JP4116490B2

JP4116490B2 - High-purity platinum group recovery method

Info

Publication number: JP4116490B2
Application number: JP2003128828A
Authority: JP
Inventors: 和彦元場; 燈文永井; 教正大塚
Original assignee: Nippon Mining and Metals Co Ltd
Current assignee: Nippon Mining Holdings Inc
Priority date: 2003-05-07
Filing date: 2003-05-07
Publication date: 2008-07-09
Anticipated expiration: 2023-05-07
Also published as: JP2004332041A

Description

【０００１】
【発明の属する技術分野】
本発明は、白金族を含有する溶液、例えば、銅電解スライムの浸出後液から白金族を回収する方法に関する。
【０００２】
【従来の技術】
従来の白金族の回収方法としては、例えば文献M.Wisniewski, Industrial applications of noble metals’extraction, Polish J.of Appl.Chem.XL,z1-2.17-26(1996)（非特許文献１）のように白金族を含む溶液からRuあるいはOsを蒸留で溶液から分離回収し、次にPd,Pt,Irをそれぞれ溶媒抽出で分離回収した後、Rhを回収する方法がある。あるいはそれより以前には分析化学的手法を用いて分離回収する方法が古くから行われている。
また一方、特開平７−３１０１２９号公報（特許文献１）では、Ｒｈと白金族元素を含む液処理として、第４アンモニウム塩型陰イオン交換樹脂を用いる方法が開示されているが、例えば、回収されたＲｈ品位は、９９.９４ｍａｓｓ％と悪く、Ｐｄ，Ｐｔ，Ｒｈの３種類の分離法のみの開示されている。
これでは、本発明の目的であるＲｕ、Ｉｒを加えた五種類以上の金属を高純度（例えば、９９.９９ｍａｓｓ％以上）において回収する手段を把握することができない。
更に、特許第２７７１２１８号公報（特許文献２）においては、硫化ジアルキルを抽出剤として用いる方法が開示されている、高純度な金属回収を具体的に開示されていない。
【０００３】
【特許文献１】
特開平７−３１０１２９号公報
【特許文献２】
特許第２７７１２１８号公報
【非特許文献１】
著作者名：M.Wisniewski, タイトル：Industrial applications of noble metals’extraction, 雑誌名：Polish J.of Appl.Chem.XL,z1-2.17-26(出版日：1996年)
【０００４】
【発明が解決しようとする課題】
しかしながら、従来の白金族回収方法、例えば前述の溶媒抽出を用いた方法では、Ru,Pd,Ir,Rhなどの分離は可能であるが、アルカリ土類あるいは重金属が取れないため回収した白金族はこれらで汚染された純度の低いものしか得られなかった。また分析化学的方法を用いると不純物は取れるものの、非常に煩雑な操作を繰返し行わなければならず、手間がかかるとともに、一次採収率も悪いため、白金族の繰返しが多くなるという欠点があった。
【課題を解決するための手段】
【０００５】
そこで、鋭意研究した結果、通常不純物として含まれるアルカリ、アルカリ土類あるいは重金属類を溶媒抽出および中和法で取り除く方法を開発することに成功し、高純度の白金族を得ることが可能となった。
【０００６】
：
すなわち本発明は、
（１）白金族を含む溶液から、RuＯ_４を蒸留により回収し、次にPd,Pt,Irを順次溶媒抽出で回収後、Rhを塩化アンモニウムにより晶析させるなどして回収する方法において、
前記白金族を含む溶液からアルカリ土類及び少なくとも Cu,Pb,Fe の一種以上をD2EHPA による溶媒抽出法で取り除き、
次にPd,Pt,Irを順次溶媒抽出で回収後、
前記溶媒抽出後の後液をｐ H=10-12 として、中和後ろ過し、残留不純物をろ液に逃がした後、Ｒｈの中和殿物を回収し、該中和殿物を塩酸で再溶解する高純度の白金族の回収方法。
（２）上記（１）記載の方法に於いて、蒸留後の溶液に過酸化水素水あるいは亜硫酸水を加え、ORPを３００〜７００ｍVに制御した後ｐH＝４.０〜５.５に調整し、
D2EHPA により溶媒抽出する高純度の白金族の回収方法。
（３）上記（１）〜（２）記載の何れかに方法に於いて、Iｒを溶媒抽出する前に、ｐH＝０.５〜１.５に調整し、酸化剤で酸化し、ついでHCｌを０.８〜１．５規定になるように加え、IrをTBP により溶媒抽出する高純度の白金族の回収方法。
【０００７】
以下本発明について、詳細に説明する。
本発明の目的は白金族を含む溶液から不純物を効率的に取り除くことである。
例えば、銅電解スライムを通常の方法で脱Cuした後、塩化浸出しAuを溶媒抽出で回収した後、SeをSO₂で還元し溶液からろ別する。ろ別したSeは純度を上げるため蒸留精製するが、Seの中に一部混ざっている白金族が蒸留残渣として回収される。この残渣を塩化焙焼し、水浸出して白金族を含んだ溶液が得られる。あるいはSe還元した後、Teを同様に還元するがこのTeを浸出しても同様の溶液が得られる。
【０００８】
この溶液を酸化剤として例えばNaBrO₃を用い4酸化ルテニウムＲｕＯ_４とし、通常の方法で蒸留し、Ru（もしOsが存在すればRu及びあるいはOs）を回収する。この場合は蒸留法なので、蒸気に随伴する液をトラップなどを設置し、注意深く吸収液に飛沫同伴しないようにすれば十分４N以上の金属を回収できる。
【０００９】
次に酸化剤が残っていると次の工程の抽出剤が劣化するため、臭素を加熱脱却する。その後、特にCrを抽出されやすくするため過酸化水素水あるいは亜硫酸水を添加してORPを３００〜７００ｍVに調整する。ORPを３００ｍＶより低くしても、過酸化水素のコストがかかるだけでＣｒの除去効果は変わらない。７００ｍＶより上げるとCrが抽出されやすくなる。この理由ははっきりしないが、６価のクロム酸イオンCr₂O₇ ^2-が関係しているものと思われる。
次いで、溶媒と攪拌混合してから、NaOHなどのアルカリを添加しｐH=４.０〜５.５に合わせる。ｐH=４.０より低い場合は、不純物が除去され難いが、ｐH＝５.５より高くしても除去率は余り上がらず、却ってRhなどのロスは増えるためである。
この操作を必要とされる純度になるまで繰り返す。
【００１０】
アルカリ土類及び重金属の大半を除いた後、PdをDHSで、Pt、IrはTBPで抽出して回収する。通常PtはORPが高いほうが抽出しやすいが（Ptの４価の方が３価より抽出されやすい）、ORPが６００ｍVを超えるとIrも抽出するため、６００ｍV以下で抽出操作を行う。ただしPtとIrを同時に抽出し、逆抽出後に分離操作を行う場合はこの限りではない。
Irを酸化する場合ｐH=0.5〜１.５で行なうと効率的に酸化される。これは酸濃度がｐH=0.5より高いと酸化剤として添加するNaClOあるいはNaBrO₃などが分解して十分Irを酸化できないためと思われる。また抽出するときの酸濃度もIrの分配係数に影響を及ぼすため、酸化処理後ＨＣｌを加えて酸濃度調整をする。酸濃度は１．５規定より低いほうが良いが、あまり低くなると分相性が悪化するため下限は、０.８規定程度が望ましい。
【００１１】
その後NaOHなどのアルカリを添加し、ｐH＝１０〜１２に調整する。ｐＨ＝１０より低くするとRhが水酸化物となって沈澱するが、Na、Cr、Ag、Pbの大部分はろ液に残留するため、D₂EHPAにより除去できなかった不純物も中和操作によって除去できる。一方ｐＨ＝１２より高くするとＲｈの溶解度が大きくなるため好ましくない。
この後塩酸を用いてロジウムの水酸化物を再溶解し塩化ロジウムの溶液とする。このときロジウム濃度を高く、例えば５０g/l保つと次の塩化アンモニウムによる晶析の場合も、分離操作を繰り返す場合であっても処理液量、使用薬品量が少なくて済むだけでなくロジウム濃度が高い状態で不純物を取り除いた方が相対的にロジウム品位が高くなって有利である。
【００１２】
Pd、Pt、Irはそれぞれ抽出溶媒から通常の方法で逆抽出し、必要であるならば、さらに周知の方法で精製することができる。以上の工程を必要な純度が得られるまで繰り返すと所望の純度の白金族が得られる。不純物濃度にもよるが４N以上の純度であるならば、通常３〜５回繰り返すことにより得られる。
【実施例】
【００１３】
（実施例１）
図１に示すフローシートに添って説明する。本実施例では、ＰｔとＩｒを同時に回収する例を示す。ＰｔとＩｒを別々に回収する際の例は、実施例4〜6に示す。
Se蒸留残渣を塩化焙焼した後、水浸出して浸出液を得た。浸出液の一部１００ｃｃをとってNaOHでｐH＝１に調整し、NaBrO₃を溶液中のRuの約３倍当量添加した後4酸化ルテニウム（ＲｕＯ_４）とし、８０℃に加熱し空気を流しながら蒸留フラスコで約４時間蒸留した。この操作を2回繰り返した。蒸留後の液はｐH＝５程度に上昇しているので、塩酸濃度１規定になるまで塩酸を加えた後、約１時間８０℃に加熱して臭素を脱却した。この液をRu蒸留後液とする。
【００１４】
Ru蒸留後液１００ｃｃをビーカにとり、過酸化水素をORPで7００mV以下になるように（３０％H₂O₂水で大体Ru蒸留後液の１／５程度）添加した後、DP8R（大八化学製）をケロシンで２０％に薄めた溶媒をO/A比１：１で加えた。溶媒と液を攪拌機で攪拌しながら、NaOH溶液を徐々に加え、ｐH＝４.５〜５.２にする。３０分攪拌を続けた後、攪拌機を止め、静置して溶媒とRu蒸留後液を分離する。分離した後、DP８R抽出後液をビーカの底から抜き出し、再度同じ操作を繰り返す。この液をDP8R後液とする。次にPdを溶媒抽出する。
【００１５】
抽出溶媒はDHS（大八化学製）をケロシンで薄め５０vol％にしたものを用いた。DHSによるPd抽出は酸濃度の高い（HCｌ３〜４規定）ほうが良好な結果が得られるが、次のTBP抽出の際ｐH=０.５〜１.５に上げる必要があるため、液量の増加を抑えるためHCｌ１規定で２回行なった。Pdを抽出した後の液をDHS後液とする。この後液にNaOHを加え、ｐH＝１に調整する。Irは４価に酸化しないと抽出しないため、NaClOの５％溶液を加えた後、８０℃に加温して１時間保持した。その後HCｌを加えｐH＝０程度に戻し余剰のCl₂を追い出す。
【００１６】
さらにHCｌを加えて１規定にしてからTBPで抽出操作を行なう。TBP（大八化学製）は稀釈せず１００vol％のまま使用した。この操作を３回繰り返した。得られた液をTBP後液とする。水溶液と溶媒の分離が不十分だとPがスポンジRhに入る場合があるため、活性炭で液中のTBPを除いた。この液にNaOHを加え、ｐH＝１１.５に調整するとRhの水酸化物が得られる。攪拌しながら８０℃に加温し、３０分保持してから１晩放冷する。ろ過洗浄したRhの沈澱をHCｌで再溶解する。得られた液を中和溶解後液とする。以上の操作で得られた
結果を表１に示す。
【００１７】
【表１】

【００１８】
以上の操作から得られたそれぞれの成分の分離液を塩化アンモニウムで結晶化させ、焙焼した結果、表２の純度のスポンジメタルが得られた。分析はスポンジメタルを粉砕後、金型でプレス成型、焼結し、マッチ棒状のサンプルにしてグローディスチャージ質量分析法（GD-MS）で行なった。
比較例として表２に示すように、DＰ8Rによる重金属除去及び後工程での中和ない場合は、純度が７１.５２ｍａｓｓ％と非常に品位が悪いＲｈしか得られない。
【００１９】
【表２】

【００２０】
以上のように実施例では４N程度の純度のメタルが得られたが、上記操作を繰り返せばさらに純度の高いメタルが得られる。
（実施例２）
（DP8Rによる溶媒抽出のPH）
【００２１】
Ｒｕ蒸留後の液とＤＰ８Ｒを１：１で混合し、ＮａＯＨ溶液でPHを調整し抽出試験を行った。不純物の抽出率とＰＨの関係を表３に示す。
【表３】

以上のように、ｐH＝４以下では不純物除去が不十分である。またｐH＝６にしても不純物除去効果は殆ど変わらないが、Rhの水酸化物ができるため害のほうが大きい。
（実施例３）
（DP8Rによる溶媒抽出のORP）
【００２２】
Ru蒸留後の液にH₂O₂あるいはS O₂を加え、ORPを調整した。それ以外は本特許の方法と同じ条件でDP8Rによる抽出を２回行なった。結果を表４に示す。
実施例の３００ｍＶ，６７１ｍＶの例では、抽出液中の不純物Ｃｒ，Ｆｅ，Ｐｂが低く好ましい値であった。
比較例のＯＲＰが、７８０ｍＶと高いものは、抽出液中の不純物Ｃｒ，Ｆｅ，Ｐｂが高く好ましい値でなかった。
【表４】

【００２３】
以上の結果の通り、ORPが十分に低下しないとFe,Pbは後工程でも比較的除去できるが、特にCrが取れにくくなり、十分な純度が得られない。
（実施例４）
（酸化剤添加時の酸濃度）
【００２４】
Irを抽出するときの条件について検討した。酸化剤を添加するときの酸濃度を変え、抽出時の分配係数を測定した。酸化剤としてはNaBrO₃を用い、Irを３価から４価にするのに必要な量の２,８００倍を加えた。抽出するときの酸濃度は５Nとした。結果を表５に示す。
【００２５】
【表５】

この結果、ｐH=1においては抽出分配係数が２１と高いが、酸濃度を３．６規定とした場合は極めて悪い抽出分配係数であった。
【００２６】
（実施例５）
（抽出時の酸濃度）
次に、酸化時の酸濃度をｐH=1で一定にし、抽出するときの酸濃度を変えて、分配係数を測定した。酸化剤はNaBrO₃で添加量は同じく当量の２,８００倍とした。結果を表６に示す。
【００２７】
【表６】

この結果、０.４規定において、抽出分配係数は１１１と高いが、液と抽出溶媒との分相性が極めて悪く、好ましくない。１.８規定以上であると抽出分配係数が小さいため好ましくない。０.９規定〜１.４規定の実施例の値が、抽出分配係数が少なくなく、分相性も良いため好ましい結果となっている。
【００２８】
（実施例６）
（中和時の水素イオン濃度）
Ir抽出後の塩化Rh液をNaOHで中和し、水酸化Rhで回収する試験を行った。４０％NaOH溶液を添加し、所定のｐHにした後、８０℃に加温して３０分保持し、放冷しながら１晩沈殿を熟成した。結果を表７に示す。ｐH=9、
ｐH=13ではRhの回収率が悪く好ましくない。ｐH=１０〜１２が回収率１００％であり、好ましかった。
【表７】

【発明の効果】
【００２９】
以上説明したように、
（１）本発明によれば不純物の高い原料から溶媒抽出により重金属のほとんどの成分を同時に除去でき、さらにDP8R等の溶媒抽出により除去できないAgや除去が十分でないCr,Pbなども中和工程で除去できるので、高純度の白金族メタルが煩雑な操作なしに収率良く得られる。
【００３０】
（２）ORPとｐHを適切な範囲に制御することにより、重金属類特にCr,Pbを大幅に低減できる。
【００３１】
（３）TBP等の溶媒抽出によりIrおよびあるいはPtを抽出する場合、ｐHを適切な条件でIr及びPtを酸化し、さらに抽出時のｐHも調整することによってIr,Ptの良好な除去回収ができる。
【００３２】
【図面の簡単な説明】
【図１】本発明の一実施例のフローシートである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for recovering a platinum group from a solution containing a platinum group, for example, a solution after leaching of copper electrolytic slime.
[0002]
[Prior art]
As a conventional platinum group recovery method, for example, the document M. Wisniewski, Industrial applications of noble metals' extraction, Polish J. of Appl. Chem. XL, z1-2.17-26 (1996) (Non-patent document 1) In addition, there is a method in which Ru or Os is separated and recovered from a solution containing platinum group by distillation, and then Pd, Pt, and Ir are separated and recovered by solvent extraction, and then Rh is recovered. Or before that, the method of separating and recovering using an analytical chemistry method has been performed for a long time.
On the other hand, JP-A-7-310129 (Patent Document 1) discloses a method using a quaternary ammonium salt type anion exchange resin as a liquid treatment containing Rh and a platinum group element. The Rh quality is as low as 99.94 mass%, and only three separation methods of Pd, Pt, and Rh are disclosed.
In this case, it is impossible to grasp a means for recovering five or more kinds of metals added with Ru and Ir, which are the object of the present invention, with high purity (for example, 99.99 mass% or more).
Furthermore, Japanese Patent No. 2771218 (Patent Document 2) does not specifically disclose high-purity metal recovery, which discloses a method using dialkyl sulfide as an extractant.
[0003]
[Patent Document 1]
JP 7-310129 A [Patent Document 2]
Japanese Patent No. 2771218 [Non-Patent Document 1]
Author name: M. Wisniewski, Title: Industrial applications of noble metals'extraction, Journal name: Polish J.of Appl. Chem. XL, z1-2.17-26 (Published: 1996)
[0004]
[Problems to be solved by the invention]
However, in the conventional platinum group recovery method, for example, the method using solvent extraction described above, it is possible to separate Ru, Pd, Ir, Rh, etc., but since the alkaline earth or heavy metal cannot be removed, the recovered platinum group is Only low purity products contaminated with these were obtained. Although analytical chemical methods can remove impurities, very complicated operations must be performed repeatedly, which is troublesome and has a disadvantage of increasing the number of repetitions of the platinum group due to poor primary yield. It was.
[Means for Solving the Problems]
[0005]
Therefore, as a result of earnest research, we succeeded in developing a method for removing alkali, alkaline earth or heavy metals usually contained as impurities by solvent extraction and neutralization methods, and it became possible to obtain a high purity platinum group. It was.
[0006]
:
That is, the present invention
(1) In a method of recovering RuO ₄ from a solution containing a platinum group by distillation, then recovering Pd, Pt, and Ir by sequential solvent extraction and then crystallizing Rh with ammonium chloride.
The alkaline earth and at least one or more of Cu, Pb, Fe are removed from the platinum group-containing solution by a solvent extraction method using D2EHPA ,
Next, Pd, Pt, and Ir are sequentially recovered by solvent extraction,
As p H = 10-12 the liquid after after the solvent extraction, filtration and after neutralization, after venting of the residual impurities in the filtrate was recovered neutralized precipitate of Rh, the neutralization buttocks product with hydrochloric acid A high purity platinum group recovery method that re-dissolves.
( 2) In the method described in ( 1 ) above, hydrogen peroxide or sulfite is added to the solution after distillation, and the ORP is controlled to 300 to 700 mV, and then adjusted to pH = 4.0 to 5.5. ,
The solvent of high purity platinum group method the recovery of the extract by D2EHPA.
( 3) In the method according to any one of (1) to ( 2) above, before extracting Ir with a solvent, pH is adjusted to 0.5 to 1.5, oxidized with an oxidizing agent, and then HCl. added so that 0.8 to 1.5 defined, high-purity method of platinum group recovery of solvent extraction of Ir by TBP.
[0007]
The present invention will be described in detail below.
An object of the present invention is to efficiently remove impurities from a solution containing a platinum group.
For example, after removing Cu electrolysis slime by a usual method, leaching with chloride and recovering Au by solvent extraction, Se is reduced with SO ₂ and filtered from the solution. Se that has been filtered is purified by distillation to increase the purity, but the platinum group partially mixed in Se is recovered as a distillation residue. The residue is chlorinated and roasted and leached with water to obtain a solution containing a platinum group. Alternatively, after reduction of Se, Te is reduced in the same manner, but a similar solution can be obtained by leaching this Te.
[0008]
This solution is made into ruthenium tetroxide ₄ using, for example, NaBrO ₃ as an oxidizing agent, and distilled by a usual method to recover Ru (Ru and / or Os if Os is present). In this case, since it is a distillation method, a sufficient amount of 4N or more metal can be recovered if a trap or the like is installed for the liquid accompanying the vapor so that it is not entrained with the absorbing liquid.
[0009]
Next, if the oxidizing agent remains, the extractant in the next step deteriorates, so bromine is removed by heating. Thereafter, in order to facilitate extraction of Cr in particular, hydrogen peroxide or sulfite is added to adjust the ORP to 300 to 700 mV. Even if ORP is made lower than 300 mV, the cost of removing hydrogen does not change with only the cost of hydrogen peroxide. When it exceeds 700 mV, Cr is easily extracted. The reason for this is not clear, but seems to be related to the hexavalent chromate ion Cr ₂ O ₇ ²⁻ .
Next, after stirring and mixing with the solvent, an alkali such as NaOH is added to adjust the pH to 4.0 to 5.5. When the pH is lower than 4.0, impurities are difficult to remove, but even when the pH is higher than 5.5, the removal rate does not increase so much, and the loss of Rh and the like increases.
This operation is repeated until the required purity is obtained.
[0010]
After removing most of the alkaline earth and heavy metals, Pd is extracted with DHS and Pt and Ir are extracted with TBP and recovered. Normally, Pt is easier to extract when ORP is higher (Pt tetravalent is easier to extract than trivalent), but when ORP exceeds 600 mV, Ir is also extracted, so extraction is performed at 600 mV or less. However, this is not the case when Pt and Ir are extracted at the same time and the separation operation is performed after back extraction.
When Ir is oxidized at a pH of 0.5 to 1.5, it is efficiently oxidized. This seems to be because when the acid concentration is higher than pH = 0.5, NaClO or NaBrO ₃ added as an oxidizing agent decomposes and Ir cannot be oxidized sufficiently. Further, since the acid concentration at the time of extraction also affects the Ir distribution coefficient, the acid concentration is adjusted by adding HCl after the oxidation treatment. The acid concentration is preferably lower than 1.5 N, but if it is too low, the phase separation deteriorates, so the lower limit is preferably about 0.8 N.
[0011]
Thereafter, an alkali such as NaOH is added to adjust the pH to 10 to 12. When pH is lower than 10, Rh becomes hydroxide and precipitates, but most of Na, Cr, Ag and Pb remain in the filtrate, so impurities that could not be removed by D ₂ EHPA are also removed by neutralization. it can. On the other hand, a pH higher than 12 is not preferable because the solubility of Rh increases.
Thereafter, the hydroxide of rhodium is redissolved with hydrochloric acid to obtain a solution of rhodium chloride. At this time, if the rhodium concentration is kept high, for example, 50 g / l, not only the subsequent crystallization with ammonium chloride, but also the separation operation is repeated, not only the amount of processing solution and the amount of chemicals used are reduced, but the rhodium concentration is reduced. It is advantageous to remove impurities in a high state because the rhodium quality is relatively high.
[0012]
Pd, Pt, and Ir are each back-extracted from the extraction solvent by a conventional method, and if necessary, can be further purified by a well-known method. By repeating the above steps until the required purity is obtained, a platinum group having a desired purity can be obtained. Although it depends on the impurity concentration, it is usually obtained by repeating 3 to 5 times if the purity is 4N or more.
【Example】
[0013]
(Example 1)
A description will be given according to the flow sheet shown in FIG. In the present embodiment, an example in which Pt and Ir are collected simultaneously is shown. Examples of recovering Pt and Ir separately are shown in Examples 4-6.
The Se distillation residue was chlorinated and roasted and then leached with water to obtain a leachate. Take 100 cc of the leachate, adjust pH to 1 with NaOH, add NaBrO ₃ to about 3 times the equivalent of Ru in the solution, then change to ruthenium tetroxide (RuO ₄ ), heat to 80 ° C. and allow air to flow Distill for about 4 hours in a distillation flask. This operation was repeated twice. Since the liquid after the distillation rose to about pH = 5, hydrochloric acid was added until the hydrochloric acid concentration became 1 N, and then bromine was removed by heating to 80 ° C. for about 1 hour. This solution is used as a solution after Ru distillation.
[0014]
After taking 100 cc of Ru-distilled solution in a beaker and adding hydrogen peroxide to an ORP of 700 mV or less (approximately 1/5 of 30% H ₂ O ₂ water, roughly 1/5 of Ru-distilled solution), DP8R (Daihachi Chemical) The solvent was diluted to 20% with kerosene and added at an O / A ratio of 1: 1. While stirring the solvent and the liquid with a stirrer, the NaOH solution is gradually added to adjust the pH to 4.5 to 5.2. After stirring for 30 minutes, the stirrer is stopped and allowed to stand to separate the solvent and the solution after Ru distillation. After separation, the DP8R extracted liquid is extracted from the bottom of the beaker, and the same operation is repeated again. This solution is used as the DP8R post-solution. Next, Pd is solvent extracted.
[0015]
As the extraction solvent, DHS (manufactured by Daihachi Chemical Co., Ltd.) diluted with kerosene to 50 vol% was used. Pd extraction with DHS gives better results when the acid concentration is higher (HC13-4N), but it is necessary to increase the pH to 0.5-1.5 at the time of the next TBP extraction. In order to suppress this, it was carried out twice according to HCI1 regulations. Let the liquid after extracting Pd be a DHS post-solution. After this, NaOH is added to the solution to adjust pH = 1. Ir does not extract unless it is oxidized to tetravalent, so a 5% solution of NaClO was added, and then heated to 80 ° C. and held for 1 hour. Thereafter, HCl is added and the pH is returned to about 0 to expel excess Cl ₂ .
[0016]
Further, add HCl to make 1 standard, and then perform extraction with TBP. TBP (manufactured by Daihachi Chemical) was used as it was at 100 vol% without dilution. This operation was repeated three times. Let the obtained liquid be TBP post-solution. If the separation between the aqueous solution and the solvent is insufficient, P may enter the sponge Rh, so the TBP in the solution was removed with activated carbon. By adding NaOH to this solution and adjusting the pH to 11.5, a hydroxide of Rh is obtained. Warm to 80 ° C. with stirring, hold for 30 minutes and allow to cool overnight. The Rh precipitate washed by filtration is redissolved with HCl. The liquid obtained is neutralized and dissolved. Table 1 shows the results obtained by the above operation.
[0017]
[Table 1]

[0018]
As a result of crystallizing the separated liquid of each component obtained from the above operation with ammonium chloride and baking it, a sponge metal having the purity shown in Table 2 was obtained. The analysis was performed by glow discharge mass spectrometry (GD-MS) after pulverizing sponge metal, press-molding and sintering with a mold, and making a match rod sample.
As shown in Table 2 as a comparative example, in the case where heavy metal removal by DP8R and neutralization in the post-process are not performed, only Rh having a purity of 71.52 mass% and very poor quality can be obtained.
[0019]
[Table 2]

[0020]
As described above, a metal having a purity of about 4N was obtained in the examples. However, if the above operation is repeated, a metal having a higher purity can be obtained.
(Example 2)
(PH for solvent extraction with DP8R)
[0021]
The liquid after Ru distillation and DP8R were mixed at a ratio of 1: 1, and the pH was adjusted with an NaOH solution to conduct an extraction test. Table 3 shows the relationship between the extraction rate of impurities and PH.
[Table 3]

As described above, impurity removal is insufficient when the pH is 4 or less. Further, even if pH = 6, the effect of removing impurities hardly changes, but the harm is greater because Rh hydroxide is formed.
(Example 3)
(ORP for solvent extraction with DP8R)
[0022]
H ₂ O ₂ or SO ₂ was added to the liquid after Ru distillation to adjust ORP. Otherwise, extraction with DP8R was performed twice under the same conditions as in the method of this patent. The results are shown in Table 4.
In the examples of 300 mV and 671 mV in Examples, impurities Cr, Fe, and Pb in the extract were low and preferable values.
When the ORP of the comparative example was as high as 780 mV, the impurities Cr, Fe, and Pb in the extract were high, which was not a preferable value.
[Table 4]

[0023]
As can be seen from the above results, if ORP is not sufficiently lowered, Fe and Pb can be relatively removed even in a later process, but Cr is difficult to remove, and sufficient purity cannot be obtained.
Example 4
(Acid concentration when oxidizing agent is added)
[0024]
The conditions for extracting Ir were examined. The acid concentration when the oxidizing agent was added was changed, and the partition coefficient during extraction was measured. NaBrO ₃ was used as the oxidizing agent, and 2,800 times the amount necessary to make Ir from trivalent to tetravalent was added. The acid concentration during extraction was 5N. The results are shown in Table 5.
[0025]
[Table 5]

As a result, the extraction partition coefficient was as high as 21 at pH = 1, but when the acid concentration was 3.6 N, the extraction partition coefficient was extremely poor.
[0026]
(Example 5)
(Acid concentration during extraction)
Next, the acid concentration during oxidation was kept constant at pH = 1, and the acid concentration during extraction was changed to measure the partition coefficient. The oxidizing agent was NaBrO ₃ and the amount added was 2,800 times the equivalent. The results are shown in Table 6.
[0027]
[Table 6]

As a result, in 0.4 regulations, the extraction partition coefficient is as high as 111, but the phase separation between the liquid and the extraction solvent is extremely poor, which is not preferable. It is not preferable that it is 1.8 or more because the extraction distribution coefficient is small. The values of the examples in the range of 0.9 to 1.4 are preferable because the extraction distribution coefficient is not small and the phase separation is good.
[0028]
(Example 6)
(Hydrogen ion concentration during neutralization)
A test was conducted in which the Rh chloride solution after Ir extraction was neutralized with NaOH and recovered with hydroxylated Rh. After adding a 40% NaOH solution to a predetermined pH, the mixture was heated to 80 ° C. and held for 30 minutes, and the precipitate was aged overnight while allowing to cool. The results are shown in Table 7. pH = 9,
A pH of 13 is not preferable because the recovery rate of Rh is poor. The pH was 10 to 12, and the recovery rate was 100%, which was preferable.
[Table 7]

【The invention's effect】
[0029]
As explained above,
(1) According to the present invention, most components of heavy metals can be simultaneously removed from a raw material with high impurities by solvent extraction, and further, Ag that cannot be removed by solvent extraction such as DP8R and Cr, Pb, etc. that are not sufficiently removed in the neutralization step. Since it can be removed, a high-purity platinum group metal can be obtained with good yield without complicated operations.
[0030]
(2) Heavy metals, particularly Cr and Pb, can be greatly reduced by controlling ORP and pH within an appropriate range.
[0031]
(3) When extracting Ir and / or Pt by solvent extraction such as TBP, Ir and Pt can be removed and recovered well by oxidizing Ir and Pt under appropriate conditions and adjusting the pH during extraction. it can.
[0032]
[Brief description of the drawings]
FIG. 1 is a flow sheet according to an embodiment of the present invention.

Claims

In a method of recovering RuO ₄ from a solution containing a platinum group by distillation, then recovering Pd, Pt, and Ir by sequential solvent extraction and then crystallizing Rh with ammonium chloride.
The alkaline earth and at least one or more of Cu, Pb, Fe are removed from the solution containing the platinum group by a solvent extraction method using D2EHPA ,
Next, Pd, Pt, and Ir are sequentially recovered by solvent extraction,
As p H = 10-12 the liquid after after the solvent extraction, filtration and after neutralization, after venting of the residual impurities in the filtrate was recovered neutralized precipitate of Rh, the neutralization buttocks product with hydrochloric acid A high purity platinum group recovery method characterized by re-dissolving.

The method according to claim 1 , wherein hydrogen peroxide or sulfite is added to the solution after distillation, the ORP is controlled to 300 to 700 mV, and then adjusted to pH = 4.0 to 5.5.
High purity platinum group method the recovery of which is characterized by solvent extraction by D2EHPA.

3. The method according to claim 1 , wherein Ir is adjusted to pH = 0.5 to 1.5, oxidized with an oxidizing agent, and then HCl is adjusted to 0.8-1 before extracting the solvent with Ir. It added to a .5 defined, high purity platinum group method the recovery of which is characterized by solvent extraction of Ir by TBP.