JPS5839896B2 - How to isolate yztrium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating and obtaining yttrium from a rare earth element mixture consisting of yttrium and a lanmetoid element, and more specifically relates to a method for separating and obtaining yttrium from a rare earth element mixture by a solvent extraction method using a single extractant. The object of the present invention is to provide a new and improved method that can very efficiently separate yttrium from yttrium.

As is well known, yttrium is an industrially important element whose oxide is used as a main component of phosphors for color televisions, but yttrium is not always found in nature as a lanmethide element (atomic number It is produced in a form that coexists with elements ranging from 57 Rammens to lutetium with atomic number 71), and their chemical properties are extremely similar. It is practically impossible to separate yttrium and lanthanide elements by chemical methods.

The so-called ion exchange resin method and solvent extraction method are known as industrial methods for separating and purifying yttrium from orchid-made elements, but the former method not only uses expensive chelating agents but also However, since it is a batch method, it has a serious drawback that productivity is not necessarily high, so the mainstream of yttrium purification technology is currently shifting to the latter solvent extraction method.

The principle of separation of rare earth elements by the solvent extraction method is as follows.

That is, for example, two types of rare earth element ions R3+
, When an aqueous solution containing R3+ is brought into contact with an organic solvent that is immiscible with the aqueous solution containing a suitable extractant, R3+,
A portion of each R3+ binds with the extractant and moves from the aqueous solution phase (hereinafter referred to as aqueous phase) to the organic solvent phase (hereinafter referred to as organic phase), and an extraction equilibrium is established between the two phases.

The ratio of the concentrations of each ion in the organic phase and the aqueous phase at this time is called the extraction and distribution ratio of each ion, and the value of this extraction and distribution ratio differs slightly depending on the type of rare earth element.

Therefore, if the extraction operation as described above is repeated in multiple stages, it should be possible in principle to separate each element, and separation is easy between elements that have a large difference in extraction distribution ratio.

However, with conventionally known extractants, the difference in extraction distribution ratio for each element is not very large (or the ratio separation coefficient is close to 1), so it is difficult to distinguish between elements using a single extractant. It is difficult to completely separate the
Therefore, particularly for the purpose of separating and purifying yttrium from lanthanide elements, a method is known in which two types of extractants are used in combination.

To explain the principle of this method, in general, the extraction and distribution ratio of lanmetoid elements increases or decreases regularly according to the order of atomic number (often increases with atomic number), but the distribution coefficient of yttrium is Which element in the series the value is closest to differs depending on each extractant.

Therefore, when the first extractant A1 was used, the extraction distribution ratio DY(A1) of yttrium was almost equal to that of neodymium No. 60, DND-(A1), and the second extractant A2 was used. Extraction distribution ratio D of yttrium
It is assumed that Y(A2W is approximately equal to that of element 68, erbium, D□(A2).

First, if the rare earth mixture is subjected to each stage of separation operation using the first extractant, it is easy to separate yttrium and heavy rare earth elements, mainly erbium.
Since it is difficult to separate yttrium from light rare earth elements mainly composed of neodymium, it can be divided into a part mainly composed of heavy rare earth elements and a part mainly composed of yttrium and light rare earth elements.

Next, if a multi-step separation operation is performed using a second extractant using this portion mainly consisting of yttrium and light rare earth elements as intermediate raw materials, it will be difficult to separate yttrium and heavy rare earth elements in this case. Since the intermediate raw material contains almost no heavy rare earth elements, this does not pose a problem, and on the other hand, it is easy to separate yttrium and light rare earth elements, so
Yztrium can be obtained in high purity.

In summary, in the separation and purification of yttrium from a mixture of rare earth elements by the solvent extraction method, two types of extractants are used in succession, each having a different relative position (extraction order) of yttrium in the lanthoide element series in terms of extraction distribution ratio. This is the basic principle.

Various combinations of such two types of extractants have been proposed in the past. For example, two types selected from acidic phosphoric acid esters, carboxylic acids, quaternary ammonium salts, etc. are used (for example, Japanese Patent Application Publication 1973-
(See Publication No. 54216).

Since such a method requires the separate management of two types of extractants, it is industrially disadvantageous, and a method for separating and purifying yttrium using a single extractant has been strongly desired.

However, although attempts have been made in the past to vary other conditions over a wide range using a single extractant, no industrially practicable method has yet been known.

The present invention aims to solve the problems in the conventional methods as described above and to provide a method for separating and purifying yttrium from a mixture of rare earth elements using a single extractant. When carboxylic acids, which are relatively inexpensive, are used as an extractant, the above-mentioned extraction distribution ratio of the Rammemaid element when the counter anion of the rare earth ion in the aqueous phase is nitrate ion NO3 and when chloride ion Cl is used. This study was completed based on the inventors' surprising new finding that the relative position (extraction order) of yttrium in the series varies widely.

That is, the method of the present invention involves contacting an aqueous solution of a salt of a rare earth element consisting of yttrium and a Lammemaid element with an organic solvent containing a carboxylic acid to separate yttrium from a Lammemaid element by a solvent extraction method. A method for separating yttrium from an orchid made element, characterized in that a step of bringing the nitrate into contact with the organic solvent and a step of bringing the aqueous solution of a nitrate of the rare earth element into contact with the organic solvent are carried out one after the other. In this method, either the extraction step from the chloride aqueous solution or the extraction step from the nitrate aqueous solution may be performed first.

Next, an embodiment of the method of the present invention according to claim 2, in which extraction from an aqueous chloride solution is performed first, will be described.

First, there is no particular restriction on the content ratio of yttrium in the rare earth element mixture supplied to the first step, and it is not true that the higher the ratio, the easier the separation and purification. If the Y2O3 content is around 60φ, such as the mixed rare earth oxide obtained as a raw material, it can be used satisfactorily.

The aqueous solution of rare earth element chloride supplied to the first step is obtained by dissolving the mixed rare earth element oxide as described above in hydrochloric acid, but it can also be obtained by dissolving the rare earth element chloride prepared in advance. It can also be obtained simply by dissolving it in water.

In either case, after dissolution, it is desirable to remove undissolved residue by a method such as filtration.

The concentration of rare earth elements in the aqueous solution of brown octopus is 0.1 mol/l
-1.5 mol/l is often used, since concentrations lower than this range are inefficient as large amounts of aqueous solution must be handled, and if the concentration is too high, This is because it has a negative effect on separation.

Furthermore, the acidity of this aqueous solution is required to be in the pH range of 2 to 4 in order to make the separation effective.

Next, as the carboxylic acid used as an extractant, any of the carboxylic acids used in combination with conventional types of extractants to separate rare earth elements can be used, such as Versatic Acid (trade name of Shell Chemical Co., Ltd.). A tertiary monovalent carboxylic acid having around 10 carbon atoms, known under the name of , is preferably used.

Hydrocarbon solvents such as kerosene and toluene are suitable as organic solvents for dissolving this substance, but since the influence of the type of solvent is relatively small, it is necessary to use a solvent that does not mix with water and can dissolve the carboxylic acid. Both can be used in almost the same way.

The concentration of carboxylic acid in the organic phase may be determined depending on each case within the range of 0.5 to 3 mol/l.

It is generally difficult to sufficiently achieve the purpose of separation by contacting the aqueous solution (aqueous phase) with the organic solvent containing carboxylic acid (organic phase) once, so it is difficult to achieve the purpose of separation sufficiently. It is desirable to carry out liquid-liquid contact.

Although the device for performing such multistage countercurrent liquid-liquid contact is not limited to a specific type, for example,
A mixer-settler type as disclosed in Japanese Patent No. 3731 is suitable.

The mixer-settler must have enough stages to achieve the desired separation.

In addition, all operating methods such as operating conditions of the mixer-settler belong to the conventionally known technology.

In the above extraction with carboxylic acid from the aqueous chloride solution, the separation coefficient between yttrium and neodymium is approximately 0.8.
On the other hand, the separation coefficient between yttrium and samarium is 2.1, so in this first step, an aqueous solution containing only yttrium and light rare earth elements, which does not contain substantially any heavy rare earth elements, is extracted. It can be easily obtained as a residual liquid.

Next, in the second step of the method of the present invention, the raffinate obtained in the first step in which the proportion of lanionoids whose extraction distribution ratio by the extractant carboxylic acid is higher than that of yttrium is reduced is chlorinated. Convert the aqueous solution to the acetate aqueous solution.

Various embodiments are possible for carrying out this step.

Of the embodiments of this second step, the simplest in principle is to add oxalic acid to the raffinate to precipitate the rare earth elements as oxalate, and then dry and calcinate this oxalate to oxidize it. This method involves dissolving the oxide in nitric acid.

However, this method is not necessarily advantageous for large-scale industrial implementation, since not only the process operations are complicated, but also a large amount of oxalic acid is required.

Even more advantageous than the above-mentioned method of obtaining rare earth element oxide and redissolving it in nitric acid is to use a device such as a mixer-settler to mix the raffinate and an organic solvent containing an appropriate extractant. Substantially the entire amount of the rare earth component is transferred to the organic phase by countercurrent contact with the organic phase to obtain a fully extracted organic phase, and then the rare earth component is transferred to the aqueous phase by back extraction using an aqueous nitric acid solution from the fully extracted organic phase. This is a method to prepare a nitrate aqueous solution.

In the above method, it is not necessarily necessary to follow the sequence of obtaining a phosphorus nitrate aqueous solution by back extraction and then supplying it to the next step.

That is, the entire extracted organic phase is subjected to the 11th step (3rd step).
The extractant-containing organic solvent is supplied from one end of the multi-stage mixer-settler to the intermediate stage of the multi-stage mixer-settler used in step 1), and the nitric acid aqueous solution is supplied as a scrubbing liquid from the other end to perform countercurrent liquid-liquid contact. By doing so, the back extraction step and the third step (extraction separation step) can be performed simultaneously.

Furthermore, it is not always necessary to obtain the entire extracted organic phase as described above.

That is, the raffinate obtained in the first step is
The extractant-containing organic solvent is supplied from one end of the multistage mixer settler and the nitric acid aqueous solution is supplied from the other end to perform countercurrent liquid-liquid contact, as described above. If so, the second step and the third step can be carried out simultaneously.

At first glance, such a method seems to omit the second step, but if we consider the internal situation of the multistage mixer settler, it is a method in which the second and third steps are carried out simultaneously. This can be easily understood by those skilled in the art, and does not fall within the technical scope of the present invention.

The carboxylic acid as extractant used in the third step does not necessarily have to be the same as that used in the first step.

However, from the purpose of the present invention, which is to simplify the process, it is preferable that these be the same, and it is also desirable that the type and concentration of the organic solvent used to dilute this be the same.

In this third step, yttrium is selectively extracted and transferred to the organic phase from a mixture of yttrium and an orchid made element having a small extraction distribution ratio from an aqueous nitrate solution, to obtain an extract containing an increased proportion of yttrium. By appropriately setting the extraction conditions, it is possible to obtain an extract containing only yttrium and substantially no lanthioide elements.

Such extraction conditions can be easily determined by a person skilled in the art through simple experiments, and therefore do not impose particularly difficult constraints.

The extract obtained in the third step is generally not used in that size, but it can be back-extracted with a suitable acid, such as an aqueous nitric acid solution, to transfer the yttrium to the aqueous phase, and then According to the method of the present invention, yttrium oxalate may be generated and calcined to form an oxide, and according to the method of the present invention, 9
Yttrium oxide having a rare earth purity of 9.9% or more can be easily produced.

The embodiment described in claim 2 in which extraction and separation from a chloride aqueous solution is performed without stirring and then extraction and separation from a nitrate aqueous solution has been described. An embodiment according to claim 3 may be adopted in which extraction separation is performed and then extraction separation from an aqueous chloride solution is performed.

These two embodiments are based on the basic principle that when using a single extractant, extraction and separation using two extraction systems with different relative positions of yttrium in the lanthanoid element series are performed before and after the extraction distribution ratio. They have something in common.

Hereinafter, embodiments of the present invention will be described as examples of measuring separation coefficients (reference examples).
Although the present invention will be explained by examples, the present invention is not limited to these embodiments.

Reference Example: 100 ml of an aqueous solution (rare earth element concentration 1 mol/1l pH approx. 3) containing mixed rare earth elements consisting of yttrium and lanthanide elements dissolved in the form of chlorides or nitrates and a kerosene solution (kerosene Using a separating funnel, 500 ml of Shoseki Solvent manufactured by Showa Sekiyu Co., Ltd. (concentration: 2 mol/11) and 60 ml of ammonia water (concentration: 2.4 mol/l) were thoroughly shaken and brought into contact. Let it stand, then let it stand.
The upper organic phase and lower aqueous phase were then separated.

The composition of rare earth elements in each of the organic and aqueous phases was investigated, and the relative separation coefficient of lanthanoid elements (L) with respect to yttrium (Y) was determined using the following relational expression.

Just L).

, (Y). are the concentrations of L and Y in the organic phase, respectively.

(L) (Y) A is the concentration of L and Y in the aqueous phase, respectively.

(CL).

, (CY). is the composition ratio of glue and Y in the organic phase.

(CL) (CY) A is the composition ratio of Y in the aqueous phase.

From these results, it is clear that the extraction position for yttrium in the orchid made element series is between neodymium and samarium when extracted from a chloride aqueous solution, and between gadolinium and terbium when extracted from a residual nitrate aqueous solution. It became.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention, in particular the embodiment according to claim 2, will be explained with reference to the accompanying drawings.

In the figure, I, n, III, IV, and V are multistage mixer settlers, respectively, and these are connected by piping as shown by the solid line (indicating the flow path for the aqueous phase) and the broken line (indicating the flow path for the organic phase). (However, ancillary equipment such as pumps, solution storage tanks, flow meters, etc. are not shown).

In this diagram, the organic phase circulating through mixer settlers ① and ② and the organic phase circulating through m, IV, and V are extractant,
Although the two circulation systems can actually be combined into one since the type and concentration of the solvent are the same, they are shown as separate circulation systems for the sake of simplicity.

Note that each stage of each □xer settler is the same size, and the capacity of one mixer chamber is approximately 2. Ol's was used.

Versatic Acid 1 for carboxylic acids as extractants
A 2 mol/11 kerosene solution (indicated by S in the figure; Showa Solvent manufactured by Showa Sekiyu Co., Ltd. was used for kerosene) was used as an organic solvent for extraction.

□The xer settler■ has 24 stages for carrying out the first step, and the 16th stage is supplied with an aqueous chloride solution of the raw rare earth element (indicated by F in the figure), and the 1st stage is The organic solvent S was supplied to the 24th stage, and an aqueous hydrochloric acid solution for scrubbing (partial back extraction) was supplied to perform multistage countercurrent liquid-liquid contact.

Aqueous ammonia was supplied to the third stage to adjust the pH.

The mixer-settler (2) is a device for regenerating the organic solvent S by total back extraction from the extract E1 flowing out from the mixer-settler (2), and since it is not directly related to the method of the present invention, detailed explanation will be omitted.

Raw material liquid F1 Extract liquid E1 flowing out from mixer settler ■
Table 2 shows the analysis results of the breakdown (φ in terms of oxide) of each rare earth element contained in the raffinate R1.

In addition, the concentration and flow rate ratio of each part supplied to mixer settler ■ and each part flowing out (the flow rate of organic solvent S1 is 1
00 and expressed as a capacity ratio) are shown in Table 3.

As can be seen by comparing the analytical values shown in Table 2 for F and R1, this step decreased the proportion of samarium-lutetium and significantly increased the proportion of yttrium in the raffinate R1.

Next, the mixer-settler (■) is for extracting and transferring the rare earth elements contained in the raffinate R1 from the mixer-settler (2) into an organic solvent to adjust the liquid supplied to the mixer-settler (2), and has four stages. have.

Concentration of each feed liquid and effluent in mixer settler■,
The analysis results of the flow rate ratio and the rare earth elements contained are shown in Tables 3 and 2.

The extract E3 flowing out from the mixer-settler ■ is supplied to the 16th stage of the mixer-settler ■ (having a total of 24 stages), and the first stage of the mixer-settler ■ contains the organic solvent S1 supplied to the mixer-settler ■ and An organic solvent S4 with the same composition is used in the 24th stage as a nitric acid aqueous solution SC4 for scrubbing.
were supplied respectively.

In addition, the third stage contains ammonia water (NH4) for pH adjustment.
0H)' was supplied.

Extraction equilibrium is established inside each membrane in the mixer-settler ■, and the rare earth elements contained in R3 and supplied are distributed between the aqueous phase and the organic phase, but in the aqueous phase, they are in the form of a nitrate aqueous solution. is in contact with the organic solvent in the organic phase.

When the mixer settler■ was operated in this way,
From the first stage, a raffinate R4 rich in rare earth elements having a smaller extraction distribution ratio than yttrium flowed out, and from the 24th stage, an extract E4 having a very low content of rare earth elements other than yttrium flowed out.

The concentration and flow rate ratio of each of the above-mentioned feed liquids and effluents are shown in Table 3. Table 2 shows the analysis results of the rare earth elements contained in the effluents R4 and E4.

□The xer settler ■ is used to recover rare earth elements (yttrium) from the extract E4 supplied from the mixer settler ■ by total back extraction. An aqueous solution of nitrate is obtained as π.

Table 3 shows the concentrations and flow rate ratios of Sr1 and R5.

When yttrium oxalate was precipitated by adding oxalic acid to the above R5 liquid and this was dried and calcined, yttrium oxide with a purity of 99.9% or more was obtained.

[Brief explanation of the drawing]

The drawing is a diagram showing the flow of an aqueous phase and an organic phase between a plurality of multi-stage □ xer settlers in one embodiment of the present invention. I, n, III, ■, V...Multi-stage mixer settler.

Claims (1)

[Scope of Claims] 1. In separating yttrium from a rank-made element by a solvent extraction method by contacting an aqueous solution of a salt of a rare earth element consisting of yttrium and a lanthioide element with an organic solvent containing a carboxylic acid, the rare earth element Separation of yttrium from lanmethide element, characterized in that the steps of contacting the organic solvent with a chloride water bath solution and the step of contacting the organic solvent with an aqueous solution of the nitrate of the rare earth element are carried out before and after. Method. 2(1) Contacting an aqueous solution of a chloride of a rare earth element consisting of yttrium and a lanthioide element with an organic solvent containing a carboxylic acid, the extraction and distribution ratio of the carboxylic acid from the aqueous chloride solution is larger than that of yttrium. a first step of extracting and transferring the lammetuid element into the organic solvent to obtain a raffinate containing a rare earth element with an increased ratio of yttrium to the lammetuid element; (2) converting the rare earth element in the raffinate to nitrate; a second step of converting the nitrate aqueous solution into an aqueous solution; (3) contacting the nitrate aqueous solution with an organic solvent containing a carboxylic acid to obtain a lanthioide element and and a third step of extracting and transferring yttrium into the organic solvent to obtain an extract containing a rare earth element in which the ratio of yttrium to rank-made elements is further increased. Method described. 3(1) An aqueous solution of a nitrate of a rare earth element consisting of yttrium and a lanmetsuide element is brought into contact with an organic solvent containing a carboxylic acid, and the extraction and distribution ratio of the carboxylic acid from the nitrate aqueous solution is larger than that of yttrium. (2) converting the rare earth elements in the extract into a chloride aqueous solution; (3) contacting the aqueous chloride solution with an organic solvent containing a carboxylic acid to convert a lanthioide element whose extraction and distribution ratio by the carboxylic acid from the aqueous chloride solution is higher than that of yttrium; and a third step of extracting and transferring the rare earth element into an organic solvent to obtain a raffinate containing a rare earth element in which the ratio of yttrium to lanthionoide elements is further increased. the method of.