Method for recovering tin from silver separation residue by using sulphur concentrate

Abstract

The application discloses a method for recovering tin from silver separation residue by using sulfur concentrate, and comprises the following steps: S1, uniformly mixing copper anode slime silver separation residue, an additive and sulfur concentrate to form spherical materials; S2, roasting the spherical materials under a protective atmosphere at a temperature of 300-800 DEG C to generate soluble sulfur-tin compounds, and obtaining roasting residue; S3, grinding the roasting residue into roasting residue powder, mixing the roasting residue powder with alkali metal salt water to carry out tin leaching reaction in an alkaline environment, and obtaining tin leaching liquid; and S4, mixing the tin leaching liquid, an oxidizing agent and a calcium-containing reagent to carry out tin precipitation reaction, filtering and drying, and obtaining tin concentrate. The application has the advantages of low cost.

Description

Technical Field

[0001] This invention relates to the field of tin recovery technology from silver slag, and in particular to a method for recovering tin from silver slag using sulfur concentrate. Background Technology

[0002] Copper anode sludge is typically treated in the following sequence: pretreatment, copper and arsenic removal, selenium distillation, gold leaching, and silver separation. The residue left after silver separation is called silver separation sludge, which contains trace amounts of gold and silver, as well as valuable metals such as tin, lead, and antimony. Tin is the most valuable metal to extract from silver separation sludge due to its high grade and high value. Simultaneously, the copper anode sludge treatment process generates a large amount of wastewater. After treatment processes such as copper precipitation, most of the valuable elements are recovered, leaving behind saline wastewater containing a significant amount of sodium salts.

[0003] Chinese patent document publication number CN 116790890 A discloses a method for recovering tin from silver-separated slag through rotary kiln roasting and wet leaching, which is suitable for industrial application. The process uses silver-separated slag, additives, and carbonaceous materials to form balls, which are then fed into a rotary kiln for roasting, followed by wet leaching with an alkali metal salt solution. However, this technical solution uses a large amount of carbonaceous materials and alkali metal salt solution, which not only increases carbon emissions but also generates high-salt wastewater.

[0004] How to reduce costs while ensuring tin recovery rate is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a low-cost method for recovering tin from silver-separated slag using sulfur concentrate.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for recovering tin from silver-separating slag using sulfur concentrate includes the following steps: S1. Mix the silver slag, additives and sulfur concentrate evenly and then form it into spherical material; S2. The spherical material is calcined at 300-800°C under a protective atmosphere to generate soluble tin sulfide compounds, resulting in calcined slag. S3. Grind the calcined slag into calcined slag powder, mix it with alkali metal brine, and carry out a tin leaching reaction in an alkaline environment to obtain a tin leaching solution. S4. Mix the tin immersion solution, oxidant and calcium-containing reagent to carry out tin precipitation reaction, filter and dry to obtain tin concentrate.

[0007] As a further improvement to the above technical solution: In step S1, the mass ratio of the silver-separating slag, additives, and sulfur concentrate is 1:0.2-0.7:0.01-0.25. Compared with the prior art, when recovering the same mass of silver-separating slag, the present invention requires less additives, thus saving costs.

[0008] In step S1, the additives include one or more of sodium sulfide, calcium sulfide, and magnesium sulfide.

[0009] In step S2, the calcination time is 1.0 to 5.0 h, and the flow rate of the protective atmosphere is 0 to 100 L / h.

[0010] In step S2, the protective atmosphere includes nitrogen.

[0011] In step S3, the alkali metal brine is sodium salt wastewater, and the liquid-to-solid ratio of the roasted slag powder and the alkali metal brine is 2.0–7.0 L / kg; the temperature of the tin leaching reaction is 50–80°C, and the time is 1–5 h.

[0012] In step S3, the sodium salt wastewater is sodium salt wastewater with a mass concentration greater than 100 g / L. In this invention, the sodium salt wastewater is the wastewater generated during the treatment of copper anode mud, thus realizing wastewater utilization and making it more environmentally friendly.

[0013] In step S4, the amount of oxidant added is 0.1 to 1.0 mol / L, and the amount of calcium-containing reagent is added according to a calcium to tin molar ratio of 1.0 to 3.0.

[0014] In step S4, the temperature of the tin precipitation reaction is 20–90°C and the time is 0.5–4 h.

[0015] In step S4, the oxidant includes one or more of hydrogen peroxide, potassium permanganate, and sodium hypochlorite.

[0016] In step S4, the calcium-containing reagent includes one or more of calcium oxide, calcium hydroxide, and calcium chloride.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention discloses a method for recovering tin from silver-separated slag using sulfur concentrate. Sulfur concentrate, a byproduct of non-ferrous mining, is cheaper than carbonaceous materials. Its main component is ferric disulfide, and the negatively valence sulfur it contains also has a reducing effect compared to carbonaceous materials. Furthermore, during roasting, sulfur concentrate provides an alkaline solid-phase reaction environment, and through an alkaline smelting process, soluble tin-sulfide compounds (such as tin polysulfides, thiostanite, and thiostannate) are generated. This invention involves mixing silver slag, additives, and sulfur concentrate to form pellets before roasting. Compared to the previous method of making pellets from silver slag and additives and then mixing them with sulfur concentrate for roasting (where the sulfur concentrate is coated on the surface of the pellets and cannot fully react with the tin in the silver slag), this invention allows the tin in the silver slag to have a larger contact area with the sulfur concentrate, resulting in a tighter contact and a more complete reaction. Furthermore, the reducing atmosphere generated inside the pellets is constrained by the pellets and is less likely to escape. In addition, the protective atmosphere during the reaction process facilitates the smooth progress of the reduction reaction. The products are not oxidized back into volatile substances such as tin dioxide and do not enter the flue gas to cause pollution, making it more environmentally friendly. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0019] The present invention will be further described in detail below. Unless otherwise specified, the instruments or materials used in the present invention are commercially available.

[0020] Example 1 like Figure 1 As shown in this embodiment, a method for recovering tin from silver-separating slag using sulfur concentrate includes the following steps: S1. Take 800g of silver slag, 30g of calcium sulfide and 300g of sulfur concentrate, mix them evenly and form them into spheres to obtain spherical material. Then, roast the spherical material in a rotary kiln at 800℃ for 1.5h with a nitrogen flow rate of 10L / h to obtain roasted slag.

[0021] During roasting, the iron sulfide in the sulfur concentrate decomposes upon heating. The resulting ferrous sulfide, sulfur, etc., react with tin dioxide to form soluble tin salts such as thiostannate. The reaction process is as follows: 2FeS2 = 2FeS + S2 SnO2+ 4FeS = Fe2SnS4+ 2FeO S2. Grind the roasted slag into roasted slag powder. Take 4L of saline wastewater (sodium salt content 105g / L) generated from the copper leaching process of the smelter (alkali metal salt wastewater contains sodium hydroxide, which is an alkaline environment. On the other hand, the product generated in step S1 will make the whole system an alkaline environment). Add the roasted slag powder while stirring, keep stirring and heat to 90℃ to carry out tin leaching reaction. After reacting for 3 hours, filter to obtain tin leaching slag and tin leaching solution. The tin leaching slag is sent to other valuable elements for recovery.

[0022] In this invention, no additional leaching agent is needed during the leaching reaction because: the soluble tin salt (such as thiostannate) generated in the preceding steps dissolves in the solution during the tin leaching reaction, and the ferrous ions are converted into iron oxide precipitate in the alkali metal salt wastewater, separating from the tin in the solution. The reaction process is as follows: 2Fe2SnS4+ 8NaOH +O2= 2Fe2O3+ 2Na4SnS4+ 4H2O S3. Add 40g of sodium hypochlorite to the tin leaching solution, and then add calcium oxide at a calcium to tin molar ratio of 1.8. Keep stirring and heat to 90℃ to carry out the tin precipitation reaction. After reacting for 3 hours, filter. The tin-precipitated liquid is sent to the wastewater treatment section. After drying the tin slag, tin concentrate is obtained. The tin direct recovery rate is 87.2%.

[0023] In the tin precipitation reaction, thiostannate is oxidized to stannate, which then reacts with calcium to precipitate the product. Possible reactions are shown below: Na4SnS4+ 4NaClO = Na4SnO4+ 4NaCl + 2S↓ Na4SnO4+ 2CaO + 2H2O = Ca2SnO4↓ + 4NaOH Example 2 This embodiment of a method for recovering tin from silver-separating slag using sulfur concentrate includes the following steps: S1. Take 700g of silver slag, 40g of magnesium sulfide and 200g of sulfur concentrate, mix them evenly and form them into spheres to obtain spherical material. Then, roast them in a rotary kiln at 800℃ for 2.5h with a nitrogen flow rate of 5L / h to obtain roasted slag.

[0024] S2. Grind the calcined slag to obtain calcined slag powder. Take 3L of saline wastewater (sodium salt content 144g / L) generated from the sodium pyroantimonate production process, add the calcined slag powder while stirring, and keep stirring and heat to 80℃ to carry out the tin leaching reaction. After reacting for 2 hours, filter to obtain tin leaching slag and tin leaching solution. The tin leaching slag is sent for recovery of other valuable elements.

[0025] S3. Add 15 g of sodium hypochlorite to the tin leaching solution, and then add calcium oxide at a calcium to tin molar ratio of 1.4. Keep stirring and heat to 85°C to carry out the tin precipitation reaction. After reacting for 2 hours, filter to obtain the tin leaching liquid and tin slag. The tin leaching liquid is sent to the wastewater treatment section for treatment, and the tin slag is dried to obtain tin concentrate. The tin direct recovery rate is 90%.

[0026] Comparative Example 1 This comparative example describes a method for recovering tin from silver-separated slag using sulfur concentrate, comprising the following steps: S1. Take 700g of silver slag and 40g of magnesium sulfide, mix them evenly and form them into spheres to obtain spherical material. Mix the spherical material with 200g of sulfur concentrate and then roast it in a rotary kiln at 800℃ for 2.5h with a nitrogen flow rate of 5L / h to obtain roasted slag.

[0027] S2. Grind the calcined slag to obtain calcined slag powder. Take 3L of saline wastewater (sodium salt content 144g / L) generated from the sodium pyroantimonate production process, add the calcined slag powder while stirring, and keep stirring and heat to 80℃ to carry out the tin leaching reaction. After reacting for 2 hours, filter to obtain tin leaching slag and tin leaching solution. The tin leaching slag is sent for recovery of other valuable elements.

[0028] S3. Add 15 g of sodium hypochlorite to the tin leaching solution, and then add calcium oxide at a calcium to tin molar ratio of 1.4. Keep stirring and heat to 85°C to carry out the tin precipitation reaction. After reacting for 2 hours, filter to obtain tin precipitate liquid and tin slag. Tin precipitate liquid is sent to the wastewater treatment section for treatment. Tin slag is dried to obtain tin concentrate. The direct tin recovery rate is 10.7%.

[0029] A comparison of Comparative Example 1 and Example 2 shows that the technical solution of preparing the silver slag, magnesium sulfide, and sulfur concentrate into spherical materials before roasting (Example 2) significantly improves the direct tin recovery rate compared to the technical solution of preparing the silver slag and magnesium sulfide into spherical materials and then adding them to the sulfur concentrate (Comparative Example 2). This is because the roasting reaction involved in this patent is a solid-solid reaction. Compared to Comparative Example 1, the sulfur concentrate and silver slag in Example 2 have a larger contact area, resulting in a more complete reaction and a greater amount of sulfur-tin compounds generated. In the subsequent leaching reaction, a leaching reaction can occur even without a leaching agent. In contrast, during roasting, only the surface layer of Comparative Example 1 is in contact with the sulfur concentrate, resulting in insufficient reaction and fewer sulfur-tin compounds generated. Consequently, the leaching reaction is less efficient in the subsequent leaching reaction, ultimately leading to a lower direct tin recovery rate.

[0030] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A method for recovering tin from silver-separating slag using sulfur concentrate, characterized in that: Includes the following steps: S1. Mix the silver slag, additives and sulfur concentrate evenly and then form it into spherical material; S2. The spherical material is calcined at 300-800°C under a protective atmosphere to generate soluble tin sulfide compounds, resulting in calcined slag. S3. Grind the calcined slag into calcined slag powder, mix it with alkali metal brine, and carry out a tin leaching reaction in an alkaline environment to obtain a tin leaching solution. S4. Mix the tin immersion solution, oxidant and calcium-containing reagent to carry out tin precipitation reaction, filter and dry to obtain tin concentrate.

2. The method for recovering tin from silver-separating slag using sulfur concentrate according to claim 1, characterized in that: In step S1, the mass ratio of the silver slag, additives and sulfur concentrate is 1:0.2-0.7:0.01-0.

25.

3. The method for recovering tin from silver-separating slag using sulfur concentrate according to claim 1 or 2, characterized in that: In step S1, the additives include one or more of sodium sulfide, calcium sulfide, and magnesium sulfide.

4. The method for recovering tin from silver-separating slag using sulfur concentrate according to claim 1, characterized in that: In step S2, the calcination time is 1.0 to 5.0 h, and the flow rate of the protective atmosphere is 0 to 100 L / h.

5. The method for recovering tin from silver-separating slag using sulfur concentrate according to claim 1 or 4, characterized in that: In step S2, the protective atmosphere includes nitrogen.

6. The method for recovering tin from silver-separating slag using sulfur concentrate according to claim 1, characterized in that: In step S3, the alkali metal brine is sodium salt wastewater, and the liquid-to-solid ratio of the roasted slag powder and the alkali metal brine is 2.0–7.0 L / kg; the temperature of the tin leaching reaction is 50–80 °C, and the time is 1–5 h.

7. The method for recovering tin from silver-separating slag using sulfur concentrate according to claim 6, characterized in that: In step S3, the sodium salt wastewater is sodium salt wastewater with a mass concentration greater than 100 g / L.

8. The method for recovering tin from silver-separating slag using sulfur concentrate according to claim 1, characterized in that: In step S4, the amount of oxidant added is 0.1 to 1.0 mol / L, and the amount of calcium-containing reagent is added according to a calcium to tin molar ratio of 1.0 to 3.

0. In step S4, the temperature of the tin precipitation reaction is 20–90°C and the time is 0.5–4 h.

9. The method for recovering tin from silver-separating slag using sulfur concentrate according to claim 8, characterized in that: In step S4, the oxidant includes one or more of hydrogen peroxide, potassium permanganate, and sodium hypochlorite.

10. The method for recovering tin from silver-separating slag using sulfur concentrate according to claim 8, characterized in that: In step S4, the calcium-containing reagent includes one or more of calcium oxide, calcium hydroxide, and calcium chloride.

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