Perfect — now we’re on **Protactinium (Pa, atomic number 91).**
Protactinium is a **rare and highly radioactive actinide**. It was discovered in 1913 (protoactinium, later renamed). It occurs naturally only in trace amounts, usually as a byproduct of **uranium decay chains** (particularly from ^235U). Because of its scarcity and radioactivity, protactinium is not mined commercially but is instead extracted in very small amounts, mainly from **uranium ores** or produced artificially in reactors.
Here are the **20 most common methods of extracting Protactinium**:
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# **20 Most Common Methods of Extracting Protactinium**
### **A. Natural Occurrence & Recovery**
1. **Recovery from Uraninite (Pitchblende)** – Pa is found in uranium ores in ppm levels.
2. **Recovery from Monazite Sands** – Trace protactinium appears alongside uranium and thorium.
3. **Extraction as a Decay Product of ^235U** – Pa-231 occurs in natural uranium decay.
4. **Geochemical Separation from Thorium-Rich Minerals** – Exploiting slight mobility differences.
5. **Recovery from Rare-Earth Ores** – Where trace actinides occur together.
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### **B. Reactor-Based Production**
6. **Neutron Irradiation of ^230Th → ^231Th → ^231Pa** – Reactor pathway to Pa-231.
7. **Neutron Irradiation of ^232Th to Breed ^233U, with Pa-233 as Intermediate** – Protactinium-233 is a key step in the thorium fuel cycle.
8. **Separation of Pa-233 During Thorium Reactor Experiments** – Avoids neutron loss to Pa.
9. **Production from ^232U Neutron Irradiation** – Alternative nuclear route.
10. **Breeding in Molten Salt Reactors** – Pa is extracted chemically before it decays to U-233.
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### **C. Laboratory & Radiochemical Separation**
11. **Precipitation as Protactinium Hydroxide (Pa(OH)₅)** – First isolation method.
12. **Precipitation as Protactinium Oxalate (Pa₂(C₂O₄)₅)** – Classic purification step.
13. **Fluoride Precipitation (PaF₅)** – Yields highly insoluble compounds.
14. **Solvent Extraction with Organic Reagents (e.g., TBP, TTA, Aliquat-336)** – Separates Pa from U and Th.
15. **Ion Exchange Chromatography** – Key method for high-purity separation in research.
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### **D. Advanced Separation Techniques**
16. **Anion Exchange in Fluoride or Chloride Media** – Exploits unique Pa chemistry.
17. **Cation Exchange in Acidic Media** – Distinguishes Pa from uranium and thorium.
18. **Liquid-Liquid Extraction in Molten Salt Systems** – Used in MSR fuel processing.
19. **Extraction with Bidentate Ligands (e.g., thenoyltrifluoroacetone)** – Laboratory-scale purification.
20. **Extraction as Protactinium Pentachloride (PaCl₅) or Pentafluoride (PaF₅)** – Used for volatile transport and purification.
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✅ **Summary:**
* Protactinium is **extremely rare** in nature and usually obtained as a **byproduct of uranium ores** or **nuclear reactor breeding cycles**.
* Separation relies heavily on **radiochemical methods** like **precipitation, solvent extraction, and ion exchange**.
* Its main importance has been in **nuclear research**, especially the **thorium fuel cycle** (Pa-233 → U-233).
* Due to cost and radioactivity, only **milligram to gram quantities** have ever been isolated for study.
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Next on the periodic table is **Uranium (U, atomic number 92).**
Would you like me to continue with the **20 most common methods of extracting Uranium**?
