KR101985629B1 - Ion exchange absorbent having high selective adsorption ability for nitrate ion and method for preparing the same - Google Patents

Abstract

The present invention relates to an ion exchange adsorbent excellent in selective adsorption performance to nitrate ions and a method for manufacturing the same. More particularly, the present invention relates to: the ion exchange adsorbent comprising a porous silica support and an alkyl group having four or more carbon atoms, and also comprising quaternary ammonium functionalized by binding to the porous silica support; and the method for manufacturing the same.

Description

TECHNICAL FIELD [0001] The present invention relates to an ion exchange sorbent having excellent selective adsorption performance against nitrate ions and a method for preparing the same.

The present invention relates to an ion-exchange adsorbent and a method for producing the same, and more particularly, to an ion-exchange adsorbent having an excellent selective adsorption performance for nitrate ion and a method for producing the same.

Recently, the amount of nitrate ions in sewage and wastewater has been increasing steadily.

Nitrate ion has low selectivity in the environment, that is, it is difficult to remove compared to other anions, but it is a substance applied to cultivated land all over the world as a main raw material of plant growth and nitrogen fertilizer. The amount of nitrate ions exposed to natural materials by fertilizers, septic tanks, livestock manure, etc. is steadily increasing, and this is becoming a major factor of eutrophication. In addition, nitrate ions can cause cyanosis (methemoglobinemia) in infants if they are exposed to the human body, and may cause stomach cancer in adults. In particular, industrial wastewater discharged from plating, powder manufacturing, and petrochemical industries contain nitrate ions in a large amount. It is known that groundwater contaminated with nitrate ions is almost impossible to recover naturally. have.

Therefore, in order to efficiently remove nitrate ions, there is a strong demand for an adsorbent or a removal method excellent in selectivity to nitrate ions.

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide an ion exchange sorbent which improves selective adsorption performance to nitrate ions by binding and functionalizing quaternary ammonium containing a relatively long alkyl group to a porous silica support, And a manufacturing method thereof.

According to an aspect of the present invention, there is provided a porous silica support comprising: a porous silica support; And an alkyl group having 4 or more carbon atoms, and quaternary ammonium functionalized by binding to the porous silica support.

At this time, the porous silica support may be any one selected from the group consisting of SBA-1, SBA-15, SBA-16, KIT-6, MCM-41, MCM-48, mesocellular silicaous foam Or a mixture of two or more of them.

The quaternary ammonium may include an alkyl group having 4 to 18 carbon atoms.

The quaternary ammonium is preferably selected from the group consisting of dimethylbutyl [3- (trimethoxysilyl) propyl] ammonium chloride, DMBAC, dimethyloctyl [3- (trimethoxysilyl) Propyl] ammonium chloride), dimethyldodecyl [3- (trimethoxysilyl) propyl] ammonium chloride, or dimethyloctyl [3- (trimethoxysilyl) propyl] Decyl [3- (trimethoxysilyl) propyl] ammonium chloride).

According to another aspect of the present invention, there is provided a method for preparing a porous silica support, comprising: (S1) reacting a porous silica support and quaternary ammonium containing an alkyl group having 4 or more carbon atoms in an organic solvent; (S2) adding deionized water to the resultant product of step (S1) and then reacting the resulting product to bind the quaternary ammonium to the porous silica support; And (S3) washing the resultant of the step (S2). The above-described method for producing an ion-exchange adsorbent of the present invention is provided.

At this time, the porous silica support in step (S1) may be activated with an acidic solution, washed with distilled water, and then dried.

The quaternary ammonium in step (S1) may be a reaction product of a silane compound and an amine compound containing an alkyl group having 4 or more carbon atoms.

The step (S3) may include washing the resultant of step (S2) with toluene and distilled water, followed by washing with a basic solution.

According to the present invention, the physico-chemical resistance of the ion-exchange adsorbent can be further improved by using a porous silica support instead of the conventionally widely used resin support.

(HCO ₃ ^- ), phosphoric acid ion (PO ₄ ^3- ), sulfate ion (SO ₄ ^2- ) and sulfuric acid ion (SO ₄ ^2- ) are formed in the water by binding and functionalization of quaternary ammonium containing a relatively long alkyl group to the porous silica support. It is possible to further improve selective adsorption performance for nitrate ions (NO ₃ ^- ) mixed with chlorine ions (Cl ^- ) and the like.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and together with the description of the invention serve to further the understanding of the technical idea of the invention, It should not be construed as limited.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram for synthesis of an ion exchange adsorbent according to an embodiment of the present invention and a comparative example. FIG.
2 is a FESEM and digital image of an ion exchange sorbent according to an embodiment and a comparative example of the present invention.
3 is a graph showing FTIR spectra of the ion-exchange adsorbent according to Examples and Comparative Examples of the present invention.
4 is a graph showing the XPS spectrum of an ion-exchange adsorbent according to Examples and Comparative Examples of the present invention.
FIG. 5 is a graph showing the results of batch experiments in which nitrate ions are removed by an ion exchange sorbent according to Examples and Comparative Examples of the present invention, according to various conditions. FIG.
6 is a graph showing the effect of a competitive anion on the removal of nitrate ions by the ion exchange adsorbent according to Examples and Comparative Examples of the present invention.
FIG. 7 is a graph showing the relative reduction rates of nitrate ion adsorption by an ion-exchange adsorbent according to Examples and Comparative Examples of the present invention in the presence of competitive anions.

Hereinafter, the present invention will be described in detail with reference to the drawings. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

Therefore, the embodiments described in the present specification and the constitutions described in the drawings are merely the most preferred embodiments of the present invention, and are not intended to represent all of the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

An ion exchange sorbent according to one aspect of the present invention comprises a porous silica support; And quaternary ammonium functionalized by binding to the porous silica support, wherein the quaternary ammonium includes an alkyl group having 4 or more carbon atoms.

The term " bond " may include physical, chemical attachment, linkage, and the like.

Conventionally, strongly basic resins such as styrene polymers have been widely used as supports for ion exchange adsorbents. However, in the present invention, the physico-chemical resistance of the ion exchange adsorbent can be further improved by using a porous silica support instead of the resin support which has been conventionally used commercially.

(HCO ₃ ^- ), phosphoric acid ion (PO ₄ ^3- ), sulfate ion (SO ₄ ^2- ) and sulfuric acid ion (SO ₄ ^2- ) are added to the porous silica support by the function of quaternary ammonium containing a relatively long alkyl group. It is possible to further improve selective adsorption performance for nitrate ions (NO ₃ ^- ) mixed with chlorine ions (Cl ^- ) and the like.

SBA-1, SBA-15, SBA-16, SBA-4, SBA-6, and SBA-16 may be used as the support. KIT-6, MCM-41, MCM-48, mesocellular siliceous foam (MCF) and silica gel, or a mixture of two or more thereof, preferably SBA-15 or silica gel have.

The quaternary ammonium of the present invention has a structure in which four hydrocarbon groups are bonded to a nitrogen atom and is functionalized by binding to the porous silica support. At least one of the four hydrocarbon groups is an alkyl group having 4 or more carbon atoms .

At this time, the quaternary ammonium may preferably include an alkyl group having 4 to 18 carbon atoms.

More specifically, quaternary ammonium containing an alkenyl group having 4 carbon atoms can be dimethylbutyl [3- (trimethoxysilyl) propyl] ammonium chloride, DMBAC) , Quaternary ammonium containing an alkyl group having 8 carbon atoms may be dimethyloctyl [3- (trimethoxysilyl) propyl] ammonium chloride, and may have a carbon number of 12 The quaternary ammonium containing an alkyl group may be dimethyldodecyl [3- (trimethoxysilyl) propyl] ammonium chloride, and may contain an alkyl group having 18 carbon atoms The quaternary ammonium may be, but is not limited to, dimethyloctadecyl [3- (trimethoxysilyl) propyl] ammonium chloride.

Meanwhile, a method for producing an ion-exchange adsorbent according to another aspect of the present invention is as follows.

First, the porous silica support and quaternary ammonium containing an alkyl group having 4 or more carbon atoms are reacted in an organic solvent (Step S1).

The porous silica support may be activated by an acidic solution, washed with distilled water, and then dried. Preferably, porous silica is added to a reaction flask, and the solution is refluxed for 8 hours with an aqueous solution of HCl to activate , And washed with distilled water and dried.

The quaternary ammonium may be a reaction product of a silane compound and an amine compound containing an alkyl group having 4 or more carbon atoms.

More specifically, by reacting (3-chloropropyl) trimethoxysilane with N, N-dimethylbutylamine, 4 (4-methylphenyl) (3-chloropropyl) trimethoxysilane and N, N-dimethyloctylamine (N, N-dimethylaniline) can be produced, (trimethoxysilyl) propyl] ammonium chloride, which is a quaternary ammonium containing an alkyl group having 8 carbon atoms, may be prepared by reacting (3-chloropropyl) trimethoxysilane with dimethyloctylamine N, N-dimethyldodecylamine to obtain dimethyldodecyl [3- (trimethoxysilyl) propyl] ammonium chloride, which is quaternary ammonium containing an alkyl group having a carbon number of 12 But is not limited to these preparations.

The organic solvent used in the step (S1) is not particularly limited, and may include any organic solvent within the range not impairing the object of the present invention, but preferably includes toluene.

Next, deionized water is added to the resultant product of step (S1) and then reacted to bond the quaternary ammonium to the porous silica support (step S2).

At this time, the deionized water plays a role to initiate the adhesion reaction by hydrolysis of the quaternary ammonium on the surface of the porous silica support, and a relatively small amount is added to the porous silica support and the quaternary ammonium .

Then, the result of step S2 is washed (step S3).

At this time, the result of step (S2) may be washed with toluene and distilled water until the pH of the solution becomes neutral, and then washed with NaCl solution or the like.

Subsequently, the resultant product is separated from the oven, dried, and then fragmented using a mortar and a pestle to complete the preparation of the ion-exchange adsorbent.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Preparation of ion exchange adsorbents

All chemicals used in the synthesis of ion exchange sorbents were purchased from Sigma Aldrich (St. Louis, Mo.) unless otherwise noted. Figure 1 schematically illustrates the synthesis process in which quaternary ammonium is functionalized by binding to SBA-15, a porous silica support.

(1) Comparative Example 1: Preparation of SBA-15 (C1Q-SBA-15) functionalized with trimethyl quaternary ammonium

First, 1 g of SBA-15 and 0.03 mol of trimethyl [3- (trimethoxysilyl) propyl] ammonium chloride, 50% in methanol, Tokyo Chemical Industry, Tokyo, Was added to 150 mL of toluene (99.5%, Daejung, Siheung, Republic of Korea) and stirred for 1 hour.

Then, 0.5 mL of deionized water as a hydrolysis attachment reaction initiator was added to the stirring mixture, and the mixture was refluxed at 100 DEG C for 48 hours.

The resulting slurry was then filtered and washed thoroughly with toluene and deionized water until the pH of the solution was neutral.

The slurry was then added to 1 L of 0.1 M NaCl solution and stirred for 6 hours.

Subsequently, the NaCl-treated slurry was separated from the oven (ThermoStable SOF-W 155, Daihan Scientific, Seoul, Korea) overnight at 65 ° C and dried.

Finally, C1Q-SBA-15 was obtained by fragmentation using a mortar and pestle.

(2) Example 1: Preparation of SBA-15 (C4Q-SBA-15) functionalized with dimethylbutyl quaternary ammonium

First, 0.1 mol of (3-chloropropyl) trimethoxysilane (≥97%) and 0.1 mol of N, N-dimethylbutylamine (99%) were reacted at 85 ° C. Dimethylbutyl [3- (trimethoxysilyl) propyl] ammonium chloride (DMBAC) was synthesized by reacting with dimethylbutyl [3- (trimethoxysilyl) propyl] ammonium chloride for 48 hours.

In 300 mL of toluene, the DMBAC was mixed with 6 g of SBA-15 and the mixture was stirred for 1 hour.

Then, 1 mL of deionized water was added to the stirring mixture as a hydrolysis attachment reaction initiator, and the mixture was refluxed at 100 DEG C for 48 hours.

The slurry was then added to 1 L of 0.1 M NaCl solution and stirred for 6 hours.

Subsequently, the NaCl-treated slurry was separated and dried in an oven (ThermoStable SOF-W 155, Daihan Scientific, Seoul, Korea) overnight at 65 ° C.

(3) Example 2: Preparation of SBA-15 (C8Q-SBA-15) functionalized with dimethyloctyl quaternary ammonium

N-dimethyloctylamine (95%) was used instead of 0.1 mol of N, N-dimethylbutylamine (99%) to obtain dimethyloctyl [3 C8Q-SBA-15 was prepared in the same manner as in Example 1, except that dimethyloctyl [3- (trimethoxysilyl) propyl] ammonium chloride was prepared.

(4) Example 3: Preparation of SBA-15 (C12Q-SBA-15) functionalized with dimethyldodecyl quaternary ammonium

(N, N-dimethyldodecylamine, 97%) instead of 0.1 mol of N, N-dimethylbutylamine (99% C12Q-SBA-15 was prepared in the same manner as in Example 1, except that the dimethyldodecyl [3- (trimethoxysilyl) propyl] ammonium chloride was used instead of 3- (trimethoxysilyl) propyl] ammonium chloride .

(5) Example 4: Preparation of SBA-15 (C18Q-SBA-15) functionalized with dimethyloctadecyl quaternary ammonium

Dimethyloctadecyl [3- (trimethoxysilyl) propyl] ammonium chloride instead of trimethyl [3- (trimethoxysilyl) propyl] C18Q-SBA-15 was prepared in the same manner as in Comparative Example 1, except that trimethoxysilyl) propyl] ammonium chloride (42% in methanol) was used.

Evaluation of surface morphology and element composition of ion exchange sorbent

The ion exchange sorbents (C1Q-, C4Q-, C8Q-, C12Q-, C18Q-SBA-15) prepared above were characterized using several techniques. The surface morphology of the adsorbent was analyzed by field emission scanning electron microscopy (FESEM, Supra 55VP, Carl Zeiss, Oberkochen, Germany).

2 is a FESEM and digital image of the ion exchange sorbent (C1Q-, C4Q-, C8Q-, C12Q-, C18Q-SBA-15) prepared above. Referring to FIG. 2, C1Q-, C12Q- and C18Q-SBA-15 are shown to be white particles with respect to the digital image, whereas C4Q- and C8Q-SBA-15 are light yellow particles. And, with respect to the FESEM image, it shows that quaternary ammonium was successfully grafted to the surface of SBA-15 particles during the functionalization process.

Fourier-transform infrared (FTIR) spectroscopy (Nicolet 6700, Thermo Fisher Scientific, Waltham, Mass., USA) was used to analyze the effect of quaternary ammonium on the adsorbent.

FIG. 3 is a graph showing the FTIR spectra of the ion exchange sorbents (C1Q-, C4Q-, C8Q-, C12Q-, C18Q-SBA-15) prepared above.

The peak at 805.5 and 1049.5 cm ^-1 in the SBA-15 spectrum is due to the stretching of the siloxane (Si-O-Si). Peaks at 1041-1055 cm ^-1 and 797-806 cm ^-1 in the spectra of C1Q-, C4Q-, C8Q-, C12Q- and C18Q-SBA-15 are also due to the stretching of the siloxane (Si-O-Si). After SBA-15 functionalization with quaternary ammonium, several new peaks appeared as evidence of successful quaternization. In the case of C1Q- and C4Q-SBA-15, peaks at 1481.4 and 1483.4 cm ^-1 are assigned to CH ₂ asymmetric bending to provide evidence of quaternary ammonium functionality. As the alkyl length increased, new peaks were observed at 1466.5 (C8Q-SBA-15), 1466.7 (C12Q-SBA-15) and 1466.6 cm- ¹ (C18Q-SBA-15). These peaks were assigned to CH ₂ or CH ₃ asymmetric bending, which is considered to be a contribution of methylene groups in the alkyl group. In the spectrum of C1Q-SBA-15, the CH stretching vibration of the alkyl group was not observed, and the CH ₃ asymmetric stretching was newly observed at 2961.8 cm ^-1 . As the length of the alkyl group increased, new peaks at 2922-2944 cm ^-1 and 2852-2856 cm ^-1 appeared in the spectra of C8Q-, C12Q- and C18Q-SBA-15. These peaks are due to the CH ₂ asymmetric stretching and the CH ₂ symmetric stretching, which is enhanced by the increase of the alkyl group length and the methylene group portion.

X-ray photoelectron spectroscopy (XPS, Sigma Probe, Kratos Analytical, Shimadzu, Japan) using Al Kα line (hv = 1253.6 eV) was used to analyze chemical bonds and components of the adsorbent.

4 is a graph showing XPS spectra of the ion exchange sorbents (C1Q-, C4Q-, C8Q-, C12Q-, C18Q-SBA-15) prepared above.

Referring to FIG. 4, in a wide scan of C1Q- to C18Q-SBA-15, the photoelectron peaks at binding energies of 103 and 153 eV are due to Si 2p and Si 2s orbital, respectively. Also, peaks of 198, 284, 400 and 532 eV were assigned to Cl 2p, C 1s, N 1s and O 1s orbits, respectively. The peaks of 103 eV (Si 2p) and 532 eV (O 1s) are characteristic peaks of SBA-15. In a high resolution scan of C 1s, the peaks had similar binding energy and full width at half maximum. The C 1s peak can be deconvoluted at 284.8 eV (C-C bond) and 286.0 eV (C-N bond), which is due to quaternary ammonium functionalization.

Evaluation of nitrate removal characteristics of ion exchange sorbents

Experiments were carried out to investigate the influence of the pH of the initial solution on nitrate removal by the ion exchange sorbents (C1Q-, C4Q-, C8Q-, C12Q-, C18Q-SBA-15) 5a.

Referring to FIG. 5A, in the case of C1Q-SBA-15, the nitrate removal capacity at pH 2 was 8.53 mg / g. As the pH was increased to 4, the removal capacity increased rapidly to 28.28 mg / g. When the pH was increased from 4 to 10, the removal capacity decreased to 15.38 mg / g. And at pH 12, the removal capacity was very low (3.73 mg / g). Samples of C4Q-SBA-15, which had the lowest removal capacity of 60.47 mg / g at pH 4 and 2.55 mg / g at pH 12, were similar to those of C1Q-SBA-15. In the case of C8Q-SBA-15, the highest nitrate removal was at pH 4 (57.59 mg / g) and the lowest nitrate removal was at pH 12 (2.36 mg / g). In the case of C12Q-SBA-15, the highest removal rate was pH 6 (48.30 mg / g) and the lowest nitrate removal rate was at pH 12 (3.73 mg / g). Finally, in the case of C18Q-SBA-15, the highest removal capacity was found at pH 4 (36.84 mg / g) and the lowest value at pH 12 (2.55 mg / g).

The experimental results show that the ability to remove nitrate by functionalized SBA-15 at pH 2 is much lower than the ability to remove functionalized SBA-15 at pH 4. This tendency is explained by the fact that the free movement of nitrate to the adsorption site can be limited at high acidic pH. And, as a result of the above experiment, it is shown that nitrate removal by functionalized SBA-15 is negligible at pH 12. This tendency is a competitive anion for the adsorption site, which is related to the presence of a large number of OH ^- ions. Overall, the functionalized SBA-15 was able to effectively remove nitrate in the range of pH 4 to 10. While the nitrate was removed by functionalized SBA-15, the nitrate ion in the aqueous solution was exchanged with the chloride ion (Cl ^- ) attached to the adsorption site of the quaternary ammonium group.

On the other hand, kinetic adsorption data along with kinetic model analysis is shown in FIG. 5B. In the case of C1Q- and C4Q-SBA-15, the adsorption of nitrate to the adsorbent reached equilibrium at a very rapid rate within 10 min. In the case of C8Q-, C12Q- and C18Q-SBA-15, the adsorption of nitrate reached equilibrium within 30 min. These results show that the nitrate removal rate is affected by the length of the functionalized SBA-15 alkyl group.

Evaluation of Effect of Alkyl Length on Nitrate Selectivity of Ion Exchanger

Experiments were conducted on the selective removal of nitrate by the ion exchange sorbent (C1Q-, C4Q-, C8Q-, C12Q-, C18Q-SBA-15) prepared above in the presence of competitive anion, Is shown in Fig.

In C1Q-SBA-15 (FIG. 6A), the effect of Cl ^- on nitrate removal was negligible, while the effect of HCO ₃ ^- , HPO ₄ ^2- and SO ₄ ^2- was notable. As the ratio of [Cl -] / [NO3 -] increased from 0 to 4, the nitrate removal capacity decreased from 20.11 to 12.05 mg / g, but HCO ₃ ^- , HPO ₄ ^2- or SO ₄ ^2- The ability to remove nitrate was drastically reduced (almost converging to zero).

C4Q-SBA-15 (FIG. 6B) and C8Q-SBA-15 (FIG. 6C) showed similar trends to C1Q-SBA-15. However, the effect of SO ₄ ^2- on nitrate removal was less than that of HCO ₃ ^- and HPO ₄ ^3- .

In the case of C12Q-SBA-15 (Fig. 6d), the effect of HCO ₃ ^- and HPO ₄ ^3- on nitrate removal was much less than in C4Q- and C8Q-SBA-15 cases.

C18Q-SBA-15 (FIG. 6E) showed a similar tendency to C12Q-SBA-15.

That is, except for C1Q-SBA-15 (Comparative Example 1), the remaining examples show that even in the presence of HCO ₃ ^- , HPO ₄ ^2- or SO ₄ ^2- , the removal capacity of nitrate ions does not decrease to converge to 0 .

On the other hand, the relative reduction rates of nitrate adsorption of SBA-15 functionalized at [competing Anion] / [NO ₃ ^- ] = 1 are shown in FIG.

For [Cl ^- ] / [NO ₃ ^- ], all functionalized SBA-15 exhibits a very low relative reduction of 0 to 5.5%.

As the alkyl length increased from C1Q- to C18Q-, the relative reduction rate of [HCO ₃ ^- ] / [NO ₃ ^- ] decreased from 92.5 to 36.6%, and the relative reduction rate of [HPO ₄ ^2- ] / [NO ₃ ^- ] The relative reduction rate decreased from 98.8 to 41.1%. In addition, the relative reduction rate of [SO ₄ ^2- ] / [NO ₃ ^- ] tended to decrease from 73.9 to 9.8% except for C12Q-SBA-15.

As a result of these experiments, it was confirmed that, in the case of having a relatively long alkyl group length, it is more effective in selective nitrate removal than in the case of having a relatively short alkyl group length.

In addition, it was confirmed that the effect of competitive anions on nitrate removal of quaternary ammonium-functionalized SBA-15 decreased in the order of HPO ₄ ^2- > HCO ₃ ^- > SO ₄ ^2- > Cl ^- .

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (8)

delete delete delete delete A process for preparing an ion exchange adsorbent comprising a porous silica support and an alkyl group having 4 or more carbon atoms and quaternary ammonium functionalized by binding to the porous silica support,
(S1) reacting a porous silica support and quaternary ammonium containing an alkyl group having 4 or more carbon atoms in an organic solvent;
(S2) adding deionized water to the resultant product of step (S1) and then reacting the resulting product to bind the quaternary ammonium to the porous silica support; And
(S3) washing the resultant of step (S2). 6. The method of claim 5,
The porous silica support of step (S1)
Activated with an acidic solution, washed with distilled water, and then dried. 6. The method of claim 5,
The quaternary ammonium in step (S1)
Wherein the reaction product is a reaction product of a silane-based compound and an amine-based compound containing an alkyl group having 4 or more carbon atoms. 6. The method of claim 5,
The step (S3)
Washing the resultant of step (S2) with toluene and distilled water, and then washing the resultant with a basic solution.

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