JPS6319576B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for effectively separating and recovering tin accompanying lead in lead smelting. In electrolytic refining of lead, tin behaves in the same way as lead and is deposited on the cathode, so it is difficult to separate and remove tin in this electrolytic refining. For this reason, the obtained cathode is melt-purified. For this melt refining, a method is adopted, for example, according to the Harris method, in which caustic soda or sodium nitrate is added to obtain a refining slag containing tin. When obtaining refining slag by adding a soda compound to a melt of tin-containing lead, including this lead cathode refining method, the refining slag contains a large amount of lead, so it is usually It was common practice to repeatedly return the lead to a reduction furnace to recover the lead as crude lead. However, in this case, since tin also enters the crude lead, it is inevitable that tin will be concentrated in the cathode again and a load will be added to the purification of the cathode. Further, when such refining slag is put into a reduction furnace, there is also the problem that the refractories in the furnace are corroded by the alkali in the refining slag. The present invention provides a method for efficiently separating and recovering tin from the refining slag generated in the lead refining process. The method involves adding sulfur to the slag and leaching it with water, thereby eluting the tin, and precipitating the tin in the solution as calcium stannate with Ca ²⁺ to separate the tin. The purpose is to recover crude tin by reducing and melting this precipitate. When caustic soda and sodium nitrate are added to a melt of tin-containing lead and melted, tin can be converted into water-soluble sodium stannate, Na ₂ [Sn(OH) ₆ ]. At that time, a part of the tin forms lead stannate, Pb [Sn(OH) ₆ ], which can be converted into water-soluble sodium stannate by the following reaction formula by adding a small amount of sulfur. Can be done. 6NaOH+4S→2Na ₂ S+Na ₂ S ₂ O ₃ +3H ₂ O Pb [Sn(OH) ₆ ]+Na ₂ S→PbS+Na ₂ [Sn(OH) ₆ ] Therefore, sulfur was added to the lead refinery slag and leached with water. Most of the tin in the refinery slag can then be leached out. A portion of the tin in the leachate is in the form of stannous, so it is converted to stannous using an oxidizing agent such as H ₂ O ₂ and then converted to water-insoluble calcium stannate using Ca ²⁺ such as slaked lime. If precipitated, tin in the leachate can be efficiently separated. After this precipitate is separated and collected from the liquid, crude tin can be recovered by blending it with a reducing agent such as coke and reducing and melting it. As described above, according to the present invention, tin, which was only an impurity in conventional lead electrolytic refining, can be selectively recovered to obtain crude tin. Furthermore, since tin, which tends to be repeatedly concentrated in the lead electrolytic refining system, can be extracted from the system, it is also possible to reduce the amount of solvent and oxidizing agent used in the melt refining method. Example 1 Melt a lead electrolytically purified cathode and add NaOH to it.
Sulfur powder was added to 5 kg of refined slag obtained by adding NaNO ₃ to
Added 150g and leached with 10ml of water. The liquid temperature rose to approximately 50°C due to the heat of reaction. Leaching was carried out for 8 hours, and the results are shown in Table 1. As shown in Table 1, the tin leaching rate was 86.0%.

[Table] Example 2 700 g of slaked lime was added to the leachate obtained in Example 1 and stirred for 3 hours to precipitate tin as calcium stannate. As shown in Table 2, the tin removal rate from the leachate was 93.7%.

[Table] Example 3 2.5 kg of the residue precipitated as calcium stannate in Example 2 was mixed with 3 kg of boric acid and 450 g of coke, and subjected to reduction melting to obtain crude tin. As shown in Table 3, tin could be collected with a reduction rate of 96.7%.

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Claims (1)

[Claims] 1. When separating and recovering tin from lead in lead smelting, lead containing tin is melted, this melt is reacted with a soda compound, the tin in the melt is converted to sodium stannate, and this sodium stannate and In lead smelting, the slag containing raw lead stannate is separated from the molten lead, sulfur is added to this lead refining slag, leaching treatment is performed with water, and then tin is precipitated as calcium stannate using Ca ²⁺ . Tin separation and recovery method.