JP7079978B2 - Palladium extractant, palladium extraction method, palladium recovery method, palladium extractor regeneration method, and palladium recovery method repeatedly. - Google Patents

Description

The present invention relates to a palladium extractant, a method for extracting palladium, a method for recovering palladium, a method for regenerating a palladium extractant, and a method for repeatedly recovering palladium.

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 collected and reused after use.
In order to supply a certain amount of platinum group metal, it is important to separate platinum group metal from used products with high efficiency.

When a plurality of types of platinum group elements are present in a commercially available extractant, it is difficult to exhibit selectivity for one of these platinum group elements. In particular, palladium and platinum are difficult to separate because they have similar chemical properties. Furthermore, the instability of the extractant has become a serious problem because the extraction conditions are under strong acidity, and the development of a new extractant is required.

An electrolytic precipitation method, an ion exchange method, and a precipitation method have been proposed for purification in the separation step of a platinum group metal, 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) is used as a known palladium extractant (for example, Patent Documents 1 and 2), and is characterized by being easily back-extracted with an aqueous ammonia solution.

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

The automobile exhaust gas catalyst containing a platinum group metal is made into an aqueous solution by acid treatment to obtain an acidic aqueous solution, and a solvent extraction method is applied to the aqueous solution. When DAS is used under these conditions, palladium is selectively extracted from the acidic aqueous solution containing palladium, platinum, rhodium, and base metal, but the DAS and the acidic aqueous solution are in contact with each other for a long time, so that the sulfide of DAS is sulfided. 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.

As described above, the present invention can selectively extract only palladium from a solution in which (1) platinum, rhodium, base metal and the like are mixed, and (2) is not oxidized even if it is in contact with an acidic solution for a long time. (3) It is an object of the present invention to provide a palladium extractant capable of extracting palladium in a short time.

As a result of diligent studies, the present inventor has found that the above problems can be solved by adopting a specific pincer type structure for the extractant.

The first aspect of the present invention is a palladium extractant containing an alkyl sulfide group-containing disubstituted aromatic compound represented by the following general formula (I) as an active ingredient.

（式中、Ｒは分岐していてもよい炭素数１～１２の炭化水素基、炭素数５～７の脂環式炭化水素基、または、炭素数７～８の芳香族炭化水素基を表す。）

(In the formula, R represents a hydrocarbon group having 1 to 12 carbon atoms which may be branched, an alicyclic hydrocarbon group having 5 to 7 carbon atoms, or an aromatic hydrocarbon group having 7 to 8 carbon atoms. .)

The second embodiment of the present invention is a step of preparing an organic phase containing the palladium extractant of the first embodiment, in which palladium is extracted into the organic phase by contacting an acidic aqueous solution containing palladium with the organic phase. It is a method for extracting palladium, which comprises a step of extracting palladium.

In the second embodiment, the acidic aqueous solution containing palladium is preferably an acid leachate obtained by converting waste containing at least various metals containing palladium into an aqueous solution by acid treatment.

In the second embodiment, the various metals containing at least palladium preferably contain at least one selected from platinum, rhodium, lanthanum, rare earths, zirconium, and base metals, in addition to palladium.

In the third embodiment of the present invention, the organic phase from which palladium is extracted obtained by the method for extracting palladium of the second embodiment is brought into contact with an aqueous solution of hydrochloric acid containing thiourea, and palladium is back-extracted into an aqueous phase. It is a method for recovering palladium having a process.

In the fourth embodiment of the present invention, the organic phase from which palladium is extracted obtained by the method for extracting palladium of the second embodiment is brought into contact with an aqueous solution of hydrochloric acid containing thiourea, and palladium is back-extracted into an aqueous phase. In addition, it is a method for regenerating a palladium extract, which comprises a step of regenerating the palladium extract of the first form in the organic phase.

A fifth aspect of the present invention is the first step of preparing an organic phase containing the palladium extractant of the first aspect, in which palladium is brought into the organic phase by contacting an acidic aqueous solution containing palladium with the organic phase. The second step and the third step of back-extracting palladium into an aqueous phase by contacting the organic phase from which palladium has been extracted with a hydrochloric acid aqueous solution containing thiourea are provided. This is a method for repeatedly recovering palladium, which can be recovered by repeating palladium while regenerating the palladium extractant by repeating the three steps.

In the fifth embodiment, after the third step, a fourth step of washing the organic phase containing the regenerated palladium extractant with distilled water is further provided, and the second step, the third step, and the fourth step are provided. It is preferable to repeat the above.

The palladium extractant of the first form can selectively extract only palladium from a solution in which platinum, rhodium, a base metal and the like are mixed, and (2) is in contact with an acidic solution for a long time. Is not oxidized, and (3) palladium can be extracted in a short time.

It is a graph which shows the extraction rate with respect to the hydrochloric acid concentration. It is a graph which shows the extraction rate with respect to the nitric acid concentration. It is a graph which shows the time dependence of the extraction rate at the time of extracting palladium from a hydrochloric acid / nitric acid mixed solution. It is a graph which shows the time dependence of the extraction rate at the time of extracting palladium from a hydrochloric acid solution. It is a figure which shows the selectivity when extracting palladium from the acid solution coexisting with palladium, platinum, rhodium, rare earth, zirconium, and a base metal. It is a figure which shows the selectivity when extracting palladium from the solution which acid-leached the automobile exhaust gas catalyst. It is a figure which shows the extraction rate (E%) and the back extraction rate (S%) when palladium is repeatedly extracted.

<Palladium extractant>
The palladium extractant according to the first embodiment of the present invention is a palladium extractant containing an alkyl sulfide group-containing disubstituted aromatic compound represented by the following general formula (I) as an active ingredient.

（式中、Ｒは分岐していてもよい炭素数１～１２の炭化水素基、炭素数５～７の脂環式炭化水素基、または、炭素数７～８の芳香族炭化水素基を表す。）

(In the formula, R represents a hydrocarbon group having 1 to 12 carbon atoms which may be branched, an alicyclic hydrocarbon group having 5 to 7 carbon atoms, or an aromatic hydrocarbon group having 7 to 8 carbon atoms. .)

According to the present inventor, the palladium extractant of the present invention has the characteristics of the pincer-type ligand, "the property of pinching the metal of the pincer ligand" and "the property of pinching the metal of the pincer ligand". By utilizing "specific capture with metal reduction (capturing Pd (II) as Pd (I))", excellent recognition, selectivity, efficiency, and speed can be exhibited as a palladium extractant. I predict that.

In the general formula (I), R in one molecule may be the same or different, but it is preferable that they are the same from the viewpoint of ease of synthesis. R is a hydrocarbon group having 1 to 12 carbon atoms which may be branched, an alicyclic hydrocarbon group having 5 to 7 carbon atoms, or an aromatic hydrocarbon group having 7 to 8 carbon atoms, and is preferably carbon. A linear or branched alkyl group having a number of 1 to 12, more preferably a linear or branched alkyl group having 6 to 10 carbon atoms, and still more preferably a linear or branched alkyl group having 7 to 9 carbon atoms. It is more preferably a straight chain alkyl group having 7 to 9 carbon atoms.

(Method for synthesizing a disubstituted aromatic compound containing an alkyl sulfide group)
The alkyl sulfide group-containing disubstituted aromatic compound of the general formula (I) can be synthesized by a known method. For example, it can be synthesized by using α, α'-dihydroxy-1,3-diisopropylbenzene as a starting material and reacting it with a predetermined thiol. The reaction can be carried out in the presence of a given catalyst in a given solvent. Examples of the thiol include alkyl thiols such as 1-octane thiol, 1-heptane thiol, 1-nonan thiol, 2-methyl-1-propane thiol and 2-ethyl hexane thiol, and fats such as cyclohexane thiol and cyclohexyl thiol. Examples thereof include cyclic thiols and aromatic thiols such as benzyl mercapton and phenylethyl mercapton.
As the solvent, for example, dichloromethane and dichloroethane can be used. As the catalyst, for example, zinc iodide can be used.
The reaction is preferably carried out in an inert atmosphere such as a nitrogen atmosphere. The reaction time and reaction temperature are not particularly limited, but are, for example, 1 hour or more, preferably 2 hours or more, and the reaction is preferably performed at around room temperature. After the reaction, the compound of the formula (I) can be obtained through a predetermined purification step.

<Palladium extraction method>
The method for extracting palladium, which is the second embodiment of the present invention, is a step of preparing an organic phase containing the palladium extractant of the first embodiment described above, in which an acidic aqueous solution containing palladium is brought into contact with the organic phase. The step of extracting palladium into the organic phase is provided. When the method for extracting palladium of the present invention is carried out, the alkyl sulfide group-containing disubstituted aromatic 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 is dissolved, palladium is transferred to the organic phase and palladium is extracted.

(Organic phase containing palladium extractant)
The solvent used for the organic phase containing the palladium 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 an alkyl sulfide group-containing disubstituted aromatic compound represented by the general formula (I), and mineral oils such as petroleum and kerosine; hexane, heptane, octane and the like. Hydrocarbons; aromatic hydrocarbons such as toluene and xylene; halogenated solvents such as carbon tetrachloride, methylene chloride, chloroform and ethylene chloride.

The concentration of the alkyl sulfide group-containing bi-substituted aromatic 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 alkyl sulfide group-containing di-substituted aromatic compound. If the concentration is too low, the palladium extraction effect cannot be obtained, so it is usually used in the range of 1 × 10 ^-3 to 1M.

(Acid aqueous solution containing palladium)
The acid concentration in the acidic aqueous solution containing palladium, for example, the hydrochloric acid concentration, the nitrate concentration, or the concentration of the hydrochloric acid-nitrate mixed solution is preferably 0.1 to 8.0 M, and corresponds to a wide range of acid concentrations. can do.

The acid contained in the acidic aqueous solution is not particularly limited as long as it is water-soluble, and an inorganic acid can be used. Examples of the inorganic acid include hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chloric acid, sulfuric acid, nitric acid, phosphoric acid, hydrogen peroxide and the like. Further, two or more kinds of acids may be contained. Hydrochloric acid, nitric acid, or mixtures thereof are preferred from the standpoint of metal solubility.

The concentration of palladium in the acidic aqueous solution containing palladium is not particularly limited, and is usually about 100 to 1000 ppm.

In the extraction method of the present invention, the acidic aqueous solution containing palladium is preferably an acid leaching solution obtained by converting waste containing at least various metals containing palladium into an aqueous solution by acid treatment, and such an acid leaching solution is targeted. By doing so, it becomes possible to further demonstrate the excellent recognition, selection system, efficiency, and speed of the palladium extractant of the present invention. Examples of the waste in which various metals including palladium are mixed include an automobile exhaust gas catalyst.

The metal other than palladium contained in the acid leachate is not particularly limited and may contain an alkali metal, an alkaline earth metal, a transition metal, a 3B metal and the like, and among them, the selectivity of the palladium extractant of the present invention. It is preferable to contain at least one selected from platinum, rhodium, lantern, rare earth, zirconium, and a base metal from the viewpoint of exhibiting the above. This makes it possible to recycle and utilize palladium, which is highly rare and useful. Further, since the amount of palladium contained in the acid leachate after separating palladium can be significantly reduced, it can also be used as an operation for removing palladium. Therefore, the present invention can also be used as a pretreatment when isolating useful metals other than palladium 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 the organic phase containing the palladium extractant and the acidic aqueous solution containing palladium and bringing them into contact with each other by stirring or the like. Shaking should usually be performed about 100 to 500 times per minute.
Further, the palladium extractant of the present invention can extract palladium in a short time, and the shaking time is about 30 minutes, so that almost the entire amount can be extracted. Further, the shaking time can be appropriately adjusted depending on the conditions of the extractant and the acidic aqueous solution. As for the shaking time, the lower limit is preferably 5 minutes or more, more preferably 10 minutes or more, further preferably 30 minutes or more, and the upper limit is preferably 2 hours or less, more preferably 1 hour or less.

<Palladium recovery method>
In the method for recovering palladium, which is the third embodiment of the present invention, the organic phase from which palladium is extracted obtained by the above-mentioned extraction method for palladium is brought into contact with an aqueous solution of hydrochloric acid containing thiourea to convert palladium into an aqueous phase. It has a process of back extraction.

(Aqueous hydrochloric acid solution containing thiourea)
The lower limit of the concentration of thiourea in the aqueous hydrochloric acid solution containing thiourea is preferably 0.01 M or more, more preferably 0.05 M or more, and the upper limit is preferably 1 M or less, more preferably 0.5 M or less.

The lower limit of the hydrochloric acid concentration in the aqueous hydrochloric acid solution containing thiourea is preferably 0.1 M or more, more preferably 0.5 M or more, and the upper limit is preferably 10 M or less, more preferably 5 M or less.

(Reverse extraction condition)
The back 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 reverse extraction operation is performed by shaking the organic phase from which palladium has been extracted and the aqueous hydrochloric acid solution containing thiourea, and bringing them into contact with each other by stirring or the like. Shaking should usually be performed about 100 to 500 times per minute. As for the shaking time, the lower limit is preferably 10 minutes or more, more preferably 20 minutes or more, further preferably 30 minutes or more, and the upper limit is preferably 3 hours or less, more preferably 2 hours or less.

By the above back extraction, almost all of palladium can be recovered from the organic phase to the aqueous phase.

<Regeneration method of palladium extractant>
In the method for regenerating the palladium extract according to the fourth embodiment of the present invention, the organic phase from which palladium is extracted obtained by the above-mentioned extraction method for palladium is brought into contact with an aqueous solution of hydrochloric acid containing thiourea to make palladium water. It is provided with a step of back-extracting the phase and regenerating the palladium extractant of the present invention in the organic phase.

From another point of view, the method for recovering palladium, which is the third aspect of the present invention, is the method for regenerating the palladium extractant according to the fourth aspect. That is, in the method for recovering palladium, after the palladium is back-extracted into the aqueous phase, the extractant of the present invention remains in the organic phase in a regenerated form.

The organic phase containing the regenerated palladium extractant is preferably washed with distilled water, if necessary, and the temperature and shaking conditions for the washing are the same as those for the reverse extraction.

<Repeated recovery method of palladium>
The method for repeatedly recovering palladium according to the fifth embodiment of the present invention is the first step of preparing an organic phase containing the palladium extractant of the first embodiment, in which an acidic aqueous solution containing palladium is brought into contact with the organic phase. The second step of extracting palladium to the organic phase and the third step of back-extracting palladium to the aqueous phase by contacting the organic phase from which palladium has been extracted with a hydrochloric acid aqueous solution containing thiourea are provided. This is a method for repeatedly recovering palladium, which can repeatedly recover palladium while regenerating the palladium extractant by repeating the second step and the third step.

In the above back extraction, almost the entire amount of palladium can be recovered in the aqueous phase. This means that in the organic phase, almost all of the palladium extractant has been regenerated to its original state (before adsorbing on palladium). Further, since the palladium extractant of the present invention has resistance to an acidic solution, it is not oxidized even if it comes into contact with the acidic solution multiple times.

Therefore, a plurality of operations of contacting the organic phase containing the palladium extractant of the present invention with an acidic aqueous solution containing palladium to extract palladium, and then contacting the organic phase with a hydrochloric acid aqueous solution containing thiourea to back-extract palladium. By repeating this process, it is possible to repeatedly extract palladium from a plurality of acid leachates while using the same palladium extractant, which is an efficient extraction method from an industrial point of view.

In the method for repeatedly recovering palladium according to the fifth aspect described above, after the third step, a fourth step of washing the organic phase containing the regenerated palladium extractant with distilled water is further provided, and the second step. It is preferable to repeat the third step and the fourth step. By this cleaning operation, when impurities are contained in the organic phase, the impurities can be removed before the next extraction step, and the extraction efficiency in the next extraction step can be improved.

<Synthesis of pincer type palladium extractant (E1)>

In a 200 mL two-necked flask, α, α'-dihydroxy-1,3-diisopropylbenzene (1.55 g, 7.98 mmol), zinc iodide (2.56 g, 8.02 mmol), and 1-octanethiol (2. 45 g, 16.78 mmol) was added to dichloromethane (50 mL), and the mixture was stirred at room temperature for 2 hours under a nitrogen atmosphere. Dichloromethane was further added to the reaction solution to dilute it, and the mixture was transferred to a 300 mL separatory funnel and washed with water. The organic layer was washed with 1 M aqueous sodium hydroxide solution and then dehydrated with anhydrous sodium sulfate. By distilling off the solvent from the organic layer after dehydration, a colorless oily substance (yield 3.45 g, yield 96%) was obtained.
The analysis results of the obtained target product are as follows.
FT-IR (ATR) ν / cm ⁻¹ : 2922 (CH), 703 (C－S). ¹ H NMR (300 MHz, CDCl ₃ , TMS) δ 7.76 (s, 1H, ArH), 7.33 (dd, 2H, Ar H ), 7.26 (t, 1H, Ar H ), 2.18 (t, 4H, -SC H _2- ), 1.70 (s, 12H, -ArC (C H ₃ ) _2- ), 1.34 (m, 4H, -SCH ₂ C H _2- ), 1.30-1.10 (m, 20H, -SCH ₂ CH ₂ (C H ₂ ) _5- ), 0.85 (t, 6H, -SCH ₂ CH ₂ (CH ₂ ) ₅ C H ₃ ).

<Palladium extraction experiment from solutions with different hydrochloric acid concentrations>
In this example, an extraction experiment was performed from a palladium-only acidic solution using a pincer-type palladium extractant (E1) as a palladium extractant (Example). Moreover, the same experiment was performed using a kind of di-n-octylsulfide (DOS) of DAS which is a known palladium extractant (comparative example). E1 was diluted with a kerosene solvent to 10 mM, and DOS was also diluted with a similar solvent to 20 mM. To 10 mL of these organic phases, an equal volume of a palladium-only solution prepared to a concentration of 100 ppm using 0.1 M to 8.0 M hydrochloric acid is added, and the mixture is vigorously shaken (300 rpm) for 1 hour to extract palladium into the organic phase. Was done.
Then, the palladium concentration in the aqueous phase was analyzed by an ICP emission spectrometer, and the extraction rate (E%) was calculated by the following formulas (1) and (2) based on the obtained results.
E% = [M] _org / [M] _{aq, init} × 100 Equation (1)
[M] _org = ([M] _{aq, init-} [M] _aq ) Equation (2)
However, [M] _org : palladium concentration in the organic phase after extraction (ppm), [M] _{aq, init} : palladium concentration in the aqueous phase before extraction (ppm), [M] _aq : aqueous phase after extraction. Palladium concentration in,
FIG. 1 shows the change in the extraction rate when the hydrochloric acid concentration is changed.

As shown in FIG. 1, as the hydrochloric acid concentration increased, when DOS (●) was used as the extractant, the extraction rate of palladium decreased to about 90%, but when E1 (■) was used, which It was found that the extraction rate was not affected even with the hydrochloric acid concentration. From this, it can be concluded that E1 is less affected than DOS and can stably extract palladium with respect to the extraction ability of palladium in the change of hydrochloric acid concentration. The acid concentration to be applied varies depending on the object to be acid-dissolved, and the extractant of the present invention that can be used in a wide range of acid concentrations is preferable from the viewpoint of eliminating the need for an acid concentration adjusting step.

<Palladium extraction experiment from solutions with different nitric acid concentrations>
In this example, E1 (Example) and DOS (Comparative Example) were used as extractants. E1 was diluted with a kerosene solvent to 10 mM, and DOS was also diluted with a similar solvent to 20 mM. To 10 mL of these organic phases, an equal volume of a palladium alone solution prepared to a concentration of 100 ppm using 0.1 M to 8.0 M nitric acid is added, and the mixture is vigorously shaken (300 rpm) for 1 hour to extract palladium into the organic phase. Was done.
Then, the palladium concentration in the aqueous phase was analyzed by an ICP emission spectrometer, and the extraction rate (E%) was determined by the above formulas (1) and (2) based on the obtained results. FIG. 2 shows the change in the extraction rate when the nitric acid concentration is changed.

As can be seen from FIG. 2, when the nitric acid concentration increased and DOS (●) was used as the extractant, the extraction rate of palladium decreased to about 70%, whereas when E1 (■) was used. Then, it was found that the extraction rate was not affected by any nitric acid concentration. From this, it can be concluded that E1 is less affected than DOS and can stably extract palladium with respect to the extraction ability of palladium in the change of nitric acid concentration. The acid concentration to be applied varies depending on the object to be acid-dissolved, and the extractant of the present invention that can be used in a wide range of acid concentrations is preferable from the viewpoint of eliminating the need for an acid concentration adjusting step.

<Time dependence of extraction rate when extracting palladium from a mixed hydrochloric acid / nitric acid solution>
In this example, E1 (Example) and DOS (Comparative Example) were used as extractants. E1 was diluted with a kerosene solvent to 10 mM, and DOS was also diluted with a similar solvent to 100 mM. To 10 mL of these organic phases, add an equal volume of a palladium-only solution prepared to a concentration of 100 ppm using a solution of 2.0 M hydrochloric acid / 1.0 M nitric acid, and shake vigorously (300 rpm) for a maximum shaking time of 168. By the time, palladium was extracted into the organic phase.
Then, the palladium concentration in the aqueous phase was analyzed by an ICP emission spectrometer, and the extraction rate (E%) was determined by the above formulas (1) and (2). FIG. 3 shows the change in the extraction rate when the shaking time from the hydrochloric acid / nitric acid mixed solution is changed.

As can be seen from FIG. 3, when DOS (●) was used, the extraction rate of palladium decreased sharply as the shaking time increased, and decreased to about 40% around the shaking time of 168 hours. , E1 (■) is not seen to decrease the extraction rate, and it can be seen that the extraction can be performed at a constant rate. From this, it can be concluded that E1 can stably extract palladium without being affected even in a mixed hydrochloric acid / nitric acid solution.

<Extraction time dependence of palladium extraction rate>
In this example, an experiment was performed using E1 (Example) and DOS (Comparative Example). E1 was diluted with a kerosene solvent to 10 mM, and DOS was also diluted with a similar solvent to 20 mM. To 10 mL of these organic phases, an equal volume of a palladium-only acidic solution prepared to a concentration of 100 ppm using 8.0 M hydrochloric acid was added, and the mixture was vigorously shaken (300 rpm) to extract palladium into the organic phase.
The extraction rate was calculated from the above equations (1) and (2) by determining the palladium concentration of the aqueous phase before and after shaking with an ICP emission spectrometer. FIG. 4 shows the change in the extraction rate when the shaking time is changed.
As shown in FIG. 4, when DOS (●) is used, it takes about 180 minutes to extract almost the entire amount of palladium, but when E1 (■) is used, it takes about 30 minutes to extract palladium. It turned out that the whole amount can be extracted. Regarding the extraction time of palladium, it was clear that E1 was faster than DOS.

<Selectability when extracting palladium from an acidic solution coexisting with palladium, platinum, rhodium, rare earth, zirconium, and base metal>
In this example, assuming an acidic solution used for palladium separation and purification from primary and secondary resources, palladium, platinum, rhodium, rare earth, zirconium, and barium, aluminum, iron, copper, zinc, and nickel coexist as base metals. The extraction rate of each metal from a 3M hydrochloric acid solution prepared so that the concentration of each metal was 100 ppm was determined (Example). An extraction experiment was also performed using a 20 mM solution obtained by diluting DOS with kerosene (comparative example). The organic phase and the aqueous phase are vigorously shaken for 1 hour (300 rpm), and then the concentration of each metal in the aqueous phase is analyzed by an ICP emission spectrometer, and the extraction rate (extraction rate) is based on the obtained result. E%) was calculated by the above equations (1) and (2). The extraction rate of each metal is shown in FIG.

As shown in FIG. 5, DOS was unable to extract the entire amount of palladium, and the extraction rate was 82.2%. Zirconium and iron, which are other metals, were also extracted to a small extent, and they were 3.5% and 3.2%, respectively. On the other hand, it was found that E1 can extract almost the entire amount of palladium at 99.9% and does not extract other metals. From this result, it can be concluded that palladium can be selectively and almost completely extracted by contacting a kerosine solution containing 10 mM E1 and a hydrochloric acid solution in which palladium, platinum, rhodium, rare earth, zirconium, and a base metal coexist. can.

<Selectability when palladium is extracted from a solution obtained by acid leaching an automobile exhaust gas catalyst>
An acid solution (Pd (II): 92.8 ppm, Pt (IV), which is a 5-fold diluted acid leachate obtained by acid-treating waste containing at least various metals including palladium discharged from a factory with distilled water. ): 54.2ppm, Rh (III): 37.2ppm, La (III): 86.7pm, Ce (III): 608.8ppm, Y (III): 3.8ppm, Zr (IV): 25.6ppm , Ba (II): 289.3 ppm, Al (III): 320.9 ppm) 10 mL (pH 0.8) was used as the aqueous phase, E1 was diluted with a kerosine solvent to make 10 mM, and the organic phase (10 mL) was used. The aqueous phase is vigorously shaken for 1 hour (300 rpm), and then the concentration of each metal in the aqueous phase is analyzed by an ICP emission analyzer, and the extraction rate (E%) is based on the obtained result. Was obtained by the above equations (1) and (2) (Example).
An extraction experiment was also performed using a 20 mM solution obtained by diluting DOS with kerosene (comparative example). The extraction rate of each metal is shown in FIG.
As shown in FIG. 6, DOS was unable to extract the entire amount of palladium, and the extraction rate was 89.6%. In addition, cerium and zirconium, which are other metals, were also slightly extracted, and they were 1.1% and 2.7%, respectively. On the other hand, it was found that E1 can extract almost all of palladium. From this result, it can be concluded that palladium can be selectively and almost completely extracted by contacting the kerosene solution having E1 of 10 mM with the acid solution.

<Reverse extraction rate when palladium is back-extracted from the organic phase in which palladium is extracted from the acid leached solution of the automobile exhaust gas catalyst>
After extracting palladium from the acid-leached solution of the automobile exhaust gas catalyst, the organic phase is separated, and the same volume of 1M hydrochloric acid, 1M nitrate, 1M sulfuric acid, 5% aqueous ammonia solution, and 0.1M thiourea are used as the aqueous phase. Using a /1.0 M sulfuric acid solution, these organic and aqueous phases were shaken for 1 hour to perform back extraction of palladium into the aqueous phase. The palladium concentration in the aqueous phase was analyzed by an ICP emission spectrometer, and the back extraction rate (S%) was calculated by the following formula (3) based on the obtained results.
S% = [Pd (II)] _aq / [Pd (II)] _org × 100 Equation (3),
However, [Pd (II)] _aq : Palladium concentration (ppm) in the aqueous phase after back extraction, [Pd (II)] _org : Palladium concentration (ppm) in the organic phase before back extraction.
Table 1 shows the back-extraction rates when each back-extracting agent is used.
As shown in Table 1, the back extraction rates of 1M hydrochloric acid, 1M nitric acid, 1M sulfuric acid, and 5% aqueous ammonia solution are 6.5% and 15.1%, respectively, due to the strong ability of E1 to capture palladium. Efficient back extraction was not possible with 8.6% and 10.4%. On the other hand, when a 0.1 M thiourea / 1.0 M hydrochloric acid solution was used, almost the entire amount of palladium could be recovered from the organic phase to the aqueous phase, and the back extraction rate was 99.9%.

That is, based on the above results, palladium is completely made by contacting the organic phase containing E1 with the acid leachate, which is an aqueous solution of waste containing at least various metals including palladium discharged from the factory by acid treatment. It is clear that palladium can be recovered by contacting the organic phase from which palladium has been extracted with a hydrochloric acid solution containing thiourea.

<Palladium is repeatedly extracted from the acid-leached solution of the secondary resource automobile exhaust gas catalyst using the organic phase containing E1 after back extraction>
The organic phase after the palladium was back-extracted was separated, contacted with equal volume of distilled water, and then the organic phase was separated. This organic phase was vigorously shaken (300 rpm) with the acid leachate for 1 hour (Ext. 2). In addition, back extraction was performed as described above (Str. 2), the organic phase was washed with distilled water, and an experiment for extracting palladium from the acid leachate was carried out. In this way, the extraction and back extraction operations were carried out a total of 5 times (Ext./Str.1 to Ext./Str.5), and after each time, the concentration of each metal in the aqueous phase was transferred to the ICP emission spectrometer. From the results of the analysis, E% and S% were determined using the above equations (1), (2) and (3). E% and S% of the reused extractant are shown in FIG.
As shown in FIG. 7, E1 as an extractant did not show any decrease in extraction efficiency and back-extraction efficiency even in a step including five extraction operations and a back-extraction operation, and separated almost the entire amount of palladium. And it can be concluded that it can be recovered.
That is, it was clarified that E1 can be repeatedly used without a decrease in the extraction rate and the back extraction rate by combining the back extraction agent and washing with distilled water after the back extraction.

As described above, the pincer-type palladium extractant of the present invention has high palladium selectivity, a high extraction rate, and can be efficiently back-extracted by using a thiourea / hydrochloric acid solution and can be reused. From these facts, it can be applied to continuous extraction and is useful from an industrial point of view. Further, the compound of the formula (I) has advantages that it is easy to synthesize, does not require a purification operation, and is easy to handle.

Claims (8)

A palladium extractant containing an alkyl sulfide group-containing disubstituted aromatic compound represented by the following general formula (I) as an active ingredient.

(In the formula, R represents a hydrocarbon group having 1 to 12 carbon atoms which may be branched, an alicyclic hydrocarbon group having 5 to 7 carbon atoms, or an aromatic hydrocarbon group having 7 to 8 carbon atoms. .) A step of preparing an organic phase containing the palladium extractant according to claim 1, and a step of extracting palladium into the organic phase by contacting an acidic aqueous solution containing palladium with the organic phase. Extraction method. The method for extracting palladium according to claim 2, wherein the acidic aqueous solution containing palladium is an acid leachate obtained by acid-treating a waste containing at least various metals containing palladium into an aqueous solution. The method for extracting palladium according to claim 3, wherein the various metals containing at least palladium include at least one selected from platinum, rhodium, lanthanum, rare earth, zirconium, and a base metal in addition to palladium. A method for recovering palladium, which comprises a step of back-extracting palladium into an aqueous phase by contacting an organic phase obtained by extracting palladium obtained by the method for extracting palladium according to claim 2 with an aqueous solution of hydrochloric acid containing thiourea. .. The organic phase obtained by the method for extracting palladium according to claim 2 is brought into contact with an aqueous hydrochloric acid solution containing thiourea to back-extract palladium into an aqueous phase, and the organic phase is claimed. A method for regenerating a palladium extract, which comprises a step of regenerating the palladium extract according to 1. A first step of preparing an organic phase containing the palladium extractant according to claim 1, a second step of extracting palladium into the organic phase by contacting an acidic aqueous solution containing palladium with the organic phase, and a second step. , The organic phase from which palladium has been extracted is brought into contact with an aqueous solution of hydrochloric acid containing thiourea to provide a third step of back-extracting palladium into an aqueous phase, and the second step and the third step are repeated. A method for repeatedly recovering palladium, which can be recovered repeatedly while regenerating the palladium extractant. The third step is further provided with a fourth step of washing the organic phase containing the regenerated palladium extractant with distilled water, and the second step, the third step, and the fourth step are repeated. 7. The method for repeatedly recovering palladium according to 7.

Images