Established Adsorption Technology for Modern Gold Processing
Gold recovery using activated carbon is the dominant processing route in modern gold mining. Operations across Africa, Australia, Central Asia, and the Americas depend on coconut shell activated carbon to extract dissolved gold from cyanide leach solutions and concentrate it into a form ready for refining. The technology has been refined over six decades and remains the most cost effective method available for recovering gold from low and medium grade ores. As an Activated Carbon Dubai, SorbiTech produces OraPure carbon engineered specifically for the demands of gold mining.
Adsorption Mechanism of Gold onto Activated Carbon
The gold recovery process begins with leaching, where crushed and ground ore is contacted with a dilute alkaline cyanide solution. Cyanide dissolves gold into a soluble aurocyanide complex that remains in solution. Activated carbon is then introduced, either directly into the leach pulp or into the clarified solution. The aurocyanide complex adsorbs onto the carbon surface, concentrating the gold by more than a thousandfold. The loaded carbon is then separated from the slurry, the gold is stripped off in a hot caustic elution stage, and the gold is recovered by electrowinning or zinc precipitation.
The carbon is then thermally regenerated in a kiln and returned to the circuit. Each batch of carbon completes many cycles of adsorption and stripping before the kinetics decline enough to require fresh carbon makeup.
CIP, CIL, and CIC Process Configurations
Activated carbon is used in three standard gold recovery configurations:
Carbon in Pulp (CIP)
Carbon is introduced after leaching is complete. It is moved counter currently through a series of adsorption tanks to maximize gold loading efficiency.
Carbon in Leach (CIL)
Carbon is added directly to the leaching stage. Leaching and adsorption occur simultaneously. This method is particularly effective for ores containing natural carbonaceous material that would otherwise adsorb dissolved gold.
Carbon in Column (CIC)
Columns filled with activated carbon are used to treat clarified solutions, typically from heap leach operations.Each configuration requires carbon with stable adsorption kinetics and high mechanical durability.
Performance Parameters for Gold Recovery Carbon
Activated carbon for gold recovery is evaluated based on three key parameters:
- K Value – equilibrium adsorption capacity for gold
- R Value – adsorption kinetics (rate of gold loading)
- Abrasion Number – resistance to mechanical degradation during handling and slurry contact
Higher values in these parameters directly improve:
- Gold recovery efficiency
- Carbon consumption per ounce of gold
- Losses due to fines generation
OraPure™ activated carbon is manufactured to achieve stable performance across these parameters, ensuring predictable operation in gold recovery. Each shipment is supplied with a certificate of analysis covering K and R values, abrasion number, iodine number, hardness, ash, moisture, and particle size distribution.
Elution, Acid Wash, and Reactivation
Loaded carbon from any of the three circuits is processed through an elution stage. The standard procedures are the AARL and Zadra processes, where hot caustic and ethanol solutions strip the gold off the carbon at temperatures of 110 to 130 degrees Celsius. The eluate, now carrying the dissolved gold, is sent to electrowinning cells where the gold is plated onto steel wool cathodes for smelting into doré bars.
After elution, the carbon is acid washed with dilute hydrochloric acid to remove inorganic foulants such as calcium carbonate, then thermally reactivated in a rotary kiln at 650 to 750 degrees Celsius. Reactivation removes residual organic foulants and restores 90 to 95 percent of the original adsorption activity. The same thermal reactivation principle is used in wastewater treatment, where spent GAC is regenerated and returned to service.
Selecting Activated Carbon for Gold Mining
The activated carbon used in gold mining is almost always coconut shell based, because the natural microporous structure of coconut shell carbon is well suited to the size of the aurocyanide complex and because coconut shell delivers the high mechanical hardness needed for slurry service. Particle size is selected based on the circuit configuration.
SorbiTech OraPure Activated Carbon for Gold Recovery & Gold Extraction
SorbiTech supplies the OraPure activated carbon line for CIP, CIL, and CIC gold recovery. The product is manufactured to consistent quality benchmarks and supported by direct technical experience in carbon performance benchmarking, circuit optimization, and elution and reactivation troubleshooting. SorbiTech serves mining operators across Africa, Central Asia, the Americas, and the Asia Pacific region. To request OraPure, to benchmark performance against your existing carbon, or to request technical support for an upgrade, contact the SorbiTech mining technical team.