The Metallurgical Complexity of Iridium Recycling

Why Iridium is Exceptionally Difficult to Recycle

Iridium’s unique properties pose challenges for recyclers:

• Highest corrosion resistance among PGMs (even insoluble in aqua regia at room temperature).
• Oxidation issues: Forms volatile IrO₃ above 1,100°C, leading to material loss.
• Alloying contaminants: Fe, Ni, or Pt from crucible holders diffuse into Ir at high temps.

 Advanced Extraction Techniques

We employ a hybrid pyro-hydrometallurgical approach:

Step 1: Alkali Fusion Pre-Treatment

• For oxide-contaminated crucibles (e.g., after sapphire growth):
  $\text{IrO}_2 + 2\text{NaOH} + \text{NaNO}_3 \rightarrow \text{Na}_2\text{IrO}_3 + \text{H}_2\text{O} + \text{NO}_2$
• Conditions: 600°C for 4 hours in nickel crucibles.

Step 2: High-Pressure Chlorination Leaching

• Process: HCl + Cl₂ gas at 200°C/5 bar in titanium reactors.
• Reaction:
  $\text{Ir} + 3\text{Cl}_2 + 2\text{HCl} \rightarrow \text{H}_2[\text{IrCl}_6]$
• Yield: 99% dissolution vs. 70% with conventional aqua regia.

Step 3: Selective Purification