A lixiviant is a chemical solution used to dissolve a target metal from ore. In gold mining the dominant lixiviant is dilute sodium cyanide. Other lixiviants include sulfuric acid (for copper oxides and uranium), thiosulfate (a niche cyanide alternative for gold), ferric chloride, and ammonia.
Why It Matters
The choice of lixiviant defines the entire flowsheet. Cyanidation requires alkaline pH, oxygen, and specific safety controls. Acid leach (copper) requires acid-resistant materials throughout the plant. Thiosulfate avoids cyanide but requires very different downstream recovery. Pick the wrong lixiviant and the project may not be technically or economically viable.
Cyanide (Gold & Silver)
The industry standard for over 95% of global primary gold production. Selective, cheap, well-understood. Operates at alkaline pH with oxygen. See cyanidation for full detail.
Sulfuric Acid (Copper, Uranium)
Copper oxide ores are heap-leached with sulfuric acid (pH 1–2). The pregnant leach solution is then processed by solvent extraction + electrowinning (SX-EW). Uranium ores are similarly acid-leached.
Alternative Gold Lixiviants
Thiosulfate, glycine, and chloride-based systems exist and may grow in jurisdictions where cyanide regulation is increasingly strict. None has yet displaced cyanide at industrial scale. Testwork on alternative lixiviants is a KCA laboratory capability where the project warrants it.
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