Method for extracting Fe ions and Ni ions, method for extracting Fe ions and Cu ions, and method for smelting Cu.

Abstract

To provide a method for efficiently extracting Fe from an aqueous solution comprising free acid such as H2SO4 and having a pH value of 0 or less.SOLUTION: The present invention provides a method for extracting Fe ions from an aqueous solution comprising free acid, in which the aqueous solution has its pH value set to 0 or less, and a solvent extraction technique using a cation-releasing extractant allows extracting Fe ions from the aqueous solution.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for extracting Fe ions from a strong acid solution containing a free acid such as H2SO4 and a method for smelting non-ferrous metals using the same.

Background Art

[0002] For example, when attempting to recover useful metals from electrolytic solutions, electrolytic tail solutions, and sludge generated in the electrolysis process of non-ferrous smelting, the electrolytic solutions and electrolytic tail solutions may contain a free acid such as H2SO4 and may also contain Fe ions. Several proposals have been made for the purpose of recovering useful metals from these solutions.

[0003] Patent Document 1 describes a method in which acid is added to nickel-containing waste liquid sludge to dissolve the solid content, calcium carbonate is then added, and the iron content (Fe 3+ 、Fe 2+ ) in the sludge solution is oxidized from Fe 2+ to Fe 3+ , and then iron-containing gypsum is removed by pH adjustment and filtration to obtain a nickel stock solution.

[0004] Patent Document 2 describes a method in which an oxidizing agent and a neutralizing agent are added to an acidic nickel aqueous solution containing zinc and iron as impurities, for example, a nickel raw material dissolution solution, to increase the pH, and zinc together with iron is removed as a precipitate to recover a high-purity nickel aqueous solution.

[0005] Patent Document 3 describes a method for removing impurity metal ions in a copper electrolytic solution, in which a chelating resin having a divinylbenzene-based copolymer, an epoxy resin, a phenol resin, a resorcin resin, or a vinyl chloride resin as a resin matrix and at least one of an aminoalkylene phosphoric acid group or its salt, an iminoalkylene phosphoric acid group or its salt, an alkylene phosphoric acid group or its salt, a phosphoric acid group or its salt, or an amidooxime group as a functional group is brought into contact with a copper electrolytic solution, and the impurity metal ions are adsorbed and removed by the chelating resin.

[0006] Patent Document 4 describes a method for purifying a liquid, which includes the steps of: contacting an electrolyte containing tin obtained in a copper electrolytic refining process with a chelate resin having phosphonic acid and sulfonic acid as functional groups to adsorb metal ions in the electrolyte onto the chelate resin; washing the chelate resin with water; and passing an eluent through the chelate resin to elute metal ions from the chelate resin. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 4216657 [Patent Document 2] Patent No. 3722254 [Patent Document 3] Special Publication No. 5-5901 [Patent Document 4] Patent No. 5539823 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, after reviewing the aforementioned prior art documents, the inventors came to the conclusion that there are the following problems. In the proposals described in Patent Documents 1 and 2, when attempting to neutralize a NiSO4 solution, CuSO4 solution, or CoSO4 solution containing free acids such as H2SO4 to extract Fe ions, if the H2SO4 concentration is high, the amount of chemicals used and the amount of by-products such as gypsum increase, making it difficult to implement economically. The proposals described in Patent Documents 3 and 4 are applied to highly acidic solutions with a high H2SO4 concentration of 200 g / L, but they are not particularly efficient methods for extracting Fe ions.

[0009] The present invention has been made under the above-described circumstances, and the problem to be solved is to provide a method for efficiently extracting Fe ions from a strong acid solution containing Fe ions and a free acid such as H2SO4. More specifically, while a method for simply and efficiently extracting Fe ions contained in a strong acid solution is desired, a treatment method for extracting the Fe ions from the strong acid solution into an organic phase using a solvent extraction method for extracting and partitioning metal elements by utilizing the phase separation between an aqueous phase and an organic phase is provided. In the present invention, "Fe ions" means 2+ Fe 3+ and includes Fe.

Means for Solving the Problem

[0010] To solve the above problems, as a result of intensive research by the present inventors, a configuration was conceived to extract the Fe ions from a strong acid solution containing Fe ions and a free acid such as H2SO4 by a solvent extraction method using a cation-releasing extractant such as H + . Conventionally, it has been known that by using a cation-releasing extractant such as H + and controlling the pH value of the aqueous solution in the range of about 0.2 to 8, the metal species to be extracted into the organic phase can be selected However, the present inventors have found that by using a cation-releasing extractant such as H + and paying attention to the free H2SO4 concentration in the strong acid aqueous solution, it is possible to efficiently extract Fe ions from an aqueous phase, which is a strong acid solution having a free H2SO4 concentration higher than these conventional ranges and containing Fe ions (for example, a strong acid solution having a pH value in the range of 0 or less), into the organic phase, and thus completed the present invention.

[0011] That is, a first invention for solving the above problems is a method for extracting Fe ions from a strong acid solution containing a free acid, which extracts Fe ions from a strong acid solution containing 98 g / L or more of free H2SO4 by a solvent extraction method using a cation-releasing extractant. A second invention is The method for extracting Fe ions from a strong acid solution containing a free acid as described in the first invention, wherein the solution contains 150 g / L or more of free H2SO4. The third invention is, The method for extracting Fe ions from a strong acid solution containing a free acid as described in the first or second invention, wherein the solution contains 150 g / L or more and 552 g / L or less of free H2SO4. The fourth invention is, This method for extracting Fe ions from a strong acid solution containing a free acid is comprising mixing an organic phase containing Fe ions obtained by the method for extracting Fe ions from a strong acid solution containing a free acid described in any of the first to third inventions with an acid weaker than the free acid, performing a solvent extraction, and back-extracting the Fe ions into an aqueous phase. The fifth invention is, This is a method for smelting non-ferrous metals, wherein the method for extracting Fe ions from a strong acid solution containing free acid, as described in any of the first to fourth inventions, is used as the method for extracting Fe ions from a strong acid solution containing free acid, which is generated in the process and contains 98 g / L or more of free H2SO4. The sixth invention is, The aforementioned solution is the solution obtained after crystallizing CuSO4 from the Cu electrolytic tail liquid. The extractant is contained in the organic phase after solvent extraction of Ni from a solution obtained by leaching Ni from a Ni-containing raw material using a cationic-releasing extractant, or it is contained in the organic phase after solvent extraction of Cu from a solution obtained by leaching Cu from a Cu-containing raw material using a cationic-releasing extractant. This is the method for smelting non-ferrous metals according to the fifth invention. [Effects of the Invention]

[0012] According to the present invention, Fe ions can be efficiently extracted from a strong acid solution containing 98 g / L or more of free H2SO4. [Brief explanation of the drawing]

[0013] [Figure 1] This is an example of a process flow when the present invention is applied to a non-ferrous metal refining process. [Figure 2]This is an example of a different process flow when the present invention is applied to a non-ferrous metal refining process. [Modes for carrying out the invention]

[0014] The inventors of this invention have studied a method for efficiently extracting Fe ions from a strong acid solution containing 98 g / L or more of free H2SO4 (for example, a strong acid solution with a pH of 0 or less). + We devised a configuration in which Fe ions are extracted into an organic phase by solvent extraction from an aqueous phase, which is a strong acid solution containing Fe ions and free H2SO4, using a cationic extractant such as [specific example of a cationic extractant]. Traditionally, H + It was known that with cationic extractants such as H, the metal species to be extracted into the organic phase can be selected by controlling the pH value of the aqueous solution within a range of approximately 0.2 to 8. However, the present inventors have discovered that H + By using an organic phase containing a cationic extractant, we discovered that Fe ions can be efficiently extracted into the organic phase from an aqueous phase, which is a strong acid solution containing 98 g / L or more of Fe ions and free H2SO4 (for example, a strong acid solution with a pH of 0 or less), which differs from the conventional range. This discovery led to the completion of the present invention.

[0015] The present invention will be described below in the following order: 1. the solution to be treated, 2. the extractant, 3. the mixing method, 4. the effect of solvent extraction, 5. the back extraction of Fe in the organic phase, and 6. examples of the application of the present invention to non-ferrous metal smelting processes, etc.

[0016] 1. Solution to be treated The solution to be treated in this invention is free sulfate ions (SO4 2- It contains 96 g / L or more, preferably 147 g / L or more of ) which translates to 98 g / L or more, preferably 150 g / L or more of free H2SO4. On the other hand, free sulfate ions (SO4 2-The pH is preferably 541 g / L or less, which corresponds to 552 g / L or less of free H2SO4. The pH is 0 or less (preferably -0.10 or less, more preferably -0.20 or less, most preferably -0.30 or less), and it is a strong acid solution containing valuable metals such as Co (cobalt), Cu (copper), and Ni (nickel), as well as Fe ions. In this invention, there is no particular limit to the lower limit of the pH of the solution to be treated, but for example, it is preferably -0.8 or higher. Furthermore, as will be described later, when the concentration of free H2SO4 in the solution to be treated is 98 g / L, the pH value of the solution is 0.00. Examples of the strong acid solutions to be treated include solutions used in the copper electrolytic refining and electrolytic extraction processes in the smelting process of non-ferrous metals (sometimes referred to as "Cu electrolyte" in this invention), solutions for recovering copper sulfate from solutions derived from the Cu electrolytic process, the solutions after recovery (sometimes referred to as "Cu crystallization solution" in this invention), solutions used for crystallization to recover nickel sulfate, or solutions after crystallization (sometimes referred to as "Ni crystallization solution" in this invention).

[0017] 2. Extractant In this invention, H is used as the extractant. + Cationic extractants that release ions or other substances can be preferably used. It has been known conventionally that in solvent extraction operations using these cationic extractants, the type of metal extracted can be selected by controlling the pH value of the solution.

[0018] H + Cationic-releasing extractants that release ions include phosphoric acid-based di(2,4,4-trimethylpentyl)phosphinic acid, bis(2,4,4-trimethylpentyl)phosphinic acid (commercially available as "CYANEX272" manufactured by CYTEC, which may be referred to as "CYANEX272" in this invention), di-2-ethylhexyl phosphoric acid (commercially available as "D2EHPA" manufactured by Solvey, which may be referred to as "D2EHPA" in this invention), and carboxylic acid-based C9H19 COOH (such as "VA-10" manufactured by Shell Chemical Co., Ltd., which is a commercially available product; in this invention, it may be referred to as "VA-10"), etc., can be preferred.

[0019] Furthermore, the cationic-releasing extractant according to the present invention is H + It does not have to be a so-called chelating agent that releases ions, etc., but has a mechanism to sequester metals (ions). For example, it does not have to be a chelating resin.

[0020] Furthermore, kerosene can preferably be used as the solvent for the organic phase containing the aforementioned extractant. The content of the extractant in the organic phase is preferably 0.1% by mass or more and 80% by mass or less.

[0021] 3.Mixing method For mixing the aqueous phase and organic phase in solvent extraction, mixing methods commonly used in solvent extraction methods can be employed, such as stirring with a stirrer or agitator, shaking with a reciprocating shaker, or manual shaking using a separatory funnel.

[0022] 4. Effects of solvent extraction The solvent extraction method described above allows for the extraction of Fe ions contained in the aqueous phase into the organic phase. Even if the aqueous phase contains Fe ions, Co ions, Cu ions, Ni ions, etc., Fe ions can be selectively extracted by selecting the appropriate extractant and controlling the pH value. When using a cationic extractant such as CYANEX272, it is preferable that the pH value of the aqueous phase at the initial stage of solvent extraction be between -0.8 and 0.00.

[0023] Details will be explained in Example 1, but the reagent contains H2SO4 as a free acid, and furthermore, Fe 2+ and Fe 3+ A sample of the solution to be treated containing was prepared. This sample of the solution to be treated was made into an aqueous phase and mixed with an organic phase containing a cation-releasing extractant, for example CYANEX272, and Fe 2+and Fe 3+ Upon extraction, the Fe contained in the sample solution being treated was found to be 2+ Approximately 50% by mass of Fe 3+ It was found that approximately 60% by mass of the substance was extracted into the organic phase. During this process, sulfur (S) was also extracted into the organic phase, and the pH value of the aqueous phase increased.

[0024] Furthermore, as will be explained in detail in the examples, Cu electrolyte or Ni crystallized solution collected from the Cu smelting process was used as the sample solution to be treated. This sample solution was used as the aqueous phase and mixed with an organic phase containing various cation-releasing extractants. When Fe ions were extracted into the organic phase, it was found that Fe ions were selectively extracted at a rate of approximately 10-70% by mass. On the other hand, Co, Cu, Ni, etc., contained in the sample solution were extracted into the organic phase at a maximum rate of only 10%, indicating that Fe ions are selectively extracted into the organic phase in this invention.

[0025] 5. Back extraction of Fe from the organic phase The present inventors have conceived of a configuration in which Fe is back-extracted from the organic phase to the aqueous phase by mixing the organic phase containing Fe produced by performing the solvent extraction according to the present invention as described above with an acid weaker than the free acid (for example, an aqueous solution of HCl, a diluted aqueous solution of H2SO4, or an aqueous solution of HNO3).

[0026] This configuration is preferable from the viewpoint of contributing to the regeneration and reuse of the organic phase by back-extracting Fe from the organic phase. As the acidic aqueous solution, diluted H2SO4 aqueous solution, HCl aqueous solution, or diluted HNO3 aqueous solution can be used. As for the concentration of the acidic aqueous solution, if it is an H2SO4 aqueous solution, the H2SO4 concentration should be less than 200 g / L, and if it is an HCl aqueous solution, it should be less than 360 g / L.

[0027] 6. Examples of application of the present invention to non-ferrous metal smelting processes, etc. The method for extracting Fe ions from a strong acid solution containing free acid according to the present invention, as described above, can be suitably used in non-ferrous metal smelting methods as a means for extracting Fe ions from a strong acid solution containing Fe ions, valuable metals, and free acid.

[0028] Furthermore, the present inventors have provided a method for extracting Fe ions from a strong acid solution containing free acid according to the present invention, wherein H is used as the organic phase for extracting Fe ions. + We conceived of a configuration that uses a cation-releasing extractant and an organic phase containing valuable metals such as Co, Cu, and Ni.

[0029] In other words, according to this configuration, for example, the solution to be treated is a strongly acidic solution such as Cu electrolyte or Ni crystallization post-solution, which is taken from the Cu smelting process described above. On the other hand, H obtained by processing various raw materials and scrap containing valuable metals + Prepare an organic phase containing a cation-releasing extractant and a valuable metal. Then, the solution to be treated, which is a strong acid solution, is converted into an aqueous phase, and H + By performing solvent extraction using a mixture of a cation-releasing extractant and an organic phase containing valuable metals, Fe ions in the solution to be treated are extracted into the organic phase, while valuable metals such as Co, Cu, and Ni in the organic phase are back-extracted into the solution to be treated. As a result, Fe ion extraction from the solution to be treated and the back extraction of valuable metals into the solution to be treated are performed simultaneously. Furthermore, it is preferable to add a configuration in which Fe is back-extracted from the organic phase to the aqueous phase by mixing the organic phase containing Fe with an aqueous solution of an acid weaker than the free acid mentioned above. The resulting Fe ions are extracted, and the solution containing the back-extracted valuable metals such as Co, Cu, and Ni is returned to the original Cu smelting process. Meanwhile, the organic phase from which the back-extracted valuable metals such as Co, Cu, and Ni, and the extracted Fe ions, can be repeatedly returned to the processing steps of various raw materials and scrap containing the original Co, Cu, Ni, etc., thereby enabling significantly more efficient processing.

[0030] The above example of an efficient processing flow will be explained with reference to Figures 1 and 2. In Figure 1, which shows an example of a process flow when the present invention is applied to a non-ferrous metal refining process, the flow in (A) involves a dry treatment (11) of the Cu smelting process, which involves secondary raw materials such as Cu ore and Cu-containing scrap according to conventional technology, and a self-smelting furnace-converter-refining furnace method, for example. The crude copper obtained from the refining furnace then becomes a Cu anode in Cu electrolysis (12), and Cu cathodes and CuSO4 are produced. One method for collecting CuSO4 is CuSO4 crystallization (13), in which CuSO4 is crystallized by utilizing the difference in solubility after further electrolytic purification called de-Cu electrolysis is performed on the Cu electrolyte (Cu electrolytic tail liquid), followed by concentration and cooling. Furthermore, crude NiSO4 crystallization (14) is performed to crystallize NiSO4, and the tail liquid is repeated to Cu electrolysis (12). Even after electrolytic purification, many Fe ions in the solution cannot be removed by the purification solution, which can lead to deterioration of the quality of CuSO4 and NiSO4. Therefore, in order to improve the quality of CuSO4 and NiSO4, it is necessary to remove some or all of the Fe ions from the solution after electrolytic purification.

[0031] On the other hand, in Figure 1, flow (B) is for extracting Ni from a raw material containing Ni, etc. First, the raw material containing Ni, etc. is leached using an acid solution (21) to obtain a leachate containing Ni, etc., which is then neutralized (22) to form an iron precipitate and undergo solid-liquid separation. Solvent extraction (23) (solvent extraction of substances other than Ni) is performed on the neutralized leachate as a purification step. In solvent extraction (23), the neutralized leachate is used as the aqueous phase, and H + As a cationic-releasing extractant, for example, an organic solvent containing D2EHPA is mixed as the organic phase, and solvent extraction is performed. As a result, Ni remains in the aqueous phase, while other heavy metals are extracted into the organic phase. Next, in solvent extraction (24), the aqueous phase in which Ni remains is used as the aqueous phase, and H + An organic solvent containing a cationic-releasing extractant is mixed as the organic phase, and solvent extraction is performed to extract Ni into the organic phase.

[0032] Next, in solvent extraction (25), the Ni crystallization solution, which is a strong acid solution produced in flow (A), is used as the aqueous phase, and H + A cation-releasing extractant is included and mixed with the organic phase from which Ni has been extracted, and solvent extraction is performed. As a result, Ni is back-extracted into the aqueous phase to become the Ni back-extracted solution, and Fe ions are extracted into the organic phase. Once solvent extraction (25) is complete, the Ni back-crystallized solution from which Ni has been back-extracted is returned to flow (A). The organic phase from which Fe ions were extracted was mixed with the aqueous phase, which is an aqueous solution of a weak acid, and back-extraction (26) was performed, H + The regenerated organic solvent containing cationic extractants such as is repeatedly used in the organic phase of solvent extraction (24), and the back-extracted liquid containing Fe is repeatedly used in the leaching (21) step into a raw material containing Ni, etc.

[0033] By implementing this configuration, the extraction of Fe ions from the Ni crystallization solution and the back extraction of the valuable metal Ni are performed simultaneously, which greatly contributes to improving productivity.

[0034] Next, we will explain a modified version of the flow described using Figure 1, with reference to Figure 2, which is an example of a different process flow when the present invention is applied to a non-ferrous metal refining process. In Figure 2, the flow of (A) is the same as the flow of (A) explained in Figure 1.

[0035] On the other hand, in Figure 2, flow (C) represents the extraction of Cu from a raw material containing Cu, etc. First, the raw material containing Cu, etc. is leached using an acid solution (31) to obtain a leachate containing Cu, etc., which is then neutralized (32) to form an iron precipitate and undergo solid-liquid separation. Next, in solvent extraction (33), the neutralized leachate is used as the aqueous phase, and an organic solvent containing a cation-releasing extractant is mixed as the organic phase. Solvent extraction is then performed to extract Cu into the organic phase.

[0036] Next, in solvent extraction (34), the Cu crystallization solution, which is a strong acid solution produced in flow (A), is used as the aqueous phase and mixed with the organic phase containing a cation-releasing extractant from which Cu has been extracted, and solvent extraction is carried out. As a result, Cu is back-extracted into the aqueous phase to become Cu back-extracted solution, and Fe ions are extracted into the organic phase. Once solvent extraction (34) is complete, the Cu back-extracted solution, from which Cu has been back-extracted, is returned to flow (A). The organic phase from which Fe ions were extracted was mixed with the aqueous phase, which is a weak acid aqueous solution, and back-extraction (35) was performed, H + The regenerated organic solvent containing a cationic extractant is repeatedly used in the organic phase of solvent extraction (33), and the back-extracted liquid containing Fe is repeatedly used in the leaching (31) step into a raw material containing Cu, etc.

[0037] By implementing this configuration, the extraction of Fe ions from the Cu crystallized liquid and the back extraction of the valuable metal Cu are carried out simultaneously, which greatly contributes to improving productivity in non-ferrous metal smelting methods. [Examples]

[0038] The present invention will be described in detail below with reference to the following examples. The present invention is not limited to the following examples.

[0039] [Example 1] In Example 1, a reagent was used to obtain a free acid containing H2SO4, and furthermore, Fe 2+ Or Fe 3+ Multiple samples containing H were prepared. Next, these samples and H + Mix with an organic phase containing the release-type extractant CYANEX272, and Fe 2+ Or Fe 3+ Fe was extracted into the organic phase using a solvent. 2+ Or Fe 3+ The extraction rate, pH values ​​at the beginning and end of the extraction process were measured. The following describes each sample individually.

[0040] <Sample (1-1)> Dilute H2SO4 with water to make an aqueous solution with an H2SO4 concentration of 150 g / L, then add FeSO4 to the aqueous solution. 4· Add 7H2O reagent (manufactured by Fujifilm Wako Pure Chemical Industries) to adjust the Fe concentration to 4.29 g / L. 2+ A sample (1-1) containing was obtained. The Fe of sample (1-1) 2+ The concentrations are listed in Table 1. Next, H + The release-type extractant CYANEX272 was diluted with kerosene (ExxonMobil, Exsol) to a 40% volume concentration to obtain an organic solvent.

[0041] Sample (1-1) was used as the aqueous phase and the aforementioned organic solvent as the organic phase. The mixture was mixed in a 100:100 ratio, and solvent extraction was performed by stirring with a stirrer equipped with a temperature control device until the aqueous and organic phases were mixed and became cloudy. During this time, concentrated H2SO4 was added to the mixture from the start of stirring until 5 minutes had passed to maintain the pH value of the aqueous and organic phase mixture at the start of stirring. Stirring was then stopped at 15 minutes from the start of stirring to separate the aqueous and organic phases, marking the end of the solvent extraction.

[0042] H2SO4 concentration in the aqueous phase at the start of stirring, Fe 2+ The concentration and pH values ​​are listed in Table 1. Furthermore, the Fe contained in the aqueous phase at the start and end of stirring 2+ The amounts of and S were measured using ICP and converted to concentrations (g / L) in the aqueous phase. Then, the amount of Fe in the aqueous phase was measured. 2+ From the concentrations of and S, use the following (Equation 1) to determine Fe 2+ The extraction rate of S was calculated. 2+ The extraction rates for S are shown in Table 1. Furthermore, the pH value of the aqueous phase at the endpoint was measured, and the H2SO4 concentration was calculated from this pH value using the following formula (Equation 2). The pH value and H2SO4 concentration are shown in Table 1. Extraction rate = [{Concentration in the initial aqueous phase (g / L) - Concentration in the final aqueous phase (g / L)} / Concentration in the initial aqueous phase (g / L)] × 100 ... (Equation 1) pH value = -LOG([H2SO4](mol / L))······(Equation 2) (However, when the H2SO4 concentration is 10 g / L or higher, i.e., when the pH value is less than 1, H2SO4 does not undergo two-stage dissociation.)

[0043] <Sample (1-2)> Sample (1-2) was obtained by performing the same procedure as for sample (1-1), except that the H2SO4 concentration in the initial aqueous phase was set to 389 g / L. The procedure was the same as for sample (1-1), except that sample (1-2) was used instead of sample (1-1).

[0044] H2SO4 concentration in the aqueous phase at the start of stirring, Fe 2+ The concentration and pH values ​​are listed in Table 1. And at the end point, Fe 2+ Table 1 shows the extraction rates of S, the pH value of the aqueous phase, and the H2SO4 concentration.

[0045] <Samples (1-3)> Sample (1-3) was obtained by performing the same procedure as for sample (1-1), except that the H2SO4 concentration in the initial aqueous phase was set to 715 g / L. The procedure was the same as for sample (1-1), except that sample (1-3) was used instead of sample (1-1).

[0046] H2SO4 concentration in the aqueous phase at the start of stirring, Fe 2+ The concentration and pH values ​​are listed in Table 1. And at the end point, Fe 2+ Table 1 shows the extraction rates of S, the pH value of the aqueous phase, and the H2SO4 concentration.

[0047] <Samples (1-4)> Sample (1-4) was obtained by performing the same procedure as for sample (1-1), except that the H2SO4 concentration in the initial aqueous phase was set to 993 g / L. The procedure was the same as for sample (1-1), except that sample (1-4) was used instead of sample (1-1).

[0048] H2SO4 concentration in the aqueous phase at the start of stirring, Fe 2+ The concentration and pH values ​​are listed in Table 1. And at the end point, Fe 2+ Table 1 shows the extraction rates of S, the pH value of the aqueous phase, and the H2SO4 concentration.

[0049] <Samples (1-5)> Sample (1-5) was obtained by performing the same procedure as for sample (1-1), except that the H2SO4 concentration in the initial aqueous phase was set to 1222 g / L. The procedure was the same as for sample (1-1), except that sample (1-5) was used instead of sample (1-1).

[0050] H2SO4 concentration in the aqueous phase at the start of stirring, Fe 2+ The concentration and pH values ​​are listed in Table 1. And at the end point, Fe 2+ Table 1 shows the extraction rates of S, the pH value of the aqueous phase, and the H2SO4 concentration.

[0051] <Samples (1-6)> Dilute H2SO4 with water to make an aqueous solution with an H2SO4 concentration of 150 g / L. Then, add Fe2(SO4)3·nH2O reagent (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to this aqueous solution to make the Fe concentration 4.34 g / L. 3+ Samples (1-6) containing the Fe of sample (1-6) were obtained. 3+ The concentrations are listed in Table 2. The procedure was the same as for sample (1-1), except that sample (1-6) was used instead of sample (1-1).

[0052] H2SO4 concentration in the aqueous phase at the start of stirring, Fe 3+ The concentration and pH values ​​are listed in Table 2. And at the end point, Fe 3+ Table 2 shows the extraction rates of S, the pH value of the aqueous phase, and the H2SO4 concentration.

[0053] <Samples (1-7)> Sample (1-7) was obtained by performing the same procedure as for sample (1-6), except that the H2SO4 concentration in the initial aqueous phase was set to 389 g / L. The procedure was the same as for sample (1-6), except that sample (1-7) was used instead of sample (1-6).

[0054] H2SO4 concentration in the aqueous phase at the start of stirring, Fe 3+ The concentration and pH values ​​are listed in Table 2. And at the end point, Fe 3+ Table 2 shows the extraction rates of S, the pH value of the aqueous phase, and the H2SO4 concentration.

[0055] <Samples (1-8)> Sample (1-8) was obtained by performing the same procedure as for sample (1-6), except that the H2SO4 concentration in the initial aqueous phase was set to 715 g / L. The procedure was the same as for sample (1-6), except that sample (1-8) was used instead of sample (1-6).

[0056] H2SO4 concentration in the aqueous phase at the start of stirring, Fe 3+ The concentration and pH values ​​are listed in Table 2. And at the end point, Fe 3+ Table 2 shows the extraction rates of S, the pH value of the aqueous phase, and the H2SO4 concentration.

[0057] <Samples (1-9)> Sample (1-9) was obtained by performing the same procedure as for sample (1-6), except that the H2SO4 concentration in the initial aqueous phase was set to 993 g / L. The procedure was the same as for sample (1-6), except that sample (1-9) was used instead of sample (1-6).

[0058] H2SO4 concentration in the aqueous phase at the start of stirring, Fe 3+ The concentration and pH values ​​are listed in Table 2. And at the end point, Fe 3+ Table 2 shows the extraction rates of S, the pH value of the aqueous phase, and the H2SO4 concentration.

[0059] <Samples (1-10)> Sample (1-10) was obtained by performing the same procedure as for sample (1-6), except that the H2SO4 concentration in the initial aqueous phase was set to 1222 g / L. The procedure was the same as for sample (1-6), except that sample (1-10) was used instead of sample (1-6).

[0060] H2SO4 concentration in the aqueous phase at the start of stirring, Fe 3+ The concentration and pH values ​​are listed in Table 2. And at the end point, Fe 3+ Table 2 shows the extraction rates of S, the pH value of the aqueous phase, and the H2SO4 concentration.

[0061] <summary> From the results in Tables 1 and 2, Fe 2+ and Fe 3+ The behavior of the substance during solvent extraction has been determined. (1) Fe 2+ Fe 3+ In both cases, it was found that extraction from the aqueous phase to the organic phase occurred depending on the H2SO4 concentration in the aqueous phase. (2) If the H2SO4 concentration at the endpoint is 200 g / L or higher, the sulfur extraction rate will increase. Furthermore, if the H2SO4 concentration is 400 g / L or higher, Fe 2+ Fe 3+ It was found that the extraction rate increased. (3) Based on (1) and (2) above, by adjusting the H2SO4 concentration in the aqueous phase, Fe can be added to the organic phase. 2+ Fe 3+ It was found that the extraction of Fe is controllable. Here, for example, in water treatment processes and non-ferrous metal smelting processes in environmental technology, solutions containing various metal ions are produced. When a desired metal is extracted from such a solution containing various metal ions by solvent extraction, the accompanying Fe 2+ Fe 3+ It was found that it can be extracted from the solution.

[0062] [Table 1] [Table 2]

[0063] [Example 2] In Example 2, a Ni crystallized solution was used, which was obtained by removing Ni from a solution containing H2SO4 and various non-ferrous metals generated in the copper smelting process using a crystallization method. This Ni crystallized solution contains Co, Cu, trace amounts of Ni, and Fe ions. This was used as a sample, and various H + Fe ions were extracted using an organic phase containing a release-type extractant. The extraction rate of Fe ions, as well as the extraction rates of Co, Cu, and Ni, and the pH value were measured during this solvent extraction.

[0064] <Sample (2-1)> Sample (2-1) was taken from the Ni crystallization slag collected from the Cu smelting process described above. Next, H + The release-type extractant D2EHPA was diluted with kerosene (same as above) to obtain an organic solvent at a concentration of 40% by volume.

[0065] Sample (2-1) was used as the aqueous phase, and the aforementioned organic solvent was used as the organic phase. They were mixed in a 100:100 (volume ratio) and stirred at 20°C using a stirrer equipped with a temperature control device until the aqueous and organic phases were mixed and the solution became cloudy. Solvent extraction was then performed. From the start of stirring until 5 minutes, the aqueous and organic phases were mixed. At 15 minutes, stirring was stopped, and the aqueous and organic phases were separated, marking the endpoint of the solvent extraction.

[0066] H2SO4 concentration and pH value in the aqueous phase at the start of stirring, and H in the organic phase + Table 3 lists the names of the release-type extractants, the mixing ratio (volume ratio) of the organic phase and aqueous phase, and the liquid temperature. Then, the amounts of Fe ions and Co, Cu, and Ni ions in the aqueous phase at the endpoint were measured by ICP and converted to concentrations (g / L) in the aqueous phase. From these concentrations in the aqueous phase, the extraction rates of Fe, Co, Cu, and Ni were calculated using the aforementioned (Equation 1). The extraction rates of Fe, Co, Cu, and Ni are shown in Table 4. Furthermore, the pH value of the aqueous phase at the endpoint was measured, and the H2SO4 concentration was calculated from this pH value using the aforementioned (Equation 2). The pH value and H2SO4 concentration are shown in Table 4.

[0067] <Sample (2-2)> Sample (2-2) was used instead of sample (2-1), and the Ni crystallization slag collected from the Cu smelting process was used as sample (2-2). On the other hand, H + As a release-type extractant, VA-10 was used instead of D2EHPA, and diluted with kerosene (same as above) to a 40% volume organic solvent. Sample (2-2) was used as the aqueous phase, and an organic solvent containing VA-10 was used as the organic phase. Solvent extraction was performed in the same manner as for sample (2-1).

[0068] H2SO4 concentration and pH value in the aqueous phase at the start of stirring, and H in the organic phase + Table 3 lists the names of the release-type extractants, the mixing ratio (volume ratio) of the organic phase and aqueous phase, and the liquid temperature. Then, the amounts of Fe ions and Co, Cu, and Ni ions in the aqueous phase at the endpoint were measured by ICP and converted to concentrations (g / L) in the aqueous phase. From these concentrations in the aqueous phase, the extraction rates of Fe, Co, Cu, and Ni were calculated using the aforementioned (Equation 1). The extraction rates of Fe, Co, Cu, and Ni are shown in Table 4. Furthermore, the pH value of the aqueous phase at the endpoint was measured, and the H2SO4 concentration was calculated from this pH value using the aforementioned (Equation 2). The pH value and H2SO4 concentration are shown in Table 4.

[0069] <Sample (2-3)> Sample (2-3) was obtained by replacing sample (2-1) with Ni crystallization slag collected from the Cu smelting process. Meanwhile, H + As a release-type extractant, instead of D2EHPA, a mixture of VA-10, D2EHPA, and TBP was diluted with kerosene (same as above) to 40% by volume to obtain an organic solvent. However, the mixing ratio was VA-10:D2EHPA:TBP = 50:100:50 (volume ratio). Solvent extraction was performed in the same manner as for sample (2-1), except that sample (2-3) was used as the aqueous phase, and an organic solvent containing VA-10, D2EHPA, and TBP was used as the organic phase, and the organic phase / aqueous phase was mixed at a volume ratio of 200:100.

[0070] H2SO4 concentration and pH value in the aqueous phase at the start of stirring, and H in the organic phase + Table 3 lists the names of the release-type extractants, the mixing ratio (volume ratio) of the organic phase and aqueous phase, and the liquid temperature. Then, the amounts of Fe ions and Co, Cu, and Ni ions in the aqueous phase at the endpoint were measured by ICP and converted to concentrations (g / L) in the aqueous phase. From these concentrations in the aqueous phase, the extraction rates of Fe, Co, Cu, and Ni were calculated using the aforementioned (Equation 1). The extraction rates of Fe, Co, Cu, and Ni are shown in Table 4. Furthermore, the pH value of the aqueous phase at the endpoint was measured, and the H2SO4 concentration was calculated from this pH value using the aforementioned (Equation 2). The pH value and H2SO4 concentration are shown in Table 4.

[0071] <Sample (2-4)> Sample (2-4) was obtained by replacing sample (2-1) with Ni crystallization slag collected from the Cu smelting process. Meanwhile, H + As a release-type extractant, CYANEX272 was diluted with kerosene (same as above) to a 40% by volume concentration to obtain an organic solvent. Solvent extraction was performed in the same manner as for sample (2-1), except that sample (2-4) was used as the aqueous phase, and an organic solvent containing CYANEX272 was used as the organic phase, and the organic phase / aqueous phase was mixed at a volume ratio of 100:250.

[0072] H2SO4 concentration and pH value in the aqueous phase at the start of stirring, and H in the organic phase + Table 3 lists the names of the release-type extractants, the mixing ratio (volume ratio) of the organic phase and aqueous phase, and the liquid temperature. Then, the amounts of Fe ions and Co, Cu, and Ni ions in the aqueous phase at the endpoint were measured by ICP and converted to concentrations (g / L) in the aqueous phase. From these concentrations in the aqueous phase, the extraction rates of Fe, Co, Cu, and Ni were calculated using the aforementioned (Equation 1). The extraction rates of Fe, Co, Cu, and Ni are shown in Table 4. Furthermore, the pH value of the aqueous phase at the endpoint was not measured.

[0073] <Samples (2-5)> Sample (2-5) was used instead of sample (2-1), which was the Ni crystallization slag collected from the Cu smelting process. On the other hand, H + As a release-type extractant, CYANEX272 was used instead of D2EHPA, and diluted with kerosene (same as above) to a 40% volume concentration to obtain an organic solvent. Solvent extraction was performed in the same manner as for sample (2-1), except that sample (2-5) was used as the aqueous phase and an organic solvent containing CYANEX272 was used as the organic phase, and the organic phase / aqueous phase was mixed at a volume ratio of 200:100.

[0074] H2SO4 concentration and pH value in the aqueous phase at the start of stirring, and H in the organic phase + Table 3 lists the names of the release-type extractants, the mixing ratio (volume ratio) of the organic phase and aqueous phase, and the liquid temperature. Then, the amounts of Fe ions and Co, Cu, and Ni ions in the aqueous phase at the endpoint were measured by ICP and converted to concentrations (g / L) in the aqueous phase. From these concentrations in the aqueous phase, the extraction rates of Fe, Co, Cu, and Ni were calculated using the aforementioned (Equation 1). The extraction rates of Fe, Co, Cu, and Ni are shown in Table 4. Furthermore, the pH value of the aqueous phase at the endpoint was measured, and the H2SO4 concentration was calculated from this pH value using the aforementioned (Equation 2). The pH value and H2SO4 concentration are shown in Table 4.

[0075] <summary> The results in Tables 3 and 4 show that Fe ions are extracted even when the cation-releasing extractant in the organic phase is replaced with another type, and that the extraction of iron into the organic phase can be controlled by adjusting the H2SO4 concentration in the aqueous phase. Furthermore, as is clear from the results for sample 2-3, it was found that it is possible to use a mixture of multiple cation-releasing extractants.

[0076] [Table 3] [Table 4]

[0077] [Example 3] In Example 3, a strong acid solution, the Ni crystallization solution, collected from the Cu smelting process was prepared and designated as sample (3-1). The typical compositional range of this sample is shown in Table 5. On the other hand, the Ni raw material was acid-leached, and the resulting leachate was neutralized. After solvent extraction of metals other than Ni from the neutralized leachate, the Ni was extracted into an organic phase containing 40% by volume of VA-10. This organic phase was designated as sample (3-2), and its composition is shown in Table 6. As shown in Table 6, small amounts of Co and Cu remained in sample (3-2).

[0078] Sample (3-1) was used as the aqueous phase and sample (3-2) as the organic phase. The organic phase / aqueous phase was mixed in a volume ratio of 500:30, and solvent extraction was performed by stirring the mixture at a liquid temperature of 20°C.

[0079] As a result, the Fe ions contained in sample (3-1) were extracted into the organic phase, and the Ni, Co, and Cu contained in sample (3-2) were back-extracted into the aqueous phase. The extraction rate of Fe, the back-extraction rates of Co, Cu, and Ni in this solvent extraction, and the pH values ​​of the aqueous phase at the beginning and end of the extraction were measured. The measurement results are shown in Table 7.

[0080] <summary> The results in Table 7 show that it is possible to simultaneously extract Fe ions from the aqueous layer, which is a strong acid solution, into the organic phase, and to back-extract Co, Cu, and Ni from the organic phase, which contains a cation-releasing extractant and also contains Co, Cu, and Ni, into the aqueous layer.

[0081] [Table 5] [Table 6] [Table 7]

[0082] [Example 4] In Example 4, an organic phase containing CYANEX272, as described in the "Sample (2-5)" section of Example 2, from which Fe, Co, Cu, and Ni ions were extracted (referred to as "Organic Phase Sample (2-5)") was mixed with an aqueous phase containing a free acid. Then, the Fe contained in the Organic Phase Sample (2-5) was back-extracted into the aqueous phase.

[0083] <Sample (4-1)> Organic phase samples (2-5) were designated as the organic phase. On the other hand, water without free acid was prepared as sample (4-1) and used as the aqueous phase. The organic phase and aqueous phase were mixed in a 5:5 ratio (by volume) and shaken at a liquid temperature of 40°C. A TAITEC DOUBLE SHAKER NR-30 was used as the shaker, and reciprocating shaking (200 rpm) was performed for 10 minutes. Table 8 shows the pH value of the aqueous phase at the endpoint. The amount of Fe ions in the aqueous phase at the endpoint was measured by ICP and converted to a concentration (g / L) in the aqueous phase. The back extraction rate of Fe was then calculated from this concentration using (Equation 1) described above. The value of this Fe back extraction rate is shown in Table 8.

[0084] <Sample (4-2)> As sample (4-2), an aqueous solution with an H2SO4 concentration of 100 g / L was prepared and used as the aqueous phase. Fe was back-extracted into the aqueous phase by using sample (4-2) instead of sample (4-1), except that the organic phase and aqueous phase were mixed in an organic phase / aqueous phase ratio of 10:10 (volume ratio). Table 8 shows the pH value of the aqueous phase and the back extraction rate of Fe at the endpoint.

[0085] <Sample (4-3)> As sample (4-3), an aqueous solution with an H2SO4 concentration of 200 g / L was prepared and used as the aqueous phase. Fe was back-extracted into the aqueous phase by using sample (4-3) instead of sample (4-1), except that the organic phase and aqueous phase were mixed in an organic phase / aqueous phase ratio of 5:5 (by volume). Table 8 shows the pH value of the aqueous phase and the back extraction rate of Fe at the endpoint.

[0086] <Sample (4-4)> As sample (4-4), an aqueous solution with an H2SO4 concentration of 200 g / L was prepared and used as the aqueous phase. Using sample (4-3) instead of sample (4-1), the organic phase and aqueous phase were mixed in a ratio of 5:5 (by volume), and the liquid temperature was set to 20°C. Except for these steps, the procedure was the same as for sample (4-1), and Fe was back-extracted into the aqueous phase. Table 8 shows the pH value of the aqueous phase and the back extraction rate of Fe at the endpoint.

[0087] <Sample (4-5)> As sample (4-5), an aqueous solution with an HCl concentration of 90 g / L was prepared and used as the aqueous phase. Fe was back-extracted into the aqueous phase by using sample (4-5) instead of sample (4-1), except that the organic phase and aqueous phase were mixed in an organic phase / aqueous phase ratio of 10:40 (volume ratio). Table 9 shows the pH value of the aqueous phase and the back extraction rate of Fe at the endpoint.

[0088] <Samples (4-6)> As sample (4-6), an aqueous solution with an HCl concentration of 180 g / L was prepared and used as the aqueous phase. Fe was back-extracted into the aqueous phase by using sample (4-6) instead of sample (4-1), except that the organic phase and aqueous phase were mixed in an organic phase / aqueous phase ratio of 10:20 (volume ratio). Table 9 shows the pH value of the aqueous phase and the back extraction rate of Fe at the endpoint.

[0089] <Samples (4-7)> As sample (4-7), an aqueous solution with an HCl concentration of 360 g / L was prepared and used as the aqueous phase. Fe was back-extracted into the aqueous phase by using sample (4-7) instead of sample (4-1), except that the organic phase and aqueous phase were mixed in an organic phase / aqueous phase ratio of 10:10 (volume ratio). Table 9 shows the pH value of the aqueous phase and the back extraction rate of Fe at the endpoint.

[0090] <summary> It was found that back-extraction of Fe from the organic phase can be performed by solvent extraction using a mixture with an aqueous phase containing H2SO4 or HCl. The back-extraction rate of Fe from the organic phase can be controlled by the concentration of H2SO4 or HCl in the aqueous phase, and by selecting appropriate concentrations, a back-extraction rate of over 80% could be achieved.

[0091] [Table 8] [Table 9]

Claims

1. The pH value is -0.8 or more and 0.00 or less and H ２ SO ４ A method for extracting Fe ions and Ni ions, comprising mixing an organic phase 1 containing an H+-releasing extractant and at least Ni ions with an aqueous phase 1 containing Fe ions, thereby extracting Fe ions into an organic phase 2 and extracting Ni ions into the aqueous phase 2.

2. The method for extracting Fe ions and Ni ions according to Claim 1, wherein the aqueous phase 1 is a solution obtained after crystallizing CuSO₄ or NiSO₄ from the Cu electrolytic tail liquid in the Cu smelting process.

3. The method for extracting Fe ions and Ni ions according to Claim 2, wherein the aqueous phase 2, after extracting Ni ions by mixing the aqueous phase 1 and the organic phase 1, is returned to the Cu smelting process, and then a Cu electrolysis process is carried out in the Cu smelting process.

4. The method for extracting Fe ions and Ni ions according to any one of claims 1 to 3, wherein after extracting Fe ions from the organic phase 2 by mixing the aqueous phase 1 and the organic phase 1, Fe ions are back-extracted into an aqueous phase 4 obtained by mixing an acid weaker than the aqueous phase 1 as an aqueous phase 3 with the organic phase 2.

5. The method for extracting Fe ions and Ni ions according to Claim 4, wherein the acid weaker than the aqueous phase 1 is an aqueous H₂SO₄ solution with a concentration of less than 200 g / L or an aqueous HCl solution with a concentration of less than 360 g / L.

6. The method for extracting Fe ions and Ni ions according to claim 4 or 5, wherein the organic phase 1 is an organic phase obtained by mixing at least the organic phase 3 after back-extraction with an aqueous phase O1 containing Ni ions, and is an organic phase after the Ni ions contained in the aqueous phase O1 have been extracted.

7. The method for extracting Fe ions and Ni ions according to Claim 6, wherein the aqueous phase O1 is obtained from the leachate of the Ni-containing raw material with an acid solution and the aqueous phase 4 after the back extraction.

8. The method for extracting Fe ions and Ni ions according to any one of claims 1 to 7, wherein the extractant is a phosphoric acid-based extractant.

9. The organic phase 1 contains not only Ni ions but also Co ions and Cu ions, The method for extracting Fe ions and Ni ions according to any one of claims 1 to 8, wherein in addition to Ni ions, Co ions and Cu ions are also extracted into the aqueous phase 2.

10. The method for extracting Fe ions and Ni ions according to any one of claims 1 to 9, wherein the organic phase 1 is the organic phase obtained after extracting Ni from the aqueous phase obtained from the leachate of a Ni-containing raw material.

11. A method for extracting Fe ions and Ni ions, comprising: mixing an organic phase 1 containing an H+-releasing extractant and at least Ni ions with an aqueous phase 1 having a pH value of -0.8 or higher and containing H₂SO₄ and Fe ions, thereby extracting Fe ions into an organic phase 2 obtained by mixing the organic phase 1 containing an H+-releasing extractant and at least Ni ions; and extracting Ni ions into the aqueous phase 2. The aqueous phase 1 is a solution obtained after crystallizing CuSO₄ or NiSO₄ from the Cu electrolytic tail liquid during the Cu smelting process. After extracting Ni ions by mixing the aqueous phase 1 and the organic phase 1, the aqueous phase 2 is returned to the Cu smelting process, and then a Cu electrolysis process is performed in the Cu smelting process. After extracting Fe ions by mixing the aqueous phase 1 and the organic phase 1, Fe ions are back-extracted into the aqueous phase 4 obtained by mixing the organic phase 2 with an acid weaker than the aqueous phase 1 as aqueous phase 3. The organic phase 1 is an organic phase obtained by mixing at least the organic phase 3 after back-extraction with the aqueous phase O1 containing Ni ions, and is the organic phase after the Ni ions contained in the aqueous phase O1 have been extracted. The aforementioned extractant is a phosphoric acid-based extractant. The aforementioned organic phase 1 also contains Co ions and Cu ions in addition to Ni ions. In addition to Ni ions, Co ions and Cu ions are also extracted into the aqueous phase 2. A method for extracting Fe ions and Ni ions.

12. A method for smelting copper, wherein the aqueous phase 2, after extracting Ni ions by mixing the aqueous phase 1 and the organic phase 1 using the Fe ion and Ni ion extraction method described in Claim 3, is returned to the Cu smelting process, and a Cu electrolysis process is performed in the Cu smelting process.

13. A method for extracting Fe ions and Cu ions, comprising: mixing an organic phase A containing an H+-releasing extractant and at least Cu ions with an aqueous phase A having a pH of -0.8 or higher and containing H₂SO₄ and Fe ions, thereby extracting Fe ions into an organic phase B obtained by mixing the organic phase A containing an H+-releasing extractant and at least Cu ions, and extracting Cu ions into the aqueous phase B.

14. The method for extracting Fe ions and Cu ions according to claim 13, wherein the aqueous phase A is a solution obtained after crystallizing CuSO₄ or NiSO₄ from the Cu electrolytic tail liquid in the Cu smelting process.

15. The method for extracting Fe ions and Cu ions according to Claim 14, wherein the aqueous phase B, after extracting Cu ions by mixing the aqueous phase A and the organic phase A, is returned to the Cu smelting process, and then a Cu electrolysis process is carried out in the Cu smelting process.

16. The method for extracting Fe ions and Cu ions according to any one of claims 13 to 15, wherein after extracting Fe ions by mixing the aqueous phase A and the organic phase A, Fe ions are back-extracted into an aqueous phase D obtained by mixing the organic phase B with an acid weaker than the aqueous phase A as the aqueous phase C.

17. The method for extracting Fe ions and Cu ions according to claim 16, wherein the acid weaker than the aqueous phase A is an aqueous H₂SO₄ solution with a concentration of less than 200 g / L or an aqueous HCl solution with a concentration of less than 360 g / L.

18. The method for extracting Fe ions and Cu ions according to claim 16 or 17, wherein the organic phase A is an organic phase obtained by mixing at least the organic phase C after back-extraction with an aqueous phase O2 containing Cu ions, and is the organic phase after extracting the Cu ions contained in the aqueous phase O2.

19. The method for extracting Fe ions and Cu ions according to claim 18, wherein the aqueous phase O2 is obtained from the leachate of the Cu-containing raw material with an acid solution and the aqueous phase D after the back extraction.

20. The method for extracting Fe ions and Cu ions according to any one of claims 13 to 19, wherein the extractant is a phosphoric acid-based extractant.

21. The method for extracting Fe ions and Cu ions according to any one of claims 13 to 20, wherein the organic phase A is the organic phase obtained after extracting Cu from the aqueous phase obtained from the leachate of a Cu-containing raw material.

22. A method for extracting Fe ions and Cu ions, comprising: mixing an organic phase A containing an H+-releasing extractant and at least Cu ions with an aqueous phase A having a pH of -0.8 or higher and containing H₂SO₄ and Fe ions, thereby extracting Fe ions into an organic phase B obtained by mixing the organic phase A containing an H+-releasing extractant and at least Cu ions, and extracting Cu ions into the aqueous phase B, The aqueous phase A is a solution obtained after crystallizing CuSO₄ or NiSO₄ from the Cu electrolytic tail liquid during the Cu smelting process. After extracting Cu ions by mixing the aqueous phase A and the organic phase A, the aqueous phase B is returned to the Cu smelting process, and then a Cu electrolysis process is performed in the Cu smelting process. After extracting Fe ions by mixing the aqueous phase A and the organic phase A, Fe ions are back-extracted into the aqueous phase D obtained by mixing the organic phase B with an acid weaker than the aqueous phase A as aqueous phase C. The organic phase A is an organic phase obtained by mixing at least the organic phase C after back-extraction with the aqueous phase O2 containing Cu ions, and is the organic phase after the Cu ions contained in the aqueous phase O2 have been extracted. The aforementioned extractant is a phosphoric acid-based extractant. A method for extracting Fe ions and Cu ions.

23. A method for smelting Cu, wherein Cu ions are extracted by mixing the aqueous phase A and the organic phase A using the Fe ion and Cu ion extraction method described in Claim 15, and the aqueous phase B is returned to the Cu smelting process, and a Cu electrolysis process is performed in the Cu smelting process.

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