JP6554745B2 - Method for extracting scandium and / or lanthanoid - Google Patents

Description

  The present invention relates to a method for extracting scandium and / or lanthanoid, and more particularly to a method for extracting scandium and / or lanthanoid using nitrilotriacetic acid triamide.

  Scandium, one of the rare earth elements (rare earth), can dramatically increase the functions and physical properties of metal materials and semiconductor materials by adding a trace amount, so structural materials, electronic materials, magnetic materials, functional materials, etc. It plays a very important role in various industrial products. For example, aluminum-scandium alloy is used as a high-performance material in aerospace parts and sporting goods (bicycles, baseball bats, shooting, etc.), and by adding scandium oxide to zirconia porcelain, cracking is prevented. It is known to be effective.

  On the other hand, scandium is an element whose supply is unstable because there is no concentrated mineral, it is produced as a by-product of other metal ores, and the country of origin is limited. In particular, since the demand for electrolyte additives for solid oxide fuel cells has increased rapidly in recent years and has been depleted from the market, it is an important issue to ensure its stability.

Further, since scandium is very similar in chemical properties to other rare earth elements, it is known that it is extremely difficult to separate only scandium from these mixtures.
As a method for recovering or purifying scandium, an aqueous solution containing scandium and an organic solvent containing trioctylphosphine oxide are mixed to extract scandium into the organic solvent, and the organic solvent, water, hydrochloric acid, sulfuric acid, oxalic acid are extracted. A method of back-extracting scandium from an organic solvent (see Patent Document 1) and a method of using a specific amide derivative as an extractant have been proposed. (See Patent Document 2).

International Publication No. 2013/190879 JP 2013-189675 A

  An object of this invention is to provide the efficient extraction method of the scandium and lanthanoid which can be utilized in the industrial field.

（式（Ａ）中、Ｒはそれぞれ独立して炭素数１〜２０の炭化水素基又は水素原子を表す。）
＜２＞ 前記準備工程で準備した酸性水溶液が、硝酸イオン（ＮＯ_３ ⁻）を含む、＜１＞
に記載のスカンジウム及び／又はランタノイドの抽出方法。
＜３＞ さらに前記液液接触工程で接触させた酸性水溶液と有機溶媒を分液する分液工程
、及び前記分液工程で分液した有機溶媒に酸性水溶液を接触させる逆抽出工程を含む、＜１＞又は＜２＞に記載のスカンジウム及び／又はランタノイドの抽出方法。
＜４＞ 前記逆抽出工程で接触させる酸性水溶液が、硫酸イオン（ＳＯ_４ ^２−）を含む、
＜３＞に記載のスカンジウム及び／又はランタノイドの抽出方法。
＜５＞ 前記準備工程で準備した酸性水溶液が、スカンジウム及びランタノイドから選択
される抽出対象元素とスカンジウム及びランタノイドから選択される非抽出対象元素とを含み、前記抽出対象元素を抽出して、前記非抽出対象元素と分離する、＜１＞〜＜４＞の何れかに記載のスカンジウム及び／又はランタノイドの抽出方法。 As a result of intensive studies to solve the above problems, the inventors of the present invention contacted an acidic aqueous solution containing scandium and / or a lanthanoid with an organic solvent in the presence of a specific nitrilotriacetic acid triamide, thereby obtaining scandium. And it discovered that a lanthanoid could be dissolved in an organic solvent and extracted efficiently, and the present invention was completed.
That is, the present invention is as follows.
<1> A preparation step of preparing an acidic aqueous solution containing scandium and / or a lanthanoid, and contacting the acidic aqueous solution prepared in the preparation step with an organic solvent in the presence of nitrilotriacetic acid triamide represented by the following general formula (A) A method for extracting scandium and / or lanthanoid, comprising a liquid-liquid contact step.

(In formula (A), R represents a C1-C20 hydrocarbon group or hydrogen atom each independently.)
<2> The acidic aqueous solution prepared in the preparation step includes nitrate ions (NO ₃ ⁻ ), <1>
The method for extracting scandium and / or lanthanoid according to claim 1.
<3> Further includes a liquid separation step of separating the acidic aqueous solution and the organic solvent contacted in the liquid-liquid contact step, and a back extraction step of bringing the acidic aqueous solution into contact with the organic solvent separated in the liquid separation step. The method for extracting scandium and / or lanthanoid according to 1> or <2>.
<4> The acidic aqueous solution to be contacted in the back extraction step includes sulfate ions (SO ₄ ²⁻ ).
The method for extracting scandium and / or lanthanoid according to <3>.
<5> The acidic aqueous solution prepared in the preparation step includes an extraction target element selected from scandium and lanthanoid and a non-extraction target element selected from scandium and lanthanoid, and extracts the extraction target element, The method for extracting scandium and / or lanthanoid according to any one of <1> to <4>, wherein the method is separated from the extraction target element.

  According to the present invention, scandium and / or lanthanoid can be extracted efficiently.

The relationship between the distribution ratio (D) of trivalent scandium ion (Sc (III)), trivalent yttrium ion (Y (III)), and various trivalent lanthanoid ions and nitrilotriacetic acid triamide concentration was expressed. It is a graph. It is a graph showing the relationship between the distribution ratio (D) of trivalent scandium ion (Sc (III)), trivalent yttrium ion (Y (III)), and various trivalent lanthanoid ions and the nitric acid concentration. . It is the graph showing the relationship between the trivalent scandium ion (Sc (III)) density | concentration in nitric acid aqueous solution, and the scandium ion (Sc (III)) density | concentration extracted in the organic phase. It is a graph showing the relationship between the distribution ratio of trivalent scandium ion (Sc (III)) and shaking time.

  In describing the present invention, specific examples will be described. However, the present invention is not limited to the following contents without departing from the gist of the present invention, and can be implemented with appropriate modifications.

（式（Ａ）中、Ｒはそれぞれ独立して炭素数１〜２０の炭化水素基又は水素原子を表す。）
本発明者らは、スカンジウムやランタノイドの効率的な抽出方法を求めて検討を重ねた結果、スカンジウム及び／又はランタノイドを含む酸性水溶液を、一般式（Ａ）で表されるニトリロ三酢酸トリアミドの存在下で有機溶媒に接触させることにより、スカンジウムを有機溶媒に溶解させて、効率良く抽出することができることを見出したのである。
ニトリロ三酢酸トリアミドは、水に対しても有機溶媒に対しても親和性が高く、またスカンジウムやランタノイドとの結合に非常に適した構造を有していると考えられる（窒素原子と３つのアミド基が、スカンジウムやランタノイドと結合に有効に作用するものと考えられる。）。そのため、水溶液と有機溶媒の液液接触によって、ニトリロ三酢酸トリアミドがスカンジウムやランタノイドと会合し、水溶液中のスカンジウムやランタノイドが有機溶媒に可溶化して、抽出されるものと考えられる。
また、ニトリロ三酢酸トリアミドは、スカンジウムやランタノイドを逆抽出し易くするという優れた特長も有している。即ち、スカンジウムやランタノイドが溶解した有機溶媒を硫酸水溶液等の酸性水溶液に接触させることによって、酸性水溶液にスカンジウムやランタノイドを溶解させて回収することが可能となるのである。
さらに、ニトリロ三酢酸トリアミドは、例えば水素イオン濃度やアニオン濃度によって、それぞれの元素に対する親和性が変化するため、特定の元素を選択的に抽出することも可能となる。そのため、例えばスカンジウム（Ｓｃ）とイットリウム（Ｙ）のように従来分離が困難であった元素同士を、効率的に抽出することが可能となり、工業廃液の処理や希土類元素（レアアース）の生産に応用することができる。
なお、「ランタノイド」とは、ランタノイドに属する金属元素を意味し、酸性水溶液や有機溶媒中の酸化数、状態等は特に限定されないものとする。
また、「一般式（Ａ）で表されるニトリロ三酢酸トリアミドの存在下」とは、通常有機溶媒にニトリロ三酢酸トリアミドが存在していることを意味し、予め有機溶媒に含有させていても、或いは酸性水溶液と有機溶媒を接触させるときに別途ニトリロ三酢酸トリアミドを添加するものであってもよいものとする。 <Method for extracting scandium and / or lanthanoid>
The method for extracting scandium and / or lanthanoid which is one embodiment of the present invention (hereinafter sometimes abbreviated as “the extraction method of the present invention”) is a preparation step (hereinafter referred to as “preparing acidic aqueous solution containing scandium and / or lanthanoid”). , And may be abbreviated as “preparation step”), and in the presence of nitrilotriacetic acid triamide represented by the following general formula (A), a liquid-liquid contact step in which the acidic aqueous solution prepared in the preparation step and an organic solvent are brought into contact Hereinafter, it may be abbreviated as “liquid-liquid contact step”).

(In formula (A), R represents a C1-C20 hydrocarbon group or hydrogen atom each independently.)
As a result of repeated investigations for an efficient method for extracting scandium and lanthanoids, the present inventors have found that an acidic aqueous solution containing scandium and / or lanthanoid is present in the presence of nitrilotriacetic acid triamide represented by the general formula (A). It was found that scandium can be dissolved in an organic solvent and extracted efficiently by contacting it with an organic solvent.
Nitrilotriacetic acid triamide has a high affinity for water and organic solvents, and is considered to have a structure that is very suitable for binding to scandium and lanthanoids (nitrogen atom and three amides). It is thought that the group effectively acts on the bond with scandium and lanthanoids). Therefore, it is considered that nitrilotriacetic acid triamide associates with scandium and lanthanoid by liquid-liquid contact between the aqueous solution and the organic solvent, so that scandium and lanthanoid in the aqueous solution are solubilized in the organic solvent and extracted.
Nitrilotriacetic acid triamide also has an excellent feature of facilitating back extraction of scandium and lanthanoids. That is, by bringing an organic solvent in which scandium or lanthanoid is dissolved into contact with an acidic aqueous solution such as an aqueous sulfuric acid solution, the scandium or lanthanoid can be dissolved and recovered in the acidic aqueous solution.
Furthermore, since nitrilotriacetic acid triamide changes the affinity for each element, for example, depending on the hydrogen ion concentration or the anion concentration, a specific element can be selectively extracted. Therefore, for example, elements that were conventionally difficult to separate, such as scandium (Sc) and yttrium (Y), can be extracted efficiently, and applied to the treatment of industrial waste liquid and the production of rare earth elements (rare earth). can do.
The “lanthanoid” means a metal element belonging to the lanthanoid, and the oxidation number, state, etc. in the acidic aqueous solution or organic solvent are not particularly limited.
Further, “in the presence of nitrilotriacetic acid triamide represented by the general formula (A)” means that nitrilotriacetic acid triamide is usually present in an organic solvent, and it may be contained in an organic solvent in advance. Alternatively, nitrilotriacetic acid triamide may be added separately when the acidic aqueous solution and the organic solvent are brought into contact with each other.

The extraction method of the present invention is a method for extracting scandium and / or lanthanoid, but the specific type of scandium and / or lanthanoid that is the extraction target element is not particularly limited, and can be appropriately selected according to the purpose. .
The lanthanoids are specifically lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium. (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).
As extraction elements, scandium (Sc), lanthanum (La), cerium (Ce)
Praseodymium (Pr), neodymium (Nd), samarium (Sm), and europium (Eu) are preferable, and scandium (Sc) is particularly preferable. If it is the above, it can be extracted particularly efficiently.
In addition, the oxidation number of scandium and lanthanoid is usually 1 to 6, and has a stable oxidation number corresponding to each element. However, trivalent, tetravalent and pentavalent are preferable, and trivalent is particularly preferable. preferable.
Further, the scandium and / or lanthanoid that is the extraction target element is not limited to one type, and two or more types of scandium and lanthanoid may be the extraction target element.

(Preparation process)
The preparation step is a step of preparing an acidic aqueous solution containing scandium and / or lanthanoid, but the preparation method is not particularly limited, and an acidic aqueous solution containing scandium and / or lanthanoid is obtained, or scandium and / or lanthanoid is obtained. An acidic aqueous solution containing may be prepared by itself.
In addition, a preparation method in the case of preparing an acidic aqueous solution containing scandium and / or lanthanoid is not particularly limited, and an acid is added to an aqueous solution containing scandium and / or lanthanoid, or scandium and / or lanthanoid is dissolved. Therefore, an acidic aqueous solution may be added, and a solution containing scandium and / or lanthanoid may be added thereto.

  The acidic aqueous solution may contain other elements as long as it contains scandium and / or lanthanoid, which are extraction target elements. Other elements include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and other alkali metal elements, beryllium (Be), magnesium (Mg), calcium (Ca) , Transition of alkaline earth metal elements such as strontium (Sr), barium (Ba), radium (Ra), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu) Examples include metal elements.

The hydrogen ion concentration of the acidic aqueous solution is usually in the range of 0.001 to 10M, preferably 2.0M or less, more preferably 1.0M or less, still more preferably 0.2M or less, and preferably 0.001M or more. More preferably, it is 0.01M or more, More preferably, it is 0.1M or more.
In addition, the hydrogen ion concentration of the acidic aqueous solution when scandium (Sc) is used as the extraction target element is preferably 2.0 M or less, more preferably 1.0 M or less, still more preferably 0.2 M or less, preferably 0. 0.001M or more, more preferably 0.01M or more, and further preferably 0.1M or more.
Further, the hydrogen ion concentration of the acidic aqueous solution when lanthanum (La) is used as the extraction target element is preferably 4M or less, more preferably 3M or less, further preferably 2M or less, preferably 0.4M or more, more preferably Is 0.5M or more, more preferably 0.6M or more.
Further, the hydrogen ion concentration of the acidic aqueous solution when cerium (Ce) is used as the extraction target element is preferably 4M or less, more preferably 3M or less, still more preferably 2M or less, preferably 0.4M or more, more preferably Is 0.5M or more, more preferably 0.6M or more.
Although the specific kind of acid used for acidic aqueous solution is not specifically limited, Inorganic acids, such as hydrochloric acid, a sulfuric acid, nitric acid, are mentioned. When hydrochloric acid is used, the acidic aqueous solution contains chloride ions (Cl ⁻ ), when sulfuric acid is used, the acidic aqueous solution contains sulfate ions (SO ₄ ²⁻ ), and when nitric acid is used, the acidic aqueous solution is It can be expressed as containing nitrate ions (NO ₃ ⁻ ). Among these, when extracting scandium, it is preferable to use nitric acid, that is, the acidic aqueous solution contains nitrate ions (NO ₃ ⁻ ).

The concentration of scandium and / or lanthanoid, which is an element to be extracted from the acidic aqueous solution, is usually greater than 0M (mol / dm ³ ) and in the range of 0.3M or less, preferably 0.2M or less, more preferably 0.15M. Hereinafter, it is more preferably 0.1M or less. Within the above range, it becomes easy to efficiently extract scandium and lanthanoids.

（式（Ａ）中、Ｒはそれぞれ独立して炭素数１〜２０の炭化水素基又は水素原子を表す。）
Ｒはそれぞれ独立して炭素数１〜２０の炭化水素基を表しているが、「炭化水素基」は、直鎖状の飽和炭化水素基に限られず、炭素−炭素不飽和結合、分岐構造、環状構造のそれぞれを有していてもよいことを意味する。また、Ｒの炭素数は、好ましくは２以上、より好ましくは３以上、さらに好ましくは４以上、さらに好ましくは６以上であり、好ましくは１８以下、より好ましくは１５以下である。
Ｒはとしては、ブチル基、ヘキシル基、ヘプチル基、オクチル基、ノニル基、デシル基、ドデシル基、２−エチルへキシル基、２，２−ジメチルへキシル基等が挙げられる。
一般式（Ａ）で表されるニトリロ三酢酸トリアミドとしては、下記式で表されるものが挙げられる。

(Liquid-liquid contact process)
The liquid-liquid contact step is a step of bringing the acidic aqueous solution prepared in the preparation step into contact with the organic solvent in the presence of nitrilotriacetic acid triamide represented by the following general formula (A). The specific type of nitrilotriacetic acid triamide is not particularly limited and can be appropriately selected according to the purpose.

(In formula (A), R represents a C1-C20 hydrocarbon group or hydrogen atom each independently.)
R each independently represents a hydrocarbon group having 1 to 20 carbon atoms, but the “hydrocarbon group” is not limited to a linear saturated hydrocarbon group, and includes a carbon-carbon unsaturated bond, a branched structure, It means that each of the ring structures may be included. Further, the carbon number of R is preferably 2 or more, more preferably 3 or more, further preferably 4 or more, further preferably 6 or more, preferably 18 or less, more preferably 15 or less.
Examples of R include a butyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group, 2-ethylhexyl group, and 2,2-dimethylhexyl group.
Examples of the nitrilotriacetic acid triamide represented by the general formula (A) include those represented by the following formula.

The amount (abundance) of the nitrilotriacetic acid triamide represented by the general formula (A) is not particularly limited and can be appropriately selected according to the purpose. However, the volume of the organic solvent is a standard (dissolved in the organic solvent). The concentration is usually 0.001 to 2 M (mol / dm ³ ), preferably 0.01 M or more, more preferably 0.05 M or more, and still more preferably 0.1 M or more. Preferably, it is 1.5M or less, More preferably, it is 1M or less, More preferably, it is 0.6M or less. Within the above range, it becomes easy to efficiently extract scandium and lanthanoids.

The operation procedure of the liquid-liquid contact step is not particularly limited, and a known operation procedure used for liquid-liquid extraction can be appropriately selected. For example, an acidic aqueous solution and an organic solvent are charged into an arbitrary container, and the acidic aqueous solution and the organic solvent are sufficiently mixed using a shaker or the like, and then phase-separated by centrifugation to perform liquid separation. . Moreover, well-known extraction apparatuses or extraction instruments, such as an extraction apparatus, such as a countercurrent extraction apparatus, a separating funnel, can also be used instead of a container.
The shaking time when shaking the acidic aqueous solution and the organic solvent is usually 5 seconds or longer, preferably 10 seconds or longer, more preferably 20 seconds or longer, and further preferably 30 seconds or longer. Within the above range, scandium can be extracted more efficiently.
The liquid-liquid contact step is not limited to once, and the contact and separation may be repeated a plurality of times. The number of liquid-liquid contact steps is usually in the range of 1 to 20 times, preferably 2 times or more, more preferably 3 times or more, still more preferably 4 times or more, preferably 15 times or less, more preferably 10 times or less, more preferably 5 times or less. Within the above range, it becomes easy to efficiently extract scandium and lanthanoids.
Moreover, the method of making acidic aqueous solution and an organic solvent contact in presence of nitrilo triacetic acid triamide represented by general formula (A), for example, includes the following methods (a) to (c).
(A) A method of bringing an organic solvent solution containing nitrilotriacetic acid triamide represented by the general formula (A) into contact with an acidic aqueous solution in a container or the like.
(B) A method of bringing an acidic aqueous solution containing nitrilotriacetic acid triamide represented by the general formula (A) into contact with an organic solvent in a container or the like.
(C) A method in which nitrilotriacetic acid triamide represented by the general formula (A), an acidic aqueous solution, and an organic solvent are put into a container or the like and brought into contact with each other.
Among these, (a) is particularly preferable because it can be extracted more efficiently.

  The organic solvent is not particularly limited, and a known one used for liquid-liquid extraction with water can be appropriately selected. Specifically, hydrocarbon solvents such as n-hexane, n-dodecane, benzene and toluene, ether solvents such as diethyl ether, 1,4-dioxane and tetrahydrofuran (THF), 1,2-dichloroethane, chloroform and the like And halogen-based solvents. Of these, hydrocarbon solvents are preferred because of their high hydrophobicity, and n-dodecane is particularly preferred.

  The volume ratio of the acidic aqueous solution to be brought into contact with the organic solvent (acidic aqueous solution / organic solvent) is not particularly limited and can be appropriately selected according to the purpose, but is usually in the range of 1/100 to 100/1, preferably Is 1/50 or more, more preferably 1/10 or more, further preferably 1/5 or more, preferably 50/1 or less, more preferably 10/1 or less, and further preferably 5/1 or less. Within the above range, it becomes easy to efficiently extract scandium and lanthanoids.

  The extraction method of the present invention may include other steps as long as it includes the above-described preparation step and liquid-liquid contact step. For example, a liquid separation step for separating an acidic aqueous solution and an organic solvent brought into contact with each other in a liquid-liquid contact step, a back extraction step for bringing an acidic aqueous solution into contact with an organic solvent separated in the liquid separation step (hereinafter referred to as “back extraction step”) And a solvent distillation step of distilling off the organic solvent or water. Hereinafter, the details of the back extraction step will be described.

(Back extraction process)
The back extraction step is a step of bringing the acidic aqueous solution into contact with the organic solvent separated in the liquid separation step, but the hydrogen ion concentration and the like of the acidic aqueous solution to be contacted in the back extraction step are not particularly limited, and are appropriately determined depending on the purpose. You can choose.
The hydrogen ion concentration of the acidic aqueous solution to be contacted in the back extraction step is usually in the range of 0.1 to 8M, preferably 7M or less, more preferably 6M or less, still more preferably 5M or less, preferably 1M or more and more. Preferably it is 2M or more, More preferably, it is 4M or more.
Further, the hydrogen ion concentration of the acidic aqueous solution in the case of back-extracting scandium (Sc) is preferably 7M or less, more preferably 6M or less, further preferably 5M or less, preferably 1M or more, more preferably 2M or more, Preferably it is 4M or more.
Moreover, the hydrogen ion concentration of the acidic aqueous solution in the case of back-extracting lanthanum (La) is preferably 0.2M or less, more preferably 0.3M or less, further preferably 0.4M or less, preferably 3M or more, More preferably, it is 3.5M or more, More preferably, it is 4M or more.
Moreover, the hydrogen ion concentration of the acidic aqueous solution in the case of back-extracting cerium (Ce) is preferably 0.2M or less, more preferably 0.3M or less, further preferably 0.4M or less, preferably 3M or more, More preferably, it is 3.5M or more, More preferably, it is 4M or more.
Although the specific kind of acid used for the acidic aqueous solution contacted at a back extraction process is not specifically limited, Inorganic acids, such as hydrochloric acid, a sulfuric acid, nitric acid, are mentioned. When hydrochloric acid is used, the acidic aqueous solution contains chloride ions (Cl ⁻ ), when sulfuric acid is used, the acidic aqueous solution contains sulfate ions (SO ₄ ²⁻ ), and when nitric acid is used, the acidic aqueous solution is It can be expressed as containing nitrate ions (NO ₃ ⁻ ). In the case of back-extracting scandium, it is preferable to use sulfuric acid, that is, the acidic aqueous solution contains sulfate ions (SO ₄ ²⁻ ).

  The operation procedure of the back extraction step is not particularly limited, and a known operation procedure used for back extraction can be appropriately selected.

The volume ratio (acidic aqueous solution / organic solvent) of the acidic aqueous solution and the organic solvent to be contacted in the back extraction step is not particularly limited and can be appropriately selected according to the purpose, but is usually 1/100 to 1
The range is 00/1, preferably 1/50 or more, more preferably 1/10 or more, still more preferably 1/5 or more, preferably 50/1 or less, more preferably 10/1 or less, and even more preferably. Is 5/1 or less. Within the above range, scandium and lanthanoid can be easily back-extracted efficiently.

（式（Ａ）中、Ｒはそれぞれ独立して炭素数１〜２０の炭化水素基又は水素原子を表す。） <Method for separating scandium and / or lanthanoid>
As described above, since nitrilotriacetic acid triamide changes the affinity for each element depending on, for example, the hydrogen ion concentration or the anion concentration, a specific element can be selectively extracted. Therefore, if the acidic aqueous solution contains an extraction target element selected from scandium and lanthanoid and a non-extraction target element selected from scandium and lanthanoid, it can also be used to extract the extraction target element and separate it from the non-extraction target element. can do.
In addition, the acidic aqueous solution contains an extraction target element selected from scandium and lanthanoid and a non-extraction target element selected from scandium and lanthanoid, and an aspect of extracting the extraction target element and separating it from the non-extraction target element is: This is one of the preferred embodiments of the extraction method of the present invention. In other words, this aspect can be expressed as follows.
In the presence of the nitrilotriacetic acid triamide represented by the following preparation step for preparing an acidic aqueous solution containing an extraction target element selected from scandium and lanthanoid and a non-extraction target element selected from scandium and lanthanoid The separation of scandium and / or lanthanoid, comprising a liquid-liquid contact step of contacting the acidic aqueous solution prepared in the preparation step with an organic solvent to extract the extraction target element and separating it from the non-extraction target element Method.

(In formula (A), R represents a C1-C20 hydrocarbon group or hydrogen atom each independently.)

Examples of scandium and / or lanthanoid that are non-extractable elements include neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), and the like.
Separation of scandium (Sc) from europium (Eu) and gadolinium (Gd) is particularly difficult, but there is a difference in the distribution ratio of these elements (see Example 1 described later). The inventors have clarified that a sufficient separation factor (see Example 1 described later) can be obtained for each other. In particular, these can be efficiently extracted and separated by selecting an extraction device, an organic solvent, an additive and the like so that the distribution ratio and the separation factor are increased.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention can be modified as appropriate without departing from the spirit of the present invention. Accordingly, the scope of the present invention should not be construed as being limited by the specific examples shown below.

準備した硝酸水溶液とｎ−ドデカン溶液を等量（容積比）容器に投入し、振とう機（ＹＳ−８Ｄ 株式会社ヤヨイ社製）を用いて、２５℃±１℃で２０分間振とうした。その後、５分間遠心分離（ＣＮ−８２０ アズワン株式会社製）を行って相分離させ、水相と有機相からそれぞれ溶液をサンプリングし、溶液中の金属イオン濃度をＩＣＰ−ＭＳ（Ａｇｉｌｅｎｔ７５００ｃｘ アジレント・テクノロジー社製）により計測して、Ｓｃ（ＩＩＩ）、Ｙ（ＩＩＩ）、及び種々のランタノイドイオンの濃度をそれぞれ定量した。得られた値からＳｃ（ＩＩＩ）、Ｙ（ＩＩＩ）、及び種々のランタノイドイオンの分配比（Ｄ）を算出し、その値とニトリロ三酢酸トリアミドとの関係をグラフにまとめた。結果を図１に示す。なお、分離比（Ｄ）、分離係数（ＳＦ_{Ｓｃ／Ｌｎ}）は、下記式により算出することができる。

図１の結果から、Ｓｃ（ＩＩＩ）、Ｙ（ＩＩＩ）、及び種々のランタノイドイオンの濃度の分配比は、何れもニトリロ三酢酸トリアミドの増加に伴って増加することが明らかである。また、いずれの濃度であっても、Ｓｃ（ＩＩＩ）とＹ（ＩＩＩ）の分離係数（ＳＦ_Ｓｃ／Ｙ）及びＳｃ（ＩＩＩ）とランタノイドイオンの分離係数（ＳＦ_{Ｓｃ／Ｌｎ}）はそれぞれ、１２００以上、４８以上となり、Ｓｃ（ＩＩＩ）とＹ（ＩＩＩ）及び種々のランタノイドイオンとの分離が可能であることが明らかである。 <Example 1: Extraction separation of scandium, yttrium and lanthanoid (dependence of distribution ratio on nitrilotriacetic acid triamide concentration)>
Trivalent scandium ion (Sm (III)), trivalent yttrium ion (Y (III)), and various trivalent lanthanoid ions (La (III), Ce (III),...) A 0.2M nitric acid aqueous solution containing 10 ppm and a nitrilotriacetic acid triamide (hereinafter sometimes abbreviated as “NTA amide”) represented by the following formula each include a predetermined concentration (0.05 to 0.4 M). Each n-dodecane solution was prepared. In addition, ultrapure water prepared using an ultra-pure analytical reagent TAMAPURE-AA-100 manufactured by Tama Chemical Co., Ltd. as nitric acid, and an ultrapure water production apparatus (Milli-Q Merck Millipore) as dilution water. A special grade reagent manufactured by Wako Pure Chemical Industries, Ltd. was used as n-dodecane.

The prepared nitric acid aqueous solution and n-dodecane solution were put into an equal volume (volume ratio) container and shaken at 25 ° C. ± 1 ° C. for 20 minutes using a shaker (YS-8D manufactured by Yayoi Co., Ltd.). Thereafter, centrifugation is performed for 5 minutes (CN-820, manufactured by AS ONE Corporation), phase separation is performed, the solution is sampled from each of the aqueous phase and the organic phase, and the metal ion concentration in the solution is determined by ICP-MS (Agilent 7500cx Agilent Technologies). And the concentrations of Sc (III), Y (III), and various lanthanoid ions were respectively quantified. The distribution ratio (D) of Sc (III), Y (III) and various lanthanoid ions was calculated from the obtained values, and the relationship between the value and nitrilotriacetic acid triamide was summarized in a graph. The results are shown in FIG. The separation ratio (D) and the separation factor (SF _{Sc / Ln} ) can be calculated by the following equations.

From the results of FIG. 1, it is clear that the distribution ratios of Sc (III), Y (III), and various lanthanoid ion concentrations all increase with an increase in nitrilotriacetic acid triamide. At any concentration, the separation factor (SF _{Sc / Y} ) of Sc (III) and _Y (III) and the separation factor (SF _{Sc / Ln} ) of Sc (III) and lanthanoid ions are 1200 or more, respectively. It is clear that Sc (III) can be separated from Y (III) and various lanthanoid ions.

<Example 2: Extraction and separation of scandium and lanthanoid (dependence of distribution ratio on nitric acid concentration)>
Sc (III) was prepared in the same manner as in Example 1 except that the concentration of nitrilotriacetic acid triamide was 0.08 M and the concentration of nitric acid (HNO ₃ ) was changed to a predetermined concentration (0.04 to 3.0 M). ), Y (III), and various lanthanoid ion concentrations were quantified, the distribution ratio (D) was calculated, and the relationship between the value and the nitric acid concentration was summarized in a graph. The results are shown in FIG.
From the results of FIG. 2, the distribution ratio of Sc (III), Y (III), and various lanthanoid ions decreases with increasing nitric acid concentration up to about 0.2M nitric acid concentration. On the other hand, La (III), Ce (III), Pr (III), and Nd (III) increase from a nitric acid concentration of 0.2 M to about 1 M, and at about 1 M or more, decrease as the nitric acid concentration increases. it is obvious. Further, for example, at a nitric acid concentration of 0.2 M, the distribution ratio of Sc (III) exceeds 1, whereas the distribution ratio of Y (III) and various lanthanoid ions is less than 1. Therefore, Sc (III) and Y ( It is clear that separation with III) and various lanthanoid ions is possible.

準備した硝酸水溶液とｎ−ドデカン溶液を等量（容積比）容器にそれぞれ投入し、振とう機を用いて、２５℃±１℃で２０分間振とうした。その後、５分間遠心分離を行って相分離させ、有機相の溶液をサンプリングし、ＩＣＰ−ＡＥＳ（ＩＣＰＳ−７５１０ 株式会社島津製作所製）によりＳｃ（ＩＩＩ）の濃度を定量した。準備した硝酸水溶液中のＳｃ（ＩＩＩ）濃度（水相中の初期濃度）と有機相中に抽出されたＳｃ（ＩＩＩ）濃度との関係をグラフにまとめた。結果を図３に示す。
図３の結果から、スカンジウムに対して十分な抽出容量を持つことは明らかである。 <Example 3: Extraction of scandium>
A 0.2M nitric acid aqueous solution containing trivalent scandium ions (Sc (III)) at a predetermined concentration (10 to 333 mM) and an n-dodecane solution containing 0.2M nitrilotriacetic acid triamide represented by the following formula: Prepared each.

The prepared nitric acid aqueous solution and n-dodecane solution were put in equal amounts (volume ratio) containers, respectively, and shaken at 25 ° C. ± 1 ° C. for 20 minutes using a shaker. Thereafter, centrifugation was performed for 5 minutes to separate the phases, the organic phase solution was sampled, and the concentration of Sc (III) was quantified by ICP-AES (ICPS-7510, manufactured by Shimadzu Corporation). The relationship between the Sc (III) concentration in the prepared aqueous nitric acid solution (initial concentration in the aqueous phase) and the concentration of Sc (III) extracted in the organic phase is summarized in a graph. The results are shown in FIG.
From the results of FIG. 3, it is clear that the extraction capacity is sufficient for scandium.

準備した硝酸水溶液とｎ−ドデカン溶液を等量（容積比）容器にそれぞれ投入し、振と
う機を用いて、２５℃±１℃で所定の時間（１０〜３００秒）振とうした。その後、５分間遠心分離を行って相分離させ、水相と有機相からそれぞれ溶液をサンプリングし、ＩＣＰ−ＡＥＳ（ＩＣＰＳ−７５１０ 株式会社島津製作所製）によりそれぞれの溶液についてＳｃ（ＩＩＩ）の濃度を定量した。得られた値からＳｃ（ＩＩＩ）の分配比（Ｄ）を算出し、その値と振とう時間との関係をグラフにまとめた。結果を図４に示す。
図４の結果から、１０秒間の振とう以降、Ｓｃ（ＩＩＩ）の分配比が一定となり、抽出平衡に達していることが明らかである。０．１Ｍのニトリロ三酢酸トリアミドを用いて、１０秒間の振とうで抽出平衡となることから、スカンジウムに対して十分に速い抽出速度を有することが明らかである。 <Example 4: Extraction of scandium (extraction speed)>
A 0.2M nitric acid aqueous solution containing 100 ppm of trivalent scandium ions (Sc (III)) and an n-dodecane solution containing 0.1M nitrilotriacetic acid triamide represented by the following formula were prepared.

The prepared nitric acid aqueous solution and n-dodecane solution were put in equal amounts (volume ratio) containers, respectively, and shaken at 25 ° C. ± 1 ° C. for a predetermined time (10 to 300 seconds) using a shaker. Thereafter, centrifugation is performed for 5 minutes to separate the phases, the solutions are sampled from the aqueous phase and the organic phase, respectively, and the concentration of Sc (III) is determined for each solution by ICP-AES (ICPS-7510, manufactured by Shimadzu Corporation). Quantified. The distribution ratio (D) of Sc (III) was calculated from the obtained value, and the relationship between the value and the shaking time was summarized in a graph. The results are shown in FIG.
From the results of FIG. 4, it is clear that after shaking for 10 seconds, the distribution ratio of Sc (III) becomes constant and the extraction equilibrium is reached. It is apparent that the extraction equilibration with 0.1 M nitrilotriacetic acid triamide has an extraction rate sufficiently high with respect to scandium since the extraction equilibrium is obtained by shaking for 10 seconds.

準備した硝酸水溶液とｎ−ドデカン溶液を等量（容積比）容器にそれぞれ投入し、振とう機を用いて、２５℃±１℃で２０分間振とうした。その後、５分間遠心分離を行って相分離させ、有機相の溶液をサンプリングし、ＩＣＰ−ＡＥＳ（ＩＣＰＳ−７５１０ 株式会社島津製作所製）により、Ｓｃ（ＩＩＩ）の濃度を定量した。
次に分離した有機相の溶液と所定の濃度（０．１〜３．０Ｍ）の硫酸水溶液を等量（容積比）容器にそれぞれ投入し、振とう機を用いて、２５℃±１℃で２０分間振とうした。その後、５分間遠心分離を行って相分離させ、水相の溶液をサンプリングし、ＩＣＰ−ＡＥＳ（ＩＣＰＳ−７５１０ 株式会社島津製作所製）により、Ｓｃ（ＩＩＩ）の濃度を定量して、逆抽出率を決定した。結果を表１に示す。なお、逆抽出率は、下記式により算出することができる。

<Example 5: Scandium extraction and back extraction (dependence of back extraction rate on sulfuric acid concentration)>
A 0.1M nitric acid aqueous solution containing 1000 ppm of trivalent scandium ions (Sc (III)) and an n-dodecane solution containing 0.08M nitrilotriacetic acid triamide represented by the following formula were prepared.

The prepared nitric acid aqueous solution and n-dodecane solution were put in equal amounts (volume ratio) containers, respectively, and shaken at 25 ° C. ± 1 ° C. for 20 minutes using a shaker. Thereafter, centrifugation was performed for 5 minutes to separate the phases, the organic phase solution was sampled, and the concentration of Sc (III) was quantified by ICP-AES (ICPS-7510, manufactured by Shimadzu Corporation).
Next, the separated organic phase solution and a sulfuric acid aqueous solution having a predetermined concentration (0.1 to 3.0 M) are put in equal amounts (volume ratio) containers, respectively, and at 25 ° C. ± 1 ° C. using a shaker. Shake for 20 minutes. Thereafter, centrifugation is performed for 5 minutes to separate the phases, the aqueous phase solution is sampled, the concentration of Sc (III) is quantified by ICP-AES (ICPS-7510, manufactured by Shimadzu Corporation), and the back extraction rate It was determined. The results are shown in Table 1. The back extraction rate can be calculated by the following formula.

<Example 6: Scandium extraction and back extraction (back extraction with hydrochloric acid)>
Extraction and back extraction were performed in the same manner as in Example 5 except that the sulfuric acid aqueous solution was changed to a 5.0 M hydrochloric acid solution, and the back extraction rate was determined. The back extraction rate was 44.9%.

  According to the extraction method of the present invention, scandium coexisting in the radioactive liquid waste can be extracted. In particular, trivalent scandium (Sc (III)) and trivalent lanthanoids, which are difficult to separate from each other, can be efficiently separated, and can be applied to the production of scandium, a kind of rare earth element (rare earth). it can.

Claims (5)

Preparation liquid for preparing scandium or an acidic aqueous solution containing scandium and a lanthanoid, and a liquid for contacting the acidic aqueous solution prepared in the preparation step with an organic solvent in the presence of nitrilotriacetic acid triamide represented by the following general formula (A) A method for extracting scandium and / or lanthanoid, comprising a liquid contact step.

(In formula (A), R represents a C1-C20 hydrocarbon group or hydrogen atom each independently.) The method for extracting scandium and / or lanthanoid according to claim 1, wherein the acidic aqueous solution prepared in the preparation step contains nitrate ions (NO ₃ ⁻ ).   Furthermore, the separation process which separates the acidic aqueous solution and organic solvent which were made to contact in the said liquid-liquid contact process, and the back extraction process which makes acidic aqueous solution contact the organic solvent separated in the said liquid separation process are included. 3. The method for extracting scandium and / or lanthanoid according to 2. The method for extracting scandium and / or lanthanoid according to claim 3, wherein the acidic aqueous solution to be contacted in the back extraction step contains sulfate ions (SO ₄ ²⁻ ). Acidic aqueous solution prepared in the preparation step comprises scandium and lanthanoid-de, separating scandium and lanthanoid in the liquid-liquid contact step, scandium and / or lanthanides according to any one of claims 1 to 4 Extraction method.

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