Methods for recovering ruthenium

Abstract

This invention provides a simple and efficient method for recovering ruthenium. [Solution] A method for recovering ruthenium, comprising the steps of: dissolving a ruthenium-containing mixture containing ruthenium and at least one of antimony, lead, and copper in an alkali to obtain an alkali molten product; adding water to the alkali molten product to obtain a ruthenium-containing solution containing ruthenium and at least one of antimony, lead, and copper; adding an alkaline earth metal salt to the ruthenium-containing solution; and recovering ruthenium from the ruthenium-containing solution, wherein the step of adding the alkaline earth metal salt increases at least one of the following in the ruthenium-containing solution: the concentration ratio of ruthenium to antimony (Ru / Sb), the concentration ratio of ruthenium to lead (Ru / Pb), and the concentration ratio of ruthenium to copper (Ru / Cu).

Description

Technical Field

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

Background Art

[0002] As a method for recovering ruthenium (Ru) from a ruthenium-containing mixture, a method using alkali melting is known. For example, Patent Document 1 discloses a method for recovering ruthenium in which a ruthenium-containing mixture is alkali-melted, the molten residue is leached with water, and a reducing agent is added.

[0003] Also, for example, Patent Document 2 discloses a method for recovering ruthenium in which an alkali melt is leached with water and then an acid is added to increase the ruthenium concentration.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] When an antimony (Sb), lead (Pb), copper (Cu), etc. are contained in a ruthenium-containing mixture, in the conventional methods described in Patent Document 1 and the like, at the time of water leaching after alkali melting, a large amount of antimony, lead, and copper are leached together with ruthenium, so there is a problem that it is difficult to concentrate ruthenium.

[0006] Also, as described in Patent Document 2, when an acid is added to a ruthenium-containing solution, there is a possibility that ruthenium is lost due to the generation of RuO4 gas or the like.

[0007] One embodiment of the present invention aims to provide a method for recovering ruthenium in a simple and efficient manner. [Means for solving the problem]

[0008] A first aspect of the present invention is: A step of obtaining an alkali molten product by alkali melting a ruthenium-containing mixture containing ruthenium and at least one of antimony, lead, and copper, A step of adding water to the aforementioned alkali molten material to obtain a ruthenium-containing solution containing ruthenium and at least one of antimony, lead, and copper, The process involves adding an alkaline earth metal salt to the ruthenium-containing solution, The process includes a step of recovering ruthenium from the ruthenium-containing solution, The ruthenium recovery method involves the step of adding the alkaline earth metal salt, thereby increasing at least one of the following in the ruthenium-containing solution: the concentration ratio of ruthenium to antimony (Ru / Sb), the concentration ratio of ruthenium to lead (Ru / Pb), and the concentration ratio of ruthenium to copper (Ru / Cu).

[0009] A second aspect of the present invention is: The ruthenium recovery method according to the first embodiment is characterized in that, in the step of adding the alkaline earth metal salt, the concentration ratio (Ru / Sb), the concentration ratio (Ru / Pb), and the concentration ratio (Ru / Cu) are all increased.

[0010] A third aspect of the present invention is: The ruthenium recovery method according to the first embodiment, wherein, in the step of adding the alkaline earth metal salt, the change in the concentration of ruthenium in the ruthenium-containing solution before and after the addition of the alkaline earth metal salt is within 15%.

[0011] A fourth aspect of the present invention is: In the step of adding the alkaline earth metal salt, the alkaline earth metal salt is added so that the pH of the ruthenium-containing solution becomes 12 or more. This is the method for recovering ruthenium according to the first aspect described above.

[0012] The fifth aspect of the present invention is In the step of adding the alkaline earth metal salt, a calcium salt is added. This is the method for recovering ruthenium according to the first aspect described above.

[0013] The sixth aspect of the present invention is In the step of recovering the ruthenium, a reducing agent is added to the ruthenium-containing solution to precipitate the ruthenium. This is the method for recovering ruthenium according to any one of the first to fifth aspects described above.

Advantages of the Invention

[0014] According to an embodiment of the present invention, it is possible to provide a method for simply and efficiently recovering ruthenium.

Brief Description of the Drawings

[0015] [Figure 1] FIG. 1 is a flowchart showing an example of a ruthenium recovery method according to a first embodiment of the present invention.

Modes for Carrying Out the Invention

[0016] [Details of Embodiments of the Present Invention] 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, and is shown by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0017] In this specification, “A to B” means a numerical range of “A or more and B or less”.

[0018] <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 starts from, for example, a ruthenium-containing mixture 10, and goes through an alkali melting step S101, a water leaching step S102, an alkaline earth metal salt addition step S103, and a reduction step S104 to recover ruthenium. In FIG. 1, L indicates the liquid side when solid-liquid separation is performed in each step, and S indicates the solid side.

[0019] The ruthenium-containing mixture 10 contains, for example, ruthenium and at least one of antimony, lead, and copper. Further, the ruthenium-containing mixture 10 may further contain, for example, arsenic (As), tin (Sn), tellurium (Te), potassium (K), sodium (Na), etc. The ruthenium-containing mixture 10 may be pulverized in advance and made into fine powder (for example, particle size of 250 μm or less). The ruthenium-containing mixture 10 may contain ruthenium, antimony, lead, and copper.

[0020] The grade (content) of each metal element contained in the ruthenium-containing mixture 10 is not particularly limited. For example, ruthenium can be 0.01 to 10% by weight, antimony can be 0.01 to 80% by weight, lead can be 0.01 to 90% by weight, copper can be 0.01 to 90% by weight, arsenic can be 0.01 to 80% by weight, tin can be 0.01 to 80% by weight, tellurium can be 0.01 to 80% by weight, potassium can be 0.01 to 10% by weight, and sodium can be 0.01 to 10% by weight. When antimony is 45% by weight or more, for example, a step of separately separating and recovering antimony may be performed. [[ID=】]

[0021] The ruthenium recovery method of this embodiment is particularly effective when the grade (mass%) of ruthenium in the ruthenium-containing mixture 10 is lower than that of antimony, lead, copper, and arsenic. Specifically, for example, the grade ratio of ruthenium to antimony (Ru / Sb) in the ruthenium-containing mixture 10 is preferably 0.01 to 1. Also, for example, the grade ratio of ruthenium to lead (Ru / Pb) is preferably 0.01 to 1. Also, for example, the grade ratio of ruthenium to copper (Ru / Cu) is preferably 0.01 to 1. Also, for example, the grade ratio of ruthenium to arsenic (Ru / As) is preferably 0.01 to 1. In particular, when the purity ratio of ruthenium to the sum of lead and antimony (Ru / (Pb+Sb)) is, for example, 0.001 to 1, it is difficult to concentrate ruthenium using conventional methods. However, with the ruthenium recovery method of this embodiment, ruthenium can be concentrated simply and efficiently.

[0022] (Alkali melting process S101) The alkali melting step S101 is a step in which, for example, the ruthenium-containing mixture 10 is mixed with an alkali metal hydroxide and heated to melt it. In other words, it is a step in which the ruthenium-containing mixture 10 is alkali-melted. Specifically, a molten product is obtained by melting a mixture of potassium hydroxide and the ruthenium-containing mixture 10 at 400 to 550°C. Potassium nitrate may be added here as an oxidizing agent. The obtained alkali molten product is then cooled to room temperature and solidified to obtain an alkali molten solidified product 11.

[0023] (Water leaching process S102) The water leaching step S102 is a step in which, for example, water is used to leach each metal element from the alkali molten solid 11 obtained in the alkali molten step S101, to obtain a ruthenium-containing solution 20 containing ruthenium and at least one of antimony, lead, and copper, and a water leaching residue 21. This step is called water leaching because water is used. After water leaching, solid-liquid separation is performed to obtain the ruthenium-containing solution 20 and the water leaching residue 21. Note that the water leaching residue 21 contains almost no ruthenium and may be discarded or used as a raw material for recovering other metals.

[0024] In the water leaching step S102, if the viscosity of the ruthenium-containing solution 20 is high in the subsequent alkaline earth metal salt addition step S103, it is preferable to add water (i.e., dilute with water) to lower the viscosity of the ruthenium-containing solution 20 so that the reaction between the ruthenium-containing solution 20 and the alkaline earth metal salt proceeds uniformly. If the pH of the ruthenium-containing solution 20 drops too low due to the addition of water, the pH may be adjusted by adding an alkaline agent (pH raising agent), for example. In this case, the alkaline agent may contain light metals, but it is preferable that it does not contain heavy metals.

[0025] (Addition of alkaline earth metal salts, step S103) Step S103, which involves adding an alkaline earth metal salt, is a step in which an alkaline earth metal salt is added to, for example, the ruthenium-containing solution 20. In this specification, magnesium (Mg) is also included in the alkaline earth metals. After adding the alkaline earth metal salt, solid-liquid separation is performed to obtain the ruthenium-containing solution 30 (after the addition of the alkaline earth metal salt) and the residue 31 after the addition of the alkaline earth metal salt.

[0026] As the alkaline earth metal salt, calcium salts are particularly preferred. Specifically, CaSO4, Ca(OH)2, CaCO3, etc., are preferred. This allows for efficient ruthenium concentration.

[0027] In the alkaline earth metal salt addition step S103, at least one of the following concentrations in the solution is increased: the ruthenium concentration ratio to antimony (Ru / Sb), the ruthenium concentration ratio to lead (Ru / Pb), and the ruthenium concentration ratio to copper (Ru / Cu). Preferably, all three concentrations (Ru / Sb, Ru / Pb, and Ru / Cu) are increased. In other words, at least one (preferably all) of the concentrations (Ru / Sb, Ru / Pb, Ru / Cu) in the ruthenium-containing solution 30 is made greater than the concentrations (Ru / Sb, Ru / Pb, Ru / Cu) in the ruthenium-containing solution 20. This means that in the alkaline earth metal salt addition step S103, ruthenium loss is suppressed and antimony, lead, and copper are removed. This allows for easy and efficient concentration of ruthenium.

[0028] Furthermore, in the alkaline earth metal salt addition step S103, it is preferable to increase the concentration ratio of ruthenium to tin (Ru / Sn) in the solution.

[0029] In the alkaline earth metal salt addition step S103, it is preferable that the concentration ratios of each component in the ruthenium-containing solution 30 (Ru / Sb, Ru / Pb, Ru / Cu, Ru / Sn) be at least twice, more preferably five times, and particularly preferably ten times, the concentration ratios of each component in the ruthenium-containing solution 20 (Ru / Sb, Ru / Pb, Ru / Cu, Ru / Sn).

[0030] In the alkaline earth metal salt addition step S103, no acid is added to the ruthenium-containing solution 20, and because the pH of the solution is high, the generation of RuO4 gas can be suppressed. Furthermore, the addition of the alkaline earth metal salt also suppresses the formation of RuO2 as a solid. Therefore, ruthenium loss can be reduced, and ruthenium can be efficiently concentrated. Specifically, in the alkaline earth metal salt addition step S103, the change in the concentration of ruthenium in the ruthenium-containing solution 30 relative to the concentration of ruthenium in the ruthenium-containing solution 20 before and after the addition of the alkaline earth metal salt can be kept within 15% (more preferably within 10%).

[0031] In the alkaline earth metal salt addition step S103, it is preferable to add the alkaline earth metal salt so that the pH of the ruthenium-containing solution 30 becomes 12 or higher. This further suppresses the generation of RuO4 gas.

[0032] Furthermore, the alkaline earth metal salt addition step S103 has the advantage of lowering the viscosity of the ruthenium-containing solution 30, which shortens the filtration time during solid-liquid separation.

[0033] Other conditions in the alkaline earth metal salt addition step S103 are, for example, as follows: ORP (Oxidation-Reduction Potential, vs. AgCl): 0~1000mV Liquid temperature: 40-80℃ Reaction time: 1-120 minutes

[0034] (Reduction process S104) The reduction step S104 is a step in which ruthenium is recovered by adding a reducing agent to the ruthenium-containing solution 30, for example, to precipitate the ruthenium. As the reducing agent, for example, alcohols such as ethanol and methanol, or inorganic reducing agents such as sodium borohydride (SBH) can be used. After adding the reducing agent, a ruthenium concentrate 50 and a reduction solution 51 can be obtained by solid-liquid separation. Since the reduction solution 51 contains almost no ruthenium, it can be discarded or used as an alkaline agent to neutralize acids in other steps.

[0035] Other conditions in the reduction process S104 are as follows, for example: pH: 10-16 ORP (Oxidation-Reduction Potential, vs. AgCl): -1000 to 100mV Liquid temperature: 0~95℃ Reaction time: 0.1-60 minutes

[0036] Through the above steps, ruthenium can be efficiently concentrated (recovered) from the ruthenium-containing mixture 10 (or ruthenium-containing solution 20). According to the ruthenium recovery method of this embodiment, depending on the ruthenium content in the ruthenium-containing mixture 10 (or ruthenium-containing solution 20), it is possible to achieve, for example, a ruthenium content in the ruthenium concentrate 50 of 20% by weight or more (preferably 40% by weight or more).

[0037] <Other embodiments of the present invention> Although embodiments of the present invention have been specifically described above, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention.

[0038] For example, in the above embodiment, if the impurity concentration in the ruthenium-containing solution 30 is not sufficiently reduced, an additional step to remove the impurities may be performed. For example, sodium hydroxide may be added to the ruthenium-containing solution 30 to further remove antimony.

[0039] In the above embodiment, the case in which a reducing agent is added to the ruthenium-containing solution 30 to recover ruthenium was described, but ruthenium may also be recovered from the ruthenium-containing solution 30 by other methods. For example, the ruthenium-containing solution 30 may be mixed with an acid such as sulfuric acid to generate a ruthenium-containing gas such as RuO4 gas, and ruthenium may be recovered from the ruthenium-containing gas.

[0040] Furthermore, in the alkaline earth metal salt addition step S103, an acid such as sulfuric acid may be added in addition to the alkaline earth metal salt to adjust the pH. For example, by adding Ca(OH)2 and H2SO4 to the ruthenium-containing solution, the same effect as when CaSO4 is added can be obtained while slightly lowering the pH. Adjusting the pH makes it easier to selectively remove specific elements (e.g., Cu). [Examples]

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

[0042] First, 1 kg of ruthenium-containing mixture 10 with the composition shown in Table 1 was prepared and subjected to an alkali melting step S101 at 400-550°C with 2 kg of KOH, followed by a water leaching step S102 at 80°C to obtain 20 L of ruthenium-containing solution 20. The obtained ruthenium-containing solution 20 was divided into 500 ml portions and designated as samples 1-7. Note that Ru / M in Table 1 indicates the concentration ratio of ruthenium to each metal element.

[0043] [Table 1]

[0044] 30 g of CaSO4 was added to 500 mL of ruthenium-containing solution 20 of sample 1, and the mixture was reacted with stirring for 90 minutes.

[0045] 30 g of Ca(OH)2 was added to 500 mL of ruthenium-containing solution 20 of sample 2, and the mixture was reacted with stirring for 90 minutes.

[0046] 30 g of CaCO3 was added to 500 mL of ruthenium-containing solution 20 of sample 3, and the mixture was reacted with stirring for 90 minutes.

[0047] 30 g of MgSO4 was added to 500 mL of ruthenium-containing solution 20 of sample 4, and the mixture was reacted with stirring for 90 minutes.

[0048] 30 g of BaSO4 was added to 500 mL of ruthenium-containing solution 20 of sample 5, and the mixture was reacted with stirring for 90 minutes.

[0049] 30 g of SrSO4 was added to 500 mL of ruthenium-containing solution 20 of sample 6, and the mixture was reacted with stirring for 90 minutes.

[0050] For comparison, 57.54 g of 98% sulfuric acid (H2SO4) was added to 500 mL of ruthenium-containing solution 20 of sample 7, and the mixture was reacted with stirring for 60 minutes.

[0051] Table 2 shows the concentrations of each element before and after the addition of each substance, as well as the concentration ratio of ruthenium to each element, for samples 1 to 7. The concentrations of each element were measured using ICP-OES (iCAP PRO XPS, ThermoFisher SIENTIFIC).

[0052] [Table 2]

[0053] As shown in Table 2, in samples 1-6 to which alkaline earth metal salts were added, at least one of the concentration ratios (Ru / Sb, Ru / Pb, Ru / Cu, Ru / Sn) increased, and in samples 1-4 and 6, all of the concentration ratios (Ru / Sb, Ru / Pb, Ru / Cu, Ru / Sn) increased. This confirms that ruthenium can be concentrated simply and efficiently by adding alkaline earth metal salts to the ruthenium-containing solution 20. In particular, sample 1 to which CaSO4 was added and sample 2 to which Ca(OH)2 was added efficiently removed antimony compared to sample 7 to which sulfuric acid was added, and the concentration ratio (Ru / Sb) increased significantly by more than 5 times.

[0054] Furthermore, as shown in Table 2, samples 1-6, to which alkaline earth metal salts were added, showed smaller fluctuations in ruthenium concentration compared to sample 7, to which sulfuric acid was added. This confirms that adding alkaline earth metal salts can concentrate ruthenium while reducing ruthenium loss. [Explanation of Symbols]

[0055] 10 Ruthenium-containing mixture 11. Alkali-molten solidified products 20 Ruthenium-containing solution 21 Water-leached residue 30 Ruthenium-containing solution (after addition of alkaline earth metal salt) 31 Residue after addition of alkaline earth metal salts 50 Ruthenium concentrate 51. Reducing solution S101 Alkali melting process S102 Water leaching process S103 Alkaline earth metal salt addition process S104 Reduction Process

Claims

1. A step of obtaining an alkali molten product by alkali melting a ruthenium-containing mixture containing ruthenium and at least one of antimony, lead, and copper, A step of adding water to the aforementioned alkali molten material to obtain a ruthenium-containing solution containing ruthenium and at least one of antimony, lead, and copper, The process involves adding an alkaline earth metal salt to the ruthenium-containing solution, The process includes a step of recovering ruthenium from the ruthenium-containing solution, A method for recovering ruthenium, wherein in the step of adding the alkaline earth metal salt, at least one of the following in the ruthenium-containing solution is increased: the concentration ratio of ruthenium to antimony (Ru / Sb), the concentration ratio of ruthenium to lead (Ru / Pb), and the concentration ratio of ruthenium to copper (Ru / Cu).

2. The method for recovering ruthenium according to claim 1, wherein in the step of adding the alkaline earth metal salt, the concentration ratio (Ru / Sb), the concentration ratio (Ru / Pb), and the concentration ratio (Ru / Cu) are all increased.

3. The method for recovering ruthenium according to claim 1, wherein, in the step of adding the alkaline earth metal salt, the change in the concentration of ruthenium in the ruthenium-containing solution before and after the addition of the alkaline earth metal salt is within 15%.

4. The method for recovering ruthenium according to claim 1, wherein in the step of adding the alkaline earth metal salt, the alkaline earth metal salt is added so that the pH of the ruthenium-containing solution becomes 12 or higher.

5. The method for recovering ruthenium according to claim 1, wherein a calcium salt is added in the step of adding the alkaline earth metal salt.

6. The method for recovering ruthenium according to any one of claims 1 to 5, wherein in the step of recovering the ruthenium, a reducing agent is added to the ruthenium-containing solution to precipitate the ruthenium.

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