KR101193454B1 - Iron powder recovery method from waste permanent magnet - Google Patents

Abstract

PURPOSE: An iron powder collecting method from waste permanent magnet is provided to prevent production of crude or emulsion in iron separation and purification processes. CONSTITUTION: An iron powder collecting method from waste permanent magnet comprises the following steps: obtaining NdFeB waste scrap powder by pulverizing the NdFeB waste permanent magnets(s110); oxidizing the NdFeB waste scrap powder; separating and purifying the NdFeB waste scrap powder by dipping the oxidized NdFeB waste scrap powder in a NaOH solution(s120); reducing by agitating a reducing agent with the iron slurry(s140); filtering the iron precipitate and washing the iron precipitate by using a washing solution(s150); and collecting the iron precipitate by drying the washed iron precipitate(s160). In the third step, the NaOH solution is mixed at 1:3-1:9 based on 1 mole of the NdFeB waste scrap powder. In the fourth step, the iron slurry is the FeCl3 slurry solution, and the reducing agent is the NaBH4 solution. [Reference numerals] (AA) Start; (BB) End; (S110) Obtaining NdFeB waste scrap powder; (S120) Oxidation roasting process; (S130) Iron slurry separation purification; (S140) Reduction reaction; (S150) Filtering/washing; (S160) Collecting iron powder

Description

Iron powder recovery method from waste permanent magnet {IRON POWDER RECOVERY METHOD FROM WASTE PERMANENT MAGNET}

The present invention relates to a method for recovering iron powder, and more particularly, by effectively recovering iron powder from NdFeB-based waste permanent magnet, it is possible to prevent the formation of an emulsion or a crude in the process of iron separation and purification. The present invention relates to a method for recovering iron powder from waste permanent magnets.

NdFeB-based permanent magnets are widely used in parts requiring high magnetic magnets such as cranking motors, computers, audio-visual components, magnetic separators, aerospace systems, and other equipment. .

The demand for NdFeB permanent magnets has soared, and the average annual growth rate of the global NdFeB permanent magnets market has been dominating the permanent magnets market for 30 ~ 70% depending on the type of magnet. Therefore, the generation of waste scrap is expected to increase rapidly due to the increased demand for NdFeB-based permanent magnets.

Generally, about 20-30% of neodymium (Nd) is contained in waste scrap powder obtained by crushing and crushing NdFeB-based permanent magnets, and recovering Nd from these NdFeB-based permanent magnets is the three major raw materials of Nd metal. It is one of the sources.

Recently, in order to make a rapid development of the electronics industry, to expand the spread of electronic devices, and to increase the processing speed, micronized, highly functionalized, diversified, and precisiond high-density electronic circuit devices have been established. It is necessary. 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.

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 neodymium, which is a rare earth element, a technology for efficiently separating and purifying iron in a separation and purification process is necessary.

Related prior arts are Korean Patent Registration No. 10-1047838 (2011.07.08 publication), which discloses a method for recovering residual actinium element in molten chloride salt, and recovers iron powder from waste permanent magnets. There is no disclosure of the technology.

An object of the present invention is made of a spherical shape, by effectively recovering the iron powder from the NdFeB-based waste permanent magnet using a reducing agent to prevent the formation of emulsion or crude in the separation and purification of iron in advance. It is to provide a method for recovering the pure iron powder having a particle average diameter of 50 to 100 nm.

Iron powder recovery method from the waste permanent magnet according to an embodiment of the present invention for achieving the above object comprises the steps of (a) crushing and grinding the NdFeB waste permanent magnet to obtain NdFeB waste scrap powder; (b) roasting the obtained NdFeB waste scrap powder; (C) separating and purifying the iron slurry by immersing the roasted NdFeB waste scrap powder in NaOH solution; (d) stirring the reduction reaction while adding a reducing agent to the separated and purified iron slurry; (e) filtering the iron precipitate precipitated by the reduction reaction, followed by washing with a washing solution; And (f) recovering the iron powder by drying the washed iron precipitate.

Iron powder recovery method from the waste permanent magnet according to the present invention, after the NdFeB waste scrap powder is subjected to roasting oxidation, immersed in NaOH solution to separate and refine the iron slurry, and then through the reduction reaction using NaBH ₄ as a reducing agent , It is spherical and can recover the pure iron powder having an average particle size of 50 ~ 100nm.

In addition, the present invention, after making the iron slurry in the waste scrap leachate of NdFeB-based permanent magnet, and recovering the iron powder using NaBH ₄ as a reducing agent, during the separation and purification of iron emulsion or crude (crud It is possible to prevent the generation of). As a result, the recovery rate of neodymium contained in the NdFeB waste permanent magnet can be improved.

1 is a flow chart showing a method for recovering iron powder from the waste permanent magnet according to an embodiment of the present invention.
Figure 2 is a photograph showing the waste scrap powder obtained by crushing and grinding the NdFeB waste permanent magnet.
FIG. 3 is a process schematic diagram illustrating the process of roasting oxide of FIG. 1.
Figure 4 shows the X-ray diffraction pattern for the samples prepared according to Examples 1 to 3.
Figure 5 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. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms, and only the present embodiments make the disclosure of the present invention complete, and the general knowledge in the technical field to which the present invention belongs. It is provided to fully convey the scope of the invention to those skilled in the art, and the invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Hereinafter, a method for recovering iron powder from waste permanent magnets according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flow chart showing a method for recovering iron powder from the waste permanent magnet according to an embodiment of the present invention.

Referring to Figure 1, the iron powder recovery method from the waste permanent magnet according to an embodiment of the present invention, NdFeB waste scrap powder obtaining step (S110), roasting oxide treatment step (S120), iron slurry separation purification step (S130), It includes a reduction reaction step (S140), filtering / washing step (S150) and iron powder recovery step (S160).

NdFeB waste scrap powder obtained

In the NdFeB waste scrap powder obtaining step (S110), the NdFeB waste permanent magnet is crushed and pulverized to obtain NdFeB waste scrap powder.

At this time, the NdFeB waste scrap powder may be obtained by crushing and crushing the NdFeB waste permanent magnet generated during dismantling of used household appliances, automobiles and the like.

On the other hand, Figure 2 is a photograph showing the waste scrap powder obtained by crushing and grinding the NdFeB waste permanent magnet.

Referring to Figure 2, NdFeB waste permanent magnet is made of NdFeB waste scrap powder having an average particle size of 100 ~ 350 mesh (mesh) by the crushing and grinding process. In this case, when the average particle size of the NdFeB waste scrap powder exceeds 100 mesh, the leaching efficiency decreases because the particle size is too large, on the contrary, when the average particle size of the NdFeB waste scrap powder is less than 350 mesh, excessive grinding cost occurs. In addition, the leaching may cause a problem in which the viscosity of the iron slurry increases rapidly.

Oxidation Oxidation  process

On the other hand, Figure 3 is a process schematic diagram showing the roasting process of FIG.

1 and 3, in the roasting oxide treatment step (S120), the waste scrap powder obtained by the waste scrap powder obtaining step (S110) is subjected to roasting treatment in an oxygen atmosphere of 600 to 800 ° C.

In the oxidation oxidation treatment step (S120), when the heat treatment temperature is less than 600 ° C., there is a fear that a sufficient oxidation reaction does not occur. On the contrary, when the heat treatment temperature exceeds 800 ° C, it is not economical because the effect against the increase in cost is insignificant. At this time, the roasting oxide treatment time can be appropriately adjusted according to the amount of waste scrap powder added, but is not particularly limited, it is preferably carried out for a sufficient time for the oxidation reaction to occur.

This roasting oxide treatment is preferably carried out to oxidize by performing the roasting treatment in the oxygen atmosphere in which oxygen gas is blown into the furnace (furnace) maintained at a high temperature of 600 ~ 800 ℃.

In this step, when the NdFeB waste scrap powder is subjected to roasting treatment, the Nd contained in the waste scrap powder And Fe may be oxidized in the form of the following formulas (1), (2) and (3).

Formula (1): 2Nd + 3 / 2O ₂ → Nd ₂ O ₃

Formula (2): 2Fe + 3 / 2O ₂ → Fe ₂ O ₃

Formula (3): Nd + Fe + 3 / 2O ₂ → NdFeO ₃

NaOH dipping

In the NaOH immersion step (S130), the iron slurry is clarified by dipping the oxidized NdFeB waste scrap powder in NaOH solution.

In this step, the immersion temperature is preferably carried out at 90 ~ 150 ℃. If the immersion temperature is less than 90 ℃ because the reaction rate is very slow, it is not preferable in terms of production yield. On the contrary, when the immersion temperature exceeds 150 ℃ it is not economical because the effect compared to the increase in the process cost is small.

In addition, in this step, for one mole of the NdFeB waste scrap powder subjected to the roasting treatment, NaOH solution is preferably mixed 1: 3 to 1: 9. With respect to 1 mole of NdFeB waste scrap powder subjected to oxidation oxidation, when the molar ratio of NaOH solution is less than 3, a part of Nd may cause a problem in that it does not participate in the hydroxylation reaction. On the contrary, when the molar ratio of NaOH solution exceeds 9 with respect to 1 mol of roasted NdFeB waste scrap powder, it is meaningless in terms of economy.

On the other hand, in this step, when the oxidation-treated NdFeB waste scrap powder is immersed in NaOH solution, the hydroxide reaction may occur in the form of the following formula (4) and (5).

Formula (4): Nd ₂ O ₃ + 6NaOH → 2Nd (OH) ₃ + 3Na ₂ O

Formula (5): Fe ₂ O ₃ + 6NaOH → 2Fe (OH) ₃ + 3Na ₂ O

Reduction reaction

In the reduction reaction step (S140), while reducing the reaction by adding a reducing agent to the separated and purified iron slurry. In this case, the iron slurry may be a FeCl ₃ slurry solution. And, the reducing agent may be used NaBH ₄ solution.

Here, the FeCl ₃ slurry solution is preferably mixed in a molar ratio of 1: 3 to 1: 5 with respect to the NaBH ₄ solution as the reducing agent. When the molar ratio of the FeCl ₃ slurry solution and the NaBH ₄ solution is less than 1: 3, the reduction reaction may not be completely performed because the molar ratio of the iron 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 NaBH ₄ solution is preferably continuously supplied in a drop-wise manner into the reactor filled with FeCl ₃ slurry solution. When supplied in a drop-wide manner continuously supplying drop by drop rather than a batch method of supplying a reducing agent at once, it is advantageous not only to secure the spherical iron powder but also to easily control the particle size. At this time, as soon as the NaBH ₄ solution, which is a reducing agent, was supplied dropwise in a reaction vessel filled with a FeCl ₃ slurry solution, bubbles immediately formed and black iron precipitates formed. It was confirmed through an experiment.

Moreover, it is preferable to add a reducing agent at the rate of 1 ml / min-5 ml / min. If the rate of addition of the reducing agent is less than 1 ml / min, there is a problem that the nucleation is small and the nuclear growth is long, resulting in coarse particle sizes. On the contrary, when the addition rate of the reducing agent exceeds 5ml / min, the 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 put into the reaction tank filled with NaBH ₄ solution FeFe ₃ slurry solution, the foaming is no longer generated, it is preferably carried out for 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 (S150), 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.

Iron powder recovery

In the iron powder recovery step (S160), 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 powder recovery method from the waste permanent magnet according to an embodiment of the present invention described above, after the NdFeB waste scrap powder is subjected to roasting oxidation, immersed in NaOH solution to separate and purify the iron slurry, using NaBH ₄ as a reducing agent Through the reduction reaction, pure iron powder having a spherical shape and having an average particle size of 50 to 100 nm can be recovered.

In addition, the present invention, after making the iron slurry in the waste scrap leachate of NdFeB-based permanent magnet, and recovering the iron powder using NaBH ₄ as a reducing agent, during the separation and purification of iron emulsion or crude (crud It is possible to prevent the generation of). As a result, the recovery rate of neodymium contained in the NdFeB waste permanent magnet 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

After the NdFeB waste permanent magnet was pulverized to 325 mesh to obtain NdFeB waste scrap powder, 100 g of the obtained NdFeB waste scrap powder was charged into a furnace and subjected to roasting treatment for 2 hours while raising the temperature to 600 ° C. Thereafter, 10 g of oxidized NdFeB waste scrap powder was immersed in 50 ml of NaOH solution to separate and purify the iron slurry.

Subsequently, while rotating at 100 rpm using an impeller (MS-5020, TOPS), droplets of NaBH ₄ (99% or more, across, USA), which is a reducing agent, were dropped into the iron slurry at a rate of 1 ml / min to provide a molar ratio with the iron slurry. After adjusting to 1: 3, the reaction was reduced at 30 ° C. for 10 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 18 hours to obtain iron powder.

Example 2

NdFeB waste permanent magnet was pulverized to 325 mesh to obtain NdFeB waste scrap powder, and then 100 g of the obtained NdFeB waste scrap powder was charged into a furnace and subjected to roasting treatment for 2 hours while raising the temperature to 700 ° C. Thereafter, 10 g of oxidized NdFeB waste scrap powder was immersed in 50 ml of NaOH solution to separate and purify the iron slurry.

Subsequently, while rotating at 200 rpm using an impeller (MS-5020, TOPS), a droplet of NaBH ₄ (99% or more, across, USA), which is a reducing agent, was dropped into the iron slurry at a rate of 3 ml / min to provide a molar ratio with the iron slurry. Was adjusted to 1: 4, and the reaction was reduced for 5 minutes at 50 ° 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 3

After the NdFeB waste permanent magnet was pulverized to 200 mesh to obtain NdFeB waste scrap powder, 100 g of the obtained NdFeB waste scrap powder was charged into a furnace and subjected to roasting treatment for 2 hours while raising the temperature to 800 ° C. Thereafter, 10 g of oxidized NdFeB waste scrap powder was immersed in 50 ml of NaOH solution to separate and purify the iron slurry.

Subsequently, while rotating at 300 rpm using an impeller (MS-5020, TOPS), NaBH ₄ (99% or more, across, USA), a reducing agent, was dropped into the iron slurry at a rate of 5 ml / min to provide a molar ratio with the iron slurry. Was adjusted to 1: 5, and then reduced at 60 ° C. for 2 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 60 ° C. for 14 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).

Table 1 shows the average particle diameter of the samples prepared according to Examples 1 to 3, Figure 4 shows the X-ray diffraction pattern for the samples prepared according to Examples 1 to 3.

[Table 1]

As shown in Table 1 and Figure 4, in the case of samples prepared according to Examples 1 to 3 it was confirmed that the average particle diameter of all 100nm or less.

And, as a result of XRD analysis, it can be seen that in the case of samples prepared according to Examples 1 to 3, most Fe powders and iron hydroxide type compounds exist. 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, Figure 5 shows a microstructure photograph of the sample prepared according to Example 3.

As shown in FIG. 5, when the shape of the iron powder was examined using an electron microscope, it was confirmed that the powder produced according to Example 3 had a monodisperse form and had a form close to a spherical shape, and the particles It was confirmed that the average diameter of was about 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: NdFeB waste scrap powder obtaining step
S120: roasting oxide treatment step
S130: Iron Slurry Separation Purification Step
S140: reduction reaction step
S150: Filtering / Washing Step
S160: Iron Powder Recovery Step

Claims (12)

(a) crushing and grinding the NdFeB waste permanent magnet to obtain NdFeB waste scrap powder;
(b) roasting the obtained NdFeB waste scrap powder;
(C) separating and purifying the iron slurry by immersing the roasted NdFeB waste scrap powder in NaOH solution;
(d) stirring the reduction reaction while adding a reducing agent to the separated and purified iron slurry;
(e) filtering the iron precipitate precipitated by the reduction reaction, followed by washing with a washing solution; And
(f) recovering the iron powder by drying the washed iron precipitate;
In the step (c), the NaOH solution is iron powder from the waste permanent magnet, characterized in that mixing 1 to 3 to 1: 9 to 1 mole of the oxidized NdFeB waste scrap powder.
The method of claim 1,
The NdFeB waste scrap powder is
A method for recovering iron powder from waste permanent magnets, characterized in that it has an average particle size of 100 to 350 mesh.
The method of claim 1,
In the step (b)
The roasting oxide treatment
A method for recovering iron powder from waste permanent magnets, which is carried out in an oxygen atmosphere at 600 to 800 ° C.
The method of claim 1,
In the step (c)
The immersion temperature is 90 ~ 150 ℃ iron powder recovery method from the permanent magnet, characterized in that.
delete The method of claim 1,
In the step (d)
Wherein said iron slurry is a FeCl ₃ slurry solution and said reducing agent is a NaBH ₄ solution.
The method of claim 6,
The FeCl ₃ slurry solution
Iron powder recovery method from the waste permanent magnet, characterized in that mixing with the NaBH ₄ solution in a molar ratio of 1: 3 to 1: 5.
The method of claim 1,
In the step (d)
The stirring is
A method for recovering iron powder from waste permanent magnets, which is performed at a speed of 100 to 300 rpm.
The method of claim 1,
In the step (d)
The reduction reaction is
Iron powder recovery method from the waste permanent magnet, characterized in that carried out for 30 to 60 ℃ for 1 to 10 minutes.
The method of claim 1,
In the step (d)
The reducing agent
A method for recovering iron powder from waste permanent magnets, which is added at a rate of 1 ml / min to 5 ml / min.
The method of claim 1,
In the step (f)
The drying is iron powder recovery method from the permanent permanent magnet, characterized in that carried out for 10 to 20 hours at 50 ~ 70 ℃.
delete

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