Solubilization method for platinum group metal and metal separation method

Abstract

To reduce energy used and CO2 emission in a solubilization method for platinum group metal by which a platinum group metal compound soluble in water and dilute acid is generated by oxidizing platinum group metal included in a raw material.SOLUTION: A solubilization method for platinum group metal includes: obtaining a heat-treated material including a water-soluble platinum group metal compound by heating a mixture of a raw material including platinum group metal and an additive including potassium carbonate, sodium carbonate, and boron oxide at a predetermined heating temperature; and separating a water solvent obtained after components of the additive are leached out of the heat-treated material, and a water leach residue of the heat treated material by immersing the heat treated material in water. The heating temperature is higher than a melting point of the mixture of potassium carbonate, sodium carbonate, and boron oxide in the additive, and is lower than a melting point of sodium carbonate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for solubilizing platinum group metals contained in a raw material to form a water-soluble platinum group metal compound, and a method for separating metals using this method. [Background technology]

[0002] Platinum group metals have excellent catalytic properties and are used in various applications, such as automobile exhaust gas purification catalysts. Platinum group metals are rare. Therefore, methods have been proposed for extracting platinum group metals from waste products such as spent catalysts, which have higher platinum group metal concentrations than natural ores.

[0003] For example, the separation method disclosed in Patent Document 1 includes a melting step in which a mixture of potassium hydroxide and boron oxide is heated to obtain a molten material; a heat-treatment step in which a mixture of the raw material, the molten material, and potassium carbonate is heated to obtain a heat-treated product; an immersion step in which the heat-treated product is immersed in water, 0.01 M hydrochloric acid, 0.1 M hydrochloric acid, and 1 M hydrochloric acid, in that order, for 2 hours each, and then each solution into which the components of the heat-treated product have been eluted by immersion and an insoluble residue are obtained; and a recovery step in which the platinum group metals dissolved in each solution are recovered, and gold is recovered as an insoluble residue. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-127493 Summary of the Invention [Problem to be solved by the invention]

[0005] The method of Patent Document 1 produces a platinum group metal solution by dissolving platinum group metals in water or a dilute acid solution, which are less expensive than aqua regia. However, the melting step and the heat treatment step for obtaining the heat-treated product require heating the mixture at a high temperature of approximately 1000°C, leaving room for improvement in terms of reducing energy consumption and CO2 emissions.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to reduce energy consumption and CO2 emissions in a method for solubilizing platinum group metals, which produces platinum group metal compounds that are soluble in water or dilute acid by oxidizing platinum group metals contained in raw materials. [Means for solving the problem]

[0007] In order to solve the above problems, a method for solubilizing a platinum group metal according to one embodiment of the present disclosure includes: a mixture of a raw material containing a platinum group metal and an additive containing potassium carbonate, sodium carbonate, and boron oxide is heated at a predetermined heating temperature to obtain a heat-treated product containing a water-soluble platinum group metal compound; and immersing the heat-treated product in water and separating the water solvent into which the additive components have been leached from the heat-treated product and the water-leached residue of the heat-treated product; The heating temperature is higher than the melting point of the mixture of potassium carbonate, sodium carbonate, and boron oxide in the additive, but lower than the melting point of sodium carbonate.

[0008] Further, a method for separating metals according to one embodiment of the present disclosure includes: immersing the water leaching residue obtained by the method for solubilizing platinum group metals in a dilute hydrochloric acid solution, and separating the acid solvent into which the platinum group metal compound has been leached and the insoluble residue; and and recovering the platinum group metal by extraction from the acid solvent. [Effects of the Invention]

[0009] According to the present disclosure, a method for solubilizing platinum group metals, which produces platinum group metal compounds that are soluble in water or dilute acid by oxidizing platinum group metals contained in raw materials, can contribute to reducing energy consumption and CO2 emissions. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a flow diagram of a method for separating metals according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In a first embodiment, a method for separating platinum group metals from a raw material containing platinum group metals will be described. In a second embodiment, a method for separating platinum group metals and Au from a raw material containing multiple types of platinum group metals and Au will be described.

[0012] [First embodiment] FIG. 1 is a flow chart of a metal separation method according to the present disclosure. The metal separation method according to a first embodiment of the present disclosure is a method for separating platinum group metals from a raw material 1 containing platinum group metals. The metal separation method includes a method for solubilizing platinum group metals contained in the raw material 1 to make them soluble in water or a dilute acid solution. The platinum group metal contained in the raw material 1 is, for example, at least one of Pd, Pt, Rh, Ir, Os, and Ru. Examples of raw material 1 containing such platinum group metals include waste automobile catalysts and electronic device scrap.

[0013] The metal separation method shown in FIG. 1 includes a heat treatment step S1, a water leaching step S2, an acid leaching step S3, and a recovery step S4.

[0014] <Heat treatment process S1> In the heat treatment step S1, a mixture of a raw material 1 containing a platinum group metal and an additive 2 is heated to obtain a heat-treated product 5. The heat-treated product 5 contains a platinum group metal compound 50, which is an oxidation product produced by heating the platinum group metal together with the additive 2.

[0015] Additive 2 is a mixture of boron oxide (BO), potassium carbonate (KCO), and sodium carbonate (NaCO). Potassium carbonate and sodium carbonate function as reactants for oxidizing platinum group metals. Boron oxide functions as a reaction aid for oxidizing platinum group metals. An example of a source of boron oxide is glass containing boron oxide. Additive 2 may contain, as an oxidizing agent, a carbonate and / or hydroxide of an alkali metal in addition to potassium carbonate and sodium carbonate. Additive 2 may also contain, as a reaction aid, at least one oxide selected from the group consisting of NaO, KO, SiO, LiO, RbO, CsO, and PO, in addition to boron oxide.

[0016] The mixture of raw material 1 and additive 2 is heated at a predetermined temperature. The heating temperature is higher than the melting point of additive 2 and lower than the melting point of sodium carbonate (851°C). The melting point of additive 2 is the melting point of the mixture of potassium carbonate, sodium carbonate, and boron oxide in additive 2. The heating time is preferably 30 minutes or more, more preferably 60 minutes or more, and even more preferably 120 minutes.

[0017] The melting points of samples were measured: a mixture of boron oxide and potassium carbonate (B2O3-75mol%K2CO3) and a mixture of boron oxide, potassium carbonate, and sodium carbonate (B2O3-36.8mol%K2CO3-50.8mol%Na2CO3). The notation B2O3-75mol%K2CO3 indicates that the mixture is boron oxide and potassium carbonate, and that the ratio of the amount of K to the total amount of B and K (=K / (K+B)) is 2.94. The same applies to B2O3-36.8mol%K2CO3-50.8mol%Na2CO3. To measure the melting points, TG / DTA analysis was performed while the samples were heated, and the melting points of each sample were estimated from the analysis results. In Table 1 below, in addition to the measurement results of the melting points of the samples, literature values ​​for the melting points of potassium carbonate, sodium carbonate, and a mixture of potassium carbonate and sodium carbonate (K2CO3-58 mol% Na2CO3) are shown.

[0018] [Table 1]

[0019] From Table 1, it can be seen that the melting point of the sample of the mixture of boron oxide, potassium carbonate, and sodium carbonate is 641°C, which is lower than the melting point of sodium carbonate alone (851°C) and lower than the melting point of the sample of the mixture of boron oxide and potassium carbonate excluding sodium carbonate (790°C). In this way, when Additive 2 contains not only potassium carbonate but also sodium carbonate, the melting point of Additive 2 is lowered due to the eutectic melting phenomenon of a multi-component system. Therefore, Additive 2 can be liquefied with less energy than when Additive 2 does not contain sodium carbonate.

[0020] It is known that the eutectic melting reaction varies depending on the mixture composition and heating temperature. Therefore, the melting point of the mixture of potassium carbonate, sodium carbonate, and boron oxide in Additive 2 varies depending on the mixture ratio of potassium carbonate, sodium carbonate, and boron oxide. Research on the eutectic melting phenomenon of boron oxide, potassium carbonate, and sodium carbonate is very limited. However, the eutectic melting phenomenon of potassium carbonate and sodium carbonate has been studied for some time, with the melting point being a minimum of approximately 710°C for K2CO3-58mol%Na2CO3, approximately 750°C for K2CO3-37mol%Na2CO3, and approximately 750°C for K2CO3-77mol%Na2CO3. Because the amount of boron oxide in Additive 2 is small compared to potassium carbonate and sodium carbonate, the main components of Additive 2 can be considered potassium carbonate and sodium carbonate. The melting behavior of Additive 2 can be predicted using the binary phase diagram of a mixture of potassium carbonate and sodium carbonate. In a mixture of potassium carbonate and sodium carbonate, if the ratio of the amount of sodium to the total amount of potassium and sodium (=Na / (K+Na) × 100) is significantly higher than 58 mol%, not only will the melting temperature increase, but the reaction between potassium carbonate and platinum group metals will decrease, potentially leading to a decrease in the dissolution rate of the platinum group metals. In light of the above, with regard to the relationship between potassium carbonate and sodium carbonate in Additive 2, the ratio of the amount of sodium to the total amount of potassium and sodium is preferably 37 mol% to 77 mol%, more preferably 37 mol% to 65 mol%. For Additive 2 with this composition, the heating temperature of the mixture of Raw Material 1 and Additive 2 in the heat treatment step S1 is preferably 650°C to 750°C, more preferably 710°C to 750°C. If the heating temperature is lower than 650°C, the molten state of Additive 2 may become unstable. On the other hand, when the heating temperature exceeds 750°C, the difference from the conventional heating temperature (approximately 1000°C) is small, making it difficult to reduce the energy used and CO2 emissions involved in solubilizing platinum group metals.

[0021] In the heat treatment step S1, the raw material 1 and the molten additive 2 are heated in a mixed state, thereby oxidizing the platinum group metal in the raw material 1 and producing a water-soluble platinum group metal compound 50, which is an oxidation product of the platinum group metal. The solution in which the platinum group metal compound 50 is dissolved in an aqueous solvent contains many anions. These anions form coordinate bonds with the platinum group metal, thereby producing a solution of the platinum group metal. In other words, the platinum group metal compound 50 contained in the heat-treated product 5 is soluble in aqueous solvents such as water and dilute hydrochloric acid solution. Here, an "aqueous solvent" is a solvent containing water as its main component.

[0022] 《Water leaching process S2》 In the water leaching step S2, the heat-treated product 5 is immersed in an aqueous solvent 6. At this time, the immersion tank in which the heat-treated product 5 is submerged in the aqueous solvent 6 may be agitated. The water immersion time is preferably 30 minutes or more, more preferably 60 minutes or more, and even more preferably approximately 120 minutes. The aqueous solvent 6 used in the water immersion may be ion-exchanged water, distilled water, pure water, or the like, or may be water containing trace amounts of impurities (e.g., chlorine, etc.), such as tap water. When the heat-treated product 5 is immersed in the aqueous solvent 6, the components of the additive 2 contained in the heat-treated product 5 are leached into the aqueous solvent 6. The residue of the heat-treated product 5 after water immersion (hereinafter referred to as "water leaching residue 51") is separated from the aqueous solvent 6 and sent to the subsequent acid leaching step S3.

[0023] The aqueous solvent 6 separated from the water leaching residue 51 contains almost no platinum group metals but contains a large amount of the components of the additive 2. Therefore, the aqueous solvent 6 separated from the water leaching residue 51 may be dried and then reused as the additive 2.

[0024] 《Acid leaching process S3》 In the acid leaching step S3, the water leaching residue 51 is immersed in an acid solvent 7. More specifically, the water leaching residue 51 is immersed stepwise in a plurality of dilute hydrochloric acid aqueous solutions of different concentrations. The concentration of the dilute hydrochloric acid aqueous solution increases step by step. For example, when acid leaching is performed in three steps, the heat-treated product 5 is immersed in a 0.01 M hydrochloric acid aqueous solution, a 0.1 M hydrochloric acid aqueous solution, and a 1 M hydrochloric acid aqueous solution in this order. Note that M=mol / dm 3Specifically, first, the water leaching residue 51 is immersed in a 0.01 M hydrochloric acid solution. Next, the solid residue that does not dissolve in the 0.01 M hydrochloric acid solution is immersed in a 0.1 M hydrochloric acid solution. Finally, the solid residue that does not dissolve in the 0.1 M hydrochloric acid solution is immersed in a 1 M hydrochloric acid solution. The immersion time in each dilute hydrochloric acid solution is preferably 30 minutes or more, more preferably 60 minutes or more, and even more preferably approximately 120 minutes. When the water leaching residue 51 or its acid leached residue is immersed in a dilute hydrochloric acid solution, the platinum group metal compound 50 contained in these residues is leached into the dilute hydrochloric acid solution used as a solvent. In this way, the dilute hydrochloric acid solution after immersion of the water leaching residue 51 or its acid leached residue is separated from the residue and sent to the recovery step S4. Alternatively, the solid residue that does not dissolve in the 1 M hydrochloric acid solution (hereinafter referred to as the "insoluble residue 52") may be sent to the recovery step S4.

[0025] In the acid leaching step S3, different solvents are used to elute the platinum group metal compound 50, thereby obtaining an acid solvent 7 in which a specific type of platinum group metal is dissolved. However, multiple types of platinum group metals may be dissolved in one solvent, or one platinum group metal may be dissolved in multiple types of solvents.

[0026] <<Recovery process S4>> In the recovery step S4, platinum group metals 53 are extracted and recovered from the acid solvent 7 into which the platinum group metals were eluted in the acid leaching step S3. In the recovery step S4, the metals may also be recovered from the insoluble residue 52. The extraction of platinum group metals 53 from the acid solvent 7 may be performed by a known solvent extraction method for platinum group metals using an organic solvent. This method of extracting platinum group metals allows selective extraction and recovery of platinum group metals from waste catalysts or scrap in a low-corrosion environment without using a strong acidic solvent such as aqua regia or concentrated hydrochloric acid, which are harmful.

[0027] Second Embodiment A metal separation method according to a second embodiment of the present disclosure is a method for separating platinum group metals and Au from a raw material 1 containing multiple types of platinum group metals and Au. The metal separation method includes a method for solubilizing platinum group metals contained in raw material 1 to make them soluble in water or a dilute acid solution.

[0028] The multiple types of platinum group metals contained in raw material 1 may be, for example, at least two selected from the group consisting of Pd, Pt, and Rh (e.g., (i) Pd and Pt, (ii) Pd and Rh, (iii) Pt and Rh, or (iv) Pd, Pt, and Rh). Examples of raw material 1 containing multiple types of platinum group metals and Au include waste automobile catalysts and electronic device scrap.

[0029] The metal separation method according to the second embodiment includes, as in the metal separation method according to the first embodiment, a heat treatment step S1, a water leaching step S2, an acid leaching step S3, and a recovery step S4, as shown in FIG.

[0030] <Heat treatment process S1> In the heat treatment step S1, a mixture of a raw material 1 containing multiple types of platinum group metals and gold and an additive 2 is heated to obtain a heat-treated product 5. The process flow of the heat treatment step S1 is the same as that of the first embodiment, and a detailed description of the heat treatment step S1 of the second embodiment will be omitted by referring to the description of the heat treatment step S1 of the first embodiment. The heat-treated product 5 produced in the heat treatment step S1 contains a water-soluble platinum group metal compound 50.

[0031] 《Water leaching process S2》 In the water leaching step S2, the heat-treated product 5 is immersed in an aqueous solvent 6 to leach the components of additive 2 contained in the heat-treated product 5 into the aqueous solvent 6. The process flow of the water leaching step S2 is the same as that of the first embodiment, and the description of the water leaching step S2 of the first embodiment will be referred to, and a detailed description of the water leaching step S2 of the second embodiment will be omitted. The water leaching residue 51, which is the residue of the heat-treated product 5 after water immersion, is separated from the aqueous solvent 6 and sent to the next acid leaching step S3.

[0032] 《Acid leaching process S3》 In the acid leaching step S3, the water leaching residue 51 is immersed in an acid solvent 7 to dissolve the platinum group metal contained in the water leaching residue 51 into the acid solvent 7. The processing flow of the acid leaching step S3 is the same as that of the first embodiment described above, and therefore, by referring to the description of the acid leaching step S3 of the first embodiment, a detailed description of the acid leaching step S3 of the second embodiment will be omitted.

[0033] In the acid leaching step S3, the acid solvent 7 in which the platinum group metals have been dissolved is separated from the residue and sent to the recovery step S4. Note that Au contained in the raw material 1 is almost insoluble in both the water solvent 6 and the acid solvent 7. Therefore, Au is mainly contained in the insoluble residue 52 that remains in the 1M hydrochloric acid solution without dissolving. The insoluble residue 52 is separated from the 1M hydrochloric acid solution and sent to the recovery step S4.

[0034] <<Recovery process S4>> In the recovery step S4, the platinum group metals 53 dissolved in the acid solvent 7 obtained in the acid leaching step S3 are extracted, and Au is recovered as an insoluble residue 52. The extraction of the platinum group metals 53 from the acid solvent 7 may be performed by a known solvent extraction method for platinum group metals using an organic solvent. Furthermore, since Au has low solubility in the water solvent 6 and the acid solvent 7, Au can be recovered as an insoluble residue 52.

[0035] [Example] In the examples described below, it was confirmed that platinum group metals were solubilized in the heat treatment step S1 when a mixture of boron oxide, potassium carbonate, and sodium carbonate was used as additive 2 and the heating temperature was 720°C (Example 1) and when a mixture of boron oxide and potassium carbonate was used as additive 2 and the heating temperature was 1000°C (Comparative Example 1).

[0036] -Experimental Method- <Heat treatment process S1> A simulated raw material containing platinum group metals and additives was mixed and placed in an alumina crucible. The mixture was heated in an electric furnace at a predetermined temperature for two hours to obtain a heat-treated product. The simulated raw material consisted of 17.6 mg of Pt, 9.6 mg of Pd, 9.3 mg of Rh, 0.981 g of Al2O3, 0.867 g of ZrO2, 0.494 g of CeO2, and impurities. Table 2 shows the additive composition and heating temperature for Example 1 and Comparative Example 1. In Example 1 and Comparative Example 1, the ratio of the total amount of Pt, Pd, and Rh in the simulated raw material to the amount of K in the additive (= K / (Pt + Pd + Rh)), i.e., the molar ratio, was 207. In Example 1 and Comparative Example 1, the ratio of the amount of K to the amount of B in the additive (= K / B), i.e., the molar ratio, was 2.94. In Example 1, the ratio of the amount of Na to the total amount of K and Na in the additive (=Na / (K+Na)), that is, the molar ratio, is 0.58. 《Water leaching process S2》 The heat-treated product was immersed in an aqueous solvent at room temperature for 1 hour, and the water leaching residue that remained undissolved in the aqueous solvent was separated from the aqueous solvent by filtration. Ion-exchanged water was used as the aqueous solvent. 《Acid leaching process S3》 The water leaching residue was immersed in an acid solvent at room temperature for 1 hour, and the acid leaching residue that remained undissolved in the acid solvent was separated from the acid solvent by filtration. 1M aqueous hydrochloric acid was used as the acid solvent.

[0037] [Table 2]

[0038] -Method for analyzing dissolution rate- In the water leaching step S2, the aqueous solvent after immersion of the heat-treated product was recovered, and the dissolution rate of the metal elements dissolved in the aqueous solvent was measured. In the acid leaching step S3, the acid solvent after immersion of the water leaching residue was recovered, and the dissolution rate of the metal elements dissolved in the acid solvent was measured. In measuring the dissolution rate, the amount [b] of each metal element dissolved in each recovered solvent was measured by ICP atomic emission spectrometry, and the amount [a] of each metal element contained in raw material 1 and additive 2 was set to 100%, and the dissolution rate of each metal element [dissolution rate (%) = b ÷ a × 100] was calculated. Note that mass was used to represent the amount of metal element. The measurement results of the dissolution rates of the metal elements are shown in Table 3.

[0039] [Table 3]

[0040] It was confirmed that metals were dissolved in both the aqueous solvent and the acid solvent in Example 1. This confirmed that the platinum group metals contained in the simulated raw material were solubilized even in Example 1, where heat treatment was performed at a lower temperature than in Comparative Example 1. In particular, higher solubilization of palladium was observed in Example 1 compared to Comparative Example 1.

[0041] [Summary] The method for solubilizing a platinum group metal according to the first aspect of the present disclosure comprises: A mixture of a raw material 1 containing a platinum group metal 53 and an additive 2 containing potassium carbonate, sodium carbonate, and boron oxide is heated at a predetermined heating temperature to obtain a heat-treated product 5 containing a water-soluble platinum group metal compound 50; and immersing the heat-treated product (5) in water and separating an aqueous solvent (6) from which the components of the additive (2) have been leached from the heat-treated product (5) and a water leaching residue (51) of the heat-treated product (5); The heating temperature is higher than the melting point of the mixture of potassium carbonate, sodium carbonate, and boron oxide in Additive 2, but lower than the melting point of sodium carbonate.

[0042] According to the above-described method for solubilizing platinum group metals, since additive 2 contains sodium carbonate, the melting point of additive 2 is lower than that of a mixture of boron oxide and potassium carbonate. Therefore, the heating temperature for the mixture of raw material 1 and additive 2 can be lowered compared to when an additive consisting of boron oxide and potassium carbonate is used. As a result, the energy used and CO2 emissions involved in solubilizing platinum group metals can be reduced.

[0043] A method for solubilizing a platinum group metal according to a second aspect of the present disclosure is the method for solubilizing a platinum group metal according to the first aspect, wherein the heating temperature is 650°C or higher and 750°C or lower.

[0044] According to the method for solubilizing platinum group metals relating to the second item, the heating temperature of the mixture of raw material 1 and additive 2 can be lowered compared to when an additive consisting of boron oxide and potassium carbonate is used.

[0045] A method for solubilizing a platinum group metal according to a third aspect of the present disclosure is the method for solubilizing a platinum group metal according to the first or second aspect, wherein the ratio of the amount of sodium to the total amount of potassium and sodium in the additive is 37 mol % or more and 77 mol % or less.

[0046] According to the method for solubilizing a platinum group metal according to the third aspect, the melting point of Additive 2 can be set in a lower range, and the heating temperature of the mixture of Raw Material 1 and Additive 2 can be lowered.

[0047] A method for solubilizing a platinum group metal according to a fourth item of the present disclosure is the method for solubilizing a platinum group metal according to any one of the first to third items, wherein the platinum group metal is at least one of Pd, Pt, Rh, Ir, Os, and Ru.

[0048] The method for solubilizing a platinum group metal according to the present disclosure is suitable for solubilizing the platinum group metals exemplified above.

[0049] The method for separating metals according to the fifth aspect of the present disclosure comprises: immersing the water leaching residue obtained by the method for solubilizing platinum group metals according to any one of items 1 to 4 in a dilute hydrochloric acid solution, and separating the acid solvent into which the platinum group metal compound has been leached and the insoluble residue; and and recovering the platinum group metal by extraction from the acid solvent.

[0050] A method for separating metals according to a sixth item of the present disclosure is the method for separating metals according to the fifth item, further comprising recovering metals from the insoluble residue.

[0051] As described above, the metal separation methods according to the fifth and sixth items can reduce the energy consumption and CO2 emissions associated with the solubilization of platinum group metals, thereby reducing the energy consumption and CO2 emissions associated with the separation of metals, including the solubilization of platinum group metals. [Explanation of symbols]

[0052] 1: Raw materials 2: Additives 5: Heat-treated material 6: Water solvent 7: Acid solvent 50:Platinum group metal compound 51: Water leaching residue 52: Insoluble residue 53: Platinum group metals

Claims

1. a method for producing a heat-treated product containing a water-soluble platinum group metal compound by heating a mixture of a raw material containing a platinum group metal and an additive containing potassium carbonate, sodium carbonate, and boron oxide at a predetermined heating temperature; immersing the heat-treated product in water and separating the water solvent into which the additive components have been leached from the heat-treated product and the water-leached residue of the heat-treated product; the heating temperature is higher than the melting point of the mixture of potassium carbonate, sodium carbonate, and boron oxide in the additive and lower than the melting point of sodium carbonate; Method for solubilizing platinum group metals.

2. The heating temperature is 650°C or higher and 750°C or lower.

2. The method for solubilizing platinum group metals according to claim 1.

3. the ratio of the amount of sodium to the total amount of potassium and sodium in the additive is 37 mol% or more and 77 mol% or less; 3. The method for solubilizing platinum group metals according to claim 1 or 2.

4. The platinum group metal is at least one of Pd, Pt, Rh, Ir, Os, and Ru; 3. The method for solubilizing platinum group metals according to claim 1 or 2.

5. immersing the water leaching residue obtained by the method for solubilizing platinum group metals according to claim 1 in a dilute hydrochloric acid solution, and separating the acid solvent into which the platinum group metal compound has been leached and the insoluble residue; and extracting and recovering the platinum group metal from the acid solvent. Methods for separating metals.

6. recovering metals from the insoluble residue. The method for separating metals according to claim 5.

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