Method for recovering lead from copper smelting dust

Abstract

To efficiently recover lead contained in copper smelting dust by being separated from copper and tin, zinc and precious metals, such as gold and silver.SOLUTION: A method for recovering lead in copper smelting dust includes: an alkali exudation step of exuding lead contained in copper smelting dust by an alkali solution; the step of carrying out solid-liquid separation of post-exudation liquid and leach residue in the alkali exudation; a neutralization step of precipitating lead by adding acid to the post-exudation liquid thus separated; and the step of recovering by solid-liquid separation of a deposit including lead.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for recovering lead from dust (dust) generated in a copper smelting process, and relates to a method for efficiently recovering lead contained in the dust by separating it from precious metals such as copper, tin, zinc, and gold and silver. [Background technology]

[0002] In the copper smelting process, for example, raw materials such as copper concentrate are melted, and separated into copper matte and slag by utilizing the difference in specific gravity of the solution. The slag is extracted, and air is blown into the copper matte to produce blister copper. The blister copper is reduced in a refining furnace and cast into an anode, and electrolytic copper is produced by electrolytic refining or the like. In such copper smelting, if the amount of lead contained in the raw materials increases, the lead concentration in the copper anode increases, which adversely affects the copper electrolytic refining process. To avoid this adverse effect, it is necessary to remove lead from the copper smelting process.

[0003] Lead is highly volatile, so it is concentrated in the dust (dust) from the copper smelting process. The dust contains volatile metals other than lead (tin, zinc, etc.), as well as copper and precious metals. In order to recover the copper and precious metals, the dust generated in the smelting process is collected and fed back to the copper smelting furnace. If the lead contained in the collected dust is separated, it can be removed from the copper smelting process.

[0004] Conventionally, a method for treating copper smelting dust and the like has been known in which copper and lead are separated by immersing the copper smelting dust in sulfuric acid to leach copper, which concentrates lead in the leaching residue to form a leaching residue (lead slag) mainly composed of lead. For example, Japanese Patent Laid-Open Publication No. 59-162233 describes a treatment method in which copper smelting dust is immersed in dilute sulfuric acid to leach copper, zinc, and arsenic, while forming a residue mainly composed of lead and bismuth.

[0005] It is also known to perform sulfuric acid leaching by adding an oxidizing agent. For example, JP 2009-242850 A describes a method of forming a slurry of lead slag, adding sulfuric acid and ferric sulfate together with air, oxidizing the copper, and leaching it with sulfuric acid to separate the lead and copper. Furthermore, JP 2013-237920 A describes a method of adding copper smelting dust to a sulfuric acid acidic solution having a pH of 1.0 or more, adding a trivalent iron compound to oxidize the copper, and leaching the copper in the dust, thereby increasing the leaching rate of copper and separating it from the lead in the leaching residue.

[0006] However, in the sulfuric acid leaching of copper smelting dust, the lead slag that is the leaching residue contains a small amount of copper, and most of the tin, gold, silver, etc. in the dust are also contained in the lead slag, making it difficult to obtain a lead product with a high lead content.In addition, various impurities in lead smelting, other than copper, remain in the lead slag without being leached, making the lead slag undesirable as a raw material for lead smelting. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 59-162233 [Patent Document 2] JP 2009-242850 A [Patent Document 3] JP 2013-237920 A Summary of the Invention [Problem to be solved by the invention]

[0008] The method of the present invention solves the above problems in the conventional sulfuric acid leaching of copper smelting dust, and is a method for efficiently recovering lead contained in copper smelting dust by separating it from precious metals such as copper, tin, zinc, and gold and silver. and a method for recovering lead comprising the following steps: [1] A method for recovering lead from copper smelting dust comprising the steps of: adding an alkaline solution to copper smelting dust containing lead and tin, and separating the lead and tin by leaching the lead at a pH of 13.0 or higher while leaving the tin in a residue; performing solid-liquid separation of the leaching solution from the leaching residue from the alkaline leaching; neutralizing the separated leaching solution by adding an acid to cause the lead to precipitate; and recovering the lead-containing precipitate by solid-liquid separation, characterized in that the lead is separated from the tin and recovered. [2] Regarding copper smelting dust, which contains tin and arsenic along with lead, In the neutralization step By neutralizing the solution at pH 11.5 or higher and pH 12.5 or lower, lead is selectively precipitated without precipitating arsenic.A method for recovering lead from copper smelting dust as described in [1] above. [3] Regarding copper smelting dust, which contains tin and soluble copper and zinc along with lead, The copper smelting dust is washed with water or acid, After washing and removing the copper and zinc A method for recovering lead from copper smelting dust as described in [1] or [2] above, which comprises subjecting the washed copper smelting dust to alkaline leaching. [Means for solving the problem]

[0009] [Specific explanation] The present invention will be specifically described below. Note that % for concentration is mass %. The treatment method of the present invention is a method for separating and recovering lead from dust generated in the copper smelting process (referred to as copper smelting dust). Copper smelting dust contains copper, zinc, tin, and small amounts of precious metals in addition to lead. The treatment method of the present invention is a method for efficiently separating and recovering lead contained in copper smelting dust from copper, tin, zinc, gold, silver, etc.

[0010] Specifically, the lead recovery method of the present invention includes the following steps: A method for recovering lead from copper smelting dust comprising: an alkaline leaching step of adding an alkaline solution to copper smelting dust containing lead and tin, and separating the lead and tin by leaching the lead at a pH of 13.0 or higher while leaving the tin in a residue; a step of performing solid-liquid separation of the leaching solution and the leaching residue from the alkaline leaching; a neutralization step of adding an acid to the separated leaching solution to precipitate the lead; and a step of recovering the lead-containing precipitate by solid-liquid separation, characterized in that the lead is separated from the tin and recovered. In addition, the lead recovery method of the present invention may include a washing step of washing the copper smelting dust with water or acid prior to the alkaline leaching step, and it is more preferable to carry out alkaline leaching on the copper smelting dust obtained by the washing (referred to as washed dust). An example of the process flow of the lead recovery method of the present invention is shown in Figure 1.

[0011] [Cleaning process] Copper smelting dust is washed with water or acid. This washing washes away soluble copper compounds contained in the copper smelting dust. For example, most of the copper contained in the copper smelting dust is copper sulfate, which dissolves in water and removes the copper. Note that the copper smelting dust slurry becomes weakly acidic due to the dissolution of copper sulfate, etc., so acid may be used instead of water for washing.

[0012] The washing process prior to the alkaline leaching removes most of the copper contained in the dust from the system, and also removes most of the zinc contained in the copper smelting dust, reducing the chemical costs required for the alkaline leaching. Note that the lead and tin other than copper contained in the copper smelting dust are in the form of oxides or sulfates, and these remain in the washed dust without being washed away.

[0013] After washing, the slurry is subjected to solid-liquid separation to recover the washed dust, and the washed liquid is sent to the outside of the system. The washed liquid contains most of the copper content of the copper smelting dust, so it can be used as a copper recovery raw material. The recovered washed dust is sent to the alkali leaching process.

[0014] [Alkaline leaching process] The cleaning dust is added to an alkaline solution to form a slurry, and the lead contained in the cleaning dust is leached out by alkaline leaching. The alkaline solution can be a common alkaline solution such as a sodium hydroxide solution or a potassium hydroxide solution.

[0015] The lead contained in cleaning dust is mainly lead sulfate (PbSO4) and lead oxide (PbO). Lead sulfate, for example, reacts with sodium hydroxide as shown in the following formula [1] to produce lead iodide ions and dissolve. Lead oxide also dissolves in the same way, but since lead oxide is more stable than lead sulfate, lead that exceeds its solubility will precipitate as lead oxide. PbSO4+ 2NaOH → HPbO2 - + Na2SO4+ H + [1]

[0016] The solubility of lead in an alkaline solution varies depending on the pH. Figure 2 shows the change in lead concentration in the solution versus pH. As shown in the graph in Figure 2, the lead concentration at pH 13.0 is 2g / L, and the lead concentration in the solution increases in proportion to the increase in pH. For example, the lead concentration at pH 13.5 is close to 6g / L, which is approximately three times the lead concentration at pH 13.0. Therefore, to leach lead using an alkaline solution, the pH of the alkaline solution is preferably 13.0 or higher, and more preferably 13.5 or higher.

[0017] On the other hand, most of the tin contained in the cleaning dust is tin oxide (SnO2), and traces of copper sulfide (CuS) remain in the cleaning dust, but these tin oxides and copper sulfides are hardly soluble in alkaline solutions. Also, the traces of precious metals such as gold and silver contained in the cleaning dust are not dissolved, so lead is selectively leached in this alkaline leaching.

[0018] [Solid-liquid separation] After alkaline leaching, the leaching solution and the leaching residue are separated into solid and liquid. The recovered leaching solution contains lead, so it is sent to a neutralization process to recover the lead. Meanwhile, the leaching residue contains tin oxide, which is difficult to leach with alkaline, a small amount of copper, and trace amounts of precious metals, so this leaching residue can be added to the raw materials repeatedly, for example in the copper smelting process, and reused.

[0019] [Neutralization process] As shown in Figure 2, the lead concentration in the solution decreases with decreasing pH, and at a pH of 12.5 the lead concentration is essentially zero. 2+ ) in the pH range of 13 or higher, for example, HPbO2 - However, when the pH is in the range of 12.5 or less, precipitation of lead oxide (PbO) occurs. Therefore, in order to recover the lead contained in the leaching solution, an acid is added to the leaching solution to neutralize it so that the pH is in the alkaline region of 12.5 or less. Here, if the raw copper smelting dust contains arsenic, the arsenic may migrate to the alkaline leaching solution. In that case, if the pH is lowered too much, arsenic oxide (As2O3) may precipitate, which may reduce the quality of the recovered lead, which is not preferable. Therefore, the pH of the neutralized solution is preferably in the alkaline region. Specifically, a pH of 10.0 or more and a pH of 12.5 or less are preferable, and a pH of 11.5 or more and a pH of 12.5 or less are more preferable. The acid used for neutralization may be a common acid such as sulfuric acid, hydrochloric acid, or nitric acid.

[0020] [Recovery process] After neutralization, solid-liquid separation is performed to recover the precipitate containing lead. This recovered lead-containing material (called lead recovery material) contains only a small amount of impurities other than lead, because lead is selectively leached out during the alkaline leaching of the cleaning dust. Therefore, the recovered lead material has a high lead content. Effect of the Invention

[0021] The lead recovered by the method of the present invention has a higher lead concentration than the lead slag obtained by sulfuric acid leaching. Specifically, for example, the lead concentration of the lead recovered by Example 1 of the present invention is 62.0%, while the lead concentration of the lead slag obtained by sulfuric acid leaching in Comparative Example 1 is 9.4%, so the lead quality of the lead recovered by the method of the present invention is significantly higher.

[0022] In the method including the washing step of the present invention, most of the copper contained in the dust is removed in the washing step, so that the burden of alkaline leaching is reduced, and a lead recovered material having a lower copper concentration and a higher lead concentration is obtained compared to the case not including the washing step. Specifically, for example, the lead concentration of the lead recovered material in Example 2, which does not include the washing step, is 38.5% (lead transfer rate 34.7%) and the copper concentration is 25.5% (copper transfer rate 9.0%), while the lead concentration of the lead recovered material in Example 1, which includes the washing step, is 62.0% (lead transfer rate 49.5%) and the copper concentration is 4.7% (copper transfer rate 1.5%), so that the copper concentration is significantly reduced while the lead concentration is remarkably high.

[0023] Furthermore, according to the lead recovery method of the present invention, a lead recovery product containing almost no tin, gold or silver can be obtained, so that the loss of valuables such as gold and silver is significantly reduced. [Brief description of the drawings]

[0024] [Figure 1] 1 is a process flow showing an example of the lead recovery method of the present invention. [Diagram 2] Graph showing change in lead concentration versus pH of alkaline solution. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Examples of the present invention will be described below together with comparative examples. Metal concentrations in the liquid and sediment were measured by ICP-AES. The concentrations of metals and other elements contained in the copper smelting dust used are shown in Table 1. The transfer rates of these metals were calculated using the following formula [2]. Transfer rate (%) = [amount of metal in collected material] / [amount of metal in dust] × 100 [2]

[0026] [Table 1]

[0027] Example 1 300g of copper smelting dust was dissolved in 1L of water and stirred for 30 minutes to make a water slurry. This was separated into solid and liquid using a suction filter to obtain a post-wash residue (washed dust) and post-wash liquid. This washed dust was dissolved in 1L of 3N NaOH solution to make an alkaline slurry, the pH was adjusted to 14 or more, and alkaline leaching was performed for 30 minutes. After leaching, the alkaline slurry was separated into solid and liquid using a suction filter to obtain a post-leaching liquid and a leaching residue. The separated post-leaching liquid was neutralized by adding sulfuric acid, and the pH was adjusted to 12.5 to precipitate lead oxide. Thereafter, the lead oxide precipitate and the neutralized liquid were separated into solid and liquid using a suction filter, and the recovered lead oxide precipitate was dried at 105°C for 12 hours to obtain a recovered lead product. The transfer rates of metals contained in the post-washing solution from the water washing, the leaching residue from the alkali leaching, and the post-neutralization solution from the neutralization treatment are shown in Table 2. The concentrations and transfer rates of metals contained in the recovered lead are shown in Table 3. As shown in Table 3, the lead concentration of the recovered lead was 60% or more, and the recovered lead was of high lead quality, containing almost no tin, gold, or silver. Furthermore, as shown in Table 2, all of the gold and silver was transferred to the leaching residue of the alkaline leaching, and was substantially not contained in the recovered lead, so the loss of gold, silver, etc. in the recovered lead could be minimized. Furthermore, as shown in Table 2, more than 80% of the copper contained in the dust was washed away by washing with water, so a lead recovered product with a low copper concentration could be obtained.

[0028] [Table 2]

[0029] [Table 3]

[0030] Example 2 300 g of copper smelting dust similar to that in Example 1 was dissolved in 1 L of 3N NaOH solution to prepare an alkaline slurry, the pH of which was adjusted to 14, and alkaline leaching was carried out for 30 minutes. After leaching, the alkaline slurry was subjected to solid-liquid separation using a suction filter to obtain a post-leaching liquid and a leaching residue. The separated post-leaching liquid was neutralized by adding sulfuric acid, and the pH was adjusted to 12.5 to precipitate lead oxide. Thereafter, the lead oxide precipitate and the neutralized liquid were subjected to solid-liquid separation using a suction filter, and the recovered lead oxide precipitate was dried at 105°C for 12 hours to obtain a recovered lead product. The transfer rates of metals contained in the leaching residue from the alkaline leaching and the post-neutralization solution are shown in Table 4. The concentrations and transfer rates of metals contained in the recovered lead are shown in Table 5. As shown in Table 5, the lead concentration was 38.5%, the tin concentration was low, and the lead recovered contained almost no gold or silver. The lead content in this example was lower than in Example 1, but this is because copper was eluted together with lead by alkaline leaching, resulting in the formation of tetrahydroxycuprate ions [Cu(OH)4 2- 〕 was formed, which consumed hydroxyl groups, lowered the pH, and reduced the lead leaching rate. In addition, the copper concentration of the lead recovered in this example is higher than that in Example 1, but this is thought to be because, since water washing is not performed in this example, copper is not washed away and remains, and this copper is leached by alkali and becomes mixed into the lead precipitate. From a comparison between this Example 1 and this Example (Example 2), it was confirmed that water washing prior to alkali leaching is effective in removing copper.

[0031] [Table 4]

[0032] [Table 5]

[0033] [Comparative Example 1: Sulfuric acid leaching] 300 g of copper smelting dust similar to that in Example 1 was dissolved in 1 L of sulfuric acid with a concentration of 200 g / L to prepare a sulfuric acid slurry, which was then subjected to sulfuric acid leaching for 30 minutes. After leaching, the sulfuric acid slurry was subjected to solid-liquid separation using a suction filtration device to obtain a leaching residue (lead slag) and a post-leaching solution. This leaching residue was dried at 105°C for 12 hours to obtain a recovered lead product. The concentration and transfer rate of metals, etc. in this recovered lead product are shown in Table 6. The transfer rate of metals, etc. to the post-leaching solution is also shown in Table 6. As shown in Table 6, the lead concentration of the lead recovered material was 9.4%, which was significantly lower than that of Examples 1 and 2. Also, although the copper concentration of the lead recovered material in this comparative example was low, the copper / lead ratio (Cu / Pb) of Example 1 was about 0.076, while the copper / lead ratio (Cu / Pb) of this comparative example was about 0.276, which was significantly higher than that of Example 1. Also, the tin concentration of this comparative example was about 10%, which is not preferable as a lead raw material. Furthermore, in this comparative example, the entire amount of lead contained in the dust was transferred to the lead recovered material, but 11% of the copper and almost all of the gold and silver were transferred to the lead recovered material, indicating a very large loss of valuable materials.

[0034] [Table 6]

Claims

1. A method for recovering lead from copper smelting dust containing lead and tin, comprising: an alkaline leaching process in which an alkaline solution is added to the copper smelting dust and the lead is leached at a liquid pH of 13.0 or higher while leaving the tin in a residue, thereby separating the lead and tin; a process for solid-liquid separation of the leaching liquid and the leaching residue from the alkaline leaching; a neutralization process in which an acid is added to the separated leaching liquid to precipitate lead; and a process for recovering the lead-containing precipitate through solid-liquid separation, characterized in that the lead is separated from the tin and recovered.

2. A method for recovering lead from copper smelting dust as described in claim 1, in which copper smelting dust containing tin and arsenic in addition to lead is neutralized in the neutralization process at a liquid pH of 11.5 or more and 12.5 or less, thereby selectively precipitating lead without precipitating arsenic.

3. For copper smelting dust containing tin and soluble copper and zinc together with lead, 3. A method for recovering lead from copper smelting dust according to claim 1 or 2, comprising washing the copper smelting dust with water or acid to remove the copper and zinc components, and then subjecting the washed copper smelting dust to alkaline leaching.

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