The Carbon-In-Leach (CIL) process is a highly efficient method for extracting gold from ore by combining cyanidation and adsorption onto activated carbon in a single integrated circuit. Widely used in modern gold mining, CIL offers advantages such as high recovery rates, reduced operational costs, and environmental sustainability compared to traditional methods.
Crushing & Grinding: Raw ore is crushed and ground into fine particles to maximize surface area for chemical reactions.
Slurry Formation: The ground ore is mixed with water to form a slurry, which is fed into the CIL circuit.
Gold Dissolution: Sodium cyanide (NaCN) is added to the slurry, dissolving gold into a liquid phase as a gold-cyanide complex (Au(CN)₂⁻).
pH Adjustment: Lime (CaO) is used to maintain an alkaline environment (pH ~10–11) to optimize cyanide efficiency and minimize volatilization.
Carbon Addition: Activated carbon granules are introduced into the leaching tanks, where they adsorb the dissolved gold-cyanide complex.
Counter-Current Flow: Slurry flows through a series of agitated tanks, while carbon moves in the opposite direction, maximizing gold recovery.
Screening: Loaded carbon is separated from the slurry via screens and washed to remove residual ore.
Elution (Gold Stripping): The gold is desorbed from the carbon using a hot (100–130°C) caustic-cyanide solution or the Zadra process.
Electrowinning: The eluted solution is passed through an electrolytic cell, where gold is plated onto steel wool cathodes.
Carbon Reactivation: Stripped carbon is thermally regenerated (600–700°C) for reuse in the circuit.
Gold Smelting: The electrowon gold sludge is dried and smelted into doré bars (typically 90–95% purity).
Detoxification: Residual cyanide in tailings is destroyed using oxidation (e.g., SO₂/air process) or natural degradation.
Environmental Safeguards: Tailings are stored in lined ponds to prevent groundwater contamination.
High Recovery Rates: >90% gold extraction efficiency.
Lower Costs: Combines leaching and adsorption, reducing infrastructure needs.
Flexibility: Effective for both free-milling and refractory ores (with pretreatment).
CIL is the standard for large-scale gold processing plants, particularly for ores with:
Fine gold particles
Low sulfide content
High silver co-extraction
Our team provides end-to-end CIL plant design, optimization, and environmental compliance solutions. Contact us for a feasibility study.
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