JP7337209B2 - Iridium recovery method - Google Patents

Description

The present invention relates to a method for recovering iridium.

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

In this slime, precious metals, rare metals, and selenium and tellurium contained in copper concentrate are also concentrated at the same time. These elements are separately separated and recovered as copper smelting by-products.

Hydrometallurgical methods are often applied to treat this slime. For example, Patent Document 1 discloses a method in which silver is recovered from slime by hydrochloric acid-hydrogen peroxide, dissolved gold is recovered by solvent extraction, and then other valuable substances are successively reduced and recovered with sulfur dioxide. Patent Document 2 discloses a method of recovering gold and silver by a similar method, then reducing and precipitating valuables with sulfur dioxide, distilling and removing only selenium, and concentrating precious metals.

The solution after recovering precious metals contains rare metal ions, tellurium, and selenium, and it is necessary to recover these valuables. Known recovery methods include a method of recovering precipitates produced by a reducing agent, and a method of mixing the whole solution with copper concentrate, drying it with a dryer, and repeating it in a smelting furnace.

In particular, the method of recovering precipitates caused by sulfur dioxide, which is disclosed 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.

In the method of recovering valuables using sulfur dioxide, valuables can be recovered by sequentially reducing them after dissolution. Platinum and palladium precipitate first. Selenium then undergoes reduction. Iridium, ruthenium, and rhodium have relatively low oxidation-reduction potentials, so they are difficult to be reduced and remain in the solution until the end. Among them, for iridium, as described in Patent Document 3, a method of separating by solvent extraction, concentrating, and then calcining and recovering is widely known.

JP-A-2001-316735 JP 2016-160479 A Japanese Patent Application Laid-Open No. 2004-332041

The iridium concentration in the copper electrolytic precipitate solution is about 1 to 70 mg/L. Iridium is an expensive metal, but at concentrations this low, smelting by solvent extraction is not cost-effective. Separation efficiency from other metals and strip efficiency are not high either.

In the recovery of iridium, the method of cementation with a base metal such as zinc has the problem that explosive hydrogen is generated intensively in a short period of time under strong acid conditions. In addition, since other elements undergoing cementation are mixed, the efficiency is low. Furthermore, the iridium-containing liquid derived from copper refining also contains arsenic, and arsenic also precipitates when a base metal is added. Furthermore, there is a possibility that nascent hydrogen may generate toxic gas.

Iridium is known for its hydroxide to precipitate in the alkaline region. However, if the iridium-containing liquid is strongly acidic, the amount of alkaline reagent added to neutralize the strong acid increases, resulting in increased costs. In addition, sodium ions and alkaline earth metal ions precipitate sparingly soluble sulfates in water even under acidic conditions, but when neutralized with an excessive amount of alkali, the sparingly soluble sulfates deposit in the pipes of manufacturing equipment. Obstruction is expected.

In addition, conventionally, a method for inexpensively and efficiently precipitating and recovering low-concentration iridium has not been known. In particular, selectivity is required under conditions where other elements coexist, but there is no known method for selectively separating and concentrating iridium.

In view of such conventional circumstances, the present invention provides a method for efficiently precipitating and recovering iridium from a hydrochloric acid acid solution containing iridium. In particular, the hydrochloric acid acid solution obtained by oxidizing and dissolving the electrolytic sediment generated in the electrolytic refining process in copper smelting is suitable as the iridium-containing hydrochloric acid solution of the present invention.

The above problems can be solved by the inventions specified below.
(1) A hydrochloric acid solution containing iridium is heated to 40° C. or higher, and a sodium thiosulfate salt or a solution containing thiosulfate ions is converted to sodium thiosulfate pentahydrate based on iridium in the hydrochloric acid solution. A method for recovering iridium, wherein the iridium is added to the acid solution of hydrochloric acid so as to be 100 times by mass or more.
(2) adding the sodium thiosulfate salt or thiosulfate ion-containing solution to the acidic hydrochloric acid solution containing iridium so that the amount of sodium thiosulfate pentahydrate is 10 g/L or more; 3. The method for recovering iridium according to .
(3) When the iridium-containing hydrochloric acid solution contains at least one of selenium and tellurium, sulfur dioxide or an aqueous solution of sulfur dioxide is added in advance to the iridium-containing hydrochloric acid solution to obtain the total amount of selenium and tellurium. adjusting the concentration to 100 mg/L or less;
The method for recovering iridium according to (1) or (2), wherein the thiosulfate sodium salt or thiosulfate ion-containing solution is added to the iridium-containing hydrochloric acid solution adjusted to the total concentration of selenium and tellurium.
(4) The method for recovering iridium according to any one of (1) to (3), wherein the iridium-containing hydrochloric acid solution is heated to 60° C. or higher.
(5) The method for recovering iridium according to any one of (1) to (4), wherein the iridium-containing hydrochloric acid solution contains arsenic.

According to the embodiments of the present invention, it is possible to provide a method for efficiently precipitating and recovering iridium from an iridium-containing hydrochloric acid solution.

4 is a graph of Na thiosulfate addition amount (g/L) vs. Ir precipitation rate (%) according to Experimental Examples 1 and 3. FIG.

Hereinafter, embodiments of the iridium recovery method of the present invention will be described. , is subject to various alterations, modifications and improvements.

<Method for collecting iridium>
In the method for recovering iridium according to the embodiment of the present invention, an iridium-containing hydrochloric acid solution is heated to 40° C. or higher, and a thiosulfate sodium salt or a thiosulfate ion-containing solution is added to the iridium in the hydrochloric acid solution. It includes a step of adding to the hydrochloric acid acid solution so that the amount becomes 100 times or more by mass in terms of sodium pentahydrate.

In the iridium recovery method according to the embodiment of the present invention, the hydrochloric acid solution containing iridium to be treated may be obtained through any treatment, but in particular, the electrolytic refining process in copper smelting The hydrochloric acid acid solution obtained by oxidizing and dissolving the electrolytic sediment generated in the step is suitable as the iridium-containing hydrochloric acid solution of the present invention. In addition, platinum group elements are concentrated together with other rare elements in the electrolytic sediment produced in the electrorefining process of non-ferrous metal smelting, especially copper smelting. Rare elements are not smelted by themselves, but are recovered as by-products of other metals or separated from recycled raw materials such as spent catalysts. Therefore, the iridium recovery method according to the embodiment of the present invention can also be applied to recycling from waste. That is, the object can be an iridium-containing hydrochloric acid solution generated in the waste treatment process.

According to Kagaku Binran, the solubility of poorly water-soluble potassium hexachloroiridium (IV) is 12.4 g/L, and the solubility of ammonium hexachloroiridium (IV) is 10.8 g/L, both of which are known in the iridium recovery method. The iridium concentration is 4 g/L. For other iridium-containing materials, too much reagent is required to recover iridium below this concentration as a precipitate. Therefore, the iridium recovery method according to the embodiment of the present invention is suitable for handling a hydrochloric acid acid solution having an iridium concentration of 4 g/L or less, although the iridium concentration in the hydrochloric acid solution is not particularly limited.

In the iridium recovery method according to the embodiment of the present invention, when the hydrochloric acid solution containing iridium to be treated is a hydrochloric acid solution obtained through a predetermined process, various metal elements other than iridium (Ir) contains.

The hydrochloric acid solution containing iridium may contain, for example, alkali metals, alkaline earth metals, antimony (Sb), bismuth (Bi), and the like. Since these do not react with thiosulfate ions, which will be described later, no special treatment is required. Arsenic (As) is relatively difficult to react with thiosulfate ions in the hydrochloric acid solution containing iridium, and thus may be contained.

Selenium (Se), tellurium (Te), copper (Cu), and the like may be contained in the hydrochloric acid acid solution containing iridium, but they are reduced by thiosulfate ions. If Ir needs to be recovered, the concentration of these metals must be reduced in advance.

Since iron (Fe) does not react with thiosulfate ions if it is divalent, it may be contained in the hydrochloric acid solution containing iridium. On the other hand, if it is trivalent, it reacts with thiosulfate ions, so it may be contained, but if it is necessary to selectively recover Ir, it is necessary to reduce it to divalent in advance. be.

As an example, a method for producing an iridium-containing hydrochloric acid acid solution from an electrolytic sediment derived from a copper electrorefining process in copper smelting will be described. First, copper is dissolved and removed with sulfuric acid from the electrolytic sediment derived from the copper electrorefining process of copper smelting. Next, concentrated hydrochloric acid and hydrogen peroxide water are added and dissolved, followed by solid-liquid separation to obtain a pregnant solution (PLS). Platinum group elements, rare metal elements, chalcogen elements, arsenic, antimony, etc. are distributed in the pregnant leach liquor (PLS), which is a chloride bath.

Precious leach liquor (PLS) is cooled once to precipitate and separate chlorides of base metals such as lead and antimony. The gold is then separated into the organic phase by solvent extraction. A widely used extractant for gold is dibutyl carbitol (DBC). Sulfur dioxide is blown into the extract to reduce and remove noble metals, selenium, and tellurium, followed by solid-liquid separation to produce a hydrochloric acid solution containing iridium.

In the method for recovering iridium according to the embodiment of the present invention, a hydrochloric acid solution containing iridium is heated to 40° C. or higher, and a sodium thiosulfate salt or a solution containing thiosulfate ions is added. Since iridium remains in the hydrochloric acid solution as a chloride complex ion, in order to efficiently precipitate iridium from the hydrochloric acid solution, the hydrochloric acid solution is heated to 40°C or higher and thiosulfate ions are added. to precipitate.

Representative sources of thiosulfate ions include commercially available sodium thiosulfate pentahydrate. It may be added as a solid sodium thiosulfate salt or as a solution containing thiosulfate ions. The thiosulfate ion source 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 as a thiosulfate ion source.

Iridium forms a chloride complex in the acid solution of hydrochloric acid. In the copper precipitate treatment step, the iridium is assumed to have a valence of 3 or less because it is reduced with sulfur dioxide. A thiosulfate ion is considered to have a single sulfur-sulfur bond, and a negative charge is localized on the sulfur element. Sulfur is a soft element, and as described above, iridium with a valence of 3 or less is also a soft ion, so they have a high affinity with each other.

The hydrochloric acid solution is heated to 40° C. or higher, and thiosulfate ions are added for precipitation. When thiosulfate ions are added to the hydrochloric acid solution heated to 40° C. or higher, the precipitation reaction proceeds and iridium can be precipitated efficiently. If the heating temperature of the hydrochloric acid solution is lower than 40°C, the speed of the precipitation reaction may slow down. The heating temperature of the hydrochloric acid solution is preferably 50° C. or higher, more preferably 60° C. or higher, and even more preferably 70° C. or higher. The upper limit of the heating temperature of the hydrochloric acid solution is not particularly limited, but may be 100° C. or lower.

The sodium thiosulfate salt or thiosulfate ion-containing solution is added to the acidic hydrochloric acid solution so that the amount of iridium in the acidic hydrochloric acid solution is 100 times or more by mass in terms of sodium thiosulfate pentahydrate. The preferred value of the mass ratio varies depending on the acid concentration of the hydrochloric acid solution, but if the thiosulfate ion is not added excessively relative to the amount of iridium, the thiosulfate ion concentration will be lower than the effective concentration, and the precipitation reaction will not occur. It may not go well. The sodium thiosulfate salt or thiosulfate ion-containing solution is more preferably added to the hydrochloric acid acid solution so that the amount of iridium in the hydrochloric acid solution is 500 times or more by mass in terms of sodium thiosulfate pentahydrate. It is even more preferable to add it to the hydrochloric acid solution so that it becomes more than twice the mass. The upper limit of the amount of sodium thiosulfate salt or thiosulfate ion-containing solution to be added is not particularly limited, but may be 1000 times or less by mass in terms of sodium thiosulfate pentahydrate.

The sodium thiosulfate salt or thiosulfate ion-containing solution is preferably added to the iridium-containing hydrochloric acid solution so that the amount is 10 g/L or more in terms of sodium thiosulfate pentahydrate. By adding a sodium thiosulfate salt or a solution containing thiosulfate ions in an amount of 10 g/L or more in terms of sodium thiosulfate pentahydrate, the thiosulfate ions function more effectively and the precipitation reaction becomes more efficient. proceed well. The sodium thiosulfate salt or thiosulfate ion-containing solution is added to the hydrochloric acid solution containing iridium in an amount of 15 g/L or more in terms of sodium thiosulfate pentahydrate, more preferably 20 g/L or more. It is more preferable to add to the hydrochloric acid solution containing iridium so that In addition, if the amount of sodium thiosulfate salt or thiosulfate ion-containing solution is too large, sulfur generated during acid decomposition may be mixed. It is preferably added to a hydrochloric acid solution containing iridium.

Thiosulfate ions tend to decompose into sulfur and sulfite ions under acidic conditions. Furthermore, if there is an oxidizing substance, it reacts with it, and some transition metal ions such as copper form sulfide and precipitate. Therefore, it is preferable to precipitate other contaminant elements with sulfur dioxide in advance. Other contaminants are, for example, selenium and tellurium. From this point of view, when the iridium-containing hydrochloric acid acid liquid contains at least one of selenium and tellurium, sulfur dioxide or an aqueous solution of sulfur dioxide is added in advance to the iridium-containing hydrochloric acid acid liquid to obtain selenium and tellurium. is preferably adjusted to 100 mg/L or less. Then, it is preferable to add the thiosulfate sodium salt or the thiosulfate ion-containing solution to the hydrochloric acid solution containing iridium with the total concentration of selenium and tellurium adjusted. It is more preferable to previously adjust the total concentration of selenium and tellurium to 50 mg/L or less, and even more preferably to 10 mg/L or less.

The precipitated iridium-containing material is separated into iridium and other contaminants by a known method after solid-liquid separation. For example, there is a method of separating and recovering iridium by solvent extraction after oxidation and dissolution. In this oxidized solution, the iridium is sufficiently concentrated to allow recovery by known solvent extractions.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these.

(Experimental example 1)
Copper was dissolved and removed with sulfuric acid from the electrolytic sediment derived from the copper electrorefining process of copper smelting. Concentrated hydrochloric acid and 60% hydrogen peroxide solution were added to dissolve the solution, followed by solid-liquid separation to obtain a pregnant solution (PLS). The PLS was cooled to 6° C. to precipitate and remove base metals. Gold was extracted by adjusting the acid concentration to 2N or more and mixing DBC (dibutyl carbitol) and PLS. The PLS after the gold extraction was heated to 70° C., and sulfur dioxide was blown into the PLS to reduce and remove the noble metals, selenium, and tellurium. This was subjected to solid-liquid separation to obtain a hydrochloric acid acid solution containing iridium.

The iridium concentration of the hydrochloric acid solution containing iridium was 26 mg/L. The iridium-containing liquid contained 1.5 g/L of arsenic, 6 mg/L of selenium, and 18 mg/L of tellurium as other elements. 200 mL of the iridium-containing hydrochloric acid solution was taken, heated to 60° C. or 80° C., and the amount (g) of sodium thiosulfate pentahydrate shown in Table 1 was added and stirred. Sampling was done once every 30 minutes while stirring. After 2 hours from the start of stirring, the reaction was stopped and the resulting precipitate was subjected to solid-liquid separation. The iridium concentration of the solution after separation (after filtration) was quantified.
All reagents were special grade manufactured by Wako Pure Chemical Industries, Ltd. The element concentration in the solution was measured by ICP-OES (SPS3100 manufactured by Seiko) after adjusting the concentration to 50 ml by taking 2 ml of the solution. Table 1 shows the evaluation results.

It can be seen from the results in Table 1 that the addition of sodium thiosulfate for reduction greatly reduces the concentration of iridium in the liquid. Since the amount added is 2 g or more, it can be seen that a high effect can be obtained when 10 g/L or more of sodium thiosulfate pentahydrate is added. Also, the liquid temperature of the hydrochloric acid solution containing iridium is very good at 60°C or higher, and the effect is even higher at 80°C.

Further, when the amount of sodium thiosulfate added increases, arsenic tends to precipitate and the concentration in the liquid tends to decrease, so the amount added is preferably 30 g/L or less as sodium thiosulfate pentahydrate.

(Experimental example 2)
200 ml of the same iridium-containing hydrochloric acid solution as in Experimental Example 1 was taken. It was heated to the temperature shown in Table 2. Next, 1 g of copper powder was added, and selenium and tellurium were removed by cementation. Next, 4 g of sodium thiosulfate pentahydrate was added to initiate the reaction, and 30 minutes and 60 minutes after the initiation of the reaction, samples were collected to terminate the reaction. For comparison, the time course of reduction with a mixture of sulfur dioxide and air (15% sulfur dioxide) at 80 to 85° C. is also shown.
Subsequent operations are in accordance with Experimental Example 1. Table 2 shows changes in the concentration of iridium over time.

From the results in Table 2, the effect was observed when the iridium-containing hydrochloric acid solution was heated to a temperature of 40°C, and the concentration of iridium was clearly reduced at a temperature of 60°C or higher. It can be seen that the temperature effect becomes significant at 70° C. or higher. At any temperature, the effect was more clearly shown than that of comparative sulfur dioxide. However, in the reduction with sulfur dioxide, the amount of evaporation was large and the final liquid volume was concentrated to 150 mL, so the apparent concentration increased with the passage of time.

(Experimental example 3)
No. 1 in Experimental Example 1 above. The amount of sodium thiosulfate added in 1 to 4 was converted to the unit of "g/L", and the relationship between this and the precipitation rate of iridium was plotted on a graph. In addition, in the graph, the iridium precipitation rate was measured in the same manner as in Experimental Example 1 with sodium thiosulfate added in an amount of 2 g/L, and plotted in the same graph. These results are shown in the graph of sodium thiosulfate addition amount (g)-Ir precipitation rate (%) in FIG.
As is clear from the graph, the rate of increase in the Ir precipitation rate was greatly improved when the added amount of sodium thiosulfate was 10 g/L or more.

Claims (5)

A hydrochloric acid solution containing iridium is heated to 40° C. or higher, and a sodium thiosulfate salt or a solution containing thiosulfate ions is added to iridium in the hydrochloric acid solution 100 times by mass in terms of sodium thiosulfate pentahydrate. A method for recovering iridium by adding to the above hydrochloric acid acid solution. 2. The solution according to claim 1, wherein the sodium thiosulfate salt or the solution containing thiosulfate ions is added to the acidic hydrochloric acid solution containing iridium so as to be 10 g/L or more in terms of sodium thiosulfate pentahydrate. Iridium recovery method. When the iridium-containing hydrochloric acid solution contains at least one of selenium and tellurium, sulfur dioxide or an aqueous solution of sulfur dioxide is added in advance to the iridium-containing hydrochloric acid solution so that the total concentration of selenium and tellurium is 100 mg. /L or less;
3. The method for recovering iridium according to claim 1, wherein the sodium thiosulfate salt or the solution containing thiosulfate ions is added to the hydrochloric acid solution containing the iridium in which the total concentration of selenium and tellurium is adjusted. The method for recovering iridium according to any one of claims 1 to 3, wherein the hydrochloric acid solution containing iridium is heated to 60°C or higher. The method for recovering iridium according to any one of claims 1 to 4, wherein the hydrochloric acid solution containing iridium contains arsenic.