The manufacturing process of antimony (Sb) involves several steps, from ore extraction to refining. Antimony is primarily obtained from its sulfide ore, stibnite (Sb₂S₃), though it can also be recovered as a byproduct of lead, copper, and silver smelting.
1. Mining & Ore Preparation
– Stibnite (Sb₂S₃) is the primary source of antimony.
– The ore is crushed, ground, and concentrated using froth flotation to increase antimony content (typically 30-60% Sb).
2. Extraction Methods
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# A) Pyrometallurgical Process (Most Common)
1. Roasting
– Stibnite concentrate is heated in air to convert sulfide to oxide:
\[
2 \text{Sb}_2\text{S}_3 + 9 \text{O}_2 → 2 \text{Sb}_2\text{O}_3 + 6 \text{SO}_2
\]
– Sulfur dioxide (SO₂) is captured for sulfuric acid production.
2. Reduction Smelting
– The oxide (Sb₂O₃) is mixed with carbon (coke/coal) and smelted at ~1000–1200°C:
\[
\text{Sb}_2\text{O}_3 + 3 \text{C} → 2 \text{Sb} + 3 \text{CO}
\]
– Impurities like iron and arsenic form slag.
3. Liquation
– Crude antimony (~90-95% Sb) is heated just above its melting point (630°C), allowing pure antimony to separate from higher-melting impurities.
# B) Hydrometallurgical Process
– Used for low-grade ores or complex concentrates.
– Leaching with alkaline solutions (NaOH/Na₂S) dissolves antimony:
\[
\text{Sb}_2\text{S}_3 + 6 \text{NaOH} → 2 \text{Na}_3\text{SbS}_3 + 3 \text{H}_2\text{O}
\]
– Antimony is then electrowon or precipitated.
3. Refining
– Electrolytic Refining: Impure antimony is dissolved in an electrolyte (e.g., SbF₃ + H₂SO₄