How to Extract Gold from Carbon: A Step-by-Step Guide to Recovery

( 300tpd Gold Mineral Processing Plant in Sudan )

Gold might glitter in jewelry, but extracting it from ore is a scientific marvel. One of the most efficient methods involves activated carbon, a porous material that acts like a magnet for gold particles. But once the carbon is loaded with gold, how do miners retrieve it? This guide breaks down the step-by-step process, from ore preparation to gleaming gold bars, in easy-to-understand terms.

Activated carbon is a gold miner's best friend because:

High Adsorption Power: Its sponge-like structure traps gold-cyanide complexes.

Cost-Efficient: Reusable and effective for large-scale operations.

Selective Binding: Captures gold while ignoring many impurities.

Before gold reaches carbon, the ore undergoes beneficiation to prepare it for extraction:

1. Crushing & Grinding:

Ore is crushed into sand-sized particles to release gold.

Ball mills grind it further into a fine powder.

2. Gravity Separation (Optional):

Shaking tables or centrifuges separate heavier gold particles from lighter waste.

3. Leaching:

A cyanide solution dissolves gold into a liquid (forming sodium gold cyanide).

4. Adsorption:

Activated carbon is mixed with the gold-rich solution, trapping gold on its surface.

1. Stripping Gold (Elution Process)

The goal is to “wash” gold off the carbon using a hot chemical bath:

Elution Solution: A mix of caustic soda (NaOH) and cyanide heated to 100–120°C.

Process: Carbon is soaked in this solution, breaking the bond between gold and carbon.

Result: Gold dissolves back into liquid, creating a pregnant eluate.

Safety Note: Elution is done in sealed tanks to protect workers from toxic fumes.

2. Electrowinning: Turning Liquid to Solid Gold

The gold-rich eluate flows into electrowinning cells:

Electric Current: Gold ions stick to stainless steel cathodes, forming a gold "sludge."

Byproducts: Impurities like copper settle separately for refining.

3. Smelting: From Sludge to Gold Bars

The gold-coated cathodes are melted in a furnace:

Fluxes (e.g., borax): Added to remove impurities, forming a glass-like slag.

Temperature: Heated to 1,064°C (gold's melting point) to pour pure gold doré bars.

4. Carbon Regeneration

The stripped carbon isn't wasted! It's recycled by:

Acid Washing: Removes mineral buildup.

Thermal Reactivation: Heated to 700°C in a kiln to restore its porous structure.

Cyanide Recycling: Closed-loop systems reuse cyanide to reduce waste.

Emissions Control: Scrubbers filter harmful gases during smelting.

Tailings Management: Neutralized waste is stored in secure, lined ponds.

CNLITE eco-friendly gold leaching reagent can 100% take place of sodium cyanide for gold processing and refining, including gold CIP, CIL, heap leaching, pool leaching and other cyanide process. Different with cyanide, it is low-toxicity, environmental-friendly and without changing the original cyanide equipment and process.

Q: How much gold can carbon hold?

A: 1 kg of carbon can trap 1–10 kg of gold, depending on ore quality and carbon type.

Q: Is activated carbon reusable?

A: Yes! Properly regenerated carbon can be reused 10–20 times.

Q: Why not burn the carbon to get gold?

A: Burning releases toxins and destroys the carbon. Elution is safer and more efficient.

Extracting gold from carbon is a blend of chemistry and engineering. By stripping gold with heat and chemicals, then plating and smelting it, miners turn carbon's hidden treasure into gleaming bars. While the process relies on careful handling of cyanide and high temperatures, modern advancements ensure it's both efficient and environmentally responsible. Next time you see gold bar, remember the journey it took—from carbon's pores to your palm.

Feel free to contact us and learn more about gold recovery solutions!