KR101480494B1 - Method of recovering europium from mixed rare earth - Google Patents

Abstract

The present invention relates to a method for separating and recovering Eu from a rare earth mixture, and more particularly, to a method for separating and recovering Eu from a rare earth mixture, A second step of reducing the Eu in the rare earth mixture by using the metal powder in an acidic condition and a non-oxidizing atmosphere; A third step of precipitating Eu by using an acid, converting it into a carbonate and leaching it; A fourth step of repeating the second step and the third step further one to three times; And a fifth step of precipitating the leachate after the fourth step and then calcining to obtain a Eu oxide, and a fifth step of recovering Eu from the rare earth mixture.

Description

[0001] The present invention relates to a method for recovering Eu from a rare earth mixture,

And separating and recovering Eu from the rare earth mixture.

Rare earths are indispensable elements used in various high-tech industries such as LED, semiconductor, wind power, and green technology. Ce, which is used as abrasive and catalyst, is the most used element among 17 rare earths. It also has the highest content in the crust and the largest content in the center ore of the light rare earth.

Among the rare earth elements, Eu has a property of being easily reduced from Eu ^{3 +} to Eu ^{2 +} . Therefore, it can be relatively easily separated from Sm and Gd by using these properties. As a method of reducing Eu, a method using metal and an electrolytic reduction method . Since Eu ^{2 +} is easily oxidized again to Eu ^{3 +} when it comes into contact with oxygen in the atmosphere, the reduction reaction of Eu must proceed in a non-oxidizing atmosphere. However, in the case of the electrolytic reduction method, such atmosphere control is not easy and there are many problems in commercial use. Therefore, although a method using a metal is more commonly used than an electrolytic reduction method, this method also has a limitation in securing purity of recovered Eu.

It is possible to provide a method of improving the purity of Eu separated and recovered from the rare earth mixture by using a metal reduction method.

One embodiment of the present invention is a method for producing a leach solution, comprising: a first step of leaching a rare earth mixture to obtain an leach solution; A second step of reducing Eu in the rare earth mixture using a metal powder in an acidic condition and a non-oxidizing atmosphere; A third step of precipitating Eu by using 1 to 2 equivalents of an acid and then converting it into a carbonate and leaching it; A fourth step of repeating the second step and the third step further one to three times; And a fifth step of precipitating the leachate after the fourth step and then calcining to obtain a Eu oxide; A method for recovering Eu from a rare earth mixture.

The first step of leaching the rare earth mixture to obtain an leach solution may be a leaching step using an acid.

A second step of reducing Eu in the rare earth mixture using a metal powder in an acidic condition and a non-oxidizing atmosphere; and the acidic condition is a pH of 2.5 to pH 3.5, and the non-oxidative atmosphere is an Ar atmosphere have.

And a second step of reducing Eu in the rare earth mixture by using a metal powder in the solution under an acidic condition and a non-oxidizing atmosphere, the metal may be zinc.

In the third step of precipitating Eu by using the above-mentioned 1 to 2 equivalents of acid and then converting it into carbonate and leaching out, the acid may be sulfuric acid.

In the fifth step of precipitating the leachate after the fourth step and calcining to obtain Eu oxide, the calcination may be performed at a temperature of 800 to 900 ° C.

According to one embodiment of the present invention, Eu can be separated into a high efficiency and purity from a rare earth mixture by limiting the sulfuric acid equivalent and repeating the process.

1 is a flowchart showing the separation and recovery of Eu using 8 equivalents of sulfuric acid from a rare earth mixture of Sm, Eu, and Gd.
FIG. 2 shows the recovery rate of Eu having an oxidation number of +2 according to the sulfuric acid equivalence ratio and the co-deposition rate of Sm and Gd having an oxidation number of +3.
3 is a flow chart of separating and recovering Eu from a rare earth mixture of Sm, Eu, and Gd using 2 equivalents of sulfuric acid and a repeating process.
4 is a graph showing the recovery of Eu according to the initial acidity of a rare earth mixture solution of Sm, Eu, and Gd.

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

One embodiment of the present invention is a method for producing a leachate, comprising: a first step of leaching a rare earth mixture to obtain an leach solution; A second step of reducing Eu in the rare earth mixture using a metal powder in an acidic condition and a non-oxidizing atmosphere; A third step of precipitating Eu by using 1 to 2 equivalents of an acid and then converting it into a carbonate and leaching it; A fourth step of repeating the second step and the third step further one to three times; And a fifth step of precipitating the leachate after the fourth step and then calcining to obtain a Eu oxide; A method for recovering Eu from a rare earth mixture.

Rare earth elements are generic names of 17 elements combined with scandium and yttrium, the 3A group of the periodic table, and the lanthanide series of 15 elements with atomic numbers of 57 to 71, and have similar chemical properties and generally have an oxidation number of +3 .

In particular, Eu has a characteristic of being easily reduced from Eu ^{3 +} to Eu ^{2 +,} and thus can be easily separated from other rare earth elements having an oxidation number of +3. However, depending on the conditions of the reduction reaction of Eu, It is difficult to ensure the purity of recovered Eu because of the reduction or the easy oxidation of Eu ^{& lt; 2 + & gt ;} to Eu < ^{3 + & gt ;} .

As used herein, leaching refers to dissolving a mixture or compound in an acid.

In FIG. 3, the step of leaching the SEG mixture with hydrochloric acid to prepare the (SEG) Cl ₃ solution corresponds to the "first step of leaching the rare earth mixture to obtain the leached solution", adjusting the pH to 3.0, Quot; second step of reducing Eu in the rare earth mixture using the metal powder under acidic conditions and non-oxidizing atmosphere "corresponding to the step of reducing Eu with zinc powder under the conditions of was precipitated in the form of EuSO ₄ is to converting the carbonate of EuCO ₃ form the subject to "after precipitation the Eu by using the acid of 1 to 2 equivalents, a third step of leaching was converted to carbonate", and after the carbonate of EuCO ₃ form a EuCl ₃ obtained by leaching with hydrochloric acid again to obtain a higher purity than EuCl ₃ through the second purification step is the "second step, and a further one to three times the three phase half The after step 4 "corresponds to, and then to precipitate the EuCl ₃ calcined to obtain an Eu ₂ O ₃ is the" precipitate the leachant after the fourth step, the calcination by a fifth step of obtaining an Eu oxide " .

A first step of leaching the rare earth mixture to obtain an extract; Will be described.

The first step of leaching the rare earth mixture to obtain an leach solution may be a leaching step using an acid.

The acid may be hydrochloric acid, but is not limited thereto. When the rare earth mixture is leached with hydrochloric acid, a chloride containing a rare earth element such as EuCl ₃ is obtained as an extract.

A second step of reducing Eu in the rare earth mixture using the metal powder under the acidic condition and the non-oxidizing atmosphere; Will be described.

The acidic condition may be a pH of from 2.5 to 3.5, and more specifically, a pH of 3.0. As shown in FIG. 4, when Eu is reduced within the pH range, the recovery of Eu is high. That is, when Eu is reduced within the above-mentioned pH range, the effect of inhibiting formation of hydroxide precipitates is obtained and the recovery rate of Eu is high. However, when pH is less than 2.5 or more than 3.5, hydroxide precipitation occurs, .

The non-oxidizing atmosphere may be an Ar atmosphere, but is not limited thereto. Since Eu ^{2 +} is easily oxidized to Eu ^{3 +} by contact with oxygen in the atmosphere, the reduction reaction from Eu ^{3 +} to Eu ^{2 +} itself must proceed in a non-oxidizing atmosphere.

The metal may be zinc but is not necessarily limited thereto. However, it is preferable to reduce Eu by using zinc when the stability at room temperature and the economic aspect are considered.

A third step of precipitating Eu by using 1 to 2 equivalents of an acid, converting it into a carbonate and leaching it; Will be described.

The acid is used in an amount of 1 to 2 equivalents, specifically 2 equivalents of an acid. When the acid used is within the equivalent range, it is possible to maximize the precipitation rate of Eu as a tree element to be separated and recovered from the rare earth mixture, minimize the co-precipitation rate of other rare earth elements, and improve the purity of recovered Eu have.

The acid may be sulfuric acid, but is not limited thereto. However, if the acid is sulfuric acid, it is preferred to make easy sulfate and Eu ^{2 +} it is possible to maximize the chimjeonyul of Eu using sulfuric acid.

When the precipitation is able Eu by using the sulfuric acid is EuSO ₄ is precipitated, and the other rare earth elements remaining in solution, it is possible to separate the Eu and other rare earth elements. Then, the precipitated EuSO ₄ is converted into carbonate by reacting with Na ₂ CO ₃ or the like to produce EuCO ₃ .

In order to leach out EuSO ₄ by using hydrochloric acid, EuSO ₄ should be converted into carbonate form of EuCO ₃ . Sulfates such as EuSO ₄ are not soluble in hydrochloric acid, so EuSO ₄ should be converted to EuCO ₃ , a carbonate form that is well soluble in hydrochloric acid.

After conversion to the carbonate it is to leaching with an acid, and in the process is to be re-oxidized to Eu ^{2 +} Eu ^3+. EuCl ₃ is obtained when leaching using hydrochloric acid after the carbonate conversion.

A fourth step of repeating the second step and the third step further one to three times; Will be described.

Even if the above-mentioned second and third steps are carried out, not only Eu but also other rare earth elements can coprecipitate and act as impurities. Accordingly, the purity of the separated and recovered Eu can be improved by repeating the second step and the third step one to three times. Specifically, the second step and the third step may be repeated one or more times.

A fifth step of precipitating the leachate after the fourth step and then calcining to obtain a Eu oxide; Will be described.

The leachate such as EuCl ₃ obtained after the fourth step is precipitated using a precipitant, and then calcined using a calcining facility to produce Eu ₂ O ₃ . The precipitant may be oxalic acid (H ₂ C ₂ O ₄ ), but is not limited thereto.

The calcination may be performed at a temperature of 800 to 900 ° C, but is not limited thereto. When the calcination is carried out within the above-mentioned temperature range, rare earth salts such as oxalate, carbonate and the like precipitated in the precipitation process are removed in the form of CO ₂ or H ₂ O, so that only Eu ₂ O ₃ remains.

Example

A rare earth mixture (SEG mixture) was leached with hydrochloric acid to prepare a solution ((SEG) Cl ₃ , (1)) mixed with SmCl ₃ , EuCl ₃ and GdCl ₃ ). Thereafter, the mixed solution was reduced using Zn powder under pH 3.0 conditions (adjusted with NH ₄ OH), and 2 equivalents of sulfuric acid was added to obtain a precipitate. The precipitate was reacted with Na ₂ CO ₃ to convert it to carbonate, and then leached again with hydrochloric acid to obtain an extract (②, EuCl ₃ produced by the first purification process). The leachate leached with hydrochloric acid (②, EuCl ₃ produced through the first purification process) was reduced again using Zn powder, and 2 equivalents of sulfuric acid was added and the process of leaching with carbonate was repeated once more . After the reprecipitation, the precipitate (③, EuCl ₃ produced by the second purification process) was precipitated with oxalic acid (H ₂ C ₂ O ₄ ) as a precipitant and calcined at 850 ° C. And calcined to obtain Eu ₂ O ₃ (④) as an oxide.

Component analysis results of ① ~ ④

The results of the analysis of the components (1) to (4) are shown in Table 1 below.

As shown in Table 1, the purity of EuCl ₃ (②) prepared through the first purification process was 90.3%, while the purity of EuCl ₃ (③) prepared through the second purification process presented through the present invention was 99.5% and 9.2%, respectively.

The purity of Eu ₂ O ₃ (④) prepared by precipitation and calcination of oxalic acid using EuCl ₃ (③) prepared by the second purification process was estimated to be 97.8%, which was estimated to have some loss in the precipitation and calcination processes .

Although the purity of Eu can be improved by repeating the purification process using the EuCl ₃ (③) solution prepared through the second purification process, this is not preferable from the viewpoint of operating cost.

Comparative Example

Except that 2 equivalents of sulfuric acid was used instead of 2 equivalents and the second purification step was not carried out. The results are shown in Table 2 below. ≪ tb >< TABLE > (5) in Table 2 below is the same as (1) in the above example, and (6) is a method in which the mixed solution (5) is reduced using Zn powder under pH 3.0 conditions (adjusted with NH ₄ OH), 8 equivalents of sulfuric acid To form a precipitate. The solution is a solution in which rare earth elements that have not been precipitated are dissolved (see FIG. 1).

As shown in the above Table 2, the precipitation rate with Eu equivalent of sulfuric acid was 90.5% in the case of the precipitation using 8 equivalents of sulfuric acid, but the coprecipitation of Sm and Gd were 15.7% and 16.3%, respectively, The purity is remarkably lowered.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And falls within the scope of the invention.

Claims (6)

Leaching the rare earth mixture to obtain an extract;
A second step of reducing Eu in the rare earth mixture using a metal powder in an acidic condition and a non-oxidizing atmosphere;
A third step of precipitating Eu by using 1 to 2 equivalents of an acid and then converting it into a carbonate and leaching it;
A fourth step of repeating the second step and the third step further one to three times; And
A fifth step of precipitating the leachate after the fourth step and then calcining to obtain Eu oxide; Lt; / RTI >
And a second step of reducing Eu in the rare earth mixture by using the metal powder under the acidic condition and non-oxidizing atmosphere of the leach solution,
Wherein the acidic condition is a pH of 2.5 to pH 3.5.
The method according to claim 1,
The first step of leaching the rare earth mixture to obtain an extract is a method of recovering Eu from a rare earth mixture leached using an acid.
The method according to claim 1,
And a second step of reducing Eu in the rare earth mixture by using the metal powder under the acidic condition and non-oxidizing atmosphere of the leach solution,
And the non-oxidizing atmosphere is an Ar atmosphere.
The method according to claim 1,
And a second step of reducing Eu in the rare earth mixture by using the metal powder under the acidic condition and non-oxidizing atmosphere of the leach solution,
Wherein said metal is zinc.
The method according to claim 1,
In the third step in which Eu is precipitated using the above-mentioned 1 to 2 equivalents of acid and then converted into a carbonate and leached,
Wherein the acid is sulfuric acid.
The method according to claim 1,
In the fifth step of precipitating the leachate after the fourth step and then calcining to obtain a Eu oxide,
Wherein said calcination is carried out at a temperature of 800 to 900 占 폚.

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