Activated carbon works through a dual mechanism of physical adsorption and chemical adsorption in gold extraction:
Physical adsorption: Activated carbon has a huge specific surface area (over 1000 m²/g) and a well-developed pore structure. It captures gold cyanide complex ions [Au(CN)₂]⁻ through van der Waals forces.
Chemical adsorption: Functional groups such as hydroxyl groups (-OH) and carboxyl groups (-COOH) on the surface of activated carbon react chemically with gold ions, forming stable chemical bonds, reducing gold ions to elemental gold and fixing them.
Ion exchange: The surface of activated carbon is charged and can exchange with gold cyanide complex anions in the solution to achieve selective enrichment.
Key advantages: Activated carbon has high selectivity for gold cyanide complexes, can specifically capture gold in an environment where multiple metal ions coexist, and is not significantly interfered by other impurities.
1️⃣ Carbon-in-Pulp (CIP)
The ore is first subjected to cyanidation leaching, where gold dissolves to form [Au(CN)₂]⁻, and then activated carbon is added for adsorption.
Process flow: Ore grinding → Cyanidation leaching → Activated carbon adsorption → Gold-loaded carbon separation → Desorption → Electrolysis → Smelting
2️⃣ Carbon-in-Leach (CIL)
Leaching and adsorption are carried out simultaneously; activated carbon is directly added to the cyanidation tank, enabling "leaching while adsorbing".
Advantages: Simplified process, gold recovery rate increased by 2-5%, suitable for processing ores containing fine-grained gold.The core of gold extraction is to capture the gold cyanide complex ion [Au(CN)₂]⁻ (with a diameter of approximately 0.5nm). Coconut shell activated carbon has a very high proportion of micropores (0.5-2nm), forming "precise capture channels" — like a "molecular sieve" customized for gold ions, which can quickly adsorb and is not easy to desorb.
Coal-based activated carbon is mainly composed of mesopores (2-50nm) and macropores. The excessively large pore size leads to unstable adsorption of gold ions, and the pores are easily occupied by other impurities, resulting in a significant decrease in adsorption efficiency and selectivity.
