⛏️ Metallurgy & Principles of Extraction

Metallurgy translates thermodynamic free energy boundaries ( $D e l t a G^{c} i r c = D e l t a H^{c} i r c - T D e l t a S^{c} i r c$ ) and electrochemical reduction principles into industrial metal isolation. Essential exam focuses include Ellingham diagram slope interpretation, froth flotation depressants, Blast furnace zone reactions, and refining methods (Mond, Van Arkel, Zone refining).

1. 📈 Ellingham Diagrams ( $D e l t a G^{c} i r c$ vs $T$ )

Ellingham diagrams plot the standard Gibbs free energy of formation of metal oxides $D e l t a G^{c} i r c$ against absolute temperature $T$ :

2 M + O_{2} \to 2 M O ⟹ Δ G^{\circ} = Δ H^{\circ} - T Δ S^{\circ}

1.1 Fundamental Thermodynamic Principles of Ellingham Diagrams:

Positive Slope for Metal Oxidation: As 1 mole of gas ( $O_{2}$ ) is consumed, $D e l t a S^{c} i r c < 0 i m p l i e s - T D e l t a S^{c} i r c > 0 i m p l i e s$ slope is positive.
Abrupt Slope Change (Break in Line): Indicates a phase transition (melting or boiling of the metal), where $D e l t a S^{c} i r c$ becomes more negative due to liquid/gas phase entropy.
The Reducing Rule: $Any metal located LOWER on the Ellingham diagram can reduce the oxide of a metal located ABOVE it!$
- Below $1350^{\circ} C$ : $M g$ line is below $A l_{2} O_{3}$ line $i m p l i e s M g$ can reduce $A l_{2} O_{3}$ .
- Above $1350^{\circ} C$ : $A l$ line is below $M g O$ line $i m p l i e s A l$ can reduce $M g O$ .
Carbon as a Universal Reducing Agent:
- $2 C + O_{2} \to 2 C O$ : Number of gas moles increases ( $D e l t a S^{c} i r c > 0$ ) $i m p l i e s$ Negative slope ( $D e l t a G^{c} i r c$ becomes more negative at high $T$ ).
- At temperatures above intersection point, Carbon or $C O$ reduces virtually any metal oxide.

2. 🌊 Concentration of Ores & Froth Flotation

Froth Collectors: Sodium ethyl xanthate, Pine oil, Fatty acids (adsorb on sulfide mineral surfaces making them hydrophobic/water-repellent).
Frothing Agents: Cresols, Pine oil (stabilize the air bubbles).
Depressants ( $N a C N$ ): Selectively separate mixed sulfide ores (e.g. $P b S + Z n S$ Galena/Sphalerite):
- $N a C N$ reacts with $Z n S$ to form soluble complex $N a_{2} [Z n (C N)_{4}]$ , preventing it from forming froth.
- $P b S$ floats up with the froth. Acidification subsequently recovers $Z n S$ .

3. 🏭 Blast Furnace Reduction of Iron ( $F e_{2} O_{3}$ )

Charge: Haematite Ore (F e_{2} O_{3}) + Coke (C) + Limestone (C a C O_{3})

Zone of Blast Furnace	Temperature Range	Chemical Reactions
Combustion Zone (Bottom)	$1900 - 2200 K$	$C + O_{2} \to C O_{2} (Δ H = - 393 kJ/mol)$ $C O_{2} + C \to 2 C O (Δ H = + 163 kJ/mol)$
Slag Formation Zone (Middle)	$1100 - 1400 K$	$C a C O_{3} \to C a O + C O_{2}$ $C a O (Basic flux) + S i O_{2} (Acidic gangue) \to {CaSiO}_{3} (Fusible Slag)$
Reduction Zone (Top)	$500 - 900 K$	$3 F e_{2} O_{3} + C O \to 2 F e_{3} O_{4} + C O_{2}$ $F e_{3} O_{4} + 4 C O \to 3 F e + 4 C O_{2}$ $F e O + C O \to F e + C O_{2}$

Pig Iron: Product obtained directly from blast furnace ( $4 %$ Carbon, brittle).
Cast Iron: Melted pig iron with scrap iron ( $3 %$ Carbon, extremely hard).
Wrought Iron: Purest commercial form of iron ( $0.1 - 0.2 %$ Carbon).

4. 💎 Metal Refining Methods Master Summary

Refining Technique	Principle	Target Metals	Chemical Reaction / Specific Conditions
Zone Refining	Fractional crystallization (impurities more soluble in molten zone)	Ultra-pure Semiconductors ( $S i, G e, G a, I n, B$ )	Circular mobile heater moving along rod in inert argon atmosphere
Mond Process	Vapor phase transport via volatile carbonyl	Nickel ( $N i$ )	$N i + 4 C O \overset{330 - 350 K}{\to} N i (C O)_{4} \overset{450 - 470 K}{\to} N i + 4 C O$
Van Arkel Method	Vapor phase transport via volatile iodide	Titanium ( $T i$ ), Zirconium ( $Z r$ )	$Z r + 2 I_{2} \overset{870 K}{\to} Z r I_{4} \overset{2075 K, Tungsten filament}{\to} Z r + 2 I_{2}$
Kroll Process	High-temperature reduction with $M g$	Titanium ( $T i$ )	$T i C l_{4} + 2 M g \overset{1000 - 1150 K}{\to} T i + 2 M g C l_{2}$
Hall-Héroult Electrolysis	Molten cryolite ( $N a_{3} A l F_{6} + C a F_{2}$ ) bath lowers MP to $950^{\circ} C$ & increases conductivity	Aluminum ( $A l$ )	Cathode: $A l^{3 +} + 3 e^{-} \to A l_{(l)}$ Carbon Anode: $C + 2 O^{2 -} \to C O_{2} + 4 e^{-}$ (consumed)
MacArthur-Forrest Cyanide	Hydrometallurgical leaching & Zinc cementation displacement	Gold ( $A u$ ), Silver ( $A g$ )	$4 A u + 8 N a C N + 2 H_{2} O + O_{2} \to 4 N a [A u (C N)_{2}] + 4 N a O H$ $2 N a [A u (C N)_{2}] + Z n \to N a_{2} [Z n (C N)_{4}] + 2 A u ↓$

⛏️ Metallurgy & Principles of Extraction ​

1. 📈 Ellingham Diagrams (DeltaGcirc vs T) ​

1.1 Fundamental Thermodynamic Principles of Ellingham Diagrams: ​

2. 🌊 Concentration of Ores & Froth Flotation ​

3. 🏭 Blast Furnace Reduction of Iron (Fe2O3) ​

4. 💎 Metal Refining Methods Master Summary ​