How to recover tin

Abstract

This tin recovery method recovers tin from a tin-containing material, and is characterized by comprising: an oxidation leaching step (S01) of oxidatively leaching the tin in the tin-containing material into a leachate consisting of a sulfuric acid acidic solution to obtain a leachate containing tin; an oxidation step (S02) of adding sodium chloride and a substance that supplies divalent copper ions to the leachate obtained in the oxidative leaching step (S01) to oxidize divalent tin ions contained in the leachate to tetravalent tin ions; and a neutralization step (S03) of neutralizing the leachate after the oxidation step (S02) to obtain a tin-containing precipitate.

Description

[Technical field]

[0001] The present invention relates to a method for recovering tin from a tin-containing material. This application claims priority based on Japanese Patent Application No. 2023-053128, filed on March 29, 2023, the contents of which are incorporated herein by reference. [Background technology]

[0002] As a conventional method for recovering tin from a tin-containing material, for example, Patent Document 1 discloses a method in which a raw material obtained by separating lead from dross generated in a lead smelting process is melted and reduced to obtain a tin-containing material (containing mainly tin and copper), which is oxidized in an NaOH solution to leach tin, and tin is recovered from this tin leachate by electrowinning. In the method disclosed in Patent Document 1, if the tin-containing material contains lead, the lead is leached together with the tin, and since this lead is a more noble element than tin, it is precipitated in preference to tin during electrowinning, so there was a problem that the tin and lead could not be separated. In addition, there was also a problem that the chemical cost was high because NaOH was used for leaching.

[0003] Furthermore, Patent Documents 2 and 3 disclose a method in which copper smelting dust is leached with hydrochloric acid or nitric acid to preferentially elute copper and lead, while concentrating and recovering tin in the leaching residue. The methods disclosed in Patent Documents 2 and 3 have the advantage that tin exists as a solid after leaching, and therefore tin can be easily recovered by solid-liquid separation. However, there is a problem in that the tin content of the recovered tin obtained is low, since many elements are not leached together with tin.

[0004] Therefore, Patent Document 4 proposes a method of oxidatively leaching tin from a tin-containing material in a sulfuric acid acidic solution, and then neutralizing the resulting leached solution to produce a tin precipitate and recover the tin. The method disclosed in Patent Document 4 makes it possible to efficiently recover tin from tin-containing materials that contain tin as well as copper and lead, and also makes it possible to obtain a tin recovered material with a higher tin quality than that obtained by hydrochloric acid leaching or nitric acid leaching. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent No. 5188768 (B) [Patent Document 2] Japanese Patent Application Publication No. 2019-151862 (A) [Patent Document 3] Japanese Patent Application Publication No. 2019-151863 (A) [Patent Document 4] Japanese Patent Application Publication No. 2022-130015 (A) Summary of the Invention [Problem to be solved by the invention]

[0006] In the method disclosed in Patent Document 4, divalent tin ions and tetravalent tin ions coexist in the leaching solution obtained by oxidative leaching of tin in a tin-containing material in a sulfuric acid solution. Here, divalent tin ions precipitate at a pH of 3.5 to 4.5, and tetravalent tin ions precipitate at a pH of 1.5 to 2.5. When the pH is neutralized to 3.5 to 4.5 in the neutralization process in order to recover divalent tin ions as a precipitate, iron and aluminum contained in the post-leaching solution also precipitate, resulting in a problem of a decline in the quality of the tin recovered as a precipitate. In addition, there is a problem in that the need to neutralize the pH to 3.5 to 4.5 increases the cost of chemicals. On the other hand, if the neutralization step is carried out to a pH of 1.5 to 2.5, divalent tin ions cannot be recovered, and the recovery rate of tin drops significantly.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a tin recovery method that can efficiently recover high-quality tin from tin-containing materials. [Means for solving the problem]

[0008] In order to solve the above problems, a tin recovery method according to a first aspect of the present invention is a method for recovering tin from a tin-containing material, the method comprising: an oxidation leaching step of oxidizing and leaching tin from the tin-containing material into a leachate comprising a sulfuric acid acidic solution to obtain a post-leachate containing tin; an oxidation step of adding sodium chloride and a substance that supplies divalent copper ions to the post-leachate obtained in the oxidation leaching step to oxidize divalent tin ions contained in the post-leachate to tetravalent tin ions; and a step of neutralizing the post-leachate after the oxidation step to obtain a post-leachate containing tin. pH 1.5 to 2.5 and a neutralization step for obtaining a tin-containing precipitate.

[0009] According to the tin recovery method of the first aspect of the present invention, there is an oxidation step in which sodium chloride and a substance that supplies divalent copper ions are added to the post-leaching solution obtained in the oxidation leaching step before the neutralization step, and divalent tin ions contained in the post-leaching solution are oxidized to tetravalent tin ions, so that the tin in the post-leaching solution can be efficiently recovered as a precipitate by neutralizing the solution to a pH of 1.5 to 2.5 in the neutralization step. In addition, the incorporation of iron and aluminum into the tin precipitate can be suppressed, and high-quality tin can be recovered.

[0010] A tin recovery method according to a second aspect of the present invention is the tin recovery method according to the first aspect, characterized in that in the oxidative leaching step, a substance that supplies divalent or trivalent iron ions is added to the leaching solution.

[0011] In the oxidation leaching process, if the tin concentration in the leachate increases, metastannic acid may precipitate, causing a decrease in the recovery rate of tin. In addition, the generated metastannic acid may easily cause clogging of the filter when the post-leachate solution is separated through a filter. In addition, if the tin-containing raw material contains iron, the iron may be preferentially oxidized in the oxidation leaching process, making it difficult for tin to be leached.

[0012] In the tin recovery method according to the second aspect of the present invention, a substance that supplies divalent or trivalent iron ions is added to the leaching solution in the oxidative leaching step, which makes it possible to suppress oxidation of iron contained in the tin-containing material and efficiently leach tin. Also, it is possible to suppress the precipitation of metastannic acid in the oxidative leaching step, which makes it possible to improve the tin recovery rate and suppress the occurrence of filter clogging. Effect of the Invention

[0013] According to the present invention, it is possible to provide a tin recovery method that can efficiently recover high-quality tin from tin-containing materials. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a flow diagram showing a tin recovery method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An example of an embodiment of the present invention will now be described.

[0016] The tin recovery method of this embodiment recovers tin from tin-containing materials produced in, for example, a lead smelting process or a copper smelting process.

[0017] As shown in FIG. 1, the tin recovery method of this embodiment includes an oxidative leaching step S01 in which tin in a tin-containing material is converted into a leachate consisting of a sulfuric acid solution, an oxidation step S02 in which divalent tin ions contained in the leachate obtained in the oxidative leaching step S01 are oxidized to tetravalent tin ions, and a neutralization step S03 in which the leachate after the oxidation step S02 is neutralized to obtain a tin-containing precipitate.

[0018] (Oxidation leaching process S01) In this oxidative leaching step S01, the tin-containing material is brought into contact with a leachate consisting of a sulfuric acid solution containing sulfuric acid, thereby oxidatively leaching the tin contained in the tin-containing material, and a leached solution containing tin is obtained by solid-liquid separation. As the tin-containing material, for example, crushed electronic substrates (crushed substrates), scrap such as solder chips, selected products of various scraps, various intermediate smelting products, and the like can be used. The sulfuric acid concentration contained in the sulfuric acid solution may be 1 g / L to 100 g / L, 100 g / L to 200 g / L, or 200 g / L to 400 g / L. Here, divalent tin ions and tetravalent tin ions coexist in the resulting leaching solution.

[0019] In this embodiment, in this oxidative leaching step S01, it is preferable to add a substance that supplies divalent or trivalent iron ions to the leaching solution (sulfuric acid solution). By supplying divalent or trivalent iron ions to the leaching solution, it is possible to suppress the oxidation of iron contained in the tin-containing material, and to promote the oxidative leaching of tin. Furthermore, even if the tin concentration in the leachate becomes high, the precipitation of tin metathionate can be suppressed, and clogging of the filter during solid-liquid separation can be suppressed.

[0020] Here, the concentration of divalent or trivalent iron ions is preferably 1 g / L or more, more preferably 5 g / L or more, while the concentration of divalent or trivalent iron ions is preferably 100 g / L or less, more preferably 50 g / L or less. The substance that supplies the divalent or trivalent iron ions is not particularly limited, but specifically, for example, ferrous sulfate, ferric sulfate, etc. can be used.

[0021] Furthermore, in the sulfuric acid leaching step S01, it is preferable to stir the mixture while blowing in air. Here, the amount of air to be blown in is preferably within a range of 10 mL to 500 mL in total per gram of Sn to be recovered. The stirring time is preferably within a range of 1 hour to 10 hours.

[0022] (Oxidation process S02) Next, sodium chloride and a substance that supplies divalent copper ions are added to the leaching solution obtained as described above, and the divalent tin ions contained in the leaching solution are oxidized to tetravalent tin ions. In this oxidation step S02, sodium chloride and divalent copper ions are added together, and the divalent tin ions are efficiently oxidized to tetravalent tin ions by the catalytic action of these ions.

[0023] Here, the concentration of sodium chloride is preferably 0.1 mol / L or more, and more preferably 1.0 mol / L or more, while the concentration of sodium chloride is preferably 10 mol / L or less, and more preferably 5 mol / L or less. The divalent copper ion concentration is preferably 0.1 g / L or more, more preferably 0.5 g / L or more, while the divalent copper ion concentration is preferably 10 g / L or less, more preferably 5 g / L or less. The substance that supplies the divalent copper ions is not particularly limited, but for example, copper(II) sulfate pentahydrate can be used. The substance supplying sodium chloride and divalent copper ions may be added to the post-leaching solution as a solid or as a liquid. The oxidation time in the oxidation step S02 may be 1 minute to 60 minutes, may be 60 minutes to 120 minutes, or may be 120 minutes to 180 minutes. The oxidation step S02 may be carried out at a temperature of 0°C to 30°C, 30°C to 60°C, or 60°C to 90°C.

[0024] (Neutralization step S03) Next, a basic agent is added to the post-leaching solution to neutralize it, thereby obtaining a tin-containing precipitate. In this embodiment, the basic agent is added until the pH becomes 1.5 to 2.5. This causes tetravalent tin ions to precipitate. On the other hand, iron and aluminum in the post-leaching solution do not precipitate at a pH of 1.5 to 2.5, but remain in the solution. After neutralization, the tin is separated into solid and liquid to obtain a recovered tin product. The basic agent to be added may be, for example, an aqueous solution of sodium hydroxide. As the basic agent, sodium hydroxide, magnesium hydroxide, etc. can be used. The neutralization reaction time in the neutralization step S03 may be 1 minute to 60 minutes, may be 60 minutes to 120 minutes, or may be 120 minutes to 180 minutes. The neutralization step S03 may be carried out at a temperature of 0°C to 30°C, 30°C to 60°C, or 60°C to 90°C.

[0025] According to the tin recovery method of the present embodiment configured as described above, there is an oxidation step S02 in which sodium chloride and a substance that supplies divalent copper ions are added to the post-leaching solution obtained in the oxidation leaching step S01 before the neutralization step S03, and the divalent tin ions contained in the post-leaching solution are oxidized to tetravalent tin ions, so that the tin in the post-leaching solution can be efficiently recovered as a tin-containing precipitate by neutralizing the solution to a pH of 1.5 to 2.5 in the neutralization step S03. In addition, the amount of basic chemicals added can be reduced, thereby reducing chemical costs. Furthermore, the incorporation of iron and aluminum into the tin-containing precipitate can be suppressed, making it possible to recover high-quality tin.

[0026] In the tin recovery method according to the present embodiment, when a substance that supplies divalent or trivalent iron ions is added to the leaching solution in the oxidation leaching step S01, oxidation of iron contained in the tin-containing material can be suppressed, and tin can be efficiently leached. In addition, precipitation of metastannic acid in the oxidation leaching step S01 can be suppressed, improving the tin recovery rate and suppressing clogging of the filter, allowing good solid-liquid separation.

[0027] Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate without departing from the technical concept of the invention. EXAMPLES

[0028] The results of confirmatory experiments conducted to confirm the effectiveness of the present invention will be described below.

[0029] Example 1 The tin-containing material was immersed in a sulfuric acid solution to obtain a leaching solution containing 20 g / L of tin, 10 g / L of iron, and 1 g / L of aluminum.

[0030] In Examples 1 to 3 of the present invention and Comparative Examples 1 to 3, sodium chloride and divalent copper ions were added to 100 mL of the post-leaching solution so as to achieve the concentrations shown in Table 1, and the solution was stirred while blowing in air, and an oxidation step was carried out to oxidize the divalent tin ions contained in the post-leaching solution to tetravalent tin. In the oxidation step, it was confirmed that all of the divalent tin was oxidized to tetravalent tin by redox titration using iodine. In Comparative Example 4, the oxidation step was not carried out.

[0031] Thereafter, a 48 vol% NaOH solution was added to the post-leaching liquid to neutralize it to the pH shown in Table 1. After the neutralization treatment, solid-liquid separation was performed to obtain the liquid and the recovered tin product. The concentration of the tin in the recovered tin was determined using ICP-AES. Table 1 shows the processing conditions for the oxidation and neutralization processes, the time required for tin oxidation, and the tin concentration in the recovered tin.

[0032] [Table 1]

[0033] As shown in Table 1, in Comparative Example 4 in which no oxidation step was performed, the Sn concentration in the recovered tin was 47%. In contrast, in Inventive Examples 1 to 3 in which sodium chloride and divalent copper ions were co-added and the oxidation step was performed, the Sn concentration in the recovered tin was improved to 63%. In Comparative Examples 1 to 3 in which sodium chloride and divalent copper ions were not added, oxidation did not proceed, and divalent tin could not be oxidized to tetravalent tin even after 480 minutes had passed. Therefore, the subsequent neutralization step was not carried out.

[0034] Example 2 250 g of tin-containing material with a particle size of 3 mm or less and a tin concentration of 11% was immersed in 1 L of sulfuric acid solution with a sulfuric acid concentration of 100 g / L, after which FeSO4·7H2O or Fe2(SO4)3·nH2O was added so that the concentrations of divalent iron and trivalent iron became the values ​​shown in Table 2, and the mixture was stirred while blowing in air to perform the oxidation leaching process. The acidic solution was sampled every 30 minutes and separated into solid and liquid using a filter, and the tin concentration in the resulting acidic solution was measured by ICP-AES. The acidic solution was sampled until the filter became clogged and could no longer be filtered, and the time elapsed from the start of stirring at that point was recorded as the time when fine particles precipitated. The oxidation leaching conditions, the tin concentration in the resulting acidic solution, the tin recovery rate, and the time until the filter became clogged and could no longer filter are shown in Table 2. The tin recovery rate was calculated using the following formula. Recovery rate (%) = [amount of tin in acidic solution] / [amount of tin in tin-containing material] x 100

[0035] [Table 2]

[0036] In Comparative Example 11, in which neither divalent nor trivalent iron was added in the oxidative leaching step, the time to filter clogging was short at 150 minutes, and the tin recovery rate was low at 27%. In contrast, in Examples 11 to 14 of the present invention, in which divalent or trivalent iron was added in the oxidation leaching process, the time when filter clogging occurred was long, at 300 minutes or more, and the tin recovery rate was high, at 73% or more. In particular, in Examples 12 and 14 of the present invention, in which the amount of divalent or trivalent iron added was 50 g / L, filter clogging did not occur even after 540 minutes had passed. In addition, the tin recovery rate was also high.

[0037] As a result of the above confirmatory experiments, it was confirmed that the present invention can provide a tin recovery method that can efficiently recover high-quality tin from tin-containing materials. [Industrial Applicability]

[0038] It is possible to provide a tin recovery method that can efficiently recover high-quality tin from tin-containing materials.

Claims

1. A method for recovering tin from a tin-containing material, comprising the steps of: an oxidation leaching step of oxidizing and leaching tin in the tin-containing material into a leachate comprising a sulfuric acid acidic solution to obtain a leachate containing tin; an oxidation step of adding sodium chloride and a substance that supplies divalent copper ions to the post-leaching solution obtained in the oxidation leaching step, thereby oxidizing divalent tin ions contained in the post-leaching solution to tetravalent tin ions; a neutralization step of neutralizing the leaching solution after the oxidation step to a pH of 1.5 to 2.5 to obtain a tin-containing precipitate; A method for recovering tin, comprising:

2. 2. The method for recovering tin according to claim 1, characterized in that in the oxidative leaching step, a substance which supplies divalent or trivalent iron ions is added to the leaching solution.

Images