Industrial Gold Recovery Process Details Using Supercritical CO2

Supercritical CO₂ Precious Metal Extraction Process

1. Feedstock Preparation

• Material Type: E-waste such as printed circuit boards, connectors, or other components with gold, silver, or platinum group metal (PGM) coatings.

• Pre-treatment: The material is shredded or crushed to increase surface area and ensure better contact with the supercritical CO₂.

• Loading: The processed material is loaded into a high-pressure extraction vessel (e.g., 10 liters in volume).

2. System Pressurization and Heating

• CO₂ Supply: Liquid CO₂ is stored in a tank and pumped into the system using a high-pressure CO₂ pump.

• Transition to Supercritical State: The extraction vessel is heated to around 31°C and pressurized to 74 bar (or higher), converting CO₂ into its supercritical state—a phase where it behaves like both a gas and a liquid.

3. Solvent Enhancement (Optional)

• A ligand or co-solvent (e.g., tributyl phosphate or other metal-binding agents) may be introduced to increase the affinity of supercritical CO₂ for metal ions, enhancing metal solubility and selectivity.

4. Extraction Phase

• Supercritical CO₂ circulates through the extraction vessel.

• It dissolves or leaches the precious metal coatings from the substrate materials.

• This process typically takes about 1 hour per cycle, depending on conditions and metal type.

5. Separation and Collection

• The metal-rich CO₂ exits the extraction chamber and passes through a separator (often a pressure drop device or cooling unit).

• The pressure is reduced or temperature altered, causing the dissolved metals to precipitate out.

• Metals are collected in a collector trap or via filtration.

6. CO₂ Recovery and Recirculation

• The now-clean CO₂ is re-condensed and recycled back into the system.

• This closed-loop design minimizes waste and makes the process highly sustainable and cost-efficient.

7. Metal Refinement

• The precipitated metals can be further refined using conventional metallurgical techniques such as electrolysis or melting.

Advantages of the Process

• Non-toxic: No cyanide or mercury is used.

• Eco-friendly: CO₂ is recyclable and has minimal environmental impact.

• Efficient: Targets only the precious metals with minimal damage to other materials.

• Scalable: Can be used in small modular setups or scaled for industrial throughput.



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