Complete Refining Methods Table
| Method | Principle | Metal/Element | Key Details |
|---|---|---|---|
| Distillation | Volatile metals vaporize; impurities stay | Zn (907°C bp), Hg (357°C bp) | Low boiling point essential |
| Liquation | Low-mp metal flows away from high-mp impurities | Sn (mp 232°C) | Sloped hearth; gravity-driven |
| Electrolytic refining | Selective electrodeposition | Cu, Zn, Al | Anode: impure; cathode: pure; anode mud = Au, Ag |
| Zone refining | Impurities concentrate in melt (k < 1) | Si, Ge, Ga | Movable heater; multiple passes; ppb purity |
| Mond process | Volatile carbonyl | Ni | Form Ni(CO)4 at 330–350 K; decompose at 450–470 K |
| Van Arkel | Volatile iodide | Ti, Zr | Form TiI4 at ~870 K; decompose on W filament at ~1700 K |
Temperature Summary for Mond and Van Arkel
| Process | Metal | Formation T | Decomposition T | Volatile Compound |
|---|---|---|---|---|
| Mond | Ni | 330–350 K (~60°C) | 450–470 K (~180°C) | Ni(CO)4 |
| Van Arkel | Ti, Zr | ~870 K (~600°C) | ~1700 K (~1430°C) | TiI4 / ZrI4 |
Anode Mud Composition in Cu Electrolytic Refining
- Falls as anode mud: Au, Ag, Pt (less electropositive, more noble, do not dissolve)
- Dissolves into solution: Fe, Zn, Ni (more electropositive, dissolve but don't deposit)
- Deposits at cathode: Only Cu (selective deposition)