JPS60103026A - Manufacture of rare earth metallic oxide - Google Patents

Abstract

PURPOSE:To manufacture rare earth metallic oxides in a high yield by adding sulfuric acid to a soln. of rare earth metallic sulfates or a recycled alkali oxalate soln., slowly adding the latter soln. to the former soln., and adding fresh oxalic acid. CONSTITUTION:Oxalic acid is added to a soln. of rare earth metallic sulfates such as a soln. of about 1.0-1.3pH prepd. by thermally decomposing ore contg. rare earth metals with concd. sulfuric acid and by carrying out leaching with water to separate thorium etc., and the resulting rare earth metallic oxalates are separated and treated with alkali to form rare earth metallic hydroxides and alkali oxalate. They are separated from each other, and the alkali oxalate is replenished with fresh oxalic acid and recycled to the next oxalating stage. At this time, sulfuric acid is added to a soln. of rare earth metallic sulfates or the alkali oxalate soln., the latter soln, is slowly added to the former soln. so as to prevent a local pH rise, and finally fresh oxalic acid is added. Rare earth metallic oxides are manufactured in a high yield.

Description

[Detailed description of the invention] The present invention relates to a method for producing rare earth oxides.

Currently, research in the field of rare earth elements and their properties has made remarkable progress, and they are used in a wide range of fields, including alloys, nuclear reactor materials, optical glass, glass abrasives, catalysts, magnetic materials, and electronic materials. ing.

Furthermore, with the recent research and development of rare earth element separation technology and high purity product refining technology, it is expected that the field of application, demand and production of rare earth elements will continue to grow in the future.

Rare earth oxides are made from a mixture of more than ten types of rare earth elements, and are made into a raw material before being used in various fields. Rare earth oxides are manufactured using Zemetime, a rare earth ore. Monazite, bastnasite, etc. are conventionally known as
The rare earth sulfuric acid solution and the insoluble residue are separated by heating and decomposing with concentrated sulfuric acid and leaching with water. There is also a method of obtaining rare earth salts by adding alkali to this rare earth sulfuric acid solution, but in this case, due to the phosphorus and acid groups present in the rare earth (lIre acid solution), rare earth salts can be obtained without hydrating rare earth. Therefore, oxalic acid is added to a sulfuric acid solution of rare earths, and the rare earth oxide crystals are collected. Because this process is relatively expensive, it is disadvantageous in terms of cost to obtain rare earth oxides by firing the crystals of the oxidized red clay as is.Therefore, we further treat the oxidized red clay with an alkali and oxidize it by hydration. The red clay and the alkali salt of oxalic acid are separated, and the hydroxide red clay is calcined to obtain rare earth oxides, and the alkali salt of oxalic acid is
Return the rare earth sulfate solution to the oxalate process,
A recycling method is being considered in which the oxalic acid lost in the previous process is replenished and converted into oxalate.

As described above, in order to produce rare earth oxides from raw rare earth ores, a large number of steps such as reactions and separations are required, and even a small loss in each step significantly reduces the final yield. If the yield decreases by a few percent in each process, the final yield will drop by a factor of 1, which is a big problem in the production of rare earths, where even a few percent change in the yield of rare earths can greatly affect the production cost. There is a strong desire to improve the yield in each step.

As a result of studying the process of recycling an alkali salt of oxalic acid to obtain oxalic acid red clay, the present inventors found that a rare earth sulfate solution is not yet available. It was discovered that the yield of oxidized red clay could be improved by changing the addition rate and order of addition, and the present invention was achieved.

That is, oxalic acid red clay obtained by adding and separating oxalic acid to a rare earth sulfate solution is treated with an alkali to separate it into hydroxide red clay and an alkali salt of oxalic acid.
In the method of replenishing oxalic acid and recycling it for the next oxidation process, a rare earth sulfuric acid bath solution or
After adding sulfuric acid to the alkaline salt bath solution of 11 acids, localized! The method for producing a rare earth oxide is characterized in that an alkali salt solution of oxalic acid is gradually added to a sulfuric acid solution of a rare earth metal so as not to increase the temperature by 1 HJm, and finally a new amount of oxalic acid is added to make up for it.

Next, a detailed explanation of the invention will be given. Rare earth sulfuric acid bath solution can be obtained by heating and decomposing raw rare earth ores with concentrated sulfuric acid, leaching with water, and separating j.lium and the like using a conventionally known method. At this time, the pH of the rare earth sulfuric acid bath solution is 1.0 ~
It is about 1.3. The alkali salt of oxalic acid that is recycled is used to improve the recovery rate of hydroxide red clay and oxalic acid burqa IJJ tray when treating the oxal oxide red clay from the previous cycle with alkali. Approximately twice the equivalent amount of alkali is used, resulting in a strongly alkaline solution with a pH of 1.2 or higher.

The amount of oxalic acid to be replenished is normally required to be around 1.3 times the theoretical equivalent in order to improve the yield of oxidized red clay.
0.4 times the theoretical equivalent was used. These methods are used to oxidize a rare earth sulfuric acid solution, but in the present invention, sulfuric acid is added to the rare earth sulfuric acid solution in advance, or to an alkali salt solution of oxalic acid, and oxalic acid is gradually added to the rare earth sulfuric acid solution. It is important to add the liquid to the alkali salt of the chlorine, and finally add the 41-carboxylic acid.

For example, a sulfuric acid solution of a rare earth element is placed in a stirred reactor, and sulfuric acid is added to the solution. The amount of sulfuric acid added (or added to the alkaline salt solution of oxalic acid) is such that the pH of the slurry of oxalic oxidized red clay becomes 1.5 or less after all the oxalic acid is added.

Next, while stirring the rare earth sulfuric acid solution, an alkali salt solution of oxalic acid is gradually added so as not to increase the local pH, and after confirming the formation of a precipitate of oxidized red clay, a supplementary amount of oxalic acid is added. The rate of addition of the alkali salt of oxalic acid is determined by the stirring conditions of the reactor (1f), for example, 200p.

In the cylindrical reaction 5, the rotation speed of the stirrer is 100-20
At Orpm, (5 to 5 of the total amount of f4H alkali salt bath solution)
As a result of adding 65% at a rate of 20%/min, a high yield was obtained without any local pH increase.

Here, if sulfuric acid is not added in advance, if sulfuric acid is added but the alkali salt bath of oxalic acid is rapidly added, or if sulfuric acid is added at the end of 1'S oxidation, , the excess alkali in the oxalic acid alnochloride bath solution temporarily raises the pH of the system, causing hydroxides and t, which have a fast reaction rate, to
-f: Something similar to J is generated, which inhibits the precipitation of the oxidized red clay, lowering the yield of the oxidized red clay, and causing the system's pl
A phenomenon was observed in which impurities in the rare earth sulfuric acid solution co-precipitated with the oxidized red clay when the oxidized red clay rose to near neutrality.

However, adding supplemental oxalic acid at the end cools the slurry bath liquid of oxalic oxidized red clay due to the endothermic effect when oxalic acid dissolves, lowering the vulgarity of oxalic oxidizing soil, and reducing the subsequent swamp filtration. This has the effect of reducing the amount of oxalate compound lost to the outside of the system due to the separation of Although it is better to lower the temperature, there is no particular limitation.

In this way, sulfuric acid is added in advance to a rare earth sulfuric acid bath or a recycled oxalic acid alkaline salt solution, and after gradually adding the oxalic acid alkaline salt solution to the rare earth sulfuric acid solution, fresh oxalic acid is added. By the method of the present invention, adding
Compared to previously reported methods, the yield of oxidized clay soil is improved by more than ten percent.

The present invention will be explained below with reference to Examples and Comparative Examples.

Example 1 Rare earth sulfuric acid solution containing 13.1y/IL of rare earth in terms of oxidized soil 10. Charge ON into a cylindrical container equipped with a stirrer, stir at a rotation speed of 150 rpm, and add 30 mg of concentrated sulfuric acid. Next, a 3 tl) sodium oxalate solution (corresponding to the alkaline salt solution of oxalic acid mentioned in the text) (1.2 times the theoretical equivalent of caustic soda was used during the alkali treatment of the oxal oxidation soil, and it had already been recycled twice) 6 .81 (0.9 theoretical equivalent times the rare earth) to 0.7I! , at a rate of 7 minutes. After the formation of a precipitate of oxalic acid oxidized soil was observed, 58y of oxalic acid (0.4 times the theoretical equivalent relative to the rare earth) was added. The pH of the obtained oxidized red clay slurry solution was 1. ．． 45 (26° C.), and the yield of oxidized soil was 98.5% in terms of oxidized soil.

Example 2 As a result of carrying out the same procedure as in Example 1 except that concentrated sulfuric acid was added to the sodium oxalate solution, the purest P
) I = 1.47 (26°C), yield of oxidized soil 9
It was 8.3%.

Example 3 Example 1 Odor-U, #The amount of sulfuric acid added was 250 ml
In addition, as a result of conducting in the same manner as the actual hfli91II, the final +)H = 0.80 (27°C), yield 98.3
%Met.

Comparative Example 1 In the method of Example 1, concentrated sulfuric acid was not added to any of the methods, and sodium truncate solution was added all at once.
The results were as follows: final pH = 3.06 (29°C),
The yield was 86.0%.

Comparative Example 2 In the method of Comparative Example 1, the order of addition of the sodium oxalate bath solution and oxalic acid was reversed, and as a result, the final pH was -3.02 (30
℃), yield was 85.7%.

Further, as a result of analyzing the oxidized soil produced in Comparative Example 1.2, it was found that it contained relatively large amounts of impurities such as phosphorus and iron.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] A recycled alkali salt solution of oxalic acid and oxalic acid are added to an aqueous solution of rare earth sulfuric acid, and the obtained oxalic acid rare earth is treated with an alkali to separate it into rare earth hydroxide and an alkali salt of oxalic acid. Rare earth oxide is fired to form rare earth oxide, and the alkali salt solution of oxalic acid is returned to the above-mentioned oxidation process, and new oxalic acid is replenished for recycling. After adding sulfuric acid to the solution, a solution of an alkaline salt of oxalic acid is gradually added to the sulfuric acid solution of the rare earth to prevent a local pH increase, and finally, a new supplementary amount of oxalic acid is added. .