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Gold extraction process by activated carbon adsorption

The process of extracting gold from cyanide pulp or solution by activated carbon adsorption includes CIP method, CIL method and CIC method.

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Fodamon engineers summarize the following steps:
A. Gold is adsorbed and leached from cyanide pulp or solution with activated carbon to produce gold-bearing carbon.
B. The desorption treatment of gold-loaded carbon makes gold on carbon re-transferred into solution and produces desorption precious solution of gold.
C. Gold is recovered from precious liquid containing gold by various methods.
D. The desorbed lean carbon is regenerated, its activity is restored, and it is returned to the adsorption operation for reuse.
 
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1. Characterization of Activated Carbon
Activated carbon can be divided into powder carbon and granular carbon from its appearance. Granular carbon can be produced from a variety of carbon-containing materials such as cellulose, wood, coconut shell, nut, and coal.
In the production of gold extraction, the activated carbon required to be used must have high hardness and wear resistance, and the adsorption activity and wear resistance are often contradictory. Activated carbon is often used according to experiment and experience in production.
 
2. Adsorption process of activated carbon
Au (CN) - diffuses to the surface of carbon particles, and diffuses and adsorbs to the interior of carbon particles.
 
3. Factors affecting the adsorption of activated carbon
3.1 The adsorption characteristics of coconut shell charcoal and apricot core charcoal are much better than those of coal charcoal and coke.
3.2 Adsorption equipment structure: Axial flow type and runoff type are common adsorptive tanks. Comparatively speaking, the resistance of Axial flow type adsorptive tank is smaller, the dead zone is smaller, and the carbon wear rate is lower, especially when double impellers are used.
3.3 Pulp properties: refers to pulp size characteristics, concentration and viscosity, organic matter content, pulp PH value, etc.
 
4. Carbon extraction equipment and process operation
4.1 Carbon extraction equipment: At present, there are three types of turbopump, jet pump and air mixing chamber.
4.2 Process operation: Carbon extraction generally starts from the first trough, then carries on the series extraction of carbon in trough by trough, and finally adds carbon in the final trough. The number of times of carbon extraction is based on the test and theoretical calculation, and the classes are unified.
 
5. Desorption of gold-loaded carbon
The experimental study shows that the adsorption process of activated carbon is actually a reversible process. When activated carbon adsorbs gold, excessive temperature, pressure, PH value and cyanide (CN-) concentration will significantly reduce the amount of gold adsorbed. Therefore, effective methods can be taken to desorb gold from gold-loaded carbon into solution.
5.1 The desorption methods of gold-loaded carbon: atmospheric temperature desorption method (also known as Zadra desorption method), pressure desorption method, alcohol desorption method, etc.
5.2 Gold-carbon desorption equipment is usually associated with electrodeposition equipment, forming a production cycle unit. The prepared gold-loaded charcoal is loaded into the desorption tower (column) and the prepared desorption liquid is pumped into the desorption electrowinning system. The specific operation mode depends on the equipment and technology used.
 
6. Regeneration of Gold-free Carbon
Activated carbon has obvious surface activity after adsorption, desorption and regeneration. After acidic regeneration, the activity of gold-removal charcoal has not been significantly improved, only half of its activity can be restored. Only thermal regeneration can make it possible to restore the activity to more than 80%.
The thermal regeneration of decarbonized charcoal is usually completed in an external heat rotary furnace. The process includes drying, carbonization and gasification stages.
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