WO2016024774A1 - Iron structure for fenton oxidation treatment of wastewater, preparation method therefor, and wastewater treatment method using same - Google Patents

Abstract

The present invention relates to an iron structure for Fenton oxidation treatment, having a novel structure, wherein a nanostructured ferric oxide in which a Fenton-like reaction is carried out on the surface thereof is formed on the surface thereof, and this nanostructure is fixed to a plate. The iron structure for Fenton oxidation treatment has excellent Fenton oxidation treatment efficiency and can be semi-permanently used, and thus can be useful in the environmental treatment process industry such as wastewater treatment.

Description

Iron structure for fenton oxidation treatment of wastewater, its manufacturing method and wastewater treatment method using the same

The present invention relates to a novel iron structure for fenton oxidation treatment of wastewater, a method for producing the same, and a wastewater treatment method using the same.

In addition to improving living standards according to industrial development, factory wastewater, livestock wastewater, and household sewage containing various and numerous types of hazardous chemicals are introduced into rivers and lakes to contaminate water supplies. In particular, trace harmful substances such as volatile organic substances, organic solvents, disinfection by-products, phenols, pesticides, polyaromatic hydrocarbons, and phthalates are extremely carcinogenic and chronic toxic. It is urgent to develop systematic and rapid response strategies and treatment technologies for regulated substances and other trace pollutants. In the case of trace contaminants, it is difficult to understand the behavior of these substances and they are converted into more harmful substances by chlorine disinfection during the purification process of drinking water, and it is difficult to remove them. It is true.

In particular, chemical treatment techniques generally include oxidation methods such as ozone, hydrogen peroxide, UV / O ₃ , UV / TiO ₂ , and fenton, among which fenton does not form chlorides and both iron and hydrogen peroxide have relatively low toxicity. The process injects Fe ²⁺ form iron salt into raw water to accelerate the generation of hydrogen peroxide and OH into raw water, and rapidly oxidizes and removes organic substances in the water. It is widely used.

However, generation of sludge in the form of a large amount of hydroxide by iron ions and over-injection of Fenton's reagent injected in liquid form are pointed out as a limitation of the technology. In order to compensate for this, the Fenton-like oxidation process using reduced-type metal iron (Fe ⁰ ) and hydrogen peroxide has been studied, and the existing Fenton reaction is performed because metal iron is used instead of iron salt with high sludge production. Minimizes the formation of hydroxide-type sludge and also prevents the by-products such as Cl ^- and SO ₄ ^2- generated when using FeCl ₂ or FeSO ₄ as iron salt. However, it is still evaluated to be economically low compared to its efficiency.

Therefore, it is necessary to develop a new iron structure that can be used semi-permanently to improve the economics and at the same time achieve excellent Fenton reaction efficiency.

The problem to be solved by the present invention is to provide a novel wastewater fenton oxidation treatment iron structure and its manufacturing method to solve the conventional problems and at the same time have an excellent Fenton reaction efficiency, and to provide a wastewater treatment method using the same do.

The present invention provides an iron structure for fenton oxidation treatment of wastewater formed by anodizing, in order to solve the above problems, the iron structure according to the present invention is a ferric oxide (Fe) oxide on the surface of the plate (plate) made of iron (Fe ⁰ ) It is characterized in that the nanostructure of Fe ₂ O ₃ ) is formed.

In addition, a Fenton-like reaction occurs on the surface of the iron structure, and the electrons are supplied to the surface from a plate made of ductile iron.

In addition, the ferric oxide nano structure is characterized in that it has a nano-leaf (Nano-leaf) shape.

The 'nano-leaf' is a shape having a leaf shape such as an irregular wire having a grphen-like shape or a face shape (the aspect ratio is close to 1) similar to graphene. It can be confirmed, more specifically in Figures 3a and 3b below.

In the iron structure for fenton oxidation treatment according to the present invention, the surface of the nanostructure is characterized in that the nanostructure of ferric oxide is hematite, and the plate is ferrous iron (Fe ⁰ ).

In addition, the present invention provides a method for producing an iron structure for fenton oxidation treatment of wastewater comprising the following steps.

(a) immersing a ferrous iron (Fe ⁰ ) plate in a mixed electrolyte solution of sodium sulfate (Na ₂ SO ₄ ) and sodium fluoride (NaF), and then applying power so that the non-ferrous iron plate becomes a positive electrode;

(b) continuing the anodic oxidation step of step (a) to oxidize the non-ferrous iron surface;

(c) annealing the surface of the oxidized zero iron plate.

According to an embodiment of the present invention, power may be applied at a voltage of 10-15 V in step (a), preferably 12 V voltage.

On the other hand, the surface of the anodized plate in step (b) is characterized in that the ferrous oxide (FeO) of the wustite crystal structure (FeO), the surface of the plate annealed in the step (c) is hematite (hematite) Ferric oxide (Fe ₂ O ₃ ) having a crystal structure.

In addition, the present invention provides a wastewater treatment method comprising the following steps using the iron structure for fenton oxidation treatment according to the present invention.

(a) preparing wastewater,

(b) injecting hydrogen peroxide and the iron structure for fenton oxidation treatment according to the present invention into the waste water.

On the other hand, the pseudo-fentone reaction occurs in the surface nanostructure of the iron structure for fenton oxidation treatment, it is characterized in that the oxidation of the organic material contained in the wastewater.

In addition, the electron is continuously supplied to the surface from the plate of the iron structure for fenton oxidation treatment.

The iron structure for the fenton oxidation catalyst according to the present invention has a nano structure formed on the surface thereof, so that the surface area is improved, the fenton oxidation treatment efficiency is excellent, and electrons are continuously supplied to the surface to enable semi-permanent use. In addition, since the nanostructures are fixed to the plate, there is an advantage of easy operation of the catalyst. In addition, it can be performed even in an alkaline state of about pH 12, there is no generation of iron sludge and economical environmental treatment process can be implemented.

Figure 1 is a cross-sectional view of the iron structure for fenton oxidation treatment according to the present invention, a cross-sectional view showing a nanostructure of ferric oxide formed on a plate of a non-ferrous iron and its surface, SEM image is an image showing a surface nanoleaf structure.

2 is a graph showing a current change curve with time during anodization according to an embodiment of the present invention.

3A and 3B are scanning microscope images showing top-view and bottom-view of the iron oxide nanostructures formed on the iron plate surface according to Example 1, respectively.

Figure 4 is an XRD graph analyzed through Crystal Impact Match for the iron structure formed on the surface of the iron plate produced according to the present invention.

Figures 5a and 5b is an external appearance image of the iron structure after the annealing process and the external appearance image of the iron structure produced by the anodizing process of Example 1 according to the present invention, respectively.

6A to 6C are graphs showing the results of Fenton experiments performed using hydrogen peroxide and commercial iron catalyst powder using hydrogen peroxide, respectively, using hydrogen peroxide and the iron structure for fenton oxidation treatment according to the present invention.

7 is a graph showing ammonia nitrogen removal efficiency according to the amount of zeolite according to an embodiment of the present invention.

8 is an image showing the result of the before and after the final treatment water treatment of livestock wastewater according to an embodiment of the present invention.

9 is a schematic diagram of an anodization process apparatus schematically showing an anodization process according to the present invention.

In the conventional Fenton reaction, iron ions are directly added, but in the Fenton like reaction, goethite, hematite, magnetite, etc. are added instead of iron ions to prevent sludge and byproducts, which are a conventional problem, and are semipermanent. There is an advantage to use. The mechanism of pseudofenton reaction is as follows (Electron transfer in Fenton like reaction (Moura et al, 2005)).

However, in spite of the efficiency of the Fenton reaction, the present invention is to provide an iron structure for the Fenton oxidation catalyst having a new structure to solve the low economic efficiency compared to the efficiency.

In addition, the iron structure for the fenton oxidation catalyst according to the present invention is an immobilized fenton reaction in the form of a plate, characterized in that the control of the catalyst is easy and can be reused.

Hereinafter, the present invention will be described in more detail.

The iron structure for fenton oxidation treatment of wastewater according to the present invention, as shown in Figure 1, the nanostructure of ferric oxide (Fe ₂ O ₃ ) is formed on the surface of the plate (plate) made of ductile iron (Fe ⁰ ) It is characterized by being.

This novel structure can be produced by forming a nanostructure of ferric oxide (Fe ₂ O ₃ ) on the surface through an anodization process and an annealing process using an iron plate as an anode.

In the nanostructure of ferric oxide (Fe ₂ O ₃ ) on the surface, the quasi-Fenton reaction with hydrogen peroxide is carried out, characterized in that the organic pollutants in the wastewater can be treated by OH radicals.

In addition, the quasi-Fenton reaction is continuously performed by continuously supplying electrons to the nanostructure of the surface in the plate made of ductile iron.

That is, after oxidizing Fe ²⁺ to Fe ³⁺ in the Fenton-like reaction on the surface, the regeneration problem is reduced by Fe ³⁺ to Fe ²⁺ due to the electron transfer by the non-ferrous iron present in the plate. Promote

In addition, the iron structure for fenton oxidation treatment according to the present invention to form a nano-structured structure having a high surface area on the surface of the iron catalyst to efficiently perform the Fenton reaction on the plate of iron iron to fix the iron catalyst to react It is called Immobilized Fenton Reaction, which is easy to control.

In addition, the nanostructure of the ferric oxide has a nano-leaf (Nano-leaf) shape, the nano-leaf (Nano-leaf) shape is graphene-like form (grphen-like) or surface shape (aspect ratio of 1 Close to the shape of the shape having a leaf shape such as an irregular wire (wire), and more specifically, it can be confirmed in FIGS. 3A and 3B below.

In addition, the surface is hematite of ferric oxide (hematite), the plate is characterized in that the ferric iron (Fe ⁰ ).

Another aspect of the invention relates to a method for producing an iron structure for fenton oxidation treatment of wastewater comprising the following steps.

(a) immersing a ferrous iron (Fe ⁰ ) plate in a mixed electrolyte solution of sodium sulfate (Na ₂ SO ₄ ) and sodium fluoride (NaF), and then applying power so that the non-ferrous iron plate becomes a positive electrode;

(b) continuing the anodic oxidation step of step (a) to oxidize the non-ferrous iron surface;

(c) annealing the surface of the oxidized zero iron plate.

According to an embodiment of the present invention, power may be applied at a voltage of 10-15 V in step (a), preferably 12 V voltage.

When applying a voltage of less than 10 V may cause a problem of lowering the oxidation degree when anodizing, and when applying a voltage of more than 15 V, iron nanostructures may be damaged by heat generation, so penton oxidation When preparing the iron nanostructures for treatment, all of the above conditions must be satisfied.

In addition, when the anodization, the reaction time may be 2-5 hours, when the reaction time is out of the range, there is a problem in the production of nanocrystalline form in the process of forming the ferric oxide (FeO) crystal form by anodization There may be a problem that the amorphous form is generated and the Fenton processing efficiency is lowered.

On the other hand, the surface of the anodized plate in step (b) is characterized in that the ferrous oxide (FeO) of the wustite crystal structure (FeO), the surface of the plate annealed in the step (c) is hematite (hematite) Ferric oxide (Fe ₂ O ₃ ) having a crystal structure.

Another aspect of the present invention relates to a wastewater treatment method comprising the following steps using the iron structure for fenton oxidation treatment according to the present invention.

(a) preparing wastewater,

(b) injecting hydrogen peroxide and the iron structure for fenton oxidation treatment according to the present invention into the waste water.

On the other hand, the pseudo-fentone reaction occurs in the surface nanostructure of the iron structure for fenton oxidation treatment, it is characterized in that the oxidation of the organic material contained in the wastewater.

In addition, the electron is continuously supplied to the surface from the plate of the iron structure for fenton oxidation treatment.

Wastewater treatment method according to an embodiment of the present invention is to be carried out in the neutral state and pH 12 alkali conditions, and the iron sludge, the process was carried out at low conditions of pH 3-5, which is a problem in the conventional Fenton process It is possible to use semi-permanent use of iron catalyst and economical environmental treatment process is possible.

Hereinafter, the present invention will be described in more detail with reference to examples and the like, but the scope and contents of the present invention are not limited or interpreted by the following examples. In addition, if it is based on the disclosure of the present invention including the following examples, it will be apparent that those skilled in the art can easily carry out the present invention, the results of which are not specifically presented experimental results, these modifications and modifications are attached to the patent It goes without saying that it belongs to the claims.

Example 1

(1) The iron used in the present invention was 99.0% in purity, and an iron plate cut to a size of 40 mm to 100 mm was used to favor anodization and electroreduction. Chemical etching was performed to remove contaminants of the organic content on the iron plate surface, and hydrofluoric acid, nitric acid, and distilled water were mixed at a volume ratio of 1: 4: 5. The iron plate sample was immersed in the prepared solution for about 30 seconds, then taken out, and ultrasonically cleaned for about 20 minutes with distilled water. At this time, the chemical etching was not performed for more than 1 minute because metal defects or toxic gases may be generated due to hydrogen embrittlement.

(2) An anodization method was performed on the iron plate sample thus pretreated as shown in FIG. 9.

As an anodizing solution, an electrolyte containing 0.25 wt% NaF in Na ₂ SO ₄ 1 M was used. For the power supply to be supplied, anodization using EG electrolyte was carried out using a PNCYS EP1605 model, and anodization was performed by a constant voltage method with a fixed voltage of 12 V.

As shown in FIG. 9, an iron plate was used as the positive electrode, and 95% platinum or copper was dissolved as the negative electrode, and the metal plates were equilibrated at 5-8 cm intervals.

The temperature was maintained at 5 ° C. through cooling water, and the anodization time was fixed at 3 hours, after which the mixture was washed with distilled water and methanol and dried at 60 ° C. in an oven.

(3) The anodized iron plate was annealed again at about 750 ° C.

(4) In the case of anodizing the initial iron plate (Fe ⁰ ), the surface is changed to wustite (FeO), and after annealing, the surface is formed of hematite (Fe ₂ O ₃ ). do.

Comparative Examples 1 to 3

In the anodization process of Example 1 was carried out in the same manner except for adjusting the voltage to 4, 8, 16V instead of 12V.

Experimental Example 1

As a result of analyzing the change of current with time during anodization, as shown in FIG. 2, when looking at the graph, the shape of the voltage current curve appearing in the general anodization step is shown in the case of 12 V as compared to 4 V, 8 V, and 16 V. It can be seen.

Through this current change pattern, the surface of the initial iron plate is changed to iron oxide in the form of nanostructure through anodization at 12V.

Experimental Example 2

3A and 3B are scanning microscope images showing a top-view and a bottom-view of an iron oxide structure formed on an iron plate surface according to Example 1, respectively, wherein the structure formed according to the present invention has a graphene-like shape (grphen- It is in the form of a nano laef with a leaf shape such as an irregular wire having a like or face shape (aspect ratio close to 1).

Experimental Example 3

The crystal form of the iron structure formed on the surface of the iron plate produced according to the present invention was confirmed through an XRD graph, and analyzed through Crystal Impact Match. The results are shown in FIG. 4.

As shown in Figure 4, the initial iron plate is a ferrous iron (Fe ⁰ , raw iron), the surface is changed to wustite (FeO (ferrous oxide)) after the anodization process, and then annealing process After passing through the surface, hematite (hematite, Fe ₂ O ₃ (ferric oxide)) can be confirmed that the change.

Experimental Example 4

The exterior image of the iron structure manufactured by the anodization process of Example 1 is as shown in Figure 5a, after which the exterior image of the iron structure undergoes an annealing process is shown in Figure 5b.

After anodization, it is dark green, and after annealing at 750 ° C, it is reddish (hematite).

Experimental Example 5

(1) Fenton experiment was performed on cyanide (plating wastewater), and pH was adjusted to 12 to prevent volatilization into HCN.

First, cyanide oxidation was carried out using only hydrogen peroxide (Daejung Chemical, purity 30%), and distilled water was used instead of hydrogen peroxide as a control experiment. The results are shown in Figure 6a below.

In FIG. 6A, silver control, silver H ₂ O ₂ 29.4 mM, silver H ₂ O ₂ 147 mM, silver H ₂ O ₂ 294 mM, silver H ₂ O ₂ 882 mM, and for each cyanide removal The primary rate constants are 5.1 × 10 ⁻⁴ (29.4 mM), 1.0 × 10 ⁻³ (147 mM), 2.1 × 10 ⁻³ (294 mM), 5.2 × 10 ⁻³ (882 mM).

When only 882 mM hydrogen peroxide was used, the cyanide compound was reduced to 80% after 360 minutes.

(2) Next, cyanide oxidation was performed using commercial iron catalyst powder in powder form with hydrogen peroxide. Distilled water was used instead of hydrogen peroxide as a control experiment. The results are shown in Figure 6b below.

In FIG. 6B, silver control, silver H ₂ O ₂ 29.4 mM, silver H ₂ O ₂ 147 mM, silver H ₂ O ₂ 294 mM, silver H ₂ O ₂ 882 mM, and for each cyanide removal The primary rate constants are 1.0 × 10 ⁻³ (29.4 mM), 3.0 × 10 ⁻³ (147 mM), 6.0 × 10 ⁻³ (294 mM), 1.2 × 10 ⁻² (882 mM).

The baseline was met after 360 minutes with commercial iron catalyst powder (0.9 g) with 882 mM hydrogen peroxide.

(3) Next, the cyanation reaction was carried out using the iron catalyst for fenton oxidation treatment including the nano-leaf structure according to the present invention, and distilled water was used instead of hydrogen peroxide as a control experiment. The results are shown in Figure 6c below.

In FIG. 6C, silver control, silver H ₂ O ₂ 29.4 mM, silver H ₂ O ₂ 147 mM, silver H ₂ O ₂ 294 mM, silver H ₂ O ₂ 882 mM, for each cyanide removal The primary ratio constants are 3.0 × 10 ⁻⁴ (29.4 mM), 4.0 × 10 ⁻³ (147 mM), 1.0 × 10 ⁻³ (294 mM), 1.7 × 10 ⁻² (882 mM).

When the iron catalyst (0.9 g) according to the present invention with hydrogen peroxide 882 mM was used, the reference value was satisfied after 180 minutes.

The reaction time was shortened by half compared with the case of using the commercial iron catalyst powder of (2).

Experimental Example 6

Next, the sample was collected from the Hamyang Livestock Wastewater Treatment Plant, and after the precipitation and dehydration process, the experiment was carried out using the filtrate, and refrigerated after storage to minimize the change in appearance.

For the preparation of the aqueous solution used in all experiments using distilled water purified to 18 m 수 -cm using a millipore system, 1 NH ₂ SO ₄ and 10 N NaOH was used as a solution for adjusting the pH.

Each experiment was conducted in a batch reactor and the solution was stirred evenly using a magnetic bar. The amount of organic matter after the reaction was measured using a total organic analyzer (Multi N / C 3100, analyticjena). In addition, the zeolite used in this experiment was purchased by using a zeolite manufactured by Wako, Japan, and the particle size of the zeolite has a size of 75 ㎛ (200 mesh). The concentration of ammonium ions was analyzed by ion-selective electrode (ISE, Neonet Dual pH meter) method, and ionic strength adjuster (ISA) was used to remove other interferences and maintain ionic strength at a constant and high value.

The livestock wastewater was treated with Fenton using 1 g of iron catalyst for fenton oxidation according to the present invention (hydrogen peroxide was fixed at 3% in the previous experiment), and the total efficiency was 80% in 60 minutes. Hematite showed 70% treatment efficiency. In the case of TOC, since the oxidized amount of organic matter is measured, it is possible to perform a complete treatment if the efficiency is 70% or more, and the iron catalyst for fenton oxidation treatment according to the present invention shows much higher efficiency than general hematite treatment. appear.

In addition, as shown in FIG. 7, ammonia nitrogen treatment efficiency was measured using zeolite in order to treat ammonia nitrogen. As a result, when 1 g of zeolite was used, the reaction efficiency was 90% at 45 minutes. When a larger amount of zeolite was added, ammonia nitrogen increased by desorption after 45 minutes.

Furthermore, as shown in FIG. 8, it is a photograph of the result of the last treatment before a livestock wastewater treatment and even ammonia nitrogen. After high turbidity was filtered to zeolite, it was confirmed that the result was a very transparent form.

The iron structure for the fenton oxidation catalyst and the wastewater treatment process using the same according to the present invention are not only excellent in fenton oxidation treatment efficiency, do not generate iron sludge, and can be used semi-permanently, which is useful for environmental treatment process industries such as wastewater treatment. Can be utilized.

Claims (11)

1. In the iron structure for fenton oxidation treatment of wastewater formed by anodization,

   The iron structure is iron structure for fenton oxidation treatment of wastewater, characterized in that the nanostructure of ferric oxide (Fe ₂ O ₃ ) is formed on the surface of the plate made of ductile iron (Fe ⁰ ).
2. The method of claim 1,

   Fenton like reaction occurs on the surface of the iron structure, the iron structure for fenton oxidation treatment of the waste water, characterized in that the electron is supplied to the surface from a plate made of iron.
3. The method of claim 1,

   The ferric oxide nanostructure of the ferric oxide has a nano-leaf (Nano-leaf) shape, characterized in that the iron structure for fenton oxidation treatment.
4. The method of claim 1,

   The ferric oxide nanostructure is a hematite (hematite) crystal structure of the iron structure for fenton oxidation treatment of waste water.
5. (a) immersing a ferrous iron (Fe ⁰ ) plate in a mixed electrolyte solution of sodium sulfate (Na ₂ SO ₄ ) and sodium fluoride (NaF), and then applying power so that the non-ferrous iron plate becomes a positive electrode;

   (b) continuing the anodic oxidation step of step (a) to oxidize the non-ferrous plate surface; And

   and (c) annealing the surface of the oxidized zero duct iron plate.
6. The method of claim 5,

   The method of manufacturing the iron structure for fenton oxidation treatment of wastewater, characterized in that the power is applied at a voltage of 10-15V in step (a).
7. The method of claim 5,

   The surface of the anodized plate in the step (b) is a method for producing an iron structure for fenton oxidation treatment of waste water, characterized in that the ferrous oxide (FeO) of the wustite crystal structure (FeO).
8. The method of claim 5,

   The surface of the plate annealed in the step (c) is a ferric oxide (Fe ₂ O ₃ ) of hematite crystal structure (Fe ₂ O ₃ ) The method for producing an iron structure for fenton oxidation treatment of waste water.
9. Preparing wastewater; And

   And injecting hydrogen peroxide and the iron structure for fenton oxidation treatment into the wastewater.
10. The method of claim 9,

    The quasi-Fenton reaction occurs in the iron structure for fenton oxidation treatment, through which the organic matter contained in the wastewater is oxidized.
11. The method of claim 9,

    Waste water treatment method characterized in that the electron is continuously supplied to the surface from the plate of the iron structure for fenton oxidation treatment.

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