KR20160083216A - water treatment membrane modified by electricity thereof method - Google Patents
water treatment membrane modified by electricity thereof method Download PDFInfo
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- KR20160083216A KR20160083216A KR1020140193252A KR20140193252A KR20160083216A KR 20160083216 A KR20160083216 A KR 20160083216A KR 1020140193252 A KR1020140193252 A KR 1020140193252A KR 20140193252 A KR20140193252 A KR 20140193252A KR 20160083216 A KR20160083216 A KR 20160083216A
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- membrane
- separation membrane
- electric field
- water treatment
- separation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0081—After-treatment of organic or inorganic membranes
- B01D67/009—After-treatment of organic or inorganic membranes with wave-energy, particle-radiation or plasma
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/35—Use of magnetic or electrical fields
Abstract
The present invention relates to a separation membrane for water treatment by electric field modification and a method of manufacturing the same, and more particularly, to a separation membrane for water treatment by applying an electric field to a water treatment separation membrane to improve water permeability, natural organic matter (NOM) And a method for producing the same. 2. Description of the Related Art
Description
The present invention relates to a separation membrane for water treatment by electric field modification and a method of manufacturing the same, and more particularly, to a separation membrane for water treatment by applying an electric field to a water treatment separation membrane to improve water permeability, natural organic matter (NOM) And a method for producing the same. 2. Description of the Related Art
The separation membrane technology is a highly separation technology for almost completely separating and removing the materials to be treated present in the treatment water according to the pore size, the pore distribution and the membrane surface charge of the membrane. In the water treatment field, the production of high quality drinking water and industrial water, And clean production processes related to the development of waste water treatment and reuse, and free circulation systems are expanding and are becoming one of the key technologies to be noticed in the 21st century.
Typical properties required for water treatment membranes include adequate porosity (number of pores) for the purpose of separation efficiency, uniform pore distribution for the purpose of improving fractionation accuracy, optimal porosity Size. In addition, chemical resistance, chemical resistance, heat resistance, and the like for chemical treatment are required as material characteristics. In addition, properties that affect the operating capability are required to have good mechanical strength to extend service life, and water permeability associated with operating costs.
To solve this problem, various polymer materials have been used. Polymer materials used in general water treatment processes include polysulfone, polyethersulfone, polyacrylonitrile, polyethylene, polypropylene Polypropylene, cellulose acetate and polyvinylidene difluoride polymer. In order to prepare the polymer as a separator, a thermally induced phase separation method or a non-solvent-derived phase separation method (Nonsolvent induced phase separation).
Korean Patent Laid-Open Publication No. 2014-0110810 discloses an excellent polyamide-based water treatment membrane and a method for producing the same, and Korean Patent Publication No. 2014-0065361 discloses a high-flow water treatment membrane having excellent chlorine resistance.
In recent years, the most important issue in the field of water treatment membranes is to produce membranes having a high removal rate and a high flow rate to minimize the energy consumed in the membrane treatment. Thus, it is possible to prepare a membrane having the above-mentioned purpose through various additives, manufacturing and process parameters. However, in the case of the additive, there is a problem that the additive is eluted at the time of membrane production and water treatment operation, Also has a problem of inducing an increase in manufacturing cost.
In addition, the problem of surface contamination of the membrane occurring during the water treatment operation becomes a recent issue. The problem of such contamination resistance is most closely related to the shortening of the life of the membrane and the increase of the water treatment cost due to replacement.
In order to solve the problem of contamination resistance, attempts have been made to improve the contamination problem by hydrophilization through production of a hydrophilic separation membrane or addition of various additives during surface modification. However, such a method has a problem that the manufacturing process becomes complicated and the economic cost increases.
Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a water treatment separator, The present invention provides a separation membrane for water treatment which is capable of controlling the removal rate of natural organic materials and has remarkably improved stain resistance, and a method for producing the same.
In addition, the water treatment membrane produced by the method of the present invention has advantages in that the manufacturing cost is lower than the cost manufactured by the conventional phase separation method, and there is no additional waste water generation in the manufacturing or water treatment operation, and is applied to various water treatment processes.
In order to solve the above-mentioned problems, the present invention provides a separation membrane for water treatment by electric field modification, characterized in that at least one of permeability and natural organic material removal rate is controlled by applying an electric field to a separation membrane produced by a phase separation method without additive ≪ / RTI >
According to a preferred embodiment of the present invention, the phase separation method of the method for producing a water treatment separation membrane of the present invention may be a heat induction phase separation method or a non-solvent induction phase separation method.
According to a preferred embodiment of the present invention, the dielectric constant of the separation membrane of the water treatment separator manufacturing method of the present invention may be 1? 10? At 1 MHz.
According to a preferred embodiment of the present invention, the zeta potential of the separation membrane in the method for preparing a separation membrane for water treatment of the present invention may be 0 mV to -20 mV at pH 7.
According to a preferred embodiment of the present invention, the separation membrane of the water treatment membrane production method of the present invention can be modified to have a positive surface by an applied electric field.
According to a preferred embodiment of the present invention, the intensity of the electric field applied to the separation membrane of the water treatment separator manufacturing method of the present invention may be 4 to 14 V / cm.
According to one preferred embodiment of the present invention, the separation membrane of the present invention for water treatment separating membrane has an increase in the removal rate of natural organic matter (NOM) by 30% or more without degradation of permeability through surface modification by an electric field .
According to a preferred embodiment of the present invention, the natural organic material of the method for preparing a separation membrane for water treatment of the present invention may include at least one of humic acid and fulvic acid.
According to a preferred embodiment of the present invention, the separation membrane of the present invention can increase the permeability by 10% or more through surface modification by an electric field.
According to a preferred embodiment of the present invention, the electric field of the method for producing a separation membrane for water treatment of the present invention can be applied to the separation membrane continuously or discontinuously during water treatment.
According to a preferred embodiment of the present invention, the separation membrane of the water treatment membrane production method of the present invention comprises a reverse osmotic (RO) membrane, a nanofilteration (NF) membrane, a microfilter And may be used for at least one of ultrafilter (UF) membranes.
According to another aspect of the present invention, there is provided a separation membrane produced by a phase separation method without an additive, wherein the separation membrane is provided with an electric field for controlling at least one of water permeability and natural organic material removal rate, do.
The separation membrane for water treatment by the electric field modification of the present invention and the manufacturing method thereof can control permeability, natural organic matter (NOM) removal rate and / or stain resistance by applying an electric field to the water treatment separation membrane.
Hereinafter, the present invention will be described in more detail.
In the separation membrane produced by the phase separation method without an additive, an electric field may be formed in the separation membrane for water treatment by electric field modification to control at least one of water permeability and natural organic material removal rate.
The separator for water treatment in the present invention may include separators of various materials commonly used in the art, preferably polysulfone separators such as polysulfone and polyester sulfone, polyamide separator, polyimide A separator, a polyester polymer, an olefin separator such as polypropylene and polyethylene, and a halogenated separator such as polybenzimidazole and polyvinylidene chloride, and more preferably a polyamide-based separator At least one of a separator, a polyvinylidene fluoride separator, and a polyethersulfone separator may be used. The preparation can be prepared by a thermal-induced phase separation method or a non-solvent-derived phase separation method, and it is advantageous not to add any additives other than the solvent.
The separation membranes enumerated above may be produced by various methods such as thermal inductive phase separation or non-solvent induction phase separation or vapor phase in-phase separation, depending on the material thereof. In the present invention, It is not limited.
As an example of this, a polyvinylidene fluoride separation membrane which can be used as a water treatment separation membrane can be produced by the following production method.
First, a polymer solution containing a polyvinylidene fluoride-based polymer and a solvent can be prepared. The polyvinylidene fluoride polymer used for the preparation of the separator may be a polyvinylidene fluoride (PVDF) homopolymer, a polyvinylidenefluoride-co-hexafluoropropylene (PVDF-HFP) copolymer, or a polyvinylidene fluoride- -chlorotrifluoroethylene), and the like. In the case of the copolymer, the PVDF is preferably 50 mol% or more.
The polyvinylidene fluoride polymer to be used is preferably a weight average molecular weight of 200,000 to 1,000,000 or less. If the molecular weight of the polyvinylidene fluoride polymer is lower than 200,000, the mechanical strength after the film formation is lowered, and if it is more than 1 million, the film formation may be difficult due to the viscosity increase.
The solvent constituting the polymer solution is not particularly limited as long as it can uniformly dissolve the polymer to prepare a separation membrane. More preferably, the solvent is selected from the group consisting of N-methylpyrrolidone, dimethylacetamide, dimethylsulfoxide, Amide, and the like. The composition of the polymer solution may preferably include 10 to 30% by weight of the polyvinylidene fluoride-based polymer and 70 to 90% by weight of the solvent. If the amount of the polyvinylidene fluoride polymer is less than 10% by weight, film formation is difficult and mechanical strength is low even after the film formation. If the amount exceeds 30% by weight, the permeability may decrease. The polyvinylidene fluoride separating membrane can be produced through a conventional porous separating membrane producing process using the polyvinylidene fluoride polymer solution thus prepared. The process for producing the porous separation membrane is not particularly limited, but preferably a separation membrane can be produced through a conventional non-solvent-derived phase separation process. Non-solvent-driven phase separation processes are well known in the art as the most commonly used method for preparing membranes.
In the present invention, an example of preparing a separator using the same will be described, but the present invention is not limited thereto and it is within the scope of the present invention to manufacture a porous separator using the polymer solution.
The separation membrane is generally used for water treatment and is used for at least one of a reverse osmosis (RO) membrane, a nanofilteration (NF) membrane, a microfilter (MF) membrane, and an ultrafilter As shown in Fig.
By using the membrane thus prepared, an electric field was applied to the membrane as a means for solving the permeability / removal rate and stain resistance, thereby solving the above problem.
It is another object of the present invention to provide a method for manufacturing a membrane for water treatment by controlling the membrane permeability and / or the removal rate of natural organic substances without changing the membrane, thereby reducing the stain resistance of the membrane.
First, the method for manufacturing a separation membrane for water treatment of the present invention controls at least one of the permeability of the separation membrane and the removal rate of natural organic materials by applying an electric field to the separation membrane.
At this time, the electric field can be applied continuously or discontinuously during the water treatment of the separator of the present invention.
The natural organic material is a substance present in a water source or a drinking water, and reacts with chlorine such as a chemical oxidizing agent during water treatment to produce disinfection by-products (DBPs) which are halogenated, and stabilize particles Or by providing an electron donor to the heterotrophic bacteria in the water supply and drainage network to cause regrowth and the like.
Such natural organic materials exist in colloidal or particulate form, and typical natural organic materials present in the raw water are composed of humic substances and non-humic substances.
The nonhumidifying material is a hydrophobic material which is composed of hydrophilic acids, proteins, amino acids and carbohydrates. It is extracted by sodium hydroxide and soluble at pH 2, and has a molecular weight Is relatively small and is between 1k and 30k Dalton.
The separation membrane according to the present invention can remove at least one of humic substances and nonhumidic materials which are natural organic matter (NOM), and preferably humic acid and fulvic acid, which are humic substances, At least one can be removed, and more preferably humic acid having a negative charge at pH 7 can be removed.
The present invention can be aimed at controlling the removal rate and / or the permeability of natural organic materials through application of electric field of the separator, taking into account the charge of the natural organic material at pH 7. [
According to the first embodiment of the present invention, the zeta potential of the separator of the present invention may be 0 mV to -20 mV at pH 7, more preferably -2 mV to -15 mV.
Further, the dielectric constant of the separator of the present invention may be 1? To 10?, More preferably 2? To 8? At 1 MHz.
At this time, the separation membrane can be modified to a positive charge due to the donnan equilibrium according to the applied electric field.
In addition, the separation membrane can increase the permeability by more than 10% through surface modification by an electric field.
If the zeta potential of the separator is less than 0 mV at pH 7, the removal rate may not be increased due to difficulty in inducing the surface charge through application of an electric field. If the separation potential exceeds -20 mV, the permeability may rapidly decrease.
Further, the electric field intensity applied to the separation membrane may be continuously applied at a rate of 4 to 14 V / cm, preferably 6 to 12 V / cm, for a predetermined time. If the electric field strength applied to the membrane is less than 4 V / cm, the degree of increase in the removal rate of natural organic matter (NOM) may be negligible, and if it exceeds 14 V / cm, it may be economically ineffective. In this way, the separation membrane to which the electric field is applied can increase the removal rate of natural organic matter (NOM) by 30% or more without decreasing the permeability.
Meanwhile, the kind of the separation membrane used in the above-described embodiment can be used without limitation of use, materials and the like as long as it satisfies the range of the permittivity according to the preferred embodiment of the present invention.
The separation membrane may be a flat membrane or a hollow fiber membrane, but more preferably a flat membrane is advantageous.
In the case of a flat membrane, the polymer solution is cast on a non-porous substrate such as a glass substrate or a metal substrate or a porous substrate such as a nonwoven fabric, and then immersed in the coagulating solution of the polymer to coagulate, wash and dry the membrane. . If the coagulating liquid temperature is below room temperature, there is a problem in productivity because the coagulating liquid is delayed when the coagulating liquid temperature is below room temperature. If the coagulating liquid temperature exceeds 60 ° C, There is a disadvantage in that the temperature decreases. The porous film may be prepared by washing with water to remove remaining solvent and unreacted polymer, and drying under an atmosphere at room temperature. The washing and drying time is not particularly limited, but is preferably 24 hours or more for washing and 12 hours or more for drying.
Meanwhile, as another manufacturing example, the hollow fiber membrane without support is discharged from the outer tube of the double nozzle maintained at a room temperature to 60 ° C, and at the same time, the inner coagulant is injected into the inner tube of the double nozzle in an amount of 1.0 to 15 ml / min. The discharged hollow fiber membrane is precipitated in an external coagulating liquid composed of water at a temperature ranging from room temperature to 60 ° C to form a hollow fiber membrane, and then the porous hollow fiber membrane can be manufactured through the same washing and drying processes as those described above.
Meanwhile, if a polyamide-based polymer or a polyethersulfone polymer is used instead of the polyvinylidene fluoride-based polymer solution through the above-described method for producing a polyvinylidene fluoride separation membrane, a polyamide-based separation membrane or polyvinylidene fluoride separation membrane .
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 exemplary embodiments. It will be understood that various changes and modifications may be made without departing from the scope of the present invention. For example, each component specifically illustrated in the embodiments of the present invention can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
The present invention will now be described more specifically 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
Preparation Example One
100 g of PVDF homopolymer (Solvay 1015, Mw; 570, 000) was charged into a flask containing 400 g of dimethyl acetamide (DAEJUNG) as a solvent, and the mixture was stirred at 200 rpm for 2 hours while keeping the temperature at 65 ° C., A polymer solution was prepared. A part of the prepared solution was poured onto a sus- pension substrate at room temperature, and then formed into a film having a thickness of 200 μm using a casting knife. The film was then washed in flowing tap water at room temperature for 24 hours. Thereafter, the membrane was dried in an oven at 80 ° C for 24 hours to prepare a porous PVDF membrane. The PVDF membrane thus prepared had an average zeta potential of -6.56 ± 0.24 mV at pH 7.
Preparation Example 2
100 g of PES (Polyethersulfone) homopolymer (Solvay veradel, Mw; 300,000) was charged into a flask containing 400 g of dimethylacetamide (DAEJUNG), and the mixture was stirred at rpm 200 for 2 hours And then a uniform polymer solution was prepared. A part of the prepared solution was poured onto a sus- pension substrate at room temperature, and then formed into a film having a thickness of 200 μm using a casting knife. The film was then washed in flowing tap water at room temperature for 24 hours. Thereafter, the resultant was dried in an oven at 80 ° C for 24 hours to prepare a porous PES membrane. The PES separator thus prepared had an average zeta potential of -13.64 ± 0.93 mV at pH 7.
Example One
The entire polyvinylidene difluoride separator of Preparation Example 1 was fed to one side of the separator by the DEAD-END method at a room temperature under a constant pressure of 2.0 atm, and the concentration and flow rate of the filtrate were measured in unit area and unit time And the humic acid removal rate and permeability were measured. At this time, an electrode was connected to the separation membrane according to the electric field application method described in the following Experimental Example, and a voltage of 0 V / cm was applied for 150 minutes. The measurement results are shown in Table 1.
Example 2
The humic acid removal rate and permeability were measured in the same manner as in Example 1.
However, a voltage of 6 V / cm was applied to the separator for 150 minutes, and the measurement results are shown in Table 1.
Example 3
The humic acid removal rate and permeability were measured in the same manner as in Example 1.
A voltage of 12 V / cm was applied to the separator for 150 minutes, and the measurement results are shown in Table 1.
Example 4
The polyester sulfon membrane of Preparation Example 2 was fed to one side of the separator by the DEAD-END method at a room temperature under a total of 2.0 atmospheres of the raw water, and the amount of permeated water was measured. The permeability was calculated in terms of the permeation amount per unit pressure. The concentration of humic acid in the filtrate was measured using an ultraviolet spectrophotometer, and then the removal rate was calculated by Equation (1). In this case, the electrodes were connected to the separator by applying the electric field described in the following Experimental Example, and a voltage of 0 V / cm was applied for 150 minutes. The measurement results are shown in Table 2
Example 5
The permeability and the removal rate were measured in the same manner as in Example 4.
However, a voltage of 6 V / cm was applied to the separator for 150 minutes, and the measurement results are shown in Table 2.
Example 6
The permeability and the removal rate were measured in the same manner as in Example 4.
However, a voltage of 12 V / cm was applied to the separator for 150 minutes, and the measurement results are shown in Table 2.
Experimental Example One
1. Application of electric field
The surface charge of the membrane was first immersed in a 30% aqueous ethanol solution for 10 minutes, and then immersed in distilled water for 30 minutes. Thereafter, the film was taken out and the specimen was burnt in a permeable cell of a sus material, and a + ve-electrode battery (6V, VECCELL) under a constant voltage was connected to each of the transparent cell and the lower cell.
2. Pitcher Measure
A 1% by weight aqueous solution of humic acid (daejung) at room temperature was pressurized at a constant pressure of 2 atm and a voltage was applied to the permeated cell with the electrodes, and then the amount of water filtered for 150 minutes in the dead- And converted into the amount L of water to be filtered per unit area (m 2 ), unit time (hr) and unit pressure (bar).
3. Measurement of removal rate
50 l of an aqueous solution containing 1% by weight of humic acid was filtered through the filter material of Example 1 or Comparative Example 1, and then the humic acid aqueous solution and the filtrate before filtration were subjected to spectrophotometry at 283 nm using a UV spectrophotometer (Varian, Cary 100) And the removal rate was calculated using the following equation (1). The results are shown in Table 2 below.
[Equation 1]
Removal rate = (initial humic acid concentration - humic acid concentration in the filtrate) / initial humic acid concentration x 100
4. Zeta-potential Measure
For the measurement of Zeta potential (Anton Paar KG, Graz, Austria), a 1 cm x 2 cm membrane sample was inserted into a holder and the electrical conductivity was adjusted to 127.8 mS / m using a KCl solution at 20 ° C. After the pH was adjusted to 4.8 using 0.1 M HCl and 0.1 M NaOH aqueous solution, the Zeta potential of the membrane was measured.
(V / cm)
(LMH)
(%)
Referring to Table 1, when a voltage of 0 V / cm was applied to the polyvinylidene fluoride separator of Preparation Example 1 as in Example 1, the humic acid removal rate was 51.63%. As in Example 2, When a voltage of 6 V / cm was applied to the vinylidene fluoride separator, the humic acid removal rate was 67.47%. When a voltage of 12 V / cm was applied to the polyvinylidene fluoride separator of Preparation Example 1 as in Example 3, % Humic acid removal rate.
In other words, when a voltage of 6 V / cm was applied to the polyvinylidene difluoride separator of Preparation Example 1, the humic acid removal rate was increased by 30.86% as compared with the case where no voltage was applied, and the polyvinylidene difluoride separator of Preparation Example 1 When the voltage of V / cm was applied, the humic acid removal rate was increased by 40.03% as compared to when no voltage was applied.
As a result, it was found that when an electric field was generated by applying a voltage to the polyvinylidene fluoride separation membrane of Preparation Example 1, the humic acid removal rate was increased
(V / cm)
(LMH)
(%)
Referring to Table 2, when a voltage of 0 V / cm was applied to the polyester sulfonate separation membrane of Preparation Example 2 as in Example 4, the permeation rate of 380 LMH was exhibited and the permeation rate of 6 V / cm The permeability of 413 LMH was shown when a voltage was applied and the permeability of 445 LMH was shown when a voltage of 12 V / cm was applied as in Example 6. [
In other words, when the voltage of 6 V / cm was applied to the polyester sulfonate membrane of preparation example 2, the permeability was increased by 11.3% and the permeability was higher than that when the voltage of 12 V / cm was applied, Which is an increase of 17%.
As a result, when the voltage of 4 to 8 V / cm was applied to the polyester sulfonate membrane of preparation example 2, it was found that the highest permeability was shown.
Claims (12)
Wherein the phase separation method is a heat induction phase separation method or a non-pulverization induction phase separation method.
Wherein the separation membrane has a dielectric constant of 1? 10? At 1 MHz.
Wherein the zeta potential of the separation membrane is 0 mV to -20 mV at a pH of 7.
Wherein the separation membrane is modified with a positive electric charge by an applied electric field.
Wherein the strength of the electric field applied to the separation membrane is 4 to 14 V / cm.
Wherein the separation membrane increases the removal rate of natural organic matter (NOM) by 30% or more without degrading the permeability through surface modification by an electric field.
Wherein the natural organic material comprises at least one of humic acid and fulvic acid. 2. The method of claim 1, wherein the natural organic material comprises at least one of humic acid and fulvic acid.
Wherein the separation membrane increases the permeability by at least 10% through surface modification by an electric field.
Wherein the electric field is applied to the separation membrane continuously or discontinuously during the water treatment.
The separation membrane is used for at least one of a reverse osmosis (RO) membrane, a nanofilteration (NF) membrane, a microfilter (MF) membrane, and an ultrafilter (UF) A process for producing a separation membrane for water treatment by electric field modification.
Wherein the separation membrane is formed with an electric field to control at least one of water permeability and natural organic material removal rate.
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