The extraction of gold by activated carbon adsorption needs to be completed through multiple steps such as desorption, reduction, separation and regeneration. The specific process is as follows:
1. Pre-treatment of gold-loaded carbon
Clean and remove impurities:
The gold-loaded carbon that has been adsorbed with gold should be cleaned with water or detergent to remove impurities on the surface and avoid interference in subsequent steps.
2. Desorption treatment
High temperature/chemical desorption:
Gold is desorbed from activated carbon to solution by heating or using chemical reagents (such as sodium cyanide solution). High temperature desorption is usually carried out at 90-130℃, while chemical desorption requires control of pH value and reagent concentration to optimize efficiency.
3. Restore gold
Add reducing agent for smelting:
Add a reducing agent (such as zinc powder, sodium borohydride, etc.) to the gold-containing solution, and heat it to high temperature (such as above 1000℃) in a furnace to reduce gold ions to metal elements. The choice of reducing agent should be adjusted according to the specific process and solution composition.
4.Separation and purification
Screening and separation:
The reduced mixture was screened to remove the residual activated carbon and impurities, and the gold particles were retained.
Secondary smelting and purification:
The separated gold particles are remelted again to remove residual impurities (such as ash, unreacted reductant, etc.) to obtain higher purity of gold.
5. Regeneration of activated carbon
Activate and restore activity:
After desorption, the lean carbon needs to be restored to its pore structure and adsorption capacity by introducing steam or chemical activation (such as acid washing) at high temperature (800-1000℃), so as to be recycled.
6. Other process supplements
Electrodeposition or displacement precipitation:
The gold-containing liquid after desorption can also directly recover gold by electroplating (electrodeposition) or displacement precipitation (such as zinc wire replacement), reducing the smelting step.
