How to recover ruthenium

Abstract

To provide a wet-type recovery method that can efficiently concentrating ruthenium.SOLUTION: A wet-type method for recovering ruthenium from solution containing ruthenium, antimony, lead and copper has an antimony removal process of adding sodium hydroxide to the solution to remove antimony. In the antimony removal process, the concentration ratio of ruthenium for antimony, the concentration ratio of lead for antimony, and the concentration ratio of copper for antimony in the solution are increased.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for recovering ruthenium. [Background technology]

[0002] A method using alkali fusion is known as a method for recovering ruthenium (Ru) from a ruthenium-containing mixture. For example, Patent Document 1 discloses a method for recovering ruthenium by alkali fusion of a ruthenium-containing mixture, leaching the molten residue with water, and adding a reducing agent. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5376437 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one embodiment of the present invention is to provide a wet recovery method that can efficiently concentrate ruthenium. [Means for solving the problem]

[0005] A first aspect of the present invention is 1. A wet process method for recovering ruthenium from a solution containing ruthenium, antimony, lead, and copper, comprising: an antimony removal step of adding sodium hydroxide to the solution to remove the antimony; In the antimony removal step, the concentration ratio of the ruthenium to the antimony, the concentration ratio of the lead to the antimony, and the concentration ratio of the copper to the antimony in the solution are increased.

[0006] A second aspect of the present invention is In the method for recovering ruthenium according to the first aspect, in the antimony removal step, a concentration ratio of the ruthenium to the antimony in the solution is made greater than 1.

[0007] A third aspect of the present invention is a reduction step in which a reducing agent is added after the antimony removal step to precipitate the ruthenium; The method for recovering ruthenium according to the first or second aspect further comprises an acid leaching step of adding an acid after the reduction step to leach the ruthenium.

[0008] A fourth aspect of the present invention is In the method for recovering ruthenium according to the third aspect, the lead is removed in the acid leaching step.

[0009] A fifth aspect of the present invention is In the method for recovering ruthenium according to the third or fourth aspect, the acid leaching step is carried out under acidic conditions with a pH of less than 0.

[0010] A sixth aspect of the present invention is The method for recovering ruthenium according to any one of the third to fifth aspects, further comprising a neutralization step of adding potassium hydroxide or sodium hydroxide after the acid leaching step to remove the copper.

[0011] A seventh aspect of the present invention is In the method for recovering ruthenium according to the sixth aspect, the neutralization step is carried out under acidic conditions with a pH of 2 or more and 4 or less. [Effects of the Invention]

[0012] According to one embodiment of the present invention, it is possible to provide a wet recovery method that can efficiently concentrate ruthenium. [Brief explanation of the drawings]

[0013] [Figure 1]FIG. 1 is a flowchart showing an example of a method for recovering ruthenium according to a first embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] <Insights gained by the inventor> First, the findings of the inventors will be explained.

[0015] When a ruthenium-containing mixture contains antimony (Sb), lead (Pb), copper (Cu), etc., it has been found that with the conventional method described in Patent Document 1 and the like, a large amount of antimony, lead, and copper dissolves together with ruthenium during water leaching after alkali fusion, making it difficult to concentrate ruthenium.

[0016] The inventors have conducted extensive research into the above-mentioned problems. As a result, they have found that ruthenium can be efficiently concentrated by, for example, adding sodium hydroxide to the ruthenium-containing solution after water leaching and before adding a reducing agent to remove antimony. According to this method, it is possible to efficiently concentrate (recover) ruthenium even when the original ruthenium grade is low.

[0017] [Details of the embodiment of the present invention] Next, an embodiment of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0018] In this specification, "A to B" means a numerical range of "A or more and B or less."

[0019] <First embodiment of the present invention> First, the ruthenium recovery method of this embodiment will be described. Fig. 1 is a flowchart showing an example of the ruthenium recovery method of this embodiment. As shown in Fig. 1, the ruthenium recovery method of this embodiment includes, for example, an alkali melting step S101, a water leaching step S102, a deantimonying step S103, a reduction step S104, a sulfuric acid leaching step S105, and a neutralization step S106. In Fig. 1, L indicates the liquid side when solid-liquid separation is performed in each step, and S indicates the solid side.

[0020] The ruthenium-containing mixture 10 contains ruthenium, antimony, lead, and copper. The ruthenium-containing mixture 10 may further contain, for example, tellurium (Te), arsenic (As), potassium (K), sodium (Na), etc. The ruthenium-containing mixture 10 may be crushed in advance to form a fine powder (for example, a particle size of 250 μm or less).

[0021] The grade (content) of each metal element contained in the ruthenium-containing mixture 10 is not particularly limited, but may be, for example, 0.01 to 10 wt % ruthenium, 0.01 to 80 wt % antimony, 0.01 to 90 wt % lead, 0.01 to 90 wt % copper, 0.01 to 80 wt % tellurium, 0.01 to 80 wt % arsenic, 0.01 to 10 wt % potassium, and 0.01 to 10 wt % sodium.

[0022] The ruthenium recovery method of this embodiment is particularly effective when the quality of ruthenium is lower than that of antimony, lead, and copper. Specifically, for example, the quality ratio of ruthenium to antimony (Ru / Sb) in the ruthenium-containing mixture 10 is preferably 0.01 to 1. Also, for example, the quality ratio of ruthenium to lead (Ru / Pb) is preferably 0.01 to 1. Also, for example, the quality ratio of ruthenium to lead (Ru / Pb) is preferably 0.01 to 1.

[0023] (Alkali melting step S101) The alkali melting step S101 is, for example, a step of alkali-melting the ruthenium-containing mixture 10. As a specific example, a mixture of the ruthenium-containing mixture 10 and potassium nitrate is introduced into a melt obtained by melting potassium hydroxide at 400 to 450° C. The resulting melt is cooled to, for example, room temperature.

[0024] (Water leaching process S102) The water leaching step S102 is a step in which, for example, water is added to the melt obtained in the alkali melting step S101 to leach out each metal element including ruthenium. After the water leaching, solid-liquid separation is performed to obtain a ruthenium-containing solution 20 containing ruthenium and a water leaching residue 21. Note that the water leaching residue 21 contains almost no ruthenium, so it may be discarded or used as a raw material for recovering other metals.

[0025] The ruthenium-containing solution 20 contains ruthenium, antimony, lead, and copper. In the ruthenium recovery method of this embodiment, the antimony, lead, and copper are removed from the ruthenium-containing solution 20 and the ruthenium is concentrated through the following steps. In other words, the ruthenium recovery method of this embodiment can be a wet method for recovering ruthenium from the ruthenium-containing solution 20.

[0026] (Antimony removal process S103) The antimony removal step S103 is, for example, a step of adding sodium hydroxide to the ruthenium-containing solution 20 obtained in the water leaching step S102 to remove antimony (antimony removal step). After the addition of sodium hydroxide, solid-liquid separation is performed to obtain a ruthenium-containing antimony removal solution 30 and an antimony removal residue 31. The ruthenium recovery method of this embodiment differs from the conventional method described in Patent Document 1 and the like in that antimony is removed before the addition of a reducing agent. This allows ruthenium to be efficiently concentrated. Note that the antimony removal residue 31 contains almost no ruthenium, so it may be discarded or used as a raw material for recovering antimony, etc.

[0027] In the antimony removal step S103, the concentration ratios of ruthenium to antimony (Ru / Sb), lead to antimony (Pb / Sb), and copper to antimony (Cu / Sb) in the solution are increased. That is, the concentration ratio (Ru / Sb) in the antimony removal solution 30 is made larger than the concentration ratio (Ru / Sb) in the ruthenium-containing solution 20, the concentration ratio (Pb / Sb) in the antimony removal solution 30 is made larger than the concentration ratio (Pb / Sb) in the ruthenium-containing solution 20, and the concentration ratio (Cu / Sb) in the antimony removal solution 30 is made larger than the concentration ratio (Cu / Sb) in the ruthenium-containing solution 20. This indicates that in the antimony removal step S103, antimony is removed before lead and copper. This makes it easier to concentrate ruthenium in the subsequent steps.

[0028] In the antimony removal step S103, it is preferable to set the concentration ratio of ruthenium to antimony (Ru / Sb) in the antimony removal solution 30 to greater than 1. This makes it easier to concentrate ruthenium in the subsequent steps.

[0029] Other conditions in the antimony removal step S103 are, for example, as follows: pH: 10-14 ORP (oxidation-reduction potential, vs AgCl): -100 to 600 mV Liquid temperature: 0 to 95°C Reaction time: 1 to 120 minutes

[0030] (Reduction step S104) The reduction step S104 is a step in which, for example, a reducing agent is added to the antimony-removed solution 30 obtained in the antimony-removing step S103 to precipitate ruthenium and the like. As the reducing agent, for example, an alcohol such as ethanol or methanol, or an inorganic reducing agent such as sodium borohydride (SBH) can be used. After the addition of the reducing agent, solid-liquid separation is performed to obtain a reduction residue 40 containing ruthenium and a reduced solution 41. Note that the reduced solution 41 contains almost no ruthenium, so it may be discarded or may be used as an alkaline agent to neutralize acids in other steps.

[0031] Other conditions in the reduction step S104 are, for example, as follows: pH: 10-16 ORP: 100 to -1000mV Liquid temperature: 0 to 95°C Reaction time: 0.1 to 60 minutes

[0032] (Sulfuric acid leaching process S105) The sulfuric acid leaching step S105 is a step in which, for example, sulfuric acid is added to the reduction residue 40 obtained in the reduction step S104 to leach ruthenium. After the addition of sulfuric acid, solid-liquid separation is performed to obtain a sulfuric acid leaching solution 50 containing ruthenium and a sulfuric acid leaching residue 51. The sulfuric acid leaching step S105 can remove, for example, lead. Note that the sulfuric acid leaching residue 51 contains almost no ruthenium, so it may be discarded or used as a raw material for recovering lead and the like.

[0033] The sulfuric acid leaching step S105 is preferably carried out under acidic conditions, for example, a pH of less than 0. That is, sulfuric acid is preferably added so that the pH is less than 0. Under conditions where the pH is 0 or higher, ruthenium may be difficult to leach. In contrast, by setting the pH to less than 0, ruthenium can be easily leached. The lower limit of the pH is not particularly limited, but is preferably -1 or higher, for example, from the viewpoint of reducing the cost of adding sulfuric acid.

[0034] Other conditions in the sulfuric acid leaching step S105 are, for example, as follows: ORP: 500-1200mV Liquid temperature: 0 to 95°C Reaction time: 1 to 60 minutes

[0035] (Neutralization step S106) The neutralization step S106 is a step in which, for example, potassium hydroxide or sodium hydroxide is added to the sulfuric acid leaching solution 50 obtained in the sulfuric acid leaching step S105 to remove copper. After the addition of potassium hydroxide or sodium hydroxide, solid-liquid separation is performed to obtain a ruthenium concentrate 60 in which ruthenium is concentrated, and a neutralized solution 61. Note that the neutralized solution 61 contains almost no ruthenium, so it may be discarded or may be used as a raw material for recovering copper and the like.

[0036] The neutralization step S106 is preferably carried out under acidic conditions, for example, at a pH of 2 to 4. That is, potassium hydroxide or sodium hydroxide is preferably added so that the pH is 2 to 4. Under conditions where the pH is outside the above range, the difference in precipitation rates between ruthenium and copper is small, and it may be difficult to separate the two. In contrast, by adjusting the pH to 2 to 4, the difference in precipitation rates between ruthenium and copper can be increased, making it easier to separate the two.

[0037] Other conditions in the neutralization step S106 are, for example, as follows: ORP: 500-1200mV Liquid temperature: 0 to 95°C Reaction time: 1 to 60 minutes

[0038] Through the above steps, ruthenium can be efficiently concentrated (recovered) from the ruthenium-containing solution 20 (or ruthenium-containing mixture 10). According to the ruthenium recovery method of this embodiment, for example, the quality of ruthenium in the ruthenium concentrate 60 can be made 40% by weight or more. Furthermore, in the ruthenium concentrate 60, the quality ratio of ruthenium to antimony (Ru / Sb) can be made 2 or more, the quality ratio of ruthenium to lead (Ru / Pb) can be made 10 or more, and the quality ratio of ruthenium to copper (Ru / Cu) can be made 10 or more.

[0039] <Other Embodiments of the Present Invention> Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the present invention.

[0040] For example, in the above embodiment, the sulfuric acid leaching step S105 is performed after the reduction step S104, in which sulfuric acid is added to leach ruthenium. However, after the reduction step S104, an acid other than sulfuric acid (e.g., hydrochloric acid or nitric acid) may be added to leach ruthenium. In this case, the sulfuric acid leaching step S105 may be referred to as an acid leaching step. Note that adding sulfuric acid is preferable from the viewpoint of efficiently removing lead. [Example]

[0041] Next, examples of the present invention will be described. These examples are merely examples of the present invention, and the present invention is not limited to these examples.

[0042] Example 1 Example 1 is an example showing a specific example of the antimony removal step S103 and the reduction step S104. First, a ruthenium-containing mixture 10 having the composition shown in Table 1 was prepared, and then subjected to an alkali melting step S101 at 400 to 450°C, followed by a water leaching step S102 to obtain a ruthenium-containing solution 20 (sample 1-1). Note that Ru / M in Table 1 indicates the purity ratio of ruthenium to each element.

[0043] [Table 1]

[0044] Next, 45 mL of 50% aqueous sodium hydroxide solution was added to 200 mL of sample 1-1 (ruthenium-containing solution 20), and the mixture was allowed to react for 45 minutes to obtain antimony-free solution 30 and antimony-free residue 31 (sample 1-1-1). The pH was 11.7, the ORP (vs. AgCl, hereinafter the same) was 77 mV, and the liquid temperature was 72°C.

[0045] Furthermore, 1.5 mL of ethanol was added as a reducing agent to antimony-free solution 30 (238 mL) of sample 1-1-1, and the mixture was allowed to react for 15 minutes to obtain reduction residue 40 and reduced solution 41 (sample 1-1-2). The pH was 11.7, the ORP was -243 mV, and the liquid temperature was 60°C. The concentration and purity of each element in samples 1-1, 1-1-1, and 1-1-2 are shown in Table 2. Note that M / Sb in Table 2 indicates the concentration ratio of each element relative to antimony. Furthermore, because sodium hydroxide was added to antimony-free solution 30 of sample 1-1-1, the sodium removal rate was not calculated.

[0046] [Table 2]

[0047] For comparison, a specific example in which the reduction step S104 was performed without the antimony removal step S103 is also shown. 0.35 g of sodium borohydride (SBH) as a reducing agent was added to 200 mL of a ruthenium-containing solution 20 (sample A-1) prepared separately from sample 1-1, and the mixture was allowed to react for 15 minutes to obtain a reduction residue 40 and a reduction solution 41 (sample A-1-1). The pH was 13.7, the ORP was -330 mV, and the liquid temperature was 60°C. The concentrations and grades of each element in sample A-1 and sample A-1-1 are shown in Table 3. Note that tellurium was below the lower limit of detection in sample A-1 and reduction solution 41 of sample A-1-1.

[0048] [Table 3]

[0049] As shown in Table 2, the concentration ratio of ruthenium to antimony (Ru / Sb) in the antimony removal solution 30 of sample 1-1-1 was 1.61. Therefore, it was confirmed that by performing the antimony removal step S103, the concentration ratio (Ru / Sb) could be made greater than 1, and most of the antimony could be removed.

[0050] Furthermore, as shown in Table 2, the concentration ratio (Ru / Sb) in the antimony-free solution 30 of sample 1-1-1 was greater than the concentration ratio (Ru / Sb) in the ruthenium-containing solution 20 of sample 1-1, the concentration ratio (Pb / Sb) in the antimony-free solution 30 of sample 1-1-1 was greater than the concentration ratio (Pb / Sb) in the ruthenium-containing solution 20 of sample 1-1, and the concentration ratio (Cu / Sb) in the antimony-free solution 30 of sample 1-1-1 was greater than the concentration ratio (Cu / Sb) in the ruthenium-containing solution 20 of sample 1-1. Therefore, it was confirmed that antimony was removed before lead and copper in the antimony-free step S103.

[0051] Furthermore, as shown in Table 3, the quality ratio of ruthenium to antimony (Ru / Sb) in the reduction residue 40 of sample A-1-1, which was subjected to the reduction step S104 without performing the antimony removal step S103, was 0.8. In contrast, as shown in Table 2, the quality ratio of ruthenium to antimony (Ru / Sb) in the reduction residue 40 of sample 1-1-2, which was subjected to the antimony removal step S103 and the reduction step S104, was 4.5. From the above, it was confirmed that ruthenium and antimony can be separated more efficiently by performing the antimony removal step S103.

[0052] Example 2 Example 2 is an example showing a specific example of the sulfuric acid leaching step S105 and the neutralization step S106. First, the reduction residue 40 of the above-mentioned sample 1-1-2 was prepared and designated as sample 2-1.

[0053] Next, 25 mL of 200 g / L sulfuric acid was added to 0.5 g of Sample 2-1, and the mixture was allowed to react for 10 minutes to obtain a sulfuric acid leaching solution 50 and a sulfuric acid leaching residue 51 (Sample 2-1-1). The pH was −0.32, the ORP was 1124 mV, and the liquid temperature was 60° C.

[0054] Furthermore, 7 mL of a 50% potassium hydroxide aqueous solution was added to a solution (100 mL) prepared by adding the sulfuric acid leaching solution 50 of sample 2-1-1 to the washing water of the sulfuric acid leaching residue 51, and the mixture was allowed to react for 15 minutes to obtain a ruthenium concentrate 60 and a neutralized solution 61 (sample 2-1-2). The pH at this time was 3.2, the ORP was 698 mV, and the solution temperature was 60°C. The concentration and purity of each element in samples 2-1, 2-1-1, and 2-1-2 are shown in Table 4.

[0055] [Table 4]

[0056] As shown in Table 4, in the sulfuric acid leaching solution 50 of sample 2-1-1, the ruthenium leaching rate was high at 80%, and the lead leaching rate was low at 6%. Therefore, it was confirmed that the sulfuric acid leaching step S105 can remove lead and efficiently separate ruthenium and lead. Also, as shown in Table 4, in sample 2-1-2, the ruthenium precipitation rate was high at 96%, and the copper precipitation rate was low at 10%. Furthermore, as shown in Tables 1, 2, and 4, in the ruthenium concentrate 60 of sample 2-1-2, the ratio of ruthenium to each element (Ru / M) was significantly higher than in the original ruthenium-containing mixture 10 and ruthenium-containing solution 20 (sample 1-1). From the above, it was confirmed that ruthenium can be efficiently recovered from the ruthenium-containing solution 20 (or ruthenium-containing mixture 10) containing ruthenium, antimony, lead, copper, and the like.

[0057] Example 3 Example 3 is an example showing another specific example of the sulfuric acid leaching step S105. First, the reduction residue 40 of the sample A-1-1 described in Example 1 was prepared.

[0058] Water alone was added to the reduction residue 40 (1.73 g) of Sample A-1-1, and the mixture was allowed to react for 15 minutes to obtain a sulfuric acid leaching solution 50 (Sample 3-1). The pH was 10.6, the ORP was 332 mV, and the liquid temperature was 60°C.

[0059] Furthermore, 0.34 mL of 200 g / L sulfuric acid was added to the sulfuric acid leaching solution 50 of Sample 3-1 and reacted for 15 minutes to obtain a sulfuric acid leaching solution 50 (Sample 3-2). At this time, the pH was 1.9, the ORP was 919 mV, and the liquid temperature was 60°C.

[0060] Furthermore, 4.83 mL of 200 g / L sulfuric acid was added to the sulfuric acid leaching solution 50 of Sample 3-2 and reacted for 15 minutes to obtain a sulfuric acid leaching solution 50 (Sample 3-3). At this time, the pH was 0.68, the ORP was 980 mV, and the liquid temperature was 60°C.

[0061] Furthermore, 14.48 mL of 200 g / L sulfuric acid was added to the sulfuric acid leaching solution 50 of Sample 3-3 and reacted for 15 minutes to obtain a sulfuric acid leaching solution 50 (Sample 3-4). At this time, the pH was −0.08, the ORP was 1024 mV, and the liquid temperature was 60° C.

[0062] In addition, Sample 2-1- described in Example 2 1 The sulfuric acid leaching solution 50 of this amount was used as Sample 3-5. Table 5 shows the leaching rates of each element in Sample 3-1, Sample 3-2, Sample 3-3, Sample 3-4, and Sample 3-5.

[0063] [Table 5]

[0064] As shown in Table 5, the ruthenium leaching rate was low, ranging from 1 to 6%, for Sample 3-1, which was added with only water, and for Samples 3-2 and 3-3, which were added with a small amount of sulfuric acid. In contrast, the ruthenium leaching rate was high, ranging from 25 to 80%, for Samples 3-4 and 3-5, which were added with a sufficient amount of sulfuric acid (e.g., an amount that would result in a pH of less than 0). Meanwhile, the lead leaching rate was low, ranging from 1 to 6%, for all samples shown in Table 5. From the above, it was confirmed that ruthenium can be efficiently leached and ruthenium and lead can be efficiently separated by performing the sulfuric acid leaching step S105 under appropriate conditions. It was also found that elements such as copper and arsenic can be efficiently separated by controlling the amount of sulfuric acid added.

[0065] Example 4 Example 4 is an example showing another specific example of the neutralization step S 106. First, the sulfuric acid leaching solution 50 of Sample 3-4 described in Example 3 was prepared.

[0066] To 50 mL of the sulfuric acid leaching solution of Sample 3-4, a predetermined amount of sodium hydroxide was added so that the pH was 3.1, and the mixture was allowed to react for 15 minutes to obtain Sample 4-1. The ORP was 706 mV and the liquid temperature was 60°C.

[0067] To 50 mL of the sulfuric acid leaching solution of Sample 3-4, a predetermined amount of sodium hydroxide was added so that the pH was 3.3, and the mixture was allowed to react for 30 minutes to obtain Sample 4-2. The ORP was 667 mV and the liquid temperature was 60°C.

[0068] To 50 ml of the sulfuric acid leaching solution of Sample 3-4, a predetermined amount of sodium hydroxide was added so that the pH was 7.7, and the mixture was allowed to react for 30 minutes to produce Sample 4-3. The ORP was 306 mV, and the solution temperature was 60°C. The precipitation rates of each element in Samples 4-1, 4-2, and 4-3 are shown in Table 6. Note that, because sodium hydroxide was added to Samples 4-1, 4-2, and 4-3, the precipitation rate of sodium was not calculated.

[0069] [Table 6]

[0070] As shown in Table 6, in Sample 4-3, in which the pH was adjusted to 7.7, there was almost no difference in the precipitation rates of antimony and copper, making it difficult to separate them. In contrast, in Samples 4-1 and 4-2, in which the pH was adjusted to about 3 (e.g., pH 2 to 4), there was a difference in the precipitation rates of antimony and copper, making it possible to separate them. From the above, it was confirmed that ruthenium and copper can be efficiently separated by performing the neutralization step S106 under appropriate conditions. [Explanation of symbols]

[0071] 10 Ruthenium-containing mixtures 20 Ruthenium-containing solution 21 Water leaching residue 30 Antimony-free solution 31 Antimony removal residue 40 Reduction residue 41 Reducing Solution 50 Sulfuric acid leaching solution 51 Sulfuric acid leaching residue 60 Ruthenium Concentrate 61 Neutralizing Solution S101 Alkali fusion process S102 Water leaching process S103 Antimony removal process S104 Reduction process S105 Sulfuric acid leaching process S106 Neutralization process

Claims

1. 1. A wet process for recovering ruthenium from a solution containing ruthenium, antimony, lead, and copper, comprising: an antimony removal step of adding sodium hydroxide to the solution to remove the antimony; In the antimony removal step, a concentration ratio of the ruthenium to the antimony, a concentration ratio of the lead to the antimony, and a concentration ratio of the copper to the antimony in the solution are increased, a reduction step in which a reducing agent is added after the antimony removal step to precipitate the ruthenium; further comprising an acid leaching step of adding sulfuric acid after the reduction step to leach the ruthenium; The method for recovering ruthenium, wherein the lead is removed in the acid leaching step.

2. 2. The method for recovering ruthenium according to claim 1, wherein the concentration ratio of the ruthenium to the antimony in the solution is set to be greater than 1 in the antimony removal step.

3. 2. The method for recovering ruthenium according to claim 1, wherein the acid leaching step is carried out under acidic conditions with a pH of less than 0.

4. 4. The method for recovering ruthenium according to claim 3, further comprising a neutralization step after the acid leaching step, in which potassium hydroxide or sodium hydroxide is added to remove the copper.

5. The method for recovering ruthenium according to claim 4, wherein the neutralization step is carried out under acidic conditions having a pH of 2 or more and 4 or less.

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