KR101351913B1 - Manufacturing method of iron nano particles using slurry reduction process - Google Patents

Abstract

By applying the slurry reduction method using FeCl ₃ as the iron precursor and NaBH ₄ as the reducing agent, the iron nano powder using the slurry reduction method to produce pure iron nano powder of spherical shape and the average particle size of 50 ~ 100nm A manufacturing method is disclosed.
Step of Example Iron nano powder production method using the slurry reduction method according to the present invention is provide a slurry FeCl ₃ solution by dissolving the (a) FeCl ₃ in distilled water (H ₂ O); (b) adding the FeCl ₃ slurry solution into a reaction tank filled with a NaBH ₄ solution as a reducing agent to perform a reduction reaction; (c) filtering the iron precipitate precipitated by the reduction reaction, followed by washing with a washing solution; And (d) drying the washed iron precipitate at 50 to 70 ° C. for 10 to 20 hours to obtain iron powder.

Description

Manufacturing method of iron nano powder using slurry reduction method {MANUFACTURING METHOD OF IRON NANO PARTICLES USING SLURRY REDUCTION PROCESS}

The present invention relates to a method for producing iron nanopowder, and more particularly, a slurry capable of producing a spherical pure iron nanopowder by applying a slurry reduction method using FeCl ₃ as an iron precursor and NaBH ₄ as a reducing agent. It relates to a method for producing iron nano powder using a reduction method.

It is necessary to establish a chemically stable and conductive fine metal powder manufacturing technology for the micronized, high-functionality, diversification and precision of high-density electronic circuit elements for the rapid development of the electronics industry, the expansion of electronic devices, and the improvement of processing speed. Do. To this end, it is necessary to develop a source technology capable of synthesizing fine metal powders and controlling their properties in an economical and environmentally friendly way.

Although the research and development of fabricated metal powders and their utilization have been considerable, the researches on the production and shape control of fine metal powders for conductive coatings and the development of coatings using metal powders are still in their infancy. There is no shape control technology, so it remains an obstacle to commercialization. In particular, since the morphology of the fine metal powder has a great influence on the conductivity of the paste, the adhesion and wettability of the coating layer, and the thermal conductivity, it is essential to establish the shape control technology of the raw metal powder for the continuous development of related industries. .

In general, the reduction of metal ions occurs as a result of oxidation and reduction reactions by electrons supplied from a reducing agent.

mMe ^{n +} + nRedmMe ⁰ + nO _X

The driving force of the above reaction is the difference between the redox potential (ΔE), which is the half reaction. At this time, the magnitude of ΔE is determined by the following equation.

ln Ke = nF ㆍ △ E / RT

In this case, the reduction reaction is thermodynamically possible when ΔE is a positive value. That is, the redox potential of the reducing agent should have a negative value than the metal ion, and the difference should be greater than 0.3 to 0.4V. If the difference is smaller, the reduction does not occur or proceeds very slowly.

Strongly positive metals such as Au, Pt, Pd, Ag, and Rh (E ₀ > 0.7V) are negative (E ₀ <-0.2V) while the reduction occurs under normal reaction conditions even with weak reducing agents. Requires a strong reducing agent or high temperature or pressure.

Therefore, in order to obtain metal powders of the same size by using reducing agents having different reducing powers, reaction temperatures are different, and similarly, metal powders of similar sizes vary in reactivity and crystallinity depending on the reducing agent used.

As described above, the growth reaction mechanism in the production process of the metal particles in the solution is as follows.

First, there is a process of growing by attaching to neutral metal atoms on the already formed particles, and second, a process of growing by agglomeration or adhesion between the already formed particles. These two distinct pathways can explain various phenomena related to the size, shape and structure of finely dispersed metals.

When the growth occurs in the first method, it develops into a regular metal crystal, and in the second method, it grows into a spherical polycrystal. In practice, however, growth and aggregation occur simultaneously in the same system, and depending on which process governs the polycrystalline, grain boundaries, density, and shape of the final particles.

The final size of the metal particles will vary depending on the degree of supersaturation, the amount of solutes involved in the nucleation step, the amount of metals involved in the system, and the cohesion. If the supersaturation of the metal atoms is high, a large number of nuclei are generated, and if the aggregation reaction mechanism is suppressed, the increase in particle size can only be expected to grow due to the consumption of the metal remaining in the solution, and thus the final particles become nano-sized. As a result, it is desirable to reduce the metal ions with a strong reducing agent in a sufficiently stabilized system to achieve dispersion of stabilized nanosize particles. If larger particles are desired by diffusion growth, a smaller number of nuclei must be produced. Such conditions can be realized by slow reaction, seed addition or gradual addition of metal ions and the existing particles are stable and therefore aggregation must be suppressed.

The final size of the metal particles grown by aggregation is determined by the strength of the dispersed ions, the surface charge of the initial particles, and the properties of the additives. By controlling such variables, monodisperse colloidal metals of various sizes can be prepared.

In particular, the ionic behavior of iron, which accounts for about 80% in the waste scrap leaching liquor of NdFeB-based permanent magnets, creates an emulsion or a crude in the separation and purification process, thereby reducing the yield of separation and purification. have.

Therefore, in order to recycle the rare earth elements neodymium and dysprosium, it is necessary to study how to accurately understand and control the ionic behavior of iron during separation and purification.

Related prior art documents include Korean Patent Registration No. 10-0966753 (Jun. 29, 2010), which discloses a method for producing iron nano powder sintered body, and discloses a method for preparing iron nano powder using a slurry reduction method. none.

An object of the present invention is to provide a method for producing a pure iron nanopowder having a spherical shape and an average particle size of 50 ~ 100 nm by applying a slurry reduction method using FeCl ₃ as an iron precursor, NaBH ₄ as a reducing agent. will be.

Comprising: Iron nano powder production method using the slurry reduction method according to an embodiment of the present invention for achieving the abovementioned objects is also provided a slurry FeCl ₃ solution by dissolving the (a) FeCl ₃ in distilled water (H ₂ O); (b) adding the FeCl ₃ slurry solution into a reaction tank filled with a NaBH ₄ solution as a reducing agent to perform a reduction reaction; (c) filtering the iron precipitate precipitated by the reduction reaction, followed by washing with a washing solution; And (d) drying the washed iron precipitate at 50 to 70 ° C. for 10 to 20 hours to obtain iron powder.

Iron nano powder production method using the slurry reduction method according to the present invention by using a slurry reduction method using FeCl ₃ as the iron precursor, NaBH ₄ as a reducing agent, it is made of spherical and the average particle size of 50 ~ 100nm pure iron Nano powder can be prepared.

In addition, the present invention utilizes the iron nano-powder manufacturing method described above, after making iron in a slurry state in the waste scrap leachate of NdFeB-based permanent magnets, when using NaBH ₄ as a reducing agent, the selective selection of rare earth elements neodymium and dysprosium There is an effect that can improve the recovery efficiency.

Therefore, by identifying the ionic behavior of iron, which accounts for about 80% in the waste scrap leaching liquor of NdFeB-based waste permanent magnets, the formation of emulsions or crudes in the process of iron separation and purification is not known. Since it can prevent, the separation and purification yield can be improved.

1 is a process flow chart showing a method for producing iron nano powder using a slurry reduction method according to an embodiment of the present invention.
2 shows a Pourbaix diagram of iron.
Figure 3 shows the X-ray diffraction pattern for the samples prepared according to Examples 1 to 3.
Figure 4 shows a microstructure photograph of the sample prepared according to Example 1.
Figure 5 shows a microstructure photograph of the sample prepared according to Example 2.
Figure 6 shows a microstructure photograph of the sample prepared according to Example 3.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and how to accomplish them, will become apparent by reference to the embodiments described in detail below with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the iron nano powder manufacturing method using a slurry reduction method according to a preferred embodiment of the present invention.

1 is a process flow chart showing a method for producing iron nano powder using a slurry reduction method according to an embodiment of the present invention.

Referring to Figure 1, the iron nano powder manufacturing method using a slurry reduction method according to an embodiment of the present invention FeCl ₃ slurry solution preparation step (S110), reduction reaction step (S120), filtering / washing step (S130) and drying step (S140).

FeCl ₃  Slurry Solution

In the FeCl ₃ slurry solution preparation step (S110), FeCl ₃ is dissolved in distilled water (H ₂ O) to prepare a FeCl ₃ slurry solution.

At this time, FeCl ₃ and distilled water reacts as in Scheme 1 below.

Scheme 1: FeCl ₃ + 3H ₂ O → Fe (OH) ₃ + 3HCl

Reduction reaction

In the reduction reaction step (S120), the FeCl ₃ slurry solution is added to a reaction tank filled with a NaBH ₄ solution as a reducing agent for reduction.

Here, the entire reaction scheme where FeCl ₃ is reduced by NaBH ₄ is the same as Scheme 2 below.

Scheme 2: 2FeCl ₃ + 6NaBH ₄ + 18H ₂ O → 2Fe + 21H ₂ + 6B (OH) ₃ + 6NaCl

Oxidation _{reaction: 2NaBH 4 + 6H 2 O →} 7H 2 + 2B (OH) 3 + 2Na + + 2e -

Reduction: Fe ³⁺ + 3e ^- → Fe

At this time, the FeCl ₃ slurry solution is preferably mixed in a molar ratio of 1: 3 to 1: 5 with respect to NaBH ₄ solution. When the molar ratio of the FeCl ₃ slurry solution and NaBH ₄ solution is less than 1: 3, the reduction reaction may not be completely performed since the molar ratio of the FeCl ₃ slurry solution to the NaBH ₄ solution is low. On the contrary, when the molar ratio of the FeCl ₃ slurry solution and the NaBH ₄ solution exceeds 1: 5, the cost increase is greater than the synergistic effect of the addition of the NaBH ₄ solution, which is not economical.

In this step, it is preferable to stir the FeCl ₃ slurry solution and NaBH ₄ solution at a speed of 100 ~ 300rpm using an impeller installed in the reactor. At this time, if the stirring speed is less than 100rpm there is a fear that uniform mixing is not made. On the contrary, when the stirring speed exceeds 300 rpm, there is a problem of only increasing the manufacturing cost without any further effect.

Here, the FeCl ₃ slurry solution is preferably continuously supplied in a drop-wise manner into the reactor filled with NaBH ₄ solution. When supplied in a drop-wide manner continuously supplying drop by drop rather than a batch method of supplying a FeCl ₃ slurry solution at a time, it is advantageous not only to secure a spherical iron powder but also to easily control the particle size. At this time, as soon as the FeCl ₃ slurry solution was supplied dropwise into the reactor filled with a reducing agent, NaBH ₄ solution, bubbles immediately formed and black iron precipitates formed. It was confirmed through an experiment.

In addition, the FeCl ₃ slurry solution is preferably added at a rate of 1 ml / min ~ 3 ml / min. If the addition rate of the FeCl ₃ slurry solution is less than 1ml / min, there is a problem that the nucleation is small and the nuclear growth is long, the particle size is coarse. On the contrary, when the addition rate of the FeCl ₃ slurry solution exceeds 3ml / min, nucleation is constant, but the aggregation of the particles is intensified, it may be difficult to produce a fine iron powder.

On the other hand, when reacting with a NaBH ₄ solution as a reducing agent to reduce the FeCl ₃ slurry solution, the reaction temperature is preferably carried out at 30 ~ 60 ℃. If the reaction temperature is less than 30 ℃ there is a problem that the reduction reaction does not occur because the temperature is too low. On the contrary, when the reaction temperature exceeds 60 ℃ there is a problem that only increases the process cost and time without any further temperature increase effect.

In this case, the reduction reaction is preferably a time point when the FeCl ₃ slurry solution is added to the reaction tank filled with NaBH ₄ solution, the foaming no longer occurs, specifically, 1 to 10 minutes. If the reduction reaction time is less than 1 minute, it may be difficult to prepare a spherical iron powder because the reaction time is too short. On the contrary, when the reduction reaction time exceeds 10 minutes, there is a problem of an increase in manufacturing cost due to the addition of a large amount of NaBH ₄ solution in order to activate the reduction reaction.

Filter / wash

In the filtering / washing step (S130), the iron precipitate precipitated by the reduction reaction is filtered and then washed with a washing solution.

At this time, in the step is washed with a washing solution while filtering the iron precipitate precipitated by the reduction reaction. At this time, the washing is preferably repeated three or more times using a washing solution consisting of a mixed solution of ethanol and distilled water.

dry

In the drying step (S140), the washed iron precipitates are dried to obtain iron powder.

At this time, the drying is preferably carried out for 10 to 20 hours at 50 ~ 70 ℃. In this step, when the drying temperature is less than 50 ℃, or when the drying time is less than 10 hours, there is a problem that the crystallinity deteriorates due to insufficient drying. On the contrary, when the drying temperature exceeds 70 ° C. or the drying time exceeds 20 hours, not only is the cause of an increase in manufacturing cost, but there is a problem in that the specific surface area decreases due to excessive drying.

Iron nano powder production method according to an embodiment of the present invention described above is made of a spherical shape by using a slurry reduction method using FeCl ₃ as an iron precursor, NaBH ₄ as a reducing agent, the pure particles having an average particle size of 50 ~ 100nm Iron nano powders can be prepared.

In addition, the present invention utilizes the iron nano-powder manufacturing method described above, after making iron in a slurry state in the waste scrap leachate of NdFeB-based permanent magnets, when using NaBH ₄ as a reducing agent, the selective selection of rare earth elements neodymium and dysprosium There is an effect that can improve the recovery efficiency.

Therefore, by identifying the ionic behavior of iron, which accounts for about 80% in the waste scrap leaching liquor of NdFeB-based waste permanent magnets, the formation of emulsions or crudes in the process of iron separation and purification is not known. Since it can prevent, the separation and purification yield can be improved.

Example

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

Details that are not described herein will be omitted since those skilled in the art can sufficiently infer technically.

1. Sample preparation

Example 1

FeCl ₃ (anhydrous, more than 98%, samchun, Korea) was dissolved in distilled water (H ₂ O) to prepare an iron slurry solution. Then, NaBH ₄ (99% or more, across, USA) as a reducing agent was dissolved in distilled water (H ₂ O) and placed in a four-necked flask. Thereafter, while rotating the NaBH ₄ solution at 200 rpm using an impeller (MS-5020, TOPS), the FeCl ₃ slurry solution was added dropwise at a rate of 1 ml / min to adjust the molar ratio with the NaBH ₄ solution to 1: 3. Thereafter, the reaction was reduced for 5 minutes at 30 ° C.

Next, after filtering the precipitated iron precipitate, the iron precipitate was washed three times using a mixed solution of ethanol and distilled water. Next, the washed iron precipitate was dried at 70 ° C. for 10 hours to obtain iron powder.

Example 2

FeCl ₃ (anhydrous, more than 98%, samchun, Korea) was dissolved in distilled water (H ₂ O) to prepare an iron slurry solution. Then, NaBH ₄ (99% or more, across, USA) as a reducing agent was dissolved in distilled water (H ₂ O) and placed in a four-necked flask. Thereafter, while rotating the NaBH ₄ solution at 150 rpm using an impeller (MS-5020, TOPS), the FeCl ₃ slurry solution was added dropwise at a rate of 2 ml / min to adjust the molar ratio with the NaBH ₄ solution to 1: 4. Thereafter, the reaction was reduced for 10 minutes at 40 ° C.

Next, after filtering the precipitated iron precipitate, the iron precipitate was washed three times using a mixed solution of ethanol and distilled water. Next, the washed iron precipitate was dried at 60 ° C. for 12 hours to obtain iron powder.

Example 3

FeCl ₃ (anhydrous, more than 98%, samchun, Korea) was dissolved in distilled water (H ₂ O) to prepare an iron slurry solution. Then, NaBH ₄ (99% or more, across, USA) as a reducing agent was dissolved in distilled water (H ₂ O) and placed in a four-necked flask. Thereafter, while rotating the NaBH ₄ solution at 100 rpm using an impeller (MS-5020, TOPS), dropping the FeCl ₃ slurry solution at a rate of 1ml / min to adjust the molar ratio with the NaBH ₄ solution to 1: 5 Thereafter, the reaction was reduced at 60 ° C. for 3 minutes.

Next, after filtering the precipitated iron precipitate, the iron precipitate was washed three times using a mixed solution of ethanol and distilled water. Next, the washed iron precipitate was dried at 50 ° C. for 20 hours to obtain iron powder.

2. Property results

1) Particle size and shape were observed using an electron microscope (Magellan 400, FEI company or JSM6380, JEOL).

2) Component analysis was performed using XRD (x-ray diffraction).

3) Particle size was analyzed using a nanoparticle size analyzer (NANOPHOX, Sympatec GmbH).

2 shows a Pourbaix diagram of iron.

As shown in FIG. 2, the apparent appearance and pH change of the solution were examined before mixing the FeCl ₃ solution and the NaBH ₄ solution. At this time, when FeCl ₃ was dissolved in water, an orange cloudy suspension was observed, and the pH was 1.7 when the pH was measured. Looking at the Puruobe diagram, it was found that most of these conditions exist in the form of Fe ³⁺ .

And, pH of NaBH ₄ as a reducing agent was used as a basic 10.0. After mixing the two solutions, it was found that the pH was 9.0 at the final state after the reaction was completed. That is, it was found that Fe ³⁺ ions which were not reduced to iron after the completion of the reaction were mostly present in the form of hydroxide in the range of pH 9-10.

Figure 3 shows the X-ray diffraction pattern for the samples prepared according to Examples 1 to 3.

As shown in FIG. 3, as a result of XRD analysis, it was found that in the samples prepared according to Examples 1 to 3, most of Fe powder and iron hydroxide type compounds were present. In particular, it was confirmed that as the molar ratio of NaBH ₄ increases, the amount of Fe (OH) ₃ decreases and the content of pure iron powder increases.

On the other hand, Figures 4 to 6 shows a microstructure picture for the samples prepared according to Examples 1 to 3.

As shown in Figures 4 to 6, as a result of looking at the shape of the iron powder using an electron microscope, it was confirmed that the powder produced in accordance with Examples 1 to 3 has a monodisperse overall form. In particular, it can be seen that the iron powder produced in Example 3 has a form closer to the spherical form compared to Examples 1 and 2, and the size was approximately 56 nm.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. These changes and modifications may be made without departing from the scope of the present invention. Accordingly, the scope of the present invention should be determined by the following claims.

S110: FeCl ₃ slurry solution preparation step
S120: reduction reaction step
S130: Filtering / Washing Step
S140: drying step

Claims (5)

(a) dissolving FeCl ₃ in distilled water (H ₂ O) to prepare a FeCl ₃ slurry solution;
(b) adding the FeCl ₃ slurry solution into a reaction tank filled with a NaBH ₄ solution as a reducing agent to perform a reduction reaction;
(c) filtering the iron precipitate precipitated by the reduction reaction, followed by washing with a washing solution; And
(d) drying the washed iron precipitates at 50 to 70 ° C. for 10 to 20 hours to obtain iron powder; iron nano powder production method using a slurry reduction method comprising a.
The method of claim 1,
The FeCl ₃ slurry solution
Iron nano powder production method using a slurry reduction method characterized in that the mixing in the molar ratio of 1: 3 to 1: 5 with respect to the NaBH ₄ solution.
The method of claim 1,
In the step (b)
The reduction reaction is
Iron nano powder production method using a slurry reduction method characterized in that performed for 1 to 10 minutes at 30 ~ 60 ℃.
The method of claim 1,
In step (b),
Iron nano powder production method using a slurry reduction method characterized in that the stirring of the FeCl ₃ slurry solution and NaBH ₄ solution at a speed of 100 ~ 300rpm using an impeller installed in the reactor.
The method of claim 1,
In the step (b)
The FeCl ₃ slurry solution
Iron nano-powder manufacturing method using a slurry reduction method characterized in that the drop in the NaWH ₄ solution filled reactor (drop-wise) method.

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