Method for recovering ruthenium and iridium

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

[Technical Field]

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

[0002] In copper pyrometallurgy, copper concentrate is melted and refined in a converter and a refining furnace to produce crude copper of 99% purity or more. After that, electrolytic refining is carried out to produce electrolytic copper of 99.99% purity or more. Valuable materials other than copper are precipitated as sediment during electrolytic refining.

[0003] This residue also contains precious metals, rare metals, and the selenium and tellurium contained in copper concentrate. These elements are separated and recovered individually as by-products of copper smelting.

[0004] Hydrometallurgical methods are often used to treat this precipitate. For example, Patent Document 1 discloses a method in which silver is recovered from the precipitate using hydrochloric acid and hydrogen peroxide, dissolved gold is recovered by solvent extraction, and then other valuables are sequentially reduced and recovered with sulfur dioxide. Patent Document 2 discloses a method in which gold and silver are recovered using a similar method, and then the valuables are reduced and precipitated with sulfur dioxide, and only selenium is distilled and removed to concentrate the precious metals.

[0005] The solution left after the precious metals have been recovered contains rare metal ions, tellurium, and selenium, and these valuable materials must be further recovered. Known methods for recovering these valuable materials include recovering the precipitate formed by the reduction agent, or mixing the solution with copper concentrate, drying it in a dryer, and then returning it to the smelting furnace.

[0006] In particular, the method of recovering precipitates produced by sulfur dioxide, as shown in Patent Document 1, has many advantages in terms of cost and production scale. In addition, since each element precipitates sequentially, it is also effective for separation and purification.

[0007] In the method of recovering valuables using sulfur dioxide, valuables can be recovered by sequential reduction after dissolution. Platinum and palladium precipitate first. Selenium is then reduced. Iridium and ruthenium have relatively low redox potentials and are therefore less susceptible to reduction, remaining in the solution until the end. As for iridium, a widely known method is to recover it by separating it through solvent extraction, concentrating it, and then calcining it, as described in Patent Document 3. Patent Document 4 also 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, and the precious metal is reduced and precipitated. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-316735 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-160479 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-332041 [Patent Document 4] Japanese Patent Application Laid-Open No. 2002-115015 Summary of the Invention [Problem to be solved by the invention]

[0009] For example, the iridium concentration in an acidic solution containing dissolved copper electrolytic deposits 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. In addition, the efficiency of separation from other metals and stripping are not high.

[0010] On the other hand, distillation recovery of ruthenium requires the use of a strong oxidizing agent such as NaBrO3. The cost of the oxidizing agent is high, and this method is not suitable for recovering ruthenium from dilute solutions with high impurities, such as precipitate solutions, where the ruthenium concentration is around 50-200 mg / L. Furthermore, ruthenium tetroxide is highly toxic, and there are safety issues with recovering it by distillation.

[0011] Cementation with a base metal such as zinc is an effective method for recovering both iridium and ruthenium, but it is difficult to separate and recover iridium and ruthenium using base metal cementation.

[0012] Furthermore, in cementation using base metals, a large amount of metal is used to increase the recovery rate. Under strongly acidic conditions, hydrogen is generated in a concentrated manner in a short period of time, causing boiling over, or the hydrogen generated by static electricity can explode. In addition, the reaction efficiency is low because other elements that undergo cementation are also present.

[0013] It is known that iridium and ruthenium precipitate as their hydroxides. However, both elements precipitate simultaneously in alkaline regions, making them impossible to separate and recover. A more general problem is the high cost of alkaline reagents when neutralizing strong acids. Furthermore, sodium ions and alkaline earth metal ions precipitate sulfates that are sparingly soluble in water, even under acidic conditions. When neutralized with excessive amounts of alkali, these sparingly soluble sulfates are expected to deposit in the piping of manufacturing equipment, causing blockages.

[0014] It is desirable to recover both ruthenium and iridium while minimizing contamination with other metals. Copper contamination is a particular concern when copper electrolytic deposits are used as raw materials. If copper is present in quantities that are difficult to remove by oxidation leaching, a separate copper removal process is required. Furthermore, no inexpensive, efficient method is known for separating and precipitating low concentrations of iridium and ruthenium from strongly acidic solutions.

[0015] In view of the above-mentioned conventional circumstances, the present invention provides a method for efficiently separating and recovering ruthenium and iridium from an acidic solution containing ruthenium and iridium. In particular, an acidic solution obtained by oxidatively dissolving an electrolytic deposit generated in an electrolytic refining step in copper smelting is a suitable target for the acidic solution containing ruthenium and iridium of the present invention. [Means for solving the problem]

[0016] The above problems can be solved by the inventions specified below. That is, the present invention includes the following inventions. [1] a ruthenium recovery step in which an acidic solution containing ruthenium, iridium, and one or more elements selected from the group consisting of copper, arsenic, and antimony is adjusted to 60°C or less, and (1) metallic iron is added so that the amount is 0.5 to 4.0 g / L, or (2) metallic iron is added until the oxidation-reduction potential using a silver / silver chloride reference electrode reaches 150 mV or less, thereby precipitating ruthenium, followed by solid-liquid separation; a sulfurization step in which the filtrate obtained by performing solid-liquid separation after precipitating the ruthenium is adjusted to 70°C or less, and one or more of hydrogen sulfide, sodium hydrosulfide, and sodium sulfide are added as a sulfurizing agent to precipitate one or more elements of copper, arsenic, and antimony; an iridium recovery step of precipitating one or more elements selected from copper, arsenic, and antimony, followed by solid-liquid separation, adjusting the temperature of the resulting filtrate to 40°C or higher, and adding sodium thiosulfate or a solution containing thiosulfate ions to precipitate iridium; A method for recovering ruthenium and iridium, comprising: [2] a ruthenium recovery step in which an acidic solution containing ruthenium, iridium, and one or more elements selected from the group consisting of copper, arsenic, and antimony is adjusted to a temperature of 40°C or higher, and (1) copper-coated iron powder is added as metallic iron so that the iron content is 0.5 to 4.0 g / L, or (2) copper-coated iron powder is added as metallic iron until the oxidation-reduction potential using a silver / silver chloride reference electrode reaches 150 mV or less, thereby precipitating ruthenium, followed by solid-liquid separation; a sulfurization step in which the filtrate obtained by performing solid-liquid separation after precipitating the ruthenium is adjusted to 70°C or less, and one or more of hydrogen sulfide, sodium hydrosulfide, and sodium sulfide are added as a sulfurizing agent to precipitate one or more elements of copper, arsenic, and antimony; an iridium recovery step of precipitating one or more elements selected from copper, arsenic, and antimony, followed by solid-liquid separation, adjusting the temperature of the resulting filtrate to 40°C or higher, and adding sodium thiosulfate or a solution containing thiosulfate ions to precipitate iridium; A method for recovering ruthenium and iridium, comprising: [3] The method for recovering ruthenium and iridium according to [1] or [2], wherein in the ruthenium recovery step, the acidic solution containing ruthenium, iridium, and one or more elements of copper, arsenic, and antimony is an acidic solution obtained by blowing sulfur dioxide or hydrogen sulfide into the acidic solution, or by adding an aldehyde reducing agent, to precipitate platinum, gold, palladium, and selenium, thereby adjusting the elemental concentrations of platinum, gold, palladium, and selenium to 10 mg / L or less. [4] The method for recovering ruthenium and iridium according to any one of [1] to [3], wherein in the ruthenium recovery step, the metallic iron is added in an amount 5 to 25 times by mass the amount of ruthenium in the acidic solution. [5] The method for recovering ruthenium and iridium according to any one of [1] to [4], wherein in the sulfurization step, at least one of hydrogen sulfide, sodium hydrosulfide, and sodium sulfide is added as the sulfurizing agent in an amount 5 to 20 times by mass the copper concentration when converted into a sulfur content concentration. [6] The method for recovering ruthenium and iridium according to any one of [1] to [5], wherein in the ruthenium recovery step, the acidic solution containing ruthenium, iridium, and one or more elements of copper, arsenic, and antimony is an acidic solution obtained after dissolving a metal electrolytic deposit. [7] The method for recovering ruthenium and iridium according to any one of [1] to [6], wherein the iridium concentration in the acidic solution in the ruthenium recovery step is 100 mg / L or less, and the sodium thiosulfate salt or the thiosulfate ion-containing solution is added in the iridium recovery step so that the concentration, calculated as sodium thiosulfate pentahydrate, is 5 g / L or more. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a method for efficiently separating and recovering ruthenium and iridium from an acidic solution containing ruthenium and iridium. [Brief explanation of the drawings]

[0018] [Figure 1]FIG. 1 is a flow diagram illustrating an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Next, the embodiments for carrying out the present invention will be described in detail. It should be understood that the present invention is not limited to the following embodiments, and that appropriate design changes, improvements, etc. may be made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

[0020] Fig. 1 shows a flow diagram that schematically illustrates one embodiment of the present invention. The flow diagram in Fig. 1 lists specific examples of each step, and the present invention is not limited to only this flow diagram. In one aspect, a method for recovering ruthenium and iridium according to an embodiment of the present invention includes a ruthenium recovery step in which an acidic solution containing ruthenium, iridium, and one or more elements selected from the group consisting of copper, arsenic, and antimony is adjusted to 60°C or below, and (1) metallic iron is added in an amount of 0.5 to 4.0 g / L, or (2) metallic iron is added until the oxidation-reduction potential (RED) using a silver / silver chloride reference electrode reaches 150 mV or less to precipitate ruthenium, followed by solid-liquid separation; a sulfurization step in which the filtrate obtained by precipitating ruthenium and performing solid-liquid separation is adjusted to 70°C or below, and one or more of hydrogen sulfide, sodium hydrosulfide, and sodium sulfide are added as a sulfiding agent to precipitate one or more elements selected from the group consisting of copper, arsenic, and antimony; and an iridium recovery step in which the filtrate obtained is adjusted to 40°C or above, and sodium thiosulfate or a solution containing thiosulfate ions is added to precipitate iridium.

[0021] In the method for recovering ruthenium and iridium according to an embodiment of the present invention, the acidic solution containing ruthenium and iridium to be treated may be obtained through any process. However, an acidic solution obtained by oxidizing and dissolving an electrolytic deposit generated in an electrolytic refining process in copper smelting is particularly suitable as the iridium-containing acidic solution of the present invention. Furthermore, the electrolytic deposit generated in the electrolytic refining process of non-ferrous metal smelting, particularly copper smelting, is enriched with platinum group elements along 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 waste catalysts. Therefore, the method for recovering ruthenium and iridium according to an embodiment of the present invention can also be applied to recycling from waste. That is, the acidic solution containing ruthenium and iridium generated in the waste treatment process can be used.

[0022] In the method for recovering ruthenium and iridium according to an embodiment of the present invention, when the acidic solution containing ruthenium and iridium to be treated is a hydrochloric acid solution obtained through a predetermined process, it contains various metal elements in addition to ruthenium (Ru) and iridium (Ir).

[0023] When replacing ruthenium with metallic iron, selenium (Se), platinum (Pt), palladium (Pd), gold (Au), silver (Ag), etc. are preferentially replaced over ruthenium. As will be explained in more detail later, the concentrations of these elements must be reduced beforehand.

[0024] As an example, we will show how to prepare a hydrochloric acid solution containing ruthenium and iridium from electrolytic deposits from the copper electrorefining process of copper smelting. First, copper is dissolved and removed from the electrolytic deposits from the copper electrorefining process using sulfuric acid. Next, concentrated hydrochloric acid and hydrogen peroxide are added to dissolve the precipitate, followed by solid-liquid separation to obtain the pregnant leach solution (PLS). Platinum group elements, rare metal elements, chalcogen elements, arsenic, antimony, etc. are distributed in the pregnant leach solution (PLS), which is a chloride bath.

[0025] The pregnant leach solution (PLS) is cooled once, and chlorides of base metals such as lead and antimony are precipitated and separated. Gold is then separated into an organic phase by solvent extraction. Dibutyl carbitol (DBC) is widely used as the gold extractant. Sulfur dioxide is blown into the extract to reduce and remove precious metals such as platinum and palladium, as well as selenium and tellurium. Subsequent solid-liquid separation produces a hydrochloric acid solution containing ruthenium and iridium.

[0026] In the method for recovering ruthenium and iridium according to an embodiment of the present invention, it is preferable to adjust the concentration of impurity elements such as platinum, gold, palladium, and selenium to 10 mg / L or less by blowing sulfur dioxide or hydrogen sulfide into an acidic solution containing ruthenium and iridium, or by adding an aldehyde reducing agent. Examples of such aldehydes include formaldehyde and methylglyoxal. Note that if the concentration of impurity elements such as platinum, gold, palladium, and selenium in the acidic solution to be treated is 10 mg / L or less, blowing in or adding the reducing agent is not necessary.

[0027] Valuable materials remaining in the acidic solution after the above-mentioned treatment include ruthenium, iridium, antimony, copper, etc. Of these, ruthenium and iridium are particularly valuable and are therefore preferably recovered. The post-reduction solution also contains arsenic at 0.5 to 3 g / L, but arsenic is relatively easy to separate from metals, and some contamination is acceptable when recovering valuable materials. It is also preferable to recover ruthenium and iridium separately from each element.

[0028] Metal cementation is an effective method for recovering ruthenium from the reduced solution. However, since the acidic solution contains arsenic, the metal must have an oxidation-reduction potential of -380 mV or higher with a silver / silver chloride reference electrode to suppress the generation of arsine. Metals that meet the conditions for cementation of ruthenium include iron, nickel, lead, and copper.

[0029] Among the metals used in ruthenium cementation, the following metals present individual problems: copper precipitates a significant amount of arsenic as copper arsenide; lead contaminates ruthenium because unreacted lead does not dissolve in the acid; and nickel is expensive. However, although metallic iron has the problem of instantaneous generation of large amounts of hydrogen during reaction, this is not a major problem if the temperature of the acidic solution is adjusted to 60°C or below, preferably 30 to 60°C, and metallic iron is added so that the concentration in the acidic solution is 0.5 to 4.0 g / L. Furthermore, adding metallic iron causes ruthenium to undergo cementation before copper and arsenic, making it possible to separate and recover it.

[0030] In the ruthenium recovery step, metallic iron is preferably added in an amount 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 solution, cementation of ruthenium by metallic iron may be insufficient. If the amount of metallic iron added is more than 25 times the mass of ruthenium in the acidic solution, it is disadvantageous in terms of cost and may result in the inclusion of impurities.

[0031] Iron powder is suitable as the metallic iron to be added due to its high reactivity. There are no particular restrictions on the quality of the metallic iron. As will be described later, the metallic iron to be added may be any metallic iron that has reducing properties, and even iron powder with a portion of its surface coated with copper (copper-coated iron powder) will function. In this case, copper-coated iron powder is added as metallic iron so that the iron content is 0.5 to 4.0 g / L. The eluted copper is precipitated and removed as sulfide after ruthenium recovery, so contamination does not pose a major problem. Furthermore, when copper-coated iron powder is used, the temperature of the acidic solution is adjusted to 40°C or higher, and the copper-coated iron powder is added so that the iron content is 0.5 to 4.0 g / L.

[0032] When metallic iron comes into contact with an acidic solution, hydrogen is generated. This hydrogen is explosive. Furthermore, if iron powder is used as metallic iron, its large surface area can cause a large amount of hydrogen to be generated in a short period of time, causing the solution to boil over. Therefore, when using iron powder, it is best to add it in multiple batches rather than all at once.

[0033] If the redox potential (reference electrode: silver / silver chloride) is used as an indicator for cementation of ruthenium, metallic iron can be added until the redox potential of the acidic solution reaches 150 mV or less. Below this potential, the ruthenium concentration drops significantly.

[0034] To avoid the risk of boiling over or explosion due to hydrogen generation, it is possible to use iron powder whose surface is partially coated with copper (copper-coated iron powder). In principle, hydrogen generation is suppressed by limiting contact between metallic iron and the acidic solution. After the copper gradually dissolves, the iron that appears on the surface reacts with ruthenium. If the copper content is too high, contact efficiency may decrease. Therefore, the copper content of the copper-coated iron powder is preferably 70% by mass or less, and more preferably 40% by mass or less.

[0035] After ruthenium is precipitated, the ruthenium-containing material obtained by solid-liquid separation is separated into iridium and other impurities by a known method. For example, after oxidative dissolution, sodium bromate is added to distill and separate ruthenium tetroxide. Iridium is sufficiently concentrated in this oxidative dissolution solution, and can also be recovered by known solvent extraction.

[0036] A sulfiding agent is added to the acidic liquid, which is the filtrate after cementation separation (solid-liquid separation) of ruthenium. Hydrogen sulfide, sodium hydrosulfide, and sodium sulfide are suitable sulfiding agents, and any one or more of these may be used. Sodium thiosulfate is also known as a sulfiding agent, but is unsuitable because it may cause some of the iridium to precipitate and be lost. The sulfiding agent precipitates copper, arsenic, antimony, and lead.

[0037] The temperature of the acidic solution during sulfurization using the sulfiding agent is adjusted to 70°C or below. If the temperature of the acidic solution is higher than 70°C, there is a risk that the precipitated copper sulfide will re-dissolve. In addition, the reducing sulfur that forms sulfides from the solution will volatilize as hydrogen sulfide, which may reduce the reaction efficiency.

[0038] The sulfurizing agent is preferably added in an amount 5 to 20 times by mass the copper concentration when converted into the sulfur content concentration. More preferably, it is added in an amount 5 to 12 times by mass. If the amount of sulfurizing agent added is less than 5 times the copper concentration, there is a risk that an excessive amount of elements to be removed by sulfurization will remain. If the amount of sulfurizing agent added is more than 20 times the copper concentration, there is a risk that the amount of precipitate produced in the subsequent iridium recovery step will be extremely small, making solid-liquid separation difficult. There is also a risk that the cost of the reagent will increase.

[0039] The sulfide precipitate separated in the sulfurization process contains valuable materials such as copper and lead, so it can be recycled into the smelting furnace and reused as a valuable raw material.

[0040] After precipitating one or more elements selected from copper, arsenic, and antimony in the sulfurization step, solid-liquid separation is performed. The resulting filtrate is adjusted to 40°C or higher, preferably 60°C or higher, and sodium thiosulfate salt or a solution containing thiosulfate ions is added to precipitate iridium. The sodium thiosulfate salt or the solution containing thiosulfate ions is added to a concentration of 5 g / L or more, calculated as sodium thiosulfate pentahydrate, to precipitate iridium. Iridium hardly precipitates with the sulfurizing agent used in the previous sulfurization step. In contrast, thiosulfate ions have coordination ability, so it is thought that reducing them after first coordinating with iridium ions will be effective in precipitating iridium.

[0041] A typical example of sodium thiosulfate salt is 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. Sodium thiosulfate pentahydrate is particularly suitable due to its low toxicity.

[0042] Addition of sodium thiosulfate 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 process is low, at 100 mg / L or less, precipitating only iridium results in a small amount of recovery, causing problems with solid-liquid separation. The presence of a moderate amount of impurities is not a problem.

[0043] When the iridium concentration in the acidic solution in the ruthenium recovery step is high, it is more efficient to recover it by precipitation with KCl or NH4Cl, but when the iridium concentration is low, at 100 mg / L or less, it is preferable to recover it by precipitation by adding sodium thiosulfate salt or a solution containing thiosulfate ions. In this case, sodium thiosulfate salt or a solution containing thiosulfate ions may be added so that the concentration, calculated as sodium thiosulfate pentahydrate, is 5 g / L or more, or 5 to 20 g / L or more.

[0044] The precipitated iridium-containing material is subjected to solid-liquid separation, followed by separation of iridium from other impurities using a known method. For example, a method of separating and recovering iridium by solvent extraction after oxidative dissolution is exemplified. The iridium recovered as a precipitate is sufficiently concentrated, and can be recovered by known solvent extraction. [Example]

[0045] The following examples are provided to provide a better understanding of the present invention and its advantages, but the present invention is not limited to these examples.

[0046] (Experimental Example 1) Copper was dissolved and removed from the electrolytic deposit from the copper electrorefining process of copper smelting using sulfuric acid. Concentrated hydrochloric acid and 60% hydrogen peroxide were added for dissolution, and solid-liquid separation was performed to obtain PLS (pregnant leach solution). The PLS was cooled to 6°C to precipitate and remove the base metals. The acid concentration was adjusted to over 1 mol / L, and DBC (dibutyl carbitol) was mixed with the PLS to extract gold. After gold extraction, the PLS was heated to 70°C, and sulfur dioxide was blown in to reduce and remove the precious metals, selenium, and tellurium. This was then subjected to solid-liquid separation to obtain a hydrochloric acid solution containing iridium.

[0047] Next, 200 mL of the sulfur dioxide reduction solution was taken and heated to 60°C. The iridium concentration of the sulfur dioxide reduction solution was 25 mg / L and the ruthenium concentration was 77 mg / L. The sulfur dioxide reduction solution also 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. The reaction was stopped after a predetermined time, and the precipitate was separated into solid and liquid. After filtration, the ORP (oxidation-reduction potential) of the solution was measured and the concentrations of various elements were quantified. All reagents used were of special grade manufactured by Wako Pure Chemical Industries, Ltd. The element concentrations in the solutions were quantified by taking 2 mL of the solution, adjusting the volume to 50 mL, and then quantifying the concentrations using ICP-OES (SPS3100 manufactured by Seiko Instruments Inc.). The precipitate solution was adjusted to 100 mL, and its concentration was determined. The results are shown in Table 1. "ND" in Table 1 indicates that the element in question was not detected.

[0048] [Table 1]

[0049] It can be seen that adding 0.1g of iron powder to 200mL of raw material solution resulted in preferential cementation of ruthenium. Furthermore, it can be seen that adding 0.3g or more of iron powder resulted in sufficient recovery of ruthenium. However, excessive iron powder increases the amount of arsenic and copper contamination. Therefore, adding 0.8g or less is preferable.

[0050] The ORP value dropped sharply when more than 0.3g of iron powder was added. This indicates that adding iron powder until the ORP reached 150mV or less was sufficient to cement ruthenium.

[0051] (Experimental Example 2) 200 mL of the same iridium-containing liquid as in Experimental Example 1 was taken and heated to 40 to 80°C. 0.6 g of iron powder was added. After stirring for 1 hour, the reaction was stopped. The filtrate was filtered and the component elements were quantified. The quantification method was the same as in Experimental Example 1. The results are shown in Table 2. "ND" in Table 2 indicates that the element in question was not detected.

[0052] [Table 2]

[0053] The results in Table 2 show that because iridium precipitates when the temperature exceeds 60°C, temperatures below 60°C are ideal for preferentially cementing ruthenium with iron powder. Copper becomes mixed in at lower temperatures, but this can be controlled by adjusting the amount of iron powder added. It is surmised that metallic copper produced by cementation would easily dissolve in acid. This is because, as Table 2 shows, the copper concentration increases as the temperature increases, and it is thought that copper cementation occurred once but then redissolved.

[0054] (Experimental 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 filtered and the amount of each element in the filtrate was quantified. The quantification method was the same as in Experimental Example 1. The results are shown in Table 3.

[0055] [Table 3]

[0056] The results in Table 3 show that ruthenium and iridium hardly produce sulfide precipitates or reduction precipitates when sodium hydrosulfide (NaSH) is added, whereas copper selectively produces sulfide precipitates.

[0057] It is widely known that copper can be converted to copper sulfide by sulfiding agents such as hydrogen sulfide and sodium sulfide, in addition to sodium hydrosulfide. The results of Experimental Example 3 showed that 1 g of sodium hydrosulfide per 200 mL of solution was effective. This corresponds to 5.8 times the sulfur concentration of sodium hydrosulfide by mass. 2 g corresponds to 11.6 times the sulfur concentration by mass. Therefore, the reducing sulfur contained in the sulfiding agent should be added in an amount 5 to 12 times the mass of copper.

[0058] (Experimental 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, and 1 g of sodium hydrosulfide was added. The mixture was stirred for 1 hour and then filtered again. The concentrations of each element in the filtrate were quantified. The filtrates were heated to 70°C, and 2 g or 4 g of sodium thiosulfate pentahydrate was added. The mixture was stirred for 1 hour and filtered, and the concentrations of each element were quantified. The quantification method was the same as in Experimental Example 1. The results are shown in Table 4 (element concentrations after sulfurization) and Table 5 (element concentrations after sodium thiosulfate addition).

[0059] [Table 4]

[0060] [Table 5]

[0061] The results in Tables 4 and 5 show that ruthenium can be cemented with iron powder, followed by sulfurization to remove copper and antimony, and the remaining iridium can be recovered using sodium thiosulfate.

[0062] Sodium thiosulfate pentahydrate was effective in recovering iridium even when added at a rate of 2g per 200mL of the target liquid, but had almost no effect on antimony. It was effective on copper, but if it was removed beforehand by sulfurization, it would not contaminate the iridium. Although the concentration was not measured, lead sulfide does not dissolve in water, and its ionization tendency is intermediate between that of iron and copper, so it is certain that it will be removed by precipitation.

[0063] Although some arsenic is mixed in, the iridium concentration in the raw liquid is low, and the arsenic compounds that precipitate during solid-liquid separation act as a filter aid. Therefore, there is no need to thoroughly remove arsenic in the sulfurization process.

[0064] (Experimental Example 5) Copper-coated iron powder was prepared as follows. Iron powder was brought into contact with a copper sulfate solution containing five times the mass of copper sulfate relative to the iron, and stirred for 20 seconds. Two copper contents were prepared: 30% and 70%. The 70% copper content was prepared at a reaction temperature of 60°C when brought into contact with the copper sulfate solution.

[0065] 200 mL of the same iridium-containing liquid as in Experimental Example 1 was heated to 60°C or 40°C. 0.4 g of copper-coated iron powder was added, stirred, and cemented for 30 minutes. The filtrate after solid-liquid separation was heated to 40°C, and sodium hydrosulfide was added and stirred for 1 hour. Considering the copper concentration, 2 g of sodium hydrosulfide was added to the 30% copper powder and 3 g to the 70% copper powder, and the mixture was filtered again. The concentration of each element in the filtrate was quantified. The filtrate was heated to 70°C, and 4 g of sodium thiosulfate pentahydrate was added. The mixture was stirred for 1 hour, filtered, and the elemental components were quantified. The quantification method was similar to that of Experimental Example 1. The results are shown in Table 6 (element concentration after cementation), Table 7 (element concentration after sulfurization), and Table 8 (element concentration after sodium thiosulfate addition). "ND" in Tables 7 and 8 indicates that the corresponding element was not detected.

[0066] [Table 6]

[0067] [Table 7]

[0068] [Table 8]

[0069] The results in Table 6 show that ruthenium can be precipitated using copper-coated iron powder. Furthermore, the amount of copper extracted was also confirmed, but as shown in Table 7, copper could be selectively removed by sulfurization. Furthermore, iridium could be finally recovered by adding sodium thiosulfate.

Claims

1. a ruthenium recovery step of adjusting the temperature of an acidic solution containing ruthenium, iridium, and one or more elements selected from the group consisting of copper, arsenic, and antimony, to 60°C or below, (1) adding metallic iron to the solution so that the amount is 0.5 to 4.0 g / L, or (2) adding metallic iron until the oxidation-reduction potential using a silver / silver chloride reference electrode reaches 150 mV or less, thereby precipitating ruthenium, followed by solid-liquid separation; a sulfurization step in which the filtrate obtained by performing solid-liquid separation after precipitating the ruthenium is adjusted to 70°C or less, and one or more of hydrogen sulfide, sodium hydrosulfide, and sodium sulfide are added as a sulfurizing agent to precipitate one or more elements of copper, arsenic, and antimony; an iridium recovery step of precipitating one or more elements selected from copper, arsenic, and antimony, followed by solid-liquid separation, adjusting the temperature of the resulting filtrate to 40°C or higher, and adding sodium thiosulfate or a solution containing thiosulfate ions to precipitate iridium; A method for recovering ruthenium and iridium, comprising:

2. a ruthenium recovery step of adjusting the temperature of an acidic solution containing ruthenium, iridium, and one or more elements selected from the group consisting of copper, arsenic, and antimony, to 40°C or higher, (1) adding copper-coated iron powder as metallic iron so that the iron content is 0.5 to 4.0 g / L, or (2) adding copper-coated iron powder as metallic iron until the oxidation-reduction potential using a silver / silver chloride reference electrode reaches 150 mV or less, thereby precipitating ruthenium, and then performing solid-liquid separation; a sulfurization step in which the filtrate obtained by performing solid-liquid separation after precipitating the ruthenium is adjusted to 70°C or less, and one or more of hydrogen sulfide, sodium hydrosulfide, and sodium sulfide are added as a sulfurizing agent to precipitate one or more elements of copper, arsenic, and antimony; an iridium recovery step of precipitating one or more elements selected from copper, arsenic, and antimony, followed by solid-liquid separation, adjusting the temperature of the resulting filtrate to 40°C or higher, and adding sodium thiosulfate or a solution containing thiosulfate ions to precipitate iridium; A method for recovering ruthenium and iridium, comprising:

3. 3. The method for recovering ruthenium and iridium according to claim 1, wherein in the ruthenium recovery step, the acidic solution containing ruthenium, iridium, and one or more elements of copper, arsenic, and antimony is an acidic solution obtained by blowing sulfur dioxide or hydrogen sulfide into the acidic solution or adding an aldehyde reducing agent to precipitate platinum, gold, palladium, and selenium, thereby adjusting the element concentrations of platinum, gold, palladium, and selenium to 10 mg / L or less.

4. 3. The method for recovering ruthenium and iridium according to claim 1, wherein the metallic iron is added in an amount 5 to 25 times by mass the amount of ruthenium in the acidic solution in the ruthenium recovery step.

5. 3. The method for recovering ruthenium and iridium according to claim 1, wherein in the sulfurization step, at least one of hydrogen sulfide, sodium hydrosulfide, and sodium sulfide is added as the sulfurizing agent in an amount 5 to 20 times by mass the copper concentration when converted into a sulfur content concentration.

6. 3. The method for recovering ruthenium and iridium according to claim 1, wherein in the ruthenium recovery step, the acidic solution containing ruthenium, iridium, and one or more elements of copper, arsenic, and antimony is an acidic solution obtained after dissolving a metal electrolytic deposit.

7. 3. The method for recovering ruthenium and iridium according to claim 1, wherein the iridium concentration in the acidic solution in the ruthenium recovery step is 100 mg / L or less, and the sodium thiosulfate salt or the thiosulfate ion-containing solution is added in the iridium recovery step so that the concentration, calculated as sodium thiosulfate pentahydrate, is 5 g / L or more.

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