JP7056887B2 - Platinum group metal precipitation separation method - Google Patents

Description

The present invention relates to a method for precipitating and separating a platinum group metal, and more particularly to a method for precipitating and separating a platinum group metal, which comprises selectively precipitating and separating rhodium using a compound having a diaminodiphenyl structure as a precipitating agent.

Platinum group metals are used as catalysts for purifying exhaust gas from automobiles, and are also widely used as catalysts for the chemical industry such as petrochemical and pharmaceutical manufacturing, and are known as extremely useful elements. Since the platinum group metal is abundant and expensive, a technique for efficiently recovering and separating the platinum group metal is required in the purification process in which the platinum group metal is mixed in the solution.

Among them, rhodium is a metal that is difficult to separate, so it is important to develop a separation technique that is selective for rhodium.
As one of the simple recovery methods for rhodium, there is a precipitation method using ammonium chloride and sodium nitrite or ammonium nitrite, but in a solution containing a platinum group metal that can be precipitated with ammonia such as platinum or palladium, first use them. Separate and recover rhodium as ammonium nitrite (Patent Document 1, Non-Patent Document 1).

As another rhodium precipitation separation method, there is a method of adding a thiol compound, a thiourea compound, or the like to a hydrochloric acid solution. In this method, palladium and platinum can also be precipitated, and these platinum group metals are precipitated preferentially over rhodium, so that they are not suitable for use in the selective separation of rhodium (Non-Patent Document 2). ).

As described above, in the conventional separation method, when trying to recover rhodium from a solution in which palladium and platinum coexist, it is necessary to separate palladium and platinum first.
As a precipitation separation method selective for rhodium, a method using a compound having benzanilide or metaphenylenediamine as a skeleton has been developed in recent years (Patent Document 2, Non-Patent Document 3-4). This method is suitable for selective recovery from a dilute solution having a rhodium concentration of about 1 mM, but its applicability to separation from a solution containing a higher concentration of rhodium of about 0.1 M is unclear. Further, considering the high cost of the recovered metal and the cost of the reagent, there is a concern that the recovery rate is about 90% and that 10 to 20 equivalents of the precipitating agent is required for the precipitation of rhodium.

As mentioned above, there are few selective and efficient separation methods for rhodium. On the other hand, as the order of separating platinum group metals, it is preferable to separate them from more expensive metals according to the market price. Therefore, if a separation technique for selectively precipitating rhodium in a hydrochloric acid solution from other platinum group metals can be developed, a purification process for platinum group metals whose separation order can be fluidly changed according to the market value of the platinum group metals can be constructed. Is also possible.

Japanese Patent Application Laid-Open No. 2015-190000 Japanese Unexamined Patent Publication No. 2017-178409

Junji Shibata, Akihiko Okuda, Resources and Materials, Vol.118, pp.1-8 (2002) J.E. Currah, W.A.E. Mcbryde, F.E. Beamish, Ind. Eng. Chem., Vol.18, pp.120-122 (1946) Katsuyuki Ishibashi, Sumito Yamakawa, Kazutoshi Haga, Kazuya Matsumoto, Mitsutoshi Terasakai, Atsushi Shibayama, Lectures on Resources and Materials, Vol.4, PY1-39 (2017) Kazutoshi Haga, Katsuyuki Ishibashi, Sumito Yamakawa, Kazuya Matsumoto, Mitsutoshi Terasakai, Atsushi Shibayama, Lectures on Resources and Materials, Vol.4,3211-22-06 (2017)

A first object of the present invention is to provide a precipitating agent capable of selectively and efficiently separating rhodium from a hydrochloric acid solution containing a platinum group metal. The second aspect of the present invention is to facilitate the recovery of platinum group metals other than rhodium contained in the solution by selectively and efficiently separating rhodium from the hydrochloric acid solution containing the platinum group metal. The purpose.

As a result of diligent studies to develop a precipitating agent that satisfies the above conditions, the present inventors have added a compound having a diaminodiphenyl structure to a hydrochloric acid solution containing a platinum group metal, depending on the concentration of hydrochloric acid. The present invention has been completed by finding that ions of a divalent, trivalent or tetravalent platinum group metal or ions of a trivalent platinum group metal can be selectively precipitated.
In the purification of platinum group metal concentrates derived from ores containing platinum group metals, industrial waste, etc., usually, these concentrates are treated with hydrochloric acid / chlorine gas to obtain a hydrochloric acid solution containing platinum group metals. Platinum group metals are separated and recovered from here, but since osmium is usually removed by dissolution treatment with hydrochloric acid / chlorine gas, palladium is divalent, rhodium is trivalent, and platinum is contained in the hydrochloric acid solution. Exists as a tetravalent ion. Iridium and ruthenium can be trivalent and tetravalent, but can easily be tetravalent.
Therefore, according to the method of the present invention, all platinum group metals or rhodium can be selectively precipitated and separated from the hydrochloric acid solution containing the platinum group metal.

（上記一般式中、Ｒ_１のうち２つ及びＲ_３のうち２つはアミノ基であり、その他のＲ_１及びＲ_３は水素原子又は炭素数１～６の炭化水素基である。Ｒ_２は、直接結合又は炭素数１～６のアルキレン基である。）
〈3〉３価のロジウムを沈殿させることを特徴とする、〈1〉又は〈2〉に記載の沈殿分離方法。
〈4〉前記３価の白金族金属を含む溶液の塩酸濃度が５Ｍ以上であることを特徴とする、〈1〉～〈3〉のいずれかに記載の沈殿分離方法。
〈5〉白金族金属のイオンを含有する塩酸溶液が、少なくともロジウムイオンとその他の白金族金属（白金，パラジウム，イリジウム、ルテニウム）のイオンを１種以上含有することを特徴とする、〈1〉～〈4〉のいずれか記載の沈殿分離方法。
〈6〉沈殿した金属を１０Ｍ 以上の塩酸で沈殿物中から溶出し、回収することを特徴とする、〈1〉～〈5〉のいずれか記載の沈殿分離方法。 That is, the present application provides the following inventions.
<1> A method for separating platinum group metal ions by precipitating from a hydrochloric acid solution containing platinum group metal ions, using a compound having a diaminodiphenyl structure as a precipitating agent and divalent in the hydrochloric acid solution. A separation method comprising precipitating ions of a trivalent or tetravalent platinum group metal or trivalent rhodium.
<2> The precipitation separation method according to <1>, wherein the precipitating agent having a diaminodiphenyl structure is a compound represented by the following general formula.

(In the above general formula, two of R ₁ and _two of R ₃ are amino groups, and the other R ₁ and R ₃ are hydrogen atoms or hydrocarbon groups having 1 to 6 carbon atoms. Is a direct bond or an alkylene group having 1 to 6 carbon atoms.)
<3> The precipitation separation method according to <1> or <2>, which comprises precipitating trivalent rhodium .
<4> The precipitation separation method according to any one of <1> to <3>, wherein the solution containing the trivalent platinum group metal has a hydrochloric acid concentration of 5 M or more.
<5> A hydrochloric acid solution containing an ion of a platinum group metal contains at least one rhodium ion and one or more ions of another platinum group metal (platinum, palladium, iridium, ruthenium), <1>. The precipitation separation method according to any one of <4>.
<6> The precipitation separation method according to any one of <1> to <5>, wherein the precipitated metal is eluted from the precipitate with hydrochloric acid of 10 M or more and recovered.

According to the present invention, a compound having a diaminodiphenyl structure is added to a hydrochloric acid solution containing a platinum group metal to form a divalent, trivalent or tetravalent platinum group metal ion or a trivalent platinum group metal ion. The divalent, trivalent, or tetravalent platinum group metal or trivalent platinum group metal can be separated directly from the hydrochloric acid solution containing the ion of the platinum group metal.
In particular, in the case of a hydrochloric acid solution of 7 M or more, only trivalent platinum group ions can be selectively precipitated, whereby rhodium can be directly separated from the hydrochloric acid solution containing a platinum group metal.
According to the present invention, it is contained in the solution by removing the ion of the divalent, trivalent or tetravalent platinum group metal or the ion of the trivalent platinum group metal from the solution containing the platinum group metal by the above method. Separation of other platinum group metals can be facilitated.

It is a graph which showed the precipitation rate of rhodium, platinum, and palladium in the hydrochloric acid solution of 0.5-10M measured in Example 1. It is a graph which showed the rhodium precipitation rate for each addition amount of the precipitating agent measured in Example 2. FIG. It is a graph which showed the redissolution and recovery rate of rhodium from the precipitate measured in Example 3 with concentrated hydrochloric acid.

The specific type of platinum group metal to be separated by the precipitation separation method of the present invention is not particularly limited, and can be appropriately selected depending on the intended purpose.
<Rhodium precipitation separation method>

（上記一般式中、Ｒ_１のうち２つ及びＲ_３のうち２つはアミノ基であり、その他のＲ_１及びＲ_３は水素原子又は炭素数１～６の炭化水素基である。Ｒ_２は直接結合又は炭素数１～６のアルキレン基である。）
上記一般式で表される構造は、低塩酸濃度では、アミノ基の窒素と２価、３価、４価の白金族イオンが配位結合により金属錯体を形成し、沈殿する。
より高濃度の塩酸濃度領域では、ジアミノジフェニル構造を有する化合物は、４つのアミノ基の水素付加により、アンモニウムの形態をとり、４価のカチオンになる。一方、白金族金属のイオンは、２価が［ＭＣｌ_４］^２－、４価が［ＭＣｌ_６］^２－の－２価の塩化物アニオンとして、また、３価が［ＭＣｌ_６］^３－の－３価の塩化物アニオンとして存在する。通常、金属錯体の沈殿物は、分子間相互作用により錯体同士が集まったクラスターである。カチオンとアニオンから構成される錯体は、電荷の中和によって０価になる。ジアミノジフェニル構造を有する化合物の四塩酸塩は、白金族金属の塩化物アニオンに対し、分子間水素結合により相互作用する架橋配位子になることが推測される。－２価の白金族金属の塩化物アニオンの場合は、－２価のアニオンと＋４価のカチオンが架橋構造を形成しようとすると電荷の中和ができない。一方、－３価の塩化物アニオンの場合は、構造中に－１価の塩素イオンを取り込み安定化することにより、－４価となるため、それが可能である。そのため、上記一般式の化合物は、低塩酸濃度では、２価、３価、４価の白金族イオン、高塩酸濃度では３価の白金族イオンの沈殿分離に非常に適していると考えられる。
本発明の沈殿法は、塩酸溶液から特別な処理を必要とせず、ロジウムを沈殿させることができ、回収に特に適しているといえる。 As a result of diligent studies for an efficient separation method for platinum group metals, the present inventors have added a compound represented by the following general formula to a hydrochloric acid solution containing a platinum group metal to obtain divalent and trivalent. It has been found that tetravalent platinum group metal ions or trivalent platinum group ions can be selectively precipitated.

(In the above general formula, two of R ₁ and _two of R ₃ are amino groups, and the other R ₁ and R ₃ are hydrogen atoms or hydrocarbon groups having 1 to 6 carbon atoms. Is a direct bond or an alkylene group having 1 to 6 carbon atoms.)
In the structure represented by the above general formula, at a low hydrochloric acid concentration, nitrogen of an amino group and divalent, trivalent, or tetravalent platinum group ions form a metal complex by a coordinate bond and precipitate.
In the higher hydrochloric acid concentration region, the compound having a diaminodiphenyl structure takes the form of ammonium by hydrogenation of four amino groups and becomes a tetravalent cation. On the other hand, the platinum group metal ion has a divalent value of [MCl ₄ ] 2-2 and a tetravalent value of [MCl ₆ ] ^2- as a ² -valent chloride anion, and a trivalent value of [MCl ₆ ] ^3- . It exists as a -3-valent chloride anion. Usually, the precipitate of a metal complex is a cluster in which the complexes are gathered by an intramolecular interaction. The complex composed of cations and anions becomes zero valence by neutralizing the charge. It is speculated that the tetrahydrochloride of the compound having a diaminodiphenyl structure becomes a bridging ligand that interacts with the chloride anion of the platinum group metal by an intermolecular hydrogen bond. In the case of a chloride anion of a divalent platinum group metal, the charge cannot be neutralized when the divalent anion and the +4 cation try to form a crosslinked structure. On the other hand, in the case of a -3-valent chloride anion, it is possible because it becomes -4 valent by incorporating and stabilizing a -1 valent chlorine ion in the structure. Therefore, it is considered that the compound of the above general formula is very suitable for precipitation separation of divalent, trivalent and tetravalent platinum group ions at a low hydrochloric acid concentration and trivalent platinum group ions at a high hydrochloric acid concentration.
It can be said that the precipitation method of the present invention is particularly suitable for recovery because rhodium can be precipitated from a hydrochloric acid solution without requiring any special treatment.

The hydrochloric acid solution to be treated by the precipitation method of the present invention may contain other elements as long as it contains rhodium to be separated. Examples of other elements include platinum group metals such as palladium (Pd), platinum (Pt), iridium (Ir), and ruthenium (Ru).

The hydrochloric acid concentration at the time of precipitating rhodium is usually in the range of 0.5 to 10 M, preferably 7.0 M or more. Within the above range, rhodium can be easily collected efficiently. Especially when it is 7.0 M or more, rhodium is selectively precipitated. The hydrochloric acid concentration for precipitating platinum and palladium is usually in the range of 0.5 to 5.0 M, preferably 3.0 M or less, and more preferably 1.0 M or less. Within the above range, platinum and palladium can be easily collected efficiently.
Within the above range, ions of these platinum group metals can be efficiently collected.

The concentration of divalent, trivalent or tetravalent platinum group ions such as palladium, platinum and rhodium to be precipitated in a hydrochloric acid solution is usually larger than 0 M and in the range of 1.0 M or less.

The amount of the precipitant added when precipitating the platinum group metal is 2 equivalents or more, more preferably 3 equivalents or more, with respect to the concentration of the dissolved platinum group metal.

Hereinafter, the present invention will be described in more detail with reference to examples, but these can be appropriately modified as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limiting by the specific examples shown below.

図１に示すとおり、塩酸濃度が５Ｍ以下では、パラジウム、白金、ロジウムを沈殿させるが、７Ｍ以上では、ロジウムを選択的に沈殿可能である。 <Example 1: Precipitation separation of platinum group metal by 3,3'-diaminobenzidine>
By dissolving palladium (II) chloride, platinum (IV) chloride acid / hexahydrate or rhodium (III) chloride / trihydrate in hydrochloric acid, a hydrochloric acid solution containing 0.1 M of palladium, platinum or rhodium can be prepared. Got ready. To 0.5 mL of these hydrochloric acid solutions, 3,3'-diaminobenzidine was added as a compound having a diaminodiphenyl structure, and the mixture was shaken for 1 hour. 3,3'-Diaminobenzidine was added in an amount of 3 equivalents relative to the concentration of palladium, platinum or rhodium. After the shaking was completed, the mixture was allowed to stand for 24 hours, the concentrations of various metals remaining in the supernatant were measured, and the precipitation rate was calculated.
The precipitation rate was calculated by substituting the measured value into the following formula. The results are shown in FIG.

As shown in FIG. 1, when the hydrochloric acid concentration is 5 M or less, palladium, platinum and rhodium are precipitated, but when the hydrochloric acid concentration is 7 M or more, rhodium can be selectively precipitated.

<Example 2: Dependence of rhodium precipitation rate on precipitant concentration>
A 7.0 M hydrochloric acid solution containing 0.1 M rhodium was prepared in the same manner as in Example 1. To 0.5 mL of this aqueous solution, 3,3'-diaminobenzidine was added in an amount of 0.25-12 equivalents with respect to the rhodium concentration. The concentration of rhodium remaining in the supernatant solution of the sample that had been allowed to stand for 24 hours and 1 week after the end of 1 hour was measured, and the precipitation rate was calculated. The results are shown in FIG.
As shown in FIG. 2, if the standing time is 24 hours, almost 100% of rhodium can be recovered by adding 3 equivalents of a precipitating agent to rhodium. Furthermore, by allowing it to stand for about one week, almost 100% of rhodium can be recovered even with 2 equivalents.

<Example 3: Recovery of rhodium from the precipitate>
A 10 M hydrochloric acid solution containing 0.1 M rhodium was prepared in the same manner as in Example 1. To 2.0 mL of this aqueous solution, 3 equivalents of 3,3'-diaminobenzidine was added to the rhodium concentration. Shaking was performed for 1 hour, after which the precipitate was collected by filtration. After washing with ethanol, it was dried. To 0.05 g of the rhodium-containing precipitate, 0.5 mL of concentrated hydrochloric acid (concentration: about 12 M) was added, and the mixture was shaken for 1 hour. After shaking, the concentration of rhodium remaining in the supernatant solution of the sample was measured for each standing time, and the recovery rate was calculated. The results are shown in FIG.
As shown in FIG. 3, it is possible to elute about 50% of rhodium in the precipitate from the precipitate and recover it by contacting it with concentrated hydrochloric acid. Since this elution method uses anion exchange between Rh and chloride ions in the precipitate, it is possible to further increase the recovery rate by increasing the volume of concentrated hydrochloric acid.

Claims (6)

A method for separating platinum group metal ions by precipitating from a hydrochloric acid solution containing platinum group metal ions. A compound having a diaminodiphenyl structure is used as a precipitating agent, and the divalent and trivalent in the hydrochloric acid solution is used. A separation method comprising precipitating ions of a tetravalent platinum group metal or trivalent rhodium. The precipitation separation method according to claim 1, wherein the precipitating agent having a diaminodiphenyl structure is a compound represented by the following general formula.

(In the above general formula, two of R ₁ and _two of R ₃ are amino groups, and the other R ₁ and R ₃ are hydrogen atoms or hydrocarbon groups having 1 to 6 carbon atoms. Is a direct bond or an alkylene group having 1 to 6 carbon atoms.) The precipitation separation method according to claim 1 or 2, wherein the trivalent rhodium is precipitated . The precipitation separation method according to any one of claims 1 to 3, wherein the hydrochloric acid concentration of the solution containing the trivalent platinum group metal is 5 M or more. Claims 1 to claim, wherein the hydrochloric acid solution containing an ion of a platinum group metal contains at least one rhodium ion and one or more ions of another platinum group metal (platinum, palladium, iridium, ruthenium). The precipitation separation method according to any one of 4. The precipitation separation method according to any one of claims 1 to 5, wherein the precipitated metal is eluted from the precipitate with hydrochloric acid of 10 M or more and recovered.

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