Production process of refined selenium

Abstract

The invention discloses a refined selenium production process, and belongs to the technical field of metallurgy. The method is characterized in that coarse selenium powder is subjected to regulation and control oxidation, melting separation, alkaline leaching and acidification reduction to obtain a high-yield fine selenium product. According to the method disclosed by the invention, the substance obtained by regulating and oxidizing the crude selenium by utilizing the melting point difference of the substance is utilized, the substance containing the selenium element is melted into the melt to be enriched by controlling the temperature, the effective separation of tellurium and selenium is realized, the substance containing the selenium element is leached by utilizing the alkaline solution of sodium sulfite and sodium hydroxide and is converted into the selenium-containing leaching solution, and the tellurium and the selenium are enriched. The pH value of the solution is adjusted to 5-6 through sulfuric acid, selenium is precipitated out, a refined selenium product with the purity reaching 99.99% is obtained, and the recovery rate of selenium exceeds 92%. The method is reasonable in design, few impurities are introduced in the process, the high recovery rate is achieved while the selenium grade exceeds 99.9%, and the selenium resource utilization rate is remarkably increased.

Description

Technical Field

[0001] The invention relates to a method for preparing refined selenium, and belongs to the technical field of crude selenium purification. Background Art

[0002] Selenium is a rare metal. With the rapid development of industries such as ceramics, dyes, solar cells, semiconductors, thermoelectric materials, and selenium-rich agricultural products, demand for selenium is growing. Selenium has become a key material driving high-tech development and new material product innovation. However, due to its concentration in the Earth's crust being only 0.05 ppm, selenium remains a severely scarce metal resource. Selenium is primarily recovered from copper anode mud. Therefore, separating and recovering selenium from crude selenium materials is extremely important for the comprehensive utilization of this resource.

[0003] Currently, crude selenium purification methods primarily include pyrometallurgical, wet, semi-wet, and physical purification. Pyrometallurgical selenium extraction has long dominated due to its adaptability to raw materials, ease of operation, and ease of industrialization. However, this process suffers from drawbacks such as high flue gas production and the generation of toxic gases such as SeO2, which severely restrict its further application. In contrast, wet selenium extraction offers advantages such as low energy consumption, clean and environmentally friendly operation, and low production costs, demonstrating promising application prospects. However, the wet process is prone to the introduction of impurities due to the wide variety of solvents, resulting in a reduced selenium extraction rate; the semi-wet selenium extraction process combines the advantages of the pyrometallurgical and wet processes by replacing the pyrometallurgical reduction smelting and oxidation refining processes with wet processing, but still does not solve the problem of easy sintering of raw materials during the early roasting process, resulting in limited selenium extraction efficiency; the physical purification method mainly uses the difference in vapor pressure between selenium and impurity components for separation; Chinese patent CN116161629A proposes a method for purifying selenium, which changes the occurrence state of impurity components through oxidation reaction and then uses vacuum distillation to achieve separation, but this method cannot effectively extract selenium in the form of CuSeO3 and PbSeO3, resulting in a selenium recovery rate of less than 80%, causing waste of resources. The limitations of these existing selenium extraction methods highlight the urgent need to develop new and efficient selenium extraction processes.

[0004] Therefore, the present invention is specially proposed to solve the above technical problems. Summary of the Invention

[0005] In response to the above technical problems existing in the prior art, the present invention provides a refined selenium production process, which can produce 99.99% refined selenium while achieving a high recovery rate and significantly improving the utilization rate of selenium resources. The process specifically comprises the following steps:

[0006] Regulated oxidation: The slurry obtained by slurrying crude selenium powder and water is mixed with hydrogen peroxide solution at room temperature and selectively oxidized, followed by solid-liquid separation. The filter residue is washed with water to obtain primary selenium;

[0007] Melting separation: heating and melting the obtained primary selenium at 130-150°C and filtering to obtain selenium melt 1; heating and melting the filter residue at 230-300°C and filtering to obtain selenium melt 2; heating and melting the filter residue at 520-540°C and filtering to obtain selenium melt 3; combining the selenium melts and cooling to obtain selenium-containing powder;

[0008] Alkaline leaching: the selenium-containing powder is stirred and leached in a mixed solution of sodium sulfite and sodium hydroxide at a reaction temperature of 92-98°C. After leaching for 3 hours, the solid-liquid separation is performed to obtain a selenium-containing leachate;

[0009] Acidification reduction: The selenium-containing leaching solution is adjusted to a pH of 5-6 with sulfuric acid to obtain a precipitate, and the precipitate is subjected to solid-liquid separation, washing, and drying to obtain refined selenium.

[0010] Preferably, the mass ratio of coarse selenium powder to water in the slurry is 1:1, the hydrogen peroxide solution and the slurry are mixed at a mass ratio of 0.15:1 and selectively oxidized, the selective oxidation time is 0.5 to 1 hour, and the mass concentration of the hydrogen peroxide solution is 30%.

[0011] The heating and melting process described herein has no particular requirements for the equipment used; any melting furnace or resistance furnace known in the art may be used. The primary selenium powder is preferably added to the furnace before or after the furnace reaches the heating and melting temperature. More preferably, the primary selenium powder is added after the furnace reaches the heating and melting temperature to prevent oxidation of elemental selenium to selenium dioxide.

[0012] The heating and melting process of the present invention is preferably carried out under closed conditions to prevent selenium from being oxidized.

[0013] In the present invention, the enclosed space is preferably evacuated or filled with protective gas or directly sealed without any treatment, and then heated and melted.

[0014] Preferably, the heating and melting time is 10 to 30 minutes.

[0015] The present invention filters the selenium melt, and the filtration device used for the filtration has an aperture of 100 to 200 meshes. There are no special requirements for the filtering device, and any device with a filtering function well known in the art can be used, specifically, but not limited to, a screen and a filter. There are no special requirements for the material of the filtering device, which can withstand the high temperature of the melt and has stable chemical properties without introducing other impurities. Specifically, it can be, but not limited to, stainless steel or ceramics.

[0016] Preferably, the particle size of the selenium-containing powder is 100 mesh.

[0017] Preferably, the selenium-containing powder is leached with a mixed solution of sodium sulfite and sodium hydroxide at a solid-liquid ratio of 1.1-1.2:10 (g / ml), the sodium sulfite concentration is 0.23-0.25 g / ml, and the sodium hydroxide concentration is 0.012-0.014 g / ml.

[0018] Preferably, the reaction temperature is 95°C.

[0019] Preferably, the coarse selenium powder comprises the following components in percentage by mass: Se 85-92%, Te 1.5-2.5%, Cu 3-5%, Pb 2-4%, and the remainder is water.

[0020] Beneficial effects of the present invention:

[0021] The present invention provides a refined selenium production process. An oxidant is first used to oxidize impurities (such as elemental tellurium, PbTe, Cu2Se, and PbSe) in crude selenium powder at room temperature into oxides (TeO2, PbSeO3, and CuSeO3) with larger particle sizes, while the elemental selenium phase remains unchanged, thereby obtaining primary selenium. The crude selenium is then oxidized using the melting point differences of the primary selenium species. Through precise temperature control and simple separation operations, the selenium-containing species are melted into a melt for enrichment. TeO2 particles with a melting point of 732°C are attached to the slag, and filtration is used to effectively separate tellurium from selenium. This method not only reduces tellurium's interference with subsequent selenium purification processes, but also improves selenium purity and the selenium yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A process flow chart of a method for preparing refined selenium provided by an embodiment of the present invention DETAILED DESCRIPTION

[0023] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0024] A refined selenium production process is provided, wherein crude selenium is subjected to regulated oxidation, melting separation, alkaline leaching and acidification reduction steps to obtain a high-yield refined selenium product.

[0025] Example 1

[0026] Regulated oxidation: 200g of crude selenium material (main components: Se85.1%, Te1.6%, Cu2.9%, Pb1.9%, the balance is water) is placed in a reactor, and after slurrying with deionized water in a ratio of 1:1, 60g of 30% hydrogen peroxide solution is added dropwise at a stirring rate of 300r / min, and the reaction is carried out for 30min. After filtering and washing with water, primary selenium is obtained.

[0027] Melting separation: Wrap the primary selenium with a 100-mesh stainless steel screen, and then place it in a crucible with a small hole at the bottom, and put a receiving basin under the crucible; turn on the power switch of the resistance furnace and let it heat normally. When the temperature in the furnace reaches 130°C, put the receiving basin and the crucible together into a closed melting electric furnace and heat and melt them. After keeping warm for 10 minutes, take them out and you can get selenium melt 1 in the receiving basin. Heat the electric furnace to 230°C to heat and melt the filter residue. After keeping warm for 10 minutes, take them out and you can get selenium melt 2 in the receiving basin. Heat the electric furnace to 520°C to heat and melt the filter residue. After keeping warm for 10 minutes, take them out and you can get selenium melt 3 in the receiving basin. Combine the selenium melts, cool and crush them to obtain 167.9g of selenium-containing powder.

[0028] Alkaline leaching: All the selenium-containing powder was dissolved in a mixed solution of 1530 g of sodium sulfite with a concentration of 0.23 g / ml and sodium hydroxide with a concentration of 0.012 g / ml. Leaching was carried out at a reaction temperature of 92° C. and a stirring rate of 300 r / min. After leaching for 3 hours, the mixture was filtered to obtain a selenium-containing leachate.

[0029] Acidification reduction: The selenium-containing leaching solution is adjusted to a pH of 5-6 with sulfuric acid to obtain a precipitate, which is filtered, washed, and dried to obtain refined selenium.

[0030] Example 2

[0031] Regulated oxidation: 200g of crude selenium material (main components: Se92.1%, Te2.5%, Cu5.1%, Pb3.9%, the balance is water) is placed in a reactor, and after slurrying with deionized water in a ratio of 1:1, 60g of 30% hydrogen peroxide solution is added dropwise at a stirring rate of 300r / min. After reaction for 30min, the mixture is filtered and washed with water to obtain primary selenium.

[0032] Melting separation: Wrap the primary selenium with a 200-mesh stainless steel screen, and then place it in a crucible with a small hole at the bottom, and put a receiving basin under the crucible; turn on the power switch of the resistance furnace and let it heat normally. When the temperature in the furnace reaches 150°C, put the receiving basin and the crucible together into a closed melting electric furnace and heat and melt them. After keeping warm for 30 minutes, take them out and obtain selenium melt 1 in the receiving basin. Heat the electric furnace to 300°C to heat and melt the filter residue. After keeping warm for 30 minutes, take them out and obtain selenium melt 2 in the receiving basin. Heat the electric furnace to 540°C to heat and melt the filter residue. After keeping warm for 30 minutes, take them out and obtain selenium melt 3 in the receiving basin. Combine the selenium melts, cool and crush them to obtain 185.1g of selenium-containing powder.

[0033] Alkaline leaching: All the selenium-containing powder was dissolved in a mixed solution of 1540 g of sodium sulfite with a concentration of 0.25 g / ml and sodium hydroxide with a concentration of 0.014 g / ml. Leaching was carried out at a reaction temperature of 98° C. and a stirring rate of 300 r / min. After leaching for 3 hours, the selenium-containing leachate was filtered to obtain.

[0034] Acidification reduction: The selenium-containing leaching solution is adjusted to a pH of 5-6 with sulfuric acid to obtain a precipitate, which is filtered, washed, and dried to obtain refined selenium.

[0035] Example 3

[0036] Regulated oxidation: 200 g of crude selenium material (main components: Se88.3%, Te1.9%, Cu3.8%, Pb3.2%, and the balance is water) is placed in a reactor, and after slurrying with deionized water in a 1:1 ratio, 60 g of 30% hydrogen peroxide solution is added dropwise at a stirring rate of 300 r / min, and the reaction is carried out for 30 minutes. The mixture is then filtered and washed with water to obtain primary selenium.

[0037] Melting separation: Wrap the primary selenium with a 150-mesh stainless steel screen, and then place it in a crucible with a small hole at the bottom, and put a receiving basin under the crucible; turn on the power switch of the resistance furnace and let it heat normally. When the temperature in the furnace reaches 135°C, put the receiving basin and the crucible together into a closed melting electric furnace and heat and melt them. After keeping warm for 20 minutes, take them out. Selenium melt 1 can be obtained in the receiving basin. Heat the electric furnace to 270°C to heat and melt the filter residue. After keeping warm for 20 minutes, take them out. Selenium melt 2 can be obtained in the receiving basin. Heat the electric furnace to 530°C to heat and melt the filter residue. After keeping warm for 20 minutes, take them out. Selenium melt 3 can be obtained in the receiving basin. Combine the selenium melts, cool and crush them to obtain 175.2g of selenium-containing powder.

[0038] Alkaline leaching: All the selenium-containing powder was dissolved in a mixed solution of 1520 g of sodium sulfite with a concentration of 0.24 g / ml and sodium hydroxide with a concentration of 0.013 g / ml. Leaching was carried out at a reaction temperature of 95° C. and a stirring rate of 300 r / min. After leaching for 3 hours, the mixture was filtered to obtain a selenium-containing leachate.

[0039] Acidification reduction: The selenium-containing leaching solution is adjusted to a pH of 5-6 with sulfuric acid to obtain a precipitate, which is filtered, washed, and dried to obtain refined selenium.

[0040] Comparative Example 1

[0041] Regulated oxidation: 200g of crude selenium material (main components: Se92.1%, Te2.5%, Cu5.1%, Pb3.9%, the balance is water) is placed in a reactor, and after slurrying with deionized water in a ratio of 1:1, 60g of 30% hydrogen peroxide solution is added dropwise at a stirring rate of 300r / min. After reaction for 30min, the mixture is filtered, washed with water, and dried to obtain primary selenium.

[0042] Alkaline leaching: All the primary selenium was dissolved in a mixed solution of 1540 g of sodium sulfite with a concentration of 0.25 g / ml and sodium hydroxide with a concentration of 0.014 g / ml. The mixture was leached at a reaction temperature of 98° C. and a stirring rate of 300 r / min. After leaching for 3 hours, the mixture was filtered to obtain a selenium-containing leachate.

[0043] Acidification reduction: The selenium-containing leaching solution is adjusted to a pH of 5-6 with sulfuric acid to obtain a precipitate, which is filtered, washed, and dried to obtain refined selenium.

[0044] Comparative Example 2

[0045] Melting separation: 200g of crude selenium material (main components: Se88.3%, Te1.9%, Cu3.8%, Pb3.2%, and the balance is water) is wrapped with a 150-mesh stainless steel screen, then placed in a crucible with a small hole at the bottom, and a receiving basin is set under the crucible; turn on the power switch of the resistance furnace and allow it to heat normally. When the furnace temperature reaches 135°C, the receiving basin and the crucible are placed together in a closed melting furnace for heating and melting. After being heat-insulated for 20 minutes, they are taken out to obtain selenium melt 1 in the receiving basin. The electric furnace is heated to 270°C and the filter residue is heated and melted. After being heat-insulated for 20 minutes, they are taken out to obtain selenium melt 2 in the receiving basin. The electric furnace is heated to 530°C and the filter residue is heated and melted. After being heat-insulated for 20 minutes, they are taken out to obtain selenium melt 3 in the receiving basin. The selenium melts are combined and cooled and crushed to obtain 156.4g of selenium-containing element powder.

[0046] Alkaline leaching: All the selenium-containing powder was dissolved in 1400 g of a mixed solution of sodium sulfite with a concentration of 0.24 g / ml and sodium hydroxide with a concentration of 0.013 g / ml. Leaching was carried out at a reaction temperature of 95° C. and a stirring rate of 300 r / min. After leaching for 3 hours, the mixture was filtered to obtain a selenium-containing leachate.

[0047] Acidification reduction: The selenium-containing leaching solution is adjusted to a pH of 5-6 with sulfuric acid to obtain a precipitate, which is filtered, washed, and dried to obtain refined selenium.

[0048] In accordance with the provisions of China's nonferrous metal industry standard YS / T223-2007, the chemical composition of the impurity elements in the refined selenium products obtained in the examples and comparative examples was quantitatively analyzed by ICP-AES. The total amount of selenium calculated by the selenium content in the product / the total amount of selenium calculated by the selenium content in the raw material was used to calculate the selenium recovery rate. The specific results are shown in Table 1.

[0049] Table 1 Data results of Examples 1 to 3 and Comparative Examples 1 to 2

[0050]

[0051]

[0052] According to the data in Table 1, the selenium content in the refined selenium products purified by Examples 1 to 3 of the present invention is as high as 99.99% or more, which fully meets the requirements of the "Nonferrous Metals Industry Standard of the People's Republic of China" (YS / T 223-2007) for Se9999 grade. In Examples 1 to 3, the Te content in the refined selenium products is only 3 to 5 ppm, which is significantly lower than the Te impurity content in Control Example 1. This shows that by precisely controlling the temperature and a simple separation step, the Te impurities after oxidation can be effectively removed. In addition, the recovery rate of selenium in Examples 1 to 3 is much higher than that in Control Example 2, which proves that alkaline leaching has a good extraction effect on selenium in the form of CuSeO3 and PbSeO3. Moreover, the recovery rate of selenium in the refined selenium product obtained in the embodiment of the present invention reaches more than 92%, which shows that while improving the purity of the refined selenium product, a higher recovery rate can also be ensured.

[0053] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A refined selenium production process, characterized in that: The following steps are involved: Regulated oxidation: The slurry obtained by slurrying crude selenium powder and water is mixed with hydrogen peroxide solution at room temperature and selectively oxidized, followed by solid-liquid separation. The filter residue is washed with water to obtain primary selenium; Melting separation: heating and melting the obtained primary selenium at 130-150°C and filtering to obtain selenium melt 1; heating and melting the filter residue at 230-300°C and filtering to obtain selenium melt 2; heating and melting the filter residue at 520-540°C and filtering to obtain selenium melt 3; combining the selenium melts and cooling to obtain selenium-containing powder; Alkaline leaching: the selenium-containing powder is stirred and leached in a mixed solution of sodium sulfite and sodium hydroxide at a reaction temperature of 92-98° C. After leaching, the solid and liquid are separated to obtain a selenium-containing leachate; Acidification reduction: The selenium-containing leaching solution is adjusted to a pH of 5-6 with sulfuric acid to obtain a precipitate, and the precipitate is subjected to solid-liquid separation, washing, and drying to obtain refined selenium.

2. A refined selenium production process according to claim 1, characterized in that, The mass ratio of crude selenium powder to water in the slurry is 1:1, the hydrogen peroxide solution and the slurry are mixed at a mass ratio of 0.15:1 and selectively oxidized, and the selective oxidation time is 0.5 to 1 hour. The mass concentration of the hydrogen peroxide solution is 30%.

3. A refined selenium production process according to claim 1, characterized in that, The heating and melting time is 10 to 30 minutes.

4. A refined selenium production process according to claim 1, characterized in that, The heating and melting is carried out under closed conditions.

5. A refined selenium production process according to claim 1, characterized in that, The particle size of the selenium-containing powder is 100 mesh.

6. A refined selenium production process according to claim 1, characterized in that, The selenium-containing powder is mixed with a solution of sodium sulfite and sodium hydroxide at a solid-liquid ratio of 1.1 to 1.2:

10. (g / ml) leaching, the sodium sulfite concentration is 0.23-0.25g / ml, and the sodium hydroxide concentration is 0.012-0.014g / ml.

7. A refined selenium production process according to claim 1, characterized in that, The reaction temperature was 95°C.

8. A refined selenium production process according to claim 1, characterized in that, The coarse selenium powder comprises the following components in percentage by mass: Se 85-92%, Te 1.5-2.5%, Cu 3-5%, Pb 2-4%, and the balance is water.

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