Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

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Factors affecting activated carbon adsorptivity (1 reply)

7 years ago
kahonde 7 years ago

kindly asking what are the factors affecting activated carbon adsorptivity?

does cyanide strength affect  carbon adsorption and if so, what concentration?

Bob Mathias
7 years ago
Bob Mathias 7 years ago

The major physical factors affecting gold adsorption onto carbon are:

  • Carbon type
  • Carbon particle size
  • Mixing efficiency
  • Slurry density
  • Temperature
  • Gold concentration in solution
  • Cyanide concentration
  • Solution pH
  • Ionic strength
  • Concentration of other metals
  • Dissolved oxygen
  • Carbon fouling






Both the loading rate and capacity of gold on carbon decrease with increasing free cyanide concentration. This is illustrated here, which shows data for tests at constant ionic strength, and the effect is attributed to increased competition of free cyanide species for adsorption sites  on the carbon. However, the selectivity of activated carbon for gold over other metal cyanide species increases with increasing cyanide concentration, as exploited in the treatment of high copper ores.  In practice, the cyanide concentration used in adsorption systems is often deter- mined by the requirements for optimal gold dissolution and by natural cyanide degradation rates within the extraction circuit (i.e., 0.1 to 0.3 g/L sodium cyanide [NaCN]). 

The Chemistry of Gold Extraction, Second Edition

During elution, the effect of cyanide on the rate of gold desorption is other. Increasing cyanide concentration increases the competition of cyanide ions with gold cyanide species for adsorption sites on the carbon and assists with the displacement of gold cyanide species from the carbon. However, the presence of free cyanide throughout the desorption process is not a requirement for effective elution and several procedures have been developed that use a cyanide presoak step followed by deionized water elution. Consequently, elution systems can be divided into those using cyanide throughout the process and those using cyanide during a pre- soak only.

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