tube of the double nozzle, and the hollow core fluid for forming the hollow was introduced into the inner tube of the double nozzle. At this time, the core solution for the hollow formation was a solution of methyl pyrrolidone (NMP): water mixing ratio of 9: 1, the feed rate of the dope solution (rpm) and the core solution inlet (cc / min) 12: It was adjusted to 4.5 and spun.

Thereafter, exposed to air with an air gap of 3 cm, and solidified by impregnating with water, which is a coagulation bath maintained at 20 ° C., after a certain period of time, the remaining solvent component contained in the hollow fiber was extracted in a washing tank, The hollow fiber was manufactured by drying under atmospheric conditions.

Helium as a carrier gas and hydrogen sulfide as a source gas were injected at a flow rate of 20 L / min on the film surface from which the solvent was extracted, and discharge treatment was performed by low temperature induction plasma treatment in a plasma apparatus. The discharge treatment rate was 30 mm / min, and was carried out at 200 W for 50 seconds to introduce sulfonated radicals to the surface of the support layer.

The plasma surface-treated hollow fiber was immersed in an aqueous solution containing 1.5% by weight of meta-phenyldiamine (MPD) for 1 hour, and then the water layer on the surface was removed by a compression method. Subsequently, the mixture was immersed in an organic solution containing 0.1% by weight of trimesoyl chloride (TMC) in ISOPAR solvent (Exxon Corp.) for 1 minute, followed by interfacial polymerization, followed by natural drying at room temperature (25 ° C) for 1 minute and 30 seconds for polyamide layer. Formed. Thereafter, it was immersed in 0.2 wt% sodium carbonate solution for 2 hours to remove unreacted residues and then washed with distilled water. The prepared composite membrane was immediately dried after immersing in 3% glycerol containing solution.

≪ Example 2 >

It was prepared in the same manner as in Example 1 except for introducing a hydrosil group radical using oxygen as a source gas instead of hydrogen sulfide.

≪ Example 3 >

It was prepared in the same manner as in Example 1 except that the discharge treatment was performed at 30 W for 10 seconds.

<Comparative Example>

Except that the plasma surface treatment of the hollow fiber support layer was prepared in the same manner as in Example 1.

<Experimental Example>

1.Divalent Ion Flow Measurement

The flow measurement method is to produce a hollow fiber module with a certain area (15.7cm ² ) and pressurize 2,000 ppm magnesium sulfate (MgSO ₄ ) raw water at 25 ° C. and 10 bar to convert the flow rate of the produced water to the value per unit pressure per unit area. Indicated.

2. Measurement of Divalent Ion Removal Rate

The divalent ion removal rate is measured by measuring the ion conductivity (TDS) of the produced water obtained through the hollow fiber membrane module when using 2,000 ppm magnesium sulfate (MgSO4) as raw water. You can get it this way.

Salt removal rate (%) = (1- (conductivity value of produced water / conductivity value of raw water)) x 100

3. Measurement of contact angle of support layer

The support layer sample is immobilized on the measurement plate and the water droplets are dropped thereon, and the water droplets are measured by capturing a camera at a frame rate of 250 fps per second from the time when the water droplets fall onto the support layer until the water is absorbed. The numerical value represents the angle of the water droplets on the support layer. The higher the value, the hydrophobic property, and the lower the hydrophilic property.

4. Initial wettability measurement

The water permeability of the dried hollow fiber membrane and the composite hollow fiber membrane were completely immersed in a 30% alcohol solution and left for 5 minutes, and then washed with pure water to measure the water permeability of the composite hollow fiber membrane with alcohol removed, respectively. Initial wettability is obtained by substituting the measured water permeability values into the following equation.

Initial Wetting (%) = (Water Permeability of Dry Hollow Fiber Membrane) / (Water Permeability of Alcohol and Pure Hollow Fiber Composite Hollow Fiber Membrane) × 100

5. Measurement of polyamide layer bonding degree

 After the membrane was immersed in 2000 ppm NaOCl for 7 days, the flow rate and the degree of back diffusion of the salt were measured.

 This is an experiment to determine the degree of bonding of the polyamide layer and the polymer support layer, and indirectly grasps the degree of bonding of the polyamide layer by observing the change in physical properties of the polyamide, which is weak to chlorine.

When the polyamide separator was immersed in 2000 ppm NaOCl for 7 days, OCl-ion attacked the NH bond in the polyamide bond to decompose the amide structure. This decomposition affects the selectivity of the separator, resulting in an increase in flow rate and a decrease in the divalent ion removal rate.

Flow rate (gfd) Divalent ions
Salt removal rate (%) Support layer contact angle
(°) Early wetting
(%) Example 1 10.37 97.5 64 78 Example 2 9.87 95.1 69 73 Example 3 8.79 94.4 69 71 Comparative Example 4.89 70.46 93 35

2000 ppm NaOCl after 7 days contact
Flow rate (gfd) 2000 ppm NaOCl after 7 days contact
Divalent ion salt removal rate (%) Example 1 11.77 95.1 Example 2 10.35 93.5 Example 3 9.98 92.2 Comparative Example 6.89 59.49

As can be seen in Tables 1 to 2, the contact angle of the surface of the support layer 1 to 3 is significantly reduced, the initial wettability is significantly increased compared to the comparative example without the plasma treatment of the nano-membrane support layer surface it can be seen that the hydrophilicity is improved. . Due to this, the polyamide layer is firmly formed, and the bonding degree with the support layer is increased, so that the damage of the polyamide layer is small because the increase in flow rate and the increase in salt diffusion during the 2000 ppm NaOCl contact is small. In addition, it can be seen that Examples 1 to 3 subjected to plasma treatment significantly improved the divalent ion salt removal rate as compared with the comparative example.

Claims (15)

(1) spinning a spinning solution containing a solvent and a hydrophobic polymer and a core solution for forming a hollow through a spinning nozzle to form a nano separator;
(2) plasma-treating the surface of the separator to introduce hydrophilic radicals;
(3) immersing the separator in an aqueous solution containing a polyfunctional amine and then contacting an organic solution containing a polyfunctional acid halogen compound to form a polyamide layer. Hollow fiber type NF (Nanofiltration) ) Method of manufacturing membrane.
The method of claim 1,
The solvent of step (1) is any one or more selected from the group consisting of N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and dimethylacetamide (DMAc) Method for producing a hollow fiber type NF (Nanofiltration) membrane, characterized in that.
The method of claim 1,
The hydrophobic polymer of step (1) is selected from the group consisting of polysulfone polymer, polyamide polymer, polyimide polymer, polyester polymer, olefin polymer, polybenzoimidazole polymer and polyvinylidene fluoride Method for producing a hollow fiber type NF (Nanofiltration) membrane, characterized in that any one or more.
The method of claim 1,
The core solution of step (1) is a method of manufacturing a hollow fiber type NF (Nanofiltration) membrane, characterized in that the mixing ratio of the organic polar solvent (solvent A) and water (solvent B) is 4: 6 to 9: 1.
5. The method of claim 4,
The organic polar solvent is any one or more selected from the group consisting of dimethyl acetamide, N-methyl-2-pyrrolidone and dimethyl formamide, the method of manufacturing a hollow fiber type NF (Nanofiltration) membrane.
The method of claim 1,
The spinning nozzle of step (1) is a multi-tubular spinning nozzle,
And discharging the spinning stock solution to the outer tube of the multi-tubular spinning nozzle and simultaneously discharging the core solution to the multi-tubular spinning nozzle inner tube.
The method of claim 1,
The plasma surface treatment of step (2) is carried out with ammonia (NH ₃ ), hydrogen sulfide (H ₂ S), oxygen (O ₂ ), nitrogen (N ₂ ), sulfuric acid (H ₂ SO ₄ ) and water (H ₂ O). Method for producing a hollow fiber type NF (Nanofiltration) membrane, characterized in that using at least one gas or liquid selected from the group consisting of.
The method of claim 1,
Plasma surface treatment of the step (2) is a method of manufacturing a hollow fiber type NF (Nanofiltration) film, characterized in that the discharge treatment for 10 to 600 seconds at 100 to 1000W.
Hollow;
A supporting layer formed along the outer periphery of the hollow; And
It comprises a polyamide layer formed along the outer periphery of the support layer,
The support layer forms a sponge like structure,
The surface of the support layer is a hollow fiber type NF (Nanofiltration) membrane, characterized in that the hydrophilic surface modified by plasma treatment.
Hollow;
A supporting layer formed along the outer periphery of the hollow; And
It comprises a polyamide layer formed along the outer periphery of the support layer,
The surface of the selective layer has a contact angle of 45 ° or less, the hollow fiber type NF (Nanofiltration) membrane, characterized in that the initial wettability of 70% or more.
10. The method of claim 9,
The support layer includes any one or more selected from the group consisting of polysulfone polymer, polyamide polymer, polyimide polymer, polyester polymer, olefin polymer, polybenzoimidazole polymer and polyvinylidene fluoride Hollow fiber type NF (Nanofiltration) membrane, characterized in that.
10. The method of claim 9,
The cross-sectional thickness of the support layer is 50 to 700um and the cross-sectional thickness of the polyamide layer is 0.1 to 1um, hollow fiber type NF (Nanofiltration) membrane.
10. The method of claim 9,
Hollow fiber type NF (Nanofiltration) membrane, characterized in that the average pore size of the support layer is 0.01 to 0.1um.
10. The method of claim 9,
The hydrophilic surface-modified selective layer has a contact angle of 45 ° or less and an initial wetting property of 70% or more, hollow fiber type NF (Nanofiltration) membrane.
10. The method of claim 9,
The hollow fiber type NF membrane is a hollow fiber type NF (Nanofiltration) membrane, characterized in that the divalent ion salt removal rate is 95% or more.

Images