JPS6065721A - Purification of rare earth element - Google Patents

Abstract

PURPOSE:To remove radioactive substances in an aqueous solution of rare earth element chloride efficiently, by removing solid materials from the aqueous solution of rare earth element chloride, adding Ba<+2> and SO4<2-> to the solution, precipitating sulfate, removing solid materials. CONSTITUTION:An ore such as monazite, etc. is decomposed with an alkali to give a rare earth element hydroxide, which is dissolved in hydrochloric acid to prepare an aqueous solution of rare earth element chloride. The aqueous solution of rare earth element chloride usually contains fine solid materials. The solid materials are removed from the aqueous solution of rare earth element chloride containing the fine solid materials and soluble radioactive substances by solid- liquid separating means such as filter press, centrifugal separator, etc. so that a solid material content in the aqueous solution is <=0.1wt%. Barium ion and sulfate ion are added to the aqueous solution of rare earth element chloride from which the solid materials are removed, barium sulfate is precipitated, and existing solid materials are removed from the aqueous solution.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying chlorinated clay, and more particularly to a method for reducing the content of radioactive substances in a chlorinated cloth aqueous solution.

Rare earth chloride aqueous solutions are intermediates for various clay products, and are generally prepared by dissolving crude hydroxide clay obtained by decomposing ores such as monazite in hydrochloric acid. Radioactive substances mainly composed of radium derived from ores are dissolved in the chlorinated cloth aqueous solution obtained in this way. Radioactive material? It is preferable to reduce the content of clay by as much as possible, since the value of the parts decreases considerably.

A known method for removing dissolved radium compounds from an aqueous solution is to add barium ions and sulfate ions to an aqueous solution to generate barium sulfate, which is then accompanied by a radium compound to precipitate. However, even when this method is applied to an aqueous rare earth chloride solution prepared from crude hydroxide clay obtained by decomposing ores such as monazite, it is difficult to remove radioactive substances to a satisfactory extent. It turned out that it was not possible.

The inventors of the present invention investigated the cause of this problem, and found that it is possible to efficiently remove the radioactive substances contained therein by unexpectedly removing the solid matter 7 suspended in the aqueous solution on the chloride cloth. I found it.

The present invention was completed based on such knowledge,
The gist of this is that from a chlorinated cloth aqueous solution containing coexisting solids and soluble radioactive materials, the amount of solids present is 0.
．． /wt% or less, barium ions and sulfate ions are added to this to precipitate sulfate, and then these solids are removed from the aqueous solution to reduce the content of radioactive substances. The main feature lies in the method for refining chloride clay.

To explain the present invention in more detail, the term chlorinated clay in the present invention refers to chlorides of elements having an atomic number of 37 to 7, as well as an element group including yttrium and scandium. The aqueous chloride solution is usually a hydroxide clay obtained by alkaline decomposition of an ore such as monazite or alkali; Prepared by dissolving hydroxide clay in hydrochloric acid. Further, the chlorinated cloth aqueous solution obtained in this manner may be subjected to various purification means to remove some impurities, elements, etc. in advance.

Fine solid matter generally coexists in these dilute chloride aqueous solutions. This is mainly impurities mixed in the raw material rare earth hydroxide, and in some cases it may also contain solid matter precipitated from the aqueous chloride clay solution. Also,
Radioactive substances derived from ores are dissolved in aqueous solution, and it is estimated that the main component is radium.1. (teii).

In the method of the present invention, such slightly 111 solids and soluble radioactive substances are first extracted from an aqueous solution on a chlorinated cloth.
By using a filter press, centrifuge, or other solid-liquid separation means, the solid content in the aqueous solution can be reduced to 0-' i! 1-filter to remove solids so that the ratio is less than #, preferably less than θθs-M<j; Solid content is 0. /weight%
From 4. If there is too much, radioactive substances will be removed in the next process1.
-I just can't do it.

In general, the smaller the amount of solids contained, the better the removal of 1 g of radioactive materials, so it is preferable to reduce the content as far as the total capacity of the 4 devices 3. , then barium ions and sulfate ions are added to form barium sulfate.Usually, P Hi Q -5 of an aqueous solution of chloride cloth is added.
barium ions and sulfate ions may be sequentially added thereto while stirring.

As the barium ion source, acid-soluble barium salts such as barium chloride and barium carbonate are used. As the sulfate ion source, sulfates soluble in acids such as sulfuric acid, ammonium sulfate, and sodium sulfate are used. It is also possible to use soluble sulfuric acid clay. The amount of barium ion added is usually 0.00 barium per liter of diluted chloride aqueous solution.
/ -5g, preferably o, s to co, Sg.

Further, sulfate ions may be added in an amount approximately equivalent to that of barium ions, but may be added in excess.

The aqueous chloride cloth solution to which barium ions and sulfate ions have been added to produce barium sulfate is then passed through a filter press, centrifuge, or other appropriate solid-liquid separation means to remove any solid particles present. . At this time, radioactive substances are also removed at the same time, so a chlorinated cloth aqueous solution with a significantly reduced content of radioactive substances can be recovered.

Hereinafter, the present invention will be further explained with reference to the examples.The present invention is not intended to be exhaustive by the following examples unless it goes beyond the gist of the present invention.

In addition, in the following Examples and Comparative Examples, the amount of solids in the rare earth chloride aqueous solution was measured using a centrifugal sedimentator H manufactured by
This is the amount of solid matter separated during centrifugal sedimentation at lθOOa for 70 minutes using the -100 type. Moreover, the amount of radioactivity is a value measured using a radioactivity measuring device TDO-10,3 type manufactured by Aloka ■.

Example: Monazite was decomposed using sodium hydroxide to form a crude hydroxide cloth consisting of about SO% cerium, about 2s% lanthanum, and 2S% other moieties, which was then dissolved in hydrochloric acid to pH 3,!
An aqueous solution of chloride on cloth was prepared. The concentration of this aqueous solution on the cloth was about 72% in terms of oxides (R2O3), and it contained about 1% of solids. This rare earth chloride aqueous solution was filtered using a filter press to reduce the solid content to 0.
It was reduced to 0q%. Add hydrogen chloride to this while stirring.
Add a 10% aqueous solution of ammonium sulfate (the amount added is barium/7 Vl), then add 7O of ammonium sulfate.
% aqueous solution (the amount added was 7.5 equivalents to barium). It was filtered using a filter press to remove the generated barium sulfate. The P solution was evaporated and concentrated and then cooled to form a solid diluted chloride (water salt). The amount of radioactivity on this chlorinated cloth was 9×/0″4 μC1/g.

In Comparative Example/Example/, diluted chloride (filtrate salt) was prepared in exactly the same manner as in Example 1, except that solids were not removed from the diluted chloride aqueous solution containing solids in the θ and s groups. Obtained. The amount of radioactivity of this product was lx70-2μC179.

Extract agent → for Hase −

Claims (1)

[Claims] (1) From a dilute aqueous chloride solution containing solids and soluble radioactive substances, the amount of solids present is o, i.
After removing solids until the weight of the solution is less than that, barium ions and sulfate ions are added to precipitate sulfate, and then these solids are removed from the aqueous solution to reduce the content of radioactive substances. A method for refining chloride clay characterized by: