JP4102052B2 - Noble metal extractant comprising thioaniline derivative and method for separating noble metal using the same - Google Patents

Description

【０００９】
式（Ｉ）中、ＲはＣ₁〜Ｃ₁₈のアルキル基またはアルケニル基であり、ｎは０または１である。
さらに、本発明に従えば、上記の抽出剤を使用する方法の発明であって、少なくともパラジウムおよび／または金を含有する金属の塩酸水溶液または硝酸水溶液と、上記の構造式（Ｉ）で表されるチオアニリン誘導体から成る貴金属抽出剤を含有する抽出溶媒とを液−液接触させることにより、パラジウムおよび／または金を該抽出溶媒中に抽出する工程を包含するパラジウムおよび／または金の分離方法が提供される。
【００１０】
【発明の実施の形態】
上記の式（Ｉ）で表されるチオアニリン誘導体は、クロロホルム、トルエンなどの一般の有機溶媒に易溶であるので、これらの有機溶媒に式（Ｉ）のチオアニリン誘導体を溶解させた抽出溶媒を用いて溶媒抽出法を実施することにより、ベースメタルや貴金属を含む各種の金属を含有する塩酸水溶液または硝酸水溶液からパラジウムと金をきわめて高い選択性で抽出することができる。
【００１１】
このように式（Ｉ）で表されるチオアニリン誘導体を含有する抽出溶媒が、特にパラジウムと金を選択的に抽出する理由は完全には解明されていないが、該チオアニリン誘導体が、平面構造を呈し易いベンゼン環に結合した２つの部位を有していること、具体的には、ＮＨ₂（アニリンとして）とイオウ原子（チオエーテルとして）とが金属に対する結合に寄与するような特殊な化学構造を有していることに由来するものと考えられる。すなわち、貴金属の中でもｄ電子を有し特に高い反応活性を有するパラジウムと金は、アニリンのアミノ基（第一級アミンであり、極めて弱い塩基性を示す）とｄ電子を介して結合するとともに、イオウ原子（貴金属に対して高い選択性を示す）を配位原子として結合して安定な平面環構造の錯体を形成するためと推測される。パラジウムおよび金以外の貴金属または白金族金属は、パラジウムや金に比べて反応活性が低いのでアニリンの選択性により抽出されないのであろう。また、銅やニッケルなどのベースメタルは、パラジウムや金と同様に平面構造（平面錯体）を形成し得るものではあるが、イオウ原子が専ら貴金属に対して選択性を有するので抽出されないと考えられる。
【００１２】
式（Ｉ）で表されるチオアニリン誘導体で好ましいのは、ｎ＝０でオルト体のもの、すなわちイオウ原子（チオエーテル）がアミノ基に対してオルト位でベンゼン環に直接結合したチオアニリン誘導体である。このようなチオアニリン誘導体を用いるとパラジウムおよび金の選択的抽出が特に高くなるが、これは、パラジウムや金が、イオウ原子、アミノ基およびベンゼン骨格と安定な５員環構造の錯体を形成するためと理解される。
【００１３】
式（Ｉ）のチオアニリン誘導体においてチオエーテルを構成するＲは、Ｃ₁〜Ｃ₁₈のアルキル基またはアルケニル基であれば基本的には適用可能であるが、その中でもアルケニル基または分枝鎖アルキル基が好ましい。これは、二重結合や枝分かれのあるアルキル鎖を導入すると、チオアニリン誘導体および該チオアニリン誘導体と金属イオン（パラジウム、金）で形成される錯体が有機溶媒に溶け易くなり、操作上好ましく、また、その結果、抽出率も高くなるからである。例えば、Ｒとして直鎖のドデシル基を導入したオルトドデシルチオアニリンを抽出剤として用いた抽出においては、有機溶媒と水層の間に沈殿が生成し、抽出率も悪くなることが見出されている。
【００１４】
上述したような点から、パラジウムおよび金を選択的に抽出する本発明の貴金属抽出剤として特に好ましいチオアニリン誘導体は、例えば、オルト（２−エチルヘキシルチオ）アニリンおよびオルトオレイルチオアニリンであり、それぞれ、式（Ｉ）において下記で表されるＲがオルト位にイオウ原子を介して結合しているものである。
【００１５】
【化３】

【００１６】
式（Ｉ）で表されるチオアニリン誘導体は、例えば、下記の反応式（II）で表されるように、チオアニリンとアルキルブロマイドまたはアルケニルブロマイドとを反応させることによって合成することができる。反応は、一般に、氷浴下（−４℃から４℃位まで）、窒素雰囲気下、相間触媒として例えばトリメチルアンモニウムクロリド、触媒として例えば水酸化ナトリウム、また、溶媒として例えばジメチルホルムアミドと水の混合溶媒（１：１）を用いて行う。
【００１７】
【化４】

【００１８】
かくして、本発明に従えば、各種の金属材料や金属製品（例えば、廃棄された電子部品）に由来し、少なくともパラジウムおよび／または金を含有し、さらに、その他の各種金属、特に、ベースメタル、またはパラジウムおよび金以外の貴金属、あるいはそれらのいずれもを含有することがある金属の塩酸水溶液または硝酸水溶液と、上述したようなチオアニリン誘導体を適当な有機溶媒に溶かした抽出溶媒とを液−液接触させることにより、パラジウムおよび／または金が該抽出溶媒中に高選択的に抽出される。
【００１９】
本発明に従い、このような抽出操作を行うに当たっては、必要に応じて、原料となる金属材料や金属製品を予め処理して、金属を含有する塩酸水溶液または硝酸水溶液とする。そのような前処理として最も一般的な方法は、金属材料や金属製品を王水に溶解してそれらの中に含まれる金属類を溶液中に溶解させた後、脱硝酸して塩酸水溶液とすることである。金属材料や金属製品の種類によっては、塩酸のみや硝酸のみで処理されている場合もあり、これらの場合には、処理後の溶液をそのまま本発明に従う抽出工程に供することができる。
【００２０】
本発明の方法に従えば、従来は不可能であった白金族金属間の効率的な分離、精製を行うこともできる。すなわち、パラジウム、およびパラジウム以外の白金族金属の１種（例えば、Ｐｔ）またはそれ以上を含有する塩酸水溶液または硝酸水溶液から、式（Ｉ）のチオアニリン誘導体から成る貴金属抽出剤を含有する抽出溶媒中にパラジウムを選択的に抽出した後、このパラジウムを逆抽出溶媒により抽出してパラジウムを含有する水溶液を得ることにより、パラジウムを分離することができる。逆抽出溶媒としては、パラジウムと錯体を形成し得るものとして知られた各種の化合物を含有する溶媒が適用可能であり、好ましい例としては、チオ尿素を含有する水溶液が挙げられる。
【００２１】
【実施例】
以下に本発明の特徴を更に具体的に明らかにするため実施例を示すが、本発明はこれらの実施例によって制限されるものではない。
実施例１：チオアニリン誘導体の合成
本発明の貴金属抽出剤として、次の反応式（III）に従い、オルト（２−エチルエヘキシルチオ）アニリン（以下、ＥＴＡと記す）およびオルトオレイルチオアニリン（以下、ＯＴＡと記す）を合成した。
【００２２】
【化５】

【００２３】
ＥＴＡは以下のように合成した。
氷浴下で窒素導入管、撹拌棒のついた500ml三つ口フラスコ内でジメチルホルムアミドと水100mlずつに水酸化ナトリウムを0.1mol（10g）溶解した溶液に窒素雰囲気下、アミノチオフェノール0.1mol（12.5g）、相間移動触媒であるセチルトリメチルアンモニウムクロリド7.5mmol（0.24g）を加えて溶解した。その溶液に2-エチルへキシルブロマイド0.06 mol（11.6g）を滴下ロートにてゆっくりと滴下し、激しく撹拌した。その後さらに氷浴下で3時間、室温（20℃前後）で24時間撹拌した。反応停止時間はＴＬＣによって決定した。（展開溶媒はヘキサン：酢酸エチル=5：1）。撹拌停止後、得られた溶液に水、クロロホルムを加え、ＤＭＦを除去したのち1規定塩酸、1規定水酸化ナトリウム、蒸留水の順で分液した。クロロホルム相を硫酸ナトリウムで脱水したのち、クロロホルムを減圧蒸留により留去した。収率は75.5％であった。得られた生成物は茶色の液体であった。
同定データ：¹H-NMR(250MHz, CDCl₃, TMS)δ(ppm)
0.84(3H, t, 7.5Hz :1)
0.87(3H, t, 7.5Hz :8)
1.22-1.49(11H, m : 2~5)
2.74(2H, d, 7.5Hz : 6)
4.17(2H, brs, NH₂)
6.67(1H, ddd, 2.5Hz, 7.5Hz, 7,5Hz : 11)
6.70(1H, dd, 1.5Hz, 7.5Hz : 10)
7.08(1H, ddd, 1.5Hz, 7.5Hz, 7.5Hz : 12)
7.35(1H, dd, 2.5Hz, 7.5Hz : 13)
【００２４】
ＯＴＡも同様に合成した。得られた生成物は茶色の液体であった。
同定データ：¹H-NMR(250MHz, CDCl₃, TMS)δ(ppm)
0.88(3H, t :1)
1.26(24H, m, 2-7 and 12-16)
1.57(2H, m : 17)
2.00(4H, m : 8 and 11)
2.72(2H, t, 7.5Hz : 18)
4.25(2H, brs, NH₂)
5.34(2H, m, 9 and 10)
6.68(1H, ddd, 7.5Hz, 7.5Hz, 2.5Hz : 21)
6.70(1H, dd, 1.3Hz, 7.5Hz, 7.5Hz : 20)
7.09(1H, ddd, 1.3Hz, 7.5Hz, 7.5Hz : 22)
7.35(1H, dd, 7.7Hz, 2.5Hz :24)
【００２５】
次に、以上のようにして合成したＥＴＡおよびＯＴＡを抽出剤として抽出実験を行った。抽出実験はすべてバッチ法で行った。ベースメタルとして銅（II）、ニッケル（II）、コバルト（II）、カドミウム（II）、亜鉛（II）、水銀（II）を用い、貴金属イオンとして金（III）、パラジウム（II）、ロジウム（III）および白金（IV）を用い、各金属イオンの初濃度が1.0mmol／dm³の水相を調製し、塩酸濃度（または硝酸濃度）を変化させた。有機相は希釈剤としてトルエンを用い、抽出剤濃度を0.01mol／dm³に調製した。各相を15mlずつ三角フラスコに取り、30℃恒温槽中で24時間振盪した。振盪後、水相を分取し、各金属イオン濃度は原子吸光光度計により求めた。
【００２６】
逆抽出実験は、抽出した有機相に含まれるパラジウムを、以下に示す逆抽出剤と振盪することによって行った。逆抽出剤は1.0mol／dm³、2.0mol／dm³アンモニア水溶液、1.0mol／dm³チオ尿素水溶液、1.0mol／dm³チオ尿素と1.0mol／dm³塩酸の混合水溶液、1.0mol／dm³チオ尿素と1.0mol／dm³チオシアン酸アンモニウム混合水溶液および1.0mol／dm³のＥＤＴＡ水溶液の６種類を用いた。
【００２７】
抽出実験の具体的な方法と結果を図１〜図３を参照しながら以下の実施例２〜実施例５に示す。図に示す各金属の抽出結果は、横軸に塩酸（または硝酸）の対数濃度、縦軸に各金属の抽出百分率をブロットしたものであり、ここで抽出百分率は次式により求めた。
Ｅ＝（Ｃ_０−Ｃｅ）×１００／Ｃ_０ 〔％〕
Ｃ_０は金属イオンの初濃度、Ｃｅは平衡後の濃度を示す。
【００２８】
実施例２：ＥＴＡによる抽出（１）
濃度が0.01mmol／dm³の抽出剤、ＥＴＡのトルエン溶液と、金属濃度0.1mmol／dm³の各塩酸溶液（0.01〜3.0mmol／dm³）を含む溶液を15mlずつとり、30℃の恒温槽中で24時間振盪させ、実験を行った。各金属の抽出結果を図１に示す。
図１に示すように、塩酸濃度に依存することなくパラジウムおよび金が100％の抽出率を示し、上述したような各種のベースメタルからの金とパラジウムの選択的抽出分離ができる。さらに現在使用されている工業用抽出剤では分離が困難であるといわれているパラジウム（II）と白金（IV）の分離が全塩酸濃度領域において可能であることもわかる。
【００２９】
実施例３：ＯＴＡによる抽出
濃度が0.01mmol／dm³の抽出剤、ＯＴＡのトルエン溶液と、金属濃度0.1mmol／dm³の各塩酸溶液（0.01〜3.0mmol／dm³）を含む溶液を15mlずつとり、30℃の恒温槽中で24時間振盪させ、実験を行った。各金属の抽出結果を図２に示す。塩酸濃度に依存することなくパラジウムおよび金が100％の抽出率を示し、上述した各種のベースメタルからの金とパラジウムの選択的抽出分離ができることを示している。さらに現在使用されている工業用抽出剤では分離が困難であるといわれているパラジウムと白金の分離が全塩酸濃度領域において可能であることもわかる。
【００３０】
実施例４：ＥＴＡによる抽出（２）
水相として、各金属イオンの硝酸塩を1.0mmol／dm³含む0.01〜3.0mol／dm³硝酸水溶液を用い、有機相として抽出剤ＥＴＡを0.01mol／dm³含むクロロホルム溶液を用いた。30℃の恒温槽中で24時間振盪させ実験を行った。図３に硝酸溶液からの各種金属の抽出実験の結果を示す。パラジウムおよび金が硝酸濃度に依存せず、全硝酸濃度領域で抽出されている。また、水銀が硝酸濃度1mol／dm³付近から急激に抽出されている。これらのことから、ベースメタルからのパラジウムおよび金が全硝酸濃度領域において分離ができ、1.0mmol／dm³以上の領域においては有害物質である水銀の分離も可能である。
【００３１】
実施例５：有機相からのパラジウムの逆抽出
ＥＴＡおよびＯＴＡを用いてパラジウムの逆抽出実験を行った。用いた逆抽出剤は既述の６種類である。
水相はパラジウム1.0mmol／dm³の1mol／dm³塩酸水溶液を、有機相はＥＴＡ（またはＯＴＡ）の0.01mol／dm³トルエン溶液を用い、それぞれ15mlずつ共栓付三角フラスコにとり、30℃恒温槽中で24時間振盪させた後に水相と有機相を分取し、水相中の金属濃度を原子吸光光度計により測定した。次に上記逆抽出溶媒10mlと分取した有機相10mlを再び共栓付三角フラスコ中で混合、30℃恒温槽中で24時間振盪させた後に水相と有機相を分取し、水相中の金属濃度を原子吸光光度計により測定し、逆抽出率を算出した。その結果を表１（ＥＴＡ）および表２（ＯＴＡ）に示す。
【００３２】
【表１】

【００３３】
【表２】

【００３４】
表１および表２に示すように、チオ尿素を含む逆抽出剤を用いることにより、100％またはこれに近い逆抽出率が得られる。このことから、ベースメタルまたは各種の白金族金属が混在する溶液から抽出されたパラジウムを更に逆抽出し、高濃度に濃縮、回収することもできることがわかる。
【００３５】
【発明の効果】
叙上のように、本発明に従えば、ワンステップで高収率に合成することができるチオアニリン誘導体から成る抽出剤を用いる溶媒抽出法により、各種のベースメタルや貴金属を含有する広範囲の濃度の塩酸水溶液または硝酸水溶液から、パラジウムおよび金を短時間で効果的に分離することができる。かくして、本発明は、各種の金属製品や金属材料からパラジウムと金を回収したり精製する新しい技術を発展に資するものである。例えば、本発明によれば、従来は分離が困難であるといわれているパラジウムと他の白金族金属（特に白金）との分離が実現され、逆抽出操作を付加することにより、パラジウムを高濃度に濃縮することもできる。
【図面の簡単な説明】
【図１】各種の金属を含有する塩酸水溶液について、抽出剤としてオルト（２−エチルヘキシルチオ）アニリンを用いて行った抽出実験の結果を示す。
【図２】各種の金属を含有する塩酸水溶液について、抽出剤としてオルトオレイルチオアニリンを用いて行った抽出実験の結果を示す。
【図３】各種の金属を含有する硝酸水溶液について、抽出剤としてオルト（２−エチルヘキシルチオ）アニリンを用いて行った抽出実験の結果を示す。[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to the technical field of separating precious metals for recovery or purification, and particularly relates to a novel precious metal extractant capable of selectively extracting palladium and gold and a method for separating precious metals using the same.
[0002]
[Prior art]
Today, precious metals are industrially used as catalysts and electronic materials for automobile exhaust gases, and many other precious metals are used around us as decorative items. Despite these demands, precious metals are rare natural resources because they are not mined as natural resources. Therefore, it is indispensable to separate a precious metal from a used metal product so that a specific precious metal can be recovered and reused, or a specific precious metal is obtained from a metal material containing many kinds of metals. For example, for the regeneration of gold, platinum, palladium and rhodium from automobile catalysts, separation between noble metals with similar properties is indispensable, and from base metals such as iron, copper and nickel contained in large amounts in ores. The separation of precious metals is also an important issue.
[0003]
Various methods have been proposed for the separation (purification) of metals including precious metals. In recent years, however, it is expected that the treatment process is relatively short and simple, and the recovery rate is high. A solvent extraction method using an appropriate extractant has attracted attention.
[0004]
Conventionally, typical industrial extractants used for separation and recovery of noble metals such as palladium and gold are dihexyl sulfide (SFI-6) and LIX oximes (for example, hydroxyoxime). They have excellent selectivity for extracting only precious metals from base metals (base metals), but select specific precious metals such as palladium and gold from multiple types of precious metals (gold, silver and platinum group metals) or platinum group metals. Extraction and separation are difficult. At present, for example, in the separation of platinum (IV) and palladium (II), separation is performed due to the difference in extraction rate using the slow extraction rate of platinum, but the extraction rate of palladium is also slow and recovery Since it takes too much time and the selectivity becomes poor, it is not yet sufficient as an industrial separation method.
[0005]
[Problems to be solved by the invention]
The object of the present invention is to overcome the above-mentioned conventional drawbacks, and to extract a new solvent that can selectively and easily separate specific noble metals from various metal products and metal materials containing base metals and noble metals. To provide technology.
[0006]
[Means for Solving the Problems]
The inventor has molecularly designed a novel extractant using NH ₂ and thioether of aniline, which is a primary amine, as donor atoms for the metal, and this extractant is used for several metals such as base metals and noble metals. It was discovered that palladium and gold can be extracted with high selectivity from an aqueous hydrochloric acid solution containing nitric acid or an aqueous nitric acid solution, and the present invention was derived.
[0007]
Thus, the present invention provides a noble metal extractant comprising a thioaniline derivative represented by the following structural formula (I).
[0008]
[Chemical 2]

[0009]
In the formula (I), R is an alkyl or alkenyl group of C ₁ -C _18, n is 0 or 1.
Furthermore, according to the present invention, there is provided an invention of a method using the above extractant, which is represented by the above-mentioned structural formula (I) and an aqueous hydrochloric acid or nitric acid solution containing at least palladium and / or gold. Provided is a method for separating palladium and / or gold, comprising a step of extracting palladium and / or gold into an extraction solvent by bringing the extraction solvent containing a noble metal extractant comprising a thioaniline derivative into liquid-liquid contact. Is done.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Since the thioaniline derivative represented by the above formula (I) is easily soluble in common organic solvents such as chloroform and toluene, an extraction solvent in which the thioaniline derivative of the formula (I) is dissolved in these organic solvents is used. By performing the solvent extraction method, palladium and gold can be extracted with extremely high selectivity from an aqueous hydrochloric acid solution or an aqueous nitric acid solution containing various metals including base metals and noble metals.
[0011]
The reason why the extraction solvent containing the thioaniline derivative represented by the formula (I) thus selectively extracts palladium and gold in particular has not been completely clarified, but the thioaniline derivative has a planar structure. It has two sites that are easily bonded to the benzene ring. Specifically, it has a special chemical structure in which NH ₂ (as aniline) and sulfur atom (as thioether) contribute to the bond to the metal. It is thought that it originates in doing. That is, among the noble metals, palladium and gold having d electrons and particularly high reaction activity are bonded to the amino group of aniline (which is a primary amine and exhibits extremely weak basicity) via d electrons, It is presumed that a sulfur atom (showing high selectivity for noble metals) is bonded as a coordination atom to form a complex having a stable planar ring structure. Noble metals or platinum group metals other than palladium and gold will not be extracted due to the selectivity of aniline because they have a lower reaction activity than palladium and gold. In addition, although base metals such as copper and nickel can form a planar structure (planar complex) like palladium and gold, they are considered not to be extracted because sulfur atoms are exclusively selective to noble metals. .
[0012]
Preferred among the thioaniline derivatives represented by the formula (I) is an ortho form of n = 0, that is, a thioaniline derivative in which a sulfur atom (thioether) is directly bonded to the benzene ring in the ortho position with respect to the amino group. When such a thioaniline derivative is used, selective extraction of palladium and gold is particularly high because palladium and gold form a complex of a stable 5-membered ring structure with a sulfur atom, an amino group, and a benzene skeleton. It is understood.
[0013]
In the thioaniline derivative of the formula (I), R constituting the thioether is basically applicable as long as it is a C _{1 to} C ₁₈ alkyl group or alkenyl group. Among them, an alkenyl group or a branched alkyl group is preferable. When a double bond or a branched alkyl chain is introduced, a thioaniline derivative and a complex formed with the thioaniline derivative and a metal ion (palladium, gold) are easily dissolved in an organic solvent, which is preferable in terms of operation. As a result, the extraction rate is also increased. For example, in the extraction using orthododecylthioaniline introduced with a linear dodecyl group as R as an extractant, it has been found that a precipitate is formed between the organic solvent and the aqueous layer, and the extraction rate is also deteriorated. Yes.
[0014]
In view of the above points, particularly preferred thioaniline derivatives as the noble metal extractant of the present invention for selectively extracting palladium and gold are, for example, ortho (2-ethylhexylthio) aniline and orthooleylthioaniline, respectively. In (I), R represented by the following is bonded to the ortho position via a sulfur atom.
[0015]
[Chemical 3]

[0016]
The thioaniline derivative represented by the formula (I) can be synthesized, for example, by reacting thioaniline with alkyl bromide or alkenyl bromide as represented by the following reaction formula (II). The reaction is generally carried out in an ice bath (from −4 ° C. to 4 ° C.) under a nitrogen atmosphere, for example, trimethylammonium chloride as the interphase catalyst, sodium hydroxide as the catalyst, and mixed solvent of dimethylformamide and water as the solvent. (1: 1).
[0017]
[Formula 4]

[0018]
Thus, according to the present invention, it is derived from various metal materials and metal products (for example, discarded electronic parts), contains at least palladium and / or gold, and further, other various metals, particularly base metal, Liquid-liquid contact between a hydrochloric acid aqueous solution or a nitric acid aqueous solution of a metal that may contain noble metals other than palladium and gold, or any of them, and an thioaniline derivative as described above in an appropriate organic solvent By doing so, palladium and / or gold are extracted with high selectivity into the extraction solvent.
[0019]
In performing such an extraction operation according to the present invention, a metal material or metal product as a raw material is treated in advance as necessary to obtain a hydrochloric acid aqueous solution or a nitric acid aqueous solution containing metal. The most common method for such pretreatment is to dissolve a metal material or metal product in aqua regia and dissolve the metals contained in the solution, and then denitrate to make a hydrochloric acid aqueous solution. That is. Depending on the type of the metal material or metal product, it may be treated with only hydrochloric acid or nitric acid. In these cases, the treated solution can be directly subjected to the extraction step according to the present invention.
[0020]
According to the method of the present invention, efficient separation and purification between platinum group metals, which has been impossible in the past, can also be performed. That is, in an extraction solvent containing a noble metal extractant comprising a thioaniline derivative of formula (I) from an aqueous hydrochloric acid or nitric acid solution containing palladium and one or more platinum group metals other than palladium (eg, Pt) or more Palladium can be separated by selectively extracting palladium with a back extraction solvent to obtain an aqueous solution containing palladium. As the back extraction solvent, a solvent containing various compounds known to be capable of forming a complex with palladium is applicable, and a preferable example includes an aqueous solution containing thiourea.
[0021]
【Example】
Examples are given below to clarify the features of the present invention more specifically, but the present invention is not limited to these examples.
Example 1: Synthesis of thioaniline derivative According to the following reaction formula (III), ortho (2-ethylhexylthio) aniline (hereinafter referred to as ETA) and orthooleylthio are used as the noble metal extractant of the present invention. Aniline (hereinafter referred to as OTA) was synthesized.
[0022]
[Chemical formula 5]

[0023]
ETA was synthesized as follows.
In a 500 ml three-necked flask equipped with a nitrogen inlet tube and a stirrer in an ice bath, 0.1 mol (10 g) of sodium hydroxide in 100 ml of dimethylformamide and 100 ml of water was dissolved in 0.1 mol of aminothiophenol (10 mol) in a nitrogen atmosphere. 12.5 g) and 7.5 mmol (0.24 g) of cetyltrimethylammonium chloride, which is a phase transfer catalyst, was added and dissolved. To the solution, 0.06 mol (11.6 g) of 2-ethylhexyl bromide was slowly added dropwise with a dropping funnel and stirred vigorously. Thereafter, the mixture was further stirred in an ice bath for 3 hours and at room temperature (around 20 ° C.) for 24 hours. The reaction stop time was determined by TLC. (Developing solvent is hexane: ethyl acetate = 5: 1). After the stirring was stopped, water and chloroform were added to the resulting solution, and after removing DMF, the solution was separated in the order of 1N hydrochloric acid, 1N sodium hydroxide and distilled water. After dehydrating the chloroform phase with sodium sulfate, chloroform was distilled off by distillation under reduced pressure. The yield was 75.5%. The product obtained was a brown liquid.
Identification data: ¹ H-NMR (250 MHz, CDCl ₃ , TMS) δ (ppm)
0.84 (3H, t, 7.5Hz: 1)
0.87 (3H, t, 7.5Hz: 8)
1.22-1.49 (11H, m: 2 to 5)
2.74 (2H, d, 7.5Hz: 6)
4.17 (2H, brs, NH ₂ )
6.67 (1H, ddd, 2.5Hz, 7.5Hz, 7,5Hz: 11)
6.70 (1H, dd, 1.5Hz, 7.5Hz: 10)
7.08 (1H, ddd, 1.5Hz, 7.5Hz, 7.5Hz: 12)
7.35 (1H, dd, 2.5Hz, 7.5Hz: 13)
[0024]
OTA was synthesized similarly. The product obtained was a brown liquid.
Identification data: ¹ H-NMR (250 MHz, CDCl ₃ , TMS) δ (ppm)
0.88 (3H, t: 1)
1.26 (24H, m, 2-7 and 12-16)
1.57 (2H, m: 17)
2.00 (4H, m: 8 and 11)
2.72 (2H, t, 7.5Hz: 18)
4.25 (2H, brs, NH ₂ )
5.34 (2H, m, 9 and 10)
6.68 (1H, ddd, 7.5Hz, 7.5Hz, 2.5Hz: 21)
6.70 (1H, dd, 1.3Hz, 7.5Hz, 7.5Hz: 20)
7.09 (1H, ddd, 1.3Hz, 7.5Hz, 7.5Hz: 22)
7.35 (1H, dd, 7.7Hz, 2.5Hz: 24)
[0025]
Next, an extraction experiment was conducted using ETA and OTA synthesized as described above as an extractant. All extraction experiments were carried out by the batch method. Copper (II), nickel (II), cobalt (II), cadmium (II), zinc (II), mercury (II) are used as base metals, and gold (III), palladium (II), rhodium (noble metal ions) Using III) and platinum (IV), an aqueous phase having an initial concentration of each metal ion of 1.0 mmol / dm ³ was prepared, and the hydrochloric acid concentration (or nitric acid concentration) was changed. The organic phase was prepared using toluene as a diluent and an extractant concentration of 0.01 mol / dm ³ . 15 ml of each phase was placed in an Erlenmeyer flask and shaken in a 30 ° C. constant temperature bath for 24 hours. After shaking, the aqueous phase was separated and the concentration of each metal ion was determined by an atomic absorption photometer.
[0026]
The back extraction experiment was performed by shaking palladium contained in the extracted organic phase with the back extractant shown below. The back extractant is 1.0 mol / dm ³ , 2.0 mol / dm ³ ammonia aqueous solution, 1.0 mol / dm ³ thiourea aqueous solution, 1.0 mol / dm ³ thiourea and 1.0 mol / dm ³ hydrochloric acid mixed aqueous solution, 1.0 mol / dm ³ Six types of thiourea and 1.0 mol / dm ³ ammonium thiocyanate mixed aqueous solution and 1.0 mol / dm ³ EDTA aqueous solution were used.
[0027]
Specific methods and results of the extraction experiment are shown in Examples 2 to 5 below with reference to FIGS. The extraction results of each metal shown in the figure were obtained by blotting the logarithmic concentration of hydrochloric acid (or nitric acid) on the horizontal axis and the extraction percentage of each metal on the vertical axis. Here, the extraction percentage was obtained by the following equation.
E = (C ₀ −Ce) × 100 / C ₀ [%]
C ₀ represents the initial concentration of metal ions, and Ce represents the concentration after equilibrium.
[0028]
Example 2: Extraction by ETA (1)
Concentration takes extractant 0.01 mmol / dm ^3, and a toluene solution of ETA, the hydrochloric acid solution of metal concentration 0.1 mmol / dm ³ solution containing a (0.01~3.0mmol / dm ³⁾ each 15 ml, constant-temperature bath at 30 ° C. Shake for 24 hours in the experiment. The extraction result of each metal is shown in FIG.
As shown in FIG. 1, palladium and gold exhibit an extraction rate of 100% without depending on the hydrochloric acid concentration, and selective extraction and separation of gold and palladium from various base metals as described above can be performed. Furthermore, it can be seen that separation of palladium (II) and platinum (IV), which is said to be difficult to separate with the industrial extractant currently used, is possible in the total hydrochloric acid concentration region.
[0029]
Example 3: Extraction <br/> concentration by OTA contains extractant of 0.01 mmol / dm ^3, and a toluene solution of OTA, the hydrochloric acid solution of metal concentration 0.1 mmol / dm ³ a (0.01~3.0mmol / dm ³⁾ 15 ml of the solution was taken and shaken in a constant temperature bath at 30 ° C. for 24 hours for the experiment. The extraction result of each metal is shown in FIG. Palladium and gold showed an extraction rate of 100% without depending on the hydrochloric acid concentration, indicating that selective extraction and separation of gold and palladium from the various base metals described above can be achieved. It can also be seen that separation of palladium and platinum, which is said to be difficult to separate with industrial extractants currently used, is possible in the total hydrochloric acid concentration region.
[0030]
Example 4: Extraction by ETA (2)
A 0.01-3.0 mol / dm ³ nitric acid aqueous solution containing 1.0 mmol / dm ³ of nitrate of each metal ion was used as the aqueous phase, and a chloroform solution containing 0.01 mol / dm ³ of the extractant ETA was used as the organic phase. The experiment was carried out by shaking in a constant temperature bath at 30 ° C. for 24 hours. FIG. 3 shows the results of an experiment for extracting various metals from the nitric acid solution. Palladium and gold do not depend on the nitric acid concentration and are extracted in the entire nitric acid concentration region. Mercury is rapidly extracted from around nitric acid concentration of 1 mol / dm ³ . Therefore, palladium and gold from the base metal can be separated in the total nitric acid concentration region, and mercury, which is a harmful substance, can be separated in the region of 1.0 mmol / dm ³ or more.
[0031]
Example 5: Back Extraction of Palladium from Organic Phase A back extraction experiment of palladium was performed using ETA and OTA. The six back extractants used are as described above.
The aqueous phase is a 1 mol / dm ³ aqueous solution of hydrochloric acid palladium 1.0 mmol / dm ^3, the organic phase is taken up in 0.01 mol / dm ³ with toluene, by 15ml each stopper Erlenmeyer flask ETA (or OTA), 30 ° C. thermostatic After shaking in a bath for 24 hours, the aqueous phase and the organic phase were separated, and the metal concentration in the aqueous phase was measured with an atomic absorption photometer. Next, 10 ml of the back extraction solvent and 10 ml of the separated organic phase were mixed again in an Erlenmeyer flask with a stopper, shaken in a thermostatic bath at 30 ° C. for 24 hours, and then separated into an aqueous phase and an organic phase. The metal concentration was measured with an atomic absorption photometer, and the back extraction rate was calculated. The results are shown in Table 1 (ETA) and Table 2 (OTA).
[0032]
[Table 1]

[0033]
[Table 2]

[0034]
As shown in Tables 1 and 2, by using a back extractant containing thiourea, a back extraction rate of 100% or close to this can be obtained. From this, it can be seen that palladium extracted from a solution in which base metal or various platinum group metals are mixed can be further back-extracted, concentrated to high concentration and recovered.
[0035]
【The invention's effect】
As described above, according to the present invention, a wide range of concentrations containing various base metals and noble metals can be obtained by a solvent extraction method using an extracting agent composed of a thioaniline derivative that can be synthesized in a high yield in one step. Palladium and gold can be effectively separated in a short time from an aqueous hydrochloric acid solution or an aqueous nitric acid solution. Thus, the present invention contributes to the development of a new technique for recovering and purifying palladium and gold from various metal products and metal materials. For example, according to the present invention, separation of palladium, which has been conventionally difficult to separate, from other platinum group metals (especially platinum) is realized, and by adding a back extraction operation, high concentration of palladium is achieved. It can also be concentrated.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows the results of an extraction experiment carried out using ortho (2-ethylhexylthio) aniline as an extractant for aqueous hydrochloric acid containing various metals.
FIG. 2 shows the results of an extraction experiment carried out using orthooleylthioaniline as an extractant for aqueous hydrochloric acid solutions containing various metals.
FIG. 3 shows the results of an extraction experiment conducted with an aqueous solution of nitric acid containing various metals using ortho (2-ethylhexylthio) aniline as an extractant.

Claims (9)

A palladium and / or gold extractant comprising an ortho thioaniline derivative represented by the following structural formula:

[In the above formula, R is an alkyl or alkenyl group of C ₁ -C _18. ] R is C ₁ ~ C ₁₈ The extractant according to claim 1, which is an alkenyl group or a branched chain alkyl group. 3. The extractant according to claim 2, comprising ortho (2-ethylhexylthio) aniline or orthooleylthioaniline. By bringing a metal-hydrochloric acid aqueous solution or nitric acid aqueous solution containing at least palladium and / or gold into contact with an extraction solvent containing the extractant according to any one of claims 1 to 3, palladium and / or gold is obtained. A method for separating palladium and / or gold, which comprises the step of extracting into the extraction solvent. 5. The method of claim 4, wherein the aqueous hydrochloric acid or nitric acid solution of the metal contains a base metal. The method according to claim 4 or 5, wherein the aqueous hydrochloric acid solution or the aqueous nitric acid solution contains a noble metal other than palladium and gold. An aqueous hydrochloric acid or nitric acid solution of metal contains palladium and a platinum group metal other than palladium, and the palladium extracted in the extraction solvent containing the extractant according to any one of claims 1 to 3 is back-extracted with a back-extraction solvent. The method according to any one of claims 4 to 6, further comprising a step of obtaining an aqueous solution containing palladium. 8. The method of claim 7, wherein the back extraction solvent is an aqueous solution containing thiourea. The method according to any one of claims 4 to 8, wherein the extractant according to claim 3 is used.

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