KR20120115939A - Method for purifying sewage-pollution water using zero valent iron/magnetite mixture - Google Patents

Abstract

PURPOSE: A sewage and wastewater treatment method is provided to shorten times needed for the entire treatment processes by collecting iron sludge and magnetite using magnetism. CONSTITUTION: A sewage and wastewater treatment method includes a process in which a fenton oxidation process is implemented using a mixed catalyst containing zerovalent iron and magnetite at the weight ratio of 1:3 to 1:4.5. The zerovalent iron and the magnetite are simultaneously introduced to implement the fenton oxidation process. Sludge generated from the fenton oxidation process is magnetism-based separated using an electromagnet.

Description

Method for purifying sewage using mixed catalysts of ferrous iron and magnetite {Method for purifying sewage-pollution water using zero valent iron / magnetite mixture}

The present invention relates to a wastewater treatment method using a fenton oxidation process, and more particularly, to a method for effectively and quickly treating wastewater using a mixed catalyst of ductile iron and magnetite.

H.J.H. The Fenton reaction, discovered by Fenton (1984), is still widely used in oxidation processes. The hydroxy radicals (OH), presented by Haber and Weiss (1934) as main oxidants in the Fenton reaction, basically occur in the following equation.

^{_{Fe 2 + + H 2 O 2}} → Fe 3 + + OH + OH - (1)

The hydroxy radical (OH) is a powerful oxidant, the reference redox potential (E °) is -2.8 Volts, and the rate of reaction of the hydroxy radical with other organic compounds is about 10 ^{9-10 10} mol ^-1 sec ^-1 . (Haag and Yao, 1992). When the organic compounds are present together, the hydroxy radicals can undergo a H abstraction reaction or an electrophilic addition reaction. The hydroxy radicals therefore have the ability to oxidize harmful organic compounds including nitrogen substituted aromatics, chlorinated aromatics, alkenes and aliphatic compounds.

The invention related to the method of using the iron oxide catalyst in the fenton oxidation process is related to the Korean Patent Registration No. 10-0495765 in the method for producing an iron oxide catalyst effective for fenton oxidation treatment, by treating the ionic iron with an alkali chemicals iron hydroxide After the preparation is described a method for producing an iron oxide catalyst for fenton oxidation treatment, which is calcined for 2 to 8 hours at a temperature between 100 to 1000 ℃, it is difficult to decompose using the iron oxide catalyst prepared by Disclosed is a method for treating wastewater or drinking water containing organic matter.

In addition, Korean Patent No. 10-0168280 discloses a method for treating a Fenton inorganic sludge generated in the Fenton treatment process of difficult-decomposable wastewater.

Usually the oxidizing effect of fenton is known to be the strongest when the pH is around 3.5. Conventional Fenton advanced oxidation treatment process can be divided into pH control, neutralization process, coagulation process, and precipitation process, and a large amount of iron sludge is generated in the neutralization process. As a result, there is a disadvantage in that the space and the residence time of the waste water increase. In particular, the problems caused by this conventional treatment technique is the fact that a large amount of iron sludge is generated and the iron color can be caused by the iron ions generated by the iron catalyst. Therefore, the development of wastewater treatment method that can solve this problem is required.

It is an object of the present invention to effectively reduce the iron color generated by the iron catalyst while maintaining the efficiency of the existing Fenton reaction, by using a mixed catalyst of ductile iron and magnetite, and also iron sludge adsorbed using magnetite magnetite It is to provide an effective wastewater treatment method which is easy to separate and reduces the total treatment time.

In order to solve the above technical problem, the present invention provides a wastewater treatment method comprising the step of performing a phenton oxidation reaction using a mixed catalyst containing a ductile iron and magnetite in a weight ratio of 1: 3 to 1: 4.5.

According to one embodiment of the present invention, it is preferable to perform a phenton oxidation reaction by simultaneously adding a duct iron and magnetite.

In addition, according to an embodiment of the present invention, the method may further include magnetic separation of the sludge produced after the Fenton oxidation reaction of the mixed catalyst, the magnetic separation may be performed using an electromagnet.

Using a mixed catalyst of ductile iron and magnetite according to the present invention can effectively reduce the color (iron ions and residual iron hydroxide) generated by the iron catalyst while maintaining the efficiency of the existing Fenton reaction. In addition, iron hydroxides produced by the Fenton reaction are adsorbed onto the magnetite surface little by little, and both iron sludge and magnetite can be recovered using magnetism. This eliminates the need for agglomeration and sedimentation tanks for iron sludge treatment following the fenton oxidation process and can significantly shorten the overall treatment time.

1 is a schematic diagram of a wastewater treatment apparatus according to the present invention.
2 is a graph showing the optimum mixing ratio of ductile iron and magnetite to reduce the iron color.
Figure 3 shows the results of X-ray diffraction (XRD) analysis of the iron catalysts used in the Fenton reaction, (a) pure magnetite, (b) pure ductile iron, (c) iron catalyst after the pentone reaction and (d) zero value After the iron / magnet mixed Fenton reaction, ●: magnetite, ○: permanent iron and ★: iron hydroxide.
Figure 4 is an oxidized decomposition picture of methyl orange by hourly Fenton reaction, from the left side of the sample (1), (2) control, (3), (4) simultaneous use of ferrous iron and magnetite, (5) ferric iron Fenton, (6 ) Indicates the case of zero iron.
5 is a graph showing (1) methyl orange oxidative decomposition results and (2) iron sludge generation amount according to each iron catalyst system.
6 is a sludge magnetic separation picture after the completion of the fenton oxidation reaction, from the left side (1) iron magnet sludge adsorption experiment by reacting the magnetite again after the reaction of the magnetite iron alone, (2) simultaneous use of the iron and magnetite from the initial reaction, (3 ) It shows the case of using iron catalyst for general Fenton (ferric chloride) and (4) using ferric iron alone.

The present invention will be described in more detail with reference to the following examples.

Wastewater treatment method according to the invention is characterized in that it comprises the step of performing a phenton oxidation reaction using a mixture containing a ductile iron and magnetite in a weight ratio of 1: 3 to 1: 4.5. According to one embodiment of the present invention, it is preferable to perform a phenton oxidation reaction by simultaneously adding a duct iron and magnetite.

In addition, according to one embodiment of the present invention, the method may further include a magnetic separation of the sludge produced after the fenton oxidation of the mixture, the magnetic separation may be performed using an electromagnet.

Example

In the present invention, the reagent was used at the same time the commercial iron powder (Acros co.) Of less than 325 mesh (<44 ㎛) and magnetite powder (Sigma co.) Of less than 5 ㎛ and the pH was adjusted using sodium hydroxide and sulfuric acid. . Hydrogen peroxide was added to start the Fenton reaction. Methyl orange was chosen as the target pollutant.

As a comparison condition, we proceeded with fenton oxidation using only ferrous iron and mixed fenton oxidation using magnetite and noble iron simultaneously. At this time, the amount of fruit was carried out under the same conditions.

Example 1 Determination of Mixed Ratio of Young's Iron and Magnetite

To determine the optimal mixing ratio of ferrous and magnetite to reduce iron color, add 0.1 g of ferrous iron and 0.01 g to 0.6 g of magnetite in an experimental 200 mL photosphere bottle and add 23 μM hydrogen peroxide. Was carried out. Table 1 below shows the results of experiments to determine the ratio of the mixed iron and magnetite.

Young's Iron Weight (mg) Hydrogen Peroxide Concentration (μM) Magnetite weight (mg) Suspended solids concentration (mg / L) Total dissolved iron ion concentration
(mg / L) 100 23 0 9.23 14.2 100 23 10 7.59 14.3 100 23 20 5.17 13.7 100 23 100 2.31 13.9 100 23 200 0.60 13.7 100 23 300 0.07 13.8 100 23 400 0.02 13.7 100 23 500 0.20 13.5 100 23 600 0.40 14.2

Table 1 shows the results of experiments on the determination of the mixed ratio of ductile iron and magnetite. The total dissolved iron ion concentration in all conditions ranged from 13.5 mg / L to 14.3 mg / L, with an average of 13.90 ± 0.26 mg / L, showing similar results. The results show that increasing the magnetite weight range from 0.1 g to 0.6 g does not affect the total dissolved iron ion concentration. In addition, as the weight of magnetite increased to 0.4g, the concentration of suspended solids as a result of Fenton's reaction continuously decreased. When the weight of magnetite was 0.5g and 0.6g, the concentration of suspended solids increased. Therefore, the result showing the optimum suspended matter reduction was confirmed that the iron color is significantly reduced when the mixing ratio of iron and magnetite is 1: 3 to 1: 4.5 weight ratio.

Example 2: Fenton comparison experiment between various iron catalysts

Methane was used as a contaminant for the comparison of Fenton's oxidation using the ferrous iron alone, Fenton's oxidation system using the ferrous iron / magnet mixture system, and the Fenton's oxidation reaction using common iron salts. . At this time, the pollutant removal concentration was measured by using an absorbance spectrophotometer, and the amount of iron hydroxide produced was measured by comparing the mass filtered by the 0.45 μm membrane using a suspended matter measuring device. Figure 3 shows the results of X-ray diffraction (XRD) analysis of the iron catalysts used in the Fenton reaction, (a) pure magnetite, (b) pure ductile iron, (c) iron catalyst after the pentone reaction and (d) zero value After the iron / magnet mixed Fenton reaction, ●: magnetite, ○: permanent iron and ★: iron hydroxide. (c) After the Fenton reaction, the intensity of the iron pick was significantly reduced compared to that of the pure iron, and the magnetite pick was also generated. This result shows that the ductile oxide finally turns into magnetite as a result of fenton oxidation using the ductile iron. (d) After the mixed ferrite / magnetite Fenton reaction, the pick of the ferrite and magnetite coexisted.

Example 3 Magnetic Recovery Experiment of Iron Sludge

After the removal of contaminants using only zero iron, the magnetite addition test and the simultaneous addition of magnetite and magnetite were performed to compare the magnetic recovery after the Fenton reaction. As a control, magnetic recovery after mixing and reacting magnetite and hydrogen peroxide. Through this experiment, it is possible to determine the point of addition of magnetite when using the magnetite / magnetite mixing system, and to determine the adsorption of iron hydroxide by magnetite. Figure 4 is an oxidized decomposition picture of methyl orange by hourly Fenton reaction, from the left side of the sample (1), (2) control, (3), (4) simultaneous use of ferrous iron and magnetite, (5) ferric iron Fenton, (6 ) Indicates the case of zero iron. Experiments were carried out while controlling the concentrations of ferrous iron, magnetite, and hydrogen peroxide.

division (One) (2) (3) (4) (5) (6) Young's Iron Weight (g) 0 0 0.1 0.1 0.1 0.1 Magnetite Weight (g) 0.462 0.462 0.462 0.462 0 0 Hydrogen Peroxide Concentration (μM) 57.6 28.8 57.6 28.8 28.8 0

In the controls (1) and (2) without adding iron, the reaction did not occur sufficiently with magnetite alone, and the reaction proceeded from the conditions (3) to (6) where the iron was present. Under conditions (6) where zero iron is present and no fruit is present, it can be seen that the reaction occurs very slowly, and after 45 minutes, the methyl orange concentration is no longer decomposed. (5) In the presence of only zero iron and hydrogen peroxide, methyl orange decomposition was completed 5 minutes after the start of the reaction, but after the completion of the reaction, iron color began to appear, and 45 minutes later, a large amount of dissolved substance (iron color) was produced. In the case of Fenton reaction after co-addition of ferrous iron and magnetite, the experiment with 57.6 μM hydrogen peroxide concentration was slower than the experiment with 28.8 μM hydrogen peroxide concentration. In the Fenton oxidation experiment, it is well known that a large amount of hydrogen peroxide acts as a scavenger in the experiment. Therefore, finding a suitable peroxide concentration in the Fenton experiment is a meaningful result. Therefore, the optimum conditions in this experiment were confirmed that the reaction rate and iron color removal are surely ensured at 100 mg of iron, 462 mg of magnetite, and 23 μM of hydrogen peroxide for 10 mg / L of methyl orange. Accordingly, it can be seen that the iron color is sufficiently removed even when the weight ratio of ductile iron and magnetite is 1: 4.5.

FIG. 5 is a graph summarizing the cases of (4), (5) and (6) among the experimental results of FIG. 4 and shows a reaction time up to 180 minutes. When only zero iron is present without hydrogen peroxide, the reaction rate of methyl orange drops markedly, and after the end of the reaction, iron color starts to appear. The reaction rate is guaranteed when there are only zero iron and hydrogen peroxide, but the iron color starts to appear after the completion of the reaction, which causes problems in practicality. However, if the magnetite is included, the reaction rate is guaranteed, and after completion of the reaction, the iron color was confirmed to inhibit the expression.

Figure 6 is a sludge magnetic separation picture after the completion of the fenton oxidation reaction, from the left side (1) iron sludge adsorption experiment by reacting magnetite again after the reaction of the magnetite iron alone (2) simultaneous use from the beginning of the ferrous iron and magnetite reaction, (3) general Use of iron catalysts for Fenton (ferric chloride), (4) ferrous iron alone experiment. (1) The experiment was carried out to confirm the order of magnetite in the wastewater treatment process. When magnetite is added after completion of the reaction, the iron color tends to be removed 60%, but the efficiency is lower than that of (2), which is the same as when iron and magnetite are used at the same time, and ferric chloride, a common Fenton iron catalyst. And it can be confirmed that the iron can not be separated magnetically when the iron is used alone.

Claims (4)

Wastewater treatment method comprising the step of performing a fenton oxidation reaction using a mixed catalyst containing a duct iron and magnetite in a weight ratio of 1: 3 to 1: 4.5. The method of claim 1,
Wastewater treatment method characterized in that the phenton oxidation reaction is carried out by simultaneously adding the ferrous iron and magnetite. The method of claim 1,
And further separating the sludge produced after the phenton oxidation of the mixed catalyst. The method of claim 1,
The magnetic separation is a wastewater treatment method, characterized in that performed using an electromagnet.

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