Method for separating and recovering selenium and tellurium from alloy smoke dust

Abstract

The invention relates to the technical field of separation and recovery of selenium and tellurium, in particular to a method for separating and recovering selenium and tellurium from alloy smoke dust. The method comprises the following steps: firstly, mixing alloy smoke dust of a smelting furnace with a sulfuric acid solution to obtain a first-section leaching solution and a first-section leaching residue; mixing the first-stage leaching residues with a selective leaching agent, and controlling the oxidation potential to obtain a second-stage leaching solution and second-stage leaching residues; then mixing the second-stage leachate with a reduction precipitator to obtain crude selenium; and mixing the second-section leaching residues with an alkali solution to obtain a third-section leaching solution and third-section leaching residues, adding concentrated acid into the third-section leaching solution, controlling the pH value, and performing solid-liquid separation after hydrolysis to obtain tellurium dioxide. According to the method, the problems of low separation efficiency and high cost of low-grade and near-content selenium and tellurium smoke dust in a traditional process are solved in one-step leaching, the purity of crude selenium and tellurium dioxide is improved by controlling process conditions, and the method is short in process flow, high in selective separation efficiency, high in comprehensive resource recovery rate and outstanding in environmental protection property and economical efficiency.

Description

Technical Field

[0001] This invention relates to the field of separation and recovery technology of selenium and tellurium, and specifically to a method for separating and recovering selenium and tellurium from alloy dust. Background Technology

[0002] Alloy dust is a special material produced during the Kaldor furnace production process and is an important raw material for extracting rare and precious metals. Recovering valuable metals from the materials produced by the Kaldor furnace, including selenium and tellurium, rare and dispersed metals with key applications in electronics, photovoltaics, chemicals, and many other fields, is crucial. Precise extraction of selenium and tellurium resources from alloy dust can prevent the waste of precious resources due to dust emissions and transform this originally uneconomical waste into high-value economic assets, effectively replacing the purchase of expensive raw materials and significantly reducing enterprise costs.

[0003] However, alloy fumes are products of high-temperature smelting processes. Selenium and tellurium often coexist in various forms (e.g., elemental, oxide, selenium / telluride, alloy) with other metals (Cu, Pb, Au, Ag, Pt, Pd, etc.). Copper, with similar content, readily forms insoluble compounds with selenium / tellurium (e.g., Cu₂Se, Cu₂Te) or competes with them during leaching, severely inhibiting the effective leaching and subsequent separation of selenium and tellurium. Furthermore, selenium and tellurium have similar chemical properties and exhibit similar dissolution behaviors under conventional acid leaching conditions, often resulting in simultaneous leaching and hindering efficient separation. Existing technologies often fail to effectively separate them during the leaching stage. For example, Chinese patent CN117107061A discloses a method for comprehensive recovery of tellurium slag, which leaches selenium and tellurium simultaneously during the second-stage leaching. Subsequent separation steps are more complex and costly (this patent uses secondary precipitation; other technologies such as solvent extraction and ion exchange can also be used), increasing process length and cost. Therefore, there is a need to develop a low-cost method that can efficiently separate and recover selenium and tellurium separately. Summary of the Invention

[0004] To address the problems of difficult, lengthy, and costly selenium-tellurium separation in existing technologies, this invention proposes a method for separating and recovering selenium and tellurium from alloy dust. The specific steps are as follows:

[0005] Step 1: Mix the alloy dust from the smelting furnace with a 10-50 g / L sulfuric acid solution at a liquid-solid ratio of 3-5:1. The alloy dust contains 1-10 wt% selenium, 0.5-5 wt% tellurium, and 15-25 wt% copper, with a selenium-tellurium content ratio of 0.5-2. After mixing, heat to 40-70°C and stir for 0.5-2 hours. After the reaction, separate the solid and liquid components to obtain a copper-containing leaching solution and a selenium-tellurium leaching residue.

[0006] Step 2: Mix the first stage of selenium-tellurium leaching residue with the selective leaching agent at a liquid-solid ratio of 1 to 6:1, then heat to 70 to 90°C, stir and react for 1 to 4 hours, control the oxidation potential to ≤800mV, and after the reaction is completed, separate the solid and liquid to obtain the second stage of selenium-containing leaching solution and the second stage of tellurium-containing leaching residue.

[0007] Step 3: Mix the two-stage selenium-containing leachate with a reducing precipitant, wherein the mass ratio of selenium to reducing precipitant in the mixture is 1:1 to 50. Then, heat the mixture to 40 to 60°C and stir for 1 to 3 hours. After the reaction is completed, separate the solid and liquid to obtain crude selenium.

[0008] Step 4: Mix the second-stage tellurium-containing leaching residue with an alkaline solution of 100-200 g / L at a liquid-solid ratio of 3-6:1, then heat to 60-90℃ and stir for 1-4 hours. After the reaction is completed, separate the solid and liquid to obtain the third-stage tellurium-containing leachate and the third-stage leaching residue.

[0009] Step 5: Add concentrated acid to the three-stage tellurium-containing leachate at a rate of 0.5-1 mL / min, with a pH gradient of ≤0.2 / min, until the pH reaches 5-7. Heat to 60-80℃ and stir for 1-3 hours. After hydrolysis, separate the solid and liquid phases to obtain tellurium dioxide.

[0010] Furthermore, the alloy dust from the smelting furnace is the alloy dust produced during the production process of the Kaldor furnace.

[0011] Furthermore, the elemental contents of the alloy dust from the Kaldor furnace are as follows: selenium content is 1-10 wt%, tellurium content is 0.5-5 wt%, copper content is 15-25 wt%, and it also includes other valuable metal elements, which are one or more of Au, Ag, Pt, Pd, Pb, and Zn.

[0012] Further, the selective leaching agent in step 2 is any one of sodium sulfite at a concentration of 50–140 g / L or sodium hypochlorite at a concentration of 30–100 g / L.

[0013] Further, the reducing precipitant in step 3 is any one of 100-300 g / L sulfuric acid, 5-15 wt% oxalic acid, and sulfur dioxide, preferably 200-300 g / L sulfuric acid.

[0014] Furthermore, when the reducing precipitant is sulfuric acid or oxalic acid, the addition rate is 1–5 mL / min; when the reducing precipitant is sulfur dioxide, the introduction rate is 0.5–2 L / min.

[0015] Furthermore, the alkaline solution mentioned in step 4 is either a sodium hydroxide solution or a sodium carbonate solution.

[0016] Further, the concentrated acid mentioned in step 5 is any one of 98 wt% sulfuric acid, 36-38 wt% hydrochloric acid, or 68-70 wt% nitric acid.

[0017] Furthermore, the stirring speed in steps 1-5 is 100-200 rpm.

[0018] The method for separating and recovering selenium and tellurium from alloy dust in this application addresses the issue that selenium in the treated alloy dust is mainly elemental, while tellurium is mainly TeO2. The content of Se and Te is similar and both are low, making traditional acid leaching prone to simultaneous dissolution of both, resulting in extremely high separation difficulty. This method first employs a single-stage sulfuric acid leaching process to preferentially separate copper, using a low-concentration sulfuric acid and utilizing Cu... 2+ High solubility in low acid and Se 4+ Te 4+ The low solubility difference avoids the dissolution of selenium and tellurium, dissolving only copper, thus preventing copper from interfering with the subsequent extraction of selenium and tellurium, while increasing the copper leaching rate to over 95%.

[0019] Subsequently, by controlling the liquid-to-solid ratio, reaction temperature, time, and type of oxidant, under the residual dilute sulfuric acid environment of the first-stage sulfuric acid leaching, the oxidation potential of the second-stage leaching process was controlled to be ≤800mV, which can oxidize Se. 0 →Se 4+ (Requires a potential of 400–500 mV), but this is insufficient to oxidize TeO2 → soluble Te. 6+ (Requires >1000mV), and the weak oxidant does not exhibit reducing properties in acidic environments, nor can it reduce or dissolve TeO2, thus achieving selective leaching of selenium, increasing the leaching rate to over 90%, and leaving tellurium and valuable metals in the second-stage leaching residue, solving the bottleneck problem of difficult separation of selenium and tellurium in one-step leaching.

[0020] Finally, this method targets the precipitation of the second-stage leachate with a higher concentration of precipitant, thereby improving the purity of crude selenium to over 92%. Furthermore, in the tellurium separation stage, by controlling the addition rate and using concentrated acid to slowly and precisely regulate the pH of the hydrolysis system, this method avoids either excessively high local acid concentrations leading to TeO2 redissolution and tellurium residue, or insufficient acid concentrations causing co-precipitation of impurities (such as Fe). 3+ (Equivalent to co-precipitation) to achieve a tellurium dioxide purity of over 90% and a recovery rate of over 95%.

[0021] In summary, the method described in this invention enables the synergistic recovery of multiple resources from alloy dust, solving the problems of low separation efficiency and high cost in traditional processes for low-grade, near-content selenium-tellurium dust. In particular, the two-stage oxidative leaching method achieves solid-liquid separation of selenium and tellurium, avoiding the subsequent separation burden caused by the co-dissolution of selenium and tellurium in existing technologies, demonstrating significant progress in low-concentration scenarios. This method features a short process flow, high selective separation efficiency, and high comprehensive resource recovery rate, exhibiting outstanding environmental friendliness and economic efficiency. Detailed Implementation

[0023] A method for separating and recovering selenium and tellurium from alloy dust, comprising the following steps:

[0024] Step 1: Mix the alloy dust from the smelting furnace with a sulfuric acid solution of 10-50 g / L (preferably 10 g / L, 20 g / L, 30 g / L, 40 g / L, or 50 g / L) at a liquid-to-solid ratio of 3-5:1 (preferably 3:1, 3.5:1, 4:1, 4.5:1, or 5:1). The alloy dust from the smelting furnace can be the alloy dust produced during the production process of the Kaldor furnace. The alloy dust contains 1-10 wt% selenium, 0.5-5 wt% tellurium, and 15-25 wt% copper, and also includes other valuable materials. The metal elements, the valuable metal elements being one or more selected from Au, Ag, Pt, Pd, Pb, and Zn, wherein the selenium-tellurium content ratio is 0.5–2; after mixing, the temperature is raised to 40–70℃ (preferably 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃), and the reaction is stirred for 0.5–2 h (preferably 0.5 h, 1 h, 1.5 h, 2 h). After the reaction is completed, solid and liquid are separated to obtain a copper-containing leaching solution and a selenium-tellurium leaching residue, i.e., copper enters the first leaching solution, and selenium, tellurium, and valuable metals enter the first leaching residue;

[0025] Step 2: Mix the first-stage selenium-tellurium leaching residue with a selective leaching agent at a liquid-solid ratio of 1–6:1 (preferably 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, more preferably 3–5:1), then heat to 70–90°C (preferably 70°C, 75°C, 80°C, 85°C, 90°C), and stir for 1–4 hours (preferably 1 hour, 2 hours, 3 hours, 4 hours), controlling the oxidation potential ≤800mV. After the reaction, separate the solid and liquid phases to obtain a second-stage selenium-containing leaching solution and a second-stage tellurium-containing leaching residue. Selenium enters the second-stage leaching solution, while tellurium and valuable gold are extracted. It belongs to the second stage leaching residue; the selective leaching agent is preferably any one of sodium sulfite at a concentration of 50-140 g / L (preferably 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L, more preferably 70-120 g / L) or sodium hypochlorite at a concentration of 30-100 g / L (preferably 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L);

[0026] Step 3: Mix the two-stage selenium-containing leachate with a reducing precipitant, wherein the mass ratio of selenium to reducing precipitant in the mixture is 1:1 to 50 (preferably 1:10 to 40). Then, heat the mixture to 40 to 60°C (preferably 40°C, 45°C, 50°C, 55°C, or 60°C) and stir for 1 to 3 hours (preferably 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours). After the reaction, separate the solid and liquid phases to obtain crude selenium. The reducing precipitant is preferably 10 to 30% (this percentage refers to...). The solution is any one of sulfuric acid (g / 100mL), oxalic acid (5-15wt%), or sulfur dioxide. When the solution is sulfuric acid or oxalic acid, the addition rate is 1-5 mL / min (preferably 1 mL / min, 2 mL / min, 3 mL / min, 4 mL / min, or 5 mL / min). When the solution is sulfur dioxide, the addition rate is 0.5-2 L / min (preferably 0.5 L / min, 1 L / min, 1.5 L / min, 2 L / min, or 2.5 L / min).

[0027] Step 4: Mix the tellurium-containing leaching residue from the second stage with an alkaline solution of 100–200 g / L (preferably 100 g / L, 125 g / L, 150 g / L, 175 g / L, or 200 g / L) at a liquid-to-solid ratio of 3–6:1 (preferably 3:1, 4:1, 5:1, or 6:1). Then, heat the mixture to 60–90°C (preferably 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 90°C, more preferably 70–90°C) and stir the mixture for 1–4 hours (preferably 1 hour, 2 hours, 3 hours, or 4 hours). After the reaction, separate the solid and liquid components to obtain a tellurium-containing leaching solution and a third-stage leaching residue. Tellurium enters the third-stage leaching solution, and valuable metals enter the third-stage leaching residue. Valuable metals can be recovered using other commonly used methods. The alkaline solution is preferably either sodium hydroxide solution or sodium carbonate solution.

[0028] Step 5: Add concentrated acid to the three-stage tellurium-containing leachate at a rate of 0.5–1 mL / min (preferably 0.5 mL / min, 0.6 mL / min, 0.7 mL / min, 0.8 mL / min, 0.9 mL / min, and 1.0 mL / min), with a pH gradient ≤0.2 / min, until the pH reaches 5–7 (preferably 5.5–6.5). Raise the temperature to 60–80°C and stir the reaction for 1–3 hours. After hydrolysis, separate the solid and liquid phases to obtain tellurium dioxide. The concentrated acid is preferably any one of 98 wt% sulfuric acid, 36–38 wt% hydrochloric acid, or 68–70 wt% nitric acid.

[0029] The stirring speed in steps 1-5 is 100-200 rpm.

[0030] Example 1:

[0031] A method for separating and recovering selenium and tellurium from alloy dust, comprising the following steps:

[0032] Step 1: Mix 100g of alloy dust from the smelting furnace with a 30g / L sulfuric acid solution at a liquid-solid mass ratio of 3:1. The alloy dust contains 2wt% selenium, 3wt% tellurium, and 20wt% copper, with the remaining elements being any one or more of Au, Ag, Pt, Pd, Pb, and Zn. After mixing, heat to 60℃ and stir at 150rpm for 0.5h. After the reaction is complete, separate the solid and liquid components to obtain a copper-containing leaching solution and a selenium-tellurium leaching residue.

[0033] Step 2: The first stage of selenium-tellurium leaching residue was mixed with 70 g / L sodium sulfite selective leaching agent at a liquid-solid mass ratio of 5:1. The mixture was then heated to 80°C and stirred at 150 rpm for 3 hours, with the oxidation potential controlled at ≤800 mV. After the reaction was completed, the solid and liquid were separated to obtain a second stage of selenium-containing leaching solution and a second stage of tellurium-containing leaching residue. The selenium leaching rate reached 95%.

[0034] Step 3: Mix the two-stage selenium-containing leachate with 10wt% oxalic acid reducing precipitant. The oxalic acid is added at a rate of 5mL / min. The mass ratio of selenium to oxalic acid in the mixture is 1:20. Then, heat the mixture to 50℃ and stir at 150rpm for 2 hours. After the reaction is complete, separate the solid and liquid to obtain crude selenium with a purity of 95%.

[0035] Step 4: Mix the second-stage tellurium-containing leaching residue with 150 g / L sodium hydroxide solution at a liquid-solid ratio of 3:1, then heat to 80°C and stir at 150 rpm for 2 hours. After the reaction is completed, separate the solid and liquid to obtain the third-stage tellurium-containing leaching solution and the third-stage leaching residue.

[0036] Step 5: Slowly add 98wt% sulfuric acid to the three-stage tellurium-containing leachate at a rate of 1mL / min, with a pH gradient of ≤0.2 / min, until the pH stabilizes at 5.5±0.2. Raise the temperature to 70℃ and stir at 150rpm for 2 hours. After hydrolysis, solid-liquid separation yields tellurium oxide with a purity of 90% and a tellurium recovery rate of 95%.

[0037] Example 2:

[0038] A method for separating and recovering selenium and tellurium from alloy dust, comprising the following steps:

[0039] Step 1: Mix 100g of alloy dust from a Kaldor furnace with a 10g / L sulfuric acid solution at a liquid-solid mass ratio of 4:1. The alloy dust contains 8wt% selenium, 4.5wt% tellurium, and 15wt% copper, with the remaining elements being any one or more of Au, Ag, Pt, Pd, Pb, and Zn. After mixing, heat to 70℃ and stir at 100rpm for 0.5h. After the reaction, separate the solid and liquid phases to obtain a copper-containing leaching solution and a selenium-tellurium leaching residue.

[0040] Step 2: The first stage of selenium-tellurium leaching residue was mixed with 120 g / L sodium sulfite selective leaching agent at a liquid-solid mass ratio of 4:1. The mixture was then heated to 90°C and stirred at 100 rpm for 1 hour, with the oxidation potential controlled at ≤800 mV. After the reaction was completed, the solid and liquid were separated to obtain a second stage of selenium-containing leaching solution and a second stage of tellurium-containing leaching residue. The selenium leaching rate reached 93%.

[0041] Step 3: Mix the two-stage selenium-containing leachate with 200 g / L sulfuric acid reducing precipitant. The sulfuric acid is added at a rate of 1 mL / min. The mass ratio of selenium to sulfuric acid in the mixture is 1:10. Then, heat the mixture to 60°C and stir it at 100 rpm for 1 hour. After the reaction is complete, separate the solid and liquid to obtain crude selenium with a purity of 92%.

[0042] Step 4: Mix the second-stage tellurium-containing leaching residue with 200 g / L sodium carbonate solution at a liquid-solid ratio of 6:1, then heat to 90°C and stir at 100 rpm for 1 hour. After the reaction is complete, separate the solid and liquid to obtain the third-stage tellurium-containing leaching solution and the third-stage leaching residue.

[0043] Step 5: Slowly add 36-37 wt% hydrochloric acid to the three-stage tellurium-containing leachate at a rate of 0.8 mL / min, with a pH change gradient ≤ 0.2 / min, until the pH stabilizes at 6.5 ± 0.2. Raise the temperature to 80℃ and stir at 100 rpm for 1 h. After hydrolysis, solid-liquid separation yields tellurium oxide with a purity of 93% and a tellurium recovery rate of 96%.

[0044] Example 3:

[0045] A method for separating and recovering selenium and tellurium from alloy dust, comprising the following steps:

[0046] Step 1: Mix 100g of alloy dust from a Kaldor furnace with a 50g / L sulfuric acid solution at a liquid-solid mass ratio of 5:1. The alloy dust contains 1.5wt% selenium, 1.5wt% tellurium, and 25wt% copper, with the remaining elements being any one or more of Au, Ag, Pt, Pd, Pb, and Zn. After mixing, heat to 40℃ and stir at 200rpm for 2 hours. After the reaction, separate the solid and liquid phases to obtain a copper-containing leaching solution and a selenium-tellurium leaching residue.

[0047] Step 2: The first stage of selenium-tellurium leaching residue was mixed with 100 g / L sodium hypochlorite selective leaching agent at a liquid-solid mass ratio of 3:1. The mixture was then heated to 70°C and stirred at 200 rpm for 4 hours, with the oxidation potential controlled at ≤800 mV. After the reaction was completed, the solid and liquid were separated to obtain a second stage of selenium-containing leaching solution and a second stage of tellurium-containing leaching residue. The selenium leaching rate reached 92%.

[0048] Step 3: Mix the two-stage selenium-containing leachate with sulfur dioxide at a flow rate of 1 L / min. The mass ratio of selenium to sulfuric acid in the mixture is 1:40. Then, heat the mixture to 40°C and stir it at 200 rpm for 3 hours. After the reaction, separate the solid and liquid to obtain crude selenium with a purity of 93%.

[0049] Step 4: Mix the second-stage tellurium-containing leaching residue with 100 g / L sodium hydroxide solution at a liquid-solid ratio of 4:1, then heat to 60°C and stir at 200 rpm for 4 hours. After the reaction is completed, separate the solid and liquid to obtain the third-stage tellurium-containing leachate and the third-stage leaching residue.

[0050] Step 5: Slowly add 68-70 wt% nitric acid to the three-stage tellurium-containing leachate at a rate of 0.5 mL / min, with a pH change gradient ≤ 0.2 / min, until the pH stabilizes at 6.0 ± 0.2. Raise the temperature to 60℃ and stir at 200 rpm for 3 hours. After hydrolysis, solid-liquid separation yields tellurium oxide with a purity of 93% and a tellurium recovery rate of 95%.

[0051] Comparative Example 1:

[0052] A method for separating and recovering selenium and tellurium from alloy dust, comprising the following steps:

[0053] Step 1: Mix 100g of alloy dust from a Kaldor furnace with a 10g / L sulfuric acid solution at a liquid-solid mass ratio of 4:1. The alloy dust contains 8wt% selenium, 4.5wt% tellurium, and 15wt% copper, with the remaining elements being any one or more of Au, Ag, Pt, Pd, Pb, and Zn. After mixing, heat to 70℃ and stir at 100rpm for 0.5h. After the reaction, separate the solid and liquid phases to obtain a copper-containing leaching solution and a selenium-tellurium leaching residue.

[0054] Step 2: Mix the first stage of selenium-tellurium leaching residue with 30% hydrogen peroxide at a liquid-solid mass ratio of 5:1, then heat to 90℃ and stir at 100 rpm for 1 hour. The oxidation potential is ≥800mV (specifically 1100mV). After the reaction, separate the solid and liquid to obtain a second stage of selenium-tellurium leaching solution and a second stage of leaching residue. The leaching rate of selenium reaches 95%, and the leaching rate of tellurium reaches 80%.

[0055] Step 3: Mix the two-stage selenium-containing tellurium leachate with 200 g / L sulfuric acid reducing precipitant, wherein the mass ratio of selenium to sulfuric acid in the mixture is 1:10. Then heat the mixture to 60°C and stir at 100 rpm for 1 hour. After the reaction is completed, separate the solid and liquid to obtain crude selenium with a purity of 80%.

[0056] Step 4: Mix the second-stage leaching residue with 200 g / L sodium carbonate solution at a liquid-solid ratio of 6:1, then heat to 90°C and stir at 100 rpm for 1 hour. After the reaction is complete, separate the solid and liquid to obtain the third-stage tellurium-containing leachate and the third-stage leaching residue.

[0057] Step 5: Slowly add 36-37 wt% hydrochloric acid to the three-stage tellurium-containing leachate at a rate of 3 mL / min until the pH stabilizes at 6.5 ± 0.2. Raise the temperature to 80℃ and stir at 100 rpm for 1 h. After hydrolysis, solid-liquid separation yields tellurium oxide with a purity of 89% and a tellurium recovery rate of 17%.

[0058] The foregoing descriptions have outlined some exemplary embodiments of the present invention. It is understood that these embodiments are merely illustrative and do not constitute a limitation on the scope of protection of the present invention. Features in these embodiments can be rearranged in suitable ways, and the resulting solutions remain within the scope of protection claimed by the present invention. All other embodiments obtained by those skilled in the art based on the foregoing embodiments without inventive effort, i.e., all modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, fall within the scope of protection claimed by the present invention.

Claims

1. A method for separating and recovering selenium and tellurium from alloy dust, characterized in that, Includes the following steps: Step 1: Mix the alloy dust from the smelting furnace with a 10-50 g / L sulfuric acid solution at a liquid-solid ratio of 3-5:

1. The alloy dust contains 1-10 wt% selenium, 0.5-5 wt% tellurium, and 15-25 wt% copper, with a selenium-tellurium content ratio of 0.5-2. After mixing, heat to 40-70°C and stir for 0.5-2 hours. After the reaction, separate the solid and liquid components to obtain a copper-containing leaching solution and a selenium-tellurium leaching residue. Step 2: Mix the first stage of selenium-tellurium leaching residue with the selective leaching agent at a liquid-solid ratio of 1 to 6:1, then heat to 70 to 90°C, stir and react for 1 to 4 hours, control the oxidation potential to ≤800mV, and after the reaction is completed, separate the solid and liquid to obtain the second stage of selenium-containing leaching solution and the second stage of tellurium-containing leaching residue. Step 3: Mix the two-stage selenium-containing leachate with a reducing precipitant, wherein the mass ratio of selenium to reducing precipitant in the mixture is 1:1 to 50. Then, heat the mixture to 40 to 60°C and stir for 1 to 3 hours. After the reaction is completed, separate the solid and liquid to obtain crude selenium. Step 4: Mix the second-stage tellurium-containing leaching residue with an alkaline solution of 100-200 g / L at a liquid-solid ratio of 3-6:1, then heat to 60-90℃ and stir for 1-4 hours. After the reaction is completed, separate the solid and liquid to obtain the third-stage tellurium-containing leachate and the third-stage leaching residue. Step 5: Add concentrated acid to the three-stage tellurium-containing leachate at a rate of 0.5-1 mL / min, with a pH gradient of ≤0.2 / min, until the pH reaches 5-7. Heat to 60-80℃ and stir for 1-3 hours. After hydrolysis, separate the solid and liquid phases to obtain tellurium dioxide.

2. The method for separating and recovering selenium and tellurium from alloy dust according to claim 1, characterized in that, The alloy dust from the smelting furnace is the alloy dust produced during the production process of the Kaldor furnace.

3. The method for separating and recovering selenium and tellurium from alloy dust according to claim 2, characterized in that, The elemental contents of the alloy dust from the Kaldor furnace are as follows: selenium content is 1-10 wt%, tellurium content is 0.5-5 wt%, copper content is 15-25 wt%, and it also includes other valuable metal elements, which are one or more of Au, Ag, Pt, Pd, Pb, and Zn.

4. The method for separating and recovering selenium and tellurium from alloy dust according to claim 1, characterized in that, The selective leaching agent mentioned in step 2 is any one of sodium sulfite at a concentration of 50–140 g / L or sodium hypochlorite at a concentration of 30–100 g / L.

5. The method for separating and recovering selenium and tellurium from alloy dust according to claim 1, characterized in that, The reducing precipitant mentioned in step 3 is any one of sulfuric acid (100-300 g / L), oxalic acid (5-15 wt%), or sulfur dioxide.

6. The method for separating and recovering selenium and tellurium from alloy dust according to claim 5, characterized in that, When the reducing precipitant is sulfuric acid or oxalic acid, the addition rate is 1–5 mL / min; when the reducing precipitant is sulfur dioxide, the introduction rate is 0.5–2 L / min.

7. The method for separating and recovering selenium and tellurium from alloy dust according to claim 1, characterized in that, The alkaline solution mentioned in step 4 is either a sodium hydroxide solution or a sodium carbonate solution.

8. The method for separating and recovering selenium and tellurium from alloy dust according to claim 1, characterized in that, The concentrated acid mentioned in step 5 is any one of 98 wt% sulfuric acid, 36-38 wt% hydrochloric acid, or 68-70 wt% nitric acid.

9. The method for separating and recovering selenium and tellurium from alloy dust according to claim 1, characterized in that, The stirring speed in steps 1-5 is 100-200 rpm.