Method and device for separating selenium and tellurium from high-tellurium coarse selenium raw material

Abstract

The application provides a method and equipment for separating selenium and tellurium from high-tellurium crude selenium raw materials. The method can selectively form tellurium polysulfide from tellurium in the crude selenium by adding sulfur in an alkaline solution, so that the metallic tellurium is converted into ions and enters the solution, and the main metallic selenium remains in the slag, thereby preliminarily and effectively separating the selenium and the tellurium, achieving a separation coefficient of 90.67%, and reducing the content of tellurium in the crude selenium raw material from 0.30% to 0.028%. The application has the advantages of good selenium and tellurium separation effect, simple operation, short process, and strong raw material adaptability.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a method and equipment for separating selenium and tellurium from high-tellurium crude selenium raw materials. Background Technology

[0002] Selenium is commonly used in sensors and infrared optical materials, pigments, and high-tech industries such as semiconductor equipment, optoelectronic equipment, and selenium solar cells. Its important role in the national economy is becoming increasingly prominent, and market demand continues to grow.

[0003] The selenium-tellurium separation methods publicly reported both domestically and internationally mainly include oxygen oxidation, vacuum distillation, and zone melting.

[0004] The mainstream traditional process is the oxygen oxidation method, which involves oxidizing and burning crude selenium raw materials to produce selenium dioxide. Selenium dioxide is water-soluble to form selenite, and ammonia water is used to adjust the pH to 4-5 to remove tellurium. This wet process is lengthy, requires sophisticated equipment, and is costly. Furthermore, the intermediate product, selenium dioxide, is a hazardous chemical, making it environmentally unfriendly. Vacuum distillation utilizes the differences in vapor pressure and evaporation rate between selenium, tellurium, and impurity elements at the same temperature. By controlling a specific temperature and vacuum level, selenium, tellurium, and some impurities volatilize and selectively condense, thus separating selenium and tellurium from impurity elements to obtain refined selenium. However, the main problem is that selenium and tellurium have similar condensation coefficients, making separation difficult. Moreover, for high-tellurium crude selenium raw materials, the separation efficiency of selenium and tellurium obtained by vacuum distillation is not high. Zone melting utilizes the difference in solubility of selenium and tellurium in their solid and molten states. It involves locally heating a narrow molten zone within a long, narrow solid ingot and slowly moving that zone. Impurity removal can be achieved by controlling the distribution of impurities during the local melting and solidification of selenium ingots. However, this method is inefficient and selenium and tellurium are prone to volatilization at high temperatures, making separation even more difficult for high-tellurium crude selenium raw materials. Therefore, existing selenium-tellurium processes have low separation efficiency and are difficult to separate selenium-tellurium mixtures.

[0005] Chinese invention patent CN105236362A discloses a method for separating and purifying selenium and tellurium from a selenium-tellurium mixture. Specifically, hydrochloric acid and hydrogen peroxide are added to the selenium-tellurium mixture to form a slurry, and the leachate is subjected to multi-stage sulfur dioxide reduction to prepare selenium powder and crude tellurium. However, the disadvantage of this process is that selenium and tellurium are leached into the solution at the same time. In the subsequent reduction process, selenium and tellurium are easily reduced into the product at the same time, resulting in low purity of the prepared selenium powder, with a purity of only 95%, and crude tellurium grade of only 90%.

[0006] Chinese invention patent CN103172038B discloses a method for separating and purifying selenium and tellurium, which mainly involves removing and purifying selenium through vacuum distillation. However, this equipment and process are not very adaptable to crude selenium raw materials, especially those from the Kaldor furnace process, which contain Te impurities (0.28%–0.32%). This is 16 times higher than the crude selenium raw material produced by the copper anode mud sulfation roasting process (Te–0.02%). Given the technical requirement of directly producing refined selenium from industrial-grade crude selenium, solving the problem of selenium-tellurium separation is quite difficult.

[0007] Chinese patent CN110745789 A discloses a method for purifying crude selenium, which involves oxidizing and adjusting the crude selenium residue before vacuum distillation. However, the direct recovery rate of the product from this process is not high because selenium is easily oxidized into compounds, making it difficult to distill and volatilize, resulting in a low direct recovery rate.

[0008] Chinese patent CN104743526A discloses a process for refining crude selenium, which involves washing the crude selenium raw material with water at a weight ratio of 1:1 2-3 times, and then adding 3-8 mg of [unspecified substance] to each ton of filter residue after filtration. 3 A sodium sulfite solution with a concentration of 150-300 g / L is heated to 95-100℃ and reacted for 2-3 hours. Ammonium sulfide is then added to the solution until no precipitate is formed. After filtration, the filter residue is discarded. The filtrate is cooled at room temperature for 48 hours, and refined selenium precipitates from the sodium sulfite solution. 15-20 kg of washed filter residue is added to each cubic meter of the solution after refined selenium precipitation for continued leaching. The precipitated refined selenium is washed until the pH of the washing solution is 7.0-7.5, dried, and then cast into selenium ingots with a purity of 99.99%. The sodium sulfite solution, after being recycled 5-7 times during the process, can be acid-regenerated and recycled by adding concentrated sulfuric acid. This invention has a simple process flow, low raw material consumption, low production cost, is environmentally friendly, has strong adaptability to raw materials, and has good economic and social benefits. The disadvantages of this method are that the selenium powder is difficult to dissolve in the leaching reaction between the crude selenium raw material and the sodium sulfite solution, resulting in a low leaching rate. Furthermore, the wet separation method is generally ineffective for high tellurium crude selenium raw materials, and the material adaptability is not strong.

[0009] Chinese invention patent application CN111517290A discloses a two-step method for preparing refined selenium. This method includes leaching and decomposition steps, specifically: dissolving crude selenium in a Na2SO3 solution and reacting at 70–100°C; obtaining filtrate a after solid-liquid separation; separating filtrate a to obtain insoluble matter b; and washing insoluble matter b with water to obtain refined selenium with a purity of 99.9% or higher. This invention has a short process flow, simple operation, introduces few impurities, and achieves a selenium purity of over 99.9%. The equipment used in this method is simple, produces no pollutants, and has low energy consumption, offering advantages such as good overall economic benefits and environmental protection. The disadvantage of this method is the low efficiency of the leaching process. For high-tellurium crude selenium raw materials, tellurium impurities are easily leached into the leachate, and after solid-liquid separation, tellurium impurities can easily enter the product. This process is suitable for crude selenium raw materials with low tellurium content.

[0010] Chinese invention patent application CN113353895A discloses a method for purifying crude selenium. Specifically, it involves adding H2O2 solution and Na2CO3 solution in a volume ratio of 1:1 to 1:3 to adjust the pH of the crude selenium residue to 6.5-7.0. The residue is then filtered to obtain a crude selenium filter cake, which is subsequently subjected to vacuum distillation at 270℃ for 1 hour at a pressure of 50-100 Pa. Condensation yields a 99% purified selenium product. This invention features a simple process, is environmentally friendly, and has strong adaptability to raw materials, resulting in significant economic and social benefits. However, this method has drawbacks: the direct selenium recovery rate is low, the slurry filtrate still contains 5.6 g / L of Se, and the purity of the purified selenium product obtained by direct distillation of the crude selenium filter cake after oxidative slurry filtration does not meet the 4N standard. This indicates that the oxidation reaction of impurities in the crude selenium residue at room temperature is incomplete, and the oxidation effect is generally poor. The slurry was prepared using 15% H2O2 by mass. According to the 2015 List of Hazardous Chemicals, H2O2 exceeding 8% is classified as a hazardous material. Summary of the Invention

[0011] To address the aforementioned problems, this invention provides a method and equipment for separating selenium and tellurium from high-tellurium crude selenium raw materials. This invention offers excellent selenium and tellurium separation, is simple to operate, has a short process, and is highly adaptable to raw materials.

[0012] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0013] A method for separating selenium and tellurium from a high-tellurium crude selenium feedstock includes the following steps:

[0014] S1, add the powdered crude selenium raw material with high tellurium content to an alkaline solution;

[0015] S2, add sulfur powder to the alkaline crude selenium slurry solution to adjust the pH value to above 9;

[0016] S3, thoroughly stir in a water bath;

[0017] S4. Vacuum filtration is performed on the slurry in S3 to obtain crude selenium.

[0018] S5 involves vacuum distilling the crude selenium after alkaline water washing to separate selenium and tellurium.

[0019] Preferably, the alkaline solution in step S1 includes sodium hydroxide solution, sodium carbonate solution, potassium hydroxide solution, and sodium bicarbonate solution; wherein the concentration of the alkaline solution is 0.5 mol / L-5 mol / L.

[0020] Preferably, in step S2, the amount of sulfur added is 5% to 30% of the mass of crude selenium.

[0021] Preferably, in step S3, the water bath heating temperature is 30℃-90℃.

[0022] Preferably, in step S3, the stirring reaction time is 1h-6h.

[0023] Preferably, in step S5, the crude selenium washed with alkaline water is placed into a vertical distillation furnace with a multi-stage condensation system for vacuum distillation.

[0024] Preferably, in step S5, the vertical distillation furnace is equipped with three heating zones: the bottom heating temperature is 300℃-600℃, the middle and upper temperature zones are kept at 0℃-100℃, the vacuum degree is 0pa-50pa, and the distillation holding time is 0h-6h.

[0025] A device for separating selenium from crude selenium raw material includes a multi-layer quartz tray at the bottom and a high-purity quartz tube at the top, with a graphite crucible for loading material disposed on the other side of the multi-layer quartz tray.

[0026] Preferably, the multi-layer quartz tower tray and the high-purity quartz tube are connected by a frosted socket seal.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. When sulfur is added to an alkaline solution, the resulting sodium polysulfide solution can selectively convert tellurium in crude selenium into tellurium polysulfide (Na2TeS4). The metallic tellurium is converted into ions and enters the solution, while the main metallic selenium remains in the slag. Thus, selenium and tellurium are initially and effectively separated, with a separation coefficient of 90.67%. The tellurium content in the crude selenium raw material is reduced from 0.30% to 0.028%.

[0029] 2. The multi-stage condensation system inside the vertical vacuum distillation furnace consists of a multi-stage reflux high-purity quartz tray at the bottom and a cylindrical high-purity quartz tube at the top of the tray. The quartz tray and the cylindrical high-purity quartz tube are connected by a frosted socket seal, which ensures that the low-boiling-point metallic selenium is distilled out and enters the upper cylindrical high-purity quartz tube, while the high-boiling-point metallic tellurium remains in the multi-stage reflux quartz tray at the bottom. Therefore, selenium and tellurium are further effectively separated.

[0030] 3. It has good Te removal effect, simple operation and short process, and strong adaptability to raw materials, especially for industrial high tellurium crude selenium raw materials. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the interior of the vacuum distillation furnace of the present invention.

[0032] In the diagram: 1. High-purity quartz tube; 2. Multi-layer quartz tray; 3. Graphite crucible. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] A method for separating selenium and tellurium from a high-tellurium crude selenium feedstock includes the following steps:

[0035] S1, add the powdered crude selenium raw material with high tellurium content to an alkaline solution; the alkaline solution in this step includes sodium hydroxide solution, sodium carbonate solution, potassium hydroxide solution, and sodium bicarbonate solution; wherein the concentration of the alkaline solution is 0.5mol / L-5mol / L.

[0036] S2, Sulfur powder is added to the alkaline crude selenium slurry solution to adjust the pH value to above 9; in this step, the amount of sulfur added is 5% to 30% of the mass of crude selenium.

[0037] In this step, the following chemical reaction occurs:

[0038] 6NaOH + 4S → 2Na₂S + Na₂S₂O₃ + 3H₂O

[0039] Na₂S + S → Na₂S₂

[0040] Te + 3Na₂S₂ → Na₂(TeS₄) + 2Na₂S

[0041] S3, thorough stirring in a water bath; in this step, the water bath heating temperature is 30℃-90℃; the stirring reaction time is 1h-6h.

[0042] S4. Vacuum filtration is performed on the slurry in S3 to obtain crude selenium.

[0043] S5 involves vacuum distilling the crude selenium after alkaline water washing to separate selenium and tellurium.

[0044] In step S5, the crude selenium washed with alkaline water is placed into a vertical distillation furnace with a multi-stage condensation system for vacuum distillation. After the reaction is completed, the refined selenium can be collected by scraping the cylindrical high-purity quartz tube at the top of the vertical distillation furnace condenser.

[0045] The preferred configuration of the vertical distillation furnace is a three-stage heating zone, with the bottom heating temperature at 300℃-600℃, the middle and upper temperature zones maintained at 0℃-100℃, the vacuum degree at 0pa-50pa, and the distillation holding time at 0h-6h.

[0046] See attached document Figure 1 A device for separating selenium and tellurium from crude selenium raw material is provided for vacuum distillation of the crude selenium. The device includes a multi-layer quartz tray 2 at the bottom and a high-purity quartz tube 1 at the top. A graphite crucible 3 is provided on the other side of the multi-layer quartz tray 2. The device can ensure that the low-boiling-point metallic selenium is distilled out and enters the upper cylindrical high-purity quartz tube, while the high-boiling-point metallic tellurium remains in the bottom multi-stage reflux quartz tray, thus achieving effective separation of the two.

[0047] The preferred configuration is a frosted socket-type sealed connection between the multi-layer quartz tray 2 and the high-purity quartz tube 1. This ensures that the low-boiling-point metallic selenium is distilled out and enters the upper cylindrical high-purity quartz tube, while the high-boiling-point metallic tellurium remains in the bottom multi-stage reflux quartz tray. Thus, selenium and tellurium are further effectively separated.

[0048] Example 1

[0049] S1. Take 150g of crude selenium raw material with high tellurium content (0.30% tellurium), add 2mol·L-1 sodium hydroxide solution to it for alkaline washing according to the liquid-solid ratio of 4:1, and adjust the pH value to above 9.

[0050] S2, add 20g of sulfur to the slurry in S2 and stir well;

[0051] S3, the slurry in S3 is stirred in a 60°C water bath for 6 hours.

[0052] S4, vacuum filtration of the slurry yields crude selenium with a lower tellurium content.

[0053] S5. Crude selenium with low tellurium content is placed in a vertical distillation furnace with a multi-stage condensation system for vacuum distillation. The bottom of the distillation furnace is heated to 600℃, and the middle and upper temperature zones are kept at 100℃. The vacuum degree is 50 Pa, and the distillation holding time is 6 hours. After the reaction is completed, the refined selenium condensed in the cylindrical high-purity quartz tube at the top of the vertical distillation furnace is collected.

[0054] Example 2

[0055] S1, take 200g of crude selenium raw material with high tellurium content (0.30% tellurium), and add 2.5mol·L⁻¹ according to a liquid-solid ratio of 3:1.-1 Alkaline washing with sodium hydroxide solution was performed to adjust the pH value to above 9;

[0056] S2, add 15g of sulfur to the slurry in S2 and stir well;

[0057] S3, stir the slurry in S3 in a 90°C water bath for 3 hours.

[0058] S4, vacuum filtration of the slurry yields crude selenium with a lower tellurium content.

[0059] S5, crude selenium with low tellurium content is placed in a vertical distillation furnace with a multi-stage condensation system for vacuum distillation. The bottom of the distillation furnace is heated to 550°C, the middle and upper temperature zones are kept at 50°C, the vacuum degree is 10 Pa, and the distillation holding time is 3 hours. After the reaction is completed, the refined selenium condensed in the cylindrical high-purity quartz tube at the top of the vertical distillation furnace is collected.

[0060] Example 3

[0061] S1. Take 100g of crude selenium raw material with high tellurium content (0.30% tellurium), add 3mol·L-1 sodium hydroxide solution to it for alkaline washing according to the liquid-solid ratio of 5:1, and adjust the pH value to above 9.

[0062] S2, add 8g of sulfur to the slurry in S2 and stir well;

[0063] S3, stir the slurry in S3 in an 80°C water bath for 5 hours.

[0064] S4, vacuum filtration of the slurry yields crude selenium with a lower tellurium content.

[0065] S5. Crude selenium with low tellurium content is placed in a vertical distillation furnace with a multi-stage condensation system for vacuum distillation. The bottom of the distillation furnace is heated to 500°C, and the middle and upper temperature zones are kept at 100°C. The vacuum degree is 20 Pa, and the distillation holding time is 6 hours. After the reaction is completed, the refined selenium condensed in the cylindrical high-purity quartz tube at the top of the vertical distillation furnace is collected.

[0066] Finally, the detection results of the examples are given. After ICP-MS analysis, the chemical composition is shown in the table below.

[0067] Example 1 Example 2 Example 3 Se 99.99％ 99.99％ 99.99％ Mg 0.0004％ 0.00001％ 0.00001％ Al 0.0009％ 0.00001％ 0.00001％ S 0.00001％ 0.0005％ 0.00002％ Si 0.00001％ 0.00001％ 0.00001％ Fe 0.00034％ 0.00001％ 0.00001％ Ni 0.0001％ 0.0001％ 0.0001％ Cu 0.00025％ 0.00001％ 0.00001％ As 0.00034％ 0.0001％ 0.0001％ Sn 0.0002％ 0.00001％ 0.00001％ Sb 0.0001％ 0.00001％ 0.00001％ Te 0.00025％ 0.0001％ 0.00012％ Hg 0.00001％ 0.00001％ 0.00001％ Pb 0.00055％ 0.00001％ 0.00001％ Bi 0.00001％ 0.00001％ 0.00001％

[0068] The characteristics of this process route are:

[0069] 1. When sulfur is added to an alkaline solution, the resulting sodium polysulfide solution can selectively convert tellurium in crude selenium into tellurium polysulfide (Na2TeS4). The metallic tellurium is converted into ions and enters the solution, while the main metallic selenium remains in the slag. Thus, selenium and tellurium are initially and effectively separated, with a separation coefficient of 90.67%. The tellurium content in the crude selenium raw material is reduced from 0.30% to 0.028%.

[0070] 2. The multi-stage condensation system inside the vertical vacuum distillation furnace consists of a bottom multi-stage reflux high-purity quartz tray and a cylindrical high-purity quartz tube at the top. The quartz trays and the cylindrical high-purity quartz tube are connected by a frosted socket seal, ensuring that low-boiling-point metallic selenium is distilled out and enters the upper cylindrical high-purity quartz tube, while high-boiling-point metallic tellurium remains in the bottom multi-stage reflux quartz tray. Therefore, selenium and tellurium are further and effectively separated. The refined selenium collected in the upper cylindrical high-purity quartz tube of the vertical distillation furnace eliminates the need for the mainstream traditional process of crude selenium oxidation and combustion followed by a long wet purification process (such as adjusting pH to 4-5 with ammonia and removing tellurium).

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for separating selenium and tellurium from a high-tellurium crude selenium raw material, characterized in that, Includes the following steps: S1, add the powdered crude selenium raw material with high tellurium content to an alkaline solution; S2, add sulfur powder to the alkaline crude selenium slurry solution to adjust the pH value to above 9; S3, thoroughly stir in a water bath; S4. Vacuum filtration is performed on the slurry in S3 to obtain crude selenium. S5, the crude selenium washed with alkaline water is vacuum distilled to separate selenium and tellurium; The alkaline solution in step S1 includes sodium hydroxide solution, sodium carbonate solution, potassium hydroxide solution, and sodium bicarbonate solution; wherein the concentration of the alkaline solution is 0.5 mol / L-5 mol / L. In step S2, the amount of sulfur added is 5% to 30% of the mass of crude selenium; In step S3, the water bath heating temperature is 30℃-90℃.

2. The method for separating selenium and tellurium from high-tellurium crude selenium raw material according to claim 1, characterized in that, In step S3, the stirring reaction time is 1h-6h.

3. The method for separating selenium and tellurium from high-tellurium crude selenium raw material according to claim 1, characterized in that, In step S5, the crude selenium washed with alkaline water is placed into a vertical distillation furnace with a multi-stage condensation system for vacuum distillation.

4. The method for separating selenium and tellurium from high-tellurium crude selenium raw material according to claim 3, characterized in that, In step S5, the vertical distillation furnace is set with three heating zones: the bottom heating temperature is 300℃-600℃, the middle and upper temperature zones are kept at 0℃-100℃, the vacuum degree is 0pa-50pa, and the distillation holding time is 0h-6h.

5. A device for separating selenium and tellurium from high-tellurium crude selenium raw material, used for vacuum distillation of crude selenium in step S5 as described in any one of claims 1-4, characterized in that, It includes a multi-layer quartz tray (2) at the bottom and a high-purity quartz tube (1) at the top, and a graphite crucible (3) for carrying material is provided on the other side of the multi-layer quartz tray (2).

6. The equipment for separating selenium and tellurium from high-tellurium crude selenium raw materials according to claim 5, characterized in that, The multi-layer quartz tower tray (2) and the high-purity quartz tube (1) are connected by a frosted socket seal.

Images