Platinum group metal recovery agent and platinum group metal recovery method

Abstract

To provide a platinum-group metal recovery agent and a platinum-group metal recovery method which are capable of recovering each of platinum and rhodium selectively at a high recovery rate.SOLUTION: The platinum-group metal recovery agent is represented by the general formula (1) in the figure. The platinum-group metal recovery method comprises using the platinum-group metal recovery agent to recover platinum or rhodium from a hydrochloric acid solution containing the platinum or rhodium, where the platinum-group metal recovery agent and the hydrochloric acid solution are mixed to cause the platinum or rhodium to precipitate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a platinum group metal recovery agent and a platinum group metal recovery method. [Background technology]

[0002] Platinum group metals are extremely important industrially, and among them, platinum, palladium, and rhodium are mainly used in automobile exhaust purification catalysts. Therefore, selective separation and recovery of platinum group metals from spent catalysts is important. Generally, methods used to recover precious metals include electrolytic deposition, cementation, ion exchange, precipitation, solvent extraction, etc. Among these methods, precipitation and solvent extraction are widely used because of their superior economical efficiency and ease of operation. As a selective recovery method for platinum group metals by precipitation, a method using amines has been investigated.

[0003] For example, Patent Document 1 discloses a rhodium recovery agent that has an amide bond and a phenylenediamine structure and is a solid that is insoluble in hydrochloric acid at a specific concentration, with the aim of recovering rhodium efficiently at low cost. Furthermore, Patent Document 2 discloses that, for the purpose of efficiently separating rhodium in particular, 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-179409 [Patent Document 2] Japanese Patent Application Publication No. 2019-206747 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventionally, in the recovery of platinum group metals by precipitation or solvent extraction, palladium is preferentially recovered, and it has been difficult to selectively recover platinum or rhodium first. Patent Documents 1 and 2 disclose methods for recovering rhodium, but they do not allow for preferential and selective recovery of platinum. Therefore, there is a need for a method that allows for preferential and selective recovery of platinum even in the presence of palladium and rhodium, and further allows for selective recovery of rhodium in the presence of palladium. Therefore, an object of the present invention is to provide a platinum group metal recovery agent and a platinum group metal recovery method that can recover platinum and rhodium selectively and at high recovery rates. [Means for solving the problem]

[0006] The present inventors have found that xylylenediamine is an excellent platinum group metal recovery agent, and that by using this platinum group metal recovery agent, platinum and rhodium can be recovered selectively and at high recovery rates, respectively. Furthermore, they have discovered a method for preferentially and selectively recovering platinum and then selectively recovering rhodium even in the presence of palladium and rhodium, which was previously difficult to achieve, and have completed the present invention.

[0007] That is, the present invention relates to a platinum group metal recovery agent represented by the following general formula (1), and 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 platinum group metal recovery agent and the hydrochloric acid solution are mixed to precipitate platinum or rhodium. [ka] [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a platinum group metal recovery agent and a platinum group metal recovery method that can recover platinum and rhodium selectively and at high recovery rates. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a graph showing the effect of hydrochloric acid concentration on platinum recovery in Example 1. [Figure 2] FIG. 10 is a diagram showing the effect of shaking time on the recovery of platinum in Example 2. [Figure 3] FIG. 10 is a graph showing the effect of the molar ratio of platinum group metal recovery agent to platinum in the recovery of platinum in Example 3. [Figure 4] FIG. 10 is a graph showing the effect of the molar ratio of the platinum group metal recovery agent to rhodium on the recovery of rhodium in Example 4. [Figure 5] FIG. 10 is a graph showing the effect of shaking time on the recovery of rhodium in Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Platinum group metal recovery agent] The platinum group metal recovery agent of the present invention is represented by the following general formula (1). [ka]

[0011] That is, the platinum group metal recovery agent of the present invention is xylylenediamine. Among xylylenediamines, the platinum group metal recovery agent is preferably at least one selected from the group consisting of m-xylylenediamine and p-xylylenediamine, and more preferably m-xylylenediamine. By using xylylenediamine, particularly m-xylylenediamine, as a platinum group metal recovery agent, platinum and rhodium can be recovered selectively and at high recovery rates. Furthermore, platinum can be preferentially and selectively recovered even in the presence of palladium and rhodium, which has been difficult to achieve in the past, and rhodium can be preferentially and selectively recovered even in the presence of palladium. The reason why platinum and rhodium can be selectively recovered by using the platinum group metal recovery agent of the present invention is not clear, but it is thought that this is because, when mixed with a hydrochloric acid solution of a platinum group metal, crystals of a specific structure are generated with each platinum group metal, allowing them to be selectively precipitated. The xylylenediamine may be used alone or in combination of two or more. When a mixture of xylylenediamines is used, it is preferable that the mixture consists of m-xylylenediamine and p-xylylenediamine.

[0012] The platinum group metal recovery agent of the present invention is xylylenediamine, but also includes the form of a xylylenediamine hydrohalide salt. The xylylenediamine hydrohalide salt is preferably xylylenediamine hydrochloride. When the platinum group metal recovery agent of the present invention is xylylenediamine hydrochloride, heat generation and changes in hydrochloric acid concentration due to a neutralization reaction can be prevented when the agent is mixed with a hydrochloric acid solution containing platinum group metals. The hydrochloric acid concentration of the hydrochloric acid solution used in the platinum group metal recovery method in this specification is the hydrochloric acid concentration after mixing with the platinum group metal recovery agent of the present invention. However, when xylylenediamine hydrochloride is used as the platinum group metal recovery agent of the present invention, the hydrochloric acid concentration does not change, so the hydrochloric acid concentration may be the same as before mixing with the platinum group metal recovery agent of the present invention.

[0013] [Platinum group metal recovery method (platinum recovery)] The platinum group metal recovery method of the present invention is capable of selectively recovering platinum and rhodium, with platinum being recovered with particular priority. A first embodiment of the platinum group metal recovery method of the present invention is a method for recovering platinum from a hydrochloric acid solution containing platinum using the platinum group metal recovery agent, in which the platinum group metal recovery agent and the hydrochloric acid solution are mixed to precipitate platinum.

[0014] According to the platinum group metal recovery method of the present invention, not only can platinum be recovered from a hydrochloric acid solution containing only platinum as a platinum group metal, but platinum can also be selectively recovered when the hydrochloric acid solution contains at least one member selected from the group consisting of palladium and rhodium. The specific method is shown below.

[0015] First, the platinum group metal recovery agent is added to a hydrochloric acid solution containing at least platinum. By using the platinum group metal recovery agent of the present invention, platinum can be selectively recovered from hydrochloric acid solutions of any hydrochloric acid concentration. 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. There are no restrictions on the concentration of platinum contained in the hydrochloric acid solution, but from the viewpoint of efficient recovery, it 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.

[0016] When adding a platinum group metal recovery agent, 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 (mol / mol)] is preferably 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. Within the above molar ratio range, the recovery rate of platinum is increased, rhodium and palladium are less likely to be contained in the precipitate, and platinum can be recovered with high purity. There are no limitations on the method for mixing the platinum group metal recovery agent with the hydrochloric acid solution, but platinum is precipitated by adding the platinum group metal recovery agent to the hydrochloric acid solution and stirring or shaking for a predetermined period of time. When the platinum group metal recovery agent of the present invention is used, precipitation occurs quickly after mixing with a hydrochloric acid solution, allowing platinum to be recovered in a short time, but the stirring or shaking time is preferably 1 minute or more, more preferably 5 minutes or more. There is no upper limit, but from the viewpoint of efficiency, 10 hours or less is preferable, and 5 hours or less is more preferable. The stirring or shaking time may be adjusted appropriately depending on the concentration of each component and the temperature. The temperature during stirring or shaking may be 0 to 100°C, and preferably 10 to 50°C.

[0017] The platinum-containing precipitate obtained as described above can be recovered by solid-liquid separation such as filtration or centrifugation. The precipitate contains platinum as ions, and also contains chloride ions and a platinum group metal recovery agent, which is xylylenediamine. Therefore, by calcining the precipitate in air, platinum can be obtained as a metal or an oxide. The calcination temperature is preferably 400 to 1000°C, more preferably 500 to 700°C. The calcination time is preferably 5 to 100 minutes, more preferably 10 to 80 minutes. By adjusting these calcination conditions, platinum can be obtained as a metal, preferably as a simple metal.

[0018] [Platinum group metal recovery method (recovery of rhodium)] The platinum group metal recovery method of the present invention can also selectively recover rhodium. A second embodiment of the platinum group metal recovery method of the present invention is a method for recovering rhodium from a hydrochloric acid solution containing rhodium using the platinum group metal recovery agent, in which the platinum group metal recovery agent and the hydrochloric acid solution are mixed to precipitate rhodium.

[0019] According to the platinum group metal recovery method of the present invention, not only can rhodium be recovered from a hydrochloric acid solution containing only rhodium as a platinum group metal, but rhodium can also be selectively recovered when the hydrochloric acid solution also contains palladium. The specific method is shown below.

[0020] First, the platinum group metal recovery agent is added to a hydrochloric acid solution containing at least rhodium. By using the platinum group metal recovery agent of the present invention, rhodium can be selectively recovered from hydrochloric acid solutions having a wide range of hydrochloric acid concentrations. The hydrochloric acid concentration of the hydrochloric acid solution containing rhodium is preferably 3 to 12 mol / L, more preferably 4 to 10 mol / L, and even more preferably 5 to 9 mol / L. Furthermore, there are no limitations on the concentration of rhodium contained in the hydrochloric acid solution, but from the viewpoint of efficient recovery, it 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.

[0021] When adding a platinum group metal recovery agent, 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 (mol / mol)] is preferably 10 or more, more preferably 15 or more, even more 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. Within the above molar ratio range, the recovery rate of rhodium is increased, palladium is less likely to be contained in the precipitate, and rhodium can be recovered with high purity.

[0022] In this method, a nucleating agent may be further mixed with the hydrochloric acid solution containing rhodium in addition to the platinum group metal recovery agent. By mixing the nucleating agent, rhodium can be recovered more selectively even with a smaller amount of platinum group metal recovery agent. When a nucleating agent is used, 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 (mol / mol)] 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. The crystal nucleating agent is preferably a fine particle that is insoluble or poorly soluble in hydrochloric acid solution, and examples thereof include inorganic oxide particles, organic compound crystals, etc. It is more preferable to use the precipitate obtained by this method as the crystal nucleating agent, and particularly it is even more preferable to use a precipitate containing crystals in which the molar ratio of rhodium atoms in the crystals to the platinum group metal recovery agent [rhodium atoms:platinum group metal recovery agent] is 1:2. 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. The amount of the nucleating agent used is not particularly limited, but is preferably 0.1 to 50 g, more preferably 0.5 to 20 g, and even more preferably 3 to 15 g, per 1 mol of rhodium in the hydrochloric acid solution.

[0023] There are no limitations on the method for mixing the platinum group metal recovery agent with the hydrochloric acid solution, but rhodium is precipitated by adding the platinum group metal recovery agent to the hydrochloric acid solution and stirring or shaking for a predetermined period of time. The stirring or shaking time is preferably 5 minutes or more, more preferably 10 minutes or more. There is no upper limit, but from the viewpoint of efficiency, it is preferably 10 hours or less, more preferably 5 hours or less. The stirring or shaking time may be adjusted appropriately depending on the concentration of each component and the temperature. The temperature during stirring or shaking may be 0 to 100°C, and preferably 10 to 50°C.

[0024] The precipitate containing rhodium obtained as described above can be recovered by solid-liquid separation such as filtration or centrifugation. The precipitate contains rhodium as ions, chloride ions, and a platinum group metal recovery agent, xylylenediamine, so that rhodium can be obtained as a metal or oxide by calcining in air. The calcination temperature is preferably 400 to 1500°C, more preferably 450 to 1200°C. The calcination time is preferably 5 to 100 minutes, more preferably 10 to 80 minutes. By adjusting these calcination conditions, rhodium can be obtained as a metal, preferably as a simple metal.

[0025] [Platinum group metal recovery method (sequential recovery of platinum and rhodium)] According to the platinum group metal recovery method of the present invention, as described above, platinum and rhodium can be each selectively recovered, and each can be recovered by separating them from a hydrochloric acid solution containing platinum and rhodium. That is, a third embodiment of the platinum group metal recovery method of the present invention is a platinum group metal recovery method that uses the platinum group metal recovery agent to separate and recover platinum and rhodium from a hydrochloric acid solution containing platinum and rhodium, and includes a platinum recovery step of mixing the platinum group metal recovery agent with the hydrochloric acid solution to obtain a platinum-containing precipitate and a rhodium-containing solution, and recovering platinum, and a rhodium recovery step of mixing the platinum group metal recovery agent with the rhodium-containing solution to obtain a rhodium-containing precipitate, and recovering rhodium. According to this method, even when the hydrochloric acid solution contains palladium, it is possible to separate and recover each of the platinum and rhodium from the hydrochloric acid solution containing platinum and rhodium. That is, in another embodiment of the method for recovering platinum group metals of the present invention, the hydrochloric acid solution contains palladium, the platinum recovery step is for obtaining a platinum-containing precipitate and a solution containing rhodium and palladium, and the rhodium recovery step is for obtaining a rhodium-containing precipitate and a solution containing palladium.

[0026] The first step of this embodiment is a platinum recovery step in which the platinum group metal recovery agent is mixed with the hydrochloric acid solution to obtain a platinum-containing precipitate and a rhodium-containing solution. This step is preferably carried out by the method and under the conditions described in the above section [Platinum Group Metal Recovery Method (Platinum Recovery)], and is preferably carried out under the following conditions, particularly from the viewpoint of obtaining a platinum-containing precipitate while preventing rhodium precipitation.

[0027] 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. Although there are no limitations on the concentrations of platinum and rhodium contained in the hydrochloric acid solution, from the viewpoint of efficient recovery, the platinum concentration contained 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.The rhodium concentration contained 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.

[0028] When adding a platinum group metal recovery agent, 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 (mol / mol)] is preferably 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. By setting the molar ratio within the above range, particularly less than 40, the recovery rate of platinum is increased, rhodium is less likely to be contained in the precipitate, and platinum can be recovered with high purity. There are no limitations on the method for mixing the platinum group metal recovery agent with the hydrochloric acid solution, but platinum is precipitated by adding the platinum group metal recovery agent to the hydrochloric acid solution and stirring or shaking for a predetermined period of time. When the platinum group metal recovery agent of the present invention is used, precipitation occurs quickly after mixing with a hydrochloric acid solution, allowing platinum to be recovered in a short time, but the stirring or shaking time is preferably 1 minute or more, more preferably 5 minutes or more. There is no upper limit, but from the viewpoint of efficiency, 10 hours or less is preferable, and 5 hours or less is more preferable. The stirring or shaking time may be adjusted appropriately depending on the concentration of each component and the temperature. The temperature during stirring or shaking may be 0 to 100°C, and preferably 10 to 50°C. The precipitate containing platinum obtained as described above can be recovered by solid-liquid separation such as filtration or centrifugation, and after recovering the precipitate, a solution containing rhodium is obtained.

[0029] The precipitate contains platinum as ions, and also contains chloride ions and a platinum group metal recovery agent, which is xylylenediamine. Therefore, by calcining the precipitate in air, platinum can be obtained as a metal or an oxide. The calcination temperature is preferably 400 to 1000°C, more preferably 500 to 700°C. The calcination time is preferably 5 to 100 minutes, more preferably 10 to 80 minutes. By adjusting these calcination conditions, platinum can be obtained as a metal, preferably as a simple metal.

[0030] The second step of this embodiment is a rhodium recovery step in which the platinum group metal recovery agent is mixed with the rhodium-containing solution obtained in the platinum recovery step to obtain a precipitate containing rhodium, and rhodium is recovered. This step is preferably carried out by the method and under the conditions described in the above section [Method for recovering platinum group metals (recovery of rhodium)], and is preferably carried out under the following conditions, particularly from the viewpoint of obtaining a precipitate containing rhodium while preventing precipitation of palladium.

[0031] The hydrochloric acid concentration of the hydrochloric acid solution containing rhodium is preferably 3 to 12 mol / L, more preferably 4 to 10 mol / L, and even more preferably 5 to 9 mol / L. Furthermore, there are no limitations on the concentration of rhodium contained in the hydrochloric acid solution, but from the viewpoint of efficient recovery, it 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.

[0032] When adding a platinum group metal recovery agent, 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 (mol / mol)] is preferably 10 or more, more preferably 15 or more, even more 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. This molar ratio includes, when any platinum group metal recovery agent added in the previous step remains in the rhodium-containing hydrochloric acid solution used in this step, this molar ratio. Within the above molar ratio range, the recovery rate of rhodium is increased, palladium is less likely to be contained in the precipitate, and rhodium can be recovered with high purity.

[0033] In this method, a nucleating agent may be further mixed with the hydrochloric acid solution containing rhodium in addition to the platinum group metal recovery agent. By mixing the nucleating agent, rhodium can be recovered more selectively even with a smaller amount of platinum group metal recovery agent. When a nucleating agent is used, 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 (mol / mol)] 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. The crystal nucleating agent is preferably a fine particle that is insoluble or poorly soluble in hydrochloric acid solution, and examples thereof include inorganic oxide particles, organic compound crystals, etc. It is more preferable to use the precipitate obtained by this method as the crystal nucleating agent, and particularly it is even more preferable to use a precipitate containing crystals in which the molar ratio of rhodium atoms in the crystals to the platinum group metal recovery agent [rhodium atoms:platinum group metal recovery agent] is 1:2. 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. The amount of the nucleating agent used is not particularly limited, but is preferably 0.1 to 50 g, more preferably 0.5 to 20 g, and even more preferably 3 to 15 g, per 1 mol of rhodium in the hydrochloric acid solution.

[0034] There are no limitations on the method for mixing the platinum group metal recovery agent with the hydrochloric acid solution, but rhodium is precipitated by adding the platinum group metal recovery agent to the hydrochloric acid solution and stirring or shaking for a predetermined period of time. The stirring or shaking time is preferably 5 minutes or more, more preferably 10 minutes or more. There is no upper limit, but from the viewpoint of efficiency, it is preferably 10 hours or less, more preferably 5 hours or less. The stirring or shaking time may be adjusted appropriately depending on the concentration of each component and the temperature. The temperature during stirring or shaking may be 0 to 100°C, and preferably 10 to 50°C.

[0035] The precipitate containing rhodium obtained as described above can be recovered by solid-liquid separation such as filtration or centrifugation. The precipitate contains rhodium as ions, chloride ions, and a platinum group metal recovery agent, xylylenediamine, so that rhodium can be obtained as a metal or oxide by calcining in air. The calcination temperature is preferably 400 to 1500°C, more preferably 450 to 1200°C. The calcination time is preferably 5 to 100 minutes, more preferably 10 to 80 minutes. By adjusting these calcination conditions, rhodium can be obtained as a metal, preferably as a simple metal.

[0036] [Precipitate] As described above, by using the platinum group metal recovery agent of the present invention, platinum group metals in a hydrochloric acid solution can be recovered as a precipitate. The resulting precipitate contains, in addition to platinum group metal atoms (platinum group metal ions), the platinum group metal recovery agent, hydrochloric acid, chloride ions, water, and the like, which are contained in the precipitate as crystals.

[0037] In the platinum recovery step of the first and third embodiments of the platinum group metal recovery method of the present invention, the platinum group metal recovery agent is mixed with a hydrochloric acid solution containing platinum to precipitate platinum. The precipitate of the present invention is obtained by these methods and includes crystals in which the molar ratio of platinum atoms in the crystals to the platinum group metal recovery agent [platinum atoms:the platinum group metal recovery agent] is 1:1. It is believed that by forming crystals in which the molar ratio of platinum atoms to the platinum group metal recovery agent is 1:1, other platinum group metal atoms are excluded from the crystals and are not incorporated into the precipitate, and therefore platinum can be selectively present in the precipitate obtained by the method.

[0038] In the rhodium recovery step of the second and third embodiments of the platinum group metal recovery method of the present invention, the platinum group metal recovery agent is mixed with a hydrochloric acid solution containing rhodium to precipitate rhodium. The precipitate of the present invention is obtained by these methods and contains crystals in which the molar ratio of rhodium atoms in the crystals to the platinum group metal recovery agent [rhodium atoms:the platinum group metal recovery agent] is 1:2. It is believed that by forming crystals in which the molar ratio of rhodium atoms to the platinum group metal recovery agent is 1:2, palladium and other metals are excluded from the crystals and are not incorporated into the precipitate, and therefore rhodium can be selectively present in the precipitate obtained by the method. [Example]

[0039] The present invention will be specifically described based on the following examples, but the present invention is not limited to these examples.

[0040] [Platinum recovery] Example 1: Effect of hydrochloric acid concentration To a hydrochloric acid solution containing 500 mg / L palladium, 1000 mg / L platinum, and 500 mg / L rhodium (concentrations shown in Figure 1), m-xylylenediamine was added as a platinum group metal recovery agent in an amount 15 times (mol / mol) the amount of platinum. Note that the m-xylylenediamine used here is the hydrochloride salt. The solution was then shaken at 25°C for 1 hour to obtain a precipitate. The resulting precipitate and solution were subjected to solid-liquid separation by centrifugation. The solution obtained after solid-liquid separation was analyzed by ICP, and the amount of platinum group metals contained in the precipitate was calculated. The relationship between hydrochloric acid concentration and metal recovery rate is shown in Figure 1. As is clear from Figure 1, by using m-xylylenediamine as a platinum group metal recovery agent, platinum can be selectively recovered as a precipitate over a wide range of hydrochloric acid concentrations above 1 mol / L.

[0041] Example 2: Effect of shaking time A precipitate and a solution were obtained in the same manner as in Example 1, except that the hydrochloric acid concentration of the hydrochloric acid solution was set to 8 mol / L and the shaking time was changed as shown in FIG. 2, and the amount of platinum group metal contained in the precipitate was calculated. The relationship between shaking time and metal recovery rate is shown in Figure 2. As is clear from Figure 2, 92% of platinum was recovered with one minute of shaking, and more than 95% of platinum was recovered as a precipitate with shaking for 10 minutes or more. Furthermore, palladium and rhodium were not recovered as a precipitate.

[0042] Example 3: Effect of the molar ratio of platinum group metal recovery agent to platinum A precipitate and a solution were obtained in the same manner as in Example 1, except that the hydrochloric acid concentration of the hydrochloric acid solution was set to 8 mol / L, the shaking time was set to 10 minutes, and the amount of platinum group metal recovery agent (m-xylylenediamine) added was changed as shown in Figure 3, and the amount of platinum group metal contained in the precipitate was calculated. Figure 3 shows the relationship between the amount of m-xylylenediamine added and the metal recovery rate. As is clear from Figure 3, when the amount of m-xylylenediamine added is 5 times (mol / mol) or more the amount of platinum, 86% or more of platinum can be recovered as a precipitate, indicating a high platinum recovery rate. Furthermore, when the amount of m-xylylenediamine added is 40 times (mol / mol) or less the amount of platinum, platinum can be selectively recovered as a precipitate.

[0043] [Recovery of rhodium] Example 4: Effect of the molar ratio of platinum group metal recovery agent to rhodium To a hydrochloric acid solution (hydrochloric acid concentration 8 mol / L) containing 500 mg / L of palladium and 500 mg / L of rhodium, m-xylylenediamine was added as a platinum group metal recovery agent in the amounts shown in Figure 4. Note that the m-xylylenediamine used here is the hydrochloride salt. The solution was then shaken at 25°C for 1 hour to obtain a precipitate. The resulting precipitate and solution were subjected to solid-liquid separation by centrifugation. The solution obtained after solid-liquid separation was analyzed by ICP, and the amount of platinum group metals contained in the precipitate was calculated. Figure 4 shows the relationship between the amount of m-xylylenediamine added and the metal recovery rate. As is clear from Figure 4, when the amount of m-xylylenediamine added is 75 times (mol / mol) or more the amount of rhodium, 90% or more of rhodium was recovered as a precipitate, resulting in a high rhodium recovery rate. Furthermore, regardless of the amount of m-xylylenediamine added, palladium was not recovered, indicating that rhodium could be selectively recovered as a precipitate.

[0044] Example 5: Effect of shaking time A precipitate and a solution were obtained in the same manner as in Example 4, except that the shaking time was changed as shown in FIG. 5, and the amount of platinum group metal contained in the precipitate was calculated. Figure 5 shows the relationship between shaking time and metal recovery rate when m-xylylenediamine was added in an amount 100 times (mol / mol) the amount of rhodium. As is clear from Figure 5, shaking for 10 minutes or more allowed more than 90% of rhodium to be recovered as a precipitate, while no palladium was recovered.

[0045] [Crystals (precipitates) containing platinum group metal atoms and platinum group metal recovery agents] <Example 6: Crystals (precipitates) containing platinum atoms and platinum group metal recovery agent> To a hydrochloric acid solution containing 1000 mg / L of platinum (hydrochloric acid concentration 8 mol / L), m-xylylenediamine was added as a platinum group metal recovery agent in an amount (mol / mol) twice the amount of platinum. Note that the m-xylylenediamine 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 left to stand for several days to obtain crystals. The obtained crystals (approximately 2 mm) and the solution were subjected to solid-liquid separation by filtration. Thermogravimetric analysis, single-crystal X-ray structural analysis, and powder X-ray diffraction analysis of the crystals revealed that the molar ratio of platinum atoms in the crystals to the platinum group metal recovery agent [platinum atoms:platinum group metal recovery agent] was 1:1.

[0046] <Example 7: Crystals (precipitates) containing rhodium atoms and platinum group metal recovery agent> To a hydrochloric acid solution containing 500 mg / L of rhodium (hydrochloric acid concentration 8 mol / L), m-xylylenediamine was added as a platinum group metal recovery agent in an amount 50 times (mol / mol) the amount of rhodium. Note that the m-xylylenediamine 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 left to stand for several days to obtain crystals. The obtained crystals (approximately 2 mm) and the solution were subjected to solid-liquid separation by filtration. The crystals were subjected to thermogravimetric analysis, single-crystal X-ray structural analysis, and powder X-ray diffraction analysis, and it was found that the molar ratio of rhodium atoms in the crystals to the platinum group metal recovery agent [rhodium atoms:platinum group metal recovery agent] was 1:2.

[0047] [Sequential recovery of platinum and rhodium] Example 8 (Platinum recovery process: First process) To a hydrochloric acid solution (hydrochloric acid concentration 8 mol / L) containing 500 mg / L of palladium, 1000 mg / L of platinum, and 500 mg / L of rhodium, m-xylylenediamine was added as a platinum group metal recovery agent in an amount 15 times (mol / mol) the amount of platinum. Note that the m-xylylenediamine used here is the hydrochloride salt. The mixture was then shaken at 25°C for 10 minutes to obtain a precipitate. The resulting precipitate and solution were then separated into solid and liquid by filtration. The solution obtained after solid-liquid separation was analyzed by ICP, and the amount of platinum group metals contained in the precipitate was calculated. The precipitate contained 96% of the amount of platinum contained in the initial hydrochloric acid solution, 3% of the amount of rhodium contained in the initial hydrochloric acid solution, and no palladium. Thermogravimetric analysis and powder X-ray diffraction analysis of the precipitate revealed that it contained crystals in which the molar ratio of platinum atoms in the crystals to the platinum group metal recovery agent [platinum atoms:platinum group metal recovery agent] was 1:1.

[0048] (Rhodium recovery process: second process) Next, m-xylylenediamine was added as a platinum group metal recovery agent to the solution obtained after the solid-liquid separation in an amount 90 times (mol / mol) relative to the amount of rhodium, and the mixture was shaken at 25°C for 10 minutes. The resulting precipitate and solution were then subjected to solid-liquid separation by filtration. Note that the m-xylylenediamine used here was in the form of hydrochloride. The solution obtained after solid-liquid separation was analyzed by ICP, and the amounts of platinum group metals contained in the precipitate were calculated. The precipitate contained 86% of the amount of rhodium contained in the initial hydrochloric acid solution, 3% of the amount of platinum contained in the initial hydrochloric acid solution, and 5% of the amount of palladium contained in the initial hydrochloric acid solution. Thermogravimetric analysis and powder X-ray diffraction analysis of the precipitate revealed that it contained crystals in which the molar ratio of rhodium atoms in the crystals to the platinum group metal recovery agent [rhodium atoms:platinum group metal recovery agent] was 1:2. The solution obtained after solid-liquid separation contained 1% of the amount of platinum contained in the original hydrochloric acid solution, 11% of the amount of rhodium contained in the original hydrochloric acid solution, and 95% of the amount of palladium contained in the original hydrochloric acid solution.

[0049] 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 recovered selectively and with a high recovery rate from a hydrochloric acid solution containing palladium, platinum, and rhodium, and rhodium can be recovered selectively and with a high recovery rate from a hydrochloric acid solution containing palladium and rhodium.

[0050] Example 9: Use of a nucleating agent in the rhodium recovery process (Platinum recovery process: First process) To a hydrochloric acid solution (hydrochloric acid concentration 8 mol / L) containing 500 mg / L of palladium, 1000 mg / L of platinum, and 500 mg / L of rhodium, m-xylylenediamine was added as a platinum group metal recovery agent in an amount 15 times (mol / mol) the amount of platinum. Note that the m-xylylenediamine used here is the hydrochloride salt. The mixture was then shaken at 25°C for 10 minutes to obtain a precipitate. The resulting precipitate and solution were then separated into solid and liquid by filtration. The solution obtained after solid-liquid separation was analyzed by ICP, and the amounts of platinum group metals contained in the precipitate were calculated. The precipitate contained 96% of the amount of platinum contained in the initial hydrochloric acid solution, 3% of the amount of rhodium contained in the initial hydrochloric acid solution, and 0.7% of the amount of palladium contained in the initial hydrochloric acid solution.

[0051] (Rhodium recovery process (example using a crystal nucleating agent): second process) Next, m-xylylenediamine was added as a platinum group metal recovery agent to the solution obtained after the solid-liquid separation in an amount 20 times (mol / mol) relative to the amount of rhodium, and five grains of crystals (approximately 2 mm in size) containing rhodium atoms and a platinum group metal recovery agent obtained in Example 7 were added as a crystal nucleating agent. The mixture was shaken at 25°C for 10 minutes, and the resulting precipitate and solution were subjected to solid-liquid separation by filtration. The m-xylylenediamine used here was the hydrochloride salt. The solution obtained after solid-liquid separation was analyzed by ICP, and the amounts of platinum group metals contained in the precipitate were calculated. The precipitate contained 93% of the amount of rhodium contained in the initial hydrochloric acid solution, 2% of the amount of platinum contained in the initial hydrochloric acid solution, and 0.6% of the amount of palladium contained in the initial hydrochloric acid solution. The solution obtained after solid-liquid separation contained 2% of the amount of platinum contained in the original hydrochloric acid solution, 4% of the amount of rhodium contained in the original hydrochloric acid solution, and 99% of the amount of palladium contained in the original hydrochloric acid solution.

[0052] As can be seen from the results of Example 9, by using a crystal nucleating agent in the rhodium recovery step, rhodium can be recovered more selectively even with a small amount of platinum group metal recovery agent.

[0053] [Recovery from simulated catalyst leaching solution] Example 10 Assuming the recovery of platinum group metals from used automobile exhaust gas purification catalysts, a leaching simulation solution (hydrochloric acid concentration 8 mol / L) containing various metals shown in Table 1 was used to carry out the platinum recovery step (first step) and rhodium recovery step (second step) using the same procedures as in Example 9. The solutions obtained after solid-liquid separation in each step were analyzed by ICP to determine the amount of each metal contained in the precipitate, and the metal recovery rate was calculated. Note that the m-xylylenediamine used in the first and second steps was in the form of hydrochloride. The results are shown in Table 1.

[0054] [Table 1]

[0055] As shown in Table 1, even when a hydrochloric acid solution containing various metals other than platinum group metals was used, platinum could be selectively recovered as a precipitate in the first step, and rhodium could be selectively recovered as a precipitate in the second step.

[0056] Example 11: Recovery of platinum (example using p-xylylenediamine as a platinum group metal recovery agent) To an 8 mol / L hydrochloric acid solution containing 500 mg / L palladium, 1000 mg / L platinum, and 500 mg / L rhodium, p-xylylenediamine was added as a platinum group metal recovery agent in an amount 15 times (mol / mol) the amount of platinum. Note that the p-xylylenediamine used here is the hydrochloride salt. The mixture was then shaken at 25°C for 1 hour to obtain a precipitate. The resulting precipitate and solution were subjected to solid-liquid separation by centrifugation. The solution obtained after solid-liquid separation was analyzed by ICP, and the amount of platinum group metals contained in the precipitate was calculated. As a result, 74% of platinum was recovered as a precipitate. In addition, only 4% of palladium and 1% of rhodium were recovered as a precipitate, demonstrating that platinum can be selectively recovered as a precipitate.

Claims

1. A method for recovering platinum from a hydrochloric acid solution containing platinum using a platinum group metal recovery agent represented by the following general formula (1), comprising mixing the platinum group metal recovery agent with the hydrochloric acid solution at a molar ratio of the platinum group metal recovery agent to the platinum contained in the hydrochloric acid solution [platinum group metal recovery agent / platinum] of 5 or more and less than 40, and precipitating platinum. 【Chemical 1】

2. 2. The method for recovering platinum group metals according to claim 1, wherein the hydrochloric acid solution contains at least one metal selected from the group consisting of palladium and rhodium.

3. A method for recovering rhodium from a hydrochloric acid solution containing rhodium (but not containing platinum) using a platinum group metal recovery agent represented by the following general formula (1), comprising mixing the platinum group metal recovery agent with the hydrochloric acid solution at a molar ratio of the platinum group metal recovery agent to the rhodium contained in the hydrochloric acid solution [platinum group metal recovery agent / rhodium] of 15 or more, and precipitating rhodium. 【Chemistry 2】

4. 4. The platinum group metal recovery method of claim 3, wherein the hydrochloric acid solution contains palladium.

5. 5. The method for recovering platinum group metals according to claim 3, 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 50 or more.

6. A platinum group metal recovery method for separating and recovering platinum and rhodium from a hydrochloric acid solution containing platinum and rhodium, using a platinum group metal recovery agent represented by the following general formula (1), comprising: a platinum recovery step of mixing the platinum group metal recovery agent with the hydrochloric acid solution at a molar ratio of the platinum group metal recovery agent to the platinum contained in the hydrochloric acid solution [platinum group metal recovery agent / platinum] of 5 or more and less than 40, to obtain a precipitate containing platinum and a solution containing rhodium, and recovering platinum; and a rhodium recovery step of mixing the platinum group metal recovery agent with the rhodium-containing solution at a molar ratio of the platinum group metal recovery agent to the rhodium contained in the hydrochloric acid solution [platinum group metal recovery agent / rhodium] of 15 or more, to obtain a precipitate containing rhodium, and recovering rhodium. 【Chemistry 3】

7. 7. The method for recovering platinum group metals according to claim 6, wherein the hydrochloric acid solution contains palladium, the platinum recovery step is for obtaining a precipitate containing platinum and a solution containing rhodium and palladium, and the rhodium recovery step is for obtaining a precipitate containing rhodium and a solution containing palladium.

8. 8. The method for recovering platinum group metals according to claim 6, wherein in the rhodium recovery step, a crystal nucleating agent is further mixed with the platinum group metal recovery agent and the solution containing rhodium.

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