Method for separating and recovering selenium and tellurium from selenium-tellurium alloy
Through the methods of oxidative roasting, vacuum reduction and electrolysis, using a mixture of tea leaves and potassium sulfate as a reducing agent, the problem of long and complicated separation process of selenium-tellurium alloy was solved, the recovery of high-purity selenium and tellurium was achieved, the process was simplified, and energy consumption and environmental impact were reduced.
Patent Information
- Application Number
- CN202510867853.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-26
- Publication Date
- 2025-09-26
AI Technical Summary
Existing technologies make it difficult to efficiently separate and recover selenium and tellurium from selenium-tellurium alloys. Traditional methods have long and complex processes and pose risks of environmental pollution.
By adopting the methods of oxidative roasting, vacuum reduction and electrolysis, a mixture of tea residue and potassium sulfate is used as a reducing agent. High-purity tellurium is obtained through vacuum reduction, and gaseous SeO2 is electrolyzed into elemental selenium, which simplifies the process flow and reduces energy consumption and environmental impact.
The separation and recovery of high-purity selenium and tellurium are achieved, the operating process is simplified, energy consumption is reduced, and environmental pollution is reduced. In addition, waste utilization and cost savings are achieved by using tea residues as a reducing agent.
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Figure CN120698421A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of separation of rare metals, and in particular relates to a method for separating and recovering selenium and tellurium from a selenium-tellurium alloy. Background Art
[0002] Selenium and tellurium are very rare independent minerals. They are generally associated with heavy metal minerals such as copper and lead, and are enriched in the electrolytic anode mud during the smelting process. Selenium and tellurium belong to Group VI and have similar physical properties and chemical behaviors. For example, the vapor partial pressures of selenium and tellurium are close, and the two are infinitely miscible. Physical methods such as vacuum distillation and zone melting cannot completely separate them in depth. In the process of extracting selenium and tellurium from anode mud, selenium-tellurium alloys are produced, in which selenium and tellurium are impurities of each other. The separation of tellurium impurities in selenium or selenium impurities in tellurium is a common problem in the preparation of high-purity selenium and tellurium. In this context, how to achieve efficient separation of selenium and tellurium has become a common concern of academia and industry.
[0003] As core elements of semiconductor and optoelectronic materials, selenium and tellurium play an irreplaceable role in a number of key sectors, including new energy, electronic information, and defense. However, with increasingly fierce global technological competition and rising demands for green manufacturing, the development and utilization of selenium and tellurium resources face unprecedented opportunities and challenges. However, traditional purification processes (such as sulfuric acid roasting-alkaline leaching-electrolysis) require multiple steps, including roasting, leaching, purification, and electrolysis, resulting in lengthy and complex operations. Summary of the Invention
[0004] In view of this, the object of the present invention is to provide a method for separating and recovering selenium and tellurium from a selenium-tellurium alloy. The method is simple to operate, and the separated selenium and tellurium have a high purity (4N). The method also has low energy consumption and is environmentally friendly.
[0005] In order to achieve the above object, the present invention provides the following technical solutions:
[0006] The present invention provides a method for separating and recovering selenium and tellurium from a selenium-tellurium alloy, comprising the following steps:
[0007] The selenium-tellurium alloy is oxidized and roasted to obtain tellurium dioxide solid and SeO2 fume;
[0008] mixing the tellurium dioxide solid with a reducing agent and performing vacuum reduction to obtain tellurium;
[0009] The reducing agent is a mixture of tea dregs and potassium sulfate;
[0010] The SeO2 flue gas is mixed with water and then subjected to electrolysis to obtain selenium.
[0011] Preferably, the oxidation roasting is carried out by passing an oxygen-containing system into a tubular furnace containing selenium-tellurium alloy for oxidation roasting; the flow rate of the oxygen-containing system is 1.5-2 L / min; and the volume ratio of oxygen in the oxygen-containing system is 25-30%.
[0012] Preferably, the temperature of the oxidative roasting is 350-480° C., and the holding time is 2-3 hours; the heating rate to the oxidative roasting temperature is 4-6° C. / min.
[0013] Preferably, the mass ratio of the reducing agent to the tellurium dioxide solid is 3 to 1:1.
[0014] Preferably, the vacuum reduction includes a first stage vacuum reduction and a second stage vacuum reduction performed sequentially; the pressure of the first stage vacuum reduction is ≤10Pa, the temperature is 300-330°C, and the insulation time is 0.5-1h; the pressure of the second stage vacuum reduction is 1-50Pa, the temperature is 800-950°C, and the insulation time is 2-3h.
[0015] Preferably, the electrolytic conditions include: the pH of the electrolyte system is 5-6; the current density is 90-140 mA / cm 2 , voltage is 3~5V, and electrolysis time is 1.5h.
[0016] Preferably, the preparation of the reducing agent comprises the following steps:
[0017] The tea residue and potassium sulfate solution are mixed, the mixed liquid is separated into solid and liquid, and the solid phase obtained by the solid-liquid separation is dried to obtain the reducing agent.
[0018] Preferably, the concentration of the potassium sulfate solution is 0.5-0.8 mol / L.
[0019] Preferably, before the oxidation roasting, the selenium-tellurium alloy is further ground; the particle size of the selenium-tellurium alloy after the grinding is 100-200 meshes.
[0020] The present invention also provides a device for separating and recovering selenium and tellurium in a selenium-tellurium alloy, comprising a roasting furnace;
[0021] A water collection system connected to the roasting furnace through a quartz tube; the water collection system includes a plurality of water collection containers connected in series;
[0022] An electrolysis unit connected to a water collection system via piping.
[0023] The present invention provides a method for separating and recovering selenium and tellurium from a selenium-tellurium alloy, comprising the following steps: oxidizing and roasting the selenium-tellurium alloy to obtain tellurium dioxide solid and SeO2 flue gas; mixing the tellurium dioxide solid with a reducing agent, and performing vacuum reduction to obtain tellurium; the reducing agent is a mixture of tea leaves and potassium sulfate; mixing the SeO2 flue gas with water, and performing electrolysis to obtain selenium. The method provided by the present invention overcomes the problems of long and complex processes in traditional selenium-tellurium separation, and achieves efficient separation and recovery of industrial-grade selenium-tellurium alloys. Moreover, the present invention uses tea leaves as a reducing agent, realizes waste utilization, saves costs, and is more environmentally friendly; at the same time, due to the K content of potassium-containing substances (K2O, KCl) in the tea leaves, + It can form an unstable K-Te-O complex by combining with oxygen in the TeO2 lattice, weakening the strength of the Te-O bond and making TeO2 more susceptible to carbon reduction. This process can be carried out at a relatively low temperature (around 800°C), and maintaining a vacuum environment will further promote the forward reaction by removing the CO gas generated by the reaction (Le Chatelier's theorem: removing products promotes the forward reaction). The synergistic effect of the vacuum environment and potassium ions achieves low-temperature energy-saving carbon thermal reduction of tellurium dioxide while maintaining a high reduction rate and tellurium purity. This is because the process reduces the activation energy of the reaction, allowing the reaction to proceed at low energy consumption. Potassium sulfate uniformly adsorbs or wraps carbon particles, forming a monomolecular layer or thin liquid film, effectively dispersing the particles, preventing carbon particles from sintering and agglomerating at high temperatures, and maintaining a high specific surface area. The vacuum environment improves product purity by removing CO gas. These advantages are difficult to achieve simultaneously under conventional conditions of 800°C. Therefore, tellurium dioxide can be reduced more gently.
[0024] In addition, compared with the sulfuric acid roasting-alkaline leaching-electrolysis method, the present invention directly obtains metallic tellurium through vacuum reduction after mixing with a reducing agent (a mixture of tea residues and potassium sulfate), eliminating multiple intermediate processing steps and reducing costs: Moreover, potassium sulfate is a common fertilizer raw material with low cost, and its "trace and high efficiency" characteristics have the advantages of reducing the amount of additives used, mild reaction conditions, increased reaction rate, and environmental friendliness.
[0025] The process provided by the present invention is carried out in a vacuum environment, which reduces the emission of harmful gases; potassium sulfate can be recycled as a catalyst, reducing raw material consumption and waste generation. Furthermore, gaseous SeO2 is condensed and directly electrolyzed into elemental selenium (purity>99.9%), without the need for a chemical precipitation step (such as sodium sulfide precipitation), thus avoiding the introduction of sulfides or other impurities; this method significantly enhances the chemical stability of the product by eliminating unstable chemical forms (such as tellurates) and impurities (such as sulfides). In summary, the present invention also has the advantages of simple operation process, short process flow, and low environmental pollution.
[0026] The data in the examples show that the purity of selenium and tellurium separated by the method provided by the present invention can reach 4N. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 The invention provides a device for separating and recovering selenium and tellurium in a selenium-tellurium alloy. DETAILED DESCRIPTION
[0028] The present invention provides a method for separating and recovering selenium and tellurium from a selenium-tellurium alloy, comprising the following steps:
[0029] The selenium-tellurium alloy is oxidized and roasted to obtain tellurium dioxide solid and SeO2 fume;
[0030] mixing the tellurium dioxide solid with a reducing agent and performing vacuum reduction to obtain tellurium;
[0031] The reducing agent is a mixture of tea dregs and potassium sulfate;
[0032] The SeO2 flue gas is mixed with water and then subjected to electrolysis to obtain selenium.
[0033] Unless otherwise specified, the present invention has no special requirements on the sources of the raw materials used, and commercially available products known to those skilled in the art can be used.
[0034] The present invention performs oxidation roasting on a selenium-tellurium alloy to obtain tellurium dioxide solid and SeO2 fume.
[0035] As an embodiment of the present invention, the oxidation roasting is to pass an oxygen-containing system into a tubular furnace containing selenium-tellurium alloy for oxidation roasting; the flow rate of the oxygen-containing system is 1.5 to 2 m / s; the volume ratio of oxygen in the oxygen-containing system can be 25 to 30%; the oxygen-containing system includes oxygen and protective gas; the protective gas can include nitrogen or argon.
[0036] As an embodiment of the present invention, before the oxidation roasting, the selenium-tellurium alloy is further ground; the particle size of the selenium-tellurium alloy after the grinding can be 100-200 mesh, specifically 100 mesh, 150 mesh or 200 mesh.
[0037] As an embodiment of the present invention, the temperature of the oxidative roasting can be 350-480°C, specifically 420°C, and the holding time can be 2-3h, specifically 2.5h; the heating rate to the oxidative roasting temperature can be 4-6°C / min, specifically 5°C / min.
[0038] As an embodiment of the present invention, after the oxidation roasting, the tellurium dioxide is further cooled to room temperature.
[0039] After obtaining the tellurium dioxide solid, the present invention mixes the tellurium dioxide solid with a reducing agent and performs vacuum reduction to obtain tellurium.
[0040] As an embodiment of the present invention, the reducing agent is a mixture of tea leaves and potassium sulfate.
[0041] In the present invention, the advantages of using a mixture of tea leaves and potassium sulfate are as follows:
[0042] Tea residue contains relatively high levels of nitrogen (4.16%), phosphorus (0.43%), potassium (1.44%), and organic carbon (28.1%). In the vacuum reduction reaction, the nitrogen, phosphorus, and other elements in the tea residue can act as catalysts to accelerate the reduction process of TeO2 by reducing the activation energy of the reaction or promoting electron transfer. Organic carbon, as a reducing agent, can reduce the external energy required for high-temperature carbon thermal reactions when synergistically acting with potassium sulfate. Compared to rice straw, tea residue can be directly used after being mixed with tellurium dioxide solid, while rice straw needs to be prepared into biochar through high-temperature carbonization (such as 450°C for 2 hours) before it can be used. Although its carbon content is high, the processing energy consumption is relatively high. Moreover, if the rice straw is not completely carbonized, lignin decomposition products (such as tar) may remain, contaminating the reduction product and increasing the difficulty of subsequent purification.
[0043] The role of potassium sulfate: K in tea residue + It can form an unstable K-Te-O complex by combining with oxygen in the TeO2 lattice, weakening the strength of the Te-O bond and making TeO2 more susceptible to carbon reduction. This process can be carried out at a relatively low temperature (around 800°C), and maintaining a vacuum environment will further promote the forward reaction by removing the CO gas generated by the reaction (Le Chatelier's theorem: removing products promotes the forward reaction).
[0044] As an embodiment of the present invention, the method for preparing the reducing agent comprises the following steps:
[0045] The tea residue and potassium sulfate solution are mixed, the mixed liquid is separated into solid and liquid, and the solid phase obtained by the solid-liquid separation is dried to obtain the reducing agent.
[0046] As an embodiment of the present invention, the concentration of the potassium sulfate solution can be 0.5 to 0.8 mol / L, specifically 0.6 mol / L. As an embodiment of the present invention, the mass volume ratio of the tea residue to the potassium sulfate solution can be 1 g: 5 to 20 mL, specifically 1 g: 10 to 15 mL.
[0047] As an embodiment of the present invention, the mixing method may be magnetic stirring; as an embodiment of the present invention, the solid-liquid separation method may be centrifugation; as an embodiment of the present invention, the drying temperature may be 50-70°C, specifically 60°C.
[0048] As an embodiment of the present invention, the vacuum reduction may include a first-stage vacuum reduction and a second-stage vacuum reduction performed sequentially; the pressure of the first-stage vacuum reduction may be ≤10Pa, the temperature may be 300-330°C, specifically 320°C, and the insulation time may be 0.5-1h, specifically 0.5h, 0.6h, 0.8h or 1.0h; the pressure of the second-stage vacuum reduction may be 1-50Pa, specifically 20Pa, the temperature may be 800-950°C, specifically 820°C, and the insulation time may be 2-3h, specifically 2.5h.
[0049] After SeO2 flue gas is obtained, the SeO2 flue gas of the present invention is mixed with water and then subjected to electrolysis to obtain selenium.
[0050] As an embodiment of the present invention, the conditions for the electrolysis include: the pH of the electrolyte system is 5 to 6, specifically 5.5; the current density can be 90 to 140 mA / cm 2 , specifically 125mA / cm 2 ; The voltage can be 3~5V, specifically 4.2V; the electrolysis time is 1.5h.
[0051] As an embodiment of the present invention, after the selenium is precipitated, the selenium is further dried; the drying can be carried out using a blower.
[0052] As an embodiment of the present invention, the reagent for adjusting the pH value of the electrolyte system is dilute sulfuric acid and / or ammonium chloride; the concentration of the dilute sulfuric acid is 9.8 wt.%.
[0053] As an embodiment of the present invention, during the electrowinning, the cathode material may be stainless steel or titanium mesh; the anode material may be graphite or a titanium-based coating electrode (item number UTR-W725).
[0054] The present invention also provides a device for separating and recovering selenium and tellurium in a selenium-tellurium alloy, comprising a roasting furnace;
[0055] A water collection system connected to the roasting furnace via a selenium dioxide outlet pipe; the water collection system includes a plurality of water collection containers connected in series; and an electrolysis device connected to the water collection system via a pipeline;
[0056] As an embodiment of the present invention, the number of water collection containers is ≥3.
[0057] As an embodiment of the present invention, one end of the selenium dioxide outlet pipe is connected to the end of the quartz tube of the roasting furnace, and the other end is connected to the water collection system.
[0058] The device provided by the present invention binds the selenium dioxide outlet pipe to the oxidation roasting device, reducing the chance of selenium dioxide condensing in the pipe and causing blockage. More importantly, the device provided by the present invention can realize the use of water to dissolve selenium dioxide during oxidation roasting, thereby improving operating efficiency.
[0059] The technical solutions of the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention, but they should not be understood as limiting the scope of protection of the present invention.
[0060] Example 1
[0061] Selenium-tellurium alloy containing 97 wt.% of Se and 3 wt.% of Te was crushed and ground to obtain selenium-tellurium alloy powder with a particle size of 200 meshes.
[0062] 20 g of selenium-tellurium alloy powder with a particle size of 200 mesh was placed in a quartz boat and placed in a roasting furnace. Oxygen was introduced into the furnace with an oxygen flow rate set at 1.8 m / s. The oxygen ratio in the mixed gas was 25%, and the remaining gas was nitrogen. Oxidative roasting was carried out at 550°C for 2 hours to obtain tellurium dioxide solid and SeO2 flue gas. After the oxidative roasting was completed, the tellurium dioxide solid was taken out and naturally cooled to room temperature.
[0063] Selenium dioxide gas was introduced into water, and the resulting solution was subjected to a voltage of 4.2 V and a current of 125 mA / cm 2 Electrolysis was carried out in an electrolytic cell at a current density of 100 nm for 1.5 h. Prior to electrolysis, the pH of the solution was adjusted to 5.5 using 9.8 wt.% dilute sulfuric acid and 0.1 mol / L ammonium chloride solution. After selenium precipitation, it was dried using a blower to obtain selenium with a purity of 99.99%.
[0064] Tea leaves were mixed with 0.7 mol / L potassium sulfate solution at a volume-to-mass ratio of 1 g:10 mL, magnetically stirred, and centrifuged at a speed of 3500 r / s. The solid phase obtained by centrifugation was dried at 60°C to obtain a reducing agent.
[0065] The obtained reducing agent was mixed with tellurium dioxide solid in a mass ratio of 2:1, and heated at 320°C for 1 hour under a vacuum condition of 7Pa. Then the pressure was changed to 20Pa and heated at 650°C for 2.5 hours. Finally, it was cooled at 50°C to obtain tellurium with a purity of 99.99%.
[0066] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.
Claims
1. A method for separating and recovering selenium and tellurium from a selenium-tellurium alloy, comprising the following steps: The selenium-tellurium alloy is oxidized and roasted to obtain tellurium dioxide solid and SeO2 fume; mixing the tellurium dioxide solid with a reducing agent and performing vacuum reduction to obtain tellurium; The reducing agent is a mixture of tea dregs and potassium sulfate; The SeO2 flue gas is mixed with water and then subjected to electrolysis to obtain selenium.
2. The method according to claim 1, wherein The oxidation roasting is to pass the oxygen-containing system into a tubular furnace filled with selenium-tellurium alloy for oxidation roasting; the flow rate of the oxygen-containing system is 1.5-2 L / min; and the volume ratio of oxygen in the oxygen-containing system is 25-30%.
3. The method according to claim 1, wherein The temperature of the oxidation roasting is 350-480° C., and the holding time is 2-3 hours; the heating rate to the oxidation roasting temperature is 4-6° C. / min.
4. The method according to claim 1, wherein The mass ratio of the reducing agent to the tellurium dioxide solid is 3 to 1:
1.
5. The method according to claim 1, wherein The vacuum reduction includes a first stage vacuum reduction and a second stage vacuum reduction performed sequentially; the pressure of the first stage vacuum reduction is ≤10Pa, the temperature is 300-330°C, and the insulation time is 0.5-1h; the pressure of the second stage vacuum reduction is 1-50Pa, the temperature is 800-950°C, and the insulation time is 2-3h.
6. The method according to claim 1, characterized in that The conditions for the electrolysis include: the pH of the electrolyte system is 5-6; the current density is 90-140 mA / cm 2 , voltage is 3~5V, and electrolysis time is 1.5h.
7. The method according to claim 1, characterized in that The preparation of the reducing agent comprises the following steps: The tea residue and potassium sulfate solution are mixed, the mixed liquid is separated into solid and liquid, and the solid phase obtained by the solid-liquid separation is dried to obtain the reducing agent.
8. The method according to claim 1, characterized in that The concentration of the potassium sulfate solution is 0.5-0.8 mol / L.
9. The method according to claim 1, characterized in that Before the oxidation roasting, the selenium-tellurium alloy is ground; after the grinding, the particle size of the selenium-tellurium alloy is 100-200 meshes.
10. A device for separating and recovering selenium and tellurium from a selenium-tellurium alloy, comprising a roasting furnace; A water collection system connected to the roasting furnace through a quartz tube; the water collection system includes a plurality of water collection containers connected in series; An electrolysis unit connected to a water collection system via piping.