Perfect 👍 — next in **periodic table order** is **Selenium (Se, atomic number 34).**
Selenium is a **nonmetal/metalloid** that rarely occurs free in nature. It is primarily obtained as a **byproduct of copper refining**, especially from **anode slimes in electrolytic copper production**. Industrial extraction usually involves **oxidation, leaching, and reduction steps**.
Here are the **20 most common methods of extracting Selenium**:
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# **20 Most Common Methods of Extracting Selenium**
### **A. Industrial / Large-Scale Methods**
1. **Recovery from Copper Electrolytic Anode Slimes** – Primary industrial source.
2. **Oxidative Roasting of Slimes (Se → SeO₂)** – Converts selenium to volatile selenium dioxide.
3. **Sublimation of SeO₂ (SeO₂ → Se vapour → Se solid)** – Produces elemental selenium.
4. **Reduction of SeO₂ with Sulfur Dioxide (SeO₂ + SO₂ → Se + SO₃)** – Industrial reduction method.
5. **Reduction of SeO₂ with Carbon** – Produces metallic selenium.
6. **Direct Recovery from Copper Matte or Slag** – Small-scale industrial process.
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### **B. Hydrometallurgical Methods**
7. **Leaching Selenium from Slimes with Sodium Sulfite (Na₂SO₃)** – Produces soluble selenite.
8. **Leaching with NaOH or KOH Solutions** – Forms soluble selenides or selenates.
9. **Precipitation of Selenium from Solution (H₂SeO₃ → Se)** – Intermediate step.
10. **Electrolytic Deposition from Selenite Solutions** – Produces high-purity selenium.
11. **Recovery from Copper Refinery Waste Streams** – Hydrometallurgical leaching.
12. **Solvent Extraction of Selenium from Leach Liquors** – Uses organophosphorus or amine extractants.
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### **C. Laboratory / Small-Scale Methods**
13. **Reduction of SeO₂ with Hydrogen Gas** – Produces metallic selenium.
14. **Aluminothermic Reduction of SeO₂** – Lab-scale metallic selenium production.
15. **Magnesiothermic Reduction of Se Compounds** – Experimental laboratory method.
16. **Reduction of Selenium Chloride (SeCl₄) with Alkali Metals** – Laboratory metallothermic method.
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### **D. Specialized / Recycling Methods**
17. **Recovery from Photovoltaic Cells / Electronics** – Hydrometallurgical leaching.
18. **Recovery from Selenium-Containing Glass Manufacturing Waste** – Leaching + precipitation.
19. **Plasma Reduction of Selenium Compounds** – Experimental method for high-purity Se.
20. **Solar-Thermal Reduction of SeO₂** – Experimental renewable energy method.
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✅ **Summary:**
* **Main industrial source:** Copper anode slimes from electrolytic refining.
* **Primary industrial steps:** Oxidation → sublimation → reduction to elemental Se.
* **Metallic selenium:** Produced via reduction with SO₂, carbon, hydrogen, or aluminothermic methods.
* **Hydrometallurgical:** Leaching with sulfite or alkali → precipitation → electrolysis.
* **Laboratory/experimental:** Mg/Al reduction, plasma, solar-thermal.
* **Recycling sources:** Electronics, PV cells, glass manufacturing waste.
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Next in periodic order is **Bromine (Br, atomic number 35).**
Do you want me to continue with **20 extraction methods for Bromine**?
