Method for separating metals and method for manufacturing metal materials

Abstract

To provide a method for separating zinc, which can efficiently separate zinc from iron-making dust at a high recovery rate.SOLUTION: The method for separating the metal includes: a lead / zinc leaching step of adding one or both of hydrochloric acid and nitric acid to iron-making dust to adjust the pH to 1.0 to 6.0, and thereby leaching lead and zinc; a lead precipitation step of adding sulfuric acid to a treated liquid after the lead / zinc leaching step to adjust the pH to 1.0 or higher, and thereby precipitating lead; a first solid-liquid separation step of solid-liquid separating a treated liquid after the lead precipitation step; an iron precipitation step of adding a first alkali and an oxidizing agent to a treated liquid after the first solid-liquid separation step, and thereby precipitating iron; a second solid-liquid separation step of solid-liquid separating a treated liquid after the iron precipitation step; a zinc precipitation step of adding a second alkali to a treated liquid after the second solid-liquid separation step, and thereby precipitating zinc; and a third solid-liquid separation step of solid-liquid separating a treated liquid after the zinc precipitation step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a method for separating metals and a method for manufacturing metallic materials. [Background technology]

[0002] Iron, a representative base metal, is used in a wide variety of industrial sectors. Although iron resources are abundant compared to rare metals, the rise of emerging economies has led to a rapid shift in the supply-demand balance. As a result, high-quality iron ore resources are becoming depleted, and companies are increasingly forced to use lower-grade ore.

[0003] In light of this situation, attempts are being made to recycle not only iron ore but also industrial waste and steel mill by-products, which are composed of multiple metals including iron, as iron sources. For example, dust generated at steel mills, such as blast furnace dust, converter dust, and electric furnace dust, contains iron, lead, zinc, carbon, etc., and these dusts (hereinafter referred to as "steelmaking dust") are being recycled as raw materials for steelmaking.

[0004] However, the amount of steelmaking dust recycled has been limited because zinc in steelmaking dust forms deposits in blast furnaces, negatively impacting blast furnace operation. Similarly, lead in steelmaking dust forms deposits in denitrification reactors of combustion gases discharged from sintering facilities, negatively impacting sintering facility operation, thus limiting the amount of steelmaking dust recycled in this case as well. Therefore, in order to promote the recycling of steelmaking dust, technologies are needed to separate and recover zinc and lead from steelmaking dust.

[0005] Methods for separating zinc and lead from steelmaking dust are broadly classified into dry and wet methods. The dry method is a technique that reduces steelmaking dust at high temperatures, causing low-boiling-point metals such as zinc to volatilize and be separated and recovered. However, the separation and recovery of zinc and lead using the dry method requires large-scale high-temperature reduction equipment, and there was a problem in that it was not economically viable for blast furnace dust or converter dust, which contain only a few percent of zinc and lead.

[0006] Therefore, in order to solve the above problems, the separation and recovery of metals such as zinc from steelmaking dust using a wet method has been considered. In the separation and recovery of zinc using the wet method, an acid is added to the steelmaking dust to dissolve the zinc, and then an alkali is added to precipitate and recover the zinc.

[0007] For example, Patent Documents 1 and 2 propose a method for recovering zinc by a wet process, in which iron dissolved along with zinc during the elution process is removed by precipitation prior to the zinc precipitation treatment.

[0008] Furthermore, Patent Document 3 proposes a method for promoting zinc leaching in a zinc leaching process in which acid is added to steelmaking dust to extract zinc, by adjusting the pH to predetermined conditions. In addition, in this method, iron is separated from the treatment liquid by adding alkali using a reaction vessel divided into multiple compartments, thereby improving the separation efficiency of zinc in the subsequent zinc precipitation process.

[0009] On the other hand, Patent Document 4 proposes a method for separating and recovering lead from lead-containing materials produced by metal refining, etc., using a wet method. In this method, lead is leached from the lead-containing material using a nitric acid solution, and then impurities in the filtrate after leaching are replaced with metallic lead. The solution after lead replacement is used as a supplemental solution in the lead electrolysis process, and electrolysis is performed to precipitate lead from the lead nitrate solution. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 53-004705 [Patent Document 2] Japanese Patent Publication No. 61-261446 [Patent Document 3] Japanese Patent Publication No. 2019-60019 [Patent Document 4] Japanese Patent Publication No. 2008-81799 [Overview of the project] [Problems that the invention aims to solve]

[0011] However, the above prior art has the following problems.

[0012] According to the methods disclosed in Patent Documents 1 and 2, it is expected that zinc can be recovered at a high concentration because iron eluted together with zinc is precipitated and removed in advance. However, in reality, there is a problem that the recovery rates of zinc and iron are lower than expected. Further, in the methods disclosed in Patent Documents 1 and 2, even if zinc can be separated and recovered from steelmaking dust, there is a problem that lead cannot be separated and recovered.

[0013] According to the method disclosed in Patent Document 3, zinc can be efficiently separated from steelmaking dust. In this case, in the zinc leaching step of adding an acid to the steelmaking dust to leach zinc, although there is a possibility that lead can be leached together with zinc by the acid, it is difficult to separately separate and recover zinc and lead. Since zinc and lead have different uses, for the recycling of steelmaking dust, it may be required to separately separate and recover lead and zinc from the steelmaking dust, and there is room for improvement in this regard.

[0014] The method disclosed in Patent Document 4 mainly relates to the separation and recovery of lead for non-ferrous metals, and relates to a treatment method for waste with a high lead content ratio. Therefore, the effect in the case where the lead content ratio is low, such as in steelmaking dust, is unclear. Further, even if the method disclosed in Patent Document 4 can be applied as a method for separating and recovering lead from steelmaking dust, there is a problem that lead and zinc cannot be separately separated from the steelmaking dust.

[0015] The present invention has been made to solve the above problems, and an object thereof is to provide a method for separating metals that can efficiently separate zinc and lead from steelmaking dust respectively. Another object of the present invention is to provide a method for manufacturing a metal material using the above method for separating metals.

Means for Solving the Problems

[0016] The gist of the present invention is as follows:

[0017] 1. A method for separating metals from steelmaking dust, A lead and zinc leaching step is performed in which hydrochloric acid and / or nitric acid are added to the aforementioned steelmaking dust to adjust the pH to 1.0 or higher and 6.0 or lower, thereby leaching out the lead and zinc contained in the steelmaking dust. A lead precipitation step is performed in which sulfuric acid is added to the treatment solution after the lead-zinc leaching step to adjust the pH to 1.0 or higher, thereby precipitating the lead contained in the treatment solution after the lead-zinc leaching step, A first solid-liquid separation step is performed to separate the treated liquid after the lead precipitation step from solid to liquid, An iron precipitation step is performed by adding a first alkali and an oxidizing agent to the processing liquid after the first solid-liquid separation step to precipitate iron, A second solid-liquid separation step is performed to separate the treated liquid after the iron precipitation step from solid to liquid, A zinc precipitation step is performed by adding a second alkali to the processing liquid after the second solid-liquid separation step to precipitate zinc, A method for separating metals, comprising a third solid-liquid separation step of separating the treated liquid after the zinc precipitation step into solid and liquid components.

[0018] 2. The method for separating metals as described in paragraph 1 above, wherein the pH is adjusted to 1.0 or higher and 2.0 or lower in the lead-zinc leaching step.

[0019] 3. The method for separating metals as described in item 1 above, wherein the leaching time in the lead-zinc leaching step is 15 minutes or more and 120 minutes or less.

[0020] 4. The method for separating metals as described in item 1 above, wherein the pH is adjusted to 1.0 or higher and 2.0 or lower in the lead precipitation step.

[0021] 5. The method for separating metals as described in item 2 above, wherein the pH is adjusted to 1.0 or higher and 2.0 or lower in the lead precipitation step.

[0022] 6. In the iron precipitation step, the pH of the treatment solution is adjusted to 4.0 or higher and 7.0 or lower. In the zinc precipitation step, the pH of the treatment solution is adjusted to 8.0 or higher and 12.0 or lower. The method for separating the metal described in item 1 above.

[0023] 7. A method for separating metals according to any one of items 1 to 6 above, further comprising at least one of the following: a lead recovery step for recovering lead separated in the first solid-liquid separation step; an iron recovery step for recovering iron separated in the second solid-liquid separation step; and a zinc recovery step for recovering zinc separated in the third solid-liquid separation step.

[0024] 8. The method for separating metals according to item 1, further comprising a fourth solid-liquid separation step of separating the treated liquid into solid and liquid phases between the lead-zinc leaching step and the lead precipitation step.

[0025] 9. The method for separating metals according to 8 above, further comprising at least one of the following: a lead recovery step for recovering lead separated in the first solid-liquid separation step; an iron recovery step for recovering iron separated in the second solid-liquid separation step; a zinc recovery step for recovering zinc separated in the third solid-liquid separation step; and a second iron recovery step for recovering iron separated in the fourth solid-liquid separation step.

[0026] 10. A method for manufacturing metal materials from ironmaking dust, A method for producing a metal material, comprising separating and recovering at least one of lead, iron, and zinc from the aforementioned ironmaking dust using the metal separation method described in 7 above.

[0027] 11. A method for manufacturing metal materials from ironmaking dust, A method for producing a metal material, comprising separating and recovering at least one of lead, iron, and zinc from the ironmaking dust using the metal separation method described in 9 above. [Effects of the Invention]

[0028] According to the present invention, zinc and lead can be efficiently separated from steelmaking dust. [Brief explanation of the drawing]

[0029] [Figure 1] This is a flowchart showing a method for separating metals in the first embodiment. [Figure 2] This diagram shows the state of iron, zinc, and lead in an aqueous solution to which hydrochloric acid has been added. [Figure 3] This is a flowchart showing a method for separating metals in a second embodiment. [Figure 4] This graph shows the relationship between the type of acid used and the leaching rate. [Figure 5] This graph shows the relationship between pH and leaching rate during the leaching process. [Figure 6] This graph shows the precipitation rates of lead, zinc, and iron in the lead precipitation process. [Figure 7] This graph shows the precipitation rates of iron and zinc in the iron precipitation process. [Modes for carrying out the invention]

[0030] Embodiments of the present invention will be described in detail below with reference to the drawings. The following description illustrates preferred embodiments of the present invention, and the invention is not limited thereto.

[0031] (First embodiment) Figure 1 is a flowchart showing a method for separating metals according to a first embodiment of the present invention. As shown in the flowchart, in the separation method according to this embodiment, the following steps (S1) to (S7) are sequentially applied to the steelmaking dust. (S1) Lead and zinc leaching process (S2) Lead precipitation process (S3) First solid-liquid separation step (S4) Iron precipitation process (S5) Second solid-liquid separation step (S6) Zinc precipitation process (S7) Third solid-liquid separation step

[0032] The above steps (S1) to (S7) can be carried out in any manner. For example, all of the above steps (S1) to (S7) may be carried out in batch mode or in continuous mode. Alternatively, some of the above steps (S1) to (S7) may be carried out in batch mode and the remaining steps may be carried out in continuous mode. However, since steelmaking dust is generated continuously in the steelmaking process, it is desirable to process the generated dust sequentially. Therefore, from the viewpoint of processing efficiency, it is preferable to carry out the above steps (S1) to (S7) in continuous mode.

[0033] Each of the above steps (S1) to (S7) can be carried out using any apparatus unless otherwise specified. The apparatus and equipment used in each step, such as reaction vessels, should preferably be made of chemically resistant material that will not be affected by the chemicals (acids, alkalis, etc.) used in each step, or should be equipped with a chemically resistant lining. The shape of the reaction vessel is not particularly limited and can be freely determined according to the installation location, etc.

[0034] <Steelmaking dust> The steelmaking dust used in this invention is not particularly limited, and any dust generated in the steelmaking process can be used. Typical examples of steelmaking dust include blast furnace dust, sintering dust, converter dust, and electric furnace dust.

[0035] Blast furnace dust may contain iron, aluminum, silicon, calcium, and other elements, as well as approximately 1-5% by weight of zinc and 0.2-3% by weight of lead. Sintered dust may contain iron, carbon, sulfur, silicon, calcium, and other elements, as well as approximately 1-5% by weight of zinc and 1-6% by weight of lead. Converter dust may contain iron, sulfur, silicon, calcium, and other elements, as well as approximately 0.2-2% by weight of zinc. These steelmaking dusts are recycled as raw materials for steelmaking, either individually or in mixtures. In this case, the zinc and lead contained in the steelmaking dust are often present as oxides.

[0036] While steelmaking dust can be used in any form, it is preferable to mix it with water to form a slurry for easier processing in subsequent steps. In this case, the ratio of steelmaking dust to water (solid-liquid ratio) can be any ratio, but it is desirable to determine it in a way that ensures uniform mixing.

[0037] <Zinc and lead leaching process> Hydrochloric acid and / or nitric acid are added to the above-mentioned steelmaking dust to adjust the pH to between 1.0 and 6.0, thereby leaching out the lead and zinc contained in the steelmaking dust (lead and zinc leaching process).

[0038] In the lead-zinc leaching process described above, it is important to use either hydrochloric acid or nitric acid, or both, as the acid. Hydrochloric acid is preferred because it yields a higher leaching rate of zinc and lead compared to nitric acid. Alternatively, a mixed acid, which is a mixture of hydrochloric acid and nitric acid, may be used. However, sulfuric acid is not included in the acid used in the lead-zinc leaching process.

[0039] Figure 2 shows the state of iron, zinc, and lead in an aqueous solution at 25°C with added hydrochloric acid, as opposed to pH. Figure 2(a) shows the state of Fe and Zn, where "Zn 2+ "Fe 2+ The symbols "Zn↓" and "Fe↓" represent states where Zn and Fe leach out, respectively, while "Zn↓" and "Fe↓" represent states where Zn and Fe precipitate, respectively. In other words, in pH range (i), both Zn and Fe leach out, while in pH range (iii), both Zn and Fe precipitate. In pH range (ii), which lies between these two ranges, Zn leaches out, but Fe precipitates. Note that even in this range, Fe may leach out if the oxidation-reduction potential (ORP) of the aqueous solution decreases. However, in any case, it can be seen that Zn leaches out when the pH is 7.0 or below.

[0040] Similarly, Figure 2(b) shows the states of existence of Fe and Pb, and "Pb 2+" indicates a state where Pb leaches out, and "Pb↓" indicates a state where Pb precipitates. That is, in pH range (i), both Pb and Fe leach out, while in pH range (iii), both Pb and Fe precipitate. And in pH range (ii) in between, Pb leaches out, but Fe precipitates. Even in this range, Fe may leach out if the oxidation-reduction potential (ORP) of the aqueous solution decreases. However, in any case, it can be seen that Pb leaches out if the pH is 6.0 or lower.

[0041] Therefore, zinc and lead can be leached by adjusting the pH to 6.0 or below. Although the above explanation uses hydrochloric acid as an example, zinc and lead can be similarly leached by adjusting the pH to 6.0 or below when using nitric acid.

[0042] For the reasons stated above, the pH in the lead-zinc leaching process should be kept below 6.0. As will be discussed later, the lead leaching rate decreases significantly between pH 3.0 and pH 2.0 as the pH is lowered. Therefore, it is preferable to keep the pH below 3.0, and more preferably below 2.0, in the lead-zinc leaching process. Here, pH refers to the pH of the mixture of ironmaking dust and acid.

[0043] On the other hand, in the lead and zinc leaching process, the pH is adjusted to 1.0 or higher. If the pH falls below 1.0, iron leaching increases, reducing the final iron recovery rate and lowering the purity of the recovered zinc and lead. Furthermore, lowering the pH below 1.0 requires the addition of large amounts of hydrochloric acid or nitric acid, which increases the consumption of chemicals and thus the processing cost.

[0044] The method of adding hydrochloric acid or nitric acid in the lead-zinc leaching process described above is not particularly limited, but can be done, for example, by using a pump. The pump is not particularly limited, and a general-purpose pump can be used. In addition, as with the addition of hydrochloric acid or nitric acid, any device such as a pump can be used when adding chemicals in each process other than the lead-zinc leaching process.

[0045] When adding hydrochloric acid or nitric acid, it is preferable to monitor the pH with a pH meter and control the amount of acid added based on the results. For example, when adding hydrochloric acid or nitric acid to steelmaking dust in a reaction vessel, it is preferable to install a pH meter in the reaction vessel and monitor the pH. In addition, similar to the addition of hydrochloric acid or nitric acid, it is preferable to monitor the pH with a pH meter when adding chemicals in each process other than the lead-zinc leaching process.

[0046] Furthermore, since steelmaking dust contains iron and other materials with a high specific gravity and tends to settle, it is preferable to stir when adding hydrochloric acid or nitric acid in the lead and zinc leaching process. For example, when adding hydrochloric acid or nitric acid in the reaction vessel, it is preferable to install a stirring device in the reaction vessel and add the hydrochloric acid or nitric acid while stirring. The method of stirring is not particularly limited, but it can be done using, for example, a general-purpose stirrer. It is desirable to determine the stirring speed by taking into consideration the ratio of steelmaking dust to water, etc., so that the concentration distribution in the vessel becomes uniform. In addition, similar to the addition of hydrochloric acid or nitric acid, it is preferable to stir by any method when adding chemicals in each process other than the lead and zinc leaching process.

[0047] Furthermore, the solid-liquid ratio of steelmaking dust to water can be any ratio as long as a uniform mixture can be achieved.

[0048] The leaching time in the lead and zinc leaching process is not particularly limited, but it is preferably between 15 minutes and 120 minutes. By leaching for 15 minutes or more, zinc and lead contained in the steelmaking dust can be leached more thoroughly. On the other hand, by leaching for 120 minutes or less, zinc and lead can be leached more effectively while suppressing the amount of iron leached out.

[0049] The reaction temperature in the lead-zinc leaching process can be arbitrarily set within a temperature range where water does not solidify or evaporate.

[0050] <Lead precipitation process> Next, sulfuric acid is added to the treatment solution after the lead-zinc leaching process to adjust the pH to 1.0 or higher, and the lead contained in the treatment solution after the lead-zinc leaching process is precipitated (lead precipitation process).

[0051] The treatment solution after the lead-zinc leaching process contains iron in addition to zinc and lead. When sulfuric acid is added to this treatment solution, lead becomes insoluble by reacting with sulfuric acid to form lead sulfide (PbSO4), while zinc and iron remain dissolved. Therefore, by adding sulfuric acid, lead can be selectively separated as lead sulfate from the treatment solution after the lead-zinc leaching process. Note that the treatment solution contains either or both of the hydrochloric acid and nitric acid added in the lead-zinc leaching process, and these acids contain sulfate ions (SO4) in the lead precipitation process. 2― It does not inhibit the reaction between lead (Pb) and nitrate. Therefore, even if hydrochloric acid or nitric acid remains in the treatment solution, lead can be separated without any problems by adding sulfuric acid.

[0052] In the lead precipitation process, sulfuric acid is added to the treatment solution after the lead and zinc leaching process to adjust the pH to 1.0 or higher. If the pH falls below 1.0, iron leaching will increase further in the lead precipitation process, reducing the final iron recovery rate and lowering the purity of the recovered zinc. Furthermore, since a large amount of sulfuric acid must be added to lower the pH below 1.0, the consumption of chemicals increases, leading to higher treatment costs.

[0053] On the other hand, if the pH exceeds 2.0, iron may precipitate along with lead depending on the oxidation-reduction potential (ORP) of the aqueous solution. Therefore, from the viewpoint of suppressing iron precipitation, it is preferable to adjust the pH to between 1.0 and 2.0 in the lead precipitation process.

[0054] As described above, in the present invention, a lead precipitation step is performed after the lead-zinc leaching step to selectively precipitate the lead contained in the treatment solution. This step allows lead to be separated from the treatment solution while zinc and iron are dissolved in the solution, thus enabling the acquisition of lead of sufficient purity for reuse as a resource.

[0055] The processing time in the lead precipitation step is not particularly limited, but it is preferably between 1 minute and 120 minutes. By making the processing time in the lead precipitation step 1 minute or longer, the lead can be insoluble even more sufficiently. On the other hand, by making the processing time in the lead precipitation step 120 minutes or less, it matches the processing time in the lead-zinc leaching step, making the entire series of processing steps (S1 to S7) more efficient.

[0056] The reaction temperature in the lead-zinc leaching process can be arbitrarily set within a temperature range where water does not solidify or evaporate.

[0057] Furthermore, in the present invention, in the lead precipitation step, it is preferable to use a reaction tank partitioned from the reaction tank in which the lead-zinc leaching step is performed, and to add sulfuric acid to the treatment liquid after the lead-zinc leaching step. For example, it is preferable to partition the reaction tank so that the volumes of each compartment are approximately the same. In this case, it is preferable to connect each compartment and use a cascade system in which the treatment liquid flows from the upstream compartment in which the lead-zinc leaching step is performed to the downstream compartment in which the lead precipitation step is performed. The method of flowing the treatment liquid between compartments is not particularly limited, but for example, a partition plate (weir) of an appropriate height can be provided between the two compartments, and the treatment liquid can flow to the downstream compartment by overflowing over the partition plate.

[0058] By using the reaction vessel described above, it is possible to prevent the sulfuric acid added in the lead precipitation process from flowing into the reaction vessel for the lead-zinc leaching process. In other words, the contamination of lead with dust that does not leach out in the lead-zinc leaching process by sulfuric acid in the reaction vessel for the lead-zinc leaching process can be reduced.

[0059] <First solid-liquid separation step> Next, the treated liquid after the lead precipitation process is subjected to solid-liquid separation (first solid-liquid separation process). In this process, the treated liquid is separated into a filtrate mainly containing zinc ions and iron ions, and solid components (lead precipitate) that have precipitated in the lead-zinc leaching process and the lead precipitation process.

[0060] The lead and zinc leaching residue produced in the lead and zinc leaching process is primarily composed of iron, with very little zinc and lead. Therefore, it can be reused as a raw material for steelmaking after a sintering process. On the other hand, the solid material produced in the lead precipitation process contains a high concentration of lead (over 60%) and can be sold or reused as lead material.

[0061] The solid-liquid separation method used in the first solid-liquid separation step is not particularly limited, and any method can be used. For example, methods such as gravity sedimentation, filtration, centrifugal separation, and filter pressing can be used individually or in combination.

[0062] The metal separation method of the present invention preferably further comprises a lead recovery step for recovering the lead separated in the first solid-liquid separation step. This allows the separated lead to be recovered and reused as a resource.

[0063] <Iron precipitation process> Next, the first alkali and oxidizing agent are added to the treatment liquid after the first solid-liquid separation step to precipitate the iron (iron precipitation step). Here, "treatment liquid after the first solid-liquid separation step" refers to the liquid portion (filtrate) after the solid component has been separated in the first solid-liquid separation step.

[0064] The lead-zinc leaching process described above is, as the name suggests, a process aimed at leaching zinc and lead. However, it is difficult to completely prevent iron leaching, so the treatment solution after the lead precipitation process contains iron ions in addition to zinc ions. Therefore, when alkali is added to the above treatment solution to precipitate and recover zinc, the iron that precipitates at the same time becomes mixed with the zinc, reducing the value of the recovered zinc material. In this invention, an iron precipitation process is performed on the treatment solution after the first solid-liquid separation process, before the zinc precipitation process, to selectively precipitate the iron contained in the treatment solution. This separates iron from the treatment solution, making it possible to separate zinc of sufficient purity for reuse as a resource in the subsequent zinc precipitation process.

[0065] (First alkali) The first alkali used in the iron precipitation process is not particularly limited and any alkali can be used. Preferably, the first alkali is at least one selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides, and more preferably, one or both of calcium hydroxide and sodium hydroxide are used. Since these alkalis are inexpensive and readily available, processing costs can be reduced.

[0066] The method for adding the first alkali is not particularly limited, but can be carried out using a general-purpose pump or the like. In this case, it is preferable to monitor the pH of the treatment solution with a pH meter and control the amount of the first alkali added based on the result.

[0067] The pH adjusted in the iron precipitation process is not particularly limited and can be arbitrarily selected by considering various conditions to allow for selective iron precipitation. A specific preferred range for pH is described below.

[0068] As can be seen from Figure 2(a), under conditions where the pH is 7 or higher, both iron and zinc precipitate. However, in the pH range of (ii), i.e., pH 4.0 to 7.0, it is possible to selectively precipitate mainly iron. Therefore, in the iron precipitation step, it is preferable to add alkali to bring the pH to the range of (ii). Although Figure 2 shows the case when hydrochloric acid is used, similarly, when nitric acid is used, if the pH is between 4.0 and 7.0, it is possible to selectively precipitate mainly iron.

[0069] Specifically, in the iron precipitation step, it is preferable to add a first alkali so that the pH is between 4.0 and 7.0 (4.0 ≤ pH ≤ 7.0). By setting the pH to 4.0 or higher, iron can be precipitated efficiently. Furthermore, by setting the pH to 7.0 or lower, only iron can be precipitated more efficiently without precipitating zinc.

[0070] Furthermore, in the pH range of (ii) in Figure 2(a), when the oxidation-reduction potential (ORP) of the aqueous solution is positive, i.e., when the ORP is oxidative, primarily iron can be selectively precipitated. Therefore, in the iron precipitation step, the oxidation-reduction potential (ORP) of the treatment solution is controlled by adding an oxidizing agent. Since iron in the treatment solution generally exists as divalent iron ions, increasing the ORP of the treatment solution (creating an oxidative atmosphere) and converting the iron ions to trivalent ensures that the iron ions are reliably precipitated.

[0071] (Oxidizing agent) The oxidizing agent is not particularly limited and any such agent can be used. Preferably, the oxidizing agent is at least one selected from the group consisting of hydrogen peroxide, hypochlorite, O2 (oxygen)-containing gas, and O3 (ozone)-containing gas.

[0072] The hypochlorite salt is preferably at least one selected from the group consisting of alkali metal salts and alkaline earth metal salts of hypochlorous acid, and more preferably sodium hypochlorite. The O2-containing gas can be O2 gas itself, but air is preferred. In other words, an O2-containing gas (e.g., air) can be added to the treatment solution as an oxidizing agent. Similarly, the O3-containing gas can be O3 gas itself, or an O3-containing gas. Among these, from the viewpoint of availability and cost, it is preferable to use at least one selected from the group consisting of hydrogen peroxide, sodium hypochlorite, and air as the oxidizing agent.

[0073] When using a gas such as air as the oxidizing agent, it is preferable to add the oxidizing agent by blowing the gas into the processing liquid.

[0074] The amount of oxidizing agent added should preferably be controlled so that the ORP of the treatment solution reaches a value suitable for iron precipitation. Note that the optimal ORP value varies depending on the pH of the treatment solution. Therefore, it is preferable to experimentally determine the optimal ORP value according to the pH of the treatment solution.

[0075] The reaction temperature in the iron precipitation process can be arbitrarily set within a temperature range where the treatment solution does not solidify or evaporate. The reaction time is preferably 15 minutes to 120 minutes, taking into consideration the treatment efficiency.

[0076] Furthermore, in the present invention, it is preferable to use a reaction vessel divided into multiple compartments in the iron precipitation step, and to add the first alkali in at least two of the multiple compartments. In the iron precipitation step, the larger the reaction vessel, the more likely it is that the pH inside the reaction vessel will be uneven. For example, the pH tends to be higher near the location where the first alkali is added, and lower at locations further away from that location, or near the location where the treatment liquid after the preceding zinc leaching step flows in. Therefore, by using a reaction vessel divided into multiple compartments as described above, the pH can be controlled within a smaller volume compartment compared to using the entire reaction vessel without divisions, thereby improving the accuracy of pH adjustment and making the pH of the entire reaction vessel uniform. As a result, the recovery rate of zinc and iron can be improved even more effectively.

[0077] The method of dividing the reactor into the aforementioned multiple compartments is not particularly limited and can be chosen arbitrarily, but it is preferable to divide the entire reactor into compartments such that the volume of each compartment is approximately the same. The number of compartments can be any number of two or more. Depending on the total volume of the reactor, it is also preferable to have three or more, or even four or more, compartments from the viewpoint of improving the accuracy of pH adjustment. On the other hand, dividing the reactor into more compartments than necessary will saturate the effect and complicate the equipment, so it is preferable to have 10 or fewer compartments.

[0078] The above-mentioned sections can be used independently, and the iron precipitation process can be performed individually in each section. However, from the viewpoint of improving the accuracy of pH adjustment and continuous processing, it is preferable to use a cascade system in which the sections are connected and the iron precipitation process is performed while the treatment liquid flows from the upstream section to the downstream section. In this case, there are no particular limitations on how the treatment liquid flows between the sections, but for example, a partition plate (weir) of an appropriate height can be provided between adjacent sections, and the treatment liquid can flow to the next section sequentially by overflowing over the partition plate.

[0079] The arrangement of each section is not particularly limited; for example, all sections can be arranged in a series, or some or all sections can be arranged in parallel. When using partition plates to divide the sections, the partition plates can be arranged parallel to each other, or they can be arranged to intersect.

[0080] It is preferable to add the first alkali in at least two of the multiple compartments described above. For example, in a cascade-type reaction vessel, it is preferable to add the first alkali in at least the upstream and downstream compartments. Furthermore, from the viewpoint of improving the accuracy of pH adjustment, it is preferable to add the first alkali in all compartments. The type and concentration of the alkali compound added to each compartment can be selected independently for each compartment, but from the viewpoint of simplifying equipment and processes, it is preferable to use the same alkali. Also, as mentioned above, since steelmaking dust contains iron and other materials with a high specific gravity and tends to settle, it is preferable to stir the contents of the tank when adjusting the pH.

[0081] <Second solid-liquid separation step> Next, the treated liquid after the iron precipitation process is subjected to solid-liquid separation (second solid-liquid separation process). In this process, the treated liquid is separated into a filtrate mainly containing zinc ions and the solid content (iron precipitate) that precipitated in the iron precipitation process. The solid content generated in the iron precipitation process contains high-purity iron and can be reused as a raw material for steelmaking after a sintering process.

[0082] The solid-liquid separation method used in the second solid-liquid separation step is not particularly limited, and any method can be used. For example, methods such as gravity sedimentation, filtration, centrifugal separation, and filter pressing can be used individually or in combination.

[0083] The metal separation method of the present invention preferably further comprises an iron recovery step for recovering the iron separated in the second solid-liquid separation step. This allows the separated iron to be recovered and reused as a resource.

[0084] <Zinc precipitation process> Next, a second alkali is added to the treated liquid after the second solid-liquid separation step to precipitate zinc (zinc precipitation step). Here, "treated liquid after the second solid-liquid separation step" refers to the liquid portion (filtrate) after the solid component has been separated in the second solid-liquid separation step.

[0085] As described above, in the present invention, a lead precipitation step is performed after the lead-zinc leaching step, the precipitated lead is separated in the first solid-liquid separation step, and then an iron precipitation step is performed, and the precipitated iron is separated in the second solid-liquid separation step. Therefore, almost only zinc is dissolved in the treatment liquid after the second solid-liquid separation step. Accordingly, by adding alkali to the treatment liquid, only zinc can be selectively precipitated.

[0086] (Second alkali) The second alkali used in the zinc precipitation step is not particularly limited and any alkali can be used. Preferably, the second alkali is at least one selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides, and more preferably, one or both of calcium hydroxide and sodium hydroxide are used. Since these alkalis are inexpensive and readily available, processing costs can be reduced.

[0087] In this invention, since sulfuric acid is used in the lead precipitation step, if an alkaline earth metal hydroxide is used as the second alkali, it may form a water-insoluble salt such as CaSO4 and precipitate together with the zinc. As a result, the zinc concentration (purity) of the solid content (precipitate) obtained in the zinc precipitation step decreases. However, if sodium hydroxide is used as the second alkali, this problem does not occur because Na2SO4 is soluble in water. Therefore, it is particularly preferable to use sodium hydroxide as the second alkali in the zinc precipitation step.

[0088] The pH adjusted in the zinc precipitation process is not particularly limited and can be any value as long as it allows zinc to precipitate. However, it is preferable to set the pH to 8.0 or higher and 12.0 or lower. Setting the pH to 8.0 or higher allows for efficient zinc precipitation. Furthermore, setting the pH to 12.0 or lower prevents the precipitated zinc from redissolving into the treatment solution, thereby further improving the zinc recovery rate.

[0089] The reaction temperature in the zinc leaching process can be arbitrarily set within a temperature range where the treatment solution does not solidify or evaporate. Furthermore, considering the zinc precipitation formation time and treatment efficiency, the reaction time is preferably between 15 minutes and 120 minutes.

[0090] <Third solid-liquid separation step> Finally, the treated liquid after the zinc precipitation step is subjected to solid-liquid separation (third solid-liquid separation step). This separates the solid components (zinc precipitate) from the treated liquid.

[0091] The solid-liquid separation method used in the third solid-liquid separation step is not particularly limited, and any method can be used. For example, methods such as gravity sedimentation, filtration, centrifugal separation, and filter pressing can be used individually or in combination.

[0092] By following the above procedure, zinc and lead can be efficiently separated from steelmaking dust. The zinc precipitate separated by the method of the present invention contains a high concentration of zinc of 40% or more, making it highly valuable as a zinc raw material.

[0093] The metal separation method of the present invention preferably further comprises a zinc recovery step for recovering the zinc separated in the third solid-liquid separation step. This allows the separated zinc to be recovered and recycled as a zinc raw material through zinc smelting or the like.

[0094] (Second embodiment) Figure 3 is a flowchart showing a method for separating zinc and lead according to a second embodiment of the present invention. As shown in the flowchart, the metal separation method in this embodiment further includes a fourth solid-liquid separation step (S11) between the lead-zinc leaching step (S1) and the lead precipitation step (S2) for solid-liquid separation of the treatment liquid.

[0095] In the first embodiment described above, the lead and zinc leaching residue generated in the lead-zinc leaching process and the solid matter generated in the lead precipitation process are simultaneously separated in the first solid-liquid separation process. On the other hand, in this embodiment, first, the leaching residue generated in the lead-zinc leaching process is separated in the fourth solid-liquid separation process, and then only the solid matter generated in the lead precipitation process is separated in the first solid-liquid separation process. This further increases the concentration of lead separated in the first solid-liquid separation process, thereby improving its value as a lead raw material.

[0096] The solid-liquid separation method used in the fourth solid-liquid separation step is not particularly limited, and any method can be used. For example, methods such as gravity sedimentation, filtration, centrifugal separation, and filter pressing can be used individually or in combination.

[0097] When performing the fourth solid-liquid separation step, it is preferable to further include a second iron recovery step for recovering the iron (leaching residue) obtained in the fourth solid-liquid separation step. The leaching residue recovered in the second iron recovery step can be reused as a raw material for steelmaking after being sintered, for example.

[0098] Furthermore, the same principles as in the first embodiment may apply to all other aspects.

[0099] (Method of manufacturing metal materials) In a method for manufacturing a metal material according to one embodiment of the present invention, at least one of lead, iron, and zinc is separated and recovered from steelmaking dust by the metal separation method described above. By this method, lead, iron, and zinc contained in steelmaking dust can be recovered and reused as a metal material. For example, zinc contained in steelmaking dust can be concentrated to produce a zinc material with a zinc content of 40% or more. Similarly, lead contained in steelmaking dust can be concentrated to produce a lead material with a lead content of 60% or more. Furthermore, all of the iron contained in steelmaking dust can be recovered and recycled.

[0100] Next, we will describe the experiments conducted to investigate the preferred conditions for the separation method of the present invention. In the following experiments, radiofrequency-induced plasma emission spectroscopy (ICP-AES) was used for the component analysis of the leachate and filtrate, and energy-dispersive X-ray spectroscopy (SEM-EDX) was used for the component analysis of the residue and precipitate.

[0101] (Influence of the type of acid) Water was added to blast furnace dust having the composition shown in Table 1 to adjust the ratio of blast furnace dust to water to 1:10 (by weight). Next, acid was added to bring the pH to 2, and the mixture was stirred for 60 minutes. After that, the leaching rates of iron, lead, and zinc were investigated. Hydrochloric acid (HCl), nitric acid (HNO3), or sulfuric acid (H2SO4) were used as the acid, and the reaction pH during the experiment was controlled to be constant using a pH controller.

[0102] [Table 1]

[0103] Figure 4 shows the relationship between the type of acid used in the leaching treatment and the leaching rate of the components contained in blast furnace dust. The leaching rate of zinc was in the range of 67-77%, and no significant change was observed depending on the type of acid used. On the other hand, the leaching rate of lead was high, ranging from 76-89%, when hydrochloric acid or nitric acid was used, but was almost 0% when sulfuric acid was used. This is thought to be because the lead in the blast furnace dust reacted with sulfuric acid to produce lead sulfide, which became insoluble. Therefore, in the above lead and zinc leaching process, at least one of hydrochloric acid and nitric acid should be used to leach lead together with zinc.

[0104] (Effect of pH) Next, water was added to blast furnace dust having the composition shown in Table 1 to adjust the ratio of blast furnace dust to water to 1:10 (by weight). Then, hydrochloric acid was added to achieve pH values ​​of 1, 2, 3, and 4, and the mixture was stirred for 60 minutes. After that, the leaching rates of iron, lead, and zinc were investigated. The reaction pH during the experiment was controlled to be constant using a pH controller.

[0105] Figure 5 shows the relationship between pH during leaching and the leaching rates of iron, lead, and zinc. The leaching rates for iron, lead, and zinc increased with decreasing pH. However, while the leaching rate of iron remained low at 0.2-3.5% regardless of pH, the leaching rates of lead and zinc varied significantly with pH. Under conditions where the pH was 3 or below, the leaching rate of lead was 18% or higher, and the leaching rate of zinc was 42% or higher. Therefore, to effectively leach lead along with zinc while suppressing iron leaching, it is preferable to set the pH to 3.0 or below. Furthermore, the leaching rates of lead and zinc increased with decreasing pH during leaching, reaching 89% and 76% respectively at pH=2. On the other hand, the leaching rate of iron was only about 2% even at pH=2. Therefore, setting the pH to 2.0 or below allows for even more efficient leaching of lead along with zinc.

[0106] (Composition of residue generated in the lead and zinc leaching process) Next, the composition of the residue generated in the lead and zinc leaching process was investigated. Specifically, hydrochloric acid was added to the above-mentioned steelmaking dust to adjust the pH to 2, and zinc and lead were leached out. Subsequently, the treated liquid was subjected to solid-liquid separation to separate the residue generated in the lead and zinc leaching process. This solid-liquid separation corresponds to the fourth solid-liquid separation process described above.

[0107] Table 2 shows the results of the component analysis of the obtained residue. As shown in this table, the lead and zinc content in the residue after the lead and zinc leaching process was 0.1% and 0.2%, respectively. These values ​​are below the standard values ​​(0.2% and 0.4%) for lead and zinc content that are generally considered recyclable as raw materials for steelmaking. From these results, it can be seen that the residue separated and recovered in the fourth solid-liquid separation process can be entirely recycled as a raw material for steelmaking, mainly composed of iron.

[0108] [Table 2]

[0109] (Composition of solids separated in the first solid-liquid separation step) Furthermore, sulfuric acid was added to the treated liquid (filtrate) after the solid-liquid separation process (fourth solid-liquid separation process) to precipitate lead while maintaining a pH of 1.0 to 2.0 (lead precipitation process). Next, the treated liquid after the lead precipitation process was subjected to solid-liquid separation (first solid-liquid separation process). Table 3 shows the results of the component analysis of the solid separated in the first solid-liquid separation process. The lead content in the precipitate after the lead separation process was 69.1%. From these results, it can be seen that lead contained in steelmaking dust can be highly concentrated, separated, and recovered.

[0110] [Table 3] [Examples]

[0111] (Example of an invention) Zinc, iron, and lead were separated from blast furnace dust according to the flow shown in Figure 1. Specifically, blast furnace dust having the composition shown in Table 1 was first introduced into a reaction vessel, and water was added to adjust it to a slurry with a blast furnace dust:water ratio of 1:10 (by weight). Then, hydrochloric acid was added to the slurry to adjust the pH to 2.0, and the leaching time was set to 60 minutes, during which the treatment liquid in the reaction vessel was stirred to leach the lead and zinc contained in the blast furnace dust (lead and zinc leaching process).

[0112] Then, sulfuric acid was added to the treatment solution after the lead-zinc leaching process to precipitate the lead (lead precipitation process). In the lead precipitation process, sulfuric acid was added to maintain the pH at 1.0 to 2.0 while stirring the treatment solution in the reaction vessel, and then it was left to stand for 15 minutes.

[0113] Subsequently, the treated liquid after the lead precipitation step was subjected to solid-liquid separation (first solid-liquid separation step).

[0114] In the first solid-liquid separation step, a first alkali and an oxidizing agent were added to the treatment liquid to precipitate iron (iron precipitation step). Specifically, sodium hydroxide as the first alkali and hydrogen peroxide as the oxidizing agent were added to the treatment liquid (filtrate) after the first solid-liquid separation step to adjust the pH to 5.0. The iron concentration in the treatment liquid was determined in advance, and an amount of hydrogen peroxide sufficient to react with all iron ions was added.

[0115] Subsequently, the treated liquid after the iron precipitation step was subjected to solid-liquid separation (second solid-liquid separation step).

[0116] To the obtained treatment solution (filtrate), an aqueous sodium hydroxide solution was added to adjust the pH to 9.0, and the zinc contained in the treatment solution was precipitated (zinc precipitation step).

[0117] Finally, the treated liquid obtained in the zinc precipitation step was subjected to solid-liquid separation to separate the precipitated zinc (third solid-liquid separation step).

[0118] <Precipitation rate in the lead precipitation process> The precipitation rates of lead, zinc, and iron in the above lead precipitation process are shown in Fig. 6. From these results, it can be seen that according to the method of the present invention, in the lead precipitation process, lead can be completely precipitated and removed without substantially precipitating iron and zinc.

[0119] Note that the "precipitation rate" of lead, zinc, and iron in the lead precipitation process is the ratio of the amounts of Pb, Zn, and Fe precipitated in the lead precipitation process to the amounts of Pb, Zn, and Fe contained in the treatment liquid subjected to the lead precipitation process. However, in this example, since the fourth solid-liquid separation process was not performed, the treatment liquid after the lead-zinc leaching process was used as the treatment liquid subjected to the lead precipitation process. The precipitation rate was measured by the following method.

[0120] (Precipitation rate of lead) Pb concentration in the treatment liquid (filtrate) after the lead-zinc leaching process: C Pb、0 (mg / L) and the Pb concentration in the treatment liquid (filtrate) after the first solid-liquid separation process: C Pb、1 (mg / L) were measured by high-frequency inductively coupled plasma atomic emission spectrometry (ICP-AES). From the obtained values, the precipitation rate of Pb was calculated by the following formula (1). Precipitation rate of lead (%) = (C Pb、0 - C Pb、1 / C Pb、0 ) × 100... (1)

[0121] (Precipitation rate of zinc) Zn concentration in the treatment liquid (filtrate) after the lead-zinc leaching process: C Zn、0 (mg / L) and the Zn concentration in the treatment liquid (filtrate) after the first solid-liquid separation process: C Zn、1 (mg / L) were measured by high-frequency inductively coupled plasma atomic emission spectrometry (ICP-AES). From the obtained values, the precipitation rate of Zn was calculated by the following formula (2). Precipitation rate of zinc (%) = (C Zn、0 - C Zn、1 / C Zn、0 ) × 100... (2) [[ID=I]]

[0122] (Precipitation rate of iron) Fe concentration in the treatment liquid (filtrate) after the lead-zinc leaching process: C Fe、0(mg / L) and Fe concentration in the processed liquid (filtrate) after the first solid-liquid separation step: C Fe、1 The concentration (mg / L) was measured by radiofrequency induction plasma emission spectroscopy (ICP-AES). From the obtained values, the precipitation rate of Fe was calculated using the following equation (3). Iron precipitate rate (%) = (C Fe、0 -C Fe、1 / C Fe、0 ) × 100…(3)

[0123] <Lead content> The precipitate obtained in the lead precipitation process described above was subjected to component analysis. The results of the component analysis are shown in Table 4. In the obtained precipitate, lead was concentrated to 69%, exceeding the lead content of 40%, which is considered to have high recovery value as a lead raw material. From these results, it can be seen that, according to the method of the present invention, lead can be separated more efficiently than from steelmaking dust, and the separated lead can be recycled as a lead raw material.

[0124] [Table 4]

[0125] <Precipitation rate in the iron precipitation process> Next, Figure 7 shows the precipitation rates of iron and zinc in the iron precipitation process described above. From these results, it can be seen that, according to the method of the present invention, iron can be completely precipitated and removed in the iron precipitation process with almost no zinc precipitated.

[0126] The "sedimentation rate" of zinc and iron in the iron precipitation process refers to the ratio of the amount of Zn or Fe precipitated in the iron precipitation process to the amount of Zn or Fe contained in the treatment solution subjected to the iron precipitation process. The said sedimentation rate was measured by the following method.

[0127] (Zinc precipitation rate) Zn concentration in the processed liquid (filtrate) after the first solid-liquid separation step: C Zn、1 (mg / L) and the Zn concentration in the processed liquid (filtrate) after the second solid-liquid separation step: C Zn、2The concentration (mg / L) was measured by radiofrequency-induced plasma emission spectroscopy (ICP-AES). From the obtained values, the precipitation rate of Zn was calculated using the following equation (4). Zinc precipitation rate (%) = (C Zn、1 -C Zn、2 / C Zn、1 ) × 100…(4)

[0128] (Iron precipitation rate) Similar to the case of zinc, the Fe concentration in the processed liquid (filtrate) after the first solid-liquid separation step: C Fe、1 (mg / L) and Fe concentration in the processed liquid (filtrate) after the second solid-liquid separation step: C Fe、2 The concentration (mg / L) was measured by radiofrequency induction plasma emission spectroscopy (ICP-AES). From the obtained values, the precipitation rate of Fe was calculated using the following equation (5). Iron precipitate rate (%) = (C Fe、1 -C Fe、2 / C Fe、1 ) × 100…(5)

[0129] <Zinc content> The precipitate formed in the above zinc precipitation process was subjected to component analysis. The results of the component analysis are shown in Table 5. From Table 5, it can be seen that the obtained precipitate was concentrated with zinc up to 44.9%, exceeding the 40% zinc content which is considered to have high recovery value as a zinc raw material. This indicates that zinc separated from steelmaking dust can be recycled as a zinc raw material.

[0130] [Table 5]

[0131] (Comparative example) For comparison, zinc and lead were separated from blast furnace dust using the same procedure as in the above-described example, except that the lead precipitation step was omitted. In other words, in the comparative example, hydrochloric acid was added to the slurry to adjust the pH to 2.0 as a lead-zinc leaching step, and the lead and zinc contained in the blast furnace dust were leached out (lead-zinc leaching step). Then, without performing a lead precipitation step involving the addition of sulfuric acid, the treated liquid after the lead-zinc leaching step was subjected to solid-liquid separation (first solid-liquid separation step).

[0132] For each of the above-described inventive examples and comparative examples, the lead removal rate was measured using the following procedure.

[0133] <Lead removal rate> The lead removal rate refers to the ratio of the amount of lead that was not recovered as solid matter (precipitate) in the first solid-liquid separation step to the amount of lead contained in the steelmaking dust before processing. The solid matter recovered in the first solid-liquid separation step consists of residue that did not dissolve in the lead-zinc leaching step (lead and zinc leaching residue) and solid matter that precipitated in the lead precipitation step, and is recovered as lead material. Therefore, the amount of lead contained in the solid matter obtained in this first solid-liquid separation step can be considered as the amount of lead that was removed.

[0134] In other words, the lead removal rate is determined by the Pb concentration of the steelmaking dust before treatment: C Pb、a (mass%), Pb concentration in the solids separated in the first solid-liquid separation step: Cp b、b The mass percentage was measured and calculated using the following formula (6). Lead removal rate (mass%) = (C Pb、b / C Pb、a ) × 100…(6)

[0135] Table 6 shows the lead removal rates in the inventive example and the comparative example. As can be seen from the results in Table 6, the lead removal rate in the comparative example was low at 0%, but in the inventive example, the lead removal rate improved to 66%. This is because, in the comparative example, where the lead precipitation process was not performed, lead could not be separated from the treated solution after the lead-zinc leaching process.

[0136] Table 6

Claims

1. A method for separating metals from steelmaking dust, A lead and zinc leaching step is performed in which hydrochloric acid and / or nitric acid are added to the aforementioned steelmaking dust to adjust the pH to 1.0 or higher and 3.0 or lower, thereby leaching out the lead and zinc contained in the steelmaking dust. A lead precipitation step is performed in which sulfuric acid is added to the treatment solution after the lead and zinc leaching step to adjust the pH to 1.0 or higher, thereby precipitating the lead contained in the treatment solution after the lead and zinc leaching step. A first solid-liquid separation step is performed to separate the treated liquid after the lead precipitation step from solid to liquid, An iron precipitation step is performed by adding a first alkali and an oxidizing agent to the processing liquid after the first solid-liquid separation step to precipitate iron, A second solid-liquid separation step is performed to separate the treated liquid after the iron precipitation step from solid to liquid, A zinc precipitation step is performed by adding a second alkali to the processing liquid after the second solid-liquid separation step to precipitate zinc, A method for separating metals, comprising a third solid-liquid separation step of separating the treated liquid after the zinc precipitation step into solid and liquid components.

2. The method for separating metals according to claim 1, wherein the pH is adjusted to 1.0 or more and 2.0 or less in the lead-zinc leaching step.

3. The method for separating metals according to claim 1, wherein the leaching time in the lead-zinc leaching step is 15 minutes or more and 120 minutes or less.

4. The method for separating metals according to claim 1, wherein the pH is adjusted to 1.0 or more and 2.0 or less in the lead precipitation step.

5. The method for separating metals according to claim 2, wherein the pH is adjusted to 1.0 or more and 2.0 or less in the lead precipitation step.

6. In the aforementioned iron precipitation step, the pH of the treatment solution is adjusted to 4.0 or higher and 7.0 or lower. In the zinc precipitation step, the pH of the treatment solution is adjusted to 8.0 or higher and 12.0 or lower. The method for separating metals according to claim 1.

7. A method for separating metals according to any one of claims 1 to 6, further comprising at least one of the following steps: a lead recovery step for recovering lead separated in the first solid-liquid separation step; an iron recovery step for recovering iron separated in the second solid-liquid separation step; and a zinc recovery step for recovering zinc separated in the third solid-liquid separation step.

8. The method for separating metals according to claim 1, further comprising a fourth solid-liquid separation step of separating the treated liquid into solid and liquid phases between the lead-zinc leaching step and the lead precipitation step.

9. A method for separating metals according to claim 8, further comprising at least one of the following: a lead recovery step for recovering lead separated in the first solid-liquid separation step; an iron recovery step for recovering iron separated in the second solid-liquid separation step; a zinc recovery step for recovering zinc separated in the third solid-liquid separation step; and a second iron recovery step for recovering iron separated in the fourth solid-liquid separation step.

10. A method for manufacturing metal materials from ironmaking dust, A method for producing a metal material, comprising separating and recovering at least one of lead, iron, and zinc from the aforementioned ironmaking dust using the metal separation method described in claim 7.

11. A method for manufacturing metal materials from ironmaking dust, A method for producing a metal material, comprising separating and recovering at least one of lead, iron, and zinc from the aforementioned ironmaking dust using the metal separation method described in claim 9.

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