KR102358097B1 - Preparation method of amorphous iron sulfide catalyst for heterogeneous Fenton oxidation reaction - Google Patents

Abstract

The present invention relates to a method for preparing an amorphous iron sulfide catalyst for heterogeneous Fenton oxidation reaction that effectively removes hardly decomposable organic materials by stabilizing iron hydroxide broken by hydrogen sulfide in an inert atmosphere.
The present invention prepares iron hydroxide for hydrogen sulfide adsorption by adding caustic soda (NaOH) or liquid slaked lime (Ca(OH) ₂ ) to acid mine drainage and mixing an inorganic binder to prepare iron hydroxide (S10); introducing hydrogen sulfide into the prepared iron hydroxide to break through the iron hydroxide to produce amorphous iron sulfide to produce amorphous iron sulfide (S20); an oxygen blocking step (S30) of supplying amorphous iron sulfide produced by reaction with hydrogen sulfide to a heat treatment apparatus and introducing an inert gas to remove oxygen; and a heat treatment step (S40) of heat-treating amorphous iron sulfide by heating a heat treatment apparatus in an inert gas atmosphere from which oxygen has been removed with an inert gas at about 100 to 800°C.

Description

Preparation method of amorphous iron sulfide catalyst for heterogeneous Fenton oxidation reaction

The present invention relates to a method for preparing an amorphous iron sulfide catalyst for heterogeneous Fenton oxidation reaction that effectively removes hardly decomposable organic materials by stabilizing iron hydroxide broken by hydrogen sulfide in an inert atmosphere.

Advanced Oxidation Technology (AOT) is a water treatment technology that can non-selectively rapidly decompose difficult-to-decompose organic pollutants by producing active oxidizing species with strong oxidizing power.

Wastewater containing organic matter is generated in the process of manufacturing various compounds and flows into rivers or seas, which is the main cause of deterioration of the natural environment. There are many types of organic matter contained in wastewater. Fundamentally, an organic material refers to a substance composed of elements such as carbon, oxygen, nitrogen, hydrogen, and sulfur, and can be broadly divided into three types, alkanes, alkenes, and alkynes, depending on the form of bonding between carbons, and each molecule has a functional group. These are combined to show the characteristics of organic matter contained in wastewater. Depending on the type of functional group, organic substances contained in wastewater are classified into aldehydes, nitriles, alcohols, amines, amides, aromatics, acids, and the like.

As described above, since the types of organic matter contained in wastewater are very diverse, it is very difficult to treat wastewater and the like.

Wastewater containing nitrogen-containing compounds in wastewater, for example, amine compounds, amide compounds, amino acid compounds, etc., is coagulated using an anionic polymer coagulant. However, since the discharged sludge contains amines, subsequent treatment is required. In addition, even when the adsorption method is used, it is difficult because the efficiency of the adsorbent is lowered due to the amine.

There are two types of methods for treating difficult-to-decompose organic matter known so far: a biological method called the activated sludge method and a chemical method. The activated sludge method takes a long time to decompose organic compounds, and the wastewater must be diluted to a concentration suitable for the growth of algae and bacteria. Therefore, this method requires a large space to equip a treatment facility, and in the case of wastewater containing aromatic organic matter, which is a difficult-to-decompose material, activated sludge is subjected to shock or is not well treated, so it is discharged without decomposition.

In addition, the chemical treatment methods currently most commonly used include iron oxidation method, ozone oxidation method, Fenton oxidation method, and the like.

Korean Patent Registration No. 10-2070919 "Catalyst, electrode and electric Fenton reaction system using same" provides crystalline iron sulfide composed of Fe _1-X S capable of decomposing difficult-to-decompose organic matter.

The crystalline iron sulfide catalyst of Korea Patent Registration No. 10-2070919 is hydrothermal synthesis, solvothermal synthesis, mechano-chemical method (ball-milling), non-template or template synthesis method. (non-templated or templated method), impregnation method, dip coating method, thermal decomposition method using Fe-S based complex, etc. There is a problem that takes

An object of the present invention is to provide a method for preparing an amorphous iron sulfide catalyst for heterogeneous Fenton oxidation reaction that effectively removes difficult-to-decompose organic substances by stabilizing iron hydroxide broken by hydrogen sulfide in an inert atmosphere.

In the method for producing an amorphous iron sulfide catalyst for heterogeneous Fenton oxidation reaction according to the present invention, caustic soda (NaOH) or liquid slaked lime (Ca(OH) ₂ ) is added to acid mine drainage, and iron hydroxide produced by mixing an inorganic binder is A preparation step of preparing iron hydroxide for adsorption of hydrogen sulfide (S10); introducing hydrogen sulfide into the prepared iron hydroxide to break through the iron hydroxide to produce amorphous iron sulfide to produce amorphous iron sulfide (S20); an oxygen blocking step (S30) of supplying amorphous iron sulfide produced by reaction with hydrogen sulfide to a heat treatment apparatus and introducing an inert gas to remove oxygen; and a heat treatment step (S40) of amorphous iron sulfide in which oxygen is removed with an inert gas in an inert gas atmosphere heat treatment apparatus by heating at about 100 to 800 ° C.

Preferably, the iron hydroxide for adsorption of hydrogen sulfide is produced by adding caustic soda (NaOH) or liquid slaked lime (Ca(OH) ₂ ) to acid mine drainage containing a large amount of iron salt or iron component, and mixing an inorganic binder. .

Preferably, the inert gas is characterized in that nitrogen gas.

Preferably, the heat treatment temperature is characterized in that 400 ~ 500 ℃.

The amorphous iron sulfide catalyst for the heterogeneous Fenton oxidation reaction of the present invention has the effect of effectively removing an amorphous and hardly decomposable organic material.

In addition, since iron hydroxide that removes hydrogen sulfide can be recycled, it is possible to economically produce amorphous iron sulfide.

In addition, when iron hydroxide is produced from iron salts or acid mine drainage and amorphous iron sulfide is produced therefrom, there is an advantage in that environmental pollution caused by discarded acid mine drainage can also be prevented.

1 is a process diagram of a method for preparing an amorphous iron sulfide catalyst for a heterogeneous Fenton oxidation reaction according to the present invention.
Figure 2 is a graph of the X-ray diffraction analysis results of the amorphous iron sulfide catalyst of Example according to the present invention.
3 is a graph of the decomposition test result of 4-chlorophenol by the amorphous iron sulfide catalyst of an embodiment according to the present invention.
4 is an analysis graph of the amount of elution of amorphous iron sulfide in the amorphous iron sulfide catalyst of an embodiment according to the present invention.

Hereinafter, the present invention will be described in detail. In the context of the present invention, the term 'heterogeneous system' means that a material reacting with a catalyst and a phase of the catalyst are different.

The method for producing an amorphous iron sulfide catalyst for heterogeneous Fenton oxidation reaction according to the present invention includes the steps of preparing iron hydroxide for hydrogen sulfide adsorption (S10), generating amorphous iron sulfide (S20), and oxygen blocking step of amorphous iron sulfide (S30) and a stabilization step (S40) of amorphous iron sulfide.

In the iron hydroxide preparation step (S10) for adsorbing hydrogen sulfide, iron hydroxide having pores and surfaces capable of adsorbing hydrogen sulfide is prepared. At this time, the iron hydroxide for adsorption of hydrogen sulfide is produced by adding caustic soda (NaOH) or liquid slaked lime (Ca(OH) ₂ ) to acid mine drainage containing a large amount of iron salt or iron component, and mixing the inorganic binder. When caustic soda or liquid slaked lime is added to the acid mine drainage, the iron compounds present in the acid mine drainage are precipitated with iron hydroxide such as FeO(OH) or Fe(OH) ₃ , and the precipitated iron hydroxide is molded into pellets, etc. to adsorb hydrogen sulfide It can be produced with an iron hydroxide adsorbent.

In the step (S20) of generating amorphous iron sulfide, hydrogen sulfide is introduced into the prepared iron hydroxide to break through the iron hydroxide to produce amorphous iron sulfide. At this time, when iron hydroxide for hydrogen sulfide adsorption is placed in the adsorption tower and biogas containing hydrogen sulfide is injected, it reacts with the iron components on the pores and surface of the iron hydroxide to produce amorphous iron sulfide. This makes it possible to produce amorphous iron sulfide while also removing hydrogen sulfide contained in biogas.

In the oxygen blocking step (S30) of the amorphous iron sulfide, the amorphous iron sulfide produced by reacting with hydrogen sulfide is supplied to the heat treatment apparatus, and oxygen is removed by introducing an inert gas. At this time, the removal of oxygen is preferably purged with nitrogen gas. When oxygen is removed in such a heat treatment device, the sulfur component of amorphous iron sulfide reacts with oxygen to form sulfur oxide (SO _x ), which can prevent the generation of toxic gas and prevent the loss of sulfur due to the formation of sulfur oxide. .

In the heat treatment step (S40) of the amorphous iron sulfide, the heat treatment is performed by heating the heat treatment apparatus in an inert gas atmosphere in which oxygen has been removed with an inert gas to about 100 to 800 °C, particularly 400 to 500 °C. At this time, above 800 ℃, Pyrrhotite (Fe _X-1 S), which is mostly iron sulfide, and Magnetite (Fe ₃ O ₄ ), which is iron oxide, exist in a mixed phase, and the iron sulfide components are melted and fixed on the surface of the heat treatment reactor. There is a problem with having a very serious villainous effect. Accordingly, in the heat treatment step, the excessively adsorbed sulfur component is converted to elemental sulfur, and inert gas and moisture are discharged. Since the amorphous iron sulfide, which has been heat treated in this way, is chemically very stable, it can be used as a catalyst for the heterogeneous Fenton oxidation reaction.

<Experimental Example 1: Confirmation experiment of amorphous iron sulfide>

Iron hydroxide was placed in the reaction tower and biogas containing hydrogen sulfide was injected. After that, iron sulfide obtained through a chemical reaction between hydrogen sulfide and iron hydroxide (Fe(OH) ₃ ) present in biogas was dried and then heat-treated at 110, 400, 800 ° C. for 2 hours in a nitrogen atmosphere to produce iron sulfide.

And, the X-ray diffraction analysis results were confirmed for each iron sulfide produced using an X-ray diffractometer (XRD), and the results were shown in the graph of FIG. 1 .

As shown in FIG. 2 , when heat-treated at 110° C., it was amorphous iron sulfide, and when heat-treated at 400° C., it was amorphous iron sulfide, but slight crystallization was confirmed. In addition, when heat-treated at 800 ° C., it was confirmed that Pyrrhotite (Fe _X-1 S) as iron sulfide and Magnetite (Fe ₃ O ₄ ) as iron oxide were present in a mixed phase.

In addition, it was confirmed that, when heat-treated at 800 °C, the melting phenomenon (melting phenomenon) of iron sulfide components proceeded and adhered to the surface of the heat treatment reactor, thereby having a very adverse effect on the process.

<Experimental Example 2: Decomposition experiment of 4-chlorophenol>

<Production of amorphous iron sulfide>

Iron hydroxide was placed in the reaction tower and biogas containing hydrogen sulfide was injected. After that, after drying iron sulfide obtained through a chemical reaction between hydrogen sulfide and iron hydroxide (Fe(OH)3) present in biogas, heat treatment is performed at 200, 300, 400, and 500° C. for 2 hours in a nitrogen atmosphere, Iron sulfide was prepared.

<Decomposition experiment of 4-chlorophenol>

The decomposition rate of 4-chlorophenol (4-chloro pheno; hereinafter referred to as '4-CP') at pH 5 using amorphous iron sulfide heat-treated at 200, 300, 400, and 500 ° C. 3 as a graph. The initial concentration of 4-CP was 1.0mM, the concentration of hydrogen peroxide (H ₂ O ₂ ) was 100 mM, the H ₂ O ₂ /4-CP ratio was 100, and the pH was fixed to 5. The amorphous iron sulfide heat-treated at 200, 300, 400, and 500 °C prepared in Examples was added at 20 g/L.

As shown in FIG. 3 , the removal rate of 4-CP was confirmed to be 95% or more within 1 hour, the removal rate of amorphous iron sulfide heat treated at 200 ° C. was the lowest, and the 4-CP removal rate of amorphous iron sulfide heat treated at 400 ~ 500 ° C. was 98% or more was maintained.

<Test of iron elution amount of amorphous iron sulfide>

In order to check the stability of amorphous iron sulfide, the amorphous iron sulfide heat-treated at 200, 300, 400, and 500 ° C. prepared in Examples was added to a solution of pH 5, and the amount of iron hydroxide eluted at pH 5 was confirmed as a graph of FIG. indicated.

As shown in FIG. 4, the elution amount of amorphous iron sulfide heat treated at 400 and 500 °C was 50-60 μM, and it was confirmed that the iron elution amount was smaller than that of amorphous iron sulfide heat treated at 200 °C and 300 °C.

As described above, as the heat treatment temperature of iron sulfide was lowered, the amount of iron eluted as iron ions increased due to a loose bond between elemental sulfur and iron, which reacted with hydroxide ions to increase the amount of particulate iron hydroxide.

Accordingly, it can be confirmed that the appropriate heat treatment temperature for amorphous iron sulfide is 400 ° C. or higher, but at 800 ° C or higher, iron sulfide is melted and it is impossible to operate the process.

It was confirmed that the effect of the heat treatment temperature of iron sulfide was not significantly different at pH 5, but the amount of catalyst converted to particulate matter increased as the stabilization temperature was lowered.

As described above, although the present invention has been described with reference to limited embodiments and drawings, the present invention is not limited thereto, and the technical idea of the present invention and the following by those of ordinary skill in the art to which the present invention pertains Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

Claims (4)

Preparing iron hydroxide for hydrogen sulfide adsorption by adding caustic soda (NaOH) or liquid slaked lime (Ca(OH) ₂ ) to acid mine drainage and preparing iron hydroxide produced by mixing an inorganic binder (S10);
introducing hydrogen sulfide into the prepared iron hydroxide to break through the iron hydroxide to produce amorphous iron sulfide to produce amorphous iron sulfide (S20);
an oxygen blocking step (S30) of supplying amorphous iron sulfide produced by reaction with hydrogen sulfide to a heat treatment apparatus and introducing an inert gas to remove oxygen;
A non-uniform iron sulfide catalyst for heterogeneous Fenton oxidation reaction, characterized in that it comprises; a heat treatment step (S40) of heat-treating amorphous iron sulfide by heating an inert gas atmosphere in which oxygen has been removed with an inert gas at 100 to 800° C. Way.
delete The method of claim 1, wherein the inert gas is nitrogen gas.
The method according to claim 1, wherein the heat treatment temperature is 400 ~ 500 ℃ method for producing an amorphous iron sulfide catalyst for heterogeneous Fenton oxidation reaction.

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