KR102558035B1 - Manufacturing method of ferrite with increased half-life - Google Patents

Abstract

The present invention relates to a method for producing ferrite with an increased half-life, and more particularly, to a method for producing ferrite with an increased half-life that can maintain a concentration of about 80% or more after 20 days or more due to a delayed self-decomposition by preparing ferrite (Na ₂ FeO ₄ ) by adding Fe powder to an aqueous NaOH solution and heating to prepare a NaFeO ₂ intermediate solution, and reacting by adding an aqueous solution of NaOCl to the NaFeO ₂ intermediate solution.

Description

Manufacturing method of ferrite with increased half-life {Manufacturing method of ferrite with increased half-life}

The present invention relates to a method for producing ferrite with an increased half-life, and more particularly, to a method for producing ferrite with an increased half-life that can maintain a concentration of about 80% or more after 20 days or more due to a delayed self-decomposition by preparing ferrite (Na ₂ FeO ₄ ) by adding Fe powder to an aqueous NaOH solution and heating to prepare a NaFeO ₂ intermediate solution, and reacting by adding an aqueous solution of NaOCl to the NaFeO ₂ intermediate solution.

Since ferrite has a higher oxidizing power than ozone, many studies have been conducted to utilize it for wastewater treatment and odor treatment. As for the manufacturing method of ferrite, the wet oxidation method is the simplest and is mainly used in the industry.

A general method for producing ferrite may proceed as shown in Scheme 1 below.

Scheme 1: 2FeCl ₃ + 10NaOH + 3NaOCl → 2Na ₂ FeO ₄ + 9NaCl + 5H ₂ O

However, when the ferrite prepared by Scheme 1 above is present in a liquid phase, its half-life is only about 6 hours even at pH 11, which is known as the most stable condition, so there was inconvenience that most of them had to be prepared and used immediately on site.

As such, the half-life according to the pH of ferrite is produced at pH 11 to 12 by NaOH in the case of the wet oxidation method.

In order to solve this problem, a method of preparing ferrite in the form of K ₂ FeO ₄ by using KOH instead of NaOH, then cooling, precipitating and drying to store in solid form has been attempted, but this method is not used well because of the difficulty of equipment that must be completely excluded during storage, which requires washing several times to increase purity.

In addition, divalent or trivalent iron salts generated as ferrite is reduced due to rapid self-decomposition of liquid ferrite (Na ₂ FeO ₄ ) become sludge and clog pipes or cause pump failure, making field use difficult.

Republic of Korea Patent Publication No. 10-2010-0068122 (2010.06.22. Publication)

An object of the present invention is to prepare a NaFeO ₂ intermediate solution by adding Fe powder to an aqueous NaOH solution and heating it, and then adding an aqueous solution of NaOCl to the NaFeO ₂ intermediate solution to react to produce ferrite (Na ₂ FeO ₄ ). It is to provide a method for producing ferrite with an increased half-life that can maintain a concentration of about 80% or more after 20 days or more due to delayed self-decomposition.

A method for producing ferrite having an increased half-life according to an embodiment of the present invention includes (a) preparing a NaFeO ₂ intermediate solution; (b) adding an aqueous solution of NaOCl to the NaFeO ₂ intermediate solution and stirring while heating to a set temperature; (c) forming Na ₂ FeO ₄ by reacting the NaFeO ₂ intermediate solution with the NaOCl aqueous solution while maintaining the set heating temperature; and (d) storing the Na ₂ FeO ₄ prepared in step (c) in an airtight container in the dark.

The step (a) may include (a-1) adding Fe powder to an aqueous solution of NaOH and stirring while heating to 130 to 150 ° C; (a-2) when the temperature reaches 130 to 150° C., reacted by maintaining for 1 to 2 hours, cooled to 95 to 105° C., and mixed with distilled water in a dropwise manner to prepare a NaFeO ₂ intermediate solution; and (a-3) storing the NaFeO ₂ intermediate solution in a closed container filled with distilled water in a dropwise manner and storing it in the dark.

In the step (a-1), 0.5 to 4.5 g of the Fe powder is added per 100 ml of the NaOH aqueous solution.

In the step (a-2), the cooling is naturally cooled for 10 to 30 minutes until the temperature reaches 95 to 105 ° C, and then mixed with distilled water in a dropwise manner to prevent coagulation.

In step (b), the NaFeO ₂ intermediate solution and the NaOCl aqueous solution are added in a weight ratio of 1:1 to 1:10.

In the step (b), the set temperature is preferably 70 ~ 90 ℃.

In the step (b), the stirring is performed for 10 to 60 minutes at a speed of 100 to 1,000 rpm.

During the stirring, ultrasonic treatment is performed together at a frequency of 30 to 45 KHz and an output voltage of 7 to 17 W.

After the step (d), the Na ₂ FeO ₄ kept in the dark in a state contained in the airtight container slows down the autolysis phenomenon and maintains a concentration of 80% or more after 20 days or more.

In the method for producing ferrite with an increased half-life according to the present invention, Fe powder is added to an aqueous solution of NaOH and heated to prepare an intermediate NaFeO ₂ solution, and then the aqueous solution of NaOCl is added to the NaFeO ₂ intermediate solution to react. By preparing ferrite (Na ₂ FeO ₄ ), the autolysis phenomenon is delayed so that the concentration can be maintained at about 80% or more even after 20 days or more.

As a result, since the ferrite manufacturing method with increased half-life according to the present invention can maintain a concentration of about 80% or more even after 20 days, long-term storage and use are easy due to the increased half-life, so long-term storage and ease of handling can be secured.

In addition, ferrite with an increased half-life produced by the method according to the present invention has a higher oxidizing power than ozone, and is therefore suitable for use in wastewater treatment, odor treatment, and the like.

1 is a process flow chart showing a method for manufacturing ferrite with an increased half-life according to an embodiment of the present invention.
Figure 2 is a photograph showing the NaFeO ₂ intermediate solution prepared according to Example 1.
Figure 3 is a photograph showing the NaFeO ₂ intermediate solution prepared according to Comparative Example 1.
4 is a photograph showing a NaFeO ₂ intermediate solution prepared according to Comparative Example 2;
5 is a photograph showing Na ₂ FeO ₄ prepared according to Example 1;
6 is a graph showing the UV absorbance measurement results for each storage period of ferrite according to Example 1 and Comparative Example 3.
7 is a graph showing the TN removal rate measurement results for each storage period of ferrite according to Example 1 and Comparative Example 3;

Hereinafter, a preferred embodiment of the present invention and the physical properties of each component will be described in detail, but this is intended to be explained in detail to the extent that those skilled in the art can easily practice the invention. This does not mean that the technical spirit and scope of the present invention are limited.

In the method for producing ferrite with an increased half-life according to an embodiment of the present invention, Fe powder is added to an aqueous solution of NaOH and heated to prepare an intermediate NaFeO ₂ solution, and then the aqueous solution of NaOCl is added to the NaFeO ₂ intermediate solution to react. By preparing ferrite (Na ₂ FeO ₄ ), the self-decomposition phenomenon is delayed, so that the concentration can be maintained at about 80% or more even after 20 days or more.

As a result, since the ferrite manufacturing method with an increased half-life according to an embodiment of the present invention can maintain a concentration of about 80% or more even after 20 days, long-term storage and use are easy due to the increased half-life, so long-term storage and ease of handling can be secured.

In this regard, a method for manufacturing ferrite having an increased half-life according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a process flow chart showing a method for manufacturing ferrite with increased half-life according to an embodiment of the present invention.

As shown in FIG. 1, the method for preparing ferrite with increased half-life according to an embodiment of the present invention includes a NaFeO ₂ intermediate solution preparation step (S110), a heating and stirring step (S120), a Na ₂ FeO ₄ formation step (S130) and a cow storage step (S140).

NaFeO ₂ Intermediate solution preparation

In the NaFeO ₂ intermediate solution preparation step (S110), a NaFeO ₂ intermediate solution is prepared.

The NaFeO ₂ intermediate solution preparation step (S110) includes a heating process, a reaction process, and a storage process.

At this time, in the heating process, Fe powder is added to the NaOH aqueous solution, and then stirred while heating to 130 to 150 ° C. Here, when the heating temperature is less than 130 ° C., there is a concern that the Fe powder may not be completely dissolved in the NaOH aqueous solution. Conversely, when the heating temperature exceeds 150 ° C., the solution turns dark green or brown and sludge is generated, making it difficult to manufacture ferrite.

In addition, in this process, stirring is preferably carried out for 30 to 60 minutes at a speed of 100 to 1,000 rpm, and more preferably carried out for 35 to 55 minutes at a speed of 200 to 500 rpm. If the stirring speed is less than 100 rpm or the stirring time is less than 30 minutes, there is a concern that the Fe powder may not be uniformly mixed with the NaOH aqueous solution. Conversely, when the stirring speed exceeds 1,000 rpm or the stirring time exceeds 60 minutes, it is not economical because it may act as a factor that only increases manufacturing cost without further effect.

During this stirring, it is more preferable to perform ultrasonic treatment at a frequency of 30 to 45 KHz and an output voltage of 7 to 17 W, which is to induce better dispersion of the Fe powder in the NaOH aqueous solution.

When such ultrasonic waves are applied, when the frequency is less than 30 KHz or the output voltage is less than 7 W, the cavitation effect according to the application of ultrasonic waves is insignificant and it is difficult to properly exhibit the effect of improving the dispersion. Conversely, when the frequency of the ultrasonic wave exceeds 45 KHz or the output voltage exceeds 17 W, there is a risk of damaging the material in the solution due to excessive ultrasonic application, which is not preferable.

Here, it is preferable to add 0.5 to 4.5 g of Fe powder per 100 ml of aqueous NaOH solution, more preferably 1 to 3 g.

In the reaction process, when the temperature reaches 130 ~ 150 ℃, maintained for 1 ~ 2 hours and reacted, cooled to 95 ~ 105 ℃, and mixed with distilled water in a dropwise manner to prepare a NaFeO ₂ intermediate solution.

In this process, NaOH and Fe powder react as shown in Reaction Formula 2 below.

Scheme 2: Fe + 2NaOH → NaFeO ₂ + H ₂

As shown in Scheme 2 above, the NaFeO ₂ intermediate solution is prepared by the reaction between Fe and 2NaOH, and H ₂ is vaporized.

At this time, cooling is carried out by natural cooling for 10 to 30 minutes until the temperature of the NaFeO ₂ intermediate solution reaches 95 to 105 ° C. at room temperature, and then mixed with distilled water in a dropwise manner to prevent coagulation. It is preferable to prevent.

In the storage process, the NaFeO ₂ intermediate solution is put in a sealed container filled with distilled water in a drop-wise manner and stored in the dark. That is, in a state where the lid of an airtight container filled with distilled water is opened, the NaFeO ₂ intermediate solution is slowly poured in a dropwise manner, put into an airtight container, and stored in a shady place.

During this storage process, it is preferable to fill 30 to 100 ml of distilled water with respect to 100 ml of the NaFeO ₂ intermediate solution. This is because the NaFeO ₂ intermediate solution may coagulate due to gelation and become unusable if the water evaporated by heating (H ₂ O) is not replenished during the reaction process. In addition, the reason for slowly pouring the NaFeO ₂ intermediate solution in a dropwise manner into an airtight container filled with distilled water is to separate it from undissolved iron powder that may remain at the bottom.

At this time, during the storage process, it is preferable to store in the dark at room temperature in an airtight state by closing the lid of the airtight container, which is to prevent the NaFeO ₂ intermediate solution from being exposed to light.

heating and stirring

In the heating and stirring step (S120), the NaOCl aqueous solution is added to the NaFeO ₂ intermediate solution, and then the mixture is stirred while heating to a set temperature.

In this step, the NaFeO ₂ intermediate solution and the NaOCl aqueous solution are preferably added at a weight ratio of 1:1 to 1:10, and more preferably at a weight ratio of 1:2 to 1:6.

In this step, the set temperature is preferably 70 ~ 90 ℃. When heated to this set temperature, the color of the solution slowly changes to purple as the temperature of the mixed solution between the NaFeO ₂ intermediate solution and the NaOCl aqueous solution increases. If the set temperature is less than 70 °C, there is a concern that the reaction between the NaFeO ₂ intermediate solution and the NaOCl aqueous solution may not be performed properly. Conversely, when the set temperature exceeds 90° C., it is not economical because it may act as a factor that only increases manufacturing cost without further effect.

At this time, stirring is preferably carried out for 10 to 60 minutes at a speed of 100 to 1,000 rpm, and more preferably for 20 to 40 minutes at a speed of 200 to 400 rpm. If the stirring speed is less than 100 rpm or the stirring time is less than 30 minutes, there is a concern that uniform mixing between the NaFeO ₂ intermediate solution and the NaOCl aqueous solution may not be achieved. Conversely, when the stirring speed exceeds 1,000 rpm or the stirring time exceeds 60 minutes, it is not economical because it may act as a factor that only increases manufacturing cost without further effect.

During this stirring, it is more preferable to perform ultrasonic treatment at a frequency of 30 to 45 KHz and an output voltage of 7 to 17 W, which is to further improve the dispersibility between the NaFeO ₂ intermediate solution and the NaOCl aqueous solution.

When such ultrasonic waves are applied, when the frequency is less than 30 KHz or the output voltage is less than 8 W, the cavitation effect according to the application of ultrasonic waves is insignificant and it is difficult to properly exhibit the effect of improving the dispersibility. Conversely, when the frequency of the ultrasonic wave exceeds 45 KHz or the output voltage exceeds 17 W, there is a risk of damaging the material in the solution due to excessive ultrasonic application, which is not preferable.

Na ₂ FeO ₄ formation

In the step of forming Na ₂ FeO ₄ (S130), the NaFeO ₂ intermediate solution and the NaOCl aqueous solution are reacted to form Na ₂ FeO ₄ while maintaining the set heating temperature.

In this step, when the set heating temperature of 70 ~ 90 ℃ is reached, the holding time is preferably carried out for 5 ~ 30 minutes, which is a stable solution through a sufficient reaction between the NaFeO ₂ intermediate solution and the NaOCl aqueous solution. This is to prepare ferrite (Na ₂ FeO ₄ ).

cow storage

In the cow storage step (S140), the Na ₂ FeO ₄ produced by the Na ₂ FeO ₄ formation step (S130) is put in an airtight container and stored in the cow.

As such, in the cow storage step (S140), Na ₂ FeO ₄ in a solution state prepared by the Na ₂ FeO ₄ forming step (S130) is slowly poured into an airtight container, and then the airtight container is closed and stored in a shady place in an airtight state.

During this process of storage in the dark, it is preferable to keep the storage in the dark at room temperature in an airtight state by covering the lid of the airtight container, which is to prevent Na ₂ FeO ₄ from being exposed to light.

As such, Na ₂ FeO ₄ stored in the dark in a sealed container slows down the autolysis phenomenon and maintains a concentration of 80% or more after 20 days or more. As a result, since Na ₂ FeO ₄ stored in the dark in a sealed container can maintain a concentration of about 80% or more even after 20 days, it is easy to store and use for a long time due to an increase in half-life, thereby securing long-term storage and ease of handling.

As described above, the method for manufacturing ferrite having an increased half-life according to an embodiment of the present invention can be completed.

As described above, in the method for producing ferrite having an increased half-life according to an embodiment of the present invention, Fe powder is added to an aqueous solution of NaOH and heated to prepare an intermediate solution of NaFeO ₂ , and then the aqueous solution of NaOCl is added to the intermediate solution of NaOCl to react to produce ferrite (Na ₂ FeO ₄ ), so that the self-decomposition phenomenon is delayed and the concentration of about 80% _or more can be maintained even after 20 days or more.

As a result, since the ferrite manufacturing method with an increased half-life according to an embodiment of the present invention can maintain a concentration of about 80% or more even after 20 days, long-term storage and use are easy due to the increased half-life, so long-term storage and ease of handling can be secured.

In addition, ferrite with an increased half-life produced by the method according to an embodiment of the present invention has a higher oxidizing power than ozone, and is therefore suitable for use in wastewater treatment, odor treatment, and the like.

Example

Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, this is presented as a preferred example of the present invention and cannot be construed as limiting the present invention by this in any sense.

Contents not described herein can be technically inferred by those skilled in the art, so descriptions thereof will be omitted.

1. Ferrite Manufacturing

Example 1

After adding 5g of Fe powder to 200ml of NaOH aqueous solution (50wt%), the mixture was stirred for 40 minutes at a rate of 250rpm while heating to 145°C.

Next, after reaching 140 ° C., maintained for 90 minutes, cooled to 100 ° C. by standing for 15 minutes.

Next, 150ml of the NaFeO ₂ intermediate solution was put in a dropwise method with the lid open of an airtight container filled with 80ml of distilled water, and then kept in the dark with the lid closed.

Next, after adding 100ml of NaOCl (12wt%) aqueous solution to 50ml of NaFeO ₂ intermediate solution, the mixture was stirred for 30 minutes at a speed of 250rpm while heating to 85°C.

Next, Na ₂ FeO ₄ was prepared by maintaining the temperature for 10 minutes in a state of reaching 85°C.

Next, the prepared Na ₂ FeO ₄ was put in an airtight container and stored in the dark.

Example 2

After adding 5g of Fe powder to 200ml of NaOH aqueous solution (50wt%), ferrite was prepared in the same manner as in Example 1, except that the mixture was stirred at a speed of 250rpm for 40 minutes while heating to 130°C.

Example 3

After adding 5 g of Fe powder to 200 ml of NaOH aqueous solution (50 wt%), ferrite was prepared in the same manner as in Example 1, except that the mixture was stirred at a speed of 250 rpm for 40 minutes while heating to 150 ° C.

Comparative Example 1

After adding 5g of Fe powder to 200ml of NaOH aqueous solution (50wt%), ferrite was prepared in the same manner as in Example 1, except that the mixture was stirred at a speed of 250rpm for 40 minutes while heating to 160°C.

Comparative Example 2

After adding 5g of Fe powder to 200ml of NaOH aqueous solution (50wt%), ferrite was prepared in the same manner as in Example 1, except that the mixture was stirred at a speed of 250rpm for 40 minutes while heating to 200°C.

Comparative Example 3

Ferrite (Na ₂ FeO ₄ ) was prepared by a general wet oxidation method.

2. Observation of solution condition

2 is a photograph showing a NaFeO ₂ intermediate solution prepared according to Example 1, FIG. 3 is a photograph showing a NaFeO ₂ intermediate solution prepared according to Comparative Example 1, and FIG. 4 is a photograph showing a NaFeO ₂ intermediate solution prepared according to Comparative Example 2.

As shown in FIG. 2, after adding 5 g of Fe powder to 200 ml of NaOH aqueous solution (50 wt%), the NaFeO ₂ intermediate solution prepared according to Example 1 heated to 145 ° C. was blue-green in color and confirmed that there was no sludge.

On the other hand, as shown in FIG. 3, it was confirmed that the NaFeO ₂ intermediate solution prepared according to Comparative Example 1 heated to 160 ° C changed the color of the solution from blue green to dark green, and it was confirmed that sludge was generated.

In addition, as shown in FIG. 4, it was confirmed that the NaFeO ₂ intermediate solution prepared according to Comparative Example 2 heated to 200° C. generated a large amount of sludge while the color of the solution changed to brown.

Meanwhile, FIG. 5 is a photograph showing Na ₂ FeO ₄ prepared according to Example 1.

As shown in FIG. 5, Na ₂ FeO ₄ prepared by adding 100 ml of an aqueous solution of NaOCl (12 wt%) to 50 ml of the NaFeO ₂ intermediate solution prepared according to Example 1 and maintaining for 10 minutes in a state of reaching 85 ° C. As shown, it can be confirmed that ferrite is well formed without sludge.

3. Property evaluation

Table 1 shows the UV absorbance measurement results for each storage period of ferrite according to Examples 1 to 3 and Comparative Example 3, and FIG. 6 is a graph showing the UV absorbance measurement results for each storage period of ferrite according to Examples 1 and Comparative Example 3.

storage period Comparative Example 3 Example 1 Example 2 Example 3 date of manufacture 3.50 8.26 8.27 8.28 4 days 0.41 7.71 7.73 7.72 8 days 0.26 7.26 7.30 7.25 12 days - 7.69 7.71 7.70 16th - 7.77 7.80 7.78 22nd - 7.64 7.67 7.65

As shown in Table 1 and FIG. 6, the UV absorbance measurement results for each storage period of ferrite according to Examples 1 to 3 and Comparative Example 3 are shown.

At this time, as a result of measuring the UV absorbance of the ferrites according to Examples 1 to 3, it can be confirmed that there is no significant change in the measured UV absorbance value (505λ) until 22 days have elapsed from the manufacturing date.

On the other hand, as a result of measuring the UV absorbance for each storage period, it was confirmed that the measured UV absorbance value (505 λ) of the ferrite according to Comparative Example 3 had already decreased to about 90% after 4 days from the manufacturing date.

As can be seen from the above experimental results, it was confirmed that the ferrites according to Examples 1 to 3 were easy to store and use for a long time due to an increased half-life.

On the other hand, Table 2 shows the T-N removal rate measurement results for each storage period of ferrite according to Examples 1 to 3 and Comparative Example 3, and FIG. 7 is a graph showing the T-N removal rate measurement results for each storage period of ferrite according to Examples 1 and Comparative Example 3.

storage period Comparative Example 3 Example 1 Example 2 Example 3 date of manufacture 31.0% 69.0% 69.3% 69.5% 4 days 2.4% 69.0% 69.2% 69.3% 8 days 1.8% 66.7% 66.8% 66.9% 12 days 1.2% 63.1% 63.2% 63.4% 16th 0.8% 64.3% 64.5% 64.7% 22nd 0.8% 63.4% 63.7% 63.8%

As shown in Table 2 and FIG. 7, the T-N removal rate measurement results for each storage period of ferrite according to Examples 1 to 3 and Comparative Example 3 are shown.

At this time, as a result of comparing the T-N removal rate measurement for each storage period of the ferrites according to Examples 1 to 3, it can be confirmed that there is no significant change in the T-N removal rate (desulfurization wastewater) until 22 days have elapsed from the manufacturing date.

On the other hand, as a result of comparing the T-N removal rate measurement of the ferrite according to Comparative Example 3, it was confirmed that the T-N removal rate (desulfurization wastewater) was lowered to less than half from the time point 4 days after the manufacturing date.

As described above, the embodiments and comparative examples of the present invention have been described in detail, but the scope of the present invention is not limited thereto, and the scope of the present invention extends to those within the scope substantially equivalent to the embodiments of the present invention.

S110: NaFeO ₂ intermediate solution preparation step
S120: heating and stirring step
S130: Na ₂ FeO ₄ formation step
S140: cow storage step

Claims (9)

(a) preparing a NaFeO ₂ intermediate solution;
(b) adding an aqueous solution of NaOCl to the NaFeO ₂ intermediate solution and stirring while heating to a set temperature;
(c) forming Na ₂ FeO ₄ by reacting the NaFeO ₂ intermediate solution with the NaOCl aqueous solution while maintaining the set heating temperature; and
(d) putting the Na ₂ FeO ₄ prepared in step (c) in an airtight container and storing it in the dark;
After the step (d), the Na ₂ FeO ₄ stored in the dark in the sealed container slows down the autolysis phenomenon and maintains a concentration of 80% or more after 20 days or more. Method for producing ferrite with increased half-life. According to claim 1,
In step (a),
(a-1) stirring while heating to 130 ~ 150 ℃ after adding Fe powder to the NaOH aqueous solution;
(a-2) when the temperature reaches 130 to 150° C., reacted by maintaining for 1 to 2 hours, cooled to 95 to 105° C., and mixed with distilled water in a dropwise manner to prepare a NaFeO ₂ intermediate solution; and
(a-3) storing the NaFeO ₂ intermediate solution in a closed container filled with distilled water in a drop-wise manner and storing it in the dark;
Method for producing ferrite with increased half-life, characterized in that it comprises a. According to claim 2,
In step (a-1),
The Fe powder is
A method for producing ferrite with increased half-life, characterized in that 0.5 to 4.5 g is added per 100 ml of the NaOH aqueous solution. According to claim 2,
In step (a-2),
The cooling
A method for producing ferrite with increased half-life, characterized in that it is naturally cooled for 10 to 30 minutes until it reaches 95 to 105 ° C., and then mixed with distilled water in a dropwise manner to prevent coagulation. According to claim 1,
In step (b),
The NaFeO ₂ intermediate solution and NaOCl aqueous solution are
A method for producing ferrite with increased half-life, characterized in that it is added in a weight ratio of 1: 1 to 1: 10. According to claim 1,
In step (b),
The set temperature is
Method for producing ferrite with increased half-life, characterized in that 70 ~ 90 ℃. According to claim 1,
In step (b),
The stirring
Method for producing ferrite with increased half-life, characterized in that carried out for 10 to 60 minutes at a speed of 100 to 1,000 rpm. According to claim 1,
When stirring,
A method for producing ferrite with increased half-life, characterized in that ultrasonic treatment is performed together at a frequency of 30 to 45 KHz and an output voltage of 7 to 17 W. delete