KR20190079113A - Catalyst and electrode and electro-fenton reaction system usingby - Google Patents

Abstract

The present invention relates to a catalyst, an electrode and an electro-Fenton reaction system using the same. The catalyst comprises bivalent iron (Fe) and at least one species of iron sulfide crystal particles represented by chemical formula 1. Chemical formula 1 is Fe_(1-X)S wherein X satisfies 0 <= X <= 0.25. According to the present invention, a generation rate of OH radicals can be increased and peeling of crystal particles in the reaction can be decreased.

Description

TECHNICAL FIELD [0001] The present invention relates to a catalyst, an electrode, and an electric Fenton reaction system using the same.

The present invention relates to a catalyst, an electrode and an electric Fenton reaction system using the same. More particularly, to a catalyst comprising iron sulfide (Fe ₁ -x S, _{0? X?} 0.25) for decomposition of refractory organic matter, an electrode coated with such a catalyst, and an electrical Fenton reaction system comprising such an electrode.

In recent years, deepening regulations on water quality and continuous improvement of water quality have been demanded in the advanced oxidation process (AOP), which oxidizes and decomposes harmful substances contained in water by adding a radical oxidizing agent having high activity to water, ). In the case of the Fenton reaction proposed as one of the typical AOPs, the ionized ^bivalent iron ion (Fe ²⁺ ) reacts with hydrogen peroxide (H ₂ O ₂ ) as a single catalytic process commercialized at the bottom / wastewater treatment plant, And the OH radical (.OH) decomposes harmful substances of toxicity by reacting with it. The following equation shows the chemical reaction formula of the Fenton reaction.

Fe ²⁺ + H ₂ O _{2 -} > Fe ³⁺ + OH ^- + ^- OH

However, in the case of the Fenton reaction, there is a problem in that there is a lack of a technique for converting an Fe (OH) ₃ sludge produced during a long reaction time to an ionized ^bivalent iron ion (Fe ²⁺ ). In order to overcome this problem, a method of suppressing the formation of sludge by controlling the pH to 3 or less during the Fenton reaction has been proposed. However, it is difficult to recover the divalent iron ions (Fe ²⁺ ) present in the sludge after the reaction, and thus it is used for limited use.

In order to overcome the conventional problems, a Fenton-like reaction in which a water-insoluble Fe-based solid is used as a donor of a divalent iron ion (Fe ²⁺ ) has been proposed. However, the continuous supply of hydrogen peroxide (H ₂ O ₂ ) is required, and the reaction between trivalent iron (Fe ³⁺ ) and hydrogen peroxide is dominant over the reaction between ferric ion (Fe ²⁺ ) and hydrogen peroxide There is a problem that the productivity of the OH radical (.OH) is insufficient as compared with the Fenton reaction.

Accordingly, the present invention is to solve various problems including the above-mentioned problems, iron sulfide, which is defined as _{Fe 1-X S (0≤X≤0.25)} ( e.g., Fe ₇ S _8, S ₉ Fe _10, Fe ₁₀ S ₁₁ , Fe ₁₁ S _12, and the like) to increase the production rate of OH radicals and to reduce the peeling phenomenon of crystal grains during the reaction.

It is another object of the present invention to improve performance and lifetime in an electric Fenton reaction system for decomposing harmful substances using a catalyst comprising Fe _1-X S as defined above.

However, these problems are exemplary and do not limit the scope of the present invention.

According to an aspect of the present invention for solving the above problems, there is provided a catalyst comprising at least one iron sulfide crystal grain including bivalent iron (Fe) and represented by the following formula (1).

[Chemical Formula 1]

Fe _1-X S

In the above formula (1), X satisfies 0? X? 0.25.

Also, according to an embodiment of the present invention, the iron sulfide crystal grains may have a porous structure.

Also, according to an embodiment of the present invention, the iron sulfide crystal grains may have a diameter of 0.1 nm to 500 탆.

Further, according to an embodiment of the present invention, the iron sulfide crystal grains may further include a transition metal.

According to an embodiment of the present invention, the transition metal may be at least one selected from the group consisting of copper (Cu), nickel (Ni), cobalt (Co), manganese (Mn), vanadium (V), titanium (Ti) (Cr), Scandium (Sc), Zn, Y, Zr, Nb, Mo, (Rh), Pd, Ag, Cd, Hf, Ta, W, Rhen, Os, Ir, Platinum (Pt) and gold (Au), or a combination thereof.

According to an aspect of the present invention, there is provided an electrode including a catalyst and a substrate on which the catalyst is formed.

According to an embodiment of the present invention, the substrate may include carbon or metal oxide, and the catalyst may include 0.01 to 50 parts by weight based on 100 parts by weight of the substrate.

According to an aspect of the present invention, there is provided an electro-Fenton reaction system including a catalyst, a substrate on which the catalyst is formed, and an electrolyte aqueous solution.

According to an embodiment of the present invention, the pH of the aqueous electrolyte solution is 5 to 10, and a power of 2 W or less may be input.

According to one embodiment of the present invention as described above, a catalyst containing at least one kind of Fe _1-X S ( _{0? X} ? 0.25) crystal grains is prepared to increase the production rate of OH radicals, The peeling phenomenon of the particles can be reduced.

Further, the present invention has an effect of improving performance and lifetime in an electric Fenton reaction system which decomposes harmful substances using a catalyst containing non-stoichiometric iron sulfide.

Of course, the scope of the present invention is not limited by these effects.

FIG. 1 is a scanning electron microscopy (SEM) photograph of crystal particles of iron sulfide according to an embodiment of the present invention.
FIG. 2 is a transmission electron microscopy (TEM) photograph of crystal particles of iron sulfide according to an embodiment of the present invention.
3 is a graph illustrating an Fe-S binary diagram according to an embodiment of the present invention.
Figure 4 is a schematic diagram illustrating an electro-Fenton reaction system comprising a catalyst according to one embodiment of the present invention.
5 is a graph showing an X-ray diffraction pattern (XRD pattern) of Examples and Comparative Examples of the present invention.
6 is a graph showing the results of an electrical Fenton reaction experiment using the catalysts of Examples and Comparative Examples of the present invention.
7 is a graph showing the results of an electrical Fenton reaction experiment using the catalysts of Examples and Comparative Examples of the present invention.
Fig. 8 is a graph showing the amount of iron (Fe) to be peeled off during the electrical Fenton reaction in Examples and Comparative Examples of the present invention.
9 is a graph showing the amount of phenol decomposed with time according to the example of the present invention and the comparative example.

The following detailed description of the invention refers to the accompanying drawings, which illustrate, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different, but need not be mutually exclusive. For example, certain features, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in connection with an embodiment. It is also to be understood that the position or arrangement of the individual components within each disclosed embodiment may be varied without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is to be limited only by the appended claims, along with the full scope of equivalents to which such claims are entitled, if properly explained. In the drawings, like reference numerals refer to the same or similar functions throughout the several views, and length and area, thickness, and the like may be exaggerated for convenience.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily carry out the present invention.

Iron sulfide and iron sulfide crystal grains

1 and 2, a catalyst containing iron sulfide crystal grains according to an embodiment of the present invention will be described.

FIG. 1 is a scanning electron microscopy (SEM) image of crystal particles of iron sulfide according to an embodiment of the present invention, and FIG. 2 is a transmission electron microscopy (TEM) image.

According to Fig. 1 and Fig. 2, the catalyst includes bivalent iron (Fe) and may include at least one iron sulfide crystal grain represented by the following formula (1).

 [Chemical Formula 1]

Fe _1-X S

In the above formula (1), X satisfies 0? X? 0.25.

In the present specification, the proposed iron sulfide specifically includes FeS ₂ and may include FeS, Fe ₃ S ₄ , Fe ₇ S ₈ , Fe ₉ S ₁₀ , Fe ₁₀ S ₁₁ , Fe ₁₁ S ₁₂ and the like .

More specifically, the iron sulfide crystal grains may contain at least one non-stoichiometric iron sulfide represented by the above formula (1). 3 is a graph illustrating an Fe-S binary diagram according to an embodiment of the present invention. According to Fig. 3, at least one species of sulfide can coexist in the non-stoichiometric iron sulfide in the range of Fe / (Fe + S) of 0.47 to 0.66. Thus, the iron sulfide crystal grains of the present invention may comprise at least one non-stoichiometric sulfide in the above region. Preferably, it may include non-stoichiometric iron sulfide on Greigite and Pyrrhotite, and more preferably Fe ₃ S ₄ and Fe ₇ S ₈ .

The catalyst can be prepared by a method that can be applied conventionally to form specific iron sulfide crystal grains. For example, it can be prepared by a method such as solvothermal synthesis, templated synthesis, thermolysis of Fe-S coordination chemistry-driven complex, and the like. In addition, hydrothermal synthesis or mechano-chemical synthesis may be used to form two or more kinds of iron sulfide phases. Specifically, the iron sulfide crystal grains contained in the catalyst can be synthesized by hydrothermal synthesis, solvothermal synthesis, mechano-chemical method (ball-milling), non-template or template synthesis, or a thermal decomposition method using Fe-S based complexes, by a method such as a thermal spraying method, a thermal spray method, a templated or templated method, an impregnation method, a dip coating method and a thermal decomposition method using Fe-S based complexes.

The larger the surface area of the catalyst, the faster the reaction rate can be. Hydrogen peroxide (H ₂ O ₂ ) and bivalent iron ions (Fe ²⁺ ) form a fast and large amount of OH radical (· OH), which can accelerate the decomposition of harmful substances.

According to Fig. 1, the iron sulfide crystal grains may have a porous structure, and the iron sulfide crystal grains may have a diameter of 0.1 nm to 500 mu m.

As shown in FIG. 1, when the size of the iron sulfide crystal grains is small and the porosity or roughness is formed on the surface, the surface area increases and the reaction with hydrogen peroxide (H ₂ O ₂ ) Can be increased. It may also be coated with stronger strength when coated on the electrode. This means that the lifetime of the electrode is increased due to the decrease of the leaching phenomenon of the catalyst due to the eddy current of the electrolyte aqueous solution and the external electric power in which the electric Fenton reaction is performed. Therefore, the iron sulfide crystal grains of the present invention have a porous rough surface property, and preferably a diameter of 50 mu m.

According to an embodiment of the present invention, the iron sulfide crystal grains may further include a transition metal, and the transition metal may include copper (Cu), nickel (Ni), cobalt (Co), manganese (Mn) ), Ti, Ce, Cr, Sc, Zn, Y, Zr, Nb, Mo, (Re), rhenium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), hafnium (Hf), tantalum (Ta), tungsten ), Osmium (Os), iridium (Ir), platinum (Pt), and gold (Au) or combinations thereof.

The iron sulfide crystal grains may further include a divalent or trivalent transition metal. Preferably, it may further include a divalent or trivalent transition metal of 4 to 6 cycles. It may further comprise a transition metal to form an iron-based bi-metallic or tri-metallic sulfide. Through this, the electrical and structural properties of the catalyst can be improved to improve the ability to generate OH radicals.

An electrode comprising a catalyst and an electrical Fenton reaction system

The electrode may comprise a catalyst and a substrate on which the catalyst is formed. The catalyst may be formed on at least one side of the substrate, and preferably, the catalyst may be coated on both sides of the substrate. The substrate may be a conductive material of a type commonly used in electrochemical reactions. For example, metals such as graphite or copper, aluminum and the like can be used.

The catalyst may be coated on the substrate using an impregnation method. At this time, it is possible to increase the surface area of the hydrogen peroxide solution and the catalytic reaction, and adjust the content of the catalyst to be coated so as to smoothly supply and receive oxygen (O ₂ ) from the substrate. According to an embodiment of the present invention, the substrate may include carbon or metal oxide, and the catalyst may include 0.01 to 50 parts by weight per 100 parts by weight of the substrate. The content of the catalyst contained in the electrode may be controlled to improve the production rate of the OH radical.

When the catalyst and the substrate are coated, a binder may be used to improve the adhesion between the catalyst and the substrate. The binder may be selected from the group consisting of polyvinylidene fluoride (PVDF), 1-methyl-2-pyrrolidinone, poly (acrylic acid), alginate, styrene butadiene rubber (Styrene butadiene rubber-carboxymethyl cellulose), polyethylene glycol (poly (ethylene glycol)), and derivatives thereof, or a combination thereof may be optionally used.

4 is a schematic diagram illustrating an Electro-Fenton reaction system 100 including a catalyst 160 according to one embodiment of the present invention.

The electrical Fenton reaction system 100 may include a catalyst 160, electrodes 130 and 140 where the catalyst 160 is formed, and an electrolyte aqueous solution 120. The electrodes 160 and 160 coated with the iron sulfide crystal particles proposed in the present invention are used to realize an immediate reaction of the hydrogen peroxide solution and the iron sulfide catalyst on the electrode surface. Therefore, it is possible to decompose the hydrogen peroxide water under specific reaction conditions by using a heterogeneous catalyst and increase the production rate of radicals (for example, · OH, · OOH, · O ₂ ^- ), thereby enabling highly efficient decomposition of harmful substances .

4, an electrical Fenton reaction system 100 may include an electrolyzer 110, an electrolyte aqueous solution 120, a first electrode 130 and a second electrode 140 . The first electrode 130 and the second electrode 140 may be connected by a power source.

The first electrode 130 and the second electrode 140 may be formed of a conductive material. For example, it may be graphite. The catalyst 160 may be coated on at least one side of the second electrode 140 and the catalyst 160 may be a catalyst containing iron sulfide crystal grains according to the embodiment of the present invention described above.

The electrolytic aqueous solution 120 is an aqueous solution used for an electrical Fenton reaction, in which a bivalent iron ion and a hydrogen peroxide water react to form an OH radical, and a harmful substance is decomposed by radicals. At this time, any one of Na ₂ SO ₄ , NaNO ₃ , NH ₄ F, KF, KCl, KBr, KI, NaF, NaCl, NaBr and NaI having a concentration of 10 ^-4 to 10 mol / Combinations may optionally be used.

Hereinafter, a process of decomposing harmful substances through a catalytic reaction occurring in the electrical Fenton reaction system 100 will be described. The reactions occurring in the electrical Fenton reaction system 100 are summarized in the following reaction formulas (1) to (4).

Reaction formula (1): 2H ₂ O -> O ₂ + 4H ⁺ + 4e ^-

Reaction formula (2): O ₂ + 2H ⁺ + 2e ^- -> H ₂ O ₂

Reaction formula (3): Fe ³⁺ + e ^- - > Fe ²⁺

Reaction formula (4): Fe ²⁺ + H ₂ O ₂ -> Fe ³⁺ + OH ^- + OH

First, water in the reaction formula (1) is decomposed into oxygen (O ₂ ) and hydrogen ions (H ⁺ ) by the oxidation reaction by the external power source at the first electrode 130. The oxygen (O ₂ ) and hydrogen ions (H ⁺ ) formed at this time are reduced at the second electrode 140 to form hydrogen peroxide (H ₂ O ₂ ). The hydrogen peroxide generated by the second crystal grains of the iron sulfide reacts with the iron (Fe ²⁺⁾ 3 iron ions (Fe ³⁺⁾ and forms an OH radical, a trivalent iron ion (Fe ³⁺⁾ is electron (e ^- ) To recover ^bivalent iron ions (Fe ²⁺ ). This solves the problem of recovery of trivalent iron ions (Fe ³⁺ ) to ^bivalent iron ions (Fe ²⁺ ) formed during the reaction of conventional divalent iron ions (Fe ²⁺ ) with hydrogen peroxide water (H ₂ O ₂ ) And supply of hydrogen peroxide (H ₂ O ₂ ) constantly by supplying oxygen (O ₂ ) due to electrolysis of water. That is, it is possible to increase the production rate of the OH radical and to continuously perform the reaction, thereby improving the performance of the decomposition reaction of the harmful substance.

OH radicals generated through the above reaction can decompose toxic harmful substances. Hazardous substances can be phenolic based toxic, carcinogenic and mutagenic substances. Specifically, a monocyclic or polycyclic aromatic material may be used as the main backbone, and may be an alkane, an alkene, an alkyne, an amine, (s), amines, amides, nitro, alcohols, ethers, halides, thiols, aldehydes, ketones, esters, Carboxylic acid and the like may be substituted or a substance containing a derivative thereof.

Meanwhile, according to an embodiment of the present invention, the pH of the aqueous electrolyte solution in which the reaction of the catalyst occurs is 5 to 10, and the electric Fenton reaction can be performed at a power of 2 W or less.

An OH radical is generated in the electrolytic aqueous solution 120 of the electric Fenton reaction, and the decomposition reaction of the harmful substance proceeds. At this time, when the pH of the electrolyte aqueous solution 120 is acidic (pH <5) or basic (pH> 10) or the external power is more than 2 W, the catalyst 160 coated on the electrodes 130, May occur. (Fe ²⁺ ) and sulfur ions (S ^{2 -} ) can change the pH of the aqueous electrolyte solution and become a main reactant for the OH radical generation reaction. When the Fenton reaction proceeds for a long time, the formation of Fe (OH) ₃ sludge decreases the production rate of OH radicals, and the efficiency and performance of degradation of harmful substances through electrical Fenton reaction are lowered. Therefore, in order to decompose harmful substances with high efficiency, the electric Fenton reaction can be performed by inputting the electric power of the electrolytic aqueous solution 120 at a pH of 5 to 10 or less and 2 W or less, 0.04 W or less of power may be input.

Hereinafter, embodiments for facilitating understanding of the present invention will be described. It should be understood, however, that the embodiments described below are for the purpose of promoting understanding of the present invention, and the embodiments of the present invention are not limited to the following embodiments.

Example 1: Fe ₃ S ₄ / Fe ₇ S ₈ &Lt; RTI ID = 0.0 &gt; non-stoichiometric &lt;

(Fe ₃ S ₄ / Fe ₇ S ₈ ) in which the crystal structures of Fe ₃ S ₄ and Fe ₇ S ₈ coexist were prepared by the hydrothermal method. Specifically, 80 mL of an aqueous solution containing 10 mmol of FeSO ₄ · 7H ₂ O and 10 mmol of L-cysteine was exposed for 24 hours at 200 ° C., followed by filtration, washing and drying to obtain Fe ₃ S ₄ / Fe ₇ S ₈ .

Comparative Example 1: FeS ₂ &Lt; / RTI &gt;

Ferric sulphide (FeS ₂ ), which has pyrite and marcasite in crystal structure, was prepared by hydrothermal synthesis. Specifically, a 60 mL aqueous solution containing 20 mmol of FeSO ₄ .7H ₂ O, 20 mmol of Na ₂ S ₂ O ₃ .5H ₂ O and 20 mmol of a sulfur element (S) was used, and under the same conditions as in Example 1 FeS ₂ was prepared.

Comparative Example 2: MS-Fe catalyst

Functional groups (for example, -SO ₃ , -SO ₄ and -S) containing a sulfur element produce doped porous iron oxide (MS-Fe) on the surface. Specifically, 50 mL of an aqueous solution containing 20 mmol of C ₂ H ₂ O ₄ .2H ₂ O and 20 mmol of FeSO ₄ .7H ₂ O was mixed with 50 mL of an aqueous solution containing 10 mmol of Na ₂ S ₂ O ₃ .5H ₂ O The mixture was stirred for 1 hour, filtered, washed, dried and calcined at 300 ° C for 1 hour to prepare MS-Fe.

Comparative Example 3: Fe ₂ O ₃ / RTI &gt;

Fe ₂ O ₃ is used as a catalyst.

Comparative Example 4: Fe ₃ O ₄ / RTI &gt;

Fe ₃ O ₄ is used as a catalyst.

Fe ₃ S ₄ / Fe ₇ S ₈ and FeS ₂ prepared in Example 1 and Comparative Example 1 were analyzed using an X-ray diffractometer (XRD), and the resulting X Ray diffraction pattern (XRD pattern).

5 is a graph showing an X-ray diffraction pattern (XRD pattern) of Examples and Comparative Examples of the present invention. Referring to FIG. 5, as a result of the analysis of the crystal structure of Example 1 and Comparative Example 1, cubic FeS ₂ (pyrite) and orthorhombic FeS ₂ (marcasite) were mixed in Comparative Example 1, ₃ S ₄ (greigite) and Fe ₃ S ₄ (pyrrhotite) are mixed. That is, Example 1 and Comparative Example 1 mean that two kinds of iron sulfide coexist.

Hereinafter, the performance of the electrical Fenton reaction using Example 1 and Comparative Examples 1 to 4 will be described with reference to FIGS. 6 to 9. FIG.

Experimental Example 1: Phenol decomposition experiment using an electric Fenton reaction

Example 1 and Comparative Examples 1 to 4 were used as OH radical (.OH) generating catalysts, electrodes were graphite electrodes, harmful substances were phenol (C ₆ H ₅ OH), and Na ₂ SO ₄ electrolyte aqueous solution To conduct an electrical Fenton reaction experiment. When the catalyst is coated on the electrode, poly (acrylic acid) is used as the binder. 0.2 g of the catalyst, 100 ml of an aqueous solution containing 0.1 mmol of phenol and 0.02 mol of Na ₂ SO ₄ is used as a reaction solution. The electrical Fenton reaction experiments are carried out at pH 7 at 0.04 W power. The conversion of phenol and the phenol consumption reaction rate constant obtained in the above experiment are shown in Fig. The rate constants were calculated assuming that phenol decomposition was a pseudo-1 ^st -order kinetic model.

6 is a graph showing the results of an electrical Fenton reaction experiment using the catalysts of Examples and Comparative Examples of the present invention. [Table 1] below is a table summarizing the above experimental results.

[Table 1]

Referring to FIG. 6 and Table 1, it can be seen that, in the case of Example 1, 90% conversion of _phenol (X _phenol = 90%) occurred over 200 minutes. The rate constant of phenol decomposition (-ln (C _phenol / C _{phenol, 0} )) has the largest value of 11.4x10 ^-3 min ^-1 . On the other hand, in the case of Comparative Examples 1 to 4, when the electrical Fenton reaction was performed for 200 minutes, the conversion rate of phenol was lower than that of Example 1, and the rate constant of the decomposition reaction rate of phenol was smaller. That is, it can be seen that the conversion rate of phenol and the rate constant of the decomposition reaction in Example 1 exhibit the greatest value. This means that Fe ₃ S ₄ / Fe ₇ S ₈ has a higher harmful substance decomposition performance and efficiency than the stoichiometric FeS ₂ or iron oxide catalyst.

Experimental Example 2: Hydrogen peroxide (H ₂ O ₂ ) Decomposition experiment

Example 1 and Comparative Example 1 were carried out in the same manner as Experimental Example 1 except that 0.5 mmol of hydrogen peroxide (H ₂ O ₂ ) instead of phenol, which is a harmful substance, was used without using electric power. The conversion of the hydrogen peroxide solution obtained in the above experiment and the rate constant of the reaction for decomposing hydrogen peroxide (H ₂ O ₂ consumption reaction rate constant) were monitored and shown in FIG.

7 is a graph showing the results of an electrical Fenton reaction experiment using the catalysts of Examples and Comparative Examples of the present invention. Table 2 below is a table summarizing the above experimental results. At this time, the rate constant is calculated assuming that the decomposition reaction of hydrogen peroxide (H ₂ O ₂ ) is a pseudo-1 ^st -order kinetic model.

[Table 2]

Referring to FIG. 7 and [Table 2], the conversion of hydrogen peroxide water was 44% and the decomposition rate constant was 3.3 x 10 ^-3 min ^-1 at 200 minutes after Fe ₃ S ₄ / Fe ₇ S ₈ of Experimental Example 1 , The conversion rate of hydrogen peroxide water was 32% and the decomposition reaction rate constant was 2.1 x 10 ^-3 min ^-1 in the case of FeS ₂ of Comparative Example 1 at the elapse of 200 minutes. This means that Fe ₃ S ₄ / Fe ₇ S ₈ has a higher OH radical production rate and efficiency than the stoichiometric FeS ₂ catalyst.

Experimental Example 3: Leaching Experiment to Measure Catalyst Durability

Example 1 and Comparative Example 1 were subjected to an electrical Fenton reaction experiment under the same conditions as in Experimental Example 1 above. After performing this step (1 ^st run), the obtained catalyst is washed and dried, and the additional electrical Fenton reaction is performed twice (2 ^nd run, 3 ^rd run) under the same condition as Experimental Example 1. The total amount of iron (Fe) leached in each reaction is shown in FIG.

Fig. 8 is a graph showing the amount of iron (Fe) to be peeled off during the electrical Fenton reaction in Examples and Comparative Examples of the present invention.

Referring to FIG. 8, when the electrical Fenton experiment was performed once, it can be seen that Fe and Fe of 5 mol.% Were exfoliated from the catalyst in Example 1 and Comparative Example 1, respectively. However, when the experiment was conducted twice and three times, it was found that iron (Fe) was hardly peeled off in Example 1, but Fe (Fe) of 6 mol% and 7 mol% was peeled off in Comparative Example 1, respectively. It can be seen that the Fe ₃ S ₄ / Fe ₇ S ₈ of the present invention has durability against the physical and chemical stimuli that occur during the reaction compared with the stoichiometric FeS ₂ catalyst. When the sulfuric iron catalyst is peeled from the electrode, the pH of the aqueous solution of the electrical Fenton reaction may be changed to affect the efficiency of the reaction. In the case of the non-stoichiometric iron sulfide catalyst of the present invention, the efficiency of the reaction can be kept high by the durability against peeling.

Experimental Example 4: Non-stoichiometric reaction test

Electron Fenton reaction experiments were performed on the electrodes of Example 1 and Comparative Example 1 and the electrodes not containing the catalyst (hereinafter, referred to as Comparative Example 5) under the same conditions as Experimental Example 1. At this time, after performing the same operation as in Experimental Example 1 for 1 hour, the electrode of Example 1 and Comparative Example 1 was replaced with a catalyst-free electrode, the reaction aqueous solution was filtered, and the experiment was conducted again. The amount of degradation of phenol over time with this method is monitored and shown in FIG.

9 is a graph showing the amount of phenol decomposed with time according to the example of the present invention and the comparative example.

9, it was found that the amounts of decomposition of phenol after 1 hour of the electrodes of Example 1, Comparative Example 1 and Comparative Example 5 were 340 ± 20, 330 ± 50, and 290 ± 20 μM, respectively, . This means that OH radical formation by Fe ₃ S ₄ / Fe ₇ S ₈ and FeS ₂ catalysts takes place on the basis of heterogeneous catalysis. In Experimental Examples 1 to 3, it was confirmed that the catalyst had excellent performance in the electric Fenton experiment using the catalyst of Example 1. This proves that the iron sulfide catalyst (Fe ₃ S ₄ / Fe ₇ S ₈ ) of the present invention has excellent performance in decomposing harmful substances compared to other catalysts.

As described above, the results of the comparison of Example 1 and Comparative Examples 1 to 5 show that the sulfurized iron catalyst of Example 1 is superior in decomposition rate of harmful substances, productivity of OH radicals, and durability of the catalyst coated on electrodes. This indicates that the performance of the electrical Fenton reaction system is improved because the production of the OH radical is increased because the catalyst according to Example 1 contains iron sulfide crystal grains containing Fe _1-X S (0 ≦ X ≦ 0.25), which is nonstoichiometric iron sulfide . Further, when the catalyst according to Example 1 is used, since the amount of iron sulfide peeled off from the electrode decreases, there is no pH change of the aqueous electrolyte solution in which the reaction is performed, and the lifetime of the electrode is increased.

Accordingly, the catalyst according to an embodiment of the present invention includes at least one kind of Fe _1-X S (0? X? 0.25), thereby increasing the production rate of OH radicals and reducing the peeling phenomenon . In addition, there is an effect of improving performance and lifetime in an electric Fenton reaction system that decomposes harmful substances using a catalyst containing Fe _1-X S (0 ≦ X ≦ 0.25).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken in conjunction with the present invention. Variations and changes are possible. Such variations and modifications are to be considered as falling within the scope of the invention and the appended claims.

100: Electrical Fenton reaction system
110: electrolyzer
120: electrolyte aqueous solution
130: first electrode
140: Second electrode
160: catalyst

Claims (9)

Divalent iron (Fe)
1. A catalyst comprising at least one iron sulfide crystal grain represented by the following formula (1).
[Chemical Formula 1]
Fe _1-X S
In the above formula (1), X satisfies 0? X? 0.25. The method according to claim 1,
Wherein the iron sulfide crystal grains have a porous structure. The method according to claim 1,
Wherein the iron sulfide crystal grains have a diameter of 0.1 nm to 500 탆. The method according to claim 1,
Wherein the iron sulfide crystal grains further comprise a transition metal. 5. The method of claim 4,
The transition metal may be at least one selected from the group consisting of Cu, Ni, Co, Mn, V, Ti, Ce, Cr, (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Ag), cadmium (Cd), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium Lt; / RTI &gt; or a combination thereof. A catalyst according to any one of claims 1 to 5; And
And a substrate on which the catalyst is formed. The method according to claim 6,
Wherein the substrate comprises carbon or metal,
Wherein the catalyst comprises 0.01 to 50 parts by weight based on 100 parts by weight of the substrate. A catalyst according to any one of claims 1 to 5;
An electrode on which the catalyst is formed; And
Electro-Fenton reaction system comprising an electrolyte aqueous solution. 9. The method of claim 8,
The pH of the electrolyte aqueous solution is 5 to 10,
Wherein an electric power of 2 W or less is input.

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