JPS5884118A - Separation of rare earth element - Google Patents

Abstract

PURPOSE:To separate a rare earth element from an aqueous soln. of a starting material in an industrially advantageous manner by feeding a specified extracting reagent easy to back-extract to the 1st stage of a multistage countercurrent extracting apparatus and dividedly adding an alkali for pH adjustment to the extraction system. CONSTITUTION:A multistage countercurrent extracting apparatus manufactured by connecting >=3 extracting and separating units in series is used. Each of the units is composed of an agitation vessel and a stationary separation vessel. An extracting reagent contg. an effective component represented by formulaI(where each of R<1> and R<2> is 6-20C straight or branched cahin alkyl) or by formula II (where each of R<3> and R<4> is 12-30C straight or branched chain alkyl) is fed to the 1st stage of said apparatus. A scrubbing soln. is fed to the last stage, an aqueous soln. of a starting material contg. rare earth elements is fed to an intermediate stage, and an alkali for pH adjustment is dividedly fed to <=2 stages from the 1st stage to the intermediate stage to which the aqueous soln. is fed. While adjusting the pH of the aqueous soln., a specified rare earth element is selectively shifted from the soln. to the extracting reagent, the reagent contg. the rare earth element is drawn from the last stage, and an aqueous phase contg. the remaining rare earth elements is drawn from the 1st stage.

Description

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

- This invention relates to an industrially advantageous method for separating rare earth elements from a water bath containing rare earth elements by a liquid-liquid extraction method.

As a method for separating rare earths from an aqueous solution using a liquid-liquid extraction method, a multistage countercurrent extraction device in which multiple stages of extraction and separation units consisting of a stirring tank and a stationary separation chamber are connected in series is used. The extraction agent is supplied to the first stage of the device, the acidic scrubbing liquid is supplied to the final stage, and the rare earth-containing raw material aqueous solution is supplied to the intermediate stage between the first stage and the final stage, and alkali is supplied to the extraction system. By doing so, the specific rare earths in the raw material aqueous solution are selectively extracted into the oil agent while adjusting the pH.
A method is known in which the extractant containing a specific rare earth element is extracted from the 88th stage and the aqueous phase containing the remaining rare earth element is extracted from the first stage (for example, in JP-A-Sho!j-/, 2 ．．
(See Publication No. 2136). The purpose of adding an alkali is to neutralize the acid liberated by the contact between the extraction agent and the clay aqueous solution and adjust the pH of the extraction system to a value corresponding to the clay to be separated. The entire required amount is added to the seventh stage along with the extraction agent.

Aqueous ammonia is known as an alkali, and Scrub G is used to extract rare earths and wash and remove rare earths other than the target rare earths contained in the extractant. is known to be used.

In the above extraction method, when an extractant containing gecoethylhexyl phosphate as an active ingredient is used, rare earths can be efficiently separated. .

Even if there are slight fluctuations in the scrubbing liquid flow rate or concentration,
It has little impact on the strength and purity of the target rare earth,
Able to drive stably. However, when using an extractant containing g-ethylhexyl phosphate as an active ingredient, it is necessary to use an acid aqueous solution with a high 1m!If to remove rare earths from the extractant containing rare earths by back extraction. In order to recover rare earths from the back extract containing rare earths obtained by back extraction, the rare earths are precipitated as hydroxides by neutralization, but when this method is used, Ml) f of the back extract It has the disadvantage of high acid loss due to its high acid content.

As an extraction agent that can perform back extraction by using an acid aqueous solution with a relatively low degree of lIs, an extraction agent containing an alkylphosphonic acid monoalkyl ester such as coethylhexylphosphonic acid mono-2-ethylhexyl ester as an active ingredient is used. agent, or di-[7,7-cymethyl--
(J',!'--dimethyl-7'-methylbutyl)-Yo-O extractants containing higher dialkyl phosphate esters such as methyloctylcholic acid as active ingredients are known. When used in the above extraction method,
The extraction efficiency of these extractants is easily affected by pH, so it is necessary to strictly control the pH 1 of the extraction system, that is, the amount of alkali added. Therefore, this control is generally extremely tight.

In addition, the extraction efficiency of these extractants depends on the amount of extractants and scrubbing liquid supplied, as well as variations in the clay composition in the rare earth-containing water ffj solution (variations are generally unavoidable when using natural materials as raw materials).
Coupled with the above-mentioned alkali problem, the industrial use of these extractants has been problematic, despite the fact that they are easy to back-extract.

As a result of intensive research to avoid the above-mentioned inconveniences, the present inventors have developed a method for separating rare earths.
Use a specific extractant that is easy to back-extract, and adjust the pH of the extraction system.
When adding alkali in parts for B111ll treatment, the influence of fluctuations in the amount of alkali on the separation of rare earths can be greatly reduced.
The present invention was developed based on the knowledge that the influence of fluctuations in liquid, scrubbing liquid, extraction agent, etc. can be reduced, and that this makes it possible to obtain an extremely industrially advantageous rare earth separation process that takes advantage of the characteristics of the skeleton extraction agent. Children run.

That is, the purpose of the present invention is to perform industrially advantageous separation of rare earth elements, and this purpose is to use a multistage countercurrent flow system in which three or more extraction separation units consisting of a stirring tank and a static tank are connected in series. Using an extraction device, the extraction agent is placed in the first stage of the device,
A scrubbing liquid is supplied to the final stage of IIl, and a rare earth-containing raw material aqueous solution is supplied to the intermediate stage between the first stage and the final stage, and the pH is adjusted by adding alkali to the extraction system.
A specific rare earth element is selectively transferred from the raw material aqueous solution to the extractant while adjusting the extraction agent, and the extractant containing the specific rare earth element is transferred from the final stage, and the aqueous phase containing the remaining rare earth element is transferred from the first stage. In the method for separating rare earths to be extracted, (1) an extractant of the general formula (wherein R' and R2 represent an alkyl group having a straight chain or a side chain having 6 to 0 carbon atoms, and are of the same type); or alkylphosphonic acid monoalkyl esters represented by the general formula (wherein R3 and R4 are linear or branched alkyl groups having carbon number/co to 30); (These may be of the same type or different types.) Using an extractant containing a higher alkyl phosphate as an active ingredient represented by This is achieved by supplying the rare earth-containing raw material aqueous solution from the first stage of the extractor and adding it in portions to at least two stages up to the membrane.

The present invention will be explained in detail below.

The rare earth-containing aqueous solution referred to in the present invention is an aqueous solution containing one or more rare earths such as metal and lanthanide, or these and other metals, and is an aqueous solution containing naturally occurring ores such as monazite and xenotime, or a chain line extracted from these. Examples include aqueous solutions obtained by dissolving concentrated rare earths, etc., in mineral acids such as nitric acid, hydrochloric acid, and sulfuric acid, and the rare earth concentration is 5-2 g atoms/t s, preferably 0. Oj −/, j I atom/1. The quality is excellent.

The "extraction agent" used in the present invention is an oil agent containing as an active ingredient an alkylphosphonic acid monoalkyl ester represented by the general formula (1) for the forefoot, or a higher dialkyl phosphate ester represented by the forefoot general formula [■], Front leg general formula (1)
Examples of R1 and R3 include λ-ethylhexyl group, octyl group, dodecyl group, octadecyl group,
7,7-dimethyl-, 2-(3',J'-dimethyl-
7'-methylbutyl)-5-methyloctyl group, etc., and R+ and R8 may be of the same type or different types.
3 and R' are cohebutylundecyl group, 7
．． 7-dimethyl-co (J', J'-dimethyl-/'-
methylbutyl)-j-methyloctyl group, λ-octyldodecyl group, 2-nonyltridecyl group, -1decyltetradecyl group, undecyltetradecyl group, --undecylpentadecyl group, λ-dodecylhexadecyl group,
Coated lysosylpentadecyl group, λ-1nodecylhegtadecyl group, etc. are opened, and Rs and R4 are formed.These alkylphosphonic acid monoalkyl esters or higher dialkyl phosphoric acid esters are liquids with high viscosity. Therefore, to facilitate the extraction operation, the hot bath medium that is usually diluted with an organic solvent is a petroleum distillate such as kerosene, or an aliphatic hydrocarbon such as hexane, octane, or decane. ethers such as dibutyl ether and diisoglobyl ether, alcohols such as n-hexanol, aromatic hydrogen oxides such as benzene, toluene, and xylene, etc. It is preferable to use the monoalkyl ester or higher dialkyl phosphate ester as a solution having a #degree of about 0.00 to 5 mol/l, preferably about 0.0 to 5 mol/l.

The amount of oil used is usually 0 for the rare earth a-containing raw material water bath liquid.
．． /~10 times the capacity.

Examples of the scrubbing liquid include a 0.0/~λN aqueous solution of a mineral acid such as nitric acid, hydrochloric acid, or sulfuric acid, preferably a water bath solution of about O,OS~IN, and usually 0.0/~λN aqueous solution with respect to the extraction agent. / ~ / times the capacity is used.

Further, examples of the alkali include an aqueous solution of a caustic alkali such as sodium hydroxide and potassium hydroxide, and aqueous ammonia.

The noise level when using an alkali varies depending on the composition of the rare earth-containing raw material water bath solution, oil agent, and scrubbing solution, as well as the type of rare earth to be separated, but in general, the amount of alkali used is approximately equivalent to the acid on the cloth to be extracted and in the scrubbing solution. As a guideline, select θ to achieve breakthrough pH. When the rare earth-containing raw material water bath solution contains free acid,
In order to neutralize the free acid, a neutralizing alkali is required in addition to the above hyalkali amount.

The alkali for neutralizing the acid in am may be introduced into the extractor together with the rare earth-containing raw material aqueous solution, but industrially, the clay-containing/JP, metal aqueous solution should be neutralized in advance using an alkali. Adjust the pH to about 2-6 11M! It is advisable to prepare the sample and feed it to the extraction device.

The multi-stage countercurrent extraction device m used in the present invention is an extraction separation unit consisting of a stirring tank and a holding tank, such as a mixer-settler or such devices connected in series, specifically, magraw hill book
Company/LI 43 years, Me Grow-H: LI
Published by Book company, Chemical Engineers Hand Ltsuku Chemical Bn
Gineers' Hand Book, No. J/-, 2
It is of the form described as Figure λ/-30 or Figure-/-37 on page 1.

The number of extraction and separation unit stages #-i should be 3 or more stages, but
The present invention can achieve great effects when using a multistage countercurrent extraction device with a large number of stages, such as 5 or more stages. In the present invention, a multistage countercurrent extraction device as described above is used, and the Extractant in the first stage, scrubbing liquid in the final stage,
In addition, the rare earth-containing raw material water bath liquid is supplied to the intermediate stage between the first stage and the final stage, and the alkali for pHyAM is supplied to at least two stages from the seventh stage to the intermediate stage to which the rare earth-containing raw material water bath liquid is supplied. Perform the extraction operation while adding in portions.

The type of rare earth to be separated,
There is an optimum level depending on the composition of each supply liquid, so it is best to determine it by experiment. Normally, this objective is often achieved by adding alkali in parts to the first stage, which supplies the extraction agent, and the intermediate stage, which supplies the clay-containing (t4') raw material aqueous solution. The cooling power pS is divided into any stage between the first stage and the intermediate stage, any stage between the first stage and the intermediate stage and the intermediate stage, or any λ stages between the first stage and the intermediate stage. Alternatively, 1111 minutes can be added on any three setups within the above range. For example, when selectively extracting samarium from a raw material aqueous solution containing a large amount of gadolinium and a small amount of europium and samarium, it is necessary to extract samarium at any stage between the sheath/stage and the middle stage, or at the first stage. Good results can be obtained by adding the alkali in portions to any one stage between the stage and the intermediate stage.

Addition of alkali to the seven stages of alkali addition RO1 is based on the total amount of alkali added to the extraction system, preferably Fi! -9', r@It is best to choose from the range of quantified authority. The division ratio when adding convex alkali in parts depends on the type of rare earth to be separated, the composition of each feed liquid supplied to the extraction device, and other conditions. There is an optimal ratio for each, and although there are no rules, for example, gadolinium and samarium can be mixed at the same time by using an extraction device with about 10-/j stages and adding alkali in portions to the first stage and the middle stage. In order to selectively extract gadolinium from the raw water bath liquid containing about 30 to 30 ml of the total alkali amount in the seventh stage.

It is preferable to add about 70~jO by weight to the intermediate stage. It is best to add about 10 to 30 weight of the total amount of alkali to the stage, and about 0 to 70 weight of the total amount to the intermediate stage. ○ Addition of alkali can also be carried out by installing separate piping for each alkali addition stage. Well, the first one also supplies the extractant.
When adding the alkali to a stage or an intermediate stage for supplying a detection-containing raw material aqueous solution, an alkali may be added in advance to the oil agent or the detection-containing raw material aqueous solution, respectively.

The extracting agent containing a specific rare earth element is extracted from the final stage of the multi-stage countercurrent extraction device, and the remaining rare earth elements are removed. The contained aqueous phase is withdrawn from the first stage of the apparatus. From the extractant containing rare earths of IP#, back extraction is carried out using an aqueous mineral acid solution such as nitric acid, hydrochloric acid, or phosphoric acid of INNF2, preferably about /,j~/IN, as a back extraction liquid. Obtaining specific rare earths as a mineral acid mound water bath sludge When performing extraction while adding a pH-adjusting alkali to the outside according to the method of the present invention, the pHwI4-adjusting alkali is added to the first stage of the multi-stage countercurrent extraction device together with the extractant. Compared to the method of supplying raw materials to a stage, even if there are fluctuations in the flow rate or concentration of the rare earth-containing raw material water bath solution, alkali, extraction agent, or scrub solution, the effect on rare earth separation is extremely small, operation management is easy, and it can be used for a long period of time. Rare earths can be separated stably over a long period of time.
Moreover, since the amount of alkali used can be reduced, it is extremely advantageous industrially.

Hereinafter, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the scope of the invention.

Examples 1 to j A multi-stage countercurrent extraction device in which /j stages of extraction separation units consisting of mixers and settlers were connected in series was used, and 1 mol of 2-ethylhexylphosphonic acid mono-2=ethylhexyl ester was added to M/stages. /l Tsurpets/,! 0 (manufactured by Esso Chemical ■, lower alkylbenzene mixture) 1? ! In the 16th stage, an iN nitric acid water bath solution of 0.31/hr was added as a scrubbing liquid, and in the 7th stage, samarium nitrate O1θO 77 mol/l gadolinium nitrate was added. , o jOII mol/l, terbium nitrate o, o o gjj mol/l, dysprosium nitrate O1Oλ/7 mol/l and yttrium nitrate 0. / / 6 mol/l of pHu rare earth-containing raw material aqueous solution / 1 hr is supplied, and 7. ri♂N*sodium oxide water bath solution,
0.0/j II in the 1st and 7th stages, respectively
The extraction operation is carried out while dividing the supply at l/hr and 0.04'/'I L/br, and extractant containing dysprosium and yttrium is supplied from the 7th stage, and tessepium, gadolinium and samarium are supplied from the 1st stage. Dysprosium and terbium were separated by extracting the aqueous phases they contained.

The residual rate of dysprosium in the resulting aqueous phase and the rate of terbium mixed into the extractant were as shown in the table below.

In addition, the results when the amount of IJum water fI solution was changed only in the 1st stage and when only the 7th stage was changed were as follows.
The results were as shown in Examples λ to D in the table below.

However, the residual rate of dysprosium in the aqueous phase and the mixing rate of terbium in the extractant are each 1 part with respect to dysprosium and terbium in the raw materials.

Comparative Examples 7 to 3 In the extraction operation in Example 1, instead of supplying the 7.9 gN aqueous sodium hydroxide solution in portions, the extraction operation was performed by supplying it only to the first stage.

In order to make the residual rate of dysprosium in the aqueous phase 6.7-, the water solubility of 7.9IrN sodium hydroxide is 0.07-
g9 tlhr is a must see.

The residual rate of dysprosium in the obtained aqueous phase and the mixing rate of terbium in the ozone and extractant were as shown in Table 2 below.

Further, the results when the amount of the sodium hydroxide aqueous solution was changed were as shown in the table below.

Table 1 Examples 6 to 10 Ten stages of extraction separation units consisting of a mixer and a set 2 are connected in series, using a nine-stage countercurrent extraction equipment case, and the first RI
IC di[7,7~dimethyl-1-''(3',3'-dimethyl-/'-methylbutyl)-j-methyloctylcholic acid, an extractant consisting of 1 mol/l of Tulpez ijOfgH/, 61/hr. , as a scrubbing liquid in the 70th stage.
jN nitric acid □, J tlhr, and terbium nitrate in the sr stage. , o cocomole/l disglosium nitrate □, 0 cocomole/l and yttrium nitrate 0. //l, pH2 containing mol/l
While supplying 91/hr of rare earth-containing raw material aqueous solution, 7. ? Add rN sodium hydroxide solution to tX/stage and third stage at 0.02j tlhr and 0.
, the extraction operation is performed in row 1 while dividing the supply with OJ tlhr.
/,, Dysprosium and terbium were separated by extracting the extractant containing dysprosium and yttrium from the 10th stage and the aqueous phase containing terbium from the 1st stage. The residual rate and the mixing rate of terbium in the extractant are as shown in Table 3 below. Also, when the amount of sodium hydroxide aqueous solution was changed only in the first stage, and when only the #I third stage was changed, The results were as shown in Examples 7 to 10 in Table 3 below.

Table 3 Ratio vNti~6 In the extraction operation in Example 6, instead of supplying the 7.9 gN aqueous sodium hydroxide solution in portions, the extraction operation was performed by supplying it only to the first stage.

7. In order to make the residual rate of dysprosium in the aqueous phase to be J and C, 7. ? 0.06 t/hr of rN sodium hydroxide solution was required.

The residual rate of dysprosium in the obtained aqueous phase and the rate of terbium mixed into the extractant were as shown in Table q below.

In addition, the results when the amount of the sodium hydroxide aqueous solution was changed were as shown in Table 1.

Output/Customer Miki Kasei Kogyo Co., Ltd. Substitute Physician 9F Physician Hasegawa - (T-Yoka 1 person)

Claims (1)

[Claims] (1) Using a multi-stage directional R extraction device in which three or more stages of extraction and separation units consisting of a stirring tank and a standing separation hinoki are connected in series, the extraction agent is supplied to the first stage of the equipment, the scrubbing liquid is supplied to the final stage, and , the rare earth-containing raw material water bath liquid is supplied to the intermediate stage between the first stage and the final stage, and a specific rare earth is selectively extracted from the raw material water bath liquid while adjusting the pH by adding alkali to the first extraction system. In a rare earth separation method in which the extractant containing a specific rare earth is extracted from the final stage and the aqueous phase containing the remaining rare earth is extracted from the first stage, In the formula, R+ and R1 represent a linear or branched alkyl group having t-200 carbon atoms, and these may be of the same type or different types. Alkyl ester or general formula (wherein R1 and R4 represent a straight or branched alkyl group having carbon number/λ~30, and these may be the same or different. Using an extractant containing a higher dialkyl phosphate ester as an active ingredient represented by A rare earth separation method characterized by dividing and adding the alkali to at least one stage of pH 1141.
1. A method for separating rare earth elements according to claim 1, wherein: 1 weight.