Platinum group metal recovery agent and platinum group metal recovery method

Abstract

A platinum group metal recovery agent represented by the following general formula (1) and a platinum group metal recovery method which is a method for recovering platinum or rhodium from a hydrochloric acid solution containing platinum or rhodium using the platinum group metal recovery agent, in which the aforementioned platinum group metal recovery agent is mixed with the aforementioned hydrochloric acid solution to precipitate platinum or rhodium.

Description

Technical Field

[0001] This invention relates to platinum group metals recovery agents and methods for recovering platinum group metals. Background Technology

[0002] Platinum group metals are extremely important metals in industry. Among them, platinum, palladium, and rhodium are mainly used as catalysts for purifying automotive exhaust gases. Therefore, selectively separating and recovering platinum group metals from used catalysts is crucial.

[0003] Typically, precious metals are recovered using methods such as electrolytic deposition, dialysis, ion exchange, precipitation, and solvent extraction. Among these methods, precipitation and solvent extraction, which offer excellent economic efficiency and operability, are widely used.

[0004] The use of amines is being investigated as a selective precipitation-based method for the recovery of platinum group metals.

[0005] For example, in Patent Document 1, a rhodium recovery agent is disclosed for the purpose of low-cost and efficient recovery of rhodium. The agent is a solid having an amide bond and a phenylenediamine structure and is insoluble in hydrochloric acid of a certain concentration.

[0006] In addition, Patent Document 2 discloses, specifically for the purpose of efficiently separating rhodium, that platinum group metals can be precipitated and recovered by adding a compound having a diaminodiphenyl structure to a hydrochloric acid solution containing platinum group metals.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2017-179409

[0010] Patent Document 2: Japanese Patent Application Publication No. 2019-206747 Summary of the Invention

[0011] The problem the invention aims to solve

[0012] Previously, when recovering platinum group metals using precipitation and solvent extraction methods, palladium was preferentially recovered, making it difficult to selectively recover platinum and rhodium beforehand. While patent documents 1 and 2 disclose methods for recovering rhodium, they do not preferentially and selectively recover platinum. Therefore, a method is needed that preferentially and selectively recovers platinum even in the presence of palladium and rhodium, and further, that selectively recovers rhodium in the presence of palladium.

[0013] Therefore, the objective of this invention is to provide a platinum group metals recovery agent and a method for recovering platinum and rhodium with selective and high recovery rates, respectively.

[0014] Solution for solving the problem

[0015] The inventors discovered that phenylenediamine is an excellent platinum group metal (PGM) recovery agent. Furthermore, they discovered a method for selectively and efficiently recovering platinum and rhodium separately using this PGM recovery agent. Moreover, they discovered a method for preferentially and selectively recovering platinum, followed by selectively recovering rhodium, even in the presence of previously difficult-to-recover palladium and rhodium, thus completing this invention.

[0016] That is, the present invention is a platinum group metal recovery agent represented by the following general formula (1) and a platinum group metal recovery method, which is a method for recovering platinum or rhodium from a hydrochloric acid solution containing platinum or rhodium using the platinum group metal recovery agent, wherein the aforementioned platinum group metal recovery agent is mixed with the aforementioned hydrochloric acid solution to precipitate platinum or rhodium.

[0017]

[0018] The effects of the invention

[0019] According to the present invention, a platinum group metal recovery agent and a method for recovering platinum and rhodium can be provided, which are capable of selectively and efficiently recovering platinum and rhodium respectively. Attached Figure Description

[0020] Figure 1 This is a graph showing the effect of hydrochloric acid concentration on the recovery of platinum in Example 1.

[0021] Figure 2 This is a graph showing the effect of oscillation time on the recovery of platinum in Example 2.

[0022] Figure 3 This is a graph showing the effect of the molar ratio of platinum group metal recovery agent to platinum in the platinum recovery of Example 3.

[0023] Figure 4 This is a graph showing the effect of the molar ratio of platinum group metal recovery agent to rhodium in the rhodium recovery of Example 4.

[0024] Figure 5 This is a graph showing the effect of oscillation time on the recovery of rhodium in Example 5. Detailed Implementation

[0025] [Platinum Group Metals Recycling Agent]

[0026] The platinum group metal recovery agent of the present invention is represented by the following general formula (1).

[0027]

[0028] That is, the platinum group metal recovery agent of the present invention is phenylenediamine. As a platinum group metal recovery agent, at least one of the group consisting of m-phenylenediamine and p-phenylenediamine is preferably selected, and m-phenylenediamine is more preferably selected.

[0029] By using phenylenediamine, particularly m-phenylenediamine, as a platinum group metal recovery agent, platinum and rhodium can be recovered selectively and with high recovery rates, respectively. Furthermore, platinum can be recovered preferentially and selectively even in the presence of previously difficult-to-recover palladium and rhodium, and rhodium can be recovered preferentially and selectively even in the presence of palladium.

[0030] The reason why platinum and rhodium can be selectively recovered separately by using the platinum group metal recovery agent of the present invention is not yet certain, but it is believed that it is because when mixed with hydrochloric acid solution of platinum group metals, it can form crystals with specific structures with the respective platinum group metals and selectively precipitate.

[0031] The aforementioned phenylenediamines can be used alone or in combination of two or more. When using a mixture of phenylenediamines, a mixture of m-phenylenediamine and p-phenylenediamine is preferred.

[0032] The platinum group metal recovery agent of the present invention is phenylenediamine, but it may also include phenylenediamine hydrohalide. As a phenylenediamine hydrohalide, phenylenediamine hydrochloride is preferred. By using phenylenediamine hydrochloride as the platinum group metal recovery agent of the present invention, exothermic reactions and changes in hydrochloric acid concentration caused by neutralization reactions can be prevented when mixed with a hydrochloric acid solution containing platinum group metals.

[0033] It should be noted that the hydrochloric acid concentration of the hydrochloric acid solution used in the platinum group metal recovery method described in this specification is the concentration after mixing with the platinum group metal recovery agent of this invention. However, when using phenylenediamine hydrochloride as the platinum group metal recovery agent of this invention, since the hydrochloric acid concentration does not change, it can also be the concentration of hydrochloric acid before mixing with the aforementioned platinum group metal recovery agent.

[0034] [Platinum Group Metals Recycling Methods (Platinum Recycling)]

[0035] The platinum group metals recovery method of the present invention is a method for selectively recovering platinum and rhodium respectively, but particularly for preferentially recovering platinum.

[0036] As a first embodiment of the platinum group metals recovery method of the present invention, it is a method for recovering platinum from a hydrochloric acid solution containing platinum using the aforementioned platinum group metals recovery agent. In this method, the aforementioned platinum group metals recovery agent is mixed with the aforementioned hydrochloric acid solution to precipitate platinum.

[0037] According to the platinum group metal recovery method of the present invention, platinum can be recovered not only from a hydrochloric acid solution containing only platinum as a platinum group metal, but also selectively when the aforementioned hydrochloric acid solution contains at least one selected from the group consisting of palladium and rhodium.

[0038] The specific method is as follows.

[0039] First, the aforementioned platinum group metal recovery agent is added to a hydrochloric acid solution containing at least platinum.

[0040] By using the platinum group metal recovery agent of the present invention, platinum can also be selectively recovered from hydrochloric acid solutions of all hydrochloric acid concentrations. The hydrochloric acid concentration of the platinum-containing hydrochloric acid solution is preferably 1 to 12 mol / L, more preferably 4 to 10 mol / L, and even more preferably 5 to 9 mol / L.

[0041] Furthermore, there is no limitation on the concentration of platinum contained in the hydrochloric acid solution, but from the viewpoint of effective recovery, it is preferred to be 100 to 10000 mg / L, more preferably 300 to 5000 mg / L, and even more preferably 500 to 2000 mg / L.

[0042] When adding the platinum group metal recovery agent, it is preferable that the molar ratio of the aforementioned platinum group metal recovery agent to the platinum contained in the aforementioned hydrochloric acid solution [platinum group metal recovery agent / platinum (moles / moles)] is 1 or more and less than 100, more preferably 2 or more and less than 40, and even more preferably 5 or more and less than 40.

[0043] If the molar ratio is within the aforementioned range, the recovery rate of platinum is improved, and the precipitate is unlikely to contain rhodium or palladium, allowing platinum to be recovered with high purity.

[0044] There are no restrictions on the method of mixing platinum group metal recovery agents with hydrochloric acid solutions. Platinum is precipitated by adding platinum group metal recovery agents to hydrochloric acid solutions and stirring or shaking for a specified time.

[0045] When using the platinum group metal recovery agent of the present invention, a precipitate is rapidly formed after mixing with hydrochloric acid solution, thus enabling platinum recovery in a short time. The stirring or shaking time is preferably 1 minute or more, more preferably 5 minutes or more. There is no upper limit, but from an efficiency point of view, it is preferably 10 hours or less, more preferably 5 hours or less. The stirring or shaking time can also be appropriately adjusted according to the concentration and temperature of each component.

[0046] The temperature during stirring or shaking can be 0 to 100°C, preferably 10 to 50°C.

[0047] As mentioned above, the resulting platinum-containing precipitate can be recovered through solid-liquid separation processes such as filtration and centrifugation.

[0048] The precipitate contains platinum in ionic form, chloride ions, and phenylenediamine, i.e., a platinum group metals recovery agent. Therefore, platinum can be obtained in metallic or oxide form by calcination in air. The calcination temperature is preferably 400–1000°C, more preferably 500–700°C. The calcination time is preferably 5–100 minutes, more preferably 10–80 minutes. By adjusting these calcination conditions, platinum can be obtained in metallic form, preferably in elemental form.

[0049] [Platinum Group Metals Recovery Methods (Rhodium Recovery)]

[0050] The platinum group metals recovery method of the present invention can also selectively recover rhodium.

[0051] As a second embodiment of the platinum group metal recovery method of the present invention, it is a method for recovering rhodium from a hydrochloric acid solution containing rhodium using the aforementioned platinum group metal recovery agent. In this method, the aforementioned platinum group metal recovery agent is mixed with the aforementioned hydrochloric acid solution to precipitate rhodium.

[0052] According to the platinum group metal recovery method of the present invention, rhodium can be recovered not only from a hydrochloric acid solution containing only rhodium as a platinum group metal, but also selectively recovered when the hydrochloric acid solution contains palladium.

[0053] The specific method is as follows.

[0054] First, the aforementioned platinum group metal recovery agent is added to a hydrochloric acid solution containing at least rhodium.

[0055] By using the platinum group metal recovery agent of the present invention, rhodium can be selectively recovered from hydrochloric acid solutions with a wide range of hydrochloric acid concentrations, but the hydrochloric acid concentration of the rhodium-containing hydrochloric acid solution is preferably 3 to 12 mol / L, more preferably 4 to 10 mol / L, and even more preferably 5 to 9 mol / L.

[0056] Furthermore, there is no limitation on the concentration of rhodium contained in the hydrochloric acid solution, but from the viewpoint of effective recovery, it is preferred to be 100 to 10000 mg / L, more preferably 300 to 5000 mg / L, and even more preferably 500 to 2000 mg / L.

[0057] When adding the platinum group metal recovery agent, the molar ratio of the aforementioned platinum group metal recovery agent to the rhodium contained in the aforementioned hydrochloric acid solution [platinum group metal recovery agent / rhodium (moles / moles)] is preferably 10 or more, more preferably 15 or more, further preferably 40 or more, and even more preferably 50 or more. There is no upper limit, but from the viewpoint of efficiency, it is preferably 200 or less.

[0058] If the molar ratio is within the aforementioned range, the recovery rate of rhodium is improved, palladium is less likely to be included in the precipitate, and rhodium can be recovered with high purity.

[0059] In this method, in addition to the aforementioned platinum group metal recovery agent, a crystallizing nucleating agent can be mixed into the hydrochloric acid solution containing rhodium. By mixing the crystallizing nucleating agent, rhodium can be further selectively recovered even with a smaller amount of platinum group metal recovery agent.

[0060] The molar ratio of the platinum group metal recovery agent to the rhodium contained in the hydrochloric acid solution when using a nucleating agent [platinum group metal recovery agent / rhodium (moles / moles)] is preferably 5 or more, more preferably 10 or more, even more preferably 15 or more, and even more preferably 20 or more. There is no upper limit, but from the viewpoint of efficiency, it is preferably 100 or less.

[0061] The nucleating agent is preferably a particulate material that is insoluble or sparingly soluble in hydrochloric acid solution. Examples of nucleating agents include inorganic oxide particles and organic compound crystals. More preferably, the precipitate obtained by this method is used as the nucleating agent, and even more preferably, the precipitate containing a crystal in which the molar ratio of rhodium atoms in the crystal to the aforementioned platinum group metal recovery agent [rhodium atom: platinum group metal recovery agent] is 1:2.

[0062] The size of the nucleating agent is preferably 5 mm or less. There is no lower limit to the size of the nucleating agent, but it is preferably 0.001 mm or more.

[0063] There is no particular limitation on the amount of crystallizing nucleating agent used, but it is preferably 0.1 to 50 g, more preferably 0.5 to 20 g, and even more preferably 3 to 15 g, relative to 1 mol of rhodium in the aforementioned hydrochloric acid solution.

[0064] There are no restrictions on the method of mixing the platinum group metal recovery agent with the hydrochloric acid solution, but it is preferred to add the platinum group metal recovery agent to the hydrochloric acid solution and stir or shake for a specified time, thereby causing rhodium to precipitate.

[0065] The stirring or shaking time is preferably 5 minutes or more, more preferably 10 minutes or more. There is no upper limit, but from an efficiency point of view, it is preferably 10 hours or less, more preferably 5 hours or less. The stirring or shaking time can also be adjusted appropriately according to the concentration and temperature of each component.

[0066] The temperature during stirring or shaking can be 0 to 100°C, preferably 10 to 50°C.

[0067] As mentioned above, the resulting rhodium-containing precipitate can be recovered through solid-liquid separation processes such as filtration and centrifugation.

[0068] The precipitate contains rhodium in ionic form, chloride ions, and phenylenediamine (a platinum group metals recovery agent). Therefore, rhodium can be obtained in metallic or oxide form by calcination in air. The calcination temperature is preferably 400–1500°C, more preferably 450–1200°C. The calcination time is preferably 5–100 minutes, more preferably 10–80 minutes. By adjusting these calcination conditions, rhodium can be obtained in metallic form, preferably in elemental form.

[0069] [Platinum Group Metals Recycling Methods (Sequential Recycling of Platinum and Rhodium)]

[0070] According to the platinum group metals recovery method of the present invention, as described above, platinum and rhodium can be selectively recovered separately, but they can also be separated and recovered separately from hydrochloric acid solutions containing platinum and rhodium.

[0071] That is, as a third embodiment of the platinum group metals recovery method of the present invention, it is a platinum group metals recovery method for separating and recovering platinum and rhodium from a hydrochloric acid solution containing platinum and rhodium using the aforementioned platinum group metals recovery agent. The method includes: a platinum recovery step of mixing the aforementioned platinum group metals recovery agent with the aforementioned hydrochloric acid solution to obtain a precipitate containing platinum and a solution containing rhodium, and recovering platinum; and a rhodium recovery step of mixing the aforementioned platinum group metals recovery agent with the aforementioned solution containing rhodium to obtain a precipitate containing rhodium, and recovering rhodium.

[0072] According to this method, even when the hydrochloric acid solution contains palladium, it is possible to separate and recover platinum and rhodium separately from the hydrochloric acid solution containing platinum. That is, in another embodiment of the platinum group metal recovery method of the present invention, the aforementioned hydrochloric acid solution contains palladium, the aforementioned platinum recovery step is to obtain a precipitate containing platinum and a solution containing rhodium and palladium, and the aforementioned rhodium recovery step is to obtain a precipitate containing rhodium and a solution containing palladium.

[0073] The initial step in this embodiment is a platinum recovery process in which the aforementioned platinum group metal recovery agent is mixed with the aforementioned hydrochloric acid solution to obtain a platinum-containing precipitate and a rhodium-containing solution.

[0074] This process is preferably carried out according to the methods and conditions described in the [Platinum Group Metals Recovery Method (Platinum Recovery)] section above. In particular, from the viewpoint of preventing rhodium precipitation and obtaining a platinum-containing precipitate, it is preferred to carry out the process under the following conditions.

[0075] The hydrochloric acid concentration of the hydrochloric acid solution containing platinum and rhodium is preferably 1 to 12 mol / L, more preferably 4 to 10 mol / L, and even more preferably 5 to 9 mol / L.

[0076] Furthermore, there is no limitation on the concentration of platinum and rhodium contained in the hydrochloric acid solution, but from the viewpoint of efficient recovery, the concentration of platinum in the hydrochloric acid solution is preferably 100 to 10,000 mg / L, more preferably 300 to 5,000 mg / L, and even more preferably 500 to 2,000 mg / L. Similarly, the concentration of rhodium in the hydrochloric acid solution is preferably 100 to 10,000 mg / L, more preferably 300 to 5,000 mg / L, and even more preferably 500 to 2,000 mg / L.

[0077] When adding the platinum group metal recovery agent, it is preferable that the molar ratio of the aforementioned platinum group metal recovery agent to the platinum contained in the aforementioned hydrochloric acid solution [platinum group metal recovery agent / platinum (moles / moles)] is 1 or more and less than 40, more preferably 2 or more and less than 40, and even more preferably 5 or more and less than 40.

[0078] In particular, by keeping the aforementioned molar ratio in the range of less than 40, the recovery rate of platinum is improved, and the precipitate is unlikely to contain rhodium, thus enabling the recovery of platinum with high purity.

[0079] There are no restrictions on the method of mixing platinum group metal recovery agents with hydrochloric acid solutions. Platinum is precipitated by adding platinum group metal recovery agents to hydrochloric acid solutions and stirring or shaking for a specified time.

[0080] When using the platinum group metal recovery agent of the present invention, a precipitate is rapidly formed after mixing with hydrochloric acid solution, thus enabling platinum recovery in a short time. The stirring or shaking time is preferably 1 minute or more, more preferably 5 minutes or more. There is no upper limit, but from an efficiency point of view, it is preferably 10 hours or less, more preferably 5 hours or less. The stirring or shaking time can be appropriately adjusted according to the concentration and temperature of each component.

[0081] The temperature during stirring or shaking can be 0 to 100°C, preferably 10 to 50°C.

[0082] As mentioned above, the obtained platinum-containing precipitate can be recovered through solid-liquid separation such as filtration and centrifugation, and the recovered precipitate yields a rhodium-containing solution.

[0083] The precipitate contains platinum in ionic form, chloride ions, and phenylenediamine, i.e., a platinum group metals recovery agent. Therefore, platinum can be obtained in metallic or oxide form by calcination in air. The calcination temperature is preferably 400–1000°C, more preferably 500–700°C. The calcination time is preferably 5–100 minutes, more preferably 10–80 minutes. By adjusting these calcination conditions, platinum can be obtained in metallic form, preferably in elemental form.

[0084] The second step in this embodiment is a rhodium recovery step in which the aforementioned platinum group metal recovery agent is mixed with a rhodium-containing solution obtained in the aforementioned platinum recovery step to obtain a rhodium-containing precipitate and recover rhodium.

[0085] This process is preferably carried out according to the methods and conditions described in the aforementioned [Platinum Group Metals Recovery Method (Rhodium Recovery)] section, and in particular, from the viewpoint of preventing palladium precipitation and obtaining a precipitate containing rhodium, it is preferred to carry out the process under the following conditions.

[0086] The hydrochloric acid concentration of the rhodium-containing hydrochloric acid solution is preferably 3 to 12 mol / L, more preferably 4 to 10 mol / L, and even more preferably 5 to 9 mol / L.

[0087] Furthermore, there is no limitation on the concentration of rhodium contained in the hydrochloric acid solution, but from the viewpoint of effective recovery, it is preferred to be 100 to 10000 mg / L, more preferably 300 to 5000 mg / L, and even more preferably 500 to 2000 mg / L.

[0088] When adding the platinum group metal recovery agent, the molar ratio of the aforementioned platinum group metal recovery agent to the rhodium contained in the aforementioned hydrochloric acid solution [platinum group metal recovery agent / rhodium (moles / moles)] is preferably 10 or more, more preferably 15 or more, further preferably 40 or more, and even more preferably 50 or more. There is no upper limit, but from an efficiency point of view, it is preferably 200 or less. This molar ratio refers to the molar ratio including the platinum group metal recovery agent when the rhodium-containing hydrochloric acid solution used in this process contains residual platinum group metal recovery agent added in the previous process.

[0089] If the molar ratio is within the aforementioned range, the recovery rate of rhodium is improved, palladium is less likely to be included in the precipitate, and rhodium can be recovered with high purity.

[0090] In this method, in addition to the aforementioned platinum group metal recovery agent, a crystallizing nucleating agent may be mixed into the hydrochloric acid solution containing rhodium. By mixing the crystallizing nucleating agent, rhodium can be further selectively recovered even with a smaller amount of platinum group metal recovery agent. For the foregoing reasons, in this method, it is preferable to mix the crystallizing nucleating agent into the hydrochloric acid solution containing rhodium, in addition to the aforementioned platinum group metal recovery agent.

[0091] The molar ratio of the aforementioned platinum group metal recovery agent to the rhodium contained in the aforementioned hydrochloric acid solution when using a crystallizing nucleating agent [platinum group metal recovery agent / rhodium (moles / moles)] is preferably 5 or more, more preferably 10 or more, even more preferably 15 or more, and even more preferably 20 or more. There is no upper limit, but from the viewpoint of efficiency, it is preferably 100 or less.

[0092] The nucleating agent is preferably a particulate material that is insoluble or sparingly soluble in hydrochloric acid solution, such as inorganic oxide particles or organic compound crystals. More preferably, the precipitate obtained by this method is used as the nucleating agent, and even more preferably, the precipitate containing a crystal in which the molar ratio of rhodium atoms in the crystal to the aforementioned platinum group metal recovery agent [rhodium atom: platinum group metal recovery agent] is 1:2.

[0093] The size of the nucleating agent is preferably 5 mm or less. There is no lower limit to the size of the nucleating agent, but it is preferably 0.001 mm or more.

[0094] There is no particular limitation on the amount of crystallizing nucleating agent used, but it is preferably 0.1 to 50 g, more preferably 0.5 to 20 g, and even more preferably 3 to 15 g, relative to 1 mol of rhodium in the aforementioned hydrochloric acid solution.

[0095] There are no restrictions on the method of mixing platinum group metal recovery agents with hydrochloric acid solutions. Rhodium is precipitated by adding platinum group metal recovery agents to hydrochloric acid solutions and stirring or shaking for a specified time.

[0096] The stirring or shaking time is preferably 5 minutes or more, more preferably 10 minutes or more. There is no upper limit, but from an efficiency point of view, it is preferably 10 hours or less, more preferably 5 hours or less. The stirring or shaking time can be adjusted appropriately according to the concentration and temperature of each component.

[0097] The temperature during stirring or shaking can be 0 to 100°C, preferably 10 to 50°C.

[0098] As mentioned above, the resulting rhodium-containing precipitate can be recovered through solid-liquid separation processes such as filtration and centrifugation.

[0099] The precipitate contains rhodium in ionic form, chloride ions, and phenylenediamine (a platinum group metals recovery agent). Therefore, rhodium can be obtained in metallic or oxide form by calcination in air. The calcination temperature is preferably 400–1500°C, more preferably 450–1200°C. The calcination time is preferably 5–100 minutes, more preferably 10–80 minutes. By adjusting these calcination conditions, rhodium can be obtained in metallic form, preferably in elemental form.

[0100] [Sediment]

[0101] As described above, by using the platinum group metal recovery agent of the present invention, platinum group metals in hydrochloric acid solution can be recovered as precipitates. The resulting precipitate contains, in addition to platinum group metal atoms (platinum group metal ions), the aforementioned platinum group metal recovery agent, hydrochloric acid, chloride ions, water, etc., which are contained in the precipitate in crystalline form.

[0102] In the platinum recovery process of the first and third embodiments of the platinum group metals recovery method of the present invention, the aforementioned platinum group metals recovery agent is mixed with a hydrochloric acid solution containing platinum to precipitate platinum.

[0103] The precipitate of the present invention is obtained by these methods and contains crystals in which the molar ratio of platinum atoms in the crystal to the aforementioned platinum group metal recovery agent [platinum atoms: the aforementioned platinum group metal recovery agent] is 1:1.

[0104] By forming crystals with a 1:1 molar ratio of platinum atoms to the aforementioned platinum group metal recovery agent, it is assumed that other platinum group metal atoms are excluded from the crystals and will not be incorporated into the precipitate. Therefore, it is believed that platinum can selectively exist in the precipitate obtained by the aforementioned method.

[0105] In the rhodium recovery process of the second and third embodiments of the platinum group metal recovery method of the present invention, the aforementioned platinum group metal recovery agent is mixed with a hydrochloric acid solution containing rhodium to precipitate rhodium.

[0106] The precipitate of the present invention is obtained by these methods and contains crystals in which the molar ratio of rhodium atoms in the crystal to the aforementioned platinum group metal recovery agent [rhodium atoms: the aforementioned platinum group metal recovery agent] is 1:2.

[0107] By forming crystals with a rhodium atom to platinum group metal recovery agent molar ratio of 1:2, it is assumed that palladium and other metals are excluded from these crystals and will not be incorporated into the precipitate. Therefore, it is believed that rhodium can selectively exist in the precipitate obtained by the aforementioned method.

[0108] Example

[0109] The present invention will be specifically described with reference to the embodiments shown below, but the present invention is not limited to these embodiments.

[0110] Platinum recycling

[0111] <Example 1: Effect of Hydrochloric Acid Concentration>

[0112] To a solution containing palladium 500 mg / L, platinum 1000 mg / L, and rhodium 500 mg / L, such as Figure 1 In a hydrochloric acid solution of the concentration shown, m-phenylenediamine was added as a platinum group metal recovery agent at a concentration 15 times (mol / mol) relative to platinum. It should be noted that the m-phenylenediamine used here is the hydrochloride salt. Afterwards, the solution was shaken at 25°C for 1 hour to obtain a precipitate. The precipitate and solution were separated by centrifugation. The amount of platinum group metals contained in the precipitate was calculated by ICP analysis of the solution obtained after solid-liquid separation.

[0113] Figure 1The relationship between hydrochloric acid concentration (HCl [M] (mol / L)) and metal recovery rate (Precipitation [%)) is shown. From Figure 1 It can be seen that by using m-phenylenediamine as a platinum group metal recovery agent, platinum can be selectively recovered as a precipitate within a wide range of hydrochloric acid concentrations above 1 mol / L.

[0114] <Example 2: The Influence of Oscillation Time>

[0115] Set the hydrochloric acid concentration of the hydrochloric acid solution to 8 mol / L, such as Figure 2 The oscillation time was changed as shown, and otherwise, precipitates and solutions were obtained in the same manner as in Example 1, and the amount of platinum group metals contained in the precipitate was calculated.

[0116] Figure 2 The relationship between oscillation time (min) and metal recovery rate (%) is shown. Figure 2 It can be seen that 92% of platinum can be recovered in 1 minute of oscillation, and more than 95% of platinum can be recovered as precipitate in oscillation of more than 10 minutes. In addition, palladium and rhodium were not recovered as precipitates.

[0117] <Example 3: Effect of the molar ratio of platinum group metal recovery agent to platinum>

[0118] Set the hydrochloric acid concentration of the hydrochloric acid solution to 8 mol / L and the shaking time to 10 minutes. Figure 3 The amount of platinum group metal recovery agent (m-phenylenediamine) added was changed as shown, and precipitates and solutions were obtained in the same manner as in Example 1, except that the amount of platinum group metals contained in the precipitate was calculated.

[0119] Figure 3 The relationship between the amount of m-phenylenediamine added (MXDA / Metal [mol / mol] (m-phenylenediamine relative to platinum group metals)) and the metal recovery rate (Precipitation [%)) is shown. Figure 3 It can be seen that when the amount of m-phenylenediamine added is more than 5 times that of platinum (mol / mol), more than 86% of platinum can be recovered as a precipitate, indicating a high platinum recovery rate. Furthermore, it can be seen that when the amount of m-phenylenediamine added is less than 40 times that of platinum (mol / mol), platinum can be selectively recovered as a precipitate.

[0120] Rhodium recovery

[0121] <Example 4: Effect of the molar ratio of platinum group metal recovery agent to rhodium>

[0122] In a hydrochloric acid solution (8 mol / L) containing 500 mg / L palladium and 500 mg / L rhodium, Figure 4 The indicated addition amount is m-phenylenediamine as a platinum group metal recovery agent. It should be noted that the m-phenylenediamine used here is its hydrochloride salt. Afterwards, the mixture was shaken at 25°C for 1 hour to obtain a precipitate. The precipitate and solution were then separated by centrifugation. The solution obtained after solid-liquid separation was analyzed using ICP to calculate the amount of platinum group metals contained in the precipitate.

[0123] Figure 4 The relationship between the amount of m-phenylenediamine added (MXDA / Metal [mol / mol] (m-phenylenediamine relative to platinum group metals)) and the metal recovery rate (Precipitation [%)) is shown. Figure 4 It is known that when the amount of m-phenylenediamine added is more than 75 times (mol / mol) that of rhodium, rhodium can be recovered as a precipitate with a recovery rate of over 90%, which is a high rhodium recovery rate. Furthermore, it is known that regardless of the amount of m-phenylenediamine added, palladium was not recovered, while rhodium can be selectively recovered as a precipitate.

[0124] <Example 5: The Influence of Oscillation Time>

[0125] Except for Figure 5 Apart from changing the oscillation time, precipitates and solutions were obtained in the same manner as in Example 4, and the amount of platinum group metals contained in the precipitate was calculated.

[0126] Figure 5 The relationship between shaking time (min) and metal recovery (%) is shown when m-phenylenediamine is added at 100 times the amount (mol / mol) relative to rhodium. Figure 5 It can be seen that under oscillation for more than 10 minutes, rhodium can be recovered as more than 90% of the precipitate, while palladium is not recovered.

[0127] [Crystals (precipitates) containing platinum group metal atoms and platinum group metal recovery agents]

[0128] <Example 6: Crystals (precipitates) containing platinum atoms and platinum group metals recovery agents>

[0129] To a hydrochloric acid solution containing 1000 mg / L platinum (8 mol / L concentration), m-phenylenediamine was added as a platinum group metal recovery agent at a concentration twice the amount of platinum (mol / mol). It should be noted that the m-phenylenediamine used here is a hydrochloride salt. The solution was then shaken at 25°C to obtain a precipitate. The hydrochloric acid solution containing the precipitate was allowed to stand for several days to obtain crystals. The resulting crystals (approximately 2 mm) and the solution were separated by filtration. Thermogravimetric analysis, single-crystal X-ray structural analysis, and powder X-ray diffraction analysis of the crystals showed that they were crystals with a platinum atom to platinum group metal recovery agent molar ratio [platinum atom: platinum group metal recovery agent] of 1:1.

[0130] <Example 7: Crystals (precipitates) containing rhodium atoms and platinum group metals recovery agents>

[0131] To a hydrochloric acid solution containing 500 mg / L rhodium (hydrochloric acid concentration 8 mol / L), m-phenylenediamine was added as a platinum group metal recovery agent at a concentration 50 times (mol / mol) relative to rhodium. It should be noted that the m-phenylenediamine used here is a hydrochloride salt. The mixture was then shaken at 25°C to obtain a precipitate. The hydrochloric acid solution containing the precipitate was allowed to stand for several days to obtain crystals. The resulting crystals (approximately 2 mm) and the solution were separated by filtration. Thermogravimetric analysis, single-crystal X-ray structural analysis, and powder X-ray diffraction analysis of the crystals showed that they were crystals with a rhodium atom to platinum group metal recovery agent molar ratio [rhodium atom: platinum group metal recovery agent] of 1:2.

[0132] [Plaque and rhodium are recycled sequentially]

[0133] <Example 8>

[0134] (Platinum recovery process: First process)

[0135] A hydrochloric acid solution (8 mol / L) containing 500 mg / L palladium, 1000 mg / L platinum, and 500 mg / L rhodium was added as a platinum group metal recovery agent at a concentration 15 times (mol / mol) relative to platinum. It should be noted that the m-phenylenediamine used here is its hydrochloride salt. The solution was then shaken at 25°C for 10 minutes to obtain a precipitate. The precipitate and solution were separated by solid-liquid separation via filtration.

[0136] The amount of platinum group metals in the precipitate was calculated by analyzing the solution obtained after solid-liquid separation using ICP. The precipitate contained 96% of the platinum contained in the original hydrochloric acid solution, 3% of the rhodium contained in the original hydrochloric acid solution, but no palladium.

[0137] Thermogravimetric analysis and powder X-ray diffraction analysis of the precipitate showed that it contained crystals in which the molar ratio of platinum atoms to the aforementioned platinum group metals recovery agent was 1:1.

[0138] (Rhodium recovery process: second process)

[0139] Next, in the solution obtained after the solid-liquid separation in the previous process, m-phenylenediamine was added as a platinum group metal recovery agent at a concentration 90 times (mol / mol) relative to rhodium. The mixture was shaken at 25°C for 10 minutes, and the resulting precipitate and solution were separated by filtration. It should be noted that the m-phenylenediamine used here is its hydrochloride salt.

[0140] The amount of platinum group metals in the precipitate was calculated by analyzing the solution obtained after solid-liquid separation using ICP. The precipitate contained 86% of the rhodium contained in the original hydrochloric acid solution, 3% of the platinum contained in the original hydrochloric acid solution, and 5% of the palladium contained in the original hydrochloric acid solution.

[0141] Thermogravimetric analysis and powder X-ray diffraction analysis of the precipitate showed that it contained crystals in which the molar ratio of rhodium atoms to the aforementioned platinum group metal recovery agent was 1:2.

[0142] The solution obtained after solid-liquid separation contains 1% platinum, 11% rhodium, and 95% palladium as contained in the original hydrochloric acid solution.

[0143] As can be seen from the results of Example 8, by using the platinum group metal recovery agent of the present invention, platinum can be selectively and with a high recovery rate recovered from a hydrochloric acid solution containing palladium, platinum and rhodium, and rhodium can be selectively and with a high recovery rate recovered from a hydrochloric acid solution containing palladium and rhodium.

[0144] <Example 9: Example of using a crystallizing nucleating agent in a rhodium recovery process>

[0145] (Platinum recovery process: First process)

[0146] A hydrochloric acid solution (8 mol / L) containing 500 mg / L palladium, 1000 mg / L platinum, and 500 mg / L rhodium was added as a platinum group metal recovery agent at a concentration 15 times (mol / mol) relative to platinum. It should be noted that the m-phenylenediamine used here is its hydrochloride salt. The solution was then shaken at 25°C for 10 minutes to obtain a precipitate. The precipitate and solution were separated by solid-liquid separation via filtration.

[0147] The amount of platinum group metals in the precipitate was calculated by analyzing the solution obtained after solid-liquid separation using ICP. The precipitate contained 96% of the platinum contained in the original hydrochloric acid solution, 3% of the rhodium contained in the original hydrochloric acid solution, and 0.7% of the palladium contained in the original hydrochloric acid solution.

[0148] (Rhodium recovery process (example using crystallizing nucleating agents): Second process)

[0149] Next, in the solution obtained after the solid-liquid separation in the previous step, m-phenylenediamine was added as a platinum group metal recovery agent at a rate of 20 times (mol / mol) relative to rhodium. Then, five crystals (approximately 2 mm in size) containing rhodium atoms and the platinum group metal recovery agent obtained in Example 7 were added as nucleating agents. The mixture was shaken at 25°C for 10 minutes, and the resulting precipitate and solution were separated by filtration. It should be noted that the m-phenylenediamine used here is its hydrochloride salt.

[0150] The amount of platinum group metals in the precipitate was calculated by analyzing the solution obtained after solid-liquid separation using ICP. The precipitate contained 93% of the rhodium contained in the original hydrochloric acid solution, 2% of the platinum contained in the original hydrochloric acid solution, and 0.6% of the palladium contained in the original hydrochloric acid solution.

[0151] The solution obtained after solid-liquid separation contains 2% platinum, 4% rhodium, and 99% palladium as contained in the original hydrochloric acid solution.

[0152] As can be seen from the results of Example 9, in the rhodium recovery process, by using a crystallization nucleating agent, even a small amount of platinum group metal recovery agent can be used to further selectively recover rhodium.

[0153] [Recovery from catalyst leaching simulation solution]

[0154] <Example 10>

[0155] The plan envisions recovering platinum group metals from used automotive exhaust purification catalysts. Using a leaching simulation solution (8 mol / L hydrochloric acid concentration) containing the various metals shown in Table 1, the platinum recovery process (first step) and rhodium recovery process (second step) were performed in the same manner as in Example 9. The solutions obtained after solid-liquid separation in each step were analyzed using ICP to determine the amount of each metal contained in the precipitate and calculate the metal recovery rate. It should be noted that the m-phenylenediamine used in the aforementioned first and second steps was a hydrochloride salt. The results are shown in Table 1.

[0156] [Table 1]

[0157]

[0158] As shown in Table 1, even when using hydrochloric acid solutions containing various metals other than the platinum group metals, platinum can be selectively recovered as a precipitate in the first process, and rhodium can be selectively recovered as a precipitate in the second process.

[0159] <Example 11: Platinum Recovery (An Example Using p-phenylenediamine as a Platinum Group Metal Recovery Agent)>

[0160] To an 8 mol / L hydrochloric acid solution containing 500 mg / L palladium, 1000 mg / L platinum, and 500 mg / L rhodium, p-phenylenediamine was added as a platinum group metal recovery agent at a concentration 15 times (mol / mol) relative to platinum. It should be noted that the p-phenylenediamine used here is its hydrochloride salt. The solution was then shaken at 25°C for 1 hour to obtain a precipitate. The precipitate and solution were separated by centrifugation. The amount of platinum group metals in the precipitate was calculated by ICP analysis of the solution obtained after solid-liquid separation.

[0161] As a result, 74% of platinum was recovered as precipitate. Furthermore, it was found that only 4% of palladium and 1% of rhodium were recovered as precipitates, demonstrating the selective recovery of platinum as a precipitate.

Claims

1. A method for recovering platinum, comprising recovering platinum from a hydrochloric acid solution containing platinum using a platinum group metal recovery agent represented by the following general formula (1), wherein the platinum group metal recovery agent is mixed with the hydrochloric acid solution to precipitate platinum.

2. The platinum recovery method according to claim 1, wherein, The platinum group metal recovery agent is at least one selected from the group consisting of m-phenylenediamine and p-phenylenediamine.

3. The platinum recovery method according to claim 1 or 2, wherein, The hydrochloric acid solution contains at least one selected from the group consisting of palladium and rhodium.

4. The platinum recovery method according to claim 1 or 2, wherein, The molar ratio of the platinum group metal recovery agent to the platinum contained in the hydrochloric acid solution [platinum group metal recovery agent / platinum] is greater than 5 and less than 40.

5. A method for recovering rhodium, comprising recovering rhodium from a hydrochloric acid solution containing rhodium using a platinum group metal recovery agent represented by the following general formula (1), wherein the platinum group metal recovery agent is mixed with the hydrochloric acid solution to precipitate rhodium.

6. The rhodium recovery method according to claim 5, wherein, The platinum group metal recovery agent is at least one selected from the group consisting of m-phenylenediamine and p-phenylenediamine.

7. The rhodium recovery method according to claim 5 or 6, wherein, The hydrochloric acid solution contains palladium.

8. The rhodium recovery method according to claim 5 or 6, wherein, The molar ratio of the platinum group metal recovery agent to the rhodium contained in the hydrochloric acid solution [platinum group metal recovery agent / rhodium] is 15 or more.

9. A method for recovering platinum group metals, comprising using a platinum group metal recovery agent represented by the following general formula (1) to separate and recover platinum and rhodium from a hydrochloric acid solution containing platinum and rhodium, the method comprising: A platinum recovery process involves mixing the platinum group metal recovery agent with the hydrochloric acid solution to obtain a platinum-containing precipitate and a rhodium-containing solution, and then recovering the platinum. A rhodium recovery process involves mixing the platinum group metal recovery agent with the rhodium-containing solution to obtain a rhodium-containing precipitate, and then recovering the rhodium.

10. The method for recovering platinum group metals according to claim 9, wherein, The platinum group metal recovery agent is at least one selected from the group consisting of m-phenylenediamine and p-phenylenediamine.

11. The method for recovering platinum group metals according to claim 9 or 10, wherein, The hydrochloric acid solution contains palladium, the platinum recovery process is to obtain a precipitate containing platinum and a solution containing rhodium and palladium, and the rhodium recovery process is to obtain a precipitate containing rhodium and a solution containing palladium.

12. The method for recovering platinum group metals according to claim 9 or 10, wherein, In the rhodium recovery process, in addition to the platinum group metal recovery agent and the rhodium-containing solution, a crystallization nucleating agent is further mixed.

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