JPH08291345A - Method for separating and recovering platinum group element in solution - Google Patents

Abstract

PURPOSE: To separate and recover platinum group elements in the form of powder or aq. soln. to allow easy treatment for reusing without addition of extraction assistants or excessive complexing agents by efficiently separating the platinum group elements with a relatively small amt. of the supercritical fluid from an aq. soln. or org. soln. of a metal salt mixture contg. the platinum group elements. CONSTITUTION: The complex of the platinum group elements is formed by the complexing agents, such as phosphines, phosphites, dialkyl sulfides, cyclopentadiene and carbon monoxide, etc., in the aq. soln. or org. soln. of the metal salt mixture contg. the platinum group elements. The supercritical fluid is brought into contact with this complex to extract the complex in the supercritical fluid. The supercritical fluid in which the complex is extracted is blown into an aq. ammonia soln. contg. hydrazine, sodium borohydride, thiourea or ammonium chloride in the state of maintaining the supercritical state, by which the platinum group elements dissolved in the form of the complex in the supercritical fluid are recovered into the aq. ammonia soln.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for separating a platinum group element from an aqueous solution or an organic solution of a metal salt mixture containing the platinum group element and recovering the platinum group element. More specifically, by supercritical extraction method, (1) nuclear fuel reprocessing, a method of separating and recovering platinum group elements from a metal salt mixture containing platinum group elements obtained in the non-ferrous metal hydrometallurgical process, or (2) platinum group The present invention relates to a method for separating and recovering platinum group elements from element scraps and the like.

[0002]

2. Description of the Related Art A method of complexing various metal elements and extracting and separating this complex with a supercritical fluid is known, for example, "Extraction method of acetylacetone complex with CO ₂ gas in supercritical state using acetylacetone as a complexing agent (N. Saito et al., Bull.C
hem.Soc.Jpn Vol.63, 1532 (1990)) "and" Supercritical extraction of metal ions from waste by selective complexation (Chie
nM. Wai et al., PNL-SA-21775 (1993)) ”and the like. The latter supercritical extraction method is an extraction method using CO ₂ gas in a supercritical state of a diethylticarbamic acid complex.

Further, a method of extracting and separating lanthanoid (III) from an aqueous nitric acid solution using a carbon dioxide supercritical fluid as a medium for extracting tributyl phosphate (hereinafter, referred to as TBP) is described as "from an aqueous solution using a carbon dioxide supercritical fluid. Extraction and Separation of Lanthanoids "(Japan Atomic Energy Society, 1994 Spring Annual Meeting, A2)
9 (March 1994) ”, and the method of extracting and separating uranium (VI) ions in nitric acid aqueous solution into supercritical carbon dioxide containing 2-3% TBP is called" supercritical carbon dioxide. " Development of extraction and separation method of metals as medium (II) "(Atomic Energy Society of Japan, 1995 Spring Annual Meeting, J2 (March 1995)). According to the above, compared with the conventional solvent extraction method, since the supercritical fluid is used instead of the organic solvent, the amount of waste organic solvent generated is reduced, and the medium is not toxic or flammable and the extraction operation safety is improved. There is a merit to do.

[0004]

However, when the acetylacetone complex or the diethylticarbamic acid complex is used, the above-mentioned 2
In the two supercritical extraction methods, when various elements and complexing agents are combined, the solubility of the complex in the supercritical fluid is very low, on the order of 0.01%, so the total amount of supercritical fluid used is very large. Therefore, there is a problem that an efficient extraction operation is difficult as an actual separation process. As a method for improving the solubility, when the extraction aid or the complexing agent is a liquid as in the above two examples, a much larger amount of complexing agent than that required for complexing the elements in the solution is used. There is a method of adding it to a solution and using a complexing agent as an extraction aid together. However, in this method, since the extraction aid is prepared by adding alcohol and various organic solvents, it eventually becomes close to the solvent extraction method, and the above-mentioned advantages over the solvent extraction method of the supercritical extraction method can be clearly stated. No, it is not preferable. In addition, the elements extracted by these methods are in the form of metal complexes, and in consideration of the treatment in a later step for reuse, powdery or aqueous solution is preferable, and in this case, supercritical extraction and continuous operation are performed. These forms are desired.

Therefore, an object of the present invention is to add an extraction aid or an excessive complexing agent to a platinum group element in a relatively small amount of a supercritical fluid from an aqueous solution or an organic solution of a metal salt mixture containing a platinum group element. It is an object of the present invention to provide a method capable of separating and recovering in the form of a powder or an aqueous solution, which can be easily processed for reuse without being used.

[0006]

Means for Solving the Problems In separating platinum group elements using a supercritical fluid, the inventors of the present invention examined combinations of complexing agents for platinum group elements, and selected specific platinum group elements and selective platinum group elements. A complex which forms a complex in the supercritical fluid and has a high solubility in the supercritical fluid was found, and the elemental complex dissolved in the supercritical fluid was added to a reducing agent such as hydrazine, thiourea,
The present invention has been achieved, focusing on the fact that it can be obtained as an aqueous solution of a metal or oxide powder or a platinum group element by blowing it into an aqueous solution containing ammonium chloride or the like in a supercritical state.

In order to achieve the above object, the method for separating a platinum group element according to the present invention comprises a phosphine, a phosphite, a dialkyl sulfide and a cyclopentadiene in an aqueous solution or an organic solution of a metal salt mixture containing a platinum group element. And a complex of the platinum group element is formed by one or more complexing agents selected from the group consisting of carbon monoxide, and the complex is brought into contact with a supercritical fluid to extract the complex into a supercritical fluid. , The complex-extracted platinum is dissolved as a complex in the supercritical fluid by blowing the supercritical fluid extracted from the complex into an aqueous ammonia solution containing hydrazine, sodium borohydride, thiourea or ammonium chloride while maintaining the supercritical state. This is a method of recovering a group element in the aqueous ammonia solution.

The present invention will be described in detail below. The aqueous solution or organic solution of the present invention can be obtained by nuclear fuel reprocessing, non-ferrous metal hydrometallurgical process or the like. Especially for spent nuclear fuel, ruthenium (R
u), rhodium (Rh), palladium (Pd), and other platinum group elements are contained in a considerable amount, and the reprocessing liquid also contains these platinum group elements. The platinum group element complex of the present invention is obtained by directly mixing an aqueous solution or an organic solution of a metal salt mixture containing a platinum group element with a complexing agent such as phosphines, phosphites, dialkyl sulfides, cyclopentadiene and carbon monoxide. In addition to the above, a complexing agent that forms a complex ion of a platinum group element is added to the above aqueous solution or organic solution to form a precursor of an extraction complex, and the above complexing agent is added to this precursor. It is also possible to form a platinum group element complex.

The complexing agent for platinum group elements, which is a feature of the present invention, is one or more complexes selected from the group consisting of phosphines, phosphites, dialkyl sulfides, cyclopentadiene and carbon monoxide. Examples include agents. Examples of phosphines include trimethylphosphine, triethylphosphine, tripropylphosphine, tributylphosphine, and the like, examples of phosphites include trimethylphosphite, triethylphosphite, tripropylphosphite, tributylphosphite, and dialkylsulfides. Examples thereof include butyl sulfide, hexyl sulfide, octyl sulfide and the like. Phosphines are phosphine complexes,
The phosphites form a phosphite complex, and the dialkyl sulfides form a dialkyl sulfide complex. Cyclopentadiene forms a cyclopentadiene complex and carbon monoxide forms a carbonyl complex.

Further, as a complexing agent for forming a complex ion of a platinum group element for forming a precursor of the extraction complex, N is N.
Examples are aCl, NH ₄ Cl, cyclooctadiene and the like. When the complexing agent is NaCl or NH ₄ Cl, a tetrachloro complex is formed as a precursor of the extracting complex, and when the complexing agent is cyclooctadiene, a cyclooctadiene complex is formed as a precursor of the extracting complex. To be done. Examples of the supercritical fluid of the present invention include CO ₂ gas, CFC gas or nitrous oxide gas in a supercritical state. CO ₂ gas, which is inexpensive and easy to handle, is preferable. The supercritical state of this CO ₂ gas is at a pressure of 150 to 350 atm and a temperature of 40 to 80 atm.
It is preferably in the range of ° C.

The platinum group element complex and the supercritical fluid may be contacted with each other by contacting the solid-liquid-separated platinum group element complex with the supercritical fluid or a reaction in which the platinum group element complex coexists. There is a method of contacting a liquid with a supercritical fluid. As shown in FIG. 1, for the latter contact, for example, the reaction solution 10 in which a complex of a platinum group element coexists is placed in a pressure-resistant extraction vessel 11 in advance, and the reaction solution 10 in the vessel 11 is transferred to a cylinder 12. It is performed by opening the supply valve 12a and blowing the stored supercritical fluid through the conduit 13. Platinum group elements dissolved in the supercritical fluid as a complex are hydrazine (N ₂ H ₄ ), sodium borohydride (NaBH ₄ ),
By blowing into an aqueous ammonia solution containing thiourea or ammonium chloride (NH ₄ Cl), the aqueous solution is back-extracted. A single separation / recovery container for storing the aqueous ammonia solution may be used, but a plurality of separation / recovery containers are preferably arranged to increase the separation / recovery rate of the platinum group element. FIG. 1 shows a multistage back-extraction process having a first stage separation / recovery container 14 and a final stage separation / recovery container 15. For ease of explanation, the separation / recovery container in the middle is not shown. In this case, the supercritical fluid from which the complex has been extracted is blown through the conduit 16 into the aqueous ammonia solution 17 stored in the first stage separation / recovery container 14 while maintaining the supercritical state. Next, the supercritical fluid discharged from the separation / recovery container 14 is blown through the conduit into the aqueous ammonia solution stored in the separation / recovery container (not shown) in a state of maintaining the supercritical state. It is blown into the aqueous ammonia solution 17 stored in the separation / recovery container 15 at the final stage while maintaining the supercritical state. The supercritical fluid discharged from the final stage separation / recovery container 15 is lowered to a predetermined pressure below the critical pressure by opening the discharge valve 19, and the complexing agent 20 is recovered in the container 21.

[0012]

[Function] In the solution of the present invention, phosphines, phosphites, dialkyl sulfides, cyclopentadiene,
When a complexing agent such as carbon monoxide is added and reacted, the resulting complex has a relatively low molecular weight and a symmetric structure, and C
It becomes chemically compatible with supercritical fluids such as O ₂ , chlorofluorocarbon, and nitrous oxide. Therefore, when this complex is brought into contact with the supercritical fluid of the present invention, the complex dissolves in the supercritical fluid with a solubility of about 10 to 100 times that of the conventional one. When the supercritical fluid obtained by extracting this complex is blown into an aqueous ammonia solution containing hydrazine, sodium borohydride, thiourea or ammonium chloride while maintaining the supercritical state, the platinum group element dissolved as a complex in the supercritical fluid Is back-extracted into the aqueous ammonia solution, i.e. separated from the complexing agent, by the reducing action in the case of sodium borohydride or hydrazine, or by complexing in the case of ammonium chloride or thiourea. Then, it is recovered in the aqueous ammonia solution in the form of a metal or oxide powder or an aqueous solution of a platinum group element. The recovered powdery platinum group element is taken out from the aqueous ammonia solution by a solid-liquid separation means such as filtration or centrifugation, and is reused. The platinum group element in the form of an aqueous solution is separated from the aqueous ammonia solution and reused by adding a reducing agent.

[0013]

EXAMPLES The present invention will now be described based on examples in order to show specific embodiments of the present invention. The examples described below do not limit the technical scope of the present invention. <Example 1> Pd, Pt, Rh, Ru, Mo, Pb, Fe, C were used as a metal element mixed simulation liquid containing a platinum group element.
An aqueous hydrochloric acid solution (free hydrochloric acid concentration of about 1.0 N) containing u and Al elements was prepared. The concentrations and compositions of the elements are as shown in Table 1.

[0014]

[Table 1]

Palladium (Pd) was added to 100 ml of this solution.
Na or NH ₄ Cl as a complex ion forming agent of Pd
NaCl / Pd or NH ₄ Cl / Pd with respect to the number of moles of
= 2 to 4 added / mixed to easily form a complex with a phosphine complexing agent, Pd tetrachloro complex ion (PdCl
₄ ^2- ) was formed. Next, tributylphosphine was added to and mixed with this solution at a ratio of twice the number of moles of Pd.
Dichlorobistributylphosphine complex (PdCl ₂
(PBu ₃ ) ₂ ) was formed. The formed complex was poorly soluble in water and was suspended in an aqueous solution. Seven pressure-resistant extraction vessels were prepared, and each vessel was filled with the solution as it was, or the complex obtained by filtering water from this solution was put into these extraction vessels, and CO ₂ or CHF ₃ (chlorofluorocarbon) in a supercritical state was placed in these extraction vessels. )
Blew in. Specifically, when blowing CO ₂ , as shown in Table 2, the pressure is 150 atm and 350 atm.
Under the two conditions of 40 ° C. and 80 ° C., and the supercritical extraction operation was performed for the times shown in Table 2. When CHF ₃ is blown in, as shown in Table 2, the pressure is set to one condition of 350 atm and the temperature is set to 40 ° C.
And the supercritical extraction operation was performed under the two conditions of 80 ° C. and the time shown in Table 2. The flow rate of CO ₂ or CHF ₃ was 3.0 ml / min on a liquid basis. After the supercritical extraction operation, the pressure of CO ₂ or CHF ₃ discharged from the extraction container was reduced to atmospheric pressure, the weight of the extracted complex was measured, and the composition of the elements of the complex was analyzed. From the measurement and analysis results, the recovery rate of Pd from the simulated aqueous solution and the solubility of the Pd complex in the supercritical fluid were determined. The results are shown in Table 2.

[0016]

[Table 2]

As is clear from Table 2, the recovery rate of Pd from the simulated aqueous solution when CO ₂ was used as the supercritical fluid was 93% even when the filtration was not carried out.
The recovery rate was as high as 7 to 98%. CO ₂ and CH
The solubility of the Pd complex in the supercritical fluid of F ₃ was 1.2% or more, which was about 100 times that in the conventional method, which was on the order of 0.01%. This is because the total amount of the supercritical fluid used for separating the Pd complex is about 1/100 of that of the conventional method, and the method of the embodiment is feasible in constructing the process and in separating operation. Proved to be a high method.

Further obtained Pd dichlorobistributylphosphine complex (hereinafter referred to as Pd-PBu ₃ complex)
0.5 g (102 mg by weight of Pd) was charged as a charged complex into each of 5 extraction containers having pressure resistance. on the other hand,
Ten pressure-resistant separation / recovery containers were prepared, and 10 ml of each of the five kinds of back extraction solutions shown in Table 3 were stored in each container. In order to realize the one-stage extraction process and the two-stage back extraction process, two separation / recovery containers were connected in series to one extraction container for each type of back extraction solution. Keep all three containers connected in series at 40 ° C, and
₂ was blown for 30 minutes at a pressure of 150 atm and a flow rate of 3.0 ml / min to perform supercritical extraction and supercritical back extraction. P in the first-stage separation / recovery container and the second-stage separation / recovery container
The back extraction recovery of d was investigated. Table 3 shows the results. 1
Since the recovery rates of Pd in the second and second stages were almost the same, Table 3 shows only the recovery rates of Pd in the separation / recovery container in the first stage. Table 3 shows the recovery form of Pd in the back extract at this time.

[0019]

[Table 3]

As is clear from Table 3, the Pd-PBu ₃ complex, which is a hardly soluble solid complex obtained by supercritical extraction, was converted into N ₂
The solution is partially dissolved in a back extract containing H ₄ , thiourea and NH ₄ Cl and recovered as an aqueous solution of Pd. In the back extract containing NaBH ₄ , the Pd-PBu ₃ complex is reduced and the metal P
It was recovered as a powdery precipitate of d. The one-stage recovery rate by the above-mentioned back extract was at least about 20%, and particularly the one using an aqueous ammonia solution containing 10% of thiourea as the back extract showed a high recovery rate of nearly 50%. Further, CO ₂ as a supercritical fluid was removed in the final trap of the discharge system of the second stage separation / recovery container to obtain a residue. Analysis of this residue revealed that P was not recovered in the two-stage back extraction process.
The total amount of d was detected.

Example 2 CHF ₃ was used as the supercritical fluid instead of CO ₂ , the charged amount of the Pd-PBu ₃ complex was adjusted to 0.5 g (Pd weight 102 mg), and N ₂ H ₄ was used as the back extract. 1-stage supercritical extraction and 2-stage supercritical back extraction were carried out in the same manner as in Example 1 except that an aqueous ammonia solution containing was used. The results are shown in Table 4.

Example 3 N ₂ O was used instead of CO ₂ as a supercritical fluid, the charged amount of Pd-PBu ₃ complex was adjusted to 0.5 g (Pd weight: 102 mg), and NH ₄ Cl was used as a back extraction liquid. Except that an aqueous ammonia solution containing
In the same manner as in Example 1, one-stage supercritical extraction and two-stage supercritical back extraction were performed. The results are shown in Table 4.

[0023]

[Table 4]

As is clear from Table 4, the recovery form of Pd according to the type of the back extract was the same as in Example 1. The recovery rate of Pd by the above-mentioned back extract was 20 to 22%, and Example 1 was used.
It was low compared to.

<Embodiment 4> Ru, Pd, Pt, Rh, Mo and P were used as a metal element mixed simulation liquid containing a platinum group element.
A hydrochloric acid-acidic (free hydrochloric acid concentration: about 0.5 N) ethanol aqueous solution containing b, Fe, Cu, and Al elements was prepared.
The element concentrations and compositions are shown in Table 5.

[0026]

[Table 5]

Ruthenium (Ru) was added to 100 ml of this solution.
Trimethyl phosphite is added as a complexing agent of 4 to 8 times the molar number of Ru and reacted at 0 ° C. under atmospheric pressure.
A methylphosphite complex of Ru (RuCl ₂ [P (OCH ₃ )] ₄ ) in which phosphorous acid was four-coordinated was formed. This complex was poorly soluble in aqueous ethanol and was obtained as a precipitate. Next, four extraction containers with pressure resistance are prepared, and the complex obtained by filtering this precipitate is put into each container, and CO ₂ or N ₂ O (nitrous oxide) in a supercritical state is put into these extraction containers.
Blew in. Specifically, when blowing CO ₂ , as shown in Table 6, the pressure is 150 atm and 350 atm.
Under the two conditions of 40 ° C. and 80 ° C., and the supercritical extraction operation was performed for the times shown in Table 6. When N ₂ O is blown in, as shown in Table 6, the pressure is set to one condition of 350 atm, the temperature is set to two conditions of 40 ° C. and 80 ° C., and the supercritical extraction operation is performed for each time shown in Table 6. It was The flow rate of CO ₂ or N ₂ O was 3.0 ml / min on a liquid basis. After the supercritical extraction operation, the pressure of CO ₂ or N ₂ O discharged from the extraction container was reduced to atmospheric pressure, the weight of the extracted complex was measured, and the composition of the elements of the complex was analyzed. From the measurement and analysis results, the recovery rate of Ru from the simulated aqueous solution and the solubility of the Ru complex in the supercritical fluid were determined. Table 6 shows the results.

[0028]

[Table 6]

As is clear from Table 6, Ru can be recovered from the simulated aqueous solution at a high recovery rate of 73% to 82%, and the other elemental composition is at most 10%, so the recovered product has a Ru content of about 90%. It was of high purity.

<Embodiment 5> Ru, Pd, Pt, Rh, Mo and P were used as a metal element mixed simulation liquid containing a platinum group element.
A hydrochloric acid-acidic (free hydrochloric acid concentration: about 0.5 N) ethanol aqueous solution containing b, Fe, Cu, and Al elements was prepared.
The concentrations and compositions of the elements are as shown in Table 7.

[0031]

[Table 7]

Ruthenium (Ru) was added to 100 ml of this solution.
Cyclooctadiene as a complexing agent for Ru in a molar number of 1
~ 2 times the ratio of addition and react at 75 ℃, atmospheric pressure, R
u cyclooctadiene complex (RuCl ₂ (C ₈ H ₁₂ ))
Was formed. Furthermore, n-Bu ₃ Sn (C
₅ H ₅ ) at a ratio of 2 to 4 times the number of moles of Ru, and
The reaction is carried out at ℃ and atmospheric pressure, and the ruthenocene complex (Ru (C ₅
H ₅ ) ₂ ). The produced complex was hardly soluble in ethanol aqueous solution and was obtained as a precipitate. Next, the complex obtained by filtering off this precipitate was put into an extraction container, and CO ₂ in a supercritical state was blown into the extraction container. Specifically, as shown in Table 8, the CO ₂ pressure was set to 150 atm and 350 atm.
Under the conditions, the temperature was set to two conditions of 40 ° C. and 80 ° C., and the supercritical extraction operation with CO ₂ was performed for the times shown in Table 8. The flow rate of CO ₂ was 3.0 ml / min on a liquid basis. C discharged from the extraction container after the supercritical extraction operation
The pressure of O ₂ was reduced to atmospheric pressure, the weight of the extracted complex was measured, and the elemental composition of the complex was analyzed. From the measurement and analysis results, the recovery rate of Ru from the simulated aqueous solution and the solubility of the Ru complex in the supercritical fluid were determined. Table 8 shows the results.

[0033]

[Table 8]

As is clear from Table 8, Ru can be recovered from the simulated aqueous solution at a high recovery rate of 78% to 88%, and the other elemental composition is at most 10%, so the recovered product has a Ru content of about 90%. It was of high purity.

<Embodiment 6> Ru, Pd, Pt, Rh, Mo and P are used as a metal element mixed simulation liquid containing a platinum group element.
A hydrochloric acid-acidic (free hydrochloric acid concentration: about 0.5 N) ethanol aqueous solution containing b, Fe, Cu, and Al elements was prepared.
The concentrations and compositions of the elements are as shown in Table 9.

[0036]

[Table 9]

Ruthenium (Ru) was added to 100 ml of this solution.
Carbon monoxide (CO) is used as a complexing agent for Ru in a molar number of 1
It was added at a ratio of 2 times and reacted at 125 ° C. and 60 atm to form a Ru carbonyl complex (Ru ₃ (CO)). The produced complex was hardly soluble in ethanol aqueous solution and was obtained as a precipitate. Next, the complex obtained by filtering off this precipitate is put into an extraction vessel, and C in a supercritical state is placed in this extraction vessel.
Blow O ₂ . Specifically, as shown in Table 10, C
The supercritical extraction operation with CO ₂ was carried out under the conditions of O ₂ pressure of 150 atm and 350 atm and the temperature of 40 ° C. and 80 ° C. for the times shown in Table 10. The flow rate of CO ₂ was 3.0 ml / min on a liquid basis. CO ₂ discharged from the extraction container after the supercritical extraction operation
The pressure of was reduced to atmospheric pressure, the weight of the extracted complex was measured, and the elemental composition of the complex was analyzed. From the measurement and analysis results, the recovery rate of Ru from the simulated aqueous solution and the solubility of the Ru complex in the supercritical fluid were determined. The results are shown in Table 10.

[0038]

[Table 10]

As is clear from Table 10, Ru can be recovered from the simulated aqueous solution at a high recovery rate of 85% to 94%, and the other elemental composition is at most 15%.
Was a high purity of about 85%.

<Example 7> As a charged complex, 0.5 ml of Pd-helxyl sulfide complex (hereinafter referred to as Pd-DHS complex) (12.5 mg by weight of Pd) was placed in each of 5 pressure-resistant extraction vessels. It was On the other hand, five pressure-resistant separation / recovery containers were prepared, and 10 ml of each of the five types of back extraction solutions shown in Table 11 were stored in each container. In order to realize the one-stage extraction process and the one-stage back extraction process, one separation / recovery container was connected in series to one extraction container for each type of back extraction solution. All of these two containers connected in series were kept at 40 ° C., and CO ₂ was supplied to all the containers at a pressure of 150 a.
Supercritical extraction and supercritical back extraction were carried out by blowing at tm at a flow rate of 3.0 ml / min for 30 minutes. The reverse extraction recovery rate of Pd in the separation / recovery container was examined. The results are shown in Table 11. The recovery form of Pd in the back extract at this time is shown in Table 1.
It is shown in FIG.

[0041]

[Table 11]

As is clear from Table 11, the recovery form of Pd depending on the type of the back extract was the same as in Example 1. The one-step recovery rate by the above-mentioned back extract was 36% or more, and particularly the one using an aqueous ammonia solution containing 10% of thiourea as a back extract showed an extremely high recovery rate of 95%.

[0043]

As described above, according to the present invention, phosphines, phosphites, dialkyl sulfides, cyclopentadiene, carbon monoxide and the like are selected as complexing agents, and the platinum group is selected by the complexing agent. When a complex of an element is formed, the complex has a relatively low molecular weight and a symmetric structure, and when the complex is brought into contact with a supercritical fluid such as CO ₂ , chlorofluorocarbon, and nitrous oxide, the complex is formed. It dissolves in a supercritical fluid with a solubility of 10 to 100 times that of the conventional one. When the supercritical fluid extracted from this complex is blown into an aqueous ammonia solution containing hydrazine, sodium borohydride, thiourea or ammonium chloride while maintaining the supercritical state,
The platinum group element dissolved in the supercritical fluid as a complex is back-extracted and recovered in the aqueous ammonia solution.

As a result, it is possible to efficiently separate the platinum group element from the aqueous solution or organic solution in which the metal salt mixture containing the platinum group element is dissolved with a relatively small amount of supercritical fluid, which is about 1/10 to 1/100 of the conventional one. In addition, the platinum group element can be recovered in the form of a metal or oxide powder which can be easily treated for reuse or an aqueous solution of the platinum group element.

[Brief description of drawings]

FIG. 1 is a block diagram of a platinum group element separation / recovery device of the present invention.

[Explanation of symbols]

 10 Reaction liquid in which complex of platinum group element coexists 11 Extraction container 12 Cylinder for storing supercritical fluid 14, 15 Separation / recovery container 17 Aqueous ammonia solution (back extraction liquid) 20 Complexing agent

Front page continuation (72) Kenji Nishimura Inventor Kenji Nishimura 14 Nakamura, Naka-cho, Ibaraki Prefecture

Claims (8)

[Claims] 1. One or more selected from the group consisting of phosphines, phosphites, dialkyl sulfides, cyclopentadiene and carbon monoxide in an aqueous solution or organic solution of a metal salt mixture containing a platinum group element. The complexing agent of the platinum group element is generated by the complexing agent of, the supercritical fluid is brought into contact with the complex to extract the complex into the supercritical fluid, and the supercritical fluid from which the complex is extracted is hydrazine or borohydride. By blowing in an aqueous ammonia solution containing sodium, thiourea or ammonium chloride while maintaining a supercritical state, the platinum group element dissolved as a complex in the supercritical fluid is recovered in the aqueous ammonia solution. A method for separating and recovering platinum group elements in a solution. 2. The phosphine is trimethylphosphine,
The method for separating and recovering a platinum group element in a solution according to claim 1, which is triethylphosphine, tripropylphosphine or tributylphosphine. 3. The method for separating and recovering a platinum group element in a solution according to claim 1, wherein the phosphite is trimethylphosphite, triethylphosphite, tripropylphosphite or tributylphosphite. 4. The method for separating and recovering a platinum group element in a solution according to claim 1, wherein the dialkyl sulfides are butyl sulfide, hexyl sulfide and octyl sulfide. 5. The platinum group element in the solution according to claim 1, wherein the platinum group element complex and the supercritical fluid are contacted with each other by contacting the solid-liquid separated platinum group element complex with the supercritical fluid. Separation / collection method. 6. The platinum group element in the solution according to claim 1, wherein the contact between the platinum group element complex and the supercritical fluid is carried out by contact between the reaction solution in which the platinum group element complex coexists and the supercritical fluid. Separation / collection method. 7. A CO ₂ gas in which the supercritical fluid is in a supercritical state,
The method for separating and recovering a platinum group element in a solution according to claim 1, which is a CFC gas or a nitrous oxide gas. 8. CO ₂ gas in a supercritical state has a pressure of 150 to
C in the temperature range of 40 to 80 ° C. in the range of 350 atm
The method for separating and recovering a platinum group element in a solution according to claim 7, which is O ₂ gas.