JP2012251238A - Method for recovering tin from arsenic-containing solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for safely and efficiently recovering tin from a tin electrowinning liquid containing arsenic.SOLUTION: The method for recovering tin from an arsenic-containing solution includes performing an electrolytic treatment of a tin electrowinning liquid containing at least arsenic, under such conditions that hydrogen generation does not occur and at the concentration of tin which is preferably 10 g/L or more. The method preferably includes a treatment which includes, when the liquid after the electrolysis is subjected to a waste liquid treatment, stopping the electrolytic treatment at a tin concentration of 10 g/L or more, then maintaining the ORP value of the liquid after the electrolysis, obtained by the electrolytic treatment, at -200 mV (vs AgCl/Ag) or more, or when the ORP value is lower than -200 mV, adding an oxidant to adjust the ORP value to -200 mV or more, and thereafter, lowering pH to convert tin into the form of a neutralized product of Sn while dissolving at least a portion of arsenic in the liquid after the electrolysis.

Description

  The present invention relates to a method for recovering tin from an arsenic-containing solution.

  Conventionally, smoke ash was leached with sulfuric acid to recover lead contained in non-ferrous smelting dry ash from non-ferrous smelting, melting furnaces for recycling raw materials such as foundations and electronic parts, and dry furnaces for melting industrial waste. Then, after making lead sulfate, smelting reduction is performed in an electric furnace.

The metal separated by this smelting reduction is subjected to soda treatment, then anode casting, and electrolytic purification using a silicofluoric acid bath or the like. Electrical lead is recovered by this electrolytic purification. On the other hand, tin is collected in the soda scum produced during the soda treatment.
Arsenic is also mixed in the soda scum, and a preferable treatment is desired from the viewpoint of handling arsenic.

As such a method for recovering electrotin, for example, in JP-A-4-191340 (Patent Document 1), after leaching a tin compound such as Na ₂ SnO ₃ , SnO ₂ , SnO with water, an alkaline solution or the like, sulfurization is performed. In this method, after removing lead and copper eluted by the above, electrolytic collection is performed and the electrodeposited metal is recovered.

JP-A-4-191340

  However, in Patent Document 1, when a tin compound is leached with water or alkali, arsenic is eluted together with tin. Therefore, arsenic is mixed into the electrolytic collection solution, and arsine gas, which is a harmful substance, is collected during the electrolytic collection of tin. There was a problem that occurred.

  Then, this invention makes it a subject to provide the method of collect | recovering tin safely and efficiently from the tin electrowinning liquid containing arsenic.

  As a result of intensive studies to solve the above problems, the present inventor has completed the following invention.

(1) A method for recovering tin from an arsenic-containing solution, in which a tin electrolytic collection solution containing at least arsenic is subjected to electrolytic treatment under conditions that do not generate hydrogen.
(2) The method according to (1), wherein the electrolytic treatment is performed at a tin concentration of 10 g / L or more.
(3) In the method described in (1) or (2), the electrolytic treatment is stopped at a tin concentration of 10 g / L or more, and the ORP value of the post-electrolysis solution obtained by the electrolytic treatment is -200 mV ( vs AgCl / Ag) or when the ORP value is lower than −200 mV, an oxidizing agent is added and adjusted to −200 mV or higher, and then the pH is lowered to reduce at least a part of arsenic. A method comprising a treatment of changing tin into a Sn neutralized form while being dissolved in a solution after electrolysis.
(4) In the method described in (3), the Sn neutralized product is further solid-liquid separated, the Sn neutralized product is redissolved in an electrolytic collection solution, and tin is recovered by electrolytic treatment. Method.
(5) In the method according to any one of (1) to (4), the tin electrowinning solution is a step of leaching with a caustic soda aqueous solution with respect to soda scum obtained by soda treatment of crude lead; A method for electrolytically collecting tin, which is a liquid after sulfidation obtained through a step of sulfiding the liquid after leaching.
(6) The method according to (3), wherein the oxidizing agent is hydrogen peroxide.

ADVANTAGE OF THE INVENTION According to this invention, the method of collect | recovering tin safely and efficiently from the tin electrowinning liquid containing arsenic can be provided. More specifically,
(1) The generation of arsine gas can be prevented by managing the Sn concentration in the tin electrolyte containing at least arsenic at 10 g / L or more.
(2) The tin in the arsenic-containing liquid can be efficiently recovered without environmental problems at the factory.

The processing method of the tin scum which is 1 aspect of this invention is shown. The concentration of As and Sn in the solution in the pH change is shown. It shows the residual ratio of As and Sn in the solution with pH change.

Hereinafter, an embodiment of a method for recovering tin from an arsenic-containing solution according to the present invention will be described.
The processing target of the method of the present invention is a tin electrolyte containing at least arsenic and containing tin. These solutions are obtained when, for example, crude lead is soda-treated and the tin contained in the soda scum obtained is recovered.

The scum after soda treatment is generally 15 to 40% by mass of tin, 0.5 to 10% by mass of arsenic, 40 to 50% by mass of lead, 5 to 10% by mass of copper, and 0.3 to 0.3% of antimony. About 2% by mass is contained.
The scum can be leached with a solution of caustic soda dissolved in warm water at a slurry concentration of 150 to 350 g / L. From the viewpoint of leaching efficiency, the temperature of the hot water is preferably about 60 to 80 ° C. The slurry concentration is adjusted so that the tin concentration in the solution after leaching is 10 g / L or more. Lead and antimony are removed from the leaching residue.
Typically, 25 to 60 g / L of tin and 5 to 10 g / L of arsenic are dissolved in the liquid after leaching. It is preferable to add a sulfiding agent, for example, sodium hydrosulfide, hydrogen sulfide gas, etc. to the solution, and perform sulfidation to remove lead and copper as sulfides.

The sulfidized solution after the sulfiding treatment generally has a pH of 10 or higher, preferably 10 to 14, more preferably 13 to 14, and this can be used as a tin electrowinning solution. Using the electrolytic collection solution, Sn electrodeposited metal is recovered by electrolytic treatment at a current density of 50 to 100 A / m ² and a liquid temperature of 50 to 80 ° C.
Here, by maintaining the Sn concentration in the tin electrowinning liquid at 10 g / L or more, hydrogen can be prevented from being generated, and as a result, generation of arsine gas can be suppressed. Furthermore, it is preferable to maintain the Sn concentration in the tin electrowinning solution at 30 g / L or more in order to obtain high current efficiency.

In addition, when the post-electrolysis solution is subjected to waste liquid treatment, it is preferable to recover as much tin as possible from the electrolytic collection solution. In other words, if the amount of tin dissolved at the end point of electrowinning increases, that is, if the Sn concentration in the tin electrowinning solution at the end point of electrowinning is high, the direct rate of tin decreases.
From the above viewpoint, in order to suppress the generation of arsine gas and prevent the direct rate of tin from being extremely lowered, electrolysis is generally performed so that the tin concentration is 10 to 50 g / L, preferably 10 to 20 g / L. Manage the end point of processing. While the tin electrowinning is continued, the tin concentration in the solution gradually decreases, but the electrolysis treatment is stopped before the Sn concentration becomes lower than 10 g / L, preferably less than 30 g / L, and the post-electrolysis solution To the neutralization process.

In the neutralization step, the redox potential (ORP) of the post-electrolysis solution is managed so as not to be less than a certain value. That is, the ORP value in the electrolytic solution is usually oxidized by electrolytic treatment, and the ORP value is usually −200 mV (vs Al / AgCl) or more, but in some cases, the ORP value is less than −200 mV. In this case, since the As removal efficiency at the time of neutralization deteriorates, it is preferably −200 mV or more, preferably −200 mV or more and −100 mV or less for reasons of chemical cost. In this case, hydrogen peroxide as an oxidizing agent is added to increase the ORP value to -200 mV or higher.
Thereafter, an acid such as sulfuric acid, hydrochloric acid or nitric acid, preferably sulfuric acid is added to lower the pH, thereby obtaining a Sn neutralized product. Although the form of this neutralized Sn product is not clear, it is an Sn compound, and any one or more of hydroxide (Sn (OH) ₄ ), Na ₂ (Sn (OH) ₆ ), Na ₂ SnO _3, etc. It is considered that Sn can be recovered in the form of the Sn compound. The Sn neutralized product is recovered by solid-liquid separation. If the pH is too high, no Sn neutralized product is produced. On the other hand, if the pH is too low, the As removal efficiency deteriorates.

Table 1 shows typical changes in tin and arsenic concentrations before and after neutralization.
FIG. 2 shows the concentration of As and Sn in the solution when the pH was lowered from pH = 13.5, and FIG. 3 shows the concentration of As and Sn when the pH was lowered from pH = 13.5. The residual ratio in liquid is shown. 2 and 3, when the pH is about 9 to 10, it can be seen that tin tends to be preferentially precipitated while at least a part of arsenic remains in the solution. It is understood that it is preferable to adjust to 10.

The post-neutralization solution can be sent to a wastewater treatment step and subjected to de-As treatment by a conventional method.
In addition, Sn neutralized material can be thrown into an electrowinning liquid and the recovery rate of tin can be raised. As one aspect of the charging, it may be charged when the Sn concentration of electrowinning decreases, and the Sn concentration is adjusted to, for example, 20 to 40 g / L, and tin is recovered as electrodeposited tin by electrowinning. it can.

  The electrodeposited tin recovered by using the present invention can have a high quality of 99.5% by mass or more. Table 2 shows data obtained in actual operation as an example.

  Examples of the present invention will be described below, but the examples are for illustrative purposes and are not intended to limit the invention.

(Example 1) (When the initial Sn concentration of the electrolytic collection solution is as high as 30 to 50 g / L)
Crude lead was treated with soda to obtain scum. The scum contained Sn: about 20% by mass, As: about 4% by mass, lead: about 30% by mass, copper: about 6% by mass, and antimony: about 5% by mass. The scum was leached with a solution (pH: 13.5) of caustic soda dissolved in hot water at 70 ° C. to a slurry concentration of 300 g / L, and Pb and Sb were dropped as residues. Sn: 30 to 50 g / L dissolved in the leachate. Pb and Cu were dropped as sulfides by adding sodium hydrosulfide to this solution and sulfiding.
The obtained post-sulfurized solution was used as an electrolytic collection solution (initial Sn: 30 to 50 g / L). This was electrolyzed at a current density of 75 A / m ² and a liquid temperature of 70 ° C. to recover Sn electrodeposited metal. It managed so that Sn density | concentration in the liquid in the end point of electrowinning might be set to 10-15 g / L. By managing the Sn concentration in the electrolytic collection solution at the end point at 10 to 15 g / L, the direct rate of Sn can be increased.
When electrolytic extraction of tin was continuously carried out under the above operating conditions, about 80% of the Sn amount dissolved in the solution by scum leaching could be recovered as electrodeposited metal by electrolytic extraction. There was no generation of arsine gas. The remaining 20% was contained in the post-electrolysis solution at a Sn concentration of 10 to 15 g / L, so it was sent to the neutralization step. Although the ORP value of the solution is oxidized to -200 mV (vs Al / AgCl, the same applies hereinafter) or more by electrolytic collection, it may be lower than -200 mV. In this case, hydrogen peroxide was added and the ORP value was adjusted to -200 mV before being sent to the neutralization step.
In the neutralization step, the post-electrolysis solution was adjusted to pH = 9 with sulfuric acid, and Sn was recovered in the form of a neutralized product. No arsine gas was generated in the neutralization process.
Table 3 shows typical changes in tin and arsenic concentrations before and after neutralization.

The drained liquid (the liquid after neutralization) was sent to the waste water treatment step and subjected to a de-As treatment.
The Sn neutralized product is used to maintain the Sn concentration at 10 g / L or more by adding when the Sn concentration of the electrolytic collection solution is lowered, and then tin is recovered as electrodeposited tin by electrolytic collection. .
As shown in Table 4, the quality of the obtained electrodeposited tin was 99.5% by mass or more. Moreover, it was possible to perform electrowinning in a safe environment that does not generate arsine gas.

(Comparative example 1) (Electrolytic collection when initial tin concentration of electrolytic collection liquid is low (9 g / L))
Unlike the above, the electrowinning liquid with a tin concentration of 9 g / L was used under the same conditions as in Example 1. When tin was electrodeposited, arsine gas was generated, which was in a dangerous state.

(Example 2) (When the Sn concentration of the electrolytic collection solution is decreased, the Sn concentration is maintained at 30 to 50 g / L)
Electrolytic extraction of Sn was performed under the same conditions as in Example 1 except that the Sn concentration in the liquid at the end point of electrolytic extraction was controlled to be 30 to 50 g / L. By managing the Sn concentration in the electrolytic collection solution at the end point at 30 to 50 g / L, the current efficiency of Sn electrolytic collection can be increased.
When tin electrowinning was continuously carried out under the above operating conditions, the current efficiency of Sn electrowinning could be maintained at 90% or more. There was no generation of arsine gas. The post-electrolysis solution having a Sn concentration of 30 g / L or less was sent to the neutralization step. Similar to Example 1, the ORP value of the solution is oxidized to −200 mV or more by electrowinning, but may be lower than −200 mV. In this case, hydrogen peroxide was added and the ORP value was adjusted to -200 mV before being sent to the neutralization step.
In the neutralization step, the post-electrolysis solution was adjusted to pH = 9 with sulfuric acid, and Sn was recovered in the form of a neutralized product. No arsine gas was generated in the neutralization process.
Table 5 shows typical changes in tin and arsenic concentrations before and after neutralization.

The drained liquid (the liquid after neutralization) was sent to the waste water treatment step and subjected to a de-As treatment.
The Sn neutralized product is used to increase the Sn concentration to 30 to 50 g / L or more by adding when the Sn concentration of the electrolytic collection solution is lowered, and then tin is electrodeposited by electrolytic collection. It was collected. As a result, the current efficiency could be increased to 94%. Further, as in Example 1, electrowinning could be performed in a safe environment where no arsine gas was generated.

(Example 3) (Electrolytic collection when initial tin concentration of electrolytic collection liquid is low (15 g / L))
Unlike the above, the electrowinning liquid is an electrowinning liquid whose initial tin concentration is 15 g / L. The other conditions are the same as in Example 1, and a safe environment in which arsine gas is not generated when tin is electrodeposited. We were able to perform electrowinning. The current efficiency was 70%.

In addition, this invention includes the following aspects.
(1) an electrowinning step of electrowinning tin while maintaining the Sn concentration in the tin electrowinning solution containing at least arsenic at 10 g / L or more;
For the post-electrolysis solution obtained in the above step, the ORP value is maintained at −200 mV (vs AgCl / Ag) or higher, or when the ORP value is lower than −200 mV, an oxidizing agent is added to increase it to −200 mV or higher. After the adjustment, a neutralization step of changing tin into a Sn neutralized form while dissolving at least a part of arsenic in the post-electrolysis solution by lowering the pH;
Method for electrolytically collecting tin containing
(2) A method for electrolytically collecting tin according to (1), wherein the Sn concentration in the tin electrolytic collection solution is maintained at 30 g / L or more.
(3) The method for electrolytically collecting tin according to (1) or (2), wherein the pH is adjusted to 9 to 10 in the neutralization step.
(4) The method for electrolytically collecting tin according to any one of (1) to (3), wherein the oxidizing agent is hydrogen peroxide.
(5) The tin electrowinning method according to any one of (1) to (4), further comprising a step of solid-liquid separation of the Sn neutralized product obtained in the above step from an arsenic component dissolved in the solution.
(6) In any one of (1) to (4), the Sn neutralized product is redissolved in a solution for electrolytic collection, and tin is recovered as electrodeposited tin by electrolytic collection. Method.
(7) In any one of (1) to (6), the tin electrowinning solution is a step of leaching a soda scum obtained by soda treatment of crude lead with a caustic soda aqueous solution, and then a solution after leaching. A method for electrolytically collecting tin, which is a liquid after sulfidation obtained through a sulfiding process.

Claims (6)

  A method for recovering tin from an arsenic-containing solution, wherein an electrolytic treatment is performed on a tin electrolysis solution containing at least arsenic under conditions that do not generate hydrogen.   The method according to claim 1, wherein the electrolytic treatment is performed at a tin concentration of 10 g / L or more.   3. The method according to claim 1, wherein the electrolytic treatment is stopped at a tin concentration of 10 g / L or more, and the ORP value is −200 mV (vs AgCl / Ag) for the post-electrolysis solution obtained by the electrolytic treatment. If the ORP value is lower than -200 mV, an oxidant is added and adjusted to -200 mV or higher, and then the pH is lowered so that at least a part of arsenic is contained in the post-electrolysis solution. A method comprising a process of changing tin into a Sn neutralized form while being dissolved.   4. The method according to claim 3, wherein the Sn neutralized product is further solid-liquid separated, the Sn neutralized product is redissolved in an electrowinning solution, and tin is recovered by electrolytic treatment.   The method according to any one of claims 1 to 4, wherein the tin electrowinning liquid is a step of leaching with a caustic soda aqueous solution to a soda scum obtained by soda treatment of crude lead, and then a liquid after leaching. A method for electrolytically collecting tin, which is a post-sulfurized solution obtained through a step of sulfidizing the steel.   4. The method of claim 3, wherein the oxidizing agent is hydrogen peroxide.

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