Metallurgy
World A — Chemistry Foundations
12.A — ORES & CONCENTRATION
VS
R12.01 Minerals vs Ores
- All ores are minerals; not all minerals are ores.
- Ores: Profitable extraction of metal.
- Gangue: Earthy/rocky impurities.
R12.02 Gravity Separation
- Hydraulic washing (Levigation).
- Based on density difference.
- Heavy ore sinks, light gangue washes away.
R12.03 Froth Flotation
- Specifically for Sulphide ores.
- Based on differential wetting.
- Ore wetted by oil (floats), Gangue by water (sinks).
R12.04 Magnetic Separation
- For ores with magnetic properties (e.g., Iron).
- Magnetic roller attracts ore.
- Non-magnetic gangue falls straight down.
R12.05 Leaching
- Chemical separation (Hydrometallurgy).
- Ore dissolves in a suitable reagent.
- Used for Aluminum (Bayer process), Gold, Silver.
12.B — CONVERSION TO OXIDE
O₂ →
→ SO₂
R12.06 Roasting
- Heating ore in the presence of excess air.
- Used for Sulphide ores (e.g., ZnS → ZnO).
- Releases SO₂ gas.
↑ CO₂
R12.07 Calcination
- Heating ore in absence/limited air.
- Used for Carbonate/Hydrated ores (ZnCO₃ → ZnO).
- Drives off moisture and CO₂.
12.C — REDUCTION TO METAL
↑ CO/CO₂
R12.08 Smelting
- Reduction using Carbon (Coke) or CO.
- Used for moderately reactive metals (Fe, Zn).
- Carried out in a Blast Furnace.
✨
R12.09 Thermite Process
- Reduction using highly reactive Aluminum.
- Highly exothermic (produces molten metal).
- Used for welding railway tracks (Fe₂O₃ + Al).
M⁺
R12.10 Electrolytic Reduction
- For highly reactive metals (Na, Mg, Al).
- Carbon reduction fails.
- Electrolysis of molten salts.
ΔG
T
R12.11 Ellingham Diagram
- Graph of ΔG vs Temperature for oxide formation.
- Predicts feasibility of thermal reduction.
- Lower line metal can reduce upper line oxide.
12.D — REFINING
Cu²⁺
R12.12 Electrolytic Refining
- Anode: Impure metal. Cathode: Pure metal.
- Pure metal deposits on cathode.
- Impurities settle as "Anode Mud" (often contains Ag/Au).
R12.13 Zone Refining
- Used for ultra-pure semiconductors (Si, Ge).
- Principle: Impurities are more soluble in the melt.
- Moving circular heater sweeps impurities to one end.
Gas
Pure M
R12.14 Vapour Phase Refining
- Metal is converted to a volatile compound.
- Compound is then decomposed at higher temp.
- Mond Process (Ni) & van Arkel Method (Zr, Ti).