JP7721064B2 - Method for separating tin and antimony - Google Patents

Description

The present invention relates to a processing method for efficiently separating tin and antimony contained in silver-lead-containing slag obtained by wet chlorination of copper electrolytic slime from the slag.

One known method involves decopperizing copper electrolytic slime and then subjecting it to a chlorination leaching process to leach gold, platinum group elements, selenium, and tellurium, separating silver chloride and lead chloride as leach slag, and recovering silver from the leach slag. Specifically, for example, one known method involves repulping the chlorination leach precipitate of copper electrolytic slime with water, adding iron powder, simultaneously reducing the silver and lead and removing the chlorine, thereby precipitating metallic silver and lead, melting this mixture in an oxidation furnace, oxidizing the lead to form slag, and separating and recovering crude metallic silver (Patent Document 1).

Also known is a method for recovering silver from a silver-lead-containing material by forming a slurry of raw materials containing silver-lead chloride with dilute sulfuric acid, adding iron powder to the slurry to reduce the silver chloride and precipitate metallic silver (silver reduction process using iron powder), adding sulfuric acid to the slurry to convert the lead chloride to lead sulfate, which is then precipitated, and recovering a mixture containing metallic silver and lead sulfate (lead sulfate formation process), reducing and smelting this mixture to form a metal containing silver and a slag containing lead sulfate, separating the metal and slag (reduction smelting process), and oxidizing and smelting the recovered metal to obtain crude silver (oxidation smelting process) (Patent Document 2).

Further, known silver recovery methods include a nitric acid leaching process in which a tin-containing silver-lead chloride raw material is carbonated to convert the lead chloride to lead carbonate, and then nitric acid is added to selectively leach the lead carbonate and perform solid-liquid separation; a hydrochloric acid leaching process in which strong hydrochloric acid is added to the nitric acid leach slag to leach the bismuth and antimony contained in the raw material and perform solid-liquid separation; an iron reduction process in which sulfuric acid is added to the hydrochloric acid leach slag, and then iron powder is added to reduce the silver chloride in the hydrochloric acid leach slag to produce crude silver; and an oxidation refining process in which soda silicate slag is added to the iron reduction slag, which is then oxidized and melted, and the tin and impurities are absorbed by the slag, allowing the crude silver to be separated and recovered (Patent Document 3).

Japanese Patent Application Laid-Open No. 2001-317636 JP 2004-190135 A Japanese Patent Application Laid-Open No. 2020-132957

In recent years, copper smelters have been actively processing recycled scrap, resulting in higher concentrations of tin and antimony in copper electrolytic slime. Tin and antimony are difficult to dissolve in chloride leaching, and tend to concentrate in chloride leaching slag along with silver chloride and lead chloride. Furthermore, when tin or antimony is heated with lead, a high-melting-point complex oxide is formed, which is difficult to melt using dry processing. Furthermore, in dry processing, an increase in the concentration of unmelted material increases the apparent viscosity of the slag, resulting in adverse effects such as silver entrapment loss in the slag and a deterioration in the fluidity of the slag. Therefore, it is necessary to separate the tin and antimony before dry processing.

The present invention provides a processing method for efficiently separating tin and antimony contained in silver-lead-containing slag from the slag.

The present invention provides a method for separating tin and antimony that solves the above problems by the following configuration.
(1) A method for separating tin and antimony, which comprises leaching a lead chloride-containing material containing tin and antimony with sulfuric acid having a concentration of 3M to 8M, and separating the liquid containing tin and antimony into solid and liquid components.
(2) The method for separating tin and antimony according to the above item [1], wherein the pulp concentration of the sulfuric acid leaching slurry of the lead chloride-containing material is 300 g/L to 1000 g/L.
(3) The method for separating tin and antimony according to the above [1] or [2], wherein the sulfuric acid leaching temperature of the lead chloride-containing material is 30°C to 90°C.

[Specific explanation]
The processing method of the present invention will now be described in detail.
The treatment method of the present invention is a method for separating tin and antimony, which comprises leaching a lead chloride-containing material containing tin and antimony with sulfuric acid having a concentration of 3M to 8M, and subjecting the liquid fraction containing tin and antimony to solid-liquid separation.

In the treatment method of the present invention, the lead chloride-containing material containing tin and antimony is, for example, a silver-lead-containing slag containing silver chloride and lead chloride as residues obtained by subjecting copper electrolytic slime to copper removal treatment followed by chlorination leaching to leach gold, platinum group elements, selenium, and tellurium. This silver-lead-containing slag contains lead chloride along with tin and antimony.

In the treatment method of the present invention, lead chloride-containing material containing tin and antimony is leached using sulfuric acid with a concentration of 3M to 8M. For example, in the case of the above-mentioned silver-lead-containing slag, the lead chloride contained in the slag reacts with sulfuric acid to form lead sulfate and hydrogen chloride, as shown in the following formula (1). Furthermore, the tin oxide contained in the slag reacts with the hydrogen chloride to form a tin chloride complex (H ₂ SnCl ₆ ) as shown in the following formula (2), and the antimony oxide contained in the slag reacts with the hydrogen chloride to form an antimony chloride complex (H ₂ SbCl ₅ ) as shown in the following formula (3), which then dissolves into the solution.

PbCl ₃ + H ₂ SO ₄ → PbSO ₄ + 2HCl... (1)
SnO ₂ +6HCl → H ₂ SnCl ₆ + 2H ₂ O... (2)
Sb ₂ O ₃ +10HCl → 2H ₂ SbCl ₅ + 3H ₂ O...(3)

If the sulfuric acid concentration is lower than 3M, the leaching effect of tin and antimony is low. On the other hand, if the sulfuric acid concentration is higher than 8M, the hydrogen chloride produced will evaporate, resulting in insufficient reaction between tin oxide and antimony oxide and hydrogen chloride, reducing the leaching effect of tin and antimony.

The silver chloride contained in the silver-lead-containing slag is not sulfated during the sulfuric acid leaching. Because lead chloride has a higher solubility in water than lead sulfate (lead chloride > lead sulfate), lead chloride dissolves and lead sulfate precipitates, resulting in the production of lead sulfate. However, because silver chloride has a lower solubility in water than silver sulfate (silver sulfate > silver chloride), the reaction from silver chloride to silver sulfate hardly progresses.

As such, in the sulfuric acid leaching described above, the presence of lead chloride promotes the leaching of tin and antimony. Typically, the chlorine chloride contained in the chlorine leaching slag after copper removal from copper electrolytic slime is greater than the amount of tin or antimony, so the chlorine dissolved from the lead chloride in the slag is enough to drive the above reaction.

The pulp concentration of the sulfuric acid leaching slurry of the above-mentioned lead chloride-containing material is preferably in the range of 300g/L to 1000g/L, and more preferably in the range of 500g/L to 1000g/L. If the concentration is less than 300g/L, the amount of chlorine dissolved will be small, and the leaching of tin and antimony will not proceed sufficiently. On the other hand, if the concentration exceeds 1000g/L, the viscosity of the slurry will increase, making it difficult to stir the entire slurry uniformly, which is undesirable.

The sulfuric acid leaching temperature is preferably 30°C to 90°C, and more preferably 60°C to 80°C. If the leaching temperature is below 30°C, the reaction rate will be slow and the leaching time will be long. If the leaching temperature is higher than 90°C, the amount of solution evaporating will be large, which is not desirable.

After the sulfuric acid leaching, solid-liquid separation can be performed to separate the tin and antimony contained in the liquid from the silver and lead contained in the leaching residue. The tin and antimony contained in the liquid can be easily recovered by neutralizing and precipitating them. Furthermore, since antimony precipitates on the acidic side during this neutralization, by first performing solid-liquid separation on the precipitated antimony, it can be separated from the tin that precipitates during subsequent neutralization.

The treatment method of the present invention allows for selective sulfuric acid leaching of tin and antimony from lead chloride-containing materials containing tin and antimony, such as the silver-lead-containing slag described above, without leaching out lead or silver. Sulfate complexes of tin and antimony are unstable and are generally difficult to form, but with the treatment method of the present invention, the coexistence of lead chloride causes chlorine to dissolve into the solution through the sulfation of the lead chloride. This chlorine then forms chloride complexes of tin and antimony, resulting in stable leaching of tin and antimony.

Since sulfuric acid is produced as a by-product of copper smelting, it can be carried out at low cost when carried out in connection with copper smelting. Furthermore, while chlorine leach slag is usually desalted before dry processing, the processing method of the present invention simultaneously separates tin and antimony and dechlorinates lead chloride, thereby reducing the burden of desalting processing.

The treatment method of Patent Document 2 also includes a sulfation step, but this is carried out after the silver reduction step. If reduction is carried out before sulfation, tin and antimony will also be reduced, making them difficult to leach with sulfuric acid. The treatment method of the present invention, in which the chlorinated leach dregs are first leached with sulfuric acid, is more suitable for separating tin and antimony.

In the processing method described in Patent Document 3, the chloride leach slag is carbonated, then leached with nitric acid to leach lead, and then leached with concentrated hydrochloric acid to leach bismuth and antimony. However, leaching with concentrated hydrochloric acid not only leaches tin and antimony, but also small amounts of silver and lead, resulting in a loss of silver and lead. Furthermore, sulfuric acid leaching is less expensive than concentrated hydrochloric acid leaching.

The following are examples of the present invention. The residues of each sample were analyzed by XRF (X-ray fluorescence analysis), and each solution was analyzed by ICP.

[Example]
To 30 g of chlorinated leach slag with the composition shown in Table 1, 60 mL of 6.5 M sulfuric acid (Sample No. A1) or 60 mL of 5.0 M sulfuric acid (Sample No. A2) was added to prepare a slurry with a pulp concentration of 500 g/L. Additionally, 6 g of chlorinated leach slag was added to prepare a slurry with a pulp concentration of 100 g/L (Sample No. A3). The pulp concentration was calculated as the mass of chlorinated leach slag (g) divided by the amount of sulfuric acid added (L). These samples were leached at 75°C for 24 hours, followed by solid-liquid separation. The leachate was analyzed by ICP, and the leach slag was analyzed by XRF. The leaching rates of each element were calculated based on the analytical values. The results are shown in Table 2.

Comparative Example
Leaching was carried out in the same manner as Sample No. 1, except that 2.0 M sulfuric acid was used (Sample No. B1). Leaching was carried out in the same manner as Sample No. 1, except that 9.0 M sulfuric acid was used (Sample No. B2). Leaching was carried out in the same manner as Sample No. 1, except that 8.0 M hydrochloric acid was used (Sample No. B3). These leachates and leach slag were analyzed in the same manner as Sample No. 1 to determine the leaching rate of each element. The results are shown in Table 2.

As shown in Table 2, in both samples A1 and A2, almost no silver or lead was eluted, and Sn and Sb were selectively leached. Furthermore, since the leaching rate of Sb was slightly reduced in sample A3, it is preferable that the pulp concentration of the slurry be higher than 100 g/L. This is thought to be because the concentration of chlorine dissolved in the solution varies depending on the pulp concentration. In sulfuric acid leaching, chlorine dissolves from lead chloride into the solution, as shown in equation (1) above. The higher the pulp concentration, the more efficiently this reaction progresses, resulting in a higher chlorine concentration in the solution. Sn and Sb do not easily form sulfate complexes, and instead tend to form chloride complexes as shown in equations (2) and (3) above, so a higher chlorine concentration makes them more soluble. A higher pulp concentration increases the chlorine concentration, and so does the leaching rate of Sn and Sb.

On the other hand, sample No. B1, which was prepared using 2.0M sulfuric acid, showed a reduced Sn leaching rate and a significant reduction in the Sb leaching rate. Furthermore, sample No. B2, which was prepared using 9.0M sulfuric acid, showed a reduced Sn leaching rate and a low Sb leaching rate. These results suggest that the sulfuric acid concentration should be higher than 2.0M and lower than 9.0M. With 2.0M sulfuric acid, the leaching reactions of equations (2) and (3) above do not proceed sufficiently. On the other hand, when 9.0M sulfuric acid is used, white smoke from hydrogen chloride is observed during leaching; at high sulfuric acid concentrations, some of the hydrogen chloride evaporates without remaining dissolved in the solution. This evaporation of hydrogen chloride reduces the chlorine concentration in the solution, which is thought to reduce the leaching rates of Sn and Sb.

Sample No. B3, which used 8.0M hydrochloric acid, had a high Sb leaching rate, but Ag and Pb were also leached, so it is not suitable for separating Sn and Sb from Ag and Pb. Although chlorides of Ag and Pb are hardly soluble, this is thought to be because they dissolve in highly concentrated hydrochloric acid by forming complexes such as [ _AgCl2 ] ⁺ and [ _PbCl4 ] ²⁺ .

Claims (3)

A method for separating tin and antimony, characterized by leaching lead chloride-containing material containing tin and antimony with sulfuric acid of 3M to 8M concentration, and then subjecting the liquid containing tin and antimony to solid-liquid separation. A method for separating tin and antimony as described in claim 1, wherein the pulp concentration of the sulfuric acid leaching slurry of the lead chloride-containing material is 300 g/L to 1000 g/L. 3. The method for separating tin and antimony according to claim 1, wherein the temperature of sulfuric acid leaching of the lead chloride-containing material is 30°C to 90°C.