JP2024031673A - Ruthenium and iridium recovery method - Google Patents

Abstract

To provide a method of recovering by efficiently separating ruthenium and iridium from an acidic solution containing ruthenium and iridium.SOLUTION: A method of recovering ruthenium and iridium includes: a ruthenium recovery process of subjecting to solid-liquid separation after precipitating ruthenium by adjusting a temperature of an acidic solution containing ruthenium and iridium, and one or more elements of copper, arsenic, and antimony to 60°C or lower, and adding metallic iron; a sulfurization process of precipitating one or more elements of copper, arsenic and antimony by adjusting a temperature of a filtrate obtained by subjecting to solid-liquid separation after precipitating ruthenium to 70°C or lower, and adding any one of hydrogen sulfide, sodium hydrogensulfide, and sodium sulfide as a sulfurizing agent; and an iridium recovery process of precipitating iridium by adjusting a temperature of a filtrate obtained by subjecting to solid-liquid separation after precipitating one or more elements of copper, arsenic, and antimony to 40°C or higher, and adding a sodium thiosulfate salt or a thiosulfate ion-containing solution.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for recovering ruthenium and iridium.

In copper pyrometallurgy, copper concentrate is melted and converted into blister copper with a purity of 99% or more in a converter or refining furnace, and then electrolytic copper with a purity of 99.99% or more is produced in an electrolytic refining process. Valuables other than copper precipitate as precipitates during electrolytic refining.

Precious metals, rare metals, and selenium and tellurium contained in copper concentrate are also concentrated in this deposit. These elements are separately separated and recovered as copper smelting by-products.

A hydrometallurgical method is often applied to treat this precipitate. For example, Patent Document 1 discloses a method in which silver is recovered from a precipitate using hydrochloric acid-hydrogen peroxide, dissolved gold is recovered by solvent extraction, and other valuables are successively reduced and recovered using sulfur dioxide. Patent Document 2 discloses a method in which gold and silver are recovered in a similar manner, then valuable materials are reduced and precipitated with sulfur dioxide, and only selenium is distilled and removed to concentrate precious metals.

The solution after recovering the precious metals contains rare metal ions, tellurium, and selenium, and it is necessary to further recover these valuables. As methods for recovering valuable materials, there are known methods such as recovering a precipitate caused by a reducing agent, and mixing the entire solution with copper concentrate, drying it with a dryer, and repeating it in a smelting furnace.

In particular, the method shown in Patent Document 1 for recovering the precipitate caused by sulfur dioxide has many advantages in terms of cost and production scale. In addition, since each element is precipitated in sequence, it is effective for separation and purification.

In the method of recovering valuable substances using sulfur dioxide, the valuable substances can be sequentially reduced and recovered after dissolution. First, platinum and palladium precipitate. Next, selenium undergoes reduction. Iridium and ruthenium have relatively low redox potentials, so they are difficult to undergo reduction and remain in the solution until the end. Regarding iridium, as described in Patent Document 3, a widely known method is to recover iridium by separating it by solvent extraction, concentrating it, and then baking it. Further, Patent Document 4 discloses a method in which a base metal selected from magnesium, aluminum, zinc, iron, tin, and lead and a mineral acid are added to an organic solvent containing iridium to reduce and precipitate the noble metal. .

Japanese Patent Application Publication No. 2001-316735 Japanese Patent Application Publication No. 2016-160479 Japanese Patent Application Publication No. 2004-332041 Japanese Patent Application Publication No. 2002-115015

For example, the iridium concentration in the acidic solution in which the copper electrolytic precipitate is dissolved is about 1 to 100 mg/L. Iridium is an expensive metal, but at such low concentrations, smelting by solvent extraction is not cost-effective. Furthermore, the efficiency of separation from other metals and the efficiency of stripping are not high.

On the other hand, to recover ruthenium by distillation, a strong oxidizing agent such as NaBrO ₃ is used. The cost of the oxidizing agent is high, and this method is not suitable for recovering ruthenium from a dilute solution with a ruthenium concentration of about 50 to 200 mg/L and many impurities, such as a precipitate solution. Furthermore, ruthenium tetroxide is highly toxic and there are safety issues in recovering it by distillation.

Cementation with base metals such as zinc is effective for both iridium and ruthenium. However, it is difficult to separate and recover iridium and ruthenium using base metal cementation.

Furthermore, cementation using base metals requires the use of a large amount of metal to increase the recovery rate. Under strong acid conditions, there is a problem that hydrogen is generated intensively in a short period of time and boils over, or hydrogen generated due to static electricity, etc., explodes. In addition, the reaction efficiency is low because other elements that undergo cementation are also present.

It is known that the hydroxides of iridium and ruthenium precipitate. However, both elements precipitate at the same time in an alkaline region and cannot be recovered separately. Furthermore, as a general problem, if strong acids are to be neutralized, the cost of alkaline reagents is high. Furthermore, sodium ions and alkaline earth metal ions precipitate sulfates that are sparingly soluble in water even under acidic conditions. When neutralized with an excessive amount of alkali, it is expected that this poorly soluble sulfate will deposit in the piping of the manufacturing equipment and cause blockage.

It is desirable to recover both ruthenium and iridium while suppressing contamination with other metals. Particularly when copper electrolytic precipitates are used as a raw material, there is a concern about copper contamination. If copper is contained in an amount that is difficult to remove by oxidative leaching, separate treatment to remove copper will be required. Furthermore, there is no known method for efficiently and inexpensively separating and precipitating low-concentration iridium and ruthenium from a strongly acidic solution.

In view of such conventional circumstances, the present invention provides a method for efficiently separating and recovering ruthenium and iridium from an acidic liquid containing ruthenium and iridium. In particular, an acidic liquid obtained by oxidizing and dissolving electrolytic precipitates generated in the electrolytic refining process in copper smelting is suitable as the acidic liquid containing ruthenium and iridium of the present invention.

The above problem can be solved by the invention specified below.
That is, the present invention includes the following inventions.
[1] Adjust the acidic liquid containing ruthenium and iridium and one or more elements of copper, arsenic, and antimony to 60°C or lower, and (1) adjust the metallic iron to 0.5 to 4.0 g/L. or (2) a ruthenium recovery step in which metal iron is added until the redox potential reaches 150 mV or less using silver/silver chloride as a reference electrode to precipitate ruthenium, and then solid-liquid separation is performed;
The filtrate obtained by solid-liquid separation after precipitating the ruthenium is adjusted to 70°C or lower, and one or more of hydrogen sulfide, sodium hydrogen sulfide, and soda sulfide is added as a sulfurizing agent to prepare copper, a sulfiding step to precipitate one or more elements among arsenic and antimony;
After precipitating one or more elements among the copper, arsenic, and antimony, solid-liquid separation is performed, the resulting filtrate is adjusted to 40°C or higher, and sodium thiosulfate salt or a solution containing thiosulfate ions is added. an iridium recovery step of precipitating iridium;
A method for recovering ruthenium and iridium, including
[2] An acidic solution containing ruthenium and iridium and one or more elements among copper, arsenic, and antimony is adjusted to a temperature of 40°C or higher, and (1) copper-coated iron powder is used as metallic iron, and the iron content is 0. .5 to 4.0 g/L, or (2) Add copper-coated iron powder as metal iron until the redox potential reaches 150 mV or less using silver/silver chloride as a reference electrode. a ruthenium recovery step in which solid-liquid separation is performed after precipitating the ruthenium;
The filtrate obtained by solid-liquid separation after precipitating the ruthenium is adjusted to 70°C or lower, and one or more of hydrogen sulfide, sodium hydrogen sulfide, and soda sulfide is added as a sulfurizing agent to prepare copper, a sulfiding step to precipitate one or more elements among arsenic and antimony;
After precipitating one or more elements among the copper, arsenic, and antimony, solid-liquid separation is performed, the resulting filtrate is adjusted to 40°C or higher, and sodium thiosulfate salt or a solution containing thiosulfate ions is added. an iridium recovery step of precipitating iridium;
A method for recovering ruthenium and iridium, including
[3] In the ruthenium recovery step, the acidic liquid containing the ruthenium and iridium and one or more elements of copper, arsenic, and antimony is prepared by blowing sulfur dioxide or hydrogen sulfide into the acidic liquid, or It is an acidic liquid after adding a reducing agent of aldehydes to precipitate platinum, gold, palladium, and selenium to adjust the concentration of each element of platinum, gold, palladium, and selenium to 10 mg/L or less, [1] Or the method for recovering ruthenium and iridium according to [2].
[4] The method for recovering ruthenium and iridium according to any one of [1] to [3], wherein in the ruthenium recovery step, the metal iron is added in an amount of 5 to 25 times the mass of ruthenium in the acidic liquid.
[5] In the sulfurizing step, one or more of hydrogen sulfide, sodium hydrogen sulfide, and soda sulfide is added as the sulfurizing agent by 5 to 20 times the copper concentration when converted to the sulfur concentration, [1] The method for recovering ruthenium and iridium according to any one of [4].
[6] In the ruthenium recovery step, the acidic liquid containing ruthenium and iridium and one or more elements of copper, arsenic, and antimony is an acidic liquid after dissolving metal electrolytic precipitates, [1 ] to [5]. The method for recovering ruthenium and iridium according to any one of [5].
[7] The iridium concentration in the acidic liquid in the ruthenium recovery step is 100 mg/L or less, and in the iridium recovery step, the sodium thiosulfate salt or thiosulfate ion-containing solution is converted to sodium thiosulfate pentahydrate. The method for recovering ruthenium and iridium according to any one of [1] to [6], wherein the ruthenium and iridium are added at a concentration of 5 g/L or more.

According to the present invention, it is possible to provide a method for efficiently separating and recovering ruthenium and iridium from an acidic liquid containing ruthenium and iridium.

1 is a flow diagram schematically illustrating an embodiment of the present invention. FIG.

Next, a mode for carrying out the present invention will be described in detail. It is understood that the present invention is not limited to the following embodiments, and that design changes, improvements, etc. may be made as appropriate based on the common knowledge of those skilled in the art without departing from the spirit of the present invention. Should.

FIG. 1 shows a flow diagram schematically illustrating one embodiment of the invention. The flowchart in FIG. 1 gives specific examples for each step, and the present invention is not limited to the flowchart. In one aspect, the method for recovering ruthenium and iridium according to an embodiment of the present invention includes adjusting an acidic liquid containing ruthenium and iridium and one or more elements among copper, arsenic, and antimony to a temperature of 60° C. or lower, (1) Add metallic iron at a concentration of 0.5 to 4.0 g/L, or (2) Add metallic iron until the redox potential reaches 150 mV or less using silver/silver chloride as a reference electrode. A ruthenium recovery process in which solid-liquid separation is performed after precipitating ruthenium, and a filtrate obtained by performing solid-liquid separation after precipitating ruthenium is adjusted to a temperature below 70°C, and hydrogen sulfide, sodium hydrogen sulfide and sulfur are used as sulfurizing agents. A sulfiding process in which one or more of copper, arsenic, and antimony is precipitated by adding one or more of soda, and a solid-liquid process after precipitating one or more of copper, arsenic, and antimony. The method includes an iridium recovery step of performing separation, adjusting the temperature of the obtained filtrate to 40° C. or higher, and adding a sodium thiosulfate salt or a solution containing thiosulfate ions to precipitate iridium.

In the ruthenium and iridium recovery method according to the embodiment of the present invention, the acidic liquid containing ruthenium and iridium to be treated may be obtained through any kind of treatment, but in particular, it may be obtained through any treatment. An acidic liquid obtained by oxidizing and dissolving electrolytic precipitates generated in the electrolytic refining process is suitable as the iridium-containing acidic liquid of the present invention. Furthermore, in electrolytic precipitates produced in the electrolytic refining process of nonferrous metal smelting, especially copper smelting, platinum group elements are concentrated together with other rare elements. Rare elements are not smelted alone, but are recovered as by-products of other metals or separated from recycled raw materials such as spent catalysts. Therefore, the method for recovering ruthenium and iridium according to the embodiment of the present invention can also be applied to recycling from waste. That is, the acidic liquid containing ruthenium and iridium generated in the waste treatment process can be targeted.

In the ruthenium and iridium recovery method according to the embodiment of the present invention, when the acidic liquid containing ruthenium and iridium to be treated is a hydrochloric acid acidic liquid obtained through a predetermined process, ruthenium (Ru) and iridium ( Contains various metal elements in addition to Ir).

When replacing ruthenium with metallic iron, selenium (Se), platinum (Pt), palladium (Pd), gold (Au), silver (Ag), etc. are preferentially replaced with ruthenium. As will be described in detail later, it is necessary to reduce the concentration of these elements in advance.

As an example, a method for producing a hydrochloric acid acidic solution containing ruthenium and iridium from an electrolytic precipitate derived from a copper electrolytic refining process of copper smelting is shown. First, copper is dissolved and removed using sulfuric acid from the electrolytic precipitate derived from the copper electrolytic refining process of copper smelting. Next, concentrated hydrochloric acid and hydrogen peroxide solution are added and dissolved, and solid-liquid separation is performed to obtain PLS (leaching liquid). Platinum group elements, rare metal elements, chalcogen elements, arsenic, antimony, etc. are distributed in the leaching solution (PLS), which is a chloride bath.

The leach liquid (PLS) is once cooled and chlorides of base metals such as lead and antimony are separated by precipitation. The gold is then separated into an organic phase by solvent extraction. Dibutylcarbitol (DBC) is widely used as a gold extractant. By blowing sulfur dioxide into the extract, precious metals such as platinum and palladium, selenium, and tellurium are reduced and removed, followed by solid-liquid separation to create a hydrochloric acid acidic solution containing ruthenium and iridium. .

In the method for recovering ruthenium and iridium according to an embodiment of the present invention, sulfur dioxide or hydrogen sulfide is blown into an acidic liquid containing ruthenium and iridium, or an aldehyde reducing agent is added to recover platinum and gold. It is preferable to adjust the concentration of impurity elements such as , palladium and selenium to 10 mg/L or less. Examples of the aldehydes include formaldehyde, methylglyoxal, and the like. Note that if the acidic liquid to be treated has a concentration of contaminant elements such as platinum, gold, palladium, and selenium of 10 mg/L or less, there is no need to blow or add the reducing agent.

Examples of valuable substances remaining in the acidic liquid after the above-mentioned treatment include ruthenium, iridium, antimony, copper, and the like. Among these, ruthenium and iridium are preferably recovered because they have particularly high added value. The reduced solution also contains 0.5 to 3 g/L of arsenic, but it is relatively easy to separate arsenic from metals, and some amount of arsenic is allowed to be mixed in when valuables are recovered. It is also preferable to recover ruthenium and iridium by element.

Cementation with metal is effective for recovering ruthenium from the reduced solution. However, since the acidic solution contains arsenic, the metal needs to have an oxidation-reduction potential of -380 mV or more using silver/silver chloride as a reference electrode in order to suppress the generation of arsine. Examples of metals that meet the cementation conditions for ruthenium include iron, nickel, lead, and copper.

Among the metals used for ruthenium cementation, the following metals have individual problems. That is, with copper, a considerable amount of arsenic is precipitated as copper arsenide, with lead, ruthenium and unreacted lead are mixed without being dissolved in acid, and with nickel, the cost becomes high. However, although metallic iron has the problem of instantaneously generating a large amount of hydrogen during the reaction, the temperature of the acidic liquid is adjusted to 60°C or less, preferably 30 to 60°C, and metallic iron is If it is added at a concentration of 4.0 g/L, there will be no major problem. Furthermore, when metallic iron is added, ruthenium undergoes cementation before copper and arsenic, making separate recovery possible.

Further, in the ruthenium recovery step, it is preferable to add metallic iron 5 to 25 times the mass of ruthenium in the acidic solution. If the amount of metallic iron added is less than 5 times the mass of ruthenium in the acidic liquid, cementation of ruthenium by metallic iron may become insufficient. Furthermore, if the amount of metallic iron added is more than 25 times the mass of ruthenium in the acidic liquid, it will be disadvantageous in terms of cost and there is a risk that impurities will be mixed in.

As the metal iron to be added, iron powder is suitable because of its good reactivity. There are no particular restrictions on the quality of metal iron. As will be described later, the metal iron to be added may be any metal that has reducing properties, and even iron powder whose surface is partially coated with copper (copper-coated iron powder) will function. In this case, copper-coated iron powder is added as metal iron so that the iron content is 0.5 to 4.0 g/L. The eluted copper is precipitated and removed as sulfide after the ruthenium is recovered, so even if it gets mixed in, it does not pose a big problem. Further, when using copper-coated iron powder, the temperature of the acidic liquid is adjusted to 40° C. or higher, and then the copper-coated iron powder is added so that the iron content is 0.5 to 4.0 g/L.

Metallic iron generates hydrogen when it comes into contact with an acidic solution. The problem with hydrogen is that it is explosive. Furthermore, if iron powder is used as the metal iron, there is the problem that because of its large surface area, a large amount of hydrogen is generated in a short period of time, causing the solution to boil over. Therefore, especially when iron powder is used, it may not be added at once but may be added in multiple batches.

If the redox potential (reference electrode: silver/silver chloride) is used as an index in the cementation of ruthenium, metallic iron may be added until the redox potential of the acidic solution reaches 150 mV or less. Below this potential, the ruthenium concentration decreases significantly.

As a way to avoid the risk of boiling over or explosion due to hydrogen generation, it is also possible to use iron powder whose surface is partially coated with copper (copper-coated iron powder). In principle, contact between metallic iron and acidic solution is restricted and hydrogen generation is suppressed. After the copper gradually dissolves, the iron that appears on the surface reacts with the ruthenium. If the copper grade is too high, the contact efficiency may deteriorate, so the copper content of the copper-coated iron powder is preferably 70% by mass or less, more preferably 40% by mass or less.

The ruthenium-containing material obtained by solid-liquid separation after precipitation of ruthenium is separated from iridium and other impurities by a known method. For example, there is a method in which sodium bromate is added after oxidative dissolution and ruthenium tetroxide is separated and recovered by distillation. Iridium is sufficiently concentrated in this oxidized solution and can be recovered by known solvent extraction.

A sulfiding agent is added to the acidic liquid that is the filtrate after ruthenium is separated by cementation (solid-liquid separation). Suitable sulfurizing agents include hydrogen sulfide, sodium hydrogen sulfide, and sodium sulfide, and one or more of these may be used. Sodium thiosulfate is also known as a sulfiding agent, but it is unsuitable because it may cause some of the iridium to precipitate and be lost. Sulfiding agents precipitate copper, arsenic, antimony, and lead.

The temperature of the acidic liquid during sulfurization using the sulfurizing agent is adjusted to 70° C. or lower. If the temperature of the acidic liquid is higher than 70°C, there is a risk that the precipitated copper sulfide will be redissolved. In addition, reducing sulfur that forms sulfides from the solution may volatilize as hydrogen sulfide, which may reduce reaction efficiency.

The sulfurizing agent is preferably added in an amount of 5 to 20 times the copper concentration when converted to the sulfur content. More preferably, it is added 5 to 12 times by mass. If the amount of the sulfiding agent added is less than 5 times the mass of the copper concentration, there is a risk that an excessive amount of the element to be removed by sulfidation may remain. If the amount of the sulfiding agent added is more than 20 times the copper concentration by mass, the amount of precipitate produced in the next step of iridium recovery may be extremely small, making solid-liquid separation difficult. Furthermore, reagent costs may also increase.

Since the sulfurized precipitate separated in the sulfurization process contains valuable materials such as copper and lead, it can be repeatedly sent to the smelting furnace and used as a raw material for valuable materials.

After precipitating one or more elements among copper, arsenic, and antimony in the sulfurization step, solid-liquid separation is performed, and the resulting filtrate is adjusted to a temperature of 40°C or higher, preferably 60°C or higher, and sodium thiosulfate or thiosulfate is added to the filtrate. A solution containing sulfate ions is added to precipitate iridium. The sodium thiosulfate salt or thiosulfate ion-containing solution is added in an amount of 5 g/L or more in terms of sodium thiosulfate pentahydrate to precipitate iridium. Iridium hardly precipitates with the sulfurizing agent used in the previous sulfurizing step. On the other hand, since thiosulfate ions have coordination ability, it is thought that reducing them after coordinating with iridium ions is effective in precipitating iridium.

Representative sodium thiosulfate salts include commercially available sodium thiosulfate pentahydrate. It may be added as a solid sodium thiosulfate salt or as a solution containing thiosulfate ions. Thiosulfate ions can also be obtained by heating sulfurous acid and elemental sulfur in an alkaline solution, but solid salts are particularly advantageous in terms of cost and ease of handling. In particular, sodium thiosulfate pentahydrate has low toxicity and is most suitable.

Addition of sodium thiosulfate salt or a solution containing thiosulfate ions produces a precipitate containing arsenic, sulfur, and iridium. When the iridium concentration in the acidic solution in the ruthenium recovery step is as low as 100 mg/L or less, if only iridium is precipitated, the amount recovered is too small, causing problems in solid-liquid separation. Containing a suitable amount of impurities is not a problem.

When the iridium concentration in the acidic solution in the ruthenium recovery process is high, it is more efficient to recover it by precipitation with KCl or NH ₄ Cl, but when the iridium concentration is dilute at 100 mg/L or less, sodium thiosulfate is used. It is preferable to precipitate and recover by adding a salt or a solution containing thiosulfate ions. In addition, at this time, sodium thiosulfate salt or a solution containing thiosulfate ions may be added in an amount of 5 g/L or more in terms of sodium thiosulfate pentahydrate, or 5 to 20 g/L or more. May be added to.

After solid-liquid separation of the precipitated iridium-containing material, iridium and other impurities are separated by a known method. For example, there is a method in which iridium is separated and recovered by solvent extraction after oxidative dissolution. The iridium recovered as a precipitate is sufficiently concentrated and can be recovered by known solvent extraction.

EXAMPLES Hereinafter, examples will be illustrated to better understand the present invention and its advantages, but the present invention is not limited to the examples.

(Experiment example 1)
Copper was dissolved and removed using sulfuric acid from electrolytic precipitates derived from the copper electrolytic refining process of copper smelting. Concentrated hydrochloric acid and 60% hydrogen peroxide solution were added and dissolved, and solid-liquid separation was performed to obtain PLS (leaching liquid). The PLS was cooled to 6° C. to precipitate and remove base metals. The acid concentration was adjusted to 1 mol/L or more, and DBC (dibutyl carbitol) and PLS were mixed to extract gold. After gold extraction, the PLS was heated to 70° C., and sulfur dioxide was blown into the PLS to reduce and remove noble metals, selenium, and tellurium. This was subjected to solid-liquid separation to obtain a hydrochloric acid acidic solution containing iridium.

Next, 200 mL of the sulfur dioxide reduced solution was collected and heated to 60°C. The iridium concentration of the solution after sulfur dioxide reduction was 25 mg/L, and the ruthenium concentration was 77 mg/L. The sulfur dioxide reduced solution contained 1.32 g/L of arsenic, 0.49 g/L of copper, and 230 mg/L of antimony as other elements. Iron powder (P80=150-200 μm) in the amount shown in Table 1 was added and stirred.
After a predetermined time, the reaction was stopped, and the precipitate was separated into solid and liquid. After filtration, the ORP (oxidation-reduction potential) of the solution was measured to determine the concentration of various elements.
All reagents used were special grade manufactured by Wako Pure Chemical Industries, Ltd. The element concentration in the solution was determined by taking 2 mL of the solution, adjusting the volume to 50 mL, and then quantifying the concentration using ICP-OES (SPS3100, manufactured by Seiko Instruments Inc.). The concentration of the precipitate solution was determined by adjusting the volume to 100 mL. The results are shown in Table 1. "ND" in Table 1 indicates that the element was not detected.

It can be seen that ruthenium could be preferentially cemented by adding 0.1 g of iron powder to 200 mL of raw material liquid. Furthermore, it can be seen that ruthenium could be sufficiently recovered by adding 0.3 g or more of iron powder. However, excessive amounts of iron powder increase the amount of arsenic and copper. Therefore, it is preferable to add 0.8 g or less.

The ORP value decreased rapidly when more than 0.3 g of iron powder was added. It is shown that ruthenium can be sufficiently cemented by adding iron powder until ORP becomes 150 mV or less.

(Experiment example 2)
200 mL of the same iridium-containing liquid as in Experimental Example 1 was taken and heated to 40 to 80°C. 0.6g of iron powder was added. After stirring for 1 hour, the reaction was stopped. After separation by filtration, the component elements of the filtrate were determined. The quantitative method is based on Experimental Example 1. The results are shown in Table 2. "ND" in Table 2 indicates that the element was not detected.

From the results in Table 2, it can be seen that if the temperature exceeds 60°C, iridium will precipitate, and therefore 60°C or lower is suitable for preferentially cementing ruthenium with iron powder. When the temperature is low, copper is mixed in, but this can be controlled by adjusting the amount of iron powder added. It is assumed that metallic copper produced by cementation is easily dissolved in acid. This is because, as shown in Table 2, the copper concentration increases as the temperature increases, it is thought that cemented copper was once formed but redissolved.

(Experiment example 3)
200 mL of the same iridium-containing liquid as in Experimental Example 1 was taken and heated to 50°C. 1 g or 2 g of sodium hydrosulfide was added and stirred for 1 hour. The filtrate was separated by filtration, and each elemental component in the filtrate was quantified. The quantitative method is based on Experimental Example 1. The results are shown in Table 3.

The results in Table 3 show that ruthenium and iridium hardly produce sulfide precipitates or reduced precipitates when sodium hydrogen sulfide (NaSH) is added. In contrast, it can be seen that copper selectively produced sulfide precipitates.

It is widely known that copper produces copper sulfide not only with sodium hydrosulfide but also with sulfurizing agents such as hydrogen sulfide and sodium sulfide. The results of Experimental Example 3 showed that 1 g of sodium hydrogen sulfide was effective for 200 mL of solution. When converted to the sulfur concentration contained in sodium hydrosulfide, it is 5.8 times the mass. 2g is 11.6 times the mass. Therefore, the reducing sulfur contained in the sulfiding agent may be added in an amount of 5 to 12 times the mass of copper.

(Experiment example 4)
200 mL of the same iridium-containing liquid as in Experimental Example 1 was taken and heated to 60°C. 0.3 g of iron powder was added, stirred, and cemented for 30 minutes. The filtrates after solid-liquid separation were each heated to 40 to 70°C, 1 g of sodium hydrogen sulfide was added, stirred for 1 hour, and filtered again. The concentration of each element in the filtrate was determined. The filtrate was heated to 70°C and 2g or 4g of sodium thiosulfate pentahydrate was added. The mixture was stirred for 1 hour and filtered, and each elemental component was quantified. The quantitative method is based on Experimental Example 1. The results are shown in Table 4 (concentration of each element after sulfurization) and Table 5 (concentration of each element after addition of sodium thiosulfate).

From the results in Tables 4 and 5, it was found that after cementing ruthenium with iron powder, copper and antimony were removed by sulfidation, and the remaining iridium could be recovered with sodium thiosulfate.

Sodium thiosulfate pentahydrate was effective in recovering iridium even when added at 2 g to 200 mL of the target solution, but had little effect on antimony. Although it is effective against copper, it will not mix with iridium unless it is removed by sulfidation beforehand. Although the concentration has not been measured, it is certain that lead is removed by precipitation, as its sulfide is insoluble in water and its ionization tendency is between that of iron and copper.

Although some arsenic is mixed in, the iridium concentration in the raw material liquid is low, and the arsenic compound that precipitates during solid-liquid separation becomes a filter aid. Therefore, it is not necessary to thoroughly remove arsenic in the sulfurization process.

(Experiment example 5)
Copper-coated iron powder was prepared as follows. It was prepared by bringing iron powder into contact with a copper sulfate solution containing copper sulfate five times the mass of iron and stirring for 20 seconds. Two types with copper contents of 30% and 70% were prepared and used. When the concentration was 70%, the reaction temperature at the time of contact with the copper sulfate solution was set to 60°C.

200 mL of the same iridium-containing liquid as in Experimental Example 1 was taken and heated to 60°C or 40°C, respectively. 0.4 g of copper-coated iron powder was added, stirred, and cemented for 30 minutes. The filtrates after solid-liquid separation were each heated to 40°C, sodium hydrosulfide was added, and the mixture was stirred for 1 hour. Considering the copper concentration, 2 g was added for 30% copper powder and 3 g was added for 70% powder, and the powder was filtered again. The concentration of each element in the filtrate was determined. The filtrate was heated to 70°C and 4g of sodium thiosulfate pentahydrate was added. The mixture was stirred for 1 hour, filtered, and each elemental component was determined. The quantitative method is based on Experimental Example 1. The results are shown in Table 6 (concentration of each element after cementation), Table 7 (concentration of each element after sulfidation), and Table 8 (concentration of each element after addition of sodium thiosulfate). "ND" in Tables 7 and 8 indicates that the element was not detected.

The results in Table 6 show that it is possible to precipitate ruthenium even when copper-coated iron powder is used. Furthermore, the amount of copper was also confirmed, and as shown in Table 7, copper could be selectively removed by sulfidation. Furthermore, iridium could finally be recovered by adding sodium thiosulfate.

Claims (7)

Adjust the acidic liquid containing ruthenium and iridium and one or more elements of copper, arsenic, and antimony to below 60°C, and (1) adjust the concentration of metallic iron to 0.5 to 4.0 g/L. or (2) a ruthenium recovery step in which metal iron is added until the redox potential reaches 150 mV or less using silver/silver chloride as a reference electrode to precipitate ruthenium, followed by solid-liquid separation;
The filtrate obtained by solid-liquid separation after precipitating the ruthenium is adjusted to 70°C or lower, and one or more of hydrogen sulfide, sodium hydrogen sulfide, and soda sulfide is added as a sulfurizing agent to prepare copper, a sulfiding step to precipitate one or more elements among arsenic and antimony;
After precipitating one or more elements among the copper, arsenic, and antimony, solid-liquid separation is performed, the resulting filtrate is adjusted to 40°C or higher, and sodium thiosulfate salt or a solution containing thiosulfate ions is added. an iridium recovery step of precipitating iridium;
A method for recovering ruthenium and iridium, including An acidic solution containing ruthenium and iridium and one or more elements among copper, arsenic, and antimony is adjusted to a temperature of 40°C or higher, and (1) copper-coated iron powder is used as metallic iron, with an iron content of 0.5 to 4.0 g/L, or (2) ruthenium was precipitated by adding copper-coated iron powder as metal iron until the redox potential reached 150 mV or less using silver/silver chloride as a reference electrode. A ruthenium recovery process that then undergoes solid-liquid separation,
The filtrate obtained by solid-liquid separation after precipitating the ruthenium is adjusted to 70°C or lower, and one or more of hydrogen sulfide, sodium hydrogen sulfide, and soda sulfide is added as a sulfurizing agent to prepare copper, a sulfiding step to precipitate one or more elements among arsenic and antimony;
After precipitating one or more elements among the copper, arsenic, and antimony, solid-liquid separation is performed, the resulting filtrate is adjusted to 40°C or higher, and sodium thiosulfate salt or a solution containing thiosulfate ions is added. an iridium recovery step of precipitating iridium;
A method for recovering ruthenium and iridium, including In the ruthenium recovery step, the acidic liquid containing ruthenium and iridium and one or more elements selected from copper, arsenic, and antimony is prepared by blowing sulfur dioxide or hydrogen sulfide into the acidic liquid, or by blowing aldehydes into the acidic liquid. Claim 1 or 2, wherein the acidic liquid is obtained by adding a reducing agent to precipitate platinum, gold, palladium, and selenium to adjust the concentration of each element of platinum, gold, palladium, and selenium to 10 mg/L or less. The described method for recovering ruthenium and iridium. The method for recovering ruthenium and iridium according to claim 1 or 2, wherein in the ruthenium recovery step, the metal iron is added in an amount of 5 to 25 times the mass of ruthenium in the acidic liquid. According to claim 1 or 2, in the sulfurizing step, at least one of hydrogen sulfide, sodium hydrogen sulfide, and sodium sulfide is added as the sulfurizing agent, which is 5 to 20 times the copper concentration when converted to the sulfur concentration. A method for recovering ruthenium and iridium. In the ruthenium recovery step, the acidic liquid containing ruthenium and iridium and one or more elements among copper, arsenic, and antimony is an acidic liquid after dissolving metal electrolytic precipitates. The method for recovering ruthenium and iridium described in . The iridium concentration in the acidic solution in the ruthenium recovery step is 100 mg/L or less, and in the iridium recovery step, the sodium thiosulfate salt or thiosulfate ion-containing solution is 5 g in terms of sodium thiosulfate pentahydrate. The method for recovering ruthenium and iridium according to claim 1 or 2, wherein the ruthenium and iridium are added in an amount of /L or more.