Methods for recovering valuable metals

Abstract

To provide a method of recovering valuable metals from wastewater containing at least platinum, tellurium, antimony, and tin, by which platinum in the wastewater can efficiently and effectively be separated from antimony and tin and then recovered.SOLUTION: The present invention provides a method of recovering valuable metals from wastewater containing at least platinum, tellurium, antimony, and tin, which includes a step of reducing the wastewater by adding a hydrazine-containing reducing agent to the wastewater, wherein the amount of pure hydrazine added to 100 L of wastewater is 1.10×60 / 100 L or less. The wastewater to be treated includes the wastewater subjected to a purification process of recovering platinum group elements by refining the platinum group element concentrate obtained by concentrating the platinum group elements contained in a copper electrolytic slime, and a wastewater treatment process in which the platinum group elements remaining in the residual liquid obtained after the purification process are concentrated to obtain platinum group lees, resulting in the separation of platinum group lees.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for recovering valuable metals from wastewater obtained by treating copper electrolytic slime and the like.

Background Art

[0002] In the copper electrolysis process in the copper smelting process, electrolytic copper is obtained as the main product, and copper electrolytic slime is obtained as an intermediate product.

[0003] Valuable metals such as gold (Au), silver (Ag), platinum group metals (PGM), selenium (Se), tellurium (Te), etc. contained in the copper concentrate are concentrated in the intermediate product copper electrolytic slime, and by treating it in a process that combines processes such as chlorine leaching and solvent extraction (hereinafter, also referred to as "valuable metal recovery process"), these valuable metals can be separated and recovered.

[0004] In the valuable metal recovery process, it is common to design so as to reduce the interest burden by shortening the period during which precious metals stay in the system by recovering precious metals at the initial stage.

[0005] For example, in Patent Document 1, when recovering precious metals from copper electrolytic slime, the copper electrolytic slime is chlorine-leached to obtain a leachate in which gold, platinum group elements, selenium, and tellurium are leached, and then gold is extracted from the leachate and reduced to recover gold as a single substance. After that, platinum group elements are extracted from the raffinate after gold extraction and concentrated to obtain an intermediate product (hereinafter, also referred to as "platinum group element concentrate (PGM concentrate, PGMconc.)"), and selenium, tellurium, etc. are sequentially recovered from the remainder. The technology is disclosed.

[0006] Note that FIG. 1 is a diagram showing the overall flow of recovering valuable metals from copper electrolytic slime.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

[0008] The technology disclosed in Patent Document 1 mentioned above is a useful technology that allows for the selective and high-yield recovery of gold, platinum group elements, selenium, and tellurium from copper electrolytic slime through only a simple wet treatment operation.

[0009] Incidentally, in such conventional technologies, as shown in Figure 2, the PGM purification wastewater, which is the residue after recovering platinum group elements in the PGM purification process for purifying platinum group element concentrates, contains platinum group elements that could not be recovered. Therefore, in order to recover these platinum group elements, the platinum group elements are concentrated in the PGM wastewater treatment process, and the resulting PGM wastewater sediment is repeatedly treated within the system.

[0010] On the other hand, the AuSb-SX back extract (hereinafter referred to as "PGM wastewater"), which is wastewater from the "AuSb-SX process" within the PGM purification pretreatment process that includes steps such as chlorine leaching, AuSb-SX, Pd-SX, and Bi-SX, contains platinum and tellurium, as well as unwanted elements such as antimony and tin.

[0011] For example, if PGM wastewater is treated in a PGM wastewater treatment process, the quality of antimony and tin in the PGM wastewater sediment increases. This leads to an increased impurity load when repeatedly treating the PGM wastewater sediment and a deterioration in filtration efficiency during leaching. Therefore, PGM wastewater has no choice but to be treated in a tellurium recovery process, which has resulted in the loss of platinum contained in the PGM wastewater.

[0012] In the tellurium recovery process, tellurium and residual selenium in the selenium recovery solution after recovering precious metals from copper electrolytic slime are recovered as sediment by reducing them using the reducing power of sulfur dioxide. At the same time, the wastewater containing precious metals, selenium, and tellurium from the process is treated to recover these substances.

[0013] This invention has been proposed in view of the above conventional circumstances, and aims to provide a method for recovering valuable metals from wastewater obtained by processing copper electrolytic slime, etc., which contains at least platinum, tellurium, antimony, and tin, in which platinum in the wastewater can be efficiently and effectively separated and recovered from antimony and tin. [Means for solving the problem]

[0014] As a result of diligent research, the inventors of this invention have discovered that by using hydrazine as a reducing agent in wastewater containing platinum, tellurium, antimony, and tin, and by adding hydrazine in a "specific amount," platinum can be preferentially reduced at a high rate, while the reduction of antimony and tin can be suppressed. This led to the completion of the present invention.

[0015] (1) The first aspect of the present invention is a method for recovering valuable metals from wastewater containing at least platinum, tellurium, antimony, and tin, comprising the step of adding a reducing agent containing hydrazine to the wastewater and performing a reduction treatment, wherein the amount of pure hydrazine added per 100 L of wastewater is 1.10 × 60 / 100 L or less.

[0016] (2) The second invention of the present invention is a method for recovering valuable metals, wherein the wastewater includes wastewater after separating the platinum group precipitate, which is obtained by purifying a platinum group element concentrate obtained by concentrating platinum group elements contained in copper electrolytic slime and recovering the platinum group elements, and a wastewater treatment step which is obtained by concentrating the platinum group elements remaining in the residual liquid obtained after the purification step to obtain platinum group precipitate.

[0017] (3) The third invention of the present invention is a method for recovering valuable metals, wherein, in the first or second invention, the amount of hydrazine purity added to 100 L of wastewater is 0.9 × 60 / 100 L or more.

[0018] (4) The fourth invention of the present invention is a method for recovering valuable metals in the first or second invention, wherein the hydrazine is a 60% concentration solution.

Advantages of the Invention

[0019] According to the present invention, platinum in wastewater can be efficiently and effectively separated and recovered from antimony and tin.

Brief Description of the Drawings

[0020] [Figure 1] It is a diagram showing the overall flow of recovering valuable metals from copper electrolytic slime. [Figure 2] It is a process diagram showing the process in which wastewater (PGM wastewater) is recovered through a purification process of purifying a platinum group element concentrate to recover platinum group elements and a wastewater treatment process of concentrating platinum group elements remaining in the residual liquid obtained from the purification process to obtain a platinum group precipitate. [Figure 3] It is a graph plotting the reduction rate of each element in PGM wastewater when reduction treatment is performed by gradually adding a 60% concentration hydrazine solution to 100 L of PGM wastewater.

Embodiments for Carrying Out the Invention

[0021] Hereinafter, specific embodiments of the present invention (hereinafter also referred to as "the present embodiments") will be described in detail. Note that the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of not changing the gist of the present invention.

[0022] The method according to the present embodiments is a method for recovering valuable metals from wastewater containing at least platinum (Pt), tellurium (Te), antimony (Sb), and tin (Sn). For example, the wastewater to be treated includes wastewater discharged by performing purification treatment or the like on copper electrolytic slime obtained as an intermediate product in the copper electrolysis process in the copper smelting process.

[0023] Specifically, the wastewater to be treated in the method according to this embodiment is obtained by purifying a platinum group element concentrate (PGM concentrate) obtained by concentrating platinum group elements contained in copper electrolysis slime to recover platinum group elements, and a wastewater treatment step of concentrating platinum group elements remaining in the residual liquid obtained through the purification step to obtain a platinum group precipitate, and can include the wastewater (PGM wastewater) after separating the platinum group precipitate.

[0024] As shown in Table 1 below, PGM wastewater is composed mainly of Pt, Sb, and Sn, and contains Te at a concentration that can potentially be recovered by reduction, excluding iron (Fe) which is an impurity. Although not particularly limited, PGM wastewater preferably has a Pt content of 0.1 g / L or more from the perspective of the reactivity of the reduction treatment described in detail later.

[0025]

Table 1

[0026] Conventionally, when attempting to reduce and recover Pt remaining in PGM wastewater, not only Pt which is the recovery target but also impurity elements such as Sb and Sn are simultaneously reduced, and there was a possibility that Sb and Sn would be mixed into the precipitate formed by concentrating Pt. Therefore, PGM wastewater was treated in the tellurium (Te) recovery process, and only Te was recovered, and valuable metals such as Pt in the PGM wastewater became recovery losses.

[0027] Therefore, as a result of intensive studies by the inventors in view of such circumstances, by using hydrazine as a reducing agent and adding the hydrazine in a specific addition amount for reduction treatment, Pt in the PGM wastewater can be preferentially reduced, and then Te is well reduced, and it was found that the reduction of Sb and Sn does not proceed. In other words, it was discovered that by adding hydrazine in a specific range of addition amounts to the composition liquid as shown in Table 1 above, Pt is preferentially reduced and the reduction of Sb and Sn is postponed.

[0028] In other words, the method according to this embodiment includes a step of reducing PGM wastewater by adding a reducing agent containing hydrazine (reduction step). In this reduction step, the reducing agent containing hydrazine is added at a rate of 1.10 × 60 / 100L or less in terms of the amount of pure hydrazine added, per 100L of PGM wastewater.

[0029] In this way, by adding hydrazine at a ratio of 1.1 × 60 / 100L or less per 100L of PGM wastewater and performing reduction treatment, the Pt contained in the PGM wastewater can be preferentially and effectively reduced at a high reduction rate, while the reduction of Sb and Sn can be suppressed. This prevents the contamination of Pt-concentrated precipitate with Sb and Sn, and effectively reduces the loss of Pt during recovery.

[0030] As mentioned above, the amount of reducing agent containing hydrazine added in the reduction process should be 1.10 × 60 / 100L or less in terms of the amount of pure hydrazine added. For example, when using a 60% hydrazine solution, the amount of pure hydrazine added per 100L of PGM wastewater should be 1.10L or less.

[0031] Figure 3 shows a graph plotting the reduction rates of each element when a reduction treatment is performed by gradually adding a 60% hydrazine solution to 100 L of PGM wastewater.

[0032] In the graph in Figure 3, we first focus on Pt, Sb, and Sn. It is shown that Pt can be reduced to a rate of over 95% by adding the reducing agent hydrazine, and that if the amount of hydrazine added (addition ratio per 100L of PGM wastewater) exceeds 1.00, almost the entire amount is reduced. 。

[0033] Furthermore, focusing on Te, when hydrazine, a reducing agent, is added, the reduction rate is insufficient at low addition ratios of 0.50 or less, resulting in a reduction rate of 50% or less. 。

[0035] The hydrazine (solution) used as the reducing agent is not particularly limited. For example, a 60% hydrazine solution can be used because it is readily available. [Examples]

[0036] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0037] The copper electrolytic slime, an intermediate product obtained from the copper electrolysis process in the copper smelting process, was subjected to a purification process to recover platinum group elements by refining the platinum group element concentrate (PGM concentrate), and a wastewater treatment process to obtain platinum group element precipitates by concentrating the platinum group elements remaining in the residual liquid obtained after the purification process. The wastewater (PGM wastewater) after separating the platinum group element precipitates was then recovered. Table 2 below shows the composition of the PGM wastewater.

[0038] [Table 2]

[0039] The recovered PGM wastewater was treated by adding a 60% hydrazine solution to it for reduction. The amount of 60% hydrazine solution (pure content) added in each example and comparative example (addition ratio per 100L of PGM wastewater) is shown in Table 3 below.

[0040] Table 3 below shows the reduction rates of each element in PGM wastewater by reduction treatment using hydrazine solution.

[0041] [Table 3]

[0042] table 3 As shown in the results, hydra is used for 100L of PGM wastewater. n addition ratio to 1.1 0 or moreBy doing so, it can be seen that the reduction of impurity elements such as antimony (Sb) and tin (Sn) is suppressed, while platinum (Pt) and tellurium (Te) can be preferentially reduced. It can be seen that when the hydrazine addition ratio exceeds 1.10, Sb and Sn begin to be reduced. It can also be seen that when the addition ratio exceeds 0.90, the reduction rate becomes 95% or higher. Furthermore, it is preferable to set the lower limit of the amount of pure hydrazine added per 100L of PGM wastewater to 0.90 × 60 / 100L or higher. For example, when using a 60% hydrazine solution, the lower limit of the amount added is 0.90 or higher. As shown in Table 3, by setting the amount of hydrazine added per 100L of PGM wastewater to 0.90 × 60 / 100L or higher, the reduction rate of Pt can be made 98% or higher. In addition, the reduction rate of tellurium can also be made at a high rate of 95% or higher, and considering the market price of Te, it may not necessarily be necessary to treat the residual liquid after reduction treatment with hydrazine in a tellurium recovery process, thus improving treatment efficiency, which is more preferable.

[0043] Furthermore, it is preferable that the amount of pure hydrazine added per 100 L of PGM wastewater is 0.90 L or more, which allows for more effective reduction of Pt and Te.

Claims

1. A method for recovering valuable metals by separating platinum from antimony and tin from wastewater containing at least platinum, tellurium, antimony, and tin, The process includes adding a reducing agent containing hydrazine to the wastewater and performing a reduction treatment, The amount of hydrazine purity added to 100 L of wastewater shall be 0.75 × 60 / 100 L or more and 1.10 × 60 / 100 L or less. The wastewater is the wastewater after a purification process in which platinum group elements contained in copper electrolytic slime are concentrated to obtain a platinum group element concentrate, and the platinum group elements are recovered by purifying the concentrate; and a wastewater treatment process in which platinum group elements remaining in the residual liquid obtained after the purification process are concentrated to obtain a platinum group precipitate, and the platinum group precipitate is separated. Methods for recovering valuable metals.

2. The amount of hydrazine pure content added to 100 L of wastewater shall be 0.90 × 60 / 100 L or more. A method for recovering valuable metals according to claim 1.

3. The hydrazine is a 60% solution. A method for recovering valuable metals according to claim 1.

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