JPS61117116A - Purification of rare earth compound - Google Patents

Abstract

PURPOSE:To obtain a rare earth compd. having low content of Pb by adding alkaline earth metal ions to aq. soln. of a rear earth compd. in the presence of H2SO4 and removing separated precipitate of sulfate of the rear earth element. CONSTITUTION:H2SO4 and a water-soluble sulfate such as ammonium sulfate are added to an aq. soln. of a rear earth compd. cong. a Pb compd. as impurity (the concn. of the rare earth compd. is preferred to be ca. 0.01-1.5mol/l) and dissolved. Alkaline earth ions are added to the above-described aq. soln. cong. SO4 ion, and a sulfate of the alkaline earth element is precipitated. The coprecipitate derived from the Pb compd. in the above-described aq. soln. and above-described sulfate is separated and removed. By this method, a rare earth compd. contg. extremely small amt. of Pb compd. is obtd. easily without generating harmful gas.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for purifying rare earth compounds. Specifically, the present invention relates to a method for obtaining a rare earth compound having an extremely low content of lead compounds.

BACKGROUND OF THE INVENTION Rare earth elements are used in a wide range of fields including electronics, but in the case of electronics materials, they are particularly required to be free of impurities.

Separation and purification of rare earth compounds is usually carried out by ion exchange methods, solvent extraction methods, etc.
In ion-exchange separation of yttrium using a complex forming agent such as or D'TPA, lead has an elution behavior similar to that of yttrium, making separation difficult. was difficult.

A known method for removing lead compounds from an aqueous solution is to generate lead sulfide from the lead in the aqueous solution using hydrogen sulfide, sodium sulfide, etc.; It is not possible to reduce the lead content to less than about 1111 g/Jl. Even when this method is applied to an aqueous solution of a rare earth compound, the rare earth compound is usually 0.03 to 1. O
It is often handled as an aqueous solution with a concentration of about mol/12, and even if the amount of lead in the aqueous solution is 1 mQ/A, the rare earth element given from this aqueous solution will be concentrated to about 9 ppm or more. Therefore, it is not sufficient as a rare earth element for the above-mentioned purpose.

Furthermore, in this method, if the aqueous solution of the rare earth compound is acidic, hydrogen sulfide is generated, which poses problems in terms of safety and operability, and there is a risk of corrosion of the equipment due to 82" remaining in the aqueous solution. There is also.

Problems to be Solved by the Invention The present invention aims to provide a method for purifying rare earth compounds that has a high lead removal rate, is safe and easy to operate, and does not generate harmful gas or corrode equipment. .

Problem, Means for Solving the Problem The inventors of the present invention have conducted extensive research in order to produce rare earth compounds with a low content of lead compounds, and have found that the lead in the aqueous solution is The present invention was based on the discovery that co-precipitation is extremely likely to occur.

The configuration of the present invention is as follows. In other words, alkaline earth element ions are added to an aqueous solution of a rare earth compound containing a lead compound as an impurity in the presence of @ acid ions, sulfate of the alkaline earth element is precipitated, and the resulting precipitate is separated and removed. This is a method for producing a compound.

The details of the present invention will be described below.

The rare earth compound referred to in the present invention has an atomic number of 57 to 71.
It refers to compounds of the element group including the elements yttrium and scandium.

In the present invention, an aqueous solution of a rare earth compound containing a lead compound as an impurity (hereinafter abbreviated as a lead-containing rare earth aqueous solution) is 1
It is an aqueous solution of acid salts such as nitrates, chlorides, and sulfates of rare earth elements, and contains lead compounds as impurities. The concentration of rare earth compound is 0.01 to 1.5
About II101/J2, preferably 0.03 to 1.0m
It is better to choose from 01/λ.

In the present invention, sulfate ions present in a lead-containing rare earth aqueous solution can be obtained by adding and dissolving sulfuric acid and water-soluble sulfates such as ammonium sulfate, sodium sulfate, potassium sulfate, copper sulfate, and zinc sulfate to the solution. It will be done. Further, when the solution is an aqueous solution of an acid salt of a rare earth element (including when a rare earth oxide or the like is dissolved in sulfuric acid), there is no need to add a raw material for sulfate ions.

Further, the alkaline earth element ions added in the present invention are ions of elements belonging to group 1rA of the periodic table,
It is produced by dissolving water-soluble salts of these elements, such as nitrates and chlorides, in water.

Among the alkaline earth elements, barium and strontium are particularly suitable for carrying out the present invention because of their low solubility in @acid salts and their safety.

The addition m of alkaline earth element ions varies depending on the type of element, and it is minimum necessary to add an amount equal to or higher than the solubility of each alkaline earth element sulfate.

, and the amount added is based on the lead in the lead-containing rare earth aqueous solution.
The amount is preferably equal to or more than 3 times the mole, preferably 3 times the mole or more. On the other hand, there is no particular problem if the amount added is too large for the lead in the lead-containing rare earth aqueous solution, but no particular effect can be expected from adding too much, and at most 5
The amount is preferably about 00 times the molar amount or 20 times the solubility of each alkaline earth element sulfate, whichever is greater.

In addition, there is no particular limit to the concentration of alkaline earth element ions added, but if the concentration is too low, the amount of liquid after addition will increase and the amount of alkaline earth element sulfate precipitated will decrease. is preferably 101111001/A or more.

In the present invention, the amount of sulfate ions present in the lead-containing rare earth aqueous solution is preferably at least equimolar, preferably at least twice the molar amount of the alkaline earth element ions added. If it is too small, the amount of alkaline earth element sulfate precipitated will be small, and the effect of the present invention cannot be expected, and a large amount of alkaline earth element ions will remain as impurities in the rare earth compound aqueous solution. .

In carrying out the present invention, l) H of a lead-containing rare earth aqueous solution
is preferably 0 to 7, preferably 1 to 6. pH is O
If it is lower, the effect of the present invention will be small and it will be impractical.

On the other hand, if the pH is higher than 7, the rare earth compound becomes a hydroxide and precipitates, which is not preferable because the loss of the rare earth compound increases.

To adjust the pH of the lead-containing rare earth aqueous solution, ammonia, sodium hydroxide, potassium hydroxide, etc. can be used.

Further, in carrying out the present invention, the temperature of the lead-containing dilute aqueous solution may be at room temperature, and the effects of the present invention will not be increased even if it is heated.

The reaction time varies depending on the type of alkaline earth element ion and the amount of addition m, but as a rough guide, 15 minutes to 6 hours are required from the time the alkaline earth element sulfate begins to precipitate.

In this way, a precipitate of alkaline earth element sulfate is formed, and by separating and removing the precipitate by means such as filtration, an aqueous solution of a rare earth compound (Pb /RE O<21) containing extremely low lead compound content is obtained. )11) is obtained.

The present invention can be applied before purifying masonry earth compounds by ion exchange, extraction, etc., or immediately before precipitating and recovering rare earth compounds from an aqueous solution of rare earth compounds after purification. If mixing of alkaline earth elements into the product rare earth compound is to be avoided, it is preferable to apply it before operations such as ion exchange and extraction.

LL Examples will be described below, but the present invention is not limited to the following examples unless the gist of the invention is exceeded.

Example 1 Yttrium 60mo 1% Dysprosium 20m0I% Terbium
20mo 1% of the above composition and RE203
140 per (representing RE: Y+Dy +Tb)
Sulfuric acid pile RE2 (SO4)s containing 0 pH lead
0.07not/J2 aqueous solution (+)H2,5) 25
0+nJ! Then, add 0.1 m of barium sulfate at room temperature while stirring.
When 15 mJ of ol/λ aqueous solution was added, the formation of a white precipitate was observed. After 30 minutes, the precipitate was filtered off using a 0.8μ Millipore filter. The lead content (■) in the obtained dilute sulfuric acid aqueous solution was 1.4 ppm per RE203.
Met. The lead content in the lake water solution was measured using a flameless atomic absorption spectrometer 5AS-70 manufactured by Seiko Electronics Co., Ltd.
The test was carried out at 5V (wavelength: 282.3nI11).

Example 2 After adding and dissolving 3.3 g of ammonium sulfate to 250 ml of a 0.4 mol/g aqueous solution of yttrium nitrate containing 11,000 pp of lead per Y203 (at this time, the pH of the solution was >2.4, and stirring at room temperature) When 25 ml of a 0.1 mol/β aqueous solution of barium nitrate was added, the formation of a white precipitate was observed.

After 1 hour, the precipitate was filtered off using a 0.8μ Millipore filter. The lead content in the obtained yttrium nitrate was 1.0% per Y2O3. It was lppm. The lead content was measured in the same manner as in Example 1.

Example 3 Yttrium 20mo 1% Gadolinium 40mo 1% Samarium
40mo 1% of the above composition and RE20
1200p per 3 (RE indicates Y+Gd +3m)
Sulfuric acid pile RE2 (804) 3 (D O105
Add strontium nitrate 0.5 mol/λ aqueous solution 15 ml to 250 n+l of mol/12 aqueous solution at room temperature while stirring.
was added, the formation of a white precipitate was observed. After 2 hours, the precipitate was filtered off using a 0.8μ Millipore filter. Obtained lIi! The amount of i-acid rare earth hydroxide liquid earth aqueous solution is 0.6 ppm per RE203.

The lead content was measured in the same manner as in Example 1.

As described in detail, according to the present invention, since hydrogen sulfide, sodium sulfide, etc. were conventionally used as a precipitant,
There were problems in terms of safety and operability due to the content of lead compounds in rare earth compounds not being sufficiently low, generation of hydrogen sulfide, and corrosion of equipment due to S2- remaining in the liquid. An extremely easy alternative to the lead sulfide precipitation method.
Moreover, it becomes possible to obtain a rare earth compound with a sufficiently low content of lead compounds without generating harmful gases, and the industrial value of the present invention is extremely large.

Claims (1)

[Scope of Claims] Alkaline earth element ions are added to an aqueous solution of a rare earth compound containing a lead compound as an impurity in the presence of sulfate ions, the sulfate of the alkaline earth element is precipitated, and the resulting precipitate is separated. A method for purifying rare earth compounds, characterized by removing them.