KR101559480B1 - Recyclable Method For Removing Toxic Anions - Google Patents

Abstract

The present invention relates to a method for removing perchlorate (ClO ₄ ^- ) and nitrate (NO ₃ ^- ), which are poisonous anions in wastewater, through a biocompatible material having ion exchange characteristics and catalytic properties and being continuously reusable. More particularly, the present invention relates to a method for removing toxic anions by adsorbing toxic anions and decomposing anions adsorbed through gaseous hydrogen gas by synthesizing an ion exchange / catalyst material with a carbon material carrying metal particles.
Since the synthesized material according to the present invention maximizes the cationic property of the surface by substituting nitrogen in the skeleton or adsorbing the cationic surfactant to the existing adsorbent carbon, Adsorption and selectivity were greatly enhanced. In addition, metal particles having a reducing function were formed on the adsorbent material, and the decomposition of the toxic anion exchanged in the liquid phase was made possible through the gas phase hydrogen under the dry and wet conditions.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing toxic anions,

The present invention relates to a method for removing perchlorate (ClO ₄ ^- ) and nitrate (NO ₃ ^- ), which are poisonous anions in wastewater, and more particularly to a method for removing perchlorate The present invention relates to a process capable of circulating a carbon skeleton by replacing nitrogen or adsorbing a cationic surfactant and completely dissolving toxic anions exchanged in a liquid phase through hydrogen in a gaseous phase.

For, ClO ₄ through a chemical reduction reaction electronic waste perchlorate ion of a number of toxic anion dissolved or the like (ClO ₄ ^{- -)} and nitrate ion (NO ₃₎ ^- a, NO ₃ ^{- -} is Cl nontoxic is N ₂ are ions that can be eco - friendly. Nonetheless, physical removal by adsorption or ion exchange is mainly used for the removal of these ions because chemical reduction reactions are only possible under unconventional conditions of high pressure / temperature which can not be used for actual water purification. However, there is a problem that the physical removal method ultimately requires post-treatment of the adsorbent material in which these toxic ions are concentrated. In addition, current microbial degradation processes use such chemical reduction. These processes are very sensitive to ion concentration, pH, etc., and require post-treatment processes that are difficult to control the operation and have low economic efficiency in removing biomass and suspended matters . Therefore, it is important to develop a catalytic process for reducing these anions in a more economical way while solving these problems.

Porous carbon (specific surface area: 50 m ² / g to 4000 m ² / g) was used as the ion exchange material in the case of a novel composite material in which the ion exchange material and the catalyst acting material used in the present invention were combined. It is an ion exchange material widely used with ion exchange resins in physical removal methods. However, despite its low cost and large surface area, the adsorbing power to perchlorate ion is too small to be used in actual process due to the negatively charged surface. Thus, adsorption of cationic surfactants to carbon surfaces or replacement of nitrogen in carbon skeletons at high temperatures enhanced adsorption capacity to perchlorate ions (R. Parette et al ., Water Res . 39: 4020, 2005; W. Chen et al ., Carbon . 43: 573, 2005).

Ion exchange resins have higher adsorption and selectivity than carbon, but they are expensive and have problems in treating solutions containing anions dissolved during regeneration. To overcome this, B. Gu and colleagues have reported that concentrated FeCl ₃ -HCl solution can effectively remove perchlorate ions from ion exchange resins (B. Gu et al ., Environ . Sci . Technol . 35: 3363,2001). At 170 ℃, the regeneration solution is reduced to Cl ^- ion using Fe (II) as a reducing agent (B. Guetal ., Environ . Sci. Technol . 37: 2291, 2003). The FeCl ₃ -HCl solution and FeCl ₂ used as regenerant and reducing materials are highly corrosive and are not economical or environmentally friendly. Generally, the removal method by physical adsorption is an economical and efficient method among the various removal methods, when the treatment-related limit of perchlorate-saturated adsorbent is solved.

The removal of perchlorate ions by microorganisms using a chemical method such as enzymatic reduction is a method that can completely decompose perchlorate ions into Cl ^- ions in the presence of a reducing agent. However, it is known that the reduction method using a noble metal or an electrode can not be performed because the reaction is very slow under general conditions (GG Lang et al ., J. Electro . Anal . Chem . 552: 197, 2003; Rusanova, M. Y et al., Electro . Chem . Acta . 51: 3097,2006). CP Huang experimented with about 78 heterogeneous catalysts, but all showed very minor reactions (DM Wang et al., Separation and Purification Technology. 60:14, 2008).

Abu-Omar and his colleagues observed that Re-based homogeneous catalysts showed high reactivity in the presence of reducing agents, organic sulfides and H ₃ PO ₂ (Abu-Omar et al ., Inorg . Chem . 34: 6239, 1995). However, homogeneous systems containing water-soluble phosphorus or sulfur-containing reducing agents despite their high reactivity are not suitable for water purification processes. Recently, Re catalyst carrying Pd using hydrogen as a reducing agent has been developed. For this catalyst system, the reaction rate represents the best in terms of the acid reduced the efficiency of the appropriate side or catalyst, there is a limit (KD Hurley et al, Environ Sci Technol 41:.... 2044, 2007). Due to the very low solubility of hydrogen in water, the concentration of very little perchlorate, and the ambiguous reaction temperature, a heterogeneous catalyst system using hydrogen gas as a reducing agent can not but exhibit low catalytic reactivity. Therefore, there is a constant need to develop a process that can completely remove toxic anions with high catalytic reactivity through economical and efficient materials that can be used in actual water purification processes and processes using the materials.

Thus, examples sought results, which form the metal clusters having a reduction catalyst function on the carbon surface, and then, in the gas phase H ₂ to the inventors more economical, environmentally friendly, yet the removal of toxic anions from the continuous process possible using (ClO ₄ ^- ) and nitrate (NO ₃ ^- ) ions in the presence of a reducing agent.

An object of the present invention is to provide a method for removing toxic anions capable of circulating through the reduction of adsorbed perchlorate (ClO ₄ ^- ) or nitrate (NO ₃ ^- ) ions in the presence of gaseous H ₂ using metal- .

In order to accomplish the above object, the present invention provides a method for manufacturing a porous carbon nanotube, comprising the steps of: (a) adsorbing a toxic anion using a porous carbon on which a metal is supported; And (b) reducing the anion exchange capacity of the porous carbon bearing the metal by using a reducing agent, wherein the anion exchange ability of the porous carbon is saturated.

The present invention also relates to a method for producing a metal oxide nanoparticle, comprising the steps of: (a) adsorbing a toxic anion using a metal-supported porous carbon; (b) reducing the anion exchange capacity of the porous carbon supported on the metal by using a reducing agent; And (c) when the metal-bearing porous carbon is reduced, repeating the steps (a) and (b) sequentially using the metal-supported porous carbon is performed, thereby providing a method for removing toxic anions capable of performing a circulation process .

In the method of removing perchlorate ion and nitrate ion which can be performed in the circulation process according to the present invention, the reaction rate can be maximized under the same temperature and pressure conditions by concentrating the toxic anion in the column before the catalytic reaction. When the anion is concentrated, The reaction rate increases proportionally to the concentration in the wastewater, which is thousands to tens of thousands times higher than the concentration in the wastewater. Compared to the conventional chemical decomposition methods (temperature, pressure, and pH) It is useful to remove toxic anion in actual water purification system because it can reduce energy and reductant consumption because it is necessary to adjust only the condition.

FIG. 1 schematically illustrates an adsorption-decomposition-adsorption circulation process of anions using the synthesized ion exchange / catalyst material.
Fig. 2 schematically shows a process in which carbon in which nitrogen is replaced by a skeleton adsorbs and regenerates toxic anions.
FIG. 3 compares the adsorption capacity and selectivity of perchlorate ion depending on the amount of Pd-loaded carbon and Pd-loaded carbon in the skeleton.
Fig. 4 compares the adsorption capacity and selectivity of perchlorate ions of Pd-supported carbon and Nd-substituted carbon and Pd-loaded carbon at an equilibrium concentration of perchlorate.
FIG. 5 shows the adsorption amount of perchlorate ion over time of carbon in which Pd is supported, nitrogen in the skeleton is substituted, and carbon in which Pd is supported.
FIG. 6 shows the degree of decomposition (a) of perchlorate ion depending on the temperature of carbon in which Pd is supported and nitrogen is substituted in the skeleton and carbon in which Pd is supported, and the degree of decomposition of perchlorate And the decomposition degree (b) of the ion.
FIG. 7 is a graph comparing the amounts of perchlorate ions adsorbed by Pd and nitrogen-bonded carbon and Pd-loaded carbon during the adsorption-decomposition-adsorption cycle.
8 compares the adsorption amounts of perchlorate ions according to the types of activated carbon (coconut-based activated carbon: GAC1, coal-based activated carbon: GAC2) and the types of cationic quaternary ammonium groups adsorbed.
9 compares the adsorption capacity and selectivity of perchlorate ions of Pd-supported and tordityl (hexadecyl) ammonium-adsorbed carbon and Pd-loaded carbon.
Fig. 10 compares the adsorption capacity and selectivity of perchlorate ion of Pd-supported and tordyl (hexadecyl) ammonium-adsorbed carbon and Pd-supported and nitrogen-substituted carbon.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is well known and commonly used in the art.

The present inventors have succeeded in synthesizing a new ion exchange / catalyst composite material in which metal particles are supported on porous carbon to combine ion exchange property and catalytic action property, and by attaching cationic functional groups to carbon to improve adsorption ability, And to develop an economical toxic anion removal process of decomposition-adsorption.

Accordingly, in one aspect, the present invention provides a method for producing a porous carbon nanotube, comprising: (a) adsorbing a toxic anion using a metal-supported porous carbon; And (b) reducing the anion exchange capacity of the porous carbon bearing the metal by using a reducing agent, when the anion exchange capacity of the porous carbon is saturated.

According to another aspect of the present invention, there is provided a method for producing a porous carbon nanotube, comprising the steps of: (a) adsorbing a toxic anion in an aqueous solution using a metal-supported porous carbon; (b) reducing the anion exchange capacity of the porous carbon supported on the metal by using a reducing agent; And (c) repeating the steps (a) and (b) sequentially using the metal-supported porous carbon when the porous carbon is reduced, .

More specifically, as shown in FIG. 1, a method for removing toxic anions using a composite material according to the present invention comprises synthesizing a composite material having ion exchange and catalytic properties to be used in a circulation process, and using the same as an adsorbent, Concentrate the toxic anions (ClO ₄ ^- , NO ₃ ^- ). In the present invention, the composite material means a porous carbon bearing metal or a material in which nitrogen is substituted for the porous carbon skeleton carrying the metal, or a carbon modified by adsorption of a cationic surfactant. The adsorption capacity and selectivity for toxic anions are improved by modifying the carbon by substituting nitrogen in the carbon skeleton for the carbon bearing the metal which acts to aid the decomposition of the toxic anion or by adsorbing the cationic surfactant. This is because the charge on the surface becomes positive and the affinity to the anion increases.

The metal may be selected from the group consisting of Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt and Au. By weight to 50% by weight of the porous carbon surface. The specific surface area of the porous carbon is 50 m ² / g to 4000 m ² / g, and when it is less than 50 m ² / g, there is a problem that the adsorption force is lowered.

When the anion exchange capacity in the composite material becomes saturated, it is separated in a water treatment process. Then, in the dry or wet condition of the composite material, a vapor phase (using H ₂ as a reducing agent) or a liquid phase formic acid as a reducing agent). At this time, in the reduction reaction, the metal particles in the composite material act as catalyst points. When the decomposition of the adsorbed toxic anions saturated with the composite material is completed, the recovered composite material is used again for the exchange of toxic anions. Based on the above processes, a circulation process of adsorption-decomposition-adsorption using a composite material can be performed.

The process may be performed in batch or column, and the reducing agent in step (b) may be hydrogen gas or formic acid.

The reduction in step (b) may be carried out stably at room temperature or at 20 to 250 ° C.

An important factor in the above processes is the thermal stability of the composite material at the decomposition temperature applied to the decomposition process of the toxic anions. Toxic anions (ClO ₄ ^- , NO ₃ ^- ), which can be applied to this process, are decomposed into ions (Cl ^- , N ₂ ) harmless to the environment in the presence of hydrogen gas acting as a reducing agent. Should be provided. Therefore, for use in the recycling process described above, the composite material, even at temperatures for toxic anion decomposition, must have thermal stability.

In the present invention, the porous carbon may be a material in which a part of the skeleton is substituted with nitrogen in an amount of 1 to 30 wt% by treatment with a nitrogen compound such as NH ₃ , urea, or melamine at a high temperature. It may also be a carbonaceous material modified in surface properties by adsorbing cationic surfactant materials on the carbon surface. The cationic surfactant materials that can be used in the present invention are preferably quaternary ammonium groups, and preferred examples thereof include trimethyl hexadecyl ammonium bromide, triethyl hexadecyl ammonium bromide, triethyl hexadecyl ammonium bromide, Tripropyl hexadecyl ammonium bromide, tributyl hexadecyl ammonium bromide, and the like, and preferably include but are not limited to the following.

designation rescue R1, R2, R3


General structure

Decyltrimethylammonium bromide
(Decyltrimethylammonium bromide, DTAB)

R ₁ = 1
R ₂ = 10 Cetyltrimethylammonium bromide
(Cetyltrimethylammonium bromide, CTAB)

R ₁ = 1
R ₂ = 16 Cetyltrimethylammonium chloride
(Cetyltrimethylammonium chloride, CTAC)

R ₁ = 1
R ₂ = 16
Tallow alkyltrimethylammonium chloride
(Tallowalkyltrimethylammonium chloride, T-50)

R ₁ = 1
R ₂ = 18 Tributylheptylammonium bromide
(Tributylheptylammonium bromide, THAB)

R ₁ = 4
R ₂ = 7 Amylistyltrimethylammonium bromide
(Myristyltrimethylammonium bromide, MTAB)

R ₁ = 1
R ₂ = 15 Tributylhexadecyl ammonium bromide
(Tributylhexadecylammonium bromide)

R ₁ = 4
R ₂ = 16 Various other structures Cetylpyridinium chloride
(Cetylpyridinium chloride, CPC)

Phenyltrimethylammonium chloride
(Phenyltrimethylammonium chloride)

Benzyldimethyldodecylammonium chloride < RTI ID = 0.0 >

Benzyldimethylhexadecylammonium chloride
(Benzyldimethylhexadecylammonium chloride)

Dicocoalkyldimethylammonium chloride
(Dicocoalkyldimethylammonium chloride, 2C-75)

Quaternary ammonium containing organosilane
(Orgamosilane quaternary ammonium)

The circulation process using the composite material of the present invention is advantageous in terms of low adsorption ability of toxic anion, problem of aftertreatment of adsorbent material, difficulty of regenerating adsorbent, low chemical solubility due to low hydrogen solubility, Toxic anion removal rate, high pressure, and temperature need to overcome the problem of increased water purification costs.

It was confirmed by ion chromatography that the composite materials synthesized in the present invention had a perchlorate adsorption amount as high as 2 to 5 times higher than that of porous carbon used as a general adsorbent in a concentration of about 10 ppm of perchlorate solution. It was also confirmed that the adsorption amount of perchlorate increased depending on the adsorbed quaternary ammonium groups. In addition to perchlorate, it was confirmed in the same way that the selectivity to perchlorate was high even in the presence of other ions such as SO ₄ ^2- .

As a result of the decomposition experiments under the dry and wet hydrogen conditions with different decomposition temperatures of the composite materials adsorbing the corresponding anions, the decomposition temperature of perchlorate in the surface of the metal clusters under dry conditions was 150 to 200 ℃ and all perchlorate ions were completely decomposed at around 200 ℃ without change of adsorbent structure. In the wet condition, the decomposition rate was 90% or more even at a low temperature of 60 ° C, and the decomposition rate was 70% or more even at room temperature.

In this case, the wet reduction process of adsorbing the anion under liquid conditions and decomposing it under hydrogen as a composite material containing water is actually carried out after the adsorption of perchlorate in the wastewater. In the column filled with the material, a large amount of moisture So that the reduction process must be carried out with water in the actual process. In addition, when considered in terms of the catalytic principle, it was judged that the spillover phenomenon in which active hydrogen diffuses along the surface of the carbon is promoted when water is present, so that the perchlorate adsorbed on the material can be more easily reacted.

Based on these results, it was confirmed that the circulation process of adsorption - decomposition - adsorption was actually performed and the anion adsorption capacity was not decreased. These results indicate that the decomposition through reduction of perchlorate and nitrate ions exchanged in the liquid phase of the present invention is suppressed by H ₂ It is possible to carry out in the presence.

[Example]

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are only for illustrating the present invention and that the scope of the present invention is not construed as being limited by these embodiments.

Example 1: Anion adsorption experiment of composite material

In order to confirm the anion adsorptivity and ion selectivity of the composite material according to the present invention, it is preferable to add carbon to the metal particle-bearing porous carbon, nitrogen to the carbon skeleton, or metal-supported porous carbon to cation Anion adsorption experiments were carried out with modified carbon by adsorbing the surfactant.

In the case of a composite material in which porous carbon is treated with a nitrogen compound such as NH ₃ , urea, or melamine at a high temperature to replace a part of the skeleton with 1 to 30 wt% of nitrogen and metal particles are carried, the amount of perchlorate Comparing the removal rates, it can be seen that when the same amount of sample is added, the perchlorate removal rate of the carbon substituted by the nitrogen skeleton is the highest. This indicates that it is possible to adsorb the same amount of perchlorate ions even with a smaller amount of carbon when compared to Pd-bearing carbon (FIG. 3).

As shown in FIG. 4, when the perchlorate ion adsorption capacity is compared at the equilibrium concentration, the carbon in which the nitrogen skeleton is substituted for both the pure solution and the simulated solution has a higher adsorption capacity than the non-carbon Able to know. This is because the surface of the activated carbon becomes positively charged with the substitution of nitrogen in the carbon skeleton, and the adsorption amount of the perchlorate ion is increased. However, despite the fact that the amount of adsorbed carbon on the nitrogen skeleton is superior to the adsorbed amount of the comparative sample in both solutions, the adsorbed amount of perchlorate ion in the simulated solution, in which other anions that compete with the perchlorate ion are present, , But it was confirmed that Pd alone in the same solution was superior to the adsorbing ability of the supported carbon.

Ion exchange was carried out in a pure solution and a simulated solution in order to analyze adsorption capacity and selectivity of percarbonate ion of carbon sample adsorbed on tributyl (hexadecyl) ammonium. In order to analyze the adsorption amount, perchlorate ion concentration of each solution before and after the exchange was analyzed by IC.

FIG. 9 is a graph showing the adsorption capacity of perchlorate ions of carbon adsorbed on tordyl (hexadecyl) ammonium and carbon carrying Pd, and FIG. 10 shows adsorption of pertyl (ammonium hexadecyl) Respectively. Here, it can be seen that the sample having the cationic surfactant bonded to the carbon substituted with the nitrogen skeleton has far superior adsorption ability of perchlorate. In addition to the solution containing only perchlorate ions, it was confirmed that even the simulated solution in which other ions are dissolved has a high selectivity because the cationic surfactant-bonded substance exhibits superior perchlorate adsorption ability.

Example 2: Perchlorate ion adsorption amount over time

In order to confirm the amount of perchlorate ion adsorption over time of the composite material, adsorption experiment of perchlorate ion was carried out batchwise. As a result, the adsorption amount of Pd on the carbon replaced with nitrogen and the adsorbed amount of Pd on common carbon showed higher adsorption amount than the simulated solution in the pure solution. In addition, most of the perchlorate ion adsorption occurs during the first 20 minutes after the start of adsorption. When the perchlorate ion adsorption rate is compared with that of the pure solution after 120 minutes, the adsorption rate of the carbon replaced with nitrogen in the skeleton is 68.8% Respectively. In the simulated solution, the adsorption rate of carbon replaced with nitrogen in the skeleton after 120 minutes was 63% and that of the common carbon was 49.4%, which shows a relatively low adsorption amount in the simulated solution, It was confirmed that the carbon substituted with nitrogen in the skeleton had a higher adsorption amount than that of the common carbon.

Example  3: Temperature dependent Perchlorate  Degree of reduction of ion

In order to confirm the anion decomposition temperature of the composite material adsorbed on the perchlorate ion, hydrogen gas was flowed into the perchlorate ions adsorbed on the sample. According to several researchers, the reduction of perchlorate ions by hydrogen gas is considered to be a very slow process from a kinetic point of view because the activation energy is large. This is because the electron arrangement of symmetrical perchlorate anions makes it difficult for hydrogen gas to attract electrons around the four oxygen atoms. However, when a catalyst such as metal particles having a reducing function is used, the activation energy is lowered to make the removal of perchlorate ions easier. Therefore, in the present invention, percarbonate ions can be easily catalytically decomposed by supporting about 1 wt% of Pd in the carbon replaced with nitrogen in the skeleton and the carbon in the comparative group.

  FIG. 6 shows the degradation rate of perchlorate according to decomposition temperature and decomposition conditions under decomposition for 10 hours under 5 bar of hydrogen. It shows the degree of reduction of perchlorate ion depending on the specific temperature of carbon substituted with nitrogen in the skeleton and general carbon. Both samples were adsorbed perchlorate ions in a 10 ppm solution of perchlorate for 12 hours, and the concentration of perchlorate ions in each solution before and after adsorption was analyzed by IC to record the initial adsorption amount. In the case of the decomposition proceeding under dry conditions, the samples dried in an oven at 100 ° C. after adsorption were kept under hydrogen gas conditions at a temperature between 60 ° C. and 210 ° C. for 2 hours, / min. In the case of an experiment in which decomposition proceeded under wet conditions, the sample containing moisture was kept at a temperature between room temperature and 210 ° C for 2 hours under hydrogen gas condition without drying the samples after adsorption, Was set at 2 [deg.] C / min. Each sample cooled under helium conditions was stirred for 12 hours in a solution of NaOH at 1000 ppm to separate the perchlorate ions remaining in the sample into solutions. The concentration of perchlorate ions in the solution was analyzed by IC and compared with the initial adsorption amount, Of perchlorate was calculated. As shown in FIG. 6, it can be seen that under the dry condition, the initial adsorption amount was removed by 100% at 200 ° C for carbon bearing Pd only, and 230 ° C for nitrogen substituted at the skeleton. After the adsorption of perchlorate, the decomposition reaction was carried out by filling the hydrogen gas without removing the water remaining in the adsorbent. As a result, the decomposition rate of perchlorate was about 20% higher in Pd / AC than in the dry condition. What is surprising is that Pd / N-AC samples show significantly higher decomposition rates at the same temperature than when decomposed under dry conditions, which means that at very low decomposition temperatures of 60 ° C, more than 90% of the adsorbed perchlorate has been decomposed. The decomposition rate was 70% at room temperature (25 ° C) without any heat source. It is expected that the decomposition rate will be more than 90% when the decomposition time is kept long at the same temperature. Therefore, it was found that the Pd / N-AC sample was able to regenerate the adsorbent with little energy.

Example  4: Depending on the type of metal Perchlorate  Decomposition Temperature of Ion

In addition to Pd, Pt and Ni metals were loaded on carbon, and the decomposition experiments of the adsorbed toxic anions were carried out. It was confirmed that the decomposition of toxic anions occurred at a lower temperature than the carbon in which no metal particles were carried.

Example  5: Functional change of composite material according to cyclic repetition

In order to confirm that general application to the actual circulation process is possible by using the composite material of the present invention, the functional change of the material due to repetition of the adsorption-catalytic decomposition (regeneration) cycle using the carbon substituted with the nitrogen skeleton is analyzed Respectively. As shown in Fig. 7, no reduction in the ion adsorption capacity of the composite material occurred during the three repeated experiments. That is, even if a composite material is applied to a water purification system, which is an actual cycle process, there is no change in the functionality of the composite material, which means that the composite material can be continuously used.

Example  6: Type of activated carbon and Cationic  Depending on the quaternary ammonium group Perchlorate  Ion adsorption amount

In order to confirm the adsorption amount of perchlorate ion depending on the type of activated carbon and the cationic quaternary ammonium group, the adsorption experiment of perchlorate ion was performed in a batch manner.

GAC1 and GAC2 were used as the activated carbon and the adsorbed cationic quaternary ammonium group was not used as the control group (pristine) and C1, C2, C3, C4 and CPC were used. Respectively.

In order to adsorb a surfactant on activated carbon, these cationic surfactants were dissolved in an amount of 15 wt% of activated carbon, and the mixture was stirred for 6 hours with activated carbon. (Trimethyl hexadecyl ammonium bromide), C2 (triethyl hexadecyl ammonium bromide), C3 (tripropyl hexadecyl ammonium bromide), C4 (tributyl hexadecyl ammonium bromide) and CPC (cetyl pyridinium chloride) depending on the structure of the ammonium part and the alkyl group length .

After the adsorption of the aqueous solution, the weakly adsorbable surfactant, which was adsorbed to the respective activated carbon, was repeatedly washed with a sufficient amount of water. After that, perchlorate (100 ppm) diluted with real wastewater from the real industry was added in a certain amount, and the mixture was stirred for 2 hours to adsorb perchlorate and the amount of perchlorate adsorption was measured by IC.

First, when the amount of perchlorate adsorption of activated carbon before adsorption of cationic surfactant was compared, the perchlorate adsorption capacity of coconut GAC1 was 10 times higher than that of GAC1, even though GAC1 had a larger surface area than coal GAC2. Also, when the amounts of perchlorate adsorbed after adsorption of cationic surfactants were compared, all of the five surfactants exhibited significantly higher adsorbability of perchlorate than GAC1. Since GAC1 has only micropores, GAC2 has both micropores and mesopores. Therefore, it is expected that this difference in adsorption capacity is due to the effect of pore structure and size on the adsorption of perchlorate and surfactant, rather than the surface area of activated carbon.

Next, the effect of surfactant on perchlorate adsorption capacity was examined. The adsorption capacity of GAC1 increased about 10 ~ 20 times and that of GAC2 about 3 ~ 5 times after surfactant adsorption. The large increase rate of GAC1 means that there exist many carboxyl groups which have negative charge on the surface of GAC1 originally. In addition, perchlorate adsorption amount varied depending on the type of surfactant. In particular, when C4 (tributyl hexadecyl ammonium) surfactant was adsorbed, both GAC1 and GAC2 exhibited the highest perchlorate adsorption capacity. In this study, it was found that C4 is the most ideal surfactant, and coal carbon with coexistence of micropores and mesopores is the most ideal carbon material.

Comparative Example  1: Anion adsorption experiment of porous carbon

Anion adsorption experiments were performed in a low concentration toxic anion solution using general porous carbon, which is an ion exchange material used in conventional physical removal methods. As a result, in the case of a general porous carbon, the amount of adsorbed ions is smaller than that of the modified carbon by replacing the nitrogen with the skeleton or adsorbing the cationic surfactant in addition to the metal-supported porous carbon and the metal-supported porous carbon It was confirmed that the decomposition of the anion by the reduction of the anion occurs at a higher temperature than that of the carbon bearing the metal particles.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. something to do. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

Claims (15)

(a) adsorbing a toxic anion by using a metal-supported porous carbon; And
(b) reducing the anion exchange capacity of the porous carbon supported on the metal by using a reducing agent,
Wherein the metal-bearing porous carbon is treated with a nitrogen compound so that a part of the skeleton is substituted with 1 wt% to 30 wt% of nitrogen.
The method according to claim 1,
(C) repeating the steps (a) and (b) sequentially by using the reduced-metal-supported porous carbon after the step (b) Removal method.
The method of claim 1 or 2, wherein the toxic anion is a perchlorate (ClO ₄ ^- ) ion or a nitrate (NO ₃ ^- ) ion.
The method of claim 1 or 2, wherein the metal is a metal selected from the group consisting of Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt and Au.
The method for removing toxic anions according to any one of claims 1 to 3, wherein the metal-supported porous carbon has metal particles on the surface of the porous carbon in a ratio of 0.01 wt% to 50 wt%.
The method of claim 1 or 2, wherein the porous carbon has a specific surface area of 50 m ² / g to 4000 m ² / g.
delete The method of claim 1, wherein the nitrogen compound is NH ₃ , urea, or melamine.
The method of claim 1 or 2, wherein the cationic surfactant is adsorbed on the metal-supported porous carbon to modify the cationic surfactant.
The method of claim 9, wherein the cationic surfactant is quaternary ammonium.
Claim 11 has been abandoned due to the set registration fee. 11. The method of claim 10, wherein the quaternary ammonium group is selected from the group consisting of trimethyl hexadecyl ammonium bromide, triethyl hexadecyl ammonium bromide, tripropyl hexadecyl ammonium bromide, Tributyl hexadecyl ammonium bromide, decyltrimethylammonium bromide (DTAB), cetyltrimethylammonium chloride (CTAC), cetyltrimethylammonium bromide (CTAB), tallowylalkylammonium bromide (TAB), tributylheptylammonium bromide (THAB), myristyltrimethylammonium bromide (MTAB), trivileylhexadecylammonium bromide (Tr), trimethylammonium chloride ibutylhexadecylammonium bromide, Cetylpyridinium chloride (CPC), Phenyltrimetylammonium chloride, Benzyldimethyldodecylammonium chloride, Benzyldimethylhexadecylammonium chloride, Diccoalkyldimethyl chloride Dicocoalkyldimethylammonium chloride (2C-75), and Organosilane quaternary ammonium containing an organic silane.
The method of claim 1 or 2, wherein the process is performed in batch or column.
The method of claim 1 or 2, wherein the reducing agent in step (b) is hydrogen gas or formic acid.
The method of claim 1 or 2, wherein the step (b) is performed at a temperature of from 20 ° C to 250 ° C.
The method of claim 1 or 2, wherein the reducing process of step (b) is performed under dry or wet conditions.

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