KR101986437B1 - Process of membrane fouling resistance based on silver-graphene oxide compounds - Google Patents

Abstract

The present invention relates to a method for reducing membrane fouling based on silver and graphene oxide. More particularly, the present invention relates to a coating method of a PVDF membrane capable of reducing fouling. The method comprises: a first step of manufacturing a silver-graphene oxide composite solution by mixing a precursor material and a graphene oxide in a solution phase; introducing the silver-graphene oxide composite solution into one side of the PVDF membrane and moving the mixed solution to the opposite side of the one side by a pressure means; and a third step of drying the PVDF membrane subjected to the second step.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for reducing film fouling based on silver and graphene oxide,

The present invention relates to a method of reducing film fouling using silver and graphene oxide, and more particularly, to a method of reducing film fouling by using silver and graphene oxide, And a method for reducing fouling.

The separation membrane for water treatment is a device for filtering the raw water according to the purpose, and in the process of filtering the raw water, a fouling phenomenon may occur in which the performance of the membrane is deteriorated due to the foreign substance blocking the pore.

The above-mentioned fouling phenomenon occurs more frequently as a large amount of dissolved organic material is contained in the raw water, and the concentration of the dissolved organic molecular material generated from molecules decomposed dead in water or synthesized by living organisms becomes high The fouling phenomenon can be intensified. In order to reduce the fouling phenomenon caused by such dissolved organic materials, various techniques for removing contaminants by physicochemically have been developed. For example, the separator may be coated with a hydrophilic material such as PEG, PVA, PVDF, In addition, there are techniques to clean organic materials that block pores by irradiating fine bubbles or ultrasonic waves directly to the separation membrane by installing a device, and techniques for adding additives that hinder the attachment of organic materials to the separation membrane coating material. However, it has been found that it is based on a coating material, which causes pore clogging of the film or physically contacts the surface of the film to lower the durability of the film. In addition, It is insufficient to secure the effect.

In addition, the technique of irradiating the micro bubbles or ultrasonic waves directly from the outside to the separation membrane and cleaning the micro bubbles or ultrasonic waves may cause loss of space and cost, and the micro bubbles or ultrasonic waves The untouched part still has the disadvantage of the presence of contaminants.

Further, for example, a technique of adding an inorganic additive to a polymer substance disclosed in Korean Patent No. 10-1738732 as a water reducing fouling reduction membrane is a method in which a perchlorate-based material is added to a porous polymer membrane to decrease the surface roughness, Despite the advantages of uniform pore size, it is still far from the conventional concept of coating a membrane with a hydrophilic material. It is a fundamental solution to prevent contaminants in the pores that interfere with smooth filtration and reduce flux. There is a disadvantage that it can not be done.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a method of coating a silver-graphene oxide composite on a PVDF membrane by a simple and easy dead-end filtration method.

It is also an object of the present invention to provide a PVDF film coated with a silver-graphene oxide composite which is effective for reducing film fouling.

According to an aspect of the present invention, there is provided a silver-graphene oxide composite solution comprising: a silver precursor material; Introducing the silver-graphene oxide composite solution into one side of the PVDF film and moving the mixed solution to the opposite side of the one side by a pressure means; And a third step of drying the PVDF film obtained by the two steps.

The present invention is advantageous in that it is possible to manufacture a PVDF membrane coated with a silver-graphene oxide composite on one side by a simple method of dead-end filtration, and is economical in process simplicity and cost.

In addition, the present invention is effective in reducing film fouling by suppressing the adhesion to organic and inorganic materials by coated silver-graphene oxide composite, enabling the film to be hydrophilic, reducing surface roughness, and having antibacterial properties.

FIG. 1 shows HR-TEM photographs (a, b) of the silver-graphene oxide composite prepared in the production example according to the present invention and the relationship (c)
FIG. 2 is a FT-IR photograph of the silver-graphene oxide composite prepared in Preparation Example according to the present invention,
Figure 3 shows the input amount of the silver-graphene oxide composite and the amount of silver-graphene oxide composite coated on PVDF according to the present invention,
4 is a SEM photograph of the PVDF film prepared in Example 1 and energy dispersive spectroscopy (EDS) results according to the present invention,
5 shows the water permeation amounts of the PVDF membranes prepared in Examples 1 to 3 and Comparative Example according to the present invention,
6 shows the water permeation amount of the PVDF membrane prepared in Examples 1 to 3 and Comparative Example according to the filter time according to the present invention,
7 shows the fouling ratio and the water recovery rate of the PVDF membranes prepared in Examples 1 to 3 and Comparative Example according to the present invention,
FIG. 8 shows cell viability and active oxygen production rates of PVDF membranes prepared in Examples 1 to 3 and Comparative Example according to the present invention.

The present invention relates to a method capable of reducing fouling through washing and drying processes after silver and graphene oxides are coated on a membrane surface by a dead-end filtration method.

Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be interpreted in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined.

Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention, and not all of the technical ideas of the present invention are described. Therefore, It should be understood that various equivalents and modifications may be present.

Hereinafter, a method of reducing film fouling based on silver and graphene oxides according to the present invention will be described in detail.

First, silver precursor material and graphene oxide are mixed in a solution phase to prepare a silver-graphene oxide composite solution.

The silver-graphene oxide composite is generally used in the art and is not particularly limited, and those obtained by direct reaction using commercially available products can be used.

For example, the present invention relates to a silver-ammonia solution prepared by mixing an aqueous ammonia solution and a silver nitrate solution into a mixed solution of a graphene oxide suspension, a polyvinylpyrrolidone solution and an? -D-glucoside, Graphene oxide complexes were prepared.

It is preferable that the silver-graphene oxide composite has a smaller particle diameter in consideration of antibacterial properties, and more specifically, an average particle diameter of silver is preferably 15 to 90 nm.

Next, the silver-graphene oxide composite solution is introduced into one side of the PVDF membrane, and the mixed solution is moved to the opposite side of the one side by the pressure means.

The present invention coating a silver-graphene oxide composite on one side of a PVDF membrane using a dead-end filtration method, specifically flowing a sample to be filtered in a direction perpendicular to the surface of the filter.

At this time, it is preferable to use the silver-graphene oxide complex solution so that the amount of the silver-graphene oxide complex coated on the PVDF film produced is 0.16855 mg or less per square meter of the unit. The amount of the silver-graphene oxide composite was calculated by measuring the amount of silver-graphene oxide that was not coated through absorption measurement but desorbed through surface cleaning, and then subtracting the amount of silver-graphene oxide from the total amount added for coating. If it exceeds the above range, the result is not attached to the PVDF film. This can be seen as the maximum amount of silver-graphene oxide the film can accommodate.

The pressure means is generally used in the art and is not particularly limited. Specifically, an inert gas such as nitrogen, argon, or the like may be used. The pressure is preferably in the range of 20 to 35 kPa considering the coating amount of silver-graphene oxide composite, the amount of silver-graphene oxide composite dispersion used for coating, and the filtration system used for coating.

Next, the PVDF membrane subjected to the dead-end filtration method is dried.

Drying is carried out using an oven in a method commonly used in the art, and drying is preferably carried out at a low temperature of 50 to 60 DEG C in consideration of the material and heat resistance of the membrane.

A washing process for removing the uncoated silver-graphene oxide complex may be further included, and it is preferable to use deionized water for washing.

The PVDF film coated with silver-graphene oxide composite on one side by the above-described manufacturing method can suppress the adhesion to organic and inorganic materials by graphene oxide, reduce the surface roughness of the film to increase the fouling resistance, The hydrophilic functional groups (hydroxyl group, carbonyl group, epoxide group) of the graphene oxide can be used to make the membrane hydrophilic. In addition, silver nanoparticles can have antimicrobial properties.

The silver-graphene oxide composite coated PVDF film prepared by the method of the present invention has a contact angle of 88.4 DEG or less, an average porosity of 55% or more, and an average pore size of 216 nm.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. , And it is natural that such variations and modifications fall within the scope of the appended claims.

Manufacturing example : Silver - Grapina  Oxide complex production

A solution of polyvinylpyrrolidone (10 ml, 4 mg / ml, molecular weight ~ 29000, Aldrich) and α-D-glucoside (800 mg, 96%, Aldrich).

Next, a silver-ammonia solution (10 ml) was added to the solution at 45 占 폚. At this time, the silver-ammonia solution was prepared by mixing silver nitrate solution (20 mg / ml,? 99.0%, Aldrich) with 2 wt% ammonia aqueous solution (28.0-30.0%, NH ₃ , Aldrich) .

Thereafter, the reaction was performed for 7 minutes, centrifuged at 10000 rpm for 10 minutes, washed with water, and dried at 80 DEG C for one day to prepare a silver-graphene oxide composite.

The silver-graphene oxide composite prepared above was subjected to high-resolution transmission electron microscopy (HR-TEM, Tecnai 20, FEI, USA) of FIG. 1 and Fourier transform infrared spectroscopy (FT- IR, NICOLET iS10, Thermo Fisher Scientific, USA). In addition, the number of particles per diameter of the particles was confirmed.

Example  1: silver- Grapina  Oxide composite is coated PVDF  membrane

The solution (10 ml) in which the silver-graphene complex solution obtained in the Preparation Example was dispersed by irradiation with ultrasonic waves for 2 hours was filtered on a PVDF membrane (pore size 0.22 μm, surface area 33.18 cm ² ) using a dead- .

At this time, the pressure was 20 kPa, followed by washing with deionized water, washing with water, and drying at 40 ° C for 1 hour to prepare a PVDF membrane coated with 0.01 mg silver-graphene oxide composite.

FIG. 3 shows the input amount of the silver-graphene oxide composite and the amount of the silver-graphene oxide composite coated on the PVDF. The amount of the silver-graphene oxide complex is 0.16855 mg per square meter Or less.

FIG. 4 shows field emission scanning electron microscopy (FE-SEM, S-4200, HITACHI, Japan) and energy dispersive spectroscopy (EDS) of a PVDF film coated with a silver- The pores of the PVDF membrane were nano - sized, and silver - graphene oxide complex was bonded on the PVDF membrane. It was confirmed that silver was sprayed.

Example  2: silver- Grapina  Oxide composite is coated PVDF  membrane

A PVDF membrane coated with 0.05 mg of a silver-graphene oxide composite was prepared in the same manner as in Example 1 except that a solution (10 ml) in which silver-graphene composite solution was dispersed by ultrasonic irradiation for 2 hours was used.

Example  3: silver- Grapina  Oxide composite is coated PVDF  membrane

A PVDF membrane coated with 0.3 mg of a silver-graphene oxide composite was prepared in the same manner as in Example 1 except that a solution (10 ml) in which a silver-graphene composite solution was dispersed by ultrasonic irradiation for 2 hours was used.

Comparative Example

PVDF membrane (pore size 0.22 μm, surface area 33.18 cm ² )

The physical properties of the PVDF membrane prepared in Example 1 and Comparative Example were measured by the following methods, and the results are shown in Table 1 below.

[How to measure]

1. Water contact angle: Measured using a Pendant Drop Tensiometer (CA, DSA100, KRUSS, Germany)

2. Porosity: Measured using the gravimetric method.

3. Average pore size: Measured using Guerout-Elford-Ferry equation

4. Surface area: A 10 μm × 10 μm membrane was measured using an atomic force microscope (AFM, XE-100, ParkSystems, Korea).

5. Surface roughness: A 10 μm × 10 μm film was measured using an atomic force microscope (AFM, XE-100, ParkSystems, Korea).

division Water contact angle (°) Porosity (%) Average pore size
(탆) Surface area
(탆 ² ) Surface roughness (nm) Ra Rq Example 1 88.40 ± 0.60 55.26 ± 0.29 0.2168 ± 0.0008 163.4 ± 0.9 176.7 ± 0.2 231.7 ± 5.0 Example 2 86.60 + - 0.10 58.66 + - 0.50 0.2041 ± 0.0021 158.7 ± 4.1 186.3 ± 0.2 250.9 ± 0.8 Comparative Example 89.45 ± 0.05 56.33 + - 0.51 0.2147 ± 0.0015 188.8 ± 5.9 203.5 ± 10.3 263.8 ± 9.7 Ra: Average surface roughness
Rq is the root-mean-square.

FIG. 5 shows water permeation amounts of the PVDF membranes prepared in Examples 1 to 3 and Comparative Examples according to the present invention, and the permeation amounts were measured using purified water and raw water.

The raw water was added to the wastewater collected at the copper sewage treatment plant, Bacillus subtilis (KCTC 1028, Korea). Tryptic Soy Agar (TSA) was 6.2 × 10 ⁶ CFUm ^{-1 in the} initial raw water.

In FIG. 5, (Jw, 1) is the permeation constant and (Jw, 0) is the permeation amount of the initial raw water, and Examples 1 to 3 are superior to the Comparative Example in water permeation amount of (Jw, 0) .

6 shows water permeation amounts of the PVDF membranes prepared in Examples 1 to 3 and Comparative Example according to the filter time according to the present invention. In FIG. 6, it can be seen that Examples 1 to 3 are superior in water permeability to the Comparative Examples even after the filter time using the membrane has elapsed.

7 shows the fouling ratio and the water recovery rate of the PVDF membranes prepared in Examples 1 to 3 and Comparative Examples according to the present invention and shows the cell viability and the production rate of active oxygen in Examples 1 to 3 Was superior.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. These changes and modifications may be made without departing from the scope of the present invention. Accordingly, the scope of the present invention should be determined by the following claims.

Claims (5)

Preparing silver -graphene oxide composite solution having an average particle size of silver of 15 to 90 nm by mixing the precursor material and graphene oxide in a solution phase;
Graphene oxide complex solution was introduced into one side of the PVDF membrane and the solution was passed through the opposite side of the PVDF membrane at a pressure of 20 kPa by dead-end filtration, in which the silver- Graphene oxide complex solution to prepare a PVDF film coated with silver-graphene oxide composite of not more than 0.16855 mg per square meter ; And
The PVDF film obtained by the above two steps was washed and then dried at 40 ° C to prepare a PVDF film having a contact angle of 88.4 ° or less, an average porosity of 55% or more, and an average pore size of 216 nm. Way.
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