A method for separating selenium and tellurium from high selenium tellurium dioxide by multi-stage conversion
By using a multi-stage conversion process to treat high-selenium tellurium dioxide, and employing multi-stage leaching and neutralization treatment with reducing agents and alkaline solutions, the problem of low selenium removal efficiency during roasting of high-selenium tellurium dioxide was solved, achieving efficient separation and recovery of selenium tellurium, and improving product purity and production efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- KUNMING UNIV OF SCI & TECH
- Filing Date
- 2026-03-02
- Publication Date
- 2026-06-09
Smart Images
Figure CN122166725A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of non-ferrous metals technology and relates to a method for separating selenium tellurium from high-selenium tellurium dioxide through multi-stage conversion. Through process optimization and technological innovation, the high-selenium tellurium dioxide generated during tellurium recovery is pretreated using a multi-stage conversion process, thereby achieving efficient separation and recovery of selenium tellurium. Background Technology
[0002] Tellurium is a rare and dispersed metal widely used in industry, defense, and cutting-edge technologies. Due to its scarcity, over 90% of tellurium originates from anode slime produced during copper smelting. High-selenium tellurium dioxide is a selenium- and tellurium-enriched neutral slag produced by the neutralization reaction with sulfuric acid in the wet tellurium recovery process from copper anode slime.
[0003] Currently, the mainstream treatment technology for high-selenium tellurium dioxide is mainly based on pyrometallurgical processes. The technical principle of this process is as follows: the high-selenium tellurium dioxide raw material is placed in thermal equipment such as an oven or rotary kiln. Through the high-temperature thermochemical action of baking and roasting, the selenium component in the raw material undergoes a thermal decomposition reaction, which is converted into a more volatile low-valence selenium oxide (such as SeO2). Then, by utilizing the difference in volatility between selenium oxide and tellurium dioxide at high temperatures, the gas phase migration and separation of the selenium component are achieved, and the purification of tellurium dioxide is finally completed.
[0004] However, this pyrometallurgical selenium removal process has clear technical limitations. First, the thermal decomposition and volatilization kinetics of selenium are hindered, leading to a significant decrease in selenium removal efficiency and failing to meet the target purification requirements. Second, to compensate for the low removal efficiency, the roasting time needs to be extended, resulting in a significant increase in the production cycle and a reduction in equipment processing capacity and production efficiency. Third, incompletely removed selenium components are prone to remain in the product as impurities, or form unstable complex oxides with tellurium dioxide during the roasting process, directly affecting the purity and quality of the final product and making it difficult to meet the quality requirements of downstream high-end applications for tellurium raw materials.
[0005] Patent document CN112159049A discloses a treatment method and apparatus for simultaneously removing selenium and sulfide pollution. This patent is essentially a wastewater purification technology, designed only to treat low-concentration ionic selenium / sulfur wastewater to achieve compliant discharge. The entire microbial and liquid-phase reaction system is unsuitable for treating high-grade, complex-phase high-selenium tellurium dioxide, lacking practical application value in the field of metallurgical resource utilization. Patent document CN115369416A discloses a method for separating and recovering sulfur and copper from copper sulfide slag, using crushing, alkali roasting, ball milling, water leaching, and electrowinning processes to achieve the separation and recovery of selenium and copper. However, this method is mainly designed for the copper-selenium system and fails to effectively treat other associated valuable elements such as arsenic and tellurium. Its high-temperature roasting has high energy consumption, and selenium is easily lost through volatilization during the process, posing an environmental pollution risk. Patent document CN115432672A discloses a method for recovering tellurium from tellurium-copper slag and producing high-purity tellurium. This patent employs a passive "mix-then-separate" technical route, resulting in a severely circuitous process. To separate the coexisting tellurium and selenium, multiple cycles of alkali dissolution and neutralization are necessary, making the process cumbersome and consuming enormous amounts of reagents. It fails to fundamentally solve the core problem of the similar chemical properties of tellurium and selenium, and suffers from inherent defects in the processing of high-selenium materials, including incomplete separation and limited product purity, resulting in low economic efficiency and production effectiveness.
[0006] Therefore, a multi-stage conversion method for separating selenium and tellurium from high-selenium tellurium dioxide was developed. This method achieves rapid separation and efficient recovery of selenium and tellurium through a multi-stage conversion system. This technology not only enables short-process separation of selenium and tellurium elements in complex phases but also provides qualified tellurium dioxide feedstock for subsequent tellurium electrowinning processes, thus improving the overall technical route for high-selenium material processing. Summary of the Invention
[0007] In order to overcome the problems existing in the above-mentioned technologies, and to solve the problems of low efficiency of traditional roasting for selenium removal, reduce production costs, and make the reaction simple and easy to operate, this invention provides a method for separating selenium tellurium from high-selenium tellurium dioxide through multi-stage conversion.
[0008] The technical solution of this invention is implemented as follows: a method for separating selenium tellurium from high-selenium tellurium dioxide through multi-stage conversion, comprising the following steps: a. Material preparation: After drying and ball milling, the high-selenium tellurium dioxide is controlled to a particle size of 100-200 mesh; b. Conversion leaching: Prepare a conversion solution with pH 8-11 containing a reducing agent at a concentration of 0.2-0.5 mol / L, add the high-selenium tellurium dioxide powder obtained in step a, and react. After the reaction is completed, perform liquid-solid separation to obtain selenium-containing tellurium slag and primary leachate. c. Secondary conversion leaching: Prepare a conversion solution with sodium hydroxide concentration of 3-5% and reducing agent concentration of 0.05-0.15 mol / L, add the selenium-containing tellurium slag obtained in step b to react, and after the reaction is completed, perform liquid-solid separation to obtain elemental selenium and secondary leaching solution. d Neutralization treatment: The leachate and secondary leachate obtained in step b and step c are mixed and treated, and an acidic reagent is added for neutralization to obtain high-purity tellurium dioxide. The high-purity tellurium dioxide is then subjected to a solution preparation process, and the resulting electrodeposition solution is introduced into an electrodeposition cell for electrodeposition. After electrodeposition is completed, it is cast to obtain 4N high-purity tellurium. Preferably, in step a, the high-selenium tellurium dioxide is produced during the wet production of tellurium from copper anode mud, and its mass percentage composition includes 40-50% tellurium, 5-8% selenium, and 0.01-0.05% lead. Preferably, in steps b and c, the reducing agent is at least one of sodium sulfide, potassium sulfide, or ammonium sulfide; Preferably, in step b, the liquid-to-solid ratio of the reaction is controlled at 4-5:1, the temperature is 30℃-50℃, and the reaction time is 2-3 hours. Preferably, in step b, the amount of the reducing agent added is 2-5 times the theoretical content of selenium. Preferably, in step c, the amount of sodium hydroxide added is 1.2-1.6 times the theoretical content of tellurium. Preferably, in step c, the amount of the reducing agent added is 0.5-1.5 times the theoretical content of tellurium. Preferably, in step c, the liquid-to-solid ratio of the reaction is 6-8:1, the reaction temperature is 30-50℃, and the reaction time is 3-4h. Preferably, in step d, the concentration of the acidic reagent is controlled between 15% and 35%; Preferably, in step d, the pH is adjusted to 5-6 during the neutralization process, and after liquid-solid separation, high-purity tellurium dioxide and the neutralized liquid are obtained.
[0009] The main chemical reaction equations involved in this invention are as follows: Primary conversion leaching: Na2SeO4+3A2S+4H2O=Se↓+3S +2NaOH+6AOH Na2SeO3+2A2S+3H2O=Se↓+2S +2NaOH+4AOH Secondary conversion leaching: TeO₂ + 2NaOH = Na₂TeO₃ + H₂O 4Na₂TeO₄ + A₂S = 4Na₂TeO₃ + A₂SO₄ Neutralization treatment: Na₂TeO₃ + H₂SO₄ = H₂TeO₃ + Na₂SO₄ H₂TeO₃ = TeO₂↓ + H₂O The method for separating selenium tellurium from high-selenium tellurium dioxide through multi-stage conversion described in this invention has outstanding substantive features and significant technical advancements compared to existing processes: This invention treats high-selenium tellurium dioxide by limiting the amount of reducing reagent added and the concentration of alkali, thereby achieving the conversion of selenium-containing tellurium substances and completing the separation of selenium and tellurium. This avoids the loss of tellurium during the traditional roasting process, provides qualified tellurium dioxide for subsequent production, shortens the tellurium production process, and has good process stability.
[0010] The present invention achieves a selenium recovery rate of up to 98% and a purity of over 95%, and a tellurium recovery rate of over 99% for tellurium dioxide products. The tellurium products produced after subsequent solvent preparation, electrowinning, and ingot casting meet the 4N requirements. Attached Figure Description
[0011] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation
[0012] This invention provides a method for separating selenium tellurium from high-selenium tellurium dioxide through a multi-stage conversion process, comprising the following steps: a. Material preparation: High-selenium tellurium dioxide is dried and ball-milled to control its particle size to 100-200 mesh. By mass percentage, the high-selenium tellurium dioxide composition includes 48.93% tellurium, 5.65% selenium, and 0.03% lead. Drying and ball-milling the high-selenium tellurium dioxide to obtain a small-particle solid powder increases its specific surface area, allowing for sufficient contact with the reducing agent during subsequent conversion, thereby accelerating the conversion rate and improving production efficiency.
[0013] b. Primary conversion leaching: Prepare a conversion solution with a pH of 8-11 and a reducing agent concentration of 0.2-0.5 mol / L. Add ball-milled high-selenium tellurium dioxide powder at a liquid-to-solid ratio of 4-5:1 and react at 30-50℃ for 2-3 hours. After the reaction, perform liquid-solid separation to obtain selenium-containing tellurium slag and primary leaching solution. In this step, the alkaline environment inhibits the hydrolysis of the sulfide reducing agent, ensuring that high-valence selenium (selenate, selenite) is efficiently reduced to elemental selenium and enters the slag phase.
[0014] c. Secondary Conversion Leaching: Prepare a conversion solution with a sodium hydroxide concentration of 3-5% and a reducing agent concentration of 0.05-0.15 mol / L. Add the selenium-containing tellurium slag obtained in step b at a liquid-to-solid ratio of 6-8:1, and react at 30-50℃ for 3-4 hours. After the reaction, perform liquid-solid separation to obtain elemental selenium and a secondary leachate. In this step, the strongly alkaline environment converts tellurium dioxide in the slag into soluble sodium tellurite, while inhibiting the dissolution of impurities. The presence of the reducing agent can reduce any tellurate present to tellurite, ensuring complete dissolution of tellurium and thus achieving complete separation from insoluble elemental selenium.
[0015] d. Neutralization treatment: Mix the primary leachate obtained in step b with the secondary leachate obtained in step c, and slowly add an acidic reagent with a mass concentration of 15-35% for neutralization, controlling the final pH value to 5-6. After the reaction, perform liquid-solid separation to obtain high-purity tellurium dioxide and the neutralized solution. During the neutralization process, the slow addition of low-concentration acid can prevent local over-acidification and avoid the formation of fine tellurium dioxide colloidal particles. At the same time, precise control of the pH at 5-6 can minimize the presence of impurity ions (such as Pb). 2+ Co-precipitation is used to ensure the purity of tellurium dioxide.
[0016] The present invention achieves a selenium recovery rate of up to 98% and a purity of over 95%, while the tellurium recovery rate of the tellurium dioxide product is over 99%. The obtained high-purity tellurium dioxide can be directly processed into an electrodeposition solution. The electrodeposition solution is introduced into an electrodeposition cell, and after electrodeposition is completed, it is cast to obtain 4N high-purity tellurium.
[0017] As a preferred embodiment, the primary conversion liquid obtained in step b can be replenished with alkaline solution and then recycled as the secondary conversion leaching medium in step c, thereby achieving the reuse of alkaline substances and water and reducing production costs.
[0018] To better understand this invention, the following detailed description of the invention is provided in conjunction with specific examples. However, the scope of this invention is not limited to the examples described below. Example 1
[0019] Primary conversion leaching: Prepare a conversion solution with pH=10 and sodium sulfide concentration of 0.35 mol / L. Add 5 kg of high-selenium tellurium dioxide powder at a liquid-to-solid ratio of 5:1, and convert at 37℃ for 2.5 h. After the reaction is complete, filter to obtain selenium-containing tellurium residue and primary leaching solution.
[0020] Secondary conversion leaching: A conversion solution with a sodium hydroxide concentration of 4% and a sodium sulfide concentration of 0.1 mol / L was prepared, and the reaction was carried out for 4 hours at a liquid-to-solid ratio of 7:1 and a reaction temperature of 42℃. After the reaction was completed, the solution was filtered to obtain the secondary leaching solution and elemental selenium.
[0021] Neutralization treatment: The primary and secondary leachates were mixed, and 20% sulfuric acid was added for neutralization, controlling the final pH to 5.5. The mixture was then filtered to obtain high-purity tellurium dioxide. The tellurium dioxide was then processed through a solution preparation-electrowinning-ingot casting process to obtain 4N tellurium.
[0022] Using the method of this embodiment, all leachate (primary and secondary leachate) was mixed and reacted with an acidic reagent to obtain high-purity tellurium dioxide. To verify the reliability of the results, two parallel samples were taken for testing, and the comparison of tellurium and selenium grades between these samples and the alkaline leaching residue is shown in Table 1: Table 1. Content of major elements (%) in high-purity tellurium dioxide and leaching residue name Se Te Pb High-purity tellurium dioxide <0.01 63.59 0.01 High-purity tellurium dioxide <0.01 58.63 <0.01 alkaline leaching residue 40.14 0.83 0.36 Example 2
[0023] The high-selenium tellurium dioxide components used in this embodiment are, by mass percentage: Te 48.93%, Se 5.65%, Pb 0.03%.
[0024] Primary conversion leaching: Prepare a conversion solution with pH=9 and sodium sulfide concentration of 0.45 mol / L. Add 5 kg of high-selenium tellurium dioxide powder at a liquid-to-solid ratio of 4:1, and convert at 32℃ for 3 hours. After the reaction is complete, filter to obtain selenium-containing tellurium residue and primary leaching solution.
[0025] Secondary conversion leaching: A conversion solution with a sodium hydroxide concentration of 3% and a sodium sulfide concentration of 0.08 mol / L was prepared and reacted for 3 hours at a liquid-to-solid ratio of 8:1 and a reaction temperature of 30℃. After the reaction was completed, the solution was filtered to obtain the secondary leaching solution and elemental selenium.
[0026] Neutralization treatment: The primary and secondary leachates were mixed, and 20% sulfuric acid was added for neutralization, controlling the final pH to 5.5. The mixture was then filtered to obtain high-purity tellurium dioxide. The tellurium dioxide was then processed through a solution preparation-electrowinning-ingot casting process to obtain 4N tellurium.
[0027] Using the method of this embodiment, all leachate (primary and secondary leachate) was mixed and reacted with an acidic reagent to obtain high-purity tellurium dioxide. To verify the reliability of the results, two parallel samples were taken for testing, and the comparison of tellurium and selenium grades between these samples and the alkaline leaching residue is shown in Table 2: Table 2. Content of major elements (%) in high-purity tellurium dioxide and alkaline leaching residue name Se Te Pb High-purity tellurium dioxide <0.01 60.25 <0.01 High-purity tellurium dioxide <0.01 62.15 <0.01 alkaline leaching residue 38.56 0.96 0.29 Example 3
[0028] The high-selenium tellurium dioxide components used in this embodiment are, by mass percentage: Te 48.93%, Se 5.65%, Pb 0.03%.
[0029] Primary conversion leaching: Prepare a conversion solution with pH=11 and sodium sulfide concentration of 0.4 mol / L. Add 5 kg of high-selenium tellurium dioxide powder at a liquid-to-solid ratio of 4:1, and convert at 40℃ for 3 hours. After the reaction is complete, filter to obtain selenium-containing tellurium residue and primary leaching solution.
[0030] Secondary conversion leaching: A conversion solution with a sodium hydroxide concentration of 5% and a sodium sulfide concentration of 0.12 mol / L was prepared, and the reaction was carried out for 3 hours at a liquid-to-solid ratio of 6:1 and a reaction temperature of 36℃. After the reaction was completed, the solution was filtered to obtain the secondary leaching solution and elemental selenium.
[0031] Neutralization treatment: The primary and secondary leachates were mixed, and 20% sulfuric acid was added for neutralization, controlling the final pH to 5.5. The mixture was then filtered to obtain high-purity tellurium dioxide. The tellurium dioxide was then processed through a solution preparation-electrowinning-ingot casting process to obtain 4N tellurium.
[0032] Using the method of this embodiment, all leachate (primary and secondary leachate) was mixed and reacted with an acidic reagent to obtain high-purity tellurium dioxide. To verify the reliability of the results, two parallel samples were taken for testing, and the comparison of tellurium and selenium grades between these samples and the alkaline leaching residue is shown in Table 3. Table 3. Content of major elements (%) in high-purity tellurium dioxide and alkaline leaching residue name Se Te Pb High-purity tellurium dioxide <0.01 59.88 <0.01 High-purity tellurium dioxide <0.01 61.33 <0.01 alkaline leaching residue 42.12 0.45 0.41 Comparative Example 1: The same high-selenium tellurium dioxide powder as in Example 1 was directly used to prepare a 5% sodium hydroxide alkaline solution without adding a reducing agent. The solution was then leached for 3 hours at a liquid-to-solid ratio of 8:1 and a reaction temperature of 45°C. After the reaction, the solution was filtered to obtain the leachate. 20% sulfuric acid was added to the leachate for neutralization to obtain the tellurium dioxide product.
[0033] The comparison of selenium and tellurium grades in tellurium dioxide obtained by direct leaching with sodium hydroxide is shown in Table 4. Table 4. Content of major elements in tellurium dioxide (%) element Se Te Pb content(%) 3.59 59.88 0.05 The experimental results of Comparative Example 1 show that when using the traditional process of adding only sodium hydroxide, selenium mainly remains in the tellurium dioxide product, with a selenium content as high as 3.59%, making effective separation impossible.
[0034] The combined data from Examples 1-3 show that by using the multi-stage conversion method of the present invention, and by introducing reducing reagents and precisely controlling reaction conditions, the selenium content in the obtained high-purity tellurium dioxide is all below 0.01%, while the tellurium content in the leaching residue (elemental selenium) is all below 1%, which significantly enhances the separation efficiency of selenium and tellurium, and ultimately achieves efficient separation and recovery of selenium and tellurium.
[0035] It should be noted that the above embodiments represent only a few preferred application examples of the present invention. Any obvious changes or modifications made by those skilled in the art based on the inspiration of the present invention after fully understanding the design concept of the present invention should be considered to fall within the scope of protection claimed by the present invention.
Claims
1. A method for separating selenium tellurium from high-selenium tellurium dioxide through multi-stage conversion, characterized in that... This includes the following steps: a. Material preparation: After drying and ball milling, the high-selenium tellurium dioxide is controlled to a particle size of 100-200 mesh; b. Conversion leaching: Prepare a conversion solution with pH 8-11 containing a reducing agent at a concentration of 0.2-0.5 mol / L, add the high-selenium tellurium dioxide powder obtained in step a, and react. After the reaction is completed, perform liquid-solid separation to obtain selenium-containing tellurium slag and primary leachate. c. Secondary conversion leaching: Prepare a conversion solution with sodium hydroxide concentration of 3-5% and reducing agent concentration of 0.05-0.15 mol / L, add the selenium-containing tellurium slag obtained in step b to react, and after the reaction is completed, perform liquid-solid separation to obtain elemental selenium and secondary leaching solution. d Neutralization treatment: The leachate obtained in step b and step c and the secondary leachate are mixed and treated, and an acidic reagent is added for neutralization to obtain high-purity tellurium dioxide. The high-purity tellurium dioxide is then subjected to a solution preparation process, and the resulting electrodeposition solution is introduced into an electrodeposition tank for electrodeposition. After electrodeposition is completed, it is cast to obtain 4N high-purity tellurium.
2. The method for separating selenium tellurium from high-selenium tellurium dioxide through multi-stage conversion according to claim 1, characterized in that: In step a, the high-selenium tellurium dioxide is produced during the wet production of tellurium from copper anode mud. The high-selenium tellurium dioxide composition includes 40-50% tellurium, 5-8% selenium, and 0.01-0.05% lead.
3. A method for separating selenium tellurium from high-selenium tellurium dioxide through multi-stage conversion according to claim 1 or 2, characterized in that: In steps b and c, the reducing agent is at least one of sodium sulfide, potassium sulfide, or ammonium sulfide.
4. A method for separating selenium tellurium from high-selenium tellurium dioxide through multi-stage conversion according to claim 1 or 2, characterized in that: In step b, the liquid-to-solid ratio of the reaction is controlled at 4-5:1, the temperature is 30℃-50℃, and the reaction time is 2-3 hours.
5. A method for separating selenium tellurium from high-selenium tellurium dioxide through multi-stage conversion according to claim 1 or 2, characterized in that: In step b, the amount of the reducing agent added is 2-5 times the theoretical content of selenium.
6. A method for separating selenium tellurium from high-selenium tellurium dioxide through multi-stage conversion according to claim 1 or 2, characterized in that: In step c, the amount of sodium hydroxide added is 1.2-1.6 times the theoretical content of tellurium.
7. A method for separating selenium tellurium from high-selenium tellurium dioxide through multi-stage conversion according to claim 1 or 2, characterized in that: In step c, the amount of the reducing reagent added is 0.5-1.5 times the theoretical content of tellurium.
8. A method for separating selenium tellurium from high-selenium tellurium dioxide through multi-stage conversion according to claim 1 or 2, characterized in that: In step c, the liquid-to-solid ratio of the reaction is 6-8:1, the reaction temperature is 30-50℃, and the reaction time is 3-4h.
9. A method for separating selenium tellurium from high-selenium tellurium dioxide through multi-stage conversion according to claim 1 or 2, characterized in that: In step d, the concentration of the acidic reagent is controlled between 15% and 35%.
10. A method for separating selenium tellurium from high-selenium tellurium dioxide through multi-stage conversion according to claim 1 or 2, characterized in that: In step d, the pH is adjusted to 5-6 during the neutralization process, and after liquid-solid separation, high-purity tellurium dioxide and the neutralized liquid are obtained.