KR20120019865A - Hydrophilizing surface-treating method of water-treatment membranes and hydrophilized water-treatment membranes - Google Patents

Abstract

PURPOSE: A hydrophilic surface treating method of water treating membranes and the water treating membranes are provided to reform the surface of the water treating membranes into hydrophilic. CONSTITUTION: A hydrophilic surface treating method of water treating membranes includes the following: water treating membranes are treated with base; and the surfaces of the water treating membranes are reformed into hydrophilic using a composition containing an oxidizer and a polymer with a hydrophilic group. The water treating membranes are capable of being treated with acid before the membranes are treated with the base. The acid is one or more selected from a group including nitric acid, hydrochloric acid, phosphoric acid, and fluoric acid. The base is one or more selected from a group including sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium permanganate, and potassium permanganate.

Description

HYDROPHILIZING SURFACE-TREATING METHOD OF WATER-TREATMENT MEMBRANES AND HYDROPHILIZED WATER-TREATMENT MEMBRANES}

The present invention relates to a method for hydrophilizing a separation membrane used for water treatment and a water treatment separation membrane hydrophilized by the above method, and more specifically, by treating a hydrophilic functional group chemically with the surface of a hydrophobic separation membrane under specific conditions, The present invention relates to a method of modifying the surface of a separator hydrophilically.

As membranes used in water treatment fields, hydrophobic polymers such as polysulfone, polycarbonate, and fluorine have excellent mechanical properties such as heat resistance, weather resistance, and strength. Recently, vinylidene fluoride resin is used for water treatment membranes.

However, since the water treatment separation membrane using a fluorine resin or the like is hydrophobic in nature, the water permeation membrane is easily contaminated by organic substances or the like contained in the water to be treated during the filtration process and the water permeation rate is lowered. Moreover, there is a problem that the amount of permeability is difficult to recover even after the regeneration treatment by physical washing such as back washing and air scrubbing.

In addition, when separating and concentrating a substance such as organic matter or protein strongly adsorbable on a hydrophobic surface easily forms a concentration polarization layer or fouling (fouling) on the surface, the permeation rate is significantly reduced and the separation performance is changed. It also shortens the life cycle, reducing process efficiency.

Therefore, various studies on surface modification of such hydrophobic water treatment membranes have been made. However, the process is too complicated and the processing cost is high. In addition, the compound is eluted during the filtration step after the hydrophilization treatment of the water treatment membrane.

It is an object of the present invention to provide a surface treatment method for modifying the surface of a hydrophobic water treatment separation membrane hydrophilically.

It is another object of the present invention to provide a water treatment separation membrane having a hydrophobic surface modified surface.

Surface treatment method of a water treatment membrane according to an embodiment of the present invention for achieving the above object, (a) treating the water treatment membrane with a base and (b) using a composition comprising a polymer having a hydrophilic group and an oxidizing agent It characterized in that it comprises a step of hydrophilizing the surface of the water treatment separation membrane.

Water treatment membrane according to another embodiment of the present invention for achieving the above object is (a) treating the water treatment membrane with a base and (b) a composition comprising a polymer having a hydrophilic group and an oxidizing agent of the water treatment membrane Characterized by a surface treatment method comprising the step of hydrophilizing the surface.

The surface treatment method of the water treatment membrane according to the present invention can significantly improve the hydrophilicity on the surface of the membrane by increasing the water permeability by chemically bonding the hydrophilic group to the hydrophobic polymer on the surface of the water treatment membrane in the atmosphere containing the oxidizing agent after the base treatment In addition, the hydrophilicity is prevented from being reduced even after a long time, so that the life of the membrane can be extended.

The hydrophilized water treatment membrane according to the present invention has the advantage that the surface is hydrophilically modified to improve the water permeability, and the contamination by organic matters is reduced to reduce the cycle time of physical washing and chemical washing to extend the life of the membrane have.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, only the present embodiments to make the disclosure of the present invention complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Hereinafter, the hydrophilized surface treatment method and the water treatment membrane of the water treatment separation membrane according to the present invention will be described in detail.

In the present invention, the kind of the water treatment separation membrane on which the hydrophilization surface treatment is performed is not particularly limited. All commonly used water treatment separators in the art may be included.

Examples of such water treatment separation membranes include polyvinylidene fluoride resins, polysulfone resins, polyethersulfone resins, polyetherimide resins, polyimide resins, polyethylene resins, polypropylene resins, and polyamide resins. It may include one resin selected from the group consisting of resins. Among them, polyvinylidene fluoride series resins having excellent ozone resistance and mechanical strength and excellent molding processability are frequently used. However, the range applied to the surface treatment method of the water treatment separation membrane according to the present invention is not limited thereto.

The hydrophilized surface treatment method of the water treatment separation membrane according to the present invention may be a polyvinylidene fluoride-based hollow fiber membrane.

In addition, the method of manufacturing the water treatment separation membrane to which the hydrophilized surface treatment method according to the present invention is applied is not particularly limited. All methods of preparing a general water treatment separator known in the art may be applied.

The hydrophilic surface treatment method of the water treatment separation membrane according to the present invention comprises (a) treating the water treatment separation membrane with a base and (b) hydrophilizing the surface of the water treatment separation membrane using a composition comprising a polymer having a hydrophilic group and an oxidizing agent. Characterized in that it comprises a step.

Also, the method may further include treating the water treatment membrane with an acid before the step (a).

Step (a) is a step of treating the water treatment membrane with a base.

The method of treating the water treatment membrane with a base is not particularly limited. For example, the base treatment may be performed by contacting the water treatment membrane with the base under certain conditions. The method of contacting the base and the water treatment membrane includes a method of immersing the water treatment membrane in a base liquid in which the base is dissolved or dispersed in a predetermined solvent, or applying the base liquid to the water treatment membrane, or coating and spraying the same. However, the surface treatment method of the water treatment separation membrane according to the present invention is not limited thereto. Under certain conditions, the base solution may be vaporized and contacted with a water treatment membrane to perform base treatment.

Preferably the base may be at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium permanganate and potassium permanganate. Of these, sodium hydroxide or potassium hydroxide is preferably used, but is not limited thereto.

The base treatment can be carried out by contacting with a base solution for 5 minutes to 24 hours at 20 ~ 90 ℃. At this time, the method of contacting the water treatment membrane with the base solution may be applied, but is not limited thereto. In addition, the base in the vapor state and the water treatment membrane may be in contact with the base treatment may proceed.

The base solution used in step (a) may be prepared by dissolving in a suitable solvent. The solvent used in the present invention may be water, alcohol or a mixed solvent of water and alcohol, but is not particularly limited thereto.

The concentration of the base solution may preferably be 5 to 25%. If the base concentration is less than 5%, the base treatment of the water treatment membrane may be less dehydrogenated. If the base concentration is more than 25%, the mechanical strength of the water treatment membrane may be decreased and other physical properties may be reduced.

Step (b) is a step of hydrophilizing the surface of the water treatment separation membrane treated with a base using a composition containing a polymer having a hydrophilic group and an oxidizing agent.

The surface of the water treatment membrane contains a hydrophobic polymer. When base treatment is performed on the surface of the water treatment separator containing a hydrophobic polymer, a double bond is formed in the chain of the hydrophobic polymer. Subsequently, when the water treatment membrane is treated with a composition containing a polymer having an oxidant and a hydrophilic group, the double bond formed in the hydrophobic polymer chain by the oxidant is converted into a single bond, and the hydrophobicity of the hydrophilic functional group of the polymer having a hydrophilic group and the surface of the water treatment membrane Chemical bonds occur between the polymers. By introducing a hydrophilic functional group to the surface of the water treatment separation membrane through the above treatment method, the surface of the water treatment separation membrane is modified to be hydrophilic.

The method of hydrophilizing the surface of the water treatment separation membrane using a composition containing a polymer having a hydrophilic group and an oxidizing agent is not particularly limited. The hydrophilization treatment step may be carried out by contacting the water treatment membrane and the composition under certain conditions.

As a method of contacting the composition and the water treatment membrane, for example, the water treatment membrane is immersed in a solution in which a polymer having a hydrophilic group and an oxidant is dissolved or dispersed in a predetermined solvent, or the solution is applied to, or coated and sprayed on, the water treatment membrane. Method and the like. However, the surface treatment method of the water treatment separation membrane according to the present invention is not limited thereto.

The oxidant may be used without limitation as long as it is a known oxidant capable of inducing an oxidation reaction to the hydrophobic polymer on the surface of the water treatment membrane. Preferably at least one selected from the group consisting of potassium permanganate, potassium peroxide, sodium hypochlorite can be used.

The polymer having a hydrophilic group may be a known polymer capable of introducing a hydrophilic functional group on the surface of the water treatment separation membrane, and is not particularly limited. Preferably, a polymer having at least one hydrophilic group selected from the group consisting of hydroxyl group, carbonyl group, sulfonic acid group, amide group and polyalkylene oxide group can be used.

Specifically, polyvinyl alcohol, polyacrylic acid, polyethylene glycol, carboxyl group-containing acrylic resin, carboxyl group-containing polyester resin, perfluoro polyester, polyamide, polyurethane resin, cellulose, or polyvinylpyrrolidone can be used. .

In step (b), the water treatment membrane is preferably heat-treated for 10 minutes to 10 hours in a temperature range of 40 to 90 ℃. When the heat treatment is performed outside the above temperature range and the heating time, problems such as insufficient hydrophilic functional group bonding to the surface of the water treatment membrane or a decrease in the permeability of the water treatment membrane may occur.

The present invention may further comprise the step of treating the water treatment membrane with an acid before step (a).

The method of treating the water treatment membrane with an acid is not particularly limited. For example, acid treatment may be performed by contacting the water treatment membrane with the acid under certain conditions. The acid and the water treatment membrane may be contacted by immersing the water treatment membrane in an acid solution in which the acid is dissolved or dispersed in a predetermined solvent, or applying the acid solution to the water treatment membrane, or coating and spraying the same. However, the surface treatment method of the water treatment separation membrane according to the present invention is not limited thereto. Under certain conditions, the acid solution may be vaporized and brought into contact with the water treatment membrane to perform acid treatment.

The acid may be at least one selected from the group consisting of nitric acid, hydrochloric acid, phosphoric acid, sulfuric acid and hydrofluoric acid. Of these, nitric acid is preferably used, but is not limited thereto.

The acid treatment can be carried out by contacting with an acid solution for 5 minutes to 24 hours at 20 ~ 90 ℃. At this time, the method of contacting the water treatment membrane with the acid solution may be applied, but is not limited thereto. In addition, the acid in the vapor state and the water treatment membrane may be in contact with the acid treatment.

The acid solution used in this step can be prepared by dissolving in a suitable solvent. The solvent used in the present invention may be water, alcohol or a mixed solvent of water and alcohol, but is not particularly limited thereto.

The concentration of the acid solution is preferably 5 to 25%. However, it is not particularly limited thereto. If the acid concentration is less than 5%, the acid treatment of the water treatment membrane may be less hydrophilized, and if the acid concentration is more than 25%, the mechanical strength of the water treatment membrane may be reduced and other physical properties may be degraded.

In the surface treatment method of the water treatment separation membrane according to the present invention, after the base treatment of the surface of the water treatment separation membrane containing a hydrophobic polymer, the surface of the water treatment separation membrane is subjected to hydrophilization treatment using a composition containing a polymer having an oxidizing agent and a hydrophilic group. In the conventional hydrophilic treatment method of the water treatment membrane, the surface of the water treatment membrane is hydrophilically modified by base treatment or acid treatment, but the surface treatment method of the water treatment membrane according to the present invention is applied to the surface of the water treatment membrane under an oxidizing atmosphere after base treatment. By introducing hydrophilic functional groups can have better water permeability and pollution resistance.

[Example]

Example 1

A hydrophilized surface treatment was performed using a polyvinylidene fluoride hollow fiber membrane. The hollow fiber membrane was immersed in an aqueous 10% sodium hydroxide solution at room temperature for 5 hours for base treatment. Subsequently, the hollow fiber membrane was immersed in an aqueous solution containing sodium hypochlorite and polyvinyl alcohol, followed by drying after heating for 2 hours at 60 ° C.

Example 2

The polyvinylidene fluoride hollow fiber membrane was subjected to a hydrophilic treatment in the same manner as in Example 1, and the acid treatment was further performed before the base treatment. The acid treatment was carried out by immersion in a 15% concentration of nitric acid solution at room temperature for 10 hours.

Comparative example

Using the polyvinylidene fluoride hollow fiber membrane, only base treatment in the same manner as in Example 1 was performed.

For Examples 1, 2, and Comparative Examples, the transmittance to contaminated water was measured. Specifically, the produced polyvinylidene fluoride hollow fiber membrane (80 strands) was immersed in ethanol, and then immersed in pure water for a long time to replace ethanol with pure water. Subsequently, the hollow fiber substituted with pure water was immersed in 10% by weight of glycerin for several hours, and then slowly dried at room temperature. This produced a module with an efficiency area of 0.06 mm ² . Thereafter, 50% by weight of the prepared module was immersed in ethanol and again immersed in pure water to keep the membrane wet. The hollow fiber membrane was supplied with 250 ppm of γ-globulin solution as inflow water, and a pressure of 0.5 bar was applied. At 5 minutes after the inflow of the influent, the amount of permeation was measured for 10 minutes, and the transmittance was measured according to the following formula.

Permeability measurement for pure water was carried out at a pressure of 0.5 bar after preparing the same hollow fiber membrane. Permeation was measured for 30 minutes when 5 minutes had elapsed after the introduction of pure water.

For Examples 1, 2 and Comparative Examples, the transmittances for the contaminated water and the pure water were measured and described in Table 1 below.

[Table 1]

Looking at Table 1, it can be seen that the hollow fiber membranes (Examples 1 and 2) in which the hydrophilic functional groups were introduced to the surface after the base treatment, compared to the hollow fiber membranes (Comparative Example) subjected to base treatment only, had a better transmittance. In addition, it can be seen that the hollow fiber membrane according to Example 2, which was further subjected to acid treatment before base treatment, had the best transmittance.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. . Therefore, the true technical protection scope of the present invention should be judged by the claims described below.

Claims (11)

(a) treating the water treatment membrane with a base; And
(b) hydrophilizing the surface of the water treatment separation membrane using a composition comprising a polymer having a hydrophilic group and an oxidizing agent.
The method of claim 1,
And treating the water treatment separation membrane with an acid before the step (a).
The method of claim 2,
The acid is a surface treatment method of a water treatment separation membrane, characterized in that it comprises at least one selected from the group consisting of nitric acid, hydrochloric acid, phosphoric acid, sulfuric acid and hydrofluoric acid.
The method of claim 2,
The acid treatment is a surface treatment method of a water treatment membrane, characterized in that the acid treatment by contacting the water treatment membrane with an acid solution for 5 minutes to 24 hours at a temperature of 20 ~ 90 ℃.
The method of claim 1,
The water treatment separator is a group consisting of polyvinylidene fluoride resin, polysulfone resin, polyether sulfone resin, polyetherimide resin, polyimide resin, polyethylene resin, polypropylene resin and polyamide resin Surface treatment method of a water treatment separation membrane, characterized in that it comprises one or more selected from.
The method of claim 1,
The base is a surface treatment method of a water treatment separation membrane, characterized in that it comprises at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium permanganate and potassium permanganate.
The method of claim 1,
The step (a) is the surface treatment method of the water treatment membrane, characterized in that the base treatment by contacting the water treatment membrane with a base solution for 5 minutes to 24 hours at 20 ~ 90 ℃.
The method of claim 1,
The oxidizing agent is a surface treatment method of a water treatment separation membrane, characterized in that at least one selected from the group consisting of potassium peroxide, potassium permanganate, sodium hypochlorite.
The method of claim 1,
The polymer having a hydrophilic group has at least one hydrophilic group selected from the group consisting of hydroxyl group, carbonyl group, sulfonic acid group, amide group and polyalkylene oxide group.
The method of claim 1,
The step (b) is a surface treatment method of the water treatment separation membrane, characterized in that the water treatment membrane is in contact with the composition for 10 minutes to 10 hours at 40 ~ 90 ℃.
A water treatment separation membrane whose surface is hydrophilized by the method of any one of claims 1 to 10.