KR101935826B1 - Method for the separation of Nd and Dy by use of REE-sulfate double salt precipitation - Google Patents

Abstract

Provided, in the present invention, is a method of separating Nd/Dy by sulfuric acid salt precipitation comprising: a step of oxidizing roasted permanent magnet scrap to obtain an oxidized roasting powder (first step); a step of extracting the roasted oxidized powder with sulfuric acid to obtain a sulfuric acid leaching solution (second step); and a step of adding sodium sulfate to the sulfuric acid leaching solution to perform a precipitation reaction of the reductive salt and recovering the filtrate (third step), and 1 to 2 equivalents of sodium sulfate is added to the sulfuric acid leaching solution. Therefore, rare-earth element such as neodymium and dysprosium can be recovered by separating iron components from waste permanent magnet scrap.

Description

Sulfuric Acid Separation Method for Nd / Dy Separation by Nd / Dy Separation Method

The present invention relates to a method for selectively separating and recovering rare earth elements, neodymium (Nd) and dysprosium (Dy), from waste permanent magnet scrap.

Rare earths are widely used in high technology industries as vitamins of industry because of various characteristics, and the demand for rare earths in Korea is continuously increasing with the growth of advanced industries such as electronics and automobiles. As can be seen from the recent regulation on export of rare earths originating from the dispute over the territorial rights of China and Japan, rare earths have some reserves in some countries, so it is essential to establish stable supply and demand methods for the continuous development of domestic industries. For this purpose, Korea, which is a resource - poor country, recently has been trying to acquire raw materials by recycling domestic waste resources along with overseas resource development.

NdFeB-based permanent magnets are widely used in automotive cranking motors, computers, audio-visual components, magnetic separators, military and aerospace systems, and other equipment requiring high magnets with reduced size and weight 1). Therefore, among the rare earth elements, neodymium (Nd) is a rare earth element which is attracting attention as a main raw material of NdFeB permanent magnet, and dysprosium (Dy) is added to improve the heat resistance of the permanent magnet. In particular, dysprosium is a rare earth element that has been scarcely selected as an export prohibited item in China. However, at present, in Korea, the motors containing permanent magnets are disposed of as scrap iron, so that the loss of rare earth resources is serious.

Therefore, it is urgent to develop the circulation utilization technology of NdFeB - based permanent permanent magnets, which is an expensive resource, as a valuable secondary resource considering the importance and rareness of rare earth resources in Korea.

In recent years, high-performance permanent magnets, which are rapidly increasing in demand, are doped with elements such as dysprosium and terbium to maintain the coercive force even in a high temperature driving environment, and the content thereof is about 4 to 7%. The increase of heavy rare earth such as dysprosium, which does not easily occur in the precipitation of sulfuric acid salt compared to light rare earth such as neodymium, greatly increases the consumption of sodium sulfate during the separation and selective recovery of rare earth element and iron by the sulfuric acid precipitation method.

In order to recover high purity neodymium and dysprosium from neodymium and dysprosium sulfate salts, it is subjected to a hydroxide-hydrochloric acid dissolution and solvent extraction process. When the dysprosium content relative to neodymium is reduced, The efficiency of the extraction process can be improved.

 Therefore, in this study, we have developed a separation and recovery method of neodymium and dysprosium by using difference of sedimentation rate of Sulfuric Acid Salts. By reducing the dysprosium content of neodymium in sediments of sulfuric acid fertilizer and the unreacted dysprosium in the Sulfuric acid salt filtrate, And to recover a high purity diruphosium.

As a prior art related to this, there is a method of recovering rare earth elements from spent permanent magnet oxide scraps disclosed in Korean Patent Registration No. 10-13923079 (published on September 17, 2012).

Korean Registered Patent No. 10-13923079 (issued on September 17, 2012)

Accordingly, the present invention discloses a method for separating rare earth elements from neodymium, which is a rare rare earth, and dysprosium, which is a heavy rare earth, by precipitation and recovering the rare earth element by leaching the pulsed permanent magnet oxide scrap.

In particular, neodymium and dysprosium are separated using a precipitation reaction, and the dysprosium can be separated and recovered in a single process by changing the sedimentation rate by adjusting the sodium sulfate input amount, the temperature and the sodium chloride input amount in the sulfuric acid leaching solution.

The problems to be solved by the present invention are not limited to the above-mentioned problem (s), and another problem (s) not mentioned can be understood by those skilled in the art from the following description.

In order to solve the above-described problems, the present invention provides a method for manufacturing a magnetic disk, comprising the steps of (1): oxidizing roasted permanent magnet scrap to obtain an oxidized roasting powder; Extracting the roasted oxidized powder with sulfuric acid to obtain a sulfuric acid leaching solution (second step); And (3) adding sodium sulfate to the sulfuric acid leaching solution to perform a precipitation reaction of the reductive salt and recovering the filtrate (step 3), wherein 1 to 2 equivalents of sodium sulfate is added to the leaching solution of sulfuric acid And a Nd / Dy separation method by a sulfuric acid salt precipitation method.

The roasting may be carried out at 600 DEG C for 5 hours.

The oxidized roasted powder may contain impurities such as neodymium (Nd) 14.0 wt%, dysprosium (Dy) 5.27 wt%, iron (Fe) 53.3 wt%, and residual impurities.

The above-described precipitation reaction may be carried out at 30 to 70 캜 for 3 hours.

Further, oxalic acid is added to the filtrate to recover the dysprosium, and the quality of the recovered dysprosium can be adjusted to 67 to 97.7%.

Further, 1 mole of sodium chloride may be added to the sulfuric acid leaching solution to perform the precipitation reaction of the salt.

Further, 0.5 to 1 mol of sodium chloride is added to the sulfuric acid leaching solution to adjust the dysprosium recovered in the filtrate to 97.3 to 98.7%.

According to the present invention, neodymium and dysprosium can be selectively separated and recovered from scrap of high-performance pulsed permanent magnets having a high content of dysprosium relative to neodymium.

It is also possible to reduce the dysprosium content relative to neodymium in the precipitate of sulfuric acid bicarbonate salt and to separate and recover dysprosium in a single process in high purity.

1 is a process flow diagram of a Nd / Dy separation method by a sulfuric acid salt precipitation method according to an embodiment of the present invention.
FIG. 2 is a graph showing the precipitation of double salt according to the reaction temperature of neodymium. FIG.
FIG. 3 is a graph showing the precipitation of bicarbonate according to the reaction temperature of dysprosium. FIG.
Fig. 4 shows XRD analysis results of sediments precipitated by adding sodium sulfate to an aqueous solution of sulfuric acid having neodymium dissolved therein.
5 shows the sedimentation rate of neodymium sulfate bisulfite according to the addition amount of sodium sulfate and the reaction temperature from an aqueous solution of neodymium sulfate.
FIG. 6 is a graph showing a change in sedimentation rate of dysprosium salt by sodium sulfate from an aqueous sulfuric acid solution in which only dysprosium is dissolved.
7 is a graph showing the precipitation rate of dysprosium salt salt by adding a small amount of neodymium aqueous solution to an aqueous solution of sulfuric acid in which dysprosium is dissolved, followed by addition of sodium sulfate.
FIG. 8 is a graph showing the sedimentation behavior of the sulfate sulphate according to the addition amount of sodium sulfate in the Nd / Dy separation method by the precipitation method of sulfuric acid salt according to the embodiment of the present invention.
FIG. 9 is a graph showing the precipitation behavior of the sulfuric acid composite salt depending on the reaction temperature and the amount of sodium sulfate added in the Nd / Dy separation method according to the present invention.
FIG. 10 is a graph showing the dysprosium content of the filtrate after the precipitation reaction of the double salt in the Nd / Dy separation method by the sulfuric acid salt precipitation method according to the embodiment of the present invention.

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

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving it will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings.

The present invention may, however, be embodied in many different forms and should not be construed as 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. To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

The Nd / Dy separation method according to the present invention is characterized in that the waste permanent magnet scrap is oxidatively roasted to obtain an oxide rosin powder (first step); Extracting the roasted oxidized powder with sulfuric acid to obtain a sulfuric acid leaching solution (second step); And adding sodium sulfate to the sulfuric acid leaching solution to perform a precipitation reaction of the reductive salt and recovering the filtrate (step 3), wherein sodium sulfate is added to the sulfuric acid leaching solution in an amount of 1 to 2 equivalents .

1 is a process flow diagram of a method for selectively recovering a rare earth element from a waste permanent magnet scrap according to an embodiment of the present invention.

Referring to FIG. 1, when the waste permanent magnet scrap is oxidized and roasted to form oxides, neodymium and dysprosium to be recovered can be selectively leached by leaching into sulfuric acid. However, when the scrap is not roasted by oxidation, a large amount of iron components are also leached It is difficult to selectively separate neodymium and dysprosium through the precipitation reaction.

The roasted oxide may be pulverized permanent magnet scrap in a muffle furnace at 600 DEG C for 5 hours (S100)

Here, the muffle furnace can be opened at intervals of 30 minutes to supply oxygen.

The oxidized roasted powder contains 14.0 wt% of neodymium (Nd), 5.27 wt% of dysprosium (Dy), 53.3 wt% of iron (Fe), and residual impurities.

Conventional pulsed permanent magnet scrap has about 19% of dysprosium compared to neodymium. In case of high heat-resistant high-performance permanent magnet, the amount of dysprosium is very high, about 37% of the content of neodymium. Therefore, when sodium sulfate is added to perform precipitation reaction, the amount of sodium sulfate should be adjusted.

The roasted oxidized powder is leached with sulfuric acid to obtain a sulfuric acid leaching solution (S200).

Wherein the sulfuric acid is 2.5 M, the light concentration is 15%, the leaching temperature is 60 ° C and the leaching time is 3 hours.

It is possible to increase the leaching rate of neodymium and dysprosium in the leaching condition and to prevent leaching of iron in a large amount.

Sodium sulfate is added to the sulfuric acid leaching solution to perform precipitation reaction (S300).

At this time, 1 to 2 equivalents of sodium sulfate may be added to the sulfuric acid leaching solution.

When sodium sulfate is added to the sulfuric acid leaching solution, the rare earths in the sulfuric acid leaching solution forms a sodium sulfate double salt and precipitates.

Since the precipitation reaction of the double salt is affected by the addition amount of sodium sulfate, neodymium and dysprosium can be separated when the precipitation reaction is controlled within the above range.

Neodymium, which is a rare rare earth, can be preferentially precipitated to 98% or more and dysprosium can be precipitated to 40% or less within the added amount of the sodium sulfate.

Since the solubility of the dysprosium is increased in the aqueous acid solution, a large amount of the dysprosium may be dissolved in the filtrate in the range of the added amount of the sodium sulfate.

Thus, the purity of dysprosium can be controlled with optimum efficiency by controlling the concentration of undissolved dysprosium in the filtrate.

The double salt precipitation reaction is carried out at 30 to 70 캜 for 3 hours.

At this time, the quality of dysprosium recovered by the addition of sodium sulfate can be adjusted to 67 to 97.7%.

Dysprosium can be recovered by adding oxalic acid to the filtrate.

In the case of adding oxalic acid to the filtrate after the addition of sodium sulfate to the sulfuric acid leaching solution, the sulfuric acid salt solution is precipitated, and the sulfate compound and oxalate precipitation process without the hydroxide conversion, hydrochloric acid dissolution and solvent extraction steps yields a high-quality dysprosium compound Can be recovered.

1 mol of sodium chloride was added to the sulfuric acid leaching solution to perform precipitation reaction can do.

0.5 to 1 mol of sodium chloride may be added to the sulfuric acid leaching solution.

When 0.5 to 1 mol of sodium chloride is added to the sulfuric acid leaching solution, the dysprosium recovered by the filtrate after the precipitation reaction by salting-out can be increased.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to the following examples.

Example 1: Selective separation of rare earth elements

The permanent magnets were used as starting materials for the permanent magnets. When the permanent magnet scrap powder is directly leached into sulfuric acid, a large amount of Fe is leached as well as Nd and Dy which are the target elements. Therefore, the permanent magnet scrap was oxidized and roasted to minimize the leaching of iron components.

The furnace used for the roasting was a muffle furnace using a siliconit heating element of 30 cm (H) x 30 cm (W) x 30 cm (L) as a heat source. Lt; / RTI >

Oxidation roasting was carried out at 600 ℃ for 5 hours, and air circulation was performed by opening the electric furnace every 30 minutes.

ingredient Nd Dy Fe content(%) 14.0 5.27 53.3

Table 1 shows the composition of the oxidized rosin powder after oxidative roasting of waste permanent magnet scrap, which was analyzed using ICP-AES (Thermo Fisher Scientific, iCAP 6000 SERIES).

The roasted oxidized roasted powder was subjected to leaching under the following conditions: a 2.5 M sulfuric acid aqueous solution, a light concentration of 15%, a leaching temperature of 60 ° C, and a leaching time of 3 hours.

ingredient Nd Dy Fe Content (mg / ml) 23.39 8.67 46.8

Table 2 shows the compositions of the sulfuric acid leaching solution. The leaching rates of neodymium, dysprosium and iron were 97.5%, 96.2% and 51.3%, respectively.

The precipitation behavior of neodymium and dysprosium was investigated by using sodium sulfate in the leaching solution.

The experimental apparatus for precipitation of rare earth sulfuric acid salt was as follows.

The precipitation reaction temperature was controlled using a hot plate equipped with a thermostat, and a precipitation reaction tank (500 ml) equipped with a condenser was used for the precipitation reaction.

When the aqueous sulfuric acid leaching solution (200 ml) reached the desired temperature, 1 to 7 equivalents of sodium sulfate (Samchon Chemical, 98.5% purity anhydrous sodium sulfate) was added. At the same time as the addition of sodium sulfate, a rare earthsulfuric acid salt precipitation reaction occurs. At this time, a rare earth fluoride salt precipitation reaction was performed while varying the amount of sodium sulfate, reaction temperature and time.

After precipitation of rare-earth-sodium sulfate, the rare-earth components of the precipitate filtrate were analyzed by ICP-AES to determine the precipitation rate of sulfuric acid salt and the dysprosium content remaining in the filtrate.

On the other hand, oxalic acid was added to the filtrate after the precipitation reaction to precipitate dysprosium oxalate and recovered.

To the sulfuric acid leachate solution, 1 mol of sodium chloride was added to perform the precipitation reaction of the double salt, and the quality of dysprosium was confirmed by the salting-out effect.

Experimental Example 1: Precipitation with sulfuric acid

Permanent magnet scrap To separate rare earth elements from rare earth (Nd, Dy) leaching solution obtained by leaching oxidized rosin powder with aqueous sulfuric acid solution. In general, trivalent rare earth elements to react with sodium sulfate in sulfuric acid medium rare earth-precipitates, forming a sodium sulfate double salt [Re and Na (SO _{4) 2].} This method is a method of separating rare earth elements from other metal elements, and has a simple process and high recoverability and high quality of recovered rare earth.

[Reaction Scheme 1]

_{Ln 2 (SO 4) 3 +} Na 2 SO 4 + xH 2 O → 2Ln · Na (SO 4) 2 · xH 2 O

Wherein Ln represents neodymium and dysprosium.

Scheme 1 shows a reaction formula of a salt precipitation reaction of sodium sulfate and heptium sulfate (Nd, Dy).

The precipitation reaction was expected to be influenced by the amount of sodium sulfate added, the reaction temperature and the reaction time. These were selected as reaction variables and the precipitation behavior of neodymium and dysprosium sulfate was confirmed.

In the conventional invention of the present invention, the sulfuric acid leaching solution was found to have a neodymium concentration of 3.5 eq. Of sodium sulfate added at a reaction temperature of 60 占 폚 for 3 hours as a result of a precipitation test of an aqueous sulfuric acid leaching solution having a neodymium content of 27 mg / ml and a dysprosium content of 5.9 mg / The recovery rate of sulfate sulfate was 97.3% and the recovery rate of dysprosium sulfate was 97.2%. According to the embodiment of the present invention, the sulfuric acid leaching solution contained dysprosium of 8.67 mg / ml and the dysprosium content was very different.

<Experimental Example 2> Sulfuric acid salt precipitation characteristics according to reaction temperature

FIG. 2 is a graph showing the precipitation of the mixed salt according to the reaction temperature of neodymium, and FIG. 3 is a graph showing the precipitation of the mixed salt according to the reaction temperature of dysprosium.

Referring to FIGS. 2 and 3, the neodymium and dysprosium compositions of the saline salt solution over the precipitation temperature and time during the precipitation reaction of the double salt at the equivalent amount of the sulfuric acid added of 3.5 equivalents are shown. In the case of neodymium, at a reaction temperature of 30 ° C., the neodymium composition of the combined filtrate filtrate after 55 hours of precipitation was 55 μg / ml. However, at the reaction temperature of 60, the neodymium composition of the filtrate filtrate was 38 ㎍ / ㎖ after 15 minutes of reaction and 31 ㎍ / ㎖ after 4 hours of reaction. Therefore, it was confirmed that the precipitation reaction temperature had a great effect on the precipitation of the bicarbonate salt.

In the case of dysprosium, the dysprosium composition of the filtrate was slightly decreased even after 3 hours at the reaction temperature of 30, and 79 μg / ml at 180 minutes and 77 μg / ml at 210 minutes, There was no significant change even if there was a slight decrease.

Therefore, the reaction time was fixed to 3 hours for the precipitation reaction parameters.

<Experimental Example 3> Sulfuric acid salt precipitation characteristics according to element species

Before performing the neodymium and dysprosium salt recovery experiments by the precipitation reaction of the precipitates from the sulfuric acid extractive powders of the permanent magnet scrap oxidized rocoxide powder as shown in Table 2, when the two elements were present in the aqueous sulfuric acid solution as a single component, Respectively.

The precipitation behavior of Neodymium - Sodium - Sulfuric Acid Salt by addition of Sodium Sulfate was investigated in an aqueous solution of sulfuric acid in which neodymium was dissolved. The neodymium sulfate aqueous solution was prepared by dissolving neodymium oxide in sulfuric acid, and the neodymium content of the aqueous sulfuric acid solution was 20.58 mg / ml.

Fig. 4 shows XRD analysis results of sediments precipitated by adding sodium sulfate to an aqueous solution of sulfuric acid having neodymium dissolved therein.

Referring to FIG. 4, it has an Nd. Na (SO ₄ ) ₂ .H ₂ O crystal structure with one crystal number attached thereto.

ingredient Nd Pr Na SO ₄ content(%) 35.0 3.0 6.1 50.2

Table 3 shows the XRD component analysis results.

Referring to Table 3, it was confirmed that the molecular weights of neodymium (including Pr) and sodium coincided stoichiometrically with the formula.

5 shows the sedimentation rate of neodymium sulfate bisulfite according to the addition amount of sodium sulfate and the reaction temperature from an aqueous solution of neodymium sulfate.

Referring to FIG. 5, when the reaction time is 3 hours, the precipitation rate of neodymium sulfate is increased as the amount of sodium sulfate added and the reaction temperature are increased, but the increase is not significant at a reaction temperature of 40 ° C. or higher and a sodium sulfate addition amount of 1.5 equivalents or higher Able to know.

It was confirmed that the increase rate of the salt recovery rate at 1.25 equivalents or more at the change of the sodium sulfate addition amount was decreased,

As the reaction temperature is increased, the precipitation rate of neodymium salt salt is slightly increased because the solubility of rare-earth chloride salt is slightly decreased with increasing temperature, and the precipitation rate of neodymium salt salt is 99% or more at reaction temperature of 40 ° C or higher and sodium sulfate addition amount of 1.5 equivalent I could.

FIG. 6 is a graph showing a change in sedimentation rate of dysprosium salt by sodium sulfate from an aqueous solution of sulfuric acid dissolved with dysprosium. FIG.

6, the dysprosium content was 7.42 mg / ml. The precipitation rate of dysprosium sulfate was 1.13% until reaching 20 equivalents of sodium sulfate when the reaction temperature was 60 and the reaction time was 3 hours. It can be seen that the precipitation in the double salt is very small.

At 40 equivalents of sodium sulfate addition, the precipitation rate of dysprosium salt was 58.2%, and 50 equivalents to 75.6%.

Therefore, it was confirmed that a very large amount of sodium sulfate was required for precipitation of diphosphonic acid salt of dysprosium in an aqueous solution of sulfuric acid compared to neodymium.

(La, Ce, Pr, Nd, Sm), a terbium group (Eu, Gd, Tb, Dy) and a yttrium group (Y, Ho, Er) are dissolved in an aqueous solution of an acid in the rare earth- , Tm, Yb, and Lu), the solubility of the sulfate increases as the atomic number or atomic weight increases. Therefore, it was confirmed that precipitation should be promoted through the common ion effect by adding excess sodium sulfate in order to increase the precipitation rate of double salt.

<Experimental Example 4> Residual salt precipitation rate with addition of neodymium

7 is a graph showing the precipitation rate of dysprosium salt salt by adding a small amount of neodymium aqueous solution to an aqueous sulfuric acid solution in which dysprosium is dissolved, followed by addition of sodium sulfate.

7, when a small amount of neodymium aqueous solution (10 to 40 ml, 20.5 mg / ml) was added to an aqueous solution of sulfuric acid having 7.42 mg / ml of dysprosium dissolved therein, and the precipitate rate of dysprosium salt was confirmed by addition of sodium sulfate (0.205 to 0.82 g of neodymium and 13.7 to 55% of Nd versus Dy) was added to the same dysprosium-containing sulfuric acid aqueous solution when 20 equivalents of sodium dodecyl sulfate was added to an aqueous sulfuric acid solution containing only dysprosium dissolved therein. The precipitation rate of dysprosium bromide increased sharply to 30 ~ 44% when added.

When dysprosium alone was solved, it was confirmed that the precipitation rate of double salt was increased from 77 to 80% by adding neodymium in a small amount of 58.2% at 40 equivalents of sodium sulfate.

Therefore, the presence of a small amount of neodymium in the aqueous sulfuric acid accelerates the precipitation of dysprosium sulfate, which is believed to increase the precipitating rate of dysprosium salt due to the coadministration effect of the neodymium sulfate salt precipitate which is relatively easily precipitated.

Also, it was confirmed that the precipitation rate of dysprosium bromide salt increases with increasing neodymium content in aqueous solution.

<Experimental Example 5> Precipitation behavior according to addition amount of sodium sulfate

FIG. 8 is a graph showing the precipitation behavior of a sulfuric acid salt depending on the amount of sodium sulfate added in a selective recovery method of rare earth elements from a used permanent magnet scrap according to an embodiment of the present invention.

Referring to FIG. 8, the precipitation rate of neodymium and dysprosium was increased with an increase in the amount of sodium sulfate in the aqueous solution of sulfuric acid leached with a large amount of neodymium. As shown in Table 2, the sedimentation rate of neodymium salt was 3.5% The precipitation rate of dysprosium salt was 48%.

And the neodymium salt precipitation rate of 99.7% and the precipitation rate of dysprosium salt salt of 94.3% were obtained at 7 equivalents of the sodium sulfate added amount.

The reason why the precipitation rate of dysprosium salt is greatly increased according to the amount of sodium sulfate added is because the neodymium content in the aqueous sulfuric acid solution is large.

The condition that the rare earths were separated from the rare earth component (Fe) and recovered more than 99% by precipitation with sodium sulfate in the aqueous sulfuric acid solution was less than 3.5 equivalents of sodium sulfate compared to the rare earth content because the dysprosium content relative to neodymium was relatively small to be.

However, the dysprosium content of the used permanent permanent magnet scrap used in this embodiment is as high as about 37% of the neodymium content.

Therefore, it was confirmed that the sedimentation behavior of neodymium and dysprosium was very different according to the addition amount of sodium sulfate. It was confirmed that neodymium and dysprosium could be separated and recovered by using this.

<Experimental Example 6> Neodymium and dysprosium separation times

Referring to FIG. 8, the precipitation rate of neodymium and dysprosium was increased with an increase in the amount of sodium sulfate added at a reaction temperature of 60 ° C and a precipitation time of 3 hours. In the case of 2 equivalents of sodium sulfate, the dysprosium salt precipitation rate was 98.3% 33.9%.

Thereafter, the sedimentation rate of neodymium salt was not significantly changed with the increase of sodium sulfate addition, but the precipitation rate of dysprosium salt increased sharply.

Therefore, in order to separate neodymium and dysprosium, neodymium is precipitated with high efficiency when the reaction temperature settling time is controlled while the addition amount of sodium sulfate is 1 to 2 equivalents, and dysprosium is left dissolved in the filtrate to separate neodymium and dysprosium And can be selectively recovered.

FIG. 9 is a graph showing the precipitation behavior of the sulfuric acid salt depending on the reaction temperature and the amount of sodium sulfate added in the selective recovery method of the rare earth element from the spent permanent magnet scrap according to the embodiment of the present invention.

9 shows the sedimentation rate of neodymium and dysprosium tetrachloride obtained by varying the reaction temperature (30 to 70) and the addition amount of sodium sulfate at 3 hours of precipitation. When the reaction temperature was 50 or higher and the sulfuric acid addition amount was 1.5 or higher, the neodymium content was 98% , Whereas dysprosium showed a precipitation rate of less than 40% in all conditions.

Thus, it was confirmed that high-quality dysprosium can be obtained by selective separation at a reaction temperature of 30 to 60 ° C.

FIG. 10 is a graph showing the dysprosium content of the filtrate after the precipitation reaction in the selective recovery of the rare earth element from the spent permanent magnet scrap according to the embodiment of the present invention.

Referring to FIG. 10, the dysprosium content increased with increasing reaction temperature and sodium sulfate addition. At a reaction temperature of 30 to 40 ° C, the addition amount of sodium sulfate had a greater effect on the dysprosium durability. Dysprosium quality remained almost constant.

In the specific example of the present invention, the dysprosium content reached 97.7% in the filtrate obtained after the precipitation of the salt in the precipitation condition at a reaction temperature of 60 ° C and a sodium sulfate addition amount of 2 equivalents.

This indicates that dysprosium of 97.7% can be recovered by precipitation using oxalic acid in the filtrate precipitation filtrate without application of other processes.

<Experimental Example 7> Dysprosium decontamination according to salting-out effect

Sulfuric acid can be used to separate heavy rare earth and rare earth rare earth by salting out, and it is possible to precipitate highly soluble sulfuric acid salt and reduce the solubility of yttrium in high temperature brine.

Sodium chloride was added to the sulfuric acid leaching solution containing neodymium and dysprosium dissolved to determine the change of sedimentation rate of neodymium and dysprosium salts and dysprosium quality.

No Nd content (mg / ml) Dy content (mg / ml) Dy elegance Experimental conditions One 246 4319 94.6 Rxn temp. 50, Na ₂ SO ₄ 2 Eq.
Rxn time 3 hrs 2 256 4443 94.3 Rxn temp. 50, Na ₂ SO ₄ 2 Eq.
Rxn time 5 hrs 3 336 4633 93.2 Rxn temp. _{60, Na 2 SO 4 1.5 Eq} .
Rxn time 3 hrs 4 299 4527 93.8 Rxn temp. _{60, Na 2 SO 4 1.5 Eq} .
Rxn time 5 hrs 5 262 4138 94.1 Rxn temp. _{70, Na 2 SO 4 1.5 Eq} .
Rxn time 3 hrs 6 193 3673 94.9 Rxn temp. _{70, Na 2 SO 4 1.5 Eq} .
Rxn time 5 hrs 7 29 1073 97.3 Rxn temp. 50, Na ₂ SO ₄ 2 Eq.
Rxn time 5 hrs, NaCl 8 24 1829 98.7 Rxn temp. _{50, Na 2 SO 4 1.5 Eq} .
Rxn time 5 hrs, NaCl

Table 4 shows the results of maximizing the deposition rate of neodymium salt and maximizing the dysprosium quality while minimizing the precipitation rate of dysprosium salt.

 When the precipitation reaction time was increased from 3 hours to 5 hours under the same conditions of the reaction temperature and the addition amount of sodium sulfate, the dysprosium durability was not significantly affected.

However, it was confirmed that the presence of sodium chloride in the same condition greatly affects the dysprosium quality.

The concentration of dysprosium increased from 94.3% to 97.3% when 1 mole of sodium chloride was added to the aqueous solution of sulfuric acid. However, the concentration of dysprosium in the aqueous sulfuric acid solution was significantly reduced from 4,633㎎ / ㎖ to 1,073 ㎎ / ㎖.

This is because of the salting effect by the addition of sodium chloride.

Therefore, 98.7% of dysprosium could be isolated under the condition that the precipitation rate of neodymium salt was increased and the precipitation rate of dysprosium was decreased. The recovery rate of dysprosium was 27.3%.

From these results, it is important to increase the precipitation rate of neodymium salt to the maximum in order to separate neodymium and dysprosium by precipitation with rare-earth sulfuric acid salt using sodium sulfate. In order to do so, a salt such as sodium chloride is added to the aqueous sulfuric acid solution to induce a salting effect It was found to be very effective.

Therefore, the method for selectively recovering rare-earth elements from waste permanent-magnet scraps according to the present invention selectively separates rare-earth elements from high-performance permanent magnets containing a high content of dysprosium of 4 to 7 wt% And provides a method for recovering the same.

Neodymium and dysprosium can be selectively separated and recovered by using the difference in solubility of neodymium and dysprosium sulfate and the difference in precipitation reaction between the sulfate and the sulfate, and oxalic acid is added to the filtrate after the salt precipitation reaction to recover high-quality dysprosium in a single process .

Although specific embodiments of the method for selectively collecting rare-earth elements from the waste permanent magnet scrap according to the present invention have been described, it will be apparent that various modifications are possible within the scope of the present invention.

Therefore, the scope of the present invention should not be construed as being limited to the embodiments described, but should be determined by equivalents to the appended claims, as well as the following claims.

It is to be understood that the foregoing embodiments are illustrative and not restrictive in all respects and that the scope of the present invention is indicated by the appended claims rather than the foregoing description, It is intended that all changes and modifications derived from the equivalent concept be included within the scope of the present invention.

Claims (7)

Oxidizing roasted permanent magnet scrap to obtain an oxidized roasting powder (first step);
Extracting the roasted oxidized powder with sulfuric acid to obtain a sulfuric acid leaching solution (second step); And
Adding sodium sulfate to the sulfuric acid leaching solution to perform a precipitation reaction of the reductive salt and recovering the filtrate (Step 3)
In the third step, 1.5 to 2 equivalents of sodium sulfate is added to the sulfuric acid leaching solution to carry out the precipitation reaction of the double salt, 1 mole of sodium chloride is added to adjust the quality of the dysprosium recovered in the filtrate through salting out to 97.3 to 98.7% And the Nd / Dy separation method by the precipitation method of sulfuric acid salt.
The method according to claim 1,
The roasted oxide
Wherein the Nd / Dy separation is carried out at 600 &lt; 0 &gt; C for 5 hours.
The method according to claim 1,
The roasted oxide powder
Characterized in that it contains impurities of 14.0 wt% of neodymium (Nd), 5.27 wt% of dysprosium (Dy), 53.3 wt% of iron (Fe) and the balance of Nd / Dy.
The method according to claim 1,
The above-
And the reaction is carried out at 30 to 60 占 폚 for 3 hours. The method of separating Nd / Dy by the precipitation of sulfuric acid salt.
The method according to claim 1,
And dysprosium is recovered by adding oxalic acid to the filtrate, wherein the quality of the recovered dysprosium is adjusted to 67 to 97.7%.
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