Extraction de l'Or par Lixiviation au Cyanure

Dissolution de l'or du minerai grâce à une chimie découverte en 1887

Metallurgy & Metal Processing Global Industrial Scale $220 billion

Aperçu

Gold cyanidation dissolves gold from crushed ore using dilute sodium cyanide solution, a process patented by MacArthur and Forrest in 1887. Despite gold's famous chemical inertness, it dissolves readily in aerated cyanide solution due to the extraordinary stability of the gold-cyanide complex [Au(CN)₂]⁻. This process recovers over 90% of gold from ore and accounts for approximately 90% of all gold produced worldwide. Gold is recovered from the cyanide solution by adsorption onto activated carbon (CIP/CIL) or by zinc cementation (Merrill-Crowe process).

Procédé chimique

Crushed and milled gold ore (typically 1-10 g Au/ton) is leached in dilute NaCN solution (0.02-0.05%) at pH 10-11 with air sparging for 24-72 hours. Gold dissolves as [Au(CN)₂]⁻. In the CIL (carbon-in-leach) process, activated carbon is added to the leach tanks to adsorb the gold complex. Loaded carbon is stripped with hot caustic cyanide, and gold is recovered by electrowinning onto steel wool cathodes, followed by smelting to dore bullion.

4Au + 8NaCN + O₂ + 2H₂O → 4Na[Au(CN)₂] + 4NaOH (Elsner equation — gold dissolution in aerated cyanide)
Au(CN)₂⁻ + C(activated) → Au(CN)₂⁻·C (carbon adsorption)
2Au(CN)₂⁻ + Zn → Zn(CN)₄²⁻ + 2Au (zinc cementation, Merrill-Crowe)

Matières premières

  • Sodium cyanide (NaCN) — Andrussow process (HCN from CH₄ + NH₃ + O₂) + NaOH (Gold complexing agent (lixiviant))
  • Crushed gold ore — Open pit or underground gold mining (Gold source (1-10 g/ton typical))
  • Calcium oxide (CaO, lime) — Calcination of limestone (pH control (maintains pH >10 to prevent HCN))

Produits finis

  • Gold dore bullion — Refined to 99.99% gold for investment, jewelry, electronics (85-95% Au, remainder Ag and base metals)
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Environmental Impact

Cyanide is extremely toxic to all forms of life. Tailings dam failures (Baia Mare 2000, Samarco 2015) have caused devastating environmental disasters. Cyanide-bearing tailings require detoxification (typically with H₂O₂ or SO₂/air). The International Cyanide Management Code provides voluntary standards. Mercury amalgamation by artisanal miners causes severe mercury pollution.

Considérations de sécurité

Innovations récentes

Thiosulfate leaching (non-toxic alternative) is commercially applied at Barrick's Goldstrike mine (Nevada).
Glycine-based gold leaching is being developed as a milder alternative.
Cyanide destruction using INCO SO₂/air process reduces WAD cyanide to <1 ppm in tailings.
Gold recovery from electronic waste (urban mining) uses selective leaching.

Échelle de production

3500

tonnes/an

$220 billion

valeur marchande

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Frequently Asked Questions

What industry uses Extraction de l'Or par Lixiviation au Cyanure?
Extraction de l'Or par Lixiviation au Cyanure is used in the metallurgy & metal processing sector at global industrial scale scale.
What process is involved in Extraction de l'Or par Lixiviation au Cyanure?
Crushed and milled gold ore (typically 1-10 g Au/ton) is leached in dilute NaCN solution (0.02-0.05%) at pH 10-11 with air sparging for 24-72 hours. Gold dissolves as [Au(CN)₂]⁻. In the CIL (carbon-in-leach) process, activated carbon is added to the leach tanks to adsorb the gold complex. Loaded car
What is the economic significance of Extraction de l'Or par Lixiviation au Cyanure?
Extraction de l'Or par Lixiviation au Cyanure has a market value of $220 billion and annual production of 3,500 tons.
What is the environmental impact of Extraction de l'Or par Lixiviation au Cyanure?
Cyanide is extremely toxic to all forms of life. Tailings dam failures (Baia Mare 2000, Samarco 2015) have caused devastating environmental disasters. Cyanide-bearing tailings require detoxification (typically with H₂O₂ or SO₂/air). The International Cyanide Management Code provides voluntary standa
What raw materials are used in Extraction de l'Or par Lixiviation au Cyanure?
The main raw materials include: Sodium cyanide (NaCN), Crushed gold ore, Calcium oxide (CaO, lime).