JP6948698B2 - Palladium / Platinum Extractor, Palladium / Platinum Separation Method - Google Patents

Description

The present invention relates to a palladium / platinum extractant and a method for separating palladium / platinum.

Most of the three platinum group metals, palladium, platinum and rhodium, are used in automobile exhaust gas catalysts. Emission regulations and tightening of regulations have spread worldwide, and the demand for these metals has increased, making it difficult to secure stable resources for these metals. In addition, the number of used automobile exhaust gas catalysts is steadily increasing along with the increase in demand. Since these metals are expensive and valuable as resources, they are recovered and reused after use. In order to supply a certain amount of platinum group metal, it is important to separate the platinum group metal from the used product with high efficiency.

Electrolytic precipitation methods, ion exchange methods, and precipitation methods have been proposed for purification in the separation step of platinum group metals, but the solvent extraction method is widely adopted from the viewpoint of selectivity, economy, and operability. .. Various extractants used for this purpose have been developed and used.

Currently, dialkyl sulfide (DAS) and tributyl phosphate (TBP) are used as extracts of palladium and platinum (for example, Patent Documents 1 and 2), the former is an aqueous ammonia solution, and the latter is a reverse with water. The feature is that it can be extracted.

Japanese Patent Application Laid-Open No. 10-130744 JP-A-2005-146326

When the platinum group metal is separated and purified by the solvent extraction method in the actual process, the component containing the platinum group metal mixed in the primary and secondary resources is an acidic aqueous solution leached using hydrochloric acid / chlorine gas or aqua regia. Is extracted. Under these conditions, when DAS is used, palladium is selectively extracted from an acidic aqueous solution containing palladium, platinum, rhodium, and a base metal, but since the DAS and the acidic aqueous solution are in contact for a long time, the sulfide of DAS The site is oxidized and the extraction capacity of palladium is reduced, resulting in poor reusability. Further, DAS has a problem that the extraction rate of palladium is slow.

On the other hand, in the case of TBP, TBP protonated with high-concentration hydrochloric acid forms an ion pair with a chloro complex of platinum for extraction, but there is a problem that selectivity for platinum is low.

As described above, the present invention can (1) selectively extract only a platinum group metal from a solution in which a platinum group metal, a rare earth, a base metal, etc. are mixed, and (2) extract the platinum group metal in a short time. (3) It is an object of the present invention to provide a palladium / platinum extractant having high stability against an acidic solution.

As a result of diligent studies, the present inventors have synthesized a novel thiodiphenol compound which becomes a cationic organic compound by contact with an acidic solution, and completed the following invention.
The first embodiment of the present invention is a palladium / platinum extractant containing a thiodiphenol compound containing an amino group represented by the following general formula (I) as an active ingredient.

（式中、Ｒ^１およびＲ^２は互いに同一でも異なっていてもよく、それぞれ分岐していてもよい炭素数１〜１２の炭化水素基である。）

(In the formula, R ¹ and R ² are hydrocarbon groups having 1 to 12 carbon atoms which may be the same or different from each other and may be branched respectively.)

A second embodiment of the present invention is a step of preparing an organic phase containing the palladium / platinum extractant of the first embodiment, by contacting the organic phase with an acidic aqueous solution containing palladium and / or platinum. , Palladium and / or platinum is a method for separating palladium and platinum, which comprises a step of extracting palladium and / or platinum into the organic phase.

In the second embodiment, it is preferable that the acidic aqueous solution containing palladium and / or platinum is an acid leachate obtained by acid-treating a waste containing at least various metals containing palladium and / or platinum into an aqueous solution.
Further, it is preferable that the various metals containing at least palladium and / or platinum contain at least one selected from rhodium, rare earths, rare metals, and base metals in addition to palladium and platinum.

The palladium / platinum extractant of the first embodiment selectively extracts only palladium and / or platinum from a solution in which various metals such as rare metals and base metals are mixed in addition to (1) palladium and / or platinum. (2) It is not oxidized even if it comes into contact with an acidic solution for a long time, and (3) Palladium and / or platinum can be extracted in a short time.

It is a graph which shows the extraction rate of palladium and platinum with respect to the extraction time. It is a graph which shows the extraction rate of palladium and platinum with respect to the hydrochloric acid concentration. It is an IR spectrum of the extractant of formula (II) before and after acid contact. It is a figure which shows the selectivity when the automobile exhaust gas catalyst is extracted from the acid leached solution by using the extractant of the formula (II).

<Palladium / platinum extractant>
The palladium / platinum extractant according to the first embodiment of the present invention contains thiodiphenol containing an amino group represented by the following general formula (I) as an active ingredient.

式中、Ｒ^１およびＲ^２は互いに同一でも異なっていてもよく、それぞれ分岐していてもよい炭素数１〜１２の炭化水素基を表す。
なお、本明細書において、「パラジウム・白金」とは、パラジウムのみ、白金のみ、または、パラジウムおよび白金の両方のいずれかを意味する。よって、パラジウム・白金抽出剤とは、パラジウムのみを抽出対象とするもの、白金のみを抽出対象とするもの、および、パラジウムおよび白金の両方を抽出対象とするもののいずれをも含む意味である。

In the formula, R ¹ and R ² may be the same or different from each other, and each represents a hydrocarbon group having 1 to 12 carbon atoms which may be branched.
In addition, in this specification, "palladium-platinum" means either palladium only, platinum only, or both palladium and platinum. Therefore, the palladium / platinum extractant means to include any of those that extract only palladium, those that extract only platinum, and those that extract both palladium and platinum.

The present inventors easily become a cationic compound by contacting the palladium / platinum extractant of the present invention with an acidic solution and undergo a protonation reaction, and the palladium exists as an anionic chloro complex in a hydrochloric acid bath. It is believed that the extraction phenomenon occurs by forming an ion pair with and / or platinum.

In the general formula (I), R ¹ and R ² may be the same or different from each other, but are preferably the same from the viewpoint of ease of synthesis. R ¹ and R ² are hydrocarbon groups having 1 to 12 carbon atoms which may be branched, respectively, preferably hydrocarbon groups having 1 to 6 carbon atoms which may be branched, and more preferably branched. It is a hydrocarbon group having 1 to 3 carbon atoms which may be used, and more preferably a linear hydrocarbon group having 1 to 3 carbon atoms.

(Method for synthesizing dialkylamino group-containing thiodiphenol compound)
The dialkylamino group-containing thiodiphenol compound of the general formula (I) can be synthesized, for example, by the following method. It can be synthesized by using 2,2'-thiobis (4-talshalbutylphenol) as a starting material and reacting it with a dialkylamine. The reaction can be carried out in a predetermined solvent at room temperature. After the reaction, the compound of the formula (I) can be obtained through a predetermined purification step.

<Palladium / platinum separation method>
The method for separating palladium / platinum, which is the second embodiment of the present invention, is a step of preparing an organic phase containing the palladium / platinum extractant of the first embodiment described above, and an acidic aqueous solution containing palladium and / or platinum. It comprises a step of extracting palladium and / or platinum into the organic phase by contacting it with the organic phase. When the method for separating palladium and platinum of the present invention is carried out, the thiodiphenol compound represented by the general formula (I) is usually dissolved in a solvent to form an organic phase. By contacting the organic phase with an acidic aqueous solution in which palladium and / or platinum is dissolved, palladium and / or platinum is transferred to the organic phase, and palladium and / or platinum is separated.

(Organic phase containing palladium / platinum extractant)
The solvent used for the organic phase containing the palladium / platinum extractant is a water-insoluble solvent, and two or more kinds of solvents may be used in combination. The water-insoluble solvent is not particularly limited as long as it can dissolve the thiodiphenol compound represented by the general formula (I), and mineral oils such as petroleum and kerosine; and aliphatic hydrocarbons such as hexane, heptane and octane. Aromatic hydrocarbons such as toluene and xylene; halogenated solvents such as carbon tetrachloride, methylene chloride, chloroform and ethylene chloride can be mentioned.

The concentration of the thiodiphenol compound represented by the general formula (I) in the organic phase is not particularly limited except that the upper limit is limited by the solubility of the thiodiphenol compound, but if the concentration is too low, palladium / platinum extraction is performed. Since no effect is obtained, it is usually used in the range of ^{1 × 10 -4 to 1M.}

(Acid aqueous solution containing palladium and / or platinum)
In an acidic aqueous solution containing palladium and / or platinum, the acid means hydrochloric acid. The concentration of the acid can be selectively extracted in a wide range of 0.01 to 8M, but from the viewpoint of increasing the extraction rate, 0.01 to 2M is preferable, 0.01 to 1M is more preferable, and 0.05. ~ 0.5M is more preferable, and 0.05 to 0.15M is particularly preferable.

The concentrations of palladium and platinum in an acidic aqueous solution containing palladium and / or platinum are not particularly limited, and are usually about 1 to 1000 ppm, respectively.

In the separation method of the present invention, the acidic aqueous solution containing palladium and / or platinum is preferably an acid leachate obtained by acid-treating a waste containing at least various metals containing palladium and / or platinum. By targeting such an acid leachate, it becomes possible to further exhibit the excellent recognition, selection system, efficiency, and speed of the palladium / platinum extractant of the present invention. Examples of wastes containing various metals including at least palladium and / or platinum include automobile exhaust gas catalysts.

The metal other than palladium and platinum contained in the acid leachate is not particularly limited, but from the viewpoint of exhibiting the selectivity of the palladium / platinum extractant of the present invention, rhodium, barium and the like which are platinum group elements other than palladium and platinum, etc. It is preferable to contain at least one selected from rare metals such as lanthanum, rare earth such as cerium, and base metals such as aluminum.

As a result, rare and useful palladium and / or platinum can be recycled. Further, since the amount of palladium and / or platinum contained in the acid leachate after separating palladium and / or platinum can be significantly reduced, it can also be used as an operation for removing palladium and / or platinum. Therefore, the present invention can also be used as a pretreatment when isolating useful metals other than palladium and / or platinum from an acid leachate obtained by converting waste into an aqueous solution by acid treatment.

(Extraction condition)
The extraction temperature is not particularly limited as long as it is equal to or lower than the boiling point of the solvent used, and is usually carried out near room temperature. The extraction operation is performed by shaking an organic phase containing a palladium / platinum extractant and an acidic aqueous solution containing palladium and / or platinum and bringing them into contact with each other by stirring or the like. Shaking is usually performed about 100 to 500 times per minute.
Further, the palladium / platinum extractant of the present invention can extract palladium and / or platinum in a short time, and the shaking time is as short as 5 minutes for palladium and 10 minutes for platinum, which is the upper limit of the extraction rate. Can be extracted. Further, the shaking time can be appropriately adjusted depending on the conditions of the extractant and the acidic aqueous solution. To exemplify the range of shaking time, the lower limit is preferably 1 minute or more, more preferably 3 minutes or more, and the upper limit is preferably 30 minutes or less, more preferably 15 minutes or less.

<Synthesis of dialkylamino group-containing thiodiphenol>

37% formaldehyde (2.5 g) in a solution of 2,2'-thiobis (4-talshalbutylphenol) (2.1 g, 6.06 mmol) in tetrahydrofuran (THF) (100 mL) in a 200 mL two-necked flask. ), Diethylamine (2.2 g, 30.3 mmol) and acetic acid (10 mL) were added, and the mixture was stirred at room temperature for 24 hours. Chloroform (100 mL) was added to the yellow oil obtained after distilling off the solvent to dissolve it. The solution was transferred to a 300 mL separatory funnel and washed with water (100 mL), 10% aqueous potassium carbonate solution and water (100 mL) again. The organic phase was dehydrated with anhydrous sodium sulfate, and then the solvent was distilled off to obtain a yellow oil. By adding hexane to this oil, a white solid of the target product was precipitated, and the solid was recovered by filtration. This solid was dissolved in methanol and recrystallized to obtain white crystals (yield 2.8 g, yield 95%).

The analysis results of the obtained target product were as follows.
FT-IR (ATR) ν / cm ^-1 : 2963, 2820, 2596, 1480, 1456, 1255. ¹ H NMR (300 MHz, CDCl ₃ , TMS) δ 7.00 (s, 2H, ArH), 6.91 (s, 2H, Ar H ), 3.78 (s, 4H, Ar-C H _2- N), 2.63 (q, 12H, -NC H _2- ), 1.24 (s, 18H, tert-Bu), 1.12 (t, 12H) , --CH ₂ -C H ₃ ). ¹³ C NMR (75 MHz, CDCl ₃ , TMS) δ 154, 142, 128, 124, 121, 120, 59, 43, 31, 34, 16. Calcd. For C ₃₀ H ₄₈ N ₂ O ₂ S · CH ₃ OH = C ₃₁ H ₅₂ N ₂ O ₃ S: C, 69.88; H, 9.84; N, 5.26. Found: C, 61.81; H, 7.51; N, 5.56.

<Extraction time dependence of palladium and platinum>
In this example, a dialkylamino group-containing thiodiphenol extractant represented by the formula (II) was used, and each shaking time was changed to carry out an extraction experiment of palladium (II) and platinum (IV). As the organic phase, 10 mL of a solution prepared by dissolving the extractant of the formula (II) in chloroform to make 1 mM was prepared, and the organic phase was prepared with 0.1 M hydrochloric acid to a concentration of 1 mM, and the single acidity of palladium and platinum was adjusted. Palladium and platinum were extracted into the organic phase by adding equal volumes of the solution and shaking vigorously (300 rpm). The shaking time was 5 to 180 minutes. For the extraction rate at each time, the metal concentration of the aqueous phase before and after shaking was determined by an ICP emission spectrometer, and the extraction rate (E%) was calculated by equations (1) and (2) based on the obtained results. I asked.

E% = [M] _org / [M] _{aq, init} x 100 (1)
[M] _org = ([M] _{aq, init} − [M] _aq ) (2)
However, [M] _org : metal concentration in the organic phase after extraction (ppm), [M] _{aq, init} : metal concentration in the aqueous phase before extraction (ppm), [M] _aq : aqueous phase after extraction. Metal concentration in (ppm)

FIG. 1 shows the change in the extraction rate when the shaking time is changed. The vertical axis is the extraction rate and the horizontal axis is the shaking time. As shown in FIG. 1, in the palladium (II) extraction experiment (◇), it was shown that almost the entire amount could be extracted with an extraction rate of 98% by shaking for 5 minutes. After 5 minutes of shaking time, the extraction rate did not change, and it became clear that the extraction rate was saturated. On the other hand, the same phenomenon was observed in the extraction (□) of platinum (IV), and the extraction rate was 77% when the shaking time was 5 minutes and 81% when the shaking time was 10 minutes. After the shaking time of 10 minutes, the extraction rate did not change and became constant. From the above, it can be concluded that the extractant of the formula (II) has the ability to extract palladium (II) and platinum (IV), and in particular, can extract palladium (II) with high efficiency.

<Extraction experiment of palladium or platinum with different hydrochloric acid concentration from a single acidic aqueous solution using a dialkylamino group-containing thiodiphenol extractant>
In this example, an extraction experiment of palladium or platinum having different hydrochloric acid concentrations from each single acidic aqueous solution was carried out using a dialkylamino group-containing thiodiphenol extractant represented by the formula (II). The extractant of formula (II) was diluted with a chloroform solvent to prepare a 1 mM organic phase. To 10 mL of this organic phase, add equal volumes of each single acidic aqueous solution of palladium or platinum prepared to a concentration of 1 mM using 0.1 M to 8.0 M hydrochloric acid, and shake vigorously (300 rpm) for 10 minutes to make it organic. Palladium or platinum was extracted into the phase. Then, the concentration of palladium or platinum in the aqueous phase was analyzed by an ICP emission spectrometer, and the extraction rate (E%) was calculated by the above formulas (1) and (2) based on the obtained results. ..
FIG. 2 shows the change in the extraction rate when the hydrochloric acid concentration of the acidic aqueous solution (aqueous phase) is changed. The vertical axis is the extraction rate and the horizontal axis is the hydrochloric acid concentration.
As shown in FIG. 2, it can be seen that the extraction rates of palladium (◇) and platinum (□) decrease as the hydrochloric acid concentration increases. The extraction behavior of both metals gives similar results, and it can be concluded that the 0.1 M hydrochloric acid concentration is the most efficient and can extract palladium and platinum.

<Stability against acid>
In this example, the stability of the extractant of formula (II) to an acidic aqueous solution was examined. The extractant of formula (II) was diluted with a chloroform solvent to obtain a 1 mM organic phase. An equal volume of 12N hydrochloric acid was added to 10 mL of these organic phases, placed in a sample tube, and stirred for 1 week. Then, the liquid was separated, the organic phase was washed with water, dehydrated and concentrated, and dried under reduced pressure. The obtained solid was analyzed by an infrared absorption spectrum analyzer, and the results are shown in FIG. The vertical axis is the transmittance and the horizontal axis is the frequency.
As shown in FIG. 3, there is almost no change in the spectrum without contact with the acid and the spectrum after contact with 12N hydrochloric acid. From this result, it can be concluded that the extractant of formula (II) is highly stable against acidic solutions.

<Extraction of palladium and platinum from acid-leached solution of automobile exhaust gas catalyst>
An aqueous solution (Pd (II): 92.8 ppm, Pt (Pd (II): 92.8 ppm, Pt), which is a 20-fold diluted acid leachate obtained by acid-treating waste containing various metals including at least palladium and platinum discharged from the factory and diluting it with distilled water. IV): 3.87 ppm, Rh (III): 3.12 ppm, La (III): 28.5 pm, Ce (III): 269.6 ppm, Ba (II): 15.5 ppm, Al (III): 501.5 ppm) 10 mL (pH 1. 0) was used as an aqueous phase, and the extractant of the formula (II) was diluted with a chloroform solvent to prepare a 10 mL (10 mM) organic phase, and the organic phase and the aqueous phase were vigorously shaken (300 rpm) for 10 minutes, and then vigorously shaken (300 rpm). The concentration of each metal in the aqueous phase was analyzed by an ICP luminescence analyzer, and the extraction rate (E%) was determined by the above formulas (1) and (2) based on the obtained results.

FIG. 4 shows the extraction amount of each metal. The vertical axis is the amount of extraction and the horizontal axis is each metal ion (the back of the figure is the concentration of each metal in the aqueous phase before extraction, and the front of the figure is the concentration of each metal moved to the organic phase).
As shown in FIG. 4, almost the entire amount of palladium could be extracted, and the extracted amount was 92.2 mgL- ¹ . It was also found that platinum was ^{able to extract a concentration of 1.4 mgL-1, which} is about half, from the aqueous phase. Aluminum, another metal, was also extracted, albeit slightly, to 3.9 mgL- ¹ . From this result, it can be concluded that the extractant of the formula (II) can extract almost all of palladium and about half of platinum from the acid leaching solution of the automobile exhaust gas catalyst containing various metals.

Claims (4)

A palladium / platinum extractant containing a thiodiphenol compound represented by the following general formula (I) as an active ingredient.

(In the formula, R ¹ and R ² are hydrocarbon groups having 1 to 6 carbon atoms which may be the same or different from each other and may be branched respectively.) The step of preparing an organic phase containing the palladium / platinum extractant according to claim 1, in which palladium and / or platinum is brought into the organic phase by contacting the organic phase with an acidic aqueous solution containing palladium and / or platinum. A method for separating palladium and platinum, which comprises a step of extracting into. The method for separating palladium and platinum according to claim 2, wherein the acidic aqueous solution containing palladium and / or platinum is an acid leachate obtained by acid-treating an automobile catalyst containing at least palladium and / or platinum. The method for separating palladium and platinum according to claim 3, wherein the acid leachate contains at least one selected from rhodium, rare earth, rare metal, and base metal in addition to palladium and platinum.

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