KR101971797B1 - Membrane for water treatment and manufacturing method for the same - Google Patents

Abstract

The present invention relates to a separation membrane apparatus for water treatment in which anti-fouling phenomenon and flux are enhanced compared with a conventional technology by using characteristics of a piezoelectric body, and a manufacturing method thereof. The method comprises: mixing PZT powder with a PVDF-added mixed solvent to form a PZT-PVDF complex solution; electrospinning the PZT-PVDF complex solution and laminating the same to form a PZT-PVDF web; and forming a membrane for water treatment, which is connected to an electric circuit and including a conductive and porous support inserted into one side or inside of a nanofiber web and laminated. When the electricity is applied to the water treatment membrane, anti-fouling characteristics and flux are enhanced.

Description

[0001] The present invention relates to a membrane for water treatment and a method for manufacturing the same,

The present invention relates to a separation membrane for water treatment and a method for producing the same, and more particularly, to a separation membrane for water treatment which improves the fouling phenomenon and flux by using characteristics of a piezoelectric body according to the temperature and flow of water, will be.

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 can occur more frequently as a large amount of dissolved organic materials are contained in the raw water. As the concentration of dissolved organic molecular substances generated from the molecules decomposed dead in the water or biologically synthesized molecules becomes higher 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, the above techniques have been based on a coating material to cause pore clogging of the film or to physically contact the surface of the film to lower the durability of the film. In addition, And it is insufficient to secure a complex effect such as improvement. 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.

Korean Patent No. 10-1738732 Korean Patent No. 10-1743642 Korean Patent No. 10-1744400 Japanese Patent Application No. 2017-018842

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made to solve the above problems, and provides a water treatment membrane capable of reducing fouling that can occur during filtration of raw water using a water treatment separator, The purpose is to.

To this end, it is necessary to avoid the conventional coating-based chemicals and to minimize the adherence of contaminants to the membrane during the filtration of raw water without using chemicals, And a method for producing the same.

In order to solve the above problems, the present invention provides a method for preparing a water treatment separator, comprising the steps of: (1) forming a PZT-PVDF complex solution by mixing PZT powder in a mixed solvent containing PVDF; Electrospinning the PZT-PVDF composite solution and then laminating the PZT-PVDF composite solution to form a PZT-PVDF web; A third step of laminating a conductive and porous support having pores relatively larger than the pores of the nano-web on one surface of the nano-fiber web; Coating the insulating and waterproof material on the opposite side of the conductive and porous support bonded with the nanoweb; And a fifth step of connecting a power source and an electric wire so as to supply electricity to the conductive and porous support.

Here, the mixed solvent may be a mixture of two or more selected from acetone, DMF, octanol, ethoxyethanol, tetradecane, pentanol, dipropylene glycol monomethyl ether and ethylene glycol, , The mixed solvent is characterized in that acetone and DMF are mixed at a weight ratio of 20:80 to 80:20.

The PZT-PVDF composite solution may be prepared by mixing 10 to 30% by weight of PVDF, 5 to 40% by weight of PZT powder, and the remainder of the mixed solvent. In the PZT-PVDF composite solution, The powder is preferably added in an amount of 10 to 25% by weight based on the total weight of the PZT-PVDF composite solution.

Further, in the method for manufacturing a water treatment separator according to the present invention, the electrospinning is characterized in that the PZT-PVDF composite solution is radiated at a rate of 0.5 to 2 μl / min.

In addition, in the method for manufacturing a separation membrane for water treatment according to the present invention, the electrospinning is characterized by a radiation voltage of 10 to 25 kV and a radiation distance of 10 to 20 cm.

The water treatment separator according to the present invention comprises a first side on which a web made by electrospinning from a PZT-PVDF complex solution is placed; A second side consisting of a conductive and porous support having a relatively large pore than the first side, the second side being in contact with the first side, the opposite side being coated with insulating and waterproof material; And the anti-fouling characteristic and the flux are improved by the ultrasonic waves which are vibrated when the first and second surfaces are in contact with each other and when electricity is applied.

Here, the conductive and porous supports are preferably metal foams or metal meshes, and the conductive and porous supports are more preferably selected from the group consisting of iron, nickel, and stainless steel.

In the water treatment separator according to the present invention, the average thickness of the nanofiber web is 100 nm to 10 μm, and the average pore size of the nanofiber web is 0.1 μm to 1 μm and the porosity is 30% or more .

Further, the water treatment separator according to the present invention is characterized in that the flux is 1000 to 20000 L / m 2 h while the contaminants adhered by the ultrasonic vibration are desorbed.

The separation membrane for water treatment according to the present invention and the method of manufacturing the same according to the present invention are characterized in that a polymer piezoelectric material is bonded on a substrate of a water treatment separation membrane composed of a polymer material by electrospinning to generate ultrasonic waves in the separation membrane itself, It is possible to reduce the amount of organic matter adhering to the filter surface without adversely affecting the filter surface.

In addition, the separator for water treatment and the method for producing the same according to the present invention have a simple structure of a conventional apparatus for reducing fouling phenomenon, and do not use chemical substances, thereby being eco-friendly.

Further, the separation membrane for water treatment of the present invention and its production method have the effect of reducing the fouling during the filtration process of the membrane, and at the same time improving the flux.

1 is a SEM photograph showing the microstructure of a PZT-PVDF web of a water treatment separator according to the present invention.
2 shows the fouling effect of the separation membrane for water treatment according to the present invention.
FIG. 3 shows the results of flux experiments of the separator for water treatment according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a separation membrane for water treatment according to the present invention and a method for producing the same will be described in detail with reference to the drawings.

The use of the terms "comprises", "having", or "having" in this application is intended to specify the presence of stated features, integers, steps, components, parts, or combinations thereof, But do not preclude the presence or addition of features, numbers, steps, operations, components, parts, or combinations thereof.

Also, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those in commonly used dictionaries are to be interpreted as having a meaning consistent with the meaning in the context of the related art and are not intended to be used in an ideal or overly formal sense unless expressly defined in the present application It is not interpreted.

The method for producing a water treatment separator according to the present invention comprises the steps of: 1) forming a PZT-PVDF complex solution by mixing PZT powder in a mixed solvent containing PVDF, electroluminating the PZT-PVDF composite solution, A second step of forming a web, a third step of laminating a conductive and porous support having pores relatively larger in porosity than the nano-web on one side of the nanofiber web, the opposite side of the conductive and porous support And a fifth step of connecting a power source and an electric wire so as to supply electricity to the conductive and porous support.

The PVDF has a considerably large dipole moment in the polymer and exhibits a high dielectric constant and has flexibility and corrosion resistance characteristic of the polymer. In addition, PVDF is easy to process, inexpensive, has excellent thermal stability and chemical resistance, and is stable in humidity-sensitive electrospinning process. The PZT [Pb (Zr _x Ti _1-x ) O ₃ ] powder is a typical piezoelectric material having various properties such as ferroelectricity, superconductivity and piezoelectricity, and is a nonvolatile memory device using ferroelectricity, Microactuators and accelerometers using piezoelectricity, infrared sensors using ultra high voltage, and infrared sensing devices. In the method for producing a water treatment separator according to the present invention, the PZT-PVDF composite solution is composed of 10 to 30% by weight of PVDF, 5 to 40% by weight of PZT powder and the remaining mixed solvent, The PZT powder is added in an amount of 10 to 25% by weight based on the total weight of the PZT-PVDF composite solution. In the above ratio, the content ratio of PVDF and PZT is optimized to maintain the physical properties that can be formed in the form of film and membrane while maintaining ductility, and to enhance the performance of the piezoelectric body that generates electricity by supplying electricity It is important to find rain. That is, if the content of PZT in the water treatment separator according to the present invention is excessively high, the ductility may be insufficient to maintain the shape of the film or the membrane. Conversely, if the content of PVDF becomes too high, The fouling removal effect may be lowered. In order to derive the optimum ratio, the membrane production characteristics and vibration efficiency were measured according to the ratio of PVDF and PZT. As a result, 10 to 30 wt% of PVDF, 10 to 60 wt% of PZT powder, Were mixed. When the PVDF content is lower than 10% by weight, the shape of the membrane is difficult to maintain. On the contrary, when the PVDF content is higher than 30% by weight, the content of the solvent is lowered and the PZT content is lowered. There has been a problem that performance is deteriorated. In the case of the PZT content, when the content of PZT is lower than 10 wt%, the vibration performance is excessively lowered and the effect of removing fouling is lowered. When the content of PZT is higher than 60 wt%, the content of the solvent is lowered, The solubility of the membrane deteriorates or the membrane is not flexible enough to maintain its shape.

The mixed solvent is preferably a mixture of two or more selected from acetone, DMF, octanol, ethoxy ethanol, tetradecane, pentanol, dipropylene glycol monomethyl ether and ethylene glycol, As the solvent, acetone and DMF are mixed and used, and the acetone and DMF are mixed at a weight ratio of 20:80 to 80:20. When the content of acetone and DMF is less than 20, the characteristics of acetone having a high volatility are lowered, so that the evaporation of the solvent becomes difficult, and the jet containing the solvent reaches the current collecting plate, so that a straight fiber form is hardly produced.

In the water treatment separator according to the present invention, a PZT-PVDF complex solution is formed by mixing PZT powder in a mixed solvent containing PVDF as described above, and the composite solution is electrospun and laminated to form a web. In this process, when the high voltage is applied to the hemispherical state where the precursor solution equilibrates between the gravity and the surface tension, the hemispherical droplet extends in a conical shape, and when the electric field exceeds a certain strength, the surface tension is overcome While the jet of the charged precursor solution continues to be released from the Taylor cone. When the viscosity of the jet is high, it is not collapsed but the air is blown toward the grounded current collecting plate, the solvent is evaporated, and the charged continuous phase is accumulated on the current collecting plate. In this process, it is important to realize the basic performance of the membrane that passes the water while filtering the contaminated material, and to realize the lamination characteristic by the spinning speed, the voltage and the radiation distance in order to maintain the piezoelectric characteristic as much as possible. In order to achieve the above object, the present invention provides a method of manufacturing a separation membrane apparatus for water treatment, wherein the electrospinning is performed at a rate of 0.1 to 2 mL / hr in a PZT-PVDF composite solution, And a radiation distance of 10 to 20 cm. When the spinning rate is lower than 0.1 mL / hr, the working efficiency is lowered. When the spinning speed is higher than 1 mL / hr, the non-fiber type nodes are generated. Also, in terms of the radiation voltage, the operation efficiency is lowered when the voltage is lower than 10 kV, and when the voltage is higher than 25 kV, the formation of the fibrous phase is caused by the overvoltage. The radiation distance in the water treatment membrane apparatus according to the present invention also exhibits similar characteristics as described above. When the radiation distance is 10 cm or less, the radiation distance becomes too close to cause a problem that the solvent can not sufficiently evaporate. On the other hand, A problem arises that the fiber phase can not reach the drum.

Upon completion of the electrospinning step, the water-treating separator according to the present invention preferably has an average thickness of the web of 100 nm to 10 μm, and the average pore size of the web is 0.1 μm to 1 μm And a porosity of 30% or more. In the above configuration, if the average thickness of the web is 100 nm or less, the durability of the web is lowered and damage is likely to occur during the water treatment. If the average thickness is 10 μm or more, the flux may be lowered and the efficiency of the separation membrane may be lowered. In addition, when the pore size of the water treatment separator according to the present invention is 0.1 μm or less, the pressure loss becomes large, the flux becomes low, and the economical efficiency decreases. When the pore size is 1 μm or more, Occurs.

In the membrane separation apparatus for water treatment according to the present invention, a conductive and porous support having pores relatively larger than the pores of the nano-web is bonded to one surface of the nano-fiber web after the steps of manufacturing the web by electrospinning as described above. Here, the role of the conductive and porous support is to transmit the electricity supplied from the external power source to the nano web composed of the piezoelectric body, and simultaneously, the water filtered through the nano web must pass through. Therefore, it is important that the pores of the conductive and porous support are relatively larger than the pores of the nanoweb. Also, in this process, the opposite side of the conductive and porous support that is bonded to the nanoweb should be coated with an insulating and waterproof material. If the insulation and the waterproof coating are not provided, the electricity supplied from the external power source may be leaked out through the water in the process of filtering the raw water, and there is a risk of electric leakage. Finally, when a power source and a wire are connected to supply the electricity to the conductive and porous support, the water treatment separator according to the present invention vibrates the nanowire composed of a piezoelectric body through electricity supplied from the outside, Improvement may occur.

The water treatment separator according to the present invention has a first surface on which a web made by electrospinning is placed from a PZT-PVDF complex solution, one surface being in contact with the first surface, and an opposite surface being coated with an insulating and waterproof material, A second surface composed of a conductive and porous support having relatively larger pores than the first surface, an anti-fouling characteristic and a flux improved by ultrasonic waves that are in contact with the first surface and the second surface and vibrate when electricity is applied . In the separation membrane for water treatment according to the present invention, the conductive and porous support is not particularly limited as long as it has a conductivity to such an extent that a current necessary for generation of ultrasonic waves can flow through the web by applying a voltage. Preferably, the support is made of metal foam or metal mesh And more preferably at least one selected from the group consisting of iron, nickel, and stainless steel. In the separator for water treatment according to the present invention, the average thickness of the nanofiber web is 100 nm to 10 μm, the average pore size of the nanofiber web is 0.1 μm to 1 μm, and the porosity is 30% or more.

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. However, the following examples are illustrative of the present invention, and the present invention is not limited to the following examples.

Example 1.

The PZT-PVDF composite solution was prepared by stirring 10% by weight of PVDF in a mixed solvent of acetone and DMF at a ratio of 50:50 for 24 hours, adding up to 20% by weight of PZT powder, and stirring for 2 hours.

Next, the PZT-PVDF composite solution was electrospun using electrospinning equipment (ESR200R2, NanoNC, Korea) and dried at 25 ° C for 8 hours to prepare a PZT-PVDF web having a thickness of 1.0 μm.

In this case, the PZT-PVDF composite solution was injected into the syringe at a rate of 1.8 mL / hr using a syringe pump. The diameter of the tip was 21-27 G, the radial voltage applied to the nozzle was 20 kV, Was maintained at 15 cm. After this step, a mesh made of stainless steel was lapped with the web and the opposite side of the laminated side was coated with polypropylene for insulation and waterproofing coating before laminating. After that, the electric wiring was connected and electric power was supplied through the power supply.

Next, the microstructure of PZT-PVDF was analyzed using SEM (SUPRA 55VP, Carl Zeiss, Oberkochen, Germany) and TEM (Tecnai F20, FEI Corp.). The pores of the nano web showed an average pore of 0.5 μm and a porosity of 25%, and resistance values were measured with a digital multitester.

Example 2.

In order to analyze the fouling improvement effect of the water treatment membrane production apparatus fabricated as in Example 1, a decrease in flux was confirmed through a fouling experiment.

50 - 200 ppm organic solution was used as a feed, and a fouling experiment was carried out using a conventional PZT / PVDF membrane with a diameter of 30 - 50 mm and a general PVDF membrane prepared in a self - made cross flow membrane module. The applied gas pressure is 0.2 - 3 bar and the cross flow rate is 10 - 500 ml / min. Also, to generate the reverse piezoelectric characteristics of the manufactured piezoelectric separator, an AC voltage of 5 - 20 V was applied to the membrane module at 5 - 500 Hz using an AC signal generator.

Example 3.

In order to analyze the flux improvement effect of the water treatment membrane device manufactured as in Example 1, a pure water flux experiment was conducted.

DI water was used as a feed, and a fuzzy experiment was carried out using a piezoelectric PZT / PVDF membrane with a diameter of 30 - 50 mm and a general PVDF membrane fabricated on a self-fabricated cross flow membrane module. The applied gas pressure is 0.2 - 3 bar and the cross flow rate is 10 - 500 ml / min. Also, to generate the reverse piezoelectric characteristics of the manufactured piezoelectric separator, an AC voltage of 5 - 20 V was applied to the membrane module at 5 - 500 Hz using an AC signal generator.

1 is a SEM photograph showing the microstructure of the PZT-PVDF web of the water treatment membrane separator according to the present invention, and shows the microstructure of the PVDF nanofiber structure according to the PZT content.

FIG. 2 is a graph showing the fouling effect of the separation membrane apparatus for water treatment according to the present invention. FIG. 2 is a graph showing the results of fouling of a pure PVDF polymer membrane and a water treatment membrane of the present invention during filtration of an organic solution of 0.2 - Fig. The water treatment separator of the present invention exhibited 0.334%, while the PVDF separation membrane exhibited 0.223. Thus, the water treatment separator of the present invention exhibited a relatively higher flux than the conventional PVDF separation membrane, and the fouling removal effect was relatively large Respectively.

FIG. 3 is a graph showing the flux experiment results of the water treatment membrane separator according to the present invention and conventional PVDF separator, wherein the hydraulic permeability (Lp) of the distilled water is measured at room temperature every minute. The trans-membrane pressure was set at 0.2 - 3 bar and the stirring speed was set at 100 - 200 rpm. The trans-membrane flow rate was confirmed by electronic weighing scale. At the same thickness, the water treatment separator of the present invention showed 5000 LMH and the PVDF separator showed 1500 LMH.

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 (13)

PVDF mixed solution is mixed with PZT powder to form a PZT-PVDF composite solution composed of 10 to 30% by weight of PVDF, 10 to 60% by weight of PZT powder and the remaining mixed solvent;
The PZT-PVDF composite solution was electrospun at a speed of 0.5 to 2 mL / hr, a radial voltage of 10 to 25 kV and a scattering distance of 10 to 20 cm, and then laminated to obtain a laminate having an average thickness of 100 nm to 10 μm and an average pore size of 0.1 μm to 1.0 and forming a PZT-PVDF nanoweb having a porosity of 30% or more;
A third step of laminating a conductive and porous support having pores relatively larger than the pores of the PZT-PVDF nanoweb on one surface of the PZT-PVDF nanoweb;
Coating the insulating and waterproof material on the opposite side of the conductive and porous support laminated with the PZT-PVDF nanoweb; And
And a fifth step of connecting a power source and an electric wire so as to supply electricity to the conductive and porous support,
The separation membrane prepared by the above method is subjected to a final flux of 1670 at an initial plus 5000 LMH at a gas pressure of 0.2 to 3 bar, a cross flow rate of 10 to 500 mL / min, an AC voltage of 5 to 500 Hz, A method for producing a water treatment separation membrane characterized by being LMH
Wherein the mixed solvent is a mixture of two or more selected from acetone, DMF, octanol, ethoxy ethanol, tetradecane, pentanol, dipropylene glycol monomethyl ether and ethylene glycol. A method for producing a water treatment separator.
2. The method of claim 2, wherein the mixed solvent is acetone and DMF mixed solvent, and the mixed solvent is mixed at a weight ratio of 20:80 to 80:20.
delete The method of claim 1, wherein the PZT powder is added in an amount of 10 to 25% by weight based on the total weight of the PZT-PVDF composite solution.
The method of claim 1, wherein the conductive and porous support is a metal foam or a metal mesh.
The method of claim 1, wherein the conductive and porous support is at least one selected from the group consisting of iron, nickel, and stainless steel.
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