A method for efficiently recovering tin resources from tin fuming furnace soot and preparing stannous sulfate

Abstract

The present invention discloses a method for efficiently recovering tin resources from fuming furnace dust and preparing stannous sulfate, belonging to the technical field of secondary tin resource recovery. This method oxidatively leaches the fuming furnace dust with a H2O2-H2SO4 mixed solution at 60-80 °C, and the obtained leachate is subjected to reduction, impurity removal and concentration crystallization to obtain stannous sulfate products; this method highly selectively converts SnS in the fuming furnace dust into stannous sulfate in an acidic oxidation environment, realizing the efficient recovery and value-added utilization of secondary tin resources, providing an economical and environmentally friendly raw material source for the production of stannous sulfate, and broadening the production path of stannous sulfate.

Description

Technical Field

[0001] The present invention relates to a method for treating the soot and dust of a tin fuming furnace, in particular to a method for efficiently recovering tin resources from the soot and dust of a tin fuming furnace and preparing stannous sulfate, belonging to the technical field of recycling of secondary tin-containing resources. Background Art

[0002] The soot and dust of a tin fuming furnace are tin-containing by-products formed during the high-temperature gasification and condensation stages in the smelting process of cassiterite. They are rich in a large amount of valuable metal tin, and at the same time are accompanied by impurities such as zinc, arsenic, iron, and silicon, and have a high recycling value. Due to the small particle size and large specific surface area of the soot and dust, and the metal elements exist in the forms of oxides, sulfides, etc., it is difficult to recycle.

[0003] In traditional treatment methods, the soot and dust of a tin fuming furnace are usually directly stockpiled or simply landfilled, which not only causes waste of resources but also may cause environmental pollution. Some processes adopt smelting reduction treatment, but have high energy consumption, serious secondary pollution, and low tin recovery rate. In contrast, through technical means such as hydrometallurgy to refine and recycle the soot and dust, not only can tin resources be effectively extracted, but other valuable metals can also be recycled synchronously to achieve the efficient comprehensive utilization of resources. Chinese Patent (CN108950222A) discloses a method for mineralizing and solidifying arsenic and synergistically recovering tin from high-arsenic tin soot and dust. The specific operation is to perform micron powder classification on the tin soot and dust after ultrasonic pretreatment, subject the ultra-fine soot and dust obtained by classification to oxygen pressure leaching, and perform a mineralizing and solidifying arsenic reaction under the coupling action of ultrasonic wave / pressure after catalytic oxidation of the leaching solution to obtain arsenic-solidified minerals; send the coarse soot and dust obtained by classification and the washed leaching residue back to the conventional tin smelting production process for recovering metallic tin. Chinese Patent (CN115786717A) discloses a method for separating and recycling tin and zinc from the soot and dust of an electric furnace for smelting tin. The specific operation is to perform water washing and dechlorination on the tin soot and dust and then perform oxygen pressure leaching. The leaching solution is a zinc sulfate solution, and the zinc sulfate solution is returned to the leaching to enrich zinc. The leaching residue is washed with water to obtain tin concentrate, and the zinc-enriched solution is used to precipitate zinc with sodium salt, and the filter residue after filtration is the zinc raw material. Although the above two methods can both achieve the efficient recovery of tin in the tin soot and dust, the recovered tin is only used as a primary smelting raw material, and the added value of the product is low. Summary of the Invention

[0004] Aiming at the technical problems existing in the current resource utilization of tin soot and dust, the purpose of the present invention is to provide a method for efficiently recovering tin resources from the soot and dust of a tin fuming furnace and preparing stannous sulfate. This method selectively leaches tin from it through wet process and removes impurity elements in the tin soot and dust through a series of impurity removal reactions to prepare a high-purity stannous sulfate product, providing a new way for the resource utilization of the soot and dust of a tin fuming furnace. Compared with the traditional process, it has the advantages of simplified process flow, low energy consumption, and environmental friendliness.

[0005] In order to achieve the above technical objectives, the present invention provides a method for efficiently recovering tin resources from the soot and dust of a tin fuming furnace and preparing stannous sulfate. In this method, the soot and dust of the tin fuming furnace are oxidatively leached with an H2O2-H2SO4 mixed solution at 60-80 °C. The obtained leachate is subjected to reduction, impurity removal, and concentration crystallization to obtain stannous sulfate products. The concentration of H2SO4 in the H2O2-H2SO4 mixed solution is 4-6 mol / L, and the concentration of H2O2 is 0.1-1 mol / L.

[0006] The key to the technical solution of the present invention lies in: aiming at the composition characteristics of tin minerals in the soot and dust of the tin fuming furnace, an H2O2-H2SO4 mixed solution is used for oxidative leaching. By precisely controlling the concentrations of sulfuric acid and hydrogen peroxide and reaction temperature and other conditions, the main component SnS in the soot and dust of the tin fuming furnace is efficiently and selectively converted into stannous sulfate (SnSO4). At the same time, a small amount of tin oxide contained in the soot and dust of the tin fuming furnace is also leached in the form of Sn 4+ form. By adding an appropriate amount of reducing agent, Sn 4+ can be reduced to Sn 2+ to ensure the purity of the stannous sulfate product. On this basis, through a series of impurity removal processes, impurity ions such as Zn, As, Fe, and Si are selectively removed, and concentration crystallization is carried out to obtain stannous sulfate products.

[0007] To efficiently and selectively convert SnS in the soot and dust of the tin fuming furnace into stannous sulfate, the concentrations of H2O2 and H2SO4 and the leaching temperature must be strictly coordinated and controlled. If the concentration of H2SO4 is too low, the decomposition of SnS is difficult. Appropriately increasing the concentration of H2SO4 can effectively promote the conversion of SnS to SnSO4, ensuring the full dissolution and recovery of SnS. If the concentration of H2SO4 is too high, it may cause Sn 2+ to be further oxidized and form by-products such as Sn(SO4)2, which not only reduces the purity of the target product but also may increase the difficulty of subsequent separation and purification. The concentration of H2O2 is not higher than 1 mol / L. By adding a small amount of H2O2, the oxidation of S 2- can be promoted, the leaching efficiency can be improved, and at the same time, the release of H2S during the decomposition of SnS can be effectively inhibited, reducing the generation of harmful gases and ensuring the safety and environmental protection of the reaction process. However, if the concentration of H2O2 is too high, it will not only cause over-oxidation but also may promote Sn ²+Further oxidation generates by-products such as Sn(SO4)2, thereby reducing the product purity of stannous sulfate. At the same time, the leaching temperature is also very important for the selective conversion of SnS into SnSO4. Appropriately increasing the temperature is conducive to the effective conversion of SnS into SnSO4, ensuring the full dissolution and recovery of tin. However, when the temperature is too high, the stability of H2O2 becomes poor and its oxidizing property increases, causing H2O2 to decompose rapidly, reducing the oxidation efficiency, not only affecting the reaction effect but also potentially increasing the reaction cost. In summary, coordinately controlling the concentrations of H2SO4 and H2O2 and the leaching temperature can achieve the efficient selective conversion of SnS in the fuming furnace dust into stannous sulfate.

[0008] As a preferred solution, the tin component in the fuming furnace dust exists in the forms of SnS and tin oxide, and the total tin grade is 40% - 60%. The tin component in the fuming furnace dust mainly exists as SnS and contains a small amount of tin oxide. Based on the fact that the tin component in the fuming furnace dust mainly exists as SnS, conventional acid leaching is difficult to achieve the leaching of tin, and existing oxidative leaching is difficult to obtain Sn 2+ 。

[0009] As a preferred solution, the fuming furnace dust is pretreated by grinding; the grinding particle size meets the requirement that the mass percentage of the particle size less than 200 mesh reaches 100%. Grinding the fuming furnace dust to a particle size less than 200 mesh, the fine particles have a high specific surface area, which can significantly improve the contact efficiency of the solid-liquid reaction, accelerate the mass transfer and chemical reaction rate during leaching, thereby effectively optimizing the reaction kinetic conditions and improving the recovery efficiency of tin resources.

[0010] As a preferred solution, the liquid-solid ratio of the oxidative leaching is 4 - 10 mL:1 g, and the leaching time is 1 - 3 h.

[0011] As a preferred solution, tin powder and iron powder are used as reducing agents during the reduction process. Tin powder and iron powder can effectively reduce Sn 4+ to Sn 2+ , and at the same time, no other impurity elements will be introduced during the reduction process, thus ensuring the purity and effect of the reaction. The dosage of tin powder or iron powder is 1.5 - 2.0 times the theoretical molar amount of tin powder or iron powder required for all Sn 4+ to be completely converted into Sn 2+ .

[0012] As a preferred solution, the impurity removal process includes hydrolysis precipitation for arsenic and iron removal, flocculation sedimentation for silicon removal, and extraction for zinc removal. Zinc, iron, arsenic, and silicon and other impurities are often contained in the fuming furnace dust. If not effectively removed, they will affect the purity and subsequent application performance of the stannous sulfate product.

[0013] As a more preferred solution, the process of hydrolytic precipitation for removing arsenic and iron is as follows: first adjust the pH to 3 - 4, then slowly add ferrous salt and hydrogen peroxide, and let it stand for sedimentation. Adjusting the pH to a weakly acidic environment of 3.0 - 4.0 can avoid the hydrolysis of Sn 2+ while slowly adding FeSO4 (measured according to the molar ratio of Fe element to As element of 2 - 4:1) and H2O2 (measured according to the molar ratio of H2O2 to As element of 1.5 - 2.0:1), oxidize Fe 2+ to Fe 3+ , and at the same time As 3+ is oxidized to As 5+ , and Fe 3+ is likely to form Fe(OH)3 colloid at about pH = 3.5, adsorb arsenate ions and form coprecipitation with Fe.

[0014] As a more preferred solution, the process of flocculation sedimentation for removing silicon is as follows: after adding polyacrylamide and stirring evenly, let it stand for sedimentation. The addition concentration of polyacrylamide is about 0.1 mg / L. After adding, perform rapid stirring and then let it stand to remove silicon in the form of flocs.

[0015] As a more preferred solution, bis(2 - ethylhexyl) phosphoric acid is used as the zinc ion extractant in the process of extraction for removing zinc. Using bis(2 - ethylhexyl) phosphoric acid (D2EHPA) as the extractant, its distribution coefficient for Zn 2+ is relatively high, while it hardly extracts Sn 2+ , thus enabling the deep removal of zinc.

[0016] Compared with the prior art, the beneficial technical effects brought by the technical solution of the present invention are as follows:

[0017] 1) The present invention uses the oxidative leaching method to treat the fuming furnace dust and simultaneously prepare stannous sulfate, which not only realizes the efficient recovery of tin resources in the fuming furnace dust, but also successfully prepares a stannous sulfate product with relatively high added value, providing a new way for the resource utilization of fuming furnace dust.

[0018] 2) The present invention makes full use of the conversion characteristics of SnS in an acidic oxidation environment. By precisely controlling the concentrations of H2O2 and H2SO4 and the reaction temperature, SnS is directly and highly selectively converted to SnSO4 in an acidic oxidation environment. Then, by adding an appropriate amount of reducing agent, a small amount of Sn 4+ is reduced to Sn 2+ , and by regulating the chemical environment of the solution, impurity ions such as Zn, As, Fe, and Si are effectively removed, thereby preparing a stannous sulfate product with relatively high purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1XRD pattern of the fuming furnace dust raw material in Example 1. Detailed implementation manners

[0020] The following examples are intended to further illustrate the content of the present invention rather than limit the protection scope of the claims of the present invention.

[0021] The following specific examples and comparative examples use the fuming furnace dust of a certain factory, with a metal Sn content of 50.5 wt.%, an S content of 11.2 wt.%, an O content of 7.4 wt.%, a Zn content of 5.0 wt.%, an Fe content of 2.7 wt.%, a Si content of 1.2 wt.%, and an As content of 0.8 wt.%. Among them, the molar ratio of SnS / SnO2 = 4.62.

[0022] Comparative Example 1

[0023] Compared with Example 1, the only difference is that the oxidative leaching uses a mixed solution of 1 mol / L H2O2 and 1 mol / L H2SO4.

[0024] Due to the too low concentration of sulfuric acid in the acid leaching process, the leaching rate may decrease.

[0025] Analysis of the experimental results: The recovery rate of metal Sn is 92.3%, and the SnSO4 content in the product is 99.1 wt.%. Although the purity of the SnSO4 product is relatively high, the recovery rate of tin is relatively low, which may be related to the insufficient concentration of H + concentration. The low concentration of H + will cause the reaction to proceed incompletely, affect the dissolution process of Sn, and thus reduce the leaching rate.

[0026] Comparative Example 2

[0027] Compared with Example 1, the only difference is that the oxidative leaching temperature is 25 °C.

[0028] Due to the too low temperature in the acid leaching process, the leaching rate may decrease.

[0029] Analysis of the experimental results: The recovery rate of metal Sn is 93.5%, and the SnSO4 content in the product is 99.1 wt.%. Although the purity of the SnSO4 product is relatively high, the recovery rate of tin is relatively low, which may be related to the relatively low reaction temperature. The lower temperature may limit the dissolution kinetics of Sn, cause the reaction to proceed incompletely, and thus reduce the leaching rate.

[0030] Comparative Example 3

[0031] Compared with Example 1, the only difference is that the oxidative leaching uses a mixed solution of 3 mol / L H2O2 and 5 mol / L H2SO4.

[0032] Due to the excessively high concentration of H2O2 during the acid leaching process, it will further promote the oxidation of Sn 2+ such that the molar ratio of Sn 2+ / Sn 4+ in the leaching solution is 2.54, indicating that a relatively large amount of Sn 2+ is oxidized to Sn 4+ .

[0033] Analysis of the experimental results shows that the recovery rate of metallic Sn is 99.2%, and the SnSO4 content in the product is 98.6 wt.%. Although the recovery rate of tin is relatively high, the product purity fails to meet the national standard. This may be related to the excessively high concentration of H2O2 during the acid leaching process, resulting in a large amount of Sn 2+ being oxidized to Sn 4+ . Although a reducing agent was subsequently added for adjustment, it still had a certain impact on the purity of the final product.

[0034] Example 1

[0035] 10 g of fuming furnace dust after uniform grinding (the particle size meets the requirement that the mass percentage of particles smaller than 200 mesh reaches 100%) is placed in a mixed solution of 1 mol / L H2O2 and 4 mol / L H2SO4, with a liquid-solid ratio of 5 mL / 1 g. Oxidative leaching is carried out at 80 °C for 2 h to directly convert SnS into SnSO4 under an acidic oxidation environment, and the molar ratio of Sn 2+ / Sn 4+ in the leaching solution is 4.61, indicating that Sn 2+ is hardly oxidized. Sn 4+ is reduced to Sn 2+ by adding iron powder as a reducing agent at 1.5 times the theoretical molar amount to ensure the purity of the stannous sulfate product; subsequent impurity removal is then carried out. First, NaOH is added to adjust the pH to 3.5, and then FeSO4 (the molar ratio of Fe to As is 3:1) and industrial hydrogen peroxide (the amount of H2O2 is 1.5 times the molar amount of As) are slowly added. After standing for 2 h, the iron salts in the solution form Fe(OH)3 colloid and adsorb As to form a coprecipitate, and the precipitate is separated by filtration. Polyacrylamide (0.1 mg / L) is added to the solution and stirred rapidly, and then the solution is left standing for 2 hours to remove silicon as flocs. D2EHPA (di(2-ethylhexyl)phosphoric acid) (measured according to 1.5 times the molar amount of Zn²⁺) is added to the solution and the pH is adjusted to 3 and stirred. After standing for 30 minutes, the loaded organic phase and the raffinate are separated, and the raffinate is concentrated and crystallized to obtain SnSO4, realizing the recovery of tin resources.

[0036] Analyze the experimental results: The recovery rate of metallic Sn is 99.1%, and the content of SnSO4 in the product is 99.4 wt.%. The recovery rate of tin is relatively high, and the product purity meets the national standard, indicating that the process conditions are reasonably optimized and the reaction process is well controlled.

[0037] Example 2

[0038] Place 10 g of granulated fuming furnace dust (the particle size meets that the mass percentage of particle size less than 200 mesh reaches 100%) after uniform grinding into a mixed solution of 0.9 mol / L H2O2 and 5 mol / L H2SO4, with a liquid-solid ratio of 5 mL / 1 g, and carry out oxidative leaching at 70 °C for 2.5 hours to directly convert SnS into SnSO4 in an acidic oxidation environment, and the molar ratio of Sn in the leaching solution 2+ / Sn 4+ = 4.60, indicating that Sn 2+ is hardly oxidized. Add 2 times the theoretical molar amount of reducing agent iron powder to reduce Sn 4+ to Sn 2+ , ensuring the purity of stannous sulfate product; then carry out impurity removal. First, adjust the pH to 3.5 with NaOH, then slowly add FeSO4 (the molar ratio of Fe to As is 3:1) and industrial hydrogen peroxide (the amount of H2O2 is 1.5 times the molar amount of As), stand for 2 h to form Fe(OH)3 colloid from the iron salt in the solution and adsorb As to form coprecipitation, and filter to separate the precipitate. Then add polyacrylamide (0.1 mg / L) to the solution and stir rapidly, and then stand the solution for 2 hours to remove silicon as flocs. Then add D2EHPA (di(2-ethylhexyl)phosphoric acid) (measured according to 1.5 times the molar amount of Zn²⁺) to the solution and adjust the pH = 3 and stir, stand for 30 minutes, separate the loaded organic phase and the raffinate, and the raffinate is concentrated and crystallized to obtain SnSO4, realizing the recovery of tin resources.

[0039] Analyze the experimental results: The recovery rate of metallic Sn is 99.4%, and the content of SnSO4 in the product is 99.4 wt.%. The recovery rate of tin is relatively high, and the product purity meets the national standard, indicating that the process conditions are reasonably optimized and the reaction process is well controlled.

[0040] Example 3

[0041] Place 10 g of granulated fuming furnace dust (the particle size meets that the mass percentage of particle size less than 200 mesh reaches 100%) after uniform grinding into a mixed solution of 0.8 mol / L H2O4 and 6 mol / L H2SO4, with a liquid-solid ratio of 5 mL / 1 g, and carry out oxidative leaching at 60 °C for 3 hours to directly convert SnS into SnSO4 in an acidic oxidation environment, and the molar ratio of Sn in the leaching solution 2+ / Sn4+ = 4.60, indicating that Sn 2+ is hardly oxidized. By adding reducing agent iron powder at 1.5 times the theoretical molar amount, Sn 4+ is reduced to Sn 2 + , ensuring the purity of stannous sulfate products; Subsequently, impurity removal is carried out. First, add NaOH to adjust the pH to 3.5, then slowly add FeSO4 (the molar ratio of Fe to As is 3:1) and industrial hydrogen peroxide (the amount of H2O2 is 1.5 times the molar amount of As), and let it stand for 2 h to form Fe(OH)3 colloid from the iron salt in the solution and adsorb As to form a coprecipitate, and filter to separate the precipitate. Then add polyacrylamide (0.1 mg / L) to the solution and stir quickly, and then let the solution stand for 2 hours to remove silicon as a floc. Then add D2EHPA (bis(2-ethylhexyl) phosphoric acid) (measured at 1.5 times the molar amount of Zn²⁺) to the solution and adjust the pH = 3 and stir, let it stand for 30 minutes, separate the loaded organic phase and the raffinate, and the raffinate is concentrated and crystallized to obtain SnSO4, realizing the recovery of tin resources.

[0042] Analyze the experimental results. The recovery rate of metallic Sn is 99.4%, and the content of SnSO4 in the product is 99.4 wt.%. The recovery rate of tin is relatively high, and at the same time, the product purity meets the national standard, indicating that the process conditions are reasonably optimized and the reaction process is well controlled.

Claims

1. A method for efficiently recovering tin resources from the soot of a tin fuming furnace and preparing stannous sulfate, characterized in that: The fuming furnace soot of tin is subjected to oxidative leaching with a H2O2-H2SO4 mixed solution at 60-80 °C. The obtained leaching solution undergoes reduction, impurity removal and concentration crystallization to obtain stannous sulfate products. The concentration of H2SO4 in the H2O2-H2SO4 mixed solution is 4-6 mol / L, and the concentration of H2O2 is 0.1-1 mol / L.

2. The method for efficiently recovering tin resources from the soot of a tin fuming furnace and preparing stannous sulfate according to claim 1, characterized in that: The tin component in the fuming furnace soot of tin exists in the forms of SnS and tin oxide, and the total tin grade is 40%-60%.

3. A method for efficiently recovering tin resources from tin fume furnace soot and preparing stannous sulfate according to claim 1 or 2, characterized in that: The fuming furnace soot of tin is pretreated by grinding; the grinding particle size meets the requirement that the mass percentage of the particle size less than 200 mesh reaches 100%.

4. A method for efficiently recovering tin resources from the soot of a tin fuming furnace and preparing stannous sulfate according to claim 1, characterized in that: The liquid-solid ratio of the oxidative leaching is 4-10 mL:1 g, and the leaching time is 1-3 h.

5. A method for efficiently recovering tin resources from the soot of a tin fuming furnace and preparing stannous sulfate according to claim 1, characterized in that: In the reduction process, tin powder and iron powder are used as reducing agents.

6. The method for efficiently recovering tin resources from the soot of a tin fuming furnace and preparing stannous sulfate according to claim 1, characterized in that: The impurity removal process includes hydrolytic precipitation for removing arsenic and iron, flocculation sedimentation for removing silicon, and extraction for removing zinc.

7. A method for efficiently recovering tin resources from the soot of a tin fuming furnace and preparing stannous sulfate according to claim 6, characterized in that: The process of hydrolytic precipitation for removing arsenic and iron is as follows: first adjust the pH to 3-4, then slowly add ferrous salt and hydrogen peroxide, and let it stand for sedimentation.

8. A method for efficiently recovering tin resources from the soot of a tin fuming furnace and preparing stannous sulfate according to claim 6, characterized in that: The process of flocculation sedimentation for removing silicon is as follows: after adding polyacrylamide and stirring evenly, let it stand for sedimentation.

9. A method for efficiently recovering tin resources from the soot of a tin fuming furnace and preparing stannous sulfate according to claim 6, characterized in that: In the process of extraction for removing zinc, bis(2-ethylhexyl) phosphoric acid is used as the zinc ion extractant.

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