JP5132226B2 - Ruthenium recovery method - Google Patents

Description

  The present invention relates to a method for recovering ruthenium, and more particularly, for example, recovering ruthenium contained in scraps of industrial products and low-concentration ruthenium-containing materials generated as a by-product in the smelting process of non-ferrous metals such as copper. On how to do.

Ruthenium has been used in recent years in the electronic industry due to its electrical and electromagnetic properties. In particular, it is used for high-capacity hard disk thin films for personal computers, hybrid integrated circuits for automobiles, and electrodes for plasma display panels. Moreover, since it has high catalytic activity, it is also used in the field of catalytic chemistry such as fuel cells.
Due to rising demand in recent years, the price of ruthenium has soared, while South Africa accounts for more than 90% of the ruthenium production in the market, and the uneven distribution of resources demands the development of ruthenium recycling technology. Yes.

  In a non-ferrous smelting process represented by copper smelting, residues containing gold, platinum group, silver, ruthenium and the like are generated as by-products. Among such by-products, gold, platinum group and silver are recovered in the purification process. On the other hand, ruthenium moves to the slag side in the oxidation process of silver refining, and most of it remains in the residue in the next selenium and tellurium recovery process and is discharged out of the system or returned to the initial stage of copper smelting. The current situation is that it cannot be recovered in the existing copper, silver and platinum group purification processes.

  Conventionally, the following methods are known as techniques for recovering ruthenium from a ruthenium-containing material.

Patent Document 1 discloses a method of extracting a ruthenium-containing material as a ruthenium chloride with chlorine gas, but in order to increase the ruthenium separation efficiency, while keeping carbon added as a reducing agent in a fluid state. There was a problem that it was difficult to control the gas flow rate because it was necessary to maintain the collection efficiency of the collection agent. In addition, the use of chlorine gas has a problem in that safety measures and a dedicated furnace are required, and the equipment cost is high. Furthermore, a method for increasing the purity of the recovered product is not described, which is insufficient as a recycling method.
JP-A-1-225730

Patent Document 2 discloses a method in which a ruthenium-containing material is reduced and roasted and then eluted with an acid. However, in complex mixed systems containing many elements other than ruthenium, the separation accuracy between ruthenium and other elements is poor, and other elements cannot be completely removed. There was a problem of being limited.
JP 2002-206122 A

Patent Document 3 discloses a method in which a ruthenium-containing material is reacted with an alkali hydroxide to extract ruthenium, then reduced with an alcohol, and purified with nitric acid. However, the separation efficiency from components other than ruthenium is poor, and especially glass components are included as impurities. For scraps in which ruthenium is dispersed or dissolved in this glass, it is a great way to extract ruthenium. Excess drug had to be used. For this reason, there existed a problem that it was difficult to collect | recover ruthenium economically.
JP 2003-201526 A

  As described above, since there are various problems in the conventional ruthenium recovery method, a method for recovering ruthenium with high purity from a substance containing a large amount of elements other than ruthenium has not yet been developed. Absent.

  The present invention has been developed in view of the above circumstances, and an object thereof is to provide a method capable of recovering high-purity ruthenium at a high recovery rate from a low-concentration ruthenium-containing material containing many elements other than ruthenium. And

Now, the inventors have repeatedly studied various methods for recovering high-purity ruthenium from a ruthenium-containing material with a high recovery rate.
As a result, even if the ruthenium concentration in the ruthenium-containing material is as low as 1% or less, ruthenium is melted in a high-temperature alkali and a reducing agent is added to the melt to form ruthenium hydroxide, which is then reduced in a reducing atmosphere. It was found that ruthenium can be recovered with high purity by heating.
The greatest feature of the present invention is that ruthenium is dissolved particularly in a high-temperature alkaline melt, and the reduction rate is controlled, so that it is simple and comparatively easy to use or generate a gas harmful to the human body. With a safe method, ruthenium can be separated from a state in which many kinds of elements are contained, and ruthenium is highly purified and can reduce the amount of chemicals used. Can be achieved.
The present invention is based on the above findings.

  That is, the gist configuration of the present invention is as follows.

1. A method for recovering metallic ruthenium from a ruthenium-containing material,
(1) an alkali melting step of melting the ruthenium-containing material in a high-temperature alkali;
(2) After cooling, after adding water to form a leaching solution, a wet leaching step in which an aqueous solution of ruthenium is obtained by solid-liquid separation;
(3) a wet reduction step of adding a reducing agent to the ruthenium aqueous solution to produce ruthenium hydroxide;
(4) a reduction step of converting the ruthenium hydroxide into metal ruthenium by heating in a reducing atmosphere;
A method for recovering ruthenium, characterized in that:

2. 2. The method for recovering ruthenium according to 1 above, wherein in the alkali melting step (1), the alkali is a hydroxide and / or a carbonate compound.

3. 3. The method for recovering ruthenium according to 1 or 2 above, wherein in the alkali melting step (1), when ruthenium-containing material is dissolved, an oxidizing agent is added to convert the metal ruthenium into ruthenium oxide.

4). 4. The method for recovering ruthenium according to any one of items 1 to 3, wherein in the alkali melting step (1), the ruthenium-containing material is melted in a silver or nickel container.

5). 5. The ruthenium recovery method according to any one of 1 to 4 above, wherein in the wet leaching step (2), an alkaline agent is added to an aqueous ruthenium solution to adjust the pH.

6). In the wet leaching step of (2), after adding silicate to the leachate and stirring, impurities are removed by solid-liquid separation, and the ruthenium according to any one of 1 to 5 above Collection method.

7). 7. The method for recovering ruthenium according to any one of 1 to 6 above, wherein in the wet leaching step (2), the solid-liquid separation is performed a plurality of times or a filter aid is added. .

8). 8. The method for recovering ruthenium according to any one of the above 1 to 7, wherein in the wet reduction step (3), the reducing agent is a solution containing a borohydride compound.

9. 9. The method for recovering ruthenium according to any one of 1 to 8, wherein a reducing agent is added at a constant rate in the wet reduction step (3).

10. 10. The method for recovering ruthenium according to any one of the above items 1 to 9, wherein an acid washing step of stirring ruthenium hydroxide in an acidic solution is performed after the wet reduction step (3).

According to the present invention, not only for a ruthenium-containing material having a somewhat high ruthenium concentration, but also for a low-concentration ruthenium-containing material having a low ruthenium concentration of several percent, the recovery rate is 80% or more and the purity is high. : It is possible to recover 99.9% or more of high purity ruthenium.
Thus, since the ruthenium recovery method of the present invention can be applied to low-concentration ruthenium-containing materials, it can also be applied to recycling of by-products generated in the smelting process of non-ferrous metals and scraps of industrial products containing ruthenium. There are advantages.

  Hereinafter, a typical embodiment of the present invention will be specifically described according to a series of steps shown in FIG.

1. Alkali melting step Ruthenium is insoluble in commonly used acidic liquids such as hydrochloric acid, nitric acid, hydrofluoric acid, and aqua regia, but has a property of quickly dissolving in high-temperature alkali. By utilizing this property, ruthenium can be extracted from a ruthenium-containing material containing many elements. In the extract, ruthenium is present in the form of RuO ₄ ²⁻ . This method using an alkali is a low cost and high safety method compared to a method in which ruthenium-containing material is chlorinated with chlorine gas to dissolve ruthenium.

  In the alkali melting step, the alkali melt is preferably 300 to 1000 ° C. More preferably, it is the range of 600-800 degreeC. This is because the reaction rate may decrease when the temperature is low, and the durability of the container may decrease when the temperature is high.

As the alkali, for example, one or both of hydroxide and carbonate can be used. Preferably, potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate and the like can be used. Particularly preferred is potassium hydroxide with high alkalinity.
The chemical reaction formula when potassium hydroxide is used as the alkali is as follows.
2KOH + RuO ₂ + 1 / 2O ₂ = K ₂ RuO ₄ + H ₂ O

In addition, when the target ruthenium containing material contains metal ruthenium, it is good to add an oxidizing agent at the time of alkali melting. At this time, the metal ruthenium is converted to ruthenium (IV) oxide by an oxidizing agent, and alkali melting can proceed rapidly.
As the oxidizing agent, for example, potassium nitrate and sodium peroxide are suitable. Particularly preferred is potassium nitrate, which has a strong oxidizing power.

  As a container used at the time of alkali melting, a silver or nickel container is suitable. This is because it is excellent in durability against high-temperature alkaline melt and does not adversely affect the quality of the recovered ruthenium.

2. Wet leaching step The alkali-melted ruthenium melt is cooled and solidified, and then dissolved in water to obtain an aqueous solution. At this time, the undissolved impurities are removed by solid-liquid separation. For solid-liquid separation, for example, a glass filter can be used. This is because the durability against alkali is excellent.

  In addition, when a ruthenium containing material contains lead, it is preferable to add a silicate to the obtained ruthenium solution, and to make it stir-react for a fixed time. As a result, the added silicate and the lead component in the solution react to form lead silicate, which can be separated from the ruthenium solution.

  When the pH of the obtained ruthenium aqueous solution is less than 14, it is desirable to increase the pH to 14 or more by adding an alkaline agent. If the pH is less than 14, impurities are likely to precipitate in the next reduction step.

3. Next, a reducing agent is added to the obtained aqueous solution to precipitate ruthenium as ruthenium hydroxide. Here, the reducing agent is not particularly limited, but a borohydride compound is particularly advantageously adapted. This is because the borohydride compound is not only inexpensive but does not affect the quality of ruthenium and the waste water treatment after the treatment is relatively easy. Particularly preferably, a safer mixed solution of sodium borohydride and sodium hydroxide can be used.
In addition, the chemical reaction formula at the time of using the mixed solution of sodium borohydride and sodium hydroxide is as follows.
8K ₂ RuO ₄ + 3NaBH ₄ + 14H ₂ O → 8Ru (OH) ₃ + 3NaBO ₂ + 16KOH

The amount of reducing agent used can be adjusted by the redox potential of the solution. For example, it is desirable to terminate the addition when the oxidation-reduction potential is lowered to a range of 50 to -100 mV with respect to the silver / silver chloride electrode. More desirably, it is in the range of 20 to 0 mV. If the addition amount is too large, impurities other than ruthenium may be precipitated. Conversely, if the addition amount is small, the ruthenium recovery rate may decrease.
In adding the reducing agent, it is desirable to gradually add the reducing agent at a constant rate in order to precipitate high-purity ruthenium hydroxide. In this addition, stirring is preferably used in combination. Furthermore, it is desirable that the borohydride compound to be added has a low concentration of 5% or less. For example, in the case of using a mixed solution of sodium borohydride and sodium hydroxide, the addition rate of the reducing agent is preferably about 0.01 to 1 g / min in terms of sodium borohydride.

After completion of the addition of the reducing agent, stirring is preferably continued for about 1 hour. This is because unreacted sodium borohydride is completely reacted to improve the recovery rate.
When the reducing solution is subjected to solid-liquid separation, pure water can be repeatedly added and filtered until the pH of the filtrate becomes neutral. Thereby, it can suppress that the purity of collection | recovery ruthenium falls by the component contained in the liquid which remains.

4). Acid Washing Step Next, in order to remove impurities from ruthenium hydroxide obtained by reduction, the ruthenium hydroxide may be stirred in an acidic solution for a certain period of time. As the acidic solution, for example, sulfuric acid, hydrochloric acid, nitric acid, aqua regia and the like can be appropriately selected and used depending on the target impurities. In particular, it is preferable to use sulfuric acid for zinc and nitric acid for lead.
After solid-liquid separation after stirring in an acidic solution, pure water is repeatedly added until the pH of the filtrate becomes neutral and filtered. Thereby, it can suppress that the purity of collection | recovery ruthenium falls by the component contained in the liquid which remains.

5. Reduction step Next, ruthenium hydroxide from which impurities have been removed is charged into a furnace in a reducing atmosphere and heated to reduce it to metallic ruthenium. When setting it as a reducing atmosphere, hydrogen gas, nitrogen gas which does not react with ruthenium, and argon gas are mixed, and it ventilates in a furnace with a fixed flow rate. At this time, the reducing atmosphere is desirably in the range of 400 to 800 ° C. More preferably, it is in the range of 500 to 700 ° C.
The chemical reaction formula at the time of the reduction reaction is as follows.
2Ru (OH) ₃ + 3H ₂ = 2Ru + 6H ₂ O

  When impurities are contained in the metal ruthenium obtained by the above reduction treatment, it is preferable to further stir in an acidic solution. The acidic solution to be used may be appropriately selected depending on the target impurity such as sulfuric acid, hydrochloric acid, nitric acid, or aqua regia. In particular, it is preferable to use sulfuric acid for zinc and nitric acid for lead. When performing solid-liquid separation after stirring in an acidic solution, it is preferable to add pure water repeatedly until the pH of the filtrate becomes neutral, and filter.

  Thus, high-purity ruthenium can be recovered from a ruthenium-containing material containing many elements other than ruthenium at a high recovery rate.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1
As a sample, a ruthenium content of 25% by mass, and iron: 20% by mass, bismuth: 10% by mass, zinc: 10% by mass, chromium: 10% by mass, cobalt: 10% by mass was used. . In this sample, ruthenium mainly takes the form of a complex oxide (Bi ₂ Ru ₂ O _6.5 ) with bismuth, and in addition, metals Ru and RuO ₂ were observed. For this sample: 86 g, potassium hydroxide 4 times in mass ratio as alkali and potassium nitrate 0.4 in mass ratio as oxidant were added and sealed in a crucible, and heated in a fixed furnace. A crucible made of nickel was used. The temperature of the fixed furnace was 750 ° C. and held for 2 hours. Then, it naturally left to cool in the furnace.
Water was added to the crucible cooled to room temperature to leach out the solid remaining in the crucible.
The obtained leachate was subjected to suction filtration with a glass filter, and solid-liquid separation was performed. The leaching residue separated as a solid contained 2% ruthenium.

In the separated liquid, a mixed solution of 12% sodium borohydride and 40% sodium hydroxide is diluted 10-fold with pure water and then stirred at a constant speed of about 1 g / min. Added with stirring. Addition of the mixed solution was performed until the redox potential of the separated solution became 0 to 20 mV from 360 mV before the addition. After completion of the addition, stirring was continued for 1 hour.
After the reduction, suction filtration was performed using a filter paper having a collected particle diameter of 1 μm to separate the solid and the liquid. At this time, pure water was repeatedly added until the pH of the filtrate became neutral, followed by filtration.

  The resulting solid contained 5% zinc in addition to ruthenium. This solid was added to a 7.5% strength sulfuric acid solution having a mass ratio of 10 times, stirred for 2 hours, and suction filtered.

  The resulting solid zinc concentration was 0.1% or less. This solid was heated in a furnace with flowing hydrogen and nitrogen gas. The heating temperature was 600 ° C. The solid obtained by cooling after heating had a mass of 20 g and a ruthenium concentration of 99.96%. The recovery rate of ruthenium was about 93%.

(Example 2)
As the sample, a solid having a ruthenium content of 40% by mass and containing 20% by mass of silicon, 4% by mass of lead, and 2% by mass of titanium was used. Ruthenium is mainly in the form of complex oxide with lead (Pb ₂ Ru ₂ O _6.5 ), and other metals, Ru and RuO _2, were recognized. For this sample: 150 g, as an alkali melt, 4 times by weight of potassium hydroxide, 1 time by weight of sodium hydroxide, and 1 time by weight of sodium hydroxide as an oxidizing agent, 0.9 times by weight of potassium nitrate were added to the crucible. Filled and heated in a fixed furnace. A crucible made of nickel was used. The temperature of the fixed furnace was 750 ° C. and held for 2 hours. Then, it naturally left to cool in the furnace.
Water was added to the crucible cooled to room temperature to leach out the solid remaining in the crucible.
To the obtained leachate, 52 g of sodium orthosilicate as a silicate for removing lead was added and stirred for 2 hours, followed by suction filtration with a glassy filter and solid-liquid separation. The leaching residue separated as a solid contained 1.3% ruthenium.

In the separated liquid, a mixed solution of 12% sodium borohydride and 40% sodium hydroxide is diluted 10 times with pure water, and then stirred with a stirrer at a constant speed of about 1 g / min. While adding. The mixed solution was added until the oxidation-reduction potential of the separated solution became 0 to 20 mV from 300 mV before the addition. After completion of the addition, stirring was continued for 1 hour.
After the reduction, suction filtration was performed using a filter paper having a collected particle diameter of 1 μm, and solid-liquid separation was performed. At this time, pure water was repeatedly added until the pH of the filtrate became neutral, followed by filtration.

  The lead concentration of the obtained solid was 0.1% or less. This solid was heated in a furnace with flowing hydrogen and nitrogen gas. The heating temperature was 600 ° C. To the solid obtained by heating and cooling, 6.5% concentration nitric acid having a mass ratio of 10 was added and stirred for 2 hours, followed by suction filtration. The obtained solid had a mass of 53 g and a ruthenium concentration of 99.92%. The recovery rate of ruthenium was about 89%.

(Example 3)
Samples with a ruthenium content of 20% by mass, including bismuth: 50% by mass, iron: 10% by mass, chromium: 5% by mass, zinc: 2% by mass, cobalt: 8% by mass It was. Ruthenium is mainly in the form of bismuth and composite oxide (Bi ₂ Ru ₂ O _6.5 ), and other metals, Ru and RuO ₂ were observed. With respect to 20 g of this sample, potassium hydroxide 2.5 times in mass ratio was added as an alkali melt, filled in a crucible, and heated in a fixed furnace. A crucible made of nickel was used. The temperature of the fixed furnace was 750 ° C. and held for 2 hours. Then, it naturally left to cool in the furnace.
Water was added to the crucible cooled to room temperature, and the solid remaining in the crucible was dissolved in the liquid. The solid that did not partially dissolve was mixed in the liquid to obtain a leachate.
The obtained leachate was subjected to suction filtration with a glass filter, and solid-liquid separation was performed. When the solid was separated, 20 g of diatomaceous earth was spread in a filter shape, and filtration was repeated three times. The impurities separated as a solid contained 0.6% ruthenium.

The pH of the obtained aqueous solution was 13.6. To this, 70 g of potassium hydroxide was added to raise the pH to 14.6. Then, after diluting a mixed solution of 2% sodium borohydride and 40% sodium hydroxide 10 times with pure water, it was added with stirring at a constant rate of about 1 g / min. . The addition of the mixed solution was performed until the redox potential of the separated solution became 0 to 20 mV from 360 mV before the addition, and stirring was continued for 1 hour after the addition was completed.
After the reduction, suction filtration was performed using a filter paper having a collected particle diameter of 1 μm, and solid-liquid separation was performed. At this time, pure water was repeatedly added and filtrated until the pH of the filtrate became neutral.

  The resulting solid contained 0.8% zinc in addition to ruthenium. This solid was added to a 7.5% strength sulfuric acid solution having a mass ratio of 10 times, stirred for 2 hours, and suction filtered. This was heated in a furnace in which hydrogen and nitrogen gas were passed. The heating temperature was 600 ° C. The solid obtained by cooling after heating had a mass: 3.3 g and a ruthenium concentration of 99.94%. The recovery rate of ruthenium was 83%.

It is a flowchart which shows the separation-and-recovery process of ruthenium concerning this invention.

Claims (10)

A method for recovering metallic ruthenium from a ruthenium-containing material,
(1) an alkali melting step of melting the ruthenium-containing material in a high-temperature alkali;
(2) After cooling, after adding water to form a leaching solution, a wet leaching step in which an aqueous solution of ruthenium is obtained by solid-liquid separation;
(3) a wet reduction step of adding a reducing agent to the ruthenium aqueous solution to produce ruthenium hydroxide;
(4) a reduction step of converting the ruthenium hydroxide into metal ruthenium by heating in a reducing atmosphere;
A method for recovering ruthenium, characterized in that:   The method for recovering ruthenium according to claim 1, wherein, in the alkali melting step (1), the alkali is a hydroxide and / or a carbonate compound.   3. The method for recovering ruthenium according to claim 1 or 2, wherein, in the alkali melting step of (1), when ruthenium-containing material is melted, an oxidizing agent is added to convert the metal ruthenium into ruthenium oxide.   The method for recovering ruthenium according to any one of claims 1 to 3, wherein in the alkali melting step (1), the ruthenium-containing material is melted in a silver or nickel container.   The method for recovering ruthenium according to any one of claims 1 to 4, wherein, in the wet leaching step (2), an alkaline agent is added to an aqueous ruthenium solution to adjust the pH.   The ruthenium according to any one of claims 1 to 5, wherein in the wet leaching step (2), impurities are removed by solid-liquid separation after adding and stirring silicate in the leachate. Recovery method.   In the wet leaching step of (2), the solid-liquid separation is performed a plurality of times or a filter aid is added to collect ruthenium according to any one of claims 1 to 6. Method.   The method for recovering ruthenium according to any one of claims 1 to 7, wherein in the wet reduction step (3), the reducing agent is a solution containing a borohydride compound.   The method for recovering ruthenium according to any one of claims 1 to 8, wherein a reducing agent is added at a constant rate in the wet reduction step (3).   The method for recovering ruthenium according to any one of claims 1 to 9, wherein an acid washing step of stirring ruthenium hydroxide in an acidic solution is performed after the wet reduction step (3).

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