KR101697848B1 - Method for manufacturing magnetic iron oxide and apparatus for removal and recovery of phosphate using the same - Google Patents

Abstract

The present invention relates to a method for producing magnetic iron powder and a method for removing and recovering phosphate from the magnetic iron powder. More particularly, the present invention relates to a method for easily and easily producing a magnetic iron powder having an excellent ability to adsorb and desorb phosphate, And more particularly, to an improved phosphate removal and recovery apparatus.
INDUSTRIAL APPLICABILITY According to the present invention, it is possible to easily produce a magnetic iron powder which is excellent in the adsorption and desorption ability of phosphate and can be reused and is useful in actual processes. In addition, when the magnetic iron powder is used in the apparatus for removing and recovering phosphate according to the present invention, high-purity phosphate can be secured and the recovered magnetic iron powder can be used repeatedly.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing magnetic iron powder and a method for removing and recovering phosphate from the same,

The present invention relates to a method for producing magnetic iron powder and a method for removing and recovering phosphate from the magnetic iron powder. More particularly, the present invention relates to a method for easily and easily producing a magnetic iron powder having an excellent ability to adsorb and desorb phosphate, And more particularly, to an improved phosphate removal and recovery apparatus.

The phosphorous obtained from the phosphate rock is used for various purposes not only in the raw materials of fertilizer but also in various fields such as medicines, semiconductors, ceramics, silk, fiber, insect repellent, sugar refining and explosives. Phosphorus is used in agricultural water, sewage, and livestock wastewater to be discharged into surrounding rivers and lakes, etc., and phosphorus compounds may also act as pollutants causing eutrophication. In many countries, such as Europe, Germany and Taiwan, regulations on phosphate additives have already been made or there is a consensus on the necessity of restriction.

Phosphorus used as a raw material of phosphor which is widely used as described above is currently being imported from China, Morocco and others all over the world. This can be sensitive to changes in the situation of foreign countries importing phosphate ore, and can affect the industry as a whole due to changes in the price of imported phosphate.

In Korea, recently, a method to improve TP (total phosphorous) management has been announced to improve the water quality of rivers and lakes, and various measures for phosphorus removal have been proposed. As a limiting factor of eutrophication, , The phosphorus concentration of effluent discharged from sewage and wastewater treatment plants is significantly reduced from 2.0 mg / L to 0.2 mg / L.

Under such circumstances, the need to efficiently remove phosphorus from wastewater and wastewater discharged to the surrounding water system and simultaneously recover it as a useful resource is increasing rapidly, and development of appropriate technology for it is required.

On the other hand, as a method for removing and recovering phosphorus in the water, ion exchange technology through struvite generation, phosphate-solubilizing fungi, or microorganisms, And biological methods. However, in general, a method of recovering phosphorus by using floating particles (mainly iron oxide particles) is widely used to adsorb phosphorus. However, this method has a disadvantage in that the iron oxide particles used after the adsorption of phosphorus have to be separated and recovered, so that the related costs are increased and the maintenance is difficult. In addition, magnetism is required to recover the iron oxide particles used. ) Particles have difficulty and troublesome to make magnetite (Fe ₃ O ₄ ) having magnetism.

On the other hand, Korean Patent No. 10-0684629 discloses a method for producing magnetite powder, but it has a disadvantage in that it is not excellent in adsorption and desorption ability of phosphate, and thus it is not enough to commercialize it in the removal and recovery process of actual phosphate.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for easily and easily producing a magnetite powder excellent in the ability of adsorbing and desorbing phosphate and an improved phosphate removal and recovery apparatus for further improving the efficiency of the magnetic iron powder .

In order to solve the above problems,

(a) preparing a mixed solution of FeCl ₂ .4H ₂ O and Fe (NO ₃ ) ₃ .9H ₂ O in a nitrogen atmosphere; (b) adjusting the pH of the mixed solution to pH 7-8 with NaOH to obtain a precipitate; (c) separating the precipitate from the mixed solution, washing with distilled water and drying; And (d) pulverizing the dried precipitate. The present invention also provides a method for producing a magnetic iron powder.

According to an embodiment of the present invention, the molar concentration ratio of FeCl ₂ .4H ₂ O and Fe (NO ₃ ) ₃ .9H ₂ O may be 1: 0.05-0.2.

According to another embodiment of the present invention, the molar concentration of FeCl ₂ .4H ₂ O is 0.2-0.4M, the molar concentration of Fe (NO ₃ ) ₃ .9H ₂ O is 0.01-0.08M, the molar concentration of NaOH Lt; / RTI >

According to another embodiment of the present invention, the washing in the step (c) is carried out 5 to 15 times, and the drying may be carried out at 60 to 80 ° C.

(A) preparing a mixed solution of FeSO ₄ .7H ₂ O and FeCl ₃ .6H ₂ O; (b) adding NaOH to the mixed solution to titrate the pH to 8-10, thereby obtaining a precipitate through coprecipitation reaction; (c) separating the precipitate, washing with distilled water and drying; And (d) pulverizing the dried precipitate. The present invention also provides a method for producing a magnetic iron powder.

According to an embodiment of the present invention, the molar concentration ratio of FeSO ₄ .7H ₂ O and FeCl ₃ .6H ₂ O may be 1: 1-3.

According to another embodiment of the present invention, the molar concentration of FeSO ₄ .7H ₂ O is 0.5-1.5M, the molar concentration of FeCl ₃ .6H ₂ O is 0.5-4.5M, the molar concentration of NaOH is 5-7M Lt; / RTI >

According to another embodiment of the present invention, the washing in the step (c) is carried out 5 to 15 times, and the drying may be carried out at 60 to 80 ° C.

The present invention also relates to a method for producing a ferrite-containing iron-containing waste water comprising a first inlet through which waste water containing phosphate is introduced, a second inlet through which the magnetic iron powder is introduced, a stirrer for mixing the magnetic iron powder with the waste water containing the phosphate, A membrane filtration tank for filtering and concentrating the chelating complex of the powder, and a first discharge portion for discharging the treated water filtered by the membrane filtration tank; A desorption tank including a third inlet through which the desorption solution flows, a second outlet through which the phosphate concentrated water drains, and an adsorption member to which the magnetic iron powder adheres; A connection pipe for allowing the mixed water, which is condensed by the membrane filtration tank and discharged from the adsorption tank, to flow into the desorption tank; And a magnetic iron powder storage tank for recovering the magnetic iron powder from the desorption bath and introducing the magnetic iron powder into the adsorption bath.

According to an embodiment of the present invention, in the adsorption tank, the phosphate contained in the inflow wastewater and the inflow magnetic iron powder may form a chelating complex by electrostatic attraction.

According to another embodiment of the present invention, in the desorption tank, the mixed water flowing through the connection pipe reacts with the desorption solution to separate the phosphate and the magnetic iron powder.

According to another embodiment of the present invention, the wastewater containing phosphate may be an anaerobic digestion decantation treated with ammonia stripping.

According to another embodiment of the present invention, the desorption solution may be NaOH aqueous solution, NaCl aqueous solution, or a mixed solution thereof.

According to another embodiment of the present invention, the desorption solution may be 20 wt% NaOH aqueous solution.

According to another embodiment of the present invention, the rotation speed of the agitator may be 50-300 rpm.

According to another embodiment of the present invention, the adsorption member may be an immersion type electromagnet.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to easily produce a magnetic iron powder which is excellent in the adsorption and desorption ability of phosphate and can be reused and is useful in actual processes.

In addition, when the magnetic iron powder is used in the apparatus for removing and recovering phosphate according to the present invention, high-purity phosphate can be secured and the recovered magnetic iron powder can be used repeatedly.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process flow chart showing a method for producing magnetic iron powder according to Example 1. FIG.
FIG. 2 is a process flow chart showing a method for producing magnetic iron powder according to Example 2. FIG.
3 is a schematic diagram of an apparatus for removing and recovering phosphate according to the present invention.
4 is a graph showing particle size distribution results of magnetic iron powder prepared according to Example 2 according to ultrasonic treatment time.
5 is a graph showing the XRD analysis results of the magnetic iron powder produced according to Example 2. Fig.
6 is a graph showing adsorption amounts of phosphate of magnetic iron powder prepared according to Example 1, Example 2, Comparative Example 1 and Comparative Example 2. FIG.
7 is a graph showing the removal ratios of phosphate of magnetic iron powder prepared according to Example 1, Example 2, Comparative Example 1 and Comparative Example 2. FIG.
8 is a graph showing the amount of phosphate adsorbed by the reaction time of the magnetic iron powder prepared according to Example 2. FIG.
FIG. 9 is a graph showing the removal rate of phosphate according to the reaction time of the magnetic iron powder produced according to Example 2. FIG.
FIG. 10 is a graph showing the amount of phosphorus powder adsorbed according to the input amount and pH of the magnetic iron powder produced according to Example 2. FIG.
11 is a graph showing the input amount of the magnetic iron powder produced according to Example 2 and the removal rate of phosphate according to pH change.
12 is a graph showing the adsorption amount of magnetic iron powder prepared according to Example 2 according to the concentration of phosphate.
13 is a graph showing removal ratios of magnetic iron powder prepared according to Example 2 according to the concentration of phosphate.
14 is a graph showing the adsorption amount of the magnetic iron powder prepared according to Example 2 according to the concentration and time of the phosphate solution.
15 is a graph showing the removal rate of the magnetic iron powder prepared according to Example 2 according to the concentration and time of the phosphate solution.
16 is a graph showing the adsorption amount of phosphate according to the presence of coexisting anions of the magnetic iron powder prepared according to Example 2. FIG.
FIG. 17 is a graph showing the removal rate of phosphate according to the presence of coexisting anions of the magnetic iron powder produced according to Example 2. FIG.
18 is a graph showing the desorption amount of phosphate depending on the type of the desorption solution of the magnetic iron powder produced according to Example 2. FIG.
19 is a graph showing the desorption rate of phosphate depending on the type of the desorption solution of the magnetic iron powder produced according to Example 2. FIG.
FIG. 20 is a graph showing the adsorption amount of phosphate according to the number of times of re-use of the magnetic iron powder produced according to Example 2. FIG.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

The present invention relates to an apparatus for easily and easily producing a magnetic iron powder (Fe ₃ O ₄ ) excellent in the ability to adsorb and desorb phosphate and, further, to remove and recover phosphates using the same.

Accordingly, the method of manufacturing a magnetic iron powder according to an embodiment of the present invention comprises the following steps.

(a) preparing a mixed solution of FeCl ₂ .4H ₂ O and Fe (NO ₃ ) ₃ .9H ₂ O in a nitrogen atmosphere; (b) adjusting the pH of the mixed solution to pH 7-8 with NaOH to obtain a precipitate; (c) separating the precipitate from the mixed solution, washing with distilled water and drying; And (d) pulverizing the dried precipitate;

Referring to FIG. 1, the method of manufacturing magnetic iron powder according to the present invention will be described step by step.

First, in step (a), FeCl ₂ .4H ₂ O, which is a ferric chloride precursor, and Fe (NO ₃ ) ₃ .9H ₂ O, which is a precursor of iron nitrate, are mixed with distilled water Mix. The above step is preferably carried out in a nitrogen atmosphere by performing nitrogen purging in order to prevent oxidation due to excessive oxygen supply. The molar concentration ratio of FeCl ₂ .4H ₂ O and Fe (NO ₃ ) ₃ .9H ₂ O is preferably 1: 0.05-0.2. When the molarity ratio is less than 1: 0.05, reduction of the magnetite yield is problematic. When the molarity ratio is more than 1: 0.2, excess ions of Fe (NO ₃ ) ₃ .9H ₂ O reagent are increased There is a problem that the number of times of washing must be increased. The molar concentration of FeCl ₂ .4H ₂ O is preferably 0.2-0.4M, and the molar concentration of Fe (NO ₃ ) ₃ .9H ₂ O is preferably 0.01-0.08M.

Next, in the step (b), the prepared mixed solution is adjusted to pH 7-8 using NaOH to obtain a precipitate. If the pH is lower than the lower limit, there is a problem that black particles of magnesium are not formed and stopped in the midst of the synthesis process, so that magnetite is not formed. If the pH is above the upper limit, NaOH is injected even after the completion of the magnetite synthesis, Can be a problem. After the step (b), a mixed solution in which magnetic iron is present as a precipitate in a liquid phase is prepared. The molar concentration of NaOH is preferably 1.5-3 M.

Next, in step (c), precipitates present in the liquid dispersion state in the mixed solution are separated, washed with distilled water and dried to obtain magnetic iron particles. At this time, the precipitate has magnetism and is separated by using an electromagnet. It is also preferred that the distilled water is washed 5 to 15 times. In the case of less than the lower limit value, detection of a large amount of residual ions is problematic. If the upper limit value is exceeded, oxidation of the magnetite may be problematic due to excessive oxygen supply. In addition, it is preferable that the drying is performed at 60-80 占 폚. If it is less than the lower limit value, there is a fear that it is not completely dried, and when it exceeds the upper limit value, it is economically meaningless.

Finally, in the step (d), the dried precipitate, that is, the magnetic iron particles are pulverized to obtain a powdered magnetic iron. At this time, in order to obtain micro-sized magnetic iron powder which is easy to apply in an actual process, it is preferable that the pulverization is pulverized using a mortar bowl.

Further, a method of manufacturing a magnetic iron powder according to an embodiment of the present invention includes the following steps.

(a) preparing a mixed solution of FeSO ₄ .7H ₂ O and FeCl ₃ .6H ₂ O; Adding NaOH to the mixed solution to titrate the pH to 8-10 to obtain a precipitate through coprecipitation reaction; (c) separating the precipitate, washing with distilled water and drying; And (d) pulverizing the dried precipitate;

Referring to FIG. 2, the process for producing magnetic iron powder according to the present invention will be described step by step.

First, in the step (a), FeSO ₄ .7H ₂ O and FeCl ₃ .6H ₂ O are specifically mixed as a raw material mixing step. At this time, it is preferable that the molar concentration ratio of FeSO ₄ .7H ₂ O and FeCl ₃ .6H ₂ O is 1: 1-3. The molar concentration ratio is 1: 1 is less than had a problem not being able to obtain a sufficient amount of the chair Seongcheol, the molar concentration ratio of 1: if it exceeds 3, FeCl ₃ and 6H remaining by over-injection of ₂ O Cl ^- There is a problem that ions are increased. In addition, the molar concentration of the FeSO ₄ 7H ₂ O and the molar concentration was 0.5-1.5M, FeCl ₃ 6H ₂ O and a is preferably 0.5-4.5M.

Next, in step (b), NaOH is added to the mixed solution to titrate the pH to 8-10, and a precipitate is obtained through coprecipitation reaction. When the molar concentration is less than the lower limit, there is a problem that a large amount of NaOH aqueous solution must be introduced. If the molar concentration exceeds the upper limit value, the NaOH aqueous solution is excessively charged There is a problem that the number of times of washing can be increased.

Next, in the step (c), the precipitate of the magnetic iron particles precipitated through the coprecipitation reaction in the step (b) is removed by attaching the precipitate to the electromagnet after removing the supernatant of the mixed solution. Thereafter, the separated precipitate is washed with distilled water and dried to obtain magnetic iron particles. The washing of the distilled water is preferably carried out by repeating 5 to 15 times. In the case of less than the lower limit value, detection of a large amount of residual ions is problematic. When the upper limit value is exceeded, oxidation of the magnetite may become problematic due to a longer contact time with oxygen having high reactivity due to excessive oxygen supply. In addition, it is preferable that the drying is performed at 60-80 占 폚. If it is less than the lower limit value, there is a fear that it is not completely dried, and when it exceeds the upper limit value, it is economically meaningless.

Finally, in the step (d), the dried precipitate, that is, the magnetic iron particles are pulverized to obtain a powdered magnetic iron. At this time, in order to obtain micro-sized magnetic iron powder which is easy to apply in an actual process, it is preferable that the pulverization is pulverized using a mortar bowl.

In addition, the present invention provides an apparatus for removing and recovering phosphate as shown in FIG. 3 in order to efficiently use the magnetic iron powder.

3, the apparatus for removing and recovering phosphorus for using the magnetic iron powder of the present invention comprises a first inlet 111 through which wastewater containing phosphate is introduced, a second inlet 112 through which the magnetic iron powder is introduced ), A stirrer 113 for mixing the phosphate-containing wastewater with the magnetic iron powder, a membrane filtration tank 114 for filtering and concentrating the chelating complex of the phosphate and the magnetic iron powder, An adsorption tank (110) including a first discharge portion (115) through which treated water is discharged; A desorption tank 120 including a third inlet 122 through which the desorption solution flows, a second outlet 123 through which the phosphate concentrated water is drained, and an adsorption member 124 to which the magnetic iron powder is adhered. A connection pipe 116 for allowing the mixed water, which is concentrated by the membrane filtration tank 114 and discharged from the adsorption tank 110, to flow into the desorption tank 120; And a magnetic iron powder storage tank (130) for recovering the magnetic iron powder from the desorption tank (120) and injecting the recovered magnetic iron powder into the adsorption tank (110).

More specifically, the apparatus for removing and recovering phosphate according to the present invention comprises an adsorption tank 110, a desorption tank 120, a connection pipe 116, and a magnetic iron powder storage tank 130.

At this time, the adsorption tank 110 includes a first inlet 111, a second inlet 112, a stirrer 113, and a membrane filtration tank 114. Waste water containing phosphate is introduced into the first inlet 111. At this time, the wastewater may be any general wastewater containing phosphate, but it is preferably an anaerobic digestion liquor that has undergone an ammonia stripping process, which is a pretreatment process of a phosphate recovery process, for efficient phosphate recovery and removal. Also, the magnetic iron powder flows through the second inflow part 112. The phosphate present in the wastewater is adsorbed to the magnetic iron powder by electrostatic attraction due to the adsorption capacity of the magnetic iron powder to form a chelating complex. At this time, it is preferable to mix the magnetic iron powder and the wastewater using the stirrer 113 so that the magnetic iron powder and the phosphate in the wastewater can smoothly form a chelating complex. At this time, it is preferable that the rotation speed of the stirrer 113 is 50-300 rpm. If the amount is less than the lower limit, the number of effective contact of the phosphate and the magnetic iron powder in the wastewater may be reduced to decrease the rate of formation of the chelating complex. If the amount exceeds the upper limit, stirring stronger than the electrostatic attraction between the magnetic iron powder and the phosphate There is a problem that the adsorption efficiency is lowered.

The wastewater containing the chelating complex of phosphate and magnetic iron powder is filtered and concentrated by membrane filtration tank 114. The membrane filtration tank is an immersion type microfiltration membrane, and the microfiltration membrane module is contained in the pressure tube. The microfiltration membrane is preferably made of a material such as cellulose acetate or polyamide. However, the microfiltration membrane is not limited thereto, and any material capable of performing the intended separation membrane function of the present invention is usable. Specifically, the wastewater containing the chelating complex is introduced by the pressure applied at the inlet of the microfiltration membrane module, and is passed through the module and is discharged as treatment water containing various impurities in addition to the chelating complex, The chelating complex is discharged in the form of a concentrated mixed water by the principle that the water is concentrated at the opposite end of the slurry. The treated water filtered by the membrane filtration tank contains various impurities except for the chelating complex and is discharged through the first discharge portion 115. The mixed water discharged from the adsorption tank 110 is concentrated by a large amount of the chelating complex of the phosphate and the magnetic iron powder. The adsorption tank 110 and the desorption And is connected to the tank 120 and is introduced into the desorption tank 120 by a connection pipe 116 through which the mixed water is introduced into the desorption tank 120 from the adsorption tank 110.

The desorption tank 120 includes a third inflow portion 122, a discharge portion 123, and an adsorption member 124. At this time, the desorption solution for desorbing the phosphate adsorbed on the magnetic iron powder reacts with the chelating complex of the phosphate and the magnetic iron powder contained in the mixed water introduced from the adsorption tank into the third inlet 122. The introduced desorbing solution is preferably an NaOH aqueous solution, an NaCl aqueous solution, or a mixed solution thereof, most preferably an aqueous 20 wt% NaOH solution as can be seen from the results of the following examples.

As described above, the chelating complex in the mixed water reacts with the desorption solution, and the phosphate adsorbed on the magnetic iron powder is desorbed and separated. At this time, the concentrated phosphate-concentrated water is discharged together through the second discharge portion, and the concentrated water contains a high concentration of phosphate in the wastewater flowing through the first inlet portion of the adsorption tank, thereby securing high-purity phosphate .

In addition, the magnetic iron powder from which the phosphate has been desorbed is collected by the adsorption member 124, collected in the magnetic iron powder storage tank 130, discharged again to the second inlet portion 112 of the adsorption tank, and reused. The adsorption member 124 may be any type as long as it generates magnetic force, but it is most preferably an immersion type electromagnet used in a form immersed in water.

As can be seen from the results of the following examples, the magnetic iron powder produced by the production method of the present invention is excellent in the adsorption and desorption efficiency and reuse efficiency of the phosphate, and is effectively used for the removal and recovery of the phosphate. It is advantageous that the magnetic iron powder can be reused while recovering the phosphate.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments and the like. It will be apparent to those skilled in the art, however, that these examples are provided for further illustrating the present invention and that the scope of the present invention is not limited thereto.

Example  One

1 L of 0.3 M FeCl ₂ .4H ₂ O (Daejung chemicals & metals, Korea) and 1 L of 0.03 M Fe (NO ₃ ) ₃ .9H ₂ O (Daejung chemicals & metals, Korea) were mixed in a nitrogen atmosphere, . The pH of the mixed solution was adjusted to 7.2 by adding 2 M of NaOH. Thereafter, the precipitate was separated, washed with distilled water ten times, and then dried at 70 ° C. Thereafter, the dried precipitate was pulverized using a mortar bowl to obtain magnetic iron powder.

Example  2

2 L of FeSO ₄ · 7H ₂ O (Daejung chemicals & metals, Korea) and 2 L of FeCl ₃ · 6H ₂ O (Daejung chemicals & metals, Korea) were mixed to prepare a mixed solution. A precipitate was obtained by performing a coprecipitation reaction by adding NaOH to the prepared mixed solution. Thereafter, the precipitate was separated, washed 10 times with distilled water, and dried at 70 ° C. Thereafter, the dried precipitate was pulverized using a mortar bowl to obtain magnetic iron powder.

Comparative Example  One

A magnetic iron powder with a particle size of 1.7 탆 was purchased from Daejung chemicals & metals, Korea.

Comparative Example  2

Magnetite (Fe ₃ O ₄ ) powder with a particle size of 50-100 nm was purchased from Sigma Aldrich, USA.

Test Example  One. Magnetic iron  Particle size analysis of powder

The particle size of the magnetic iron powder prepared according to Example 2 was analyzed with a laser particle size analyzer (BT-2000, K-ONE, Korea) according to the ultrasonic treatment time.

4 is a graph showing particle size distribution results of magnetic iron powder prepared according to Example 2 according to ultrasonic treatment time.

Thus, it was confirmed that the magnetic iron powder prepared according to Example 2 had a particle size distribution in a wide range of 1 - 100 μm. This is presumably because the magnetic iron powder according to the present invention was pulverized by using a mortar bowl instead of a mechanical force after the dried precipitate was obtained. Therefore, the magnetic iron powder produced according to the production method of the present invention has a wide particle size distribution in the range of micro size as compared with the nano size which is difficult to apply in the actual process, and thus can be usefully applied in actual processes. Further, it has been confirmed that the range of the particle size distribution narrows as the ultrasonic treatment time becomes longer and the average particle size becomes smaller, so that a magnetic iron powder of a desired size can be easily obtained.

Test Example  2. XRD  Measure

The magnetic iron powder prepared according to Example 2 was analyzed by X-ray diffractometer (New D8-Advance, Bruker-AXS, Germany).

5 is a graph showing the XRD analysis results of the magnetic iron powder produced according to Example 2. Fig.

As a result, it was confirmed that magnetite (Fe ₃ O ₄ ), which is the object of the present invention, is mostly produced although the hematite (Fe 2 O 3) is produced in the magnetic iron powder produced according to Example 2.

Test Example  3. Comparison measurement of phosphate adsorption characteristics

Experiments were conducted to compare phosphorus adsorption characteristics of the magnetic iron powder prepared according to Examples 1 and 2 and the magnetic iron powder according to Comparative Examples 1 and 2.

The experiment was carried out by batch experiment. First, KH ₂ PO ₄ The 500 mg / L phosphate solution prepared by using the reagent was titrated with 0.1 M HCl and 0.1 M NaOH to pH 4.0 and 7.0, respectively. Then, 1 g of each magnetic iron powder was put into a 50 ml conical tube, and 30 ml of each phosphate solution was added. The reaction was carried out at room temperature for 120 minutes at a speed of 250 rpm using a Shaker (SH-800S, Seyoung Scientific, Korea), and then the suspension containing the magnetic iron particles adsorbed on the respective phosphates was filtered using a 0.45 μm filter paper.

After filtration, the filtrate was sampled and analyzed using a UV-spectrophotometer (DR-3900, Hach, USA). The adsorption amount and the removal rate of phosphorus were as shown in Table 1 (adsorption amount) Respectively.

6 is a graph showing adsorption amounts of phosphate of magnetic iron powder prepared according to Example 1, Example 2, Comparative Example 1 and Comparative Example 2. FIG.

7 is a graph showing the removal ratios of phosphate of magnetic iron powder prepared according to Example 1, Example 2, Comparative Example 1 and Comparative Example 2. FIG.

Comparative Example 1 Comparative Example 2 Example 1 Example 2 pH 4.0 4.8 5.3 9.2 14.9 pH 7.0 4.6 5.1 8.2 13.3

Comparative Example 1 Comparative Example 2 Example 1 Example 2 pH 4.0 32.3 35.4 61.7 99.0 pH 7.0 30.7 33.9 54.6 88.3

As a result of the measurement, it was confirmed that the adsorption efficiency of the magnetic iron powder produced according to Examples 1 and 2 of the present invention was much better than those of Comparative Examples 1 and 2. In particular, the magnetic iron powder prepared according to Example 2 showed a phosphate removal rate of 99% at pH 4.0 and a phosphorous removal rate of 88% or more even at pH 7.0, thereby confirming that it can be effectively applied to an anaerobic digestion effluent I could.

Test Example  4. Measurement of phosphate adsorption characteristics with reaction time

The characteristics of the phosphate adsorption according to the reaction time of the magnetic iron powder prepared according to Example 2 were measured.

The experiment was carried out by batch experiment. First, KH ₂ PO ₄ The 500 mg / L phosphate solution prepared by using the reagent was titrated to pH 4.0 with 0.1 M HCl. Then, 1 g of magnetic iron powder was put into a 50 ml conical tube, and 30 ml of phosphate solution, each of which was adjusted to pH 4.0, was added. Samples were taken at 1, 5, 10, 15, 30, 60 and 120 minutes while reacting at room temperature for 120 minutes at a speed of 250 rpm using a Shaker (SH-800S, Seyoung Scientific, Korea) Was filtered using a 0.45 μm filter paper.

After filtration, the filtrate was sampled and analyzed using a UV-spectrophotometer (DR-3900, Hach, USA). The adsorption amount and removal rate of phosphorus are shown in Tables 3, 8 and 9.

8 is a graph showing the amount of phosphate adsorbed by the reaction time of the magnetic iron powder prepared according to Example 2. FIG.

FIG. 9 is a graph showing the removal rate of phosphate according to the reaction time of the magnetic iron powder produced according to Example 2. FIG.

Time (min) Adsorbed (mg PO ₄ ^{3 -} / g MIO) Phosphate removal (%) 0 0 0 One 12.5 83.5 5 13.5 90.2 10 14.5 96.9 15 14.7 98.2 30 14.8 98.7 60 14.8 99.0 120 14.9 99.0

As a result of measurement, the magnetic iron powder prepared according to Example 2 of the present invention was very active in the initial adsorption reaction, and the phosphate removal rate was 83% or more at 1 minute, and the phosphate removal rate was 98% or more at 15 minutes , It was confirmed that the equilibrium of phosphate adsorption reached almost 15 minutes.

Test Example  5. Magnetic iron  The amount of powder pH  Determination of phosphate adsorption characteristics according to changes

In order to determine the optimum adsorption pH and the amount of the titania powder, the adsorption characteristics of the phosphate were measured according to the pH change and the amount of the magnetic iron powder prepared according to Example 2.

The experiment was carried out by batch experiment. First, KH ₂ PO ₄ The 500 mg / L phosphate solution prepared with the reagents was prepared at pH 4.0, 5.0, 6.0, and 7.0 using 0.1 M HCl and 0.1 M NaOH, respectively. Then, 0.25, 0.5, 0.75, 1.0, 1.5 and 2.0 g of magnetic iron powder were put into a 50 ml conical tube, and 30 ml of phosphate solution was added according to each pH condition. After reacting at room temperature for 120 minutes at a speed of 250 rpm using a Shaker (SH-800S, Seyoung Scientific, Korea), the suspension containing the magnetic iron-adsorbed phosphate was filtered through a 0.45 μm filter paper .

After filtration, the filtrate was sampled and analyzed using a UV-spectrophotometer (DR-3900, Hach, USA). The adsorption amount and the removal rate of phosphorus were as shown in Table 4 (adsorption amount) Respectively.

FIG. 10 is a graph showing the amount of phosphorus powder adsorbed according to the input amount and pH of the magnetic iron powder produced according to Example 2. FIG.

11 is a graph showing the input amount of the magnetic iron powder produced according to Example 2 and the removal rate of phosphate according to pH change.

MIO Input (g / L) pH 4.0 pH 5.0 pH 6.0 pH 7.0 8.3 29.4 29.1 27.7 26.3 16.7 26.4 26.1 24.8 21.9 25.0 18.7 18.4 18.0 16.8 33.3 14.9 14.8 14.8 13.3 50.0 10.0 9.9 9.9 9.3 66.7 7.5 7.4 7.4 7.0

MIO Input (g / L) pH 4.0 pH 5.0 pH 6.0 pH 7.0 8.3 48.9 48.3 46 43.6 16.7 88.0 87.3 82.7 73.2 25.0 93.5 92.1 90.2 84.2 33.3 99.0 98.5 98.8 88.3 50.0 99.6 98.8 98.9 92.6 66.7 99.6 99.0 99.0 93.2

As a result, the adsorption amount and the removal rate were not significantly different at pH 4.0, 5.0 and 6.0, and the adsorption amount and the removal rate were decreased at pH 7.0, but there was almost no difference. It was also confirmed that the removal rate of phosphate exceeded 98% when 33.3 g / L of magnetic iron powder was added to 500 mg / L of phosphate solution.

Test Example  6. Measurement of Phosphate Adsorption Characteristics by Phosphate Concentration

The adsorption characteristics of the magnetic iron powder prepared according to Example 2 according to the change of the phosphate concentration were measured.

The experiment was carried out by batch experiment. First, KH ₂ PO ₄ 500-5000 mg / L of each phosphate solution prepared by using the reagent was titrated to pH 4.0 with 0.1M HCl. 1 g of magnetic iron powder was placed in a 50 ml conical tube and 30 ml of phosphate buffer solution, pH 4.0, was added. After reacting at room temperature for 120 minutes at a speed of 250 rpm using a Shaker (SH-800S, Seyoung Scientific, Korea), each sample was filtered with a 0.45 μm filter paper.

After filtration, the filtrate was sampled and analyzed using a UV-spectrophotometer (DR-3900, Hach, USA). The adsorption amount and removal rate of phosphorus are shown in Tables 6, 12 and 13.

12 is a graph showing the adsorption amount of magnetic iron powder prepared according to Example 2 according to the concentration of phosphate.

13 is a graph showing removal ratios of magnetic iron powder prepared according to Example 2 according to the concentration of phosphate.

Phosphate concentration
(mg / L) Adsorbed
_{^{(mg PO 4 3 - / g}} MIO) Phosphate removal (%) 500 14.9 99.0 1000 26.5 88.3 1500 32.3 71.9 2000 37.7 62.9 2500 43.6 58.1 3000 45.4 50.4 3500 46.8 44.6 4000 46.6 38.9 4500 46.8 34.7 5000 46.9 31.2

As a result of measurement, it was found that the adsorption amount of the magnetic iron powder was increased as the concentration of the phosphate was increased. When the concentration of the phosphate was 3500 ppm or more, the adsorption amount was not substantially increased. The maximum adsorption limit of the magnetic iron powder was measured as 45-47 mg PO ₄ ^{3 -} / g.

Test Example  7. Measurement of phosphate adsorption characteristics with phosphate concentration and time

The adsorption characteristics of the magnetic iron powder prepared according to Example 2 with respect to the concentration of phosphate were measured with time.

The experiment was carried out by batch experiment. First, KH ₂ PO ₄ 1500, 2500, and 3500 mg / L of each phosphate solution prepared by using the reagent was titrated to pH 4.0 with 0.1 M HCl. 1 g of magnetic iron powder was placed in a 50 ml conical tube and 30 ml of phosphate buffer solution, pH 4.0, was added. Samples were collected at 1, 5, 10, 15, 30, 60, and 120 minutes at room temperature using a Shaker (SH-800S, Seyoung Scientific, Korea) at a speed of 250 rpm for 120 minutes. Was filtered using a 0.45 μm filter paper. After filtration, the filtrate was sampled and analyzed using a UV-spectrophotometer (DR-3900, Hach, USA). The adsorption amount and removal rate of phosphorus are shown in Tables 7, 14 and 15 below.

14 is a graph showing the adsorption amount of the magnetic iron powder prepared according to Example 2 according to the concentration and time of the phosphate solution.

15 is a graph showing the removal rate of the magnetic iron powder prepared according to Example 2 according to the concentration and time of the phosphate solution.

Time (min) Adsorbed (mg PO ₄ ^{3 -} / g MIO) Phosphate removal (%) 1500 mg / L PO ₄ ^{3 -} 2500 mg / L PO ₄ ^{3 -} 3500 mg / L PO ₄ ^{3 -} 1500 mg / L PO ₄ ^{3 -} 2500 mg / L PO ₄ ^{3 -} 3500 mg / L PO ₄ ^{3 -} 0 0 0 0 0 0 0 One 20.6 27.4 30.8 45.7 36.5 29.3 5 25.9 35.0 36.4 57.6 46.7 34.7 10 26.9 37.1 38.6 59.9 49.5 36.7 15 28.3 39.5 39.9 62.9 52.6 38.0 30 29.6 40.6 41.3 65.8 54.1 39.3 60 31.4 42.0 44.7 69.8 56.0 42.5 120 32.3 43.7 46.6 71.8 58.3 44.4

As a result of the measurement, it was confirmed that, in the case of the magnetic iron powder produced according to Example 2 of the present invention, even if the concentration of the phosphate is different, the adsorption characteristics of the phosphate are substantially similar with respect to the reaction time.

Test Example  8. Coexisting anion  Determination of phosphate adsorption characteristics by presence

The phosphate adsorption characteristics of the magnetic iron powder prepared according to Example 2 of the present invention were measured in the presence of various coexisting anions.

The experiment was conducted as a batch experiment, with the co-anionic reagent Na2SO4, NaNO3, Na2CO3, was used as NaCl, in each of _{500 mg / L Sulfate (SO 4} 2 -), Nitrate (NO 3 -), Carbonate (CO 3 ^{2 -} ), Chloride (Cl ^- ) and KH ₂ PO ₄ The mixed solution prepared by using the reagent was titrated to pH 4.0 with 0.1 M HCl. 1 g of magnetic iron powder was placed in a 50 ml conical tube and 30 ml of each solution was added to the solution. Samples were collected at 1, 5, 10, 15, 30, 60, and 120 minutes at room temperature using a Shaker (SH-800S, Seyoung Scientific, Korea) at a speed of 250 rpm for 120 minutes. Was filtered using a 0.45 μm filter paper. After filtration, the filtrate was sampled and analyzed using a UV-spectrophotometer (DR-3900, Hach, USA). The adsorption amount and removal rate of phosphorus are shown in Tables 8, 16 and 17 below.

16 is a graph showing the adsorption amount of phosphate according to the presence of coexisting anions of the magnetic iron powder prepared according to Example 2. FIG.

FIG. 17 is a graph showing the removal rate of phosphate according to the presence of coexisting anions of the magnetic iron powder produced according to Example 2. FIG.

Time (min) Adsorbed (mg PO ₄ ^{3 -} / g MIO) Phosphate removal (%) Control SO ₄ ^{2 -} NO ₃ ^- CO ₃ ^{2 -} Cl ^- Control SO ₄ ^{2 -} NO ₃ ^- CO ₃ ^{2 -} Cl ^- 0 0 0 0 0 0 0 0 0 0 0 One 12.5 12.3 10.2 12.3 10.2 83.5 82.2 68.1 82.0 68.2 5 13.5 13.8 11.5 14.2 11.4 90.2 92.1 76.7 94.7 73.1 10 14.5 13.9 12.2 14.7 11.7 96.9 92.6 81.4 98.0 77.8 15 14.7 14.1 12.8 14.8 11.9 98.2 94.0 85.6 98.8 79.3 30 14.8 14.3 13.0 14.9 12.2 98.7 95.5 86.8 99.4 81.0 60 14.8 14.6 13.2 15.0 12.3 99.0 97.1 88.0 99.7 81.9 120 14.9 14.7 13.2 15.0 12.3 99.0 97.8 88.3 99.8 82.1

As a result of the measurement, it was confirmed that the adsorption amount and the removal rate were decreased to some extent when NO ₃ ^- and Cl ^- coexist. However, when SO ₄ ^{2 -} coexists, it has little effect on the adsorption amount and removal rate, and it can be confirmed that the adsorption amount and removal rate are improved when CO ₃ ^{2 -} coexists.

Test Example  9. Magnetic iron  Measurement of recovery characteristics of powders

The recovery characteristics of the magnetic iron powder prepared according to Example 2 of the present invention were measured.

First, 1 g of magnetic iron powder was added to 30 ml of 500 mg / L Phosphate solution using a 50 ml conical tube and titrated to pH 4.0. One sample is filtered using 0.45 ㎛ filter paper and weighed using an electronic balance (HR-200, A & D, Japan). The remaining three samples were dispersed in 200 ml of distilled water using a 250 ml beaker as a reactor and placed on a 100 mm diameter electric magnet (JL-9A, JL magnet, korea) Min for 30 minutes. After 1 minute, the supernatant in the beaker was removed, and the magnetic iron powder in the beaker was washed with distilled water and filtered. Then, the weight was measured and the results of the recovery experiment are shown in Table 9 below.

Inaccessibility 1.4930g Weight (filter + MIO) Weight (MIO) Recovery ratio Recall experiment 1 1.4847 0.9917 99.17% Recovery experiment 2 1.4756 0.9826 98.26% Recall experiment 3 1.4803 0.9873 98.73% Average 1.4802 0.9872 98.72%

As a result of the measurement, it was confirmed that the amount of magnetic iron powder lost during the recovery process by magnetic is only about 1.3% on average, and it can be seen that the magnetic iron powder according to the manufacturing method of the present invention is usefully applied in actual processes there was.

Test Example  10. Of the desorbing solution  Determination of phosphate desorption characteristics by type

The desorption characteristics of phosphate of the magnetic iron powder prepared according to Example 2 were measured according to the type of the desorption solution.

(PH 6.08), 3% NaOH (pH 12.73), 20% NaOH (pH 13.06), 30% NaCl + 3% NaOH (pH 12.58), 40% NaCl + 2% NaOH , 50% NaCl + 1% NaOH (pH 12.28) was used.

18 is a graph showing the desorption amount of phosphate depending on the type of the desorption solution of the magnetic iron powder produced according to Example 2. FIG.

19 is a graph showing the desorption rate of phosphate depending on the type of the desorption solution of the magnetic iron powder produced according to Example 2. FIG.

Time (min) Pure water
_{^{(mg PO 4 3 - / g}} MIO) 3% NaOH
_{^{(mg PO 4 3 - / g}} MIO) 20% NaOH
_{^{(mg PO 4 3 - / g}} MIO) 30% NaCl
+
3% NaOH
_{^{(mg PO 4 3 - / g}} MIO) 40% NaCl
+
2% NaOH
_{^{(mg PO 4 3 - / g}} MIO) 50% NaCl
+
1% NaOH
_{^{(mg PO 4 3 - / g}} MIO) 0 0 0 0 0 0 0 One 0.015 7.22 14.35 10.26 9.81 9.19 5 0.021 8.23 14.44 11.20 11.41 10.75 10 0.009 8.84 14.73 11.65 12.31 11.64 15 0.030 8.93 14.96 11.91 12.56 11.91 30 0.042 9.45 14.97 12.03 12.71 12.31 60 0.024 9.82 14.97 12.06 12.89 12.38

Time (min) Pure water
(Desorption efficiency (%)) 3% NaOH
(Desorption efficiency (%)) 20% NaOH
(Desorption efficiency (%)) 30% NaCl
+
3% NaOH
(Desorption efficiency (%)) 40% NaCl
+
2% NaOH
(Desorption efficiency (%)) 50% NaCl
+
1% NaOH
(Desorption efficiency (%)) 0 0 0 0 0 0 0 One 0.10 48.17 95.83 68.48 65.51 61.33 5 0.14 54.92 96.42 74.74 76.17 71.82 10 0.06 58.98 98.36 77.79 82.18 77.71 15 0.20 59.61 99.84 79.53 83.86 79.47 30 0.28 62.45 99.90 80.28 84.86 82.18 60 0.16 65.55 99.96 80.54 86.08 82.64

The desorption efficiency was found to be more than 80% for 30% NaCl + 3% NaOH, 40% NaCl + 2% NaOH and 50% NaCl + 1% NaOH, %, It was confirmed that 20% NaOH was the most preferable as the desorption solution.

Test Example  11. Magnetic iron  Measurement of Adsorption and Desorption Characteristics of Phosphate by Powder Reuse Times

Reuse evaluation was carried out to measure the adsorption and desorption characteristics of phosphate according to the number of times of re-use of the magnetic iron powder produced according to Example 2.

The experiment was carried out as a batch experiment. 500 mg / L of phosphate solution was titrated to pH 4.0 with 0.1 M HCl and 20% NaOH was prepared. 1 g of magnetic iron powder was placed in a 50 ml conical tube and 30 ml of phosphate buffer solution, pH 4.0, was added.

Thereafter, the cells were reacted at a speed of 50 rpm for 60 minutes using a multi-rotator (GTR-100, Green Tech, Korea) and then centrifuged at 1500 rpm using a Multi Purpose Centrifuge (HA1000-6, Hanil Science industrial, Centrifugation was carried out at a rate of 5 minutes, the supernatant was removed, and this procedure was repeated five times with one cycle.

Each sample was filtered using a 0.45 μm filter paper, and analyzed by using a UV-spectrophotometer (DR-3900, Hach, USA). The results are shown in Table 12 and FIG.

FIG. 20 is a graph showing the adsorption amount of phosphate according to the number of times of re-use of the magnetic iron powder produced according to Example 2. FIG.

Cycle Adsorption efficiency
(%) Desorption efficiency
(%) One 99.9 99.9 2 99.0 99.5 3 96.4 94.9 4 92.2 89.0 5 88.9 87.0

As a result of the measurement, it was confirmed that the adsorption rate of phosphorus was 92% or more and the adsorption rate of phosphorus was 89% or more until the fourth reuse. As a result, it was confirmed that the magnetic iron powder according to the present invention can be reused rather than one-time, and thus it can be effectively applied in actual processes.

110: adsorption tank 120: desorption tank
130: magnetic iron powder storage tank 111: first inlet
112: second inlet 113: stirrer
114: membrane filtration tank 115: first discharge section
116: connector 122: third inlet
123: second discharge portion 124: suction member

Claims (16)

(a) preparing a mixed solution of FeCl ₂ .4H ₂ O and Fe (NO ₃ ) ₃ .9H ₂ O in a nitrogen atmosphere;
(b) adjusting the pH of the mixed solution to pH 7-8 with NaOH to obtain a precipitate;
(c) separating the precipitate from the mixed solution, washing with distilled water and drying; And
(d) pulverizing the dried precipitate,
The molar concentration ratio of FeCl ₂ .4H ₂ O and Fe (NO ₃ ) ₃ .9H ₂ O is 1: 0.05-0.2,
Wherein the molar concentration of FeCl ₂ .4H ₂ O is 0.2-0.4M, the molar concentration of Fe (NO ₃ ) ₃ .9H ₂ O is 0.01-0.08M, and the molar concentration of NaOH is 1.5-3M. And a process for producing the ferromagnetic iron powder. delete delete The method according to claim 1,
Wherein the washing of step (c) is performed 5 to 15 times, and the drying is performed at 60 to 80 ° C. (a) preparing a mixed solution of FeSO ₄ .7H ₂ O and FeCl ₃ .6H ₂ O;
(b) adding NaOH to the mixed solution to titrate the pH to 8-10, thereby obtaining a precipitate through coprecipitation reaction;
(c) separating the precipitate, washing with distilled water and drying; And
(d) pulverizing the dried precipitate,
The molar concentration ratio of FeSO ₄ .7H ₂ O and FeCl ₃ .6H ₂ O is 1: 1-3,
Wherein the molar concentration of FeSO ₄ .7H ₂ O is 0.5-1.5M, the molar concentration of FeCl ₃ .6H ₂ O is 0.5-4.5M, and the molar concentration of NaOH is 5-7M. A method for producing an acceptor cast iron powder. delete delete 6. The method of claim 5,
Wherein the washing of step (c) is performed 5 to 15 times, and the drying is performed at 60 to 80 ° C. A first inlet through which wastewater containing phosphate is introduced, a second inlet through which the magnetic iron powder is introduced, a stirrer for mixing the magnetic iron powder with the wastewater containing the phosphate, a chelating complex of the phosphate and the magnetic iron powder A membrane filtration tank for filtrating and concentrating the filtrate, and a first discharge portion for discharging the treated water filtered by the membrane filtration tank;
A desorption tank including a third inlet through which the desorption solution flows, a second outlet through which the phosphate concentrated water drains, and an adsorption member to which the magnetic iron powder adheres;
A connection pipe for allowing the mixed water, which is condensed by the membrane filtration tank and discharged from the adsorption tank, to flow into the desorption tank; And
And a magnetic iron powder storage tank for recovering the magnetic iron powder from the desorption tank and introducing the magnetic iron powder into the adsorption tank. 10. The method of claim 9,
Wherein the phosphate contained in the influent wastewater and the influent magnetic iron powder form a chelating complex by electrostatic attraction in the adsorption tank. 10. The method of claim 9,
Wherein the mixed water flowing through the connection pipe in the desorption tank reacts with the desorption solution to separate the phosphate and the magnetic iron powder. 10. The method of claim 9,
Wherein the wastewater containing phosphate is an anaerobic digestion decantation treated by ammonia stripping. 10. The method of claim 9,
Wherein the desorbing solution is a NaOH aqueous solution, an NaCl aqueous solution, or a mixed solution thereof. 13. The method of claim 12,
Wherein the desorption solution is a 20 wt% NaOH aqueous solution. 10. The method of claim 9,
Wherein the rotating speed of the agitator is 50-300 rpm. 10. The method of claim 9,
Wherein the adsorption member is an immersion type electromagnet.

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