JP2018162473A - Noble metal recovery method - Google Patents
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Abstract
Description
本発明は、貴金属の回収方法に関する。 The present invention relates to a method for recovering a noble metal.
廃材等からの貴金属回収では、通常、白金（Ｐｔ）等の貴金属を酸に溶解させた後、分離精製等の工程を経て、最終的に化成品やインゴット等を再製している。 In the recovery of precious metals from waste materials and the like, usually, a precious metal such as platinum (Pt) is dissolved in an acid, followed by steps such as separation and purification, and finally, chemical products and ingots are finally remanufactured.
宝飾品等、廃材中の貴金属濃度が充分高い場合は、貴金属を王水等の酸に直接溶解させた後に分離精製を行う（湿式法）。これに対して、自動車用排ガス浄化触媒等、廃材中の貴金属濃度が希薄な場合は、貴金属が銅や鉄等と合金を形成することを利用し、貴金属をこれらのコレクターメタルに吸収させる、いわゆる乾式製錬を用いて貴金属を濃縮する手法（乾式法）が用いられる。 When the precious metal concentration in the waste materials such as jewelry is sufficiently high, separation and purification are performed after dissolving the precious metal directly in an acid such as aqua regia (wet method). On the other hand, when the concentration of noble metals in waste materials such as exhaust gas purification catalysts for automobiles is dilute, the so-called collector metals absorb the noble metals by utilizing the formation of alloys with copper, iron, etc. A technique (dry process) of concentrating noble metals using dry smelting is used.
乾式製錬により、廃材中の貴金属はコレクターメタルと合金を形成する。コレクターメタルは貴金属に対して過剰量投入されるため、硫酸浸出等を行って銅や鉄等の卑な金属を溶解除去する。貴金属は硫酸にはほとんど溶解しないため、残渣中には貴金属が濃縮されることとなる。回収した残渣は王水等を用いて溶解させた後、貴金属同士を分離精製する。 By dry smelting, the precious metal in the waste material forms an alloy with the collector metal. Since an excessive amount of the collector metal is added to the noble metal, sulfuric acid leaching is performed to dissolve and remove base metals such as copper and iron. Since noble metals hardly dissolve in sulfuric acid, the noble metals are concentrated in the residue. The collected residue is dissolved using aqua regia etc., and then the noble metals are separated and purified.
上述のように、貴金属の回収では、通常、王水等の酸による溶解工程が含まれる。その理由は、溶媒抽出法やイオン交換樹脂法といった分離精製工程においては、溶液中で貴金属イオン、さらにいえば貴金属−塩化物イオンといった錯イオンを生成させる必要があるからである。 As described above, the recovery of the noble metal usually includes a dissolution step using an acid such as aqua regia. The reason is that in the separation and purification process such as the solvent extraction method and the ion exchange resin method, it is necessary to generate noble metal ions, more specifically complex ions such as noble metal-chloride ions, in the solution.
分離精製工程を円滑に行うためには、あらかじめ貴金属は錯イオンへと変化させておくことが望ましい。しかし、自動車用排ガス浄化触媒やガラス溶解用ルツボ、宝飾品等、貴金属の用途の大半は金属状態での使用を前提としている。また、乾式製錬後の貴金属も金属状態を維持している。 In order to perform the separation and purification process smoothly, it is desirable to change the noble metal into a complex ion in advance. However, most uses of precious metals, such as automobile exhaust gas purification catalysts, glass melting crucibles, and jewelry, are premised on use in a metallic state. Moreover, the noble metal after dry smelting also maintains a metallic state.
そのため、酸溶解工程では貴金属の酸化（イオン化）反応と錯イオン形成反応による溶解、という２つの反応を進ませることが肝要である。しかし、貴金属は水素よりも貴であるため、水素イオンを含む酸というだけでは貴金属をイオン化させることはできず、水素イオンよりも強力な酸化剤が必要である。 For this reason, it is important to advance two reactions in the acid dissolution process, namely, oxidation (ionization) reaction of noble metal and dissolution by complex ion formation reaction. However, since noble metals are more noble than hydrogen, an acid containing hydrogen ions cannot ionize the noble metal, and a stronger oxidizing agent than hydrogen ions is required.
貴金属はイオン化が困難な元素群であるが、王水等を用いることで程度差はあるものの溶解させることができる。この理由は、王水中で生成する酸化剤が貴金属を酸化させ、さらに王水中の塩化物イオン等が貴金属イオンと錯形成するためである。 Noble metals are a group of elements that are difficult to ionize, but can be dissolved to some extent by using aqua regia. This is because the oxidant generated in the aqua regia oxidizes the noble metal, and further, chloride ions and the like in the aqua regia complex with the noble metal ion.
以下に王水中の酸化剤生成反応について説明する。王水は濃塩酸と濃硝酸を体積比３：１で混合した混酸であり、下記の反応によって酸化剤である塩素（Ｃｌ２）及び塩化ニトロシル（ＮＯＣｌ）が生成する。 The oxidant formation reaction in aqua regia will be described below. Aqua regia is a mixed acid in which concentrated hydrochloric acid and concentrated nitric acid are mixed at a volume ratio of 3: 1, and chlorine (Cl 2 ) and nitrosyl chloride (NOCl), which are oxidizing agents, are generated by the following reaction.
３ＨＣｌ ＋ ＨＮＯ３ → Ｃｌ２ ＋ ＮＯＣｌ ＋ ２Ｈ２Ｏ ・・・（１） 3HCl + HNO 3 → Cl 2 + NOCl + 2H 2 O (1)
上記反応式により生成した塩素及び塩化ニトロシルが貴金属を酸化させる役割を果たす。 Chlorine and nitrosyl chloride generated by the above reaction formula serve to oxidize noble metals.
しかし、塩素や塩化ニトロシルといった酸化剤は極めて毒性及び腐食性が高く、常温では気体となって系外へ散逸する。そのため厳重な除害処理が必要であり、設備の維持管理コストが高額になるという問題がある。 However, oxidizers such as chlorine and nitrosyl chloride are extremely toxic and corrosive and become gaseous at room temperature and dissipate out of the system. Therefore, a strict removal process is required, and there is a problem that the maintenance cost of the equipment becomes high.
また、王水による溶解では、王水に含まれる硝酸が後段の分離精製工程を阻害する問題もある。分離精製工程の一つである溶媒抽出法では、抽出剤と硝酸が接触すると抽出剤が酸化され、貴金属の抽出効率が低下する。そのため、王水溶解では蒸発乾固と塩酸添加を繰り返す硝酸の除去工程（脱硝）が必要であり、この脱硝工程に手間がかかる問題がある。 Further, in dissolution with aqua regia, there is a problem that nitric acid contained in aqua regia inhibits the subsequent separation and purification process. In the solvent extraction method, which is one of the separation and purification steps, when the extractant comes into contact with nitric acid, the extractant is oxidized and the extraction efficiency of the noble metal decreases. Therefore, aqua regia dissolution requires a nitric acid removal step (denitration) that repeats evaporation to dryness and hydrochloric acid addition, and this denitration step is troublesome.
貴金属を溶解する方法としては、王水を用いる以外にも、塩酸に塩素ガスを通気する方法（例えば、特許文献１）や、塩酸に過酸化水素水を添加する方法（例えば、特許文献２）、オゾンを含む溶液を用いる方法（例えば、特許文献３）などが挙げられる。しかし、いずれも有毒な酸化剤を発生ないし使用する問題があり、安全性に優れているとはいえない。 As a method for dissolving the noble metal, besides using aqua regia, a method of ventilating chlorine gas into hydrochloric acid (for example, Patent Document 1), a method of adding hydrogen peroxide water to hydrochloric acid (for example, Patent Document 2) And a method using a solution containing ozone (for example, Patent Document 3). However, there is a problem of generating or using a toxic oxidant, and it cannot be said that it is excellent in safety.
貴金属の酸への溶解を容易にするため、貴金属に前処理を施す手法も提案されている。例えば特許文献４では、貴金属をＣａやＭｇ等の異種金属と合金化させることにより、貴金属を酸に容易に溶解できることが記載されている。しかし、この方法では合金形成後も貴金属が金属状態であるために、溶解には王水等の酸化剤を含む酸が必要となる。 In order to facilitate the dissolution of the noble metal in the acid, a method for pretreating the noble metal has also been proposed. For example, Patent Document 4 describes that a noble metal can be easily dissolved in an acid by alloying the noble metal with a different metal such as Ca or Mg. However, in this method, since the noble metal is in a metal state even after the alloy is formed, an acid containing an oxidizing agent such as aqua regia is required for dissolution.
また、特許文献５では、貴金属を異種金属と合金化させた後、塩化処理及び／又は酸化処理する前処理方法が提案されている。この方法では塩化処理又は酸化処理を経ることで貴金属がイオン化するため、王水等を用いることなく貴金属を溶解できる。しかし、合金化処理及び塩化処理において金属蒸気や塩素ガスといった有毒ガスの発生、使用を伴うという問題がある。 Patent Document 5 proposes a pretreatment method in which a noble metal is alloyed with a dissimilar metal and then chlorinated and / or oxidized. In this method, since the noble metal is ionized through chlorination or oxidation, the noble metal can be dissolved without using aqua regia. However, there is a problem that toxic gas such as metal vapor and chlorine gas is generated and used in alloying treatment and chlorination treatment.
以上のことから、発明者らは王水や金属蒸気等の有毒ガスを使用、発生させることなく貴金属を溶解させる手法について鋭意検討した。その結果、複合酸化物を経由することにより貴金属の単体を塩酸だけで溶解できることを見出した（特許文献６）。特許文献６では、Ｐｔ等の貴金属とリチウム塩を混合、加熱することにより、Ｌｉ２ＰｔＯ３のような複合酸化物を形成させる。得られた複合酸化物中で、貴金属は酸化状態となっているため、塩酸のような酸化剤を含まない酸だけで貴金属を容易に溶解させることができる。 In view of the above, the inventors diligently studied a method for dissolving noble metals without using or generating toxic gases such as aqua regia or metal vapor. As a result, it was found that a single noble metal can be dissolved only with hydrochloric acid by passing through a complex oxide (Patent Document 6). In Patent Document 6, a complex oxide such as Li 2 PtO 3 is formed by mixing and heating a noble metal such as Pt and a lithium salt. Since the noble metal is in an oxidized state in the obtained composite oxide, the noble metal can be easily dissolved only with an acid that does not contain an oxidizing agent such as hydrochloric acid.
王水に対する貴金属の溶解性は元素毎に異なっており、ＰｔやＰｄは比較的溶解が容易な部類である。これに対して、ＩｒやＲｈ、Ｒｕは、王水を用いてもなお溶解が困難である。複合酸化物を経由して貴金属を回収する手法では、毒性の高い王水や金属蒸気等を用いることなく、これらの難溶性貴金属を酸に溶解できる。しかし、ＩｒやＲｈ、Ｒｕの溶解率は２０〜４０％程度と低い水準に留まっていた。 The solubility of noble metals in aqua regia is different for each element, and Pt and Pd are relatively easy to dissolve. In contrast, Ir, Rh, and Ru are still difficult to dissolve even when aqua regia is used. In the method of recovering the noble metal via the complex oxide, these hardly soluble noble metals can be dissolved in the acid without using highly toxic aqua regia or metal vapor. However, the dissolution rate of Ir, Rh, and Ru remained at a low level of about 20 to 40%.
Ｉｒ等の難溶性貴金属は、単体としてよりは他の金属、例えばＰｔ等と合金を形成させて用いられることが多い。合金形成により耐酸性等の化学的特性や、強度等の機械的特性を向上させることができるが、回収の観点からは合金化による耐酸性の向上は貴金属の溶解をさらに困難なものとする。本発明は、このような難溶性貴金属を含む合金を、酸溶液に容易に溶解させることが課題である。 A hardly soluble noble metal such as Ir is often used by forming an alloy with another metal, such as Pt, rather than as a single substance. Chemical formation such as acid resistance and mechanical characteristics such as strength can be improved by forming an alloy, but from the viewpoint of recovery, improvement of acid resistance by alloying makes it more difficult to dissolve noble metals. An object of the present invention is to easily dissolve an alloy containing such a hardly soluble noble metal in an acid solution.
発明者らは、貴金属単体よりも溶解が困難な貴金属含有合金について、特許文献６に基づき塩酸による浸出が可能か検討した。 The inventors examined whether noble metal-containing alloys that are more difficult to dissolve than a single noble metal can be leached with hydrochloric acid based on Patent Document 6.
特許文献６の実施例を参考に、貴金属合金の一種であるＰｔ−Ｐｄ合金とＬｉ２ＣＯ３を空気中で加熱（８００℃、２４時間）した後、塩酸による貴金属溶解（１２Ｍ塩酸、８０℃、９時間）を試みた。 With reference to the example of Patent Document 6, after heating a Pt—Pd alloy which is a kind of noble metal alloy and Li 2 CO 3 in air (800 ° C., 24 hours), dissolution of the noble metal with hydrochloric acid (12 M hydrochloric acid, 80 ° C. 9 hours).
その結果、加熱後に貴金属含有複合酸化物であるＬｉ２ＰｔＯ３及びＬｉ２ＰｄＯ２が得られたものの、塩酸に対する貴金属の溶解率はＰｔ、Ｐｄそれぞれ３６．６重量％、５７．３重量％に過ぎず、Ｐｔ−Ｐｄ合金を完全に溶解させることはできなかった。 As a result, Li 2 PtO 3 and Li 2 PdO 2 , which are noble metal-containing composite oxides, were obtained after heating, but the dissolution rates of noble metal in hydrochloric acid were 36.6% by weight and 57.3% by weight, respectively. However, the Pt—Pd alloy could not be completely dissolved.
上記に鑑みて、本発明の一形態においては、安全性に優れた高効率の、貴金属を含む合金から貴金属を回収する方法を提供することを課題とする。 In view of the above, an object of one embodiment of the present invention is to provide a highly efficient method for recovering a noble metal from a noble metal-containing alloy having excellent safety.
上記点に鑑みた本発明の一形態は、貴金属の回収方法であって、貴金属を含む合金と炭酸リチウムとを混合し、加熱して、貴金属及びリチウムを含む複合酸化物を形成する複合酸化物形成工程と、前記複合酸化物と酸溶液とを、当該酸溶液の、大気圧下における沸点から４００℃までの温度範囲で接触させ、前記酸溶液中に貴金属成分を浸出させる浸出工程とを有する。 One aspect of the present invention in view of the above points is a method for recovering a noble metal, in which an alloy containing a noble metal and lithium carbonate are mixed and heated to form a composite oxide containing the noble metal and lithium. A forming step, and a leaching step in which the complex oxide and the acid solution are brought into contact with each other in a temperature range from a boiling point of the acid solution to a temperature of 400 ° C. under atmospheric pressure, and a noble metal component is leached into the acid solution. .
本発明によれば、溶解が極めて困難な貴金属含有合金であっても、王水等を用いることなく貴金属を容易に溶解させることができる。そのため、王水に由来する塩素ガス、塩化ニトロシル等の有毒な酸化剤の発生や、処理困難な廃液の発生等を回避することができ、安全性に優れた貴金属含有合金の溶解方法とすることができる。 According to the present invention, even a noble metal-containing alloy that is extremely difficult to dissolve can easily dissolve the noble metal without using aqua regia or the like. Therefore, it is possible to avoid generation of toxic oxidants such as chlorine gas derived from aqua regia, nitrosyl chloride, generation of waste liquid that is difficult to process, etc., and to make the precious metal-containing alloy excellent in safety. Can do.
［複合酸化物形成工程］
本発明の一形態では、まず、貴金属を含む合金と炭酸リチウムとを混合し、加熱して、貴金属及びリチウムを含む複合酸化物を形成する複合酸化物形成工程を行う。
[Composite oxide formation process]
In one embodiment of the present invention, first, a composite oxide forming step is performed in which an alloy containing a noble metal and lithium carbonate are mixed and heated to form a composite oxide containing the noble metal and lithium.
（対象とする合金の組成）
本発明で処理対象となる貴金属含有合金（貴金属を含む合金）は、Ｐｔ（白金）、Ｐｄ（パラジウム）、Ｒｈ（ロジウム）、Ｉｒ（イリジウム）、Ｒｕ（ルテニウム）のいずれか一種以上を含んでいればよく、Ｐｔ−Ｉｒ合金（ガソリンエンジン用スパークプラグ等に使用され得る）やＰｔ−Ｒｈ合金（熱電対等に使用され得る）、Ｐｔ−Ｒｕ合金（燃料電池触媒等に使用され得る）、Ｐｄ−Ａｕ合金（歯科用クラウン等に使用され得る）等を例示できる。また、貴金属含有合金の組成は、上記貴金属と上記貴金属以外の元素とから構成されていてもよく、例えばＰｔ−Ｆｅ合金（磁気記録材料等に使用され得る）やＰｔ−Ｃｏ−Ｃｒ合金、Ｃｏ−Ｃｒ−Ｐｔ−Ｒｕ合金（ハードディスク用磁気ビット等に使用され得る）、Ｐｄ−Ｃｕ合金（水素分離膜等に使用され得る）等も処理対象に含めることができる。
(Composition of the target alloy)
The noble metal-containing alloy (alloy containing a noble metal) to be treated in the present invention contains at least one of Pt (platinum), Pd (palladium), Rh (rhodium), Ir (iridium), and Ru (ruthenium). Pt—Ir alloy (which can be used for a spark plug for a gasoline engine, etc.), Pt—Rh alloy (which can be used for a thermocouple, etc.), Pt—Ru alloy (which can be used for a fuel cell catalyst, etc.), Pd -An Au alloy (which can be used for a dental crown or the like) can be exemplified. The composition of the noble metal-containing alloy may be composed of the noble metal and an element other than the noble metal. For example, a Pt—Fe alloy (which can be used for a magnetic recording material), a Pt—Co—Cr alloy, Co A -Cr-Pt-Ru alloy (which can be used for a magnetic bit for a hard disk or the like), a Pd-Cu alloy (which can be used for a hydrogen separation membrane or the like), or the like can also be included in the processing target.
（加熱前の成形、粉砕等加工）
処理対象となる貴金属含有合金が、ある程度の体積を有するものである場合、例えば、ルツボ等である場合は、必要に応じて切断や圧延等の成形処理を行ってもよい。これらの処理を施すことにより、貴金属合金の比表面積を増大でき、後段の複合酸化物形成をより容易に行うことができる。
(Processing such as molding and grinding before heating)
When the precious metal-containing alloy to be processed has a certain volume, for example, a crucible or the like, a forming process such as cutting or rolling may be performed as necessary. By performing these treatments, the specific surface area of the noble metal alloy can be increased, and the subsequent formation of the complex oxide can be performed more easily.
また、ガイシ等の材料中に貴金属合金が埋包されている場合は、粉砕等を行うことにより貴金属合金をあらかじめ露出させておくことが好ましい。これにより、貴金属合金がアルカリ金属塩と接触できるので、加熱処理により容易に複合酸化物を形成することができ、塩酸等による溶解も容易となる。 Further, when the noble metal alloy is embedded in a material such as insulator, it is preferable to expose the noble metal alloy in advance by pulverization or the like. Thereby, since the noble metal alloy can come into contact with the alkali metal salt, the composite oxide can be easily formed by heat treatment, and dissolution with hydrochloric acid or the like is also facilitated.
（複合酸化物の形成）
貴金属含有合金と炭酸リチウムとを混合して接触させ、加熱（焼成）することにより、貴金属を含む複合酸化物が得られる。この複合酸化物形成工程においては、下記反応式のように酸素が消費されるため、酸素存在下で、例えば空気や純酸素等の雰囲気中で加熱処理を行うことが好ましい。
(Formation of complex oxide)
A composite oxide containing a noble metal is obtained by mixing a noble metal-containing alloy and lithium carbonate, bringing them into contact with each other, and heating (firing). In this complex oxide formation step, oxygen is consumed as shown in the following reaction formula. Therefore, it is preferable to perform heat treatment in the presence of oxygen, for example, in an atmosphere such as air or pure oxygen.
Ｐｔ ＋ Ｌｉ２ＣＯ３ ＋ Ｏ２ → Ｌｉ２ＰｔＯ３ ＋ ＣＯ２ ・・・（２）
なお、複合酸化物形成工程では、貴金属含有合金を、炭酸リチウムの固体と接触させてもよいし、炭酸リチウムの融液を接触させてもよい。
Pt + Li 2 CO 3 + O 2 → Li 2 PtO 3 + CO 2 (2)
In the composite oxide forming step, the noble metal-containing alloy may be brought into contact with a lithium carbonate solid, or a lithium carbonate melt may be brought into contact therewith.
（加熱温度及び加熱時間）
上記の複合酸化物形成のための加熱温度及び加熱時間については、試料中の貴金属を複合酸化物へと変化できる条件であればよい。複合酸化物の生成挙動は貴金属の種類によって異なるので、反応が進む範囲で加熱温度を自由に設定できる。例えば４００℃から１３００℃の範囲、より好ましくは５００℃から１０００℃の範囲、さらに好ましくは６００℃から８００℃の範囲である。炭酸リチウムを用いた場合では、６００℃から８００℃程度で加熱処理を行うことにより貴金属含有複合酸化物が得られる。
(Heating temperature and heating time)
The heating temperature and heating time for forming the complex oxide may be any conditions as long as the noble metal in the sample can be changed to the complex oxide. Since the formation behavior of the composite oxide varies depending on the type of noble metal, the heating temperature can be freely set within the range in which the reaction proceeds. For example, it is in the range of 400 ° C to 1300 ° C, more preferably in the range of 500 ° C to 1000 ° C, and still more preferably in the range of 600 ° C to 800 ° C. In the case of using lithium carbonate, a noble metal-containing composite oxide can be obtained by performing a heat treatment at about 600 ° C. to 800 ° C.
加熱時間は、対象となる貴金属合金の形態や加熱条件、例えば加熱温度や酸素分圧等に依存するが、貴金属の反応率を考慮して、例えば３０分から４８時間の範囲、より好ましくは１時間から１２時間の範囲等に設定できる。処理対象が触媒等の微粒子である場合は、数時間という比較的短時間の加熱処理によって貴金属合金を完全に複合酸化物へと変化できるが、板材等のかさ高い形態の場合は、複合酸化物形成が完了するまでに時間がかかるため、加熱時間を長く設定する必要がある。加熱後も未反応の貴金属合金が残存していると、酸による溶解が困難なものとなるため、加熱処理によって貴金属合金を完全に複合酸化物へと変化させることが好ましい。 The heating time depends on the form of the noble metal alloy to be used and the heating conditions, such as the heating temperature and the oxygen partial pressure, but in consideration of the reaction rate of the noble metal, for example, in the range of 30 minutes to 48 hours, more preferably 1 hour. To 12 hours. When the object to be treated is fine particles such as a catalyst, the noble metal alloy can be completely changed to a composite oxide by a heat treatment of a relatively short time of several hours. Since it takes time to complete the formation, it is necessary to set the heating time longer. If an unreacted noble metal alloy remains even after heating, it becomes difficult to dissolve with an acid. Therefore, it is preferable to completely change the noble metal alloy into a composite oxide by heat treatment.
（加熱時の酸素分圧）
式（２）に示したように、複合酸化物の生成反応においては空気中の酸素が消費される。そのため、反応時に酸素分圧を上げることにより、複合酸化物の形成速度を増大でき、短時間のうちに反応を終了させることができる。そのためには、例えば、初期雰囲気の酸素分圧を上げておくこともできるし、反応の開始から終了にかけて消費される酸素を常に補うようにしておくことができる。酸素分圧を上げるための具体的な手法は特に限定されないが、例えば、空気をフローしたり（通過させたり）、純酸素ガスをフローする等の手法を適宜選択することができる。このような空気又は純酸素ガスのフローは、空気フローであれば３００ｍＬ／分から１０００ｍＬ／分の範囲の流量で、純酸素ガスフローであれば１５０ｍＬ／分から５００ｍＬ／分の範囲の流量で行うことが好ましい。空気中の酸素分圧（ｐＯ２）の値は０．２であるが、ｐＯ２が高いほど複合酸化物の形成が進むと考えられることから、ｐＯ２が０．２から１．０である範囲で加熱処理を行うことが好ましい。
(Partial oxygen pressure during heating)
As shown in Formula (2), oxygen in the air is consumed in the formation reaction of the composite oxide. Therefore, by increasing the oxygen partial pressure during the reaction, the formation rate of the complex oxide can be increased, and the reaction can be completed within a short time. For this purpose, for example, the oxygen partial pressure in the initial atmosphere can be increased, or oxygen consumed from the start to the end of the reaction can always be supplemented. Although the specific method for raising the oxygen partial pressure is not particularly limited, for example, a method of flowing (passing) air or flowing pure oxygen gas can be appropriately selected. Such air or pure oxygen gas flow may be performed at a flow rate in the range of 300 mL / min to 1000 mL / min for an air flow, and at a flow rate in the range of 150 mL / min to 500 mL / min for a pure oxygen gas flow. preferable. Although the value of the partial pressure of oxygen in the air (pO 2) is 0.2, it is considered a form of pO 2 is higher composite oxide proceeds, pO 2 is 1.0 0.2 It is preferable to perform heat treatment in a range.
（加熱後の磨砕処理）
加熱処理後に得られる複合酸化物は、ミル等による磨砕処理を行ってもよい。磨砕処理によって複合酸化物の粒子径を小さくでき、これにより、後述の溶解処理（浸出工程）において複合酸化物と酸との接触面積を増大でき溶解速度を増大できる。磨砕方法としては、例えばボールミルやジェットミル等を使用することができる。
(Grinding after heating)
The composite oxide obtained after the heat treatment may be subjected to a grinding treatment with a mill or the like. The particle diameter of the composite oxide can be reduced by the grinding treatment, whereby the contact area between the composite oxide and the acid can be increased in the dissolution treatment (leaching step) described later, and the dissolution rate can be increased. As the grinding method, for example, a ball mill or a jet mill can be used.
［浸出工程］
上述のように複合酸化物を得た後、複合酸化物と酸溶液とを、酸溶液の、大気圧下における沸点以上４００℃以下の温度範囲で接触させ、前記酸溶液中に貴金属成分を浸出させる浸出工程を行う。この工程において、複合酸化物中に含まれる少なくとも１種の貴金属を酸溶液に浸出させることができる。
[Leaching process]
After obtaining the composite oxide as described above, the composite oxide and the acid solution are brought into contact with each other in the temperature range of the acid solution from the boiling point to 400 ° C. under atmospheric pressure, and the noble metal component is leached into the acid solution. The leaching process is performed. In this step, at least one kind of noble metal contained in the composite oxide can be leached into the acid solution.
（貴金属成分の浸出に用いる酸の種類）
貴金属成分の浸出は、複合酸化物を酸溶液中に溶解させることによって行うことができる。ここで、溶解に用いる酸としては、貴金属を溶解できるものであればよく、塩酸や硝酸、硫酸、フッ酸、リン酸、ギ酸、及び酢酸等を用いることができる。また、必要に応じてこれらの酸を混合してもよい。複合酸化物を溶解させるための酸は、溶液の形態、具体的には水溶液の形態で使用することが好ましい。
(Types of acids used for leaching precious metal components)
The leaching of the noble metal component can be performed by dissolving the composite oxide in an acid solution. Here, the acid used for dissolution may be any acid that can dissolve a noble metal, and hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, phosphoric acid, formic acid, acetic acid, and the like can be used. Moreover, you may mix these acids as needed. The acid for dissolving the composite oxide is preferably used in the form of a solution, specifically in the form of an aqueous solution.
（溶解処理に用いる酸の量及び濃度）
溶解処理に用いる酸溶液中の酸の濃度及び酸溶液の量としては、材料中の貴金属を溶解するのに充分な濃度及び量であればよい。例えば、１２Ｍ塩酸（濃塩酸）や１５Ｍ硝酸（濃硝酸）等を用いることができる。
(Amount and concentration of acid used for dissolution treatment)
The concentration of the acid in the acid solution used for the dissolution treatment and the amount of the acid solution may be any concentration and amount sufficient to dissolve the noble metal in the material. For example, 12M hydrochloric acid (concentrated hydrochloric acid), 15M nitric acid (concentrated nitric acid), or the like can be used.
溶解に用いる酸溶液の酸濃度の範囲は特に制限はなく、現実的な速度で貴金属溶解が進めばよい。例えば塩酸を用いる場合は、０．１Ｍから１２Ｍの範囲、より好ましくは３Ｍから１０Ｍの範囲である。濃硝酸を用いる場合は、０．１Ｍから１５Ｍの範囲、より好ましくは１Ｍから１２Ｍの範囲である。 The range of the acid concentration of the acid solution used for dissolution is not particularly limited, and the dissolution of the noble metal may proceed at a realistic rate. For example, when hydrochloric acid is used, it is in the range of 0.1M to 12M, more preferably in the range of 3M to 10M. When concentrated nitric acid is used, it is in the range of 0.1M to 15M, more preferably in the range of 1M to 12M.
（溶解温度）
酸溶液の、大気圧下での沸点以上の温度とすることで、貴金属の溶解速度を増大できる。例えば塩酸（塩酸水溶液）の沸点は濃度依存性を示すことが知られており、濃度６Ｍのとき沸点が極大（１１０℃）となる。したがって、６Ｍの塩酸を用いる場合は１１０℃以上の溶解温度とすればよい。別の濃度の塩酸を用いる場合には、１１０℃より低い温度以上の温度であっても、貴金属の溶解速度を良好に増大させることができる。
(Melting temperature)
By setting the temperature of the acid solution to a temperature equal to or higher than the boiling point under atmospheric pressure, the dissolution rate of the noble metal can be increased. For example, it is known that the boiling point of hydrochloric acid (hydrochloric acid aqueous solution) shows concentration dependence, and the boiling point becomes maximum (110 ° C.) when the concentration is 6M. Therefore, when 6M hydrochloric acid is used, the melting temperature may be 110 ° C. or higher. When hydrochloric acid having a different concentration is used, the dissolution rate of the noble metal can be increased satisfactorily even at a temperature lower than 110 ° C.
溶解温度をさらに高温、例えば１８０℃や２００℃とすることで貴金属の溶解処理をさらに迅速に行うことができる。塩酸を用いて溶解処理を行う場合、溶解温度が高すぎると貴金属が還元、析出するため、溶解温度は、好ましくは４００℃以下、より好ましくは３００℃以下、さらに好ましくは２５０℃以下とすることができる。また、好ましくは１１０℃から４００℃の範囲、より好ましくは１６０℃から３００℃の範囲、さらに好ましくは１８０℃から２５０℃の範囲とすることができる。 By further increasing the melting temperature, for example, 180 ° C. or 200 ° C., the precious metal can be dissolved more rapidly. When the dissolution treatment is carried out using hydrochloric acid, the noble metal is reduced and precipitated if the dissolution temperature is too high. Therefore, the dissolution temperature is preferably 400 ° C. or lower, more preferably 300 ° C. or lower, and even more preferably 250 ° C. or lower. Can do. Moreover, it is preferably in the range of 110 ° C to 400 ° C, more preferably in the range of 160 ° C to 300 ° C, and still more preferably in the range of 180 ° C to 250 ° C.
塩酸以外にも濃硝酸（沸点８３℃）やフッ酸（沸点９６℃）、リン酸（沸点１５８℃）等を適宜使用することができる。また、濃硫酸（沸点３３７℃）は他の酸類よりも著しく沸点が高いため、溶解温度を高く設定できる。濃硫酸を用いた場合、溶解温度は、好ましくは３５０℃から４００℃の範囲である。 In addition to hydrochloric acid, concentrated nitric acid (boiling point 83 ° C.), hydrofluoric acid (boiling point 96 ° C.), phosphoric acid (boiling point 158 ° C.) and the like can be used as appropriate. Concentrated sulfuric acid (boiling point 337 ° C.) has a remarkably higher boiling point than other acids, so that the dissolution temperature can be set high. When concentrated sulfuric acid is used, the dissolution temperature is preferably in the range of 350 ° C to 400 ° C.
（溶解時間）
溶解時間は複合酸化物中の貴金属合金が充分に溶解できれば特に制限はない。溶解させる貴金属の量や酸溶液の量、溶解温度等にもよるが、溶解時間は３０分から２４時間の範囲、より好ましくは１時間から１２時間の範囲、さらに好ましくは２時間から６時間の範囲である。
(Dissolution time)
The dissolution time is not particularly limited as long as the noble metal alloy in the composite oxide can be sufficiently dissolved. Depending on the amount of precious metal to be dissolved, the amount of acid solution, the dissolution temperature, etc., the dissolution time is in the range of 30 minutes to 24 hours, more preferably in the range of 1 hour to 12 hours, and still more preferably in the range of 2 hours to 6 hours. It is.
（容器の構造）
浸出工程に用いる容器は、用いる酸溶液を沸点以上で保持できれば材質や容量、構造等に特に制限はない。大気圧下で酸溶液を、その酸溶液の沸点以上の温度に保持することができない場合には、耐圧容器を用いることが好ましい。また、溶解処理中に発生する圧力は、用いる酸溶液の種類や保持温度、容器体積に対する酸溶液の充填率等に依存して変化し得るが、ボンベ等を用いて外部からの加圧を行ってもよい。
(Container structure)
The container used for the leaching step is not particularly limited in material, capacity, structure, etc., as long as the acid solution used can be maintained at a boiling point or higher. When the acid solution cannot be maintained at a temperature equal to or higher than the boiling point of the acid solution under atmospheric pressure, it is preferable to use a pressure vessel. In addition, the pressure generated during the dissolution treatment may vary depending on the type of acid solution used, the holding temperature, the filling rate of the acid solution relative to the container volume, etc., but external pressure is applied using a cylinder or the like. May be.
（溶解助剤の添加）
溶解工程において、酸溶液の他に溶解助剤として金属塩等を添加してもよい。複合酸化物中で酸化状態となっている貴金属は、酸溶液中の塩化物イオン等と錯形成して溶解する。そのため、塩化物イオン源等を酸溶液に添加することにより、貴金属の溶解を促進できる。溶解助剤は貴金属イオンと錯形成できればよく、例えば塩化物や硝酸塩、硫化物、硫酸塩、フッ化物、リン酸塩等を任意に添加できる。また、必要に応じてこれらのうち複数を添加してもよい。
(Addition of dissolution aid)
In the dissolution step, a metal salt or the like may be added as a dissolution aid in addition to the acid solution. The noble metal in an oxidized state in the complex oxide is dissolved by complex formation with chloride ions and the like in the acid solution. Therefore, the dissolution of the noble metal can be promoted by adding a chloride ion source or the like to the acid solution. The dissolution aid only needs to be able to form a complex with the noble metal ion. For example, chloride, nitrate, sulfide, sulfate, fluoride, phosphate, and the like can be arbitrarily added. Moreover, you may add two or more of these as needed.
（貴金属の分離精製及び回収）
浸出工程後の貴金属回収の手法については特に制限はなく、既存の分離精製方法等を適用することができる。本発明によれば貴金属錯イオンが溶解生成物となるため、溶媒抽出法、イオン交換樹脂法、沈殿析出法といった手法により貴金属を分離、抽出できる。
(Preparation and recovery of precious metals)
There is no particular limitation on the method for recovering the precious metal after the leaching step, and an existing separation and purification method or the like can be applied. According to the present invention, since the noble metal complex ions are dissolved products, the noble metals can be separated and extracted by a technique such as a solvent extraction method, an ion exchange resin method, or a precipitation method.
以下、実施例を挙げて本発明をさらに詳細に説明する。本実施例においては、複合酸化物を経由してもなお溶解が困難な貴金属合金を、沸点を以上の温度で塩酸に浸漬させることにより容易に溶解できることが明らかとなっているが、本発明は、提示された例に限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to examples. In this example, it is clear that a noble metal alloy that is still difficult to dissolve even through a complex oxide can be easily dissolved by immersing the boiling point in hydrochloric acid at the above temperature. It is not limited to the examples presented.
［Ｐｔ−Ｐｄ合金］
（実施例１−１〜実施例１−４）
（Ｐｔ−Ｐｄ合金とＬｉ塩との加熱（複合酸化物の形成））
貴金属合金としてＰｔ−Ｐｄ合金（Ｐｔ：８５重量％、Ｐｄ：１５重量％）２５０ｍｇと、Ｌｉ２ＣＯ３ ３７９ｍｇとを混合した。ここでは貴金属とＬｉとが完全に反応できるよう、貴金属合金に対して過剰量のＬｉ塩を用いた。貴金属に対するＬｉ塩の混合比、すなわち、Ｌｉ／（Ｐｔ＋Ｐｄ）は、原子比で７．２であった。次に、混合後の試料を、アルミナ製ボートに乗せて電気管状炉の炉芯管（いすゞ製作所製、ＥＰＫＲＯ−１３Ｋ、炉口径 ５０ｍｍ、長さ １０００ｍｍ）に挿入し、空気中、８００℃で所定時間加熱した。加熱時間は、実施例１−１は６時間、実施例１−２は１２時間、実施例１−３は１８時間、実施例１−４は２４時間であった。
[Pt-Pd alloy]
(Example 1-1 to Example 1-4)
(Pt—Pd alloy and Li salt heating (formation of composite oxide))
As a noble metal alloy, 250 mg of a Pt—Pd alloy (Pt: 85 wt%, Pd: 15 wt%) and 379 mg of Li 2 CO 3 were mixed. Here, an excessive amount of Li salt was used with respect to the noble metal alloy so that the noble metal and Li could react completely. The mixing ratio of Li salt to noble metal, that is, Li / (Pt + Pd) was 7.2 in atomic ratio. Next, the mixed sample was placed on an alumina boat and inserted into a furnace core tube (EPKRO-13K, furnace diameter 50 mm, length 1000 mm, manufactured by Isuzu Seisakusho), and predetermined in air at 800 ° C. Heated for hours. The heating time was 6 hours for Example 1-1, 12 hours for Example 1-2, 18 hours for Example 1-3, and 24 hours for Example 1-4.
（空気中で加熱処理を行って得た試料のＸＲＤプロファイル）
加熱処理（焼成）によって複合酸化物が形成できたことを確認するため、粉末エックス線回折（ＸＲＤ）測定を行った。図１（ａ）〜（ｃ）は８００℃でそれぞれ６時間、１２時間、２４時間加熱した試料（実施例１−１、実施例１−２、及び実施例１−４）のＸＲＤプロファイルであり、いずれも貴金属とリチウムとの複合酸化物であるＬｉ２ＰｔＯ３及びＬｉ２ＰｄＯ２に由来する回折ピークが確認できた。
(XRD profile of sample obtained by heat treatment in air)
Powder X-ray diffraction (XRD) measurement was performed in order to confirm that the composite oxide could be formed by heat treatment (firing). FIGS. 1A to 1C are XRD profiles of samples (Example 1-1, Example 1-2, and Example 1-4) heated at 800 ° C. for 6 hours, 12 hours, and 24 hours, respectively. In both cases, diffraction peaks derived from Li 2 PtO 3 and Li 2 PdO 2 which are complex oxides of noble metal and lithium were confirmed.
（Ｌｉ−Ｐｔ、Ｌｉ−Ｐｄ複合酸化物の塩酸溶解（貴金属成分の浸出））
実施例１−１〜実施例１−４で得た試料の全量（貴金属として２５０ｍｇ含有）と、１２Ｍ塩酸１０ｍＬとをＰＴＦＥ（ポリテトラフルオロエチレン）製の内筒（容量２５ｍＬ）に投入し、ステンレス製の耐圧外筒容器（三愛科学株式会社製、ＨＵ―２５）にマウントして密閉した後、１８０℃で２時間保持した。保持終了後、固液分離のためＰＴＦＥフィルタを用いて減圧濾過を行った。
(Li-Pt, Li-Pd composite oxide dissolved in hydrochloric acid (leaching of noble metal components))
The total amount of the sample obtained in Example 1-1 to Example 1-4 (containing 250 mg of noble metal) and 10 mL of 12 M hydrochloric acid were put into an inner cylinder (capacity 25 mL) made of PTFE (polytetrafluoroethylene), and stainless steel was added. After mounting and sealing on a pressure-resistant outer cylinder container (manufactured by Sanai Kagaku Co., Ltd., HU-25), it was kept at 180 ° C. for 2 hours. After completion of the holding, vacuum filtration was performed using a PTFE filter for solid-liquid separation.
２４時間加熱試料（実施例１−４）では固液分離後も残渣が確認されなかったことから、Ｐｔ、Ｐｄとも完全に溶解できたことがわかった。これに対して、６時間加熱試料、１２時間加熱試料、及び１８時間加熱試料（実施例１−１〜実施例１−３）では残渣が確認されたことから、誘導結合プラズマ発光分光分析法（ＩＣＰ−ＡＥＳ）により溶液試料中の貴金属濃度を分析し、溶解率を算出した。その結果、表１に示すように、６時間加熱試料（実施例１−１）ではＰｔ溶解率が２９．９重量％、Ｐｄ溶解率が２７．５重量％であった。また、１２時間加熱試料（実施例１−２）ではＰｔ溶解率が７１．１重量％、Ｐｄ溶解率が６８．８重量％であり、１８時間加熱試料（実施例１−３）ではＰｔ溶解率が７２．８重量％、Ｐｄ溶解率が７８．３重量％であった。 In the 24-hour heated sample (Example 1-4), no residue was confirmed even after solid-liquid separation, indicating that both Pt and Pd were completely dissolved. On the other hand, since the residue was confirmed in the 6-hour heated sample, the 12-hour heated sample, and the 18-hour heated sample (Example 1-1 to Example 1-3), inductively coupled plasma emission spectroscopy ( ICP-AES) analyzed the noble metal concentration in the solution sample, and calculated the dissolution rate. As a result, as shown in Table 1, the 6-hour heated sample (Example 1-1) had a Pt dissolution rate of 29.9% by weight and a Pd dissolution rate of 27.5% by weight. Further, the 12-hour heated sample (Example 1-2) has a Pt dissolution rate of 71.1% by weight and a Pd dissolution rate of 68.8% by weight, and the 18-hour heated sample (Example 1-3) has a Pt dissolution rate. The rate was 72.8% by weight, and the Pd dissolution rate was 78.3% by weight.
（実施例１−５〜実施例１−８）
加熱処理に対する酸素分圧の影響を調べるため、純酸素フロー及びエアフロー（毎分３００ｍＬ）を行った以外は、実施例１−１と同様の方法で複合酸化物を得た。但し、焼成温度の時間は、表１に示す通りとした。
(Example 1-5 to Example 1-8)
In order to investigate the influence of the oxygen partial pressure on the heat treatment, a composite oxide was obtained in the same manner as in Example 1-1 except that pure oxygen flow and air flow (300 mL per minute) were performed. However, the firing temperature time was as shown in Table 1.
（純酸素フローを行って得た試料のＸＲＤプロファイル）
図２（ａ）に純酸素フロー下、８００℃で１２時間加熱した試料（実施例１−７）のＸＲＤプロファイルを示す。また、図２（ｂ）にエアフロー下、８００℃で１２時間加熱（焼成）した試料（実施例１−８）のＸＲＤプロファイルを示す。実施例１−１〜実施例１−４と同様、Ｌｉ２ＰｔＯ３及びＬｉ２ＰｄＯ２が得られたことが分かった。
(XRD profile of sample obtained by pure oxygen flow)
FIG. 2A shows an XRD profile of a sample (Example 1-7) heated at 800 ° C. for 12 hours under a pure oxygen flow. FIG. 2B shows an XRD profile of a sample (Example 1-8) heated (baked) at 800 ° C. for 12 hours under airflow. Same manner as Examples 1-1 to 1-4, it was found that Li 2 PtO 3 and Li 2 PdO 2 was obtained.
（塩酸溶解の結果）
表１に示すように、純酸素フロー、空気フローを併用することにより、いずれの実施例も、同じ焼成時間のフローなしの実施例で得られた、ＰｔとＰｄの溶解率が共に増加した。純酸素フローを行って８００℃で１２時間の加熱により得た試料（実施例１−７）について、実施例１−１と同様の方法で溶解処理とＩＣＰ分析を行った結果、Ｐｔ溶解率は９７．３重量％、Ｐｄ溶解率は９８．８重量％であった。また、エアフロー（空気フロー）を行って得た試料（実施例１−８）についても同様に溶解処理とＩＣＰ分析を行った結果、Ｐｔ溶解率は９４．３重量％、Ｐｄ溶解率は８８．９重量％であり、試料中の貴金属の大半を溶解させることができた。実施例１−７及び実施例１−８（純酸素フローを行った試料及びエアフローを行った試料）では加熱時間を１２時間としており、フローを行わなかったこと以外は同じ条件で複合酸化物の形成を行った実施例１−２と比較して、溶解率が向上していることが分かった。また、実施例１−７及び実施例１−８はともに、フローを行わず加熱時間を２４時間とした場合（実施例１−４）と比較して加熱時間を約半分に短縮したものであるが、実施例１−４に近い高い溶解率で貴金属を塩酸へ溶解できるとわかった。
(Results of hydrochloric acid dissolution)
As shown in Table 1, the combined use of pure oxygen flow and air flow increased both the dissolution rates of Pt and Pd obtained in the examples with no flow for the same firing time. A sample (Example 1-7) obtained by performing pure oxygen flow and heating at 800 ° C. for 12 hours was subjected to dissolution treatment and ICP analysis in the same manner as in Example 1-1. It was 97.3% by weight, and the Pd dissolution rate was 98.8% by weight. In addition, the sample (Example 1-8) obtained by performing air flow (air flow) was similarly subjected to dissolution treatment and ICP analysis. As a result, the Pt dissolution rate was 94.3% by weight and the Pd dissolution rate was 88. It was 9% by weight, and most of the noble metals in the sample could be dissolved. In Example 1-7 and Example 1-8 (sample subjected to pure oxygen flow and sample subjected to air flow), the heating time was set to 12 hours, and the composite oxide was subjected to the same conditions except that the flow was not performed. It was found that the dissolution rate was improved as compared with the formed Example 1-2. Further, in both Example 1-7 and Example 1-8, the heating time was shortened to about half compared to the case where the flow was not performed and the heating time was 24 hours (Example 1-4). However, it turned out that a noble metal can be melt | dissolved in hydrochloric acid with the high dissolution rate close | similar to Example 1-4.
また、純酸素フローを行い加熱時間を１２時間よりも短くした場合（実施例１−５及び実施例１−６）であっても、Ｐｔ、Ｐｄについて共に５０％を超える十分な溶解率を得ることができた。加熱時間を９時間とした場合（実施例１−６）では、Ｐｔ溶解率は９４．８重量％、Ｐｄ溶解率は９１．４重量％であった。加熱時間を６時間とした場合（実施例１−５）では、Ｐｔ溶解率は６０．５重量％、Ｐｄ溶解率は５９．３重量％であった。 Moreover, even when pure oxygen flow is performed and the heating time is shorter than 12 hours (Example 1-5 and Example 1-6), a sufficient dissolution rate exceeding 50% is obtained for both Pt and Pd. I was able to. When the heating time was 9 hours (Example 1-6), the Pt dissolution rate was 94.8% by weight and the Pd dissolution rate was 91.4% by weight. When the heating time was 6 hours (Example 1-5), the Pt dissolution rate was 60.5% by weight and the Pd dissolution rate was 59.3% by weight.
（実施例１−９）
貴金属合金の組成を変えても複合酸化物の形成及び溶解が可能か検討した。Ｐｔ−Ｐｄ合金（Ｐｔ：８０重量％、Ｐｄ：２０重量％、２５０ｍｇ）とＬｉ２ＣＯ３（２２０．９ｍｇ）を実施例１−４と同様にして８００℃、２４時間加熱した。ここでＬｉ／（Ｐｔ＋Ｐｄ）比は４．０となる。
(Example 1-9)
It was investigated whether composite oxides could be formed and dissolved even when the composition of the noble metal alloy was changed. A Pt—Pd alloy (Pt: 80 wt%, Pd: 20 wt%, 250 mg) and Li 2 CO 3 (220.9 mg) were heated at 800 ° C. for 24 hours in the same manner as in Example 1-4. Here, the Li / (Pt + Pd) ratio is 4.0.
（Ｐｔ−Ｐｄ合金組成を変えて得た試料のＸＲＤプロファイル）
図３に、Ｐｔ−Ｐｄ合金組成を変えて得た試料（実施例１−９）のＸＲＤプロファイルを示す。実施例１−１〜実施例１−８と同様、Ｌｉ２ＰｔＯ３及びＬｉ２ＰｄＯ２が得られたことが分かった。
(XRD profile of a sample obtained by changing the Pt—Pd alloy composition)
FIG. 3 shows an XRD profile of a sample (Example 1-9) obtained by changing the Pt—Pd alloy composition. Same manner as Examples 1-1 to 1-8, it was found that Li 2 PtO 3 and Li 2 PdO 2 was obtained.
（塩酸溶解の結果）
実施例１−１と同様の方法で溶解処理とＩＣＰ分析を行った結果、実施例１−９においては、Ｐｔ溶解率は９９．４重量％、Ｐｄ溶解率は９６．７重量％であり、試料中の貴金属の大半を溶解させることができた。
(Results of hydrochloric acid dissolution)
As a result of performing dissolution treatment and ICP analysis in the same manner as in Example 1-1, in Example 1-9, the Pt dissolution rate was 99.4% by weight, and the Pd dissolution rate was 96.7% by weight. Most of the precious metals in the sample could be dissolved.
実施例１−１〜実施例１−９では、耐圧容器を用いて酸溶液の沸点以上で複合酸化物中の貴金属を浸出していた。これに対して、大気圧下、酸溶液の沸点を下回る低温で浸出を行った場合には、貴金属含有合金を完全に溶解させることは困難である。下記では比較のため、貴金属合金を複合酸化物へと変化させた後、大気圧下で浸出試験を行った結果について述べる。 In Example 1-1 to Example 1-9, the noble metal in the composite oxide was leached above the boiling point of the acid solution using a pressure vessel. On the other hand, when leaching is performed at a low temperature below the boiling point of the acid solution under atmospheric pressure, it is difficult to completely dissolve the noble metal-containing alloy. For comparison, the results of a leaching test under atmospheric pressure after changing a noble metal alloy into a composite oxide are described below.
（比較例１）
（Ｌｉ−Ｐｔ、Ｌｉ−Ｐｄ複合酸化物の塩酸溶解）
実施例１−４で得たものと同様の、８００℃２４時間加熱試料（Ｌｉ２ＰｔＯ３及びＬｉ２ＰｄＯ２を含む）の全量（貴金属として２５０ｍｇ含有）に１２Ｍ塩酸２０ｍＬを加え、撹拌子による撹拌を行いながら８０℃で９時間保持した後、固液分離を行い溶液試料と残渣を得た。
(Comparative Example 1)
(Li-Pt, Li-Pd composite oxide dissolved in hydrochloric acid)
20 mL of 12M hydrochloric acid was added to the total amount (containing 250 mg as a noble metal) of a heated sample (containing Li 2 PtO 3 and Li 2 PdO 2 ) similar to that obtained in Example 1-4 at 24O 0 C for 24 hours. After stirring for 9 hours at 80 ° C. with stirring, solid-liquid separation was performed to obtain a solution sample and a residue.
溶解試験後、残渣が確認されたことからＩＣＰ測定により溶液試料中の貴金属濃度を決定し、溶解率を算出した。その結果、Ｐｔ溶解率は３６．６重量％、Ｐｄ溶解率は５７．３重量％であった。 Since the residue was confirmed after the dissolution test, the concentration of noble metal in the solution sample was determined by ICP measurement, and the dissolution rate was calculated. As a result, the Pt dissolution rate was 36.6% by weight, and the Pd dissolution rate was 57.3% by weight.
（比較例２）
実施例１−７で得たものと同様の、純酸素フロー、８００℃１２時間加熱試料の全量（貴金属として２５０ｍｇ含有）を、比較例１と同様に塩酸へ溶解させた。溶解試験後、残渣が確認されたことからＩＣＰ測定により溶液試料中の貴金属濃度を決定し、溶解率を算出した。その結果、Ｐｔ溶解率は３３．１重量％、Ｐｄ溶解率は５６．３重量％であった。
(Comparative Example 2)
The same pure oxygen flow as that obtained in Example 1-7 and a heated sample at 800 ° C. for 12 hours (containing 250 mg of noble metal) was dissolved in hydrochloric acid in the same manner as in Comparative Example 1. Since the residue was confirmed after the dissolution test, the concentration of noble metal in the solution sample was determined by ICP measurement, and the dissolution rate was calculated. As a result, the Pt dissolution rate was 33.1% by weight, and the Pd dissolution rate was 56.3% by weight.
上記結果から、酸溶液の沸点を下回る低温という溶解条件の下では、酸溶液の沸点以上の高温で浸出を行った場合よりも溶解率が低く、貴金属含有合金を完全に溶解させることが困難であることが実証された。 From the above results, it is difficult to completely dissolve the noble metal-containing alloy under the dissolution condition of a low temperature lower than the boiling point of the acid solution, compared to the case where leaching is performed at a temperature higher than the boiling point of the acid solution. It was proved to be.
図４に、上記実施例１−１〜実施例１−９のうち代表的な実施例、及び比較例１、２について、Ｐｔの溶解率及びＰｄの溶解率をグラフで表した。同じ温度、同じ時間の焼成時間で比較すると、酸溶液の沸点以上である１８０℃で複合酸化物の浸出を行った例では、酸溶液の沸点を下回る８０℃で浸出を行った比較例よりも、Ｐｔ溶解率及びＰｄ溶解率が向上している点が、明らかとなっている。 FIG. 4 is a graph showing the dissolution rate of Pt and the dissolution rate of Pd for representative examples and Comparative Examples 1 and 2 among Examples 1-1 to 1-9. When compared at the same temperature and firing time at the same time, the example in which the composite oxide was leached at 180 ° C., which is higher than the boiling point of the acid solution, was compared with the comparative example in which leaching was performed at 80 ° C., which is lower than the boiling point of the acid solution. It is clear that the Pt dissolution rate and the Pd dissolution rate are improved.
以上のＰｔ−Ｐｄ合金についての結果を、表１にまとめる。 The results for the above Pt—Pd alloys are summarized in Table 1.
［Ｐｔ−Ｉｒ合金］
（実施例２−１〜実施例２−５）
Ｐｔ−Ｉｒ合金（Ｐｔ：８０重量％、Ｉｒ：２０重量％）２５０ｍｇと、Ｌｉ２ＣＯ３ １９０ｍｇとを混合した。Ｌｉ／（Ｐｔ＋Ｉｒ）は、原子比で４．０であった。得られた混合物を実施例１−１〜実施例１−４と同様にして空気中で、８００℃で所定時間加熱した。加熱時間は、実施例２−１は３時間、実施例２−２は６時間、実施例２−３は９時間、実施例２−４は１２時間、実施例２−５は２４時間であった。
[Pt-Ir alloy]
(Example 2-1 to Example 2-5)
250 mg of Pt—Ir alloy (Pt: 80 wt%, Ir: 20 wt%) and 190 mg of Li 2 CO 3 were mixed. Li / (Pt + Ir) was 4.0 in atomic ratio. The obtained mixture was heated in air at 800 ° C. for a predetermined time in the same manner as in Example 1-1 to Example 1-4. The heating time was 3 hours for Example 2-1, 6 hours for Example 2-2, 9 hours for Example 2-3, 12 hours for Example 2-4, and 24 hours for Example 2-5. It was.
（空気中で加熱処理を行って得た試料のＸＲＤプロファイル）
加熱処理によって複合酸化物が形成できたことを確認するため、ＸＲＤ測定を行った。図５（ａ）〜（ｅ）は、８００℃でそれぞれ３、６、９、１２、２４時間加熱した試料（実施例２−１〜実施例２−５）のＸＲＤプロファイルであり、いずれも貴金属とリチウムの複合酸化物であるＬｉ２ＰｔＯ３又はＬｉ２ＩｒＯ３に由来する回折ピークが確認できた。Ｌｉ２ＰｔＯ３とＬｉ２ＩｒＯ３は結晶学的に同形であり、ＸＲＤプロファイルはほぼ同じ形状を示す。そのため、生成物はＬｉ２ＰｔＯ３とＬｉ２ＩｒＯ３との混合物、又はＬｉ２（Ｐｔ，Ｉｒ）Ｏ３のような固溶体であったと考えられる。
(XRD profile of sample obtained by heat treatment in air)
In order to confirm that the complex oxide was formed by the heat treatment, XRD measurement was performed. FIGS. 5A to 5E are XRD profiles of samples (Example 2-1 to Example 2-5) heated at 800 ° C. for 3, 6, 9, 12, and 24 hours, respectively. A diffraction peak derived from Li 2 PtO 3 or Li 2 IrO 3 , which is a composite oxide of lithium and lithium, was confirmed. Li 2 PtO 3 and Li 2 IrO 3 are crystallographically isomorphic and the XRD profiles show almost the same shape. Therefore, the product is considered to be a mixture of Li 2 PtO 3 and Li 2 IrO 3 or a solid solution such as Li 2 (Pt, Ir) O 3 .
（Ｌｉ−Ｐｔ、Ｌｉ−Ｉｒ複合酸化物の塩酸溶解）
実施例２−１〜実施例２−５で得られた試料の全量を用いて実施例１−１〜実施例１−４と同様に溶解試験を行った。その結果、２４時間加熱試料（実施例２−５）では残渣が確認されなかったことから、Ｐｔ、Ｉｒとも完全に溶解できたことがわかった。
(Li-Pt, Li-Ir composite oxide dissolved in hydrochloric acid)
A dissolution test was performed in the same manner as in Example 1-1 to Example 1-4 using the entire amount of the sample obtained in Example 2-1 to Example 2-5. As a result, since no residue was confirmed in the 24-hour heated sample (Example 2-5), it was found that both Pt and Ir could be completely dissolved.
また、実施例２−５以外の試料では残渣が確認されたことから、ＩＣＰ分析により貴金属溶解率を算出した。その結果、３時間加熱試料（実施例２−１）ではＰｔ溶解率が２１．０重量％、Ｉｒ溶解率が２０．６重量％であった。６時間加熱試料（実施例２−２）ではＰｔ溶解率が５４．９重量％、Ｉｒ溶解率が５３．７重量％であった。また、９時間加熱試料（実施例２−３）ではＰｔ溶解率が７９．６重量％、Ｉｒ溶解率が７９．１重量％であった。１２時間加熱試料（実施例２−４）ではＰｔ溶解率が９９．２重量％、Ｐｄ溶解率が９８．４重量％であった。 Moreover, since the residue was confirmed in samples other than Example 2-5, the precious metal dissolution rate was computed by ICP analysis. As a result, in the sample heated for 3 hours (Example 2-1), the Pt dissolution rate was 21.0% by weight and the Ir dissolution rate was 20.6% by weight. The sample heated for 6 hours (Example 2-2) had a Pt dissolution rate of 54.9% by weight and an Ir dissolution rate of 53.7% by weight. The 9-hour heated sample (Example 2-3) had a Pt dissolution rate of 79.6% by weight and an Ir dissolution rate of 79.1% by weight. In the sample heated for 12 hours (Example 2-4), the Pt dissolution rate was 99.2% by weight and the Pd dissolution rate was 98.4% by weight.
（実施例２−６）
次に、低濃度の塩酸を用いて複合酸化物中に存在する貴金属を溶出できるかについて試験した。実施例２−５における焼成によって得られた試料と同じ試料を、３Ｍ塩酸を用いた以外は実施例１−１と同様の手法にて溶解試験を行った。溶解試験後、残渣が確認されたことからＩＣＰ測定により溶液試料中の貴金属濃度を決定し、溶解率を算出した。その結果、Ｐｔ溶解率は７１．９重量％、Ｉｒ溶解率は７６．１重量％であった。
(Example 2-6)
Next, it was tested whether the noble metal which exists in complex oxide can be eluted using low concentration hydrochloric acid. The same sample as the sample obtained by baking in Example 2-5 was subjected to a dissolution test in the same manner as in Example 1-1 except that 3M hydrochloric acid was used. Since the residue was confirmed after the dissolution test, the concentration of noble metal in the solution sample was determined by ICP measurement, and the dissolution rate was calculated. As a result, the Pt dissolution rate was 71.9% by weight, and the Ir dissolution rate was 76.1% by weight.
一般に、Ｐｔ−Ｉｒ合金は王水に対しても溶解が極めて困難であり、合金中のＩｒ濃度が高いほど酸への溶解速度が低下する。しかも、本実施例で用いたＰｔ８０重量％、Ｉｒ２０重量％という合金組成は、実用されるＰｔ−Ｉｒ合金の中でもＩｒ濃度が最も高いものである。本発明によれば、このような難溶性貴金属を多量に含む合金でさえ、王水を用いることなく、且つ比較的低濃度の酸に容易に溶解させることができる。 In general, a Pt—Ir alloy is very difficult to dissolve even in aqua regia, and the higher the Ir concentration in the alloy, the lower the dissolution rate in acid. In addition, the alloy composition of 80% by weight of Pt and 20% by weight of Ir used in this example has the highest Ir concentration among the practical Pt—Ir alloys. According to the present invention, even an alloy containing a large amount of such a hardly soluble noble metal can be easily dissolved in a relatively low acid without using aqua regia.
（比較例３）
（Ｌｉ−Ｐｔ、Ｌｉ−Ｉｒ複合酸化物の塩酸溶解）
実施例２−５における空気中での焼成によって得られた８００℃２４時間加熱試料（Ｌｉ２ＰｔＯ３及びＬｉ２ＩｒＯ３を含む）の全量を、比較例１と同様に塩酸へ溶解させた。つまり、耐圧容器を用いず、１２Ｍ塩酸に８０℃で９時間の条件で浸出を行った。溶解試験後、残渣が確認されたことからＩＣＰ測定により溶液試料中の貴金属濃度を決定し、溶解率を算出した。その結果、Ｐｔ溶解率は８．４重量％、Ｉｒ溶解率は１０．７重量％であった。
(Comparative Example 3)
(Li-Pt, Li-Ir composite oxide dissolved in hydrochloric acid)
The total amount of the 800 ° C. 24-hour heated sample (including Li 2 PtO 3 and Li 2 IrO 3 ) obtained by firing in air in Example 2-5 was dissolved in hydrochloric acid in the same manner as in Comparative Example 1. That is, leaching was performed in 12 M hydrochloric acid at 80 ° C. for 9 hours without using a pressure vessel. Since the residue was confirmed after the dissolution test, the concentration of noble metal in the solution sample was determined by ICP measurement, and the dissolution rate was calculated. As a result, the Pt dissolution rate was 8.4% by weight and the Ir dissolution rate was 10.7% by weight.
比較例３から、難溶性貴金属であるＩｒが含まれる場合、酸溶液の沸点を下回る低温の溶解条件のもとでは、貴金属の完全溶解は困難であるとわかった。 From Comparative Example 3, it was found that when Ir, which is a hardly soluble noble metal, is contained, complete dissolution of the noble metal is difficult under low temperature dissolution conditions below the boiling point of the acid solution.
図６に、上記実施例２−１〜実施例２−６及び比較例３について、Ｐｔの溶解率及びＩｒの溶解率をグラフで表した。酸溶液の沸点以上である１８０℃で複合酸化物の浸出を行った実施例２−１〜実施例２−６では、酸溶液の沸点を下回る８０℃で９時間の浸出を行った比較例３よりも、Ｐｔ溶解率及びＩｒ溶解率が向上している点が、明らかとなっている。 FIG. 6 is a graph showing the dissolution rate of Pt and the dissolution rate of Ir for Example 2-1 to Example 2-6 and Comparative Example 3. In Example 2-1 to Example 2-6 in which the complex oxide was leached at 180 ° C., which is higher than the boiling point of the acid solution, Comparative Example 3 in which leaching was performed for 9 hours at 80 ° C. below the boiling point of the acid solution. It is clear that the Pt dissolution rate and the Ir dissolution rate are improved.
以上のＰｔ−Ｉｒ合金についての結果を、表２にまとめる。 The results for the above Pt—Ir alloys are summarized in Table 2.
［Ｐｔ−Ｒｈ合金］
（実施例３−１〜実施例３−５）
Ｐｔ−Ｒｈ合金（Ｐｔ：９０重量％、Ｒｈ：１０重量％）２５０ｍｇと、Ｌｉ２ＣＯ３ ２０６ｍｇとを混合した。Ｌｉ／（Ｐｔ＋Ｒｈ）は、原子比で４．０であった。得られた混合物を実施例１−１と同様にして空気中で８００℃で所定時間加熱した。加熱時間は、実施例３−１は３時間、実施例３−２は６時間、実施例３−３は９時間、実施例３−４は１２時間、実施例３−５は２４時間であった。
[Pt-Rh alloy]
(Example 3-1 to Example 3-5)
250 mg of Pt—Rh alloy (Pt: 90 wt%, Rh: 10 wt%) was mixed with 206 mg of Li 2 CO 3 . Li / (Pt + Rh) was 4.0 in atomic ratio. The obtained mixture was heated in air at 800 ° C. for a predetermined time in the same manner as in Example 1-1. The heating time was 3 hours for Example 3-1, 6 hours for Example 3-2, 9 hours for Example 3-3, 12 hours for Example 3-4, and 24 hours for Example 3-5. It was.
（空気中で加熱処理を行って得た試料のＸＲＤプロファイル）
加熱処理によって複合酸化物が形成できたことを確認するため、ＸＲＤ測定を行った。図７（ａ）〜（ｅ）は、８００℃でそれぞれ３、６、９、１２、２４時間加熱した試料（実施例３−１〜実施例３−５）のＸＲＤプロファイルであり、いずれも貴金属とリチウムの複合酸化物であるＬｉ２ＰｔＯ３又はＬｉ２ＲｈＯ３に由来する回折ピークが確認できた。Ｌｉ２ＰｔＯ３とＬｉ２ＲｈＯ３は結晶学的に同形であり、ＸＲＤプロファイルはほぼ同じ形状を示す。そのため、生成物はＬｉ２ＰｔＯ３とＬｉ２ＲｈＯ３との混合物、又はＬｉ２（Ｐｔ，Ｒｈ）Ｏ３のような固溶体であったと考えられる。
(XRD profile of sample obtained by heat treatment in air)
In order to confirm that the complex oxide was formed by the heat treatment, XRD measurement was performed. 7A to 7E are XRD profiles of samples (Examples 3-1 to 3-5) heated at 800 ° C. for 3, 6, 9, 12, and 24 hours, respectively, and all are noble metals. A diffraction peak derived from Li 2 PtO 3 or Li 2 RhO 3 , which is a composite oxide of lithium and lithium, was confirmed. Li 2 PtO 3 and Li 2 RhO 3 are crystallographically isomorphic, and the XRD profiles show almost the same shape. Therefore, it is considered that the product was a mixture of Li 2 PtO 3 and Li 2 RhO 3 or a solid solution such as Li 2 (Pt, Rh) O 3 .
（Ｌｉ−Ｐｔ、Ｌｉ−Ｒｈ複合酸化物の塩酸溶解）
実施例３−１〜実施例３−５で得られた試料の全量を用いて、実施例１−１と同様に溶解試験を行った。その結果、いずれも残渣が確認されたことから、ＩＣＰ分析により貴金属溶解率を算出した。その結果、３時間加熱試料（実施例３−１）ではＰｔ溶解率が３７．２重量％、Ｒｈ溶解率が３７．７重量％であった。また、６時間加熱試料（実施例３−２）ではＰｔ溶解率が６５．９重量％、Ｒｈ溶解率が６７．９重量％であった。９時間加熱試料（実施例３−３）ではＰｔ溶解率が８８．６重量％、Ｒｈ溶解率が９０．６重量％であった。１２時間加熱試料（実施例３−４）ではＰｔ溶解率９１．３重量％、Ｒｈ溶解率が９３．６重量％であった。２４時間加熱試料（実施例３−５）ではＰｔ溶解率７６．５重量％、Ｒｈ溶解率が７４．７重量％であった。
(Li-Pt, Li-Rh composite oxide dissolved in hydrochloric acid)
A dissolution test was performed in the same manner as in Example 1-1, using the entire amount of the sample obtained in Example 3-1 to Example 3-5. As a result, since any residue was confirmed, noble metal dissolution rate was calculated by ICP analysis. As a result, the 3-hour heated sample (Example 3-1) had a Pt dissolution rate of 37.2% by weight and an Rh dissolution rate of 37.7% by weight. Further, in the 6-hour heated sample (Example 3-2), the Pt dissolution rate was 65.9% by weight and the Rh dissolution rate was 67.9% by weight. In the 9-hour heated sample (Example 3-3), the Pt dissolution rate was 88.6% by weight and the Rh dissolution rate was 90.6% by weight. In the sample heated for 12 hours (Example 3-4), the Pt dissolution rate was 91.3 wt% and the Rh dissolution rate was 93.6 wt%. In the 24-hour heated sample (Example 3-5), the Pt dissolution rate was 76.5% by weight, and the Rh dissolution rate was 74.7% by weight.
以上の結果から、酸溶液の沸点以上の高温で溶解処理（浸出処理）を行うことにより、王水を用いることなく、Ｐｔ−Ｒｕ合金からＰｔ及びＲｕを十分に浸出させることができることが分かった。なお、Ｐｔ−Ｒｕ合金では、１８０℃、２時間という溶解条件の下では、１２時間加熱試料が最も高い溶解率を示すことが分かった。 From the above results, it was found that Pt and Ru can be sufficiently leached from the Pt—Ru alloy without using aqua regia by performing dissolution treatment (leaching treatment) at a temperature higher than the boiling point of the acid solution. . In the case of the Pt—Ru alloy, it was found that the sample heated for 12 hours showed the highest dissolution rate under the melting condition of 180 ° C. for 2 hours.
（実施例３−６）
実施例３−５における２４時間の焼成により得られた試料と同じ試料を用いて、溶解温度を１８０℃から２００℃に変えて実施例１−１と同様に塩酸による溶解試験を行った。その結果、残渣が確認されなかったことから、溶解条件を変更することで、試料中のＰｔ及びＲｈを完全に溶解できることが分かった。
(Example 3-6)
Using the same sample as the sample obtained by firing for 24 hours in Example 3-5, the dissolution temperature was changed from 180 ° C. to 200 ° C., and a dissolution test with hydrochloric acid was performed in the same manner as in Example 1-1. As a result, since a residue was not confirmed, it was found that Pt and Rh in the sample could be completely dissolved by changing the dissolution conditions.
（実施例３−７）
次に、比較的低濃度の塩酸を用いて複合酸化物中に存在する貴金属を溶出できるか試験した。実施例３−５で得られた試料の全量を、３Ｍ塩酸を用いた以外は、実施例１−１と同様の手法にて溶解試験を行った。溶解試験後、残渣が確認されたことからＩＣＰ測定により溶液試料中の貴金属濃度を決定し、溶解率を算出した。その結果、Ｐｔ溶解率は１．８重量％、Ｒｈ溶解率は１．１重量％であった。
(Example 3-7)
Next, it was tested whether the noble metal which exists in complex oxide could be eluted using comparatively low concentration hydrochloric acid. A dissolution test was performed on the total amount of the sample obtained in Example 3-5 in the same manner as in Example 1-1 except that 3M hydrochloric acid was used. Since the residue was confirmed after the dissolution test, the concentration of noble metal in the solution sample was determined by ICP measurement, and the dissolution rate was calculated. As a result, the Pt dissolution rate was 1.8% by weight and the Rh dissolution rate was 1.1% by weight.
（比較例４）
（Ｌｉ−Ｐｔ、Ｌｉ−Ｒｈ複合酸化物の塩酸溶解）
実施例３−５で得た８００℃２４時間加熱試料（Ｌｉ２ＰｔＯ３及びＬｉ２ＲｈＯ３を含む）の全量を比較例１と同様に塩酸へ溶解させた。つまり、耐圧容器を用いず、１２Ｍ塩酸に８０℃、９時間の条件で貴金属成分の浸出を行った。溶解試験後、残渣が確認されたことからＩＣＰ測定により溶液試料中の貴金属濃度を決定し、溶解率を算出した。その結果、Ｐｔ溶解率は０．６重量％、Ｒｈ溶解率は０．５重量％であった。
(Comparative Example 4)
(Li-Pt, Li-Rh composite oxide dissolved in hydrochloric acid)
The whole amount of the sample heated at 800 ° C. for 24 hours (including Li 2 PtO 3 and Li 2 RhO 3 ) obtained in Example 3-5 was dissolved in hydrochloric acid in the same manner as in Comparative Example 1. That is, the precious metal component was leached into 12 M hydrochloric acid at 80 ° C. for 9 hours without using a pressure vessel. Since the residue was confirmed after the dissolution test, the concentration of noble metal in the solution sample was determined by ICP measurement, and the dissolution rate was calculated. As a result, the Pt dissolution rate was 0.6% by weight and the Rh dissolution rate was 0.5% by weight.
比較例４の結果から、難溶性貴金属であるＲｈが含まれる場合、酸溶液の沸点以上での溶解処理が必要であり、常温での貴金属の完全溶解は困難であるとわかった。この比較例４の結果は、３Ｍ塩酸を用いた上記実施例３−７と比較した場合、Ｐｔ、Ｒｈ溶解率共に下回っている。この比較より、実施例３−７のような、酸溶液の沸点以上である温度で貴金属成分の浸出を行う方法では、希塩酸を用いた場合であっても、１２Ｍ塩酸を用いるが酸溶液の沸点を下回る温度で浸出を行った場合（比較例４）と比較して、より高い貴金属溶解率を達成できることがわかった。 From the results of Comparative Example 4, it was found that when Rh, which is a hardly soluble noble metal, is contained, a dissolution treatment at a temperature equal to or higher than the boiling point of the acid solution is necessary, and complete dissolution of the noble metal at room temperature is difficult. The result of Comparative Example 4 is lower than both the Pt and Rh dissolution rates when compared with Example 3-7 using 3M hydrochloric acid. From this comparison, in the method of leaching the noble metal component at a temperature equal to or higher than the boiling point of the acid solution as in Example 3-7, even when dilute hydrochloric acid is used, 12M hydrochloric acid is used, but the boiling point of the acid solution is It was found that a higher precious metal dissolution rate can be achieved as compared with the case where leaching is performed at a temperature lower than (Comparative Example 4).
以上のＰｔ−Ｒｈ合金についての結果を、表３にまとめる。 The results for the above Pt—Rh alloys are summarized in Table 3.
［Ｐｔ−Ｒｕ合金］
（実施例４）
カーボン粉末に担持したＰｔ−Ｒｕ合金（Ｐｔ含有率：３２．４重量％、Ｒｕ含有率１６．８重量％）２５０ｍｇと、Ｌｉ２ＣＯ３ ２４６ｍｇとを混合した。Ｌｉ／（Ｐｔ＋Ｒｕ）は原子比で４．０であった。得られた混合物を実施例１−１と同様にして、８００℃で加熱したが、焼成時間は１時間とした。
[Pt-Ru alloy]
Example 4
250 mg of a Pt—Ru alloy (Pt content: 32.4 wt%, Ru content 16.8 wt%) supported on carbon powder and 246 mg of Li 2 CO 3 were mixed. Li / (Pt + Ru) was 4.0 by atomic ratio. The obtained mixture was heated at 800 ° C. in the same manner as in Example 1-1, but the firing time was 1 hour.
（空気中で加熱処理を行って得た試料のＸＲＤプロファイル）
加熱処理によって複合酸化物が形成できたことを確認するため、ＸＲＤ測定を行った。図９は、８００℃で１時間加熱した試料（実施例４）のＸＲＤプロファイルであり、貴金属とリチウムの複合酸化物であるＬｉ２ＰｔＯ３、及びＬｉ２ＲｕＯ３に由来する回折ピークが確認できた。
(XRD profile of sample obtained by heat treatment in air)
In order to confirm that the complex oxide was formed by the heat treatment, XRD measurement was performed. FIG. 9 is an XRD profile of a sample (Example 4) heated at 800 ° C. for 1 hour, and diffraction peaks derived from Li 2 PtO 3 and Li 2 RuO 3 which are complex oxides of noble metal and lithium can be confirmed. It was.
（Ｌｉ−Ｐｔ、Ｌｉ−Ｒｕ複合酸化物の塩酸溶解）
実施例４で得られた試料の全量を用いて、実施例１−１と同様に溶解試験を行った。その結果、残渣が確認されなかったことから、Ｐｔ、Ｒｕとも完全に溶解できたことがわかった。
(Li-Pt, Li-Ru composite oxide dissolved in hydrochloric acid)
Using the entire amount of the sample obtained in Example 4, a dissolution test was performed in the same manner as in Example 1-1. As a result, since no residue was confirmed, it was found that both Pt and Ru could be completely dissolved.
以上のＰｔ−Ｒｕ合金についての結果を、表４にまとめる。 The results for the above Pt—Ru alloys are summarized in Table 4.
本発明は廃材等に含まれる貴金属合金から貴金属成分を回収するリサイクル分野への利用が見込まれる。 The present invention is expected to be used in the recycling field for recovering precious metal components from precious metal alloys contained in waste materials and the like.
Claims (5)
前記複合酸化物と酸溶液とを、当該酸溶液の、大気圧下における沸点から４００℃までの温度範囲で接触させ、前記酸溶液中に貴金属成分を浸出させる浸出工程と
を有することを特徴とする貴金属の回収方法。 A composite oxide forming step of mixing an alloy containing a noble metal and lithium carbonate and heating to form a composite oxide containing the noble metal and lithium;
A leaching step of bringing the complex oxide into contact with the acid solution in a temperature range of the acid solution from a boiling point under atmospheric pressure to 400 ° C., and leaching a noble metal component into the acid solution. To collect precious metals.
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